Thiol status and cytopathological effects of acrolein in normal and xeroderma pigmentosum skin fibroblasts.

Thiol redox status was determined in normal human skin fibroblasts and a DNA repair-deficient xeroderma pigmentosum (XP) fibroblast cell line (XP12BE, group A), and cytotoxic and genotoxic effects of the thiol-reactive aldehyde acrolein were studied in these cell types. Normal cells contained higher amounts of the reduced glutathione and cysteine respectively, and higher amounts of these thiols as protein-bound disulfides than the XP cells. However, in both cell types total glutathione was present in 6- to 7-fold higher amounts than total cysteine, and total protein thiols corresponded to approximately 30% of total thiols. A 1 h exposure to acrolein caused a quantitatively similar depletion of reduced glutathione and free protein thiols in both cell types, without causing changes in the thiol redox state. However, acrolein caused higher toxicity measured as trypan blue exclusion, and also a higher extent of DNA single-strand breaks in the XP cells than in the normal cells. Exposure to acrolein, followed by incubation in fresh medium resulted in continued formation of DNA single-strand breaks in the normal cells, whereas no such accumulation occurred in the XP cells. In the normal cells, the DNA single-strand breaks accumulated to a similar extent as in the presence of 1-beta-D-arabinofuranosyl-cytosine and hydroxyurea, i.e. two agents which together efficiently inhibit DNA repair synthesis. The results indicate quantitative and qualitative differences in the thiol redox state between normal and XP cells, and that these differences may contribute to the higher cytotoxicity and genotoxicity of acrolein in XP cells. Moreover, the results indicate that acrolein is a potent inhibitor of DNA excision repair.