Novel functions of thrombomodulin in inflammation

Thrombomodulin: a multifunctional receptor modulating the endothelial quiescence

Thrombomodulin (TM) is a type 1 receptor best known for its function as an anticoagulant cofactor for thrombin activation of protein C on the surface of vascular endothelial cells. In addition to its anticoagulant cofactor function, TM also regulates fibrinolysis, complement, and inflammatory pathways. TM is a multidomain receptor protein with a lectin-like domain at its N-terminus that has been shown to exhibit direct anti-inflammatory functions. This domain is followed by 6 epidermal growth factor-like domains that support the interaction of TM with thrombin. The interaction inhibits the procoagulant function of thrombin and enables the protease to regulate the anticoagulant and fibrinolytic pathways by activating protein C and thrombin-activatable fibrinolysis inhibitor. TM has a Thr/Ser-rich region immediately above the membrane surface that harbors chondroitin sulfate glycosaminoglycans, and this region is followed by a single-spanning transmembrane and a C-terminal cytoplasmic domain. The structure and physiological function of the extracellular domains of TM have been extensively studied, and numerous excellent review articles have been published. However, the physiological function of the cytoplasmic domain of TM has remained poorly understood. Recent data from our laboratory suggest that intracellular signaling by the cytoplasmic domain of TM plays key roles in maintaining quiescence by modulating phosphatase and tensin homolog signaling in endothelial cells. This article briefly reviews the structure and function of extracellular domains of TM and focuses on the mechanism and possible physiological importance of the cytoplasmic domain of TM in modulating phosphatase and tensin homolog signaling in endothelial cells.

Mechanisms regulating heterogeneity of hemostatic gene expression in endothelial cells

The hemostatic system involves an array of circulating coagulation factors that work in concert with platelets and the vascular endothelium to promote clotting in a space- and time-defined manner. Despite equal systemic exposure to circulating factors, bleeding and thrombotic diseases tend to prefer specific sites, suggesting an important role for local factors. This may be provided by endothelial heterogeneity. Endothelial cells differ not only between arteries, veins, and capillaries but also between microvascular beds from different organs, which present unique organotypic morphology and functional and molecular profiles. Accordingly, regulators of hemostasis are not uniformly distributed in the vasculature. The establishment and maintenance of endothelial diversity are orchestrated at the transcriptional level. Recent transcriptomic and epigenomic studies have provided a global picture of endothelial cell heterogeneity. In this review, we discuss the organotypic differences in the hemostatic profile of endothelial cells; we focus on 2 major endothelial regulators of hemostasis, namely von Willebrand factor and thrombomodulin, to provide examples of transcriptional mechanisms that control heterogeneity; finally, we consider some of the methodological challenges and opportunities for future studies.

Genome-wide identification of endosialin family of C-type lectins in common carp (Cyprinus carpio) and their response following Aeromonas hydrophila infection

The endosialin family is the group XIV of C-type lectin, regulating several processes involved in innate immunity and inflammation. Endosialin family genes have been extensively studied in human and mammals, however, rarely reported in teleost. In the present study, a set of 8 endosialin family genes was identified across the entire common carp genome. Functional domain and motif prediction and phylogenetic analysis supported their annotation and orthologies. Through examining gene copy number across several vertebrates, endosialin family genes were found have undergone gene duplication. Most of the endosialin family genes were ubiquitously expressed during common carp early developmental stages, and presented tissue-specific expression patterns in various healthy tissues, with relatively high expression in intestine, liver, gill, spleen and kidney, indicating their likely essential roles in maintaining homeostasis and host immune response. After Aeromonas hydrophila infection, gene thbd-1, thbd-2 and cd93-2 were significantly up-regulated at one or more timepoints in spleen and kidney, while gene cd248a-1, cd248a-2, cd248b-1, cd248b-2, and cd93-1 were significantly down-regulated. Taken together, all these results suggested that endosialin family genes were involved in host immune response to A. hydrophila infection in common carp, and provided fundamental genomic resources for better understanding the critical roles of endosialin family on the primary innate immune processes in teleost.

Coagulation Dysfunction in Acute Respiratory Distress Syndrome and Its Potential Impact in Inflammatory Subphenotypes

The Acute Respiratory Distress Syndrome (ARDS) has caused innumerable deaths worldwide since its initial description over five decades ago. Population-based estimates of ARDS vary from 1 to 86 cases per 100,000, with the highest rates reported in Australia and the United States. This syndrome is characterised by a breakdown of the pulmonary alveolo-epithelial barrier with subsequent severe hypoxaemia and disturbances in pulmonary mechanics. The underlying pathophysiology of this syndrome is a severe inflammatory reaction and associated local and systemic coagulation dysfunction that leads to pulmonary and systemic damage, ultimately causing death in up to 40% of patients. Since inflammation and coagulation are inextricably linked throughout evolution, it is biological folly to assess the two systems in isolation when investigating the underlying molecular mechanisms of coagulation dysfunction in ARDS. Although the body possesses potent endogenous systems to regulate coagulation, these become dysregulated and no longer optimally functional during the acute phase of ARDS, further perpetuating coagulation, inflammation and cell damage. The inflammatory ARDS subphenotypes address inflammatory differences but neglect the equally important coagulation pathway. A holistic understanding of this syndrome and its subphenotypes will improve our understanding of underlying mechanisms that then drive translation into diagnostic testing, treatments, and improve patient outcomes.

VEGF-Induced Endothelial Podosomes via ROCK2-Dependent Thrombomodulin Expression Initiate Sprouting Angiogenesis

[Figure: see text].

Protective Effects of Recombinant Human Soluble Thrombomodulin on Lipopolysaccharide-Induced Acute Kidney Injury

Thrombomodulin (TM) is a single transmembrane, multidomain glycoprotein receptor for thrombin, and is best known for its role as a cofactor in a clinically important natural anticoagulant pathway. In addition to its anticoagulant function, TM has well-defined anti-inflammatory properties. Soluble TM levels increase significantly in the plasma of septic patients; however, the possible involvement of recombinant human soluble TM (rTM) transduction in the pathogenesis of lipopolysaccharide (LPS)-induced nephrotoxicity, including acute kidney injury (AKI), has remained unclear. Mice were injected intraperitoneally with 15 mg/kg LPS. rTM (3 mg/kg) or saline was administered to the animals before the 3 and 24 h LPS-injection. At 24 and 48 h, blood urea nitrogen, the inflammatory cytokines in sera and kidney, and histological findings were assessed. Cell activation and apoptosis signal was assessed by Western blot analysis. In this study using a mouse model of LPS-induced AKI, we found that rTM attenuated renal damage by reducing both cytokine and cell activation and apoptosis signals with the accumulation of CD4+ T-cells, CD11c+ cells, and F4/80+ cells via phospho c-Jun activations and Bax expression. These findings suggest that the mechanism underlying these effects of TM may be mediated by a reduction in inflammatory cytokine production in response to LPS. These molecules might thereby provide a new therapeutic strategy in the context of AKI with sepsis.

Thrombomodulin Regulation of Mitogen-Activated Protein Kinases

The multifaceted role of mitogen-activated protein kinases (MAPKs) in modulating signal transduction pathways in inflammatory conditions such as infection, cardiovascular disease, and cancer has been well established. Recently, coagulation factors have also emerged as key players in regulating intracellular signaling pathways during inflammation. Among coagulation factors, thrombomodulin, as a high affinity receptor for thrombin on vascular endothelial cells, has been discovered to be a potent anti-inflammatory and anti-tumorigenic signaling molecule. The protective signaling function of thrombomodulin is separate from its well-recognized role in the clotting cascade, which is to function as an anti-coagulant receptor in order to switch the specificity of thrombin from a procoagulant to an anti-coagulant protease. The underlying protective signaling mechanism of thrombomodulin remains largely unknown, though a few published reports link the receptor to the regulation of MAPKs under different (patho)physiological conditions. The goal of this review is to summarize what is known about the regulatory relationship between thrombomodulin and MAPKs.

Complement-coagulation connections

: Complement and coagulation are evolutionarily related proteolytic cascades in the blood that are critical for effecting an appropriate innate response to injury that limits bleeding and infection, while promoting healing. Although often viewed as distinct, it has long been recognized that cross-talk likely exists between these pathways. Only recently have molecular links been established. These are providing insights that are revealing opportunities for the development of novel therapeutic strategies to better treat a wide range of thrombotic, inflammatory, immune, infectious, and malignant diseases. In this brief review, the complex relationship between complement and coagulation is highlighted, underlining some of the newly uncovered interactions, in the hopes of stimulating innovative research that will yield improvements in patient outcomes.

CD93 regulates central nervous system inflammation in two mouse models of autoimmune encephalomyelitis

Microglia and non-professional immune cells (endothelial cells, neurons) participate in the recognition and removal of pathogens and tissue debris in the injured central nervous system through major pro-inflammatory processes. However, the mechanisms involved in regulating these responses remain ill-characterized. We herein show that CD93, also known as complement C1qRp/AA4 stem cell marker, has an important role in the regulation of inflammatory processes. The role of CD93 was evaluated in two models of neuroinflammation. We used the MOG-experimental autoimmune encephalomyelitis (EAE) model and the antibody-dependent EAE (ADEAE), which were induced in wild-type and CD93 knockout mice. We found that CD93 was highly expressed by neurons, endothelial cells and microglia (ramified >> amoeboid). Astrocytes and oligodendrocytes did not to express CD93. We further observed that CD93-deficient (CD93^-/- ) mice presented a more robust brain and spinal cord inflammation in EAE and ADEAE. Encephalitis in CD93^-/- was characterized by increased numbers of infiltrating M1 macrophages (CD11c⁺ CD206^- ) and amoeboid microglia exhibiting a more activated phenotype (Tomato Lectin^high Cox2^high ). Damage to and leakage through the blood-brain barrier was increased in CD93^-/- animals and was associated with a more robust neuronal injury when compared with wild-type EAE mice. We propose that CD93 is an important neuro-immune regulator to control central nervous system inflammation.

The thrombomodulin lectin-like domain does not change host responses to tuberculosis

Tuberculosis (TB), caused by Mycobacterium (M.) tuberculosis, is a devastating infectious disease causing many deaths world-wide. Thrombomodulin (TM) is a multidomain glycoprotein expressed on all vascular endothelial cells. We here studied the role of the lectin-like domain of TM, responsible for a variety of anti-inflammatory properties of TM, during TB. We compared the extent of TM-expression in human lung tissue of TB and control patients. The, the role of the lectin-like domain of TM was investigated by comparing mice lacking this domain (TMLeD/LeD mice) with wild-type (WT) mice during experimental lung TB induced by infection with M. tuberculosis via the airways. Lungs were harvested for analyses at two, six and 29 weeks after infection. Lung TM-expression was downregulated in TB patients, which was not related to changes in the amount of endothelium in infected lungs. TMLeD/LeD mice showed unaltered mycobacterial loads in lungs, liver and spleen during experimental TB. Additionally, lung histopathology and cytokine concentrations were largely similar in TMLeD/LeD and WT mice, while total leukocyte counts were increased in lungs of TMLeD/LeD mice after 29 weeks of infection. Mortality did not occur in either group. The lectin-like domain of TM does not play an important role in the host response to M. tuberculosis infection in mice.

The Vitamin E Analog Gamma-Tocotrienol (GT3) and Statins Synergistically Up-Regulate Endothelial Thrombomodulin (TM)

Statins; a class of routinely prescribed cholesterol-lowering drugs; inhibit 3-hydroxy-3-methylglutaryl-coenzymeA reductase (HMGCR) and strongly induce endothelial thrombomodulin (TM); which is known to have anti-inflammatory; anti-coagulation; anti-oxidant; and radioprotective properties. However; high-dose toxicity limits the clinical use of statins. The vitamin E family member gamma-tocotrienol (GT3) also suppresses HMGCR activity and induces TM expression without causing significant adverse side effects; even at high concentrations. To investigate the synergistic effect of statins and GT3 on TM; a low dose of atorvastatin and GT3 was used to treat human primary endothelial cells. Protein-level TM expression was measured by flow cytometry. TM functional activity was determined by activated protein C (APC) generation assay. Expression of Kruppel-like factor 2 (KLF2), one of the key transcription factors of TM, was measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR). TM expression increased in a dose-dependent manner after both atorvastatin and GT3 treatment. A combined treatment of a low-dose of atorvastatin and GT3 synergistically up-regulated TM expression and functional activity. Finally; atorvastatin and GT3 synergistically increased KLF2 expression. These findings suggest that combined treatment of statins with GT3 may provide significant health benefits in treating a number of pathophysiological conditions; including inflammatory and cardiovascular diseases.

Biomaterials trigger endothelial cell activation when co-incubated with human whole blood

Endothelial cell activation resulting from biomaterial contact or biomaterial-induced blood activation may in turn also affect hemostasis and inflammatory processes in the blood. Current in vitro hemocompatibility assays typically ignore these modulating effects of the endothelium. This study describes a co-incubation system of human whole blood, biomaterial and endothelial cells (ECs) that was developed to overcome this limitation. First, human endothelial cells were characterized in terms of their expression of coagulation- and inflammation-relevant markers in response to various activators. Subsequently, their capacity to regulate hemostasis as well as complement and granulocyte activation was monitored in a hemocompatibility assay. After blood contact, quiescent ECs exhibited anticoagulant and anti-inflammatory properties. When they were co-incubated with surfaces exhibiting pro-coagulant or pro-inflammatory characteristics, the ECs down-regulated coagulation but not complement or leukocyte activation. Analysis of intracellular levels of the endothelial activation markers E-selectin and tissue factor showed that co-incubation with model surfaces and blood significantly increased the activation state of ECs. Finally, the coagulation- and inflammation-modulating properties of the ECs were tested after blood/biomaterial exposure. Pre-activation of ECs by biomaterials in the blood induced a pro-coagulant and pro-inflammatory state of the ECs, wherein the pro-coagulant response was higher for biomaterial/blood pre-activated ECs than for TNF-α-pre-activated cells. This work provides evidence that biomaterials, even without directly contacting the endothelium, affect the endothelial activation state with and have consequences for plasmatic and cellular reactions in the blood.

Reincarnation of ancient links between coagulation and complement

Throughout evolution, organisms have developed means to contain wounds by simultaneously limiting bleeding and eliminating pathogens and damaged host cells via the recruitment of innate defense mechanisms. Disease emerges when there is unchecked activation of innate immune and/or coagulation responses. A key component of innate immunity is the complement system. Concurrent excess activation of coagulation and complement - two major blood-borne proteolytic pathways - is evident in numerous diseases, including atherosclerosis, diabetes, venous thromboembolic disease, thrombotic microangiopathies, arthritis, cancer, and infectious diseases. Delineating the cross-talk between these two cascades will uncover novel therapeutic insights.

Hypothermia and rewarming induce gene expression and multiplication of cells in healthy rat prostate tissue

Prostate cancer has been extensively studied, but cellular stress responses in healthy prostate tissue are rarely investigated. Hypothermia is known to cause alterations in mRNA and protein expressions and stability. The aim of this study was to use normal rat prostate as a model in order to find out consequences of cold exposure and rewarming on the expressions of genes which are either members or functionally/structurally related to erythroblastic leukemia viral oncogene B (ErbB) signaling pathway. Relative mRNA expressions of amphiregulin (AMR), cyclin D1 (CyD1), cyclin-dependent kinase inhibitor 1A (p21), transmembrane form of the prostatic acid phosphatase (PAcP), thrombomodulin (TM) and heat shock transcription factor 1 (HSF1) in rat ventral prostate were quantified in mild (2 or 4.5 h at room temperature) and severe (2 or 4.5 h at +10°C) hypothermia and in rewarming after cold exposure (2 h at +10°C followed by 2 h at room temperature or 3 h at +28°C). AMR protein level, apoptotic Bcl-2 associated X protein to B-cell CLL/lymphoma 2 (Bax/Bcl-2) mRNA ratio and proliferative index Ki-67 were determined. 4.5-h mild hypothermia, 2-h severe hypothermia and rewarming increased expression of all these genes. Elevated proliferation index Ki-67 could be seen in 2-h severe hypothermia, and the proliferation index had its highest value in longer rewarming with totally recovered normal body temperature. Pro-apoptotic tendency could be seen in 2-h mild hypothermia while anti-apoptosis was predominant in 4.5-h mild hypothermia and in shorter rewarming with only partly recovered body temperature. Hypothermia and following rewarming promote the proliferation of cells in healthy rat prostate tissue possibly via ErbB signaling pathway.

Low-dose irradiation affects expression of inflammatory markers in the heart of ApoE -/- mice

Epidemiological studies indicate long-term risks of ionizing radiation on the heart, even at moderate doses. In this study, we investigated the inflammatory, thrombotic and fibrotic late responses of the heart after low-dose irradiation (IR) with specific emphasize on the dose rate. Hypercholesterolemic ApoE-deficient mice were sacrificed 3 and 6 months after total body irradiation (TBI) with 0.025, 0.05, 0.1, 0.5 or 2 Gy at low (1 mGy/min) or high dose rate (150 mGy/min). The expression of inflammatory and thrombotic markers was quantified in frozen heart sections (CD31, E-selectin, thrombomodulin, ICAM-1, VCAM-1, collagen IV, Thy-1, and CD45) and in plasma samples (IL6, KC, MCP-1, TNFα, INFγ, IL-1β, TGFβ, INFγ, IL-10, sICAM-1, sE-selectin, sVCAM-1 and fibrinogen) by fluorescence analysis and ELISA. We found that even very low irradiation doses induced adaptive late responses, such as increases of capillary density and changes in collagen IV and Thy-1 levels indicating compensatory regulation. Slight decreases of ICAM-1 levels and reduction of Thy 1 expression at 0.025–0.5 Gy indicate anti-inflammatory effects, whereas at the highest dose (2 Gy) increased VCAM-1 levels on the endocardium may represent a switch to a pro-inflammatory response. Plasma samples partially confirmed this pattern, showing a decrease of proinflammatory markers (sVCAM, sICAM) at 0.025–2.0 Gy. In contrast, an enhancement of MCP-1, TNFα and fibrinogen at 0.05–2.0 Gy indicated a proinflammatory and prothrombotic systemic response. Multivariate analysis also revealed significant age-dependent increases (KC, MCP-1, fibrinogen) and decreases (sICAM, sVCAM, sE-selectin) of plasma markers. This paper represents local and systemic effects of low-dose irradiation, including also age- and dose rate-dependent responses in the ApoE^-/- mouse model. These insights in the multiple inflammatory/thrombotic effects caused by low-dose irradiation might facilitate an individual evaluation and intervention of radiation related, long-term side effects but also give important implications for low dose anti-inflammatory radiotherapy.

The efficacy of recombinant human soluble thrombomodulin for the treatment of shiga toxin-associated hemolytic uremic syndrome model mice

BACKGROUND

Recombinant human soluble thrombomodulin (rhTM) is a promising therapeutic natural anticoagulant that is comparable to antithrombin, tissue factor pathway inhibitor and activated protein C. In order to clarify the efficacy of rhTM for the treatment of typical hemolytic uremic syndrome (t-HUS), we examined changes in renal damage in t-HUS mice treated with rhTM or vehicle alone.

METHODS

We used severe and moderate t-HUS mice injected with shiga toxin (Stx) and lipopolysaccharide (LPS). The severe t-HUS mice were divided into two subgroups [an rhTM subgroup (Group A) and a saline subgroup (Group B)] along with the moderate t-HUS mice [an rhTM subgroup (Group C) and a saline subgroup (Group D)]. Groups E and F were healthy mice treated with rhTM or saline, respectively.

RESULTS

All mice in Group B died at 80-90 h post-administration of Stx2 and LPS whereas all mice in Group A remained alive. Loss of body weight, serum creatinine level, endothelial injury and mesangiolysis scores at 24 h after administration in the t-HUS mice treated with rhTM were lower than those in t-HUS mice treated with saline. The levels of hemoglobin at 6 h and platelet counts at 24 h after administration in Group A were higher than those in Group B. Serum interleukin (IL)-6, IL-1β and tumor necrotic factor (TNF)-α levels at 24 h after administration in Group A were lower than those in Group B. Serum C5b-9 levels at 24 h after the administration and serum fibrinogen degradation product (FDP) at 72 h after the administration of Stx2 and LPS were lower in Group A than in Group B.

CONCLUSIONS

These results indicate that rhTM might afford an efficacious treatment for t-HUS model mice via the inhibition of further thrombin formation and amelioration of hypercoagulant status.

Changes in cardiac thrombomodulin and heat shock transcription factor 1 expression and peripheral thrombomodulin and catecholamines during hypothermia in rats

Effects of hypothermia and rewarming on thrombomodulin, catecholamines and heat shock transcription factor 1 (HSF1) were studied in rats. The aims of this study were to clarify whether cold stress, under anesthesia, is sufficient to change levels of thrombomodulin in healthy endothelium and in the circulation and whether adrenaline, noradrenaline and HSF1 could act as regulators in the process. Rats were divided into control, mild hypothermia (2 and 4.5 hours at + 21 °C; MH1, MH2), severe hypothermia (2 and 4.5 h at + 10 °C; SH1, SH2) and two rewarming groups (2 h at + 10 °C followed by 2 h at + 21 °C or 3 h at + 28 °C; SHW1, SHW2) (n = 15/group, except n = 6 in MH1). Fentanyl-fluanisone-midazolam was used as anesthetic. Low levels of thrombomodulin in plasma and myocardial arterioles/venules measured by ELISA and immunohistochemistry were associated with significant increase of thrombomodulin transcript level in SH1 rats analyzed by quantitative PCR. Plasma adrenaline correlated negatively with the relative amount of myocardial thrombomodulin transcripts and positively with plasma thrombomodulin in SH. Transcript levels of thrombomodulin and HSF1 correlated strongly (r = 0.83; p < 0.001) in SH. Plasma/urine ratio of thrombomodulin and plasma adrenaline (r = 0.87; p = 0.005) or noradrenaline (r = 0.78; p = 0.023) were strongly correlated in SHW1 rats. Hence, cellular and soluble levels of thrombomodulin are modified by cold stress in healthy rats, possibly via catecholamines and HSF1.

Thrombomodulin protects against lung damage created by high level of oxygen with large tidal volume mechanical ventilation in rats

Background

Ventilator-induced lung injury (VILI) is associated with inflammatory responses in the lung. Thrombomodulin (TM), a component of the coagulation system, has anticoagulant and anti-inflammatory effects. We hypothesized that the administration of recombinant human soluble TM (rhsTM) would block the development of lung injury.

Methods

Lung injury was induced by high tidal volume ventilation for 2 h with 100% oxygen in rats. Rats were ventilated with a tidal volume of 35 ml/kg with pretreatment via a subcutaneous injection of 3 mg/kg rhsTM (HV (high tidal volume)/TM) or saline (HV/SAL) 12 h before mechanical ventilation. Rats ventilated with a tidal volume of 6 ml/kg under 100% oxygen with rhsTM (LV (low tidal volume)/TM) or saline (LV/SAL) were used as controls. Lung protein permeability was determined by Evans blue dye (EBD) extravasation.

Results

Lung injury was successfully induced in the HV/SAL group compared with the LV/SAL group, as shown by the significant decrease in arterial oxygen pressure (PaO₂), increased protein permeability, and increase in mean pulmonary artery pressure (mPAP) and ratio of mean pulmonary artery pressure to mean artery pressure (Pp/Ps). Treatment of rats with lung injury with rhsTM (HV/TM) significantly attenuated the decrease in PaO₂ and the increase in both mPAP and Pp/Ps, which was associated with a decrease in the lung protein permeability. Lung tissue mRNA expressions of interleukin (IL)-1α, IL-1β, IL-6, tumor necrosis factor-α, and macrophage inflammatory protein (MIP)-2 were significantly higher in HV than in LV rats. Rats with VILI treated with rhsTM (HV/TM) had significantly lower mRNA expressions of IL-1α, IL-1β, IL-6, and MIP-2 than those expressions in HV/SAL rats.

Conclusions

Administration of rhsTM may prevent the development of lung injury created by high level of oxygen with large tidal volume mechanical ventilation, which has concomitant decrease in proinflammatory cytokine and chemokine expression in the lung.

Late inflammatory and thrombotic changes in irradiated hearts of C57BL/6 wild-type and atherosclerosis-prone ApoE-deficient mice

BACKGROUND AND PURPOSE

Radiation-induced heart disease represents a late complication of thoracic radiotherapy. We investigated the inflammatory and thrombotic response after local heart irradiation in wild-type and atherosclerosis-prone mice.

MATERIAL AND METHODS

Atherosclerosis-prone ApoE(-/-) and C57BL/6 wild-type mice were sacrificed 20, 40, and 60 weeks after irradiation with 0.2, 2, 8, or 16 Gy. The expression of CD31, vascular cell adhesion molecule-1 (VCAM-1), thrombomodulin (TM), and CD45 were quantified by immunofluorescence staining of heart tissue sections.

RESULTS

Microvascular density decreased at 40 weeks after 16 Gy in C57BL/6 but not in ApoE(-/-) mice. CD31 expression declined in C57BL/6 mice at 40 weeks (8 Gy), but increased in ApoE(-/-) mice at 20 (2/8/16 Gy) and 60 weeks (16 Gy). Capillary area decreased in C57BL/6 at 40 weeks (8/16 Gy) but increased in ApoE(-/-) mice at 20 weeks (16 Gy). Endocardial VCAM-1 expression remained unchanged. TM-positive capillaries decreased at 40 weeks (8/16 Gy) in C57BL/6 and at 60 weeks (2/16 Gy) in ApoE(-/-) mice. Leukocyte infiltration transiently rose 40 weeks after 8 Gy (only ApoE(-/-)) and 16 Gy. After receiving a low irradiation dose of 0.2 Gy, no significant changes were observed in any of the mouse models.

CONCLUSION

This study demonstrated that local heart irradiation affects microvascular structure and induces inflammatory/thrombotic responses in mice in a dose- and time-dependent manner. Thereby, significant prothrombotic changes were found in both strains, although they were progressive in ApoE(-/-) mice only. Proinflammatory responses, like the increase of adhesion molecules and leukocyte infiltration, were more pronounced and occurred at lower doses in ApoE(-/-) vs. C57BL/6 mice. These findings indicate that metabolic risk factors, such as decreased ApoE lipoproteins, may lead to an enhanced proinflammatory and prothrombotic late response in locally irradiated hearts.

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.

Late effects of local irradiation on the expression of inflammatory markers in the Arteria saphena of C57BL/6 wild-type and ApoE-knockout mice

Combined action of irradiation (IR), shear stress, and high blood pressure is well recognized to induce damage to vasculature, while data on pathological effects of IR in large peripheral vessels with low blood pressure are scarce. The purpose of the present study was hence to investigate time- and dose-dependent effects of local IR on inflammatory and prothrombotic processes in the Arteria (A.) saphena of C57BL/6 wild-type and apolipoprotein E (ApoE)-knockout mice. Single doses of 2, 5, 8, 10, or 16 Gy were locally delivered to the A. saphena of the left leg of the animals. The expression of CD31, intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E-selectin, monocyte chemoattractant protein-1 (MCP-1), and thrombomodulin (TM) was quantified by semiautomatic TissueFax fluorescence analysis in frozen arterial sections. Follow-up periods were 3, 6, 9, 12, or 18 months. Protein expression in the arterial wall displayed dose-dependent changes. Proinflammatory reactions were observed for CD31, E-selectin, ICAM, and VCAM already at doses of 2 Gy. Anti-inflammatory changes were detected for MCP-1 and TM. The effects were more pronounced in wild-type versus ApoE(-/-) mice. Changes remain mostly transient up to 16 Gy. Dose- and time-dependent changes in inflammatory and thrombotic mediators in the wall of the A. saphena were found after local IR but did not transform into histopathological consequences.

Effect of thrombomodulin on the development of monocrotaline-induced pulmonary hypertension

PURPOSE

The purpose of the present study was to investigate whether thrombomodulin (TM) prevents the development of pulmonary hypertension (PH) in monocrotaline (MCT)-injected rats.

METHODS

Human recombinant TM (3 mg/kg/2 days) or saline were given to MCT-injected male Sprague-Dawley rats for 19 (n = 14) or 29 (n = 11) days. Control rats (n = 6) were run for 19 days. The mean pulmonary artery pressure (mPAP), right ventricular hypertrophy (RVH), percentages of muscularized peripheral arteries (%muscularization), and medial wall thickness of small muscular arteries (%MWT) were measured. To determine inflammatory and coagulation responses, broncho-alveolar lavage fluid (BALF) was analyzed in another set of rats (n = 29). Western blotting for endothelial nitric oxide synthase (eNOS) and phosphorylated eNOS (peNOS) in the lung tissue was performed in separate rats (n = 13). Survival was determined in 60 rats.

RESULTS

MCT increased mPAP, RVH, %muscularization, and %MWT. TM treatment significantly reduced mPAP, %muscularization, and %MWT in peripheral arteries with an external diameter of 50-100 μm in 19 days after MCT injection, but the effect was lost after 29 days. MCT increased the levels of tumor necrosis factor alpha, monocyte chemoattractant protein-1, and thrombin-antithrombin complex in BALF. Expression of eNOS increased in MCT rats, while peNOS decreased. The relative amount of peNOS to total eNOS increased in MCT/TM rats compared to MCT/Vehicle rats. A Kaplan-Meier survival curve showed no difference with and without TM.

CONCLUSION

Although the administration of TM might slightly delay the progression of MCT-induced PH, the physiological significance for treatment is limited, since the survival rate was not improved.

Thrombomodulin and the vascular endothelium: insights into functional, regulatory, and therapeutic aspects

Thrombomodulin (TM) is a 557-amino acid protein with a broad cell and tissue distribution consistent with its wide-ranging physiological roles. When expressed on the lumenal surface of vascular endothelial cells in both large vessels and capillaries, its primary function is to mediate endothelial thromboresistance. The complete integral membrane-bound protein form displays five distinct functional domains, although shorter soluble (functional) variants comprising the extracellular domains have also been reported in fluids such as serum and urine. TM-mediated binding of thrombin is known to enhance the specificity of the latter serine protease toward both protein C and thrombin activatable fibrinolysis inhibitor (TAFI), increasing their proteolytic activation rate by almost three orders of magnitude with concomitant anticoagulant, antifibrinolytic, and anti-inflammatory benefits to the vascular wall. Recent years have seen an abundance of research into the cellular mechanisms governing endothelial TM production, processing, and regulation (including flow-mediated mechanoregulation)--from transcriptional and posttranscriptional (miRNA) regulation of TM gene expression, to posttranslational processing and release of the expressed protein--facilitating greater exploitation of its therapeutic potential. The goal of the present paper is to comprehensively review the endothelial/TM system from these regulatory perspectives and draw some fresh conclusions. This paper will conclude with a timely examination of the current status of TM's growing therapeutic appeal, from novel strategies to improve the clinical efficacy of recombinant TM analogs for resolution of vascular disorders such as disseminated intravascular coagulation (DIC), to an examination of the complex pleiotropic relationship between statin treatment and TM expression.

Free fatty acids inhibit TM-EPCR expression through JNK pathway: an implication for the development of the prothrombotic state in metabolic syndrome

Metabolic syndrome is associated with significant hypercoagulable prothrombotic tendency; however, the mechanism for the prothrombotic state is not completely understood. We hypothesize that higher circulating plasma free fatty acids (FFAs) in metabolic syndrome inhibit the endothelial thrombomodulin (TM)-endothelial protein C receptor (EPCR) pathway, thereby promoting thrombus formation. Human umbilical vein endothelial cells were cultured in media supplemented with various doses of palmitic acid (PA), in the presence or absence of JNK inhibitor, and the expression of TM and EPCR was measured by western blot. The thrombotic state of high fat fed C57BL/6J mice was examined by tail bleeding time and deep venous thrombosis (DVT) model. As a result, PA inhibited the expression of TM and EPCR in endothelial cells, and this effect was blunted by inhibiting JNK signaling. High fat diet fed mice had higher level of circulating FFAs and exhibited prothrombotic state, evidenced by increased tail bleeding time and enlarged thrombotic size in DVT model, compared to the control diet fed mice. Hence, FFAs inhibit TM-EPCR-Protein C system in endothelial cells through activating JNK signaling, which may be a mechanism for the prothrombotic state in metabolic syndrome.

Dengue virus enhances thrombomodulin and ICAM-1 expression through the macrophage migration inhibitory factor induction of the MAPK and PI3K signaling pathways

Dengue virus (DV) infections cause mild dengue fever (DF) or severe life-threatening dengue hemorrhagic fever (DHF). The mechanisms that cause hemorrhage in DV infections remain poorly understood. Thrombomodulin (TM) is a glycoprotein expressed on the surface of vascular endothelial cells that plays an important role in the thrombin-mediated activation of protein C. Prior studies have shown that the serum levels of soluble TM (sTM) and macrophage migration inhibitory factor (MIF) are significantly increased in DHF patients compared to levels in DF patients or normal controls. In this study, we investigated how MIF and sTM concentrations are enhanced in the plasma of DHF patients and the potential effect of MIF on coagulation through its influence on two factors: thrombomodulin (TM) and intercellular adhesion molecule-1 (ICAM-1) in endothelial cells and monocytes. Recombinant human macrophage migration inhibitory factor (rMIF) was used to treat monocytic THP-1 cells and endothelial HMEC-1 cells or primary HUVEC cells. The subsequent expression of TM and ICAM-1 was assessed by immunofluorescent staining and flow cytometry analysis. Additionally, the co-incubation of THP-1 cells with various cell signaling pathway inhibitors was used to determine the pathways through which MIF mediated its effect. The data provided evidence that severe DV infections induce MIF expression, which in turn stimulates monocytes or endothelial cells to express TM and ICAM-1 via the Erk, JNK MAPK and the PI3K signaling pathways, supporting the idea that MIF may play an important role as a regulator of coagulation.

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.

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.

Macrophage migration inhibitory factor induces ICAM-1and thrombomobulin expression in vitro

Macrophage migration inhibitory factor (MIF) is an important cytokine in the modulation of inflammatory and immune responses, but its role in coagulation remains to be elucidated. In this study, we investigated the potential role of MIF in coagulation through its influence on two factors, thrombomodulin (TM) and intercellular adhesion molecule-1 (ICAM-1). Recombinant human MIF was added to human microvascular endothelial cell line (HMEC-1) to investigate its influence on the expression of TM and ICAM-1. The results showed that both TM and ICAM-1 were induced with MIF addition in a dose-dependent and time-dependent manner. The expression of ICAM-1 and TM was increased as MIF doses were increased, with the highest expression seen at 12 hr after 400 ng/ml of MIF treatment. Besides, anti-MIF antibody treatment reduced the TM expression in HMEC-1 cells. In conclusion, our data support a role of MIF as an important factor in the regulation of coagulation.

Thrombomodulin alfa in the treatment of infectious patients complicated by disseminated intravascular coagulation: subanalysis from the phase 3 trial

To investigate treatment effects of thrombomodulin alfa (TM-α) in patients with disseminated intravascular coagulation (DIC) having infection as the underlying disease, retrospective subanalysis of a double-blind, randomized controlled phase 3 trial was conducted. In the phase 3 trial, 227 DIC patients (full-analysis set) having infection and/or hematologic malignancy as the underlying disease received either TM-α (0.06 mg·kg for 30 min once daily) or heparin (8 U·kg·h for 24 h) for 6 days using the double-dummy method. Among these patients, 147 patients with noninfectious comorbidity leading to severe thrombocytopenia (e.g., hematologic malignancy, or aplastic anemia) were excluded from the present analysis, and 80 patients with infectious disease and DIC were extracted and subjected to the present retrospective subanalysis. Disseminated intravascular coagulation resolution rates were determined using the DIC diagnostic criteria for critically ill patients at 7 days, and mortality rates were evaluated at 28 days. In the TM-α and heparin groups, DIC resolution rates were 67.5% (27/40) and 55.6% (20/36), and 28-day mortality rates were 21.4% (9/42) and 31.6% (12/38), respectively. Mortality rates of patients who recovered from DIC were 3.7% (1/27) in the TM-α group and 15% (3/20) in the heparin group. These results suggest TM-α may be valuable in the treatment of DIC associated with infection.

Thrombomodulin is a determinant of metastasis through a mechanism linked to the thrombin binding domain but not the lectin-like domain

Thrombomodulin (TM) is a predominantly endothelial transmembrane glycoprotein that modulates hemostatic function through a domain that controls thrombin-mediated proteolysis and an N-terminal lectin-like domain that controls inflammatory processes. To test the hypothesis that TM is a determinant of malignancy and dissect the importance of these functional domains in cancer biology, metastatic potential was evaluated in TM(Pro) mice expressing a mutant form of TM with reduced thrombin affinity and TM(LeD) mice lacking the N-terminal lectin-like domain. Studies of TM(Pro) mice revealed that TM is a powerful determinant of hematogenous metastasis. TM(Pro) mice exhibited a strongly prometastatic phenotype relative to control mice that was found to result from increased survival of tumor cells newly localized to the lung rather than any alteration in tumor growth. The impact of the TM(Pro) mutation on metastasis was dependent on both tumor cell-associated tissue factor and thrombin procoagulant function. In contrast, expression of a mutant form of TM lacking the lectin-like domain had no significant impact on metastasis. These studies directly demonstrate for the first time that TM-mediated regulation of tumor cell-driven procoagulant function strongly influences metastatic potential and suggest that endothelial cell-associated modulators of hemostasis may represent novel therapeutic targets in limiting tumor dissemination.

Alternative pathway activation of complement by Shiga toxin promotes exuberant C3a formation that triggers microvascular thrombosis

Shiga toxin (Stx)-producing E.coli O157:H7 has become a global threat to public health; it is a primary cause of diarrhea-associated hemolytic uremic syndrome (HUS), a disorder of thrombocytopenia, microangiopathic hemolytic anemia, and acute renal failure with thrombi occluding renal microcirculation. In this study, we explored whether Stx triggers complement-dependent microvascular thrombosis in in vitro and in vivo experimental settings of HUS. Stx induced on human microvascular endothelial cell surface the expression of P-selectin, which bound and activated C3 via the alternative pathway, leading to thrombus formation under flow. In the search for mechanisms linking complement activation and thrombosis, we found that exuberant complement activation in response to Stx generated an increased amount of C3a that caused further endothelial P-selectin expression, thrombomodulin (TM) loss, and thrombus formation. In a murine model of HUS obtained by coinjection of Stx2 and LPS and characterized by thrombocytopenia and renal dysfunction, upregulation of glomerular endothelial P-selectin was associated with C3 and fibrin(ogen) deposits, platelet clumps, and reduced TM expression. Treatment with anti-P-selectin Ab limited glomerular C3 accumulation. Factor B-deficient mice after Stx2/LPS exhibited less thrombocytopenia and were protected against glomerular abnormalities and renal function impairment, indicating the involvement of complement activation via the alternative pathway in the glomerular thrombotic process in HUS mice. The functional role of C3a was documented by data showing that glomerular fibrin(ogen), platelet clumps, and TM loss were markedly decreased in HUS mice receiving C3aR antagonist. These results identify Stx-induced complement activation, via P-selectin, as a key mechanism of C3a-dependent microvascular thrombosis in diarrhea-associated HUS.

Thrombin-induced activation of astrocytes in mixed rat hippocampal cultures is inhibited by soluble thrombomodulin

Thrombin, a serine protease known for its role in coagulation, also induces a variety of protease activated receptor (PAR)-mediated responses in the central nervous system that contribute to many brain pathologies. Since the proteolytic specificity of thrombin is uniquely controlled by thrombomodulin (TM), we investigated the mechanisms by which thrombin and a recombinant soluble form of human TM (Solulin, INN: sothrombomodulin alpha; rhsTM) could influence rat hippocampal cultures. Treatment of hippocampal cultures with thrombin for up to 48h resulted in a significant morphological rearrangement with the formation of expansive cell-free areas (CFAs) and a reduction in cell viability; both effects were blocked by rhsTM. Treatment with the selective PAR-1 agonist, TRAP (SFLLRN) caused the formation of CFAs, suggesting that CFA formation involved PAR-1 signaling. Astrocytes prepared from PAR-1(-/-) mice also had an attenuated CFA response to thrombin. Thrombin-induced CFA formation was a consequence of cell movement and substantial changes in cell morphology, rather than due to cell detachment. Immunocytochemical and functional analyses revealed that the thrombin-sensitive cells within these hippocampal cultures were astrocytes. The effects of thrombin on CFA development were mediated by astrocyte-specific release of intracellular calcium and signalling through ERK1/2. rhsTM was able to attenuate thrombin-induced ERK1/2 phosphorylation. Finally, astrocytes were shown to maintain thrombin-sensitivity following neuronal depletion with NMDA, a result which was confirmed with pure astrocyte cultures. Hence thrombin mediates PAR-1-induced activation of hippocampal astrocytes, but not neurons, in a process that can be modulated by rhsTM.

Endosialin: from vascular target to biomarker for human sarcomas

Biomarkers have been the focus of investigations to diagnose disease, track response to therapy and predict prognosis. Meanwhile, the identification of new targets for therapeutic intervention is an ongoing quest in the field of oncology. The recognition of endosialin as an antigen that is selectively overexpressed in human tumor tissues offers new strategies for treating cancer. Not only do the tumor vasculature and stromal compartments upregulate endosialin but, importantly, the malignant cells of sarcomas strongly express endosialin as well. A diagnostic assay that measures the intensity of endosialin expression in malignant tissues would assist in selecting patients that could benefit from an antiendosialin therapy. Thus, endosialin holds potential value both as a therapeutic target and as a biomarker for certain human cancers.

The envelope glycoprotein domain III of Dengue virus type 2 induced the expression of anticoagulant molecules in endothelial cells

Dengue virus (DV) causes a non-specific febrile illness known as Dengue fever (DF), and a severe life-threatening illness, Dengue hemorrhagic fever/Dengue shock syndrome (DHF/DSS). Hemostatic changes induced by this virus involve three main factors: thrombocytopenia, endothelial cell damage, and significant abnormalities of the coagulation and fibrinolysis systems. The pathogenesis of bleeding in DV infections remains unknown. In this article, we focused on the DV activating endothelial cells and altering the parameters of hemostasis system. The expression of hemostasis-related factors, Thrombomodulin, TF, TFPI, t-PA, and PAI-1, in DV-infected cells were determined by RT-PCR. Flow cytometry analysis and immunofluorescence staining confirmed that the expression levels of TM in the DV-infected HMEC-1 and THP-1 cells were increased. In addition, the purified recombinant domain III of the envelope glycoprotein of DV (EIII) could induce the expression of TM in the HMEC-1 cells and THP-1 cells. The TM expression induced by DV or EIII in the endothelial cells and monocytic cells suggests that the EIII of DV plays an important role in the pathogenesis of DHF/DSS.

Regulation of inflammation by the protein C system

OBJECTIVE

To review new findings about the function of the protein C system during inflammation and coagulation.

MAIN FINDINGS

Coagulation proteases and their cofactors modify the outcome of severe inflammation by engaging signaling-competent cell surface receptors. The central effector protease of the protein C pathway, activated protein C, interacts with the endothelial cell protein C receptor, protease-activated receptors, and other receptors to exert multiple effects on hemostasis and immune cell function. Thrombomodulin controls the complement arm of the innate immune system in a thrombin-dependent manner through activation of the thrombin activatable inhibitor of fibrinolysis, and in a thrombin-independent, constitutive manner via its lectin-like extracellular domain; and inhibits the inflammatory effects of high-mobility box group 1 protein. Protein S not only suppresses coagulation as an enhancing cofactor for the coagulation inhibitors activated protein C and tissue factor pathway inhibitor but also is also a physiologic ligand for the Tyro/axl/Mer-family of receptor tyrosine kinases that mediate an anti-inflammatory regulatory loop of dendritic cell and monocyte inflammatory function.

CONCLUSIONS

The immune-regulatory capacity of the protein C pathway and its individual components emerge as the dominant action of this pathway in the setting of severe inflammation.

JNK-ATF-2 inhibits thrombomodulin (TM) expression by recruiting histone deacetylase4 (HDAC4) and forming a transcriptional repression complex in the TM promoter

Thrombomodulin (TM) is an important vascular protective molecule that has anticoagulant, anti-inflammatory and anti-apoptotic properties. TM is downregulated in many thrombotic and vascular diseases. However, the mechanisms responsible for TM suppression are not completely understood. In this study, we investigated the mechanism involved in fatty acid-induced suppression of TM expression in human aortic endothelial cells. We found that palmitic acid inhibited TM expression through the JNK and p38 pathways. ATF-2, a JNK and p38 target transcription factor, was involved in the suppression. ATF-2 can bind to the TM promoter, recruit HDAC4 and form a transcriptional repression complex in the promoter, which may lead to chromatin condensation and transcriptional arrest. This study provides novel insight into TM down-regulation by stress signaling pathways.

Degradation of vascular endothelial thrombomodulin by arginine- and lysine-specific cysteine proteases from Porphyromonas gingivalis

BACKGROUND

The endothelial cell surface glycoprotein thrombomodulin (TM) inhibits vascular coagulation and inflammation via regulation of thrombin-mediated activation of protein C. Porphyromonas gingivalis is the major periodontopathic bacterium and has been found in vessel walls and atherosclerotic lesions in humans. P. gingivalis-derived cysteine proteases (gingipains) are known to enhance inflammatory and coagulant responses of vascular endothelial cells. However, it has not been elucidated whether gingipains affect vascular endothelial TM.

METHODS

Purified arginine-specific gingipains (Rgps) and lysine-specific gingipain (Kgp) from P. gingivalis were used to investigate the effects of gingipains on recombinant human TM by immunoblot analyses. Flow cytometry and activated protein C assay were carried out to examine the effects of gingipains on vascular endothelial cell surface TM. Immunohistochemistry was performed to investigate TM expression in microvascular endothelia in gingival tissues taken from patients with periodontitis.

RESULTS

Rgps and Kgp cleaved TM in vitro. Endothelial cell surface TM was also degraded by Rgps. Thrombin-mediated activation of protein C was reduced by Rgps through TM inactivation. Gingival microvascular endothelial TM was reduced in patients with periodontitis.

CONCLUSIONS

P. gingivalis gingipains induced the degradation and inactivation of endothelial TM, which may promote vascular coagulation and inflammation. In addition, in vivo relevance was demonstrated by reduced expression of TM in gingival microvascular endothelia in patients with periodontitis, which may be involved in the pathogenesis of periodontitis.

Hemostasis and inflammation: two of a kind?

Hemostasis is a defense mechanism to stop bleeding. Activated by vessel wall injury, it consists of intertwined activation of platelets and the coagulation cascade, tightly controlled by natural anticoagulants and the fibrinolytic system.

Gene Expression Studies Reveal That DNA Damage, Vascular Perturbation, and Inflammation Contribute to the Pathogenesis of Carbonyl Sulfide Neurotoxicity

Carbonyl sulfide (COS) is an odorless gas that produces highly reproducible lesions in the central nervous system. In the present study, the time course for the development of the neurotoxicological lesions was defined and the gene expression changes occurring in the posterior colliculus upon exposure to COS were characterized. Fischer 344 rats were exposed to 0 or 500 ppm COS for one, two, three, four, five, eight, or ten days, six hours per day. On days 1 and 2, no morphological changes were detected; on day 3, 10/10 (100%) rats had necrosis in the posterior colliculi; and on day 4 and later, necrosis was observed in numerous areas of the brain. Important gene expression changes occurring in the posterior colliculi after one or two days of COS exposure that were predictive of the subsequent morphological findings included up-regulation of genes associated with DNA damage and G1/S checkpoint regulation (KLF4, BTG2, GADD45g), apoptosis (TGM2, GADD45g, RIPK3), and vascular mediators (ADAMTS, CTGF, CYR61, VEGFC). Proinflammatory mediators (CCL2, CEBPD) were up-regulated prior to increases in expression of the astrocytic marker GFAP and macrophage marker CSF2rb1. These gene expression findings were predictive of later CNS lesions caused by COS exposure and serve as a model for future investigations into the mechanisms of disease in the central nervous system.

IL-32-dependent effects of IL-1beta on endothelial cell functions

Increasing evidence demonstrates that interleukin (IL)-32 is a pro-inflammatory cytokine, inducing IL-1alpha, IL-1beta, IL-6, tumor necrosis factor (TNF)-alpha, and chemokines via nuclear factor (NF)-kappaB, p38 mitogen-activated protein kinase (MAPK), and activating protein (AP)-1 activation. Here we report that IL-32 is expressed and is also functional in human vascular endothelial cells (EC) of various origins. Compared with primary blood monocytes, high levels of IL-32 are constitutively produced in human umbilical vein EC (HUVEC), aortic macrovascular EC, and cardiac as well as pulmonary microvascular EC. At concentrations as low as 0.1 ng/ml, IL-1beta stimulated IL-32 up to 15-fold over constitutive levels, whereas 10 ng/ml of TNFalpha or 100 ng/ml of lipopolysaccharide (LPS) were required to induce similar quantities of IL-32. IL-1beta-induced IL-32 was reduced by inhibition of the IkappaB kinase-beta/NF-kappaB and ERK pathways. In addition to IL-1beta, pro-coagulant concentrations of thrombin or fresh platelets increased IL-32 protein up to 6-fold. IL-1beta and thrombin induced an isoform-switch in steady-state mRNA levels from IL-32alpha/gamma to beta/epsilon. Adult EC responded in a similar fashion. To prove functionality, we silenced endogenous IL-32 with siRNA, decreasing intracellular IL-32 protein levels by 86%. The knockdown of IL-32 resulted in reduction of constitutive as well as IL-1beta-induced intercellular adhesion molecule-1 (ICAM-1) (of 55% and 54%, respectively), IL-1alpha (of 62% and 43%), IL-6 (of 53% and 43%), and IL-8 (of 46% and 42%). In contrast, the anti-inflammatory/anti-coagulant CD141/thrombomodulin increased markedly when IL-32 was silenced. This study introduces IL-32 as a critical regulator of endothelial function, expanding the properties of this cytokine relevant to coagulation, endothelial inflammation, and atherosclerosis.

A review of pulmonary coagulopathy in acute lung injury, acute respiratory distress syndrome and pneumonia

Enhanced bronchoalveolar coagulation is a hallmark of many acute inflammatory lung diseases such as acute lung injury, acute respiratory distress syndrome and pneumonia. Intervention with natural anticoagulants in these diseases has therefore become a topic of interest. Recently, new data on the role of pulmonary coagulation and inflammation has become available. The aim of this review is to summarize these findings. Furthermore, the results of anticoagulant therapeutic interventions in these disorders are discussed.