Co-exposure to polystyrene nanoparticles and cypermethrin regulates ferroptosis-mediated hepatic steatosis via the GPX4/SREBP1/SCD1 molecular axis

• PS-NPs adsorb cypermethrin (CY) and enhance its hepatotoxicity. • Co-exposure to PS-NPs and CY triggers ferroptosis-mediated hepatic steatosis. • GPX4, as a central hub, links ferroptosis and lipid synthesis. • Activation of the SREBP1/SCD1 pathway drives lipid metabolic reprogramming. • Up- or down-regulating GPX4 expression could relieve or aggravate liver lipid degeneration. Cypermethrin (CY), a pyrethroid insecticide, accumulated in aquatic environments and exertd toxic effects on aquatic organisms, impairing their development, nervous system, and immune function. Polystyrene nanoparticles (PS-NPs) readily adsorbed organic contaminants like CY, forming complex pollution systems that resulted in synergistic toxicities. However, the mechanisms behind their hepatotoxicity remained unclear. In this study, both in vivo and in vitro experiments demonstrated that co-exposure to PS-NPs and CY significantly induced liver injury and steatosis in zebrafish larvae, while activating the key lipid synthesis regulator sterol regulatory element-binding protein 1 (SREBP1) in Hep G2 cells. This process displayed typical features of ferroptosis, including oxidative stress, mitochondrial damage, iron dysregulation, and suppression of the antioxidant enzyme glutathione peroxidase 4 (GPX4). Correlation analysis showed a close association between ferroptosis and steatosis. Physiological and genetic verification revealed that Erastin aggravated lipid accumulation by inhibiting GPX4 expression, activating the SREBP1/SCD1 lipid synthesis pathway. Conversely, Ferrostatin-1 (Fer-1), a ferroptosis inhibitor, alleviated oxidative stress, iron overload, and lipid accumulation, while GPX4 overexpression reversed SREBP1/SCD1 activation and improved lipid accumulation, peroxidation, and ferroptosis. This study revealed a novel mechanism by which PS-NPs and CY co-exposure induced ferroptosis-mediated hepatic steatosis through GPX4. These findings provided new insights into the hepatometabolic toxicity of complex pollutants and identified potential targets for preventing related liver diseases.