Atherosclerosis and Angiotensin II in Hypercholesterolemia and Diabetes. a Role for at₁ Receptors Beyond Hypertension

Abstract

The pathophysiological continuum that presumably begins with endothelial injury and dysfunction and ends with the fibronecrotic plaque, occlusive coronary artery disease, and diabetes-related nephropathy is potentially influenced by an association between hyper-glycemia, hypercholesterolemia and activation of the renin-angiotensin system. It is known that the resultant proliferative and progressive responses of the arterial wall in atherosclerosis and glomerulosclerosis are the culmination of the effects of a variety of mitogenic and inhibitory hormonal and trophic factors exerting their actions at stages that may be far removed both spatially and temporally from the initial injurious event. These processes are likely also at work in the diabetic kidney, but are not as well investigated. Regardless of the initiating mechanism, the vascular endothelium, inflammatory cell infiltration and the resultant tissue response have become the focus of attention in the pathogenesis of both atherosclerosis and diabetic nephropathy. A vast array of effects of angiotensin II likely to be mediated through both type 1 and type 2 angiotensin receptors are now described in the literature. Current data indicates that the role of angiotensin II in vascular remodeling and renal injury may originate from a local tissue source rather than the circulation. Regardless of its origin, angiotensin peptides and angiotensin receptors may contribute in significant ways to the atherogenic processes. While the stages of atherosclerosis and renal diabetic nephropathy in humans and animals are well defined morphologically, the mechanisms within vascular and renal tissues that contribute to these pathologies represent a spectrum of events occurring in different microenvironments over prolonged periods. This review describes well-established and novel aspects of angiotensin II-mediated actions as they relate to hypercholesterolemia-induced atherogenesis and diabetic nephropathy, and suggests potential pathways where angiotensin II might be substantially involved through the AT₁ receptor in these processes, and thus may be blocked by AT₁ receptor antagonists.