Structure and function of matrix metalloproteinases and TIMPs

Metastasis-associated C4.4A, a GPI-anchored protein cleaved by ADAM10 and ADAM17

Metalloproteases play a complex role in tumor progression. While the activity of some ADAM, ADAMTS and matrix metalloproteases (MMPs) seems to be protumorigenic, the activity of others seems to prevent tumor progression. The identification of the array of substrates of a given metalloprotease (degradome) seems an adequate approach to predict the effect of the inhibition of a metalloprotease in tumors. Here, we present the proteomic identification of a novel substrate for ADAM10 and -17. We used SILAC (Stable Isotope Labeling by Amino acids in Cell culture), a proteomic technique based on the differential metabolic labeling of cells in different conditions. This was applied to MCF7 cells derived from an invasive mammary tumor, and the same cells expressing shRNAs that knock down ADAM10 or -17. Following this approach, we have identified C4.4A as a substrate to both metalloproteases. Since C4.4A is likely involved in tumor invasion, these results indicate that the cleavage of C4.4A by ADAM10 and ADAM17 contributes to tumor progression.

Role of the hemopexin domain of matrix metalloproteinases in cell migration

The biological functions of matrix metalloproteinases (MMPs) extend beyond extracellular matrix degradation. Non-proteolytic activities of MMPs are just beginning to be understood. Herein, we evaluated the role of proMMPs in cell migration. Employing a Transwell chamber migration assay, we demonstrated that transfection of COS-1 cells with various proMMP cDNAs resulted in enhancement of cell migration. Latent MMP-2 and MMP-9 enhanced cell migration to a greater extent than latent MMP-1, -3, -11 and -28. To examine if proteolytic activity is required for MMP-enhanced cell migration, three experimental approaches, including fluorogenic substrate degradation assay, transfection of cells with catalytically inactive mutant MMP cDNAs, and addition of hydroxamic acid-derived MMP inhibitors, were employed. We demonstrated that the proteolytic activities of MMPs are not required for MMP-induced cell migration. To explore the mechanism underlying MMP-enhanced cell migration, structure-function relationship of MMP-9 on cell migration was evaluated. By using a domain swapping approach, we demonstrated that the hemopexin domain of proMMP-9 plays an important role in cell migration when examined by a transwell chamber assay and by a phagokinetic migration assay. TIMP-1, which interacts with the hemopexin domain of proMMP-9, inhibited cell migration, whereas TIMP-2 had no effect. Employing small molecular inhibitors, MAPK and PI3K pathways were found to be involved in MMP-9-mediated cell migration. In conclusion, we demonstrated that MMPs utilize a non-proteolytic mechanism to enhance epithelial cell migration. We propose that hemopexin homodimer formation is required for the full cell migratory function of proMMP-9.

Unstable coronary plaques and cardiac events in myocardial infarction-prone Watanabe heritable hyperlipidemic rabbits: questions and quandaries

PURPOSE OF REVIEW

Use of suitable animal models is essential for investigation of the mechanisms underlying cardiac events and development of the therapeutic strategies; however, ideal animal models that can recapitulate human coronary atherosclerosis and subsequent acute myocardial infarction are still lacking. In this article, we review the insights learned from myocardial infarction-prone Watanabe heritable hyperlipidemic (designated as WHHLMI) rabbits and discuss the possibility of using this model for the study of human acute coronary syndromes.

RECENT FINDINGS

The vulnerable plaques of human coronary arteries are histologically characterized by a large lipid core and a thin fibrous cap with inflammatory cells. Recent studies have revealed that inflammatory cells and inflammatory mediators (such as cytokines and matrix metalloproteinases) play an important role in the plaque rupture.

SUMMARY

We developed the WHHLMI rabbit that shows spontaneous myocardial infarction caused by coronary atherosclerosis. The coronary lesions of WHHLMI rabbits have features of fatty streaks, fibrous plaques, and fibroatheromatous plaques. Some plaques contain a lipid core and a thin fibrous cap similar to human vulnerable plaques. In spite of this, the plaque rupture is not observed in WHHLMI rabbits, suggesting that other additional factors such as mechanical stress are required to trigger the rupture. WHHLMI rabbits may become an important means for elucidating the possible mechanisms of plaque rupture by exposing the plaques to additional risk factors beyond hyperlipidemia.

Plant extracellular matrix metalloproteinases

The plant extracellular matrix (ECM) includes a variety of proteins with critical roles in the regulation of plant growth, development, and responses to pests and pathogens. Several studies have shown that various ECM proteins undergo proteolytic modification. In mammals, the extracellular matrix metalloproteinases (MMPs) are known modifiers of the ECM, implicated in tissue architecture changes and the release of biologically active and/or signalling molecules. Although plant MMPs have been identified, little is known about their activity and function. Plant MMPs show structural similarity to mammalian MMPs, including the presence of an auto-regulatory cysteine switch domain and a zinc-binding catalytic domain. Plant MMPs are differentially expressed in cells and tissues during plant growth and development, as well as in response to several biotic and abiotic stresses. The few gene expression and mutant analyses to date indicate their involvement in plant growth, morphogenesis, senescence and adaptation and response to stress. In order to gain a further understanding of their function, an analysis and characterisation of MMP proteins, their activity and their substrates during plant growth and development are still required. This review describes plant MMP work to date, as well as the variety of genomic and proteomic methodologies available to characterise plant MMP activity, function and potential substrates.

Proteases and bone remodelling

Bone remodelling is regulated by osteogenic cells which act individually through cellular and molecular interaction. These interactions can be established either through a cell-cell contact, involving molecules of the integrin family, or by the release of many polypeptidic factors and/or their soluble receptor chains. Proteolytic shedding of membrane-associated proteins regulates the physiological activity of numerous proteins. Proteases located on the plasma membrane, either as transmembrane proteins or anchored to cell-surface molecules, serve as activators or inhibitors of different cellular and physiological processes. This review will focus on the role of the proteases implicated in bone remodelling either through the proteolytic degradation of the extracellular matrix or through their relations with osteogenic factors. Their implication in bone tumor progression will be also considered.

A new redox-dependent mechanism of MMP-1 activity control comprising reduced low-molecular-weight thiols and oxidizing radicals

Matrix metalloproteinases (MMPs), a family of zinc-dependent proteinases, participate in remodeling and degradation of the extracellular matrix proteins. The activity of MMPs is thought to be predominately posttranslationally regulated via proteolytic activation of precursor zymogens or via their naturally occurring endogenous inhibitors. Here, using recombinant MMP-1, we investigated new redox-dependent mechanisms of proteinase activity regulation by low-molecular-weight thiols. We find that glutathione (GSH), cysteine, homocysteine, and N-acetylcysteine at physiological concentrations competitively reduce MMP-1 activity up to 75% with an efficiency of cysteine > or = GSH > homocysteine > N-acetylcysteine. In contrast, S-derivatized thiols completely lack this inhibitory activity. Interestingly, the competitive GSH-mediated inhibition of MMP-1-activity can be fully reversed abrogated by oxidizing radicals like (*)NO(2) or Trolox radicals, here generated by UVA irradiation of nitrite or Trolox, two relevant agents in human skin physiology. This redox-dependent reactivation of the inactive GSH-MMP-1-complex comprises GSH oxidation and is significantly inhibited in the presence of ascorbic acid, an effective (*)NO(2) and Trolox radical scavenger. We here offer a new concept of redox-sensitive control of MMP-1 activity based on the inhibitory effect of reduced thiols and reactivation by a mechanism comprising derivatization or oxidation of the MMP-1-bound inhibitory-acting thiol.

Tissue inhibitor of metalloproteinases-4. The road less traveled

Tissue inhibitors of metalloproteinases (TIMPs) regulate diverse processes, including extracellular matrix (ECM) remodeling, and growth factors and their receptors' activities through the inhibition of matrix metalloproteinases (MMPs). Recent evidence has shown that this family of four members (TIMP-1 to TIMP-4) can also control other important processes, such as proliferation and apoptosis, by a mechanism independent of their MMP inhibitory actions. Of these inhibitors, the most recently identified and least studied is TIMP-4. Initially cloned in human and, later, in mouse, TIMP-4 expression is restricted to heart, kidney, pancreas, colon, testes, brain and adipose tissue. This restricted expression suggests specific and different physiological functions. The present review summarizes the information available for this protein and also provides a putative structural model in order to propose potential relevant directions toward solving its function and role in diseases such as cancer.

Macrophage roles following myocardial infarction

Following myocardial infarction (MI), circulating blood monocytes respond to chemotactic factors, migrate into the infarcted myocardium, and differentiate into macrophages. At the injury site, macrophages remove necrotic cardiac myocytes and apoptotic neutrophils; secrete cytokines, chemokines, and growth factors; and modulate phases of the angiogenic response. As such, the macrophage is a primary responder cell type that is involved in the regulation of post-MI wound healing at multiple levels. This review summarizes what is currently known about macrophage functions post-MI and borrows literature from other injury and inflammatory models to speculate on additional roles. Basic science and clinical avenues that remain to be explored are also discussed.

Matrix metalloproteinase inhibition reduces contraction by dupuytren fibroblasts

PURPOSE

Dupuytren's disease is a common fibroproliferative condition of the hand characterized by fibrotic lesions (nodules and cords), leading to disability through progressive digital contracture. Although the etiology of the disease is poorly understood, recent evidence suggests that abnormal matrix metalloproteinase (MMP) activity may play a role in cell-mediated collagen contraction and tissue scarring. The aim of this study was to investigate the efficacy of ilomastat, a broad-spectrum MMP inhibitor, in an in vitro model of Dupuytren fibroblast-mediated contraction.

METHODS

Nodule-derived and cord-derived fibroblasts were isolated from Dupuytren patients; carpal ligament-derived fibroblasts acted as control. Stress-release fibroblast-populated collagen lattices (FPCLs) were used as a model of contraction. FPCLs were allowed to develop mechanical stress (48 hours) during treatment with ilomastat (0-100 micromol/L), released, and allowed to contract over a 48-hour period. Contraction was estimated by measuring lattice area compared with untreated cells or treatment with a control peptide. MMP-1, MMP-2, and MT1-MMP levels were assessed by zymography, Western blotting, and enzyme-linked immunosorbent assay.

RESULTS

Nodule-derived fibroblasts contracted lattices (69% +/- 2) to a greater extent than did cord-derived (55% +/- 3) or carpal ligament-derived (55% +/- 1) fibroblasts. Exposure to ilomastat led to significant inhibition of lattice contraction by all fibroblasts, although a reduction in lattice contraction by nodule-derived fibroblasts was most prominent (84% +/- 8). In addition, treatment with ilomastat led to a concomitant suppression of MMP-1 and MMP-2 activity, whereas MT1-MMP activity was found to be upregulated.

CONCLUSIONS

Our results demonstrate that inhibition of MMP activity results in a reduction in extracellular matrix contraction by Dupuytren fibroblasts and suggest that MMP activity may be a critical target in preventing recurrent contracture caused by this disease.

Identification of amino acid residues of matrix metalloproteinase-7 essential for binding to cholesterol sulfate

Matrix metalloproteinase-7 (MMP-7; matrilysin) induces homotypic adhesion of colon cancer cells by cleaving cell surface protein(s) and enhances their metastatic potential. Our previous study (Yamamoto, K., Higashi, S., Kioi, M., Tsunezumi, J., Honke, K., and Miyazaki, K. (2006) J. Biol. Chem. 281, 9170-9180) demonstrated that binding of MMP-7 to cell surface cholesterol sulfate (CS) is essential for the cell membrane-associated proteolytic action of the protease. To determine the region of MMP-7 essential for binding to CS, we constructed chimeric proteases consisting of various parts of MMP-7 and those of the catalytic domain of MMP-2; the latter protease does not have an affinity for CS. Studies of these chimeric proteases and other mutants of MMP-7 revealed that Ile29, Arg33, Arg51, and Trp55, in the internal sequence, and the C-terminal three residues corresponding to residues 171-173 of MMP-7 are essential for binding to CS. An MMP-7 mutant, which had the internal 4 residues at positions 29, 33, 51, and 55 of MMP-7 replaced with the corresponding residues of MMP-2 and the C-terminal 3 residues deleted, had essentially no affinity for CS. This mutant and wild-type MMP-7 showed similar proteolytic activity toward fibronectin, whereas the mutant lacked the ability to induce the colon cancer cell aggregation. In the three-dimensional structure of MMP-7, the residues essential for binding to CS are located on the molecular surface in the opposite side of the catalytic cleft of the protease. Therefore, it is assumed that the active site of MMP-7 bound to cell surface is directed outside. We speculate that the direction of the cell-bound MMP-7 makes it feasible for the protease to cleave its substrates on cell surface.

Metastasis is strongly reduced by the matrix metalloproteinase inhibitor Galardin in the MMTV-PymT transgenic breast cancer model

Matrix metalloproteinases (MMP) have several roles that influence cancer progression and dissemination. However, low molecular weight metalloproteinase inhibitors (MPI) have not yet been tested in transgenic/spontaneous metastasis models. We have tested Galardin/GM6001, a potent MPI that reacts with most MMPs, in the MMTV-PymT transgenic breast cancer model. We followed a cohort of 81 MMTV-PymT transgenic mice that received Galardin, placebo, or no treatment. Galardin treatment was started at age 6 weeks with 100 mg/kg/d, and all mice were killed at age 13.5 weeks. Galardin treatment significantly reduced primary tumor growth. Final tumor burden in Galardin-treated mice was 1.69 cm3 compared with 3.29 cm3 in placebo-treated mice (t test, P = 0.0014). We quantified the total lung metastasis volume in the same cohort of mice. The median metastasis volume was 0.003 mm(3) in Galardin-treated mice compared with 0.56 mm(3) in placebo-treated mice (t test, P < 0.0001). Thus, metastasis burden was reduced more than 100-fold, whereas primary tumor size was reduced only 2-fold. We also found that primary tumors from Galardin-treated mice exhibited a lower histopathologic tumor grade, increased collagen deposition, and increased MMP-2 activity. MMPs are known to have tumor-promoting and tumor-inhibitory effects, and several clinical trials of broad-spectrum MPIs have failed to show promising effects. The very potent antimetastatic effect of Galardin in the MMTV-PymT model does, however, show that it may be possible to find broad-spectrum MPIs with favorable inhibition profiles, or perhaps combinations of monospecific MPIs, for future clinical application.

Matrix metalloproteinase inhibitors reduce collagen gel contraction and alpha-smooth muscle actin expression by periodontal ligament cells

BACKGROUND AND OBJECTIVE

Orthodontic tooth movement requires remodeling of the periodontal tissues. The matrix metalloproteinases (MMPs) degrade the extracellular matrix components of the periodontal ligament, while the tissue inhibitors of metalloproteinases (TIMPs) control their activity. Synthetic MMP inhibitors have been developed to inhibit MMP activity. In this study, periodontal ligament cells in contracting collagen gels served as a model for enhanced periodontal remodeling. The effect of MMP inhibitors on gel contraction and on MMP and TIMP expression was analyzed.

MATERIAL AND METHODS

Human periodontal ligament cells were cultured in three-dimensional collagen gels and incubated with the MMP inhibitors BB94, CMT-3, doxycycline and Ilomastat. Gel contraction was determined using consecutive photographs. The relative amounts of MMPs and TIMPs were analyzed using substrate zymography and mRNA expression using quantitative polyermase chain reaction.

RESULTS

All MMP inhibitors reduced MMP activity to about 20% of the control activity. They all reduced contraction, but CMT-3 and doxycycline had the strongest effect. These inhibitors also reduced MMP-2, MMP-3 and alpha-smooth muscle actin mRNA expression. The expression of MMP-1 mRNA seemed to be increased by CMT-3. No effects were found on the amounts of MMPs and TIMPs.

CONCLUSION

Synthetic MMP inhibitors strongly reduced gel contraction by periodontal ligament cells. This was primarily caused by an inhibitory effect on MMP activity, which reduces matrix remodeling. In addition, alpha-smooth muscle actin expression was reduced by CMT-3 and doxycycline, which limits the contractile activity of the fibroblasts.

Calcium pentosan polysulfate is a multifaceted exosite inhibitor of aggrecanases

Degradation of the cartilage proteoglycan aggrecan is a key early event in the development of osteoarthritis. Adamalysin with thrombospondin motifs (ADAMTS) -4 and ADAMTS-5 are considered to be the main enzymes responsible for aggrecan breakdown, making them attractive drugs targets. Here we show that calcium pentosan polysulfate (CaPPS), a chemically sulfated xylanopyranose from beechwood, is a multifaceted exosite inhibitor of the aggrecanases and protects cartilage against aggrecan degradation. CaPPS interacts with the noncatalytic spacer domain of ADAMTS-4 and the cysteine-rich domain of ADAMTS-5, blocking activity against their natural substrate aggrecan with inhibitory concentration 50 values of 10-40 nM but only weakly inhibiting hydrolysis of a nonglycosylated recombinant protein substrate. In addition, CaPPS increased cartilage levels of tissue inhibitor of metalloproteinases-3 (TIMP-3), an endogenous inhibitor of ADAMTS-4 and -5. This was due to the ability of CaPPS to block endocytosis of TIMP-3 mediated by low-density lipoprotein receptor-related protein. CaPPS also increased the affinity of TIMP-3 for ADAMTS-4 and -5 by more than 100-fold, improving the efficacy of TIMP-3 as an aggrecanase inhibitor. Studies with TIMP-3-null mouse cartilage indicated that CaPPS inhibition of aggrecan degradation is TIMP-3 dependent. These unique properties make CaPPS a prototypic disease-modifying agent for osteoarthritis.

Increased release and activity of matrix metalloproteinase-9 in patients with mandibuloacral dysplasia type A, a rare premature ageing syndrome

Mandibuloacral dysplasia type A (MADA; OMIM 248370), a rare disorder caused by mutation in the LMNA gene, is characterized by post-natal growth retardation, craniofacial and skeletal anomalies (mandibular and clavicular hypoplasia, acroosteolysis, delayed closure of cranial sutures, low bone mass and joint contractures), cutaneous changes and partial lipodystrophy. Little is known about the molecular mechanisms by which LMNA mutations produce bone alterations. An altered bone extracellular matrix (ECM) remodelling could play a pivotal role in this disorder and influence part of the typical bone phenotype observed in patients. Therefore, we have focused our investigation on matrix metalloproteinases (MMPs), which are degradative enzymes involved in ECM degradation and ECM remodelling, thus likely contributing to the altered bone mineral density and bone metabolism values seen in five MADA patients. We evaluated the serum levels of several MMPs involved in bone development, remodelling and homeostasis, such as MMP-9, -2, -3, -8 and -13, and found that only the 82 kDa active enzyme forms of MMP-9 are significantly higher in MADA sera compared with healthy controls (n = 16). The serum level of MMP-3 was instead lower in all patients. No significant differences were observed between controls and MADA patients for the serum levels of MMP-2, -8 and -13 and of tissue inhibitor of metalloproteinase 2, a natural inhibitor of MMP-9. Similarly, normal serum levels of tumour necrosis factor alpha (TNF-alpha), interleukin (IL)-6 and IL-1beta were detected. These data suggest a possible involvement of MMP-9 in MADA disease, underlying the potential use in diagnosis and therapy.

Progress in matrix metalloproteinase research

Matrix metalloproteinases (MMPs) are now acknowledged as key players in the regulation of both cell-cell and cell-extracellular matrix interactions. They are involved in modifying matrix structure, growth factor availability and the function of cell surface signalling systems, with consequent effects on cellular differentiation, proliferation and apoptosis. They play central roles in morphogenesis, wound healing, tissue repair and remodelling in response to injury and in the progression of diseases such as arthritis, cancer and cardiovascular disease. Because of their wide spectrum of activities and expression sites, the elucidation of their potential as drug targets in disease or as important features of the repair process will be dependent upon careful analysis of their role in different cellular locations and at different disease stages. Novel approaches to the specific regulation of individual MMPs in different contexts are also being developed.

Cleavage and functional loss of human apolipoprotein E by digestion of matrix metalloproteinase-14

By means of a degradomic approach applying proteomic techniques, we previously suggested that apolipoprotein E (apoE) is a substrate of matrix metalloproteinase-14 (MMP-14). Here we confirm that apoE is, in fact, a substrate of MMP-14 and also of MMP-7 and MMP-2 to a lesser extent. The 34 kDa apoE protein was initially processed by MMP-14 into fragments with molecular masses of 28, 23, 21, and 11 kDa. MMP-14 cleavage sites within the apoE protein were determined by C-terminal labeling of MMP-14-digested apoE fragments with isotope ((18)O/(16)O = 1:1) and identification of the doublet fragments or peptides showing 2 Da difference by MS, along with N-terminal sequencing of the fragments. It was determined that the primary MMP-14 cleavage sites were A(176)-I(177), P(183)-L(184), P(202)-L(203), and Q(249)-I(250). The MMP-14-mediated cleavage of apoE was consistent regardless of whether apoE existed in its lipid-bound or lipid-free form. Upon digestion with MMP-14, apoE loses its ability to suppress the platelet-derived growth factor-induced migration of rat vascular smooth muscle cells. Considering the important role of apoE for lipid metabolism and atherosclerosis protection, our findings suggest that MMP-14 plays an essential role for the development of hyperlipidemia and atherosclerosis as a result of degradation of apoE.

Dynamic changes in matrix metalloprotienase activity within the human myocardial interstitium during myocardial arrest and reperfusion

BACKGROUND

Past studies have clearly established that matrix metalloproteinases (MMPs) contribute to adverse myocardial remodeling with ischemia and reperfusion. However, these studies measured MMP levels in extracted samples, and therefore whether and to what degree actual changes in interstitial MMP activity occur within the human myocardium in the context of ischemia/reperfusion remained unknown.

METHODS AND RESULTS

The present study directly quantified MMP interstitial activity within the myocardium of patients (n=14) undergoing elective cardiac surgery during steady-state conditions, as well as during and following an obligatory period of myocardial arrest and reperfusion achieved by cardiopulmonary bypass. Interstitial MMP activity was continuously monitored using a validated MMP fluorogenic substrate, a microdialysis system placed within the myocardium, and in-line fluorescent detection system. MMP activity, as measured by fluorescent emission, reached a stable steady state level by 10 minutes after deployment of the microdialysis system. During initiation of cardiopulmonary bypass, MMP activity increased by 20% from baseline values (P<0.05), and then rapidly fell with cardiac arrest and longer periods of cardiopulmonary bypass. However, with restoration of myocardial blood flow and separation from cardiopulmonary bypass, MMP interstitial activity increased by over 30% from baseline (P<0.05).

CONCLUSIONS

The present study directly demonstrated that MMP proteolytic activity exists within the human myocardial interstitium and is a dynamic process under conditions such as myocardial arrest and reperfusion.

Matrix metalloproteinase 1 (MMP1) is associated with early-onset lung cancer

Matrix metalloproteinases (MMP) play a key role in the breakdown of extracellular matrix and in inflammatory processes. MMP1 is the most highly expressed interstitial collagenase degrading fibrillar collagens. Overexpression of MMP1 has been shown in tumor tissues and has been suggested to be associated with tumor invasion and metastasis. Nine haplotype tagging and additional two intronic single nucleotide polymorphisms (SNP) of MMP1 were genotyped in a case control sample, consisting of 635 lung cancer cases with onset of disease below 51 years of age and 1,300 age- and sex-matched cancer-free controls. Two regions of linkage disequilibrium (LD) of MMP1 could be observed: a region of low LD comprising the 5' region including the promoter and a region of high LD starting from exon 1 to the end of the gene and including the 3' flanking region. Several SNPs were identified to be individually significantly associated with risk of early-onset lung cancer. The most significant effect was seen for rs1938901 (P = 0.0089), rs193008 (P = 0.0108), and rs996999 (P = 0.0459). For rs996999, significance vanished after correction for multiple testing. For each of these SNPs, the major allele was associated with an increase in risk with an odds ratio between 1.2 and 1.3 (95% confidence interval, 1.0-1.5). The haplotype analysis supported these findings, especially for subgroups with high smoking intensity. In summary, we identified MMP1 to be associated with an increased risk for lung cancer, which was modified by smoking.

Protective action of doxycycline against diabetic cardiomyopathy in rats

BACKGROUND AND PURPOSE

Reactive oxygen and nitrogen species play an important role in the development of diabetic cardiomyopathy. They can activate matrix metalloproteinases (MMPs), and MMP-2 in particular is known to mediate early consequences of oxidative stress injury in the heart. Therefore, we investigated the role of MMP-2 and the effect of the MMP inhibitor doxycycline on the changes of heart function caused by diabetes.

EXPERIMENTAL APPROACH

Using streptozotocin-induced diabetic rats, we evaluated the effect of doxycycline on both mechanical and electrical function of isolated hearts, papillary muscle and cardiomyocytes.

KEY RESULTS

Doxycycline abolished the diabetes-induced depression in left ventricular developed pressure and the rates of changes in developed pressure in isolated hearts and normalized the prolongation of the action potential in papillary muscles. In cardiomyocytes isolated from doxycycline-treated diabetic rats, the altered kinetic parameters of Ca(2+) transients, depressed Ca(2+) loading of sarcoplasmic reticulum and basal intracellular Ca(2+) level, and the spatio-temporal properties of Ca(2+) sparks were significantly restored. Gelatin zymography and western blot data indicated that the diabetes-induced alterations in MMP-2 activity and protein level, level of tissue inhibitor of matrix metalloproteinase-4 and loss of troponin I were restored to control levels with doxycycline.

CONCLUSIONS AND IMPLICATIONS

Our data suggest that these beneficial effects of doxycycline on the mechanical, electrical and biochemical properties of the diabetic rat heart appear, at least in part, to be related to inhibition of MMP activity, implying a role for MMPs in the development of diabetic cardiomyopathy.

Epilysin (MMP-28)--structure, expression and potential functions

Epilysin (MMP-28) is the newest member of the matrix metalloproteinase (MMP) family of extracellular proteases. Together the MMPs can degrade almost all components of the extracellular matrix (ECM). MMPs also regulate cell behaviour by releasing growth factors and biologically active peptides from the ECM by modulating cell surface receptors and adhesion molecules and by regulating the activity of mediators of the inflammatory pathways. Epilysin differs from most other MMPs as it is expressed in a number of normal tissues, suggestive of functions in tissue homeostasis. The epilysin homologue in Xenopus laevis (XMMP-28) is expressed in neural tissues, where it cleaves the neural cell adhesion molecule. Enhanced expression of epilysin has been observed in basal keratinocytes during wound healing and in different forms of cancer. There are, however, also reports on the downregulation of epilysin in malignant cells. The roles of epilysin in cancer seem to vary based on tumor type and stage of the disease. Importantly, epilysin can induce stable epithelial to mesenchymal transition (EMT) when overexpressed in epithelial lung carcinoma cells. Transforming growth factor beta (TGF-beta) is a crucial mediator of this process, which was characterized by the loss of E-cadherin and increased cell migration and invasion. Current results suggest a plausible interaction between epilysin and TGF-beta also under physiological circumstances, where epilysin activity may not induce EMT but, instead, trigger less permanent changes in TGF-beta signalling and cell motility.

A macrophage cell model for selective metalloproteinase inhibitor design

The desire to inhibit zinc-dependent matrix metalloproteinases (MMPs) has, over the course of the last 30 years, led to the development of a plethora of MMP inhibitors that bind directly to the active-site metal. With one exception, all of these drugs have failed in clinical trials, due to many factors, including an apparent lack of specificity for MMPs. To address the question of whether these inhibitors are selective for MMPs in a biological setting, a cell-based screening method is presented to compare the relative activities of zinc, heme iron, and non-heme iron enzymes in the presence of these compounds using the RAW264.7 macrophage cell line. We screened nine different zinc-binding groups (ZBGs), four established MMP inhibitors (MMPis), and two novel MMP inhibitors developed in our laboratory to determine their selectivities against five different metalloenzymes. Using this model, we identified two nitrogen donor compounds--2,2'-dipyridylamine (DPA) and triazacyclononane (TACN)--as the most selective ZBGs for zinc metalloenzyme inhibitor development. We also demonstrated that the model could predict known nonspecific interactions of some of the most commonly used MMPis, and could also give cross-reactivity information for newly developed MMPis. This work demonstrates the utility of cell-based assays in both the design and the screening of novel metalloenzyme inhibitors.

Extracellular matrix profiles in the progression to heart failure. European Young Physiologists Symposium Keynote Lecture-Bratislava 2007

The myocardial extracellular matrix (ECM), which preserves the geometry and integrity of the myocardium, is a dynamic structure whose component proteins are maintained by a finely controlled homeostatic balance between deposition and degradation. One of the key targets in cardiology is the elucidation of the molecular mechanisms which mediate pathological remodelling of this matrix causing the transition from compensatory hypertrophy to congestive decompensated heart failure. In response to injury or increased workload, cardiac remodelling including myocyte hypertrophy, develops as the heart attempts to compensate for increased wall stresses. Persistence of these stresses over extended time periods leads to disruption of ECM homeostasis resulting in irreversible maladaptive cardiac remodelling, ventricular dilatation and finally heart failure. ECM remodelling is regulated by the matrix metalloproteinases (MMPs) and their endogenous inhibitors (TIMPs). Clinical studies and experimental models of cardiac disease states have reported alterations in the balance between the MMPs and TIMPs in the failing heart and crucially at intermediate time points in the progression to failure. This article reviews the recent clinical, genetic and experimental approaches employed to compare ECM, MMP and TIMP profiles in healthy, compensated and failing hearts and identifies common themes in the perturbation of ECM homeostasis in the transition to heart failure.

Effect of parenteral zinc sulfate on colon anastomosis repair in the rat

BACKGROUND AND AIMS

To prevent colonic anastomotic dehiscence, pharmaceutical interventions should inhibit degradation of existing submucosal collagen fibers and accelerate the synthesis of new collagen molecules. Zinc has multiple functions in collagen metabolism and was recently found beneficial in colonic anastomosis repair. We have investigated the effect of daily intraperitoneal zinc (2 mg/kg) injections on the development of the biomechanical integrity of left colon anastomoses.

MATERIALS AND METHODS

Sixty Sprague-Dawley male rats (median 245 g) were allocated to treatment with zinc sulfate in saline (n = 30) or with saline alone (n = 30) starting 1 h before the anastomoses were made. Serum zinc levels and anastomotic breaking strength were determined on postoperative days 3 (n = 30) and 7 (n = 30). The initial breaking strength or suture-binding capacity was determined in additional ten non-treated animals (277 g).

RESULTS

The breaking strength of the anastomoses decreased in the two groups combined (n = 30) by 50% (p < 0.001) on day 3 but was regained by postoperative day 7 compared with the initial anastomotic biomechanical strength. Serum zinc levels also increased from day 3 to day 7 in both intervention groups and correlated significantly with breaking strength (r = 0.57, p < 0.001). Although the median serum zinc level was 14% higher (p < 0.01) on day 7 in zinc-treated than in saline-treated animals, the breaking strength did not differ significantly between zinc-treated and saline-treated rats on either day 3 (p = 0.95) or day 7 (p = 0.70).

CONCLUSION

In contrast to previous report in rabbits, we failed to demonstrate the beneficial effects of parenteral zinc supplementation on colon anastomosis repair in a rat model.

Cardiac-restricted overexpression of extracellular matrix metalloproteinase inducer causes myocardial remodeling and dysfunction in aging mice

The matrix metalloproteinases (MMPs) play a pivotal role in adverse left ventricular (LV) myocardial remodeling. The transmembrane protein extracellular MMP inducer (EMMPRIN) causes increased MMP expression in vitro, and elevated levels occur in patients with LV failure. However, the direct consequences of a prolonged increase in the myocardial expression of EMMPRIN in vivo remained unexplored. Cardiac-restricted EMMPRIN expression (EMMPRINexp) was constructed in mice using the full-length human EMMPRIN gene ligated to the myosin heavy chain promoter, which yielded approximately a twofold increase in EMMPRIN compared with that of the age/strain-matched wild-type (WT) mice; EMMPRINexp (n=27) and WT (n=33) mice were examined at 3.2+/-0.1 or at 13.3+/-0.5 mo of age (n=43 and 26, respectively). LV end-diastolic volume (EDV) was similar in young EMMPRINexp and WT mice (54+/-2 vs. 57+/-3 microl), but LV ejection fraction (EF) was reduced (51+/-1 vs. 57+/-1%; P<0.05). In old EMMPRINexp mice, LV EDV was increased compared with WT mice values (76+/-3 vs. 58+/-3 microl; P<0.05) and LV EF was significantly reduced (45+/-1 vs. 57+/-2%; P<0.05). In EMMPRINexp old mice, myocardial MMP-2 and membrane type-1 MMP levels were increased by >50% from WT values (P<0.05) and were accompanied by a twofold higher collagen content (P<0.05). Persistent myocardial EMMPRINexp in aging mice caused increased levels of both soluble and membrane type MMPs, fibrosis, and was associated with adverse LV remodeling. These findings suggest that EMMPRIN is an upstream signaling pathway that can play a mechanistic role in adverse remodeling within the myocardium.

Mechanisms of arterial remodeling in hypertension: coupled roles of wall shear and intramural stress

Hypertension causes and is caused by significant changes in the structure and function of arteries. Diverse data collected over the past four decades reveal that many of these changes result from a mechanical stress or strain mediated reorganization and turnover of cells and extracellular matrix in vasoaltered states that promotes a “mechanical homeostasis.” This paper reviews diverse data on the mechanobiological behaviors of vascular cells (endothelial, smooth muscle, and fibroblasts) and associated changes that manifest at the tissue level. Although experimental design is often motivated by the thought that altered flow largely affects arterial caliber and altered pressure largely affects wall thickness, all three primary descriptors of vessel geometry (radius, thickness, length) are coupled strongly to all three primary measures of stress (wall shear, circumferential, axial). Hence, mechanobiological responses by resident cells should likewise be expected to be sensitive to all three primary stresses. It also appears that cellular production of vasoactive molecules, growth factors, cytokines, matrix proteins, and proteases depends nonlinearly, often sigmoidally, on changes in stress. This suggests that there is a need to quantify coupled, nonlinear “mechanical dose response curves” that correlate altered stresses with cellular activity; moreover, mathematical models can help integrate such information across multiple length scales (from molecule to cell and tissue) and time scales (from minutes to days and months). For example, quantification of stress mediated synthesis and cross-linking of collagen organization within the hypertensive arterial wall, and associated signaling pathways, may suggest new therapeutic strategies based on targeted levels of inhibition.

Prolonged increases in vein wall tension increase matrix metalloproteinases and decrease constriction in rat vena cava: Potential implications in varicose veins

BACKGROUND

Increased venous hydrostatic pressure plays a role in the pathogenesis of varicose veins. Increased expression of matrix metalloproteinases (MMPs) has been identified in varicose veins. Also, we have shown that MMP-2 inhibits venous contraction. However, the relation between venous pressure, MMP expression, and venous dysfunction is unclear. The purpose of this study was to test the hypothesis that prolonged increases in venous wall tension cause overexpression of MMPs and decreased contractility, which in turn promote venous dilation.

METHODS

Circular segments of inferior vena cava (IVC) were isolated from male Sprague-Dawley rats and suspended between two wires in Krebs solution. Preliminary vein wall tension-contraction relation showed maximal potassium chloride (KCl) (96 mmol/L) contraction at 0.5 g basal tension, which remained steady with increases in tension up to 2 g. Vein segments were subjected to either control (0.5 g) or high (2 g) basal tension for short (1 hour) or long duration (24 hours). Isometric contraction in response to phenylephrine (Phe, 10(-5) mol/L), angiotensin II (AngII, 10(-6) mol/L), and KCl was measured. The veins were frozen to determine the expression and localization of MMPs using immunoblots and immunohistochemistry.

RESULTS

In IVC segments subjected to 0.5 g tension for 1 hour, Phe and AngII produced significant contraction. At higher 2 g basal tension for 24 hours, both Phe and AngII contractions were significantly reduced. Reduction in KCl contraction was also observed at high 2 g basal tension for 24 hours, suggesting that the reduction in vein contraction is not specific to a particular receptor, and likely involves inhibition of a post-receptor contraction mechanism. In vein segments under 2 g tension for 24 hours and treated with TIMP-1, Phe, AngII, and KCl contractions were partially restored, suggesting the involvement of MMPs. IVC immunoblot analysis demonstrated prominent bands corresponding to MMP-2 and MMP-9 protein. High 2 g wall tension for 24 hours was associated with marked increase in the amount of MMP-2 and -9 relative to the housekeeping protein actin. There was a correlation between MMP expression and decreased vein contraction. Also, significant increases in MMP-2 and -9 immunostaining were observed in IVC segments subjected to high 2 g tension for 24 hours. Both MMP-2 and MMP-9 caused significant inhibition of Phe contraction in IVC segments.

CONCLUSIONS

In rat IVC, increases in magnitude and duration of wall tension is associated with reduced contraction and overexpression of MMP-2 and -9. In light of our findings that MMP-2 and -9 promote IVC relaxation, the data suggest that protracted increases in venous pressure and wall tension increase MMPs expression, which in turn reduce venous contraction and lead to progressive venous dilation.

MT1-MMP regulates urothelial cell invasion via transcriptional regulation of Dickkopf-3

Membrane type-1 matrix metalloproteinase (MT1-MMP) is a zinc-binding endopeptidase, which plays a crucial role in tumour growth, invasion and metastasis. We have shown previously that MT1-MMP has higher expression levels in the human urothelial cell carcinoma (UCC) tissue. We show here that siRNA against MT1-MMP blocks invasion in UCC cell lines. Invasion is also blocked by broad-spectrum protease and MMP inhibitors including tissue inhibitor of metalloproteinase-1 and -2. Membrane type-1-MMP can also regulate transcription. We have used expression arrays to identify genes that are differentially transcribed when siRNA is used to suppress MT1-MMP expression. Upon MT1-MMP knockdown, Dickkopf-3 (DKK3) expression was highly upregulated. The stability of DKK3 mRNA was unaffected under these conditions, suggesting transcriptional regulation of DKK3 by MT1-MMP. Dickkopf-3 has been previously shown to inhibit invasion. We confirm that the overexpression of DKK3 leads to decreased invasive potential as well as delayed wound healing. We show for the first time that the effects of MT1-MMP on cell invasion are mediated in part through changes in DKK3 gene transcription.

Advances in assays of matrix metalloproteinases (MMPs) and their inhibitors

Matrix metalloproteinases (MMPs) play an important role in many physiological and pathological processes. To assay the activities of MMPs is important in diagnosis and therapy of the MMPs associated diseases, such as neoplastic, rheumatic and cardiovascular diseases. Several assay systems have been developed, which include bioassay, zymography assay, immunoassay, fluorimetric assay, radio isotopic assay, phage-displayed assay, multiple-enzyme/multiple-reagent assay and activity-based profiling assay. The principle, application, advantage and disadvantage of these assays have been reviewed in this article.

The design of inhibitors for medicinally relevant metalloproteins

A number of metalloproteins are important medicinal targets for conditions ranging from pathogenic infections to cancer. Many but not all of these metalloproteins contain a zinc(II) ion in the protein active site. Small-molecule inhibitors of these metalloproteins are designed to bind directly to the active site metal ions. In this review several metalloproteins of interest are discussed, including matrix metalloproteinases (MMPs), histone deacetylases (HDACs), anthrax lethal factor (LF), and others. Different strategies that have been employed to design effective inhibitors against these proteins are described, with an effort to highlight the strengths and drawbacks of each approach. An emphasis is placed on examining the bioinorganic chemistry of these metal active sites and how a better understanding of the coordination chemistry in these systems may lead to improved inhibitors. It is hoped that this review will help inspire medicinal, biological, and inorganic chemists to tackle this important problem by considering all aspects of metalloprotein inhibitor design.

IL-13 attenuates vascular tube formation via JAK2-STAT6 pathway

BACKGROUND

Interleukin (IL)-13, which is a cytokine produced by type 2 helper T cells, has pathophysiological roles in allergic inflammation and fibrosis formation. IL-13 shares many functional properties with IL-4, which is known to inhibit angiogenesis.

METHODS AND RESULTS

The effects of IL-13 on angiogenesis were examined using human coronary artery endothelial cells (HCAECs), in addition to investigating the mechanism(s) of this action. Using an in vitro assay of angiogenesis it was demonstrated that IL-13, as well as IL-4, significantly inhibited capillary-like tube formation. Migration of HCAECs, considered to be a process of new capillary tube formation, was also significantly inhibited by IL-13. IL-13 activated signal transduction and transcription 6 (STAT6) as a result of the activation of Janus kinase 2 (JAK2). The inhibitory effect of IL-13 on angiogenesis was abolished by depletion of JAK2 and STAT6 by RNA interference.

CONCLUSION

IL-13 has anti-angiogenic activity as a result of activation of JAK2 and subsequent activation of STAT6.

Matrix metalloproteinase levels in children with aggressive periodontitis

BACKGROUND

Matrix metalloproteinases (MMPs) are a family of host-derived proteinases reported to mediate multiple functions associated with periodontal destruction and inflammation. Most of the existing data have been gathered from adults with chronic periodontitis. The purpose of this study was to determine the MMP levels in a cohort of African American children with and without aggressive periodontitis.

METHODS

Gingival crevicular fluid (GCF) was collected in a cohort of 44 African American children, 7 to 19 years of age, with and without aggressive periodontitis (AgP) and compared to healthy unrelated children and to adults with chronic periodontitis (CP). GCF volume was determined with a calibrated gingival fluid meter. The samples were assayed for MMP-1, -2, -3, -8, -9, -12, and -13 using fluorimetric substrates.

RESULTS

The MMP levels from diseased sites in the subjects with AgP were statistically higher (P <0.05) in almost all instances than those associated with the unrelated controls or with the subjects with CP. MMP-8 was significantly elevated in the diseased sites of the children with AgP relative to non-diseased sites in the same children (P = 0.002), as well as the siblings, non-diseased controls, and subjects with CP (P < or =0.0001). There was no positive correlation between probing depth and any MMP level.

CONCLUSIONS

MMP levels were elevated in AgP sites relative to non-diseased sites in the same subjects, in siblings, and in unrelated controls. MMPs associated with the AgP sites in children were generally elevated compared to an adult cohort with a history of CP.

Matrix metalloproteinases and bone

Matrix metalloproteinases (MMPs) are members of a family of zinc-dependent proteolytic enzymes. Several of the MMPs are expressed at high levels in bone and cartilage in mammals including humans and mice and are capable of cleaving native, undenatured collagens with long uninterrupted triple helices; these MMPs therefore potentially function as collagenases in vivo. Several MMPs expressed in the skeleton appear to function in endochondral ossification during embryonic development and in modeling and remodeling of bone postnatally and later in life. Different functions of MMPs have been elucidated through observations of spontaneous mutations in MMP genes in humans and of targeted mutations in Mmp genes and collagen (substrate) genes in mice. Potential mechanisms to account for effects of these mutations are considered in this review.

The role of megsin, a serine protease inhibitor, in diabetic mesangial matrix accumulation

In diabetic nephropathy decreased activities of matrix metalloproteinase (MMP)-2, MMP-9 and plasmin contribute to mesangial matrix accumulation. Megsin, a novel member of the serine protease inhibitor superfamily, is predominantly expressed in mesangial cells and is up-regulated in diabetic nephropathy and its overexpression spontaneously induces progressive mesangial expansion in mice. High-glucose stimulated megsin mRNA expression in an in vivo model of type II diabetic nephropathy as well as in vitro in cultured mesangial cells. Megsin potentially inhibits total enzymatic activities of MMP-2 and -9 and plasmin, indicating decreased degradation of mesangial matrix. A specific monoclonal anti-megsin neutralizing antibody restored MMP activity in a transforming growth factor-beta independent manner. Our study suggests that the mesangial matrix accumulation caused by hyperglycemia in diabetes might be due at least in part to up-regulation of megsin which can inhibit plasmin and MMP activities.

Zinc metalloproteins as medicinal targets

Zinc bioinorganic chemistry has emphasized the role of the metal ion on the structure and function of the protein. There is, more recently, an increasing appreciation of the role of zinc proteins in a variety of human diseases. This critical review, aimed at both bioinorganic and medicinal chemists, shows how apparently widely-diverging diseases share the common mechanistic approaches of targeting the essential function of the metal ion to inhibit activity. Protein structure and function is briefly summarized in the context of its clinical relevance. The status of current and potential inhibitors is discussed along with the prospects for future developments (162 references).

Potentiation and priming of platelet activation: a potential target for antiplatelet therapy

Ischemic cardiovascular events represent the leading cause of mortality and morbidity worldwide, and platelet aggregation and thrombus formation are the main effectors of acute arterial ischemic events. Although antiplatelet therapy is the cornerstone of antithrombotic treatment of ischemic cardiovascular disorders, available antiplatelet agents have less than satisfactory efficacy; thus, the identification of novel potential target candidates for antiplatelet therapy is highly warranted. Recent evidence suggests that several molecules that amplify the aggregation response of platelets to activating stimuli, which are either released by platelets (potentiating molecules) or present in the milieu before platelets get activated (primers), play a major role in pathologic thrombus formation without being significantly involved in primary haemostasis. These molecules appear to be a particularly appealing novel potential pharmacologic target for antiplatelet therapy. Here, we review the present knowledge on some molecules acting as potentiators or primers of platelet activation and discuss their possible pharmacologic modulation for antithrombotic purposes.

MMP19 is essential for T cell development and T cell-mediated cutaneous immune responses

Matrix metalloproteinase-19 (MMP19) affects cell proliferation, adhesion, and migration in vitro but its physiological role in vivo is poorly understood. To determine the function of MMP19, we generated mice deficient for MMP19 by disrupting the catalytic domain of mmp19 gene. Although MMP19-deficient mice do not show overt developmental and morphological abnormalities they display a distinct physiological phenotype. In a model of contact hypersensitivity (CHS) MMP19-deficient mice showed impaired T cell-mediated immune reaction that was characterized by limited influx of inflammatory cells, low proliferation of keratinocytes, and reduced number of activated CD8(+) T cells in draining lymph nodes. In the inflamed tissue, the low number of CD8(+) T cells in MMP19-deficient mice correlated with low amounts of proinflammatory cytokines, especially lymphotactin and interferon-inducible T cell alpha chemoattractant (I-TAC). Further analyses showed that T cell populations in the blood of immature, unsensitized mice were diminished and that this alteration originated from an altered maturation of thymocytes. In the thymus, thymocytes exhibited low proliferation rates and the number of CD4(+)CD8(+) double-positive cells was remarkably augmented. Based on the phenotype of MMP19-deficient mice we propose that MMP19 is an important factor in cutaneous immune responses and influences the development of T cells.

Inhibiting metalloproteases with PD 166793 in heart failure: impact on cardiac remodeling and beyond

Metalloproteinases (MMPs, also called matrixins) are extracellular proteolytic enzymes involved in the degradation of both matrix and nonmatrix proteins. Currently, 25 MMPs have been identified in humans, and the overexpression of one or more MMPs has been implicated in several pathologies, spanning from cancer to rheumathoid arthritis to cardiovascular disease. While research over the past 20 years has focused on understanding MMP biology and selectively inhibiting MMP activity, key issues that remain to be addressed include MMP roles in the context of normal versus pathological conditions and whether globally inhibiting MMPs improves or deteriorates overall organ function. In terms of cardiovascular disease, increased MMP expression has been demonstrated in the setting of myocardial ischemia, reperfusion injury, and during the progression to congestive heart failure. MMPs are also major contributors to the progression of atherosclerotic lesions. In this review, we focus on cardiovascular effects produced by PD 166793, a wide-broad spectrum MMP inhibitor, originally developed by Parke-Davis (now Pfizer). We will briefly review its structure, mechanism of action, and inhibitory capacity. Finally, we will illustrate the cardiac contexts, both in vivo and in vitro, in which PD166793 administration has proven beneficial.