Anti-atherosclerotic effects of angiotensin fragments & non-AT1 receptors: Validation as innovative therapeutic targets

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In Australia the largest cause of death is coronary heart disease (CHD) leading to heart attacks or stroke and claiming a staggering 28,000 lives a year. Atherosclerosis is one of the leading causes of cardiovascular disease, with diseased vessels not able to fully dilate and the plaque that has built up inside these vessels impeding blood flow and possibly rupturing, resulting in heart attacks and stroke. One of the major players in the development and progression of atherosclerosis is the hormone, angiotensin II. Angiotensin II has been found to trigger many factors that cause thickening of the vessel wall, inflammation and imbalances in vasodilator capacity (e.g. oxidative stress and endothelial dysfunction), all of which contribute to atherosclerosis. Clinical trials with drugs that inhibit the formation of angiotensin II (ACE inhibitors), or block the action of angiotensin II (angiotensin receptor antagonists), have demonstrated a significant decrease in mortality in patients with high risk for cardiovascular disease. However their mechanism(s) of action are not fully understood as the circulating levels of shorter fragments of angiotensin II (such as Ang IV and Ang (1-7)) are raised in the blood when these drugs are used and may contribute to the protective effects of these drugs. Importantly, we have found that both Ang IV and Ang (1-7) have protective effects in atherosclerotic blood vessels. Therefore, we hypothesise that fragments of angiotensin II (such as Ang IV and others) exert anti-atherogenic effects via distinct binding sites that oppose the effects caused by angiotensin II, and that these may be partly responsible for the cardio-protective effects of the ACE inhibitors and angiotensin receptor antagonists. Thus, information gained in our study will be useful in directing future prescription practices in clinical management of CHD and stroke, and for designing new therapeutic compounds for the management of atherosclerosis.