The brain-derived neurotrophic factor, nerve growth factor, neurotrophin-3, and induced nitric oxide synthase expressions after low-level laser therapy in an axonotmesis experimental model

Light Therapy in Chronic Migraine

PURPOSE OF REVIEW

This review assesses the effectiveness and safety of light therapy, particularly green light therapy, as an emerging non-pharmacological treatment for chronic migraine (CM). It aims to highlight alternative or complementary approaches to traditional pharmacological remedies, focusing the need for diverse treatment options.

RECENT FINDINGS

Despite sensitivity to light being a defining feature of migraine, light therapy has shown promising signs in providing substantial symptom relief. Studies have provided insights into green light therapy's role in managing CM. These studies consistently demonstrate its efficacy in reducing the frequency, severity, and symptoms of migraines. Additional benefits observed include improvements in sleep quality and reductions in anxiety. Importantly, green light therapy has been associated with minimal side effects, indicating its potential as a suitable option for migraine sufferers. In addition to green light, other forms of light therapy, such as infrared polarized light, low-level laser therapy (LLLT), and intravascular irradiation of blood (ILIB), are also being explored with potential therapeutic effects. Light therapies, especially green light therapy, are recognized as promising, safe, and non-pharmacological interventions for treating CM. They have been shown to be effective in decreasing headache frequency and enhancing the overall quality of life. However, current studies, often limited by small sample sizes, prompt more extensive clinical trials to better understand the full impact of light therapies. The exploration of other light-based treatments, such as LLLT and ILIB, warrants further research to broaden the scope of effective migraine management strategies.

Enhancing nerve regeneration in infraorbital nerve injury rat model: effects of vitamin B complex and photobiomodulation

Orofacial nerve injuries may result in temporary or long-term loss of sensory function and decreased quality of life in patients. B vitamins are required for DNA synthesis and the repair and maintenance of phospholipids. In particular, vitamins B1, B6, and B12 are essential for neuronal function. Deficiency in vitamin B complex (VBC) has been linked to increased oxidative stress, inflammation and demyelination. Photobiomodulation (PBM) has antioxidant activity and is neuroprotective. In addition, a growing literature attests to the positive effects of PBM on nerve repair. To assess the effect of PBM and VBC on regenerative process we evaluated the expression of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), myelin basic protein (MBP), laminin and neurofilaments (NFs) using Western blotting to identify regenerative pattern after chronic constriction injury of the infraorbital nerve (CCI IoN) treated by PBM, VBC or its combination. After CCI IoN, the rats were divided into six groups naive, sham, injured (CCI IoN), treated with photobiomodulation (904 nm, 6.23 J/cm2, CCI IoN + PBM), treated with VBC (containing B1, B6 and B12) 5 times, CCI IoN + VBC) and treated with PBM and VBC (CCI IoN + VBC + PBM). The treatments could revert low expression of BDNF, MBP and laminin. Also reverted the higher expression of neurofilaments and enhanced expression of NGF. PBM and VBC could accelerate injured infraorbital nerve repair in rats through reducing the expression of neurofilaments, increasing the expression of BDNF, laminin and MBP and overexpressing NGF. These data support the notion that the use of PBM and VBC may help in the treatment of nerve injuries. This finding has potential clinical applications.

Photobiomodulation as a Potential Therapy for Erectile Function: A Preclinical Study in a Cavernous Nerve Injury Model

PURPOSE

To identify the optimal photobiomodulation (PBM) parameters using molecular, histological, and erectile function analysis in cavernous nerve injury.

MATERIALS AND METHODS

A cavernous nerve injury was induced in 8-week-old C57BL/6J male mice that were subsequently divided randomly into age-matched control groups. Erectile function tests, penile histology, and Western blotting were performed 2 weeks after surgery and PBM treatment.

RESULTS

The PBM treatment was administered for five consecutive days with a light-emitted diode (LED) device that delivers 660 nm±3% RED light, and near infra-red 830 nm±2% promptly administered following nerve-crushing surgery and achieved a notable restoration of erectile function approximately 90% of the control values. Subsequent in-vitro and ex-vivo analyses revealed the regeneration of neurovascular connections in both the dorsal root ganglion and major pelvic ganglion, characterized by the sprouting of neurites. Furthermore, the expression levels of neurotrophic, survival, and angiogenic factors exhibited a substantial increase across all groups subjected to PBM treatment.

CONCLUSIONS

The utilization of PBM employing LED with 660 nm, 830 nm, and combination of both these wavelengths, exhibited significant efficacy to restore erectile function in a murine model of cavernous nerve injury. Thus, the PBM emerges as a potent therapeutic modality with notable advantages such as efficacy, noninvasiveness, and non-pharmacological interventions for erectile dysfunction caused by nerve injury.

Effects of NGF and Photobiomodulation Therapy on Crush Nerve Injury and Fracture Healing: A Stereological and Histopathological Study in an Animal Model

Study Design

A stereological and histopathological study in an animal model.

Objective

This study explores the effects of the nerve growth factor and photobiomodulation therapy on the damaged nerve tissue and fracture healing.

Methods

A total of 24 rabbits were divided into 4 groups: control group (n = 5), nerve growth factor (NGF) group (n = 7), photobiomodulation (PBMT) group (n = 6), and nerve growth factor and photobiomodulation therapy (NGF+PBMT) group (n = 6). The vertical fracture was performed between the mental foramen and the first premolar, and the mental nerve was crushed for 30 seconds with a standard serrated clamp with a force of approximately 50 N in all groups. The control group received an isotonic solution (.02 mL, .09% NaCl) to the operation site locally. The NGF group received 1 μg human NGF-β/.9% .2 mL NaCl solution for 7 days locally. The PBMT group received PBMT treatment (GaAlAs laser, 810 nm, .3 W, 18 J/cm2) every 48 hours for 14 sessions following the surgery. The NGF+PBMT group received both NGF and PBMT treatment as described above. After 28 days, the bone tissues and mental nerves from all groups were harvested and histologically and stereologically analyzed.

Results

According to the stereological results, the volume of the new vessel and the volume of the new bone were significantly higher in the PBMT group than in other groups (P < .001). According to the histopathological examinations, higher myelinated axons were observed in experimental groups than in the control group.

Conclusions

As a result, PBMT has beneficial effects on bone regeneration. Based on the light microscopic evaluation, more regenerated axon populations were observed in the NGF group than in the PBMT and PBMT + NGF groups in terms of myelinated axon content.

Effects of Low-Level Laser Therapy and Purified Natural Latex (Hevea brasiliensis) Protein on Injured Sciatic Nerve in Rodents: Morpho-Functional Analysis

The present study analyzed the effects of low-level laser therapy (LLLT) and the purified natural latex protein (Hevea brasiliensis, F1 protein) on the morpho-function of sciatic nerve crush injuries in rats. One-hundred and eight male Wistar rats were randomly allocated to six groups (n = 18): 1. Control; 2. Exposed (nerve exposed); 3. Injury (injured nerve without treatment); 4. LLLT (injured nerve irradiated with LLLT (15 J/cm2, 780 nm)); 5. F1 (injured nerve treated with F1 protein (0.1%)); and 6. LLLT + F1 (injured nerve treated with LLLT and F1). On the 1st, 7th, 14th, and 56th days after injury, a functional sensory analysis of mechanical allodynia and mechanical hyperalgesia and a motor analysis of grip strength and gait were performed. After 3, 15, and 57 days, the animals were euthanized for morphometric/ultrastructural analyses. The treatments applied revealed improvements in morphometric/ultrastructural parameters compared to the injured group. Sensory analyses suggested that the improvements observed were associated with time progression and not influenced by the treatments. Motor analyses revealed significant improvements in grip strength from the 7th day in the LLLT group and in gait from the 56th day in all treated groups. We concluded that even though the morphological analyses showed improvements with the treatments, they did not influence sensory recovery, and LLLT improved motor recovery.

Non-Pharmacological Therapeutic Options for the Treatment of Alzheimer’s Disease

Alzheimer’s disease is a growing global crisis in need of urgent diagnostic and therapeutic strategies. The current treatment strategy mostly involves immunotherapeutic medications that have had little success in halting disease progress. Hypotheses for pathogenesis and development of AD have been expanded to implicate both organ systems as well as cellular reactions. Non-pharmacologic interventions ranging from minimally to deeply invasive have attempted to address these diverse contributors to AD. In this review, we aim to delineate mechanisms underlying such interventions while attempting to provide explanatory links between the observed differences in disease states and postulated metabolic or structural mechanisms of change. The techniques discussed are not an exhaustive list of non-pharmacological interventions against AD but provide a foundation to facilitate a deeper understanding of the area of study.

Efficacy of LED Photobiomodulation for Functional and Axonal Regeneration After Facial Nerve Section-Suture

Facial nerve damage can lead to partial or total facial nerve palsy. Photobiomodulation has been reported to improve and accelerate functional recovery following peripheral nerve lesion, depending on the type of lesion and the light exposure parameters used. The aim of this study was to investigate the effects of infrared exposure on functional and axonal regeneration after section-suture of the distal branches of the facial nerve: the buccal and marginal mandibular branches and the distal pes. The animals underwent surgery and were irradiated with infrared light at 850 nm twice daily from day 1 to day 16. The recovery of facial function was then studied at both the behavioral and morphological levels. Behavioral analyses were performed by videoscoring with a high-speed camera and using various devices to assess the recovery of whisker movement on the lesioned side from day 1 to day 30. We also assessed nasal deviation toward the intact side and the ability to close the ipsilateral eyelid completely from day 1 to day 38 and from day 1 to day 50, respectively. For morphological analyses, we assessed the re-establishment of facial motoneuron labeling with Fluorogold®, an immunofluorescent retrograde marker of axonal transport injected into the vibrissae, on D10, D14 and D30. We found that whisker movements recovery was significantly faster in treated than in control mice. A complete disappearance of nasal deviation was observed at 2 weeks in infrared-treated lesioned mice and at 5 weeks in controls. Complete eyelid closure was observed 3 weeks after surgery in treated animals and 6 weeks after surgery in controls. Finally, normal fluorogold labeling of the facial nuclei complex was restored 30 days after surgery in the treated animals, but no such restoration was ever observed in control animals. In conclusion, our data show that IR treatment at a distal site has a significant positive effect on facial nerve recovery. These findings pave the way for the clinical use of infrared photobiomodulation in patients with nerve lesions.

Photobiomodulation at a wavelength of 633 nm leads to faster functional recovery than 804 nm after facial nerve injury

We analyzed the effects of photobiomodulation (PBM) of various wavelengths on regeneration of the facial nerve using in vitro and in vivo experimental models. We assessed the antioxidative effect of PBM in geniculate ganglion neurons irradiated with a diode laser at 633 nm, 780 nm and 804 nm. Wavelengths of 633 and 780 nm but not 804 nm inhibited cell death by oxidative stress. We assessed the effects of PBM on functional and morphologic recovery in rats divided into control, facial nerve damage (FND) and FND irradiated with a 633 nm or 804 nm lasers. Injured rats treated with 633-nm light had better facial palsy scores, larger axon diameter and higher expression of Schwann cells compared with the FND group. No positive results were observed in rats irradiated at 804-nm light. These findings indicate that 633-nm PBM promotes accelerated nerve regeneration and improved functional recovery in an injured facial nerve.

Efficacy of low-level laser therapy in nerve injury repair-a new era in therapeutic agents and regenerative treatments

BACKGROUND

Traumatic nerve injuries may result in severe motor dysfunctions. Although the microenvironment of peripheral axons favors their regeneration, regenerative process is not always successful.

PURPOSE

We reviewed and discussed the main findings obtained with low-level laser therapy (LLLT), a therapeutic intervention that has been employed in order to achieve an optimized regeneration process in peripheral axons.

SCOPE

Disseminating the best available evidence for the effectiveness of this therapeutic strategy can potentially improve the statistics of success in the clinical treatment of nerve injuries. We found evidence that LLLT optimizes the regeneration of peripheral axons, improving motor function, especially in animal models. Nonetheless, further clinical evidence is still needed before LLLT can be strongly recommended. Although the results are promising, the elucidation of the mechanisms of action and safety assessment are necessary to support highquality clinical studies.

CONCLUSION

The present careful compilation of findings with consistent pro-regenerative evidence and published in respected scientific journals can be valuable for health professionals and researchers in the field, possibly contributing to achieve more promising results in future randomized controlled trials and interventions, providing better prognosis for clinical practice.

Synergistic effects of combined therapy with transcranial photobiomodulation and enriched environment on depressive- and anxiety-like behaviors in a mice model of noise stress

The development of anxiety and depression due to chronic exposure to noise stress has remained as an unsolved health problem so far. Despite the studies suggesting the neuroenhancement effects of transcranial photobiomodulation (tPBM) and housing in an enriched environment (EE), the combined effects of these treatments have not been elucidated yet. Also, there is no available data on the relationship between the application of tPBM and hippocampal brain-derived neurotrophic factor (BDNF) expression in animal models of stress. The present study aims to investigate the application of the tPBM and EE (alone or in combination) on depressive- and anxiety-like behaviors in a mice model of noise stress. Mice were divided into five groups: control, noise, noise + EE, noise + tPBM, and noise + EE + tPBM. Except for the control group, other groups were subjected to 110 dB SPL white noise for 4 h/day for 14 consecutive days and received their respective treatments. Forced Swimming Test (FST) was used to evaluate depressive-like behaviors. Elevated Plus Maze (EPM) and Open Field Test (OFT) were used to evaluate anxiety-like behaviors. BDNF, tyrosine receptor kinase B (TrkB), and cAMP response element-binding (CREB) protein levels in the hippocampus were determined by the Western blot method, and also serum corticosterone levels were assessed using an ELISA kit. Exposure to noise stress significantly elevated serum corticosterone level; downregulated hippocampal BDNF, TrkB, and CREB protein expressions; and resulted in depressive- and anxiety-like behaviors. While, the application of tPBM (810 nm wavelength, 8 J/cm² fluence, 10 Hz pulsed wave mode), housing in EE, and their combination lowered corticosterone levels, upregulated the BDNF/TrkB/CREB signaling pathway in the hippocampus, and improved behavioral outcomes in noise stress subjected mice. Our finding revealed the improving effects of tPBM and EE on depressive and anxiety-like behaviors induced by noise stress, possibly by augmenting the BDNF/TrkB/CREB signaling pathway.

Main Morphological Characteristics of Tubular Polymeric Scaffolds to Promote Peripheral Nerve Regeneration-A Scoping Review

The "nerve guide conduits" (NGC) used in nerve regeneration must mimic the natural environment for proper cell behavior.

OBJECTIVE

To describe the main morphological characteristics of polymeric NGC to promote nerve regeneration.

METHODS

A scoping review was performed following the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) criteria in the PubMed, Web of Science, Science Direct, and Scientific Electronic Library Online (SciELO) databases. Primary studies that considered/evaluated morphological characteristics of NGC to promote nerve regeneration were included.

RESULT

A total of 704 studies were found, of which 52 were selected. The NGC main morphological characteristics found in the literature were: (I) NGC diameter affects the mechanical properties of the scaffold. (II) Wall thickness of NGC determines the exchange of nutrients, molecules, and neurotrophins between the internal and external environment; and influences the mechanical properties and biodegradation, similarly to NGC (III) porosity, (IV) pore size, and (V) pore distribution. The (VI) alignment of the NGC fibers influences the phenotype of cells involved in nerve regeneration. In addition, the (VII) thickness of the polymeric fiber influences neurite extension and orientation.

CONCLUSIONS

An NGC should have its diameter adjusted to the nerve with wall thickness, porosity, pore size, and distribution of pores, to favor vascularization, permeability, and exchange of nutrients, and retention of neurotrophic factors, also favoring its mechanical properties and biodegradability.

Mechanisms and Pathways of Pain Photobiomodulation: A Narrative Review

A growing body of evidence supports the modulation of pain by light exposure. As such, phototherapy is being increasingly utilized for the management of a variety of pain conditions. The modes of delivery, and hence applications of phototherapy, vary by wavelength, intensity, and route of exposure. As such, differing mechanisms of action exist depending upon those parameters. Cutaneous application of red light (660 nm) has been shown to reduce pain in neuropathies and complex regional pain syndrome-I, whereas visual application of the same wavelength of red light has been reported to exacerbate migraine headache in patients and lead to the development of functional pain in animal models. Interestingly visual exposure to green light can result in reduction in pain in variety of pain conditions such as migraine and fibromyalgia. Cutaneous application typically requires exposure on the order of minutes, whereas visual application requires exposure on the order of hours. Both routes of exposure elicit changes centrally in the brainstem and spinal cord, and peripherally in the dorsal root ganglia and nociceptors. The mechanisms of photobiomodulation of pain presented in this review provide a foundation in furtherance of exploration of the utility of phototherapy as a tool in the management of pain. PERSPECTIVE: This review synopsizes the pathways and mechanisms through which light modulates pain and the therapeutic utility of different colors and exposure modalities of light on pain. Recent advances in photobiomodulation provide a foundation for understanding this novel treatment for pain on which future translational and clinical studies can build upon.

Effects of 660-nm and 780-nm Laser Therapy on ST88-14 Schwann Cells

The aim of the present study was to evaluate the comparative effects of red (660-nm) and near-infrared (780-nm) low-level laser therapy (LLLT) on viability, mitochondrial activity, morphology and gene expression of growth factors on Schwann cells (SC). ST88-14 cells were grown in RPMI 1640 with 10 mM of HEPES, 2 mM of glutamine, 10% fetal bovine serum and 1% antibiotic-antimycotic solution at 37°C in humidified atmosphere of 5% CO₂ . Cells were detached with trypsin and centrifugated at 231 g for 5 min at 10°C, and the pellet (8 × 10⁴  cells/tube) was irradiated at the bottom of 50 ml polypropylene tube with a Twin-Laser system (660 and 780 nm, 40 mW, 1 mW cm^-2 , 3.2 and 6.4 J, 80 and 160 J cm^-2 with 80 and 160 s). After 1, 3 and 7 days, the analysis was performed. After irradiation, the SC increase mitochondrial activity, gene expression of the neural growth factors NGF and BDNF, and cell migration and increase the G2/M cells. SC showed neuronal morphology, normal F-actin cytoskeleton organization and positive labeling for S100. PBM increased metabolic activity, mitosis and gene expression when irradiated with red and infrared LLLT. An increase in cell migration was obtained when irradiated with infrared LLLT.

Effects of the Association between Photobiomodulation and Hyaluronic Acid Linked Gold Nanoparticles in Wound Healing

Healing is the process responsible for restoring the integrity of the body's internal or external structures when they rupture. Photobiomodulation (PBM) stands out as one of the most efficient resources in the treatment of epithelial lesions, as well as hyaluronic acid (HA), which has been emerging as a new molecule for the treatment of dermal and epidermal lesions. The biological application of gold nanoparticles (GNPs) shows promising results. This study aimed to investigate the possible anti-inflammatory and antioxidant effects of the association between PBM and GNPs-linked HA in an epithelial lesion model. Fifty Wistar rats were randomly distributed in the Control Group (CG); (PBM); (PBM + HA); (PBM + GNPs); (PBM + GNPs-HA). The animals were anesthetized, trichotomized, and induced to a surgical incision in the dorsal region. Topical treatment with HA (0.9%) and/or GNPs (30 mg/kg) occurred daily associated with 904 nm laser irradiation, dose of 5 J/cm², which started 24 h after the lesion and was performed daily until the seventh day. The levels of proinflammatory (IL1 and TNFα), anti-inflammatory (IL10 and IL4) and growth factors (FGF and TGFβ) cytokines and oxidative stress parameters were evaluated, besides histological analysis through inflammatory infiltrate, fibroblasts, new vessels, and collagen production area. Finally, for the analysis of wound size reduction, digital images were performed and subsequently analyzed by the IMAGEJ software. The treated groups showed a decrease in proinflammatory cytokine levels and an increase in anti-inflammatory cytokines. TGFβ and FGF levels also increased in the treated groups, especially in the combination therapy group (PBM + GNPs-HA). Regarding the oxidative stress parameters, MPO, DCF, and Nitrite levels decreased in the treated groups, as well as the oxidative damage (Carbonyl and Thiol groups). In contrast, antioxidant defense increased in the groups with the appropriate therapies proposed compared to the control group. Histological sections were analyzed where the inflammatory infiltrate was lower in the PBM + GNPs-HA group. The number of fibroblasts was higher in the PBM and PBM + HA treated groups, whereas collagen production was higher in all treated groups. Finally, in the analysis of the wound area contraction, the injury group presented a larger area in cm² compared to the other groups. Taken together, these results allow us to observe that the combination of PBM + GNPs-HA optimized the secretion of anti-inflammatory cytokines, proliferation and cell differentiation growth factors, and made an earlier transition to the chronic phase, contributing to the repair process.

Photobiomodulation in Sciatic Nerve Crush Injuries in Rodents: A Systematic Review of the Literature and Perspectives for Clinical Treatment

Objective : The aim of the study was to perform a literature review to analyze the effect of photobiomodulation in experimental studies on peripheral nerve regeneration after sciatic nerve crush injury in rodents. Methods: A bibliographic search was performed in the electronic databases, including MEDLINE (PubMed), SCOPUS, and SciELO, from 2008 to 2018. Results: A total of 1912 articles were identified in the search, and only 19 fulfilled all the inclusion criteria. Along with the parameters most found in the manuscripts, the most used wavelengths were 660 nm and 830 nm, power of 30 and 40 mW, and energy density of 4 and 10 J/cm² . For total energy throughout the intervention period, the lowest energy found with positive effects was 0.70 J, and the highest 1.141 J. Seventeen studies reported positive effects on nerve regeneration. The variables selected to analyze the effect were: Sciatic Functional Index (SFI), Static Sciatic Index (SSI), morphometric, morphological, histological, zymographic, electrophysiological, resistance mechanics and range of motion (ROM). The variety of parameters used in the studies demonstrated that there is yet no pre-determined protocol for treating peripheral nerve regeneration. Only two studies by different authors used the same power, energy density, beam area, and power density. Conclusion: It was concluded that the therapeutic window of the photobiomodulation presents a high variability of parameters with the wavelength (632.8 to 940 nm), power (5 to 170 mW) and energy density (3 to 280 J /cm² ), promoting nerve regeneration through the expression of cytokines and growth factors that aid in modulating the inflammatory process, improving morphological aspects, restoring the functionality to the animals in a brief period.

Photobiomodulation After Neurotization (Oberlin Procedure) in Brachial Plexus Injury: A Randomized Control Trial

Objective: To investigate effect of photobiomodulation (PBM) on nerve regeneration after neurotization with the Oberlin Procedure (ulnar fascicle to motor branch to biceps) to restore elbow flexion in patients with brachial plexus injury. Materials and methods: This prospective randomized controlled trial was conducted with 14 patients with high brachial plexus injury who underwent neurotization with the Oberlin Procedure to restore elbow flexion. The patients were randomly allocated to two groups of equal numbers: control group and PBM group. In this study, the PBM used has a wavelength of 808 nm, 50 mW power, continuous mode emission, 4 J/cm² dosimetry, administered daily for 10 consecutive days, with an interval of 2 days (weekends). The outcome of surgery was assessed after 1, 2, 3, and 6 months. The nonparametric Mann-Whitney U-test and chi-square test were utilized to compare the results between both groups. Results: After 3 months postoperatively, more patients in the PBM group had demonstrated signs of reinnervation and the mean muscle power was significantly higher in the PBM group. No adverse effects resulted from the administration of PBM. Conclusions: PBM is a treatment modality that can improve nerve regeneration after neurotization with the Oberlin Procedure.

Transcranial photobiomodulation prevents anxiety and depression via changing serotonin and nitric oxide levels in brain of depression model mice: A study of three different doses of 810 nm laser

OBJECTIVES

The effectiveness of transcranial photobiomodulation (TPBM) in treating anxiety and depression disorders is a demonstrated and identified issue. However, the optimum therapeutic dose and the underlying mechanism of action are not fully understood. In this study, the therapeutic effects of three different near-infrared (NIR) doses on anxiety- and depression-like behaviors as well as cerebral levels of serotonin (5-HT) and nitric oxide (NO) were evaluated in a mouse model of chronic restraint stress (CRS).

MATERIALS AND METHODS

CRS procedure (3 hours/day, over 3 weeks) was performed as a typical stress model to study anxiety and depression along with laser treatment (3 times/week, over 3 weeks), which began simultaneously with CRS. A NIR diode laser (810 nm wavelength, 10 Hz) with the output power of 200 mW and power density of 4.75 W/cm² was implemented to deliver three different doses of 4, 8, and 16 J/cm² to the cerebral cortex of mice. Behavioral experiments including open field, tail suspension, and elevated plus maze tests as well as serum cortisol levels were assessed to evaluate the anti-anxiety and anti-depressive effects of NIR TPBM. The changes of 5-HT and NO levels in the prefrontal cortex (PFC) and hippocampus (Hipp) were assessed.

RESULTS

CRS procedure induced anxiety- and depression-like behaviors, increased serum cortisol levels, decreased 5-HT and increased NO levels in the PFC and Hipp areas. NIR TPBM improved behavioral results, decreased serum cortisol levels, increased 5-HT and decreased NO concentrations in the PFC and Hipp. A dose of 8 J/cm² of NIR TPBM showed the maximum effects on behavioral and molecular results, while a decline was observed from the optimum effects at both lower (4 J/cm² ) and higher (16 J/cm² ) doses.

CONCLUSION

Our results demonstrated that NIR TPBM had an anti-anxiety and anti-depressive effect in CRS mice, which is probably linked to increasing 5-HT and decreasing NO levels in the PFC and Hipp areas. Also, the maximum anti-anxiety and anti-depressive effect was produced at dose of 8 J/cm² . Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Growth factors expression and ultrastructural morphology after application of low-level laser and natural latex protein on a sciatic nerve crush-type injury

The effects of low-level laser therapy (LLLT) and natural latex protein (F1, Hevea brasiliensis) were evaluated on crush-type injuries (15kg) to the sciatic nerve in the expressions of nerve growth factor (NGF) and vascular endothelium growth factor (VEGF) and ultrastructural morphology to associate with previous morphometric data using the same protocol of injury and treatment. Thirty-six male rats were allocated into six experimental groups (n = 6): 1-Control; 2-Exposed nerve; 3-Injured nerve; 4-LLLT (15J/cm², 780nm, 30mW, Continuous Wave) treated injured nerve; 5-F1 (0,1mg) treated injured nerve; and 6-LLLT&F1 treated injured nerve. Four or eight weeks after, sciatic nerve samples were processed for analysis. NGF expression were higher (p<0.05) four weeks after in all injured groups in comparison to Control (Med:0.8; Q1:0; Q3:55.5%area). Among them, the Injured (Med:70.7; Q1:64.4; Q3:77.5%area) showed the highest expression, and F1 (Med:17.3; Q1:14.1; Q3:21.7%area) had the lowest. At week 8, NGF expressions decreased in the injured groups. VEGF was expressed in all groups; its higher expression was observed in the injured groups 4 weeks after (Injured. Med:29.5; F1. Med:17.7 and LLLT&F1. Med:19.4%area). At week 8, a general reduction of VEGF expression was noted, remaining higher in F1 (Med:35.1; Q1.30.6; Q3.39.6%area) and LLLT&F1 (Med:18.5; Q1:16; Q3:25%area). Ultrastructural morphology revealed improvements in the treated groups; 4 weeks after, the F1 group presented greater quantity and diameter of the nerve fibers uniformly distributed. Eight weeks after, the F1 and LLLT&F1 showed similar characteristics to the non-injured groups. In summary, these results and our previous studies indicated that F1 and LLLT may favorably influence the healing of nerve crush injury. Four weeks after nerve injury F1 group showed the best results suggesting recovery acceleration; at 8th week F1 and LLLT&F1 groups presented better features and higher vascularization that could be associated with VEGF maintenance.

Use of low-power He-Ne laser therapy to accelerate regeneration processes of injured sciatic nerve in rabbit

Background

Photostimulation using low-power laser had been used for nervous repair with interesting results. This study aimed to evaluate the influence of 20 mW low-power He-Ne laser on the regeneration of a peripheral sciatic nerve after trauma using the Albino rabbit as an animal model for experimental treatment.

Methods

Six adult male rabbits were randomly assigned into two equal groups (control- and laser-treated). General anesthesia was administered intramuscularly, and exploration of the sciatic nerve was done in the lateral aspect of the legs. Complete longitudinal and reverse sections of the nerve were performed, which was followed by crushing of the neural sheath. Treatment was carried out directly after the trauma. Irradiation doses of low-level laser therapy (LLLT-31.5 J/cm²) with once a day application for 10 consecutive days and observed for 30 days. The animals were followed up for an extra 2 weeks. Two important factors were examined histopathology and functionality of the nerve.

Results

Compared to the control group, significant variations in regeneration were observed, including thicker nerve fibers, and more regular myelin layers in the treated group.

Conclusions

The results of the present study suggest that laser therapy may be a viable approach for nerve regeneration and repair.

Photobiomodulation Therapy (PBMT) in Peripheral Nerve Regeneration: A Systematic Review

Photobiomodulation therapy (PBMT) has been investigated because of its intimate relationship with tissue recovery processes, such as on peripheral nerve damage. Based on the wide range of benefits that the PBMT has shown and its clinical relevance, the aim of this research was to carry out a systematic review of the last 10 years, ascertaining the influence of the PBMT in the regeneration of injured peripheral nerves. The search was performed in the PubMed/MEDLINE database with the combination of the keywords: low-level laser therapy AND nerve regeneration. Initially, 54 articles were obtained, 26 articles of which were chosen for the study according to the inclusion criteria. In the qualitative aspect, it was observed that PBMT was able to accelerate the process of nerve regeneration, presenting an increase in the number of myelinated fibers and a better lamellar organization of myelin sheath, besides improvement of electrophysiological function, immunoreactivity, high functionality rate, decrease of inflammation, pain, and the facilitation of neural regeneration, release of growth factors, increase of vascular network and collagen. It was concluded that PBMT has beneficial effects on the recovery of nerve lesions, especially when related to a faster regeneration and functional improvement, despite the variety of parameters.

Analysis of the variation in low-level laser energy density on the crushed sciatic nerves of rats: a morphological, quantitative, and morphometric study

The objective of this study was to evaluate three energy densities of low-level laser therapy (LLLT, GaAlAs, 780 nm, 40 mW, 0.04 cm²) for the treatment of lesions to peripheral nerves using the sciatic nerve of rats injured via crushing model (15 kgf, 5.2 MPa). Thirty Wistar rats (♂, 200-250 g) were divided into five groups (n = 6): C-control, not injured, and irradiated; L0-injured nerve without irradiation; L4-injured nerve irradiated with LLLT 4 J/cm² (0.16 J); L10-injured nerve irradiated with LLLT 10 J/cm² (0.4 J); and L50-injured nerve irradiated with LLLT 50 J/cm² (2 J). The animals were sacrificed 2 weeks after the injury via perfusion with glutaraldehyde (2.5%, 0.1 M sodium cacodylate buffer). The nerve tissue was embedded in historesin, cut (3 μm), mounted on slides, and stained (Sudan black and neutral red). The morphological and quantitative analysis (myelin and blood capillary densities) and morphometric parameters (maximum and minimum diameters of nerve fibers, axon diameter, G-ratio, myelin sheath thickness) were assessed using the ImageJ software. ANOVA (parametric) or Kruskal-Wallis (nonparametric) tests were used for the statistical analysis. Groups L0, L4, L10, and L50 exhibited diminished values of all the quantitative and morphometric parameters in comparison to the control group. The morphological, quantitative, and morphometric data revealed improvement after injury in groups L4, L10, and L50 (irradiated groups) compared to the injured-only group (L0); the best results, in general, were observed for the L10 group after 15 days of nerve injury.

Low-level laser irradiation modulates brain-derived neurotrophic factor mRNA transcription through calcium-dependent activation of the ERK/CREB pathway

Low-level laser (LLL) irradiation has been reported to promote neuronal differentiation, but the mechanism remains unclear. Brain-derived neurotrophic factor (BDNF) has been confirmed to be one of the most important neurotrophic factors because it is critical for the differentiation and survival of neurons during development. Thus, this study aimed to investigate the effects of LLL irradiation on Bdnf messenger RNA (mRNA) transcription and the molecular pathway involved in LLL-induced Bdnf mRNA transcription in cultured dorsal root ganglion neurons (DRGNs) using Ca²⁺ imaging, pharmacological detections, RNA interference, immunocytochemistry assay, Western blot, and qPCR analysis. We show here that LLL induced increases in the [Ca²⁺] _i level, Bdnf mRNA transcription, cAMP-response element-binding protein (CREB) phosphorylation, and extracellular signal-regulated kinase (ERK) phosphorylation, mediated by Ca²⁺ release via inositol triphosphate receptor (IP3R)-sensitive calcium (Ca²⁺) stores. Blockade of Ca²⁺ increase suppressed Bdnf mRNA transcription, CREB phosphorylation, and ERK phosphorylation. Downregulation of phosphorylated (p)-CREB reduced Bdnf mRNA transcription triggered by LLL. Furthermore, blockade of ERK using PD98059 inhibitor reduced p-CREB and Bdnf mRNA transcription induced by LLL. Taken together, these findings establish the Ca²⁺-ERK-CREB cascade as a potential signaling pathway involved in LLL-induced Bdnf mRNA transcription. To our knowledge, this is the first report of the mechanisms of Ca²⁺-dependent Bdnf mRNA transcription triggered by LLL. These findings may help further explore the complex molecular signaling networks in LLL-triggered nerve regeneration in vivo and may also provide experimental evidence for the development of LLL for clinical applications.

Low-level laser therapy attenuates the acute inflammatory response induced by muscle traumatic injury

The purpose of this work was to investigate the effect of early and long-term low-level laser therapy (LLLT) on oxidative stress and inflammatory biomarkers after acute-traumatic muscle injury in Wistar rats. Animals were randomly divided into the following four groups: control group (CG), muscle injury group (IG), CG + LLLT, and IG + LLLT: laser treatment with doses of 3 and 5 J/cm(2). Muscle traumatic injury was induced by a single-impact blunt trauma in the rat gastrocnemius. Irradiation for 3 or 5 J/cm(2) was initiated 2, 12, and 24 h after muscle trauma induction, and the treatment was continued for five consecutive days. All the oxidant markers investigated. namely thiobarbituric acid-reactive substance, carbonyl, superoxide dismutase, glutathione peroxidase, and catalase, were increased as soon as 2 h after muscle injury and remained increased up to 24 h. These alterations were prevented by LLLT at a 3 J/cm(2) dose given 2 h after the trauma. Similarly, LLLT prevented the trauma-induced proinflammatory state characterized by IL-6 and IL-10. In parallel, trauma-induced reduction in BDNF and VEGF, vascular remodeling and fiber-proliferating markers, was prevented by laser irradiation. In order to test whether the preventive effect of LLLT was also reflected in muscle functionality, we tested the locomotor activity, by measuring distance traveled and the number of rearings in the open field test. LLLT was effective in recovering the normal locomotion, indicating that the irradiation induced biostimulatory effects that accelerated or resolved the acute inflammatory response as well as the oxidant state elicited by the muscle trauma.

Low-level laser therapy for traumatic brain injury in mice increases brain derived neurotrophic factor (BDNF) and synaptogenesis

Transcranial low-level laser (light) therapy (LLLT) is a new non-invasive approach to treating a range of brain disorders including traumatic brain injury (TBI). We (and others) have shown that applying near-infrared light to the head of animals that have suffered TBI produces improvement in neurological functioning, lessens the size of the brain lesion, reduces neuroinflammation, and stimulates the formation of new neurons. In the present study we used a controlled cortical impact TBI in mice and treated the mice either once (4 h post-TBI, 1-laser), or three daily applications (3-laser) with 810 nm CW laser 36 J/cm(2) at 50 mW/cm(2). Similar to previous studies, the neurological severity score improved in laser-treated mice compared to untreated TBI mice at day 14 and continued to further improve at days 21 and 28 with 3-laser being better than 1-laser. Mice were sacrificed at days 7 and 28 and brains removed for immunofluorescence analysis. Brain-derived neurotrophic factor (BDNF) was significantly upregulated by laser treatment in the dentate gyrus of the hippocampus (DG) and the subventricular zone (SVZ) but not in the perilesional cortex (lesion) at day 7 but not at day 28. Synapsin-1 (a marker for synaptogenesis, the formation of new connections between existing neurons) was significantly upregulated in lesion and SVZ but not DG, at 28 days but not 7 days. The data suggest that the benefit of LLLT to the brain is partly mediated by stimulation of BDNF production, which may in turn encourage synaptogenesis. Moreover the pleiotropic benefits of BDNF in the brain suggest LLLT may have wider applications to neurodegenerative and psychiatric disorders. Neurological Severity Score (NSS) for TBI mice.

Low-level laser therapy for prevention of noise-induced hearing loss in rats

Noninvasive low-level laser therapy (LLLT) is neuroprotective, but the mechanism of this effect is not fully understood. In this study, the use of LLLT as a novel treatment for noise-induced hearing loss (NIHL) is investigated. Sprague-Dawley rats were exposed to intense noise and their right ears were irradiated with an 808nm diode laser at an output power density of 110 or 165mW/cm(2) for a 30min period for 5 consecutive days. Measurement of the auditory brainstem response revealed an accelerated recovery of auditory function in the groups treated with LLLT compared with the non-treatment group at days 2, 4, 7 and 14 after noise exposure. Morphological observations also revealed a significantly higher outer hair cell survival rate in the LLLT groups. Immunohistochemical analyses for inducible nitric oxide synthase (iNOS) and cleaved caspase-3 were used to examine oxidative stress and apoptosis. Strong immunoreactivities were observed in the inner ear tissues of the non-treatment group, whereas these signals were decreased in the LLLT group at 165mW/cm(2) power density. Our findings suggest that LLLT has cytoprotective effects against NIHL via the inhibition of iNOS expression and apoptosis.