Rab5a promotes cytolethal distending toxin B-induced cytotoxicity and inflammation.

Chen, Ming-Xian; Chen, Yu; Fu, Rui; Mao, Guo-Qun; Liu, Sai-Yue; Shen, Tang-Biao

The cytolethal distending toxin (Cdt) B subunit (CdtB) induces significant cytotoxicity and inflammation in many cell types that are involved in the pathogenesis of post-infectious irritable bowel syndrome (PI-IBS). However, the underlying mechanisms remain unclear. This study tested the potential role of Rab small GTPase 5a (Rab5a) in the process. We tested mRNA and protein expression of proinflammatory cytokines (IL-1β and IL-6) in THP-1 macrophages by qPCR and ELISA assays, respectively. In the primary colonic epithelial cells, Cdt treatment induced CdtB-Rab5a-cellugyrin association. Rab5a silencing, by target small hairpin (sh) RNAs, largely inhibited CdtB-induced cytotoxicity and apoptosis in colon epithelial cells. CRISPR/Cas9-mediated Rab5a knockout also attenuated CdtB-induced colon epithelial cell death. Conversely, forced overexpression of Rab5a intensified CdtB-induced cytotoxicity. In THP-1 human macrophages, Rab5a shRNA or knockout significantly inhibited CdtB-induced mRNA expression and production of proinflammatory cytokines (IL-1β and IL-6). Rab5a depletion inhibited activation of nuclear factor-κB (NF-κB) and JNK signaling in CdtB-treated THP-1 macrophages. Rab5a appears essential for CdtB-induced cytotoxicity in colonic epithelial cells and proinflammatory responses in THP-1 macrophages.