Regulation of Rat Organic Anion Transporters in Bile Salt–Induced Cholestatic Hepatitis: Effect of Ursodeoxycholate

Abstract

Hepatic uptake of organic anions, including bile salts, is mediated by members of the organic anion-transporting polypeptide (Oatp) family. In rat liver, Oatp1 (Slc21a1), Oatp2 (Slc21a5), and Oatp4 (Slca10) are expressed at the basolateral membrane of hepatocytes and may be differentially regulated under pathophysiologic conditions such as cholestasis. The aim of this study was to determine the effects of cholic acid (CA) and ursodeoxycholic acid (UDCA) on the expression of Oatp4 compared with Ntcp, Oatp1, and Oatp2. Wistar rats were fed with CA (0.5%) or both CA (0.5%) and UDCA (0.25%) for 3 weeks. Oatp expression was studied by Northern and Western blot analysis as well as immunofluorescence analysis. Transport function was compared measuring biliary secretion of 14 C-CA and 14 Ctaurocholic acid (TCA). In CA-fed animals, biliary secretion of 14 C-CA and 14 C-TCA was markedly delayed over 40 minutes compared with controls. Accordingly, Oatp4 protein was significantly down-regulated in CA-fed animals together with Oatp1 and Ntcp. Cofeeding of CA plus UDCA prevented the impairment of 14 C-CA and 14 C-TCA secretion and the downregulation of Oatp4. Oatp4 messenger RNA (mRNA) levels did not differ significantly between bile salt-fed groups, suggesting a posttranscriptional effect of CA on Oatp4 expression. In contrast to Oatp1 and Oatp4, Oatp2 protein expression was increased by CA feeding, indicating a differential regulation of Oatp transporters. In conclusion, we show that CA feeding may cause cholestasis associated with a posttranscriptional down-regulation of Oatp4. UDCA may prevent impairment of hepatic function by restoring hepatic transporter expression. (HEPATOLOGY 2003;38:187-195.)

Biotransformation of Lithocholic Acid by Rat Hepatic Microsomes: Metabolite Analysis by Liquid Chromatography/Mass Spectrometry

“…Lithocholic acid concentrations of 5 to 10 M have been reported in the liver of cholestatic patients and in rat models of biliary cholestasis (Jezequel et al, 1994;Fischer et al, 1996;Erlinger, 1997;Setchell et al, 1997;Hofmann, 2002;Berta et al, 2003;Rost et al, 2003;De Gottardi et al, 2004). A lithocholic acid concentration of 100 M was found to be saturating for hepatic microsomal MDCA formation in the present study.…”

“…In comparison, the major bile acids in human liver, which are cholic acid and CDCA, and the major bile acids in rat liver, which are cholic acid and muricholic acid, are present at concentrations that are 5 to 10 times greater (Setchell et al, 1997). Hepatic lithocholic acid concentrations are elevated in patients with cholestatic liver disease (Jezequel et al, 1994;Fischer et al, 1996;Erlinger, 1997;Hofmann, 2002;Berta et al, 2003;De Gottardi et al, 2004) and in rat models of biliary cholestasis (Setchell et al, 1997;Rost et al, 2003). The accumulation of lithocholic acid and other hydrophobic bile acids in liver has been implicated as a major factor contributing to liver injury in cholestasis because of the inherent cytotoxicity of this hydrophobic bile acid.…”

Long-Term Effect of Treating Pregnant Rats with Ursodeoxycholic Acid on the Congenital Impairment of Bile Secretion Induced in the Pups by Maternal Cholestasis

“…In adult rats fed with an excess of BAs, changes in the expression of the sinusoidal carriers involved in BA uptake have been reported previously (Rost et al, 2003). However, this did not occur in OCP pups, and hence, impaired liver uptake probably did not account for the reduction in TCAstimulated bile secretion.…”

Regulation of Mouse Organic Anion-Transporting Polypeptides (Oatps) in Liver by Prototypical Microsomal Enzyme Inducers That Activate Distinct Transcription Factor Pathways

“…Lipopolysaccharide dramatically decreases Oatp1a1, 1a4, and 1b2 mRNA expression in rats and Oatp1b2 in mice . Cholic acid, an Oatp substrate, increases Oatp1a4 but decreases Oatp1b2 protein expression in rats (Rost et al, 2003). Carbon tetrachloride decreases mRNA expression of Oatp1a1 and 1a4 in rats and mice, but not 1b2 (Geier et al, 2002;Aleksunes et al, 2005).…”