title: Nuclear translocation of endonuclease G and apoptosis-inducing factor during acetaminophen-induced liver cell injury.
abstract: Mitochondrial dysfunction and internucleosomal DNA fragmentation are well-recognized features of acetaminophen (AAP)-induced hepatocyte cell death. However, the endonucleases responsible for this effect have not been identified. Apoptosis-inducing factor (AIF) and endonuclease G are nucleases located in the intermembrane space of mitochondria. AIF is thought to trigger chromatin condensation and induce cleavage of DNA into high molecular weight fragments (50-300 kb), and endonuclease G can produce oligonucleosomal DNA fragments. Therefore, the objective of this investigation was to test the hypothesis that endonuclease G and AIF could be involved in AAP-induced nuclear DNA fragmentation. Using immunofluorescence microscopy, it was shown that in primary cultured mouse hepatocytes, endonuclease G and AIF translocated to the nucleus between 3 and 6 h after exposure to 5 mM AAP. In contrast, other mitochondrial intermembrane proteins such as cytochrome c or the second mitochondria-derived activator of caspases (Smac) did not accumulate in the nucleus. The translocation of AIF and endonuclease G correlated with mitochondrial dysfunction as indicated by the progressive loss of the mitochondrial membrane potential (measured with the JC-1 assay) and the appearance of nuclear DNA fragments in the cytosol (determined by an anti-histone ELISA). Pretreatment with 20mM N-acetylcysteine prevented mitochondrial dysfunction, the nuclear translocation of endonuclease G and AIF, and the nuclear DNA fragmentation. The data support the conclusion that endonuclease G and AIF translocate to the nucleus in response to AAP-induced mitochondrial dysfunction and may be responsible, at least in part, for the initial DNA fragmentation during AAP hepatotoxicity.
authors.affiliation: Liver Research Institute, University of Arizona, College of Medicine, Tucson, Arizona 85724, USA.
authors.forename: Mary Lynn
authors.initials: ML
authors.lastname: Bajt
authors.forename: Cathleen
authors.initials: C
authors.lastname: Cover
authors.forename: John J
authors.initials: JJ
authors.lastname: Lemasters
authors.forename: Hartmut
authors.initials: H
authors.lastname: Jaeschke
mesh_terms: D000082:Acetaminophen / Q000633:toxicity*; D000111:Acetylcysteine / Q000494:pharmacology; D021581:Active Transport, Cell Nucleus; D000818:Animals; D051033:Apoptosis Inducing Factor / Q000378:metabolism*; D051017:Apoptosis Regulatory Proteins; D001562:Benzimidazoles / Q000378:metabolism; D002232:Carbocyanines / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000187:drug effects* / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D045304:Cytochromes c / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D004706:Endodeoxyribonucleases / Q000378:metabolism*; D022781:Hepatocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D008809:Mice, Inbred C3H; D008856:Microscopy, Fluorescence / Q000379:methods; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D024101:Mitochondrial Proteins / Q000378:metabolism
chemical_list: D051033:Apoptosis Inducing Factor; D051017:Apoptosis Regulatory Proteins; D001562:Benzimidazoles; D002232:Carbocyanines; D002352:Carrier Proteins; C499605:Diablo protein, mouse; D024101:Mitochondrial Proteins; C068624:5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolocarbocyanine; D000082:Acetaminophen; D045304:Cytochromes c; D004706:Endodeoxyribonucleases; C052391:endonuclease G; D000111:Acetylcysteine