Improvements in clinical signs of Parkinson's disease using photobiomodulation: a prospective proof-of-concept study

Interplay between the glymphatic system and neurotoxic proteins in Parkinson's disease and related disorders: current knowledge and future directions

Parkinson's disease is a common neurodegenerative disorder that is associated with abnormal aggregation and accumulation of neurotoxic proteins, including α-synuclein, amyloid-β, and tau, in addition to the impaired elimination of these neurotoxic protein. Atypical parkinsonism, which has the same clinical presentation and neuropathology as Parkinson's disease, expands the disease landscape within the continuum of Parkinson's disease and related disorders. The glymphatic system is a waste clearance system in the brain, which is responsible for eliminating the neurotoxic proteins from the interstitial fluid. Impairment of the glymphatic system has been proposed as a significant contributor to the development and progression of neurodegenerative disease, as it exacerbates the aggregation of neurotoxic proteins and deteriorates neuronal damage. Therefore, impairment of the glymphatic system could be considered as the final common pathway to neurodegeneration. Previous evidence has provided initial insights into the potential effect of the impaired glymphatic system on Parkinson's disease and related disorders; however, many unanswered questions remain. This review aims to provide a comprehensive summary of the growing literature on the glymphatic system in Parkinson's disease and related disorders. The focus of this review is on identifying the manifestations and mechanisms of interplay between the glymphatic system and neurotoxic proteins, including loss of polarization of aquaporin-4 in astrocytic endfeet, sleep and circadian rhythms, neuroinflammation, astrogliosis, and gliosis. This review further delves into the underlying pathophysiology of the glymphatic system in Parkinson's disease and related disorders, and the potential implications of targeting the glymphatic system as a novel and promising therapeutic strategy.

Photobiomodulation in the aging brain: a systematic review from animal models to humans

Aging is a multifactorial biological process that may be associated with cognitive decline. Photobiomodulation (PBM) is a non-pharmacological therapy that shows promising results in the treatment or prevention of age-related cognitive impairments. The aim of this review is to compile the preclinical and clinical evidence of the effect of PBM during aging in healthy and pathological conditions, including behavioral analysis and neuropsychological assessment, as well as brain-related modifications. 37 studies were identified by searching in PubMed, Scopus, and PsycInfo databases. Most studies use wavelengths of 800, 810, or 1064 nm but intensity and days of application were highly variable. In animal studies, it has been shown improvements in spatial memory, episodic-like memory, social memory, while different results have been found in recognition memory. Locomotor activity improved in Parkinson disease models. In healthy aged humans, it has been outlined improvements in working memory, cognitive inhibition, and lexical/semantic access, while general cognition was mainly enhanced on Alzheimer disease or mild cognitive impairment. Anxiety assessment is scarce and shows mixed results. As for brain activity, results outline promising effects of PBM in reversing metabolic alterations and enhancing mitochondrial function, as evidenced by restored CCO activity and ATP levels. Additionally, PBM demonstrated neuroprotective, anti-inflammatory, immunomodulatory and hemodynamic effects. The findings suggest that PBM holds promise as a non-invasive intervention for enhancing cognitive function, and in the modulation of brain functional reorganization. It is necessary to develop standardized protocols for the correct, beneficial, and homogeneous use of PBM.

Photobiomodulation in the infrared spectrum reverses the expansion of circulating natural killer cells and brain microglial activation in Sanfilippo mice

Sanfilippo syndrome results from inherited mutations in genes encoding lysosomal enzymes that catabolise heparan sulfate (HS), leading to early childhood-onset neurodegeneration. This study explores the therapeutic potential of photobiomodulation (PBM), which is neuroprotective and anti-inflammatory in several neurodegenerative diseases; it is also safe and PBM devices are readily available. We investigated the effects of 10-14 days transcranial PBM at 670 nm (2 or 4 J/cm2/day) or 904 nm (4 J/cm2/day) in young (3 weeks) and older (15 weeks) Sanfilippo or mucopolysaccharidosis type IIIA (MPS IIIA) mice. Although we found no PBM-induced changes in HS accumulation, astrocyte activation, CD206 (an anti-inflammatory marker) and BDNF expression in the brains of Sanfilippo mice, there was a near-normalisation of microglial activation in older MPS IIIA mice by 904 nm PBM, with decreased IBA1 expression and a return of their morphology towards a resting state. Immune cell immunophenotyping of peripheral blood with mass cytometry revealed increased pro-inflammatory signalling through pSTAT1 and p-p38 in NK and T cells in young but not older MPS IIIA mice (5 weeks of age), and expansion of NK, B and CD8+ T cells in older affected mice (17 weeks of age), highlighting the importance of innate and adaptive lymphocytes in Sanfilippo syndrome. Notably, 670 and 904 nm PBM both reversed the Sanfilippo-induced increase in pSTAT1 and p-p38 expression in multiple leukocyte populations in young mice, while 904 nm reversed the increase in NK cells in older mice. In conclusion, this is the first study to demonstrate the beneficial effects of PBM in Sanfilippo mice. The distinct reduction in microglial activation and NK cell pro-inflammatory signalling and number suggests PBM may alleviate neuroinflammation and lymphocyte activation, encouraging further investigation of PBM as a standalone, or complementary therapy in Sanfilippo syndrome.

Devices used for photobiomodulation of the brain-a comprehensive and systematic review

A systematic review was conducted to determine the trends in devices and parameters used for brain photobiomodulation (PBM). The revised studies included clinical and cadaveric approaches, in which light stimuli were applied to the head and/or neck. PubMed, Scopus, Web of Science and Google Scholar databases were used for the systematic search. A total of 2133 records were screened, from which 97 were included in this review. The parameters that were extracted and analysed in each article were the device design, actuation area, actuation site, wavelength, mode of operation, power density, energy density, power output, energy per session and treatment time. To organize device information, 11 categories of devices were defined, according to their characteristics. The most used category of devices was laser handpieces, which relate to 21% of all devices, while 28% of the devices were not described. Studies for cognitive function and physiological characterisation are the most well defined ones and with more tangible results. There is a lack of consistency when reporting PBM studies, with several articles under defining the stimulation protocol, and a wide variety of parameters used for the same health conditions (e.g., Alzheimer's or Parkinson's disease) resulting in positive outcomes. Standardization for the report of these studies is warranted, as well as sham-controlled comparative studies to determine which parameters have the greatest effect on PBM treatments for different neurological conditions.

Nonmedication Devices in Development for the Treatment of Alzheimer's Disease

 Huge investments continue to be made in treatment for Alzheimer's disease (AD), with more than one hundred drugs currently in development. Pharmacological approaches and drug development, particularly those targeting amyloid-β, have dominated the therapeutic landscape. At the same time, there is also a growing interest in devices for treating AD. This review aimed to identify and describe devices under development for AD treatment. In this review, we queried the devices that are in development for the treatment of AD. PubMed was searched through the end of 2021 using the terms "device," "therapeutics," and "Alzheimer's" for articles that report on devices to treat AD. Ten devices with 31 references were identified as actively being developed for the treatment of AD. Many of these devices are far along in development. Device-based therapies are often overlooked when evaluating treatment approaches to AD. However, many devices for treating AD are in development and some show promising results.

Dose response of transcranial near infrared light stimulation on brain functional connectivity and cognition in older adults-A randomized comparison

Photobiomodulation, also called low-level light therapy, has been reported in animal studies to have an effect on brain activity and cognition. However, studies in humans regarding its effect on cognition and brain functional connectivity, and the required dose threshold for achieving the same have been very limited. We compared the effects of different doses of photobiomodulation (PBM) on cognition and resting state brain functional connectivity in 25 cognitively normal adults aged 55-70 years. They were randomized to a single session of the sham group, "low-dose" and "high-dose" groups receiving NIR light with transcranial fluence of 26 and 52 J/cm2 respectively, and intranasal fluence of 9 and 18 J/cm2 respectively. There was a significant increase in resting state functional connectivity of the left superior frontal gyrus (SFG) with the left planum temporale (PT), p = 0.0016, and with the left inferior frontal gyrus, pars triangularis, p = 0.0235 in the "high-dose" group only compared to the "sham" group. There was also a significant improvement in visual search and processing speed (p = 0.012) in the "high-dose" group. Replication of these findings in an adequately powered randomized sham-controlled study in healthy older adults can pave the way for clinical application of NIRL as a therapeutic modality in patients with Alzheimer's disease.

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.

Photobiomodulation for Neurodegenerative Diseases: A Scoping Review

Neurodegenerative diseases involve the progressive dysfunction and loss of neurons in the central nervous system and thus present a significant challenge due to the absence of effective therapies for halting or reversing their progression. Based on the characteristics of neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD), which have prolonged incubation periods and protracted courses, exploring non-invasive physical therapy methods is essential for alleviating such diseases and ensuring that patients have an improved quality of life. Photobiomodulation (PBM) uses red and infrared light for therapeutic benefits and functions by stimulating, healing, regenerating, and protecting organizations at risk of injury, degradation, or death. Over the last two decades, PBM has gained widespread recognition as a non-invasive physical therapy method, showing efficacy in pain relief, anti-inflammatory responses, and tissue regeneration. Its application has expanded into the fields of neurology and psychiatry, where extensive research has been conducted. This paper presents a review and evaluation of studies investigating PBM in neurodegenerative diseases, with a specific emphasis on recent applications in AD and PD treatment for both animal and human subjects. Molecular mechanisms related to neuron damage and cognitive impairment are scrutinized, offering valuable insights into PBM's potential as a non-invasive therapeutic strategy.

Parkinson's Disease and Photobiomodulation: Potential for Treatment

Parkinson's disease is the second most common neurodegenerative disease and is increasing in incidence. The combination of motor and non-motor symptoms makes this a devastating disease for people with Parkinson's disease and their care givers. Parkinson's disease is characterised by mitochondrial dysfunction and neuronal death in the substantia nigra, a reduction in dopamine, accumulation of α-synuclein aggregates and neuroinflammation. The microbiome-gut-brain axis is also important in Parkinson's disease, involved in the spread of inflammation and aggregated α-synuclein. The mainstay of Parkinson's disease treatment is dopamine replacement therapy, which can reduce some of the motor signs. There is a need for additional treatment options to supplement available medications. Photobiomodulation (PBM) is a form of light therapy that has been shown to have multiple clinical benefits due to its enhancement of the mitochondrial electron transport chain and the subsequent increase in mitochondrial membrane potential and ATP production. PBM also modulates cellular signalling and has been shown to reduce inflammation. Clinically, PBM has been used for decades to improve wound healing, treat pain, reduce swelling and heal deep tissues. Pre-clinical experiments have indicated that PBM has the potential to improve the clinical signs of Parkinson's disease and to provide neuroprotection. This effect is seen whether the PBM is directed to the head of the animal or to other parts of the body (remotely). A small number of clinical trials has given weight to the possibility that using PBM can improve both motor and non-motor clinical signs and symptoms of Parkinson's disease and may potentially slow its progression.

Recent advances in light energy biotherapeutic strategies with photobiomodulation on central nervous system disorders

Transcranial photobiomodulation refers to irradiation of the brain through the skull using low-intensity red or near-infrared light, which is the most commonly studied method of light energy biotherapy for central nervous system disorders. The absorption of photons by specific chromophores within the cell elevates ATP synthesis, reduces oxidative stress damage, alleviates inflammation or mediates the activation of transcription factors and signaling mediators through secondary mediators, which in turn trigger downstream signaling pathways to cause a series of photobiological effects including upregulation of neurotrophic factors. Multiple mechanisms are simultaneously involved in the pathological process of central nervous system disorders. The pleiotropic treatment of transcranial photobiomodulation towards multiple targets plays a beneficial role in improving hemodynamics, neural repair and improving behaviors in central nervous system disorders such as ischemic stroke, traumatic brain injury, neurodegenerative diseases, epilepsy and depression. This review mainly introduces the mechanism and recent preclinical and clinical advances of transcranial photobiomodulation for central nervous system disorders, which will provide a reference for clinicians to understand and engage in related studies, and calls for more and larger studies to validate and develop a wider application of transcranial photobiomodulation in central nervous system.

Transcranial photobiomodulation for brain diseases: review of animal and human studies including mechanisms and emerging trends

The brain diseases account for 30% of all known diseases. Pharmacological treatment is hampered by the blood-brain barrier, limiting drug delivery to the central nervous system (CNS). Transcranial photobiomodulation (tPBM) is a promising technology for treating brain diseases, due to its effectiveness, non-invasiveness, and affordability. tPBM has been widely used in pre-clinical experiments and clinical trials for treating brain diseases, such as stroke and Alzheimer's disease. This review provides a comprehensive overview of tPBM. We summarize emerging trends and new discoveries in tPBM based on over one hundred references published in the past 20 years. We discuss the advantages and disadvantages of tPBM and highlight successful experimental and clinical protocols for treating various brain diseases. A better understanding of tPBM mechanisms, the development of guidelines for clinical practice, and the study of dose-dependent and personal effects hold great promise for progress in treating brain diseases.

A novel transcranial photobiomodulation device to address motor signs of Parkinson's disease: a parallel randomised feasibility study

BACKGROUND

Parkinson's disease is a progressive neurological disease with limited treatment options. Animal models and a proof-of-concept case series have suggested that photobiomodulation may be an effective adjunct treatment for the symptoms of Parkinson's disease. The aim was to determine the safety and feasibility of transcranial photobiomodulation (tPBM) to reduce the motor signs of Parkinson's disease.

METHODS

In this double-blind, randomised, sham-controlled feasibility trial, patients (aged 59-85 years) with idiopathic Parkinson's disease were treated with a tPBM helmet for 12 weeks (72 treatments with either active or sham therapy; stage 1). Treatment was delivered in the participants' homes, monitored by internet video conferencing (Zoom). Stage 1 was followed by 12 weeks of no treatment for those on active therapy (active-to-no-treatment group), and 12 weeks of active treatment for those on sham (sham-to-active group), for participants who chose to continue (stage 2). The active helmet device delivered red and infrared light to the head for 24 min, 6 days per week. The primary endpoints were safety and motor signs, as assessed by a modified Movement Disorders Society revision of the Unified Parkinson's Disease Rating Scale Part III (MDS-UPDRS-III)-motor scale. This trial is registered with ANZCTR, ACTRN 12621001722886.

FINDINGS

Between Dec 6, 2021, and Aug 12, 2022, 20 participants were randomly allocated to each of the two groups (10 females plus 10 males per group). All participants in the active group and 18 in the sham group completed 12 weeks of treatment. 14 participants in the sham group chose to continue to active treatment and 12 completed the full 12 weeks of active treatment. Treatment was well tolerated and feasible to deliver, with only minor, temporary adverse events. Of the nine suspected adverse events that were identified, two minor reactions may have been attributable to the device in the sham-to-active group during the active treatment weeks of the trial. One participant experienced temporary leg weakness. A second participant reported decreased fine motor function in the right hand. Both participants continued the trial. The mean modified MDS-UPDRS-III scores for the sham-to-active group at baseline, after 12 weeks of sham treatment, and after 12 weeks of active treatment were 26.8 (sd 14.6), 20.4 (sd 12.8), and 12.2 (sd 8.9), respectively, and for the active-to-no-treatment group these values were 21.3 (sd 9.4), 16.5 (sd 9.4), and 15.3 (sd 10.8), respectively. There was no significant difference between groups at any assessment point. The mean difference between groups at baseline was 5.5 (95% confidence interval (CI) -2.4 to 13.4), after stage 1 was 3.9 (95% CI -3.5 to 11.3 and after stage 2 was -3.1 (95% CI 2.7 to -10.6).

INTERPRETATION

Our findings add to the evidence base to suggest that tPBM is a safe, tolerable, and feasible non-pharmaceutical adjunct therapy for Parkinson's disease. While future work is needed our results lay the foundations for an adequately powered randomised placebo-controlled clinical trial.

FUNDING

SYMBYX Pty Ltd.

Use of 31 P magnetisation transfer magnetic resonance spectroscopy to measure ATP changes after 670 nm transcranial photobiomodulation in older adults

Mitochondrial function declines with age, and many pathological processes in neurodegenerative diseases stem from this dysfunction when mitochondria fail to produce the necessary energy required. Photobiomodulation (PBM), long-wavelength light therapy, has been shown to rescue mitochondrial function in animal models and improve human health, but clinical uptake is limited due to uncertainty around efficacy and the mechanisms responsible. Using 31 P magnetisation transfer magnetic resonance spectroscopy (MT-MRS) we quantify, for the first time, the effects of 670 nm PBM treatment on healthy ageing human brains. We find a significant increase in the rate of ATP synthase flux in the brain after PBM in a cohort of older adults. Our study provides initial evidence of PBM therapeutic efficacy for improving mitochondrial function and restoring ATP flux with age, but recognises that wider studies are now required to confirm any resultant cognitive benefits.

Prefrontal photobiomodulation produces beneficial mitochondrial and oxygenation effects in older adults with bipolar disorder

There is growing evidence of mitochondrial dysfunction and prefrontal cortex (PFC) hypometabolism in bipolar disorder (BD). Older adults with BD exhibit greater decline in PFC-related neurocognitive functions than is expected for age-matched controls, and clinical interventions intended for mood stabilization are not targeted to prevent or ameliorate mitochondrial deficits and neurocognitive decline in this population. Transcranial infrared laser stimulation (TILS) is a non-invasive form of photobiomodulation, in which photons delivered to the PFC photo-oxidize the mitochondrial respiratory enzyme, cytochrome-c-oxidase (CCO), a major intracellular photon acceptor in photobiomodulation. TILS at 1064-nm can significantly upregulate oxidized CCO concentrations to promote differential levels of oxygenated vs. deoxygenated hemoglobin (HbD), an index of cerebral oxygenation. The objective of this controlled study was to use non-invasive broadband near-infrared spectroscopy to assess if TILS to bilateral PFC (Brodmann area 10) produces beneficial effects on mitochondrial oxidative energy metabolism (oxidized CCO) and cerebral oxygenation (HbD) in older (≥50 years old) euthymic adults with BD (N = 15). As compared to sham, TILS to the PFC in adults with BD increased oxidized CCO both during and after TILS, and increased HbD concentrations after TILS. By significantly increasing oxidized CCO and HbD concentrations above sham levels, TILS has the potential ability to stabilize mitochondrial oxidative energy production and prevent oxidative damage in the PFC of adults with BD. In conclusion, TILS was both safe and effective in enhancing metabolic function and subsequent hemodynamic responses in the PFC, which might help alleviate the accelerated neurocognitive decline and dysfunctional mitochondria present in BD.

Temporal and spectral analyses of EEG microstate reveals neural effects of transcranial photobiomodulation on the resting brain

Introduction

The quantification of electroencephalography (EEG) microstates is an effective method for analyzing synchronous neural firing and assessing the temporal dynamics of the resting state of the human brain. Transcranial photobiomodulation (tPBM) is a safe and effective modality to improve human cognition. However, it is unclear how prefrontal tPBM neuromodulates EEG microstates both temporally and spectrally.

Methods

64-channel EEG was recorded from 45 healthy subjects in both 8-min active and sham tPBM sessions, using a 1064-nm laser applied to the right forehead of the subjects. After EEG data preprocessing, time-domain EEG microstate analysis was performed to obtain four microstate classes for both tPBM and sham sessions throughout the pre-, during-, and post-stimulation periods, followed by extraction of the respective microstate parameters. Moreover, frequency-domain analysis was performed by combining multivariate empirical mode decomposition with the Hilbert-Huang transform.

Results

Statistical analyses revealed that tPBM resulted in (1) a significant increase in the occurrence of microstates A and D and a significant decrease in the contribution of microstate C, (2) a substantial increase in the transition probabilities between microstates A and D, and (3) a substantial increase in the alpha power of microstate D.

Discussion

These findings confirm the neurophysiological effects of tPBM on EEG microstates of the resting brain, particularly in class D, which represents brain activation across the frontal and parietal regions. This study helps to better understand tPBM-induced dynamic alterations in EEG microstates that may be linked to the tPBM mechanism of action for the enhancement of human cognition.

Exploring the Therapeutic Effects of Multifunctional N-Salicylic Acid Tryptamine Derivative against Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide. Neuroinflammation and oxidative stress play an important role in the whole course of PD, which have been the focus of PD drug development. In our previous research, a series of N-salicylic acid tryptamine derivatives were synthesized, and the biological evaluation showed that the compound LZWL02003 has good anti-neuroinflammatory activity and displayed great therapeutic potency for neurodegenerative disease models. In this work, the neuroprotective efficiency of LZWL02003 against PD in vitro and in vivo has been explored. It was found that LZWL02003 could protect human neuron cells SH-SY5Y from MPP+-induced neuronal damage by inhibiting ROS generation, mitochondrial dysfunction, and cellular apoptosis. Moreover, LZWL02003 could improve cognition, memory, learning, and athletic ability in a rotenone-induced PD rat model. In general, our study has demonstrated that LZWL02003 has good activity against PD in in vitro and in vivo experiments, which can potentially be developed into a therapeutic candidate for PD.

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.

The Effects and Mechanisms of PBM Therapy in Accelerating Orthodontic Tooth Movement

Malocclusion is one of the three major diseases, the incidence of which could reach 56% of the imperiled oral and systemic health in the world today. Orthodontics is still the primary method to solve the problem. However, it is clear that many orthodontic complications are associated with courses of long-term therapy. Photobiomodulation (PBM) therapy could be used as a popular way to shorten the course of orthodontic treatment by nearly 26% to 40%. In this review, the efficacy in cells and animals, mechanisms, relevant cytokines and signaling, clinical trials and applications, and the future developments of PBM therapy in orthodontics were evaluated to demonstrate its validity. Simultaneously, based on orthodontic mechanisms and present findings, the mechanisms of acceleration of orthodontic tooth movement (OTM) caused by PBM therapy were explored in relation to four aspects, including blood vessels, inflammatory response, collagen and fibers, and mineralized tissues. Also, the cooperative effects and clinical translation of PBM therapy in orthodontics have been explored in a growing numbers of studies. Up to now, PBM therapy has been gaining popularity for its non-invasive nature, easy operation, and painless procedures. However, the validity and exact mechanism of PBM therapy as an adjuvant treatment in orthodontics have not been fully elucidated. Therefore, this review summarizes the efficacy of PBM therapy on the acceleration of OTM comprehensively from various aspects and was designed to provide an evidence-based platform for the research and development of light-related orthodontic tooth movement acceleration devices.

Neurodegenerative and Neurodevelopmental Diseases and the Gut-Brain Axis: The Potential of Therapeutic Targeting of the Microbiome

The human gut microbiome contains the largest number of bacteria in the body and has the potential to greatly influence metabolism, not only locally but also systemically. There is an established link between a healthy, balanced, and diverse microbiome and overall health. When the gut microbiome becomes unbalanced (dysbiosis) through dietary changes, medication use, lifestyle choices, environmental factors, and ageing, this has a profound effect on our health and is linked to many diseases, including lifestyle diseases, metabolic diseases, inflammatory diseases, and neurological diseases. While this link in humans is largely an association of dysbiosis with disease, in animal models, a causative link can be demonstrated. The link between the gut and the brain is particularly important in maintaining brain health, with a strong association between dysbiosis in the gut and neurodegenerative and neurodevelopmental diseases. This link suggests not only that the gut microbiota composition can be used to make an early diagnosis of neurodegenerative and neurodevelopmental diseases but also that modifying the gut microbiome to influence the microbiome-gut-brain axis might present a therapeutic target for diseases that have proved intractable, with the aim of altering the trajectory of neurodegenerative and neurodevelopmental diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, autism spectrum disorder, and attention-deficit hyperactivity disorder, among others. There is also a microbiome-gut-brain link to other potentially reversible neurological diseases, such as migraine, post-operative cognitive dysfunction, and long COVID, which might be considered models of therapy for neurodegenerative disease. The role of traditional methods in altering the microbiome, as well as newer, more novel treatments such as faecal microbiome transplants and photobiomodulation, are discussed.

A Holistic Perspective on How Photobiomodulation May Influence Fatigue, Pain, and Depression in Inflammatory Bowel Disease: Beyond Molecular Mechanisms

BACKGROUND

Numerous mechanisms, mostly molecular, have been tested and proposed for photobiomodulation. Photobiomodulation is finding a niche in the treatment of conditions that have no gold-standard treatment or only partially effective pharmacological treatment. Many chronic conditions are characterised by symptoms for which there is no cure or control and for which pharmaceuticals may add to the disease burden through side effects. To add quality to life, alternate methods of symptom management need to be identified.

OBJECTIVE

To demonstrate how photobiomodulation, through its numerous mechanisms, may offer an adjunctive therapy in inflammatory bowel disease. Rather than considering only molecular mechanisms, we take an overarching biopsychosocial approach to propose how existing evidence gleaned from other studies may underpin a treatment strategy of potential benefit to people with Crohn's disease and ulcerative colitis.

MAIN FINDINGS

In this paper, the authors have proposed the perspective that photobiomodulation, through an integrated effect on the neuroimmune and microbiome-gut-brain axis, has the potential to be effective in managing the fatigue, pain, and depressive symptoms of people with inflammatory bowel disease.

Remote photobiomodulation targeted at the abdomen or legs provides effective neuroprotection against parkinsonian MPTP insult

Photobiomodulation (PBM)-the irradiation of tissue with low-intensity light-mitigates neuropathology in rodent models of Parkinson's disease (PD) when targeted at the head ('transcranial PBM'). In humans, however, attenuation of light energy by the scalp and skull necessitates a different approach. We have reported that targeting PBM at the body also protects the brain by a mechanism that spreads from the irradiated tissue ('remote PBM'), although the optimal peripheral tissue target for remote PBM is currently unclear. This study compared the neuroprotective efficacy of remote PBM targeting the abdomen or leg with transcranial PBM, in mouse and non-human primate models of PD. In a pilot study, the neurotoxin MPTP was used to induce PD in non-human primates; PBM (670 nm, 50 mW/cm2 , 6 min/day) of the abdomen (n = 1) was associated with fewer clinical signs and more surviving midbrain dopaminergic cells relative to MPTP-injected non-human primates not treated with PBM. Validation studies in MPTP-injected mice (n = 10 per group) revealed a significant rescue of midbrain dopaminergic cells in mice receiving PBM to the abdomen (~80%, p < .0001) or legs (~80%, p < .0001), with comparable rescue of axonal terminals in the striatum. Strikingly, this degree of neuroprotection was at least as, if not more, pronounced than that achieved with transcranial PBM. These findings confirm that remote PBM provides neuroprotection against MPTP-induced destruction of the key circuitry underlying PD, with both the abdomen and legs serving as viable remote targets. This should provide the impetus for a comprehensive investigation of remote PBM-induced neuroprotection in other models of PD and, ultimately, human patients.

A Randomized Placebo-Controlled Study of a Transcranial Photobiomodulation Helmet in Parkinson's Disease: Post-Hoc Analysis of Motor Outcomes

Emerging evidence is increasingly supporting the use of transcranial photobiomodulation (tPBM) to improve symptoms of neurodegenerative diseases, including Parkinson's disease (PD). The objective of this study was to analyse the safety and efficacy of tPBM for PD motor symptoms. The study was a triple blind, randomized placebo-controlled trial with 40 idiopathic PD patients receiving either active tPBM (635 nm plus 810 nm LEDs) or sham tPBM for 24 min per day (56.88J), six days per week, for 12 weeks. The primary outcome measures were treatment safety and a 37-item MDS-UPDRS-III (motor domain) assessed at baseline and 12 weeks. Individual MDS-UPDRS-III items were clustered into sub-score domains (facial, upper-limb, lower-limb, gait, and tremor). The treatment produced no safety concerns or adverse events, apart from occasional temporary and minor dizziness. There was no significant difference in total MDS-UPDRS-III scores between groups, presumably due to the placebo effect. Additional analyses demonstrated that facial and lower-limb sub-scores significantly improved with active treatment, while gait and lower-limb sub-scores significantly improved with sham treatment. Approximately 70% of participants responded to active treatment (≥5 decrease in MDS-UPDRS-III score) and improved in all sub-scores, while sham responders improved in lower-limb sub-scores only. tPBM appears to be a safe treatment and improved several PD motor symptoms in patients that responded to treatment. tPBM is proving to be increasingly attractive as a possible non-pharmaceutical adjunct therapy.

A systematic review of the effects of transcranial photobiomodulation on brain activity in humans

In recent years, transcranial photobiomodulation (tPBM) has been developing as a promising method to protect and repair brain tissues against damages. The aim of our systematic review is to examine the results available in the literature concerning the efficacy of tPBM in changing brain activity in humans, either in healthy individuals, or in patients with neurological diseases. Four databases were screened for references containing terms encompassing photobiomodulation, brain activity, brain imaging, and human. We also analysed the quality of the included studies using validated tools. Results in healthy subjects showed that even after a single session, tPBM can be effective in influencing brain activity. In particular, the different transcranial approaches - using a focal stimulation or helmet for global brain stimulation - seemed to act at both the vascular level by increasing regional cerebral blood flow (rCBF) and at the neural level by changing the activity of the neurons. In addition, studies also showed that even a focal stimulation was sufficient to induce a global change in functional connectivity across brain networks. Results in patients with neurological disease were sparser; nevertheless, they indicated that tPBM could improve rCBF and functional connectivity in several regions. Our systematic review also highlighted the heterogeneity in the methods and results generated, together with the need for more randomised controlled trials in patients with neurological diseases. In summary, tPBM could be a promising method to act on brain function, but more consistency is needed in order appreciate fully the underlying mechanisms and the precise outcomes.

Advances in photobiomodulation for cognitive improvement by near-infrared derived multiple strategies

Cognitive function is an important ability of the brain, but cognitive dysfunction can easily develop once the brain is injured in various neuropathological conditions or diseases. Photobiomodulation therapy is a type of noninvasive physical therapy that is gradually emerging in the field of neuroscience. Transcranial photobiomodulation has been commonly used to regulate neural activity in the superficial cortex. To stimulate deeper brain activity, advanced photobiomodulation techniques in conjunction with photosensitive nanoparticles have been developed. This review addresses the mechanisms of photobiomodulation on neurons and neural networks and discusses the advantages, disadvantages and potential applications of photobiomodulation alone or in combination with photosensitive nanoparticles. Photobiomodulation and its associated strategies may provide new breakthrough treatments for cognitive improvement.

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.

Photophysical Mechanisms of Photobiomodulation Therapy as Precision Medicine

Despite a significant focus on the photochemical and photoelectrical mechanisms underlying photobiomodulation (PBM), its complex functions are yet to be fully elucidated. To date, there has been limited attention to the photophysical aspects of PBM. One effect of photobiomodulation relates to the non-visual phototransduction pathway, which involves mechanotransduction and modulation to cytoskeletal structures, biophotonic signaling, and micro-oscillatory cellular interactions. Herein, we propose a number of mechanisms of PBM that do not depend on cytochrome c oxidase. These include the photophysical aspects of PBM and the interactions with biophotons and mechanotransductive processes. These hypotheses are contingent on the effect of light on ion channels and the cytoskeleton, the production of biophotons, and the properties of light and biological molecules. Specifically, the processes we review are supported by the resonant recognition model (RRM). This previous research demonstrated that protein micro-oscillations act as a signature of their function that can be activated by resonant wavelengths of light. We extend this work by exploring the local oscillatory interactions of proteins and light because they may affect global body circuits and could explain the observed effect of PBM on neuro-cortical electroencephalogram (EEG) oscillations. In particular, since dysrhythmic gamma oscillations are associated with neurodegenerative diseases and pain syndromes, including migraine with aura and fibromyalgia, we suggest that transcranial PBM should target diseases where patients are affected by impaired neural oscillations and aberrant brain wave patterns. This review also highlights examples of disorders potentially treatable with precise wavelengths of light by mimicking protein activity in other tissues, such as the liver, with, for example, Crigler-Najjar syndrome and conditions involving the dysregulation of the cytoskeleton. PBM as a novel therapeutic modality may thus behave as "precision medicine" for the treatment of various neurological diseases and other morbidities. The perspectives presented herein offer a new understanding of the photophysical effects of PBM, which is important when considering the relevance of PBM therapy (PBMt) in clinical applications, including the treatment of diseases and the optimization of health outcomes and performance.

Can transcranial photobiomodulation improve cognitive function? A systematic review of human studies

BACKGROUND

Transcranial photobiomodulation (tPBM) has been studied for over a decade as a possible cognitive intervention.

OBJECTIVE

To evaluate the effect of tPBM for enhancing human cognitive function in healthy adults and remediating impaired cognitive function in adults with cognitive disorders.

METHODS

A systematic literature search from three electronic databases (PubMed, Scopus, Web of Science) was conducted from 1987 to May 2022. The cognitive function being evaluated included learning and memory, attention, executive function, language, and global cognitive function.

RESULTS

Of the 35 studies identified, 29 (82.9 %) studies reported positive improvement in cognitive functions after tPBM. All nine studies on participants with subjective memory complaints, mild cognitive impairment, and dementia, showed positive outcomes. Seven (87.5 %) studies on traumatic brain injury (TBI) patients also showed positive results. A series of clinical trials on stroke patients showed positive trends on improved neurological deficit at first, but was prematurely terminated later at phase III due to the lack of statistical significance. One of the most common protocols for clinical populations employed devices delivering near-infrared light (810 nm), the irradiance of 20-25 mW/cm², and fluence of 1-10 J/cm². While this was common, the reviewed protocols also included other wavelengths of light ranging from visible, red (630-635 nm) to invisible near-infrared maximum wavelengths of 1060-1068 nm.

CONCLUSIONS

tPBM seems to improve cognitive function. However, only half of the reviewed clinical trials were randomized control trials, further investigation is warranted.

The effectiveness of photobiomodulation therapy in modulation the gut microbiome dysbiosis related diseases

Maintaining a healthy balance between commensal, and pathogenic bacteria within the gut microbiota is crucial for ensuring the overall health, and well-being of the host. In fact, by affecting innate, and adaptive immune responses, the gut microbiome plays a key role in maintaining intestinal homeostasis and barrier integrity. Dysbiosis is the loss of beneficial microorganisms and the growth of potentially hazardous microorganisms in a microbial community, which has been linked to numerous diseases. As the primary inducer of circadian rhythm, light can influence the human intestinal microbiome. Photobiomodulation therapy (PBMT), which is the use of red (630-700 nm), and near-infrared light (700 and 1200 nm), can stimulate healing, relieve pain, and reduce inflammation, and affect the circadian rhythm and gut microbiome beneficially. Our focus in this paper is on the effects of PBMT on gut microbiota, to provide an overview of how it can help control gut microbiota dysbiosis-related disorders.

Photobiomodulation and nitric oxide signaling

Nitric oxide (NO) is a well-known gaseous mediator that maintains vascular homeostasis. Extensive evidence supports that a hallmark of endothelial dysfunction, which leads to cardiovascular diseases, is endothelial NO deficiency. Thus, restoring endothelial NO represents a promising approach to treating cardiovascular complications. Despite many therapeutic agents having been shown to augment NO bioavailability under various pathological conditions, success in resulting clinical trials has remained elusive. There is solid evidence of diverse beneficial effects of the treatment with low-power near-infrared (NIR) light, defined as photobiomodulation (PBM). Although the precise mechanisms of action of PBM are still elusive, recent studies consistently report that PBM improves endothelial dysfunction via increasing bioavailable NO in a dose-dependent manner and open a feasible path to the use of PBM for treating cardiovascular diseases via augmenting NO bioavailability. In particular, the use of NIR light in the NIR-II window (1000-1700 nm) for PBM, which has reduced scattering and minimal tissue absorption with the largest penetration depth, is emerging as a promising therapy. In this review, we update recent findings on PBM and NO.

The distinguishing electrical properties of cancer cells

In recent decades, medical research has been primarily focused on the inherited aspect of cancers, despite the reality that only 5-10% of tumours discovered are derived from genetic causes. Cancer is a broad term, and therefore it is inaccurate to address it as a purely genetic disease. Understanding cancer cells' behaviour is the first step in countering them. Behind the scenes, there is a complicated network of environmental factors, DNA errors, metabolic shifts, and electrostatic alterations that build over time and lead to the illness's development. This latter aspect has been analyzed in previous studies, but how the different electrical changes integrate and affect each other is rarely examined. Every cell in the human body possesses electrical properties that are essential for proper behaviour both within and outside of the cell itself. It is not yet clear whether these changes correlate with cell mutation in cancer cells, or only with their subsequent development. Either way, these aspects merit further investigation, especially with regards to their causes and consequences. Trying to block changes at various levels of occurrence or assisting in their prevention could be the key to stopping cells from becoming cancerous. Therefore, a comprehensive understanding of the current knowledge regarding the electrical landscape of cells is much needed. We review four essential electrical characteristics of cells, providing a deep understanding of the electrostatic changes in cancer cells compared to their normal counterparts. In particular, we provide an overview of intracellular and extracellular pH modifications, differences in ionic concentrations in the cytoplasm, transmembrane potential variations, and changes within mitochondria. New therapies targeting or exploiting the electrical properties of cells are developed and tested every year, such as pH-dependent carriers and tumour-treating fields. A brief section regarding the state-of-the-art of these therapies can be found at the end of this review. Finally, we highlight how these alterations integrate and potentially yield indications of cells' malignancy or metastatic index.

Defining and evaluating the Hawthorne effect in primary care, a systematic review and meta-analysis

In 2015, we conducted a randomized controlled trial (RCT) in primary care to evaluate if posters and pamphlets dispensed in general practice waiting rooms enhanced vaccination uptake for seasonal influenza. Unexpectedly, vaccination uptake rose in both arms of the RCT whereas public health data indicated a decrease. We wondered if the design of the trial had led to a Hawthorne effect (HE). Searching the literature, we noticed that the definition of the HE was unclear if stated. Our objectives were to refine a definition of the HE for primary care, to evaluate its size, and to draw consequences for primary care research. We designed a Preferred Reporting Items for Systematic reviews and Meta-Analyses review and meta-analysis between January 2012 and March 2022. We included original reports defining the HE and reports measuring it without setting limitations. Definitions of the HE were collected and summarized. Main published outcomes were extracted and measures were analyzed to evaluate odds ratios (ORs) in primary care. The search led to 180 records, reduced on review to 74 for definition and 15 for quantification. Our definition of HE is "an aware or unconscious complex behavior change in a study environment, related to the complex interaction of four biases affecting the study subjects and investigators: selection bias, commitment and congruence bias, conformity and social desirability bias and observation and measurement bias." Its size varies in time and depends on the education and professional position of the investigators and subjects, the study environment, and the outcome. There are overlap areas between the HE, placebo effect, and regression to the mean. In binary outcomes, the overall OR of the HE computed in primary care was 1.41 (95% CI: [1.13; 1.75]; I 2 = 97%), but the significance of the HE disappears in well-designed studies. We conclude that the HE results from a complex system of interacting phenomena and appears to some degree in all experimental research, but its size can considerably be reduced by refining study designs.

Photobiomodulation for modulation of neuropathic pain and improvement of scar tissue

BACKGROUND

This case-report explores the effects of photobiomodulation therapy (PBMT) on the healing of scar tissue. The patient was a 32-year old female two years post cholecystectomy resulting in a 15 cm linear scar that was causing severe pain.

METHODS

Treatment was initiated using the BIOFLEX® therapist device which consists of LED arrays and laser probes of a specific wavelength, power and frequency applied directly on the skin overlying the scar. The frequency and duration of treatment was every other day for six weeks in a clinic setting, followed by three times a week for two months at home. Then the patient continued to use the BIOFLEX® therapist home device on an as-needed basis.

FINDINGS

The final result of this patient's treatment was significant flattening and decreased redness of her scar. Her self-reported pain decreased to a 6/10. At the one year follow up, the patient reported that she stopped taking her opioids, antidepressant and sleeping pills and that her pain decreased to a 4/10. At the last review her pain score was 1/10; and she had returned to work and took Tylenol (acetaminophen) occasionally for breakthrough pain.

CONCLUSIONS

We attribute the patient's improvement in scar appearance and pain symptoms to PBMT. Since pain is often associated with depressed mood and sleep disturbances, it cannot be determined whether PBMT was the direct or indirect cause of this patient's improved mood. For future studies, we propose the use of control subjects with similar scars treated with sham treatment compared to those who will receive the PBMT and observed for the same duration of time and compare the overall results.

LAY SUMMARY

Dermatological applications, especially wound healing; are accepted indications for photobiomodulation therapy (PBMT). The expansion into other clinical applications, particularly neurological ones show potential benefit. We present a case of a patient with a hypertrophic scar associated with severe neuropathic pain and concurrent depression, all of which improved directly or indirectly with PBMT. Although the original focus of treatment was dermatological the improvement in pain plus the discontinuation of therapy (opioids, antidepressants and benzodiazepines) were considered to be due to the PBMT.

Protocol for randomized controlled trial to evaluate the safety and feasibility of a novel helmet to deliver transcranial light emitting diodes photobiomodulation therapy to patients with Parkinson’s disease

Introduction

Parkinson’s disease (PD) is the second most common, progressive, and debilitating neurodegenerative disease associated with aging and the most common movement disorder. Photobiomodulation (PBM), the use of non-thermal light for therapeutic purposes using laser or light emitting diodes (LED) is an emerging non-invasive treatment for a diverse range of neurological conditions. The main objectives of this clinical trial are to investigate the feasibility, safety, tolerability, and efficacy of a novel transcranial LED helmet device (the “PDNeuro”) in the alleviation of symptoms of PD.

Methods and analysis

This is a 24-week, two-arm, triple-blinded randomized placebo-controlled clinical trial of a novel transcranial “PDNeuro” LED Helmet, comparing an active helmet to a sham helmet device. In a survey, 40 PD participants with Hoehn and Yahr Stage I–III during ON periods will be enrolled and randomly assigned into two groups. Both groups will be monitored weekly for the safety and tolerability of the “PDNeuro” LED Helmet. Clinical signs and symptoms assessed will include mobility, fine motor skills and cognition, with data collected at baseline, 12 weeks, and 24 weeks. Assessment tools include the TUG, UPDRS, and MoCA all validated for use in PD patients. Patient’s adherence to the device usage and participant drop out will be monitored weekly. At 12 weeks both placebo and treatment groups will crossover and placebo participants offered the treatment. The main indicator for clinical efficacy of the “PDneuro” Helmet is evidence of sustained improvements in motor and non-motor symptoms obtained from participant self-reported changes, carer reporting of changes and objective reassessment by the investigators. The outcomes will assist in a future larger randomized trial design.

Clinical Trial Registration

[https://www.anzctr.org.au], identifier [12621001722886].

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.

Therapeutic Potential of Photobiomodulation for Chronic Kidney Disease

Chronic kidney disease (CKD) is a growing global public health problem. The implementation of evidence-based clinical practices only defers the development of kidney failure. Death, transplantation, or dialysis are the consequences of kidney failure, resulting in a significant burden on the health system. Hence, innovative therapeutic strategies are urgently needed due to the limitations of current interventions. Photobiomodulation (PBM), a form of non-thermal light therapy, effectively mitigates mitochondrial dysfunction, reactive oxidative stress, inflammation, and gut microbiota dysbiosis, all of which are inherent in CKD. Preliminary studies suggest the benefits of PBM in multiple diseases, including CKD. Hence, this review will provide a concise summary of the underlying action mechanisms of PBM and its potential therapeutic effects on CKD. Based on the findings, PBM may represent a novel, non-invasive and non-pharmacological therapy for CKD, although more studies are necessary before PBM can be widely recommended.

Photobiomodulation Therapy and Cell Therapy Improved Parkinson's Diseases by Neuro-regeneration and Tremor Inhibition

Introduction: Parkinson's disease (PD) is a progressive and severe neurodegenerative disorder of the central nervous system (CNS). The most prominent features of this disease are cell reduction in the substantia nigra and accumulation of α-synuclein, especially in the brainstem, spinal cord, and cortical areas. In addition to drug-based treatment, other therapies such as surgery, cell therapy, and laser therapy can be considered. In this study, articles on cell therapy and laser therapy for PD have been collected to evaluate the improvement of motor function, cell differentiation, and dopaminergic cell proliferation. Methods: Articles were collected from four electronic databases: PubMed, Scopus, Google Scholar, and Web of Science from 2010 to 2022. The keywords were "photobiomodulation", "low-level light therapy", "Low-level laser therapy", "near-infrared light", "Parkinson's disease", "Parkinsonism", and "stem cell therapy". About 100 related articles were included in the study. Results: The results of the studies showed that cell therapy and laser therapy are useful in the treatment of PD, and despite their limitations, they can be useful in improving PD. Conclusion: Concomitant use of cell therapy and photobiomodulation therapy can improve the symptoms of PD.

Therapeutic Devices for Motor Symptoms in Parkinson’s Disease: Current Progress and a Systematic Review of Recent Randomized Controlled Trials

Background

Pharmacotherapy is the first-line treatment option for Parkinson’s disease, and levodopa is considered the most effective drug for managing motor symptoms. However, side effects such as motor fluctuation and dyskinesia have been associated with levodopa treatment. For these conditions, alternative therapies, including invasive and non-invasive medical devices, may be helpful. This review sheds light on current progress in the development of devices to alleviate motor symptoms in Parkinson’s disease.

Methods

We first conducted a narrative literature review to obtain an overview of current invasive and non-invasive medical devices and thereafter performed a systematic review of recent randomized controlled trials (RCTs) of these devices.

Results

Our review revealed different characteristics of each device and their effectiveness for motor symptoms. Although invasive medical devices are usually highly effective, surgical procedures can be burdensome for patients and have serious side effects. In contrast, non-pharmacological/non-surgical devices have fewer complications. RCTs of non-invasive devices, especially non-invasive brain stimulation and mechanical peripheral stimulation devices, have proven effectiveness on motor symptoms. Nearly no non-invasive devices have yet received Food and Drug Administration certification or a CE mark.

Conclusion

Invasive and non-invasive medical devices have unique characteristics, and several RCTs have been conducted for each device. Invasive devices are more effective, while non-invasive devices are less effective and have lower hurdles and risks. It is important to understand the characteristics of each device and capitalize on these.

Remote Photobiomodulation Treatment for the Clinical Signs of Parkinson's Disease: A Case Series Conducted During COVID-19

Objective: To assess whether remote application of photobiomodulation (PBM) is effective in reducing clinical signs of Parkinson's disease (PD). Background: PD is a progressive neurodegenerative disease for which there is no cure and few treatment options. There is a strong link between the microbiome-gut-brain axis and PD. PBM in animal models can reduce the signs of PD and protect the neurons from damage when applied directly to the head or to remote parts of the body. In a clinical study, PBM has been shown to improve clinical signs of PD for up to 1 year. Methods: Seven participants were treated with PBM to the abdomen and neck three times per week for 12 weeks. Participants were assessed for mobility, balance, cognition, fine motor skill, and sense of smell on enrolment, after 12 weeks of treatment in a clinic and after 33 weeks of home treatment. Results: A number of clinical signs of PD were shown to be improved by remote PBM treatment, including mobility, cognition, dynamic balance, spiral test, and sense of smell. Improvements were individual to the participant. Some improvements were lost for certain participants during at-home treatment, which coincided with a number of enforced coronavirus disease 2019 (COVID-19) pandemic lockdown periods. Conclusions: Remote application of PBM was shown to be an effective treatment for a number of clinical signs of PD, with some being maintained for 45 weeks, despite lockdown restrictions. Improvements in clinical signs were similar to those seen with the application of remote plus transcranial PBM treatment in a previous study. Clinical Trial Registration number: U1111-1205-2035.

A Perspective on the Potential of Opsins as an Integral Mechanism of Photobiomodulation: It's Not Just the Eyes

Objective: To investigate the potential relationship between opsins and photobiomodulation. Background: Opsins and other photoreceptors occur in all phyla and are important in light-activated signaling and organism homeostasis. In addition to the visual opsin systems of the retina (OPN1 and OPN2), there are several non-visual opsins found throughout the body tissues, including encephalopsin/panopsin (OPN3), melanopsin (OPN4), and neuropsin (OPN5), as well as other structures that have light-sensitive properties, such as enzymes, ion channels, particularly those located in cell membranes, lysosomes, and neuronal structures such as the nodes of Ranvier. The influence of these structures on exposure to light, including self-generated light within the body (autofluorescence), on circadian oscillators, and circadian and ultradian rhythms have become increasingly reported. The visual and non-visual phototransduction cascade originating from opsins and other structures has potential significant mechanistic effects on tissues and health. Methods: A PubMed and Google Scholar search was made using the search terms "photobiomodulation", "light", "neuron", "opsins", "neuropsin", "melanopsin", "encephalopsin", "rhodopsin", and "chromophore". Results: This review was examined the influence of neuropsin (also known as kallikrein 8), encephalopsin, and melanopsin specifically on ion channel function, and more broadly on the central and peripheral nervous systems. The relationship between opsins 3, 4, and 5 and photobiomodulation mechanisms was evaluated, along with a proposed role of photobiomodulation through opsins and light-sensitive organelles as potential alleviators of symptoms and accelerators of beneficial regenerative processes. The potential clinical implications of this in musculoskeletal conditions, wounds, and in the symptomatic management of neurodegenerative disease was also examined. Conclusions: Systematic research into the pleotropic therapeutic role of photobiomodulation, mediated through its action on opsins and other light-sensitive organelles may assist in the future execution of safe, low-risk precision medicine for a variety of chronic and complex disease conditions, and for health maintenance in aging.

Microbiome Changes in Humans with Parkinson's Disease after Photobiomodulation Therapy: A Retrospective Study

There is a paucity of information on the effect of photobiomodulation therapy on gut microbiome composition. Parkinson’s disease is a progressive neurological disorder with few management options, although the gut microbiome has been suggested as a potential avenue of treatment. We retrospectively analysed the microbiome from human stool samples from a previously published study, which had demonstrated the efficacy of photobiomodulation to treat Parkinson’s patients’ symptoms. Specifically, we have observed changes in the microbiome of Parkinson’s patients after a 12-week treatment regimen with photobiomodulation to the abdomen, neck, head and nose. Noted were positive changes in the Firmicutes to Bacteroidetes (F:B) ratio, which is often interpreted as a proxy for gut health.