Effect of age on the formation and repair of UV photoproducts in human skin in situ

Ultraviolet radiation (UVR)-induced photoproducts can be measured by a numb er of methods. The newly developed P-32-postlabelling method is feasible in molecular epidemiological studies due to its sensitivity, specificity and little amount DNA needed. We applied the P-32-postlabelling method to inves tigate the induction and repair of photoproducts (cyclobutane pyrimidine di mers (CPDs) and 6-4 photoproducts) after UVR in human skin in situ and stud ied the effects of age, skin type and gender. The study included 30 subject s aged 32-78 years. The photoproduct induction levels varied 7- to 15-fold between the individuals tested. All four types of photoproducts were induce d at a higher frequency in the older population (greater than or equal to 5 0 years) than in the younger population(< 50 years). Individuals with skin type I and II had a higher CPD induction frequency than individuals with sk in type III and IV, Tn both cases, the differences in thymidylyl (3'-5') th ymidylyl (3'-5')-2'-deoxycytidine induction reached statistical significant levels (p < 0.05). Photoproduct repair rates 24 h and 48 h after UV irradi ation showed a large inter-individual variation. No clear effects of age, s kin type or gender on DNA repair could be detected. Our data suggest that U V-induced DNA photoproduct levels increase with age. (C) 2000 Published by Elsevier Science B.V. All rights reserved.