Endothelial cells inhibit flow-induced smooth muscle cell migration: role of plasminogen activator inhibitor-1

A Review of Functional Analysis of Endothelial Cells in Flow Chambers

The vascular endothelial cells constitute the innermost layer. The cells are exposed to mechanical stress by the flow, causing them to express their functions. To elucidate the functions, methods involving seeding endothelial cells as a layer in a chamber were studied. The chambers are known as parallel plate, T-chamber, step, cone plate, and stretch. The stimulated functions or signals from endothelial cells by flows are extensively connected to other outer layers of arteries or organs. The coculture layer was developed in a chamber to investigate the interaction between smooth muscle cells in the middle layer of the blood vessel wall in vascular physiology and pathology. Additionally, the microfabrication technology used to create a chamber for a microfluidic device involves both mechanical and chemical stimulation of cells to show their dynamics in in vivo microenvironments. The purpose of this study is to summarize the blood flow (flow inducing) for the functions connecting to endothelial cells and blood vessels, and to find directions for future chamber and device developments for further understanding and application of vascular functions. The relationship between chamber design flow, cell layers, and microfluidics was studied.

Effects of Puerarin on the Prevention and Treatment of Cardiovascular Diseases

Puerarin, an isoflavone glycoside derived from Pueraria lobata (Willd.) Ohwi, has been identified as a pharmacologically active component with diverse benefits. A large number of experimental and clinical studies have demonstrated that puerarin is widely used in the treatment of a variety of diseases. Among them, cardiovascular diseases (CVDs) are the leading cause of death in the world, and therefore remain one of the most prominent global public health concerns. In this review, we systematically analyze the preclinical investigations of puerarin in CVDs, such as atherosclerosis, cardiac hypertrophy, heart failure, diabetic cardiovascular complications, myocardial infarction, stroke and hypertension. In addition, the potential molecular targets of puerarin are also discussed. Furthermore, we summarize the clinical trails of puerarin in the treatment of CVDs. Finally, the therapeutic effects of puerarin derivatives and its drug delivery systems are overviewed.

Developmental mechanisms regulating the formation of smooth muscle layers in the mouse uterus†

Uterine smooth muscle cells differentiate from mesenchymal cells, and gap junctions connect the muscle cells in the myometrium. At the neonatal stage, a uterine smooth muscle layer is situated away from the epithelium when smooth muscle cells are grafted near the epithelium, suggesting that the epithelium plays an important role in differentiation, proliferation, and/or migration of smooth muscle cells. In this study, developmental mechanisms regulating the formation of the smooth muscle layers in the mouse uterus were analyzed using an in vitro culture model. Differentiation of smooth muscle cells occurs at a neonatal stage because ACTA2 gene expression was increased at the outer layer, and GJA1 was not expressed in cellular membranes of uterine smooth muscle cells by postnatal day 15. To analyze the effects of the epithelium on the differentiation of smooth muscle cells, a bulk uterine mesenchymal cell line was established from p53−/− mice at postnatal day 3 (P3US cells). Co-culture with Müllerian ductal epithelial cells (E1 cells) induced repulsive migration of ACTA2-positive cells among bulk P3US cells from E1 cells, but it had no effects on the migration of any of 100% ACTA2-positive or negative smooth muscle cell lines cloned from P3US cells. Thus, uterine epithelial cells indirectly affected the repulsive migration of smooth muscle cells via mesenchymal cells. Conditioned medium by E1 cells inhibited differentiation into smooth muscle cells of clonal cells established from P3US cells. Therefore, the uterine epithelium inhibits the differentiation of stem-like progenitor mesenchymal cells adjacent to the epithelium into smooth muscle cells.

Effects of Caveolin-1-ERK1/2 pathway on endothelial cells and smooth muscle cells under shear stress

Hemodynamic forces have an important role in venous intimal hyperplasia, which is the main cause of arteriovenous fistula dysfunction. Endothelial cells (ECs) constantly exposed to the shear stress of blood flow, converted the mechanical stimuli into intracellular signals, and interacted with the underlying vascular smooth muscle cells (VSMCs). Caveolin-1 is one of the important mechanoreceptors on cytomembrane, which is related to vascular abnormalities. Extracellular signal-regulated kinase1/2 (ERK1/2) pathway is involved in the process of VSMCs proliferation and migration. In the present study, we explore the effects of Caveolin-1-ERK1/2 pathway and uremia toxins on the endothelial cells and VSMCs following shear stress application. Different shear stress was simulated with a ECs/VSMCs cocultured parallel-plate flow chamber system. Low shear stress and oscillating shear stress up-regulated the expression of fibroblast growth factor-4, platelet-derived growth factor-BB, vascular endothelial growth factor-A, ERK1/2 phosphorylation in endothelial cells, and proliferation and migration of VSMCs but down-regulated the Caveolin-1 expression in endothelial cells. Uremia toxin induces the proliferation and migration of VSMCs but not in a Caveolin-1-dependent manner in the static environment. Low shear stress-induced proliferation and migration of VSMCs is inhibited by Caveolin-1 overexpression and ERK1/2 suppression. Shear stress-regulated VSMC proliferation and migration is an endothelial cells-dependent process. Low shear stress and oscillating shear stress exert atherosclerotic influences on endothelial cells and VSMCs. Low shear stress modulated proliferation and migration of VSMCs through Caveolin-1-ERK1/2 pathway, which suggested that Caveolin-1 and ERK1/2 can be used as a new therapeutic target for the treatment of arteriovenous fistula dysfunction.

Impact statement

Venous intimal hyperplasia is the leading cause of arteriovenous fistula (AVF) dysfunction. This article reports that shear stress-regulated vascular smooth muscle cells (VSMCs) proliferation and migration is an endothelial cell (EC)-dependent process. Low shear stress (LSS) and oscillating shear stress (OSS) exert atherosclerotic influences on the ECs and VSMCs. LSS-induced proliferation and migration of VSMCs is inhibited by Caveolin-1 overexpression and extracellular signal-regulated kinase1/2 (ERK1/2) suppression, which suggested that Caveolin-1 and ERK1/2 can be used as a new therapeutic target for the treatment of AVF dysfunction.

Monoether-Tagged Biodegradable Polycarbonate Preventing Platelet Adhesion and Demonstrating Vascular Cell Adhesion: A Promising Material for Resorbable Vascular Grafts and Stents

We developed a biodegradable polycarbonate that demonstrates antithrombogenicity and vascular cell adhesion via organocatalytic ring-opening polymerization of a trimethylene carbonate (TMC) analogue bearing a methoxy group. The monoether-tagged polycarbonate demonstrates a platelet adhesion property that is 93 and 89% lower than those of poly(ethylene terephthalate) and polyTMC, respectively. In contrast, vascular cell adhesion properties of the polycarbonate are comparable to those controls, indicating a potential for selective cell adhesion properties. This difference in the cell adhesion property is well associated with surface hydration, which affects protein adsorption and denaturation. Fibrinogen is slightly denatured on the monoether-tagged polycarbonate, whereas fibronectin is highly activated to expose the RGD motif for favorable vascular cell adhesion. The surface hydration, mainly induced by the methoxy side chain, also contributes to slowing the enzymatic degradation. Consequently, the polycarbonate exhibits decent blood compatibility, vascular cell adhesion properties, and biodegradability, which is promising for applications in resorbable vascular grafts and stents.

Nicotine facilitates VSMC dysfunction through a miR-200b/RhoGDIA/cytoskeleton module

Nicotine can induce the abnormal migration and proliferation of vascular smooth muscle cells (VSMCs). We have previously shown that cytoskeletal proteins and RhoGDIA, a negative regulator of the Rho GTPase pathway, are involved in the nicotine-induced dysfunction of VSMCs. Here, we found that nicotine can activate the Rho GTPase pathway and induce the synthesis of the cytoskeletal proteins in VSMCs through the activation of intracellular downstream signaling pathways, including targets such as MYPT1, PAK1 and PI3K/AKT. Upon nicotine treatment, the mRNA level of RhoGDIA is increased but protein level is decreased both in vitro and in vivo, which suggested a mechanism of post-translational regulation. By the dual luciferase reporter assay, we identified the microRNA-200b (miR-200b) as a modulator of the behavioural changes of VSMCs in response to nicotine through targeting RhoGDIA directly. Introducing miR-200b inhibitors into cultured VSMCs significantly attenuated cell proliferation and migration. Additionally, we found that hypomethylation in the CpG island shore region of miR-200b was responsible for the nicotine-induced miR-200b up-regulation in VSMCs. The study demonstrates that nicotine facilitates VSMC dysfunction through a miR-200b/RhoGDIA/cytoskeleton module through the hypomethylation of miR-200b promoter and suggests that epigenetic modifications may play an important role in the pathological progression.

Randomized Comparison of the Crush Versus the Culotte Stenting for Coronary Artery Bifurcation Lesions

Background:

The crush and the culotte stenting were both reported to be effective for complex bifurcation lesion treatment. However, their comparative performance remains elusive.

Methods:

A total of 300 patients with coronary bifurcation lesions were randomly assigned to crush (n = 150) and culotte (n = 150) treatment. The primary endpoint was the occurrence of major adverse cardiac events (MACEs) at 12 months including cardiac death, myocardial infarction, stent thrombosis, and target vessel revascularization. Index lesion restenosis at 12 months was a secondary endpoint. The surface integrals of time-averaged wall shear stress at bifurcation sites were also be quantified.

Results:

There were no significant differences in MACE rates between the two groups at 12-month follow-up: Crush 6.7%, culotte 5.3% (P = 0.48). The rates of index lesion restenosis were 12.7% versus 6.0% (P = 0.047) in the crush and the culotte groups, respectively. At 12-month follow-up, the surface integrals of time-averaged wall shear stress at bifurcation sites in the crush group were significantly lower than the culotte group ([5.01 ± 0.95] × 10⁻⁴ Newton and [6.08 ± 1.16] × 10⁻⁴ Newton, respectively; P = 0.003).

Conclusions:

Both the crush and the culotte bifurcation stenting techniques showed satisfying clinical and angiographic results at 12-month follow-up. Bifurcation lesions treated with the culotte technique tended to have lower restenosis rates and more favorable flow patterns.

Attenuation of Neointimal Vascular Smooth Muscle Cellularity in Atheroma by Plasminogen Activator Inhibitor Type 1 (PAI-1)

Rupture of vulnerable atheroma often underlies acute coronary syndromes. Vulnerable plaques exhibit a paucity of vascular smooth muscle cells (VSMCs) in the cap. Therefore, decreased VSMC migration into the neointima may predispose to vulnerability. The balance between cell surface plasminogen activator activity and its inhibition [mediated primarily by plasminogen activator inhibitor type 1 (PAI-1)] modulates migration of diverse types of cells. We sought to determine whether increased expression of PAI-1 would decrease migration of VSMCs in vitro and neointimal cellularity in vivo in apolipo-protein E knockout (ApoE−-/–) mice fed a high-fat diet. Increased vessel wall expression of PAI-1 in transgenic mice was induced with the SM22α promoter. VSMC migration through Matrigel in vitro was quantified with laser scanning cytometry. Expression of PAI-1 was increased threefold in the aortic wall of SM22-PAI transgene-positive mice. Neointimal cellularity of vascular lesions was decreased by 26% ( p=0.01; n=5 each) in ApoE−-/– mice with the SM22-PAI transgene compared with ApoE−-/– mice. VSMCs explanted from transgene-positive mice exhibited twofold greater expression of PAI-1 and their migration was attenuated by 27% ( p=0.03). Accordingly, increased expression of PAI-1 protein by VSMCs reduces their migration in vitro and their contribution to neointimal cellularity in vivo.

Tubular Compressed Collagen Scaffolds for Ureteral Tissue Engineering in a Flow Bioreactor System

Ureteral replacement by tissue engineering might become necessary following tissue loss after excessive ureteral trauma, after retroperitoneal cancer, or even after failed reconstructive surgery. This need has driven innovation in the design of novel scaffolds and specific cell culture techniques for urinary tract reconstruction. In this study, compressed tubular collagen scaffolds were evaluated, addressing the physical and biological characterization of acellular and cellular collagen tubes in a new flow bioreactor system, imitating the physiological pressure, peristalsis, and flow conditions of the human ureter. Collagen tubes, containing primary human smooth muscle and urothelial cells, were evaluated regarding their change in gene and protein expression under dynamic culture conditions. A maximum intraluminal pressure of 22.43 ± 0.2 cm H2O was observed in acellular tubes, resulting in a mean wall shear stress of 4 dynes/cm(2) in the tubular constructs. Dynamic conditions directed the differentiation of both cell types into their mature forms. This was confirmed by their gene expression of smooth muscle alpha-actin, smoothelin, collagen type I and III, elastin, laminin type 1 and 5, cytokeratin 8, and uroplakin 2. In addition, smooth muscle cell alignment predominantly perpendicular to the flow direction was observed, comparable to the cell orientation in native ureteral tissue. These results revealed that coculturing human smooth muscle and urothelial cells in compressed collagen tubes under human ureteral flow-mimicking conditions could lead to cell-engineered biomaterials that might ultimately be translated into clinical applications.

Vitronectin-binding PAI-1 protects against the development of cardiac fibrosis through interaction with fibroblasts

Plasminogen activator inhibitor-1 (PAI-1) promotes or abates fibrotic processes occurring in different organs. Binding of PAI-1 to vitronectin, an extracellular matrix component, may inhibit vitronectin-integrin complex-mediated cellular responses in pathophysiological conditions. To investigate the importance of plasmin suppression vs vitronectin-binding pathways of PAI-1 in cardiac fibrosis, we studied uninephrectomized mice fed a high salt diet and infused with angiotensin II (Ang II) together with different PAI-1 variants, including PAI-1AK (AK) that inhibits plasminogen activators but does not bind vitronectin, PAI-1RR (RR) that binds vitronectin but does not have protease inhibitory effects or control PAI-1 (CPAI), the control mutant that has similar molecular backbone and half-life as AK and RR while retaining all functions of native PAI-1. Compared with RR and CPAI, non-vitronectin-binding AK significantly increased expression of cardiac fibroblast marker, periostin (Ang+AK 8.40±3.55 vs Ang+RR 2.23±0.44 and Ang+CPAI 2.33±0.12% positive area, both P<0.05) and cardiac fibrosis (Ang+AK 1.79±0.26% vs Ang+RR 0.91±0.18% and Ang+CPAI 0.81±0.12% fibrotic area, both P<0.05), as well as Col1 mRNA (Ang+AK 12.81±1.84 vs Ang+RR 4.04±1.06 and Ang+CPAI 5.23±1.21 fold increase, both P<0.05). To elucidate mechanisms underlying the protective effects of vitronectin-binding PAI-1 against fibrosis, fibroblasts from normal adult human ventricles were stimulated with Ang and different PAI-1 variants. Protease inhibitory AK and CPAI increased supernatant fibronectin, while decreasing plasminogen activator/plasmin activities and matrix metalloproteinase. RR and CPAI variants significantly reduced fibroblast expression of integrin β3, vitronectin level in the supernatant and fibroblast adhesion to vitronectin compared with the non-vitronectin-binding AK. Further, RR and CPAI preserved apoptotic, decreased anti-apoptotic and proliferative activities in fibroblasts. Thus, PAI-1 promotes or protects against development of cardiac fibrosis differentially through the protease inhibitory pathway or through its binding to vitronectin.

Endothelial function and germ-line ACE I/D, eNOS and PAI-1 gene profiles in patients with coronary slow flow in the Canakkale population: multiple thrombophilic gene profiles in coronary slow flow

Background

We examined the effects of ACE, PAI-1 and eNOS gene polymorphisms on endothelial function. The genes are related to atherosclerosis and endothelial dysfunction in coronary slow flow (CSF).

Methods

Thirty-three patients with angiographically proven CSF and 48 subjects with normal coronary flow were enrolled in this study. Coronary flow patterns were determined by the thrombolysis in myocardial infarction (TIMI) frame count method. Endothelial function was assessed in the brachial artery by endothelium-dependent flow-mediated dilatation (FMD). PAI-1 4G/5G, eNOS T-786C and ACE I/D polymorphisms were determined by polymerase chain reaction (PCR) amplification.

Results

No difference was found between the groups regarding age, heart rate and blood pressure. Males were more prevalent among patients with CSF than control subjects (58.8 vs 29.8%, p = 0.009). Mean TIMI frame counts were significantly higher in CSF patients (24.2 ± 4.0 vs 13.1 ± 2.5 fpm, p = 0.001). FMD was significantly lower in CSF patients than in the controls (4.9 ± 6.6 vs 7.9 ± 5.6%, p = 0.029). TIMI frame count and FMD were found to be negatively correlated in a correlation analysis (r = –0.269, p = 0.015). PAI-1 4G/5G, eNOS T-786C and ACE I/D polymorphisms were similar in the two groups.

Conclusions

This study showed that endothelial function was impaired in patients with CSF. PAI-1, ACE and eNOS polymorphisms were not related to CSF in our study population.

Fluid Mechanics, Arterial Disease, and Gene Expression

This review places modern research developments in vascular mechanobiology in the context of hemodynamic phenomena in the cardiovascular system and the discrete localization of vascular disease. The modern origins of this field are traced, beginning in the 1960s when associations between flow characteristics, particularly blood flow-induced wall shear stress, and the localization of atherosclerotic plaques were uncovered, and continuing to fluid shear stress effects on the vascular lining endothelial) cells (ECs), including their effects on EC morphology, biochemical production, and gene expression. The earliest single-gene studies and genome-wide analyses are considered. The final section moves from the ECs lining the vessel wall to the smooth muscle cells and fibroblasts within the wall that are fluid me chanically activated by interstitial flow that imposes shear stresses on their surfaces comparable with those of flowing blood on EC surfaces. Interstitial flow stimulates biochemical production and gene expression, much like blood flow on ECs.

Biomechanical regulation of vascular smooth muscle cell functions: from in vitro to in vivo understanding

Vascular smooth muscle cells (VSMCs) have critical functions in vascular diseases. Haemodynamic factors are important regulators of VSMC functions in vascular pathophysiology. VSMCs are physiologically active in the three-dimensional matrix and interact with the shear stress sensor of endothelial cells (ECs). The purpose of this review is to illustrate how haemodynamic factors regulate VSMC functions under two-dimensional conditions in vitro or three-dimensional co-culture conditions in vivo. Recent advances show that high shear stress induces VSMC apoptosis through endothelial-released nitric oxide and low shear stress upregulates VSMC proliferation and migration through platelet-derived growth factor released by ECs. This differential regulation emphasizes the need to construct more actual environments for future research on vascular diseases (such as atherosclerosis and hypertension) and cardiovascular tissue engineering.

MicroRNA 329 suppresses angiogenesis by targeting CD146

CD146, an endothelial biomarker, has been shown to be aberrantly upregulated during pathological angiogenesis and functions as a coreceptor for vascular endothelial growth factor receptor 2 (VEGFR-2) to promote disease progression. However, the regulatory mechanisms of CD146 expression during angiogenesis remain unclear. Using a microRNA screening approach, we identified a novel negative regulator of angiogenesis, microRNA 329 (miR-329), that directly targeted CD146 and inhibited CD146-mediated angiogenesis in vitro and in vivo. Endogenous miR-329 expression was downregulated by VEGF and tumor necrosis factor alpha (TNF-α), resulting in the elevation of CD146 in endothelial cells. Upregulation of CD146 facilitated an endothelial response to VEGF-induced SRC kinase family (SKF)/p38 mitogen-activated protein kinase (MAPK)/NF-κB activation and consequently promoted endothelial cell migration and tube formation. Our animal experiments showed that treatment with miR-329 repressed excessive CD146 expression on blood vessels and significantly attenuated neovascularization in a mouse model of pathological angiogenesis. Our findings provide the first evidence that CD146 expression in angiogenesis is regulated by miR-329 and suggest that miR-329 could present a potential therapeutic tool for the treatment of angiogenic diseases.

Plasminogen activator inhibitor-1 inhibitors: a patent review (2006-present)

INTRODUCTION

Plasminogen activator inhibitor-1 (PAI-1), the serine protease inhibitor (serpin), binds to and inhibits the plasminogen activators-tissue-type plasminogen activator (tPA) and the urokinase-type plasminogen activator (uPA). This results in both a decrease in plasmin production and a decrease in the dissolution of fibrin clots. Elevated levels of PAI-1 are correlated with an increased risk for cardiovascular disease and have been linked to obesity and metabolic syndrome. Consequently, the pharmacological suppression of PAI-1 might prevent or treat vascular disease.

AREAS COVERED

This article provides an overview of the patenting activity on PAI-1 inhibitors. Patents filed by pharmaceutical companies or individual research groups are described, and the biological and biochemical evaluation of the inhibitors, including in vitro and in vivo studies, is discussed. An overview of patents pertaining to using these inhibitors for treating various diseases is also included.

EXPERT OPINION

Although there is still no PAI-1 inhibitor being evaluated in a clinical setting or approved for human therapy, research in this field has progressed, and promising new compounds have been designed. Most research has focused on improving the pharmacological profile of these compounds, which will hopefully allow them to proceed to clinical studies. Despite the need for further testing and research, the potential use of PAI-1 inhibitors for treating cardiovascular disease appears quite promising.

CD146 is a coreceptor for VEGFR-2 in tumor angiogenesis

CD146 is a novel endothelial biomarker and plays an essential role in angiogenesis; however, its role in the molecular mechanism underlying angiogenesis remains poorly understood. In the present study, we show that CD146 interacts directly with VEGFR-2 on endothelial cells and at the molecular level and identify the structural basis of CD146 binding to VEGFR-2. In addition, we show that CD146 is required in VEGF-induced VEGFR-2 phosphorylation, AKT/p38 MAPKs/NF-κB activation, and thus promotion of endothelial cell migration and microvascular formation. Furthermore, we show that anti-CD146 AA98 or CD146 siRNA abrogates all VEGFR-2 activation induced by VEGF. An in vivo angiogenesis assay showed that VEGF-promoted microvascular formation was impaired in the endothelial conditional knockout of CD146 (CD146EC-KO). Our animal experiments demonstrated that anti-CD146 (AA98) and anti-VEGF (bevacizumab) have an additive inhibitory effect on xenografted human pancreatic and melanoma tumors. The results of the present study suggest that CD146 is a new coreceptor for VEGFR-2 and is therefore a promising target for blocking tumor-related angiogenesis.

Role of endothelial shear stress in stent restenosis and thrombosis: pathophysiologic mechanisms and implications for clinical translation

Restenosis and thrombosis are potentially fatal complications of coronary stenting with a recognized multifactorial etiology. The effect of documented risk factors, however, cannot explain the preponderance of certain lesion types, stent designs, and implantation configurations for the development of these complications. Local hemodynamic factors, low endothelial shear stress (ESS) in particular, are long known to critically affect the natural history of atherosclerosis. Increasing evidence now suggests that ESS may also contribute to the development of restenosis and thrombosis upon stenting of atherosclerotic plaques, in conjunction with well-appreciated risk factors. In this review, we present in vivo and mechanistic evidence associating ESS with the localization and progression of neointimal hyperplasia and in-stent clotting. Clinical studies have associated stent design features with the risk of restenosis. Importantly, computational simulations extend these observations by directly linking specific stent geometry and positioning characteristics with the post-stenting hemodynamic milieu and with the stent's thrombogenicity and pro-restenotic potential, thereby indicating ways to clinical translation. An enhanced understanding of the pathophysiologic role of ESS in restenosis and thrombosis might dictate hemodynamically favorable stent designs and deployment configurations to reduce the potential for late lumen loss and thrombotic obstruction. Recent methodologies for in vivo ESS profiling at a clinical level might allow for early identification of patients at high risk for the development of restenosis or thrombosis and might thereby guide individualized, risk-tailored treatment strategies to prevent devastating complications of endovascular interventions.

Fluid flow mechanotransduction in vascular smooth muscle cells and fibroblasts

Understanding how vascular wall endothelial cells (ECs), smooth muscle cells (SMCs), and fibroblasts (FBs) sense and transduce the stimuli of hemodynamic forces (shear stress, cyclic strain, and hydrostatic pressure) into intracellular biochemical signals is critical to prevent vascular disease development and progression. ECs lining the vessel lumen directly sense alterations in blood flow shear stress and then communicate with medial SMCs and adventitial FBs to regulate vessel function and disease. Shear stress mechanotransduction in ECs has been extensively studied and reviewed. In the case of endothelial damage, blood flow shear stress may directly act on the superficial layer of SMCs and transmural interstitial flow may be elevated on medial SMCs and adventitial FBs. Therefore, it is also important to investigate direct shear effects on vascular SMCs as well as FBs. The work published in the last two decades has shown that shear stress and interstitial flow have significant influences on vascular SMCs and FBs. This review summarizes work that considered direct shear effects on SMCs and FBs and provides the first comprehensive overview of the underlying mechanisms that modulate SMC secretion, alignment, contraction, proliferation, apoptosis, differentiation, and migration in response to 2-dimensional (2D) laminar, pulsatile, and oscillating flow shear stresses and 3D interstitial flow. A mechanistic model of flow sensing by SMCs is also provided to elucidate possible mechanotransduction pathways through surface glycocalyx, integrins, membrane receptors, ion channels, and primary cilia. Understanding flow-mediated mechanotransduction in SMCs and FBs and the interplay with ECs should be helpful in exploring strategies to prevent flow-initiated atherosclerosis and neointima formation and has implications in vascular tissue engineering.

NADPH oxidase 4 mediates reactive oxygen species induction of CD146 dimerization in VEGF signal transduction

CD146 dimerization plays an important role in tumor-induced angiogenesis. Stimulation of target cells with vascular endothelial growth factor (VEGF), a major angiogenic factor produced by tumor cells, elicits a burst of reactive oxygen species (ROS) that enhances angiogenesis. However, the molecular mechanism coupling CD146 dimerization with the VEGF-related oxidant-generating apparatus has not been elucidated. Here, we show that CD146 dimerization is induced by VEGF and is significantly diminished by pretreatment with diphenylene iodonium, an inhibitor of NADPH oxidase, suggesting a potential role for NADPH oxidase (NOX) in VEGF-induced CD146 dimerization. Importantly, we found that overexpression of NADPH oxidase 4 (NOX4), which is the predominant NOX expressed in endothelial cells, significantly enhances VEGF-induced ROS generation and CD146 dimerization. By contrast, these VEGF effects were dramatically attenuated after transfection with siRNA to reduce NOX4 expression. Furthermore, expression of Rac1 N17, a dominant negative mutant of Rac1, a member of the Rho family of small GTPases, suppressed VEGF-induced ROS generation and CD146 dimerization. These studies show for the first time that VEGF alteration of CD146 dimerization is mediated via a NOX4-dependent pathway and provide novel insight into the significant role of NOX in redox regulation of the dimerization of cell adhesion molecules.

Lovastatin inhibits gap junctional communication in cultured aortic smooth muscle cells

BACKGROUND

Gap junctions, which serve as intercellular channels that allow the passage of ions and other small molecules between neighboring cells, play an important role in vital functions, including the regulation of cell growth, differentiation, and development. Statins, the 3-hydroxy-3-methylglutaryl-coenzymeA (HMG-CoA) reductase inhibitors, have been shown to inhibit the migration and proliferation of smooth muscle cells (SMCs) leading to an antiproliferative effect. Recent studies have shown that statins can reduce gap junction protein connexin43 (Cx43) expression both in vivo and in vitro. However, little work has been done on the effects of statins on gap junctional intercellular communication (GJIC). We hypothesized in this study that lovastatin inhibits vascular smooth muscle cells (VSMCs) migration through the inhibition of the GJIC.

METHODS

Rat aortic SMCs (RASMCs) were exposed to lovastatin. Vascular smooth muscle cells migration was then assessed with a Transwell migration assay. Gap junctional intercellular communication was determined by using fluorescence recovery after photobleaching (FRAP) analysis, which was performed with a laser-scanning confocal microscope.

RESULTS

The migration of the cultured RASMCs were detected by Transwell system. Cell migration was dose-dependently inhibited with lovastatin. Compared with that in the control (110 ± 26), the number of migrated SMCs was significantly reduced to 72 ± 24 (P < .05), 62 ± 18 (P < .01), and 58 ± 19 (P < .01) at the concentration of 0.4, 2, and 10 umol/L, per field. The rate of fluorescence recovery (R) at 5 minutes after photobleaching was adopted as the functional index of GJIC. The R- value of cells exposed to lovastatin 10 umol/L for 48 hours was 24.38% ± 4.84%, whereas the cells in the control group had an R- value of 36.11% ± 10.53%, demonstrating that the GJIC of RASMCs was significantly inhibited by lovastatin (P < .01). Smaller concentrations of lovastatin 0.08 umol/L did not change gap junction coupling (P > .05).

CONCLUSIONS

These results suggest that lovastatin inhibits migration in a dose-dependent manner by attenuating JIC. Suppression of gap junction function could add another explanation of statin-induced antiproliferative effect.

Normal shear stress and vascular smooth muscle cells modulate migration of endothelial cells through histone deacetylase 6 activation and tubulin acetylation

Endothelial cells (ECs) line the innermost of the blood vessel wall and are constantly subjected to shear stress imposed by blood flow. ECs were also influenced by the neighboring vascular smooth muscle cells (VSMCs). The bidirectional communication between ECs and VSMCs modulates vascular homeostasis. In this study, the involvement of histone deacetylase 6 (HDAC6) in modulating migration of ECs co-cultured with VSMCs by the normal level of laminar shear stress (NSS) was investigated. ECs was either cultured alone or co-cultured with VSMCs under static conditions or subjected to NSS of 15 dyne/cm2 by using a parallel-plate co-culture flow chamber system. It was demonstrated that both NSS and VSMCs could increase EC migration. The migration level of ECs co-cultured with VSMCs under NSS was not higher than that under the static condition. The process of EC migration regulated by VSMCs and NSS was associated with the increased expression of HDAC6 and low level of acetylated tubulin. The increase in HDAC6 expression was accompanied by a time-dependent decrease in the acetylation of tubulin in ECs co-cultured with VSMCs. Inhibition of the HDAC6 by siRNA or tributyrin, an inhibitor of HDACs, induced a parallel alteration in the migration and the acetylated tubulin of ECs co-cultured with VSMCs. It was observed by immunofluorescence staining that the acetylated tubulin was distributed mostly around the cell nucleus in ECs co-cultured with VSMCs. The results suggest that the NSS may display a protective function on the vascular homeostasis by modulating EC migration to a normal level in a VSMC-dependent manner. This modulation process involves the down-regulation of acetylated tubulin which results from increased HDAC6 activity in ECs.

Shear stress and plaque development

Although traditional cardiovascular risk factors 'prime the soil' for atherogenesis systemically, atherosclerosis primarily occurs in a site-specific manner with a predilection towards the inner wall of curvatures and outer wall of bifurcations with sparing of flow-dividers. Wall shear stress is a frictional force exerted parallel to the vessel wall that leads to alteration of the endothelial phenotype, endothelial cell signaling, gene and protein expression leading to a proinflammatory phenotype, reduced nitric oxide availability and disruption of the extracellular matrix, which in turn leads to plaque development. Clinical and experimental data are emerging that suggest the pathobiology associated with abnormal wall shear stress results in atherosclerotic plaque development and progression.

Comparison of artery organ culture and co-culture models for studying endothelial cell migration and its effect on smooth muscle cell proliferation and migration

Arterial restenosis associated with intimal hyperplasia is the major cause of long-term failure of vascular interventions. Endothelium injury and the proliferation and migration of smooth muscle cells (SMC) are key events in the development of intimal hyperplasia. The objectives of this study were to develop an ex vivo artery injury model for studying endothelial cell (EC) migration and to compare it with an in vitro co-culture arterial wall injury model in terms of the effect of flow on EC migration and its effect on SMC migration and proliferation. Our results demonstrated that shear flow improves reendothelialization in the injured area by promoting EC migration. The migration distance of ECs is much smaller in the arteries than in an in vitro cell culture model (3.57+/-1.29 mm vs. 5.2+/-1.4 cm, p<0.001). SMC proliferation was significantly less in the EC intact and reendothelialization areas than in the EC denuded areas indicating that reendothelialization suppresses SMC proliferation. Our models provide a new approach to study techniques to enhance endothelium healing.

Antimetastatic potential of PAI-1-specific RNA aptamers

The serine protease inhibitor plasminogen activator inhibitor-1 (PAI-1) is increased in several cancers, including breast, where it is associated with a poor outcome. Metastatic breast cancer has a dismal prognosis, as evidenced by treatment goals that are no longer curative but are largely palliative in nature. PAI-1 competes with integrins and the urokinase plasminogen activator receptor on the surface of breast cancer cells for binding to vitronectin. This results in the detachment of tumor cells from the extracellular matrix, which is critical to the metastatic process. For this reason, we sought to isolate RNA aptamers that disrupt the interaction between PAI-1 and vitronectin. Through utilization of combinatorial chemistry techniques, aptamers have been selected that bind to PAI-1 with high affinity and specificity. We identified two aptamers, WT-15 and SM-20, that disrupt the interactions between PAI-1 and heparin, as well as PAI-1 and vitronectin, without affecting the antiprotease activity of PAI-1. Furthermore, SM-20 prevented the detachment of breast cancer cells (MDA-MB-231) from vitronectin in the presence of PAI-1, resulting in an increase in cellular adhesion. Therefore, the PAI-1 aptamer SM-20 demonstrates therapeutic potential as an antimetastatic agent and could possibly be used as an adjuvant to traditional chemotherapy for breast cancer.

PAI-1 and kidney fibrosis

Substantial evidence demonstrates a link of increased plasminogen activator inhibitor-1 (PAI-1) and glomerulosclerosis and kidney fibrosis, providing a novel therapeutic option for prevention and treatment of chronic kidney diseases. Several mechanisms contributing to increased PAI-1 will be addressed, including classic key profibrotic factors such as the renin-angiotensin-system (RAS) and transforming growth factor-beta (TGF-b???and novel molecules identified by proteomic analysis, such as thymosin- b4. The fibrotic sequelae caused by increased PAI-1 in kidney depend not only on its classic inhibition of tissue-type and urokinase-type plasminogen activators (tPA and uPA), but also its influence on cell migration.

Acetaldehyde stimulates monocyte adhesion in a P-selectin- and TNFalpha-dependent manner

OBJECTIVE

The aim of this study was to determine the effects of acetaldehyde on various steps of the monocyte recruitment cascade.

METHODS

Human umbilical venous endothelial cells (HUVEC), primary blood monocytes (PBM) and THP-1 monocytes, were treated with acetaldehyde (0.1-0 microM) for 6h. Monocyte adherence experiments were performed using 2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein-acetoxymethylester labeled PBM or (3)H-thymidine labeled THP-1 cells. HUVEC TNFalpha mRNA and protein levels were determined by quantitative real-time PCR and immunoassay, respectively, and HUVEC P-selectin and monocyte CCR2 expression were determined by FACS analysis.

RESULTS

Acetaldehyde dose-dependently increased the number of CCR2 positive THP-1 monocytes, with a maximal increase of approximately 50% observed in the presence of 10 microM acetaldehyde. There was a significant increase in both the number of P-selectin positive cells and P-selectin receptor density when HUVEC were incubated with acetaldehyde. HUVEC TNFalpha mRNA expression and secretion were enhanced by acetaldehyde. Moreover, acetaldehyde increased THP-1 and PBM adhesion to HUVEC. Inhibition of P-selectin or TNFalpha, using antibodies or siRNA-directed gene knockdown, attenuated acetaldehyde-induced monocyte adhesion. In conclusion, acetaldehyde increased the number of CCR2 positive monocytes and stimulated endothelial cell P-selectin and TNFalpha expression. Moreover, acetaldehyde increased monocyte adhesion to endothelial cells, an effect that was both P-selectin- and TNFalpha-dependent.

CONCLUSION

These effects of acetaldehyde may contribute, in part, to the increase in coronary heart disease that is associated with binge patterns of alcohol consumption.

Ang II-stimulated migration of vascular smooth muscle cells is dependent on LR11 in mice

Medial-to-intimal migration of SMCs is critical to atherosclerotic plaque formation and remodeling of injured arteries. Considerable amounts of the shed soluble form of the LDL receptor relative LR11 (sLR11) produced by intimal SMCs enhance SMC migration in vitro via upregulation of urokinase-type plasminogen activator receptor (uPAR) expression. Here, we show that circulating sLR11 is a novel marker of carotid intima-media thickness (IMT) and that targeted disruption of the LR11 gene greatly reduces intimal thickening of arteries through attenuation of Ang II-induced migration of SMCs. Serum concentrations of sLR11 were positively correlated with IMT in dyslipidemic subjects, and multivariable regression analysis suggested sLR11 levels as an index of IMT, independent of classical atherosclerosis risk factors. In Lr11-/- mice, femoral artery intimal thickness after cuff placement was decreased, and Ang II-stimulated migration and attachment of SMCs from these mice were largely abolished. In isolated murine SMCs, sLR11 caused membrane ruffle formation via activation of focal adhesion kinase/ERK/Rac1 accompanied by complex formation between uPAR and integrin alphavbeta3, a process accelerated by Ang II. Overproduction of sLR11 decreased the sensitivity of Ang II-induced activation pathways to inhibition by an Ang II type 1 receptor blocker in mice. Thus, we demonstrate a requirement for sLR11 in Ang II-induced SMC migration and propose what we believe is a novel role for sLR11 as a biomarker of carotid IMT.

Endothelial injury induces vascular smooth muscle cell proliferation in highly localized regions of a direct contact co-culture system

Though previous studies have indicated a relationship between the proliferation of endothelial cells and vascular smooth muscle cells (VSMCs) in co-culture, the results have been contradictory and the signaling mechanism poorly understood. In this transmembrane co-culture study, VSMCs and endothelial cells were grown to confluence on opposite sides of a microporous membrane to mimic the intima/media border of vessels. The endothelial layer was injured, and then cultured for 3 days, resulting in partial re-endothelialization. VSMC proliferation across from the injured/partially recovered endothelial region was significantly higher than across from the de-endothelialized region (a sevenfold increase) and the uninjured region (a threefold increase). ELISA indicated that PDGF, which was undetectable in uninjured co-culture and homotypic controls, increased after injury and the addition of a piperazinyl-quinazoline carboxamide PDGF receptor inhibitor blocked VSMC proliferation across from the injured/partially recovered region. We conclude that co-culture signaling initiated by endothelial cell injury locally stimulates VSMC proliferation and that this signaling could be mediated by PDGF-BB.

Ethanol stimulates endothelial cell angiogenic activity via a Notch- and angiopoietin-1-dependent pathway

AIMS

Our aims were to determine the effect of alcohol (EtOH) on endothelial angiogenic activity and to delineate the cell signalling mechanisms involved.

METHODS AND RESULTS

Treatment of human umbilical vein endothelial cells (HUVECs) with EtOH (1-100 mM, 24 h) dose-dependently increased their network formation on Matrigel (an index of angiogenesis) with a maximum response (2.5- to 3-fold increase) at 25 mM. Ethanol also stimulated the proliferation (by cell count and proliferating cell nuclear antigen expression) and migration (by scratch wound assay) of HUVECs. In parallel cultures, EtOH stimulated Notch receptor (1 and 4) and Notch target gene (hrt-1, -2, and -3) mRNA and protein expression and enhanced CBF-1/RBP-Jk promoter activity. EtOH also stimulated, at the mRNA and protein level, the expression of angiopoietin-1 (Ang1) and its Tie2 receptor in these cells. Knockdown of Notch 1 or 4 by siRNA or inhibition of Notch-mediated, CBF-1/RBP-Jk-regulated gene expression by the Epstein-Barr virus-encoded protein RPMS-1 inhibited both ethanol-induced Ang1/Tie2 expression in HUVECs and their network formation on Matrigel. Moreover, knockdown of Ang1 or Tie2 by siRNA inhibited ethanol-induced endothelial network formation.

CONCLUSION

These data demonstrate that ethanol, at levels consistent with moderate consumption, enhances endothelial angiogenic activity in vitro by stimulating a novel Notch/CBF-1/RBP-JK-Ang1/Tie2-dependent pathway. These actions of ethanol may be relevant to the cardiovascular effects of alcohol consumption purported by epidemiological studies.

Fat-covered vein graft

Vein graft is widely used in peripheral vascular surgery. Many free flaps and replantation failures are the result of technical problems in performing the anastomoses. A remarkable number of these technical errors are caused by tension or improper placement of the surgical union. Use of a vein graft may prevent tensioning and give us a more accessible repair site. However, the use of a graft not only doubles the repair side, but may also increase the risk of circulatory disturbance. Many technical, mechanical, and histological factors were cited as factors in the formation of thrombus. The use of a vein graft with a fatty tissue cover may prevent many of the potential risk factors.

Effects of reduced cyclic stretch on vascular smooth muscle cell function of pig carotids perfused ex vivo

BACKGROUND

With advancing age arteries stiffen, reducing arterial compliance and leading to the development of systolic hypertension and to a substantial increase in pulse pressure. An augmented pulse pressure can be a predictor of the development of hypertension, which has been linked to several cardiovascular diseases including atherosclerosis, and to pathologies such as diabetes and renal dysfunction. In this study, we tested the hypothesis that reduced wall compliance induces pulse-pressure-mediated changes in arterial wall metabolism and remodeling.

METHODS

Porcine carotid arteries were perfused for 24 h using an ex vivo arterial support system. Control arteries were exposed to a pulse shear stress (6 +/- 3 dynes/cm(2)) combined with a pulse pressure of 80 +/- 10 mm Hg, yielding a physiological cyclic stretch of 4-5%. A reduced compliance group was also studied, in which arteries were wrapped with an external band, thereby decreasing cyclic stretch to levels <1%.

RESULTS

The experimentally reduced compliance caused a decreased contraction capacity induced by norepinephrine(NE), and this was associated with lower levels of alpha-smooth muscle cell-actin (alpha-SMC-actin) and desmin protein expressions. Arteries that were exposed to a reduced cyclic stretch exhibited a higher level of matrix metalloproteinase-2 (MMP-2) expression activity as well as an increase in Ki67 expression, thereby suggesting that matrix degradation and cellular proliferation had been initiated. Furthermore, the expression of plasminogen activator inhibitor-1 (PAI-1) in stiffened arteries was lower than in the control arteries.

CONCLUSIONS

These findings underline the importance of cyclic stretch in the maintenance of a differentiated and fully functional phenotype of vascular SMCs, as well as in the regulation of migratory properties, proliferation, and matrix turnover.

Modulation of glomerulosclerosis

Regardless of the initial injury, the long-term consequence for the patient depends upon the ensuing balance of profibrotic vs reparative modulators activated. The glomerulus has some capacity for repair. Even when sclerosis has developed with accumulation of extracellular matrix, this lesion may be remodeled, with a change in balance between profibrotic and antifibrotic and collagen synthesis vs proteolytic mediators. We will focus here on the interplay between mediators of fibrosis and reparative mechanisms and potential regression of fibrosis. Based on the clinical efficacy of interventions that inhibit angiotensin, we will focus on factors related to the renin-angiotensin system.

Plasminogen activator inhibitor-1 4G4G genotype is associated with myocardial infarction but not with stable coronary artery disease

BACKGROUND

A case control study was conducted to test the hypothesis that plasminogen activator inhibitor type-1 (PAI-1) 4G/5G gene polymorphism confers an increased risk for myocardial infarction (MI) in patients with known coronary atherosclerosis.

METHODS

One hundred fifty-six consecutive patients who presented with acute MI and 111 stable coronary artery disease (SCAD) patients with documented critical coronary artery stenoses were prospectively enrolled. PAI-1 4G/5G gene polymorphism and conventional atherosclerotic risk factors were studied in all patients. PAI-1 4G/5G gene polymorphism was studied in another 281 healthy blood bank donors.

RESULTS

The frequency 4G4G genotype was significantly higher in the MI group as compared to SCAD group (32.7% vs. 15.3%, P = 0.001) while it was not statistically significant between MI and healthy control groups (32.7% vs. 26.0%, P = 0.136). Comparing with healthy controls SCAD group had significantly lower frequency of 4G4G genotype (P = 0.024). In comparison with SCAD group PAI-1 4G/4G genotype, male sex and smoking habits favored to MI in univariate analysis with a P value of less than 0.2. These variables were included in multivariate regression model to estimate the associated risk for MI. PAI-1 4G/4G genotype was the only independent variable (OR 2.67, 95%CI 1.43-4.96, P = 0.002) associated with MI in this regression model. Comparing with healthy control group 4G4G genotype was not associated with MI (OR 1.38, 95%CI 0.90-2.12). However, presence of 4G4G genotype had a protective effect against development of SCAD (OR 0.52, 96%CI 0.29-0.92).

CONCLUSION

Compared to patients with critical coronary stenoses, PAI-1 4G/4G genotype was found to be an independent predictor for development of MI in this population. PAI-1 4G4G genotype have a protective effect against development of high grade stable coronary stenoses.

Role of endothelial shear stress in the natural history of coronary atherosclerosis and vascular remodeling: molecular, cellular, and vascular behavior

Although the entire coronary tree is exposed to the atherogenic effect of the systemic risk factors, atherosclerotic lesions form at specific arterial regions, where low and oscillatory endothelial shear stress (ESS) occur. Low ESS modulates endothelial gene expression through complex mechanoreception and mechanotransduction processes, inducing an atherogenic endothelial phenotype and formation of an early atherosclerotic plaque. Each early plaque exhibits an individual natural history of progression, regression, or stabilization, which is dependent not only on the formation and progression of atherosclerosis but also on the vascular remodeling response. Although the pathophysiologic mechanisms involved in the remodeling of the atherosclerotic wall are incompletely understood, the dynamic interplay between local hemodynamic milieu, low ESS in particular, and the biology of the wall is likely to be important. In this review, we explore the molecular, cellular, and vascular processes supporting the role of low ESS in the natural history of coronary atherosclerosis and vascular remodeling and indicate likely mechanisms concerning the different natural history trajectories of individual coronary lesions. Atherosclerotic plaques associated with excessive expansive remodeling evolve to high-risk plaques, because low ESS conditions persist, thereby promoting continued local lipid accumulation, inflammation, oxidative stress, matrix breakdown, and eventually further plaque progression and excessive expansive remodeling. An enhanced understanding of the pathobiologic processes responsible for atherosclerosis and vascular remodeling might allow for early identification of a high-risk coronary plaque and thereby provide a rationale for innovative diagnostic and/or therapeutic strategies for the management of coronary patients and prevention of acute coronary syndromes.

Adequate design of customized cDNA macroarray for convenient multiple gene expression analysis

To establish a convenient, cost-effective, and reasonably reliable method for monitoring multiple gene expression using customized membrane-based macroarray, we constructed a cDNA macroarray with multiple probes for 13 human vascular endothelial genes and assessed the accuracy of the macroarray measurements. For each gene, two cDNA probes (450-550 bp) were designed from different regions (coding region and 3'-untranslated region [3'-UTR], respectively) on the basis of simple criteria concerning length and sequence specificity and spotted on the macroarray. In addition, unmodified oligonucleotide probes (80 mer) targeted to a unique sequence from the coding region of each gene were spotted on the same macroarray. Using this macroarray, shear stress-induced mRNA expression changes were analyzed in human coronary artery endothelial cells. Comparison of the expression ratios obtained with those measured using quantitative real-time polymerase chain reaction (PCR) as a reference method revealed that cDNA probes designed from a sequence within the coding region provided a highly accurate expression profile, whereas results obtained from oligonucleotide probes showed no correlation with real-time PCR data, which might be caused by inadequate immobilization of oligonucletotide probes on the nylon membrane. In addition, we observed that cDNA probes targeting different regions of a gene yielded different signal intensities. Most cDNA probes designed from a sequence within the coding region showed detectable signals, whereas few cDNA probes designed from 3'-UTR did.

Resveratrol, a Polyphenolic Phytostilbene, Inhibits Endothelial Monocyte Chemotactic Protein-1 Synthesis and Secretion

BACKGROUND/AIMS

Resveratrol is a naturally occurring polyphenol phytoestrogen and one of several constituents of red wine thought to be cardioprotective. We investigated the effect of resveratrol on the expression of the atherogenic chemokine, monocyte chemotactic protein-1 (MCP-1).

METHODS

Human umbilical vein endothelial cells were stimulated with interleukin-1beta (IL-1beta) in the absence or presence of resveratrol. MCP-1 levels were determined by ELISA and MCP-1 mRNA was measured.

RESULTS

Resveratrol (1-100 microM) dose-dependently inhibited IL-1beta-stimulated MCP-1 secretion, with approximately 45% inhibition at 50 microM resveratrol. This was a Gi-protein- and NO-dependent effect. Resveratrol also significantly inhibited MCP-1 gene expression in a Gi-protein-dependent but NO-independent manner. While resveratrol had no effect on MCP-1 mRNA degradation, it inhibited MCP-1 promoter activity and reduced nuclear factor kappaB and activator protein-1 binding activity induced by IL-1beta. Moreover, while hemoxygenase-1 (HO-1) expression was induced by resveratrol in human umbilical vein endothelial cells, neither treatment with the HO-1 inhibitor tin-protoporphyrin IX nor siRNA-directed knockdown of HO-1 had any effect on the inhibition of MCP-1 mRNA or protein secretion by resveratrol.

CONCLUSION

These data demonstrate an inhibitory effect of resveratrol on MCP-1 synthesis and secretion, mediated via distinct signaling pathways. The inhibition of MCP-1 may represent a novel cardioprotective mechanism of resveratrol.

Effect of pharmacologic plasminogen activator inhibitor-1 inhibition on cell motility and tumor angiogenesis

BACKGROUND

Plasminogen activator inhibitor-1 (PAI-1) is integrally involved in tumorigenesis by impacting on both proteolytic activity and cell migration during angiogenesis.

OBJECTIVES

We hypothesized that an orally active small molecule inhibitor of PAI-1 (PAI-039; tiplaxtinin) could affect smooth muscle cell (SMC) attachment and migration in vitro on a vitronectin matrix, and exhibit antiangiogenic activity in vivo.

METHODS

In vitro assays were used to assess the mechanism of inhibition of PAI-1 by PAI-039 using wild-type PAI-1 in the presence or absence of vitronectin and wild-type PAI-1 and specific PAI-1 mutants in SMC adhesion and migration assays. An in vivo tumor angiogenesis model was used to assess the effect of PAI-039 administration on neovascularization in a Matrigel implant.

RESULTS

PAI-039 dose-dependently inhibited soluble, but not vitronectin-bound, PAI-1. Cell adhesion assays using PAI-1 mutants unable to bind vitronectin (PAI-1K) or inactivate proteases (PAI-1R) further suggested that PAI-039 inactivated PAI-1 by binding near its vitronectin domain. In a tumor angiogenesis model, PAI-039 treatment of wild-type mice dose-dependently decreased hemoglobin concentration and endothelial cell staining within the Matrigel implant, indicating reduced angiogenesis, but exhibited no in vivo efficacy in PAI-1 null mice.

CONCLUSIONS

Administration of an orally active PAI-1 inhibitor prevented angiogenesis in a Matrigel implant. The lack of activity of PAI-039 against wild-type PAI-1 bound to vitronectin and PAI-1K suggests PAI-039 binding near the vitronectin-binding site. Our studies further substantiate a role for PAI-1 in cellular motility and tumor angiogenesis, and suggest for the first time that these effects can be modulated pharmacologically.

Shear stress protects against endothelial regulation of vascular smooth muscle cell migration in a coculture system

Vascular endothelial cells (ECs) are constantly exposed to blood flow-induced shear stress; these forces strongly influence the behaviors of neighboring vascular smooth muscle cells (VSMCs). VSMC migration is a key event in vascular wall remodeling. In this study, the authors assessed the difference between VSMC migration in VSMC/EC coculture under static and shear stress conditions. Utilizing a parallel-plate coculture flow chamber system and Transwell migration assays, they demonstrated that human ECs cocultured with VSMCs under static conditions induced VSMC migration, whereas laminar shear stress (1.5 Pa, 15 dynes/cm2) applied to the EC side for 12 h significantly inhibited this process. The changes in VSMC migration is mainly dependent on the close interactions between ECs and VSMCs. Western blotting showed that there was a consistent correlation between the level of Akt phosphorylation and the efficacy of shear stress-mediated EC regulation of VSMC migration. Wortmannin and Akti significantly inhibited the EC-induced effect on VSMC Akt phosphorylation and migration. These results indicate that shear stress protects against endothelial regulation of VSMC migration, which may be an atheroprotective function on the vessel wall.

Shear stress contributes to t-PA mRNA expression in human endothelial progenitor cells and nonthrombogenic potential of small diameter artificial vessels

Seeding endothelial progenitor cells (EPCs) onto the surface of vascular grafts has been proved to be a promising strategy to improve nonthrombogenic potentials of small diameter artificial vessels. Here, we investigated whether in vitro shear stress modulates the tissue-type plasminogen activator (t-PA) secretion and mRNA expression in human EPCs and improves patency of the EPC-seeded polyurethane small diameter vascular grafts implanted in the canine carotid artery in vivo. In vitro shear stress, in a dose-dependent manner, increased t-PA secretion and mRNA expression of human EPCs. The in vivo implantation of EPC-seeded vascular grafts remained highly patent in shear stress pretreatment compared with stationary condition. The present findings demonstrate for the first time that in vitro shear stress can enhance t-PA secretion and gene expression in human EPCs, which contributes to improvement in nonthrombogenic potentials of EPC-seeded small diameter artificial vessels with maintenance of in vivo highly patency rate.

Effect of Fluid Shear Stress on Migration of Vascular Smooth Muscle Cells in Cocultured Model

Migration of smooth muscle cells (SMCs) in hyperplasia is thought to have a correlation with blood flow conditions. In this study, the effect of shear stress applied to endothelial cells (ECs) on SMC migration was examined using a newly designed EC-SMC coculture model (CM), in which bovine SMCs and ECs were separated by a collagen layer and a membrane filter. After exposing the CM to shear stresses of 0.5, 1.0, or 1.5 Pa for 48 h, the number of SMCs migrating into the collagen layer was counted. Under static conditions, the migration of SMCs in the CM increased compared with SMCs cultured alone. Shear stress of 1.5 Pa significantly suppressed the SMC migration (p < 0.05) compared with the static CM. Media conditioned with the CM exposed to shear stress of 1.0 Pa (p < 0.05) and 1.5 Pa (p < 0.005) exhibited reduction in activated matrix metalloproteinase-2 (MMP-2) compared with the static CM, as analyzed by zymography. Addition of an inhibitor of nitric oxide (NO) synthase, N (omega)-nitro-L: -arginine methyl ester, to the media inhibited the effect of 1.5 Pa shear stress on SMC migration but MMP-2 activity was unaffected. These results suggest that physiological shear stress has protective roles in atherosclerogenesis.

Arterial Wall Response to ex vivo Exposure to Oscillatory Shear Stress

BACKGROUND

The aim of this study was to analyze the arterial wall response to plaque-prone hemodynamic environments, known to occur mainly in areas of arterial trees such as bifurcations and branching points. In these areas, the vasculature is exposed to cyclically reversing flow that induces an endothelial dysfunction predisposing thus arteries to local development of atherosclerotic plaques.

METHODS

We used an ex vivo perfusion system that allows culturing arterial segments under different hemodynamic conditions. Porcine carotid arteries were exposed for 3 days to unidirectional high and low shear stress (6 +/- 3 and 0.3 +/- 0.1 dyn/cm(2)) as well as to oscillatory shear stress (0.3 +/- 3 dyn/cm(2)). This latter condition mimics the hemodynamics present at plaque-prone areas. At the end of the perfusion, the influence of different flow patterns on arterial metabolism was assessed in terms of matrix turnover as well as of smooth muscle cell function, differentiation and migration.

RESULTS

Our results show that after 3 days of perfusion none of the applied conditions influence smooth muscle cell phenotype retaining their full contraction capacity. However, an increase in the expression level of matrix metalloproteinase-2 and -9, as well as a decrease in plasminogen activator inhibitor-1 expression were observed in arteries exposed to oscillatory shear stress when compared to arteries exposed to unidirectional shear stress.

CONCLUSION

These observations suggest that plaque-prone hemodynamic environment triggers a vascular wall remodelling process and promotes changes in arterial wall metabolism, with important implication in atherogenesis.

Shear stress-stimulated endothelial cells induce smooth muscle cell chemotaxis via platelet-derived growth factor-BB and interleukin-1alpha

OBJECTIVE

Vascular smooth muscle cell (SMC) migration is critical to the development of atherosclerosis and neointimal hyperplasia. Hemodynamic forces such as shear stress and cyclic strain stimulate endothelial cell signal-transduction pathways, resulting in the secretion of several factors, including SMC chemoattractants such as platelet-derived growth factor (PDGF). We hypothesized that mechanical forces stimulate endothelial cells to secrete SMC chemoattractants to induce migration via the mitogen-activated protein kinase (MAPK) pathway.

METHODS

Bovine aortic endothelial cells were exposed to shear stress, cyclic strain, or static conditions for 16 hours. The resulting conditioned medium was used as a SMC chemoattractant in a Boyden chamber. Activation of SMC extracellular signal-regulated protein kinase 1/2 (ERK1/2) was assessed by Western blot analysis. Pathways were inhibited with anti-PDGF-BB or anti-interleukin-1alpha (IL-1alpha) antibodies, or the ERK1/2 upstream pathway inhibitor PD98059.

RESULTS

Conditioned medium from endothelial cells exposed to shear stress corresponding to arterial levels of shear stress stimulated SMC migration but lower levels of shear stress or cyclic strain did not. Both PDGF-BB and IL-1alpha were secreted into the conditioned medium by endothelial cells stimulated with shear stress. Both PDGF-BB and IL-1alpha stimulated SMC chemotaxis but were not synergistic, and both stimulated SMC ERK1/2 phosphorylation. Inhibition of PDGF-BB or IL-1alpha inhibited SMC chemotaxis and ERK1/2 phosphorylation.

CONCLUSION

Shear stress stimulates endothelial cells to secrete several SMC chemoattractants, including PDGF-BB and IL-1alpha; both PDGF-BB and IL-1alpha stimulate SMC chemotaxis via the ERK1/2 signal-transduction pathway. These results suggest that the response to vascular injury may have a common pathway amenable to pharmacologic manipulation.

CLINICAL RELEVANCE

One difficulty in the pharmacologic treatment of atherosclerosis or neointimal hyperplasia leading to restenosis is the multiplicity of activated pathways and thus potential treatment targets. This study demonstrates that shear stress, a hemodynamic force that may be a biologically relevant stimulus to induce vascular pathology, stimulates endothelial cells to secrete PDGF-BB and IL-1alpha. Both of these mediators stimulate the SMC ERK1/2 pathway to induce migration, a critical event in the pathogenesis of atherosclerosis and neointimal hyperplasia. Therefore, this study suggests a relevant common target pathway in SMC that is amenable to manipulation for clinical treatment.