Inflammation and apoptosis in Clostridium difficile enteritis is mediated by PGE2 up-regulation of Fas ligand

Background& Aims: Clostridium difficile toxin A causes acute inflammation and fluid secretion in experimental animals and patients with C difficile infection. We previously reported that toxin A increased cyclooxygenase-2/prostaglandin E-2 (PGE(2)) expression and apoptosis in human colonocytes. Here, we assessed the role of secreted PGE2 in inflammation and enterocyte apoptosis in toxin A enteritis. Methods: Effects of PGE2 and PGE2 blockade on toxin A-induced apoptosis of human colonocytes (NCM460) and of PGE2 or toxin A on the Fas ligand (FasL) induction were analyzed by flow cytometry and Western blot. Functional activity of elevated FasL on colonocytes was assessed by coculture of colonocytes with Fas bearing Jurkat T cells. The involvement of PGE(2)-dependent Fas/FasL activation in toxin A enteritis was further assessed in either scid or FasL and Fas deficient mice. Results: inhibition of cyclooxygenase-2 by NS-398 and of PGE2 using a blocking antibody markedly attenuated apoptosis in colonocytes exposed to toxin A. Enhanced expression and release of FasL followed PGE2 or toxin A exposure in vivo and in vitro and also was significantly attenuated by treatment with NS-398 and PGE2 blocking antibody. PGE2 acting through an EP1 receptor activated nuclear factor-kappa B, which induced transcription of FasL. Toxin A enteritis was accompanied by increased cellular infiltration, fluid secretion, and mucosal damage in control mice, but this response was markedly reduced in both Fas-/- and FasL-/- mice. Conclusions: Toxin A enteritis involves release of PGE2, which activates the Fas/FasL system, causing enterocyte apoptosis and inflammation.