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

Cytokine-mediated impairment of viability and metabolic function of epithel ial cells has been suggested as a possible early pathogenic event in the de velopment of inflammatory bowel disease (IBD). It is currently unknown whet her pro-inflammatory cytokines have a direct effect on human nontransformed colonic epithelial cells. We investigated the effects of TNF alpha, IFN ga mma and IL-1 beta on viability, short chain fatty acid (butyrate) oxidation and IL-8 secretion in human colonic epithelial cell cultures in vitro obta ined from macroscopically normal mucosa from IBD patients and controls. Col onic crypts were isolated from endoscopical biopsies by ultra-short (10 min ) EDTA/EGTA treatment, and exposed to TNF alpha, IFN gamma and IL-1 beta fo r 24 hours. The combination of TNF alpha + 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 TNF<alpha> (median 88 %) (P<0.05), but not IFN<gamma> alone (median 78 %), whereas IL-1 beta had no significant effect. Cells from IBD patients were significantly less sensitive to TNF alpha + IFN gamma exposure (median 74 %) compared to cells from controls (median 58 %) (P < 0.05). Butyrate oxidation, as measured by entrapment of (CO2)-C-14, was not inhibited in cells exposed to TNF<alpha> + IFN gamma, neither from controls (median 112%) nor from IBD patients (me dian 108%), suggesting a relative increase of this specific metabolic funct ion in living cells in response to immunoinflammatory stress. IL-8 levels i n cell supernatants were increased by TNF alpha + IFN gamma, supporting the role of the epithelium in signalling between luminal factors and mucosal i mmune cells. In conclusion, we report that TNF alpha and IFN gamma damage a nd 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.