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 lin e (XP12BE, group A), and cytotoxic and genotoxic effects of the thiol- reactive aldehyde acrolein were studied in these cell types. Normal ce ll contained higher amounts of the reduced glutathione and cysteine re spectively, and higher amounts of these thiols as protein-bound disulf ides than the XP cells. However, in both cell types total glutathione was present in 6- to 7-fold higher amounts than total cysteine, and to tal protein thiols corresponded to approximately 30% of total thiols. A 1 h exposure to acrolein caused a quantitatively similar depletion o f reduced glutathione and free protein thiols in both cell types, with out 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 re sulted in continued formation of DNA single-strand breaks in the norma l cells, whereas no such accumulation occurred in the XP cells. In the normal cells, the DNA single-strand breaks accumulated to a similar e xtent as in the presence Of 1-beta-D-arabino-furanosyl-cytosine and hy droxyurea, i.e. two agents which together efficiently inhibit DNA repa ir synthesis. The results indicate quantitative and qualitative differ ences in the thiol redox state between normal and XP cells, and that t hese differences may contribute to the higher cytotoxicity and genotox icity of acrolein in XP cells. Moreover, the results indicate that acr olein is a potent inhibitor of DNA excision repair.