RESPONSES OF ANTIOXIDANT ENZYMES AND HEAT SHOCK PROTEINS IN DROSOPHILA TO TREATMENT WITH A PESTICIDE MIXTURE

The effects of a mixture of seven pesticides were examined on the expression of antioxidant enzymes, Mn superoxide dismutase (Mn-SOD), catalase (CAT), glutathione synthetase (GS), and heat shock proteins (HSP) 26, 60, 70 and 83 in adult fruit flies (Drosophila melanogaster Oregon R). The flies were reared under controlled conditions on artificial diets and treated with a mixture of seven pesticides (molinate, thiobencarb, linuron, phorate, primiphos-methyl, fenvalerate and lambda-cyhalothrin) commonly found in water, at concentrations of 0.1, 0.5 and 1 parts per billion (ppb) for 1 and 5 days. Quantitative real-time PCR (qRT-PCR) analysis of Mn-SOD, CAT and GS expression revealed that the analyzed markers responded significantly to pesticide-induced oxidative stress, in particular on the 5th day of treatment. On the 1st day of treatment, the relative expression of HSP26 and HSP60 genes increased only after exposure to the highest concentrations of pesticides, whereas HSP70 and HSP83 expression increased after exposure to 0.5 and 1 ppb. After five days of treatment, the expression of all HSP genes was increased after exposure to all pesticide concentrations. A positive correlation was determined between the relative expression levels of some HSPs (except HSP60), and antioxidant genes. The observed changes in antioxidant enzyme and HSP mRNA levels in D. melanogaster suggest that the permissible limits of pesticide concentrations for clean drinking water outlined in the regulations of several countries are potentially cytotoxic. The presented findings lend support for reevaluation of these limits.