Angiotensin in Critical Care.

This article is one of ten reviews selected from the Annual Update in Intensive Care and Emergency Medicine 2018. Other selected articles can be found online at https://www.biomedcentral.com/collections/annualupdate2018 . Further information about the Annual Update in Intensive Care and Emergency Medicine is available from http://www.springer.com/series/8901 .

Uptake and metabolism of the novel peptide angiotensin-(1-12) by neonatal cardiac myocytes.

BACKGROUND: Angiotensin-(1-12) [Ang-(1-12)] functions as an endogenous substrate for the productions of Ang II and Ang-(1-7) by a non-renin dependent mechanism. This study evaluated whether Ang-(1-12) is incorporated by neonatal cardiac myocytes and the enzymatic pathways of ¹²5I-Ang-(1-12) metabolism in the cardiac myocyte medium from WKY and SHR rats. METHODOLOGY/PRINCIPAL FINDINGS: The degradation of ¹²5I-Ang-(1-12) (1 nmol/L) in the cultured medium of these cardiac myocytes was evaluated in the presence and absence of inhibitors for angiotensin converting enzymes 1 and 2, neprilysin and chymase. In both strains uptake of ¹²5I-Ang-(1-12) by myocytes occurred in a time-dependent fashion. Uptake of intact Ang-(1-12) was significantly greater in cardiac myocytes of SHR as compared to WKY. In the absence of renin angiotensin system (RAS) enzymes inhibitors the hydrolysis of labeled Ang-(1-12) and the subsequent generation of smaller Ang peptides from Ang-(1-12) was significantly greater in SHR compared to WKY controls. ¹²5I-Ang-(1-12) degradation into smaller Ang peptides fragments was significantly inhibited (90% in WKY and 71% in SHR) in the presence of all RAS enzymes inhibitors. Further analysis of peptide fractions generated through the incubation of Ang-(1-12) in the myocyte medium demonstrated a predominant hydrolytic effect of angiotensin converting enzyme and neprilysin in WKY and an additional role for chymase in SHR. CONCLUSIONS/SIGNIFICANCE: These studies demonstrate that neonatal myocytes sequester angiotensin-(1-12) and revealed the enzymes involved in the conversion of the dodecapeptide substrate to biologically active angiotensin peptides.

Papel de las aminopeptidasas en el control neuroendocrino de la presión arterial en animales de experimentación / Role of aminopeptidases in the neuroendocrine control of blood pressure in experimental animals

En el control de la presión arterial participan varias enzimas proteolíticas–incluidas en el llamado sistema renina-angiotensina– que producen diversos péptidos activos que son los agentes efectivos del sistema. El estudio de estas enzimas resulta esencial para conocer en profundidad el mecanismo de control de la presión arterial y puede ofrecer la posibilidad de controlar dicho sistema con fármacos. Una glutamato aminopeptidasa transforma la angiotensina II en angiotensina III. Ésta a su vez es transformada en angiotensina IV por la alanina o arginina aminopeptidasa. La angiotensina I, por acción de la aspartato aminopeptidasa, se transforma en angiotensina 2-10, a la que se han atribuido acciones contrapuestas a las hipertensivas de la angiotensina II. La angiotensina III es la forma más activa de las angiotensinas cerebrales y tiene un efecto estimulador tónico de la presión arterial. El estudio de la inhibición de la glutamato aminopeptidasa, por lo tanto, ha permitido el desarrollo de agentes que actúan eficazmente reduciendo la presión arterial. Asimismo, el desarrollo de activadores de la aspartatoaminopeptidasa constituye otro posible objetivo para el diseño de nuevos agentes antihipertensivos. Nuestro grupo de investigación ha observado que las lesiones unilaterales del sistema nigroestriatal en ratas da lugar a modificaciones simultáneas de la presión arterial y de la actividad aminopeptidásica cerebral y plasmática, curiosamente dependiente del lado de la lesión. Esta posible interacción entre presión arterial, actividad aminopeptidásica y asimetría cerebral, que daría lugar a una respuesta neuroendocrina diferenciada sobre el control de la presión arterial, podría ayudarnos a comprender el mecanismo íntimo por el cual el cerebro controla en la circulación la presión arterial (AU)

Control of blood pressure is partially accomplished by several proteolyticenzymes included in the renin-angiotensin system. These enzymes produce several peptides that form the active components of the system. Study of these enzymes is essential for a deep understanding of blood pressure control and could offer the possibility of controlling this system pharmacologically. Glutamyl aminopeptidase converts angiotensin II into angiotensin III, which in turn is converted into angiotensin IV by an alanylor arginyl aminopeptidase. Angiotensin I, through the action of aspartylaminopeptidase, is converted intoangiotensin 2-10, which may counteract the hypertensive actions of angiotensin II. Angiotensin III is the most active form of brain angiotensins and has a tonic stimulatory effect on blood pressure. Analysis of glutamyl-aminopeptidase inhibition has allowed the development of agents that effectively reduce blood pressure. Moreover, the development of as partyl-aminopeptidase activators could be another goal, with a view to designing new antihypertensive agents. Our group has observed that unilateral lesions of the nigrostriatal pathway in rat brain produce simultaneous modifications in blood pressure and aminopeptidase activities, both in brain and plasma, curiously depending on the side of the lesion. This possible interaction among blood pressure, aminopeptidase activities and brain asymmetry, which could produce a differentiated neuroendocrine response on blood pressure control, may help us to understand the deep mechanism by which the brain is able to control blood pressure peripherally (AU)