piR-16404 drives ferroptotic liver injury via CASTOR1/mTORC1/GPX4 dysregulation in HepG2 cells and mice: a novel toxicity mechanism of N, N-dimethylformamide.

N, N-dimethylformamide (DMF), a widely used industrial solvent including new energy technologies, induces hepatotoxicity through poorly understood mechanisms. This study demonstrates that DMF exposure triggers ferroptosis in hepatocytes, characterized by glutathione depletion, iron accumulation, and lipid peroxidation both in vitro (0-160 mM DMF exposure) and in vivo (0, 750 mg/kg and 1500 mg/kg of DMF exposure). Transmission electron microscopy revealed ferroptotic mitochondrial damage, while biochemical assays confirmed GPX4 suppression and elevated 4-HNE levels. piRNA sequencing identified piR-16404 as significantly downregulated following DMF exposure. Functional studies showed piR-16404 overexpression attenuated DMF-induced ferroptosis by targeting CASTOR1, an arginine sensor for mTORC1. Mechanistically, piR-16404 binds CASTOR1's 3'-UTR to promote its degradation, thereby reactivating mTORC1-GPX4 signaling. In vivo supplementation of agomir-piR-16404 ameliorated DMF-induced liver injury, reducing serum ALT/AST by 42-58% and restoring hepatic GPX4 expression. Our findings establish ferroptosis as a key pathway in DMF hepatotoxicity and identify the piR-16404-CASTOR1-mTORC1 axis as a novel therapeutic target, providing new insights into environmental chemical-induced liver injury mechanisms.