Bile acids inhibit tumour necrosis factor α‐induced interleukin‐8 production in human colon epithelial cells

To clarify the regulatory mechanism of the production of various inflammatory mediators by intestinal epithelial cells, the effect of bile acids (tauroursodeoxycholate, TUDC; taurochenodeoxycholate, TCDC; and taurocholate, TC) on the cytokine‐induced production of interleukin (IL)‐8 in a human colon epithelial cell line (HT‐29) was examined. HT‐29 cells were incubated for 24 h in a culture medium containing tumour necrosis factor α (TNFα; 1 ng/mL) and/or interleukin (IL)‐1 β (1 ng/mL) in the presence or absence of bile acids. The IL‐8 concentration in the medium was measured by an enzyme‐linked immunosorbent assay. The binding assay of TNFα was performed using [125I]‐TNFα (100 pmol/L). Interleukin‐8 production during incubation with TNFα was markedly reduced in the presence of 0.5 and 1 mmol/L TUDC, 0.5 and 1 mmol/L TCDC and 0.5 and 1 mmol/L TC, by 56, 85, 86, 91, 37 and 70%, respectively. The IL‐8 production during incubation with IL‐1ß was not significantly reduced in the presence of these bile acids. The specific binding of TNFα to cells was inhibited 33, 47, and 14% by 1 mmol/L TUDC, TCDC and TC, respectively. These findings suggest that bile acids inhibit TNFα‐induced IL‐8 production by the colonic cells. The suppression may be partly due to inhibition of TNFα binding to the cells by bile acids.