Therapeutic effect of whole bear bile and its components against croton oil-induced rectal inflammation in rats

Bear bile has been used as a therapeutic for cerebral and coronary thrombosis, convulsion, hepatitis, jaundice, and abscess in traditional oriental medicine. In recent decades, the effects of bile acids on cancer, cholestasis, and liver injury have been investigated in many studies. In this study, we investigated the anti-inflammatory effects of whole bear bile (WBB) and its two major components, chenodeoxycholic acid (CDCA) and ursodeoxycholic acid (UDCA), on rectal inflammation in rats. Bile acids in WBB were quantitatively analyzed by HPLC. Rectal inflammation was induced in male Sprague-Dawley rats by insertion of croton oil-saturated cotton tips. WBB, UDCA or CDCA solution was orally administered to rats one hour after induction of rectal inflammation. Rats were sacrificed 4 or 24 hours after induction of rectal inflammation. The evaluation included measurement of weight and thickness of rectum and histopathologic examination of rectal tissue. Furthermore, we examined the inhibitory effect of WBB, UDCA or CDCA against NO production in LPS-stimulated RAW 264.7 cells. The contents of UDCA and CDCA in WBB were 39.26 μg/mg and 47.11 μg/mg, respectively. WBB treatment significantly reduced the weight and thickness of rectum compared with UDCA or CDCA treatment. The inhibition of NO production by WBB, UDCA and CDCA in LPS-stimulated RAW 264.7 cells was much higher than that by the control. And, WBB treatment suppressed the induction of NO synthase in rectum homogenates. These results suggest that the anti-inflammatory effect of WBB is related to the suppression of NO synthase induction and the inhibition of NO production by UDCA, CDCA and other bile acids of WBB.