Abstract

Myocardial infarction (MI) remains one of the leading causes of mortality worldwide, and cardiomyocyte death plays a critical role in cardiac remodeling after MI. Ferroptosis is a recently identified form of iron-dependent programmed cell death that has been shown to be involved in the progression of various cardiovascular diseases, including MI. Bromodomain-containing protein 4 (BRD4) is an epigenetic reader and a key regulator of cell survival. In this study, we screened an epigenetic target library containing 773 small-molecule compounds and found that (+)-JQ-1(hereafter abbreviated as JQ-1), a BRD4-specific inhibitor, markedly attenuated ferroptosis induced by erastin (a ferroptosis inducer) in cardiomyocytes. Both prophylactic and therapeutic JQ-1 administration significantly improved cardiac remodeling and reduced cardiomyocyte ferroptosis in mice with MI. Mechanistically, JQ-1 protected cardiomyocytes from erastin-induced ferroptosis by downregulating the expression of nicotinate phosphoribosyltransferase (NAPRT) and upregulating the expression of nicotinamide phosphoribosyltransferase (NAMPT) and sirtuin1 (SIRT1). Inhibition of NAMPT or SIRT1 abrogated the protection conferred by JQ-1 in erastin-treated H9C2 cardiomyocytes. The combination of proteolysis-targeting chimeras (PROTACs) with JQ-1 (JQ-1-PROTAC) promoted BRD4 protein degradation and rescued erastin-induced ferroptosis in H9C2 cardiomyocytes, and prevented erastin-induced ferroptosis in human cardiomyocytes. Thus, JQ-1 can protect cardiomyocytes from ferroptosis through the NAMPT-SIRT1 pathway, and JQ-1-based therapy may serve as a novel promising strategy to improve cardiac remodeling after MI.