In the United States, cardiovascular disease is the leading cause of death for both men and women. More than one million people suffer from heart attacks every year in the United States alone. Cardiac ischemia, a condition characterized by reduced blood flow and oxygen to the heart muscle, or myocardium, is one hallmark of cardiovascular disease that can ultimately lead to a heart attack, or myocardial infarction. Cardiovascular disease can also result in restricted blood flow and reduced oxygen supply to other areas of the body resulting in ischemic injuries to various organs and tissues, including the brain, which can lead to stroke.
Re-establishment of blood flow, or reperfusion, and re-oxygenation of the affected area following an ischemic episode is critical to limit irreversible damage. However, reperfusion also brings potentially damaging consequences, such as reperfusion injury, which is caused by the restoration of coronary blood flow after an ischemic episode and results from the generation and accumulation of reactive oxygen and nitrogen species during reperfusion. Ischemia-reperfusion injury is biochemically characterized by a depletion of oxygen during an ischemic event, a resultant increase in intracellular calcium levels, followed by reoxygenation and the concomitant generation of reactive oxygen species during reperfusion (Piper, H. M., Abdallah, C., Schafer, C., The first minutes of reperfusion: a window of opportunity for cardioprotection. Annals of Thoracic Surgery 2003, 75:644; Yellon, D. M., Hausenloy, D. J., Myocardial reperfusion injury. New England Journal of Medicine 2007, 357:1121). Reperfusion injury may be responsible for as much as 50% of the damage to the heart following a myocardial infarction (Yellon, D. M., Hausenloy, D. J., Myocardial reperfusion injury. New England Journal of Medicine 2007, 357:1121).
The prevalence of cardiovascular disease in the United States, and throughout the world, necessitates the development of therapies and therapeutic agents that can effectively prevent, reduce, or counteract ischemia and ischemia-reperfusion injury resulting from a heart attack or stroke. Current therapies for treating ischemia and ischemia-reperfusion injury caused by myocardial infarction, such as mechanical ischemic preconditioning, have proven to be clinically impractical, while other therapies, such as antagonists to block the influx of calcium and scavengers of reactive oxygen species, have yielded disappointing clinical outcomes (Otani, H., Ischemic preconditioning: From molecule mechanisms to therapeutic opportunities. Antioxidants & Redox Signaling, 2008, 10:207; Yellon, D. M., Hausenloy, D. J., Myocardial reperfusion injury. New England Journal of Medicine 2007, 357:1121).
Thus, there is a significant need for new and more effective therapies and therapeutic agents for the treatment of ischemia and ischemia-reperfusion injuries resulting from cardiovascular disease and other conditions.