Propolis Improved Methomyl-Induced Neurotoxicity in the Developing Brain of Albino Rats

Methomyl pesticide is still widely used for controlling pests on crops throughout developing countries, which poses a great risk to neural development during pregnancy. The beneficial role of propolis has recently been proven. The aim of the present study was to investigate the effects of methomyl exposure on pre- and postnatal development of the brain in rat fetuses and pups in terms of oxidative stress, histopathology, ultrastructural alterations, molecular changes, and cognition. Additionally, we aimed to investigate the possible mitigating effect of propolis on methomyl-induced neurotoxicity. Methomyl induced oxidative stress in the developing brain as evidenced by increased MDA activity, and decreased SOD, catalase, and GPx activity. It also induced vacuolation, necrotic foci, and disorganization of the cerebral cortical layer. Comet assay analysis revealed increased degradation of DNA in the neuronal cells of both fetuses and pups. The PCR results revealed increased expression of Iba-1 genes specific for microglial cells, and decreased the expression of the neuronal gene NeuN. Ultrastructurally, there was cytoplasmic rarefaction, organelle degeneration, and nuclear alterations. Moreover, methomyl altered cognitive function and impaired the spatial learning and memory functions of the rat pups. Propolis administration led to an evident amelioration of all these neurotoxic effects. In conclusion, methomyl exposure during pregnancy could have deleterious effects on brain development and propolis could be used as a potential neuroprotective supplement during pregnancy.