Oxidative stress response, epigenetic and behavioral alterations in Caenorhabditis elegans exposed to organophosphorus pesticide quinalphos

Abstract

Abstract Quinalphos (QP), an organophosphate pesticide is used worldwide in agricultural practices. Extensive use of pesticides creates toxicological and environmental nuisances on non-target organisms, where it severely affects cholinergic neurons in higher animals and also induces Parkinson, Alzheimer's disease and male sterility in humans. This study evaluated the sublethal effects of QP using Caenorhabditis elegans on the endpoints of body bend frequency, head thrash frequency, feeding activity for the assay as toxicity parameters. To assess the molecular-level effect, expression pattern of genes associated with locomotion (unc-47, unc-13), pharyngeal pumping (egl-30), epigenetic modulation (utx-1), and oxidative stress (daf-2, daf-16, age-1 and glod-4) was investigated by semi-quantitative PCR. The LC50 value of QP was 0.0323 mM for 1 h of exposure, and L4-stage worms were exposed to sublethal concentrations of 0.00344 mM. After QP exposure, body bend frequency, head thrash frequency and feeding behavior of worms was significantly decreased. Expression analysis results indicate that QP exposure leads to the up-regulation in expression of some stress genes (daf-16 and glod-4) and pharyngeal pumping (egl-30), while other genes responsible for stress like daf-2 and age-1, locomotion (unc-13 and unc-47) and epigenetic modulation (utx-1) are down-regulated. Subsequently, transgenic worms expressing daf-16::GFP were exposed to QP, where induced expression of DAF-16 was evident. Overall, it appears to recruit daf-2/insulin receptor and daf-16/FOXO-dependent pathways to rescue the animals from QP-mediated oxidative stress. Alterations in the expression of many genes by QP are unveiled for the first time in this study, which could serve as biomarkers for monitoring QP exposure.