Repeated exposure of human skin fibroblasts to UVB at subcytotoxic level triggers premature senescence through the TGF-β1 signaling pathway

Abstract

Premature senescence of human diploid fibroblasts (HDFs) can be induced by exposures to a variety of oxidative stress and DNA damaging agents. In this study we developed a robust model of UVB-induced premature senescence of skin HDFs. After a series of 10 subcytotoxic (nonproapoptotic) exposures to UVB at 250 mJ/cm 2 , the socalled biomarkers of senescence were markedly expressed: growth arrest, senescence-associated β-galactosidase activity, senescence-associated gene overexpression, deletion in mitochondrial DNA. A set of 44 stress-and senescence-associated genes were found to be differentially expressed in this model, among which clusterin/ apolipoprotein J (apo J) and transforming growth factor-β1 (TGF-β1). Transfection of apo J cDNA provided protection against premature senescence-inducing doses of UVB and other stressful agents. Neutralizing antibodies against TGF-β1 or its receptor II (TβRII) sharply attenuated the senescence-associated features, suggesting a role for TGF-β1 in UVB-induced premature senescence. Both the latent and active forms of TGF-β1 were increased with time after the last UVB stress. Proteasome inhibition was ruled out as a potential mechanism of UVB-induced stress-induced premature senescence (SIPS). This model represents an alternative in vitro model in photoaging research for screening potential anti-photoaging compounds.Supplementary material available online at

Human lung fibroblasts prematurely senescent after exposure to ionizing radiation enhance the growth of malignant lung epithelial cells in vitro and in vivo

“…In addition, it has been shown that oxidative stress and stress-induced TGF-β1 overexpression can induce premature senescence that can be blocked by antioxidants or antibodies against TGF-β1 or its respective receptor (32,35,48). However, in our experiments the presence of antioxidants or an inhibitor of TGF-β receptor, during the whole period of irradiation and the time needed for the appearance of the senescent phenotype, was unable to prevent this phenomenon.…”

“…Next, we tried to investigate the mechanisms responsible for the induction of premature senescence by repeated doses of ionizing radiation. It has been shown that ionizing radiation generates reactive oxygen species and activates TGF-β, two well known inducers of premature senescence (31,32). In addition, it also provokes the activation of p38 MAPK ( Fig.…”

Expression profiling of senescent-associated genes in human dermis from young and old donors. Proof-of-concept study

“…The value of the technology of low density DNA arrays used in this study has been extensively demonstrated previously in a variety of models, as diverse as hepato-toxicology (de Longueville et al 2002), breast cancer (Gillet et al 2006), skin irritation (Borlon et al 2007b), response to UVB stress (Borlon et al 2007c;Debacq-Chainiaux et al 2005) and cell senescence (de Magalhaes et al 2004;Pascal et al 2005;Zdanov et al 2006). Numerous verifications with real time RT-PCR have been done on all these models.…”

“…More than 40 verifications with real-time RT PCR of the relative gene expression level obtained with this microarray have already been done in several senescence-related models (Borlon et al 2007a;de Magalhaes et al 2004;Debacq-Chainiaux et al 2005;Zdanov et al 2006). Nevertheless, further verifications were done in the studies.…”

“…This choice was first based on several published studies related to skin ageing and in vitro senescence of skin fibroblasts where GAPDH was selected as housekeeper (Basu-Modak et al 2003;Brink et al 2000;Debacq-Chainiaux et al 2005;Seo et al 2003). However, we checked the relevance of GAPDH as the reference housekeeping gene in this part of the work by real time RT-PCR.…”