title: Ataxia telangiectasia mutated inhibits oxidative stress-induced apoptosis by regulating heme oxygenase-1 expression.
abstract: Ataxia telangiectasia (AT) is caused by mutational inactivation of the ataxia telangiectasia mutated (Atm) gene, which is involved in DNA repair. Increased oxidative stress has been shown in human AT cells and neuronal tissues of Atm-deficient mice. Heme oxygenase-1 (HO-1) is an inducible antioxidant enzyme and protects cells against oxidative stress. The purpose of this study is to determine whether ATM induces antioxidant enzyme HO-1 and protects cells from oxidative stress-mediated apoptosis by driving the activation of PKC-δ and NF-κB, by increasing cell viability, and by downregulating DNA fragmentation and apoptotic indicators (apoptosis-inducing factor and cleaved caspase-3). AT fibroblasts stably transfected with human full-length ATM cDNA (YZ5 cells) or the empty vector (MOCK cells) were treated with H2O2 as a source of reactive oxygen species (ROS). As a result, transfection with ATM inhibited ROS-induced cell death and DNA fragmentation in MOCK cells. Transfection with ATM induced expression of HO-1 which was mediated by PKC-δ and NF-κB in H2O2-treated MOCK cells. ZnPP, an HO-1 inhibitor, and transfection with HO-1 siRNA increased ROS levels and apoptosis, whereas hemin, an HO-1 activator, reduced ROS levels and apoptosis in H2O2-treated YZ5 cells. Rottlerin, a PKC-δ inhibitor, inhibited NF-κB activation and HO-1 expression in H2O2-treated YZ5 cells. MOCK cells showed increased cell death, DNA fragmentation, and apoptotic indicators compared to YZ5 cells exposed to H2O2. In addition, transfection with p65 siRNA increased ROS levels and DNA fragmentation, but decreased HO-1 protein levels in H2O2-treated YZ5 cells. In conclusion, ATM induces HO-1 expression via activation of PKC-δ and NF-κB and inhibits oxidative stress-induced apoptosis. A loss of HO-1 induction may explain why AT patients are vulnerable to oxidative stress.
authors.affiliation: Department of Pharmacology, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea.
authors.forename: Ji Hoon
authors.initials: JH
authors.lastname: Yu
authors.affiliation: Department of Pharmacology, Yonsei University College of Medicine, Seoul 120-752, Republic of Korea.
authors.forename: Soon Ok
authors.initials: SO
authors.lastname: Cho
authors.affiliation: Department of Food and Nutrition, Brain Korea 21 PLUS Project, College of Human Ecology, Yonsei University, Seoul 120-749, Republic of Korea.
authors.forename: Joo Weon
authors.initials: JW
authors.lastname: Lim
authors.affiliation: Department of Food and Nutrition, Brain Korea 21 PLUS Project, College of Human Ecology, Yonsei University, Seoul 120-749, Republic of Korea.
authors.forename: Nanhee
authors.initials: N
authors.lastname: Kim
authors.affiliation: Department of Food and Nutrition, Brain Korea 21 PLUS Project, College of Human Ecology, Yonsei University, Seoul 120-749, Republic of Korea. Electronic address: kim626@yonsei.ac.kr.
authors.forename: Hyeyoung
authors.initials: H
authors.lastname: Kim
mesh_terms: D017209:Apoptosis / Q000235:genetics / Q000502:physiology; D064007:Ataxia Telangiectasia Mutated Proteins / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D002460:Cell Line; D002470:Cell Survival / Q000235:genetics / Q000502:physiology; D053938:DNA Fragmentation; D024202:Electrophoretic Mobility Shift Assay; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D018384:Oxidative Stress / Q000235:genetics / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D051547:Heme Oxygenase-1; D064007:Ataxia Telangiectasia Mutated Proteins
keywords: Apoptosis; Ataxia telangiectasia mutated; Heme oxygenase-1; Oxidative stress