Enantioselective apoptosis and oxidative damage induced by individual isomers of profenofos in primary hippocampal neurons

The purpose of this study was to investigate the apoptosis-related cytotoxic effects and molecular mechanisms of individual isomers of profenofos (PFF) on primary hippocampal neurons at 1.0 to 20 mg L−1. The cell viability and lactate dehydrogenase (LDH) efflux indicated that (−)­PFF exposure was associated with more toxic effects than (+)­PFF above the concentration of 5 mg L−1 (P < 0.5). Flow cytometric results showed that the percentages of apoptotic cells incubated with 20 mg L−1 (−)­PFF, (+)­PFF and rac-PFF for 24 h reached 23.4%, 9.2% and 14.2% (P < 0.01), respectively. Hippocampal neurons incubated with (−)­PFF, (+)­PFF and rac-PFF exhibited a dose-dependent accumulation of intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) and a dose-dependent inhibition of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activity, implying that the defense system of the tests induces oxidative damage. A statistically significant difference was observed between the two enantiomers at 5 mg L−1 and above. Moreover, the results showed that (−)­PFF exposure caused a significant loss in mitochondrial transmembrane potential (MMP), an upregulation of Ca2+ and Bax protein expression, a downregulation of Bcl-2 protein expression, and the activation of caspase-3 and caspase-9 in a dose-dependent manner; (+)­PFF and rac-PFF exhibited these effects to a lesser degree. All results suggest that PFF induced apoptosis in rat hippocampal neurons via the mitochondria-mediated pathway, and oxidative stress is one of the factors of PFF-induced apoptosis. In addition, (−)­PFF appears to play an important role in oxidative stress and apoptosis, indicating that enantioselectivity should be considered when assessing ecotoxicological effects and health risks of chiral pesticides.