Unveiling the gut-brain axis: How chronic exposure to arsenic-induced microglial pyroptosis drives Alzheimer's disease-like pathology.

Arsenic, a pervasive environmental contaminant in groundwater, poses a severe global threat to public health. Chronic arsenic exposure has been linked to neurological impairment, however, its specific pathogenic mechanism and whether the gut-brain axis plays a key role remain unclear. This study investigated the role of gut microbiota and its metabolite indoxyl sulfate (IS) in mediating chronic exposure to arsenic-induced cognitive impairment and Alzheimer's disease (AD)-like pathology, with a specific focus on microglial pyroptosis. We found that chronic arsenic exposure induced cognitive dysfunction and intestinal barrier injury, disrupted gut microbiota composition, promoted IS accumulation in serum and brain, and activated the AhR/NF-κB/NLRP3 signaling pathway, triggering microglial pyroptosis and elevating AD-like pathological markers in mice. Meanwhile, fecal microbiota transplantation (FMT) from arsenic-exposed mice recapitulated cognitive impairment, elevated IS levels, and neuroinflammation in recipient mice. Furthermore, arsenic upregulated hepatic IS-synthesis genes (CYP2E1, Sult1d1) and downregulated renal IS-excretion gene (ABCG2). In vitro, arsenic and IS co-exposure promoted M1 polarization and enhanced pyroptosis by activating the AhR/NF-κB/NLRP3 signaling pathway, while suppressing phagocytosis-related proteins (TREM2, SYK and CD36). Furthermore, SiAhR treatment could alleviated microglial inflammatory injury and enhancing the microglia's phagocytic capacity induced by arsenic and IS co-exposure in BV2 cells through inhibiting the AhR/NF-κB/NLRP3-mediated pyroptosis signaling pathway. In conclusion, chronic arsenic exposure induced cognitive impairment and AD-like pathological via the gut microbiota-AhR-pyroptosis cascade, where in IS accumulation served a key mediator. These findings provide new insights into preventing arsenic-related cognitive damage.