Taurolithocholic acid exerts cholestatic effects via phosphatidylinositol 3-kinase-dependent mechanisms in perfused rat livers and rat hepatocyte couplets.
Taurolithocholic acid (TLCA) is a potent cholestatic agent. Our recent work suggested that TLCA impairs hepatobiliary exocytosis, insertion of transport proteins into apical hepatocyte membranes, and bile flow by protein kinase Cepsilon (PKCepsilon)-dependent mechanisms. Products of phosphatidylinositol 3-kinases (PI3K) stimulate PKCepsilon. We studied the role of PI3K for TLCA-induced cholestasis in isolated perfused rat liver (IPRL) and isolated rat hepatocyte couplets (IRHC). In IPRL, TLCA (10 micromol/liter) impaired bile flow by 51%, biliary secretion of horseradish peroxidase, a marker of vesicular exocytosis, by 46%, and the Mrp2 substrate, 2,4-dinitrophenyl-S-glutathione, by 95% and stimulated PI3K-dependent protein kinase B, a marker of PI3K activity, by 154% and PKCepsilon membrane binding by 23%. In IRHC, TLCA (2.5 micromol/liter) impaired canalicular secretion of the fluorescent bile acid, cholylglycylamido fluorescein, by 50%. The selective PI3K inhibitor, wortmannin (100 nmol/liter), and the anticholestatic bile acid tauroursodeoxycholic acid (TUDCA, 25 micromol/liter) independently and additively reversed the effects of TLCA on bile flow, exocytosis, organic anion secretion, PI3K-dependent protein kinase B activity, and PKCepsilon membrane binding in IPRL. Wortmannin also reversed impaired bile acid secretion in IRHC. These data strongly suggest that TLCA exerts cholestatic effects by PI3K- and PKCepsilon-dependent mechanisms that are reversed by tauroursodeoxycholic acid in a PI3K-independent way.
Beuers
Ulrich
U
Department of Medicine II-Grosshadern, Klinikum of the University of Munich, 81377 Munich, Germany. beuers@med2.med.uni-muenchen.de
Denk
Gerald U
GU
Soroka
Carol J
CJ
Wimmer
Ralf
R
Rust
Christian
C
Paumgartner
Gustav
G
Boyer
James L
JL
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D000838:Anions; D001647:Bile Acids and Salts / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002756:Cholagogues and Choleretics / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005089:Exocytosis; D022781:Hepatocytes / Q000201:enzymology* / Q000378:metabolism; D006735:Horseradish Peroxidase / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology* / Q000378:metabolism; D008297:Male; D010477:Perfusion; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011233:Precipitin Tests; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases; D021381:Protein Transport; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D013655:Taurochenodeoxycholic Acid / Q000494:pharmacology; D013658:Taurolithocholic Acid / Q000737:chemistry* / Q000378:metabolism; D013997:Time Factors; D000077191:Wortmannin
D000730:Androstadienes; D000838:Anions; D001647:Bile Acids and Salts; D002756:Cholagogues and Choleretics; D004791:Enzyme Inhibitors; D006735:Horseradish Peroxidase; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D013655:Taurochenodeoxycholic Acid; D013658:Taurolithocholic Acid; D000077191:Wortmannin; C031655:ursodoxicoltaurine