Adaptative response to enhanced basal oxidative damage in sod mutants from Saccharomyces cerevisiae

We investigated the adaptative response of S. cerevisiae in sod mutants (sod1 Delta, sod2 Delta and sod1 Delta sod2 Delta) after H2O2 treatment in the stationary phase. sod2 Delta and sod1 Delta sod2 Delta demonstrated the highest levels of GSH in the control, suggesting that pathways which include GSH protect these double mutants against oxidative stress. In addition, sod1 Delta and sod1 Delta sod2 Delta had higher iron levels than the wild-type, independently of H2O2 stress. Fe levels were increased in sod2 Delta following H2O2 In addition, the sod2 Delta mutant was more sensitive to H2O2 treatment than the wild-type. These results suggest that sod2 Delta sensibility may be associated with (OH)-O-center dot production by the Fenton reaction. This increased iron demand in the sod2 Delta mutant may be a reflection of the cells' efforts to reconstitute proteins that are inactivated in conditions of excess superoxide. MDA levels were assayed by HPLC in these mutants. The highest MDA levels could be observed after 10mM H2O2 treatment in the sod1 Delta sod2 Delta double mutant. After treatment with a GSH inhibitor, the MDA level was still higher in the same strain. Thus, both direct and indirect GSH pathways are involved in the protection of lipid membranes and proteins in these mutants and may constitute an adaptative response to enhanced basal oxidative damage produced by superoxide.