心肌顿抑与血管紧张素受体表达的研究进展

心肌顿抑是心脏直视手术和介入治疗后心功能障碍的主要病理基础,其确切的发病机制至今尚未阐明。近年来的研究表明,心肌缺血再灌注后肾素一血管紧张素系统被激活,局部心肌中血管紧张素受体表达增高,引起Ca^2＋超负荷,促进缺血再灌注损伤的病理生理改变,很可能是造成心肌顿抑的关键机制。这些研究进展为进一步揭示心肌顿抑机制提供了新的理论和实验依据。     

抗肝纤维化的新靶点:Na~+/H~+交换泵

Na+ /H+ 交换泵 (NHE)是调节细胞内pH和容积的重要膜蛋白。对启动细胞增殖、分化和凋亡起重要作用。NHE参与介导细胞因子和氧应激激活肝贮脂细胞和胶原的合成 ,因而与肝纤维化的形成密切相关。NHE有望成为重要的抗肝纤维化药物的靶点。     

姜黄素通过激活ATRAP信号通路抑制血管紧张素Ⅱ诱导的心肌肥大

目的探究姜黄素抑制血管紧张素Ⅱ(AngⅡ)诱导的心肌肥厚相关病理机制。方法 MTT法和乳酸脱氢酶试剂盒检测姜黄素的心肌细胞毒性;200 nmol·L~(-1) AngⅡ孵育心肌细胞24 h诱导心肌肥厚;α-actinin染色观察心肌细胞形态大小;q PCR检测心肌肥大标记物ANF、BNP、β-MHC的m RNA水平;通过Western blot检测AngⅡ受体的抑制蛋白ATRAP的表达情况。结果姜黄素对心肌细胞无明显毒性;200 nmol·L~(-1)的AngⅡ刺激心肌细胞24 h显著诱导心肌细胞肥大;ANP、BNP、β-MHC的m RNA水平显著增高;AngⅡ受体的抑制蛋白ATRAP表达明显降低;姜黄素预作用细胞1 h显著抑制AngⅡ诱导的心肌肥大,逆转AngⅡ降低的ATRAP表达。结论姜黄素抑制AngⅡ诱导的心肌肥大可能与其激活ATRAP信号通路有关。     

血管紧张素Ⅱ致心肌肥大及机制

心肌肥大是一个适应性的生理过程,它可以引起呼吸困难、心绞痛、晕厥、头晕、心悸等症状.无论是血压还是血容量增加都会造成左心室的肥大(LVH),这种肥大是以心脏和血管结构改变以及心肌重建为特征的.左心室肥大过程中细胞的紊乱是心室组织两类主要细胞即心肌细胞和纤维原细胞改变引起的.大部分关于心肌肥大的研究,都常使用培养的新生大鼠心室细胞(NRVMs).在心脏病变过程中,心肌细胞的肥大使心脏变大,同时伴随着单个细胞的增大,使收缩蛋白质如肌球蛋白重链的含量增加,并使诸如编码心钠素(ANF)的胚胎基因等过度表达.     

治疗心肌肥厚药物的进展

本文就近3年治疗心肌肥厚（特别是左室肥厚）的药物的研究进展作了综述,主要讨论了血管紧张素转换酶抑剂、血管紧张素Ⅱ受体Ⅰ阻断剂,钙拮抗剂、利尿剂等。对各类药物的治疗效果作出评价。并就心肌肥厚药物治疗的未来对策作了探讨。     

Na~+/H~+交换泵在人肺癌组织中的表达

目的 为了探讨肺癌细胞NHE-1基因的表达情况。方法 采用了mRNA原位杂交和图像分析技术对27例人肺癌手术切除的新鲜标本进行有关NHE-1基因表达水平方面的研究,并对其pH调节的分子机制和特点进行了初步探讨。结果 肺癌组织细胞的NHE-1 mRNA表达水平显著的高于正常肺组织(P<0.001)。结论 人肺癌组织细胞通过上调NHE-1基因表达以增加其细胞膜NHE-1的数量分布,这可能是在整体条件下pH调节的主要分子机制和特点。NHE-1基因的超表达对维持人肺癌细胞在机体内的抗凋亡生长起着重要作用,因此在以pH调节机制为靶点的肿瘤治疗研究领域中此项研究具有积极意义。     

黄芪甲苷通过激活Sirt3抑制血管紧张素Ⅱ诱导的心肌肥大及氧化应激

目的研究Sirt3在黄芪甲苷抑制血管紧张素Ⅱ诱导的心肌肥大和氧化应激中的作用。方法α-actinin染色检测心肌细胞大小;MitoSOX染色检测ROS;Real time PCR检测心肌肥大标记物ANP、BNP和β-MHC的mRNA水平;Western blot法检测心肌细胞肥大信号通路蛋白水平。结果100nmol·L-1血管紧张素Ⅱ处理心肌细胞48 h,心肌细胞面积与ANP、BNP、β-MHC mRNA水平显著增加,ROS水平及NOX-2、NOX-4表达显著增加,Sirt3表达显著降低;黄芪甲苷预处理心肌细胞1 h显著抑制血管紧张素Ⅱ诱导的上述效应。Sirt3-siRNA干预Sirt3蛋白水平,显著抑制黄芪甲苷的心肌肥厚抑制作用以及抗氧化作用,上调ROS水平,促进心肌肥大。结论黄芪甲苷通过激活Sirt3抑制血管紧张素Ⅱ诱导的心肌肥大以及氧化应激。     

血管紧张素受体拮抗剂对心肌肥厚的防治作用

左室心肌肥厚是引起心血管疾病发生率与死亡率增高的危险因素之一。而血管紧张素Ⅱ（AngiotensinⅡ，AngⅡ）在心肌肥厚形成中起着重要的作用。AngⅡ受体拮抗剂通过选择性拮抗AngⅡ受体亚型AT1介导的生理效应而具有防治心肌肥厚的作用。本文就其在防治心肌肥厚可能的作用途径进行了综述。同时为寻找新的抗心肌肥厚药物提供了一些思路。     

缬沙坦对兔髂动脉内皮损伤后转化生长因子β1表达的影响

目的 探讨血管紧张素Ⅱ(AngⅡ)受体拮抗剂缬沙坦对兔髂动脉内皮损伤后转化生长因子β1(TGF-β1)表达的影响。方法 新西兰兔24只随机平分为3组,普通饲料喂饲组(G1),高脂饮食喂饲+动脉内皮损伤组(G2),高脂饮食喂饲+动脉内皮损伤+缬沙坦治疗组(G3),G2、G3应用球囊损伤髂动脉内皮加高脂饲养的方法建立兔动脉粥样硬化狭窄模型,术后4周采用免疫组织化学和反转录聚合酶链反应(RT—PCR)技术对兔髂动脉壁TGF-β1表达的情况进行观察。结果 G2、G3TGF-β1蛋白和TGF-β1mRNA表达均显著高于G1,而G3 TGF-β1蛋白和TGF-β1mRNA表达显著低于G2(P<0.01)。此外,还观察到TGF-β1mRNA表达水平与内膜/中膜比值呈正相关(r=0.941,P<0.01)。结论 缬沙坦对内皮损伤后的血管病变有部分保护作用,其机制可能是部分通过下调TGF-β1的表达,减轻血管损伤后新生内膜的增生。     

AT1R-Crim1信号通路在乳鼠肥大心室肌细胞Kir2.1 mRNA和蛋白表达调控中的作用

目的 探讨血管紧张素Ⅱ受体1型(AT1R)—半胱氨酸丰富跨膜成骨蛋白调控因子(Crim1)信号通路在乳鼠肥大心室肌细胞编码内向整流钾电流离子通道的Kir2.1 mRNA和蛋白表达调控中的作用.方法 分离1 d龄SD大鼠乳鼠心室获心室肌细胞,给予腺病毒空载体(Ad-Null)、Crim1基因重组腺病毒载体(Ad-Crim...     

Comparison of the protective actions of Na+/H+ and Na+/Ca2+ exchange inhibitors in ischemic/reperfused rat hearts

The protective effects of the Na⁺/H⁺ exchange inhibitors amiloride, EIPA (5‐(N‐ethyl‐N‐isopropyl)‐amiloride), and HOE 694 (3‐methylsulfonyl‐4‐(1‐piperidino) benzoyl‐guanidine) and the Na⁺/Ca²⁺ exchange inhibitor, DCB (3,4‐Dichlorobenzamil) on ischemia (30 min) / reperfusion (30 min) injury were studied using Langendorff perfused rat hearts. EIPA and HOE 694 given before ischemia protected the heart during reperfusion from mechanical and metabolic disturbances. A weak protective effect was observed with amiloride, but not with DCB. The cardioprotective efficacies of these compounds correlated with their potencies as Na⁺/H⁺ exchange inhibitors as assessed by the NH₄Cl prepulse method. None of the inhibitors was effective when given at reperfusion. EIPA and HOE 694 decreased myocardial rigidity as assessed by the resting tension (RT) which elevated during reperfusion. EIPA led to a more marked attenuation of RT elevation during reperfusion rather than ischemia, whereas diltiazem, a Ca²⁺ channel blocker, suppressed RT elevation during ischemia but did not cause a further attenuation of RT during reperfusion. Treatment with EIPA as well as diltiazem before ischemia showed a direct negative chronotropic effect. Cardioprotective effects were also observed with diltiazem. These results suggest that Na⁺/H⁺ exchange plays a more important role in ischemia‐reperfusion‐induced myocardial injury than does Na⁺/Ca²⁺ exchange. The cardioprotective effects of EIPA appear to be produced by Ca²⁺ channel blockade during ischemia and by Na⁺/H⁺ exchange inhibition during reperfusion. Drug Dev. Res. 48:160–170, 1999. © 1999 Wiley‐Liss, Inc.     

Activity of the Na+/H+ exchanger contributes to cardiac damage following ischaemia and reperfusion

1. The present review considers the evidence that Na+-H+ exchange activity contributes to cardiac damage following ischaemia and reperfusion. The basic mechanism involved is that protons are produced during ischaemia and leave the myocytes on the Na+/H+ exchanger during either ischaemia and/or reperfusion. The resulting elevation of [Na+]i causes Ca2+ loading through the Na+/Ca2+ exchanger and the elevated [Ca2+]i is thought to lead to myocardial damage. 2. Inhibition of the Na+/H+ exchanger during ischaemia and/or reperfusion produces a substantial cardioprotective effect by blocking the damage caused by the coupled exchanger mechanism described above. Preconditioning also produces a cardioprotective effect and the evidence that this also involves the Na+/H+ exchanger is reviewed. 3. The intracellular mechanisms associated with ischaemic damage and preconditioning are of great interest because they may provide targets for potential therapeutic interventions. The intracellular regulation of the Na+/H+ exchanger appears to be an important component of these pathways and may become a focus for therapeutic approaches.     

Na+/H+交换器抑制剂的研究与开发

综述Na^ ／H^ 交换器的病理作用及Na^ ／H^ 交换器抑制剂的研究与开发。Na^ ／H^ 交换器为细胞膜上的一种转运蛋白质，对细胞内pH起调控作用，目前已知其有6个亚型，其中亚型1在心肌缺血再灌注损伤过程中发挥重要作用，故而Na^ ／H^ 交换器抑制剂对缺血再灌注心肌具有保护作用。     

ACTIVATION OF Na+/H+ EXCHANGE IS UNNECESSARY IN THE INDUCTION OF c-fos mRNA IN SERUM-STIMULATED VASCULAR SMOOTH MUSCLE CELLS

1. The effects of extracellular Na+ concentration ([Na+]o) on serum-stimulated c-fos mRNA induction in vascular smooth muscle cells (VSMC) were studied to examine whether the activation of Na+/H+ exchange and the following intracellular alkalinization are necessary in the induction of c-fos in VSMC. 2. When monitored with 2', 7'-bis (carboxylethyl)-5(6)-carboxyfluorescein, the reduction in [Na+]o in HCO(3-)-free buffer caused a dose-dependent inhibition of Na(+)-dependent intracellular pH recovery in acid-loaded VSMC. In addition, serum-stimulated intracellular alkalinization in VSMC was completely blocked by the removal of extracellular Na+. 3. By contrast, c-fos induction, quantified by slit blot hybridization of c-fos mRNA, was not fully inhibited by the reduction of [Na+]o. Furthermore, amiloride and ethylisopropyl-amiloride, inhibitors of Na+/H+ exchange, only partially blocked c-fos induction by serum. 4. We concluded from the observation above, that the intracellular alkalinization caused by the activation of Na+/H+ exchange was unnecessary in serum-stimulated induction of c-fos mRNA in VSMC.     

The epithelial brush border Na+/H+ exchanger NHE3 associates with the actin cytoskeleton by binding to ezrin directly and via PDZ domain-containing Na+/H+ exchanger regulatory factor (NHERF) proteins

1. The Na(+)/H(+) exchanger NHE3 associates with the actin cytoskeleton by binding ezrin both directly and indirectly. Both types of interaction are necessary for acute regulation of NHE3. Most acute regulation of NHE3 occurs by changes in trafficking via effects on exocytosis and/or endocytosis. However, NHE3 activity can also be regulated without changing the surface expression of NHE3 (change in turnover number). 2. A positive amino acid cluster in the a-helical juxtamembrane region in the COOH-terminus of NHE3 (amino acids K516, R520 and R527) is necessary for binding to the protein 4.1, ezrin, radixin, moesin (FERM) domain III of ezrin. Direct binding of NHE3 to ezrin is necessary for many aspects of basal trafficking, including basal exocytosis, delivery from the synthetic pathway and movement of NHE3 in the brush border (BB), which probably contributes to endocytosis over a prolonged period of time. 3. In addition, NHE3 binds indirectly to ezrin. The PDZ domain-containing proteins Na(+)/H(+) exchanger regulatory factor (NHERF) 1 and NHERF2, as intermediates in linking NHE3 to ezrin, are necessary for many aspects of NHE3 regulation. The binding of NHERF-ezrin/radixin/moesin to NHE3 occurs in the cytosolic domain of NHE3 between amino acids 475 and 689. This NHERF binding is involved in the formation of the NHE3 complex and restricts NHE3 mobility in the BB. However, it is dynamic; for example, changing in some cases of signalling. Furthermore, NHERF binding is necessary for lysophosphatidic acid stimulation of NHE3 and inhibition of NHE3 by Ca(2+), cAMP and cGMP.     

Effects of volume depletion and NaHCO3 loading on the expression of Na+/H+ exchanger isoform 3, Na+: HCO3- cotransporter type 1 and nitric oxide synthase in rat kidney

1. The effects of volume depletion and NaHCO(3) loading on the expression of Na(+)/H(+) exchanger isoform 3 (NHE3), Na(+) : HCO(3)(-) cotransporter type 1 (NBC1) and neuronal (n) and inducible (i) isoforms of nitric oxide synthase (NOS) were determined in rat kidney. 2. Adult male Sprague-Dawley rats were used. Rats were divided into four groups: (i) euvolaemic (EC); (ii) hypovolaemic (HC); (iii) euvolaemia with NaHCO(3) loading (EB); and (iv) hypovolaemia with NaHCO(3) loading (HB). The expression of NHE3, NBC1, nNOS and iNOS proteins was determined in the cortex of the kidney by immunoblotting and immunohistochemistry. Tissue content of nitric oxide (NO) metabolites (NO(x)) were also determined in the cortex using a colourimetric assay. 3. Compared with the EC group, the expression of NHE3 and NBC1 was increased in the HC group and decreased in the EB group. Comparing the EB and HB groups, the expression of NHE3 and NBC1 was higher in the latter group. The expression of NHE3 was decreased and that of NBC1 was increased in the HB group compared with the HC group. The NO(x) content and nNOS expression were decreased in the hypovolaemic (HC) and NaHCO(3)-loaded (EB and HB) rats. Moreover, the expression of iNOS was decreased in the HB group compared with the other groups. 4. An altered volume status and NaHCO(3) loading may affect the regulation of NHE3 and NBC1 in the kidney and the endogenous NO system may play a role in the observed effects.     

Characterization of interactions of Na+/H+ exchanger regulatory factor‐1 with the parathyroid hormone receptor and phospholipase C*

Abstract: The Na⁺/H⁺ exchanger regulatory factor‐1 (NHERF1) is a molecular scaffold important for the signaling of the G‐protein coupled receptor for the parathyroid hormone (PTH1R). The two PDZ (PSD‐95, Discs‐large, ZO1) domains of NHERF1 through association with the C‐termini of PTH1R and phospholipase C enhance the signaling pathway associated with PTH. To examine these interactions, we have produced the individual PDZ1 and PDZ2 domains as well as the tandem PDZ1–PDZ2 domains (PDZ12) of NHERF1 and have characterized the binding affinities of the C‐terminal motifs of PTH1R and PLCβ using fluorescence anisotropy. Circular dichroism indicates that the PDZ1 and PDZ2 are properly folded. Based on fluorescence anisotropy we find that the C‐terminus of PTH1R, containing ETVM, has similar affinities (approximately 10 μm ) for both PDZ1 and PDZ2. The PTH1R displayed reduced binding affinity for the tandem PDZ12 (16 μm ) compared with the individual domains or a solution of equal molar concentrations of PDZ1 and PDZ2 (5.8 μm ), suggesting negative cooperativity between the PDZ domains or intervening region. The C‐termini of PLCβ (both β1 and β2 isozymes were examined, containing DTPL and ESRL, respectively) displayed a diminished affinity for PDZ2 (approximately 30 μm ) over that of PDZ1 (approximately 8 μm ). Finally, we demonstrate trans PDZ1–PDZ2 association that is enhanced in the presence of the C‐terminus of PTH1R or PLCβ, suggesting oligomerization of NHERF as a mode for enhancing the signaling associated with PTH.     

Therapeutic potential of H3-receptor agonists in myocardial infarction

Sympathetic over-activity accompanied by excessive noradrenaline (NA) release within the heart is a recognised cause of dysfunction in myocardial ischaemia. Myocardial infarction is often accompanied by arrhythmias with high morbidity and mortality. Indeed, NA enhances intracellular Ca²⁺by increasing its influx through voltage-dependent channels, mobilising it from intracellular stores and favouring its inward transport by Na⁺/Ca²⁺ exchange. Ca²⁺ overload eventually results in dysrhythmia and uncoordinated myocyte contraction. Moreover, NA increases metabolic demand. In concert with other contributing factors, this will aggravate the primary ischaemia and initiate a vicious cycle that can culminate in myocardial damage and heart failure. Therefore, reduction of NA release from cardiac sympathetic nerves is an important protective measure. Adrenergic nerves possess inhibitory receptors, such as ₂-adrenoceptors, adenosine A₁-receptors and histamine H₃-receptors (H₃R). In myocardial infarction, NA is released by both exocytotic (Ca²⁺-dependent) and carrier-mediated (Na⁺/H⁺ exchange-dependent) mechanisms, associated with short-term and protracted ischaemia, respectively. Unlike ₂-adrenoceptor agonists that reduce NA exocytosis, but enhance carrier-mediated NA release, H₃R agonists inhibit both exocytotic and carrier-mediated NA release. Moreover, unlike adenosine A₁-receptor agonists, H₃R agonists do not depress sinoatrial and atrioventricular nodes, nor cause bronchoconstriction. Therefore, stimulation of H₃R on cardiac sympathetic nerve endings is an important new way to protect the heart from the consequences of ischaemia and infarction. Although H₃R agonists alleviate reperfusion arrhythmias in isolated hearts by reducing NA release, this protective action needs to be demonstrated in classical in vivo models of occlusion/reperfusion. Regardless, H₃R agonists offer the promise of a novel strategy in the treatment of myocardial ischaemia and infarction.