TFPI from erythroblasts drives heme production in central macrophages promoting erythropoiesis in polycythemia.

Bleeding and thrombosis are known as common complications of polycythemia for a long time. However, the role of coagulation system in erythropoiesis is unclear. Here, we discover that an anticoagulant protein tissue factor pathway inhibitor (TFPI) plays an essential role in erythropoiesis via the control of heme biosynthesis in central macrophages. TFPI levels are elevated in erythroblasts of human erythroblastic islands with JAK2V617F mutation and hypoxia condition. Erythroid lineage-specific knockout TFPI results in impaired erythropoiesis through decreasing ferrochelatase expression and heme biosynthesis in central macrophages. Mechanistically, the TFPI interacts with thrombomodulin to promote the downstream ERK1/2-GATA1 signaling pathway to induce heme biosynthesis in central macrophages. Furthermore, TFPI blockade impairs human erythropoiesis in vitro, and normalizes the erythroid compartment in mice with polycythemia. These results show that erythroblast-derived TFPI plays an important role in the regulation of erythropoiesis and reveal an interplay between erythroblasts and central macrophages.

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.

Thrombomodulin Switches Signaling and Protease-Activated Receptor 1 Cleavage Specificity of Thrombin.

BACKGROUND: Cleavage of the extracellular domain of PAR1 (protease-activated receptor 1) by thrombin at Arg41 and by APC (activated protein C) at Arg46 initiates paradoxical cytopathic and cytoprotective signaling in endothelial cells. In the latter case, the ligand-dependent coreceptor signaling by EPCR (endothelial protein C receptor) is required for the protective PAR1 signaling by APC. Here, we investigated the role of thrombomodulin in determining the specificity of PAR1 signaling by thrombin. METHODS: We prepared a PAR1 knockout (PAR1-/-) EA.hy926 endothelial cell line by CRISPR/Cas9 and transduced PAR1-/- cells with lentivirus vectors expressing PAR1 mutants in which either Arg41 or Arg46 was replaced with an Ala. Furthermore, human embryonic kidney 293 cells were transfected with wild-type or mutant PAR1 cleavage reporter constructs carrying N-terminal Nluc (NanoLuc luciferase) and C-terminal enhanced yellow fluorescent protein tags. RESULTS: Characterization of transfected cells in signaling and receptor cleavage assays revealed that, upon interaction with thrombomodulin, thrombin cleaves Arg46 to elicit cytoprotective effects by a ß-arrestin-2 biased signaling mechanism. Analysis of functional data and cleavage rates indicated that thrombin-thrombomodulin cleaves Arg46>10-fold faster than APC. Upon interaction with thrombin, the cytoplasmic domain of thrombomodulin recruited both ß-arrestin-1 and -2 to the plasma membrane. Thus, the thrombin cleavage of Arg41 was also cytoprotective in thrombomodulin-expressing cells by ß-arrestin-1-biased signaling. APC in the absence of EPCR cleaved Arg41 to initiate disruptive signaling responses like thrombin. CONCLUSIONS: These results suggest that coreceptor signaling by thrombomodulin and EPCR determines the PAR1 cleavage and signaling specificity of thrombin and APC, respectively.

Thrombomodulin Regulates PTEN/AKT Signaling Axis in Endothelial Cells.

BACKGROUND: We recently demonstrated that deletion of thrombomodulin gene from endothelial cells results in upregulation of proinflammatory phenotype. In this study, we investigated the molecular basis for the altered phenotype in thrombomodulin-deficient (TM-/-) cells. METHODS: Different constructs containing deletions or mutations in the cytoplasmic domain of thrombomodulin were prepared and introduced to TM-/- cells. The phenotype of cells expressing different derivatives of thrombomodulin and tissue samples of thrombomodulin-knockout mice were analyzed for expression of distinct regulatory genes in established signaling assays. RESULTS: The phosphatase and tensin homolog were phosphorylated and its recruitment to the plasma membrane was impaired in TM-/- cells, leading to hyperactivation of AKT (protein kinase B) and phosphorylation-dependent nuclear exclusion of the transcription factor, forkhead box O1. The proliferative/migratory properties of TM-/- cells were enhanced, and cells exhibited hypersensitivity to stimulation by angiopoietin 1 and vascular endothelial growth factor. Reexpression of wild-type thrombomodulin in TM-/- cells normalized the cellular phenotype; however, thrombomodulin lacking its cytoplasmic domain failed to restore the normal phenotype in TM-/- cells. Increased basal permeability and loss of VE-cadherin were restored to normal levels by reexpression of wild-type thrombomodulin but not by a thrombomodulin construct lacking its cytoplasmic domain. A thrombomodulin cytoplasmic domain deletion mutant containing 3-membrane-proximal Arg-Lys-Lys residues restored the barrier-permeability function of TM-/- cells. Enhanced phosphatase and tensin homolog phosphorylation and activation of AKT and mTORC1 (mammalian target of rapamycin complex 1) were also observed in the liver of thrombomodulin-KO mice. CONCLUSIONS: These results suggest that the cytoplasmic domain of thrombomodulin interacts with the actin cytoskeleton and plays a crucial role in regulation of phosphatase and tensin homolog/AKT signaling in endothelial cells.

GroEL of Porphyromonas gingivalis-induced microRNAs accelerate tumor neovascularization by downregulating thrombomodulin expression in endothelial progenitor cells.

We found that GroEL in Porphyromonas gingivalis accelerated tumor growth and increased mortality in tumor-bearing mice; GroEL promoted proangiogenic function, which may be the reason for promoting tumor growth. To understand the regulatory mechanisms by which GroEL increases the proangiogenic function of endothelial progenitor cells (EPCs), we explored in this study. In EPCs, MTT assay, wound-healing assay, and tube formation assay were performed to analyze its activity. Western blot and immunoprecipitation were used to study the protein expression along with next-generation sequencing for miRNA expression. Finally, a murine tumorigenesis animal model was used to confirm the results of in vitro. The results indicated that thrombomodulin (TM) direct interacts with PI3 K/Akt to inhibit the activation of signaling pathways. When the expression of TM is decreased by GroEL stimulation, molecules in the PI3 K/Akt signaling axis are released and activated, resulting in increased migration and tube formation of EPCs. In addition, GroEL inhibits TM mRNA expression by activating miR-1248, miR-1291, and miR-5701. Losing the functions of miR-1248, miR-1291, and miR-5701 can effectively alleviate the GroEL-induced decrease in TM protein levels and inhibit the proangiogenic abilities of EPCs. These results were also confirmed in animal experiments. In conclusion, the intracellular domain of the TM of EPCs plays a negative regulatory role in the proangiogenic capabilities of EPCs, mainly through direct interaction between TM and PI3 K/Akt to inhibit the activation of signaling pathways. The effects of GroEL on tumor growth can be reduced by inhibiting the proangiogenic properties of EPCs through the inhibition of the expression of specific miRNAs.

Whole blood thrombin generation shows a significant hypocoagulable state in patients with decompensated cirrhosis.

BACKGROUND: Patients with cirrhosis have a normal to increased thrombin generation (TG) capacity in platelet-poor plasma (PPP). By reflecting the contribution of all circulating blood cells, whole blood (WB) TG may allow a more physiological assessment of coagulation. OBJECTIVES: We compared WB-TG vs PPP-TG in patients with cirrhosis. METHODS: Assessment of coagulation included routine tests, factor VIII, natural anticoagulants, PPP-TG, and WB-TG. TG assays were performed with and without thrombomodulin. Twenty-five healthy subjects were included as controls. RESULTS: We included 108 patients (Child-Pugh A/B/C, 44/24/40). Compared with controls, patients had significantly lower platelet count, longer international normalized ratio, higher FVIII, and lower levels of protein C/S and antithrombin. Regarding thrombomodulin-modified TG assays, in compensated cirrhosis, both PPP-TG and WB-TG indicated an increased TG capacity, as reflected by an endogenous thrombin potential (ETP) significantly higher than controls. In contrast, in decompensated cirrhosis, PPP-TG indicated a hypercoagulable state with increased ETP, higher peak height, and shorter time-to-peak than controls, whereas WB-TG revealed a progressive impairment of TG kinetics and total capacity, ultimately resulting in a profound hypocoagulable state in patients with Child-Pugh C cirrhosis (ie, significant prolongation of lag time and time-to-peak with reduction of both ETP and peak height). In decompensated patients, bacterial infections and severity of anemia were associated with a further reduction of both ETP and peak height. CONCLUSION: Compensated cirrhosis is associated with an increased TG capacity. In decompensated cirrhosis, contrary to PPP-TG, which indicates hypercoagulability, WB-TG shows a significant hypocoagulable state. The clinical value of these findings deserves further investigation.

Acute respiratory distress syndrome, acute kidney injury, and mortality after trauma are associated with increased circulation of syndecan-1, soluble thrombomodulin, and receptor for advanced glycation end products.

BACKGROUND: Disruption of the vascular endothelium and endothelial glycocalyx (EG) has been described after severe trauma. Plasma has been suggested to restore microvascular integrity by preservation and repair of the EG. We sought to evaluate whether plasma administered in a 1:1:1 ratio was associated with less endothelial marker circulation than a 1:1:2 ratio. METHODS: This is a secondary analysis of the PROPPR trial, which investigated post-traumatic resuscitation with platelets, plasma, and red blood cells in a 1:1:1 ratio compared with a 1:1:2 ratio. Syndecan-1, soluble thrombomodulin (sTM), and receptor for advanced glycation end products (RAGE) were quantified for each treatment group on admission and at 2 hours, 4 hours, 6 hours, 12 hours, 24 hours, 48 hours, and 72 hours. Patients were excluded if they did not survive longer than 3 hours or had data from fewer than two time points. RESULTS: Three hundred eight patients in the 1:1:1 group and 291 in the 1:1:2 group were analyzed. There were no statistically significant differences in syndecan-1, sTM, or RAGE between treatment groups at any time point ( p > 0.05). Patients who developed acute respiratory distress syndrome, acute kidney injury, and death had significantly elevated biomarker expression at most time points when compared with patients who did not develop these sequelae ( p < 0.05). CONCLUSION: Administration of FFP in a 1:1:1 ratio does not consistently affect circulation of endothelial biomarkers following significant trauma when compared with a 1:1:2 ratio. The development of post-traumatic ARDS, AKI, and death was associated with increased endothelial biomarker circulation. LEVEL OF EVIDENCE: Therapeutic/Care Management; Level III.

Effect of 5% albumin on endothelial glycocalyx degradation during off-pump coronary artery bypass.

PURPOSE: The integrity of the endothelial glycocalyx (EG), a critical player in vascular homeostasis, reportedly influences the outcomes of critically ill patients. We investigated the effect of 5% albumin, which preserved EG integrity in preclinical studies, vs balanced crystalloid solution on EG degradation in patients undergoing off-pump coronary surgery. METHODS: Patients were randomized to receive either 5% albumin (N = 51) or balanced crystalloid solution (Plasma-Lyte [Baxter Incorporated, Seoul, Republic of Korea]; N = 53) for intravenous volume replacement during surgery (double-blinded). The primary outcome was plasma syndecan-1 concentration, a marker of EG degradation, measured after anesthetic induction (baseline), completion of grafting, and sternal closure. Secondary outcomes were atrial natriuretic peptide (ANP), tumour necrosis factor (TNF)-α, soluble thrombomodulin, and perioperative fluid balance. RESULTS: The mean (standard deviation) fluid requirements were 833 (270) mL and 1,323 (492) mL in the albumin and Plasma-Lyte group, respectively (mean difference, -489 mL; 95% confidence interval [CI], -643 to -335; P < 0.001). Plasma syndecan-1 concentration increased after completion of grafting (median difference, 116 ng·mL-1; 95% CI, 67 to 184; P < 0.001) and sternal closure (median difference, 57 ng·mL-1; 95% CI, 36 to 80; P < 0.001) compared with those at baseline, without any intergroup differences. Atrial natriuretic peptide, TNF-α, and soluble thrombomodulin concentrations were similar between the two groups. The amount of chest tube drainage was greater in the albumin group than that in the Plasma-Lyte group (median difference, 190 mL; 95% CI, 18 to 276; P = 0.03). CONCLUSION: Off-pump coronary surgery was associated with significant EG degradation. Yet, intraoperative fluid therapy with 5% albumin could not ameliorate EG degradation when compared with balanced crystalloid solution. TRIAL REGISTRATION: ClinicalTrials.gov (NCT03699462); first posted 9 October 2018.

RéSUMé: OBJECTIF: L'intégrité du glycocalyx endothélial (GE), un acteur essentiel de l'homéostasie vasculaire, influencerait le devenir des patient·es gravement malades. Nous avons étudié l'effet de l'albumine à 5 %, qui préservait l'intégrité du GE dans les études précliniques, par rapport à une solution cristalloïde équilibrée sur la dégradation du GE chez les patient·es bénéficiant d'une chirurgie coronarienne à cœur battant. MéTHODE: Les patient·es ont été randomisé·es à recevoir soit de l'albumine à 5 % (N = 51) ou de la solution cristalloïde équilibrée (Plasma-Lyte [Baxter Incorporated, Séoul, République de Corée]; N = 53) pour le remplacement du volume intraveineux pendant la chirurgie (en double aveugle). Le critère d'évaluation principal était la concentration plasmatique de syndécan-1, un marqueur de la dégradation du GE, mesurée après l'induction de l'anesthésie (ligne de base), la fin de la greffe et la fermeture du sternum. Les critères d'évaluation secondaires étaient le peptide natriurétique auriculaire (ANP), le facteur de nécrose tumorale (TNF)-α, la thrombomoduline soluble et le bilan hydrique périopératoire. RéSULTATS: Les besoins liquidiens moyens (écart type) étaient de 833 (270) mL et 1323 (492) mL dans les groupes albumine et Plasma-Lyte, respectivement (différence moyenne, −489 mL; intervalle de confiance [IC] à 95 %, −643 à −335; P < 0,001). La concentration plasmatique de syndécan-1 a augmenté après la fin de la greffe (différence médiane, 116 ng·mL−1; IC 95 %, 67 à 184; P < 0,001) et la fermeture du sternum (différence médiane, 57 ng·mL−1; IC 95 %, 36 à 80; P < 0,001) par rapport aux concentrations au départ, sans différences intergroupe. Les concentrations de peptide natriurétique auriculaire, de TNF-α et de thrombomoduline soluble étaient similaires entre les deux groupes. La quantité de drainage du drain thoracique était plus importante dans le groupe albumine que dans le groupe Plasma-Lyte (différence médiane, 190 mL; IC 95 %, 18 à 276; P = 0,03). CONCLUSION: La chirurgie coronarienne à cœur battant a été associée à une dégradation significative du glycocalyx endothélial. Pourtant, la fluidothérapie peropératoire avec 5 % d'albumine n'a pas pu améliorer la dégradation du GE par rapport à une solution cristalloïde équilibrée. ENREGISTREMENT DE L'éTUDE: ClinicalTrials.gov (NCT03699462); enregistrée pour la première fois le 9 octobre 2018.

Chondrocyte Thrombomodulin Protects against Osteoarthritis.

Osteoarthritis (OA) is a prevalent form of arthritis that affects over 32.5 million adults worldwide, causing significant cartilage damage and disability. Unfortunately, there are currently no effective treatments for OA, highlighting the need for novel therapeutic approaches. Thrombomodulin (TM), a glycoprotein expressed by chondrocytes and other cell types, has an unknown role in OA. Here, we investigated the function of TM in chondrocytes and OA using various methods, including recombinant TM (rTM), transgenic mice lacking the TM lectin-like domain (TMLeD/LeD), and a microRNA (miRNA) antagomir that increased TM expression. Results showed that chondrocyte-expressed TM and soluble TM [sTM, like recombinant TM domain 1 to 3 (rTMD123)] enhanced cell growth and migration, blocked interleukin-1ß (IL-1ß)-mediated signaling and protected against knee function and bone integrity loss in an anterior cruciate ligament transection (ACLT)-induced mouse model of OA. Conversely, TMLeD/LeD mice exhibited accelerated knee function loss, while treatment with rTMD123 protected against cartilage loss even one-week post-surgery. The administration of an miRNA antagomir (miR-up-TM) also increased TM expression and protected against cartilage damage in the OA model. These findings suggested that chondrocyte TM plays a crucial role in counteracting OA, and miR-up-TM may represent a promising therapeutic approach to protect against cartilage-related disorders.

COMBINATION THERAPY WITH A SENSE OLIGONUCLEOTIDE TO INDUCIBLE NITRIC OXIDE SYNTHASE MRNA AND HUMAN SOLUBLE THROMBOMODULIN IMPROVES SURVIVAL OF SEPSIS MODEL RATS AFTER PARTIAL HEPATECTOMY.

ABSTRACT: Sepsis after a major hepatectomy is a critical problem. In septic shock, the inflammatory mediator, nitric oxide (NO), is overproduced in hepatocytes and macrophages. The natural antisense (AS) transcripts, non-coding RNAs, are transcribed from a gene that encodes inducible nitric oxide synthase (iNOS). iNOS AS transcripts interact with and stabilize iNOS mRNAs. A single-stranded "sense oligonucleotide" (designated as SO1) corresponding to the iNOS mRNA sequence inhibits mRNA-AS transcript interactions and reduces iNOS mRNA levels in rat hepatocytes. In contrast, recombinant human soluble thrombomodulin (rTM) treats disseminated intravascular coagulopathy by suppressing coagulation, inflammation, and apoptosis. In this study, the combination therapy of SO1 and a low dose of rTM was evaluated for hepatoprotection in a rat septic shock model after partial hepatectomy. Rats underwent 70% hepatectomy, followed by intravenous (i.v.) injection of lipopolysaccharide (LPS) after 48 h. SO1 was injected (i.v.) simultaneously with LPS, whereas rTM was injected (i.v.) 1 h before LPS injection. Similarly to our previous report, SO1 increased survival after LPS injection. When rTM, which has different mechanisms of action, was combined with SO1, it did not interfere with the effect of SO1 and showed a significant increase in survival compared with LPS alone treatment. In serum, the combined treatment decreased NO levels. In the liver, the combined treatment inhibited iNOS mRNA and protein expression. A decreased iNOS AS transcript expression by the combined treatment was also observed. The combined treatment decreased mRNA expression of the inflammatory and pro-apoptotic genes while increasing that of the anti-apoptotic gene. Furthermore, the combined treatment reduced the number of myeloperoxidase-positive cells. These results suggested that the combination of SO1 and rTM has therapeutic potential for sepsis.

Targeting senescent hepatocytes using the thrombomodulin-PAR1 inhibitor vorapaxar ameliorates NAFLD progression.

BACKGROUND AND AIMS: Senescent hepatocytes accumulate in parallel with fibrosis progression during NASH. The mechanisms that enable progressive expansion of nonreplicating cell populations and the significance of that process in determining NASH outcomes are unclear. Senescing cells upregulate thrombomodulin-protease-activated receptor-1 (THBD-PAR1) signaling to remain viable. Vorapaxar blocks the activity of that pathway. We used vorapaxar to determine if and how THBD-PAR1 signaling promotes fibrosis progression in NASH. APPROACH AND RESULTS: We evaluated the THBD-PAR1 pathway in liver biopsies from patients with NAFLD. Chow-fed mice were treated with viral vectors to overexpress p16 in hepatocytes and induce replicative senescence. Effects on the THBD-PAR1 axis and regenerative capacity were assessed; the transcriptome of p16-overexpressing hepatocytes was characterized, and we examined how conditioned medium from senescent but viable (dubbed "undead") hepatocytes reprograms HSCs. Mouse models of NASH caused by genetic obesity or Western diet/CCl 4 were treated with vorapaxar to determine effects on hepatocyte senescence and liver damage. Inducing senescence upregulates the THBD-PAR1 signaling axis in hepatocytes and induces their expression of fibrogenic factors, including hedgehog ligands. Hepatocyte THBD-PAR1 signaling increases in NAFLD and supports sustained hepatocyte senescence that limits effective liver regeneration and promotes maladaptive repair. Inhibiting PAR1 signaling with vorapaxar interrupts this process, reduces the burden of 'undead' senescent cells, and safely improves NASH and fibrosis despite ongoing lipotoxic stress. CONCLUSION: The THBD-PAR1 signaling axis is a novel therapeutic target for NASH because blocking this pathway prevents accumulation of senescing but viable hepatocytes that generate factors that promote maladaptive liver repair.

DNA methylation changes and increased mRNA expression of coagulation proteins, factor V and thrombomodulin in Fuchs endothelial corneal dystrophy.

Late-onset Fuchs endothelial corneal dystrophy (FECD) is a disease affecting the corneal endothelium (CE), associated with a cytosine-thymine-guanine repeat expansion at the CTG18.1 locus in the transcription factor 4 (TCF4) gene. It is unknown whether CTG18.1 expansions affect global methylation including TCF4 gene in CE or whether global CE methylation changes at advanced age. Using genome-wide DNA methylation array, we investigated methylation in CE from FECD patients with CTG18.1 expansions and studied the methylation in healthy CE at different ages. The most revealing DNA methylation findings were analyzed by gene expression and protein analysis. 3488 CpGs had significantly altered methylation pattern in FECD though no substantial changes were found in TCF4. The most hypermethylated site was in a predicted promoter of aquaporin 1 (AQP1) gene, and the most hypomethylated site was in a predicted promoter of coagulation factor V (F5 for gene, FV for protein). In FECD, AQP1 mRNA expression was variable, while F5 gene expression showed a ~ 23-fold increase. FV protein was present in both healthy and affected CE. Further gene expression analysis of coagulation factors interacting with FV revealed a ~ 34-fold increase of thrombomodulin (THBD). THBD protein was detected only in CE from FECD patients. Additionally, we observed an age-dependent hypomethylation in elderly healthy CE.Thus, tissue-specific genome-wide and gene-specific methylation changes associated with altered gene expression were discovered in FECD. TCF4 pathological methylation in FECD because of CTG18.1 expansion was ruled out.

Investigation of cofactor activities of endothelial microparticle-thrombomodulin with liposomal surrogate.

Thrombomodulin (TM) is a type I transmembrane glycoprotein mainly expressed on the endothelial cells, where it binds thrombin to form the thrombin-TM complex that can activate protein C and thrombin-activable fibrinolysis inhibitor (TAFI) and induce anticoagulant and anti-fibrinolytic reactions, respectively. Cell activation and injury often sheds microparticles that contain membrane TM, which circulate in biofluids like blood. However, the biological function of circulating microparticle-TM is still unknown even though it has been recognized as a biomarker of endothelial cell injury and damage. In comparison with cell membrane, different phospholipids are exposed on the microparticle surface due to cell membrane ''flip-flop'' upon cell activation and injury. Liposomes can be used as a microparticle mimetics. In this report, we prepared TM-containing liposomes with different phospholipids as surrogates of endothelial microparticle-TM and investigated their cofactor activities. We found that liposomal TM with phosphatidylethanolamine (PtEtn) showed increased protein C activation but decreased TAFI activation in comparison to liposomal TM with phosphatidylcholine (PtCho). In addition, we investigated whether protein C and TAFI compete for the thrombin/TM complex on the liposomes. We found that protein C and TAFI did not compete for the thrombin/TM complex on the liposomes with PtCho alone and with low concentration (5%) of PtEtn and phosphatidylserine (PtSer), but competed each other on the liposomes with higher concentration (10%) of PtEtn and PtSer. These results indicate that membrane lipids affect protein C and TAFI activation and microparticle-TM may have different cofactor activities in comparison to cell membrane TM.

Sex-dependent balance between thrombin and plasmin generation in the presence of thrombomodulin.

BACKGROUND: Assessing simultaneous generation of thrombin (TG) and plasmin (PG) is an approach to evaluate the balance between coagulation and fibrinolysis with sensitivity to predict endogenous thrombin and plasmin generation. The addition of thrombomodulin (TM), provides the essential component for thrombin activation of protein C and thrombin-activatable fibrinolysis inhibitor. However, the influence of sex on the balance between TG and PG with and without TM addition has not been investigated to date. OBJECTIVES: To investigate the possible sex-based differences in TG and PG in the presence and absence of TM. METHODS: Simultaneous TG and PG were measured in plasma samples obtained from 17 males and 17 females upon tissue factor and tissue plasminogen activator addition. Thrombin- and plasmin-specific fluorogenic substrates Z-Gly-Gly-Arg-AMC and Boc-Glu-Lys-Lys-AMC were used in the study. Thrombin and plasmin peak height (TPH and PPH) and production rate (TPR and PPR) values were determined. To evaluate the balance between TG and PG, the ratios between TPH and PPH (TPH/PPH) and TPR and PPR (TPR/PPR) were calculated. RESULTS AND CONCLUSIONS: TPH between males and females demonstrated significant difference regardless of TM addition. TPR demonstrated differences between males and females only upon TM addition, while PG parameters was not dependent on the sex of the donor. TM significantly lowered TPH/PPH in males, and enhanced TPR/PPR in females. Thus, TPH/PPH and TPR/PPR significantly differed between men and women. Our results indicate that TM may act differently in males and females by shifting the underlying TG/PG balance to fibrinolysis in males and to coagulation in females.

A missense mutation in lectin domain of thrombomodulin causing functional deficiency.

Thrombomodulin (TM) functions in coagulation, fibrinolysis and inflammation by its cofactor activity for protein C, thrombin-activatable fibrinolysis inhibitor (TAFI) activation and high mobility group box 1 (HMGB1) degradation induced by thrombin. It has been widely reported that mutations in TM are related to thromboembolic diseases but hardly in lectin domain. Here we report our findings about the functional deficiencies in TM caused by substitution of aspartate with tyrosine at residue 126. Three patients suffering from recurrent thromboembolic diseases were identified with this mutation and their plasma soluble TM levels were decreased. Transfected cells expressing wild-type TM or the variant and corresponding proteins were used to examine TM functions in vitro. The cofactor activity of the mutant for protein C, TAFI activation was reduced to approximately 50% and 60% respectively. Loss in anti-inflammation due to weakened HMGB1 degradation was also observed. And the study with thrombosis models of mice suggested the decreased inhibition of thrombus development of the mutant. Together the results showed deleterious changes on TM function caused by this mutation, which may explain the thrombophilia tendency of the patients. This work provided supportive evidence that mutation in lectin domain of TM might be related to thrombotic diseases and may help us better understand the physiological roles of TM.

Thrombin cleaves recombinant soluble thrombomodulin into a lectin-like domain fragment and a fragment with protein C-activating cofactor activity.

Thrombomodulin (TM) is a transmembrane protein that plays an important role in regulating the coagulation system by acting as a cofactor for thrombin in protein C activation. Additionally, TM is involved in inflammation. Previous studies have shown that soluble fragments of TM of varying sizes, which are derived from membrane-bound TM, are present in plasma and urine. Soluble fragments of TM are speculated to exhibit biological activity. Among these, a lectin-like domain fragment (TMD1) is of particular importance. Recombinant TMD1 has previously been shown to attenuate lipopolysaccharide-induced inflammation. Here, we report that thrombin cleaves recombinant soluble TM, which is used for the treatment of disseminated intravascular coagulation associated with sepsis, into TMD1 and a fragment comprising the C-terminal portion of TM (TMD23), the latter of which retains the cofactor activity for activating protein C. Our findings suggest that thrombin not only activates protein C on membrane-bound TM but may also cleave TM to generate TMD1.

Epigenetic repression of THBD transcription by BRG1 contributes to deep vein thrombosis.

BACKGROUND: Deep vein thrombosis (DVT) with its major complication, pulmonary embolism, is a global health problem. Endothelial dysfunction is involved in the pathogenesis of DVT. We have previously demonstrated that endothelial specific deletion of Brahma-related gene 1 (BRG1) ameliorates atherosclerosis and aneurysm in animal models. Whether endothelial BRG1 contributes to DVT development remains undetermined. METHODS: DVT was induced in mice by ligation of inferior vena cava. Deletion of BRG1 in endothelial cells was achieved by crossing the Cdh5-ERT-Cre mice with the Brg1loxp/loxp mice. RESULTS: Here we report that compared to the wild type mice, BRG1 conditional knockout (CKO) mice displayed substantially decreased DVT susceptibility characterized by decreased weight and size of thrombus and reduced immune infiltration. In endothelial cells, thrombomodulin (THBD) expression was significantly decreased by TNF-α stimulation, while BRG1 knockdown or inhibition recovered THBD expression. Further analysis revealed that BRG1 deficiency decreased the CpG methylation levels of the THBD promoter induced by TNF-α. Mechanistically, BRG1 directly upregulated DNMT1 expression after TNF-α treatment in endothelial cells. More importantly, administration of a small-molecule BRG1 inhibitor PFI-3 displayed potent preventive and therapeutic potentials in the DVT model. CONCLUSIONS: Our findings implicate BRG1 as an important regulator of DVT pathogenesis likely through epigenetic regulation of THBD expression in endothelial cells and provide translational proof-of-concept for targeting BRG1 in DVT intervention.

Role of the lectin-like domain of thrombomodulin in septic cardiomyopathy.

AIMS: Septic cardiomyopathy is a severe complication of sepsis and septic shock. This study aimed to evaluate the role of thrombomodulin and its lectin-like domain (LLD-TM) in the development of septic cardiomyopathy and the link between LLD-TM, HMGB-1, and toll-like receptors 2/4 (TLR 2/4) to intracellular mechanisms resulting in reduced cardiac function. MATERIALS AND METHODS: Sepsis was induced using a polymicrobial peritoneal infection model in wildtype and mice lacking the lectin-like domain of thrombomodulin (TMLeD/LeD), and severity of disease and cardiac function was compared. Cell cultures of cardiomyocytes were prepared from hearts harvested from wildtype and TMLeD/LeD mice. Cultures of neonatal cardiomyocytes were transfected with complete human thrombomodulin or human thrombomodulin deficient of LLD-TM and when TLR-2 and/or TLR-4 were blocked. All cultures were challenged with inflammatory stimuli. KEY FINDINGS: Lack of the LLD-TM results in a significant increase in severity of disease, decreased survival and impaired cardiac function in septic mice. In vivo and in vitro analyses of cardiomyocytes displayed high levels of inflammatory cytokines causing cardio-depression. In vitro results showed a strong correlation between elevated HMGB-1 levels and elevated troponin-1 levels. No connection was found between HMGB-1 and TLR-2 and/or -4 signalling pathways. Phospholamban mediated dysregulation of calcium homeostasis resulted in a general impairment after sepsis induction, but showed no connection to LLD-TM. SIGNIFICANCE: Lack of LLD-TM results in an increase in general severity of disease, decreased survival and impaired cardiac function in sepsis. TLR-2 and TLR 4 do not participate as mediating factors in the development of septic cardiomyopathy.

MiR-550a-3p restores damaged vascular smooth muscle cells by inhibiting thrombomodulin in an in vitro atherosclerosis model.

Thrombomodulin (TM) is involved in the pathological process of atherosclerosis; however, the underlying mechanism remains unclear. Oxidised low-density lipoprotein (Ox-LDL; 100 µg/mL) was used to induce human vascular smooth muscle cells (HVSMCs) into a stable atherosclerotic cell model. The expression levels of miR-550a-3p and TM were detected by real-time reverse transcription-polymerase chain reaction. Cell proliferation was estimated using CCK8 and EDU assays. Wound scratch and transwell assays were used to measure the ability of cells to invade and migrate. Propidium iodide fluorescence-activated cell sorting was used to detect apoptosis and cell cycle changes. A dual-luciferase reporter assay was performed to determine the binding of miR-550a-3p to TM. Our results suggested the successful development of a cellular atherosclerosis model. Our data revealed that TM overexpression significantly promoted the proliferation, invasion, migration, and apoptosis of HVSMCs as well as cell cycle changes. Upregulation of miR-550a-3p inhibited the growth and metastasis of HVSMCs. Furthermore, miR-550a-3p was confirmed to be a direct target of TM. Restoration of miR-550a-3p expression rescued the effects of TM overexpression. Thus, miR-550a-3p might play a role in atherosclerosis and, for the first time, normalised the function of injured vascular endothelial cells by simultaneous transfection of TM and miR-550a-3p. These results suggest that the miR-550a-3p/TM axis is a potential therapeutic target for atherosclerosis.

Biomarkers of heatstroke-induced organ injury and repair.

NEW FINDINGS: What is the topic of this review? The status and potential role of novel biological markers (biomarkers) that can help identify the patients at risk of organ injury or long-term complications following heatstroke. What advances does it highlight? Numerous biomarkers were identified related to many aspects of generalized heatstroke-induced cellular injury and tissue damage, and heatstroke-provoked cardiovascular, renal, cerebral, intestinal and skeletal muscle injury. No novel biomarkers were identified for liver or lung injury. ABSTRACT: Classic and exertional heatstroke cause acute injury and damage across numerous organ systems. Moreover, heatstroke survivors may sustain long-term neurological, cardiovascular and renal complications with a persistent risk of death. In this context, biomarkers, defined as biological samples obtained from heatstroke patients, are needed to detect early organ injury, and predict outcomes to develop novel organ preservation therapeutic strategies. This narrative review provides preliminary insights that will guide the development and future utilization of these biomarkers. To this end, we have identified numerous biomarkers of widespread heatstroke-associated cellular injury, tissue damage and repair (extracellular heat shock proteins 72 and 60, high mobility group box protein 1, histone H3, and interleukin-1α), and other organ-specific biomarkers including those related to the cardiovascular system (cardiac troponin I, endothelium-derived factors, circulation endothelial cells, adhesion molecules, thrombomodulin and von Willebrand factor antigen), the kidneys (plasma and urinary neutrophil gelatinase-associated lipocalin), the intestines (intestinal fatty acid-binding protein 2), the brain (serum S100ß and neuron-specific enolase) and skeletal muscle (creatine kinase, myoglobin). No specific biomarkers have been identified so far for liver or lung injury in heatstroke. Before translating the identified biomarkers into clinical practice, additional preclinical and clinical prospective studies are required to further understand their clinical utility, particularly for the biomarkers related to long-term post-heatstroke health outcomes.