Near infrared transcranial laser therapy applied at various modes to mice following traumatic brain injury significantly reduces long-term neurological deficits

The Effect of Intranasal Plus Transcranial Photobiomodulation on Neuromuscular Control in Individuals with Repetitive Head Acceleration Events

Objective: This proof-of-concept study was to investigate the relationship between photobiomodulation (PBM) and neuromuscular control. Background: The effects of concussion and repetitive head acceleration events (RHAEs) are associated with decreased motor control and balance. Simultaneous intranasal and transcranial PBM (itPBM) is emerging as a possible treatment for cognitive and psychological sequelae of brain injury with evidence of remote effects on other body systems. Methods: In total, 43 (39 male) participants, age 18-69 years (mean, 49.5; SD, 14.45), with a self-reported history of concussive and/or RHAE and complaints of their related effects (e.g., mood dysregulation, impaired cognition, and poor sleep quality), completed baseline and posttreatment motor assessments including clinical reaction time, grip strength, grooved pegboard, and the Mini Balance Evaluation Systems Test (MiniBEST). In the 8-week interim, participants self-administered itPBM treatments by wearing a headset comprising four near-infrared light-emitting diodes (LED) and a near-infrared LED nasal clip. Results: Posttreatment group averages in reaction time, MiniBEST reactive control subscores, and bilateral grip strength significantly improved with effect sizes of g = 0.75, g = 0.63, g = 0.22 (dominant hand), and g = 0.34 (nondominant hand), respectively. Conclusion: This study provides a framework for more robust studies and suggests that itPBM may serve as a noninvasive solution for improved neuromuscular health.

Traumatic Brain Injury and Neuromodulation Techniques in Rehabilitation: A Scoping Review

BACKGROUND AND OBJECTIVES

Traumatic Brain Injury (TBI) is a condition in which an external force, usually a violent blow to the head, causes functional impairment in the brain. Neuromodulation techniques are thought to restore altered function in the brain, resulting in improved function and reduced symptoms. Brain stimulation can alter the firing of neurons, boost synaptic strength, alter neurotransmitters and excitotoxicity, and modify the connections in their neural networks. All these are potential effects on brain activity. Accordingly, this is a promising therapy for TBI. These techniques are flexible because they can target different brain areas and vary in frequency and amplitude. This review aims to investigate the recent literature about neuromodulation techniques used in the rehabilitation of TBI patients.

MATERIALS AND METHODS

The identification of studies was made possible by conducting online searches on PubMed, Web of Science, Cochrane, Embase, and Scopus databases. Studies published between 2013 and 2023 were selected. This review has been registered on OSF (JEP3S).

RESULTS

We have found that neuromodulation techniques can improve the rehabilitation process for TBI patients in several ways. Transcranial Magnetic Stimulation (TMS) can improve cognitive functions such as recall ability, neural substrates, and overall improved performance on neuropsychological tests. Repetitive TMS has the potential to increase neural connections in many TBI patients but not in all patients, such as those with chronic diffuse axonal damage.

CONCLUSIONS

This review has demonstrated that neuromodulation techniques are promising instruments in the rehabilitation field, including those affected by TBI. The efficacy of neuromodulation can have a significant impact on their lives and improve functional outcomes for TBI patients.

Photobiomodulation therapy restores olfactory function impaired by photothrombosis in mouse olfactory bulb

An ischemic stroke typically accompanies numerous disorders ranging from somatosensory dysfunction to cognitive impairments, inflicting patients with various neurologic symptoms. Among pathologic outcomes, post-stroke olfactory dysfunctions are frequently observed. Despite the well-known prevalence, therapy options for such compromised olfaction are limited, likely due to the complexity of olfactory bulb architecture, which encompasses both the peripheral and central nervous systems. As photobiomodulation (PBM) emerged for treating ischemia-associated symptoms, the effectiveness of PBM on stroke-induced impairment of olfactory function was explored. Novel mouse models with olfactory dysfunctions were prepared using photothrombosis (PT) in the olfactory bulb on day 0. The post-PT PBM was performed daily from day 2 to day 7 by irradiating the olfactory bulb via an 808 nm laser with a fluence of 40 J/cm2 (325 mW/cm2 for 2 min per day). The buried food test (BFT) was used to score behavioral acuity in food-deprived mice to assess the olfactory function before PT, after PT, and after PBM. Histopathological examinations and cytokine assays were performed on the mouse brains harvested on day 8. The results from BFT were specific to an individual, with positive correlations between the baseline latency time measured before PT and its alteration at the ensuing stages for both the PT and PT + PBM groups. Also, the correlation analysis in both groups showed highly similar, significant positive relationships between the early and late latency time change independent of PBM, implicating a common recovery mechanism. Particularly, PBM treatment accelerated the recovery of impaired olfaction following PT by suppressing inflammatory cytokines and enhancing both glial and vascular factors (e.g., GFAP, IBA-1, and CD31). PBM therapy during the acute phase of ischemia improves the compromised olfactory function by modulating microenvironments and inflammation status of the affected tissue.

Photobiomodulation in Acute Traumatic Brain Injury: A Systematic Review and Meta-Analysis

Photobiomodulation (PBM) is a therapeutic modality that has gained increasing interest in neuroscience applications, including acute traumatic brain injury (TBI). Its proposed mechanisms for therapeutic effect when delivered to the injured brain include antiapoptotic and anti-inflammatory effects. This systematic review summarizes the available evidence for the value of PBM in improving outcomes in acute TBI and presents a meta-analysis of the pre-clinical evidence for neurological severity score (NSS) and lesion size in animal models of TBI. A systematic review of the literature was performed, with searches and data extraction performed independently in duplicate by two authors. Eighteen published articles were identified for inclusion: seventeen pre-clinical studies of in vivo animal models and one clinical study in human patients. The available human study supports safety and feasibility of PBM in acute moderate TBI. For pre-clinical studies, meta-analysis for NSS and lesion size were found to favor intervention versus control. Subgroup analysis based on PBM parameter variables for these outcomes was performed. Favorable parameters were identified as: wavelengths in the region of 665 nm and 810 nm; time to first administration of PBM ≤4 h; total number of daily treatments ≤3. No differences were identified between pulsed and continuous wave modes or energy delivery. Mechanistic substudies within included in vivo studies are presented and were found to support hypotheses of antiapoptotic, anti-inflammatory, and pro-proliferative effects, and a modulation of cellular metabolism. This systematic review provides substantial meta-analysis evidence of the benefits of PBM on functional and histological outcomes of TBI in in vivo mammalian models. Study design and PBM parameters should be closely considered for future human clinical studies.

The effect of photobiomodulation on the brain during wakefulness and sleep

Over the last seventy years or so, many previous studies have shown that photobiomodulation, the use of red to near infrared light on body tissues, can improve central and peripheral neuronal function and survival in both health and in disease. These improvements are thought to arise principally from an impact of photobiomodulation on mitochondrial and non-mitochondrial mechanisms in a range of different cell types, including neurones. This impact has downstream effects on many stimulatory and protective genes. An often-neglected feature of nearly all of these improvements is that they have been induced during the state of wakefulness. Recent studies have shown that when applied during the state of sleep, photobiomodulation can also be of benefit, but in a different way, by improving the flow of cerebrospinal fluid and the clearance of toxic waste-products from the brain. In this review, we consider the potential differential effects of photobiomodulation dependent on the state of arousal. We speculate that the effects of photobiomodulation is on different cells and systems depending on whether it is applied during wakefulness or sleep, that it may follow a circadian rhythm. We speculate further that the arousal-dependent photobiomodulation effects are mediated principally through a biophoton – ultra-weak light emission – network of communication and repair across the brain.

Transcranial Laser Therapy Does Not Improve Cognitive and Post-Traumatic Stress Disorder-Related Behavioral Traits in Rats Exposed to Repetitive Low-Level Blast Injury

Many military veterans who experienced blast-related traumatic brain injuries (TBIs) in the conflicts in Iraq and Afghanistan suffer from chronic cognitive and mental health problems, including post-traumatic stress disorder (PTSD). Transcranial laser therapy (TLT) uses low-power lasers emitting light in the far- to near-infrared ranges. Beneficial effects of TLT have been reported in neurological and mental-health-related disorders in humans and animal models, including TBI. Rats exposed to repetitive low-level blast develop chronic cognitive and PTSD-related behavioral traits. We tested whether TLT treatment could reverse these traits. Rats received a 74.5-kPa blast or sham exposures delivered one per day for 3 consecutive days. Beginning at 34 weeks after blast exposure, the following groups of rats were treated with active or sham TLT: 1) Sham-exposed rats (n = 12) were treated with sham TLT; 2) blast-exposed rats (n = 13) were treated with sham TLT; and 3) blast-exposed rats (n = 14) were treated with active TLT. Rats received 5 min of TLT five times per week for 6 weeks (wavelength, 808 nm; power of irradiance, 240 mW). At the end of treatment, rats were tested in tasks found previously to be most informative (novel object recognition, novel object localization, contextual/cued fear conditioning, elevated zero maze, and light/dark emergence). TLT did not improve blast-related effects in any of these tests, and blast-exposed rats were worse after TLT in some anxiety-related measures. Based on these findings, TLT does not appear to be a promising treatment for the chronic cognitive and mental health problems that follow blast injury.

Photobiomodulation Promotes Hippocampal CA1 NSC Differentiation Toward Neurons and Facilitates Cognitive Function Recovery Involving NLRP3 Inflammasome Mitigation Following Global Cerebral Ischemia

Our recent study revealed that photobiomodulation (PBM) inhibits delayed neuronal death by preserving mitochondrial dynamics and function following global cerebral ischemia (GCI). In the current study, we clarified whether PBM exerts effective roles in endogenous neurogenesis and long-lasting neurological recovery after GCI. Adult male rats were treated with 808 nm PBM at 20 mW/cm² irradiance for 2 min on cerebral cortex surface (irradiance ∼7.0 mW/cm², fluence ∼0.8 J/cm² on the hippocampus) beginning 3 days after GCI for five consecutive days. Cognitive function was evaluated using the Morris water maze. Neural stem cell (NSC) proliferation, immature neurons, and mature neurons were examined using bromodeoxyuridine (BrdU)-, doublecortin (DCX)-, and NeuN-staining, respectively. Protein expression, such as NLRP3, cleaved IL1β, GFAP, and Iba1 was detected using immunofluorescence staining, and ultrastructure of astrocyte and microglia was observed by transmission electron microscopy. The results revealed that PBM exerted a markedly neuroprotective role and improved spatial learning and memory ability at 58 days of ischemia/reperfusion (I/R) but not at 7 days of reperfusion. Mechanistic studies revealed that PBM suppressed reactive astrocytes and maintained astrocyte regeneration at 7 days of reperfusion, as well as elevated neurogenesis at 58 days of reperfusion, as evidenced by a significant decrease in the fluorescence intensity of GFAP (astrocyte marker) but unchanged the number of BrdU-GFAP colabeled cells at the early timepoint, and a robust elevation in the number of DCX-NeuN colabeled cells at the later timepoint in the PBM-treated group compared to the GCI group. Notably, PBM treatment protected the ultrastructure of astrocyte and microglia cells at 58 days but not 7 days of reperfusion in the hippocampal CA1 region. Furthermore, PBM treatment significantly attenuated the GCI-induced immunofluorescence intensity of NLRP3 (an inflammasome component), cleaved IL1β (reflecting inflammasome activation) and Iba1, as well as the colocalization of NLRP3/GFAP or cleaved IL-1β/GFAP, especially in animals subjected to I/R at 58 days. Taken together, PBM treatment performed postischemia exerted a long-lasting protective effect on astrocytes and promoted endogenous neurogenesis in the hippocampal CA1 region, which might contribute to neurological recovery after GCI.

Current application and future directions of photobiomodulation in central nervous diseases

Photobiomodulation using light in the red or near-infrared region is an innovative treatment strategy for a wide range of neurological and psychological conditions. Photobiomodulation can promote neurogenesis and elicit anti-apoptotic, anti-inflammatory and antioxidative responses. Its therapeutic effects have been demonstrated in studies on neurological diseases, peripheral nerve injuries, pain relief and wound healing. We conducted a comprehensive literature review of the application of photobiomodulation in patients with central nervous system diseases in February 2019. The NCBI PubMed database, EMBASE database, Cochrane Library and ScienceDirect database were searched. We reviewed 95 papers and analyzed. Photobiomodulation has wide applicability in the treatment of stroke, traumatic brain injury, Parkinson's disease, Alzheimer's disease, major depressive disorder, and other diseases. Our analysis provides preliminary evidence that PBM is an effective therapeutic tool for the treatment of central nervous system diseases. However, additional studies with adequate sample size are needed to optimize treatment parameters.

Transcranial photobiomodulation in the management of brain disorders

Transcranial photobiomodulation (tPBM) is the process of delivering light photons through the skull to benefit from its modifying effect. Brain disorders are important health problems. The aim of this review was to determine the existing evidence of effectiveness, useful parameters, and safety of tPBM in the management of traumatic brain injury, stroke, Parkinson, and Alzheimer's disease as the common brain disorders. Four online databases, including Cochrane, Pub Med, Embase, and Google scholar were searched according to the Preferred Reporting Items for Systematic Reviews and meta-analyses (PRISMA) guidelines. 4728 articles were obtained in the initial search. Only those articles that were published until September 2020 and designed as randomized clinical trials (RCTs) or animal-controlled studies were included. 6 RCTs, 2 related supplementary articles, and 38 controlled animal studies met the inclusion criteria of this study. No RCTs were performed in the fields of Alzheimer's and Parkinson's diseases. The human RCTs and animal studies reported no adverse events resulted from the use of tPBM. Useful parameters of tPBM were identified according to the controlled animal studies. Since the investigated RCTs had no homogenous results, making an evidence-based decision for definite therapeutic application of tPBM is still unattainable. Altogether, these data support the need for large confirmatory well-designed RCTs for using tPBM as a novel, safe, and easy-to-administer treatment of brain disorders.

EVIDENCE BEFORE THIS STUDY

High prevalence and complications of brain disorders and also side effects of neuropsychiatric medications have encouraged researchers to find alternative therapeutic techniques which tPBM can be one of them. In present review we tried to determine the existing evidence of effectiveness, useful parameters, and safety of tPBM in the management of traumatic brain injury, stroke, Alzheimer, and Parkinson's disease as common brain disorders. Four online databases, including "Cochrane", "Pub Med", "Embase", and "Google scholar" were searched. Only those articles that were published until September 2020 and designed as RCTs or animal-controlled studies were included. Search keywords were the followings: transcranial photobiomodulation" OR "transcranial low-level laser therapy" AND "stroke" OR "traumatic brain injury" OR "Alzheimer" OR "Parkinson". Several studies have confirmed effectiveness of tPBM in treatment of different brain disorders but the level of evidence of its effectiveness remain to be determined.

ADDED VALUE OF THIS STUDY

In this study we systematically reviewed human RCTs to determine the existing evidence of tPBM effectiveness in management of four mentioned brain disorders. Since the outcomes of the reviewed RCTs were not homogeneous, further well-designed RCTs are required to decide more definitively on the evidence of this noninvasive and probably safe therapeutic intervention. We hypothesized that non-homogeneous outcomes could be due to inefficiency of PBM parameters. Controlled animal studies have the advantage of using objective tests to evaluate the results and compare them with the control group. We determined useful tPBM parameters based on these studies.

IMPLICATIONS OF ALL THE AVAILABLE EVIDENCE

This research is part of our main project of tinnitus treatment using photobiomodulation (PBM). Evidence of central nervous system involvement in tinnitus led us to believe that treatment protocol of tinnitus should also include transcranial PBM. The determined useful parameters can be helpful in designing more efficient tPBM protocols in the management of brain disorders and tinnitus as a common debilitating symptom that can be associated with these disorders.

[Terahertz modulated infrared radiation in the complex treatment of patients in the acute period of ischemic stroke]

Ischemic stroke (IS) is a serious medical and social problem due to the widespread prevalence, profound and long-term disability of patients. The effectiveness of pharmaceutical neuroprotection in IS remains low which necessitates the investigation of new therapeutic methods in post-stroke patients.

OBJECTIVE

The rationale for the use of infrared (IR) radiation with terahertz (THz) modulation in the complex treatment of patients in the acute period of IS.

MATERIAL AND METHODS

The results of transcranial application of IR radiation with THz modulation in 112 patients in the acute period of IS are presented. In the main group (38 patients) the infrared radiation with THz modulation was used on the projection of the IS focus in addition to basic drug therapy; in the control group (37 patients) - basic drug therapy; in the placebo group (37 patients) the physiotherapy was mimicked. The data of neurological status and neuro-functional indicators were assessed using the NIHSS, MMSE, Rankin, and Rivermid scales. Cerebral blood flow was examined using duplex scanning of brachiocephalic vessels.

RESULTS

The inclusion in the complex treatment of IR radiation with THz modulation on the projection of the IS focus in the acute period contributed to a significant regression of neurological deficit, a complete recovery of cognitive functions and an increase in daily activity due to the restoration of adequate blood supply on the side of the affected hemisphere.

CONCLUSION

A pathogenesis justified method of treating acute IS is proposed which can increase the effectiveness of early neurorehabilitation measures. An early improvement in cerebral hemoperfusion led to the creation of optimal conditions for the survival of neural structures and the preservation of their functional activity that demonstrated the neuroprotective feasibility of early inclusion of IR radiation with THz modulation in the complex treatment of patients in the acute period of IS.

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

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

Changes in Brain Function and Structure After Self-Administered Home Photobiomodulation Treatment in a Concussion Case

Traumatic brain injury (TBI) is a common neurological disorder among athletes. Although there are no widely accepted treatments for TBI, new investigational approaches, such as photobiomodulation (PBM), are being tested. PBM is a light therapy that uses red to near-infrared (NIR) light to stimulate, heal, and protect tissue that has been injured or is at risk of dying. Benefits following transcranial PBM treatments in animal models of acute TBI and a small number of chronic TBI patients have been reported. However, the human PBM TBI studies published to date have been based on behavioral assessments. This report describes changes in behavioral and neuroimaging measures after 8 weeks of PBM treatments. The subject was a 23-year professional hockey player with a history of concussions, presumed to have caused his symptoms of headaches, mild anxiety, and difficulty concentrating. He treated himself at home with commercially available, low-risk PBM devices that used light-emitting diodes (LEDs) to emit 810-nm light pulsing at 10 or 40 Hz delivered by an intranasal and four transcranial modules that targeted nodes of the default mode network (DMN) with a maximum power density of 100 mW/cm². After 8 weeks of PBM treatments, increased brain volumes, improved functional connectivity, and increased cerebral perfusion and improvements on neuropsychological test scores were observed. Although this is a single, sport-related case with a history of concussions, these positive findings encourage replication studies that could provide further validation for this non-invasive, non-pharmacological modality as a viable treatment option for TBI.

Mitochondria as a target for neuroprotection: role of methylene blue and photobiomodulation

Mitochondrial dysfunction plays a central role in the formation of neuroinflammation and oxidative stress, which are important factors contributing to the development of brain disease. Ample evidence suggests mitochondria are a promising target for neuroprotection. Recently, methods targeting mitochondria have been considered as potential approaches for treatment of brain disease through the inhibition of inflammation and oxidative injury. This review will discuss two widely studied approaches for the improvement of brain mitochondrial respiration, methylene blue (MB) and photobiomodulation (PBM). MB is a widely studied drug with potential beneficial effects in animal models of brain disease, as well as limited human studies. Similarly, PBM is a non-invasive treatment that promotes energy production and reduces both oxidative stress and inflammation, and has garnered increasing attention in recent years. MB and PBM have similar beneficial effects on mitochondrial function, oxidative damage, inflammation, and subsequent behavioral symptoms. However, the mechanisms underlying the energy enhancing, antioxidant, and anti-inflammatory effects of MB and PBM differ. This review will focus on mitochondrial dysfunction in several different brain diseases and the pathological improvements following MB and PBM treatment.

Photobiomodulation by diffusing optical fiber on spinal cord: A feasibility study in piglet model

Previous studies on spinal cord injury (SCI) have confirmed that percutaneous photobiomodulation (PBM) therapy can ameliorate immunoinflammatory responses at sites of injury, accelerate nerve regeneration, suppress glial scar formation and promote the subsequent recovery of locomotor function. The current study was performed to evaluate a large-animal model employing implanted optical fibers to accurately irradiate targeted spinal segments. The method's feasibility and irradiation parameters that do not cause phototoxic reaction were determined, and the methodology of irradiating the spinal cord with near-infrared light was investigated in detail. A diffusing optical fiber was implanted above the T9 spinal cord of Bama miniature pigs and used to transfer near-infrared light (810 nm) onto the spinal cord surface. After daily irradiation with 200, 300, 500 or 1000 mW for 14 days, both sides of the irradiated area of the spinal cord were assessed for temperature changes. The condition of the spinal cord and the position of optical fiber were investigated by magnetic resonance imaging (MRI), and different parameters indicating temperature increases or phototoxicity were measured on the normal spinal cord surface due to light irradiation (ie, heat shock responses, inflammatory reactions and neuronal apoptosis), and the animals' lower-limb neurological function and gait were assessed during the irradiation process. The implanted device was stable inside the freely moving animals, and light energy could be directly projected onto the spinal cord surface. The screening of different irradiation parameters preliminary showed that direct irradiation onto the spinal cord surface at 200 and 300 mW did not significantly increase the temperature, stress responses, inflammatory reactions and neural apoptosis, whereas irradiation at 500 mW slightly increased these parameters, and irradiation at 1000 mW induced a significant temperature increase, heat shock, inflammation and apoptosis responses. HE staining of spinal cord tissue sections did not reveal any significant structural changes of the tissues compared to the control group, and the neurological function and gait of all irradiated animals were normal. In this study, we established an in-vivo optical fiber implantation method, which might be safe and stable and could be used to directly project light energy onto the spinal cord surface. This study might provide a new perspective for clinical applications of PBM in acute SCI.

Light-Emitting Diode Photobiomodulation After Cerebral Ischemia

Photobiomodulation (PBM) therapy is a promising therapeutic approach for several pathologies, including stroke. The biological effects of PBM for the treatment of cerebral ischemia have previously been explored as a neuroprotective strategy using different light sources, wavelengths, and incident light powers. However, the capability of PBM as a novel alternative therapy to stimulate the recovery of the injured neuronal tissue after ischemic stroke has been poorly explored. The aim of this study was to investigate the low-level light irradiation therapy by using Light Emitting Diodes (LEDs) as potential therapeutic strategy for stroke. The LED photobiomodulation (continuous wave, 830 nm, 0.2–0.6 J/cm²) was firstly evaluated at different energy densities in C17.2 immortalized mouse neural progenitor cell lines, in order to observe if this treatment had any effect on cells, in terms of proliferation and viability. Then, the PBM-LED effect (continuous wave, 830 nm, 0.28 J/cm² at brain cortex) on long-term recovery (12 weeks) was analyzed in ischemic animal model by means lesion reduction, behavioral deficits, and functional magnetic resonance imaging (fMRI). Analysis of cellular proliferation after PBM was significantly increased (1 mW) in all different exposure times used; however, this effect could not be replicated in vivo experimental conditions, as PBM did not show an infarct reduction or functional recovery. Despite the promising therapeutic effect described for PBM, further preclinical studies are necessary to optimize the therapeutic window of this novel therapy, in terms of the mechanism associated to neurorecovery and to reduce the risk of failure in futures clinical trials.

Laser Light Therapy in Inflammatory, Musculoskeletal, and Autoimmune Disease

PURPOSE OF REVIEW

The goal of this review is to summarize the field to date and to discuss strengths and limitations of low-level laser (light) therapy (LLLT) for the future investigation as a treatment of inflammatory disease.

RECENT FINDINGS

LLLT is a promising therapeutic, particularly for those diseases of skin and joints because they are most accessible to treatment. Indeed, the known mechanisms of LLLT support its use for anti-inflammatory purposes, as well as stimulation of tissue growth and repair. Although the standard of care for the majority of inflammatory diseases is immunosuppressive agents such as corticosteroids with undesirable toxicities, LLLT offers a unique approach by being non-invasive and incurring minimal side effects. It is also relatively inexpensive and accessible and even has the possibility to be patient directed at home. There is evidence that LLLT is able to modulate the immune system at the skin and joint, and it has been shown to be efficacious in humans by affecting bacterial colonization as it may pertain to chronic rhinosinusitis. However, there is variability in the methods of laser application as well as a lack of evidence for laser type, dose-ranging studies, and wavelength selection that create barriers to the implementation of LLLT without further more rigorous and standardized study. The heterogeneity makes it difficult to draw strong conclusions about the efficacy of LLLT and its mechanisms.

Pulsed Near Infrared Transcranial and Intranasal Photobiomodulation Significantly Modulates Neural Oscillations: a pilot exploratory study

Transcranial photobiomodulation (tPBM) is the application of low levels of red or near-infrared (NIR) light to stimulate neural tissues. Here, we administer tPBM in the form of NIR light (810 nm wavelength) pulsed at 40 Hz to the default mode network (DMN), and examine its effects on human neural oscillations, in a randomized, sham-controlled, double-blinded trial. Using electroencephalography (EEG), we found that a single session of tPBM significantly increases the power of the higher oscillatory frequencies of alpha, beta and gamma and reduces the power of the slower frequencies of delta and theta in subjects in resting state. Furthermore, the analysis of network properties using inter-regional synchrony via weighted phase lag index (wPLI) and graph theory measures, indicate the effect of tPBM on the integration and segregation of brain networks. These changes were significantly different when compared to sham stimulation. Our preliminary findings demonstrate for the first time that tPBM can be used to non-invasively modulate neural oscillations, and encourage further confirmatory clinical investigations.

Transcranial photobiomodulation with 1064-nm laser modulates brain electroencephalogram rhythms

Noninvasive transcranial photobiomodulation (tPBM) with a 1064-nm laser has been reported to improve human performance on cognitive tasks as well as locally upregulate cerebral oxygen metabolism and hemodynamics. However, it is unknown whether 1064-nm tPBM also modulates electrophysiology, and specifically neural oscillations, in the human brain. The hypothesis guiding our study is that applying 1064-nm tPBM of the right prefrontal cortex enhances neurophysiological rhythms at specific frequency bands in the human brain under resting conditions. To test this hypothesis, we recorded the 64-channel scalp electroencephalogram (EEG) before, during, and after the application of 11 min of 4-cm-diameter tPBM (CW 1064-nm laser with 162    mW / cm 2 and 107    J / cm 2 ) to the right forehead of human subjects ( n = 20 ) using a within-subject, sham-controlled design. Time-resolved scalp topographies of EEG power at five frequency bands were computed to examine the tPBM-induced EEG power changes across the scalp. The results show time-dependent, significant increases of EEG spectral powers at the alpha (8 to 13 Hz) and beta (13 to 30 Hz) bands at broad scalp regions, exhibiting a front-to-back pattern. The findings provide the first sham-controlled topographic mapping that tPBM increases the strength of electrophysiological oscillations (alpha and beta bands) while also shedding light on the mechanisms of tPBM in the human brain.

Transcranial Near-infrared Laser Therapy in Improving Cognitive Recovery of Function Following Traumatic Brain Injury

Abstract: Traumatic brain injury (TBI) has turned into a major health and socioeconomic problem affecting young people and military personnel. Numerous TBI patients experienced the sequela of brain injury called cognitive impairment, which re-duced functions in attention, working memory, motivation, and execution. In recent years, transcranial near-infrared laser therapy (tNiRLT) as a possible therapy has been gradually applied in treating cognitive impairment post-TBI. In the present review, the biological mechanisms of transcranial tNiRLT for TBI are synthesized mainly based on the photonic impact of chronic mild TBI. Various exciting molecular events possibly occur during the procedure, such as stimulation of ATP pro-duction, regional cerebral blood flow, acupoint, neurogenesis and synaptogenesis, as well as a reduction in anti-inflammatory effect. Some animal experiments and clinical studies of tNiRLT for TBI are outlined. Several labs have displayed that tNiRLT is effective not only in improving neurological functions but also in increasing memory and learning capacity in ro-dent animals’ model of TBI. In a 2 patients case report and a 11-case series, cognitive functions were ameliorated. Efficacy on cognitive and emotional effects was also observed in a double-blind, controlled clinical study. Several Randomized, paral-lel, double blind, sham-controlled trials are underway, aiming to evaluate the efficacy of tLED on cognitive functions and neuropsychiatric status in participants post-TBI. Therefore, tNiRLT is a promising method applied to cognitive impairment following TBI.

Photobiomodulation for traumatic brain injury and stroke

There is a notable lack of therapeutic alternatives for what is fast becoming a global epidemic of traumatic brain injury (TBI). Photobiomodulation (PBM) employs red or near-infrared (NIR) light (600-1100nm) to stimulate healing, protect tissue from dying, increase mitochondrial function, improve blood flow, and tissue oxygenation. PBM can also act to reduce swelling, increase antioxidants, decrease inflammation, protect against apoptosis, and modulate microglial activation state. All these mechanisms of action strongly suggest that PBM delivered to the head should be beneficial in cases of both acute and chronic TBI. Most reports have used NIR light either from lasers or from light-emitting diodes (LEDs). Many studies in small animal models of acute TBI have found positive effects on neurological function, learning and memory, and reduced inflammation and cell death in the brain. There is evidence that PBM can help the brain repair itself by stimulating neurogenesis, upregulating BDNF synthesis, and encouraging synaptogenesis. In healthy human volunteers (including students and healthy elderly women), PBM has been shown to increase regional cerebral blood flow, tissue oxygenation, and improve memory, mood, and cognitive function. Clinical studies have been conducted in patients suffering from the chronic effects of TBI. There have been reports showing improvement in executive function, working memory, and sleep. Functional magnetic resonance imaging has shown modulation of activation in intrinsic brain networks likely to be damaged in TBI (default mode network and salience network).

Transcranial Low-Level Laser (Light) Therapy for Brain Injury

BACKGROUND

Low-level laser therapy (LLLT) or photobiomodulation (PBM) is a possible treatment for brain injury, including traumatic brain injury (TBI).

METHODS

We review the fundamental mechanisms at the cellular and molecular level and the effects on the brain are discussed. There are several contributing processes that have been proposed to lead to the beneficial effects of PBM in treating TBI such as stimulation of neurogenesis, a decrease in inflammation, and neuroprotection. Both animal and clinical trials for ischemic stroke are outlined. A number of articles have shown how transcranial LLLT (tLLLT) is effective at increasing memory, learning, and the overall neurological performance in rodent models with TBI.

RESULTS

Our laboratory has conducted three different studies on the effects of tLLLT on mice with TBI. The first studied pulsed against continuous laser irradiation, finding that 10 Hz pulsed was the best. The second compared four different wavelengths, discovering only 660 and 810 nm to have any effectiveness, whereas 732 and 980 nm did not. The third looked at varying regimens of daily laser treatments (1, 3, and 14 days) and found that 14 laser applications was excessive. We also review several studies of the effects of tLLLT on neuroprogenitor cells, brain-derived neurotrophic factor and synaptogenesis, immediate early response knockout mice, and tLLLT in combination therapy with metabolic inhibitors.

CONCLUSIONS

Finally, some clinical studies in TBI patients are covered.

Remote tissue conditioning - An emerging approach for inducing body-wide protection against diseases of ageing

We have long accepted that exercise is 'good for us'; that - put more rigorously - moderate exercise is associated with not just aerobic fitness but also reduced morbidity and reduced mortality from cardiovascular disease and even malignancies. Caloric restriction (moderate hunger) and our exposure to dietary phytochemicals are also emerging as stresses which are 'good for us' in the same sense. This review focuses on an important extension of this concept: that stress localized within the body (e.g. in a limb) can induce resilience in tissues throughout the body. We describe evidence for the efficacy of two 'remote' protective interventions - remote ischemic conditioning and remote photobiomodulation - and discuss the mechanisms underlying their protective actions. While the biological phenomenon of remote tissue conditioning is only partially understood, it holds promise for protecting critical-to-life tissues while mitigating risks and practical barriers to direct conditioning of these tissues.

Low-Level Laser Irradiation Improves Motor Recovery After Contusive Spinal Cord Injury in Rats

This study investigated the therapeutic effects of low-level laser irradiation (LLLI) on the recovery of motor function and its underlying mechanisms in rats with spinal cord injury (SCI). The spinal cord was contused at the T11 level using a New York University impactor. Thirty-eight rats were randomly divided into four groups: LLLI with 0.08 J, 0.4 J, 0.8 J, and sham. We transcutaneously applied at the lesion site of the spinal contusive rats 5 min after injury and then daily for 21 days. The Basso, Beattie and Bresnahan (BBB) locomotor scale and combined behavioral score (CBS) were used to evaluate motor function. The spinal segments of rostral and caudal from the lesion site, the epicenter, and L4-5 were collected from normal and the all groups at 7 days after SCI. The expression of tumor necrosis factor-α (TNF-α) and inducible nitric oxide synthase (iNOS) was compared across groups in all regions. In the present study, LLLI with 0.4 J and 0.8 J led to a significant improvement in motor function compared to sham LLLI, which significantly decreased TNF-α expression at the lesion epicenter and reduced iNOS expression in the caudal segment for all LLLI groups and in the L4-5 segments for the 0.4 J and 0.8 J groups when compared to sham LLLI group. Our results demonstrate that transcutaneous LLLI modulate inflammatory mediators to enhance motor function recovery after SCI. Thus, LLLI in acute phase after SCI might have therapeutic potential for neuroprotection and restoration of motor function following SCI.

Repeated transcranial low-level laser therapy for traumatic brain injury in mice: biphasic dose response and long-term treatment outcome

We previously showed that near-infrared laser photobiomodulation (PBM) (810 nm, CW, 18 J/cm² , 25 mW/cm² ) delivered to the mouse daily for 3-days after a controlled cortical impact traumatic brain injury (TBI) gave a significant improvement in neurological/cognitive function. However the same parameters delivered 14X daily gave significantly less benefit. This biphasic dose response intrigued us, and we decided to follow the mice that received 3X or 14X laser treatments out to 56-days post-TBI. We found the 14X group showed worse neurological function than the no-treatment TBI group at 2-weeks, but started to improve steadily during the next 6-weeks, and by 56-days were significantly better than the no-treatment TBI mice, but still worse than the 3X mice. A marker of activated glial cells (GFAP) was significantly increased in the brain regions (compared to both untreated TBI and 3X groups) at 4-weeks in the 14X group, but the GFAP had fallen to low levels in both 3X and 14X groups by 8-weeks. We conclude that an excessive number of laser-treatments delivered to mice can temporarily inhibit the process of brain repair stimulated by tPBM, but then the inhibitory effect ceases, and brain repair can resume. The mechanism may be temporary induction of reactive gliosis.

Combination therapies for neurobehavioral and cognitive recovery after experimental traumatic brain injury: Is more better?

Traumatic brain injury (TBI) is a significant health care crisis that affects two million individuals in the United Sates alone and over ten million worldwide each year. While numerous monotherapies have been evaluated and shown to be beneficial at the bench, similar results have not translated to the clinic. One reason for the lack of successful translation may be due to the fact that TBI is a heterogeneous disease that affects multiple mechanisms, thus requiring a therapeutic approach that can act on complementary, rather than single, targets. Hence, the use of combination therapies (i.e., polytherapy) has emerged as a viable approach. Stringent criteria, such as verification of each individual treatment plus the combination, a focus on behavioral outcome, and post-injury vs. pre-injury treatments, were employed to determine which studies were appropriate for review. The selection process resulted in 37 papers that fit the specifications. The review, which is the first to comprehensively assess the effects of combination therapies on behavioral outcomes after TBI, encompasses five broad categories (inflammation, oxidative stress, neurotransmitter dysregulation, neurotrophins, and stem cells, with and without rehabilitative therapies). Overall, the findings suggest that combination therapies can be more beneficial than monotherapies as indicated by 46% of the studies exhibiting an additive or synergistic positive effect versus on 19% reporting a negative interaction. These encouraging findings serve as an impetus for continued combination studies after TBI and ultimately for the development of successful clinically relevant therapies.

Traumatic Axonal Injury: Mechanisms and Translational Opportunities

Traumatic axonal injury (TAI) is an important pathoanatomical subgroup of traumatic brain injury (TBI) and a major driver of mortality and functional impairment. Experimental models have provided insights into the effects of mechanical deformation on the neuronal cytoskeleton and the subsequent processes that drive axonal injury. There is also increasing recognition that axonal or white matter loss may progress for years post-injury and represent one mechanistic framework for progressive neurodegeneration after TBI. Previous trials of novel therapies have failed to make an impact on clinical outcome, in both TBI in general and TAI in particular. Recent advances in understanding the cellular and molecular mechanisms of injury have the potential to translate into novel therapeutic targets.

Multiple therapeutic targets are emerging that offer the potential to reduce secondary brain injury at a cellular level. These include cytoskeletal and membrane stabilisation, control of calcium flux and calpain activation, optimisation of cellular energetics, and modulation of the inflammatory response.

Wallerian degeneration, as occurs following an axonal injury, is an active, cell-autonomous death pathway that involves failure of axonal transport to deliver key enzymes involved in NAD biosynthesis.

Chronic microglial activation occurs following traumatic brain injury (TBI) and may persist for decades afterwards. This ongoing response has been linked to long-term neurodegeneration, particularly of white matter tracts.

Phagoptosis is the process whereby physiologically stressed but otherwise viable neurons are phagocytosed by microglia in response to a range of eat-me signals induced by tissue injury.

Turning On Lights to Stop Neurodegeneration: The Potential of Near Infrared Light Therapy in Alzheimer's and Parkinson's Disease

Alzheimer's and Parkinson's disease are the two most common neurodegenerative disorders. They develop after a progressive death of many neurons in the brain. Although therapies are available to treat the signs and symptoms of both diseases, the progression of neuronal death remains relentless, and it has proved difficult to slow or stop. Hence, there is a need to develop neuroprotective or disease-modifying treatments that stabilize this degeneration. Red to infrared light therapy (λ = 600-1070 nm), and in particular light in the near infrared (NIr) range, is emerging as a safe and effective therapy that is capable of arresting neuronal death. Previous studies have used NIr to treat tissue stressed by hypoxia, toxic insult, genetic mutation and mitochondrial dysfunction with much success. Here we propose NIr therapy as a neuroprotective or disease-modifying treatment for Alzheimer's and Parkinson's patients.

Low-level laser therapy ameliorates disease progression in a mouse model of multiple sclerosis

Multiple sclerosis (MS) is an autoimmune demyelinating inflammatory disease characterized by recurrent episodes of T cell-mediated immune attack on central nervous system (CNS) myelin, leading to axon damage and progressive disability. The existing therapies for MS are only partially effective and are associated with undesirable side effects. Low-level laser therapy (LLLT) has been clinically used to treat inflammation, and to induce tissue healing and repair processes. However, there are no reports about the effects and mechanisms of LLLT in experimental autoimmune encephalomyelitis (EAE), an established model of MS. Here, we report the effects and underlying mechanisms of action of LLLT (AlGaInP, 660 nm and GaAs, 904 nm) irradiated on the spinal cord during EAE development. EAE was induced in female C57BL/6 mice by immunization with MOG35-55 peptide emulsified in complete Freund's adjuvant. Our results showed that LLLT consistently reduced the clinical score of EAE and delayed the disease onset, and also prevented weight loss induced by immunization. Furthermore, these beneficial effects of LLLT seem to be associated with the down-regulation of NO levels in the CNS, although the treatment with LLLT failed to inhibit lipid peroxidation and restore antioxidant defense during EAE. Finally, histological analysis showed that LLLT blocked neuroinflammation through a reduction of inflammatory cells in the CNS, especially lymphocytes, as well as preventing demyelination in the spinal cord after EAE induction. Together, our results suggest the use of LLLT as a therapeutic application during autoimmune neuroinflammatory responses, such as MS.

Transcranial Near-Infrared Laser Transmission (NILT) Profiles (800 nm): Systematic Comparison in Four Common Research Species

Background and Purpose

Transcranial near-infrared laser therapy (TLT) is a promising and novel method to promote neuroprotection and clinical improvement in both acute and chronic neurodegenerative diseases such as acute ischemic stroke (AIS), traumatic brain injury (TBI), and Alzheimer’s disease (AD) patients based upon efficacy in translational animal models. However, there is limited information in the peer-reviewed literature pertaining to transcranial near-infrared laser transmission (NILT) profiles in various species. Thus, in the present study we systematically evaluated NILT characteristics through the skull of 4 different species: mouse, rat, rabbit and human.

Results

Using dehydrated skulls from 3 animal species, using a wavelength of 800nm and a surface power density of 700 mW/cm2, NILT decreased from 40.10% (mouse) to 21.24% (rat) to 11.36% (rabbit) as skull thickness measured at bregma increased from 0.44 mm in mouse to 0.83 mm in rat and then 2.11 mm in rabbit. NILT also significantly increased (p<0.05) when animal skulls were hydrated (i.e. compared to dehydrated); but there was no measurable change in thickness due to hydration.

In human calvaria, where mean thickness ranged from 7.19 mm at bregma to 5.91 mm in the parietal skull, only 4.18% and 4.24% of applied near-infrared light was transmitted through the skull. There was a slight (9.2-13.4%), but insignificant effect of hydration state on NILT transmission of human skulls, but there was a significant positive correlation between NILT and thickness at bregma and parietal skull, in both hydrated and dehydrated states.

Conclusion

This is the first systematic study to demonstrate differential NILT through the skulls of 4 different species; with an inverse relationship between NILT and skull thickness. With animal skulls, transmission profiles are dependent upon the hydration state of the skull, with significantly greater penetration through hydrated skulls compared to dehydrated skulls. Using human skulls, we demonstrate a significant correlation between thickness and penetration, but there was no correlation with skull density. The results suggest that TLT should be optimized in animals using novel approaches incorporating human skull characteristics, because of significant variance of NILT profiles directly related to skull thickness.

Neuroplastic effects of transcranial near-infrared stimulation (tNIRS) on the motor cortex

Near-infrared light stimulation of the brain has been claimed to improve deficits caused by traumatic brain injury and stroke. Here, we exploit the effect of transcranial near-infrared stimulation (tNIRS) as a tool to modulate cortical excitability in the healthy human brain. tNIRS was applied at a wavelength of 810 nm for 10 min over the hand area of the primary motor cortex (M1). Both single-pulse and paired-pulse measures of transcranial magnetic stimulation (TMS) were used to assess levels of cortical excitability in the corticospinal pathway and intracortical circuits. The serial reaction time task (SRTT) was used to investigate the possible effect of tNIRS on implicit learning. By evaluating the mean amplitude of single-pulse TMS elicited motor-evoked-potentials (MEPs) a significant decrease of the amplitude was observed up to 30 min post-stimulation, compared to baseline. Furthermore, the short interval cortical inhibition (SICI) was increased and facilitation (ICF) decreased significantly after tNIRS. The results from the SRTT experiment show that there was no net effect of stimulation on the performance of the participants. Results of a study questionnaire demonstrated that tNIRS did not induce serious side effects apart from light headache and fatigue. Nevertheless, 66% were able to detect the difference between active and sham stimulation conditions. In this study we provide further evidence that tNIRS is suitable as a tool for influencing cortical excitability and activity in the healthy human brain.

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.

Clinical utility of brain stimulation modalities following traumatic brain injury: current evidence

Traumatic brain injury (TBI) remains the main cause of disability and a major public health problem worldwide. This review focuses on the neurophysiology of TBI, and the rationale and current state of evidence of clinical application of brain stimulation to promote TBI recovery, particularly on consciousness, cognitive function, motor impairments, and psychiatric conditions. We discuss the mechanisms of different brain stimulation techniques including major noninvasive and invasive stimulations. Thus far, most noninvasive brain stimulation interventions have been nontargeted and focused on the chronic phase of recovery after TBI. In the acute stages, there is limited available evidence of the efficacy and safety of brain stimulation to improve functional outcomes. Comparing the studies across different techniques, transcranial direct current stimulation is the intervention that currently has the higher number of properly designed clinical trials, though total number is still small. We recognize the need for larger studies with target neuroplasticity modulation to fully explore the benefits of brain stimulation to effect TBI recovery during different stages of recovery.

Transcranial low-level laser therapy enhances learning, memory, and neuroprogenitor cells after traumatic brain injury in mice

The use of transcranial low-level laser (light) therapy (tLLLT) to treat stroke and traumatic brain injury (TBI) is attracting increasing attention. We previously showed that LLLT using an 810-nm laser 4 h after controlled cortical impact (CCI)-TBI in mice could significantly improve the neurological severity score, decrease lesion volume, and reduce Fluoro-Jade staining for degenerating neurons. We obtained some evidence for neurogenesis in the region of the lesion. We now tested the hypothesis that tLLLT can improve performance on the Morris water maze (MWM, learning, and memory) and increase neurogenesis in the hippocampus and subventricular zone (SVZ) after CCI-TBI in mice. One and (to a greater extent) three daily laser treatments commencing 4-h post-TBI improved neurological performance as measured by wire grip and motion test especially at 3 and 4 weeks post-TBI. Improvements in visible and hidden platform latency and probe tests in MWM were seen at 4 weeks. Caspase-3 expression was lower in the lesion region at 4 days post-TBI. Double-stained BrdU-NeuN (neuroprogenitor cells) was increased in the dentate gyrus and SVZ. Increases in double-cortin (DCX) and TUJ-1 were also seen. Our study results suggest that tLLLT may improve TBI both by reducing cell death in the lesion and by stimulating neurogenesis.

Neurological and psychological applications of transcranial lasers and LEDs

Transcranial brain stimulation with low-level light/laser therapy (LLLT) is the use of directional low-power and high-fluency monochromatic or quasimonochromatic light from lasers or LEDs in the red-to-near-infrared wavelengths to modulate a neurobiological function or induce a neurotherapeutic effect in a nondestructive and non-thermal manner. The mechanism of action of LLLT is based on photon energy absorption by cytochrome oxidase, the terminal enzyme in the mitochondrial respiratory chain. Cytochrome oxidase has a key role in neuronal physiology, as it serves as an interface between oxidative energy metabolism and cell survival signaling pathways. Cytochrome oxidase is an ideal target for cognitive enhancement, as its expression reflects the changes in metabolic capacity underlying higher-order brain functions. This review provides an update on new findings on the neurotherapeutic applications of LLLT. The photochemical mechanisms supporting its cognitive-enhancing and brain-stimulatory effects in animal models and humans are discussed. LLLT is a potential non-invasive treatment for cognitive impairment and other deficits associated with chronic neurological conditions, such as large vessel and lacunar hypoperfusion or neurodegeneration. Brain photobiomodulation with LLLT is paralleled by pharmacological effects of low-dose USP methylene blue, a non-photic electron donor with the ability to stimulate cytochrome oxidase activity, redox and free radical processes. Both interventions provide neuroprotection and cognitive enhancement by facilitating mitochondrial respiration, with hormetic dose-response effects and brain region activational specificity. This evidence supports enhancement of mitochondrial respiratory function as a generalizable therapeutic principle relevant to highly adaptable systems that are exquisitely sensitive to energy availability such as the nervous system.

Transcranial low-level laser therapy improves neurological performance in traumatic brain injury in mice: effect of treatment repetition regimen

Low-level laser (light) therapy (LLLT) has been clinically applied around the world for a spectrum of disorders requiring healing, regeneration and prevention of tissue death. One area that is attracting growing interest in this scope is the use of transcranial LLLT to treat stroke and traumatic brain injury (TBI). We developed a mouse model of severe TBI induced by controlled cortical impact and explored the effect of different treatment schedules. Adult male BALB/c mice were divided into 3 broad groups (a) sham-TBI sham-treatment, (b) real-TBI sham-treatment, and (c) real-TBI active-treatment. Mice received active-treatment (transcranial LLLT by continuous wave 810 nm laser, 25 mW/cm², 18 J/cm², spot diameter 1 cm) while sham-treatment was immobilization only, delivered either as a single treatment at 4 hours post TBI, as 3 daily treatments commencing at 4 hours post TBI or as 14 daily treatments. Mice were sacrificed at 0, 4, 7, 14 and 28 days post-TBI for histology or histomorphometry, and injected with bromodeoxyuridine (BrdU) at days 21–27 to allow identification of proliferating cells. Mice with severe TBI treated with 1-laser Tx (and to a greater extent 3-laser Tx) had significant improvements in neurological severity score (NSS), and wire-grip and motion test (WGMT). However 14-laser Tx provided no benefit over TBI-sham control. Mice receiving 1- and 3-laser Tx had smaller lesion size at 28-days (although the size increased over 4 weeks in all TBI-groups) and less Fluoro-Jade staining for degenerating neurons (at 14 days) than in TBI control and 14-laser Tx groups. There were more BrdU-positive cells in the lesion in 1- and 3-laser groups suggesting LLLT may increase neurogenesis. Transcranial NIR laser may provide benefit in cases of acute TBI provided the optimum treatment regimen is employed.

Transcranial low level laser (light) therapy for traumatic brain injury

We review the use of transcranial low-level laser (light) therapy (LLLT) as a possible treatment for traumatic-brain injury (TBI). The basic mechanisms of LLLT at the cellular and molecular level and its effects on the brain are outlined. Many interacting processes may contribute to the beneficial effects in TBI including neuroprotection, reduction of inflammation and stimulation of neurogenesis. Animal studies and clinical trials of transcranial-LLLT for ischemic stroke are summarized. Several laboratories have shown that LLLT is effective in increasing neurological performance and memory and learning in mouse models of TBI. There have been case report papers that show beneficial effects of transcranial-LLLT in a total of three patients with chronic TBI. Our laboratory has conducted three studies on LLLT and TBI in mice. One looked at pulsed-vs-continuous wave laser-irradiation and found 10 Hz to be superior. The second looked at four different laser-wavelengths (660, 730, 810, and 980 nm); only 660 and 810 nm were effective. The last looked at different treatment repetition regimens (1, 3 and 14-daily laser-treatments).

Near-infrared photobiomodulation in an animal model of traumatic brain injury: improvements at the behavioral and biochemical levels

OBJECTIVE

The purpose of this was to evaluate the neuroprotective effects of near-infrared (NIR) light using an in-vivo rodent model of traumatic brain injury (TBI), controlled cortical impact (CCI), and to characterize changes at the behavioral and biochemical levels.

BACKGROUND DATA

NIR upregulates mitochondrial function, and decreases oxidative stress. Mitochondrial oxidative stress and apoptosis are important in TBI. NIR enhanced cell viability and mitochondrial function in previous in-vitro TBI models, supporting potential NIR in-vivo benefits.

METHODS

Sprague-Dawley rats were divided into three groups: severe TBI, sham surgery, and anesthetization only (behavioral response only). Cohorts in each group were administered either no NIR or NIR. They received two 670 nm LED treatments (5 min, 50 mW/cm(2), 15 J/cm(2)) per day for 72 h (chemical analysis) or 10 days (behavioral). During the recovery period, animals were tested for locomotor and behavioral activities using a TruScan device. Frozen brain tissue was obtained at 72 h and evaluated for apoptotic markers and reduced glutathione (GSH) levels.

RESULTS

Significant differences were seen in the TBI plus and minus NIR (TBI+/-) and sham plus and minus NIR (S+/-) comparisons for some of the TruScan nose poke parameters. A statistically significant decrease was found in the Bax pro-apoptotic marker attributable to NIR exposure, along with lesser increases in Bcl-2 anti-apoptotic marker and GSH levels.

CONCLUSIONS

These results show statistically significant, preclinical outcomes that support the use of NIR treatment after TBI in effecting changes at the behavioral, cellular, and chemical levels.