Ang II-Induced Hypertension: Role of AT2 in End Organ Damage

高血压和心肌肥厚是心功能不全进展的主要危险因素 充血性心力衰竭(CHF)的发展。激活肾素-血管紧张素系统，从而导致 血管紧张素Ⅱ(Ang II)的释放在这些病理过程中起着重要作用。两种主要类型的 血管紧张素Ⅱ受体ATI和AT2已被鉴定。已知血管紧张素II对心脏的有害影响是 由于血管紧张素II 1型受体拮抗剂(ATR)抑制ATI，由AT-I激活介导 Ant)改善心功能，逆转左心室重构，延长心力衰竭患者的生存时间。 我们和其他人已经证明，Atrant的作用部分是通过激活AT2来介导的。它有 也有研究表明，激活AT2刺激激动素的释放；然而，涉及的确切机制(S)是 不太为人所知。我们也不知道AT2的心脏保护作用是否部分是由于一种直接的相互作用 用激动素B！和/或B2受体。因此，我们建议测试慢性激活的一般假设 AT2通过增加激肽原酶活性，包括组织和血浆激肽释放酶来引起激肽释放。在……里面 除了激动素的释放外，AT2的激活还通过降低激肽释放酶-激动素系统(KKS)的活性来增强激肽释放酶-激动素系统 血管紧张素转换酶(ACE)和/或与B2或B1激动素受体形成异二聚体， 导致NO/cGMP的释放和心血管保护作用。我们建议结合使用 生理、分子和药理学方法和几种生物工程小鼠品系来测试这一点 假设。在目标I中，我们将检验AT2诱导的激动素增加是由于a)增加的假设 组织激肽释放酶(TK)的表达；b)通过激活组织前激肽释放酶来增加激肽原酶的活性 激肽释放酶；以及c)血浆前激肽释放酶通过已知的血管内皮细胞的Pro羧基肽酶(PRCP)激活。 膜结合型血浆前激肽释放酶激活剂。在AIM II中，我们将检验这样一个假设，即心血管疾病 AT^ANT的保护作用部分是通过AT_2诱导血管紧张素转换酶活性降低而实现的 和/或由于异二聚化而与B2直接相互作用。在Aim III中，我们将检验假设 AT2和/或B的表达增加，保护心脏免受血管紧张性高血压和心脏疾病的影响 Mi后重塑，并有助于Atrant的治疗效果。在目标4中，我们将检验这一假设 AT2在血管系统中的过度表达是通过释放激动素和NO来保护的，而高水平的AT2 CMS中的过度表达(超过AT！表达)是有害的，因为1)直接作用于 自分泌方式的CMS，有助于CM肥大；以及2)AT2与或启动AT2 与AT^激活类似的信令事件。我们相信这些研究将会加深我们对 血管紧张素转换酶2的生理和病理生理作用及其与激肽释放酶-激动素系统和铅的相互作用 保护心脏，以及促进制定更好的高血压治疗策略和 缺血性心脏病。 缩写：Ang II=血管紧张素II；AT，AT2=血管紧张素1型和2型受体；ACE= 血管紧张素转换酶；ANT=拮抗剂；BK=缓激肽；B2=激动素受体；BNP=脑 利钠肽；CHF=充血性心力衰竭；cGMP=鸟苷3‘，5’环一磷酸；CMS= 心肌细胞；COX-2=环氧合酶-2；ECs=内皮细胞；EOD=终末器官损伤；ERK= 细胞外信号调节激酶；hmwk=高分子量激肽原；KKS=激肽释放酶-激肽系统； LMWK=低分子激肽原；LV=左心室；MAPK=丝裂原活化蛋白激酶；ML= 心肌梗死；NO=一氧化氮；NOS=一氧化氮合酶；PGE2=前列腺素E2；PK=血浆 激肽释放酶；PKC=蛋白激酶C；PLA2=磷脂酶A2；PTP=蛋白酪氨酸磷酸酶；PP2A= 蛋白磷酸酶-2A；PRCP=脯氨酸羧肽酶；RAS=肾素-血管紧张素系统；TG=转基因； Tk=组织激肽释放酶；-/-=基因敲除。 PHS 398/2590(09/04版，2006年4月重新发布)Page197延续格式页面 首席调查员/项目主任(最后、第一、中间)：杨晓平，医学博士/Carretero，Oscar A.，医学博士 一个。

Hypertension and cardiac hypertrophy are major risk factors for progression of cardiac dysfunction and development of congestive heart failure (CHF). Activation of the renin-angiotensin system, which leads to release of angiotensin II (Ang II), plays an important role in these pathological processes. Two major types of Ang II receptors, ATi and AT2, have been identified. The detrimental cardiac effects of Ang II are known to be mediated by activation of AT-i, since suppression of ATi with angiotensin II type 1 receptor antagonists (ATr ant) improves cardiac function, regresses left ventricular remodeling and prolongs survival in patients with HF. We and others have demonstrated that the effects of ATrant are mediated in part by activation of AT2. It has also been shown that activation of AT2 stimulates kinin release; however, the exact mechanism(s) involved is not well known. Nor do we know whether the cardioprotective effect of AT2 is due in part to a direct interaction with kinin B! and/or B2 receptors. Thus we propose to test the general hypothesis that chronic activation of AT2 causes kinin release by increasing kininogenase activity, includingtissue andplasma kallikrein. In addition to kinin release, activation ofAT2 potentiates the kallikrein-kinin system (KKS)by decreasing angiotensin-converting enzyme (ACE) and/or forming heterodimers with the B2 or B1 kinin receptors, leading to release of NO/cGMP and cardiovascular protection. We propose to use a combination of physiological, molecular, and pharmacological approaches and several lines of bioengineered mice to test this hypothesis. In Aim I, we will test the hypothesis that the AT2-induced increase in kinins is due to a) increased tissue kallikrein (TK)expression; b) increased kininogenase activity by activation of tissue prekallikrein to kallikrein; and c) activation of plasma prekallikrein via prolylcarboxypeptidase (PRCP), a known endothelial membrane-bound plasma prekallikrein activator. In Aim II, we will test the hypothesis that the cardiovascular protective effect of AT^ant is mediated in part by AT2-induced potentiation of kinins due to decreased ACE and/or a direct interaction with B2 due to heterodimerization. In Aim III, we will test the hypothesis that increased expression of AT2 and/or B, protects the heart from Ang ll-induced hypertension and cardiac remodeling post-Mi and contributes to the therapeutic effect of ATrant. In Aim IV, we will test the hypothesis that overexpression of AT2 in the vasculature is protective via release of kinins and NO, whereas high-level overexpression in CMs (exceeding AT! expression) is detrimental due to 1) increased kinins that act directly on CMs in an autocrine fashion, contributing to CM hypertrophy; and 2) AT2 interaction with or initiation of signaling events similar to AT^ activation. We believe these studies will enhance our understanding of the physiological and pathophysiological role of AT2 and how it interacts with the kallikrein-kinin system and leads to cardioprotection, as well as facilitate the development of better therapeutic strategies for hypertension and ischemic heart disease. Abbreviations: Ang II = angiotensin II; AT, and AT2 = angiotensin type 1 and type 2 receptors; ACE = angiotensin-converting enzyme; ant = antagonist; BK = bradykinin; B2 = B2 kinin receptors; BNP = brain natriuretic peptide; CHF = congestive heart failure; cGMP = guanosine 3',5'cyclic monophosphate; CMs = cardiomyocytes; COX-2 = cyclooxygenase-2; ECs = endothelial cells; EOD = end organ damage; ERK = extracellular signal-regulated kinase; HMWK = high-molecular weight kininogen; KKS = kallikrein-kinin system; LMWK = low-molecular-weight kininogen; LV = left ventricle; MAPK = mitogen-activated protein kinase; Ml = myocardial infarction; NO = nitric oxide; NOS = nitric oxide synthase; PGE2 = prostaglandin E2; PK = plasma kallikrein; PKC = protein kinase C; PLA2 = phospholipase A2; PTP = protein tyrosine phosphatase; PP2A = protein phosphatase-2A; PRCP = prolylcarboxypeptidase; RAS = renin-angiotensin system;Tg = transgenic; TK = tissue kallikrein; -/- = gene knockout. PHS 398/2590 (Rev.09/04, Reissued4/2006) Page197 Continuation Format Page Principal Investigator/Program Director (Last, First, Middle): Yang, Xiao-Ping, M.D./CarreterO,Oscar A., M.D. A.