Imidacloprid-induced oxidative stress in honey bees and the antioxidant action of caffeine

The use of pesticides on crops contributes to the decline of bee populations, and in this sense, bioactive nutrients have been studied to counteract this effect. We suppose that caffeine might be one of these nutrients. We exposed honey bees ( Apis mellifera L.) to 0.7 or 2.0 ng/mL imidacloprid, 5.0 μg/mL caffeine in syrup, or 5.0 μg/mL caffeine in syrup plus 0.7 or 2.0 ng/mL imidacloprid. After 72 h, the oxidative status and the food intake were verified. Imidacloprid increased glutathione peroxidase and catalase activities. Caffeine alone or with 2.0 ng/mL imidacloprid also stimulated the activity of glutathione peroxidase but did not alter the effect of the insecticide on the catalase activity. A significant reduction in the concentration of the thiol group of proteins was observed in the two imidacloprid-fed groups, and the addition of caffeine protected these groups. Imidacloprid increased the malondialdehyde concentration while the addition of caffeine partially decreased this effect. Food intake was higher for bees treated with 2.0 ng/mL imidacloprid. Our results show that imidacloprid increased the food intake resulting in oxidative damage, which was partially reversed by caffeine. From these findings, it is inferred that caffeine treatments can be used to mitigate the sublethal effects of this insecticide on honey bees.