At the interface of fibrinolysis and inflammation: the role of urokinase-type plasminogen activator in the leukocyte extravasation cascade

Extracellular matrix-related and serine protease proteins in the amniotic fluid of women with early preterm labor: Association with spontaneous preterm birth, intra-amniotic inflammation, and microbial invasion of the amniotic cavity

PROBLEM

We aimed to determine whether altered levels of various extracellular matrix (ECM)-related and serine protease proteins in the amniotic fluid (AF) are associated with imminent spontaneous preterm birth (SPTB; ≤7 days) and intra-amniotic inflammation and/or microbial invasion of the amniotic cavity (IAI/MIAC) in women with early preterm labor (PTL).

METHOD OF STUDY

This retrospective cohort study included 252 women with singleton pregnancies undergoing transabdominal amniocentesis who demonstrated PTL (24-31 weeks). The AF was cultured for microorganism detection to characterize MIAC. IL-6 concentrations were determined in the AF samples to identify IAI (≥2.6 ng/mL). The following mediators were measured in the AF samples using ELISA: kallistatin, lumican, MMP-2, SPARC, TGFBI, and uPA.

RESULTS

Kallistatin, MMP-2, TGFBI, and uPA levels were significantly higher and SPARC and lumican levels were significantly lower in the AF of women who spontaneously delivered within 7 days than in the AF of those who delivered after 7 days; the levels of the first five mediators were independent of baseline clinical variables. In the multivariate analysis, elevated levels of kallistatin, MMP-2, TGFBI, and uPA and low levels of lumican and SPARC in the AF were significantly associated with IAI/MIAC and MIAC, even after adjusting for the gestational age at sampling. The areas under the curves of the aforementioned biomarkers ranged from 0.58 to 0.87 for the diagnoses of each of the corresponding endpoints.

CONCLUSION

ECM-related (SPARC, TGFBI, lumican, and MMP-2) and serine protease (kallistatin and uPA) proteins in the AF are involved in preterm parturition and regulation of intra-amniotic inflammatory/infectious responses in PTL.

High-throughput analysis of amniotic fluid proteins associated with histological chorioamnionitis in preterm premature rupture of membranes using an antibody-based microarray

PROBLEM

To identify potential proteins in the amniotic fluid (AF) that may be associated with histologic chorioamnionitis (HCA) in patients with preterm premature rupture of membranes (PPROM) using antibody-based microarray analysis.

METHOD OF STUDY

This was a retrospective cohort study involving 100 singleton pregnant women with PPROM at 24-34 weeks who underwent amniocentesis and delivered within 120 h of amniocentesis. First, the AF proteomes of 15 patients with PPROM and HCA were compared with those of 15 gestational age-matched patients without HCA using a protein microarray. Next, 12 candidate proteins associated with HCA were further validated in 100 consecutive patients with PPROM by ELISA.

RESULTS

Of 507 proteins assessed in the microarray analysis, 46 showed significant intergroup differences. Further quantification confirmed that the levels of EN-RAGE, IL-6, MMP-9, TNFR2, SPARC, TSP2, and uPA were higher in the AF of PPROM patients with HCA than in those without. Multivariate analyses also showed that elevated AF EN-RAGE, IL-6, MMP-9, and TNFR2 levels were independently associated with HCA when adjusted for baseline variables. The frequency of the highest quartile of the aforementioned proteins significantly increased as the total grade of HCA increased; the risk of HCA significantly increased with increasing AF levels of each protein (P for trend < .001).

CONCLUSIONS

Using protein-antibody microarray technology, we discovered several potential AF proteins (EN-RAGE, IL-6, MMP-9, and TNFR2) independently associated with HCA in patients with PPROM. Furthermore, we demonstrated a direct correlation between the gradation of the intra-amniotic inflammatory response and HCA severity.

Gene expression of fibrinolytic markers in coronary thrombi

BACKGROUND

The fibrinolytic system plays an important role in coronary artery atherothrombosis, and especially circulating plasminogen-activator inhibitor (PAI) type 1 (PAI-1) associates with increased mortality, infarct size and heart failure in patients with myocardial infarction (MI). In a cross-sectional study, we aimed to study whether genes encoding tissue plasminogen activator (tPA), urinary-type plasminogen activator (uPA), PAI-1 and PAI-2 are expressed in coronary thrombi from acute ST-elevation MI (STEMI) patients. Any relations to myocardial injury measured by peak troponin T, time from symptom onset to Percutaneous Coronary Intervention (PCI), and to different cell types present in the thrombi were also explored.

METHODS

Intracoronary thrombi were aspirated from 33 STEMI patients treated with primary PCI. The thrombi were snap-frozen for gene expression analyses, relatively quantified by RT PCR. Peripheral blood samples were drawn. Correlations were performed by Spearmans rho.

RESULTS

The genes were present in 74-94% of the thrombi. Median peak troponin T was 3434 μ/L and median ischemic time 152 min. There were no significant correlations between the measured genes and troponin T, or ischemic time. Genes encoding tPA, u-PA, PAI-1 and PAI-2 all correlated significantly to the presence of monocytes/macrophages (CD68) in the thrombi (p = 0.028, p < 0.001, p = 0.003, p < 0.001). PAI-1 and PAI-2 also correlated to endothelial cells (CD31) (p = 0.002, p = 0.016). uPA associated with neutrophil granulocytes (CD 66b) (p = 0.019).

CONCLUSION

Genes encoding tPA, uPA, PAI-1 and PAI-2 were highly expressed in human coronary thrombi from STEMI patients, indicating fibrinolytic regulators playing active roles in the thrombi, although not related to myocardial injury. All markers related to the presence of monocytes/macrophages, indicating connection to local inflammatory cells.

TRIAL REGISTRATION

The study is registered at clinicaltrials.gov with identification number NCT02746822 .

Vitronectin stabilizes intravascular adhesion of neutrophils by coordinating β2 integrin clustering

The recruitment of neutrophils from the microvasculature to the site of injury or infection represents a key event in the inflammatory response. Vitronectin (VN) is a multifunctional macromolecule abundantly present in blood and extracellular matrix. The role of this glycoprotein in the extravasation process of circulating neutrophils remains elusive. Employing advanced in vivo/ex vivo imaging techniques in different mouse models as well as in vitro methods, we uncovered a previously unrecognized function of VN in the transition of dynamic to static intravascular interactions of neutrophils with microvascular endothelial cells. These distinct properties of VN require the heteromerization of this glycoprotein with plasminogen activator inhibitor-1 (PAI- 1) on the activated venular endothelium and subsequent interactions of this protein complex with the scavenger receptor low-density lipoprotein receptor-related protein-1 on intravascularly adhering neutrophils. This induces p38 mitogen-activated protein kinases-dependent intracellular signaling events which, in turn, regulates the proper clustering of the b2 integrin lymphocyte function associated antigen-1 on the surface of these immune cells. As a consequence of this molecular interplay, neutrophils become able to stabilize their adhesion to the microvascular endothelium and, subsequently, to extravasate to the perivascular tissue. Hence, endothelial-bound VN-PAI-1 heteromers stabilize intravascular adhesion of neutrophils by coordinating b2 integrin clustering on the surface of these immune cells, thereby effectively controlling neutrophil trafficking to inflamed tissue. Targeting this protein complex might be beneficial for the prevention and treatment of inflammatory pathologies.

The fibrinolytic system in the cornea: A key regulator of corneal wound healing and biological defense

The cornea is a relatively unique tissue in the body in that it possesses specific features such as a lack of blood vessels that contribute to its transparency. The cornea is supplied with soluble blood components such as albumin, globulin, and fibrinogen as well as with nutrients, oxygen, and bioactive substances by diffusion from aqueous humor and limbal vessels as well as a result of its exposure to tear fluid. The healthy cornea is largely devoid of cellular components of blood such as polymorphonuclear leukocytes, monocytes-macrophages, and platelets. The location of the cornea at the ocular surface renders it susceptible to external insults, and its avascular nature necessitates the operation of healing and defense mechanisms in a manner independent of a direct blood supply. The fibrinolytic system, which was first recognized for its role in the degradation of fibrin clots in the vasculature, has also been found to contribute to various biological processes outside of blood vessels. Fibrinolytic factors thus play an important role in biological defense of the cornea. In this review, we address the function of the fibrinolytic system in corneal defense including wound healing and the inflammatory response.

A rare coding mutation in the MAST2 gene causes venous thrombosis in a French family with unexplained thrombophilia: The Breizh MAST2 Arg89Gln variant

Rare variants outside the classical coagulation cascade might cause inherited thrombosis. We aimed to identify the variant(s) causing venous thromboembolism (VTE) in a family with multiple relatives affected with unprovoked VTE and no thrombophilia defects. We identified by whole exome sequencing an extremely rare Arg to Gln variant (Arg89Gln) in the Microtubule Associated Serine/Threonine Kinase 2 (MAST2) gene that segregates with VTE in the family. Free-tissue factor pathway inhibitor (f-TFPI) plasma levels were significantly decreased in affected family members compared to healthy relatives. Conversely, plasminogen activator inhibitor-1 (PAI-1) levels were significantly higher in affected members than in healthy relatives. RNA sequencing analysis of RNA interference experimental data conducted in endothelial cells revealed that, of the 13,387 detected expressed genes, 2,354 have their level of expression modified by MAST2 knockdown, including SERPINE1 coding for PAI-1 and TFPI. In HEK293 cells overexpressing the MAST2 Gln89 variant, TFPI and SERPINE1 promoter activities were respectively lower and higher than in cells overexpressing the MAST2 wild type. This study identifies a novel thrombophilia-causing Arg89Gln variant in the MAST2 gene that is here proposed as a new molecular player in the etiology of VTE by interfering with hemostatic balance of endothelial cells.

Extracellular histones promote fibrinolysis by single-chain urokinase-type plasminogen activator in a factor seven activating protease-dependent way

INTRODUCTION

Extracellular histones inhibit tissue plasminogen activator (t-PA)-mediated fibrinolysis by modifying fibrin structure and rheological properties. However, other plasminogen activators involved in intravascular and extravascular fibrinolysis have not been considered yet.

OBJECTIVES

We investigated the effect of histones on fibrinolysis driven by different plasminogen activators.

METHODS

Clot lysis induced by t-PA, urokinase (u-PA) and its single chain precursor (scu-PA) was evaluated by turbidimetry. Conversion of scu-PA to u-PA and activation of factor seven activating protease (FSAP) were assessed by fluorogenic and chromogenic assays, respectively.

RESULTS

Histones delayed t-PA- and u-PA-mediated fibrinolysis but strongly accelerated scu-PA-driven clot lysis through the enhancement of scu-PA to u-PA conversion. This effect required a plasma factor identified as FSAP by the following findings: 1) histones enhanced neither scu-PA activation nor scu-PA-mediated clot lysis under purified conditions; 2) in plasma, the enhancement of fibrinolytic activity by histones was abolished by a neutralizing anti-FSAP antibody; and 3) histones promoted the activation of plasma FSAP. The effect of the natural mixture of histones on scu-PA-driven fibrinolysis was differentially recapitulated by the individual recombinant histones, H4 displaying the strongest activity. When complexed to DNA, histones still accelerated scu-PA-mediated fibrinolysis but with a lesser efficiency due to a reduced FSAP activation. Finally, preincubation of histones with heparin or activated protein C, two known inhibitors of histones, further amplified histone-mediated boost of scu-PA-driven fibrinolysis.

CONCLUSIONS

Enhancement of FSAP-mediated scu-PA activity by histones may play yet unforeseen roles in intravascular fibrinolysis and contribute to extravascular proteolysis and tissue damage.

Therapeutics targeting the fibrinolytic system

The function of the fibrinolytic system was first identified to dissolve fibrin to maintain vascular patency. Connections between the fibrinolytic system and many other physiological and pathological processes have been well established. Dysregulation of the fibrinolytic system is closely associated with multiple pathological conditions, including thrombosis, inflammation, cancer progression, and neuropathies. Thus, molecules in the fibrinolytic system are potent therapeutic and diagnostic targets. This review summarizes the currently used agents targeting this system and the development of novel therapeutic strategies in experimental studies. Future directions for the development of modulators of the fibrinolytic system are also discussed.

The fibrinolytic system was originally identified to dissolve blood clots, and is shown to have important roles in other pathological processes, including cancer progression, inflammation, and thrombosis. Molecules or therapeutics targeting fibrinolytic system have been successfully used in the clinical treatments of cancer and thrombotic diseases. The clinical studies and experimental models targeting fibrinolytic system are reviewed by Haili Lin at Sanming First Hosipital, Mingdong Huang at Fuzhou University in China, and Peng Xu at A*STAR in Singapore to demonstrate fibrinolytic system as novel therapeutic targets. As an example, the inhibition of fibrinolytic system protein can be used to suppress cancer prolifieration and metastasis. This review also discusses the potential therapeutic effects of inhibitiors of fibrinolytic system on inflammatory disorders.

SerpinB2 inhibits migration and promotes a resolution phase signature in large peritoneal macrophages

SerpinB2 (plasminogen activator inhibitor type 2) has been called the "undecided serpin" with no clear consensus on its physiological role, although it is well described as an inhibitor of urokinase plasminogen activator (uPA). In macrophages, pro-inflammatory stimuli usually induce SerpinB2; however, expression is constitutive in Gata6+ large peritoneal macrophages (LPM). Interrogation of expression data from human macrophages treated with a range of stimuli using a new bioinformatics tool, CEMiTool, suggested that SerpinB2 is most tightly co- and counter-regulated with genes associated with cell movement. Using LPM from SerpinB2-/- and SerpinB2R380A (active site mutant) mice, we show that migration on Matrigel was faster than for their wild-type controls. Confocal microscopy illustrated that SerpinB2 and F-actin staining overlapped in focal adhesions and lamellipodia. Genes associated with migration and extracellular matrix interactions were also identified by RNA-Seq analysis of migrating RPM from wild-type and SerpinB2R380A mice. Subsequent gene set enrichment analyses (GSEA) suggested SerpinB2 counter-regulates many Gata6-regulated genes associated with migration. These data argue that the role of SerpinB2 in macrophages is inhibition of uPA-mediated plasmin generation during cell migration. GSEA also suggested that SerpinB2 expression (likely via ensuing modulation of uPA-receptor/integrin signaling) promotes the adoption of a resolution phase signature.

Urokinase-Type Plasminogen Activator System in Norm and in Life-Threatening Processes (Review)

The multifunctional urokinase-type plasminogen activator system (uPA-system) includes serine proteinase — uPA or urokinase, its receptor (uPAR) and two inhibitors (PAI-1 and PAI-2). The review discusses the structural features and involvement of the system components in the development of life-threatening processes including carcinogenesis, inflammation, neurogenesis and fibrinolysis, in regulation of which the destruction of extracellular matrix (ECM), cell mobility and signaling inside and outside the cell play a decisive role. uPA triggers the processes by activating the plasminogen and its convertion into plasmin involved in the activation of matrix metalloproteinases (MMPs) in addition to the regulation of fibrinolysis. MMPs can hydrolyze all the major ECM components and therefore play a key role in invasion, metastasis, and cell mobility. MMPs activates a cassette of biologically active regulatory molecules and release them from ECM. uPAR, PAI-1 and PAI-2 are responsible for regulation of the uPA activity. In addition, being a signaling receptor, uPAR along with MMPs lead to the stimulation of a number of signaling pathways that are associated with the regulation of proliferation, apoptosis, adhesion, growth and migration of cells contributing to tumor progression, inflammation, chemotaxis, and angiogenesis. Effective participation of the uPA system components in ECM destruction and regulation of intracellular and extracellular signaling pathways demonstrates that the system significantly contributes to the regulation of various physiological and pathological processes.

Plasminogen Activator Inhibitor-1 Promotes Neutrophil Infiltration and Tissue Injury on Ischemia-Reperfusion

OBJECTIVE

Ischemia-reperfusion (I/R) injury significantly contributes to organ dysfunction and failure after myocardial infarction, stroke, and transplantation. In addition to its established role in the fibrinolytic system, plasminogen activator inhibitor-1 has recently been implicated in the pathogenesis of I/R injury. The underlying mechanisms remain largely obscure.

APPROACH AND RESULTS

Using different in vivo microscopy techniques as well as ex vivo analyses and in vitro assays, we identified that plasminogen activator inhibitor-1 rapidly accumulates on microvascular endothelial cells on I/R enabling this protease inhibitor to exhibit previously unrecognized functional properties by inducing an increase in the affinity of β2 integrins in intravascularly rolling neutrophils. These events are mediated through low-density lipoprotein receptor-related protein-1 and mitogen-activated protein kinase-dependent signaling pathways that initiate intravascular adherence of these immune cells to the microvascular endothelium. Subsequent to this process, extravasating neutrophils disrupt endothelial junctions and promote the postischemic microvascular leakage. Conversely, deficiency of plasminogen activator inhibitor-1 effectively reversed leukocyte infiltration, microvascular dysfunction, and tissue injury on experimental I/R without exhibiting side effects on microvascular hemostasis.

CONCLUSIONS

Our experimental data provide novel insights into the nonfibrinolytic properties of the fibrinolytic system and emphasize plasminogen activator inhibitor-1 as a promising target for the prevention and treatment of I/R injury.

Plasminogen Activator Inhibitor Type-1 as a Regulator of Fibrosis

Fibrosis is known as a frequent and irreversible pathological condition which is associated with organ failure. Tissue fibrosis is a central process in a variety of chronic progressive diseases such as diabetes, hypertension, and persistent inflammation. This state could contribute to chronic injury and the initiation of tissue repair. Fibrotic disorders represent abnormal wound healing with defective matrix turnover and clearance that lead to excessive accumulation of extracellular matrix components. A variety of identified growth factors, cytokines, and persistently activated myofibroblasts have critical roles in the pathogenesis of fibrosis. Irrespective of etiology, the transforming growth factor-β pathway is the major driver of fibrotic response. Plasminogen activator inhibitor-1 (PAI-1) is a crucial downstream target of this pathway. Transforming growth factor-β positively regulates PAI-1 gene expression via two main pathways including Smad-mediated canonical and non-canonical pathways. Overexpression of PAI-1 reduces extracellular matrix degradation via perturbing the plasminogen activation system. Indeed, elevated PAI-1 levels inhibit proteolytic activity of tissue plasminogen activator and urokinase plasminogen activator which could contribute to a variety of inflammatory elements in the injury site and to excessive matrix deposition. This review summarizes the current knowledge of critical pathways that regulate PAI-1 gene expression and suggests effective approaches for the treatment of fibrotic disease. J. Cell. Biochem. 119: 17-27, 2018. © 2017 Wiley Periodicals, Inc.

Aged neutrophils contribute to the first line of defense in the acute inflammatory response

Under steady-state conditions, aged neutrophils are removed from the circulation in bone marrow, liver, and spleen, thereby maintaining myeloid cell homeostasis. The fate of these aged immune cells under inflammatory conditions, however, remains largely obscure. Here, we demonstrate that in the acute inflammatory response during endotoxemia, aged neutrophils cease returning to the bone marrow and instead rapidly migrate to the site of inflammation. Having arrived in inflamed tissue, aged neutrophils were found to exhibit a higher phagocytic activity as compared with the subsequently recruited nonaged neutrophils. This distinct behavior of aged neutrophils under inflammatory conditions is dependent on specific age-related changes in their molecular repertoire that enable these "experienced" immune cells to instantly translate inflammatory signals into immune responses. In particular, aged neutrophils engage Toll-like receptor-4- and p38 MAPK-dependent pathways to induce conformational changes in β2 integrins that allow these phagocytes to effectively accomplish their mission in the front line of the inflammatory response. Hence, ageing in the circulation might represent a critical process for neutrophils that enables these immune cells to properly unfold their functional properties for host defense.

Leucocyte expression of genes implicated in the plasminogen activation cascade is modulated by yoghurt peptides

The urokinase-plasminogen activator (u-PA), its receptor (u-PAR) and the inhibitors of u-PA (PAI-1 and PAI-2) provide a multi-molecular system in leucocytes that exerts pleiotropic functions influencing the development of inflammatory and immune responses. The objective of the present study was to examine the ability of water soluble extracts (WSE) obtained from traditional Greek yoghurt made from bovine or ovine milk to modulate the expression of u-PA, u-PAR, PAI-1 and PAI-2 in ovine monocytes and neutrophils. WSE were obtained from 8 commercial traditional type Greek yoghurts made from ovine or bovine milk. WSE upregulated the expression of all 4 u-PA related genes in monocytes but the upregulation was much higher in the PAI-1 (10-fold) than in u-PA and u-PAR (3–4 fold) thus, shifting the system towards inhibition. In line with this observation, WSE reduced total and membrane-bound u-PA activity in monocytes. In neutrophils, WSE caused small (50–60%) but significant (P < 0·05) reductions in expression of u-PAR and PAI-2 but had no effect on expression of u-PA, PAI-1 and on total cell-associated and membrane-bound u-PA activity. WSE from yoghurts made from bovine or ovine milk were essentially equally effective in affecting the u-PA system except for the u-PAR gene in ovine neutrophils that was affected (reduced) by the ovine and not the bovine WSE. In conclusion, peptides present in WSE modulated the expression of u-PA related genes but the effect was much more prominent in monocytes than in neutrophils.

Platelets Guide Leukocytes to Their Sites of Extravasation

Effective immune responses require the directed migration of leukocytes from the vasculature to the site of injury or infection. How immune cells “find” their site of extravasation remains largely obscure. Here, we identified a previously unrecognized role of platelets as pathfinders guiding leukocytes to their exit points in the microvasculature: upon onset of inflammation, circulating platelets were found to immediately adhere at distinct sites in venular microvessels enabling these cellular blood components to capture neutrophils and, in turn, inflammatory monocytes via CD40-CD40L-dependent interactions. In this cellular crosstalk, ligation of PSGL-1 by P-selectin leads to ERK1/2 MAPK-dependent conformational changes of leukocyte integrins, which promote the successive extravasation of neutrophils and monocytes to the perivascular tissue. Conversely, blockade of this cellular partnership resulted in misguided, inefficient leukocyte responses. Our experimental data uncover a platelet-directed, spatiotemporally organized, multicellular crosstalk that is essential for effective trafficking of leukocytes to the site of inflammation.

This study identifies a previously unanticipated role for platelets as pathfinders, guiding leukocytes to the sites at which they can exit the microvasculature; this process appears to be critical for an effective immune response.

White blood cells (leukocytes) are the effector cells of the immune system. The movement (extravasation) of leukocytes from the bloodstream to the surrounding tissue is a prerequisite for proper host defense. Platelets are anucleate cell particles that circulate in the blood and play a fundamental role in hemostasis. Here, we report a previously unrecognized function of platelets as "pathfinders" guiding leukocytes to their site of extravasation. Upon onset of the inflammatory response, platelets were found to immediately adhere to specific sites in the smallest venular microvessels. At these "hot spots", platelets capture intravascularly crawling neutrophils and, in turn, inflammatory monocytes. The cellular crosstalk arising from these interactions leads to conformational changes of distinct adhesion molecules on the surface of leukocytes, subsequently promoting the extravasation of these immune cells to the inflamed tissue. Conversely, blockade of this cellular partnership leads to misguided and inefficient leukocyte responses. Thus, platelet-directed guidance of leukocytes to confined sites of extravasation appears to be a critical step in the recruitment process of immune cells, which might emerge as a promising therapeutic target for the prevention and treatment of inflammatory pathologies.

Over-expression of cathepsin B in hepatocellular carcinomas predicts poor prognosis of HCC patients

Background

Several studies have found that Cathepsin B (CTSB) is up-regulated in many tumor types and facilitates tumor progression. However, the role of CTSB in hepatocellular carcinoma (HCC) progression remains unclear. This study was aimed at investigating the expression and role of CTSB in HCC in a large set of samples and cell lines (MHCC-97H and MHCC-97 L), and evaluating the clinical and prognostic significance of CTSB protein in patients with HCC.

Methods

The expression of CTSB was examined in HCC tissue and cell lines by Western-blotting, Real-time PCR, and immunohistochemical staining. Wound healing assay and invasion assay were used to verify the effect of CTSB on the migration and invasion ability of HCC cell lines. Tumor formation assay in nude mice was used to analyze the effect of CTSB on the tumorigenicity of HCC cell lines.

Results

The status of CTSB protein in carcinoma tissues is much higher than that in paracarcinoma tissues. The overall survival of the patients with high CTSB expression was significantly shorter than the low CTSB expression group. High CTSB expression was significantly correlated with advanced clinical staging, histological grade, and tumor recurrence. In vitro and in vivo experiments demonstrated that over-expression of CTSB in MHCC-97 L cells promoted cell invasion and tumor progression ability. Down-regulation of CTSB in MHCC-97H showed the opposite effects. These phenotypic changes caused by CTSB knockdown or over-expression correlated with expression of the matrix metallopeptidase MMP-9. Moreover, multivariate analysis suggested that CTSB expression might be an independent prognostic indicator for the survival of HCC patients after curative surgery.

Conclusions

CTSB might be involved in the development and progression of HCC as an oncogene, and thereby may be a valuable prognostic marker for HCC patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-016-0503-9) contains supplementary material, which is available to authorized users.

Spatiotemporal Expression Dynamics of Selectins Govern the Sequential Extravasation of Neutrophils and Monocytes in the Acute Inflammatory Response

Objective—

Leukocyte recruitment to the site of inflammation is a key event in a variety of cardiovascular pathologies. Infiltrating neutrophils constitute the first line of defense that precedes a second wave of emigrating monocytes reinforcing the inflammatory reaction. The mechanisms initiating this sequential process remained largely obscure.

Approach and Results—

Using advanced in vivo microscopy and in vitro/ex vivo techniques, we identified individual spatiotemporal expression patterns of selectins and their principal interaction partners on neutrophils, resident/inflammatory monocytes, and endothelial cells. Coordinating the intraluminal trafficking of neutrophils and inflammatory monocytes to common sites of extravasation, selectins assign different sites to these immune cells for their initial interactions with the microvascular endothelium. Whereas constitutively expressed leukocyte L-selectin/CD62L and endothelial P-selectin/CD62P together with CD44 and P-selectin glycoprotein ligand-1/CD162 initiate the emigration of neutrophils, de novo synthesis of endothelial E-selectin/CD62E launches the delayed secondary recruitment of inflammatory monocytes. In this context, P-selectin/CD62P and L-selectin/CD62L together with P-selectin glycoprotein ligand-1/CD162 and CD44 were found to regulate the flux of rolling neutrophils and inflammatory monocytes, whereas E-selectin/CD62E selectively adjusts the rolling velocity of inflammatory monocytes. Moreover, selectins and their interaction partners P-selectin glycoprotein ligand-1/CD162 and CD44 differentially control the intraluminal crawling behavior of neutrophils and inflammatory monocytes collectively enabling the sequential extravasation of these immune cells to inflamed tissue.

Conclusions—

Our findings provide novel insights into the mechanisms initiating the sequential infiltration of the perivascular tissue by neutrophils and monocytes in the acute inflammatory response and might thereby contribute to the development of targeted therapeutic strategies for prevention and treatment of cardiovascular diseases.

Components of the plasminogen activation system promote engraftment of porous polyethylene biomaterial via common and distinct effects

Rapid fibrovascularization is a prerequisite for successful biomaterial engraftment. In addition to their well-known roles in fibrinolysis, urokinase-type plasminogen activator (uPA) and tissue plasminogen activator (tPA) or their inhibitor plasminogen activator inhibitor-1 (PAI-1) have recently been implicated as individual mediators in non-fibrinolytic processes, including cell adhesion, migration, and proliferation. Since these events are critical for fibrovascularization of biomaterial, we hypothesized that the components of the plasminogen activation system contribute to biomaterial engraftment. Employing in vivo and ex vivo microscopy techniques, vessel and collagen network formation within porous polyethylene (PPE) implants engrafted into dorsal skinfold chambers were found to be significantly impaired in uPA-, tPA-, or PAI-1-deficient mice. Consequently, the force required for mechanical disintegration of the implants out of the host tissue was significantly lower in the mutant mice than in wild-type controls. Conversely, surface coating with recombinant uPA, tPA, non-catalytic uPA, or PAI-1, but not with non-catalytic tPA, accelerated implant vascularization in wild-type mice. Thus, uPA, tPA, and PAI-1 contribute to the fibrovascularization of PPE implants through common and distinct effects. As clinical perspective, surface coating with recombinant uPA, tPA, or PAI-1 might provide a novel strategy for accelerating the vascularization of this biomaterial.

miR-193b directly targets STMN1 and uPA genes and suppresses tumor growth and metastasis in pancreatic cancer

Pancreatic cancer has the poorest prognosis among all cancer types, due to its late diagnosis and the lack of effective therapies. Therefore, identification of novel gene targets, which are differentially expressed in pancreatic cancer and functionally involved in the malignant phenotype, is critical to achieve early diagnosis and develop effective therapeutic strategies. microRNAs (miRNAs) are small non-coding RNAs, which negatively regulate the expression of their targets. Due to their various targets, miRNAs play a key role in a number of physiological processes and in oncogenesis. Therefore, investigating the role of miRNAs in tumor may contribute to the development of new diagnostic and therapeutic tools for various types of cancer, including pancreatic cancer. Here, we investigated the role of miR-193b in pancreatic cancer. Our data showed that the expression of miR-193b is markedly decreased in pancreatic cancer tissues compared to adjacent healthy tissues. The Panc-1 cell line transfected with the miR‑193b exhibited significantly decreased proliferative, migratory, and invasive ability compared to untransfected cells. Moreover, miR-193b inhibited the expression of stathmin 1 (STMN1) and urokinase-type plasminogen activator (uPA) in Panc-1 cells. These data suggest that miR-193b acts as a tumor suppressor in pancreatic cancer. Therefore, miR-193b may constitute a promising therapeutic agent for the suppression of pancreatic cancer cell growth and metastasis.

Bacteria under stress by complement and coagulation

The complement and coagulation systems are two related protein cascades in plasma that serve important roles in host defense and hemostasis, respectively. Complement activation on bacteria supports cellular immune responses and leads to direct killing of bacteria via assembly of the Membrane Attack Complex (MAC). Recent studies have indicated that the coagulation system also contributes to mammalian innate defense since coagulation factors can entrap bacteria inside clots and generate small antibacterial peptides. In this review, we will provide detailed insights into the molecular interplay between these protein cascades and bacteria. We take a closer look at how these pathways are activated on bacterial surfaces and discuss the mechanisms by which they directly cause stress to bacterial cells. The poorly understood mechanism for bacterial killing by the MAC will be reevaluated in light of recent structural insights. Finally, we highlight the strategies used by pathogenic bacteria to modulate these protein networks. Overall, these insights will contribute to a better understanding of the host defense roles of complement and coagulation against bacteria.

Cathepsin B: multiple roles in cancer

Proteases, including intracellular proteases, play roles at many different stages of malignant progression. Our focus here is cathepsin B, a lysosomal cysteine cathepsin. High levels of cathepsin B are found in a wide variety of human cancers, levels that often induce secretion and association of cathepsin B with the tumor cell membrane. In experimental models, such as transgenic models of murine pancreatic and mammary carcinomas, causal roles for cathepsin B have been demonstrated in initiation, growth/tumor cell proliferation, angiogenesis, invasion, and metastasis. Tumor growth in transgenic models is promoted by cathepsin B in tumor-associated cells, for example, tumor-associated macrophages, as well as in tumor cells. In transgenic models, the absence of cathepsin B has been associated with enhanced apoptosis, yet cathepsin B also has been shown to contribute to apoptosis. Cathepsin B is part of a proteolytic pathway identified in xenograft models of human glioma; targeting only cathepsin B in these tumors is less effective than targeting cathepsin B in combination with other proteases or protease receptors. Understanding the mechanisms responsible for increased expression of cathepsin B in tumors and association of cathepsin B with tumor cell membranes is needed to determine whether targeting cathepsin B could be of therapeutic benefit.

Tissue plasminogen activator promotes postischemic neutrophil recruitment via its proteolytic and nonproteolytic properties

OBJECTIVE

Neutrophil infiltration of the postischemic tissue considerably contributes to organ dysfunction on ischemia/reperfusion injury. Beyond its established role in fibrinolysis, tissue-type plasminogen activator (tPA) has recently been implicated in nonfibrinolytic processes. The role of this serine protease in the recruitment process of neutrophils remains largely obscure.

APPROACH AND RESULTS

Using in vivo microscopy on the postischemic cremaster muscle, neutrophil recruitment and microvascular leakage, but not fibrinogen deposition at the vessel wall, were significantly diminished in tPA(-/-) mice. Using cell transfer techniques, leukocyte and nonleukocyte tPA were found to mediate ischemia/reperfusion-elicited neutrophil responses. Intrascrotal but not intra-arterial application of recombinant tPA induced a dose-dependent increase in the recruitment of neutrophils, which was significantly higher compared with stimulation with a tPA mutant lacking catalytic activity. Whereas tPA-dependent transmigration of neutrophils was selectively reduced on the inhibition of plasmin or gelatinases, neutrophil intravascular adherence was significantly diminished on the blockade of mast cell activation or lipid mediator synthesis. Moreover, stimulation with tPA caused a significant elevation in the leakage of fluorescein isothiocyanate dextran to the perivascular tissue, which was completely abolished on neutrophil depletion. In vitro, tPA-elicited macromolecular leakage of endothelial cell layers was abrogated on the inhibition of its proteolytic activity.

CONCLUSIONS

Endogenously released tPA promotes neutrophil transmigration to reperfused tissue via proteolytic activation of plasmin and gelatinases. As a consequence, tPA on transmigrating neutrophils disrupts endothelial junctions allowing circulating tPA to extravasate to the perivascular tissue, which, in turn, amplifies neutrophil recruitment through the activation of mast cells and release of lipid mediators.

Regulation of monocyte/macrophage function by factor VII activating protease (FSAP)

OBJECTIVE

Factor VII activating protease (FSAP) is a novel regulator of vascular inflammation and hemostasis. However, the molecular mechanism by which circulating FSAP influences inflammatory events and progression of atherosclerosis is not yet entirely understood. Here we have investigated the influence of FSAP on monocyte/macrophage functions.

METHODS

We stimulated human monocyte-derived macrophages with FSAP and analyzed their cellular responses.

RESULTS

FSAP induced IκB-dependent NF-κB activation in a time- and concentration-dependent fashion. FSAP also activated the phosphorylation and proteolytic degradation of the inhibitor protein IκBα. The phosphorylation of the p65 subunit of NF-κB was induced by FSAP, which is known to contribute to the enhancement of DNA-binding activity of NF-κB. Concomitantly, FSAP up-regulated the expression of pro-inflammatory cytokines, matrix metalloproteinases, cell adhesion molecules and tissue factor. In the presence of FSAP there was increased monocytes adhesion and transendothelial migration in a beta2 integrin dependent manner.

CONCLUSIONS

Our findings suggest that FSAP activates the NF-κB pathway and the associated downstream pro-inflammatory factors in monocytic cells. This adds to a spectrum of FSAP effects on the vascular system that may explain its association with cardiovascular diseases.