S-adenosylmethionine and cAMP confer differential cytoprotection against bile acid-induced apoptosis in canine renal tubular cells and primary rat hepatocytes.
Cholestasis results in the accumulation of cytotoxic bile acids in the body. The cytoprotective effect of S-adenosylmethionine (SAMe) and cAMP were compared in two in vitro models of bile acid-induced apoptosis. Primary cultures of rat hepatocytes and canine renal tubular cells (Madin-Darby canine kidney [MDCK] cells stably transfected with the conjugated bile salt transporter, sodium [Na+]/taurocholate cotransporting polypeptide [Ntcp]) were treated with conjugated bile acids and monitored for apoptosis. Glycine-conjugated bile acids caused similar amounts of apoptosis, whereas taurine-conjugated bile acids were five to 10 times more toxic in MDCK-Ntcp cells than in hepatocytes. Treatment with the 1,4-butanedisulfonate salt of SAMe (500 microM) or the stable chlorophenylthio-cAMP analogue (100 microM) inhibited bile acid-induced apoptosis in hepatocytes by 70% and 40%, respectively. In MDCK-Ntcp cells, SAMe inhibited apoptosis by 20%, but cAMP was without effect. Immunoblotting for activation of putative survival kinases in cAMP-treated cells (phosphorylated protein kinase B [Akt] or mitogen-activated protein kinase [MAPK]) was done using phosphospecific antibodies. cAMP increased Akt phosphorylation threefold in hepatocytes but not in MDCK-Ntcp cells. Activation of p42/p44 MAPK was inhibited by cAMP in both cells. SAMe protects against bile acid-induced apoptosis in hepatocytes and MDCK-Ntcp cells. The cytoprotective effect of cAMP is seen only in hepatocytes and may reflect tissue-specific activation of Akt.
Webster
Cynthia R L
CR
Department of Clinical Sciences, Tufts University, 200 Westboro Road, North Grafton, MA 01536, USA.
Boria
Pedro
P
Usechak
Paul
P
Anwer
M Sawkat
MS
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001647:Bile Acids and Salts / Q000494:pharmacology; D002460:Cell Line / Q000187:drug effects; D002478:Cells, Cultured; D002779:Cholestasis / Q000378:metabolism / Q000662:veterinary; D000242:Cyclic AMP / Q000008:administration & dosage / Q000494:pharmacology*; D004283:Dog Diseases / Q000378:metabolism; D004285:Dogs; D022781:Hepatocytes / Q000187:drug effects; D007668:Kidney / Q000166:cytology / Q000187:drug effects; D008099:Liver / Q000166:cytology / Q000187:drug effects; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D012436:S-Adenosylmethionine / Q000008:administration & dosage / Q000494:pharmacology*
D001647:Bile Acids and Salts; D012436:S-Adenosylmethionine; D000242:Cyclic AMP; D020928:Mitogen-Activated Protein Kinases