Regulation of the autoactivation of human 72-kDa progelatinase by tissue inhibitor of metalloproteinases-2

Tissue Inhibitor of Matrix Metalloproteinases-1 (TIMP-1) and Pulmonary Involvement in COVID-19 Pneumonia

Background: The aim of the study was to longitudinally evaluate the association between MMP-2, MMP-9, TIMP-1 and chest radiological findings in COVID-19 patients. Methods: COVID-19 patients were evaluated based on their hospital admission (baseline) and three months after hospital discharge (T post) and were stratified into ARDS and non-ARDS groups. As a control group, healthy donors (HD) were enrolled. Results: At the baseline, compared to HD (n = 53), COVID-19 patients (n = 129) showed higher plasma levels of MMP-9 (p < 0.0001) and TIMP-1 (p < 0.0001) and the higher plasma activity of MMP-2 (p < 0.0001) and MMP-9 (p < 0.0001). In the ARDS group, higher plasma levels of MMP-9 (p = 0.0339) and TIMP-1 (p = 0.0044) and the plasma activity of MMP-2 (p = 0.0258) and MMP-9 (p = 0.0021) compared to non-ARDS was observed. A positive correlation between the plasma levels of TIMP-1 and chest computed tomography (CT) score (ρ = 0.2302, p = 0.0160) was observed. At the T post, a reduction in plasma levels of TIMP-1 (p < 0.0001), whereas an increase in the plasma levels of MMP-9 was observed (p = 0.0088). Conclusions: The positive correlation between TIMP-1 with chest CT scores highlights its potential use as a marker of fibrotic burden. At T post, the increase in plasma levels of MMP-9 and the reduction in plasma levels of TIMP-1 suggested that inflammation and fibrosis resolution were still ongoing.

Functional expression and purification of the untagged C-terminal domain of MMP-2 from Escherichia coli inclusion bodies

The C-terminal domain (CTD) of MMP-2, which includes a hemopexin-like domain, has been increasingly studied as an alternative target in developing selective intervention strategies towards MMP-2. Moreover, The CTD itself has been implicated in a growing number of biological events, either MMP-dependent or -independent. The production of CTD, however, has been mostly based on the uncontrolled lysis of the latent ProMMP-2 or fusion protein expression that leaves a fusion tag. In this work we present a facile production of the untagged CTD in E. coli. The target protein was expressed as inclusion bodies, and we established an efficient wash and refolding strategy that allows us to obtain the target protein in extremely high purity. The yield was established at ~6 mg/L of the culture medium, which would greatly facilitate the production and hence the biological study of CTD. The method described herein might also prove useful for related (domain) proteins in MMP family and beyond.

Engineered Peptide Macrocycles Can Inhibit Matrix Metalloproteinases with High Selectivity

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases at the intersection of health and disease due to their involvement in processes such as tissue repair and immunity as well as cancer and inflammation. Because of the high structural conservation in the catalytic domains and shallow substrate binding sites, selective, small-molecule inhibitors of MMPs have remained elusive. In a tour-de-force peptide engineering approach combining phage-display selections, rational design of enhanced zinc chelation, and d-amino acid screening, we succeeded in developing a first synthetic MMP-2 inhibitor that combines high potency (K_i =1.9±0.5 nm), high target selectivity, and proteolytic stability, and thus fulfills all the required qualities for in cell culture and in vivo application. Our work suggests that selective MMP inhibition is achievable with peptide macrocycles and paves the way for developing specific inhibitors for application as chemical probes and potentially therapeutics.

Influence of phase I periodontal therapy on levels of matrix metalloproteinase 1 and tissue inhibitor of metalloproteinase 1

BACKGROUND

Matrix metalloproteinase-1 (MMP-1) is a member of a family of enzymes that can degrade most extracellular matrix macromolecules. Extracellularly, MMPs are controlled by tissue inhibitors of metalloproteinases (TIMPs) and by mechanisms of pro-MMP activation. Levels of MMPs and TIMPs change during healing, inflammation, and normal tissue turnover. Herein we aimed to evaluate the levels of MMP-1 and TIMP-1 in gingival crevicular fluid (GCF) from periodontally healthy patients (control group) and chronic periodontitis patients before and after phase 1 therapy.

METHODS

In this study we examined 30 patients who had chronic periodontitis with probing depth sites ⩾5 mm and a clinical attachment level (CAL) ⩾5 mm. We included 30 periodontally healthy patients as a control. Clinical measurements such as plaque (PI) and gingival (GI) indices, papillary bleeding index (PBI), probing depths (PD), and CAL were recorded both before treatment (BT) and after phase I periodontal treatment (AT). Assays for MMP-1 and TIMP-1 were performed with an enzyme-linked immunosorbent assay (ELISA) method.

RESULTS

All clinical parameters were significantly reduced at the post-therapy visit. MMP-1 levels were significantly higher in patients BT than the controls; however, the patients AT were not statistically different than the controls. TIMP-1 levels in patients BT were significantly lower than in the controls and significantly lower than patients AT. We observed a significant positive correlation between GCF volume and MMP-1 levels. Furthermore, TIMP-1 levels were significantly negatively correlated with both GCF volume and all clinical parameters.

CONCLUSIONS

We observed that as the extent of periodontal destruction increases, MMP-1 concentration increases and TIMP-1 concentration decreases in GCF. When chronic periodontitis patients were treated by scaling and root planing (SRP), the average MMP-1 concentrations decreased and TIMP-1 concentrations increased in GCF.

Expressions of MMPs and TIMP-1 in gastric ulcers may differentiate H. pylori-infected from NSAID-related ulcers

Background. Two major causes of gastric ulcers are Helicobacter pylori (H. pylori) infection and nonsteroidal anti-inflammatory drug (NSAID) use. Aims. This study aimed to determine if there were different expressions of matrix metalloproteinases (MMPs) and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) between H. pylori-infected and NSAID-related ulcers. Methods. The 126 gastric ulcer patients (H. pylori infected n = 46; NSAID related n = 30; combined with two factors n = 50) provided ulcer and nonulcer tissues for assessment of MMP-3, -7, and -9 and TIMP-1 expression by immunohistochemical staining. Results. Gastric ulcer tissues had significantly higher MMP-3, -7, and -9 and TIMP-1 expressions than nonulcer tissues (P < 0.05). H. pylori-infected gastric ulcers had even higher MMP-7, MMP-9, and TIMP-1 expressions in epithelial cells than NSAID-related gastric ulcers (P < 0.05). In patients with the two combined factors, gastric ulcers expressed similar proportions of antral ulcers and MMP-7 and MMP-9 intensities to NSAID-related gastric ulcers, but lower MMP-9 and TIMP-1 than H. pylori-infected gastric ulcers (P < 0.05). Conclusions. H. pylori-infected gastric ulcers express higher MMP-7, MMP-9, and TIMP-1 than NSAID-related ulcers. In patients with the two combined factors, ulcer location and MMP-7 and MMP-9 intensities are similar to NSAID use.

Hydroxyproline-containing collagen analogs trigger the release and activation of collagen-sequestered proMMP-2 by competition with prodomain-derived peptide P33-42

Background

Fibrolytic and profibrotic activities of the matrix metalloproteinases (MMPs)-2 and -9 play a central role in liver fibrosis. Since binding to the extracellular matrix influences the activity of both gelatinases, here the role of fibrillar collagens as the most abundant matrix components in fibrotic tissue was investigated.

Results

In situ zymography and immunohistology showed association of enzymatically inactive prodomain-containing proMMP-2 and proMMP-9 but not of their activated forms to fibrillar collagen structures, which are not substrates of these gelatinases. In solid-phase binding studies with human collagens and collagen fragments, up to 45% of [¹²⁵I]-labeled proMMP-2 and proMMP-9 but not of active (act)MMP-2 and actMMP-9 were retained by natural collagenous molecules and by synthetic analogs containing repeated Gly-Pro-Hyp triplets (GPO). Surface plasmon resonance yielded binding constants for the interaction of collagen type I (CI) with proMMP-2 and proMMP-9 in a nanomolar range. Values for actMMP-2 and actMMP-9 were 30-40 times higher. Tenfold molar excesses of (GPO)₁₀ reduced the interaction of CI with pro- and actMMP-2 by 22- or 380-fold and resulted in prodomain release accompanied by high enzymatic activation and activity. Pointing to gelatine substrate displacement, higher (GPO)₁₀ concentrations blocked the enzymatic activity. The MMP-2 prodomain-derived collagen-binding domain peptide (P_33-42) binds to the collagen-binding domain of MMP-2, thereby preserving enzymatic inactivity. Synthetic P_33-42 peptide competed with proMMP-2 binding to CI and prevented (GPO)₁₀-mediated proMMP-2 activation. In contrast to (GPO)₁₀, P_33-42 did not activate proMMP-2, making triple helical and hydroxyproline-containing (GPO)₁₀ unique in modulating gelatinase availability and activity.

Conclusions

These findings suggest novel strategies using collagen analogs for the resolution of liver fibrosis via fibrotic matrix-sequestered gelatinases.

Impaired remodeling phase of fracture repair in the absence of matrix metalloproteinase-2

The matrix metalloproteinase (MMP) family of extracellular proteases performs crucial roles in development and repair of the skeleton owing to their ability to remodel the extracellular matrix (ECM) and release bioactive molecules. Most MMP-null skeletal phenotypes that have been previously described are mild, thus permitting the assessment of their functions during bone repair in the adult. In humans and mice, MMP2 deficiency causes a musculoskeletal phenotype. In this study, we assessed the role of MMP2 during mouse fracture repair and compared it with the roles of MMP9 and MMP13. Mmp2 was expressed at low levels in the normal skeleton and was broadly expressed in the fracture callus. Treatment of wild-type mice with a general MMP inhibitor, GM6001, caused delayed cartilage remodeling and bone formation during fracture repair, which resembles the defect observed in Mmp9(-/-) mice. Unlike Mmp9- and Mmp13-null mutations, which affect both cartilage and bone in the callus, the Mmp2-null mutation delayed bone remodeling but not cartilage remodeling. This remodeling defect occurred without changes in either osteoclast recruitment or vascular invasion of the fracture callus compared with wild type. However, we did not detect changes in expression of Mmp9, Mmp13 or Mt1-Mmp (Mmp14) in the calluses of Mmp2-null mice compared with wild type by in situ hybridization, but we observed decreased expression of Timp2 in the calluses of Mmp2-, Mmp9- and Mmp13-null mice. In keeping with the skeletal phenotype of Mmp2-null mice, MMP2 plays a role in the remodeling of new bone within the fracture callus and impacts later stages of bone repair compared with MMP9 and MMP13. Taken together, our results indicate that MMPs play unique and distinct roles in regulating skeletal tissue deposition and remodeling during fracture repair.

The regulatory mechanism of extracellular Hsp90{alpha} on matrix metalloproteinase-2 processing and tumor angiogenesis

Heat shock protein 90α (Hsp90α) is a ubiquitously expressed molecular chaperone that is essential for eukaryotic homeostasis. Hsp90α can also be secreted extracellularly, where it has been shown to be involved in tumor metastasis. Extracellular Hsp90α interacts with and promotes the proteolytic activity of matrix metalloproteinase-2 (MMP-2). However, the regulatory mechanism of Hsp90α on MMP-2 activity is still unknown. Here we show that Hsp90α stabilizes MMP-2 and protects it from degradation in tumor cells. Further investigation reveals that this stabilization effect is isoform-specific, ATP-independent, and mediated by the interaction between the Hsp90α middle domain and the MMP-2 C-terminal hemopexin domain. Moreover, this mechanism also applies to endothelial cells that secrete more Hsp90α in their proliferating status. Furthermore, endothelial cell transmigration, Matrigel plug, and tumor angiogenesis assays demonstrate that extracellular Hsp90α promotes angiogenesis in an MMP-2-dependent manner. In sum, this study provides new insights into the molecular mechanism of how Hsp90α regulates its extracellular client proteins and also reveals for the first time the function of extracellular Hsp90α in promoting tumor angiogenesis.

Hexane–ethanol extract ofGlycyrrhiza uralensiscontaining licoricidin inhibits the metastatic capacity of DU145 human prostate cancer cells

Licorice extracts are known to exhibit anti-carcinogenic activities. However, chronic licorice consumption can lead to serious side effects due to the presence of considerable quantities of glycyrrhizin, which causes severe hypokalaemia and hypertension. In the present study, we evaluated the effects of a hexane–ethanol extract ofGlycyrrhiza uralensis(HEGU), which lacks glycyrrhizin, on the metastatic characteristics of DU145 prostate cancer cells. HEGU inhibited basal and epidermal growth factor-induced cell migration, invasion and adhesion in a dose-dependent fashion. HEGU significantly suppressed the secretion and activation of the matrix metalloproteinase (MMP)-2 and MMP-9. The secretion of tissue inhibitor of metalloproteinase (TIMP)-1 was reduced, but that of TIMP-2 was increased in HEGU-treated cells. HEGU reduced the protein levels of integrin-α2, the intercellular adhesion molecule, and the vascular cell adhesion molecule. An active fraction of HEGU was separated via column chromatography, and the structure of the active component, licoricidin, was identified via1H NMR and13C NMR. The treatment of DU145 cells with licoricidin induced a reduction in cell migration and the secretion of MMP-9, TIMP-1, urokinase-type plasminogen activator and vascular endothelial growth factor, as well as in the expression of adhesion molecules. These results indicate that HEGU, which contains licoricidin, is a potent anti-metastatic agent, which can markedly inhibit the metastatic and invasive capacity of malignant prostate cancer cells. The observed reductions in the activation of proteases and the levels of adhesion molecules may constitute a component of the mechanisms by which HEGU inhibits the migration and adhesion of prostate cancer cells.

Changes in TIMP-1 and -2 expression in the early stage of porcine serum-induced liver fibrosis in rats

It is widely recognized that tissue inhibitors of metalloproteinases (TIMPs), especially TIMP-1 and -2, play a key role in the progression of hepatic fibrosis. In the present study, we examined the changes in TIMP-1 and -2 expressions in the early stage of porcine serum (PS)-induced liver fibrosis in Brown Norway (BN) and Wistar rats. The rats were injected intraperitoneally with 0.5 ml/head of PS twice a week for up to 8 weeks and examined at 2, 4 and 8 weeks. Hepatic fibrosis and inflammatory cell infiltration developed at 4 and 8 weeks in BN and Wistar rats, respectively, and formation of pseudolobules was detected at 8 weeks in rats of both strains. The expression of liver TIMP-1 and -2 mRNAs significantly increased at 8 weeks in rats of both strains. At the same time, TIMP-1 and -2 activities were also detected in the liver of both strains. On the other hand, the expression of serum TIMP-1 and -2 proteins increased earlier (at 4 weeks for TIMP-1 and at 2 or 4 weeks for TIMP-2) than that of liver TIMP-1 and -2 mRNAs did. Although there are some reports suggestive of why the elevation of serum TIMP-1 and -2 proteins preceded that of liver TIMP-1 and -2 mRNAs, the exact reason is still obscure. In conclusion, the present study showed for the first time the mode of TIMP-1 and -2 expression and activity in the early stage of PS-induced rat liver fibrosis model.

ProMMP-2: TIMP-1 complexes identified in plasma of healthy individuals

Activation of MMPs in tissues is an important component of tissue injury. Based on earlier reports that (latent) proMMP-2 is incapable of forming a complex with TIMP-1, we reasoned that the identification of MMP-2:TIMP-1 complexes in blood might serve as a surrogate marker ("smoking gun") of MMP-2 activation in tissues. Using specific antibodies, we developed a sensitive and specific assay to detect MMP-2:TIMP-1 complexes. We were perplexed to find that approximate 40% of plasma specimens from healthy individuals had detectable levels of the MMP-2:TIMP-1 complexes. Employing recombinant TIMP-1 bound Sepharose beads and Western blots, we demonstrated binding between recombinant proMMP-2 and TIMP-1 proteins. Recombinant MMP-2 lacking the catalytic domain also bound to TIMP-1 coated beads. These data are consistent with TIMP-1 binding to the hemopexin or hinge domain of proMMP-2. The explanation for the presence of plasma proMMP-2:TIMP-1 complexes in selected healthy individuals remains to be determined. In contrast to our immunoassay and bead-binding experiments, proMMP-2 failed to bind to immobilized TIMP-1 employing surface plasmon resonance technology. Additional studies are needed to clarify these contrasting results.

Matrix metalloproteinase-8 (MMP-8) is the major collagenase in human dentin

OBJECTIVE

Previously an unidentified collagenolytic metalloprotease together with gelatinase (matrix metalloproteinase-2, MMP-2), and enamelysin (MMP-20) have been detected in human dentin. The aim of the study was to characterize dentinal collagenolytic enzymes. Furthermore, we hypothesized that the dentinal MMPs are protected by the mineral phase, and studied the stability of dentinal MMPs.

DESIGN

To characterize dentinal collagenolytic enzymes, we used Western blotting with specific antibodies against MMP collagenases (MMP-1, -8, and -13) and cathepsin K. MMP-8 immunofluorometric assay (IFMA) was also used for MMP-8 detection, and functional collagenase activity was examined with type I collagen degradation assay. The stability of dentinal MMPs was examined by autoclaving dentin blocks before protein extraction and subsequent examination of protein levels and the activities of dentin collagenase and gelatinases.

RESULTS

MMP-8 (collagenase-2) was detected in dentin both with Western blot and IFMA, and dentinal samples also cleaved the intact type I collagen into characteristic 3/4(alphaA)-cleavage products in vitro. No other collagenases or cathepsin K were detected. In autoclaved samples no MMP-8 was found, but gelatinase activity was observed in protein fractions of mineralized dentin.

CONCLUSIONS

MMP-8 represents the major collagenase in human dentin. Unlike MMP-8, dentinal gelatinases can be detected after autoclave treatment of dentin, indicating their high resistance to external sample treatment procedures.

Keratoconus: Matrix metalloproteinase-2 activation and TIMP modulation

Keratoconus is an ocular condition that causes corneal thinning, cone formation and scarring. In view of a hypothesis that activated MMP-2 may initiate or facilitate disease progression, the MMP-2/TIMP systems of stromal cells derived from normal and keratoconic corneas have been compared. To achieve this, stromal cell cultures were established from normal, clear keratoconic (KCS-1) and scarred keratoconic (KCS-2) corneas. The secreted MMP-2 was assayed using [(3)H]Type IV collagen and analysed by zymography. Optimally maintained and nutrient deprived cells were subsequently incubated with [(3)H]lysine. The secreted radiolabelled macromolecules were separated and quantified. The results obtained indicated that optimally maintained KCS-1 stromal cells produced more MMP-2 than normal stromal cells but not TIMP. Nutrient deprivation induced MMP-2 activation and cell death. Surviving cells upregulated TIMP-1 synthesis and in this respect became similar to the KCS-2 stromal cells that did not excessively generate activated MMP-2 or die as a consequence of nutrient deprivation. From these results, it was concluded that KCS-1 stromal cells over-expressed MMP-2 without increasing TIMP production. This may facilitate MMP-2 activation in vivo and hence advance the keratoconic condition. KCS-2 cultures over-expressed both MMP-2 and TIMP-1. Because TIMP-1 inhibits MMP-2 activity and protects against cell death it may be of significance in initiating repair processes and curtailing keratoconus.

Alterations in vascular matrix metalloproteinase due to ageing and chronic hypertension: effects of endothelin receptor blockade

OBJECTIVE

To determine the effects of age and dual endothelin (ET)A/ETB receptor antagonism (bosentan) on aortic matrix metalloproteinase (MMP) abundance and tissue inhibitor of metalloproteinase (TIMP) expression in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR).

METHODS

Male SHR and control WKY rats were randomly assigned to receive placebo or bosentan (100 mg/kg per day) for 3 months. Animals were killed under terminal anaesthesia at either 20 weeks (adult) or 17-20 months (senescent). Aortic gelatinase activity was determined by zymography, whereas MT-1 MMP and TIMP-1 expression were assessed by immunoblotting.

RESULTS

In WKY rats, aortic MMP-2 but not proMMP-2 activity was 3.6-fold higher (P < 0.02) in the senescent compared with the adult group. TIMP-1 (twofold) and MT-1 MMP (3.8-fold) expression increased (P < 0.05) with age in the WKY groups. Short-term hypertension (adult SHR versus adult WKY) increased MMP-2 to 74.7 +/- 14.1 from 18.9 +/- 3.5 arbitrary units (AU) (P = 0.0012), but did not alter proMMP-2 activity. This increased further on progression to chronic hypertension (117.4 +/- 12.2 versus 74.7 +/- 14.1 AU; P < 0.02). Bosentan decreased MMP-2 (78.9 +/- 3.8 versus 117.4 +/- 12.2 AU; P = 0.014) and proMMP-2 activity (P < 0.006) in the senescent SHR group.

CONCLUSION

Ageing and the development/progression of hypertension are associated with increased MMP-2 activity in the aorta, which is consistent with ongoing remodelling of the vasculature. However, the underlying mechanisms regulating MMP-2 abundance in ageing and hypertension appear to be divergent, as MT-1 MMP expression is differentially altered. Dual ETA/ETB receptor antagonism did not alter the age-dependent increase in aortic MMP activity in normotensive rats. However, bosentan decreased pro and active MMP-2 activity in senescent SHR rats, indicating that ET modulates late events in vascular remodelling in hypertension.

Impaired degradation of matrix collagen in human gingival fibroblasts by the antiepileptic drug phenytoin

BACKGROUND

Gingival overgrowth (GO) is a serious adverse effect associated with the administration of phenytoin (PHT), with PHT-induced GO characterized by a massive accumulation of extracellular matrix components, especially collagen, in gingival connective tissues. However, the etiology of such collagen accumulation is still largely unknown. We examined the effects of PHT on the collagen degradation process leading to collagen accumulation in human gingival fibroblasts (HGF).

METHODS

HGFs were cultured with various concentrations of PHT and viable cell numbers and collagen amounts were determined. Gene and protein expressions of matrix metalloproteinases (MMP) and tissue inhibitors of MMPs (TIMP) were quantified with reverse transcription-polymerase chain reaction (RT-PCR) analyses and Western blotting, respectively. Cellular endocytosis of collagen was assayed using flow-cytometric analysis. The effects of PHT on extracellular signal-regulated kinase 1/2 (ERK1/2) and inhibitor kappaB-alpha (IkappaB-alpha) were assayed.

RESULTS

The proliferation of HGFs was not affected by PHT, whereas it significantly increased collagen accumulation. Further, the expressions of MMP-1, -2, and -3 were markedly suppressed by PHT, whereas that of TIMP-1 was induced in a dose- and time-dependent manner. PHT also markedly prevented collagen endocytosis by HGFs, which was associated with the suppression of alpha2beta1-integrin expression. In addition, the phosphorylation of ERK1/2 and IkappaB-alpha degradation were suppressed by PHT.

CONCLUSIONS

These results suggest that PHT causes an impaired degradation of collagen by suppression of enzymatic degradation with MMPs/TIMP-1 and alpha2beta1-integrin-mediated endocytosis. Those alterations are likely mediated through the cellular signaling pathways of ERK1/2 and nuclear factor kappaB. These synergistic effects may cause collagen accumulation, leading to GO.

Tissue distribution, inhibition and activation of gelatinolytic activities in Atlantic cod (Gadus morhua)

Gelatinolytic activities in fish tissues with properties like matrix metalloproteinases (MMPs) have been paid little attention. However, they have been proposed to participate in post mortem degradation during storage and the disintegration of pericellular connective tissue during spawning. In this paper the distribution of gelatinolytic activities in liver, heart, muscle, gill, and male and female gonad of Atlantic cod (Gadus morhua) was studied by using gelatin SDS-PAGE, proteinase inhibitors, gelatin and lentil lectin Sepharose affinity chromatography. The amount of gelatin degrading enzymes varied from tissue to tissue. Most of the gelatin binding enzymes were found to be matrix metalloproteinases by adding galardin, a broad range MMP inhibitor, to the incubation buffer. A 72 kDa form of cod gelatin degrading enzyme had properties similar to human proMMP-2, as it could be activated by p-aminophenylmercuric acetate and trypsin. Like the human MMP-2 it did not bind to lentil lectin. An 83 kDa cod gelatin degrading enzyme had properties similar to the 92 kDa progelatinase B (proMMP-9). These properties were also similar to that of the 72 kDa form, except that the 83 kDa cod gelatinase was bound to lentil lectin, showing that it is a glycoprotein like MMP-9.

Activation of caspases-8 and -10 by FLIP(L)

The first step in caspase activation is transition of the latent zymogen to an active form. For the initiator caspases, this occurs through dimerization of monomeric zymogens at an activating complex. Recent studies have suggested that FLIP(L) [FLICE-like inhibitory protein, long form; FLICE is FADD (Fas-associated death domain protein)-like interleukin-1beta-converting enzyme], previously thought to act solely as an inhibitor of caspase-8 activation, can under certain circumstances function to enhance caspase activation. Using an in vitro induced-proximity assay, we demonstrate that activation of caspases-8 and -10 occurs independently of cleavage of either the caspase or FLIP(L). FLIP(L) activates caspase-8 by forming heterodimeric enzyme molecules with substrate specificity and catalytic activity indistinguishable from those of caspase-8 homodimers. Significantly, the barrier for heterodimer formation is lower than that for homodimer formation, suggesting that FLIP(L) is a more potent activator of caspase-8 than is caspase-8 itself.

The effects of preeclampsia and oxygen environment on endothelial release of matrix metalloproteinase-2

BACKGROUND

There is evidence of altered vascular endothelial function in women with preeclampsia as well as in the endothelial cells from umbilical vessels of preeclamptic pregnancies. Matrix metalloproteinase (MMP)-2 is elevated in the plasma of preeclamptic women and is a mediator of vascular reactivity; however, whether MMP-2 release is altered in preeclamptic endothelial cells is unknown. We hypothesize that MMP-2 release is enhanced in endothelial cells from preeclamptic compared with uncomplicated pregnancies and that this phenomenon may be mediated by an oxygen-dependent mechanism. Our specific hypothesis is that cells from normal pregnancies will demonstrate enhanced MMP-2 release at low oxygen (< 0.5%, 2%) compared to high oxygen (20%), thus mimicking the behavior of preeclamptic cells.

METHODS

Human umbilical vein endothelial cells (HUVECs) from preeclamptic pregnancies (n = 4) and normal pregnancies (n = 4) were incubated for 12 hr in standard culture conditions (20% oxygen). In a separate series of experiments, HUVECs from normal pregnancies (n = 6) were incubated for 12 hr at < 0.5%, 2%, and 20% oxygen. Supernatants were analyzed for MMP-2 and tissue inhibitors of metalloproteinases (TIMP)-1 and -2.

RESULTS

The HUVECs from women with preeclampsia demonstrated significantly enhanced release of MMP-2 (p < 0.05), TIMP-1 (p < 0.001), and TIMP-2 (p = 0.01) compared to normal cells. MMP-2 release from HUVECs from uncomplicated pregnancies was significantly elevated at 2% oxygen compared to < 0.5% and 20% oxygen (p < 0.05). TIMP-1 and -2 secretion was not altered with varying oxygen.

CONCLUSIONS

Preeclamptic endothelial cells demonstrate significantly enhanced MMP-2, TIMP-1 and TIMP-2 release compared to normal cells. Our data show that there are significant effects of oxygen tension on MMP-2 release from normal cells; however, the magnitude of the enhanced release is small when compared to the differences in MMP-2 release in cells from preeclamptic and normal pregnancies. Furthermore, TIMP-1 and -2 release is not affected by changes in oxygen. It is unlikely that oxygen is a key mediator of the enhanced MMP-2, TIMP-1 and TIMP-2 release observed in preeclamptic cells.

Matrix metalloproteinase activity and immunohistochemical profile of matrix metalloproteinase-2 and -9 and tissue inhibitor of metalloproteinase-1 during human dermal wound healing

Proteolytic activity is required for the turnover of the extracellular matrix during wound healing. Matrix metalloproteinases can collectively cleave all components of the extracellular matrix, with the endogenous tissue inhibitor of metalloproteinase-1 regulating their activity. Breast tissue taken at varying postoperative times (n= 92) or during surgery (controls, n= 17), was used to investigate the temporal and spatial activity of matrix metalloproteinase-2 and -9 and tissue inhibitor of metalloproteinase-1 during human wound healing. Matrix metalloproteinase activity, determined using a quenched fluorescence substrate assay, increased during early healing (3-8 weeks) compared to controls, and then decreased between 24 and 36 weeks after surgery (p < 0.05 until 24 weeks, Mann-Whitney U-test). Immunohistochemistry scores for matrix metalloproteinase-9 expression were significantly elevated compared to controls in scar endothelial cells and fibroblasts from 2 until 12 and 20 weeks, respectively. Matrix metalloproteinase-2 staining was observed exclusively in fibroblasts, reaching maximum levels 8-12 weeks after surgery, decreasing by 1.5 years but remaining significantly increased. Tissue inhibitor of metalloproteinase-1 staining was relatively sparse but was significantly increased until 8 weeks after surgery. These results show that matrix metalloproteinases are present at elevated levels during early wound healing, when angiogenesis occurs, and suggest that matrix metalloproteinase-9 may play a significant role. The later expression of matrix metalloproteinase-2 and -9 in fibroblasts suggests a role in extracellular matrix remodeling.

Site-specific inductive and inhibitory activities of MMP-2 and MMP-3 orchestrate mammary gland branching morphogenesis

During puberty, mouse mammary epithelial ducts invade the stromal mammary fat pad in a wave of branching morphogenesis to form a complex ductal tree. Using pharmacologic and genetic approaches, we find that mammary gland branching morphogenesis requires transient matrix metalloproteinase (MMP) activity for invasion and branch point selection. MMP-2, but not MMP-9, facilitates terminal end bud invasion by inhibiting epithelial cell apoptosis at the start of puberty. Unexpectedly, MMP-2 also represses precocious lateral branching during mid-puberty. In contrast, MMP-3 induces secondary and tertiary lateral branching of ducts during mid-puberty and early pregnancy. Nevertheless, the mammary gland is able to develop lactational competence in MMP mutant mice. Thus, specific MMPs refine the mammary branching pattern by distinct mechanisms during mammary gland branching morphogenesis.

Identification of a region of beta-amyloid precursor protein essential for its gelatinase A inhibitory activity

Because beta-amyloid precursor protein (APP) has the abilities both to interact with extracellular matrix and to inhibit gelatinase A activity, this molecule is assumed to play a regulatory role in the gelatinase A-catalyzed degradation of extracellular matrix. To determine a region of APP essential for the inhibitory activity, we prepared various derivatives of APP. Functional analyses of proteolytic fragments of soluble APP (sAPP) and glutathione S-transferase fusion proteins, which contain various COOH-terminal parts of sAPP, showed that a site containing residues 579-601 of APP(770) is essential for the inhibitory activity. Moreover, a synthetic decapeptide containing the ISYGNDALMP sequence corresponding to residues 586-595 of APP(770) had a gelatinase A inhibitory activity slightly higher than that of sAPP. Studies of deletion of the NH(2)- and COOH-terminal residues and alanine replacement of internal residues of the decapeptide further revealed that Tyr(588), Asp(591), and Leu(593) of APP mainly stabilize the interaction between gelatinase A and the inhibitor. We also found that the residues of Ile(586), Met(594), and Pro(595) modestly contribute to the inhibitory activity. The APP-derived decapeptide efficiently inhibited the activity of gelatinase A (IC(50) = 30 nm), whereas its inhibitory activity toward membrane type 1 matrix metalloproteinase was much weaker (IC(50) = 2 microm). The decapeptide had poor inhibitory activity toward gelatinase B, matrilysin, and stromelysin (IC(50) > 10 microm). The APP-derived inhibitor formed a complex with active gelatinase A but not with progelatinase A, and the complex formation was prevented completely by a hydroxamate-based synthetic inhibitor. Therefore, the decapeptide region of APP is likely an active site-directed inhibitor that has high selectivity toward gelatinase A.

Matrix metalloproteinase activity correlates with blastema formation in the regenerating MRL mouse ear hole model

The MRL mouse was proposed as a model of mammalian regeneration because it can close ear holes completely with the restoration of normal tissue. This regeneration process involves the formation of a blastema during healing, the re-appearance of cartilage and hair follicles, and healing without scarring. Such a process requires extensive tissue remodeling. To characterize differences in ear wounding responses between regenerating and nonregenerating mice, we examined and compared the extracellular matrix remodeling and the matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) response in the MRL and C57BL/6 mouse strains after injury. We found a correlation between the MRL's ability to break down the basement membrane, form a blastema, and close ear hole wounds and an inflammatory response with neutrophils and macrophages seen in the ear after injury. These cells were positive for MMP-2 and MMP-9 as well as TIMP-2 and TIMP-3. Clear differences between the MRL and B6 response to injury were seen that could explain the differences in healing and blastema formation in the MRL and lack of it in the B6 mice. This finding was further supported by enzyme activity as determined by gelatin zymography.

Expression of TIMP-1 in Pichia pastoris. Selection of an anti-TIMP-1 specific single-chain Fv antibody from a large non-immune library

To quantitate tissue inhibitor of metalloproteinase (TIMP)-1 in biological samples, a strategy for isolation of monoclonal antibodies was applied that employs a phage-displayed single-chain Fv (scFv). In order to obtain sufficient amounts of TIMP-1 to use as an antigen, high-level expression in Pichia pastoris was achieved under the control of the AOX-1 promotor. Purified protein antigen was then used for panning to achieve enrichment of specific phage from naive scFv library. In five subsequent panning rounds, antibody fragments that display specificity to TIMP-1 were selected. Regions encoding scFv were subcloned into a vector allowing production of scFv-alkaline phosphatase (AP) fusion proteins. Two such conjugates displaying dose-dependent reactivity with TIMP-1 were isolated and characterised, providing the basis for the construction of a TIMP-1 quantitation assay based entirely on recombinant proteins.

The reprolysin jararhagin, a snake venom metalloproteinase, functions as a fibrillar collagen agonist involved in fibroblast cell adhesion and signaling

The integrins alpha(2)beta(1) and alpha(1)beta(1) have been shown to modulate cellular activities of fibroblasts on contact with fibrillar collagen. Previously it has been shown that collagen binding to alpha(2)beta(1) regulates matrix metalloproteinase MMP-1 and membrane-type MT1-MMP expression. Jararhagin is a snake venom metalloproteinase of the Reprolysin family of zinc metalloproteinases, containing a metalloproteinase domain followed by disintegrin-like and cysteine-rich domains. Jararhagin blocks type I collagen-induced platelet aggregation by binding to the alpha(2)beta(1) integrin and inhibiting collagen-mediated intracellular signaling events. Here we present evidence that, in contrast to the observations in platelets, jararhagin binding to the integrin receptor alpha(2)beta(1) in fibroblasts produces collagen-like cell signaling events such as up-regulation of MMP-1 and MT1-MMP. Inactivation of the metalloproteinase domain had no effect on these properties of jararhagin. Thus, in fibroblasts the snake venom metalloproteinase jararhagin functions as a collagen-mimetic substrate that binds to and activates integrins. Given the homology between the metalloproteinase, disintegrin-like and cysteine-rich domains of jararhagin and those of the members of the ADAMs (a disintegrin-like and metalloproteinase) family of proteins, this work demonstrates the potential of the disintegrin-like/cysteine-rich domains in the ADAMs as cellular signaling agents to elicit responses relevant to the biological function of these proteins.

The high molecular weight urinary matrix metalloproteinase (MMP) activity is a complex of gelatinase B/MMP-9 and neutrophil gelatinase-associated lipocalin (NGAL). Modulation of MMP-9 activity by NGAL

Detection of matrix metalloproteinase (MMP) activities in the urine from patients with a variety of cancers has been closely correlated to disease status. Among these activities, the presence of a group of high molecular weight (HMW) MMPs independently serves as a multivariate predictor of the metastatic phenotype (). The identity of these HMW MMP activities has remained unknown despite their novelty and their potentially important applications in non-invasive cancer diagnosis and/or prognosis. Here, we report the identification of one of these HMW urinary MMPs of approximately 125-kDa as being a complex of gelatinase B (MMP-9) and neutrophil gelatinase-associated lipocalin (NGAL). Multiple biochemical approaches verified this identity. Analysis using substrate gel electrophoresis demonstrated that the 125-kDa urinary MMP activity co-migrates with purified human neutrophil MMP-9 x NGAL complex. The 125-kDa urinary MMP-9 x NGAL complex was recognized by a purified antibody against human NGAL as well as by a monospecific anti-human MMP-9 antibody. Furthermore, these same two antibodies were independently capable of specifically immunoprecipitating the 125-kDa urinary MMP activity in a dose-dependent manner. In addition, the complex of MMP-9 x NGAL could be reconstituted in vitro by mixing MMP-9 and NGAL in gelatinase buffers with pH values in the range of urine and in normal urine as well. Finally, the biochemical consequences of the NGAL and MMP-9 interaction were investigated both in vitro using recombinant human NGAL and MMP-9 and in cell culture by overexpressing NGAL in human breast carcinoma cells. Our data demonstrate that NGAL is capable of protecting MMP-9 from degradation in a dose-dependent manner and thereby preserving MMP-9 enzymatic activity. In summary, this study identifies the 125-kDa urinary gelatinase as being a complex of MMP-9 and NGAL and provides evidence that NGAL modulates MMP-9 activity by protecting it from degradation.

Remodeling of extracellular matrix in gastric ulceration

The quality of ulcer repair remains crucial for the stability of the injured tissue and for preventing recurrence. Therefore, we studied the temporo-spatial expression of the fibrillar and basement membrane collagens (types I, III, and IV), the collagenase MMP-2 as well as its inhibitor TIMP-1 before and after oral administration of basic fibroblast growth factor (b-FGF) over 30 days in acetic acid-induced rat gastric ulcers. The alterations and the exact location of the mRNA transcripts and their precipitated proteins were visualized by means of radioactive in situ hybridization and immunohistochemistry. Our data show that hybridization signals of procollagen I could first be identified 2 hours after ulcer induction. After 12 hours the ulcer was established and the mRNA was enhanced at the ulcer margin. After 24-48 hours the other procollagen transcripts were detected and all were further upregulated over the mesenchymal cells of all gastric layers up to 21 days, then declined at 30 days. In contrast, MMP-2 became prominent after 48 hours and up to 21 days. TIMP-1 was enhanced at 72 hours. After oral administration of b-FGF the transcriptional activity of the procollagens and MMP-2 was not significantly altered, while ulcer diameter was significantly reduced. We conclude that the early onset and long duration of collagens' expression points to their central structural and functional role in gastric ulcer healing. MMP-2 seems to be involved in both active ulceration and ECM remodeling. The timing of TIMP/MMP expression may be critical for proper restoration of gastric wall integrity.

Expression of MMP2, MMP9, MT1-MMP, TIMP1, and TIMP2 mRNA in valvular lesions of the heart

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) play an important role in several diseases. This study was undertaken to investigate the mRNA synthesis of MMP2, MMP9, membrane-type 1 (MT1)-MMP, and matrix metalloproteinase inhibitors TIMP1 and TIMP2 by in situ hybridization in a set of heart mitral and aortic valves operatively removed due to degenerative or inflammatory valvular diseases. The material consisted of 21 valves, eight with endocarditis and 13 with a degenerative valvular disease. The samples were studied by in situ hybridization with specific probes for MMP2, MMP9, MT1-MMP, TIMP1, and TIMP2. Synthesis of MMP2 mRNA was found in seven valves, five with endocarditis and two with degenerative valvular disease. Signals for MMP9 mRNA were found in two cases with endocarditis and five cases with degenerative valvular disease. No signal for MT1-MMP mRNA was found in the lesions. TIMP1 mRNA, on the other hand, was found in 17 cases, both endocarditis and degenerative valvular disease. TIMP2 mRNA was found in three cases of endocarditis. The signals for MMP2, MMP9, TIMP1, and TIMP2 mRNA were localized in endothelial cells and in fibroblast-like cells expressing alpha-smooth muscle actin, thus showing myofibroblast-type differentiation. The results show that matrix metalloproteinases MMP2 and MMP9, and matrix metalloproteinase inhibitors TIMP1 and TIMP2 mRNAs are synthesized in diseased valves and suggest that they may contribute to matrix remodelling in valvular disease.

Type I Collagen Stabilization of Matrix Metalloproteinase-2

The activity of matrix metalloproteinase-2 (MMP-2) is regulated stringently on the posttranslational level. MMP-2 efficiently undergoes autolysis into inactive polypeptides in vitro, prompting the hypothesis that MMP-2 autolysis may function as an alternative mechanism for posttranslational control of MMP-2 in vivo. Moreover, MMP-2 binds to intact type I collagen fibrils; however, the functional consequences of this interaction have not been fully elucidated. To test the hypothesis that MMP-2 binding to type I collagen functions as a positive regulator of MMP-2 proteolytic potential, the effect of type I collagen on MMP-2 activity, inhibition by tissue inhibitor of metalloproteinase-2 (TIMP-2), and enzyme stability was examined. Here, we report that purified MMP-2 binds but does not cleave intact type I collagen. The presence of type I collagen affects neither enzymatic activity against a quenched fluorescent peptide substrate nor the kinetics of inhibition by TIMP-2. However, MMP-2 is stabilized from autolysis in the presence of type I collagen, but not by elastin, fibrinogen, or laminin. These data provide biochemical evidence that MMP-2 exosite interactions with type I collagen may function in the posttranslational control of MMP-2 activity by reducing the rate of autolytic inactivation.

Effects of relaxin on matrix remodeling enzyme activity of cultured equine ovarian stromal cells

Relaxin participates in extracellular matrix (ECM) remodeling in many reproductive organs, including the ovary, by regulating proteolytic enzyme activity. Accumulated evidence indicates this action of relaxin is involved in ovarian follicle development and ovulation. Equine follicles are embedded in cortex that is at the center of the ovary and they must expand/emigrate to the fossa, the only site in the ovary for ovulation. Due to the tremendous expansion of the follicle in this species, we hypothesized that ovarian stromal remodeling would be extensive. Therefore, cultured equine ovarian stromal cell (EOSC) lines were obtained from stroma at the apex of large follicles and the effects of relaxin on gelatinases A and B, tissue inhibitors of matrix metalloproteinases (TIMPs), plasminogen activators (PAs) and PA inhibitor-1 (PAI-1) activities were assessed. Our results showed that equine relaxin increased the activity of total gelatinase A (both pro forms and mature forms) and latent progelatinase B present in conditioned medium, latent progelatinase A present in cell extracts, and TIMP-1 and TIMP-2 present in conditioned medium. This study also revealed that equine relaxin increased the urokinase-type PA activity in conditioned medium and cell extracts, tissue-type PA activity in ECM and PAI-1 activity in conditioned medium. These results suggest that relaxin may contribute to equine follicle growth and migration, and facilitate ovulation by modulating the degradation of ECM in ovarian stromal tissue.

Role of interleukin-1 in induction of matrix metalloproteinases synthesized by rat temporomandibular joint chondrocytes and disc cells

To identify cartilage-degrading enzymes and cell types that can be specifically induced by interleukin-1 (IL-1)alpha, we studied matrix metalloproteinase (MMP) activities of cultured rat temporomandibular joint (TMJ) chondrocytes and disc cells. The cells were isolated from TMJs pre-injected with normal physiological saline (CR) or recombinant human IL-1alpha (AR). MMP activities in the conditioned media were assayed by gelatin enzymography, and they were identified by Western blot analyses. MMP mRNAs in these cells were also detected by RT-PCR. IL-1alpha significantly induced an increase of active MMP9 as well as pro- and active MMP3, but had no effect on the MMP2 activity in both types of cells. MMP3 and MMP9 mRNAs were also inducible in these cells by IL-1alpha stimulation. Furthermore, disc cells were more susceptible to IL-1alpha than chondrocytes. AR cells spontaneously produced the same MMPs in vitro as the CR cells synthesized under IL-1alpha stimulation. The results indicate that MMP9 and MMP3 were predominantly produced by disc cells, and these may be considered to play a pivotal role in ECM degradation during pathological conditions of the TMJ, such as IL-1-induced TMJ arthritis.

The isolation, characterization, and molecular cloning of a 75-kDa gelatinase B-like enzyme, a member of the matrix metalloproteinase (MMP) family. An avian enzyme that is MMP-9-like in its cell expression pattern but diverges from mammalian gelatinase B in sequence and biochemical properties

We have isolated a novel 75-kDa gelatinase from a chicken macrophage cell line, HD11. Biochemical and immunological characterization of the purified enzyme demonstrated that it is distinct from the chicken 72-kDa gelatinase A (MMP-2). The enzyme is capable of specific gelatin binding and rapid gelatin cleavage. Incubation with an organomercurial compound (p-aminophenylmercuric acetate) induces proteolytic processing and activation of this enzyme, and the resultant gelatinolytic activity is sensitive to both zinc chelators and tissue inhibitors of metalloproteinases. A full-length cDNA for the enzyme has been cloned, and sequence analysis demonstrated that the enzyme possesses the characteristic multidomain structure of an MMP gelatinase including a cysteine switch prodomain, three fibronectin type II repeats, a catalytic zinc binding region, and a hemopexin-like domain. The 75-kDa gelatinase is produced by phorbol ester-treated chicken bone marrow cells, monocytes, and polymorphonuclear leukocytes, cell types that charac- teristically produce the 92-kDa mammalian gelatinase B (MMP-9). The absence of a 90-110-kDa gelatinase in these cell types indicates that the 75-kDa gelatinase is likely the avian counterpart of gelatinase B. However, the protein is only 59% identical to human gelatinase B, whereas all previously cloned chicken MMP homologues are 75-90% identical to their human counterparts. In addition, the new 75-kDa chicken gelatinase lacks the type V collagen domain that is found in all mammalian gelatinase Bs. Furthermore, the secreted enzyme appears structurally distinct from known gelatinase Bs and the activated enzyme can cleave fibronectin, which is not a substrate for mammalian gelatinase B. Thus the results of this study indicate that a second MMP gelatinase exists in chickens, and although it is MMP-9/gelatinase B-like in its overall domain structure and expression pattern, it appears to be biochemically divergent from mammalian gelatinase B.

The expression of metalloproteinase-2, -9, and -14 and of tissue inhibitors-1 and -2 is developmentally modulated during osteogenesis in vitro, the mature osteoblastic phenotype expressing metalloproteinase-14

During osteogenesis, in vitro, of tibial-derived rat osteoblasts (ROB) and derived clones, changes occur in the interactions of mature osteoblasts with the endogenous extracellular matrix (ECM) and these culminate in the formation of tridimensional nodules, which become sites of mineral deposition. We investigated if these changes might be mediated by remodeling of ECM, and we focused our study on the neutral metalloproteinases (MMPs), known agents of matrix remodeling, and on their tissue inhibitors (TIMPs). We report that during in vitro differentiation, osteoblasts express the secreted MMP-2 and -9 and the membrane gelatinase MMP-14. These, along with the tissue inhibitors TIMP-1 and -2, are developmentally regulated according to the maturation stage of osteoblasts. Their levels change in a similar association with osteoblast phenotypic maturation in different populations of ROB, which take different times to complete osteogenesis in vitro. MMP-14 expression coincides in both cell populations with the mature osteoblastic phenotype and is localized in the cells forming nodules. MMP-2 and -9 are expressed diffusely in the osteoblast population. Developmentally associated changes in the activation of MMP-2 are detected, associated in their timing with the expression of MMP-14 in both populations of ROB, and MMP-14 activates pro-MMP-2 in vitro. Expression of messenger RNAs (mRNAs) for the three MMPs increases up to the time of nodule formation. At this stage, TIMP-1 mRNA levels are lowest. TIMP-2 mRNA decreases throughout osteogenesis. In situ hybridization in 7-day-old rat tibias shows the strongest expression of MMP-14 among osteogenic cells, in lining osteoblasts on the newly formed trabeculae under the growth plate, and on the endosteal surface of cortical bone. Our data support the concept that the developmentally regulated expression of MMP-14 triggers localized proteolysis within the osteogenic population, concomitant in vitro to nodule formation.

Inflammation dampened by gelatinase A cleavage of monocyte chemoattractant protein-3

Tissue degradation by the matrix metalloproteinase gelatinase A is pivotal to inflammation and metastases. Recognizing the catalytic importance of substrate-binding exosites outside the catalytic domain, we screened for extracellular substrates using the gelatinase A hemopexin domain as bait in the yeast two-hybrid system. Monocyte chemoattractant protein-3 (MCP-3) was identified as a physiological substrate of gelatinase A. Cleaved MCP-3 binds to CC-chemokine receptors-1, -2, and -3, but no longer induces calcium fluxes or promotes chemotaxis, and instead acts as a general chemokine antagonist that dampens inflammation. This suggests that matrix metalloproteinases are both effectors and regulators of the inflammatory response.

Matrix metalloproteinase 2: involvement in keratoconus

PURPOSE

The activation of matrix metalloproteinase-2 (MMP-2) is postulated to be a crucial pathogenic factor behind progressive and chronic diseases in which basement membranes are disrupted. An ocular example is keratoconus. The purpose of the present enquiry was therefore to investigate and compare the activities of the MMP-2 secreted by keratocytes of normal and keratoconic corneas.

METHODS

The spectrum of MMP-2 activities secreted by cultures of keratocytes derived from normal and keratoconic corneas was analysed by zymography. Subsequently, selected preparations were assayed for peptidase activity, using Type I, Type III, Type IV and Type V collagen as substrate, under native conditions and after treatment with a variety of putative activating reagents.

RESULTS

Although MMP-2 of Mr 65,000 on SDS gelatin polyacrylamide gels is the major protease secreted by keratocytes of normal corneas, the keratocytes of early-phase keratoconic corneas secrete an additional zymographic activity of Mr 61,000. From their N-terminal amino acid sequences, both these proteins were shown to be conformers of proMMP-2. Treatment with SDS followed by protein fractionation was required to achieve in vitro activation of the MMP-2 secreted by normal corneal keratocytes. Treatment with SDS alone partially activated the enzyme produced by early-phase keratoconic corneal keratocytes. This procedure and autocatalysis, yielded an enzyme of Mr 43,000 that selectively hydrolysed Type IV and denatured Type 1 collagen.

CONCLUSIONS

The zymographic gelatinase activities of apparent Mr 65,000 and 61,000 are conformers of corneal proMMP-2. Activated enzyme, of Mr 43,000, is more readily generated from protein preparations of the culture media of early phase keratoconic corneal keratocytes than from protein preparations of the culture media of normal corneal keratocytes.

Inactive matrix metalloproteinase 2 is a normal constituent of human glomerular basement membrane. An immuno-electron microscopic study

Remodelling of the extracellular matrix requires tight control not only of matrix synthesis, but also of matrix degradation. Control of matrix degradation is achieved mainly through the matrix metalloproteinase (MMP) enzymes. In the glomerulus, MMP-2 and MMP-9 are believed to be particularly important, as they have activity against type IV collagen. This study has demonstrated by immuno-electron microscopy that most of the immunoreactivity for MMP-2 in the normal glomerulus is located within the glomerular basement membranes and mesangial matrix. mRNA for MMP-2 is also detectable in normal glomeruli, but the other main gelatinase, MMP-9, could not be localized by immuno-electron microscopy. In the normal glomerulus, it seemed likely that MMP-2 is present in an inactive form. To confirm this, in situ zymography was carried out using frozen sections of normal kidney. Baseline activity of normal kidney was relatively weak, but this was dramatically increased by chemical activation of metalloproteinases. The results imply that MMP-2, in an inactive form, is a normal constituent of the extracellular matrix and glomerular basement membranes. Activation would presumably render the matrix 'self-degrading'; membrane-bound MMPs (MT-MMPs) seem particularly likely to be involved in leukocyte penetration of basement membranes in inflammation.

Increased production of matrix metalloproteinase-3 and tissue inhibitor of metalloproteinase-1 by inflamed mucosa in inflammatory bowel disease

Inflammatory bowel diseases (IBD) are characterized by a sustained inflammatory cascade that gives rise to the release of mediators capable of degrading and modifying bowel wall structure. Our aims were (i) to measure the production of matrix metalloproteinase-3 (MMP-3), and its tissue inhibitor, tissue inhibitor of metalloproteinase-1 (TIMP-1), by inflamed and uninflamed colonic mucosa in IBD, and (ii) to correlate their production with that of proinflammatory cytokines and the anti-inflammatory cytokine, IL-10. Thirty-eight patients with IBD, including 25 with Crohn's disease and 13 with ulcerative colitis, were included. Ten controls were also studied. Biopsies were taken from inflamed and uninflamed regions and inflammation was graded both macroscopically and histologically. Organ cultures were performed for 18 h. Tumour necrosis factor-alpha (TNF-alpha), IL-6, IL-1beta, IL-10, MMP-3 and TIMP-1 concentrations were measured using specific immunoassays. The production of both MMP-3 and the TIMP-1 were either undetectable or below the sensitivity of our immunoassay in the vast majority of uninflamed samples either from controls or from those with Crohn's disease or ulcerative colitis. In inflamed mucosa, the production of these mediators increased significantly both in Crohn's disease (P < 0.01 and 0.001, respectively) and ulcerative colitis (P < 0.001 and 0.001, respectively). Mediator production in both cases was significantly correlated with the production of proinflammatory cytokines and IL-10, as well as with the degree of macroscopic and microscopic inflammation. Inflamed mucosa of both Crohn's disease and ulcerative colitis show increased production of both MMP-3 and its tissue inhibitor, which correlates very well with production of IL-1beta, IL-6, TNF-alpha and IL-10.

Post-translational proteolytic processing of procollagen C-terminal proteinase enhancer releases a metalloproteinase inhibitor

Activity of matrix metalloproteinases (MMP) is regulated by a family of proteins called tissue inhibitors of metalloproteinases (TIMP). Four TIMPs have been cloned, and their molecular weights range from 29,000 to 20,000. By reverse zymography, we have observed a metalloproteinase inhibitor with an apparent molecular weight of 16, 500 from medium conditioned by human brain tumor cells. Antibodies directed against TIMPs failed to react with the 16,500 molecular weight inhibitor, indicating that it was not a truncated form of a known TIMP. The inhibitor was isolated from conditioned medium using affinity and ion exchange chromatography. N-terminal sequences of the inhibitor matched amino acid sequences within the C-terminal domain of a protein known as procollagen C-terminal proteinase enhancer (PCPE). Thus, the inhibitor was named CT-PCPE. Comparison of the N-terminal domain of TIMP with CT-PCPE revealed that both contained six cysteine residues. As in the case of TIMP, reduction and alkylation abolished the inhibitory activity of CT-PCPE. Purified CT-PCPE inhibited MMP-2 with an IC(50) value much greater than that of TIMP-2. This implies that MMPs may not be the physiologic targets for CT-PCPE inhibition. However, these results suggest that CT-PCPE may constitute a new class of metalloproteinase inhibitor.

eNOS gene transfer inhibits smooth muscle cell migration and MMP-2 and MMP-9 activity

Vascular smooth muscle cell (SMC) migration is a critical step in the development of neointima after angioplasty. Matrix metalloproteinases (MMPs) degrade the basement membrane and the extracellular matrix, facilitating SMC migration. Transfer of the endothelial nitric oxide synthase (eNOS) gene to the injury site inhibits neointima formation. Neither the signaling pathways leading to NO-mediated inhibition of SMC migration and proliferation nor the alterations in these pathways have been characterized. We hypothesize that NO inhibits SMC migration in part by regulating MMP activity. To test this hypothesis, we transfected cultured rat aortic SMCs with replication-deficient adenovirus containing bovine eNOS gene and analyzed the conditioned medium for MMP activity. We observed that eNOS gene transfer significantly (P<0.05) inhibited SMC migration and significantly (P<0.05) decreased MMP-2 and MMP-9 activities in the conditioned medium. Similarly, addition of the NO donor DETA NONOate and 8-bromo-cGMP to the culture medium significantly decreased MMP-2 and MMP-9 activities in the conditioned medium collected 24 hours after treatment. Furthermore, Western blot analysis of the conditioned medium collected from eNOS gene-transfected SMCs showed a significant increase in tissue inhibitor of metalloproteinases-2 (TIMP-2) levels. Our data suggest that NO decreases MMP-2 and MMP-9 activities and increases TIMP-2 secretion, and this shifts the balance of MMP activity, which may favor the inhibition of cell migration because of inhibition of extracellular matrix degradation.

Gelatinase A expression in endothelial cells is regulated by at least two cis-acting promoter elements

Increased expression of gelatinase A is associated with both angiogenesis and alterations in blood vessel structure. Heart-derived endothelial cells derived from spontaneously hypertensive rats (SHR) were found to express significantly more gelatinase A in culture, both at the protein and mRNA level, than endothelial cells from normotensive Wistar-Kyoto (WKY) rats. Other matrix metalloproteinases, as well as their tissue inhibitors, were not differentially regulated. A 1683 bp gelatinase A promoter fragment linked to a luciferase reporter demonstrated up to 40-fold more activity when transfected into SHR-derived cells versus WKY-derived cells. The promoter region between -1324 and -1272, previously termed RE1, contributed up to a five-fold increase in basal promoter activity in both cells, but contributed only 12% of the promoter activity in SHR-derived cells compared to 85% in WKY-derived cells. In SHR-derived cells, but not in WKY-derived cells, a second region between -1435 and -1375, termed RE2, contributed 60% of the total activity of the 1683 bp promoter fragment. Both electrophoretic mobility shift assays and Southwestern blots demonstrated differences in RE2-specific binding factors in nuclear extracts derived from the two cell types. SHR-derived endothelial cells thus represent a new model system to study the regulation of gelatinase A expression, which itself may contribute to the abnormal vascular structure seen in the SHR.

Clinical usefulness of serum matrix metalloproteinase-2 concentration in patients with chronic viral liver disease

BACKGROUND/AIMS

The production of matrix metalloproteinase (MMP)-2 was reported to be increased in chronically diseased livers. Our aims in the present study were to elucidate the clinical usefulness of the serum MMP-2 concentration in chronic viral liver disease.

METHODS

We measured serum MMP-2 concentrations with a sandwich enzyme immunoassay in 62 patients with chronic hepatitis, 35 patients with liver cirrhosis, 55 patients with hepatocellular carcinoma and 24 healthy individuals. The assay detects proMMP-2 and proMMP-2 complexed with tissue inhibitor of metalloproteinase-2, but not active forms of MMP-2. The liver MMP-2 content was also measured in autopsied cirrhotic and non-cirrhotic livers. Gelatin zymography and gel filtration chromatography were carried out using the serum.

RESULTS

The serum MMP-2 concentration was significantly increased in the liver cirrhosis and hepatocellular carcinoma patients, but not in the patients with chronic hepatitis. There was no significant difference in the serum MMP-2 level between the liver cirrhosis and hepatocellular carcinoma groups. In the patients with chronic viral liver disease, serum MMP-2 concentration showed the best correlation with the degree of liver fibrosis and with serum hyaluronate level. The zymography of serum showed the majority of MMP-2 in serum exists as a proMMP-2. The chromatography of serum revealed a single peak at the position of about 90 kDa corresponding to an MMP-2 complexed with tissue inhibitor of metalloproteinases-2. The liver MMP-2 content was markedly increased in the cirrhotic livers compared with the non-cirrhotic livers, and was positively correlated with the liver collagen content. When investigating the utility of the serum MMP-2 test for differentiating liver cirrhosis from chronic hepatitis, the utility of serum MMP-2 was equal to that of serum hyaluronate, which is known as the best current test for diagnosing liver cirrhosis.

CONCLUSIONS

The serum MMP-2 concentration reflects mainly the amount of proMMP-2 complexed with tissue inhibitor of metalloproteinase-2. The serum MMP-2 level was markedly increased in cirrhotic patients, and may be explained by an overproduction in the cirrhotic liver. In the clinical state, the measurement of serum MMP-2 was as useful a test for diagnosing liver cirrhosis as is the serum hyaluronate level.

Tissue inhibitors of metalloproteinases: role in liver fibrosis and alcoholic liver disease

In liver fibrosis, activated hepatic stellate cells (HSC) play a major role in the deposition of excess extracellular matrix, including fibrillar collagens type I and type III. In addition to matrix protein synthesis, HSC regulate matrix degradation in the liver. This is mediated via a combination of synthesis of matrix (pro)metalloproteinases, which activate these zymogens via specific mechanisms and by inhibiting the active matrix-degrading enzymes via expression of tissue inhibitors of metalloproteinases (TIMPs). There are currently four members of the TIMP family described and of these, both TIMP-1 and TIMP-2 are synthesised by HSC. These observations have led to the suggestion that inhibition of matrix degradation mediated by a change in HSC-expression of TIMPs relative to metalloproteinases, such as interstitial collagenase, may contribute to progression of liver fibrosis. This hypothesis is supported by studies of human liver disease in which TIMP-1 expression is upregulated 5-fold in cirrhotic compared with normal liver. TIMP-1 and TIMP-2 expression is also upregulated in animal models of progressive fibrosis, whereas expression of collagenase is unchanged. In a model which is characterized by natural resolution of liver fibrosis, degradation of the deposited fibrillar liver matrix is accompanied by rapid down-regulation of TIMP-1 expression. In alcoholic liver disease, the role of TIMPs has not been studied exhaustively, but the evidence currently available supports a role for inhibition of matrix degradation by TIMPs in this progressive fibrotic liver disease.

Tissue inhibitors of metalloproteinases (TIMP) in invasion and proliferation

Tissue inhibitors of matrix metalloproteinases (TIMPs) are a family of natural inhibitors that control the activity of matrix metalloproteinases (MMPs) in the extracellular matrix (ECM). Four members of this family have been so far characterized in a variety of species. These inhibitors share a similar structural feature characterized by the presence of 12 cysteine residues involved in disulfide bonds and a similar function by their ability to form inhibitory complexes with MMPs. The role of TIMPs in cancer has been the subject of conflicting reports with an antitumor activity reported by some investigators and a growth stimulation activity reported by others. Here we will discuss a series of data obtained in our laboratory supporting a role of TIMPs not only as inhibitors of invasion but also as regulators of cell growth. Using placental development as an example of a regulated invasive process, we have observed that the levels of TIMP-2 and TIMP-3 steadily increase between day 14.5 and 17.5 post-coitus. TIMPs are selectively expressed by spongiotrophoblastic cells that separate the labyrinthine zone, rich in fetal blood vessels and maternal blood sinuses, from the zone of giant cells forming the border between fetal and maternal tissues. TIMPs are also potent inhibitors of tumor growth in vivo. In melanoma cells, we have previously reported that over-expression of TIMP-2 inhibits the growth of tumors implanted in the skin of scid mice. This growth inhibition seems independent of angiogenesis but dependent on the collagen matrix. We observed that in the presence of fibrillar type I collagen, melanoma cells undergo a growth arrest at the G1 to S interphase transition of the cell cycle. This arrest is specific to the fibrillar structure of collagen because it is not observed in the presence of non-fibrillar collagen or other ECM components. It is associated with a specific upregulation of the cyclin inhibitor p27KIP1. The data therefore indicate that anchorage independent cells remain sensitive to growth regulatory signals that originate from the ECM and that these signals can specifically block tumor cell cycle. Thus our concept of the role of protease inhibitors such as TIMPs in cancer has substantially changed from an initial focus on inhibition of tumor invasion and metastasis to a broader focus on being molecules that--via their function as regulators of the ECM homeostasis--can control tumor cell growth.

Equine TIMP-1 and TIMP-2: identification, activity and cellular sources

Matrix metalloproteinases (MMPs) are the main enzymes involved in connective tissue turnover. Regulation of MMPs is achieved by controlling production, activation of the pro-enzymes together with the presence of inhibitors, such as, tissue inhibitors of metalloproteinases (TIMPS). The presence of TIMPs in equine synovial fluid was assessed by the ability of the fluid to inhibit equine MMP-9 activity using a gelatin degradation ELISA. The cellular source of the TIMPs was determined using culture supernatants of resident articular cells (chondrocytes and synovial fibroblasts) and invading inflammatory cells (polymorph neutrophils [PMN] and peripheral blood monocytes [PBM]). The TIMPs were characterised further using reverse zymography, affinity chromatography and N-terminal amino acid sequencing. Synovial fluid was recovered from horses with articular sepsis and aseptic joint disease (AJD) and compared with that from normal horses (n = 4). TIMP activity was minimal in articular sepsis but significantly increased, albeit a small increase, in AJD when compared to normal (P<0.05). Cell culture supernatants from synovial fibroblasts, chondrocytes and PBMs contained TIMP activity, although supernatants from PMN cell culture did not. Reverse zymography of synovial fluid recovered from normal and AJD horses showed two protein bands, 22 and 28 kDa in size, exhibiting inhibitory activity against MMP-9. Reverse zymography of culture supernatants of synovial fibroblasts and chondrocytes gave similar results whereas the culture supernatants from PMNs and PBMs showed the presence of only the 28 kDa protein. The N-terminal amino acid sequence was obtained for the 22 kDa protein and revealed a 66% homology with human TIMP-2. The identification of TIMPs in equine synovial fluids and cell culture supernatants suggest that they may have a fundamental role in the homeostasis of the normal joint and in the excess proteolysis which occurs in articular disease in the horse.

Regulated expression of matrix metalloproteinases and TIMP in nephrogenesis

The roles of the matrix metalloproteinases (MMPs) and their specific inhibitors, the tissue inhibitors of metalloproteinases (TIMP), in embryologic development in general, and in nephrogenesis in particular, have not been fully elucidated. The activities of these enzymes and their inhibitors may be critical in the extensive extracellular matrix remodeling that accompanies the formation of the full complement of mature nephrons in the developing kidney. The temporal and spatial expression of two critical basal lamina modifying enzymes, the 72 kDa gelatinase A (MMP-2) and the 92 kDa gelatinase B (MMP-9), as well as TIMP-1, -2, and -3 molecules were evaluated in the developing rat kidney. Additionally, transcripts for the recently described membrane-associated matrix metalloproteinase, MT1-MMP (MMP-14), which can act as an activating receptor for MMP-2/TIMP-2 complexes (Strongin et al.[1995] J. Biol. Chem. 270:5331-5338) were localized by in situ hybridization. Our immunohistochemical data demonstrate distinct localization of MMP-2 within immature nephron structures undergoing epithelial differentiation, while MMP-9 localizes only to the invading vascular structures within immature glomeruli. In contrast, by in situ hybridization, MMP-2 transcripts localize to the background undifferentiated mesenchyme and not to those structures undergoing epithelial differentiation. In a pattern similar to the MMP-2 protein, MT1-MMP transcripts were found within developing epithelial structures. Neither MMP-2, MMP-9 nor MT1-MMP were detected in mature nephrons. TIMP-2 and -3 follow a pattern of expression similar to the MMP-2 protein. We conclude that MMP-2 and TIMP play important roles in the remodeling of basal laminae associated with the epithelial structures of the developing kidney, that these enzymes are temporally and spatially regulated, and that the co-localization of MT1-MMP to sites of basement membrane remodeling suggests a potential role for this molecule as a receptor for and/or modulator of MMP-2/TIMP complexes.