Clinical studies have suggested that myocardial iron is a risk factor for left 
ventricular remodeling in patients after myocardial infarction. Ferroptosis has 
recently been reported as a mechanism of iron-dependent nonapoptotic cell death. 
However, ferroptosis in the heart is not well understood. Mechanistic target of 
rapamycin (mTOR) protects the heart against pathological stimuli such as 
ischemia. To define the role of cardiac mTOR on cell survival in iron-mediated 
cell death, we examined cardiomyocyte (CM) cell viability under excess iron and 
ferroptosis conditions. Adult mouse CMs were isolated from cardiac-specific mTOR 
transgenic mice, cardiac-specific mTOR knockout mice, or control mice. CMs were 
treated with ferric iron [Fe(III)]-citrate, erastin, a class 1 ferroptosis 
inducer, or Ras-selective lethal 3 (RSL3), a class 2 ferroptosis inducer. 
Live/dead cell viability assays revealed that Fe(III)-citrate, erastin, and RSL3 
induced cell death. Cotreatment with ferrostatin-1, a ferroptosis inhibitor, 
inhibited cell death in all conditions. mTOR overexpression suppressed 
Fe(III)-citrate, erastin, and RSL3-induced cell death, whereas mTOR deletion 
exaggerated cell death in these conditions. 2',7'-Dichlorodihydrofluorescein 
diacetate measurement of reactive oxygen species (ROS) production showed that 
erastin-induced ROS production was significantly lower in mTOR transgenic versus 
control CMs. These findings suggest that ferroptosis is a significant type of 
cell death in CMs and that mTOR plays an important role in protecting CMs 
against excess iron and ferroptosis, at least in part, by regulating ROS 
production. Understanding the effects of mTOR in preventing iron-mediated cell 
death will provide a new therapy for patients with myocardial infarction. NEW & 
NOTEWORTHY Ferroptosis has recently been reported as a new form of 
iron-dependent nonapoptotic cell death. However, ferroptosis in the heart is not 
well characterized. Using cultured adult mouse cardiomyocytes, we demonstrated 
that the mechanistic target of rapamycin plays an important role in protecting 
cardiomyocytes against excess iron and ferroptosis.