Hypotensive effect induced by microinjection of Alamandine, a derivative of angiotensin-(1-7), into caudal ventrolateral medulla of 2K1C hypertensive rats.

In the present study we evaluated the cardiovascular effects produced by microinjection of the new component of the renin-angiotensin system, alamandine, into caudal ventrolateral medulla of urethane-anesthetized normotensive and hypertensive 2K1C rats. The participation of different angiotensin receptors in the effects of alamandine was also evaluated. Microinjection of angiotensin-(1-7) was used for comparison. The microinjection of 4, 40 and 140pmol of alamandine or angiotensin-(1-7) into caudal ventrolateral medulla induced similar hypotensive effects in Sham-operated rats. However, contrasting with angiotensin-(1-7), in 2K1C rats the MAP response to the highest dose of alamandine was similar to that observed with saline. The microinjection of A-779, a selective Mas receptor antagonist, blunted the angiotensin-(1-7) effects but did not block the hypotensive effect of alamandine in Sham or in 2K1C rats. However, microinjection of D-Pro7-angiotensin-(1-7), a Mas/MrgD receptor antagonist, blocked the hypotensive effect induced by both peptides. Furthermore, microinjection of PD123319, a putative AT2 receptor antagonist blocked the hypotensive effect of alamandine, but not of angiotensin-(1-7), in Sham and 2K1C rats. Microinjection of the AT1 receptor antagonist, losartan, did not alter the hypotensive effect of angiotensin-(1-7) or alamandine in both groups. These results provide new insights about the differential mechanisms participating in the central cardiovascular effects of alamandine and angiotensin-(1-7) in normotensive and 2K1C hypertensive rats.

Angiotensin-converting enzyme 2/angiotensin-(1-7)/Mas axis protects against lung fibrosis by inhibiting the MAPK/NF-κB pathway.

Accumulating evidence has demonstrated that up-regulation of the angiotensin (Ang)-converting enzyme (ACE)/AngII/AngII type 1 receptor (AT1R) axis aggravates pulmonary fibrosis. The recently discovered ACE2/Ang-(1-7)/Mas axis, which counteracts the activity of the ACE/AngII/AT1R axis, has been shown to protect against pulmonary fibrosis. However, the mechanisms by which ACE2 and Ang-(1-7) attenuate pulmonary fibrosis remain unclear. We hypothesized that up-regulation of the ACE2/Ang-(1-7)/Mas axis protects against bleomycin (BLM)-induced pulmonary fibrosis by inhibiting the mitogen-activated protein kinase (MAPK)/NF-κB pathway. In vivo, Ang-(1-7) was continuously infused into Wistar rats that had received BLM or AngII. In vitro, human fetal lung-1 cells were pretreated with compounds that block the activities of AT1R, Mas (A-779), and MAPKs before exposure to AngII or Ang-(1-7). The human fetal lung-1 cells were infected with lentivirus-mediated ACE2 before exposure to AngII. In vivo, Ang-(1-7) prevented BLM-induced lung fibrosis and AngII-induced lung inflammation by inhibiting the MAPK phosphorylation and NF-κB signaling cascades. However, exogenous Ang-(1-7) alone clearly promoted lung inflammation. In vitro, Ang-(1-7) and lentivirus-mediated ACE2 inhibited the AngII-induced MAPK/NF-κB pathway, thereby attenuating inflammation and α-collagen I production, which could be reversed by the Mas inhibitor, A-779. Ang-(1-7) inhibited AngII-induced lung fibroblast apoptotic resistance via inhibition of the MAPK/NF-κB pathway and activation of the BCL-2-associated X protein/caspase-dependent mitochondrial apoptotic pathway. Ang-(1-7) alone markedly stimulated extracellular signal-regulated protein kinase 1/2 phosphorylation and the NF-κB cascade. Up-regulation of the ACE2/Ang-(1-7)/Mas axis protected against pulmonary fibrosis by inhibiting the MAPK/NF-κB pathway. However, close attention should be paid to the proinflammatory effects of Ang-(1-7).

Toxicological and toxicokinetic analysis of angiotensin (1-7) in two species.

The objectives of this study were to determine the potential systemic and local toxicity, as well as evaluate the toxicokinetic (TK) profile of angiotensin (1-7) [A(1-7)] when administered daily via subcutaneous injection for 28 days to Sprague-Dawley rats and Beagle dogs. A(1-7) is a member of the renin-angiotensin system and has undergone clinical evaluation for the treatment of chemotherapy-induced myelosuppression. In this present study, A(1-7) was given at 10 mg/(kg day) for 28 days to rats and canines. At day 27, blood was harvested to evaluate the TK parameters. On day 28, systemic toxicology was evaluated. Following A(1-7) administration for 27 days, no plasma A(1-7) accumulation was detected in canines; however, increased A(1-7) plasma concentrations were detected in rats. Despite the accumulation observed in rats, no detectable toxicity was found following A(1-7) administration for 28 days. The TK analysis of A(1-7) revealed a plasma half-life of 20-30 min in both rats and canines. The time to maximum plasma concentration was found to be 15 and 26.25 min in rats and canines, respectively. This study shows that subcutaneous administration of A(1-7) at 10 mg/(kg day) for 28 days did not lead to any detectable toxicities in either rats or canines.

Angiotensin-(1-7) infusion is associated with increased blood pressure and adverse cardiac remodelling in rats with subtotal nephrectomy.

ACE (angiotensin-converting enzyme) 2 is expressed in the heart and kidney and metabolizes Ang (angiotensin) II to Ang-(1-7) a peptide that acts via the Ang-(1-7) or mas receptor. The aim of the present study was to assess the effect of Ang-(1-7) on blood pressure and cardiac remodelling in a rat model of renal mass ablation. Male SD (Sprague-Dawley) rats underwent STNx (subtotal nephrectomy) and were treated for 10 days with vehicle, the ACE inhibitor ramipril (oral 1 mg·kg(-1) of body weight·day(-1)) or Ang-(1-7) (subcutaneous 24 µg·kg(-1) of body weight·h(-1)) (all n = 15 per group). A control group (n = 10) of sham-operated rats were also studied. STNx rats were hypertensive (P<0.01) with renal impairment (P<0.001), cardiac hypertrophy (P<0.001) and fibrosis (P<0.05), and increased cardiac ACE (P<0.001) and ACE2 activity (P<0.05). Ramipril reduced blood pressure (P<0.01), improved cardiac hypertrophy (P<0.001) and inhibited cardiac ACE (P<0.001). By contrast, Ang-(1-7) infusion in STNx was associated with further increases in blood pressure (P<0.05), cardiac hypertrophy (P<0.05) and fibrosis (P<0.01). Ang-(1-7) infusion also increased cardiac ACE activity (P<0.001) and reduced cardiac ACE2 activity (P<0.05) compared with STNx-vehicle rats. Our results add to the increasing evidence that Ang-(1-7) may have deleterious cardiovascular effects in kidney failure and highlight the need for further in vivo studies of the ACE2/Ang-(1-7)/mas receptor axis in kidney disease.

Chronic angiotensin (1-7) injection accelerates STZ-induced diabetic renal injury.

AIM: The renin-angiotensin system (RAS) plays a critical role in blood pressure control and body fluid and electrolyte homeostasis. In the past few years, angiotensin (Ang) (1-7) has been reported to counteract the effects of Ang II and was even considered as a new therapeutical target in RAS. The present study aimed to investigate the effect of Ang (1-7) administration on a diabetic animal model and the modulation on local RAS. METHODS: Streptozotocin (STZ) injection-induced diabetic rats were used in the experiment. The animals were divided into 3 groups: (1) control; (2) STZ-induced diabetes; and (3) STZ-induced diabetes with chronic Ang (1-7) treatment [D+Ang(1-7)]. In the D+Ang(1-7) group, a dose of 25 microg x kg(-1) x h(-1) of Ang (1-7) was continually injected through the jugular vein by embedding miniosmotic pump for 6 weeks. Plasma glucose, ratio of kidney to body weight, and 24 h urine protein and serum creatinine were monitored by conventional measurement. Plasma and renal Ang II levels were measured by radioimmunoassay. Ang-converting enzyme (ACE), ACE2, Ang II type 1 (AT1) receptor, Ang II type 2 (AT2) receptor, Ang (1-7) Mas receptor, and TGF- beta1 mRNA levels were measured by real time PCR; ACE, ACE2, and TGF- beta1 protein levels were analyzed by Western blotting. RESULTS: The renal function of diabetic rats was significantly retrogressed when compared with that of control rats. After the treatment by constant Ang (1-7) vein injection for 6 weeks, renal function was found to be even worse than diabetic rats, and both TGF-beta1 mRNA and protein levels were elevated in the D+Ang(1-7) group compared with the diabetic rats. The real-time PCR result also showed an increase in ACE mRNA expression and decrease in ACE2 mRNA level in the D+Ang(1-7) group when compared with diabetic rats. The number of AT1 receptors increased in the Ang (1-7)-injected group, while the number of AT2 and Mas receptors decreased. CONCLUSION: Exogenous Ang (1-7) injection did not ameliorate STZinduced diabetic rat renal injury; on the contrary, it accelerated the progressive diabetic nephropathies.

The deleterious effects of exogenous angiotensin I and angiotensin II on myocardial ischemia-reperfusion injury.

Angiotensin II is well known to have a cardiotoxic effects. However, it is still unclear whether exogenous angiotensin I or angiotensin II has a deleterious effect on myocardial ischemia-reperfusion injury. To examine this deleterious effects, we administered angiotensin I and angiotensin II to perfused hearts before ischemia, and measured creatine kinase (CK) release and cardiac function during subsequent reperfusion. Wistar Kyoto rats were used and the hearts were perfused by the Langendorff technique at a constant flow (10 ml/min). Seven hearts were perfused for 20 min and then subjected to 15 min of global ischemia (Control). In the experimental groups, during the 5 min before ischemia, we administered 100 ng/ml angiotensin I (Ang I; n = 9), 1 microgram/ml enalaprilat (ACEI; n = 5), both agents (ACEI + Ang I) (n = 6), or 10 ng/ml angiotensin II (Ang II; n = 6). The perfusates were then sampled to measure angiotensin II. After 15 min of ischemia, the hearts were reperfused with control perfusate. Throughout the 20 min of reperfusion, the effluent was collected to measure cumulative CK release. Angiotensin I increased coronary perfusion pressure (CPP) by 32 +/- 4 mmHg, however, the angiotension converting enzyme inhibitor inhibited the increase of CPP by angiotension I (11 +/- 1 mmHg) (p < 0.01). The contents of angiotensin II in the effluent in Ang I and Ang I + ACEI were 11.5 +/- 1.9 ng/ml and 4.0 +/- 0.5 ng/ml (p < 0.01). After 20 min of reperfusion, the left ventricular developed pressure was unchanged in all of the groups. CPP was also unchanged by ischemia in all of the groups.(ABSTRACT TRUNCATED AT 250 WORDS)