In Vitro Evaluation of the Combined Toxicity of Pirimiphos-methyl and Piperonyl Butoxide

Pirimiphos-methyl (PMM) and piperonyl butoxide (PBO) are commonly used in crops to combat pests. This study examined their cytotoxicity and genotoxicity in various cell lines (RAW 264-7, H9C2, HepG2, HEK 293) across different exposure times. HepG2 cells showed heightened sensitivity to the combination (MIX) at 100 µg/mL after 48 and 72 hours, with no genotoxic effects observed in both HepG2 and mouse whole blood cells. HEK 293 cells experienced cytotoxicity at higher concentrations of PMM, PBO, and MIX (50 and 100 µg/mL) after 48 and 72 hours. H9C2 cells exhibited the most pronounced cytotoxicity with MIX at 100 µg/mL at all time points evaluated. RAW 264-7 cells were sensitive to high concentrations (50 and 100 µg/mL) after 72 hours. Interestingly, non-toxic concentrations of MIX (5 µg/mL) inhibited 100% of nitric oxide production and significantly reduced TNF and IL-6 levels in RAW 264-7 cells stimulated with LPS. Higher concentrations of PMM and PBO individually also reduced TNF and IL-6 production, suggesting immunomodulatory effects at low concentrations without associated toxicity. These results underscore the importance of considering both concentration and exposure time when assessing toxicity, especially in chronic exposure scenarios common in real biological environments.