Stimulation of the AT2 receptor reduced atherogenesis in ApoE^−/−/AT1A^−/− double knock out mice

Abstract 

AT1 receptor blockers (ARB) and in part ACE inhibitors (ACI) potentially exert beneficial effects on atherogenesis independent of AT1 receptor inhibition. These pleiotropic effects might be related to angiotensin II mediated activation of the AT2 receptor. To analyze this hypothesis we investigated the development of atherosclerosis and the role of ACIs and ARBs in apolipoprotein E-deficient (ApoE^−/−) mice and in ApoE/AT1A receptor double knockout mice (ApoE^−/−/AT1A^−/−). ApoE^−/− mice and ApoE^−/−/AT1A^−/− mice were fed cholesterol-rich diet for 7weeks. Vascular oxidative stress, endothelial dysfunction, and atherosclerotic lesion formation were evident in ApoE^−/− mice, but were markedly reduced in ApoE^−/−/AT1A^−/− mice. Concomitant treatment of ApoE^−/−/AT1A^−/− mice with either telmisartan or ramipril had no additional effect on blood pressure, vascular oxidative stress, AT2 receptor expression, and endothelial function. Remarkably, atherosclerotic lesion formation was increased in ramipril treated ApoE^−/−/AT1A^−/− mice compared to untreated ApoE^−/−/AT1A^−/− mice whereas pharmacological AT1 receptor inhibition with telmisartan had no additional effect on atherogenesis. Moreover, chronic AT2 receptor inhibition with PD123,319 significantly increased plaque development in ApoE^−/−/AT1A^−/− mice. In additional experiments, direct AT2 receptor stimulation reduced atherogenesis in ApoE^−/−/AT1A^−/− mice. Taken together, our data demonstrate a relevant antiatherosclerotic role of the AT2 receptor in atherosclerotic mice and provide novel insight in RAS-physiology.

Keywords: Hypercholesterolemia, Angiotensin, Endothelium, Atherosclerosis, Free radicals