Ang-1、Ang-2及Tie-2在前列腺癌中的表达

很多细胞因子参与癌症的发生发展,其中参与血管新生的血管生成素(Ang)在肿瘤中的作用愈发明显.研究表明[1]在大多数癌组织中Ang-1,Ang-2及其受体Tie-2的表达激活,具有调控肿瘤新生血管形成及重建的作用.本文探讨前列腺癌组织中Ang-1、Ang-2及其受体Tie-2与前列腺癌血管生成的关系.     

菩人丹超微粉对糖尿病大鼠视网膜血管生成素-2表达的影响

目的探讨菩人丹超微粉(PRD)对糖尿病大鼠视网膜血管生成素-2(Ang-2)表达的影响。方法 36只Wistar大鼠随机分为3组,正常对照组、糖尿病模型组和PRD治疗组,每组12只。糖尿病模型组和PRD治疗组大鼠均采用链脲佐菌素(STZ)连续腹腔注射建立2型糖尿病大鼠模型,以血糖≥16.7 mmol/L为成模标准。模型成功建立后,模型组大鼠不再作任何处理;PRD治疗组大鼠给予PRD灌胃(1.8 g·kg-1·d-1)3个月。采用免疫组织化学染色法、Western印迹法和逆转录聚合酶链反应(RT-PCR)分别检测视网膜Ang-2蛋白及mRNA的表达。结果糖尿病模型大鼠视网膜Ang-2蛋白及mRNA表达均明显高于正常对照组(P<0.01)。PRD治疗组大鼠视网膜Ang-2蛋白及mRNA表达均明显低于糖尿病模型组(P<0.01)。结论 PRD可通过下调糖尿病大鼠视网膜Ang-2的表达,发挥对糖尿病视网膜损伤的保护作用。     

玻璃体血管生成素2浓度与糖尿病玻璃体出血的相关性

目的探讨血管生成素2（Ang-2）与糖尿病玻璃体出血的相关性。方法用ELISA法分别检测糖尿病玻璃体出血患者31例和非糖尿病视网膜脱离患者25例玻璃体和血浆Ang-2浓度。统计分析玻璃体Ang-2浓度、血浆Ang-2浓度、血压、血脂、FPG及HbA1c等指标与糖尿病玻璃体出血的关系。结果糖尿病玻璃体出血患者玻璃体Ang-2浓度（中位数：3765ng/L）较非糖尿病视网膜脱离组（274ng/L）显著升高（P〈0.05）,糖尿病组玻璃体Ang-2浓度（3765ng/L）高于同组患者血浆Ang-2浓度（2716ng/L）。以行玻璃体切除术患者为整体,是否糖尿病玻璃体出血为因变量进行logistic回归分析,玻璃体Ang-2浓度和HbA1c水平进入回归方程。结论玻璃体Ang-2浓度升高是糖尿病玻璃体出血的重要独立危险因素之一。     

糖尿病鼠肾小管周围新生血管与促血管生长因子关系研究

目的探讨促血管生成素-2(Ang-2)和血管内皮生长因子(VEGF)在糖尿病肾脏血管新生中的作用及其意义。方法2004年3月至2005年3月在四川大学华西医院用SD大鼠建立链唑霉素(STZ)诱导的糖尿病肾病模型,定量分析肾脏VEGF和Ang-2的表达变化,用逆转录聚合酶链式反应技术(RT-PCR)检测肾脏VEGF、Ang-2的mRNA的表达。结果糖尿病组肾脏VEGFmRNA表达从2周开始持续上调,16～20周达高峰;免疫组化显示糖尿病组各时点肾小管的VEGF着染均强于对照组;糖尿病组仅于16周和20周时探及肾组织Ang-2mRNA表达,12～24周免疫组化显示皮质区管周Ang-2着染管周微血管,整个实验期间对照组未探及Ang-2mRNA和蛋白表达;VEGF与Ang-2的改变呈正相关。结论糖尿病肾脏中后期皮质区存在Ang-2着染的新生管周微血管,VEGF与Ang-2参与糖尿病肾脏新生血管生成。     

血管紧张素转换酶2、氧化应激与血压调控研究进展

高血压病是一类环境、遗传因素共同作用的复杂的多基因疾病,其发病机制至今尚未被完全阐明。肾素血管紧张素系统(renin-angiotensin system,RAS)在调节水盐代谢、维持血容量与血管张力、氧化应激水平以及调控心、肾脏功能等方面起着极其重要的作用,是机体内调控血压稳定的最重要机制之一,其活性异常参与高血压病的发病过程。新近发现的血管紧张素转换酶2(angiotensin convertingenzyme 2,ACE2)是人类ACE的第一个同源酶。ACE2不仅能直接高效降解ACE的作用产物血管紧张素Ⅱ(angiotensinⅡ,AngⅡ)而生成Ang-(1-7),还能竞争性地作用于ACE的底物AngⅠ,使之产生Ang-(1-9),后者经ACE或中性肽链内切酶作用进一步水解为舒血管物质肽Ang-(1-7)。AngⅡ是心血管系统中氧自由基生成和氧化应激的重要激活物,NADPH氧化酶是其中的重要参与者。在ACE2基因敲除的小鼠中NADPH氧化酶的活性明显增加,加重AngⅡ介导的心血管组织氧化损伤。ACE2基因能促进Ang-(1-7)的生成,后者可直接对抗AngⅡ引发的血管收缩、管壁增厚、血管外周阻力增加和氧化应激等作用。另外,Ang-(1-7)是一种内源性ACE抑制剂,还可增强缓激肽的降压效应,增加一氧化氮和前列环素等扩血管物质的释放,通过Mas受体实现其扩张血管、降低血压水平及减轻氧化损伤等作用。ACE2活性或表达异常通过促使氧化应激增加可能导致高血压。新的RAS系统参与氧化应激及血压调控主要依赖于两条路径:ACE-AngⅡ-AT1轴与ACE2-Ang-(1-7)-Mas轴,而ACE和ACE2基因是其中的关键作用子。由于ACE2、Ang-(1-7等)新成员的加入,RAS体系较以往变得更富挑战性,同时为高血压的防治带来新的契机。通过改善ACE2表达和/或活性,可降低机体内氧化应激水平,导致血压下调,从而在高血压中发挥心血管保护功效。ACE2基因、氧化应激和高血压三者之间关系密不可分,通过调节ACE     

糖尿病肾病患者血清血管内皮生长因子和血管生成素-2的测定及临床意义

目的探讨糖尿病肾病患者血清血管内皮生长因子(VEGF)及血管生成素(Ang)-2的水平变化及其临床意义。方法选取糖尿病患者68例,其中糖尿病非肾病(DM1)26例,糖尿病肾病42例,按照尿微量白蛋白排泄率(UAER)将其分为微量蛋白尿组(DM2)24例及大量蛋白尿组(DM3)18例,对照组20例,分别测定患者VEGF、Ang-2及糖化皿红蛋白(HbA1c)水平。结果各DM组之间HbA1c水平无明显差异,各组患者之间血清VEGF及Ang-2水平有显著性差异,均高于对照组(P<0.05);DM2较DM1组及DM3较DM2组患者血清VEGF及Ang-2明显升高(P<0.05)。结论血清VEGF及Ang-2参与了糖尿病肾病的发生及发展,其水平与糖尿病肾病严重程度呈正相关,血清VEGF与Ang-2水平呈正相关。     

肾素-血管紧张素系统的回顾

肾素-血管紧张素系统(RAS)新成员的发现,改变了既往认为只有血管紧张素转化酶(ACE)催化生成的血管紧张素(Ang)Ⅱ才产生致病作用的观点,证明肾素与前肾素-肾素受体(RPR)的结合及AngⅣ与胰岛素调控氨基肽酶受体(IRAP)的结合同样也会产生致病作用。新发现的ACE2催化Ang-(1-7)和Ang-(1-9)的生成,Ang-(1-7)与Mas受体和Ang-(1-9)与AT2受体结合之后,可产生心血管保护作用,但RAS的致病作用仍然占优势。RAS新成员的发现,对认识RAS抑制剂的临床研究结果提供了新的理论依据。     

血管生成素在糖尿病微血管病变中表达及调节作用的研究进展

血管生成素(Ang)是一组分泌型生长因子,特异性作用于血管内皮细胞,可参与新生血管的形成与调控。在缺氧、高糖、炎症因子等异常因素刺激下,参与糖尿病微血管病变的发生、发展。Ang及其受体Tie-2与血管内皮生长因子(VEGF)共同参与生理和病理性血管的形成。该文对Ang在糖尿病微血管病变中表达及调节作用的研究进展进行综述。     

靶向血管生成素-2基因短发夹RNA真核表达载体的构建及内质网应激状态下对人脐静脉内皮细胞凋亡影响的观察

目的构建人血管生成素-2(Ang-2)短发夹RNA(shRNA)真核表达质粒,观察其在内质网应激(ERS)状态下对人脐静脉内皮细胞(HUVECs)增殖和凋亡的影响,探讨Ang-2基因在ERS状态下介导血管内皮细胞凋亡的作用和机制。方法采用DNA重组技术根据人Ang-2mRNA序列设计并合成2条shRNA寡核苷酸片段,构建表达质粒并通过脂质体介导转染HUVECs,对Ang-2基因进行RNA沉默,采用RT-PCR和Western blot分别检测Ang-2在ERS状态下mRNA及蛋白质的表达。结果经双酶切和测序鉴定证实,2个shRNA表达载体均构建成功。与空白对照、阴性对照组相比,Ang2-1-shRNA、Ang2-2-shRNA组HUVECs中Ang-2基因mRNA及蛋白表达水平均降低,其中,Ang2-1-shRNA干扰效果最强。Ang-2mRNA和蛋白的抑制率分别达79.29%、68.21%。沉默Ang-2基因可增加ERS状态下HUVECs细胞活力及抑制其凋亡。结论成功构建靶向Ang-2基因的shRNA真核表达载体,Ang-2基因沉默对ERS状态下HUVECs凋亡有抑制作用。Ang-2基因可抑制血管内皮细胞体外增殖,增强ERS状态下HUVECs凋亡。     

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。     

Mechanism of high glucose induced angiotensin II production in rat vascular smooth muscle cells

Angiotensin II (Ang II), a circulating hormone that can be synthesized locally in the vasculature, has been implicated in diabetes-associated vascular complications. This study was conducted to determine whether high glucose (HG) (approximately 23.1 mmol/L), a diabetic-like condition, stimulates Ang II generation and the underlying mechanism of its production in rat vascular smooth muscle cells. The contribution of various enzymes involved in Ang II generation was investigated by silencing their expression with small interfering RNA in cells exposed to normal glucose (approximately 4.1 mmol/L) and HG. Angiotensin I (Ang I) was generated from angiotensinogen by cathepsin D in the presence of normal glucose or HG. Although HG did not affect the rate of angiotensinogen conversion, it decreased expression of angiotensin-converting enzyme (ACE), downregulated ACE-dependent Ang II generation, and upregulated rat vascular chymase-dependent Ang II generation. The ACE inhibitor captopril reduced Ang II levels in the media by 90% in the presence of normal glucose and 19% in HG, whereas rat vascular chymase silencing reduced Ang II production in cells exposed to HG but not normal glucose. The glucose transporter inhibitor cytochalasin B, the aldose reductase inhibitor alrestatin, and the advanced glycation end product formation inhibitor aminoguanidine attenuated HG-induced Ang II generation. HG caused a transient increase in extracellular signal-regulated kinase (ERK)1/2 phosphorylation, and ERK1/2 inhibitors reduced Ang II accumulation by HG. These data suggest that polyol pathway metabolites and AGE can stimulate rat vascular chymase activity via ERK1/2 activation and increase Ang II production. In addition, decreased Ang II degradation, which, in part, could be attributable to a decrease in angiotensin-converting enzyme 2 expression observed in HG, contributes to increased accumulation of Ang II in vascular smooth muscle cells by HG.     

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(ET 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3 H 胸腺嘧啶 (3 H 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合成 ,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ET 1诱导的血管平滑肌细胞增殖。     

Angiopoietin-2 displays VEGF-dependent modulation of capillary structure and endothelial cell survival in vivo

Modulation of Tie2 receptor activity by its angiopoietin ligands is crucial for angiogenesis, blood vessel maturation, and vascular endothelium integrity. It has been proposed that angiopoietins 1 (Ang1) and 2 (Ang2) are pro- and anti-angiogenic owing to their respective agonist and antagonist signaling action through the Tie2 receptor. The function of Ang2 has remained controversial, however, with recent reports suggesting that in some circumstances, it may be pro-angiogenic. We have examined this issue using the transient ocular microvessel network called the pupillary membrane as a unique in vivo model for studying the effects of vascular regulators. We show that in vivo, in the presence of endogenous vascular endothelial growth factor (VEGF)-A, Ang2 promotes a rapid increase in capillary diameter, remodeling of the basal lamina, proliferation and migration of endothelial cells, and stimulates sprouting of new blood vessels. By contrast, Ang2 promotes endothelial cell death and vessel regression if the activity of endogenous VEGF is inhibited. These observations support a model for regulation of vascularity where VEGF can convert the consequence of Ang2 stimulation from anti- to pro-angiogenic.     

Angiopoietin/Tie2系统在血管新生与成熟过程中的表达及意义

血管的新生和成熟需要经过血管内皮细胞与血管周围细胞间相互作用等一系列复杂的生物学过程,这一过程受到多种细胞因子的调控。促血管生成素(angiopoietin,Ang)是近年发现的一个与血管新生与成熟密切相关的家族,包括4个成员,即Ang1、Ang2、Ang3和Ang4,其共同的特异性受体为Tie2。Ang及受体Tie2在生理性血管形成过程中对新生血管的形成、重构及成熟发挥重要的调控作用。另有研究显示,Ang/Tie2系统也参与了缺血后再灌、肿瘤及视网膜病变等多种病理性血管的形成过程。研究Ang/Tie2系统的生物学效应以及其在血管新生与成熟过程中的表达及意义,有助于深入了解相关疾病的发病机制并为疾病的治疗提供新线索。     

Long-term and sustained COMP-Ang1 induces long-lasting vascular enlargement and enhanced blood flow

Vascular enlargement is a characteristic feature of angiopoietin-1 (Ang1)-induced changes in adult blood vessels. However, it is unknown whether tissues having Ang1-mediated vascular enlargement have more blood flow or whether the enlargement is reversible. We have recently created a soluble, stable and potent Ang1 variant, COMP-Ang1. In the present study, we investigated the effects of varied dose and duration of COMP-Ang1 on vascular enlargement and blood flow in the tracheal microvasculature of adult mice and explored a possible mechanism of long-lasting vascular enlargement. We found that COMP-Ang1 administered by adenoviral vector induced long-lasting vascular enlargement and increased tracheal blood flow. In contrast, short-term administration of COMP-Ang1 recombinant protein induced transient vascular enlargement that spontaneously reversed within a month. In both cases, the vascular enlargement resulted from endothelial proliferation. The COMP-Ang1-induced vascular remodeling is mediated mainly through Tie2 activation. Sustained overexpression of Tie2 could participate in the maintenance of vascular changes. Together, our findings indicate that sustained treatment with COMP-Ang1 can produce long-lasting vascular enlargement and increased blood flow.     

Angiotensin II-stimulated collagen synthesis in aortic adventitial fibroblasts is mediated by connective tissue growth factor

Angiotensin II (Ang II), a potent mediator of vascular remodeling, can stimulate the synthesis of extracellular matrix in vascular cells. Recent studies indicate that connective tissue growth factor (CTGF) is involved in collagen synthesis. There is also increasing evidence that adventitial fibroblasts (AFs) are actively involved in vascular remodeling. However, whether collagen synthesis by AFs is mediated by CTGF, or whether it is relevant to Ang II, has not been studied. The present study was conducted to determine whether CTGF is expressed in AFs, and if so, whether the CTGF produced by AFs participates in collagen synthesis. The AFs were isolated from thoracic aorta of Wistar-Kyoto rats (WKY). The expression of CTGF was measured by Western blot or real-time PCR. Collagen synthesis was assessed by [(3)H]proline incorporation. Our results suggested that CTGF was expressed in AFs and secreted into medium. Ang II increased CTGF mRNA and protein expression in a time- and dose-dependent manner, with the maximal protein increase occurring at 24 h with an Ang II dose of 10(-7) mol/L, and this increase was inhibited by the Ang II receptor type 1 (AT(1)-R) antagonist losartan, but not by the Ang II receptor type 2 (AT(2)-R) antagonist PD123319. Ang II dose-dependently stimulated the incorporation of [(3)H]proline into cultured AFs, and this effect was inhibited by a CTGF antisense oligodeoxynucleotide. Overexpression of CTGF by pcDNA3.1(+)/CTGF increased [(3)H]proline incorporation in cultured AFs. The results demonstrated that, in cultured AFs, Ang II increased CTGF production via AT(1)-R, which could be mediators of collagen synthesis by Ang II. This finding suggests that CTGF might be a novel target for antifibrotic therapy in vascular diseases.     

Intrarenal angiotensin II and hypertension

Elevations in intrarenal angiotensin II (Ang II) cause reductions in renal function and sodium excretion that contribute to progressive hypertension and lead to renal and vascular injury. Augmentation of intrarenal Ang II occurs by several processes, leading to levels much greater than can be explained from the circulating levels. In Ang II-dependent hypertension, Ang II is internalized via an AT1 receptor mechanism, but there is also sustained intrarenal production of Ang II. Ang II exerts a positive feedback action on intrarenal angiotensinogen (AGT) mRNA and protein. The increased intrarenal AGT production is associated with increased intrarenal and intracellular Ang II contents and urinary AGT excretion rates. The increased urinary AGT indicates spillover of AGT into distal nephron segments supporting enhanced distal Ang II formation and sodium reabsorption. The augmentation of intrarenal Ang II provides the basis for sustained actions on renal function, sodium excretion, and maintenance of hypertension.     

Hepatocyte growth factor mediates angiopoietin-induced smooth muscle cell recruitment

Communication between endothelial cells (ECs) and mural cells is critical in vascular maturation. Genetic studies suggest that angiopoietin/Tie2 signaling may play a role in the recruitment of pericytes or smooth muscle cells (SMCs) during vascular maturation. However, the molecular mechanism is unclear. We used microarray technology to analyze genes regulated by angiopoietin-1 (Ang1), an agonist ligand for Tie2, in endothelial cells (ECs). We observed that hepatocyte growth factor (HGF), a mediator of mural cell motility, was up-regulated by Ang1 stimulation. We confirmed this finding by Northern blot and Western blot analyses in cultured vascular endothelial cells. Furthermore, stimulation of ECs with Ang1 increased SMC migration toward endothelial cells in a coculture assay. Addition of a neutralizing anti-HGF antibody inhibited Ang1-induced SMC recruitment, indicating that the induction of SMC migration by Ang1 was caused by the increase of HGF. Interestingly, Ang2, an antagonist ligand of Tie2, inhibited Ang1-induced HGF production and Ang1-induced SMC migration. Finally, we showed that deletion of Tie2 in transgenic mouse reduced HGF production. Collectively, our data reveal a novel mechanism of Ang/Tie2 signaling in regulating vascular maturation and suggest that a delicate balance between Ang1 and Ang2 is critical in this process.     

A local pre-receptor mechanism of hormone stimulus amplification: focus on angiotensin II in resistance blood vessels

BACKGROUND: The in-vivo correlation between vascular tone and the concentration of free angiotensin (Ang) II at the level of the arterioles, under (patho)physiological conditions, is not known. OBJECTIVE: To examine the in-vivo kinetics of binding of Ang II to Ang II type 1 (AT1) receptors in vascular tissue. METHODS AND RESULTS: A plane vascular smooth muscle (VSM) sheet containing a single layer of cells, at one side exposed to Ang II, was the starting point for designing a mathematical model based on local receptor density and geometric considerations and on kinetic parameters of Ang II diffusion and Ang II-AT1 receptor complex formation and internalization. Calculations demonstrate that a diffusing Ang II molecule at short distance from the receptor has an almost 100% chance to be actually bound, so that the apparent binding rate constant (per unit of receptor concentration) is greatly augmented. This pre-receptor stimulus amplification (PRESTAMP) mechanism is sustained by AT1 receptor-mediated endocytosis and receptor recycling. On the other hand, PRESTAMP also enhances endocytotic receptor downregulation, and calculations predict that steady-state levels of Ang II above threshold have relatively little additional effect. CONCLUSION: The results explain why physiological concentrations of free Ang II far below the equilibrium dissociation constant of its reaction with AT1 receptors are sufficient to increase vascular resistance, and why a correlation between blood pressure and the concentration of free Ang II is often difficult to demonstrate.