Relationship between cholestasis and altered progesterone metabolism in the placenta-maternal liver tandem

In intrahepatic cholestasis of pregnancy (ICP), there are elevated maternal serum levels of total bile acids, progesterone, and some sulfated metabolites, such as allopregnanolone sulfate, which inhibits canalicular function. To investigate the relationship between cholestasis and the expression of crucial enzymes involved in progesterone metabolism in the liver and placenta. Obstructive cholestasis was induced by bile duct ligation (BDL). RT-qPCR (mRNA) and western blot (protein) were used to determine expression levels. Srd5a1 and Akr1c2 enzymatic activities were assayed by substrate disappearance (progesterone and 5α-dihydroprogesterone, respectively), measured by HPLC-MS/MS. BDL induced decreased Srd5a1 and Akr1c2 expression and activity in rat liver, whereas both enzymes were up-regulated in rat placenta. Regarding sulfotransferases, Sult2b1 was also moderately up-regulated in the liver. In placenta from ICP patients, SRD5A1 and AKR1C2 expression was elevated, whereas both genes were down-regulated in liver biopsies collected from patients with several liver diseases accompanied by cholestasis. SRD5A1 and AKR1C2 expression was not affected by incubating human hepatoma HepG2 cells with FXR agonists (chenodeoxycholic acid and GW4064). Knocking-out Fxr in mice did not reduce Srd5a1 and Akr1c14 expression, which was similarly down-regulated by BDL. SRD5A1 and AKR1C2 expression was markedly altered by cholestasis. This was enhanced in the placenta but decreased in the liver, which is not mediated by FXR. These results suggest that the excess of progesterone metabolites in the serum of ICP patients can involve both enhanced placental production and decreased hepatic clearance. The latter may also occur in other cholestatic conditions.