The influence of oxygen toxicity on yeast mother cell-specific aging

The effect of deleting both catalase genes and of increased oxygen as well as paraquat (a Dro-oxidant) on the replicative life span of yeast mother ce lls has been investigated to test the so-called oxygen theory of aging. Thi s is well established in higher organisms,but has not been extensively test ed in the unicellular yeast model system. Life span determinations were per formed in ambient air or in a controlled atmosphere (55% oxygen) and an iso genic series of strains deleted for one or both yeast catalases was used an d compared with wild type. In the absence of cellular catalase, increased o xygen caused a marked decrease in life span that could be completely revers ed by adding 1 mM GSH, a physiological antioxidant, to the yeast growth med ium. In a second unrelated strain, the effects were similar although even t he wild type showed a decrease in life span when oxygen was increased. The effect could again be compensated by addition of extracellular GSH. Our res ults show that manipulating the detoxification of reactive oxygen species h as a profound effect on yeast aging. These findings are discussed in the li ght of recent results relating to oxygen toxicity in the aging process of h igher organisms. (C) 2000 Elsevier Science Inc. All rights reserved.