Hyperthermia-induced heat shock activates the transcription factor C/EBP-β and augments IL-6 production in human intestinal epithelial cells

Interleukin (IL)-6 production is increased in gut mucosa during sepsis and endotoxemia. The heat shock response augments IL-6 production under these conditions, but the mechanism is not known. We hypothesized that heat shock stimulates IL-6 production in enterocytes by increasing expression and activity of the transcription factor C/EBP. Cultured Caco-2 cells, a human intestinal epithelial cell line, underwent induction of the heat shock response by hyperthermia (43°C for 1 hour). Other cells were kept at 37°C. Cells were then treated with 0.5 ng/mL human recombinant IL-1β for 4 hours. C/EBP-β and δ DNA binding activity was determined by electrophoretic mobility shift assay and supershift analysis. In additional experiments, Caco-2 cells were transfected with expression plasmids for C/EBP-β and δ, after which cells were subjected to hyperthermia and treatment with IL-1β. C/EBP-β, but not δ, protein levels and DNA binding activity were increased in Caco-2 cells expressing the heat shock response. Induction of the heat shock response augmented IL-6 production in IL-1β–treated cells overexpressing C/EBP-β, but not δ. Increased IL-6 production in IL-1β–treated enterocytes expressing the heat shock response might be caused by upregulated expression and activity of C/EBP-β. Because recent studies suggest that IL-6 might be an antiinflammatory cytokine and might exert protective effects in gut mucosa and enterocytes, understanding mechanisms by which the heat shock response augments IL-6 production might have important clinical implications.