The herbicide acetochlor causes lipid peroxidation by inhibition of glutathione peroxidase activity.

Metabolic syndrome is increasing worldwide, particularly in rural communities, where residents have a higher risk of exposure to pesticides. We investigated whether six commonly used agricultural pesticides on corn and soy fields possess adipogenic and metabolic disruption activity. Exposure to two of these pesticides, the herbicides acetochlor and metolachlor, induced adipogenesis in vitro in mouse 3T3-L1 preadipocytes. The most potent compound, acetochlor, was selected for further studies in zebrafish. Acetochlor exposure induced morphological malformations and lethality in zebrafish larvae with an EC50 of 7.8 µM and LC50 of 12 µM. Acetochlor exposure at 10 nM resulted in lipid accumulation in zebrafish larvae when simultaneously fed a high-cholesterol diet. To decipher the molecular mechanisms behind acetochlor action, we performed transcriptomic and lipidomic analyses of exposed animals. The combined omics results suggested that acetochlor exposure increased Nrf2 activity in response to reactive oxygen species, as well as induced lipid peroxidation and ferroptosis. We further discovered that acetochlor structurally shares a chloroacetamide group with known inhibitors of glutathione peroxidase 4 (GPX4). Computational docking analysis suggested that acetochlor covalently binds to the active site of GPX4. Consistent with this prediction, Gpx activity was efficiently repressed by acetochlor in zebrafish, whereas lipid peroxidation was increased. We propose that acetochlor disrupts lipid homeostasis by inhibiting GPX activity, resulting in the accumulation of lipid peroxidation, 4-hydroxynonenal, and reactive oxygen species, which in turn activate Nrf2. Because metolachlor, among other acetanilide herbicides, also contains the chloroacetamide group, inhibition of GPX activity may represent a novel, common molecular initiating event of metabolic disruption.