Raloxifene suppresses chemically-induced oxidative hepatocyte injury in vitro and in vivo by targeting protein disulfide isomerase.

Ferroptosis, often characterized by glutathione depletion-associated oxidative stress and lipid peroxidation, contributes importantly to many pathological conditions, including drug-induced liver injury. Protein disulfide isomerase (PDI or PDIA1) has emerged as a pivotal upstream regulator of chemically-triggered ferroptosis and also an important therapeutic target. In this work, we identified raloxifene (RAL), a clinically-used selective estrogen receptor modulator, as a suppressor of chemically-induced oxidative ferroptosis and liver toxicity both in vitro and in vivo. Mechanistically, RAL can interact directly with PDI in both purified systems and cultured hepatocytes, leading to inhibition of its enzymatic activity. This inhibition decreases the dimerization (i.e., catalytic activation) of the inducible nitric oxide synthase (iNOS) and the subsequent buildup of cellular nitric oxide (NO), and these changes are associated with reduced accumulation of cellular reactive oxygen species, including lipid peroxides. RAL treatment markedly mitigates acetaminophen-evoked liver injury in vivo, as reflected by normalized serum enzyme levels, decreased lipid oxidative damage, and improved tissue morphology. Together, these results reveal that RAL can effectively limit oxidative ferroptotic injury in hepatocytes in both cellular and animal settings via its direct inhibition of PDI-mediated oxidative signaling cascade. The findings reveal a novel estrogen receptor-independent, PDI-targeted mechanism for the hepatoprotective actions of RAL, and also illustrate its promise for treating ferroptosis-associated liver injuries.