The P450 epoxygenase pathway breaks down arachidonic acid into epoxyeicosatrienoic acids (EETs). EETs are metabolized by soluble epoxide hydrolase (sEH) into the less active products dihydroxyepoxyeicosatrienoic acids. In the current proposal, the hypothesis that sEH inhibition is protective against ischemic injury in the heart will be tested. Plan. Selective drug inhibitors of sEH and P450 epoxygenase, and transgenic sEH-deficient mouse models, will be used to interrogate the role of sEH and EETs in myocardial ischemic tolerance.
Four Specific Aims will be examined to determine: 1. if sEH inhibition and gene deletion is cardioprotective; 2. if sEH cardioprotection is specifically mediated by EETs; 3. the spatial and temporal expression of sEH within the normal and ischemic heart; and 4. the molecular mechanism of cardioprotection. Methods. Experiments will be conducted in anesthetized mice subjected to acute myocardial ischemia-reperfusion induced by reversible coronary ligation, and in cultured cardiomyocytes subjected to oxygen and glucose deprivation (OGD). Myocardial infarct size will be assessed with triphenyltetrazolium staining, cardiac function with a left ventricular conductance catheter, and in vitro cell death by propidium iodide uptake. Measurement of EETs will be performed by liquid chromatography/mass spectrometry. Findings to Date. Immunohistochemistry studies show the presence of sEH in heart muscle cells, as well as in nerve fibers and intrinsic cardiac adrenergic cells. Additional preliminary data show reduced infarct size in sEH deficient mice following induced heart attack, and improved survival of isolated heart muscle cells subjected to OGD, when treated with sEH inhibitor. Clinical Relevance. The proposed studies will characterize the pathophysiological role of sEH in myocardial ischemia, and represent the first evaluation of sEH inhibitors as a prophylaxis against, and a therapeutic treatment of, myocardial infarction. Potential Impact on Veteran's Health Care. Given that a recent prospective study suggests an association between post-traumatic stress disorder and the development of coronary heart disease, and other data suggest that combat exposure results in long-term adverse effects on cardiovascular risk, there is likely to be an increase in veteran morbidity and mortality due to cardiovascular disease. The currently proposed studies are significant in terms of clinical implications for limiting cardiac damage in the vulnerable veteran population.
Heart disease is the leading cause of death in men and women. According to the American Heart Association, death from cardiovascular disease in males has been decreasing over the past few decades (from ~ 500,000 deaths/year in 1980 to ~ 440,000 deaths/year in 2000), due in part to improved detection and treatment of ischemic heart disease. However, current demographics show a high incidence of obesity, hypertension, and diabetes in young adults that herald a large increase in heart disease and cardiovascular mortality. In addition, a recent prospective study suggests that there is an association between post-traumatic stress disorder and the development of coronary heart disease, and other data suggest that combat exposure results in higher heart disease risk factors that result in long-term adverse effects on cardiovascular risk. Much research has been conducted on agents that confer tolerance to myocardial ischemia but large-scale translation of these drugs into clinical practice has not achieved wide-spread implementation. The currently proposed studies offer an alternative mode of achieving cardioprotection, that is, by blocking an endogenous enzyme that normally degrades protective substances that are produced by the heart itself during ischemia. Thus, the proposed project represents a novel approach to limiting cardiac damage that has substantial implications for the health and well-being of the American population. Data from the Office of Policy and Planning at the Department of Veterans Affairs indicate that as of 2000 there were ~26.5 million veterans in the US, and that in 2006 > $31 million was spent by the Department of Veterans Affairs on medical expenditures. The per capita cost for Veterans Affairs patients treated for acute myocardial infarction (AMI) in FY 1999 was ~$15,000. Thus the currently proposed studies are significant in terms of clinical implications for limiting cardiac damage in the vulnerable veteran population and for fiscal health of the Department of Veterans Affairs.