The integrity of intestinal epithelium is essential for maintaining gut homeostasis, and acts as both a microbiota barrier and a sensor to activate appropriate immune responses. Dysregulated and excessive programmed cell death of intestinal epithelial cells (IECs) is related to the pathogenesis of inflammatory bowel disease (IBD). However, how IEC death might be triggered, particularly from pro-inflammatory cytokines, remains unclear. The aim of this study is to understand how physiological ligands elevated in the inflamed intestine might cause IEC death and thereby contribute to IBD pathogenesis.
Human small intestine organoids were derived and differentiated into different intestinal cell types, and these were treated with inflammatory cytokines observed in IBD patients: tumor necrosis factor (TNF) and interferon-gamma (IFNγ). The combination of these two inflammatory ligands acted in concert to induce undifferentiated intestinal organoid death, as measured and quantified over time by Incucyte live cell analysis. However, organoids differentiated into an enterocyte-like phenotype were markedly more sensitive to death following TNF and IFNγ treatment. Mechanistically, TNF and IFNγ treatment of intestinal organoids revealed changes in the levels of several critical cell death regulators, and an increase in inducible nitric oxide synthase (iNOS) and its product nitric oxide, which we have recently implicated in executing an inflammatory cell death and COVID-19 disease severity. By delineating the molecular pathway by which excess inflammation can cause intestinal cell death in humans, new therapeutic targets for IBD might be uncovered.