Angiotensin II and Cardiovascular Disease: Balancing Pathogenic and Protective Pathways

The renin-angiotensin-aldosterone system (RAAS) is a hormone system that controls blood pressure and fluid and electrolyte balance. Angiotensin II, a key effector, is produced from angiotensin I by angiotensin-converting enzyme (ACE) and exerts its effects through binding to its type 1 (AT1R) or type 2 (AT2R) receptors. AT1R activation promotes vasoconstriction, oxidative stress, endothelial dysfunction, peripheral vascular resistance, and atherosclerosis, all of which substantially contribute to cellular senescence and organismal ageing. Conversely, AT2R activation counteracts these effects by inducing vascular relaxation and attenuating vascular cell proliferation and migration, offering protection against occlusive vascular disease. Additionally, conversion of angiotensin II to angiotensin (1-7) or angiotensin I to angiotensin (1-9) by ACE2 provides further cardiovascular protection by lowering oxidative stress, inflammation, and abnormal cell growth. Bearing these in mind, measures to control angiotensin II synthesis or receptor activity have been at the forefront of antihypertensive treatment. This paper briefly reviews the RAAS and explores the dual role of angiotensin II in promoting disease and mediating vascular protection, with a focus on its impact on ageing and cardiovascular pathology.