Myocardial infarction is a life-threatening cardiovascular disease that affects more than 800,000 Americans annually. Up to 50% of the heart damage that occurs during a heart attack is from reperfusion injury. We identified the protein complex that mediates reperfusion injury as well as another protein that regulates activity of the complex. We have designed a peptide mimicking this regulatory protein's action and plan to test it in cultured cardiomyocytes and a mouse model of myocardial infarction. During this 6-month period, we will be able to complete cell culture and initial rodent testing of multiple candidate peptides, if needed.