Inhibition of renin–angiotensin system attenuates periadventitial inflammation and reduces atherosclerotic lesion formation

Recent evidence indicates that renin–angiotensin system (RAS) plays an important role in the pathogenesis of atherosclerosis. It was reported that inhibition of RAS with angiotensin II type 1 receptor blockers (ARBs) or angiotensin converting enzyme inhibitors (ACEIs) is effective in prevention of atherosclerosis. Here, we investigated the effects of an ARB or/and an ACEI on atherosclerosis development and periadventitial inflammation in apolipoprotein E (ApoE)-deficient mice. RT-PCR revealed that major RAS components were expressed in periaortic tissue. Ang II infusion significantly increased accumulation of bone marrow derived cells into both neointima (p < 0.05) and periaortic tissue (p < 0.01). Male ApoE- deficient mice were treated with either vehicle, TA606A (10 mg/kg/day, ARB), imidapril (3 mg/kg/day, ACEI) or TA606A plus imidapril (TA606A 10 mg/kg/day + imidapril 3 mg/kg/day, ARB + ACEI) for 24 weeks starting at 12 weeks of age. ARB, ACEI, and ARB + ACEI significantly reduced atherosclerotic lesion formation in aorta compared with vehicle (p < 0.05), with reduced expression of monocyte chemoattractant protein-1 in periaortic tissues (p < 0.01). Neither blood pressure nor heart rate was changed by the treatments at these lower doses. Imidapril significantly reduced lipid deposition in atheroma and plasminogen activator inhibitor-1 expression in periadventitial tissue (p < 0.05, respectively). Imidapril and combination therapy significantly attenuated macrophage infiltration into the atherosclerotic plaque (p < 0.05, respectively). All treatments reduced macrophage accumulation in the periadventitial tissue 12 weeks after treatment (p < 0.05, respectively). These results suggest that inhibition of renin–angiotensin system attenuates periadventitial inflammation and reduces atherosclerotic lesion formation.