Acute and chronic effects of different bile acids on indomethacin-induced intestinal inflammation.

The role of bile acids in the pathogenesis of bowel inflammation is unknown. The objective of this study was to determine whether urso- (UDC), cheno- (CDC), and taurochenodeoxycholic acid (TCDC) exert a pro- or antiinflammatory action in the acute and chronic phase of the indomethacin model of a long lasting ileitis in rats. Short-term and long-term inflammatory responses (48 h and 10 days, respectively) after two subcutaneous indomethacin (Indo) injections were elicited in rat small bowel and mesentery. To distinguish between common and model-specific effects bile acids were tested also in another model of acute inflammation induced by mesenteric superfusion with leukotriene B4(LTB4). The number of adherent and emigrated leukocytes, leukocyte rolling velocity, and venular wall shear rate were monitored in normal and inflamed postcapillary venules, and fecal pH of ileal contents which has been shown to correlate with degree of inflammation was measured, 6.5- and 2.3-fold increases in leukocyte adherence and comparable increments in leukocyte emigration were observed 48 h and ten days after indomethacin treatment, respectively. UDC, CDC, and TCDC (10 mg/kg) given daily from Indo administration until the experiment attenuated the leukocyte adherence and emigration responses elicited by indomethacin in short- and long-term inflammation. This effect was accompanied by a significant increase of fecal pH which had been lowered by indomethacin. None of the bile acids reduced the LTB4-induced increases in adherence and emigration. Oral administration of UDC, CDC, and TCDC reduces leukocyte adhesion and emigration in acute and chronic stages of Indo-induced inflammation. This could be due to the alkalizing effect of these bile acids on fecal pH which has been shown to correlate with a decrease of leukocyte-endothelial cell interactions but--according to the missing effectiveness in another model of intestinal inflammation--not to specific influences on leukocyte-endothelial cell adhesion.