Probiotic Lactobacillus reuteri Y7 Protects Against Blue Light–Induced Retinal Degeneration via Antioxidant Defense, Anti-Inflammatory Action, and Gut–Retina Axis Modulation

Chronic exposure to short-wavelength blue light induces oxidative stress, inflammation, and apoptosis in retinal tissues, contributing to vision loss. This study investigated the protective effects of <i>Lactobacillus reuteri</i> Y7, a human-derived probiotic, against blue light-induced retinal damage in mice. Male C57BL/6 mice were exposed to 400 lux blue light for 35 days and received either low- or high-dose Y7, lutein, or no intervention. Retinal morphology, inflammatory gene expression, gut barrier integrity, and gut microbiota composition were assessed. Low-dose Y7 promoted microbial diversity and enrichment of short-chain fatty acid-producing taxa, while high-dose Y7 favored enrichment of <i>Akkermansia</i>, <i>Parasutterella</i>, and <i>Bacteroides</i>, enhancing mucosal barrier function and metabolic regulation. Both doses attenuated retinal inflammation, preserved retinal layers, and improved gut barrier integrity, with high-dose Y7 matching or exceeding lutein's protective effects. Mechanistic insights suggest a gut-retina axis whereby microbial metabolites modulate oxidative stress, inflammation, and vascular homeostasis. These findings highlight <i>L. reuteri</i> Y7 as a potential non-invasive strategy for retinal degeneration prevention, with efficacy comparable to dietary antioxidants. Future studies should explore long-term safety, metabolite-mediated mechanisms, and comparative efficacy with other antioxidants.