6-Chloronicotinic Acid Induces Toxicity in Mouse Neural Stem Cells via the C3ar1 Signaling

Neural stem cells (NSCs) are essential for brain development due to their ability to proliferate and differentiate into various neural cell types. Neonicotinoid insecticides (NNIs), which have replaced traditional pesticides, are now widely used and frequently detected in environmental and biological samples. Prenatal exposure to NNIs has been associated with an increased risk of neurodevelopmental disorders in offspring, yet the causal relationship and the underpinning mechanism remain to be clarified. As one of the primary metabolites of chloropyridinyl neonicotinoids, 6-chloronicotinic acid (6-ClNA) has been identified as a potential neurotoxin, though its effects on NSCs have not been fully explored. Here, we demonstrate that 6-ClNA exposure significantly disrupted NSC proliferation and differentiation in vitro. Transcriptomic analyses revealed that 6-ClNA altered the expression of pathways related to proliferation, apoptosis, and inflammation, with notable activation of the C3ar1/C1qa signaling axis. Genetic ablation of C3ar1 using siRNA markedly restored NSC proliferation and neurosphere formation, as well as reduced apoptosis, suggesting a central role of C3ar1/C1qa in mediating 6-ClNA's neurotoxic effects. These findings imply that early-life exposure to NNIs may affect the fitness and function of NSCs, wherein the C3ar1 pathway plays an indispensable role.