Identification of p53-dependent genes potentially involved in UVB-mediated premature senescence of human skin fibroblasts using siRNA technology

Premature senescence of skin human diploid fibroblasts is induced after a series of 10 sublethal exposures to UVB at 2.5 kJ/m(2) with appearance of several biomarkers of cellular senescence like senescence-associated beta-galactosidase activity (SA beta-gal) and cell cycle arrest. Herein it is shown that the induction of UVB-induced premature senescence is associated with a transient increase of protein abundance and DNA-binding activity of p53. Silencing p53 expression with small interfering RNA (siRNA) affected the basal level of SA beta-gal and proliferative potential, but did not prevent UVB-induced increase of SA beta-gal and decrease of DNA synthesis. We used a senescence-specific low-density DNA array and p53 siRNA to study the mRNA abundance of 240 senescence-related genes and identified several potential p53-dependent genes differentially expressed after the repeated exposures to UVB.     

Serum N-glycan profile shift during human ageing

Biomarkers indicating biological age are of significant interest for prevention, diagnosis and monitoring (and the treatment) of age-related diseases. We previously reported an alteration of serum N-glycan profile in old humans using “DNA Sequencer Adapted-Fluorophore Assisted Carbohydrate Electrophoresis” (DSA-FACE). To validate the shift in serum N-glycan profile during ageing, we studied serum N-glycan profiles in different age groups of healthy volunteers, patients with dementia, and patients with Cockayne syndrome, a genetic DNA repair disorder involving neurodegeneration and premature ageing. We found that the log of the ratio of two glycans (NGA2F and NA2F), named GlycoAgeTest, remained steady up to the age of 40 years and thereafter gradually increased to reach its highest level in nonagenarians. Patients with dementia or Cockayne syndrome had a higher GlycoAgeTest level than age-matched healthy individuals. We thus demonstrate that the value of GlycoAgeTest is better than chronological age for estimating the physiological age of a human individual, and that it could be used as an ageing biomarker for healthy humans. Our data indicate that the GlycoAgeTest could be used as a non-invasive surrogate marker for general health, for forecasting disease progression during ageing, and for monitoring the efficacy of anti-ageing food compounds.     

Identification of potential anti-photoageing algal compounds using an in-vitro model of photoageing

Stress-induced premature senescence (SIPS) has been proposed as an in-vitro model for testing the long-term effects of stressful events and to find molecules/natural extracts that protect against such stress. Premature senescence of human skin diploid fibroblasts (HDFs) can be induced by repeated subcytotoxic exposure to UVB, with the appearance of so-called biomarkers of senescence such as growth arrest, senescence-associated beta-galactosidase activity, senescence-associated gene over-expression and the common 4977-bp mitochondrial DNA deletion. This model of UVB-induced premature senescence has been acknowledged as a robust in-vitro model in photoageing research. In this study, the potential anti-photoageing effects of a series of algal extracts were tested. The appearance of the biomarkers of UVB-induced premature senescence of HDFs was studied with or without algal extracts. One algal extract was shown to be particularly protective against UVB-induced SIPS. The results obtained here reinforce the notion that UVB-induced premature senescence of HDFs can be used to screen potential anti-photoageing compounds.     

Heme oxygenase-1 and interleukin-11 are overexpressed in stress-induced premature senescence of human WI-38 fibroblasts induced by <Emphasis Type="Italic">tert</Emphasis>-butylhydroperoxide and ethanol

Acute repeated exposures to subcytotoxic concentrations of tert-butylhydroperoxide and ethanol trigger premature senescence of human diploid fibroblasts. In the present work we found an increased mRNA and protein level of interleukin-11 and heme oxygenase-1 in premature senescence of WI-38 human diploid foetal lung fibroblasts induced by both tert-butylhydroperoxide and ethanol. We tested whether interleukin-11 and heme oxygenase-1 could protect against tert-butylhydroperoxide- or ethanol-induced premature senescence when stable overexpression was established using a retroviral vector-based transduction. No protective effect was found against the decrease of the proliferative potential, the increase of the proportion of senescence-associated ss-galactosidase positive cells and the increase of the mRNA levels of six senescence-associated genes.     

p53 and ATF-2 partly mediate the overexpression of COX-2 in H2O2-induced premature senescence of human fibroblasts

Cyclooxygenase-2 and release of prostaglandin E2 are up-regulated in replicative senescence of dermal and prostate fibroblasts and in H₂O₂-induced premature senescence of IMR-90 lung fibroblasts expressing the catalytic subunit of telomerase. Inhibition of cyclooxygenase-2 activity by specific chemical inhibitor or siRNA attenuates the H₂O₂-induced increase of senescence associated β-galactosidase positive cells and attenuates growth arrest. In this work, p38^MAPK activation and increased DNA binding activities of ATF-2 and p53 are shown to mediate cyclooxygenase-2 overexpression in premature senescence.