title: Ethanol-induced mitophagy in liver is associated with activation of the PINK1-Parkin pathway triggered by oxidative DNA damage.
abstract: Mitophagy is a cytoprotective mechanism against mitochondrial damaging agents. Studies demonstrating morphological evidence for the involvement of the PINK1-Parkin pathway in the hepatocyte mitophagic response to ethanol toxicity, and potential links to apoptosis and mitochondrial alterations such as spheroid formation are still lacking. We addressed these unresolved issues using a rat model of binge alcohol exposure. Adult rats were injected with ethanol (5g/kg) and liver samples were taken at 0, 3, 6, and 24 hours after ethanol administration and processed for light and electron microscopic studies. Ethanol induced a low level of hepatocyte apoptosis, peaking at 3 h and decreasing significantly by 24 h. In contrast, there was enhanced formation of mitophagic vacuoles in the majority of normal hepatocytes of ethanol-treated rats (ETRs), which peaked at 6 h and was maintained up to 24 h based on electron microscopy and TUNEL/LC3 double labelling. Moreover, enhanced mitophagy in ETR hepatocytes was confirmed by increased LC3 puncta formation, and co-localization of Parkin and LC3 with mitochondrial and lysosomal markers. Immunoelectron microscopy demonstrated the localization of PINK1 and Parkin to damaged mitochondria of ETR hepatocytes, which was consistent with co-localization of Parkin with 8-OHdG, a marker of oxidative mitochondrial DNA damage. Furthermore, electron microscopy showed enhanced formation of mitochondrial spheroids in ETR hepatocytes. These data are the first direct morphological evidence linking PINK1-Parkin pathway activation to the enhanced mitophagic response of hepatocytes to ethanol toxicity. Ethanol-induced hepatic mitophagy may be a prosurvival mechanism, which may have therapeutic implications.
authors.affiliation: Department of Anatomy and Cell Biology, Division of Life Sciences, Osaka Medical College, Daigaku Machi, Takatsuki, Osaka, Japan. nabileidm@yahoo.com or nabil@osaka-med.ac.jp.
authors.forename: Nabil
authors.initials: N
authors.lastname: Eid
authors.affiliation: Department of Anatomy and Cell Biology, Division of Life Sciences, Osaka Medical College, Daigaku Machi, Takatsuki, Osaka, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Ito
authors.affiliation: Department of Anatomy and Cell Biology, Division of Life Sciences, Osaka Medical College, Daigaku Machi, Takatsuki, Osaka, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Horibe
authors.affiliation: Osaka Medical College, Daigaku Machi, Takatsuki, Osaka, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Otsuki
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D004249:DNA Damage / Q000187:drug effects / Q000502:physiology*; D004195:Disease Models, Animal; D000431:Ethanol / Q000633:toxicity; D005455:Fluorescent Antibody Technique; D020287:In Situ Nick-End Labeling; D008099:Liver / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D008297:Male; D063306:Mitophagy / Q000187:drug effects* / Q000502:physiology; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D000099202:PTEN-Induced Putative Kinase
chemical_list: D000431:Ethanol; D011494:Protein Kinases; D044767:Ubiquitin-Protein Ligases; D000099202:PTEN-Induced Putative Kinase; C111567:parkin protein