Pre-conditioning with near infrared photobiomodulation reduces inflammatory cytokines and markers of oxidative stress in cochlear hair cells

Peri-Traumatic Near-Infrared Light Treatment Attenuates the Severity of Noise-Induced Hearing Loss by Rescuing (Type I) Spiral Ganglion Neurons in Mice

BACKGROUND

Previous studies have shown that multiple post-traumatic irradiations of the cochlea with near-infrared light (NIR) can significantly reduce noise-induced hearing loss. However, a single NIR pre-treatment was shown to have the same effect. Extending the pre-treatment time did not result in any further reduction in hearing loss. The present study investigated whether a combined NIR pre- and post-treatment had an increased effect on hearing preservation.

METHODS

Frequency-specific auditory brainstem potential thresholds (ABR) were determined in young adult mice. One group (n = 8) underwent NIR irradiation (808 nm, 120 mW, 15 min) of the cochlea, followed by a 30 min noise exposure (5-20 kHz, 115 dB SPL). A post-NIR treatment was administered for 30 min immediately following the noise trauma. After 14 days, hearing loss was determined by ABR measurements. The results were compared with a trauma-only group (n = 8) and an untreated control group (n = 5). Subsequently, the spiral ganglion neuron density was investigated.

RESULTS

A peri-traumatic NIR treatment resulted in a significantly lower hearing loss compared to the trauma-only group. Hearing protection in these animals significantly exceeded the effect of an exclusive pre- or post-treatment across all frequencies. A loss of spiral ganglion neurons in the trauma-only group was observed, which was significantly rescued by the peri-traumatic NIR treatment.

CONCLUSIONS

A single peri-traumatic NIR treatment seems to be the more effective approach for the preservation of hearing thresholds after noise trauma compared to an isolated pre- or post-treatment. One target of the protective effect seems to be the spiral ganglion.

Near-infrared light therapy normalizes amyloid load, neuronal lipid membrane order, rafts and cholesterol level in Alzheimer's disease

Cholesterol dysregulation, disorder of neuronal membrane lipid packing, and lipid rafts lead to the synthesis and accumulation of toxic amyloid-β (Aβ), contributing to the development of Alzheimer's disease (AD). Our study shows that near-infrared (NIR) transcranial photobiomodulation therapy (tPBMT) can reduce Aβ load and restore the properties of neuronal plasma membrane, including Aβ production, bilayer order, rafts, lipid content, and Ca2+ channels during AD. Mice in the experiments were exposed to 808-nm LED for 1 h daily over 3 months. In the APOE transgenic model with cholesterol dysregulation, the cholesterol levels increased by 22 times, causing healthy neurons to produce toxic Aβ three times faster, increasing its load by five times. Consequently, Aβ disrupts the membrane bilayer and prompts the formation of lipid rafts and pores. NIR-tPBMT can nearly half attenuate Aβ load, restore membrane lipid order and rigidity, reduce the number of lipid rafts, modulate cholesterol synthesis, normalize Ca2+ influx by activated endocytosis, and reduce neuronal death. The Ca2+ influx induced by light does not cause excitotoxicity but modulates Ca2+/calmodulin signaling involved in AD mechanisms and cell viability. The transcriptome analysis of the brain cortex and hippocampus shows that light can downregulate Ca2+/calmodulin-dependent AD-risk genes BACE, PSEN, and APP, and normalize cholesterol homeostasis via the HMGCR, DHCR7, and INSIG1 genes. Additionally, light enhances neuron resistance to the endoplasmic reticulum stress via activating transcription factors of the unfolded protein response. Thus, red/NIR light could be promising in combating AD, restoring synaptic plasticity in degenerating neurons and reducing Aβ load.

The Application of PBM Therapy in Patients Subjected to Oral GVHD: A Review

Background: Oral graft-versus-host disease (GVHD) is characterized by mucosal lesions, salivary gland dysfunction etc., accompanied by pain and oral dysfunction. The efficacy of photobiomodulation (PBM) in managing pain and inflammation has been demonstrated. PBM has been applied in oral GVHD and is regarded as a potent adjunctive therapy. Objective: To review the application of PBM for oral GVHD and summarize its biological mechanisms and recommended parameters. Materials and Methods: The article provides an overview of the therapeutic effects of PBM in oral GVHD cases. It analyzes the biological mechanisms from different aspects and explores the potential prospects of PBM, and appropriate parameters and frequency for GVHD are recommended. Conclusions: The efficacy of PBM in oral GVHD has been demonstrated through symptom alleviation and function improvement. It is recommended as an adjuvant therapy for oral GVHD. However, further research is required to explore optimal devices, parameters, and potential complications associated with using PBM in oral GVHD.

Unleashing light's healing power: an overview of photobiomodulation for Alzheimer's treatment

Aim: Photobiomodulation involves the use of low-level light therapy or near-infrared light therapy found to be useful in the treatment of a wide range of neurological diseases. Objective: The aim is to review the mechanism and clinical applications of photobiomodulation therapy (PBMT) in managing Alzheimer's disease. Methods: To ensure that the consensus statement accurately reflects both the experts' viewpoint and the most recent developments in the field, the expert opinions were recorded and thoroughly reviewed. Results: PBMT elicits reduction of beta-amyloid plaque, restoration of mitochondrial function, anti-inflammatory and antioxidant properties with a stimulation in ATP synthesis. Conclusion: The PBMT could be helpful in patients non-responsive to traditional pharmacological therapy providing significant aid in the management of Alzheimer's disease when introduced into the medical field.

Examining the utility of near infrared light as pre-exposure therapy to mitigate temporary noise-induced hearing loss in humans

Introduction

This study sought to determine the effect of Occupational Safety and Health Administration (OSHA) compliant noise on auditory health and assess whether pre-noise near infrared (NIR) light therapy can mitigate the effects of noise exposure.

Methods

Over four visits, participants (n = 30, NCT#: 03834714) with normal hearing completed baseline hearing health assessments followed by exposure to open ear, continuous pink noise at 94 dBA for 15 min. Immediately thereafter, post-noise hearing tests at 3000, 4000, and 6000 Hz and distortion product otoacoustic emissions (DPOAEs) were conducted along with the Modified Rhyme Test (MRT), Masking Level Difference Test (MLD), and Fixed Level Frequency Tests (FLFT) [collectively referred to as the Central and Peripheral Auditory Test Battery (CPATB)] to acquire baseline noise sensitivity profiles. Participants were then randomized to either Active or Sham NIR light therapy for 30 min binaurally to conclude Visit 1. Visit 2 (≥24 and ≤ 48 h from Visit 1) began with an additional 30-min session of Active NIR light therapy or Sham followed by repeat CPATB testing and noise exposure. Post-noise testing was again conducted immediately after noise exposure to assess the effect of NIR light therapy. The remaining visits were conducted following ≥2 weeks of noise rest in a cross-over design (i.e., those who had received Active NIR light therapy in Visits 1 and 2 received Sham therapy in Visits 3 and 4).

Results

Recovery hearing tests and DPOAEs were completed at the end of each visit. Participants experienced temporary threshold shifts (TTS) immediately following noise exposure, with a mean shift of 6.79 dB HL (±6.25), 10.61 dB HL (±6.89), and 7.30 dB HL (±7.25) at 3000, 4000, and 6000 Hz, respectively, though all thresholds returned to baseline at 3000, 4000, and 6000 Hz within 75 min of noise exposure. Paradoxically, Active NIR light therapy threshold shifts were statistically higher than Sham therapy at 3000 Hz (p = 0.04), but no other differences were observed at the other frequencies tested. An age sub-analysis demonstrated that TTS among younger adults were generally larger in the Sham therapy group versus Active therapy, though this was not statistically different. There were no differences in CPATB test results across Active or Sham groups. Finally, we observed no changes in auditory function or central processing following noise exposure, suggestive of healthy and resilient inner ears.

Conclusion

In this study, locally administered NIR prior to noise exposure did not induce a significant protective effect in mitigating noise-induced TTS. Further exploration is needed to implement effective dosage and administration for this promising otoprotective therapy.

Music as a unique source of noise-induced hearing loss

Music is among the most important artistic, cultural, and entertainment modalities in any society. With the proliferation of music genres and the technological advances that allow people to consume music in any location and at any time, music over-exposure has become a significant public health issue. Music-induced hearing loss has a great deal in common with noise-induced hearing loss. However, there are important differences that make music a unique insult to the auditory system and a unique threat to public health. Its unique properties also make it a potentially valuable asset in sound conditioning paradigms. This review discusses hearing loss from noise and music, comparing and contrasting the two. Recent research on music-induced hearing loss is reviewed, followed by discussion of the differences in music-induced hearing loss between performers and consumers. The review concludes with a discussion of the potential of music as a sound conditioning stimulus to protect against acquired hearing loss.

The In-Vitro Effect of Homeopathically Prepared Rubus idaeus and 680 nm Laser Irradiation on Cervical Cancer Cells

BACKGROUND

 Cervical cancer (CC) is the second leading cancer in women and is the most common in those aged 15 to 44 years. Medicinal plant extracts have been used as homeopathic preparations for health benefits. Rubus idaeus (RI) is used to treat disorders of the female genital tract and produces cytotoxic effects. However, the use of homeopathically prepared RI in combination with low level laser therapy has not previously been explored.

AIM

 The study aims to investigate the in-vitro effects of homeopathically prepared RI alone and in combination as a potential photosensitizer with Low-level laser irradiation (LLLI) at fluencies of 5, 10, and 15 J/cm².

METHODS

 HeLa CC cells were treated with RI (D3, D6, and 30cH homeopathic preparations). Cells were then treated with RI IC₅₀ and 680 nm laser diode at 5, 10, and 15 J/cm² fluencies, and the results compared with untreated control cells. Trypan blue viability, lactate dehydrogenase (LDH) cytotoxicity, and adenosine triphosphate (ATP) proliferation assays were used to analyze the cellular dose-responses along with inverted microscopy, Hoechst staining and Annexin-V/PI staining.

RESULTS

 RI D3 alone demonstrated an ability to reduce cellular viability to 59% and also to reduce ATP levels. The subsequent combined treatment protocol of RI D3 with all fluencies of laser demonstrated an increase in cellular ATP and increased LDH levels compared with the control.

CONCLUSION

 The increased ATP and LDH levels observed in the combined treatment protocol of 680 nm laser and RI D3 at fluencies of 5, 10 and 15 J/cm², show that the Warburg effect might have been induced in the CC cells - an increase in glucose uptake and the preferential production of lactate, even in the presence of oxygen. More research, including work on other cell lines, needs to be conducted to identify if RI and perhaps a different wavelength of laser irradiation could have potential in inducing cell death in cancer cells.

Photobiomodulation in 3D tissue engineering

SIGNIFICANCE

The method of photobiomodulation (PBM) has been used in medicine for a long time to promote anti-inflammation and pain-resolving processes in different organs and tissues. PBM triggers numerous cellular pathways including stimulation of the mitochondrial respiratory chain, alteration of the cytoskeleton, cell death prevention, increasing proliferative activity, and directing cell differentiation. The most effective wavelengths for PBM are found within the optical window (750 to 1100 nm), in which light can permeate tissues and other water-containing structures to depths of up to a few cm. PBM already finds its applications in the developing fields of tissue engineering and regenerative medicine. However, the diversity of three-dimensional (3D) systems, irradiation sources, and protocols intricate the PBM applications.

AIM

We aim to discuss the PBM and 3D tissue engineered constructs to define the fields of interest for PBM applications in tissue engineering.

APPROACH

First, we provide a brief overview of PBM and the timeline of its development. Then, we discuss the optical properties of 3D cultivation systems and important points of light dosimetry. Finally, we analyze the cellular pathways induced by PBM and outcomes observed in various 3D tissue-engineered constructs: hydrogels, scaffolds, spheroids, cell sheets, bioprinted structures, and organoids.

RESULTS

Our summarized results demonstrate the great potential of PBM in the stimulation of the cell survival and viability in 3D conditions. The strategies to achieve different cell physiology states with particular PBM parameters are outlined.

CONCLUSIONS

PBM has already proved itself as a convenient and effective tool to prevent drastic cellular events in the stress conditions. Because of the poor viability of cells in scaffolds and the convenience of PBM devices, 3D tissue engineering is a perspective field for PBM applications.

Photobiomodulation therapy for osteoarthritis: Mechanisms of action

Photobiomodulation (PBM) is a non-invasive therapeutic modality with demonstrated effects in many fields related to regenerative medicine. In the field of orthopedics, in particular, PBM at various wavelengths has demonstrated the capacity to trigger multiple biological effects associated with protective mechanisms in musculoskeletal tissues. The articles cited in this review show that devices operating close to or within the near infrared range at low intensities can provoke responses which favor the shift in the predominant catabolic microenvironment typically seen in degenerative joint diseases, especially osteoarthritis (OA). These responses include proliferation, differentiation and expression of proteins associated with stable cell cycles. Additionally, PBM can also modulate oxidative stress, inflammation and pain by exerting regulatory effects on immune cells and blocking the transmission of pain through sensory neuron fibers, without adverse events. Collectively, these effects are essential in order to control the progression of OA, which is in part attributed to exacerbated inflammation and degradative enzymatic reactions which gradually contribute to the destruction of joint tissues. PBM may offer medical experts ease of application, financial viability, efficacy and lack of serious adverse events. Therefore, it may prove to be a suitable ally in the management of mild to moderate degrees of OA. This review explores and discusses the principal biological mechanisms of PBM and how the produced effects may contribute to the amelioration of osteoarthritic progression. Literature was reviewed using PubMed and Google Scholar in order to find studies describing the mechanisms of PBM. The investigation included a combination of nomenclature such as: “photobiomodulation”, “phototherapy”, “laser therapy”, “PBM”, “osteoarthritis”, low level light therapy”, “inflammation” and “cartilage”. We considered only articles written in English, with access to the full text.

Low-level light pre-conditioning promotes C2C12 myoblast differentiation under hypoxic conditions

Exercise, especially anaerobic one, can gradually increase muscle mass over time as a result of adaptive responses of muscle cells to ensure metabolic homeostasis in the tissue. Low-level light therapy (LLLT) or photobiomodulation exhibits beneficial effects on promoting muscular functions, regeneration, and recovery from exhausting exercise, although the underlying cellular mechanisms remain poorly understood. We found that hypoxia, a condition following anaerobic exercise, significantly impeded myotube differentiation from myoblasts. However, this adverse effect was blunted greatly by pre-exposure of myoblast cells to a 980 nm laser at 0.1 J/cm² , resulting in almost nearly normal myotube differentiation. LLL pre-treatment enhanced myotube formation by 80%, with a tubular diameter of 4.28 ± 0.11 μm on average, representative of a 53.4% increase over sham light treatment. The normalized myoblast differentiation concurred with 68% more mitochondrial mass and myogenin expression over controls. Moreover, LLL pre-treatment appeared to enhance glucose uptake, prevent energy metabolic switch from oxidative phosphorylation to glycolysis, and diminish lactate production under hypoxic conditions. The observation provides valuable guidance with respect to the timing of LLLT and its potential effects on muscle strengths in concert with anaerobic exercise.

Autophagy and Apoptosis Induced in U87 MG Glioblastoma Cells by Hypericin-Mediated Photodynamic Therapy Can Be Photobiomodulated with 808 nm Light

Glioblastoma is one of the most aggressive types of tumors. Although few treatment options are currently available, new modalities are needed to improve prognosis. In this context, photodynamic therapy (PDT) is a promising adjuvant treatment modality. In the present work, hypericin-mediated PDT (hypericin-PDT, 2 J/cm²) of U87 MG cells is combined with (2 min, 15 mW/cm² at 808 nm) photobiomodulation (PBM). We observed that PBM stimulates autophagy, which, in combination with PDT, increases the treatment efficacy and leads to apoptosis. Confocal fluorescence microscopy, cytotoxicity assays and Western blot were used to monitor apoptotic and autophagic processes in these cells. Destabilization of lysosomes, mitochondria and the Golgi apparatus led to an increase in lactate dehydrogenase activity, oxidative stress levels, LC3-II, and caspase-3, as well as a decrease of the PKCα and STAT3 protein levels in response to hypericin-PDT subcellular concentration in U87 MG cells. Our results indicate that therapeutic hypericin concentrations can be reduced when PDT is combined with PBM. This will likely allow to reduce the damage induced in surrounding healthy tissues when PBM-hypericin-PDT is used for in vivo tumor treatments.

High-frequency near-infrared diode laser irradiation suppresses IL-1β-induced inflammatory cytokine expression and NF-κB signaling pathways in human primary chondrocytes

Osteoarthritis (OA) and rheumatoid arthritis (RA) are common inflammation-associated cartilage degenerative diseases. Recent studies have shown that low-level diode laser treatment can reduce inflammatory cytokine expressions in cartilage. We recently reported that high-frequency low-level diode laser irradiation attenuates matrix metalloproteinases (MMPs) expression in human primary chondrocytes. However, the molecular mechanism underlying the effect of high-frequency low-level diode laser on chondrocytes remains unclear. Therefore, we aimed to elucidate the effect of high-frequency low-level diode laser irradiation on inflammatory cytokine expression in human primary chondrocytes. Normal human articular chondrocytes were treated with recombinant interleukin-1 beta (IL-1β) for 30 min or 24 h and irradiated with a high-frequency NIR diode laser at 8 J/cm². The expression of IL-1β, interleukin-6, and tumor necrosis factor-alpha was assessed using western blot analysis. To evaluate the nuclear factor-kappa B (NF-κB) signaling pathway, the phosphorylation, translocation, and DNA-binding activity of NF-κB were detected using western blot analysis, immunofluorescence analysis, electrophoretic mobility shift assay, and enzyme-linked immunosorbent assay analysis. High-frequency low-level diode laser irradiation decreased inflammatory cytokine expression in IL-1β-treated chondrocytes. Moreover, high-frequency low-level diode laser irradiation decreased the phosphorylation, nuclear translocation, and DNA-binding activity of NF-κB in the IL-1β-treated state. However, irradiation alone did not affect NF-κB activity. Thus, high-frequency low-level diode laser irradiation at 8 J/cm² can reduce inflammatory cytokine expressions in normal human articular chondrocytes through NF-κB regulation. These findings indicate that high-frequency low-level diode laser irradiation may reduce the expression of inflammatory cytokines in OA and RA.

Metabolic reprogramming of inner ear cell line HEI-OC1 after dexamethasone application

INTRODUCTION

One approach to dampen the inflammatory reactions resulting from implantation surgery of cochlear implant hearing aids is to embed dexamethasone into the matrix of the electrode carrier. Possible side effects for sensory cells in the inner ear on the metabolomics have not yet been evaluated.

OBJECTIVE

We examined changes in the metabolome of the HEI-OC1 cell line after dexamethasone incubation as a cell model of sensory cells of the inner ear.

RESULTS AND CONCLUSION

Untargeted GC-MS-profiling of metabolic alterations after dexamethasone treatment showed that dexamethasone had antithetical effects on the metabolic signature of the cells depending on growth conditions. The differentiated state of HEI-OC1 cells is better suited for elucidating metabolic changes induced by external factors. Dexamethasone treatment of differentiated cells led to an increase in intracellular amino acids and enhanced glucose uptake and β-oxidation in the cells. Increased availability of precursors for glycolysis and ATP production by β-oxidation stabilizes the energy supply in the cells, which could be assumed to be beneficial in coping with cellular stress. We found no negative effects of dexamethasone on the metabolic level, and changes may even prepare sensory cells to better overcome cellular stress following implantation surgery.

Photobiomodulation preconditioned human semen protects sperm cells against detrimental effects of cryopreservation

The biological consequences of semen samples preconditioning with photobiomodulation (PBM) were studied on human sperm cells post cryopreservation. Donated semen samples were collected from 22 married men with normal sperm parameters according to World Health Organization (WHO) criteria. Included samples were divided into control and PBM-preconditioning (one session, 810 nm, diode laser, and 0.6 J/cm2) groups before cryopreservation procedure. Progressive sperm motility (PSM), morphology, viability, sperm mitochondrial membrane potential(MMP), intracellular reactive oxygen species (ROS) and lipid peroxidation of sperm cells were assessed post thawing. PBM preconditioning of cryopreserved semen samples most prominently increased the PSM percentage 30 min post thawing (p = 0.000).Application of PBM before cryopreservation significantly increased the number of viable spermatozoa (p = 0.000), increased significantly the number of spermatozoa with high MMP (p = 0.004) and decreased significantly the number of spermatozoa with low MMP post-thawing(P = 0. 007)compared to control group. Cryopreserved human sperm cells with PBM preconditioning showed significant decrease in the levels of intracellular ROS (47.66 ± 2.14 versus 60.42 ± 3.16, p = 0.002) and lipid peroxidation (3.06 ± 0.13 versus 3.68 ± 0.27, p = 0.05)compared to control group. Our findings, as the first evidence, indicated that PBM-preconditioning of human semen before cryopreservation provides a real and substantial advantage. This might lead to a novel strategy in improving PBM application in the procedures of assisted reproductive technologies.

Effect of light emitting diode photobiomodulation on murine macrophage function after Bothrops envenomation

Several reports have suggested that photobiomodulation, owing to its analgesic, anti-inflammatory, and healing effects, may be an effective therapeutic option for local effects of snakebites when the availability and accessibility of conventional serum therapy are inefficient and far from medical care centers. Although there have been studies that demonstrate the application of photobiomodulation in the treatment of local adverse events due to snakebites from snakes of the genus Bothrops, its role in the activation of leukocytes, particularly macrophages, has not been evaluated. Here, we assessed the effect of light-emitting diode (LED) treatment on macrophage activation induced by B. jararacussu venom (BjV). LED treatment caused an increase in the viability of macrophages incubated with BjV. This treatment reduced reactive oxygen species (ROS) and nitric oxide (NO) production by macrophages after incubation with BjV. However, LED treatment did not interfere with IL-1β and IL-10 production by macrophages after incubation with BjV. In conclusion, this study showed that LED treatment has the potential to be used in combination with conventional serum therapy to prevent or minimize the progression of local to severe symptoms after Bothrops envenomation.

Neuroprotective Effect of Near-Infrared Light in an Animal Model of CI Surgery

INTRODUCTION

The preservation of residual hearing has become an important consideration in cochlear implant (CI) recipients in recent years. It was the aim of the present animal experimental study to investigate the influence of a pretreatment with near-infrared (NIR) light on preservation of sensory hair cells and residual hearing after cochlear implantation.

METHODS

NIR was applied unilaterally (15 min, 808 nm, 120 mW) to 8 guinea pigs, immediately before a bilateral scala tympani CI electrode insertion was performed. The nonirradiated (contralateral) side served as control. Twenty-eight days postoperatively, auditory brainstem responses (ABRs) were registered from both ears to screen for hearing loss. Thereafter, the animals were sacrificed and inner hair cells (IHCs) and outer hair cells (OHCs) were counted and compared between NIR-pretreated and control (contralateral) cochleae.

RESULTS

There was no IHC loss upon cochlear implantation. OHC loss was most prominent on both sides at the apical part of the cochlea. NIR pretreatment led to a statistically significant reduction in OHC loss (by 39.8%). ABR recordings (across the frequencies 4-32 kHz) showed a statistically significant difference between the 2 groups and corresponds well with the apical structural damage. Hearing loss was reduced by about 20 dB on average for the NIR-pretreated group (p ≤ 0.05).

DISCUSSION/CONCLUSION

A single NIR pretreatment in this animal model of CI surgery appears to be neuroprotective for residual hearing. This is in line with other studies where several NIR posttreatments have protected cochlear and other neural tissues. NIR pretreatment is an inexpensive, effective, and noninvasive approach that can complement other ways of preserving residual hearing and, hence, should deserve further clinical evaluation in CI patients.

Near-infrared-light pre-treatment attenuates noise-induced hearing loss in mice

Noise induced hearing loss (NIHL) is accompanied by a reduction of cochlear hair cells and spiral ganglion neurons. Different approaches have been applied to prevent noise induced apoptosis / necrosis. Physical intervention is one technique currently under investigation. Specific wavelengths within the near-infrared light (NIR)-spectrum are known to influence cytochrome-c-oxidase activity, which leads in turn to a decrease in apoptotic mechanisms. It has been shown recently that NIR can significantly decrease the cochlear hair cell loss if applied daily for 12 days after a noise exposure. However, it is still unclear if a single NIR-treatment, just before a noise exposure, could induce similar protective effects. Therefore, the present study was conducted to investigate the effect of a single NIR-pre-treatment aimed at preventing or limiting NIHL. The cochleae of adult NMRI-mice were pre-treated with NIR-light (808 nm, 120 mW) for 5, 10, 20, 30 or 40 minutes via the external ear canal. All animals were noised exposed immediately after the pre-treatment by broad band noise (5–20 kHz) for 30 minutes at 115 dB SPL. Frequency specific ABR-recordings to determine auditory threshold shift were carried out before the pre-treatment and two weeks after the noise exposure. The amplitude increase for wave IV and cochlear hair cell loss were determined. A further group of similar mice was noise exposed only and served as a control for the NIR pre-exposed groups. Two weeks after noise exposure, the ABR threshold shifts of NIR-treated animals were significantly lower (p < 0.05) than those of the control animals. The significance was at three frequencies for the 5-minute pre-treatment group and across the entire frequency range for all other treatment groups. Due to NIR light, the amplitude of wave four deteriorates significantly less after noise exposure than in controls. The NIR pre-treatment had no effect on the loss of outer hair cells, which was just as high with or without NIR-light pre-exposure. Relative to the entire number of outer hair cells across the whole cochlea, outer hair cell loss was rather negligible. No inner hair cell loss whatever was detected. Our results suggest that a single NIR pre-treatment induces a very effective protection of cochlear structures from noise exposure. Pre-exposure of 10 min seems to emerge as the optimal dosage for our experimental setup. A saturated effect occurred with higher dosage-treatments. These results are relevant for protection of residual hearing in otoneurosurgery such as cochlear implantation.

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 reduces cell death and cytokine production in C2C12 cells exposed to Bothrops venoms

Snakebites caused by the genus Bothrops are often associated with severe and complex local manifestations such as edema, pain, hemorrhage, and myonecrosis. Conventional treatment minimizes the systemic effects of venom; however, their local action is not neutralized. The purpose of this study was to evaluate the effect of photobiomodulation (PBM) on C2C12 muscle cells exposed to B. jararaca, B. jararacussu, and B. moojeni venoms on events involved in cell death and the release of inflammatory mediators. Cells were exposed to venoms and immediately irradiated with low-level laser (LLL) application in continuous wave at the wavelength of 660 nm, energy density of 4.4 J/cm², power of 10 mW, area of 0.045 cm², and time of 20 s. Cell integrity was analyzed by phase contrast microscope and cell death was performed by flow cytometry. In addition, interleukin IL1-β, IL-6, and IL-10 levels were measured in the supernatant. Our results showed that the application of PBM increases cell viability and decreases cell death by apoptosis and necrosis. Moreover, the release of pro-inflammatory interleukins was also reduced. The data reported here indicate that PBM resulted in cytoprotection on myoblast C2C12 cells after venom exposure. This protection involves the modulation of cell death mechanism and decreased pro-inflammatory cytokine release.

Red and near-infrared light induces intracellular Ca2+ flux via the activation of glutamate N-methyl-D-aspartate receptors

Red and near-infrared (NIR) light effect on Ca²⁺ ions flux through the influence on N-methyl-D-aspartate receptors (NMDARs) and their functioning in HeLa cells was studied in vitro. Cells were irradiated by 650 and 808 nm laser light at different power densities and doses and the obtained effect was compared with that caused by the pharmacological agents. The laser light was found to elevate Ca²⁺ influx into cell cytoplasm in a dose-dependent manner without changes of the NMDAR functioning. Furthermore, the light of both wavelengths demonstrated the ability to elevate Ca²⁺ influx under the pharmacological blockade of NMDARs and also might partially abolish the blockade enhancing Ca²⁺ influx after selective stimulation of the receptors with NMDA. Simultaneously, the light at moderate doses demonstrated a photobiostimulating effect on cells. Based on our experiments and data reported in the literature, we suggest that the low-power visible and NIR light can instigate a cell membrane depolarization via nonthermal activation, resulting in the fast induction of Ca²⁺ influx into cells. The obtained results also demonstrate that NIR light can be used for nonthermal and nonpharmacological stimulation of NMDARs in cancer cells.

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.

Applications of photobiomodulation in hearing research: from bench to clinic

Hearing loss is very common and economically burdensome. No accepted therapeutic modality for sensorineural hearing loss is yet available; most clinicians emphasize rehabilitation, placing hearing aids and cochlear implants. Photobiomodulation (PBM) employs light energy to enhance or modulate the activities of specific organs, and is a popular non-invasive therapy used to treat skin lesions and neurodegenerative disorders. Efforts to use PBM to improve hearing have been ongoing for several decades. Initial in vitro studies using cell lines and ex vivo culture techniques have now been supplanted by in vivo studies in animals; PBM protects the sensory epithelium and triggers neural regeneration. Many reports have used PBM to treat tinnitus. In this brief review, we introduce PBM applications in hearing research, helpful protocols, and relevant background literature.

Photobiomodulation therapy reduces acute pain and inflammation in mice

Photobiomodulation (PBM) is a therapy suggested for the treatment of pain and inflammation. Different mechanisms have been proposed to explain the analgesic and inflammatory effects of photobiomodulation, but there are still gaps on the mechanisms underlying. The objective was to investigate the analgesic and anti-inflammatory effect of red LED, as well as to investigate the possible mechanism of action in acute nociception models. Radiation was applied with red LED (660 nm, 215 mW, 84.64 mW/cm², 2.531 J/cm² (30s); 5.07 J/cm² (60s) 7.61 J/cm² (90s) and 10.15 J/cm² (120 s)). The red LED applied 60 s before the experiments, promoted reduction of the nociceptive neurogenic (1st phase) and inflammatory pain (2nd phase) induced by intraplantar (i.pl.) injection of formalin. This effect duration in the second phase was 180 min after pretreatment of the LED. Red LED also reduced nociception induced by intraperitoneal injection of acetic acid. Furthermore, red LED prevented nociception induced by i.pl. injection of cinnamaldehyde, capsaicin, menthol and acidified saline. It was demonstrate the involvement of glutamatergic system with the reduction the nociception induced by glutamate. The red LED was able to prevent nociception induced by intracellular signaling cascades activators, phorbol 12-myristate 13-acetate (PMA), bradykinin, forskolin and prostaglandin. In addition, red LED, respectively, from 30 to 90s demonstrated an antiedematogenic effect on ear edema and reduction the migration of inflammatory cells induced by single application of croton oil. Thus, the new findings in this study support some underlying mechanism by which red LED phototherapy reduces acute pain. However, need further clarification regarding analgesic and anti-inflammatory effect of the photobiomodulation in preclinical studies.

Photobiomodulation prevents DNA fragmentation of alveolar epithelial cells and alters the mRNA levels of caspase 3 and Bcl-2 genes in acute lung injury

Acute respiratory distress syndrome (ARDS) and acute lung injury (ALI) are defined as pulmonary inflammation that could occur from sepsis and lead to pulmonary permeability and alveolar edema making them life-threatening diseases. Photobiomodulation (PBM) properties have been widely described in the literature in several inflammatory diseases; although the mechanisms of action are not always clear, this could be a possible treatment for ARDS/ALI. Thus, the aim of this study was to evaluate the mRNA levels from caspase-3 and BCL-2 genes and DNA fragmentation in lung tissue from Wistar rats affected by ALI and subjected to photobiomodulation by exposure to a low power infrared laser (808 nm; 100 mW; 3.571 W cm-2; four points per lung). Adult male Wistar rats were randomized into 6 groups (n = 5, for each group): control, PBM10 (10 J cm-2, 2 J and 2 seconds), PBM20 (20 J cm-2, 5 J and 5 seconds), ALI, ALI + PBM10 and ALI + PBM20. ALI was induced by intraperitoneal Escherichia coli lipopolysaccharide injection. Lung samples were collected and divided for mRNA expression of caspase-3 and Bcl-2 and DNA fragmentation quantifications. Data show that caspase-3 mRNA levels are reduced and Bcl-2 mRNA levels increased in ALI after low power infrared laser exposure when compared to the non-exposed ALI group. DNA fragmentation increased in inflammatory infiltrate cells and reduced in alveolar cells. Our research shows that photobiomodulation can alter relative mRNA levels in genes involved in the apoptotic process and DNA fragmentation in inflammatory and alveolar cells after lipopolysaccharide-induced acute lung injury. Also, inflammatory cell apoptosis is part of the photobiomodulation effects induced by exposure to a low power infrared laser.

Mechanisms and Mitochondrial Redox Signaling in Photobiomodulation

Photobiomodulation (PBM) involves the use of red or near-infrared light at low power densities to produce a beneficial effect on cells or tissues. PBM therapy is used to reduce pain, inflammation, edema, and to regenerate damaged tissues such as wounds, bones, and tendons. The primary site of light absorption in mammalian cells has been identified as the mitochondria and, more specifically, cytochrome c oxidase (CCO). It is hypothesized that inhibitory nitric oxide can be dissociated from CCO, thus restoring electron transport and increasing mitochondrial membrane potential. Another mechanism involves activation of light or heat-gated ion channels. This review will cover the redox signaling that occurs in PBM and examine the difference between healthy and stressed cells, where PBM can have apparently opposite effects. PBM has a marked effect on stem cells, and this is proposed to operate via mitochondrial redox signaling. PBM can act as a preconditioning regimen and can interact with exercise on muscles.