Objective: The interaction between the renin-angiotensin system and toll-like receptors (TLRs) in the pathogenesis of advanced atherosclerotic plaques is not well understood. We studied the effects of the renin inhibitor aliskiren on the progression of advanced atherosclerotic plaque in apolipoprotein E-deficient (ApoE(-/-)) mice with a special focus on plaque neovessel formation.
Methods and results: Four-wk-old ApoE(-/-) mice were fed a high-fat diet for 8 wks, and the mice were randomly assigned to one of three groups and administered a vehicle, hydralazine, or aliskiren for an additional 12 wks. Aliskiren reduced the atherosclerotic plaque area and plaque neovessel density. It increased the plaque collagen and elastin contents, and reduced plasma angiotensin II levels and plaque macrophage infiltration and cathepsin S (CatS) protein. Aliskiren also decreased the levels of AT1R, gp91phox, TLR2, monocyte chemotactic protein-1, and CatS mRNAs in the aortic roots. Hydralazine had no beneficial vascular effects, although its administration resulted in the same degree of blood pressure reduction as aliskiren. CatS deficiency mimicked the aliskiren-mediated vasculoprotective effect in the ApoE(-/-) mice, but aliskiren showed no further benefits in ApoE(-/-) CatS(-/-) mice. In vitro, TLR2 silencing reduced CatS expression induced by angiotensin II. Moreover, aliskiren or the inhibition of CatS impaired the endothelial cell angiogenic action in vitro or/and ex vivo.
Conclusion: Renin inhibition appears to inhibit advanced plaque neovessel formation in ApoE(-/-) mice and to decrease the vascular inflammatory action and extracellular matrix degradation, partly by reducing AT1R/TLR2-mediated CatS activation and activity, thus regressing advanced atherosclerosis.
Keywords: Aliskiren; Angiotensin II; Atherosclerosis; Cathepsin S; Toll-like receptor 2.
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