Biological and pathobiological functions of gelatinase dimers and complexes

N-Terminomic Identification of Intracellular MMP-2 Substrates in Cardiac Tissue

Proteases are enzymes that induce irreversible post-translational modifications by hydrolyzing amide bonds in proteins. One of these proteases is matrix metalloproteinase-2 (MMP-2), which has been shown to modulate extracellular matrix remodeling and intracellular proteolysis during myocardial injury. However, the substrates of MMP-2 in heart tissue are limited, and lesser known are the cleavage sites. Here, we used degradomics to investigate the substrates of intracellular MMP-2 in rat ventricular extracts. First, we designed a novel, constitutively active MMP-2 fusion protein (MMP-2-Fc) that we expressed and purified from mammalian cells. Using this protease, we proteolyzed ventricular extracts and used subtiligase-mediated N-terminomic labeling which identified 95 putative MMP-2-Fc proteolytic cleavage sites using mass spectrometry. The intracellular MMP-2 cleavage sites identified in heart tissue extracts were enriched for proteins primarily involved in metabolism, as well as the breakdown of fatty acids and amino acids. We further characterized the cleavage of three of these MMP-2-Fc substrates based on the gene ontology analysis. We first characterized the cleavage of sarco/endoplasmic reticulum calcium ATPase (SERCA2a), a known MMP-2 substrate in myocardial injury. We then characterized the cleavage of malate dehydrogenase (MDHM) and phosphoglycerate kinase 1 (PGK1), representing new cardiac tissue substrates. Our findings provide insights into the intracellular substrates of MMP-2 in cardiac cells, suggesting that MMP-2 activation plays a role in cardiac metabolism.

Structural and functional role of invariant water molecules in matrix metalloproteinases: a data-mining approach

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases known to degrade extracellular matrix (ECM). Being involved in many biological and physiological processes of tissue remodeling, MMPs play a crucial role in many pathological conditions such as arthritis, cancer, cardiovascular diseases, etc. Typically, MMPs possess a propeptide, a zinc-containing catalytic domain, a hinge region and a hemopexin domain. Based on their structural domain organization and substrates, MMPs are classified into six different classes, viz. collagenases, stromelysins, gelatinases, matrilysins, membrane-type and other MMPs. As per previous studies, a set of invariant water (IW) molecules of MMP-1 (a collagenase) play a significant role in stabilizing their catalytic domain. However, a functional role of IW molecule in other classes of MMPs has not been reported yet. Thus, in this study, IW molecules of MMPs from different classes were located and their plausible role(s) have been assigned. The results suggest that IW molecules anchor the structurally and functionally essential metal ions present in the vicinity of the active site of MMPs. Further, they (in)directly interlink different structural features and bridge the active site metal ions of MMPs. This study provides the key IW molecules that are structurally and functionally relevant to MMPs and hence, in turn, might facilitate the development of potent generalized inhibitor(s) against different classes of MMPs. Communicated by Ramaswamy H. Sarma.

A genetic investigation of equine recurrent uveitis in the Icelandic horse breed

Equine recurrent uveitis (ERU) is an autoimmune disease defined by inflammation of the uveal tract of the eye. The cause of ERU is thought to be complex, involving both genetic and environmental factors. The purpose of this study was to investigate potential genetic risk factors for ERU in the Icelandic horse. Fifty-six Icelandic horses (11 affected with ERU and 45 controls) living in Denmark and the USA, eight years or older, were included in the study. A case-control GWAS was performed using the GGP Equine 80K array on the Illumina Infinium HD Beadchip using 40 horses. A mixed linear model analysis identified a single SNP on ECA 11 (BIEC2_141650; NC_009154.3:g.3817009A>G) that reached genome-wide significance (p = 1.79 × 10^-7 ). This variant was within an intron of tissue inhibitor of metalloproteinase 2 (TIMP2), a gene previously implicated in ERU. Sanger sequencing identified a single coding variant in this gene; however it was a synonymous mutation (NC_009154.3:g.3858193C>T) and was not perfectly concordant with ERU phenotype (p = 0.68). Further investigation of TIMP2 is warranted. Additional horses and markers are needed to identify other potential loci worthy of further investigation as contributors to ERU risk in Icelandic horses.

Inhibitory Effects of Gyeji-Tang on MMP-9 Activity and the Expression of Adhesion Molecules in IL-4- and TNF-α-Stimulated BEAS-2B Cells

Gyeji-tang (GJT), a traditional herbal formula composed of five herbal medicines, is commonly used to treat the common cold, exogenous febrile disease, fever and headaches in Korea, China and Japan. Although various pharmacological activities of GJT have been reported in several studies, the effect of GJT water extract (GJTWE) on airway inflammation has not yet been investigated. This study aimed to evaluate the effects of GJTWE on airway inflammation-related factors using human bronchial epithelial BEAS-2B cells, and to identify the phytochemicals in GJTWE by ultra-performance liquid chromatography-diode array detector-tandem mass spectrometry (UPLC-DAD-MS/MS) analysis. GJTWE significantly decreased the production of chemokines, including eotaxin-3, eotaxin-1, regulated on activation normal T-cell expressed and secreted (RANTES), and matrix metalloproteinase-9, and the expression of the adhesion molecules, intercellular adhesion molecule-1 and vascular cell adhesion molecule-1, in interleukin-4 + tumor necrosis factor-α (IT)-stimulated BEAS-2B cells. In the UPLC-DAD-MS/MS analysis, 21 phytochemicals, including six flavonoids, two chalcones, five terpenoids, six phenolics, one phenylpropanoid and one coumarin, were identified in GJTWE. The findings suggested that GJTWE might exhibit anti-inflammatory effects on airway inflammation by regulating the expression of inflammatory response-related factors in IT-stimulated BEAS-2B cells; further studies are required to determine the bioactive compounds involved in the inhibition of airway inflammation.

Cissus quadrangularis (veldt grape) attenuates disease progression and anatomical changes in mono sodium iodoacetate (MIA)-induced knee osteoarthritis in the rat model

The Cissus quadrangularis (CQ) stem has interesting nutritional and pharmacological properties to promote the health of the skeletal system. It is a well-recognized plant in the conventional system of medicine in India for treating bone and joint-associated complications. This study focuses on identifying the active constituents from the stem and root extracts of CQ and validating its anti-osteoarthritic activity by the in vivo model. Notable levels of phenolics and flavonoids were found in the ethanol extracts of both CQ stem (CQSE) and root (CQRE), among other solvent fractions. UPLC-MS/MS analysis of these selective extracts resulted in different classes of active compounds from both positive and negative ionization modes. By analyzing their mass spectra and fragmentation pattern, 25 active compounds were identified. The CQSE and CQRE extracts, along with the standard drug (naproxen), were further tested in mono-sodium iodoacetate-induced experimental OA animals. The modulatory effects of the test extracts were assessed by haematology, synovial and cartilage marker profiling, radiology and histopathological analysis. The in vivo findings from the biochemical and physiological studies have led to the conclusion that the CQSE extract is a good choice for the management of OA. The results were substantially better than CQ root extract and naproxen drug-treated groups. Thus, CQS has bioactive constituents, which could facilitate recovery from joint tissue damage, cellular metabolism and associated risk factors attributable to dysfunctions in OA incidence and progression.

Glycemic Response and Bioactive Properties of Gluten-Free Bread with Yoghurt or Curd-Cheese Addition

The influence of flour replacement by yogurt or curd-cheese additions (from 10% to 20%, w/w) on the glycemic response and bioactivity improvements of gluten-free bread was evaluated. Starch digestibility, measured by an in vitro digestion model, was applied to determine the effect on starch fractions. The bread glycemic index was calculated. Bread antioxidant capacity (2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) and ferric-ion-reducing antioxidant power (FRAP) methods) and total phenolic compounds were assessed. Anti-inflammatory properties according to enzymatic matrix metalloproteinase (MMP)-9 inhibitory activity were also studied. Considering the higher level of both dairy products tested (20%, w/w) and comparing with control bread results, a reduction of around 35% in the glycemic response of curd cheese bread was achieved, resulting in intermediate index level (glycemic index (GI) 55-69), with yogurt bread still showing a high glycemic index (GI > 70). In terms of bread bioactivity, curd cheese bread expressed better reducing power effects, whereas yogurt bread showed more effective radical-scavenging capacity. An increase in bread phenolic compounds by yogurt (55.3%) and curd cheese (73.0%) additions (at 20%) were also registered. MMP-9 inhibition activity was higher in the dairy bread than in control bread, suggesting an improvement in terms of anti-inflammatory properties. The supplementation of the gluten-free bread by yogurt or curd cheese was shown to be a promising strategy to reduce the glycemic response and to improve the bioactive properties of the bread, that which can contribute to preventive diets of celiac patients and irritable bowel syndrome individuals.

Disturbed balance in the expression of MMP9 and TIMP3 in cerebral amyloid angiopathy-related intracerebral haemorrhage

Cerebral amyloid angiopathy (CAA) is characterized by the deposition of the amyloid β (Aβ) protein in the cerebral vasculature and poses a major risk factor for the development of intracerebral haemorrhages (ICH). However, only a minority of patients with CAA develops ICH (CAA-ICH), and to date it is unclear which mechanisms determine why some patients with CAA are more susceptible to haemorrhage than others. We hypothesized that an imbalance between matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) contributes to vessel wall weakening. MMP9 plays a role in the degradation of various components of the extracellular matrix as well as of Aβ and increased MMP9 expression has been previously associated with CAA. TIMP3 is an inhibitor of MMP9 and increased TIMP3 expression in cerebral vessels has also been associated with CAA. In this study, we investigated the expression of MMP9 and TIMP3 in occipital brain tissue of CAA-ICH cases (n = 11) by immunohistochemistry and compared this to the expression in brain tissue of CAA cases without ICH (CAA-non-haemorrhagic, CAA-NH, n = 18). We showed that MMP9 expression is increased in CAA-ICH cases compared to CAA-NH cases. Furthermore, we showed that TIMP3 expression is increased in CAA cases compared to controls without CAA, and that TIMP3 expression is reduced in a subset of CAA-ICH cases compared to CAA-NH cases. In conclusion, in patients with CAA, a disbalance in cerebrovascular MMP9 and TIMP3 expression is associated with CAA-related ICH.

Molecular Interactions Stabilizing the Promatrix Metalloprotease-9·Serglycin Heteromer

Previous studies have shown that THP-1 cells produced an SDS-stable and reduction-sensitive complex between proMMP-9 and a chondroitin sulfate proteoglycan (CSPG) core protein. The complex could be reconstituted in vitro using purified serglycin (SG) and proMMP-9 and contained no inter-disulfide bridges. It was suggested that the complex involved both the FnII module and HPX domain of proMMP-9. The aims of the present study were to resolve the interacting regions of the molecules that form the complex and the types of interactions involved. In order to study this, we expressed and purified full-length and deletion variants of proMMP-9, purified CSPG and SG, and performed in vitro reconstitution assays, peptide arrays, protein modelling, docking, and molecular dynamics (MD) simulations. ProMMP-9 variants lacking both the FnII module and the HPX domain did not form the proMMP-9∙CSPG/SG complex. Deletion variants containing at least the FnII module or the HPX domain formed the proMMP-9∙CSPG/SG complex, as did the SG core protein without CS chains. The interacting parts covered large surface areas of both molecules and implicated dynamic and complementary ionic, hydrophobic, and hydrogen bond interactions. Hence, no short single interacting linear motifs in the two macromolecules could explain the strong SDS-stable and reduction-sensitive binding.

MMP-2 and MMP-9 in Human Peripheral Blood: Optimizing Gelatinase Calibrator for Degradome Research and Discovering a Novel Gelatinolytic Enzyme

Matrix metalloprotease-2 and -9 (gelatinase A and B, respectively) are enzymes crucially involved in a plethora of physiopathological conditions. Gelatin zymography is considered one of the major qualitative/semiquantitative assays for simultaneously determining zymogenic, active, and complexed forms of gelatinases. Critical steps are represented by variations in sample collection methods, molecular weight standard calibrators, and different zymography assay protocols. A normalization of these aspects is required for reducing discrepancies in technical procedures and interpreting results among different laboratories. In this study, we describe a novel protocol for gelatin zymography with increased pore size, which improves the separation of gelatinases with different molecular weights. A new method for obtaining gelatinase calibrator for gelatin zymography, by extracting MMP-2 and MMP-9 from peripheral blood, is also reported. Our method provides a gelatinase calibrator with enhanced stability both at room temperature and during multiple freeze-thaw cycles. This calibrator preparation is also suitable for in vitro post-translational modifications. For the first time, the improved zymography protocol allowed us to reveal in human peripheral blood samples new gelatinolytic bands resolved at very high molecular weight, likely complexes of MMP-9, undetectable with classical zymography protocols.

Method for Determining Gelatinolytic Activity in Tissue Extracts: Real-Time Gelatin Zymography

To explore the physiological or pathological roles of proteases, it is important to be able to detect and precisely localize them in a tissue, to differentiate between inactive and active forms, as well as to quantify and determine the nature of the enzyme that degrades a given substrate. Here we present a protocol for real-time gelatin zymography that is very useful for the detection of gelatin-degrading proteases in tissue extracts. This method uses fluorescence-labeled gelatin and therefore we also present an easy, fast, and cheap method for labeling gelatin with 2-methoxy-2,4-diphenyl-3(2H)-furanone (MDPF).

Remote ischemic preconditioning attenuates intestinal mucosal damage: insight from a rat model of ischemia-reperfusion injury

Background

Remote ischemic preconditioning (RIPC) is a phenomenon, whereby repeated, non-lethal episodes of ischemia to an organ or limb exert protection against ischemia–reperfusion (I/R) injury in distant organs. Despite intensive research, there is still an apparent lack of knowledge concerning the RIPC-mediated mechanisms, especially in the intestine. Aim of this study was to evaluate possible protective effects RIPC on intestinal I/R injury.

Methods

Thirty rats were randomly assigned to four groups: I/R; I/R + RIPC; Sham; Sham + RIPC. Animals were anesthetized and the superior mesenteric artery was clamped for 30 min, followed by 60 min of reperfusion. RIPC-treated rats received 3 × 5 min of bilateral hindlimb I/R prior to surgery, sham groups obtained laparotomy without clamping. After I/R injury serum/tissue was analyzed for: Mucosal damage, Caspase-3/7 activity, expression of cell stress proteins, hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) production, Hypoxia-inducible factor-1α (HIF-1α) protein expression and matrix metalloproteinase (MMP) activity.

Results

Intestinal I/R resulted in increased mucosal injury (P < 0.001) and elevated Caspase-3/7 activity (P < 0.001). RIPC significantly reduced the histological signs of intestinal I/R injury (P < 0.01), but did not affect Caspase-3/7 activity. Proteome profiling suggested a RIPC-mediated regulation of several cell stress proteins after I/R injury: Cytochrome C (+ 157%); Cited-2 (− 39%), ADAMTS1 (+ 74%). Serum concentrations of H₂O₂ and MDA remained unchanged after RIPC, while the reduced intestinal injury was associated with increased HIF-1α levels. Measurements of MMP activities in serum and intestinal tissue revealed an attenuated gelatinase activity at 130 kDa within the serum samples (P < 0.001) after RIPC, while the activity of MMPs within the intestinal tissue was not affected by I/R injury or RIPC.

Conclusions

RIPC ameliorates intestinal I/R injury in rats. The underlying mechanisms may involve HIF-1α protein expression and a decreased serum activity of a 130 kDa factor with gelatinase activity.

Electronic supplementary material

The online version of this article (10.1186/s12967-019-1885-4) contains supplementary material, which is available to authorized users.

Method for Determining Gelatinolytic Activity in Tissue: In Situ Gelatin Zymography

To explore the physiological or pathological roles of proteases, it is important to be able to detect and precisely localize them in a tissue, to differentiate between inactive and active forms, as well as to quantify and determine the nature of the enzyme that degrades a given substrate. Here we present an in situ gelatin zymography method that allows for a precise localization of active gelatin-degrading enzymes in a tissue section. In this method, dye-quenched gelatin is put on top of a tissue section. During an incubation period, active gelatinolytic enzymes will degrade the substrate and fluorescent signals are emitted from the locations of these enzymes.

The selectivity of galardin and an azasugar-based hydroxamate compound for human matrix metalloproteases and bacterial metalloproteases

Inhibitors targeting bacterial enzymes should not interfere with enzymes of the host, and knowledge about structural determinants for selectivity is important for designing inhibitors with a therapeutic potential. We have determined the binding strengths of two hydroxamate compounds, galardin and compound 1b for the bacterial zinc metalloproteases, thermolysin, pseudolysin and auerolysin, known to be bacterial virulence factors, and the two human zinc metalloproteases MMP-9 and MMP-14. The active sites of the bacterial and human enzymes have huge similarities. In addition, we also studied the enzyme-inhibitor interactions by molecular modelling. The obtained Ki values of galardin for MMP-9 and MMP-14 and compound 1b for MMP-9 are approximately ten times lower than previously reported. Compound 1b binds stronger than galardin to both MMP-9 and MMP-14, and docking studies indicated that the diphenyl ether moiety of compound 1b obtains more favourable interactions within the S´1-subpocket than the 4-methylpentanoyl moiety of galardin. Both compounds bind stronger to MMP-9 than to MMP-14, which appears to be due to a larger S´1-subpocket in the former enzyme. Galardin, but not 1b, inhibits the bacterial enzymes, but the galardin Ki values were much larger than for the MMPs. The docking indicates that the S´1-subpockets of the bacterial proteases are too small to accommodate the diphenyl ether moiety of 1b, while the 4-methylpentanoyl moiety of galardin enters the pocket. The present study indicates that the size and shape of the ligand structural moiety entering the S´1-subpocket is an important determinant for selectivity between the studied MMPs and bacterial MPs.

Matrix Metalloproteinase 9 Displays a Particular Time Response to Acute Stress: Variation in Its Levels and Activity Distribution in Rat Hippocampus

A single stress exposure facilitates memory formation through neuroplastic processes that reshape excitatory synapses in the hippocampus, probably requiring changes in extracellular matrix components. We tested the hypothesis that matrix metalloproteinase 9 (MMP-9), an enzyme that degrades components of extracellular matrix and synaptic proteins such as β-dystroglycan (β-DG₄₃), changes their activity and distribution in rat hippocampus during the acute stress response. After 2.5 h of restraint stress, we found (i) increased MMP-9 levels and potential activity in whole hippocampal extracts, accompanied by β-DG₄₃ cleavage, and (ii) a significant enhancement of MMP-9 immunoreactivity in dendritic fields such as stratum radiatum and the molecular layer of hippocampus. After 24 h of stress, we found that (i) MMP-9 net activity rises at somatic field, i.e., stratum pyramidale and granule cell layers, and also at synaptic field, mainly stratum radiatum and the molecular layer of hippocampus, and (ii) hippocampal synaptoneurosome fractions are enriched with MMP-9, without variation of its potential enzymatic activity, in accordance with the constant level of cleaved β-DG₄₃. These findings indicate that stress triggers a peculiar timing response in the MMP-9 levels, net activity, and subcellular distribution in the hippocampus, suggesting its involvement in the processing of substrates during the stress response.

Determination of Genes Related to Uveitis by Utilization of the Random Walk with Restart Algorithm on a Protein-Protein Interaction Network

Uveitis, defined as inflammation of the uveal tract, may cause blindness in both young and middle-aged people. Approximately 10–15% of blindness in the West is caused by uveitis. Therefore, a comprehensive investigation to determine the disease pathogenesis is urgent, as it will thus be possible to design effective treatments. Identification of the disease genes that cause uveitis is an important requirement to achieve this goal. To begin to answer this question, in this study, a computational method was proposed to identify novel uveitis-related genes. This method was executed on a large protein–protein interaction network and employed a popular ranking algorithm, the Random Walk with Restart (RWR) algorithm. To improve the utility of the method, a permutation test and a procedure for selecting core genes were added, which helped to exclude false discoveries and select the most important candidate genes. The five-fold cross-validation was adopted to evaluate the method, yielding the average F1-measure of 0.189. In addition, we compared our method with a classic GBA-based method to further indicate its utility. Based on our method, 56 putative genes were chosen for further assessment. We have determined that several of these genes (e.g., CCL4, Jun, and MMP9) are likely to be important for the pathogenesis of uveitis.

Decreased homodimerization and increased TIMP-1 complexation of uteroplacental and uterine arterial matrix metalloproteinase-9 during hypertension-in-pregnancy

Preeclampsia is a complication of pregnancy manifested as hypertension-in-pregnancy (HTN-Preg) and often intrauterine growth restriction (IUGR). Placental ischemia could be an initiating event, but the molecular mechanisms are unclear. To test the hypothesis that dimerization of matrix metalloproteinases (MMPs) plays a role in HTN-Preg and IUGR, the levels/activity of MMP-9, tissue inhibitor of metalloproteinase (TIMP-1), and their dimerization forms were measured in the placenta, uterus, and uterine artery of normal pregnant (Preg) rats and a rat model of reduced uteroplacental perfusion pressure (RUPP). Consistent with our previous report, blood pressure (BP) was higher, pup weight was lower, and gelatin zymography showed different gelatinolytic activity for pro-MMP-9, MMP-9, pro-MMP-2 and MMP-2 in RUPP vs Preg rats. Careful examination of the zymograms showed additional bands at 200 and 135kDa. Western blots with MMP-9 antibody suggested that the 200kDa band was a MMP-9 homodimer. Western blots with TIMP-1 antibody as well as reverse zymography suggested that the 135kDa band was a MMP-9/TIMP-1 complex. The protein levels and gelatinase activity of MMP-9 homodimer were decreased while MMP-9/TIMP-1 complex was increased in placenta, uterus and uterine artery of RUPP vs Preg rats. The epidermal growth factor (EGF) receptor blocker erlotinib and protein kinase C (PKC) inhibitor bisindolylmaleimide decreased MMP-9 homodimer and increased MMP-9/TIMP-1 complex in placenta, uterus and uterine artery of Preg rats. EGF and the PKC activator phorbol-12,13-dibutyrate (PDBu) reversed the decreases in MMP-9 homodimer and the increases in MMP-9/TIMP-1 complex in tissues of RUPP rats. Thus, the increased BP and decreased pup weight in placental ischemia model of HTN-Preg are associated with a decrease in MMP-9 homodimer and an increase in MMP-9/TIMP-1 complex in placenta, uterus, and uterine artery, which together would cause a net decrease in MMP-9 activity and reduce uteroplacental and vascular remodeling in the setting of HTN-Preg and IUGR. Enhancing EGFR/PKC signaling may reverse the MMP-9 unfavorable dimerization patterns and thereby promote uteroplacental and vascular remodeling in preeclampsia.

Proteins in Soy Might Have a Higher Role in Cancer Prevention than Previously Expected: Soybean Protein Fractions Are More Effective MMP-9 Inhibitors Than Non-Protein Fractions, Even in Cooked Seeds

The search for anticancer MMP-9 inhibitors (MMPIs) in food products has become a major goal for research. MMPIs in soy have been related only to saponins and isoflavones, but recently, low specific protein fractions in soybeans were shown to reduce MMP-9 activity as well. The present work aimed at comparing the MMPI potential of protein fractions (P) and non-protein fractions (NP) isolated from soybean seeds, before and after soaking and cooking, mimicking dietary exposures. Reverse and substrate zymography, as well as a fluoregenic DQ gelatin assay were used to evaluate MMP-9 activities. Colon cancer cell migration and proliferation was also tested in HT29 cells. Regarding MMP-9 inhibition, proteins in soy presented IC₅₀ values 100 times lower than non-protein extracts, and remained active after cooking, suggesting that proteins may be more effective MMP-9 inhibitors than non-protein compounds. Using the determined IC₅₀ concentrations, NP fractions were able to induce higher inhibitions of HT29 cell migration and proliferation, but not through MMP-9 inhibition, whilst protein fractions were shown to specifically inhibit MMP-9 activity. Overall, our results show that protein fractions in soybeans might have a higher role in soy-related cancer prevention as MMPIs than previously expected. Being nontoxic and active at lower concentrations, the discovery of these heat-resistant specific MMPI proteins in soy can be of significant importance for cancer preventive diets, particularly considering the increasing use of soy proteins in food products and the controversy around isoflavones amongst consumers.

Recruitment of Matrix Metalloproteinase-9 (MMP-9) to the Fibroblast Cell Surface by Lysyl Hydroxylase 3 (LH3) Triggers Transforming Growth Factor-β (TGF-β) Activation and Fibroblast Differentiation

Solid tumor growth triggers a wound healing response. Similar to wound healing, fibroblasts in the tumor stroma differentiate into myofibroblasts (also referred to as cancer-associated fibroblasts) primarily, but not exclusively, in response to transforming growth factor-β (TGF-β). Myofibroblasts in turn enhance tumor progression by remodeling the stroma. Among proteases implicated in stroma remodeling, matrix metalloproteinases (MMPs), including MMP-9, play a prominent role. Recent evidence indicates that MMP-9 recruitment to the tumor cell surface enhances tumor growth and invasion. In the present work, we addressed the potential relevance of MMP-9 recruitment to and activity at the surface of fibroblasts. We show that recruitment of MMP-9 to the fibroblast cell surface occurs through its fibronectin-like (FN) domain and that the molecule responsible for the recruitment is lysyl hydroxylase 3 (LH3). Functional assays suggest that both pro- and active MMP-9 trigger α-smooth muscle actin expression in cultured fibroblasts, reflecting myofibroblast differentiation, possibly as a result of TGF-β activation. Moreover, the recombinant FN domain inhibited both MMP-9-induced TGF-β activation and α-smooth muscle actin expression by displacing MMP-9 from the fibroblast cell surface. Together our results uncover LH3 as a new docking receptor of MMP-9 on the fibroblast cell surface and demonstrate that the MMP-9 FN domain is essential for the interaction. They also show that the recombinant FN domain inhibits MMP-9-induced TGF-β activation and fibroblast differentiation, providing a potentially attractive therapeutic reagent toward attenuating tumor progression where MMP-9 activity is strongly implicated.

Proteases and protease inhibitors of urinary extracellular vesicles in diabetic nephropathy

Diabetic nephropathy (DN) is one of the major complications of diabetes mellitus (DM), leads to chronic kidney disease (CKD), and, ultimately, is the main cause for end-stage kidney disease (ESKD). Beyond urinary albumin, no reliable biomarkers are available for accurate early diagnostics. Urinary extracellular vesicles (UEVs) have recently emerged as an interesting source of diagnostic and prognostic disease biomarkers. Here we used a protease and respective protease inhibitor array to profile urines of type 1 diabetes patients at different stages of kidney involvement. Urine samples were divided into groups based on the level of albuminuria and UEVs isolated by hydrostatic dialysis and screened for relative changes of 34 different proteases and 32 protease inhibitors, respectively. Interestingly, myeloblastin and its natural inhibitor elafin showed an increase in the normo- and microalbuminuric groups. Similarly, a characteristic pattern was observed in the array of protease inhibitors, with a marked increase of cystatin B, natural inhibitor of cathepsins L, H, and B as well as of neutrophil gelatinase-associated Lipocalin (NGAL) in the normoalbuminuric group. This study shows for the first time the distinctive alterations in comprehensive protease profiles of UEVs in diabetic nephropathy and uncovers intriguing mechanistic, prognostic, and diagnostic features of kidney damage in diabetes.

Neutrophil Gelatinase-Associated Lipocalin (NGAL), Pro-Matrix Metalloproteinase-9 (pro-MMP-9) and Their Complex Pro-MMP-9/NGAL in Leukaemias

Matrix metalloproteinase (MMP)-9 and neutrophil gelatinase-associated lipocalin (NGAL) have gained attention as cancer biomarkers. The inactive zymogen form of MMP-9 (pro-MMP-9) also exists as a disulphide-linked heterodimer bound to NGAL in humans. Leukaemias represent a heterogeneous group of neoplasms, which vary in their clinical behavior and pathophysiology. In this review, we summarize the current literature on the expression profiles of pro-MMP-9 and NGAL as prognostic factors in leukaemias. We also report the expression of the pro-MMP-9/NGAL complex in these diseases. We discuss the roles of (pro)-MMP-9 (active and latent forms) and NGAL in tumour development, and evaluate the mechanisms by which pro-MMP-9/NGAL may influence the actions of (pro)-MMP-9 and NGAL in cancer. Emerging knowledge about the coexpression and the biology of (pro)-MMP-9, NGAL and their complex in cancer including leukaemia may improve treatment outcomes.

Culture media from hypoxia conditioned endothelial cells protect human intestinal cells from hypoxia/reoxygenation injury

Remote ischemic preconditioning (RIPC) is a phenomenon, whereby short episodes of non-lethal ischemia to an organ or tissue exert protection against ischemia/reperfusion injury in a distant organ. However, there is still an apparent lack of knowledge concerning the RIPC-mediated mechanisms within the target organ and the released factors. Here we established a human cell culture model to investigate cellular and molecular effects of RIPC and to identify factors responsible for RIPC-mediated intestinal protection. Human umbilical vein cells (HUVEC) were exposed to repeated episodes of hypoxia (3 × 15 min) and conditioned culture media (CM) were collected after 24h. Human intestinal cells (CaCo-2) were cultured with or without CM and subjected to 90 min of hypoxia/reoxygenation injury. Reverse transcription-polymerase chain reaction, Western blotting, gelatin zymography, hydrogen peroxide measurements and lactate dehydrogenase (LDH) assays were performed. In HUVEC cultures hypoxic conditioning did not influence the profile of secreted proteins but led to an increased gelatinase activity (P<0.05) in CM. In CaCo-2 cultures 90 min of hypoxia/reoxygenation resulted in morphological signs of cell damage, increased LDH levels (P<0.001) and elevated levels of hydrogen peroxide (P<0.01). Incubation of CaCo-2 cells with CM reduced the hypoxia-induced signs of cell damage and LDH release (P<0.01) and abrogated the hypoxia-induced increase of hydrogen peroxide. These events were associated with an enhanced phosphorylation status of the prosurvival kinase Erk1/2 (P<0.05) but not Akt and STAT-5. Taken together, CM of hypoxia conditioned endothelial cells protect human intestinal cells from hypoxia/reoxygenation injury. The established culture model may help to unravel RIPC-mediated cellular events and to identify molecules released by RIPC.

Inflammatory and microenvironmental factors involved in breast cancer progression

The primary reason for the high mortality rate of breast cancer is metastasis, which can result in a poor survival rate. The tumor environment is important for promotion and invasion of cancer cells. Recent studies have shown that inflammation is associated with breast cancer. Therefore, it is important to investigate the role of the inflammatory and microenvironment in breast cancer progression and metastasis. The present review summarizes some of the markers for inflammation and breast cancer invasion, which may aid in the design of an appropriate therapy for metastatic breast cancer. The following four inflammatory markers are discussed in this review: (1) Tumor associated macrophages (TAMs); (2) Matrix metalloproteinases (MMPs); (3) Sphingosine 1-phosphate (S1P); (4) C-reactive protein (CRP). TAMs are commonly found in breast cancer patients, and high infiltration is positively correlated with poor prognosis and low survival rate. MMPs are well-known for their roles in the degradation of ECM components when cancer cells invade and migrate. MMPs are also associated with inflammation through recruitment of a variety of stromal cells such as fibroblasts and leukocytes. S1P is an inflammatory lipid and is involved in various cellular processes such as proliferation, survival, and migration. Recent studies indicate that S1P participates in breast cancer invasion in various ways. CRP is used clinically to indicate the outcome of cancer patients as well as acute inflammatory status. This review summarizes the current understanding on the role of S1P in CRP expression which promotes the breast epithelial cell invasion, suggesting a specific mechanism linking inflammation and breast cancer. The present review might be useful for understanding the relationship between inflammation and breast cancer for the development of pharmacological interventions that may control the primary molecules involved in the breast cancer microenvironment.

Tissue- and cell-specific co-localization of intracellular gelatinolytic activity and matrix metalloproteinase 2

Matrix metalloproteinase 2 (MMP-2) is a proteolytic enzyme that degrades extracellular matrix proteins. Recent studies indicate that MMP-2 also has a role in intracellular proteolysis during various pathological conditions, such as ischemic injuries in heart and brain and in tumor growth. The present study was performed to map the distribution of intracellular MMP-2 activity in various mouse tissues and cells under physiological conditions. Samples from normal brain, heart, lung, liver, spleen, pancreas, kidney, adrenal gland, thyroid gland, gonads, oral mucosa, salivary glands, esophagus, intestines, and skin were subjected to high-resolution in situ gelatin zymography and immunohistochemical staining. In hepatocytes, cardiac myocytes, kidney tubuli cells, epithelial cells in the oral mucosa as well as in excretory ducts of salivary glands, and adrenal cortical cells, we found strong intracellular gelatinolytic activity that was significantly reduced by the metalloprotease inhibitor EDTA but not by the cysteine protease inhibitor E-64. Furthermore, the gelatinolytic activity was co-localized with MMP-2. Western blotting and electron microscopy combined with immunogold labeling revealed the presence of MMP-2 in different intracellular compartments of isolated hepatocytes. Our results indicate that MMP-2 takes part in intracellular proteolysis in specific tissues and cells during physiological conditions.

Matrix metalloproteinase-9 inhibition reduces inflammation and improves motility in murine models of postoperative ileus

BACKGROUND & AIMS

Matrix metalloproteinase (MMP)-9, a member of the gelatinase family of MMPs, mediates leukocyte migration during inflammation. Inflammation contributes to development of postoperative ileus (POI), which is caused by physical disturbances to the bowel during abdominal surgery. We evaluated the role of MMP-9 in POI and investigated whether disruption of MMP-9 or administration of an inhibitor of MMP-9 activity reduced cellular inflammation and bowel dysmotility in rat and mouse models of POI.

METHODS

Mice and rats underwent laparotomy and bowel manipulation; bowel tissues were collected 3 to 24 hours later and analyzed by real-time reverse-transcriptase polymerase chain reaction, immunoblot, in situ zymography, and functional analyses.

RESULTS

Bowel manipulation resulted in a time-dependent increase in MMP-9 expression within the intestinal muscularis; increases in MMP-9 messenger RNA were inducible nitric oxide synthase dependent. Immunoblot analyses confirmed the presence of the proenzyme and the catalytically active form of MMP-9. Administration of MMP-2/MMP-9 II, a dual active-site inhibitor, reduced the number of myeloperoxidase-positive immune cells that infiltrated the muscularis and prevented the surgically induced reduction in bowel smooth muscle contractility. Zymography analysis, performed in muscularis whole mounts in situ, indicated that MMP-9 and not MMP-2 mediated the gelatinase activity observed in infiltrating cells. MMP-9 knockout mice were protected from the inflammation and dysmotility associated with POI.

CONCLUSIONS

MMP-9 mediates cellular inflammatory responses within the intestinal muscularis in mouse and rat models of POI. Inhibition of MMP-9 activity reduced recruitment of immune cells to the intestinal muscularis, preventing loss of smooth muscle contractility. Induction of MMP-9 expression requires inducible nitric oxide synthase.

Structure of collagenase G reveals a chew-and-digest mechanism of bacterial collagenolysis

Collagen constitutes one third of the body protein in humans, reflecting its extraordinary role in health and disease. Of similar importance, therefore, are the idiosyncratic proteases that nature evolved for collagen remodeling. Intriguingly, the most efficient collagenases are those that enable clostridial bacteria to colonize their host tissues, but despite intense studies, the structural and mechanistic basis of these enzymes has remained elusive. Here we present the crystal structure of collagenase G from Clostridium histolyticum at 2.55 Å resolution. By combining the structural data with enzymatic and mutagenesis studies, we derive a conformational two-state model of bacterial collagenolysis, in which the recognition and unraveling of collagen microfibrils into triple helices as well as the unwinding of the latter go hand in hand with collagenase opening and closing.

Biosynthesis of promatrix metalloproteinase-9/chondroitin sulphate proteoglycan heteromer involves a Rottlerin-sensitive pathway

Background

Previously we have shown that a fraction of the matrix metalloproteinase-9 (MMP-9) synthesized by the macrophage cell line THP-1 was bound to a chondroitin sulphate proteoglycan (CSPG) core protein as a reduction sensitive heteromer. Several biochemical properties of the enzyme were changed when it was bound to the CSPG.

Methodology/Principal Findings

By use of affinity chromatography, zymography, and radioactive labelling, various macrophage stimulators were tested for their effect on the synthesis of the proMMP-9/CSPG heteromer and its components by THP-1 cells. Of the stimulators, only PMA largely increased the biosynthesis of the heteromer. As PMA is an activator of PKC, we determined which PKC isoenzymes were expressed by performing RT-PCR and Western Blotting. Subsequently specific inhibitors were used to investigate their involvement in the biosynthesis of the heteromer. Of the inhibitors, only Rottlerin repressed the biosynthesis of proMMP-9/CSPG and its two components. Much lower concentrations of Rottlerin were needed to reduce the amount of CSPG than what was needed to repress the synthesis of the heteromer and MMP-9. Furthermore, Rottlerin caused a minor reduction in the activation of the PKC isoenzymes δ, ε, θ and υ (PKD3) in both control and PMA exposed cells.

Conclusions/Significance

The biosynthesis of the proMMP-9/CSPG heteromer and proMMP-9 in THP-1 cells involves a Rottlerin-sensitive pathway that is different from the Rottlerin sensitive pathway involved in the CSPG biosynthesis. MMP-9 and CSPGs are known to be involved in various physiological and pathological processes. Formation of complexes may influence both the specificity and localization of the enzyme. Therefore, knowledge about biosynthetic pathways and factors involved in the formation of the MMP-9/CSPG heteromer may contribute to insight in the heteromers biological function as well as pointing to future targets for therapeutic agents.

Limitations in bonding to dentin and experimental strategies to prevent bond degradation

The limited durability of resin-dentin bonds severely compromises the lifetime of tooth-colored restorations. Bond degradation occurs via hydrolysis of suboptimally polymerized hydrophilic resin components and degradation of water-rich, resin-sparse collagen matrices by matrix metalloproteinases (MMPs) and cysteine cathepsins. This review examined data generated over the past three years on five experimental strategies developed by different research groups for extending the longevity of resin-dentin bonds. They include: (1) increasing the degree of conversion and esterase resistance of hydrophilic adhesives; (2) the use of broad-spectrum inhibitors of collagenolytic enzymes, including novel inhibitor functional groups grafted to methacrylate resins monomers to produce anti-MMP adhesives; (3) the use of cross-linking agents for silencing the activities of MMP and cathepsins that irreversibly alter the 3-D structures of their catalytic/allosteric domains; (4) ethanol wet-bonding with hydrophobic resins to completely replace water from the extrafibrillar and intrafibrillar collagen compartments and immobilize the collagenolytic enzymes; and (5) biomimetic remineralization of the water-filled collagen matrix using analogs of matrix proteins to progressively replace water with intrafibrillar and extrafibrillar apatites to exclude exogenous collagenolytic enzymes and fossilize endogenous collagenolytic enzymes. A combination of several of these strategies should result in overcoming the critical barriers to progress currently encountered in dentin bonding.

Disease and gender-specific dysregulation of NGAL and MMP-9 in type 1 diabetes mellitus

Neutrophil gelatinase-associated lipocalin (NGAL), a biomarker of renal injury, can bind matrix metalloproteinase-9 (MMP-9) and inhibit its degradation, thereby sustaining MMP-9 proteolytic activity. MMP-9 is produced by renal podocytes, and podocyte MMP production can be modified by high ambient glucose levels. Moreover, dysregulation of MMP-9 activity, gene expression, or urine concentrations has been demonstrated in T2DM-associated nephropathy and in non-diabetic proteinuric renal diseases. Our objective was to determine whether NGAL/MMP-9 dysregulation might contribute to or serve as a biomarker of diabetic nephropathy in type 1 DM (T1DM). Plasma MMP-9, and urine NGAL and MMP-9 concentrations were measured in 121 T1DM and 55 control subjects and examined relative to indicators of glycemia, renal function, and degree of albuminuria. T1DM was associated with a significant increase in urinary excretion of both NGAL and MMP-9, and urine NGAL:Cr (NGAL corrected to urine creatinine) and urine MMP-9:Cr concentrations were highly correlated with each other. Both were also positively correlated with measurements of glycemic control and with albuminuria. Plasma MMP-9, urine MMP-9, and urine NGAL concentrations were significantly higher in females compared to males, and urine MMP-9:Cr concentrations displayed a menstrual cycle specific pattern. Increased urinary excretion of NGAL and MMP-9 supports a role for NGAL/MMP-9 dysregulation in renal dysfunction; moreover, gender-specific differences could support a gender contribution to pathological mechanisms or susceptibility for the development of renal complications in diabetes mellitus.

Plasma levels of matrix metalloproteinase-9 in chronic urticaria patients correlate with disease severity and C-reactive protein but not with circulating histamine-releasing factors

BACKGROUND

Matrix metalloproteinase-9 (MMP-9) is an endopeptidase produced by many inflammatory cells that has been found in increased amounts in plasma from patients with chronic urticaria (CU).

OBJECTIVE

To evaluate plasma levels of MMP-9 and its tissue inhibitor of metalloproteinase-1 (TIMP-1) in CU patients in relation with disease severity, C-reactive protein (CRP) and circulating histamine-releasing factors.

METHODS

Fifty-two consecutive CU patients were included in the study and disease activity was graded from 0 to 3. Plasma MMP-9, TIMP-1 and CRP levels were measured by enzyme immunoassays. Circulating histamine-releasing factors were assessed using in vivo (autologous serum skin test) and in vitro (basophil histamine release) tests. Seven CU patients were studied both during active disease and during remission. Thirty healthy subjects were used as normal controls.

RESULTS

Plasma levels of MMP-9, TIMP-1 and CRP were significantly higher in CU patients than in healthy controls (P=0.0001, 0.003 and 0.005, respectively) and a trend towards a higher MMP-9/TIMP-1 molar ratio was found (P=0.051). A significant correlation was found between plasma MMP-9 levels and urticaria severity score (r=0.48, P<0.0001). CRP levels correlated with MMP-9 levels (r=0.37, P=0.008) and CU severity score (r=0.52, P=0.0001), but not with TIMP-1 (r=0.13) concentrations. MMP-9, TIMP-1 and CRP plasma levels and MMP-9/TIMP-1 molar ratio did not differ in patients either with or without an evidence of circulating histamine-releasing factors. Seven patients evaluated during remission showed a significant reduction of MMP-9 and CRP plasma levels.

CONCLUSION

Plasma levels of MMP-9 and its inhibitor TIMP-1 are increased in CU patients. MMP-9 levels are associated with disease severity and CRP levels, but not with skin reactivity to autologous serum and with circulating histamine-releasing factors. These findings suggest that in CU there is an ongoing inflammatory process independent of the presence of circulating histamine-releasing factors.

Effect of a sequential training programme on inflammatory, prothrombotic and vascular remodelling biomarkers in hypertensive overweight patients with or without metabolic syndrome

BACKGROUND

It is not known whether serum level of vascular remodelling parameters, such as matrix metalloproteinases could be modulated by physical activity and whether the eventual change could be influenced by metabolic syndrome (MS) diagnosis.

DESIGN

Open, intervention study to evaluate the effects of a sequential physical activity training on inflammatory, prothrombotic and vascular remodelling biomarkers in overweight patients with and without MS.

METHODS

We enrolled 80 overweight patients (mean age: 62.9+/-8.3 years; male : female = 36 : 44) with newly diagnosed hypertension, with or without MS. After 3 months of American Heart Association step 2 diet, they followed a sequential training programme including 56 days of added three metabolic equivalent tasks/week and 56 days of six metabolic equivalent tasks/week.

RESULTS

All patients experienced a significant decrease in body mass index, waist circumference and blood pressure after both the training phases. High-density lipoprotein-cholesterolemia, triglycerides, and glycaemia significantly improved only after the intensive training phase compared with the baseline in MS patients. Prothrombotic parameters improved irrespectively from the MS diagnosis. High-sensitivity C-reactive protein P level significantly decreased towards baseline and towards the previous phase, after exercise intensification, but only in MS patients. The plasma level of matrix metalloproteinase 2 and 9, and their activated forms improved significantly when compared with the baseline both after the first and the second training period, independently from the MS diagnosis.

CONCLUSION

Diagnosis of MS is a determinant of changes in metabolic and inflammatory biomarkers, but not of the prothrombotic and vascular remodelling ones in a sample of overweight hypertensive patients.

Detection of matrix metallopeptidase-9-like proteins in Trypanosoma cruzi

In this study, the cell-associated and extracellular peptidases of Trypanosoma cruzi grown in modified Roitman's complex (MRC) medium were analyzed by measuring peptidase activity in gelatin-containing zymograms. Our results showed that the cell-associated peptidases as well as peptidases extracellularly released by T. cruzi displayed two distinct proteolytic classes: cysteine and metallopeptidase activities. The major cysteine peptidase, cruzipain, synthesized by T. cruzi cells was detected in cellular parasite content, as a 50kDa reactive polypeptide, after probing with anti-cruzipain antibody. In addition, metallo-type peptidases belonging to the matrix metallopeptidase-9 (MMP-9) family were revealed, after Western blotting, as a 97kDa protein band in cellular extract and an 85kDa polypeptide in both cellular and secreted parasite extracts. The MMP-9-like activity present in cells and spent culture medium was immunoprecipitated by an anti-MMP-9 polyclonal antibody. The surface location of MMP-9-like proteins in T. cruzi was also evidenced by means of flow cytometry analysis. Furthermore, doxycycline that has direct MMP-9 inhibiting properties in vitro, inhibited MMP-9-like activities in gel zymography, immunoprecipitation and flow cytometry analyses. This is the first report of the presence of MMP-9-like molecules in T. cruzi. The presence of a matrix extracellular-degrading enzyme may play a role in the T. cruzi-host cell interaction, making this enzyme a potential target for future drug development against this pathogenic trypanosomatid.

Gelatin in situ zymography on fixed, paraffin-embedded tissue: zinc and ethanol fixation preserve enzyme activity

In situ zymography is a method for the detection and localization of enzymatic activity in tissue sections. This method is used with frozen sections because routine fixation of tissue in neutral-buffered formalin inhibits enzyme activity. However, frozen sections present with poor tissue morphology, making precise localization of enzymatic activity difficult to determine. Ethanol- and zinc-buffered fixative (ZBF) are known to preserve both morphological and functional properties of the tissue well, but it has not previously been shown that these fixatives preserve enzyme activity. In the present study, we show that in situ zymography can be performed on ethanol- and ZBF-fixed paraffin-embedded tissue. Compared with snap-frozen tissue, ethanol- and ZBF-fixed tissue showed stronger signals and superior morphology, allowing for a much more precise detection of gelatinolytic activity. Gelatinolytic enzymes could also be extracted from both ethanol- and ZBF-fixed tissue. The yield, as analyzed by SDS-PAGE gelatin zymography and Western blotting, was influenced by the composition of the extraction buffer, but was generally lower than that obtained from unfixed tissue.

Matrix metalloproteinase-2 and myocardial oxidative stress injury: beyond the matrix

Matrix metalloproteinase (MMP)-2 belongs to a family of zinc-dependent proteases which are best known for their ability to proteolyse extracellular matrix proteins throughout the body, including the cardiovascular system. Increased MMP-2 activity has been demonstrated in myocardial ischaemia and reperfusion injury and the progression to congestive heart failure, with most evidence to date for its role in cardiac remodelling. Recent evidence, however, shows that MMP-2 also co-localizes with and proteolyses specific protein targets within the cardiomyocyte to cause acute, reversible contractile dysfunction, challenging the conventional wisdom on the 'extracellular matrix only' actions of this enzyme. In this review, we discuss the recent upsurge in MMP-2 research with regards to its activation by non-proteolytic pathways in the setting of enhanced oxidative stress in the heart. We will focus on the consequences of intracellular actions of MMP-2 within the cardiomyocyte and its regulation at several levels including its expression, post-translational modifications, and regulation by endogenous tissue inhibitors of metalloproteinases, caveolin, and small molecule MMP inhibitors. MMP-2 is emerging as an important signalling protease implicated in the proteolytic regulation of various intracellular proteins in myocardial oxidative stress injury.