Low intensity light stimulates nitrite-dependent nitric oxide synthesis but not oxygen consumption by cytochrome c oxidase: Implications for phototherapy

Cardio-metabolic health and sleep quality in adults at risk for Type 2 Diabetes using the Fos Biomedical Non-Transdermal Patch System via photo-biomodulation: A randomized, placebo-controlled crossover trial

Background

The impact of the Fos Biomedical non-transdermal patch system (NTPS) that stimulates the skin with low light levels to generate photo-biomodulation (PBM) effects on cardio-metabolic health and sleep quality is unclear. We examined the impact of FBPS compared with placebo on cardio-metabolic risk and sleep quality in persons at risk for type 2 diabetes mellitus (T2DM).

Methods

The study was a randomized, controlled, double-blind, crossover trial of 39 adults (mean age 64.4 years; 28 women, 11 men; 38 Caucasians, 1 African American) at risk for T2DM assigned to one of two possible sequence permutations of two treatments (Fos Biomedical NTPS and placebo), with an 8-week washout period. Fos Biomedical NTPSs are designed to stimulate the skin with low light levels to produce PBM effects. Participants were instructed to apply the active or placebo patches above and below the belly button for 12 h each day for 12 weeks. Primary outcome measure was glycated hemoglobin (HbA1c). Secondary outcome measures included insulin sensitivity, lipid profile, blood pressure, body composition, C-reactive protein, endothelial function, and sleep quality.

Results

Compared with the placebo, the Fos Biomedical NTPS did not improve glycemic control: HbA1c (0.1 ± 0.2 % vs. 0.1 ± 0.2 %; p = 0.5154). Compared with placebo, Fos Biomedical NTPS reduced endothelial function (-1.7 ± 12.1 % vs. 3.9 ± 10.0 %; p = 0.0344) while other markers of cardiovascular risk (i.e., body composition, blood pressure, lipid profile, and inflammatory biomarker) and sleep quality were unaffected (p > 0.05).

Conclusions

Photo-biomodulation generated from Fos Biomedical NTPS did not improve biomarkers of cardio-metabolic risk and sleep quality among those at risk for T2DM.

Clinical trial registration number

NCT05628597.

ACUTE ATROPHIC EVOLUTION OF DRUSENOID PIGMENT EPITHELIUM DETACHMENT AFTER PHOTOBIOMODULATION

PURPOSE

The aim of this study was to report the acute onset of macular atrophy soon after photobiomodulation (PBM) administration in a patient with intermediate age-related macular degeneration.

METHODS

Optical coherence tomography was performed in the study eye before and after PBM.

RESULTS

A patient with drusenoid pigment epithelium detachment (D-PED) underwent PBM. A few weeks after PBM, the D-PED collapsed, resulting in complete retinal pigment epithelium and outer retinal atrophy with visual acuity worsening.

CONCLUSION

Thinning of the outer retinal layers over a D-PED and posterior hypertransmission may represent bad prognostic factors for PBM, accelerating the lesion's natural history toward atrophic evolution.

Short-term effectiveness and safety of photobiomodulation on low-to-moderate myopia

To find and assess the effectiveness and safety of short-term Photobiomodulation (PBM) treatment in children with low-to-moderate myopia. Children with low-to-moderate myopia were recruited and divided into PBM or control groups based on whether they received PBM treatment. The PBM group underwent a three-month treatment with a 650 nm low-energy semiconductor laser, while the control group did not receive any therapeutic intervention. At the end of the trial, the changes in spherical equivalent refractive (SER) and axial length (AL) before and after treatment were compared between the PBM group and the control group to evaluate the effectiveness of PBM in preventing myopia. The best corrected visual acuity (BCVA), nerve fiber layer thickness (RNFLT), ganglion cell layer thickness (GCLT), central point retinal thickness (CPRT), 3-mm subfield central retinal thickness (3 mm-CRT), superficial retinal vascular density (SCP), and central choroid thickness (CCT) were self-compared to assess the safety of PBM. A total of 57 subjects were prospectively followed from October 2020 to September 2021, comprising 28 participants (56 eyes) in the PBM group and 29 participants (58 eyes) in the control group. After three months of treatment, the AL decreased by 0.07 ± 0.11 mm, and the SER decreased by -0.12 ± 0.39 D in the PBM group. However, both SER and AL increased in the control group. Furthermore, there were statistically significant differences between the PBM and control groups (p < 0.01). The BCVA, RNFLT, GCLT, CPRT, and 3 mm-CRT remained almost unchanged in the PBM group; The SCP decreased from 0.37 ± 0.03 to 0.35 ± 0.02 in the PBM group with a statistically significant difference before and after treatment (p = 0.045). The CCT increased from 255 ± 41 µm to 274 ± 29 µm in the PBM group without any significant difference before and after treatment. The administration of PBM significantly suppresses the elevation of AL and SER following a three-month duration. No significant adverse effects were observed on visual function and retinal morphology.Trial Registration: This study is registered at https://clinicaltrials.gov/ (registration number: NCT04604405).

Pulsed Red Photobiomodulation Boosts the Inhibition of Oxytocin-Induced Primary Dysmenorrhea in Mice by Suppressing Oxidative Stress and Inflammation

Increasing evidence has underscored the pivotal role of red photobiomodulation (R-PBM) in analgesic and anti-inflammatory processes; nonetheless, research concerning the effects of pulsed wave on primary dysmenorrhea (PD) remains sparse. This study found that pulsed R-PBM significantly diminished pain responses and levels of PGF2α/PGE2, mitigated uterine swelling, augmented antioxidant capacity, and lowered MDA concentrations, which outperformed continuous wave at the same average irradiance. Furthermore, PW treatment substantially reduced ROS levels and enhanced cell viability in PGF2α induced HUSM cells. NOS levels, especially iNOS, were markedly diminished in the uteri of PD mice, accompanied by significant alterations in inflammation-related genes (Jun, Fos, IL1rn, IL17b) and protein levels, along with pronounced downregulation of calcium ion concentrations after pulsed R-PBM intervention. These findings indicated that pulsed R-PBM may mitigate pain by modulating ROS and NO/NOS, mediated oxidative stress and inflammatory responses. Consequently, pulsed R-PBM emerges as a promising therapeutic strategy for PD.

Photobiomodulation for diabetes and its complications: a review of general presentation, mechanisms and efficacy

Diabetes mellitus is a metabolic disease that is marked by persistent hyperglycemia due to inadequate insulin secretion or insulin resistance. Its prevalence is increasing yearly. Diabetes mellitus can lead to serious health complications that are the primary cause of mortality and disability among diabetic patients, including diabetic retinopathy, diabetic foot ulcers, diabetic peripheral neuropathy, and diabetic periodontitis, and so on. Traditional treatments for diabetes and its complications still suffer from limited clinical efficacy and high therapeutic side effects. Photobiomodulation (PBM), which utilizes low levels of red or near-infrared laser to irradiate cells and tissues, has been shown to be efficacious for a wide range of organ damage. In this study, we focus on the application of PBM in diabetes and its complications and mechanisms, as well as the advantages, disadvantages with the aim of developing new ideas for the application of PBM.

40 Hz light preserves synaptic plasticity and mitochondrial function in Alzheimer's disease model

Alzheimer's disease (AD) is the most prevalent type of dementia. Its causes are not fully understood, but it is now known that factors like mitochondrial dysfunction, oxidative stress, and compromised ion channels contribute to its onset and progression. Flickering light therapy has shown promise in AD treatment, though its mechanisms remain unclear. In this study, we used a rat model of streptozotocin (STZ)-induced AD to evaluate the effects of 40 Hz flickering light therapy. Rats received intracerebroventricular (ICV) STZ injections, and 7 days after, they were exposed to 40 Hz flickering light for 15 min daily over seven days. Cognitive and memory functions were assessed using Morris water maze, novel object recognition, and passive avoidance tests. STZ-induced AD rats exhibited cognitive decline, elevated reactive oxygen species, amyloid beta accumulation, decreased serotonin and dopamine levels, and impaired mitochondrial function. However, light therapy prevented these effects, preserving cognitive function and synaptic plasticity. Additionally, flickering light restored mitochondrial metabolites and normalized ATP-insensitive mitochondrial calcium-sensitive potassium (mitoBKCa) channel activity, which was otherwise downregulated in AD rats. Our findings suggest that 40 Hz flickering light therapy could be a promising treatment for neurodegenerative disorders like AD by preserving synaptic and mitochondrial function.

Long-term safety of photobiomodulation exposure to beta cell line and rat islets in vitro and in vivo

This study evaluates the safety and potential benefits of PBM on pancreatic beta cells and islets. PBM was applied to insulin-secreting cell lines (MIN6) and rat pancreatic islets using a 670 nm light source, continuous output, with a power density of 2.8 mW/cm², from 5 s to several 24 h. Measure of cell viability, insulin secretion, mitochondrial function, ATP content, and cellular respiration were assessed. Additionally, a diabetic rat model is used for islet transplantation (pre-conditioning with PBM or not) experiments. Short and long-term PBM exposure did not affect beta cell islets viability, insulin secretion nor ATP content. While short-term PBM (2 h) increases superoxide ion content, this was not observed for long exposure (24 h). Mitochondrial respirations were slightly decreased after PBM. In the islet transplantation model, both pre-illuminated and non-illuminated islets improved metabolic control in diabetic rats with a safety profile regarding the post-transplantation period. In summary, for the first time, long-term PBM exhibited safety in terms of cell viability, insulin secretion, energetic profiles in vitro, and post-transplantation period in vivo. Further investigation is warranted to explore PBM's protective effects under conditions of stress, aiding in the development of innovative approaches for cellular therapy.

Photobiomodulation use in ophthalmology - an overview of translational research from bench to bedside

Photobiomodulation (PBM) refers to the process in which wavelengths of light are absorbed by intracellular photoacceptors, resulting in the activation of signaling pathways that culminate in biological changes within the cell. PBM is the result of low-intensity light-induced reactions in the cell in contrast to thermal photoablation produced by high-intensity lasers. PBM has been effectively used in the clinic to enhance wound healing and mitigate pain and inflammation in musculoskeletal conditions, sports injury, and dental applications for many decades. In the past 20 years, experimental evidence has shown the benefit of PBM in increasing numbers of retinal and ophthalmic conditions. More recently, preclinical findings in ocular models have been translated to the clinic with promising results. This review discusses the preclinical and clinical evidence of the effects of PBM in ophthalmology and provides recommendations of the clinical use of PBM in the management of ocular conditions.

Experimental study on the safety of photobiologic regulation therapy in the treatment of some non-epidermal tumors

This study investigates the impact of Photobiomodulation (PBM) at different wavelengths on non-superficial cancer cells. Utilizing three laser protocols (650 nm, 810 nm, and 915 nm), the research explores cytotoxic effects, ROS generation, and cell migration. Results reveal varied responses across cell lines, with 810 nm PBM inducing significant ROS levels and inhibiting PAN-1 cell migration. The study suggests potential therapeutic applications for PBM in non-superficial cancers, emphasizing the need for further exploration in clinical settings.

Photobiomodulation Therapy on Brain: Pioneering an Innovative Approach to Revolutionize Cognitive Dynamics

Photobiomodulation (PBM) therapy on the brain employs red to near-infrared (NIR) light to treat various neurological and psychological disorders. The mechanism involves the activation of cytochrome c oxidase in the mitochondrial respiratory chain, thereby enhancing ATP synthesis. Additionally, light absorption by ion channels triggers the release of calcium ions, instigating the activation of transcription factors and subsequent gene expression. This cascade of events not only augments neuronal metabolic capacity but also orchestrates anti-oxidant, anti-inflammatory, and anti-apoptotic responses, fostering neurogenesis and synaptogenesis. It shows promise for treating conditions like dementia, stroke, brain trauma, Parkinson's disease, and depression, even enhancing cognitive functions in healthy individuals and eliciting growing interest within the medical community. However, delivering sufficient light to the brain through transcranial approaches poses a significant challenge due to its limited penetration into tissue, prompting an exploration of alternative delivery methods such as intracranial and intranasal approaches. This comprehensive review aims to explore the mechanisms through which PBM exerts its effects on the brain and provide a summary of notable preclinical investigations and clinical trials conducted on various brain disorders, highlighting PBM's potential as a therapeutic modality capable of effectively impeding disease progression within the organism-a task often elusive with conventional pharmacological interventions.

Effect of photobiomodulation on the efficacy of anesthesia in maxillary permanent molar teeth with molar incisor hypomineralization: A randomized clinical trial

BACKGROUND

Difficulty in anesthetizing teeth that have been diagnosed with molar incisor hypomineralization (MIH) is a frequently reported clinical problem. The effects of low-level laser application (photobiomodulation) on the efficacy of anesthesia during the dental treatment of patients with MIH have not yet been studied.

AIM

To assess the effects of photobiomodulation therapy (PBMT) on the efficacy of anesthesia in maxillary permanent molar teeth with MIH.

DESIGN

This prospective, parallel-arm control, randomized, triple-blind clinical trial included children aged 7-12 years. Maxillary permanent first molar teeth with MIH that required pulpotomy treatment were included. Seventy participants were randomly divided into two groups: experimental (with PBMT) and control (placebo). In the experimental group, before the administration of local infiltration anesthesia, PBMT (diode laser: 940 nm; continuous mode; 0.5 W; 78 J/cm2) was applied to the oral mucosa for 60 s each. In the control group, the laser probe was channeled toward the mucosa but was not activated. Pain scores were evaluated during the access cavity preparation of the pulpotomy treatment (when using the dentin cutting handpiece and while entering into the pulp) using the Face, Legs, Activity, Cry, Consolability (FLACC) scale. Additional anesthesia requirements were assessed in both groups. The data obtained were analyzed for statistical significance (p < .05). The chi-squared test was used to determine the effect of PBMT on categorical outcomes.

RESULTS

The no-pain scores of the experimental group were higher than those of the control group (29% vs. 20%). Moderate-to-high pain was more frequent in the control group than in the experimental group (43% vs. 20%). While 31% of the experimental group required supplemental anesthesia, 49% of the control group required supplemental anesthesia during pulpotomy of the tooth with MIH. No statistical difference, however, was found between the two groups in terms of pain scores and the need for supplemental anesthesia (p = .235, p = .143).

CONCLUSIONS

Anesthesia with and without PBMT caused no difference in pain during the treatment of maxillary molar teeth with MIH.

Effect of photobiomodulation on alleviating primary dysmenorrhea caused by PGF2α

Photobiomodulation (PBM) has attracted widespread attention in suppressing various pain and inflammation. Primary dysmenorrhea (PD) primarily occurs in adolescents and adult females, and the limited effectiveness and side effects of conventional treatments have highlighted the urgent need to develop and identify new adjunct therapeutic strategies. In this work, the results of pain and PGs demonstrated that 850 nm, 630 nm, and 460 nm all exhibited pain inhibition, decreased PGF2α and upregulated PGE2, while 630 nm PBM has better effectiveness. Then to explore the underlying biological mechanisms of red light PBM on PD, we irradiated prostaglandin-F2α induced HUSM cells and found that low-level irradiance can restore intracellular calcium ion, ROS, ATP, and MMP levels to normal levels. And, red light enhanced cell viability and promoted cell proliferation for normal HUSM cells. Therefore, this study proposes that red light PBM may be a promising approach for the future clinical treatment of PD.

Brain photobiomodulation therapy on neurological and psychological diseases

Photobiomodulation (PBM) therapy is an innovative treatment for neurological and psychological conditions. Complex IV of the mitochondrial respiratory chain can be stimulated by red light, which increases ATP synthesis. In addition, the ion channels' light absorption causes the release of Ca2+, which activates transcription factors and changes gene expression. Neuronal metabolism is improved by brain PBM therapy, which also promotes synaptogenesis and neurogenesis as well as anti-inflammatory. Its depression-treating potential is attracting attention for other conditions, including Parkinson's disease and dementia. Giving enough dosage for optimum stimulation using the transcranial PBM technique is challenging because of the rapidly increasing attenuation of light transmission in tissue. Different strategies like intranasal and intracranial light delivery systems have been proposed to overcome this restriction. The most recent preclinical and clinical data on the effectiveness of brain PBM therapy are studied in this review article.

Exploring the effect of photobiomodulation and gamma visual stimulation induced by 808 nm and visible LED in Alzheimer's disease mouse model

Although photobiomodulation (PBM) and gamma visual stimulatqion (GVS) have been overwhelmingly explored in the recent time as a possible light stimulation (LS) means of Alzheimer's disease (AD) therapy, their effects have not been assessed at once. In our research, the AD mouse model was stimulated using light with various parameters [continuous wave (PBM) or 40 Hz pulsed visible LED (GVS) or 40 Hz pulsed 808 nm LED (PBM and GVS treatment)]]. The brain slices collected from the LS treated AD model mice were evaluated using (i) fluorescence microscopy to image thioflavine-S labeled amy-loid-β (Aβ) plaques (the main hallmark of AD), or (ii) two-photon excited fluorescence (TPEF) imaging of unlabeled Aβ plaques, showing that the amount of Aβ plaques was reduced after LS treatment. The imaging results correlated well with the results of Morris water maze (MWM) test, which demonstrated that the spatial learning and memory abilities of LS treated mice were noticeably higher than those of untreated mice. The LS effect was also assessed by in vivo nonlinear optical imaging, revealing that the cerebral amyloid angiopathy decreased spe-cifically as a result of 40 Hz pulsed 808 nm irradiation, on the contrary, the angiopathy reversed after visible 40 Hz pulsed light treatment. The obtained results provide useful reference for further optimization of the LS (PBM or GVS) parameters to achieve efficient phototherapy of AD.

The Mechanisms and Efficacy of Photobiomodulation Therapy for Arthritis: A Comprehensive Review

Rheumatoid arthritis (RA) and osteoarthritis (OA) have a significant impact on the quality of life of patients around the world, causing significant pain and disability. Furthermore, the drugs used to treat these conditions frequently have side effects that add to the patient's burden. Photobiomodulation (PBM) has emerged as a promising treatment approach in recent years. PBM effectively reduces inflammation by utilizing near-infrared light emitted by lasers or LEDs. In contrast to photothermal effects, PBM causes a photobiological response in cells, which regulates their functional response to light and reduces inflammation. PBM's anti-inflammatory properties and beneficial effects in arthritis treatment have been reported in numerous studies, including animal experiments and clinical trials. PBM's effectiveness in arthritis treatment has been extensively researched in arthritis-specific cells. Despite the positive results of PBM treatment, questions about specific parameters such as wavelength, dose, power density, irradiation time, and treatment site remain. The goal of this comprehensive review is to systematically summarize the mechanisms of PBM in arthritis treatment, the development of animal arthritis models, and the anti-inflammatory and joint function recovery effects seen in these models. The review also goes over the evaluation methods used in clinical trials. Overall, this review provides valuable insights for researchers investigating PBM treatment for arthritis, providing important references for parameters, model techniques, and evaluation methods in future studies.

Nitric Oxide Induced by Ammonium/Nitrate Ratio Ameliorates Low-Light Stress in Brassica pekinesis: Regulation of Photosynthesis and Root Architecture

Low-light intensity affects plant growth and development and, finally, causes a decrease in yield and quality. There is a need for improved cropping strategies to solve the problem. We previously demonstrated that moderate ammonium:nitrate ratio (NH₄⁺:NO₃^-) mitigated the adverse effect caused by low-light stress, although the mechanism behind this alleviation is unclear. The hypothesis that the synthesis of nitric oxide (NO) induced by moderate NH₄⁺:NO₃^- (10:90) involved in regulating photosynthesis and root architecture of Brassica pekinesis subjected to low-light intensity was proposed. To prove the hypothesis, a number of hydroponic experiments were conducted. The results showed that in plants exposed to low-light intensity, the exogenous donors NO (SNP) and NH₄⁺:NO₃^- (N, 10:90) treatments significantly increased leaf area, growth range, and root fresh weight compared with nitrate treatment. However, the application of hemoglobin (Hb, NO scavenger), N-nitro-l-arginine methyl ester (L-NAME, NOS inhibitor), and sodium azide (NaN₃, NR inhibitor) in N solution remarkably decreased the leaf area, canopy spread, the biomass of shoot and root, the surface area, and volume and tips of the root. The application of N solution and exogenous SNP significantly enhanced Pn (Net photosynthetic rate) and rETR (relative electron transport rates) compared with solo nitrate. While all these effects of N and SNP on photosynthesis, such as Pn, Fv/Fm (maximum quantum yield of PSII), Y(II) (actual photosynthetic efficiency), qP (photochemical quenching), and rETR were reversed when the application of Hb, L-NAME, and NaN₃ in N solution. The results also showed that the N and SNP treatments were more conducive to maintaining cell morphology, chloroplast structure, and a higher degree of grana stacking of low-light treated plants. Moreover, the application of N significantly increased the NOS and NR activities, and the NO levels in the leaves and roots of mini Chinese cabbage seedlings treated with N were significantly higher than those in nitrate-treated plants. In conclusion, the results of this study showed that NO synthesis induced by the appropriate ammonia-nitrate ratio (NH₄⁺:NO₃^- = 10:90) was involved in the regulation of photosynthesis and root structure of Brassica pekinesis under low-light stress, effectively alleviating low-light stress and contributing to the growth of mini Chinese cabbage under low-light stress.

LIGHTSITE II Randomized Multicenter Trial: Evaluation of Multiwavelength Photobiomodulation in Non-exudative Age-Related Macular Degeneration

INTRODUCTION

Photobiomodulation (PBM) represents a potential treatment for non-exudative age-related macular degeneration (AMD). PBM uses wavelengths of light to target components of the mitochondrial respiratory chain to improve cellular bioenergetic outputs. The aim of this study was to further investigate the effects of PBM on clinical, quality of life (QoL) and anatomical outcomes in subjects with intermediate stage non-exudative AMD.

METHODS

The multicenter LIGHTSITE II study was a randomized clinical trial evaluating safety and efficacy of PBM in intermediate non-exudative AMD. The LumiThera Valeda® Light Delivery System delivered multiwavelength PBM (590, 660 and 850 nm) or sham treatment 3 × per week over 3-4 weeks (9 treatments per series) with repeated treatments at baseline (BL), 4 and 8 months. Subjects were enrolled with 20/32 to 20/100 best-corrected visual acuity (BCVA) and no central geographic atrophy (GA) within the central fovea (500 μm).

RESULTS

LIGHTSITE II enrolled 44 non-exudative AMD subjects (53 eyes). PBM-treated eyes showed statistically significant improvement in BCVA at 9 months (n = 32 eyes, p = 0.02) with a 4-letter gain in the PBM-treated group versus a 0.5-letter gain in the sham-treated group (ns, p < 0.1) for patients that received all 27 PBM treatments (n = 29 eyes). Approximately 35.3% of PBM-treated eyes showed ≥ 5-letter improvement at 9 months. Macular drusen volume was not increased over time in the PBM-treated group but did show increases in the sham-treated group. While PBM and sham groups both showed GA lesion growth in the trial period, there was 20% less growth in the PBM group over 10 months, suggesting potential disease-modifying effects. No safety concerns or signs of phototoxicity were observed.

CONCLUSION

These results confirm previous clinical testing of multiwavelength PBM and support treatment with Valeda as a novel therapy with a unique mechanism of action as a potential treatment for non-exudative AMD.

TRIAL REGISTRATION

Clinicaltrial.Gov Registration Identifier: NCT03878420.

Photobiomodulation ameliorates inflammatory parameters in fibroblast-like synoviocytes and experimental animal models of rheumatoid arthritis

Introduction

Rheumatoid arthritis (RA) is a chronic destructive inflammatory disease that afflicts over one percent of the world’s population. Current pharmacological treatments remain relatively ineffective. In this context, photobiomodulation (PBM) is a potential resource for the treatment of RA. This study investigates investigate the anti-arthritic effects and related mechanisms of PBM on fibroblast-like synoviocytes (FLSs) from RA patients and a mouse model of collagen-induced arthritis (CIA).

Methods

The RA-FLSs were irradiated with a light emitting diode (LED) at a wavelength of 610 nm for 20 min, and the corresponding power intensities were 5 and 10 mW/cm2. After the LED irradiation, cell viability, proliferation, migration, and invasion assays were performed. Male DBA/1J mice were used to establish an animal model of CIA. Light stimulation with 10 mW/cm2 was applied to the ankle joints via direct contact with the skin for 40 min, daily for 2 weeks.

Results and Discussion

PBM significantly reduced tumor necrosis factor (TNF)-α-induced increase in proliferation, migration, and invasion in RA-FLSs, and downregulated the activation of nuclear factor-κappa B (NF-κB) and NLRP3 inflammasome by TNF-α. Moreover, PBM greatly inhibited the induction and development of CIA, resulting in the inhibition of synovial inflammation and cartilage degradation. PBM therapy decreased the serum levels of pro-inflammatory cytokines, while increasing the anti-inflammatory cytokines. PBM suppressed the translocation of NF-κB and activation of NLRP3 inflammasome in the ankle joint. Furthermore, PBM showed a more pronounced anti-arthritic effect when combined with methotrexate (MTX), a disease-modifying anti-rheumatic drug (DMARD). The results showed that the effectiveness of MTX + PBM in CIA is superior to that of either MTX or PBM and that both work synergistically. Therefore, PBM with LED may be a potential therapeutic intervention for against RA.

Photobiomodulation and nitric oxide signaling

Nitric oxide (NO) is a well-known gaseous mediator that maintains vascular homeostasis. Extensive evidence supports that a hallmark of endothelial dysfunction, which leads to cardiovascular diseases, is endothelial NO deficiency. Thus, restoring endothelial NO represents a promising approach to treating cardiovascular complications. Despite many therapeutic agents having been shown to augment NO bioavailability under various pathological conditions, success in resulting clinical trials has remained elusive. There is solid evidence of diverse beneficial effects of the treatment with low-power near-infrared (NIR) light, defined as photobiomodulation (PBM). Although the precise mechanisms of action of PBM are still elusive, recent studies consistently report that PBM improves endothelial dysfunction via increasing bioavailable NO in a dose-dependent manner and open a feasible path to the use of PBM for treating cardiovascular diseases via augmenting NO bioavailability. In particular, the use of NIR light in the NIR-II window (1000-1700 nm) for PBM, which has reduced scattering and minimal tissue absorption with the largest penetration depth, is emerging as a promising therapy. In this review, we update recent findings on PBM and NO.

1270 nm near-infrared light as a novel vaccine adjuvant acts on mitochondrial photoreception in intradermal vaccines

With the development of laser technology in the 1960s, a technique was developed to inject intradermal vaccines immediately after irradiating the skin with laser light to elicit an adjuvant effect, referred to as "laser adjuvant." We have been investigating the mechanism of laser adjuvant in influenza mouse models using noninvasive continuous-wave (CW) near-infrared (NIR) light mainly at a wavelength of 1064 nm, and have shown that the production of reactive-oxygen-species (ROS) in the skin and mast cells in the skin tissue plays an important role in the laser adjuvant effect. The new wavelength of 1270 nm NIR light is characterized by its ability to elicit the same vaccine adjuvant effect as other wavelengths at a lower energy, and may be suitable for clinical applications. In this study, we investigated the physiological activity of CW1270 nm NIR light in mast cells, its biological activity on mouse skin, and the durability of the vaccine adjuvant effect in influenza vaccine mouse models. We show that irradiation of mast cells with 1270 nm NIR light produced ROS and ATP, and irradiation of isolated mitochondria also produced ATP. In mouse skin, the relative expression levels of chemokine mRNAs, such as Ccl2 and Ccl20, were increased by irradiation with 1270 and 1064 nm NIR light at minimum safe irradiance. However, the relative expression of Nfkb1 was increased at 1064 nm, but not at 1270 nm. Serum anti-influenza IgG antibody titers increased early after immunization with 1064 nm, whereas with 1270 nm, there was not only an early response of antibody production but also persistence of antibody titers over the medium- to long-term. Thus, to our knowledge, we show for the first time that 1270 nm NIR light induces ROS and ATP production in mitochondria as photoreceptors, initiating a cascade of laser adjuvant effects for intradermal vaccines. Additionally, we demonstrate that there are wavelength-specific variations in the mechanisms and effects of laser adjuvants. In conclusion, CW1270 nm NIR light is expected to be clinically applicable as a novel laser adjuvant that is equivalent or superior to 1064 nm NIR light, because it can be operated at low energy and has a wavelength-specific adjuvant effect with medium- to long-lasting antibody titer.

Near-infrared II photobiomodulation augments nitric oxide bioavailability via phosphorylation of endothelial nitric oxide synthase

There is solid evidence of the beneficial effect of photobiomodulation (PBM) with low-power near-infrared (NIR) light in the NIR-I window in increasing bioavailable nitric oxide (NO). However, it is not established whether this effect can be extended to NIR-II light, limiting broader applications of this therapeutic modality. Since we have demonstrated PBM with NIR laser in the NIR-II window, we determined the causal relationship between NIR-II irradiation and its specific biological effects on NO bioavailability. We analyzed the impact of NIR-II irradiation on NO release in cultured human endothelial cells using a NO-sensitive fluorescence probe and single-cell live imaging. Two distinct wavelengths of NIR-II laser (1064 and 1270 nm) and NIR-I (808 nm) at an irradiance of 10 mW/cm2 induced NO release from endothelial cells. These lasers also enhanced Akt phosphorylation at Ser 473, endothelial nitric oxide synthase (eNOS) phosphorylation at Ser 1177, and endothelial cell migration. Moreover, the NO release and phosphorylation of eNOS were abolished by inhibiting mitochondrial respiration, suggesting that Akt activation caused by NIR-II laser exposure involves mitochondrial retrograde signaling. Other inhibitors that inhibit known Akt activation pathways, including a specific inhibitor of PI3K, Src family PKC, did not affect this response. These two wavelengths of NIR-II laser induced no appreciable NO generation in cultured neuronal cells expressing neuronal NOS (nNOS). In short, NIR-II laser enhances bioavailable NO in endothelial cells. Since a hallmark of endothelial dysfunction is suppressed eNOS with concomitant NO deficiency, NIR-II laser technology could be broadly used to restore endothelial NO and treat or prevent cardiovascular diseases.

The comparison of calcium hydroxide + biostimulation, calcium hydroxide, formocresol, and MTA pulpotomies without biostimulation in primary teeth: 12-months clinical and radiographic follow-up

This study has aimed to evaluate the clinical and radiographic success rates of calcium hydroxide pulpotomy (CH) with biostimulation (PBMT) and compare them to that of CH, formocresol (FC), mineral trioxide aggregate (MTA) pulpotomies without PBMT in primary molars. A total of 172 pulpotomies were performed on primary first or second mandibular molars in 94 children who were 5-8 years old. The pulpotomy procedure was performed with four different techniques. In the PBMT group, before the CH placement, 820-nm diode laser radiation was applied to each pulp-stump for 12 s (10 mW, 2.5 J/cm²). The clinical (lack of spontaneous pain, abscess or fistula, and pathological mobility) and radiographic success (lack of periapical/furcal lesions and internal/external resorption) were recorded at 6 and 12 months. The data was statistically evaluated. p value < 0.05 was considered as significant. After 12 months, the clinical and radiographic success rate (a tooth with at least one of the findings was considered unsuccessful) was 97%/92% for FC and 97%/95%, 87%/73%, and 71%/45% for MTA, CH + PBMT, and CH, respectively. There was no significant difference between the CH + PBMT and the other groups in clinical success, while a significant difference was found between CH and FC, MTA groups. In radiographic success, there was a significant difference between the CH and the other groups. No significant difference was found between the 6th- and 12th-month results in clinical success for all the groups. A decrease in success over time was seen only in the CH group for radiographic results. CH without PBMT showed the worst clinical and radiographic results among the groups. CH + PBMT showed similar clinical success compared to the MTA and FC groups. In radiographic success, CH + PBMT showed higher success compared to CH, but this success was not high as compared to MTA and FC.

Effects of light-emitting diode therapy on cardiovascular and salivary nitrite responses in postmenopausal women submitted to a single bout of high-intensity interval training

The aim of the present study was to analyze the effects of light-emitting diode therapy (LEDT) on cardiovascular effort during a single bout of high-intensity interval training (HIIT) and on blood pressure (BP), salivary nitrite, and heart rate variability (HRV) responses after the exercise session in postmenopausal women. Sixteen postmenopausal women between 50 and 70 years of age participated in the present study. The intervention comprised two sessions: placebo plus HIIT and LEDT plus HIIT, with a 14-day interval between sessions. The oxygen uptake (VO₂), heart rate (HR), and rating of perceived exertion (RPE) were monitored throughout the HIIT sessions. Salivary samples were taken before, immediately post, and 30' and 60' post-HIIT sessions for nitric oxide (NO) analysis. In addition, HR and BP were checked before, 15 min, 30 min, 45 min, and 60 min post-HIIT sessions. HR data were used to calculate the HRV indices. Cardiovascular parameters during HIIT and BP, HRV, and NO responses were not different between placebo and LEDT conditions (p > 0.05). BP responses increased after compared to pre-exercise (p < 0.01). HRV was impaired post- compared to pre-exercise (p < 0.05). LEDT did not improve physiological performance during HIIT and did not accelerate the recovery of BP and autonomic modulation or change the NO release after exercise in postmenopausal women.

Mechanistic Approaches to the Light-Induced Neural Cell Differentiation: Photobiomodulation vs Low-Dose Photodynamic Therapy

BACKGROUND

Neurodegenerative diseases are the results of irreversible damages in the neuronal cells by affecting vital functions temporarily or even permanently. The use of light for the treatment of these diseases is an emerging promising innovative method. Photobiomodulation (PBM) and Photodynamic Therapy (PDT) are the modalities that have a wide range of use in medicine and have opposite purposes, biostimulation and cell death respectively.

METHODS

In this study, we aimed to compare these two modalities (PDT and PBM) at low-level intensities and create a stimulatory effect on the differentiation of PC12 cells. Three different energy densities (1, 3, and 5 J/cm²) were used in PBM and Chlorin e6-mediated PDT applications upon irradiation with 655-nm laser light. The light-induced differentiation profile of PC12 cells was analyzed by morphological examinations, qRT-PCR, cell viability assay, and some mechanistic approaches such as; the analysis of intracellular ROS production, NO release, and mitochondrial membrane potential change.

RESULTS

It has been observed that both of these modalities were successful at neural cell differentiation. PBM at 1 J/cm² and low-dose PDT at 3 J/cm² energy densities provided the best differentiation profiles which were proved by the over-expressions of SYN-1 and GAP43 genes. It was also observed that intracellular ROS production and NO release had pivotal roles in these mechanisms with more cell differentiation obtained especially in low-dose PDT application.

CONCLUSION

It can be concluded that light-induced mechanisms with properly optimized light parameters have the capacity for neural cell regeneration and thus, can be a successful treatment for incurable neurodegenerative diseases.

670nm photobiomodulation modulates bioenergetics and oxidative stress, in rat Müller cells challenged with high glucose

Diabetic retinopathy (DR), the most common complication of diabetes mellitus, is associated with oxidative stress, nuclear factor-κB (NFκB) activation, and excess production of vascular endothelial growth factor (VEGF) and intracellular adhesion molecule-1 (ICAM-1). Muller glial cells, spanning the entirety of the retina, are involved in DR inflammation. Mitigation of DR pathology currently occurs via invasive, frequently ineffective therapies which can cause adverse effects. The application of far-red to near-infrared (NIR) light (630-1000nm) reduces oxidative stress and inflammation in vitro and in vivo. Thus, we hypothesize that 670nm light treatment will diminish oxidative stress preventing downstream inflammatory mechanisms associated with DR initiated by Muller cells. In this study, we used an in vitro model system of rat Müller glial cells grown under normal (5 mM) or high (25 mM) glucose conditions and treated with a 670 nm light emitting diode array (LED) (4.5 J/cm2) or no light (sham) daily. We report that a single 670 nm light treatment diminished reactive oxygen species (ROS) production and preserved mitochondrial integrity in this in vitro model of early DR. Furthermore, treatment for 3 days in culture reduced NFκB activity to levels observed in normal glucose and prevented the subsequent increase in ICAM-1. The ability of 670nm light treatment to prevent early molecular changes in this in vitro high glucose model system suggests light treatment could mitigate early deleterious effects modulating inflammatory signaling and diminishing oxidative stress.

Effect of Red-to-Near Infrared Light and a Nitric Oxide Donor on the Oxygen Consumption of Isolated Cytochrome c Oxidase

Objective: To study the effects of 670 and 830 nm irradiation on oxygen consumption by cytochrome c oxidase (CCO) in a Clark electrode type reaction chamber. To explore the effect of irradiation on the nitric oxide (NO) donor-induced inhibition of oxygen consumption. Background: Most theories of photobiomodulation (PBM) involve the enzyme CCO as a cellular target for red-to-near infrared light (R-NIR) irradiation. Attempts to measure the effect of irradiation on the kinetics of CCO have failed to demonstrate a significant effect. It remains to explore the effects of irradiation on the consumption of oxygen. NO has been proposed as a possible mediator for PBM due to its inhibitory effects on CCO. Studying the effect of R-NIR on NO-induced inhibition of oxygen consumption is needed to explore this thesis. Methods: Oxygen consumption assays at 22°C were performed in a Mitocell MT200A system equipped with a 1302 oxygen electrode. R-NIR irradiation at 670 nm (41 mW/cm²) or 830 nm (31 mW/cm²) was provided to the reaction mixture. Calculated second-order rate constants were compared with control runs at four cytochrome c concentrations. Assays were also performed with or without NO donor and/or light for two substrate concentrations. Results: Kinetics constants for oxygen consumption with or without R-NIR showed no significant differences with either wavelength at any substrate concentration. The NO donor showed significant inhibition that was not relieved by irradiation. Conclusions: This lack of effect by R-NIR calls into question both the CCO activity model and the NO inhibition relief model of PBM.

Current Applications and Future Perspectives of Fluorescence Light Energy Biomodulation in Veterinary Medicine

The purpose of this review is to determine the state of the art of the mode of action and potential applications of fluorescence photobiomodulation in veterinary medicine. After a summary of the assets that have led the translation of such light-based therapies from bench side into clinical use, recent advances in canine dermatology using this brand-new approach are presented, and future scenarios where this type of care may provide benefits over the current standard care are highlighted.

Light therapy: a new option for neurodegenerative diseases

ABSTRACT

Given the increasing incidence of neurodegenerative disease (ND), recent research efforts have intensified the search for curative treatments. Despite significant research, however, existing therapeutic options for ND can only slow down the progression of the disease, but not provide a cure. Light therapy (LT) has been used to treat some mental and sleep disorders. This review illustrates recent studies of the use of LT in patients with ND and highlights its potential for clinical applications. The literature was collected from PubMed through June 2020. Selected studies were primarily English articles or articles that could be obtained with English abstracts and Chinese main text. Articles were not limited by type. Additional potential publications were also identified from the bibliographies of identified articles and the authors' reference libraries. The identified literature suggests that LT is a safe and convenient physical method of treatment. It may alleviate sleep disorders, depression, cognitive function, and other clinical symptoms. However, some studies have reported limited or no effects. Therefore, LT represents an attractive therapeutic approach for further investigation in ND. LT is an effective physical form of therapy and a new direction for research into treatments for ND. However, it requires further animal experiments to elucidate mechanisms of action and large, double-blind, randomized, and controlled trials to explore true efficacy in patients with ND.

Photobiomodulation with 590 nm Wavelength Delays the Telomere Shortening and Replicative Senescence of Human Dermal Fibroblasts In Vitro

Background: Cellular senescence is one of the major factors contributing to the aging process. Photobiomodulation (PBM) is known to trigger an array of cellular responses, but there are no data on how it affects the process of cellular senescence. In this study, we analyze the effect of PBM on the cellular senescence and telomere dynamics. Methods: Human dermal fibroblasts were irradiated by a panel of light-emitting diodes with 590 nm and dose 30 J/cm² accumulated over 1200 sec repeated in 4-day cycle within 40 days. After the last cycle of PBM treatment, the difference in number of senescent cells between PBM treated groups end nontreated control groups was measured by senescent sensitive β-galactosidase assay, and the difference in average telomere length between the experimental end control groups was analyzed using relative human telomere length quantitative Polymerase Chain Reaction (qPCR) assay. Results: After 10 cycles of irradiation, the percentage of senescent cells in PBM-treated cultures was 19.7% ± 4.5%, p < 0.05 smaller than the percentage of senescent cells in the control group, and their relative telomere length was 1.19 ± 0.09-fold, p < 0.05 greater than nontreated controls. Conclusions: Our study demonstrates for the first time that PBM with appropriate parameters can delay the attrition of the telomeres and the entry of cells into senescence, suggesting a potential involvement of telomerase reactivation. A hypothetical mechanism for this light-induced antiaging effect is discussed.

Wavelength- and irradiance-dependent changes in intracellular nitric oxide level

SIGNIFICANCE

Photobiomodulation (PBM) refers to the beneficial effects of low-energy light absorption. Although there is a large body of literature describing downstream physiological benefits of PBM, there is a limited understanding of the molecular mechanisms underlying these effects. At present, the most popular hypothesis is that light absorption induces release of nitric oxide (NO) from the active site of cytochrome c oxidase (COX), allowing it to bind O2 instead. This is believed to increase mitochondrial respiration, and result in greater overall health of the cell due to increased adenosine triphosphate production.

AIM

Although NO itself is a powerful signaling molecule involved in a host of biological responses, less attention has been devoted to NO mechanisms in the context of PBM. The purpose of our work is to investigate wavelength-specific effects on intracellular NO release in living cells.

APPROACH

We have conducted in-depth dosimetry analyses of NO production and function in an in vitro retinal model in response to low-energy exposure to one or more wavelengths of laser light.

RESULTS

We found statistically significant wavelength-dependent elevations (10% to 30%) in intracellular NO levels following laser exposures at 447, 532, 635, or 808 nm. Sequential or simultaneous exposures to light at two different wavelengths enhanced the NO modulation up to 50% of unexposed controls. Additionally, the immediate increases in cellular NO levels were independent of the function of NO synthase, depended greatly on the substrate source of electrons entering the electron transport chain, and did not result in increased levels of cyclic guanosine monophosphate.

CONCLUSIONS

Our study concludes the simple model of light-mediated release of NO from COX is unlikely to explain the wide variety of PBM effects reported in the literature. Our multiwavelength method provides a novel tool for studying immediate and early mechanisms of PBM as well as exploring intracellular NO signaling networks.

Improvements in Gulf War Illness Symptoms After Near-Infrared Transcranial and Intranasal Photobiomodulation: Two Case Reports

At least one-fourth of US veterans who served in the 1990-1991 Gulf War (GW) are affected by the chronic symptomatic illness known as Gulf War illness (GWI). This condition typically includes some combination of fatigue, headaches, cognitive dysfunction, musculoskeletal pain, and respiratory, gastrointestinal and dermatologic complaints. To date, effective treatments for GWI have been elusive. Photobiomodulation (PBM) describes the non-pharmacological, non-thermal use of light to stimulate, heal, and protect tissue that has either been injured, is degenerating, or else is at risk of dying. Significant benefits have been reported following application of transcranial PBM to humans with acute stoke, traumatic brain injury (TBI), and dementia. This report describes the first documentation of improved GWI symptoms in two GW veterans following 12 weeks of PBM treatments.

What Lies at the Heart of Photobiomodulation: Light, Cytochrome C Oxidase, and Nitric Oxide-Review of the Evidence

Objective: The underlying mechanisms of photobiomodulation (PBM) remain elusive. The most attractive hypotheses revolve around the role of cytochrome c oxidase (CCO) and cellular energetics. Background: No reliable demonstration of any PBM-related light-induced mechanistic effect on CCO has been reported. Studies on PBM have proven to be either nonreproducible, of questionable relevance, or involve wavelengths unlikely to be operative in vivo. The literature reveals very few demonstrable mechanistic light effects of any sort on CCO. Nitric oxide (NO) is involved in a number of the reported light effects on CCO. NO inhibits CCO at high reductive pressures by binding to the heme a3 moiety. This complex is white light labile. Methods: The reported photolability of the heme-NO complex seems to be a prime target for PBM studies, as removal of inhibiting NO from the active site of CCO could restore normal activity to inhibited CCO. Another aspect of CCO-NO chemistry has been revealed that shows intriguing possibilities. Results: A novel nitrite reductase activity of solubilized mitochondria has been demonstrated attributable to CCO. NO production was optimal under hypoxic conditions. It was also found that 590 nm irradiation increased NO production by enhancing NO release. The presence of cellular NO has usually been considered metabolically detrimental, but current thinking has expanded the importance and the physiological roles of NO. Evidence shows that NO production is likely to play a role in cardioprotection and defenses against hypoxic damage. Conclusions: Studies combining PBM and hypoxia also point to a connection between light irradiation, hypoxia protection, and NO production. This leads the authors to the possibility that the intrinsic nature of PBM involves the production of NO. The combination of CCO and hemoglobin/myoglobin NO production with photorelease of NO may constitute the heart of PBM.

The combination of low level laser therapy and efavirenz drastically reduces HIV infection in TZM-bl cells

Background

Human immunodeficiency virus (HIV) infection remains a global health challenge despite the use of antiretroviral therapy, which has led to a significant decline in the mortality rates. Owing to the unavailability of an effective treatment to completely eradicate the virus, researchers continue to explore new methods. Low level laser therapy (LLLT) has been widely used to treat different medical conditions and involves the exposure of cells or tissues to low levels of red and near infrared light. The study aimed to determine the effect of combining two unrelated therapies on HIV infection in TZM-bl cells.

Methods

In the current study, LLLT was combined with efavirenz, an HIV reverse transcriptase inhibitor to establish their impact on HIV infection in TZM-bl cells. Both the HIV infected and uninfected cells were laser irradiated using a wavelength of 640 nm with fluencies of 2–10 J/cm².

Results

The impact of HIV, efavirenz and irradiation were determined 24 h post irradiation using biological assays. Luciferase assay results showed that the combination of LLLT and efavirenz significantly reduced HIV infection in cells, despite the undesirable effects observed in the cells as demonstrated by cell morphology, proliferation and cell integrity assay. Flow cytometry results demonstrated that cell death was mainly through necrosis while fluorescence microscopy showed the production of reactive oxygen species in HIV infected cells.

Conclusion

Efavirenz and LLLT significantly reduced HIV infection in TZM-bl cells. Furthermore, the death of HIV infected cells was due to necrosis.

The photobiomodulation (658, 830 and 904nm) on wound healing in histomorphometric analysis

Abstract Introduction: Photobiomodulation (PBM) assists in the processes of angiogenesis and cellular mitosis after skin lesion, contributing to tissue repair. Objective: to investigate the effects of photobiomodulation (during the proliferative phase) of 658 nm, 830 nm and 904 nm in the repair of skin lesions in an animal model. Method: 658 nm (G658), 830 nm (G830), 904 nm (G904) PBM, and control group (CG) integrated the research. We submitted the animals to an excisional wound and treatment at different wavelengths for 14 days. On the seventh and 14-1485004059th postoperative days, we calculated the area and percentage of lesion contraction. The animals were sacrificed on the 14-1485004056th postoperative day and cutaneous section of the injured region was collected for histomorphometric evaluation of the cellularity, neovascularization, thickness of the epidermis and volume density of collagen fibers colored with H&E and Picross Sirius respectively. For the statistical analysis, we applied the ANOVA test. Results: the G658 presented higher cellularity than GC (p = 0.03). The animals in the G658 group showed a significant increase in the neovascularization in relation to the CG (p = 0.01). Type III collagen significantly increased in G904 compared to G830 (p < 0.0001) and CG (p < 0.0001). The G658 had a significant increase in type III collagen fibers compared to G830 (p < 0.0001) and GC (p < 0.0001). We found no significant difference in the thickness of the epidermis, wound area, and in the percentage wound of contraction between the analyzed groups. Conclusion: PBM was effective to stimulate the tissue repair process, with better results for the 658 nm wavelength.

Penetration Profiles of Visible and Near-Infrared Lasers and Light-Emitting Diode Light Through the Head Tissues in Animal and Human Species: A Review of Literature

Background and objective: Photobiomodulation (PBM) therapy is a promising and noninvasive approach to stimulate neuronal function and improve brain repair. The optimization of PBM parameters is important to maximize effectiveness and tolerability. Several studies have reported on the penetration of visible-to-near-infrared (NIR) light through various animal and human tissues. Scientific findings on the penetration of PBM light vary, likely due to use of different irradiation parameters and to different characteristics of the subject such as species, age, and gender. Materials and methods: In this article, we review published data on PBM penetration through the tissues of the head in both animal and human species. The patterns of visible-to-NIR light penetration are summarized based on the following study specifications: wavelength, coherence, operation mode, beam type and size, irradiation site, species, age, and gender. Results: The average penetration of transcranial red/NIR (630-810 nm) light ranged 60-70% in C57BL/6 mouse (skull), 1-10% in BALB/c mouse (skull), 10-40% in Sprague-Dawley rats (scalp plus skull), 20% in Oryctolagus cuniculus rabbit (skull), 0.11% in pig (scalp plus skull), and 0.2-10% in humans (scalp plus skull). The observed variation in the reported values is due to the difference in factors (e.g., wavelengths, light coherence, tissue thickness, and anatomic irradiation site) used by researchers. It seems that these data challenge the applicability of the animal model data on transcranial PBM to humans. Nevertheless, two animal models seem particularly promising, as they approximate penetration in humans: (I) Penetration of 808 nm laser through the scalp plus skull was 0.11% in the pig head; (II) Penetration of 810 nm laser through intact skull was 1.75% in BALB/c mouse. Conclusions: In conclusion, it is worthwhile mentioning that since the effectiveness of brain PBM is closely dependent on the amount of light energy reaching the target neurons, further quantitative estimation of light penetration depth should be performed to validate the current findings.

Photonic Therapy in Periodontal Diseases an Overview with Appraisal of the Literature and Reasoned Treatment Recommendations

Recent reviews and meta-analyses of the literature over the past quarter-century have failed to provide enough evidence to prove or disprove the actual utility of photonic therapy in periodontitis, alone or adjunctive to conventional approaches. This apparent paradox has been explained by the many physical, molecular, biological, anatomical, and technical variables of photonic treatments, which can differ in light-emitting devices (laser or LED), wavelengths, irradiation power and modes, clinical objectives, follow-up times, disease grading, and assessment methods. This multi-faceted, controversial scenario has led practitioners to underestimate the actual potential of photonic therapy in periodontal diseases. In this critical appraisal of the literature, we have briefly summarized the main photonic therapies and instruments used in Periodontology, highlighting their main characteristics and limitations. Then, we have tried to identify and discuss the key methodological issues which can have an impact on the outcome of photonic therapies. Our main goal was to identify the best parameters, settings, and methodologies to perform effective periodontal photonic treatments and to extrapolate some recommendations for clinical use. Should these recommendations find a consensus among periodontologists and be adopted in future clinical studies, they will hopefully contribute to dissipate the present confusion and uncertainty on this complex matter.

Photobiomodulation induces hypotensive effect in spontaneously hypertensive rats

To evaluate whether acute photobiomodulation can elicit a hypotensive effect in spontaneously hypertensive rats (SHR). Male SHR were submitted to the implantation of a polyethylene cannula into the femoral artery. After 24 h, baseline measurements of the hemodynamic parameters: systolic, diastolic, and mean arterial pressure, and heart rate were accomplished for 1 h. Afterwards, laser application was simulated, and the hemodynamic parameters were recorded for 1 h. In the same animal, the laser was applied at six different positions of the rat's abdomen, and the hemodynamic parameters were also recorded until the end of the hypotensive effect. The irradiation parameters were red wavelength (660 nm); average optical power of 100 mW; 56 s per point (six points); spot area of 0.0586 cm²; and irradiance of 1.71 W/cm² yielding to a fluency of 96 J/cm² per point. For measuring plasma NO levels, blood was collected before the recording, as well as immediately after the end of the mediated hypotensive effect. Photobiomodulation therapy was able to reduce the systolic arterial pressure in 69% of the SHR submitted to the application, displaying a decrease in systolic, diastolic, and mean arterial pressure. No change in heart rate was observed. Nevertheless, there was an increase in serum nitric oxide levels in the SHR responsive to photobiomodulation. Our results suggest that acute irradiation with a red laser at 660 nm can elicit a hypotensive effect in SHR, probably by a mechanism involving the release of NO, without changing the heart rate.

Under the spotlight: mechanisms of photobiomodulation concentrating on blue and green light

Photobiomodulation (PBM) describes the application of light at wavelengths ranging from 400-1100 nm to promote tissue healing, reduce inflammation and promote analgesia. Traditionally, red and near-infra red (NIR) light have been used therapeutically, however recent studies indicate that other wavelengths within the visible spectrum could prove beneficial including blue and green light. This review aims to evaluate the literature surrounding the potential therapeutic effects of PBM with particular emphasis on the effects of blue and green light. In particular focus is on the possible primary and secondary molecular mechanisms of PBM and also evaluation of the potential effective parameters for application both in vitro and in vivo. Studies have reported that PBM affects an array of molecular targets, including chromophores such as signalling molecules containing flavins and porphyrins as well as components of the electron transport chain. However, secondary mechanisms tend to converge on pathways induced by increases in reactive oxygen species (ROS) production. Systematic evaluation of the literature indicated 72% of publications reported beneficial effects of blue light and 75% reported therapeutic effects of green light. However, of the publications evaluating the effects of green light, reporting of treatment parameters was uneven with 41% failing to report irradiance (mW cm-2) and 44% failing to report radiant exposure (J cm-2). This review highlights the potential of PBM to exert broad effects on a range of different chromophores within the body, dependent upon the wavelength of light applied. Emphasis still remains on the need to report exposure and treatment parameters, as this will enable direct comparison between different studies and hence enable the determination of the full potential of PBM.

Photobiomodulation Therapy in Veterinary Medicine: A Review

Laser therapy, or photobiomodulation, has rapidly grown in popularity in human and veterinary medicine. With a number of proposed indications and broad, sometimes anecdotal, use in practice, research interest has expanded aimed at providing scientific support. Recent studies have shown that laser therapy alters the inflammatory and immune response as well as promotes healing for a variety of tissue types. This review will cover the history of the modality, basic principles, proposed mechanisms of action, evidence-based clinical indications, and will guide the practitioner through its application in practice.

Wavelength-dependence of vasodilation and NO release from S-nitrosothiols and dinitrosyl iron complexes by far red/near infrared light

Far red/near infrared (R/NIR) energy is a novel therapy, but its mechanism of action is poorly characterized. Cytochrome c oxidase (Cco) of the mitochondrial electron transport chain is considered the primary photoacceptor for R/NIR to photolyze a putative heme nitrosyl in Cco to liberate free nitric oxide (NO). We previously observed R/NIR light directly liberates NO from nitrosylated hemoglobin and myoglobin, and recently suggested S-nitrosothiols (RSNO) and dinitrosyl iron complexes (DNIC) may be primary sources of R/NIR-mediated NO. Here we indicate R/NIR light exposure induces wavelength dependent dilation of murine facial artery, with longer wavelengths (740, and 830 nm) exhibiting reduced potency when compared to 670 nm. R/NIR also stimulated NO release from pure solutions of low molecular weight RSNO (GSNO and SNAP) and glutathione dinitrosyl iron complex (GSH-DNIC) in a power- and wavelength-dependent manner, with the greatest effect at 670 nm. NO release from SNAP using 670 was nearly ten-fold more than GSNO or GSH-DNIC, with no substantial difference in NO production at 740 nm and 830 nm. Thermal effects of irradiation on vasodilation or NO release from S-nitrosothiols and DNIC was minimal. Our results suggest 670 nm is the optimal wavelength for R/NIR treatment of certain vascular-related diseases.

Brain Photobiomodulation Therapy: a Narrative Review

Brain photobiomodulation (PBM) therapy using red to near-infrared (NIR) light is an innovative treatment for a wide range of neurological and psychological conditions. Red/NIR light is able to stimulate complex IV of the mitochondrial respiratory chain (cytochrome c oxidase) and increase ATP synthesis. Moreover, light absorption by ion channels results in release of Ca²⁺ and leads to activation of transcription factors and gene expression. Brain PBM therapy enhances the metabolic capacity of neurons and stimulates anti-inflammatory, anti-apoptotic, and antioxidant responses, as well as neurogenesis and synaptogenesis. Its therapeutic role in disorders such as dementia and Parkinson's disease, as well as to treat stroke, brain trauma, and depression has gained increasing interest. In the transcranial PBM approach, delivering a sufficient dose to achieve optimal stimulation is challenging due to exponential attenuation of light penetration in tissue. Alternative approaches such as intracranial and intranasal light delivery methods have been suggested to overcome this limitation. This article reviews the state-of-the-art preclinical and clinical evidence regarding the efficacy of brain PBM therapy.

Effects of high-frequency near-infrared diode laser irradiation on the proliferation and migration of mouse calvarial osteoblasts

Laser irradiation activates a range of cellular processes and can promote tissue repair. Here, we examined the effects of high-frequency near-infrared (NIR) diode laser irradiation on the proliferation and migration of mouse calvarial osteoblastic cells (MC3T3-E1). MC3T3-E1 cells were cultured and exposed to high-frequency (30 kHz) 910-nm diode laser irradiation at a dose of 0, 1.42, 2.85, 5.7, or 17.1 J/cm². Cell proliferation was evaluated with BrdU and ATP concentration assays. Cell migration was analyzed by quantitative assessment of wound healing using the Incucyt^® ZOOM system. In addition, phosphorylation of mitogen-activated protein kinase (MAPK) family members including p38 mitogen-activated protein kinase (p38), stress-activated protein kinase/Jun-amino-terminal kinase (SAPK/JNK), and extracellular signal-regulated protein kinase (ERK)1/2) after laser irradiation was examined with western blotting. Compared to the control, cell proliferation was significantly increased by laser irradiation at a dose of 2.85, 5.7, or 17.1 J/cm². Laser irradiation at a dose of 2.85 J/cm² induced MC3T3-E1 cells to migrate more rapidly than non-irradiated control cells. Irradiation with the high-frequency 910-nm diode laser at a dose of 2.85 J/cm² induced phosphorylation of MAPK/ERK1/2 15 and 30 min later. However, phosphorylation of p38 MAPK and SAPK/JNK was not changed by NIR diode laser irradiation at a dose of 2.85 J/cm². Irradiation with a high-frequency NIR diode laser increased cell division and migration of MT3T3-E1 cells, possibly via MAPK/ERK signaling. These observations may be important for enhancing proliferation and migration of osteoblasts to improve regeneration of bone tissues.

Red/near infrared light stimulates release of an endothelium dependent vasodilator and rescues vascular dysfunction in a diabetes model

Peripheral artery disease (PAD) is a morbid condition whereby ischemic peripheral muscle causes pain and tissue breakdown. Interestingly, PAD risk factors, e.g. diabetes mellitus, cause endothelial dysfunction secondary to decreased nitric oxide (NO) levels, which could explain treatment failures. Previously, we demonstrated 670nm light (R/NIR) increased NO from nitrosyl-heme stores, therefore we hypothesized R/NIR can stimulate vasodilation in healthy and diabetic blood vessels. Vasodilation was tested by ex vivo pressure myography in wild type C57Bl/6, endothelial nitric oxide synthase (eNOS) knockout, and db/db mice (10mW/cm² for 5min with 10min dark period). NOS inhibition with N-Nitroarginine methyl ester (L-NAME) or the NO scavenger Carboxy-PTIO (c-PTIO) tested the specificity of NO production. 4,5-Diaminofluorescein diacetate (DAF-2) measured NO in human dermal microvascular endothelial cells (HMVEC-d). R/NIR significantly increased vasodilation in wild type and NOS inhibited groups, however R/NIR dilation was totally abolished with c-PTIO and blood vessel denudation. Interestingly, the bath solution from intact R/NIR stimulated vessels could dilate light naïve vessels in a NO dependent manner. Characterization of the bath identified a NO generating substance suggestive of S-nitrosothiols or non heme iron nitrosyl complexes. Consistent with the finding of an endothelial source of NO, intracellular NO increased with R/NIR in HMVEC-d treated with and without L-NAME (1mM), yet c-PTIO (100µm) reduced NO production. R/NIR significantly dilated db/db blood vessels. In conclusion, R/NIR stimulates vasodilation by release of NO bound substances from the endothelium. In a diabetes model of endothelial dysfunction, R/NIR restores vasodilation, which lends the potential for new treatments for diabetic vascular disease.

The impact of wavelengths of LED light-therapy on endothelial cells

Low level light therapy receives increasing interest in the fields of tissue regeneration and wound healing. Several in vivo studies demonstrated the positive effects of LLLT on angiogenesis. This study aimed to investigate the underlying properties in vitro by comparing the effects of light therapy by light emitting diodes of different wavelengths on endothelial cells in vitro. Human umbilical vein endothelial cells were treated with either 475 nm, 516 nm or 635 nm light. Control cells were not illuminated. 2D proliferation was quantified by manual counting. HUVEC migration was analyzed by performing a 2D wound scratch assay and a 3D bead assay. The influence of LLLT on early vasculogenic events was determined in a 3D fibrin co-culture model with adipose-derived stem cells. Stimulation with both red and green pulsed LED light significantly increased HUVEC proliferation and 3D migration. Moreover, HUVEC showed increased 2D migration potential with green light stimulation. The treatment with blue light was ineffective. Several parameters showed that green light was even more potent to stimulate proliferation and migration of endothelial cells than clinically well-established red light therapy. Further studies have to focus on intracellular mechanisms induced by different wavelengths in order to optimize this promising therapy in tissue regeneration.