title: Genistein protects against UVB-induced senescence-like characteristics in human dermal fibroblast by p66Shc down-regulation.
abstract: BACKGROUND
  Genistein, as an active compound of dietary antioxidants, has shown considerable promise as an effective agent against aging process. However, the effect of genistein on skin photoaging and the associated mechanism remain unclear.
  
  
  OBJECTIVE
  To delineate the effect of genistein on UVB-induced senescence in human dermal fibroblasts (HDFs) with emphasis on the mechanism of oxidative pathway regulated by p66Shc involved in the events.
  
  
  METHODS
  HDFs were induced to premature senescence by repetitive subcytotoxic doses of UVB irradiation. Cellular apoptosis and DNA cell cycle were analyzed using flow cytometry. Intracellular levels of superoxide dismutase (SOD) and malondialdehyde (MDA) were detected by ELISA. Mutation levels of two large deletions of mitochondrial DNA, 4977bp and 3895bp deletion, were determined by quantitative PCR. Western blot was applied to detect the expression and activation of p66Shc (the 66-kilodalton isoform of the growth factor adapter Shc) and FKHRL1 (a forkhead protein that is intimately linked with intracellular oxidation).
  
  
  RESULTS
  Strong activity of senescence-associated beta-galactosidase (SA-beta-gal), high percent of cell apoptosis as well as cell cycle arrest in G0/G1 phase, and increased intracellular oxidative stress were observed in HDFs irradiated by UVB. Genistein exerted dramatically protective effects on HDFs in a dose-dependent manner. Elevated copy numbers of large deletions in mitochondrial DNA were also inhibited by genistein. Down-regulation of total and phosphorylated p66Shc on Ser36, as well as FKHRL1 and its phosphorylation on Thr32, were observed after genistein treatment.
  
  
  CONCLUSIONS
  The results indicate that genistein protects UVB-induced senescence-like characteristics in HDFs via maintenance of antioxidant enzyme activities and modulation of mitochondrial oxidative stress through down-regulation of a p66Shc-dependent signaling pathway, which may provide potential prevention against skin aging and even photoaging.
authors.affiliation: Department of Dermatology, 1st Affiliated Hospital, Zhejiang University School of Medicine, 79# Qing Chun Road, Hangzhou 310003, China.
authors.forename: Yi Na
authors.initials: YN
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Wu
authors.forename: Hong Chao
authors.initials: HC
authors.lastname: Chen
authors.forename: Hong
authors.initials: H
authors.lastname: Fang
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000528:radiation effects; D002453:Cell Cycle / Q000528:radiation effects; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000187:drug effects* / Q000528:radiation effects*; D004272:DNA, Mitochondrial / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D015536:Down-Regulation / Q000528:radiation effects*; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000378:metabolism; D019833:Genistein / Q000494:pharmacology*; D006801:Humans; D009154:Mutation / Q000528:radiation effects; D055765:Shc Signaling Adaptor Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000528:radiation effects; D012867:Skin / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D015595:Skin Aging / Q000528:radiation effects; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D000975:Antioxidants; D004272:DNA, Mitochondrial; C499517:FOXO3 protein, human; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; C528024:SHC1 protein, human; D055765:Shc Signaling Adaptor Proteins; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D019833:Genistein