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Biphasic Dose Response in Low Level Light Therapy – An Update

Ying-Ying Huang, Sulbha K Sharma, Michael R Hamblin - Published online 2011 Sep 2. doi: 10.2203/dose-response.11-009.Hamblin (Publication)
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Low-level laser (light) therapy (LLLT) has been known since 1967 but still remains controversial due to incomplete understanding of the basic mechanisms and the selection of inappropriate dosimetric parameters that led to negative studies. The biphasic dose-response or Arndt-Schulz curve in LLLT has been shown both in vitro studies and in animal experiments. This review will provide an update to our previous () coverage of this topic. In vitro mediators of LLLT such as adenosine triphosphate (ATP) and mitochondrial membrane potential show biphasic patterns, while others such as mitochondrial reactive oxygen species show a triphasic dose-response with two distinct peaks. The Janus nature of reactive oxygen species (ROS) that may act as a beneficial signaling molecule at low concentrations and a harmful cytotoxic agent at high concentrations, may partly explain the observed responses in vivo. Transcranial LLLT for traumatic brain injury (TBI) in mice shows a distinct biphasic pattern with peaks in beneficial neurological effects observed when the number of treatments is varied, and when the energy density of an individual treatment is varied. Further understanding of the extent to which biphasic dose responses apply in LLLT will be necessary to optimize clinical treatments.

Keywords: low level laser therapy, photobiomodulation, biphasic dose response, reactive oxygen species, nitric oxide, traumatic brain injury

INTRODUCTION

Low level laser (light) therapy (LLLT) employs visible (generally red) or near-infrared light generated from a laser or light emitting diode (LED) system to treat diverse injuries or pathologies in humans or animals. The light is typically of narrow spectral width between 600nm – 1000nm. The fluence (energy density) used is generally between 1 and 20 J/cm2 while the irradiance (power density) can vary widely depending on the actual light source and spot size; values from 5 to 50 mW/cm2 are common for stimulation and healing, while much higher irradiances (up to W/cm2) can be used for nerve inhibition and pain relief. LLLT is typically used to promote tissue regeneration, reduce swelling and inflammation and relieve pain and is often applied to the injury for 30 seconds to a few minutes or so, a few times a week for several weeks. Unlike other medical laser procedures, LLLT is not an ablative or thermal mechanism, but rather a photochemical effect comparable to photosynthesis in plants whereby the light is absorbed and exerts a chemical change.

Within a decade of the introduction of LLLT in the 1970s it was realized that more does not necessarily mean better. The demonstration of the biphasic dose response curve in LLLT has been hampered by disagreement about exactly what constitutes a “dose”. Many practitioners concentrate on fluence as the principle metric of dose, while others prefer irradiance or illumination time. The use of very small spot sizes by some practitioners has led to the assertion that they delivered hundreds of mW/cm2 from a 50 mW laser. While this statement is mathematically correct it can give the impression that much higher doses of light were given than actually were delivered.

Two years ago we reviewed () the biphasic dose response in LLLT and found many reports in the literature concerning biphasic dose responses observed in cell cultures, some in animal experiments but no clinical reports. We now believe that the time is right to revisit this interesting topic for two reasons. Firstly because we have found more instances in our laboratory both in vitro with cultured cortical neurons, and in vivo with LLLT of traumatic brain injuries in mouse models. Secondly because advances have been made in mechanistic understanding of how LLLT works at a cellular level that may explain why a little light may be beneficial and at the same time a lot of light might be harmful.

MECHANISMS OF LOW LEVEL LIGHT THERAPY

Basic photobiophysics and photochemistry

According to the First Law of Photochemistry, the photons of light must be absorbed by some molecular photoacceptors or chromophores for photochemistry to occur ().The mechanism of LLLT at the cellular level has been attributed to the absorption of monochromatic visible and near infrared (NIR) radiation by components of the cellular respiratory chain (). Phototherapy is characterized by its ability to induce photobiological processes in cells. The effective tissue penetration of light and the specific wavelength of light absorbed by photoacceptors are two of the major parameters to be considered in light therapy. In tissue there is an “optical window” that runs approximately from 650 nm to 1200 nm where the effective tissue penetration of light is maximized. Therefore the use of LLLT in animals and patients almost exclusively involves red and near-infrared light (600–1100-nm) (). The action spectrum (a plot of biological effect against wavelength) shows which specific wavelengths of light are most effectively used for biological endpoints as well as for further investigations into cellular mechanisms of phototherapy (). Fluence (J/cm2) is often referred to as “dose”, though many authors and practitioners of LLLT also refer to energy (Joules) as dose. Not only is this confusing to the novice student of LLLT but it also assumes that the product of power and time (and more importantly power density and time) is the goal rather than the right combination of individual values. This lack of reciprocity has been shown many times before and since our first paper on biphasic dose response and several more authors have reported finding these effects since. Examples of recently published “dose-rate” effects are also reviewed later in this article.

Mitochondrial Respiration and Cytochrome c oxidase

Mitochondria play an important role in energy generation and metabolism and are involved in current research about the mechanism of LLLT effects. The absorption of monochromatic visible and NIR radiation by components of the cellular respiratory chain has been considered as the primary mechanism of LLLT at the cellular level (). Cytochrome c oxidase (Cco) is proposed to be the primary photoacceptor for the red-NIR light range in mammalian cells. Absorption spectra obtained for biological responses to light were found to be very similar to the absorption spectra of Cco in different oxidation states ().LLLT on isolated mitochondria increased proton electrochemical potential, ATP synthesis (), increased RNA and protein synthesis () and increases in oxygen consumption, mitochondrial membrane potential, and enhanced synthesis of NADH and ATP.

ROS release and Redox signaling pathway

Mitochondria are an important source of reactive oxygen species (ROS) within most mammalian cells. Mitochondrial ROS may act as a modulatable redox signal, reversibly affecting the activity of a range of functions in the mitochondria, cytosol and nucleus. ROS are very small molecules that include oxygen ions such as superoxide, free radicals such as hydroxyl radical, hydrogen peroxide, and organic peroxides. ROS are highly reactive with biological molecules such as proteins, nucleic acids and unsaturated lipids. ROS are also involved in the signaling pathways from mitochondria to nuclei. It is thought that cells have ROS or redox sensors whose function is to detect potentially harmful levels of ROS that may cause cell damage, and then induce expression of anti-oxidant defenses such as superoxide dismutase and catalase.

LLLT was reported to produce a shift in overall cell redox potential in the direction of greater oxidation () and increased ROS generation and cell redox activity have been demonstrated (). These cytosolic responses may in turn induce transcriptional changes. Several transcription factors are regulated by changes in cellular redox state, but the most important one is nuclear factor κB (NF-κB). Figure 1 graphically illustrates some of the intracellular signaling pathways that are proposed to occur after LLLT.

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Schematic depiction of the cellular signaling pathways triggered by LLLT. After photons are absorbed by chromophores in the mitochondria, respiration and ATP is increased but in addition signaling molecules such as reactive oxygen species (ROS) and nitric oxide (NO) are also produced.

NO release and NO signaling

There have been reports of the production and/or release of NO from cells after in vitro LLLT. It is possible that the delivery of low fluences of red/NIR light produces a small amount of NO from mitochondria by dissociation from intracellular stores (), such as nitrosothiols (), NO bound to hemoglobin or myoglobin (; ) or by dissociation of NO from Cco () as depicted in Figure 2. A second mechanism for NO production is by light-mediated increase of the nitrite reductase activity of cytochrome c oxidase (). A third possibility is that light can cause increase of the activity of an isoform of nitric oxide synthase (), possibly by increasing intracellular calcium levels. This low concentration of NO produced by illumination is proposed to be beneficial through cell-signaling pathways ().

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One possible theory that can explain the simultaneous increase in respiration an production of nitric oxide is the photodissociation of bound NO that is inhibiting cytochrome c oxidase by displacing oxygen.

BIPHASIC DOSE RESPONSES IN LLLT

Many reports of biphasic dose responses in LLLT were reviewed in our previous contribution and for convenience we have assembled these reports into Tables. Table 1 lists reports on cultured cells in vitro, Table 2 lists those reports in animal models in vivo, while Table 3 contains the only report of biphasic dose response in clinical studies.

TABLE 1.

Biphasic dose response studies of LLLT in vitro.

Year Cells Laser characteristics Fluence Irradiance Reference
1978 Lymphocytes in vitro   “threshold phenomenon”  
1990 Macrophage cell lines (U-937) 820nm Laser; 120mW/cm2; 2.4J/ cm2 to 9.6J/cm2 Cell proliferation: Maximum at 7.2J/cm2 least at 9.6J/cm2  
1991 Macrophage cell lines (U-937) 820nm Laser; 2.4J/cm2 or 7.2J/cm2; 400mW/ cm2 or 800mW/ cm2   cell proliferation increased at 400mW/ cm2; Cell viability reduced at 800mW/cm2
1994 Human oral mucosal fibroblast cells 812nm laser; 4.5mW/cm2; Cell proliferation peak at 0.45 J/cm2; less at 1.422J/cm2  
2001 Chinese hamster ovary and human fibroblast cells He-Ne laser;1.25 mW/cm2; 0.06 to 0.6J/cm2 Cell proliferation peak at 0.18 J/cm2; less at 0.6J/cm2.  
2003 human fibroblast cells 628nm LED; 11.46 mW/cm2; 0, 0.44, 0.88, 2.00, 4.40, and 8.68 J /cm2 Cell proliferation maximum at 0.88 J/cm2; reduced at 8.68 J/cm2  
2005 Human HEP-2 and murine L-929 cell lines 670 nm LED; 5 J/cm2 per treatment; Total 50J/cm2/day; 1 to 4 treatments/day Cell proliferation bigger at 2 treatments/day  
2005 Hela cells wavelength range of 580–860 nm DNA synthesis rate maximum at 0.1 J/cm2 with 0.8 mW/cm2  
2005 Wounded fibroblasts 632.8nm laser; 2mW/cm2; 0.5, 2.5, 5.0 or 10.0 J/cm2 Cell proliferation maximum at a single dose of 2.5J/cm2; Cellular damage at 10J/cm2  
2006 Wounded fibroblasts 632.8nm laser; 5.0 J/ cm2 or 16J/ cm2 Cell proliferation and cell viability increased at 5 J/cm2; decreased at 10 and 16 J/cm2  
2006 Wounded fibroblasts 632.8nm laser; 5.0 J/cm2 or 16J/cm2 Cell migration and proliferation increased at a single dose of 5.0 J/cm2 and two or three doses of 2.5 J/cm2; inhibited at 16 J/cm2  
2007 Human Neural Progenitor Cells (NHNPCs) 810nm; 0.2J/ cm2; 50mW/cm2 and 100mW/ cm2   Neurite outgrowth greater at 50mW/cm2; less at 100mW/cm2 Anders et al. 2007
2009 Rheumatoid arthritis synoviocytes 810nm laser_1, 3, 5, 10, 20 and 50 J/cm2 Cell proliferation increased at 5 J/cm2 (16.7 mW/cm2); Lower at 50 J/cm2  
2009 Mouse embryonic fibroblasts 810nm laser; 0.003,0.03,0.3,3 or 30J/cm2 NF-κB activation maximum at 0.3 J/cm2; decreased at 3 J/cm2 and 30 J/cm2  

TABLE 2.

Biphasic dose response studies of LLLT in vivo (animal models).

Year Tissue Laser characteristics Fluence Irradiance Reference
1979 wound closure He-Ne laser4 J/cm2   Wound healing best at 45 mW/cm2; least at 12.4 mW/cm2
2001 Induced heart attacks in rats 810 nm laser; 2.5 to 20mW/cm2 ;   Reductions of infarct size maximum at 5mW/cm2
Lower effects both at 2.5mW/cm2 and 20mW/cm2
2005 Mouse pleurisy induced by Carrageenan 650nm laser; 2.5 mW in 0.08 cm2; 3 J/cm2, 7.5 J/cm2, and 15 J/cm2 Inflammatory cell migration reduction most at 7.5 J/cm2; Less at 3 and 15 J/cm2  
2007 Healing of pressure ulcers in mice 670nm LED; 5 J/cm2 at 0.7, 2, 8 or 40mW/cm2   Healing significant improved only at 8mW/cm2;Less at 0.7, 2, and 40 mW/cm2
2007 Full thickness dorsal excisional wound in BALB/c mice a single exposure from 635, 670, 720 or 820nm filtered lamp; 1, 2, 10 and 50 J/cm2; 100 mW/cm2 10, 20, 100 and 500 seconds Healing effect best at 2 J/cm2 for 635nm light; worse at 50 J/cm2 for most wavelengths compared to no treatment 820nm was the best wavelength
2007 Inflammatory arthritis induced by zymosan in rats 810-nm laser; 3 and 30 J/cm2; 5 mW/cm2 and 50 mW/cm2 30 J/cm2 was better than 3 J/cm2 at 50mW/cm2 3 J/cm2 has effective at 5mW/cm2 but not 50mW/cm2

TABLE 3.

Biphasic dose response studies of LLLT in clinical studies.

Year Patients Laser characteristics Fluence Irradiance Reference
1997 Patients with post herpetic neuralgia of the facial type 830nm lasers; 60mW laser and 150mW laser; irradiance point at 4mm in diameter   Pain reduction greater at 150mW laser; less at 60mW laser when exposure to the same time.

Figure 3 shows a 3D depiction of the Arndt Schulz model to illustrate a possible dose “sweet spot” at the target tissue. This graph suggests that insufficient power density or too short a time will have no effect on the pathology, that too much power density and / or time may have inhibitory effects and that there may be an optimal balance between power density and time that produces a maximal beneficial effect. There even may be a (low) power density for which infinite irradiation time would only have positive effects and no inhibitory effect. We believe that the absolute figures will be different at different wavelengths, tissue types, redox states, and may be affected further by different pulse parameters.

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Three-dimensional model of the Arndt-Schulz curve illustrating how either irradiance or illumination time (fluence) can have biphasic dose response effects in LLLT.

CURRENT BIPHASIC DOSE RESPONSE STUDIES IN LLLT

In this section we cover the new reports of biphasic dose responses in LLLT that have been published in the last two years since our previous review.

In an oral mucositis hamster model Lopes and coworkers () delivered 660-nm laser at two different irradiances (55 mW/cm2 for 16 seconds per point or 155 mW/cm2 for 6 seconds per point). Both regimens delivered 0.9 J/cm2 per point. On day 7, 11 and 15 the authors reported reduced severity of clinical mucositis and lower levels of COX-2 staining in the 55 mW/cm2 group and that the 155 mW/cm2 had no significant differences when compared with controls. This data is summarized in Figure 4.

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Mean grading of oral mucositis (OM) in a hamster cheek pouch model treated with 0.9 J/cm2 of 660-nm laser at two different irradiances (55 mW/cm2 for 16 seconds per point or 155 mW/cm2 for 6 seconds per point). Graph redrawn from data contained in ().

Gal et al () compared the effects of delivering 5 J/cm2 of 670-nm laser at different power densities on wound tensile strength in a rat model. They found (Figure 5) that 670 nm laser achieved a significant effect using 4mW/cm2 applied for 1,250 seconds (20 mins 50 seconds) but that this effect was lost if the same 5J/cm2 fluence was delivered at 15 mW/cm2 for 333 seconds (5 mins 33 seconds).

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Mean wound tensile strength obtained after delivering 5 J/cm2 of 670-nm laser at different power densities (4mW/cm2 applied for 1,250 seconds or 15 mW/cm2 for 333 seconds). Graph redrawn from data contained in ().

() studied the effects of different influences of 980 nm laser on a human fibroblast in vitro model of wound healing. A small pipette was used to induce a wound in fibroblast cell cultures, which were exposed to a range of laser doses (1.5–66 J/cm2). Exposure to low- and medium-dose laser light accelerated cell growth, whereas high-intensity light negated the beneficial effects of laser exposure as shown in Figure 6.

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Mean percentage of healing induced in a scratch wounded culture of human fibroblasts using different fluences (constant time, increasing irradiance) of 980-nm laser. Graph redrawn from data contained in ().

() performed a dose response study by applying a 7 mW HeNe (632.8-nm) laser with a power density of 4 mW/cm2 to 15×15 mm excisional wounds on Swiss albino mice for a range of irradiation times from 249 seconds (4.15 mins) up to 2,290 seconds (41.46 mins). As Figure 7 shows, there was a clear biphasic response (including a possible inhibitory effect) with changes in irradiation time and therefore fluence.

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Mean area under the curve of wound area over time in a mouse excisional wound healing model treated with a 7 mW (power density of 4 mW/cm2) HeNe (632.8-nm) laser for times ranging from 249 to 2,290 seconds. Graph redrawn from data contained in ().

BIPHASIC LLLT DOSE RESPONSE STUDIES IN CULTURED NEURONS AND TRAUMATIC BRAIN INJURY MODELS IN MICE

LLLT studies on cultured cortical neurons

In order to elucidate the mechanism responsible for the beneficial effect reported by LLLT for brain related disorders, we carried out studies to look into effects of 810 nm laser on different cellular signaling molecules in primary cortical neurons. The primary cortical neurons were isolated from brains taken from embryonic mice. We irradiated the neurons with different fluences of 0.03, 0.3, 3, 10 or 30 J/cm2 delivered at a constant irradiance of 25 mW/cm2, and subsequently the intracellular levels of ROS, mitochondrial membrane potential (MMP) and ATP was measured. The changes in mitochondrial function were studied in terms of ATP and MMP. Low-level light was found to induce a significant increase in ATP and MMP at lower fluences and a decrease at higher fluence. ROS was induced significantly by light at all light doses but there was a distinctive pattern of a double peak with the first peak coinciding with the other peaks of ATP and MMP at 3 J/cm2 (Figure 8). However in contrast to ATP and MMP there was a second larger rise in ROS at 30 J/cm2 that coincided with the reduction in MMP below baseline. The results of the this study suggested that LLLT at lower fluences is capable of inducing mediators of cell signaling process which in turn may be responsible for the biomodulatory effects of the low level laser. Conversely at higher fluences beneficial mediators are reduced but potentially harmful mediators are increased. Thus this study offered an explanation for the biphasic dose response induced by LLLT.

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Mean expression levels of reactive oxygen species (ROS, measured by MitoSox red fluorescence), mitochondrial membrane potential (MMP, measured by red/green fluorescence ration of JC1 dye) and ATP (measured by firefly luciferase assay) in primary mouse cortical neurons treated with various fluences of 810-laser delivered at 25 mW/cm2 over times varying from 1.2 to 1200 seconds.

LLLT in a mouse model of traumatic brain injury

We have been studying the effect of transcranial laser (810-nm) on mouse models of traumatic brain injury. The model involves a controlled cortical impact using a pneumatic piston device through a craniotomy followed by closure of the head. This injury can be adjusted in severity to produce a neurological severity score (NSS based on a panel of standardized behavioral tests) of 7–8 on a scale of 0 (normal mice) to 10 (severe brain injury that causes death). The basic finding was that delivering a single dose of 36 J/cm2 810-nm laser delivered at 50 mW/cm2 (12 minutes illumination time) in a spot of 1-cm diameter centered on the top of the mouse head at a time point of 4 hours post-TBI was highly effective in ameliorating the neurological symptoms suffered by the mice (Figure 9A). When we delivered 10 times as much 810-nm laser (360 J/cm2 at 500 mW/cm2) also taking 12 minutes the beneficial effect totally disappeared, and at early time points (1–6 days) the high fluence appeared to be worse than no treatment (Figure 9B).

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Transcranial laser therapy (36 J/cm2 of 810-nm laser delivered at 50 mW/cm2 (12 minutes illumination time) in a spot of 1-cm diameter centered on the top of the mouse head) was used to treat mice with controlled cortical impact TBI four hours after injury. (A) Significant improvement in neurological severity score continuing for 4 weeks after a single treatment. (B) Delivering ten times more light by increasing irradiance tenfold (500 mW/cm2) loses all therapeutic benefit, and produces worse performance soon after laser. (C) Repeating beneficial laser treatment daily for 14 days loses benefit in performance after 5 days.

When we repeated the effective laser treatments 14 times (36 J/cm2 delivered at 50-mW/cm2 once a day for 14 days starting 4 hours post-TB) we found a very interesting result (Figure 9C). For the first 4 days the improvement in NSS in the repeated laser group was marginally better than the single treatment. However on day 5 the gradual improvement ceased and as the laser was repeated the NSS got closer to that of untreated TBI mice until at day 14 it actually crossed over. Although the differences were not statistically significant it appeared that from day 16 until day 28 the mice that received 14 laser treatments did worse than those that received no treatment at all.

POSSIBLE EXPLANATIONS FOR BIPHASIC DOSE RESPONSE IN LLLT

The triphasic dose response we have observed for ROS production in cultured cortical neurons (see Fig 7) suggests an explanation for the biphasic dose response. The hypothesis is that there are two kinds of ROS. Good ROS are produced at fairly low fluences of light. The reason for the production of good ROS is likely to be connected with stimulation of mitochondrial electron transport as shown by increases in MMP and increases in ATP production. These good ROS can initiate beneficial cell signaling pathwas leading to activation of redox sensitive transcription factors such as NF-κB (; ). NF-κB activation induces expression of a large number of gene products related to cell proliferation and survival (; ). As the fluence of light is increased the beneficial ROS production in the mitochondria decreases in tandem with reductions in MMP and a drop-off in ATP production. Then when even more light is delivered there is a second peak in ROS production, which we will call bad ROS. Bad ROS can damage the mitochondria leading to a drop in MMP below baseline levels and presumably can lead to initiation of apoptosis by the mitochondrial pathway including cytochrome c release. It remains to be seen whether the good and bad ROS are identical species and just differ in amount, or whether they are chemically different species. For instance it may be hypothesized that the good ROS consists mainly of superoxide while the bad ROS consists of more damaging ROS such as hydroxyl radicals and peroxynitrite. In Figure 7 we used just one type of fluorescent ROS indicator (mitoSOX red), which is commonly supposed to be specific for superoxide but will likely also be activated by hydroxyl radicals and peroxynitrite.

There have been several studies showing that relatively high doses of light can induce apoptosis in various cell types via ROS-mediated signaling pathways (). Meanwhile, there is an important proapoptotic signaling pathway has been identified which involv
Original Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3315174/


Effect of NASA light-emitting diode irradiation on wound healing

Whelan HT1, Smits RL Jr, Buchman EV, Whelan NT, Turner SG, Margolis DA, Cevenini V, Stinson H, Ignatius R, Martin T, Cwiklinski J, Philippi AF, Graf WR, Hodgson B, Gould L, Kane M, Chen G, Caviness J. - J Clin Laser Med Surg. 2001 Dec;19(6):305-14. (Publication)
Study showed increases in growth of 155-171% of normal human epithelial cells and an improvment of greater than 40% in musculoskeletal training injuries in Navy SEAL
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OBJECTIVE:

The purpose of this study was to assess the effects of hyperbaric oxygen (HBO) and near-infrared light therapy on wound healing.

BACKGROUND DATA:

Light-emitting diodes (LED), originally developed for NASA plant growth experiments in space show promise for delivering light deep into tissues of the body to promote wound healing and human tissue growth. In this paper, we review and present our new data of LED treatment on cells grown in culture, on ischemic and diabetic wounds in rat models, and on acute and chronic wounds in humans.

MATERIALS AND METHODS:

In vitro and in vivo (animal and human) studies utilized a variety of LED wavelength, power intensity, and energy density parameters to begin to identify conditions for each biological tissue that are optimal for biostimulation.

RESULTS:

LED produced in vitro increases of cell growth of 140-200% in mouse-derived fibroblasts, rat-derived osteoblasts, and rat-derived skeletal muscle cells, and increases in growth of 155-171% of normal human epithelial cells. Wound size decreased up to 36% in conjunction with HBO in ischemic rat models. LED produced improvement of greater than 40% in musculoskeletal training injuries in Navy SEAL team members, and decreased wound healing time in crew members aboard a U.S. Naval submarine. LED produced a 47% reduction in pain of children suffering from oral mucositis.

CONCLUSION:

We believe that the use of NASA LED for light therapy alone, and in conjunction with hyperbaric oxygen, will greatly enhance the natural wound healing process, and more quickly return the patient to a preinjury/illness level of activity. This work is supported and managed through the NASA Marshall Space Flight Center-SBIR Program.

Read more at: https://pdfs.semanticscholar.org/1f5b/0a4ce02a9c58dfd8531552fd2d2e2f3e701e.pdf

Original Source: https://www.ncbi.nlm.nih.gov/pubmed/11776448

A Preliminary Study of the Safety of Red Light Phototherapy of Tissues Harboring Cancer

- Photomedicine and Laser Surgery (Publication)
This study anaylizes the effect of whole-body LLLT on tissues harboring cancer and concluded that suggests that LLLT at these parameters may be safe even when malignant lesions are present.
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Abstract

Objective: Red light phototherapy is known to stimulate cell proliferation in wound healing. This study investigated whether low-level light therapy (LLLT) would promote tumor growth when pre-existing malignancy is present. Background data: LLLT has been increasingly used for numerous conditions, but its use in cancer patients, including the treatment of lymphedema or various unrelated comorbidities, has been withheld by practitioners because of the fear that LLLT might result in initiation or promotion of metastatic lesions or new primary tumors. There has been little scientific study of oncologic outcomes after use of LLLT in cancer patients. Methods: A standard SKH mouse nonmelanoma UV-induced skin cancer model was used after visible squamous cell carcinomas were present, to study the effects of LLLT on tumor growth. The red light group (n=8) received automated full body 670 nm LLLT delivered twice a day at 5 J/cm2 using an LED source. The control group (n=8) was handled similarly, but did not receive LLLT. Measurements on 330 tumors were conducted for 37 consecutive days, while the animals received daily LLLT. Results: Daily tumor measurements demonstrated no measurable effect of LLLT on tumor growth. Conclusions: This experiment suggests that LLLT at these parameters may be safe even when malignant lesions are present. Further studies on the effects of photoirradiation on neoplasms are warranted.

Introduction

Low-level light therapy (LLLT) is being used increasingly for the treatment of a variety of conditions including trauma, wound healing, arthritis, musculoskeletal disorders, and dental and cosmetic applications.14 The current therapeutic approach is to be cautious of potential harmful effects from the use of LLLT in patients with cancer. Its use for the management of lymphedema and other complications in cancer patients has been withheld because of the fear that LLLT might promote metastasis.5,6. This approach is summarized by the review of Hawkins et al., which stated that “LLLT should be avoided or given with special caution in…patients with cancer if there is any doubt of a recurrence of metastases.…Although LLLT has not induced cancer in any of the reported studies, the precise reactions of existing tumors to LLLT are unknown.”6 There is little scientific evidence available as regards oncologic outcomes and local responses to LLLT in cancer patients. Although it is unlikely that LLLT would induce de novo cancer development as there is no evidence that LLLT causes DNA damage, its effects on cellular proliferation have been the empiric basis for withholding treatment in cancer patients.

Red light is known to have a mitogenic effect based on its ability to activate cell division at certain spectral and dose ranges in vitro.79 We are aware only of two studies on the effects of LLLT on cancer.10,11 Revazova demonstrated the acceleration of tumor growth by 633 nm laser irradiation at 3.5 J/cm2 three times per week for 2 weeks in a model of human gastric adenocarcinoma transplanted into immunodeficient athymic nude mice.11 This suggests that LLLT is indeed capable of activating tumor growth under conditions that exclude immune resistance. In another study, the irradiation of squamous cell carcinomas (SCC) in the hamster cheek pouch with 660 nm light at 56 J/cm2 and a 3 mm spot caused significant progression of the severity of SCC as judged by histology.10 The bulk of literature on the topic of LLLT and cancer does not address the question of LLLT effects on tumor growth.

The present study investigated the potential promotion of tumor growth by LLLT cause by the stimulation of cellular proliferation in cancerous cells. A standard nonmelanoma mouse skin cancer model was used to test the effect of automated full body photoirradiation twice a day at 670 nm and at an energy density 2.5 J/cm2 on tumor growth in already developed lesions.

We hypothesized that the systemic effects of phototherapy with red light might offset activation of cell division observed in vitro.

Discussion

The use of phototherapy in the treatment of cancer patients has been controversial. Current recommendations suggest that therapy should be carefully considered and used cautiously in patients with cancer, and that treatment in areas bearing tumors should be avoided. This empiric advice is based on our current knowledge of the experimental acceleration of cellular proliferation and stimulation of wound healing and tissue repair as demonstrated in both animal models and clinical scenarios.1618

There have been few studies that have investigated the influence of LLLT on tumors and tumor growth. The hamster cheek pouch DMBA-induced oral SCC has been recently investigated by Monteiro et al.10 The authors treated the oral cavity with 660 nm LLLT after induction of tumors. Histological evaluation demonstrated an increase in the progression and severity of SCC.10

Liebow et al. had also demonstrated an apparent stimulation of tumor induction and growth after CO2 laser incisions were created in cheek pouch tissue that had been transformed as a result of DMBA painting.19,20 Both the Montiero and Liebow investigations involved manipulations of tissue that had been manipulated into a transformed field as a result of DMBA induction. This process inevitably results in tumor formation and it is well known that scalpel incisions and other perturbations of the epithelium can stimulate tumor induction. It is also well known that these tumors are dependent upon epidermal growth factor (EGF) for growth.21 Saliva contains significant concentrations of EGF and other growth factors and cytokines. Inflammation results in consumption and degradation of these growth factors, and processes that reduce or modulate the inflammatory response similarly affect tumor development in these tissues. CO2 laser use results in a reduction and delay in the inflammatory response.2225 This particular laser is capable of inducing heat shock proteins by a mechanism similar to that observed in modification of wound healing and scar formation in laser-assisted-scar-healing (LASH) in humans.26,27 Similarly, phototherapy at 660 nm is known to reduce inflammation.28

Both of these studies demonstrate that the local milieu is important in the induction and proliferation of malignant lesions. However, it would not be appropriate to make generalizations about all types of cancers based on this very specific model and tumor system.

The model

We chose a model that can produce a large number of malignant cutaneous lesions economically and automatically (Fig. 2), provides a way to irradiate them with red light automatically (Fig. 3), and allows us to monitor the growth of these tumors daily. This experimental model (Fig. 1) induces spontaneous and genetically heterogeneous nonmelanoma skin cancers on the backs of hairless mice after UV damage. The induction of cancer by UV exposure is a random process and involves a combination of randomly induced mutations in multiple genes per tumor. The tumors produced by this model are heterogeneous, which is more representative of a wider range of clinically observed cancers as contrasted to models that use genetically homogeneous cancer cell lines. Although nonmelanoma skin cancer is not as deadly as other cancers in humans, it is a true cancer genetically and functionally and therefore with the effects of red light, LLLT in the presence of these neoplasms is relevant to the potential effects of red light therapy on other types of cancer.

The advantage of SKH-1 mouse cancer model is that the cells producing cancer in the overwhelming majority are epidermal keratinocytes, that is the fast-dividing keratinocytes of the lowest layer of epidermis, which is very thin in mice, less than 0.05 mm. Therefore, the tumors grow on the surface of the skin and a very minor part of each tumor is below the surface.2933 Early investigations using the SKH-1 model documented the high degree of histologic similarity in the numerous cutaneous malignant lesions produced in this model.2933 In addition, the high throughput method of periodic photographing the tumors and measuring their diameter on the photographs, a well-established method of measurement, fosters the analysis of hundreds of tumors longitudinally, which is not possible with other end-point methods, such as histology. The majority of the research studies utilizing this SKH-1 cancer model use the size of the visible tumor as a function of time as a measure of tumor proliferation.12,3441

The sensitivity of the model to detect small therapeutic effects is limited by the fact that the tumors in treatment and control groups are by their nature different genetically, as each tumor is a result of random mutagenic events. Although this difference is of no significance, because of large numbers of medium-sized tumors in both groups, the individual random mutations resulting in the induction of small numbers of large fast growing tumors potentially affected the overall statistical results. This limitation can be overcome in the future by increasing the number of mice treated or by measuring baseline growth rates for each tumor before the beginning of red light therapy, and then comparing the growth rate of each tumor before and after beginning the therapy.

Automation and human interventions

We have developed a new method that uses a well-characterized animal model for the study of the effects of LLLT on cancer. The advantage of this model is that the setup minimizes the human factor, both in influencing mouse behavior and in data analysis. The mice are irradiated automatically and the tumors are sized across time using image morphometry blinded to treatment, thus excluding human bias.

Evidence supporting the safety of red light

This study aimed to maximize the healing and activation effects while avoiding the inhibitory effects of red light. We selected the red light dose and fluence very conservatively based on our prior studies on wound healing.13 Treated mice received two irradiations per day at 8 mW/cm2 fluence for 312 sec per session, resulting in a total dose density of 2.5 J/cm2 per session (5 J/cm2 per day). This regimen is in general agreement with the one used by Erdle et al.14 Erdle et al. used the same red light source and mouse strain (SKH-1), measured incisional wound healing, and demonstrated the high efficiency of chronic daily treatment at a dose of 3.6 J/cm2 (either 450 sec at 8 mW/cm2 or 37 min at 1.6 mW/cm2).

This study documented the absence of strong positive or negative effects of LLLT on tumor growth in this model and red light treatment parameters. Prior studies using the same red LLLT system demonstrated that these parameters stimulate wound healing.13 The present study provides some evidence that phototherapy at these parameters should not be empirically contraindicated in the treatment of patients with cancer. Our qualitative observations of improvement in skin quality at early time points, and relief of sickness behavior at later stages of the investigation, are also suggestive of the fact that the light was capable of producing beneficial effects for the whole animal despite the presence of tumors. It should be recognized, however, that the present study delivers, essentially, whole body therapy to the affected individual, rather than treating a specific area.

The small but statistically significant decrease in tumor area observed on days 16–23 demonstrates the ability of our model to detect small changes in tumor volume because of the low degree of random histotype variability in the model and the high number of examined tumors and time points. An additional explanation as to why red light was beneficial at days 16–23 may be the stimulation of antitumor immune activity or, perhaps, a local photodynamic effect as a result of red light activation of endogenous porphyrins present in tumors in and around areas of spontaneous hemorrhage and necrosis. Red light treatment was qualitatively observed to relieve sickness behavior, which suggests that there was an improved host response and increased antitumor immunity; at least until the tumor burden overwhelmed these effects. Future studies directed at studying these immune effects would be helpful in determining the biological basis for these observations.

Targets of the red light

Important factors to consider are: what tissues were reached by the red light during whole body phototherapy as was the case in this study, and which chromophores are absorbing the light. Because the mice have hairless fair skin, the light was not shielded by hair or melanin. The necrotic tissue covering some of the tumors might have shielded some tumor cells from the red light and/or may have generated local photodynamic effects caused by interaction with endogenous porphyrins. Much of the light likely did penetrate deeper in the mouse, potentially stimulating lymphatic vessels, lymph nodes, internal organs such as the spleen, and, possibly, even the bone marrow. It is likely that both actively dividing tumor cells and immune cells including white blood cells; immune cells infiltrating the skin such as mast cells, dendritic cells, neutrophils, and other, lymphatic vessels and nodes; bone marrow; and, possibly, spleen were absorbing and being activated by the light treatments.

As this study suggests that the outcome of red light therapy depends upon competition between possible activation of tumor growth on the one hand, and improvement of systemic antitumor immune response on the other, future studies should address the issue of local versus systemic red light therapy. Treatment was systemic in this case because of whole-body photoirradiation. Specific studies would be helpful, particularly if treatment can be isolated and directed solely to healthy tissues, both tumor-bearing and healthy tissue, or tumors alone.

Conclusions

The present study failed to demonstrate a harmful effect of whole-body red LLLT on tumor growth in an experimental model of UV-induced SCC. There was a transient and small reduction in relative tumor area in the treatment group compared with controls. This study suggests that LLLT should not be withheld from cancer patients on an empiric basis. Further investigations designed to build upon these observations and determine the mechanism for the host–tumor responses noted during the early treatment phase are warranted.


Original Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3423866/

When is the best moment to apply photobiomodulation therapy (PBMT) when associated to a treatmill endurance-training program? A randomized, triple-blinded, placebo-controlled clinical trial.

Eduardo Foschini MirandaShaiane Silva TomazoniPaulo Roberto Vicente de PaivaHenrique Dantas PintoDenis SmithLarissa Aline SantosPaulo de Tarso Camillo de CarvalhoErnesto Cesar Pinto Leal-Junior - Lasers in Medical Science May 2018 (Publication)
A studying showing the benefits of using LEDT before and after a cardio workout.
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Abstract

Photobiomodulation therapy (PBMT) employing low-level laser therapy (LLLT) and/or light emitting diode therapy (LEDT) has emerged as an electrophysical intervention that could be associated with aerobic training to enhance beneficial effects of aerobic exercise. However, the best moment to perform irradiation with PBMT in aerobic training has not been elucidated. The aim of this study was to assess the effects of PBMT applied before and/or after each training session and to evaluate outcomes of the endurance-training program associated with PBMT. Seventy-seven healthy volunteers completed the treadmill-training protocol performed for 12 weeks, with 3 sessions per week. PBMT was performed before and/or after each training session (17 sites on each lower limb, using a cluster of 12 diodes: 4 × 905 nm super-pulsed laser diodes, 4 × 875 nm infrared LEDs, and 4 × 640 nm red LEDs, dose of 30 J per site). Volunteers were randomized in four groups according to the treatment they would receive before and after each training session: PBMT before + PBMT after, PBMT before + placebo after, placebo before + PBMT after, and placebo before + placebo after. Assessments were performed before the start of the protocol and after 4, 8, and 12 weeks of training. Primary outcome was time until exhaustion; secondary outcome measures were oxygen uptake and body fat. PBMT applied before and after aerobic exercise training sessions (PBMT before + PBMT after group) significantly increased (p < 0.05) the percentage of change of time until exhaustion and oxygen uptake compared to the group treated with placebo before and after aerobic exercise training sessions (placebo before + placebo after group) at 4th, 8th, and 12th week. PBMT applied before and after aerobic exercise training sessions (PBMT before + PBMT after group) also significantly improved (p < 0.05) the percentage of change of body fat compared to the group treated with placebo before and after aerobic exercise training sessions (placebo before + placebo after group) at 8th and 12th week. PBMT applied before and after sessions of aerobic training during 12 weeks can increase the time-to-exhaustion and oxygen uptake and also decrease the body fat in healthy volunteers when compared to placebo irradiation before and after exercise sessions. Our outcomes show that PBMT applied before and after endurance-training exercise sessions lead to improvement of endurance three times faster than exercise only.

Introduction

Physical activity is recommended and beneficial for both asymptomatic persons and individuals with chronic diseases [1, 2]. Aerobic endurance is considered a useful tool for the assessment of physical fitness and the detection of changes in aerobic fitness resulting from systematic training [3].

Regular aerobic exercise has various beneficial metabolic, vascular, and cardiorespiratory effects [4]. Additionally, it decreases body fat and increases muscle mass, muscle strength, and bone density [5]. Moreover, it improves self-esteem and physical and mental health and reduces the incidence of anxiety and depression [4, 6].

Various ergogenic agents, such as whey protein [7], caffeine [8], creatine [9], and neuromuscular electrical stimulation [10], are currently used to increase the benefits of aerobic training. Photobiomodulation therapy (PBMT) has emerged as an electrophysical intervention that could be associated with aerobic training to enhance beneficial effects of aerobic exercise, since several studies used PBMT to improve physical performance when associated with different kinds of exercise [11, 12, 13, 14].

Several studies have recently used PBMT to improve muscle performance during aerobic activities in healthy adults [15, 16, 17, 18] and postmenopausal women [19, 20]. However, to the best of our knowledge, the best moment to perform irradiation with PBMT in aerobic training has not been yet elucidated.

For instance, the current literature shows that the application of PBMT before progressive aerobic exercise has ergogenic effects and acutely increases the time until exhaustion, covered distance, and pulmonary ventilation and decreases the score of dyspnea during progressive cardiopulmonary test [15]. In addition, PBMT irradiation performed prior to aerobic exercises improves the exercise performance by decreasing the exercise-induced oxidative stress and muscle damage [18] and increasing the oxygen extraction by peripheral muscles [16]. When performed during aerobic training sessions, PBMT improves the quadriceps power and reduces the peripheral fatigue in postmenopausal women [19, 20]. Additionally, when applied after the sessions of endurance-training program, PBMT leads to a greater fatigue reduction than endurance training without PBMT irradiation [17].

Therefore, the optimal moment to perform PBMT in aerobic training is still open to discussion. With this perspective in mind, we aimed to assess the effects of PBMT applied at different time points (before and/or after) of each training session and its potential effects on the outcomes of an endurance-training program (aerobic exercise).

Materials and methods

Study design and protocol

We performed a triple-blind (assessors, therapists, and volunteers), placebo-controlled, randomized clinical trial. The study was conducted in the Laboratory of Phototherapy in Sports and Exercise.

Ethical aspects

All participants signed informed consent prior to enrollment and the study was approved by the research ethics committee of Nove de Julho University (process 553.831) and registered at Clinical Trials.gov (NCT02874976).

Sample

The sample size was calculated assuming a type I error of 0.05 and a type II error of 0.2, based on previous study [21], and the primary established outcome was the time until exhaustion.

Inclusion and exclusion criteria

We recruited 96 healthy volunteers (48 men and 48 women) between 18 and 35 years of age and without training or involvement in a regular exercise program (i.e., exercise more than once per week) [22, 23]. Volunteers were excluded if they had any skeletal muscle injury, used any nutritional supplement or pharmacologic agent, presented with signs or symptoms of any disease (i.e., neurologic, inflammatory, pulmonary, metabolic, oncologic), or had a history of cardiac arrest that might limit performance of high-intensity exercises. Volunteers that were unable to attend a minimum rate of 80% of the training sessions and volunteers with immune diseases that require continuous use of anti-inflammatory drugs were also excluded.

Randomization and blinding procedures

Volunteers were distributed in four experimental groups (24 volunteers in each group) through a simple drawing of lots (A, B, C, or D) that determined the moment they would receive active and/or placebo PBMT treatment:
  • PBMT + PBMT: volunteers were treated with active PBMT before and after each training session.

  • PBMT + placebo: volunteers were treated with active PBMT before and placebo PBMT after each training session.

  • Placebo + PBMT: volunteers were treated with placebo PBMT before and active PBMT after each training session.

  • Placebo + placebo: volunteers were treated with placebo PBMT before and after each training session.

Randomization labels were created by using a randomization table at a central office where a series of sealed, opaque, and numbered envelopes ensured confidentiality. The researcher who programmed the PBMT device (manufactured by Multi Radiance Medical™, Solon, OH, USA) based on the randomization results was not involved in any other procedure of the study. He was instructed not to inform the participants or other researchers of the PBMT program (active or placebo). None of the researchers involved in aerobic endurance-training assessments and data collection knew which program corresponded to active or placebo PBMT.

Identical PBMT devices were used in both programs (active or placebo) by a researcher who was not involved in any phase of the projected data collection to ensure the study blinding. All displays and sounds emitted were identical regardless of the selected program. The active PBMT treatment did not demonstrate discernable amounts of heat [24].

Therefore, volunteers were unable to differentiate between active or placebo treatments. All volunteers were required to wear opaque goggles during treatments to safety and to maintain the triple-blind design.

Procedures

The study included three sessions of aerobic endurance training per week performed over 12 weeks, and each session lasted 30 min; the load for each exercise session (treadmill speed) progressed constantly in order to keep subjects’ heart rate between 70 and 80% from maximum heart rate. The assessments were conducted before the start of the training protocol and after 4, 8, and 12 weeks of training. A summary of the study design is presented in Fig. 1.
Fig. 1

CONSORT flowchart

Cardiopulmonary exercise test

Participants performed a standardized progressive cardiopulmonary exercise test on a treadmill with a fixed inclination of 1% until exhaustion. They began the test with a 3-min warm-up at a velocity of 3 km/h. Next, the treadmill velocity was increased by 1 km/h at 1-min intervals until the velocity of 16 km/h was reached. Participants were instructed to use hand signals to request termination of the test at any time. A 3-min recovery phase at a velocity of 6 km/h was allowed after each test [18]. During testing, we monitored the rates of oxygen uptake (VO2), carbon dioxide production measured with a VO 2000 gas analyzer (Inbrasport, Indústria Brasileira de Equipamentos Médico-Desportivos LTDA, Porto Alegre, RS, Brazil), total time until exhaustion, and heart rate measured with a digital electrocardiograph (Medical Graphs Ergomet, São Paulo, SP, Brazil).

These data were used to evaluate the performance of participants during progressive cardiopulmonary exercise testing, because this test is currently the most widely used in the literature for this purpose [25]. The entire test was monitored by electrocardiogram and blood pressure measurement. If any abnormal heart rate or blood pressure changes were observed or if the test was terminated prematurely on request, the test was stopped, and the volunteer’s data were deleted.

Body composition assessment

Body composition was assessed by the same technician (blinded to volunteer’s allocation in different experimental groups) using the procedures established by ISAK [26]. Measurements of height, body mass, and skinfolds were used to establish the percentage of fat [26].

Aerobic training protocol

Aerobic treadmill training, associated or not with PBMT, was performed three times a week for 12 weeks, each session lasting 30 min, with training intensity kept between 70 and 80% of maximum heart rate [27]; changes in running speed (training load) were constantly performed to achieve the 70–80% heart rate.

Training was interrupted based on the criteria established by the guidelines of the American Heart Association. Training intensity was monitored by a heart rate monitor manufactured by Polar®.

Photobiomodulation therapy

PBMT was applied employing MR4 Laser Therapy Systems outfitted with LaserShower 50 4D emitters (both manufactured by Multi Radiance Medical, Solon, OH, USA). The cluster style emitter contains 12 diodes composing of four super-pulsed laser diodes (905 nm, 0.3125 mW average power, and 12.5 W peak power for each diode), four red LED diodes (640 nm, 15 mW average power for each diode), and four infrared LEDs diodes (875 nm, 17.5 mW average power for each diode).

The cluster probe was selected due to the available coverage area and to reduce the number of sites needing treatment. Treatment was applied in direct contact with the skin with a slight applied overpressure to nine sites on extensor muscles of the knee (Fig. 2a), six sites on knee flexors of the knee, and two sites on the calf (Fig. 2b) of both lower limbs [15, 28]. To ensure blinding, the device emitted the same sounds and regardless of the programmed mode (active or placebo). The researcher, who was blinded to randomization and the programming of PBMT device, performed the PBMT.
Fig. 2

a Treatment sites at knee extensor muscles. b Treatment sites at knee flexor and ankle plantar flexor muscles

PBMT parameters and irradiation sites were selected based upon previous positive outcomes demonstrated with the same family of device [13, 15, 28, 29]. Table 1 provides a full description of the PBMT parameters. The volunteers received PBMT or placebo from 5 to 10 min before and/or after aerobic training sessions.

 

Statistical analysis

The obtained results were tested for their normality through the Shapiro-Wilk test. Since the data showed a normal distribution, two-way ANOVA test with Bonferroni post hoc analysis was applied. The data were described as mean values with the respective standard deviations and both absolute and percentage values were analyzed. Graphical data are described as mean and standard errors of mean (SEM). The level of statistical significance was p < 0.05.

Results

After data collection, we analyzed the results of 77 volunteers of both genders (PBMT + PBMT: 18 volunteers; PBMT + placebo: 21 volunteers; placebo + PBMT: 18 volunteers; and placebo + placebo: 20 volunteers) that had completed the aerobic training protocol after 12 weeks (Fig. 1). None of the recruited volunteers were excluded due abnormal heart rate or blood pressure during the execution of procedures of this study. The characteristics of the volunteers are summarized in Table 2.

 
 

As shown in Table 2, no statistically significant differences (p > 0.05) were found for anthropometric variables and baseline data among the different experimental study groups.

Table 3 shows all results of cardiopulmonary progressive test in absolute values for different variables analyzed in all experimental groups of this study. We observed a statistically significant improvement in oxygen uptake when PBMT was performed before and after training sessions (PBMT + PBMT group), comparing baseline values vs 4-, 8-, and 12-week values (p < 0.001). The same was observed for pulmonary ventilation, comparing baseline values vs 8- and 12-week values (p = 0.0018 and p = 0.003, respectively), and for time until exhaustion, comparing baseline values vs 4-, 8-, and 12-week values (p < 0.001).
Table 3

Progressive endurance test variables

   

Baseline

4 weeks

8 weeks

12 weeks

VO2 (mL/kg/min)

PBMT + PBMT

35.8 ± 9.5

40.2 ± 10.2*

41.5 ± 10.4*

42.5 ± 11.2*

PBMT + Placebo

34.8 ± 7.0

37.6 ± 7.0

38.6 ± 8.0

38.2 ± 7.0

Placebo + PBMT

35.2 ± 8.9

36.6 ± 8.1

38.6 ± 8.3

38.5 ± 8.3

Placebo + placebo

36.2 ± 7.7

36.8 ± 8.0

37.6 ± 7.5

38.4 ± 10.1

VCO2 (mL/kg/min)

PBMT + PBMT

38.7 ± 7.0

40.4 ± 8.6

41.3 ± 7.8

41.4 ± 8.7

PBMT + placebo

38.,5 ± 7.8

39.5 ± 6.6

41.7 ± 7.9

41.9 ± 6.8

Placebo + PBMT

38.5 ± 9.5

38.2 ± 9.5

41.5 ± 8.4

40.7 ± 9.6

Placebo + placebo

38.8 ± 10.6

40.7 ± 9.4

43.1 ± 13.4

40.9 ± 10.5

VE (mL/kg/min)

PBMT + PBMT

73.6 ± 22.8

77.9 ± 21.5

83.5 ± 24.5*

85.3 ± 22.5*

PBMT + Placebo

70.6 ± 20.3

71.0 ± 23.1

78.1 ± 23.0

77.2 ± 22.1

Placebo + PBMT

66.2 ± 25.3

70.6 ± 24.2

73.9 ± 20.6

73.4 ± 20.7

Placebo + placebo

69.9 ± 17.9

70.8 ± 18.8

70.3 ± 22.4

77.1 ± 18.3

Time until exhaustion (s)

PBMT + PBMT

681.5 ± 111.9

752.1 ± 111.7*

787.7 ± 114.2*

808.5 ± 124.5*

PBMT + placebo

698.7 ± 131.1

739.3 ± 142.2

773.4 ± 165.9

792.1 ± 186.9

Placebo + PBMT

693.1 ± 106.9

738.4 ± 116.6

766.1 ± 121.0

797.0 ± 139.0

Placebo + placebo

699.5 ± 137.3

720.2 ± 150.0

741.3 ± 154.3*

766.1 ± 159.8*

Data is expressed in average and standard deviation (±)

VO 2 oxygen uptake, VCO 2 carbon dioxide production, VE pulmonary ventilation

*Statistically significant difference compared to baseline (p < 0.05)

Furthermore, PBMT applied before and after each aerobic exercise training session (PBMT + PBMT group) significantly increased (p < 0.05) the percentage change of oxygen consumption and time-to-exhaustion compared to the group treated with placebo before and after each aerobic exercise training session (placebo + placebo group) from 4th to 12th week. Similarly, PBMT applied before and after each aerobic exercise training session (PBMT + PBMT group) significantly improved (p < 0.05) the percentage change of body fat compared to group treated with placebo before and after each aerobic exercise training session (placebo + placebo group). The outcomes are summarized in Figs. 3, 4, and 5, respectively.

Fig. 3

Percentage of change in time-to-exhaustion. The data are presented in mean and SEM. Letter a indicates statistical significance between PBMT + PBMT and placebo + placebo (p < 0.05)

Fig. 4

Percentage of change in maximum oxygen uptake. The data are presented in mean and SEM. Letter a indicates statistical significance between PBMT + PBMT and placebo + placebo (p < 0.05)

Fig. 5

Percentage of change in body fat. The data are presented in mean and SEM. Letter a indicates statistical significance between PBMT + PBMT and placebo + placebo (p < 0.05)

Discussion

To the best of our knowledge, this is the first study aiming to test the optimal moment to perform PBMT in an aerobic training protocol (before, after, or before and after training). Few studies have assessed chronic effects of PBMT [17, 20, 21]; however, PBMT has been applied at different moments (before, after, or during exercise) of the aerobic training program. Briefly, we observed that the combination of super-pulsed lasers and LEDs applied before and after exercise sessions increased the oxygen uptake, time-to-exhaustion, and reduced body fat in healthy sedentary volunteers after 12 weeks of aerobic training.

Paolillo et al. [20] investigated the effects of PBMT applied during the sessions of aerobic training on the treadmill in 20 postmenopausal women. The training was performed twice a week for 3 months, with an intensity of 85–90% of maximum heart rate. The volunteers received LED therapy with 850 nm, 31 mW/cm2, 30 min irradiation, and 14,400 J applied bilaterally to the tight regions. PBMT increased the exercise tolerance time when compared to the control group. These data corroborate with the results of our study, however, we used different light sources and wavelengths simultaneously (4 × 905 nm super-pulsed lasers, 4 × 875 nm infrared LEDs, and 4 × 640 nm red LEDs) to irradiate the volunteers and we found an increase in exercise tolerance of 13.4%. The magnitude of the difference in outcomes between studies might be related to the used irradiation protocol (in our study, the volunteers were irradiated before and after the aerobic training sessions, while Paolillo et al. [20] irradiated volunteers during the training sessions).

The same authors [21] also investigated the effects of PBMT (infrared LEDs—850 nm) when applied during treadmill training in 45 postmenopausal women. The training was performed twice a week for 6 months, and each training session lasted 45 min. The authors found a significant increase in exercise tolerance, and metabolic equivalents, and a longer duration of Bruce test. In our study, the association of PBMT before and after sessions of the aerobic training program was able to increase the oxygen consumption (with 18.7%) and time-to-exhaustion (with 13.4%) and improve the percentage of change of body fat (with 13.9%) after only 12 weeks of aerobic training.

Duarte et al. [30] evaluated the effects of PBMT (808 nm) associated with aerobic and resistance training performed three times a week for 16 weeks in obese women. The authors found a significant decrease in the percentage of fat and in neck and waist circumference. It is important to highlight that in our study, we observed statistically significant improvement in the percentage of change of body fat (13.9%) after only 12 weeks of aerobic training when associated with PBMT before and after the training sessions. We believe that the association of PBMT before and after training was able to enhance the performance and the tolerance of the volunteers during the aerobic training protocol, favoring the reduction of the body fat at the end of the 12 weeks of training.

It is interesting how outcomes in the fourth week for PBMT + PBMT group were similar to those of placebo + placebo group (or exercise alone) in the 12th week. This means that PBMT with optimal irradiation protocol (before and after exercise training sessions) can increase the endurance capacity of volunteers three times faster than exercise alone.

Regarding the mechanisms of the observed effects, we strongly believe that mitochondrial activity modulation is the key mechanism, despite the fact that our study only focused on clinical and functional aspects and not on mechanisms. Hayworth et al. [31] demonstrated that the activity of cytochrome c oxidase is enhanced by PBMT with a single wavelength in skeletal muscle fibers of rats. More recently, Albuquerque-Pontes et al. [32] showed that PBMT with different wavelengths (660, 830, or 905 nm) was able to increase the expression of cytochrome c oxidase in the intact skeletal muscle tissue in different time windows (5 min to 24 h after irradiation), which means that the muscle metabolism can be improved through the action of PBMT. These findings help us to explain the increase in performance observed by the use of PBMT associated with an aerobic training protocol and provide the rationale for the concurrent use of different wavelengths at the same time, which can represent a therapeutic advantage in various clinical situations.

In fact, different studies have shown that the concurrent use of different light sources and wavelengths enhances muscular performance [13, 14, 15, 28, 29, 33] decreases pain [34


Original Source: https://link-springer-com.colorado.idm.oclc.org/article/10.1007%2Fs10103-017-2396-2

Light-emitting diode therapy in exercise-trained mice increases muscle performance, cytochrome c oxidase activity, ATP and cell proliferation

Cleber Ferraresi, Nivaldo Antonio Parizotto, Marcelo Victor Pires de Sousa, Beatriz Kaippert, Ying?Ying Huang, Tomoharu Koiso, Vanderlei Salvador Bagnato, Michael R. Hamblin - Wiley Online Library/ 09-01-2015 (Publication)
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Abstract

Light-emitting diode therapy (LEDT) applied over the leg, gluteus and lower-back muscles of mice using a LED cluster (630 nm and 850 nm, 80 mW/cm2, 7.2 J/cm2) increased muscle performance (repetitive climbing of a ladder carrying a water-filled tube attached to the tail), ATP and mitochondrial metabolism; oxidative stress and proliferative myocyte markers in mice subjected to acute and progressive strength training. Six bi-daily training sessions LEDT-After and LEDT-Before-After regimens more than doubled muscle performance and increased ATP more than tenfold. The effectiveness of LEDT on improving muscle performance and recovery suggest applicability for high performance sports and in training programs.

 

Positioning of the mice and light-emitting diode therapy (LEDT) applied on mouse legs, gluteus and lower-back muscles without contact.

Introduction

Low-level laser (light) therapy has several applications in medicine such as treatment of pain 1, 2, tendinopathies 3 and acceleration of tissue repair 2, 4. Since the 1960s when the first laser (Light Amplification by Stimulated Emission of Radiation) devices were constructed, many applications of this therapy and its mechanisms of action have been investigated around the world 5.

Light therapy can be delivered by different light sources such as diode lasers or light emitting diodes (LEDs). These light sources differ in monochromaticity and coherence, since diode lasers are coherent with a tiny spectral bandwidth and less divergence of the light beams compared to the light emitted by LEDs 5. The spectral regions generally used for light therapy range between red (600 nm) to near infrared (1,000 nm) with total power in range of 1 mW–500 mW and power density (irradiance) in the range of range 1 mW–5 W/cm2 5. These lasers and LEDs are considered to produce equivalent effects on the tissue if the dose of light delivered/applied is in accordance with the possible biphasic dose?response previously reported 5-7. The light?tissue interaction depends on light absorption by specific structures in the cells that are known as chromophores 8-11.

Recently light therapy using lasers and LEDs has been used to increase muscle performance in exercises involving strength 12 or fatigue resistance 13-15; and light therapy may have a role to play in preparing athletes competing in high performance sports. Recent reviews have reported positive effects of light therapy on muscle performance, highlighting protection from exercise?induced muscle damage 16; an increased number of repetitions in maximum exertion tests 17; increased workload, torque and muscle fatigue resistance in training programs; as well as an overview of the main possible mechanisms of action of the light therapy on muscle tissue 18.

Several biological factors govern success or optimum performance in sports that involve high?intensity exercise, or alternatively involve endurance exercise, that both require muscle adaptation during pre?competition training programs. Among these factors are the depletion of the energy supply for muscle contraction which comprises adenosine triphosphate (ATP) and glycogen; accumulation of possibly deleterious metabolites from energy metabolism such as lactate, adenosine diphosphate (ADP), adenosine monophosphate (AMP), ions Ca2+ and H+; production of reactive oxygen species (ROS) 19-22; and the recovery process from microlesions or muscle damage 23. Light therapy seems to be able to benefit all these ”limitations” since its mechanism of action involves the improvement of mitochondrial metabolism and increased ATP synthesis 24, 25 owing to increased activity of cytochrome c oxidase (COX) in the electron transport chain (ETC) 9, 25, 26; reduction of reactive oxygen species (ROS) or improvement of oxidative stress defense 27, 28; and can stimulate faster muscle repair due to an increased proliferation and differentiation of muscle cells 29.

Experimental and clinical trials with different methodologies have reported the benefits of light therapy on muscle performance when applied before 15, 30, 31 or after exercise 12, 13, 32. However there is no consensus about the best time regimen for use of light therapy 18. The best wavelength (red or infrared) to stimulate muscle cells and increase muscle performance is also unclear.

In the current study we used an experimental model of mice exercising on a ladder similar to that reported in a previous study 33, in order to simulate a clinical strength training program that would allow us to identify which light therapy regimen would be better to increase muscle performance. Four different regimens of light therapy were applied to the mouse leg, gluteus and lower?back muscles during a training program: sham; before; before?after; and after each training session. Light therapy was delivered from LEDs (LEDT) with two simultaneous wavelengths (red and infrared). Assessment of muscle performance (load, number of repetitions, muscle work and power), markers of cellular energy and metabolism (ATP, glycogen and COX), oxidative stress markers (protein carbonyls, glutathione, catalase activity, lipid peroxidation, protein thiols) and muscle cell proliferation (BrdU – 5?bromo?2′?deoxyuridine) and adult myonuclei (DAPI – 4′,6?diamidino?2?phenylindole) were carried out.

Materials and methods

Animals

This study was performed with 8 week?old male Balb/c mice, weighing on average 22.22 g (SEM 0.24), housed at five mice per cage and kept on a 12 hour light 12 hour dark cycle. The 22 animals were provided by Charles River Inc and were provided with water and fed ad libitum at the animal facility of Massachusetts General Hospital. All procedures were approved by the IACUC of Massachusetts General Hospital (protocol #2014N000055) and met the guidelines of the National Institutes of Health.

Experimental groups

Twenty?two animals were randomly allocated into 4 exercise groups with 5 animals in each group, and 2 animals were allocated into an ”absolute” control group:

  • LEDT?Sham group: animals were treated with sham LEDT (LEDT device in placebo mode) over both legs, gluteus and lower?back muscles 5 minutes before each training session on ladder.

  • LEDT?Before: animals were treated with real LEDT over both legs, gluteus and lower?back muscles 5 minutes before each training session on ladder.

  • LEDT?Before?After: animals were treated with real LEDT over both legs, gluteus and lower?back muscles 5 minutes before and 5 minutes after each training session on ladder.

  • LEDT?After: animals were treated with real LEDT over both legs, gluteus and lower?back muscles 5 minutes after each training session on ladder.

  • Control: animals were not subjected to any LEDT or exercise or muscle performance assessment.

Ladder

An inclined ladder (80°) with dimensions of 100 cm × 9 cm (length and width, respectively) with bars spaced at 0.5 cm intervals was used in this study as reported in a previous study 33 (Figure 1).

Ladder. Inclined ladder (80°) with 100 cm × 9 cm (length and width, respectively) used for the training program and muscle performance assessments. Falcon tube filled with water and attached to the mouse tail.

Load

A Falcon tube (50 ml) was filled with measured volumes of water and weighed using a precise scale. The target load was achieved adding or removing water from the tube and then this tube was attached to the mouse tail using adhesive tape (Figure 1). All loads were calculated in grams.

Procedures

The schedule of the various exercise procedures is described in Table 1.

Table 1. Schedule for exercise procedures

Day

Procedure

# repetitions

Load

Day 1

Familiarization

4 × 10 = 40

zero

Day 2

3RM baseline

3

Starting at 2 × BWa

Day 3

Training 1

5 × 10 = 50

0.8 × 3RMb

Day 5

Training 2

5 × 10 = 50

0.9 × 3RM

Day 7

Training 3

5 × 10 = 50

1.0 × 3RM

Day 9

Training 4

5 × 10 = 50

1.1 × 3RM

Day 11

Training 5

5 × 10 = 50

1.2 × 3RM

Day 13

Training 6

5 × 10 = 50

1.3 × 3RM

Day 14

3RM final

3

Starting at 3 × BW

  • a : body weight
  • b : average load carried during 3RM baseline measurement

Familiarization with ladder?climbing

All experimental groups, except Control group, were familiarized with climbing the ladder one day before the start of muscle performance assessment and training. The familiarization procedure was 4 sets of 10 climbs on the ladder (repetitions) with rest periods of 2 minutes between individual sets. No load was attached to the mouse tail during this procedure.

Three repetitions maximum load (3RM)

This test was the first evaluation of muscle performance and was set as the average of the maximum load carried by each animal during 3 consecutive full climbs of the inclined ladder (3RM). Slight pressure with tweezers was applied on mouse tail if the animal stopped during a climb. The test was stopped when mice were not able to climb or lost their grip on the ladder due to failure of concentric muscle contraction. The first attempt included a load corresponding to 200% of the individual mouse body weight. A maximum of 3 climb attempts was applied. If a mouse finished the climb the load was increased by 10% for the next climb, while if the mouse failed to finish a climb, the load was decreased by 10% for the next climb. The 3RM evaluation was performed twice; the first time was 24 h after familiarization procedure (baseline) and the second time was 24 h after the last training session (final).

Acute strength training protocol

After 24 h from initial 3RM baseline assessment, all experimental groups, except Control, were subjected to 6 training sessions carried out on alternate days (every 48 h). Each training session consisted of 5 sets of 10 repetitions (climbs) on the ladder with a rest period of 2 minutes between each set. If the animal could not complete a set or failed during a climb, the distance climbed (in cm) was measured and the rest period was started immediately. During some repetitions, a slight pressure on the mouse tail was performed with tweezers to stimulate the animal to climb and complete the exercise. If after three applications of gentle pressures the mouse could not resume climbing, and stopped or lost its grip on the ladder, the set of repetitions was stopped and the rest interval was started.

The number of repetitions in each set was measured as well as the time spent to complete the exercise. These data were used to calculate the muscle work and muscle power in each training session. The load of each training session was progressively increased and calculated as percentages of the 3RM (in grams) measured at baseline as follows: first training (80%), second training (90%), third training (100%), fourth training (110%), fifth training (120%) and sixth training (130%).

Light?emitting diode therapy (LEDT)

A non?commercial cluster of 40 LEDs (20 red – 630 ± 10 nm; 20 infrared – 850 ± 20 nm) with diameter of 76 mm was used in this study. A complete description of the LEDT parameters is presented in Table 2. The optical power reaching the surface of the mouse skin was measured with an optical energy meter PM100D Thorlabs® fitted with a sensor S142C (area of 1.13 cm2). All mice (except mice in Control) were shaved and fixed on a plastic plate using adhesive tapes. Afterwards, in accordance with experimental group, these animals were treated with LEDT over both legs, gluteus and lower?back muscles at a distance of 45 mm (without contact) (Figure 2). Irradiation lasted 90 s per session with fixed parameters as described in Table 1. LEDT placebo had no energy (0 J) and no power (0 mW) applied over the targeted muscles. The light dose was based on the possible biphasic dose response reported previously 5, 6. Moreover, dual wavelengths were chosen to function at the same time in this study based on specificities of the chromophores in the cells and therefore optimizing the effects of the light therapy (LEDT) by a double band of absorption 8-11.

LEDT. Positioning of the mice and light?emitting diode therapy (LEDT) applied on mouse legs, gluteus and lower?back muscles without contact.

 

Muscle performance

The 3RM test was the first evaluation for muscle performance. This test measured the maximum load (in grams) carried by each animal during 3 consecutive full climbs on the inclined ladder.

During each training session the load, number of repetitions (rep), distance climbed and time spent to complete each repetition were recorded. These data were used to calculate muscle work and power.

Although the ladder had a total length of 100 cm available the maximum distance available to climb was set at 70 cm in order to avoid the load touching the floor. Thereby the muscle work was calculated as follows:

Work (J) = mgh

where ”m” is mass of the load (grams converted to kilogram) in each training session plus mouse body mass (values converted to kilogram); ”g” is acceleration due to gravity and ”h” is the distance climbed (converted to meters). Results were obtained in Joules (J) and presented as average ± standard error of mean (SEM) for each group at each training session.

Muscle power was calculated from results of muscle work (J) and time spent (s) to perform all repetitions of each set at all training sessions as follows:

Power (mW) = J/s

where ”J” is Joule and represents the muscle work performed and ”s” is time in seconds. Result were obtained in milliwatts (mW) and presented as average ± standard error of mean (SEM) per each group at each training session.

Muscular ATP

The gastrocnemius muscle from one leg of each animal was used for analysis of muscular ATP. Muscle samples were thawed in ice for 5 min, homogenized at a proportion of 3–4 mg of tissue to 500 µl of 10% perchloric acid (HClO4) following procedures previously published 34. Afterwards, an aliquot of 10 µl of the muscle homogenate plus 40 µl of CellTiter Glo Luminescent Cell Viability Assay mix (Promega), totaling 50 µl, were placed in the well microplate (CostarTM 96?Well White Clear?Bottom Plates). Luminescence signals were measured in a SpectraMax M5 Multi?Mode Microplate Reader (Molecular Devices, Sunnyvale, CA) with integration time of 5 s to increase low signals 34. A standard curve was prepared using ATP standard (Sigma) according to manufacturer's guidelines and then ATP concentration was calculated in nanomol (nmol) per milligram (mg) of protein. An aliquot of muscle homogenate was used to quantify the total protein by QuantiProTM BCA Assay kit (Sigma?Aldrich) following manufacturer's guidelines.

Muscular glycogen

Quadriceps femoris muscles were thawed in ice for 30 min and muscular glycogen was measured in 50 mg of quadriceps femoris tissue homogenized with 6 N NaOH at a proportion of 50 mg/ml. A standard curve was prepared using absolute ethanol (100%), K2SO4 (10%), phenol (4.1%) and 1 mM of glucose (2%) according to Dubois et al. 35. Optical density was read at 480 nm in spectrophotometer (EvolutionTM 300 UV?Vis, software VISPRO – Thermo Scientific). Data were normalized per mg of muscle tissue.

Oxidative stress markers

Protein carbonyl: Quadriceps femoris muscles were homogenized in deionized water (dH2O) at a proportion of 10 mg/200 µl. Protein carbonyl content was quantified using Protein Carbonyl Content Assay kit (Biovision) with the colorimetric method and following manufacturer's guidelines. All results were normalized per total protein quantified by QuantiProTM BCA Assay kit (Sigma?Aldrich) following manufacturer's guidelines.

Glutathione: Quadriceps femoris muscles were homogenized in 100 mM ice cold phosphate buffer (pH = 7.4) at a proportion of 10 mg/250 µl. Phosphate buffer was prepared with dibasic (Na2HPO4) and monobasic (NaH2PO4) sodium phosphate at equal proportions. Total and oxidized glutathione analysis was carried out with Glutathione Colorimetric Assay kit (ARBOR Assays) following manufacturer's guidelines. In addition, all results were normalized per total protein of the samples using QuantiProTM BCA Assay kit (Sigma?Aldrich) following manufacturer's guidelines.

Catalase activity: Quadriceps femoris muscles were homogenized in cold assay buffer provided in a Catalase Activity Assay kit (Biovision) at a proportion of 50 mg/100 µl. This analysis used the colorimetric method and followed manufacture's guidelines.

Lipid peroxidation using TBARS (Thiobarbituric Acid Reactive Substances): Quadriceps femoris muscles were homogenized with RIPA Buffer (Sigma?Aldrich) at a proportion of 25 mg/250 µl. Next, TBARS Colorimetric Assay kit (Cayman Chemical) was used following manufacturer's guidelines.

Protein Thiols: Quadriceps femoris muscles were homogenized in ice cold 100 mM phosphate buffer at a proportion of 10 mg/250 µl. Next, a Fluorescent Protein Thiol Detectiont kit (ARBOR Assays) was used following manufacturer's guidelines. In addition, all results were normalized per total protein quantified by QuantiProTM BCA Assay kit (Sigma?Aldrich) following manufacturer's guidelines.

Immunofluorescence analyses

5?bromo?2′?deoxyuridine (BrdU): BrdU reagent (Sigma?Aldrich) was diluted in saline solution (PBS) at a concentration of 10 mg/ml. Next, during the last 8 days of the experiment all animals (including Control group) received a single daily intra peritoneal injection (50 mg/kg) of BrdU. Mice were anesthetized and submitted to surgical procedures described previously. Gastrocnemius muscles were embedded in paraffin, cut in axial slices of 5 µm thickness from the muscle belly region by a microtome and mounted on slides for immunohistochemical procedures. Briefly, slides were deparaffinized with graded ethanol and then passed through antigen retrieval solution in a water bath pre?heated at 98 °C for 30 min. Afterwards slides were washed and incubated for 15 min at room temperature with 0.1% Triton X?100 TBS for cell membrane permeabilization, washed again and incubated for 30 min in protein blocking solution consisting of 3% BSA (Bovine Serum Albumin – Sigma) and 10% goat serum in TBS. Next, slides were immunostained with sheep anti?BrdU (Ab1893 – Abcam, Cambridge, MA) at 1 : 50 working concentration and selected anti?sheep (Alexa Fluor® 647 – Invitrogen) fluorescent secondary antibody matched to the primary antibody to stain at 1 : 200 working concentration. Finally, slides were cover?slipped with mounting media containing DAPI (4′,6?diamidino?2?phenylindole) (Invitrogen). Cells positively stained for BrdU were imaged using confocal microscope (Olympus America Inc. Center Valley, PA, USA) from three random fields. BrdU and DAPI staining were quantified using software Image J (NIH, Bethesda, MD).

Cytochrome c oxidase subunit IV (COX IV): Gastrocnemius muscles were subjected to the same procedures described for BrdU staining. Slides were immunostained with rabbit anti?COX IV (Cell Signaling Technology®) at 1 : 500 working concentration and selected anti?rabbit (Alexa Fluor® 680 – Invitrogen) secondary antibody matched with primary antibody to stain at 1 : 200 working concentration. Cells positively stained for COX IV were imaged using confocal microscopy as above and then the red channel of the exported images was changed to yellow.

Statistical analysis

Shapiro?Wilk's W test verified the normal distribution of the data. All experimental groups subjected to training protocols were compared at each training session for number of repetitions, muscle work and muscle power using one?way analysis of variance (ANOVA) and Tukey HSD post?hoc test. The load of 3RM among these same groups was compared by Two?way ANOVA with repeated measures (baseline versus final) and Tukey HSD post?hoc test. For muscular ATP, glycogen, oxidative stress markers and immunofluorescence stains, all experimental groups were compared by one?way ANOVA and Tukey's HSD post?hoc test. Significance was set at p < 0.05.

 

Results

Muscle performance

3RM: The final load 3RM was significantly higher (p < 0.05) in all experimental groups at the end of the experiment period compared to baseline. The final load of LEDT?After (92.28 g, SEM 0.82) was higher than LEDT?Sham (59.58 g, SEM 5.28; p < 0.001) and LEDT?Before (78.98 g, SEM 1.96; p = 0.020). In addition, LEDT?Sham had a significantly lower final load (p < 0.001) compared to LEDT?Before as well as LEDT?Before/After (83.91 g, SEM 1.49) (Figure 4A).

Muscle performance (n = 5 animals per group). (A) Baseline and Final test of 3 repetitions maximum (3RM) measuring the total load carried by mice during this test. * statistical significance (p < 0.05) comparing the final 3RM load between groups. (B) Number of repetitions or climbs performed by each group treated with different regimens of LEDT during the progressive training program. (C) Muscle power developed by each group treated with different regimens of LEDT during the progressive training program. (D) Muscle work developed by each group treated with different regimens of LEDT during the progressive training program. * statistical significance (p < 0.05) compared to LEDT?Sham. # statistical significance (p < 0.05) compared to LEDT?After. & statistical significance (p < 0.05) compared to LEDT?Before. Abbreviations: LEDT = light?emitting diode therapy; LEDT?Sham (Sham – S) = LEDT placebo (LEDT device in placebo mode) on muscles immediately before (5 minutes) each training session on ladder; LEDT?Before (Before – B) = LEDT applied on muscles immediately before (5 minutes) each training session on ladder; LEDT?Before?After (Before?After – A?B) = LEDT applied on muscles immediately before (5 minutes) and immediately after (5 minutes) each training session on ladder; LEDT?After (After – A) = LEDT applied on muscles immediately after (5 minutes) each training session on ladder. The load of 3RM at baseline versus final was analyzed by Two?way analysis of variance (ANOVA) with repeated measures. Number of repetitions, muscle work and power were analyzed by One?way ANOVA.

Number of repetitions: There were significantly differences (p < 0.05) between all groups in each training session (Figure 4B). At 80% of 3RM (first session): animals in LEDT?Before and LEDT?Before?After groups performed more repetitions compared to animals in LEDT?Sham and LEDT?After (p < 0.01) groups. At 90% of 3RM (second session): animals in LED?Sham group performed fewer repetitions than animals in LEDT?Before, LEDT?Before?After and LEDT?After groups (p < 0.001). At 100% of 3RM (third session): animals in LEDT?Sham group performed fewer repetitions compared to animals in LEDT?Before (p = 0.014), LED?Before?After (p = 0.010) and LEDT?After (p = 0.002) groups. At 110% of 3RM (fourth session): animals in LEDT?Sham group performed fewer repetitions than animals in LEDT?Before?After (p = 0.013) and LEDT?After (p = 0.009) groups. At 120% of 3RM (fifth session): animals in LEDT?After group performed more repetitions than animals in LEDT?Before (p = 0.022) and LEDT?Sham (p < 0.001) groups. In addition, animals in LEDT?Sham performed fewer repetitions than animals in LEDT?Before (p = 0.022), LEDT?Before?After and LEDT?After (p < 0.001) groups. At 130% of 3RM (sixth session): animals in LEDT?Before?After and LEDT?After groups performed more repetitions than animals in LEDT?Sham (p < 0.001) and LEDT?Before (p < 0.01) groups.

Muscle Power: At 80% of 3RM there were no significant differences among all groups (p > 0.05). At 90% of 3RM: animals in LEDT?Sham group had lower muscle power compared to animals in LEDT?Before, LEDT?Before?After and LEDT?After (p < 0.01) groups. At 100% of 3RM: animals in LEDT?Sham group had lower muscle power than animals in LEDT?Before?After (p = 0.025) and LEDT?After (p = 0.007) groups. At 110% of 3RM: animals in LEDT?Before?After group developed more muscle power than animals in LEDT?Sham (p < 0.001) and LEDT?Before (p = 0.013) groups. In addition, animals in LEDT?After group had more muscle power than animals in LEDT?Sham (p = 0.002) group. At 120% of 3RM: animals in LEDT?Before?After and LEDT?After groups developed more muscle power than animals in LEDT?Sham and LEDT?Before (p < 0.001) groups. At 130% of 3RM: animals in LEDT?Before?After group developed more muscle power than animals in LEDT?Sham and LEDT?Before (p < 0.001) as well as LEDT?After (p = 0.001) groups. In addition, animals in LEDT?After group had more muscle power than animals in LEDT?Sham (p < 0.001) and LEDT?Before (p = 0.004) groups. Finally, animals in LEDT?Before group had major muscle power than animals in LEDT?Sham (p = 0.020) group (Figure 4C).

Muscle Work: Similar to results presented in Figure 4B, at 80% of 3RM only animals in LEDT?Before and LEDT?Before?After groups performed more muscle work compared to LEDT?Sham (p < 0.05) group (Figure 4D). At 90% of 3RM: animals in LEDT?Sham group performed less muscle work than animals in LEDT?Before, LEDT?Before?After and LEDT?After (p < 0.001) groups. These results were similar at 100% of 3RM (p < 0.001). At 110% of 3RM: animals in LEDT?Sham group had lower muscle work compared to animals in LEDT?Before?After (p = 0.015) and LEDT?After (p = 0.011) groups. At 120% of 3RM: animals in LEDT?Sham group performed lower muscle work compared to animals in LEDT?Before (p = 0.027) and LEDT?Before?After and LEDT?After (p < 0.001) groups. In addition, animals in LEDT?After group performed more muscle work than animals in LEDT?Before (p = 0.026) group. At 130% of 3RM: animals in LEDT?Before?After and LEDT?After groups performed more muscle work than animals in LEDT?Sham (p < 0.001) and LEDT?Before (p < 0.01) groups (Figure 4D).

Muscle ATP content

Animals in LEDT?After group had significantly (p < 0.001) more ATP concentration (1,367.64 nmol/ mg protein, SEM 105.30) compared to animals in LEDT?Sham (15.85 nmol/mg protein, SEM 5.14), LEDT?Before (81.00 nmol/ mg protein, SEM 10.11), LEDT?Before?After (687.62 nmol/ mg protein, SEM 11.76) and Control (17.53 nmol/mg protein, SEM 7.47) groups. In addition, animals in LEDT?Before?After group had also major contents of ATP compared to animals in LEDT?Before, LEDT?Sham and Control (p < 0.001) groups (Figure 5A).

 

 

Muscular ATP and glycogen contents (n = 5 animals per group). (A) Adenosine triphosphate (ATP) contents in gastrocnemius muscle after the training program. (B) Glycogen contents in quadriceps femoris muscles after the training program. * statistical significance (p < 0.05). Abbreviations: LEDT = light?emitting diode therapy; LEDT?Sham (Sham – S) = LEDT placebo (LEDT device in placebo mode) on muscles immediately before (5 minutes) each training session on ladder; LEDT?Before (Before – B) = LEDT applied on muscles immediately before (5 minutes) each training session on ladder; LEDT?Before?After (Before?After – A?B) = LEDT applied on muscles immediately before (5 minutes) and immediately after (5 minutes) each training session on ladder; LEDT?After (After – A) = LEDT applied on muscles immediately after (5 minutes) each training session on ladder. Control (C) = no exercise or muscle performance assessment. Comparisons among all groups were conducted using One?way analysis of variance (ANOVA).

 

 

Muscle glycogen content

Animals in LEDT?After (137.76 nmol/mg tissue, SEM 11.40) and LEDT?Before?After (144.44 nmol/ mg tissue, SEM 16.23) groups had significantly higher concentrations of glycogen in quadriceps femoris muscles (p < 0.001) compared to animals in LEDT?Sham (31.36 nmol/mg tissue, SEM 7.45), LEDT?Before (52.76 nmol/mg tissue, SEM 6.53) and Control (58.78 nmol/ mg tissue, SEM 7.17) groups (Figure 5B).

Oxidative stress markers

Total glutathione: Animals in Control group (1.33 µM/µg protein, SEM 0.11) had a significantly higher concentration of total glutathione compared to animals in LEDT?Sham (0.097 µM/µg protein, SEM 0.046; p = 0.005) and LEDT?Before (1.00 µM/µg protein, SEM 0.02; p = 0.010) groups (Figure 6A).

Oxidative stress markers (n = 5 animals per group) in quadriceps femoris muscles. (A) Total Glutathione (reduced glutathione – GSH). (B) Oxidized Glutathione (GSSG). (C) Protein Carbonyl. (D) Catalase activity. (E) Lipid peroxidation using TBARS (Thiobarbituric Acid Reactive Substances). (F) Protein Thiol. * statistical significance (p < 0.05). Abbreviations: LEDT = light?emitting diode therapy; LEDT?Sham (Sham – S) = LEDT placebo (LEDT device in placebo mode) on muscles immediately before (5 minutes) each training session on ladder; LEDT?Before (Before – B) = LEDT applied on muscles immediately before (5 minutes) each training session on ladder; LEDT?Before?After (Before?After – A?B) = LEDT applied on muscles immediately before (5 minutes) and immediately after (5 minutes) each training session on ladder; LEDT?After (After – A) = LEDT applied on muscles immediately after (5 minutes) each training session on ladder. Control (C) = no exercise or muscle performance assessment. Comparisons among all groups were conducted using One?way analysis of variance (ANOVA).

Oxidized glutathione: Animals in LEDT?Sham group (0.005 µM/µg protein, SEM 0.001) had significantly minor concentration of glutathione oxidized compared to animals in LEDT?Before (0.20 µM/µg protein, SEM 0.002; p = 0.015), LEDT?Before?After (0.035 µM/µg protein, SEM 0.003; p < 0.001), LEDT?After (0.041 µM/µg protein, SEM 0.003; p < 0.001) and Control (0.027 µM/µg protein, SEM 0.007; p = 0.006) groups. In addition, animals in LEDT?Before group had significantly minor concentration of oxidized glutathione compared to animals in LEDT?After (p < 0.001) and LEDT?Before?After (p = 0.024) groups (Figure 6B).

Protein carbonyl: Animals in LEDT?After group (1.40 nmol/µg protein, SEM 0.15) had significantly lower concentrations of protein carbonyls compared to animals in LEDT?Sham (6.31 nmol/µg protein, SEM 1.09; p = 0.030), LEDT?Before (6.81 nmol/µg protein, SEM 1.21; p = 0.040) and LEDT?Before?After (8.27 nmol/µg protein, SEM 2.35; p = 0.008) groups (Figure 6C).

Catalase activity: Animals in LEDT?Sham group (2.11 nmol/min/ml, SEM 0.10) had significantly lower catalase activity (p < 0.01) compared to animals in LEDT?Before?After (4.33 nmol/min/ml, SEM 0.62), LEDT?After (4.22 nmol/min/ml, SEM 0.37) and Control (4.47 nmol/min/ml, SEM 0.52) groups (Figure 6D).

Lipid peroxidation using TBARS: There were no significant differences between any of the groups (p > 0.05) assessed. Animals in Control group had a concentration of 21.29 µM (SEM 1.13); animals in LEDT?Sham had 21.12 µM (SEM 2.86); animals in LEDT?Before had 23.87 µM (SEM 1.13); animals in LEDT?Before?After had 19.19 µM (SEM 1.01) and animals in LEDT?After had 19.55 µM (SEM 1.24) (Figure 6E).

Protein
Original Source: https://onlinelibrary-wiley-com.colorado.idm.oclc.org/doi/full/10.1002/jbio.201400087


Effect of near-infrared light-emitting diodes on nerve regeneration.

Ishiguro M, Ikeda K, Tomita K - J Orthop Sci. 2010 Mar (Publication)
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Background: Photobiomodulation by red to near-infrared light-emitting diodes (LEDs) has been reported to accelerate wound healing, attenuate degeneration of an injured optic nerve, and promote tissue growth. The purpose of this study was to investigate the effect of LEDs on nerve regeneration. A histological study as well as a measurement of antioxidation levels in the nerve regeneration chamber fluid was performed.

Methods: For the histological study, the bilateral sciatic nerves were transected, and the left proximal stump and the right distal stump were inserted into the opposite ends of a silicone chamber, leaving a 10-mm gap. Light from an LED device (660 nm, 7.5 mW/cm2) was irradiated for 1 hr per day. At 3 weeks after surgery, regenerated tissue was fixed and examined by light microscopy. For the antioxidation assay of chamber fluid, the left sciatic nerve and a 2-mm piece of nerve from the proximal stump were transected and inserted into opposite sides of a silicone chamber leaving a 10-mm gap. LEDs were irradiated using the same parameters as those described in the histological study. At 1, 3, and 7 days after surgery, antioxidation of the chamber fluid was measured using an OXY absorbent test.

Results: Nerve regeneration was promoted in the LED group. Antioxidation of the chamber fluid significantly decreased from 3 days to 7 days in the control group. In the LED group, antioxidation levels did not decrease until 7 days.

Conclusions: Chamber fluid is produced from nerve stumps after nerve injury. This fluid contains neurotrophic factors that may accelerate axonal growth. Red to near-infrared LEDs have been shown to promote mitochondrial oxidative metabolism. In this study, LED irradiation improved nerve regeneration and increased antioxidation levels in the chamber fluid. Therefore, we propose that antioxidation induced by LEDs may be conducive to nerve regeneration.

Original Source: https://www.ncbi.nlm.nih.gov/pubmed/20358337

A NASA discovery has current applications in orthopaedics

Howard B. Cotler, MD, FACS, FAAOS - Curr Orthop Pract. 2015 Jan; 26(1): 72–74 (Publication)
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Low-level laser therapy (LLLT) has been actively used for nearly 40 yr, during which time it has been known to reduce pain, inflammation, and edema. It also has the ability to promote healing of wounds, including deep tissues and nerves, and prevent tissue damage through cell death. Much of the landmark research was done by the National Aeronautics and Space Administration (NASA), and these studies provided a springboard for many additional basic science studies. Few current clinical studies in orthopaedics have been performed, yet only in the past few years have basic science studies outlined the mechanisms of the effect of LLLT on the cell and subsequently the organism. This article reviews the basic science of LLLT, gives a historical perspective, and explains how it works, exposes the controversies and complications, and shows the new immediately applicable information in orthopaedics.

Key Words: Laser, LED, NASA, orthopaedic, injury

BACKGROUND

The pursuit of space travel has opened new areas for study and knowledge. Space medicine has had applications in various subspecialties. Although some think there is little application in orthopaedics, it may be that there has been much discovered but little appreciated. The National Aeronautics and Space Administration (NASA) was established by the United States government in 1958 as a civilian space program for aeronautics and aerospace research. In 1959 the Astronaut Corps was founded. The insertion of humans into space presented many challenges from a biologic standpoint. Astronauts in space perform physically demanding work in a challenging environment that includes among other hazards, microgravity, which is known to have an adverse effect on bone and muscle to the extent that it places an increased risk for musculoskeletal injury. There is a threefold higher injury rate during mission periods than outside of mission periods for astronauts, and it has been observed that wounds heal more slowly in orbit.

In 1993, Quantum Devices (Barneveld, WI) developed a light-emitting diode (LED) for NASA to use in their plant growth experiments. The experiments demonstrated that red LED wavelengths could boost plant growth, but coincidentally the scientist’s skin lesions began to heal faster as well. NASA subsequently began to study the use of LED to increase the metabolism of human cells and stem the loss of bone and muscle in astronauts.

Dr. Harry T. Whelan, a professor of pediatric neurology at the University of Wisconsin, began the study of LEDs and lasers, receiving grants from NASA and and the National Institutes of Health. He determined that astronauts get four problems: immune deficiency, pituitary insufficiency, delayed wound healing, and muscle and bone atrophy. He observed these results in the laboratory.

MECHANISMS OF ACTION

From a historical perspective we now know that light has a biologic effect, but what we need to know is how energy from lasers and LEDs work on a cellular level and what the optimal light parameters are for different uses.

The power plant of cells is located in the mitochondria that are able to produce cellular energy or adenosine triphosphate (ATP) from pyruvate and oxygen. When tissues are stressed or ischemic, mitochondria make their own mitochondrial nitric acid (MtNO), which competes with oxygen. The MtNO bind to cytochrome C oxidase (CcO) that displaces oxygen. This subsequently reduces ATP synthesis and increased oxidative stress, which leads to inflammation. Hypoxic or stressed tissues are affected by LLLT in four stages: (1) light energy is absorbed by cytochrome C oxidase, triggering several downstream effects; (2) nitric oxide is released; (3) ATP is increased; and (4) oxidative stress is reduced. These biochemical intermediates affect components in the cytosol, cell membrane, and nucleus that control gene transcription, cell proliferation, migration necrosis, and inflammation. Cells in blood and lymph, which have been light activated, can travel a distance for systemic effects.,

APPLICATIONS

The four common targets for LLLT are:

  • L – lymph nodes to reduce edema and inflammation.
  • I – site of injury to promote healing and reduce inflammation.,
  • N – nerves to induce analgesia.
  • T – trigger points to reduce muscle spasms.,

LLLT is a transcutaneous procedure with no invasive portion. The physician determines the correct synchronizations of continuous or pulsed laser emission. Penetration depth is determined by wavelength and power. The U.S. Navy research determined 810 nm to be optimal for penetration. Treatment times are in the range of 30 s to 1 min, but there are many areas treated for comprehensible protocol, which often takes approximately 30 min to perform. For stimulating repair and decreasing inflammation, 2.5 Hz pulse is recommended, while a continuous beam is ideal for analgesia and tender points.

ADMINISTRATION

The Federal Drug Administration (FDA) approved the use of LLLT in 2003. In some states, a prescription is mandatory before treatment. Treatment can be administered by a certified therapist, radiology technologist, or a physician. European sports therapists have used LLLT for over a decade; however, they report only a 50% success rate,, which may be due to inconsistent laser parameters and dose. Recent advances by researchers at Harvard Medical School have clarified the mechanism by which there is biphasic dose response.,

Side effects and complications can result from traditional treatments for musculoskeletal pathology. Nonsteroidal antiinflammatories can cause ulcer disease, hypertension, bleeding, and cardiac events. Steroids (oral and/or epidural) can result in infections (including epidural), bleeding, ulcers, avascular necrosis, and tissue fragility. Studies have found LLLT to have no side effects or adverse events beyond those reported for placebo.

With over 4000 basic science research and clinical studies according to pubmed.gov, and low complication rate, LLLT should be considered as a first-line treatment option for conditions such as acute neck or back pain, tendinitis, plantar fasciitis, mild carpal tunnel sndrome, and ligamentous sprains. Its safety profile provides a persuasive argument, with the added benefits of accelerated healing, tissue remodeling, pain relief, and decreased inflammation. LLLT subsequently has been accepted by both the British and Canadian health services. Although approved by the FDA, LLLT has not been recognized or accepted by Medicare or insurance companies because it is viewed as investigational treatment.

Clinical practice guidelines of the American Academy of Orthopaedic Surgeons (AAOS) in 2008 on treatment of carpal tunnel syndrome included laser treatment but carried no recommendations for or against its use because there is insufficient evidence. The literature on LLLT for the treatment of lymphedema, wound healing, prevention of oral mucositis, or for pain demonstrates inconsistent results and methodological weaknesses as per the Blue Cross Blue Shield of Kansas Medical Policy, March 12, 2013. More up-to-date, prospective studies, using newer treatment guidelines by clinicians, are needed to provide a complete picture of efficacy and cost-effectiveness.

CONCLUSION

LLLT will not replace orthopaedic surgery for structural pathology, but it may be useful as an adjunct therapy for patients seeking noninvasive symptomatic treatment or accelerated wound healing.

Footnotes

Financial Disclosure: Dr. Cotler is in private practice and owns Gulf Coast Spine Care Ltd., PA and Laser Health Spa, LLC. He received no financial suport for this manuscript.

REFERENCES

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Original Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4272231/

Comparison between cold water immersion therapy (CWIT) and light emitting diode therapy (LEDT) in short-term skeletal muscle recovery after high-intensity exercise in athletes--preliminary results.

Leal Junior EC1, de Godoi V, Mancalossi JL, Rossi RP, De Marchi T, Parente M, Grosselli D, Generosi RA, Basso M, Frigo L, Tomazoni SS, Bjordal JM, Lopes-Martins RA. - Lasers Med Sci. 2011 Jul;26(4):493-501. doi: 10.1007/s10103-010-0866-x. Epub 2010 Nov 19. (Publication)
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Intro: In the last years, phototherapy has becoming a promising tool to improve skeletal muscle recovery after exercise, however, it was not compared with other modalities commonly used with this aim. In the present study we compared the short-term effects of cold water immersion therapy (CWIT) and light emitting diode therapy (LEDT) with placebo LEDT on biochemical markers related to skeletal muscle recovery after high-intensity exercise. A randomized double-blind placebo-controlled crossover trial was performed with six male young futsal athletes. They were treated with CWIT (5°C of temperature [SD ±1°]), active LEDT (69 LEDs with wavelengths 660/850 nm, 10/30 mW of output power, 30 s of irradiation time per point, and 41.7 J of total energy irradiated per point, total of ten points irradiated) or an identical placebo LEDT 5 min after each of three Wingate cycle tests. Pre-exercise, post-exercise, and post-treatment measurements were taken of blood lactate levels, creatine kinase (CK) activity, and C-reactive protein (CRP) levels. There were no significant differences in the work performed during the three Wingate tests (p > 0.05). All biochemical parameters increased from baseline values (p < 0.05) after the three exercise tests, but only active LEDT decreased blood lactate levels (p = 0.0065) and CK activity (p = 0.0044) significantly after treatment. There were no significant differences in CRP values after treatments. We concluded that treating the leg muscles with LEDT 5 min after the Wingate cycle test seemed to inhibit the expected post-exercise increase in blood lactate levels and CK activity. This suggests that LEDT has better potential than 5 min of CWIT for improving short-term post-exercise recovery.

Background: In the last years, phototherapy has becoming a promising tool to improve skeletal muscle recovery after exercise, however, it was not compared with other modalities commonly used with this aim. In the present study we compared the short-term effects of cold water immersion therapy (CWIT) and light emitting diode therapy (LEDT) with placebo LEDT on biochemical markers related to skeletal muscle recovery after high-intensity exercise. A randomized double-blind placebo-controlled crossover trial was performed with six male young futsal athletes. They were treated with CWIT (5°C of temperature [SD ±1°]), active LEDT (69 LEDs with wavelengths 660/850 nm, 10/30 mW of output power, 30 s of irradiation time per point, and 41.7 J of total energy irradiated per point, total of ten points irradiated) or an identical placebo LEDT 5 min after each of three Wingate cycle tests. Pre-exercise, post-exercise, and post-treatment measurements were taken of blood lactate levels, creatine kinase (CK) activity, and C-reactive protein (CRP) levels. There were no significant differences in the work performed during the three Wingate tests (p > 0.05). All biochemical parameters increased from baseline values (p < 0.05) after the three exercise tests, but only active LEDT decreased blood lactate levels (p = 0.0065) and CK activity (p = 0.0044) significantly after treatment. There were no significant differences in CRP values after treatments. We concluded that treating the leg muscles with LEDT 5 min after the Wingate cycle test seemed to inhibit the expected post-exercise increase in blood lactate levels and CK activity. This suggests that LEDT has better potential than 5 min of CWIT for improving short-term post-exercise recovery.

Abstract: Abstract In the last years, phototherapy has becoming a promising tool to improve skeletal muscle recovery after exercise, however, it was not compared with other modalities commonly used with this aim. In the present study we compared the short-term effects of cold water immersion therapy (CWIT) and light emitting diode therapy (LEDT) with placebo LEDT on biochemical markers related to skeletal muscle recovery after high-intensity exercise. A randomized double-blind placebo-controlled crossover trial was performed with six male young futsal athletes. They were treated with CWIT (5°C of temperature [SD ±1°]), active LEDT (69 LEDs with wavelengths 660/850 nm, 10/30 mW of output power, 30 s of irradiation time per point, and 41.7 J of total energy irradiated per point, total of ten points irradiated) or an identical placebo LEDT 5 min after each of three Wingate cycle tests. Pre-exercise, post-exercise, and post-treatment measurements were taken of blood lactate levels, creatine kinase (CK) activity, and C-reactive protein (CRP) levels. There were no significant differences in the work performed during the three Wingate tests (p > 0.05). All biochemical parameters increased from baseline values (p < 0.05) after the three exercise tests, but only active LEDT decreased blood lactate levels (p = 0.0065) and CK activity (p = 0.0044) significantly after treatment. There were no significant differences in CRP values after treatments. We concluded that treating the leg muscles with LEDT 5 min after the Wingate cycle test seemed to inhibit the expected post-exercise increase in blood lactate levels and CK activity. This suggests that LEDT has better potential than 5 min of CWIT for improving short-term post-exercise recovery.

Original Source: http://www.ncbi.nlm.nih.gov/pubmed/21088862

Second International Conference on Near-Field Optical Analysis: Photodynamic Therapy & Photobiology Effect

- Proceedings of the Second International Conference on NOA : May 31 - June 1,2001 (Publication)
This extensive 105 page document showed the ability of the LED to speed the rate of healing, we hypothesized that using the LED for wounds aboard the submarine would increase the rate of healing.
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Please click on the original URL to see the complete study.


Original Source: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20030001592.pdf

Calculating model of light transmission efficiency of diffusers attached to a lighting cavity

Ching-Cherng Sun1*, Wei-Ting Chien1, Ivan Moreno2, Chih-To Hsieh1, Mo-Cha Lin1, Shu-Li Hsiao3, and Xuan-Hao Lee1 - (Publication)
This study analyses the losses associated with using a diffuser in an LED system. Losses range from 80 to 60% in general
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15. B. Chevalier, M. G. Hutchins, A. Maccari, F. Olive, H. Oversloot, W. Platzer, P. Polato, A. Roos, J. L. J. Rosenfeld, T. Squire, and K. Yoshimura, “Solar energy transmittance of translucent samples: A comparison between large and small integrating sphere measurements,” Sol. Energy Mater. Sol. Cells 54(1-4), 197–202 (1998). 16. I. Moreno, M. Avendaño-Alejo, and R. I. Tzonchev, “Designing light-emitting diode arrays for uniform near-field irradiance,” Appl. Opt. 45(10), 2265–2272 (2006). 17. Labsphere, Inc., A Guide to Integrating Sphere Theory and Applications, at http://www.labsphere.com/18. R. W. Boyd, Radiometry and the Detection of Optical Radiation (Wiley, New York, 1983). 19. D. Terr, “Weighted Mean” From MathWorld-A Wolfram Web Resource, created by Eric W. Weisstein. http://mathworld.wolfram.com/WeightedMean.html20. C. C. Sun, W. T. Chien, I. Moreno, C. C. Hsieh, and Y. C. Lo, “Analysis of the far-field region of LEDs,” Opt. Express 17(16), 13918–13927 (2009). 21. I. Moreno, and C. C. Sun, “Modeling the radiation pattern of LEDs,” Opt. Express 16(3), 1808–1819 (2008). 22. I. Schnitzer, E. Yablonovitch, C. Caneau, T. J. Gmitter, and A. Scherer, “30% external quantum efficiency from surface textured, thin-film light-emitting diodes,” Appl. Phys. Lett. 63(16), 2174 (1993). 1. Introduction Lighting and display are one of the most important branches of technology in the beginning of the XXI century. In lighting, the impact is from the growth of solid-state lighting device such as light emitting diodes (LEDs), which enable more color saturation, life time, design freedom and environmental benefit. However, owing to the point-source nature and high luminance of the LED, much glare occurs when the optical design does not address eye care [1,2]. This is usually solved by enlarging the effective area of the light source. There are many ways to increase the emitting area [3,4]. A simple, low-cost, and widely used method is to place the light sources into a cavity covered with a diffuse translucent sheet. The diffuser scatters the transmitted light, and reflects a significant fraction of the incident light back into the cavity, eventually homogenizing the spatial light distribution. Figure 1 shows some examples of lighting cavities assembled with LEDs behind a diffuser plate. The diffuser spreads the optical flux across a larger area so that the LEDs cannot be seen by an observer and the glare effect is reduced. Figure 1(b) shows an example where one diffuser is applied to an LED luminaire. A large cavity with an LED array behind the diffuser also allows light painting of ceilings [5]. Fig. 1. (a) A simple lighting cavity, with and without diffuser. (b) An example of LED luminaire with and without a covering diffuser sheet. (c) A direct LED backlight (of a television display) without diffuser. In addition to lighting, the light source enlargement also is employed in liquid crystal display (e.g. television, laptop, and monitor), where the backlight component transforms a set of line or point light sources into a plane light source as large as the screen size. In backlight technology, a low cost approach that allows high-dynamic range is called direct-view backlighting [5–8]. In such a case, a diffuser instead of a light guide plate is the key component. In a direct backlight, a diffuser covers the chamber that contains the light sources, #122015 - $15.00 USDReceived 24 Dec 2009; revised 13 Feb 2010; accepted 5 Mar 2010; published 11 Mar 2010(C) 2010 OSA15 March 2010 / Vol. 18, No. 6 / OPTICS EXPRESS 6138e.g. an LED array. An open chamber of a direct LED backlight is shown in Fig. 1(c), which in operation is covered with a diffuser. Although lighting and display are different topics, both have a common demand, to keep the optical efficiency as high as possible. The general way to manage the optical power of a lighting cavity covered with diffusers (LCCD) is to make a simulation with ray tracing program using a very large amount of rays [9]. However, the scattering model of diffusers is complex [10], the diffuser properties may vary from one to another manufacturer, and many optical parameters of the diffuser and the optical cavity should be known so that the cavity simulation becomes very difficult and time consuming. Then the usual way to get the optical efficiency is the experimental measurement [6]. This is why a practical method to calculate the optical efficiency is demanded. The balance between light extraction efficiency and illumination uniformity or glare comfort of the LCCD relies heavily on the overall light transmission of the diffuser. In other words, the diffuser attached to a lighting cavity (DALC) is the dominant factor of the LCCD optical efficiency. In this paper, we present a simplified optical model to calculate the transmission efficiency of a DALC. Section 3 presents the equations to compute the overall transmission efficiency. In Section 4 the model is demonstrated by several experimental measurements by using bulk-scattering diffusers. Section 5 shows how the cavity walls and source placement influence the light extraction efficiency. Before explaining the model, we would like to describe the optical cavity structure in the next section. 2. Optical cavity with diffusers There may be a wide variety of cavity shapes, but the squared chamber is the most popular [3,4,6–11]. Therefore, we consider the basic LCCD to be a box coated with reflecting films [see Fig. 2(a)]. Typically, an optical cavity is covered with one or two diffusers, and the light sources are located on the bottom plane. The cavity has four reflective sidewalls, i.e. except the light sources and the diffuser all the other surfaces are coated (or covered) with reflective film. This enables the light reflected back to be incident on the diffuser again through multiple reflections and then the overall transmission efficiency of the DALC increases. Fig. 2. (a) Optical cavity with 1 and 2 diffusers. (b) Diffuser plate. R0 and T0 are the single-shot power reflection and transmission efficiency at normal incidence, respectively. Here Φin is the input light flux at normal incidence, ΦT is the total transmitted light flux to the right of diffuser, ΦR is the total reflected light flux to the left of diffuser. φn and φm are the light fluxes associated to each ray of light reflected and transmitted, respectively. We consider that the diffuser is a non-structured scattering plate, i.e. its optical properties randomly scatter the incident light rays [12]. In the practice, the transmission and reflection properties of randomly scattering diffusers are not ideal [12–15]. For example, the transmitted light through a diffusing plate is a mixture of two angular radiation patterns (a direct and a diffuse component), and the direct-diffuse ratio increases as a function of wavelength [13–15]. This effect is large at near-infrared wavelengths, but low at the visible range [13,14]. #122015 - $15.00 USDReceived 24 Dec 2009; revised 13 Feb 2010; accepted 5 Mar 2010; published 11 Mar 2010(C) 2010 OSA15 March 2010 / Vol. 18, No. 6 / OPTICS EXPRESS 6139Another non-ideality of random diffusers is that the center of the angular distribution of the transmitted light depends on the angle of incidence of light (see Appendix and references [10,12]). Because we are considering the total extracted flux (integration of the angular radiation pattern) in the visible range, these non-idealities have little effect in the total efficiency. This is why we use the single-shot transmission and reflection efficiency in our analysis [Fig. 2(b)]. The term “single-shot” refers to the behavior of one beam of light that interacts only one time with an optical surface. The light sources can be arranged in a variety of configurations to achieve spatially uniform emission of light from a backlight or luminaire. The placement of sources inside the LCCD may strongly influence the illumination uniformity, but slightly influences the overall light extraction. If LEDs are used as the light sources, the divergence angle of the LED will decide the thickness of the cavity for the uniformity issue [6,16]. In general, a thick LCCD is needed for narrow beam LEDs, and a thin cavity is associated with wide beam LEDs. The enlargement of LED divergent angle through first-level (package level) optical design usually causes the degradation of luminance (lm/m2sr) from the cavity. Therefore, in many cases when considering the effect of thickness, energy efficiency, uniformity, optical design and assembling way, it makes sense to use two diffusers in a cavity. Generally, more scatterings of light cause more uniformity and smaller thickness of the cavity, but also cause lower luminance. Thus, a heavy-doped diffuser or two light-doped diffusers is/are used in a thin cavity to achieve high uniformity [16]. Once we have described the LCCD structure, we proceed to estimate the flux transmission efficiency of the DALC in the following section. 3. Light transmission efficiency The optical transmission efficiency of the DALC is the ratio of the output luminous flux using diffuser to the output luminous flux without diffuser [Fig. 3(a)]. The complexity of the scattering theory and the difficulty of the multiple calculations involved, make intractable the exact computation of the optical efficiency of a DALC. We overcame these problems by carrying out the calculation with a single light ray that is representative of all the scattered rays. Then we obtain a simple approximation but very close solution rather than the exact but very complex answer. A similar approach is widely used in the theory of integrating spheres, where the radiation exchange within a spherical enclosure of diffuse surfaces simplifies to a single ray of light [17,18]. The theory analyses the multiple reflections of a single ray inside the integrating sphere. This ray is representative of all the scattered rays because the fraction of light flux that it transports from one point to another is independent of the incidence angle. #122015 - $15.00 USDReceived 24 Dec 2009; revised 13 Feb 2010; accepted 5 Mar 2010; published 11 Mar 2010(C) 2010 OSA15 March 2010 / Vol. 18, No. 6 / OPTICS EXPRESS 6140Fig. 3. (a) Defining the optical efficiency of the diffuser incorporated into the cavity. (b) Multiple reflections of the equivalent ray of light inside the chamber incorporated with one single diffuser. Here the T is the one-shot transmission efficiency of the diffuser plate; the R is the one-shot reflection efficiency of the diffuser; and Rb is the one-shot reflection efficiency of the inner surfaces. Here, the key idea is to consider only one ray of light instead all the scattered rays. Due to the statistical nature of the scattering process in the diffuser and internal walls, the equivalent ray must be representative of the average. Therefore, in order to deduce the efficiency equation we use a single ray that is incident at an equivalent angle of incidence. The calculation of the effective angle is described in the Appendix. For example, if the scattering power of the inner walls is low (for example the silver coatings used in Sections 4 and 5), and if the LEDs used have a Lambertian radiation pattern (typical of high power LEDs), the analysis shows that the effective angle is ~45º. But if the internal walls show strong scattering (for example white scatter sheets), the effective angle of incidence reduces to ~30º due to the multiplication of scattering events. Taking into account this simplification we calculate the optical efficiency for a single equivalent ray of light. The multiple reflections involved, make the computation to be a sum. As shown in Fig. 3(b), the optical efficiency of the DALC is 22,1bbbTT TR R TR RR Rη= +++⋅⋅⋅ =(1) where T and R are the one-shot transmission and reflection efficiency of the diffuser, respectively. And Rb is the reflection efficiency of the other surfaces in the cavity. Note that T, R, and Rb must be measured at the equivalent angle of incidence. Also note that absorption is implicitly included in this calculation, and then not only T but also R must be experimentally measured. For example, the one-shot absorption of the diffusers used in our measurements can be deduced from the sum of T and R measurements shown in Fig. 11 in the Appendix. In the case of two diffusers, first we have to consider the reflected lights between the two diffuser plates [Fig. 4(a)]. As shown in Fig. 4(b), the transmission (T12) and reflection efficiency (R12) of the two-diffuser system are 221 2121 2121212(1),1T TTT TR RR RR R=+ ++⋅⋅⋅ =(2) 222221122211212212(1),1T RRRT RR RR RRR R= +https://www.osapublishing.org/DirectPDFAccess/8171EA5B-D2EE-124F-C2ADF67F49446E25_196561/oe-18-6-6137.pdf?da=1&id=196561&seq=0


Is light-emitting diode phototherapy (LED-LLLT) really effective?

Won-Serk Kim1 and R Glen Calderhead2 - Laser Ther. 2011; 20(3): 205–215. (Publication)
This summary publication shows LED phototherapy is proving to have more and more viable applications in many fields of medicine.
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Background: Low level light therapy (LLLT) has attracted attention in many clinical fields with a new generation of light-emitting diodes (LEDs) which can irradiate large targets. To pain control, the first main application of LLLT, have been added LED-LLLT in the accelerated healing of wounds, both traumatic and iatrogenic, inflammatory acne and the patient-driven application of skin rejuvenation.

Rationale and Applications: The rationale behind LED-LLLT is underpinned by the reported efficacy of LED-LLLT at a cellular and subcellular level, particularly for the 633 nm and 830 nm wavelengths, and evidence for this is presented. Improved blood flow and neovascularization are associated with 830 nm. A large variety of cytokines, chemokines and macromolecules can be induced by LED phototherapy. Among the clinical applications, non-healing wounds can be healed through restoring the collagenesis/collagenase imbalance in such examples, and ‘normal’ wounds heal faster and better. Pain, including postoperative pain, postoperative edema and many types of inflammation can be significantly reduced.

Experimental and clinical evidence: Some personal examples of evidence are offered by the first author, including controlled animal models demonstrating the systemic effect of 830 nm LED-LLLT on wound healing and on induced inflammation. Human patients are presented to illustrate the efficacy of LED phototherapy on treatment-resistant inflammatory disorders.

Conclusions: Provided an LED phototherapy system has the correct wavelength for the target cells, delivers an appropriate power density and an adequate energy density, then it will be at least partly, if not significantly, effective. The use of LED-LLLT as an adjunct to conventional surgical or nonsurgical indications is an even more exciting prospect. LED-LLLT is here to stay.

Keywords: Grotthus-Draper law, nonhealing wound, photochemical cascade, photophysical reaction, irritant contact dermatitis, dissecting cellulitis, acne rosacea

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INTRODUCTION

High level laser treatment (HLLT) means that high levels of incident laser power are used to deliberately destroy a specific target through a light-heat transduction process to induce photothermal damage of varying degrees. HLLT is used in many surgical fields, but probably most commonly in dermatologic, aesthetic or plastic surgery. On the other hand, when a laser or other appropriate light source is used on tissue at low incident levels of photon energy, none of that energy is lost as heat but instead the energy from the absorbed photons is transferred directly to the absorbing cell or chromophore, causing photoactivation of the target cells and some kind of change in their associated activity. In clinical applications, this was termed ‘low level laser therapy’ (LLLT) by Ohshiro and Calderhead in 1988,1) with ‘photobiomodulation’ or ‘photoactivation’ referring to the activity at a cellular and molecular level.

Genesis of LLLT

In the late 1960's, the early days of the clinical application of the laser, there was fear that laser energy could induce carcinogenesis as a side effect of the use of the laser in surgery and medicine. To assess this, in a paper published in 1968, the late Professor Endrè Mester, the recognized father of phototherapy from Semmelweis University, Budapest, applied daily doses of low incident levels of defocused ruby laser energy to the shaved dorsum of rats.2) No carcinogenetic changes were noted at all, but Mester incidentally discovered that LLLT accelerated hair regrowth in the laser-irradiated animals. Furthermore, during this period, early adopters of the surgical laser were reporting interesting and beneficial effects of using the laser as a scalpel compared with the conventional cold steel instrument, such as reduced inflammation, less postoperative pain, and better wound healing. Mester's experiments helped to show that it was the ‘L’ of laser, namely light, that was associated with these effects due to the bioactivative levels of light energy which exist simultaneously at the periphery of the photosurgical destructive zone, as illustrated in Figure 1.An external file that holds a picture, illustration, etc. Object name is islsm-20-205-g001.jpg

Fig. 1:

Range of typical bioreactions associated with a surgical laser and their approximate temperature range. Note that some degree of photoactivation almost always occurs simultaneously with HLLT-mediated reactions. (Data adapted from Calderhead RG: Light/tissue interaction in photosurgery and phototherapy. In Calderhead RG. Photobiological Basics of Photosurgery and Phototherapy, 2011, Hanmi Medical Publishers, Seoul. pp 47–89)

In the 1970's, many clinicians, inspired by Mester's major publication in 1969 on the significantly successful use of LLLT for the treatment of nonhealing or torpid crural ulcers, started to apply LLLT clinically, particularly in France and Russia, and this spread to Japan, Korea, and other Asian countries in the early 1980's. However, it was still looked on as ‘black magic’ by the mainstream medicoscientific world in the USA. The first Food and Drug Administration (FDA) approval for laser diode phototherapy was not granted till 2002, but even then the sceptics were not silenced.

LLLT with Lasers

LLLT was first completely limited to treatment with laser sources, such as the helium neon (HeNe) laser in the visible red at 632.8 nm, various semiconductor (diode) lasers (visible red to near infrared, most notable being the GaAlAs at 830 nm) or defocused beams of a surgical laser (Nd:YAG or CO2, for example).3) There are several mechanisms which have been reported as to how LLLT can induce a biomodulative effect (Table 1). In the case of LLLT with laser sources, these effects were achieved athermally and atraumatically through the special properties associated with the ‘coherence’ of laser energy, namely monochromaticity, directionality or collimation, and the photons all in phase temporally and spatially. Another phenomenon associated only with laser energy is the so-called ‘speckle’ phenomenon. When the spot from a 670 nm laser pointer is closely examined over a period of time, for example, it appears to be composed of exceptionally brighter spots of light energy which are constantly in motion: these are laser speckles. Speckles have their own characteristics, including high energy and polarization, and these intense spots of polarized light were associated with specific reactions in the absorbing target or chromophore.

Table 1:

Major mechanisms associated with photobioactivation and LLLT

Mild thermal (<40°C)

Biochemical

Bioelectric

Bioenergetic

? Nerve conduction

(Mitochondrial events)

? Electromotive action on membrane bound ion transport mechanisms

? Rotational & vibrational changes to membrane molecule electrons

 

? ATP production

 

 

 

? Release of nitric oxide (NO)

 

 

 

? Very low levels of reactive oxygen species (ROS)

 

 


? Capillary dilatation

? Fibroblast proliferation ? Collagen & elastin synthesis

? Intracellular extra-cellular ion gradient changes

? Stimulation of acupuncture meridian points


 

? Mast cell degranulation: cytokine, chemokine and trophic factor release

? Depolarization of synaptic cleft ? closure of synaptic gate

? Increased biophotonic activity


 

? Macrophage activity (chemotaxis & internalization) ? release of FGF

? Activation of the dorsal horn gate control mechanism ? pain transmission slowed, pain control increased

 


 

? Keratinocyte activity cytokine release in epidermis and dermis

 

 

 


 

 

? Opiate and nonopiate pain control (endorphins, dynorphins and enkephalins)

 

 

 


 

 

? RNA/DNA synthesis

 

 

 


 

 

? Enzyme production

 

 

 


 

 

? Superoxide dismutase (SOD) production

 

 

 

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Up until the end of the 1990's, phototherapy was dominated by these laser sources, because although LEDs were cheap and cheerful, they were highly divergent with low and unstable output powers, and a wide waveband. With very few exceptions, old generation LEDs were incapable of producing really useful clinical reactions in tissue. It was easy to source a ‘red’ LED (output spread over approximately 600 – 700 nm) but it was more or less impossible to source LEDs at specific nominal wavelengths, for example 633 nm, similar to the HeNe laser.

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LED PHOTOTHERAPY

Enter the NASA Light-Emitting Diode (LED)

All this changed in 1998 with the development of the so-called ‘NASA LED’ by Prof Harry Whelan and his group at the NASA Space Medicine Laboratory, which offered clinicians and researchers a useful phototherapy source having less divergence, much higher and more stable output powers, and quasimonochromaticity whereby nearly all of the photons were at the rated wavelength.4) This new generation of LEDs also had its own phenomenon associated with photon intensity, namely photon interference, whereby intersecting beams of LED energy from individual LEDs produced photon interference, increasing the photon intensity dramatically and thus offering much higher photon intensities than the older generation. For LEDs emitting at visible red and near IR wavelengths, the greatest photon intensity was actually seen beneath the surface of the target tissue, due to the combination of the photon interference phenomenon and the excellent tissue scattering characteristics of light at these wavebands.5) This phenomenon, together with quasimonochromaticity, meant that the new generation of LEDs was a clinically viable source for phototherapy.6) ‘Low level laser therapy’ was therefore renamed by the US photobiologist, Kendric C Smith, as ‘low level light therapy’, to encompass LED energy.7) Accordingly, useful bioreactions could then be achieved with LEDs through cellular photoactivation without heat or damage, as shown by Whelan and colleagues in their early NASA LED wound healing studies.8)

Although visible and near-infrared light energy induce the same tri-stage process in target cells, namely photon absorption, intracellular signal transduction and the final cellular photoresponse,9) it should be noted that both wavebands have different primary targets and photoreactions in target cells. Visible light is principally a photochemical reaction, acting directly and mostly on cytochrome-c oxidase, the end terminal enzyme in the cellular mitochondrial respiratory chain,10) and mainly responsible for inducing adenosine triphosphate (ATP) synthesis, the fuel of the cell and indeed the entire metabolism. Infrared light on the other hand induces a primary photophysical reaction in the cell membrane thereby kick-starting the cellular membrane transport mechanisms such as the Na++K++ pump,6) and this in turn induces as a secondary reaction the same photochemical cascade as seen with visible light, so the end result is the same even though the target is different as illustrated schematically in Figure 2.An external file that holds a picture, illustration, etc. Object name is islsm-20-205-g002.jpg Fig. 2:

The process of cellular photoactivation by low level light therapy (LLLT). Visible light induces a primary photochemical response particularly associated with mitochondrial cytochrome c-oxidase, whereas near IR induces a primary photophysical response in the cellular and organelle membranes. However the eventual photoresponse is the same. (Based on data from Karu & Smith, Refs 6 & 9)

LED phototherapy at appropriate wavelengths and parameters has now been well-reported in a large number of pan-speciality applications.11) How and where does LED phototherapy work? When we consider investigating how LED phototherapy or LLLT can bring about and influence the molecular mechanism for cell proliferation, we should recognize that LLLT not only has an effect on various signaling processes, but it can also significantly induce the production of cytokines, such as a number of growth factors, interleukins and various macromolecules (Table 2).12)

Table 2:

Molecular level activation by LLLT with appropriate LEDs (From Ref 12)
Classification Molecules LLLT-Associated Biological Effects
Growth factors BNF, GDNF, FGF, bFGF, IGF-1, KGF, PDGF, TGF-?, VEGF Proliferation
    Differentiation
    Bone nodule formation

Interleukins IL-1?, IL-2, IL-4, IL-6, IL-8 Proliferation
    Migration
    Immunological activation

Inflammatory cytokines PGE2, COX2, IL1?, TNF-? Acceleration/Inhibition of inflammation

Small molecules ATP, cGMP, ROS, CA++, NO, H+ Normalization of cell function
    Pain relief
    Wound healing
    Mediation of cellular activities
    Migration
    Angiogenesis

Journal of Biomedical Science 2009, 16:4

Phototherapy is Becoming Mainstream

The increasing number of papers on LLLT in the Photobiomodulation sessions presented at the 2010 and especially the 2011 meetings of the American Society for Lasers in Medicine and Surgery (ASLMS) bear witness to the fact that LLLT is no longer quite the bête noir it used to be in the USA, although there is still too much skepticism, and it has achieved a reliable status worldwide. LED phototherapy has now been well-proven to work, and is reported to be effective in a large variety of clinical indications such as pain attenuation, wound healing, skin rejuvenation, some viral diseases, allergic rhinitis, other allergy-related conditions and so on.

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APPLICATIONS OF LLLT WITH LEDs

When we confirm in what fields LLLT phototherapy has been most used through a review of the literature, the main application is for pain control, with pain of almost all aetiologies responding well.11) For example, 830 nm LED phototherapy significantly reduced both acute and chronic pain in professional athletes.13) The first author has been using LED in the control of herpes zoster pain for some time, and also for intractable postherpetic neuralgia, corroborating previous studies with 830 nm LLLT for this indication.14,15) This and other chronic pain entities have been historically very hard to control, but the good efficacy of LED phototherapy has been well recognized. From the large body of work from Rochkind and colleagues in Israel, LED phototherapy can help nerve regeneration, so it has been used for spinal cord injuries,16) and many different types of neurogenic abnormality. In the case of the dental clinic and for the osseointegration of implants and prostheses in maxillofacial surgery it has been used for guided bone regeneration.17) At present, the research into and development of new applications for LED phototherapy, especially in the processes of inflammatory cell regulation, are being assiduously studied in the dermatology field.

Fast taking over from pain attenuation, and particularly in the dermatology field, wound healing with LED phototherapy has attracted much attention. Reports have shown that, after making uniform burn wounds with a surgical laser, LED phototherapy of experimental wounds induces faster and better organized healing than in the control unirradiated wounds. This is due to the effect of 830 nm phototherapy on raising the action potential the wound-healing cells, at all three phases of the process, particularly mast cells,18) macrophages19) and neutrophils20) in the inflammatory stage; fibroblasts in the proliferative phase (Personal Communication, Prof. Park, Seoul National University, Seoul, South Korea: unpublished data); and fibroblast-myofibroblast transformation in the remodeling phase.21) As an additional mechanism, it has also been shown that 830 nm phototherapy increased the early vascular perfusion of axial pattern flaps in a controlled speckle flowmetry Doppler trial in the rat model, with actual flap survival significantly better in the irradiated than in the unirradiated control animals.22)

In another very popular indication, studies have reported on the use of LED phototherapy for the rejuvenation of chronologically and photodamaged skin.23,24) Lee and colleagues, in a randomized controlled study, showed that fibroblasts examined with transmission electron microscopy appeared more active, collagen and elastin synthesis was increased and tissue inhibitors of matric metalloproteinases was increased, as a result of which, effective rejuvenation could be achieved which was maintained up to 12 weeks after the final treatment session. Patient satisfaction scores bore these histopathological findings out (Figure 3).24) We must never forget that good skin rejuvenation is firmly based on the wound healing process, particularly neocollagenesis. LED phototherapy has also been reported as being very effective in the prophylaxis against scar formation, due amongst other factors to the response to photomediated interleukin-6 signaling.12) Hair loss is another field where LED phototherapy may well have real efficacy, with red and infrared being the wavelengths of choice.2527) Figure 4 illustrates schematically the mechanisms already confirmed underlying the three main endpoints of 830 nm LLLT, namely wound healing, the anti-inflammatory response through acceleration and quenching of the post-wound inflammatory phase and pain attenuation.

An external file that holds a picture, illustration, etc. Object name is islsm-20-205-g003.jpg

Fig. 3:

Patient satisfaction curves compared for LED-mediated skin rejuvenation with 633 nm alone, 633 nm + 830 nm combined and 830 nm on its own, showing the numbers of patients who rated their improvement as excellent on a 5-scale rating. The first set of columns represents the findings immediately after the 8th of 8 weekly sessions, twice per week for 4 weeks. The 2nd, 3rd and 4th sets of columns are the findings at post-treatment weeks 4, 6 and 8 respectively. At all stages, LED phototherapy with 830 nm produced superior satisfaction. The increase over the post-treatment period is interesting, suggesting improved results through continued tissue remodeling as part of the LED-mediate wound healing process. (Data adapted from Ref 24)

  An external file that holds a picture, illustration, etc. Object name is islsm-20-205-g004.jpg

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Original Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3799034/

Home Search Introduction

Ken Teegardin - (Video)
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Welcome to the laser-therapy.us research tool. This tool is a searchable collection of technical publications, books, videos and other resources about the use of lasers for photobiomodulation. This tool includes almost the entire U.S. library of medicine research papers on LLLT, videos from Youtube associated with therapy lasers and the tables of contents from laser therapy books. This allows users to search for a keyword or condition and see resources about using lasers to treat that condition. All the resources include links to the original source so we are not making any statement about the use of lasers for treating non-FDA cleared application, we are simple summarizing what others have said.  Where every possible, we have included a link to the orginal publication.

Here are some of our favorite queries:

This tool uses a broad match query so:

  • It does not correct spelling and searches only cold laser related subjects so do not use LLLT, cold or laser in the search bar
  • It works better with shorter search terms or even parts of search terms
  • It searches all the available fields so you can enter a body part, author, condition or laser brand.
  • Where ever possible, the detailed section about the resource will link to the sources.
  • This system is only for photobiomodulation or cold laser therapy research (including LLLT, laser acupuncture and high power laser therapy) only. It does NOT include photodynamic laser therapy (where the laser is used to react with a pharmaceutical), hot surgery lasers or cosmetic lasers. It does include some resources on weight loss and smoking cessation.

The results of the search are sorted based on 3 quality factors on a scale of 1 to 10 with 10 being the best score. Originally all the resources were given a 5-5-5 until they could be individually evaluated. These scores are purely opinion and are only used to simplify the rank of the results from more valuable to least valuable. This should not be considered a critique of any work. This system was created to help researchers (including ourselves) find the most usable resources for any cold laser therapy research. The resources are assigned values based on the following 3 factors:

  • Efficacy: The resource (especially research papers) should show a significant improvement in the condition being treated. Resources that show better results are given a higher quality score.
  • Detail: The source must give enough information that the results can be duplicated. If a resource lacks too many details that it cannot be recreated, it is given a lower detail score.
  • Lack of Bias: Many resources are created to try and show that one device is superior to its competition. Many manufacturers have staff that crank out biased papers on a regular basis on the hope that this will make their product look superior. If the author of the resource is paid by a manufacturer of the resource appears to be biased towards one device and not one technology, the resource has much less value.

Over the past few years of working with research, we found that a majority of the published resources are lacking in one of these three ranking factors.
The original goal of this research tool was to tie published resources to the protocols in the laser-therapy.us library. This connection allows users to trace each protocol back to a list of resources so the protocol can be researched and improved.

General Comments


POWER
When many of the first research papers were published, the most power laser available for therapy were less than 100mW and many systems had to be pulsed to keep the laser from burning out too quickly. Today, system are available that will deliver up to 60,000mW of continuous output. Because of these power limitation, many early studies were limited to extremely low dosages by today’s standards. It takes a 50mW system 17 minutes to deliver 50 joules at the surface of the skin. If this was spread over a large area of damage or was treating a deeper problem, the actual dosages were much less than 1J/cm2.  Today, we know that these dosages typically produce very little or no results.
WAVELENGTH
About 80% of the resources in this database are in the near infrared wavelength. There is also some interest in the red wavelength (600 to 660nm) . Other wavelengths like blue, purple, and green have very little scientific research behind them and have not gotten much traction in the core therapy market with the exception of some fringe consumer products.
Legal Disclaimer
This research tool is free to use but we make no claims about the accuracy of the information. It is an aggregation of existing published resources and it is up to the user to determine if the source of the resources has any value. The information provided through this web site should not be used for diagnosing or treating a health problem or disease. If you have or suspect you may have a health problem, you should consult your local health care provider.



The query result(s) can be shared using the following direct link. Anyone who clicks on this link in an email or on a web site will be shown the current results for the query.
https://www.laser-therapy.us/research/index.cfm?researchinput=bedsum