Characterization and activation of procollagenase from human polymorphonuclear leucocytes. N-terminal sequence determination of the proenzyme and various proteolytically activated forms

Cathepsin G promotes arteriovenous fistula maturation by positively regulating the MMP2/MMP9 pathway

BACKGROUND

Arteriovenous fistula (AVF) is currently the preferred vascular access for hemodialysis patients. However, the low maturation rate of AVF severely affects its use in patients. A more comprehensive understanding and study of the mechanisms of AVF maturation is urgently needed.

METHODS AND RESULTS

In this study, we downloaded the publicly available datasets (GSE119296 and GSE220796) from the Gene Expression Omnibus (GEO) and merged them for subsequent analysis. We screened 84 differentially expressed genes (DEGs) and performed the functional enrichment analysis. Next, we integrated the results obtained from the degree algorithm provided by the Cytohubba plug-in, Molecular complex detection (MCODE) plug-in, weighted gene correlation network analysis (WGCNA), and Least absolute shrinkage and selection operator (LASSO) logistic regression. This integration allowed us to identify CTSG as a hub gene associated with AVF maturation. Through the literature search and Pearson's correlation analysis, the genes matrix metalloproteinase 2 (MMP2) and MMP9 were identified as potential downstream effectors of CTSG. We then collected three immature clinical AVF vein samples and three mature samples and validated the expression of CTSG using immunohistochemistry (IHC) and double-immunofluorescence staining. The IHC results demonstrated a significant decrease in CTSG expression levels in the immature AVF vein samples compared to the mature samples. The results of double-immunofluorescence staining revealed that CTSG was expressed in both the intima and media of AVF veins. Moreover, the expression of CTSG in vascular smooth muscle cells (VSMCs) was significantly higher in the mature samples compared to the immature samples. The results of Masson's trichrome and collagen I IHC staining demonstrated a higher extent of collagen deposition in the media of immature AVF veins compared to the mature. By constructing an in vitro CTSG overexpression model in VSMCs, we found that CTSG upregulated the expression of MMP2 and MMP9 while downregulating the expression of collagen I and collagen III. Furthermore, CTSG was found to inhibit VSMC migration.

CONCLUSIONS

CTSG may promote AVF maturation by stimulating the secretion of MMP2 and MMP9 from VSMCs and reducing the extent of medial fibrosis in AVF veins by inhibiting the secretion of collagen I and collagen III.

Correlations between different protein species of oral rinse MMP-8 and patient-related factors

OBJECTIVES

The aim of this study is to examine correlations between different oral rinse matrix metalloproteinase (MMP)-8 protein species in western blot (WB) analysis, quantitative MMP-8 measurements, and patient-related factors. Elevated activated MMP-8 (aMMP-8) associate with periodontitis and a diagnostic point-of-care technology has been developed based on aMMP-8. In WB, different MMP-8 protein species can be analyzed. Relative abundancy of fragmented 20-25 kDa forms in WB has been associated with and reflects MMP-8 activation and related fragmentation and elevated quantitative aMMP-8 measurements.

MATERIAL AND METHODS

A random sample of 192 participants from a periodontal disease screening study was used for this study. Oral rinse samples for biomarker analyses were collected before clinical periodontal examinations. aMMP-8 immunofluorometric (IFMA) and WB analysis (utilizing the same monoclonal antibody, 8708), polymorphonuclear leukocyte (PMN) elastase activity test and tissue inhibitor of metalloproteinases (TIMP)-1 ELISA levels were performed from the oral rinse samples. Distinct MMP-8 protein species were differentiated in the WB analysis. Principal component (PC) analysis was conducted to explore correlation patterns between the different species. Adjusted correlation analysis between the extracted PCs of WB and aMMP-8 IFMA levels and multilevel regression analysis were conducted to explore if the other periodontal disease-related biomarkers and clinical surrogate measures and patient-related factors are co-variating with the extracted components.

RESULTS

Distinct correlation patterns between the MMP-8 protein species were observed. The first four PCs explained 89% of the whole variance in PC analysis. Statistically significant correlation (p < 0.05) were observed as follows: PC1 positively with 21 kDa (r = .69) and 25 kDa fragments (r = .55) and negatively with 150 kDa complexes (r = -.46). PC2 correlated with 45 (r = .70) and 55 kDa (r = .65) activated forms, PC3 with 70-80 kDa latent proforms (r = .63) and 90-100 kDa complexes (r = .67), and PC4 with 35 kDa fragments (r = .81). There were significant correlations between quantitative (IFMA) aMMP-8 measurements and PC1 (p < 0.001), PC2 (<0.05) and PC3 (<0.05) but not with PC4. In multilevel regression models age, PMN elastase activity, TIMP-1 levels, and a number of 4-5 mm periodontal pockets were associated with PC1, nonsmoking with PC2, age and PMN elastase activity with PC3, and age and smoking with PC4.

CONCLUSIONS

Relative abundancy of fragmented 21-25 kDa protein species was correlated with the quantitative aMMP-8 (IFMA) measurements, which is in line with previous results. Different patient-related factors (smoking, age, proteolytic activity) may modify the formation of different MMP-8 protein species in oral rinse samples and may cause variability in quantitative aMMP-8 measurement.

Proteomic profile and protease activity in the skin mucus of greater amberjack (Seriola dumerili) infected with the ectoparasite Neobenedenia girellae - An immunological approach

Skin mucus is considered the first barrier against diseases in fish. The skin mucus protein profile of the greater amberjack (Seriola dumerili) and its changes due to experimental infection with Neobenedenia girellae were studied by combining 2-DE-MS/MS and gel-free LC-MS/MS proteomic approaches. The 2-DE results led to the identification of 69 and 55 proteins in noninfected and infected fish, respectively, and revealed that keratins were specifically cleaved in parasitized fish. Therefore, the skin mucus of the infected fish showed a higher protease activity due to, at least in part, an increase of metal-dependent protease and serine-type protease activities. Additionally, through a gel-free LC-MS/MS analysis, 1377 and 1251 different proteins were identified in the skin mucus of healthy and parasitized fish, respectively. The functional analysis of these proteins demonstrated a statistical overrepresentation of ribosomal proteins (a well-known source of antimicrobial peptides) in N. girellae-infected fish. In contrast, the components of membranes and protein transport GO categories were underrepresented after infection. Immune system process-related proteins constituted 2.5% of the total skin mucosal proteins. Among these skin mucosal proteins, 14 and 15 proteins exclusive to non-parasitized and parasitized fish were found, respectively, including specific serine-type proteases and metalloproteases in the parasitized fish. Moreover, the finding of tryptic peptides exclusive to some bacterial genera, obtained by gel-free LC-MS/MS, allowed us to construct a preliminary map of the microbiota living in the mucus of S. dumerili, with Pseudomonas and Paracoccus the most represented genera in both noninfected and infected fish.

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.

Domain structure and function of matrix metalloprotease 23 (MMP23): role in potassium channel trafficking

MMP23 is a member of the matrix metalloprotease family of zinc- and calcium-dependent endopeptidases, which are involved in a wide variety of cellular functions. Its catalytic domain displays a high degree of structural homology with those of other metalloproteases, but its atypical domain architecture suggests that it may possess unique functional properties. The N-terminal MMP23 pro-domain contains a type-II transmembrane domain that anchors the protein to the plasma membrane and lacks the cysteine-switch motif that is required to maintain other MMPs in a latent state during passage to the cell surface. Instead of the C-terminal hemopexin domain common to other MMPs, MMP23 contains a small toxin-like domain (TxD) and an immunoglobulin-like cell adhesion molecule (IgCAM) domain. The MMP23 pro-domain can trap Kv1.3 but not closely-related Kv1.2 channels in the endoplasmic reticulum, preventing their passage to the cell surface, while the TxD can bind to the channel pore and block the passage of potassium ions. The MMP23 C-terminal IgCAM domain displays some similarity to Ig-like C2-type domains found in IgCAMs of the immunoglobulin superfamily, which are known to mediate protein-protein and protein-lipid interactions. MMP23 and Kv1.3 are co-expressed in a variety of tissues and together are implicated in diseases including cancer and inflammatory disorders. Further studies are required to elucidate the mechanism of action of this unique member of the MMP family.

Profibrotic activities for matrix metalloproteinase-8 during bleomycin-mediated lung injury

Matrix metalloproteinase-8 (MMP-8) is a potent interstitial collagenase thought to be expressed mainly by polymorphonuclear neutrophils. To determine whether MMP-8 regulates lung inflammatory or fibrotic responses to bleomycin, we delivered bleomycin by the intratracheal route to wild-type (WT) versus Mmp-8(-/-) mice and quantified MMP-8 expression, and inflammation and fibrosis in the lung samples. Mmp-8 steady state mRNA and protein levels increase in whole lung and bronchoalveolar lavage samples when WT mice are treated with bleomycin. Activated murine lung fibroblasts express Mmp-8 in vitro. MMP-8 expression is increased in leukocytes in the lungs of patients with idiopathic pulmonary fibrosis compared with control lung samples. Compared with bleomycin-treated WT mice, bleomycin-treated Mmp-8(-/-) mice have greater lung inflammation, but reduced lung fibrosis. Whereas bleomycin-treated Mmp-8(-/-) and WT mice have similar lung levels of several pro- and antifibrotic mediators (TGF-β, IL-13, JE, and IFN-γ), Mmp-8(-/-) mice have higher lung levels of IFN-γ-inducible protein-10 (IP-10) and MIP-1α. Genetically deleting either Ip-10 or Mip-1α in Mmp-8(-/-) mice abrogates their lung inflammatory response to bleomycin, but reconstitutes their lung fibrotic response to bleomycin. Studies of bleomycin-treated Mmp-8 bone marrow chimeric mice show that both leukocytes and lung parenchymal cells are sources of profibrotic MMP-8 during bleomycin-mediated lung fibrosis. Thus, during bleomycin-mediated lung injury, MMP-8 dampens the lung acute inflammatory response, but promotes lung fibrosis by reducing lung levels of IP-10 and MIP-1α. These data indicate therapeutic strategies to reduce lung levels of MMP-8 may limit fibroproliferative responses to injury in the human lung.

Purification of MMPs and TIMPs

A number of matrix metalloproteinases (MMPs) and their endogenous inhibitors called tissue inhibitors of metalloproteinases (TIMPs) from natural sources have been identified. This chapter describes the purification methods of MMPs-1, -2, -3, -7, -8, -9, -10, -12, and -13 and TIMPs-1 and -2. The sources of the proteins and assay methods to detect their activities are also described.

Matrix metalloproteinase-8 inactivates macrophage inflammatory protein-1 alpha to reduce acute lung inflammation and injury in mice

To determine the role of matrix metalloproteinase-8 (MMP-8) in acute lung injury (ALI), we delivered LPS or bleomycin by the intratracheal route to MMP-8(-/-) mice versus wild-type (WT) mice or subjected the mice to hyperoxia (95% O(2)) and measured lung inflammation and injury at intervals. MMP-8(-/-) mice with ALI had greater increases in lung polymorphonuclear neutrophils (PMNs) and macrophage counts, measures of alveolar capillary barrier injury, lung elastance, and mortality than WT mice with ALI. Bronchoalveolar lavage fluid (BALF) from LPS-treated MMP-8(-/-) mice had more MIP-1alpha than BALF from LPS-treated WT mice, but similar levels of other pro- and anti-inflammatory mediators. MIP-1alpha(-/-) mice with ALI had less acute lung inflammation and injury than WT mice with ALI, confirming that MIP-1alpha promotes acute lung inflammation and injury in mice. Genetically deleting MIP-1alpha in MMP-8(-/-) mice reduced the increased lung inflammation and injury and mortality in MMP-8(-/-) mice with ALI. Soluble MMP-8 cleaved and inactivated MIP-1alpha in vitro, but membrane-bound MMP-8 on activated PMNs had greater MIP-1alpha-degrading activity than soluble MMP-8. High levels of membrane-bound MMP-8 were detected on lung PMNs from LPS-treated WT mice, but soluble, active MMP-8 was not detected in BALF samples. Thus, MMP-8 has novel roles in restraining lung inflammation and in limiting alveolar capillary barrier injury during ALI in mice by inactivating MIP-1alpha. In addition, membrane-bound MMP-8 on activated lung PMNs is likely to be the key bioactive form of the enzyme that limits lung inflammation and alveolar capillary barrier injury during ALI.

Increased local matrix metalloproteinase-8 expression in the periodontal connective tissues of smokers with periodontal disease

Matrix metalloproteinase (MMP)-8 has been associated with the progression of periodontitis, a common inflammatory disease of the supporting structures of the teeth, and with other degradative diseases. Tobacco smokers are at high risk of developing periodontitis that may progress more rapidly and respond poorly to treatment. Therefore, MMP-8 expression was determined by immunofluorescence staining in 60 random, computer-selected fields in the excised periodontal tissues of smokers and non-smokers, balanced for age, gender, and periodontal status. Immunofluorescence intensity, representing MMP-8 expression, in the periodontal tissues of smokers (30 fields from 6 subjects, mean 1154+/-124 units) was significantly higher than that in the periodontal tissues of non-smokers (30 fields from 6 subjects, mean 817+/-60 units; p < 0.05). Serum MMP-8 concentrations were measured by ELISA and compared in a larger group of smokers (n = 20) and age- and gender-balanced non-smokers (n = 20). Systemic MMP-8 concentrations in smokers and non-smokers were not significantly different (p > 0.05). A local tobacco-related increase in MMP-8 burden may contribute to periodontal disease progression in tobacco smokers. This finding may also have relevance to other tobacco-induced inflammatory diseases, such as vascular and pulmonary diseases.

Gelatinase B [matrix metalloproteinase (MMP)-9] and collagenases (MMP-8/-13) are upregulated in cerebrospinal fluid during aseptic and bacterial meningitis in children

We investigated the protein expression of gelatinases [matrix metalloproteinase (MMP)-2 and -9] and collagenases (MMP-8 and -13) in cerebrospinal fluid (CSF) from patients with bacterial (BM, n = 17) and aseptic (AM, n = 14) meningitis. In both, MMP-8 and -9 were increased in 100% of patients, whereas MMP-13 was detectable in 53% and 82% respectively. Three patients with clinical signs of meningitis, without CSF pleocytosis, scored positive for all three MMPs. MMP-8 appeared in two isoforms, granulocyte-type [polymorphonuclear cell (PMN)] and fibroblast/macrophage (F/M) MMP-8. Analysis of kinetic changes from serial lumbar punctures showed that these MMPs are independently regulated, and correlate only partly with CSF cytosis or levels of the endogenous inhibitor, tissue inhibitor of matrix metalloproteinase-1. In vitro, T cells, peripheral blood mononuclear cells (PBMCs) and granulocytes (PMN) release MMP-8 and -9, whereas MMP-13 could be found only in the former two cell types. Using models of exogenous (n-formyl-Met-Leu-Phe, T cell receptor cross-linking) and host-derived stimuli (interleukin-2), the kinetics and the release of the MMP-8, -9 and -13 showed strong variation between these immune cells and suggest release from preformed stocks. In addition, MMP-9 is also synthesized de novo in PBMCs and T cells. In conclusion, invading immune cells contribute only partially to MMPs in CSF during meningitis, and parenchymal cells are an equally relevant source. In this context, in patients with clinical signs of meningitis, but without CSF pleocytosis, MMPs seem to be a highly sensitive marker for intrathecal inflammation. The present data support the concept that broad-spectrum enzyme inhibition targeting gelatinases and collagenases is a potential strategy for adjunctive therapy in infectious meningitis.

Regulation of matrix metalloproteinases: an overview

Matrix metalloproteinases (MMPs) are a major group of enzymes that regulate cell-matrix composition. MMP genes show a highly conserved modular structure. Ample evidence exists on the role of MMPs in normal and pathological processes, including embryogenesis, wound healing, inflammation, arthritis, cardiovascular diseases, pulmonary diseases and cancer. The expression patterns of MMPs have interesting implications for the use of MMP inhibitors as therapeutic agents. Insights might be gained as to the preference for a general MMP inhibitor as opposed to an inhibitor designed to be specific for certain MMP family members as it relates to a defined disease state, and may give clues to potential side effects. The signalling pathways that lead to induction of expression of MMPs are still incompletely understood, but certain patterns are beginning to emerge. Regarding inhibition of MMP expression at the level of kinase pathways, it is possible that selective chemical inhibitors for distinct signalling pathways (e.g. MAPK, PKC) will hopefully, soon be available for initial clinical trials. Overexpression of selective dual specificity MAPK phosphatases have been shown to prevent MMP promoter activation which could also be used as a novel strategy to prevent activation of AP-1 and ETS transcription factors and MMP promoters in vivo. Interactions between members of different transcription factors provide fine-tuning of the transcriptional regulation of MMP promoter activity. MMPs play a crucial role in tumor invasion. Although the expression of MMPs in malignancies has been studied widely, the specific role of distinct MMPs in the progression of cancer may be more complex than has been assumed. For example, it has recently been shown that MMP-3, MMP-7, MMP-9 and MMP-12 can generate angiostatin from plasminogen, indicating that their expression in peritumoral area may in fact serve to limit angiogenesis and thereby inhibit tumor growth and invasion. The recent view about the role of stromal cells in the progression of cancer cell growth and metastasis is particularly interesting, and additional studies about the regulation of MMP gene expression and activity in malignancies are needed to understand the role and regulation of MMPs in tumor cell invasion.

Regulation of matrix metalloproteinases: an overview

Matrix metalloproteinases (MMPs) are a major group of enzymes that regulate cell-matrix composition. MMP genes show a highly conserved modular structure. Ample evidence exists on the role of MMPs in normal and pathological processes, including embryogenesis, wound healing, inflammation, arthritis, cardiovascular diseases, pulmonary diseases and cancer. The expression patterns of MMPs have interesting implications for the use of MMP inhibitors as therapeutic agents. Insights might be gained as to the preference for a general MMP inhibitor as opposed to an inhibitor designed to be specific for certain MMP family members as it relates to a defined disease state, and may give clues to potential side effects. The signalling pathways that lead to induction of expression of MMPs are still incompletely understood, but certain patterns are beginning to emerge. Regarding inhibition of MMP expression at the level of kinase pathways, it is possible that selective chemical inhibitors for distinct signalling pathways (e.g. MAPK, PKC) will hopefully, soon be available for initial clinical trials. Overexpression of selective dual specificity MAPK phosphatases have been shown to prevent MMP promoter activation which could also be used as a novel strategy to prevent activation of AP-1 and ETS transcription factors and MMP promoters in vivo. Interactions between members of different transcription factors provide fine-tuning of the transcriptional regulation of MMP promoter activity. MMPs play a crucial role in tumor invasion. Although the expression of MMPs in malignancies has been studied widely, the specific role of distinct MMPs in the progression of cancer may be more complex than has been assumed. For example, it has recently been shown that MMP-3, MMP-7, MMP-9 and MMP-12 can generate angiostatin from plasminogen, indicating that their expression in peritumoral area may in fact serve to limit angiogenesis and thereby inhibit tumor growth and invasion. The recent view about the role of stromal cells in the progression of cancer cell growth and metastasis is particularly interesting, and additional studies about the regulation of MMP gene expression and activity in malignancies are needed to understand the role and regulation of MMPs in tumor cell invasion.

Membrane-bound matrix metalloproteinase-8 on activated polymorphonuclear cells is a potent, tissue inhibitor of metalloproteinase-resistant collagenase and serpinase

Little is known about the cell biology or the biologic roles of polymorphonuclear cell (PMN)-derived matrix metalloproteinase-8 (MMP-8). When activated with proinflammatory mediators, human PMN release only approximately 15-20% of their content of MMP-8 ( approximately 60 ng/10(6) cells) exclusively as latent pro-MMP-8. However, activated PMN incubated on type I collagen are associated with pericellular collagenase activity even when bathed in serum. PMN pericellular collagenase activity is attributable to membrane-bound MMP-8 because: 1) MMP-8 is expressed in an inducible manner in both pro- and active forms on the surface of human PMN; 2) studies of activated PMN from mice genetically deficient in MMP-8 (MMP-8(-/-)) vs wild-type (WT) mice show that membrane-bound MMP-8 accounts for 92% of the MMP-mediated, PMN surface type I collagenase activity; and 3) human membrane-bound MMP-8 on PMN cleaves types I and II collagens, and alpha(1)-proteinase inhibitor, but is substantially resistant to inhibition by tissue inhibitor of metalloproteinase-1 (TIMP-1) and TIMP-2. Binding of MMP-8 to the PMN surface promotes its stability because soluble MMP-8 has t(1/2) = 7.5 h at 37 degrees C, but membrane-bound MMP-8 retains >80% of its activity after incubation at 37 degrees C for 18 h. Studies of MMP-8(-/-) vs WT mice given intratracheal LPS demonstrate that 24 h after intratracheal LPS, MMP-8(-/-) mice have 2-fold greater accumulation of PMN in the alveolar space than WT mice. Thus, MMP-8 has an unexpected, anti-inflammatory role during acute lung injury in mice. TIMP-resistant, active MMP-8 expressed on the surface of activated PMN is likely to be an important form of MMP-8, regulating lung inflammation and collagen turnover in vivo.

Matrix metalloproteinase-8 is expressed in human chorion during labor

OBJECTIVE

The purpose of this study was to investigate the expression of matrix metalloproteinase-8 by human fetal membranes during labor.

STUDY DESIGN

Fetal membranes were obtained from women who underwent normal labor or elective cesarean delivery at term. Matrix metalloproteinase-8 levels in fetal membranes were determined by enzyme-linked immunosorbent assay and Western blot; the expression of the matrix metalloproteinase-8 gene was detected by reverse transcription-polymerase chain reaction. Immunohistochemistry and in situ hybridization was performed to localize matrix metalloproteinase-8 protein and messenger RNA in intact membranes.

RESULTS

Matrix metalloproteinase-8 protein levels were increased 5-fold in fetal membranes from labor compared with membranes that were obtained from cesarean delivery. Western blots confirmed the presence of matrix metalloproteinase-8 in protein extracts. Reverse transcription-polymerase chain reaction, in situ hybridization, and immunohistochemistry demonstrated that matrix metalloproteinase-8 messenger RNA and protein were expressed almost exclusively in the chorion after labor.

CONCLUSION

We conclude that matrix metalloproteinase-8 is produced primarily by chorionic cells in human fetal membranes and that the level of matrix metalloproteinase-8 protein and messenger RNA expression in fetal membranes increases during labor.

Cysteine peptidases of mammals: their biological roles and potential effects in the oral cavity and other tissues in health and disease

Cysteine peptidases (CPs) are phylogenetically ubiquitous enzymes that can be classified into clans of evolutionarily independent proteins based on the structural organization of the active site. In mammals, two of the major clans represented in the genome are: the CA clan, whose members share a structure and evolutionary history with papain; and the CD clan, which includes the legumains and caspases. This review focuses on the properties of these enzymes, with an emphasis on their potential roles in the oral cavity. The human genome encodes at least (but possibly no more than) 11 distinct enzymes, called cathepsins, that are members of the papain family C1A. Ten of these are present in rodents, which also carry additional genes encoding other cathepsins and cathepsin-like proteins. Human cathepsins are best known from the ubiquitously expressed lysosomal cathepsins B, H, and L, and dipeptidyl peptidase I (DPP I), which until recently were considered to mediate primarily "housekeeping" functions in the cell. However, mutations in DPP I have now been shown to underlie Papillon-Lefevre syndrome and pre-pubertal periodontitis. Other cathepsins are involved in tissue-specific functions such as bone remodeling, but relatively little is known about the functions of several recently discovered enzymes. Collectively, CPs participate in multiple host systems that are active in health and in disease. They are involved in tissue remodeling and turnover of the extracellular matrix, immune system function, and modulation and alteration of cell function. Intracellularly, CPs function in diverse processes including normal protein turnover, antigen and proprotein processing, and apoptosis. Extracellularly, they can contribute directly to the degradation of foreign proteins and the extracellular matrix. However, CPs can also participate in proteolytic cascades that amplify the degradative capacity, potentially leading to pathological damage, and facilitating the penetration of tissues by cancer cells. We know relatively little regarding the role of human CPs in the oral cavity in health or disease. Most studies to date have focused on the potential use of the lysosomal enzymes as markers for periodontal disease activity. Human saliva contains high levels of cystatins, which are potent CP inhibitors. Although these proteins are presumed to serve a protective function, their in vivo targets are unknown, and it remains to be discovered whether they serve to control any human CP activity.

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.

Modulation of the catalytic activity of neutrophil collagenase MMP-8 on bovine collagen I. Role of the activation cleavage and of the hemopexin-like domain

The cleavage of bovine collagen I by neutrophil collagenase MMP-8 has been followed at pH 7.4, 37 degrees C. The behavior of the whole enzyme molecule (whMMP-8), displaying both the catalytic domain and the hemopexin-like domain, has been compared under the same experimental conditions with that of the catalytic domain only. The main observation is that whMMP-8 cleaves bovine collagen I only at a single specific site, as already reported by many others (Mallya, S. K., Mookhtiar, K. A., Gao, Y., Brew, K., Dioszegi, M., Birkedal-Hansen, H., and van Wart, H. E. (1990) Biochemistry 29, 10628-10634; Knäuper, V., Osthues, A., DeClerk, Y. A., Langley, K. A., Bläser, J., and Tschesche, H. (1993) Biochem. J. 291, 847-854; Marini, S., Fasciglione, G. F., De Sanctis, G., D'Alessio, S., Politi, V., and Coletta, M. (2000) J. Biol. Chem. 275, 18657-18663), whereas the catalytic domain lacks this specificity and cleaves the collagen molecule at multiple sites. Furthermore, a meaningful difference is observed for the cleavage features displayed by two forms of the catalytic domain, which differ for the N terminus resulting from the activation process (i.e. the former Met(80) of the proenzyme (MetMMP-8) and the former Phe(79) of the proenzyme (PheMMP-8)). Thus, the PheMMP-8 species is characterized by a much faster k(cat)/K(m), fully attributable to a lower K(m), suggesting that the conformation of the catalytic domain, induced by the insertion of this N-terminal residue in a specific pocket (Reinemer, P., Grams, F., Huber, R., Kleine, T., Schnierer, S., Piper, M., Tschesche, H., and Bode, W. (1994) FEBS Lett. 338, 227-233), brings about a better, although less discriminatory, recognition process of cleavage site(s) on bovine collagen I.

Increase in milk metalloproteinase activity and vascular permeability in bovine endotoxin-induced and naturally occurring Escherichia coli mastitis

An endotoxin-induced mastitis model was used to study permeability changes associated with increased milk matrix metalloproteinase (MMP) activity in early inflammation. One quarter of two cows was inoculated with endotoxin (Escherichia coli 055:B5). Blood, milk, and whey were collected before and repeatedly after inoculation for 48 h. The profile and amounts of gelatinolytic MMPs were determined by zymography; gelatinase A (72 kD MMP-2) and gelatinase B (92 kD MMP-9) were identified by Western immunoblotting. Bovine serum albumin (BSA) and trypsin inhibitor capacity (TIC) were used as markers of capillary permeability with parallel examination of neutrophil penetration from blood to milk. Five clinical E. coli mastitis milk samples and five milk samples from cows with healthy udders were analyzed to detect whether increased levels of gelatinolytic MMP-2 and MMP-9 have a role in naturally occurring mastitis with endotoxin involvement. Milk MMP levels increased 2h after the endotoxin challenge. Both MMP-2 and MMP-9 were involved in this early proteolytic event. These increased MMP levels are associated with increased capillary permeability, evidenced first by the penetration of small molecular weight proteins, such as BSA and TIC. Later, 6-12h post endotoxin inoculation, neutrophilic leucocytes also entered the site, as they require larger tissue damage in basal membrane and interstitial tissue structures than BSA and TIC to extravasate. In naturally occurring disease, increased MMP-2 and MMP-9 levels were detected in milk. Thus, gelatinases, especially MMP-2, are involved in the early degradation of the blood-milk barrier, which precedes the penetration of blood-derived cellular components into milk in endotoxin-induced mastitis. In the future, measuring MMP in milk/whey might be a useful tool for diagnosing early mastitis.

Ultraviolet irradiation increases matrix metalloproteinase-8 protein in human skin in vivo

Humans express three distinct collagenases, MMP-1, MMP-8, and MMP-13, that initiate degradation of fibrillar type I collagen. We have previously reported that ultraviolet irradiation causes increased expression of MMP-1, but not MMP-13, in keratinocytes and fibroblasts in human skin in vivo. We report here that ultraviolet irradiation increases expression of MMP-8 in human skin in vivo. Western analysis revealed that levels of the full-length, 85 kDa proenzyme form of MMP-8 increased significantly within 8 h post ultraviolet irradiation (2 minimal erythema doses). Increased full-length MMP-8 protein was associated with infiltration into the skin of neutrophils, which are the major cell type that expresses MMP-8. Immunofluorescence revealed coexpression of MMP-8 and neutrophil elastase, a marker for neutrophils. Immunohistology demonstrated MMP-8 expression in neutrophils in the papillary dermis between 4 and 8 h post ultraviolet irradiation, and in the epidermis at 24 h post radiation. MMP-8 mRNA expression was not detected in nonirradiated or ultraviolet-irradiated human skin, indicating that increased MMP-8 following ultraviolet irradiation resulted from preexisting MMP-8 protein in infiltrating neutrophils. Pretreatment of skin with the glucocorticoid clobetasol, but not all-trans retinoic acid, significantly blocked ultraviolet-induced increases in MMP-8 protein levels, and neutrophil infiltration. In contrast, all-trans retinoic acid and clobetasol were equally effective in blocking ultraviolet induction of MMP-1 and degradation of collagen in human skin in vivo. Taken together, these data demonstrate that ultraviolet irradiation increases MMP-8 protein, which exists predominantly in a latent form within neutrophils, in human skin in vivo. Although ultraviolet irradiation induces both MMP-1 and MMP-8, ultraviolet-induced collagen degradation is initiated primarily by MMP-1, with little, if any, contribution by MMP-8.

Characterization of proteases in the skin mucus of Atlantic salmon (Salmo salar) infected with the salmon louse (Lepeophtheirus salmonis) and in whole-body louse homogenate

As part of an investigation of the biochemical interactions between the salmon louse Lepeophtheirus salmonis and Atlantic salmon Salmo salar, we characterized protease activity in the skin mucus of noninfected Atlantic salmon and Atlantic salmon infected with L. salmonis and in an L. salmonis whole-body homogenate. Zymography revealed that mucus from infected salmon contained a series of low-molecular-mass (17-22 kDa) serine proteases that were not present in the mucus of noninfected salmon. Based on molecular mass, inhibition studies, and affinity chromatography, the series of proteases was identified as being trypsin-like. Similar proteases were observed in the L. salmonis homogenate and in mucus from noninfected Atlantic salmon following a 1-hr incubation with live L. salmonis. An antibody raised against Atlantic salmon trypsin failed to recognize any proteases in the mucus of noninfected salmon or infected salmon or in the L. salmonis homogenate. Collectively, these findings suggest that the trypsin-like proteases present in the mucus of infected Atlantic salmon were produced by L. salmonis, possibly to aid in feeding and evasion of host immune responses.

Matrix metalloproteases: variations on a theme

The family of proteins called matrix metalloproteinases (MMPs) are a class of structurally related proteins that are collectively responsible for the metabolism of extracellular matrix proteins. These zinc and calcium dependent enzymes, which include the collagenases, stromelysins and gelatinases, are involved in normal tissue remodelling processes such as wound healing, pregnancy and angiogenesis. Under physiological conditions, in addition to the regulated proteolyses of inactive precursors to the active form, the degradative nature of these enzymes are precisely controlled by endogenous inhibitors (TIMPs). The excess syntheses and production of these proteins lead to the accelerated matrix degradation associated with diseases such as arthritis, cancer and multiple sclerosis. The MMPs have therefore proved to be attractive targets for structure based drug design. The pursuit of low molecular weight inhibitors of these proteins have encouraged structural studies on several members of family, so that the molecular details of enzyme-inhibitor interactions of the MMPs have become available. These studies provide insights into the basic structural framework of the MMP superfamily and reveal characteristics which promote specificity between individual members. The analyses of the three dimensional structure of the MMPs in the context of their primary sequence and the design and selectivity of low molecular weight inhibitors of the superfamily is the subject of this review.

Collagenase 2 (MMP-8) expression in murine tissue-remodeling processes. Analysis of its potential role in postpartum involution of the uterus

Neutrophil collagenase or collagenase 2 (MMP-8) is unique among the family of matrix metalloproteinases (MMPs) because of its exclusive pattern of expression in inflammatory conditions. At present, no evidence of the occurrence of this enzyme in tissues other than human has been reported. In this work, we have cloned the murine homologue of human collagenase 2. The isolated cDNA contains an open reading frame coding for a polypeptide of 465 amino acids, which is 74% identical to its human counterpart. The mouse collagenase 2 exhibits the domain structure characteristic of several MMPs, including a signal sequence, a prodomain with the cysteine residue essential for enzyme latency, an activation locus with the Zinc-binding site, and a COOH-terminal fragment with sequence similarity to hemopexin. It also contains the three conserved residues (Tyr-209, Asp-230, and Gly-232) located around the Zinc-binding site and are distinctive of the collagenase subfamily. Northern blot analysis of RNAs isolated from a variety of mouse tissues revealed that collagenase 2 is expressed at late stages during mouse embryogenesis, coinciding with the appearance of hematopoietic cells. In addition, collagenase 2 was highly expressed in the postpartum uterus starting at 1 day postpartum and extending up to 5 days. Enzymatic analysis revealed that matrilysin, another MMP overexpressed in uterine tissue, is able to activate murine procollagenase 2. These data suggest that both enzymes could form an activation cascade resulting in the generation of the collagenolytic activity required during the process of massive connective tissue resumption occurring in the involuting uterus.

Roles of the matrix metalloproteinases in mammary gland development and cancer

Tissue remodeling is a key process involved in normal development, wound healing, bone remodeling, and embryonic implantation, as well as pathological conditions such as tumor invasion and metastasis, and angiogenesis. The degradation of the extracellular matrix that is associated with those processes is mediated by a number of families of extracellular proteinases. These families include the serine proteinases, such as the plasminogen-urokinase plasminogen activator system and leukocyte elastases, the cysteine proteinases, like cathepsin D and L, and the zinc-dependent matrix metalloproteinases (MMPs) [1]. Accumulating evidence has highlighted the central role of MMP-driven extracellular matrix remodeling in mammary gland development and breast cancer.

Activation mechanism of meprins, members of the astacin metalloendopeptidase family

Meprins are mammalian zinc metalloendopeptidases with protease domains structurally related to astacin, the prototype of the "astacin family" of metalloproteases. Mature, active astacins are produced by proteolytic removal of an activation peptide to generate a new NH2-terminal residue. Structural studies indicate that the NH2-terminal ammonium group inserts into a water-filled cavity adjacent to the active site to form a salt bridge with a Glu residue that is conserved in all astacins. A similar interaction is known to play a crucial role in the activation of trypsin, resulting in the hypothesis that this salt bridge is required for the activation of astacin-like proteases. In this study, we have used the mouse meprin alpha subunit as a model to test this hypothesis of zymogen activation of the astacins. Mutants were generated to vary the NH2-terminal residue of the mature meprin alpha subunit (Asn78) and its putative salt bridge partner (Glu178). In addition, mutants creating NH2-terminal extensions and truncations were expressed in human embryonic kidney 293 cells. The recombinant proteins were activated by limited protease digestion and assayed for enzymatic activity and thermal stability. Point mutations of Asn78 resulted in enzymes with activity comparable to the wild-type enzyme, indicating that the structure of this side chain is not essential for activity. NH2-terminal extension mutants of meprin alpha retained partial activity, with greater decreases against peptide relative to protein substrates. A mutant with a deletion of Asn78 to disrupt salt bridge formation with Glu178 had full activity, indicating that the putative salt bridge with Glu178 is not essential for enzyme activity. However, all changes in meprin alpha subunit NH2-terminal structure were found to decrease the thermal stability of the enzyme. These observations and additional data indicate that the zymogen activation mechanism of meprin and other astacins differs from that of the trypsin family of enzymes, and has some features in common with matrixins. It is proposed that prosequence removal of astacins allows the formation of hydrogen bonds involving the two NH2-terminal residues that are critical for enzyme structure.

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.

Activation of human neutrophil procollagenase by nitrogen dioxide and peroxynitrite: a novel mechanism for procollagenase activation involving nitric oxide

The involvement of nitric oxide (NO) and its reactive intermediates such as nitrogen dioxide (NO2) and peroxynitrite (ONOO-) in the activation of matrix metallo-proteinase was investigated. The human neutrophil procollagenase (matrix metalloproteinase-8) (M(r), 85 kDa) was purified to homogeneity from human neutrophils by using column chromatography. After incubation of human neutrophil procollagenase with various nitrogen oxide-generating systems, collagenolytic activity in each reaction system was measured. In addition, neutrophil collagenase activity was determined by assessment of proteolysis of human alpha 1-protease inhibitor. NO was formed by the propylamine NONOate, and NO2 was generated by oxidation of NO with 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (carboxy-PTIO). NO2, formed by NONOate and carboxy-PTIO, and the synthetic ONOO- exhibited strong activation of the procollagenase at 1-20 microM. Significant activation of the procollagenase was observed with use of authentic NO2 gas as well. Constant flux infusion of ONOO- into the procollagenase solution resulted in stronger procollagenase activation than did a bolus addition of ONOO- to the reaction mixture. However, NO showed only weak activating potential under the aerobic (ambient) condition; an NO concentration of more than 10 mM was needed for appreciable activation of the procollagenase. Of considerable importance was the fact that NO participates in activation of the neutrophil collagenase through its conversion to NO2 or ONOO- in human neutrophils. These results suggest that NO2 and ONOO- may be potent activators of human neutrophil procollagenase.

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.

Activation of human matrix metalloproteinases by various bacterial proteinases

Matrix metalloproteinases (MMPs) are zinc-containing proteinases that participate in tissue remodeling under physiological and pathological conditions. To test the involvement of bacterial proteinases in tissue injury during bacterial infections, we investigated the activation potential of various bacterial proteinases against precursors of MMPs (proMMPs) purified from human neutrophils (proMMP-8 and -9) and from human fibrosarcoma cells (proMMP-1). Each proMMP was subjected to treatment with a series of bacterial proteinases at molar ratios of 0.01-0.1 (bacterial proteinase to proMMP), and activities of MMPs generated were determined. Among six different bacterial proteinases, thermolysin family enzymes (family M4) such as Pseudomonas aeruginosa elastase, Vibrio cholerae proteinase, and thermolysin strongly activated all three proMMPs via limited proteolysis to generate active forms of the MMPs. N-terminal sequence analysis of the active MMPs revealed that cleavage occurred at the Val82-Leu83 and Thr90-Phe91 bonds of proMMP-1 and proMMP-9, respectively, which are located near the N terminus of the catalytic domain of MMPs. In contrast, Serratia 56-kDa proteinase and Pseudomonas alkaline proteinase, both of which are classified as members of the serralysin subfamily of zinc metalloproteinases (family M10), and Serratia 73-kDa thiol proteinase did not evidence proteolytic processing or activation of proMMP-1, -8, and -9 under these experimental conditions. These results indicate that bacterial proteinases may play an important role in tissue destruction and disintegration of extracellular matrix at the site of infections.

Design and synthesis of heterotrimeric collagen peptides with a built-in cystine-knot. Models for collagen catabolism by matrix-metalloproteases

A heterotrimeric collagen peptide was designed and synthesized which contains the collagenase cleavage site (P4-P'9/10) of type I collagen linked to a C-terminal cystine-knot, and N-terminally extended with (Gly-Pro-Hyp)5 triplets for stabilization of the triple-helical conformation. By employing a newly developed regioselective cysteine pairing strategy based exclusively on thiol disulfide exchange reactions, we succeeded in assembling in high yields and in a reproducible manner the triple-stranded cystine peptide. While the single chains showed no tendency to self-association into triple helices, the heterotrimer (alpha1 alpha2 alpha1') was found to exhibit a typical collagen-like CD spectrum at room temperature and a melting temperature (Tm) of 33 degrees C. This triple-helical collagen-like peptide is cleaved by the full-length human neutrophil collagenase (MMP-8) at a single locus fully confirming the correct raster of the heterotrimer. Its digestion proceeds at rates markedly higher than that of a single alpha1' chain. In contrast, opposite digestion rates were measured with the catalytic Phe79-MMP-8 domain of HNC. Moreover, the full-length enzyme exhibits Km values of 5 microM and 1 mM for the heterotrimer and the single alpha1' chain, respectively, which compare well with those reported for collagen type I (approximately 1 microM), gelatine (approximately 10 microM) and for octapeptides of the cleavage sequence (> or = 1 mM). The high affinity of the MMP-8 for the triple-helical heterotrimer and the fast digestion of this collagenous peptide confirm the decisive role of the hemopexin domain in recognition and possibly, partial unfolding of collagen.

The recombinant catalytic domain of membrane-type matrix metalloproteinase-1 (MT1-MMP) induces activation of progelatinase A and progelatinase A complexed with TIMP-2

A truncated form of the membrane-type matrix metalloproteinase-1 [(Ala21-Ile318)proMT1-MMP] lacking the hemopexin-like and trans-membrane domain was produced in E. coli. We demonstrate that the recombinant proenzyme was autoproteolytically processed to a fully active catalytic domain with N-terminal Ile114. The catalytic domain of MT1-MMP initiated the activation of progelatinase A and progelatinase A complexed with tissue inhibitor of metalloproteinases-2 (TIMP-2). As a typical soluble metalloproteinase it was able to cleave physiologic as well as synthetic substrates. Our kinetic data demonstrate that TIMP-2 is a potent inhibitor for the recombinant enzyme.

Secretion of type-1-fimbriae binding proteins from human neutrophil granulocytes

Granule matrix proteins secreted from human neutrophils after ionomycin stimulation were separated by SDS-PAGE, blotted onto a polyvinylidene diflouride (PVDF) membrane and overlaid with the mannose-binding lectin concanavalin A (Con A) or Escherichia coli bacteria exposing type-I-fimbriae. Four proteins of approximately 30, 40, 70 and 80 kD, respectively, derived from both the azurophil and the specific granules were shown to expose mannose-containing structures by binding of Con A. Such reactivity was also shown for a 90-kD protein from the light membrane fraction enriched in plasma membrane and secretory vesicles. When blots of granule matrix proteins were exposed to type-I-fimbriated bacteria, a total of seven proteins was recognized; four of the five Con A-binding proteins (40, 70, 80 and 90 kD) was detected also by the bacteria in addition to three proteins not detected by Con A (50, 60 and 100 kD). The role of the secreted type-1-fimbriae binding proteins as anti-adhesin candidates is discussed.

Biochemical characterization of human collagenase-3

The cDNA of a novel matrix metalloproteinase, collagenase-3 (MMP-13) has been isolated from a breast tumor library (Freije, J. M. P., Dicz-Itza, I., Balbin, M., Sanchez, L. M., Blasco, R., Tolivia, J., and López-Otin, C. (1994) J. Biol. Chem. 269, 16766-16773), and a potential role in tumor progression has been proposed for this enzyme. In order to establish the possible role of collagenase-3 in connective tissue turnover, we have expressed and purified recombinant human procollagenase-3 and characterized the enzyme biochemically. The purified procollagenase-3 was shown to be glycosylated and displayed a M(r) of 60,000, the N-terminal sequence being LPLPSGGD, which is consistent with the cDNA-predicted sequence. The proenzyme was activated by p-aminophenylmercuric acetate or stromelysin, yielding an intermediate form of M(r) 50,000, which displayed the N-terminal sequence L58EVTGK. Further processing resulted in cleavage of the Glu84-Tyr85 peptide bond to the final active enzyme (M(r) 48,000). Trypsin activation of procollagenase-3 also generated a Tyr85 N terminus, but it was evident that the C-terminal domain was rapidly lost, and hence the collagenolytic activity diminished. Analysis of the substrate specificity of collagenase-3 revealed that soluble type II collagen was preferentially hydrolyzed, while the enzyme was 5 or 6 times less efficient at cleaving type I or III collagen. Fibrillar type I collagen was cleaved with comparable efficiency to the fibroblast and neutrophil collagenases (MMP-1 and MMP-8), respectively. Unlike these collagenases, gelatin and the peptide substrates Mea-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH2 and Mca-Pro-Cha-Gly-Nva-His-Ala-Dpa-NH2 were efficiently hydrolyzed as well, as would be predicted from the similarities between the active site sequence of collagenase-3 (MMP-13) and the gelatinases A and B. Active collagenase-3 was inhibited in a 1:1 stoichiometric fashion by the tissue inhibitors of metalloproteinases, TIMP-1, TIMP-2, and TIMP-3. These results suggest that in vivo collagenase-3 could play a significant role in the turnover of connective tissue matrix constituents.

Activation of human neutrophil procollagenase by stromelysin 2

Neutrophil procollagenase (MMP-8) was efficiently activated by incubation with active stromelysin 2 (MMP-10). A single-step activation mechanism involving the cleavage of the Gly78-Phe79 peptide bond at the end of the propeptide domain was observed. Determination of the collagenolytic activity revealed the generation of active neutrophil collagenase displaying high specific activity. When compared with the specific activity following mercurial activation, which generates active collagenase by autoproteolytic cleavage of either Phe79-Met8O or Met8O-Leu81 peptide bonds [Bläser, J., Knäuper, V., Osthues, A., Reinke, H. & Tschesche, H. (1991) Eur J. Biochem. 202, 1223-1230], the specific activity of the stromelysin-2-activated enzyme was considerably higher. Thus, human neutrophil procollagenase was 'superactivated' by stromelysin 2, as was recently shown for the stromelysin-1-activated enzyme [Knäuper, V., Wilhelm, S. M., Seperack, P. K., De Clerck, Y. A., Langley, K. E., Osthues, A. & Tschesche, H. 1993 a) Biochem. J. 295, 581-586].

Human matrix metalloproteinase specificity studies using collagen sequence-based synthetic peptides

The matrix metalloproteinase (MMP)/matrixin family has been implicated in both normal tissue remodeling and a variety of diseases associated with abnormal turnover of extracellular matrix components. To better understand MMP behaviors and to aid in the design of MMP inhibitors, a variety of sequence specificity studies have been performed using collagen sequence-based peptides and MMP family members. Results of these studies have been valuable for defining the differences in MMPs and for creating fluorogenic substrates that can continuously monitor MMP activity. However, these studies have also demonstrated that these peptides may not be very good models of native MMP substrates, and that the additivity principle is not always applicable for designing synthetic MMP substrates.

Metalloproteinase inhibitors and the prevention of connective tissue breakdown

The primary agents responsible for cartilage and bone destruction in joint diseases are active proteinases degrading collagen and proteoglycan. All four main classes of proteolytic enzymes are involved in either the normal turnover of connective tissue or its pathological destruction. These proteinases are made by different cells found within the joints. Both extracellular and intracellular pathways exist, and individual enzymes can be inhibited by specific proteinaceous inhibitors that block their activity. Recent research has implicated the matrix metalloproteinases in many of the processes involved in joint diseases. Conventional treatments do little to affect the underlying disease processes, and recently, the use of proteinase inhibitors has been suggested as a new therapeutic approach. A large variety of different synthetic approaches have been used and highly effective metalloproteinase inhibitors have been designed, synthesised and tested. These metalloproteinase inhibitors can prevent the destruction of animal cartilage in model systems and slow the progression of human tumours. Future patient trials will test the effectiveness of these compounds in vivo for the treatment of joint diseases.

Metalloproteases and serineproteases are involved in the cleavage of the two tumour necrosis factor (TNF) receptors to soluble forms in the myeloid cell lines U-937 and THP-1

The proteolytic processing of the two TNF receptors (TNF-R55 and TNF-R75) into soluble forms was investigated in the myeloid cell lines U-937 and THP-1. Phorbol myristate acetate (PMA) rapidly stimulated release of soluble forms of both TNF-receptors. Incubations were made with PMA and protease inhibitors directed against different target protease groups. The serineprotease inhibitors TPCK and dichloroisocoumarin and the metalloprotease inhibitor 1,10-phenanthroline reduced PMA-induced release of both soluble receptor forms with about 60-70%. Furthermore, 1,10-phenanthroline also reduced PMA-induced down-regulation of TNF-receptors in both cell lines as judged by TNF-binding to cells. Reduced down-regulation and TNF-receptor shedding by 1,10-phenanthroline was reversed by Zn2+, indicating involvement of a Zn(2+)-dependent metalloprotease. Thus, both serine proteases and metalloproteases are involved in the processing of TNF-receptors.

Characterization of the Phe-81 and Val-82 human fibroblast collagenase catalytic domain purified from Escherichia coli

Soluble recombinant human fibroblast collagenase catalytic domain was highly expressed and purified from Escherichia coli. The expression construct utilized the T7 gene 10 promoter for transcription of a two-cistron messenger RNA which encoded the ubiquitin-collagenase catalytic domain fusion protein as the second cistron. The ubiquitin domain was attached to the collagenase catalytic domain with the linker sequences Gly-Gly-Thr-Gly-Asp-Val-Ala-Gln (wild type) or Gly-Gly-Thr-Gly-Asp-Val-Gly-His (mutant) which served as cleavage sites for in vitro activation. The last four residues of the linker were included based on the crystal structure of human prostromelysin-1 catalytic domain. Soluble fusion proteins purified from E. coli retained the proteolytic activity of the collagenase catalytic domain. The collagenase catalytic domain was released by either autoproteolytic or stromelysin-1-catalyzed cleavage, purified to homogeneity, and separately possess Phe-81, Val-82, or Leu-83 as the amino-terminal residue. Very similar kcat/Km values were determined for the Phe-81 and Val-82 forms using continuous fluorogenic and chromogenic peptide cleavage assays.

Proteolytic and non-proteolytic activation of human neutrophil progelatinase B

The activation of human neutrophil progelatinase B (pro-HNG) by a variety of proteolytic and non-proteolytic activators has been investigated. A quantitative comparison of the activation efficiencies of treatments previously reported to activate pro-HNG or the related gelatinase B species produced by other cells demonstrates that stromelysin and trypsin are good activators. HgCl2 is a moderately effective activator, while p-chloromercuribenzoate and NaOCl are poor activators. It is also shown that human matrilysin and human fibroblast-type collagenase can activate pro-HNG by a mechanism that is very similar to that of stromelysin. Initially, these proteinases hydrolyze the Glu40-Met41 bond in the propeptide domain to generate an 88 kDa inactive HNG species. Collagenase also generates a 68 kDa HNG species through hydrolysis of the Ala74-Met75 bond. Ultimately, treatment with either matrilysin, collagenase or trypsin results in the production of a 65 kDa active form of HNG that arises from hydrolysis of the Arg87-Phe88 bond. This is the same active species produced on activation by stromelysin. This cleavage site is downstream of the 'cysteine-switch' residue located at position 80 and releases it, accounting for the permanent activation of the enzyme. These results suggest that matrilysin and collagenase may be physiologically relevant activators of pro-HNG and/or other progelatinase B species. Activation by HgCl2 produces an active 68 kDa enzyme due to autolytic hydrolysis of the Ala74-Met75 bond. This species retains the cysteine switch residue; however, it is shown that it is only active in the continued presence of HgCl2. Removal of the HgCl2 restores latency, indicating that this species is reversibly activated by HgCl2, which functions by complexing the sulfhydryl group of the cysteine switch residue and keeping it dissociated from the active site zinc atom. Thus, in spite of reports to the contrary, the cysteine switch mechanism can account for the latency and activation of pro-HNG.

Cellular source, activation and inhibition of dental plaque collagenase

Dental plaque is the major aetiological factor in periodontal diseases and contains several proteolytic enzymes. The origin of these proteinases is, however, poorly studied. This study was undertaken to characterize collagenase present in dental plaque of adult periodontitis patients. Vertebrate-type rather than bacterial-derived collagenase activity was detected in extracts of both supra- and subgingival dental plaque extracts of adult periodontitis patients. Dental plaque collagenase was found to exist predominantly in autoactive form. Dental plaque collagenase from periodontally healthy individuals existed in latent from. Latent dental plaque collagenase from periodontitis lesions could be activated by a 95 kD chymotrypsin-like proteinase from Treponema denticola and human leukocyte cathepsin G but not by human plasmin. Incubation of purified latent leukocyte collagenase with whole cells of Fusobacterium nucleatum, Eubacterium saburreum, Prevotella buccae and Porphyromonas gingivalis, however, did not result to the activation of the enzyme. Doxycycline in vitro inhibited dental plaque collagenase with an IC50-value of 20 microM. Dental plaque collagenase degraded more efficiently type I and II collagens than type III collagen. Western-blot analysis with specific anti-human neutrophil collagenase-antibody revealed that both in supra- and subgingival dental plaque extracts dental plaque collagenase had undergone proteolytic conversion from an 80 kD proform to a 58 kD active form which is associated with catalytic autoactivity as measured by functional collagenase assay. This reflects proteolytic activation of leukocyte collagenase in dental plaque probably by other proteases derived from potent periodontopathogenic bacteria such as T. denticola or other PMN proteases such as cathepsin G.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of a cleavage-site-specific monoclonal antibody for detecting metalloproteinase-derived aggrecan fragments: detection of fragments in human synovial fluids

We have developed a monoclonal antibody AF-28 that specifically recognizes a neo-epitope on polypeptides with N-terminal FFGVG ... sequences. This sequence is found at the N-terminus of aggrecan fragments that have been digested with matrix metalloproteinases (MMPs). By immunoblotting, monoclonal antibody AF-28 specifically detected G2 fragments derived from an aggrecan G1-G2 substrate digested with stromelysin, collagenase, gelatinase and matrilysin, but failed to detect G2 fragments obtained from elastase, trypsin or cathepsin B digests. Undigested G1-G2 was not detected. In addition, AF-28 antibody detected fragments derived from whole aggrecan and this detection did not require prior treatment with chondroitinase or keratanase. Competition experiments confirmed that peptides containing internal ... FFGVG ... sequences were not detected by the antibody, while native MMP-digested aggrecan fragments and a synthetic 32-mer peptide with FFGVG ... N-termini were equally competitive on a molar basis. An FFGVG 5-mer, and an FGVGGEEDI9-mer which lacked the N-terminal phenylalanine residue, were 50 times and 230 times respectively less competitive than the FFGVG ... 32-mer. Two fragments from the interglobular domain, F342-F373 and F342-D441, that are predicted products of G1-G2 digestion by neutrophil collagenase but have not previously been detected, could be detected with AF-28. The epitope recognized by AF-28 was also detected in human synovial fluids by Western blot analysis. A broad band of 100-200 kDa was detected in some patients and a dominant band of 40-60 kDa was found in two patients. The size of this small fragment corresponds with that seen for the porcine F342-E373 product and may represent the natural physiological product of aggrecan cleaved in vivo at both the MMP site (... DIPEN341 decreases F342FGVG ...) and the aggrecanase site (... ITEGE373 decreases A374RGSVI ...).

A helping hand for collagenases: the haemopexin-like domain

The structures of the C-terminal domains of rabbit haemopexin and full-length porcine fibroblast collagenase reveal a common beta-propeller fold with pseudo-fourfold symmetry. The interactions of these haemopexin-like domains with target proteins and ligands is, however, still a matter of debate.

The metzincins--topological and sequential relations between the astacins, adamalysins, serralysins, and matrixins (collagenases) define a superfamily of zinc-peptidases

The three-dimensional structures of the zinc endopeptidases human neutrophil collagenase, adamalysin II from rattle snake venom, alkaline proteinase from Pseudomonas aeruginosa, and astacin from crayfish are topologically similar, with respect to a five-stranded beta-sheet and three alpha-helices arranged in typical sequential order. The four proteins exhibit the characteristic consensus motif HEXXHXXGXXH, whose three histidine residues are involved in binding of the catalytically essential zinc ion. Moreover, they all share a conserved methionine residue beneath the active site metal as part of a superimposable "Met-turn." This structural relationship is supported by a sequence alignment performed on the basis of topological equivalence showing faint but distinct sequential similarity. The alkaline proteinase is about equally distant (26% sequence identity) to both human neutrophil collagenase and astacin and a little further away from adamalysin II (17% identity). The pairs astacin/adamalysin II, astacin/human neutrophil collagenase, and adamalysin II/human neutrophil collagenase exhibit sequence identities of 16%, 14%, and 13%, respectively. Therefore, the corresponding four distinct families of zinc peptidases, the astacins, the matrix metalloproteinases (matrixins, collagenases), the adamalysins/reprolysins (snake venom proteinases/reproductive tract proteins), and the serralysins (large bacterial proteases from Serratia, Erwinia, and Pseudomonas) appear to have originated by divergent evolution from a common ancestor and form a superfamily of proteolytic enzymes for which the designation "metzincins" has been proposed. There is also a faint but significant structural relationship of the metzincins to the thermolysin-like enzymes, which share the truncated zinc-binding motif HEXXH and, moreover, similar topologies in their N-terminal domains.

Neutrophil collagenase (MMP-8) cleaves at the aggrecanase site E373-A374 in the interglobular domain of cartilage aggrecan

Native and recombinant neutrophil collagenase (MMP-8) was shown to cleave at the E373-A374 'aggrecanase' site in the interglobular domain of aggrecan. The time course of digestion in vitro showed that MMP-8 cleaved initially at N341-F342, the predominant metalloproteinase site, before cleaving at the E373-A374 site. A synthetic peptide, IPENFFG, inhibited cleavage at E373-A374 but not N341-F342 in vitro, indicating that the E373-A374 sequence was a less preferred site for MMP-8 cleavage than N341-F342. IPENFFG also inhibited release of A374 RGSVI fragments from cartilage in explant culture, suggesting that a metalloproteinase cleaved at the aggrecanase site in situ. The possibility remains that 'aggrecanase' may be a metalloproteinase in cartilage.

Structural implications for the role of the N terminus in the 'superactivation' of collagenases. A crystallographic study

For the collagenases PMNL-CL and FIB-CL, the presence of the N-terminal Phe79 correlates with an increase in proteolytic activity. We have determined the X-ray crystal structure of the recombinant Phe79-Gly242 catalytic domain of human neutrophil collagenase (PMNL-CL, MMP-8) using the recently solved model of the Met80-Gly242 form for phasing and subsequently refined it to a final crystallographic R-factor of 18.0% at 2.5 A resolution. The PMNL-CL catalytic domain is a spherical molecule with a flat active site cleft separating a smaller C-terminal subdomain from a bigger N-terminal domain, that harbours two zinc ions, namely a 'structural' and a 'catalytic' zinc, and two calcium ions. The N-terminal segment prior to Pro86, which is disordered in the Met80-Gly242 form, packs against a concave hydrophobic surface made by the C-terminal helix. The N-terminal Phe79 ammonium group makes a salt link with the side chain carboxylate group of the strictly conserved Asp232. Stabilization of the catalytic site might be conferred via strong hydrogen bonds made by the adjacent, likewise strictly conserved Asp233 with the characteristic 'Met-turn', which forms the base of the active site residues.