Gene transfer of the urokinase-type plasminogen activator receptor-targeted matrix metalloproteinase inhibitor TIMP-1.ATF suppresses neointima formation more efficiently than tissue inhibitor of metalloproteinase-1

Molecular imaging of the urokinase plasminogen activator receptor: opportunities beyond cancer

The urokinase plasminogen activator receptor (uPAR) plays a multifaceted role in almost any process where migration of cells and tissue-remodeling is involved such as inflammation, but also in diseases as arthritis and cancer. Normally, uPAR is absent in healthy tissues. By its carefully orchestrated interaction with the protease urokinase plasminogen activator and its inhibitor (plasminogen activator inhibitor-1), uPAR localizes a cascade of proteolytic activities, enabling (patho)physiologic cell migration. Moreover, via the interaction with a broad range of cell membrane proteins, like vitronectin and various integrins, uPAR plays a significant, but not yet completely understood, role in differentiation and proliferation of cells, affecting also disease progression. The implications of these processes, either for diagnostics or therapeutics, have received much attention in oncology, but only limited beyond. Nonetheless, the role of uPAR in different diseases provides ample opportunity to exploit new applications for targeting. Especially in the fields of oncology, cardiology, rheumatology, neurology, and infectious diseases, uPAR-targeted molecular imaging could offer insights for new directions in diagnosis, surveillance, or treatment options.

Circulating heat shock protein 27 as a novel marker of subclinical atherosclerosis in type 2 diabetes: a cross-sectional community-based study

Background

Heat shock protein 27 (HSP27) has been proposed as a vital protective factor in atherosclerosis. The objective of the present study was to evaluate the association between circulating HSP27 and carotid intima–media thickness (IMT) in individuals with type 2 diabetes and to determine whether HSP27 represents an independent marker of subclinical atherosclerosis in this patient population.

Methods

We performed a cross-sectional community-based study in 186 Chinese subjects with a median duration of type 2 diabetes of 8.2 years who underwent ultrasound carotid IMT measurement. Serum HSP27 levels were assessed by ELISA.

Results

Serum HSP27 levels were significantly higher in the IMT (+, > 1.0 mm) group than in the IMT (−, ≤1.0 mm) group, with the median values of 8.80 ng/mL (5.62–12.25) and 6.93 ng/mL (4.23–9.60), respectively (P = 0.006). The discriminative value of HSP27 to evaluate IMT was 7.16 ng/mL and the area under the curve was 0.72 (95%CI = 0.64–0.80, P = 0.0065). Spearman’s rank correlation analysis demonstrated that the concentrations of circulating HSP27 were positively associated with carotid IMT (r = 0.198, P = 0.007) and blood urea nitrogen (r = 0.170, P < 0.05). Furthermore, in the logistic model, serum HSP27 levels were found to be independent predictors for carotid IMT in type 2 diabetic patients after adjustment for onset age of diabetes, blood pressure, total cholesterol and C-reactive protein (OR = 1.085, P = 0.022).

Conclusions

Circulating HSP27, positively correlates with carotid IMT, is an independent predictor for early atherosclerotic changes in diabetes, and may represent a novel marker of subclinical atherosclerosis in type 2 diabetes.

Inflammation in Vein Graft Disease

Bypass surgery is one of the most frequently used strategies to revascularize tissues downstream occlusive atherosclerotic lesions. For venous bypass surgery the great saphenous vein is the most commonly used vessel. Unfortunately, graft efficacy is low due to the development of vascular inflammation, intimal hyperplasia and accelerated atherosclerosis. Moreover, failure of grafts leads to significant adverse outcomes and even mortality. The last couple of decades not much has changed in the treatment of vein graft disease (VGD). However, insight is the cellular and molecular mechanisms of VGD has increased. In this review, we discuss the latest insights on VGD and the role of inflammation in this. We discuss vein graft pathophysiology including hemodynamic changes, the role of vessel wall constitutions and vascular remodeling. We show that profound systemic and local inflammatory responses, including inflammation of the perivascular fat, involve both the innate and adaptive immune system.

Extracellular Release and Signaling by Heat Shock Protein 27: Role in Modifying Vascular Inflammation

Heat shock protein 27 (HSP27) is traditionally viewed as an intracellular chaperone protein with anti-apoptotic properties. However, recent data indicate that a number of heat shock proteins, including HSP27, are also found in the extracellular space where they may signal via membrane receptors to alter gene transcription and cellular function. Therefore, there is increasing interest in better understanding how HSP27 is released from cells, its levels and composition in the extracellular space, and the cognate cell membrane receptors involved in effecting cell signaling. In this paper, the knowledge to date, as well as some emerging paradigms about the extracellular function of HSP27 is presented. Of particular interest is the role of HSP27 in attenuating atherogenesis by modifying lipid uptake and inflammation in the plaque. Moreover, the abundance of HSP27 in serum is an emerging new biomarker for ischemic events. Finally, HSP27 replacement therapy may represent a novel therapeutic opportunity for chronic inflammatory disorders, such as atherosclerosis.

Vein graft failure: from pathophysiology to clinical outcomes

Occlusive arterial disease is a leading cause of morbidity and mortality worldwide. Aside from balloon angioplasty, bypass graft surgery is the most commonly performed revascularization technique for occlusive arterial disease. Coronary artery bypass graft surgery is performed in patients with left main coronary artery disease and three-vessel coronary disease, whereas peripheral artery bypass graft surgery is used to treat patients with late-stage peripheral artery occlusive disease. The great saphenous veins are commonly used conduits for surgical revascularization; however, they are associated with a high failure rate. Therefore, preservation of vein graft patency is essential for long-term surgical success. With the exception of 'no-touch' techniques and lipid-lowering and antiplatelet (aspirin) therapy, no intervention has hitherto unequivocally proven to be clinically effective in preventing vein graft failure. In this Review, we describe both preclinical and clinical studies evaluating the pathophysiology underlying vein graft failure, and the latest therapeutic options to improve patency for both coronary and peripheral grafts.

Regulation and involvement of matrix metalloproteinases in vascular diseases

Matrix metalloproteinases (MMPs) are a family of zinc dependent endopeptidases whose main function is to degrade and deposit structural proteins within the extracellular matrix (ECM). A dysregulation of MMPs is linked to vascular diseases. MMPs are classified into collagenases, gelatinases, membrane-type, metalloelastase, stromelysins, matrilysins, enamelysins, and unclassified subgroups. The production of MMPs is stimulated by factors such as oxidative stress, growth factors and inflammation which lead to its up- or down-regulation with subsequent ECM remodeling. Normally, excess activation of MMPs is controlled by their endogenous inhibitors, tissue inhibitors of metalloproteinases (TIMPs). An imbalance of MMPs and TIMPs has been implicated in hypertension, atherosclerotic plaque formation and instability, aortic aneurysms and varicose vein wall remodeling. Also, recent evidence suggests epigenetic regulation of some MMPs in angiogenesis and atherosclerosis. Over the years, pharmacological inhibitors of MMPs have been used to modify or prevent the development of the disease with some success. In this review, we discuss recent advances in MMP biology, and their involvement in the manifestation of vascular disease.

The urokinase system in the pathogenesis of atherosclerosis

Atherogenesis refers to the development of atheromatous plaques in the inner lining of the arteries. These atherosclerotic lesions are characterized by accumulation of monocyte-derived macrophage-foam cells loaded with cholesterol, which eventually undergo apoptotic death, leading finally to formation of the necrotic core of the plaque. Atheroma formation also involves the recruitment of smooth muscle cells (SMC) from the media into the intima, where they proliferate and form the neointima in a process called "remodeling". Cells in the advanced atherosclerotic plaques express high levels of the serine protease urokinase-type plasminogen activator (uPA) and its receptor (uPAR). uPA is a multi-functional multi-domain protein that is not only a regulator of fibrinolysis, but it is also associated with several acute and chronic pathologic conditions. uPA mediate the extracellular matrix (ECM) degradation, and plays a pivotal role in cell adhesion, migration and proliferation, during tissue remodeling. On cell surface uPA binds to the high affinity urokinase receptor, providing a strictly localized proteolysis of ECM proteins. The uPA/uPAR complex also activates intracellular signaling, thus regulating cellular function. An imbalance in the uPA/uPAR system leads to dis-orders in tissue structure and function. This review summarizes recent progress in understanding the role and mechanisms of the uPA/uPAR system in atherogenesis.

Urokinase receptor associates with myocardin to control vascular smooth muscle cells phenotype in vascular disease

OBJECTIVE

The urokinase-type plasminogen activator (uPA) and its specific receptor (uPAR) are a potent multifunctional system involved in vascular remodeling. The goal of the study was to unravel the mechanisms of uPA/uPAR-directed vascular smooth muscle cell (VSMC) differentiation.

METHODS AND RESULTS

Using cultured human primary VSMCs, we identified a new molecular mechanism controlling phenotypic modulation in vitro and in vivo. We found that the urokinase-type plasminogen activator receptor (uPAR) acts together with the transcriptional coactivator myocardin to regulate the VSMC phenotype. uPAR, a glycosylphosphatidylinositol-anchored cell-surface receptor family member, undergoes ligand-induced internalization and nuclear transport in VSMCs. Platelet-derived growth factor receptor β and SUMOylated RanGAP1 mediate this trafficking. Nuclear uPAR associates with myocardin, which is then recruited from the promoters of serum response factor target genes and undergoes proteasomal degradation. This chain of events initiates the synthetic VSMC phenotype. Using mouse carotid artery ligation model, we show that this mechanism contributes to adverse vascular remodeling after injury in vivo. We then cultured cells on a microstructured biomaterial and found that substrate topography induced uPAR-mediated VSMC differentiation.

CONCLUSIONS

These findings reveal the transcriptional activity of uPAR, controlling the differentiation of VSMCs in a vascular disease model. They also suggest a new role for uPAR as a therapeutic target and as a marker for VSMC phenotyping on prosthetic biomaterials.

Dose-dependent effect of rosuvastatin in the regulation of metalloproteinase expression

BACKGROUND

The importance of rosuvastatin at therapeutic dosage in regulating the release, activity, protein level, and expression of matrix metalloproteinases (MMP)-2 and MMP-9 was investigated.

METHODS

Human umbilical artery smooth muscle cells were stimulated, in vitro, in a serum-free medium with rosuvastatin at various concentrations (2, 4, 7, and 10 ng/mL, which correspond to the maximal plasma concentration observed in healthy men after a daily oral intake of 5, 10, 20, and 40 mg, respectively). The release of MMP-2 and MMP-9 in the conditioned medium was assessed by enzyme-linked immunosorbent assay and confirmed by Western blot, the activity and expression were determined by zymography and polymerase chain reaction, respectively.

RESULTS

Human umbilical artery smooth muscle cells stimulated with rosuvastatin at 7 and 10 ng/mL had a significant lower release, activity, protein level, and expression of MMP-2 and MMP-9, when compared with those stimulated at 2 and 4 ng/mL (MMP-2 =p < 0.0001 and p < 0.0001, respectively; MMP-9 =p < 0.0001 and p < 0.0001, respectively).

CONCLUSION

The effects of rosuvastatin in reducing MMP-2 and MMP-9, which might stabilize the atherosclerotic plaques, are dose-dependent.

A novel urokinase receptor-targeted inhibitor for plasmin and matrix metalloproteinases suppresses vein graft disease

AIMS

Matrix metalloproteinases (MMP) and plasminogen activator (PA)/plasmin-mediated proteolysis, especially at the cell surface, play important roles in matrix degeneration and smooth muscle cell migration, which largely contributes to vein graft failure. In this study, a novel hybrid protein was designed to inhibit both protease systems simultaneously. MMP and plasmin activity were inhibited at the cell surface by this hybrid protein, consisting of the receptor-binding amino-terminal fragment (ATF) of urokinase-type PA, linked to both the tissue inhibitor of metalloproteinases (TIMP-1) and bovine pancreas trypsin inhibitor (BPTI), a potent protease inhibitor. The effect of overexpression of this protein on vein graft disease was studied.

METHODS AND RESULTS

A non-viral expression vector encoding the hybrid protein TIMP-1.ATF.BPTI was constructed and validated. Next, cultured segments of human veins were transfected with this vector. Expressing TIMP-1.ATF.BPTI in vein segments resulted in a mean 36 ± 14% reduction in neointima formation after 4 weeks. In vivo inhibition of vein graft disease by TIMP-1.ATF.BPTI is demonstrated in venous interpositions placed into carotid arteries of hypercholesterolaemic APOE*3Leiden mice. After 4 weeks, vein graft thickening was significantly inhibited in mice treated with the domains TIMP-1, ATF, or BPTI (36-49% reduction). In the TIMP-1.ATF.BPTI-treated mice, vein graft thickening was reduced by 67±4%, which was also significantly stronger when compared with the individual components.

CONCLUSION

These data provide evidence that cell surface-bound inhibition of the PA and MMP system by the hybrid protein TIMP-1.ATF.BPTI, overexpressed in distant tissues after electroporation-mediated non-viral gene transfer, is a powerful approach to prevent vein graft disease.

Urokinase-receptor-mediated phenotypic changes in vascular smooth muscle cells require the involvement of membrane rafts

The cholesterol-enriched membrane microdomains lipid rafts play a key role in cell activation by recruiting and excluding specific signalling components of cell-surface receptors upon receptor engagement. Our previous studies have demonstrated that the GPI (glycosylphosphatidylinositol)-linked uPAR [uPA (urokinase-type plasminogen activator) receptor], which can be found in lipid rafts and in non-raft fractions, can mediate the differentiation of VSMCs (vascular smooth muscle cells) towards a pathophysiological de-differentiated phenotype. However, the mechanism by which uPAR and its ligand uPA regulate VSMC phenotypic changes is not known. In the present study, we provide evidence that the molecular machinery of uPAR-mediated VSMC differentiation employs lipid rafts. We show that the disruption of rafts in VSMCs by membrane cholesterol depletion using MCD (methyl-beta-cyclodextrin) or filipin leads to the up-regulation of uPAR and cell de-differentiation. uPAR silencing by means of interfering RNA resulted in an increased expression of contractile proteins. Consequently, disruption of lipid rafts impaired the expression of these proteins and transcriptional activity of related genes. We provide evidence that this effect was mediated by uPAR. Similar effects were observed in VSMCs isolated from Cav1Z(-/-) (caveolin-1-deficient) mice. Despite the level of uPAR being significantly higher after the disruption of the rafts, uPA/uPAR-dependent cell migration was impaired. However, caveolin-1 deficiency impaired only uPAR-dependent cell proliferation, whereas cell migration was strongly up-regulated in these cells. Our results provide evidence that rafts are required in the regulation of uPAR-mediated VSMC phenotypic modulations. These findings suggest further that, in the context of uPA/uPAR-dependent processes, caveolae-associated and non-associated rafts represent different signalling membrane domains.

Thoracic aortic dissection: are matrix metalloproteinases involved?

Thoracic aortic dissection, one of the major diseases affecting the aorta, carries a very high mortality rate. Improving our understanding of the pathobiology of this disease may help us develop medical treatments to prevent dissection and subsequent aneurysm formation and rupture. Dissection is associated with degeneration of the aortic media. Recent studies have shown increased expression and activation of a family of proteolytic enzymes-called matrix metalloproteinases (MMPs)-in dissected aortic tissue, suggesting that MMPs may play a major role in this disease. Inhibition of MMPs may be beneficial in reducing MMP-mediated aortic damage associated with dissection. This article reviews the recent literature and summarizes our current understanding of the role of MMPs in the pathobiology of thoracic aortic dissection. The potential importance of MMP inhibition as a future treatment of aortic dissection is also discussed.

Rosuvastatin regulates vascular smooth muscle cell phenotypic modulation in vascular remodeling: Role for the urokinase receptor

The urokinase (uPA)/urokinase receptor (uPAR) multifunctional system is an important mediator of migration and proliferation of vascular smooth muscle cells (VSMC). However, whether uPA/uPAR-directed mechanisms are involved in the beneficial effects of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors on vascular remodeling remains unexplored. In this study, we have investigated the effect of the hydrophilic statin rosuvastatin on neointimal remodeling, and the role of uPAR. Using an ex vivo organ and in vitro cell culture models we demonstrate that rosuvastatin decreases injury-induced neointima formation and proliferation of medial VSMC in porcine coronary arteries, as well as migration and proliferation of human coronary VSMC. Studies on the underlying mechanisms show that rosuvastatin impairs VSMC transition from their physiological contractile to the pathophysiological synthetic phenotype. These effects are mediated, at least in part, via uPAR, as confirmed by means of rosuvastatin-directed uPAR expression and uPAR silencing in both models. Our findings provide evidence that rosuvastatin modulates VSMC phenotypic changes and subsequently their proliferation and migration, and indicate the important role for uPAR in these processes. This mechanism contributes to the beneficial non-lipid lowering effect of rosuvastatin on negative vascular remodeling.

Avenues for immunomodulation and graft protection by gene therapy in transplantation

Organ transplantation represents the only definitive therapy for many causes of end-organ failure. However, the universal success of this therapy is limited by chronic allograft rejection, the side effects of chronic immunosuppressive therapy, and a severe shortage of donor organs. Presently, the success of solid-organ transplantation depends on the continuous administration of toxic and nonspecific immunosuppressive agents, therapies that present risks for opportunistic infection, malignancy, and a variety of agent-specific side effects. To promote the use of transplantation with limited risk of long-term sequelae, three dominant research challenges emerge: (i) elimination of the need for exogenous immunosuppression by immunological tolerance induction; (ii) prevention of chronic rejection/graft dysfunction; and (iii) expansion of available organs for transplantation. Gene therapy may provide significant advances and solutions in each of these areas. Rejection of the graft in the immediate post-transplant period has been attacked through the transfer of immunomodulatory molecules in addition to tolerance inducing approaches. Chronic graft rejection may be similarly addressed through permanent tolerance induction or alternatively through the introduction of molecules to resist chronic graft damage. Genetic manipulation of stem cells may ultimately produce transgenic animals to serve as tissue donors to overcome the limited donor organ supply. This review will highlight ongoing developments in the translation of gene therapy approaches to the challenges inherent in transplantation.

Single Nucleotide Polymorphisms of Tissue Inhibitor of Metalloproteinase Genes in Familial Moyamoya Disease

OBJECTIVE

The genes encoding tissue inhibitor of metalloproteinase (TIMP) 4 and TIMP2 span chromosomes 3p24.2-p26 and 17q25, respectively, which are the locations of familial moyamoya disease (FMMD) genes. We investigated single nucleotide polymorphisms of the TIMP2 and TIMP4 genes in FMMD patients to determine genetic predispositions.

METHODS

Eleven blood samples from FMMD patients were recruited. Controls included 50 blood samples from patients with nonfamilial moyamoya disease (MMD) and another 50 blood samples from non-MMD persons. We evaluated the promoter regions, exon-intron junctions, and the exons of the TIMP2 and TIMP4 genes by direct sequencing, and compared single nucleotide polymorphisms frequencies among the study groups.

RESULTS

A significantly higher frequency of a heterozygous genotype was found in the TIMP2 promoter region at position -418 in FMMD; that is, the G/C heterozygous genotype at position -418 was observed in nine of 11 patients with FMMD, in 16 out of 50 nonfamilial MMD control participants, and in 14 out of 50 non-MMD control participants (FMMD versus nonfamilial MMD: odds ratio, 9.56; 95% confidence interval, 1.85-49.48; P = 0.005; and FMMD versus non-MMD: odds ratio, 10.50; 95% confidence interval, 2.02-54.55; P = 0.001). This base at position -418 corresponds to the third base of the GAGGCTGGG sequence, an Sp1 binding site. Thus, changes in this position may influence Sp1 binding and subsequent transcription of the gene.

CONCLUSION

Our findings suggest that the presence of a G/C heterozygous genotype at position -418 in TIMP2 promoter could be a genetic predisposing factor for FMMD.

Metalloproteinases in Development and Progression of Vascular Disease

Remodeling of the vascular wall plays a role in many physiological processes, but also in the pathogenesis of major cardiovascular diseases such as restenosis and atherosclerosis. Remodeling requires proteolytic activity to degrade components of the extracellular matrix; this can be generated by the matrix metalloproteinase(MMP) system alone or in concert with the fibrinolytic (plasminogen/plasmin) system. Several lines of evidence suggest that the MMP system plays a role in vascular smooth muscle cell migration and neointima formation after vascular injury. In atherosclerotic lesions, active MMPs may contribute to plaque destabilisation by degrading extracellular matrix components, but may also promote aneurysm formation by proteolytic degradation of the elastic lamina. The MMP system may therefore represent a potential therapeutic target for treatment of restenosis or atherosclerosis.

Overexpression of a hybrid gene consisting of the amino-terminal fragment of urokinase and carboxyl-terminal domain of bikunin suppresses invasion and migration of human ovarian cancer cellsin vitro

A Kunitz-type protease inhibitor, bikunin, is known to suppress the invasion and metastasis of cancer cells. HI8, a carboxyl-terminal domain of bikunin, is an active site of this glycoprotein. To increase its affinity for cancer cells, we constructed a chimeric gene, ATF-HI8, and investigated the anti-invasive and anti-migratory activity of ATF-HI8 on ovarian cancer cells. ATF-HI8-expressing plasmid and ATF-expressing plasmid were introduced into the highly invasive and metastatic ovarian cancer cell line HRA. The properties of the established cell line (HRA/ATF-HI8) were compared to those of the HRA/ATF and the HRA/luciferase (HRA/LUC, control) cell lines in terms of cell proliferation, invasion and migration. As a result, (i) there were no differences in cell proliferation between HRA/ATF-HI8 and HRA/LUC; (ii) the invasion and migration of HRA/ATF-HI8 cells were significantly inhibited compared to those of HRA/LUC cells; (iii) the migration, but not the invasion, of HRA/ATF cells was significantly inhibited compared to that of HRA/LUC. These results indicate that the overexpression of ATF-HI8 inhibits the invasion and migration of ovarian cancer cells without affecting cell proliferation and suggest that HI8 is involved in the anti-invasive and the anti-migratory activities, and the addition of ATF brought about the increase in the anti-migratory activity of HI8. The above findings suggest the applicability of therapeutic strategies targeting the inhibition of peritoneal invasion and dissemination of ovarian cancer by the use of the chimeric gene ATF-HI8.

Involvement of membrane-type matrix metalloproteinases (MT-MMPs) in capillary tube formation by human endometrial microvascular endothelial cells: role of MT3-MMP

In the endometrium, angiogenesis is a physiological process, whereas in most adult tissues neovascularization is initiated only during tissue repair or pathological conditions. Pericellular proteolysis plays an important role in angiogenesis being required for endothelial cell migration, invasion, and tube formation. We studied the expression of proteases by human endometrial microvascular endothelial cells (hEMVECs) and their involvement in the formation of capillary tubes and compared these requirements with those of foreskin MVECs (hFMVECs). Inhibition of urokinase and matrix metalloproteinase (MMP) both reduced tube formation in a fibrin or fibrin/collagen matrix. hEMVECs expressed various MMP mRNAs and proteins; in particular MMP-1, MMP-2, and membrane-type (MT)1-, MT3-, and MT4-MMPs. MT3- and MT4-MMP mRNA expressions were significantly higher in hEMVECs than in hFMVECs. Other MT-MMP mRNAs and MMP-9 were hardly detectable. Immunohistochemistry confirmed the presence of MT3-MMP in endothelial cells of endometrial tissue. Overexpression of tissue inhibitor of MMP (TIMP)-1 or TIMP-3 by adenoviral transduction of hEMVECs reduced tube formation to the same extent, whereas only TIMP-3 was able to inhibit tube formation by hFMVECs. Tube formation by hEMVECs was partly inhibited by the presence of anti-MT3-MMP IgG. Thus, in contrast to tube formation by hFMVECs, which largely depends on MT1-MMP, capillary-like tube formation by hEMVECs is, at least in part, regulated by MT3-MMP.

Matrix metalloproteinases and atherosclerosis

Atherosclerosis is a major cause of coronary heart disease, and matrix metalloproteinases (MMPs) play an important role in atherosclerosis by degrading the extracellular matrix, which results in cardiovascular remodeling. Recent studies have identified enhanced expression of MMPs in the atherosclerotic lesion and their contribution to weakening of the vascular wall by degrading the extracellular matrix. The transcription, enzyme processing, and specific inhibition of MMPs by tissue inhibitors of matrix metalloproteinase (TIMPs) regulate these effects. These processes are also modified by inflammatory cytokines and cell-cell contact signaling. Both animal experiments and clinical sample analysis have shown that balance in expression and activation of MMPs and inhibition by TIMPs is critical for the development of stenotic and aneurysmal change. Polymorphism in the MMP gene promoter contributes to inter-individual differences in susceptibility to coronary heart disease. The development of therapeutic drugs specifically targeting MMPs may thus be useful for the prevention of atherosclerotic lesion progression, plaque rupture, and restenosis.

Tissue inhibitor of metalloproteinases-4 suppresses vascular smooth muscle cell migration and induces cell apoptosis

In a previous study, we have demonstrated that overexpression of the tissue inhibitors of metalloproteinases-4 (TIMP-4) can inhibit the neointima formation in the rat carotid model. To define the functions of tissue inhibitor of metalloproteinases-4 (TIMP-4) in SMCs, we transduced human TIMP-4 cDNA into rat aortic SMCs by using adenoviral vector. Overexpression of TIMP-4 blocked the conversion of pro-MMP-2 to the active form and inhibited basic fibroblast growth factor-induced migration by 56.7% (p < 0.01). Overexpression of TIMP-4 markedly increased apoptotic cell death without changing their proliferation. Importantly, overexpression of human TIMP-4 in the wall of balloon-injured rat carotid artery also increased SMC apoptosis. The percentages of TUNEL-positive cells of total cells increased significantly in AdTIMP-4 infected group compared with AdGFP infected group. These findings demonstrate that TIMP-4 can inhibit SMCs migration and induce apoptosis in vitro and in vivo, which may generate new targets for prevention and treatment of vascular diseases.

Native matrix metalloproteinase characteristics may influence early stenosis of venous versus arterial coronary artery bypass grafting conduits

PURPOSE

Stenosis and occlusion rates of internal mammary artery (IMA) and saphenous vein (SV) coronary artery bypass grafts (CABGs) are markedly different, which result from respective disparities in vascular remodeling. Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) regulate vascular structure and may have important influence on graft patency. However, the MMP milieu and expression profile of the IMA and SV have not been contrasted. Therefore, the aim of this study was to assess and compare the native MMP systems in IMA vs SV conduits.

METHODS

IMA (n = 10) and SV (n = 10) specimens were obtained from patients undergoing CABG surgery. Protein levels of MMP-1, MMP-2, and MMP-9, TIMP-1, a membrane-bound MMP activator (MT1-MMP), and an extracellular MMP inducer protein (EMMPRIN) were determined by immunoblotting and quantified by densitometric analysis. MMP-2 and MMP-9 activity was determined by gelatin zymography.

RESULTS

MMP-2 levels were significantly higher in SV (2,218 +/- 351 pixels) vs IMA (1,012 +/- 213 pixels) specimens (mean +/- SEM]). There were no significant differences in MMP-1, MMP-9, or TIMP-1 content; however, MT1-MMP and EMMPRIN levels were significantly lower in SV (847 +/- 190 pixels, 1,742 +/- 461 pixels) vs IMA conduits (2,590 + 403 pixels, 5,606 + 678 pixels), respectively (p < 0.05). MMP-9 activity was similar while MMP-2 activity was significantly increased in SV vs IMA specimens.

CONCLUSIONS

SV and IMA conduits harbor the same MMP molecular constituents. However, MMP-2 levels and activity are significantly more abundant in the SV compared to the IMA. These differences may contribute to the early pathologic remodeling of the SV vs IMA conduit following CABG surgery.

Membrane associated proteases and their inhibitors in tumour angiogenesis

Cell surface proteolysis is an important mechanism for generating biologically active proteins that mediate a range of cellular functions and contribute to biological processes such as angiogenesis. Although most studies have focused on the plasminogen system and matrix metalloproteinases (MMPs), recently there has been an increase in the identification of membrane associated proteases, including serine proteases, ADAMs, and membrane-type MMPs (MT-MMPs). Normally, protease activity is tightly controlled by tissue inhibitors of MMPs (TIMPs) and plasminogen activator inhibitors (PAIs). The balance between active proteases and inhibitors is thought to determine the occurrence of proteolysis in vivo. High concentrations of proteolytic system components correlate with poor prognosis in many cancers. Paradoxically, high (not low) PAI-1 or TIMP concentrations predict poor survival in patients with various cancers. Recent observations indicate a much more complex role for protease inhibitors in tumour progression and angiogenesis than initially expected. As knowledge in the field of protease biology has improved, the unforeseen complexities of cell associated enzymes and their interaction with physiological inhibitors have emerged, often revealing unexpected mechanisms of action.

Identification, purification and partial characterization of tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) in bovine pulmonary artery smooth muscle

Bovine pulmonary artery smooth muscle tissue possesses the tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) as revealed by immunoblot studies of the cytosolic fraction with polyclonal TIMP-1 antibody. In this report, we described the purification and partial characterization of the inhibitor from the cytosolic fraction of the smooth muscle. This inhibitor was purified by a series of anion-exchange, gel filtration and affinity chromatographic procedure. The purified inhibitor showed an apparent molecular mass of 30 kDa in SDS-PAGE. Amino terminal sequence analysis for the first 22 amino acids of the purified inhibitor was also found to be identical to bovine TIMP-1. This glycosylated inhibitor was found to be active against matrix metalloproteinase-9 (MMP-9, gelatinase B), the ambient matrix metalloproteinase in the pulmonary smooth muscle. The purified TIMP-1 was also found to be sensitive to pure rabbit and human fibroblast collagenase and type IV collagenase. In contrast, it had minimum inhibitory activity against bacterial collagenase. It was also found to be inactive against the serine proteases trypsin and plasmin. The inhibitor was heat and acid resistant and it had the sensitivity to trypsin degradation and reduction-alkylation.

Adenoviral delivery of a constitutively active retinoblastoma mutant inhibits neointima formation in a human explant model for vein graft disease

Intimal hyperplasia resulting from vascular injury remains a major obstacle in the long-term success of coronary artery bypass grafts. Inhibition of smooth muscle cell (SMC) proliferation using adenoviral gene transfer of cell cycle inhibitors resulted in reduced neointima formation in various animal models. However, little is known about the effect on human SMCs and neointima formation. Here we report the effects of infection with an adenoviral vector encoding a constitutively active form of the retinoblastoma gene (Ad. delta Rb) on proliferation of human saphenous vein SMCs (HSVSMCs) and neointima formation in organ cultures of human saphenous vein. Proliferation of SMCs was inhibited dose-dependently after infection with Ad. delta Rb. A near-total inhibition was found at an Ad. delta Rb concentration of 10(8) pfu/ml. Organ cultures of human saphenous vein segments were used to evaluate the effect of Ad. delta Rb infection on neointima formation and vein graft disease. Segments cultured for 4 weeks develop a neointima that is morphologically highly similar to early initimal lesions found in pathological vein grafts in vivo. Infection of saphenous vein segments with 2 x 10(9) pfu/ml Ad. delta Rb resulted in a 59% reduction of neointimal area when compared to uninfected counterparts, whereas infection with control adenovirus, Ad.LacZ, had no significant effect. The results of this study show that Ad. delta Rb gene transfer might be an efficient approach to prevent neointima formation in human saphenous vein grafts.