Examination of the effects of Campylobacter concisus zonula occludens toxin on intestinal epithelial cells and macrophages

Vikneswari Mahendran, Fang Liu, Stephen M. Riordan, Michael C. Grimm, Mark M. Tanaka, Li Zhang

Campylobacter concisus is a Gram-negative bacterium that is associated with inflammatory bowel disease (IBD). Some C. concisus strains carry zonula occludens toxin (zot) gene which has polymorphisms. This study investigated the effects of C. concisus Zot on intestinal epithelial cells and macrophages using cell line models. Campylobacter concisus zot (808T) gene, a polymorphism that is associated with active IBD, was cloned and expressed in Escherichia coli. The effects of C. concisus Zot on intestinal epithelial barrier were examined using Caco-2 cell model. Apoptosis induced by C. concisus Zot in Caco-2 cells was assessed by measuring the levels of caspase 3/7. The production of pro-inflammatory cytokines induced by C. concisus Zot in HT-29 cells and in THP-1 macrophage-like cells was measured using ELISA kits. Whether exposure to C. concisus Zot can affect the responses of macrophages to E. coli K12 was also investigated. Campylobacter concisus Zot caused prolonged intestinal epithelial barrier damage, induced intestinal epithelial cell apoptosis, induced epithelial production of TNF-α and IL-8 and upregulated TNF-α in THP-1 macrophage-like cells. Pre-exposure to C. concisus Zot significantly enhanced the production of TNF-α and IL-8 as well as phagocytosis by THP-1 macrophage-like cells in response to E. coli K12. This study suggests that C. concisus Zot may have enteric pathogenic potential by damaging intestinal epithelial barrier, inducing intestinal epithelial and macrophage production of proinflammatory cytokines in particular TNF-α and enhancing the responses of macrophages to other enteric bacterial species.