Activation of human neutrophil procollagenase by stromelysin 2

Updated Views on Neutrophil Responses in Ischemia-Reperfusion Injury

Ischemia-reperfusion injury is an inevitable event during organ transplantation and represents a primary risk factor for the development of early graft dysfunction in lung, heart, liver, and kidney transplant recipients. Recent studies have implicated recipient neutrophils as key mediators of this process and also have found that early innate immune responses after transplantation can ultimately augment adaptive alloimmunity and affect late graft outcomes. Here, we discuss signaling pathways involved in neutrophil recruitment and activation after ischemia-mediated graft injury in solid organ transplantation with an emphasis on lung allografts, which have been the focus of recent studies. These findings suggest novel therapeutic interventions that target ischemia-reperfusion injury-mediated graft dysfunction in transplant recipients.

Current Perspectives on the Role of Matrix Metalloproteinases in the Pathogenesis of Basal Cell Carcinoma

Basal cell carcinoma (BCC) is the most common skin malignancy, which rarely metastasizes but has a great ability to infiltrate and invade the surrounding tissues. One of the molecular players involved in the metastatic process are matrix metalloproteinases (MMPs). MMPs are enzymes that can degrade various components of the extracellular matrix. In the skin, the expression of MMPs is increased in response to various stimuli, including ultraviolet (UV) radiation, one of the main factors involved in the development of BCC. By modulating various processes that are linked to tumor growth, such as invasion and angiogenesis, MMPs have been associated with UV-related carcinogenesis. The sources of MMPs are multiple, as they can be released by both neoplastic and tumor microenvironment cells. Inhibiting the action of MMPs could be a useful therapeutic option in BCC management. In this review that reunites the latest advances in this domain, we discuss the role of MMPs in the pathogenesis and evolution of BCC, as molecules involved in tumor aggressiveness and risk of recurrence, in order to offer a fresh and updated perspective on this field.

Protease propeptide structures, mechanisms of activation, and functions

Proteases are a diverse group of hydrolytic enzymes, ranging from single-domain catalytic molecules to sophisticated multi-functional macromolecules. Human proteases are divided into five mechanistic classes: aspartate, cysteine, metallo, serine and threonine proteases, based on the catalytic mechanism of hydrolysis. As a protective mechanism against uncontrolled proteolysis, proteases are often produced and secreted as inactive precursors, called zymogens, containing inhibitory N-terminal propeptides. Protease propeptide structures vary considerably in length, ranging from dipeptides and propeptides of about 10 amino acids to complex multifunctional prodomains with hundreds of residues. Interestingly, sequence analysis of the different protease domains has demonstrated that propeptide sequences present higher heterogeneity compared with their catalytic domains. Therefore, we suggest that protease inhibition targeting propeptides might be more specific and have less off-target effects than classical inhibitors. The roles of propeptides, besides keeping protease latency, include correct folding of proteases, compartmentalization, liganding, and functional modulation. Changes in the propeptide sequence, thus, have a tremendous impact on the cognate enzymes. Small modifications of the propeptide sequences modulate the activity of the enzymes, which may be useful as a therapeutic strategy. This review provides an overview of known human proteases, with a focus on the role of their propeptides. We review propeptide functions, activation mechanisms, and possible therapeutic applications.

Comparison of rapid MMP-8 and interleukin-6 point-of-care tests to identify intra-amniotic inflammation/infection and impending preterm delivery in patients with preterm labor and intact membranes. J Matern Fetal Neonatal Med 2018;31:228-244. [PMID: 28081646 PMCID: PMC5769687 DOI: 10.1080/14767058.2017.1281904]

OBJECTIVE

Among patients presenting with preterm labor and intact membranes, those with intra-amniotic inflammation have adverse obstetrical and neonatal outcomes. The diagnosis of intra-amniotic inflammation can easily be made by detecting an elevated concentration of the cytokine interleukin (IL)-6 or the enzyme neutrophil collagenase, also known as matrix metalloproteinase (MMP)-8. The diagnostic performances of MMP-8 and IL-6 enzyme-linked immunosorbent assay tests are similar. Recently, a rapid test has become available for point-of-care determination of either MMP-8 or IL-6. The objectives of this study were to compare the diagnostic indices and predictive values between the rapid MMP-8 and IL-6 tests for the identification of intra-amniotic inflammation in patients with preterm labor and intact membranes.

MATERIALS AND METHODS

We performed a retrospective cohort study including 124 women with singleton pregnancies who presented with symptoms of preterm labor and underwent transabdominal amniocentesis for the evaluation of microbial invasion of the amniotic cavity (MIAC). MIAC was defined according to amniotic fluid culture results (aerobic and anaerobic bacteria as well as genital Mycoplasmas). Amniotic fluid white blood cell (WBC) counts were determined using a hemocytometer chamber. An elevated amniotic fluid MMP-8 concentration was assessed using Yoon's MMP-8 Check® (cutoff: 10 ng/mL). An elevated amniotic fluid IL-6 concentration was scored when there was a positive result for the lateral flow-based immunoassay (cutoff: ≥745 pg/mL and ≥1000 pg/mL). In order to objectively compare rapid MMP-8 and rapid IL-6 tests to identify intra-amniotic inflammation, an amniotic fluid WBC count of ≥50 cells/mm3 was used to define intra-amniotic inflammation.

RESULTS

(1) The rapid tests had the same sensitivity for the detection of intra-amniotic inflammation [85.7% (18/21) for all]; (2) the specificity of the rapid MMP-8 test was higher than that of the rapid IL-6 test (cutoff: 745 pg/mL) for the identification of intra-amniotic inflammation [72.8% (75/103) vs. 64.1% (66/103); p < 0.05]; and (3) there were no differences in the sensitivity and specificity between the rapid MMP-8 test and the rapid IL-6 test (cutoff:1000 pg/mL) in the identification of intra-amniotic inflammation. Of 13 patients with discrepant results between the rapid MMP-8 and rapid IL-6 tests, two had a positive MMP-8 but a negative rapid IL-6 test, and both delivered preterm - one within 24 h, and the other within 10 days - and both had acute histologic chorioamnionitis. On the other hand, there were 11 patients with a positive rapid IL-6 but a negative rapid MMP-8 result: 10 delivered preterm, 3 had acute histologic chorioamnionitis and 1 had subacute chorionitis.

CONCLUSION

We conclude that the rapid MMP-8 test has a better specificity than the rapid IL-6 (cutoff: 745 pg/mL) assay for the detection of intra-amniotic infection. Moreover, we observed that among patients who were not identified as having intra-amniotic infection or inflammation by the standard cultivation technique and amniotic fluid WBC count, those who had a positive MMP-8 rapid test delivered preterm and had acute histologic chorioamnionitis.

Biochemical and Biological Attributes of Matrix Metalloproteinases

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases that are involved in the degradation of various proteins in the extracellular matrix (ECM). Typically, MMPs have a propeptide sequence, a catalytic metalloproteinase domain with catalytic zinc, a hinge region or linker peptide, and a hemopexin domain. MMPs are commonly classified on the basis of their substrates and the organization of their structural domains into collagenases, gelatinases, stromelysins, matrilysins, membrane-type (MT)-MMPs, and other MMPs. MMPs are secreted by many cells including fibroblasts, vascular smooth muscle (VSM), and leukocytes. MMPs are regulated at the level of mRNA expression and by activation of their latent zymogen form. MMPs are often secreted as inactive pro-MMP form which is cleaved to the active form by various proteinases including other MMPs. MMPs cause degradation of ECM proteins such as collagen and elastin, but could influence endothelial cell function as well as VSM cell migration, proliferation, Ca²⁺ signaling, and contraction. MMPs play a role in tissue remodeling during various physiological processes such as angiogenesis, embryogenesis, morphogenesis, and wound repair, as well as in pathological conditions such as myocardial infarction, fibrotic disorders, osteoarthritis, and cancer. Increases in specific MMPs could play a role in arterial remodeling, aneurysm formation, venous dilation, and lower extremity venous disorders. MMPs also play a major role in leukocyte infiltration and tissue inflammation. MMPs have been detected in cancer, and elevated MMP levels have been associated with tumor progression and invasiveness. MMPs can be regulated by endogenous tissue inhibitors of metalloproteinases (TIMPs), and the MMP/TIMP ratio often determines the extent of ECM protein degradation and tissue remodeling. MMPs have been proposed as biomarkers for numerous pathological conditions and are being examined as potential therapeutic targets in various cardiovascular and musculoskeletal disorders as well as cancer.

Visfatin Destabilizes Atherosclerotic Plaques in Apolipoprotein E-Deficient Mice

Objectives

Although there is evidence that visfatin is associated with atherogenesis, the effect of visfatin on plaque stability has not yet been explored.

Methods

In vivo, vulnerable plaques were established by carotid collar placement in apolipoprotein E–deficient (ApoE^−/−) mice, and lentivirus expressing visfatin (lenti-visfatin) was locally infused in the carotid artery. The lipid, macrophage, smooth muscle cell (SMC) and collagen levels were evaluated, and the vulnerability index was calculated. In vitro, RAW264.7 cells were stimulated with visfatin, and the MMPs expressions were assessed by western blot and immunofluorescence. And the mechanism that involved in visfatin-induced MMP-8 production was investigated.

Results

Transfection with lenti-visfatin significantly promoted the expression of visfatin which mainly expressed in macrophages in the plaque. Lenti-visfatin transfection significantly promoted the accumulation of lipids and macrophages, modulated the phenotypes of smooth muscle cells and decreased the collagen levels in the plaques, which significantly decreased the plaque stability. Simultaneously, transfection with lenti-visfatin significantly up-regulated the expression of MMP-8 in vivo, as well as MMP-1, MMP-2 and MMP-9. Recombinant visfatin dose- and time-dependently up-regulated the in vitro expression of MMP-8 in macrophages. Visfatin promoted the translocation of NF-κB, and inhibition of NF-κB significantly reduced visfatin-induced MMP-8 production.

Conclusions

Visfatin increased MMP-8 expression, promoted collagen degradation and increased the plaques vulnerability index.

Glycogen synthase kinase 3 inhibition stimulates human cartilage destruction and exacerbates murine osteoarthritis

OBJECTIVE

To assess the role of glycogen synthase kinase 3 (GSK-3) as a regulator of cartilage destruction in human tissue and a murine model of osteoarthritis (OA).

METHODS

Surgical destabilization of the medial meniscus (DMM) was performed to induce experimental murine OA, and joint damage was assessed histologically. Bovine nasal and human OA cartilage samples were incubated with interleukin-1 (IL-1) plus oncostatin M (OSM) and GSK-3 inhibitor. Collagen and proteoglycan release was assessed by hydroxyproline measurement and dye binding assay, collagenase activity was assessed by bioassay, and gene expression was analyzed by real-time polymerase chain reaction. Human articular chondrocytes were isolated by enzymatic digestion and cultured prior to gene silencing and immunoblotting of cell lysates and nuclear fractions.

RESULTS

Mice treated with GSK-3 inhibitor exhibited significantly greater cartilage damage compared with sham-operated control mice. GSK-3 inhibition in bovine cartilage dramatically accelerated IL-1 plus OSM-stimulated degradation, concomitant with a profound increase in collagenase activity. GSK-3 inhibitor induced collagen release from human OA cartilage in the presence of IL-1 plus OSM and increased proteoglycan loss. Gene expression profiling of resorbing OA cartilage revealed a marked procatabolic switch in gene expression upon GSK-3 inhibition. This was mirrored in human articular chondrocytes following GSK3 silencing, particularly with the GSK-3β isoform. GSK-3 inhibition or silencing led to enhanced IL-1 plus OSM-stimulated abundance and activity of Jun, and silencing of c-jun ameliorated GSK-3 inhibitor-mediated procatabolic gene expression.

CONCLUSION

GSK-3 is an important regulator of matrix metalloproteinase (MMP)-mediated joint destruction, the inhibition of which by proinflammatory stimuli de-represses catabolic gene expression. Therapeutic strategies that maintain cartilage GSK-3 activity may therefore help curtail aberrant MMP activity during pathologic joint destruction.

Increased Levels of Metalloproteinase 10 and Hemostatic Markers in Patients With Noncomplicated Primary Varicose Veins

The purpose of the study was to analyze a systemic activation of hemostasis and concentration of matrix metalloproteinase 10 (MMP-10) in patients with primary varicose veins (PVVs). A study group consisted of 41 patients with noncomplicated PVVs. A control group consisted of 30 age- and sex-matched healthy individuals without varicose veins. The concentration of d-dimers (DD), prothrombin fragments 1 and 2 (F1+2), antigen of von Willebrand factor (vWF), and activity of plasminogen activator inhibitor (PAI-1) in plasma and concentration of MMP-10 in serum were analyzed. In patients with PVVs, higher concentrations of DD (P < .001), F1+2 (P < .001), vWF (P = .027), MMP-10 (P = .006), and higher activity of PAI-1 (P < .001) were observed. However, no correlation between the concentrations of MMP-10 and prothrombotic markers was found. Noncomplicated PVVs are associated with systemic, prothrombotic activation of hemostasis and increased concentration of MMP-10, suggesting a prothrombotic and proinflammatory state.

Role of matrix metalloproteinase-8 in atherosclerosis

Plaque rupture is the main cause of acute myocardial infarction and stroke. Atherosclerotic plaques have been described to be vulnerable and more prone to rupture when they are characterized by thin, highly inflamed, and collagen-poor fibrous caps and contain elevated levels of proteases, including metalloproteinases (MMPs). Initiation of collagen breakdown in plaques requires interstitial collagenases, a MMP subfamily consisting of MMP-1, MMP-8, and MMP-13. Previous reports demonstrated that MMP-1 and MMP-13 might be overexpressed in both human and experimental atherosclerosis. Since neutrophils have been only recently reported in atherosclerotic plaques, the role of MMP-8 (formerly known as “neutrophil collagenase”) was only marginally evaluated. In this paper, we will update and comment on evidence of the most relevant regulatory pathways and activities mediated by MMP-8 in atherogenesis.

Matrix metalloproteinase-10 is upregulated by thrombin in endothelial cells and increased in patients with enhanced thrombin generation

OBJECTIVE

Thrombin is a multifunctional serine protease that promotes vascular proinflammatory responses whose effect on endothelial MMP-10 expression has not previously been evaluated.

METHODS AND RESULTS

Thrombin induced endothelial MMP-10 mRNA and protein levels, through a protease-activated receptor-1 (PAR-1)-dependent mechanism, in a dose- and time-dependent manner. This effect was mimicked by a PAR-1 agonist peptide (TRAP-1) and antagonized by an anti-PAR-1 blocking antibody. MMP-10 induction was dependent on extracellular regulated kinase1/2 (ERK1/2) and c-jun N-terminal kinase (JNK) pathways. By serial deletion analysis, site-directed mutagenesis and electrophoretic mobility shift assay an AP-1 site in the proximal region of MMP-10 promoter was found to be critical for thrombin-induced MMP-10 transcriptional activity. Thrombin and TRAP-1 upregulated MMP-10 in murine endothelial cells in culture and in vivo in mouse aorta. This effect of thrombin was not observed in PAR-1-deficient mice. Interestingly, circulating MMP-10 levels (P<0.01) were augmented in patients with endothelial activation associated with high (disseminated intravascular coagulation) and moderate (previous acute myocardial infarction) systemic thrombin generation.

CONCLUSIONS

Thrombin induces MMP-10 through a PAR-1-dependent mechanism mediated by ERK1/2, JNK, and AP-1 activation. Endothelial MMP-10 upregulation could be regarded as a new proinflammatory effect of thrombin whose pathological consequences in thrombin-related disorders and plaque stability deserve further investigation.

CCAAT/enhancer binding protein beta mediates expression of matrix metalloproteinase 13 in human articular chondrocytes in inflammatory arthritis

OBJECTIVE

To determine the function of CCAAT/enhancer binding protein beta (C/EBPbeta) in the expression of matrix metalloproteinase 13 (MMP-13) in chondrocytes in inflammatory arthritis.

METHODS

Cartilage obtained from patients with rheumatoid arthritis and osteoarthritis was immunostained for expression of C/EBPbeta or MMP-13. Interleukin-1beta- or tumor necrosis factor alpha (TNFalpha)-stimulated chondrocytes were subjected to Western blotting and real-time reverse transcriptase-polymerase chain reaction (RT-PCR). MMP-13 promoter assays were conducted, and the C/EBPbeta response element was characterized by deletion and mutation analysis. C-28/I2 cells were treated with TNFalpha and subjected to chromatin immunoprecipitation (ChIP) assays. Finally, C/EBPbeta-liver-enriched activator protein (LAP) was overexpressed in C-28/I2 cells or cartilage tissues, and MMP-13 expression was analyzed.

RESULTS

C/EBPbeta and MMP-13 expression was colocalized in chondrocytes in arthritic cartilage. MMP-13 promoter activity was stimulated by C/EBPbeta overexpression in a dose-dependent manner. Luciferase assays revealed that a -981-bp promoter had the greatest activity, while deletion to -936 bp strongly diminished promoter activity. Luciferase activity was repressed to basal levels by mutations in potential C/EBP binding sites. The stimulatory effects of C/EBPbeta overexpression were diminished by mutation. ChIP assays revealed that TNFalpha treatment enhanced the binding of C/EBPbeta to the MMP-13 promoter. When C/EBPbeta-LAP was overexpressed in C-28/I2 cells, endogenous MMP-13 expression was stimulated up to 32-fold as detected by real-time RT-PCR. Furthermore, following adenoviral overexpression of C/EBPbeta-LAP in organ culture of articular cartilage, stimulation of MMP-13 was also detected by immunohistochemistry.

CONCLUSION

C/EBPbeta directly binds to the MMP-13 promoter region and stimulates the expression of MMP-13 in chondrocytes in inflammatory arthritis.

The effect of a hydroxamic acid-containing polymer on active matrix metalloproteinases

Matrix metalloproteinase (MMP) sequestering polymer microspheres were prepared by a post-polymerization hydroxamic acid derivatization of poly(methyl methacrylate-co-methacrylic acid). The microspheres were designed to selectively bind MMPs from solutions on contact through a direct interaction between the polymer-bound hydroxamic acid groups and the characteristic catalytic site zinc atom common to all MMPs. MMP activity assays showed that the hydroxamic acid microspheres reduce MMP activity on contact in a time and concentration-dependent fashion. This effect was observed for several MMP subclasses (MMP-2, -3, -8 and -13) suggesting that the microspheres possess a broad-spectrum MMP binding capacity. However, inactive pro-forms of MMPs showed little binding affinity for the microspheres indicating that the interaction was dependent on MMP activation. The preferential binding of active MMPs was confirmed by MMP-3 and MMP-8 activation studies, which demonstrated significant increases in microsphere binding on activation. The MMP sequestering effect of the microspheres was also demonstrated in a physiologically relevant solution (human chronic wound fluid extract) indicating that the binding interaction was effective in a multi-component, competitive adsorption environment. Thus, the hydroxamic acid-containing microspheres may find use as localized, broad-spectrum MMP inhibitors for the treatment of a number of disease conditions characterized by elevated MMP activity.

Molecular dynamics simulations of the active matrix metalloproteinase-2: positioning of the N-terminal fragment and binding of a small peptide substrate

Herein we use different computational methods to study the structure and energetic stability of the catalytic domain of the active MMP-2 enzyme considering two different orientations of its N-terminal coil. The first orientation is largely solvent accessible and corresponds to that observed in the 1CK7 crystal structure of the proenzyme. In the second orientation, the N-terminal coil is packed against the Omega-loop and the alpha3-helix of the MMP-2 enzyme likewise in the so-called "superactivated" form of other MMPs. Binding to the MMP-2 catalytic domain of a short peptide substrate, which mimics the sequence of the alpha1 chain of collagen type I, is also examined considering again the two configurations of the N-terminal coil. All these MMP-2 models are subject to 20 ns molecular dynamics (MD) simulations followed by MM-PBSA (Molecular Mechanics Poisson-Boltzmann Surface Area) calculations. The positioning of the N-terminal coil in the "superactivated" form is found to be energetically favored for the MMP-2 enzyme. Moreover, this configuration of the N-terminal moiety can facilitate the binding of peptide substrates. Globally, the results obtained in this study could be relevant for the structural-based design of specific MMP inhibitors.

The carbon monoxide-releasing molecule tricarbonyldichlororuthenium(II) dimer protects human osteoarthritic chondrocytes and cartilage from the catabolic actions of interleukin-1beta

We have investigated the effects of a carbon monoxide-releasing molecule, tricarbonyldichlororuthenium(II) dimer (CORM-2), on catabolic processes in human osteoarthritis (OA) cartilage and chondrocytes activated with interleukin-1beta. In these cells, proinflammatory cytokines induce the synthesis of matrix metalloproteinases (MMPs) and aggrecanases, including members of a disintegrin and metalloproteinase with thrombospondin domain (ADAMTS) family, which may contribute to cartilage loss. CORM-2 down-regulated MMP-1, MMP-3, MMP-10, MMP-13, and ADAMTS-5 in OA chondrocytes, and it inhibited cartilage degradation. These effects were accompanied by increased aggrecan synthesis and collagen II expression in chondrocytes. Our results also indicate that the inhibition of extracellular signal-regulated kinase 1/2 and p38 activation by CORM-2 may contribute to the maintenance of extracellular matrix homeostasis. These observations suggest that CORM-2 could exert chondroprotective effects due to the inhibition of catabolic activities and the enhancement of aggrecan synthesis.

Individual matrix metalloproteinases control distinct transcriptional responses in airway epithelial cells infected with Pseudomonas aeruginosa

Airway epithelium is the initial point of host-pathogen interaction in Pseudomonas aeruginosa infection, an important pathogen in cystic fibrosis and nosocomial pneumonia. We used global gene expression analysis to determine airway epithelial transcriptional responses dependent on matrilysin (matrix metalloproteinase 7 [MMP-7]) and stromelysin-2 (MMP-10), two MMPs induced by acute P. aeruginosa pulmonary infection. Extraction of differential gene expression (EDGE) analysis of gene expression changes in P. aeruginosa-infected organotypic tracheal epithelial cell cultures from wild-type, Mmp7-/-, and Mmp10-/- mice identified 2,091 matrilysin-dependent and 1,628 stromelysin-2-dependent genes that were differentially expressed. Key node network analysis showed that these MMPs controlled distinct gene expression programs involved in proliferation, cell death, immune responses, and signal transduction, among other host defense processes. Our results demonstrate discrete roles for these MMPs in regulating epithelial responses to Pseudomonas infection and show that a global genomics strategy can be used to assess MMP function.

Independent association of matrix metalloproteinase-10, cardiovascular risk factors and subclinical atherosclerosis

OBJECTIVES

Circulating levels of matrix metalloproteinase (MMP)-10 are related to inflammation in asymptomatic subjects with cardiovascular risk factors. Whether MMP-10 is associated with the severity of atherosclerosis remains to be determined. This study examines the relationship of systemic MMP-10 levels with atherosclerotic risk factors and subclinical atherosclerosis.

METHODS AND RESULTS

Circulating levels of MMP-1, -9 and -10, and markers of inflammation [fibrinogen, interleukin-6, von Willebrand factor, and high-sensitivity C-reactive protein (hs-CRP)] were measured in 400 subjects (mean age 54.3 years, 77.7% men) with cardiovascular risk factors but free from clinical cardiovascular disease. Subclinical atherosclerosis was evaluated by both the mean carotid intima-media thickness (IMT) and the presence of atherosclerotic plaques with the use of B-mode ultrasound in all subjects. MMP-10 levels were positively correlated with fibrinogen (r = 0.24, P < 0.001), hs-CRP (r = 0.14, P < 0.01) and carotid IMT (r = 0.17, P < 0.01). The association between MMP-10 and IMT remained significant in multiple regression analysis (P < 0.02) when controlling for traditional atherosclerotic risk factors and inflammatory markers. Such an association was not observed for MMP-1 and -9. Subjects in the highest MMP-10 tertile had significantly higher carotid IMT (adjusted odds ratio 6.3, 95% confidence interval 1.3-31.4, P = 0.024). In addition, MMP-10 levels were significantly higher in patients with carotid plaques (n = 78) than in those with no plaques after adjusting for age and sex (P < 0.01).

CONCLUSION

Higher serum MMP-10 levels were associated with inflammatory markers, increased carotid IMT and atherosclerotic plaques in asymptomatic subjects. Circulating MMP-10 may be useful to identify subclinical atherosclerosis in subjects free from cardiovascular disease.

Cell-cell contact activation of fibroblasts increases the expression of matrix metalloproteinases

BACKGROUND

We recently found that direct homotypic cell-cell contacts between human dermal fibroblasts induce a novel form of cell activation leading to non-apoptotic programmed cell death. As the major features of this process we identified massive induction of cyclo-oxygenase-2 and production of inflammatory prostaglandins. On the surface of the decomposing spheroids, activation of the major extracellular proteolytic cascade, plasminogen activation, associated with surface exposure of alpha-enolase, took place.

AIM

To further characterize pericellular proteolysis by cell-cell contact-activated fibroblasts we studied the role of the other major extracellular proteolytic system, matrix metalloproteinases (MMPs).

METHODS

MMP expression in fibroblast clusters and monolayers was compared using mRNA microarrays and immunoblot analyses. The activities of MMPs were confirmed using MMP inhibitors and caseinolysis.

RESULTS

In microarrays MMP-1, -10, and -14 (MT1-MMP) were induced 5.8-, 106-, and 5.6-fold, respectively. These findings were confirmed by immunoblotting. Radial caseinolysis showed low level of proteolytic activity in spheroid-conditioned media; ilomastat, a general inhibitor of MMPs, suppressed 50% of the proteolytic activity thus confirming it to be at least in part due to MMPs. A cocktail of tetracycline-derived MMP inhibitors suppressed lactate dehydrogenase (LDH) release only 11%, and if combined with aprotinin 28%.

CONCLUSIONS

Cell-cell contact activation of fibroblasts induced MMP-1, -10, and MT1-MMP expression, suggesting similar signaling to that in inflammation and cancer.

Levels of matrix metalloproteinase (MMP)-1 in paired sera and synovial fluids of juvenile idiopathic arthritis patients: relationship to inflammatory activity, MMP-3 and tissue inhibitor of metalloproteinases-1 in a longitudinal study

OBJECTIVES

To measure levels of the collagenases matrix metalloproteinase (MMP)-1 and -13 in the synovial fluid (SF) and serum of patients with juvenile idiopathic arthritis (JIA), and to correlate these measurements with inflammatory activity, levels of the collagenase activator MMP-3 and the tissue inhibitor of metalloproteinases-1 (TIMP-1).

METHODS

Levels of MMP-1, -3, -13 and TIMP-1 were measured in paired SF and serum from 82 JIA patients using enzyme-linked immunsorbent assay and compared between subtypes and patients of different ages and disease durations. These levels were also correlated to the active joint count (AJC) and standard measures of inflammatory activity and therapeutic response, including erythrocyte sedimentation rate (ESR) and platelet count (PLT).

RESULTS

MMP-1 was detected in JIA SF and correlated with PLT. MMP-3 levels were high in SF and detectable in serum where they correlated with PLT, ESR and AJC. MMP-13, however, was not detected in SF or serum. No differences were observed between patients grouped by subtype, age or disease duration. MMP-3 contributed the majority of total MMP in SF samples resulting in excess MMP levels over TIMP-1.

CONCLUSIONS

MMP-1 is up-regulated in SF concordant with inflammatory activity in JIA. This was true for patients in all JIA subtypes and age groups, suggesting that the capability for degradation of type II collagen is present in early disease, and throughout the disease course. MMP-3 may be important in the activation of collagenases and the saturation of exogenous inhibitors. Serum MMP-3 may therefore be a useful, measurable and specific marker of active disease in JIA.

MMP-1 activation by serine proteases and MMP-10 induces human capillary tubular network collapse and regression in 3D collagen matrices

Previous work has shown that endothelial cell (EC)-derived matrix metalloproteinases (MMPs) regulate regression of capillary tubes in vitro in a plasmin- and MMP-1 dependent manner. Here we report that a number of serine proteases can activate MMP-1 and cause capillary tube regression; namely plasma kallikrein, trypsin, neutrophil elastase, cathepsin G, tryptase and chymase. Plasma prekallikrein failed to induce regression without coactivators such as high molecular weight kininogen (HMWK) or coagulation Factor XII. The addition of trypsin, the neutrophil serine proteases (neutrophil elastase and cathepsin G) and the mast cell serine proteases (tryptase and chymase) each caused MMP-1 activation and collagen type I proteolysis, capillary tubular network collapse, regression and EC apoptosis. Capillary tube collapse is accompanied by collagen gel contraction, which is strongly related to the wound contraction that occurs during regression of granulation tissue in vivo. We also report that proMMP-10 protein expression is markedly induced in ECs undergoing capillary tube morphogenesis. Addition of each of the serine proteases described above led to activation of proMMP-10, which also correlated with MMP-1 activation and capillary tube regression. Treatment of ECs with MMP-1 or MMP-10 siRNA markedly delayed capillary tube regression, whereas gelatinase A (MMP-2), gelatinase B (MMP-9) and stromelysin-1 (MMP-3) siRNA-treated cells behaved in a similar manner to controls and regressed normally. Increased expression of MMP-1 or MMP-10 in ECs using recombinant adenoviral delivery markedly accelerated serine protease-induced capillary tube regression. ECs expressing increased levels of MMP-10 activated MMP-1 to a greater degree than control ECs. Thus, MMP-10-induced activation of MMP-1 correlated with tube regression and gel contraction. In summary, our work demonstrates that MMP-1 zymogen activation is mediated by multiple serine proteases and MMP-10, and that these events are central to EC-mediated collagen degradation and capillary tube regression in 3D collagen matrices.

A proteomic approach to identify substrates of matrix metalloproteinase-14 in human plasma

Matrix metalloproteinases (MMPs) are a family of zinc-containing endopeptidases that proteolyze extracellular matrix components as well as a variety of functional proteins. Here we describe a "degradomics" method that efficiently identifies substrates of MMP-14 in a complex protein mixture, such as plasma. Plasma proteins were incubated in the presence or absence of the MMP-14 catalytic domain and displayed on two-dimensional (2-D) gels. After a comparison of the gels, we selected 40 protein spots that reproducibly showed disparities. Upon in-gel digestion, mass determination, and peptide mass fingerprinting, we identified 15 different proteins from 31 spots. These proteins included six known substrates and nine potential substrates of MMP-14. Among the latter, the purified forms of apolipoprotein A-I, apolipoprotein E, and plasma gelsolin were cleaved in vitro by MMP-14, confirming that each of them is a novel substrate of MMP-14. These results demonstrate that our method rapidly and selectively identifies MMP-14 substrates from human plasma proteins. This method would thus constitute a powerful tool for identifying the substrates of MMPs and other proteases in highly complex mixtures of proteins and would enhance our understanding of the biological roles of these enzymes.

An adverse role for matrix metalloproteinase 12 after spinal cord injury in mice

We investigated the role of matrix metalloproteinases (MMPs) in acute spinal cord injury (SCI). Transcripts encoding 22 of the 23 known mammalian MMPs were measured in the mouse spinal cord at various time points after injury. Although there were significant changes in the expression levels of multiple MMPs, MMP-12 was increased 189-fold over normal levels, the highest of all MMPs examined. To evaluate the role of MMP-12 in SCI, spinal cord compression was performed in wild-type (WT) and MMP-12 null mice. Behavioral analyses were conducted for 4 weeks using the Basso-Beattie-Bresnahan (BBB) locomotor rating scale as well as the inclined plane test. The results show that MMP-12 null mice exhibited significantly improved functional recovery compared with WT controls. Twenty-eight days after injury, the BBB score in the MMP-12 group was 7, representing extensive movement of all three hindlimb joints, compared with 4 in the WT group, representing only slight movement of these joints. Furthermore, MMP-12 null mice showed recovery of hindlimb strength more rapidly than control mice, with significantly higher inclined plane scores on days 14 and 21 after SCI. Mechanistically, there was decreased permeability of the blood-spinal barrier and reduced microglial and macrophage density in MMP-12 null mice compared with WT controls. This is the first study to profile the expression patterns of a majority of the known MMPs after spinal cord compression. The data indicate that MMP-12 expression after spinal cord trauma is deleterious and contributes to the development of secondary injury in SCI.

Release and activation of matrix metalloproteinase 8 from human neutrophils triggered by the leukotoxin of Actinobacillus actinomycetemcomitans

Matrix metalloproteinase 8 (MMP 8) degrades type I collagen and may be involved in the pathogenesis of periodontitis. Latent MMP 8 is stored in neutrophil granules and can be activated when released extracellularly. The periodontitis-associated bacterium Actinobacillus actinomycetemcomitans produces an RTX-toxin, leukotoxin, that degranulates and lyses human neutrophils. This study deals with the ability of leukotoxic A. actinomycetemcomitans to trigger the release and activation of MMP 8. Whole bacteria of three A. actinomycetemcomitans strains or leukotoxin purified from the highly toxic strain HK 1519 were incubated with human neutrophils. The extracellularly released latent and active forms of MMP 8 were detected by an immunoblot technique using specific antibodies against the protease. The activity of MMP 8 was determined by a collagen degradation assay. All strains induced release and activation of MMP 8. The effect was more pronounced under aerobic than anaerobic conditions and correlated with the leukotoxicity of the strains. Pure leukotoxin also induced MMP 8 release and activation in a concentration-dependent manner. Under aerobic conditions, oxidising substances formed by the neutrophils contributed to the rapid activation of the latent enzyme. Upon anaerobic incubation, the activation was slow and mainly caused by other proteases released during neutrophil degranulation. The activation was totally abolished in the presence of serum, probably due to the serum-protease inhibitors. Compared to the calcium ionophore A 23187, a well-known stimulus of neutrophil degranulation, leukotoxin was a more powerful inducer of MMP 8 release, since it triggered the process at a 1000-fold lower concentration. The present findings reveal a specific mechanism that can be induced by A. actinomycetemcomitans leukotoxin and which may contribute to the degradation of periodontal tissues under certain conditions.

Differential patterns of stromelysin-2 (MMP-10) and MT1-MMP (MMP-14) expression in epithelial skin cancers

Co-expression of several members of the matrix metalloproteinase (MMP) family is characteristic of human malignant tumours. To investigate the role of stromelysin-2 (MMP-10) in growth and invasion of skin tumours, we studied cutaneous carcinomas with high metastatic capacity (squamous cell carcinomas, SCCs), only locally destructive tumours (basal cell carcinomas, BCCs) and pre-malignant lesions (Bowen's disease and actinic keratosis) using in situ hybridization. Expression of MMP-10 was compared with that of stromelysin-1 (MMP-3) and of MT1-MMP, the expression of which has been shown to correlate with tumour invasiveness. MMP-10 was expressed in 13/21 SSCs and 11/19 BCCs only in epithelial laminin-5 positive cancer cells, while premalignant lesions were entirely negative. MT1-MMP mRNA was detected in 19/21 SCCs both in epithelial cancer cells and stromal fibroblasts and in 14/18 BCCs only in fibroblasts. The level of MMP-10 was upregulated in a cutaneous SCC cell line (UT-SCC-7) by transforming growth factor-alpha and keratinocyte growth factor, and by interferon-gamma in combination with transforming growth factor-beta1 and tumour necrosis factor-alpha both in UT-SCC-7 and HaCaT cells. Our results show that MMP-10 expression does not correlate with the invasive behaviour of tumours as assessed by their histology and MT1-MMP expression, but may be induced by the wound healing and inflammatory matrix remodelling events associated with skin tumours.

Catalytic activities of membrane-type 6 matrix metalloproteinase (MMP25)

This study describes the biochemical characterisation of the catalytic domain of membrane-type 6 matrix metalloproteinase (MT6-MMP, MMP25, leukolysin). Its activity towards synthetic peptide substrates, components of the extracellular matrix and inhibitors of MMPs was studied and compared with MT1-MMP, MT4-MMP and stromelysin-1. We have found that MT6-MMP is closer in function to stromelysin-1 than MT1 and MT4-MMP in terms of substrate and inhibitor specificity, being able to cleave type-IV collagen, gelatin, fibronectin and fibrin. However, it differs from stromelysin-1 and MT1-MMP in its inability to cleave laminin-I, and unlike stromelysin-1 cannot activate progelatinase B. Our findings suggest that MT6-MMP could play a role in cellular migration and invasion of the extracellular matrix and basement membranes and its activity may be tightly regulated by all members of the TIMP family.

Biochemical characterization of the catalytic domain of human matrix metalloproteinase 19. Evidence for a role as a potent basement membrane degrading enzyme

We have recently cloned MMP-19, a novel matrix metalloproteinase, which, due to unique structural features, was proposed to represent the first member of a new MMP subfamily (Pendás, A. M., Knäuper, V. , Puente, X. S., Llano, E., Mattei, M. G., Apte, S., Murphy, G., and López-Otin, C. (1997) J. Biol. Chem. 272, 4281-4286). A recombinant COOH-terminal deletion mutant of MMP-19 (proDelta(260-508)MMP-19), comprising the propeptide and the catalytic domain, was expressed in Escherichia coli, refolded, and purified. Interestingly, we found that proDelta(260-508)MMP-19 has the tendency to autoactivate, whereby the Lys(97)-Tyr(98) peptide bond is hydrolyzed, resulting in free catalytic domain. Mutation of two residues (Glu(88) --> Pro and Pro(90) --> Val) within the propeptide latency motif did not prevent autoactivation but the autolysis rate was somewhat reduced. Analysis of the substrate specificity revealed that the catalytic domain of MMP-19 was able to hydrolyze the general MMP substrate Mca-Pro-Leu-Gly-Dpa-Ala-Arg-NH(2) and, with higher efficiency, the stromelysin substrate Mca-Pro-Leu-Ala-Nva-Dpa-Ala-Arg-NH(2). Kinetic analysis of the interactions of the catalytic domain of MMP-19 with the natural MMP inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), showed strong inhibition using TIMP-2, TIMP-3, and TIMP-4, while TIMP-1 was less efficient. We also demonstrated that synthetic hydroxamic acid-based compounds efficiently inhibited the enzyme. The catalytic domain of MMP-19 was able to hydrolyze the basement membrane components type IV collagen, laminin, and nidogen, as well as the large tenascin-C isoform, fibronectin, and type I gelatin in vitro, suggesting that MMP-19 is a potent proteinase capable of hydrolyzing a broad range of extracellular matrix components. Neither the catalytic domain nor the full-length MMP-19 was able to degrade triple-helical collagen. Finally, and in contrast to studies with other MMPs, MMP-19 catalytic domain was not able to activate any of the latent MMPs tested in vitro.

Recognition and catabolism of synthetic heterotrimeric collagen peptides by matrix metalloproteinases

BACKGROUND

The general consensus is that interstitial collagens are digested by collagenases and denatured collagen by gelatinases, although processing of fibrillar and acetic-acid-soluble collagen by gelatinase A has also been reported. One of the main difficulties in studying the mechanism of action of these matrix metalloproteinases (MMPs) derives from the physicochemical properties of the natural triple-helical collagen, which makes it difficult to handle.

RESULTS

Synthetic heterotrimeric collagenous peptides that contain the collagenase cleavage site of human collagen type I and differ in the thermal stability of the triple-helical fold were used to mimic natural collagen and gelatin, respectively. Results from digestion of these substrates by fibroblast and neutrophil collagenases (MMP-1 and MMP-8), as well as by gelatinase A (MMP-2), confirmed that the two classes of enzymes operate within the context of strong conformational dependency of the substrates. It was also found that gelatinases and collagenases exhibit two distinct proteolytic mechanisms: gelatinase digests the gelatin-like heterotrimer rapidly in individual steps with intermediate releases of partially processed substrate into the medium, whereas collagenases degrade the triple-helical heterotrimer by trapping it until scission through all three alpha chains is achieved.

CONCLUSIONS

The results confirm the usefulness of synthetic heterotrimeric collagenous peptides in the folded and unfolded state as mimics of the natural substrates collagen and gelatin, respectively, to gain a better a insight into the proteolytic mechanisms of matrix metalloproteinases.

Insights into MMP-TIMP interactions

The proteolytic activity of the matrix metalloproteinases (MMPs) involved in extracellular matrix degradation must be precisely regulated by their endogenous protein inhibitors, the tissue inhibitors of metalloproteinases (TIMPs). Disruption of this balance can result in serious diseases such as arthritis and tumor growth and metastasis. Knowledge of the tertiary structures of the proteins involved in such processes is crucial for understanding their functional properties and to interfere with associated dysfunctions. Within the last few years, several three-dimensional structures have been determined showing the domain organization, the polypeptide fold, and the main specificity determinants of the MMPs. Complexes of the catalytic MMP domains with various synthetic inhibitors enabled the structure-based design and improvement of high-affinity ligands, which might be elaborated into drugs. Very recently, structural information also became available for some TIMP structures and MMP-TIMP complexes, and these new data elucidated important structural features that govern the enzyme-inhibitor interaction.

The Human Antibacterial Cathelicidin, hCAP-18, Is Synthesized in Myelocytes and Metamyelocytes and Localized to Specific Granules in Neutrophils

hCAP-18 is the only human member of the antibacterial and endotoxin-binding family of proteins known as cathelicidins. The antibacterial and endotoxin binding domains reside in the C-terminal 37 amino acids of the protein (LL-37) and this is believed to be unleashed from the neutralizing N-terminus by proteases from peroxidase positive granules. In human neutrophils, peroxidase positive and peroxidase negative granules can be subdivided into granule subsets that differ in protein content and ability to be exocytosed. To determine the localization of hCAP-18, we performed high-resolution immuno-electron microscopy and subcellular fractionation on Percoll density gradients. Biosynthesis of hCAP-18 was investigated in isolated human bone marrow cells. hCAP-18 was found to colocalize and comobilize with lactoferrin, but not with gelatinase in subcellular fractions. This was confirmed by electron microscopy. hCAP-18 is synthesized at the same stage of myeloid cell maturation as lactoferrin, and is efficiently targeted to granules. Like the peroxidase negative granule's matrix metalloproteinases, collagenase and gelatinase, hCAP-18 is also stored in unprocessed form. hCAP-18 is a major protein of specific granules where it is present in equimolar ratio with lactoferrin.

The Human Antibacterial Cathelicidin, hCAP-18, Is Synthesized in Myelocytes and Metamyelocytes and Localized to Specific Granules in Neutrophils

hCAP-18 is the only human member of the antibacterial and endotoxin-binding family of proteins known as cathelicidins. The antibacterial and endotoxin binding domains reside in the C-terminal 37 amino acids of the protein (LL-37) and this is believed to be unleashed from the neutralizing N-terminus by proteases from peroxidase positive granules. In human neutrophils, peroxidase positive and peroxidase negative granules can be subdivided into granule subsets that differ in protein content and ability to be exocytosed. To determine the localization of hCAP-18, we performed high-resolution immuno-electron microscopy and subcellular fractionation on Percoll density gradients. Biosynthesis of hCAP-18 was investigated in isolated human bone marrow cells. hCAP-18 was found to colocalize and comobilize with lactoferrin, but not with gelatinase in subcellular fractions. This was confirmed by electron microscopy. hCAP-18 is synthesized at the same stage of myeloid cell maturation as lactoferrin, and is efficiently targeted to granules. Like the peroxidase negative granule's matrix metalloproteinases, collagenase and gelatinase, hCAP-18 is also stored in unprocessed form. hCAP-18 is a major protein of specific granules where it is present in equimolar ratio with lactoferrin.

Activation of type IV procollagenases by human tumor-associated trypsin-2

Increased production of proteinases, such as matrix metalloproteinases (MMPs), is a characteristic feature of malignant tumors. Some human cancers and cell lines derived from them also express trypsinogen, but the function of the extrapancreatic trypsin has remained unclear. In this study we cloned and sequenced trypsinogen-2 cDNA from human COLO 205 colon carcinoma cells and characterized the ability of the enzyme to activate latent human type IV procollagenases (proMMP-2 and proMMP-9). As shown by cloning and N-terminal amino acid sequencing, the amino acid sequence of tumor-associated trypsin-2 is identical to that of pancreatic trypsin-2. We found that both pancreatic trypsin-2 and tumor cell-derived trypsin-2 are efficient activators of proMMP-9 and are capable of activating proMMP-9 at a molar ratio of 1:1000, the lowest reported so far. Human trypsin-2 was a more efficient activator than widely used bovine trypsin and converted the 92-kDa proMMP-9 to a single 77-kDa product that was not fragmented further. The single peptide bond cleaved by trypsin-2 in proMMP-9 was Arg87-Phe88. The generation of the 77-kDa species coincided with the increase in specific activity of MMP-9. In contrast, trypsin-2 only partially activated proMMP-2. Trypsin-2 cleaved the Arg99-Lys100 peptide bond of proMMP-2 generating 62-65-kDa MMP-2 species. Trypsin-2-induced proMMP-2 and -9 conversions were inhibited by tumor-associated trypsin inhibitor added either prior to or during activation indicating that proMMPs were not activated autocatalytically. Trypsin-2 also activated proMMPs associated with tissue inhibitor of matrix metalloproteinases, the complexes of which are thought to be the major MMP forms in vivo. The ability of human tumor cell-derived trypsin-2 to activate latent MMPs suggests a role for trypsin-2 in initiating the proteinase cascade that mediates tumor invasion and metastasis formation.

The role of the C-terminal domain of human collagenase-3 (MMP-13) in the activation of procollagenase-3, substrate specificity, and tissue inhibitor of metalloproteinase interaction

Recombinant human procollagenase-3 and a C-terminal truncated form (Delta249-451 procollagenase-3) have been stably expressed in myeloma cells and purified. The truncated proenzyme could be processed by aminophenylmercuric acetate via a short-lived intermediate form (N-terminal Leu58) to the final active form (N-terminal Tyr85). The kinetics of activation were not affected by removal of the hemopexin-like C-terminal domain. The specific activities of both collagenase-3 and Delta249-451 collagenase-3 were found to be similar using two quenched fluorescent substrates, but Delta249-451 collagenase-3 failed to cleave native triple helical collagens (types I and II) into characteristic one- and three-quarter fragments. It was noted, however, that the beta1,2(I) chains of type I collagen were susceptible to Delta249-451 collagenase-3, which indicates that the catalytic domain displays telopeptidase activity, thereby generating alpha1,2(I) chains that are slightly shorter than those in native type I collagen. It can be concluded that the C-terminal domain is only essential for the triple helicase activity of collagenase-3. Binding of procollagenase-3 and active collagenase-3 to type I collagen is mediated by the C-terminal domain. Both collagenase-3 and Delta249-451 collagenase-3 hydrolyzed the large tenascin C isoform, fibronectin, recombinant fibronectin fragments, and type IV, IX, X, and XIV collagens; thus, these events were independent from C-terminal domain interactions. In contrast, the minor cartilage type XI collagen was resistant to cleavage. Kinetic analysis of the mechanism of inhibition of wild-type and Delta249-451 collagenase-3 by wild-type and mutant tissue inhibitors of metalloproteinase (TIMPs) revealed that the association rates for complex formation were influenced by both N- and C-terminal domain interactions. The C-terminal domain of wild-type collagenase-3 promoted increased association rates with the full-length inhibitors TIMP-1 and TIMP-3 and the hybrid N.TIMP-2/C.TIMP-1 by a factor of up to 33. In contrast, the association rates for complex formation with TIMP-2 and N.TIMP-1/C.TIMP-2 were only marginally affected by C-terminal domain interactions.

Matrix metalloproteinases, tumor necrosis factor and multiple sclerosis: an overview

The matrix metalloproteinases (MMPs) are a family of at least 14 zinc-dependent enzymes which are known to degrade the protein components of extracellular matrix. In addition, MMPs and related enzymes can also process a number of cell surface cytokines, receptors, and other soluble proteins. In particular we have shown that the release of the pro-inflammatory cytokine, tumor necrosis factor-alpha, from its membrane-bound precursor is an MMP-dependent process. MMPs are expressed by the inflammatory cells which are associated with CNS lesions in animal models of multiple sclerosis (MS) and in tissue from patients with the disease. MMP expression will contribute to the tissue destruction and inflammation in MS. Drugs which inhibit MMP activity are effective in animal models of MS and may prove to be useful therapies in the clinic.