Dexamethasone protects enterocytes from TNF-alpha-induced apoptosis

摘要

TNF-alpha, a key inflammatory mediator in Crohn's disease, is known to alter intestinal epithelial cell turnover, resulting in pathological epithelial functions. Previous studies showed that TNF-alpha in combination with IFN7 markedly inhibited normal intestinal epithelial cell growth and induced a high degree of enterocyte apoptosis.Aim: To test the hypothesis that the glucocorticosteroid, dexamethasone, protects enterocytes from TNMFN-induced apoptosis.Methods/results: The non-transformed human intestinal epithelial cell line, HIEC, was stimulated with recombinant TNF-alpha 1-100 ng/ml plus IFN-gamma 300U/ml alone or in the presence of dexamethasone 10-1000nmol/L for up to 48h. TNF/IFN induced HIEC apoptosis in a dose-dependent manner with a maximum apoptosis rate of 73 +- 8% (p<0.01) after 48 h. Typical signs of apoptosis, such as the loss of membrane asymmetry, condensation and fragmentation of the DNA as well as the formation of apoptotic bodies were observed in TNF/IFN-stimulated cells by immunofluorescence, confocal and electron microscopy. In the presence of dexamethasone, no induction of apoptosis occurred after stimulation with TNF/IFN (14 +- 6%) even at the highest cytokine concentrations used. Receptor-expression analysis of the p55 and p75-TNF-R showed no effect of dexamethasone at the receptor level.