Antioxidants protect the yeastSaccharomyces cerevisiaeagainst hypertonic stress

Abstract

Yeast (Saccharomyces cerevisiae) mutants lacking CuZnSOD have been reported to be hypersensitive to hypertonic media and to show increased oxidative damage. This study demonstrates that hypertonic medium (containing 0.8 M NaCl) increases the generation of superoxide and other reactive species in yeast cells. Other sequelae of exposure to hypertonic medium include oxidation of cellular low-molecular weight thiols and decrease in total antioxidant capacity of cellular extracts. deltasod1 mutant is more sensitive than a wild-type strain to colony growth inhibition on a hypertonic medium. Anaerobic conditions, ascorbate, glutathione, cysteine and dithiothreitol are able to ameliorate this growth inhibition but a range of other antioxidants does not protect. The protective ability of the antioxidants does not correlate with the rate of their reactions with superoxide but seems to be conditioned by low redox potential for one-electron oxidation of free radicals of the antioxidants. It suggests that repair of low-redox potential targets rather than prevention of their damage by superoxide is important in the antioxidant protection against oxidative stress induced by hypertonic conditions.

A Simple Growth Test of a Saccharomyces cerevisiae Cu, Zn-Superoxide Dismutase-Deficient Mutant in Hypertonic Medium for Biological Evaluation of Antioxidants

“…The SOD1Δ strain exhibited high sensitivity to paraquat and methionine auxotrophy (data not shown), that was observed with previously isolated Sod1-lacking mutants (Bilinski et al, 1985;Chang and Kosman, 1990). Osmotic stress also hampers the growth of yeast cells, and the SOD1 mutants are oversensitive to hypertonic medium (e.g., one containing 0.8 M NaCl) (Garay-Arroyo et al, 2003;Koziol et al, 2005). We compared cell growth under aerobic conditions of the SOD1Δ strain with that of wild-type yeast in YPD liquid media containing various concentrations of sorbitol, and also observed growth inhibition of the SOD1Δ strain at high concentrations of sorbitol ( Fig.…”

“…This suggests that inactivation of such antioxidants during cultivation is not responsible for the absence of growth restoration in SOD1Δ cells. Koziol et al (2005) established a similar method using another Sod1-deficient strain, and also found that a limited number of antioxidants (AsA and thiols) were able to improve the growth of the cells under hyperosmosis. Other categories of antioxidants, including Trolox, melatonin, and TEMPO, had no effect.…”

“…NaCl increases the generation of superoxide and other ROS, as well as the oxidation of cellular low-molecular weight thiols in yeast cells (Koziol et al, 2005). ROS directly oxidize lysine, arginine, proline and threonine residues of protein to yield carbonyl derivatives (Berlett and Stadtman, 1997).…”

“…This effect is mediated by oxidative stress, since the SOD1Δ strain is oversensitive to hypertonic medium compared to wild-type yeast, and ROS accumulate in yeast cells exposed to hypertonic media (Garay-Arroyo et al, 2003;Koziol et al, 2005). These obvious phenotypes of SOD1Δ could be reversed by the addition of L-ascorbic acid (AsA), a potent antioxidant (Krzepilko et al, 2004;Zyracka et al, 2005a;Koziol et al, 2005, Saffi et al, 2006. Compensation of the Sod1 defect by an antioxidant implies that the mutant yeast can be used as a biosensor to antioxidants (Zyracka et al, 2005b).…”

Investigation of the effect of intracolonic melatonin gel formulation on acetic acid-induced colitis

“…Cells have been known to be hypersensitive to hypertonic media and to show an increased oxidative damage (Koziol et al, 2005). In the present study, colon cells encounter multiple stress conditions, such as acetic acid-induced colitis and hyperosmotic stress with intracolonic gel containing Naalginate.…”