Apelin-APJ系统在心血管疾病研究进展

Apelin是最近发现的一种血管内皮源性肽,APJ是它的内源性配体。Apelin/APJ系统在体内系统广泛,它在心血管疾病的作用被日益重视,Apelin/APJ系统和心衰、高血压、急性冠脉综合征及心律失常等心血管疾病的相关性成为新近心血管研究的新方向和热点,现对Apelin/APJ系统在心血管疾病中研究作一阐述。     

Apelin/APJ系统的生物特性及其与疾病的关系

Apelin/APJ系统有抑制细胞凋亡和修复细胞功能等作用。近年来,越来越多的研究表明Apelin/APJ系统可能参与一些疾病起病和进展过程,检测Apelin水平对判断疾病预后具有一定的临床价值。同时,Apelin治疗后显示出的疗效使其成为药物研发的新靶点。     

Apelin-13生物功能研究进展

Apelin是由77个氨基酸构成的多肽,其受体为血管紧张素样G蛋白偶联受体(APJ)。Apelin/APJ系统在外周与中枢均有广泛分布;Apelin-13是Apelin亚型之一,具有较强的生物活性。本文综述了Apelin-13参与心血管系统、呼吸系统、神经系统、消化系统和内分泌系统等生理病理过程调节的研究新进展。     

Apelin/APJ系统在脂多糖诱导大鼠肺微血管内皮细胞损伤中的变化及其作用研究

目的探讨Apelin/APJ系统在脂多糖诱导大鼠肺微血管内皮细胞(PMVECs)损伤中的变化,并研究Apelin的作用及机制。方法采用植块法培养大鼠PMVECs,VIII因子相关抗原免疫细胞化学染色进行鉴定。噻唑蓝(MTT)比色法测定PMVECs活力;RT-PCR法检测Apelin、APJ m RNA表达的变化;Western blot法检测大鼠PMVECs中PCNA蛋白表达及Akt的磷酸化水平。结果 LPS在短时间内能够使Apelin、APJ m RNA表达水平呈代偿性上升(P<0.01),但随着作用时间延长,基因表达受到明显抑制,低于对照组(P<0.05或P<0.01),提示Apelin/APJ系统可能参与了LPS诱导的大鼠PMVECs损伤。MTT结果表明,10-9~10-6mol·L-1的Apelin明显促进了大鼠PMVECs增殖(P<0.05或P<0.01),且具有一定的浓度和时间依赖性。而且,Apelin还不同程度地改善了LPS诱导的PMVECs细胞损伤(P<0.05或P<0.01)。另外,Western blot结果显示,Apelin还明显逆转了LPS诱导的PCNA蛋白表达和Akt磷酸化水平的降低(P<0.05或P<0.01)。结论 Apelin/APJ系统参与了LPS诱导的大鼠PMVECs损伤。Apelin对于维护肺微血管内皮细胞功能,干预LPS诱导的PMVECs损伤起着重要作用,可能与其激活Akt磷酸化通路有关。     

Apelin抑制血管平滑肌细胞向成骨细胞分化

目的研究apelin对VSMCs向成骨细胞分化的作用以及作用机制。方法以体外培养的钙化型血管平滑肌细胞(CVMSCs)作为血管钙化的研究模型,通过检测碱性磷酸酶(ALP)活性以及骨钙素的分泌观察apelin与VSMCs向成骨细胞分化之间的关系,应用细胞外调节蛋白激酶(ERK)抑制剂、磷脂酰激醇3-激酶(PI3-K)抑制剂以及APJ的小干扰RNA(APJ siRNA)观察涉及的信号通路。结果Apelin抑制ALP活性、骨钙素分泌以及矿化结节的形成。CVSMCs表达APJ蛋白。Apelin激活ERK和蛋白激酶B(AKT,PI3-K的下游子)。应用siRNA沉默APJ取消了apelin对ERK和Akt活化的抑制作用。而且,抑制APJ表达、ERK或PI3-K的活化逆转了apelin对ALP活性的影响。结论 Apelin通过APJ/ERK和APJ/PI3-K/AKT信号途径抑制CVSMCs向成骨细胞分化。Apelin可能对动脉钙化有保护作用。     

侧脑室慢性灌流(pyr1)apelin-13对大鼠心血管功能的影响

<正>Apelin/APJ系统是新发现的调节心血管功能的信号分子系统[1-2]。我们近来发现,Apelin和APJ的mRNA和蛋白水平在自发性高血压大鼠的延髓头端腹外侧核较对照正常血压大鼠明显增加[3]。Apelin是否可以通过中枢通路调控心血管功能,以及是否具有长期效应,尚未见报道。本实验观察侧脑室慢性灌流(pyr1)apelin-13对大鼠动脉血压、心率、交感神经活性、血管升压素(arginine vasopressin,AVP)释放以及压力反射敏感性的影响,以明确apelin/APJ的心血管长期调控效应。     

利多卡因调控Apelin/APJ系统对脓毒症相关性脑病大鼠的脑保护作用

目的 探究利多卡因对脓毒症相关性脑病模型大鼠的脑保护作用及机制。方法 将40只大鼠按随机数字表法分为对照组、模型组、利多卡因组、利多卡因＋血管紧张素受体AT1相关的受体蛋白拮抗剂Apelin13（F13A）组,每组10只。除对照组外,其余3组大鼠均构建脓毒症相关性脑病模型,利多卡因组和利多卡因＋F13A组造模后即刻给予利多卡因10 mg/kg负荷剂量,随后尾iv利多卡因10 mg/kg并持续3 h,利多卡因＋F13A组同时ip APJ拮抗剂F13A 100 μg/kg。24 h后,Morris水迷宫实验检测各组大鼠认知功能,酶联免疫吸附（ELISA）法检测各组大鼠血清白细胞介素（IL）-6、IL-10、肿瘤坏死因子-α（TNF-α）水平,苏木精-伊红（HE）染色观察各组大鼠脑组织病理变化,TdT介导的dUTP缺口末端标记法（TUNEL）和神经元特异核蛋白（NeuN）双免疫荧光染色检测各组大鼠脑组织皮质内神经元凋亡,免疫荧光双染法观察各组大鼠脑组织皮质内Apelin与APJ表达,实时荧光定量逆转录聚合酶链反应（RT-qRCR）检测各组大鼠脑组织Apelin和APJ的mRNA表达,蛋白质免疫印迹（Western blotting）法检测各组大鼠脑组织Apelin和APJ的蛋白表达。结果 与模型组比较,利多卡因组大鼠逃避潜伏期缩短,通过目标象限次数增加（P＜0.05）,血清IL-6、TNF-α水平降低而IL-10水平显著升高（P＜0.05）,海马区神经元损伤明显减轻,形态和分布均趋于正常,脑组织皮质内凋亡神经元数目减少（P＜0.05）;Apelin与APJ荧光染色表达均明显增强,脑组织内Apelin、APJ的mRNA与蛋白相对表达量均显著上调（P＜0.05）;与利多卡因组比较,利多卡因＋F13A组大鼠逃避潜伏期延长,通过目标象限次数减少（P＜0.05）,血清IL-6、TNF-α水平升高,血清IL-10水平显著降低（P＜0.05）,海马区神经元损伤加重,有大量细胞肿胀与细胞核固缩,脑组织皮质内凋亡神经元数目增加（P＜0.05）。同时,Apelin与APJ荧光染色表达均明显减弱,脑组织内Apelin、APJ的mRNA与蛋白相对表达量均显著下调（P＜0.05）。结论 利多卡因能够改善脓毒症相关性脑病模型大鼠脑损伤,抑制炎症反应,并减少神经元凋亡,其机制可能与激活Apelin/APJ系统有关。     

药物新靶点脂肪细胞因子Apelin的研究概况

目的:了解药物新靶点脂肪细胞因子Apelin的相关研究进展。方法:根据文献,综述了Apelin的分子生物学特征、分布、生物学功能及其与各系统疾病的关系等方面的研究进展。结果与结论:Apelin位于X染色体的q25～26.1段,由77个氨基酸组成,在人体脂肪组织中广泛分布。其生物学功能包括心血管系统中内皮依赖性舒血管、降压的作用等,中枢神经系统中与精氨酸加压素的相互作用等,免疫系统中抵抗人类获得性免疫缺陷病毒感染的作用等,内分泌系统中抑制胰岛素释放与调节血液内环境稳定的作用等。Apelin与心血管系统疾病高血压、冠心病、心力衰竭等关系密切;Apelin及其受体APJ异常,可能涉及某些神经系统疾病的发病过程;Apelin与免疫缺陷疾病和获得性免疫缺陷综合征相关;Apelin与内分泌系统疾病肥胖、糖尿病关系密切。其有望成为心血管、免疫、中枢神经、内分泌等系统疾病潜在的药物治疗靶点。     

高盐上调压力超负荷大鼠的脑内APJ受体表达

目的观察高盐对压力超负荷大鼠的交感神经活性和脑内Apelin和APJ系统的影响。方法♂SD大鼠,在肾动脉分支上方部分结扎腹主动脉,建立主动脉缩窄大鼠模型。术后4周,分别给予含8%Na Cl的高盐饲料或含0.3%Na Cl的常规饲料,喂养1周后,记录各组大鼠的血流动力学变化;ELISA分析24 h尿去甲肾上腺素(NE)水平;real-time RCR和Western blot方法观察室旁核Apelin和APJ的表达变化。另一组实验中,在给予高盐饲料的同时使用Alzet微渗透泵侧脑室灌流ML221或benzamil,观察24 h尿NE水平和心脏指数(HW/BW)变化。此外,在正常SD大鼠侧脑室灌流高钠脑脊液1周后,观察大鼠血压、24 h尿NE和APJ表达水平的变化。结果压力超负荷大鼠给予高盐饮食1周后,平均动脉血压(MAP)、心率(HR)、左室收缩末期压(LVESP)和24 h尿NE水平,以及室旁核的APJ mRNA和蛋白表达均较对照明显增加(P<0.05);而假手术组大鼠在进食高盐饲料后,血流动力学、24 h尿NE水平和APJ表达均未见明显改变。在侧脑室分别灌注APJ受体拮抗剂ML221或ENa C拮抗剂benzamil后,可以明显抑制高盐引发的压力超负荷大鼠24h尿NE水平和HW/BW比值变化(P<0.01)。在正常血压大鼠侧脑室灌注高Na+脑脊液1周后,也可出现脑内APJ表达上调以及MAP、HR和尿NE水平升高(P<0.01)。结论高盐可以增加压力超负荷大鼠模型的交感神经活性,而该效应与脑内的APJ受体表达上调和Na+敏感性增加密切相关。APJ受体可能是脑内盐敏感性形成的重要调控靶点。     

Apelin-APJ系统研究进展

Apelins是由同一基因编码的具有不同分子结构的一组内源性活性肽,该类肽通过作用于7次跨膜的G蛋白偶联受体APJ而参与心血管功能、体液平衡、神经系统功能、胰岛素敏感性、摄食与饮水行为控制等多种生理与病理状态的调节,apelin-APJ系统有望成为心衰、高血压等心血管疾病以及肥胖相关疾病的治疗靶点。     

Modulation of the apelin/APJ system in heart failure and atherosclerosis in man

Background and purpose:

The aim of this study was to determine whether the apelin/APJ system is altered in human cardiovascular disease by investigating whether the expression of apelin or its receptor is altered at the protein level.

Experimental approach:

Radioligand binding studies were used to determine apelin receptor density in human cardiac tissues. Apelin peptide levels in cardiovascular tissues were determined by radioimmunoassay. In vitro pharmacology was used to assess vasoactive properties of apelin in human coronary artery. Localization of apelin and its receptor in coronary artery was determined using immunohistochemistry.

Key results:

Apelin receptor density was significantly decreased in left ventricle from patients with dilated cardiomyopathy or ischaemic heart disease compared with controls, but apelin peptide levels remained unchanged. Apelin was up-regulated in human atherosclerotic coronary artery and this additional peptide localized to the plaque, colocalizing with markers for macrophages and smooth muscle cells. Apelin potently constricted human coronary artery.

Conclusions and implications:

We have detected changes in the apelin/APJ system in human diseased cardiac and vascular tissue. The decrease in receptor density in heart failure may limit the positive inotropic actions of apelin, contributing to contractile dysfunction. The contribution of the increased apelin levels in atherosclerotic coronary artery to disease progression remains to be determined. These data suggest a potential role for the apelin/APJ system in human cardiovascular disease.     

Putative role for apelin in pressure/volume homeostasis and cardiovascular disease

Apelin is a peptide recently isolated from bovine stomach extracts which appears to act as an endogenous ligand for the previously orphaned G-protein-coupled APJ receptor. The apelin gene encodes for a pre-propeptide consisting of 77 amino acids with mature apelin likely to be derived from the C-terminal region as either a 36, 17 or 13 amino acid peptide. Apelin mRNA expression and peptide immunoreactivity has been described in a variety of tissues including gastrointestinal tract, adipose tissue, brain, kidney, liver, lung and at various sites within the cardiovascular system. Apelin is strongly expressed in the heart with expression also present in the large conduit vessels, coronary vessels and endothelial cells. Message expression for the APJ receptor is similarly distributed throughout the brain and periphery, again including cardiovascular tissue. Consistent with this pattern of distribution, apelin and APJ have been shown to exhibit some role in the regulation of fluid homeostasis. In addition, a growing number of studies have reported cardiovascular actions of apelin. Not only has apelin been observed to alter arterial pressure, but the peptide also exhibits endothelium-dependent vasodilator actions in vivo and positive inotropic actions in the isolated heart. Furthermore, differences in apelin and APJ expression have been described in patients with congestive heart failure and circulating levels of apelin are also reported to change in heart failure. Taken together, these studies suggest a role for apelin in pressure/volume homeostasis and in the pathophysiology of cardiovascular disease. As such, manipulation of this peptide system may offer benefit to the syndrome of heart failure with potential clinical applications in humans.     

Update on apelin peptides as putative targets for cardiovascular drug discovery

Introduction: The physiological importance of GPCR/ligand pathways is highlighted by the fact that numerous pathologies are attributed to their signaling dysfunction. Over 50% of the pharmaceutical drugs currently used to treat human disease are based on compounds that interact with GPCRs. Apelin/APJ constitutes a novel endogenous peptide/GPCR system proposed to be involved in a wide range of physiological functions. Early evidence suggests that apelin/APJ may hold promise as a target for development of novel therapeutic agents which may counteract a number of pathologies including cardiovascular disease. Despite advances in treatment of cardiovascular disease, incidence, prevalence, morbidity and economic costs remain high necessitating the development of new treatment paradigms. Areas covered: This review summarizes apelin/APJ structure, distribution and regulation; presents evidence for a role of apelin in pressure/volume homeostasis and in the pathophysiology of cardiovascular disease; summarizes data on beneficial effects of apelin in preclinical, animal models of cardiovascular disease and measurement of plasma levels of apelin across the full spectrum of cardiovascular disease in humans; and notes the first studies describing bioactivity of apelin peptides in human healthy volunteers and patients with heart failure. Expert opinion: More clarity is needed on the precise physiological/pathophysiological role of the apelin/APJ system in human health and disease. Nonetheless, preclinical studies and initial studies in humans show that APJ antagonism may represent a novel therapeutic target for patients with cardiovascular disease. Development of appropriately validated assays for apelin will clarify circulating levels of the peptide in health and disease. Development of suitable agonists/antagonists will pave the way for much needed future studies essential for advancing this promising field of drug discovery.     

Update on apelin peptides as putative targets for cardiovascular drug discovery

Introduction: The physiological importance of GPCR/ligand pathways is highlighted by the fact that numerous pathologies are attributed to their signaling dysfunction. Over 50% of the pharmaceutical drugs currently used to treat human disease are based on compounds that interact with GPCRs. Apelin/APJ constitutes a novel endogenous peptide/GPCR system proposed to be involved in a wide range of physiological functions. Early evidence suggests that apelin/APJ may hold promise as a target for development of novel therapeutic agents which may counteract a number of pathologies including cardiovascular disease. Despite advances in treatment of cardiovascular disease, incidence, prevalence, morbidity and economic costs remain high necessitating the development of new treatment paradigms.

Areas covered: This review summarizes apelin/APJ structure, distribution and regulation; presents evidence for a role of apelin in pressure/volume homeostasis and in the pathophysiology of cardiovascular disease; summarizes data on beneficial effects of apelin in preclinical, animal models of cardiovascular disease and measurement of plasma levels of apelin across the full spectrum of cardiovascular disease in humans; and notes the first studies describing bioactivity of apelin peptides in human healthy volunteers and patients with heart failure.

Expert opinion: More clarity is needed on the precise physiological/pathophysiological role of the apelin/APJ system in human health and disease. Nonetheless, preclinical studies and initial studies in humans show that APJ antagonism may represent a novel therapeutic target for patients with cardiovascular disease. Development of appropriately validated assays for apelin will clarify circulating levels of the peptide in health and disease. Development of suitable agonists/antagonists will pave the way for much needed future studies essential for advancing this promising field of drug discovery.     

Apelin in the control of body fluid homeostasis and cardiovascular functions

The discovery of apelin, an endogenous ligand of the orphan APJ receptor is an important advance for fundamental research and clinical medicine. Apelin and its receptor have a wide tissue distribution not only in the brain but also in peripheral organs including kidney, heart, vessels, and adipose tissue. Apelin is implicated in many physiological and pathophysiological processes such as the regulation of body fluid homeostasis, cardiovascular functions, glucose homeostasis, cell proliferation, and angiogenesis. This review focuses on, i) the various signaling cascades evoked upon stimulation of the apelin receptor by the different molecular forms of apelin found in vivo, ii) the distribution of apelin and its receptor in the brain and the cardiovascular system, iii) the opposing actions of vasopressin and apelin in the regulation of water balance at the central and kidney levels, and on the cardiovascular system regarding regulation of arterial blood pressure, vascular tone, and cardiac function.     

葛根素对低O_2高CO_2肺动脉高压大鼠肺组织中Apelin及其受体的影响

目的探讨葛根素对慢性低O2高CO2肺动脉高压大鼠肺组织中Apelin及其受体APJ的影响,为拓展其临床应用提供依据。方法清洁级SD♂大鼠30只,随机分成:正常对照组(N组)、低O2高CO24wk组(F组)和低O2高CO24wk+葛根素组(P组)。放免法测定血浆与肺组织匀浆的Apelin-36水平,RT-PCR检测肺组织Apelin与APJ基因表达。结果①右心室重量比RV/(LV+S):F组明显高于N组(P<0.01),而P组明显低于F组(P<0.01);平均肺动脉压(mPAP):F组明显高于N组(P<0.01),而P组低于F组(P<0.05);平均颈动脉压(mCAP)3组间比较差异无统计学意义(P>0.05)。②血浆Apelin-36浓度:F组明显高于N组(P<0.01),P组又高于F组(P<0.05)。肺组织匀浆Apelin-36浓度:F组高于N组(P<0.05),P组又比F组高(P<0.05)。③肺组织ApelinmRNA水平:F组高于N组(P<0.05),P组低于F组(P<0.05)。④肺组织APJmRNA水平:F组低于N组(P<0.05),而P组明显高于F组(P<0.01)。结论葛根素防治低O2高CO2大鼠肺动脉高压的机制可能部分与调节肺组织Apelin-APJ相关。     

The apelin-APJ system in heart failure: pathophysiologic relevance and therapeutic potential

Apelin is the endogenous ligand for the previously orphaned G protein-coupled receptor, APJ. This novel peptidic signalling pathway is widely represented in the heart and vasculature, and is emerging as an important regulator of cardiovascular homeostasis. In preclinical models, apelin causes nitric oxide-dependent vasodilatation, reduces ventricular preload and afterload, and increases cardiac contractility in rats with normal and failing hearts. Apelin-APJ signalling also attenuates ischemic myocardial injury and maintains cardiac performance in ageing and chronic pressure overload. Downregulation of apelin and APJ expression coincides with declining cardiac performance raising the possibility that diminished apelin-APJ activity may have pathophysiologic implications. At present, data from human studies is limited but changes in apelin and APJ expression in patients with chronic heart failure parallel those seen in preclinical models. Detailed clinical investigation is now required to establish the role of apelin in human cardiovascular physiology and pathophysiology, and to determine the therapeutic potential of augmenting apelin signalling in patients with heart failure.     

The apelin receptor inhibits the angiotensin II type 1 receptor via allosteric trans-inhibition

Background and Purpose

The apelin receptor (APJ) is often co-expressed with the angiotensin II type-1 receptor (AT1) and acts as an endogenous counter-regulator. Apelin antagonizes Ang II signalling, but the precise molecular mechanism has not been elucidated. Understanding this interaction may lead to new therapies for the treatment of cardiovascular disease.

Experimental Approach

The physical interaction of APJ and AT1 receptors was detected by co-immunoprecipitation and bioluminescence resonance energy transfer (BRET). Functional and pharmacological interactions were measured by G-protein-dependent signalling and recruitment of β-arrestin. Allosterism and cooperativity between APJ and AT1 were measured by radioligand binding assays.

Key Results

Apelin, but not Ang II, induced APJ : AT1 heterodimerization forced AT1 into a low-affinity state, reducing Ang II binding. Likewise, apelin mediated a concentration-dependent depression in the maximal production of inositol phosphate (IP₁) and β-arrestin recruitment to AT1 in response to Ang II. The signal depression approached a limit, the magnitude of which was governed by the cooperativity indicative of a negative allosteric interaction. Fitting the data to an operational model of allosterism revealed that apelin-mediated heterodimerization significantly reduces Ang II signalling efficacy. These effects were not observed in the absence of apelin.

Conclusions and Implications

Apelin-dependent heterodimerization between APJ and AT1 causes negative allosteric regulation of AT1 function. As AT1 is significant in the pathogenesis of cardiovascular disease, these findings suggest that impaired apelin and APJ function may be a common underlying aetiology.

Linked Article

This article is commented on by Goupil et al., pp. 1101–1103 of this issue. To view this commentary visit http://dx.doi.org/10.1111/bph.12040     

The apelinergic system: a promising therapeutic target

Importance of the field: Apelin is a bioactive peptide known as the ligand of the G-protein-coupled receptor APJ. In recent years, there has been a growing body of evidence regarding the importance of apelin and APJ in the pathophysiology of cardiovascular, metabolic and gastrointestinal diseases, brain signalling, HIV infection and tumor angiogenesis. Therefore, the apelinergic system is involved in the pathogenesis of several diseases that represent a major burden to our society.

Areas covered in this review: The goal of this paper is to give an up-to-date review of existing information on apelin/APJ since the discovery of apelin in 1998, with particular focus on their involvement in the regulation of human body systems and potential therapeutic applications.

What the reader will gain: An overview of the most important physiological functions of the apelinergic system and the diseases that may benefit in the future from its modulation as a therapeutic target.

Take home message: Today, the established biological effects of apelin involve major cardiovascular actions, neoangiogenesis, immunologic modulation and insulinemia control as well as body fluid and glucose homeostasis. However, the physiological and pathophysiological role of endogenous apelin is still unsettled and a better and profound knowledge of this system in humans is necessary for the development of novel apelinergic-based therapeutic targets.     

Opioid receptors mediate inotropic and depressor effects of apelin in rats with 2K1C‐induced chronic renovascular hypertension

Apelin receptors (APJ) cross‐talk with other G‐protein‐coupled receptors. However, the role of APJ interaction with opioid receptors (OPR) on the cardiovascular effects of apelin in hypertension is not clear. Renovascular hypertension was induced by placing a Plexiglas clip on the left kidney of rats. After 16 weeks, F13A (an APJ antagonist), naloxone (a general OPR inhibitor), and nor‐binaltorphimine dihydrochloride (nor‐BNI; a selective inhibitor of KOR) were given prior to injections of apelin at doses of 40 and 60 μg/kg. The arterial systolic/diastolic blood pressure and left ventricular contractility responses were then evaluated. The arterial systolic/diastolic blood pressure in sham and 2K1C rats was 110/71 mm Hg and 171/124 mm Hg, respectively. The hypotensive effects of apelin at both doses were inhibited by F13A and naloxone. Nor‐BNI completely inhibited the effects of apelin 40 on arterial pressure, and decreased the effects of 60 μg/kg. KOR inhibition also prevented the compensation for the decrease in the left ventricle +dp/dt max and ?dp/dt max caused by apelin 60. The simultaneous inhibition of OPR and APJ reduced arterial pressure and increased cardiac contractility. Findings showed that the OPR, particularly KOR, mediate the inotropic, lusitropic, and depressor effects of apelin. The interaction of the OPR and APJ augments the inotropic and vasodepressor effects of apelin. This interaction may have potential clinical applications in cardiac failure since opioids are currently used in the treatment of myocardial infarction and stroke, and apelin has been introduced as a potential therapeutic agent in cardiovascular complications.