Background-Angiotensin-converting enzyme 2 (ACE2) has emerged as a novel regulator of cardiac function and arterial pressure by converting angiotensin II (Ang II) into the vasodilator and antitrophic heptapeptide, angiotensin-(1-7) [Ang-(1-7)]. As the only known human homolog of ACE, the demonstration that ACE2 is insensitive to blockade by ACE inhibitors prompted us to define the effect of ACE inhibition on the ACE2 gene. Methods and Results-Blood pressure, cardiac rate, and plasma and cardiac tissue levels of Ang II and Ang-(1-7), together with cardiac ACE2, neprilysin, Ang II type 1 receptor (AT 1 ), and mas receptor mRNAs, were measured in Lewis rats 12 days after continuous administration of vehicle, lisinopril, losartan, or both drugs combined in their drinking water. Equivalent decreases in blood pressure were obtained in rats given lisinopril or losartan alone or in combination. ACE inhibitor therapy caused a 1.8-fold increase in plasma Ang-(1-7), decreased plasma Ang II, and increased cardiac ACE2 mRNA but not cardiac ACE2 activity. Losartan increased plasma levels of both Ang II and Ang-(1-7), as well as cardiac ACE2 mRNA and cardiac ACE2 activity. Combination therapy duplicated the effects found in rats medicated with lisinopril, except that cardiac ACE2 mRNA fell to values found in vehicle-treated rats. Losartan treatment but not lisinopril increased cardiac tissue levels of Ang II and Ang-(1-7), whereas none of the treatments had an effect on cardiac neprilysin mRNA. Conclusions-Selective blockade of either Ang II synthesis or activity induced increases in cardiac ACE2 gene expression and cardiac ACE2 activity, whereas the combination of losartan and lisinopril was associated with elevated cardiac ACE2 activity but not cardiac ACE2 mRNA. Although the predominant effect of ACE inhibition may result from the combined effect of reduced Ang II formation and Ang-(1-7) metabolism, the antihypertensive action of AT 1 antagonists may in part be due to increased Ang II metabolism by ACE2.

Abstract-We investigated in Lewis normotensive rats the effect of coronary artery ligation on the expression of cardiac angiotensin-converting enzymes (ACE and ACE 2) and angiotensin II type-1 receptors (AT 1a -R) 28 days after myocardial infarction. Losartan, olmesartan, or the vehicle (isotonic saline) was administered via osmotic minipumps for 28 days after coronary artery ligation or sham operation. Coronary artery ligation caused left ventricular dysfunction and cardiac hypertrophy. These changes were associated with increased plasma concentrations of angiotensin I, angiotensin II, angiotensin-(1-7), and serum aldosterone, and reduced AT 1a -R mRNA. Cardiac ACE and ACE 2 mRNAs did not change. Both angiotensin II antagonists attenuated cardiac hypertrophy; olmesartan improved ventricular contractility. Blockade of the AT 1a -R was accompanied by a further increase in plasma concentrations of the angiotensins and reduced serum aldosterone levels. Both losartan and olmesartan completely reversed the reduction in cardiac AT 1a -R mRNA observed after coronary artery ligation while augmenting ACE 2 mRNA by approximately 3-fold. Coadministration of PD123319 did not abate the increase in ACE 2 mRNA induced by losartan. ACE 2 mRNA correlated significantly with angiotensin II, angiotensin-(1-7), and angiotensin I levels. These results provide evidence for an effect of angiotensin II blockade on cardiac ACE 2 mRNA that may be due to direct blockade of AT 1a receptors or a modulatory effect of increased angiotensin-(1-7).

Peptide hormones such as ANG II and endothelin contribute to cardiac remodeling after myocardial infarction by stimulating myocyte hypertrophy and myofibroblast proliferation. In contrast, angiotensin-(1-7) [ANG-(1-7)] infusion after myocardial infarction reduced myocyte size and attenuated ventricular dysfunction and remodeling. We measured the effect of ANG-(1-7) on protein and DNA synthesis in cultured neonatal rat myocytes to assess the role of the heptapeptide in cell growth. ANG-(1-7) significantly attenuated either fetal bovine serum-or endothelin-1-stimulated [3 H]leucine incorporation into myocytes with no effect on, the selective ANG type 1-7 (AT1-7) receptor antagonist, blocked the ANG-(1-7)-mediated reduction in protein synthesis in cardiac myocytes, whereas the AT1 and AT2 angiotensin peptide receptors were ineffective. Serum-stimulated ERK1/ERK2 mitogen-activated protein kinase activity was significantly decreased by ANG-(1-7) in myocytes, a response that was also blocked by ]-ANG-(1-7). Both rat heart and cardiac myocytes express the mRNA for the mas receptor, and a 59-kDa immunoreactive protein was identified in both extracts of rat heart and cultured myocytes by Western blot hybridization with the use of an antibody to mas, an ANG-(1-7) receptor. Transfection of cultured myocytes with an antisense oligonucleotide to the mas receptor blocked the ANG-(1-7)-mediated inhibition of serum-stimulated MAPK activation, whereas a sense oligonucleotide was ineffective. These results suggest that ANG-(1-7) reduces the growth of cardiomyocytes through activation of the mas receptor. Because ANG-(1-7) is elevated after treatment with angiotensin-converting enzyme inhibitors or AT1 receptor blockers, ANG-(1-7) may contribute to their beneficial effects on cardiac dysfunction and ventricular remodeling after myocardial infarction. cardiac hypertrophy; mitogen-activated protein kinases [ANG-(1-7)] is an endogenous peptide hormone that produces unique physiological responses that are often opposite to those of the well-characterized angiotensin peptide ANG II (15). The ability of ANG II to increase blood pressure is documented; it is a potent vasoconstrictor, it stimulates thirst and aldosterone release, and inhibition of its production or effect with the use of angiotensin-converting enzyme (ACE) inhibitors or ANG type 1 (AT 1 ) receptor antagonists reduces mean arterial pressure (45). In addition, ANG II stimulates vascular growth as well as hypertrophy in terminally differentiated cells. In contrast, ANG-(1-7) reduces the blood pressure of hypertensive dogs and rats (4, 33), alters renal fluid absorption (11,19,22), causes vasodilation (6, 34, 35), and participates in the antihypertensive responses to ACE inhibition or AT 1 receptor blockade in hypertensive rats (24,25). In addition, we showed that ANG-(1-7) reduces vascular growth in vitro and in vivo (17,42,44), suggesting that ANG-(1-7) may act as an endogenous regulator of cell growth. Thus ANG-(1-7) opposes both the pressor and proliferative effects of ...

Our data revealed a role for ACE2 in Ang-(1-7) formation from Ang II in the kidney of normotensive rats as primarily reflected by the increased ACE2 activity measured in renal membranes from the kidney of rats given either lisinopril or losartan. The data further indicate that increased levels of Ang-(1-7) in the urine of animals after ACE inhibition or AT(1) receptor blockade reflect an intrarenal formation of the heptapeptide.

The mRen2.Lewis congenic strain is an estrogen-sensitive model of hypertension whereby estrogen depletion produces a significant and sustained increase in blood pressure. The recent identification of G protein-coupled receptor 30 (GPR30) as a third estrogen receptor isotype prompted us to test the hypothesis that this novel receptor exhibits beneficial cardiovascular actions in the hypertensive female mRen2.Lewis rat. Intact female, ovariectomized female (OVX), and male mRen2.Lewis rats were treated with the selective GPR30 agonist G-1 or vehicle via osmotic minipump for 2 wk. G-1 significantly reduced systolic blood pressure in OVX (178 +/- 7 to 142 +/- 10 mm Hg, P < 0.001, n = 8) but not intact female (144 +/- 3 to 143 +/- 5 mm Hg, P > 0.05, n = 5) or male mRen2.Lewis rats (207 +/- 7 to 192 +/- 5 mm Hg, P > 0.05, n = 7). G-1 did not alter uterine or body weight in OVX, suggesting activation of a receptor distinct from estrogen receptor-alpha and -beta. In isolated aortic rings from OVX, G-1 reduced constriction in response to angiotensin II. Vascular angiotensin-converting enzyme and angiotensin type 1 receptor mRNA were also lower, whereas angiotensin-converting enzyme-2 mRNA was increased. G-1 treatment in OVX was not associated with alterations in either endothelial nitric oxide synthase expression or acetylcholine-induced relaxation. Immunohistochemical staining for GPR30 was evident in both the intima and media of the aorta. We conclude that the novel estrogen receptor GPR30 may contribute to the beneficial cardiovascular actions of estrogen in female mRen2.Lewis rats through regulation of vascular components of the renin-angiotensin system.