Toxic Effects of Neonicotinoid Insecticide Imidacloprid and Polystyrene Microplastics on Rat Neuroblastoma B104 Cells

Imidacloprid (IMI) and polystyrene microplastics (PS-MPs) are common environmental pollutants, posing potential risks to ecosystems and human health. However, there is limited research on their toxic effects on nerve cells, particularly under combined exposure conditions. This study aimed to evaluate the toxic effects of IMI and PS-MPs alone and in combination on rat neuroblastoma B104 cells. Based on a cell viability assay (48 h), the No Observed Adverse Effect Levels of IMI and PS-MPs were 260 mg/L and <150 mg/L, respectively. To study their effects on the cholinergic system and oxidative stress, similar concentrations of IMI (2.6, 26, 260 mg/L) and PS-MPs (3, 30, 300 mg/L), alone and in combination, were exposed to B104 cells for 48 h. The results showed that IMI alone decreased acetylcholine (ACh) and acetylcholinesterase (AChE) contents, PS-MPs alone increased ACh and AChE contents, and under the combined condition, the effect of PS-MPs predominated over IMI. Both IMI and PS-MPs alone decreased the ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG), indicating oxidative stress, and under the combined condition, the ratio of GSH/GSSG decreased more, but were less than the sum of the decreases that were observed under treatment by both compounds alone. The combined exposure exhibited antagonistic effects on all endpoints. Results of this study provides a scientific basis for the environmental risk assessment of microplastics and neonicotinoid pesticides.