Transcranial near-infrared light in treatment of neurodegenerative diseases

Non-invasive therapeutics for neurotrauma: a mechanistic overview

Traumatic brain injury is a leading cause of death and a major risk factor for the development of both memory and motor disorders. To date, there are no proven interventions to improve patient outcome after neurotrauma. A promising avenue of treatment has emerged in the use of non-invasive therapies for recovery after brain injury. A number of non-invasive brain stimulation techniques have been developed, such as transcranial direct current stimulation, transcranial magnetic stimulation and vagus nerve stimulation, as well as low intensity ultrasound stimulation and photobiomodulation therapy. However, standardized treatment regimens have not been developed. There is a clear need to better understand the underlying mechanisms of non-invasive therapeutics on brain injury pathology so as to more effectively guide treatment strategy. Here we review the current literature of non-invasive therapies in preclinical neurotrauma and offer insight into the potential mechanism of action and novel targets for the treatment of traumatic brain injury.

Brain photobiomodulation: a potential treatment in Alzheimer's and Parkinson's diseases

Alzheimer's Disease (AD) and Parkinson's Disease (PD) are common neurodegenerative diseases, characterized by the progressive loss of synapses and neurons, leading to cognitive and motor decline. Their pathophysiology includes cerebral lesions, oxidative stress, neuroinflammation as well as brain-gut axis microbiota dysbiosis. Preclinical investigations demonstrated that brain photobiomodulation (bPBM) reduces oxidative stress and inflammation, increases cerebral blood flow and enhance neurogenesis and synaptogenesis, which makes bPBM a promising treatment in AD and PD. This review focuses on the clinical application of bPBM in AD and PD. It aims to provide a scientific overview of the current clinical knowledge, review recent clinical studies findings, and describe future directions and upcoming clinical studies. So far, several clinical studies investigated bPBM therapy, at various parameters, both in patients with AD and related dementia, and PD. All demonstrate bPBM safety and bring valuable clinical information regarding efficacy, with particularly promising results in AD. However, their exploratory design and inconsistent quality lead to a low level of evidence, which currently does not support the widespread use of bPBM in clinical practice. Future clinical research should address two gaps: the need for robust double-blinded RCTs vs sham with a higher number of patients and a longer follow-up, and the need for research focusing on dosimetry to determine which bPBM parameters are optimal. The ongoing or unpublished clinical studies on bPBM should fill in this gap.

Near-Infrared Stimulation in Psychiatry Disorders: A Systematic Review of Efficacy and Biological Mechanisms

BACKGROUND

Photobiomodulation (PBM), also referred to as low-level light therapy (LLLT), is an emerging non-pharmacological approach. This treatment is considered low-risk, cost-effective, and non-invasive, utilizing near-infrared light (NIR). The purpose of this paper is to explore the underlying mechanism of action and conduct a systematic review of pre-clinical and clinical research on the use of PBM for psychiatric disorders.

METHODS

A search on the PubMed, Cochrane Library, and EMBASE databases was performed on 18 and 26 January 2024. Publications focused on PBM treatment in psychiatric disorders such as major depressive disorder, general anxiety disorder, dementia, Parkinson's disease, traumatic brain injury, schizophrenia, and sexual disfunctions were included (n = 23).

RESULTS

Near-infrared stimulation is presented as an effective method, comparable to psychopharmacological treatment. The primary suggested mechanism for PBM is the stimulation of mitochondrial metabolism following the absorption of NIR energy by cytochrome C oxidase. Because of the method of implementation, which omits the liver metabolism of cytochrome P450, PMB is recognized as safe as it does not interact with other drugs.

LIMITATIONS

Clinical studies vary in terms of population and treatment parameters, and most do not include a suitable control group.

CONCLUSIONS

Preliminary results support the potential of NIR stimulation as a novel and innovative treatment for psychiatry. Further studies are needed to estimate the proper protocols of parameters singly for any disease.

Photobiomodulation therapy facilitates transplantation of dental pulp stem cells for spinal cord injury

BACKGROUND

While dental pulp stem cells (DPSCs) show therapeutic potential for spinal cord injury (SCI), post-traumatic oxidative stress and mitochondrial dysfunction critically compromise grafted cell survival. Photobiomodulation therapy (PBMT) is a noninvasive approach that may enhance regenerative efficacy. This study investigates whether PBMT improves the survival and neural differentiation of transplanted DPSCs in SCI models.

METHODS

In vitro, the anti-apoptotic effects of PBMT were investigated in H2O2-induced DPSCs injury model via TUNEL staining, flow cytometry, biochemical assays and transmission electron microscopy. In vivo, spinal cord restoration was evaluated using behavioral tests and histological staining, and the survival status and neural differentiation of grafted DPSCs were respectively tracked through bioluminescence imaging and immunofluorescent staining in DPSCs co-expressing luciferin and green fluorescent protein (Luc-GFP-DPSCs) transplanted SCI mice with/without PBMT.

RESULTS

PBMT demonstrated protective effects by relieving apoptosis and oxidative stress in engrafted DPSCs in vitro. Furthermore, PBMT-assisted DPSCs transplantation significantly promoted cell survival and neural differentiation, achieving superior functional recovery compared to transplantation alone.

CONCLUSIONS

PBMT facilitates DPSCs transplantation in SCI through mitigation of oxidative apoptosis and enhancement of grafted cell survival and differentiation.

Effects of whole-head 810 nm near-infrared therapy on cognitive and neuropsychiatric symptoms in Alzheimer's disease: A pilot study

BackgroundAlzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by significant cognitive and behavioral impairments. Near-infrared (NIR) light treatment has shown potential in cognitive improvement in previous studies. However, clinical trials of NIR for AD remain limited.ObjectiveThis study investigated the safety and effects of whole-head 810 nm NIR therapy in AD patients, including long-term efficacy.MethodsAn open-label pilot study on whole-head NIR treatment for AD patients was conducted. Nine AD patients completed 4-month treatment (810 nm, 100 mW/cm², 30 min/session, 6 sessions weekly). Safety and efficacy were evaluated at baseline, months 2 and 4, and 2-month post-treatment.ResultsAfter four months of whole-head NIR treatment, mean changes from baseline on the Mini-Mental State Examination were 3.2 (p = 0.02). Mean changes from baseline on the Alzheimer's Disease Assessment Scale-Cognitive were -5.0 (p = 0.05), mean changes from baseline on the Montreal Cognitive Assessment were 1.9 (p = 0.12). Mean changes from baseline on the Neuropsychiatric Inventory were -4.2 (p = 0.47). These benefits were sustained two months at least. With no device-related adverse effects were reported.ConclusionsWhole-head 810 nm NIR light is safe and offers promising benefits for AD patients. To fully confirm its efficacy, durability, and underlying mechanisms, further large-scale randomized controlled trials are necessary.

Site- and electroencephalogram-frequency-specific effects of 800-nm prefrontal transcranial photobiomodulation on electroencephalogram global network topology in young adults

Significance

Transcranial photobiomodulation (tPBM) is an optical intervention that effectively enhances human cognition. However, limited studies have reported the effects of tPBM on electrophysiological brain networks.

Aim

We aimed to investigate the site- and electroencephalogram (EEG)-frequency-specific effects of 800-nm prefrontal tPBM on the EEG global network topology of the human brain, so a better understanding of how tPBM alters EEG brain networks can be achieved.

Approach

A total of 26 healthy young adults participated in the study, with multiple visits when either active or sham tPBM interventions were delivered to either the left or right forehead. A 19-channel EEG cap recorded the time series before and after the 8-min tPBM/sham. We used graph theory analysis (GTA) and formulated adjacency matrices in five frequency bands, followed by quantification of normalized changes in GTA-based global topographical metrics induced by the respective left and right tPBM/sham interventions.

Results

Statistical analysis indicated that the effects of 800-nm prefrontal tPBM on the EEG global topological networks are both site- and EEG-frequency-dependent. Specifically, our results demonstrated that the left 800-nm tPBM primarily enhanced the alpha network efficiency and information transmission, whereas the right 800-nm tPBM augmented the clustering ability of the EEG topological networks and improved the formation of small-worldness of the beta waves across the entire brain.

Conclusions

The study concluded that 800-nm prefrontal tPBM can enhance global connectivity patterns and information transmission in the human brain, with effects that are site- and EEG-frequency-specific. To further confirm and better understand these findings, future research should correlate post-tPBM cognitive assessments with EEG network analysis.

Transcranial optogenetic brain modulator for precise bimodal neuromodulation in multiple brain regions

Transcranial brain stimulation is a promising technology for safe modulation of brain function without invasive procedures. Recent advances in transcranial optogenetic techniques with external light sources, using upconversion particles and highly sensitive opsins, have shown promise for precise neuromodulation with improved spatial resolution in deeper brain regions. However, these methods have not yet been used to selectively excite or inhibit specific neural populations in multiple brain regions. In this study, we created a wireless transcranial optogenetic brain modulator that combines highly sensitive opsins and upconversion particles and allows for precise bimodal neuromodulation of multiple brain regions without optical crosstalk. We demonstrate the feasibility of our approach in freely behaving mice. Furthermore, we demonstrate its usefulness in studies of complex behaviors and brain dysfunction by controlling extorting behavior in mice in food competition tests and alleviating the symptoms of Parkinson's disease. Our approach has potential applications in the study of neural circuits and development of treatments for various brain disorders.

The Optical Parameter Optimization for Brain Implant Alzheimer Sensor Using Phototherapy Angle and Wavelength Simulation (PAWS) Methodology

Photonic therapy is emerging as a promising method in neuroscience for addressing Alzheimer's disease (AD). This study uses computational simulations to investigate the impact of specific wavelengths emitted by photodiodes on the light absorption rates in brain tissue for brain implant sensors. Additionally, it presents a novel methodology that enhances light absorption via multi-parameter optimization. By adjusting the angle and wavelength of the incident light, the absorption rate was significantly enhanced using four photodiodes, each emitting at 660 nm with a power input of 3 mW. Notably, an incident angle of 20 degrees optimized light absorption and minimized thermal effects on brain tissue. The findings indicate that photodiodes within the near-infrared spectrum are suitable for low-temperature therapeutic applications in brain tissues, affirming the viability of non-invasive and safe photonic therapy. This research contributes foundational data for advancing brain implant photonic sensor design and therapeutic strategies. Furthermore, it establishes conditions for achieving high light absorption rates with minimal heat generation, identifying optimal parameters for efficient energy transfer.

Differences between long- and short-wavelength light-induced retinal damage and the role of PARP-1 in retinal injury induced by blue light

Photobiomodulation (PBM) therapy uses light of different wavelengths to treat various retinal degeneration diseases, but the potential damage to the retina caused by long-term light irradiation is still unclear. This study were designed to detect the difference between long- and short-wavelength light (650-nm red light and 450-nm blue light, 2.55 mW/cm2, reference intensity in PBM)-induced injury. In addition, a comparative study was conducted to investigate the differences in retinal light damage induced by different irradiation protocols (short periods of repeated irradiation and a long period of constant irradiation). Furthermore, the protective role of PARP-1 inhibition on the molecular mechanism of blue light-induced injury was confirmed by a gene knockdown technique or a specific inhibitor through in vitro and in vivo experiments. The results showed that the susceptibility to retinal damage caused by irradiation with long- and short-wavelength light is different. Shorter wavelength lights, such as blue light, induce more severe retinal damage, while the retina exhibits better resistance to longer wavelength lights, such as red light. In addition, repeated irradiation for short periods induces less retinal damage than constant exposure over a long period. PARP-1 plays a critical role in the molecular mechanism of blue light-induced damage in photoreceptors and retina, and inhibiting PARP-1 can significantly protect the retina against blue light damage. This study lays an experimental foundation for assessing the safety of phototherapy products and for developing target drugs to protect the retina from light damage.

Simultaneous MEG and EEG source imaging of electrophysiological activity in response to acute transcranial photobiomodulation

Introduction

Transcranial photobiomodulation (tPBM) is a non-invasive neuromodulation technique that improves human cognition. The effects of tPBM of the right forehead on neurophysiological activity have been previously investigated using EEG in sensor space. However, the spatial resolution of these studies is limited. Magnetoencephalography (MEG) is known to facilitate a higher spatial resolution of brain source images. This study aimed to image post-tPBM effects in brain space based on both MEG and EEG measurements across the entire human brain.

Methods

MEG and EEG scans were concurrently acquired for 6 min before and after 8-min of tPBM delivered using a 1,064-nm laser on the right forehead of 25 healthy participants. Group-level changes in both the MEG and EEG power spectral density with respect to the baseline (pre-tPBM) were quantified and averaged within each frequency band in the sensor space. Constrained modeling was used to generate MEG and EEG source images of post-tPBM, followed by cluster-based permutation analysis for family wise error correction (p < 0.05).

Results

The 8-min tPBM enabled significant increases in alpha (8-12 Hz) and beta (13-30 Hz) powers across multiple cortical regions, as confirmed by MEG and EEG source images. Moreover, tPBM-enhanced oscillations in the beta band were located not only near the stimulation site but also in remote cerebral regions, including the frontal, parietal, and occipital regions, particularly on the ipsilateral side.

Discussion

MEG and EEG results shown in this study demonstrated that tPBM modulates neurophysiological activity locally and in distant cortical areas. The EEG topographies reported in this study were consistent with previous observations. This study is the first to present MEG and EEG evidence of the electrophysiological effects of tPBM in the brain space, supporting the potential utility of tPBM in treating neurological diseases through the modulation of brain oscillations.

Directed physiological networks in the human prefrontal cortex at rest and post transcranial photobiomodulation

Cerebral infra-slow oscillation (ISO) is a source of vasomotion in endogenic (E; 0.005-0.02 Hz), neurogenic (N; 0.02-0.04 Hz), and myogenic (M; 0.04-0.2 Hz) frequency bands. In this study, we quantified changes in prefrontal concentrations of oxygenated hemoglobin (Δ[HbO]) and redox-state cytochrome c oxidase (Δ[CCO]) as hemodynamic and metabolic activity metrics, and electroencephalogram (EEG) powers as electrophysiological activity, using concurrent measurements of 2-channel broadband near-infrared spectroscopy and EEG on the forehead of 22 healthy participants at rest. After preprocessing, the multi-modality signals were analyzed using generalized partial directed coherence to construct unilateral neurophysiological networks among the three neurophysiological metrics (with simplified symbols of HbO, CCO, and EEG) in each E/N/M frequency band. The links in these networks represent neurovascular, neurometabolic, and metabolicvascular coupling (NVC, NMC, and MVC). The results illustrate that the demand for oxygen by neuronal activity and metabolism (EEG and CCO) drives the hemodynamic supply (HbO) in all E/N/M bands in the resting prefrontal cortex. Furthermore, to investigate the effect of transcranial photobiomodulation (tPBM), we performed a sham-controlled study by delivering an 800-nm laser beam to the left and right prefrontal cortex of the same participants. After performing the same data processing and statistical analysis, we obtained novel and important findings: tPBM delivered on either side of the prefrontal cortex triggered the alteration or reversal of directed network couplings among the three neurophysiological entities (i.e., HbO, CCO, and EEG frequency-specific powers) in the physiological network in the E and N bands, demonstrating that during the post-tPBM period, both metabolism and hemodynamic supply drive electrophysiological activity in directed network coupling of the prefrontal cortex (PFC). Overall, this study revealed that tPBM facilitates significant modulation of the directionality of neurophysiological networks in electrophysiological, metabolic, and hemodynamic activities.

Unlocking the Power of Light on the Skin: A Comprehensive Review on Photobiomodulation

Photobiomodulation (PBM) is a procedure that uses light to modulate cellular functions and biological processes. Over the past decades, PBM has gained considerable attention for its potential in various medical applications due to its non-invasive nature and minimal side effects. We conducted a narrative review including articles about photobiomodulation, LED light therapy or low-level laser therapy and their applications on dermatology published over the last 6 years, encompassing research studies, clinical trials, and technological developments. This review highlights the mechanisms of action underlying PBM, including the interaction with cellular chromophores and the activation of intracellular signaling pathways. The evidence from clinical trials and experimental studies to evaluate the efficacy of PBM in clinical practice is summarized with a special emphasis on dermatology. Furthermore, advancements in PBM technology, such as novel light sources and treatment protocols, are discussed in the context of optimizing therapeutic outcomes and improving patient care. This narrative review underscores the promising role of PBM as a non-invasive therapeutic approach with broad clinical applicability. Despite the need for further research to develop standard protocols, PBM holds great potential for addressing a wide range of medical conditions and enhancing patient outcomes in modern healthcare practice.

Transcranial Irradiation Mitigates Paradoxical Sleep Deprivation Effect in an Age-Dependent Manner: Role of BDNF and GLP-1

The growing prevalence of aged sleep-deprived nations is turning into a pandemic state. Acute sleep deprivation (SD) accompanies aging, changing the hippocampal cellular pattern, neurogenesis pathway expression, and aggravating cognitive deterioration. The present study investigated the ability of Near Infra Red (NIR) light laser to ameliorate cognitive impairment induced by SD in young and senile rats. Wistar rats ≤ 2 months (young) and ≥ 14 months (senile) were sleep-deprived for 72 h with or without transcranial administration of NIR laser of 830 nm. Our results showed that NIR photobiomodulation (PBM) attenuated cognitive deterioration made by SD in young, but not senile rats, while both sleep-deprived young and senile rats exhibited decreased anxiety (mania)-like behavior in response to PBM. NIR PBM had an inhibitory effect on AChE, enhanced the production of ACh, attenuated ROS, and regulated cell apoptosis factors such as Bax and Bcl-2. NIR increased mRNA expression of BDNF and GLP-1 in senile rats, thus facilitating neuronal survival and differentiation. The present findings also revealed that age exerts an additive factor to the cellular assaults produced by SD where hippocampal damages made in 2-month rats were less severe than those of the aged one. In conclusion, NIR PBM seems to promote cellular longevity of senile hippocampal cells by combating ROS, elevating neurotrophic factors, thus improving cognitive performance. The present findings provide NIR as a possible candidate for hippocampal neuronal insults accompanying aging and SD.

Photomodulatory effects in the hypothalamus of sleep-deprived young and aged rats

Insufficient sleep is associated with impaired hypothalamic activity and declined attentional performance. In this study, alterations in the hypothalamus of REM sleep-deprived (SD) young and aged rats, and the modulatory effect of near-infrared (NIR) laser were investigated. Forty-eight male Wistar rats (24 young at 2 months and 24 senile at 14 months) were divided into three groups: the control, the SD group subjected to 72 hr of sleep deprivation, and the transcranial-NIR laser-treated (TLT) group subjected to SD for 72 hr and irradiated with 830 nm laser. The hypothalamic levels of oxidative stress, inflammatory biomarkers, antioxidant enzymes, mitochondrial cytochrome C oxidase (CCO), apoptotic markers (BAX, BCL-2), and neuronal survival-associated genes (BDNF, GLP-1) were evaluated. Furthermore, the hypothalamic tissue alterations were analyzed via histological examination. The results revealed that TLT treatment has enhanced the antioxidant status, prevented oxidative insults, suppressed neuroinflammation, regulated CCO activity, reduced apoptotic markers, and tuned the survival genes (BDNF & GLP-1) in hypothalamic tissue of SD young and aged rats. Microscopically, TLT treatment has ameliorated the SD-induced alterations and restored the normal histological features of hypothalamus tissue. Moreover, the obtained data showed that SD and NIR laser therapy are age-dependent. Altogether, our findings emphasize the age-dependent adverse effects of SD on the hypothalamus and suggest the use of low-laser NIR radiation as a potential non-invasive and therapeutic approach against SD-induced adverse effects in young and aged animals.

Dosimetry in cranial photobiomodulation therapy: effect of cranial thickness and bone density

This research aims to examine the influence of human skull bone thickness and density on light penetration in PBM therapy across different wavelengths, focusing on how these bone characteristics affect the absorption of therapeutic light. Analyses explored the effect of skull bone density and thickness on light penetration in PBM, specifically using Low-Level Laser Therapy (LLLT) for efficacy prediction. Measurements of bone thickness and density were taken using precise tools. This approach emphasizes LLLT's significance in enhancing PBM outcomes by assessing how bone characteristics influence light penetration. The study revealed no significant correlation between skull bone density and thickness and light penetration capability in photobiomodulation (PBM) therapy, challenging initial expectations. Wavelengths of 405 nm and 665 nm showed stronger correlations with bone density, suggesting a significant yet weak impact. Conversely, wavelengths of 532 nm, 785 nm, 810 nm, 830 nm, 980 nm, and 1064 nm showed low correlations, indicating minimal impact from bone density variations. However, data variability (R2 < 0.4) suggests that neither density nor thickness robustly predicts light power traversing the bone, indicating penetration capability might be more influenced by bone thickness at certain wavelengths. The study finds that the effectiveness of photobiomodulation (PBM) therapy with bone isn't just based on bone density and thickness but involves a complex interplay of factors. These include the bone's chemical and mineral composition, light's wavelength and energy dose, treatment duration and frequency, and the precise location where light is applied on the skull.

Phototherapy for age-related brain diseases: Challenges, successes and future

Brain diseases present a significant obstacle to both global health and economic progress, owing to their elusive pathogenesis and the limited effectiveness of pharmaceutical interventions. Phototherapy has emerged as a promising non-invasive therapeutic modality for addressing age-related brain disorders, including stroke, Alzheimer's disease (AD), and Parkinson's disease (PD), among others. This review examines the recent progressions in phototherapeutic interventions. Firstly, the article elucidates the various wavelengths of visible light that possess the capability to penetrate the skin and skull, as well as the pathways of light stimulation, encompassing the eyes, skin, veins, and skull. Secondly, it deliberates on the molecular mechanisms of visible light on photosensitive proteins, within the context of brain disorders and other molecular pathways of light modulation. Lastly, the practical application of phototherapy in diverse clinical neurological disorders is indicated. Additionally, this review presents novel approaches that combine phototherapy and pharmacological interventions. Moreover, it outlines the limitations of phototherapeutics and proposes innovative strategies to improve the treatment of cerebral disorders.

Mitochondrial dysfunction and neurological disorders: A narrative review and treatment overview

Mitochondria play a vital role in the nervous system, as they are responsible for generating energy in the form of ATP and regulating cellular processes such as calcium (Ca2+) signaling and apoptosis. However, mitochondrial dysfunction can lead to oxidative stress (OS), inflammation, and cell death, which have been implicated in the pathogenesis of various neurological disorders. In this article, we review the main functions of mitochondria in the nervous system and explore the mechanisms related to mitochondrial dysfunction. We discuss the role of mitochondrial dysfunction in the development and progression of some neurological disorders including Parkinson's disease (PD), multiple sclerosis (MS), Alzheimer's disease (AD), depression, and epilepsy. Finally, we provide an overview of various current treatment strategies that target mitochondrial dysfunction, including pharmacological treatments, phototherapy, gene therapy, and mitotherapy. This review emphasizes the importance of understanding the role of mitochondria in the nervous system and highlights the potential for mitochondrial-targeted therapies in the treatment of neurological disorders. Furthermore, it highlights some limitations and challenges encountered by the current therapeutic strategies and puts them in future perspective.

Oligodendrocyte progenitor cells in Alzheimer's disease: from physiology to pathology

Oligodendrocyte progenitor cells (OPCs) play pivotal roles in myelin formation and phagocytosis, communicating with neighboring cells and contributing to the integrity of the blood-brain barrier (BBB). However, under the pathological circumstances of Alzheimer's disease (AD), the brain's microenvironment undergoes detrimental changes that significantly impact OPCs and their functions. Starting with OPC functions, we delve into the transformation of OPCs to myelin-producing oligodendrocytes, the intricate signaling interactions with other cells in the central nervous system (CNS), and the fascinating process of phagocytosis, which influences the function of OPCs and affects CNS homeostasis. Moreover, we discuss the essential role of OPCs in BBB formation and highlight the critical contribution of OPCs in forming CNS-protective barriers. In the context of AD, the deterioration of the local microenvironment in the brain is discussed, mainly focusing on neuroinflammation, oxidative stress, and the accumulation of toxic proteins. The detrimental changes disturb the delicate balance in the brain, impacting the regenerative capacity of OPCs and compromising myelin integrity. Under pathological conditions, OPCs experience significant alterations in migration and proliferation, leading to impaired differentiation and a reduced ability to produce mature oligodendrocytes. Moreover, myelin degeneration and formation become increasingly active in AD, contributing to progressive neurodegeneration. Finally, we summarize the current therapeutic approaches targeting OPCs in AD. Strategies to revitalize OPC senescence, modulate signaling pathways to enhance OPC differentiation, and explore other potential therapeutic avenues are promising in alleviating the impact of AD on OPCs and CNS function. In conclusion, this review highlights the indispensable role of OPCs in CNS function and their involvement in the pathogenesis of AD. The intricate interplay between OPCs and the AD brain microenvironment underscores the complexity of neurodegenerative diseases. Insights from studying OPCs under pathological conditions provide a foundation for innovative therapeutic strategies targeting OPCs and fostering neurodegeneration. Future research will advance our understanding and management of neurodegenerative diseases, ultimately offering hope for effective treatments and improved quality of life for those affected by AD and related disorders.

Transcranial photobiomodulation therapy associated with cardiorespiratory rehabilitation in spastic subjects

The objective of this study was to evaluate the effects of cardiorespiratory rehabilitation (CR) and transcranial photobiomodulation (tPBM) on exercise tolerance (ET), heart rate variability (HRV), and peripheral muscle activity in individuals with spasticity. Fifteen participants with spasticity were randomly assigned to two groups: the tPBM group (tPBMG) consisted of eight volunteers who underwent tPBM (on mode) and CR, while the control group (CG) consisted of seven volunteers who underwent simulated tPBM (off mode) and CR. The CR program included 12 weeks of treatment, twice a week for one hour, involving aerobic exercises and lower limb strengthening. For tPBM, a cluster with three lasers (λ = 680 nm, 808 nm), with a power of 100 mW/laser and energy of 36 J, applied to the F7, F8, and Fpz points. The following parameters were evaluated after 8 and 12 weeks: ET, HRV, and surface electromyography (EMG) of the rectus femoris muscle during orthostasis (ORT), isometric squatting (ISOM), and isotonic squatting (ISOT). Both groups showed a 40% increase in ET for the CG and a 30% increase for the tPBMG. The CG had more pronounced parasympathetic modulation alterations during post-exercise effort and recovery compared to the tPBMG. The EMG results showed that the tPBMG exhibited progressive improvement in muscle activity during ISOM and ISOT, as well as a decrease in the interlimb difference. In conclusion, both CR and tPBMG demonstrated improvements in ET. However, tPBMG specifically showed promising effects on HRV modulation and peripheral muscle electrical activity, providing additional benefits compared to CR alone.

Effectiveness of photobiomodulation for people with age-related cognitive impairment: a systematic review and meta-analysis

The increasing incident of age-related cognitive impairment worldwide and the lack of pharmaceutical treatments emphasizes the value of non-pharmaceutical therapy. Emerging evidence suggested photobiomodulation (PBM) is a popular intervention to brain disorder; however, it remains unclear the efficacy of PBM for patients with age-related cognitive impairment. The purpose of this systematic review is to compare the different parameters used in PBM, analyze the beneficial effects of PBM as a potential therapy for age-related cognitive impairment. Five electronic database, PubMed, Web of Science, Cochrane Library, CINAHL, and PsycINFO, were systematically searched from inception to November 2021. Relevant randomized controlled trials (RCTs) were screened and assessed for risk of bias. Eleven RCTs evaluating PBM interventions were included. The systematic review and meta-analysis has been registered in PROSPERO(CRD42022374562). Results showed that PBM had a significant moderated effect on global cognition function (SMD=0.51, 95% CI [0.162, 0.864], p=0.004). We found that multiple wavelength PBM (SMD=0.648, 95% CI [0.220, 1.075], p=0.003) had significant effects while single wavelength PBM was non-significant (SMD=0.385, 95% CI [-0.168, 0.987], p=0.172). Laser effect (SMD=0.682, 95% CI [0.37, 0,994], p<0.001) was larger than LED effect (SMD=0.582, 95% CI [0.269, 0.895], p<0.001). PBM in clinical setting (SMD=0.468, 95% CI [0.050, 0.887], p=0.028) had significant effect, but there was no significant effect of home-used PBM (SMD=0.616, 95% CI [-0.121, 1.354], p=0.101). The pool effect of multi-modality PBM (SMD=0.720, 95% CI [0.027, 1.414], p=0.040) was significantly higher in the studies of transcranial irradiation (SMD=0.616, 95% CI [-0.121, 1.354], p=0.010). Cumulative irradiation time was a moderator between the PBM and cognitive function improvement. Photobiomodulation have the potential to improve cognitive function in aging adults. Cumulative irradiation duration, light source, device type, penetration modality, and intervention site can affect the effectiveness of PBM intervention.

Directed physiological networks in the human prefrontal cortex at rest and post transcranial photobiomodulation

Cerebral infra-slow oscillation (ISO) is a source of vasomotion in endogenic (E; 0.005-0.02 Hz), neurogenic (N; 0.02-0.04 Hz), and myogenic (M; 0.04-0.2 Hz) frequency bands. In this study, we quantified changes in prefrontal concentrations of oxygenated hemoglobin ( Δ [ H b O ] ) and redox-state cytochrome c oxidase ( Δ [ C C O ] ) as hemodynamic and metabolic activity metrics, and electroencephalogram (EEG) powers as electrophysiological activity, using concurrent measurements of 2-channel broadband near-infrared spectroscopy and EEG on the forehead of 22 healthy participants at rest. After preprocessing, the multi-modality signals were analyzed using generalized partial directed coherence to construct unilateral neurophysiological networks among the three neurophysiological metrics (with simplified symbols of HbO, CCO, and EEG) in each E/N/M frequency band. The links in these networks represent neurovascular, neurometabolic, and metabolicvascular coupling (NVC, NMC, and MVC). The results illustrate that the demand for oxygen by neuronal activity and metabolism (EEG and CCO) drives the hemodynamic supply (HbO) in all E/N/M bands in the resting prefrontal cortex. Furthermore, to investigate the effect of transcranial photobiomodulation (tPBM), we performed a sham-controlled study by delivering an 800-nm laser beam to the left and right prefrontal cortex of the same participants. After performing the same data processing and statistical analysis, we obtained novel and important findings: tPBM delivered on either side of the prefrontal cortex triggered the alteration or reversal of directed network couplings among the three neurophysiological entities (i.e., HbO, CCO, and EEG frequency-specific powers) in the physiological network in the E and N bands, demonstrating that during the post-tPBM period, both metabolism and hemodynamic supply drive electrophysiological activity in directed network coupling of the PFC. Overall, this study revealed that tPBM facilitates significant modulation of the directionality of neurophysiological networks in electrophysiological, metabolic, and hemodynamic activities.

Photons Induce Vesicular Exocytotic Release of Glutamate in a Power-Dependent Way

Increasing evidence indicates that photobiomodulation, based on tissue irradiation with photons in the red to near-infrared spectrum, may be an effective therapeutic approach to central nervous system disorders. Although nervous system functionality has been shown to be affected by photons in animal models, as well as in preliminary evidence in healthy subjects or in patients with neuropsychiatric disorders, the mechanisms involved in the photobiomodulation effects have not yet been clarified. We previously observed that photobiomodulation could stimulate glutamate release. Here, we investigate mechanisms potentially involved in the glutamate-releasing effect of photons from adult mouse cerebrocortical nerve terminals. We report evidence of photon ability to induce an exocytotic vesicular release of glutamate from the terminals of glutamatergic neurons in a power-dependent way. It can be hypothesized that photobiomodulation, depending on the potency, can release glutamate in a potentially neurotoxic or physiological range.

Photobiomodulation in Alzheimer's Disease-A Complementary Method to State-of-the-Art Pharmaceutical Formulations and Nanomedicine?

Alzheimer's disease (AD), as a neurodegenerative disorder, usually develops slowly but gradually worsens. It accounts for approximately 70% of dementia cases worldwide, and is recognized by WHO as a public health priority. Being a multifactorial disease, the origins of AD are not satisfactorily understood. Despite huge medical expenditures and attempts to discover new pharmaceuticals or nanomedicines in recent years, there is no cure for AD and not many successful treatments are available. The current review supports introspection on the latest scientific results from the specialized literature regarding the molecular and cellular mechanisms of brain photobiomodulation, as a complementary method with implications in AD. State-of-the-art pharmaceutical formulations, development of new nanoscale materials, bionanoformulations in current applications and perspectives in AD are highlighted. Another goal of this review was to discover and to speed transition to completely new paradigms for the multi-target management of AD, to facilitate brain remodeling through new therapeutic models and high-tech medical applications with light or lasers in the integrative nanomedicine of the future. In conclusion, new insights from this interdisciplinary approach, including the latest results from photobiomodulation (PBM) applied in human clinical trials, combined with the latest nanoscale drug delivery systems to easily overcome protective brain barriers, could open new avenues to rejuvenate our central nervous system, the most fascinating and complex organ. Picosecond transcranial laser stimulation could be successfully used to cross the blood-brain barrier together with the latest nanotechnologies, nanomedicines and drug delivery systems in AD therapy. Original, smart and targeted multifunctional solutions and new nanodrugs may soon be developed to treat AD.