The major objective of this proposal is to characterize the ability of cocoa and the flavanol, epicatechin, to reduce short and long-term ischemia-reperfusion induced myocardial injury in rats. Furthermore, we wish to provide evidence for the ability of cocoa and epicatechin to reduce neutrophil-mediated myocardial ischemia-reperfusion (IR) injury via a nitric oxide (NO) dependent mechanism. Polyphenols are widely distributed in plants and are known as flavonoids. Evidence indicates a negative correlation between consumption of flavonoid-rich foods and incidence of cardiovascular (CVD) disease. Cocoa powder is more than 10% flavanols (catechin and epicatechin) by weight. Interest in the beneficial effects of flavonols emerged from observations in Kuna Indians who have a very low incidence of CVD and consume minimally processed cocoa beverages. There are clues as to the mechanisms that explain cocoa effects. The consumption of flavanol rich cocoa leads to vasodilation which can be reversed by the use of an NO synthesis inhibitor. Other beneficial effects include the inhibition of platelet and leucocyte adhesion, low-density lipoprotein oxidation, reactive oxygen species (ROS) generation, eicosanoid synthesis and insulin resistance. Recent reports associate the beneficial effects of cocoa to the actions of epicatechin. The consumption of epicatechin by humans reproduces the vasodilatory effects of cocoa as well as its antioxidant and insulin sensitizing actions. Vasodilatory effects can be replicated by the use of epicatechin metabolites on isolated blood vessel preparations. Preliminary studies performed in a rat model of myocardial IR injury indicate epicatechin can exert cardioprotective effects. Treatment also reduces myocardial inflammation. Interestingly injury appears to require the presence of blood borne cells. Given the well documented beneficial effects of cocoa derived flavanols on cardiovascular parameters it is possible that these compounds may significantly reduce tissue injury and ultimately, improve long term organ structure/function. The requirement of blood to mediate tissue injury also suggests the involvement of neutrophils. With these issues in mind we propose to examine the following specific aims:
Aim 1 will test the hypothesis that the administration of cocoa or epicatechin to rats leads to a reduction in myocardial IR injury and improves long term outcome. Rats will be subjected to 45 min of IR injury. Infarct size as well as myocardial injury-induced changes in cardiac structure/function will be determined up to 4 weeks post IR. ROS generation, NO production and anti-inflammatory endpoints will be determined. Studies will include the use of dose-response schemes and plasma transfusions to test for the """"""""transferability"""""""" of protection.
Aim 2 will test the hypothesis that cocoa or epicatechin treatment reduces in vivo PMN adhesion/trapping as well as their activation state.
Aim 3 will test the hypothesis that cocoa or epicatechin induced increases in nitric oxide modulate (at least in part) the anti-adhesive effects of flavanols on PMN.
The major goal of this proposal is to characterize the ability of cocoa derived flavanols specifically epicatechin, to reduce short and long-term ischemia-reperfusion induced heart injury and to identify the role played by inflammatory cells. Given the focus on the effects of dark chocolate related flavanols we therefore address a topic relevant to the field of complementary and alternative medicine.
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