Matrix metalloproteinase 2 releases active soluble ectodomain of fibroblast growth factor receptor 1

Myocardial matrix metalloproteinase-2: inside out and upside down

Since their inaugural discovery in the early 1960s, matrix metalloproteinases (MMPs) have been shown to mediate multiple physiological and pathological processes. In addition to their canonical function in extracellular matrix (ECM) remodeling, research in the last decade has highlighted new MMP functions, including proteolysis of novel substrates beyond ECM proteins, MMP localization to subcellular organelles, and proteolysis of susceptible intracellular proteins in those subcellular compartments. This review will provide a comparison of the extracellular and intracellular roles of MMPs, illustrating that MMPs are far more interesting than the one-dimensional view originally taken. We focus on the roles of MMP-2 in cardiac injury and repair, as this is one of the most studied MMPs in the cardiovascular field. We will highlight how understanding all dimensions, such as localization of activity and timing of interventions, will increase the translational potential of research findings. Building upon old ideas and turning them inside out and upside down will help us to better understand how to move the MMP field forward.

Specific matrix metalloproteinases play different roles in intraplaque angiogenesis and plaque instability in rabbits

BACKGROUND

Ectopic angiogenesis within the intima and media is considered to be a hallmark of advanced vulnerable atherosclerotic lesions. Some studies have shown that specific matrix metalloproteinases (MMPs) might play different roles in angiogenesis. Therefore, we investigated the predominant effects of specific MMPs in intraplaque angiogenesis and plaque instability in a rabbit model of atherosclerosis.

METHODS AND RESULTS

New Zealand rabbits underwent balloon injury of the abdominal artery and ingestion of a high-cholesterol (1%) diet to establish an atherosclerotic animal model. At weeks 4, 6, 8, 10, and 12 after balloon injury, five rabbits were euthanized and the abdominal aorta was harvested. Blood lipid analysis, intravascular ultrasound imaging, pathologic and immunohistochemical expression studies, and western blotting were performed. From weeks 4 to 12, the expression of MMP-1, -2, -3, and -9 and vascular endothelial growth factor A (VEGF-A) increased with atherosclerotic plaque development in the abdominal aorta, while the expression of MMP-14 substantially decreased. The vulnerability index (VI) gradually increased over time. Intraplaque neovessels appeared at week 8. The microvessel density (MVD) was greater at week 12 than at week 8. The VI, MVD, and VEGF-A level were positively correlated with the MMP-1, -2,-3, and -9 levels within plaques. Negative correlations were noted between the MMP-14 level and the VI, MVD, and VEGF-A level.

CONCLUSION

Upregulation of MMP-1, -2, -3, and -9 and downregulation of MMP-14 may contribute to intraplaque angiogenesis and plaque instability at the advanced stage of atherosclerosis in rabbits.

Roles of matrix metalloproteinases and their natural inhibitors in prostate cancer progression

Matrix metalloproteinases (MMPs), a group of zinc-dependent endopeptidases involved in the degradation of the extracellular matrix, play an important role in tissue remodeling associated with various physiological processes such as morphogenesis, angiogenesis, and tissue repair, as well as pathological processes including cirrhosis, arthritis and cancer. The MMPs are well established as mediators of tumor invasion and metastasis by breaking down connective tissue barriers. Although there has been a vast amount of literature on the role of MMPs in invasion, metastasis and angiogenesis of various cancers, the role of these endopeptidases in prostate cancer progression has not been systematically reviewed. This overview summarizes findings on the tissue and blood expression of MMPs, their function, regulation and prognostic implication in human prostate cancer, with a focus on MMP-2, -7, -9, MT1-MMP and tissue inhibitor of metalloproteinase 1 (TIMP-1). This review also summarizes the efficacy and failure of early-generation matrix metalloproteinase inhibitors (MMPIs) in the treatment of metastatic prostate cancer and highlights the lessons and challenges for next generation MMPIs.

Matrix metalloproteinase-9-null mice are resistant to TGF-β-induced anterior subcapsular cataract formation

Epithelial-mesenchymal transition (EMT) is associated with fibrotic diseases in the lens, such as anterior subcapsular cataract (ASC) formation. Often mediated by transforming growth factor (TGF)-β, EMT in the lens involves the transformation of lens epithelial cells into a multilayering of myofibroblasts, which manifest as plaques beneath the lens capsule. TGF-β-induced EMT and ASC have been associated with the up-regulation of two matrix metalloproteinases (MMPs): MMP-2 and MMP-9. The current study used MMP-2 and MMP-9 knockout (KO) mice to further determine their unique roles in TGF-β-induced ASC formation. Adenoviral injection of active TGF-β1 into the anterior chamber of all wild-type and MMP-2 KO mice led to the formation of distinct ASC plaques that were positive for α-smooth muscle actin, a marker of EMT. In contrast, only a small proportion of the MMP-9 KO eyes injected with adenovirus-expressing TGF-β1 exhibited ASC plaques. Isolated lens epithelial explants from wild-type and MMP-2 KO mice that were treated with TGF-β exhibited features indicative of EMT, whereas those from MMP-9 KO mice did not acquire a mesenchymal phenotype. MMP-9 KO mice were further bred onto a TGF-β1 transgenic mouse line that exhibits severe ASC formation, but shows a resistance to ASC formation in the absence of MMP-9. These findings suggest that MMP-9 expression is more critical than MMP-2 in mediating TGF-β-induced ASC formation.

Upregulated expression and activation of membrane‑associated proteases in esophageal squamous cell carcinoma

To better understand the role of membrane-associated proteolytic systems in the development of esophageal cancer, we studied the expression of two serine proteases, fibroblast activation protein-α (FAP-α) and dipeptidyl peptidase IV (DPPIV) and three metalloproteinases, matrix metalloproteinase (MMP)-2, MMP-9 and MT1-MMP in 24 primary esophageal squamous cell carcinoma (ESCC) tissues and paired non-cancer tissues. Using reverse-transcription PCR, western blotting and zymography, we showed that both serine proteases and all three metalloproteinases were highly altered in ESCC. A positive correlation between the expression of FAP-α and DPPIV and the activity of both gelatinases was found. This may indicate that these proteolytic systems are tightly linked to each other and collectively are involved in the process of ECM degradation that facilitates cancer cell invasion and metastasis.

Functional polymorphisms in the matrix metalloproteinase genes and their association with bladder cancer risk and recurrence: a mini-review

Molecular pathogenesis of muscle invasive bladder cancer and non-muscle invasive bladder cancer is incompletely elucidated. It is believed that matrix metalloproteinases, which are involved in the processes of uncontrolled extracellular matrix substrates degradation and participate in modulating the activity of a variety of non-matrix proteins, can contribute to carcinogenesis. Polymorphisms in the MMP genes associated with unique genomic changes in bladder cancer patients are still being investigated to discover direct links with pathophysiological mechanisms. Because of the functional polymorphisms in the MMP genes, which have a proven or likely effect on their protein expression, they could possibly affect the tumor process. The current mini-review synthesizes findings regarding the association of genetic polymorphisms in the MMP genes with bladder cancer risk and recurrence in patients. We discuss the current views on the feasibility of genetic polymorphisms in the MMP1, 2, 3, 7, 8, 9 and 12 genes as a risk, and prognostic markers for patients with bladder cancer. The majority of the research described in the present mini-review proves that the genetic polymorphism in the MMP1 (rs1799750) is the most widely studied, and suggests that the rare genotype, 2G2G, of that gene might show increased susceptibility for bladder cancer, especially among smokers. However, existing statistically significant associations between the genetic polymorphisms in the MMP genes and bladder cancer risk have not been clearly shown, and further studies are necessary in order to positively confirm them or dispel potential false hopes.

Matrix metalloproteinases in inflammation

BACKGROUND

Matrix metalloproteinases (MMPs) are a family of ubiquitously expressed zinc-dependent endopeptidases with broad substrate specificity and strictly regulated tissue specific expression. They are expressed in physiological situations and pathological conditions involving inflammation. MMPs regulate several functions related to inflammation including bioavailability and activity of inflammatory cytokines and chemokines. There is also evidence that MMPs regulate inflammation in tumor microenvironment, which plays an important role in cancer progression.

SCOPE OF REVIEW

Here, we discuss the current view on the role of MMPs in the regulation of inflammation.

MAJOR CONCLUSIONS

MMPs modulate inflammation by regulating bioavailability and activity of cytokines, chemokines, and growth factors, as well as integrity of physical tissue barriers. MMPs are also involved in immune evasion of tumor cells and in regulation of inflammation in tumor microenvironment.

GENERAL SIGNIFICANCE

There is increasing evidence for non-matrix substrates of MMPs that are related to regulation of inflammatory processes. New methods have been employed for identification of the substrates of MMPs in inflammatory processes in vivo. Detailed information on the substrates of MMPs may offer more specific and effective ways of inhibiting MMP function by blocking the cleavage site in substrate or by inhibition of the bioactivity of the substrate. It is expected, that more precise information on the MMP-substrate interaction may offer novel strategies for therapeutic intervention in inflammatory diseases and cancer without blocking beneficial actions of MMPs. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

[Changes in serum vascular endothelial growth factor and matrix metalloproteinase-9 after video-assisted thoracoscopic surgery and thoracotomic Lobectomy in the treatment of patients with non-small cell lung cancer]

BACKGROUND AND OBJECTIVE

Vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9) are important factors in angiogenesis. These factors function in the angiogenesis of lung cancers. The aim of this study is to determine the changes in serum VEGF and MMP-9 after patients with NSCLC were subjected to lobectomy. The aim of this study is also to compare the differences in the changes observed between video-assisted thoracoscopic surgery (VATS) and traditional open surgery (TOS).

METHODS

A total of 43 consecutive patients with NSCLC were recruited from October 2010 to August 2012. All of these patients underwent lobectomy and systematic mediastinal lymphadenectomy. Blood was drawn from these patients to measure the serum levels of VEGF and MMP-9 in the morning before surgery and on postoperative days 1, 2, 3, and 7 (POD1, POD2, POD3, and POD7, respectively). Perioperative variations in serum VEGF and MMP-9 were also observed. Using different surgical options, we divided the patients into two groups: VATS group (25 patients) and TOS group (18 patients). The differences in the changes in serum VEGF and MMP-9 were then compared between the two groups.

RESULTS

After surgery, the serum VEGF and MMP-9 of patients with NSCLC initially increased and subsequently decreased. The peak levels were observed on POD2 and POD3, and these levels were significantly higher than the preoperative levels (P=0.031, P=0.020). On POD7, the serum VEGF and MMP-9 remained higher than the preoperative levels. In VATS and TOS groups, the serum VEGF and MMP-9 levels also initially increased and subsequently decreased. The TOS group showed a more evident variation. However, no significant statistical differences in the changes of VEGF and MMP-9 were found between the two groups (F=2.022, P=0.163; F=1.703, P=0.199).

CONCLUSIONS

Serum VEGF and MMP-9 remarkably increase in TOS group and VATS group. Although the serum level of VEGF an MMP-9 in TOS group were higher than that in VATS group. But no significant difference was observed between VATS and TOS group.

Matrix metalloproteinases in coronary artery disease

Matrix metalloproteinases (MMP) are a family of zinc-containing endoproteinases that degrade extracellular matrix (ECM) components. MMP have important roles in the development, physiology and pathology of cardiovascular system. Metalloproteases also play key roles in adverse cardiovascular remodeling, atherosclerotic plaque formation and plaque instability, vascular smooth muscle cell (SMC) migration and restenosis that lead to coronary artery disease (CAD), and progressive heart failure. The study of MMP in developing animal model cardiovascular systems has been helpful in deciphering numerous pathologic conditions in humans. Increased peripheral blood MMP-2 and MMP-9 in acute coronary syndrome (ACS) may be useful as noninvasive tests for detection of plaque vulnerability. MMP function can be modulated by certain pharmacological drugs that can be exploited for treatment of ACS. CAD is a polygenic disease and hundreds of genes contribute toward its predisposition. A large number of sequence variations in MMP genes have been identified. Case-control association studies have highlighted their potential association with CAD and its clinical manifestations. Although results thus far are inconsistent, meta-analysis has demonstrated that MMP-3 Glu45Lys and MMP-9 1562C/T gene polymorphisms were associated with CAD risk.

Matrix metalloproteinase-2 deletions protect against hemorrhagic transformation after 1 h of cerebral ischemia and 23 h of reperfusion

Although elevated matrix metalloproteinase (MMP)-2 levels were highly related to the degradation of tight junction (TJ) proteins and basal lamina and neuronal injury after ischemia, until very recently, little experimental evidence was available to test the role of the MMP-2 knockout (KO) in blood-brain-barrier (BBB) injury and the development of hemorrhage transformation (HT). Here, we assessed the role of the MMP-2 KO in BBB injury, HT and other brain injuries after 1h of ischemia and 23 h of reperfusion. Middle cerebral artery occlusion (MCAO) was performed in MMP-2 KO mice. Reperfusion was started 1h after the onset of MCAO. All mice were sacrificed 24h after the MCAO. MMP-2 deficiency reduced the decrease in protein levels of collagen IV and cellular membrane occludin (p<0.01 and 0.05 vs. wild-type (WT), respectively) and attenuated increase in cytosol occludin level in ischemic brain (p<0.01 vs. WT). The hemorrhage volume and brain infarction were significantly decreased in both the cortex and striatum in the MMP-2 KO mice (p<0.01 vs. WT). The MMP-2 KO also had reduced brain swelling in the cortex and improved neurological deficits (p<0.01 vs. WT). These studies provide direct evidence that targeting MMP-2 will effectively protect against collagen and occludin loss and HT after ischemia and reperfusion.

The role of microglia and matrix metalloproteinases involvement in neuroinflammation and gliomas

Matrix metalloproteinases (MMPs) are involved in the pathogenesis of neuroinflammatory diseases (such as multiple sclerosis) as well as in the expansion of malignant gliomas because they facilitate penetration of anatomical barriers (such as the glia limitans) and migration within the neuropil. This review elucidates pathomechanisms and summarizes the current knowledge of the involvement of MMPs in neuroinflammation and glioma, invasion highlighting microglia as major sources of MMPs. The induction of expression, suppression, and multiple pathways of function of MMPs in these scenarios will also be discussed. Understanding the induction and action of MMPs might provide valuable information and reveal attractive targets for future therapeutic strategies.

Signal-dependent Elk-1 target genes involved in transcript processing and cell migration

Elk-1 was regarded as a transcription factor engaged mainly in the regulation of cell growth, differentiation, and survival. Recent findings show the engagement of Elk-1 in the control of expression of genes encoding proteins involved in transcript turnover, such as MCPIP1/ZC3H12A and tristetraprolin (TTP/ZFP36). Thus, Elk-1 plays an important role in the control of gene expression not only through the stimulation of expression of transcription factors, but also through regulation of transcript half-live. Moreover, Elk-1 is engaged in the regulation of expression of genes encoding proteins that control proteolytic activity, such as inhibitor of plasminogen activator-1 (PAI-1) and metalloproteinases-2 and -9 (MMP-2 and MMP-9). This review summarizes the biological roles of proteins with expression regulated by Elk-1, involved in transcripts turnover or in cell migration. The broad range of function of these proteins illustrates the complex role of Elk-1 in the regulation of cancer and inflammation.

Matrix metalloproteinase-2 and -9 as promising benefactors in development, plasticity and repair of the nervous system

It has been 50 years since Gross and Lapiere discovered collagenolytic activity during tadpole tail metamorphosis, which was later on revealed as MMP-1, the founding member of the matrix metalloproteinases (MMPs). Currently, MMPs constitute a large group of endoproteases that are not only able to cleave all protein components of the extracellular matrix, but also to activate or inactivate many other signaling molecules, such as receptors, adhesion molecules and growth factors. Elevated MMP levels are associated with an increasing number of injuries and disorders, such as cancer, inflammation and auto-immune diseases. Yet, MMP upregulation has also been implicated in many physiological functions such as embryonic development, wound healing and angiogenesis and therefore, these proteinases are considered to be crucial mediators in many biological processes. Over the past decennia, MMP research has gained considerable attention in several pathologies, most prominently in the field of cancer metastasis, and more recent investigations also focus on the nervous system, with a striking emphasis on the gelatinases, MMP-2 and MMP-9. Unfortunately, the contribution of these gelatinases to neuropathological disorders, like multiple sclerosis and Alzheimer's disease, has overshadowed their potential as modulators of fundamental nervous system functions. Within this review, we wish to highlight the currently known or suggested actions of MMP-2 and MMP-9 in the developing and adult nervous system and their potential to improve repair or regeneration after nervous system injury.

Matrix metalloproteinases as potential targets in the venous dilation associated with varicose veins

Varicose veins (VVs) are a common venous disease of the lower extremity characterized by incompetent valves, venous reflux, and dilated and tortuous veins. If untreated, VVs could lead to venous thrombosis, thrombophlebitis and chronic venous leg ulcers. Various genetic, hormonal and environmental factors may lead to structural changes in the vein valves and make them incompetent, leading to venous reflux, increased venous pressure and vein wall dilation. Prolonged increases in venous pressure and vein wall tension are thought to increase the expression/activity of matrix metalloproteinases (MMPs). Members of the MMPs family include collagenases, gelatinases, stromelysins, matrilysins, membrane- type MMPs and others. MMPs are known to degrade various components of the extracellular matrix (ECM). MMPs may also affect the endothelium and vascular smooth muscle, causing changes in the vein relaxation and contraction mechanisms. Endothelial cell injury also triggers leukocyte infiltration, activation and inflammation, which lead to further vein wall damage. The vein wall dilation and valve dysfunction, and the MMP activation and superimposed inflammation and fibrosis would lead to progressive venous dilation and VVs formation. Surgical ablation is an effective treatment for VVs, but may be associated with high recurrence rate, and other less invasive approaches that target the cause of the disease are needed. MMP inhibitors including endogenous tissue inhibitors (TIMPs) and pharmacological inhibitors such as zinc chelators, doxycycline, batimastat and marimastat, have been used as diagnostic and therapeutic tools in cancer, autoimmune and cardiovascular disease. However, MMP inhibitors may have side effects especially on the musculoskeletal system. With the advent of new genetic and pharmacological tools, specific MMP inhibitors with fewer undesirable effects could be useful to retard the progression and prevent the recurrence of VVs.

Matrix metalloproteinase-2 as a target for head and neck cancer therapy

INTRODUCTION

Matrix metalloproteinase (MMP)-2 is a zinc-dependent proteinase that is capable of cleaving all extracellular matrix (ECM) substrates. Degradation of the matrix is a key event in the progression, invasion, and metastasis of potentially malignant and malignant lesions of the head and neck. Therefore, blocking MMP-2 expression or activity may present a promising strategy for anticancer treatment.

AREAS COVERED

Current understanding of the molecular mechanisms that govern MMP-2 regulation and its tumorigenic effects, and that are involved in the initiation and progression of head and neck cancers, in particular the emerging role of MMP-2 in cell migration, which is a prerequisite for tumor metastasis. MMP-2 gene polymorphisms, cellular substrates, and interacting proteins are summarized. The current state of drugs that target this enzyme, either alone or in combination with other targeted agents are also discussed.

EXPERT OPINION

MMP-2 has long been a drug target. The current status of MMP-2 inhibitors as anticancer agents and their failure in the clinic is discussed in light of new data on the MMP-2s role as a cell surface transducer - data that may lead to the design and development of novel, MMP-2-targeting inhibitors.

Plasma matrix metalloproteinases and postmenopausal breast cancer risk: a nested case-control study in the Multiethnic Cohort study

The survival of malignant breast cells depends upon the remodeling of the extracellular matrix, including complex interactions with matrix metalloproteinases (MMPs). It has been hypothesized that circulating MMPs may serve as early indicators of breast cancer development in hospital-based case-control studies. A nested case-control study of the association of pre-diagnostic plasma levels of MMPs with the subsequent risk of postmenopausal breast cancer was conducted within the Multiethnic Cohort. During the follow-up period, 713 women with incident invasive breast cancer were identified and individually (1:1) matched to controls. Four types of MMPs (1, 2, 3, and 7) were analyzed by microsphere immunofluorescence assay. Mean plasma levels of MMPs did not differ significantly between cases and controls; nor were there differences in breast cancer risk by MMP level. No difference in the risk of breast cancer by plasma level of the MMPs was found within strata of age, or ethnicity, although MMP-1 levels were positively associated with breast cancer risk in obese women and women by hormone replacement medications (P values for interaction <0.05). Few significant differences in risk by levels of the MMPs were found by any of the clinical variables. Circulating MMPs were not associated with postmenopausal breast cancer risk.

FGFR1 cleavage and nuclear translocation regulates breast cancer cell behavior

FGFR1 cleavage by Granzyme B induces its nuclear translocation, in which it stimulates cell migration through effects on gene expression.

FGF-10 and its receptors, FGFR1 and FGFR2, have been implicated in breast cancer susceptibility and progression, suggesting that fibroblast growth factor (FGF) signaling may be co-opted by breast cancer cells. We identify a novel pathway downstream of FGFR1 activation, whereby the receptor is cleaved and traffics to the nucleus, where it can regulate specific target genes. We confirm Granzyme B (GrB) as the protease responsible for cleavage and show that blocking GrB activity stopped FGFR1 trafficking to the nucleus and abrogates the promigratory effect of FGF stimulation. We confirm the in vivo relevance of our findings, showing that FGFR1 localized to the nucleus specifically in invading cells in both clinical material and a three-dimensional model of breast cancer. We identify target genes for FGFR1, which exert significant effects on cell migration and may represent an invasive signature. Our experiments identify a novel mechanism by which FGF signaling can regulate cancer cell behavior and provide a novel therapeutic target for treatment of invasive breast cancer.

Effects of molecular weight and loading on matrix metalloproteinase-2 mediated release from poly(ethylene glycol) diacrylate hydrogels

Herein, we report on continued efforts to understand an implantable poly(ethylene glycol) diacrylate (PEGDA) hydrogel drug delivery system that responds to extracellular enzymes, in particular matrix metalloproteinase-2 (MMP-2) to provide controlled drug delivery. By attaching peptide as pendant groups on the hydrogel backbone, drug release occurs at an accelerated rate in the presence of active protease. We investigated MMP-2 entry and optimized parameters of the drug delivery system. Mesh size for different PEGDA molecular weight macromers was measured with PEGDA 3,400 hydrogels having a mesh size smaller than the dimensions of MMP-2 and PEGDA 10,000 and PEGDA 20,000 hydrogels having mesh sizes larger than MMP-2. Purified MMP-2 increased release of peptide fragment compared to buffer at several loading concentrations. Cell-stimulated release was demonstrated using U-87 MG cells embedded in collagen. GM6001, an MMP inhibitor, diminished release and altered the identity of the released peptide fragment. The increase in ratio of release from PEGDA 10,000 and PEGDA 20,000 hydrogels compared to PEGDA 3,400 hydrogels suggests MMP-2 enters the hydrogel. PEGDA molecular weight of 10,000 and 15 % (w/V) were the optimal conditions for release and handling. The use of protease-triggered drug delivery has great advantage particularly with the control of protease penetration as a parameter for controlling rate of release.

Matrix metalloproteinase-2 or -9 deletions protect against hemorrhagic transformation during early stage of cerebral ischemia and reperfusion

MMP-9 deficiency protected against photochemical thrombosis-induced brain hemorrhagic transformation (HT), but it did not protect against tissue plasminogen activator-induced brain hemorrhage. The roles of MMP-2 and/or MMP-9 knockout (KO) in mechanical reperfusion induced HT after ischemia have not been investigated. Here we assessed the effects of MMP-2 KO, MMP-9 KO and MMP-2/9 double KO (dKO) in protecting against mechanical reperfusion induced HT and other brain injuries after the early stages of cerebral ischemia in mice of the same genetic background. Middle cerebral artery occlusion (MCAO) was performed in mice. Reperfusion was started at 1 or 1.5h after onset of MCAO. All mice were sacrificed 8h after MCAO. We found that both pro- and active MMP-2 and MMP-9 levels were significantly elevated in the early ischemic brain. After the early stages of ischemia and reperfusion, the hemorrhagic incidence was reduced in the cortex of MMP-2 KO mice (p<0.05 vs. WT). The hemorrhagic volume was significantly decreased in the cortexes of MMP-2 and/or -9 knockout mice (MMP-9 KO vs. WT: p<0.01, MMP-2 KO and dKO vs. WT: p<0.001). In the basal ganglia, MMP-2 KO and MMP-2/9 dKO mice displayed a remarkable decrease in hemorrhagic volume (p<0.01 or 0.05 vs. WT), but MMP-9 KOs did not protect against hemorrhage. MMP-2 and/or -9 knockout mice displayed significantly decreased infarction volume in both the cortex and striatum, in addition to improved neurological function (p<0.001 vs. WT). The results suggested that MMP-2 deficiency and MMP-2 and MMP-9 double deficiency were more protective than MMP-9 deficiency against HT after the early stages of ischemia and reperfusion. These studies increase our understanding of MMP-2 and MMP-9 in HT development and will help to selectively target MMPs to protect the post-ischemic brain from injury and HT.

Matrix metalloproteinase 2 induces epithelial-mesenchymal transition in proximal tubules from the luminal side and progresses fibrosis in mineralocorticoid/salt-induced hypertensive rats

OBJECTIVES

Excess mineralocorticoids such as deoxycorticosterone acetate (DOCA) together with salt are known to cause tubulointerstitial fibrosis, but the mechanisms underlying fibrosis progression are unclear. Therefore, we investigated the role of matrix metalloproteinase 2 (MMP2) in the epithelial-mesenchymal transition and fibrosis progression.

METHODS

Uninephrectomized rats drank 0.9% NaCl and 0.3% KCl solution and were treated with DOCA alone, DOCA + spironolactone, or vehicle for 1, 4, or 8 weeks. SBP, kidney function and morphology, and kidney and urine MMP2 activity were compared among the groups.

RESULTS

At week 4, the DOCA-treated group exhibited hypertension, tubulointerstitial fibrosis, increased MMP2 activity in the kidney and urine, and overexpression of MMP2 in proximal tubule cells and MMP14 in apical membranes; these results were more pronounced at week 8. At week 8, the proximal tubule cell apicolateral surface proteins villin, claudin 2, and E-cadherin were downregulated, and the mesenchymal marker α-smooth muscle actin was upregulated in the tubulointerstitium of DOCA-treated rats. These DOCA/salt-induced changes (except for hypertension) and fibrosis progression observed at week 8 were reversed by TISAM (a selective MMP2 inhibitor), which was administered from week 4 to week 8. All of the effects of DOCA/salt at week 8 were attenuated by spironolactone.

CONCLUSION

Eight weeks of treatment with DOCA/salt activated MMP2, primarily on the apical surface of proximal tubule cells, which induced epithelial-mesenchymal transition from the luminal side and promoted tubulointerstitial fibrosis progression. These MMP2-induced changes occurred via downstream processes regulated by mineralocorticoid receptors.

Decreased oxygen tension lowers reactive oxygen species and apoptosis and inhibits osteoblast matrix mineralization through changes in early osteoblast differentiation

Accumulating data show that oxygen tension can have an important effect on cell function and fate. We used the human pre-osteoblastic cell line SV-HFO, which forms a mineralizing extracellular matrix, to study the effect of low oxygen tension (2%) on osteoblast differentiation and mineralization. Mineralization was significantly reduced by 60-70% under 2% oxygen, which was paralleled by lower intracellular levels of reactive oxygen species (ROS) and apoptosis. Following this reduction in ROS the cells switched to a lower level of protection by down-regulating their antioxidant enzyme expression. The downside of this is that it left the cells more vulnerable to a subsequent oxidative challenge. Total collagen content was reduced in the 2% oxygen cultures and expression of matrix genes and matrix-metabolizing enzymes was significantly affected. Alkaline phosphatase activity and RNA expression as well as RUNX2 expression were significantly reduced under 2% oxygen. Time phase studies showed that high oxygen in the first phase of osteoblast differentiation and prior to mineralization is crucial for optimal differentiation and mineralization. Switching to 2% or 20% oxygen only during mineralization phase did not change the eventual level of mineralization. In conclusion, this study shows the significance of oxygen tension for proper osteoblast differentiation, extra cellular matrix (ECM) formation, and eventual mineralization. We demonstrated that the major impact of oxygen tension is in the early phase of osteoblast differentiation. Low oxygen in this phase leaves the cells in a premature differentiation state that cannot provide the correct signals for matrix maturation and mineralization.

New functions of the fibrinolytic system in bone marrow cell-derived angiogenesis

Angiogenesis is a process by which new blood vessels form from preexisting vasculature. This process includes differentiation of angioblasts into endothelial cells with the help of secreted angiogenic factors released from cells such as bone marrow (BM)-derived cells. The fibrinolytic factor plasmin, which is a serine protease, has been shown to promote endothelial cell migration either directly, by degrading matrix proteins such as fibrin, or indirectly, by converting matrix-bound angiogenic growth factors into a soluble form. Plasmin can also activate other pericellular proteases such as matrix metalloproteinases (MMPs). Recent studies indicate that plasmin can additionally alter cellular adhesion and migration. We showed that factors of the fibrinolytic pathway can recruit BM-derived hematopoietic cells into ischemic/hypoxic tissues by altering the activation status of MMPs. These BM-derived cells can function as accessory cells that promote angiogenesis by releasing angiogenic signals. This review will discuss recent data regarding the role of the fibrinolytic system in controlling myeloid cell-driven angiogenesis. We propose that plasmin/plasminogen may be a potential target not only for development of effective angiogenic therapeutic strategies for the treatment of cancer, but also for development of strategies to promote ischemic tissue regeneration.

A secreted MMP is required for reepithelialization during wound healing

Matrix metalloproteinases (MMPs) are extracellular proteases highly expressed at wound sites. However, the precise function of MMPs during reepithelialization in vivo has been elusive in mammalian models because of the high level of redundancy among the 24 mammalian MMPs. For this reason we used Drosophila melanogaster, whose genome encodes only two MMPs-one secreted type (Mmp1) and one membrane-anchored type (Mmp2)-to study the function and regulation of the secreted class of MMPs in vivo. In the absence of redundancy, we found that the Drosophila secreted MMP, Mmp1, is required in the epidermis to facilitate reepithelialization by remodeling the basement membrane, promoting cell elongation and actin cytoskeletal reorganization, and activating extracellular signal-regulated kinase signaling. In addition, we report that the jun N-terminal kinase (JNK) pathway upregulates Mmp1 expression after wounding, but that Mmp1 is expressed independent of the JNK pathway in unwounded epidermis. When the JNK pathway is ectopically activated to overexpress Mmp1, the rate of healing is accelerated in an Mmp1-dependent manner. A primary function of Mmp1, under the control of the JNK pathway, is to promote basement membrane repair, which in turn may permit cell migration and the restoration of a continuous tissue.

Matrix metalloproteinase inhibitors as investigative tools in the pathogenesis and management of vascular disease

Matrix metalloproteinases (MMPs) are proteolytic enzymes that degrade various components of the extracellular matrix (ECM). MMPs could also regulate the activity of several non-ECM bioactive substrates and consequently affect different cellular functions. Members of the MMPs family include collagenases, gelatinases, stromelysins, matrilysins, membrane-type MMPs, and others. Pro-MMPs are cleaved into active MMPs, which in turn act on various substrates in the ECM and on the cell surface. MMPs play an important role in the regulation of numerous physiological processes including vascular remodeling and angiogenesis. MMPs may also be involved in vascular diseases such as hypertension, atherosclerosis, aortic aneurysm, and varicose veins. MMPs also play a role in the hemodynamic and vascular changes associated with pregnancy and preeclampsia. The role of MMPs is commonly assessed by measuring their gene expression, protein amount, and proteolytic activity using gel zymography. Because there are no specific activators of MMPs, MMP inhibitors are often used to investigate the role of MMPs in different physiologic processes and in the pathogenesis of specific diseases. MMP inhibitors include endogenous tissue inhibitors (TIMPs) and pharmacological inhibitors such as zinc chelators, doxycycline, and marimastat. MMP inhibitors have been evaluated as diagnostic and therapeutic tools in cancer, autoimmune disease, and cardiovascular disease. Although several MMP inhibitors have been synthesized and tested both experimentally and clinically, only one MMP inhibitor, i.e., doxycycline, is currently approved by the Food and Drug Administration. This is mainly due to the undesirable side effects of MMP inhibitors especially on the musculoskeletal system. While most experimental and clinical trials of MMP inhibitors have not demonstrated significant benefits, some trials still showed promising results. With the advent of new genetic and pharmacological tools, disease-specific MMP inhibitors with fewer undesirable effects are being developed and could be useful in the management of vascular disease.

Human matrix metalloproteinases: an ubiquitarian class of enzymes involved in several pathological processes

Human matrix metalloproteinases (MMPs) belong to the M10 family of the MA clan of endopeptidases. They are ubiquitarian enzymes, structurally characterized by an active site where a Zn(2+) atom, coordinated by three histidines, plays the catalytic role, assisted by a glutamic acid as a general base. Various MMPs display different domain composition, which is very important for macromolecular substrates recognition. Substrate specificity is very different among MMPs, being often associated to their cellular compartmentalization and/or cellular type where they are expressed. An extensive review of the different MMPs structural and functional features is integrated with their pathological role in several types of diseases, spanning from cancer to cardiovascular diseases and to neurodegeneration. It emerges a very complex and crucial role played by these enzymes in many physiological and pathological processes.

Matrix metalloproteinase-2 polymorphisms and clinical outcome of Chinese patients with nonsmall cell lung cancer treated with first-line, platinum-based chemotherapy

BACKGROUND

Matrix metalloproteinase-2 (MMP-2) is well known for its critical role in cell survival and cancer development. It also plays an important role in hematopoietic recovery after chemotherapy-induced myelosuppression. In this study, the authors investigated the association of MMP-2 polymorphisms with treatment efficacy and the occurrence of severe toxicity in patients with nonsmall cell lung cancer (NSCLC) who were receiving first-line, platinum-based chemotherapy.

METHODS

A pharmacogenetic association study was performed in 663 Chinese patients who had inoperable stage III/IV NSCLC and were receiving first-line, platinum-based regimens. Information about objective response, progression-free survival, overall survival, grade 3 or 4 gastrointestinal toxicity (nausea/vomiting), and hematologic toxicity (neutropenia, anemia, thrombocytopenia) was available. Sixteen tag single nucleotide polymorphisms (SNPs) of MMP-2 were assessed.

RESULTS

In 7 polymorphisms, significant associations were observed with the incidence of grade 3 or 4 neutropenia. The variant homozygotes of reference SNP rs12934241 exhibited the most significant effect on the risk of neutropenia, leading to an incidence rate that increased from 12.3% (for the C/C genotype) to 50% (for the T/T genotype; odds ratio, 8.33; P = 8.8 × 10(-5)). Stratified analyses indicated that rs12934241 exhibited a much stronger influence in the cisplatin-gemcitabine regimen subgroup than subgroups that received other regimens (P(interaction) = .003). Further haplotype analyses produced results that were consistent with results from single-SNP analyses. However, no significant association was observed between MMP-2 polymorphisms and treatment efficacy, including response rate, clinical benefit, progression-free survival, and overall survival.

CONCLUSIONS

To the authors' knowledge, this study provides the first evidence for a predictive role of MMP-2 polymorphisms in the variability of severe chemotherapy-related neutropenia among Chinese patients with platinum-treated, advanced NSCLC.

New facets of matrix metalloproteinases MMP-2 and MMP-9 as cell surface transducers: outside-in signaling and relationship to tumor progression

This review focuses on matrix metalloproteinases (MMPs)-2 (gelatinase A) and -9 (gelatinase B), both of which are cancer-associated, secreted, zinc-dependent endopeptidases. Gelatinases cleave many different targets (extracellular matrix, cytokines, growth factors, chemokines and cytokine/growth factor receptors) that in turn regulate key signaling pathways in cell growth, migration, invasion, inflammation and angiogenesis. Interactions with cell surface integral membrane proteins (CD44, αVβ/αβ1/αβ2 integrins and Ku protein) can occur through the gelatinases' active site or hemopexin-like C-terminal domain. This review evaluates the recent literature on the non-enzymatic, signal transduction roles of surface-bound gelatinases and their subsequent effects on cell survival, migration and angiogenesis. Gelatinases have long been drug targets. The current status of gelatinase inhibitors as anticancer agents and their failure in the clinic is discussed in light of these new data on the gelatinases' roles as cell surface transducers - data that may lead to the design and development of novel, gelatinase-targeting inhibitors.

Murine mesenchymal stem cells suppress T lymphocyte activation through IL-2 receptor α (CD25) cleavage by producing matrix metalloproteinases

Mesenchymal stem cells (MSCs) are multipotent, non-hematopoietic stem cells that exhibit the capacity to inhibit the proliferation of a variety of immune cells. However, the underlying mechanisms of the immunosuppressive effects of MSCs are still obscure. Therefore, we attempted to identify the mechanisms underlying immunosuppression toward the activated T lymphocytes by MSCs in a murine model. In particular, we aimed to find possible factors derived from MSCs that drive this phenomenon. We found that T lymphocytes incubated with conditioned media of MSCs (MSC CM) entered into apoptosis and were subjected to cell cycle arrest during the course of activation, and these phenomena were accompanied by the reduction of IL-2 production. Specifically, matrix metalloproteinases (MMPs) derived from MSCs caused cleavage of IL-2 receptor α (CD25) from the surface of activated T cells, and as a consequence, IL-2 signaling in response to engagement of the IL-2 receptor (IL-2R) was downregulated. The inhibition of MMP activity in the MSC CM by GM6001 abrogated CD25 cleavage and restored IL-2 production from the activated splenocytes. However, the blockade of MMP activity could not fully restore the proliferative response and apoptosis of T cells altered by MSC CM. In conclusion, MSC-derived MMPs have a significant role in the suppression of IL-2 production through induction of CD25 cleavage and have a partial role in the suppression of T cell proliferation.

Barx2 and Fgf10 regulate ocular glands branching morphogenesis by controlling extracellular matrix remodeling

The lacrimal gland (LG) develops through branching morphogenesis and produces secretions, including tears, that lubricate and protect the ocular surface. Despite the prevalence of LG disorders such as dry eye, relatively little is known about the regulation of LG development. In this study, we show that the homeobox transcription factor Barx2 is highly expressed in conjunctival epithelium, eyelids and ocular [lacrimal, harderian (HG), and meibomian (MG)] glands and is necessary for normal ocular gland and eyelid development. Barx2(-/-) mice show defective LG morphogenesis, absence of the HG, and defects in MG and eyelid fusion. Ex vivo antisense assays confirm the requirement for Barx2 in LG bud elongation and branching. Gene expression profiles reveal decreased expression of several adhesion and matrix remodeling molecules in Barx2(-/-) LGs. In culture, Barx2 regulates expression of matrix metalloproteinases (MMPs) and epithelial cell migration through the extracellular matrix. Fibroblast growth factors are crucial regulators of LG development and we show that Barx2 is required for Fgf10-induced LG bud elongation and that both Barx2 and Fgf10 cooperate in the regulation of MMPs. Together, these data suggest a mechanism for the effects of loss of Barx2 on ocular gland development. Intriguingly, salivary glands that also express a high level of Barx2 develop normally in Barx2(-/-) mice and do not show altered levels of MMPs. Thus, the function of Barx2 is specific to ocular gland development. Based on our data, we propose a functional network involving Barx2, Fgf10 and MMPs that plays an essential role in regulating branching morphogenesis of the ocular glands.

Ligand activation leads to regulated intramembrane proteolysis of fibroblast growth factor receptor 3

FGFR3 is implicated in several human diseases. Following activation and endocytosis, FGFR3 undergoes sequential ectodomain and intramembrane cleavages to generate a soluble cytoplasmic fragment that can translocate to the nucleus.

Fibroblast growth factor receptor 3 (FGFR3) is a major negative regulator of bone growth that inhibits the proliferation and differentiation of growth plate chondrocytes. Activating mutations of its c isoform cause dwarfism in humans; somatic mutations can drive oncogenic transformation in multiple myeloma and bladder cancer. How these distinct activities arise is not clear. FGFR3 was previously shown to undergo proteolytic cleavage in the bovine rib growth plate, but this was not explored further. Here, we show that FGF1 induces regulated intramembrane proteolysis (RIP) of FGFR3. The ectodomain is proteolytically cleaved (S1) in response to ligand-induced receptor activation, but unlike most RIP target proteins, it requires endocytosis and does not involve a metalloproteinase. S1 cleavage generates a C-terminal domain fragment that initially remains anchored in the membrane, is phosphorylated, and is spatially distinct from the intact receptor. Ectodomain cleavage is followed by intramembrane cleavage (S2) to generate a soluble intracellular domain that is released into the cytosol and can translocate to the nucleus. We identify the S1 cleavage site and show that γ-secretase mediates the S2 cleavage event. In this way we demonstrate a mechanism for the nuclear localization of FGFR3 in response to ligand activation, which may occur in both development and disease.

Loss of matrix metalloproteinase-2 amplifies murine toxin-induced liver fibrosis by upregulating collagen I expression

BACKGROUND AND AIMS

Matrix metalloproteinase-2 (MMP-2), a type IV collagenase secreted by activated hepatic stellate cells (HSCs), is upregulated in chronic liver disease and is considered a profibrotic mediator due to its proliferative effect on cultured HSCs and ability to degrade normal liver matrix. Although associative studies and cell culture findings suggest that MMP-2 promotes hepatic fibrogenesis, no in vivo model has definitively established a pathologic role for MMP-2 in the development and progression of liver fibrosis. We therefore examined the impact of MMP-2 deficiency on liver fibrosis development during chronic CCl(4) liver injury and explored the effect of MMP-2 deficiency and overexpression on collagen I expression.

METHODS

Following chronic CCl(4) administration, liver fibrosis was analyzed using Sirius Red staining with quantitative morphometry and real-time polymerase chain reaction (PCR) in MMP-2-/- mice and age-matched MMP-2+/+ controls. These studies were complemented by analyses of cultured human stellate cells.

RESULTS

MMP-2-/- mice demonstrated an almost twofold increase in fibrosis which was not secondary to significant differences in hepatocellular injury, HSC activation or type I collagenase activity; however, type I collagen messenger RNA (mRNA) expression was increased threefold in the MMP-2-/- group by real-time PCR. Furthermore, targeted reduction of MMP-2 in cultured HSCs using RNA interference significantly increased collagen I mRNA and protein, while overexpression of MMP-2 resulted in decreased collagen I mRNA.

CONCLUSIONS

These findings suggest that increased MMP-2 during the progression of liver fibrosis may be an important mechanism for inhibiting type I collagen synthesis by activated HSCs, thereby providing a protective rather than pathologic role.

Cell cycle regulation during proliferation and differentiation of mammalian muscle precursor cells

Proliferation and differentiation of muscle precursor cells are intensively studied not only in the developing mouse embryo but also using models of skeletal muscle regeneration or analyzing in vitro cultured cells. These analyses allowed to show the universality of the cell cycle regulation and also uncovered tissue-specific interplay between major cell cycle regulators and factors crucial for the myogenic differentiation. Examination of the events accompanying proliferation and differentiation leading to the formation of functional skeletal muscle fibers allows understanding the molecular basis not only of myogenesis but also of skeletal muscle regeneration. This chapter presents the basis of the cell cycle regulation in proliferating and differentiating muscle precursor cells during development and after muscle injury. It focuses at major cell cycle regulators, myogenic factors, and extracellular environment impacting on the skeletal muscle.

Mmp23b promotes liver development and hepatocyte proliferation through the tumor necrosis factor pathway in zebrafish

The matrix metalloproteinase (MMP) family of proteins degrades extracellular matrix (ECM) components as well as processes cytokines and growth factors. MMPs are involved in regulating ECM homeostasis in both normal physiology and disease pathophysiology. Here we report the critical roles of mmp23b in normal zebrafish liver development. Mmp23b was initially identified as a gene linked to the genomic locus of an enhancer trap transgenic zebrafish line in which green fluorescent protein (GFP) expression was restricted to the developing liver. Follow-up analysis of mmp23b messenger RNA (mRNA) expression confirmed its liver-specific expression pattern. Morpholino knockdown of mmp23b resulted in defective hepatocyte proliferation, causing a reduction in liver size while maintaining relatively normal pancreas and gut development. Genetically, we showed that mmp23b functions through the tumor necrosis factor (TNF) signaling pathway. Antisense knockdown of tnfa or tnfb in zebrafish caused similar reductions of liver size, whereas overexpression of tnfa or tnfb rescued liver defects in mmp23b morphants but not vice versa. Biochemically, MMP23B, the human ortholog of Mmp23b, directly interacts with TNF and mediates its release from the cell membrane in a cell culture system. Because mmp23b/MMP23B is highly conserved, our findings in zebrafish warrant further investigation of its role in regulating liver development in mammals.

Variability in melanoma metalloproteinase expression profiling

The proteolytic activities of a disintegrin and metalloproteinase (ADAM); a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS), and matrix metalloproteinase (MMP) families play important roles in normal and multiple pathological conditions. These metalloproteases have potential roles in the degradation of the ECM and in the processing of bioactive molecules. In the present study, RNA was isolated from multiple normal fibroblast and metastatic melanoma cell lines, as well as the isogenic normal tissue and tumor samples, and the gene expression levels of six ADAMs, eight MMPs, and four ADAMTSs were analyzed by real-time PCR. This approach allowed for detected changes in mRNA expression of the individual metalloproteinase genes to be compared between normal and metastatic states and also between tissue and cultured cells. Increased gene expression of several ADAM and MMP family members (MMP1, MMP8, MMP15, and ADAM15) occurred in melanoma tissue and was replicated in tissue cultures. In general, the level of ADAM and MMP mRNA expression was several-fold higher in cultured cells compared with the isogenic tissue from which they were derived. Passage-dependent expression patterns were observed for MMP8 and MMP9 in in-house-derived metastatic melanoma cell lines. This reiterates earlier suggestions that experiments using cells that have been maintained in culture should be interpreted with great care.

Acute venous occlusion enhances matrix metalloprotease activity: Implications on endothelial dysfunction

Venous hypertension is associated with microvascular inflammation, restructuring, and apoptosis, but the cellular and molecular mechanisms underlying these events remain uncertain. In the present study, we tested the hypothesis that elevated venous pressure and reduction of shear stress induce elevated enzymatic activity. This activity in turn may affect endothelial surface receptors and promote their dysfunction. Using a rodent model for venous hypertension using acute venular occlusion, microzymographic techniques for enzyme detection, and immunohistochemistry for receptor labeling, we found increased activity of the matrix metalloproteases (MMPs) -1, -8, and -9 and tissue inhibitors of metalloproteases (TIMPs) -1 and -2 in both high- and low-pressure regions. In this short time frame, we also observed that elevated venule pressure led to two different fates for the vascular endothelial growth factor receptor-2 (VEGFR2); in higher-pressure upstream regions, some animals exhibited higher VEGFR2 expression, while others displayed lower levels upstream compared to their downstream counterparts with lower pressure. VEGFR2 expression was, on average, more pronounced upon application of MMP inhibitor, suggesting possible cleavage of the receptor by activated enzymes in this model. We conclude that venous pressure elevation increases enzymatic activity which may contribute to inflammation and endothelial dysfunction associated with this disease by influencing critical surface receptors.

Osteochondral plate angiogenesis: a new treatment target in osteoarthritis

Healthy adult joint cartilage contains neither blood vessels nor nerves. Osteoarthritic cartilage, in contrast, may be invaded by blood vessels from the subchondral bone. The mechanisms underlying cartilage angiogenesis in osteoarthritis are unclear but may involve hypertrophic chondrocyte differentiation. Active research is under way to identify the factors involved in cartilage angiogenesis. Here, we discuss the pathophysiological mechanisms of osteoarthritic cartilage angiogenesis based on evidence from a systematic literature review of articles retrieved via PubMed and ISI Web of Knowledge. Our conclusions suggest new research perspectives and treatment options.

MMP13 mediates cell cycle progression in melanocytes and melanoma cells: in vitro studies of migration and proliferation

Background

Melanoma cells are usually characterized by a strong proliferative potential and efficient invasive migration. Among the multiple molecular changes that are recorded during progression of this disease, aberrant activation of receptor tyrosine kinases (RTK) is often observed. Activation of matrix metalloproteases goes along with RTK activation and usually enhances RTK-driven migration. The purpose of this study was to examine RTK-driven three-dimensional migration of melanocytes and the pro-tumorigenic role of matrix metalloproteases for melanocytes and melanoma cells.

Results

Using experimental melanocyte dedifferentiation as a model for early melanomagenesis we show that an activated EGF receptor variant potentiates migration through three-dimensional fibrillar collagen. EGFR stimulation also resulted in a strong induction of matrix metalloproteases in a MAPK-dependent manner. However, neither MAPK nor MMP activity were required for migration, as the cells migrated in an entirely amoeboid mode. Instead, MMPs fulfilled a function in cell cycle regulation, as their inhibition resulted in strong growth inhibition of melanocytes. The same effect was observed in the human melanoma cell line A375 after stimulation with FCS. Using sh- and siRNA techniques, we could show that MMP13 is the protease responsible for this effect. Along with decreased proliferation, knockdown of MMP13 strongly enhanced pigmentation of melanocytes.

Conclusions

Our data show for the first time that growth stimuli are mediated via MMP13 in melanocytes and melanoma, suggesting an autocrine MMP13-driven loop. Given that MMP13-specific inhibitors are already developed, these results support the evaluation of these inhibitors in the treatment of melanoma.

Physiology and pathophysiology of matrix metalloproteases

Matrix metalloproteases (MMPs) comprise a family of enzymes that cleave protein substrates based on a conserved mechanism involving activation of an active site-bound water molecule by a Zn(2+) ion. Although the catalytic domain of MMPs is structurally highly similar, there are many differences with respect to substrate specificity, cellular and tissue localization, membrane binding and regulation that make this a very versatile family of enzymes with a multitude of physiological functions, many of which are still not fully understood. Essentially, all members of the MMP family have been linked to disease development, notably to cancer metastasis, chronic inflammation and the ensuing tissue damage as well as to neurological disorders. This has stimulated a flurry of studies into MMP inhibitors as therapeutic agents, as well as into measuring MMP levels as diagnostic or prognostic markers. As with most protein families, deciphering the function(s) of MMPs is difficult, as they can modify many proteins. Which of these reactions are physiologically or pathophysiologically relevant is often not clear, although studies on knockout animals, human genetic and epigenetic, as well as biochemical studies using natural or synthetic inhibitors have provided insight to a great extent. In this review, we will give an overview of 23 members of the human MMP family and describe functions, linkages to disease and structural and mechanistic features. MMPs can be grouped into soluble (including matrilysins) and membrane-anchored species. We adhere to the 'MMP nomenclature' and provide the reader with reference to the many, often diverse, names for this enzyme family in the introduction.

Temporal and spatial expression of matrix metalloproteinases and tissue inhibitors of metalloproteinases following myocardial infarction

Following a myocardial infarction (MI), the homeostatic balance between matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) is disrupted as part of the left ventricle (LV) response to injury. The full complement of responses to MI has been termed LV remodeling and includes changes in LV size, shape and function. The following events encompass the LV response to MI: (1) inflammation and LV wall thinning and dilation, (2) infarct expansion and necrotic myocyte resorption, (3) accumulation of fibroblasts and scar formation, and (4) endothelial cell activation and neovascularization. In this review, we will summarize MMP and TIMP roles during these events, focusing on the spatiotemporal localization and MMP and TIMP effects on cellular and tissue-level responses. We will review MMP and TIMP structure and function, and discuss specific MMP roles during both the acute and chronic phases post-MI, which may provide insight into novel therapeutic targets to limit adverse remodeling in the MI setting.

Molecular mediators of angiogenesis

Angiogenesis, or the formation of new blood vessels from the preexisting vasculature, is a key component in numerous physiologic and pathologic responses and has broad impact in many medical and surgical specialties. In this review, we discuss the key cellular steps that lead to the neovascularization of tissues and highlight the main molecular mechanisms and mediators in this process. We include discussions on proteolytic enzymes, cell-matrix interactions, and pertinent cell signaling pathways and end with a survey of the mechanisms that lead to the stabilization and maturation of neovasculatures.

The regulatory crosstalk between kinases and proteases in cancer

Kinases and proteases are responsible for two fundamental regulatory mechanisms--phosphorylation and proteolysis--that orchestrate the rhythms of life and death in all organisms. Recent studies have highlighted the elaborate interplay between both post-translational regulatory systems. Many intracellular or pericellular proteases are regulated by phosphorylation, whereas multiple kinases are activated or inactivated by proteolytic cleavage. The functional consequences of this regulatory crosstalk are especially relevant in the different stages of cancer progression. What are the clinical implications derived from the fertile dialogue between kinases and proteases in cancer?

AP-1 (Fra-1/c-Jun)-mediated induction of expression of matrix metalloproteinase-2 is required for 15S-hydroxyeicosatetraenoic acid-induced angiogenesis

To understand the involvement of matrix metalloproteinases (MMPs) in 15(S)-hydroxyeicosatetraenoic acid (15(S)-HETE)-induced angiogenesis, we have studied the role of MMP-2. 15(S)-HETE induced MMP-2 expression and activity in a time-dependent manner in human dermal microvascular endothelial cells (HDMVECs). Inhibition of MMP-2 activity or depletion of its levels attenuated 15(S)-HETE-induced HDMVEC migration, tube formation, and Matrigel plug angiogenesis. 15(S)-HETE also induced Fra-1 and c-Jun expression in a Rac1-MEK1-JNK1-dependent manner. In addition, 15(S)-HETE-induced MMP-2 expression and activity were mediated by Rac1-MEK1-JNK1-dependent activation of AP-1 (Fra-1/c-Jun). Cloning and site-directed mutagenesis of MMP-2 promoter revealed that AP-1 site proximal to the transcriptional start site is required for 15(S)-HETE-induced MMP-2 expression, and Fra-1 and c-Jun are the essential components of AP-1 that bind to MMP-2 promoter in response to 15(S)-HETE. Hind limb ischemia led to an increase in MEK1 and JNK1 activation and Fra-1, c-Jun, and MMP-2 expression resulting in enhanced neovascularization and recovery of blood perfusion in wild-type mice as compared with 12/15-Lox(-/-) mice. Together, these results provide the first direct evidence for a role of 12/15-Lox-12/15(S)-HETE axis in the regulation of ischemia-induced angiogenesis.

Spatial restriction of FGF signaling by a matrix metalloprotease controls branching morphogenesis

FGF signaling is a central regulator of branching morphogenesis processes, such as angiogenesis or the development of branched organs including lung, kidney, and mammary gland. The formation of the air sac during the development of the Drosophila tracheal system is a powerful genetic model to investigate how FGF signaling patterns such emerging structures. This article describes the characterization of the Drosophila matrix metalloprotease Mmp2 as an extracellular inhibitor of FGF morphogenetic function. Mmp2 expression in the developing air sac is controlled by the Drosophila FGF homolog Branchless and then participates in a negative feedback and lateral inhibition mechanism that defines the precise pattern of FGF signaling. The signaling function for MMPs described here may not be limited to branching morphogenesis processes.

Role of matrix metalloproteinases in epithelial migration

In response to injury, epithelial cells migrate across the denuded tissue to rapidly close the wound and restore barrier, thereby preventing the entry of pathogens and leakage of fluids. Efficient, proper migration requires a range of processes, acting both inside and out of the cell. Among the extracellular responses is the expression of various matrix metalloproteinases (MMPs). Though long thought to ease cell migration simply by breaking down matrix barriers, findings from various models demonstrate that MMPs facilitate (and sometimes repress) cell movement by other means, such as affecting the state of cell-matrix interactions or proliferation. In this Prospect, we review some key data indicting how specific MMPs function via their activity as proteinases to control closure of epithelial wounds.