IL-1 beta-induced apoptosis in rat gastric enterochromaffin-like cells is mediated by iNOS, NF-kappa B and Bax protein

Background & Aims: Enterochromaffin-like (ECL) cells are histamine-containing endocrine cells in the gastric mucosa. Previous studies have shown that the proinflammatory cytokine interleukin (IL)-1 beta present during chronic gastritis inhibits histamine synthesis in ECL cells and leads to sustained functional impairment. This study investigated the effects of IL-1 beta on ECL cell apoptosis and the related signal-transduction mechanisms. Methods: ECL cells were isolated by pronase digestion and a combination of elutriation, gradient centrifugation, and 48-hour culture (purity greater than or equal to 90%). Apoptosis was measured by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling reaction and cell death detection enzyme-linked immunosorbent assay. Results: IL-1 beta (100 pg/ mi) increased the rate of programmed cell death 2-3 fold in ECL cells after 24 hours of incubation (total of 12%-14%). This effect was completely inhibited by the NF-kappa B inhibitor, proteasome inhibitor I, and the nitric oxide synthase inhibitor (iNOS) N-G-monomethyl-L-arginine (10(-4) mol/L), but not by the caspase 3 inhibitor, Asp-Glu-Val-Asp-CHO. Western blot analysis, reverse-transcription polymerase chain reaction (PCR), and in situ PCR showed that IL-1 beta induced gene expression (after 2-4 hours) and protein synthesis (6-18 hours) of the iNOS isoform in ECL cells. Bax protein expression was increased in response to IL-1 beta. In contrast, bcl-2 gene expression was increased in response to basic fibroblast growth factor, which has been shown to counteract IL-1 beta- induced apoptosis. Conclusions: These data suggest that IL-1 beta induces programmed cell death in isolated rat ECL cells via activation of NF-kappa B, iNOS, and the Bax protein.