Interplay between up-regulation of cytochrome-c-oxidase and hemoglobin oxygenation induced by near-infrared laser

Transcranial photobiomodulation changes topology, synchronizability, and complexity of resting state brain networks

Objective. Transcranial photobiomodulation (tPBM) is a recently proposed non-invasive brain stimulation approach with various effects on the nervous system from the cells to the whole brain networks. Specially in the neural network level, tPBM can alter the topology and synchronizability of functional brain networks. However, the functional properties of the neural networks after tPBM are still poorly clarified.Approach. Here, we employed electroencephalography and different methods (conventional and spectral) in the graph theory analysis to track the significant effects of tPBM on the resting state brain networks. The non-parametric statistical analysis showed that just one short-term tPBM session over right medial frontal pole can significantly change both topological (i.e. clustering coefficient, global efficiency, local efficiency, eigenvector centrality) and dynamical (i.e. energy, largest eigenvalue, and entropy) features of resting state brain networks.Main results. The topological results revealed that tPBM can reduce local processing, centrality, and laterality. Furthermore, the increased centrality of central electrode was observed.Significance. These results suggested that tPBM can alter topology of resting state brain network to facilitate the neural information processing. On the other hand, the dynamical results showed that tPBM reduced stability of synchronizability and increased complexity in the resting state brain networks. These effects can be considered in association with the increased complexity of connectivity patterns among brain regions and the enhanced information propagation in the resting state brain networks. Overall, both topological and dynamical features of brain networks suggest that although tPBM decreases local processing (especially in the right hemisphere) and disrupts synchronizability of network, but it can increase the level of information transferring and processing in the brain network.

Acute Photobiomodulation by LED Does Not Alter Muscle Fatigue and Cycling Performance

PURPOSE

The purpose of the present study was to investigate the ergogenic effects of two doses of photobiomodulation therapy (PBMT) in comparison to placebo on markers of respiratory and muscle activity, blood acid-base, ion and lactate concentrations, indicators of muscle fatigue (global, central, and peripheral), and time to exhaustion in severe-intensity cycling.

METHODS

Two separate studies were performed, both in a pseudorandomized and balanced, crossover design. In study 1, 14 male recreational cyclists completed three constant-load, severe-intensity cycling bouts that were duration matched. The PBMT (18 × 38 cm array with 200 diodes) treatments occurred before bouts at 260, 130, or 0 J (placebo) doses. EMG activity of selected lower limb musculature was assessed during each bout. Maximal voluntary contractions of knee extension with peripheral nerve stimulations and EMG activity evaluation of vastus lateralis was also performed before and after cycling. In study 2, 13 recreational cyclists performed three bouts of constant-load, severe-intensity cycling until exhaustion, preceded by PBMT as detailed previously. Blood lactate concentrations, respiratory responses, EMG activity, and capillary gasometry aspects were monitored.

RESULTS

In both studies, there were no interactions effects (time-condition) on the EMG activity, which was displayed as root mean square (P ≥ 0.168) and median frequency (P ≥ 0.055) during cycling. In study 1, there were no interaction effects on the indicators of muscle fatigue after exercise (P ≥ 0.130). In study 2, there were no differences on time to exhaustion (P = 0.353) and no interaction effects among the physiological responses monitored (P ≥ 0.082).

CONCLUSIONS

Based on our findings, the PBMT at 260- and 130-J doses does not have a beneficial effect on muscle fatigue, cycling performance, metabolic parameters, and muscle activity in male recreational cyclists.

Methylene blue and photobiomodulation recover cognitive impairment in hepatic encephalopathy through different effects on cytochrome c-oxidase

Mitochondrial dysfunction plays a central role in hepatic encephalopathy (HE), due to changes in enzyme cytochrome c-oxidase (CCO), causing a decline in brain metabolism. We used an HE animal model and applied intracranial administration of methylene blue (MB) and transcranial photobiomodulation (PBM), both targeting CCO, to determine their differential effects on recovering cognition. Five groups of rats were used: sham-operated group + saline (SHAM + SAL, n = 6), hepatic encephalopathy + SAL (HE + SAL, n = 7), SHAM + methylene blue (SHAM + MB, n = 7), HE + MB (n = 7), HE + PBM (n = 7). PBM animals were exposed transcranially to 670 +/- 10 nm LED light at a dose of 9 J/cm2 once a day for 7 days, and the MB and SAL groups were injected with 2.2 μg/0.5 μL in the accumbens. Cognitive dysfunction was evaluated on a striatal stimulus-response task using the Morris water maze. Our results showed cognitive improvement in the HE group when treated with MB. This improvement was accompanied by a decrease in CCO activity in the prefrontal cortex, dorsal striatum, and dorsal hippocampus. When comparing MB and PBM, we found that, although both treatments effectively improved the HE-memory deficit, there was a differential effect on CCO. A general decrease in CCO activity was found in the prefrontal and entorhinal cortices, dorsal striatum, and hippocampus when PBM, compared to MB, was applied. Our results suggest that mitochondrial dysfunction and brain metabolic decline in HE might involve CCO alteration and can be improved by administering MB and PBM.

Effects of Physical Stimulation in the Field of Oral Health

Physical stimulation has been widely used in clinical medicine and healthcare due to its noninvasiveness. The main applications of physical stimulation in the oral cavity include laser, ultrasound, magnetic field, and vibration, which have photothermal, cavitation, magnetocaloric, and mechanical effects, respectively. In addition, the above four stimulations with their unique biological effects, which can play a role at the gene, protein, and cell levels, can provide new methods for the treatment and prevention of common oral diseases. These four physical stimulations have been used as important auxiliary treatment methods in the field of orthodontics, implants, periodontal, dental pulp, maxillofacial surgery, and oral mucosa. This paper systematically describes the application of physical stimulation as a therapeutic method in the field of stomatology to provide guidance for clinicians. In addition, some applications of physical stimulation in specific directions are still at the research stage, and the specific mechanism has not been fully elucidated. To encourage further research on the oral applications of physical stimulation, we elaborate the research results and development history of various physical stimuli in the field of oral health.

Photobiomodulation effect of red LED (630 nm) on the free radical levels produced by pulp cells under stress conditions

The aim of this study was to assess the ability of red light emitting diodes (LED) to modulate oxidative stress in human dental pulp fibroblasts (HDPFs) when different irradiation parameters are employed. Cells from primary teeth were seeded (100,000 cells/well) in 24-well plates in culture medium (DMEM). At 24 h after incubation, the culture medium was replaced with DMEM containing 10 μg/mL lipopolysaccharide (LPS). Thereafter, the cells were irradiated (LED 630 nm, 0.04 W/cm² and 0.08 W/cm²) at 0 J/cm² (control group), 4 J/cm², 15 J/cm², and 30 J/cm²; and their viability (MTT assay), number (Trypan Blue), synthesis of nitric oxide (NO) (Griess reagent), and reactive oxygen species (ROS) (fluorescence probe, DCFH-DA) were assessed. The Kruskal-Wallis and Mann-Whitney statistical tests using Bonferroni correction were employed (significance level of 5%). Compared to that in control fibroblasts, increased viability was observed in HDPFs exposed to LPS and irradiated with 15 J/cm² and 30 J/cm² at 0.04 W/cm² and 4 J/cm² and 15 J/cm² at 0.08 W/cm² (p < 0.05). Exposure to 4 J/cm² at 0.04 W/cm² and 15 J/cm² and 30 J/cm² at 0.08 W/cm² modulated the oxidative stress in cells relative to that observed in non-irradiated LPS-treated pulp cells (p < 0.05). It was concluded that the irradiation strategies of using red LED with radiant exposures of 15 J/cm² and 30 J/cm² at 0.04 W/cm² and 15 J/cm² at 0.08 W/cm² were the best parameters to decrease NO and ROS concentration and to stimulate viability of HDPFs exposed to LPS challenge.

Mechanistic aspects of photobiomodulation therapy in the nervous system

Photobiomodulation therapy (PBMT) previously known as low-level laser therapy (LLLT) has been used for over 30 years, to treat neurological diseases. Low-powered lasers are commonly used for clinical applications, although recently LEDs have become popular. Due to the growing application of this type of laser in brain and neural-related diseases, this review focuses on the mechanisms of laser action. The most important points to consider include the photon absorption by intracellular structures; the effect on the oxidative state of cells; and the effect on the expression of proteins involved in oxidative stress, inflammation, pain, and neuronal growth.

Transcranial laser stimulation: Mitochondrial and cerebrovascular effects in younger and older healthy adults

BACKGROUND

Transcranial laser stimulation is a novel method of noninvasive brain stimulation found safe and effective for improving prefrontal cortex neurocognitive functions in healthy young adults. This method is different from electric and magnetic stimulation because it causes the photonic oxidation of cytochrome-c-oxidase, the rate-limiting enzyme for oxygen consumption and the major intracellular acceptor of photons from near-infrared light. This photobiomodulation effect promotes mitochondrial respiration, cerebrovascular oxygenation and neurocognitive function. Pilot studies suggest that transcranial photobiomodulation may also induce beneficial effects in aging individuals.

OBJECTIVES

Randomized, sham-controlled study to test photobiomodulation effects caused by laser stimulation on cytochrome-c-oxidase oxidation and hemoglobin oxygenation in the prefrontal cortex of 68 healthy younger and older adults, ages 18-85.

METHODS

Broadband near-infrared spectroscopy was used for the noninvasive quantification of bilateral cortical changes in oxidized cytochrome-c-oxidase and hemoglobin oxygenation before, during and after 1064-nm wavelength laser (IR-A laser, area: 13.6 cm², power density: 250 mW/cm²) or sham stimulation of the right anterior prefrontal cortex (Brodmann Area 10).

RESULTS

As compared to sham control, there was a significant laser-induced increase in oxidized cytochrome-c-oxidase during laser stimulation, followed by a significant post-stimulation increase in oxygenated hemoglobin and a decrease in deoxygenated hemoglobin. Furthermore, there was a greater laser-induced effect on cytochrome-c-oxidase with increasing age, while laser-induced effects on cerebral hemodynamics decreased with increasing age. No adverse laser effects were found.

CONCLUSION

The findings support the use of transcranial photobiomodulation for cerebral oxygenation and alleviation of age-related decline in mitochondrial respiration. They justify further research on its therapeutic potential in neurologic and psychiatric diseases.

Photobiomodulation 30 min or 6 h Prior to Cycling Does Not Alter Resting Blood Flow Velocity, Exercise-Induced Physiological Responses or Time to Exhaustion in Healthy Men

Purpose

The aim of the current study was to investigate the effects of photobiomodulation therapy (PBMT) applied 30 min or 6 h prior to cycling on blood flow velocity and plasma nitrite concentrations at rest, time to exhaustion, cardiorespiratory responses, blood acid-base balance, and K⁺ and lactate concentrations during exercise.

Methods

In a randomized, crossover design, 13 healthy untrained men randomly completed four cycling bouts until exhaustion at the severe-intensity domain (i.e., above respiratory compensation point). Thirty minutes or 6 h prior to the cycling trials, participants were treated with PBMT on the quadriceps, hamstrings, and gastrocnemius muscles of both limbs using a multi-diode array (11 cm × 30 cm with 264 diodes) at doses of 152 J or a sham irradiation (with device turned off, placebo). Blood samples were collected before and 30 min or 6 h after treatments to measure plasmatic nitrite concentrations. Doppler ultrasound exams of the femoral artery were also performed at the same time points. Cardiorespiratory responses, blood acid-base balance, and K⁺ and lactate concentrations were monitored during exercise sessions.

Results

PBMT did not improve the time to exhaustion (p = 0.30). At rest, no differences were found in the peak systolic velocity (p = 0.97) or pulsatility index (p = 0.83) in the femoral artery, and in plasma nitrite concentrations (p = 0.47). During exercise, there were no differences for any cardiorespiratory response monitored (heart rate, p = 0.15; oxygen uptake, p = 0.15; pulmonary ventilation, p = 0.67; carbon dioxide output, p = 0.93; and respiratory exchange ratio, p = 0.32), any blood acid-base balance indicator (pH, p = 0.74; base excess, p = 0.33; bicarbonate concentration, p = 0.54), or K⁺ (p = 0.22) and lactate (p = 0.55) concentrations.

Conclusions

PBMT at 152 J applied 30 min or 6 h before cycling at severe-intensity did not alter resting plasma nitrite and blood flow velocity in the femoral artery, exercise-induced physiological responses, or time to exhaustion in healthy untrained men.

Transcranial Photobiomodulation to Improve Cognition in Gulf War Illness

Introduction: Approximately 25-30% of veterans deployed to Kuwait, 1990-91, report persistent multi-symptom Gulf War Illness (GWI) likely from neurotoxicant exposures. Photobiomodulation (PBM) in red/near-infrared (NIR) wavelengths is a safe, non-invasive modality shown to help repair hypoxic/stressed cells. Red/NIR wavelengths are absorbed by cytochrome C oxidase in mitochondria, releasing nitric oxide (increasing local vasodilation), and increasing adenosine tri-phosphate production. We investigated whether PBM applied transcranially could improve cognition, and health symptoms in GWI. Materials and Methods: Forty-eight (40 M) participants completed this blinded, randomized, sham-controlled trial using Sham or Real, red/NIR light-emitting diodes (LED) applied transcranially. Fifteen, half-hour transcranial LED (tLED) treatments were twice a week (7.5 weeks, in-office). Goggles worn by participant and assistant maintained blinding for visible red. Pre-/Post- testing was at Entry, 1 week and 1 month post- 15th treatment. Primary outcome measures were neuropsychological (NP) tests; secondary outcomes, Psychosocial Questionnaires, including PTSD. Results: Primary Analyses (all participants), showed improvement for Real vs. Sham, for Digit Span Forwards (p < 0.01); and a trend for Trails 4, Number/Letter Sequencing (p < 0.10). For secondary outcomes, Real group reported more improvement on the SF-36V Plus, Physical Component Score (p < 0.08). Secondary Analyses included only subjects scoring below norm (50%ile) at Entry, on specific NP test/s. Real and Sham improved at 1 week after 15th treatment; however, at 1 month, only those receiving Real improved further: Digit Span Total, Forwards and Backwards; Trails 4, Number/Letter Sequencing; California Verbal Learning Test-II, long delay free recall; Continuous Performance Test-II, False Alarm Rate; and Color-Word Interference, Stroop, Trial 3, Inhibition; Sham group worsened, toward Entry values. Only those with more post-traumatic stress disorder (PTSD) symptomatology at Entry, receiving Real, continued to have additional PTSD reduction at 1 month; Sham regressed. Conclusion: This study was underpowered (n = 48), with large heterogeneity at Entry. This likely contributed to significance or trend to significance, for only two of the NP tests (Digit Span Forwards; Trails 4, Number/Letter Sequencing) and only one general health measure, the SF-36V Plus, Physical Component Score. More subjects receiving Real, self-reported increased concentration, relaxation and sleep. Controlled studies with newer, transcranial LED home treatment devices are warranted; this is expected to increase enrollment. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT01782378.

Photobiomodulation and Sida tuberculata combination declines the inflammation's markers in knee-induced osteoarthritis

The aim of this study was to assess potential combination effects of photobiomodulation therapy (PBMT) with Sida tuberculata extracts on the oxidative stress and antioxidant activity, as well as on the inflammatory process. Rats with knee osteoarthritis (OA) were treated with S. tuberculata extracts and PBMT (904 nm, 18 J/cm²). The animals were evaluated for nociception and edema. The blood, knee lavage and structures, spinal cord, and brainstem were collected for biochemical analyses (lipid peroxidation, protein carbonyl content, superoxide dismutase activity, non-protein thiol levels, and measurement of nitrite/nitrate). The knee structures were also used to measure cytokine levels. PBMT lowered the damage due to oxidative stress in the knee and at distant sites from the lesion. PBMT also reduced the levels of nitric oxide and cytokines, which could explain the nociception reduction mechanism. Similarly, S. tuberculata decreased the damage by oxidative stress, levels of nitrite/nitrate, and cytokines. The therapy combination reduced levels of cytokines and nitrite/nitrate. PBMT and S. tuberculata extracts reduced the oxidative stress and inflammation. It is noteworthy that PBMT increased the antioxidant activity in the knee and at sites distant from the lesion, contributing to a more significant decrease in nociception. The combination of therapies did not present significant effects on the analyzed parameters. Therefore, it is suggested that PBM is sufficient to minimize the signs and symptoms of the knee OA in our rat model.

Photobiomodulation and diffusing optical fiber on spinal cord's impact on nerve cells from normal spinal cord tissue in piglets

Experts have proven that photobiological regulation therapy for spinal cord injury promotes the spinal repair following injury. The traditional irradiation therapy mode is indirect (percutaneous irradiation), which could significantly lower the effective use of light energy. In earlier studies, we developed an implantable optical fiber that one can embed above the spinal cord lamina, and the light directly is cast onto the surface of the spinal cord in a way that can dramatically improve energy use. Nonetheless, it remains to be seen whether near-infrared light diffused by embedded optical fiber can have side effects on the surrounding nerve cells. Given this, we implanted optical fiber on the lamina of a normal spinal cord to observe the structural integrity of the tissue using morphological staining; we also used immunohistochemistry to detect inflammatory factors. Considering the existing studies, we meant to determine that the light energy diffused by embedded optical fiber has no side effect on the normal tissue. The results of this study will lay a foundation for the clinical application of the treatment of spinal cord injury by near-infrared light irradiation.

A Potential Role for Photobiomodulation Therapy in Disease Treatment and Prevention in the Era of COVID-19

COVID-19 is an evolving pandemic that has far reaching global effects, with a combination of factors that makes the virus difficult to contain. The symptoms of infection can be devastating or at the least very debilitating for vulnerable individuals. It is clear that the elderly are at most risk of the adverse impacts of the virus, including hospitalization and death. Others at risk are those with comorbidities such as cardiovascular disease and metabolic conditions and those with a hyper-excitable immune response. Treatment options for those with acute responses to the virus are limited and there is an urgent need for potential strategies that can mitigate these severe effects. One potential avenue for treatment that has not been explored is the microbiome gut/lung axis. In addition to those severely affected by their acute reaction to the virus, there is also a need for treatment options for those that are slow to recover from the effects of the infection and also those who have been adversely affected by the measures put in place to arrest the spread of the virus. One potential treatment option is photobiomodulation (PBM) therapy. PBM has been shown over many years to be a safe, effective, non-invasive and easily deployed adjunctive treatment option for inflammatory conditions, pain, tissue healing and cellular energy. We have also recently demonstrated the effectiveness of PBM to alter the gut microbiome. PBM therapy is worthy of consideration as a potential treatment for those most vulnerable to COVID-19, such as the elderly and those with comorbidities. The treatment may potentially be advantageous for those infected with the virus, those who have a slow recovery from the effects of the virus and those who have been denied their normal exercise/rehabilitation programs due to the isolation restrictions that have been imposed to control the COVID-19 pandemic.

Biological non-ablative repair of lumbar discs by transforaminal intradiscal laser irradiation: MRI quantitative analysis of the effects-preliminary report

Degenerative disc disease is a significant reason for low back pain. Low-level laser irradiation (LLLI) of cartilage results in its reshaping and combines with regenerative reaction. A certain pattern of lumbar disc irradiation induces healing reaction and formation of new cartilage. Quantitative MRI analysis of regenerative response of the cartilage is the subject of this investigation. Fifty-one lumbar discs of 28 patients with discogenic low back pain underwent irradiation with 1.56-μm Er fiber laser (1.2 W). Quantitative MRI analysis is performed in STIR regime within 0.93-14.80 months. Signal intensity is estimated from irradiated discs and control measured from adjacent non-irradiated discs and vertebral bones. T2 WI follow-up is performed within a long period (up to 5 years) in selected cases. The mean value of MRI signal intensity from the irradiated discs increased by 14% (p <<< 0.001). The control bone measurement revealed no difference in signal intensity (p = 0.83). The adjacent non-irradiated discs slightly increased their signal (p < 0.05). T2 WI follow-up within 5 years revealed a steady increase of the signal and the irradiated discs healing. LLLI of degenerated intervertebral discs by 1.56-μm Er fiber laser produces increase of MRI disc signal within the first year after treatment that confirms regenerative response of the disc and could lay in the basis of clinical improvement. Further assessment on the effect is mandatory.

Effects of photobiomodulation and swimming on gene expression in rats with the tibialis anterior muscle injury

The aim of the present study was to evaluate the effects of photobiomodulation (low-level laser therapy (LLLT)) and aquatic exercise on the expression of genes related to muscle regeneration in rats. Wistar rats were divided into five groups: control group (n = 15), non-treated injury group (n = 15), injury+LLLT group (n = 15), injury+aquatic exercise group (n = 15), and injury+LLLT+aquatic exercise group (n = 15). Cryoinjury was performed on the belly of the tibialis anterior (TA) muscle. LLLT was performed daily with an AlGaAs laser (830 nm; beam spot of 0.0324 cm², output power of 100 mW, energy density of 180 J/cm², and 58-s exposure time). Animals were euthanized at 7, 14, and 21 days. The TA muscles were removed for gene expression analysis of TGF-β, Myogenin, and MyoD. The results were statistically analyzed at a significance level of 5%. The cryoinjury increased the expression of genes related to muscle regeneration-MyoD, Myogenin, and TGF-β-compared to the control group (p < 0.05); the photobiomodulation increased the expression of these genes at day 7 (p < 0.05), decreasing until day 21; and the aquatic exercise increases the expression of the three genes over time. When the two treatments were combined, the expression of the analyzed genes also increased over time. In summary, the results of our study suggest that photobiomodulation (LLLT), when applied alone in cryoinjury, is able to increase the gene expression of MyoD, Myogenin, and TGF-β at the acute phase, while when combined with aquatic exercises, there is an increase in expression of these genes specially at the long-term treatment.

Differential effects of photobiomodulation interval schedules on brain cytochrome c-oxidase and proto-oncogene expression

Significance: Transcranial photobiomodulation (PBM) is a noninvasive neuromodulation technique capable of producing changes in the mitochondrial cytochrome c-oxidase (CCO) activity of neurons. Although the application of PBM in clinical practice and as a neurophysiological tool is increasing, less is known about how different treatment time intervals may result in different outcomes. Aim: We evaluated the effects of different PBM treatment intervals on brain metabolic activity through the CCO and proto-oncogene expression (c-Fos). Approach: We studied PBM effects on brain CCO and c-Fos expression in three groups of animals: Control (CN, n = 8 ), long interval PBM treatment (LI, n = 5 ), and short interval PBM treatment (SI, n = 5 ). Results: Increased CCO activity in the LI group, compared to the SI and CN groups, was found in the prefrontal cortices, dorsal and ventral striatum, and hippocampus. Regarding c-Fos expression, we found a significant increase in the SI group compared to LI and CN, whereas LI showed increased c-Fos expression compared to CN in the cingulate and infralimbic cortices. Conclusions: We show the effectiveness of different PBM interval schedules in increasing brain metabolic activity or proto-oncogene expression.

Phototherapy as a Rational Antioxidant Treatment Modality in COVID-19 Management; New Concept and Strategic Approach: Critical Review

The COVID-19 pandemic has taken the entire globe by storm. The pathogenesis of this virus has shown a cytokine storm release, which contributes to critical or severe multi-organ failure. Currently the ultimate treatment is palliative; however, many modalities have been introduced with effective or minimal outcomes. Meanwhile, enormous efforts are ongoing to produce safe vaccines and therapies. Phototherapy has a wide range of clinical applications against various maladies. This necessitates the exploration of the role of phototherapy, if any, for COVID-19. This critical review was conducted to understand COVID-19 disease and highlights the prevailing facts that link phototherapy utilisation as a potential treatment modality for SARS-CoV-2 viral infection. The results demonstrated phototherapy's efficacy in regulating cytokines and inflammatory mediators, increasing angiogenesis and enhancing healing in chronic pulmonary inflammatory diseases. In conclusion, this review answered the following research question. Which molecular and cellular mechanisms of action of phototherapy have demonstrated great potential in enhancing the immune response and reducing host-viral interaction in COVID-19 patients? Therefore, phototherapy is a promising treatment modality, which needs to be validated further for COVID-19 by robust and rigorous randomised, double blind, placebo-controlled, clinical trials to evaluate its impartial outcomes and safety.

Effect of photobiomodulation therapy on radiodermatitis in a mouse model: an experimental animal study

This study aimed to evaluate the effect of photobiomodulation (PBM) for prevention of radiodermatitis in an irradiated mouse model and compare the efficacy of PBM using 633- or 830-nm wavelengths. Irradiated mice were randomly distributed into three groups: A (633 nm), B (830 nm), and C (without PBM). On post-irradiation days 7 and 21, we compared acute damage and recovery in treated skin samples to non-irradiated skin using H&E, Masson's trichrome, anti-CD45 and PCNA immunohistochemistry, and a TUNEL assay. Grade 3 radiodermatitis was evident only in group C. Compared with that in group C, the skin in groups A and B had significantly less epidermal hyperplasia, inflammatory cell infiltration, and thinner dermis on day 7 and less inflammatory cell infiltration, fewer apoptotic cells, and thinner dermis on day 21. However, there was no significant difference between groups A and B. This study indicates PBM could prevent severe radiodermatitis by reducing epidermal and dermal damage, inflammation, and apoptosis. There was no difference in PBM efficacy between the 633- and 830-nm wavelengths.

Light-emitting diode irradiation induces AKT/mTOR-mediated apoptosis in human pancreatic cancer cells and xenograft mouse model

The beneficial effects of light-emitting diode (LED) irradiation have been reported in various pathologies, including cancer. However, its effect in pancreatic cancer cells remains unclear. Herein, we demonstrated that blue LED of 460 nm regulated pancreatic cancer cell proliferation and apoptosis by suppressing the expression of apoptosis-related factors, such as mutant p53 and B-cell lymphoma 2 (Bcl-2), and decreasing the expression of RAC-β serine/threonine kinase 2 (AKT2), the phosphorylation of protein kinase B (AKT), and mammalian target of rapamycin (mTOR). Blue LED irradiation also increased the levels of cleaved poly-(ADP-ribose) polymerase (PARP) and caspase-3 in pancreatic cancer cells, while it suppressed AKT2 expression and inhibited tumor growth in xenograft tumor tissues. In conclusion, blue LED irradiation suppressed pancreatic cancer cell and tumor growth by regulating AKT/mTOR signaling. Our findings indicated that blue LEDs could be used as a nonpharmacological treatment for pancreatic cancer.

ILIB (intravascular laser irradiation of blood) as an adjuvant therapy in the treatment of patients with chronic systemic diseases-an integrative literature review

To perform an integrative review of the literature on the effectiveness of intravascular laser irradiation of blood (ILIB) as an adjunct therapy in the treatment of chronic systemic diseases. This is an integrative literature review that included non-randomized and randomized controlled clinical trials that specifically evaluated the therapeutic effect of ILIB on chronic systemic diseases, without restriction of time, and written in English. The Medical Publications (PubMed)/MEDLINE database was used. MeSH (Medical Subject Headings) was used to select search descriptors with the Boolean operators "AND/OR." After applying the inclusion and exclusion criteria, 13 articles were selected. Coronary diseases were the most prevalent, followed by type 2 diabetes mellitus, with the coronary artery being the most widely used access route for ILIB application. Despite the varied parameters and protocols for using this kind of therapy, all studies have shown satisfactory results in the patients' clinical condition. ILIB proved to be effective in all organic systems, showing some positive result. However, studies on the effect of this therapy on various diseases are still scarce in the literature, and there is a need for more well-designed clinical trials to better understand the role of ILIB in various systemic diseases.

Patterns of oral mucositis in advanced oral squamous cell carcinoma patients managed with prophylactic photobiomodulation therapy-insights for future protocol development

To characterize oral sites affected by radiation-induced oral mucositis (OM) and related clinical outcomes in oral cancer patients subjected to prophylactic photobiomodulation therapy (PBMT). This study included advanced oral squamous cell carcinoma (OSCC) patients treated with prophylactic PBMT for OM. The site distribution of OM, OM grading (CTCAE NCI, Version 4.0, 2010), OM-related pain (VAS), analgesic protocol (WHO Analgesic Ladder), and use of enteral nutrition were evaluated weekly during treatment. Data analysis was performed using descriptive statistics expressed as median values and percentages. A total of 145 OSCC patients were included. OM most frequently affected the lateral border of the tongue (44.1%), buccal mucosa (37.2%), and labial mucosa (33.8%). Keratinized oral mucosa sites, including the tongue dorsum (6.21%), retromolar trigone (8.3%), and hard palate (2.76%), were less frequently affected. Peak OM scores were observed at weeks 5, 6, and 7, with severe OM (NCI grades 3 and 4) rates of 11%, 20%, and 25%, respectively. The cumulative occurrence of severe OM was 23%, which developed as early as week 3 and as late as week 7. The highest mean value of OM-related pain (2.7) was observed at the sixth week, and 13.8% of the patients required feeding support. This study showed, compared with studies that did not provide PBMT, reduced severity of mucositis, reduced pain and analgesic use, and reduced tube feeding in patients treated with PBMT. OM involving keratinized and non-keratinized surfaces should be included in the prophylactic PBMT to reduce severe OM in future studies.

Does low-level laser therapy affect the survival of patients with head and neck cancer?

Low-level laser therapy (LLLT) is used in patients with head and neck cancer (HNC) for treatment-related mucositis. There is conflicting evidence as to whether LLLT leads to the proliferation of tumor cells and whether it interferes with the tumoricidal effect of radiotherapy or chemoradiotherapy, if the tumor lies within the LLLT field. Using fuzzy matching, 126 HNC patients who had received LLLT including the tumor region and 126 matching HNC patients without LLLT (controls) treated at the Department of Otorhinolaryngology, Head & Neck Surgery, Medical University of Innsbruck, were identified. The overall survival was compared using the Kaplan-Meier analysis. Fuzzy matching yielded 2 patient samples well comparable in terms of risk of death. The survival did not significantly differ between patients with and without LLLT (p = 0.18). An increased risk of death in HNC patients who received LLLT covering the tumor region was not observed in our study.

Prophylactic photobiomodulation therapy using 660 nm diode laser for oral mucositis in paediatric patients under chemotherapy: 5-year experience from a Brazilian referral service

The use of photobiomodulation therapy (PBMT) in the prevention of oral mucositis (OM) in paediatric care has increased. In this article, we report data of paediatric oncology/haematopoietic stem cell transplantation (HSCT) patients treated with PBMT to prevent chemotherapy-induced OM. A retrospective study was conducted at a Brazilian referral service. Prophylactic PBMT was used in children and adolescents (≤ 17 years) following the protocol: InGaAIP, 660 nm, 100 mW, 2 J, 3.33 W/cm², and 20 s per point. Demographic data and OM severity scores were assessed. A regression model tested the association between OM with prophylactic PBMT and antineoplastic therapy. A total of 148 individuals who had undergone 358 chemotherapy cycles were analysed. A higher occurrence of OM was observed in HSCT and osteosarcoma (OS) patients. Except for HSCT, OM was associated with methotrexate (MTX) use in all disease groups. PBMT significantly reduced OM severity in acute lymphoblastic leukaemia (ALL) and OS patients. OM grade was 3.16 and 5.45 times higher among individuals with ALL and OS, who had not undergone prophylactic PBMT compared with those who had undergone prophylactic PBMT (p < 0.001). PBMT prevented chemotherapy-induced OM. Individuals who used MTX and did not undergo prophylactic PBMT were at increased risk of OM.

Photobiomodulation-Underlying Mechanism and Clinical Applications

The purpose of this study is to explore the possibilities for the application of laser therapy in medicine and dentistry by analyzing lasers' underlying mechanism of action on different cells, with a special focus on stem cells and mechanisms of repair. The interest in the application of laser therapy in medicine and dentistry has remarkably increased in the last decade. There are different types of lasers available and their usage is well defined by different parameters, such as: wavelength, energy density, power output, and duration of radiation. Laser irradiation can induce a photobiomodulatory (PBM) effect on cells and tissues, contributing to a directed modulation of cell behaviors, enhancing the processes of tissue repair. Photobiomodulation (PBM), also known as low-level laser therapy (LLLT), can induce cell proliferation and enhance stem cell differentiation. Laser therapy is a non-invasive method that contributes to pain relief and reduces inflammation, parallel to the enhanced healing and tissue repair processes. The application of these properties was employed and observed in the treatment of various diseases and conditions, such as diabetes, brain injury, spinal cord damage, dermatological conditions, oral irritation, and in different areas of dentistry.

Effect of photobiomodulation on cellular migration and survival in diabetic and hypoxic diabetic wounded fibroblast cells

A disrupted wound repair process often leads to the development of chronic wounds, and pose a major physical, social and economic inconvenience on patients and the public health sector. Chronic wounds are a common complication seen in diabetes mellitus (DM), and often the severity necessitates amputation of the lower limbs. Recently, there has been increasing evidence that photobiomodulation (PBM) initiates wound healing, including increased protein transcription for cell proliferation, viability, migration and tissue reepithelialisation. Here, the hypothesis that PBM at a wavelength of 660 nm and energy density of 5 J/cm² regulates wound repair in diabetic wounded and hypoxic diabetic wounded fibroblasts by enhancing cell migration and survival was investigated. PBM increased migration and survival in diabetic wounded and hypoxic diabetic wounded fibroblasts. Our findings suggest that PBM enhances migration and survival in diabetic wounded and hypoxic diabetic wounded fibroblasts, indicating that this therapeutic method may be beneficial against chronic wounds in diabetic patients.

Learning Hemodynamic Effect of Transcranial Infrared Laser Stimulation Using Longitudinal Data Analysis

Transcranial infrared laser stimulation (TILS) is a promising noninvasive intervention for neurological diseases. Though some experimental work has been done to understand the mechanism of TILS, the reported statistical analysis of data is quite simple and could not provide a comprehensive picture on the effect of TILS. This study learns the effect of TILS on hemodynamics of the human brain from experimental data using longitudinal data analysis methods. Specifically, repeated measures analysis of variance (ANOVA) is first applied to confirm the significance of the TILS effect and its characteristics. Based on that, two parametric mixed-effect models and non-parametric functional mixed-effect model are proposed to model the population-level performance and individual variation of this effect. Interpretations on the fitted models are provided, and comparison of the three proposed models in terms of fitting and prediction performance is made to select the best model. According to the selected model, TILS increases the concentration of oxygenated hemoglobin in the brain and this effect sustains even after the treatment stops. Also, there is considerable variation among individual responses to TILS.

Photobiomodulation therapy increases functional capacity of patients with chronic kidney failure: randomized controlled trial

Photobiomodulation (PBM) has been used in different populations as a strategy to attenuate muscle fatigue and improve exercise performance. Recent findings demonstrated that a single session with specific PBM doses during hemodialysis (HD) increased the upper limb muscle strength of chronic kidney failure (CKF) patients. Now, the primary objective of this study was to evaluate the chronic effect of PBM on the functional capacity of this population. Secondarily, we aimed at investigating the effects of PBM on the patients' strength, muscle thickness and echogenicity, perception of pain, fatigue, and quality of life. A randomized controlled trial was conducted in which the intervention group (IG, n = 14) received 24 sessions of PBM (810 nm, 5 diodes × 200 mW, 30 J/application site) on lower limb during HD. The control group (CG, n = 14) did not receive any physical therapy intervention, it only underwent HD sessions. As a result, there was an increase in the functional capacity (assessed through the six-minute walk test) for the IG compared with the CG [50.7 m (CI95% 15.63; 85.72), p = 0.01, large effect size, d = 1.12], as well as an improvement on lower limb muscle strength (assessed through the sit-and-stand test) [- 7.4 s (CI95% - 4.54; - 10.37), p = 0.00, large effect size, d = 1.99]. For other outcomes evaluated, no significant difference between-group was observed. Finally, PBM applied as monotherapy for 8 weeks in the lower limb improves functional capacity and muscle strength of CKF patients.

Quantum biology in low level light therapy: death of a dogma

Background

It is shown that despite exponential increase in the number of clinically exciting results in low level light therapy (LLLT), scientific progress in the field is retarded by a wrong fundamental model employed to explain the photon-cell interaction as well as by an inadequate terminology. This is reflected by a methodological stagnation in LLLT, persisting since 1985. The choice of the topics is, by necessity, somewhat arbitrary. Obviously, we are writing more about the fields we know more about. In some cases, there are obvious objective reasons for the choice. Progress in LLLT is currently realized by a trial and error process, as opposed to a systematic approach based on a valid photon-cell interaction model.

Methods

The strategy to overcome the current problem consists in a comprehensive analysis of the theoretical foundation of LLLT, and if necessary, by introducing new interaction models and checking their validity on the basis of the two pillars of scientific advance (I) agreement with experiment and (II) predictive capability. The list of references used in this work, does contain a representative part of what has been done in the photon-cell interaction theory in recent years, considered as ascertained by the scientific community.

Results

Despite the immense literature on the involvement of cytochrome c oxidase (COX) in LLLT, the assumption that COX is the main mitochondrial photoacceptor for R-NIR photons no longer can be counted as part of the theoretical framework proper, at least not after we have addressed the misleading points in the literature. Here, we report the discovery of a coupled system in mitochondria whose working principle corresponds to that of field-effect transistor (FET). The functional interplay of cytochrome c (emitter) and COX (drain) with a nanoscopic interfacial water layer (gate) between the two enzymes forms a biological FET in which the gate is controlled by R-NIR photons. By reducing the viscosity of the nanoscopic interfacial water layers within and around the mitochondrial rotary motor in oxidatively stressed cells R-NIR light promotes the synthesis of extra adenosine triphosphate (ATP).

Conclusions

Based on the results of our own work and a review of the published literature, we present the effect of R-NIR photons on nanoscopic interfacial water layers in mitochondria and cells as a novel understanding of the biomedical effects R-NIR light. The novel paradigm is in radical contrast to the theory that COX is the main absorber for R-NIR photons and responsible for the increase in ATP synthesis, a dogma propagated for more than 20 years.

Transcranial Photobiomodulation (tPBM) With 1,064-nm Laser to Improve Cerebral Metabolism of the Human Brain In Vivo

BACKGROUND AND OBJECTIVES

In our previous proof-of-principle study, transcranial photobiomodulation (tPBM) with 1,064-nm laser was reported to significantly increase concentration changes of oxygenated hemoglobin (∆[HbO]) and oxidized-state cytochrome c oxidase (∆[oxi-CCO]) in the human brain. This paper further investigated (i) its validity in two different subsets of young human subjects at two study sites over a period of 3 years and (ii) age-related effects of tPBM by comparing sham-controlled increases of ∆[HbO] and ∆[oxi-CCO] between young and older adults.

STUDY DESIGN/MATERIALS AND METHODS

We measured sham-controlled ∆[HbO] and ∆[oxi-CCO] using broadband near-infrared spectroscopy (bb-NIRS) in 15 young (26.7 ± 2.7 years of age) and 5 older (68.2 ± 4.8 years of age) healthy normal subjects before, during, and after right-forehead tPBM/sham stimulation with 1,064-nm laser. Student t tests were used to test statistical differences in tPBM-induced ∆[HbO] and ∆[oxi-CCO] (i) between the 15 young subjects and those of 11 reported previously and (ii) between the two age groups measured in this study.

RESULTS

Statistical analysis showed that no significant difference existed in ∆[HbO] and ∆[oxi-CCO] during and post tPBM between the two subsets of young subjects at two study sites over a period of 3 years. Furthermore, the two age groups showed statistically identical net increases in sham-controlled ∆[HbO] and ∆[oxi-CCO].

CONCLUSIONS

This study provided strong evidence to validate/confirm our previous findings that tPBM with 1,064-nm laser enables to increase cerebral ∆[HbO] and ∆[oxi-CCO] in the human brain, as measured by bb-NIRS. Overall, it demonstrated the robust reproducibility of tPBM being able to improve cerebral hemodynamics and metabolism of the human brain in vivo in both young and older adults. Lasers Surg. Med. © 2020 The Authors. Lasers in Surgery and Medicine published by Wiley Periodicals, Inc.

Polarized light therapy: Shining a light on the mechanism underlying its immunomodulatory effects

This study investigates the immunomodulatory effects of polychromatic polarized light therapy (PLT) on human monocyte cells. While there is some evidence demonstrating a clinical effect in the treatment of certain conditions, there is little research into its mechanism of action. Herein, U937 monocyte cells were cultured and exposed to PLT. The cells were then analyzed for change in expression of genes and cell surface markers relating to inflammation. It was noted that 6 hours of PLT reduced the expression of the CD14, MHC I and CD11b receptors, and increased the expression of CD86. It was also shown that PLT caused downregulation of the genes IL1B, CCL2, NLRP3 and NOD1, and upregulation of NFKBIA and TLR9. These findings imply that PLT has the capacity for immunomodulation in human immune cells, possibly exerting an anti-inflammatory effect.

Insulin resistance is improved in high-fat fed mice by photobiomodulation therapy at 630 nm

Photobiomodulation therapy (PBMT) in the infrared spectrum exerts positive effects on glucose metabolism, but the use of PBMT at the red spectrum has not been assessed. Male Swiss albino mice were divided into low-fat control and high-fat diet (HFD) for 12 weeks and were treated with red (630 nm) PBMT or no treatment (Sham) during weeks 9 to 12. PBMT was delivered at 31.19 J/cm² , 60 J total dose per day for 20 days. In HFD-fed mice, PBMT improved glucose tolerance, insulin resistance and fasting hyperinsulinemia. PBMT also reduced adiposity and inflammatory infiltrate in adipose tissue. Phosphorylation of Akt in epididymal adipose tissue and rectus femoralis muscle was improved by PBMT. In epididymal fat PBMT reversed the reduced phosphorylation of AS160 and the reduced Glut4 content. In addition, PBMT reversed the alterations caused by HFD in rectus femoralis muscle on proteins involved in mitochondrial dynamics and β-oxidation. In conclusion, PBMT at red spectrum improved insulin resistance and glucose metabolism in HFD-fed mice.

High-throughput single-cell live imaging of photobiomodulation with multispectral near-infrared lasers in cultured T cells

SIGNIFICANCE

Photobiomodulation is a well-established therapeutic modality. However, the mechanism of action is poorly understood, due to lack of research in the causal relationship between the near-infrared (NIR) light irradiation and its specific biological effects, hindering broader applications of this technology.

AIM

Since biological chromophores typically show several absorption peaks, we determined whether specific effects of photobiomodulation are induced with a combination of two wavelengths at a certain range of irradiance only, rather than a single wavelength of NIR light.

APPROACH

In order to analyze a wide array of combinations of multispectral NIR light at various irradiances efficiently, we developed a new optical platform equipped with two distinct wavelengths of NIR lasers by high-throughput multiple dosing for single-cell live imaging. Two wavelengths of 1064 and 1270 nm were selected based on their photobiomodulatory effects reported in the literature.

RESULTS

A specific combination of wavelengths at low irradiances (250 to 400  mW  /  cm2 for 1064 nm and 55 to 65  mW  /  cm2 for 1270 nm) modulates mitochondrial retrograde signaling, including intracellular calcium and reactive oxygen species in T cells. The time-dependent density functional theory computation of binding of nitric oxide (NO) to cytochrome c oxidase indicates that the illumination with NIR light could result in the NO release, which might be involved in these changes.

CONCLUSIONS

This optical platform is a powerful tool to study causal relationship between a specific parameter of NIR light and its biological effects. Such a platform is useful for a further mechanistic study on not only photobiomodulation but also other modalities in photomedicine.

Photobiomodulation therapy in knee osteoarthritis reduces oxidative stress and inflammatory cytokines in rats

Knee osteoarthritis (OA) is a chronic disease that causes pain and gradual degeneration of the articular cartilage. In this study, MIA-induced OA knee model was used in rats to test the effects of the photobiomodulation therapy (PBM). We analyzed the inflammatory process (pain and cytokine levels), and its influence on the oxidative stress and antioxidant capacity. Knee OA was induced by monosodium iodoacetate (MIA) intra-articular injection (1.5 mg/50 μL) and the rats were treated with eight sessions of PBM 3 days/week (904 nm, 6 or 18 J/cm² ). For each animal, mechanical and cold hyperalgesia and spontaneous pain were evaluated; biological analyses were performed in blood serum, intra-articular lavage, knee structures, spinal cord and brainstem. Cytokine assays were performed in knee, spinal cord and brainstem samples. The effects of the 18 J/cm² dose of PBM were promising in reducing pain and neutrophil activity in knee samples, together with reducing oxidative stress damage in blood serum and spinal cord samples. PBM improved the antioxidant capacity in blood serum and brainstem, and decreased the knee pro-inflammatory cytokine levels. Our study demonstrated that PBM decreased oxidative damage, inflammation and pain. Therefore, this therapy could be an important tool in the treatment of knee OA.

Laser photobiomodulation for cartilage defect in animal models of knee osteoarthritis: a systematic review and meta-analysis

To review and assess the efficacy of laser photobiomodulation for cartilage defect in animal models of knee osteoarthritis (KOA). Medline, Web of Science, and EMBASE were searched. Studies were considered if the global quality score of cartilage were parallelly reported between laser and untreated control groups. The methodological quality of each study was assessed using a modified 10-item checklist. The effect size was estimated by standardized mean difference (SMD) and pooled based on the random-effects model. Stratified analysis and regression analysis were conducted to partition potential heterogeneity. An adjusted significant level of 0.01 was acceptable. Five hundred eight initial search recordings were identified, of which 14 studies (including 274 animals) were included for quantitative analysis. The global quality scores mostly weighted by the structural integrity and chondrocyte distribution were measured by different four scales including Histologic Histochemical Grading System (HHGS), Osteoarthritis Research Society International (OARSI), Pineda, and Huang. There were considerable variances on laser parameters and irradiation time among those included studies. Overall, a moderate level of methodological qualities was determined. The synthesis results indicated that the SMD effect size was significantly larger in HHGS (z = 2.61, P = 0.01) and Huang (z = 4.90, P < 0.01) groups. Stratified by irradiance, SMD of low (< 1 W/cm²) but not high (≥ 1 W/cm²) level estimated significant difference (z = 5.62, P < 0.01). Meta-regression identified a significant association for SMDs and irradiation time (P < 0.01). Yet, Egger's test detected small study effect (P < 0.01). No individual study with significant variance was found in homogeneity tests. The results demonstrated the positive effect of laser photobiomodulation for cartilage defect in animal models of KOA under proper irradiance and adequate irradiation time.

Energy-dependent effect trial of photobiomodulation on blood pressure in hypertensive rats

The main purpose of this work was to construct an energy-dependent response curve of photobiomodulation on arterial pressure in hypertension animal model. To reach this objective, we have used a two-kidney one clip (2K-1C) rat model. Animals received acute laser light irradiation (660 nm) on abdominal region using different energy (0.6, 1.8, 3.6, 7.2, 13.8, 28.2, 55.8, and 111.6 J), the direct arterial pressure was measured by femoral cannulation, and systolic arterial pressure (SAP), diastolic arterial pressure (DAP), heart rate (HR), and time of effect were obtained. Our results indicated that 660 nm laser light presents an energy-dependent hypotensive effect, and 28.2 J energy irradiation reached the maximum hypotensive effect, inducing a decreased SAP, DAP, and HR (decrease in SAP: - 19.23 ± 1.82 mmHg, n = 11; DAP: - 9.57 ± 2.23 mmHg, n = 11; HR: - 39.15 ± 5.10 bpm, n = 11; and time of hypotensive effect: 3068.00 ± 719.00 s, n = 11). The higher energy irradiation evaluated (111.6 J) did not induce a hypotensive effect and induced an increase in HR (21.69 ± 7.89 bpm, n = 7). Taken together, our results indicate that red laser energy irradiation from 7.2 to 55.8 J is the effective therapeutic window to reduce SAP, DAP, MAP, and HR and induce a long-lasting hypotensive effect in rats, with effect loss at higher energy irradiation (111.6 J).

Low-level laser therapy improves pain in postcesarean section: a randomized clinical trial

This study aimed to evaluate the effect of low-level laser therapy (LLLT) on immediate postpartum pain relief during cesarean section. A randomized, parallel controlled trial was carried out. In total, 88 women with immediate postpartum were divided into 4 groups: control group (n = 22), placebo group (n = 22), experimental group I (n = 22, dose of 4 J/cm²), and experimental group II (n = 22, dose of 2 J/cm²). The pain measured by Numeric Rating Scale (NRS), algometry, and Global Change Perception Scale (GCPS) was assessed at 12, 20-24, and 44-48 h postpartum. Two LLLT sessions were performed at 12 and 24 h postpartum. A significant interaction was observed between time versus group for NRS F (2.40) = 36.80, p < 0.001 and algometry F (1.70) = 27.18, p < 0.001. GCPS revealed a significant difference between the groups during second (p = 0.04) and third evaluation (p = 0.04). The NRS and algometry presented a large effect size for the experimental groups. LLLT is an efficient method to reduce pain and enhance the GCP in postcesarean section. No significant clinical differences were found between the laser doses.

Acute effects of photobiomodulation therapy applied to respiratory muscles of chronic obstructive pulmonary disease patients: a double-blind, randomized, placebo-controlled crossover trial

To investigate the effects of photobiomodulation applied to respiratory muscles on lung function, thoracoabdominal mobility, respiratory muscle strength, and functional capacity in COPD patients. This is a randomized double-blind crossover clinical trial. Twelve male COPD patients participated in the study. Participants were randomly allocated to receive two photobiomodulation sessions, 1 week apart: (1) an effective photobiomodulation session applied at the main respiratory muscles by means of a cluster with 69 light-emitting diodes (LEDs), containing 35 red (630 ± 10 nm; 10 mW; 0.2 cm²) and 34 near-infrared (830 ± 20 nm; 10 mW; 0.2 cm²) LEDs and (2) a sham photobiomodulation session, following the same procedures without emitting light. The primary outcomes were pulmonary function (spirometric indexes); thoracoabdominal mobility (cirtometry); respiratory muscle strength (maximal respiratory pressures), assessed at three moments: (1) baseline, (2) 1 h after intervention, and (3) 24 h after intervention; and the functional capacity, assessed by the 6-min walk test (6MWT) at baseline and 24 h after intervention. No significant interactions were found for spirometric variables, maximal respiratory pressures, and cirtometry. However, there was a Time × Condition interaction (F = 18.63; p = 0.001; η²_p = 0.62) in the walked distance on the 6MWT, with a significant increase after photobiomodulation intervention (p < 0.01) compared with the baseline. Photobiomodulation applied to respiratory muscles was effective in improving acute functional capacity in COPD patients. To the best of our knowledge, this is the first study assessing the effects of photobiomodulation applied to respiratory muscles in patients with COPD.

Cognitive Enhancement by Transcranial Photobiomodulation Is Associated With Cerebrovascular Oxygenation of the Prefrontal Cortex

Transcranial infrared laser stimulation (TILS) is a novel, safe, non-invasive method of brain photobiomodulation. Laser stimulation of the human prefrontal cortex causes cognitive enhancement. To investigate the hemodynamic effects in prefrontal cortex by which this cognitive enhancement occurs, we used functional near-infrared spectroscopy (fNIRS), which is a safe, non-invasive method of monitoring hemodynamics. We measured concentration changes in oxygenated and deoxygenated hemoglobin, total hemoglobin and differential effects in 18 healthy adults during sustained attention and working memory performance, before and after laser of the right prefrontal cortex. We also measured 16 sham controls without photobiomodulation. fNIRS revealed large effects on prefrontal oxygenation during cognitive enhancement post-laser and provided the first demonstration that cognitive enhancement by transcranial photobiomodulation is associated with cerebrovascular oxygenation of the prefrontal cortex. Sham control data served to rule out that the laser effects were due to pre-post task repetition or other non-specific effects. A laser-fNIRS combination may be useful to stimulate and monitor cerebrovascular oxygenation associated with neurocognitive enhancement in healthy individuals and in those with prefrontal hypometabolism, such as in cognitive aging, dementia and many neuropsychiatric disorders.

Effects of a single treatment with two nonthermal laser wavelengths on chronic neck and shoulder pain

Introduction

Nonthermal lasers provide pain relief for a variety of musculoskeletal disorders and improve physical functioning. A nonthermal laser that employs a 635 nm red diode is cleared for the temporary reduction of neck and shoulder pain of musculoskeletal origin. As a 405 nm violet laser has shown synergy with the 635 nm red laser when used together for treating other conditions, the objective of this study was to compare the efficacy of 635 nm red and 405 nm violet lasers vs the 635 nm red laser for treating neck and shoulder pain of musculoskeletal origin.

Materials and methods

Otherwise healthy adult subjects with chronic neck or shoulder pain for ≥30 days were enrolled and randomized to receive a single 13-min treatment with combined red and violet lasers (n=44) or the red laser alone (n=43). The primary efficacy measure was change in baseline VAS pain scores 3 mins after treatment. Subject success was predefined as a ≥30% decrease in VAS scores and study success was predefined as 65±5% individual subject successes.

Results

Among subjects treated with the red and violet lasers, mean VAS neck and shoulder pain scores decreased from 65.0 to 35.2 (p<0.0001). Most subjects in the study (75%) achieved ≥30% decrease in VAS scores. The decreased mean (SD) VAS scores remained 29.6 (16.7) and 29.3 (19.2) after 24 and 48 hrs, respectively. The secondary efficacy measures of change in range of motion ROM) and patient satisfaction also improved. There were no adverse events.

Conclusion

Overall, treatment with the red and violet lasers outperformed the FDA-approved red laser with respect to change in pain scores and improvement in shoulder ROM.

Photobiomodulation for Alzheimer's Disease: Has the Light Dawned?

Next to cancer, Alzheimer's disease (AD) and dementia is probably the most worrying health problem facing the Western world today. A large number of clinical trials have failed to show any benefit of the tested drugs in stabilizing or reversing the steady decline in cognitive function that is suffered by dementia patients. Although the pathological features of AD consisting of beta-amyloid plaques and tau tangles are well established, considerable debate exists concerning the genetic or lifestyle factors that predispose individuals to developing dementia. Photobiomodulation (PBM) describes the therapeutic use of red or near-infrared light to stimulate healing, relieve pain and inflammation, and prevent tissue from dying. In recent years PBM has been applied for a diverse range of brain disorders, frequently applied in a non-invasive manner by shining light on the head (transcranial PBM). The present review discusses the mechanisms of action of tPBM in the brain, and summarizes studies that have used tPBM to treat animal models of AD. The results of a limited number of clinical trials that have used tPBM to treat patients with AD and dementia are discussed.

Light-emitting diode irradiation using 660 nm promotes human fibroblast HSP90 expression and changes cellular activity and morphology

We evaluated changes in cell viability and morphology in response to low-level light irradiation and underlying variations in the levels of heat shock proteins (HSPs). Human fibroblasts were irradiated with a light-emitting diode (LED) array at 660 nm (50 mW for 15, 30, and 60 minutes). Cell viability and morphological changes were evaluated via epifluorescence analysis; we also assessed cell viability and length changes. The expression levels of adenosine triphosphate (ATP) and various HSPs (HSP27, 60, 70, and 90) were analyzed by immunohistochemical staining, Western blotting and microarray analysis. After LED irradiation, cellular viability and morphology changed. Of the several HSPs analyzed, the HSP90 level increased significantly, suggesting that this protein played roles in the morphological and cellular changes. Thus, low-level irradiation triggered cellular changes mediated by increased HSP90 expression; this may explain why skin irradiation enhances wound-healing.

1064 nm Nd:YAG laser light affects transmembrane mitochondria respiratory chain complexes

Photobiomodulation (PBM) is a non-plant-cell manipulation through a transfer of energy by means of light sources at the non-ablative or thermal intensity. Authors showed that cytochrome-c-oxidase (complex IV) is the specific chromophore's target of PBM at the red (600-700 nm) and NIR (760-900 nm) wavelength regions. Recently, it was suggested that the infrared region of the spectrum could influence other chromospheres, despite the interaction by wavelengths higher than 900 nm with mitochondrial chromophores was not clearly demonstrated. We characterized the interaction between mitochondria respiratory chain, malate dehydrogenase, a key enzyme of Krebs cycle, and 3-hydroxyacyl-CoA dehydrogenase, an enzyme involved in the β-oxidation (two mitochondrial matrix enzymes) with the 1064 nm Nd:YAG (100mps and 10 Hz frequency mode) irradiated at the average power density of 0.50, 0.75, 1.00, 1.25 and 1.50 W/cm² to generate the respective fluences of 30, 45, 60, 75 and 90 J/cm² . Our results show the effect of laser light on the transmembrane mitochondrial complexes I, III, IV and V (adenosine triphosphate synthase) (window effects), but not on the extrinsic mitochondrial membrane complex II and mitochondria matrix enzymes. The effect is not due to macroscopical thermal change. An interaction of this wavelength with the Fe-S proteins and Cu-centers of respiratory complexes and with the water molecules could be supposed.

Photobiomodulation effect on local hemoglobin concentration assessed by near-infrared spectroscopy in humans

Exposure of biological tissue to photobiomodulation therapy (PBMT) seems to increase the oxygen availability and mitochondrial electrochemical activity. With the advancement of new technologies, such as near-infrared spectroscopy (NIRS), information can be obtained about the balance between oxygen utilization and delivery by assessing local oxy- ([O₂Hb]) and deoxy-myohemoglobin ([HHb]) concentrations, both measured in micromolars (μM). Consequently, NIRS can be used to study ("in vivo") PBMT effects on the oxidative system, including oxygen availability. Thus, the main objective of the present study was to use NIRS to investigate the acute effects of PBMT by light-emitting diode (LED) on the oxygen delivery and utilization in humans. Twelve healthy young participants were treated with a LED device (850 nm, 50 mW, 2 J) and placebo applied over the proximal third of the flexor carpi ulnaris muscle of the left or right forearm selected in a random order. The LED was applied in direct contact with skin and the device was switched on for 40 s in 4 different interventions (I₁, I₂, I₃ and I₄) with a 3-min interval between interventions. The placebo condition was considered as the period before the first PBMT. The NIRS device was used to evaluate the relative changes in [O₂Hb] and [HHb] before and after placebo and interventions. We found that PBMT statistically increased the [O₂Hb] in 0.39 μM. These results demonstrate the potential of PBMT to increase oxygen availability.

Assessment of photobiomodulation therapy by an 8l0-nm diode laser on the reversal of soft tissue local anesthesia in pediatric dentistry: a preliminary randomized clinical trial

During the injection of local anesthesia in pediatric dental procedures, from the injection time until the elimination of tissue anesthesia, inevitable problems were reported. According to the encouraging results of previous studies addressing the positive effects of laser therapy on increasing the microcirculation, we aimed to investigate the clinical effect of photobiomodulation therapy on the reversal of soft tissue anesthesia in children. Using a split-mouth design, 34 children aged 4 to 8 years old, candidate for receiving local infiltration injection at both right and left side in mandible, were enrolled in the study. The mandibular right and left quadrants were randomly assigned to groups of laser or sham laser: in laser side, patients received 810-nm laser irradiation, and in the sham laser group, the patients had the laser in off mode at 45 min after injection with an interval of 7-10 days between two sessions of each quadrant treatments. The degree of anesthesia was evaluated using the palpation technique alternately every 15 min. Data were analyzed using paired sample t test and multiple linear regression test. The mean duration of anesthesia expressed in minutes was equal to 145.15 ± 23.27 and 188.82 ± 12.31 for the laser group and sham laser group, respectively. There was a significant difference in duration of anesthesia between two groups (P < 0.001). Considering the results and limitations of the present study, photobiomodulation therapy by 810-nm diode laser can be proposed as a non-invasive method in order to reduce the duration of anesthesia in pediatric patients.

Effect of single and multiple doses of low-level laser therapy on viability and proliferation of stem cells from human exfoliated deciduous teeth (SHED)

The present study aimed to evaluate in vitro whether the low-level laser (LLL) delivering fractionated total energy (multiple irradiation) or single irradiation stimulates regeneration-associated events (viability and proliferation) in stem cells from human exfoliated deciduous teeth (SHED). Cells received LLL irradiation (InGaAlP-660 nm), according to the following experimental groups: G1 (single irradiation 2.5 J/cm², 10 mW, 10 s, 0.10 J), G2 (single irradiation 5.0 J/cm², 10 mW, 20 s, 0.20 J), G3 (single irradiation 7.5 J/cm², 10 mW, 30 s, 0.30 J), G4 (two irradiations 2.5 J/cm², 10 mW, 10 s; total energy 0.20 J), G5 (three irradiations 2.5 J/cm², 10 mW, 10 s; total energy 0.30 J), and G6 (non-irradiated). Cell viability was assessed by MTT and trypan blue exclusion (TBE) methods, while cell proliferation was evaluated by crystal violet (CV) and sulforhodamine B (SRB) assays after 24, 48, and 72 h after the first irradiation. By MTT, there was no difference between groups at 24 and 72 h. At 48 h, the groups subjected to multiple irradiation (G4 and G5) presented higher cell viability rates. The average percentages of viable cells for all groups by TBE method were 91.04%, 96.63%, and 97.48% at 24, 48, and 72 h, respectively. By CV, there was no significant difference between groups at 24 and 48 h; at 72 h, G2, G3, and G4 presented higher cell proliferation. By SRB, G1 and G4 presented lower proliferation rates in all the periods. When the groups presenting the same total energy were compared, G2 (0.20 J) presented lower cell viability rates and higher cell proliferation rates in comparison with G4; G3 (0.30 J) presented similar results to those of G5, with higher cell viability and proliferation. The application of laser delivering fractionated total energy (two or three applications of 2.5 J/cm²) induced higher cell viability at 48 h, while the single irradiation with 2.5 J/cm² did not stimulate metabolic activity in such period and the proliferation over time. The 5.0 and 7.5 J/cm² single doses and the three applications of 2.5 J/cm² maintained cell viability and stimulated proliferation of SHED at 72 h.