Plasma levels of fibrinolytic proteins and the risk of myocardial infarction in men

Tale of two systems: the intertwining duality of fibrinolysis and lipoprotein metabolism

Fibrinolysis is an enzymatic process that breaks down fibrin clots, while dyslipidemia refers to abnormal levels of lipids and lipoproteins in the blood. Both fibrinolysis and lipoprotein metabolism are critical mechanisms that regulate a myriad of functions in the body, and the imbalance of these mechanisms is linked to the development of pathologic conditions, such as thrombotic complications in atherosclerotic cardiovascular diseases. Accumulated evidence indicates the close relationship between the 2 seemingly distinct and complicated systems-fibrinolysis and lipoprotein metabolism. Observational studies in humans found that dyslipidemia, characterized by increased blood apoB-lipoprotein and decreased high-density lipoprotein, is associated with lower fibrinolytic potential. Genetic variants of some fibrinolytic regulators are associated with blood lipid levels, supporting a causal relationship between these regulators and lipoprotein metabolism. Mechanistic studies have elucidated many pathways that link the fibrinolytic system and lipoprotein metabolism. Moreover, profibrinolytic therapies improve lipid panels toward an overall cardiometabolic healthier phenotype, while some lipid-lowering treatments increase fibrinolytic potential. The complex relationship between lipoprotein and fibrinolysis warrants further research to improve our understanding of the bidirectional regulation between the mediators of fibrinolysis and lipoprotein metabolism.

Association of the metabolic syndrome with PAI 1act and clot lysis time over a 10-year follow up in an African population

BACKGROUND AND AIMS

The association between the metabolic syndrome (MetS) and plasminogen activator inhibitor-1 (PAI-1) has been well established in cross-sectional studies. It is less clear whether this translates into decreased clot lysis rates and very little information is available on non-European populations. Little is known regarding prospective associations and whether clot lysis progressively worsens in MetS individuals over time. We determined the prospective association of MetS with PAI-1 activity (PAI-1_act) and clot lysis time (CLT) over a 10-year period.

METHODS AND RESULTS

As many as 2010 African men and women aged ≥30 years were stratified according to MetS status and number of MetS criteria (0-5). We also determined the contribution of the PAI-1 4G/5G polymorphism to these associations and identified which MetS criteria had the strongest associations with PAI-1_act and CLT. Both PAI-1_act and CLT remained consistently elevated in individuals with MetS throughout the 10-year period. PAI-1_act and CLT did not increase more over time in MetS individuals than in controls. The 4G/5G genotype did not influence the association of PAI-1_act or clot lysis with MetS. Increased waist circumference, increased triglycerides and decreased HDL-C were the main predictors of PAI-1_act and CLT.

CONCLUSIONS

Black South Africans with MetS had increased PAI-1_act and longer CLTs than individuals without MetS. The inhibited clot lysis in MetS did, however, not deteriorate over time compared to controls. Of the MetS criteria, obesity and altered lipids were the main predictors of PAI-1_act and CLT and are thus potential targets for prevention strategies to decrease thrombotic risk.

Targeted proteomics for evaluating risk of venous thrombosis following traumatic lower-leg injury or knee arthroscopy

INTRODUCTION

Patients with lower-leg cast immobilization and patients undergoing knee arthroscopy have an increased risk of venous thrombosis (VT). Guidelines are ambiguous about thromboprophylaxis use, and individual risk factors for developing VT are often ignored. To assist in VT risk stratification and guide thromboprophylaxis use, various prediction models have been developed. These models depend largely on clinical factors and provide reasonably good C-statistics of around 70%. We explored using protein levels in blood plasma measured by multiplexed quantitative targeted proteomics to predict VT. Our aim was to assess whether a VT risk prediction model based on absolute plasma protein quantification is possible.

METHODS

We used internal standards to quantify proteins in less than 10 μl plasma. We measured 270 proteins in samples from patients scheduled for knee arthroscopy or with lower-leg cast immobilization. The two prospective POT-(K)CAST trails allow complementary views of VT signature in blood, namely pre and post trauma, respectively. From approximately 3000 patients, 31 patients developed VT who were included and matched with double the number of controls.

RESULTS

Top discriminating proteins between cases and controls included APOC3, APOC4, APOC2, ATRN, F13B, and F2 in knee arthroscopy patients and APOE, SERPINF2, B2M, F13B, AFM, and C1QC in patients with lower-leg cast. A logistic regression model with cross-validation resulted in C-statistics of 88.1% (95% CI: 85.7-90.6%) and 79.6% (95% CI: 77.2-82.0%) for knee arthroscopy and cast immobilization groups respectively.

CONCLUSIONS

Promising C-statistics merit further exploration of the value of proteomic tests for predicting VT risk upon additional validation.

Quantitative analysis of clot density, fibrin fiber radius, and protofibril packing in acute phase myocardial infarction

INTRODUCTION

Coronary artery disease is associated with impaired clot structure. The aim of this study was to investigate acute phase myocardial infarction (AMI) and provide detailed quantitative analysis of clot ultrastructure.

MATERIALS AND METHODS

Clot formation and breakdown, pore size, fiber density, fiber radius and protofibril packing were investigated in plasma clots from AMI patients. These data were compared to those from healthy controls.

RESULTS

Analysis on clot formation using turbidity showed increased lag time, suggesting changes in protofibril packing and increased fiber size for AMI patients compared to healthy controls. Additionally, increased average rate of clotting and decreased time to maximum absorbance in AMI patients suggest that clots formed more quickly. Moreover, we observed increased time from max OD to max rate of lysis. Increased fibrinogen and decreased plasminogen in AMI patients were accounted for in represented significant differences. AMI samples showed increased time to 25% and 50% lysis, but no change in 75% lysis, representative of delayed lysis onset, but expediated lysis once initiated. These data suggest that AMI patients formed less porous clots made from more densely packed fibers with decreased numbers of protofibrils, which was confirmed using decreased permeation and increased fiber density, and decreased turbidimetry.

CONCLUSIONS

AMI plasma formed clots that were denser, less permeable, and lysed more slowly than healthy controls. These findings were confirmed by detailed analysis of clot ultrastructure, fiber size, and protofibril packing. Dense clot structures that are resistant to lysis may contribute to a prothrombotic milieu in AMI.

Effect of α2-plasmin inhibitor heterogeneity on the risk of venous thromboembolism

INTRODUCTION

Alpha2-plasmin inhibitor (α2-PI) has a heterogeneous composition in the plasma. Both N- and C-terminal cleavages occur that modify the function of the molecule. C-terminal cleavage converts the plasminogen-binding form (PB-α2-PI) to a non-plasminogen-binding form (NPB-α2-PI). N-terminal cleavage by soluble fibroblast activation protein (sFAP) results in a form shortened by 12 amino acids, which is more quickly cross-linked to fibrin. The p.Arg6Trp polymorphism of α2-PI affects N-terminal cleavage. In this work, we aimed to investigate the association between α2-PI heterogeneity and the risk of venous thromboembolism.

MATERIALS AND METHODS

Two hundred and eighteen patients with venous thromboembolism (VTE) and the same number of age and sex-matched healthy controls were enrolled. Total-α2-PI, PB-α2-PI and NPB-α2-PI antigen levels, α2-PI activity, sFAP antigen levels and p.Arg6Trp polymorphism were investigated.

RESULTS

Total-α2-PI and NPB-α2-PI levels were significantly elevated in VTE patients, while PB-α2-PI levels did not change. Elevated NPB-α2-PI levels independently associated with VTE risk (adjusted OR: 9.868; CI: 4.095-23.783). Soluble FAP levels were significantly elevated in the VTE group, however, elevated sFAP levels did not show a significant association with VTE risk. The α2-PI p.Arg6Trp polymorphism did not influence VTE risk, however, in the case of elevated sFAP levels the carriage of Trp6 allele associated with lower VTE risk.

CONCLUSION

Our results showed that the elevation of total-α2-PI levels in VTE is caused by the elevation of NPB-α2-PI levels. Elevated sFAP level or p.Arg6Trp polymorphism alone did not influence VTE risk. However, an interaction can be detected between the polymorphism and high sFAP levels.

Blood Adipokins in Young People with Early Ischemic Heart Disease on the Background of Abdominal Obesity

Aim      To study blood adipokines spectrum in people aged 25-44 years with early ischemic heart disease (IHD), including that associated with abdominal obesity (AO).Material and methods  A cross-sectional study was performed on a random sample of the population aged 25-44 years in Novosibirsk. 1457 subjects (653 men, 804 women) were evaluated. This study included 123 people divided into four study subgroups: subgroup 1, with IHD associated with AO (n=24); subgroup 2, with IHD and without AO (n=25); subgroup 3, without IHD and with AO (n=44); and subgroup 4, without either IHD or AO (n=30). Concentrations of serum adipokines were measured simultaneously by multiplex assay with a Luminex MAGPIX flow fluorometer and by immune enzyme assay with a MULTISCAN analyzer.Results Subjects with early IHD had lower blood concentrations of adipsin and visfatin than subjects without IHD. Subjects with early IHD associated with AO had higher blood concentrations of adipsin, plasminogen activator inhibitor-1, and leptin and lower concentrations of monocyte chemoattractant protein-1 (MCP-1) and visfatin compared to subjects with early IHD and without AO. The multivariate logistic regression analysis showed that lower blood concentrations of MCP-1 were associated with a likelihood of early IHD.Conclusion      In young people aged 25-44 years, lower blood concentrations of MCP-1 were associated with a likelihood of early IHD, including that associated with AO.

Fibrinolysis in Acute and Chronic Cardiovascular Disease

The formation of an obstructive thrombus within an artery remains a major cause of mortality and morbidity worldwide. Despite effective inhibition of platelet function by modern antiplatelet therapies, these agents fail to fully eliminate atherothrombotic risk. This may well be related to extensive vascular disease, beyond the protective abilities of the treatment agents used. However, recent evidence suggests that residual vascular risk in those treated with modern antiplatelet therapies is related, at least in part, to impaired fibrin clot lysis. In this review, we attempt to shed more light on the role of hypofibrinolysis in predisposition to arterial vascular events. We provide a brief overview of the coagulation system followed by addressing the role of impaired fibrin clot lysis in acute and chronic vascular conditions, including coronary artery, cerebrovascular, and peripheral vascular disease. We also discuss the role of combined anticoagulant and antiplatelet therapies to reduce the risk of arterial thrombotic events, addressing both efficacy and safety of such an approach. We conclude that impaired fibrin clot lysis appears to contribute to residual thrombosis risk in individuals with arterial disease on antiplatelet therapy, and targeting proteins in the fibrinolytic system represents a viable strategy to improve outcome in this population. Future work is required to refine the antithrombotic approach by modulating pathological abnormalities in the fibrinolytic system and tailoring therapy according to the need of each individual.

How I treat unexplained arterial thrombosis

Most arterial thrombotic events have a clear atherosclerotic or cardioembolic etiology, but hematologists are frequently asked to assist in the diagnosis and management of a patient with a nonatherosclerotic and noncardioembolic arterial event, referred to here as an unexplained arterial thrombosis. Because there is an assorted list of factors that can precipitate an arterial event, we present a systematic diagnostic approach to ensure consideration of not only primary hypercoagulable disorders, but also pro-thrombotic medications or substances, vascular and anatomic abnormalities, and undiagnosed systemic disorders, such as malignancy and autoimmune diseases. We also review existing literature of the role of hypercoagulable disorders in arterial thrombosis and discuss our approach to thrombophilia workup in patients after an unexplained arterial event. We conclude with 3 representative cases to both illustrate the application of the outlined diagnostic schema and discuss common management considerations, specifically the selection of anticoagulation vs antiplatelet therapy for secondary prevention.

Role, Laboratory Assessment and Clinical Relevance of Fibrin, Factor XIII and Endogenous Fibrinolysis in Arterial and Venous Thrombosis

Diseases such as myocardial infarction, ischaemic stroke, peripheral vascular disease and venous thromboembolism are major contributors to morbidity and mortality. Procoagulant, anticoagulant and fibrinolytic pathways are finely regulated in healthy individuals and dysregulated procoagulant, anticoagulant and fibrinolytic pathways lead to arterial and venous thrombosis. In this review article, we discuss the (patho)physiological role and laboratory assessment of fibrin, factor XIII and endogenous fibrinolysis, which are key players in the terminal phase of the coagulation cascade and fibrinolysis. Finally, we present the most up-to-date evidence for their involvement in various disease states and assessment of cardiovascular risk.

Carboxypeptidase U (CPU, TAFIa, CPB2) in Thromboembolic Disease: What Do We Know Three Decades after Its Discovery?

Procarboxypeptidase U (proCPU, TAFI, proCPB2) is a basic carboxypeptidase zymogen that is converted by thrombin(-thrombomodulin) or plasmin into the active carboxypeptidase U (CPU, TAFIa, CPB2), a potent attenuator of fibrinolysis. As CPU forms a molecular link between coagulation and fibrinolysis, the development of CPU inhibitors as profibrinolytic agents constitutes an attractive new concept to improve endogenous fibrinolysis or to increase the efficacy of thrombolytic therapy in thromboembolic diseases. Furthermore, extensive research has been conducted on the in vivo role of CPU in (the acute phase of) thromboembolic disease, as well as on the hypothesis that high proCPU levels and the Thr/Ile325 polymorphism may cause a thrombotic predisposition. In this paper, an overview is given of the methods available for measuring proCPU, CPU, and inactivated CPU (CPUi), together with a summary of the clinical data generated so far, ranging from the current knowledge on proCPU concentrations and polymorphisms as potential thromboembolic risk factors to the positioning of different CPU forms (proCPU, CPU, and CPUi) as diagnostic markers for thromboembolic disease, and the potential benefit of pharmacological inhibition of the CPU pathway.

Alpha2-Antiplasmin: The Devil You Don't Know in Cerebrovascular and Cardiovascular Disease

Alpha2-antiplasmin (α2AP), the fast-reacting, serine protease inhibitor (serpin) of plasmin, was originally thought to play a key role in protection against uncontrolled, plasmin-mediated proteolysis of coagulation factors and other molecules. However, studies of humans and mice with genetic deficiency of α2AP have expanded our understanding of this serpin, particularly in disease states. Epidemiology studies have shown an association between high α2AP levels and increased risk or poor outcome in cardiovascular diseases. Mechanistic studies in disease models indicate that α2AP stops the body's own fibrinolytic system from dissolving pathologic thrombi that cause venous thrombosis, pulmonary embolism, arterial thrombosis, and ischemic stroke. In addition, α2AP fosters the development of microvascular thrombosis and enhances matrix metalloproteinase-9 expression. Through these mechanisms and others, α2AP contributes to brain injury, hemorrhage and swelling in experimental ischemic stroke. Recent studies also show that α2AP is required for the development of stasis thrombosis by inhibiting the early activation of effective fibrinolysis. In this review, we will discuss the key role played by α2AP in controlling thrombosis and fibrinolysis and, we will consider its potential value as a therapeutic target in cardiovascular diseases and ischemic stroke.

Terminal Phase Components of the Clotting Cascade in Patients with End-Stage Renal Disease Undergoing Hemodiafiltration or Hemodialysis Treatment

Hemostasis disorder in patients with end-stage renal disease (ESRD) is frequently associated with bleeding diathesis but it may also manifest in thrombotic complications. Analysis of individual coagulation and fibrinolytic factors may shed light on the background of this paradox situation. Here we explored components essential for fibrin formation/stabilization in ESRD patients being on maintenance hemodiafiltration (HDF) or hemodialysis (HD). Pre-dialysis fibrinogen, factor XIII (FXIII) antigen concentrations and FXIII activity were elevated, while α₂-plasmin inhibitor (α₂PI) activity decreased. The inflammatory status, as characterized by C-reactive protein (CRP) was a key determinant of fibrinogen concentration, but not of FXIII and α₂PI levels. During a 4-h course of HDF or HD, fibrinogen concentration and FXIII levels gradually elevated. When compensated for the change in plasma water, i.e., normalized for plasma albumin concentration, only FXIII elevation remained significant. There was no difference between HDF and HD treatments. Individual HDF treatment did not influence α₂PI activity, however after normalization it decreased significantly. HD treatment had a different effect, α₂PI activities became elevated but the elevation disappeared after normalization. Elevated fibrinogen and FXIII levels in ESRD patients might contribute to the increased thrombosis risk, while decreased α₂PI activity might be associated with elevated fibrinolytic potential.

Biomarkers of coagulation and fibrinolysis in acute myocardial infarction: a joint position paper of the Association for Acute CardioVascular Care and the European Society of Cardiology Working Group on Thrombosis

The formation of a thrombus in an epicardial artery may result in an acute myocardial infarction (AMI). Despite major advances in acute treatment using network approaches to allocate patients to timely reperfusion and optimal antithrombotic treatment, patients remain at high risk for thrombotic complications. Ongoing activation of the coagulation system as well as thrombin-mediated platelet activation may both play a crucial role in this context. Whether measurement of circulating biomarkers of coagulation and fibrinolysis could be useful for risk stratification in secondary prevention is currently not fully understood. In addition, measurement of such biomarkers could be helpful to identify thrombus formation as the leading mechanism for AMI. The introduction of biomarkers of myocardial injury such as high-sensitivity cardiac troponins made rule-out of AMI even more precise. However, elevated markers of myocardial injury cannot provide proof of a type 1 AMI, let alone thrombus formation. The combined measurement of markers of myocardial injury with biomarkers reflecting ongoing thrombus formation might be helpful for the fast and correct diagnosis of an atherothrombotic type 1 AMI. This position paper gives an overview of the current knowledge and possible role of biomarkers of coagulation and fibrinolysis for the diagnosis of AMI, risk stratification, and individualized treatment strategies in patients with AMI.

The Role of Secretory Activity Molecules of Visceral Adipocytes in Abdominal Obesity in the Development of Cardiovascular Disease: A Review

Adipose tissue is considered one of the endocrine organs in the body because of its ability to synthesize and release a large number of hormones, cytokines, and growth and vasoactive factors that influence a variety of physiological and pathophysiological processes, such as vascular tone, inflammation, vascular smooth muscle cell migration, endothelial function, and vascular redox state. Moreover, genetic factors substantially contribute to the risk of obesity. Research into the biochemical effects of molecules secreted by visceral adipocytes as well as their molecular genetic characteristics is actively conducted around the world mostly in relation to pathologies of the cardiovascular system, metabolic syndrome, and diabetes mellitus. Adipokines could be developed into biomarkers for diagnosis, prognosis, and therapeutic targets in different diseases. This review describes the relevance of secretory activity molecules of visceral adipocytes in cardiovascular disease associated abdominal obesity.

Successful aging: insights from proteome analyses of healthy centenarians

Healthy aging depends on a complex gene-environment network that is ultimately reflected in the expression of different proteins. We aimed to perform a comparative analysis of the plasma proteome of healthy centenarians (n=9, 5 women, age range 100–103 years) with a notably preserved ambulatory capacity (as a paradigm of ‘successful’ aging), and control individuals who died from a major age-related disease before the expected life expectancy (n=9, 5 women, age range: 67–81 years), and while having impaired ambulatory capacity (as a paradigm of ‘unsuccessful’ aging). We found that the expression of 49 proteins and 86 pathways differed between the two groups. Overall, healthy centenarians presented with distinct expression of proteins/pathways that reflect a healthy immune function, including a lower pro-inflammatory status (less ‘inflammaging’ and autoimmunity) and a preserved humoral immune response (increased B cell-mediated immune response). Compared with controls, healthy centenarians also presented with a higher expression of proteins involved in angiogenesis and related to enhanced intercellular junctions, as well as a lower expression of proteins involved in cardiovascular abnormalities. The identification of these proteins/pathways might provide new insights into the biological mechanisms underlying the paradigm of healthy aging.

A new ELISA method for the measurement of total α2-plasmin inhibitor level in human body fluids

The ever-increasing research efforts to develop new antithrombotic therapies have led to the reassessment of the role of alpha-2-plasmin inhibitor (α₂-PI) in pathological conditions. In particular, experimental stroke studies have suggested correlation between increased free α2-PI level and mortality. However there are only a small number of well-characterized and specific assays available for the measurements of free α₂-PI. In plasma α₂-PI undergoes both N- and/or C-terminal cleavages resulting four isoforms with modified susceptibility to FXIII catalyzed cross-linking to fibrin and/or loss of plasmin(ogen) binding. Present paper describes a new sandwich ELISA method for the determination of free total α₂-PI in plasma and other body fluids. A newly generated biotinylated monoclonal antibody recognizes and captures all the four N- and/or C-terminally modified isoforms of α₂-PI while HRPO-labeled polyclonal anti-α₂-PI antibody detects the captured antigen. Performing the 2-step assay in streptavidin-coated microplate can be completed within three hours. The assay is well reproducible, total (within laboratory) imprecision in the normal, pathological and very low ranges were 7.4%, 9.1% and < 19%, respectively. When examining the plasma samples of 197 healthy volunteers, 100 acute ischemic stroke patients and 102 patients with venous thrombosis, strong correlation was observed between total α2-PI antigen levels and α2-PI activity for each group. Using the assay a reference interval of 45-86 mg/L was established for total α₂-PI mass concentration in the plasma. α₂-PI levels were also measured in cerebrospinal fluid samples of 47 individuals the median value and range was 132 (36-379) μg/L. In conclusion, our ELISA enables accurate and fast measurement of total free α₂-PI in human body fluids.

Plasminogen activator inhibitor 1 in acute coronary syndromes

Plasminogen activator inhibitor 1 (PAI-1) is the main regulator of endogenous fibrinolysis, overriding the impact of other constituents of fibrinolysis. In plasma, it can be found in three forms: active, latent and inactive. There are numerous commercially available tests, analysing the activity of PAI-1 or the antigen level, with variable correlations between the two. PAI-1 has been extensively studied regarding incidence and outcomes of acute coronary syndromes, and showed positive association with both in numerous studies. Higher PAI-1 has been associated with worse short- and long-term outcomes. Studies are more consistent in the primary percutaneous coronary intervention era. Higher rise of PAI-1 within the first 24 h of acute myocardial infarction has been linked to some of its high-risk features. The circadian pattern of PAI-1 kinetics has been previously described, and the mechanisms behind this phenomenon and its impact on the incidence of acute coronary syndromes are well known. Further investigations are needed to test the safety and efficacy of PAI-1 as a pharmacological target in cardiovascular diseases.

Relationship between dietary quality, determined by DASH score, and cardiometabolic health biomarkers: A cross-sectional analysis in adults

BACKGROUND AND AIMS

The relationship between dietary patterns and cardiometabolic disease is of increasing interest. However, limited data regarding the association between dietary quality and biomarkers of cardiometabolic health exist. Therefore the aim of this work was to examine potential associations between dietary quality, assessed using the Dietary Approaches to Stop Hypertension (DASH) dietary quality score, adiposity and biomarkers of glucose homeostasis, lipoprotein metabolism and inflammation in a cross-sectional sample of 1493 men and women.

METHODS

Anthropometric measurements included BMI, hip and waist circumference (WC). Serum acute-phase reactants, adipocytokines, pro-inflammatory cytokines and white blood cell (WBC) counts were determined. Lipoprotein particle size and subclass concentrations were measured using nuclear magnetic resonance (NMR) spectroscopy. Insulin resistance was calculated by homeostasis model assessment (HOMA-IR).

RESULTS

Higher dietary quality was associated with lower BMI (P < 0.05), WC (P < 0.001), tumour necrosis factor α (TNF-α), interleukin 6 (IL-6), WBC and plasminogen activator inhibitor-1 (PAI-1) concentrations (P < 0.01) and reduced insulin resistance (P < 0.05). In addition less small low density lipoprotein (LDL) and small high density lipoprotein (HDL) particles and less large very low density lipoprotein (VLDL) particles were observed among those with better dietary quality (P < 0.001). Individuals in the top DASH quartile had a 54% and 48% lower likelihood of central obesity and metabolic syndrome (MetS), respectively, than those in the lowest DASH quartile (P < 0.05).

CONCLUSIONS

Our data suggest that higher quality diet is associated with improved adiposity measures and a less insulin resistant, pro-inflammatory, pro-thrombotic and pro-atherogenic cardiometabolic profile which may impact on central obesity and MetS risk. These findings, which may be of clinical and public health significance in terms of dietary approaches to promote cardiometabolic health, warrant further examination.

Regulation of plasminogen activation on cell surfaces and fibrin

The fibrinolytic system dissolves fibrin and maintains vascular patency. Recent advances in imaging analyses allowed visualization of the spatiotemporal regulatory mechanism of fibrinolysis, as well as its regulation by other plasma hemostasis cofactors. Vascular endothelial cells (VECs) retain tissue-type plasminogen activator (tPA) after secretion and maintain high plasminogen (plg) activation potential on their surfaces. As in plasma, the serpin, plasminogen activator inhibitor type 1 (PAI-1), regulates fibrinolytic potential via inhibition of the VEC surface-bound plg activator, tPA. Once fibrin is formed, plg activation by tPA is initiated and effectively amplified on the surface of fibrin, and fibrin is rapidly degraded. The specific binding of plg and tPA to lytic edges of partly degraded fibrin via newly generated C-terminal lysine residues, which amplifies fibrin digestion, is a central aspect of this pathophysiological mechanism. Thrombomodulin (TM) plays a role in the attenuation of plg binding on fibrin and the associated fibrinolysis, which is reversed by a carboxypeptidase B inhibitor. This suggests that the plasma procarboxypeptidase B, thrombin-activatable fibrinolysis inhibitor (TAFI), which is activated by thrombin bound to TM on VECs, is a critical aspect of the regulation of plg activation on VECs and subsequent fibrinolysis. Platelets also contain PAI-1, TAFI, TM, and the fibrin cross-linking enzyme, factor (F) XIIIa, and either secrete or expose these agents upon activation in order to regulate fibrinolysis. In this review, the native machinery of plg activation and fibrinolysis, as well as their spatiotemporal regulatory mechanisms, as revealed by imaging analyses, are discussed.

A history of early stent thrombosis is associated with prolonged clot lysis time

It has been demonstrated that formation of compact plasma fibrin clots resistant to plasmin-mediated lysis characterises patients following instent thrombosis (IST). The relationship between defective fibrinolysis, reflected as prolonged clot lysis time (CLT) and IST is unclear. We sought to investigate whether patients with acute and subacute IST have impaired fibrinolytic capacity. We studied 41 definite IST patients, including 15 with acute and 26 with subacute IST experienced 2–73 months prior to enrollment, versus 41 controls matched for demographics, cardiovascular risk factors, concomitant treatment and angiographic/stent parameters. CLT, reflecting lysis of a tissue factor-induced plasma clot by exogenous tissue plasminogen activator, together with plasminogen activator inhibitor-1 (PAI-1) antigen and activity, thrombin-activatable fibrinolysis inhibitor (TAFI) antigen and activity, thrombomodulin (TM), plasminogen and α2-antiplasmin (α2AP) were measured. There were no inter-group differences in angiographic parameters, indication to the first PCI, culprit vessel or a type of stent. Patients with IST had 11% longer CLT (p=0.005) and 13% higher PAI-1 antigen (p=0.04) compared to controls. There were positive correlations in both groups between CLT and PAI-1 antigen and TAFI activity (all p<0.001). Multiple regression analysis showed that CLT (odds ratio [OR]=1.04 per 1 minute, 95% CI 1.01–1.08, p=0.02) and platelet count (OR=1.01 per 1,000/μl, 95% CI 1.00–1.02, p=0.034) were independent predictors of IST (R2=0.28, p<0.05). Concluding, impaired fibrinolytic potential, that is in part determined by plasma PAI-1 antigen and TAFI activity, characterises patients with a history of acute and subacute IST, which might help identify patients at higher risk of IST.

Mechanisms of thrombosis in systemic lupus erythematosus and antiphospholipid syndrome

The presence of antiphospholipid antibodies is one of the most common acquired risk factors for thrombosis. Antiphospholipid antibodies is a collective term for a set of autoantibodies with closely related but different specificity. Experiments in which isolated patient antibodies were injected into mice have shown that a specific subset of autoantibodies, those directed against the first domain of plasma protein β₂-glycoprotein I, can explain the increased risk of thrombosis. Experiments performed with these mice have shown that autoantibodies against β₂-glycoprotein I bind to and activate cells such as endothelial cells, monocytes, and platelets. Activation of these cells, all involved in the regulation of hemostasis, results in a shift towards a prothrombotic state. How this process is regulated, whether this is the only mechanism involved, and whether this is the only subpopulation responsible for the increased thrombotic risk is unknown. In this review, we will critically discuss what is known and what is debatable on the pathophysiology of antiphospholipid syndrome.

Cumulative Exposure to High-Sensitivity C-Reactive Protein Predicts the Risk of Cardiovascular Disease

BACKGROUND

One measurement of hs-CRP (high-sensitivity C-reactive protein) is associated with increased risk of cardiovascular disease (CVD). The objective of this study was to characterize the association of cumulative exposure to increased hs-CRP with incident cardiovascular events.

METHODS AND RESULTS

We included 53 065 participants with hs-CRP measured at 3 examinations in 2006, 2008, and 2010. Cumulative exposure to hs-CRP was calculated as the weighted sum of the average hs-CRP level for each time interval (level×time). Participants were classified into nonexposed group (hs-CRP<3.0 mg/L in all 3 examinations), 1-exposed group (hs-CRP≥3.0 mg/L in 1 of the 3 examinations), 2-exposed group (hs-CRP≥3.0 mg/L in 2 of the 3 examinations), and 3-exposed group (hs-CRP≥3.0 mg/L in 3 examinations). Cox proportional hazards models were used to assess the association of cumulative hs-CRP with incident CVD. The study showed a dose-response pattern with risk of CVD and myocardial infarction as the number of years of exposure to hs-CRP increases. Participants in the 3-exposed group had significantly increased CVD risk with hazard ratio (95% confidence interval) of 1.38 (1.11-1.72), in comparison with 1.28 (1.07-1.52) for participants in the 2-exposed group and 1.13 (0.97-1.31) for those in the 1-exposed group (P<0.05); meanwhile, the similar and significant associations were also observed for myocardial infarction with respective hazard ratio (95% confidence interval) of 2.13 (1.42-3.18), 1.60 (1.12-2.27), and 1.57 (1.17-2.10). The associations between stroke and cumulative hs-CRP were not statistically significant (P=0.360).

CONCLUSIONS

Cumulative exposure to hs-CRP was dose dependently associated with a subsequent increased risk of CVD and myocardial infarction.

CLINICAL TRIAL REGISTRATION

URL: https://www.clinicaltrials.gov/. Unique identifier: ChiCTR-TNC-11001489.

Causal Effect of Plasminogen Activator Inhibitor Type 1 on Coronary Heart Disease

Background

Plasminogen activator inhibitor type 1 (PAI‐1) plays an essential role in the fibrinolysis system and thrombosis. Population studies have reported that blood PAI‐1 levels are associated with increased risk of coronary heart disease (CHD). However, it is unclear whether the association reflects a causal influence of PAI‐1 on CHD risk.

Methods and Results

To evaluate the association between PAI‐1 and CHD, we applied a 3‐step strategy. First, we investigated the observational association between PAI‐1 and CHD incidence using a systematic review based on a literature search for PAI‐1 and CHD studies. Second, we explored the causal association between PAI‐1 and CHD using a Mendelian randomization approach using summary statistics from large genome‐wide association studies. Finally, we explored the causal effect of PAI‐1 on cardiovascular risk factors including metabolic and subclinical atherosclerosis measures. In the systematic meta‐analysis, the highest quantile of blood PAI‐1 level was associated with higher CHD risk comparing with the lowest quantile (odds ratio=2.17; 95% CI: 1.53, 3.07) in an age‐ and sex‐adjusted model. The effect size was reduced in studies using a multivariable‐adjusted model (odds ratio=1.46; 95% CI: 1.13, 1.88). The Mendelian randomization analyses suggested a causal effect of increased PAI‐1 level on CHD risk (odds ratio=1.22 per unit increase of log‐transformed PAI‐1; 95% CI: 1.01, 1.47). In addition, we also detected a causal effect of PAI‐1 on elevating blood glucose and high‐density lipoprotein cholesterol.

Conclusions

Our study indicates a causal effect of elevated PAI‐1 level on CHD risk, which may be mediated by glucose dysfunction.

Hypofibrinolysis in diabetes: a therapeutic target for the reduction of cardiovascular risk

An enhanced thrombotic environment and premature atherosclerosis are key factors for the increased cardiovascular risk in diabetes. The occlusive vascular thrombus, formed secondary to interactions between platelets and coagulation proteins, is composed of a skeleton of fibrin fibres with cellular elements embedded in this network. Diabetes is characterised by quantitative and qualitative changes in coagulation proteins, which collectively increase resistance to fibrinolysis, consequently augmenting thrombosis risk. Current long-term therapies to prevent arterial occlusion in diabetes are focussed on anti-platelet agents, a strategy that fails to address the contribution of coagulation proteins to the enhanced thrombotic milieu. Moreover, antiplatelet treatment is associated with bleeding complications, particularly with newer agents and more aggressive combination therapies, questioning the safety of this approach. Therefore, to safely control thrombosis risk in diabetes, an alternative approach is required with the fibrin network representing a credible therapeutic target. In the current review, we address diabetes-specific mechanistic pathways responsible for hypofibrinolysis including the role of clot structure, defects in the fibrinolytic system and increased incorporation of anti-fibrinolytic proteins into the clot. Future anti-thrombotic therapeutic options are discussed with special emphasis on the potential advantages of modulating incorporation of the anti-fibrinolytic proteins into fibrin networks. This latter approach carries theoretical advantages, including specificity for diabetes, ability to target a particular protein with a possible favourable risk of bleeding. The development of alternative treatment strategies to better control residual thrombosis risk in diabetes will help to reduce vascular events, which remain the main cause of mortality in this condition.

Peripheral Inflammatory Biomarkers for Myocardial Infarction Risk: A Prospective Community-Based Study

BACKGROUND

Most previous studies regarding chronic inflammation and risk of myocardial infarction (MI) have lacked repeated measures of high-sensitivity C-reactive protein (hs-CRP) and/or white blood cell (WBC) count over time. We examined whether cumulative average and longitudinal changes in these biomarkers were associated with subsequent MI risk.

METHODS

In this prospective, community-based study, we included 82544 Chinese participants [66796 men and 15748 women; mean (SD) age 55.1 (9.86) y] without prior cardiovascular diseases or cancer at baseline (2006-2007). hs-CRP, WBC and other clinical covariates were assessed at baseline and every 2 years during follow-up.

RESULTS

During 6 years of follow-up (2006-2012), we documented 714 incident MI cases. Higher baseline and cumulative average concentrations of hs-CRP and/or WBC were consistently associated with increased risk of MI (P_trend <0.001 for both). Longitudinal increase in hs-CRP (P_trend <0.001), but not WBC, was also associated with a higher future risk of MI, after adjustment for their baseline values and other covariates. Each 1-mg/L increment per year in hs-CRP was associated with a 9.3% increase in risk for future MI [hazard ratio (HR) = 1.09, 95% CI, 1.03; 1.17]. Participants with high-grade inflammatory status (hs-CRP ≥10 mg/L and WBC ≥10 × 10⁹/L) had a higher risk of MI occurring <3 months after hs-CRP/WBC assessments vs those with hs-CRP <0.5 mg/L and WBC <5 × 10⁹/L (HR = 6.64; 95% CI, 1.49-29.6), as compared with MI occurring ≥4 years (HR = 2.95; 95% CI, 0.90, 9.65).

CONCLUSIONS

Plasma hs-CRP concentration and WBC predicted MI risk. Longitudinal increase in hs-CRP was also associated with a higher risk of MI.

α2-Antiplasmin: New Insights and Opportunities for Ischemic Stroke

Thrombotic vascular occlusion is the leading cause of ischemic stroke. High blood levels of α₂-antiplasmin (a2AP), an ultrafast, covalent inhibitor of plasmin, have been linked in humans to increased risk of ischemic stroke and failure of tissue plasminogen activator (tPA) therapy. Consistent with these observations, a2AP neutralizes the therapeutic benefit of tPA therapy in experimental stroke. In addition, a2AP has deleterious, dose-related effects on ischemic brain injury in the absence of therapy. Experimental therapeutic inactivation of a2AP markedly reduces microvascular thrombosis, ischemic brain injury, brain swelling, brain hemorrhage, and death after thromboembolic stroke. These data provide new insights into the critical importance of a2AP in the pathogenesis of ischemic brain injury and suggest that transiently inactivating a2AP may have therapeutic value in ischemic stroke.

Circulating levels of plasminogen and oxidized phospholipids bound to plasminogen distinguish between atherothrombotic and non-atherothrombotic myocardial infarction

Oxidized phospholipids (OxPL) are abundant in atherosclerotic plaques. They are also bound to circulating plasminogen after myocardial infarction (MI), and their binding to plasminogen may accentuate fibrinolysis. We sought to assess whether circulating levels of plasminogen and OxPL bound to plasminogen (OxPL-PLG) increase following acute MI and whether this increase differs between atherothrombotic (Type 1) and non-atherothrombotic (Type 2) MI. We measured circulating levels of plasminogen and OxPL-PLG at 0, 6, 24, 48 h, and >3 months (stable state) following acute MI and following an angiogram for stable coronary artery disease (CAD). Forty-nine subjects met the criteria for acute MI, of whom 34 had clearly defined atherothrombotic (n = 22) or non-atherothrombotic (n = 12) MI; 15 patients met the criteria for stable CAD. Mean baseline levels of plasminogen and OxPL-PLG were lower in the acute MI group than in the stable CAD group (9.75 vs 20.2, p < 0.0001 for plasminogen and 165.5 vs 275.1, p = 0.0002 for OxPL-PLG) and did not change over time or between time points, including the 3-month follow-up. Mean baseline levels of plasminogen and OxPL-PLG were also lower in atherothrombotic (Type 1) than in non-atherothrombotic (Type 2) MI subjects (8.65 vs 12.1, p < 0.03 for plasminogen and 164.5 vs 245.7, p = 0.02 for OxPL-PLG), and this relationship did not change over time or between time points. Plasminogen and OxPL-PLG were lower in patients presenting with an acute MI than in those with stable CAD and also in those with atherothrombotic MI (Type 1) vs. those with non-atherothrombotic MI (Type 2). These findings persisted at a median follow-up of 3 months post-MI. The association of plasminogen and OxPL-PLG with acute MI, particularly atherothrombotic MI (Type 1), could reflect a reduced fibrinolytic capacity, associated with an increased risk of atherothrombotic events differentiating stable CAD from unstable CAD and atherothrombotic MI (Type 1) from non-atherothrombotic MI (Type 2). Additional study with a larger sample size is warranted.

Plasminogen activator inhibitor and the risk of cardiovascular disease: The Framingham Heart Study

INTRODUCTION

Although plasminogen activator inhibitor (PAI-1) plays a key regulatory role in fibrinolysis, it has not been clearly shown to independently predict cardiovascular disease (CVD) among individuals without prior CVD. We investigated, in the Framingham Heart Study offspring cohort, whether PAI-1 predicted CVD risk among individuals without prior CVD.

METHODS

Plasma PAI-1 antigen and tissue plasminogen activator (TPA) antigen were measured in 3203 subjects without prior CVD between 1991 and 1995; average follow-up of 10 years. PAI-1 was remeasured 4 years after baseline, to determine the effect of serial change on risk.

RESULTS

PAI-1 levels (mean ± SD) were 29.1 ng/ml (19.2) versus 22.1 (16.5) for those and without incident CVD; p<0.001, and TPA levels were 12.0 ng/ml (5.7) versus 9.0 (4.7); p<0.001. PAI-1 and TPA antigen levels had a strong unadjusted linear relation with incident CVD (p<0.001). After adjustment for conventional risk factors, the hazard ratios (HRs) for higher quartiles of PAI-1, compared with the lowest, were 1.9, 1.9, 2.6 (linear trend p=0.006), and 1.6, 1.6, 2.9 (p<0.001) for TPA antigen. The adjusted HRs for increasing quartiles of serial change in PAI-1 at 4 years, compared with the lowest, were 0.9, 0.8, 1.3 (p=0.050). C statistic assessment showed that adding PAI-1 or TPA to conventional risk factors resulted in small increases in discrimination and modest reclassification of risk, which was statistically significant for TPA (net reclassification 6.8%, p=0.037) but not PAI-1 (4.8%, p=0.113).

CONCLUSION

PAI-1 and TPA antigen levels are predictive of CVD events after accounting for established risk factors. A serial increase in PAI-1 is associated with a further increase in risk. These findings support the importance of fibrinolytic potential in CVD.

The association of clot lysis time with total obesity is partly independent from the association of PAI-1 with central obesity in African adults

INTRODUCTION

Preliminary evidence indicates that the association of fibrinolytic potential, measured as clot lysis time (CLT), with body composition may differ from that of plasminogen activator inhibitor type-1 (PAI-1). We therefore investigated the association between fibrinolytic markers (plasminogen activator inhibitor type-1 activity (PAI-1act) and CLT) and body composition using detailed body composition analyses.

MATERIALS AND METHODS

Data from 1288 Africans were cross-sectionally analyzed. Body composition analysis included BMI, waist circumference (WC); waist to height ratio (WHtR), skinfolds and body fat percentage measured with air-displacement plethysmography and bioelectrical impedance analysis.

RESULTS

PAI-1act and CLT were significantly higher in women than in men, despite adjustment for differences in body composition. PAI-1act and CLT showed similar linear positive relationships with body composition (BMI, WC, WHtR, skinfolds) in men. In women CLT also showed a linear relationship with body composition, while PAI-1act levels plateaued at higher BMI and did not differ across skinfold categories. PAI-1act showed stronger correlations with body composition markers in men than it did in women, while no sex differences existed for CLT. PAI-1act associated more strongly with central obesity, while CLT associated with total body fat.

CONCLUSIONS

Observed differences may be related to differences in adipose tissue type, distribution and sequence of accumulation between sexes. PAI-1act is strongly influenced by accumulation of visceral adipose tissue, whereas CLT is associated with obesity independent of type and sequence of body fat accumulation in this African adult study population.

Attenuation of spontaneous thrombolytic activity measured by the global thrombosis test in male habitual smokers

Smoking is known as one of the major risk factors for atherothrombotic cardiovascular diseases. We investigated the susceptibility to thrombosis in habitual smokers by using the global thrombosis test (GTT), by which both clot formation and clot lysis activities can be evaluated simultaneously in native blood samples in vitro. Subjects were 139 men participating in a periodic health checkup examination, and an informed consent for the subjects was obtained as a document. Using GTT, occlusion time (OT: the time taken for clot formation in the blood sample) and lysis time (LT: the time taken for lysis of the clot that had been formed) were measured. LT was significantly (p = 0.029) longer in smokers [median with range, 1,794 (1,080-6,000) s (n = 76)] than in nonsmokers [median with range, 1,530 (792-3,800) s (n = 63)], while there was no significant difference in OT between smokers and nonsmokers. In smokers, LT was significantly correlated with daily cigarette consumption but not with Brinkman index. LT measured in nine smokers at 3 months after quitting their habitual smoking was significantly shorter than LT measured before the cessation of smoking. Since prolongation of LT implies existence of thrombogenic tendency, smokers are thought to be more susceptible to thrombosis due to decreased fibrinolytic activity, and no smoking for even a short term may be effective for improving fibrinolytic activity in smokers.

Genetic variants in PLG, LPA, and SIGLEC 14 as well as smoking contribute to plasma plasminogen levels

Plasminogen is the precursor of the serine protease plasmin, a central enzyme of the fibrinolytic system. Plasma levels of plasminogen vary by almost 2-fold among healthy individuals, yet little is known about its heritability or genetic determinants in the general population. In order to identify genetic factors affecting the natural variation of plasminogen levels, we performed a genome-wide association study and linkage analysis in a sample of 3456 young healthy individuals who participated in the Genes and Blood Clotting Study (GABC) or the Trinity Student Study (TSS). Heritability of plasminogen levels was 48.1% to 60.0%. Tobacco smoking and female sex were associated with higher levels of plasminogen. In the meta-analysis, 11 single-nucleotide polymorphisms (SNPs) in 2 regions reached genome-wide significance (P < 5.0E-8). Of these, 9 SNPs were near the PLG or LPA genes on Chr6q26, whereas 2 were on Chr19q13 and 5' upstream of SIGLEC14. These 11 SNPs represented 4 independent signals and collectively explained 6.8% of plasminogen level variation in the study populations. The strongest association was observed for a nonsynonymous SNP in the PLG gene (R523W). Individuals bearing an additional copy of this allele had an average decrease of 13.4% in plasma plasminogen level.

Increased incorporation of antiplasmin into the fibrin network in patients with type 1 diabetes

OBJECTIVE

Diabetes is associated with various vascular complications and is suggested to induce a prothrombotic state. In the current study, we characterized antiplasmin incorporation into fibrin in relation to other fibrinolytic compounds in patients with type 1 diabetes.

RESEARCH DESIGN AND METHODS

A total of 236 patients with type 1 diabetes and 78 control subjects were investigated. The incorporation of antiplasmin into the fibrin network and the plasma levels of plasminogen activator inhibitor type 1 (PAI-1) activity, tissue plasminogen activator (tPA) activity, tPA/PAI-1 complex, plasmin-antiplasmin complex, antiplasmin, factor XIII, and d-dimer were measured. In addition, we used global assays to study fibrinolysis.

RESULTS

The incorporation of antiplasmin into the fibrin network was significantly higher in patients with type 1 diabetes than in control subjects without diabetes (1.65 ± 0.25 vs. 1.35 ± 0.18 mg/L, respectively; P < 0.0001). The patients also had lower PAI-1 activity (2.19 units/mL [interquartile range 0.96-5.42] vs. 4.25 units/mL [1.95-9.0]; P = 0.0012) and antiplasmin level in plasma (78.5 ± 13.3 vs. 83.2 ± 15.4 mg/L; P < 0.05), resulting in a higher fibrinolytic capacity (shorter clot lysis time; P = 0.0090). We did not find any important sex differences regarding fibrinolysis in the patients or in the control subjects.

CONCLUSIONS

Patients with type 1 diabetes incorporate more antiplasmin into the fibrin network than control subjects without diabetes do and have a reduced PAI-1 activity and a shorter clot lysis time. These results suggest that patients with type 1 diabetes produce a fibrin clot that is more resistant to fibrinolysis, which, however, may be counteracted by an increased fibrinolytic potential in plasma.

Impact of stearic acid and oleic acid on hemostatic factors in the context of controlled diets consumed by healthy men

The effects of stearic acid (STA) on cardiovascular disease risk beyond lipid and lipoprotein risk factors, including hemostasis, are unclear, particularly when compared with unsaturated fatty acids. The aim of the present study is to compare the effects of STA with those of oleic acid (OL) on markers of hemostasis. In a randomized crossover study, 50 men consumed six controlled diets for 5 weeks each (39% energy from fat, 15% energy from protein, 46% energy from carbohydrate (CHO)). Fat (8% energy) was replaced across diets by: STA, OL, CHO (control), trans fatty acids (TFAs), TFA/STA and 12:0–16:0 saturated fatty acids. Factor VIIc, plasminogen activator inhibitor-1 (PAI-1) and plasmin alpha-2-antiplasmin complex concentrations were not different between OL and STA (P>0.05). Compared with control, OL increased factor VIIc and PAI-1 (P⩽0.05), whereas there were no differences with STA (P>0.05). STA and OL similarly affect markers of hemostasis in healthy men, within the context of a highly controlled diet.

Modulation of inflammatory and hemostatic markers in obstructive sleep apnea patients treated with mandibular advancement splints: a parallel, controlled trial

STUDY OBJECTIVE

Obstructive sleep apnea (OSA) is associated with systemic inflammation and a hypercoagulable state. The current study aim was to investigate whether mandibular advancement splint (MAS) therapy affects inflammatory and hemostatic parameters in patients with mild-to-moderate OSA.

METHODS

Twenty-two patients with mild-to-moderate OSA and 16 control subjects were studied. OSA subjects were treated with a titratable MAS for 6 months. Baseline plasma C-reactive protein, interleukin-1β, interleukin-10, interleukin-6, P-selectin, fibrinogen, D-dimer, plasminogen activator inhibitor-1 (PAI-1), thrombin-antithrombin complex, activated thrombin-activatable fibrinolysis inhibitor (TAFIa), 6-keto-PGF1α, glucose, and fibrin clot lysis time (CLT) were measured in all subjects. After 3 months of MAS therapy, measurements were repeated for the 22 patients, and after 6 months all measurements were repeated for all study subjects.

RESULTS

MAS treatment reduced significantly AHI at 3 months (24 vs 13.1/h) and further improved it at 6 months (13.1 vs 7.05/h). Compared with controls, OSA subjects had a significant higher baseline mean levels of fibrinogen, TAFIa, 6-keto-PGF1α, and glucose. MAS treatment significantly improved levels of IL-1β, D-dimer, TAFIa, and CLT. Despite residual apneas, MAS treatment group presented similar measured homeostatic and inflammatory levels to controls except for glucose.

CONCLUSION

Treatment with MAS in mild-to-moderate OSA subjects improves the inflammatory profile and homeostatic markers.

CITATION

Niżankowska-Jędrzejczyk A; Almeida FR; Lowe AA; Kania A; Nastałek P; Mejza F; Foley JH; Niżankowska-Mogilnicka E; Undas A. Modulation of inflammatory and hemostatic markers in obstructive sleep apnea patients treated with mandibular advancement splints: a parallel, controlled trial.

Expression of uPA, tPA, and PAI-1 in Calcified Aortic Valves

Purpose. Our physiopathological assumption is that u-PA, t-PA, and PAI-1 are released by calcified aortic valves and play a role in the calcification of these valves. Methods. Sixty-five calcified aortic valves were collected from patients suffering from aortic stenosis. Each valve was incubated for 24 hours in culture medium. The supernatants were used to measure u-PA, t-PA, and PAI-1 concentrations; the valve calcification was evaluated using biphotonic absorptiometry. Results. Aortic stenosis valves expressed normal plasminogen activators concentrations and overexpressed PAI-1 (u-PA, t-PA, and PAI-1 mean concentrations were, resp., 1.69 ng/mL ± 0.80, 2.76 ng/mL ± 1.33, and 53.27 ng/mL ± 36.39). There was no correlation between u-PA and PAI-1 (r = 0.3) but t-PA and PAI-1 were strongly correlated with each other (r = 0.6). Overexpression of PAI-1 was proportional to the calcium content of the AS valves. Conclusions. Our results demonstrate a consistent increase of PAI-1 proportional to the calcification. The overexpression of PAI-1 may be useful as a predictive indicator in patients with aortic stenosis.

Detection of hypofibrinolysis in stable coronary artery disease using the overall haemostatic potential assay

INTRODUCTION

Patients with stable coronary artery disease (CAD) are at risk of arterial thrombosis causing myocardial infarction. Detection of global haemostatic markers of hypercoagulability and hypofibrinolysis may be important for risk stratification and individualised treatment. We examined overall haemostatic potential (OHP) and thrombin generation in a group of stable CAD patients. We also sought to investigate associations between fibrinolytic inhibitors and abnormal global fibrinolysis in these patients.

MATERIALS AND METHODS

Blood samples were collected from 56 patients defined by coronary anatomy as symptomatically stable CAD. Medications were recorded. Samples were analysed using the global coagulation assays OHP and thrombin generation (calibrated automated thrombogram, CAT), platelet aggregometry measured by Multiplate®, and levels of plasminogen activator inhibitor-1 (PAI-1) antigen measured by ELISA. Results were compared with a reference group of healthy controls.

RESULTS

Stable CAD patients displayed increased fibrin and thrombin generation and impaired fibrinolysis (decreased overall fibrinolytic potential, OFP, and increased clot lysis time) compared with healthy controls. No effect of antiplatelet agents or other medications on these parameters was observed using platelet-poor plasma. After multivariate adjustment, OFP of healthy individuals was significantly associated with fibrinogen, but in CAD patients PAI-1 became an important determinant.

CONCLUSIONS

Hypercoagulability of plasma is observed in stable CAD, with both increased thrombin generation and reduced fibrinolytic potential making a significant contribution. The OHP assay may provide a simple method of identifying hypercoagulability in individual patients.

Fibrinolytic proteins in human bile accelerate lysis of plasma clots and induce breakdown of fibrin sealants

OBJECTIVE

We investigated the effect of human bile on the stability of plasma clots and of fibrin sealants.

BACKGROUND

Fibrin sealants are extensively used in liver surgery, for example, during liver resections. Although these sealants have been developed to induce hemostasis, in practice these products are actually mainly used to seal dissected bile ducts to prevent postsurgical bile leakage.

METHODS

We performed in vitro assays in which clotting and lysis of human plasma clots or fibrin sealants was studied in presence or absence of human bile.

RESULTS

Addition of bile to human plasma resulted in a dose-dependent increase in clotting time, and a dose-dependent decrease in clot lysis time. Bile also accelerated lysis of in vitro clotted fibrin sealants. Immunodepletion of tissue-type plasminogen activator (tPA) resulted in partial depletion of the lysis promoting activity of bile. Immunodepletion of both tPA and lysine-binding proteins from bile fully abolished the lytic activity, suggesting that tPA and plasminogen present in human bile are responsible for the lysis-promoting effect. Surprisingly, addition of high dose plasminogen activator inhibitor type 1 (PAI-1) to bile did not attenuate the lytic activity toward fibrin sealants, which suggested that tPA in a biliary environment may be unsusceptible to PAI-1 inhibition. Indeed, bile acids were shown to prevent tPA from interacting with PAI-1, although preformed complexes were not destabilized upon addition of bile acids.

CONCLUSIONS

These combined results suggest that the presence of tPA and other fibrinolytic proteins in human bile results in lysis of plasma clots or fibrin sealants, which potentially could affect the efficacy of the latter products.

Biological variation in tPA-induced plasma clot lysis time

Hypofibrinolysis is a risk factor for venous and arterial thrombosis, and can be assessed by using a turbidimetric tPA-induced clot lysis time (CLT) assay. Biological variation in clot lysis time may affect the interpretation and usefulness of CLT as a risk factor for thrombosis. Sufficient information about assay variation and biological variation in CLT is not yet available. Thus, this study aimed to determine the analytical, within-subject and between-subject variation in CLT. We collected blood samples from 40 healthy individuals throughout a period of one year (average 11.8 visits) and determined the CLT of each plasma sample in duplicate. The mean (± SD) CLT was 83.8 (± 11.1) minutes. The coefficients of variation for total variation, analytical variation, within-subject variation and between-subject variation were 13.4%, 2.6%, 8.2% and 10.2%, respectively. One measurement can estimate the CLT that does not deviate more than 20% from its true value. The contribution of analytical variation to the within-subject variation was 5.0%, the index of individuality was 0.84 and the reference change value was 23.8%. The CLT was longer in the morning compared to the afternoon and was slightly longer in older individuals (> 40 years) compared to younger (≤40 years) individuals. There was no seasonal variation in CLT and no association with air pollution. CLT correlated weakly with fibrinogen, C-reactive protein, prothrombin time and thrombin generation. This study provides insight into the biological variation of CLT, which can be used in future studies testing CLT as a potential risk factor for thrombosis.

Intact thrombin generation and decreased fibrinolytic capacity in patients with acute liver injury or acute liver failure

BACKGROUND

It has been well established that hemostatic potential in patients with chronic liver disease is in a rebalanced status due to a concomitant decrease in pro- and antihemostatic drivers. The hemostatic changes in patients with acute liver injury/failure (ALI/ALF) are similar but not identical to the changes in patients with chronic liver disease and have not been studied in great detail.

OBJECTIVE

To assess thrombin generation and fibrinolytic potential in patients with ALI/ALF.

METHODS

We performed thrombin generation tests and clot lysis assays in platelet-poor plasma from 50 patients with ALI/ALF. Results were compared with values obtained in plasma from 40 healthy volunteers.

RESULTS AND CONCLUSION

The thrombin generation capacity of plasma from patients with ALI/ALF sampled on the day of admission to hospital was indistinguishable from that of healthy controls, provided thrombomodulin was added to the test mixture. Fibrinolytic capacity was profoundly impaired in patients with ALI/ALF on admission (no lysis in 73.5% of patients, compared with 2.5% of the healthy controls), which was associated with decreased levels of the plasminogen and increased levels of plasminogen activator inhibitor type 1. The intact thrombin generating capacity and the hypofibrinolytic status persisted during the first week of admission. Patients with ALI/ALF have a normal thrombin generating capacity and a decreased capacity to remove fibrin clots. These results contrast with routine laboratory tests such as the PT/INR, which are by definition prolonged in patients with ALI/ALF and suggest a bleeding tendency.

Oxidized phospholipids are present on plasminogen, affect fibrinolysis, and increase following acute myocardial infarction

OBJECTIVES

This study sought to assess whether plasminogen, which is homologous to lipoprotein (a) [Lp(a)], contains proinflammatory oxidized phospholipids (OxPL) and whether this has clinical relevance.

BACKGROUND

OxPL measured on apolipoprotein B-100 (OxPL/apoB), primarily reflecting OxPL on Lp(a), independently predict cardiovascular disease (CVD) events.

METHODS

The authors examined plasminogen from commercially available preparations and plasma from chimpanzees; gorillas; bonobos; cynomolgus monkeys; wild-type, apoE(-/-), LDLR(-/-), and Lp(a)-transgenic mice; healthy humans; and patients with familial hypercholesterolemia, stable CVD, and acute myocardial infarction (AMI). Phosphocholine (PC)-containing OxPL (OxPC) present on plasminogen were detected directly with liquid chromatography-mass spectrometry (LC-MS/MS) and immunologically with monoclonal antibody E06. In vitro clot lysis assays were performed to assess the effect of the OxPL on plasminogen on fibrinolysis.

RESULTS

LC-MS/MS revealed that OxPC fragments were covalently bound to mouse plasminogen. Immunoblot, immunoprecipitation, density gradient ultracentrifugation, and enzyme-linked immunosorbent assay analyses demonstrated that all human and animal plasma samples tested contained OxPL covalently bound to plasminogen. In plasma samples subjected to density gradient fractionation, OxPL were present on plasminogen (OxPL/plasminogen) in non-lipoprotein fractions but on Lp(a) in lipoprotein fractions. Plasma levels of OxPL/apoB and OxPL/apo(a) varied significantly (>25×) among subjects and also strongly correlated with Lp(a) levels. In contrast, OxPL/plasminogen levels were distributed across a relatively narrow range and did not correlate with Lp(a). Enzymatic removal of OxPL from plasminogen resulted in a longer lysis time for fibrin clots (16.25 vs. 11.96 min, p = 0.007). In serial measurements over 7 months, OxPL/plasminogen levels did not vary in normal subjects or in patients with stable CVD, but increased acutely over the first month and then slowly decreased to baseline in patients following AMI.

CONCLUSIONS

These data demonstrate that plasminogen contains covalently bound OxPL that influence fibrinolysis. OxPL/plasminogen represent a second major plasma pool of OxPL, in addition to those present on Lp(a). OxPL present on plasminogen may have pathophysiological implications in AMI and atherothrombosis.

Effects of pharmacological suppression of plasminogen activator inhibitor-1 in myocardial remodeling after ischemia reperfusion injury

Plasminogen activator inhibitor-1 (PAI-1) contributes to cardiac ventricular remodeling because migration of inflammatory cells and attenuation of extracellular matrix degradation are caused by plasmin and matrix metalloproteinase. However, the roles of PAI-1 in myocardial ischemia reperfusion (I/R) injury and the following inflammatory response have not yet been well elucidated. To clarify the role of PAI-1 in myocardial I/R injury, we used a specific PAI-1 inhibitor (IMD-1622) in a rat model. The left anterior descending coronary artery was ligated and reperfusion was performed by loosening the suture after 30 minutes of arterial occlusion. A single administration of IMD-1622 (20 mg/kg) or vehicle was given intraperitoneally and then the rats were sacrificed on day 1 or day 14 after I/R. Blood pressure, echocardiograms, histopathology, and molecular examination were performed. The examinations revealed that PAI-1 inhibitor showed limited effects on cardiac dysfunction and ventricular remodeling after I/R. We conclude that the pharmacological inhibition of PAI-1 may not affect ventricular remodeling after myocardial I/R injury.

Effects of plasminogen activator inhibitor-1-specific RNA aptamers on cell adhesion, motility, and tube formation

The serine protease inhibitor (serpin) plasminogen activator inhibitor-1 (PAI-1) is associated with the pathophysiology of several diseases, including cancer and cardiovascular disease. The extracellular matrix protein vitronectin increases at sites of vessel injury and is also present in fibrin clots. Integrins present on the cell surface bind to vitronectin and anchor the cell to the extracellular matrix. However, the binding of PAI-1 to vitronectin prevents this interaction, thereby decreasing both cell adhesion and migration. We previously developed PAI-1-specific RNA aptamers that bind to (or in the vicinity of) the vitronectin binding site of PAI-1. These aptamers prevented cancer cells from detaching from vitronectin in the presence of PAI-1, resulting in an increase in cell adhesion. In the current study, we used in vitro assays to investigate the effects that these aptamers have on human aortic smooth muscle cell (HASMC) and human umbilical vein endothelial cell (HUVEC) migration, adhesion, and proliferation. The PAI-1-specific aptamers (SM20 and WT15) increased attachment of HASMCs and HUVECs to vitronectin in the presence of PAI-1 in a dose-dependent manner. Whereas PAI-1 significantly inhibited cell migration through its interaction with vitronectin, both SM20 and WT15 restored cell migration. The PAI-1 vitronectin binding mutant (PAI-1AK) did not facilitate cell detachment or have an effect on cell migration. The effect on cell proliferation was minimal. Additionally, both SM20 and WT15 promoted tube formation on matrigel that was supplemented with vitronectin, thereby reversing the PAI-1's inhibition of tube formation. Collectively, results from this study show that SM20 and WT15 bind to the PAI-1's vitronectin binding site and interfere with its effect on cell migration, adhesion, and tube formation. By promoting smooth muscle and endothelial cell migration, these aptamers can potentially eliminate the adverse effects of elevated PAI-1 levels in the pathogenesis of vascular disease.

Fibrin clot structure and function: a role in the pathophysiology of arterial and venous thromboembolic diseases

The formation of fibrin clots that are relatively resistant to lysis represents the final step in blood coagulation. We discuss the genetic and environmental regulators of fibrin structure in relation to thrombotic disease. In addition, we discuss the implications of fibrin structure for treatment of thrombosis. Fibrin clots composed of compact, highly branched networks with thin fibers are resistant to lysis. Altered fibrin structure has consistently been reported in patients with several diseases complicated by thromboembolic events, including patients with acute or prior myocardial infarction, ischemic stroke, and venous thromboembolism. Relatives of patients with myocardial infarction or venous thromboembolism display similar fibrin abnormalities. Low-dose aspirin, statins, lowering of homocysteine, better diabetes control, smoking cessation, and suppression of inflammatory response increase clot permeability and susceptibility to lysis. Growing evidence indicates that abnormal fibrin properties represent a novel risk factor for arterial and venous thrombotic events, particularly of unknown etiology in young and middle-aged patients.

Antiphospholipid syndrome: laboratory detection, mechanisms of action and treatment

The antiphospholipid syndrome (APS) identifies a condition at increased risk of vascular occlusion and/or pregnancy complications. Patients are defined as having APS if they have at least one clinical (vascular occlusion and/or pregnancy complications) and one laboratory criterion at the same time. The laboratory criteria that define APS are repeated positivity (confirmed 12 weeks apart) for lupus anticoagulants and/or antibodies targeted against cardiolipin or β(2) -glycoprotein I immobilized on solid surfaces. Over the years, APS has attracted the interest of many medical specialties. The aim of this review is to provide an update on (i) the laboratory criteria that determine the presence of APS, (ii) how the antibodies increase the risk of vascular occlusion and foetal loss and (iii) the treatment of the related clinical events.