Smooth muscle cell matrix metalloproteinase production is stimulated via alpha(v)beta(3) integrin

Interleukin-1beta induces osteopontin expression in pulmonary fibroblasts

Osteopontin is a multifunctional matricellular protein identified as one of the most upregulated genes in pulmonary fibrosis. Experimental animal models have identified early pro-fibrotic cytokines as essential to the pathogenesis of inflammation-induced pulmonary fibrosis. However, the principal sources of osteopontin in the fibroproliferative lung, and the factors responsible for its induction, have not been fully defined. We isolated primary rat lung fibroblasts in culture to examine the expression and regulation of lung fibroblast-derived osteopontin. Our results demonstrate a potent and dramatic increase in osteopontin expression induced by interleukin-1beta (IL-1beta), whereas tumor necrosis factor-alpha, transforming growth factor-beta, and angiotensin II had minimal effect. Stimulation with IL-1beta resulted in the secretion of soluble osteopontin protein. We found that osteopontin expression by IL-1beta was regulated via signaling primarily through the mitogen-activated protein kinase member ERK1/2, partially by p38 MAPK, but not at all by JNK. Finally, the mechanism of IL-1beta increase in osteopontin mRNA requires de novo transcription and translation. In conclusion, we find that osteopontin is expressed by primary lung fibroblasts and is potently upregulated by the early inflammatory and pro-fibrotic cytokine IL-1beta. Activated fibroblasts may be a significant source of osteopontin production during lung fibrogenesis.

[Osteopontin, a multi-faceted molecule]

Osteopontin (OPN) was initially isolated from bovine bone cortex, as a complex syalilated phospho-glyco-protein of around 60 kDa, with many postranslational modifications. It has been long considered a structural bone protein linking bone cells to the bone extracellular matrix (osteo : bone, pontin : bridge). It has been cloned for the first time in 1986. Since then, it was established that it is part of a protein family called SIBLINGs, which genes share common expression in bone and tooth, and encode among others a RGD motif. OPN is an intracellular as well as secreted protein, which binds to multiple organic or mineral ligands, like the integrin receptor alphaVbeta3, CD44, factor H and hydroxyapatite, depending on its final configuration (phosphorylation state). Pleiotropic functions of osteopontin have been demonstrated, and the osteopontin knock out phenotype in mice gave some new insight on the implication of the molecule in vivo. Osteopontin inhibits mineralization in bone and urine. Besides, it is a strong chemoattractive and proinflammatory molecule, implicated in tumors, like breast or prostate cancers, and in the defense against various infectious agents like tuberculosis, listeria or herpes. More recently, its key implication in TH1 mediated autoimmune diseases like multiple sclerosis and its animal model experimental autoimmune encephalomyelitis has been demonstrated. Osteopontin is a valuable therapeutic target in the animal model, and a biological tool correlating with clinical disease activity in humans. Structural, functional and pathological aspects of osteopontin are reviewed, as well as the osteopontin deficient phenotype in mouse.

Local delivery of osteopontin attenuates vascular remodeling by altering matrix metalloproteinase-2 in a rabbit model of aortic injury

OBJECTIVE

Vascular remodeling, often accelerated after cardiovascular procedures, may result in stenosis or aneurysm formation. The bone-associated protein osteopontin has been suggested to be involved in vascular remodeling, yet the effect of locally applied osteopontin in an acute vascular injury model of aortic calcification has not been examined.

METHODS

Vascular healing of rabbit thoracic aortas treated locally with recombinant osteopontin (dose: 1 microg; n = 16) or albumin (control, n = 16) after acute injury created by end-to-end anastomosis was evaluated. Matrix metalloproteinase-2 level was quantified by gelatin zymography. Proliferation of smooth muscle cells was detected by immunostaining for proliferative cell nuclear antigen.

RESULTS

Osteopontin-treated aortas showed significantly diminished vascular remodeling with less calcification (P = .001) and reduced anastomotic luminal stenosis (4% vs 28%, P = .002) compared with controls 2 months postsurgery. Moreover, osteopontin-treated aortas revealed a thickened adventitia with increased fibrosis (P = .006). Matrix metalloproteinase-2 level was up-regulated 2-fold with osteopontin treatment compared with control at 1 week, returning to baseline by 1 month. Staining for proliferation cell nuclear antigen disclosed an increase in proliferation cell nuclear antigen-positive smooth muscle cells in the media of osteopontin-treated aortas at 1 week, normalizing by 1 month.

CONCLUSIONS

These data suggest a beneficial effect of locally applied osteopontin after acute injury possibly by altering matrix metalloproteinase-2 activity and smooth muscle cell proliferation. Brief application of osteopontin may effectively enhance vascular healing by reducing calcification and thus maintaining luminal integrity. The role of the osteopontin-related increase in adventitial fibrosis on vascular healing has to be explored.

Pioglitazone inhibits MMP-1 expression in vascular smooth muscle cells through a mitogen-activated protein kinase-independent mechanism

Antidiabetic drug thiazolidinedione (TZD) also has anti-atherogenic effects. Among these effects, inhibition of smooth muscle cell (SMC) migration is considered to be essential. However, the mechanism whereby TZD inhibits SMC migration is not well understood. Since it is known that matrix metalloproteinases (MMPs) play a permissive role for SMC migration, we determined if TZD inhibits the upregulation of MMP-1 expression in SMCs by oxidized LDL (oxLDL), a potent stimulator for atherogenesis. Results showed that oxLDL markedly stimulated MMP-1 secretion, mRNA expression, and MMP-1 promoter activity, but pioglitazone significantly inhibited the oxLDL-upregulated MMP-1 expression. In an attempt to explore the signaling mechanism by which pioglitazone inhibits the oxLDL-upregulated MMP-1 expression, we found that extracellular signal-regulated kinase (ERK) and c-Jun-N-terminal kinase (JNK) pathways were required for the oxLDL-stimulated MMP-1 expression, but pioglitazone failed to antagonize the activation of ERK and JNK by oxLDL. Finally, our AP-1 activity assay showed that pioglitazone inhibited oxLDL-stimulated c-Jun activity. Taken together, the present study indicates that pioglitazone inhibits oxLDL-stimulated MMP-1 expression in VSMCs by inhibiting c-Jun transcriptional activity through a mitogen-activated protein kinase (MAPK)-independent mechanism.

Pharmacological treatment for prevention of restenosis

Coronary artery disease (CAD) is the leading cause of mortality and morbidity among adults in the Western world. Coronary artery bypass grafting and percutaneous coronary interventions (PCI) have gained widespread acceptance for the treatment of symptomatic CAD. There has been an explosive growth worldwide in the utilisation of PCI, such as balloon angioplasty and stenting, which now accounts for over 50% of coronary revascularisation. Despite the popularity of PCI, the problem of recurrent narrowing of the dilated artery (restenosis) continues to vex investigators. In recent years, significant advances have occurred in the understanding of restenosis. Two processes seem to contribute to restenosis: remodelling (vessel size changes) and intimal hyperplasia (vascular smooth muscle cell [VSMC] proliferation and extracellular matrix [ECM] deposition). Despite considerable efforts, pharmacological approaches to decrease restenosis have been largely unsuccessful and the only currently applied modality to reduce the restenosis rate is stenting. However, stenting only prevents remodelling and does not inhibit intimal hyperplasia. Several potential targets for inhibiting restenosis are currently under investigation including platelet activation, the coagulation cascade, VSMC proliferation and migration, and ECM synthesis. In addition, new approaches for local drug therapy, such as drug eluting stents, are currently being evaluated in preclinical and clinical studies. In this article, we critically review the current status of drugs that are being evaluated for restenosis at various stages of development (in vitro, preclinical animal models and human trials).

Alpha V integrin prolongs collagenase production through Jun activation binding protein 1

Robust expression of alphav integrin and matrix metalloproteinase 1 (MMP1) plays an important role in cancer metastasis and wound healing. A patient with an abnormal scar that appeared stretched and thinned out was found to have fibroblasts that overexpressed alphav integrin; therefore, a relationship between alphav integrin expression and MMP1 production was sought. A yeast 2 hybrid screen revealed alphav integrin interacts with jun activation binding domain-1 (JAB1). Mesenchymal-derived cells were transfected with the alphav integrin gene and incorporated into collagen lattices. Transfected cells maximally contracted collagen lattices beginning on day 5, whereas control transfected cells did not contract lattices. Late-phase collagen lattice contraction was inhibited by a pan-MMP inhibitor, BB4. Overexpression of alphav correlated with enhanced MMP1 transcription, as determined by a luciferase assay (P < or = 0.05). Diminution of JAB1 with JAB1 antisense abolished alphav integrin up-regulation of MMP1. We conclude alphav integrin signals through JAB1 to prolong MMP1 production and that this signaling pathway in fibroblasts may lead to abnormal scarring.

RGD-containing fibrillin-1 fragments upregulate matrix metalloproteinase expression in cell culture: a potential factor in the pathogenesis of the Marfan syndrome

The Marfan syndrome (MFS), a relatively common autosomal dominant disorder of connective tissue, is caused by mutations in the gene for fibrillin-1 (FBN1). Fibrillin-1 is the main component of the 10- to 12-nm microfibrils that together with elastin form elastic fibers found in tissues such as the aortic media. Recently, FBN1 mutations have been shown to increase the susceptibility of fibrillin-1 to proteolysis in vitro, and other findings suggest that up-regulation of matrix metalloproteinases (MMP), as well as fragmentation of microfibrils, could play a role in the pathogenesis of MFS. In the present work, we have investigated the influence of fibrillin-1 fragments on the expression of MMP-1, MMP-2, and MMP-3 in a cell culture system. Cultured human dermal fibroblasts were incubated with several different recombinant fibrillin-1 fragments. The expression level of MMP-1, MMP-2, and MMP-3, was determined by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), and the concentration of the corresponding proteins was estimated by quantitative Western blotting. Our results establish that treatment of cultured human dermal fibroblasts with recombinant fibrillin-1 fragments containing the arginine-glycine-aspartic acid (RGD) integrin-binding motif of fibrillin-1 induces up-regulation of MMP-1 and MMP-3. A similar effect was seen upon stimulation with a synthetic RGD peptide. The expression of MMP-2 was not influenced by treatment. Our results suggest the possibility that fibrillin fragments could themselves have pathogenic effects by leading to up-regulation of MMPs, which in turn may be involved in the progressive breakdown of microfibrils thought to play a role in MFS.

Implications of proprotein Convertase 5 (PC5) in the arterial restenotic process in a porcine model

INTRODUCTION

Convertases (PCs), especially PC5, have been detected in various layers of atherosclerotic and injured arteries. We postulate that PCs could be important enzymes in vascular disease thus studied PC5 expression in a porcine balloon and stent coronary arterial vascular injury model.

METHODS

Immunohistochemistry and in situ hybridization of slides of porcine arteries from paraffin blocks were studied 1, 7, 14 and 28 days post injury.

RESULTS

Immunohistochemistry studies show expression of PC5 in control artery endothelial cells, weak medial smooth muscle cell (SMC) staining and strong staining in the small nerves of the adventitia. At 7, 14 and 28 days postinjury, there is strong positive PC5 staining of the neointimal cells and the adventitial vasa vasora and myofibroblasts. Colocalization immunohistochemistry confirms the smooth muscle staining properties of the myofibroblast-like cells in both these locations. Single-label immunohistochemistry studies show the same cells to stain strongly positive with TGF-B, PDGF, matrix metalloproteinase-2 (MMP-2) and MMP-9.

CONCLUSION

PC5 may be involved in the process of arterial injury via its effect on growth factors (GFs) and mediators. These preliminary observations suggest that the convertases, especially PC5, represent a target for future study in the process of arterial injury.

The role of osteopontin in lung disease

Osteopontin (Opn) is a multifunctional protein independently discovered by investigators from diverse scientific backgrounds and implicated in a broad array of pathological processes. Opn exists both intra- and extracellularly and in numerous pre- and post-translational isoforms. Structurally Opn resembles a matrix protein yet it has well-characterized cytokine like properties including the regulation of cellular migration and cell-mediated immunity. It has thus been classified as both a matricellular protein and a cytokine. Opn is among the most abundantly expressed proteins in a range of lung diseases and has been shown to regulate aspects of pulmonary granuloma formation, fibrosis, and malignancy. Future studies will explore the diagnostic and therapeutic potential of modulating the function of Opn in vivo.

Gene expression profile in human late radiation enteritis obtained by high-density cDNA array hybridization

Late radiation enteritis is a sequela of radiation therapy to the abdomen. The pathogenic process is poorly understood at the molecular level. cDNA array analysis was used to provide new insights into the pathogenesis of this disorder. Gene profiles of six samples of fibrotic bowel tissue from patients with radiation enteritis and six healthy bowel tissue samples from patients without radiation enteritis were compared using membrane-based arrays containing 1314 cDNAs. Results were confirmed with real-time RT-PCR and Western blot analysis. Array analysis identified many differentially expressed genes involved in fibrosis, stress response, inflammation, cell adhesion, intracellular and nuclear signaling, and metabolic pathways. Increased expression of genes coding for proteins involved in the composition and remodeling of the extracellular matrix, along with altered expression of genes involved in cell- to-cell and cell-to-matrix interactions, were observed mainly in radiation enteritis samples. Stress, inflammatory responses, and antioxidant metabolism were altered in radiation enteritis as were genes coding for recruitment of lymphocytes and macrophages. The Rho/HSP27 (HSPB1)/zyxin pathway, involved in tissue contraction and myofibroblast transdifferentiation, was also altered in radiation enteritis, suggesting that this pathway could be related to the fibrogenic process. Our results provide a global and integrated view of the alteration of gene expression associated with radiation enteritis. They suggest that radiation enteritis is a dynamic process involving constant remodeling of each structural component of the intestinal tissue, i.e. the mucosa, the mesenchyme, and blood vessels. Functional studies will be necessary to validate the present results.

Alphavbeta3-integrin antagonists inhibit thrombin-induced proliferation and focal adhesion formation in smooth muscle cells

Alphavbeta3-integrin antagonists reduced neointimal formation following vascular injury in eight different animal models. Because alpha-thrombin contributes to neointimal formation, we examined the hypothesis that alphavbeta3-integrins influence alpha-thrombin-induced signaling. Cultured rat aortic smooth muscle cells (RASMC) expressed alphavbeta3-integrins as demonstrated by immunofluorescence microscopy and fluorescence-activated cell sorting analysis. Proliferative responses to alpha-thrombin were partially inhibited by anti-beta3-integrin monoclonal antibody F11 and by cyclic RGD peptides. Immunofluorescence microscopy showed that alpha-thrombin stimulated a rapid increase in the formation of focal adhesions as identified by vinculin staining and that this effect was partially inhibited by alphavbeta3 antagonists. Beta3-integrin staining was diffuse in quiescent RASMC and did not concentrate at sites of focal adhesions following thrombin treatment. Alpha-thrombin elicited a time-dependent increase in activation of c-Jun NH2-terminal kinase-1 (JNK1) and in tyrosine phosphorylation of focal adhesion kinase (FAK). Alphavbeta3-integrin antagonists partially inhibited increases in JNK1 activity but had no effect on FAK phosphorylation. In SMC isolated from beta3-integrin-deficient mice, focal adhesion formation was impaired in response to thrombin but not sphingosine-1-phosphate, a potent activator of Rho. In summary, alphavbeta3-integrins play an important role in alpha-thrombin-induced proliferation and focal adhesion formation in RASMC.

Teriparatide (human parathyroid hormone (1-34)) inhibits osteogenic vascular calcification in diabetic low density lipoprotein receptor-deficient mice

Cardiovascular calcification is a common consequence of diabetes. High fat diets induce diabetes and arterial calcification in male low density lipoprotein receptor (LDLR) -/- mice; calcification occurs via Msx2 signaling that promotes the osteogenic differentiation of arterial myofibroblasts. We studied regulation of arterial osteogenesis by human parathyroid hormone (PTH) (1-34) (also called teriparatide) in LDLR -/- mice fed diabetogenic diets for 4 weeks. LDLR -/- mice were treated with vehicle or 0.4 mg/kg of PTH(1-34) subcutaneously five times/week. Gene expression was determined from single aortas and hind limb RNA by fluorescence reverse transcription-PCR. Valve calcification was determined by histological staining of cardiac sections using image analysis to quantify valve leaflet mineralization. PTH(1-34) increased bone mineral content (by dual energy x-ray absorptiometry) in LDLR -/- mice, with induction of osseous osteopontin (OPN) expression and serum OPN levels (>150 nM); PTH(1-34) did not significantly change serum glucose, lipids, body weight, or fat mass. PTH(1-34) suppressed aortic OPN and Msx2 expression >50% and decreased cardiac valve calcification 80% (8.3 +/- 1.5% versus 1.4 +/- 0.5%; p < 0.001). Of the known circulating regulators of vascular calcification (OPN, osteoprotegerin, and leptin), PTH(1-34) regulated only serum OPN. We therefore studied actions of PTH(1-34) and OPN in vitro on cells induced to mineralize with Msx2. OPN (5-50 nM) reversed Msx2-induced mineralization. PTH(1-34) inhibited mineralization by 40% and down-regulated Msx2 in aortic myofibroblasts. PTH(1-34) inhibits vascular calcification and aortic osteogenic differentiation via direct actions and potentially via circulating OPN. PTH(1-34) exerts beneficial actions at early stages of macrovascular disease responses to diabetes and dyslipidemia.

Osteopontin inhibits interleukin-1beta-stimulated increases in matrix metalloproteinase activity in adult rat cardiac fibroblasts: role of protein kinase C-zeta

We have shown that osteopontin (OPN), an extracellular matrix protein, plays an important role in post myocardial infarction (MI) remodeling by promoting collagen synthesis and accumulation. Interleukin-1beta (IL-1beta), increased in the heart following MI, increases matrix metalloproteinase (MMP) activity in cardiac fibroblasts in vitro. Here, we show that OPN alone has no effect on MMP activity or expression. However, it reduces IL-1beta-stimulated increases in MMP activity and expression in adult rat cardiac fibroblasts. Pretreatment with bovine serum albumin had no effect on MMP activity or protein content, whereas GRGDS (glycine-arginine-glycine-aspartic acid-serine)-pentapeptide (which interrupts binding of RGD-containing proteins to cell surface integrins) and monoclonal antibody m7E3 (a rat beta3 integrins antagonist) inhibited the effects of OPN. Inhibition of PKC using chelerythrine inhibited the activities of both MMP-2 and MMP-9. Stimulation of cells using IL-1beta increased phosphorylation and translocation of PKC to membrane fractions, which was inhibited by OPN. OPN inhibited IL-1beta-stimulated increases in translocation of PKC-zeta from cytosolic to membrane fractions. Furthermore, the levels of phospho-PKC-zeta were lower in the cytosolic fractions of OPN knock-out mice hearts as compared with wild type 6 days post-MI. Inhibition of PKC-zeta using PKC-zeta pseudosubstrate inhibited IL-1beta-stimulated increases in MMP-2 and MMP-9 activities. These observations suggest that OPN, acting via beta3 integrins, inhibits IL-1beta-stimulated increases in MMP-2 and MMP-9 activity, at least in part, via the involvement of PKC-zeta. Thus, OPN may play a key role in collagen deposition during myocardial remodeling following MI by modulating cytokine-stimulated MMP activity.

Activated integrin alphavbeta3 cooperates with metalloproteinase MMP-9 in regulating migration of metastatic breast cancer cells

Expression of adhesion receptor integrin alphavbeta3 in an activated functional form strongly promotes metastasis in human breast cancer cells. Here, we report that alphavbeta3 cooperates with matrix metalloproteinase type 9 (MMP-9) in breast cancer cell migration. This cooperation is regulated by the activation state of the integrin. Expression of activated alphavbeta3 in metastatic variants of MDA-MB 435 human breast cancer cells and primary metastatic cells from breast cancer patients strongly enhanced migration toward vitronectin and fibrinogen. This enhancement was mediated by a soluble factor produced by breast cancer cells expressing activated alphavbeta3. When transferred, this factor also up-regulated alphavbeta3-dependent migration of breast cancer cells that express the nonactivated integrin. The factor was identified as metalloproteinase MMP-9. Whereas all tested breast cancer cell variants produced latent MMP-9, only those with activated alphavbeta3 produced the mature form of this metalloproteinase. Recombinant mature MMP-9, but not latent MMP-9 or either form of MMP-2, enhanced alphavbeta3-dependent breast cancer cell migration. The migratory response was inhibited by tissue inhibitors of metalloproteinase or when MMP-9 was depleted from the inducing supernatants. The results indicate a causal relationship between the expression of activated integrin alphavbeta3 and production of enzymatically active MMP-9 in metastatic breast cancer cells. These molecules cooperate to enhance breast cancer cell migration toward specific matrix proteins, and this may contribute to the strongly enhanced metastatic capacity of breast cancer cells that express activated alphavbeta3.

Latent transforming growth factor-beta binding protein-1, a component of latent transforming growth factor-beta complex, accelerates the migration of aortic smooth muscle cells in diabetic rats through integrin-beta3

Aortic smooth muscle cells (SMCs) of diabetic animals have unique properties, including the overexpression of transforming growth factor-beta (TGF-beta) type II receptor, fibronectin, and platelet-derived growth factor beta-receptor. TGF-beta1 is produced and secreted as latent high-molecular weight complex consisting of mature TGF-beta1, latency-associated peptide (LAP), and a latent TGF-beta1 binding protein (LTBP-1). LAP has an important function in the latency of TGF-beta complex, but the role of LTBP-1 is not known in diabetic angiopathy. SMC migration from the medial layer to the intimal layer of an artery is an initial major process of the formation of intimal thickening of an artery. Migration activities of SMCs from diabetic rat with 1-500 pg/ml of LTBP-1 increased significantly compared with that without LTBP-1. LTBP-1 at 10-500 pg/ml stimulated the migration of diabetic SMCs more than SMCs from control rat. An anti-integrin-beta(3) antibody reduced LTBP-1-stimulated migration of diabetic SMCs to 51% compared with no antibody, but it did not reduce that of control SMCs. Furthermore, cross-linking experiments show that LTBP-1 binds integrin-beta(3) in diabetic SMCs much more than in control SMCs in coincidence with the increase of integrin-beta(3) in diabetic aorta by immunohistochemistry. Taken together, these observations suggest that LTBP-1 plays a critical role in intimal thickening of diabetic artery through the acceleration of SMC migration via integrin-beta(3).

Vascular collagens: spotlight on the role of type VIII collagen in atherogenesis

Collagens play a central role in maintaining the integrity and stability of the undiseased as well as of the atherosclerotic vessel wall. An imbalanced metabolism may lead to uncontrolled collagen accumulation reducing vessel wall velocity, frequently resulting in arterial occlusion or thrombosis. A reduced production of collagen and its uncontrolled degradation may affect the stability of the vessel wall and especially of the atherosclerotic plaques by making them prone to rupture and aneurysm. This review presents an overview on the four groups of vascular collagens and on their role in atherogenesis. The major focus was to highlight the extraordinary role and importance of the short chain network forming type VIII collagen in the extracellular matrix of undiseased arteries and of atherosclerotic plaques. The molecular structure of type VIII collagen, its cellular origin, its implication in atherogenesis, its temporal and spatial expression patterns in human and experimental models of atherogenesis, the factors modulating its expression, and--not at least--its potential function is discussed.

Signaling pathways transduced through the elastin receptor facilitate proliferation of arterial smooth muscle cells

In this report we demonstrate that soluble peptides, elastin degradation products stimulate proliferation of arterial smooth muscle cells. We show that these effects are due to generation of intracellular signals transduced through the cell surface elastin receptor, which consists of peripheral 67-kDa elastin-binding protein (EBP) (spliced variant of beta-galactosidase), immobilized to the transmembrane sialidase and the protective protein. We found that elastin receptor-transduced signaling triggers activation of G proteins, opening of l-type calcium channels, and a sequential activation of tyrosine kinases: FAK, c-Src, platelet-derived growth factor-receptor kinase and then Ras-Raf-MEK1/2-ERK1/2 phosphorylation cascade. This, in turn, causes an increase in expression of cyclins and cyclin-dependent kinases, and a consequent increase in cellular proliferation. The EBP-transduced signals also induce tyrosine kinase-dependent phosphorylation of beta-tubulin, LC3, microtubule-associated protein 1, and alpha-actin and troponin-T, which could be linked to reorganization of cytoskeleton. We have also disclosed that induction of these signals can be abolished by anti-EBP antibody or by galactosugars, which cause shedding of EBP from the cell surface. Moreover, elastin-derived peptides did not induce proliferation of EBP-deficient cells derived from patients bearing a nonsense mutation of the beta-galactosidase gene or sialidase-deficient cells from patients with congenital sialidosis.

Involvement of tumor cell integrin alpha v beta 3 in hematogenous metastasis of human melanoma cells

Early metastasis is the primary cause of death in melanoma patients. The adhesion receptor integrin alpha v beta 3 contributes to tumor cell functions that are potentially involved in melanoma growth and metastasis. We tested whether integrin alpha v beta 3 supports metastasis of human melanoma cells when injected into the bloodstream of immune deficient mice. Comparing variants of the same melanoma cell type that expressed either alpha v beta 3, alpha IIb beta 3 or no beta 3 integrin, we found that only alpha v beta 3 strongly supported metastasis. Inhibition of tumor cell alpha v beta 3 function reduced melanoma metastasis significantly and prolonged animal survival. To understand mechanisms that allow alpha v beta 3, but not alpha IIb beta 3 to support melanoma metastasis, we analyzed proteolytic and migratory activities of the melanoma cell variants. Melanoma cells expressing alpha v beta 3, but not those expressing alpha IIb beta 3 or no beta 3 integrin, produced the active form of metalloproteinase MMP-2 and expressed elevated mRNA levels of MT1-MMP and TIMP-2. This indicates an association between alpha v beta 3 expression and protease processing. Furthermore, alpha v beta 3 expression was required for efficient melanoma cell migration toward the matrix proteins fibronectin and vitronectin. The results suggest that expression of integrin alpha v beta 3 promotes the metastatic phenotype in human melanoma by supporting specific adhesive, invasive and migratory properties of the tumor cells and that the related integrin alpha IIb beta 3 cannot substitute for alpha v beta 3 in this respect.

Metalloproteinase inhibitor attenuates neointima formation and constrictive remodeling after angioplasty in rats: augmentative effect of alpha(v)beta(3) receptor blockade

Release of matrix metalloproteinases (MMP) from smooth muscle and foam cells following arterial injury facilitates cell migration, neointimal hyperplasia, and vessel wall remodeling. Inhibition of MMP activity using the hydroxamate, zinc-chelating mimicers of collagen, Batimastat and Marimastat, has shown efficacy in reducing constrictive vascular remodeling 6 weeks after experimental angioplasty but not intimal hyperplasia. Vitronectin receptor (alpha(v)beta(3)) blockade interferes with binding of this integrin to MMP-2 and proteolyzed collagen, thereby reducing cell invasion. This study tests the effect of MMP inhibition, with and without vitronectin receptor (alpha(v)beta(3)) blockade, on neointima formation and arterial remodeling in a long-term model (up to 212 months) of balloon injury in vivo. Male Sabra rats were treated with Batimastat (BB-94, British Biotech Pharmaceuticals Ltd., 30 mg/kg, intraperitoneally) and/or the alpha(v)beta(3) receptor inhibiting RGD peptide, G-Pen-GRGDSPCA (GIBCO BRL, 0.1 micromol), administered as a perivascular gel to the common carotid artery after balloon injury. Animals were sacrificed 3, 14, 25, and 75 days (n=21, 23, 22, and 21) after injury. Animals treated with BB-94, peptide, or both had markedly increased absolute luminal area with markedly reduced luminal cross-sectional-area narrowing by neointima and intima-to-media area ratio at all time points except for 3 days after balloon injury versus non-treated, ballooned animals. Combined treatment was significantly more effective than either one alone. Constrictive remodeling, most marked 212 months after balloon injury, was prevented at this time point in all treated animals. The pattern of reduction in luminal narrowing, neointimal formation, and constrictive remodeling across treatment groups correlated very significantly with the reduction in tissue MMP activity as determined by zymography at 3 days. Confirmation of the efficacy of this strategy in larger animals should be the next step toward testing the applicability of this novel approach to the interventional setting.

Matrix metalloproteinases and atherosclerotic plaque instability

BACKGROUND

There is growing interest in the role of matrix metalloproteinases in atherosclerosis. Excessive tissue remodelling and increased matrix metalloproteinase activity have been demonstrated during atherosclerotic plaque disruption, a frequent predeterminant of ischaemic cardiac events and stroke. These enzymes represent a potential target for therapeutic intervention to modify vascular pathology.

METHODS

The core of this review is derived from a Medline database literature search.

RESULTS

There is convincing evidence of increased matrix metalloproteinase activity during acute plaque disruption. Evidence for an imbalance promoting increased matrix degradation is less well documented. However, studies of matrix metalloproteinase inhibition in models of vascular disease suggest a potential therapeutic benefit.

CONCLUSION

In vivo studies of matrix metalloproteinase inhibition are required to study the potential for reversal or deceleration of the excessive tissue remodelling that accompanies acute plaque disruption.

Production of matrix metalloproteinase-9 in CaCO-2 cells in response to inflammatory stimuli

Matrix metalloproteinase-9 (MMP-9) may play an important role in the development of inflammatory bowel disease (IBD). However, the cellular source of MMP-9 in the inflamed mucosa of IBD remains unclear. Here we report that MMP-9 mRNA is expressed in CaCO-2 cells, an intestinal epithelial cell line, and that its expression is upregulated by inflammatory stimuli. Stimulation of CaCO-2 cells with interleukin-1beta (IL-1beta) or tumor necrosis factor-alpha (TNF-alpha) led to a dose-dependent increase in expression and secretion of MMP-9. In contrast, bacterial lipopolysaccharide (LPS) failed to induce expression or secretion of MMP-9, suggesting that an inflammatory reaction leading to cytokine release is a necessary step for the induction of MMP-9 release in intestinal epithelial cells. Additional studies show that induction of MMP-9 mRNA peaked at 16 h of IL-1beta stimulation, whereas expression of monocyte chemoattractant protein-1 (MCP-1) and IL-8 both peaked at 3 h of stimulation. Treatment of CaCO-2 cells with rosiglitazone, a peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonist, significantly reduced secretion of MMP-9, indicating that agents that activate PPAR-gamma may have therapeutic use in patients with IBD.