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 = 48s vs. SCFA + CLP = 32s, p<0.01) and correlated with hippocampal c-Fos restoration (R 2 = 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.