title: Hypoxia induces mitochondrial DNA damage and stimulates expression of a DNA repair enzyme, the Escherichia coli MutY DNA glycosylase homolog (MYH), in vivo, in the rat brain.
abstract: Hypoxia-associated, acutely reduced blood oxygenation can compromise energy metabolism, alter oxidant/antioxidant balance and damage cellular components, including DNA. We show in vivo, in the rat brain that respiratory hypoxia leads to formation of the oxidative DNA lesion, 8-hydroxy-2'-deoxyguanosine (oh8dG), a biomarker for oxidative DNA damage and to increased expression of a DNA repair enzyme involved in protection of the genome from the mutagenic consequences of oh8dG. The enzyme is a homolog of the Escherichia coli MutY DNA glycosylase (MYH), which excises adenine residues misincorporated opposite the oxidized base, oh8dG. We have cloned a full-length rat MYH (rMYH) cDNA, which encodes 516 amino acids, and by in situ hybridization analysis obtained expression patterns of rMYH mRNA in hippocampal, cortical and cerebellar regions. Ensuing hypoxia, mitochondrial DNA damage was induced and rMYH expression strongly elevated. This is the first evidence for a regulated expression of a DNA repair enzyme in the context of respiratory hypoxia. Our findings support the premise that oxidative DNA damage is repaired in neurons and the possibility that the hypoxia-induced expression of a DNA repair enzyme in the brain represents an adaptive mechanism for protection of neuronal DNA from injurious consequences of disrupted energy metabolism and oxidant/antioxidant homeostasis.
authors.affiliation: Department of Surgery, The University of Texas Medical Branch, Galveston, Texas 77550, USA.
authors.forename: Heung-Man
authors.initials: HM
authors.lastname: Lee
authors.forename: Cheng
authors.initials: C
authors.lastname: Wang
authors.forename: Zhaoyong
authors.initials: Z
authors.lastname: Hu
authors.forename: George H
authors.initials: GH
authors.lastname: Greeley
authors.forename: Wojciech
authors.initials: W
authors.lastname: Makalowski
authors.forename: Helen L
authors.initials: HL
authors.lastname: Hellmich
authors.forename: Ella W
authors.initials: EW
authors.lastname: Englander
mesh_terms: D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D001921:Brain / Q000378:metabolism* / Q000473:pathology; D003001:Cloning, Molecular; D004249:DNA Damage; D045647:DNA Glycosylases; D004260:DNA Repair; D004272:DNA, Mitochondrial / Q000378:metabolism*; D006147:Guanine / Q000031:analogs & derivatives* / Q000378:metabolism; D002534:Hypoxia, Brain / Q000378:metabolism* / Q000473:pathology; D017403:In Situ Hybridization; D008297:Male; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017386:Sequence Homology, Amino Acid; D015854:Up-Regulation
chemical_list: D004272:DNA, Mitochondrial; D012333:RNA, Messenger; C024829:8-hydroxyguanine; D006147:Guanine; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C061738:mutY adenine glycosylase