AIM: Programmed necrosis( necroptosis) and apoptosis are crucially involved in multiple severe cardiac pathological conditions,including myocardial infarction,ischemia / reperfusion( I / R) injury,and heart failure. Whereas apoptotic signaling is well defined,the mechanisms underlying cardiomyocyte necroptosis remain elusive. METHODS AND RESULTS: Here we show that both m RNA and protein levels of receptor-interacting protein 3( RIP3) in the hearts are increased by I / R injury and doxorubicin( Dox) treatment.In mice,RIP3 deficiency ameliorates myocardial necroptosis and heart failure induced by I / R(30-min ischemia /4-h or 8-week reperfusion) or Dox treatment(20 mg / kg or 5 mg / kg × 4,i. p.). RIP3 overexpression induces cardiomyocyte necroptosis evidenced by decreased intracellular ATP level and increased lactate dehydrogenase concentration in cell culture medium. RIP3 triggers myocardial necroptosis via activation of Ca~(2+)/ calmodulin-dependent protein kinase II( Ca MKII),rather than the well-established RIP3 partners,RIP1 and MLKL( mixed lineage kinase domain-like protein). Specifically,our data indicate that I / R and Dox markedly activate myocardial Ca MKII in wild-type but not RIP3-deficient mice,and that Ca MKII inhibition or RIP3 deficiency protect the heart from I / Rand Dox-induced cardiomyocyte necroptosis,cardiac remodeling and heart failure. Mechanistically,RIP3 activates Ca MKII via both direct phosphorylation and indirect reactive oxidative species-dependent oxidation,and subsequently triggers opening of the mitochondrial permeability transition pore( m PTP) and myocardial necroptosis. CONCLUSION: These findings identify Ca MKII as a novel RIP3 substrate and delineate a RIP3-Ca MKII-m PTP myocardial necroptosis pathway,a promising target for the treatment of cardiac ischemic and oxidative damage,and heart failure. AIM: Programmed necrosis (necroptosis) and apoptosis are crucially involved in multiple severe cardiac pathological conditions, including myocardial infarction, ischemia / reperfusion (I / R) injury, and heart failure. Whereas apoptotic signaling is well defined, the mechanisms underlying cardiomyocyte necroptosis remain elusive. METHODS AND RESULTS: Here we show that both m RNA and protein levels of receptor-interacting protein 3 (RIP3) in the hearts are increased by I / R injury and doxorubicin (Dox) treatment.In mice, RIP3 deficiency ameliorates myocardial necroptosis and heart failure induced by I / R (30-min ischemia / 4-h or 8-week reperfusion) or Dox treatment (20 mg / kg or 5 mg / kg × 4, ip) RIP3 triggers myocardial necroptosis via activation of Ca ~ (2 +) / calmodulin-dependent protein kinase II (Ca MKII), rather than intracellular ATP level and increased lactate dehydrogenase concentration in cell culture medium Specifically, our data indicates that I / R and Dox markedly activate myocardial Ca MKII in wild-type but not RIP3-deficient mice, and that Ca MKII inhibition or RIP3 deficiency protect the heart from I / Rand Dox-induced cardiomyocyte necroptosis, cardiac remodeling and heart failure. Mechanistically, RIP3 activates Ca MKII via both direct phosphorylation and indirect reactive oxidative species-dependent oxidation, and subsequently triggers opening of the mitochondrial permeability transition pore (m PTP) and myocardial necroptosis. CONCLUSION: These findings identify Ca MKII as a novel RIP3 substrate and delineate a RIP3-Ca MKII-m PTP myocardial necroptosis pathway, a promising target for the treatment of cardiac ischemic and oxidative damage , and heart failure.