Lead Triggers Hepatocyte Ferroptosis Through Coordinated Mitochondrial Injury and ER Stress-Mediated Autophagic Degradation of GPX4.

Lead (Pb) is one of the major heavy metal pollutants that induces multi-organ toxicity. Liver is the primary target of Pb, the exposure of which induces hepatotoxicity by triggering hepatocyte cell death. Ferroptosis, a novel iron-dependent form of regulated cell death, has recently been implicated in a variety of heavy metal-induced organ injuries. In this study, we have identified that ferroptosis is involved in acute Pb exposure-induced liver injury. Our results showed that Pb (1 mM) induced ferroptosis in Hepa1-6 cells, as evidenced by the increase of intracellular ferrous levels and lipid peroxidation. Ferrostatin-1 (Fer-1, 20 μM), a ferroptosis inhibitor, alleviated the hepatocyte cell death. Mechanistically, Pb impaired mitochondria and promoted mitochondrial superoxide production. The mitochondrial reactive oxygen species (ROS) subsequently led to lipid peroxidation, and activated endoplasmic reticulum (ER) stress, which in turn promoted autophagy. The induced-autophagy facilitated the degradation of GPX4 and contributed to the destabilization of SLC7A11. MitoTEMPO (200 μM), a mitochondria-targeted antioxidant, effectively attenuated Pb-induced ferroptosis by reducing lipid peroxidation, relieving ER stress, and stabilizing SLC7A11 and GPX4. Furthermore, tauroursodeoxycholic acid (TUDCA, 800 μM in vitro and 150 mg/kg in vivo), a chemical chaperone, protected against Pb-induced hepatocyte ferroptosis and liver injury by preserving mitochondrial integrity, suppressing ER stress dependent autophagy, and restoring SLC7A11 and GPX4 expression. Our results indicated that mitochondrial ROS may serve as the upstream trigger of Pb-induced ferroptosis, not only facilitating lipid peroxidation, but also impairing the antioxidant defense system. Collectively, our findings reveal a novel hierarchical cascade, mitochondrial ROS-driven ER stress leading to autophagic degradation of GPX4, as a core mechanism of Pb-induced hepatic ferroptosis. Furthermore, TUDCA was identified as a potential therapeutic agent for Pb-induced hepatotoxicity.