OXIDATIVE DNA-DAMAGE AND CELLULAR-SENSITIVITY TO OXIDATIVE STRESS IN HUMAN AUTOIMMUNE-DISEASES

Objectives-To estimate the extent of genomic DNA damage and killing of lymphocytes by reactive oxygen intermediates in autoimmune diseases. Methods-8-Oxo-7-hydrodeoxyguanosine (8-oxodG), a promutagenic DNA lesi on induced by reactive oxygen intermediates, was measured by high perf ormance liquid chromatography, coupled with electrochemical detection, in hydrolysates of DNA which had been extracted from lymphocyte and p olymorphonuclear leucocyte fractions of human blood. In addition, huma n primary blood lymphocytes stimulated by concanavalin A were assayed for cytotoxicity induced by hydrogen peroxide on day 0, by assessing c ell proliferation during seven days of culture. Results-Constitutive 8 -oxodG was detectable (mean (2 SEM) moles 8-oxodG/10(6) moles deoxygua nosine) in DNA isolated from normal human blood lymphocytes (68 (8), n =26) and polymorphonuclear leucocytes (118 (24), n=24). Lymphocyte DNA from donors with the following inflammatory autoimmune diseases conta ined significantly higher levels of 8-oxodG than that from healthy don ors: rheumatoid arthritis (98 (16)), systemic lupus erythematosus (137 (28)), vasculitis (100 (32)), and Behcet's disease (92 (19)). Lymphoc yte 8-oxodG levels in non-autoimmune controls and patients with sclero derma were not significantly different from those of healthy controls. The levels of 8-oxodG were significantly higher in the DNA from norma l polymorphonuclear leucocytes than in paired DNA samples from normal lymphocytes, but there were no differences between levels of 8-oxodG i n polymorphonuclear leucocytes from normal subjects and the patients s tudied. Levels of 8-oxodG did not correlate with disease duration, dis ease severity, or age. Lymphocytes from patients with systemic lupus e rythematosus and rheumatoid arthritis, but not those with scleroderma, also showed cellular hypersensitivity to the toxic effects of hydroge n peroxide. Conclusion-There was increased genomic DNA damage, and inc reased susceptibility to cytotoxic killing by hydrogen peroxide, in ly mphocytes from patients with certain autoimmune diseases. These result s might be explained by defective repair of DNA damage or by increased production of reactive oxygen intermediates in inflammation. Although more direct studies are needed, the evidence available favours the fo r former explanation.