The bile acid taurochenodeoxycholate activates a phosphatidylinositol 3-kinase-dependent survival signaling cascade.

TitleThe bile acid taurochenodeoxycholate activates a phosphatidylinositol 3-kinase-dependent survival signaling cascade.
Publication TypeJournal Article
Year of Publication2000
AuthorsRust C, Karnitz LM, PayĆ” CV, Moscat J, Simari RD, Gores GJ
JournalJ Biol Chem
Date Published2000 Jun 30
KeywordsAdenoviridae, Animals, Apoptosis, Bile Acids and Salts, Cell Survival, Dactinomycin, Dose-Response Relationship, Drug, Enzyme Activation, Glycochenodeoxycholic Acid, Immunoblotting, Luciferases, NF-kappa B, Oncogene Protein v-akt, Phosphatidylinositol 3-Kinases, Plasmids, Protein Kinase C, Protein Synthesis Inhibitors, Rats, Retroviridae Proteins, Oncogenic, Signal Transduction, Taurochenodeoxycholic Acid, Transfection, Tumor Cells, Cultured

Liver injury during cholestasis reflects a balance between the effects of toxic and nontoxic bile acids. However, the critical distinction between a toxic and nontoxic bile acid remains subtle and unclear. For example, the glycine conjugate of chenodeoxycholate (GCDC) induces hepatocyte apoptosis, whereas the taurine conjugate (TCDC) does not. We hypothesized that the dissimilar cellular responses may reflect differential activation of a phosphatidylinositol 3-kinase (PI3K)-dependent signaling pathway. In the bile acid-transporting McNtcp.24 rat hepatoma cell line, TCDC, but not GCDC, stimulated PI3K activity. Consistent with this observation, inhibition of PI3K rendered TCDC cytotoxic, and constitutive activation of PI3K rendered GCDC nontoxic. Both Akt and the atypical protein kinase C isoform zeta (PKCzeta) have been implicated in PI3K-dependent survival signaling. However, TCDC activated PKCzeta, but not Akt. Moreover, inhibition of PKCzeta converted TCDC into a cytotoxic agent, whereas overexpression of wild-type PKCzeta blocked GCDC-induced apoptosis. We also demonstrate that TCDC activated nuclear factor kappaB (NF-kappaB) in a PI3K- and PKCzeta-dependent manner. Moreover, inhibition of NF-kappaB by an IkappaB super-repressor rendered TCDC cytotoxic, suggesting that NF-kappaB is also necessary to prevent the cytotoxic effects of TCDC. Collectively, these data suggest that some hydrophobic bile acids such as TCDC activate PI3K-dependent survival pathways, which prevent their otherwise inherent toxicity.

Alternate JournalJ Biol Chem
PubMed ID10770953
Grant ListAI36079 / AI / NIAID NIH HHS / United States
CA73622 / CA / NCI NIH HHS / United States
DK41876 / DK / NIDDK NIH HHS / United States
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Jorge Moscat, Ph.D.

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