[Chronic cholestatic liver diseases : Differential diagnosis, pathogenesis and current treatment in adults]. / Chronische cholestatische Leberkrankheiten : Differenzialdiagnose, Pathogenese und aktuelle Therapie beim Erwachsenen.

In the long-term course chronic cholestasis regularly leads to fibrotic restructuring and ultimately to functional failure of the liver, independent of the cause. Cholestatic diseases are often clinically asymptomatic. In order to avoid progression, early diagnosis of the underlying disease and a targeted therapy are therefore decisive. The differential diagnoses of chronic cholestasis are broad; therefore, algorithms are of assistance in the diagnostic work-up. A better understanding of the pathogenesis is now leading to the development of new therapeutic agents in addition to ursodeoxycholic acid, which has long been known for its anticholestatic effects. Obeticholic acid and, in the near future, bezafibrate are therapeutic options. The possibilities for genetic diagnostics of unclear cholestasis syndromes improve the understanding of the pathogenesis of many diseases and are being introduced increasingly earlier into the clinical routine.

Tauroursodeoxycholic acid exerts anticholestatic effects by a cooperative cPKC alpha-/PKA-dependent mechanism in rat liver.

OBJECTIVE: Ursodeoxycholic acid (UDCA) exerts anticholestatic effects in part by protein kinase C (PKC)-dependent mechanisms. Its taurine conjugate, TUDCA, is a cPKC alpha agonist. We tested whether protein kinase A (PKA) might contribute to the anticholestatic action of TUDCA via cooperative cPKC alpha-/PKA-dependent mechanisms in taurolithocholic acid (TLCA)-induced cholestasis. METHODS: In perfused rat liver, bile flow was determined gravimetrically, organic anion secretion spectrophotometrically, lactate dehydrogenase (LDH) release enzymatically, cAMP response-element binding protein (CREB) phosphorylation by immunoblotting, and cAMP by immunoassay. PKC/PKA inhibitors were tested radiochemically. In vitro phosphorylation of the conjugate export pump, Mrp2/Abcc2, was studied in rat hepatocytes and human Hep-G2 hepatoma cells. RESULTS: In livers treated with TLCA (10 micromol/l)+TUDCA (25 micromol/l), combined inhibition of cPKC by the cPKC-selective inhibitor Gö6976 (100 nmol/l) or the non-selective PKC inhibitor staurosporine (10 nmol/l) and of PKA by H89 (100 nmol/l) reduced bile flow by 36% (p<0.05) and 48% (p<0.01), and secretion of the Mrp2/Abcc2 substrate, 2,4-dinitrophenyl-S-glutathione, by 31% (p<0.05) and 41% (p<0.01), respectively; bile flow was unaffected in control livers or livers treated with TUDCA only or TLCA+taurocholic acid. Inhibition of cPKC or PKA alone did not affect the anticholestatic action of TUDCA. Hepatic cAMP levels and CREB phosphorylation as readout of PKA activity were unaffected by the bile acids tested, suggesting a permissive effect of PKA for the anticholestatic action of TUDCA. Rat and human hepatocellular Mrp2 were phosphorylated by phorbol ester pretreatment and recombinant cPKC alpha, nPKC epsilon, and PKA, respectively, in a staurosporine-sensitive manner. CONCLUSION: UDCA conjugates exert their anticholestatic action in bile acid-induced cholestasis in part via cooperative post-translational cPKC alpha-/PKA-dependent mechanisms. Hepatocellular Mrp2 may be one target of bile acid-induced kinase activation.