Effects of imidacloprid on detoxifying enzyme glutathione S-transferase on Folsomia candida (Collembola)

Chemical analyses of the environment can document contamination by various xenobiotics, but it is also important to understand the effect of pollutants on living organisms. Thus, in the present work, we investigated the effect of the pesticide imidacloprid on the detoxifying enzyme glutathione S-transferase (GST) from Folsomia candida (Collembola), a standard test organism for estimating the effects of pesticides and environmental pollutants on non-target soil arthropods. Test animals were treated with different concentrations of imidacloprid for 48 h. Changes in steady-state levels of GST messenger RNA (mRNA) and GST enzyme activity were investigated. Extracted proteins were separated according to their sizes by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the resolved protein bands were detected by silver staining. The size of the glutathione (GSH) pool in Collembola was also determined. A predicted protein sequence of putative GSTs was identified with animals from control group. A 3-fold up-regulation of GST steady-state mRNA levels was detected in the samples treated with 5.0 mg L⁻¹ imidacloprid compared to the control, while a 2.5- and 2.0- fold up-regulation was found in organisms treated with 2.5 and 7.5 mg L⁻¹ imidacloprid, respectively. GST activity increased with increasing imidacloprid amounts from an initial activity of 0.11 μmol min⁻¹ mg⁻¹ protein in the control group up to 0.25 μmol min⁻¹ mg⁻¹ protein in the sample treated with the 5.0 mg L⁻¹ of pesticide. By contrast, the total amount of GSH decreased with increasing imidacloprid concentration. The results suggest that the alteration of GST activity, steady-state level of GST mRNA, and GSH level may be involved in the response of F. candida to the exposure of imidacloprid and can be used as biomarkers to monitor the toxic effects of imidacloprid and other environmental pollutants on Collembola.