title: Loss of proliferative capacity and induction of senescence in oxidatively stressed human fibroblasts.
abstract: Cellular senescence can result from short, dysfunctional telomeres, oxidative stress, or oncogene expression, and may contribute to aging. To investigate the role of cellular senescence in aging it is necessary to define the time-dependent molecular events by which it is characterized. Here we investigated changes in levels of key proteins involved in cell cycle regulation, DNA replication, and stress resistance in senescing human fibroblasts following oxidative stress. An immediate response in stressed cells was dephosphorylation of retinoblastoma (Rb) and cessation of DNA synthesis. This was followed by sequential induction of p53, p21, and p16. Increase in hypophosphorylated Rb and induction of p53 and p21 by a single stress treatment was transient, whereas sustained induction or dephosphorylation were achieved by a second stress. Down-regulation of the critical DNA replication initiation factor Cdc6 occurred early after stress concurring with p53 induction, and was followed by a decrease in Mcm2 levels. A late event in the stress-induced molecular sequence was the induction of SOD1, catalase, and HSP27 coinciding with development of the fully senescent phenotype. Our data suggest that loss of proliferative capacity in oxidatively stressed cells is a multistep process regulated by time-dependent molecular events that may play differential roles in induction and maintenance of cellular senescence.
authors.affiliation: Department of Clinical Biochemistry, University of Cambridge, Cambridge CB2 2QR, United Kingdom. jhc36@cam.ac.uk
authors.forename: Jian-Hua
authors.initials: JH
authors.lastname: Chen
authors.forename: Kai
authors.initials: K
authors.lastname: Stoeber
authors.forename: Sarah
authors.initials: S
authors.lastname: Kingsbury
authors.forename: Susan E
authors.initials: SE
authors.lastname: Ozanne
authors.forename: Gareth H
authors.initials: GH
authors.lastname: Williams
authors.forename: C Nicholas
authors.initials: CN
authors.lastname: Hales
mesh_terms: D015153:Blotting, Western; D001973:Bromodeoxyuridine / Q000494:pharmacology; D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured; D016922:Cellular Senescence; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D015536:Down-Regulation; D005347:Fibroblasts / Q000166:cytology* / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D018613:Microscopy, Confocal; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism*; D010641:Phenotype; D010766:Phosphorylation; D016160:Retinoblastoma Protein / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D013997:Time Factors; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: C066503:CDC6 protein, S cerevisiae; D018797:Cell Cycle Proteins; D016160:Retinoblastoma Protein; D029701:Saccharomyces cerevisiae Proteins; D016159:Tumor Suppressor Protein p53; D004247:DNA; D006861:Hydrogen Peroxide; D001973:Bromodeoxyuridine; D010100:Oxygen