Strong protection by bazedoxifene against chemically-induced ferroptotic neuronal death in vitro and in vivo

Ferroptosis, a form of regulated cell death associated with glutathione depletion and excess lipid peroxidation, can be induced in cultured cells by chemicals (e.g., erastin and RSL3). It has been shown that protein disulfide isomerase (PDI) is a mediator of chemically-induced ferroptosis and also a crucial target for ferroptosis protection. The present study reports that bazedoxifene (BAZ), a selective estrogen receptor modulator, is an inhibitor of PDI and can strongly rescue neuronal cells from chemically-induced oxidative ferroptosis. We find that BAZ can directly bind to PDI and inhibit its catalytic activity. Computational modeling analysis reveals that BAZ forms a hydrogen bond with PDI's His256 residue. Inhibition of PDI by BAZ markedly reduces iNOS and nNOS dimerization (i.e., catalytic activation) and NO accumulation, and these effects of BAZ are associated with reductions in cellular ROS and lipid-ROS and protection against chemically-induced ferroptosis. In addition, the direct antioxidant activity of BAZ may also partially contribute to its protection against chemically-induced ferroptosis. In vivo animal experiments show that mice treated with BAZ are strongly protected against kainic acid-induced oxidative hippocampal neuronal injury and memory deficits. Together, these results reveal that BAZ is a potent inhibitor of PDI and can strongly protect against chemically-induced ferroptosis in hippocampal neurons both in vitro and in vivo. This work provides evidence for an estrogen receptor-independent, PDI-mediated novel mechanism of neuroprotection by BAZ.