Partial purification of collagenase and gelatinase from human polymorphonuclear leucocytes. Analysis of their actions on soluble and insoluble collagens

Association between matrix metalloproteinase-9-1562C/T gene polymorphism and MMP-9 serum level in rheumatoid arthritis

BACKGROUND

Rheumatoid arthritis (RA) is an autoimmune disease indicated by joint inflammation and cartilage destruction. Matrix metalloproteinase (MMP) enzymes play an influential role in inflammation by affecting the invasion and degradation of anatomical barriers. In this way, the current study investigated the relationship between the MMP-9-1562C/T gene polymorphism and this enzyme's serum level in RA.

METHODS

The serum levels of MMP-9 in RA patients and healthy controls were measured using the enzyme-linked immunosorbent assay (ELISA). RA was confirmed using rheumatoid factor (RF), anti-cyclic citrullinated peptide (anti-CCP), and C-reactive protein (CRP). Then the MMP-9-1562C/T gene polymorphism was analyzed utilizing polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). Also, multivariate analysis investigated the connection between this polymorphism and the risk of RA.

RESULTS

In this study, the increase of MMP-9 in patients due to the development of single nucleotide polymorphism in the promoter region of this gene (-1562 C→T) was confirmed by increasing the frequency of heterozygous genotype (CT). Logistic regression analysis also demonstrated that the chance of development of RA is higher in people with CT/CC genotype than in other alleles.

CONCLUSIONS

We demonstrated that MMP-9-1562C/T gene polymorphism can play a significant role in the occurrence of RA.

Hydrolyzed Collagen Powder Dressing Improves Wound Inflammation, Perfusion, and Breaking Strength of Repaired Tissue

Objective: Hydrolyzed collagen-based matrices are widely used as wound care dressings. Information on the mechanism of action of such dressings is scanty. The objective of this study was to test the effect of a specific hydrolyzed collagen powder (HCP), which is extensively used for wound care management in the United States. Approach: The effects of HCP on resolution of wound inflammation, perfusion, closure, and breaking strength of the repaired skin were studied in an experimental murine model. Results: In early (day 7) inflammatory phase of wound macrophages, HCP treatment boosted phagocytosis and efferocytosis of wound-site macrophages. In these cells, inducible reactive oxygen species were also higher on day (d) 7. HCP treatment potentiated the expression of anti-inflammatory interleukin (IL)-10 cytokine and proangiogenic vascular endothelial growth factor (VEGF) production. Excisional wounds dressed with HCP showed complete closure on day 21, while the control wounds remained open. HCP treatment also demonstrated improved quality of wound healing as marked by the improved breaking strength of the closed wound tissue/repaired skin. Innovation: These data represent first evidence on the mechanism of action of clinically used HCP. Conclusion: HCP dressing favorably influenced both wound inflammation and vascularization. Improved breaking strength of HCP-treated repaired skin lays the rationale for future studies testing the hypothesis that HCP-treated closed wounds would show fewer recurrences.

Uncovering Mediators of Collagen Degradation in the Tumor Microenvironment

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Collagen cleavage in tumors is primarily mediated by FAP⁺ cancer-associated fibroblasts.

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Collagen fibers are cleaved in an MMP-dependent manner.

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Released collagen fragments are internalized by M2-like tumor-associated macrophages and cancer-associated fibroblasts.

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The mannose receptor is central in collagen internalization by tumor-associated macrophages.

Increased remodeling of the extracellular matrix in malignant tumors has been shown to correlate with tumor aggressiveness and a poor prognosis. This remodeling involves degradation of the original extracellular matrix (ECM) and deposition of a new tumor-supporting ECM. The main constituent of the ECM is collagen and collagen turnover mainly occurs in a sequential manner, where initial proteolytic cleavage of the insoluble fibers is followed by cellular internalization of large well-defined collagen fragments for lysosomal degradation. However, despite extensive research in the field, a lack of consensus on which cell types within the tumor microenvironment express the involved proteases still exists. Furthermore, the relative contribution of different cell types to collagen internalization is not well-established. Here, we developed quantitative ex vivo collagen degradation assays and show that the proteases responsible for the initial collagen cleavage in two murine syngeneic tumor models are matrix metalloproteinases produced by cancer-associated fibroblasts and that collagen degradation fragments are endocytosed primarily by tumor-associated macrophages and cancer-associated fibroblasts from the tumor stroma. Using tumors from mannose receptor-deficient mice, we show that this receptor is essential for collagen-internalization by tumor-associated macrophages. Together, these findings identify the cell types responsible for the entire collagen degradation pathway, from initial cleavage to endocytosis of fragments for intracellular degradation.

Immune Modulatory Properties of Collagen in Cancer

During tumor growth the extracellular matrix (ECM) undergoes dramatic remodeling. The normal ECM is degraded and substituted with a tumor-specific ECM, which is often of higher collagen density and increased stiffness. The structure and collagen density of the tumor-specific ECM has been associated with poor prognosis in several types of cancer. However, the reason for this association is still largely unknown. Collagen can promote cancer cell growth and migration, but recent studies have shown that collagens can also affect the function and phenotype of various types of tumor-infiltrating immune cells such as tumor-associated macrophages (TAMs) and T cells. This suggests that tumor-associated collagen could have important immune modulatory functions within the tumor microenvironment, affecting cancer progression as well as the efficacy of cancer immunotherapy. The effects of tumor-associated collagen on immune cells could help explain why a high collagen density in tumors is often correlated with a poor prognosis. Knowledge about immune modulatory functions of collagen could potentially identify targets for improving current cancer therapies or for development of new treatments. In this review, the current knowledge about the ability of collagen to influence T cell activity will be summarized. This includes direct interactions with T cells as well as induction of immune suppressive activity in other immune cells such as macrophages. Additionally, the potential effects of collagen on the efficacy of cancer immunotherapy will be discussed.

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.

Activity-dependent interdomain dynamics of matrix metalloprotease-1 on fibrin

The roles of protein conformational dynamics and allostery in function are well-known. However, the roles that interdomain dynamics have in function are not entirely understood. We used matrix metalloprotease-1 (MMP1) as a model system to study the relationship between interdomain dynamics and activity because MMP1 has diverse substrates. Here we focus on fibrin, the primary component of a blood clot. Water-soluble fibrinogen, following cleavage by thrombin, self-polymerize to form water-insoluble fibrin. We studied the interdomain dynamics of MMP1 on fibrin without crosslinks using single-molecule Forster Resonance Energy Transfer (smFRET). We observed that the distance between the catalytic and hemopexin domains of MMP1 increases or decreases as the MMP1 activity increases or decreases, respectively. We modulated the activity using (1) an active site mutant (E219Q) of MMP1, (2) MMP9, another member of the MMP family that increases the activity of MMP1, and (3) tetracycline, an inhibitor of MMP1. We fitted the histograms of smFRET values to a sum of two Gaussians and the autocorrelations to an exponential and power law. We modeled the dynamics as a two-state Poisson process and calculated the kinetic rates from the histograms and autocorrelations. Activity-dependent interdomain dynamics may enable allosteric control of the MMP1 function.

Enhanced efficiency in isolation and expansion of hAMSCs via dual enzyme digestion and micro-carrier

A two-stage method of obtaining viable human amniotic stem cells (hAMSCs) in large-scale is described. First, human amniotic stem cells are isolated via dual enzyme (collagenase II and DNAase I) digestion. Next, relying on a culture of the cells from porous chitosan-based microspheres in vitro, high purity hAMSCs are obtained in large-scale. Dual enzymatic (collagenase II and DNase I) digestion provides a primary cell culture and first subculture with a lower contamination rate, higher purity and a larger number of isolated cells. The obtained hAMSCs were seeded onto chitosan microspheres (CM), gelatin-chitosan microspheres (GCM) and collagen-chitosan microspheres (CCM) to produce large numbers of hAMSCs for clinical trials. Growth activity measurement and differentiation essays of hAMSCs were realized. Within 2 weeks of culturing, GCMs achieved over 1.28 ± 0.06 × 107 hAMSCs whereas CCMs and CMs achieved 7.86 ± 0.11 × 106 and 1.98 ± 0.86 × 106 respectively within this time. In conclusion, hAMSCs showed excellent attachment and viability on GCM-chitosan microspheres, matching the hAMSCs' normal culture medium. Therefore, dual enzyme (collagenase II and DNAase I) digestion may be a more useful isolation process and culture of hAMSCs on porous GCM in vitro as an ideal environment for the large-scale expansion of highly functional hAMSCs for eventual use in stem cell-based therapy.

Five-decade-delayed closed flexor tendon rupture due to Galeazzi dislocation fracture associated with Behçet syndrome: A case report

INTRODUCTION

Closed flexor tendon rupture after a malunited distal radius fracture is rare and usually becomes apparent early after the fracture. Most cases are accompanied by a severe distal radio-ulnar joint capsule injury, wherein bone protrusion (as a spur) directly stresses the tendons. We experienced a nonspecific flexor tendon rupture associated with an old fracture and the presence of collagen disease.

PRESENTATION OF CASE

A 63-year-old woman presented with delayed complete rupture of the flexor digitorum profundus (FDP) of the fifth digit. Her history included closed fracture on the left wrist at age 13 years. At 27 years, she was diagnosed with Behçet syndrome and commenced oral prednisolone 10 mg/day. At the current admission, physical examination revealed that she was incapable of fifth finger flexion after minor passive extension. The fifth digit FDP rupture appeared to be due to damage at the wrist-level fracture site. A tiny capsule rupture was seen on the volar side of the distal radio-ulnar joint. We resected ulnar head osteophytes protruding from the capsule hole and transferred tendon from the fifth FDP to the fourth FDP.

CONCLUSION

Reportedly, metalloproteases weaken tendon structure by acting as a collagenase in patients with Behçet syndrome. Also, vasculitis next to a tendon and steroid intake are considered to impede the tendon repair process. Hence, even minor trauma may lead to complete tendon rupture. Although an injury seems slight, we should take into account the possible history of bone and joint trauma.

Mechanism of drug-induced gingival overgrowth revisited: a unifying hypothesis

Drug-induced gingival overgrowth (DIGO) is a disfiguring side effect of anti-convulsants, calcineurin inhibitors, and calcium channel blocking agents. A unifying hypothesis has been constructed which begins with cation flux inhibition induced by all three of these drug categories. Decreased cation influx of folic acid active transport within gingival fibroblasts leads to decreased cellular folate uptake, which in turn leads to changes in matrix metalloproteinases metabolism and the failure to activate collagenase. Decreased availability of activated collagenase results in decreased degradation of accumulated connective tissue which presents as DIGO. Studies supporting this hypothesis are discussed.

Gelatinase B/MMP-9 in Tumour Pathogenesis and Progression

Since its original identification as a leukocyte gelatinase/type V collagenase and tumour type IV collagenase, gelatinase B/matrix metalloproteinase (MMP)-9 is now recognised as playing a central role in many aspects of tumour progression. In this review, we relate current concepts concerning the many ways in which gelatinase B/MMP-9 influences tumour biology. Following a brief outline of the gelatinase B/MMP-9 gene and protein, we analyse the role(s) of gelatinase B/MMP-9 in different phases of the tumorigenic process, and compare the importance of gelatinase B/MMP-9 source in the carcinogenic process. What becomes apparent is the importance of inflammatory cell-derived gelatinase B/MMP-9 in tumour promotion, early progression and triggering of the "angiogenic switch", the integral relationship between inflammatory, stromal and tumour components with respect to gelatinase B/MMP-9 production and activation, and the fundamental role for gelatinase B/MMP-9 in the formation and maintenance of tumour stem cell and metastatic niches. It is also apparent that gelatinase B/MMP-9 plays important tumour suppressing functions, producing endogenous angiogenesis inhibitors, promoting inflammatory anti-tumour activity, and inducing apoptosis. The fundamental roles of gelatinase B/MMP-9 in cancer biology underpins the need for specific therapeutic inhibitors of gelatinase B/MMP-9 function, the use of which must take into account and substitute for tumour-suppressing gelatinase B/MMP-9 activity and also limit inhibition of physiological gelatinase B/MMP-9 function.

SLIT3 is increased in supracervical human foetal membranes and in labouring myometrium and regulates pro-inflammatory mediators

PROBLEM

Inflammation is associated with preterm birth, a worldwide healthcare issue. SLIT3 has a role in inflammation, and thus, the purpose of this study was to determine the effect of SLIT3 on labour mediators in human gestational tissues.

METHOD OF STUDY

SLIT3 protein expression was performed using immunohistochemistry in foetal membranes and myometrium with no labour and after labour. Foetal membranes were also obtained from a distal site (DS) and supracervical site (overlying the cervix; SCS). SLIT3 gene silencing was achieved using siRNA in primary amnion and myometrial cells. Pro-inflammatory and pro-labour mediators were evaluated by qRT-PCR, ELISA and gelatin zymography.

RESULTS

SLIT3 expression was greater in foetal membranes from the SCS compared with DS and in myometrium after term spontaneous labour onset. SLIT3 siRNA in primary amnion and myometrial cells decreased IL-1β-induced pro-inflammatory cytokine gene expression and release (IL-6 and IL-8) and MMP-9 gene expression and release. In amnion cells, SLIT3 siRNA knockdown decreased IL-1β-induced COX-2 expression and prostaglandin PGE2 release. There was no effect of SLIT3 siRNA on IL-1β-induced NF-κB transcriptional activity.

CONCLUSION

Our results demonstrate that SLIT3 is increased with labour, and both our amnion and our myometrial studies describe a pro-inflammatory effect of SLIT3 in these tissues.

Proteomic Identification of Matrix Metalloproteinase Substrates in the Human Vasculature

Background—

Matrix metalloproteinases (MMPs) play a key role in cardiovascular disease, in particular aneurysm formation and plaque rupture. Surprisingly, little is known about MMP substrates in the vasculature.

Methods and Results—

We used a proteomics approach to identify vascular substrates for 3 MMPs, 1 of each of the 3 major classes of MMPs: Human arteries were incubated with MMP-3 (a member of stromelysins), MMP-9 (considered a gelatinase), and MMP-14 (considered a member of the collagenases and of the membrane-bound MMPs). Candidate substrates were identified by mass spectrometry based on increased release from the arterial tissue on digestion, spectral evidence for proteolytic degradation after gel separation, and identification of nontryptic cleavage sites. Using this approach, novel candidates were identified, including extracellular matrix proteins associated with the basement membrane, elastic fibers (emilin-1), and other extracellular proteins (periostin, tenascin-X). Seventy-four nontryptic cleavage sites were detected, many of which were shared among different MMPs. The proteomics findings were validated by immunoblotting and by digesting recombinant/purified proteins with exogenous MMPs. As proof-of-principle, results were related to in vivo pathology by searching for corresponding degradation products in human aortic tissue with different levels of endogenous MMP-9.

Conclusions—

The application of proteomics to identify MMP targets is a new frontier in cardiovascular research. Our current classification of MMPs based on few substrates is an oversimplification of a complex area of biology. This study provides a more comprehensive assessment of potential MMP substrates in the vasculature and represents a valuable resource for future investigations.

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.

Site specific cleavage mediated by MMPs regulates function of agrin

BACKGROUND

Agrin is the key inducer of postsynaptic differentiations at the neuromuscular junction. The multidomain heparan sulfate proteoglycan is mediating via its N-terminal segment the interaction with laminin, whereas the C-terminal portion is responsible for Dystroglycan binding and clustering of the Acetylcholine receptor. Matrix metalloproteinases (MMP) are known to play essential roles in matrix remodeling, degradation and regulation of extracellular signaling networks.

PRINCIPAL FINDINGS

Site-specific processing of Agrin provides key insight into regulatory effects of Matrix metalloproteinases (MMPs). Here, we present a detailed study of agrin processing by different MMPs together with a molecular understanding of binding and cleavage at both terminal fragments. The data suggest for a regulatory effect of MMP cleavage at particularly important functional sites of agrin. Cleave of agrin abolishes the agrin-laminin complex formation and the Acetylcholine receptor clustering at the neuromuscular junction.

CONCLUSION/SIGNIFICANCE

Agrin is a target of specific MMP processing resulting in agrin subfragments with different regulatory activities. MMP processing is a powerful tool to regulate extracellular signaling networks.

Updated biological roles for matrix metalloproteinases and new "intracellular" substrates revealed by degradomics

Shotgun proteomics techniques are conceptually unbiased, but data interpretation and follow-up experiments are often constrained by dogma, established beliefs that are accepted without question, that can dilute the power of proteomics and hinder scientific progress. Proteomics and degradomics, the characterization of all proteases, inhibitors, and protease substrates by genomic and proteomic techniques, have exponentially expanded the known substrate repertoire of the matrix metalloproteinases (MMPs), even to include intracellular proteins with newly recognized extracellular functions. Thus, the dogma that MMPs are dowdy degraders of extracellular matrix has been resolutely overturned, and the metamorphosis of MMPs into modulators of multiple signaling pathways has been facilitated. Here we review progress made in the field of degradomics and present a current view of the MMP degradome.

Distribution of collagenase and cell types in sterile ulceration of human corneal grafts

Extensive clinical and experimental evidence has suggested a role for corneal epithelium, keratocytes, and acute inflammatory cells in sterile corneal ulceration, although the precise role of these cell types in stromal matrix degradation has not been elucidated. We studied two corneal buttons and two whole corneas from 4 patients with corneal grafts and sterile stromal ulceration. Each cornea was divided into several sections and examined morphologically, while adjacent sections were placed in tissue culture and assayed for collagenase activity against type I collagen. In each case, collagenase activity was present in tissue from ulcerating and nonulcerating areas and, in most regions assayed, exceeded collagenase activity in normal control peripheral donor corneas. Collagenase levels were not always greatest in areas of most advanced ulceration. Although polymorphonuclear leukocytes were extensively present histologically in two cases, one case had a mixed inflammatory cell population at the site of ulceration, and another had only keratocytes (fibroblasts) present in the entire cornea. We conclude that regional differences in collagen degradation are due not only to the presence of collagenase, but also to cellular and humoral activators and inhibitors that determine collagenolytic activity.

MMP-12 catalytic domain recognizes triple helical peptide models of collagen V with exosites and high activity

Matrix metalloproteinase (MMP)-12 (or metalloelastase) efficiently hydrolyzed the gelatinase-selective alpha1(V)436-447 fluorescent triple helical peptide (THP) when the substrate was submicromolar. The sequence of this THP was derived from collagen V, a component of collagen I fibrils. The hemopexin domains of MMP-12 and -9 each increased k(cat)/K(m) toward this substrate by decreasing K(m), just as the hemopexin domain of MMP-1 enhances its triple helical peptidase activity. Non-fluorescent alpha1(V) THP subtly perturbed amide NMR chemical shifts of MMP-12 not only in the active site cleft but also at remote sites of the beta-sheet and adjoining loops. The alpha1(V) THP protected MMP-12 from the NMR line broadening effects of Gd .EDTA in the active site cleft and more dramatically in the V-B loop next to the primed subsites. Mutagenesis of the exosite in the V-B loop at Thr-205 and His-206 that vary among MMP sequences established that this site supports the high specific activity toward alpha1(V) fluorescent THP without affecting general MMP activity. Surprisingly the alpha1(V) THP also protected novel surfaces in the S-shaped metal-binding loop and beta-strands III and V that together form a pocket on the remote side of the zinc binding site. The patterns of protection suggest bending of the triple helical peptide partly around the catalytic domain to reach novel exosites. Partial unwinding or underwinding of the triple helix could accompany this to facilitate its hydrolysis.

Extracellular collagenases and the endocytic receptor, urokinase plasminogen activator receptor-associated protein/Endo180, cooperate in fibroblast-mediated collagen degradation

The collagens of the extracellular matrix are the most abundant structural proteins in the mammalian body. In tissue remodeling and in the invasive growth of malignant tumors, collagens constitute an important barrier, and consequently, the turnover of collagen is a rate-limiting process in these events. A recently discovered turnover route with importance for tumor growth involves intracellular collagen degradation and is governed by the collagen receptor, urokinase plasminogen activator receptor-associated protein (uPARAP or Endo180). The interplay between this mechanism and extracellular collagenolysis is not known. In this report, we demonstrate the existence of a new, composite collagen breakdown pathway. Thus, fibroblast-mediated collagen degradation proceeds preferentially as a sequential mechanism in which extracellular collagenolysis is followed by uPARAP/Endo180-mediated endocytosis of large collagen fragments. First, we show that collagen that has been pre-cleaved by a mammalian collagenase is taken up much more efficiently than intact, native collagen by uPARAP/Endo180-positive cells. Second, we demonstrate that this preference is governed by the acquisition of a gelatin-like structure by the collagen, occurring upon collagenase-mediated cleavage under native conditions. Third, we demonstrate that the growth of uPARAP/Endo180-deficient fibroblasts on a native collagen matrix leads to substantial extracellular accumulation of well defined collagen fragments, whereas, wild-type fibroblasts possess the ability to direct an organized and complete degradation sequence comprising both the initial cleavage, the endocytic uptake, and the intracellular breakdown of collagen.

Activity of matrix metalloproteinase-9 against native collagen types I and III

Interstitial collagen types I, II and III are highly resistant to proteolytic attack, due to their triple helical structure, but can be cleaved by matrix metalloproteinase (MMP) collagenases at a specific site, approximately three-quarters of the length from the N-terminus of each chain. MMP-2 and -9 are closely related at the structural level, but MMP-2, and not MMP-9, has been previously described as a collagenase. This report investigates the ability of purified recombinant human MMP-9 produced in insect cells to degrade native collagen types I and III. Purified MMP-9 was able to cleave the soluble, monomeric forms of native collagen types I and III at 37 degrees C and 25 degrees C, respectively. Activity against collagens I and III was abolished by metalloproteinase inhibitors and was not present in the concentrated crude medium of mock-transfected cells, demonstrating that it was MMP-9-derived. Mutated, collagenase-resistant type I collagen was not digested by MMP-9, indicating that the three-quarters/one-quarter locus was the site of initial attack. Digestion of type III collagen generated a three-quarter fragment, as shown by comparison with MMP-1-mediated cleavage. These data demonstrate that MMP-9, like MMP-2, is able to cleave collagens I and III in their native form and in a manner that is characteristic of the unique collagenolytic activity of MMP collagenases.

Differentiation of secreted and membrane-type matrix metalloproteinase activities based on substitutions and interruptions of triple-helical sequences

The turnover of the collagen triple-helical structure (collagenolysis) is a tightly regulated process in normal physiology and has been ascribed to a small number of proteases. Several members of the matrix metalloproteinase (MMPs) family possess collagenolytic activity, and the mechanisms by which these enzymes process triple helices are beginning to be unraveled. The present study has utilized two triple-helical sequences to compare the cleavage-site specificities of 10 MMPs. One substrate featured a continuous Gly-Xxx-Yyy sequence (Pro-Leu-Gly approximately Met-Arg-Gly), while the other incorporated an interruption in the Gly-Xxx-Yyy repeat (Pro-Val-Asn approximately Phe-Arg-Gly). Both sequences were selectively cleaved by MMP-13 while in linear form, but neither proved to be selective within a triple helix. This suggests that the conformational presentation of substrate sequences to a MMP active site is critical for enzyme specificity, in that activities differ when sequences are presented from an unwound triple helix versus an independent single strand. Differences in specificity between secreted and membrane-type (MT) MMPs were also observed for both sequences, where MMP-2 and MT-MMPs showed an ability to hydrolyze a triple helix at an additional site (Gly-Gln bond). Interruption of the triple helix had different effects on secreted MMPs and MT-MMPs, because MT-MMPs could not hydrolyze the Asn-Phe bond but instead cleaved the triple helix closer to the C terminus at a Gly-Gln bond. It is possible that MT-MMPs have a requirement for Gly in the P1 subsite to be able to efficiently process a triple-helical molecule. Analysis of individual kinetic parameters and activation energies indicated different substrate preferences within secreted MMPs, because MMP-13 preferred the interrupted sequence, while MMP-8 showed little discrimination between non-interrupted and interrupted triple helices. On the basis of the present and prior studies, we can assign unique triple-helical peptidase behaviors to the collagenolytic MMPs. Such differences may be significant for understanding MMP mechanisms of action and aid in the development of selective MMP inhibitors.

The Roles of Substrate Thermal Stability and P2 and P1′ Subsite Identity on Matrix Metalloproteinase Triple-helical Peptidase Activity and Collagen Specificity

The hydrolysis of collagen (collagenolysis) is one of the committed steps in extracellular matrix turnover. Within the matrix metalloproteinase (MMP) family distinct preferences for collagen types are seen. The substrate determinants that may guide these specificities are unknown. In this study, we have utilized 12 triple-helical substrates in combination with 10 MMPs to better define the contributions of substrate sequence and thermal stability toward triple helicase activity and collagen specificity. In general, MMP-13 was found to be distinct from MMP-8 and MT1-MMP(Delta279-523), in that enhanced substrate thermal stability has only a modest effect on activity, regardless of sequence. This result correlates to the unique collagen specificity of MMP-13 compared with MMP-8 and MT1-MMP, in that MMP-13 hydrolyzes type II collagen efficiently, whereas MMP-8 and MT1-MMP are similar in their preference for type I collagen. In turn, MMP-1 was the least efficient of the collagenolytic MMPs at processing increasingly thermal stable triple helices and thus favors type III collagen, which has a relatively flexible cleavage site. Gelatinases (MMP-2 and MMP-9(Delta444-707)) appear incapable of processing more stable helices and are thus mechanistically distinct from collagenolytic MMPs. The collagen specificity of MMPs appears to be based on a combination of substrate sequence and thermal stability. Analysis of the hydrolysis of triple-helical peptides by an MMP mutant indicated that Tyr(210) functions in triple helix binding and hydrolysis, but not in processing triple helices of increasing thermal stabilities. Further exploration of MMP active sites and exosites, in combination with substrate conformation, may prove valuable for additional dissection of collagenolysis and yield information useful in the design of more selective MMP inhibitors.

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.

Protease analysis by neoepitope approach reveals the activation of MMP-9 is achieved proteolytically in a test tissue cartilage model involved in bone formation

A principle of regulation of matrix metalloproteinase (MMP) activity has been introduced as the cysteine-switch mechanism of activation (Springman et al. 1990). According to this mechanism, a critical Cys residue found in the auto-inhibitory propeptide domain of latent proenzyme is important to determine whether or not activation is turned on or off. The mechanism further allows for multiple modes of activation. To determine whether or not activation is accomplished proteolytically within a rat test cartilage model, protease analysis by the neoepitope approach, which relies upon a set of antibodies, was applied. One is used to identify the MMP-9 proenzyme bearing the critical cysteine residue, the other to identify any enzyme present bearing a new NH2-terminus 89FQTFD. This is indicative of MMP-9 lacking the cysteine switch. The antibody set has been applied to frozen tissue sections and analyzed by light and electron microscopic methods. Results reveal that activation of the MMP-9 protease involves limited proteolysis resulting in propeptide domain release. Here we report the observed changes of protease form to indigenous cells and extracellular matrix, thereby making it possible to uncover the features of MMP-9 activation within a specified set of tissue circumstances where a cartilage model is transformed into definitive bone. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials.

Inhibition of endogenous nitric oxide in the heart enhances matrix metalloproteinase-2 release

Matrix metalloproteinase (MMP) activity is upregulated in pathologies such as atherosclerosis during which endogenous nitric oxide (NO) biosynthesis is reduced. Diminished levels of NO, an antioxidant species, may result in higher oxidative stress. Oxidants are capable of activating MMPs from their zymogen forms. We examined whether basal biosynthesis of NO in the coronary circulation regulates MMP-2 activity. In isolated rat hearts perfused with Krebs-Henseleit buffer at a constant flow of 10 ml min(-1), we measured the release of MMP-2 into the coronary effluent by gelatin zymography. The main gelatinolytic activity of 72-kDa corresponds to MMP-2. Infusion of the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) concentration dependently increased coronary perfusion pressure (CPP) (by 48+/-11 mmHg with 100 microM) and enhanced the release of the 72-kDa MMP-2 in the effluent. Coinfusion of the NO donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP, 1 microM) with L-NAME abolished both the increase in CPP and the enhanced MMP-2 release. The thromboxane A2 mimetic U46619 increased CPP to the same extent as L-NAME without increasing 72-kDa activity in the effluent, suggesting that MMP-2 release is not caused simply by enhanced perfusion pressure. Infusion of either L-NAME or U46619 did not significantly enhance LDH release. L-NAME infusion concentration dependently increased the level of lipid hydroperoxides in homogenates prepared from the perfused hearts. Coinfusion of SNAP prevented this increase. These data reveal another cytoprotective mechanism of endogenous NO biosynthesis in the heart, the inhibition of MMP-2 release.

Induced sputum matrix metalloproteinase-9 correlates with lung function and airway inflammation in children with cystic fibrosis

Matrix metalloproteinases (MMPs) degrade extracellular matrix and are implicated in causing airway damage in chronic inflammatory lung diseases, including cystic fibrosis (CF). Our primary objective was to examine the relationship between matrix metalloproteinase-9 (MMP-9) and pulmonary function, as measured by forced expiratory volume in 1 sec (FEV1), in children with CF. We measured MMP-9 and its natural tissue inhibitor of metalloproteinase-1 (TIMP-1) in induced sputum from 18 clinically stable CF children with normal to mildly abnormal lung function and 7 healthy control children. Measures of airway inflammation from induced sputum included cell counts and differentials, interleukin-8 (IL-8), neutrophil elastase, MMP-9, and TIMP-1. Infection was assessed through quantitative bacterial counts. Induced sputum levels of MMP-9 and TIMP-1 were significantly increased in children with CF compared with healthy controls. Also, the MMP-9/TIMP-1 molar ratio was higher in the CF group. Among CF children, there was a significant inverse relationship between MMP-9 and FEV1. In addition, sputum MMP-9 and TIMP-1 concentrations significantly correlated with total white cells and neutrophils, IL-8, and neutrophil elastase. Neither MMP-9 nor TIMP-1 correlated with airway infection. We conclude that clinically stable CF children with normal to mildly abnormal lung function have an increased burden of MMP-9 in their airways. The observed relationships of MMP-9 with lung function and other measures of airway inflammation suggest that this enzyme may be a useful marker of airway injury and airflow obstruction in persons with CF.

Identifying novel endpoints for cystic fibrosis clinical trials

Clinical and translational research in cystic fibrosis (CF) is hampered by a lack of biomarkers that can be used to identify promising new therapies. In particular, validated protein biomarkers are needed to evaluate emerging candidate anti-inflammatory and antimicrobial treatments. Noninvasively obtained biomarkers are especially desirable in children where repeatedly sampling the airway is difficult. To more quickly identify and validate candidate protein biomarkers, it will be essential to pursue a phased approach to biomarker development in a large, well-characterized CF patient population. New high-throughput technologies that can simultaneously examine the expression of thousands of genes and proteins are accelerating the discovery of potential biomarkers. It is hoped that individual biomarkers, or more likely a panel of validated markers, will predict clinical outcomes such as susceptibility to rapid disease progression or response to treatment and therefore, greatly improve stratification for future CF clinical trials.

Unstable Carotid Plaques Exhibit Raised Matrix Metalloproteinase-8 Activity

BACKGROUND

The fibrous cap of atherosclerotic plaques is composed predominantly of type I and III collagen. Unstable carotid plaques are characterized by rupture of their cap, leading to thromboembolism and stroke. The proteolytic mechanisms causing plaque disruption are undefined, but the collagenolytic matrix metalloproteinase (MMP) -1, -8, and -13 may be implicated. The aim of this study was to quantify the concentrations of these collagenases in carotid plaques and to determine their relationship to markers of plaque instability.

METHODS AND RESULTS

Atherosclerotic plaques were collected from 159 patients undergoing carotid endarterectomy. The presence and timing of carotid territory symptoms were ascertained. Preoperative embolization was recorded by transcranial Doppler. Each plaque was assessed for histological features of instability. Plaque MMP concentrations were quantified with ELISA. Significantly higher concentrations of active MMP-8 were observed in the plaques of symptomatic patients (20.5 versus 11.4 ng/g; P=0.0002), in plaques of emboli-positive patients (22.7 versus 13.5 ng/g; P=0.0037), and in those plaques showing histological evidence of rupture (20.8 versus 14.7 ng/g; P=0.0036). No differences were seen in the levels of MMP-1 and MMP-13. Immunohistochemistry, in situ hybridization, and colocalization studies confirmed the presence of MMP-8 protein and mRNA within the plaque, which colocalized with macrophages.

CONCLUSIONS

These data suggest that the active form of MMP-8 may be partly responsible for degradation of the collagen cap of atherosclerotic plaques. This enzyme represents an attractive target for drug therapy aimed at stabilizing vulnerable plaques.

The role of matrix metalloproteinase 9 in the pathogenesis of chronic lymphocytic leukaemia

Matrix metalloproteinases (MMPs) are important for the pathogenesis and progression of different tumours. MMPs-2 and -9 are the principal MMPs produced by lymphocytes; these enzymes can degrade a number of matrix proteins but are the two main MMPs that digest type IV collagen, the major component of basement membranes. Therefore, these enzymes are potentially important for tissue invasion and remodelling by malignant lymphocytes. This study showed that chronic lymphocytic leukaemia (CLL) cells produce and secrete variable amounts of pro-MMP-9, but no MMP-2 or tissue inhibitor of metalloproteinase 1 (TIMP-1). The pro-enzyme was found in monomeric and dimeric forms and also complexed with lipocalin. Moreover, a small fraction of secreted monomer became associated with the cell surface and activated upon cell adhesion to insolubilized type IV collagen. High levels of intracellular MMP-9 were associated with advanced (stage C) disease and with poor patient survival. Immunohistochemical studies demonstrated that MMP-9 was associated with areas of tissue invasion and remodelling. The relatively specific MMP-9 inhibitors, Ro31-9790 (3 micromol/l) and TIMP-1, reduced CLL-cell migration through type IV collagen and through endothelial monolayers suggesting that the enzyme may also be important in malignant cell entry and egress to and from involved tissue. Our data raise the possibility that MMP-9 modulation may have therapeutic potential in advanced CLL.

Role of collagen type II and perlecan in skeletal development

The cartilage extracellular matrix is composed of a dense collagen network that entraps a range of other specialized proteins important for the proper formation and function of the tissue. Loss of two abundant cartilage components, type II collagen and perlecan, has drastic effects on skeletal development. Both collagen II and perlecan mutants have severe and lethal chondrodysplasia characterized by disorganized growth plate, lack of collagen network, defective endochondral bone formation, and abnormal intervertebral disk development. To test whether the reduced collagen density in the perlecan-null cartilage is due to enhanced activity of collagen-degrading proteinases, we have analyzed gelatinase expression and activity in the mutant tissue. Immunohistochemical analysis revealed a weak, but clear, expansion of MMP-9 deposition into the hypertrophic zone of the perlecan-null growth plate. However, in situ and SDS-PAGE zymography showed that the activity of gelatinases (MMP-2 and MMP-9) is not altered in perlecan-null cartilage, suggesting that they are not primarily linked to the reduced fibrillar network observed in the mutant. Likewise, intercrossing of perlecan mutants onto an MMP-9-null background could not rescue the ultrastructural abnormalities of the perlecan-deficient cartilage.

The role of phospholipases A2 in the stimulation of neutrophil motility by cobra venoms

Neutrophil (PMN) accumulation frequently occurs at the site of snakebite as part of the inflammatory response to envenoming. We demonstrate here that the venoms of the cobras, Naja naja and N. mossambica, and two purified venom phospholipase A(2)s (PLA(2)s) isolated from the latter venom, stimulate CD11b translocation from the PMN granule store to the plasma membrane and enhance neutrophil motility on collagen-coated surfaces. These effects were partially attenuated by the PLA(2) inhibitor, aristolochic acid, and almost completely abolished by the specific cytosolic PLA(2) inhibitor, methylarachidonylfluorophosphonate (MAFP). Annexin V and inhibitors of collagenase, cyclo-oxygenase and lipo-oxygenase, all inhibited PMN motility to a variable extent. FACS analysis and confocal microscopy showed that Annexin V interfered with binding and rapid endocytosis of the venom PLA(2). These results indicate that venom and venom PLA(2) preparations first caused a non-enzymatic stimulation of PMN leading to the activation of cytosolic PMN PLA(2) and production of arachidonate metabolites involved in stimulation of PMN degranulation and motility. The evidence suggests that venom PLA(2) then interacts with anionic phospholipids exposed on stimulated PMN, becomes endocytosed, and then contributes itself to the production of chemoattractants responsible for PMN accumulation at the site of the snakebite.

Vascular tissue fragility assessed by a new double stain method

Although matrix metalloproteinases (MMPs) are known to be involved in the development of atherosclerosis and the instability of atheromatous plaques, much remains to be learned about their roles at the tissue level. To help clarify this area, we established a new double staining method using film in situ zymography and immunohistochemistry. Using this technique, a comprehensive analysis of the gelatinolytic activity in human vessel tissue demonstrated that gelatinolytic activity is enhanced in the shoulder region and fibrous cap at superficial areas of the atheromatous plaque in the presence of thrombolysis. Enzyme assay clarified high activity in the superficial area (7.50 +/- 5.04 U/mg weight; P < 0.001). Gelatin zymography also indicated that addition of the antiplatelet agent, trapidil, alters the amount of secretion of MMP-2 and MMP-9 and their activation ratio. This novel approach to detect the activity of gelatinases in resected tissues may aid in the selection of optimal treatment of individual patients.

The role of matrix metalloproteinases in rheumatoid tendon disease

In rheumatoid arthritis (RA) invasive tenosynovitis is associated with an increase in tendon rupture, although little is known about the mechanisms involved. We obtained specimens of noninvasive encapsulating tenosynovium, invasive tenosynovium, and wrist joint synovium from 28 rheumatoid patients. In vitro production of the matrix metalloproteinase (MMP) enzymes, MMP-8 and -9, and total collagenase activity were measured. Invasive tenosynovium produced highest levels of the collagenase MMP-8 and displayed significantly greater ability to degrade collagen type I than encapsulating tenosynovium. Levels of the gelatinase enzyme MMP-9 were similar in all groups. These results show that invasive tenosynovium is more destructive than encapsulating tenosynovium at a molecular level, providing an explanation for the increased tendon rupture associated with invasive tenosynovitis in RA.

Recruitment of stem and progenitor cells from the bone marrow niche requires MMP-9 mediated release of kit-ligand

Stem cells within the bone marrow (BM) exist in a quiescent state or are instructed to differentiate and mobilize to circulation following specific signals. Matrix metalloproteinase-9 (MMP-9), induced in BM cells, releases soluble Kit-ligand (sKitL), permitting the transfer of endothelial and hematopoietic stem cells (HSCs) from the quiescent to proliferative niche. BM ablation induces SDF-1, which upregulates MMP-9 expression, and causes shedding of sKitL and recruitment of c-Kit+ stem/progenitors. In MMP-9-/- mice, release of sKitL and HSC motility are impaired, resulting in failure of hematopoietic recovery and increased mortality, while exogenous sKitL restores hematopoiesis and survival after BM ablation. Release of sKitL by MMP-9 enables BM repopulating cells to translocate to a permissive vascular niche favoring differentiation and reconstitution of the stem/progenitor cell pool.

Differential regulation of collagen degradation by rabbit keratocytes and polymorphonuclear leukocytes

PURPOSE

Both activated keratocytes and infiltrated polymorphonuclear leukocytes (PMNs) contribute to corneal ulceration by degrading stromal collagen. The regulation of such collagen degradation by inflammatory cytokines was investigated with rabbit keratocytes and PMNs cultured in three-dimensional collagen gels.

METHODS

Rabbit keratocytes or PMNs were cultured for 24 h in three-dimensional gels of type I collagen in the presence of plasminogen and various concentrations of either interleukin (IL)-1alpha, IL-6, IL-8, or tumor necrosis factor-alpha (TNF-alpha). Degradation of collagen during culture was assessed by measurement of released hydroxyproline.

RESULTS

IL-1alpha increased the amount of collagen degraded by keratocytes or PMNs in a dose-dependent manner, whereas IL-6 had no effect on collagen degradation by either cell type. IL-8 increased the extent of collagen degradation by PMNs but not that by keratocytes, and TNF-alpha promoted collagen degradation by keratocytes but not that by PMNs.

CONCLUSION

Inflammatory cytokines regulate collagen degradation by rabbit keratocytes and PMNs in culture in a differential manner, and therefore may contribute to the roles of these cells in corneal ulceration.

Matrix metalloproteinase-9 promotes neutrophil migration and alveolar capillary leakage in pancreatitis-associated lung injury in the rat

BACKGROUND & AIMS

In pancreatitis-associated lung injury, neutrophils (PMN) access the lung by migration through endothelial basement membranes. We hypothesize that degeneration of the basement membrane by specific PMN-produced matrix metalloproteinases (MMPs) may facilitate this process.

METHODS

Mild or severe pancreatitis was induced in rats and the consequent pulmonary injury characterized. MMP-2 and MMP-9 activity in supernatant of PMN cultures and homogenates of lungs were assessed by zymography and Western blot. Congruence of PMN and MMP expression in lung tissue was evaluated by neutrophil depletion and fluorescent immunohistochemistry (IHC). The contribution of MMPs to PMN transmigration and lung injury was tested with the MMP inhibitor batimastat (BB-94) in vitro (PMN transmigration across matrigel chambers) and in vivo (myeloperoxidase activity and Evans blue in broncho-alveolar lavage fluid).

RESULTS

MMP-9 was highly expressed in lungs and supernatant of neutrophil cultures in severe pancreatitis, and, to a lesser degree, in mild pancreatitis. Lung IHC showed colocalization of MMP-9 and PMN. PMN depletion simultaneously reduced neutrophil infiltration and MMP-9 levels in lung tissue. Trypsin, interleukin 1 beta, and tumor necrosis factor (TNF)-alpha all potently stimulated MMP-9 release from PMN. BB-94 significantly reduced TNF-alpha-induced PMN transmigration across matrigel and ameliorated transendothelial PMN migration and protein leak in severe pancreatitis.

CONCLUSIONS

MMP-9 secretion by PMN can be stimulated by trypsin and proinflammatory cytokines and increases in pancreatitis in proportion to its severity. MMP inhibition reduces PMN transmigration and reduces resultant alveolar-capillary leakage. These findings suggest an important role for MMP-9 from PMN in the pathogenesis of pancreatitis-associated lung injury.

Enzymes active in the areas undergoing cartilage resorption during the development of the secondary ossification center in the tibiae of rats aged 0-21 days: II. Two proteinases, gelatinase B and collagenase-3, are implicated in the lysis of collagen fibrils

In the transformation of the cartilaginous epiphysis into bone, the first indication of change in the surfaces destined for resorption is the cleavage of aggrecan core protein by unidentified matrix metalloproteinases (MMPs) (Lee et al., this issue). In cartilage areas undergoing resorption, the cleavage leaves as superficial, 6-microm-thick band of matrix, referred to as "pre-resorptive layer." This layer harbors G1-fragments of the aggrecan core protein within a framework of collagen-rich fibrils exhibiting various stages of degeneration. Investigation of this layer in every resorption area by gelatin histozymography and TIMP-2 histochemistry demonstrates the presence of an MMP whose histozymographic activity is inhibited by such a low dose of the inhibitor CT1746 as to identify it as gelatinase A or B. Attempts at blocking the histozymographic reactions with neutralizing antibodies capable of inhibiting either gelatinase A or B reveals that only those against gelatinase B do so. Immunostaining of sections with anti-gelatinase B IgG confirms the presence of gelatinase B in every pre-resorptive layer, that is, at the blind end of excavated canals (stage I; 6-day-old rats), at sites along the walls of the forming marrow space (stage II; 7days), at sites within the walls of this space as it becomes the ossification center (stage III; 9 days) and along the wall of the maturing center (stage IV; 10-21 days). We also report the presence of collagenase-3 in precisely the same sites, possibly as active enzyme, but this remains to be proven. Because the results reveal that collagenase-3 is present beside gelatinase B in every pre-resorptive layer and, because these sites exhibit various signs of degradation including fibrillar debris, reduction in fibril number, or overt loss, we propose that gelatinase B and collagenase-3 mediate the lysis of this pre-resorptive layer-most likely through a cooperative attack leading to the disintegration of the collagen fibril framework.

Enzymes active in the areas undergoing cartilage resorption during the development of the secondary ossification center in the tibiae of rats ages 0-21 days: I. Two groups of proteinases cleave the core protein of aggrecan

The formation of a secondary ossification center in the cartilaginous epiphysis of long bones requires the excavation of canals and marrow space and, therefore, the resorption of cartilage. On the assumption that its resorption requires the lysis of the major cartilage component aggrecan, it was noted that the core protein may be cleaved in vitro by proteinases from two subfamilies: matrix metalloproteinases (MMPs) and aggrecanases. Such cleavage results in aggrecan being replaced by a fragment of itself referred to as a "G1-fragment." To find out if this cleavage occurs in the developing epiphysis of the rat tibia, the approach has been to localize the G1 fragments. For this purpose two neoepitope antisera were applied, one capable of recognizing the MMP-generated G1-fragment that bears the C-terminus ...FVDIPEN341 and the other capable of recognizing the aggrecanase-generated G1-fragment that carries the C-terminus ...NITEGE373. With the aid of these antisera, we report here that aggrecan cleavage is localized to newly developed sites of erosion. Thus, at 6 days of age, canals allowing the entry of capillaries are dug out from the surface of the epiphysis in a radial direction (stage I), whereas immunostaining indicative of aggrecan cleavage by MMPs appears at the blind end of each canal. The next day, the canal blind ends fuse to create a marrow space in the epiphysis (stage II), whereas immunostaining produced by MMPs occurs along the walls of this space. By 9 days, clusters of hypertrophic chondrocytes are scattered along the marrow space wall to initiate the formation of the secondary ossification center (stage III), where the resorption sites are unreactive to either antiserum. From the 9th to the 21st day, the center keeps on enlarging and, as the distal wall of the marrow space recedes, it is intensely immunostained with both antisera indicating that both MMPs and aggrecanases are involved in this resorption. We conclude, that both enzyme subfamilies contribute to the lysis of aggrecan. However, the results suggest that the respective subfamilies target different sites and even stages of development in the tissue, suggesting some diversity in the mode of aggrecan lysis during the excavation of a secondary ossification center.

Inostamycin, an inhibitor of cytidine 5'-diphosphate 1,2-diacyl-sn-glycerol (CDP-DG): inositol transferase, suppresses invasion ability by reducing productions of matrix metalloproteinase-2 and -9 and cell motility in HSC-4 tongue carcinoma cell line

Inostamycin is an inhibitor of cytidine 5'-diphosphate 1,2-diacyl-sn-glycerol (CDP-DG): inositol transferase. It significantly reduced epidermal growth factor (EGF)-induced in vitro invasion of the tongue carcinoma cell line, HSC-4, through reconstituted basement membrane Matrigel. Since phosphatidylinositol (PI) 4,5-biphosphate is important for signal transduction through protein kinase C and actin reorganisation, we further examined the effect of inostamycin on production of two matrix metalloproteinases (MMPs), MMP-2 and -9, and on cell motility. Zymographic analysis showed that inostamycin suppressed pro-MMP-2 and pro-MMP-9 levels at a dose-dependent fashion, while MMP-2 activity was not significantly affected. By reverse transcription-polymerase chain reaction, it was found that inostamycin diminished steady state levels of MMP-2 and -9 but not membrane type 1-MMP mRNA expressions. Inostamycin partially blocked both EGF- and phorbol 12-myristate 13-acetate-stimulated pro-MMP-9 production. A cytoplasmic calcium chelator (BAPTA-AM) dramatically elevated pro- MMP-9 and slightly elevated pro-MMP-2 secretions. EGF-stimulated motility of HSC-4 cells was suppressed by inostamycin treatment along with reduction of actin cytoskeletal reorganisation, filopodia formation and cdc42 expression. These results suggested that inostamycin would be useful for an anti-invasive agent in tongue cancer.

Biomechanical regulation of matrix metalloproteinase-9 in cultured chondrocytes

Abnormal mechanical loading of joints may induce degeneration of articular cartilage. Shear stress is one mode of mechanical loading that may regulate chondrocyte metabolism. We investigated the mechanism by which shear stress induces the gene encoding matrix metalloproteinase-9, a mediator of the progressive degradation of articular cartilage in osteoarthritis. In vitro experiments using passaged rabbit chondrocytes in monolayer culture subjected to a shear stress of 16 dyn/cm2 (1.6 Pa) in a flow channel showed increased expression of the matrix metalloproteinase-9 gene. The induction of matrix metalloproteinase-9 appeared to depend on a region in the 5' promoter of the gene that contains a 12-0-tetradecanoylphorbol 13-acetate-responsive element. Transfection experiments using a construct containing a luciferase reporter driven by a 12-0-tetradecanoylphorbol 13-acetate-responsive element indicated that shear stress activated a 12-0-tetradecanoylphorbol 13-acetate-responsive element-mediated transcription in chondrocytes. Similar experiments showed that shear stress induced a matrix metalloproteinase-9 promoter construct (matrix metalloproteinase-9-luciferase). Shear stress activated c-Jun NH2-terminal kinase, extracellular signal-regulated kinase, and p38. Transfection of matrix metalloproteinase-9-luciferase together with the dominant negative mutant of c-Jun NH2-terminal kinase, but not with that of extracellular signal-regulated kinase or p38, attenuated the shear-induced matrix metalloproteinase-9 promoter activity. In addition, transfection of constructs encoding dominant negative mutants of Ras, Rac, and Cdc42 attenuated the induction of c-Jun transcriptional activity by shear stress. Thus. shear stimulation of chondrocytes stimulates Ras, Rac, and Cdc42, which subsequently activate c-Jun NH2-terminal kinase to induce a 12-0-tetradecanoylphorbol 13-acetate-responsive element-mediated expression of matrix metalloproteinase-9.

Identification of structural elements important for matrix metalloproteinase type V collagenolytic activity as revealed by chimeric enzymes. Role of fibronectin-like domain and active site of gelatinase B

Digestion of type V collagen by the gelatinases is an important step in tumor cell metastasis because this collagen maintains the integrity of the extracellular matrix that must be breached during this pathological process. However, the structural elements that provide the gelatinases with this unique proteolytic activity among matrix metalloproteinases had not been thoroughly defined. To identify these elements, we examined the substrate specificity of chimeric enzymes containing domains of gelatinase B and fibroblast collagenase. We have found that the addition of the fibronectin-like domain of gelatinase B to fibroblast collagenase is sufficient to endow the enzyme with the ability to cleave type V collagen. In addition, the substitution of the catalytic zinc-binding active site region of fibroblast collagenase with that of gelatinase B increased the catalytic efficiency of the enzyme 3- to 4-fold. This observation led to the identification of amino acid residues, Leu(397), Ala(406), Asp(410), and Pro(415), in this region of gelatinase B that are important for its efficient catalysis as determined by substituting these amino acids with the corresponding residues from fibroblast collagenase. Leu(397) and Ala(406) are important for the general proteolytic activity of the enzyme, whereas Asp(410) and Pro(415) specifically enhance its ability to cleave type V collagen and gelatin, respectively. These data provide fundamental information about the structural elements that distinguish the gelatinases from other matrix metalloproteinases in terms of substrate specificity and catalytic efficiency.

Effects of bisphosphonate on matrix metalloproteinase enzymes in human periodontal ligament cells

BACKGROUND

The host response is a critical component in the pathogenesis of periodontitis. In fact, the clinical benefits associated with regulating the host response have been demonstrated in studies using several different classes of drugs. Biophosphates are one host-modulating class of drugs that has demonstrated this ability. These drugs are clinically effective at reducing bone resorption and have shown the ability to inhibit host degradative enzymes, specifically the matrix metalloproteinases (MMPs). Therefore, the purpose of this study was to investigate the regulatory effects of a bisphosphonate, tiludronate, on MMP levels and activity in human periodontal cells.

METHODS

MMP-1 and MMP-3 were assessed in cultured human periodontal ligament cells treated with a bisphosphonate, tiludronate. Reverse transcription-polymerase chain reaction was used to identify mRNA levels for both enzymes, and also for tissue inhibitors (TIMP-1). Enzyme immunoassay (EIA) and immunocytochemistry were used to assess MMP proteins in these cell cultures. Enzyme activity was assessed using FITC-conjugated substrates and quantitated using spectrophotofluorometry.

RESULTS

Tiludronate significantly inhibited both MMP-1 and MMP-3 activity in a concentration-dependent manner. A maximal reduction in activity of 35% was achieved for each of the enzymes at a 10(-4) M concentration. Tiludronate did not have a significant effect on the mRNA levels for MMP-1, MMP-3, or TIMP-1. Similarly, there were no effects noted for either MMP-1 or MMP-3 on the protein level.

CONCLUSIONS

This study demonstrates an inhibitory effect of tiludronate on the activity of both MMP-1 and MMP-3. These effects appear to occur without altering either mRNA or protein levels for these enzymes, supporting a possible mechanism of action that involves the ability of bisphosphonates to chelate cations from the MMPs. Furthermore, these results support the continued investigation of these drugs as potential therapeutic agents in periodontal disease.

Effect of galardin on collagen degradation by Pseudomonas aeruginosa

The authors examined the effect of a synthetic peptidyl hydroxamate inhibitor of matrix metalloproteinase, Galardin, on collagen degradation by Pseudomonas aeruginosa (P. aeruginosa) in the presence or absence of keratocytes. Type I collagen gels, with or without suspended keratocytes, were incubated under medium containing sterile P. aeruginosa culture broth and/or Galardin for 24 hr. Degradation of collagen fibrils during culture was measured by the release of hydroxyproline. The conditioned media were also subjected to gelatin zymography and Western blotting to analyse the activation, by P. aeruginosa factor(s), of matrix metalloproteinases (MMPs) released by keratocytes. The effects of protease inhibitors, aprotinin, leupeptin and pepstatin, on collagen degradation by P. aeruginosa were also examined. P. aeruginosa broth by itself induced collegen gel degradation. When keratocytes were present, P. aeruginosa broth increased the amount of degraded collagen even further. Galardin significantly reduced the amounts of collagen degraded by P. aeruginosa culture broth, whether keratocytes were present or absent in the gel. However, the protease inhibitors had no inhibitory effects on collagen degradation. Gelatin zymography and Western blotting revealed that inactive proMMP-1, -2 and -3, released by keratocytes, were converted to active forms in the presence of P. aeruginosa broth. Galardin decreased the amounts of active MMPs and increased those of inactive proMMPs, suggesting that Galardin inhibited the activation of proMMPs by P. aeruginosa. The present results suggest that Galardin inhibits the keratocyte-mediated collagen degradation by P. aeruginosa culture broth, resulting from preventing the conversion of proMMPs to active MMPs.

Active gelatinase B is identified by histozymography in the cartilage resorption sites of developing long bones

In order to determine which proteinases mediate the resorption of endochondral cartilage in the course of long bone development, a novel assay called "histozymography" has been developed. In this assay, frozen sections of tibial head from 21-day-old rats are placed for 4 hr at room temperature on light-exposed photographic emulsion (composed of silver grains embedded in gelatin). We report a localized but complete digestion of emulsion gelatin facing two tissue sites which are, therefore, presumed to contain an active proteinase. One of the sites is localized at the growth plate surface forming the epiphysis/metaphysis interface. The other consists of small patches located within the epiphysis at the edge of the marrow space. Both sites are engaged in the resorption of endochondral cartilage. In both sites, inhibitor tests have established that the involved proteinase is a gelatinase. Furthermore, the use of neutralizing antibodies against gelatinase A or B have demonstrated that only those that are specific for the latter block the reaction. That gelatinase B is present in the two sites has been confirmed by light microscopic immunohistochemistry. Finally, when immunoelectron microscopy is used for fine localization of the cartilage structures that form the epiphysis/metaphysis interface, the enzyme is detected within the 0.5-microm thick edge of the cartilage, and outside the cartilage, it is present in debris composed of type II collagen-rich fibrils in various states of digestion. It is concluded that gelatinase B attacks the edge of an endochondral cartilage and helps to solubilize the type II-collagen-rich fibrillar framework, which is then released as debris for further digestion. This final step opens the way to invasion by capillaries, thereby making possible the replacement of cartilage by bone. Dev Dyn 1999;215:190-205.

Platelet-activating factor increases the expression of metalloproteinase-9 in human bronchial epithelial cells

Platelet-activating factor (PAF) plays an important role in the pathogenesis of bronchial asthma. To investigate the role of PAF in the maintenance and remodeling of the extracellular matrix, we evaluated the expression of matrix metalloproteinase-2 and matrix metalloproteinase-9 from human bronchial epithelial cells after PAF treatment. Gelatin zymography of human bronchial epithelial cell-conditioned media showed major pro-matrix metalloproteinase-9 and minor pro-matrix metalloproteinase-2 expression and these expressions were totally inhibited by the metalloproteinase inhibitor EDTA. The identification of matrix metalloproteinase-9 was confirmed by Western blot analysis. Northern blotting and zymography demonstrated that PAF induced the mRNA of matrix metalloproteinase-9 from human bronchial epithelial cells and an increase in the gelatinolytic activity of pro-matrix metalloproteinase-9 but not in that of pro-matrix metalloproteinase-2. Lyso-PAF did not induce matrix metalloproteinase-9 mRNA or the gelatinolytic activity of pro-matrix metalloproteinase-9. CV6209, an receptor antagonist of PAF, reduced the increases of pro-matrix metalloproteinase-9 mRNA and gelatinolytic activity induced by PAF. Another receptor antagonist of PAF, hexanolamine PAF, did not inhibit the increases in the synthesis or release of pro-matrix metalloproteinase induced by PAF. Based on these results, we propose that matrix metalloproteinase-9 may be actively involved in the PAF-induced physiopathological remodeling in human bronchial epithelial cells.

Human neutrophils secrete gelatinase B in vitro and in vivo in response to endotoxin and proinflammatory mediators

Bacterial sepsis is characterized by a systemic inflammatory state, with activation of numerous cell types. Phagocytes participate in this phenomenon by secreting various proinflammatory cytokines and enzymes. Matrix metalloproteinases (MMPs) such as gelatinases are produced by phagocytes and are thought to play an important role in processes of cell transmigration and tissue remodeling. In this work, we show that endotoxin (lipopolysaccharide [LPS]) and other inflammatory mediators, such as tumor necrosis factor (TNF), interleukin-8, and granulocyte colony-stimulating factor, induce a rapid (within 20 min) release of gelatinase-B (MMP-9) zymogen in whole human blood, as determined by gelatin zymography. The polymorphonuclear neutrophil was identified as the cell responsible for this rapid secretion, as a result of the release of preformed enzymes stored in granules. Normal human subjects given LPS intravenously showed a similar pattern of proMMP-9 secretion, with maximum plasma levels reached 1.5 to 3 h after LPS administration (P = 0.0009). Prior administration of TNF receptor:Fc, a potent TNF antagonist, to subjects given LPS, only partially blunted the release of proMMP-9 (P = 0.033). Ibuprofen, a cyclooxygenase inhibitor, did not alter this pattern of release. Increased levels of proMMP-9 and proMMP-2, as well as activated forms of MMP-9, were found in plasma from two patients with gram-negative sepsis. The levels of MMPs paralleled the severity of clinical condition and a marker of the severity of sepsis, plasma procalcitonin. These data indicate that MMPs are released in whole blood in response to various inflammatory mediators and that they could serve as sensitive and early markers for cell activation during the course of bacterial sepsis.