Isolation and preliminary characterization of a Chinese hamster ovary cell line with high-degree resistance to hydrogen peroxide

We have isolated and conducted preliminary characterization of a cell line derived from the Chinese hamster ovary cell line AA8, which we have designated AG8 and which is highly resistant to the cytotoxic effects of H2O2 (similar to 17-fold when the H2O2 treatment was at 37 degrees; similar to 11-fold when the H2O2 treatment was at 4 degrees). AG8 cells were moderately (but significantly; P < 0.05) cross resistant to CdCl2 (similar to 4-fold), NaAsO2 (similar to 2.3-fold), t-butyl hydroperoxide (similar to 2.9-fold), cumene hydroperoxide (similar to 3-fold), menadione (similar to 1.7-fold) and HgCl2 (similar to 1.5-fold), but were not significantly cross-resistant to hyperthermia (43 degrees), 254 nm UV light, Cs-137 gamma-rays, and 42-MeV (p --> Be+) fast neutrons. As regards their biochemical status, AG8 and AA8 cells contain similar non protein sulfhydryl levels per milligram of protein. Catalase activity (assessed by both spectrophotometry and polarography) was significantly higher in AG8 than in AA8 cells irrespective of whether enzyme activity was expressed per 10(6) cells (similar to 3.6-fold increase) or per milligram of protein (similar to 1.6-fold increase). AG8 cells also exhibited significantly greater glutathione reductase activity than wild-type cells when the data were expressed per 10(6) cells (similar to 2.9-fold) or per milligram of protein (similar to 1.3-fold). Glutathione peroxidase activity was immeasurably low in both cell lines. The susceptibility of the two cell lines to H2O2-mediated generation of DNA single-strand breaks (as measured by alkaline elution) indicated a slightly (similar to 1.5 fold) decreased yield in the resistant AG8 cell line. The two cell lines repaired these breaks with similar kinetics. In contrast, no measurable induction of DNA double-strand breaks (as measured by pulsed-field gel electrophoresis) was apparent in either cell line after survival-curve range concentrations of H2O2. On the basis of these data, it appears that the AG8 phenotype involves two previously identified resistance mechanisms, namely an adaptive component that may or may not involve increased antioxidant capacity, and a second component that does involve increased antioxidant (primarily catalase) capacity.