Modulation of exogenous and endogenous levels of thioredoxin in human skinfibroblasts prevents DNA damaging effect of ultraviolet A radiation

Thioredoxin (Trx) plays important biological roles both intra- and extracel lularly via thiol redox control. We have previously demonstrated that Trx e xhibited protective effects against UVA cytotoxicity in human skin fibrobla sts. As an extension of the latter investigation, the present work is aimed at assessing ability of Trx to maintain genomic integrity in human skin fi broblasts upon exposure to UVA radiation. Indeed, UVA (320-380 nm) is mutag enic and induces genomic damage to skin cells. The alkaline comet assay was used in association with DNA repair enzyme including formamido pyrimidine glycosylase (Fpg) and endonuclease III (endo III) to estimate the amount of modified bases together with the level of strand breaks and alkali-labile sites. The HPLC-EC assay was applied to assess 8-oxo-7,8-dihydro-2'-deoxygu anosine (8-oxodGuo) levels and to permit the calibration of comet assay as previously described. We reported that overexpression of human Trx (transie nt transfection) as well as exogenous human recombinant Trx added to the cu lture medium, decreased the level of DNA damage in UVA irradiated cells. In terestingly, transfection appeared to prevent UVA-induced 8-oxodGuo (3.06 a u per Joules.cm(-2) compared to 4.94 au per Joules.cm(-2) for nontransfecte d cells). Moreover, Trx accumulates into nuclei in transfected cells. This finding supports the notion that Trx is important for the maintenance of th e integrity of genetic information. This work demonstrated that under condi tions of UVA oxidative stress, Trx prevented the WA-induced DNA damage. (C) 2001 Elsevier Science Inc.