Thrombomodulin gene mutations associated with myocardial infarction

Endothelium-Mimetic Surface Modification Improves Antithrombogenicity and Enhances Patency of Vascular Grafts in Rats and Pigs

We first identified thrombomodulin (TM) and endothelial nitric oxide (NO) synthase as key factors for the antithrombogenic function of the endothelium in human atherosclerotic carotid arteries. Then, recombinant TM and an engineered galactosidase responsible for the conversion of an exogenous NO prodrug were immobilized on the surface of the vascular grafts. Surface modification by TM and NO cooperatively enhanced the antithrombogenicity and patency of vascular grafts. Importantly, we found that the combination of TM and NO also promoted endothelialization, whereas it reduced adverse intimal hyperplasia, which is critical for the maintenance of vascular homeostasis, as confirmed in rat and pig models.

Machine learning approach combined with causal relationship inferring unlocks the shared pathomechanism between COVID-19 and acute myocardial infarction

Background

Increasing evidence suggests that people with Coronavirus Disease 2019 (COVID-19) have a much higher prevalence of Acute Myocardial Infarction (AMI) than the general population. However, the underlying mechanism is not yet comprehended. Therefore, our study aims to explore the potential secret behind this complication.

Materials and methods

The gene expression profiles of COVID-19 and AMI were acquired from the Gene Expression Omnibus (GEO) database. After identifying the differentially expressed genes (DEGs) shared by COVID-19 and AMI, we conducted a series of bioinformatics analytics to enhance our understanding of this issue.

Results

Overall, 61 common DEGs were filtered out, based on which we established a powerful diagnostic predictor through 20 mainstream machine-learning algorithms, by utilizing which we could estimate if there is any risk in a specific COVID-19 patient to develop AMI. Moreover, we explored their shared implications of immunology. Most remarkably, through the Bayesian network, we inferred the causal relationships of the essential biological processes through which the underlying mechanism of co-pathogenesis between COVID-19 and AMI was identified.

Conclusion

For the first time, the approach of causal relationship inferring was applied to analyzing shared pathomechanism between two relevant diseases, COVID-19 and AMI. Our findings showcase a novel mechanistic insight into COVID-19 and AMI, which may benefit future preventive, personalized, and precision medicine.

Graphical abstract

Markers of Hereditary Thrombophilia with Unclear Significance

Thrombophilia leads to an increased risk of venous thromboembolism. Widely accepted risk factors for thrombophilia comprise deficiencies of protein C, protein S, and antithrombin, as well as the factor V "Leiden" mutation, the prothrombin G20210A mutation, dysfibrinogenemia, and, albeit less conclusive, increased levels of factor VIII. Besides these established markers of thrombophilia, risk factors of unclear significance have been described in the literature. These inherited risk factors include deficiencies or loss-of-activity of the activity of ADAMTS13, heparin cofactor II, plasminogen, tissue factor pathway inhibitor (TFPI), thrombomodulin, protein Z (PZ), as well as PZ-dependent protease inhibitor. On the other hand, thrombophilia has been linked to the gain-of-activity, or elevated levels, of α2-antiplasmin, angiotensin-converting enzyme, coagulation factors IX (FIX) and XI (FXI), fibrinogen, homocysteine, lipoprotein(a), plasminogen activator inhibitor-1 (PAI-1), and thrombin-activatable fibrinolysis inhibitor (TAFI). With respect to the molecular interactions that may influence the thrombotic risk, more complex mechanisms have been described for endothelial protein C receptor (EPCR) and factor XIII (FXIII) Val34Leu. With focus on the risk for venous thrombosis, the present review aims to give an overview on the current knowledge on the significance of the aforementioned markers for thrombophilia screening. According to the current knowledge, there appears to be weak evidence for a potential impact of EPCR, FIX, FXI, FXIII Val34Leu, fibrinogen, homocysteine, PAI-1, PZ, TAFI, and TFPI on the thrombotic risk.

A novel homozygous variant of the thrombomodulin gene causes a hereditary bleeding disorder

We report a 19-year-old Vietnamese woman who experienced several life-threatening bleeding events, including ovarian hemorrhage. Blood analysis revealed a decreased fibrinogen level with markedly elevated fibrinogen/fibrin degradation products and D-dimer levels. Despite hemostatic surgery and administration of several medications, such as nafamostat mesylate, tranexamic acid, and unfractionated heparin, the coagulation abnormalities were not corrected, and the patient experienced repeated hemorrhagic events. We found that administration of recombinant human thrombomodulin (rhTM) remarkably improved the patient's pathophysiology. Screening and sequencing of the TM gene (THBD) revealed a previously unreported homozygous variation: c.793T>A (p.Cys265Ser). Notably, the Cys265 residue forms 1 of 3 disulfide bonds in the epidermal growth factor (EGF)-like domain 1 of TM. Transient expression experiments using COS-1 cells demonstrated markedly reduced expression of TM-Cys265Ser on the plasma membrane relative to wild-type TM. The TM-Cys265Ser mutant was intracellularly degraded, probably because of EGF-like domain 1 misfolding. The reduced expression of TM on the endothelial cell membrane may be responsible for the disseminated intravascular-coagulation-like symptoms observed in the patient. In summary, we identified a novel TM variant, c.793T>A (p.Cys265Ser). Patients homozygous for this variant may present with severe bleeding events; rhTM should be considered a possible treatment option for these patients.

Effect of gene polymorphism on bleeding complications in Chinese Han patients taking warfarin

PURPOSE

The purpose of this study was to analyse the effects of demographic factors, clinical factors, and genetic polymorphisms of related gene loci on warfarin bleeding-related complications in the Han population.

METHODS

Retrospective medical record review. The study cases were patients treated at the Fujian Medical University Union Hospital from March 2016 to February 2020, and all received regular warfarin anticoagulation treatment for at least 3 months, and were provided the initial standard dose and stable dose of warfarin.

RESULTS

Data were collected from 451 qualifying patients (47% male, 53% female). The average age of patients was 53.8 ± 12.2 years, and the average body surface area was 1.6 ± 0.18 m². There were nine major bleeding events and 141 minor bleeding events. In the univariate logistic analysis, the p-value of the four factors body weight, body surface area (BSA), amiodarone, and rs429358 was < 0.10. However, the final p-values for amiodarone and rs429358 were < 0.05 in the multifactorial logistic analysis.

CONCLUSIONS

The ApoE (rs429358) gene polymorphism influences bleeding complications in Chinese Han patients treated with warfarin. The sample size of this study was relatively small; hence an international study with a larger sample size is needed in the future.

Thrombomodulin gene polymorphism and the occurrence and prognostic value of sepsis acute kidney injury

ABSTRACT

To investigate the relationship between thrombomodulin (THBD) gene single nucleotide polymorphisms (SNPs) and susceptibility to sepsis and the occurrence and prognosis of acute kidney injury (AKI) in sepsis patients.The genotypes of THBD gene rs1962, rs3176123, and rs1042580 in 178 sepsis patients with AKI, 243 sepsis patients without AKI (No AKI), and 103 healthy controls were analyzed by direct sequencing. Enzyme-linked immunosorbent assay (ELISA) was used to detect the plasma THBD protein levels. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic value of plasma THBD levels in sepsis, AKI, and death of sepsis patients.The C allele carriers of THBD gene rs1962 were more likely to develop AKI and sepsis than the T allele carriers (OR = 1.61, 95% CI: 1.18-2.19, P < .01; OR = 2.16, 95% CI: 1.42-3.29, P < .01). The rs3176123 G allele was associated with an increased risk of AKI in sepsis patients (OR = 1.41, 95% CI: 1.06-1.88, P = .02), the G allele had a significant association with a higher risk of sepsis susceptibility (OR = 1.91, 95% CI: 1.33-2.75, P < .01). Sepsis patients of rs1042580 C allele had a lower risk of AKI than those of T allele (OR = 0.58, 95% CI: 0.37-0.91, P = .02), the C allele was related to a reduced risk of sepsis susceptibility (OR = 0.38, 95% CI: 0.26-0.55, P < .01). The THBD gene rs1962, rs3176123, and rs1042580 TGT haplotype was linked to higher risk of AKI in patients with sepsis (OR = 1.96, 95%CI: 1.14-3.38, P = .02). Sepsis patients with the THBD gene rs1962 TC + CC genotype had a higher risk of death than those with TT genotype (OR = 10.93, 95%CI: 5.05-26.96, P < .01), but there was no significant difference in the risk of death in sepsis patients with different genotypes at rs3176123 and rs1042580 (P > .05).The THBD gene rs1962, rs3176123, and rs1042580 SNPs are significantly associated with sepsis susceptibility and the risk of AKI. The rs1962 SNP is related to the risk of death in sepsis patients.

Clinical, laboratory, and genetic risk factors for thrombosis in sickle cell disease

Sickle cell disease (SCD) patients are at a four- to 100-fold increased risk for thrombosis compared with the general population, although the mechanisms and risk factors are not clear. We investigated the incidence and predictors for thrombosis in a retrospective, longitudinal cohort of 1193 pediatric and adult SCD patients treated at our institution between January 2008 and December 2017. SCD diagnosis and thrombotic complications were identified using International Classification of Diseases coding and verified through medical chart review. Clinical and laboratory data were extracted from the medical records. With a median follow-up of 6.4 years, 208 (17.4%) SCD patients experienced 352 thrombotic events (64 strokes, 288 venous thromboembolisms [VTE]). Risk factors for stroke included older age and HbSS/Sβ0-genotype and a lower hemoglobin (Hb) F% in the subset of HbSS/Sβ0-genotype patients (P < .05). VTE risk was independently associated with lower estimated glomerular filtration rate, hydroxyurea (HU) use, HbSS/Sβ0 genotype, and higher white blood cell (WBC) counts and Hb (P ≤ .03). Two thrombomodulin gene variants previously associated with thrombosis in the general African American population, THBD rs2567617 (minor allele frequency [MAF] 0.25; odds ratio [OR], 1.5; P = .049) and THBD rs1998081 (MAF, 0.24; OR, 1.5; P = .059), were associated with thrombosis in this cohort. In summary, thrombotic complications are common, and several traditional and SCD-specific risk factors are associated with thrombotic risk. Future studies integrating clinical, laboratory, and genetic risk factors may improve our understanding of thrombosis and guide intervention practices in SCD.

Does administration of eicosapentaenoic acid increase soluble thrombomodulin level in statin-treated patients with stable coronary artery disease?

Interventions targeting the serum eicosapentaenoic acid (EPA)/arachidonic acid (AA) ratio could be useful for the prevention of coronary artery disease (CAD). Few data exist regarding the effects of administration of EPA on the serum levels of soluble thrombomodulin (sTM) as a marker of endothelial damage, or on the relationship between the sTM and EPA/AA ratio in patients with CAD receiving statin treatment. We assigned stable CAD patients already receiving statin therapy to an EPA group (1800 mg/day: n = 50) or control group (n = 50). A significant increase of the sTM level was observed in the EPA group as compared to that in the control group 0.40 (0.10/0.70) FU/mL vs. 0.20 (0/0.40) FU/mL, p = 0.004 at the 6-month follow-up examination. Multivariate regression analysis after adjustments for coronary risk factors and changes of the serum lipid levels identified an increased EPA/AA ratio as an independent predictor of increased serum sTM level (β = 0.244, p = 0.02). The results suggest that an increased sTM level caused by additional administration of EPA to statin might be associated with an increased EPA/AA ratio. The increase of the serum sTM after administration of EPA might reflect an increase of the TM expression on the endothelial surface rather than endothelial damage in CAD patients under statin treatment.Clinical Trial Registration Information UMIN ( http://www.umin.ac.jp/ ), Study ID: UMIN000010452.

Association of Thrombomodulin Gene Polymorphism (C1418T) With Coronary Artery Disease in Pakistani Population

Objectives

To find out the association between Thrombomodulin gene polymorphism (C1418T) with coronary artery disease in population of Karachi, Pakistan.

Methods

This case-control study was conducted in Tabba Heart Institute in collaboration with the National Institute of Blood Diseases, Karachi. We compared C/T dimorphism in 92 cases with 90 control subjects by allele-specific amplification. The results of PCR were confirmed by Gene sequencing. All the laboratory methods were strictly in compliance with the international standards. All variables that were either statistically significant in the univariate analyses or potentially important with respect to prevention or biologically relevant variables were included in logistic-regression analyses. Potential confounding was assessed with the use of multivariate models adjusted for participant's characteristics and other major risk factors for coronary artery disease. All reported p values are two-tailed, with statistical significance at p value < 0.05.

Results

The frequency of CC, C/T and TT genotype was 81 (90%), 6 (6.7%) 3 (3.3%) in controls and 67 (72.8%), 20 (21.7%) and 5 (5.4%) in cases respectively. In cases group the CT/TT genotypes were found to be significantly highly represented among the patients with coronary artery diseases when compared with control group (p-value 0.009).

Conclusion

TM C1418T polymorphism emerges as a risk marker in Coronary Artery Disease patients in the population of Karachi, Pakistan.

Uncertain thrombophilia markers

The development of venous thromboembolism (VTE), which includes deep-vein thrombosis and pulmonary embolism, may be associated with inherited or acquired risk factors that can be measured in plasma or DNA testing. The main inherited thrombophilias include the plasma deficiencies of the natural anticoagulants antithrombin, protein C and S; the gain-of-function mutations factor V Leiden and prothrombin G20210A; some dysfibrinogenaemias and high plasma levels of coagulation factor VIII. Besides these established biomarkers, which usually represent the first-level laboratory tests for thrombophilia screening, a number of additional abnormalities have been less consistently associated with an increased VTE risk. These uncertain causes of thrombophilias will be discussed in this narrative review, focusing on their clinical impact and the underlying pathogenetic mechanisms. Currently, there is insufficient ground to recommend their inclusion within the framework of conventional thrombophilia testing.

A Thrombomodulin Gene Polymorphism (C1418T) Is Associated with Early Outcomes in Patients Undergoing Coronary Artery Bypass Graft Surgery with a Conventional Cardiopulmonary Bypass during Hospitalization

Background: Thrombomodulin (TM) is a type of cell membrane-bound anticoagulant protein cofactor in the thrombin-mediated activation of protein C. Previous evidence has shown an association between TM polymorphisms and systemic inflammation. Conventional cardiopulmonary bypass (CPB), beating-heart CPB, and off-pump techniques have been widely used in cardiac surgery. However, these techniques may also cause systemic inflammatory responses in the patients. Whether TM polymorphisms are associated with systemic inflammation after cardiac surgery is still unclear. Methods: We analyzed the TM gene C1418T polymorphisms in 347 patients who underwent coronary artery bridge graft (CABG) surgery using allele-specific primers in a PCR assay. The clinical data during the hospital stay were collected and tested for correlations with the TM gene C1418T polymorphisms. Results: We separated the patients into two groups based on their TM C1418T genotype (CC genotype group and CT/TT genotype group). The days spent in an intensive care unit (ICU) and the incidence of fever in the ICU were significantly lower in the beating-heart CPB and off-pump groups than in the conventional CPB group. Additionally, the TM gene C1418T polymorphisms did not affect the early outcomes in patients in the beating-heart CPB and off-pump groups. Interestingly, in the conventional CPB group, patients with the CC genotype had a lower rate of fever, shorter duration of fever, and delay of ICU when compared with the CT/TT genotype. Conclusion: Surgeons may use a patient’s TM gene C1418T polymorphism to predict the strength of systemic inflammation and speculate on early outcomes during hospitalization before conventional CPB is performed.

Thrombomodulin gene proximal promoter polymorphisms in premature acute coronary syndrome patients in Bahrain

Thrombomodulin is expressed on endothelial cells and monocytes (mTM) where it has an anticoagulant function. Enzymatic cleavage from the cell surface produces soluble thrombomodulin (sTM) in plasma. Abnormal levels of sTM and mutations in the thrombomodulin gene (THBD) are linked to cardiovascular disease. The aim of this study was to investigate THBD proximal promoter mutations and levels of sTM and mTM in men presenting with premature acute coronary syndrome (ACS). This prospective cross-sectional study included 100 adult men with premature ACS (age <55 years) and 60 healthy age-matched controls. Plasma sTM was assayed by ELISA. mTM expression was assessed by flow cytometry with CD141 antibody. The -33 G/A polymorphism was identified by PCR-restriction fragment length polymorphism analysis and the THBD proximal promoter region was sequenced. Significantly lower sTM (P < 0.001) and higher mTM (P < 0.001) were seen in ACS patients. Heterozygous THBD promoter polymorphisms -33 G/A and -9/-10 GG/AT were found in eight patients and five control individuals. In patients and control individuals, allele frequencies of A were 0.02 and 0.025, and that of AT were 0.025 and 0.017, respectively. There were no significant associations of these polymorphisms with ACS, sTM levels or mTM expression. THBD polymorphisms -33 G/A and -9/-10 GG/AT are present in low frequency in our patient population, and are more frequent in the South Asians as compared to the Arabs. The frequency of -33 G/A is lower, whereas that of -9/-10 GG/AT is higher than that reported in the Orientals. The presence of THBD proximal promoter polymorphisms do not explain variations in levels of sTM and mTM in this patient population.

Systems analysis of gene ontology and biological pathways involved in post-myocardial infarction responses

Background

Pathway analysis has been widely used to gain insight into essential mechanisms of the response to myocardial infarction (MI). Currently, there exist multiple pathway databases that organize molecular datasets and manually curate pathway maps for biological interpretation at varying forms of organization. However, inconsistencies among different databases in pathway descriptions, frequently due to conflicting results in the literature, can generate incorrect interpretations. Furthermore, although pathway analysis software provides detailed images of interactions among molecules, it does not exhibit how pathways interact with one another or with other biological processes under specific conditions.

Methods

We propose a novel method to standardize descriptions of enriched pathways for a set of genes/proteins using Gene Ontology terms. We used this method to examine the relationships among pathways and biological processes for a set of condition-specific genes/proteins, represented as a functional biological pathway-process network. We applied this algorithm to a set of 613 MI-specific proteins we previously identified.

Results

A total of 96 pathways from Biocarta, KEGG, and Reactome, and 448 Gene Ontology Biological Processes were enriched with these 613 proteins. The pathways were represented as Boolean functions of biological processes, delivering an interactive scheme to organize enriched information with an emphasis on involvement of biological processes in pathways. We extracted a network focusing on MI to demonstrate that tyrosine phosphorylation of Signal Transducer and Activator of Transcription (STAT) protein, positive regulation of collagen metabolic process, coagulation, and positive/negative regulation of blood coagulation have immediate impacts on the MI response.

Conclusions

Our method organized biological processes and pathways in an unbiased approach to provide an intuitive way to identify biological properties of pathways under specific conditions. Pathways from different databases have similar descriptions yet diverse biological processes, indicating variation in their ability to share similar functional characteristics. The coverages of pathways can be expanded with the incorporation of more biological processes, predicting involvement of protein members in pathways. Further, detailed analyses of the functional biological pathway-process network will allow researchers and scientists to explore critical routes in biological systems in the progression of disease.

Single-Nucleotide Polymorphisms Within the Thrombomodulin Gene (THBD) Predict Mortality in Patients With Graft-Versus-Host Disease

PURPOSE

Steroid-refractory graft-versus-host disease (GVHD) is a major and often fatal complication after allogeneic stem-cell transplantation (alloSCT). Although the pathophysiology of steroid refractoriness is not fully understood, evidence is accumulating that endothelial cell stress is involved, and endothelial thrombomodulin (THBD) plays a role in this process. Here we assess whether single-nucleotide polymorphisms (SNPs) within the THBD gene predict outcome after alloSCT.

PATIENTS AND METHODS

Seven SNPs within the THBD gene were studied (rs1962, rs1042579, rs1042580, rs3176123, rs3176124, rs3176126, and rs3176134) in a training cohort of 306 patients. The relevant genotypes were then validated in an independent cohort (n = 321).

RESULTS

In the training cohort, an increased risk of nonrelapse mortality (NRM) was associated with three of seven SNPs tested: rs1962, rs1042579 (in linkage disequilibrium with rs3176123), and rs1042580. When patients were divided into risk groups (one v no high-risk SNP), a strong correlation with NRM was observed (hazard ratio [HR], 2.31; 95% CI, 1.36 to 3.95; P = .002). More specifically, NRM was predicted by THBD SNPs in patients who later developed GVHD (HR, 3.03; 95% CI, 1.61 to 5.68; P < .001) but not in patients without GVHD. In contrast, THBD SNPs did not predict incidence of acute GVHD. Multivariable analyses adjusting for clinical variables confirmed the independent effect of THBD SNPs on NRM. All findings could be reproduced in the validation cohort.

CONCLUSION

THBD SNPs predict mortality of manifest GVHD but not the risk of acquiring GVHD, supporting the hypothesis that endothelial vulnerability contributes to GVHD refractoriness.

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

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

Common genetic risk factors for venous thrombosis in the Chinese population

Venous thrombosis is a major medical disorder caused by both genetic and environmental factors. Little is known about the genetic background of venous thrombosis in the Chinese population. A total of 1,304 individuals diagnosed with a first venous thrombosis and 1,334 age- and sex-matched healthy participants were enrolled in this study. Resequencing of THBD (encoding thrombomodulin) in 60 individuals with venous thrombosis and 60 controls and a functional assay showed that a common variant, c.-151G>T (rs16984852), in the 5' UTR significantly reduced the gene expression and could cause a predisposition to venous thrombosis. Therefore, this variant was genotyped in a case-control study, and results indicated that heterozygotes had a 2.80-fold (95% confidence interval = 1.88-4.29) increased risk of venous thrombosis. The THBD c.-151G>T variant was further investigated in a family analysis involving 176 first-degree relatives from 38 index families. First-degree relatives with this variant had a 3.42-fold increased risk of venous thrombosis, and their probability of remaining thrombosis-free was significantly lower than that of relatives without the variant. In addition, five rare mutations that might be deleterious were also identified in thrombophilic individuals by sequencing. This study is the largest genetic investigation of venous thrombosis in the Chinese population. Further study on genetics of thrombosis should focus on resequencing of THBD and other hemostasis genes in different populations.

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

Background and methods

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

Methods

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

Conclusion

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

Treatment with activated protein C (aPC) is protective during the development of myocardial fibrosis: an angiotensin II infusion model in mice

Aims

Myocardial fibrosis contributes to the development of heart failure. Activated Protein C (aPC) is a circulating anticoagulant with anti-inflammatory and cytoprotective properties. Using a model of myocardial fibrosis second to Angiotensin II (AngII) infusion, we investigated the novel therapeutic function aPC in the development of fibrosis.

Methods and Results

C57Bl/6 and Tie2-EPCR mice were infused with AngII (2.0 µg/kg/min), AngII and aPC (0.4 µg/kg/min) or saline for 3d. Hearts were harvested and processed for analysis or used for cellular isolation. Basic histology and collagen deposition were assessed using histologic stains. Transcript levels of molecular mediators were analyzed by quantitative RT-PCR. Mice infused with AngII exhibited multifocal areas of myocardial cellular infiltration associated with significant collagen deposition compared to saline control animals (p<0.01). AngII-aPC infusion inhibited this cellular infiltration and the corresponding collagen deposition. AngII-aPC infusion also inhibited significant expression of the pro-fibrotic cytokines TGF-β1, CTGF and PDGF found in AngII only infused animals (p<0.05). aPC signals through its receptor, EPCR. Using Tie2-EPCR animals, where endothelial cells over-express EPCR and exhibit enhanced aPC-EPCR signaling, no significant reduction in cellular infiltration or fibrosis was evident with AngII infusion suggesting aPC-mediate protection is endothelial cell independent. Isolated infiltrating cells expressed significant EPCR transcripts suggesting a direct effect on infiltrating cells.

Conclusions

This data indicates that aPC treatment abrogates the fibrogenic response to AngII. aPC does not appear to confer protection by stimulating the endothelium but by acting directly on the infiltrating cells, potentially inhibiting migration or activation.

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

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

Association of thrombomodulin gene polymorphisms and plasma thrombomodulin levels with acute myocardial infarction in north Indian patients

This is the first study from north India that investigated the association of thrombomodulin (TM) polymorphisms with acute myocardial infarction (AMI) in 350 patients (≤ 40 years, n = 184 and ≥ 60 years, n = 166) and 350 matched-controls. The TM polymorphisms were determined by polymerase chain reaction-single-stranded conformational polymorphism and DNA sequencing. The TM 1418TT genotype (odds ratio [OR] 2.8; 95% confidence interval [CI] 1.3-6.4; P = .012) was independent risk predictor of young AMI as were hypertension (OR 3.3; 95% CI 1.8-5.9; P < .001), diabetes mellitus (OR 14.3; 95% CI 2.9-44.6; P = .001), smoking (OR 13.8; 95% CI 7.7-24.7; P < .001), family history (OR 1.8; 95% CI 1.1-3.3; P = .045), high body mass index (OR 2.2; 95% CI 1.3-3.6; P = .002), and high waist-hip ratio (OR 4.1; 95% CI 2.4-7.1; P < .001). Mean plasma TM also showed association with young AMI (P < .001). Smoking carriers of TM 1418CT + TT genotype had significantly higher risk of AMI (OR 12.8; 95% CI 6.0-27.3; P < .001) when compared with nonsmoking noncarriers. In conclusion, TM 1418C/T polymorphism is independent predictor of AMI and synergies with smoking.

Thrombomodulin gene variants are associated with increased mortality after coronary artery bypass surgery in replicated analyses

BACKGROUND

We tested the hypothesis that genetic variation in thrombotic and inflammatory pathways is independently associated with long-term mortality after coronary artery bypass graft (CABG) surgery.

METHODS AND RESULTS

Two separate cohorts of patients undergoing CABG surgery at a single institution were examined, and all-cause mortality between 30 days and 5 years after the index CABG was ascertained from the National Death Index. In a discovery cohort of 1018 patients, a panel of 90 single-nucleotide polymorphisms (SNPs) in 49 candidate genes was tested with Cox proportional hazard models to identify clinical and genomic multivariate predictors of incident death. After adjustment for multiple comparisons and clinical predictors of mortality, the homozygote minor allele of a common variant in the thrombomodulin (THBD) gene (rs1042579) was independently associated with significantly increased risk of all-cause mortality (hazard ratio, 2.26; 95% CI, 1.31 to 3.92; P=0.003). Six tag SNPs in the THBD gene, 1 of which (rs3176123) in complete linkage disequilibrium with rs1042579, were then assessed in an independent validation cohort of 930 patients. After multivariate adjustment for the clinical predictors identified in the discovery cohort and multiple testing, the homozygote minor allele of rs3176123 independently predicted all-cause mortality (hazard ratio, 3.6; 95% CI, 1.67 to 7.78; P=0.001).

CONCLUSIONS

In 2 independent cardiac surgery cohorts, linked common allelic variants in the THBD gene are independently associated with increased long-term mortality risk after CABG and significantly improve the classification ability of traditional postoperative mortality prediction models.

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

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

Inherited Thrombophilia

Inherited thrombophilia can be defined as a genetically determined predisposition to the development of thromboembolic complications. Since the discovery of activated protein C resistance in 1993, several additional disorders have been described and, at present, it is possible to identify an inherited predisposition in about 60 to 70% of patients with such complications. These inherited prothrombotic risk factors include qualitative or quantitative defects of coagulation factor inhibitors, increased levels or function of coagulation factors, defects of the fibrinolytic system, altered platelet function, and hyperhomocysteinemia. In this review, the main inherited prothrombotic risk factors are analyzed from epidemiological, laboratory, clinical, and therapeutic points of view. Finally, we discuss the synergism between genetic and acquired prothrombotic risk factors in particular conditions such as childhood and pregnancy.

Variation in 24 hemostatic genes and associations with non-fatal myocardial infarction and ischemic stroke

BACKGROUND

Arterial thrombosis involves platelet aggregation and clot formation, yet little is known about the contribution of genetic variation in fibrin-based hemostatic factors to arterial clotting risk. We hypothesized that common variation in 24 coagulation-fibrinolysis genes would contribute to risk of incident myocardial infarction (MI) or ischemic stroke (IS).

METHODS

We conducted a population-based, case-control study. Subjects were hypertensive adults and postmenopausal women 30-79 years of age, who sustained a first MI (n = 856) or IS (n = 368) between 1995 and 2002, and controls matched on age, hypertension status, and calendar year (n = 2,689). We investigated the risk of MI and IS associated with (i) global variation within each gene as measured by common haplotypes and (ii) individual haplotypes and single nucleotide polymorphisms (SNPs). Significance was assessed using a 0.2 threshold of the false discovery rate q-value, which accounts for multiple testing.

RESULTS

After accounting for multiple testing, global genetic variation in factor (F) VIII was associated with IS risk. Two haplotypes in FVIII and one in FXIIIa1 were significantly associated with increased IS risk (all q-values < 0.2). A plasminogen gene SNP was associated with MI risk. All are new discoveries not previously reported. Another 24 tests had P-values < 0.05 and q-values > 0.2 in MI and IS analyses, 23 of which are new and hypothesis generating.

CONCLUSIONS

Apart from the association of FVIII variation with IS, we found little evidence that common variation in the 24 candidate fibrin-based hemostasis genes strongly influences arterial thrombotic risk, but our results cannot rule out small effects.

Association of polymorphisms in platelet and hemostasis system genes with acute myocardial infarction

BACKGROUND

Genetic polymorphisms may affect the balance between coagulation and fibrinolysis and thereby affect individual vulnerability to acute myocardial infarction (MI) among patients with underlying coronary atherosclerosis.

METHODS

We enrolled 1375 patients with an initial clinical presentation of coronary disease. We genotyped 49 single nucleotide polymorphisms (SNPs) in 9 coagulation system genes and compared patients who had an initial acute MI with patients who presented with stable exertional angina.

RESULTS

An SNP in CD36 (rs3211956) was significantly (P = .04) more common among patients who presented with acute MI (minor allele frequency 10.5%) than patients with stable exertional angina (minor allele frequency 8.0%). This association became marginally significant, however, after adjustment for conventional cardiac risk factors in an additive genetic model (odds ratio 1.34, CI 1.00-1.88, P = .053). An SNP in ITGB3 (Leu59Pro, rs5918) was slightly, but not significantly (P = .083), more common among patients with acute MI (minor allele frequency 14.5%) than among patients with stable exertional angina (minor allele frequency 12.0%). Two linked SNPs in THBD (Ala473Val, rs1042579; and rs3176123) were slightly, but not significantly (P = .079 and 0.052, respectively), less common among patients with acute MI (minor allele frequency 16.1%) than among patients with stable exertional angina (18.7% and 19.0%, respectively).

CONCLUSIONS

Four SNPs in platelet glycoprotein and hemostatic genes were nominally associated with acute MI rather than stable exertional angina as the initial clinical presentation of coronary artery disease. These findings are suggestive but require independent confirmation in larger studies.

Noninvasive assessment of preclinical atherosclerosis

Initially considered as a semipermeable barrier separating lumen from vessel wall, the endothelium is now recognised as a complex endocrine organ responsible for a variety of physiological processes vital for vascular homeostasis. These include the regulation of vascular tone, luminal diameter, and blood flow; hemostasis and thrombolysis; platelet and leucocyte vessel-wall interactions; the regulation of vascular permeability; and tissue growth and remodelling. The endothelium modulates arterial stiffness, which precedes overt atherosclerosis and is an independent predictor of cardiovascular events. Unsurprisingly, dysfunction of the endothelium may be considered as an early and potentially reversible step in the process of atherogenesis and numerous methods have been developed to assess endothelial status and large artery stiffness. Methodology includes flow-mediated dilatation of the brachial artery, assessment of coronary flow reserve, carotid intimamedia thickness, pulse wave analysis, pulse wave velocity, and plethysmography. This review outlines the various modalities, indications, and limitations of available methods to assess arterial dysfunction and vascular risk.

Circulating activated protein C is reduced in young survivors of myocardial infarction and inversely correlates with the severity of coronary lesions

BACKGROUND

Cardiovascular risk factors for myocardial infarction (MI) are less frequent in younger than in older MI survivors. Therefore, the thrombotic component of MI may play a more important role at a young age. As activated protein C (APC) provides systemic anticoagulant and anti-inflammatory protection, a low plasma APC level may be an arterial thrombotic risk factor.

AIM

To determine whether there is an association between reduced APC levels and early MI and severe coronary lesions.

METHODS

APC was measured in 231 young MI survivors and 231 controls.

RESULTS

Low APC levels were significantly associated with MI. Compared with the fourth quartile, the odds ratio (OR) for APC values in the first quartile was 3.7 [95% confidence interval (CI) = 2.1-6.4], and 3.2 (1.5-7.0) after adjustment for cardiovascular risk factors. Moreover, each decrease of 0.43 ng mL(-1) (1 SD) in APC increased the OR 1.7 times (1.4-2.2), and 1.5 times (1.2-1.9) after adjustment for cardiovascular risk factors. Low APC levels were also associated with the number of coronary arteries affected and with the severity of coronary lesions (P < 0.001).

CONCLUSIONS

There is a significant association between low circulating APC levels and both early MI and the extent and severity of coronary atherosclerosis, which might be related to the anticoagulant and anti-inflammatory properties of APC.

Association study of the thrombomodulin −33G>A polymorphism with coronary artery disease and myocardial infarction in Chinese Han population

BACKGROUND

Thrombomodulin (TM) is the anticoagulant endothelial cell membrane-bound protein cofactor in the thrombin-mediated activation of protein C. Recently, conflicting data have been reported regarding the possible contribution of the TM -33G>A polymorphism to coronary artery disease (CAD) or myocardial infarction (MI) in some Asian populations. We investigated this polymorphism in northern Han Chinese.

METHODS

We performed a case-control study, including 808 patients with angiographically verified CAD or a history of an acute MI and 813 age- and sex-matched controls. The TM -33G>A polymorphism was determined by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) analysis.

RESULTS

We did not find a significant difference in the frequency of the A allele between CAD patients (11%) and controls (9.8%; P=0.249), between MI patients (11.5%) and controls (P=0.163), or between premature MI patients (11.7%) and controls (P=0.265). Similarly, the difference of the genotypic distributions could be neglected across the groups: GG: (GA/AA) was 81.4%:18.6% in controls, 79.7%:20.3% in patients with CAD, 78.8%:21.2% in patients with MI, and 77.7%:22.3% in patients with premature MI, respectively (vs. controls, all P>0.05). The lack of association also persisted after adjusting for other conventional risk factors.

CONCLUSIONS

Our results seemed not to support a significant association of the TM -33G>A polymorphism with CAD, MI or premature MI in our population.

Thrombomodulin gene polymorphisms or haplotypes as potential risk factors for venous thromboembolism: a population-based case-control study

Dysfunction of the protein C anticoagulant system is associated with venous thromboembolism (VTE) and thrombomodulin (TM) is a critical cofactor within the protein C system. The aim of this study was to test the hypotheses that polymorphisms or haplotypes within the TM gene are common risk factors for VTE. We screened the TM putative promoter, exon and 3'-untranslated region for sequence variations in a random sample (n = 266) of consecutive idiopathic, objectively confirmed non-Olmsted County VTE patients referred to the Mayo Clinic. We then genotyped a sample of Olmsted County, MN residents with a first lifetime, objectively confirmed VTE in the 25-year period, 1966-90 (n = 223), and a sample of Olmsted County residents without VTE (n = 237) for polymorphisms either discovered in the screening population or previously published, and tested for an association of VTE with TM genotype or haplotypes using unconditional logistic regression and generalized linear models, respectively. We also genotyped these Olmsted County cases and controls at 20 'null' genetic maker loci and tested for population admixture. Nine novel and three previously described mutations were identified in the screening population. Mutations within the TM promoter, EGF(1-5), serine/threonine-rich, transmembrane, and cytoplasm regions were absent or uncommon. TM845G-->A (Ala25Thr; lectin region), TM2136T-->C (Ala455Val; EGF(6) region), TM2470C deletion (3'-untranslated region), and 4363A-->G (3'-flanking region) were more common, but were not associated with VTE by genotype or haplotype. Null genetic marker allele frequencies did not differ significantly among cases and controls. We conclude that polymorphisms or haplotypes within the TM gene are not common risk factors for incident VTE.

A combination of two common thrombomodulin gene variants (-1208-1209TTdelTT and A455V) influence risk of coronary heart disease: a prospective study in men

In a previous case control study of myocardial infarction (MI), we identified risk associated with the combination of two variants in the thrombomodulin (TM) gene (-1208-1209TTdelTT and A455V) and an interaction with increased body mass index (BMI). The rare alleles at these two common variant sites in the TM gene occur in most individuals on the same allele (V/delTT) and are in strong linkage disequilibrium (Delta=0.67, P <0.0005). We have extended these findings in a prospective study of 2700 UK middle age men; the second Northwick Park Heart Study (NPHSII), in which 227 coronary heart disease (CHD) events have been reported to date. Risk was analysed by tertile of BMI, systolic blood pressure (SBP) and triglyceride. The strongest risk for the V/delTT haplotype was in the mid- and top-tertile of triglyceride; RR 1.95 (CI 1.12-3.40) and 1.77 (CI 1.02-3.09), respectively, compared to non-carriers in the lowest tertile (after adjusting for age, practice, smoking, SBP, BMI; interaction P=0.016). No significant risk was identified for increased triglyceride levels in those with the common TM haplotype. There was a suggestion for greater inflammatory response (C-reactive protein levels, CRP) in those with V/delTT compared to those with the common allele, as triglyceride levels increased. Overall, these findings may suggest that the common TM allele confers protection against the adverse CHD effect of either plasma triglyceride-containing lipoproteins, or the underlying atherosclerotic mechanism of the metabolic syndrome, and that this process is defective in carriers of V/delTT.

Thrombomodulin Ala455Val Polymorphism and the risk of cerebral infarction in a biracial population: the Stroke Prevention in Young Women Study

Background

The genes encoding proteins in the thrombomodulin-protein C pathway are promising candidate genes for stroke susceptibility because of their importance in thrombosis regulation and inflammatory response. Several published studies have shown that the Ala455Val thrombomodulin polymorphism is associated with ischemic heart disease, but none has examined the association with stroke. Using data from the Stroke Prevention in Young Women Study, we sought to determine the association between the Ala455Val thrombomodulin polymorphism and the occurrence of ischemic stroke in young women.

Methods

All 59 hospitals in the greater Baltimore-Washington area participated in a population-based case-control study of stroke in young women. We compared 141 cases of first ischemic stroke (44% black) among women 15 to 44 years of age with 210 control subjects (35% black) who were identified by random digit dialing and frequency matched to the cases by age and geographical region of residence. Data on historical risk factors were collected by standardized interview. Genotyping of the thrombomodulin Ala455Val polymorphism was performed by pyrosequencing.

Results

The A allele (frequency = 0.85) was associated with stroke under the recessive model. After adjustment for age, race, cigarette smoking, hypertension, and diabetes, the AA genotype, compared with the AV and VV genotypes combined, was significantly associated with stroke (odds ratio 1.9, 95% CI 1.1–3.3). The AA genotype was more common among black than white control subjects (81% versus 68%) but there was no significant interaction between the risk genotype and race (adjusted odds ratio 2.7 for blacks and 1.6 for whites). A secondary analysis removing all probable (n = 16) and possible (n = 15) cardioembolic strokes demonstrated an increased association (odds ratio 2.2, 95% CI 1.2–4.2).

Conclusions

Among women aged 15 to 44 years, the AA genotype is more prevalent among blacks than whites and is associated with increased risk of early onset ischemic stroke. Removing strokes potentially related to cardioembolic phenomena increased this association. Further studies are needed to determine whether this polymorphism is functionally related to thrombomodulin expression or whether the association is due to population stratification or linkage to a nearby functional polymorphism.

The 161TT genotype in the exon 6 of the peroxisome-proliferator-activated receptor γ gene is associated with premature acute myocardial infarction and increased lipid peroxidation in habitual heavy smokers

PPAR (peroxisome-proliferator-activated receptor) is a nuclear receptor. Activation of PPARγ by its ligands could modulate gene transcription, thereby leading to multiple anti-atherogenic and fibrinolytic effects. However, the association between the 161T allele in exon 6 of the PPARγ gene and premature AMI (acute myocardial infarction) is not clear. We recruited 146 patients with premature AMI (onset age ≤50 years) and 146 controls. The C161T polymorphism was examined using PCR and restriction-fragment-length polymorphism. Plasma levels of Ab-ox-LDL (antibody against oxidized low-density lipoprotein) were measured in 27 male smokers, whose genotypes have been identified. The frequency of the PPARγ TT genotype among patients with AMI was significantly higher than that in controls [13% compared with 5.5%; OR (95% CI) 2.7, (1.1–6.5), where OR and CI are odds ratio and confidence interval respectively]. This association was not observed in CC or CT genotypes. Using multivariate logistic regression analyses, we found that the homozygous TT genotype [OR (95% CI), 3.1 (1.2–7.9)], smoking [OR (95% CI), 3.5, (2.1–6.0)], hypertension [OR (95% CI), 3.6, (1.9–6.9)] and diabetes mellitus [OR (95% CI), 3.5 (1.5–8.4)] were independent risk factors for premature AMI. Plasma levels of Ab-ox-LDL were significantly higher in healthy volunteers with the TT genotype compared with those with the CC genotype (49.3±18.1 compared with 24.2±15.2 units/l respectively; P=0.02). Therefore in our study we observed an association between the PPARγ 161 TT genotype and premature AMI. Lipid peroxidation was significantly influenced by the 161T allele.

Relation of thrombomodulin gene polymorphisms to acute myocardial infarction in patients <or =50 years of age

Full-length sequencing of the thrombomodulin (TM) gene was obtained in 20 patients with premature acute myocardial infarction (AMI). Clinically relevant polymorphisms were identified and further evaluated in 145 patients with premature AMI and 143 controls. Despite the fact that TM promoter G-33A and C1418T polymorphisms are common in the Chinese population, the association between G-33A mutation and premature AMI indicates that we must focus on promoter G-33A polymorphism rather than C1418T polymorphism in terms of the role of TM gene mutation on premature AMI.

Genetic variation in the human thrombomodulin promoter locus and prognosis after acute coronary syndrome

INTRODUCTION

Endothelial thrombomodulin (TM) plays a critical role in both anticoagulation and anti-inflammation. An impaired TM cofactor function or reduced TM gene expression could constitute a prethrombotic abnormality leading to acute coronary events. Mutations in the TM gene occur, but their functional consequences on the expression and activity of the gene are not yet fully understood.

MATERIALS AND METHODS

We performed a prospective study investigating the prevalence of TM mutations in the promoter region in 182 patients with acute coronary syndrome as well as in a control group. The patients were followed-up after 30 days and after 2 years for acute myocardial infarction (MI) and mortality.

RESULTS AND CONCLUSIONS

We identified 10 point mutations and 2 small deletions: -1861 C/A, -1852 C/G, -1803 G/C, -1752 G/C, -1213/1212 delTT, -1089 C/G, -1088 C/T, -1083/1082 delCC, -1066 A/C, -801 C/G, -651 A/C and -52 G/A. Two of the mutations, -1752 G/C and -1213/1212 delTT, were frequent in the patients as well as in the controls, while all the others were rare. The only significant finding was that both -1752 G/C and -1213/1212 delTT were associated with a lower than normal risk of suffering a clinical event among smokers at 30 days and 2 years. We did not gain any support for the hypothesis that TM mutations confer an increased risk of MI or mortality.

Thrombomodulin

Since its discovery as a critical cofactor in the initiation of the protein C (PC) anticoagulant pathway [1,2], biochemical and structural investigations, combined with in vivo analyses of genetically engineered mice have revealed new, and in part PC- and thrombin-independent aspects of thrombomodulin (TM) function in fibrinolysis and inflammation, and in embryogenesis. This review summarizes more recent structural and functional investigations of TM, gives an overview of the association of TM gene polymorphisms with human disease, and provides a synopsis of what is know about TM function in disease states of thrombosis, stroke, arteriosclerosis, and cancer. Newly emerging aspects of TM function in inflammation and embryogenesis are presented and discussed in detail.

Circulating thrombomodulin levels are related to latent progression of atherosclerosis in hypertensive patients

The present study was designed to test the hypothesis that circulating levels of thrombomodulin are elevated in patients with hypertension in proportion to the severity of the vascular damage. A cross-sectional study was carried out using a population consisting of 96 patients with essential hypertension without clinically evident cardiovascular disease (mean age: 65 +/- 10 years) and 99 healthy normotensive control subjects (64 +/- 9 years). Blood was sampled and serum concentrations of soluble thrombomodulin were measured using an enzyme immunoassay method. We calculated the ratio of the concentration of thrombomodulin to that of creatinine, because soluble thrombomodulin is excreted by the kidney and the serum level of thrombomodulin was correlated with that of creatinine (p < 0.05). The association between the ratio and other clinical variables was investigated. The ratio of the thrombomodulin to creatinine concentrations was higher in hypertensive (29.3 +/- 10.9) than in control subjects (24.4 +/- 5.9; p < 0.0001). Systolic blood pressure was correlated with the ratio but the ratio showed no correlation with serum lipid levels when analyzed using data from all subjects. In hypertensive patients, the ratio correlated with the grade of sclerotic, but not hypertensive, changes in the fundus oculi (Scheie's classification, p < 0.001). Furthermore, the ratio correlated with brachial-ankle pulse wave velocity (p < 0.001). However, no correlation was detected between the ratio and blood pressure. These results suggest that circulating levels of thrombomodulin are elevated in hypertensive patients as compared to normotensive subjects and that the thrombomodulin level may be a molecular marker of the latent progression of atherosclerosis in hypertensive patients.

A monoclonal antibody against activated protein C allows rapid detection of activated protein C in plasma and reveals a calcium ion dependent epitope involved in factor Va inactivation

Activated protein C (APC) serves as an 'on demand' anticoagulant. Defects in the APC anticoagulant pathway are underlying risk factors for the development of venous and arterial thrombosis. APC has recently been shown to significantly reduce mortality in patients with severe sepsis, presumably by virtue of its ability to down-regulate coagulation as well as inflammation. Our objective was to develop an assay that, for the first time, permits rapid detection of plasma APC. This assay will expedite studies of APC in a variety of vascular disease states including sepsis, severe atherosclerosis, diabetes, and vasculitis. By generating a highly APC-specific monoclonal antibody (HAPC 1555), we have developed an assay that, for the first time, allows rapid detection of plasma APC. The Kd measured for the interaction between APC and HAPC 1555 based on BIAcore studies and binding to immobilized HAPC on microtiter plates is 6.2 +/- 0.9 and 8.8 +/- 1.0 nmol L(-1), respectively. The interaction between HAPC 1555 and APC is Ca2+-dependent, with a Ca2+ concentration of 313 +/- 48 micro mol L(-1) required for half maximal binding. HAPC 1555 interferes with APC-mediated inactivation of factor (F)Va in the presence and absence of phospholipids, suggesting that HAPC 1555 binds to the FVa binding domain of APC. When HAPC 1555 was used in an APC enzyme capture assay, therapeutic APC levels could be measured in 1.5 h, and physiologic levels of APC could be detected between 3 and 19 h. APC levels were also shown to vary markedly in patients with severe sepsis. The rapidity of our APC assay makes APC detection in patients practical clinically. This assay will expedite studies of APC in a variety of vascular disease states including sepsis, severe atherosclerosis, diabetes, and vasculitis.

Prospective study of the A455V polymorphism in the thrombomodulin gene, plasma thrombomodulin, and incidence of venous thromboembolism: the LITE Study

Plasma thrombomodulin (soluble TM; sTM) is considered to be a marker of endothelial injury, but a recent report indicated that the relationship of sTM with thrombosis is complex. Venous thromboembolic events were identified in adults in two longitudinal cohort studies, the Atherosclerosis Risk in Communities Study and the Cardiovascular Health Study, totaling 21 690 participants. After 8 years of follow-up, sTM was measured in baseline plasma of 305 participants who developed venous thrombosis and 607 who did not. Thrombomodulin A455V genotype was determined in 302 cases and 626 controls. There was no difference in the prevalence of the three TM genotypes between cases and controls and no difference in age-adjusted mean values of sTM by genotype. There were no associations of age-adjusted sTM or TMA455V genotype with overall venous thromboembolism or with thrombosis in any subtype of venous thromboembolism.

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

Thrombomodulin (TM) is a vascular endothelial cell (EC) receptor that is a cofactor for thrombin-mediated activation of the anticoagulant protein C. The extracellular NH(2)-terminal domain of TM has homology to C-type lectins that are involved in immune regulation. Using transgenic mice that lack this structure (TM(LeD/LeD)), we show that the lectin-like domain of TM interferes with polymorphonuclear leukocyte (PMN) adhesion to ECs by intercellular adhesion molecule 1-dependent and -independent pathways through the suppression of extracellular signal-regulated kinase (ERK)(1/2) activation. TM(LeD/LeD) mice have reduced survival after endotoxin exposure, accumulate more PMNs in their lungs, and develop larger infarcts after myocardial ischemia/reperfusion. The recombinant lectin-like domain of TM suppresses PMN adhesion to ECs, diminishes cytokine-induced increase in nuclear factor kappaB and activation of ERK(1/2), and rescues ECs from serum starvation, findings that may explain why plasma levels of soluble TM are inversely correlated with cardiovascular disease. These data suggest that TM has antiinflammatory properties in addition to its role in coagulation and fibrinolysis.

Mutations in the thrombomodulin gene are rare in patients with severe thrombophilia

Because thrombomodulin plays a key role in the protein C pathway, we evaluated the contribution of thrombomodulin gene mutations to venous thrombosis. We examined 38 patients with recurrent, documented thrombotic events at a young age and a positive family history. Twelve individuals with low levels of soluble thrombomodulin in plasma were also studied. Finally, the allelic frequency of the Ala455Val polymorphism was estimated in 192 patients with at least one thrombotic event and in 369 age- and sex-matched asymptomatic controls. Two mutations were identified; G/A-201, in a severely thrombophilic patient and G/T 1456, in a patient with low soluble thrombomodulin levels. The first mutation has been reported by some, but not others, to be associated with moderately reduced levels of thrombomodulin. The second was identified previously in a patient with low soluble thrombomodulin, but expression studies failed to show functional changes in the mutant. Thrombomodulin gene mutations thus appear to be rare even in highly selected thrombophilic patients, and possibly functionally irrelevant. The allelic frequency of the Ala455Val polymorphism was identical in patients and controls. Considering the lack of a phenotype and the costly screening procedure, we recommend that thrombomodulin defects be sought only for research purposes.

Naturally occurring mutations in the thrombomodulin gene leading to impaired expression and function

Sporadic mutations in the thrombomodulin (TM) gene occur in patients with both arterial and venous thrombosis, but the effects of these mutations on expression and function are largely unexplored. Full-length wild-type TM complementary DNA (cDNA) was incorporated into vector pcDNA6 for transfection into COS-7 cells for transient expression. Mutagenesis was performed to create 7 TM mutants with natural mutations either previously identified (Ala25Thr, Gly61Ala, Asp468Tyr, Pro477Ser, Pro483Leu) or reported here (an 11-base pair [bp] deletion, del791-801, leading to STOP306, and a missense mutation, Arg385Ser). Four mutations were found to detrimentally affect the level of expression of the TM protein. Of the missense mutations, 3 had reduced expression compared to wild-type TM (100%), Arg385Ser (50.2% +/- 5%, P <.001), Pro477Ser (76.8% +/- 1%, P <.001), Pro483Leu (82.1% +/- 8%, P <.007). No TM protein expression could be detected on the cell surface for mutation del791-801. The cofactor activity of TM in protein C activation was also evaluated. The Michaelis constant (K(m)) for wild-type thrombin-TM complex was 634 +/- 6 nmol/L. Two mutants, with Arg385Ser and Pro477Ser, had increased (P <.0001) K(m), 2967 +/- 283 nM, and 2342 +/- 219 nM, respectively, demonstrating impaired function of the thrombin-TM complex. This work presents biochemical evidence that certain (but not all) natural mutations in the TM gene reduce expression and impair function of the protein on the cell surface, and helps clarify the suggested contribution that these mutations might make to the risk of thromboembolic disease.

Association of G-33A polymorphism in the thrombomodulin gene with myocardial infarction in Koreans

Thrombomodulin (TM), a thrombin receptor expressed on the endothelial surface, is known to play an important role in the anti-thrombogenic system in vivo. In this study, we examined the effects of 3 single-nucleotide polymorphisms (SNPs) in the TM gene (G-33A, C1418T and C1922T) on the development of myocardial infarction (MI) in Koreans. We found that G-33A was a common SNP (the minor allele frequency was 0.09) in Koreans. Eighty-five MI patients who had received coronary angiography were enrolled and were divided into 3 groups according to the number of coronary arteries in which stenosis was found angiographically (1-vessel disease (1VD) to 3-vessel disease (3VD)). The criterion of coronary stenosis was 50% or more stenosis on angiography. In addition, 102 controls (CONT) who had no significant stenosis were employed. The number of AA/GA genotypes of G-33A was found to be significantly greater in the 1VD than in the CONT (p=0.004 by chi2-test) while no significant difference was found between the multivessel disease (2-3VD) and the CONT. Multiple logistic analysis showed that G-33A was an independent risk factor for the 1VD with an odds ratio of 4.63 (95% confidence interval; 1.62-13.3). C1418T and C1922T were both in linkage disequilibrium with G-33A; however, they were not independent risks for either the 1VD or the 2-3VD. A reporter gene assay showed that G-33A had a significant effect on the TM promoter activity. These results indicated that G-33A polymorphism in TM might be a genetic risk factor for myocardial infarction.