Evaluation of radioprotective action of compounds using Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae serves as a model eukaryotic system to screen radioprotectors that can be used primarily in radiotherapy as well as in occupational workers in nuclear and allied industries. A number of antioxidants are suggested to be radioprotectors by virtue of their ability to quench reactive oxygen species, but their radioprotective action has not been investigated so far. In this study, a number of antioxidants were tested for their efficacy in radioprotection using yeast cells. Sulfhydryl compounds (disulfiram at 100 and 200 microM) and reduced glutathione (10 and 100 mM), purified compounds of plant origin, such as curcumin (1 mM, 10 mM, and 100 mM), quercetin (100 and 500 microM), rutin (100 and 200 microM), ellagic acid (100,200, and 500 microM) and gallic acid (100 and 500 microM)-were studied. The results revealed that all compounds, except gallic acid, specifically protected normal yeast cells from gamma-radiation damage. Using rad 52 mutants, which lack recombinational DNA repair pathway, it has been found that protection was solely brought about by reducing DNA damage rather than by interfering with DNA repair. Results with DNA repair polymerase further substantiated this contention. We conclude that simple eukaryotic yeast cells can serve as a test system not only for rapid screening of radiomodifiers but also to study their mode of action.