BACKGROUND - Sepsis and endotoxemia are associated with increased mucosal production of complement component C3; the enterocyte may be a source of C3 in these conditions.
OBJECTIVE - To test the hypothesis that interleukin 1beta (IL-1beta) and tumor necrosis factor alpha (TNF-alpha) regulate the production of C3 in the enterocyte at the transcriptional level and that this regulation is potentiated by interferon gamma (IFN-gamma).
METHODS - Cultured Caco-2 cells, a human intestinal epithelial cell line, were treated with various concentrations of human recombinant IL-1beta (0.005-1.25 ng/mL) or TNF-alpha (1-1000 U/mL) with or without the addition of IFN-gamma (250 U/mL). C3 levels in the culture medium were measured by enzyme-linked immunosorbent assay and cellular messenger RNA levels by Northern blot analysis.
RESULTS - Treatment of the Caco-2 cells with IL-1beta or TNF-alpha resulted in a time- and dose-dependent increase in C3 production. The use of IFN-gamma alone did not affect C3 production but potentiated the effect of IL-1beta and TNF-alpha in a synergistic manner. C3 messenger RNA levels were increased following stimulation with either cytokine.
CONCLUSIONS - C3 production in the enterocyte is regulated by IL-1beta and TNF-alpha at the transcriptional level, and this response is potentiated by IFN-gamma. The results suggest that C3 production in the intestinal mucosa may be regulated locally by cytokines in a paracrine or autocrine manner.