N-Methyldopamine and ibopamine can prevent chemically-induced oxidative ferroptosis in vitro and in vivo.

Oxidative ferroptotic cell death can be selectively induced in cultured cells by chemicals like erastin (an inhibitor of system Xc^-) and RSL3 (an inhibitor of glutathione peroxidase 4). It was recently revealed that protein disulfide isomerase (PDI) is an upstream mediator of chemically-induced ferroptosis and thus also a drug target for ferroptosis protection. Here, we report that N-methyldopamine (MD), a metabolite of dopamine, can protect against erastin- and RSL3-induced ferroptosis in cultured cells, including rat hepatocytes and rat cardiomyocytes. Ibopamine, a prodrug that can release MD in vivo, also exhibits a similar cytoprotective effect in cultured cells in vitro. Mechanistically, MD can bind to PDI in live cells, and can also inhibit PDI's catalytic activities in vitro, likely through covalent interactions. Inhibition of PDI by MD markedly abrogates chemically-induced, PDI-mediated nitric oxide synthase (NOS) dimerization (ie, catalytic activation) and nitric oxide (NO) accumulation, which is followed by reduced buildup of cellular reactive oxygen species (ROS) and lipid-ROS. These changes resulting from the inhibition of PDI-mediated NOS activation and reduction in cellular NO and ROS/lipid-ROS levels jointly contribute, in a predominant manner, to the prevention of chemically-induced ferroptosis by MD. In addition, animal studies showed that MD and ibopamine each can prevent acetaminophen-induced liver injury in mice. In conclusion, the results of this study demonstrate that MD can prevent chemically-induced ferroptosis both in vitro and in vivo through inhibition of PDI-mediated NOS dimerization and NO accumulation. SIGNIFICANCE STATEMENT: It was recently shown that PDI is a pivotal upstream mediator of chemically-induced oxidative ferroptosis and thus a drug target for ferroptosis protection. This study reports that N-methyldopamine, a metabolite of dopamine, is an inhibitor of PDI, and can prevent chemically-induced ferroptosis both in vitro and in vivo. Ibopamine, a prodrug designed to release N-methyldopamine following oral administration, is also highly effective as a cytoprotective agent. This work reveals the PDI-mediated mechanism of cytoprotection by N-methyldopamine and its prodrug ibopamine.