Evaluation of perinatal exposure of glyphosate and its mixture with 2,4-D and dicamba οn liver redox status in Wistar rats

Abstract

Wide-scale emergence of glyphosate-resistant weeds has led to an increase in the simultaneous application of herbicide mixtures exacerbated by the introduction of crops tolerant to glyphosate plus dicamba or glyphosate plus 2,4-D. This raises serious concerns regarding the environmental and health risks resulting from increased exposure to a mixture of herbicide active ingredients. We evaluated hepatotoxic effects following perinatal exposure to glyphosate alone or in combination with 2,4-D and dicamba from gestational day-6 until adulthood in Wistar rats. Animals were administered with glyphosate at the European Union (EU) acceptable daily intake (ADI; 0.5 mg/kg bw/day) and no-observed-adverse-effect level (NOAEL; 50 mg/kg bw/day). A mixture of glyphosate with 2,4-D (0.3 mg/kg bw/day) and dicamba (0.02 mg/kg bw/day) with each at their EU ADI was evaluated. Redox status was determined by measuring levels of reduced glutathione, decomposition rate of Η₂Ο₂, glutathione reductase, glutathione peroxidase, total antioxidant capacity, thiobarbituric reactive substances, and protein carbonyls. Gene expression analysis of Nr1d1, Nr1d2, Clec2g, Ier3, and Gadd45g associated with oxidative damage to DNA, was also performed. Analysis of liver samples showed that exposure to the mixture of the three herbicides induced a marked increase in the concentration of glutathione and malondialdehyde indicative of a disturbance in redox balance. Nevertheless, the effect of increased lipid peroxidation was not discernible following a 3-month recuperation period where animals were withdrawn from pesticide exposure post-weaning. Interestingly, toxic effects caused by prenatal exposure to the glyphosate NOAEL were present after the same 3-month recovery period. No statistically significant changes in the expression of genes linked with genotoxicity were observed. Our findings reinforce the importance of assessing the combined effects of chemical pollutants at doses that are asserted by regulatory agencies to be safe individually.

Keywords: 2,4-D; Dicamba; Glyphosate; Oxidative stress; Pesticide mixtures; Pregnancy.