Subcellular distribution and cytokine- and chemokine-regulated secretion of leukolysin/MT6-MMP/MMP-25 in neutrophils

Single-cell analysis defines highly specific leukemia-induced neutrophils and links MMP8 expression to recruitment of tumor associated neutrophils during FGFR1 driven leukemogenesis

BACKGROUND

Leukemias driven by activated, chimeric FGFR1 kinases typically progress to AML which have poor prognosis. Mouse models of this syndrome allow detailed analysis of cellular and molecular changes occurring during leukemogenesis. We have used these models to determine the effects of leukemia development on the immune cell composition in the leukemia microenvironment during leukemia development and progression.

METHODS

Single cell RNA sequencing (scRNA-Seq) was used to characterize leukemia associated neutrophils and define gene expression changes in these cells during leukemia progression.

RESULTS

scRNA-Seq revealed six distinct subgroups of neutrophils based on their specific differential gene expression. In response to leukemia development, there is a dramatic increase in only two of the neutrophil subgroups. These two subgroups show specific gene expression signatures consistent with neutrophil precursors which give rise to immature polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs). Analysis of gene expression in these precursor cells identified pathways that were specifically upregulated, the most pronounced of which involved matrix metalloproteinases Mmp8 and Mmp9, during leukemia progression. Pharmacological inhibition of MMPs using Ilomastat preferentially restricted in vitro migration of neutrophils from leukemic mice and led to a significantly improved survival in vivo, accompanied by impaired PMN-MDSC recruitment. As a result, levels of T-cells were proportionally increased. In clinically annotated TCGA databases, MMP8 was shown to act as an independent indicator for poor prognosis and correlated with higher neutrophil infiltration and poor pan-cancer prognosis.

CONCLUSION

We have defined specific leukemia responsive neutrophil subgroups based on their unique gene expression profile, which appear to be the precursors of neutrophils specifically associated with leukemia progression. An important event during development of these neutrophils is upregulation MMP genes which facilitated mobilization of these precursors from the BM in response to cancer progression, suggesting a possible therapeutic approach to suppress the development of immune tolerance.

Association between the Reduced Expression of RECK and Neutrophilic Inflammation in Chronic Obstructive Pulmonary Disease

INTRODUCTION

Reversion-inducing cysteine-rich protein with Kazal motifs (RECK), a recently discovered inhibitor of matrix metalloproteinase (MMP). There is a large number of chronic obstructive pulmonary disease (COPD) patients worldwide; however, the role of RECK on COPD has not been studied. This study explored the expression of RECK in COPD patients and its effect on neutrophil function to provide a new scientific basis for the prevention and treatment of COPD.

METHOD

Fifty patients with acute exacerbation of COPD and fifty healthy controls were enrolled in the study. RECK was detected in lung tissue, sputum, and plasma of subjects as well as in BEAS-2B cells stimulated with cigarette smoke extract (CSE) by immunohistochemistry, ELISA, and qRT-PCR. Meanwhile, lung function (FEV1%pred) and inflammatory cytokines (IL-6 and IL-8) were examined, and correlation analysis was performed with RECK expression. The effect of RECK on proliferation, apoptosis, migration, and inflammatory cytokines and its potential mechanism was further quantified by neutrophil stimulated with recombinant human RECK protein (rhRECK) combined with CSE using CCK8, flow cytometry, Transwell assay, qRT-PCR, ELISA, and Western analysis.

RESULTS

RECK was mainly expressed on airway epithelial cells in normal lung tissue and was significantly diminished in COPD patients. The levels of RECK in sputum and plasma were also significantly decreased in COPD patients. Pearson correlation analysis showed that RECK level in plasma was positively correlated with FEV1%pred (r = 0.458, p < 0.001) and negatively correlated with IL-6 and IL-8 (r = -0.386, -0.437; p = 0.006, 0.002) in COPD patients. The expression of RECK was decreased in BEAS-2B stimulated with CSE. The migration, inflammation, and MMP-9 expression of neutrophils were promoted by CSE, while inhibited by rhRECK.

CONCLUSION

RECK is low expressed in COPD patients and negatively correlated with inflammation. It may inhibit the inflammation and migration of neutrophils by downregulating MMP-9.

Emerging roles of MT-MMPs in embryonic development

Membrane-type matrix metalloproteinases (MT-MMPs) are cell membrane-tethered proteinases that belong to the family of the MMPs. Apart from their roles in degradation of the extracellular milieu, MT-MMPs are able to activate through proteolytic processing at the cell surface distinct molecules such as receptors, growth factors, cytokines, adhesion molecules, and other pericellular proteins. Although most of the information regarding these enzymes comes from cancer studies, our current knowledge about their contribution in distinct developmental processes occurring in the embryo is limited. In this review, we want to summarize the involvement of MT-MMPs in distinct processes during embryonic morphogenesis, including cell migration and proliferation, epithelial-mesenchymal transition, cell polarity and branching, axon growth and navigation, synapse formation, and angiogenesis. We also considered information about MT-MMP functions from studies assessed in pathological conditions and compared these data with those relevant for embryonic development.

Current Perspectives on the Role of Matrix Metalloproteinases in the Pathogenesis of Basal Cell Carcinoma

Basal cell carcinoma (BCC) is the most common skin malignancy, which rarely metastasizes but has a great ability to infiltrate and invade the surrounding tissues. One of the molecular players involved in the metastatic process are matrix metalloproteinases (MMPs). MMPs are enzymes that can degrade various components of the extracellular matrix. In the skin, the expression of MMPs is increased in response to various stimuli, including ultraviolet (UV) radiation, one of the main factors involved in the development of BCC. By modulating various processes that are linked to tumor growth, such as invasion and angiogenesis, MMPs have been associated with UV-related carcinogenesis. The sources of MMPs are multiple, as they can be released by both neoplastic and tumor microenvironment cells. Inhibiting the action of MMPs could be a useful therapeutic option in BCC management. In this review that reunites the latest advances in this domain, we discuss the role of MMPs in the pathogenesis and evolution of BCC, as molecules involved in tumor aggressiveness and risk of recurrence, in order to offer a fresh and updated perspective on this field.

Targeting MMP-Regulation of Inflammation to Increase Metabolic Tolerance to COVID-19 Pathologies: A Hypothesis

Many individuals infected with the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) develop no or only mild symptoms, but some can go on onto develop a spectrum of pathologies including pneumonia, acute respiratory distress syndrome, respiratory failure, systemic inflammation, and multiorgan failure. Many pathogens, viral and non-viral, can elicit these pathologies, which justifies reconsidering whether the target of therapeutic approaches to fight pathogen infections should be (a) the pathogen itself, (b) the pathologies elicited by the pathogen interaction with the human host, or (c) a combination of both. While little is known about the immunopathology of SARS-CoV-2, it is well-established that the above-mentioned pathologies are associated with hyper-inflammation, tissue damage, and the perturbation of target organ metabolism. Mounting evidence has shown that these processes are regulated by endoproteinases (particularly, matrix metalloproteinases (MMPs)). Here, we review what is known about the roles played by MMPs in the development of COVID-19 and postulate a mechanism by which MMPs could influence energy metabolism in target organs, such as the lung. Finally, we discuss the suitability of MMPs as therapeutic targets to increase the metabolic tolerance of the host to damage inflicted by the pathogen infection, with a focus on SARS-CoV-2.

An integrative model of pathway convergence in genetically heterogeneous blast crisis chronic myeloid leukemia

Targeted therapies against the BCR-ABL1 kinase have revolutionized treatment of chronic phase (CP) chronic myeloid leukemia (CML). In contrast, management of blast crisis (BC) CML remains challenging because BC cells acquire complex molecular alterations that confer stemness features to progenitor populations and resistance to BCR-ABL1 tyrosine kinase inhibitors. Comprehensive models of BC transformation have proved elusive because of the rarity and genetic heterogeneity of BC, but are important for developing biomarkers predicting BC progression and effective therapies. To better understand BC, we performed an integrated multiomics analysis of 74 CP and BC samples using whole-genome and exome sequencing, transcriptome and methylome profiling, and chromatin immunoprecipitation followed by high-throughput sequencing. Employing pathway-based analysis, we found the BC genome was significantly enriched for mutations affecting components of the polycomb repressive complex (PRC) pathway. While transcriptomically, BC progenitors were enriched and depleted for PRC1- and PRC2-related gene sets respectively. By integrating our data sets, we determined that BC progenitors undergo PRC-driven epigenetic reprogramming toward a convergent transcriptomic state. Specifically, PRC2 directs BC DNA hypermethylation, which in turn silences key genes involved in myeloid differentiation and tumor suppressor function via so-called epigenetic switching, whereas PRC1 represses an overlapping and distinct set of genes, including novel BC tumor suppressors. On the basis of these observations, we developed an integrated model of BC that facilitated the identification of combinatorial therapies capable of reversing BC reprogramming (decitabine+PRC1 inhibitors), novel PRC-silenced tumor suppressor genes (NR4A2), and gene expression signatures predictive of disease progression and drug resistance in CP.

Neutrophil-derived granule cargoes: paving the way for tumor growth and progression

Neutrophils are the key cells of our innate immune system mediating host defense via a range of effector functions including phagocytosis, degranulation, and NETosis. For this, they employ an arsenal of anti-microbial cargoes packed in their readily mobilizable granule subsets. Notably, the release of granule content is tightly regulated; however, under certain circumstances, their unregulated release can aggravate tissue damage and could be detrimental to the host. Several constituents of neutrophil granules have also been associated with various inflammatory diseases including cancer. In cancer setting, their excessive release may modulate tissue microenvironment which ultimately leads the way for tumor initiation, growth and metastasis. Neutrophils actively infiltrate within tumor tissues, wherein they show diverse phenotypic and functional heterogeneity. While most studies are focused at understanding the phenotypic heterogeneity of neutrophils, their functional heterogeneity, much of which is likely orchestrated by their granule cargoes, is beginning to emerge. Therefore, a better understanding of neutrophil granules and their cargoes will not only shed light on their diverse role in cancer but will also reveal them as novel therapeutic targets. This review provides an overview on existing knowledge of neutrophil granules and detailed insight into the pathological relevance of their cargoes in cancer. In addition, we also discuss the therapeutic approach for targeting neutrophils or their microenvironment in disease setting that will pave the way forward for future research.

Designing Enzyme-responsive Biomaterials

Enzymes are a class of protein that catalyze a wide range of chemical reactions, including the cleavage of specific peptide bonds. They are expressed in all cell types, play vital roles in tissue development and homeostasis, and in many diseases, such as cancer. Enzymatic activity is tightly controlled through the use of inactive pro-enzymes, endogenous inhibitors and spatial localization. Since the presence of specific enzymes is often correlated with biological processes, and these proteins can directly modify biomolecules, they are an ideal biological input for cell-responsive biomaterials. These materials include both natural and synthetic polymers, cross-linked hydrogels and self-assembled peptide nanostructures. Within these systems enzymatic activity has been used to induce biodegradation, release therapeutic agents and for disease diagnosis. As technological advancements increase our ability to quantify the expression and nanoscale organization of proteins in cells and tissues, as well as the synthesis of increasingly complex and well-defined biomaterials, enzyme-responsive biomaterials are poised to play vital roles in the future of biomedicine.

Matrix metalloproteinases participation in the metastatic process and their diagnostic and therapeutic applications in cancer

Matrix metalloproteinases (MMPs) participate from the initial phases of cancer onset to the settlement of a metastatic niche in a second organ. Their role in cancer progression is related to their involvement in the extracellular matrix (ECM) degradation and in the regulation and processing of adhesion and cytoskeletal proteins, growth factors, chemokines and cytokines. MMPs participation in cancer progression makes them an attractive target for cancer therapy. MMPs have also been used for theranostic purposes in the detection of primary tumor and metastatic tissue in which a particular MMP is overexpressed, to follow up on therapy responses, and in the activation of cancer cytotoxic pro-drugs as part of nano-delivery-systems that increase drug concentration in a specific tumor target. Herein, we review MMPs molecular characteristics, their synthesis regulation and enzymatic activity, their participation in the metastatic process, and how their functions have been used to improve cancer treatment.

Different Faces for Different Places: Heterogeneity of Neutrophil Phenotype and Function

As the most abundant leukocytes in the circulation, neutrophils are committed to innate and adaptive immune effector function to protect the human body. They are capable of killing intruding microbes through various ways including phagocytosis, release of granules, and formation of extracellular traps. Recent research has revealed that neutrophils are heterogeneous in phenotype and function and can display outstanding plasticity in both homeostatic and disease states. The great flexibility and elasticity arm neutrophils with important regulatory and controlling functions in various disease states such as autoimmunity and inflammation as well as cancer. Hence, this review will focus on recent literature describing neutrophils' variable and diverse phenotypes and functions in different contexts.

Granulopoiesis and granules of human neutrophils

Granules are essential for the ability of neutrophils to fulfill their role in innate immunity. Granule membranes contain proteins that react to environmental cues directing neutrophils to sites of infection and initiate generation of bactericidal oxygen species. Granules are densely packed with proteins that contribute to microbial killing when liberated to the phagosome or extracellularly. Granules are, however, highly heterogeneous and are traditionally subdivided into azurophil granules, specific granules, and gelatinase granules in addition to secretory vesicles. This review will address issues pertinent to formation of granules, which is a process intimately connected to maturation of neutrophils from their precursors in the bone marrow. We further discuss possible mechanisms by which decisions are made regarding sorting of proteins to constitutive secretion or storage in granules and how degranulation of granule subsets is regulated.

Matrix metalloproteinase collagenolysis in health and disease

The proteolytic processing of collagen (collagenolysis) is critical in development and homeostasis, but also contributes to numerous pathologies. Mammalian interstitial collagenolytic enzymes include members of the matrix metalloproteinase (MMP) family and cathepsin K. While MMPs have long been recognized for their ability to catalyze the hydrolysis of collagen, the roles of individual MMPs in physiological and pathological collagenolysis are less defined. The use of knockout and mutant animal models, which reflect human diseases, has revealed distinct collagenolytic roles for MT1-MMP and MMP-13. A better understanding of temporal and spatial collagen processing, along with the knowledge of the specific MMP involved, will ultimately lead to more effective treatments for cancer, arthritis, cardiovascular conditions, and infectious diseases. This article is part of a Special Issue entitled: Matrix Metalloproteinases edited by Rafael Fridman.

Both Drosophila matrix metalloproteinases have released and membrane-tethered forms but have different substrates

Matrix metalloproteinases (MMPs) are extracellular proteases that can cleave extracellular matrix and alter signaling pathways. They have been implicated in many disease states, but it has been difficult to understand the contribution of individual MMPs, as there are over 20 MMPs in vertebrates. The vertebrate MMPs have overlapping substrates, they exhibit genetic redundancy and compensation, and pharmacological inhibitors are non-specific. In contrast, there are only two MMP genes in Drosophila, DmMmp1 and DmMmp2, which makes Drosophila an attractive system to analyze the basis of MMP specificity. Previously, Drosophila MMPs have been categorized by their pericellular localization, as Mmp1 appeared to be secreted and Mmp2 appeared to be membrane-anchored, suggesting that protein localization was the critical distinction in this small MMP family. We report here that products of both genes are found at the cell surface and released into media. Additionally, we show that products of both genes contain GPI-anchors, and unexpectedly, that GPI-anchored MMPs promote cell adhesion when they are rendered inactive. Finally, by using new reagents and assays, we show that the two MMPs cleave different substrates, suggesting that this is the important distinction within this smallest MMP family.

Matrix metalloproteinases as reagents for cell isolation

Cell isolation methods for therapeutic purposes have seen little advancement over the years. The original methods of stem cell and islet isolation using bacterial collagenases were developed in the early 1980s and are still used today. Bacterial collagenases are subject to autodegradation, and isolates obtained with these enzymes may be contaminated with endotoxins, reducing cell viability and contributing to toxicity in downstream applications. Here we describe a novel method for isolation of mesenchymal stem cells from adipose tissue (ADSC) utilizing recombinantly produced matrix metalloproteases (MMPs). The ADSCs isolated by MMPs displayed essentially identical morphological and phenotypical characteristics to cells isolated by bacterially-derived collagenase I and Liberase™. Samples isolated with MMPs and Liberase™ had comparable levels of CD73, CD90, and CD105. The adipogenic and osteogenic potential of the ADSCs isolated by MMPs was retained as compared to cells isolated with Liberase™. However, ADSCs isolated by Liberase™ displayed 6% contamination with other cells as per negative markers revealed by PE staining, as opposed to<1% for all MMP-treated samples. MMP-based cell isolation may contribute to optimization of transplantation technology.

MMP-25 Metalloprotease Regulates Innate Immune Response through NF-κB Signaling

Matrix metalloproteases (MMPs) regulate innate immunity acting over proinflammatory cytokines, chemokines, and other immune-related proteins. MMP-25 (membrane-type 6-MMP) is a membrane-bound enzyme predominantly expressed in leukocytes whose biological function has remained largely unknown. We have generated Mmp25-deficient mice to elucidate the in vivo function of this protease. These mutant mice are viable and fertile and do not show any spontaneous phenotype. However, Mmp25-null mice exhibit a defective innate immune response characterized by low sensitivity to bacterial LPS, hypergammaglobulinemia, and reduced secretion of proinflammatory molecules. Moreover, these immune defects can be tracked to a defective NF-κB activation observed in Mmp25-deficient leukocytes. Globally, our findings provide new mechanistic insights into innate immunity through the activity of MMP-25, suggesting that this proteinase could be a potential therapeutic target for immune-related diseases.

Pathophysiological changes induced by Pseudomonas aeruginosa infection are involved in MMP-12 and MMP-13 upregulation in human carcinoma epithelial cells and a pneumonia mouse model

Pseudomonas aeruginosa infections persist in patients with cystic fibrosis (CF) and drive lung disease progression. P. aeruginosa potently activates the innate immune system mostly through the recognition of pathogen-associated molecular patterns, such as flagellin. Matrix metalloproteinases 12 and 13 (MMP-12 and MMP-13, respectively) exacerbate chronic lung infection and inflammation by promoting uncontrolled tissue rearrangements and fibrosis, yet the underlying molecular mechanisms by which this occurs remain largely unknown. In this study, we used quantitative bacteriology, histological examination, and proinflammatory cytokine levels to evaluate the effects of MMP-12 and MMP-13 on P. aeruginosa strain K-induced infection and pneumonia in H292 epithelial cells and mice, respectively. Under inflammatory stimulation, mRNA and protein expression levels of proinflammatory mediators were higher in strain K-infected mice and cells than in uninfected counterparts, in which MMP-12 and MMP-13 expression reached levels similar to those observed in epithelial cells. Moreover, we also found that the NF-κB pathway might be involved in the induction of cytokines in response to strain K infection. Taken together, these data suggest that MMP-12 and MMP-13 alter strain K infection in mice and play a role in inflammatory regulation by modulating cytokine levels.

Membrane-type matrix metalloproteinases: Their functions and regulations

Membrane-type matrix metalloproteinases (MT-MMPs) form a subgroup of the matrix metalloproteinase (MMP) family, and there are 6 MT-MMPs in humans. MT-MMPs are further sub-classified into type I transmembrane-type (MT1, -MT2-, MT3- and MT5-MMPs) and glycosylphosphatidylinositol (GPI)-anchored type (MT4- and MT6-MMPs). In either case MT-MMPs are tethered to the plasma membrane, and this cell surface expression provides those enzymes with unique functionalities affecting various cellular behaviours. Among the 6 MT-MMPs, MT1-MMP is the most investigated enzyme and many of its roles and regulations have been revealed to date, but the potential roles and regulatory mechanisms of other MT-MMPs are gradually getting clearer as well. Further investigations of MT-MMPs are likely to reveal novel pathophysiological mechanisms and potential therapeutic strategies for different diseases in the future.

Mmp25β facilitates elongation of sensory neurons during zebrafish development

Matrix metalloproteinases (MMPs) are a large and complex family of zinc-dependent endoproteinases widely recognized for their roles in remodeling the extracellular matrix (ECM) during embryonic development, wound healing, and tissue homeostasis. Their misregulation is central to many pathologies, and they have therefore been the focus of biomedical research for decades. These proteases have also recently emerged as mediators of neural development and synaptic plasticity in vertebrates, however, understanding of the mechanistic basis of these roles and the molecular identities of the MMPs involved remains far from complete. We have identified a zebrafish orthologue of mmp25 (a.k.a. leukolysin; MT6-MMP), a membrane-type, furin-activated MMP associated with leukocytes and invasive carcinomas, but which we find is expressed by a subset of the sensory neurons during normal embryonic development. We detect high levels of Mmp25β expression in the trigeminal, craniofacial, and posterior lateral line ganglia in the hindbrain, and in Rohon-Beard cells in the dorsal neural tube during the first 48 h of embryonic development. Knockdown of Mmp25β expression with morpholino oligonucleotides results in larvae that are uncoordinated and insensitive to touch, and which exhibit defects in the development of sensory neural structures. Using in vivo zymography, we observe that Mmp25β morphant embryos show reduced Type IV collagen degradation in regions of the head traversed by elongating axons emanating from the trigeminal ganglion, suggesting that Mmp25β may play a pivotal role in mediating ECM remodeling in the vicinity of these elongating axons.

Neutrophils and emerging targets for treatment in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is characterized by a decreased airflow due to airway narrowing that, once it occurs, is not fully reversible. The disease usually is progressive and associated with an enhanced inflammatory response in the lungs after exposure to noxious particles or gases. After removal of the noxious particles, the inflammation can continue in a self-sustaining manner. It has been established that improper activation of neutrophils lies at the core of the pathology. This paper provides an overview of the mechanisms by which neutrophils can induce the pulmonary damage of COPD. As the pathogenesis of COPD is slowly being unraveled, new points of intervention are discovered, some of which with promising results.

Neutrophil extracellular traps induce endothelial dysfunction in systemic lupus erythematosus through the activation of matrix metalloproteinase-2

RATIONALE

The structural and functional integrity of the endothelium is crucial in maintaining vascular homeostasis and preventing atherosclerosis. Patients with systemic lupus erythematosus (SLE) have an increased risk of developing endothelial dysfunction and premature cardiovascular disease. Neutrophil extracellular trap (NET) formation is increased in SLE and has been proposed to contribute to endothelial damage, but the mechanism remains unclear.

OBJECTIVE

To determine the mechanism by which enhanced NET formation by low-density granulocytes (LDGs) in SLE contributes to endothelial damage and disrupts the endothelium.

RESULTS

The putative role of NET-externalised matrix metalloproteinases (MMPs) in altering the functional integrity of the endothelium was examined. MMP-9 externalised by lupus LDGs during NET formation specifically impaired murine aortic endothelium-dependent vasorelaxation and induced endothelial cell apoptosis. Endothelial dysfunction correlated with the activation of endothelial MMP-2 by MMP-9 present in NETs, while inhibition of MMP-2 activation restored endothelium-dependent function and decreased NET-induced vascular cytotoxicity. Moreover, immunogenic complexes composed of MMP-9 and anti-MMP-9 were identified in SLE sera. These complexes, as well as anti-MMP-9 autoantibodies, induced NETosis and enhanced MMP-9 activity.

CONCLUSIONS

These observations implicate activation of endothelial MMP-2 by MMP-9 contained in NETs as an important player in endothelial dysfunction, and MMP-9 as a novel self-antigen in SLE. These results further support that aberrant NET formation plays pathogenic roles in SLE.

Clinical significance of sIL-2R levels in B-cell lymphomas

Elevated soluble interleukin-2 receptor (sIL-2R) in sera is observed in patients with malignant lymphoma (ML). Therefore, sIL-2R is commonly used as a diagnostic and prognostic marker for ML, but the mechanisms responsible for the increase in sIL-2R levels in patients with B-cell lymphomas have not yet been elucidated. We first hypothesized that lymphoma cells expressing IL-2R and some proteinases such as matrix metalloproteinases (MMPs) in the tumor microenvironment can give rise to increased sIL-2R in sera. However, flow cytometric studies revealed that few lymphoma cells expressed IL-2R α chain (CD25) in diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL), and most CD25-expressing cells in the tumor were T-cells. Distinct correlations between CD25 expression on B-lymphoma cells and sIL-2R levels were not observed. We then confirmed that MMP-9 plays an important role in producing sIL-2R in functional studies. Immunohistochemical (IHC) analysis also revealed that MMP-9 is mainly derived from tumor-associated macrophages (TAMs). We therefore evaluated the number of CD68 and CD163 positive macrophages in the tumor microenvironment using IHC analysis. A positive correlation between the levels of sIL-2R in sera and the numbers of CD68 positive macrophages in the tumor microenvironment was confirmed in FL and extranodal DLBCL. These results may be useful in understanding the pathophysiology of B-cell lymphomas.

Serum biomarkers in elderly asthma

OBJECTIVE

Asthma is usually misdiagnosed and under-treated in the elderly population, resulting in complications and increased severity to the patient. In this review, we describe some of the most important serum markers of asthma studied so far, reporting their outcomes and possible prediction of asthma in the elderly population.

METHODS

The PubMed electronic database was used to search for promising serum biomarkers of asthma studied in original articles published in peer-reviewed journals from 2000 to January 2013.

RESULTS

A total of 13 relevant serum biomarkers were selected, including IgE, CRP, high sensitive CRP, IL-6, IL-8, IL-17, TNF-α, neopterin, serum amyloid A, eosinophil cationic protein, leukolysin, YKL-40 and soluble CD86.

CONCLUSIONS

Although the major focus of treatment and research has been on allergic asthma, several forms of the disease are recognized, such as neutrophilic asthma, which is characteristic of older patients. Different phenotypes imply different treatments and so it becomes important to correctly determine which type of asthma the patient is suffering from. Serum markers capable of supporting a diagnosis of asthma are needed in order to counter mistreatment and misdiagnosis with other obstructive airways disease (OAD) in elderly patients. As convenient as serum markers may seem to be, a marker capable of accurately identifying asthma with sufficient specificity is yet to be found.

Membrane-type 6 matrix metalloproteinase regulates the activation-induced downmodulation of CD16 in human primary NK cells

CD16 (FcγRIIIa), the low-affinity receptor for IgG, expressed by the majority of human NK cells, is a potent activating receptor that facilitates Ab-dependent cell-mediated cytotoxicity (ADCC). ADCC dysfunction has been linked to cancer progression and poor prognosis for chronic infections, such as HIV; thus, understanding how CD16 expression is regulated by NK cells has clinical relevance. Importantly, CD16 cell-surface expression is downmodulated following NK cell activation and, in particular, exposure to stimulatory cytokines (IL-2 or IL-15), likely owing to the action of matrix metalloproteinases (MMPs). In this article, we identify membrane-type 6 (MT6) MMP (also known as MMP25) as a proteinase responsible for CD16 downmodulation. IL-2-induced upregulation of MT6/MMP25 cell-surface expression correlates with CD16 downmodulation. MT6/MMP25, sequestered in intracellular compartments in unstimulated NK cells, translocates to the cell surface after stimulation; moreover, it polarizes to the effector-target cell interface of the CD16-mediated immunological synapse. siRNA-mediated disruption of MT6/MMP25 expression enhances the ADCC capacity of NK cells, emphasizing the important functional role of MT6/MMP25 in the regulation of ADCC activity. Thus, this study uncovers a previously unknown role of MT6/MMP25 in human NK cells, and suggests that inhibition of MT6/MMP25 activity could improve ADCC efficacy of therapeutically administered NK cells that require IL-2 for culture and expansion.

Membrane-type matrix metalloproteinases: key mediators of leukocyte function

Leukocytes are major cellular effectors of the immune response. To accomplish this task, these cells display a vast arsenal of proteinases, among which, members of the MMP family are especially important. Leukocytes express several members of the MMP family, including secreted- and membrane-anchored MT- MMPs, which synergistically orchestrate an appropriate proteolytic reaction that ultimately modulates immunological responses. The MT-MMP subfamily comprises TM- and GPI-anchored proteinases, which are targeted to well-defined membrane microdomains and exhibit different substrate specificities. Whereas much information exists on the biological roles of secreted MMPs in leukocytes, the roles of MT-MMPs remain relatively obscure. This review summarizes the current knowledge on the expression of MT-MMPs in leukocyte and their contribution to the immune responses and to pathological conditions.

Interstitial collagen catabolism

Interstitial collagen mechanical and biological properties are altered by proteases that catalyze the hydrolysis of the collagen triple-helical structure. Collagenolysis is critical in development and homeostasis but also contributes to numerous pathologies. Mammalian collagenolytic enzymes include matrix metalloproteinases, cathepsin K, and neutrophil elastase, and a variety of invertebrates and pathogens possess collagenolytic enzymes. Components of the mechanism of action for the collagenolytic enzyme MMP-1 have been defined experimentally, and insights into other collagenolytic mechanisms have been provided. Ancillary biomolecules may modulate the action of collagenolytic enzymes.

Role of Proteases in Inflammatory Lung Diseases

Proteases are enzymes that have the capacity to hydrolyze peptide bonds and degrade other proteins. Proteases can promote inflammation by regulating expression and activity of different pro-inflammatory cytokines, chemokines and other immune components in the lung compartment. They are categorized in three major subcategories: serine proteases, metalloproteases and cysteine proteases especially in case of lung diseases. Neutrophil-derived serine proteases (NSPs), metalloproteases and some mast cell-derived proteases are mainly focused here. Their modes of actions are different in different diseases for e.g. NE induces the release of IL-8 from lung epithelial cells through a MyD88/IRAK/TRAF-6-dependent pathway and also through EGFR MAPK pathway. NSPs contribute to immune regulation during inflammation through the cleavage and activation of specific cellular receptors. MMPs can also influence the progression of various inflammatory processes and there are many non-matrix substrates for MMPs, such as chemokines, growth factors and receptors. During lung inflammation interplay between NE and MMP is an important significant phenomenon. They have been evaluated as therapeutic targets in several inflammatory lung diseases. Here we review the role of proteases in various lung inflammatory diseases with emphasis on their mode of action and contribution to immune regulation during inflammation.

The history of matrix metalloproteinases: milestones, myths, and misperceptions

Since the discovery of tadpole collagenase in 1962, the matrix metalloproteinase (MMP) family has emerged as a significant proteinase group with recognized effects on the cardiovascular system. Over the last 40 years, many milestones have been achieved, from the identification of the first MMP, to the generation of the first MMP cDNA clone and null mouse, to the clinical approval of the first MMP inhibitor. Over the years, a few myths and misunderstandings have interwoven into the truths. In this review, we will discuss the major milestones of MMP research, as well as review the misinterpretations and misperceptions that have evolved. Clarifying the confusions and dispelling the myths will both provide a better understanding of MMP properties and functions and focus the cardiovascular field on the outstanding research questions that need to be addressed.

Biochemical characterization and N-terminomics analysis of leukolysin, the membrane-type 6 matrix metalloprotease (MMP25): chemokine and vimentin cleavages enhance cell migration and macrophage phagocytic activities

The neutrophil-specific protease membrane-type 6 matrix metalloproteinase (MT6-MMP)/MMP-25/leukolysin is implicated in multiple sclerosis and cancer yet remains poorly characterized. To characterize the biological roles of MT6-MMP, it is critical to identify its substrates for which only seven are currently known. Here, we biochemically characterized MT6-MMP, profiled its tissue inhibitor of metalloproteinase inhibitory spectrum, performed degradomics analyses, and screened 26 chemokines for cleavage using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. MT6-MMP processes seven each of the CXC and CC chemokine subfamilies. Notably, cleavage of the neutrophil chemoattractant CXCL5 activates the chemokine, thereby increasing its agonist activity, indicating a feed-forward mechanism for neutrophil recruitment. Likewise, cleavage also activated CCL15 and CCL23 to increase monocyte recruitment. Utilizing the proteomics approach proteomic identification of cleavage site specificity (PICS), we identified 286 peptidic cleavage sites spanning from P6 to P6′ from which an unusual glutamate preference in P1 was identified. The degradomics screen terminal amine isotopic labeling of substrates (TAILS), which enriches for neo-N-terminal peptides of cleaved substrates, was used to identify 58 new native substrates in fibroblast secretomes after incubation with MT6-MMP. Vimentin, cystatin C, galectin-1, IGFBP-7, and secreted protein, acidic and rich in cysteine (SPARC) were among those substrates we biochemically confirmed. An extracellular “moonlighting” form of vimentin is a chemoattractant for THP-1 cells, but MT6-MMP cleavage abolished monocyte recruitment. Unexpectedly, the MT6-MMP-cleaved vimentin potently stimulated phagocytosis, which was not a property of the full-length protein. Hence, MT6-MMP regulates neutrophil and monocyte chemotaxis and by generating “eat-me” signals upon vimentin cleavage potentially increases phagocytic removal of neutrophils to resolve inflammation.

Human matrix metalloproteinases: an ubiquitarian class of enzymes involved in several pathological processes

Human matrix metalloproteinases (MMPs) belong to the M10 family of the MA clan of endopeptidases. They are ubiquitarian enzymes, structurally characterized by an active site where a Zn(2+) atom, coordinated by three histidines, plays the catalytic role, assisted by a glutamic acid as a general base. Various MMPs display different domain composition, which is very important for macromolecular substrates recognition. Substrate specificity is very different among MMPs, being often associated to their cellular compartmentalization and/or cellular type where they are expressed. An extensive review of the different MMPs structural and functional features is integrated with their pathological role in several types of diseases, spanning from cancer to cardiovascular diseases and to neurodegeneration. It emerges a very complex and crucial role played by these enzymes in many physiological and pathological processes.

Regulation of matrix metalloproteinases activity studied in human endometrium as a paradigm of cyclic tissue breakdown and regeneration

When abundant and activated, matrix metalloproteinases (MMPs, or matrixins) degrade most, if not all, constituents of the extracellular matrix (ECM). The resulting massive tissue breakdown is best exemplified in humans by the menstrual lysis and shedding of the endometrium, the mucosa lining the uterus. After menstruation, MMP activity needs to be tightly controlled as the endometrium regenerates and differentiates to avoid abnormal tissue breakdown while allowing tissue repair and fine remodelling to accommodate implantation of a blastocyst. This paper reviews how MMPs are massively present and activated in the endometrium at menstruation, and how their activity is tightly controlled at other phases of the cycle. Progesterone represses expression of many but not all MMPs. Its withdrawal triggers focal expression of MMPs specifically in the areas undergoing lysis, an effect mediated by local cytokines such as interleukin-1α, LEFTY-2, tumour necrosis factor-α and others. MMP-3 is selectively expressed at that time and activates proMMP-9, otherwise present in latent form throughout the cycle. In addition, a large number of neutrophils loaded with MMPs are recruited at menstruation through induction of chemokines, such as interleukin-8. At the secretory phase, progesterone repression of MMPs is mediated by transforming growth factor-β. Tissue inhibitors of metalloproteinases (TIMPs) are abundant at all phases of the cycle to prevent any undue MMP activity, but are likely overwhelmed at menstruation. At other phases of the cycle, MMPs can elude TIMP inhibition as exemplified by recruitment of active MMP-7 to the plasma membrane of epithelial cells, allowing processing of membrane-associated growth factors needed for epithelial repair and proliferation. Finally, receptor-mediated endocytosis through low density lipoprotein receptor-related protein-1 (LRP-1) efficiently clears MMP-2 and -9 at the proliferative and secretory phases. This mechanism is probably essential to prevent any excessive ECM degradation by the active form of MMP-2 that is permanently present. However, shedding of the ectodomain of LRP-1 specifically at menstruation prevents endocytosis of MMPs allowing full degradation of the ECM. Thus endometrial MMPs are regulated at the levels of transcription, release from infiltrating neutrophils, activation, binding to the cell membrane, inhibition by TIMPs and endocytic clearance by LRP-1. This allows tight control during endometrial growth and differentiation but results in a burst of activity for menstrual tissue breakdown. This article is part of a Special Issue entitled: Proteolysis 50 years after the discovery of lysosome.

Neutrophils, from marrow to microbes

Neutrophils are produced in the bone marrow from stem cells that proliferate and differentiate to mature neutrophils fully equipped with an armory of granules. These contain proteins that enable the neutrophil to deliver lethal hits against microorganisms, but also to cause great tissue damage. Neutrophils circulate in the blood as dormant cells. At sites of infection, endothelial cells capture bypassing neutrophils and guide them through the endothelial cell lining whereby the neutrophils are activated and tuned for the subsequent interaction with microbes. Once in tissues, neutrophils kill microorganisms by microbicidal agents liberated from granules or generated by metabolic activation. As a final act, neutrophils can extrude stands of DNA with bactericidal proteins attached that act as extracellular traps for microorganisms.

New Strategies for the Next Generation of Matrix-Metalloproteinase Inhibitors: Selectively Targeting Membrane-Anchored MMPs with Therapeutic Antibodies

MMP intervention strategies have met with limited clinical success due to severe toxicities. In particular, treatment with broad-spectrum MMP-inhibitors (MMPIs) caused musculoskeletal pain and inflammation. Selectivity may be essential for realizing the clinical potential of MMPIs. Here we review discoveries pinpointing membrane-bound MMPs as mediators of mechanisms underlying cancer and inflammation and as possible therapeutic targets for prevention/treatment of these diseases. We discuss strategies to target these therapeutic proteases using highly selective inhibitory agents (i.e., human blocking antibodies) against individual membrane-bound MMPs.

Gene expression analysis in induced sputum from welders with and without airway-related symptoms

PURPOSE

To identify changes in gene expression in the airways among welders, with and without lower airway symptoms, working in black steel.

METHODS

Included were 25 male, non-smoking welders. Each welder was sampled twice; before exposure (after vacation), and after 1 month of exposure. From the welders (14 symptomatic, of whom 7 had asthma-like symptoms), RNA from induced sputum was obtained for gene expression analysis. Messenger RNA from a subset of the samples (n = 7) was analysed with microarray technology to identify genes of interest. These genes were further analysed using quantitative PCR (qPCR; n = 22).

RESULTS

By comparing samples before and after exposure, the microarray analysis resulted in several functional annotation clusters: the one with the highest enrichment score contained "response to wounding", "inflammatory response" and "defence response". Seven genes were analysed by qPCR: granulocyte colony-stimulating factor 3 receptor (CSF3R), superoxide dismutase 2, interleukin 8, glutathione S-transferase pi 1, tumour necrosis factor alpha-induced protein 6 (TNFAIP6), interleukin 1 receptor type II and matrix metallopeptidase 25 (MMP25). Increased levels of CSF3R, TNFAIP6 and MMP25 were indicated among asthmatic subjects compared to non-symptomatic subjects, although the differences did not reach significance.

CONCLUSIONS

Workers' exposure to welding fumes changed gene expression in the lower airways in genes involved in inflammatory and defence response. Thus, microarray and qPCR technique can demonstrate markers of exposure to welding fumes and possible disease-related markers. However, further studies are needed to verify genes involved and to further characterise the mechanism for welding fumes-associated lower airway symptoms.

Cancer dissemination--lessons from leukocytes

Cancer cells can move through tissues in a variety of different ways. In some cases, an epithelial-to-mesenchymal transition enables cancer cells to acquire fibroblast-like migratory properties. However, it is also becoming apparent that some cancer cells move in an amoeboid way similar to leukocytes. This theme will be the focus of the review, where we will discuss the similarities and differences between the mechanisms used by cancer cells and leukocytes to cross parenchymal basement membranes, move through interstitial tissue, and enter and exit the vasculature. Further, we propose that the ability to switch between different migratory mechanisms is critical for cells to relocate from one tissue to another.

Physiology and pathophysiology of matrix metalloproteases

Matrix metalloproteases (MMPs) comprise a family of enzymes that cleave protein substrates based on a conserved mechanism involving activation of an active site-bound water molecule by a Zn(2+) ion. Although the catalytic domain of MMPs is structurally highly similar, there are many differences with respect to substrate specificity, cellular and tissue localization, membrane binding and regulation that make this a very versatile family of enzymes with a multitude of physiological functions, many of which are still not fully understood. Essentially, all members of the MMP family have been linked to disease development, notably to cancer metastasis, chronic inflammation and the ensuing tissue damage as well as to neurological disorders. This has stimulated a flurry of studies into MMP inhibitors as therapeutic agents, as well as into measuring MMP levels as diagnostic or prognostic markers. As with most protein families, deciphering the function(s) of MMPs is difficult, as they can modify many proteins. Which of these reactions are physiologically or pathophysiologically relevant is often not clear, although studies on knockout animals, human genetic and epigenetic, as well as biochemical studies using natural or synthetic inhibitors have provided insight to a great extent. In this review, we will give an overview of 23 members of the human MMP family and describe functions, linkages to disease and structural and mechanistic features. MMPs can be grouped into soluble (including matrilysins) and membrane-anchored species. We adhere to the 'MMP nomenclature' and provide the reader with reference to the many, often diverse, names for this enzyme family in the introduction.

MT6-MMP is present in lipid rafts and faces inward in living human PMNs but translocates to the cell surface during neutrophil apoptosis

Polymorphonuclear neutrophils (PMNs) are the first line of defense against invading organisms in humans; in addition, PMNs contribute to the linking of innate and adaptive immunity. To fulfill their biological behavior, PMNs utilize an arsenal of proteolytic enzymes, including members of the matrix metalloproteinase family of zinc-dependent endopeptidases. PMNs express high levels of MT6-MMP (MMP-25), a glycosyl-phosphatidylinositol-anchored MMP, that belongs to the subfamily of membrane-anchored matrix metalloproteinases. Due to the paucity of information on MT6-MMP in primary cells, we set to investigate the localization and potential function of MT6-MMP in human PMNs. We found that MT6-MMP is present in the membrane, granules and nuclear/endoplasmic reticulum/Golgi fractions of PMNs where it is displayed as a disulfide-linked homodimer of 120 kDa. Stimulation of PMNs resulted in secretion of active MT6-MMP into the supernatants. Membrane-bound MT6-MMP, conversely, is located in the lipid rafts of resting PMNs and stimulation does not alter this location. In addition, TIMP-2, a natural inhibitor of MT6-MMP, does not co-localize with it in the lipid rafts. Interestingly, living PMNs do not display MT6-MMP on the cell surface. However, induction of apoptosis induces MT6-MMP relocation on PMNs' cell surface. Our studies suggest that metalloproteinases may play a role in respiratory burst and IL-8 secretion, but not chemotaxis or granulocyte macrophage colony-stimulating factor-induced survival. Collectively, these results provide new insights on the role of MT6-MMP in the physiology of human PMNs.

Serum metalloproteinase leukolysin (MMP-25/MT-6): a potential metabolic marker for atopy-associated inflammation

BACKGROUND

Leukolysin is a novel matrix metalloproteinase (MMP-25/MT-6) released mainly by granulocytic cells, primarily neutrophils, which are implicated in chronic airways inflammation.

OBJECTIVE

To determine if leukolysin might be a serum marker for atopic asthma or chronic obstructive pulmonary disease (COPD).

METHODS

Three study populations were evaluated: (1) nuclear families with medical history of atopic asthma (N=337), (2) married-in individuals from an independent study of asthma genetics (N=122) and (3) randomly selected males with diagnosis of COPD (N=100). Each person was screened for asthma or COPD symptoms, respiratory function by standardized spirometry and serum total IgE and leukolysin and anti-IL1 levels by immunoassay. Study groups (1 and 2) were also screened by skin prick test using a battery of 14 common aeroallergens. Heritability estimates for leukolysin and total IgE were made by variance components analysis.

RESULTS

For those without asthma or who had asthma defined as having symptoms, a physician's diagnosis and bronchial hyper-reactivity as demonstrated by reversibility in response to albuteral and/or bronchial reactivity as measured by a methacholine challenge, serum leukolysin levels were found to be higher for those with any positive skin test result. This paralleled trends for serum total IgE. In the nuclear families and COPD patients, serum leukolysin levels were significantly elevated for those who also had elevated total IgE levels (log[IgE]>2.0) compared with those with lower IgE (log[IgE]<2.0). Serum IL-1 levels correlated with the leukolycin levels. In contrast to IgE, leukolysin showed no apparent inherited component.

CONCLUSION

Among individuals with history of chronic airways inflammation (asthma and COPD) serum leukolysin may be a metabolic marker associated with chronic atopy-associated respiratory inflammation. Common factors may stimulate increased production or release of both leukolysin from myeloid cells and IgE from lymphoid cells.

Effect of exercise on gene expression profile in unfractionated peripheral blood leukocytes

A 4-h bout of exercise induces immunomodulatory effects. Peripheral blood was withdrawn before, and at 4, 8 and 24h after the start of exercise. RNA from the unfractionated white blood cells was analyzed using Agilent human 44K microarray. The expression profiles were sorted into seven clusters based on their unique time-dependent kinetics. In a separate experiment, cell-specific markers were collected and compared among the members in each cluster. Two clusters were assigned as representing neutrophils, one as NK cells, and another mostly as T cells. Three clusters seemed to be mixtures of several cell types. Extension of this approach to other systems is discussed.

The roles of antimicrobial peptides in innate host defense

Antimicrobial peptides (AMPs) are multi-functional peptides whose fundamental biological role in vivo has been proposed to be the elimination of pathogenic microorganisms, including Gram-positive and -negative bacteria, fungi, and viruses. Genes encoding these peptides are expressed in a variety of cells in the host, including circulating phagocytic cells and mucosal epithelial cells, demonstrating a wide range of utility in the innate immune system. Expression of these genes is tightly regulated; they are induced by pathogens and cytokines as part of the host defense response, and they can be suppressed by bacterial virulence factors and environmental factors which can lead to increased susceptibility to infection. New research has also cast light on alternative functionalities, including immunomodulatory activities, which are related to their unique structural characteristics. These peptides represent not only an important component of innate host defense against microbial colonization and a link between innate and adaptive immunity, but also form a foundation for the development of new therapeutic agents.

IL-8 induces exocytosis of arginase 1 by neutrophil polymorphonuclears in nonsmall cell lung cancer

Arginase 1 (ARG1) inhibits T-cell proliferation by degrading extracellular arginine, which results in decreased responsiveness of T cells to CD3/TCR stimulation. In humans, ARG1 is stored in inactive form within granules of polymorphonuclear neutrophils (PMNs) and gets activated on release. We studied the role of PMNs-related ARG1 activity in nonsmall cell lung cancer (NSLC), in which tumor-infiltrating lymphocytes showed reduced proliferation in response to CD3/TCR triggering. Patients with NSCLC had increased ARG1 plasma levels as compared to healthy controls. Furthermore, immunohistochemistry showed that tumor-infiltrating PMNs display reduced intracellular ARG1, in comparison to intravascular or peritumoral PMNs, suggesting a role of tumor microenvironment in ARG1 release. Indeed, supernatants of NSCLC cell lines induced exocytosis of ARG1 from PMNs. All (4/4) NSCLC cell lines and all (7/7) CD14- cell samples from NSCLC expressed interleukin (IL)-8 mRNA, whereas TNFalpha mRNA was expressed by 1 cell line and by 2 tumor specimens. Furthermore, all NSCLC cell lines secreted immunoreactive IL-8, albeit at different levels. IL-8 was as effective as TNFalpha in triggering ARG1 release and the 2 cytokines acted synergistically. Secreted ARG1 was biologically active and catabolized extracellular arginine. The supernatant of IL-8 gene-silenced NSCLC cells did not mediate ARG1 release by PMNs. Altogether these findings demonstrate a role of IL-8 in ARG1 exocytosis by PMNs and indicate that, due at least in part to IL-8 secreted by NSCLC cells, PMNs infiltrating NSCLC release ARG1. This phenomenon could contribute to local immune suppression.

Differential Processing of {alpha}- and {beta}-Defensin Precursors by Matrix Metalloproteinase-7 (MMP-7)

Proteolytic processing of defensins is a critical mode of posttranslational regulation of peptide activity. Because mouse alpha-defensin precursors are cleaved and activated by matrix metalloproteinase-7 (MMP-7), we determined if additional defensin molecules, namely human neutrophil defensin pro-HNP-1 and beta-defensins, are targets for MMP-7. We found that MMP-7 cleaves within the pro-domain of the HNP-1 precursor, a reaction that does not generate the mature peptide but produces a 59-amino acid intermediate. This intermediate, which retains the carboxyl-terminal end of the pro-domain, had antimicrobial activity, indicating that the residues important for masking defensin activity reside in the amino terminus of this domain. Mature HNP-1 was resistant to processing by MMP-7 unless the peptide was reduced and alkylated, demonstrating that only the pro-domain of alpha-defensins is normally accessible for cleavage by this enzyme. From the 47-residue HBD-1 precursor, MMP-7 catalyzed removal of 6 amino acids from the amino terminus. Neither a 39-residue intermediate form of HBD-1 nor the mature 36-residue form of HBD-1 was cleaved by MMP-7. In addition, both pro-HBD-2, with its shorter amino-terminal extension, and pro-HBD-3 were resistant to MMP-7. However, human and mouse beta-defensin precursors that lack disulfide bonding contain a cryptic MMP-7-sensitive site within the mature peptide moiety. These findings support and extend accumulating evidence that the native three-dimensional structure of both alpha- and beta-defensins protects the mature peptides against proteolytic processing by MMP-7. We also conclude that sites for MMP-7 cleavage are more common at the amino termini of alpha-defensin rather than beta-defensin precursors, and that catalysis at these sites in alpha-defensin pro-domains results in acquisition of defensin activity.

Matrix metalloproteinase proteolysis of the myelin basic protein isoforms is a source of immunogenic peptides in autoimmune multiple sclerosis

Background

Matrix metalloproteinases (MMPs) play a significant role in the fragmentation of myelin basic protein (MBP) and demyelination leading to autoimmune multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE). The classic MBP isoforms are predominantly expressed in the oligodendrocytes of the CNS. The splice variants of the single MBP gene (Golli-MBP BG21 and J37) are widely expressed in the neurons and also in the immune cells. The relative contribution of the individual MMPs to the MBP cleavage is not known.

Methodology/Principal Findings

To elucidate which MMP plays the primary role in cleaving MBP, we determined the efficiency of MMP-2, MMP-8, MMP-9, MMP-10, MMP-12, MT1-MMP, MT2-MMP, MT3-MMP, MT4-MMP, MT5-MMP and MT6-MMP in the cleavage of the MBP, BG21 and J37 isoforms in the in vitro cleavage reactions followed by mass-spectroscopy analysis of the cleavage fragments. As a result, we identified the MMP cleavage sites and the sequence of the resulting fragments. We determined that MBP, BG21 and J37 are highly sensitive to redundant MMP proteolysis. MT6-MMP (initially called leukolysin), however, was superior over all of the other MMPs in cleaving the MBP isoforms. Using the mixed lymphocyte culture assay, we demonstrated that MT6-MMP proteolysis of the MBP isoforms readily generated, with a near quantitative yield, the immunogenic N-terminal 1–15 MBP peptide. This peptide selectively stimulated the proliferation of the PGPR7.5 T cell clone isolated from mice with EAE and specific for the 1–15 MBP fragment presented in the MHC H-2^U context.

Conclusions/Significance

In sum, our biochemical observations led us to hypothesize that MT6-MMP, which is activated by furin and associated with the lipid rafts, plays an important role in MS pathology and that MT6-MMP is a novel and promising drug target in MS especially when compared with other individual MMPs.

Doxycycline therapy for abdominal aneurysm: Improved proteolytic balance through reduced neutrophil content

BACKGROUND

Matrix metalloproteinase-9 (MMP-9) is thought to play a central role in abdominal aortic aneurysm (AAA) initiation. Doxycycline, a tetracycline analogue, has direct MMP-9-inhibiting properties in vitro, and it effectively suppresses AAA development in rodents. Observed inhibition of AAA progression, and contradictory findings in human studies evaluating the effect of doxycycline therapy on aortic wall MMP-9, suggest that the effects of doxycycline extend beyond MMP-9 inhibition and that the effect may be dose-dependent.

METHODS

This clinical trial evaluated the effect of 2 weeks of low- (50 mg/d), medium- (100 mg/d), or high-dose (300 mg/d) doxycycline vs no medication in four groups of 15 patients undergoing elective AAA repair. The effect of doxycycline treatment on MMP and cysteine proteases, and their respective inhibitors, was evaluated by quantitative polymerase chain reaction, Western blot analysis, immunocapture protease activity assays, and immunohistochemistry.

RESULTS

Doxycycline was well tolerated and no participants dropped out. Doxycycline treatment reduced aortic wall MMP-3 and MMP-25 messenger RNA expression (P < .045 and P < .014, respectively), selectively suppressed neutrophil collagenase and gelatinase (MMP-8 and MMP-9) protein levels (P < .013 and <.004, respectively), and increased protein levels of the protease inhibitors tissue inhibitor of metalloproteinase 1 and cystatin C (P < .029). As for the apparent selective effect on neutrophil-associated proteases, we sought for a reducing effect on aortic wall neutrophil content that was indeed confirmed by immunohistochemical analysis that revealed a 75% reduction in aneurysm wall neutrophil content (P < .001).

CONCLUSIONS

Independent of its dose, short-term preoperative doxycycline therapy improves the proteolytic balance in AAA, presumably through an effect on aortic wall neutrophil content. This study provides a rationale for doxycycline treatment in patients with an AAA as well as in other (vascular) conditions involving neutrophil influx such as Kawasaki disease and Behçet disease.

Attacking the multi-tiered proteolytic pathology of COPD: new insights from basic and translational studies

Protease activity in inflammation is complex. Proteases released by cells in response to infection, cytokines, or environmental triggers like cigarette smoking cause breakdown of the extracellular matrix (ECM). In chronic inflammatory diseases like chronic obstructive pulmonary disease (COPD), current findings indicate that pathology and morbidity are driven by dysregulation of protease activity, either through hyperactivity of proteases or deficiency or dysfunction their antiprotease regulators. Animal studies demonstrate the accuracy of this hypothesis through genetic and pharmacologic tools. New work shows that ECM destruction generates peptide fragments active on leukocytes via neutrophil or macrophage chemotaxis towards collagen and elastin derived peptides respectively. Such fragments now have been isolated and characterized in vivo in each case. Collectively, this describes a biochemical circuit in which protease activity leads to activation of local immunocytes, which in turn release cytokines and more proteases, leading to further leukocyte infiltration and cyclical disease progression that is chronic. This circuit concept is well known, and is intrinsic to the protease-antiprotease hypothesis; recently analytic techniques have become sensitive enough to establish fundamental mechanisms of this hypothesis, and basic and clinical data now implicate protease activity and peptide signaling as pathologically significant pharmacologic targets. This review discusses targeting protease activity for chronic inflammatory disease with special attention to COPD, covering important basic and clinical findings in the field; novel therapeutic strategies in animal or human studies; and a perspective on the successes and failures of agents with a focus on clinical potential in human disease.