The Synthesis of Cyclonucleotides with Fixed Glycosidic Bond Linkages as Putative Agonists for P2-Purinergic Receptors

Abstract

Cyclonucleotides with fixed glycosidic bond linkages were investigated as possible ligands for purinoceptors in PC12 cells. P₂Y₂-purinoceptors were not activated by the ATP analogue, 8,2′-thioanhydroadenosine-5′-triphosphate (4) and only weakly by the UTP analogue, 2,2′-anhydrouridine-5′-triphosphate (6). However, both analogues were agonists for P2X₂-purinoceptors although the potencies were approximately 30-fold less than that of the parent nucleotides.     

mESC衍生内皮祖细胞定向分化为血管内皮细胞促伤口愈合

缺血性功能障碍是重要的全球健康问题。血管内皮细胞 (vascular endothelial cell, VEC) 在血管生成和创面修复中发挥关键作用,血管重建不足可导致慢性不愈合伤口。因此,了解有效的血管内皮细胞生成策略有助于受损组织中的血管再生。胚胎干细胞 (embryonic stem cell, ESC) 在组织的内皮化研究中应用广泛。内皮祖细胞 (endothelial progenitor cell, EPC) 是血管内皮细胞发育中不可或缺的部分。本研究目的在于找到一种小鼠胚胎干细胞 (mouse embryonic stem cell, mESC) 衍生为内皮祖细胞的快速、易筛选且高重复性的方法,并从内皮祖细胞定向分化中获得存活率高和功能性好的血管内皮细胞。结果表明,胚胎干细胞通过10 ng/mL VEGF和5 ng/mL bFGF定向诱导分化为增殖能力强的“铺路石”样祖细胞。同时,差异贴壁法有助于EPC的筛选。而EPC可诱导3 d的祖细胞高表达CD133和CD34(相对表达量分别为0.88 ± 0.04和2.12 ± 0.02);采用acctuse酶消化祖细胞,并在50 ng/mL VEGF和25 ng/mL bFGF的条件下诱导7 d分化为血管内皮样细胞,该细胞不仅高表达内皮细胞标志基因CD31、CD144、LAMA5、Tek、KDR和vWF,高表达标志蛋白CD31、CD144、LAMA5(相对表达量分别为1.07 ± 0.03、0.60 ± 0.02和0.70 ± 0.02),而且具有良好的迁移、成管和Weibel Palade (W-P) 小体形成能力。随后,将PBS、EPC和VEC分别应用于大小相同的创面治疗,EPC和VEC均能加快组织愈合程度(相对愈合率分别为78.93 ± 75.35%、95.57 ± 83.73%和100.00 ± 0.00%),VEC明显增强了伤口的血管生成能力和炎症反应。该研究初步证实,mESC衍生的EPC定向诱导7 d后可分化为血管内皮细胞。此内皮细胞具有较好的组织修复功能,干细胞促进血管生成的生理途径有望成为组织重塑的新靶点。     

Regulation of Vascular Endothelial Growth Factor Receptor-2 (Flk-1) Expression in Vascular Endothelial Cells

We have previously reported the existence of a synergistic interaction between vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) in the induction of angiogenesisin vitro.Here we demonstrate that bFGF increases VEGF receptor-2 (VEGFR-2/Flk-1) expression: mRNA levels were increased by 4.5- to 8.0-fold and total protein by 2.0- to 3.5-fold, in bovine microvascular endothelial (BME), aortic endothelial (BAE), and transformed fetal aortic (GM7373) endothelial cells. VEGF itself did not affect VEGFR-2 expression, and neither bFGF nor VEGF altered expression of FGF receptor-1. We also show that synergism occurs at the level of proliferation when this is measured in a three-dimensional but not in a conventional two-dimensional assay. Differences in the level of VEGFR-2 expression were also observed when cells were grown on or within collagen gels under different conditions: mRNA levels were lowest under sparse conditions, increased 20- to 26-fold at confluence, and increased even further (57-fold) when cells were cultured in suspension in three-dimensional collagen gels. Finally, a synergistic increase was seen in the level of expression of urokinase and urokinase receptor mRNAs when cells were exposed to bFGF and VEGF for 4 days. These findings demonstrate that the level of VEGFR-2 expression can be modulated by environmental factors including cytokines and the geometry of the culture conditions and provide some insight into the mechanisms of synergism between bFGF and VEGF in the induction of angiogenesisin vitro.     

间充质干细胞向内皮细胞的分化及其在血管组织工程中的应用

利用间充质干细胞(menchymal stem cells,MSCs)的多向分化能力,将其诱导成为内皮细胞(endothelial cells,ECs),可解决血管组织工程中自体血管细胞作为种子细胞所面临的细胞来源及成体细胞增殖能力有限的问题.MSCs可从多种组织中分离获得,目前应用于血管组织工程的3种MSCs主要源于骨髓、脂肪和肌肉.MSCs的分化可由多种刺激触发,在其向ECs的分化过程中生长因子、支架性质和机械应力等因素起着重要的作用.而以MSCs分化为ECs为基础的组织工程血管在动物模型中展现出促血管生成能力和良好的通畅性,但目前其在临床上的应用较少,需进一步研究,并有许多问题仍待探究.     

Vascular Endothelial Growth Factor Receptor-2 Activates ADP-ribosylation Factor 1 to Promote Endothelial Nitric-oxide Synthase Activation and Nitric Oxide Release from Endothelial Cells

Vascular endothelial growth factor (VEGF) induces angiogenesis and regulates endothelial function via production and release of nitric oxide (NO), an important signaling molecule. The molecular basis leading to NO production involves phosphatidylinositiol-3 kinase (PI3K), Akt, and endothelial nitric-oxide synthase (eNOS) activation. In this study, we have examined whether small GTP-binding proteins of the ADP-ribosylation factor (ARF) family act as molecular switches to regulate signaling cascades activated by VEGF in endothelial cells. Our results show that this growth factor can promote the rapid and transient activation of ARF1. In endothelial cells, this GTPase is present on dynamic plasma membrane ruffles. Inhibition of ARF1 expression, using RNA interference, markedly impaired VEGF-dependent eNOS phosphorylation and NO production by preventing the activation of the PI3K/Akt signaling axis. Furthermore, our data indicate that phosphorylation of Tyr⁸⁰¹, on VEGF receptor 2, is essential for activating Src- and ARF1-dependent signaling events leading to NO release from endothelial cells. Lastly, this mediator is known to regulate a broad variety of endothelial cell functions. Depletion of ARF1 markedly inhibits VEGF-dependent increase of vascular permeability as well as capillary tubule formation, a process important for angiogenesis. Taken together, our data indicate that ARF1 is a novel modulator of VEGF-stimulated NO release and signaling in endothelial cells.     

内皮祖细胞与血管重新内皮化

血管内皮是循环血液和血管壁组织间的一层天然屏障,在维持血管的正常形态和功能中起重要作用。内皮受损后可引起炎症反应、单核细胞浸润和血管平滑肌细胞增生,促发动脉粥样硬化和再狭窄。因此,直接修复受损血管内皮,促使血管重新内皮化已经成为防止动脉粥样硬化及再狭窄领域的重要课题。大量研究表明,内皮祖细胞(EPC)参与受损血管的重新内皮化。该文就内皮祖细胞的来源、鉴定、参与重新内皮化进行综述。     

血管内皮生长因子及其受体在斑马鱼胚胎血管发育中的作用

血管内皮生长因子(vascular endothelial growth factor,VEGF)是一种多功能的细胞因子,其主要作用是促进血管内皮细胞增殖和增加血管通透性,是肿瘤及正常组织血管生成的中心调控因素。以VEGF为靶点的肿瘤血管靶向性治疗成为近几年肿瘤治疗的新途径。斑马鱼作为一种重要的模式生物,被广泛用于胚胎的分子发育机制、疾病模型的构建以及药物筛选等研究中。文章对斑马鱼作为心血管系统研究模型的优势及其血管研究方法做一阐述,重点对斑马鱼VEGF及其受体的最新研究进展做了介绍,并展望了其发展前景。     

Eicosanoid Signaling and Vascular Dysfunction: Methylmercury-Induced Phospholipase D Activation in Vascular Endothelial Cells

Mercury, especially methylmercury (MeHg), is implicated in the etiology of cardiovascular diseases. Earlier, we have reported that MeHg induces phospholipase D (PLD) activation through oxidative stress and thiol-redox alteration. Hence, we investigated the mechanism of the MeHg-induced PLD activation through the upstream regulation by phospholipase A₂ (PLA₂) and lipid oxygenases such as cyclooxygenase (COX) and lipoxygenase (LOX) in the bovine pulmonary artery endothelial cells (BPAECs). Our results showed that MeHg significantly activated both PLA₂ (release of [³H]arachidonic acid, AA) and PLD (formation of [³²P]phosphatidylbutanol) in BPAECs in dose- (0–10 μM) and time-dependent (0–60 min) fashion. The cPLA₂-specific inhibitor, arachidonyl trifluoromethyl ketone (AACOCF₃), significantly attenuated the MeHg-induced [³H]AA release in ECs. MeHg-induced PLD activation was also inhibited by AACOCF₃ and the COX- and LOX-specific inhibitors. MeHg also induced the formation of COX- and LOX-catalyzed eicosanoids in ECs. MeHg-induced cytotoxicity (based on lactate dehydrogenase release) was protected by PLA₂-, COX-, and LOX-specific inhibitors and 1-butanol, the PLD-generated PA quencher. For the first time, our studies showed that MeHg activated PLD in vascular ECs through the upstream action of cPLA₂ and the COX- and LOX-generated eicosanoids. These results offered insights into the mechanism(s) of the MeHg-mediated vascular endothelial cell lipid signaling as an underlying cause of mercury-induced cardiovascular diseases.     

血管内皮标记物及血管内皮生长因子在胸水细胞中的表达和意义

探讨CD31、CD34、CD105及VEGF在胸水中的表达.应用免疫细胞化学染色,免疫荧光染色,Western-blot技术检测200例非小细胞肺癌患者胸水、30例增生胸水和20例炎性胸水中CD31、CD34、CD105及VEGF的表达.CD31、CD34、CD105及VEGF在非小细胞肺癌胸水中的表达量明显高于增生和炎性胸水表达(P＜0.05).非小细胞肺癌胸水患者CD31、CD34、CD105及VEGF高表达,并且在存在着肿瘤细胞血管样管型结构中表达量明显高于未发现肿瘤细胞血管样管型的胸腔积液.检测CD31、CD34、CD105及VEGF在胸腔积液中的表达情况可能对判断患者的预后有一定价值.     

Immunolocalization of P2Y4 and P2Y2 Purinergic Receptors in Strial Marginal Cells and Vestibular Dark Cells

K+ secretion by strial marginal cell and vestibular dark cell epithelia is regulated by UTP and ATP at both the apical and basolateral membranes, suggesting control by P2Y2 and/or P2Y4 purinergic receptors. Immunolocalization was used to determine the identity and distribution of these putative receptors. Membrane proteins from gerbil brain, gerbil vestibular labyrinth and gerbil stria vascularis were isolated and analyzed by Western blot. P2Y2 antibody stained one band at 42 kDa for each tissue, whereas P2Y4 antibody stained 3 bands on gerbil brain (75, 55 and 36 kDa), one band on gerbil stria vascularis (55 kDa) and two bands on vestibular labyrinth (42 and 56 kDa). All bands were absent when the antibodies were blocked with their respective antigenic peptide. P2Y4 was immunolocalized by fluorescence confocal microscopy to only the apical membrane of strial marginal cells and vestibular dark cells and was similar to apical immunostaining of KCNE1 in the same cells. By contrast, P2Y2 was observed on the basolateral but not the apical membrane of dark cells. Similarly, in the stria vascularis P2Y2 was observed in the basolateral region but not the apical membrane of marginal cells. Additional staining was observed in the spiral ligament underlying the stria vascularis. These findings identify the molecular bases of the regulation of K+ secretion by apical and basolateral UTP in the inner ear.     

Endothelial Heparan Sulfate 6-O-Sulfation Levels Regulate Angiogenic Responses of Endothelial Cells to Fibroblast Growth Factor 2 and Vascular Endothelial Growth Factor

Fibroblast growth factor 2 (FGF2) and vascular endothelial growth factor 165 (VEGF₁₆₅) are potent pro-angiogenic growth factors that play a pivotal role in tumor angiogenesis. The activity of these growth factors is regulated by heparan sulfate (HS), which is essential for the formation of FGF2/FGF receptor (FGFR) and VEGF₁₆₅/VEGF receptor signaling complexes. However, the structural characteristics of HS that determine activation or inhibition of such complexes are only partially defined. Here we show that ovarian tumor endothelium displays high levels of HS sequences that harbor glucosamine 6-O-sulfates when compared with normal ovarian vasculature where these sequences are also detected in perivascular area. Reduced HS 6-O-sulfotransferase 1 (HS6ST-1) or 6-O-sulfotransferase 2 (HS6ST-2) expression in endothelial cells impacts upon the prevalence of HS 6-O-sulfate moieties in HS sequences, which consist of repeating short, highly sulfated S domains interspersed by transitional N-acetylated/N-sulfated domains. 1–40% reduction in 6-O-sulfates significantly compromises FGF2- and VEGF₁₆₅-induced endothelial cell sprouting and tube formation in vitro and FGF2-dependent angiogenesis in vivo. Moreover, HS on wild-type neighboring endothelial or smooth muscle cells fails to restore endothelial cell sprouting and tube formation. The affinity of FGF2 for HS with reduced 6-O-sulfation is preserved, although FGFR1 activation is inhibited correlating with reduced receptor internalization. These data show that 6-O-sulfate moieties in endothelial HS are of major importance in regulating FGF2- and VEGF₁₆₅-dependent endothelial cell functions in vitro and in vivo and highlight HS6ST-1 and HS6ST-2 as potential targets of novel antiangiogenic agents.     

A Role for Cadherin-5 in Regulation of Vascular Endothelial Growth Factor Receptor 2 Activity in Endothelial Cells

FLK-1/vascular endothelial growth factor receptor 2 (VEGFR-2) is one of the receptors for VEGF. In this study we examined the effect of cell density on activation of VEGFR-2. VEGF induces only very slight tyrosine phosphorylation of VEGFR-2 in confluent (95-100% confluent) pig aortic endothelial (PAE) cells. In contrast, robust VEGF-dependent tyrosine phosphorylation of VEGFR-2 was observed in cells plated in sparse culture conditions (60-65% confluent). A similar cell density-dependent phenomenon was observed in different endothelial cells but not in NIH-3T3 fibroblast cells expressing VEGFR-2. Stimulating cells with high concentrations of VEGF or replacing the extracellular domain of VEGFR-2 with that of the colony-stimulating factor 1 receptor did not alleviate the sensitivity of VEGFR-2 to cell density, indicating that the confluent cells were probably not secreting an antagonist to VEGF. Furthermore, in PAE cells, ectopically introduced platelet-derived growth factor alpha receptor could be activated at both high and low cell density conditions, indicating that the density effect was not universal for all receptor tyrosine kinases expressed in endothelial cells. In addition to lowering the density of cells, removing divalent cations from the medium of confluent cells potentiated VEGFR-2 phosphorylation in response to VEGF. These findings suggested that cell-cell contact may be playing a role in regulating the activation of VEGFR-2. To this end, pretreatment of confluent PAE cells with a neutralizing anti-cadherin-5 antibody potentiated the response of VEGFR-2 to VEGF. Our data demonstrate that endothelial cell density plays a critical role in regulating VEGFR-2 activity, and that the underlying mechanism appears to involve cadherin-5.     

人血管内皮细胞文库的构建

<正> 人体内大约有10~(12)个内皮细胞,它们均位于血管的内面,其面积约1000m~2,内皮细胞不仅为血液流动、防止血凝提供了一个光滑的表面,而且亦是防止某些细胞因子和细胞成分粘附和迁移的屏障。内皮细胞具有广泛的合成能力,可以产生几十种生物活性物质。另外,内皮细胞与血管平滑肌细胞及多种细胞有着广泛的相互作用。这种相互作用对维持机体     

Acetylbritannilactone Modulates Vascular Endothelial Growth Factor Signaling and Regulates Angiogenesis in Endothelial Cells

The present study was conducted to determine the effects of 1-O-acetylbritannilactone (ABL), a compound extracted from Inula britannica L., on vascular endothelial growth factor (VEGF) signaling and angiogenesis in endothelial cells (ECs). We showed that ABL promotes VEGF-induced cell proliferation, growth, migration, and tube formation in cultured human ECs. Furthermore, the modulatory effect of ABL on VEGF-induced Akt, MAPK p42/44, and p38 phosphorylation, as well as on upstream VEGFR-2 phosphorylation, were associated with VEGF-dependent Matrigel angiogenesis in vivo. In addition, animals treated with ABL (26 mg/kg/day) recovered blood flow significantly earlier than control animals, suggesting that ABL affects ischemia-mediated angiogenesis and arteriogenesis in vivo. Finally, we demonstrated that ABL strongly reduced the levels of VEGFR-2 on the cell surface, enhanced VEGFR-2 endocytosis, which consistent with inhibited VE-cadherin, a negative regulator of VEGF signaling associated with VEGFR-2 complex formation, but did not alter VE-cadherin or VEGFR-2 expression in ECs. Our results suggest that ABL may serve as a novel therapeutic intervention for various cardiovascular diseases, including chronic ischemia, by regulating VEGF signaling and modulating angiogenesis.     

Expression of VEGF Receptors on Endothelial Cells in Mouse Skeletal Muscle

VEGFR surface localization plays a critical role in converting extracellular VEGF signaling towards angiogenic outcomes, and the quantitative characterization of these parameters is critical for advancing computational models; however the levels of these receptors on blood vessels is currently unknown. Therefore our aim is to quantitatively determine the VEGFR localization on endothelial cells from mouse hindlimb skeletal muscles. We contextualize this VEGFR quantification through comparison to VEGFR-levels on cells in vitro. Using quantitative fluorescence we measure and compare the levels of VEGFR1 and VEGFR2 on endothelial cells isolated from C57BL/6 and BALB/c gastrocnemius and tibialis anterior hindlimb muscles. Fluorescence measurements are calibrated using beads with known numbers of phycoerythrin molecules. The data show a 2-fold higher VEGFR1 surface localization relative to VEGFR2 with 2,000–3,700 VEGFR1/endothelial cell and 1,300–2,000 VEGFR2/endothelial cell. We determine that endothelial cells from the highly glycolytic muscle, tibialis anterior, contain 30% higher number of VEGFR1 surface receptors than gastrocnemius; BALB/c mice display ∼17% higher number of VEGFR1 than C57BL/6. When we compare these results to mouse fibroblasts in vitro, we observe high levels of VEGFR1 (35,800/cell) and very low levels of VEGFR2 (700/cell), while in human endothelial cells in vitro, we observe that the balance of VEGFRs is inverted, with higher levels VEGFR2 (5,800/cell) and lower levels of VEGFR1 (1,800/cell). Our studies also reveal significant cell-to-cell heterogeneity in receptor expression, and the quantification of these dissimilarities ex vivo for the first time provides insight into the balance of anti-angiogenic or modulatory (VEGFR1) and pro-angiogenic (VEGFR2) signaling.     

Characterization of Muscarinic Acetylcholine Receptors in Cultured Bovine Aortic Endothelial Cells

Abstract

The binding characteristics of [³H]quinuclidinyl benzilate ([³H]QNB) to isolated crude membranes of cultured bovine aortic endothelial cells were investigated. [³H]QNB bound to endothelial cell membranes with high affinity (k_D = 0.056 nM) and limited capacity (132 fmol/mg DNA). The binding specificity, order of affinity and inhibition constants (K_i) were determined by displacement of bound [³H]QNB with unlabeled ligands. The order of affinity was QNB > atropine > 4-diphenylacetoxy-N-methyl-piperidine methiodide (4-DAMP) > p-fluoro-hexahydro-sila-difenidol (p-F-HHSiD) (M₃ antagonist) > pirenzepine (M₁ antagonist) > AFDX-116 (M₂ antagonist) > (4-hydroxy-2-butynyl) trimethylammonium chloride m-chlorocarbanilate (McN-A-343, M₁ agonist). These observations suggest that muscarinic receptors of endothelial cells in culture are likely to be of M₃ and M₁ subtype. Northern blot analysis of receptor subtypes using cDNA probes did not provide conclusive results due to the low level expression of these receptors in cultured cells. Solubilization of protein bound [³H]QNB with 1% digitonin and 0.02% cholate followed by analysis on sucrose density gradients demonstrated the presence of a specifically bound [³H]QNB-protein complex sedimenting at the 6.2S region of the gradient. These data demonstrate the presence of muscarinic acetylcholine receptor protein in cultured bovine aortic endothelial cells.