Santos, R. A. S. | Search bioRxiv

bioRxiv2024

Angiotensin-(1-5) is a Potent Endogenous Angiotensin AT2-Receptor Agonist

BackgroundThe renin-angiotensin system involves many more enzymes, receptors and biologically active peptides than originally thought. With this study, we investigated whether angiotensin-(1-5) [Ang-(1-5)], a 5-amino acid fragment of angiotensin II, has biological activity, and through which receptor it elicits effects. MethodsThe effect of Ang-(1-5) (1{micro}M) on nitric oxide release was measured by DAF-FM staining in human aortic endothelial cells (HAEC), or Chinese Hamster Ovary (CHO) cells stably transfected with the angiotensin AT2-receptor (AT2R) or the receptor Mas. A potential vasodilatory effect of Ang-(1-5) was tested in mouse mesenteric and human renal arteries by wire myography; the effect on blood pressure was evaluated in normotensive C57BL/6 mice by Millar catheter. These experiments were performed in the presence or absence of a range of antagonists or inhibitors or in AT2R-knockout mice. Binding of Ang-(1-5) to the AT2R was confirmed and the preferred conformations determined by in silico docking simulations. The signaling network of Ang-(1-5) was mapped by quantitative phosphoproteomics. ResultsKey findings included: (1) Ang-(1-5) induced activation of eNOS by changes in phosphorylation at Ser1177eNOS and Tyr657eNOS and thereby (2) increased NO release from HAEC and AT2R-transfected CHO cells, but not from Mas-transfected or non-transfected CHO cells. (3) Ang-(1-5) induced relaxation of preconstricted mouse mesenteric and human renal arteries and (4) lowered blood pressure in normotensive mice - effects which were respectively absent in arteries from AT2R-KO or in PD123319-treated mice and which were more potent than effects of the established AT2R-agonist C21. (5) According to in silico modelling, Ang-(1-5) binds to the AT2R in two preferred conformations, one differing substantially from where the first five amino acids within angiotensin II bind to the AT2R. (6) Ang-(1-5) modifies signaling pathways in a protective RAS-typical way and with relevance for endothelial cell physiology and disease. ConclusionsAng-(1-5) is a potent, endogenous AT2R-agonist.

pharmacology and toxicology↗

bioRxiv2024

Evidence that the monoamine oxidase B (MAO-B) plays a central role in the inotropic dysfunction induced by genetic deletion of the Mas-related-G protein-coupled receptor D (MrgD) in mice

The renin-angiotensin system (RAS) plays a critical role in the regulation of the cardiovascular system. The Mas-related G protein receptor member D (MrgD) is the receptor of alamandine, and both are components of the RAS noncanonical arm. Alamandine/MrgD induces vasodilation, anti-inflammatory, anti-fibrotic and anti-oxidative effects. In contrast, Mrgd gene deletion leads to a remarkable dilated cardiomyopathy (DCM) in mice. Here, we aimed to investigate the molecular mechanisms of DCM triggered by the deletion of MrgD in the left ventricle and isolated ventricular cardiomyocytes from 8-12 weeks old mice using phosphoproteomics. Our findings revealed an increased oxidative stress not caused by angiotensin II/AT1 hyperactivation but instead due to the up-regulation of the monoamine oxidase B (MAO-B), leading to a higher catabolism of dopamine and epinephrine in the MrgD-KO cardiac tissues. The oxidative environment induced by MAO-B hyperactivation seems to be the cause of the observed alteration in ionic dynamics - altered Ca2+ transient and Na+/K+-ATPase activity - leading to altered resting membrane potential (RMP) and decreased contraction of MrgD-KO cardiomyocytes. In addition, cardiac Troponin-I phosphorylation, and Titin dephosphorylation seem to contribute to the contractile dysfunction observed in MrgD-KO. The treatment of cardiomyocytes from MrgD-KO mice with the MAO-B inhibitor Pargyline reverted the observed impaired contraction, corroborating the hypothesis that MAO-B hyperactivation is, at least partially, the cause of the failing heart observed in MrgD-KO mouse. The findings reported here provide important insights into the pathogenesis of heart failure and suggest a potential therapeutic target (MrgD activation) for managing failing hearts.

physiology↗