Alamandine Attenuates Angiotensin Ii–induced Hypertension and Cardiac Dysfunction via Immune and Renin Angiotensin System Modulation

Objective: Alamandine is a recently identified heptapeptide of the renin–angiotensin system (RAS), structurally related to angiotensin-(1–7) and generated from angiotensin II (ANG II) or angiotensin A. Acting through the Mas-related G protein–coupled receptor D (MrgD), alamandine is increasingly recognized as a key component of the protective, counter-regulatory arm of the RAS and exerts antihypertensive, vasodilatory, anti-inflammatory, antioxidant and antifibrotic effects in experimental models of cardiovascular diseases. We have previously demonstrated that alamandine attenuates isoproterenol-induced cardiac remodeling and dysfunction in rats. However, its role in ANG II–induced hypertension and cardiac dysfunction remains unclear. In this study, we examined whether alamandine counteracts Ang II–driven hypertension and cardiac impairment in rats. Design and method: In this study, Sprague–Dawley rats (n=6/group) received a 2-week subcutaneous infusion of vehicle (saline), ANG II (150 ng/kg/min), ANG II plus alamandine (50 ng/kg/min), or alamandine alone via mini-osmotic pumps. Left ventricular (LV) function and cardiac dynamics were assessed by echocardiography. Results: Compared with vehicle, ANG II significantly (*p<0.05) increased blood pressure (BP: 92.2 ± 2.6 to 112.1 ± 4.8 mmHg*), an effect that was reversed by alamandine (90.1 ± 4.5 mmHg*). Rats treated with alamandine alone had no effect on BP. Alamandine also improved LV function by reducing ANG II–induced increases in LV end-diastolic volume (491 ± 27 to 354 ± 34* mL) and shortening isovolumetric contraction (27.7 ± 3.0 to 18.9 ± 0.9* ms) and relaxation (26.1 ± 3.5 to 17.5 ± 1.2* ms) times. Flow cytometric analysis revealed that alamandine reduced ANG II–induced cardiac immune cell infiltration, including CD45 cells, CD4 T cells, B cells, and NK cells, while increasing monocyte-derived M2 macrophages. Consistently, alamandine suppressed cardiac inflammatory responses by decreasing interleukin-1beta and tumor necrosis factor-alpha mRNA expression and modulated the cardiac RAS by downregulating angiotensin-converting enzyme (ACE) and AT1 receptor expression while enhancing ACE2 expression in the LV of the heart. Conclusions: Collectively, these findings demonstrate that alamandine protects against ANG II–induced hypertension and cardiac dysfunction, likely by limiting immune activation and inflammatory signaling, supporting its therapeutic potential in cardiovascular diseases.