cAMP inhibits bile acid-induced apoptosis by blocking caspase activation and cytochrome c release.
We have previously shown that cAMP protects against bile acid-induced apoptosis in cultured rat hepatocytes in a phosphoinositide 3-kinase (PI3K)-dependent manner. In the present studies, we investigated the mechanisms involved in this anti-apoptotic effect. Hepatocyte apoptosis induced by glycodeoxycholate (GCDC) was associated with mitochondrial depolarization, activation of caspases, the release of cytochrome c from the mitochondria, and translocation of BAX from the cytosol to the mitochondria. cAMP inhibited GCDC-induced apoptosis, caspase 3 and caspase 9 activation, and cytochrome c release in a PI3K-dependent manner. cAMP activated PI3K in p85 immunoprecipitates and resulted in PI3K-dependent activation of the survival kinase Akt. Chemical inhibition of Akt phosphorylation with SB-203580 partially blocked the protective effect of cAMP. cAMP resulted in wortmannin-independent phosphorylation of BAD and was associated with translocation of BAD from the mitochondria to the cytosol. These results suggest that GCDC-induced apoptosis in cultured rat hepatocytes proceeds through a caspase-dependent intracellular stress pathway and that the survival effect of cAMP is mediated in part by PI3K-dependent Akt activation at the level of the mitochondria.
Department of Clinical Science, Tufts University School of Veterinary Medicine, North Grafton, Massachusetts 01536, USA. cynthia.leveille-webster@tufts.edu
Cynthia R L
CR
Webster
Paul
P
Usechak
M Sawkat
MS
Anwer
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001647:Bile Acids and Salts / Q000378:metabolism / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000378:metabolism; D061945:Caspase Inhibitors; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000494:pharmacology*; D003574:Cytochrome c Group / Q000037:antagonists & inhibitors*; D019610:Cytoprotection / Q000502:physiology; D004789:Enzyme Activation / Q000187:drug effects; D006002:Glycodeoxycholic Acid / Q000494:pharmacology; D022781:Hepatocytes / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein
D001647:Bile Acids and Salts; D002352:Carrier Proteins; D061945:Caspase Inhibitors; D000242:Cyclic AMP; D003574:Cytochrome c Group; D006002:Glycodeoxycholic Acid; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein; C494821:Bad protein, rat; C494828:Bax protein, rat; C494813:Bcl2l1 protein, rat; C494920:Akt1 protein, rat