Effect of Green-Synthesized Curcumin-Coated Silver Nanoparticles on the Hippocampal Tissue in Chlorpyrifos-Exposed...

Pubertal modifications are likely to affect various regions of the central nervous system (CNS) structure and functioning by multiple mechanisms. The development of the CNS during this period makes this system highly susceptible to environmental pollutants and other toxic agents and drugs. Chlorpyrifos (CPF) is an organophosphate pesticide with well-known neurotoxic effects. It was found that natural antioxidant supplementation could ameliorate CPF-induced CNS damage. There is strong evidence regarding the protective effects of curcumin against CPF toxicity. Numerous attempts have been performed to potentiate the bioavailability of curcumin, including formulations with nanoparticles. Silver nanoparticles (AgNPs) are broadly applied in biomedicine due to their exceptional physicochemical characteristics. Nonetheless, several issues remain about their safety and efficacy, specifically in the nervous system, according to recent literature from 2022-2025. Therefore, this study aimed to investigate the effects of curcumin-coated silver nanoparticles on the hippocampus of CPF-exposed and non-exposed rats during the puberty stage.

In this experimental study, 42 male Wistar rats aged 30 days were randomly divided into 7 groups, including control, oil, and CPF (5 mg/kg) groups, as well as four groups receiving curcumin-coated green silver nanoparticles (CUR-AgNPs) at doses of 40 and 80 μg/kg, both with and without CPF administration. After 30 days, all rats were anesthetized, and blood and hippocampal samples were collected to measure biochemical parameters including acetylcholinesterase (AChE), malondialdehyde (MDA), superoxide dismutase (SOD), and nitric oxide (NO), and subjected to histopathological examination.

Significant changes were observed in the levels of tissue and serum AChE activity, as well as tissue MDA, among the CPF group compared with the control group (P<0.001). However, no statistically significant differences were found in the mean levels of tissue NO and SOD between the two groups. CUR-AgNPs did not exhibit any change in the serum AChE activity and also in the mean tissue levels of MDA, NO, and SOD, as well as histopathological findings in the CPF-exposed group compared with the non-treated CPF-exposed group. However, histopathological examination indicated the incidence of necrotic neurons and severe eosinophilic cytoplasmic contraction in the CPF, CPF+ CUR-AgNPs and CUR-AgNPs groups.

Curcumin, as a potent antioxidant, could prevent AgNPs-induced oxidative stress; however, it was not able to prevent the accumulation and direct toxic effect of AgNPs in the neurons and resulted in direct toxic damage in the tissue through disruption of calcium homeostasis and mitochondrial dysfunction. Future studies are needed to determine the exact mechanisms involved in the direct toxic effect of CUR-AgNPs in the various brain regions.

This study indicated that administration of CUR-AgNPs at doses of 40 and 80 μg/kg could induce neurotoxicity in the hippocampal tissue of male rats during the developmental puberty stage.