Short-chain fatty acids attenuate sepsis-induced gut dysbiosis and hippocampal neuroinflammation via NLRP6 inflammasome activation in mice.

BACKGROUND: Sepsis-associated encephalopathy (SAE) is a critical complication of sepsis, yet the mechanisms linking gut dysbiosis to hippocampal neuroinflammation remain poorly understood. Our previous work identified sepsis-induced hippocampal neuroinflammation; here, we investigated the role of gut microbiota-derived short-chain fatty acids (SCFAs) and NLRP6 inflammasome signaling in this process. METHODS: Sepsis was induced in C57BL/6 mice via cecal ligation and puncture (CLP). Gut microbiota composition, SCFA levels, intestinal barrier integrity, and NLRP6 inflammasome activity were analyzed. Colon organoids and NLRP6-silenced CT26 cells were employed to validate SCFA-NLRP6 interactions. Hippocampal neuroinflammation (microglial/astrocytic activation, cytokine levels) and cognitive function (Morris water maze, Barnes maze) were assessed post-SCFA treatment. RESULTS: CLP-induced sepsis triggered hippocampal neuroinflammation, characterized by microglial proliferation (IBA-1+), astrocyte activation (GFAP+), and neuronal dysfunction (reduced c-Fos). Septic mice showed gut dysbiosis (increased Firmicutes/Proteobacteria, decreased α-diversity), reduced SCFA levels, and impaired intestinal barrier integrity (decreased ZO-1/occludin expression, P < 0.05). SCFA supplementation restored gut microbiota homeostasis (β-diversity: P = 0.019 vs. CLP), enhanced intestinal tight junction proteins (ZO-1: 1.8-fold increase, P < 0.01), and activated NLRP6 inflammasomes in colonic tissues (NLRP6: 2.1-fold increase, caspase-1: 1.6-fold increase, P < 0.01). NLRP6 knockdown abolished SCFA-mediated IL-18 secretion ( P < 0.001). Behaviorally, SCFAs ameliorated cognitive deficits in septic mice (escape latency: CLP = 48 s vs. SCFA + CLP = 32 s, P < 0.01) and correlated with hippocampal c-Fos restoration ( R2 = 0.839 for propionate, P = 0.01). CONCLUSIONS: Sepsis disrupts the gut-brain axis by impairing intestinal barrier integrity and NLRP6 inflammasome function, exacerbating hippocampal neuroinflammation. SCFAs mitigate these effects via NLRP6-dependent mechanisms, highlighting their therapeutic potential for SAE. This study provides the first evidence linking SCFA-mediated NLRP6 activation to neuroprotection in sepsis, offering novel insights for targeting the gut microbiota in critical care.