Novel treatments are necessary to reduce the burden of cardiovascular disease (CVD). Alamandine binds to MrgD and is reported to induce vasodilation via stimulation of endothelial nitric oxide synthase (eNOS), but its role in atherogenic blood vessels is yet to be determined. To determine the vasoactive role of alamandine and its precursor AngA in diseased aorta, New Zealand White rabbits were fed a diet containing 1% methionine + 0.5% cholesterol + 5% peanut oil for 4 weeks (MC, n = 5) or control (n = 6). In abdominal aorta, alamandine (1 μM) was added 30 min before a dose-response curve to angiotensin II or AngA (1 nM-1 μM), and immunohistochemistry was used to identify MrgD receptors and eNOS. The thoracic aorta, renal, carotid and iliac arteries were mounted in organ baths. Rings were precontracted with phenylephrine, then a bolus dose of alamandine (1 μM) was added 10 min before a dose-response curve to acetylcholine (0.01 μM-10 μM). The MrgD receptor was localized to normal and diseased aorta and colocalized with eNOS. In control but not diseased blood vessels, alamandine enhanced acetylcholine-mediated vasodilation in the thoracic aorta and the iliac artery (P < 0.05) and reduced it in the renal artery (P < 0.05). In control abdominal aorta, AngA evoked less desensitization than AngII (P < 0.05) and alamandine reduced AngA-mediated vasoconstriction (P < 0.05). In MC, AngA constriction was markedly reduced vs. control (P < 0.05). The vasoactivity of alamandine and AngA are reduced in atherogenesis. Its role in the prevention of CVD remains to be validated.

A growing body of evidence suggests that the vascular actions of Ang-(1-7) appear to involve increased production of nitric oxide (NO), an important vasodilator, through the activation of MasR, thus indicating the involvement of the MasR in preventing endothelial dysfunction. However, it is unknown whether the MasR could be involved in the progression of the next step in atherosclerosis, neo-intimal formation. To determine whether the deletion of the MasR is involved in the development of intimal thickening in an in vitro model. Mice [three background controls (C57Bl/6) and 3 MasR (-/-)] were killed and the aortas excised and cleaned of connective tissue and cut into 3 mm rings. Rings were placed in an organ culture medium for 5 weeks, embedded in paraffin, cut at 5 μm and stained with haematoxylin and eosin and Masson's trichrome. In addition, aortic reactivity was measured in organ baths. After 5 weeks of culture, the intima:media ratio increased in the aortas from MasR (-/-) mice compared to the control group by 4.5-fold (P < 0.01). However, no significant difference in nuclei area count (cell proliferation) between the MasR (-/-) mice and control group was observed (0.87 ± 0.29% vs. 0.94 ± 0.18%, respectively, P = ns). Functional studies showed only a minor vasoconstrictive and full vasodilative response. This study shows that the deletion of the MasR causes marked increase in the aortic intima:media ratio, which is not due to generalized cellular proliferation. These results provide a functional role for the MasR in atherogenesis.