Differential pattern of inflammatory molecule regulation in intestinal epithelial cells stimulated with IL-1

To better predict the consequences of blocking signal transduction pathways as a means of controlling intestinal inflammation, we are characterizing the pathways up-regulated by IL-1 in intestinal epithelial cells (IEC). IL-1 beta induced increased mRNA levels of MIP-2, MCP-1, RANTES, inducible NO synthase (MOS), and cyclooxygenase-2 (COX-2) in the IEC-18 cell line. IL-1 beta activated NF-kappa B but not ERK or p38. Infecting cells with adenovirus expressing a mutated gene for I kappa B alpha (I kappa BAA) blocked IL-1-induced mRNA increases in MIP-2, MCP-1, and iNOS but not COX-2 or RANTES. Expression of I kappa BAA attenuated the IL-1-induced increase in COX-2 protein. Unexpectedly, RANTES mRNA increased, and protein was secreted by cells expressing I kappa BAA in the absence of IL-1. Adenovirus-expressing I kappa BAA, blocking protein synthesis, and IL-1 beta all resulted in activation of JNK. The JNK inhibitor SP600125 prevented the RANTES increases by all three stimuli. A human enterocyte line was similarly examined, and both NF-kappa B and JNK regulate IL-1-induced RANTES secretion. We conclude that in IEC-18, IL-1 beta-induced increases in mRNA for MIP-2, MCP-1, and iNOS are NF-kappa B-dependent, whereas regulation of RANTES mRNA is independent of NF-kappa B but is positively regulated by JNK. IL-1 beta-induced mRNA increases in COX-2 mRNA are both NF-kappa B- and MAPK-independent but the translation of COX-2 protein is NF-kappa B-dependent. This pattern of signaling due to a single stimulus exposed the complexities of regulating inflammatory genes in IEC.