Chinese hamster fibroblasts overexpressing CuZn-superoxide dismutase undergo a global reduction in antioxidants and an increasing sensitivity of DNA to oxidative damage.

Transfection of a CuZn-superoxide dismutase (SOD) expression vector into V79 Chinese hamster cells produced clones in which CuZn-SOD activities were 2.2-3.5-fold higher than in the parental cells. An overall moderate reduction of glutathione peroxidase, glutathione reductase and glucose-6-phosphate dehydrogenase activities and of both GSSG and total glutathione levels was found. In one particular clone the catalase activity was also reduced. The pro-oxidant status established by the lower level of antioxidant defence rendered the SOD-overexpressing cells more sensitive to the production of 8-oxo-2'-deoxyguanosine by hydrogen peroxide. The data are discussed in terms of a model resembling the bacterial sox RS system.