Protein Z (PZ) and plasminogen activator inhibitor-1 (PAI-1) plasma levels in patients with previously untreated Hodgkin lymphoma (HL).

PURPOSE: The role of Protein Z (PZ) in conditions, such as thrombosis, inflammation or cancer, is under investigation. Plasminogen Activator Inhibitor-1 (PAI-1) is an acute phase reactant that promotes thrombosis and tumorigenesis. Subject of this work was to study PZ and PAI-1 in patients with Hodgkin Lymphoma (HL), a malignancy with inflammatory background and relatively low incidence of thrombosis. METHODS: Newly diagnosed patients were enrolled in the study. Healthy individuals were used as controls. RESULTS: PZ levels were higher in patients compared to controls (not significantly), while PAI-1 levels were significantly higher in patients. Both PZ and PAI-1 concentrations did not correlate with most of patients' characteristics. Lower PZ levels at diagnosis were associated with presence of B symptoms and positive final positron emission tomography (PET) and higher baseline PAI-1 levels with positive final PET, too. PZ had a declining trend, but PAI-1 increased initially and decreased thereafter, during the treatment period. CONCLUSIONS: Conclusively, PAI-1, but not PZ, seems to be an acute phase protein in HL. Lower PZ and higher PAI-1 levels at diagnosis may be indicative of aggressive disease. These results need further verification.

Evaluation of the role of the new INNOVANCE PFA P2Y test cartridge in detection of clopidogrel resistance.

Light transmittance aggregometry (LTA) has been extensively used in monitoring clopidogrel therapy. However, the availability of simple and rapid point-of-care platelet function assays is of great clinical importance. Thus, the manufacturer of the Platelet Function Analyzer (PFA)-100 System has recently produced the INNOVANCE PFA P2Y test cartridge. We assessed the ability of this new test to reliably detect clopidogrel resistance. We enrolled 90 consecutive patients with coronary artery disease receiving chronic clopidogrel maintenance therapy in combination with aspirin. Twenty healthy volunteers served as controls. Clopidogrel resistance was simultaneously analysed by the INNOVANCE PFA P2Y test cartridge, ADP-induced LTA, the flow-cytometric vasodilator-stimulated phosphoprotein (VASP)-phosphorylation assay and the multiple electrode aggregometry (Multiplate). Agreement among the four platelet function methods by two was assessed using Cohen's kappa coefficient. According to the cut-off points for clopidogrel resistance proposed by the literature, agreement was fair between INNOVANCE PFA-100 P2Y and LTA (74.4%) and Multiplate (75.6%), while poor agreement was noticed in VASP assay (63.3%). Based on cut-off points indicating a higher thrombotic risk, agreement between the PFA-100 System and the other three methods did not significantly differ compared to the previous cut-offs (72.2%, 71.1% and 55.1%, respectively). The INNOVANCE PFA-100 P2Y test seems to be comparable to other established platelet function assays in detecting clopidogrel resistance. However, the modest agreement among platelet function methods makes the performance of platelet function testing crucial with more than one technique in order to reliably identify poor responders to clopidogrel treatment.

Angiotensin converting enzyme (ACE) insertion/deletion (I/D) polymorphism and circulating ACE levels are not associated with outcome in critically ill septic patients.

BACKGROUND: In critically ill patients independent studies have shown contradictory findings regarding the prognostic significance of the D/D genotype of the I/D angiotensin converting enzyme (ACE) polymorphism. The study aim was to evaluate the effect of both ACE I/D polymorphism and ACE serum levels on the clinical outcomes of critically ill septic patients. METHODS: This study recruited 186 Caucasian patients with sepsis, severe sepsis or septic shock. Epidemiological, clinical data, co-morbidities and severity scores were recorded. Measurements of serum ACE activity and genotyping for ACE I/D polymorphism were carried out. Primary outcomes were the 28- and the 90-day mortality; secondary outcomes included the number of days without renal or cardiovascular failure and ventilation-free days over the 28-day period following study enrolment. RESULTS: Neither 28- nor 90-day mortality were associated with ACE I/D polymorphism (p=0.59 and 0.34, respectively) or circulating ACE levels (p=0.17 and 0.25, respectively). Similarly, ACE polymorphism and levels were not related to ventilation-free days (p=0.14 and 0.25, respectively), days without cardiovascular failure (p=0.14 and 0.81, respectively) and days without renal failure (p=0.64 and 0.27, respectively). CONCLUSIONS: Neither ACE I/D polymorphism nor serum ACE levels seem to be significant prognostic factors of clinical outcomes in septic, critically ill patients.

Evaluation of a reverse-hybridization StripAssay for the detection of genetic polymorphisms leading to acenocoumarol sensitivity.

Acenocoumarol is mainly catabolized by CYP2C9 isoform of cytochrome P450 (CYP) liver complex and exerts its anticoagulant effect through the inhibition of Vitamin K Epoxide Reductase (VKOR). The most important genetic polymorphisms which lead to an impaired enzymatic activity and therefore predispose to acenocoumarol sensitivity, are considered to be CYP2C9*2 (Arg144Cys), CYP2C9*3 (Ile359Leu) and VKORC1-1639G>A, respectively. In this study we compared the results of the PGXThrombo StripAssay kit (ViennaLab Diagnostics,Vienna, Austria) with direct DNA sequencing and in house Restriction Fragment Length Polymorphisms (RFLP) for the detection of the aforementioned Single Nucleotide Polymorphisms (SNPs). The reverse hybridization StripAssay was found to be equally effective with RFLP and direct DNA sequencing for the detection of CYP2C9*2 and CYP2C9*3 polymorphisms, respectively. The comparison of the RFLP reference method with the reverse hybridization StripAssay for the detection of VKORC1-1639 G>A polymorphism showed that the reverse hybridization StripAsssay might misclassify some A/A homozygotes as heterozygotes. Optimization of the hybridization procedures may eliminate the extra low signal band observed in some samples at the reverse hybridization StripAssay and improve its diagnostic value.

Reduced carriership of 4G allele of plasminogen activator inhibitor-1 4G/5G polymorphism in very young survivors of myocardial infarction.

There are limited and controversial data regarding the impact of 4G/5G polymorphism of the plasminogen activator inhibitor-1 (PAI-1) gene in the pathogenesis of premature myocardial infarction (MI). We explored whether 4G/5G polymorphism of the PAI-1 gene is associated with the development of MI

Carotid Stent Restenosis and Thrombosis in Rabbits: The Effect of Antiplatelet Agents.

BACKGROUND: The purpose of the study was the comparative assessment of ticagrelor and clopidogrel effects on carotid post-balloon injury (PBI) and on post carotid artery stenting (CAS) rate of in-stent restenosis (ISR) and in-stent thrombosis in atherosclerotic rabbits. METHODS: Forty-eight New Zealand white rabbits on high-fat diet were randomized into 4 groups: A1: PBI and clopidogrel (30 mg/kg/d), A2: PBI and ticagrelor (21 mg/kg twice daily), B1: PBI, CAS, and clopidogrel (30 mg/kg/d), B2: PBI, CAS, and ticagrelor (21 mg/kg twice daily). All rabbits received orally aspirin (10 mg/kg/d) and interventions were performed in their right carotid arteries (RCAs). Optical coherence tomography (OCT) and carotid angiography were performed at end point, while platelet aggregation and lipid profile were measured. After euthanasia both carotids were obtained for histological examination. RESULTS: In B1 group, 3 rabbits presented thrombotic total occlusion of the stents, while none such episode was observed in B2 group. The neointimal areas in RCAs, calculated by OCT, did not differ between A1 and A2 groups, and between B1 and B2 groups (P > .05). From the histological findings, the intima/(media + intima) percentage (%) in RCAs of balloon-injured rabbits did not present any difference between groups (P = .812). Similarly, the immunohistochemically determined accumulation of endothelial cells and macrophages on vascular walls was equivalent between groups (P > .05). CONCLUSION: Following carotid balloon injury and stenting, clopidogrel and ticagrelor did not show any differential effects on the extent of neointimal formation and ISR in atherosclerotic rabbits receiving aspirin. Three thrombotic stent occlusions were noted in the clopidogrel treatment group, but this finding was not statistically significant.

The impact of the PAI-1 4G/5G polymorphism on the outcome of patients with ALI/ARDS.

INTRODUCTION: Increased levels of plasminogen activator inhibitor-1 (PAI-1) have been associated with worse outcome in ALI/ARDS. A single guanosine insertion/deletion (4G/5G) polymorphism in the promoter region of the PAI-1 gene, may play an important role in the regulation of PAI-1 expression. The objective of the study was to evaluate the effect of this polymorphism on the outcome of critically ill patients with ALI/ARDS. MATERIALS AND METHODS: 52 consecutive ventilated patients with ALI/ARDS were studied. Bronchoalveolar lavage was performed within 48 hours from diagnosis. Measurement of plasma and BALF PAI-1 activity and D-dimers levels, and 4G/5G genotyping of PAI-1 were carried out. The primary outcome was 28-day mortality, and secondary outcomes included organ dysfunction and ventilator-free days. RESULTS: 17 patients were homozygotes for the 4G allele. Severity scores were not different between subgroups upon study enrollment. 28-day mortality was 70.6% and 42.9% for the 4G-4G and the non-4G-4G patients, respectively (p=0.06). PAI-1 activity levels and D-dimer in plasma and BALF were not significantly different between the 4G-4G and the non-4G-4G subgroups. In the multivariate analysis, genotype 4G/4G was the only variable independently associated with 28-day mortality (Odds Ratio=9.95, 95% CI: 1.79-55.28, p=0.009). Furthermore, genotype 4G/4G and plasma PAI-1 activity levels were independently negatively associated with ventilator free days (p=0.033 and p=0.008, respectively). CONCLUSIONS: ALI/ARDS patients, homozygous for the 4G allele of the PAI-1 gene, experienced higher 28-day mortality. This genotype was associated with a reduction in the number of days of unassisted ventilation and was inversely associated with the number of days without organ failure.

Lack of association of angiotensin-converting enzyme insertion/deletion polymorphism and myocardial infarction at very young ages.

We examined whether angiotensin-converting enzyme (ACE) insertion (I)/deletion (D) polymorphism is associated with the development of myocardial infarction (MI) at < or = 35 years of age. The study sample consisted of 201 patients with premature MI and 140 age- and sex-matched healthy individuals. No difference was found in the distribution of ACE genotypes between the patients and controls. A higher prevalence of the DD genotype among hypertensives was found compared with the non-hypertensive patients (62.5% vs 35.6%, p = 0.01). ACE polymorphism is not associated with the development of premature MI and this might be due to the low prevalence of hypertension in young coronary patients.

Factor XIII Val34Leu polymorphism and the risk of myocardial infarction under the age of 36 years.

There are limited and controversial data regarding the impact of factor XIII (FXIII) Val34Leu polymorphism in the pathogenesis of premature myocardial infarction (MI). We examined whether FXIII Val34Leu polymorphism is associated with the development of early MI. We recruited 159 consecutive patients who had survived their first acute MI under the age of 36 years (mean age = 32.1 +/- 3.6 years, 138 were men). The control group consisted of 121 healthy individuals matched with cases for age and sex, without a family history of premature coronary heart disease (CHD). FXIII Val34Leu polymorphism was tested with polymerase chain reaction and reverse hybridization. There was a lower prevalence of carriers of the Leu34 allele in patients than in controls (30.2 vs. 47.1%, p = 0.006). FXIII Val34Leu polymorphism was associated with lower risk for acute MI after adjusting for major cardiovascular risk factors (odds ratio [OR] = 0.51, 95% confidence interval [CI] 0.27-0.95, p = 0.03). Subgroup analysis according to angiographic findings ("normal" coronary arteries [n = 29] or significant CHD [n = 130]) showed that only patients with MI and significant CHD had lower prevalence of carriers of the Leu34 allele compared to controls after adjusting for major cardiovascular risk factors (OR = 0.42, 95% CI 0.22-0.83, p = 0.01). Our data indicate that FXIII Val34Leu polymorphism has a protective effect against the development of MI under the age of 36 years, particularly in the setting of significant CHD.

Monitoring aspirin treatment in patients with thrombocytosis: comparison of the platelet function analyzer (PFA)-100 with optical aggregometry.

Aspirin provides satisfactory protection against thrombotic episodes in essential thrombocythemia (ET), but at higher platelet counts has been less effective. Our aim was to compare the platelet function analyzer (PFA)-100 with optical aggregometry in order to determine a reliable method in monitoring aspirin's influence on platelet function in patients with thrombocytosis. We studied 36 patients with thrombocytosis. Sixteen of them, receiving aspirin, composed group A, while group B consisted of 20 patients not taking aspirin. In all patients, we compared the platelet function measured by classic optical aggregation tests with closure times (CT) obtained by the PFA-100. The definition of platelet responses as normal or pathological showed that PFA-100 collagen and/or epinephrine (CEPI) CTs and epinephrine-induced aggregometry is the pair of methods with the higher agreement in monitoring of platelet dysfunction due to ASA treatment (a=94%). Satisfactory results were also obtained for group B (a=81%). The comparison between PFA-100 CEPI CTs and arachidonic acid-induced aggregometry exhibited moderate agreement both in the total number of patients and in group A (a=79% and 94%, respectively). PFA-100 collagen and/or ADP (CADP) CTs and ADP-induced aggregometry were not concordant. The PFA-100 system appears to be a reliable and rapid method in the assessment of aspirin's antiplatelet effect in patients with thrombocytosis. Regarding aggregometry, the selection of the inducer, its concentration and cut-off points is crucial in defining the response to antiaggregating agents. It still remains to determine whether there is any relevance between the measurements obtained by these methods and clinical outcome in thrombocythemic patients.

Prevalence of prothrombotic polymorphisms in Greece.

The aim of this study was to assess the prevalence of several polymorphisms in genes that are involved in several pathways such as hemostasis, fibrinolysis, platelet membrane receptor activity, endothelial integrity and function, lipid metabolism, and regulation of blood pressure in healthy subjects of Greek origin. Most of these polymorphisms are mainly associated with conditions such as venous thromboembolism and atherothrombosis, and their prevalence has not been studied yet in Greece. We tested 140 healthy individuals for factor V (FV)1691G/A, FV4070G/A, FII 20210G/A, factor XIII (FXIII) exon 2G/T, fibrinogen beta-455G/A, plasminogen activator inhibitor-1 (PAI-1)-675 4G/5G, human platelet antigens 1 (HPA1) a/b, apolipoprotein B (ApoB) 10708 G/A, apolipoprotein E (ApoE) E2, E3, and E4, angiotensin-converting enzyme (ACE) D/I, 5,10 methylenetetrahydrofolate reductase (MTHFR) 677C/T, and MTHFR 1298A/C polymorphisms using a PCR and reverse hybridization technique that detects all of them simultaneously. The allele frequencies observed are in accordance with those reported in other Caucasian populations and almost identical to those of East Mediterranean populations. This first report from Greece may serve as a baseline for planning further investigations of these polymorphisms in association with several clinical entities and for launching guidelines for patient testing of various disease settings in this population.

Association between the plasminogen activator inhibitor-1 4G/5G polymorphism and venous thrombosis. A meta-analysis.

The effect of the 675 insertion/deletion (4G/5G) polymorphism of plasminogen activator inhibitor-1 (PAI-1) gene on the risk of venous thromboembolism (VTE) remains controversial. In this study, we performed a meta-analysis of published data regarding this issue. A comprehensive electronic search was carried out up until September 2006. A total of 22 articles were included in the analysis that was performed using random effects models. Eighteen papers, concerning patients without another known risk factor, comprised 2,644 cases and 3,739 controls. The alleles contrast (4G vs. 5G allele) yielded a statistically significant odds ratio (OR) of 1.153 (95% confidence interval [CI]: 1.068-1.246). In a sub-analysis of five studies that included 256 cases with another genetic risk factor and 147 controls, the combined per-allele OR was still significant (OR: 1.833,95% CI: 1.325-2.536). On the contrary, the analysis of five studies regarding cases with a non-genetic risk factor for VTE (antiphospholipid antibody syndrome, Behcet disease) provided insignificant results in all aspects. There was no evidence for heterogeneity and publication bias in all analyses. Based on our findings, the 4G allele appears to increase the risk of venous thrombosis, particularly in subjects with other genetic thrombophilic defects. Recommendation for detection of this polymorphism in evaluating thrombophilia in such patients might be considered.

Integrin, alpha 2 gene C807T polymorphism and risk of ischemic stroke: a meta-analysis.

INTRODUCTION: Platelet adhesion to fibrillar collagen via the membrane glycoprotein (GP) Ia/IIa (alpha2beta1), is a crucial event in the pathogenesis of arterial occlusive disorders. The C807T single nucleotide polymorphism of the integrin, alpha 2 (ITGA2) gene has been shown to correlate with the platelet GPIa/IIa density. Consequently, subjects with the 807T allele, who express the highest receptor density, might have an increased potential of platelet adhesion and, hence an increased risk of cerebrovascular disease. However, the research findings remain controversial. MATERIALS AND METHODS: A comprehensive electronic search was carried out up until November 2005 and 7 independent studies with a maximum of 774 cases and 1074 controls were analyzed using random effects models. RESULTS: The pooled frequency of the T allele was 36.33% in cases and 37.01% in controls. The T versus the C allele contrast gave an OR of 1.11 (95% confidence interval=0.827-1.499). All the other comparisons failed to show any significant result. Age, sex, and cardiovascular risk factors were included as covariates into a meta-regression model without a significant finding. CONCLUSIONS: This meta-analysis do not support an association between the C807T polymorphism of ITGA2 gene and stroke, but given the significant between study heterogeneity and the small number of studies, the summary effect should be interpreted carefully.

Plasminogen activator inhibitor-1 4G/5G polymorphism and risk of ischemic stroke: a meta-analysis.

This study investigated the hypothesis that the insertion/deletion (4G/5G) polymorphism of the plasminogen activator inhibitor type-1 gene affects the risk for ischemic stroke, since results concerning this association have been controversial. We therefore performed a meta-analysis of published data regarding this issue. A comprehensive electronic search was carried out until January 2006. The analysis was performed using random-effects models and meta-regression. Eighteen eligible studies were retrieved (15 case-control studies and three cohort studies). The case-control studies included 3104 cases and 4870 control individuals concerning the contrast of 4G/4G versus remaining genotypes. The 4G pooled allele frequencies in cases and controls were 54.21 and 54.75%, respectively. Overall, the per-allele odds ratio of the 4G allele was 0.98 (95% confidence interval, 0.858-1.121). Regarding genotypes, we derived nonsignificant odds ratios in all contrasts. The subanalysis including the three studies with a prospective design in the 4G/4G versus 5G/5G contrast derived a significant result (relative risk, 0.523; 95% confidence interval, 0.353-0.775), but the estimated effect size was insignificant when cohort and case-control studies were analyzed together (relative risk, 0.848; 95% confidence interval, 0.662-1.087). We failed to demonstrate a significant association between the 4G/5G polymorphism and ischemic stroke under basal conditions. Determination of plasminogen activator inhibitor type-1 function seems of much higher clinical value than determination of the 4G/5G polymorphism. The effect of this genotype on risk of ischemic stroke in acute stressful diseases and the role of cohort studies in genetic epidemiology, however, warrant further investigation.

Antiphospholipid syndrome: a predisposing factor for early onset HELLP syndrome.

Hemolysis elevated liver enzymes low platelets syndrome (HELLP) is a relatively rare pregnancy-related thrombotic microangiopathic disorder, usually observed during the third trimester. Its incidence seems to be increased in patients with antiphospholipid syndrome (APS). In this report, we describe a 33-year-old pregnant woman with previously known primary APS who developed early onset HELLP syndrome during the 15th week of gestation. We also review the literature about this interesting relationship between APS and HELLP.

Redox imbalance, macrocytosis, and RBC homeostasis.

The erythrocyte represents a major component of the antioxidant capacity of the blood through the enzymes contained in the cell, the glutathione system, and the low-molecular-weight antioxidants of the erythrocyte membrane. A further major red blood cell contribution is in regenerating consumed redox equivalents via the oxidative pentose phosphate pathway and glutathione reductase. Moreover, its extracellular antioxidant capacity, its mobility, and the existence of reducing equivalents far in excess of its normal requirements make erythrocytes function as an effective oxidative sink in the organism. That is why red blood cell metabolism and homeostasis strongly affect the antioxidant properties of the whole body. Conversely, the relation between macrocytosis and oxidative stress has not been fully delineated. Reviewing the mechanisms involved in red blood cell homeostasis in cases of redox imbalance is crucial in identification of factors that could potentially improve erythrocyte survival and defense against oxidant damage.

Endothelial Protein C Receptor Gene Variants and Risk of Thrombosis.

Endothelial protein C receptor (EPCR) is a candidate mediator in the pathogenesis of thrombosis, as several data in the literature indicate that polymorphisms such as EPCR 4678G/C and 4600A/G are associated with either protective effect or increased risk of thrombosis, respectively. We investigated the prevalence of these polymorphisms in patients with thrombotic disorders as well as their impact on the risk of thrombosis, the age of first thrombotic episode, and recurrence. The prevalence of the rare EPCR alleles 4600G and 4678C was comparable in patients and controls. However, in a subset analysis, we observed that 4600G allele was more prevalent among patients who developed thrombosis at younger age (<35 years). Moreover, the prevalence of 4678C allele was significantly lower in younger patients compared to older patients. Neither polymorphism seemed to have an impact on recurrence regardless of age. Soluble EPCR levels were elevated in 4600AG patients compared to controls while 4678CC patients presented with lower levels of soluble form of EPCR compared to carriers of at least 1 4678G allele. Our data suggest that either the lack of the protective EPCR 4678C allele or the presence of EPCR 4600G allele may be associated with earlier development of thrombosis.

P-selectin and antibodies against heparin-platelet factor 4 in patients with venous or arterial diseases after a 7-day heparin treatment.

BACKGROUND: We investigated heparin influence on P-selectin (platelet adhesion molecule), and the association of P-selectin with antibodies against heparin-platelet factor 4, known mediators of heparin induced thrombocytopenia (HIT) occurring in about 5% of vascular patients. STUDY DESIGN: This cohort study included 78 patients, 22 to 90 years old (mean age +/- SD, 66.5 +/- 12.2 years), suffering from arterial thromboembolism (n = 43), deep vein thrombosis (n = 21), and peripheral arterial occlusive disease (PAOD) (n = 14). Plasma P-selectin was tested by ELISA before heparin administration (day 1), and under heparin treatment (day 7). HIT antibodies on day 7 were assayed using a sandwich-type ELISA. Platelets and fibrinogen were measured on days 1 and 7. P-selectin was also examined in 30 healthy controls, 22 to 81 years old (49.8 +/- 16.4 years). RESULTS: On day 7, patients with PAOD had increased P-selectin and HIT antibodies, and decreased platelets compared with patients with arterial thromboembolism or deep vein thrombosis, in whom P-selectin decreased, and HIT antibodies were mostly negative. Fibrinogen increased in all patients. HIT antibody titers and P-selectin were positively associated and were increased in nine patients who developed lower limb artery occlusion or bypass thrombosis, stroke, or myocardial infarction during hospitalization (days 5 to 24). Five of these patients suffered from PAOD and the majority had taken heparin in the past. CONCLUSIONS: P-selectin and HIT antibodies could be useful markers of HIT syndrome-associated thromboses during hospitalization of vascular patients receiving heparin. In arterial thromboembolism or deep vein thrombosis, P-selectin decreases without HIT antibody development. In PAOD, their concomitant increase may alert the surgeon to forthcoming life-threatening complications.

Retinal vein occlusion: genetic predisposition and systemic risk factors.

The role of systemic risk factors (age, smoking, diabetes, arterial hypertension) in the development of retinal vein occlusion (RVO) is well established. However, the association of RVO with genetic predisposition to thrombosis remains poorly understood. The aim of the study was to assess any possible additional effect of genetic predisposition to the already well known 'classical' risk factors of RVO in a cohort of elderly Greek patients. Fifty-one elderly patients with RVO and 51 healthy individuals matched for age and sex were evaluated for systemic risk factors (smoking, diabetes, dyslipidemia, arterial hypertension) and coagulation defects (lupus anticoagulant, natural inhibitors of coagulation). Additionally, genotyping was performed for mutations/polymorphisms involved in haemostasis such as: FV G1691A, FV G4070A, FIIG 20210A, MTHFR C677T and A1298C, PAI-1-675 4G/5G, F XIII exon 2G/T, EPCR A4600G and G4678C. We identified systemic risk factors in the majority of the patients Hypertension (P=0.001), dyslipidemia (P=0.029) and diabetes (P=0.01) are associated with RVO in the majority of the patients. The prevalence of prothrombotic risk factors was not significantly different in the patients with RVO compared to controls. Apart from systemic risk factors, genetic predisposition to thrombosis does not seem to have an important association with RVO in this group of elderly patients.

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.