Angiotensin-[1-12] interacts with angiotensin type I receptors

Abstract

Angiotensin-(1-12) [Ang-(1-12)], a newer member of angiotensin peptides, is proposed to be converted enzymatically to angiotensin I (Ang I) and to angiotensin II (Ang II); the latter being the bioactive peptide. We studied the Ang-(1-12) and Ang II responses in COS-7 cells or CHO cells transfected with 5 μg AT1R by monitoring [Ca2+]i using the Fluo-4. Ang II (1 pM-1μM) and Ang-(1-12) (5 pM-5 μM) increased [Ca2+]i with an EC50 of 0.19 nM and 24 nM in COS-7 cells; and 0.65 nM and 28.7 nM in CHO cells. The AT1R antagonist losartan (1 nM-10 μM) suppressed [Ca2+]i induced by Ang-(1-12) and Ang II. In CHO cells transfected with 5 μg AT2R, Ang II (1 pM-1μM) increased [Ca2+]i, with an EC50 of 9.68 nM; whereas, Ang-(1-12) (5 pM-5 μM) failed to elicit a significant change in [Ca2+]i. In CHO cells transfected with AT1R, Ang-(1-12) stimulated ERK phosphorylation with a potency 300-fold less than that of Ang II. To evaluate the activity of Ang-(1-12) on native AT1R, whole cell patch recordings were made from neurons in the rat hypothalamic slices. Ang II or Ang-(1-12) ejected by pressure from a micropipette elicited a membrane depolarization; the latter was blocked by losartan (10 μM), and not affected by the AT2R antagonist PD 123319 (10 μM), nor by the angiotensin converting enzyme inhibitor captopril (10 μM). Our result shows that Ang-(1-12) may produce its biological activity by acting directly on AT1R, albeit at a concentration higher than that of Ang II.

Intracrine angiotensin II functions originate from noncanonical pathways in the human heart

“…The fall in cardiac and renal Ang-(1-12) content induced by a 7-day treatment with RAS inhibitors was interpreted by the authors to reflect a fall in cardiac and renal angiotensinogen gene expression (96). Ang-(1-12) functional responses appear to be primarily mediated through its conversion to Ang II (24). In this elegantly conducted study, Chan et al (24) showed that Ang-(1-12) aug-mented intracellular Ca ϩϩ mobilization and phosphorylated ERK in COS-7 and Chinese Hamster Ovary cells transiently transfected with AT 1 receptor cDNA at concentrations 40-to 100-fold higher than Ang II.…”

Functional and molecular evidence for expression of the renin angiotensin system and ADAM17-mediated ACE2 shedding in COS7 cells

“…Previous studies have suggested that COS7 cells lack endogenous AT 1 R, AT 2 R, and Mas receptors (3,4,16,23,28,30,40,51). However, basal expression and activity of MAS and AT 1 R were detected in nontransfected or vector-control transfected COS7 cells (16,40,51).…”

“…The versatility of COS7 cells allows the study of the functional regulation of single genes as well as the functional reconstitution of multiprotein complexes, including components of the RAS (3,4,16,23,28,30,40,51). Interestingly, COS7 cells functionally express a myriad of genes previously assumed to be absent (1, 2, 21).…”

New Components of the Renin-Angiotensin-Aldosterone System and Oxidative Stress

“…Ang-(1-12) can be degraded into smaller peptides such as Ang-(1-7) by ACE, neprilysin or chymase [64]. Ang-(1-12) was also reported to bind AT 1 receptors, serving not only as a substrate for smaller active peptides, but also as a ligand [65]. This peptide does not exist in human tissues.…”