Shedding of Syndecan-1/CXCL1 Complexes by Matrix Metalloproteinase 7 Functions as an Epithelial Checkpoint of Neutrophil Activation

Cellular Mechanisms of Lung Injury: Current Perspectives

The alveolar-capillary barrier includes microvascular endothelial and alveolar epithelial cells and their matrices, and its disruption is a critical driver of lung injury during development of acute respiratory distress syndrome. In this review, we provide an overview of the structure and function of the alveolar-capillary barrier during health and highlight several important signaling mechanisms that underlie endothelial and epithelial injury during critical illness, emphasizing areas with potential for development of therapeutic strategies targeting alveolar-capillary leak. We also emphasize the importance of biomarker and preclinical studies in developing novel therapies and highlight important areas warranting future investigation.

Matrix metalloproteinases mediate influenza A-associated shedding of the alveolar epithelial glycocalyx

BACKGROUND

The alveolar epithelium is protected by a heparan sulfate-rich, glycosaminoglycan layer called the epithelial glycocalyx. It is cleaved in patients with acute respiratory distress syndrome (ARDS) and in murine models of influenza A (IAV) infection, shedding fragments into the airspace from the cell surface. Glycocalyx shedding results in increased permeability of the alveolar-capillary barrier, amplifying acute lung injury. The mechanisms underlying alveolar epithelial glycocalyx shedding in IAV infection are unknown. We hypothesized that induction of host sheddases such as matrix metalloproteinases (MMPs) during IAV infection results in glycocalyx shedding and increased lung injury.

MATERIALS AND METHODS

We measured glycocalyx shedding and lung injury during IAV infection with and without treatment with the pan-MMP inhibitor Ilomastat (ILO) and in an MMP-7 knock out (MMP-7KO) mouse. C57BL/6 or MMP-7KO male and female mice were given IAV A/PR/8/34 (H1N1) at 30,000 PFU/mouse or PBS intratracheally. For some experiments, C56BL/6 mice were infected in the presence of ILO (100mg/kg) or vehicle given daily by IP injection. Bronchoalveolar lavage (BAL) and lung tissue were collected on day 1, 3, and 7 for analysis of glycocalyx shedding (BAL Syndecan-1) and lung injury (histology, BAL protein, BAL cytokines, BAL immune cell infiltrates, BAL RAGE). Expression and localization of the sheddase MMP-7 and its inhibitor TIMP-1 was examined by RNAScope. For in vitro experiments, MLE-12 mouse lung epithelial cells were cultured and treated with active or heat-inactivated heparinase (2.5 U/mL) prior to infection with IAV (MOI 1) and viral load and MMP-7 and TIMP-1 expression analyzed.

RESULTS

IAV infection caused shedding of the epithelial glycocalyx into the BAL. Inhibition of MMPs with ILO reduced glycocalyx shedding by 36% (p = 0.0051) and reduced lung epithelial injury by 40% (p = 0.0404). ILO also reduced viral load by 68% (p = 0.027), despite having no significant effect on lung cytokine production. Both MMP-7 and its inhibitor TIMP-1 were upregulated in IAV infected mice: MMP-7 colocalized with IAV, while TIMP-1 was limited to cells adjacent to infection. However, MMP-7KO mice had similar glycocalyx shedding, epithelial injury, and viral load compared to WT littermates, suggesting redundancy in MMP sheddase function in the lung. In vitro, heparinase treatment before infection led to a 52% increase in viral load (p = 0.0038) without altering MMP-7 or TIMP-1 protein levels.

CONCLUSIONS

Glycocalyx shedding and MMPs play key roles in IAV-induced epithelial injury, with significant impact on IAV viral load. Further studies are needed to understand which specific MMPs regulate lung epithelial glycocalyx shedding.

Strategies to attenuate maladaptive inflammatory response associated with cardiopulmonary bypass

Cardiopulmonary bypass (CPB) initiates an intense inflammatory response due to various factors: conversion from pulsatile to laminar flow, cold cardioplegia, surgical trauma, endotoxemia, ischemia-reperfusion injury, oxidative stress, hypothermia, and contact activation of cells by the extracorporeal circuit. Redundant and overlapping inflammatory cascades amplify the initial response to produce a systemic inflammatory response, heightened by coincident activation of coagulation and fibrinolytic pathways. When unchecked, this inflammatory response can become maladaptive and lead to serious postoperative complications. Concerted research efforts have been made to identify technical refinements and pharmacologic interventions that appropriately attenuate the inflammatory response and ultimately translate to improved clinical outcomes. Surface modification of the extracorporeal circuit to increase biocompatibility, miniaturized circuits with sheer resistance, filtration techniques, and minimally invasive approaches have improved clinical outcomes in specific populations. Pharmacologic adjuncts, including aprotinin, steroids, monoclonal antibodies, and free radical scavengers, show real promise. A multimodal approach incorporating technical, circuit-specific, and pharmacologic strategies will likely yield maximal clinical benefit.

Progress in Biomarkers Related to Biliary Atresia

Biliary atresia (BA) is a congenital cholestatic disease that can seriously damage children's liver function. It is one of the main reasons for liver transplantation in children. Early diagnosis of BA is crucial to the prognosis of patients, but there is still a lack of reliable non-invasive diagnostic methods. Additionally, as some children are in urgent need of liver transplantation, evaluating the stage of liver fibrosis and postoperative native liver survival in children with BA using a straightforward, efficient, and less traumatic method is a major focus of doctors. In recent years, an increasing number of BA-related biomarkers have been identified and have shown great potential in the following three aspects of clinical practice: diagnosis, evaluation of the stage of liver fibrosis, and prediction of native liver survival. This review focuses on the pathophysiological function and clinical application of three novel BA-related biomarkers, namely MMP-7, FGF-19, and M2BPGi. Furthermore, progress in well-known biomarkers of BA such as gamma-glutamyltransferase, circulating cytokines, and other potential biomarkers is discussed, aiming to provide a reference for clinical practice.

The role of inflammatory mediators and matrix metalloproteinases (MMPs) in the progression of osteoarthritis

Osteoarthritis (OA) is a chronic musculoskeletal disorder characterized by an imbalance between (synthesis) and catabolism (degradation) in altered homeostasis of articular cartilage mediated primarily by the innate immune system. OA degenerates the joints resulting in synovial hyperplasia, degradation of articular cartilage with damage of the structural and functional integrity of the cartilage extracellular matrix, subchondral sclerosis, osteophyte formation, and is characterized by chronic pain, stiffness, and loss of function. Inflammation triggered by factors like biomechanical stress is involved in the development of osteoarthritis. In OA apart from catabolic effects, anti-inflammatory anabolic processes also occur continually. There is also an underlying chronic inflammation present, not only in cartilage tissue but also within the synovium, which perpetuates tissue destruction of the OA joint. The consideration of inflammation in OA considers synovitis and/or other cellular and molecular events in the synovium during the progression of OA. In this review, we have presented the progression of joint degradation that results in OA. The critical role of inflammation in the pathogenesis of OA is discussed in detail along with the dysregulation within the cytokine networks composed of inflammatory and anti-inflammatory cytokines that drive catabolic pathways, inhibit matrix synthesis, and promote cellular apoptosis. OA pathogenesis, fluctuation of synovitis, and its clinical impact on disease progression are presented here along with the role of synovial macrophages in promoting inflammatory and destructive responses in OA. The role of interplay between different cytokines, structure, and function of their receptors in the inter-cellular signaling pathway is further explored. The effect of cytokines in the increased synthesis and release of matrix-decomposing proteolytic enzymes, such as matrix metalloproteinase (MMPs) and a disintegrin-like and metalloproteinase with thrombospondin motif (ADAMTS), is elaborated emphasizing the potential impact of MMPs on the chondrocytes, synovial cells, articular and periarticular tissues, and other immune system cells migrating to the site of inflammation. We also shed light on the pathogenesis of OA via oxidative damage particularly due to nitric oxide (NO) via its angiogenic response to inflammation. We concluded by presenting the current knowledge about the tissue inhibitors of metalloproteinases (TIMPs). Synthetic MMP inhibitors include zinc binding group (ZBG), non-ZBG, and mechanism-based inhibitors, all of which have the potential to be therapeutically beneficial in the treatment of osteoarthritis. Improving our understanding of the signaling pathways and molecular mechanisms that regulate the MMP gene expression, may open up new avenues for the creation of therapies that can stop the joint damage associated with OA.

Soluble vascular endothelial glycocalyx proteoglycans as potential therapeutic targets in inflammatory diseases

Reducing the activity of cytokines and leukocyte extravasation is an emerging therapeutic strategy to limit tissue-damaging inflammatory responses and restore immune homeostasis in inflammatory diseases. Proteoglycans embedded in the vascular endothelial glycocalyx, which regulate the activity of cytokines to restrict the inflammatory response in physiological conditions, are proteolytically cleaved in inflammatory diseases. Here we critically review the potential of proteolytically shed, soluble vascular endothelial glycocalyx proteoglycans to modulate pathological inflammatory responses. Soluble forms of the proteoglycans syndecan-1, syndecan-3 and biglycan exert beneficial anti-inflammatory effects by the removal of chemokines, suppression of proinflammatory cytokine expression and leukocyte migration, and induction of autophagy of proinflammatory M1 macrophages. By contrast, soluble versikine and decorin enhance proinflammatory responses by increasing inflammatory cytokine synthesis and leukocyte migration. Endogenous syndecan-2 and mimecan exert proinflammatory effects, syndecan-4 and perlecan mediate beneficial anti-inflammatory effects and glypican regulates Hh and Wnt signaling pathways involved in systemic inflammatory responses. Taken together, targeting the vascular endothelial glycocalyx-derived, soluble syndecan-1, syndecan-2, syndecan-3, syndecan-4, biglycan, versikine, mimecan, perlecan, glypican and decorin might be a potential therapeutic strategy to suppress overstimulated cytokine and leukocyte responses in inflammatory diseases.

Bioinformatic Analysis of the CXCR2 Ligands in Cancer Processes

Human CXCR2 has seven ligands, i.e., CXCL1, CXCL2, CXCL3, CXCL5, CXCL6, CXCL7, and CXCL8/IL-8-chemokines with nearly identical properties. However, no available study has compared the contribution of all CXCR2 ligands to cancer progression. That is why, in this study, we conducted a bioinformatic analysis using the GEPIA, UALCAN, and TIMER2.0 databases to investigate the role of CXCR2 ligands in 31 different types of cancer, including glioblastoma, melanoma, and colon, esophageal, gastric, kidney, liver, lung, ovarian, pancreatic, and prostate cancer. We focused on the differences in the regulation of expression (using the Tfsitescan and miRDB databases) and analyzed mutation types in CXCR2 ligand genes in cancers (using the cBioPortal). The data showed that the effect of CXCR2 ligands on prognosis depends on the type of cancer. CXCR2 ligands were associated with EMT, angiogenesis, recruiting neutrophils to the tumor microenvironment, and the count of M1 macrophages. The regulation of the expression of each CXCR2 ligand was different and, thus, each analyzed chemokine may have a different function in cancer processes. Our findings suggest that each type of cancer has a unique pattern of CXCR2 ligand involvement in cancer progression, with each ligand having a unique regulation of expression.

The role of the alveolar epithelial glycocalyx in acute respiratory distress syndrome

The alveolar epithelial glycocalyx is a dense anionic layer of glycosaminoglycans (GAGs) and proteoglycans that lines the apical surface of the alveolar epithelium. In contrast to the pulmonary endothelial glycocalyx, which has well-established roles in vascular homeostasis and septic organ dysfunction, the alveolar epithelial glycocalyx is less understood. Recent preclinical studies demonstrated that the epithelial glycocalyx is degraded in multiple murine models of acute respiratory distress syndrome (ARDS), particularly those that result from inhaled insults (so-called "direct" lung injury), leading to shedding of GAGs into the alveolar airspaces. Epithelial glycocalyx degradation also occurs in humans with respiratory failure, as quantified by analysis of airspace fluid obtained from ventilator heat moisture exchange (HME) filters. In patients with ARDS, GAG shedding correlates with the severity of hypoxemia and is predictive of the duration of respiratory failure. These effects may be mediated by surfactant dysfunction, as targeted degradation of the epithelial glycocalyx in mice was sufficient to cause increased alveolar surface tension, diffuse microatelectasis, and impaired lung compliance. In this review, we describe the structure of the alveolar epithelial glycocalyx and the mechanisms underlying its degradation during ARDS. We additionally review the current state of knowledge regarding the attributable effect of epithelial glycocalyx degradation in lung injury pathogenesis. Finally, we address glycocalyx degradation as a potential mediator of ARDS heterogeneity, and the subsequent value of point-of-care quantification of GAG shedding to potentially identify patients who are most likely to respond to pharmacological agents aimed at attenuating glycocalyx degradation.

Integrated analysis of multiple microarray studies to establish differential diagnostic models of Crohn's disease and ulcerative colitis based on a metalloproteinase-associated module

Background

The ulcerative colitis (UC) and Crohn's disease (CD) subtypes of inflammatory bowel disease (IBD) are autoimmune diseases influenced by multiple complex factors. The clinical treatment strategies for UC and CD often differ, indicating the importance of improving their discrimination.

Methods

Two methods, robust rank aggregation (RRA) analysis and merging and intersection, were applied to integrate data from multiple IBD cohorts, and the identified differentially expressed genes (DEGs) were used to establish a protein-protein interaction (PPI) network. Molecular complex detection (MCODE) was used to identify important gene sets. Two differential diagnostic models to distinguish CD and UC were established via a least absolute shrinkage and selection operator (LASSO) logistic regression, and model evaluation was performed in both the training and testing groups, including receiver operating characteristic (ROC) curves, calibration plots and decision curve analysis (DCA). The potential value of MMP-associated genes was further verified using different IBD cohorts and clinical samples.

Results

Four datasets (GSE75214, GSE10616, GSE36807, and GSE9686) were included in the analysis. Both data integration methods indicated that the activation of the MMP-associated module was significantly elevated in UC. Two LASSO models based on continuous variable (Model_1) and binary variable (Model_2) MMP-associated genes were established to discriminate CD and UC. The results showed that Model_1 exhibited good discrimination in the training and testing groups. The calibration analysis and DCA showed that Model_1 exhibited good performance in the training group but failed in the testing group. Model_2 exhibited good discrimination, calibration and DCA results in the training and testing groups and exhibited greater diagnostic value. The effects of Model_1 and Model_2 were further verified in a new IBD cohort of GSE179285. The MMP genes exhibited high value as biomarkers for the discrimination of IBD patients using published cohort and immunohistochemistry (IHC) staining data. The MMP-associated gene levels were statistically significantly positively correlated with the levels of the differentially expressed cell types, indicating their potential value in differential diagnosis. The single-cell analysis confirmed that the expression of ANXA1 in UC was higher than that in CD.

Conclusion

MMP-associated modules are the main differential gene sets between CD and UC. The established Model_2 overcomes batch differences and has good clinical applicability. Subsequent in-depth research investigating how MMPs are involved in the development of different IBD subtypes is necessary.

The Role of Matrix Metalloproteinase in Inflammation with a Focus on Infectious Diseases

Matrix metalloproteinases (MMPs) are involved in extracellular matrix remodeling through the degradation of extracellular matrix components and are also involved in the inflammatory response by regulating the pro-inflammatory cytokines TNF-α and IL-1β. Dysregulation in the inflammatory response and changes in the extracellular matrix by MMPs are related to the development of various diseases including lung and cardiovascular diseases. Therefore, numerous studies have been conducted to understand the role of MMPs in disease pathogenesis. MMPs are involved in the pathogenesis of infectious diseases through a dysregulation of the activity and expression of MMPs. In this review, we discuss the role of MMPs in infectious diseases and inflammatory responses. Furthermore, we present the potential of MMPs as therapeutic targets in infectious diseases.

New Insights into the Alveolar Epithelium as a Driver of Acute Respiratory Distress Syndrome

The alveolar epithelium serves as a barrier between the body and the external environment. To maintain efficient gas exchange, the alveolar epithelium has evolved to withstand and rapidly respond to an assortment of inhaled, injury-inducing stimuli. However, alveolar damage can lead to loss of alveolar fluid barrier function and exuberant, non-resolving inflammation that manifests clinically as acute respiratory distress syndrome (ARDS). This review discusses recent discoveries related to mechanisms of alveolar homeostasis, injury, repair, and regeneration, with a contemporary emphasis on virus-induced lung injury. In addition, we address new insights into how the alveolar epithelium coordinates injury-induced lung inflammation and review maladaptive lung responses to alveolar damage that drive ARDS and pathologic lung remodeling.

Extracellular vesicles in idiopathic pulmonary fibrosis: pathogenesis and therapeutics

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease that occurs due to increased fibrosis of lung tissue in response to chronic injury of the epithelium. Therapeutic options for IPF remain limited as current therapies only function to decrease disease progression. Recently, extracellular vesicles (EVs), including exosomes and microvesicles, have been recognized as paracrine communicators through the component cargo. The population of cell-specific microRNAs and proteins present in EVs can regulate gene expressions of recipient cells, resulting in modulation of biological activities. EV cargoes reflect cell types and their physiological and pathological status of donor cells. Many current researches have highlighted the functions of EVs on the epithelial phenotype and fibroproliferative response in the pathogenesis of IPF. Furthermore, some native EVs could be used as a cell-free therapeutic approach for IPF as vehicles for drug delivery, given their intrinsic biocompatibility and specific target activity. EV-based therapies have been proposed as a new potential alternative to cell-based approaches. The advantage is that EVs, depending on their source, may be less immunogenic than their parental cells, likely due to a lower abundance of transmembrane proteins such as major histocompatibility complex (MHC) proteins on the surface. In the last decade, mesenchymal stem cell (MSC)-derived EVs have been rapidly developed as therapeutic products ready for clinical trials against various diseases. Considering EV functional complexity and heterogeneity, there is an urgent need to establish refined systemic standards for manufacturing processes and regulatory requirements of these medicines. This review highlights the EV-mediated cellular crosstalk involved in IPF pathogenesis and discusses the potential for EV-based therapeutics as a novel treatment modality for IPF.

Syndecan-1 in liver pathophysiology

Syndecan-1 is a heparan sulfate/chondroitin sulfate proteoglycan (PG) of the cell surface and the extracellular matrix, which regulates a broad spectrum of physiological and pathological processes such as cell proliferation, migration, inflammation, matrix remodeling, wound healing, or tumorigenesis. Syndecan-1 represents the major PG of the liver, expressed by hepatocytes and cholangiocytes, and its elevated expression is a characteristic feature of liver diseases. The highest syndecan-1 expression is found in liver cirrhosis and in hepatocellular carcinoma (HCC) developed in cirrhotic livers. In addition, as being a hepatitis C receptor, hepatitis C virus (HCV) infected livers produce extremely large amounts of syndecan-1. The serum levels of the cleaved (shedded) extracellular domain has clinical significance, as its increased concentration reflects on poor prognosis in cirrhosis as well as in cancer. In vivo experiments confirmed that syndecan-1 protects against early stages of fibrogenesis mainly by enhanced clearance of transforming growth factor beta (TGFβ1) and thrombospondin-1 via circulation, and against hepatocarcinogenesis by interfering with several signaling pathways and enhancing cell cycle blockade. In addition, syndecan-1 is capable to hinder lipid metabolism and ribosomal biogenesis in induced cancer models.. These observations together with its participation in the uptake of viruses (e.g. HCV, SARS-CoV-2) indicate that syndecan-1 is a central player in liver pathologies.

Contemporary Concise Review 2021: Interstitial lung disease

The last 2 years have presented previously unforeseen challenges in pulmonary medicine. Despite the significant impact of the SARS‐CoV‐2 pandemic on patients, clinicians and communities, advances in the care and understanding of interstitial lung disease (ILD) continued unabated. Recent studies have led to improved guidelines, better understanding of the role for antifibrotics in fibrosing ILDs, prognostic indicators and novel biomarkers. In this concise contemporary review, we summarize many of the important studies published in 2021, highlighting their relevance and impact to the management and knowledge of ILD.

MMP-7 marks severe pancreatic cancer and alters tumor cell signaling by proteolytic release of ectodomains

Pancreatic cancer incurs the worst survival rate of the major cancers. High levels of the protease matrix metalloproteinase-7 (MMP-7) in circulation correlate with poor prognosis and limited survival of patients. MMP-7 is required for a key path of pancreatic tumorigenesis in mice and is present throughout tumor progression. Enhancements to chemotherapies are needed for increasing the number of pancreatic tumors that can be removed and for preventing relapses after surgery. With these ends in mind, selective inhibition of MMP-7 may be worth investigation. An anti-MMP-7 monoclonal antibody was recently shown to increase the susceptibility of several pancreatic cancer cell lines to chemotherapeutics, increase their apoptosis, and decrease their migration. MMP-7 activities are most apparent at the surfaces of innate immune, epithelial, and tumor cells. Proteolytic shedding of multiple protein ectodomains by MMP-7 from such cell surfaces influence apoptosis, proliferation, migration, and invasion. These activities warrant targeting of MMP-7 selectively in pancreatic cancer and other tumors of mucosal epithelia. Competitive and non-competitive modes of MMP-7 inhibition are discussed.

Suppressing Syndecan-1 Shedding to Protect Against Renal Ischemia/Reperfusion Injury by Maintaining Polarity of Tubular Epithelial Cells

ABSTRACT

Syndecan-1 (SDC-1), a type of heparan sulfate proteoglycan on the surface of epithelial cells, is involved in maintaining cell morphology. Loss of cell polarity constitutes the early stage of ischemic acute kidney injury (AKI). This study investigated the role of SDC-1 shedding in I/R-induced AKI and the underlying mechanisms. Levels of the shed SDC-1 in the serum were measured with ELISA 12 and 24 h after reperfusion in renal I/R model mice. Na+/K+-ATPase-α1 expression was evaluated using western blotting in vivo and immunofluorescence in hypoxia/reoxygenation (H/R) cysts. Renal tubular epithelial cell apoptosis was measured using TUNEL in vivo and flow cytometry in vitro. Furthermore, plasma syndecan-1 (pSDC-1) levels were measured in patients at the time of anesthesia resuscitation after cardiac surgery. We found that shed SDC-1 levels increased and Na+/K+-ATPase-α1 expression decreased after H/R in the three-dimensional (3D) tubular model, and this state was exacerbated with extended period of hypoxia. After the inhibition of SDC-1 shedding by GM6001, SDC-1 and Na+/K+-ATPase-α1 expression was restored, while H/R-induced apoptosis was decreased. In vivo, SDC-1 shedding was induced by renal I/R and was accompanied with a loss of renal tubular epithelial cell polarity and increased apoptosis. GM6001 pretreatment protected against I/R injury by alleviating the disruption of cell polarity and apoptosis. pSDC-1 levels were significantly higher in AKI patients than in non-AKI patients. ROC curve showed that the accuracy of pSDC-1 for AKI prediction was 0.769. In conclusion, inhibition of I/R-induced SDC-1 shedding could contribute to renal protection by restoring the loss of cell polarity and alleviating apoptosis in tubular epithelial cells.

The NF-κB-regulated miR-221/222/syndecan-1 axis restores intestinal mucosal barrier function in radiation enteritis

PURPOSE

Radiation enteritis (RE) is the most common complication of pelvic radiotherapy, but proven therapies are lacking. Barrier function defects are closely associated with numerous inflammatory disorders. In this study, we investigated whether barrier dysfunction contributes to RE and whether syndecan-1 (Sdc1) protects intestinal barrier function in RE. The mechanism was also elucidated.

MATERIALS AND METHODS

Blood, urine, and tissue samples were collected from 21 patients with cervical cancer who experienced RE during radiotherapy and used to detect inflammatory responses and barrier function. The role of Sdc1 in barrier function was examined in cultured fetal human colon (FHC) cells exposed to radiation and an induced mouse RE model. Barrier function was determined by zonula occludens (ZO)-1 and occludin expression, transepithelial electrical resistance (TEER), and FITC-dextran (FD4) flux. The role of the nuclear factor (NF)-κB-P65 pathway was detected by Western blotting and chromatin immunoprecipitation. The role of miR-221/222 was assessed by real-time PCR and luciferase reporter assays.

RESULTS

Patients with RE exhibited obvious pathological and ultra-microstructural inflammatory injury and barrier disruption in the intestinal mucosa, as well as higher serum lipopolysaccharide (LPS), LPS-binding protein, and cytokine levels and a higher urine lactulose/mannitol ratio. Sdc1 overexpression in irradiated FHC cells reversed TEER suppression, repressed FD4 flux, and upregulated ZO-1 and occludin expression. Exogenous low-molecular-weight heparin supplementation in RE mice ameliorated the activity of enteritis and barrier defects. Mechanistically, irradiation-activated P65 increased the transcription of miR-221/222 via direct binding to their promoter regions, and miR-221/222 then post-transcriptionally suppressed the Sdc1 gene by binding to its 3'-untranslated region.

CONCLUSIONS

Sdc1 protects barrier function and controls inflammation during RE under transcriptional regulation by the NF-κB pathway and miR-221/222. The network including NF-κB, miR-221/222, and Sdc1 is important in the pathogenesis of RE. Sdc1 might represent a therapeutic target for novel anti-RE strategies.

CXCL1: Gene, Promoter, Regulation of Expression, mRNA Stability, Regulation of Activity in the Intercellular Space

CXCL1 is one of the most important chemokines, part of a group of chemotactic cytokines involved in the development of many inflammatory diseases. It activates CXCR2 and, at high levels, CXCR1. The expression of CXCL1 is elevated in inflammatory reactions and also has important functions in physiology, including the induction of angiogenesis and recruitment of neutrophils. Due to a lack of reviews that precisely describe the regulation of CXCL1 expression and function, in this paper, we present the mechanisms of CXCL1 expression regulation with a special focus on cancer. We concentrate on the regulation of CXCL1 expression through the regulation of CXCL1 transcription and mRNA stability, including the involvement of NF-κB, p53, the effect of miRNAs and cytokines such as IFN-γ, IL-1β, IL-17, TGF-β and TNF-α. We also describe the mechanisms regulating CXCL1 activity in the extracellular space, including proteolytic processing, CXCL1 dimerization and the influence of the ACKR1/DARC receptor on CXCL1 localization. Finally, we explain the role of CXCL1 in cancer and possible therapeutic approaches directed against this chemokine.

Antifibrotics Modify B-Cell-induced Fibroblast Migration and Activation in Patients with Idiopathic Pulmonary Fibrosis

B-cell activation is increasingly linked to numerous fibrotic lung diseases, and it is well known that aggregates of lymphocytes form in the lung of many of these patients. Activation of B-cells by pattern recognition receptors (PRRs) drives the release of inflammatory cytokines, chemokines, and metalloproteases important in the pathophysiology of pulmonary fibrosis. However, the specific mechanisms of B-cell activation in patients with idiopathic pulmonary fibrosis (IPF) are poorly understood. Herein, we have demonstrated that B-cell activation by microbial antigens contributes to the inflammatory and profibrotic milieu seen in patients with IPF. B-cell stimulation by CpG and β-glucan via PRRs resulted in activation of mTOR-dependent and independent pathways. Moreover, we showed that the B-cell-secreted inflammatory milieu is specific to the inducing antigen and causes differential fibroblast migration and activation. B-cell responses to infectious agents and subsequent B-cell-mediated fibroblast activation are modifiable by antifibrotics, but each seems to exert a specific and different effect. These results suggest that, upon PRR activation by microbial antigens, B-cells can contribute to the inflammatory and fibrotic changes seen in patients with IPF, and antifibrotics are able to at least partially reverse these responses.

Endothelial glycocalyx during early reperfusion in patients undergoing cardiac surgery

Background

Experimental cardiac ischemia-reperfusion injury causes degradation of the glycocalyx and coronary washout of its components syndecan-1 and heparan sulfate. Systemic elevation of syndecan-1 and heparan sulfate is well described in cardiac surgery. Still, the events during immediate reperfusion after aortic declamping are unknown both in the systemic and in the coronary circulation.

Methods

In thirty patients undergoing aortic valve replacement, arterial concentrations of syndecan-1 and heparan sulfate were measured immediately before and at one, five and ten minutes after aortic declamping (reperfusion). Parallel blood samples were drawn from the coronary sinus to calculate trans-coronary gradients (coronary sinus–artery).

Results

Compared with immediately before aortic declamping, arterial syndecan-1 increased by 18% [253.8 (151.6–372.0) ng/ml vs. 299.1 (172.0–713.7) ng/ml, p < 0.001] but arterial heparan sulfate decreased by 14% [148.1 (135.7–161.7) ng/ml vs. 128.0 (119.0–138.2) ng/ml, p < 0.001] at one minute after aortic declamping. There was no coronary washout of syndecan-1 or heparan sulfate during reperfusion. On the contrary, trans-coronary sequestration of syndecan-1 occurred at five [-12.96 ng/ml (-36.38–5.15), p = 0.007] and at ten minutes [-12.37 ng/ml (-31.80–6.62), p = 0.049] after reperfusion.

Conclusions

Aortic declamping resulted in extracardiac syndecan-1 release and extracardiac heparan sulfate sequestration. Syndecan-1 was sequestered in the coronary circulation during early reperfusion. Glycocalyx has been shown to degrade during cardiac surgery. Besides degradation, glycocalyx has propensity for regeneration. The present results of syndecan-1 and heparan sulfate sequestration may reflect endogenous restoration of the damaged glycocalyx in open heart surgery.

Elevated plasma levels of syndecan-1 and soluble thrombomodulin predict adverse outcomes in thrombotic thrombocytopenic purpura

Immune-mediated thrombotic thrombocytopenic purpura (iTTP) is a potentially fatal blood disorder resulting from acquired deficiency of plasma ADAMTS13 activity. Despite recent advances in early diagnosis and novel therapeutics, the mortality rate of acute iTTP remains as high as 10% to 20%. Moreover, a reliable clinical and laboratory parameter that predicts disease severity and outcomes is lacking. We show in the present study that plasma levels of syndecan-1 (Sdc-1) and soluble thrombomodulin (sTM) on admission were dramatically increased in patients with acute iTTP and remained substantially elevated in a subset of patients compared with healthy controls. The elevated admission plasma levels of Sdc-1 and sTM were associated with abnormal Glasgow coma scale scores, low estimated glomerular filtration rates, the need for intensive care, and in-hospital mortality rates. Moreover, a further simultaneous increase in plasma Sdc-1 and sTM levels at the time of clinical response/remission (eg, when normalization of platelet counts and substantial reduction of serum lactate dehydrogenase activity were achieved) was highly predictive of iTTP recurrence. These results demonstrate that endothelial injury, resulting from disseminated microvascular thromboses, is severe and persistent in patients with acute iTTP. Plasma levels of Sdc-1 and sTM on admission and in remission are predictive of in-hospital mortality and recurrence of acute iTTP, respectively. Thus, an incorporation of such novel plasma biomarkers into the risk assessment in acute iTTP may help implement a more vigorous and intensive therapeutic strategy for these patients.

The Endothelial Glycocalyx as a Target of Ischemia and Reperfusion Injury in Kidney Transplantation-Where Have We Gone So Far?

The damage of the endothelial glycocalyx as a consequence of ischemia and/or reperfusion injury (IRI) following kidney transplantation has come at the spotlight of research due to potential associations with delayed graft function, acute rejection as well as long-term allograft dysfunction. The disintegration of the endothelial glycocalyx induced by IRI is the crucial event which exposes the denuded endothelial cells to further inflammatory and oxidative damage. The aim of our review is to present the currently available data regarding complex links between shedding of the glycocalyx components, like syndecan-1, hyaluronan, heparan sulphate, and CD44 with the activation of intricate immune system responses, including toll-like receptors, cytokines and pro-inflammatory transcription factors. Evidence on modes of protection of the endothelial glycocalyx and subsequently maintenance of endothelial permeability as well as novel nephroprotective molecules such as sphingosine-1 phosphate (S1P), are also depicted. Although advances in technology are making the visualization and the analysis of the endothelial glycocalyx possible, currently available evidence is mostly experimental. Ongoing progress in understanding the complex impact of IRI on the endothelial glycocalyx, opens up a new era of research in the field of organ transplantation and clinical studies are of utmost importance for the future.

Matrilysins and Stromelysins in Pathogenesis and Diagnostics of Cancers

Matrix metalloproteinases (MMPs) are endopeptidases which are widely studied in terms of their role in the physiological and pathological processes in the organism. In this article, we consider usefulness of matrilysins and stromelysins in pathogenesis and diagnostic of the most common malignancies in the world, e.g., lung, breast, prostate, and colorectal cancers. In all of the mentioned cancers, matrilysins and stromelysins have a pivotal role in their development and also may have diagnostic utility. Influence to the cancerous process is connected with specific dependencies between these enzymes and components of the extracellular matrix (ECM), non-matrix components like cell surface components. All the information provided below allows to take a closer look at matrilysins and stromelysins and their functions in the cancer development.

Heparan Sulfate Proteoglycans Biosynthesis and Post Synthesis Mechanisms Combine Few Enzymes and Few Core Proteins to Generate Extensive Structural and Functional Diversity

Glycosylation is a common and widespread post-translational modification that affects a large majority of proteins. Of these, a small minority, about 20, are specifically modified by the addition of heparan sulfate, a linear polysaccharide from the glycosaminoglycan family. The resulting molecules, heparan sulfate proteoglycans, nevertheless play a fundamental role in most biological functions by interacting with a myriad of proteins. This large functional repertoire stems from the ubiquitous presence of these molecules within the tissue and a tremendous structural variety of the heparan sulfate chains, generated through both biosynthesis and post synthesis mechanisms. The present review focusses on how proteoglycans are “gagosylated” and acquire structural complexity through the concerted action of Golgi-localized biosynthesis enzymes and extracellular modifying enzymes. It examines, in particular, the possibility that these enzymes form complexes of different modes of organization, leading to the synthesis of various oligosaccharide sequences.

Role of syndecan-1 in the interaction between dendritic cells and T cells

Syndecan-1 (Sdc-1) is a heparan sulfate proteoglycan that can bind cytokines and chemokines via its heparan sulfate side chains, and has immunomodulatory properties in experimental models. Sdc-1 expression has been reported on dendritic cells (DC) and T cells. The potential role of Sdc-1 in DC-T cell interaction has not been investigated yet. We postulate that Sdc-1 is involved in DC-T cell interaction and may influence graft survival in an allogeneic transplant model. Sdc-1 expression on bone marrow-derived DC and T cells was analyzed by flow cytometry. Unstimulated and LPS stimulated Sdc-1 deficient DC were evaluated in vitro for phenotype and stimulatory capacity in mixed lymphocyte reaction. Sdc-1 deficient T cells were evaluated for proliferative capacity and differentiation in a mixed lymphocyte reaction and a proliferation assay. Allograft survival was evaluated in a fully MHC mismatched heterotopic heart transplant model, with either Sdc-1 deficient donors or recipients. Sdc-1 was expressed on the cell surface of unstimulated and LPS matured DC. Sdc-1 deficiency had no effect on expression of co-stimulatory molecules, cytokine production or T cell stimulatory capacity as compared to WT DC. Sdc-1 expression was not detectable on WT T cells, although intracellular Sdc-1 expression could be demonstrated after ConA activation. Sdc-1 deficient T cells showed reduced proliferation upon DC or ConA stimulation and reduced IL-17 production upon ConA stimulation, compared to WT T cells. Sdc-1 deficiency of either allograft or recipient did not prolong allograft survival. In conclusion, Sdc-1 is expressed on the cell surface of DC, where its absence does not affect DC phenotype or T cell stimulatory capacity. Sdc-1 is intracellularly expressed in ConA activated T cells. Sdc-1 deficiency in T cells results in a reduced proliferative response in vitro, as induced by DC and ConA. Sdc-1 deficiency in donor or recipient does not affect allograft survival.

Effect of GM6001 on the expression of syndecan-1 in rats with acute kidney injury and its protective effect on the kidneys

Expression of syndecan-1 (SDC-1) in rats with acute kidney injury and the protective effect of GM6001 on the kidney were investigated. Fifty SD rats were selected and randomly divided into control group (CG) (n=15), treatment control group (TCG) (n=10), module group (MG) (n=15) and treatment group (TG) (n=10). In TG, the model of acute renal injury (AKI) in rats was established after pretreatment of intraperitoneal injection of GM6001 one day before modeling. In MG, the same amount of saline was injected intraperitoneally one day before modeling and the same treatment was done on the day of modeling. In CG, the same amount of saline was injected intraperitoneally one day before modeling but the model was not made. In TCG, rats were pretreated with intraperitoneal injection of GM6001 one day before modeling but the model was not made. The contents of blood urea nitrogen (BUN) in serum, serum creatinine (SCR), uric acid (UA) and blood β2-microglobulin (β2-MG) were detected by ELISA. The content of SDC-1 in renal tissues was detected by qRT-PCR and western blotting. Expression of SDC-1 in renal tissue of 24 rats after modeling was lower than that of MG (P<0.050). SDC-1 expression was the highest in TG (P<0.05). Compared with before modeling, the contents of BUN, SCR, UA and β2-MG in MG and TG increased (P<0.05). After modeling, the contents of serum BUN, SCR, UA and β2-MG in TG were significantly lower than those in MG (P<0.05). The levels of SDC-1 in renal tissue of rats with acute kidney injury increased. After GM6001 treatment, SDC-1 levels can be improved and has a certain protective effect on the kidneys.

Prolonged Cardiopulmonary Bypass is Associated With Endothelial Glycocalyx Degradation

BACKGROUND

The endothelial glycocalyx (EG) is involved in critical regulatory mechanisms that maintain endothelial vascular integrity. We hypothesized that prolonged cardiopulmonary bypass (CPB) may be associated with EG degradation. We performed an analysis of soluble syndecan-1 levels in relation to duration of CPB, as well as factors associated with cell stress and damage, such as mitochondrial DNA (mtDNA) and inflammation.

METHODS

Blood samples from subjects undergoing cardiac surgery with CPB (n = 54) were obtained before and during surgery, 4-8 h and 24 h after completion of CPB, and on postoperative day 4. Flow cytometry was used to determine subpopulations of white blood cells. Plasma levels of mtDNA were determined using quantitative polymerase chain reaction and plasma content of shed syndecan-1 was measured. To determine whether syndecan-1 was signaling white blood cells, the effect of recombinant syndecan-1 on mobilization of neutrophils from bone marrow was tested in mice.

RESULTS

CPB is associated with increased mtDNA during surgery, increased syndecan-1 blood levels at 4-8 h, and increased white blood cell count at 4-8 h and 24 h. Correlation analysis revealed significant positive associations between time on CPB and syndecan-1 (r_s = 0.488, P < 0.001) and level of syndecan-1 and neutrophil count (r_s = 0.351, P = 0.038) at 4-8 h. Intravenous administration of recombinant syndecan-1 in mice resulted in a 2.5-fold increase in the number of circulating neutrophils, concurrent with decreased bone marrow neutrophil number.

CONCLUSIONS

Longer duration of CPB is associated with increased plasma levels of soluble syndecan-1, a signal for EG degradation, which can induce neutrophil egress from the bone marrow. Development of therapy targeting EG shedding may be beneficial in patients with prolonged CPB.

Structural Insights Into How Proteoglycans Determine Chemokine-CXCR1/CXCR2 Interactions: Progress and Challenges

Proteoglycans (PGs), present in diverse environments, such as the cell membrane surface, extracellular milieu, and intracellular granules, are fundamental to life. Sulfated glycosaminoglycans (GAGs) are covalently attached to the core protein of proteoglycans. PGs are complex structures, and are diverse in terms of amino acid sequence, size, shape, and in the nature and number of attached GAG chains, and this diversity is further compounded by the phenomenal diversity in GAG structures. Chemokines play vital roles in human pathophysiology, from combating infection and cancer to leukocyte trafficking, immune surveillance, and neurobiology. Chemokines mediate their function by activating receptors that belong to the GPCR class, and receptor interactions are regulated by how, when, and where chemokines bind GAGs. GAGs fine-tune chemokine function by regulating monomer/dimer levels and chemotactic/haptotactic gradients, which are also coupled to how they are presented to their receptors. Despite their small size and similar structures, chemokines show a range of GAG-binding geometries, affinities, and specificities, indicating that chemokines have evolved to exploit the repertoire of chemical and structural features of GAGs. In this review, we summarize the current status of research on how GAG interactions regulate ELR-chemokine activation of CXCR1 and CXCR2 receptors, and discuss knowledge gaps that must be overcome to establish causal relationships governing the impact of GAG interactions on chemokine function in human health and disease.

Intravenous antagomiR-494 lessens brain-infiltrating neutrophils by increasing HDAC2-mediated repression of multiple MMPs in experimental stroke

Neutrophil infiltration and phenotypic transformation are believed to contribute to neuronal damage in ischemic stroke. Emerging evidence suggests that histone deacetylase 2 (HDAC2) is an epigenetic regulator of inflammatory cells. Here, we aimed to investigate whether microRNA-494 (miR-494) affects HDAC2-mediated neutrophil infiltration and phenotypic shift. MiR-494 levels in neutrophils from acute ischemic stroke (AIS) patients were detected by real-time PCR. Chromatin Immunoprecipitation (ChIP)-Seq was performed to clarify which genes are the binding targets of HDAC2. Endothelial cells and cortical neurons were subjected to oxygen-glucose deprivation (OGD), transwell assay was conducted to examine neutrophil migration through endothelial cells, and neuronal injury was examined after stimulating with supernatant from antagomiR-494-treated neutrophils. C57BL/6J mice were subjected to transient middle cerebral artery occlusion (MCAO) and antagomiR-494 was injected through tail vein immediately after reperfusion, and neutrophil infiltration and phenotypic shift was examined. We found that the expression of miR-494 in neutrophils was significantly increased in AIS patients. HDAC2 targeted multiple matrix metalloproteinases (MMPs) and Fc-gamma receptor III (CD16) genes in neutrophils of AIS patients. Furthermore, antagomiR-494 repressed expression of multiple MMPs genes, including MMP7, MMP10, MMP13, and MMP16, which reduced the number of brain-infiltrating neutrophils by regulating HDAC2. AntagomiR-494 could also exert its neuroprotective role through inhibiting the shift of neutrophils toward pro-inflammatory N1 phenotype in vivo and in vitro. Taken together, miR-494 may serve as an alternative predictive biomarker of the outcome of AIS patients, and antagomiR-494 treatment decreases the expression of multiple MMPs and the infiltration of neutrophils and inhibits the shift of neutrophils into N1 phenotype partly by targeting HDAC2.

Syndecans in Inflammation at a Glance

Syndecans are transmembrane proteoglycans with heparan and chondroitin sulfate chains attached to their extracellular domain. Like many proteoglycans, they interact with a large number of ligands, such as growth factors, adhesion receptors, soluble small molecules, proteinases, and other extracellular matrix proteins to initiate downstream signaling pathways. Syndecans play a major role in inflammation, mainly by regulating leukocyte extravasation and cytokine function. At the same time, syndecans can undergo cytokine mediated changes in their expression levels during inflammation. The function of syndecans during inflammation appears to depend on the stage of inflammation, sulfation of heparan/chondroitin sulfate chains, the rate of ectodomain shedding and the solubility of the ectodomains. From the current literature, it is clear that syndecans are not only involved in the initial recruitment of pro-inflammatory molecules but also in establishing a balanced progression of inflammation. This review will summarize how cell surface and soluble syndecans regulate multiple aspects of inflammation.

Structural basis of chemokine interactions with heparan sulfate, chondroitin sulfate, and dermatan sulfate

Chemokines play diverse roles in human pathophysiology, ranging from trafficking leukocytes and immunosurveillance to the regulation of metabolism and neural function. Chemokine function is intimately coupled to binding tissue glycosaminoglycans (GAGs), heparan sulfate (HS), chondroitin sulfate (CS), and dermatan sulfate (DS). Currently, very little is known about how the structural features and sequences of a given chemokine, the structure and sulfation pattern of a given GAG, and structural differences among GAGs and among chemokines impact binding interactions. In this study, we used solution NMR spectroscopy to characterize the binding interactions of two related neutrophil-activating chemokines, CXCL1 and CXCL5, with HS, CS, and DS. For both chemokines, the dimer bound all three GAGs with higher affinity than did the monomer, and affinities of the chemokines for CS and DS were lower than for HS. NMR-based structural models reveal diverse binding geometries and show that the binding surfaces for each of the three GAGs were different between the two chemokines. However, a given chemokine had similar binding interactions with CS and DS that were different from HS. Considering the fact that CXCL1 and CXCL5 activate the same CXCR2 receptor, we conclude that GAG interactions play a role in determining the nature of chemokine gradients, levels of free chemokine available for receptor activation, how chemokines bind their receptors, and that differences in these interactions determine chemokine-specific function.

Syndecan-1 promotes lung fibrosis by regulating epithelial reprogramming through extracellular vesicles

Idiopathic pulmonary fibrosis (IPF) is a chronic and fatal lung disease. A maladaptive epithelium due to chronic injury is a prominent feature and contributor to pathogenic cellular communication in IPF. Recent data highlight the concept of a "reprogrammed" lung epithelium as critical in the development of lung fibrosis. Extracellular vesicles (EVs) are potent mediator of cellular crosstalk, and recent evidence supports their role in lung pathologies such as IPF. Here, we demonstrate that syndecan-1 is overexpressed by the epithelium in the lungs of IPF patients and in murine models after bleomycin injury. Moreover, we find that syndecan-1 is a pro-fibrotic signal that alters alveolar type II (ATII) cell phenotypes by augmenting TGFβ and Wnt signaling among other pro-fibrotic pathways. Importantly, we demonstrate that syndecan-1 controls the packaging of several anti-fibrotic microRNAs into EVs that have broad effects over several fibrogenic signaling networks as a mechanism of regulating epithelial plasticity and pulmonary fibrosis. Collectively, our work reveals new insight into how EVs orchestrate cellular signals that promote lung fibrosis and demonstrate the importance of syndecan-1 in coordinating these programs.

Serum matrix metalloproteinase levels in polymyositis/dermatomyositis patients with interstitial lung disease

OBJECTIVE

We aimed to clarify the clinical significance of serum levels of MMPs in interstitial lung disease (ILD) complicated with PM/DM (PM/DM-ILD).

METHODS

We retrospectively analysed serum levels of seven subsets of MMPs in 52 PM/DM-ILD patients diagnosed at Kyoto University Hospital or Tenri Hospital from January 2005 to December 2014. The patients were sub-grouped based on the presence of anti-amimoacyl-tRNA synthetase antibody (anti-ARS antibody), anti-melanoma differentiation-associated protein 5 antibody (anti-MDA5 antibody) or lack of the antibodies (ARS-ILD, MDA5-ILD and other-ILD groups, respectively) and independently analysed. Eighteen PM/DM patients without ILD and 55 healthy control were also analysed. Associations between serum levels of MMPs and clinical findings including mortality were analysed.

RESULTS

Among the MMPs analysed, MMP-7 serum levels in the ARS-ILD group were significantly higher compared with those in any of the other groups of PM/DM patients or in healthy controls. On the other hand, in the MDA5-ILD group, serum MMP-7 levels >5.08 ng/ml were associated with worse overall survival both in univariate (P = 0.017; odds ratio 18.0; 95% CI 1.69, 192.00) and multivariate (P = 0.027; odds ratio 14.60; 95% CI 1.11, 192.00) analyses. Immunohistochemical analysis suggested that MMP-7 was expressed in type II alveolar epithelial cells adjacent to the fibrotic lesions.

CONCLUSION

Serum MMP-7 levels were higher in anti-ARS antibody-positive PM/DM-ILD patients, while higher serum MMP-7 levels among anti-MDA5 antibody-positive PM/DM-ILD patients were associated with a worse prognosis. Fibrotic processes may be associated with the elevation of serum MMP-7 levels.

Syndecan-1 Shedding Inhibition to Protect Against Ischemic Acute Kidney Injury Through HGF Target Signaling Pathway

BACKGROUND

The hepatocyte growth factor (HGF) target pathway plays pivotal renoprotective roles after acute kidney injury. Syndecan-1 (SDC-1) serves as the coreceptor for HGF. Shedding of SDC-1 is involved in various pathological processes. Thus, we hypothesized that ischemia/reperfusion injury induced SDC-1 shedding, and inhibiting SDC-1 shedding would protect against kidney injury by potentiating activation of the HGF receptor mesenchymal epithelial transition factor (c-Met).

METHODS

Expression of SDC-1 and its sheddases were observed in kidneys of sham and ischemia/reperfusion (I/R) mice. To inhibit SDC-1 shedding, mice were injected with the sheddase inhibitor GM6001 before I/R surgery, and then, renal inflammation, tubular apoptosis, and activation of the c-Met/AKT/glycogen synthase kinase-3β (GSK-3β) pathway were analyzed. In vitro, human proximal tubular cell lines were pretreated with GM6001 under hypoxia/reperfusion conditions. The apoptosis and viability of cells and expression of c-Met/AKT/GSK-3β pathway components were evaluated. The relationship was further confirmed by treatment with SU11274, a specific inhibitor of phospho-c-Met.

RESULTS

Shedding of SDC-1 was induced after ischemia/reperfusion injury both in vivo and in vitro. GM6001 pretreatment suppressed SDC-1 shedding, alleviated renal inflammation and tubular apoptosis, and upregulated phosphorylation of the c-Met/AKT/GSK-3β pathway. In vitro, pretreatment with GM6001 also decreased hypoxia/reperfusion-induced cell apoptosis and promoted activation of the c-Met pathway. In addition, the cytoprotective role of GM6001 was attenuated by suppressing c-Met phosphorylation with SU11274.

CONCLUSIONS

Our findings suggest that inhibiting I/R-induced SDC-1 shedding protected against ischemic acute kidney injury by potentiating the c-Met/AKT/GSK-3β pathway.

Macrophage MMP10 Regulates TLR7-Mediated Tolerance

Using an in vivo model of tolerance to TLR7-induced skin inflammation, we found a critical role for macrophage-derived MMP10 in mediating immune hypo-responsiveness. Cutaneous exposure to Imiquimod (IMQ), a TLR7 agonist, induced acute expression of pro-inflammatory factors (IL1β, IL6, CXCL1) and neutrophil influx equally in both wildtype and Mmp10 ^-/- mice. However, whereas subsequent exposure (11 and 12 days later) to IMQ led to marked abrogation of pro-inflammatory factor expression in wildtype mice, Mmp10 ^-/- mice responded similarly as they did to the first application. In addition, the second exposure led to increased expression of negative regulators of TLR signaling (TNFAIP3, IRAK3) and immunosuppressive cytokines (IL10, TGFβ1) in wildtype mice but not in Mmp10 ^-/- mice. In vitro studies demonstrated that prior exposure of IMQ to bone marrow-derived macrophages (BMDM) made wildtype cells refractory to subsequent stimulation but did not for Mmp10 ^-/- macrophages. These findings expand the critical roles MMP10 plays in controlling macrophage activation to indicate that the development of immune tolerance to TLR7 ligand is dependent on this macrophage-derived proteinase.

Matrix metalloproteinases in emphysema

Several studies have implicated a causative role for specific matrix metalloproteinases (MMPs) in the development and progression of cigarette smoke-induced chronic obstructive pulmonary disease (COPD) and its severe sequela, emphysema. However, the precise function of any given MMP in emphysema remains an unanswered question. Emphysema results from the degradation of alveolar elastin - among other possible mechanisms - a process that is often thought to be caused by elastolytic proteinases made by macrophages. In this article, we discuss the data suggesting, supporting, or refuting causative roles of macrophage-derived MMPs, with a focus on MMPs-7, -9, -10, -12, and 28, in both the human disease and mouse models of emphysema. Findings from experimental models suggest that some MMPs, such as MMP-12, may directly breakdown elastin, whereas others, particularly MMP-10 and MMP-28, promote the development of emphysema by influencing the proteolytic and inflammatory activities of macrophages.

Syndecan-1 inhibits early stages of liver fibrogenesis by interfering with TGFβ1 action and upregulating MMP14

Increased expression of syndecan-1 is a characteristic feature of human liver cirrhosis. However, no data are available on the significance of this alteration. To address this question we designed a transgenic mouse strain that driven by albumin promoter, expresses human syndecan-1 in the hepatocytes. Liver cirrhosis was induced by thioacetamide in wild type and hSDC1^+/+ mice of the identical strain. The process of fibrogenesis, changes in signal transduction and proteoglycan expression were followed. In an in vitro experiment, the effect of syndecan-1 overexpression on the action of TGFβ1 was determined. Human syndecan-1 and TGFβ1 levels were measured by ELISA in the circulation. Without challenge, no morphological differences were observed between wild type and transgenic mice livers, although significant upregulation of phospho-Akt and FAK was observed in the latter. Fibrogenesis in the transgenic livers, characterized by picrosirius staining, collagen type I, and SMA levels, lagged behind that of control in the first and second months. Changes in signal transduction involved in the process of fibrogenesis, as SMAD, MAPK, Akt and GSK, pointed to the decreased effect of TGFβ1, and this was corroborated by the decreased mRNA expression of TIEG and the growth factor itself. In vitro experiments exposing the LX2 hepatic stellate cell line to conditioned media of wild type and syndecan-1 transfected Hep3B cell lines proved that medium with high syndecan-1 content inhibits TGFβ1-induced upregulation of SMA, TIEG, collagen type I and thrombospondin-1 expression. Detection of liver proteoglycans and heparan sulfate level revealed that their amounts are much higher in control transgenic liver, than that in the wild type. However, it decreases dramatically as a result of shedding after hepatic injury. Shedding is likely promoted by the upregulation of MMP14. As syndecan-1 can bind thrombospondin-1, and as our result demonstrated that the same is true for TGFβ1, shed syndecan-1 can remove the growth factor and its activator together into the systemic circulation.Taking together, our results indicate that the effect of syndecan-1 is accomplished on two levels: a, the shedded syndecan can bind, inhibit and remove TGFβ1; b, interferes with the activation of TGFβ1 by downregulation and binding thrombospondin-1, the activator of the growth factor. However, by the end of the fourth month the protective effect was lost, which is explained by the considerable decrease of syndecan-1 and the almost complete loss of heparan sulfate from the surface of hepatocytes.

Proteoglycans as Immunomodulators of the Innate Immune Response to Lung Infection

Proteoglycans (PGs) are complex, multifaceted molecules that participate in diverse interactions vital for physiological and pathological processes. As structural components, they provide a scaffold for cells and structural organization that helps define tissue architecture. Through interactions with water, PGs enable molecular and cellular movement through tissues. Through selective ionic interactions with growth factors, chemokines, cytokines, and proteases, PGs facilitate the ability of these soluble ligands to regulate intracellular signaling events and to influence the inflammatory response. In addition, recent findings now demonstrate that PGs can activate danger-associated molecular patterns (DAMPs) and other signaling pathways to influence production of many of these soluble ligands, indicating a more direct role for PGs in influencing the immune response and tissue inflammation. This review will focus on PGs that are selectively expressed during lung inflammation and will examine the novel emerging concept of PGs as immunomodulatory regulators of the innate immune responses in lungs.

Glycan Activation of a Sheddase: Electrostatic Recognition between Heparin and proMMP-7

Heparan sulfate proteoglycans activate the matrix metalloproteinase-7 zymogen (proMMP-7) and recruit it in order to shed proteins from cell surfaces. This occurs in uterine and mammary epithelia, bacterial killing, lung healing, and tumor cell signaling. Basic tracks on proMMP-7 recognize polyanionic heparin, according to nuclear magnetic resonance and mutations disruptive of maturation. Contacts and proximity measurements guided docking of a heparin octasaccharide to proMMP-7. The reducing end fits into a basic pocket in the pro-domain while the chain continues toward the catalytic domain. Another oligosaccharide traverses a basic swath remote on the catalytic domain and inserts its reducing end into a slot formed with the basic C terminus. This latter association appears to support allosteric acceleration of proteolysis. The modes of binding account for extended, heterogeneous assemblies of proMMP-7 with heparinoids during maturation and for bridging to pro-α-defensins and proteoglycans. These associations support proteolytic release of activities at epithelial cell surfaces.

Microbial Antigens Stimulate Metalloprotease-7 Secretion in Human B-Lymphocytes Using mTOR-Dependent and Independent Pathways

Metalloproteinases (MMPs) contribute to tissue remodeling and acute inflammation not only by degrading extracellular matrix proteins but also by controlling the influx of chemokines through the regulation and shedding of syndecans. B-lymphocytes, in addition to their well-known function as antibody producing cells, participate in the innate immune response by secreting inflammatory cytokines and chemokines. However, there is little information about the role of B-lymphocytes in the regulation of MMPs; consequently, herein we investigated whether activated human circulating B-lymphocytes contributed to the secretion of MMPs. We demonstrate that B-lymphocytes activated by un-methylated CpG motifs, found in bacterial DNA, and β-glucans, found in the cell wall of fungi, both induced MMP-7. Interestingly, while CpG-stimulated cells activated the mTOR pathway via TLR9 receptor to induced MMP-7, β-glucan-stimulated cells were mTOR-independent and used Dectin-1 receptor. B-lymphocytes did not seem to have a major role in the secretion of tissue inhibitors of metalloproteinases (TIMPs). However, secreted MMP-7 participated in the shedding of Syndecan-4 from the surface of B-lymphocytes. In conclusion, circulating human B-lymphocytes contribute to the regulation of the innate immune system by participating in the secretion of MMP-7 which in turn is important for the shedding of Syndecan-4 in response to infectious stimuli.

Matrix Metalloproteinases and Leukocyte Activation

As their name implies, matrix metalloproteinases (MMPs) are thought to degrade extracellular matrix proteins, a function that is indeed performed by some members. However, regardless of their cell source, matrix degradation is not the only function of these enzymes. Rather, individual MMPs have been shown to regulate specific immune processes, such as leukocyte influx and migration, antimicrobial activity, macrophage activation, and restoration of barrier function, typically by processing a range of nonmatrix protein substrates. Indeed, MMP expression is low under steady-state conditions but is markedly induced during inflammatory processes including infection, wound healing, and cancer. Increasing research is showing that MMPs are not just a downstream consequence of a generalized inflammatory process, but rather are critical factors in the overall regulation of the pattern, type, and duration of immune responses. This chapter outlines the role of leukocytes in tissue remodeling and describes recent progress in our understanding of how MMPs alter leukocyte activity.

Stromelysin-2 (MMP10) Moderates Inflammation by Controlling Macrophage Activation

Several members of the matrix metalloproteinase (MMP) family control a range of immune processes, such as leukocyte influx and chemokine activity. Stromelysin-2 (MMP10) is expressed by macrophages in numerous tissues after injury; however, little is known of its function. In this study, we report that MMP10 is expressed by macrophages in human lungs from patients with cystic fibrosis and induced in mouse macrophages in response to Pseudomonas aeruginosa infection both in vivo and by isolated resident alveolar and bone marrow-derived macrophages (BMDM). Our data indicates that macrophage MMP10 serves a beneficial function in response to acute infection. Whereas wild-type mice survived infection with minimal morbidity, 50% of Mmp10(-/-) mice died and all showed sustained weight loss (morbidity). Although bacterial clearance and neutrophil influx did not differ between genotypes, macrophage numbers were ∼3-fold greater in infected Mmp10(-/-) lungs than in wild-types. Adoptive transfer of wild-type BMDM normalized infection-induced morbidity in Mmp10(-/-) recipients to wild-type levels, demonstrating that the protective effect of MMP10 was due to its production by macrophages. Both in vivo and in cultured alveolar macrophages and BMDM, expression of several M1 macrophage markers was elevated, whereas M2 markers were reduced in Mmp10(-/-) tissue and cells. Global gene expression analysis revealed that infection-mediated transcriptional changes persisted in Mmp10(-/-) BMDM long after they were downregulated in wild-type cells. These results indicate that MMP10 serves a beneficial role in response to acute infection by moderating the proinflammatory response of resident and infiltrating macrophages.