Probiotic Lactobacillus rhamnosus alleviates microcystin-LR induced visual system defects and dysfunction in zebrafish by modulating apoptosis, retinal inflammation, and phototransduction.

Microcystin-LR (MC-LR) is a highly toxic category of biotoxins that can damage eye development and retinal structure in zebrafish, while probiotics can largely benefit the function of the retina. Although they both act on the visual system, whether probiotics can alleviate the visual damage caused by MC-LR in fish and the underlying mechanisms remains unclear. In this study, we exposed adult zebrafish for 28 days at MC-LR concentrations of 0, 2.20, and 22.00 µg/L with or without the probiotic Lactobacillus rhamnosus in the diet. MC-LR exposure alone resulted in structural damage to the retina and abnormal phototropic behavior, whereas L. rhamnosus could alleviate these damages. Biochemical analyses showed that MC-LR-induced abnormalities in apoptosis of ocular cells, retinal inflammatory responses, neurotransmission, and phototransduction were restored in the L. rhamnosus treatment group, indicating L. rhamnosus alleviated MC-LR-induced defects in the visual system and dysfunctions. This study underlines the defensive role of probiotics in protecting the host from environmental pollutants, which may provide guidance for the application of probiotics in aquaculture.