Background: Sun irradiation causes skin ageing and cancer through the accumulation of damage to cell components. Intrinsic ageing is also associated with accumulation of oxidized macromolecules.
Objectives: In this study we investigated the effects of sun exposure on response to an acute in vitro oxidative stress (H(2)O(2)) using normal human fibroblasts prepared from biopsies from 10 volunteers taken from sun-protected and sun-exposed sites.
Methods: Time-course experiments measuring repair of DNA strand-breaks and formamidopyrimidine DNA N-glycosylase-sensitive sites were conducted using the single-cell gel electrophoresis (comet) assay.
Results: Our results demonstrated that repair of strand-breaks was slower in sun-exposed compared with sun-protected cells. Interestingly, ageing was also associated with decreased DNA repair capacities for single-strand breaks in both sun-exposed and sun-protected cells whereas for formamidopyrimidine glycosylase (Fpg)-sensitive sites, this feature was in evidence only in sun-protected cells. Smoking, associated with age, was shown to have a markedly negative impact on DNA repair.
Conclusions: Taken together our data suggest that stresses like ageing, sun exposure and smoking might have an additive effect contributing to the overall heterogeneity and decrease of DNA repair capacities in human cells and so increase the danger of sun exposure for health. They also emphasize the importance of the quality of the biological samples when repair studies on skin cells are to be conducted.