Atrazine herbicide cause cell damages in Saccharomyces cerevisiae, probably due aslowdown of glutathione redox cycle

Abstract

Atrazine (ATZ) has been used extensively as an herbicide, mainly due to its relatively low cost and ease of application. Previous studies have shown that many pollutants are redox active being able to enter microorganisms, causing a univalent reduction of dioxygen with reactive oxygen species (ROS) formation. These products can severely attack cell membranes causing lipid peroxidation. Many cells have developed antioxidative defence system, consisting of ROS-scavenging enzymes, e.g. glutathione peroxidase (GPx) or catalases (CTT1, CTA1), and antioxidants, e.g. glutathione (GSH). Catalases and GPx can catalyze H2O2 reduction to H2O and GPx can also scavenge lipid hydroperoxides, converting them in correspondent alcohols. ROS can be produced in cells not only as by-products of normal cellular metabolism but also under stress situations as contact with xenobiotics. So far, the oxidative stress responses to several pollutants as atrazine have been examined in bacteria plants and animals, but few studies have shown the response of antioxidant enzymes in S. cerevisiae to herbicides stress. So, the purpose of the present work was to evaluate the antioxidant response by yeast to atrazine exposure. Saccharomyces cerevisiae UE-ME3 a wild-type yeast deposited in the collection of laboratory of Enology, University of Evora, at mid-exponential phase were inoculated in YEPD medium, 2% (w/v) glucose, at 28°C, and shaken 150 rpm for 72 h in presence of 5 or 50 M ATZ and compared with control (YEPD). Yeasts were harvested by centrifugation at 3000 g for 10 min and washed with ultra-pure sterile water. The obtained cells were suspended in 10 mM phosphate buffer pH 7.0, and disrupted by sonication. The post-12 000 g supernatants were used for ROS, malondialdheyde (MDA), glutathione (GSH) and glutathione disulfide (GSSG) determination by fluorescence as well as alkaline phosphatase (ALP), CTT1, CTA1, glutathione reductase (GR), GPx and glucose 6-phosphate dehydrogenase (G6PD) activities by molecular absorption spectrometry. The statistical analyses were performed by ANOVA I and Duncan test (p < 0.01), using SPSS for Windows, version 22. The results showed a decrease in biomass, GSH/GSSG ratio, GR and GPx activities in the cells grown in presence of 5 or 50 lM atrazine.Additionally, it was also detected an increase in ROS and MDA contents as well as in CTT1, G6PD and ALP activities of cells exposed to 50 lM atrazine. In conclusion, the exposure to 50 lM atrazine, a triazine herbicide, caused oxidative stress and cell damages in wild-type S. cerevisiae UE-ME3, probably due a slowdown of glutathione redox cycle, despite a protection resulting from an increase of cytoplasmic activities catalase and ALP.