LACTOBACILLUS RHAMNOSUS AMELIORATES NEURAL AND CARDIOVASCULAR SYSTEM DAMAGE INDUCED BY TRIBUTYLTIN (TBT) EXPOSURE IN ZEBRAFISH

This study utilized zebrafish (<italic>Danio rerio</italic>) as a model to investigate the ameliorative effects and underlying mechanisms of dietary supplementation with the probiotic <italic>Lactobacillus rhamnosus</italic> on toxicity induced by tributyltin (TBT). Adult zebrafish were divided into three groups: a DMSO control group, a TBT group (2 μg/L TBT), and a TBT+PRO group (2 μg/L TBT supplemented with <italic>L. rhamnosus</italic>), and were fed accordingly for 21 days. The results showed that compared to TBT exposure alone, co-supplementation with <italic>L. rhamnosus</italic> significantly increased the abundances of Firmicutes and <italic>Lacticaseibacillus</italic> in the intestine; increased intestinal wall thickness and alleviated villi damage; reduced cerebral ventricle enlargement, and mitigated inflammatory cell infiltration and vacuolation in heart tissue. At the molecular level, the expression of pro-inflammatory factors (<italic>tnf-α</italic>, <italic>il-1β</italic>) was significantly downregulated, while the expression of the anti-inflammatory factor (<italic>il-10</italic>) was significantly upregulated in the intestine, brain, and heart. The expression of intestinal tight junction protein genes (<italic>claudin-2</italic>, <italic>zo-1</italic>) increased, leading to reduced intestinal permeability. Furthermore, lipopolysaccharide (LPS) levels were significantly decreased in the brain, serum, and intestine; the overexpression of hypothalamic-pituitary-interrenal (HPI) axis-related genes (<italic>crhr2</italic>, <italic>mr</italic>, <italic>pomc</italic>) was suppressed; the expression of key neuronal genes (<italic>α1-tubulin</italic>, <italic>bdnf</italic>, <italic>shha</italic>) was restored; cortisol (Cor) levels were significantly reduced; and the expression of apoptosis-related genes (<italic>caspase-3</italic>, <italic>caspase-9</italic>, <italic>bax</italic>) in the heart was significantly downregulated. These results indicate that <italic>L. rhamnosus</italic> can modulate the gut microbiota balance, reduce LPS levels, inhibit HPI axis overactivation, and alleviate inflammatory and apoptotic responses, thereby ameliorating TBT-induced damage to the nervous and cardiovascular systems in zebrafish. This study provides a theoretical basis and practical strategies for the bioremediation of TBT pollution and the application of probiotics in aquaculture.