Vallejo Marta, Briz Oscar, Serrano Maria A, Monte Maria J, Marin Jose J G
Laboratory of Experimental Hepatology and Drug Targeting, University of Salamanca, Salamanca, Spain.
J Hepatol. 2006 Jun;44(6):1150-7. doi: 10.1016/j.jhep.2005.09.017. Epub 2005 Nov 7.
BACKGROUND/AIMS: Progesterone metabolites such as 5alpha-pregnan-3alpha-ol-20-one (PM4) are elevated in serum of women with intrahepatic cholestasis of pregnancy (ICP).
METHODS/RESULTS: When assayed in isolated perfused rat liver, PM4 did not induce cholestasis, whereas sulfated PM4 (PM4-S), which unlike PM4 is secreted into bile, reduced bile flow and bile acid (BA) output. Whether PM4-S inhibited the bile salt export pump (BSEP) was investigated. Radiolabeled methylesters (ME) of cholic acid and chenodeoxycholic acid were taken up by Xenopus laevis oocytes co-expressing rat BSEP and human carboxylesterase-1 (CES1), efficiently hydrolyzed to free BAs by CES1 and subsequently exported by BSEP. Rifampicin or cyclosporin A in the extracellular medium had no effect on BA efflux. In contrast, estradiol 17beta-D-glucuronide and several progesterone metabolites, including PM4-S, induced a marked non-competitive trans-inhibition of BSEP-mediated BA efflux (Ki=20-60 microM). Mitochondrial activity was markedly impaired in oocytes incubated with BA-MEs, but not with free BAs. Co-expression of CES1 and BSEP partly protected oocytes from this toxic effect. Trans-inhibition of BSEP abolished this protection.
Several estrogens and progesterone metabolites are able to induce trans-inhibition of BSEP and the subsequent toxicity induced by the accumulation of BAs, which may play a role in the etiopathogenesis of ICP.
背景/目的：妊娠肝内胆汁淤积症（ICP）女性血清中孕酮代谢产物如5α-孕烷-3α-醇-20-酮（PM4）水平升高。
方法/结果：在离体灌注大鼠肝脏中检测时，PM4未诱导胆汁淤积，而与PM4不同的是，硫酸化PM4（PM4-S）分泌到胆汁中，可降低胆汁流量和胆汁酸（BA）输出量。研究了PM4-S是否抑制胆盐输出泵（BSEP）。共表达大鼠BSEP和人羧酸酯酶-1（CES1）的非洲爪蟾卵母细胞摄取胆酸和鹅去氧胆酸的放射性标记甲酯（ME），由CES1有效地水解为游离BA，随后由BSEP输出。细胞外培养基中的利福平或环孢素A对BA流出无影响。相反，17β-D-葡萄糖醛酸雌二醇和几种孕酮代谢产物，包括PM4-S，诱导对BSEP介导的BA流出有明显的非竞争性反式抑制作用（Ki = 20 - 60 μM）。用BA-ME孵育的卵母细胞中线粒体活性明显受损，但用游离BA孵育则不然。CES1和BSEP的共表达部分保护卵母细胞免受这种毒性作用。BSEP的反式抑制消除了这种保护作用。
几种雌激素和孕酮代谢产物能够诱导BSEP的反式抑制以及随后由BA积累引起的毒性，这可能在ICP的发病机制中起作用。
