Different responses to angiotensin-(1-7) in young, aged and diabetic rabbit corpus cavernosum.

We evaluated the ability of angiotensin-(1-7) [Ang-(1-7)] to produce relaxation of the corpus cavernosum of New Zealand White rabbits. The reactivity of corpus cavernosal strips isolated from young rabbits (8-10 months old) was assessed in organ-bath chambers. Cumulative concentration response curves for Ang-(1-7), angiotensin II (Ang II), carbachol and sodium nitroprusside (SNP) were established. Ang-(1-7) (10(-12) to 10(-5)M) produced a concentration-dependent relaxation of the corpus cavernosal strips with a pD(2) value of 9.8+/-0.3. Ang-(1-7)-induced maximal relaxant response was reduced by 48+/-2%, 57+/-3% and 76+/-2% in the presence of A-779 (10(-6)M), a selective Ang-(1-7) receptor (AT(1-7)) antagonist, nitro-l-arginine methyl ester (l-NAME) (10(-4)M), an inhibitor of nitric oxide (NO) synthase, or iberiotoxin (5 x 10(-8)M), an inhibitor of calcium-activated potassium (BK) channels, respectively. In contrast, Ang II-induced contraction was increased in the presence of A-779. Carbachol-, SNP- and Ang-(1-7)-induced relaxations were significantly reduced whereas Ang-II induced contraction was significantly increased in the cavernosum strips from older (18-24 months old) and diabetic rabbits compared to the young. Pre-incubation of the cavernosum strips obtained from young, older or diabetic rabbits with Ang-(1-7) resulted in a significant attenuation of Ang II-induced contraction. In conclusion, these results demonstrate that Ang-(1-7) can produce nitric oxide-dependent relaxation of the corpus cavernosum through activation of AT(1-7) and BK channels. Older and diabetic animals showed impaired Ang-(1-7)-mediated relaxation suggesting that aging and diabetes related erectile dysfunction (ED) may be partly due to decreased Ang-(1-7)-mediated relaxation of the corpus cavernosum. Acute pre-incubation with Ang-(1-7) was effective in attenuating Ang II-induced contraction of rabbit corpus cavernosum suggesting that the possible role of Ang-(1-7) in treatment of ED should be investigated.     

Suppressing inflammation by inhibiting the NF-κB pathway contributes to the neuroprotective effect of angiotensin-(1-7) in rats with permanent cerebral ischaemia

BACKGROUND AND PURPOSE

Angiotensin-(1-7) [Ang-(1-7)] has anti-inflammatory effects in peripheral organs, but its effects in ischaemic stroke are unclear as yet. We investigated whether its anti-inflammatory effect contributes to the neuroprotection induced by Ang-(1-7) in a rat model of permanent middle cerebral artery occlusion (pMCAO).

EXPERIMENTAL APPROACH

We infused Ang-(1-7), Mas receptor antagonist A-779, angiotensin II type 2 receptor antagonist PD123319 or artificial CSF into the right lateral ventricle of male Sprague-Dawley rats from 48 h before onset of pMCAO until the rats were killed. Twenty-four hours after pMCAO, the neuroprotective effect of Ang-(1-7) was analysed by evaluating infarct volume and neurological deficits. The levels of oxidative stress were detected by spectrophotometric assay. The activation of NF-κB was assessed by Western blot and immunohistochemistry analysis. The level of COX-2 was tested by Western blot analysis and concentrations of pro-inflammatory cytokines were measured by elisa.

KEY RESULTS

Infusion of Ang-(1-7), i.c.v., significantly reduced infarct volume and improved neurological deficits. It decreased the levels of oxidative stress and suppressed NF-κB activity, which was accompanied by a reduction of pro-inflammatory cytokines and COX-2 in the peri-infarct regions. These effects of Ang-(1-7) were reversed by A-779 but not by PD123319. Additionally, infusion of A-779 alone increased oxidative stress levels and enhanced NF-κB activity, which was accompanied by an up-regulation of pro-inflammatory cytokines and COX-2.

CONCLUSION AND IMPLICATIONS

Our findings indicate that suppressing NF-κB dependent pathway via Mas receptor may represent one mechanism that contributes to the anti-inflammatory effects of Ang-(1-7) in rats with pMCAO.     

Angiotensin-(1–7) induces cerebral ischaemic tolerance by promoting brain angiogenesis in a Mas/eNOS-dependent pathway

Background and Purpose

As a newer component of the renin–angiotensin system, angiotensin-(1–7) [Ang-(1–7) ] has been shown to facilitate angiogenesis and protect against ischaemic damage in peripheral tissues. However, the role of Ang-(1–7) in brain angiogenesis remains unclear. The aim of this study was to investigate whether Ang-(1–7) could promote angiogenesis in brain, thus inducing tolerance against focal cerebral ischaemia.

Experimental Approach

Male Sprague-Dawley rats were i.c.v. infused with Ang-(1–7), A-779 (a Mas receptor antagonist), L-NIO, a specific endothelial NOS (eNOS) inhibitor, endostatin (an anti-angiogenic compound) or vehicle, alone or simultaneously, for 1–4 weeks. Capillary density, endothelial cell proliferation and key components of eNOS pathway in the brain were evaluated. Afterwards, rats were subjected to permanent middle cerebral artery occlusion (pMCAO), and regional cerebral blood flow (rCBF), infarct volume and neurological deficits were measured 24 h later.

Key Results

Infusion of Ang-(1–7) for 4 weeks significantly increased brain capillary density via promoting endothelial cell proliferation, which was accompanied by eNOS activation and up-regulation of NO and VEGF in brain. These effects were abolished by A-779 or L-NIO. More importantly, Ang-(1–7) improved rCBF and decreased infarct volume and neurological deficits after pMCAO, which could be reversed by A-779, L-NIO or endostatin.

Conclusions and Implications

This is the first evidence that Ang-(1–7) promotes brain angiogenesis via a Mas/eNOS-dependent pathway, which enhances tolerance against subsequent cerebral ischaemia. These findings highlight brain Ang-(1–7)/Mas signalling as a potential target in stroke prevention.     

Angiotensin-(1-7) is involved in the endothelium-dependent modulation of phenylephrine-induced contraction in the aorta of mRen-2 transgenic rats

1. The contribution of the local vascular production of angiotensin-(1-7) [Ang-(1-7)] to the control of alpha-adrenergic-induced contractions in the aorta of Sprague-Dawley (SD) and TGR(mRen-2)27 [mRen-2] rats was studied. 2. In mRen-2 rats, contractile responses to phenylephrine were diminished as compared to control SD rats in endothelium containing but not in endothelium-denuded vessels. L-NAME increased contractile responses to phenylephrine in mRen-2 rats and, after nitric oxide synthase blockade, responses to phenylephrine became comparable in both strains. 3. Inhibition of angiotensin-converting enzyme (ACE) by captopril potentiated contractile responses in mRen-2 rats and diminished contractile responses in SD rats, both effects being dependent on the presence of a functional endothelium. The effect of captopril in mRen-2 rats was abolished in vessels pre-incubated with Ang-(1-7). 4. Blockade of Ang-(1-7) and bradykinin (BK) receptors by A-779 and HOE 140 respectively, increased phenylephrine-induced contraction in mRen-2, but not in SD rats. This effect was seen only in endothelium-containing vessels. 5. Angiotensin II AT(1) and AT(2) receptor blockade by CV 11974 and PD 123319 did not affect the contractile responses to phenylephrine in aortas of transgenic animals but diminished the response in SD rats. This effect was only seen in the presence of a functional endothelium. 6. It is concluded that the decreased contractile responses to phenylephrine in aortas of mRen-2 rats was dependent on an intact endothelium, the local release and action of Ang-(1-7) and bradykinin.     

Evidence for a functional cardiac interaction between losartan and angiotensin-(1-7) receptors revealed by orthostatic tilting test in rats

1. Studies have shown that the angiotensin II (Ang II) AT1 receptor antagonist, losartan, accentuates the orthostatic hypotensive response in anesthetized rats, and there is evidence indicating that this effect is not exclusively mediated by AT1 receptors. 2. We investigated whether the pronounced orthostatic cardiovascular response observed in losartan-treated rats involves an interference with angiotensin-(1-7) (Ang-(1-7)) receptors. 3. Urethane-anesthetized rats were submitted to orthostatic stress (90 degree head-up tilt for 2 min). Intravenous injection of losartan (1 mg kg(-1), n=9) significantly accentuated the decrease in mean arterial pressure (MAP) induced by head-up tilt (-33+/-6% after losartan vs -15+/-8% control tilt). This effect was accompanied by a significant bradycardia (-8+/-3% after losartan vs -3+/-3% control tilt). Another AT1 antagonist, candesartan, did not potentiate the decrease of MAP and did not change the cardiac response induced by head-up tilt. Strikingly, administration of the Ang-(1-7) antagonist, A-779 (10 nmol kg(-1), n=5), totally reversed the bradycardic effect caused by losartan and this effect was accompanied by a tendency towards attenuation of the hypotensive response caused by losartan. 4. These findings indicate that the marked orthostatic cardiovascular response is specific for losartan, and that it may be due, in part, to an interaction of this antagonist with Ang-(1-7) receptors, probably at the cardiac level.     

Angiotensin-(1-7) blockade attenuates captopril- or hydralazine-induced cardiovascular protection in spontaneously hypertensive rats treated with NG-nitro-L-arginine methyl ester

We assessed the contribution of angiotensin-(1-7) [Ang-(1-7)] to captopril-induced cardiovascular protection in spontaneously hypertensive rats (SHRs) chronically treated with the nitric oxide synthesis inhibitor NG-nitro-L-arginine methyl ester (SHR-l). NG-nitro-L-arginine methyl ester (80 mg/L) administration for 3 weeks increased mean arterial pressure (MAP) from 196 ± 6 to 229 ± 3 mm Hg (P < 0.05). Treatment of SHR-l with Ang-(1-7) antagonist [d-Ala7]-Ang-(1-7) (A779; 744 μg·kg(-1)·d(-1) ip) further elevated MAP to 253 ± 6 mm Hg (P < 0.05 vs SHR-l or SHR). Moreover, A779 treatment attenuated the reduction in MAP and proteinuria by either captopril (300 mg/L in drinking water) or hydralazine (1.5 mg·kg(-1)·d(-1) ip). In isolated perfused hearts, the recovery of left ventricular function from global ischemia was enhanced by captopril or hydralazine treatment and was exacerbated with A779. The Ang-(1-7) antagonist attenuated the beneficial effects of captopril and hydralazine on cardiac function. Recovery from global ischemia was also improved in isolated SHR-l hearts acutely perfused with captopril during both the perfusion and reperfusion periods. The acute administration of A779 reduced the beneficial actions of captopril to improve recovery after ischemia. We conclude that during periods of reduced nitric oxide availability, endogenous Ang-(1-7) plays a protective role in effectively buffering the increase in blood pressure and renal injury and the recovery from cardiac ischemia. Moreover, Ang-(1-7) contributes to the blood pressure lowering and tissue protective actions of captopril and hydralazine in a model of severe hypertension and end-organ damage.     

Interaction of bradykinin and angiotensin in the regulation of blood pressure in conscious rats

1. The interaction between bradykinin (BK) and the renin-angiotensin system was studied in conscious, catheterized rats. 2. Intravenous injection of BK induced dose-dependent decreases in blood pressure in normotensive Wistar and Wistar-Kyoto rats and spontaneously hypertensive rats. Pretreatment with the angiotensin-converting enzyme (ACE) inhibitor captopril markedly enhanced the effect of BK, such that the dose-response curve shifted significantly to the left in all three strains. 3. In a second series of experiments, captopril did not change basal blood pressure, but blocked the pressor response to angiotensin I (AI), but not angiotensin II (AII). 4. The partial agonist Sar1-Ala8-angiotensin II (SAR) increased blood pressure and blocked the pressor response to subsequent AII treatment. 5. After pretreatment with BK (50 micrograms/kg), captopril evoked a decrease in blood pressure, while still blocking the effect of AI. 6. After pretreatment with BK, SAR decreased blood pressure, while still antagonizing the action of AII. 7. These results suggest that ACE plays a role in the inactivation of circulating BK in normotensive and hypertensive rats. Conversely, BK can influence the activity of the renin-angiotensin system, probably by interacting with ACE.     

Angiotensin-(1–7) counteracts the effects of Ang II on vascular smooth muscle cells,vascular remodeling and hemorrhagic stroke: Role of the NFкB inflammatory pathway

Angiotensin (Ang)-(1–7) is a potential vasoprotective peptide. In the present study, we investigated its counteractive effects to Ang II on vascular smooth muscle cells (VSMCs) and intracerebral hemorrhagic stroke (ICH) through inflammatory mechanism. In in vitro experiments, human brain VSMCs (HBVSMCs) were treated with vehicle, Ang II, Ang II + Ang-(1–7), Ang II + A-779 or Ang II + Ang-(1–7) + A-779 (Mas receptor antagonist). HBVSMC proliferation, migration and apoptosis were determined by methyl thiazolyltetrazolium, wound healing assay and flow cytometry, respectively. In in vivo experiments, C57BL/6 mice were divided into vehicle, Ang II, Ang II + Ang-(1–7), Ang II + A-779 or Ang II + Ang-(1–7) + A-779 groups before they were subjected to collagenase-induced ICH or sham surgery. Hemorrhage volume and middle cerebral artery (MCA) remodeling were determined by histological analyses. Levels of NFκB, inhibitor of κBα (IκBα), tumor necrosis factor-α (TNF-α), monocyte chemoattractant protein 1 (MCP-1) and interleukin (IL-8) were measured by western blot or ELISA. We found that 1) Ang II increased HBVSMC migration, proliferation and apoptosis, and increased the blood pressure (BP), neurological deficit score, MCA remodeling and hemorrhage volume in ICH mice. 2) Ang-(1–7) counteracted these effects of Ang II, which was independent of BP, with the down-regulation of NFκB, up-regulation of IκBα, and decreased levels of TNF-α, MCP-1 and IL-8. 3) The beneficial effects of Ang-(1–7) could be abolished by A-779. In conclusion, Ang-(1–7) counteracts the effects of Ang II on ICH via modulating NFκB inflammation pathway in HBVSMCs and cerebral microvessels.     

The effect of peptidase inhibitors on bradykinin-induced bronchoconstriction in guinea-pigs in vivo.

1. Bradykinin (BK) instilled directly into the airway lumen caused bronchoconstriction in anaesthetized, mechanically ventilated guinea-pigs in the presence of propranolol (1 mg kg-1 i.v.). The geometric mean dose of BK required to produce 100% increase in airway opening pressure (PD100) was 22.9 nmol (95% c.i. 11.7-44.6 nmol). 2. The dose-response curve for the effect of instilled BK was significantly shifted to the left by the angiotensin converting enzyme (ACE) inhibitor, captopril (5 and 50 nmol instillation, PD100 = 3.0, 95% c.i. 0.98-8.9, and 2.0 nmol, 95% c.i. 0.65-6.2 nmol, respectively). 3. The neutral endopeptidase (NEP) inhibitor, phosphoramidon (5 and 50 nmol instillation) also shifted the dose-response curve for the effect of instilled BK; the PD100 values = 2.2 (95% c.i. 0.40-11.7) and 1.8 nmol (95% c.i. 0.87-3.5 nmol), respectively. 4. After pretreatment with captopril (50 nmol) and phosphoramidon (50 nmol) in combination, the dose-response curve for the effect of instilled BK (PD100 = 1.1 nmol, 95% c.i. 0.37-3.2 nmol) was similar to that obtained in the presence of each inhibitor used alone. 5. The kinase I inhibitor, DL-2-mercaptomethyl-3-guanidinoethylthiopropionic acid (50 nmol instillation) failed to alter the dose-response curve to instilled BK (PD100 = 14.6 nmol, 95% c.i. 6.7-32.0 nmol). 6. These data suggest that both ACE and NEP degrade BK in the airway lumen, but that kininase I is not involved.     

Angiotensin-(1-7) induces peripheral antinociception through mas receptor activation in an opioid-independent pathway

The G protein-coupled receptor Mas was recently described as an angiotensin-(1-7) [Ang-(1-7)] receptor. In the present study, we demonstrate an antinociceptive effect of Ang-(1-7) for the first time. Additionally, we evaluated the anatomical localization of Mas in the dorsal root ganglia using immunofluorescence. This is the first evidence indicating that this receptor is present in sensitive neurons. The antinociceptive effect was demonstrated using the rat paw pressure test. For this test, sensitivity is increased by intraplantar injection of prostaglandin E(2). Ang-(1-7) administered locally into the right hind paw elicited a dose-dependent antinociceptive effect. Because the higher dose of Ang-(1-7) did not produce an effect when injected into the contralateral paw, this effect was considered local. The specific antagonist for the Mas receptor, A-779, inhibited the peripheral antinociception induced by exposure to 4 μg/paw Ang-(1-7) in a dose-dependent manner. The highest dose completely reversed the antinociceptive effect induced by Ang-(1-7), suggesting that the Mas receptor is an obligatory component in this process and that other angiotensin receptors may not be involved. When injected alone, the antagonist was unable to induce hyperalgesia or antinociception. Alternatively, naloxone was unable to inhibit the antinociceptive effect induced by Ang-(1-7), suggesting that endogenous opioid peptides may not be involved in this response. These data provide the first anatomical basis for the physiological role of Ang-(1-7) in the modulation of pain perception via Mas receptor activation in an opioid-independent pathway. Taken together, these results provide new perspectives for the development of a new class of analgesic drugs.     

Effects of captopril on the human foetal placental circulation: an interaction with bradykinin and angiotensin I.

1. The mechanism underlying the foetal toxicity induced by captopril is not well understood. Since bradykinin and angiotensin II appear to be important in the regulation of the placental circulation, experiments were performed to assess the effects of captopril on the vascular actions of these peptides on the human foetal placental circulation. 2. Full-term human placentas, obtained from normal pregnancy, were perfused with a modified Tyrode solution bubbled with O2 using a pulsatile pump. The placental perfusion pressure was measured with a Statham pressure transducer and recorded continuously on a Hewlett-Packard polygraph. 3. Bradykinin (0.1, 0.3 and 1.0 nmol) injected into the placental arterial circulation produced an increase in placental perfusion pressure in all experiments. This effect of bradykinin was significantly inhibited by indomethacin (3 x 10(-7) M). 4. Captopril (10(-7) M) significantly potentiated the pressor effect of bradykinin on the human placental circulation (n = 6). This effect of captopril was reversed by indomethacin (3 x 10(-7) M). 5. Angiotensin I (n = 6) and angiotensin II (n = 6), injected into the placental arterial circulation, both produced dose-dependent increases in placental perfusion pressure. The dose-response curves to angiotensin I (n = 6) were significantly displaced to the right by captopril in a concentration-dependent manner. 6. We suggest that the toxic effects of captopril on the foetus, rather than reflecting an inhibition of angiotensin II formation, may instead be related to a potentiation of the vasoconstrictor effect of bradykinin on the foetal placental circulation, thereby reducing blood flow and causing foetal damage. The reasons for this are discussed.(ABSTRACT TRUNCATED AT 250 WORDS)     

N,N'-〔2,2'-二硫双(苯甲酰)〕-双 N-环己烷甘氨酸的降压作用

用麻醉大鼠观察了Ｎ，Ｎ′－〔２，２′－二硫双（苯甲酰）〕－双Ｎ－环己烷甘氨酸（ＤＧ－Ｉ）对血流动力学的影响、对肾血管性高血压的抗高血压作用及对ＡＩ、ＢＫ血压反应影响。ＤＧ－Ｉ２ｍｇ·ｋｇ－１ｉｖ可降低正常麻醉大鼠之ＳＡＰ、ＤＡＰ，不伴有ＬＶＰ、±ｄＰ／ｄｔｍａｘ下降，亦无反射性ＨＲ增快。ＤＧ－Ｉ２，４ｍｇ·ｋｇ－１ｉｖ可使肾血管性高血压大鼠血压下降，４ｍｇ·ｋｇ－１组伴有ＨＲ减慢。ＤＧ－Ｉ依剂量抑制ＡＩ之升压效应并增强ＢＫ之降压反应。结果表明ＤＧ－Ｉ具有血管紧张素转化酶抑制剂之特点，其降压作用与此有关。     

Characterization of Angiotensin-(1-7) effects on the cardiovascular system in an experimental model of type-1 diabetes

Although exogenous administration of Angiotensin-(1-7) [Ang-(1-7)] can prevent development of diabetes induced end-organ damage, little is known about the role of endogenous Ang-(1-7) in diabetes and requires further characterization. Here, we studied the effects of chronically inhibiting endogenous Ang-(1-7) formation with DX600, a selective angiotensin converting enzyme-2 (ACE2) inhibitor, on renal and cardiac NADPH oxidase (NOX) activity, vascular reactivity and cardiac function in a model of Type-1 diabetes. The contribution of endogenous Ang-(1-7) to the protective effects of Losartan and Captopril and that of prostaglandins to the cardiovascular effects of exogenous Ang-(1-7) were also examined. Cardiac and renal NOX activity, vascular reactivity to endothelin-1 (ET-1) and cardiac recovery from ischemia/reperfusion (I/R) injury were evaluated in streptozotocin-treated rats. Chronic treatment with DX600 exacerbated diabetes-induced increase in cardiac and renal NOX activity. Diabetes-induced abnormal vascular reactivity to ET-1 and cardiac dysfunction were improved by treatment with Ang-(1-7) and worsened by treatment with DX600 or A779, a Mas receptor antagonist. Ang-(1-7)-mediated improvement in cardiac recovery or vascular reactivity was attenuated by Indomethacin. Captopril and Losartan-induced improvement in cardiovascular function was attenuated when these drugs were co-administered with A779. Ang-(1-7)-mediated decrease in renal NOX activity was prevented by indomethacin. Losartan also decreased renal NOX activity that could be attenuated with A779 co-treatment. In conclusion, endogenous Ang-(1-7) inhibits diabetes-induced cardiac/renal NOX activity and end-organ damage, and mediates the actions of Captopril and Losartan. Further, prostaglandins are important intermediaries in the beneficial effects of Ang-(1-7) in diabetes. Combining either Losartan or Captopril with Ang-(1-7) had additional beneficial effects in preventing diabetes-induced cardiac dysfunction and this may represent a novel therapeutic strategy. Collectively, these data shed new insights into the likely mechanism of action through which the ACE2/Ang-(1-7)/Mas receptor axis prevents Type 1 diabetes-induced cardiovascular dysfunction.     

Angiotensin converting enzyme inhibitors and expression of des-Arg9-BK (kinin B1) receptors in vivo

The effect of the selective kinin B1 receptor agonist des-Arg9-BK was studied on blood pressure and on the in vitro aorta of rabbits pretreated 18 h earlier with lipopolysaccharide from E. coli, an infusion of bradykinin or with one of three angiotensin converting enzyme inhibitors captopril, enalapril or teprotide. The hypotensive response in vivo and contractile response seen on the in vitro aorta was selectively increased to des-Arg9-BK in all pretreated groups compared to controls, effects which were blocked by the selective competitive kinin B1 receptor antagonist des-Arg9-[Leu8]BK. Dexamethasone given to lipopolysaccharide pretreated rabbits had no effect on the increased hypotensive response seen with des-Arg9-BK. The skin vascular permeability response to des-Arg9-BK, bradykinin and histamine remained unchanged in the groups pretreated with lipopolysaccharide or captopril compared to controls. The possible mechanism(s) whereby angiotensin converting enzyme inhibitors produce this effect and the possible relevance to the inflammatory side-effects seen with this group of drugs is discussed.     

The effect of captopril on the reflex control heart rate: possible mechanisms.

Angiotensin converting enzyme inhibitors reduce blood pressure without reflex tachycardia, possibly as a result of enhanced hypothesis that this results from the removal of the parasympathetic activity. We examined the vagolytic action of angiotensin II or alternatively by acetylcholinesterase inhibition. Both captopril and [Sar1ala8] angiotensin II, (saralasin), caused modest falls in blood pressure, without increasing heart rate in normotensive subjects. Captopril and saralasin significantly attenuated the vagally mediated heart rate slowing after facial immersion in water. There was a close correlation between the effects produced by captopril and saralasin on the diving reflex. Infusion of subpressor doses of angiotensin II, reversed the hypotensive effect of captopril and returned the bradycardia after facial immersion to placebo level. In vitro neither captopril nor enalapril or lisinopril affected bovine erythrocyte acetylcholinesterase activity. The parasympathetic effect of angiotensin converting enzyme inhibitors appear to reflect a direct consequence of the removal of angiotensin II.     

Angiotensin-(1-7) inhibits allergic inflammation, via the MAS1 receptor, through suppression of ERK1/2- and NF-κB-dependent pathways

BACKGROUND AND PURPOSE Angiotensin-(1-7) [Ang-(1-7)] has anti-inflammatory effects in models of cardiovascular disease and arthritis, but its effects in asthma are unknown. We investigated whether Ang-(1-7) has anti-inflammatory actions in a murine model of asthma. EXPERIMENTAL APPROACH The effects of Ang-(1-7) alone or in combination with the MAS1 receptor antagonist, A779, were evaluated over a 4 day period in an ovalbumin-challenged mouse model of allergic asthma. On day 5, bronchoalveolar lavage was performed, and lungs were sectioned and assessed histologically for quantification of goblet cells, perivascular and peribronchial inflammation and fibrosis. Biochemical analysis of the pro-inflammatory ERK1/2 and IκB-α was assessed. In addition, the effect of Ang-(1-7) on proliferation of human peripheral blood mononuclear cells (HPBMC) was investigated. KEY RESULTS Ang-(1-7) attenuated ovalbumin-induced increases in total cell counts, eosinophils, lymphocytes and neutrophils. Ang-(1-7) also decreased the ovalbumin-induced perivascular and peribronchial inflammation, fibrosis and goblet cell hyper/metaplasia. Additionally, Ang-(1-7) reduced the ovalbumin-induced increase in the phosphorylation of ERK1/2 and IκB-α. These effects of Ang-(1-7) were reversed by the MAS1 receptor antagonist A779. Furthermore, Ang-(1-7) inhibited phytohaemagglutinin (PHA)-induced HPBMC proliferation. CONCLUSION AND IMPLICATIONS Ang-(1-7), via its MAS1 receptor, acts as an anti-inflammatory pathway in allergic asthma, implying that activation of the MAS1 receptor may represent a novel approach to asthma therapy.     

The role of bradykinin, AT2 and angiotensin 1-7 receptors in the EDRF-dependent vasodilator effect of angiotensin II on the isolated mesenteric vascular bed of the rat

1. The mechanisms involved in the vasodilator actions of angiotensin II (Ang II) have not yet been completely elucidated. We investigated the potential mechanisms that seem to be involved in the Ang II vasodilator effect using rat isolated mesenteric vascular bed (MVB). 2. Under basal conditions, Ang II does not affect the perfusion pressure of MVB. However, in vessels precontracted with norepinephrine, Ang II induces vasodilation followed by vasoconstriction. Vasoconstrictor, but not the vasodilation of Ang II, is inhibited by AT(1) antagonist (losartan). The vasodilator effect of Ang II was not inhibited by AT(2), angiotensin IV and angiotensin 1-7 receptor antagonists alone (PD 123319, divalinal, A 779, respectively). 3. The vasodilator effect of Ang II is significantly reduced by endothelial removal (deoxycholic acid), but not by indomethacin. Inhibition of NO-synthase by N(G)-nitro-l-arginine methyl ester (l-NAME) and guanylyl cyclase by 1H-[1,2,3] oxadiazolo [4,4-a] quinoxalin-1-one (ODQ) reduces the vasodilator effect of Ang II. This effect is also reduced by tetraethylammonium (TEA) or l-NAME, and a combination of l-NAME plus TEA increases the inhibitory effect of the antagonists alone. However, indomethacin does not change the residual vasodilator effect observed in vessels pretreated with l-NAME plus TEA. 4. In vessels precontracted with norepinephrine and depolarized with KCl 25 mm or treated with Ca(2+)-dependent K(+) channel blockers (charybdotoxin plus apamin), the effect of Ang II was significantly reduced. However, this effect is not affected by ATP and voltage-dependent K(+) channel blockers (glybenclamide and 4-aminopyridine). 5. Inhibition of kininase II with captopril significantly potentiates the vasodilator effect of bradykinin (BK) and Ang II in the rat MVB. The inhibitory effect of the B(2) receptor antagonist HOE 140 on the vasodilator effect of Ang II is further enhanced by PD 123319 and/or A 779. 6. The present findings suggest that BK plays an important role in the endothelium-dependent vasodilator effect of Ang II. Probably, the link between Ang II and BK release is modulated by receptors that bind PD 123319 and A 779.     

Conversion of angiotensin I to angiotensin II and inactivation of bradykinin in canine peripheral vascular beds

We studied the effects of angiotensin I (AI), angiotensin II (AII), and bradykinin (BK) on systemic blood pressure and blood flow in the renal, mesenteric, coeliac, external iliac, and internal iliac vascular beds in the presence and absence of the converting enzyme inhibitor captopril in pentobarbital-anesthetized dogs. AI and AII caused dose-dependent pressor responses and blood flow reductions, and BK caused dose-related depressor responses and an increase in blood flow. The pressor response to AI was decreased and the depressor response to BK was potentiated by captopril. However, the effectiveness of captopril was greater when the peptides were injected intravenously than when they were injected intraaortically. The average conversion of AI to AII in the mesenteric, coeliac, external iliac, internal iliac, and renal vascular beds was 45.7, 31.6, 30.6, 28.0, and 8.9%, respectively. The dose ratio of equipotent BK-induced responses before and after captopril in the mesenteric, coeliac, external iliac, internal iliac, and renal vascular beds was 4.6, 3.5, 2.8, 2.5 and 1.4, respectively. This order was similar to that of the percentage conversion of AI to AII. These results suggest that the greatest proportion of angiotensin conversion and BK inactivation occurs in the pulmonary circulation and that the least proportion occurs in the kidney.     

Participation of kinins in the captopril-induced inhibition of intimal hyperplasia caused by interruption of carotid blood flow in the mouse

1. In the rat balloon injury model, angiotensin-converting enzyme (ACE) inhibitors prevent vascular remodelling by inhibiting angiotensin II generation and kinin breakdown. We investigated if ACE inhibition also prevents the structural vascular responses to disruption of carotid artery blood flow and if kinin potentiation plays a role in such a protection. 2. Morphometric analysis of the structural alterations caused by ligation of the left carotid artery was performed 14 days after surgery in J129Sv wild-type mice (B(2)(+/+)) drinking normal tap water or water containing captopril (120 mg kg(-1) per day). In addition, the effect of captopril on vascular remodelling was tested in B(2)(+/+) given the bradykinin (BK) B(1) receptor antagonist des-Arg(9)-[Leu(8)]-BK (DALBK, 50 nmol kg(-1) per day, intraperitoneally) or the BK B(2) receptor antagonist D-Arg, [Hyp(3),Thi(5)D-Tic(7),Oic(8)]-BK (icatibant, 1 micromol kg(-1) per day, intraperitoneally), and in B(2) receptor gene knockout mice (B(2)(-/-)). 3. Interruption of blood flow resulted in carotid artery intimal hyperplasia and media thickening in untreated B(2)(+/+), these responses being partially suppressed by captopril. The inhibition of intimal thickening exerted by captopril was reduced in B(2)(+/+) given DALBK or icatibant (P<0.05 for both comparisons) as well as in B(2)(-/-) (P<0.05). Neither antagonism of kinin receptors nor disruption of the B(2) receptor gene altered the suppressive effect of captopril on media thickening. The protection of vascular wall structure was independent of the reduction in blood pressure by captopril. 4. These results demonstrate that kinins participate in the inhibitory effect of captopril on intimal hyperplasia via B(1) and B(2) receptor signalling. Our findings may have important implications in treating vascular remodelling evoked by altered shear stress conditions.