Inhibition of MMP-9-dependent degradation of gelatin, but not other MMP-9 substrates, by the MMP-9 hemopexin domain blades 1 and 4

11 p.-5 fig.-1 tab.Degradation and remodeling of the extracellular matrix by matrix metalloproteinases (MMPs) plays important roles in normal development, inflammation, and cancer. MMP-9 efficiently degrades the extracellular matrix component gelatin, and the hemopexin domain of MMP-9 (PEX9) inhibits this degradation. To study the molecular basis of this inhibition, we generated GST fusion proteins containing PEX9 or truncated forms corresponding to specific structural blades (B1-B4) of PEX9. GST-PEX9 inhibited MMP-9-driven gelatin proteolysis, measured by gelatin zymography, FITC-gelatin conversion, and DQ-gelatin degradation assays. However, GST-PEX9 did not prevent the degradation of other MMP-9 substrates, such as a fluorogenic peptide, αB crystalline, or nonmuscular actin. Therefore, PEX9 may inhibit gelatin degradation by shielding gelatin and specifically preventing its binding to MMP-9. Accordingly, GST-PEX9 also abolished the degradation of gelatin by MMP-2, confirming that PEX9 is not an MMP-9 antagonist. Moreover, GST-B4 and, to a lesser extent, GST-B1 also inhibited gelatin degradation by MMP-9, indicating that these regions are responsible for the inhibitory activity of PEX9. Accordingly, ELISAs demonstrated that GST-B4 and GST-B1 specifically bound to gelatin. Our results establish new functions of PEX9 attributed to blades B4 and B1 and should help in designing specific inhibitors of gelatin degradation.This work was supported by Grant SAF2012-31613 and Red Temática de Investigación Cooperativa en Cáncer Grant RD12/0036/0061 from the Ministry of Economy and Competitivity (Spain) (to A. G.-P.); by Grant S2010/ BMD-2314 (to A. G.-P.) from the Comunidad de Madrid/European Union;and by the Concerted Research Actions Grant GOA 2013–2015 and the fund for Scientific Research of Flanders (to G. O.).Peer reviewe

Differential inhibition of activity, activation and gene expression of MMP-9 in THP-1 cells by azithromycin and minocycline versus bortezomib : a comparative study

Gelatinase B or matrix metalloproteinase-9 (MMP-9) (EC 3.4.24.35) is increased in inflammatory processes and cancer, and is associated with disease progression. In part, this is due to MMP-9-mediated degradation of extracellular matrix, facilitating influx of leukocytes into inflamed tissues and invasion or metastasis of cancer cells. MMP-9 is produced as proMMP-9 and its propeptide is subsequently removed by other proteases to generate proteolytically active MMP-9. The significance of MMP-9 in pathologies triggered the development of specific inhibitors of this protease. However, clinical trials with synthetic inhibitors of MMPs in the fight against cancer were disappointing. Reports on active compounds which inhibit MMP-9 should be carefully examined in this regard. In a considerable set of recent publications, two antibiotics (minocycline and azythromycin) and the proteasome inhibitor bortezomib, used in cancers, were reported to inhibit MMP-9 at different stages of its expression, activation or activity. The current study was undertaken to compare and to verify the impact of these compounds on MMP-9. With exception of minocycline at high concentrations (>100 μM), the compounds did not affect processing of proMMP-9 into MMP-9, nor did they affect direct MMP-9 gelatinolytic activity. In contrast, azithromycin specifically reduced MMP-9 mRNA and protein levels without affecting NF-κB in endotoxin-challenged monocytic THP-1 cells. Bortezomib, although being highly toxic, had no MMP-9-specific effects but significantly upregulated cyclooxygenase-2 (COX-2) activity and PGE2 levels. Overall, our study clarified that azithromycin decreased the levels of MMP-9 by reduction of gene and protein expression while minocycline inhibits proteolytic activity at high concentrations

Systemic ablation of MMP9 triggers invasive growth and metastasis of pancreatic cancer via deregulation of IL-6 expression in the bone marrow

Matrix metalloproteinase 9 (MMP9/Gelatinase B) is overexpressed in pancreatic ductal adenocarcinoma (PDAC) and plays a central role in tumor cell invasion and metastasis. Here we complemented mechanistic insights in the cancer biology of MMP9 and investigated the effects of specific long-term loss-of-function, by genetic ablation, of MMP9 on PDAC initiation and progression in the well-established KPC mouse model of spontaneous PDAC. Tumor growth and progression were analyzed by histopathology and immunohistochemistry. Invasive growth of PDAC cells was analyzed by both in vitro (proliferation, survival, migration, invasion assays) and in vivo (experimental metastasis assays) methods. Retroviral shRNAi was used to knockdown target genes (MMP9, IL6R). Gene expression was analyzed by qRT-PCR, immunoblot, ELISA, in situ hybridization and zymography. PDAC tumors from MMP9-deficient mice were dramatically larger, more invasive and contained more stroma. Yet, ablation of MMP9 in PDAC cells did not directly promote invasive growth. Interestingly, systemic ablation of MMP9 led to increased IL-6 levels resulting from abrogation of MMP9-dependent SCF-signaling in the bone marrow (BM). IL-6 levels in MMP9-/- mice were sufficient to induce invasive growth and STAT3 activation in PDAC cells via IL-6 receptor (IL6R). Interference with IL6R blocked the increased invasion and metastasis of PDAC cells in MMP9-deficient hosts. In conclusion, ablation of systemic MMP9 initiated fatal communication between maintenance of physiological functions of MMP9 in the BM and invasive growth of PDAC via the IL-6/IL6R/STAT3 axis. Implications: Thus, the beneficial effects of host MMP9 on PDAC are an important caveat for the use of systemic MMP9 inhibitors in cancer

MMP-9/Gelatinase B Degrades Immune Complexes in Systemic Lupus Erythematosus

Systemic Lupus Erythematosus (SLE) is a common and devastating autoimmune disease, characterized by a dysregulated adaptive immune response against intracellular antigens, which involves both autoreactive T and B cells. In SLE, mainly intracellular autoantigens generate autoantibodies and these assemble into immune complexes and activate the classical pathway of the complement system enhancing inflammation. Matrix metalloproteinase-9 (MMP-9) levels have been investigated in the serum of SLE patients and in control subjects. On the basis of specific studies, it has been suggested to treat SLE patients with MMP inhibitors. However, some of these inhibitors induce SLE. Analysis of LPR−/−MMP-9−/− double knockout mice suggested that MMP-9 plays a protective role in autoantigen clearance in SLE, but the effects of MMP-9 on immune complexes remained elusive. Therefore, we studied the role of MMP-9 in the clearance of autoantigens, autoantibodies and immune complexes and demonstrated that the lack of MMP-9 increased the levels of immune complexes in plasma and local complement activation in spleen and kidney in the LPR−/− mouse model of SLE. In addition, we showed that MMP-9 dissolved immune complexes from plasma of lupus-prone LPR−/−/MMP-9−/− mice and from blood samples of SLE patients. Surprisingly, autoantigens incorporated into immune complexes, but not immunoglobulin heavy or light chains, were cleaved by MMP-9. We discovered Apolipoprotein-B 100 as a new substrate of MMP-9 by analyzing the degradation of immune complexes from human plasma samples. These data are relevant to understand lupus immunopathology and side-effects observed with the use of known drugs. Moreover, we caution against the use of MMP inhibitors for the treatment of SLE

Proteases in cancer drug delivery

Whereas protease inhibitors have been developed successfully against hypertension and viral infections, they have failed thus far as cancer drugs. With advances in cancer profiling we now better understand that the tumor "degradome" (i.e. the repertoire of proteases and their natural inhibitors and interaction partners) forms a complex network in which specific nodes determine the global outcome of manipulation of the protease web. However, knowing which proteases are active in the tumor micro-environment, we may tackle cancers with the use of Protease-Activated Prodrugs (PAPs). Here we exemplify this concept for metallo-, cysteine and serine proteases. PAPs not only exist as small molecular adducts, containing a cleavable substrate sequence and a latent prodrug, they are presently also manufactured as various types of nanoparticles. Although the emphasis of this review is on PAPs for treatment, it is clear that protease activatable probes and nanoparticles are also powerful tools for imaging purposes, including tumor diagnosis and staging, as well as visualization of tumor imaging during microsurgical resections

Physiological fibrin hydrogel modulates immune cells and molecules and accelerates mouse skin wound healing

IntroductionWound healing is a complex process to restore homeostasis after injury and insufficient skin wound healing is a considerable problem in medicine. Whereas many attempts of regenerative medicine have been made for wound healing with growth factors and cell therapies, simple pharmacological and immunological studies are lagging behind. We investigated how fibrin hydrogels modulate immune cells and molecules in skin wound healing in mice.MethodsPhysiological fibrin hydrogels (3.5 mg/mL fibrinogen) were generated, biophysically analyzed for stiffness and protein contents and were structurally studied by scanning electron microscopy. Physiological fibrin hydrogels were applied to full thickness skin wounds and, after 3 days, cells and molecules in wound tissues were analyzed. Leukocytes, endothelial cells, fibroblasts and keratinocytes were explored with the use of Flow Cytometry, whereas cytokines and matrix metalloproteinases were analyzed with the use of qPCR, ELISAs and zymography. Skin wound healing was analyzed microscopically at day 3, macroscopically followed daily during repair in mice and compared with commercially available fibrin sealant Tisseel.ResultsExogenous fibrin at physiological concentrations decreased neutrophil and increased non-classical Ly6Clow monocyte and resolutive macrophage (CD206+ and CX3CR1+) populations, at day 3 after injury. Fibrin hydrogel reduced the expression of pro-inflammatory cytokines and increased IL-10 levels. In line with these findings, gelatinase B/MMP-9 was decreased, whereas gelatinase A/MMP-2 levels remained unaltered. Frequencies of dermal endothelial cells, fibroblasts and keratinocytes were increased and keratinocyte migration was enhanced by fibrin hydrogel. Importantly, physiological fibrin accelerated the healing of skin wounds in contrast to the highly concentrated fibrin sealant Tisseel, which delayed wound repair and possessed a higher fiber density.ConclusionCollectively, we show that adding a tailored fibrin hydrogel scaffold to a wound bed positively influences the healing process, modulating leukocyte populations and inflammatory responses towards a faster wound repair

Synthesis and functionalization of protease-activated nanoparticles with tissue plasminogen activator peptides as targeting moiety and diagnostic tool for pancreatic cancer

Background: Functionalized nanoparticles (NPs) are one promising tool for detecting specific molecular targets and combine molecular biology and nanotechnology aiming at modern imaging. We aimed at ligand-directed delivery with a suitable target-biomarker to detect early pancreatic ductal adenocarcinoma (PDAC). Promising targets are galectins (Gal), due to their strong expression in and on PDAC-cells and occurrence at early stages in cancer precursor lesions, but not in adjacent normal tissues. Results: Molecular probes (10-29 AA long peptides) derived from human tissue plasminogen activator (t-PA) were selected as binding partners to galectins. Affinity constants between the synthesized t-PA peptides and Gal were determined by microscale thermophoresis. The 29 AA-long t-PA-peptide-1 with a lactose-functionalized serine revealed the strongest binding properties to Gal-1 which was 25-fold higher in comparison with the native t-PA protein and showed additional strong binding to Gal-3 and Gal-4, both also over-expressed in PDAC. t-PA-peptide-1 was selected as vector moiety and linked covalently onto the surface of biodegradable iron oxide nanoparticles (NPs). In particular, CAN-doped maghemite NPs (CAN-Mag), promising as contrast agent for magnetic resonance imaging (MRI), were selected as magnetic core and coated with different biocompatible polymers, such as chitosan (CAN-Mag-Chitosan NPs) or polylactic co glycolic acid (PLGA) obtaining polymeric nanoparticles (CAN-Mag@PNPs), already approved for drug delivery applications. The binding efficacy of t-PA-vectorized NPs determined by exposure to different pancreatic cell lines was up to 90%, as assessed by flow cytometry. The in vivo targeting and imaging efficacy of the vectorized NPs were evaluated by applying murine pancreatic tumor models and assessed by 1.5 T magnetic resonance imaging (MRI). The t-PA-vectorized NPs as well as the protease-activated NPs with outer shell decoration (CAN-Mag@PNPs-PEG-REGAcp-PEG/tPA-pep1Lac) showed clearly detectable drop of subcutaneous and orthotopic tumor staining-intensity indicating a considerable uptake of the injected NPs. Post mortem NP deposition in tumors and organs was confirmed by Fe staining of histopathology tissue sections. Conclusions: The targeted NPs indicate a fast and enhanced deposition of NPs in the murine tumor models. The CAN-Mag@PNPs-PEG-REGAcp-PEG/tPA-pep1Lac interlocking steps strategy of NPs delivery and deposition in pancreatic tumor is promising

Structural and functional comparisons of MMP-9 forms

Matrix metalloproteinases (MMPs) constitute a family of soluble or membrane bound Zn2+-dependent endopeptidases. In the human species, this group contains more than 20 multidomain enzymes, including collagenases, gelatinases, metalloelastases, matrilysins, stromelysins and membrane-typeMMPs. These proteases are associated with physiological processes such as reproduction, organogenesis, bone remodeling, vasculogenesis and wound healing. Besides, they are also involved in a variety of pathologies, such as acute and chronic inflammation (e.g. rheumatoid arthritis and multiple sclerosis), cancer cell invasion and metastasis as well as cardiovascular, brain and lung diseases.MMPs are multi-domain enzymes which contain a propeptide, a catalytic domain, a Zn2+-binding domain and, in most instances, also a hemopexin-like domain. The site of active proteolysis is a combination of the catalytic domain and the Zn2+-bindingdomain which holds the active zinc ion. The hemopexin-like domain is involved in the binding of a range of proteins, including substrates, cellular receptors and TIMPs. A most studied and structurally complex memberof the MMP family is MMP-9 or gelatinase B. Although all members of theMMP family possess similar characteristics, MMP-9 is exceptional. Firstly, since MMP-9 is a gelatinase, it has an additional fibronectin-like domain which improves the ability of the molecule to bind and digest large substrates (e.g. gelatins). Secondly, MMP-9 contains a prominent O-glycosylated domain. This domain is highly glycosylated and is referred to as a flexible linker since it lends the molecule the high degree of flexibility necessary for moving along collagen fibrils. Finally, besides monomers, MMP-9 has the remarkable ability to form multimers.Literature on MMP-9 is increasing exponentially each year which makes it challenging to gain an overview on the current status of MMP-9 research. We extracted and summarized the literature highlights from the past decade. Despite the significance of MMP-9, many of its structural and functional features remain elusive. To date, the exact MMP-9 structural characterization is limited to its N-terminal and C-terminal domains and no in-depth information is available on MMP-9 multimerization. In order to clarify the structure and function of homomultimeric MMP-9, a stable full-length MMP-9 mutant was generated and produced at high yield. A protocol for separating MMP-9 monomers from multimers was optimized. A detailed analysis based on biochemical and biophysical methods yielded informationon the trimeric structure of MMP-9. Atomic force microscopic images de visu elucidated this new trimeric structure of MMP-9 multimers. Comparative analysis of structure and function revealed that TIMP-1 binds more tightly to MMP-9 homomultimers than to monomers. In view of TIMP-1-free MMP-9 secretion by neutrophils this may indicate a different functional role for MMP-9 trimers. This new insight might be critical to understand basic biological processes including inflammation, cancer cell invasion,metastasis and angiogenesis.Several MMP inhibitors (MMPIs) weredeveloped during the past 20 years. Against all odds, most clinical trials with MMPIs had poor outcomes and severe side-effects were observed. Many explanations have been postulated, but the main problem was low selectivity of the used MMPIs, which results in a disturbance of the proteolytic network and in an inhibition of antitargets. New directions for MMP targeting strategies include (i) the development of more specific MMPIs that target a single function of the MMP and (ii) the alternative use of MMPs. For the discovery of MMPIs which target distal domains, a suitable screening method has to be developed. The use of fluorogenic naturalsubstrates rather than small peptides allowed the detection of inhibitors of the fibronectin repeats, compared to small peptides. Alternative strategies for the use of MMP-9 include exploitation of the presence of active MMP-9 in diseased tissues to activate a specific drug system, as exemplified with MMP-9 substrate-loaded nanoparticles.status: publishe

Homotrimeric MMP-9 is an active hitchhiker on alpha-2-macroglobulin partially escaping protease inhibition and internalization through LRP-1

Proteolysis is a crucial process in life, tightly controlled by numerous natural protease inhibitors. In human blood, alpha-2-macroglobulin is an emergency protease inhibitor preventing coagulation and damage to endothelia and leukocytes. With the use of a unique protease trapping mechanism, alpha-2-macroglobulin lures active proteases into its snap-trap, shields these from potential substrates and 'flags' their complex for elimination by receptor-mediated endocytosis. Matrix metalloprotease-9/gelatinase B is a secreted protease increased in blood of patients with inflammations, vascular disorders and cancers. Matrix metalloprotease-9 occurs as monomers and stable homotrimers, but the reason for their co-existence remains obscure. We discovered that matrix metalloprotease-9 homotrimers undergo reduced anti-proteolytic regulation by alpha-2-macroglobulin and are able to travel as a proteolytically active hitchhiker on alpha-2-macroglobulin. As a comparison, we revealed that monomeric active matrix metalloprotease-9 is efficiently trapped by human plasma alpha-2-macroglobulin and this masks the detection of activated matrix metalloprotease-9 with standard analysis techniques. In addition, we show that alpha-2-macroglobulin/trimer complexes escape clearance through the receptor low-density lipoprotein receptor-related protein 1, also known as the alpha-2-macroglobulin receptor. Thus, the biochemistry and biology of matrix metalloprotease-9 monomers and trimers are completely different as multimerization enables active matrix metalloprotease-9 to partially avoid alpha-2-macroglobulin regulation both by direct protease inhibition and by removal from the extracellular space by receptor-mediated endocytosis. Finally, for the biomarker field, the analysis of alpha-2-macroglobulin/protease complexes with upgraded technology is advocated as a quotum for protease activation in human plasma samples.status: publishe

Glycosylation of matrix metalloproteases and tissue inhibitors: present state, challenges and opportunities

Matrix metalloproteases (MMPs) are crucial components of a complex and dynamic network of proteases. With a wide range of potential substrates, their production and activity are tightly controlled by a combination of signalling events, zymogen activation, post-translational modifications and extracellular inhibition. Slight imbalances may result in the initiation or progression of specific disease states, such as cancer and pathological inflammation. As glycosylation modifies the structures and functions of glycoproteins and many MMPs contain N- or O-linked oligosaccharides, we examine, compare and evaluate the evidence for whether glycosylation affects MMP catalytic activity and other functions. It is interesting that the catalytic sites of MMPs do not contain O-linked glycans, but instead possess a conserved N-linked glycosylation site. Both N- and O-linked oligosaccharides, attached to specific protein domains, endow these domains with novel functions such as the binding to lectins, cell-surface receptors and tissue inhibitors of metalloproteases (TIMPs). Validated glycobiological data on N- and O-linked oligosaccharides of gelatinase B/MMP-9 and on O-linked structures of membrane-type 1 MMP/MMP-14 indicate that in-depth research of other MMPs may yield important insights, e.g. about subcellular localizations and functions within macromolecular complexes.status: publishe