Microbial metabolite trimethylamine N-oxide exacerbated microglial-mediated neuroinflammation in hemorrhagic stroke

BACKGROUND: Trimethylamine-N-oxide (TMAO), a metabolite produced by gut microbiota, has been linked to brain disease; however, its role in intracerebral hemorrhage (ICH) remains unclear. METHODS: Animal experiments were conducted to demonstrate the effects of TMAO on collagenase-induced rat models of ICH. Neurological function was evaluated using the modified neurological severity score (mNSS), and neuronal damage was assessed by NeuN staining. Microglial activation and pro-inflammatory cytokine expression were examined. To further investigate the mechanism of TMAO, we performed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis on its predicted molecular targets. BV2 microglia were treated with TMAO to assess the levels of reactive oxygen species (ROS), cyclooxygenase-2 (COX-2), NOD-like receptor protein 3 (NLRP3), and caspase-1. Moreover, ICH rats were intragastrically treated with TMAO precursor L-carnitine (LC), and antibiotic cocktail treatment was used to deplete the gut microbiota, then assessed the effect. RESULTS: Our results showed that TMAO administration exacerbated neurological deficits and microglial-mediated neuroinflammation in ICH rats. NOD-like receptor signaling pathway was a key mechanism promoting ICH pathogenesis and confirmed that TMAO supplementation exacerbated microglial activation by regulating NLRP3 inflammasome activity in vitro. Moreover, gut microbiota depletion attenuated TMAO-induced activation of NLRP3 and the subsequent neuroinflammatory response in ICH. CONCLUSION: Collectively, these findings showed that Microbial Metabolite TMAO contributes to ICH-induced neuroinflammation by activating the NLRP3 signaling pathway.