血管紧张素Ⅱ2型受体基因缺失不影响肾素-血管紧张素系统

基于目前对血管紧张素Ⅱ2型受体(AT2)功能的认识,认为血管紧张素Ⅱ1型受体(AT1)和AT2受体有相互拮抗作用.依据上述论点,本研究利用AT2受体基因敲出小鼠,观察了AT2受体缺失后是否造成肾素-血管紧张素系统其它成分代偿性紊乱.结果发现,AT2受体基因缺失小鼠血浆和肾组织中血管紧张素Ⅱ的浓度以及肾组织中肾素、AT1A受体的基因表达均未发生明显改变,表明AT2受体缺失未对肾素-血管紧张素系统产生显著影响,AT2受体的功能已被代偿,但代偿途径尚有待于进一步研究.     

血管紧张素Ⅱ受体拮抗剂在心血管疾病中的应用

体内调节血压及水电解质平衡的主要系统是肾素—血 管紧张素—醛固酮系统（ＲＡＳ）,而ＲＡＳ最终通过血管紧张 素Ⅱ（ＡＴⅡ）与各组织细胞膜上的特异受体结合而发挥作 用,而血管紧张素Ⅱ受体拮抗剂能在受体水平上选择性地 抑制ＡＴⅡ作用,病人耐受性好,在心血管疾病的防治中有 其广阔的应用价值。 １　ＡＴ受体及其拮抗剂 　　已证明ＡＴⅡ是有若干生物学作用,包括血管收缩,升 高血压,刺激肾小管钠重吸收,刺激肾上腺生成醛固酮,促 进血管加压素及儿茶酚胺释放（肾上腺和神经原性）。而 ＡＴⅡ通过与细胞膜…     

血管紧张素II2型受体基因缺失不影响肾素—血管紧张素系统

基于目前对血管紧张素Ⅱ２型受体（ＡＴ２）功能的认识,认为血管紧张素Ⅱ１型受体（ＡＴ１）和ＡＴ２受体有相互拮抗作用。依据上述论点,本研究利用ＡＴ２受体基因敲出小鼠,观察了ＡＴ２受体缺失后是否造成肾素－血管紧张素系统其它成分代偿性紊乱。结果发现,ＡＴ２受体基因缺失小鼠血浆和肾组织中血管紧张素Ⅱ的浓度以及肾组织中肾素、ＡＴ１Ａ受体的基因表达均未发生明显改变,表明ＡＴ２受体缺失未对肾素－血管紧张素系统产生     

基于神经激素系统治疗肺动脉高压进展

肺动脉高压（pulmonary hypertension, PH）是一种进行性进展的致死性心肺疾病,最终会导致右心衰竭和死亡,其发病率和死亡率逐年上升。目前PH的发病机制尚不明确,且缺乏有效的治疗手段。最近的研究表明,在PH患者及动物模型中存在自主神经系统（autonomic nervous system, ANS）失衡和肾素-血管紧张素-醛固酮系统（renin-angiotensinaldosterone system, RAAS）激活的现象,参与促进PH发生发展,并且与PH患者预后紧密相关。综述了针对神经激素系统的干预方法对PH的作用及相应机制,包括α/β受体阻滞剂、β3受体激动剂、肺动脉去神经、肾去神经、交感神经节阻滞、迷走神经刺激及RAAS抑制剂,以期为PH治疗提供新的手段。     

肾素-血管紧张素-醛固酮系统在咸味觉功能及摄钠调控中的作用

咸味觉感受功能对摄钠行为的引导和调控至关重要,体钠平衡失调将引起一系列神经内分泌变化以产生钠欲,并伴有咸味觉感受功能的变化.肾素-血管紧张素-醛固酮系统(renin-angiotensin-aldosterone system,RAAS)的多个成分在体钠平衡失调对咸味觉功能的调控中扮演重要角色.外周及脑源性血管紧张素II(angiotensin II,ANG II)和醛固酮(aldosterone,ALD)可协同作用于中枢相应敏感神经元,调控动物咸味觉喜好及敏感性,进而调控摄钠行为,并帮助机体维持体钠平衡.     

血管紧张素转换酶2-血管紧张素1-7-Mas轴对血管作用的研究进展

血管紧张素转换酶2（ACE2）和Mas受体的发现使人们对肾素-血管紧张素（RAS）有了更全面的认识。ACE2可水解血管紧张素Ⅰ和血管紧张素Ⅱ直接或间接生成血管紧张素1-7（Ang 1-7）,并与高血压的形成密切相关。Ang 1-7主要通过Mas受体引起血管舒张、抑制细胞增殖。ACE2-Ang1-7-Mas轴的发现为RAS的研究、高血压等心血管疾病的防治和新药开发提供了新的思路和方向。     

肾素-血管紧张素系统与糖尿病心肌病关系的研究进展

糖尿病时,肾素-血管紧张素系统(renin-angiotensin system,RAS)被激活,升高的血管紧张素Ⅱ(Ang Ⅱ)通过细胞表面的AT1受体,刺激心肌成纤维细胞增生及胶原代谢改变,引起心脏结构重塑,导致心肌间质及血管周围纤维化,胶原含量增多和排列紊乱,造成心室肌僵硬而影响舒张功能,出现糖尿病心肌病(diabetic cardiomyopathy,DCM)的临床症状.本文从RAS的主要成分Ang Ⅱ、Ang-(1-7)、Ac-SDKP和血管紧张素受体(ATR)与内皮素、活性氧、转化生长因子-β1、核因子-κB、信号转导系统以及细胞凋亡之间的相互作用,阐述RAS在糖尿病心肌病发生发展中所起的重要作用.     

血管紧张素-(1-7)的舒血管效应

实验采用兔外周动脉离体标本,在预收缩血管后,用血管紧张素[angiotensin-(1-7),Ang-(1-7)]舒张血管,比较Ang-(1-7)对外周各血管床的舒张效应并分析其产生机制。结果显示：(1)Ang-(1-7)可剂量依赖性舒张血管,但舒张作用有所不同;(2)Ang-(1-7)的舒张作用在很大程度上依赖于内皮的NO系统;(3)Ang-(1-7)的舒张血管效应不通过AT1和AT2受体。上述结果提示：Ang-(1-7)可能作用于内皮上的非AT1和AT2受体,通过调节NO释放而起舒血管作用。     

作为肾素-血管紧张素系统调节器和SARS病毒受体的人血管紧张素转换酶2

人血管紧张素转换酶2(ACE2)是目前已知的惟一的人血管紧张素转换酶(ACE)的同源物,是一种新型的金属羧肽酶,很多特性与ACE截然不同.ACE2在肾素-血管紧张素系统(RAS)中具有独特的作用,调节心脏功能和机体血压.最近ACE2被鉴定为SARS病毒的功能受体.ACE2已经成为目前药物研发的新靶点.对ACE2的认识才刚刚开始,有待进-步深入研究.     

闭锁卵泡中肾素—血管紧张素质系统的变化

目的：探讨卵巢局部的肾素－血管紧张素系统（RAS）在卵泡闭锁中的作用。方法：应用卵巢细胞双室培养,放射免疫测定（RIA）及免疫组化方法研究猪卵巢的健康卵泡和闭锁卵泡的颗粒细胞和卵泡内膜细胞与RAS的关系;观察了血管紧张素Ⅱ（AngⅡ)拮抗剂Saralasin及血管紧张素转换酶（ACE）抑制剂Captopril的作用。结果（1）与健康卵泡相比较,闭锁卵泡的卵泡液及卵泡内膜细胞培养液中的AngⅡ浓度明显升高,肾素浓度则明显降低;而颗粒细胞培养液中的AngⅡ和肾素浓度均无明显改变;（2）闭锁卵泡切片的AngⅡ,2型血管紧张素Ⅱ受体（AT2）染色明显强于健康卵泡;AngⅡ和AT2水平在双室培养的闭锁卵泡的卵泡内膜细胞中明显强于健康卵泡的卵泡内膜细胞;健康和闭锁卵泡的颗粒细胞中的AngⅡ,AT2水平变化不大;（3）双室培养中加入Saralasin或Captopril培养48h后,（a)与健康卵泡相比,闭锁卵泡的卵泡内膜细胞培养液中的AngⅡ浓度显降低,肾素浓度明显升高;（b)健康和闭锁卵泡的卵泡内膜细胞AngⅡ和AT2免疫组化染色均呈现下降,（c)RIA结果显示,健康和闭锁卵泡的颗粒细胞培养液中的AngⅡ和肾素浓度无明显变化;免疫组化结果显示,颗粒细胞的AngⅡ,AT2水平亦无显改变。结论：卵泡闭锁与卵巢RAS密切相关,AngⅡ和AT2是卵泡闭锁的重要相关因子;卵泡闭锁过程中卵巢局部的RAS变化主要发生在卵泡内膜细胞;Saralasin和Captopril可能通过调节卵巢RAS而具有抑制卵泡闭锁的作用。     

An update on non-peptide angiotensin receptor antagonists and related RAAS modulators

The renin-angiotensin-aldosterone-system (RAAS) is an important regulator of blood pressure and fluid-electrolyte homeostasis. RAAS has been implicated in pathogenesis of hypertension, congestive heart failure, and chronic renal failure. Aliskiren is the first non-peptide orally active renin inhibitor approved by FDA. Angiotensin Converting Enzyme (ACE) Inhibitors are associated with frequent side effects such as cough and angio-oedema. Recently, the role of ACE2 and neutral endopeptidase (NEP) in the formation of an important active metabolite/mediator of RAAS, ang 1-7, has initiated attempts towards development of ACE2 inhibitors and combined ACE/NEP inhibitors. Furukawa and colleagues developed a series of low molecular weight nonpeptide imidazole analogues that possess weak but selective, competitive AT1 receptor blocking property. Till date, many compounds have exhibited promising AT1 blocking activity which cause a more complete RAAS blockade than ACE inhibitors. Many have reached the market for alternative treatment of hypertension, heart failure and diabetic nephropathy in ACE inhibitor intolerant patients and still more are waiting in the queue. But, the hallmark of this area of drug research is marked by a progress in understanding molecular interaction of these blockers at the AT1 receptor and unraveling the enigmatic influence of AT2 receptors on growth/anti-growth, differentiation and the regeneration of neuronal tissue. Different modeling strategies are underway to develop tailor made molecules with the best of properties like Dual Action (Angiotensin And Endothelin) Receptor Antagonists (DARA), ACE/NEP inhibitors, triple inhibitors, AT2 agonists, AT1/TxA2 antagonists, balanced AT1/AT2 antagonists, and nonpeptide renin inhibitors. This abstract gives an overview of these various angiotensin receptor antagonists.     

Angiotensin II receptors-antagonists, molecular biology, and signal transduction

The renin-angiotensin-aldosterone system (RAAS) plays an important role in both the short-term and long-term regulation of arterial blood pressure, and fluid and electrolyte balance. The RAAS is a dual hormone system, serving as both a circulating and a local tissue hormone system (i.e., local mediator) as well as neurotransmitter or neuromediator functions in CNS. Control of blood pressure by the RAAS is exerted through multiple actions of angiotensin II, a small peptide which is a potent vasoconstrictor hormone implicated in the genesis and maintenance of hypertension. Hypertension is a primary risk factor associated with cardiovascular, cerebral and renal vascular disease. One of the approaches to the treatment of hypertension, which may be considered as a major scientific advancement, involves the use of drugs affecting the RAAS. Pharmacological interruption of the RAAS was initially employed in the late 1970s with the advent of the angiotensin converting enzyme (ACE) inhibitor, captopril. ACE inhibitors have since gained widespread use in the treatment of mild to moderate hypertension, congestive heart failure, myocardial infarction, and diabetic nephropathy. As the roles of the RAAS in the pathophysiology of several diseases was explored, so did the realization of the importance of inhibiting the actions of angiotensin II. Although ACE inhibitors are well tolerated, they are also involved in the activation of bradykinin, enkephalins, and other biologically active peptides. These actions result in adverse effects such as cough, increased bronchial reactivity, and angioedema. Thus, the goal of achieving a more specific blockade of the effects of angiotensin II than is possible with ACE inhibition. The introduction of the nonpeptide angiotensin II receptor antagonist losartan in 1995 marked the achievement of this objective and has opened new vistas in understanding and controlling the additional biological effects of angiotensin II. Complementary investigations into the cloning and sequencing of angiotensin II receptors have demonstrated the existence of a family of angiotensin II receptor subtypes. Two major types of angiotensin II receptors have been identified in humans. The type 1 receptor (AT1) mediates most known effects of angiotensin II. The type 2 receptor (AT2), for which no precise function was known in the past, has gained importance recently and new mechanisms of intracellular signalling have been proposed. This review presents recent advances in angiotensin II receptor pharmacology, molecular biology, and signal transduction, with particular reference to the AT1 receptor. Excellent reviews have appeared recently on this subject.     

Addressing the theoretical and clinical advantages of combination therapy with inhibitors of the renin–angiotensin–aldosterone system: Antihypertensive effects and benefits beyond BP control

AimsThis article reviews the importance of the renin–angiotensin–aldosterone system (RAAS) in the cardiometabolic continuum; presents the pros and cons of dual RAAS blockade with angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs); and examines the theoretical and practical benefits supporting the use of direct renin inhibitors (DRIs) in combination with ACEIs or ARBs.Main methodsThe author reviewed the literature for key publications related to the biochemical physiology of the RAAS and the pharmacodynamic effects of ACEIs, ARBs, and DRIs, with a particular focus on dual RAAS blockade with these drug classes.Key findingsAlthough ACEI/ARB combination therapy produces modest improvement in BP, it has not resulted in the major improvements predicted given the importance of the RAAS across the cardiorenal disease continuum. This may reflect the fact that RAAS blockade with ACEIs and/or ARBs leads to exacerbated renin release through loss of negative-feedback inhibition, as well as ACE/aldosterone escape through RAAS and non-RAAS-mediated mechanisms. Plasma renin activity (PRA) is an independent predictor of morbidity and mortality, even for patients receiving ACEIs and ARBs. When used alone or in combination with ACEIs and ARBs, the DRI aliskiren effectively reduces PRA. Reductions in BP are greater with these combinations, relative to the individual components alone.SignificanceIt is possible that aliskiren plus either an ACEI or ARB may provide greater RAAS blockade than monotherapy with ACEIs or ARBs, and lead to additive improvement in BP and clinically important outcomes.     

Renin-angiotensin system inhibition on noradrenergic nerve terminal function in pacing-induced heart failure

Chronic angiotensin-converting enzyme (ACE) inhibition has been shown to improve cardiac sympathetic nerve terminal function in heart failure. To determine whether similar effects could be produced by angiotensin II AT(1) receptor blockade, we administered the ACE inhibitor quinapril, angiotensin II AT(1) receptor blocker losartan, or both agents together, to rabbits with pacing-induced heart failure. Chronic rapid pacing produced left ventricular dilation and decline of fractional shortening, increased plasma norepinephrine (NE), and caused reductions of myocardial NE uptake activity, NE histofluorescence profile, and tyrosine hydroxylase immunostained profile. Administration of quinapril or losartan retarded the progression of left ventricular dysfunction and attenuated cardiac sympathetic nerve terminal abnormalities in heart failure. Quinapril and losartan together produced greater effects than either agent alone. The effect of renin-angiotensin system inhibition on improvement of left ventricular function and remodeling, however, was not sustained. Our results suggest that the effects of ACE inhibitors are mediated via the reduction of angiotensin II and that angiotensin II plays a pivotal role in modulating cardiac sympathetic nerve terminal function during development of heart failure. The combined effect of ACE inhibition and angiotensin II AT(1) receptor blockade on cardiac sympathetic nerve terminal dysfunction may contribute to the beneficial effects on cardiac function in heart failure.     

Novel aspects of angiotensin II action in the heart. Implications to myocardial ischemia and heart failure

The influence of angiotensin II (Ang II) on cardiac structural and electrophysiological remodeling was discussed including the novel concept that the renin angiotensin aldosterone is involved in the regulation heart cell volume. Particular attention was given to the role of Ang II AT1 receptors as mechanosensors which are activated by mechanic stretch independently of Ang II. These findings highly suggest that RAS inhibitors or AT1 receptor blockers have additional beneficial therapeutics effects by changing mechanical transduction. The influence of cell swelling on cell communication as well as the effect of Ang II on cell volume and the consequent activation of ionic channels and the generation of cardiac arrhythmias was reviewed. The discovery of ACE2 and its relevance to heart pathology was also discussed.     

Blockade of angiotensin AT1a receptor signaling reduces tumor growth,angiogenesis, and metastasis

It was reported that angiotensin II stimulates angiogenesis in vivo, and angiotensin-converting enzyme (ACE) inhibitors inhibit angiogenesis. We found that an AT1-receptor (AT1-R) antagonist, TCV-116, inhibited tumor growth, tumor-associated angiogenesis, and metastasis in a murine model. Tumor growth of Sarcoma 180 (S-180) cells and of fibrosarcoma (NFSA) cells was strongly inhibited by administration of TCV-116 in the diet at a dose of approximately 100 mg/kg/day. This reduction was accompanied with a marked reduction in tumor-associated angiogenesis. The same treatment also reduced the lung metastasis of intravenously injected Lewis lung carcinoma cells. These effects of TCV-116 were equivalent to those of the ACE inhibitor, lisinopril. In S-180 and NFSA tumor tissues, ACE and AT1a receptor (AT1a-R) mRNAs were expressed when assessed with RT-PCR. AT1b receptor and AT2 receptor, however, were not detected. Immunoreactive AT1-R was detected mainly on the neovascularized vascular endothelial cells in which expression was reduced by TCV-116 and lisinopril. These results suggested that TCV-116 inhibits the angiogenesis, growth, and metastasis of tumors highly dependent on AT1a-R blockade. Blockade of AT1a-R signaling may therefore become an effective novel strategy for tumor chemoprevention.     

Direct positive chronotropic action by angiotensin II in the isolated mouse atrium

We observed the direct positive chronotropic effect of angiotensin II in mouse atria and characterized its pharmacological property. C57BL/6J mice were anesthetized with pentobarbital and hearts were quickly excised. Atrial preparations including right and left atrium were isolated and suspended in the organ bath filled with Krebs-Henseleit solution gassed with 95% O2 and 5% CO2. Angiotensin II at concentrations of 10(-10) to 10(-6) M caused concentration-dependent increase in heart rate, and the maximal response was about 13% of that by isoproterenol. The effect was blocked by the selective AT1-receptor antagonist, losartan at concentrations of 10(-6) M, but not by the selective beta-blocker, nadolol at concentration of 10(-5) M. Furthermore, angiotensin I also caused concentration-dependent increase in heart rate, and the effect was blocked by angiotensin converting enzyme (ACE) inhibitor, captopril at concentrations of 10(-6) M. These results suggested that angiotensin I is converted to angiotensin II via ACE system in mice atria, and regulate heart rate through AT1-receptor stimulation, not by beta-adrenergic receptor.     

The potential therapeutic use of renin–angiotensin system inhibitors in the treatment of inflammatory diseases

Inflammation is a normal part of the immune response to injury or infection but its dysregulation promotes the development of inflammatory diseases, which cause considerable human suffering. Nonsteroidal anti-inflammatory agents are the most commonly prescribed agents for the treatment of inflammatory diseases, but they are accompanied by a broad range of side effects, including gastrointestinal and cardiovascular events. The renin–angiotensin system (RAS) is traditionally known for its role in blood pressure regulation. However, there is increasing evidence that RAS signaling is also involved in the inflammatory response associated with several disease states. Angiotensin II increases blood pressure by binding to angiotensin type 1 (AT₁) receptor, and direct renin inhibitors, angiotensin-converting enzyme (ACE) inhibitors and AT₁ receptor blockers (ARBs) are clinically used as antihypertensive agents. Recent data suggest that these drugs also have anti-inflammatory effects. Therefore, this review summarizes these recent findings for the efficacy of two of the most widely used antihypertensive drug classes, ACE inhibitors and ARBs, to reduce or treat inflammatory diseases such as atherosclerosis, arthritis, steatohepatitis, colitis, pancreatitis, and nephritis.