Direct AT2 receptor stimulation is athero-protective and stabilizes plaque in Apolipoprotein E-deficient mice

BackgroundThe angiotensin II type 2 receptor (AT2R) has been suggested to have an athero-protective role, however no studies have investigated the effect of direct stimulation of this receptor in atherosclerosis. Thus this study aimed to determine the effect of direct AT2R stimulation in setting of atherosclerosis, using the known AT2R agonist, CGP42112.Methods and resultsApolipoprotein E-deficient (ApoE−/−) mice were fed a high fat (21%) diet for 16 weeks, with subcutaneous infusions of CGP42112 (1, 5 or 10 μg/kg/min) administered via osmotic mini-pumps in the final 4 weeks. CGP42112 treatment at all doses significantly improved endothelial function (p < 0.001) when compared to acetylcholine mediated-vasorelaxation in aorta taken from vehicle-treated ApoE−/− mice. In aortic segments adjacent to those used for vascular reactivity studies, CGP42112 treatment at all doses concomitantly increased eNOS immunoreactivity and protein levels whilst superoxide (O2−) production was significantly (p < 0.01) decreased compared to levels measured in aorta from vehicle-treated ApoE−/− mice. Moreover, CGP42112 (1 μg/kg/min) treatment significantly attenuated (p < 0.05) atherosclerotic lesion progression (assessed as both lipid deposits and luminal encroachment in thoracic aorta and aortic arch) and significantly increased plaque stability in the brachiocephalic artery, a region normally prone to rupture. Both the vaso- and athero-protective effects of CGP42112 (1 μg/kg/min) were reversed with co-infusion of the AT2R antagonist, PD123319, but not the MasR antagonist, A779.ConclusionFor the first time we have shown that direct stimulation of the AT2R improves endothelial function, reduces atherosclerotic lesion progression and mediates plaque stability with these effects at least partly due to restoration of nitric oxide bioavailability.