Elsevier

Experimental Gerontology

Volume 35, Issue 1, February 2000, Pages 63-70
Experimental Gerontology

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

https://doi.org/10.1016/S0531-5565(99)00087-XGet rights and content

Abstract

The effect of deleting both catalase genes and of increased oxygen as well as paraquat (a pro-oxidant) on the replicative life span of yeast mother cells has been investigated to test the so-called oxygen theory of aging. This is well established in higher organisms, but has not been extensively tested in the unicellular yeast model system. Life span determinations were performed in ambient air or in a controlled atmosphere (55% oxygen) and an isogenic series of strains deleted for one or both yeast catalases was used and compared with wild type. In the absence of cellular catalase, increased oxygen caused a marked decrease in life span that could be completely reversed by adding 1 mM GSH, a physiological antioxidant, to the yeast growth medium. In a second unrelated strain, the effects were similar although even the wild type showed a decrease in life span when oxygen was increased. The effect could again be compensated by addition of extracellular GSH. Our results show that manipulating the detoxification of reactive oxygen species has a profound effect on yeast aging. These findings are discussed in the light of recent results relating to oxygen toxicity in the aging process of higher organisms.

Introduction

Yeast mother cell-specific aging has been reviewed recently Jazwinski 1999, Johnson et al 1999 and is now a well recognized model system for the aging processes of higher cells and, perhaps, higher organisms. In yeast only the mother cell ages, whereas the daughter cells, with the exception of the daughters of very old mothers (Kennedy et al., 1994), reset their clock to zero (Jazwinski, 1993). This is different from cellular clonal aging as observed in cell cultures of mammalian fibroblasts. However, some of the phenotypic manifestations of senescence are strikingly similar in yeast mother cells and in cultured human cells. For instance, old cells are much bigger than young cells Egilmez et al 1990, Mortimer and Johnston 1959, Nestelbacher et al 1999, they lose cellular polarity (pointing to a cytoskeletal defect) and the cell surface is deformed and looks “folded” (Pichová et al., 1997). The cell cycle (Mortimer and Johnston, 1959) and protein synthesis (Motizuki and Tsurugi, 1992) are much slower than in young cells.

For higher organisms (flies, worms, mammals and others), the so called “oxygen theory of aging” was first formulated by Harman (1962) and is now well established Ames et al 1993, Gems 1999, Orr and Sohal 1994, Sohal and Weindruch 1996, Martin et al 1996. The theory implies that old cells accumulate and ultimately cannot repair or remove biomolecules that have been damaged by reactive oxygen species (ROS) originating from a “leaky” mitochondrial respiratory chain or from other oxidative processes in the cell, generically called “oxidative stress.” This would imply some kind of error catastrophe (damaged molecules leading to the generation of more damaged molecules) or could simply mean that old cellular material accumulates in the mother cell, but not in the daughter cell. Targets for this process may be DNA, proteins, lipids and other molecules. The accumulation of mutations in chromosomal DNA is logically excluded as a cause for yeast mother cell-specific aging because the last daughter cells of old mother cells due to semiconservative replication should carry the same mutations as the mother leading to clonal aging, which is not observed. However, old yeast mother cells do accumulate extrachromosomal rDNA circles (Sinclair and Guarente, 1997) which are very infrequently inherited by daughters because they don’t carry a centromere. Here we want to underscore the fact that yeast mother cell-specific aging is clearly a polygenic process that depends on multiple causative environmental and internal conditions. Thus the theory based on generation of rDNA circles and the oxygen theory of aging are not mutually exclusive, because targets other than DNA for oxidative damage are quite plausible. We expect that oxidative damage could be one, but by no means the only cause of yeast mother cell-specific aging. Surprisingly, very few published investigations of the influence of oxygen toxicity on yeast aging exist. Both, Wawryn et al. (1999) and Barker et al. (1999) show that disruption of the superoxide dismutase (SOD)-encoding genes shorten the life span of yeast. The SODs and catalases together are sufficient to detoxify superoxide. We have therefore undertaken to investigate the influence of mutations in the yeast catalase genes (blocking one pathway for detoxification of ROS) and of changes in oxygen partial pressure on yeast mother cell-specific aging. Our results seem to strongly support a role for oxygen toxicity in yeast mother cell-specific aging.

Section snippets

Strains and growth media

The haploid Saccharomyces cerevisiae strain W303eA (MATa; ura3–1; leu2–3,112; trp1–1; his3–11,15; ade2–1; can1–100) was obtained from P. Slonimski (Gif-sur-Yvette). The haploid S. cerevisiae strain JC482 (MATa; ura3–52; leu2; his4–539) was obtained from J. Cannon (Cannon and Tatchell, 1987). The single and double mutant strains were constructed in W303eA by standard genetic manipulations (Kaiser et al., 1994). Both the CTA1 and CTT1 genes were disrupted by replacement with URA3 and combined by

Results

In this study we used two different haploid wild type (WT) laboratory yeast strains, W303eA and JC482.Yeast aging studies require a strictly isogenic system consisting of a WT strain and the mutant(s) to be studied due to the polygenic nature of the aging process and due to the fact that different WT laboratory strains display a very different replicative life span (Jazwinski, 1993). W303eA is a strain used by the current European program for systematic functional analysis of yeast open reading

Discussion

The above results indicate an important role for oxygen toxicity in the yeast mother cell-specific aging process. It is generally difficult to establish a causal relationship and to discriminate between causal and accidental phenomena in aging research, however, the following observations are in favor of our hypothesis. It was carefully checked that throughout the life span determinations the dividing cells always experienced an excess of nutrients. At the end of the life span determination

Acknowledgements

We are grateful to Ian Dawes for many discussions and for his advice during the course of this work.

References (29)

  • C.M. Grant et al.

    Glutathione is an essential metabolite required for resistance to oxidative stress in the yeast Saccharomyces cerevisiae

    Curr Genet

    (1996)
  • Grant, C. M., Perrone, G., & Dawes, I. W. (1998). Glutathione and catalase provide overlapping defenses for protection...
  • D. Harman

    Role of free radicals in mutation, cancer, aging and maintenance of life

    Rad Res

    (1962)
  • S.M. Jazwinski

    Genes of youthgenetics of aging in baker’s yeast

    ASM News

    (1993)
  • Cited by (54)

    • Yeast as a model organism for aging research

      2021, Handbook of the Biology of Aging
    • A budding topic: Modeling aging and longevity in yeast

      2018, Conn's Handbook of Models for Human Aging
    • The roles of thiol oxidoreductases in yeast replicative aging

      2010, Mechanisms of Ageing and Development
      Citation Excerpt :

      It has been shown that oxidative damage increases during replicative aging in yeast and the absence of antioxidant genes causes further accumulation of this damage (Nestelbacher et al., 2000; Grzelak et al., 2006). There are many antioxidant enzymes, such as superoxide dismutases, catalases and methionine sulfoxide reductases, that were shown to affect the replicative life span (RLS) in yeast and other organisms (Nestelbacher et al., 2000; Fabrizio et al., 2004; Unlu and Koc, 2007; Radyuk et al., 2009). However, there are also contrasting data suggesting that deletion of enzymes involved in redox control does not influence RLS or even increases it in yeast.

    View all citing articles on Scopus

    We are grateful for the support from FWF (Austria) (No. P11064-MOB).

    View full text