Human Neural Stem Cells Are More Vulnerable to Damage from Pesticide-Induced Oxidative Stress After Differentiation

Organophosphate (OP) and carbamate pesticides are widely employed in agriculture to facilitate the production of economically viable crops. However, pesticide contamination of food, water, and air leads to undesired human exposure. Neuronal tissue may be particularly vulnerable to pesticide toxicity during periods of neurodevelopment. Hence, this study aimed to investigate the neurotoxicity of three pesticide compounds, namely chlorpyrifos-oxon (CPO), azamethiphos (AZO), and aldicarb, on human neural progenitor cells (hNPCs) and whether toxicity differed between undifferentiated and differentiated stem cells. Undifferentiated and differentiated hNPCs were exposed to these neurotoxicants at concentrations of 0–200 µM for 24 h, and cell viability was evaluated using 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays. The impact of the neurotoxicants on cellular bioenergetics was determined by quantifying cellular ATP levels and the production of reactive oxygen species (ROS) using a 2′,7′-dichlorofluorescein diacetate (DCFDA) assay. Concentration–response curves were also generated to measure their relative inhibition of AChE. The neurotoxicants induced concentration-dependent reductions in cell viability (p < 0.0001), cellular ATP levels (p < 0.0001), and the inhibition of AChE (p < 0.0001). Notably, differentiated neurons displayed higher sensitivity than undifferentiated neural stem cells (NSCs), with a toxicity threshold of ≥1 µM. ROS levels were significantly increased (p < 0.0001) following neurotoxicant exposures, more so in differentiated cells, with levels that correlated with cytotoxicity, cell death, and the induction of oxidatively damaged proteins in surviving cells. These findings suggest a central role of oxidative stress and protein oxidation in mediating the neurotoxic effects of pesticide compounds on NSCs. Furthermore, the heightened susceptibility of NSCs to pesticide toxicity after differentiation is indicative of human vulnerability during periods of neurodevelopment.