title: Terminally differentiated muscle cells are defective in base excision DNA repair and hypersensitive to oxygen injury.
abstract: The differentiation of skeletal myoblasts is characterized by permanent withdrawal from the cell cycle and fusion into multinucleated myotubes. Muscle cell survival is critically dependent on the ability of cells to respond to oxidative stress. Base excision repair (BER) is the main repair mechanism of oxidative DNA damage. In this study, we compared the levels of endogenous oxidative DNA damage and BER capacity of mouse proliferating myoblasts and their differentiated counterpart, the myotubes. Changes in the expression of oxidative stress marker genes during differentiation, together with an increase in 8-hydroxyguanine DNA levels in terminally differentiated cells, suggested that reactive oxygen species are produced during this process. The repair of 2-deoxyribonolactone, which is exclusively processed by long-patch BER, was impaired in cell extracts from myotubes. The repair of a natural abasic site (a preferred substrate for short-patch BER) also was delayed. The defect in BER of terminally differentiated muscle cells was ascribed to the nearly complete lack of DNA ligase I and to the strong down-regulation of XRCC1 with subsequent destabilization of DNA ligase IIIalpha. The attenuation of BER in myotubes was associated with significant accumulation of DNA damage as detected by increased DNA single-strand breaks and phosphorylated H2AX nuclear foci upon exposure to hydrogen peroxide. We propose that in skeletal muscle exacerbated by free radical injury, the accumulation of DNA repair intermediates, due to attenuated BER, might contribute to myofiber degeneration as seen in sarcopenia and many muscle disorders.
authors.affiliation: Department of Environment and Primary Prevention, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Narciso
authors.forename: Paola
authors.initials: P
authors.lastname: Fortini
authors.forename: Deborah
authors.initials: D
authors.lastname: Pajalunga
authors.forename: Annapaola
authors.initials: A
authors.lastname: Franchitto
authors.forename: Pingfang
authors.initials: P
authors.lastname: Liu
authors.forename: Paolo
authors.initials: P
authors.lastname: Degan
authors.forename: Mathilde
authors.initials: M
authors.lastname: Frechet
authors.forename: Bruce
authors.initials: B
authors.lastname: Demple
authors.forename: Marco
authors.initials: M
authors.lastname: Crescenzi
authors.forename: Eugenia
authors.initials: E
authors.lastname: Dogliotti
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects*; D002457:Cell Extracts; D049109:Cell Proliferation / Q000187:drug effects; D053904:DNA Breaks, Single-Stranded; D004260:DNA Repair / Q000187:drug effects*; D006706:Homeostasis / Q000187:drug effects; D007700:Kinetics; D051379:Mice; D032342:Muscle Cells / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D032446:Myoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D010100:Oxygen / Q000633:toxicity*; D013997:Time Factors
chemical_list: D002457:Cell Extracts; D010100:Oxygen