Abstract

Pedersen G, Saermark T, Bendtzen K, Brynskov J. Cultures of human colonic epithelial cells isolated from endoscopical biopsies from patients with inflammatory bowel disease. Effect of IFN-gamma, TNFa and IL-1b on viability, butyrate oxidation and IL-8 secretion. Autoimmunity 2000; 32:255-263.

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, IFN-gamma 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, IFN-gamma and IL-1beta for 24 hours. The combination of TNFalpha+IFN-gamma 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 IFN-gamma alone (median 78%), whereas IL-1beta had no significant effect. Cells from IBD patients were significantly less sensitive to TNFalpha + IFN-gamma 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 + IFN-gamma, 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 + IFN-gamma, supporting the role of the epithelium in signalling between luminal factors and mucosal immune cells. In conclusion, we report that TNFalpha and IFN-gamma 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.