Identification and characterization of alamandine-(1-5), a new component of the Renin-Angiotensin System with unique properties
Authors: Dias Melissa Tainan Silva , Gonçalves Sthefanie Chaves de Almeida , da Silva Filipe Alex , Rodrigues-Ribeiro Lucas , Ferraz Kamylle Silva , Scalzo Sérgio , F. Itaborahy Matheus , Soares Nícia Pedreira , Alves Pereira Danilo Augusto , Soares Pedro Alves , Dutra João Batista Rodrigues , de Barros Carolina Fonseca , Vieira-Machado Uri Flegler , Feng Isadora Zhong Liang Ferreira , Ventris de Godoy Ana Caroline , Monteiro Adelson Héric Alves , Eliezeck Marcos , Sanches Bruno , Monteiro André , de Bessa Amanda de Sá Martins , Davel Ana Paula , Nóbrega Natália , Rezende Ribeiro Júlia , Dias-Pinto Maria Luiza , Silva Bruno Durante da , Souza Leandro Eziquiel de , Silva Amanda de A. , Bader Michael , Alenina Natália , Capettini Luciano dos Santos Aggum , Campagnole-Santos Maria José , Verano-Braga Thiago , Fontes Marco Antônio Peliky , Haibara Andrea Siqueira , Vilella Daniel Campos , Irigoyen Maria Claudia , Marins Fernanda Ribeiro , de Castro Carlos Henrique , Simões-e-Silva Ana Cristina , Leite Maria de Fátima , Guatimosim Silvia , Santos Robson A. S. 
Published: April 2024

The renin-angiotensin system (RAS) comprises a biochemical cascade that hydrolyzes angiotensinogen into several different bioactive peptides, which can activate different receptors promoting plenty of specific effects. The aim of this study was to evaluate the presence of the putative product of alamandine, the pentapeptide alamandine-(1-5) in the circulation and its biological activity. To accomplish this we have used mass spectrometry (MALDI/TOF/TOF, LC-MS/MS) and several methodologies including isolated blood vessels, isolated perfused hearts, isolated cardiomyocytes, blood pressure recording in freely-moving normotensive and hypertensive rats (SHR), high resolution echocardiography (VEVO 2100), central administration (ICV infusion and microinjection in the insular cortex), cell culture (endothelial cells and GPCR-transfected CHO cells) and wild type and Mas, MrgD or AT2R deficient mice. Our results show that alamandine-(1-5) circulates in the human and rodent blood and promotes many biological central and peripheral actions. More importantly, its plasma concentration is increased in pediatric nephropathic patients. A major role for plasma ACE activity in the formation of alamandine-(1-5) from alamandine was observed using plasma samples from Angiotensinogen-KO mice. Alamandine-(1-5) increased Baroreflex sensitivity and produced a long-lasting (∼6 hours) anti-hypertensive effect in SHR, associated with a significant reduction in cardiac output. A particularly important effect of this pentapeptide was observed in isolated perfused heart and cardiomyocyte contractility (reduced inotropism). It was capable of stimulating NO production through all receptors from the renin-angiotensin protective arm, (MAS, MrgD and AT2R) in CHO-transfected cells. Our data shows that Alamandine-(1-5) exhibits selective actions that set it apart from traditional concepts of the vasodilatory axis of the RAS and that are possibly intricately linked to a complex interplay between Mas, MrgD and AT2 receptors. This novel finding suggests that RAS may possess a complexity that surpasses our current understanding.