Regulation of endothelial thrombomodulin expression by inflammatory cytokines is mediated by activation of nuclear factor-kappa B

Chemokine Fractalkine and Non-Obstructive Coronary Artery Disease-Is There a Link?

Non-obstructive coronary artery disease (NO-CAD) constitutes a heterogeneous group of conditions collectively characterized by less than 50% narrowing in at least one major coronary artery with a fractional flow reserve (FFR) of ≤0.80 observed in coronary angiography. The pathogenesis and progression of NO-CAD are still not fully understood, however, inflammatory processes, particularly atherosclerosis and microvascular dysfunction are known to play a major role in it. Chemokine fractalkine (FKN/CX3CL1) is inherently linked to these processes. FKN/CX3CL1 functions predominantly as a chemoattractant for immune cells, facilitating their transmigration through the vessel wall and inhibiting their apoptosis. Its concentrations correlate positively with major cardiovascular risk factors. Moreover, promising preliminary results have shown that FKN/CX3CL1 receptor inhibitor (KAND567) administered in the population of patients with ST-elevation myocardial infarction (STEMI) undergoing percutaneous coronary intervention (PCI), inhibits the adverse reaction of the immune system that causes hyperinflammation. Whereas the link between FKN/CX3CL1 and NO-CAD appears evident, further studies are necessary to unveil this complex relationship. In this review, we critically overview the current data on FKN/CX3CL1 in the context of NO-CAD and present the novel clinical implications of the unique structure and function of FKN/CX3CL1 as a compound which distinctively contributes to the pathomechanism of this condition.

Tissue Injury Protection: The Other Face of Anticoagulant Treatments in the Context of Ischemia and Reperfusion Injury with a Focus on Transplantation

Organ transplantation has enhanced the length and quality of life of patients suffering from life-threatening organ failure. Donors deceased after brain death (DBDDs) have been a primary source of organs for transplantation for a long time, but the need to find new strategies to face organ shortages has led to the broadening of the criteria for selecting DBDDs and advancing utilization of donors deceased after circulatory death. These new sources of organs come with an elevated risk of procuring organs of suboptimal quality. Whatever the source of organs for transplant, one constant issue is the occurrence of ischemia-reperfusion (IR) injury. The latter results from the variation of oxygen supply during the sequence of ischemia and reperfusion, from organ procurement to the restoration of blood circulation, triggering many deleterious interdependent processes involving biochemical, immune, vascular and coagulation systems. In this review, we focus on the roles of thrombo-inflammation and coagulation as part of IR injury, and we give an overview of the state of the art and perspectives on anticoagulant therapies in the field of transplantation, discussing benefits and risks and proposing a strategic guide to their use during transplantation procedures.

Endothelial cell dysfunction in cardiac disease: driver or consequence?

The vascular endothelium is a multifunctional cellular system which directly influences blood components and cells within the vessel wall in a given tissue. Importantly, this cellular interface undergoes critical phenotypic changes in response to various biochemical and hemodynamic stimuli, driving several developmental and pathophysiological processes. Multiple studies have indicated a central role of the endothelium in the initiation, progression, and clinical outcomes of cardiac disease. In this review we synthesize the current understanding of endothelial function and dysfunction as mediators of the cardiomyocyte phenotype in the setting of distinct cardiac pathologies; outline existing in vivo and in vitro models where key features of endothelial cell dysfunction can be recapitulated; and discuss future directions for development of endothelium-targeted therapeutics for cardiac diseases with limited existing treatment options.

Initial Tumor Necrosis Factor-Alpha and Endothelial Activation Are Associated with Hemorrhagic Complications during Extracorporeal Membrane Oxygenation

Studies on inflammatory markers, endothelial activation, and bleeding during extracorporeal membrane oxygenation (ECMO) are lacking. Blood samples were prospectively collected after ECMO initiation from 150 adult patients who underwent ECMO for respiratory failure between 2018 and 2021. After excluding patients who died early (within 48 h), 132 patients were finally included. Their tumor necrosis factor-alpha (TNF-α), tissue factor (TF), soluble thrombomodulin (sTM), and E-selectin levels were measured. A Cox proportional hazards regression model was used to estimate the hazard ratio for hemorrhagic complications during ECMO. The 132 patients were divided into hemorrhagic (n = 23, H group) and non-complication (n = 109, N group) groups. The sequential organ failure assessment score, hemoglobin level, and ECMO type were included as covariates in all Cox models to exclude the effects of clinical factors. After adjusting for these factors, initial TNF-α, TF, sTM, E-selectin, and activated protein C levels were significantly associated with hemorrhagic complications (all p < 0.001). TNF-α, TF, and E-selectin better predicted hemorrhagic complications than the model that included only the aforementioned clinical factors (clinical factors only (area under the curve [AUC]: 0.804), reference; TNF-α (AUC: 0.914); TF (AUC: 0.915); E-selectin (AUC: 0.869)). Conclusions: TNF-α levels were significantly predictive of hemorrhagic complications during ECMO.

High risk oral contraceptive hormones do not directly enhance endothelial cell procoagulant activity in vitro

BACKGROUND

Oral contraceptive (OC) use increases venous thromboembolism risk 2-5-fold. Procoagulant changes can be detected in plasma from OC users even without thrombosis, but cellular mechanisms that provoke thrombosis have not been identified. Endothelial cell (EC) dysfunction is thought to initiate venous thromboembolism. It is unknown whether OC hormones provoke aberrant procoagulant activity in ECs.

OBJECTIVE

Characterize the effect of high-risk OC hormones (ethinyl estradiol [EE] and drospirenone) on EC procoagulant activity and the potential interplay with nuclear estrogen receptors ERα and ERβ and inflammatory processes.

METHODS

Human umbilical vein and dermal microvascular ECs (HUVEC and HDMVEC, respectively) were treated with EE and/or drospirenone. Genes encoding the estrogen receptors ERα and ERβ (ESR1 and ESR2, respectively) were overexpressed in HUVEC and HDMVEC via lentiviral vectors. EC gene expression was assessed by RT-qPCR. The ability of ECs to support thrombin generation and fibrin formation was measured by calibrated automated thrombography and spectrophotometry, respectively.

RESULTS

Neither EE nor drospirenone, alone or together, changed expression of genes encoding anti- or procoagulant proteins (TFPI, THBD, F3), integrins (ITGAV, ITGB3), or fibrinolytic mediators (SERPINE1, PLAT). EE and/or drospirenone did not increase EC-supported thrombin generation or fibrin formation, either. Our analyses indicated a subset of individuals express ESR1 and ESR2 transcripts in human aortic ECs. However, overexpression of ESR1 and/or ESR2 in HUVEC and HDMVEC did not facilitate the ability of OC-treated ECs to support procoagulant activity, even in the presence of a pro-inflammatory stimulus.

CONCLUSIONS

The OC hormones EE and drospirenone do not directly enhance thrombin generation potential of primary ECs in vitro.

NDRG1 Signaling Is Essential for Endothelial Inflammation and Vascular Remodeling

BACKGROUND

NDRG-1 (N-myc downstream-regulated gene 1) is a member of NDRG family that plays essential roles in cell differentiation, proliferation, and stress responses. Although the expression of NDRG1 is regulated by fluid shear stress, its roles in vascular biology remain poorly understood. The purpose of the study is to determine the functional significance of NDRG1 in vascular inflammation and remodeling.

METHODS AND RESULTS

By using quantitative polymerase chain reaction, western blot, and immunohistochemistry, we demonstrate that the expression of NDRG1 is markedly increased in cytokine-stimulated endothelial cells and in human and mouse atherosclerotic lesions. To determine the role of NDRG1 in endothelial activation, we performed loss-of-function studies using NDRG1 short hairpin RNA. Our results demonstrate that NDRG1 knockdown by lentivirus bearing NDRG1 short hairpin RNA substantially attenuates both IL-1β (interleukin-1β) and TNF-α (tumor necrosis factor-α)-induced expression of cytokines/chemokines and adhesion molecules. Intriguingly, inhibition of NDRG1 also significantly attenuates the expression of procoagulant molecules, such as PAI-1 (plasminogen activator inhibitor type 1) and TF (tissue factor), and increases the expression of TM (thrombomodulin) and t-PA (tissue-type plasminogen activator), thus exerting potent antithrombotic effects in endothelial cells. Mechanistically, we showed that NDRG1 interacts with orphan Nur77 (nuclear receptor) and functionally inhibits the transcriptional activity of Nur77 and NF-κB (nuclear factor Kappa B) in endothelial cells. Moreover, in NDRG1 knockdown cells, both cytokine-induced mitogen-activated protein kinase activation, c-Jun phosphorylation, and AP-1 (activator protein 1) transcriptional activity are substantially inhibited. Neointima and atherosclerosis formation induced by carotid artery ligation and arterial thrombosis were markedly attenuated in endothelial cell-specific NDRG1 knockout mice compared with their wild-type littermates.

CONCLUSIONS

Our results for the first time identify NDRG1 as a critical mediator implicated in regulating endothelial inflammation, thrombotic responses, and vascular remodeling, and suggest that inhibition of NDRG1 may represent a novel therapeutic strategy for inflammatory vascular diseases, such as atherothrombosis and restenosis.

Simplex cerebral cavernous malformations with MAP3K3 mutation have distinct clinical characteristics

Objectives

To investigate the clinical characteristics of cerebral cavernous malformations (CCMs) with MAP3K3 somatic mutation.

Methods

We performed a retrospective review of our CCMs database between May 2017 and December 2019. The patients with simplex CCMs identified to harbor a MAP3K3 or CCM gene somatic mutation were included. Clinical characteristics were recorded. Univariate and multivariate logistic analyses were used to assess the risk factors associated with hemorrhage events of CCMs. To explore the underlying mechanism, we transfected MEKK3-I441M-overexpressing and CCM2-knockdown lentiviruses into human umbilical vein endothelial cells (HUVECs) and investigated thrombomodulin (TM) and tight junctions (TJs) protein expression by western blotting and immunofluorescence. Finally, immunohistochemistry was used to validate TM and TJs protein expression in surgical samples.

Results

Fifty simplex CCMs patients were included, comprising 38 MAP3K3 mutations and 12 CCM gene mutations. Nine (23.7%) patients with MAP3K3 mutations and 11(91.7%) patients with CCM gene mutations exhibited overt hemorrhage, respectively. Multivariate logistic analyses revealed that MAP3K3 mutation was associated with a lower risk of hemorrhage events. In the vitro experiments, ZO-1 expression was not reduced in MEKK3-I441M-overexpressing HUVECs compared with wild type, whereas it was significantly decreased in CCM2-knockdown HUVECs compared with control. In the MEKK3-I441M-overexpressing HUVECs, TM expression was increased, and the NF-κB pathway was significantly activated. After treatment with an NF-κB signaling inhibitor, TM expression was further upregulated. Meanwhile, TM expression was increased, but the NF-κB pathway was not activated in CCM2-knockdown HUVECs. Accordingly, immunohistochemistry showed that ZO-1 expression in the MAP3K3-mutant samples was significantly higher than that in the CCM-mutant samples. TM expression in the MAP3K3-mutant lesions was significantly lower than that in the CCM-mutant samples.

Conclusion

Simplex CCMs with MAP3K3 mutation occasionally present with overt hemorrhage, which is associated with the biological function of MAP3K3 mutation.

Unlocking the Untapped Potential of Endothelial Kinase and Phosphatase Involvement in Sepsis for Drug Treatment Design

Sepsis is a devastating clinical condition that can lead to multiple organ failure and death. Despite advancements in our understanding of molecular mechanisms underlying sepsis and sepsis-associated multiple organ failure, no effective therapeutic treatment to directly counteract it has yet been established. The endothelium is considered to play an important role in sepsis. This review highlights a number of signal transduction pathways involved in endothelial inflammatory activation and dysregulated endothelial barrier function in response to sepsis conditions. Within these pathways – NF-κB, Rac1/RhoA GTPases, AP-1, APC/S1P, Angpt/Tie2, and VEGF/VEGFR2 – we focus on the role of kinases and phosphatases as potential druggable targets for therapeutic intervention. Animal studies and clinical trials that have been conducted for this purpose are discussed, highlighting reasons why they might not have resulted in the expected outcomes, and which lessons can be learned from this. Lastly, opportunities and challenges that sepsis and sepsis-associated multiple organ failure research are currently facing are presented, including recommendations on improved experimental design to increase the translational power of preclinical research to the clinic.

Aberrant stromal tissue factor localisation and mycolactone-driven vascular dysfunction, exacerbated by IL-1β, are linked to fibrin formation in Buruli ulcer lesions

Buruli ulcer (BU) is a neglected tropical disease caused by subcutaneous infection with Mycobacterium ulcerans and its exotoxin mycolactone. BU displays coagulative necrosis and widespread fibrin deposition in affected skin tissues. Despite this, the role of the vasculature in BU pathogenesis remains almost completely unexplored. We hypothesise that fibrin-driven ischemia can be an ‘indirect’ route to mycolactone-dependent tissue necrosis by a mechanism involving vascular dysfunction. Here, we tracked >900 vessels within contiguous tissue sections from eight BU patient biopsies. Our aim was to evaluate their vascular and coagulation biomarker phenotype and explore potential links to fibrin deposition. We also integrated this with our understanding of mycolactone’s mechanism of action at Sec61 and its impact on proteins involved in maintaining normal vascular function. Our findings showed that endothelial cell dysfunction is common in skin tissue adjacent to necrotic regions. There was little evidence of primary haemostasis, perhaps due to mycolactone-dependent depletion of endothelial von Willebrand factor. Instead, fibrin staining appeared to be linked to the extrinsic pathway activator, tissue factor (TF). There was significantly greater than expected fibrin staining around vessels that had TF staining within the stroma, and this correlated with the distance it extended from the vessel basement membrane. TF-induced fibrin deposition in these locations would require plasma proteins outside of vessels, therefore we investigated whether mycolactone could increase vascular permeability in vitro. This was indeed the case, and leakage was further exacerbated by IL-1β. Mycolactone caused the loss of endothelial adherens and tight junctions by the depletion of VE-cadherin, TIE-1, TIE-2 and JAM-C; all Sec61-dependent proteins. Taken together, our findings suggest that both vascular and lymphatic vessels in BU lesions become “leaky” during infection, due to the unique action of mycolactone, allowing TF-containing structures and plasma proteins into skin tissue, ultimately leading to local coagulopathy and tissue ischemia.

To date, the debilitating skin disease Buruli ulcer remains a public health concern and financial burden in low or middle-income countries, especially in tropical regions. Late diagnosis is frequent in remote areas, perhaps due to the painlessness of the disease. Hence patients often present with large, destructive opened ulcers leading to delayed wound closure or even lifelong disability. The infectious agent produces a toxin called mycolactone that drives the disease. We previously found evidence that the vascular system is disrupted by mycolactone in these lesions, and now we have further explored potential explanations for these findings by looking at the expression of vascular markers in BU. In a detailed analysis of patient skin punch biopsies, we identified distinct expression patterns of certain proteins and found that tissue factor, which initiates the so-called extrinsic pathway of blood clotting, is particularly important. Mycolactone is able to disrupt the barrier function of the endothelium, further aggravating the diseased phenotype, which may explain how clotting factors access the tissue. Altogether, such localised hypercoagulation in Buruli ulcer skin lesions may contribute to the development of the lesion.

Stable expression of the human thrombomodulin transgene in pig endothelial cells is associated with a reduction in the inflammatory response

BACKGROUND

Xenotransplantation is associated with an inflammatory response. The proinflammatory cytokine, TNF-α, downregulates the expression of thrombomodulin (TBM), and induces coagulation dysfunction. Although human (h) TBM-transgenic pigs (p) have been developed to reduce coagulation dysfunction, the effect of TNF-α on the expression of hTBM and its functional activity has not been fully investigated. The aims of this study were to investigate (i) whether the expression of hTBM on pig (p) cells is down-regulated during TNF-α stimulation, and (ii) whether cells from hTBM pigs regulate the inflammatory response.

METHODS

TNF-α-producing T, B, and natural killer cells in blood from baboons with pig heart or kidney xenografts were investigated by flow cytometry. TNF-α staining in the grafts was detected by immunohistochemistry. Aortic endothelial cells (AECs) from GTKO/CD46 and GTKO/CD46/hTBM pigs were stimulated by hTNF-α, and the expression of the inflammatory/coagulation regulatory protein, TBM, was investigated.

RESULTS

After pig organ xenotransplantation, there was a trend to increases in TNF-α-producing T and natural killer cells in the blood of baboons. In vitro observations demonstrated that after hTNF-α stimulation, there was a significant reduction in the expression of endogenous pTBM on pAECs, and a significant increase in the expression of inflammatory molecules. Blocking of NF-κB signaling significantly up-regulated pTBM expression, and suppressed the inflammatory response induced by hTNF-α in pAECs. Whereas the expression of pTBM mRNA was significantly reduced by hTNF-α stimulation, hTBM expression on the GTKO/CD46/hTBM pAECs was not affected. Furthermore, after hTNF-α stimulation, there was significant suppression of expression of inflammatory molecules on GTKO/CD46/hTBM pAECs compared to GTKO/CD46 pAECs.

CONCLUSIONS

The stable expression of hTBM in pig cells may locally regulate the inflammatory response. This will help suppress the inflammatory response and prevent coagulation dysregulation after xenotransplantation.

A high-fat diet delays plasmin generation in a thrombomodulin-dependent manner in mice

Obesity is a prevalent prothrombotic risk factor marked by enhanced fibrin formation and suppressed fibrinolysis. Fibrin both promotes thrombotic events and drives obesity pathophysiology, but a lack of essential analytical tools has left fibrinolytic mechanisms affected by obesity poorly defined. Using a plasmin-specific fluorogenic substrate, we developed a plasmin generation (PG) assay for mouse plasma that is sensitive to tissue plasminogen activator, α2-antiplasmin, active plasminogen activator inhibitor (PAI-1), and fibrin formation, but not fibrin crosslinking. Compared with plasmas from mice fed a control diet, plasmas from mice fed a high-fat diet (HFD) showed delayed PG and reduced PG velocity. Concurrent to impaired PG, HFD also enhanced thrombin generation (TG). The collective impact of abnormal TG and PG in HFD-fed mice produced normal fibrin formation kinetics but delayed fibrinolysis. Functional and proteomic analyses determined that delayed PG in HFD-fed mice was not due to altered levels of plasminogen, α2-antiplasmin, or fibrinogen. Changes in PG were also not explained by elevated PAI-1 because active PAI-1 concentrations required to inhibit the PG assay were 100-fold higher than circulating concentrations in mice. HFD-fed mice had increased circulating thrombomodulin, and inhibiting thrombomodulin or thrombin-activatable fibrinolysis inhibitor (TAFI) normalized PG, revealing a thrombomodulin- and TAFI-dependent antifibrinolytic mechanism. Integrating kinetic parameters to calculate the metric of TG/PG ratio revealed a quantifiable net shift toward a prothrombotic phenotype in HFD-fed mice. Integrating TG and PG measurements may define a prothrombotic risk factor in diet-induced obesity.

Acute purpura fulminans-a rare cause of skin necrosis: A single-institution clinicopathological experience

BACKGROUND

Purpura fulminans, an uncommon syndrome of intravascular thrombosis with hemorrhagic infarction of the skin, is often accompanied by disseminated intravascular coagulation (DIC) and multi-organ failure, and may ultimately lead to death.

METHODS

Herein, we document 13 skin biopsies from 11 adult patients with the clinical diagnosis of sepsis and confirmed histopathologic diagnosis of intravascular thrombosis and/or DIC, compatible with acute infectious purpura fulminans (AIPF). Detailed history and clinical examination were performed, and the lesions were correlated with histopathologic findings. Any underlying medical disease was taken into consideration.

RESULTS

There were 5 males and 6 females with lower extremity or peri-incisional purpuric skin lesions. The most important comorbidities identified were a history of surgical procedure or neoplasm, although 4 patients had no relevant underlying history. Most skin biopsies revealed focal epidermal ischemia or necrosis and 3 showed full-thickness epidermal necrosis. In the underlying dermis, there were fibrin thrombi in superficial and deep blood vessels with acute inflammation. Changes of an inflammatory destructive vasculitis were identified in 5 cases. No bacteria or fungi were identified on histopathology.

CONCLUSIONS

AIPF is a rapidly-progressing medical emergency which may be identified by histopathology in culture-negative cases. Biopsies may show neutrophilic infiltrate without infective organisms.

Low Vitamin D Serum Level Is Associated with HDL-C Dyslipidemia and Increased Serum Thrombomodulin Levels of Insulin-Resistant Individuals

BACKGROUND

Insulin-resistant individuals are known to have dyslipidemia and are predicted to be at high risk of cardiovascular events. Vitamin D deficiency was shown to be associated with dyslipidemia; however, the type of dyslipidemia associated with vitamin D deficiency in insulin-resistant individuals is not determined. Furthermore, there is evidence linking insulin resistance with low-grade inflammation suggesting levels of pro-inflammatory cytokines to be increased in insulin-resistant states.

OBJECTIVE

This study was performed to evaluate the impact of vitamin D deficiency, defined as serum level of 25(OH)D below 20 ng/mL, on lipid profile and inflammatory markers such as interleukin (IL-6) and IL-8, as well as soluble thrombomodulin (TM) in the serum of insulin-resistant individuals.

METHODS

A total of 4114 individuals had simultaneous serum 25(OH)D, insulin, and lipid panel testing during 2013 as part of the United Arab Emirates National Diabetes and Lifestyle (UAEDIAB) study. Multivariate logistic regression analysis was used to assess the association between serum level of 25(OH)D and lipid profile in insulin-sensitive versus -resistant individuals. The lipid panel was stratified into high total cholesterol (TC: >6.2 mmol/L), high low-density lipoprotein-cholesterol (LDL-C: >2.59 mmol/L), high triglycerides (TG: >2.3 mmol/L), and low high-density lipoprotein-cholesterol (HDL-C: <1.55 mmol/L) dyslipidemia. Furthermore, the immunomodulatory and vasculoprotective effects of 25(OH)D were assessed by measuring the levels of IL-6, IL-8, and soluble TM in serum using ELISA.

RESULTS

More than half of the 4114 individuals were insulin resistant (n=2760, 67%) and around one-fifth of them were vitamin D-deficient (n=796, 19%). After adjusting for age, gender, body mass index, smoking, ethnicity, and educational level, the only dyslipidemia associated with vitamin D-deficient-insulin-resistant individuals (OR 2.09 [95]; P=0.009) was lower HDL-C. Furthermore, deficient 25(OH)D individuals with low HDL-C levels had higher circulatory IL-6 and IL-8 levels, and higher serum soluble TM compared to individuals with sufficient 25(OH)D and normal lipid profiles (median, IL-6 pg/mL 0.82 vs 1.71, P=0.001; median, IL-8 pg/mL 51.31 vs 145.6, P=0.003; and median, soluble TM ng/mL 5.19 vs 7.38, P<0.0001; in sufficient vs deficient groups, respectively).

CONCLUSION

The results of our study showed that in insulin-resistant individuals, vitamin D deficiency status is associated with HDL-C dyslipidemia and higher serum inflammatory and endothelial damage markers.

The transcription factor ERG regulates a low shear stress-induced anti-thrombotic pathway in the microvasculature

Endothelial cells actively maintain an anti-thrombotic environment; loss of this protective function may lead to thrombosis and systemic coagulopathy. The transcription factor ERG is essential to maintain endothelial homeostasis. Here, we show that inducible endothelial ERG deletion (ErgiEC-KO) in mice is associated with spontaneous thrombosis, hemorrhages and systemic coagulopathy. We find that ERG drives transcription of the anticoagulant thrombomodulin (TM), as shown by reporter assays and chromatin immunoprecipitation. TM expression is regulated by shear stress (SS) via Krüppel-like factor 2 (KLF2). In vitro, ERG regulates TM expression under low SS conditions, by facilitating KLF2 binding to the TM promoter. However, ERG is dispensable for TM expression in high SS conditions. In ErgiEC-KO mice, TM expression is decreased in liver and lung microvasculature exposed to low SS but not in blood vessels exposed to high SS. Our study identifies an endogenous, vascular bed-specific anticoagulant pathway in microvasculature exposed to low SS.

Altered fibrin clot properties in advanced lung cancer: strong impact of cigarette smoking

BACKGROUND

Dense fibrin networks resistant to lysis have been reported in patients at high risk of thromboembolism. Little is known about fibrin clot properties in cancer. We investigated fibrin clot properties and their determinants in patients with inoperable lung cancer.

METHODS

We enrolled 150 patients with advanced lung cancer prior to therapy and 90 control subjects matched by age, sex, cardiovascular disease, and diabetes. Plasma clot permeability (K_s), turbidimetric analysis of clot formation, clot lysis time (CLT), microparticle-associated tissue factor (MP-TF) activity, thrombin generation, and serum cotinine levels were determined.

RESULTS

Lung cancer patients, compared with controls, formed at a faster rate (- 8.1% lag phase) denser plasma fibrin networks (- 27.2% K_s) that displayed impaired lysis (+ 26.5% CLT), along with 19.5% higher MP-TF activity and 100% higher peak thrombin generated, also after adjustment for potential confounders. Cotinine levels were associated with fibrin maximum absorbance (r = 0.20, p = 0.016) and K_s (r = - 0.50, p < 0.0001) in cancer patients. On multivariate regression analysis, an increase in cotinine levels was a predictor of low K_s (the lower quartile, < 5.8 × 10^-9 cm²; odds ratio = 1.21 per 10 ng/ml, 95% confidence interval 1.02-1.46), but not CLT.

CONCLUSION

Advanced lung cancer is associated with the prothrombotic plasma clot phenotype largely driven by smoking.

Myricetin attenuates LPS-induced inflammation in RAW 264.7 macrophages and mouse models

Aim: Acute lung injury is a common clinical syndrome associated with significant morbidity. Myricetin has been demonstrated to inhibit inflammation in a variety of diseases. In this study, we aimed to investigate the protective effects of myricetin on inflammation in lipopolysaccharide-stimulated RAW 264.7 cells and lipopolysaccharide-induced lung injury model. Results/methodology: In this study, we detected the anti-inflammatory effects of myricetin by ELISA, RT-PCR and Western blot, respectively. Myricetin significantly inhibited the production of the proinflammatory cytokines in vitro and in vivo. It exerted an anti-inflammatory effect through suppressing the NF-κB p65 and AKT activation in NF-κB pathway and JNK, p-ERK and p38 in MAPK signaling pathway. Conclusion: Myricetin alleviated acute lung injury by inhibiting macrophage activation, and inhibited inflammation in vitro and in vivo. It may be a potential therapeutic candidate for the prevention of inflammatory diseases.

Lipopolysaccharide Downregulates Kruppel-Like Factor 2 (KLF2) via Inducing DNMT1-Mediated Hypermethylation in Endothelial Cells

KLF2 plays a protective role in antiinflammation and endothelial function, and can be regulated by promoter methylation alteration. Lipopolysaccharide (LPS) is a mediator of inflammatory responses, which causes epigenetic change of certain genes in host cells. We thus aimed to determine whether LPS could control the KLF2 expression by inducing methylation in promoter region. DNA methylation of 16 CpG sites within KLF2 promoter region was detected by bisulfite sequencing PCR. Results showed that methylation at 12 CpG sites were significantly increased in HUVECs after exposure to LPS among the total 16 sites, and the average level was increased by 57%. The KLF2 expressions assessed by reverse transcription quantitative real-time PCR and Western blot were significantly downregulated compared that without LPS simulation. Moreover, both messenger RNA and protein levels of KLF2 in HUVEC co-treated with LPS and DNA methyltransferase (DNMT) 1 small interfering RNA were dramatically higher than that treated with LPS only. Similar result was obtained when the cells were incubated in combination with LPS and 5-aza-2'-deoxycytidine (AZA), suggesting that the reduction of KLF2 expression induced by LPS can be reversed by DNMT1 inhibition. Finally, the presence of AZA changed the expression of genes that depends on KLF2 in LPS-stimulated HUVECs, which downregulated the E-selectin and VCAM and increased the eNOS and thrombomodulin expression. Our data demonstrated that LPS exposure resulted in hypermethylation in KLF2 promoter in HUVECs, which subsequently led to downregulation of the KLF2 expression. The study suggested that epigenetic alteration is involved in LPS-induced inflammatory response and provided a new insight into atherogenesis.

Effects of alloantibodies to human leukocyte antigen on endothelial expression and serum levels of thrombomodulin

Essentials The effect of alloantibodies on the endothelial expression of thrombomodulin is unknown. Thrombomodulin was quantified in stimulated endothelial cells and measured in serum samples. Anti-human leukocyte antigen (HLA) I vs. II antibodies have different effects on thrombomodulin. Anti-HLA II antibodies may promote a prothrombotic state and contribute to microangiopathy.

SUMMARY

Rationale Thrombomodulin (TBM) is an anticoagulant and anti-inflammatory transmembrane protein expressed on endothelial cells. Donor-specific alloantibodies, particularly those against human leukocyte antigen (HLA) class II, are associated with microvascular endothelial damage in solid allografts. Objective Our aim was to characterize the effects of anti-HLA antibodies on endothelial expression of TBM, and in particular, the differential effects of anti-HLA class I compared with those of anti-HLA class II. Methods We used human glomerular microvascular endothelial cells to examine TBM expression on anti-HLA-treated cells, and we tested sera from transplant recipients for soluble TBM. Results We found that whereas membrane TBM expression increased in a dose-dependent manner in the presence of anti-HLA class I antibodies, treatment with anti-HLA class II led to minimal TBM expression on the endothelial surface but to a cytosolic accumulation. Platelet adhesion studies confirmed the functional impact of anti-HLA class II. Quantitative densitometry of the membrane lysates further suggested that anti-HLA class II impairs TBM glycosylation. Furthermore, we found a significant association between the presence of circulating anti-HLA class II antibodies in transplant recipients and low serum levels of TBM. Conclusion These results indicate that ligation of anti-HLA class I and II antibodies produces different effects on the endothelial expression of TBM and on serum levels of TBM in transplant recipients. Anti-HLA class II antibodies may be associated with a prothrombotic state, which could explain the higher occurrence of microangiopathic lesions in the allograft and the poor outcomes observed in patients with these alloantibodies.

Carbon monoxide-releasing molecule-2 suppresses thrombomodulin and endothelial protein C receptor expression of human umbilical vein endothelial cells induced by lipopolysaccharide in vitro

OBJECTIVE

The aim of this study was to observe the counter-effect of carbon monoxide-releasing molecule-2 (CORM-2) on lipopolysaccharide (LPS)-suppressed thrombomodulin (TM) and endothelial protein C receptor (EPCR) expressions from human umbilical vein endothelial cell (HUVEC), and to reveal its mechanisms.

METHODS

HUVECs were divided into 5 treatment groups, wherein reagents were added simultaneously. TM and EPCR proteins of the cells and the culture medium levels of soluble TM, soluble EPCR, and matrix metalloproteinase-2 (MMP-2) were detected after administration, whereas mRNA levels of TM and EPCR, as well as nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activity among groups, were also evaluated.

RESULTS

No significant difference was observed in any indicator between CORM-2 and sham groups. Addition of LPS produced drastic increase in MMP-2 expression, NF-κB activity, shedding of TM and EPCR (into the culture medium), as well as remarkable decrease in both mRNA and protein expressions of TM and EPCR, and cell viability. LPS + CORM-2 treatment significantly reduced the increase in MMP-2, NF-κB activity, and TM/EPCR shedding, whereas maintained both mRNA and protein levels of TM and EPCR, and preserved cell viability.

CONCLUSIONS

CORM-2 protects HUVEC from LPS-induced injury, by way of suppressing NF-κB activity, which downregulates TM and EPCR mRNAs. It also decreases MMP-2 expression and prevents the shedding of TM and EPCR from the surface of endothelial cells, so as to preserve their protective effect.

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.

Myeloid thrombomodulin lectin-like domain inhibits osteoclastogenesis and inflammatory bone loss

Osteoclastogenesis is an essential process during bone metabolism which can also be promoted by inflammatory signals. Thrombomodulin (TM), a transmembrane glycoprotein, exerts anti-inflammatory activities such as neutralization of proinflammatory high-mobility group box 1 (HMGB1) through TM lectin-like domain. This study aimed to identify the role of myeloid TM (i.e., endogenous TM expression on the myeloid lineage) in osteoclastogenesis and inflammatory bone loss. Using human peripheral blood mononuclear cells and mouse bone marrow-derived macrophages, we observed that the protein levels of TM were dramatically reduced as these cells differentiated into osteoclasts. In addition, osteoclastogenesis and extracellular HMGB1 accumulation were enhanced in primary cultured monocytes from myeloid-specific TM-deficient mice (LysMcre/TM^flox/flox) and from TM lectin-like domain deleted mice (TM^LeD/LeD) compared with their respective controls. Micro-computerized tomography scans showed that ovariectomy-induced bone loss was more pronounced in TM^LeD/LeD mice compared with controls. Finally, the inhibiting effects of recombinant TM lectin-like domain (rTMD1) on bone resorption in vitro, and bone loss in both the ovariectomized model and collagen antibody-induced arthritis model has been detected. These findings suggested that the myeloid TM lectin-like domain may inhibit osteoclastogenesis by reducing HMGB1 signaling, and rTMD1 may hold therapeutic potential for inflammatory bone loss.

Thrombomodulin Expression in Tissues From Dogs With Systemic Inflammatory Disease

Thrombomodulin (TM) is a membrane glycoprotein expressed on endothelial cells, which plays a major role in the protein C anticoagulation pathway. In people with inflammation, TM expression can be down-regulated on endothelial cells and a soluble form released into circulation, resulting in increased risk of thrombosis and disseminated intravascular coagulation. TM is present in dogs; however, there has been minimal investigation of its expression in canine tissues, and the effects of inflammation on TM expression in canine tissues have not been investigated. The objective of this study was to evaluate endothelial TM expression in tissues from dogs with systemic inflammatory diseases. A retrospective evaluation of tissue samples of lung, spleen, and liver from dogs with and without systemic inflammatory diseases was performed using immunohistochemistry (IHC) and a modified manual IHC scoring system. TM expression was significantly reduced in all examined tissues in dogs diagnosed with septic peritonitis or acute pancreatitis.

[Multiple myeloma and venous thrombosis. Which thromboprophylaxis should be given?]

Multiple myeloma is a malignant plasma cells dyscrasia that mainly affects patients older than 65 years. These patients are at a higher risk for venous thromboembolism (VTE) because of cancer status, intrinsic risk factors, and exposure to prothrombotic therapies. The risk for VTE appears higher during the first months of myeloma treatment and decreases over time. Exposure to immunomodulatory drugs (IMIDs) such as thalidomide or lenalidomide in association with high doses of dexamethasone or anthracyclin-based chemotherapy is associated with a four-fold increased risk for VTE. Low-dose aspirin, preventive-dose of low molecular weight heparin (LMWH) or vitamin K antagonists were tested for primary prevention of VTE in myeloma patients receiving chemotherapy. The International Myeloma Working Group (IMWG) suggests stratifying VTE risk to decide which patients should receive VTE prevention. Then, the IMWG suggests giving low-dose aspirin to low VTE risk patients and LMWH or vitamin K antagonists to patients at high risk for VTE. For daily practice, it seems reasonable to start preventive doses of LMWH for 3 to 6 months in ambulatory myeloma patients receiving combined therapy with IMID and in all myeloma patients admitted to hospital.

Antithrombotic Effects of Nur77 and Nor1 Are Mediated Through Upregulating Thrombomodulin Expression in Endothelial Cells

OBJECTIVE

Thrombomodulin is highly expressed on the lumenal surface of vascular endothelial cells (ECs) and possesses potent anticoagulant, antifibrinolytic, and anti-inflammatory activities in the vessel wall. However, the regulation of thrombomodulin expression in ECs remains largely unknown.

APPROACHES AND RESULTS

In this study, we characterized nuclear receptor 4A family as a novel regulator of thrombomodulin expression in vascular ECs. We demonstrated that both nuclear receptors 4A, Nur77 and Nor1, robustly increase thrombomodulin mRNA and protein levels in human vascular ECs and in mouse liver tissues after adenovirus-mediated transduction of Nur77 and Nor1 cDNAs. Moreover, Nur77 deficiency and knockdown of Nur77 and Nor1 expression markedly attenuated the basal and vascular endothelial growth factor165-stimulated thrombomodulin expression. Mechanistically, we found that Nur77 and Nor1 increase thrombomodulin expression by acting through 2 different mechanisms. We showed that Nur77 barely affects thrombomodulin promoter activity, but significantly increases thrombomodulin mRNA stability, whereas Nor1 enhances thrombomodulin expression mainly through induction of Kruppel-like factors 2 and 4 in vascular ECs. Furthermore, we demonstrated that both Nur77 and Nor1 significantly increase protein C activity and inhibit tumor necrosis factor α-induced prothrombotic effects in human ECs. Deficiency of Nur77 increases susceptibility to arterial thrombosis, whereas enhanced expression of Nur77 and Nor1 protects mice from arterial thrombus formation.

CONCLUSIONS

Our results identified nuclear receptors 4A as novel regulators of thrombomodulin expression and function in vascular ECs and provided a proof-of-concept demonstration that targeted increasing expression of Nur77 and Nor1 in the vascular endothelium might represent a novel therapeutic approach for the treatment of thrombotic disorders.

Vascular endothelial cell Toll-like receptor pathways in sepsis

The endothelium forms a vast network that dynamically regulates vascular barrier function, coagulation pathways and vasomotor tone. Microvascular endothelial cells are uniquely situated to play key roles during infection and injury, owing to their widespread distribution throughout the body and their constant interaction with circulating blood. While not viewed as classical immune cells, endothelial cells express innate immune receptors, including the Toll-like receptors (TLRs), which activate intracellular inflammatory pathways mediated through NF-κB and the MAP kinases. TLR agonists, including LPS and bacterial lipopeptides, directly upregulate microvascular endothelial cell expression of inflammatory mediators. Intriguingly, TLR activation also modulates microvascular endothelial cell permeability and the expression of coagulation pathway intermediaries. Microvascular thrombi have been hypothesized to trap microorganisms thereby limiting the spread of infection. However, dysregulated activation of endothelial inflammatory pathways is also believed to lead to coagulopathy and increased vascular permeability, which together promote sepsis-induced organ failure. This article reviews vascular endothelial cell innate immune pathways mediated through the TLRs as they pertain to sepsis, highlighting links between TLRs and coagulation and permeability pathways, and their role in healthy and pathologic responses to infection and sepsis.

Recent advances in disseminated intravascular coagulation: endothelial cells and fibrinolysis in sepsis-induced DIC

Endothelial cells are highly active, sensing and responding to signals from extracellular environments. They act as gatekeepers, mediating the recruitment and extravasation of proinflammatory leukocytes to the sites of tissue damage or infection. Endothelial cells participate in fibrinolysis by secreting tissue-type plasminogen activator, which converts plasminogen to active enzyme plasmin through constitutive and regulated pathways. Fibrinolysis systems and inflammation are tightly linked, as both responses are major host defense systems against both healing processes of tissue repair as well as pathogenic microorganisms. Endothelial cell dysfunction is one of the early signs of systemic inflammation, and it is a trigger of multiple organ failure in sepsis. The marked increase in plasminogen activator inhibitor-1 level causes fibrinolytic shutdown in endotoxemia or sepsis and is one of the most important predictors of multiple organ dysfunction during sepsis-induced disseminated intravascular coagulation (DIC). Leukocytes exhibit the first-line response to microorganisms. Leukocyte-derived elastase degrades cross-linked fibrin to yield molecular species distinct from those generated by plasmin. The alternative systems for fibrinolysis that interact with the plasminogen activator-plasmin systems may play crucial roles in the lysis of fibrin clots in sepsis-induced DIC.

Endothelial cell dysfunction in viral hemorrhage and edema

The endothelium maintains a vascular barrier by controlling platelet and immune cell interactions, capillary tone and interendothelial cell (EC) adherence. Here we suggest common elements in play during viral infection of the endothelium that alter normal EC functions and contribute to lethal hemorrhagic or edematous diseases. In viral reservoir hosts, infection of capillaries and lymphatic vessels may direct immunotolerance without disease, but in the absence of these cognate interactions they direct the delayed onset of human disease characterized by thrombocytopenia and vascular leakage in a severe endothelial dysfunction syndrome. Here we present insight into EC controls of hemostasis, immune response and capillary permeability that are altered by viral infection of the endothelium.

IKKβ regulates endothelial thrombomodulin in a Klf2-dependent manner

BACKGROUND

Endothelial thrombomodulin (TM) is critically involved in anticoagulation, anti-inflammation, cytoprotection and normal fetal development. Tumor necrosis factor alpha (TNFα) suppresses TM expression.

OBJECTIVE

TNFα has been shown to down-regulate TM partly via activation of nuclear factor kappa B (NF-κB). However, because the TM promoter lacks an NF-κB binding site, the direct involvement of NF-κB has been controversial. We investigated the role of the upstream regulatory serine kinase, inhibitory kappa-B kinase-β (IKKβ), in TM expression and function with or without TNFα treatment.

METHODS

Inhibition of IKKβ was achieved by specific chemical inhibitors, siRNA or shRNA. TM expression was assessed by qRT-PCR, Western blot, flow cytometry, luciferase reporter assay and chromatin immune-precipitation (ChIP) assay. TM function was estimated by generation of activated protein C (APC). NF-κB activation was determined by immunocytochemistry.

RESULTS AND CONCLUSIONS

IKKβ inhibition increased TM expression and function, and attenuated TNFα-mediated TM down-regulation. In contrast, inhibition of downstream canonical NF-κB protein family members p50 and p65 (RelA) failed to up-regulate TM expression and did not affect IKKβ inhibition-mediated TM over-expression. However, knockdown of cRel and RelB, family members of the canonical and non-canonical NF-κB pathway, respectively, resulted in TM over-expression. IKKβ inhibition caused over-expression, increased promoter activity and enhanced binding of Krüppel-like factor 2 (Klf2) to the TM promoter, which positively regulates TM expression. Finally, knockdown of Klf2 completely attenuated IKKβ inhibition-mediated TM up-regulation. We conclude that IKKβ regulates TM in a Klf2-dependent manner.

Thrombomodulin expression regulates tumorigenesis in bladder cancer

Background

The identification of potential tumor markers will help improve therapeutic planning and patient management. Thrombomodulin (TM) is a sensitive urothelial marker. TM was reported to be one of the endogenous anti-metastatic factors and has diagnostic and prognostic values for the progression of carcinoma. In the present study, we examine the role of TM in bladder cancer.

Methods

We studied the role of TM in tumor behavior and related signaling pathways in vitro using the human bladder cancer cell lines HT1376, HT1197, J82 and T24, and in vivo using animal models. We also selected clinical specimens from 100 patients with bladder cancer for immunohistochemical staining to evaluate the predictive capacity of TM in tumor invasiveness.

Results

The data revealed that positive immunoreactivity for TM was inversely correlated with clinical stage and DNA methyltransferase 1 immunoreactivity. Decreased TM expression could predict the aggressive tumor growth and advanced clinical stage in bladder cancer. When TM was inhibited, tumor growth rate and invasion ability were augmented in vitro and in vivo. The underlying changes included increased cell proliferation, enhanced epithelial-mesenchymal transition (EMT) and angiogenesis. Moreover, inhibition of NF-κB activation significantly increased TM expression and attenuated tumor aggressiveness in bladder cancer.

Conclusions

TM plays an important role in bladder cancer tumor aggressiveness in vitro and in vivo and is a clinically significant predictor that may represent a suitable therapeutic target for bladder cancer.

Influence of proinflammatory stimuli on the expression of vascular ribonuclease 1 in endothelial cells

Extracellular RNA (eRNA) released under injury or pathological conditions has been identified as a yet unrecognized vascular alarm signal to induce procoagulant, permeability-promoting, and proinflammatory activities. eRNA-induced functions were largely prevented by administration of RNase1 as a natural blood vessel-protective antagonist of eRNA. The aim of this study was to investigate the inflammatory regulation of endothelial cell RNase1, which is partly stored in Weibel-Palade bodies of these cells. Long-term treatment of human umbilical vein endothelial cells (HUVECs) with inflammatory agents like tumor necrosis factor α (TNF-α) or interleukin 1β (IL-1β), but not with eRNA, significantly decreased the release (34 ± 5%; 34 ± 7% of control) as well as the cellular expression (19.5 ± 5%; 33 ± 8% of control) of RNase1. Down-regulation of RNase1 by TNF-α stimulation or RNase1 siRNA knockdown increased the permeability of HUVEC monolayers, demonstrated by dearrangement of VE-cadherins at cell-cell borders. Mechanistically, cytokine-induced decrease of RNase1 expression did not involve the nuclear factor κ B (NFκB) signaling pathway but epigenic modifications. Since inhibition of histone deacetylases resulted in recovery of RNase1 expression and secretion after cytokine treatment, an acetylation-dependent process of RNase1 regulation is proposed. These results indicate that cytokine-mediated down-regulation of RNase1 in endothelial cells may aggravate eRNA-induced inflammatory activities and thereby disturbs the vascular homeostasis of the extracellular RNA/RNase system.

UVB irradiation regulates ERK1/2- and p53-dependent thrombomodulin expression in human keratinocytes

Thrombomodulin (TM) is highly expressed in endothelial cells and acts as a natural anticoagulation factor to maintain circulation homeostasis. TM is an interesting molecule with many physiological functions, including anti-inflammation, anti-thrombosis, and carcinogenesis inhibition. TM can also be detected on the spinous layer of epidermal keratinocytes. However, the role of epidermal TM is still under investigation. In this study, we investigated keratinocyte TM expression and regulation in response to sub-cytotoxic ultraviolet B (UVB) irradiation. Oxidative stress was assessed with DCF and the results revealed that UVB irradiation significantly and dose-dependently augmented reactive oxygen species (ROS) production in HaCaT cells. In addition, low-dose UVB irradiation decreased TM mRNA and protein levels. Blocking ROS production and ERK activation prevented UVB-induced TM down-regulation. The nuclear p53 accumulation and TM promoter binding was observed within 3 h after UVB exposure. Small interfering RNA-mediated p53 knockdown disrupted the UVB-mediated TM protein down-regulation. Our study demonstrates that UVB irradiation results in ROS accumulation and ERK activation, which causes the nuclear p53 accumulation and TM promoter binding to inhibit TM expression. This study provides novel evidence demonstrating that p53 serves as a key regulator of keratinocyte TM expression.

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.

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.

Correlation of circulating dehydroepiandrosterone with activated protein C generation and carotid intima-media thickness in male patients with type 2 diabetes

AIMS

Dehydroepiandrosterone exerts a protective effect against cardiovascular diseases. However, the relationship of dehydroepiandrosterone with the anticoagulant factor activated protein C, generated by the thrombin-thrombomodulin complex on vascular endothelial cells, remains unknown. This study aimed at studying the relationship between dehydroepiandrosterone and activated protein C generation in patients with Type 2 diabetes.

METHODS

Sixty-two male patients with Type 2 diabetes were enrolled in this study. Data obtained from 40 healthy male subjects were used as controls. The plasma levels of dehydroepiandrosterone, the activated protein C-protein C inhibitor complex, high-sensitivity C-reactive protein and monocyte chemoattractant protein-1 were measured by enzyme immunoassays. Carotid intima-media thickness was measured by ultrasonography.

RESULTS

The plasma levels of dehydroepiandrosterone (5.15 ± 2.81 vs. 3.76 ± 2.16 ng/ml; P < 0.005) and the activated protein C-protein C inhibitor complex (1.90 ± 1.07 vs. 1.02 ± 0.51 ng/ml; P < 0.001) were significantly lower in patients with diabetes than in normal subjects. Univariate analysis showed a significant correlation of the plasma level of dehydroepiandrosterone with that of the activated protein C-protein C inhibitor complex (r = 0.48, P < 0.001), high-sensitivity C-reactive protein (r = -0.30, P < 0.05) and with the mean intima-media thickness (r = -0.28, P < 0.05) in patients with diabetes. Stepwise multiple regression analysis showed that the plasma level of dehydroepiandrosterone is significantly correlated with the plasma levels of the activated protein C-protein C inhibitor complex (F = 18.06) and high-sensitivity C-reactive protein (F = 4.94). There was no correlation between the plasma levels of dehydroepiandrosterone and monocyte chemoattractant protein-1.

CONCLUSIONS

These results suggest that lower circulating levels of dehydroepiandrosterone are associated with decreased activated protein C generation and higher intima-media thickness in patients with Type 2 diabetes.

Targeting recombinant thrombomodulin fusion protein to red blood cells provides multifaceted thromboprophylaxis

Thrombin generates fibrin and activates platelets and endothelium, causing thrombosis and inflammation. Endothelial thrombomodulin (TM) changes thrombin's substrate specificity toward cleavage of plasma protein C into activated protein C (APC), which opposes its thrombotic and inflammatory activities. Endogenous TM activity is suppressed in pathologic conditions, and antithrombotic interventions involving soluble TM are limited by rapid blood clearance. To overcome this problem, we fused TM with a single chain fragment (scFv) of an antibody targeted to red blood cells. scFv/TM catalyzes thrombin-mediated generation of activated protein C and binds to circulating RBCs without apparent damage, thereby prolonging its circulation time and bioavailability orders of magnitude compared with soluble TM. In animal models, a single dose of scFv/TM, but not soluble TM, prevents platelet activation and vascular occlusion by clots. Thus, scFv/TM serves as a prodrug and provides thromboprophylaxis at low doses (0.15 mg/kg) via multifaceted mechanisms inhibiting platelets and 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.

Regulation of thrombomodulin expression in prostate cancer cells

In carcinomas the expression of thrombomodulin (TM) is inversely correlated with tumour progression and metastasis. In the present study a decreased TM expression in human prostate cancer cell lines, LNCaP, DU-145, and PC-3, in relation to normal prostate epithelial cells (PrEC) is shown. Sequencing and methylation-specific high resolution melting (MS-HRM) analyses of bisulphite-modified genomic DNA indicates a high degree of methylation in DU-145 cells and lesser degrees in PC-3 and LNCaP cells, whereas in PrEC the TM promoter is unmethylated. The expression of TM is negatively regulated by NF-κB- and GSK3-β-dependent signalling pathways and positively regulated by retinoic acid and transcription factor Sp1 in PrEC, LNCaP and PC-3 cells, but not in DU-145 cells. However, exposure of DU-145 cells to the demethylating agent, 5-aza-2'deoxycytidine, restores the TM expression and its control by retinoic acid, NF-κB- and GSK3-β-dependent signalling. In conclusion, the study establishes that in prostate cancer cell lines relative to PrEC the TM is down-regulated and that the TM promoter is hypermethylated, which seems to be responsible for the down-regulation and failed regulation of TM expression in DU-145 cells.

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.

Constitutive induction of pro-inflammatory and chemotactic cytokines in cystathionine beta-synthase deficient homocystinuria

Cystathionine beta-synthase (CBS) deficient homocystinuria (HCU) is an inherited metabolic defect that if untreated, typically results in cognitive impairment, connective tissue disturbances, atherosclerosis and thromboembolic disease. In recent years, chronic inappropriate expression of the inflammatory response has emerged as a major driving force of both thrombosis and atherosclerotic lesion development. We report here a characterization of the abnormalities in cytokine expression induced in both a mouse model of HCU and human subjects with the disease in the presence and absence of homocysteine lowering therapy. HCU mice exhibited highly significant induction of the pro-inflammatory cytokines Il-1alpha, Il-1beta and TNF-alpha. Similarly, in untreated/poorly compliant human subjects with HCU we observed constitutive induction of multiple pro-inflammatory cytokines (IL-1alpha, IL-6, TNF-alpha, Il-17 and IL-12(p70)) and chemotactic chemokines (fractalkine, MIP-1alpha and MIP-1beta) compared to normal controls. These HCU patients also exhibited significant induction of IL-9, TGF-alpha and G-CSF. The expression levels of anti-inflammatory cytokines were unaffected in both HCU mice and human subjects with the disease. In the human subjects, homocysteine lowering therapy was associated with either normalization or significant reduction of all of the pro-inflammatory cytokines and chemokines investigated. We conclude that HCU is a disease of chronic inflammation and that aberrant cytokine expression has the potential to contribute to multiple aspects of pathogenesis. Our findings indicate that anti-inflammatory strategies could serve as a useful adjuvant therapy for this disease.

Low venous thromboembolic risk with bortezomib in multiple myeloma and potential protective effect with thalidomide/lenalidomide-based therapy: review of data from phase 3 trials and studies of novel combination regimens

Patients with multiple myeloma (MM) are at elevated risk of venous thromboembolism (VTE), specifically deep vein thrombosis (DVT) and pulmonary embolism (PE). VTE risk in MM is increased by various patient- and disease-related factors. The type of anti-MM therapy represents a key factor, with a substantially elevated VTE risk in patients treated with the immunomodulatory drugs (IMiDs) thalidomide or lenalidomide in combination with dexamethasone and/or chemotherapy; VTE risk with lenalidomide-dexamethasone is further increased with concomitant erythropoietin. By contrast, treatment with the proteasome inhibitor bortezomib, alone or in combination, does not increase VTE risk; rates of DVT/PE do not appear affected by the use of erythropoiesis-stimulating agents. Bortezomib has shown antihemostatic effects in patients with relapsed or refractory MM, which supports that it exerts antithrombotic actions and thus potentially provides a protective effect in combination with regimens with an elevated VTE risk. Herein, we review data from phase 3 trials of bortezomib- and/or IMiD-based therapy in frontline MM, together with other studies of novel combination regimens. Despite the confounding effect of variable VTE prophylaxis, bortezomib-based regimens were typically associated with DVT/PE rates of ≤5%, similar to those seen with melphalan-prednisone and dexamethasone, whereas IMiD-based bortezomib-free regimens were generally associated with higher rates. Direct comparisons of regimens of thrombogenic potential with or without bortezomib demonstrated lower VTE risk with bortezomib. Between-study comparisons of VTE risk support these findings. Taken together, these data confirm the low VTE risk associated with bortezomib and support a potential protective effect of bortezomib in combination with IMiD-based regimens associated with elevated VTE risk.