Biomolecular alterations by chronic sub-lethal exposure of Malathion and Paraquat in Drosophila melanogaster: study on pesticide tolerance in insects

Pesticides exert a wide variety of functions for controlling pests. At low doses the pests are not much affected and parallel to that a chance of tolerance has been expected. In this study a population of fruit flies Drosophila melanogaster was grown under various doses of insecticide Malathion and herbicide Paraquat. Lower than the sub-lethal doses (0.2 micromolar), various biomolecular alterations in terms of protein oxidation (Advanced Oxidation Protein Products, AOPP), lipid peroxidation (Malondialdehyde, MDA), sialic acids, total thiols, Cupric Ion Reducing Antioxidant Capacity (CUPRAC) and 2,2 '-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radical scavenging activity have been observed. Positive alteration in AOPP for both Malathion and Paraquat treated fruit flies as well as increased MDA content in Paraquat treated flies are the alterations in the fruit fly population because of oxidative stress. The unaffected MDA, sialic acid content and CUPRAC antioxidant capacity for Malathion treated flies demonstrates the diminished effects of oxidative stress exerted through Malathion. There is increase sialic acid and CUPRAC antioxidant capacity after treatment of Paraquat. There is also an increase in total thiols and ABTS cation radical scavenging activity after treatment of both Malathion and Paraquat. These results evidently show that improved antioxidant mechanisms effectively alleviate the oxidative stress exerted by pesticides. This study is clearly reflecting that oxidative stress generated by the sub lethal doses of pesticides can be diminished and certain tolerance level is also achieved by the insects in terms of increased antioxidant defence and longevity.