Induction of Phenotypes Resembling CuZn-Superoxide Dismutase Deletion in Wild-Type Yeast Cells:  An in Vivo Assay for the Role of Superoxide in the Toxicity of Redox-Cycling Compounds

Abstract

Yeast (Saccharomyces cerevisiae) lacking the enzyme CuZn-superoxide dismutase (sod1delta) display a large number of dioxygen sensitive phenotypes, such as amino acid auxotrophies, sensitivity to elevated temperatures, and sensitivity to 100% dioxygen, which are attributed to superoxide stress. Such cells are exquisitely sensitive to small amounts of the herbicide paraquat (methyl viologen), which is known to produce high fluxes of superoxide in vivo via a redox-cycling mechanism. We report that dioxygen sensitive phenotypes similar to those seen in sod1delta cells can be induced in wild-type cells by treatment with moderate concentrations of paraquat or diquat, another bipyridyl herbicide, providing strong evidence that the mechanism of toxicity for both of these compounds is attributable to superoxide stress. Certain redox-cycling quinone compounds (e.g., menadione and plumbagin) are also far more toxic toward sod1delta than to wild type. However, treatment of wild-type yeast with menadione or plumbagin did not induce sod1delta-like phenotypes, although toxicity was evident. Thus, their toxicity in wild type cells is predominantly, but not exclusively, due to mechanisms unrelated to superoxide production. Further evidence for a different basis of toxicity toward wild-type yeast in these two classes of redox-cycling compounds includes the observations that (i) growth in low oxygen alleviated the effects of paraquat and diquat but not those of menadione or plumbagin and (ii) activity of the superoxide sensitive enzyme aconitase is affected by very low concentrations of paraquat but only by higher, growth inhibitory concentrations of menadione. These results provide the basis for an easy qualitative assay of the contribution of redox-cycling to the toxicity of a test compound. Using this method, we analyzed the Parkinsonism-inducing compound 1-methyl-4-phenylpyridinium and found that redox cycling and superoxide toxicity are not the predominant factor in its toxic mechanism.

The genetic basis for variation in resistance to infection in the Drosophila melanogaster genetic reference panel

“…Our current study shows that resistance to both Ma549 and PA14 correlates with survival times on paraquat but not menadione sodium bisulfite (MSB). Toxicity of paraquat is primarily due to production of superoxides whereas MSB toxicity is due to electrophilic attack [109], suggesting that the ability to alleviate or tolerate superoxide stress is a feature of a generalized defense response to multiple pathogens. Drosophila shows circadian regulation of response to oxidative stress [110], so between-line variation in these rhythms may influence how they respond to ROS produced during infection.…”

Trans-sulfuration Pathway Seleno-amino Acids Are Mediators of Selenomethionine Toxicity in Saccharomyces cerevisiae*

“…To probe superoxide production in vivo during SeMet treatment, we assayed the activity of aconitase, a 4Fe-4S-containing enzyme sensitive to superoxide-induced stress (46). As shown in Fig.…”

Oxidative stress response and virulence factors in Candida glabrata clinical isolates

“…Thus, compared with the ATCC 2001 reference strain, all clinical isolates were susceptible to three drugs inducing oxidative stress, which indicates that under normal conditions phagocytic cells could destroy them during infection of patients. However, compared with S. cerevisiae (Batova et al 2010;Wallace et al 2005), the C. glabrata clinical isolates were less sensitive to all three drugs irrespective of their susceptibility to fluconazole (Berila et al 2009). The mean relative CSH of 38 isolates was 21.9 and ranged from 1.92 to 56.96 (Fig.…”

“…CTBT and menadion increase the intracellular production of superoxide (Batova et al 2010;Wallace et al 2005) that is detoxified by superoxide dismutases to H 2 O 2 , which is subsequently detoxified by catalase to water and oxygen (Wallace et al 2005). All isolates were sensitive to H 2 O 2 (40 mmol/L) with exception of the isolate 11 displaying a lower MIC for this drug (10 millimoles per liter).…”