Response of antioxidant and detoxification enzyme activities in Cydia pomonella (Lepidoptera: Tortricidae) exposed to acetamiprid

Abstract

Introduction: Control strategies used against Cydia pomonella (L), includes application of neonicotinoid insecticides such as acetamiprid. In the valleys of Río Negro and Neuquén, non-target adults of the codling moth may be exposed to sublethal concentrations of pesticides. The stress, caused by this exposure might activate antioxidant and detoxification systems to maintain the redox homeostasis which are essential for the physiological health of the insect. Objective: The objective of this study was to evaluate the effects of different sublethal concentrations of acetamiprid on cytochrome P450 monooxygenases (CYP450) activity and the antioxidant system in adults of C. pomonella. Materials and Methods: One-two days-old adult moths from a field population (FP) and a laboratory susceptible strain (LSS) were exposed for 24 h to dry residues of acetamiprid applied to glass cups and their lifts (1 mL of insecticide dissolved in acetone: 6.25, 25, 50, 100 and 200 ppm) or acetone alone. The enzymatic activities were quantified in the supernatant of body homogenates: (a) CYP450, assessed by a fluorometric protocol using 7-ethoxycumarine (7-EC) as substrate (ECOD); (b) glutathione S-transferases, with 1-chloro-2,4-dinitrobenzene (CDNB) and GSH as substrates; and (c) catalases (CAT), determined by recording the decomposition of H2O2. GSH content was measured using the Ellman reagent (5,5´-dithiobis(2 nitrobenzoic acid-DTNB). Protein concentration was quantified using Lowry assays. Results: In untreated adults, ECOD activity was significantly lower in LSS than in FP (P < 0.05). In adult exposed to acetamiprid, ECOD activity was significantly higher in the FP at 50 and 100 ppm respectively. None of the concentrations applied modified the ECOD activity in the LSS respect to untreated ones. GST activity in FP adults exposed to 25 ppm of acetamiprid was significantly higher than untreated adults (P < 0.05). LSS individuals were not affected by any of the concentrations of acetamiprid tested. CAT activity from adults of both LSS and FP were unaffected by the concentrations of acetamiprid evaluated. The GSH content from FP adults was significantly higher at 25 ppm and 100 ppm respect to the control group (P < 0.05). LSS adults showed a significant increase of GSH content at 100 ppm compared to the control group (P < 0.05). Conclusion: CYP450 activity increased in a concentration-dependent manner (6.25 to 100 ppm) in FP. A similar profile was observed for the GSH content in both FP and LSS. These results suggests that the increase of GSH content is a response to the oxidative stress generated by CYP450 or acetamiprid.