IQGAP1 promotes the phenotypic switch of vascular smooth muscle by myocardin pathway: a potential target for varicose vein

Recently, the architectural remodeling of venous vessel wall ranks as the basis of varicose veins development based on the phenotypic state of vascular smooth muscle cells (VSMCs). In this study, we firstly demonstrated an obvious up-regulation of IQ-domain GTPase-activating protein 1 (IQGAP1) in patients with varicose veins. Importantly, following stimulation with PDGF-BB for 4 h, a common inducer of phenotypic switch in VSMCs, a dramatically time-dependent increase in IQGAP1 expression was observed in human venous smooth muscle cells (HUVSMCs), concomitant with the down-regulation of SMC markers [including α-smooth muscle actin (SMA), smooth muscle calponin (CNN), SM22α (SM22)], suggesting a critical function of IQGAP1 during the switch of synthetic VSMC phenotype. Further analysis ascertained that IQGAP1 overexpression significantly inhibited the expression of SMA, SM and CNN, while its silencing dramatically promoted their expression levels. Moreover, the elevated IQGAP1 enhanced cell proliferation, migration and rearrangement. Mechanism assay confirmed that IQGAP1 overexpression notably blocked myocardin levels. Importantly, after transfection with myocardin siRNA, IQGAP1 down-regulation-induced decrease in cell proliferation, migration and cell rearrangement was remarkably attenuated. Together, these results demonstrated that IQGAP1 may regulate the phenotypic switch of VSMCs by myocardin pathway, which is critical for the pathological progression of varicose vein. Therefore, this study supports a prominent insight into how IQGAP1 possesses its benefit function in varicose veins development by regulating vascular remodeling.     

Implication of adenylyl cyclase 8 in pathological smooth muscle cell migration occurring in rat and human vascular remodelling

Recently, we discovered on primary cell cultures that adenylyl cyclase type 8 (AC8) was involved in the transition of rat vascular smooth muscle cells (VSMCs) to an inflammatory phenotype. Here we demonstrate, in human vessels displaying early or advanced atherosclerotic lesions, that: (a) only intimal VSMCs strongly express AC8; and (b) very few AC8‐positive VSMCs were detected in the medial layer, either in atherosclerotic or healthy arteries. Furthermore, over‐expressing AC8 in primary rat VSMC cultures triggered the recolonization of a wounded zone and similar results were obtained in the presence of mitomycin, a potent inhibitor of proliferation. This phenomenon was prevented by silencing AC8. Indeed, in IL‐1β‐treated cells, AC8 silencing halted migration and decreased the matrix‐metalloproteinases 2/9 secretion, known to be involved in VSMC migration. In vivo, we showed: (a) a pronounced up‐regulation of AC8 expression in highly migrating VSMCs of the injured rat carotid artery; (b) an undetectable AC8 labelling in re‐endothelized vessels where neo‐intimal thickening had stopped. From our data, we conclude that AC8 expression appears closely linked to the properties developed by VSMCs in atherosclerosis and post‐angioplasty neo‐intima formation leading to restenosis. In addition, it reinforces the idea that VSMC responses to their cell environment greatly depend on the AC isoforms expressed and attributes a new role for AC8 in these pathological vascular processes. Copyright © 2010 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Role of parnaparin in atherosclerosis

Atherosclerosis is characterized by a proliferation of vascular smooth muscle cells (VSMCs) and their migration to the intima, which induces thickening of the intima itself, but the mechanism remains poorly understood. Low molecular weight heparin (LMWH) inhibits the proliferation of VSMCs. Previous studies have shown that a LMWH, parnaparin (PNP), acts on the processes of atherogenesis and atheroprogression in experimental animal models. The aim of this study was to investigate the involvement of oxidative stress, inflammation and VSMCs in the regulation of vascular wall homeostasis. We also considered the possibility of restoring vascular pathological changes using PNP treatment. In order to evaluate vascular remodelling in this study we have analysed the morphological changes in aortas of an animal model of atherosclerosis, apolipoprotein E‐deficient mice (ApoE?/?) fed with a normal or a western diet without treatment or treated with PNP. We also analysed, by immunohistochemistry, the expression of proteins linked to atherogenesis and atheroprogression – an enzyme involved in oxidative stress, iNOS, examples of inflammatory mediators, such as tumour necrosis factor alpha (TNF‐α), interleukins 1 and 6 (IL‐1 and IL‐6), and markers of VSMC changes, in particular plasminogen activator inhibitor‐1 and thrombospondin‐1 (PAI‐1 and TSP‐1). Our results could suggest that PNP downregulates VSMC proliferation and migration, mediated by PAI‐1 and TSP‐1, and reduces inflammation and oxidative stress in vessels. These data suggested that LMWH, in particular PNP, could be a theoretically practical tool in the prevention of atherosclerotic vascular modification.     

Stimulation of vascular smooth muscle cell migration by macrophage migration inhibitory factor

Macrophage migration inhibitory factor (MIF) is a well known proinflammatory factor that influences the migration and proliferation of various cell types, predominantly monocytes and macrophages. Recent evidence suggests an important role for MIF in the progression of atherosclerosis and restenosis. For this reason, we studied the effect of MIF on platelet-derived growth factor-BB (PDGF-BB)-induced migration and PDGF receptor protein expression in vascular smooth muscle cells (VSMCs). Furthermore, the possibility of MIF influencing the migration of VSMCs was investigated. Our results show that short-term incubation of MIF is able to enhance PDGF-BB-induced migration. Long-term incubation decreases PDGF-BB-induced migration, but preserves a short-term stimulatory effect. These effects are not regulated at the level of PDGF receptor protein expression. MIF also acts as a chemoattractant for VSMCs, with a maximum response at 15 ng/ml. In contrast, the proliferation of VSMCs was unaffected by MIF. We conclude that MIF has a biphasic effect on VSMC migration. It remains unclear whether this effect is direct or involves the secretion of unidentified promigratory factors. Exogenous MIF does not stimulate VSMC proliferation; however, a role for MIF in proliferation cannot be fully ruled out. In view of the known key contributions of macrophage-derived MIF and VSMCs, the observed effects may well play a role in the progression of atherosclerosis and restenosis.     

去甲肾上腺素对血管平滑肌细胞增殖和骨架蛋白表达的影响

目的:研究去甲肾上腺素(NE)对血管平滑肌细胞(VSMC)骨架蛋白表达与增殖之间的关系,探讨神经因素对VSMC的调控作用.方法:体外培养大鼠主动脉VSMC,用BrdU标记增殖的细胞;免疫荧光方法检测细胞骨架蛋白SM α-actin、β-tubulin和desmin的表达.结果:血清培养对VSMC有明显促增殖作用,而血清饥饿则能可逆性抑制VSMC增殖;NE能明显促VSMC增殖和下调SM22α的表达;随血清培养SM α-actin表达减少,血清饥饿培养可使SM α-actin表达可逆性上调;β-tubulin和desmin随血清培养其表达减少更明显,第6代基本不表达,而血清饥饿也不能上调其表达,NE对SM α-actin、β-tubulin和desmin的表达有下调作用.结论:NE可促进VSMC增殖和下调SM α-actin、β-tubulin和Desmin骨架蛋白的表达作用.     

同型半胱氨酸促进大鼠血管平滑肌细胞增殖和表型转化

目的:研究同型半胱氨酸(Hcy)对大鼠血管平滑肌细胞(VSMCs)表型转化和增殖的影响,以期为Hcy作为动脉粥样硬化(AS)独立危验因子的分子机制提供证据。方法:体外培养大鼠血管平滑肌细胞,用不同浓度的Hcy作用于细胞24h后:(1)MTT法测定细胞的增殖率;(2)流式细胞术检测细胞周期;(3)半定量RT-PCR法检测平滑肌22α(SM22α)mRNA的表达;(4)透射电镜观察VSMCs的形态学特征,确定其表型转换特征。结果:Hcy可导致细胞增殖率增加;G0/G1期细胞逐渐减少,S期细胞逐渐增多;SM22α mRNA表达下调,Hcy浓度增至1000μmol/L时差异显著;透射电镜显示,高浓度Hcy作用后VSMCs胞浆中内质网、高尔基复合体明显增多、胞核大、染色质疏松。结论:Hcy促进VSMCs增殖的同时可促进其表型的转化。     

降钙素基因相关肽对血管平滑肌表型转化和增殖的影响

目的 探讨降钙素基因相关肽(CGRP)对大鼠血管平滑肌细胞(VSMCs)表型转化和增殖的影响以及它们之间的关系.方法 取大鼠主动脉先体外培养8d后再贴块培养(VSMCs);对照组直接用贴块法培养细胞.实验分为CGRP作用组和无CGRP作用组.用5-BrdU标记平滑肌细胞增殖变化;RT-PCR检测HRG-1和SM22α表达变化.结果 血管经体外培养8d后再贴壁培养的平滑肌细胞可见大量棕黄色标记增殖的细胞核,HRG-1和SM22α mRNA表达明显减少;而CGRP作用组标记的血管平滑肌增殖细胞明显减少,HRG-1和SM22α mRNA表达明显上调.结论 CGRP对VSMCs增殖有抑制作用并同时可使VSMCs从合成型向收缩型转化.     

Disruption of actin cytoskeleton mediates loss of tensile stress induced early phenotypic modulation of vascular smooth muscle cells in organ culture

Aorta organ culture has been widely used as an ex vivo model for studying vessel pathophysiology. Recent studies show that the vascular smooth muscle cells (VSMCs) in organ culture undergo drastic dedifferentiation within the first few hours (termed early phenotypic modulation). Loss of tensile stress to which aorta is subject in vivo is the cause of this early phenotypic modulation. However, no underlying molecular mechanism has been discovered thus far. The purpose of the present study is to identify intracellular signals involved in the early phenotypic modulation of VSMC in organ culture. We find that the drastic VSMC dedifferentiation is accompanied by accelerated actin cytoskeleton dynamics and downregulation of SRF and myocardin. Among the variety of signal pathways examined, increasing actin polymerization by jasplakinolide is the only one hindering VSMC dedifferentiation in organ culture. Moreover, jasplakinolide reverses actin dynamics during organ culture. Latrunculin B (disrupting actin cytoskeleton) and jasplakinolide respectively suppressed and enhanced the expression of VSMC markers, SRF, myocardin, and CArG-box-mediated SMC promoters in PAC1, a VSMC line. These results identify actin cytoskeleton degradation as a major intracellular signal for loss of tensile stress-induced early phenotypic modulation of VSMC in organ culture. This study suggests that disrupting actin cytoskeleton integrity may contribute to the pathogenesis of vascular diseases.     

Platelet-derived growth factor receptors expressed in response to injury of differentiated vascular smooth muscle in vitro: effects on Ca2+ and growth signals.

Vascular smooth muscle cells (VSMCs) in the intact vascular wall are differentiated for contraction, whereas the response to vascular injury involves transition towards a synthetic phenotype, with increased tendency for proliferation. Platelet-derived growth factor (PDGF) is thought to be important for this process. We investigated expression and functional coupling of PDGF receptors (PDGFRs) alpha and beta in rat tail arterial rings kept in organ culture, in order to capture early events in the phenotypic transition. In freshly dissected rings no PDGFR immunoreactivity was found in medial VSMCs, whereas PDGFR alpha was detected in nerve fibres. After organ culture for 1-4 days PDGFR alpha and beta as well as phospholipase Cgamma2 (PLCgamma2), known to couple to PDGFR, were expressed in VSMCs within 100 microm of the cut ends. Calponin, a marker for the contractile phenotype, was decreased near the injured area, suggesting that cells were in transition towards synthetic phenotype. In these cells, which showed functional Ca2+-release from the sarcoplasmic reticulum, PDGF-AB (100 ng x mL(-1)) had no effect on [Ca2+]i, whereas cultured VSMCs obtained from explants of rat tail arterial rings responded to PDGF-AB with an increase in [Ca2+]i. However, PDGFR within the cultured rings coupled to growth signalling pathways, as PDGF-AB caused a tyrphostin AG1295-sensitive activation of extracellular signal-regulated kinases 1 and 2 and of [3H]-thymidine incorporation. Thus, early expression of PDGFR in VSMC adjacent to sites of vascular injury coincides with signs of dedifferentiation. These receptors couple to growth signalling, but do not activate intracellular Ca2+ release.     

不同体外条件培养对大鼠血管平滑肌细胞表型、增殖和细胞骨架的影响

目的 探讨不同体外培养条件与血管平滑肌细胞(VSMCs)表型、增殖和细胞骨架蛋白表达之间的差异及生物学意义。 方法 体外培养大鼠主动脉血管平滑肌细胞,实验分为6组：2代对照组、2代血清饥饿组、4代对照组、4代血清饥饿组、6代对照组和6代血清饥饿组;用5-Brdu标记增殖细胞;RT-PCR检测表型基因SM22ɑ mRNA的表达;免疫细胞化学检测细胞骨架蛋白SMɑ-actin、β-Tubulin和Desmin的表达。 结果 体外培养的VSMCs,随培养代数的增多,细胞骨架蛋白表达减少,电镜超微结构可见胞质中内质网、高尔基体等细胞器增多,有大量的分泌小泡;血清饥饿胞中线粒体增多并电子密度增高。 血清培养条件下SMɑ-actin随培养代数的增加其表达减少,血清饥饿培养可使SMɑ-actin表达可逆性上调;β-Tubulin和Desmin随培养代数的增加表达减少更明显,而血清饥饿上调作用也不明显,至第6代基本不表达。 结论 血清培养和血清饥饿培养在不同代中对VSMCs表型转化、增殖和细胞骨架有着不同的影响,它们之间存在着内在的联系,在维持细胞形态、收缩功能和血管重构方面起了重要作用。β-Tubulin和Desmin表达消失可能具有重要生物学意义。     

Gastrodin inhibits cell proliferation in vascular smooth muscle cells and attenuates neointima formation in vivo

Vascular smooth muscle cell (VSMC) proliferation plays a critical role in the development of vascular diseases. In the present study, we tested the efficacy and the mechanisms of action of gastrodin, a bioactive component of the Chinese herb Gastrodia elata Bl, in relation to platelet-derived growth factor-BB (PDGF-BB)-dependent cell proliferation and neointima formation after acute vascular injury. Cell experiments were performed with VSMCs isolated from rat aortas. WST and BrdU incorporation assays were used to evaluate VSMC proliferation. Eight-week-old C57BL/6?mice were used for the animal experiments. Gastrodin (150?mg/kg/day) was administered in the animal chow for 14?days, and the mice were subjected to wire injury of the left carotid artery. Our data demonstrated that gastrodin attenuated the VSMC proliferation induced by PDGF-BB, as assessed by WST assay and BrdU incorporation. Gastrodin influenced the S-phase entry of VSMCs and stabilised p27Kip1 expression. In addition, pre-incubation with sinomenine prior to PDGF-BB stimulation led to increased smooth muscle-specific gene expression, thereby inhibiting VSMC dedifferentiation. Gastrodin treatment also reduced the intimal area and the number of PCNA-positive cells. Furthermore, PDGF-BB-induced phosphorylation of ERK1/2, p38 MAPK, Akt and GSK3β was suppressed by gastrodin. Our results suggest that gastrodin can inhibit VSMC proliferation and attenuate neointimal hyperplasia in response to vascular injury. Furthermore, the ERK1/2, p38 MAPK and Akt/GSK3β signalling pathways were found to be involved in the effects of gastrodin.     

miR-146b-5p promotes VSMC proliferation and migration

Vascular smooth muscle cells (VSMCs) play pivotal roles in the development of vascular diseases. While microRNAs are important in vascular pathologies, a few is known about their functional roles in VSMC phenotypes. We profiled microRNA expression in PDGF-BB treated VSMCs and found microRNA-146b-5p (miR-146b-5p) was upregulated. Inhibition of miR-146b-5p blocked in response to PDGF while reducing VSMC proliferation and migration. These studies implicate miR-146b-5p as necessary for PDGF-induced VSMC phenotype transition. Downstream miR-146b-5p targets modulating VSMC phenotypes will be further identified. Our study will help to understand the role of VSMCs in the pathology of vascular diseases.     

Transgenic mice expressing mutant Notch3 develop vascular alterations characteristic of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an increasingly recognized adult-onset autosomal dominant vascular dementia, caused by highly stereotyped mutations in the Notch3 receptor. CADASIL is a widespread angiopathy characterized by a degeneration of vascular smooth muscle cells (VSMCs) and the abnormal accumulation of electron-dense granular material called GOM and Notch3 protein, because of an impaired clearance. Evidence that VSMCs are the primary target of the pathogenic process is supported by the restricted expression of Notch3 in these cells but mechanisms of their degeneration remain essentially unknown. We generated transgenic mice in which the SM22alpha promoter drove, in VSMCs, the expression of a full-length human Notch3 carrying the Arg90Cys mutation, a CADASIL archetypal mutation. Transgenic mice showed no evidence of prominent brain parenchyma damage but demonstrated the two hallmarks of the CADASIL angiopathy, GOM deposits and Notch3 accumulation, within both the cerebral and peripheral arteries. Of interest, arteries of the tail were more severely affected with prominent signs of VSMC degeneration. Time-course analysis of vessel changes revealed that disruption of normal VSMC anchorage to adjacent extracellular matrix and cells, VSMC cytoskeleton changes as well as starting signs of VSMC degeneration, which were detected around 10 months of age, preceded Notch3 and GOM accumulation appearance, which were observed only by 14 to 16 months of age. In conclusion, we have generated transgenic mice that recapitulate the characteristic vascular lesions observed in CADASIL. Our results indicate that Notch3 or GOM accumulation are unlikely to be the prerequisites for the induction of VSMC degeneration and suggest that degeneration of VSMCs may rather be triggered by the disruption of their normal anchorage, based on the important role of adhesion for cell survival.     

miR-145对血管平滑肌细胞生物活性及SM22α mRNA表达的作用*

目的：探究miR-145 对血管平滑肌细胞（VSMC）的生物活性及对SM22α mRNA 表达的作用。方法： VSMC分为3 组,增殖VSMC组（ 增殖组）、增殖VSMC + 转染miR-145-NC 组（ 空载体组）、增殖VSMC+转染 miR-145 组（ 增殖转染组）。采用RT-PCR 检测VSMC中SM22α mRNA、miR-145 的表达;免疫印迹检测cyclin E、p27 蛋白水平;Transwell 小室检测VSMC侵袭能力;MTT检测VSMC活力;流式细胞术检测VSMC凋亡率。 结果：增殖组VSMC中SM22α mRNA、miR-145 水平与空载体组相比数值较为接近;与增殖组及空载体组相比, 增殖转染组VSMC中miR-145、SM22α mRNA 表达升高。增殖组VSMC中cyclin E、p27 蛋白水平与空载体组相 比无差异;增殖转染组cyclin E 蛋白水平低于空载体组、增殖组,p27 蛋白水平高于空载体组、增殖组。增殖组 VSMC迁移数量与空载体组相比无差异;增殖转染组VSMC迁移数量明显低于空载体组、增殖组。增殖组与空载 体组VSMC在不同时间点的OD 值均较为接近;增殖转染组OD 值在不同时间点均低于空载体组、增殖组。增殖 组VSMC凋亡率与空载体组数值接近,组间比较差距较小;增殖转染组VSMC凋亡率较空载体组和增殖组升高。 结论：过表达miR-145 通过促进SM22α 水平增加,抑制血管平滑肌细胞的增殖,并促进其凋亡。     

Platelet‐derived growth factor receptors expressed in response to injury of differentiated vascular smooth muscle in vitro: effects on Ca2+ and growth signals

Vascular smooth muscle cells (VSMCs) in the intact vascular wall are differentiated for contraction, whereas the response to vascular injury involves transition towards a synthetic phenotype, with increased tendency for proliferation. Platelet‐derived growth factor (PDGF) is thought to be important for this process. We investigated expression and functional coupling of PDGF receptors (PDGFRs) α and β in rat tail arterial rings kept in organ culture, in order to capture early events in the phenotypic transition. In freshly dissected rings no PDGFR immunoreactivity was found in medial VSMCs, whereas PDGFR α was detected in nerve fibres. After organ culture for 1–4 days PDGFR α and β as well as phospholipase Cγ2 (PLCγ2), known to couple to PDGFR, were expressed in VSMCs within 100 μm of the cut ends. Calponin, a marker for the contractile phenotype, was decreased near the injured area, suggesting that cells were in transition towards synthetic phenotype. In these cells, which showed functional Ca²⁺‐release from the sarcoplasmic reticulum, PDGF‐AB (100 ng mL^–1) had no effect on [Ca²⁺]_i, whereas cultured VSMCs obtained from explants of rat tail arterial rings responded to PDGF‐AB with an increase in [Ca²⁺]_i. However, PDGFR within the cultured rings coupled to growth signalling pathways, as PDGF‐AB caused a tyrphostin AG1295‐sensitive activation of extracellular signal‐regulated kinases 1 and 2 and of [³H]‐thymidine incorporation. Thus, early expression of PDGFR in VSMC adjacent to sites of vascular injury coincides with signs of dedifferentiation. These receptors couple to growth signalling, but do not activate intracellular Ca²⁺ release.     

生理性周期性张应变通过激活AMPK磷酸化抑制血管平滑肌细胞迁移

目的 探讨细胞能量代谢的关键调节因子 AMP激活的蛋白激酶AMPK在血管平滑肌细胞（vascular smooth muscle cells, VSMCs）响应生理性周期性张应变力学刺激后对VSMCs迁移的影响。方法 采用 Flexcell-5000T体外细胞张应变加载系统,对大鼠原代培养的 VSMCs 施加10%幅度、1.25 Hz 频率的周期性张应变,模拟VSMCs在体内的生理性力学环境;以未加载周期性张应变的静态细胞为对照组,Western blotting 检测 VSMCs的 p-AMPK蛋白表达;划痕实验检测 VSMCs 迁移功能。结果 与静态组的细胞相比,生理性周期性张应变加载24 h后显著减少划痕愈合面积,提示生理性周期性张应变抑制VSMCs迁移;生理性周期性张应变加载3 h后,VSMCs的p-AMPK蛋白表达显著升高,而加载24 h后p-AMPK蛋白表达显著降低。在生理性周期性张应变加载条件下,孵育AMPK抑制剂可以在张应变加载3 h后显著降低 p-AMPK蛋白表达,而在张应变加载24 h后显著促进VSMCs迁移;在静态条件下孵育AMPK激活剂 AICAR 3 h后显著诱导p-AMPK蛋白表达,孵育24 h后显著抑制VSMCs迁移;提示p-AMPK蛋白表达参与调控VSMCs迁移。结论 生理性周期性张应变能通过激活p-AMPK蛋白表达,进而抑制VSMCs迁移,提示生理性周期性张应变调控VSMCs迁移对维持血管稳态具有重要意义。