Polyamine depletion induces rapid NF-kappa B activation in IEC-6 cells

The proliferation of the rat intestinal mucosal IEC-6 cell line requires po lyamines, whose synthesis is catalyzed by the enzyme ornithine decarboxylas e (ODC). ODC inhibition leads to polyamine depletion, as well as inhibition of both cell proliferation and apoptosis by regulating gene expression. Th e NF-kappaB transcription factor regulates genes involved in apoptotic, imm une, and inflammatory responses. In the present study we tested the hypothe sis that NF-KB is activated following ODC inhibition. We found that the inh ibition of ODC by a-difluoromethylornithine (DFMO) resulted in a similar to 50% decrease in intracellular putrescine levels within Ih. NF-KB is activa ted by DFMO through the degradation of the inhibitory protein I kappaB alph a that sequesters NF-kappaB in the cytoplasm. The DFMO-induced NF-KB comple xes contain the p65 and p50 members of the Rel protein family. DFMO-induced NF-kappaB activation was accompanied by the translocation of p65 from the cytoplasm into the nucleus. DFMO selectively inhibited a gene reporter cons truct dependent on the kappaB site present in the HLA-B7 gene. In contrast, DFMO had no effect on a gene reporter construct dependent on the kappaB si te present in the interleukin-8 gene. Thus, we report that ODC inhibition a ctivates the NF-KB transcription factor, which may mediate the altered phys iological state of intestinal cells that occurs following polyamine depleti on.