High fluoride exposure disrupts gut microbiota and induces intestinal barrier damage via RhoA/ROCK-mediated cytoskeletal remodeling

Fluoride pollution-whether of geological or anthropogenic origin-disrupts gut microbiota-host homeostasis and compromises the intestinal barrier. We established an acute high-fluoride mouse model via intragastric NaF, integrating metagenomics, metabolomics, and molecular biological techniques to clarify the underlying mechanism of enhanced intestinal permeability caused by fluoride exposure in vivo. Mechanistically, high fluoride exposure activates the RhoA/ROCK signaling pathway, increases the level of phosphorylated myosin light chain (p-MLC), induces filamentous actin (F-actin) rearrangement, and disrupts the apical junctional complex (AJC)-characterized by downregulated expression or abnormal localization of AJC-related proteins (ZO-1, Claudin-1, β-catenin, Occludin). It also alters the morphology of intestinal epithelial cells, ultimately increasing ileal permeability. At the microbiota level, high fluoride disrupted the ileal microbiota; specifically, at the species level, Bifidobacterium sp. SO1 and Schaalia turicensis were identified as the key species with high specificity and high occupancy under fluoride exposure. Lactobacillus and Akkermansia were abnormally enriched in the intestines of mice exposed to fluoride. Metabolomic analysis revealed that high fluoride exposure enriched multiple pathways including linoleic acid metabolism and sphingolipid metabolism, altering the levels of 11 cytoskeleton-related metabolites. Correlation analysis confirmed that Bifidobacterium sp. SO1 and Schaalia turicensis were strongly correlated with damage phenotypes, pathway molecules, and metabolites, indicating that these two strains are closely associated with cytoskeleton changes and increased intestinal permeability under high fluoride exposure. Collectively, our findings reveal that gut microbiota drive fluoride-induced intestinal barrier dysfunction through the "microbiota-RhoA/ROCK-cytoskeleton" axis, highlighting a novel host-microbe interaction mechanism underlying environmental toxin-mediated gut injury.