Photobiomodulation for Alzheimer's Disease: Translating Basic Research to Clinical Application

Promising Strategies to Reduce the SARS-CoV-2 Amyloid Deposition in the Brain and Prevent COVID-19-Exacerbated Dementia and Alzheimer's Disease

The COVID-19 pandemic, caused by infection with the SARS-CoV-2 virus, is associated with cognitive impairment and Alzheimer's disease (AD) progression. Once it enters the brain, the SARS-CoV-2 virus stimulates accumulation of amyloids in the brain that are highly toxic to neural cells. These amyloids may trigger neurological symptoms in COVID-19. The meningeal lymphatic vessels (MLVs) play an important role in removal of toxins and mediate viral drainage from the brain. MLVs are considered a promising target to prevent COVID-19-exacerbated dementia. However, there are limited methods for augmentation of MLV function. This review highlights new discoveries in the field of COVID-19-mediated amyloid accumulation in the brain associated with the neurological symptoms and the development of promising strategies to stimulate clearance of amyloids from the brain through lymphatic and other pathways. These strategies are based on innovative methods of treating brain dysfunction induced by COVID-19 infection, including the use of photobiomodulation, plasmalogens, and medicinal herbs, which offer hope for addressing the challenges posed by the SARS-CoV-2 virus.

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

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

Photobiomodulation in experimental models of Alzheimer's disease: state-of-the-art and translational perspectives

Alzheimer's disease (AD) poses a significant public health problem, affecting millions of people across the world. Despite decades of research into therapeutic strategies for AD, effective prevention or treatment for this devastating disorder remains elusive. In this review, we discuss the potential of photobiomodulation (PBM) for preventing and alleviating AD-associated pathologies, with a focus on the biological mechanisms underlying this therapy. Future research directions and guidance for clinical practice for this non-invasive and non-pharmacological therapy are also highlighted. The available evidence indicates that different treatment paradigms, including transcranial and systemic PBM, along with the recently proposed remote PBM, all could be promising for AD. PBM exerts diverse biological effects, such as enhancing mitochondrial function, mitigating the neuroinflammation caused by activated glial cells, increasing cerebral perfusion, improving glymphatic drainage, regulating the gut microbiome, boosting myokine production, and modulating the immune system. We suggest that PBM may serve as a powerful therapeutic intervention for AD.

Photobiomodulation's potential as a non-invasive therapy for alzheimer's disease and minimal cognitive impairment: A 12-week investigation

BACKGROUND

Alzheimer's Disease (AD), undergoing a faster increase in occurrence than any other type of dementia, lacks a curative remedy despite advanced discoveries. To explore the realm of non-pharmacologic therapies, our study evaluates the 12-week impact of non-invasive Photobiomodulation (PBM) on cognitive and psychological aspects in individuals with AD and minimal cognitive impairment (MCI). The urgency of exploring innovative interventions is underscored by the rising occurrence of AD, particularly in regions with aging populations like Iran.

METHOD

13 patients (6 case patients and 7 control patients) participated in the study. Sham treatment was administered to seven individuals, while another six received PBM treatment over 12 weeks, with daily at-home LED (810 nm wavelength) device usage lasting 20 min. Initially, the patient and their caregiver participated in two hospital sessions to acquaint them with the device's operation.

RESULTS

The mean reduction of Hamilton's anxiety questionnaire score was 3.33±6.08 in the intervention group and 2.00±3.46 in the control group (p-value=0.836). The mean score reduction of the Hamilton depression questionnaire was 3.16±3.86 in the intervention group and 4.85±6.20 in the control group (p-value=0.836). The mean score of the DAD questionnaire in the intervention group before the study was 25.50±13.13 and after the intervention was 29.83±12.12 (p-value=0.084) and in the control group it was 29.71±8.19 and after the study was 29±0.972 (p-value = 0.526). The mean changes in the DAD questionnaire score in the intervention group increased by 4.33±4.92 and decreased by 0.71±2.81 in the control group (p-value=0.041).

CONCLUSION

In general, PBM appears to hold promise as a potentially safe method for enhancing the cognitive, functional, and psychological status of individuals with Alzheimer's disease, though further research with larger sample size and cautious interpretation are warranted.

Mitochondrial dysfunction in neurodegenerative disorders

Recent advances in understanding the role of mitochondrial dysfunction in neurodegenerative diseases have expanded the opportunities for neurotherapeutics targeting mitochondria to alleviate symptoms and slow disease progression. In this review, we offer a historical account of advances in mitochondrial biology and neurodegenerative disease. Additionally, we summarize current knowledge of the normal physiology of mitochondria and the pathogenesis of mitochondrial dysfunction, the role of mitochondrial dysfunction in neurodegenerative disease, current therapeutics and recent therapeutic advances, as well as future directions for neurotherapeutics targeting mitochondrial function. A focus is placed on reactive oxygen species and their role in the disruption of telomeres and their effects on the epigenome. The effects of mitochondrial dysfunction in the etiology and progression of Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson's disease, and Huntington's disease are discussed in depth. Current clinical trials for mitochondria-targeting neurotherapeutics are discussed.

Technology of the photobiostimulation of the brain's drainage system during sleep for improvement of learning and memory in male mice

In this study on healthy male mice using confocal imaging of dye spreading in the brain and its further accumulation in the peripheral lymphatics, we demonstrate stronger effects of photobiomodulation (PBM) on the brain's drainage system in sleeping vs. awake animals. Using the Pavlovian instrumental transfer probe and the 2-objects-location test, we found that the 10-day course of PBM during sleep vs. wakefulness promotes improved learning and spatial memory in mice. For the first time, we present the technology for PBM under electroencephalographic (EEG) control that incorporates modern state of the art facilities of optoelectronics and biopotential detection and that can be built of relatively cheap and commercially available components. These findings open a new niche in the development of smart technologies for phototherapy of brain diseases during sleep.

Photobiomodulation reduces neuropathic pain after spinal cord injury by downregulating CXCL10 expression

BACKGROUND

Many studies have recently highlighted the role of photobiomodulation (PBM) in neuropathic pain (NP) relief after spinal cord injury (SCI), suggesting that it may be an effective way to relieve NP after SCI. However, the underlying mechanisms remain unclear. This study aimed to determine the potential mechanisms of PBM in NP relief after SCI.

METHODS

We performed systematic observations and investigated the mechanism of PBM intervention in NP in rats after SCI. Using transcriptome sequencing, we screened CXCL10 as a possible target molecule for PBM intervention and validated the results in rat tissues using reverse transcription-polymerase chain reaction and western blotting. Using immunofluorescence co-labeling, astrocytes and microglia were identified as the cells responsible for CXCL10 expression. The involvement of the NF-κB pathway in CXCL10 expression was verified using inhibitor pyrrolidine dithiocarbamate (PDTC) and agonist phorbol-12-myristate-13-acetate (PMA), which were further validated by an in vivo injection experiment.

RESULTS

Here, we demonstrated that PBM therapy led to an improvement in NP relative behaviors post-SCI, inhibited the activation of microglia and astrocytes, and decreased the expression level of CXCL10 in glial cells, which was accompanied by mediation of the NF-κB signaling pathway. Photobiomodulation inhibit the activation of the NF-κB pathway and reduce downstream CXCL10 expression. The NF-κB pathway inhibitor PDTC had the same effect as PBM on improving pain in animals with SCI, and the NF-κB pathway promoter PMA could reverse the beneficial effect of PBM.

CONCLUSIONS

Our results provide new insights into the mechanisms by which PBM alleviates NP after SCI. We demonstrated that PBM significantly inhibited the activation of microglia and astrocytes and decreased the expression level of CXCL10. These effects appear to be related to the NF-κB signaling pathway. Taken together, our study provides evidence that PBM could be a potentially effective therapy for NP after SCI, CXCL10 and NF-kB signaling pathways might be critical factors in pain relief mediated by PBM after SCI.

A randomized, blinded study of photobiomodulation in a mouse model of Alzheimer's disease showed no preventive effect

Photobiomodulation (PBM), the process of exposing tissue to red or near-infrared light, has become a topic of great interest as a therapy for diverse pathologies, including neurodegenerative disorders. Here, we aimed to evaluate the potential beneficial effect of PBM on Alzheimer's disease (AD) using behavioral and histological readouts from a well-established transgenic murine AD model (5xFAD mice) in a randomized and fully blinded long-term in-vivo study following GLP (Good Laboratory Practices) guidelines. The heads of the mice were illuminated with no (sham), low or high power 810 nm light, three times a week for 5 months from the first to the sixth month of life corresponding to the prodromal phase of the pathology. The results showed that there were no significant differences between the groups in behavioral tests, including the Morris water maze, novel object recognition, and Y-maze. Similarly, histological analyses showed no differences in amyloid load, neuronal loss or microglial response. In conclusion, under the conditions of our experiment, we were unable to demonstrate any therapeutic effect of PBM for AD. This study calls for further evidence and caution when considering PBM as an effective treatment for AD.

Effect of transcranial photobiomodulation on electrophysiological activity of brain in healthy individuals: A scoping review

BACKGROUND OBJECTIVE

Transcranial photobiomodulation (tPBM) is a safe and non-invasive treatment that has recently emerged as an effective technique to apply near-infrared or red light to activate neural tissues. The objective is to review the literature on the effect of tPBM on electrophysiological activity in healthy individuals.

METHODS

Literature was searched through PubMed, Scopus, Web of Science, Cumulated Index to Nursing and Allied Health Literature (CINAHL), Embase, and Ovid for transcranial photobiomodulation therapy in healthy individuals age group 18-80 years of either gender having electroencephalography as an outcome. Critical appraisal of included Randomized Controlled Trials and non-randomized experimental studies was done using Joanna Briggs Institute (JBI) critical appraisal tool.

RESULTS

A database search yielded a total of 4156 results. After eliminating 2626 duplicates, 1530 records were left. 32 articles were considered for full-text screening after 1498 records were excluded through title and abstract screening. 10 articles were included in this review. tPBM has been found to increase the higher electrophysiological oscillations and there is inconclusive evidence targeting the lower oscillatory electrophysiological frequencies.

CONCLUSION

Transcranial photobiomodulation can have promising effects on the electrophysiological activity of the brain in healthy individuals.

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.

Current emerging novel therapies for Alzheimer's disease and the future prospects of magneto-mechanical force therapy

Alzheimer's disease (AD) is the most common neurodegenerative disease among the elderly, and the morbidity increases with the aging population aggravation. The clinical symptoms of AD mainly include cognitive impairment and memory loss, which undoubtedly bring a huge burden to families and society. Currently, the drugs in clinical use only improve the symptoms of AD but do not cure or prevent the progression of the disease. Therefore, it is urgent for us to develop novel therapeutic strategies for effective AD treatment. To provide a better theoretical basis for exploring novel therapeutic strategies in future AD treatment, this review introduces the recent AD treatment technologies from three aspects, including nanoparticle (NP) based drug therapy, biological therapy and physical therapy. The nanoparticle-mediated therapeutic approaches at the nanomaterial-neural interface and biological system are described in detail, and in particular the magneto-regulated strategies by magnetic field actuating magnetic nanoparticles are highlighted. Promising application of magneto-mechanical force regulated strategy in future AD treatment is also addressed, which offer possibilities for the remote manipulation in a precise manner. In the future, it may be possible for physicians to realize a remote, precise and effective therapy for AD using magneto-mechanical force regulated technology based on the combination of magnetic nanoparticles and an external magnetic field.

Mechanisms of phototherapy of Alzheimer's disease during sleep and wakefulness: the role of the meningeal lymphatics

With the increase in the aging population, the global number of people with Alzheimer's disease (AD) progressively increased worldwide. The situation is aggravated by the fact that there is no the effective pharmacological therapy of AD. Photobiomodulation (PBM) is non-pharmacological approach that has shown very promising results in the therapy of AD in pilot clinical and animal studies. However, the mechanisms of therapeutic effects of PBM for AD are poorly understood. In this study on mice, we demonstrate that photodynamic effects of 5-aminolevulenic acid and laser 635 nm cause reduction of network of the meningeal lymphatic vessels (MLVs) leading to suppression of lymphatic removal of beta-amyloid (Aβ) from the right lateral ventricle and the hippocampus. Using the original protocol of PBM under electroencephalographic monitoring of wakefulness and sleep stages in non-anesthetized mice, we discover that the 7-day course of PBM during deep sleep vs. wakefulness provides better restoration of clearance of Aβ from the ventricular system of the brain and the hippocampus. Our results shed light on the mechanism of PBM and show the stimulating effects of PBM on the brain lymphatic drainage that promotes transport of Aβ via the lymphatic pathway. The effects of PBM on the brain lymphatics in sleeping brain open a new niche in the study of restorative functions of sleep as well as it is an important informative platform for the development of innovative smart sleep technologies for the therapy of AD.

Repeated Transcranial Photobiomodulation with Light-Emitting Diodes Improves Psychomotor Vigilance and EEG Networks of the Human Brain

Transcranial photobiomodulation (tPBM) has been suggested as a non-invasive neuromodulation tool. The repetitive administration of light-emitting diode (LED)-based tPBM for several weeks significantly improves human cognition. To understand the electrophysiological effects of LED-tPBM on the human brain, we investigated alterations by repeated tPBM in vigilance performance and brain networks using electroencephalography (EEG) in healthy participants. Active and sham LED-based tPBM were administered to the right forehead of young participants twice a week for four weeks. The participants performed a psychomotor vigilance task (PVT) during each tPBM/sham experiment. A 64-electrode EEG system recorded electrophysiological signals from each participant during the first and last visits in a 4-week study. Topographical maps of the EEG power enhanced by tPBM were statistically compared for the repeated tPBM effect. A new data processing framework combining the group's singular value decomposition (gSVD) with eLORETA was implemented to identify EEG brain networks. The reaction time of the PVT in the tPBM-treated group was significantly improved over four weeks compared to that in the sham group. We observed acute increases in EEG delta and alpha powers during a 10 min LED-tPBM while the participants performed the PVT task. We also found that the theta, beta, and gamma EEG powers significantly increased overall after four weeks of LED-tPBM. Combining gSVD with eLORETA enabled us to identify EEG brain networks and the corresponding network power changes by repeated 4-week tPBM. This study clearly demonstrated that a 4-week prefrontal LED-tPBM can neuromodulate several key EEG networks, implying a possible causal effect between modulated brain networks and improved psychomotor vigilance outcomes.

Use of either transcranial or whole-body photobiomodulation treatments improves COVID-19 brain fog

There is increasing recognition of post-COVID-19 sequelae involving chronic fatigue and brain fog, for which photobiomodulation (PBM) therapy has been utilized. This open-label, pilot, human clinical study examined the efficacy of two PBM devices, for example, a helmet (1070 nm) for transcranial (tPBM) and a light bed (660 and 850 nm) for whole body (wbPBM), over a 4-week period, with 12 treatments for two separate groups (n = 7 per group). Subjects were evaluated with a neuropsychological test battery, including the Montreal Cognitive Assessment (MoCA), the digit symbol substitution test (DSST), the trail-making tests A and B, the physical reaction time (PRT), and a quantitative electroencephalography system (WAVi), both pre- and post- the treatment series. Each device for PBM delivery was associated with significant improvements in cognitive tests (p < 0.05 and beyond). Changes in WAVi supported the findings. This study outlines the benefits of utilizing PBM therapy (transcranial or whole-body) to help treat long-COVID brain fog.

Phototherapy of Alzheimer's Disease: Photostimulation of Brain Lymphatics during Sleep: A Systematic Review

The global number of people with Alzheimer's disease (AD) doubles every 5 years. It has been established that unless an effective treatment for AD is found, the incidence of AD will triple by 2060. However, pharmacological therapies for AD have failed to show effectiveness and safety. Therefore, the search for alternative methods for treating AD is an urgent problem in medicine. The lymphatic drainage and removal system of the brain (LDRSB) plays an important role in resistance to the progression of AD. The development of methods for augmentation of the LDRSB functions may contribute to progress in AD therapy. Photobiomodulation (PBM) is considered to be a non-pharmacological and safe approach for AD therapy. Here, we highlight the most recent and relevant studies of PBM for AD. We focus on emerging evidence that indicates the potential benefits of PBM during sleep for modulation of natural activation of the LDRSB at nighttime, providing effective removal of metabolites, including amyloid-β, from the brain, leading to reduced progression of AD. Our review creates a new niche in the therapy of brain diseases during sleep and sheds light on the development of smart sleep technologies for neurodegenerative diseases.

Microbiota-gut-brain axis and related therapeutics in Alzheimer's disease: prospects for multitherapy and inflammation control

Alzheimer's disease (AD) is the most common type of dementia in the elderly and causes neurodegeneration, leading to memory loss, behavioral disorder, and psychiatric impairment. One potential mechanism contributing to the pathogenesis of AD may be the imbalance in gut microbiota, local and systemic inflammation, and dysregulation of the microbiota-gut-brain axis (MGBA). Most of the AD drugs approved for clinical use today are symptomatic treatments that do not improve AD pathologic changes. As a result, researchers are exploring novel therapeutic modalities. Treatments involving the MGBA include antibiotics, probiotics, transplantation of fecal microbiota, botanical products, and others. However, single-treatment modalities are not as effective as expected, and a combination therapy is gaining momentum. The purpose of this review is to summarize recent advances in MGBA-related pathological mechanisms and treatment modalities in AD and to propose a new concept of combination therapy. "MGBA-based multitherapy" is an emerging view of treatment in which classic symptomatic treatments and MGBA-based therapeutic modalities are used in combination. Donepezil and memantine are two commonly used drugs in AD treatment. On the basis of the single/combined use of these two drugs, two/more additional drugs and treatment modalities that target the MGBA are chosen based on the characteristics of the patient's condition as an adjuvant treatment, as well as the maintenance of good lifestyle habits. "MGBA-based multitherapy" offers new insights for the treatment of cognitive impairment in AD patients and is expected to show good therapeutic results.

Effect of 650 nm laser photobiomodulation therapy on the HT-7 (shenmen) acupoint in the Mus musculus model of Parkinson's disease

Background

Parkinson's disease is one of the neurodegenerative conditions that impacts 1-2% of the world's population. The only effective therapy for this condition today is to restore the biochemical function of the diseased dopamine neurons by giving them Levodopa or L-3,4-dihydroxyphenylalanine (l-DOPA). The risk of progenitor stem cells, though, is the growth of teratomas or the uncontrolled growth of cells. As a result, an alternative or additional method is needed, such as photobiomodulation therapy using a laser diode. In this research, male mice (Mus musculus), which were used as models for Parkinson's disease in an in vivo paraquat study, to determine the optimal dose of photobiomodulation therapy and a laser diode was used as a treatment.

Methods

The three sample groups are Group P-L- (control group, induced by 0.9% NaCl), Group P + L- (only caused by paraquat), and Group P + L+. (Treatment group, treated by paraquat and photobiomodulation therapy with a laser diode). Photobiomodulation treatment doses of 0.14 J, 0.29 J, 0.37 J, 0.76 J, 1.14 J, and 1.52 J were used in the P+L+ subgroups (6 groups). The laser diode generated a continuous wave with a wavelength of 658 nm, a beam spot of 2.10 mm, and an output power of 15.42 mW. After treatment, the histopathology results of each sample were inspected under a microscope.

Result

In Parkinson's disease-affected mice, paraquat has been shown to reduce the number of neurons. According to the results of the histopathological examination, photobiomodulation therapy using a laser diode (P + L+) on the HT-7 (Shenmen) may raise the quantity of neurons and the proportion of healthy cells in the mouse brain.

Conclusion

The effective radiated energy of the photobiomodulation therapy using laser diode treatment on the muscle musculus cell model of Parkinson's disease is 0.76 J.

Mitochondrial Dysfunction and Parkinson's Disease: Pathogenesis and Therapeutic Strategies

Parkinson's disease (PD) is a common age-related neurodegenerative disorder whose pathogenesis is not completely understood. Mitochondrial dysfunction and increased oxidative stress have been considered as major causes and central events responsible for the progressive degeneration of dopaminergic (DA) neurons in PD. Therefore, investigating mitochondrial disorders plays a role in understanding the pathogenesis of PD and can be an important therapeutic target for this disease. This study discusses the effect of environmental, genetic and biological factors on mitochondrial dysfunction and also focuses on the mitochondrial molecular mechanisms underlying neurodegeneration, and its possible therapeutic targets in PD, including reactive oxygen species generation, calcium overload, inflammasome activation, apoptosis, mitophagy, mitochondrial biogenesis, and mitochondrial dynamics. Other potential therapeutic strategies such as mitochondrial transfer/transplantation, targeting microRNAs, using stem cells, photobiomodulation, diet, and exercise were also discussed in this review, which may provide valuable insights into clinical aspects. A better understanding of the roles of mitochondria in the pathophysiology of PD may provide a rationale for designing novel therapeutic interventions in our fight against PD.

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.

Photobiomodulation attenuates oligodendrocyte dysfunction and prevents adverse neurological consequences in a rat model of early life adversity

Rationale: Adverse experiences in early life including abuse, trauma and neglect, have been linked to poor physical and mental health outcomes. Emerging evidence implies that those who experienced early life adversity (ELA) are more likely to develop cognitive dysfunction and depressive-like symptoms in adulthood. The molecular mechanisms responsible for the negative consequences of ELA, however, remain unclear. In the absence of effective management options, anticipatory guidance is the mainstay of ELA prevention. Furthermore, there is no available treatment that prevents or alleviates the neurologic sequelae of ELA, especially traumatic stress. Hence, the present study aims to investigate the mechanisms for these associations and evaluate whether photobiomodulation (PBM), a non-invasive therapeutic procedure, can prevent the negative cognitive and behavioral manifestations of ELA in later life. Methods: ELA was induced by repeated inescapable electric foot shock of rats from postnatal day 21 to 26. On the day immediately following the last foot shock, 2-min daily PBM treatment was applied transcranially for 7 consecutive days. Cognitive dysfunction and depression-like behaviors were measured by a battery of behavioral tests in adulthood. Subsequently, oligodendrocyte progenitor cells (OPCs) differentiation, the proliferation and apoptosis of oligodendrocyte lineage cells (OLs), mature oligodendrocyte, myelinating oligodendrocyte, the level of oxidative damage, reactive oxygen species (ROS) and total antioxidant capacity were measured and analyzed using immunofluorescence staining, capillary-based immunoassay (ProteinSimple®) and antioxidant assay kit. Results: The rats exposed to ELA exhibited obvious oligodendrocyte dysfunction, including a reduction in OPCs differentiation, diminished generation and survival of OLs, decreased OLs, and decreased matured oligodendrocyte. Furthermore, a deficit in myelinating oligodendrocytes was observed, in conjunction with an imbalance in redox homeostasis and accumulated oxidative damage. These alternations were concomitant with cognitive dysfunction and depression-like behaviors. Importantly, we found that early PBM treatment largely prevented these pathologies and reversed the neurologic sequelae resulting from ELA. Conclusions: Collectively, these findings provide new insights into the mechanism by which ELA affects neurological outcomes. Moreover, our findings support that PBM may be a promising strategy to prevent ELA-induced neurologic sequelae that develops later in life.

Photobiomodulation for Alzheimer's disease: photoelectric coupling effect on attenuating Aβ neurotoxicity

Alzheimer's disease (AD) and dementia are the most worrying health problems faced by people globally today. Although the pathological features of AD consisting of amyloid-beta (Aβ) plaques in the extracellular space (ECS) and intracellular tau tangles are well established, the developed medicines targeting these two proteins have not obtained the expected clinical effects. Photobiomodulation (PBM) describes the therapeutic use of red light (RL) or near-infrared light (NIR) to serve as a noninvasive neuroprotective strategy for brain diseases. The present review discusses the mechanisms of the photoelectric coupling effect (light energy-induced special electronic transition-related alterations in protein structure) of PBM on reducing Aβ toxicity. On the one hand, RL or NIR can directly disassemble Aβ in vitro and in vivo. On the other hand, formaldehyde (FA)-inhibited catalase (CAT) and H2O2-inactived formaldehyde dehydrogenase (FDH) are formed a vicious circle in AD; however, light energy not only activates FDH to degrade excessive FA (which crosslinks Aβ monomer to form Aβ oligomers and senile plaques) but also sensitizes CAT to reduce hydrogen peroxide levels (H2O2, which can facilitate Aβ aggregation and enhance FA generation). In addition, it also activates mitochondrial cytochrome-c to produce ATP in the neurons. Clinical trials of phototherapeutics or oral coenzyme Q10 have shown positive effects in AD patients. Hence, a promising strategy combined PBM with nanopacked Q10 has been proposed to apply for treating AD.

Best Medicine for Dementia: The Life-Long Defense of the Brain

This review deals with an unwelcome reality about several forms of dementia, including Alzheimer's disease- that these dementias are caused, in part or whole, by the aging of the vasculature. Since the vasculature ages in us all, dementia is our fate, sealed by the realit!ies of the circulation; it is not a disease with a cure pending. Empirically, cognitive impairment before our 7th decade is uncommon and considered early, while a diagnosis in our 11th decade is late but common in that cohort (>40%). Projections from earlier ages suggest that the prevalence of dementia in people surviving into their 12th decade exceeds 80%. We address the question why so few of many interventions known to delay dementia are recognized as therapy; and we try to resolve this few-and-many paradox, identifying opportunities for better treatment, especially pre-diagnosis. The idea of dementia as a fate is resisted, we argue, because it negates the hope of a cure. But the price of that hope is lost opportunity. An approach more in line with the evidence, and more likely to limit suffering, is to understand the damage that accumulates with age in the cerebral vasculature and therefore in the brain, and which eventually gives rise to cognitive symptoms in late life, too often leading to dementia. We argue that hope should be redirected to delaying that damage and with it the onset of cognitive loss; and, for each individual, it should be redirected to a life-long defense of their brain.

New insight into brain disease therapy: nanomedicines-crossing blood-brain barrier and extracellular space for drug delivery

INTRODUCTION

Brain diseases including brain tumor, Alzheimer's disease, Parkinson's disease, etc. are difficult to treat. The blood-brain barrier (BBB) is a major obstacle for drug delivery into the brain. Although nano-package and receptor-mediated delivery of nanomedicine markedly increases BBB penetration, it yet did not extensively improve clinical cure rate. Recently, brain extracellular space (ECS) and interstitial fluid (ISF) drainage in ECS have been found to determine whether a drug dissolved in ISF can reach its target cells. Notably, an increase in tortuosity of ECS associated with slower ISF drainage induced by the accumulated harmful substances, such as: amyloid-beta (Aβ), α-synuclein, and metabolic wastes, causes drug delivery failure.

AREAS COVERED

The methods of nano-package and receptor-mediated drug delivery and the penetration efficacy of nanomedicines across BBB and ECS are assessed.

EXPERT OPINION

Invasive delivering drug via ECS and noninvasive near-infrared photo-sensitive nanomedicines may provide a promising benefit to patients with brain disease.

Transcranial near-infrared light in treatment of neurodegenerative diseases

Light is a natural agent consisting of a range of visible and invisible electromagnetic spectrum travels in waves. Near-infrared (NIR) light refers to wavelengths from 800 to 2,500 nm. It is an invisible spectrum to naked eyes and can penetrate through soft and hard tissues into deep structures of the human body at specific wavelengths. NIR light may carry different energy levels depending on the intensity of emitted light and therapeutic spectrum (wavelength). Stimulation with NIR light can activate intracellular cascades of biochemical reactions with local short- and long-term positive effects. These properties of NIR light are employed in photobiomodulation (PBM) therapy, have been linked to treating several brain pathologies, and are attracting more scientific attention in biomedicine. Transcranial brain stimulations with NIR light PBM in recent animal and human studies revealed a positive impact of treatment on the progression and improvement of neurodegenerative processes, management of brain energy metabolism, and regulation of chronic brain inflammation associated with various conditions, including traumatic brain injury. This scientific overview incorporates the most recent cellular and functional findings in PBM with NIR light in treating neurodegenerative diseases, presents the discussion of the proposed mechanisms of action, and describes the benefits of this treatment in neuroprotection, cell preservation/detoxification, anti-inflammatory properties, and regulation of brain energy metabolism. This review will also discuss the novel aspects and pathophysiological role of the glymphatic and brain lymphatics system in treating neurodegenerative diseases with NIR light stimulations. Scientific evidence presented in this overview will support a combined effort in the scientific community to increase attention to the understudied NIR light area of research as a natural agent in the treatment of neurodegenerative diseases to promote more research and raise awareness of PBM in the treatment of brain disorders.

Photobiomodulation Therapy through a Novel Flat-Top Hand-Piece Prototype Improves Tissue Regeneration in Amphioxus (Branchiostoma lanceolatum): Proposal of an Ethical Model for Preclinical Screening

Despite the literature providing compelling evidence for the medical efficacy of photobiomodulation (PBM) therapy, its consistency in terms of accuracy and standardization needs improving. Identification of new technology and reliable and ethical biological models is, therefore, a challenge for researchers working on PBM. We tested the reliability of PBM irradiation through a novel delivery probe with a flat-top beam profile on the regenerating amphioxus Branchiostoma lanceolatum. The caudalmost 9 ± 1 myotomes, posterior to the anus, were excised using a sterile lancet. Animals were randomly split into three experimental groups. In the control group, the beam area was bounded with the 635-nm red-light pointer (negligible power, <0.5 mW) and the laser device was coded to irradiate 810 nm and 0 W. In Group laser-1, the beam area was bounded with the same 635-nm red-light pointer and irradiated at 810 nm, 1 W in CW for 60 s, spot-size 1 cm2, 1 W/cm2, 60 J/cm2, and 60 J; irradiation was performed every day for two weeks. In Group laser-2, the beam area was bounded with the same 635-nm red-light pointer and irradiated at 810 nm, 1 W in CW for 60 s, spot-size 1 cm2, 1 W/cm2, 60 J/cm2, and 60 J; irradiation was performed on alternate days for four weeks. We observed that PBM improved the natural wound-healing and regeneration process. The effect was particularly evident for the notochord. Daily irradiation better supported the regenerative process.

Phototherapy for Cognitive Function in Patients With Dementia: A Systematic Review and Meta-Analysis

Background

Dementia is a major health burden worldwide. As numerous pharmacological trials for dementia have failed, emerging phototherapy studies have evaluated the efficacy of alternative therapies for cognition.

Objective

The objective of this study was to evaluate the association between phototherapy and changes in cognitive deficits in patients with dementia.

Methods

PubMed, Embase, Web of Science, PsycINFO, CINAHL, and Cochrane Central Register of Controlled Trials were searched from inception to 27 March 2022. Inclusion criteria were controlled clinical trials of phototherapy interventions reporting pre-post changes in global cognitive function and subdomains in patients with dementia. Data were extracted by two independent reviewers and pooled in random-effects models. Subgroup and meta-regression analyses were conducted to investigate the sources of heterogeneity.

Results

Our analyses included 13 studies enrolling a total of 608 participants. Phototherapy showed significant associations with improvements of global cognitive function (standardized mean difference [SMD], 0.63; 95% confidence interval [CI], 0.33-0.94; P < 0.001) and subdomains, especially with respect to attention, executive function, and working memory. Near-infrared (NIR) light-emitting diodes (LEDs) photobiomodulation (SMD, 0.91; 95% CI, 0.46-1.36; P < 0.001) and lasers (SMD, 0.99; 95% CI, 0.56-1.43; P < 0.001) showed more significant associations with improved cognitive functions when compared with normal visible light. In addition, the effect sizes of short-term effects (SMD, 0.63; 95% CI, 0.33-0.94; P < 0.001) were larger than effects assessed in long-term follow-up (SMD, 0.49; 95% CI, -0.24-1.21; P = 0.189).

Conclusion

In this meta-analysis, phototherapy interventions were associated with cognitive improvement in patients with dementia. NIR LEDs and lasers had advantages over normal visible light. Domain-specific effects were indicated for attention, executive function, and working memory. Short-term improvement after phototherapy was supported, while evidence for long-term benefits was lacking. Stronger evidence for individualized parameters, such as optimal dosing, is needed in the future.

Systematic Review Registration

[https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=267596], identifier [CRD42021267596].

Near-infrared light reduces glia activation and modulates neuroinflammation in the brains of diet-induced obese mice

Neuroinflammation is a key event in neurodegenerative conditions such as Alzheimer's disease (AD) and characterizes metabolic pathologies like obesity and type 2 diabetes (T2D). Growing evidence in humans shows that obesity increases the risk of developing AD by threefold. Hippocampal neuroinflammation in rodents correlates with poor memory performance, suggesting that it contributes to cognitive decline. Here we propose that reducing obesity/T2D-driven neuroinflammation may prevent the progression of cognitive decline associated with AD-like neurodegenerative states. Near-infrared light (NIR) has attracted increasing attention as it was shown to improve learning and memory in both humans and animal models. We previously reported that transcranial NIR delivery reduced amyloid beta and Tau pathology and improved memory function in mouse models of AD. Here, we report the effects of NIR in preventing obesity-induced neuroinflammation in a diet-induced obese mouse model. Five-week-old wild-type mice were fed a high-fat diet (HFD) for 13 weeks to induce obesity prior to transcranial delivery of NIR for 4 weeks during 90-s sessions given 5 days a week. After sacrifice, brain slices were subjected to free-floating immunofluorescence for microglia and astrocyte markers to evaluate glial activation and quantitative real-time polymerase chain reaction (PCR) to evaluate expression levels of inflammatory cytokines and brain-derived neurotrophic factor (BDNF). The hippocampal and cortical regions of the HFD group had increased expression of the activated microglial marker CD68 and the astrocytic marker glial fibrillary acidic protein. NIR-treated HFD groups showed decreased levels of these markers. PCR revealed that hippocampal tissue from the HFD group had increased levels of pro-inflammatory interleukin (IL)-1β and tumor necrosis factor-α. Interestingly, the same samples showed increased levels of the anti-inflammatory IL-10. All these changes were attenuated by NIR treatment. Lastly, hippocampal levels of the neurotrophic factor BDNF were increased in NIR-treated HFD mice, compared to untreated HFD mice. The marked reductions in glial activation and pro-inflammatory cytokines along with elevated BDNF provide insights into how NIR could reduce neuroinflammation. These results support the use of NIR as a potential non-invasive and preventive therapeutic approach against chronic obesity-induced deficits that are known to occur with AD neuropathology.

[Transcranial photobiomodulation in therapy of neurodegenerative diseases of the brain: theoretical background and clinical effectiveness]

Transcranial photobiomodulation (tPBM) is a form of light therapy that uses monochromatic visible and infrared light from non-ionizing radiation sources (lasers, LEDs) placed on the scalp, forehead, or intranasally to project light directly to target areas of the brain. Accumulated experimental and clinical data indicate the safety and potential efficacy of tPBM in some central nervous system diseases.This article briefly reviews the general concepts of tPBM, the results of experimental and clinical studies on the efficacy of tPBM in Alzheimer's disease, Parkinson's disease, and brain stroke. The possible mechanisms of the tPBM therapeutic effect and the need to choose optimal exposure parameters are discussed. Although the evidence base regarding the efficacy of tPBM in neurodegenerative and vascular brain diseases is still insufficient, analysis of the published data justifies considering tPBM as a promising method of adjuvant therapy for some central nervous system diseases.

Tumor radiosensitization by photobiomodulation

PURPOSE

To investigate the safety of photobiomodulation therapy (PBM) in tumors and its potential as a radiosensitizer when combined with radiotherapy.

METHODS

We have performed in vitro experiments in A431 cells to assess proliferation and cell cycle after PBM, as well as clonogenic assay and H2AX-gamma immunolabeling to quantify double strand breaks after the combination of PBM and radiation. In vivo experiments in xenografts included Kaplan-Meier survival analysis, optical coherence tomography (OCT) and histological analysis.

RESULTS

PBM did not induce proliferation in vitro, but increased the G2/M fraction by 27% 24h after illumination, resulting in an enhancement of 30% in radiation effect in the clonogenic assay. The median survival of the PBM-RT group increased by 4 days and the hazard ratio was 0.417 (CI 95%: 0.173-1.006) when compared to radiation alone. OCT analysis over time demonstrated that PBM increases tumor necrosis due to radiation, and histological analysis showed that illumination increased cell differentiation and angiogenesis, which may play a role in the synergetic effect of PBM and radiation.

CONCLUSION

PBM technique may be one of the most appropriate approaches for radiosensitizing tumors while protecting normal tissue because of its low cost and low training requirements for staff.

Photobiomodulation Therapy for Dementia: A Systematic Review of Pre-Clinical and Clinical Studies

BACKGROUND

Photobiomodulation (PBM) involves the use of red and/or near-infrared light from lasers or LEDs to improve a wide range of medical disorders. Transcranial PBM, sometimes accompanied by intranasal PBM, has been tested to improve many brain disorders, including dementia.

OBJECTIVE

To conduct a systematic review according to PRISMA guidelines of pre-clinical and clinical studies reporting the use of PBM, which were considered relevant to dementia.

METHODS

Literature was searched between 1967 and 2020 using a range of keywords relevant to PBM and dementia. The light source and wavelength(s), output power, irradiance, irradiation time, fluence or total energy (dose), operation mode (continuous or pulsed) irradiation, approach and site, number of treatment sessions, as well as study outcome(s) were extracted.

RESULTS

Out of 10,473 initial articles, 36 studies met the inclusion criteria. Nine articles reported in vitro studies, 17 articles reported studies in animal models of dementia, and 10 studies were conducted in dementia patients. All of the included studies reported positive results. The clinical studies were limited by the small number of patients, lack of placebo controls in some instances, and only a few used objective neuroimaging methods.

CONCLUSION

The preliminary evidence of clinical benefit, the lack of any adverse effects, and the remarkable ease of use, suggest larger clinical trials should be conducted as soon as possible.

Exploring the Use of Intracranial and Extracranial (Remote) Photobiomodulation Devices in Parkinson's Disease: A Comparison of Direct and Indirect Systemic Stimulations

In recent times, photobiomodulation has been shown to be beneficial in animal models of Parkinson's disease, improving locomotive behavior and being neuroprotective. Early observations in people with Parkinson's disease have been positive also, with improvements in the non-motor symptoms of the disease being evident most consistently. Although the precise mechanisms behind these improvements are not clear, two have been proposed: direct stimulation, where light reaches and acts directly on the distressed neurons, and remote stimulation, where light influences cells and/or molecules that provide systemic protection, thereby acting indirectly on distressed neurons. In relation to Parkinson's disease, given that the major zone of pathology lies deep in the brain and that light from an extracranial or external photobiomodulation device would not reach these vulnerable regions, stimulating the distressed neurons directly would require intracranial delivery of light using a device implanted close to the vulnerable regions. For indirect systemic stimulation, photobiomodulation could be applied to either the head and scalp, using a transcranial helmet, or to a more remote body part (e.g., abdomen, leg). In this review, we discuss the evidence for both the direct and indirect neuroprotective effects of photobiomodulation in Parkinson's disease and propose that both types of treatment modality, when working together using both intracranial and extracranial devices, provide the best therapeutic option.