血管紧张素—（1—7）在内皮素诱导血管平滑肌细胞增殖反应中的作用

目的：探讨血管紧张素－（1－7）[Ang-(1-7)]在内皮素－1（-1)诱导血管平滑肌细胞增殖反应中的作用。方法：在ET－1诱导培养的SD大鼠主动脉血管平滑肌细胞模型中,应用Ang-(1-7)通过,测定^3H-胸腺嘧啶（^3H-TdR)掺入的方法,观察血管平滑肌细胞增殖情况。结果Ang-(1-7)呈剂量性抑制ET－1诱导血管平滑肌细胞的DNA民,其作用受体不是血管紧张素Ⅱ受体1（AT1）或血管紧张素Ⅱ受体2（AT2）,而是通过一种特殊受体介导。结论：Ang-(1-7)能抑制T－1诱导的血管平滑肌增殖。     

血管紧张素（1～7）舒血管机制的研究

目的　探讨血管紧张素(1～7)［Ang(1～7)］对血管功能的作用及机制。方法　应用生理多导仪测定存在和去除内皮后,血管对血管紧张素的反应;用钙敏感指示剂Fura-2/AM检测血管平滑肌细胞（VSMC）内游离钙离子浓度（［Ca2+］i）;RT-PCR检测VSMC血管紧张素受体（ATR）mRNA表达。结果　Ang(1～7)明显抑制AngⅡ对动脉环的收缩作用,在内皮完整的动脉环比去除内皮的动脉环作用更明显;Ang(1～7)同样明显抑制AngⅡ诱导的VSMC［Ca2+］i上升幅度;AngⅡ能下调AT1RmRNA,而Ang(1～7)上调AT1RmRNA,AngⅡ和Ang(1～7)对AT2RmRNA影响不明显。结论　Ang(1～7)通过作用于血管内皮及VSMC内钙信号发挥抑制血管平滑肌收缩的作用。     

血管紧张素（1—7）舒血管机制的研究

目的 探讨血管紧张素（1－7）[Ang(1-7)]对血管功能的作用及机制。方法 应用生理多导仪测定存在和去除内皮后,血管对血管紧张素的反应;用钙敏感指示剂Fura-2/AM检测血管平滑肌细胞（VSMC）内游离钙离子浓度（[Ca^2 ]i);RT－PCR检测VSMC血管紧张素受体（ATR）mRNA表达。结果 Ang(1-7)明显抑制AngⅡ对动脉环的收缩作用,在内皮完整的动脉环比去除内皮的动脉环作用更明显;Ang(1-7)同样明显抑制AngⅡ诱导的VSMC[Ca^2 ]i上升幅度;AngⅡ能下调AT1RmRNA,而Ang(1-7)上调AT1RmRNA,AngⅡ和Ang(1-7)对AT2RmRNA影响不明显。结论 Ang(1-7)通过作用于血管内皮及VSMC内钙信号发挥抑制血管平滑肌收缩的作用。     

血管紧张素Ⅰ抑制血管紧张素Ⅱ诱导的血管平滑肌细胞增殖

目的探讨血管紧张素-(1-7)[Ang-(1-7)]对血管紧张素Ⅱ(AngⅡ)诱导的大鼠血管平滑肌细胞(VSMCs)增殖的影响。方法采用组织贴块法培养VSMCs,取生长良好的第3～5代细胞用于实验。随机分为对照组、AngⅡ组、Ang-(1-7)组、AngⅡ Ang-(1-7)组、AngⅡ Ang-(1-7) (A-779)组,通过3H胸腺嘧啶(3H-TdR)掺入法测定VSMCs的DNA合成,用结晶染色的方法检测细胞数目,观察VSMCs的增殖情况。结果①与对照组比,AngⅡ(100nmol/L)孵育细胞24h后可明显诱导VSMCs3H-TdR掺入量增加;Ang-(1-7)(1000nmol/L)可减少3H-TdR掺入量。②与AngⅡ组比较,Ang-(1-7)(10nmol/L、100nmol/L、1000nmol/L)呈浓度依赖性的抑制AngⅡ诱导的VSMCs3H-TdR掺入量。加入Ang-(1-7)特异性受体阻断剂A-779后,Ang-(1-7)此作用消失。③结晶染色结果显示,AngⅡ可诱导VSMCs数目明显增加(P<0.05)。Ang-(1-7)可抑制AngⅡ诱导的VSMCs增加,亦呈浓度依赖性(P<0.05)。结论Ang-(1-7)能抑制基础和AngⅡ诱导的VSMCs增殖,通过其特异性受体发挥作用。     

血管紧张素Ⅱ对血管平滑肌细胞血管紧张素Ⅱ受体1、2mRNA表达的影响

目的:观察血管紧张素Ⅱ(angiotensinⅡ,AngⅡ)对血管平滑肌细胞(VSMC)血管紧张素Ⅱ受体1(AT1R)、血管紧张素Ⅱ受体2(AT2R)mRNA表达的影响。方法:人脐带动脉平滑肌细胞体外原代培养,AngⅡ干预后RT-PCR测定VSMC的AT1R、AT2R mRNA的表达,并观察AT1R阻滞剂氯沙坦、AT2R阻滞剂PD123319对AngⅡ上述诱导作用的影响。结果:1AngⅡ作用于VSMC后,AT1R mRNA表达增强(P0.01),氯沙坦阻断AT1R后,AT1R mRNA表达显著下降(P0.01),PD123319阻断AT2R后,AT1R mRNA表达无显著性变化;2AngⅡ作用于VSMC后,AT2R mRNA表达无显著性增强,氯沙坦及PD123319作用后,AT2R mRNA表达也未见显著性变化。结论:1AngⅡ可诱导VSMC AT1R mRNA表达,AT1R在此过程中起重要介导作用,AT1R阻滞剂氯沙坦可有效抑制AngⅡ的这种诱导作用;2相对于AT1R,AngⅡ不能诱导VSMC AT2R mRNA表达增加。所以推测AngⅡ差异化诱导VSMC AT1R、AT2R mRNA表达,导致AT1R、AT2R失衡。     

神经酰胺在血管紧张素Ⅱ诱导的内皮细胞凋亡中的作用

目的探讨神经酰胺(CE)是否介导血管紧张素Ⅱ(AngⅡ)诱导的内皮细胞(EC)凋亡。方法体外培养脐静脉EC,分别用血管紧张素Ⅱ1型受体(AT1R)拮抗剂氯沙坦、血管紧张素Ⅱ2型受体(AT2R)拮抗剂PD123319、CE合成酶抑制剂烟曲霉素B1(FB1)预处理细胞,再加入AngⅡ24h后与对照组比较观察细胞凋亡情况;用高效液相色谱(HPLC)检测上述各处理组细胞内CE浓度的变化。结果PD123319和FB1明显减少AngⅡ诱导的EC凋亡(P<0.05),氯沙坦反而增加AngⅡ诱导的EC凋亡(P<0.05);HPLC显示PD123319组和FB1组抑制了CE的合成。结论AngⅡ通过AT2诱导EC凋亡,AT2可以促发CE含量增加。     

神经酰胺在血管紧张素Ⅱ诱导的内皮细胞凋亡中的作用

目的 探讨神经酰胺(CE)是否介导血管紧张素Ⅱ(Ang Ⅱ)诱导的内皮细胞(EC)凋亡.方法 体外培养脐静脉EC,分别用血管紧张素Ⅱ 1型受体(AT1R)拮抗剂氯沙坦、血管紧张素Ⅱ2型受体(AT2R)拮抗剂PD123319、CE合成酶抑制剂烟曲霉素B1(FB1)预处理细胞,再加入Ang Ⅱ24 h后与对照组比较观察细胞凋亡情况;用高效液相色谱(HPLC)检测上述各处理组细胞内CE浓度的变化.结果 PD123319和FB1明显减少Ang Ⅱ诱导的EC凋亡(P＜0.05),氯沙坦反而增加Ang Ⅱ诱导的EC凋亡(P＜0.05);HPLC显示PD123319组和FB1组抑制了CE的合成.结论 Ang Ⅱ通过AT2诱导EC凋亡,AT2可以促发CE含量增加.     

肾上腺髓质素抑制血管紧张素Ⅱ刺激血管平滑肌细胞增生作用

目的　观察肾上腺髓质素 (adrenomedullinADM)对血管紧张素Ⅱ (AngⅡ )刺激血管平滑肌细胞增生作用的影响。方法　测定ADM、AngⅡ对细胞3H leu掺入及 (MAPK)和 (PKC)活性的作用。结果　AngⅡ促进细胞3H leu掺入及MAPK和PKC活性增加 ;ADM对细胞3H leu掺入及MAPK、PKC活性均无明显影响 ,但呈浓度依赖方式抑制AngⅡ促细胞3H leu掺入及MAPK活性增加。结论　ADM通过抑制AngⅡ对MAPK的激活 ,拮抗其促血管平滑肌细胞增生作用。     

血管紧张素Ⅱ2型受体与血管再狭窄

血管紧张素Ⅱ(AngⅡ)是血管紧张素系统的重要效应分子,对于心血管系统的血流动力学和结构的调节至关重要,它通过促进平滑肌细胞增殖、迁移及胞外基质的合成而参与高血压、动脉粥样硬化(AS)和血管再狭窄的病理过程。人体内主要存在两种AngⅡ受体———1型受体(AT1R)和2型受体(AT2R),两者在生理学、药理学和生物学等方面均不相同。已知AngⅡ大部分心血管作用由AT1R介导,而对于AT2R在血管再狭窄中的作用目前尚不明确,本文就此方面的研究成果作一综述。1AT2R的组织分布AT2R在胚胎组织中含量丰富,但在成年组织仅分布于肾上腺、心脏、脑…     

肾素-血管紧张素系统阻滞剂抗纤维化的研究进展

肾素-血管紧张素系统（RAS）在体内有多种生物学活性,包括在血管系统收缩血管、增加血容量和升高血压,在组织器官也有相应的活性。RAS 在心血管系统平衡和心血管疾病的发展中作用重大［1］。肾素转变为血管紧张素原（AGT）再转变为血管紧张素Ⅰ（AngⅠ）,然后在血管紧张素转换酶（ACE）的作用下转变为血管紧张素Ⅱ（AngⅡ）,促进血管收缩和醛固酮的释放。AngⅡ是整个 RAS 的核心,是整个 RAS 系统最主要的生物活性分子［1］。迄今为止,已经发现了4种血管紧张素的受体,即 AT1、AT2、AT3、AT4,AT1进一步分为 AT1a 和 AT1b,ATⅡ可以和 AT1和 AT2结合［2］。AT1介导了 AngⅡ的大部分作用,如收缩血管、升高血压、促进细胞增殖和炎症反应等,而对AT2我们则知之甚少。我们常见的血管紧张素受体拮抗剂（ARB）类药物,均是选择性 AT1阻滞剂。     

Angiotensin-(1-7) downregulates the angiotensin II type 1 receptor in vascular smooth muscle cells

Angiotensin (Ang)-(1-7) is a biologically active peptide of the renin-angiotensin system that has both vasodilatory and antiproliferative activities that are opposite the constrictive and proliferative effects of angiotensin II (Ang II). We studied the actions of Ang-(1-7) on the Ang II type 1 (AT(1)) receptor in cultured rat aortic vascular smooth muscle cells to determine whether the effects of Ang-(1-7) are due to its regulation of the AT(1) receptor. Ang-(1-7) competed poorly for [(125)I]Ang II binding to the AT(1) receptor on vascular smooth muscle cells, with an IC(50) of 2.0 micromol/L compared with 1.9 nmol/L for Ang II. The pretreatment of vascular smooth muscle cells with Ang-(1-7) followed by treatment with acidic glycine to remove surface-bound peptide resulted in a significant decrease in [(125)I]Ang II binding; however, reduced Ang II binding was observed only at micromolar concentrations of Ang-(1-7). Scatchard analysis of vascular smooth muscle cells pretreated with 1 micromol/L Ang-(1-7) showed that the reduction in Ang II binding resulted from a loss of the total number of binding sites [B(max) 437.7+/-261.5 fmol/mg protein in Ang-(1-7)-pretreated cells compared with 607.5+/-301.2 fmol/mg protein in untreated cells, n=5, P<0.05] with no significant effect on the affinity of Ang II for the AT(1) receptor. Pretreatment with the AT(1) receptor antagonist L-158,809 blocked the reduction in [(125)I]Ang II binding by Ang-(1-7) or Ang II. Pretreatment of vascular smooth muscle cells with increasing concentrations of Ang-(1-7) reduced Ang II-stimulated phospholipase C activity; however, the decrease was significant (81.2+/-6.4%, P<0.01, n=5) only at 1 micromol/L Ang-(1-7). These results demonstrate that pharmacological concentrations of Ang-(1-7) in the micromolar range cause a modest downregulation of the AT(1) receptor on vascular cells and a reduction in Ang II-stimulated phospholipase C activity. Because the antiproliferative and vasodilatory effects of Ang-(1-7) are observed at nanomolar concentrations of the heptapeptide, these responses to Ang-(1-7) cannot be explained by competition of Ang-(1-7) at the AT(1) receptor or Ang-(1-7)-mediated downregulation of the vascular AT(1) receptor.     

Angiotensin II induces endothelin-1 gene expression via extracellular signal-regulated kinase pathway in rat aortic smooth muscle cells

OBJECTIVE: Angiotensin II (Ang II) increases vascular endothelin-1 (ET-1) tissue levels, which in turn mediate a major part of Ang II-stimulated vascular growth and hypertension in vivo. Ang II also stimulates reactive oxygen species (ROS) generation in vascular smooth muscle cells (SMCs). However, whether ROS are involved in Ang II-induced ET-1 gene expression and the related intracellular mechanisms in vascular SMCs remains to be determined. METHODS: Cultured rat aortic SMCs were stimulated with Ang II, [3H]thymidine incorporation and the ET-1 gene expression was examined. Antioxidants pretreatment on Ang II-induced extracellular signal-regulated kinase (ERK) phosphorylation were performed to elucidate the redox-sensitive pathway in proliferation and ET-1 gene expression. RESULTS: Ang II-increased DNA synthesis was inhibited by AT(1) receptor antagonist (olmesartan) and ET(A) receptor antagonist (BQ485). ET-1 gene was induced with Ang II as revealed by Northern blotting and promoter activity assay. Ang II-increased intracellular ROS levels were inhibited by olmesartan and antioxidants. Antioxidants suppressed Ang II-induced ET-1 gene expression and ERK phosphorylation. An ERK inhibitor U0126 fully inhibited Ang II-induced ET-1 expression. Co-transfection of dominant negative mutant of Ras, Raf and MEK1 attenuated the Ang II-increased ET-1 promoter activity, suggesting that the Ras-Raf-ERK pathway is required for Ang II-induced ET-1 gene. Truncation and mutational analysis of the ET-1 gene promoter showed that activator protein-1 (AP-1) binding site was an important cis-element in Ang II-induced ET-1 gene expression. Moreover, Ang II- or H(2)O(2)-induced AP-1 reporter activities were also inhibited by antioxidants. CONCLUSIONS: Our data suggest that ROS are involved in Ang II-induced proliferation and the redox-sensitive ERK pathway plays a role in ET-1 gene expression in rat aortic SMCs.     

Role of angiotensin type-1 and angiotensin type-2 receptors in the expression of vascular integrins in angiotensin II-infused rats

Angiotensin II plays an important role in vascular remodeling through effects that involve, in part, interactions of vascular smooth muscle cells with extracellular matrix via integrins, which belong to a family of transmembrane receptors. We hypothesized that angiotensin (Ang) II regulates expression of vascular integrins and their ligands in experimental hypertension. Rats were infused subcutaneously with Ang II and received angiotensin type-1 (AT1) receptor blocker losartan, the AT1/angiotensin type-2 (AT2) [Sar1-Ile8]-Ang II, or the vasodilator hydralazine for 7 days. Osteopontin and integrin subunit expression were evaluated immunohistochemically. Ang II enhanced vascular alpha8, beta1, beta3 integrins and osteopontin expression, which were significantly reduced by losartan, [Sar1-Ile8]-Ang II, and hydralazine. Although Ang II increased vascular alpha5 subunit expression, this was additionally increased by losartan. Losartan was the only treatment that induced alpha1 subunit expression. These results demonstrate that AT1 and AT2 receptors have countervailing effects on vascular integrin subunit expression that may influence their effects on vascular remodeling and extracellular matrix composition.     

Angiopoietin-1 regulates endothelial cell survival through the phosphatidylinositol 3'-Kinase/Akt signal transduction pathway

Angiopoietin-1 (Ang1) is a strong apoptosis survival factor for endothelial cells. In this study, the receptor/second messenger signal transduction pathway for the antiapoptotic effect of Ang1 on human umbilical vein endothelial cells was examined. Pretreatment with soluble Tie2 receptor, but not Tie1 receptor, blocked the Ang1-induced antiapoptotic effect. Ang1 induced phosphorylation of Tie2 and the p85 subunit of phosphatidylinositol 3'-kinase (PI 3'-kinase) and increased PI 3'-kinase activity in a dose-dependent manner. The PI 3'-kinase-specific inhibitors wortmannin and LY294002 blocked the Ang1-induced antiapoptotic effect. Ang1 induced phosphorylation of the serine-threonine kinase Akt at Ser473 in a PI 3'-kinase-dependent manner. Expression of a dominant-negative form of Akt reversed the Ang1-induced antiapoptotic effect. Ang1 mRNA and protein were present in vascular smooth muscle cells but not in endothelial cells. Cultured vascular smooth muscle cells, but not human umbilical vein endothelial cells, secreted Ang1. These findings indicate that the Tie2 receptor, PI 3'-kinase, and Akt are crucial elements in the signal transduction pathway leading to endothelial cell survival induced by the paracrine activity of Ang1.     

Identification and characterization of functional angiotensin II type 1 receptors on immortalized human fetal aortic vascular smooth muscle cells

Studies investigating the mechanisms that govern the expression of the human angiotensin II type 1 receptor (hAT(1)R) gene have progressed slowly due to the lack of human cell lines that express the AT(1)R. Recently, however, an immortalized human fetal aortic vascular smooth muscle cell line (FLTR) was generated using an amphotropic recombinant retroviral construct containing the E6/E7 open reading frames of the human papillomavirus type 16. Radioligand binding studies were undertaken to determine whether angiotensin II (Ang II) receptors were expressed on these cells. FLTR cell membranes were shown to express high-affinity Ang II receptors having a B(max) value of 324+/-43 fmol/mg protein and a K(d) of 0.36+/-0.1 nM. In both membranes and intact cells, Ang II, Ang III and the selective AT(1)R antagonist, Losartan, all had a high affinity for the receptor, suggesting that FLTR cells express the AT(1)R subtype. The expression of the hAT(1)R was validated by Northern and Western blot and RT-PCR experiments. In intact FLTR cells, Ang II (100 nM) evoked an increase in intracellular calcium ([Ca(2+)](i)) and induced hyperplasia. Additionally, our results demonstrated that FLTR cells were readily transfected, and hAT(1)R promoter luciferase constructs exhibited robust promoter activity (i.e. approximately 22-fold increase over pGL3-Basic only). Finally, our results demonstrated that the hAT(1)R gene is differentially regulated in FLTR cells vs. H295-R cells, a human adrenocarcinoma cell line that also abundantly expresses the AT(1)R. Taken together, our results suggest that FLTR cells express functional AT(1)Rs and will provide an excellent model system in which to investigate hAT(1)R gene regulation.     

Angiotensin II-induced mitogenesis of spontaneously hypertensive rat-derived cultured smooth muscle cells is dependent on autocrine production of transforming growth factor-beta.

Angiotensin II (Ang II) has been implicated in the regulation of smooth muscle cell proliferation after vascular injury, but the molecular mechanisms of this effect remain obscure. The aims of the present study were 1) to determine if Ang II was mitogenic (in a defined serum-free medium) for aortic smooth muscle cells derived from spontaneously hypertensive rats, either alone or in combination with epidermal growth factor, basic fibroblast growth factor, or platelet-derived growth factor-BB; and 2) to determine if the Ang II effects were mediated by autocrine production of transforming growth factor-beta (TGF-beta). Results demonstrated that Ang II increased the proliferative response of smooth muscle cells to epidermal growth factor or platelet-derived growth factor-BB. Ang II alone and in combination with basic fibroblast growth factor induced a small delayed increase (48-72 hours after treatment) in DNA synthesis and [3H]thymidine labeling indexes without an increase in cell number. Ang II effects were at least partially mediated by autocrine production of active TGF-beta in that 1) treatment with Ang II increased TGF-beta activity in conditioned media and 2) TGF-beta neutralizing antibody inhibited Ang II-induced increases in DNA synthesis. However, treatment with exogenous TGF-beta at concentrations induced by Ang II failed to elicit a mitogenic response, thus implicating other autocrine factors in mediation of Ang II effects. Results suggest a potential mechanism whereby Ang II might regulate smooth muscle cell mitogenesis after vascular injury.     

Angiotensin II activates intermediate-conductance Ca2+ -activated K+ channels in arterial smooth muscle cells

Angiostensin II (Ang II) regulates the migration and proliferation of vascular smooth muscle cells. Recent studies indicate that intermediate-conductance Ca2+ -activated K+ (IKca) channels have an important role in cell migration and proliferation. It is not known, however, whether the action of Ang II is linked to IKca channel regulation. Here, we investigated the modulation of IKca channels by Ang II in artery smooth muscle cells. Functional IKca channel expression in cultured embryonic rat aorta smooth muscle (A10) cells was studied using the patch-clamp technique. These cells predominantly express IKca channels. In contrast, large-conductance Ca2+ -activated K+ (BKca) currents were rarely observed in excised patches. Ang II increased the IKca current in a contration-dependent manner. Losartan (1.0 microM), an AT1 selective antagonist, abolished the activation of IKca channels by Ang II. Pretreatment with 100 microM myristoylated protein kinase C inhibitor peptide 20-28 or 10 microM GF109203X completely abolished the AngII-induced activation of IKca currents, whereas the action of Ang II was not prevented in the presence of 100 microM Rp-cyclic 3', 5'-hydrogen phosphotiate adenosine triethylammonium, a protein kinase A inhibitor, or 1.0 microM KT-5823, a protein kinase G inhibitor. A membrane permeant analogue of diacylglycerol 1, 2-dioctanoyl-sn-glycerol (10 microM) induced the activation of IKca currents. These data suggest that Ang II activates IKca channels through the activation of protein kinase C, and the AT1 receptor is involved in the regulation of these channels.     

Angiotensin II increases proto-oncogene expression and phosphoinositide turnover in vascular smooth muscle cells via the angiotensin II AT1 receptor.

OBJECTIVES: The aim of this study was to determine which angiotensin II receptor (AT receptor) mediates proto-oncogene expression and phosphoinositide metabolism in vascular smooth muscle cells in vitro. DESIGN: The AT receptor antagonists DuP753 (losartan), an AT1 antagonist, and PD 123319, an AT2 antagonist, were used to characterize AT receptors on cultured vascular smooth muscle cells derived from the rat mesenteric artery and to identify which receptor subtype mediates the angiotensin II-induced increase in proto-oncogene expression and phosphoinositide metabolism. METHODS: Rat mesenteric artery vascular smooth muscle cells were grown using standard cell culture methods. Proto-oncogene induction was measured using Northern blotting. Phosphoinositide breakdown was assessed by measuring [3H]-inositol phosphates released from prelabelled cells. RESULTS: Receptor-binding studies revealed that the AT1 receptor predominated on vascular smooth muscle cells. Incubation of quiescent cells with 0.1 mumol/l angiotensin II resulted in a 65% increase in total [3H]-inositol phosphates released compared with unstimulated cells and in a rapid accumulation of c-fos messenger RNA (mRNA). Pre-incubation of the cells with 10(-5) mol/l PD 123319 had no effect on either total inositol phosphates release or c-fos mRNA induction. Both responses, however, were totally abolished by pre-incubation of the cells with 10(-5) mol/l losartan or saralasin. CONCLUSIONS: Angiotensin II acts through the AT1 receptor to increase c-fos expression and phosphoinositide turnover in vascular smooth muscle cells. These mechanisms may be important in angiotensin II-induced smooth muscle hypertrophy.