Human hepatic mitochondria generate reactive oxygen species and undergo the permeability transition in response to hydrophobic bile acids.
OBJECTIVE
Hydrophobic bile acids accumulate in the liver during cholestasis and are believed to cause hepatocellular necrosis and apoptosis in part through induction of the mitochondrial permeability transition (MPT) and the mitochondrial generation of oxidative stress. The purpose of this study was to determine if human hepatic mitochondria respond to bile acids in this manner.


METHODS
The MPT was measured spectrophotometrically and morphologically in normal human liver mitochondria exposed to glycochenodeoxycholic acid (GCDC) with and without cyclosporin A, an inhibitor of the MPT, antioxidants, and tauroursodeoxycholic acid (TUDC). Hydroperoxide generation was measured by dichlorofluorescein fluorescence. Cytochrome c and apoptosis-inducing factor were assessed by immunoblotting.


RESULTS
GCDC induced the MPT in a dose-dependent manner, which was inhibited by cyclosporin A, alpha-tocopherol, beta-carotene, idebenone, and TUDC. GCDC stimulated reactive oxygen species generation and release of cytochrome c and apoptosis-inducing factor, which were significantly inhibited by the antioxidants, cyclosporin A, and TUDC.


CONCLUSIONS
Mitochondrial pathways of cell death are stimulated in human hepatic mitochondria exposed to GCDC consistent with the role of mitochondrial dysfunction in the pathogenesis of cholestatic liver injury. These results parallel those reported in rodents, supporting the extrapolation of mechanistic studies of bile acid toxicity from rodent to humans.
Sokol
Ronald J
RJ
Department of Pediatrics, University of Colorado School of Medicine, and the Pediatric General Clinical Research Center, The Children's Hospital, Denver, Colorado 80218-1088, USA. Sokol.Ronald@tchden.org
Dahl
Rolf
R
Devereaux
Michael W
MW
Yerushalmi
Baruch
B
Kobak
Gregory E
GE
Gumpricht
Eric
E
D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001647:Bile Acids and Salts / Q000494:pharmacology*; D016572:Cyclosporine / Q000494:pharmacology; D045304:Cytochromes c; D004305:Dose-Response Relationship, Drug; D005999:Glycochenodeoxycholic Acid / Q000494:pharmacology; D022781:Hepatocytes / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology; D006801:Humans; D006861:Hydrogen Peroxide; D007473:Ion Channels; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013053:Spectrophotometry; D013655:Taurochenodeoxycholic Acid / Q000494:pharmacology
D000975:Antioxidants; D001647:Bile Acids and Salts; D007473:Ion Channels; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D017382:Reactive Oxygen Species; D013655:Taurochenodeoxycholic Acid; C031655:ursodoxicoltaurine; D005999:Glycochenodeoxycholic Acid; D016572:Cyclosporine; D045304:Cytochromes c; D006861:Hydrogen Peroxide