IL-1β and TNF-α Do Not Decrease Protein Levels of the Apical Sodium-Dependent Bile Acid Transporter in IEC-6 Cells

in the small intestine after indomethacin treatment.Methods: Male SD rats without fasting were given indomethacin (10 mg/kg) SC and killed 24 h later to examine hemorrhagic lesions developed in the small intestine.Lubiprostone (0.1 mg/kg) was given PO as a single injection 30 min before the administration of indomethacin.AE3-208 (EP4 antagonist; 3 mg/kg) or CFTR(inh)-172 (CFTR inhibitor; 1 mg/kg) was given IP 30 min before lubiprostone.The expression of iNOS and TNFα mRNAs was examined by RT-PCR.Results: Indomethacin caused hemorrhagic lesions in the small intestine, accompanied by the up-regulation of iNOS and TNFα mRNA expressions as well as enterobacterial invasion.Lubiprostone potently prevented the ulcerogenic response to indomethacin, with concomitant inhibition of the upregulation of iNOS and TNFα expressions and bacterial invasion.These effects of lubiprostone were significantly abrogated by pretreatment of AE3-208, the EP4 antagonist.By the way, since the activation of CFTR chloride channels depends on cAMP signaling, it is possible that CFTR/chloride secretion contributes to the protective mechanism of lubiprostone mediated by the EP4 receptor/cAMP system.However, pretreatment of the animals with CFTR(inh)-172 did not affect the protective effect of lubiprostone against indomethacininduced intestinal lesions.Conclusion: Lubiprostone prevents indomethacin-induced small intestinal lesions via the EP4 receptor-dependent mechanism, and this effect may be associated with suppression of the expression of inflammatory mediators such as iNOS and TNFα, the important pathogenic factors in the enteropathy.In addition, it is unlikely that CFTR chloride channels contribute to the protective effect of lubiprostone against NSAID-induced small intestinal damage.