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-1β induced increased mRNA levels of MIP-2, MCP-1, RANTES, inducible NO synthase (iNOS), and cyclooxygenase-2 (COX-2) in the IEC-18 cell line. IL-1β activated NF-κB but not ERK or p38. Infecting cells with adenovirus expressing a mutated gene for IκBα (IκBα) blocked IL-1-induced mRNA increases in MIP-2, MCP-1, and iNOS but not COX-2 or RANTES. Expression of IκBAA attenuated the IL-1-induced increase in COX-2 protein. Unexpectedly, RANTES mRNA increased, and protein was secreted by cells expressing IκBAA in the absence of IL-1. Adenovirus-expressing IκBAA, blocking protein synthesis, and IL-1β 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-κB and JNK regulate IL-1-induced RANTES secretion. We conclude that in IEC-18, IL-1β-induced increases in mRNA for MIP-2, MCP-1, and iNOS are NF-KB-dependent, whereas regulation of RANTES mRNA is independent of NF-κB but is positively regulated by JNK. IL-1β-induced mRNA increases in COX-2 mRNA are both NF-κB- and MAPK-independent but the translation of COX-2 protein is NF-κB-dependent. This pattern of signaling due to a single stimulus exposed the complexities of regulating inflammatory genes in IEC.