Photobiomodulation using an 830-nm laser alleviates hippocampal reactive gliosis and cognitive dysfunction in a mouse model of adolescent chronic alcohol exposure.

Abstract

Chronic alcoholism is known to have detrimental effects on the brain, including cognitive impairment, neurotransmitter imbalances, and brain atrophy. The hippocampus, crucial for spatial memory and cognitive functions, is particularly susceptible to alcohol-induced changes. Photobiomodulation (PBM), a non-invasive therapeutic method that utilizes red or near-infrared light, has shown promising applications in the central and peripheral nervous systems. Near-infrared (NIR) light, in particular, has been shown to prevent apoptosis, and neuroinflammation, as well as to improve cognitive functions. In this study, we aimed to investigate whether 830-nm laser irradiation could mitigate cognitive deficits in a chronic alcohol mouse model. Chronic alcoholism was induced in C57BL/6 mice through continuous ethanol gavage for 4 weeks at a dosage of 5 g/kg/day. Gavaging was performed 3 times per week for 4 weeks. Mice were transcranial irradiated by 830-nm laser, following making a chronic alcohol mouse model. Laser irradiation (50 mW/cm²) was performed 5 times per week for 3 weeks. To verify memory and cognitive defeats of a chronic alcohol mouse model, we performed animal behavior tasks such as Morris water maze, Y maze, and novel objective recognition. Our results confirmed the cognitive impairment in the chronic alcohol mouse model compared to the control group in conducted tasks. However, cognitive and spatial memory significantly improved following 830-nm laser irradiation. Additionally, we confirmed whether the behavior tasks result from histological changes. We performed immunofluorescence staining in the hippocampus region (CA3, CA1 and hilus) using astrocyte (GFAP) and microglia (Iba1) markers. As a result, reactive astrocyte was significantly increased in the chronic alcohol mouse model compared to control mice, whereas the number of GFAP-positive cells was significantly reduced by 830-nm laser irradiation. These findings indicate that chronic alcohol exposure induces spatial memory and cognitive impairment, which can be effectively rescued through near-infrared laser irradiation.