The lectin-like domain of thrombomodulin confers protection from neutrophil-mediated tissue damage by suppressing adhesion molecule expression via nuclear factor kappaB and mitogen-activated protein kinase pathways

PAMPs and DAMPs as triggers for DIC

Thrombosis is generally considered harmful because it compromises the blood supply to organs. However, recent studies have suggested that thrombosis under certain circumstances plays a major physiological role in early immune defense against invading pathogens. This defensive role of thrombosis is now referred to as immunothrombosis. Activated monocytes and neutrophils are two major inducers of immunothrombosis. Monocytes and neutrophils are activated when they detect pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). Detection of PAMPs and DAMPs triggers tissue factor expression on monocytes and neutrophil extracellular trap (NET) release by neutrophils, promoting immunothrombosis. Although tissue factor-mediated and NET-mediated immunothrombosis plays a role in early host defense against bacterial dissemination, uncontrolled immunothrombosis may lead to disseminated intravascular coagulation.

Effects of Tityus serrulatus scorpion venom on thromboelastogram in rats

Thromboelastometry was used to evaluate blood coagulation in anesthetized rats after intravenous administration of Tityus serrulatus scorpion venom (Tx). Tracheostomy followed by catheterization of the left jugular vein and right carotid artery were performed for Tx or Ringer's lactate solution injection and blood sample harvesting, respectively. Blood samples were obtained at the beginning of the experiments (baseline) and at two, five, 15, 30, and 60 min after intoxication. The following coagulation parameters were analyzed: CT (Clotting Time), CFT (Clotting Formation Time), Alpha Angle (α), MCF (Maximum Clot Firmness) and TPI (Thrombodynamic Potential Index). Toxin-induced hypercoagulability was demonstrated at the 15 and 60 min. We hypothesize Tx-induced hypercoagulability and enhanced clot formation could be explained by catecholamine release, systemic inflammatory response, and complement system activation, at least in the first hour after envenomation. Further studies are needed to determine the molecular mechanism of Tx-induced coagulopathy.

Role of tissue factor in Mycobacterium tuberculosis-induced inflammation and disease pathogenesis

Tuberculosis (TB) is a chronic lung infectious disease characterized by severe inflammation and lung granulomatous lesion formation. Clinical manifestations of TB include hypercoagulable states and thrombotic complications. We previously showed that Mycobacterium tuberculosis (M.tb) infection induces tissue factor (TF) expression in macrophages in vitro. TF plays a key role in coagulation and inflammation. In the present study, we investigated the role of TF in M.tb-induced inflammatory responses, mycobacterial growth in the lung and dissemination to other organs. Wild-type C57BL/6 and transgenic mice expressing human TF, either very low levels (low TF) or near to the level of wild-type (HTF), in place of murine TF were infected with M.tb via aerosol exposure. Levels of TF expression, proinflammatory cytokines and thrombin-antithrombin complexes were measured post M.tb infection and mycobacterial burden in the tissue homogenates were evaluated. Our results showed that M.tb infection did not increase the overall TF expression in lungs. However, macrophages in the granulomatous lung lesions in all M.tb-infected mice, including low TF mice, showed increased levels of TF expression. Conspicuous fibrin deposition in the granuloma was detected in wild-type and HTF mice but not in low TF mice. M.tb infection significantly increased expression levels of cytokines IFN-γ, TNF-α, IL-6 and IL-1ß in lung tissues. However, no significant differences were found in proinflammatory cytokines among the three experimental groups. Mycobacterial burden in lungs and dissemination into spleen and liver were essentially similar in all three genotypes. Our data indicate, in contrast to that observed in acute bacterial infections, that TF-mediated coagulation and/or signaling does not appear to contribute to the host-defense in experimental tuberculosis.

Thrombomodulin modulates cell migration in human melanoma cell lines

Malignant melanoma cells are known to have altered expressions of growth factors as compared with normal melanocytes. Thrombomodulin (TM) is a thrombin receptor on endothelial cells that converts thrombin from a procoagulant to an anticoagulant enzyme. TM expression is downregulated in tumor cells, and this phenomenon correlates with tumor cell invasiveness and a poor prognosis in patients with cancer. In this study, we evaluated TM expression in two human melanoma cell lines that are known to have either low (WM35) or high (A375) aggressive phenotypes. Analysis by quantitative real-time PCR (qPCR) showed that the mRNA expression of TM is modestly (WM35) or dramatically (A375) downregulated in melanoma cells, as compared with human primary melanocytes. TM expression levels inversely correlated with in-vitro migration properties of tumor cells. In addition, interleukin-8 expression also correlated with the degree of aggressiveness, as indicated by high expression levels of this cytokine in A375 cells. Overexpression of TM in A375 cells by transient transfection reversed their aggressive phenotype and dramatically decreased interleukin-8 expression by these cells. Taken together, these results suggest that downregulation of TM plays a crucial role in melanocyte transformation and melanoma progression.

Thrombomodulin alleviates murine GVHD in association with an increase in the proportion of regulatory T cells in the spleen

Recombinant human soluble thrombomodulin (rTM), a potent anticoagulant, has been used for the treatment of disseminated intravascular coagulation in Japan since 2008. Interestingly, rTM possesses anti-inflammatory and cytoprotective functions. This study examined whether rTM alleviates GVHD in a murine hematopoietic SCT (HSCT) model. Use of rTM significantly improved the survival of mice on day 28 of transplantation (survival rate 70% in rTM - treated mice vs 35% in control, P<0.05) in association with a significant decrease in plasma levels of IL-6, IFN-γ and high-mobility group B1 DNA-binding protein on day 7 of HSCT. Intriguingly, the proportion of regulatory T cells in the spleen was significantly increased in rTM-treated mice on day 7 of transplantation compared with control diluent-treated mice. In addition, elevated plasma levels of TM and fibrin/fibrinogen degradation product were noted in HSCT-recipient mice, suggesting coagulopathy caused by endothelial cell damage in this GVHD model. The use of rTM potently decreased these levels. Importantly, rTM did not hamper the anti-GVL and engraftment of hematopoietic cells. Taken together, the use of rTM may prevent GVHD and serve as a potential therapeutic strategy to improve clinical outcomes in individuals who receive HSCT.

Prognostic significance of urokinase-type plasminogen activator and its receptor in patients with systemic inflammatory response syndrome

BACKGROUND

This study aimed to determine the plasma levels of urokinase-type plasminogen activator (uPA), urokinase-type plasminogen activator receptor (uPAR), D-dimer, IL-6 and TNF-α and observe the relations among uPA, uPAR, D-dimer, IL-6 and TNF-α in patients with systemic inflammatory response syndrome (SIRS).

METHODS

A prospective, clinical case-control study was conducted in patients with SIRS at age of more than 55 years old treated during 2008-2010 at Wuhan Central Hospital. Venous blood samples were collected by routine venipuncture. Eighty-five patients were divided into two groups according to diagnostic criteria of SIRS: SIRS patients from intensive care units (n=50), and non-SIRS patients from medical wards (n=35). Thirty healthy blood donors who visited the General Health Check-up Division at Wuhan Central Hospital served as controls. Excluded from the study were (1) those patients with pregnancy; (2) those with cancer; (3) those died after admission into the ICU in 7 days; (4) those received cardiopulmonary resuscitation; (5) those who had previous blood system diseases; and (6) those with SIRS before admission into the ICU. The levels of uPA, uPAR, D-D, IL-6 and TNF-α in blood were detected by commercial enzyme-linked immunosorbent assay (ELISA) kit. The data were analyzed using SPSS version 17.0 and expressed as mean ± standard. Student's t test and the Mann-Whitney U test were used in the analysis. The relations of uPA, uPAR and D-dimer, IL-6 TNF-α levels were analyzed using Spearman's rank-order correlation coefficient test.

RESULTS

The plasma levels of uPA, uPAR, D-dimer,IL-6 and TNF-α in the patients with SIRS were obviously higher than those in the non-SIRS patients and controls (P<0.001). Correlation analysis showed a positive correlation between uPAR and IL-6 levels (r=0.395, P=0.004) and between uPAR and TNF-α levels (r=0.606, P<0.001), but no correlation between uPAR and D-dimer levels (r=0.069, P=0.632). No correlation was observed between uPA, D-dimer, IL-6 and TNF-α levels (P>0.05). The establishment of ROC curve was based on the levels of uPAR, D-dimer, IL-6 and TNF-α in 24 hours for the diagnosis of multiple organ dysfunction syndrome (MODS), and the ROC areas under the curve were 0.76, 0.58, 0.86 and 0.83, respectively.

CONCLUSIONS

uPA and uPAR play a major role in patients with SIRS in the process of coagulation disorder, but the mechanism of SIRS is not the same. uPAR may play a central role in the development of SIRS to MODS.

The coagulation system in melioidosis: from pathogenesis to new treatment strategies

Melioidosis, caused by the Gram-negative bacterium Burkholderia pseudomallei, is a dreadful disease common in South-East Asia and Northern Australia and is characterized by chronic suppurative lesions and pneumonia. Melioidosis may evolve into severe sepsis with multi-organ failure with high mortalities, despite proper antibiotic therapy. Besides activation of a strong pro-inflammatory host response, the coagulation system plays an important role during melioidosis, which is thought to be host-protective. In particular, a procoagulant state together with downregulation of anticoagulant pathways and activation of fibrinolysis are present, all closely interrelated with parameters of inflammation. This review presents an overview of recent studies in which the role of coagulation, anti-coagulation and fibrinolysis during melioidosis was investigated both in patients and in experimental settings.

Activated protein C based therapeutic strategies in chronic diseases

Activated protein C (aPC) is a natural anticoagulant and a potent anti-inflammatory and cytoprotective agent. At the expense of increased bleeding risk aPC has been used - with some success - in sepsis. The design of cytoprotective-selective aPC variants circumvents this limitation of increased bleeding, reviving the interest in aPC as a therapeutic agent. Emerging studies suggest that aPC`s beneficial effects are not restricted to acute illness, but likewise relevant in chronic diseases, such as diabetic nephropathy, neurodegeneration or wound healing. Epigenetic regulation of gene expression, reduction of oxidative stress, and regulation of ROS-dependent transcription factors are potential mechanisms of sustained cytoprotective effects of aPC in chronic diseases. Given the available data it seems questionable whether a unifying mechanism of aPC dependent cytoprotection in acute and chronic diseases exists. In addition, the signalling pathways employed by aPC are tissue and cell specific. The mechanistic insights gained from studies exploring aPC`s effects in various diseases may hence lay ground for tissue and disease specific therapeutic approaches. This review outlines recent investigations into the mechanisms and consequences of long-term modulation of aPC-signalling in models of chronic diseases.

Thrombomodulin modulates dendritic cells via both antagonism of high mobility group protein B1 and an independent mechanism

BACKGROUND

Thrombomodulin treatment modulates the properties of dendritic cells (DCs) converting them from immunogenic to tolerogenic and inducing its own expression on DCs. Thrombomodulin binds to the inflammatory mediator, high mobility group protein B1 (HMGB1), antagonizing signalling through its receptor, receptor for advanced glycation end products (RAGE).

METHODS

To test if soluble thrombomodulin could antagonize HMGB1 signaling via RAGE on DCs. DCs were prepared from mouse bone marrow cells or human monocytes. In some experiments dendritic cells were sorted into thrombomodulin+ and thrombomodulin- populations. Expression of surface maturation markers was determined by flow cytometry following treatment with thrombomodulin in the presence or absence of HMGB1.

RESULTS

Thrombomodulin+ dendritic cells secrete less HMGB1 into the medium. HMGB1 reduces the effects of thrombomodulin on expression of DC maturation markers. Treatment with thrombomodulin reduces the expression of maturation markers such as CD80 and CD86 and increases the expression of thrombomodulin on the DC surface. Treatment of DCs with neutralizing anti-HMGB1 antibody acted synergistically with thrombomodulin in increasing thrombomodulin expression on DCs. Treatment with thrombomodulin can still reduce the expression of surface markers on DCs derived from mice that are deficient in RAGE showing that thrombomodulin can affect DCs by an alternative mechanism.

CONCLUSIONS

The results of this study show that thrombomodulin modulates DCs both by antagonizing the interaction of HMGB1 with RAGE and by an independent mechanism.

The role of platelets in coagulation dysfunction in xenotransplantation, and therapeutic options

Xenotransplantation could resolve the increasing discrepancy between the availability of deceased human donor organs and the demand for transplantation. Most advances in this field have resulted from the introduction of genetically engineered pigs, e.g., α1,3-galactosyltransferase gene-knockout (GTKO) pigs transgenic for one or more human complement-regulatory proteins (e.g., CD55, CD46, CD59). Failure of these grafts has not been associated with the classical features of acute humoral xenograft rejection, but with the development of thrombotic microangiopathy in the graft and/or consumptive coagulopathy in the recipient. Although the precise mechanisms of coagulation dysregulation remain unclear, molecular incompatibilities between primate coagulation factors and pig natural anticoagulants exacerbate the thrombotic state within the xenograft vasculature. Platelets play a crucial role in thrombosis and contribute to the coagulation disorder in xenotransplantation. They are therefore important targets if this barrier is to be overcome. Further genetic manipulation of the organ-source pigs, such as pigs that express one or more coagulation-regulatory genes (e.g., thrombomodulin, endothelial protein C receptor, tissue factor pathway inhibitor, CD39), is anticipated to inhibit platelet activation and the generation of thrombus. In addition, adjunctive pharmacologic anti-platelet therapy may be required. The genetic manipulations that are currently being tested are reviewed, as are the potential pharmacologic agents that may prove beneficial.

Thrombomodulin domain 1 ameliorates diabetic nephropathy in mice via anti-NF-κB/NLRP3 inflammasome-mediated inflammation, enhancement of NRF2 antioxidant activity and inhibition of apoptosis

AIMS/HYPOTHESIS

Chronic inflammatory processes have been increasingly shown to be involved in the pathogenesis of diabetes and diabetic nephropathy. Recently, we demonstrated that a lectin-like domain of thrombomodulin (THBD), which is known as THBD domain 1 (THBDD1) and which acts independently of protein C activation, neutralised an inflammatory response in a mouse model of sepsis. Here, therapeutic effects of gene therapy with adeno-associated virus (AAV)-carried THBDD1 (AAV-THBDD1) were tested in a mouse model of type 2 diabetic nephropathy.

METHODS

To assess the therapeutic potential of THBDD1 and the mechanisms involved, we delivered AAV-THBDD1 (10(11) genome copies) into db/db mice and tested the effects of recombinant THBDD1 on conditionally immortalised podocytes.

RESULTS

A single dose of AAV-THBDD1 improved albuminuria, renal interstitial inflammation and glomerular sclerosis, as well as renal function in db/db mice. These effects were closely associated with: (1) inhibited activation of the nuclear factor κB (NF-κB) pathway and the NACHT, LRR and PYD domains-containing protein 3 (NLRP3) inflammasome; (2) promotion of nuclear factor (erythroid-derived 2)-like 2 (NRF2) nuclear translocation; and (3) suppression of mitochondria-derived apoptosis in the kidney of treated mice.

CONCLUSIONS/INTERPRETATION

AAV-THBDD1 gene therapy resulted in improvements in a model of diabetic nephropathy by suppressing the NF-κB-NLRP3 inflammasome-mediated inflammatory process, enhancing the NRF2 antioxidant pathway and inhibiting apoptosis in the kidney.

Recombinant human thrombomodulin suppresses experimental abdominal aortic aneurysms induced by calcium chloride in mice

OBJECTIVE

To investigate whether recombinant thrombomodulin containing all the extracellular domains (rTMD123) has therapeutic potential against aneurysm development.

SUMMARY BACKGROUND DATA

The pathogenesis of abdominal aortic aneurysm (AAA) is characterized by chronic inflammation and proteolytic degradation of extracellular matrix. Thrombomodulin, a transmembrane glycoprotein, exerts anti-inflammatory activities such as inhibition of cytokine production and sequestration of proinflammatory high-mobility group box 1 (HMGB1) to prevent it from engaging the receptor for advanced glycation end product (RAGE) that may sustain inflammation and tissue damage.

METHODS

The in vivo effects of treatment and posttreatment with rTMD123 on aortic dilatation were measured using the CaCl2-induced AAA model in mice.

RESULTS

Characterization of the CaCl2-induced model revealed that HMGB1 and RAGE, both localized mainly to macrophages, were persistently upregulated during a 28-day period of AAA development. In vitro, rTMD123-HMGB1 interaction prevented HMGB1 binding to macrophages, thereby prohibiting activation of HMGB1-RAGE signaling in macrophages. In vivo, short-term treatment with rTMD123 upon AAA induction suppressed the levels of proinflammatory cytokines, HMGB1, and RAGE in the aortic tissue; reduced the infiltrating macrophage number; and finally attenuated matrix metalloproteinase production, extracellular matrix destruction, and AAA formation without disturbing vascular calcification. Consistently, posttreatment with rTMD123 seven days after AAA induction alleviated vascular inflammation and retarded AAA progression.

CONCLUSIONS

These data suggest that rTMD123 confers protection against AAA development. The mechanism of action may be associated with reduction of proinflammatory mediators, blockade of macrophage recruitment, and suppression of HMGB1-RAGE signaling involved in aneurysm formation and downstream macrophage activation.

Post-marketing surveillance of thrombomodulin alfa, a novel treatment of disseminated intravascular coagulation - safety and efficacy in 1,032 patients with hematologic malignancy

INTRODUCTION

Post-marketing surveillance of thrombomodulin alfa (TM-α) was performed to evaluate safety and efficacy in patients with disseminated intravascular coagulation (DIC) with hematologic malignancy.

MATERIALS AND METHODS

All patients treated with TM-α from May 2008 to April 2010 in Japan were included. Information about baseline characteristics, safety, and efficacy were collected. The DIC resolution rate, survival rate on Day 28 after the last TM-α administration, and changes in DIC score and coagulation tests were evaluated.

RESULTS

The underlying diseases associated with DIC were acute myeloid leukemia (except for acute promyelocytic leukemia, n=350), lymphoma (n=199), acute promyelocytic leukemia (n=172), acute lymphoblastic leukemia (n=156), myelodysplastic syndromes (n=61), and other (n=94). The incidence rates of bleeding-related adverse events and adverse drug reactions were 17.8% and 4.6%, respectively. In subjects with bleeding symptoms at baseline, 55.0% were assessed as disappeared or improved based on symptoms after TM-α treatment. The DIC resolution and survival rates were 55.9% and 70.7%, respectively. The DIC score and coagulation tests including thrombin-antithrombin complex (TAT) were significantly improved. Coagulation tests were significantly improved after TM-α treatment even in subjects whose clinical course of underlying disease was assessed as unchanged or exacerbated.

CONCLUSIONS

This surveillance confirmed the safety and efficacy of TM-α in clinical practice, thus TM-α may be an ideal treatment for patients with DIC based upon hematologic malignancy.

The C-Terminal Domain of Thrombomodulin Regulates Monocyte Migration with Interleukin-6 Stimulation

Thrombomodulin (TM) is expressed on the surface of monocyte, which is important in the regulation of cell migration, proliferation, and inflammatory responses. In a previous study, we demonstrated that TM on monocyte is negatively associated with cell migration. However, the mechanisms involved in this process are unclear, therefore, we explored the mechanisms in this study. Chemotactic assays and immunofluorescence showed that TM siRNA increased the Chemotaxis of the IL-6-activated THP-1, and aggravated actin assembly relative to the IL-6-treated control. In contrast, cells overexpressing plasmids containing full-length or domain 5 of TM followed by IL-6 treatment displayed lower Chemotaxis and less actin assembly. Western blot analysis showed that TM knockdown markedly increased cytoskeleton components cofilin and LIMK1 phosphorylation in IL-6-treated THP-1, whereas, transfected cells with HA-TM FL or HA-TM D5, but not HA-TM Dl-3 plasmids, reversed the effects. Activation of ERK1/2 and JNK/SAPK, upstream regulators of cytoskeleton components, were also inhibited in overexpressed group. Immunoprecipitation assay demonstrated that actin interacts with TM and intersectin1 in THP-1. Decreased interaction between intersectin1 and actin in TM knockdowns suggested that the interaction is mediated by TM. Our findings indicate that TM domain 5 is a negative regulator and seems to have the ability to inhibit paxillin, cofilin, LIMK1, and actin activation. The mechanisms for the repression effect of domain 5 may be mediated by inhibition of the ERK1/2 and JNK/SAPK activation. Expression of domain 5 of TM may represent a promising approach for controlling monocyte migration, and TM may have potential applications in treatment of inflammatory diseases.

Thrombomodulin's lectin-like domain reduces myocardial damage by interfering with HMGB1-mediated TLR2 signalling

AIMS

Thrombomodulin (TM), via its lectin-like domain (LLD), exhibits anti-inflammatory properties partly by sequestering the pro-inflammatory cytokine, high-mobility group box 1 (HMGB1). Since myocardial damage after ischaemia and reperfusion is mediated by inflammation, we evaluated the cardioprotective effects of the LLD of TM. Using an in vivo mouse model of transient ischaemia and in vitro models of cardiomyocyte hypoxia, we assessed the ability of the LLD to suppress HMGB1-mediated activation of the receptors, receptor for advanced glycation endproducts (RAGEs) and Toll-like receptors (TLRs) 2 and 4.

METHODS AND RESULTS

Thirty-minute myocardial ischaemia was induced in isoflurane-anaesthetized mice followed by 24 h of reperfusion in wild-type (WT) mice, in mice lacking the LLD of TM (TM(LeD/LeD) mice), and in WT with systemic overexpression of the LLD of TM induced by hydrodynamic transfection. Infarct size, HMGB1 protein, and apoptotic cells were significantly increased in TM(LeD/LeD) mice when compared with WT. Neonatal rat cardiomyocytes transfected with TLR2-, TLR4-, and RAGE-siRNA were exposed to hypoxia (0.8% O2) and reoxygenation (21% O2). HMGB1 augmented hypoxia-induced apoptosis in TLR2- but not in RAGE- or TLR4-suppressed cells. Administration of HMGB1- and TLR2-blocking antibodies in TM(LeD/LeD) mice prior to myocardial ischaemia diminished apoptosis. Therapeutic systemic gene therapy using the LLD reduced the infarct size and HMGB1 protein levels 24 h after reperfusion.

CONCLUSION

The LLD of TM suppresses HMGB1-induced and TLR2-mediated myocardial reperfusion injury and apoptosis in vitro and in vivo.

Pathogenesis of disseminated intravascular coagulation in patients with acute promyelocytic leukemia, and its treatment using recombinant human soluble thrombomodulin

Acute promyelocytic leukemia (APL) is an uncommon subtype of acute myelogenous leukemia characterized by the proliferation of blasts with distinct morphology, a specific balanced reciprocal translocation t(15;17), and life-threatening hemorrhage caused mainly by enhanced fibrinolytic-type disseminated intravascular coagulation (DIC). The introduction of all-trans retinoic acid (ATRA) into anthracycline-based induction chemotherapy regimens has dramatically improved overall survival of individuals with APL, although hemorrhage-related death during the early phase of therapy remains a serious problem. Moreover, population-based studies have shown that the incidence of early death during induction chemotherapy is nearly 30 %, and the most common cause of death is associated with hemorrhage. Thus, development of a novel treatment strategy to alleviate abnormal coagulation in APL patients is urgently required. Recombinant human soluble thrombomodulin (rTM) comprises the active extracellular domain of TM, and has been used for treatment of DIC since 2008 in Japan. Use of rTM in combination with remission induction chemotherapy, including ATRA, produces potent resolution of DIC without exacerbation of bleeding tendency in individuals with APL. This review article discusses the pathogenesis and features of DIC caused by APL, as well as the possible anticoagulant and anti-leukemic action of rTM in APL patients.

Recombinant human soluble thrombomodulin is active against hemophagocytic lymphohistiocytosis associated with acquired immunodeficiency syndrome

A 39-year-old man was admitted to our hospital to initiate highly active anti-retroviral therapy (HAART) for documented acquired immune deficiency syndrome. The HIV load was 2.5 million copies/mL and the CD4-positive lymphocyte count was only 52 cells/µL at presentation. The HAART regimen consisted of lamivudine and abacavir as the backbone, plus raltegravir and lopinavir/ritonavir as the base. The day after initiating HAART, his body temperature rose to 102.4 °F (39.1 °C), accompanied by elevated levels of liver enzymes, neutropenia, coagulopathies, and an extremely high serum ferritin level, prompting us to suspect hemophagocytic lymphohistiocytosis (HLH) and disseminated intravascular coagulation (DIC). To correct the coagulation abnormalities, recombinant thrombomodulin (rTM) was initiated at 375 U/kg. Surprisingly, fever resolved almost immediately, in parallel with dramatic decreases in serum levels of ferritin and liver enzymes and prompt normalization of coagulopathy with only two doses of rTM. The patient subsequently developed amebiasis, which was successfully treated using metronidazole. In summary, the use of rTM dramatically improved not only DIC, but also HLH, suggesting potent anti-inflammatory effects of the agent. Although further clinical reports and trials are needed, rTM appears to provide an additional therapeutic option in the management of HLH.

Thrombomodulin Gene Polymorphism (C1418T) is Associated with the Development of Coronary Allograft Vasculopathy

Thrombomodulin (TM) is the endothelial cell membrane-bound anticoagulant protein cofactor in the thrombin-mediated activation of protein C. Previous evidence has been reported regarding the association between TM polymorphisms and coronary artery disease. Allograft rejection-mediated vasculopathy is the main cause of death at more than one year after heart transplantation. However, whether TM polymorphism is associated with allograft rejection is still unclear. We analyzed the TM gene polymorphism C1418T using allele-specific primers in a PCR assay in 60 patients who underwent heart transplantation. The retrospective clinical data were collected and tested for any correlations with the TM gene polymorphism. We separated the patients into 2 groups according to their TM genotype (group 1: CC genotype; group 2: CT or TT genotype). Additionally, we generated expression constructs (TM full length-C1418 and TM full length-T1418) and performed in vitro studies to explore the correlation between the TM C1418T polymorphism and the migration of smooth muscle progenitor cells and monocytes, which may be involved in the development of vasculopathy. The results showed that the levels of CD68, C4d, PAS, and Masson staining in the CT/TT genotype group increased at year 1 and continued to increase throughout the 3 years. These levels were higher than those observed in the CC genotype group. The ISHLT-WF2004 grade of the CT/TT genotype group was significantly different from that of the CC genotype group at the same time point post-transplantation. The coronary allograft vasculopathy (CAV) score was significantly different between the CC and CT/TT genotype groups at 1 and 3 years post-transplantation. Our in vitro studies demonstrate that both smooth muscle progenitor cells and monocytic THP-1 cells with either the CT-1418 or the TT-1418 TM genotype have higher migratory abilities than cells with the CC-1418 genotype. Our results support a significant association between the TM C1418T polymorphism and the development of CAV after heart transplantation in the short- to medium-term.

Differential gene expression in thrombomodulin (TM; CD141)(+) and TM(-) dendritic cell subsets

Previously we have shown in a mouse model of bronchial asthma that thrombomodulin can convert immunogenic conventional dendritic cells into tolerogenic dendritic cells while inducing its own expression on their cell surface. Thrombomodulin⁺ dendritic cells are tolerogenic while thrombomodulin⁻ dendritic cells are pro-inflammatory and immunogenic. Here we hypothesized that thrombomodulin treatment of dendritic cells would modulate inflammatory gene expression. Murine bone marrow-derived dendritic cells were treated with soluble thrombomodulin and expression of surface markers was determined. Treatment with thrombomodulin reduces the expression of maturation markers and increases the expression of TM on the DC surface. Thrombomodulin treated and control dendritic cells were sorted into thrombomodulin⁺ and thrombomodulin⁻ dendritic cells before their mRNA was analyzed by microarray. mRNAs encoding pro-inflammatory genes and dendritic cells maturation markers were reduced while expression of cell cycle genes were increased in thrombomodulin-treated and thrombomodulin⁺ dendritic cells compared to control dendritic cells and thrombomodulin⁻ dendritic cells. Thrombomodulin-treated and thrombomodulin⁺ dendritic cells had higher expression of 15-lipoxygenase suggesting increased synthesis of lipoxins. Thrombomodulin⁺ dendritic cells produced more lipoxins than thrombomodulin⁻ dendritic cells, as measured by ELISA, confirming that this pathway was upregulated. There was more phosphorylation of several cell cycle kinases in thrombomodulin⁺ dendritic cells while phosphorylation of kinases involved with pro-inflammatory cytokine signaling was reduced. Cultures of thrombomodulin⁺ dendritic cells contained more cells actively dividing than those of thrombomodulin⁻ dendritic cells. Production of IL-10 is increased in thrombomodulin⁺ dendritic cells. Antagonism of IL-10 with a neutralizing antibody inhibited the effects of thrombomodulin treatment of dendritic cells suggesting a mechanistic role for IL-10. The surface of thrombomodulin⁺ dendritic cells supported activation of protein C and procarboxypeptidase B2 in a thrombomodulin-dependent manner. Thus thrombomodulin treatment increases the number of thrombomodulin⁺ dendritic cells, which have significantly altered gene expression compared to thrombomodulin⁻ dendritic cells in key immune function pathways.

Recombinant thrombomodulin of different domains for pharmaceutical, biomedical, and cell transplantation applications

Thrombomodulin (TM) is a membrane glycoprotein mainly expressed by vascular endothelial cells and is involved in many physiological and pathological processes, such as coagulation, inflammation, cancer development, and embryogenesis. Human TM consists of 557 amino acids divided into five distinct domains: N-terminal lectin-like domain (designated as TMD1); six epidermal growth factor (EGF)-like domain (TMD2); Ser/Thr-rich domain (TMD3); transmembrane domain (TMD4); and cytoplasmic tail domain (TMD5). The different domains are responsible for different biological functions of TM. In the past decades, various domains of TM have been cloned and expressed for TM structural and functional study. Further, recombinant TMs of different domains show promising antithrombotic and anti-inflammatory activity in both rodents and primates and a recombinant soluble TM has been approved for therapeutic application. This review highlights recombinant TMs of diverse structures and their biological functions, as well as the complex interactions of TM with factors involved in the related biological processes. Particularly, recent advances in exploring recombinant TM of different domains for pharmaceutical, biomedical, and cell transplantation applications are summarized.

Critical role of non-muscle myosin light chain kinase in thrombin-induced endothelial cell inflammation and lung PMN infiltration

The pathogenesis of acute lung injury (ALI) involves bidirectional cooperation and close interaction between inflammatory and coagulation pathways. A key molecule linking coagulation and inflammation is the procoagulant thrombin, a serine protease whose concentration is elevated in plasma and lavage fluids of patients with ALI and acute respiratory distress syndrome (ARDS). However, little is known about the mechanism by which thrombin contributes to lung inflammatory response. In this study, we developed a new mouse model that permits investigation of lung inflammation associated with intravascular coagulation. Using this mouse model and in vitro approaches, we addressed the role of non-muscle myosin light chain kinase (nmMLCK) in thrombin-induced endothelial cell (EC) inflammation and lung neutrophil (PMN) infiltration. Our in vitro experiments revealed a key role of nmMLCK in ICAM-1 expression by its ability to control nuclear translocation and transcriptional capacity of RelA/p65 in EC. When subjected to intraperitoneal thrombin challenge, wild type mice showed a marked increase in lung PMN infiltration via expression of ICAM-1. However, these responses were markedly attenuated in mice deficient in nmMLCK. These results provide mechanistic insight into lung inflammatory response associated with intravascular coagulation and identify nmMLCK as a critical target for modulation of lung inflammation.

A novel strategy for hemolytic uremic syndrome: successful treatment with thrombomodulin α

Hemolytic uremic syndrome (HUS) is a life-threatening infectious disease in childhood for which there is no confirmed therapeutic strategy. Endothelial inflammation leading to microthrombosis formation via complement activation is the main pathology of HUS. Thrombomodulin is an endothelial membrane protein that has anticoagulation and anti-inflammatory effects, including the suppression of complement activity. Recombinant human soluble thrombomodulin (rTM) is a novel therapeutic medicine for disseminated intravascular coagulation. We administered rTM to 3 patients with HUS for 7 days and investigated the outcomes in view of the patients' prognoses, changes in biochemical markers, complications, and adverse effects of rTM. Symptoms and laboratory data improved after initiation of rTM in all 3 patients. Abnormal activation of complements was also dramatically suppressed in 1 patient. The patients recovered without any complications or adverse effects of rTM. They were discharged having normal neurologic status and with no renal dysfunction. To our knowledge, this is the first report of rTM being used to treat HUS. These case reports show the positive effect of rTM in patients with HUS. Randomized controlled studies should be performed to assess the efficacy and safety of rTM for children with HUS.

Effects of a thrombomodulin-derived peptide on monocyte adhesion and intercellular adhesion molecule-1 expression in lipopolysaccharide-induced endothelial cells

PURPOSE

It has been documented that GC31, a 31-animo acid peptide from human thrombomodulin, has potent anti-inflammatory properties in endotoxin-induced uveitis and lipopolysaccharide (LPS)-induced RAW264.7 cells, while the role of GC31 in the endothelial cells has not yet been fully understood. Therefore, the aim of this study was to explore the effect of GC31 on intercellular adhesion molecule-1 (ICAM-1) expression in LPS-activated endothelial cells.

METHODS

Human umbilical vein endothelial cells (HUVECs) were incubated with LPS (1 μg/ml) and peptide GC31 or control peptide VP30 simultaneously. ICAM-1 messenger RNA and protein levels were evaluated with real-time PCR and western blot. The adhesion of U937 cells labeled with CM-H2DCFDA to HUVECs was examined with fluorescence microscope. Extracellular signal-regulated kinase-1/2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK) activation, inhibitor of nuclear factor kappa B alpha (IκBα) degradation, and nuclear factor kappa B (NF-κB) nuclear translocation were detected with western blot.

RESULTS

Upon LPS stimulation, GC31 suppressed the mRNA and protein expression of ICAM-1 in HUVECs and remarkably reduced monocyte-endothelial cell adhesion in a dose-dependent manner. Furthermore, GC31 significantly inhibited the degradation of IκBα and nuclear translocation of NF-κB and moderately blocked the activation of p38 MAPK and ERK1/2 in activated HUVECs.

CONCLUSIONS

Our results suggested that GC31 suppressed LPS-mediated ICAM-1 expression by inhibiting the activation of NF-κB and partially by attenuating the activity of ERK1/2 and p38 MAPK in vascular endothelium, which may contribute to ameliorating vascular inflammatory diseases, such as uveitis.

The endothelial protein C receptor and activated protein C play a limited role in host defense during experimental tuberculosis

The protein C (PC) system is an important regulator of both coagulation and inflammation. Activated PC (APC), together with its receptor the endothelial protein C receptor (EPCR), has anticoagulant and anti-inflammatory properties. During tuberculosis (TB), a devastating chronic pulmonary disease caused by Mycobacterium (M.) tuberculosis, both a local inflammatory reaction characterised by the recruitment of mainly mononuclear cells and the formation of pulmonary granulomas as well as activation of coagulation occurs as part of the host immune response. We investigated the role of EPCR and APC in a mouse model of TBusing mice overexpressing EPCR (Tie2-EPCR), mice deficient for EPCR (EPCR-/-), mice treated with APC-inhibiting antibodies and mice overexpressing APC (APChigh) and compared them with wild-type (WT) mice. Blood and organs were harvested to quantify bacterial loads, cellular influxes, cytokines, histopathology and coagulation parameters. Additionally observation studies were performed. Lung EPCR expression was upregulated during experimental TB. No significant differences in bacterial growth were seen between WT and Tie2-EPCR mice. However, Tie2-EPCR mice had decreased pulmonary coagulation activation, displayed an increased influx of macrophages 2 and 6 weeks after infection, but no increase in other proinflammatory markers. On the other hand, in EPCR-/--mice coagulation activation was decreased 6 weeks post-infection, with little impact on other inflammation markers. APC-overexpression or treatment with anti-(A)PC antibodies displayed minimal effects during experimental TB. In conclusion, EPCR and APC play a limited role in the host response during experimental pulmonary TB.

Thrombomodulin regulates keratinocyte differentiation and promotes wound healing

The membrane glycoprotein thrombomodulin (TM) has been implicated in keratinocyte differentiation and wound healing, but its specific function remains undetermined. The epidermis-specific TM knockout mice were generated to investigate the function of TM in these biological processes. Primary cultured keratinocytes obtained from TM(lox/lox); K5-Cre mice, in which TM expression was abrogated, underwent abnormal differentiation in response to calcium induction. Poor epidermal differentiation, as evidenced by downregulation of the terminal differentiation markers loricrin and filaggrin, was observed in TM(lox/lox); K5-Cre mice. Silencing TM expression in human epithelial cells impaired calcium-induced extracellular signal-regulated kinase pathway activation and subsequent keratinocyte differentiation. Compared with wild-type mice, the cell spreading area and wound closure rate were lower in keratinocytes from TM(lox/lox); K5-Cre mice. In addition, the lower density of neovascularization and smaller area of hyperproliferative epithelium contributed to slower wound healing in TM(lox/lox); K5-Cre mice than in wild-type mice. Local administration of recombinant TM (rTM) accelerated healing rates in the TM-null skin. These data suggest that TM has a critical role in skin differentiation and wound healing. Furthermore, rTM may hold therapeutic potential for the treatment of nonhealing chronic wounds.

Association of thrombomodulin Ala455Val dimorphism and inflammatory cytokines with carotid atherosclerosis in the Chinese Han population

Background and methods

It has been reported that C/T dimorphism at position 1418 of the thrombomodulin gene causes a cytosine (C) transition to thymidine (T), resulting in an alanine (A) to valine (V) substitution at amino acid position 455 (TM455). TM455 had been found not only in African American and American whites, but also in whites in The Netherlands and Sweden. Among these populations, the C/C genotype is predominant, although the distribution of this dimorphism is different. Thrombomodulin is an important anticoagulant protein that is downregulated in endothelial cells overlying atherosclerotic plaques and is also an anti-inflammatory molecule. TM455 is located in the last epidermal growth factor-like repeat of thrombomodulin, which is functionally important for protein C activation and thrombin binding. The distribution of thrombomodulin polymorphism and association between TM455, inflammatory cytokines, and carotid atherosclerosis in the Chinese Han population is unclear.

Methods

This thrombomodulin dimorphism was analyzed by allele-specific amplification in 144 patients with carotid atherosclerosis and in 384 healthy controls. TM455 was found in the Chinese Han population, but the genotype frequency and distribution of each genotype in this population differed substantially from that in other ethnic subgroups. The C/T and T/T genotypes were predominant in the Chinese Han population, and the frequency of the T allele in this population (63.8%) was much higher than that in whites in The Netherlands (18%), Sweden (26.1%), and the US (18.4%), and in blacks in the US (7.6%). The frequencies of these single nucleotide polymorphisms complied well with the Hardy-Weinberg equilibrium in healthy individuals. The C allele was significantly more common among patients with carotid atherosclerosis than in controls (P < 0.05). The frequency of the C allele was 45.5% in patients and 36.2% in controls. The thrombomodulin Ala455 genotypes C/C and C/T were significantly more common than the T/T genotype in patients with carotid atherosclerosis in the Chinese Han population. In addition, higher baseline levels of tumor necrosis factor alpha (55.45 ± 11.58 pg/mL versus 52.70 ± 10.74 pg/mL; P < 0.05), interleukin-6 (31.53 ± 10.51 pg/mL versus 27.73 ± 8.37 pg/mL; P < 0.01), and C-reactive protein (6.65 ± 2.01 mg/L versus 4.06 ± 1.03 mg/L; P < 0.01) were observed in patients with carotid atherosclerosis than in controls. Interestingly, compared with baseline inflammatory cytokine levels in those with the Val/Val genotype, higher baseline tumor necrosis factor alpha, interleukin-6, and C-reactive protein levels were observed for the Ala/Ala genotype in both patients with carotid atherosclerosis and healthy controls.

Conclusion

Our results support a significant association between thrombomodulin Ala455Val dimorphism, inflammatory cytokines, and carotid atherosclerosis in the Chinese Han population.

Soluble thrombomodulin levels in plasma of multiple sclerosis patients and their implication

Thrombomodulin (TM) on the cell-surface of cerebrovascular endothelial cells (CECs) is released into blood upon CEC damage. TM promotes activation of protein C (APC), an anticoagulant, anti-inflammatory, neuroprotective molecule that protects CECs and impedes inflammatory cell migration across the blood-brain barrier (BBB). Multiple sclerosis (MS) is associated with CEC damage and BBB dysfunction. We evaluated soluble TM (sTM) levels as a biomarker of BBB integrity and whether glatiramer acetate (GA) influenced sTM levels in MS patients. sTM levels quantified by 2-site ELISA from sera of healthy controls and systemic lupus erythematosus (SLE) patients (CEC-damage positive control) were compared with levels from patients with relapsing-remitting (RRMS) or secondary-progressive MS (SPMS), stratified as: RRMS/GA/no relapse, RRMS/GA/in relapse, RRMS no GA/no relapse, RRMS/no GA/in relapse; and SPMS/no GA. Additionally, soluble endothelial protein C receptor (sEPCR) levels were assessed in the non-stratified MS group, SLE patients, and controls. sTM levels were highest in RRMS patients taking GA with or without relapse, followed in decreasing order by SLE, RRMS/no GA/in relapse, SPMS, RRMS/no GA/no relapse, healthy controls. sEPCR levels were highest in MS patients, then SLE, then controls. sTM may be a useful biomarker of BBB integrity in RRMS patients. Further evaluation of sEPCR is needed. The finding that the highest sTM levels were in RRMS patients taking GA is interesting and warrants further investigation.

Lack of the lectin-like domain of thrombomodulin worsens Shiga toxin-associated hemolytic uremic syndrome in mice

Shiga toxin (Stx)-producing Escherichia coli is a primary cause of diarrhea-associated hemolytic uremic syndrome (HUS), a disorder of thrombocytopenia, microangiopathic hemolytic anemia, and acute renal failure. The pathophysiology of renal microvascular thrombosis in Stx-HUS is still ill-defined. Based on evidence that abnormalities in thrombomodulin (TM), an anticoagulant endothelial glycoprotein that modulates complement and inflammation, predispose to atypical HUS, we assessed whether impaired TM function may adversely affect evolution of Stx-HUS. Disease was induced by coinjection of Stx2/LPS in wild-type mice (TM(wt/wt)) and mice that lack the lectin-like domain of TM (TM(LeD/LeD)), which is critical for its anti-inflammatory and cytoprotective properties. After Stx2/LPS, TM(LeD/LeD) mice exhibited more severe thrombocytopenia and renal dysfunction than TM(wt/wt) mice. Lack of lectin-like domain of TM resulted in a stronger inflammatory reaction after Stx2/LPS with more neutrophils and monocytes/macrophages infiltrating the kidney, associated with PECAM-1 and chemokine upregulation. After Stx2/LPS, intraglomerular fibrin(ogen) deposits were detected earlier in TM(LeD/LeD) than in TM(wt/wt) mice. More abundant fibrin(ogen) deposits were also found in brain and lungs. Under basal conditions, TM(LeD/LeD) mice exhibited excess glomerular C3 deposits, indicating impaired complement regulation in the kidney that could lead to local accumulation of proinflammatory products. TM(LeD/LeD) mice with HUS had a higher mortality rate than TM(wt/wt) mice. If applicable to humans, these findings raise the possibility that genetic or acquired TM defects might have an impact on the severity of microangiopathic lesions after exposure to Stx-producing E. coli infections and raise the potential for using soluble TM in the treatment of Stx-HUS.

CD248 expression on mesenchymal stromal cells is required for post-natal and infection-dependent thymus remodelling and regeneration

The role of mesenchymal stromal cells (MSCs) in regulating immune responses in the thymus is currently unclear. Here we report the existence and role of a MSC population in the thymus that expresses the pericyte and MSC marker CD248 (endosialin). We show using a CD248-deficient mouse model, that CD248 expression on these cells is required for full post-natal thymus development and regeneration post-Salmonella infection. In CD248^−/− mice the thymus is hypocellular and regeneration is poorer, with significant loss of all thymocyte populations. This identifies the requirement of CD248 to maintain optimal thymic cellularity post-partum and infection.

Thrombomodulin as a regulator of the anticoagulant pathway: implication in the development of thrombosis

Thrombomodulin is a cell surface-expressed glycoprotein that serves as a cofactor for thrombin-mediated activation of protein C (PC), an event further amplified by the endothelial cell PC receptor. The PC pathway is a major anticoagulant mechanism that downregulates thrombin formation and hedges thrombus formation. The objectives of this review were to review recent findings regarding thrombomodulin structure, its involvement in the regulation of hemostasis and further discuss the implication, if any, of the genetic polymorphisms in the thrombomodulin gene in the risk of development of thrombosis. We performed a literature search by using electronic bibliographic databases. Although the direct evaluation of risk situations associated with thrombomodulin mutations/polymorphisms could be of clinical significance, it appears that mutations that affect the function of thrombomodulin are rarely associated with venous thromboembolism. However, several polymorphisms are reported to be associated with increased risk for arterial thrombosis. Additionally studies on knock out mice as well studies on humans bearing rare mutations suggest that thrombomodulin dysfunction may be implicated in the pathogenesis of myocardial infraction.

Thrombomodulin protects endothelial cells from a calcineurin inhibitor-induced cytotoxicity by upregulation of extracellular signal-regulated kinase/myeloid leukemia cell-1 signaling

OBJECTIVE

We have recently reported that recombinant human soluble thrombomodulin (rTM) counteracted capillary leakage associated with engraftment, as well as sinusoidal obstructive syndrome after hematopoietic stem cell transplantation. These observations prompted us to explore whether rTM possessed cytoprotective effects on endothelial cells.

METHODS AND RESULTS

Exposure of human umbilical vein endothelial cells to rTM induced expression of antiapoptotic protein myeloid leukemia cell-1 through the activation of extracellular signal-regulated kinase in these cells. Additional studies found that exposure of human umbilical vein endothelial cells to cyclosporine A and FK506, an immunosuppressant used for the individuals receiving hematopoietic stem cell transplantation, induced apoptosis, which was attenuated when human umbilical vein endothelial cells were exposed to these agents in the presence of rTM. Further studies using deletion mutants of thrombomodulin (TM) identified that the epidermal growth factor domain of TM possessed cytoprotective effects. A single nucleotide substitution at codon 376 or 424 of TM, which impairs the ability of TM to produce activated protein C or bind to thrombin, respectively, did not hamper the cytoprotective effects of TM, which suggested that cytoprotective effects of rTM were distinctive from those of activated protein C.

CONCLUSIONS

TM may be useful for prevention, as well as treatment of endothelial cell damage after hematopoietic stem cell transplantation.

Pathogenic and Diagnostic Potential of BLCA-1 and BLCA-4 Nuclear Proteins in Urothelial Cell Carcinoma of Human Bladder

Transitional cell carcinoma (TCC) of the bladder is one of the most common malignancies of genitourinary tract. Patients with bladder cancer need a life-long surveillance, directly due to the relatively high recurrence rate of this tumor. The use of cystoscopy represents the gold standard for the followup of previously treated patients. Nevertheless, several factors, including cost and invasiveness, render cystoscopy not ideal for routine controls. Advances in the identification of specific alterations in the nuclear structure of bladder cancer cells have opened novel diagnostic landscapes. The members of nuclear matrix protein family BLCA-1 and BLCA-4, are currently under evaluation as bladder cancer urinary markers. They are involved in tumour cell proliferation, survival, and angiogenesis. In this paper, we illustrate the role of BLCA-1 and BLCA-4 in bladder carcinogenesis and their potential exploitation as biomarkers in this cancer.

Therapeutic modulation of coagulation and fibrinolysis in acute lung injury and the acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) and acute lung injury (ALI) are characterized by excessive intraalveolar fibrin deposition, driven, at least in part by inflammation. The imbalance between activation of coagulation and inhibition of fibrinolysis in patients with ALI/ARDS favors fibrin formation and appears to occur both systemically and in the lung and airspace. Tissue factor (TF), a key mediator of the activation of coagulation in the lung, has been implicated in the pathogenesis of ALI/ARDS. As such, there have been numerous investigations modulating TF activity in a variety of experimental systems in order to develop new therapeutic strategies for ALI/ARDS. This review will summarize current understanding of the role of TF and other proteins of the coagulation cascade as well the fibrinolysis pathway in the development of ALI/ARDS with an emphasis on the pathways that are potential therapeutic targets. These include the TF inhibitor pathway, the protein C pathway, antithrombin, heparin, and modulation of fibrinolysis through plasminogen activator- 1 (PAI-1) or plasminogen activators (PA). Although experimental studies show promising results, clinical trials to date have proven unsuccessful in improving patient outcomes. Modulation of coagulation and fibrinolysis has complex effects on both hemostasis and inflammatory pathways and further studies are needed to develop new treatment strategies for patients with ALI/ARDS.

Monocytic thrombomodulin triggers LPS- and gram-negative bacteria-induced inflammatory response

Sepsis results from the host hyperinflammatory response to bacterial infection, causing multiple organ failure and high mortality. We previously demonstrated that LPS binds to monocytic membrane-bound thrombomodulin (TM), but the role of monocytic TM in LPS-induced inflammation remains unknown. In this study, we demonstrated that TM knockdown in human monocytic cells attenuated LPS-induced signaling pathways and cytokine production. Coimmunoprecipitation and immunofluorescence assays showed that monocytic TM interacted with the LPS receptors, CD14 and TLR4/myeloid differentiation factor-2 (MD-2) complex, indicating that it binds to LPS and triggers an LPS-induced inflammatory response by interacting with the CD14/TLR4/MD-2 complex. We also found that monocytic TM knockdown reduced cytokine production induced by gram-negative bacteria Klebsiella pneumoniae, suggesting that monocytic TM plays an important role in gram-negative bacteria-induced inflammation. To further investigate the function of monocytic TM in vivo, myeloid-specific TM-deficient mice were established and were found to display improved survival that resulted from the attenuation of septic syndrome, including reduced systemic inflammatory response and resistance to bacterial dissemination, after K. pneumoniae infection or cecal ligation and puncture surgery. The inhibition of bacterial dissemination in mice with a deficiency of myeloid TM may be caused by the early increase in neutrophil infiltration. Therefore, we conclude that monocytic TM is a novel component in the CD14/TLR4/MD-2 complex and participates in the LPS- and gram-negative bacteria-induced inflammatory response.

The role of thrombomodulin lectin-like domain in inflammation

Thrombomodulin (TM) is a cell surface glycoprotein which is widely expressed in a variety of cell types. It is a cofactor for thrombin binding that mediates protein C activation and inhibits thrombin activity. In addition to its anticoagulant activity, recent evidence has revealed that TM, especially its lectin-like domain, has potent anti-inflammatory function through a variety of molecular mechanisms. The lectin-like domain of TM plays an important role in suppressing inflammation independent of the TM anticoagulant activity. This article makes an extensive review of the role of TM in inflammation. The molecular targets of TM lectin-like domain have also been elucidated. Recombinant TM protein, especially the TM lectin-like domain may play a promising role in the management of sepsis, glomerulonephritis and arthritis. These data demonstrated the potential therapeutic role of TM in the treatment of inflammatory diseases.

Heme oxygenase-1 modulates thrombomodulin and activated protein C levels to attenuate lung injury in cecal ligation and puncture-induced acute lung injury mice

Acute lung injury (ALI) is often associated with sepsis and is the most common cause of acute respiratory failure. The authors evaluated the role of the heme oxygenase (HO)/carbon monoxide (CO) system on lung injury in a cecal ligation and puncture (CLP)-induced mouse model of ALI. The authors established CLP-induced ALI in C57BL/6 mice. They pretreated CLP-induced mice with HO-1 inducer (hemin) or HO-1 inhibitor (Zn protoporphyrin [Znpp]) and determined various lung injury parameters including partial pressure of arterial oxygen, thrombosis, edema, and plasma malondialdehyde (MDA), and myeloperoxidase (MPO) level. Enzyme-linked immunosorbent assay (ELISA) was performed to measure plasma thrombomodulin (TM) and activated protein C (APC) levels. TM and HO-1 expression in lung tissue was evaluated by immunofluorescence staining and Western blotting. Survival rate was also monitored. CLP-induced ALI was associated with decreased partial pressure of arterial oxygen, and increased thrombosis, edema, and plasma MDA, and MPO level. Plasma TM was significantly up-regulated, whereas cell surface TM in lung tissue was significantly decreased in the CLP group compared to the sham animals. Pretreatment with hemin caused up-regulation of HO-1 expression and improved partial pressure of arterial oxygen. Hemin pretreatment also caused a significant decrease in plasma TM along with increased cell surface TM expression in lung tissue, suggesting attenuation of lung injury. Survival data showed that no difference for survival between CLP animals pretreated with hemin or Znpp. Taken together, HO-1 exerts its protective effects on CLP-induced ALI via regulating cell surface TM and APC expression and modulating blood coagulation.

Sirt1 protects against thrombomodulin down-regulation and lung coagulation after particulate matter exposure

Exposure to ambient particulate matter (PM) air pollution has been reported to trigger inflammation and thrombosis. However, molecular mechanisms underlying the modulation of coagulation pathways in PM-induced thrombosis remain largely unknown. We report here that Sirt1, a member of class III histone deacetylase, controls lung inflammation and coagulation after PM exposure. Sirt1 knock-out mice exhibited aggravated lung vascular leakage and inflammation after PM exposure, which was correlated with increased NF-κB acetylation and activation. Furthermore, Sirt1 knock-out mice were highly susceptible to PM-induced lung coagulation as demonstrated by increased fibrin formation. The increased fibrin formation was associated with reduced tissue factor pathway inhibitor (TFPI) expression and increased plasminogen activator inhibitor-1 (PAI-1) activity in the lungs, thus favoring elevated coagulation and disrupted fibrinolysis responses. Thrombomodulin (TM), a central player of the anticoagulant protein C system, is regulated by Kruppel-like factor 2 (KLF2) at the transcriptional level. Our data show that PM exposure led to decreased lung KLF2 and TM expression in wild-type mice, and lung KLF2 and TM protein levels were further decreased in Sirt1 knock-out mice. Importantly, Sirt1 gene delivery inhibited TM and KLF2 down-regulation and reduced lung coagulation after PM exposure. Collectively, our studies indicate that Sirt1 functions as a suppressor of coagulation after particulate matter exposure.

NEU1 and NEU3 sialidase activity expressed in human lung microvascular endothelia: NEU1 restrains endothelial cell migration, whereas NEU3 does not

The microvascular endothelial surface expresses multiple molecules whose sialylation state regulates multiple aspects of endothelial function. To better regulate these sialoproteins, we asked whether endothelial cells (ECs) might express one or more catalytically active sialidases. Human lung microvascular EC lysates contained heat-labile sialidase activity for a fluorogenic substrate, 2'-(4-methylumbelliferyl)-α-D-N-acetylneuraminic acid (4-MU-NANA), that was dose-dependently inhibited by the competitive sialidase inhibitor, 2,3-dehydro-2-deoxy-N-acetylneuraminic acid but not its negative control. The EC lysates also contained sialidase activity for a ganglioside mixture. Using real time RT-PCR to detect mRNAs for the four known mammalian sialidases, NEU1, -2, -3, and -4, NEU1 mRNA was expressed at levels 2700-fold higher that those found for NEU2, -3, or -4. Western analyses indicated NEU1 and -3 protein expression. Using confocal microscopy and flow cytometry, NEU1 was immunolocalized to both the plasma membrane and the perinuclear region. NEU3 was detected both in the cytosol and nucleus. Prior siRNA-mediated knockdown of NEU1 and NEU3 each decreased EC sialidase activity for 4-MU-NANA by >65 and >17%, respectively, and for the ganglioside mixture by 0 and 40%, respectively. NEU1 overexpression in ECs reduced their migration into a wound by >40%, whereas NEU3 overexpression did not. Immunohistochemical studies of normal human tissues immunolocalized NEU1 and NEU3 proteins to both pulmonary and extrapulmonary vascular endothelia. These combined data indicate that human lung microvascular ECs as well as other endothelia express catalytically active NEU1 and NEU3. NEU1 restrains EC migration, whereas NEU3 does not.

Thrombomodulin: a bifunctional modulator of inflammation and coagulation in sepsis

Deregulated interplay between inflammation and coagulation plays a pivotal role in the pathogenesis of sepsis. Therapeutic approaches that simultaneously target both inflammation and coagulation hold great promise for the treatment of sepsis. Thrombomodulin is an endogenous anticoagulant protein that, in cooperation with protein C and thrombin-activatable fibrinolysis inhibitor, serves to maintain the endothelial microenvironment in an anti-inflammatory and anticoagulant state. A recombinant soluble form of thrombomodulin has been approved to treat patients suffering from disseminated intravascular coagulation (DIC) and has thus far shown greater therapeutic potential than heparin. A phase II clinical trial is currently underway in the USA to study the efficacy of thrombomodulin for the treatment of sepsis with DIC complications. This paper focuses on the critical roles that thrombomodulin plays at the intersection of inflammation and coagulation and proposes the possible existence of interactions with integrins via protein C. Finally, we provide a rationale for the clinical application of thrombomodulin for alleviating sepsis.

Thrombomodulin and its role in inflammation

The goal is to provide an extensive review of the physiologic role of thrombomodulin (TM) in maintaining vascular homeostasis, with a focus on its anti-inflammatory properties. Data were collected from published research. TM is a transmembrane glycoprotein expressed on the surface of all vascular endothelial cells. Expression of TM is tightly regulated to maintain homeostasis and to ensure a rapid and localized hemostatic and inflammatory response to injury. By virtue of its strategic location, its multidomain structure and complex interactions with thrombin, protein C (PC), thrombin activatable fibrinolysis inhibitor (TAFI), complement components, the Lewis Y antigen, and the cytokine HMGB1, TM exhibits a range of physiologically important anti-inflammatory, anti-coagulant, and anti-fibrinolytic properties. TM is an essential cofactor that impacts on multiple biologic processes. Alterations in expression of TM and its partner proteins may be manifest by inflammatory and thrombotic disorders. Administration of soluble forms of TM holds promise as effective therapies for inflammatory diseases, and infections and malignancies that are complicated by disseminated intravascular coagulation.

Soluble thrombomodulin reduces inflammation and prevents microalbuminuria induced by chronic endothelial activation in transgenic mice

Chronic kidney disease pathogenesis involves both tubular and vascular injuries. Despite abundant investigations to identify the risk factors, the involvement of chronic endothelial dysfunction in developing nephropathies is insufficiently explored. Previously, soluble thrombomodulin (sTM), a cofactor in the activation of protein C, has been shown to protect endothelial function in models of acute kidney injury. In this study, the role for sTM in treating chronic kidney disease was explored by employing a mouse model of chronic vascular activation using endothelial-specific TNF-α-expressing (tie2-TNF) mice. Analysis of kidneys from these mice after 3 mo showed no apparent phenotype, whereas 6-mo-old mice demonstrated infiltration of CD45-positive leukocytes accompanied by upregulated gene expression of inflammatory chemokines, markers of kidney injury, and albuminuria. Intervention with murine sTM with biweekly subcutaneous injections during this window of disease development between months 3 and 6 prevented the development of kidney pathology. To better understand the mechanisms of these findings, we determined whether sTM could also prevent chronic endothelial cell activation in vitro. Indeed, treatment with sTM normalized increased chemokines, adhesion molecule expression, and reduced transmigration of monocytes in continuously activated TNF-expressing endothelial cells. Our results suggest that vascular inflammation associated with vulnerable endothelium can contribute to loss in renal function as suggested by the tie2-TNF mice, a unique model for studying the role of vascular activation and inflammation in chronic kidney disease. Furthermore, the ability to restore the endothelial balance by exogenous administration of sTM via downregulation of specific adhesion molecules and chemokines suggests a potential for therapeutic intervention in kidney disease associated with chronic inflammation.

The recombinant lectin-like domain of thrombomodulin inhibits angiogenesis through interaction with Lewis Y antigen

Lewis Y Ag (LeY) is a cell-surface tetrasaccharide that participates in angiogenesis. Recently, we demonstrated that LeY is a specific ligand of the recombinant lectin-like domain of thrombomodulin (TM). However, the biologic function of interaction between LeY and TM in endothelial cells has never been investigated. Therefore, the role of LeY in tube formation and the role of the recombinant lectin-like domain of TM-TM domain 1 (rTMD1)-in antiangiogenesis were investigated. The recombinant TM ectodomain exhibited lower angiogenic activity than did the recombinant TM domains 2 and 3. rTMD1 interacted with soluble LeY and membrane-bound LeY and inhibited soluble LeY-mediated chemotaxis of endothelial cells. LeY was highly expressed on membrane ruffles and protrusions during tube formation on Matrigel. Blockade of LeY with rTMD1 or Ab against LeY inhibited endothelial tube formation in vitro. Epidermal growth factor (EGF) receptor in HUVECs was LeY modified. rTMD1 inhibited EGF receptor signaling, chemotaxis, and tube formation in vitro, and EGF-mediated angiogenesis and tumor angiogenesis in vivo. We concluded that LeY is involved in vascular endothelial tube formation and rTMD1 inhibits angiogenesis via interaction with LeY. Administration of rTMD1 or recombinant adeno-associated virus vector carrying TMD1 could be a promising antiangiogenesis strategy.

Solulin reduces infarct volume and regulates gene-expression in transient middle cerebral artery occlusion in rats

Background

Thrombolysis after acute ischemic stroke has only proven to be beneficial in a subset of patients. The soluble recombinant analogue of human thrombomodulin, Solulin, was studied in an in vivo rat model of acute ischemic stroke.

Methods

Male SD rats were subjected to 2 hrs of transient middle cerebral artery occlusion (tMCAO). Rats treated with Solulin intravenously shortly before reperfusion were compared to rats receiving normal saline i.v. with respect to infarct volumes, neurological deficits and mortality. Gene expression of IL-6, IL-1β, TNF-α, MMP-9, CD11B and GFAP were semiquantitatively analyzed by rtPCR of the penumbra.

Results

24 hrs after reperfusion, rats were neurologically tested, euthanized and infarct volumes determined. Solulin significantly reduced mean total (p = 0.001), cortical (p = 0.002), and basal ganglia (p = 0.036) infarct volumes. Hippocampal infarct volumes (p = 0.191) were not significantly affected. Solulin significantly downregulated the expression of IL-1β (79%; p < 0.001), TNF-α (59%; p = 0.001), IL-6 (47%; p = 0.04), and CD11B (49%; p = 0.001) in the infarcted cortex compared to controls.

Conclusions

Solulin reduced mean total, cortical and basal ganglia infarct volumes and regulated a subset of cytokines and proteases after tMCAO suggesting the potency of this compound for therapeutic interventions.

Human thrombomodulin knock-in mice reveal differential effects of human thrombomodulin on thrombosis and atherosclerosis

OBJECTIVE

We sought to develop a murine model to examine the antithrombotic and antiinflammatory functions of human thrombomodulin in vivo.

METHODS AND RESULTS

Knock-in mice that express human thrombomodulin from the murine thrombomodulin gene locus were generated. Compared with wild-type mice, human thrombomodulin knock-in mice exhibited decreased protein C activation in the aorta (P<0.01) and lung (P<0.001). Activation of endogenous protein C following infusion of thrombin was decreased by 90% in knock-in mice compared with wild-type mice (P<0.05). Carotid artery thrombosis induced by photochemical injury occurred more rapidly in knock-in mice (12±3 minutes) than in wild-type mice (31±6 minutes; P<0.05). No differences in serum cytokine levels were detected between knock-in and wild-type mice after injection of endotoxin. When crossed with apolipoprotein E-deficient mice and fed a Western diet, knock-in mice had a further decrease in protein C activation but did not exhibit increased atherosclerosis.

CONCLUSION

Expression of human thrombomodulin in place of murine thrombomodulin produces viable mice with a prothrombotic phenotype but unaltered responses to systemic inflammatory or atherogenic stimuli. This humanized animal model will be useful for investigating the function of human thrombomodulin under pathophysiological conditions in vivo.