Campylobacter concisus upregulates PD-L1 mRNA expression in IFN-γ sensitized intestinal epithelial cells and induces cell death in esophageal epithelial cells

Introduction:Campylobacter concisus is an oral bacterium that is associated with inflammatory bowel disease (IBD) and Barrett’s esophagus (BE). Programmed cell death ligand-1 (PD-L1) is an immune checkpoint protein that is used by tumor cells for immune evasion and has increased expression in patients with IBD and BE. We examined whether C. concisus upregulates PD-L1 expression in intestinal and esophageal epithelial cells. Methods: Human intestinal epithelial HT-29 cells and esophageal epithelial FLO-1 cells with and without interferon (IFN)-γ sensitization were incubated with C. concisus strains. The level of PD-L1 mRNA was quantified using quantitative real-time PCR. Cytokines were measured using Enzyme-Linked Immunosorbent Assay (ELISA). Apoptosis of HT-29 and FLO-1 cells were measured using caspase 3/7 assay. Results: We found that intestinal epithelial cells with IFN-γ sensitization incubated with C. concisus significantly upregulated PD-L1 expression and significantly increased the production of interleukin (IL)-8. Whereas, PD-L1 expression was significantly inhibited in IFN-γ sensitized FLO-1 cells incubated with C. concisus strains. Furthermore, FLO-1 cells with and without IFN-γ sensitization incubated with C. concisus strains both had significantly higher levels of cell death. Conclusion:C. concisushas the potential to cause damage to both intestinal and esophageal epithelial cells, however, with different pathogenic effects.