Chen et al. found that knockdown of TLR4 and NADPH oxidase 4 (NOX4) in rats with heart failure resulted in the elevated expression of GPX4 and FTH-1, reduced the free iron level in cardiomyocytes, significantly attenuated left ventricular remodelling, and prevented cardiomyocyte death. The gene discussed is NOX4; the disease is heart failure.