Pesticides induced oxidative stress in thymocytes

The role of oxidative stress in immune cell toxicity caused by the pesticides lindane, malathion and permethrin was investigated in thymic cells from C57BL/6 mice. Thymocytes treated with any of these pesticides ( concentrations ranging between 50-150 mu M) were found to generate both superoxide (O-center dot(2)-) and H2O2. The production of center dot O-2(-) was detected with hydroethidine-ethidium bromide assay. H2O2 production was monitored with a flow cytometric fluorescent (DCFH-DA) assay. All three pesticides stimulated center dot O-2(-) release after 5 min exposure. Lindane and permethrin, but not malathion, continued to have significant (p <= 0.05) effects on center dot O-2(-) generation following 15 min of exposure. The lindane + malathion mixture was found to cause more-than-additive increase in center dot O-2(-) production compared to individual pesticide treatments ( at both 5 and 15 min). However, the effect of the lindane + permethrin mixture was not significantly different than individual components of this mixture. The effects of these pesticides on levels of antioxidant enzymes were also investigated, and only mixtures were found to have significant ( p <= 0.05) effects. Thus, lindane + malathion and lindane + permethrin mixtures increased total superoxide dismutase ( SOD) specific activity, had no effect on catalase levels and inhibited GSH-peroxidase and GSH-reductase specific activities. Although the results of these studies do not explain the mechanism of action of these pesticides on the generation of center dot O-2(-) and H2O2, it is worthy of note that mixtures of these chemicals have oxidative responses greater than those of single chemicals.