LDL increases inactive tissue factor on vascular smooth muscle cell surfaces: hydrogen peroxide activates latent cell surface tissue factor

BACKGROUND: Tissue factor, which is required for the initiation of the extrinsic coagulation cascade, is known to be upregulated in cells within atherosclerotic lesions, including smooth muscle cells. Tissue factor expression on the smooth muscle cell surface could be of pathological significance as a contributor to plaque growth, thrombus formation, and the acute coronary syndrome after plaque rupture. METHODS AND RESULTS: In this study, we show that LDL increased tissue factor mRNA and cell surface protein in smooth muscle cells without a marked increase in surface tissue factor activity. Hydrogen peroxide activated tissue factor on the cell surface but did not increase tissue factor mRNA or cell surface protein. Sequentially added LDL and hydrogen peroxide increased mRNA, cell surface protein, and activity; surface activity was greater than that observed with hydrogen peroxide alone. The action of hydrogen peroxide did not involve a regulatory mechanism associated with the cytoplasmic tail of tissue factor because a truncated tissue factor lacking the cytoplasmic tail was activated by hydrogen peroxide. CONCLUSIONS: These results suggest a novel 2-step pathway for increased tissue factor activity on smooth muscle cell surfaces in which lipoproteins regulate synthesis of a latent tissue factor and oxidants activate the protein complex.     

Release of active tissue factor by human arterial smooth muscle cells

Tissue factor (TF), the initiator of coagulation, is thought to function predominantly at the cell surface. Recent data have suggested that active TF is present extracellularly in atherosclerotic plaques, the arterial wall, and the blood. This study was conducted to determine whether smooth muscle cells (SMCs), a major source of arterial TF, could generate extracellular TF. Active TF accumulated in the medium of cultured human SMCs, representing approximately 10% of that measured in the underlying cells at 24 hours. Platelet-derived growth factor, phorbol ester, and tumor necrosis factor-alpha caused approximately 3-fold increases in TF activity in the medium. Release of TF into the medium was dependent on the presence of the TF transmembrane domain but not the cytoplasmic domain. Antibodies to TF precipitated most of the activity from the culture medium, whereas antibodies to the beta(1)-integrin subunit precipitated approximately 33% of the activity. Treatment with detergent or phosphatidylserine:phosphatidylcholine did not increase activity, suggesting that all TF released by SMCs was in the appropriate lipid milieu and not encrypted. Western blotting showed that the medium contained full-length TF protein. Fluorescent cytometry showed that extracellular TF was present largely in particles < or =200 nm, which had a density of 1.10 g/mL. We hypothesize that active extracellular TF found in the injured arterial wall and atherosclerotic plaques derives, in part, from SMC microparticles.     

Hepatocyte growth factor mediates angiopoietin-induced smooth muscle cell recruitment

Communication between endothelial cells (ECs) and mural cells is critical in vascular maturation. Genetic studies suggest that angiopoietin/Tie2 signaling may play a role in the recruitment of pericytes or smooth muscle cells (SMCs) during vascular maturation. However, the molecular mechanism is unclear. We used microarray technology to analyze genes regulated by angiopoietin-1 (Ang1), an agonist ligand for Tie2, in endothelial cells (ECs). We observed that hepatocyte growth factor (HGF), a mediator of mural cell motility, was up-regulated by Ang1 stimulation. We confirmed this finding by Northern blot and Western blot analyses in cultured vascular endothelial cells. Furthermore, stimulation of ECs with Ang1 increased SMC migration toward endothelial cells in a coculture assay. Addition of a neutralizing anti-HGF antibody inhibited Ang1-induced SMC recruitment, indicating that the induction of SMC migration by Ang1 was caused by the increase of HGF. Interestingly, Ang2, an antagonist ligand of Tie2, inhibited Ang1-induced HGF production and Ang1-induced SMC migration. Finally, we showed that deletion of Tie2 in transgenic mouse reduced HGF production. Collectively, our data reveal a novel mechanism of Ang/Tie2 signaling in regulating vascular maturation and suggest that a delicate balance between Ang1 and Ang2 is critical in this process.     

Expression of connective tissue growth factor in asthmatic airway smooth muscle cells

There is strong evidence to implicate transforming growth factor-beta in the remodeling that occurs in asthma, as levels are increased in bronchial lavage fluid and gene expression is increased in bronchial tissue. Transforming growth factor-beta is also known to increase the release of collagen from airway smooth muscle. Here we identify for the first time a possible mechanism for the effects of transforming growth factor-beta. Transforming growth factor-beta specifically induces mRNA and protein for connective tissue growth factor in airway smooth muscle, and moreover, we report that the connective tissue growth factor response is greater in airway smooth muscle cultured from patients with asthma compared with patients without asthma. This occurs at both the level of mRNA (37.53 +/- 11.62- and 13.59 +/- 3.12-fold increase at 24 hours compared with time 0, respectively, p < 0.02) and protein production (67.57 +/- 27.80- and 3.58 +/- 0.6-fold increase at 24 hours compared with time 0, respectively, p < 0.03). The differential connective tissue growth factor response to transforming growth factor-beta in asthmatic airway smooth muscle identifies a potential role for connective tissue growth factor in the remodeling that is characteristic of severe persistent asthma.     

猪冠状动脉介入损伤后血管壁平滑肌细胞增生与血浆组织因子水平的关系

目的 探讨猪冠状动脉介入损伤后损伤局部血管壁平滑肌细胞增生程度与血浆组织因子水平的关系.方法 制作猪冠状动脉介入损伤模型,测量介入手术前后血浆组织因子浓度以及损伤局部血管壁平滑肌细胞迁移、增牛情况,探讨二者之间的联系.结果 30例血管标本均存在不同程度的平滑肌细胞增生,其中60%的标本达到再狭窄标准.再狭窄组术后血浆组织冈子水平显著高于非再狭窄组(术后30 min 688.36±91.57 ng/L比514.87±68.73 ng/L,术后24 h 706.09±89.59ng/L比539.22±70.51 ng/L,P均＜0.05);血管损伤后血管段新牛内膜而积与术后各时点外周血组织因子浓度正相关(r30min=0.834,r24h=0.810,P均＜0.05).结论 冠状动脉介入术后血浆组织因子水平显著升高,并且其升高程度与介入局部平滑肌细胞增生程度正相关,可能作为预测介入术后再狭窄的一项检测指标.     

巨噬细胞集落刺激因子与血管平滑肌细胞增殖

目的一些以血管平滑肌细胞（ＶＳＭＣ）增殖为特点的血管疾病，在病变部位常有巨噬细胞浸润。本研究巨噬细胞集落刺激因子（ＭＣＳＦ）在ＶＳＭＣ生长调节中的作用。方法实验采用培养大鼠主动脉ＶＳＭＣ，细胞增殖观察指标采用氚标胸腺嘧啶核苷掺入法，并用Ｎｏｒｔｈｅｒｎｂｌｏｔ技术测定原癌基因表达。结果（１）Ｌ９２９细胞上清液（富含ＭＣＳＦ）及重组ＭＣＳＦ以剂量依赖关系刺激氚标胸腺嘧啶核苷掺入；（２）ＶＳＭＣ在接受刺激后表达某些原癌基因，如ｃｆｏｓ、ｃｍｙｃ、ｅｒｇ１和ＪｕｎＢ；（３）凝血酶、ＰＤＧＦ、ｂＦＧＦ与ＭＣＳＦ在促增殖作用上具有协同作用。结论ＭＣＳＦ与其它生长因子协同作用，通过自分泌／旁分泌机制调控ＶＳＭＣ增殖，从而可能在血管病变的形成和进展中起重要作用     

Effects of smooth muscle cell derived growth factor (SDGF) in combination with other growth factors on smooth muscle cells

Recently intimal thickening was shown to be due to stimulation of proliferation of arterial smooth muscle cells (SMC) by autocrine secretion of growth factor(s). We have reported that cultured rabbit aortic SMC secrete a growth factor (SDGF) distinct from other known growth factors. This paper reports on studies on the biological characteristics of SDGF. Putative "competence" and "progression" growth factors synergistically stimulated DNA synthesis of cultured rabbit aortic SMC. Conditioned medium (CM) from SMC containing SDGF stimulated DNA synthesis in SMC synergistically with either the competence factors or the progression factors. This synergistic effect was also observed in the presence of optimal concentrations of both competence and progression factors. The continuous presence of CM was essential for its stimulation of DNA synthesis whereas the presence of PDGF for only the first 4 h of culture was sufficient to induce maximum stimulation of DNA synthesis. These results suggest that SDGF is a new growth factor distinct from either competence or progression factors and that it stimulates a different pathway in SMC from those stimulated by other known growth factors.     

Connective tissue growth factor induces extracellular matrix in asthmatic airway smooth muscle

Transforming growth factor (TGF)-beta and connective tissue growth factor may be implicated in extracellular matrix protein deposition in asthma. We have recently reported that TGF-beta increased connective tissue growth factor expression in airway smooth muscle cells isolated from patients with asthma. In this study, we examined fibronectin and collagen production and signal transduction pathways after stimulation with TGF-beta and connective tissue growth factor. In both asthmatic and nonasthmatic airway smooth muscle cells, TGF-beta and connective tissue growth factor led to the production of fibronectin and collagen I. Fibronectin and collagen expression was extracellular regulated kinase-dependent in both cell types but phosphoinositide-3 kinase-dependent only in asthmatic airway smooth muscle cells. p38 was implicated in fibronectin but not collagen expression in both cell types. TGF-beta induction of fibronectin and collagen was in part mediated by an autocrine action of connective tissue growth factor. Phosphorylation of SMAD-2 may represent an additional pathway because this was increased in asthmatic cells. Our results suggest that these two cytokines may be important in the deposition of extracellular matrix proteins and that the signal transduction pathways may be different in asthmatic and nonasthmatic cells.     

Rapid release of active tissue factor from human arterial smooth muscle cells under flow conditions

Circulating tissue factor (TF) is an important determinant of coronary thrombosis. Among other cell types, such as monocytes, vascular smooth muscle cells (SMCs) are capable of releasing TF. When studied under static conditions, SMCs do release TF, but this process is slow and, thus, cannot explain the elevated levels of circulating TF, as observed in patients with acute coronary syndromes. The present study demonstrates that cultured human mammary artery SMCs very rapidly (minutes) release active, microparticle-bound TF when exposed to flow conditions. There was a clear log-linear correlation between the shear rate (range 10 s(-1) to 1500 s(-1)) and the procoagulant activity of SMC perfusates. Flow-dependent release of TF was transient (10 minutes) and did not measurably reduce cell surface TF content. Interestingly, a time-dependent (t(1/2) 30 minutes) re-exposure of releasable TF was detected after a no-flow period. These data demonstrate that SMCs may become a pathophysiologically relevant source of TF that can be rapidly released into the circulation in situations in which endothelial damage occurs and SMCs come into a close contact with the flowing blood.