Clostridium innocuum is an emerging spore-forming anaerobe that is often observed in Clostridioides difficile-associated inflammatory bowel disease (IBD) exacerbations. Unlike C. difficile, C. innocuum neither produces toxins nor possesses toxin-encoding genetic loci, but is commonly found in both intestinal and extra-intestinal infections. Membrane lipid rafts are composed of dynamic assemblies of cholesterol and sphingolipids, allowing bacteria to gain access to cells. However, the direct interaction between C. innocuum and lipid rafts that confers bacteria the ability to disrupt the intestinal barrier and induce pathogenesis remains unclear. In this study, we investigated the associations among nucleotide-binding oligomerization domain containing 2 (NOD2), lipid rafts, and cytotoxicity in C. innocuum-infected gut epithelial cells. Our results revealed that lipid rafts were involved in C. innocuum-induced NOD2 expression and nuclear factor (NF)-κB activation, triggering an inflammatory response. Reducing cholesterol by simvastatin significantly dampened C. innocuum-induced cell death, indicating that the C. innocuum-induced pathogenicity of cells was lipid raft-dependent. These results demonstrate that NOD2 mobilization into membrane rafts in response to C. innocuum-induced cytotoxicity results in aggravated pathogenicity.
Keywords: Clostridium innocuum; cholesterol; cytotoxicity; inflammation; lipid rafts.