Hypochlorous acid-mediated mitochondrial dysfunction and apoptosis in human hepatoma HepG2 and human fetal liver cells: role of mitochondrial permeability transition.
Liver cirrhosis is often preceded by overt signs of hepatitis, including parenchymal cell inflammation and infiltration of polymorphonuclear (PMN) leukocytes. Activated PMNs release both reactive oxygen species and reactive halogen species, including hypochlorous acid (HOCl), which are known to be significantly cytotoxic due to their oxidizing potential. Because the role of mitochondria in the hepatotoxicity attributed to HOCl has not been elucidated, we investigated the effects of HOCl on mitochondrial function in the human hepatoma HepG2 cell line, human fetal liver cells, and isolated rat liver mitochondria. We show here that HOCl induced mitochondrial dysfunction, and apoptosis was dependent on the induction of the mitochondrial permeability transition (MPT), because HOCl induced mitochondrial swelling and collapse of the mitochondrial membrane potential with the concomitant release of cytochrome c. These biochemical events were inhibited by the classical MPT inhibitor cyclosporin A (CSA). Cell death induced by HOCl exhibited several classical hallmarks of apoptosis, including annexin V labeling, caspase activation, chromatin condensation, and cell body shrinkage. The induction of apoptosis by HOCl was further supported by the finding that CSA and caspase inhibitors prevented cell death. For the first time, these results show that HOCl activates the MPT, which leads to the induction of apoptosis and provides a novel insight into the mechanisms of HOCl-mediated cell death at sites of chronic inflammation.
Whiteman
Matthew
M
Department of Biochemistry, Faculty of Medicine, National University of Singapore, 8 Medical Drive, Republic of Singapore 117597. bchwnl@nus.edu.sg
Rose
Peter
P
Siau
Jia Ling
JL
Cheung
Nam Sang
NS
Tan
Gek San
GS
Halliwell
Barry
B
Armstrong
Jeffrey S
JS
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001865:Bongkrekic Acid / Q000494:pharmacology; D006528:Carcinoma, Hepatocellular; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D056486:Chemical and Drug Induced Liver Injury / Q000209:etiology; D016572:Cyclosporine / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism; D006801:Humans; D006997:Hypochlorous Acid / Q000494:pharmacology*; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000196:embryology; D008564:Membrane Potentials / Q000187:drug effects; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000502:physiology; D008933:Mitochondrial Swelling / Q000187:drug effects; D010539:Permeability / Q000187:drug effects; D051381:Rats
D001865:Bongkrekic Acid; D006997:Hypochlorous Acid; D016572:Cyclosporine; D045304:Cytochromes c; C505407:CASP3 protein, human; C505520:CASP7 protein, human; C505410:Casp3 protein, rat; D053148:Caspase 3; D053179:Caspase 7; D020169:Caspases