Herbicide and Amino Acid Synergy: Effects on Yeast Stress Biomarkers

Abstract

Employing biological models to study the combined effects of environmentally circulating xenobiotics offers a sustaina- ble approach to understanding their interaction mechanisms with living organisms. Although the use of atrazine (ATZ) and S-ethyl-N,N-dipropylthiocarbamate (EPTC) has been heavily restricted or not approved for agricultural crops in European Union member states, these herbicides remain widely used in several countries that export food to the EU. Furthermore, ATZ and EPTC residues remain elevated in European soil because of consecutive years of agronomic use. However, studies investigating their combined effects in eukaryotic systems are still limited. On the other hand, proline (Pro) protects living cells from stress by neutralizing reactive oxygen species (ROS), such as hydroxyl radical. This study aimed to assess the response of Saccharomy- ces cerevisiae, a unicellular eukaryotic organism, to individ- uals and combined exposures to EPTC, ATZ, and Pro, with particular emphasis on oxidative stress markers. Combined exposure to ATZ and EPTC triggered distinct responses in S. cerevisiae compared to individual treatments. Notably, it resulted in a decrease in total non-protein thiol content, glutathione (GSH) levels, and the activities of glutathione reductase (GR) and cytoplasmic catalase (Ctt), accompa- nied by an increase in ROS levels. These changes suggest that the dual exposure to EPTC and ATZ induced oxidative stress in S. cerevisiae, likely due to the decrease in the an- tioxidant activities of GR, which regenerates GSH, and Ctt, which scavenges hydrogen peroxide. The presence of Pro in the culture medium reversed the conditions of oxidative stress in terms of non-protein total thiols, ROS, and Ctt ac- tivity.