Cultures of human colonic epithelial cells isolated from endoscopical biopsies from patients with inflammatory bowel disease. Effect of IFNgamma, TNFalpha and IL-1beta on viability, butyrate oxidation and IL-8 secretion.

Cytokine-mediated impairment of viability and metabolic function of epithelial cells has been suggested as a possible early pathogenic event in the development of inflammatory bowel disease (IBD). It is currently unknown whether pro-inflammatory cytokines have a direct effect on human nontransformed colonic epithelial cells. We investigated the effects of TNFalpha, IFNgamma and IL-1beta on viability, short chain fatty acid (butyrate) oxidation and IL-8 secretion in human colonic epithelial cell cultures in vitro obtained from macroscopically normal mucosa from IBD patients and controls. Colonic crypts were isolated from endoscopical biopsies by ultra-short (10 min) EDTA/EGTA treatment, and exposed to TNFalpha, IFNgamma and IL-1beta for 24 hours. The combination of TNFalpha+IFNgamma induced a significant decrease in cell viability as judged by methyltetrazoleum (MTT) metabolism which decreased to median 68% of unexposed cultures (P < 0.01). This effect was more pronounced than that observed after addition of TNFalpha (median 88%) (P < 0.05), but not IFNgamma alone (median 78%), whereas IL-1beta had no significant effect. Cells from IBD patients were significantly less sensitive to TNFalpha + IFNgamma exposure (median 74%) compared to cells from controls (median 58 %) (P < 0.05). Butyrate oxidation, as measured by entrapment of 14CO2, was not inhibited in cells exposed to TNFalpha + IFNgamma, neither from controls (median 112%) nor from IBD patients (median 108%), suggesting a relative increase of this specific metabolic function in living cells in response to immunoinflammatory stress. IL-8 levels in cell supernatants were increased by TNFalpha + IFNgamma, supporting the role of the epithelium in signalling between luminal factors and mucosal immune cells. In conclusion, we report that TNFalpha and IFNgamma damage and influence human colonic epithelial cell function in vitro and that such mechanisms, if operative in vivo, also may be involved in the pathogenesis of IBD.