Deficient t-PA Release and Elevated PA Inhibitor Levels in Patients with Spontaneous or Recurrent Deep Venous Thrombosis

Clot or Not? Reviewing the Reciprocal Regulation Between Lipids and Blood Clotting

Both hyperlipidemia and thrombosis contribute to the risks of atherosclerotic cardiovascular diseases, which are the leading cause of death and reduced quality of life in survivors worldwide. The accumulation of lipid-rich plaques on arterial walls eventually leads to the rupture or erosion of vulnerable lesions, triggering excessive blood clotting and leading to adverse thrombotic events. Lipoproteins are highly dynamic particles that circulate in blood, carry insoluble lipids, and are associated with proteins, many of which are involved in blood clotting. A growing body of evidence suggests a reciprocal regulatory relationship between blood clotting and lipid metabolism. In this review article, we summarize the observations that lipoproteins and lipids impact the hemostatic system, and the clotting-related proteins influence lipid metabolism. We also highlight the gaps that need to be filled in this area of research.

Chemical Adjustment of Fibrinolysis

Fibrinolysis is the process of the fibrin-platelet clot dissolution initiated after bleeding has been stopped. It is regulated by a cascade of proteolytic enzymes with plasmin at its core. In pathological cases, the balance of normal clot formation and dissolution is replaced by a too rapid lysis, leading to bleeding, or an insufficient one, leading to an increased thrombotic risk. The only approved therapy for emergency thrombus lysis in ischemic stroke is recombinant tissue plasminogen activator, though streptokinase or urokinase-type plasminogen activators could be used for other conditions. Low molecular weight compounds are of great interest for long-term correction of fibrinolysis dysfunctions. Their areas of application might go beyond the hematology field because the regulation of fibrinolysis could be important in many conditions, such as fibrosis. They enhance or weaken fibrinolysis without significant effects on other components of hemostasis. Here we will describe and discuss the main classes of these substances and their mechanisms of action. We will also explore avenues of research for the development of new drugs, with a focus on the use of computational models in this field.

Proteomic biomarkers of sleep apnea

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is characterized by recurrent partial to complete upper airway obstructions during sleep, leading to repetitive arousals and oxygen desaturations. Although many OSA biomarkers have been reported individually, only a small subset have been validated through both cross-sectional and intervention studies. We sought to profile serum protein biomarkers in OSA in unbiased high throughput assay.

METHODS

A highly multiplexed aptamer array (SomaScan) was used to profile 1300 proteins in serum samples from 713 individuals in the Stanford Sleep Cohort, a patient-based registry. Outcome measures derived from overnight polysomnography included Obstructive Apnea Hypopnea Index (OAHI), Central Apnea Index (CAI), 2% Oxygen Desaturation index, mean and minimum oxygen saturation indices during sleep. Additionally, a separate intervention-based cohort of 16 individuals was used to assess proteomic profiles pre- and post-intervention with positive airway pressure.

RESULTS

OAHI was associated with 65 proteins, predominantly pathways of complement, coagulation, cytokine signaling, and hemostasis which were upregulated. CAI was associated with two proteins including Roundabout homolog 3 (ROBO3), a protein involved in bilateral synchronization of the pre-Bötzinger complex and cystatin F. Analysis of pre- and post intervention samples revealed IGFBP-3 protein to be increased while LEAP1 (Hepicidin) to be decreased with intervention. An OAHI machine learning classifier (OAHI >=15 vs OAHI<15) trained on SomaScan protein measures alone performed robustly, achieving 76% accuracy in a validation dataset.

CONCLUSIONS

Multiplex protein assays offer diagnostic potential and provide new insights into the biological basis of sleep disordered breathing.

Pharmacological Targeting of Plasminogen Activator Inhibitor-1 Decreases Vascular Smooth Muscle Cell Migration and Neointima Formation

OBJECTIVE

Plasminogen activator inhibitor-1 (PAI-1), a serine protease inhibitor that promotes and inhibits cell migration, plays a complex and important role in adverse vascular remodeling. Little is known about the effects of pharmacological PAI-1 inhibitors, an emerging drug class, on migration of vascular smooth muscle cells (SMCs) and endothelial cells (ECs), crucial mediators of vascular remodeling. We investigated the effects of PAI-039 (tiplaxtinin), a specific PAI-1 inhibitor, on SMC and EC migration in vitro and vascular remodeling in vivo.

APPROACH AND RESULTS

PAI-039 inhibited SMC migration through collagen gels, including those supplemented with vitronectin and other extracellular matrix proteins, but did not inhibit migration of PAI-1-deficient SMCs, suggesting that its antimigratory effects were PAI-1-specific and physiologically relevant. However, PAI-039 did not inhibit EC migration. PAI-039 inhibited phosphorylation and nuclear translocation of signal transducers and activators of transcription-1 in SMCs, but had no discernable effect on signal transducer and activator of transcription-1 signaling in ECs. Expression of low-density lipoprotein receptor-related protein 1, a motogenic PAI-1 receptor that activates Janus kinase/signal transducers and activators of transcription-1 signaling, was markedly lower in ECs than in SMCs. Notably, PAI-039 significantly inhibited intimal hyperplasia and inflammation in murine models of adverse vascular remodeling, but did not adversely affect re-endothelialization after endothelium-denuding mechanical vascular injury.

CONCLUSIONS

PAI-039 inhibits SMC migration and intimal hyperplasia, while having no inhibitory effect on ECs, which seems to be because of differences in PAI-1-dependent low-density lipoprotein receptor-related protein 1/Janus kinase/signal transducer and activator of transcription-1 signaling between SMCs and ECs. These findings suggest that PAI-1 may be an important therapeutic target in obstructive vascular diseases characterized by neointimal hyperplasia.

Recurrence and Late Sequelae after First-Time Deep Vein Thrombosis: Relationship to Initial Signs

Objective:

To investigate the relation between initial symptoms and long-term sequelae in first-time deep venous thrombosis (DVT).

Design:

Follow-up study of patients 6 years after an episode of suspected symptomatic DVT.

Setting:

Vascular laboratory, University Hospital of Lund.

Patients:

66 patients, 19 with femoral DVT, 20 with calf DVT and 27 with normal phlebograms at initial investigation.

Main outcome measures:

Symptoms and signs of chronic venous insufficiency (CVI), foot volumetry and measurement of plasminogen activator inhibitor 1 (PAI-1) activity. Initial clinical signs and results at phlebography were compared with findings at follow-up.

Results:

Of patients with DVT, 11 (28%) had been treated for a recurrent DVT during follow-up. No relation was found between initial signs of DVT and late signs of CVI. Patients with DVT had significantly more signs of CVI but symptoms did not differ between the groups. Mean levels of PAI-1 activity were similar in the three groups, and patients with recurrent DVT did not differ. Refilling flow was related to the clinical CVI-score, and expelled volume was inversely related to the extension of DVT at phlebography.

Conclusion:

The recurrence rate is high in first-time DVT, but symptoms are mostly mild as long as after 6 years. There is a poor correlation between symptoms of CVI and objective findings. The late development of CVI cannot be predicted from the clinical signs in the acute phase. Levels of PAI-1 do not correlate with the degree of CVI.

A Case of Unexplained Cerebral Sinus Thrombosis in a 22-Year-Old Obese Caucasian Woman

Herein, we present the case of a 22-year old obese Caucasian woman female with no acquired thrombophilic risk factors who was diagnosed with extensive cerebral sinus thrombosis. A detailed thrombophilia workup demonstrated persistently elevated plasminogen activator inhibitor 1 (PAI-1) activity levels, with an elevated PAI-1 antigen concentration and homozygosity for the PAI-1 4G allele (4G/4G genotype). The patient was treated with indefinite warfarin anticoagulation medication due to the unprovoked nature of her thrombotic event. Disturbances in the fibrinolytic system, in particular PAI-1, have been related to an increased risk of arterial and venous thrombosis. In this article, we discuss the pathophysiology of hypofibrinolysis associated with elevated PAI-1 levels and the PAI-1 4G/5G polymorphism.

Assessment of Anti-Tissue Type Plasminogen Activator Antibodies in Patients With Prosthetic Heart Valve Thrombosis: The ATA Trial

BACKGROUND

Thrombolysis is an effective treatment strategy for prosthetic valve thrombosis (PVT). Recombinant tissue-type plasminogen activator (rt-PA) is widely used as a thrombolytic agent. Infusion of rt-PA may trigger the production of anti-tissue plasminogen activator (tPA) antibodies (ATAs). We aimed to evaluate the possible relationship between ATA levels and PVT formation, and the role of baseline ATA levels on outcomes of thrombolytic therapy in patients with PVT.

METHODS

This prospective, single-center cohort study included 28 patients with PVT undergoing thrombolysis and 31 controls with normal prostheses. Plasma samples were collected from patients with PVT at baseline and at 15th, 30th, 90th, and 180th days after thrombolysis and from controls at baseline only. The ATA levels were assessed in human plasma by an enzyme-linked immunosorbent assay.

RESULTS

Baseline ATA-immunoglobulin (Ig) G and IgM were significantly higher in patients with PVT than in controls. The levels of IgM and IgG peaked at 15th and 30th days after rt-PA infusion, respectively. Subtherapeutic international normalized ratio and baseline ATA-IgM were independent predictors of PVT. Thrombolysis failed in 6 patients (21%) in whom baseline IgM levels were significantly higher than successfully lysed patients. Rethrombosis occurred in 9 patients (32%) in whom baseline IgG levels were significantly higher than those without rethrombosis. There was a moderate positive correlation between baseline and 15th-day IgM levels and the dose of rt-PA needed for successful lysis.

CONCLUSION

The ATA levels tended to be higher in patients with PVT at the time of initial diagnosis compared to controls without PVT. In addition, such patients with PVT and high ATA levels may be at high risk for failed thrombolysis or rethrombosis.

Residual vein thrombosis and onset of post-thrombotic syndrome: influence of the 4G/5G polymorphism of plasminogen activator inhibitor-1 gene

BACKGROUND

Plasminogen activator inhibitor-1 (PAI-1) is the most important inhibitor of plasminogen activator. The functional 4G/5G polymorphism of the gene coding for PAI-1 may affect PAI-1 plasmatic activity, influencing the imbalance between coagulation and fibrinolysis cascades. In this prospective cohort analytic study, we investigated the role of this single nucleotide polymorphism in the persistence of thrombotic lesion and the occurrence of post-thrombotic syndrome.

PATIENTS/METHODS

In a group of 168 patients with post-surgical deep vein thrombosis of the legs, we analyzed the 4G/5G polymorphism in the promoter of PAI-1 gene and plasmatic PAI-1 activity. Enrolled patients were divided in two groups: patients with 4G/5G polymorphism and increased PAI-1 activity (n=85) and patients without 4G/5G polymorphism and normal PAI-1 activity (n=83). All patients were treated according to current protocols and re-examined after 3, 12 and 36 months in order to evaluate the persistence of thrombotic lesion and the occurrence of post-thrombotic syndrome.

RESULTS

We found a significantly increased PAI activity in carrier of the 4G allele, who experienced much more frequently a persistence of thrombosis after 3, 12 and 36 months and/or the development of post-thrombosis syndrome, in spite of the anticoagulant treatment.

CONCLUSIONS

These data not only confirm the role played by PAI-1 activity and by the 4G/5G SNP of the PAI-1 gene, but also suggest that current therapeutic protocols, recommending the administration of low weight molecular heparin and oral anticoagulant for the treatment of deep vein thrombosis, could be non sufficient for patients genetically predisposed to a less efficient clot lysis.

Metformin: an old drug with new potential

Metformin is the most commonly prescribed antidiabetic oral agent. It has also been used off-label for polycystic ovarian syndrome, steatohepatitis, and HIV-associated metabolic abnormalities. However, this oldie is a newbie for the oncologist. Population studies have suggested that metformin decreased the incidence and mortality rates of cancer in diabetic patients. With better understanding of its mechanisms of antitumor activity, metformin may become a new drug for cancer in combination with chemotherapy or targeted therapy.

Coagulation abnormalities in osteonecrosis and bone marrow edema syndrome

The aim of this review was to provide information about the variety of thrombophilic and hypofibrinolytic markers that are possible risk factors for the development of osteonecrosis and bone marrow edema syndrome. A total of 48 parameters were identified in 45 studies that included 2163 patients. The most frequently reported laboratory findings included altered serum concentrations of lipoproteins, decreased concentration and function of fibrinolytic agents, increased levels of thrombophilic markers, and several single nucleotide polymorphisms. Despite inhomogeneities in reported parameters, results, patients' collectives, and treatment strategies, these data suggest that coagulation abnormalities may play an important role in the emergence of osteonecrosis and bone marrow edema syndrome.

Association between venous thromboembolism and plasma levels of both soluble fibrin and plasminogen-activator inhibitor 1 in 170 patients undergoing total hip arthroplasty

BACKGROUND AND PURPOSE

Markers of coagulation and fibrinolysis, such as soluble fibrin (SF), D-dimer, and plasminogen activator inhibitor 1 (PAI-1), have been developed in order to determine thrombotic tendency. We investigated whether these markers could be used to diagnose venous thromboembolism (VTE) in the early phase after primary total hip arthroplasty (THA).

METHODS

This prospective study involved 2 groups: an intermittent pneumatic compression (IPC) group (67 patients who underwent IPC only as prophylaxis for VTE) and a fondaparinux (FPX) group (103 patients who received IPC and FPX postoperatively). Plasma levels of SF and PAI-1 were measured on postoperative day 1. To diagnose postoperative VTE, multi-detector row computed tomography (MDCT) and duplex ultrasonography (US) were performed on postoperative day 7.

RESULTS

VTE was detected postoperatively in 17 cases in the IPC group (25%) and in 8 cases in the FPX group (6%). In the IPC group, plasma levels of SF and PAI-1 were higher in patients with VTE (p < 0.01) than in those without VTE. On the other hand, in the FPX group there were no differences in the levels of SF or PAI-1 measured before administration of FPX on postoperative day 1. The diagnostic criterion of an increase in SF or PAI-1 above the cutoff level (19.8 µg/mL and 53.5 ng/mL, respectively) provided a sensitivity of 100% and a specificity of 67% in the IPC group. In addition, when this criterion was applied to FPX patients, 7 of the 8 patients with VTE met the criterion, and there was a negative agreement rate of 48/49.

INTERPRETATION

Screening using the cutoff levels of SF and PAI-1 may be useful and shows high sensitivity in predicting postoperative VTE in the early phase after THA.

Maximal PAI-1 inhibition in vivo requires neutralizing antibodies that recognize and inhibit glycosylated PAI-1

Plasminogen activator inhibitor-1 (PAI-1) regulates the activity of t-PA and u-PA and is an important inhibitor of the plasminogen activator system. Elevated PAI-1 levels have been implicated in the pathogenesis of several diseases. Prior to the evaluation of PAI-1 inhibitors in humans, there is a strong need to study the effect of PAI-1 inhibition in mouse models. In the current study, four monoclonal antibodies previously reported to inhibit recombinant PAI-1 in vitro, were evaluated in an LPS-induced endotoxemia model in mice. Both MA-33H1F7 and MA-MP2D2 exerted a strong PAI-1 inhibitory effect, whereas for MA-H4B3 and MA-124K1 no reduced PAI-1 activity was observed in vivo. Importantly, the lack of PAI-1 inhibition observed for MA-124K1 and MA-H4B3 in vivo corresponded with the absence of inhibition toward glycosylated mouse PAI-1 in vitro. Three potential N-glycosylation sites were predicted for mouse PAI-1 (i.e. N209, N265 and N329). Electrophoretic mobility analysis of glycosylation knock-out mutants before and after deglycosylation indicates the presence of glycan chains at position N265. These data demonstrate that an inhibitory effect toward glycosylated PAI-1 is a prerequisite for efficient PAI-1 inhibition in mice. Our data also suggest that PAI-1 inhibitors for use in humans must preferably be screened on glycosylated PAI-1 and not on recombinant non-glycosylated PAI-1.

Significant associations of PAI-1 genetic polymorphisms with osteonecrosis of the femoral head

BACKGROUND

The pathogenesis of osteonecrosis of the femoral head (ONFH) has been implicated in hypofibrinolysis and blood supply interruption. Previous studies have demonstrated that decreased fibrinolytic activity due to elevated plasminogen activator inhibitor-1 (PAI-1) levels correlates with ONFH pathogenesis. The -675 4G/5G single nucleotide polymorphism (SNP rs1799889) in the PAI-1 gene promoter is associated with PAI-1 plasma level. We investigated whether rs1799889 and two other SNPs of the PAI-1 gene (rs2227631, -844 G/A in the promoter; rs11178, +10700 C/T in the 3'UTR) are associated with increased ONFH risk.

METHODS

Three SNPs in PAI-1 were genotyped in 206 ONFH patients and 251 control subjects, using direct sequencing and a TaqMan® 5' allelic discrimination assay. We performed association analysis for genotyped SNPs and haplotypes with ONFH.

RESULTS

The 4G allele of rs1799889, A allele of rs2227631, and C allele of rs11178 were significantly associated with increased ONFH risk (p = 0.03, p = 0.003, and p = 0.002, respectively). When we divided the population according to gender, an association between the three SNPs and increased risk of ONFH was found only in men. In another subgroup analysis based on the etiology of ONFH, rs2227631 (A allele) and rs11178 (C allele) in the idiopathic subgroup (p = 0.007 and p = 0.021) and rs1799889 (4G allele) and rs11178 (C allele) in the alcohol-induced subgroup (p = 0.042 and p = 0.015) were associated with increased risk of ONFH. In addition, a certain haplotype (A-4G-C) of PAI-1 was also significantly associated with ONFH (p < 0.001).

CONCLUSION

Our findings demonstrated that three SNPs (rs1799889, rs2227631, and rs11178) of the PAI-1 gene were associated with ONFH risk. This study also suggests that PAI-1 SNPs may play an important role in ONFH.

Plasminogen activator inhibitor-1 (PAI-1): a key factor linking fibrinolysis and age-related subclinical and clinical conditions

INTRODUCTION

The close relationship existing between aging and thrombosis has growingly been studied in this last decade. The age-related development of a prothrombotic imbalance in the fibrinolysis homeostasis has been hypothesized as the basis of this increased cardiovascular and cerebrovascular risk. Fibrinolysis is the result of the interactions among multiple plasminogen activators and inhibitors constituting the enzymatic cascade, and ultimately leading to the degradation of fibrin. The plasminogen activator system plays a key role in a wide range of physiological and pathological processes.

METHODS

Narrative review.

RESULTS

Plasminogen activator inhibitor-1 (PAI-1) is a member of the superfamily of serine-protease inhibitors (or serpins), and the principal inhibitor of both the tissue-type and the urokinase-type plasminogen activator, the two plasminogen activators able to activate plasminogen. Current evidence describing the central role played by PAI-1 in a number of age-related subclinical (i.e., inflammation, atherosclerosis, insulin resistance) and clinical (i.e., obesity, comorbidities, Werner syndrome) conditions is presented.

CONCLUSIONS

Despite some controversial and unclear issues, PAI-1 represents an extremely promising marker that may become a biological parameter to be progressively considered in the prognostic evaluation, in the disease monitoring, and as treatment target of age-related conditions in the future.

Coagulation and fibrinolysis in diabetes

Atherothrombotic complications are the main cause of mortality in subjects with diabetes. Premature atherosclerosis, increased platelet reactivity and activation of coagulation factors with associated hypofibrinolysis all contribute to increased cardiovascular risk in this population. Blood clot formation represents the last step in the atherothrombotic process, and the structure of the fibrin network has a role in determining predisposition to cardiovascular disease. In this review, we discuss alterations in coagulation factor plasma levels and/or activity in diabetes and clarify their role in predisposition to cardiovascular events. The effect of diabetes on fibrin network structure/fibrinolysis is reviewed and potential mechanisms that modify clot properties are discussed. Finally, modulation of clotting potential by the various therapeutic agents used in diabetes is examined. Understanding the mechanisms by which diabetes influences the coagulation pathway will help to develop more effective treatment strategies to reduce thrombotic events in subjects with this condition.

Plasminogen activator inhibitor-1 (PAI-1) gene 4G/5G promoter polymorphism is seen in higher frequency in the Indian patients with deep vein thrombosis

INTRODUCTION

A number of prothrombotic and fibrinolytic disorders may lead to venous thrombosis. A 4G/5G polymorphism located in the promoter region of plasminogen activator inhibitor-1 (PAI-1) gene has been found to be commonly associated with the levels of PAI-1 and might be a risk factor for deep vein thrombosis (DVT). The aim of this study was to look for the potential association of this polymorphism with DVT in the Asian Indian population.

MATERIAL AND METHODS

A total of 110 consecutive patients (M:F = 62:48) with idiopathic DVT and equal number of age- and sex-matched healthy controls were the study participants. All study participants were typed for the PAI-1 4G/ 5G polymorphism, factor V Leiden, factor V Hong Kong/Cambridge mutations, and HR2 haplotype.

RESULT

The variant allele for the PAI-1 4G/5G polymorphism showed both genotypic (P = .0013, chi(2) = 10.303; odds ratio [OR] = 3.75) as well as allelic association (P = .0004, chi(2) = 12.273; OR = 1.99) with DVT. Factor V Leiden and factor V HR2 haplotype were observed in 10 (9.0%) and 13 (11.8%) patients, respectively. None of the study participants showed the factor V Hong Kong Cambridge mutations.

CONCLUSION

Our study shows the association of 4G allele with DVT in Asian Indian population. The higher prevalence of 4G polymorphism in patients with DVT (compared with controls) seen in our study is in concordance with previous reports from the Caucasian population.

Toxicogenomic analysis of mainstream tobacco smoke-exposed mice reveals repression of plasminogen activator inhibitor-1 gene in heart

Tobacco smoking is associated with cardiovascular pathology. However, the molecular mechanisms of tobacco smoke exposure that lead to initiation or exacerbation of cardiovascular disease are unclear. In this study, the effects of mainstream tobacco smoke (MTS) on global transcription in the heart were investigated. Male C57B1/CBA mice were exposed to MTS from 2 cigarettes daily, 5 days/wk for 6 or 12 wk. Mice were sacrificed immediately, or 6 wk following the last cigarette. High-density DNA microarrays were used to characterize global gene expression changes in whole heart. Fifteen genes were significantly differentially expressed following exposure to MTS. Among these genes, cytochrome P-450 1A1 (Cyp1A1) was upregulated by 12-fold, and Serpine-1 (plasminogen activator inhibitor-1, PAI-1) was downregulated by 1.7-fold. Concomitant increase in Cyp1A1 protein levels and decrease in total and active PAI-1 protein was observed in tissue extracts by Western blot assay and enzyme-linked immunosorbent assay (ELISA), respectively. Observed changes were transient and were partially reversed during break periods. Thus, gene expression profiling of heart tissue revealed a novel cardiovascular mechanism operating in response to MTS. Our results suggest a potential role for PAI-1 in MTS-induced cardiovascular pathology.

Shadows of complexity: what biological networks reveal about epistasis and pleiotropy

Pleiotropy, in which one mutation causes multiple phenotypes, has traditionally been seen as a deviation from the conventional observation in which one gene affects one phenotype. Epistasis, or gene-gene interaction, has also been treated as an exception to the Mendelian one gene-one phenotype paradigm. This simplified perspective belies the pervasive complexity of biology and hinders progress toward a deeper understanding of biological systems. We assert that epistasis and pleiotropy are not isolated occurrences, but ubiquitous and inherent properties of biomolecular networks. These phenomena should not be treated as exceptions, but rather as fundamental components of genetic analyses. A systems level understanding of epistasis and pleiotropy is, therefore, critical to furthering our understanding of human genetics and its contribution to common human disease. Finally, graph theory offers an intuitive and powerful set of tools with which to study the network bases of these important genetic phenomena.

Design, synthesis, and evaluation of orally active inhibitors of plasminogen activator inhibitor-1 (PAI-1) production

A novel series of butadiene-imide 1 (T-686) derivatives having an inhibitory activity against PAI-1 production was synthesized and evaluated their biological activities and DMPK profiles, in which 15k (T-2639) was selected as the best compound based on its strong antithrombotic activity and good bioavailability.

Some antiphospholipid antibodies bind to hemostasis and fibrinolysis proteases and promote thrombosis

It is generally accepted that the major autoantigen for antiphospholipid antibodies (aPL) is β2glycoprotein I (β2GPI). Interestingly, some aPL bind to β2GPI and the homologous enzymatic domains of several proteases involved in hemostasis and fibrinolysis, and correspondingly hinder anticoagulant regulation and resolution of clots. These findings are consistent with several early findings of aPL and provide a new perspective about some aPL in terms of their binding specificities and related functional properties in promoting thrombosis. In addition, homologous enzymatic domains of the involved proteases share conformation epitope(s) with β2GPI, thus providing a possible structural basis for some non-mutually exclusive mechanisms of aPL-mediated thrombosis.

Cardiovascular disease and heritability of the prothrombotic state

Atherothrombotic disease remains a major cause of mortality worldwide, and family clustering suggests an important contribution of genetic factors to disease pathogenesis. Thrombus formation represents the final step in atherothrombosis, a process influenced by genetic and environmental factors. A major difficulty of investigating the genetic regulation of thrombotic conditions is the complexity of the phenotype and the relatively modest effects of individual genetic variations. We address in this review genetic aspects involved in regulating thrombosis potential and their impact on the development of atherothrombotic disease. The effects of common genetic polymorphisms in clotting factors are discussed and examples of complex gene-gene and gene-environment interactions are highlighted. Understanding the effects of genetic factors on predisposition to thrombotic disease and unravelling the complex gene-environment interactions will help to better understand the pathophysiology of this complex condition, which will enable the development of new preventative and treatment strategies.

A PAI-1 (SERPINE1) polymorphism predicts osteonecrosis in children with acute lymphoblastic leukemia: a report from the Children's Oncology Group

As glucocorticoid use increased in acute lymphoblastic leukemia, osteonecrosis became an increasingly frequent complication. Besides increased age, host risk factors are poorly defined. We tested whether 12 polymorphisms were associated with osteonecrosis among patients 10 years and older treated on the CCG1882 protocol. Candidate genes (TYMS, MTHFR, ABCB1, BGLAP, ACP5, LRP5, ESR1, PAI-1, VDR, PTH, and PTHR) were chosen based on putative mechanisms underlying osteonecrosis risk. All children received dexamethasone, with doses varying by treatment arm. A PAI-1 polymorphism (rs6092) was associated with risk of osteonecrosis in univariate (P = .002; odds ratio = 2.79) and multivariate (P = .002; odds ratio = 2.89) analyses (adjusting for gender, age, and treatment arm). Overall, 21 of 78 (26.9%) children with PAI-1 GA/AA genotypes, versus 25 of 214 (11.7%) children with GG genotype, developed osteonecrosis. PAI-1 polymorphisms and PAI-1 serum levels have previously been associated with thrombosis. We conclude that PAI-1 genetic variation may contribute to risk of osteonecrosis.

Autoantibodies to plasminogen and tissue plasminogen activator in women with recurrent pregnancy loss

Reduced fibrinolytic activity has been described in primary anti-phospholipid syndrome (PAPS), and may be responsible for thrombotic events. Antibodies to tissue type plasminogen activator (t-PA) or plasminogen (PLG) might contribute to the hypofibrinolytic state in autoimmune diseases, but the clinical significance of these antibodies is still unclear in recurrent pregnancy loss (RPL). The aim of this study is to evaluate the prevalence and clinical significance of anti-PLG and anti-t-PA antibodies in 87 patients with a history of RPL: 54 women with well-defined PAPS (mean age 32.5 years; range 26-38) and 33 women with unexplained RPL (mean age 30 years; range 24-39). IgG anti-PLG antibodies were found in 20 and four patients from the group with RPL/PAPS and unexplained RPL, respectively; IgG anti-t-PA antibodies were found in 11 and two patients from the above two groups, respectively. IgG anti-PLG antibodies were associated with the high risk of RPL (OR 7.2, P = 0.004), especially with RPL/PAPS (OR 11.2, P < 0.001) evaluated by Fisher's exact test, while IgG anti-t-PA were associated with RPL/PAPS (OR 10.0, P = 0.01) but not with RPL (OR 6.8, P = 0.06). A significant inhibition of exogenous fibrinolysis was observed by IgG fractions from patients with anti-PLG or anti-t-PA antibodies on microplates and on the human umbilical vein endothelial cells, compared with those from healthy controls. The prevalence of IgG anti-PLG antibodies was high in RPL patients, especially in RPL/PAPS, while the prevalence of IgG anti-t-PA antibodies was high in RPL/PAPS but not in RPL, and some of them might inhibit fibrinolysis in patients.

Gender-specific correlations of plasminogen activator inhibitor-1 and tissue plasminogen activator levels with cardiovascular disease-related traits

BACKGROUND

The purpose of this study was to examine the correlations between plasma levels of plasminogen activator inhibitor-1 (PAI-1) and tissue plasminogen activator (t-PA) and cardiovascular disease-related traits in a general population and whether these correlations differed between females and males.

METHODS

Plasma PAI-1 and t-PA antigen levels and C-reactive protein (CRP), HDL-cholesterol, triglycerides, total cholesterol, systolic blood pressure, diastolic blood pressure, urinary albumin excretion, and glucose were measured in the population-based PREVEND study in Groningen, the Netherlands (n = 2527).

RESULTS

Except for CRP and total cholesterol levels, all traits were significantly different between gender (P < 0.001). PAI-1 levels were correlated with all measured cardiovascular disease-related traits (P < 0.01) in both females and males. Except for urinary albumin excretion, similar results, albeit less significant, were found for t-PA levels. Age-adjusted correlations between PAI-1 and CRP, triglycerides, total cholesterol, systolic blood pressure, and diastolic blood pressure differed significantly between females and males (P < 0.01). Many of the gender differences were predominantly present between premenopausal females and males.

CONCLUSION

PAI-1 and t-PA levels were correlated with cardiovascular disease-related traits in subjects obtained from the general population and several of these correlations differed across gender. The correlations found in the present study suggest the presence of coordinated patterns of cardiovascular risk factors and indicate which traits might influence PAI-1 and t-PA levels and thereby provide a framework and potential tool for therapeutic intervention to reduce thromboembolic events in the general population.

Role of clotting factors and fibrin structure in predisposition to atherothrombotic disease

Atherothrombotic disease is a multifactorial disorder that develops secondary to a complex gene-environment interaction. The formation of an obstructive thrombus represents the final stage of the atherothrombotic process, and understanding the mechanisms involved in clot formation is essential in order to develop new preventive and therapeutic strategies aimed at decreasing mortality and morbidity from the disease. Studies have demonstrated an important correlation between final clot structure and predisposition to atherothrombotic disease. Both genetic and environmental factors contribute to the final ultrastructure of the clot, which, in turn, influences an individual's risk of the disease. This paper reviews the factors involved in determining clot structure. The role of commonly used therapeutic agents in modulating clot structure will also be discussed.

Antibodies to tissue-type plasminogen activator (t-PA) in patients with inflammatory bowel disease: high prevalence, interactions with functional domains of t-PA and possible implications in thrombosis

BACKGROUND

Patients with inflammatory bowel disease (IBD) have an increased prevalence of thromboembolic events. The pathogenetic mechanisms of these events include reduced fibrinolysis, which may be caused by antibodies to tissue-type plasminogen activator (t-PA).

OBJECTIVES

To evaluate anti-t-PA antibodies in patients with IBD, considering clinical, biochemical and functional characteristics.

PATIENTS AND METHODS

We immunoenzymatically measured anti-t-PA antibodies in plasma from 97 consecutive IBD patients and 97 age- and sex-matched healthy controls. We also assessed the antibody interactions with different epitopes of t-PA, the antibody inhibition on t-PA activity and the correlations with clinical features and other serum antibodies.

RESULTS

IBD patients had higher median anti-t-PA antibody levels (5.4 U mL(-1) vs. 4.0 U mL(-1); P < 0.0001): 18 patients were above the 95th percentile of the controls (OR 5.3; 95% CI 1.7-16.3; P < 0.003), and the six with a history of thrombosis tended to have high levels (6.9 U mL(-1)). Anti-t-PA antibody levels did not correlate with IBD type, activity, location or treatment, or with age, sex, acute-phase reactants or other antibodies. The anti-t-PA antibodies were frequently IgG1 and bound t-PA in fluid phase; they recognized the catalytic domain in 10 patients and the kringle-2 domain in six. The IgG fraction from the three patients with the highest anti-t-PA levels slightly reduced t-PA activity in vitro.

CONCLUSIONS

The prevalence of anti-t-PA antibodies is high in IBD patients. By binding the catalytic or kringle-2 domains of t-PA, these antibodies could lead to hypofibrinolysis and contribute to the prothrombotic state of IBD.

Coagulation and atherothrombotic disease

Atherothrombotic disease arises secondary to a complex gene-environment interaction. In the initial stages, the condition is clinically silent but with more advanced disease, an occlusive thrombus is formed resulting in the classical clinical manifestations. Both environmental factors and genetic variations in elements of the clotting cascade influence thrombosis risk by inducing quantitative and qualitative changes in the mature protein, which may affect the final structure of the clot and determine its resistance to lysis. Understanding the fine details of gene-environment interactions in relation to thrombus formation will help to shed more light on disease pathogenesis. Consequently, this will allow the development of more efficacious treatment strategies and will also help to identify subjects at risk, thereby enabling the introduction of early preventative measures.

Sequence variations within the genes related to hemostatic imbalance and their impact on coronary artery disease in Turkish population

Coronary artery disease (CAD) is reported to be associated with some genetic risk factors. Since identification of genetic risk factors for CAD in different ethnic groups is important for the development of new intervention and prevention programs, we investigated the association between the R353Q and -323ins10 polymorphisms in Factor VII gene, C677T mutation in MTHFR, Factor V Leiden and PT G20210A mutations and CAD in Turkish population. The promoter region of the PAI-1 gene was also screened by SSCA (single-stranded conformation analysis) using specifically designed primers. 137 CAD patients with early onset documented by coronary angiography and 41 individuals who had no significant coronary stenosis by angiography as control group were screened for the identification of the polymorphisms. In conclusion, Factor V Leiden was found to be an independent genetic risk factor for CAD in Turkish population. Combined risk assessment indicated that the coexistence of two other inherited thrombophilia markers, namely MTHFR C677T and PT G20210A with Factor V Leiden may increase the risk of the development of the disease in this population. The results of the present study show that there is no statistically significant association between the two polymorphisms in Factor VII gene, MTHFR C677T polymorphism, PT G20210A polymorphism, 4G/5G polymorphism of PAI-1 and CAD in Turkish population.

Identification of polyclonal and monoclonal antibodies against tissue plasminogen activator in the antiphospholipid syndrome

OBJECTIVE

To test the hypotheses that some plasmin-reactive anticardiolipin antibodies (aCL) may bind to tissue plasminogen activator (tPA) and that some of the tPA-reactive aCL may inhibit tPA activity.

METHODS

We studied the reactivity of 8 patient-derived monoclonal aCL with tPA and examined the presence of IgG anti-tPA antibodies in patients with the antiphospholipid syndrome (APS). The effects of the reactive monoclonal aCL on the activity of tPA were also examined.

RESULTS

Six patient-derived plasmin-reactive monoclonal aCL bound to tPA. Analysis of plasma samples revealed that 10 of 80 APS patients (12.5%) and 1 of 81 systemic lupus erythematosus patients (1.2%) had antibodies against fibrin-associated tPA, based on a cutoff value equal to the mean + 2SD of the level in 28 normal subjects. Of the 6 tPA-reactive monoclonal aCL, 2 of them (CL1 and CL15) inhibited tPA activity.

CONCLUSION

Some of the plasmin-reactive aCL in APS patients may bind to tPA. Of the tPA-reactive aCL, some (such as CL1 and CL15) may inhibit tPA activity and, thus, may be prothrombotic in the host.

Regulation of lipopolysaccharide-induced lung inflammation by plasminogen activator Inhibitor-1 through a JNK-mediated pathway

The neutrophil is of undoubted importance in lung inflammation after exposure to LPS. We have shown recently that systemic inhibition of JNK decreased neutrophil recruitment to the lung after exposure to LPS, although the mechanisms underlying this inhibition are incompletely understood. As plasminogen activator inhibitor-1 (PAI-1) accentuates cell migration, with JNK activation recently shown to up-regulate PAI-1 expression, this suggested that systemic JNK inhibition may down-regulate LPS-induced pulmonary neutrophil recruitment through a decrease in PAI-1 expression. We show in this study that exposure of mice to aerosolized LPS increased PAI-1 expression in the lung and alveolar compartment, which was decreased by pretreatment with the JNK inhibitor SP600125. Exogenous, intratracheally administered PAI-1 prevented the inhibition of pulmonary neutrophil recruitment in the setting of systemic JNK inhibition, thereby suggesting a role for PAI-1 in the JNK-mediated pathway regulating LPS-induced neutrophil recruitment. In addition, PAI-1(-/-) mice had a decrease in neutrophil recruitment to the alveolar compartment after exposure to LPS, compared with wild-type controls, further suggesting a role for PAI-1 in LPS-induced lung inflammation. An increase in the intravascular level of KC is a likely mechanism for the inhibition of pulmonary neutrophil recruitment after LPS exposure in the setting of decreased PAI-1 expression, as systemic KC levels after exposure to LPS were increased in PAI-1-deficient mice and in mice pretreated with SP600125, with augmentation of intravascular KC levels inhibiting neutrophil recruitment to the lung after exposure to LPS.

The effects of short-term raloxifene therapy on fibrinolysis markers: TAFI, tPA, and PAI-1

BACKGROUND

Markers of fibrinolysis, thrombin-activatable fibrinolysis inhibitor (TAFI), tissue-type plasminogen activator (tPA), and plasminogen activator inhibitor-1 (PAI-1) levels were studied for the evaluation of short-term effects of raloxifene administration in postmenopausal women.

METHODS

Thirty-nine postmenopausal women with osteopenia or osteoporosis were included in this prospective, controlled clinical study. Twenty-five women were given raloxifene hydrochloride (60 mg/day) plus calcium (500 mg/day). Age-matched controls (n = 14) were given only calcium. Plasma TAFI, tPA, and PAI-1 antigen levels were measured at baseline and after 3 months of treatment by commercially available ELISA kits. Variations of individuals were assessed by Wilcoxon's test. Relationship between those markers and demographic characteristics were investigated.

RESULTS

Three months of raloxifene treatment was associated with a significant decrease in the plasma TAFI antigen concentrations (16% change, P < 0.01), and a significant increase in tPA antigen concentrations (25% change, P < 0.05). A significant correlation was found between baseline TAFI antigen concentrations and the duration of amenorrhea (P < 0.05; r = 0.33).

CONCLUSION

We suggest that the increased risk of venous thromboembolism due to raloxifene treatment may be related to increased tPA levels, but not TAFI levels.

Is tissue-plasminogen activator gene polymorphism a risk factor for venous thromboembolism in every population?

BACKGROUND

Tissue-plasminogen activator is a key protein of fibrinolytic system. In recent years the relation between t-PA, its genetic polymorphisms and arterial or venous thrombosis were investigated in different populations. The aim of this study is to investigate the role of t-PA gene polymorphism in Turkish venous thromboembolism (VTE) patients.

METHODS

A case-control study was performed. We investigated the t-PA insertion/deletion (I/D) polymorphism in 93 VTE patients and 146 controls without VTE. Recurrent cases and documented risk factors for PTE were recorded.

RESULTS

Cases and controls did not differ with respect to the different t-PA genotypes. The prevalence of I allele was 44.1%, 44.5% in cases and controls respectively (OR = 0.95, 95% CI: 0.78-1.24, p > 0.05). Different t-PA genotypes had no effect on recurrent disease. No gender difference was observed with respect to the different t-PA genotypes. There was no significant difference for genotype frequency between PTE patients with documented risk factors and unprovoked cases.

CONCLUSIONS

In conclusion there was no association between t-PA genotype and VTE in this group of Turkish population. It was also found that genotype frequencies for t-PA in both VTE and control subjects seems different from those reported from western part of the world. ABBREVIATED ABSTRACT: The aim of this study is to investigate the role of t-PA gene polymorphism in Turkish VTE patients. We investigated 93 VTE patients and 146 controls without VTE. Cases and controls did not differ with respect to the different t-PA genotypes. The prevalence of I allele was 44.1%, 44.5% in cases and controls respectively (OR = 0.95, 95% CI: 0.78-1.24, p > 0.05). Different t-PA genotypes had no effect on recurrent disease. No gender difference was observed with respect to the different t-PA genotypes. There was no significant difference for genotype frequency between PTE patients with documented risk factors and unprovoked cases. In conclusion there was no association between t-PA genotype and VTE in this group of Turkish population. It was also found that genotype frequencies for t-PA in both VTE and control subjects seems different from those reported from western part of the world.

Synthesis and SAR of 2-carboxylic acid indoles as inhibitors of plasminogen activator inhibitor-1

We synthesized and evaluated a novel series of 2-carboxylic acid indole-based inhibitors of plasminogen activator inhibitor-1 (PAI-1). Systematic modification of the N-1 position and the 5-position of the indole scaffold resulted in the identification of several compounds that showed good potency against PAI-1 in the spectrophotometric assay. This potency did not always translate to the antibody assay. Solubility and serum protein binding studies on selected analogs revealed that protein binding might be a factor in the poor correlation between the two assays.

The length of the reactive center loop modulates the latency transition of plasminogen activator inhibitor-1

Plasminogen activator inhibitor-1 (PAI-1) belongs to the serine protease inhibitor (serpin) protein family, which has a common tertiary structure consisting of three beta-sheets and several alpha-helices. Despite the similarity of its structure with those of other serpins, PAI-1 is unique in its conformational lability, which allows the conversion of the metastable active form to a more stable latent conformation under physiological conditions. For the conformational conversion to occur, the reactive center loop (RCL) of PAI-1 must be mobilized and inserted into the major beta-sheet, A sheet. In an effort to understand how the structural conversion is regulated in this conformationally labile serpin, we modulated the length of the RCL of PAI-1. We show that releasing the constraint on the RCL by extension of the loop facilitates a conformational transition of PAI-1 to a stable state. Biochemical data strongly suggest that the stabilization of the transformed conformation is owing to the insertion of the RCL into A beta-sheet, as in the known latent form. In contrast, reducing the loop length drastically retards the conformational change. The results clearly show that the constraint on the RCL is a factor that regulates the conformational transition of PAI-1.