Interleukin-1, interleukin-8, tumour necrosis factor alpha and interferon gamma stimulate DNA synthesis but have no effect on apoptosis in small-intestinal cell lines

Objectives Cytokines stimulate lymphocyte cell proliferation and affect cel l division in several other cell types. Helicobacter pylori-induced gastrit is and coeliac disease are characterized by an increased cell proliferation in association with an increased production of proinflammatory cytokines, which could contribute to these cell kinetic changes. Our aim is to examine in vitro whether cytokines usually present in the gastrointestinal mucosa affect DNA synthesis and apoptosis in a rat and a human small-intestinal ce ll line. Methods IEC-6 and FHs-74 cells were incubated for 24 h with 10(-13) -10(-9) M of tumour necrosis factor alpha (TNF-alpha), interleukin-1 beta (IL-1 be ta), interleukin-2 (IL-2), interleukin-6 (IL-6), interleukin-8 (IL-8), tran sforming growth factor-beta (TGF-beta) and interferon gamma (IFN-gamma). IE C-6 cells were also incubated with 10(-13)-10(-9) M of interleukin-1 alpha (IL-1 alpha) and 10(-8) M Of interleukin-1 receptor antagonist (IL-1ra), Th e cells were labelled with H-3-methyl thymidine for the final 4 hours, and then processed for autoradiography. DNA synthesis was evaluated by the labe lling index (LI%). Apoptosis was evaluated in IEC-6 cells by changes in mem brane lipid asymmetry using annexin-V binding to externalized phosphatidyls erine (flow cytometry) and by estimating the caspase activity. Results TNF-alpha, IL-1 beta, IL-8 and IFN-gamma significantly and markedly increased the LI, even at low concentrations (P < 0.0001), in both IEC-6 a nd FHs-74 cells, as did IL-1<alpha> in IEC-6 cells. TGF-beta significantly reduced the LI in both cell lines (P < 0.0001), whereas IL-2, IL-6 and IL-1 ra did not affect DNA synthesis significantly. None of IL-1<beta>, IL-8, TN F-alpha or IFN-gamma affected apoptosis in IEC-6 cells. Conclusion TNF-alpha, IL-1 alpha, IL-1 beta, 1L-8 and IFN-gamma stimulated DNA synthesis in a human and a rat small-intestinal cell line. The cytokine s exert their mitogenic action directly on the intestinal cells via specifi c receptors, Our findings indicate that pro-inflammatory cytokines may part icipate in the regulation of the gastrointestinal epithelial cell prolifera tion in health and disease. Eur J Gastroenterol Hepatol 13:551 - 559 (C) 20 01 Lippincott Williams & Wilkins.