Genetic and Environmental Determinants of Fibrin Structure and Function

Impaired thrombolysis: a novel cardiovascular risk factor in end-stage renal disease

AIMS

End-stage renal disease (ESRD) patients have an excess cardiovascular risk, above that predicted by traditional risk factor models. Prothrombotic status may contribute to this increased risk. Global thrombotic status assessment, including measurement of occlusion time (OT) and thrombolytic status, may identify vulnerable patients. Our aim was to assess overall thrombotic status in ESRD and relate this to cardiovascular risk.

METHODS AND RESULTS

Thrombotic and thrombolytic status of ESRD patients (n = 216) on haemodialysis was assessed using the Global Thrombosis Test. This novel, near-patient test measures the time required to form (OT) and time required to lyse (lysis time, LT) an occlusive platelet thrombus. Patients were followed-up for 276 ± 166 days for major adverse cardiovascular events (MACE, composite of cardiovascular death, non-fatal MI, or stroke). Peripheral arterial or arterio-venous fistula thrombosis was a secondary endpoint. Occlusion time was reduced (491 ± 177 vs. 378 ± 96 s, P < 0.001) and endogenous thrombolysis was impaired (LT median 1820 vs.1053 s, P < 0.001) in ESRD compared with normal subjects. LT ≥ 3000 s occurred in 42% of ESRD patients, and none of the controls. Impaired endogenous thrombolysis (LT ≥ 3000 s) was strongly associated MACE (HR = 4.25, 95% CI = 1.58-11.46, P = 0.004), non-fatal MI and stroke (HR = 14.28, 95% CI = 1.86-109.90, P = 0.01), and peripheral thrombosis (HR = 9.08, 95% CI = 2.08-39.75, P = 0.003). No association was found between OT and MACE.

CONCLUSION

Impaired endogenous thrombolysis is a novel risk factor in ESRD, strongly associated with cardiovascular events.

Fibrinolysis alterations in infertile women during controlled ovarian stimulation: influence of BMI and genetic components

INTRODUCTION

Ovarian stimulation protocols have been described to induce prothrombotic phenotype through alterations of both coagulation and fibrinolysis pathways. We investigated fibrinolytic changes during ovarian stimulation through a global test (CLT) and PAI-1 and TAFI concentrations at different times of ovarian stimulation procedure, and the influence of polymorphisms in genes encoding for fibrinogen chains (FGA, FGB, FGG), t-PA (PLAT), TAFI (CBP2), FXIII (FXIIA1, FXIIIB), plasminogen (PLG) and PAI-1 (PAI1) on their intermediate phenotype.

MATERIALS AND METHODS

We evaluated fibrinolytic and genetic parameters in 110 infertile women undergoing ovarian stimulation procedure (in vitro fertilization, IVF or intracytoplasmic sperm injection, ICSI). All women were observed during the mid-luteal phase of cycle (T(0)) and on day 5 (T(1)), 7 (T(2)) and 9 (T(3)) of the ovarian stimulation.

RESULTS

Significant changes in fibrinolytic parameters from T(0) to T(3) of ovarian stimulation were found (CLT p=0.003; TAFI p=0.009 and PAI-1 p=0.003). CLT values, TAFI and PAI-1 concentrations significantly increased from baseline to T(1) (p<0.0001, p=0.01, p=0.005, respectively)(,) and decreased at T(2,) but remained higher than those at T(0). Moreover, at baseline overweight women showed longer CLT, higher TAFI and PAI-1 concentrations than normal weight women, as well as at T(1) two-fold longer CLT and higher PAI-1 concentrations were observed (p=0.001 and p=0.05, respectively). Significant differences of TAFI and PAI-1 concentrations during ovarian stimulation according to TAFI and PAI1 polymorphisms were observed.

CONCLUSIONS

This study shows alterations of fibrinolysis and suggests the contribution of TAFI and PAI1 genes in modulating fibrinolysis changes during the ovarian stimulation cycle.

The impact of blood coagulability on atherosclerosis and cardiovascular disease

Although the link between blood coagulation and atherogenesis has been long postulated, only recently, and through the extensive work on transgenic mice, crossbred on an atherogenic background, has the direction of this interaction become visible. In general, hypercoagulability in mice tends to increase atherosclerosis, whereas hypocoagulability reduces the atherosclerotic burden, depending on the mouse model used. The information on a direct relationship between coagulation and atherosclerosis in humans, however, is not that clear. Almost all coagulation proteins, including tissue factor, are found in atherosclerotic lesions in humans. In addition to producing local fibrin, a matrix for cell growth, serine proteases such as thrombin may be very important in cell signaling processes, acting through the activation of protease-activated receptors (PARs). Activation of PARs on vascular cells drives many complex processes involved in the development and progression of atherosclerosis, including inflammation, angiogenesis, and cell proliferation. Although current imaging techniques do not allow for a detailed analysis of atherosclerotic lesion phenotype, hypercoagulability, defined either by gene defects of coagulation proteins or elevated levels of circulating markers of activated coagulation, has been linked to atherosclerosis-related ischemic arterial disease. New, high-resolution imaging techniques and sensitive markers of activated coagulation are needed in order to study a causal contribution of hypercoagulability to the pathophysiology of atherosclerosis. Novel selective inhibitors of coagulation enzymes potentially have vascular effects, including inhibition of atherogenesis through attenuation of inflammatory pathways. Therefore, we propose that studying the long-term vascular side effects of this novel class of oral anticoagulants should become a clinical research priority.

Complement C3 is a novel plasma clot component with anti-fibrinolytic properties

BACKGROUND AND METHOD

Increased plasma clot density and prolonged lysis times are associated with cardiovascular disease. In this study, we employed a functional proteomics approach to identify novel clot components which may influence clot phenotypes.

RESULTS

Analysis of perfused, solubilised plasma clots identified inflammatory proteins, including complement C3, as novel clot components. Analysis of paired plasma and serum samples confirmed concentration-dependent incorporation of C3 into clots. Surface plasmon resonance indicated high-affinity binding interactions between C3 and fibrinogen and fibrin. Turbidimetric clotting and lysis assays indicated C3 impaired fibrinolysis in a concentration-dependent manner, both in vitro and ex vivo.

CONCLUSION

These data indicate functional interactions between complement C3 and fibrin leading to prolonged fibrinolysis. These interactions are physiologically relevant in the context of protection following injury and suggest a mechanistic link between increased plasma C3 concentration and acute cardiovascular thrombotic events.

High frequency ultrasound imaging of whole blood gelation and retraction during in vitro coagulation

Blood coagulation is a series of biochemical reactions resulting in the mechanical transformation of liquid blood into a gel. As a consequence, ultrasound, being mechanical waves, can provide specific details on the dynamics of coagulation. In fact, previous high-frequency ultrasound monitoring studies have shown drastic changes in ultrasound velocity and attenuation during whole blood coagulation and a model discussing the observed mechanical transformations was proposed. In this paper, a technique of visualization of the clotting mechanism is introduced, which complements and revises the previous hypotheses. This method is based on the monitoring of scatterers (red blood cells) movement through a time correlation of 20 MHZ rf signals. It allows the computing of both a displacement map revealing local details and disparities and a parameter quantifying the global structural behavior. Qualitative results for two typical samples show that the technique provides new insights on the gelation dynamics. A quantitative analysis computed from 12 healthy subjects found that the changes in the structural parameters are significantly correlated to the changes in velocity and attenuation, both dependent on the mechanical transformations in the sample. The previous model is therefore revised and a new way to measure gel and retraction times is proposed.

Marrubiin, a constituent of Leonotis leonurus, alleviates diabetic symptoms

AIMS

Marrubiin and an organic extract of Leonotis leonurus were tested in vitro and in vivo for their antidiabetic and anti-inflammatory activities.

MATERIALS AND METHODS

INS-1 cells were cultured under normo- and hyperglycemic conditions conditions. An in vivo animal model confirmed the biological activities of marrubiin and the organic extract observed in the studies in vitro.

RESULTS

The stimulatory index of INS-1 cells cultured under hyperglycemic conditions was significantly increased in cells exposed to the organic extract and marrubiin, relative to the hyperglycaemic conditions. Insulin and glucose transporter-2 gene expressions were significantly increased by the organic extract and marrubiin. Similarly, the extract and marrubiin resulted in an increase in respiratory rate and mitochondrial membrane potential under hyperglycaemic conditions. Marrubiin increased insulin secretion, HDL-cholesterol, while it normalized total cholesterol, LDL-cholesterol, atherogenic index, IL-1β and IL-6 levels in an obese rat model.

CONCLUSION

The results provide evidence that marrubiin, a constituent of Leonotis leonurus, alleviates diabetic symptoms.

Sonography characteristics of the intra-graft thrombus: association with procedure success and procedure time of percutaneous transluminal angioplasty for thrombosed prosthetic dialysis graft

Percutaneous transluminal angioplasty (PTA) for thrombosed dialysis graft is both difficult and time-consuming that may increase radiation exposure. A predictor of PTA success and procedure time has not been identified yet. Sonography data and the PTA results of 88 grafts were reviewed retrospectively. The echogenicity of the majority of the intra-graft thrombus and the presence/absence of thrombus free space in the grafts were examined. The association between the sonography findings and PTA procedure success and procedure time was analyzed. The echogenicity of the intra-graft thrombus and presence/absence of thrombus free space were the major determinants of procedure success and procedure time. Higher intra-graft echogenicity and lack of thrombus free space were associated with more procedure failures (p < 0.01 vs. p = 0.04) and longer procedure times (p = 0.03 vs. p < 0.01). Thrombi from occluded dialysis grafts may differ in resistance to mechanical/pharmacological thrombolysis. Sonography characteristics of the intra-graft thrombus may help to differentiate them.

FXIII-A Leu34 genetic variant in premature coronary artery disease: a genotype--phenotype case control study

The FXIII-A Leu34 genetic variant increases and accelerates fibrin stabilisation; however, its association with premature coronary artery disease (CAD) and thrombotic events remains controversial. FXIII Val34Leu genotype was determined in 242 young individuals (<45 years old) who survived a myocardial infarction (MI) and 242 healthy controls matched for age and gender. We evaluated its effect on long-term clinical outcome defined as a composite of cardiovascular death, recurrent MI and urgent revascularisation. In addition, fibrin clot stiffness (elastic modulus or EM) and response to rt-PA-mediated fibrinolysis (fibrinolysis rate) were measured ex vivo using the Hemodyne analyser and confocal microscopy as surrogate endpoint. FXIII-A Leu34 genetic variant was not associated with premature CAD (adj. odds ratio 0.83 [0.49-1.4]) nor did it influence clinical outcome in patients, during a median follow-up of 6.3 (± 2.4) years. Patients produced stiffer fibrin clots (median [IQR] EM = 20.3 [14.9-28.1] vs. 12.8 [9.6-17.1] kdynes/cm²; p<0.0001) and displayed reduced response to fibrinolysis with lower fibrinolysis rate (6.7 [3.4-11.0] vs. 9.0 [5.0-16.7] sec-¹ x 10(-4); p<0.0001) than healthy controls. Carriage of factor XIII-A Leu34 led to a stepwise decrease in fibrinolysis rate with a significant gene-dose-effect in patients (7.7 [4.1-12.2] vs. 4.8 [3.0-8.5] vs. 4.3 [2.4-8.1] sec-¹ x 10(-4), for wild-type, heterozygous and homozygous, p for trend = 0.003) and a non-significant trend in controls (p = 0.01). In conclusion, FXIII-A Leu34 is a polymorphism which provides a strong resistance to fibrinolysis with a gene-dose effect, but does not relate to premature CAD or to recurrent coronary events in this study.

Chronic kidney disease-related atherosclerosis - proteomic studies of blood plasma

Background

Atherosclerosis is considered the major cause of the dramatic increase in cardiovascular mortality among patients suffering from chronic kidney disease (CKD). Although the close connection between atherosclerosis and kidney dysfunction is undeniable, factors enhancing CKD-mediated plaque formation are still not well recognized.

Results

To increase our knowledge of this process we carried out a comparative proteomic analysis of blood plasma proteins isolated from 75 patients in various stages of renal dysfunction (CKD group), 25 patients with advanced cardiovascular disease (CVD group) and 25 healthy volunteers (HV group). The collected samples were subjected to 2D electrophoresis. Then, individual proteins were identified by mass spectrometry. The comparative analysis involving CKD and HV groups showed a differential accumulation of α-1-microglobulin, apolipoprotein A-IV, γ-fibrinogen and haptoglobin in patients with kidney disease. Exactly the same proteins were identified as differentially expressed when proteomes of CVD patients and HV were compared. However, a direct comparison of CKD and CVD groups revealed significant differences in the accumulation of two proteins: α-1-microglobulin and apolipoprotein A-IV.

Conclusions

The obtained results indicate that at least two processes differentially contribute to the plaque formation in CKD- and CVD-mediated atherosclerosis. It seems that the inflammatory process is more intense in CKD patients. On the other hand, the down- and up-regulation of apolipoprotein A-IV in CVD and CKD groups, respectively, suggests that substantial differences exist in the efficacy of cholesterol transport in both groups of patients.

Role of fibrin structure in thrombosis and vascular disease

Fibrin clot formation is a key event in the development of thrombotic disease and is the final step in a multifactor coagulation cascade. Fibrinogen is a large glycoprotein that forms the basis of a fibrin clot. Each fibrinogen molecule is comprised of two sets of Aα, Bβ, and γ polypeptide chains that form a protein containing two distal D regions connected to a central E region by a coiled-coil segment. Fibrin is produced upon cleavage of the fibrinopeptides by thrombin, which can then form double-stranded half staggered oligomers that lengthen into protofibrils. The protofibrils then aggregate and branch, yielding a three-dimensional clot network. Factor XIII, a transglutaminase, cross-links the fibrin stabilizing the clot protecting it from mechanical stress and proteolytic attack. The mechanical properties of the fibrin clot are essential for its function as it must prevent bleeding but still allow the penetration of cells. This viscoelastic property is generated at the level of each individual fiber up to the complete clot. Fibrinolysis is the mechanism of clot removal, and involves a cascade of interacting zymogens and enzymes that act in concert with clot formation to maintain blood flow. Clots vary significantly in structure between individuals due to both genetic and environmental factors and this has an effect on clot stability and susceptibility to lysis. There is increasing evidence that clot structure is a determinant for the development of disease and this review will discuss the determinants for clot structure and the association with thrombosis and vascular disease.

Plasma fibrin clot properties in atopic dermatitis: links between thrombosis and atopy

Myocardial infarction and ischemic stroke are associated with formation of dense fibrin clots resistant to lysis. Although pro- and antithrombotic alterations have been reported in atopy, fibrin clot function has not been studied in atopic patients. The aim of the current study was to investigate fibrin clot properties in patients with atopic dermatitis (AD). Plasma fibrin clot permeability, turbidity and clot lysis were assessed in 130 consecutive AD patients, aged 29.7 +/- 11 [+/-SD] years (mean SCORAD index, 32.4 +/- 14.9), free of thrombotic events. A control group comprised 130 healthy controls matched for demographics. Patients with AD had lower clot permeability (7.12 +/- 1.87 vs. 9.32 +/- 0.86 x 10(-9) cm(2); P < 0.0001), increased fiber thickness (maximum clot absorbancy at 405 nm, 4.03 +/- 0.54 vs. 3.47 +/- 0.25), faster clot formation (the lag phase, 39.16 +/- 4.61 vs. 43.05 +/- 4.56 s), higher maximum D-dimer levels released from clots, reflecting increased clot mass (4.05 +/- 0.57 vs. 3.47 +/- 0.25 mg/l; P < 0.0001), lower rate of D-dimer release (0.073 +/- 0.01 vs. 0.078 +/- 0.01 mg/l/min; P < 0.0001), and prolonged fibrinolysis time (9.26 +/- 1.47 vs. 7.81 +/- 1.17 min; P < 0.0001) compared with controls. Concomitant asthma (n = 36; 27.7%) was related to a higher rate of D-dimer release from clots than the remainder (0.075 +/- 0.01 vs. 0.072 +/- 0.01 mg/l/min, respectively; P = 0.03). Altered plasma fibrin clot properties associated with reduced efficiency of fibrinolysis can be detected in AD patients, which might represent a novel mechanism that modulates a hemostatic balance in atopy.

Architecture of intraluminal thrombus removed from abdominal aortic aneurysm

Little is known about architecture of intraluminal thrombus (ILT) in abdominal aortic aneurysm (AAA). We present a 74-year-old woman with AAA and high cardiovascular risk. Scanning electron microscopy of ILT removed during surgery showed that its luminal layer is relatively rich in fibrin fibers forming irregular compact structure with low amounts of erythrocytes and platelets, while abluminal portion is composed of densely packed fibrin with caniculi. The structure of ILT may differ largely among AAA patients contrary to previous findings and may reveal large dense fibrin-rich areas deprived of cells, which impair fibrinolysis and stabilize the thrombus size.

Acute cigarette smoke exposure reduces clot lysis--association between altered fibrin architecture and the response to t-PA

BACKGROUND

Enhanced thrombolysis is a proposed mechanism for reduced mortality in cigarette smokers with STEMI ("smoker's paradox"). The mechanisms remain unclear but studies suggest fibrin architecture (FA) may affect thrombolysis. Our group has previously shown that acute cigarette smoke exposure (CSE) alters FA. This study was done to evaluate the association between FA, thrombolysis and CSE.

METHODS AND RESULTS

Otherwise healthy smokers (n=22) were studied before and after smoking two cigarettes. Non-smokers (n=22) served as controls. Two ex-vivo models were used to evaluate clot lysis of venous blood and these data were compared to FA as determined by SEM. In the first model, clot lysis in a glass tube at 60minutes after addition of t-PA was measured. The second model quantified lysis utilizing thromboelastography. With the latter, after a clot reached maximum strength, t-PA was added and clot lysis at 60min was noted. SEM studies were performed on platelet poor plasma mixed with thrombin and FA was examined at 20K. Clot lysis was similar in both groups except that post-smoking, TEG showed a significantly lower lysis compared to pre- and non-smoking clots. SEM analysis showed significantly thinner fibers and denser clots post-smoking.

CONCLUSIONS

Venous clots from smokers failed to show an enhanced lysis when exposed to t-PA. In fact, acute CSE was associated with changes in FA and increased resistance to thrombolysis. These findings in part may explain enhanced thrombogenicity but suggest that mechanisms other than enhanced fibrinolysis are likely to be responsible for "smoker's paradox."

Gel point and fractal microstructure of incipient blood clots are significant new markers of hemostasis for healthy and anticoagulated blood

Here we report the first application of a fractal analysis of the viscoelastic properties of incipient blood clots. We sought to ascertain whether the incipient clot's fractal dimension, D(f,) could be used as a functional biomarker of hemostasis. The incipient clot is formed at the gel point (GP) of coagulating blood, the GP demarcating a functional change from viscoelastic liquid to a viscoelastic solid. Incipient clots formed in whole healthy blood show a clearly defined value of D(f) within a narrow range that represents an index of clotting in health, where D(f) = 1.74 (± 0.07). A significant relationship is found between the incipient clot formation time, T(GP), and the activated partial thromboplastin time, whereas the association of D(f) with the microstructural characteristics of the incipient clot is supported by its significant correlation with fibrinogen. Our study reveals that unfractionated heparin not only prolongs the onset of clot formation but has a significant effect on its fractal microstructure. A progressive increase in unfractionated heparin concentration results in a linear decrease in D(f) and a corresponding prolongation in T(GP). The results represent a new, quantitative measure of clot quality derived from measurements on whole blood samples.

Unfavorably altered fibrin clot properties in patients with active rheumatoid arthritis

OBJECTIVE

Altered fibrin clot properties have been reported in cardiovascular diseases (CVD) and inflammatory states. Given increased prevalence of CVD in patients with rheumatoid arthritis (RA), we investigated whether fibrin characteristics are also altered in RA patients.

PATIENTS AND METHODS

We studied 46 consecutive RA patients versus 50 controls matched for age and gender. Ex vivo plasma clot permeability, turbidity, tissue-type plasminogen activator (tPA)-induced fibrinolysis, and scanning electron microscopy (SEM) images of clots were evaluated.

RESULTS

Patients with RA had lower clot permeability, faster clot formation, higher maximum clot absorbency indicating thicker fibrin fibers, maximum clot mass and prolonged fibrinolysis time than controls. Maximum rates of clot lysis were similar in both groups. SEM images showed formation of dense clots with many projections on fibrin fibers. Clot permeability inversely correlated with fibrinogen, tPA, plasminogen activator inhibitor-1 (PAI-1), CRP, platelet count, disease activity score (DAS28) and a marker of oxidative stress, 8-iso-prostaglandin F2alpha (r from -0.44 to -0.79; all, p<0.0001). Similar positive associations were found for clot lysis time (r 0.44 to 0.69; all, p<0.01). Multiple regression analysis showed that fibrinogen was the only independent predictor of clot permeability (R2=0.87, p<0.0001) and lysis time (R2=0.80, p<0.003) in RA. Maximum D-dimer levels released from clots, maximum clot turbidity and the time of clot formation were predicted by PAI-1 (all, p<0.05).

CONCLUSION

We showed unfavorably altered plasma fibrin clot structure and function in RA, which might contribute to an increased risk of thrombotic events in this disease.

Physiology of hemostasis: with relevance to current and future laboratory testing

This article briefly details the physiologic and interdependent mechanisms of vascular hemostasis, with an eye toward how the laboratory can assist in diagnosing and maintaining the balance of procoagulant and anticoagulant functions. These functions include determining characteristics of the blood vessel wall, platelet components and receptor-ligand interactions critical for hemostasis, the regulation of thrombin generation and its effects, and the complex fibrinolytic pathways that complete the coagulation cascade.

Fibrin clot properties in acute ischemic stroke: relation to neurological deficit

INTRODUCTION

Hypercoagulable state occurs in patients with acute vascular events. We wondered whether clot structure/function is altered in acute ischemic stroke (AIS), like in acute myocardial infarction.

PATIENTS AND METHODS

In 45 consecutive patients with AIS (24M, 21F), aged 67.4+/-10.9 years, and 45 healthy controls matched for age and sex, we investigated plasma fibrin clot structure/function by permeation, turbidity, and efficiency of fibrinolysis.

RESULTS

Compared to controls, AIS patients produced clots that had 30.5% less porous network (p<0.0001), were less susceptible to fibrinolysis (10.8% longer lysis time, p=0.001), were 20.5% more compact (p<0.0001), had 17.1% higher clot mass (p<0.0001), and showed increased (by 10.2%) overall fiber thickness (p<0.0001) with 8% shorter lag phase of fibrin formation (p=0.0002). Maximum rate of D-dimer release from clots was similar. Multiple regression analyses for all subjects (n=90) showed that being a stroke patient (p<0.0001), fibrinogen (p<0.0001) and lipoprotein(a) (p=0.0075) were independent predictors of clot permeability (model R2 0.79). Only fibrinogen (p<0.0001) and lipoprotein(a) (p=0.0026) predicted lysis time. All other fibrin parameters were predicted only by being a stroke patient. Clot compaction was associated with neurological deficit on admission (r=-0.81; p<0.0001) and at discharge (r=-0.69; p<0.0001). Patients with 0 or 1 point in the modified Rankin scale (n=19) had 13.3% higher clot permeability compared to the remainder (p=0.02).

CONCLUSIONS

This study is the first to show that AIS is associated with unfavorably altered fibrin clot properties that might correlate with neurological deficit.

Altered fibrin clot structure/function in patients with idiopathic venous thromboembolism and in their relatives

We tested the hypothesis that fibrin structure/function is unfavorably altered in patients after idiopathic venous thromboembolism (VTE) and their relatives. Ex vivo plasma fibrin clot permeability, turbidimetry, and efficiency of fibrinolysis were investigated in 100 patients with first-ever VTE, including 34 with pulmonary embolism (PE), 100 first-degree relatives, and 100 asymptomatic controls with no history of thrombotic events. Known thrombophilia, cancer, trauma, and surgery were exclusion criteria. VTE patients and their relatives were characterized by lower clot permeability (P < .001), lower compaction (P < .001), higher maximum clot absorbancy (P < .001), and prolonged clot lysis time (P < .001) than controls, with more pronounced abnormalities, except maximum clot absorbance, in the patients versus relatives (all P < .01). Fibrin clots obtained for PE patients were more permeable, less compact, and were lysed more efficiently compared with deep-vein thrombosis patients (all P < .05) with no differences in their relatives. Being VTE relative, fibrinogen, and C-reactive protein were independent predictors of clot permeability and fibrinolysis time in combined analysis of controls and relatives. We conclude that altered fibrin clot features are associated with idiopathic VTE with a different profile of fibrin variables in PE. Similar features can be detected in VTE relatives. Fibrin properties might represent novel risk factors for thrombosis.

Effects of cigarette smoke exposure on clot dynamics and fibrin structure: an ex vivo investigation

OBJECTIVE

The purpose of this study was to examine the effect of cigarette smoke exposure (CSE) on clot dynamics and fibrin architecture and to isolate the relative contribution of platelets and fibrinogen to clot dynamics.

METHODS AND RESULTS

From young healthy males smokers (n=34) and nonsmokers (n=34) a baseline blood was drawn, and smokers had another blood draw after smoking 2 regular cigarettes. Using thromboelastography (TEG) the degree of platelet-fibrin interaction was measured. In additional experiments, abciximab (20 microg/mL) was added to the smokers samples (n=27) to reduce the effects of platelet function from the TEG parameters. The maximum clot strength (G) obtained with abciximab measured mainly the contribution of fibrinogen to clot strength (GF). By subtracting GF from G, the contribution of platelets to clot strength (GP) was presumed. A significant difference was found for all TEG parameters between nonsmokers versus postsmoking and pre- versus postsmoking samples. Postsmoking both GF and GP were significantly higher as compared to presmoking. On electron microscopy and turbidity analysis, postsmoking fibrin clots were significantly different compared to presmoking and nonsmoking samples.

CONCLUSIONS

Acute CSE changes clot dynamics and alters fibrin architecture. Both functional changes in fibrinogen and platelets appear to contribute to heightened thrombogenicity after acute CSE.

High prevalence of dysfibrinogenemia among patients with chronic thromboembolic pulmonary hypertension

The mechanism by which chronic thromboembolic pulmonary hypertension (CTEPH) develops after acute pulmonary thromboembolism is unknown. We previously reported that fibrin from CTEPH patients is relatively resistant to fibrinolysis in vitro. In the present study, we performed proteomic, genomic, and functional studies on fibrin(ogen) to investigate whether abnormal fibrin(ogen) might contribute to the pathogenesis of CTEPH. Reduced and denatured fibrinogen from 33 CTEPH patients was subjected to liquid chromatography-mass spectrometry analysis. Fibrinogen from 21 healthy controls was used to distinguish atypical from commonly occurring mass peaks. Atypical peaks were further investigated by targeted genomic DNA sequencing. Five fibrinogen variants with corresponding heterozygous gene mutations (dysfibrinogenemias) were observed in 5 of 33 CTEPH patients: Bbeta P235L/gamma R375W, Bbeta P235L/gamma Y114H, Bbeta P235L, Aalpha L69H, and Aalpha R554H (fibrinogens(San Diego I-V)). Bbeta P235L was found in 3 unrelated CTEPH patients. Functional analysis disclosed abnormalities in fibrin polymer structure and/or lysis with all CTEPH-associated mutations. These results suggest that, in some patients, differences in the molecular structure of fibrin may be implicated in the development of CTEPH after acute thromboembolism.

Altered fibrin clot structure/function in patients with cryptogenic ischemic stroke

BACKGROUND AND PURPOSE

We tested the hypothesis that fibrin structure/function is unfavorably altered in patients with cryptogenic ischemic stroke.

METHODS

Ex vivo plasma fibrin clot permeability, turbidimetry, and efficiency of fibrinolysis were determined in 89 patients with patent foramen ovale (PFO) and a history of first-ever stroke, 58 patients with first-ever stroke and no PFO, and 120 healthy controls.

RESULTS

Stroke patients, evaluated 3 to 19 months after the event, and controls did not differ with regard to age, sex, smoking, and fibrinogen. Stroke patients with or without PFO had lower clot permeability (P<0.0001), faster fibrin polymerization (P<0.0001), prolonged clot lysis time (P<0.0001), higher maximum D-dimer levels released from clots (P<0.0001), and maximum rate of D-dimer release (P=0.02) than controls. Time from stroke occurrence showed no association with any clot variables. Scanning electron microscopy of fibrin clots showed increased fiber diameter and density in stroke patients. Clots from stroke patients with PFO were more permeable and showed shorter lysis time compared to those without PFO, and this was related to lower proportion of smokers in the former group.

CONCLUSIONS

Altered fibrin clot structure and resistance to fibrinolysis are associated with cryptogenic stroke.

Congenital disorder of glycosylation Ia: new differentially expressed proteins identified by 2-DE

Congenital disorders of glycosylation (CDG) comprise a family of inherited multisystemic disorders resulting from the deficiency of glycosylation pathways. N-glycosylation defects are classified as two biochemical and genetic established types, of which CDG-Ia is the most frequent. We performed 2-DE proteomic analysis on serum from two functional hemizygous CDG-Ia patients bearing T237M and D65Y missense changes. Comparative analysis of control/patient serum proteome allowed us to identify differential expression of 14 proteins. The most remarkable groups included proteins involved in immune response, coagulation mechanism and tissue protection against oxidative stress. The patient bearing D65Y mutation had less favourable clinical outcome and showed more abnormalities in the spot patterns, suggesting that the proteomic results might also be correlated with the phenotype of CDG patients. This study describes for the first time the differential expression of alpha(2)-macroglobulin, afamin, fibrin and fibrinogen in CDG disorder and shows how the proteomic approach might be useful for understanding its physiopathology.

Fibrin architecture in clots: a quantitative polarized light microscopy analysis

Fibrin plays a vital structural role in thrombus integrity. Thus, the ability to assess fibrin architecture has a potential to provide insight into thrombosis and thrombolysis. Fibrin has an anisotropic molecular structure, which enables it to be seen with polarized light. Therefore, we aimed to determine if automated polarized light microscopy methods of quantifying two structural parameters; fibrin fiber bundle orientation and fibrin's optical retardation (OR: a measure of molecular anisotropy) could be used to assess thrombi. To compare fibrin fiber bundle orientation we analyzed picrosirius red-stained sections obtained from clots formed: (A) in vitro, (B) in injured and stenotic coronary arteries, and (C) in surgically created aortic aneurysms (n=6 for each group). To assess potential changes in OR, we examined fibrin in picrosirius red-stained clots formed after ischemic preconditioning (10 min ischemia+10 min reflow; a circumstance shown to enhance lysability) and in control clots (n=8 each group). The degree of fibrin organization differed significantly according to the location of clot formation; fibrin was most aligned in the aneurysms and least aligned in vitro whereas fibrin in the coronary clots had an intermediate organization. The OR of fibrin in the clots formed after ischemic preconditioning was lower than that in controls (2.9+/-0.5 nm versus 5.4+/-1.0 nm, P<0.05). The automated polarized light analysis methods not only enabled fibrin architecture to be assessed, but also revealed structural differences in clots formed under different circumstances.

Hyperglycemia is associated with enhanced thrombin formation, platelet activation, and fibrin clot resistance to lysis in patients with acute coronary syndrome

OBJECTIVE

Acute hyperglycemia on admission for acute coronary syndrome worsens the prognosis in patients with and without known diabetes. Postulated mechanisms of this observation include prothrombotic effects. The aim of this study was to evaluate the effect of elevated glucose levels on blood clotting in acute coronary syndrome patients.

RESEARCH DESIGN AND METHODS

We studied 60 acute coronary syndrome patients within the first 12 h after pain onset, including 20 subjects with type 2 diabetes, 20 subjects with no diagnosed diabetes but with glucose levels >7.0 mmol/l, and 20 subjects with glucose levels <7.0 mmol/l. We determined generation of thrombin-antithrombin complexes (TATs) and soluble CD40 ligand (sCD40L), a platelet activation marker, at the site of microvascular injury, together with ex vivo plasma fibrin clot permeability and lysis time.

RESULTS

The acute coronary syndrome patients with no prior diabetes but elevated glucose levels had increased maximum rates of formation and total production of TATs (by 42.9%, P < 0.0001, and by 25%, P < 0.0001, respectively) as well as sCD40L release (by 16.2%, P = 0.0011, and by 16.3%, P < 0.0001, respectively) compared with those with normoglycemia, whereas diabetic patients had the highest values of TATs and sCD40L variables (P < 0.0001 for all comparisons). Patients with hyperglycemia, with no previously diagnosed diabetes, had longer clot lysis time (by approximately 18%, P < 0.0001) similar to that in diabetic subjects, but not lower clot permeability compared with that in normoglycemic subjects.

CONCLUSIONS

Hyperglycemia in acute coronary syndrome is associated with enhanced local thrombin generation and platelet activation, as well as unfavorably altered clot features in patients with and without a previous history of diabetes.

Fibrinogen gene variation and ischemic stroke

BACKGROUND

Plasma fibrinogen level and fibrin clot structure are heritable traits that may be of importance in the pathogenesis of ischemic stroke.

OBJECTIVES

To investigate associations between variation in the fibrinogen gamma (FGG), alpha (FGA) and beta (FGB) genes, fibrinogen level, and ischemic stroke.

METHODS

The Sahlgrenska Academy Study on Ischemic Stroke comprises 600 cases and 600 matched population controls. Stroke subtypes were defined according to TOAST criteria. Plasma fibrinogen level was measured by an automated clot-rate assay. Eight tagging single nucleotide polymorphisms (SNPs) were selected to capture genetic variation in the FGA, FGG, and FGB genes.

RESULTS

Plasma fibrinogen was independently associated with overall ischemic stroke and all subtypes, both in the acute stage (P < 0.001) and at three-month follow-up (P < 0.05). SNPs belonged to two haplotype blocks, one containing the FGB gene and the other the FGG and FGA genes. FGB haplotypes were associated with fibrinogen level (P < 0.01), but not with ischemic stroke. In contrast, FGG/FGA haplotypes showed independent association to ischemic stroke but not to fibrinogen level. In an additive model with the most common FGG/FGA haplotype (A1) as reference, the adjusted odds ratios of ischemic stroke were 1.4 [95% confidence interval (95% CI) 1.1-1.8], P < 0.01, 1.4 (95% CI 1.0-1.8), P < 0.05, and 1.5 (95% CI 1.0-2.1), P < 0.05 for the A2, A3, and A4 FGG/FGA haplotypes, respectively.

CONCLUSION

FGG/FGA haplotypes show association to ischemic stroke. This association is independent of fibrinogen level, thus suggesting that the association between ischemic stroke and variation at the FGG/FGA genes is mediated by qualitative rather than quantitative effects on fibrin(ogen).

Coagulation factor XIII gene variation, oral contraceptives, and risk of ischemic stroke

Prothrombotic conditions are associated with ischemic stroke in young women. In particular, the combination of oral contraceptive use and prothrombotic genetic variants appears to increase the risk of ischemic stroke. We performed a population-based case-control study in 190 women aged 20 to 49 years with ischemic stroke and 767 women without cardiovascular disease stratified for age, calendar year of the index event, and residence. A total of 4 variants of coagulation factor XIII subunit A and B genes (F13A1 and F13B) were investigated. The Phe allele of the F13A1 Tyr204Phe variant was present in 59 (31%) patients and 43 (6%) controls; the odds ratio for ischemic stroke was 9.1 for Phe/Phe and Phe/Tyr versus Tyr/Tyr genotype; the 95% confidence interval was 5.5 to 15. Homozygous genotypes (Phe/Phe) conferred a higher risk (odds ratio, 77; 95% confidence interval, 7.0-848) than heterozygous (Tyr/Phe) genotypes (odds ratio, 8.2; 95% confidence interval, 4.9-14). The risk of ischemic stroke was further increased in carriers of the 204Phe allele using oral contraceptives (odds ratio, 20; 95% confidence interval, 9-46) compared with nonusers with Tyr/Tyr genotype. In conclusion, the F13A1 204Phe allele was strongly associated with ischemic stroke in young women. Oral contraceptive use further increased the risk of ischemic stroke.

Genetic variation in 1253 immune and inflammation genes and risk of non-Hodgkin lymphoma

Smaller-scale evaluations suggest that common genetic variation in candidate genes related to immune function may predispose to the development of non-Hodgkin lymphoma (NHL). We report an analysis of variants within genes associated with immunity and inflammation and risk of NHL using a panel of 9412 single-nucleotide polymorphisms (SNPs) from 1253 genes in a study of 458 patients with NHL and 484 frequency-matched controls. We modeled haplotypes and risk of NHL, as well as the main effects for all independent SNPs from a gene in multivariate logistic regression models; we separately report results for nonsynonymous (ns) SNPs. In gene-level analyses, the strongest findings (P < or = .001) were for CREB1, FGG, MAP3K5, RIPK3, LSP1, TRAF1, DUSP2, and ITGB3. In nsSNP analyses, the strongest findings (P < or = .01) were for ITGB3 L59P (odds ratio [OR] = 0.66; 95% confidence interval [CI] 0.52-0.85), TLR6 V427A (OR = 5.20; CI 1.77-15.3), SELPLG M264V (OR = 3.20; CI 1.48-6.91), UNC84B G671S (OR = 1.50; CI 1.12-2.00), B3GNT3 H328R (OR = 0.74; CI 0.59-0.93), and BAT2 V1883L (OR = 0.64; CI 0.45-0.90). Our results suggest that genetic variation in genes associated with immune response (TRAF1, RIPK3, BAT2, and TLR6), mitogen-activated protein kinase (MAPK) signaling (MAP3K5, DUSP2, and CREB1), lymphocyte trafficking and migration (B3GNT3, SELPLG, and LSP1), and coagulation pathways (FGG and ITGB3) may be important in the etiology of NHL, and should be prioritized in replication studies.

No-reflow phenomenon after acute myocardial infarction is associated with reduced clot permeability and susceptibility to lysis

OBJECTIVE

We assessed the relationship between fibrin clot properties and the no-reflow phenomenon after primary coronary intervention (PCI).

METHODS AND RESULTS

Epicardial blood flow was assessed by TIMI scale and corrected TIMI frame count (cTFC), and perfusion by TIMI Myocardial Perfusion Grade (TMPG) after PCI during ST-segment elevation myocardial infarction (STEMI). Fibrin clot permeability (K(s)) and susceptibility to lysis in assays using exogenous thrombin (t(50%)) and without thrombin (t(TF)) were determined in 30 no-reflow patients (TIMI < or = 2) and in 31 controls (TIMI-3) after uneventful 6 to 14 months from PCI. Patients with TIMI < or = 2 had lower K(s) by 18% (P<0.0001) and prolonged fibrinolysis by 33% for t(50%) (P<0.0001) and by 45% for t(TF) (P<0.0001). cTFC was correlated with K(s) (r=-0.56, P<0.0001), t(50%) (r=0.49, P<0.001), and t(TF) (r=0.54, P<0.001). K(s) increased in a stepwise fashion with TIMI flow (P<0.0001) and TMPG (P<0.0001), whereas both fibrinolysis times decreased with TIMI flow (P<0.0001 for both) and TMPG (P<0.01 for both). Multiple regression models showed that only K(s) and fibrinogen were independent predictors of cTFC (P<0.05 for both), TIMI < or = 2 flow (P<0.05 for both) and TMPG-0/1 (P<0.05 for both).

CONCLUSIONS

Survivors of myocardial infarction with a history of the no-reflow after PCI are characterized with more compact fibrin network and its resistance to lysis.

Reduced clot permeability and susceptibility to lysis in patients with acute coronary syndrome: effects of inflammation and oxidative stress

BACKGROUND

Stable angina is associated with unfavorable fibrin structure/function. It is not known how acute coronary syndromes (ACS) affect fibrin architecture.

OBJECTIVE

We investigated fibrin clot properties and their determinants in ACS patients.

PATIENTS AND METHODS

Clot permeability, turbidity and fibrinolysis were assessed in 40 patients with ACS versus 40 controls with stable angina matched for age, sex, and risk factors.

RESULTS

Patients with ACS had lower clot permeability (p=0.001), faster fibrin polymerization (p=0.008), and prolonged fibrinolysis time (p<0.0001) than controls. C-reactive protein (CRP) and 8-epi-prostaglandin F(2alpha), a marker of oxidative stress, were the only independent predictors of clot permeability (R(2)=-0.74; p<0.0001 and R(2)=-0.65; p<0.0001, respectively) and fibrinolysis time in ACS patients (R(2)=0.60; p<0.0001 and R(2)=0.59; p=0.0002, respectively). In angina patients, fibrinogen and CRP predicted permeability (R(2)=-0.71; p<0.0001 and R(2)=-0.62; p<0.0001), and D-dimer predicted lysis time (R(2)=0.54; p=0.0005). In regression analysis models incorporating all patients, the only independent predictor of all clot variables was being an ACS patient (R(2) 0.51 to 0.85; p<0.001).

CONCLUSIONS

This first study of clot properties in patients during an ACS demonstrated that compared with stable angina patients, their clots are composed of dense networks that are more resistant to lysis and these features are correlated with raised CRP and oxidative stress.

Genetic polymorphisms associated with priapism in sickle cell disease

Priapism occurs in 30-45% of male patients with sickle cell disease (SCD), but the possible influence of genetic risk factors on the incidence of priapism is not well understood. We examined genetic polymorphisms in 199 unrelated, adult (>18 years), male patients with Hb SS and Hb Sbeta(0)-thalassaemia, 83 (42%) of whom reported a history of priapism. Candidate genes for association with priapism were identified based on their involvement in adhesion, coagulation, inflammation and cell signalling. Additionally, we examined genes involved in nitric oxide biology (NOS2, NOS3, SLC4A1), as well as polymorphisms in the klotho (KL) gene, which has previously been associated with priapism. Strong evidence of association was found for single nucleotide polymorphisms in transforming growth factor-beta receptor, type III (TGFBR3) (rs7526590; P = 0.00058), aquaporin (AQP1) (rs10244884; P = 0.00068), integrin alphav (ITGAV) (rs3768780; P = 0.00090), and the A1 subunit of coagulation factor XIII (F13A1) (hcv1860621; P = 0.00156). Associations with TGFBR3, AQP1, and ITGAV remained significant after adjusting for multiple testing, using the Benjamini-Hochberg procedure. Our data suggest that genes involved in the TGFbeta pathway, coagulation, cell adhesion and cell hydration pathways may be important in risk for priapism.

Plasma levels of fibrinogen and C-reactive protein are related to interleukin-6 gene −572C>G polymorphism in subjects with and without hypertension

Hypertension is an important risk factor for cardiovascular diseases. There is increasing evidence suggesting that inflammation is involved in the development of hypertension. Interleukin-6 (IL-6) is an important mediator of inflammatory response and the major regulator of hepatic production of acute phase proteins, such as fibrinogen and C-reactive protein (CRP), which have been associated with hypertension and cardiovascular diseases. Therefore, we studied the association of single nucleotide polymorphism (SNP) in the IL-6 gene (IL6) promoter with plasma levels of fibrinogen, CRP and hypertension. Five hundred and two Hong Kong Chinese subjects (282 normotensives and 220 hypertensives) were recruited. IL-6 gene promoter was examined for polymorphism and the study subjects were genotyped for any SNP identified. The IL6 -572C>G polymorphism (rs1800796) was found with a frequency of 0.23 for the minor G allele. Subjects with the -572G allele had significantly higher plasma fibrinogen (3.06+/-0.57 vs 2.83+/-0.60, P=0.002) and CRP (interquartile range 0.33-1.56 vs 0.12-0.93, P=0.003) levels than those without. The -572C>G polymorphism was found to be an independent predictor of fibrinogen and CRP levels after adjusting for confounding factors. Plasma concentrations of fibrinogen and CRP correlated with systolic blood pressure. However, the -572C/G genotype frequencies did not differ between hypertensive and normotensive subjects, and there was no association between -572C>G polymorphism and blood pressure. Our results provide evidence that there is a clear genetic influence of IL6 -572C>G polymorphism on plasma levels of fibrinogen and CRP, but this polymorphism does not lead to elevated blood pressure.

Fibrinogen Aα-Thr312Ala and factor XIII-A Val34Leu polymorphisms in idiopathic venous thromboembolism

INTRODUCTION

Fibrinogen Aalpha-Thr312Ala and Factor XIII Val34Leu polymorphisms have been shown to modify fibrin clot structure and function. However, clinical studies have yielded conflicting results on their possible association with venous thromboembolism (VTE).

METHODS

We studied the association between these two polymorphisms and VTE in a hospital-based case-control study. We also assessed whether an independent or interactive association exists between Aalpha-fibrinogen Thr312Ala and FXIII Val34Leu polymorphisms and VTE. Fibrinogen Aalpha-Thr312Ala and FXIII Val34Leu polymorphisms were determined after PCR and restriction endonuclease digestion in 286 patients with idiopathic VTE and 286 age- and gender-matched controls. Results were analysed using a conditional logistic regression model for matched series.

RESULTS

The Fg-Aalpha 312Ala allele was associated with higher risk of VTE (OR 1.5; 95% CI: 1.1 to 2.2, p=0.01) while the FXIII 34Leu allele appeared protective (OR 0.7; 95% CI: 0.6 to 0.9, p=0.02). Both alleles demonstrated an independent association with idiopathic VTE after adjustment for Factor V Leiden and G20210A prothrombin polymorphisms. There was no interaction between the fibrinogen Aalpha-Thr312Ala and FXIII Val34Leu polymorphisms for the risk of VTE.

CONCLUSION

In this case-control study, the fibrinogen Fg-Aalpha 312Ala allele was associated with an increased risk of VTE. The FXIII 34Leu allele was also significantly associated with a lower risk of VTE without any interaction between the two polymorphisms studied.

Altered Fibrin Architecture Is Associated With Hypofibrinolysis and Premature Coronary Atherothrombosis

OBJECTIVE

Hypofibrinolysis promotes atherosclerosis progression and recurrent ischemic events in premature coronary artery disease. We investigated the role of fibrin physical properties in this particular setting.

METHODS AND RESULTS

Biomarkers of recurrent thrombosis and premature coronary artery disease (CAD) were measured in 33 young post-myocardial infarction patients with angiographic-proven CAD and in 33 healthy volunteers matched for age and sex. Ex vivo plasma fibrin physical properties were assessed by measuring fibrin rigidity and fibrin morphological properties using a torsion pendulum and optical confocal microscopy. The fibrinolysis rate was derived from continuous monitoring of the viscoelastic properties after addition of lytic enzymes. Young CAD patients had a significant increase in plasma concentration of fibrinogen, von Willebrand factor, plasminogen activator inhibitor type 1, and lipoprotein(a) as compared with controls (P<0.05). Fibrin of young CAD patients was stiffer (P=0.002), made of numerous (P=0.002) and shorter fibers (P=0.04), and lysed at a slower rate than that of controls (P=0.03). Fibrin stiffness was an independent predictor for both premature CAD and hypofibrinolysis.

CONCLUSIONS

This first detailed study of clot properties in such a group of patients demonstrated that abnormal plasma fibrin architecture is an important feature of both premature CAD and fibrinolysis rate. The determinants of this particular phenotype warrant further investigation.

A classification of the fibrin network structures formed from the hereditary dysfibrinogens

OBJECTIVE

The main objective was to study the relationships of the molecular defects in 38 dysfibrinogens with their fibrin networks.

METHODS AND RESULTS

Scanning electron microscopic analyses revealed that all the fibrins formed under the same conditions had networks composed of either normal thickness fibers or thin fibers, accompanied by a variety of alterations in the network structure and characteristics. We classified these fibrin networks into five classes, designated normal, less-ordered, porous A, porous B and lace-like networks. The dysfibrinogens with defects in fibrinopeptide A release or the E:D binding sites formed normal or less-ordered networks, while those with defects in the D:D association formed porous A networks composed of many tapered terminating fibers, despite having fibers of normal width, and containing many pores or spaces. The porous B and lace-like networks were composed of highly branched thin fibers because of defects in the lateral association among protofibrils, and the major difference between them was the porosity of the porous B networks. All the porous B networks were easily damaged by mechanical stress, whereas the lace-like networks retained high resistance to such stress, indicating that the network strength was not dependent on the fiber width, but on the porosity that led to fragility of the network.

CONCLUSION

Impairment of the D:D association is the major disturbing factor that leads to the formation of porous fibrin networks. The porosity may be introduced by severe impairment of the D:D association, as well as the lateral association, as has often been observed by extra glycosylation or defects in Ca2+ binding.