Biochemical and Biophysical Research Communications, 10 August 2012, Vol.424(4), pp.758-764
► We demonstrate substantial antiapoptotic effects of TβMCA on hepatocyte apoptosis. ► TβMCA prevents bile acid-induced breakdown of the mitochondrial membrane potential (MMP). ► TβMCA also restores the MMP when the free fatty acid palmitate is used as a hepatotoxin. β-Muricholic acid (βMCA) is a trihydroxylated bile acid that constitutes the major bile acid in rat and mouse. βMCA is more hydrophilic than ursodeoxycholic acid and has been evaluated for dissolution of cholesterol gallstones. Since it is unknown if βMCA has beneficial effects on hepatocyte cell death we determined the effect of tauro-βMCA (TβMCA) on apoptosis . Human Ntcp-transfected HepG2 cells and primary hepatocytes from rat and mouse were incubated with the proapoptotic glycochenodeoxycholic acid (GCDCA) as well as the free fatty acid palmitate in the absence and presence of TβMCA. Apoptosis was quantified using caspase 3/7-assays and after Hoechst 33342 staining. The mitochondrial membrane potential (MMP) was measured fluorometrically using JC-1 (5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethyl-benzimidazol-carbocyaniniodide). Immunoblotting was performed against the proapoptotic Bcl-2-protein Bax. In Ntcp-HepG2 cells, GCDCA markedly increased apoptosis after 4 h. Co-incubation with TβMCA reduced apoptosis to 49% ( 〈 0.01 vs. GCDCA, each; = 6). While GCDCA (100 μmol/L) reduced the MMP to 34% after 6 h, combination treatment with TβMCA restored the MMP to control levels at all time points ( = 4). TβMCA also restored breakdown of the MMP induced by palmitate. GCDCA induced a translocation of Bax from the cytosol to mitochondria that was inhibited by simultaneous treatment with TβMCA in eqimolar concentrations. TβMCA restricts hepatocellular apoptosis induced by low micromolar concentrations of GCDCA or palmitate via inhibition of Bax translocation to mitochondria and preservation of the MMP. Thus, further studies are warranted to evaluate a potential use of TβMCA in ameliorating liver injury in cholestasis.
Cholestasis ; Bile Acid ; Apoptosis ; Mitochondrial Membrane Potential ; Biology ; Chemistry ; Anatomy & Physiology
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