Photobiomodulation Therapy: A Novel Therapeutic Approach to Alzheimer's Disease Made Possible by the Evidence of a Brain-Gut Interconnection.

The evidence of brain-gut interconnections in Alzheimer's disease (AD) opens novel avenues for the treatment of a pathology for which no definitive treatment exists. Gut microbiota and bacterial translocation may produce peripheral inflammation and immune modulation, contributing to brain amyloidosis, neurodegeneration, and cognitive deficits in AD. The gut microbiota can be used as a potential therapeutic target in AD. In particular, photobiomodulation (PBM) can affect the interaction between the microbiota and the immune system, providing a potential explanation for its restorative properties in AD-associated dysbiosis. PBM is a safe, non-invasive, non-ionizing, and non-thermal therapy that uses red or near-infrared light to stimulate the cytochrome c oxidase (CCO, complex IV), the terminal enzyme of the mitochondrial electron transport chain, resulting in adenosine triphosphate synthesis. The association of the direct application of PBM to the head with an abscopal and a systemic treatment through simultaneous application to the abdomen provides an innovative therapeutic approach to AD by targeting various components of this highly complex pathology. As a hypothesis, PBM might have a significant role in the therapeutic options available for the treatment of AD.

Translation from Preclinical Research to Clinical Trials: Brain-Gut Photobiomodulation Therapy for Alzheimer's Disease.

Recently, novel non-pharmacological interventions, such as photobiomodulation (PBM) therapy, have shown promise for the treatment of Alzheimer's disease (AD). This article outlines the translation from the preclinical to clinical stages of an innovative brain-gut PBM therapy in a mouse model of AD, a pilot clinical trial involving mild-to-moderate AD patients, and a continuing pivotal clinical trial with a similar patient population. In a mouse model of AD (Aß25-35), daily application of brain-gut PBM therapy to both the head and the abdomen produced a neuroprotective effect against the neurotoxic effects of an Aß25-35 peptide injection by normalizing all the modified behavioral and biochemical parameters. The pilot clinical trial to evaluate brain-gut PBM therapy demonstrated the tolerability and feasibility of the novel PBM-based treatment for mild-to-moderate AD patients. Compared to the sham patients, the PBM-treated patients had lower Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog) comprehension sub-scores, higher forward verbal spans, and lower Trail Making Test (TMT) Part B (TMT-B) execution times, which suggest an improvement in cognitive functions. This pilot study provided important information for the design of a novel pivotal clinical trial, currently in progress, to assess the efficacy of brain-gut PBM therapy in a larger sample of AD patients. This pivotal clinical trial could demonstrate that brain-gut PBM therapy is a safe, well-tolerated, and efficient disease-modifying treatment for mild-to-moderate AD patients and that it has medical and economic benefits.

Restorative effects of probiotics on memory impairment in sleep-deprived mice.

BACKGROUND: Insufficient sleep is a serious public health epidemic in modern society, impairing memory and other cognitive functions. In this study, partial sleep deprivation (SD) was used to induce cognitive impairment in mice to determine the effects of probiotics on subsequent cognitive deficits. METHODS: Lactiplantibacillus plantarum Lp-115 (Lp-115), Lacticaseibacillus paracasei Lpc-37 (Lpc-37), Bifidobacterium animalis subsp. lactis 420 (B420) and their combination were administered to mice subjected to partial SD and compared with non-SD and SD vehicle groups. Mice were administered a daily oral gavage containing either 1 × 109 colony forming units (CFU) of single-strain, 1.5 × 109 CFU of multi-strain (5 × 108 CFU/strain), or vehicle for thirty days prior to and for nine days during a behavioural test paradigm. The novel object recognition (NOR) test, spontaneous alternation Y-maze (Y-maze), and the step-through passive avoidance (STPA) task were applied to evaluate learning and memory performance following partial SD. RESULTS: Partial SD had a significant impact on cognitive function in vehicle mice. Intervention with Lpc-37 significantly improved recognition memory deficits in the NOR test, spatial working memory deficits in the Y-maze, and contextual long-term memory impairments in the STPA task, in mice subjected to partial SD compared to the SD vehicle group. The multi-strain significantly improved recognition memory deficits in the NOR test and spatial working memory deficits in the Y-maze in mice subjected to partial SD compared to the SD vehicle group. CONCLUSIONS: These findings demonstrate that Lpc-37 and the multi-strain may play a role in alleviating memory impairments and improve cognitive function in partially sleep-deprived mice.

Strain specific stress-modulating effects of candidate probiotics: A systematic screening in a mouse model of chronic restraint stress.

BACKGROUND: Changes in the gut microbiota have been implicated in mood and cognition. In rodents, supplementation with certain bacteria have been shown to alleviate adverse effects of stress on gut microbiota composition and behaviour, but little is known of how the performance of different strains compare to each other. We took a systematic approach to test the efficacy of twelve candidate probiotic strains from ten species/sub-species of Bifidobacterium and Lactobacillus on behaviours and neuroendocrine responses of chronically stressed mice. METHODS: The strains were tested in four screening experiments with non-stressed and chronically stressed vehicle groups. The three most efficacious strains were re-tested to validate the results. Mice were administered a daily oral gavage containing either 1 × 109 colony forming units (CFU) of selected candidate probiotic or saline solution for one week prior to and for three weeks during daily chronic restraint stress. Behavioural tests including the elevated plus maze, open field, novel object recognition, and forced swim test were applied during week five. Corticosterone and adrenocorticotropic hormone (ACTH) were analysed to measure the neuroendocrine response to stress. Plasma and tissue samples were collected for biomarker analyses. RESULTS: Of the twelve candidate probiotics, Lactobacillus paracasei Lpc-37, Lactobacillus plantarum LP12407, Lactobacillus plantarum LP12418 and Lactobacillus plantarum LP12151 prevented stress-associated anxiety and depression-related behaviours from developing compared with chronically stressed vehicle mice. In addition, Lpc-37 improved cognition. CONCLUSION: This systematic screening indicates species- and strain-dependent effects on behavioural outcomes related to stress and further suggests that strains differ from each other in their effects on potential mechanistic outcomes.

Neuroprotective effect of a new photobiomodulation technique against Aß25-35 peptide-induced toxicity in mice: Novel hypothesis for therapeutic approach of Alzheimer's disease suggested.

INTRODUCTION: Photobiomodulation was assessed as a novel treatment of Alzheimer's disease (AD) by the use of a new device RGn500 combining photonic and magnetic emissions in a mouse model of AD. METHODS: Following the injection of amyloid ß 25-35 peptide in male Swiss mice, RGn500 was applied once a day for 7 days either on the top of the head or the center of abdomen or both. RESULTS: RGn500 daily application for 10 min produced a neuroprotective effect on the neurotoxic effects of amyloid ß 25-35 peptide injection when this type of photobiomodulation was applied both on the head and on the abdomen. Protection was demonstrated by memory restoration and on the normalization of key markers of AD (amyloid ß 1-42, pTau), oxidative stress (lipid peroxidation), apoptosis (Bax/Bcl2) and neuroinflammation. DISCUSSION: RGn500 displays therapeutic efficacy similar to other pharmacological approaches evaluated in this model of AD.

Enhanced antidepressant efficacy of sigma1 receptor agonists in rats after chronic intracerebroventricular infusion of beta-amyloid-(1-40) protein.

Treatment of depressive symptoms in patients suffering from neurodegenerative disorders remains a challenging issue, since few available antidepressants present an adequate efficacy during pathological aging. Previous reports suggested that selective sigma(1) receptor agonists might constitute putative candidates. We here examined the pharmacological efficacy of igmesine and (+)-SKF-10,047 and the sigma(1) receptor-related neuroactive steroid dehydroepiandrosterone sulfate, in rats infused intracerebroventricularly during 14 days with the beta-amyloid-(1-40) protein and then submitted to the conditioned fear stress test. Igmesine and (+)-SKF-10,047 significantly reduced the stress-induced motor suppression at 30 and 6 mg/kg, respectively, in beta-amyloid-(40-1)-treated control rats. Active doses were decreased, to 10 and 3 mg/kg, respectively, in beta-amyloid-(1-40)-treated animals. The dehydroepiandrosterone sulfate effect was also facilitated, both in dose (10 vs. 30 mg/kg) and intensity, in beta-amyloid-(1-40)-treated rats. Neurosteroid levels were measured in several brain structures after beta-amyloid infusion, in basal and stress conditions. Progesterone levels, both under basal and stress-induced conditions, were decreased in the hippocampus and cortex of beta-amyloid-(1-40)-treated rats. The levels in pregnenolone, dehydroepiandrosterone and their sulfate esters appeared less affected by the beta-amyloid infusion. The sigma(1) receptor agonist efficacy is known to be inversely correlated to brain progesterone levels, synthesized mainly by neurons that are mainly affected by the beta-amyloid toxicity. The present study suggests that sigma(1) receptor agonists, due to their enhanced efficacy in a nontransgenic animal model, may alleviate Alzheimer's disease-associated depressive symptoms.

Enhanced antidepressant effect of sigma(1) (sigma(1)) receptor agonists in beta(25-35)-amyloid peptide-treated mice.

This study examined the antidepressant efficacy of the selective sigma(1) receptor agonists igmesine or PRE-084 in mice injected intracerebroventricularly (i.c.v.) with beta(25-35)-amyloid peptide and submitted to the forced swim test. Beta(25-35) peptide-injected animals developed memory deficits after 8 days contrarily to controls injected with scrambled beta(25-35) peptide or vehicle solution. In the forced swim test, the i.c.v. treatment failed to affect the immobility duration, but the antidepressant effect of the sigma(1) agonists was facilitated in beta(25-35) animals. Igmesine reduced immobility duration at 30 versus 60 mg/kg in control groups. PRE-084 decreased immobility duration at 30 and 60 mg/kg only in beta(25-35) animals. Desipramine reduced the immobility duration similarly among groups and fluoxetine appeared less potent in beta(25-35) animals. The beta(25-35) animals exhibited decreased progesterone levels in the hippocampus (-47%). The behavioural efficacy of sigma(1) agonists is known to depend on neuro(active)steroids levels synthesised by glial cells and neurones, which are affected by the beta-amyloid toxicity. This behavioural study suggests that sigma(1) agonists, due to their enhanced efficacy, may allow to alleviate the depressive symptoms associated with Alzheimer's disease.

The antidepressant-like effect induced by the sigma(1) (sigma(1)) receptor agonist igmesine involves modulation of intracellular calcium mobilization.

RATIONALE: Activation of the neuronal sigma(1) (sigma(1)) receptor potentiates calcium mobilization, leading to effective modulation of postsynaptic responses to neurotransmitters. At the behavioral level, sigma(1) agonists modulate learning, response to stress and depression. In particular, the selective sigma(1) agonist igmesine reduced immobility in the forced swimming test. OBJECTIVES AND METHODS: We investigated the effect of modulators of Ca(2+) influx and mobilization, administered intracerebroventricularly at doses ineffective alone, on the igmesine effect. The tricyclic antidepressant desipramine was also studied for comparison. RESULTS: The calcium chelator EGTA blocked both igmesine and desipramine-induced decreases of immobility duration, indicating the importance of extracellular Ca(2+) influx in the initial action of each compound. Both L- and N-type voltage-dependent calcium channel (VDCC) appeared involved in the sigma(1) agonist effect. Verapamil, an L-type VDCC antagonist or omega-conotoxin GVI, a N-type VDCC antagonist, blocked whereas (-)-Bay K8644, a L-type VDCC agonist, potentiated the igmesine effect. Mobilization of intracellular Ca(2+) stores is involved selectively in the effect mediated by the sigma(1) receptor, since the membrane permeable intracellular Ca(2+) chelator EGTA/AM affected only the igmesine effect. Inositol 1,4,5-trisphosphate (InsP(3)) receptor-sensitive Ca(2+) pools appeared primarily involved, rather than Ca(2+)/caffeine-sensitive Ca(2+) pools. Indeed, the InsP(3) receptor positive modulator bradykinin potentiated, whereas the InsP(3) receptor antagonist xestospongin C blocked the igmesine effect. The ryanodine receptor agonist caffeine failed to affect the efficacy of igmesine, whereas the antagonist ryanodine reduced it. CONCLUSIONS: The sigma(1) receptor-mediated behavioral effect is dependent not only on rapid Ca(2+) influx, as observed for a classical antidepressant, but also on intracellular Ca(2+) mobilization.