Levels of Lipoprotein (a) in patients with coronary artery disease with and without inflammatory rheumatic disease: a cross-sectional study

OBJECTIVES

Patients with various inflammatory rheumatic diseases (IRDs) have increased risk of atherothrombotic disease. Lipoprotein (a) (Lp(a)) is a risk factor for atherosclerosis but its role in IRD with accompanying coronary artery disease (CAD) is still unclear. We aimed to examine if serum Lp(a) levels differed between CAD patients with and without accompanying IRD.

DESIGN

A cross-sectional observational, patient-based cohort study.

SETTING

Referred centre for coronary artery bypass grafting in the South Eastern part of Norway.

PARTICIPANTS

67 CAD patients with IRD (CAD/IRD) and 52 CAD patients without IRD (CAD/non-IRD). All patients were Caucasians, aged >18 years, without any clinically significant infection or malignancy.

METHODS

Lp(a) levels in serum were analysed by particle enhanced immunoturbidimetric assay, and Lp(a) levels were related to clinical and biochemical characteristics of the patient population.

RESULTS

We found no differences in serum levels of Lp(a) between CAD patients with and without IRD. In general, we found that Lp(a) correlated poorly with clinical and biochemical parameters including C reactive protein with the same pattern in the CAD/non-IRD and CAD/IRD groups.

CONCLUSIONS

Our data do not support a link between inflammation and Lp(a) levels in CAD and in general Lp(a) levels were not correlated with other risk factors for cardiovascular disease.

Stimulated Glanzmann’s Thrombasthenia Platelets Produce Microvesicles

The mechanism of formation of platelet-derived microvesicles remains controversial.

The aim of the present work was to study the formation of microvesicles in view of a possible involvement of the GPIIb-IIIa complex, and of exposure of negatively charged phospholipids as procoagulant material on the platelet surface. This was studied in blood from three Glanzmann’s thrombasthenia patients lacking GPIIb-IIIa and healthy blood donors. MAb FN52 against CD9 which activates the complement system and produces microvesicles due to a membrane permeabilization, ADP (9.37 μM), and the thrombin receptor agonist peptide SFLLRN (100 μM) that activates platelets via G-proteins were used as inducers. In a series of experiments platelets were also preincubated with PGE1 (20 μM). The number of liberated microvesicles, as per cent of the total number of particles (including platelets), was measured using flow cytometry with FITC conjugated antibodies against GPIIIa or GPIb. Activation of GPIIb-IIIa was detected as binding of PAC-1, and exposure of aminophospholipids as binding of annexin V. With normal donors, activation of the complement system induced a reversible PAC-1 binding during shape change. A massive binding of annexin V was seen during shape change as an irreversible process, as well as formation of large numbers of microvesicles (60.6 ±2.7%) which continued after reversal of the PAC-1 binding. Preincubation with PGE1 did not prevent binding of annexin V, nor formation of microvesicles (49.5 ± 2.7%), but abolished shape change and PAC-1 binding after complement activation. Thrombasthenic platelets behaved like normal platelets after activation of complement except for lack of PAC-1 binding (also with regard to the effect of PGE1 and microvesicle formation). Stimulation of normal platelets with 100 μM SFLLRN gave 16.3 ± 1.2% microvesicles, and strong PAC-1 and annexin V binding. After preincubation with PGE1 neither PAC-1 nor annexin V binding, nor any significant amount of microvesicles could be detected. SFLLRN activation of the thrombasthenic platelets produced a small but significant number of microvesicles (6.4 ± 0.8%). Incubation of thrombasthenic platelets with SFLLRN after preincubation with PGE1, gave results identical to those of normal platelets. ADP activation of normal platelets gave PAC-1 binding, but no significant annexin V labelling, nor production of microvesicles. Thus, different inducers of the shedding of microvesicles seem to act by different mechanisms. For all inducers there was a strong correlation between the exposure of procoagulant surface and formation of microvesicles, suggesting that the mechanism of microvesicle formation is linked to the exposure of aminophospholipids. The results also show that the GPIIb-IIIa complex is not required for formation of microvesicles after activation of the complement system, but seems to be of importance, but not absolutely required, after stimulation with SFLLRN.

Aggregated, Conformationally Changed Fibrinogen Exposes the Stimulating Sites for t-PA-Catalysed Plasminogen Activation

The present paper shows that conformationally changed fibrinogen can expose the sites Aα-(148-160) and γ-(312-324) involved in stimulation of the tissue-type plasminogen activator (t-PA)-catalysed plasminogen activation. The exposure of the stimulating sites was determined by ELISA using mABs directed to these sites, and was shown to coincide with stimulation of t-PA-catalysed plasminogen activation as assessed in an assay using a chromogenic substrate for plasmin. Gel permeation chromatography of fibrinogen conformationally changed by heat (46.5° C for 25 min) demonstrated the presence of both aggregated and monomeric fibrinogen. The aggregated fibrinogen, but not the monomeric fibrinogen, had exposed the epitopes Aα-(148-160) and γ-(312-324) involved in t-PA-stimulation. Fibrinogen subjected to heat in the presence of 3 mM of the tetrapeptide GPRP neither aggregates nor exposes the rate-enhancing sites. Thus, aggregation and exposure of t-PA-stimulating sites in fibrinogen seem to be related phenomena, and it is tempting to believe that the exposure of stimulating sites is a consequence of the conformational changes that occur during aggregation, or self-association. Fibrin monomers kept in a monomeric state by a final GPRP concentration of 3 mM do not expose the epitopes Aα-(148-160) and γ-(312-324) involved in t-PA-stimulation, whereas dilution of GPRP to a concentration that is no longer anti-polymerizing, results in exposure of these sites. Consequently, the exposure of t-PA-stimulating sites in fibrin as well is due to the conformational changes that occur during selfassociation.

Thrombus-Related Uptake and Vascular Clearance of 131 I-Fibrin des-AABB as Compared to 125 I-Fibrinogen in Patients with Established Venous Thrombosis

Thrombus-related uptake of 131 I-fibrin des-AABB has been compared to that of 125 I-fibrinogen in 13 patients with established venous thrombosis. Both tracers originated from a common pool of β-alanine precipitated fibrinogen. Scan-recordings were performed as a radiofibrin(ogen) uptake test. Uptake characteristics of des-AABB fibrin were similar to those of fibrinogen, when measured as percentage of concomitant radioactivity over the heart. Due to its longer circulation time, fibrinogen was superior to fibrin des-AABB for the detection of venous thrombi.

Circulating des-AABB fibrin was cleared biphasically, with an initial rapid decline followed by a gradual exponential decrease. Mean half-lives were 5.5 ± SD 3.5 hr and 10 ± SD 3.5 hr, respectively. The elimination rates were uninfluenced by thrombus activity, as judged by the fibrin(ogen) uptake test. Metabolic half-life of fibrinogen in the total material was 62 ± SD 19 hr. Dissociation of fibrinogen and soluble des-AABB fibrin clearance rates was evident, describing their own, independent elimination patterns, probably reflecting different clearing mechanisms.

Visualization of von Willebrand Factor Multimers by Enzyme-Conjugated Secondary Antibodies

A method for visualization of the multimeric forms of von Willebrand Factor (vWF) in plasma and platelets is described. The method is based upon: 1) Separation of the vWF multimers by SDS-agarose electrophoresis, 2) Subsequent blotting of the vWF multimers onto nitrocellulose, 3) Immunolocalization and visualization of the vWF pattern by the sequential incubation of the blot with a) primary vWF antiserum, b) peroxidase- or beta-galactosidase-conjugated secondary antibodies and a relevant chromogenic substrate.

Binding of Various Thrombin Fractions to Fibrin and the Influence of AT-III on Their Adsorption

Human thrombin with high affinity for fibrin was obtained by subjecting purified thrombin to affinity chromatography on Sepharose insolubilized fibrin monomers, after addition of a radioiodinated subsample of thrombin, molar ratio 1:600. As judged by radioprofiling of the electrophoretic distribution of high-affinity thrombin on 10 per cent polyacrylamide gel containing urea/SDS, the preparation consisted of 70 per cent a-thrombin, 28 per cent β-thrombin and only 2 per cent γ-thrombin. Although a-thrombin was bound more strongly to insolubilized fibrin monomers than the other subfractions, complete separation of the individual components could not be achieved.

High-affinity thrombin was employed for studies on thrombin adsorption to polymerized fibrin, assuming equal behaviour of labelled and unlabelled thrombin.

o avoid passive entrapment of thrombin within the fibrin meshwork at physiological pH, ionic strength and calcium concentration, the optimal fibrinogen concentration was found to be 2.94 umol/1. During such conditions, adsorption of thrombin to polymerized fibrin did not exceed 65 per cent of added thrombin, despite an increasing availability of fibrin-related thrombin binding domains obtained by reducing the thrombin concentration.

Adsorption of thrombin to polymerized fibrin increased by 25 per cent when the ionic strength was reduced to 0.05 mol/1. These findings suggest the presence of thrombin subfractions with different affinities for polymerized fibrin.

Aggregates of high-affinity thrombin formed during its preparation by affinity chromatography, but were prevented by adding polyethylene glycol (m.w. 6,000, final conc. 6.6 g/1). Such aggregates were not inactivated by AT-III, but could still adsorb to polymerized fibrin.

In its monomeric form fibrin-adsorbed thrombin was inactivated by AT-III and could then be extruded from the clot upon syneresis and retraction, but a small fraction remained attached to polymerized fibrin, exhibiting minor amidolytic activity.

A New Dysfibrinogenemia: Fibrinogen Oslo IV

A family with dysfibrinogenemia is described. The abnormal fibrinogen occurred in three successive generations indicating a dominant hereditary pattern. Thrombin and reptilase times were about twice the normal value. This was shown to be caused by a polymerization defect, fibrinopeptide release being normal. Platelet aggregation was undisturbed, indicating normal platelet-fibrinogen binding. The bleeding time was normal and there was no bleeding tendency. However, an obscure recurrent pulmonary ailment may, or may not, be related to the dysfibrinogenemia. The abnormal fibrinogen was tentatively termed Oslo IV.

Demonstration of Platelet-Derived Microvesicles in Blood from Patients with Activated Coagulation and Fibrinolysis Using a Filtration Technique and Western Blotting

Platelet vesiculation in vitro is correlated to platelet activation. It was therefore considered of interest to see if microvesicles (MV) are present in blood in clinical situations associated with platelet activation in vivo. Patients with both activated coagulation and fibrinolysis, implying that thrombin has been generated, suit such a purpose. Thus, the aim of this study was to investigate whether microvesicles could be detected in patients with activated coagulation and fibrinolysis, as diagnosed by the presence of soluble fibrin (positive ethanol gelation tests) and positive tests for fibrin degradation products (FDP). Platelet-rich plasma was prepared from citrated blood from patients (n = 22) and healthy controls (n = 32) matched as to age and sex. The intact platelets were removed from plasma by centrifugation. Any MV present were isolated from the platelet-free plasma by a filtration procedure, washed, solubilized in Triton X-100 and subjected to SDS-PAGE with Western blotting using a MAb against GPIIba as an indicator of the presence of microvesicles. All of the 22 patients showed the presence of microvesicles detectable by the content of GPIIba, whereas this could be observed in only 4 out of the 32 normal controls and then in small or trace amounts only. The presence of microvesicles among cell-derived material in the plasma of two of the patients was also confirmed by electron microscopy. To the best of our knowledge this is the first report on the presence of microvesicles in plasma from patients with both activated coagulation and fibrinolysis. Thus, the isolation of the microvesicles by the filtration technique allowed studies of the chemical composition of the microvesicles, and demonstrated the presence of microvesicles in situations where platelets are expected to have been activated in vivo and a tendency to thrombosis exists.

Comparison of Three D-Dimer Assays for the Diagnosis of DVT: ELISA, Latex and an Immunofiltration Assay (NycoCard D-Dimer)

Ninety-two consecutive patients referred for suspicion of deep venous thrombosis (DVT) were analyzed for D-dimer using ELISA, latex test, and a new immunofiltration method (NycoCard D-Dimer). Contrast venography verified the diagnosis in 40, and excluded the diagnosis in 52 patients. The sensitivity, negative predictive values, specificity and positive predictive values were, for ELISA 98%, 95%, 38% and 54, for NycoCard D-Dimer 100%, 100%, 42% and 57% and for the latex test 73%, 78%, 75%, and 69%, respectively. Sensitivity and specificity were inversely related with increasing pathological cutoff value. Comparison of test results by concentration category revealed a good agreement between ELISA and NycoCard D-Dimer, but to less extent between latex and the two other tests. It is concluded that NycoCard D-Dimer and D-dimer ELISA are well-suited as exclusion tests for DVT. A plasma sample is tested with NycoCard D-Dimer in less than 2 min. Thus, this test combines advantageous analytical properties comparable to the ELISA-test, with rapidity and simplicity comparable to the latex test.

The Difference Between Platelet and Plasma FXIII Used to Study the Mechanism of Platelet Microvesicle Formation

The formation of microvesicles from platelets was induced either by activation of the complement system by a monoclonal antibody to CD9, or by incubation of platelets with the calcium ionophore A23187. A filter technique to isolate the microvesicles without plasma contamination is described. The microvesicles contained FXIIIa2 from the platelet cytoplasm which shows that these particles contain significant amounts of intracellular material. This was shown by the use of crossed immunoelectrophoresis with rabbit antibodies to total human platelet proteins in the second dimension gel and polyclonal antibodies against the a- and b-subunit of FXIII in the intermediate gel. The FXIIIa2 in the microvesicle was found to be functional as an enzyme. To prove this, it was shown that FXIII in its immunoprecipitate arc could catalyze the incorporation of monodansylcadaverine into casein as identified by fluorescence of this arc in ultraviolet light. The observation that the plasma form of FXIII (FXIIIa2b2) was absent from the microvesicles collected by the filtration technique, whereas it was present in platelet fragments obtained by mechanical disruption by ultrasonication, indicates that the activation-dependent microvesicles are formed by a true budding process with the inclusion of intracellular, but not extracellular material.

Cross-Linked αsγt-Chain Hybrids in Plasma Clots Studied by 1D- and 2D Electrophoresis and Western Blotting

Fibrinogen and fibrin related chains in reduced human plasma as well as the bonds interlinking partially cross-linked fibrin from plasma clots have been studied by means of 1D- and 2D electrophoresis and Western blotting. Immunovisualization of reduced plasma or partially cross-linked fibrin with monoclonal antibodies specific for the α-chains or the γ-chains have shown that several bands represent material belonging to both chains. In order to decide whether these bands constitute αγ-chain hybrids or superimposed α- and γ-chain dimers, the cross-linked material was separated according to both isoelectric point (pI) and molecular weight (MW) using Pharmacia’s Multiphor II system. Western blotting of the second dimension gels revealed that partially cross-linked fibrin contains αsγt-chain hybrids and γ- polymers, in addition to the well-known γ-dimers and α-polymers. The main αsγt-chain hybrid has a pI between that of the α- and the γ-chains, a MW of about 200 kDa and contains Aα-chains with intact fibrinopeptide A (FPA). It was also observed that soluble fibrinogen/fibrin complexes as well as partially cross-linked fibrin contain degraded α-dimers with MWs close to the γ-dimers. These findings demonstrate that factor XIII-catalyzed cross-linking of fibrin is a more complex phenomenon than earlier recognized.

Identification of Platelet Antigens by Monoclonal Antibodies Using Crossed Immunoelectrophoresis with Immunoblotting of the Monoclonal Antibody

A method is described for the identification of antigens by monoclonal antibodies. This is applicable whenever precipitating antibodies to the same antigens from a different species are available. The method is based upon: 1) Separation and immunoprécipitation of cellular proteins with a polyspecific antiserum in crossed immunoelectrophoresis in the presence of the non-denaturing detergent Triton X-100 and the monoclonal antibody. 2) Coprecipitation of the monoclonal antibody with its antigen. 3) Subsequent passive transfer of the monoclonal antibody in the antibody-antigen complex onto a nitrocellulose membrane. 4) Visualization of the blotted antibody using an enzyme-linked secondary antibody and a chromogenic substrate. 5) Identification of the corresponding antigen by comparisons to the immunoprecipitate pattern of the original immunoplate. To test this method we have analyzed the detection of the antigens recognized by six previously described monoclonal antibodies against platelet membrane proteins and von Willebrand factor. Specific immunoblots were obtained in each case using small amounts of monoclonal antibodies. Thus, the technique provides an alternative when epitopes are denatured by SDS, and avoids the use of radioactively labelled monoclonal antibodies.

Persistently Elevated Levels of von Willebrand Factor Antigen in HIV Infection

Levels of circulating von Willebrand factor (vWf) antigen are thought to reflect endothelial involvement in various disorders. In the present study we found markedly elevated plasma levels of vWf in HIV-infected patients demonstrated on both cross-sectional and longitudinal testing. Notably, we found that a persistent rise in vWf antigen was associated with progression of HIV-related disease. This elevation of vWf antigen represented functionally normal vWf as evaluated by plasma FVIII, ristocetin cofactor assay and vWf multimer analyses. While HIV-infected patients showed enhanced platelet activation, platelets did not contribute substantially to the increased vWf levels. The high vWf levels were significantly correlated with high viral load, and during HAART, the pronounced decline in HIV RNA levels was accompanied by a corresponding decrease in vWf. The persistent elevation of functionally normal vWf during HIV infection, most probably reflecting a persistent endothelial cell activation, may have an important role in the pathogenesis of HIV infection.

Is a Prolonged Bleeding Time Associated with an Increased Risk of Hemorrhage after Liver Biopsy?

Bleeding time determination is not advised as a general preoperative hemostasis screening test, but it might be useful in some patient groups. Patients referred for liver biopsy frequently have coagulation disturbances and are at risk of hemorrhage. In this prospective study 219 liver biopsies were carried out regardless of a prolonged bleeding time, but with minimum requirements for hemoglobin concentration, platelet count, and tests of the internal and external coagulation pathways. The bleeding time was prolonged in the case of 48 (22%) of the biopsies. Significant bleeding as defined by a hemoglobin decrease of ≥2.0 g/dl occurred in nine patients. Three of these patients were bone marrow transplanted. Patients with a prolonged bleeding time carried a five times higher risk of bleeding (odds ratio = 5.0; confidence interval = 1.1-21.8; p = 0.019). We conclude that the bleeding time may give additional information on the risk of bleeding in some patient groups undergoing liver biopsy.

Protein C Deficiency caused by Homozygosity for a Novel PROC D180G Mutation – in vitro Expression and Structural Analysis of the Mutation

Homozygosity for a novel D180G mutation in the protease domain of protein C, associated with plasma protein C activity and antigen levels of 8% of normal was identified in a thrombosis prone family. Transient expression of protein C in HK-293 cells and analysis of protein C antigen in culture media and cell lysates showed that the secretion of mutant protein as compared with wild-type protein was reduced by 79% while the intracellular contents were similar. Computer analysis of the X-ray structure of activated protein C and of a theoretical model of the zymogen predicts that the mutation destabilises the molecule locally. Our results are compatible with a relatively unstable mutant molecule that could be trapped inside the cell and degraded. However, if secreted the mutant molecule could have a relatively normal catalytic activity and structure consistent with the plasma levels of protein C activity and the late onset of thrombosis.

Microvesicles Bind Soluble Fibrinogen, Adhere to Immobilized Fibrinogen and Coaggregate with Platelets

In the present study we have investigated whether platelet derived microvesicles can bind soluble fibrinogen, bind to immobilized fibrinogen, and coaggregate with platelets. Flow cytometry was used for studies on binding of soluble fibrinogen and coaggregation, whereas ELISA wells were used to study binding of microvesicles to immobilized fibrinogen. Biotinylated microvesicles produced by stimulation with A23187, thrombin or SFLLRN of platelets which had been surface-labelled with biotin, were used both for the coaggregation experiments and for the binding studies with immobilized fibrinogen. Unlabelled microvesicles and biotinylated fibrinogen were employed when studying binding of soluble fibrinogen to the microvesicles. For the flow cytometry, the biotinylated proteins were reacted with avidin or streptavidin which was PE-conjugated, whereas the same substances were conjugated with alkaline phosphatase for the ELISA studies. The microvesicles formed after stimulation of platelets by SFLLRN or A23187 clearly bound the soluble, biotinylated fibrinogen. Moreover, isolated biotinylated microvesicles added to washed platelets prior to activation, were associated to the microaggregates that formed after stimulation. A significant binding of biotinylated microvesicles to immobilized fibrinogen could also be detected. The binding of micro-vesicles to soluble and immobilized fibrinogen and association to platelets was clearly specific and at least partly dependent on the GPIIb-IIIa complex, as all of these phenomena could be prevented or reduced by addition of the c7E3 Fab which blocks the activated form of this receptor complex. From these in vitro results it is clear that microvesicles can bind to immobilized fibrinogen, bind soluble fibrinogen and are able to coaggregate with platelets. It may be speculated that these results also reflect a haemostatic role of microvesicles in vivo.

Increased Potency and Decreased Elimination of Lamifiban, a GPIIb-IIIa Antagonist, in Patients with Severe Renal Dysfunction

Activation of the platelet membrane receptor glycoprotein (GP) IIb-IIIa is essential for thrombus formation. The novel nonpeptide GPIIb-IIIa antagonist, lamifiban, represents a promising approach for antiplatelet therapy in patients with cardiovascular disease. Since renal impairment frequently occurs in these patients, we designed a phase I study to assess the tolerability, pharmacodynamics and pharmacokinetics of lamifiban in patients with renal impairment. Four healthy volunteers (Group 1) with creatinine clearance (CLCR) >75 ml/min, eight patients (Group 2) with mild to moderately impaired renal function (CLCR 30-74 ml/min) and eight patients (Group 3) with severe renal impairment (CLCR 10-29 ml/min) were studied. They received stepwise increased doses of lamifiban intravenously (IV). There was a linear relationship between the systemic clearance of the drug and renal function (R2 = 0.86). The mean plasma concentration required for half-maximal inhibition of thrombin-receptor agonist peptide (TRAP) induced platelet aggregation (EC50) ex vivo was 21, 28 and 11 ng/ml in Groups 1, 2 and 3. The patients in Group 3 were sensitized to the anti-platelet effect allowing an 18-fold dosage reduction without compromising the pharmacodynamics. In conclusion, the decreased clearance of lamifiban may act in concert with increased potency of the drug in patients with severe renal impairment, and the drug dosage should be reduced accordingly.

Effects of two differently heparin-coated extracorporeal circuits on markers for brain and myocardial dysfunction

Objective: The two most commonly used heparin-coated systems for cardiopulmonary bypass (CPB) are the Carmeda Bio-Active Surface (CBAS) (Medtronic, Minneapolis, MN, USA) and the Duraflo II coating (Baxter Healthcare, Irvine, CA, USA). The two surfaces are technically unequal and previous experimental studies have demonstrated disparities in effects on the immune system and blood cells. However, little is known concerning the influence of the two surfaces on markers for brain and myocardial dysfunction.

Methods: Forty patients undergoing elective, primary coronary bypass grafting with CPB were prospectively randomized to either the CBAS system or the Duraflo II circuit. During and after CPB, biological markers for brain dysfunction and myocardial injury were analysed.

Results: Both markers for brain dysfunction S-100B and neuron-specific enolase (NSE) increased significantly during CPB ( p =0.01). The elevation during bypass correlated significantly with the duration of CPB ( r = 0.39 and r= 0.38, respectively, both p< 0.02). NSE was somewhat more elevated in the Duraflo II group at the end of CPB ( p =0.01) and 5 h after CPB ( p= 0.02); for S-100B, there were no intergroup differences. Also, the markers related to myocardial injury, myoglobin and creatine kinase (CK-MB) mass increased during CPB ( p= 0.01), while elevation of troponin-I occurred 5 h after CPB ( p= 0.01). There were no statistically significant intergroup differences. No significant correlation was seen between the release of cardiac markers and the duration of CPB. The clinical course was similar in both groups.

Conclusions: Except for a slightly higher elevation of NSE at the end of CPB and 5 h after CPB in the Duraflo II group, there were no significant differences between the CBAS group and the Duraflo II group concerning markers for brain and myocardial dysfunction.

Off-pump cardiac surgery abolishes complement activation

Background. This prospective randomized study compared the inflammatory response in patients undergoing elective on-pump and off-pump coronary artery bypass grafting. Patients and methods. Forty-four patients undergoing elective coronary artery bypass grafting were recruited with 22 patients randomized to on-pump heart surgery and 22 patients to off-pump coronary bypass surgery. Plasma levels of C3bc, the terminal SC5b-9 complement complex, myeloperoxidase, β -thromboglobulin and prothrombin fragment F1 + 2 were measured before the operation, intraoperatively, at termination of the operation, and two hours post-operatively. Results. Complement was markedly activated in the on-pump group as indicated by a significant increase in C3bc and SC5b-9 (p < 0.001 for both), whereas no complement activation was seen in the off-pump group (p = 0.001 between the groups). In contrast, both groups showed significant activation of neutrophils, platelets and coagulation, as indicated by an early increase in myeloperoxidase and a post-operative increase in β-thromboglobulin and F1 + 2, respectively. Notably, there were no inter-group differences with regard to neutrophil and platelet activation, whereas coagulation activation was more pronounced in the off-pump group (p < 0.01). Conclusions. Off-pump surgery completely eliminated the heart-lung machine-induced complement activation. Neutrophils and platelets were equally activated in both groups, whereas coagulation was enhanced post-operatively in the off-pump group. Perfusion (2007) 22, 251—256.

The ethanol gelation test and thrombosis

Intravascular fibrin formation takes place during thrombus formation or by activation of coagulation in circulating blood. Incorporation of fibrin in thrombi may be detected by usine 125I-labelled fibrinogen. Soluble fibrin may be present during thrombophilic states or during thromboembolic complications and diseminated intravascular coagulation (DIC) and may be detected and quantitated by various techniques such as N-terminal amino acid analysi, chromatographic procedures and so-called paracoagulation test, using ethanol or protamine sulfate. Finally, transformation of fibrinogen to fibrin may be indirectly assayed by quantitation of fibrinopeptide A released, by immunological technique. For routine purposes and especially in emergency situation, rapid and simple tests are required. In these circumstances, only the paracoagulation tests are at hand. Below, the present situation with regard to the ethanol gelation test (EGT) is outlined.

Glycoprotein IIb-IIIa on platelet-derived microparticles, and microparticle structures studied by electron microscopy, confocal laser microscopy and crossed radio-immunoelectrophoresis

Shedding of microparticles from the platelet surface is usually associated with exposure of platelet procoagulant activity. Platelet-derived microparticles have been detected in blood in various disease states. In vitro, platelet stimulation with a number of different agonists results in formation of microparticles. In the present study, microparticles induced by platelet stimulation by calcium ionophore or by membrane incorporation of the terminal complement complex C5b-9 were studied using electron microscopy, confocal laser microscopy, flow cytometry and radio-immunoelectrophoresis. When studied by electron microscopy, microparticle morphology was found to be dependent upon the induction method. Platelet stimulation with the calcium ionophore resulted in smaller, more homogeneous and electron dense microparticles than those induced by insertion of the terminal complement complex. With flow cytometry and confocal laser immunofluorescence microscopy, microparticle GPIIb-IIIa was demonstrated using a FITC-conjugated antibody to GPIIIa. Surface-bound GPIIb-IIIa was demonstrated on the microparticles by immunoelectron microscopy. Crossed immunoelectrophoresis of detergent-solubilized microparticles visualized a very prominent GPIIb-IIIa immunoprecipitate arc, and binding of [(125)1]fibrinogen to microparticle GPIIb-IIIa was demonstrated by radio-immunoelectrophoresis. This suggests that the activated GPIIb-IIIa complex is preserved intact during the shedding of microparticles from the platelet surface.

Increased YKL-40 expression in patients with carotid atherosclerosis

OBJECTIVE

We hypothesized a role for the inflammatory protein YKL-40 in atherogenesis and plaque destabilization based on its role in macrophage activation, tissue remodeling, and angiogenesis.

METHODS

Serum YKL-40 levels were measured by enzyme immunoassay in 89 patients with carotid atherosclerosis and 20 healthy controls. Carotid expression of YKL-40 was examined by real time RT-PCR in 57 of the patients. Regulation and effect of YKL-40 were examined in THP-1 monocytes.

RESULTS

Our main findings were: (1) serum YKL-40 levels were significantly elevated in patients with carotid atherosclerosis, with particularly high levels in those with symptomatic disease; (2) patients with recent ischemic symptoms (within 2 months) had higher YKL-40 mRNA levels in carotid plaque than other patients; (3) in vitro, the beta-adrenergic receptor agonist isoproterenol, toll-like receptor (TLR) 2 and TLR4 agonists, and in particular releasate from activated platelets significantly increased the expression of YKL-40 in THP-1 monocytes and (4) in vitro, YKL-40 increased matrix metalloproteinase-9 expression and activity in THP-1 monocytes, involving activation of p38 mitogen-activated protein kinase.

CONCLUSIONS

Our findings suggest that YKL-40 might be a marker of plaque instability, potentially reflecting macrophage activation and matrix degradation within the atherosclerotic lesion.

Variability in aggregometry response before and after initiation of clopidogrel therapy

BACKGROUND

Evaluation of clopidogrel therapy by in vitro methods has limitations which may be of clinical importance. We wanted to explore the variability in aggregometry response in aspirin sensitive patients before and after initiation of clopidogrel therapy.

METHODS

ADP 9.37 microM, AA 1.2mM and TRAP 25 mM stimulated light transmissions aggregometry (LTA) were performed twice before (Exams 1 and 2; 3 weeks apart)-and within one year after-initiation of clopidogrel therapy (Exam 3) in 79 patients treated with PCI. Repeated ADP aggregometry was also performed in 16 healthy volunteers in order to estimate LTA measurement error.

RESULT

Inter-individual differences in ADP aggregation e.g. at Exam 1 were substantial (range 17-77%, SD 15.8%). Intra-individual changes between Exams 1 and 2 were significant (-27 to +36%, SD 14.6%, p<0.05). Inter-individual differences at Exam 3 (on clopidogrel treatment) were larger than expected from Exams 1 and 2 (p<0.01). AA aggregation was the same before and during clopidogrel treatment. In controls, inter-individual differences were smaller at ADP 10 than at ADP 5 microM.

CONCLUSIONS

Inter-individual differences in ADP aggregation were significant both before and during clopidogrel therapy, and there were significant intra-individual variations over time. Therefore, prediction of aggregometry response before or during clopidogrel therapy based on single tests may be unreliable. Inter-individual differences in healthy controls are smaller at high concentrations of ADP, and comparisons of aggregometry response should be performed with caution unless ADP concentrations are standardized.

Results from clinical trials on ST‐elevation myocardial infarction in a historic perspective with some pathophysiological aspects

OBJECTIVE

Since the publication of the large trials on streptokinase and aspirin improving mortality related to an acute ST-elevation myocardial infarction (STEMI) there has been numerous studies on improving treatment results with new fibrinolytics, adjuvant heparin therapy and primary percutaneous intervention (PCI). The aim of the present overview is, in a historic perspective, to link some of the pathophysiology of mechanisms related to plaque rupture and following thrombosis to the effects of drug combinations and PCI observed in major clinical trials conducted in patients with STEMI.

DESIGN

The overview comprises short analyses of the initial streptokinase trials (GISSI-1 and ISIS-2), the comparisons between streptokinase and tissue plasminogen activator (rt-PA) and the role of adjuvant heparin treatment (GISSI-2, ISIS-3, GUSTO I). Also included is the comparison between the new bolus-teplases and traditional, accelerated infusion of rt-PA (GUSTO III and ASSENT-2) and between unfractionated heparin (UFH) and low molecular weight heparin (LWMH) given in addition to tenecteplase (ASSENT-3). The pathophysiology of the antiplatelet and antithrombin effects is described, in order to elucidate the treatment differences observed in the trials. In addition, the role of primary PCI is discussed in view of the results in a recent meta-analysis of controlled comparisons with fibrinolytic therapy.

RESULTS

Based upon these trials it seems that the optimal thrombolytic treatment is a combination of a bolus-teplase (tenecteplae) and LMWH given on top of aspirin. Primary PCI may be the most optimal treatment, provided given early following STEMI (<1 h), but whether PCI is the best alternative for all patients with STEMI is still a matter of debate.

CONCLUSION

During the last 15 years the optimal antithrombotic treatment of STEMI has developed from a combination of streptokinase and aspirin to the new bolus-teplases combined with LMWH and aspirin. The use of primary PCI may be a better alternative than fibrinolytic therapy, but such a statement needs confirmation in a large comparison between PCI and a quick infusion of modern fibrinolytic agents.

Children with acute lymphoblastic leukaemia have high plasma levels of total homocysteine at time of diagnosis

OBJECTIVE

Cancer can induce venous thromboembolic complications for various reasons. As part of a greater study, acquired and congenital prothrombotic risk factors were investigated in children with leukaemia or non-Hodgkin's lymphoma and compared with similar investigations in children with congenital heart defects.

MATERIAL AND METHODS

Blood samples were taken from 60 children with newly diagnosed leukaemia or lymphoma and 133 children with congenital heart defects in the course of a scheduled cardiac catheterization. When children with cancer were in remission, analyses of acquired prothrombotic risk factors were repeated. Children with cancer were observed for symptoms of thromboembolism throughout their treatment period.

RESULTS

Total homocysteine levels were significantly raised in children with cancer (median value 10.0 micromol/L) as compared with the levels in children with congenital heart diseases (5.0 micromol/L) (p<0.001), while children with acute lymphoblastic leukaemia had the highest values. The median level of lipoprotein(a) was slightly increased in children with newly diagnosed leukaemia or lymphoma (105 mg/L versus 100 mg/L, p<0.001), and levels of coagulation inhibitors were higher (p<0.001). Total homocysteine levels normalized when children attained remission of cancer disease. Two children had symptoms of acute thrombosis.

CONCLUSIONS

Raised concentrations of total homocysteine were frequent in children with newly diagnosed cancer, but this normalized when the children were in remission. The clinical significance of our observations and the impact on venous thromboembolism have yet to be defined.

Pattern of acute drug poisoning in Oslo

All 1742 admissions occasioned by acute drug poisoning to a medical ward in Oslo during the periods 1958--60, 1963--65, 1966--69 and 1970--73 have been reviewed. The number of admissions per annum in these periods was 99, 119, 128 and 144, respectively. Because the hospital situation and number of inhabitants in the city remained fairly constant from 1958 to 1973, the increasing figures were assumed to reflect a corresponding increase in the incidence of acute drug poisoning in Oslo. The incidence was estimated to be within the range of 1--2 per 1000 inhabitants per annum. No female predominance was noted except for the age group under 30 years. The occurrence of barbiturate poisonings decreased markedly during the peroids studied, whereas those due to non-barbiturate hypnotics, tranquillizers and tricyclic antidepressants showed a proportionate increase. Slightly less than one fourth of the females and half of the males had taken alcohol. More males (43%) than females (13%) also were alcoholics. A suicidal intention was, however, found more frequently among females (70%) than males (43%). The hospital mortality was approximately 1 %. No death was associated with tricyclic antidepressants, which in the last study period had been ingested by approximately 10% of all patients.

New biomarkers in an acute model of live Escherichia coli-induced sepsis in pigs

We developed a live Escherichia coli model of acute sepsis in pigs with emphasize on biomarkers reflecting the early inflammatory response of sepsis. Healthy pigs, 25-35 kg, were challenged intravenously (IV) (n = 12) or intrapulmonary (n = 6) with live E. coli and observed for 3 and 5 h respectively. Control pigs received culture medium (n = 6 + 3). Haemodynamic parameters and a broad panel of inflammatory mediators were measured. The dose of bacteria was carefully titrated to obtain a condition resembling the early phase of human septic shock. The IV group displayed a pro-inflammatory response [significant increase in tumour necrosis factor-alpha, interleukin (IL)-6 and IL-8] and an early anti-inflammatory response (significant increase in IL-10). For the first time, we demonstrate a significant increase in IL-12 and matrix metalloproteinase-9 (MMP) early in pig sepsis. Coagulation was activated (significant increase in thrombin-antithrombin complexes) and there was a significant decrease in the serum proteins suggesting capillary leakage. Haemodynamic parameters reflected a septic condition with significant decrease in systemic blood pressure, increases in heart rate, pulmonary artery pressure and base deficit. None of these changes was observed in the control group. Interleukin-1beta and vascular endothelial growth factor increased in both groups. Nitric oxide measurements suggested an initial pulmonary vascular endothelial inflammatory response. The intrapulmonary group, which did not resemble septic condition, showed a substantial increase in MMP-9. In this porcine model of sepsis, IL-12 and MMP-9 were detected for the first time. These biomarkers may have an impact in the understanding and future treatment of sepsis.

Syndecan-1 plasma levels during coronary artery bypass surgery with and without cardiopulmonary bypass

The glycocalyx covering the endothelium is shed during ischemia and reperfusion. The shedding is accompanied by increased levels of the glycocalyx component syndecan-1 in the circulation. Our aim was to compare plasma levels of syndecan-1 in patients undergoing coronary artery bypass grafting (CABG), with or without the use of cardiopulmonary bypass (CPB). Syndecan-1 plasma concentrations were measured in patients undergoing CABG on-pump (n = 22) or off-pump (n = 22). The syndecan-1 concentration increased significantly from 29.5 ± 4.6 ng/mL at baseline to 98.7 ± 9.8 ng/mL (p < 0.01) after the start of CPB or 30 minutes after the induction of anesthesia in the off-pump group. There were no significant differences in peak syndecan-1 plasma concentrations between on-pump and off-pump patients. Plasma levels of syndecan-1 increased significantly during CABG, with or without the use of CPB. There were no significant differences in syndecan-1 concentrations in the two groups.

Plasma levels of granzyme B are increased in patients with lipid-rich carotid plaques as determined by echogenicity

Increased echolucency of carotid plaques is associated with an increased risk of ischemic stroke. Inflammation and apoptosis of vascular smooth muscle cells in the arterial wall are involved in the atherosclerotic process and destabilization of the plaque. Granzyme B (GrB) is a key mediator of T cell-mediated cytotoxicity, and we therefore hypothesized that this protease could distinguish echolucent from other plaques. Ultrasound-determined echolucency of atherosclerotic plaques was assessed prior to carotid endarterectomy/angioplasty in 57 consecutively recruited patients with high-grade internal carotid stenosis. Plasma levels of GrB were measured by enzyme immunoassay prior to surgery. Patients with carotid atherosclerosis had significantly higher plasma levels of GrB compared to healthy controls (n=16) (p<0.01), with particularly high levels in those with an echolucent lesion. While there were no differences in traditional cardiovascular risk factors or CRP between those with echolucent (n=16) and those with echogenic/heterogeneous (n=41) plaques, the echolucent group had markedly raised plasma levels of GrB (p<0.01). Patients with high levels of circulating granzyme B also had more ischemic lesions on cerebral MRI prior to surgery. Raised plasma levels of GrB in echolucent carotid plaques with increased frequency of cerebrovascular events suggest that GrB may be a marker of plaque instability.

Clopidogrel increases expression of chemokines in peripheral blood mononuclear cells in patients with coronary artery disease: results of a double-blind placebo-controlled study

BACKGROUND

Chemokines and platelet activation are both important in atherogenesis. Platelet inhibitors are widely used in coronary artery disease (CAD), and we hypothesized that the platelet inhibitor clopidogrel could modify chemokines in CAD patients.

OBJECTIVES

We sought to investigate the effect of clopidogrel on the expression of chemokines and chemokine receptors in peripheral blood mononuclear cells (PBMC) in CAD patients.

PATIENTS/METHODS

Thirty-seven patients with stable angina were randomized to clopidogrel (n = 18) or placebo (n = 19). PBMC, blood platelets and plasma were collected at baseline and after 7-10 days in the patients, and in 10 healthy controls. mRNA levels of chemokines and chemokine receptors in PBMC were analyzed by ribonuclease protection assays and real-time reverse transcriptase polymerase chain reaction. Platelet activation was studied by flow cytometry.

RESULTS

(i) At baseline, the gene expression of the regulated on activation normally T-cell expressed and secreted (RANTES) chemokines and macrophage inflammatory peptide (MIP)-1beta in PBMC, the expression of CD62P and CD63 on platelets and the levels of platelet-derived microparticles (PMP) were elevated in angina patients comparing healthy controls; (ii) markers of platelet activation were either reduced (CD63) or unchanged (CD62P, PMP, beta-thromboglobulin) during clopidogrel therapy; (iii) in contrast, clopidogrel significantly up-regulated the gene expression of RANTES and MIP-1beta in PBMC, while no changes were found in the placebo group; (iv) a stable adenosine 5'-diphosphate metabolite attenuated the release of MIP-1beta, but not of RANTES, from activated PBMC in vitro.

CONCLUSIONS

Even if we do not argue against a beneficial role for clopidogrel in CAD, our findings may suggest potential inflammatory effects of clopidogrel in CAD.

Triglyceride-rich HDL3 from patients with familial hypercholesterolemia are less able to inhibit cytokine release or to promote cholesterol efflux

Familial hypercholesterolemia (FH) is associated with heterogeneity of the onset and severity of coronary heart disease (CHD). In this study, we investigated different low-grade proinflammatory markers and the atheroprotective function of the HDL3 subfraction in FH-patients (n = 13) with identical LDL-receptor mutations and in age- and sex-matched healthy controls (n = 11). Compared with healthy controls, FH-patients had greater gene expressions of the proatherogenic mediators TNF-alpha and IL-8 in circulating peripheral blood mononuclear cells. In addition, they had a higher serum concentration of intercellular adhesion molecule-1 (ICAM-1) and a lower net antioxidant capacity. FH-derived HDL3 with a high level of triglycerides had a reduced capacity to inhibit the release of IL-8 from TNF-alpha-stimulated human umbilical vein endothelial cells (HUVEC) [1.864 mg/L (1.461-2.208 mg/L) vs. 1.466 mg/L (1.225-1.643 mg/L); P < 0.05; median (range)], and a reduced capacity to promote cholesterol efflux from lipid-loaded macrophages [12% (12-14%) vs. 15% (14-18%); P < 0.05; median (range)] compared with HDL3 with a lower triglyceride content. Notably, the degree of inhibition of IL-8 release from HUVEC by HDL3 was correlated with the ability of HDL3 to promote cholesterol efflux (r = -0.80, P = 0.03). In conclusion, compared with healthy controls, FH-patients are characterized by higher levels of low-grade proinflammatory markers, and FH-derived HDL3 with high triglyceride content may be more proatherogenic. These triglyceride rich-HDL3 might be partly responsible for the phenotypic variation among FH-patients with identical LDL-receptor mutations.

Development of a time-resolved immunofluorometric assay for quantifying platelet-derived microparticles in human plasma

Platelet-derived microparticles (PMPs) are considered a marker of platelet activation. They vary considerably in size, and flow cytometry, the predominant method used to assay PMPs, is only detecting larger PMPs (>0.1 microm). We describe here a method that quantifies the amount of PMP-located GPIIb antigen in detergent-treated platelet-free plasma (PPP) by means of a one-step time-resolved immunofluorometric assay (TR-IFMA). This assay uses a streptavidin-coated microwell plate and two different monoclonal antibodies to GPIIb (CD41), one conjugated to biotin and the other labeled with europium ion. A wide linear range standard curve with low background and a high sensitivity was obtained. Pre-assay ultracentrifugation or filtration of PPP extensively reduced the fluorometric signal, indicating that the GPIIb antigen is mainly particle-located. A strong correlation between the amount of GPIIb and PMP as detected by flow cytometry was found. Consequently, the assay can be used to study PMP-related phenomena and, in contrast to flow cytometry, can be used on frozen samples and is independent of PMP size.

Intermittent saline flushes during haemodialysis do not alleviate coagulation and clot formation in stable patients receiving reduced doses of dalteparin

BACKGROUND

Heparin-free haemodialysis (HD) with intermittent saline flushes (ISF) in patients with bleeding risk is widely used. The aim of this study was to investigate if ISF reduce coagulation and clotting in stable patients receiving reduced doses of dalteparin.

METHODS

Inclusion criteria were stable chronic HD patients >or=18 years of age and haemoglobin >or=11 g/dl. Exclusion criteria were use of warfarin and acetylsalicylic acid. Six HD sessions were evaluated per patient. Dalteparin was given as one bolus dose at start of HD (50% of the conventional dose). In HD number 1, 3 and 5, 100 ml saline solution was flushed through the filter each 30 min. In HD 2, 4 and 6, no ISF were given. Potential clotting in the bubble trap was visually observed each hour and graded on a 4-point scale: 1 = normal, 2 = fibrinous ring, 3 = clot formation and 4 = coagulated system. The dialyser was visually inspected at the end of each session: 1 = normal, 2 = a few blood stripes (affecting less than 5% of the surface fibres), 3 = many blood stripes (more than 5% of the fibres) and 4 = coagulated filter. The coagulation marker PF1+2, the platelet activation marker beta-TG and anti-FXa activity were repeatedly measured during HD.

RESULTS

Six men and two women were included. In four cases (four different patients), HD was stopped due to a coagulated system, all cases on days with ISF performed. Multiple linear regression analyses with repeated measurements showed that ISF adjusted for dalteparin dose/kg significantly increased mean clot in the bubble trap, estimate (B) = 0.717, P = 0.0001 and also showed that ISF increased PF1+2, B = 0.16, P = 0.001 when adjusted for anti-FXa activity and hours of dialysis, whereas beta-TG was only borderline increased, B = 0.09, P = 0.055.

CONCLUSIONS

ISF during HD does not alleviate visible clotting or intravascular coagulation activity in stable patients receiving reduced doses of dalteparin and polysulphone dialysers. Whether this applies to unstable patients with increased bleeding risk not receiving any anticoagulation remains to be shown.

Effects of platelets and platelet-derived material on the activated partial thromboplastin time (Cephotest) coagulation test

OBJECTIVE

The Cephotest is an activated partial thromboplastin time (APTT) test used to measure the activity of the intrinsic pathway of coagulation. To perform this test, blood is usually centrifuged to obtain plasma that is almost without erythrocytes and leucocytes and with only a minimal amount of platelets.

MATERIAL AND METHODS

In the present experiments blood was centrifuged at different speeds to produce either platelet-poor plasma (PPP) or platelet-rich plasma (PRP). PPP and PRP obtained from the same whole blood samples from each of several persons were tested in pairs using the standard Cephotest reagent to observe the consequences of Cephotest being performed on plasma containing platelets. The same procedure was used with a Cephotest reagent with a reduced concentration of phosphatidylserine. In succeeding experiments the PRP was preincubated with SFLLRN or Ca-ionophore to activate the platelets, a procedure also known to produce platelet-derived microparticles. PPP and PRP were compared by thrombin time and reptilase time tests to find out at which stage platelets might influence the Cephotest.

RESULTS

The results showed that the platelets did influence Cephotest when using both the regular reagent and the phospholipid-reduced agent. When using the regular reagent, PRP showed a tendency towards a longer APTT than PPP. It is suggested that this was caused by platelets consuming some of the first traces of thrombin generated.

CONCLUSIONS

When using the phospholipid-reduced reagent, PRP showed a shorter APTT than PPP, probably because the platelets contributed phosphatidylserine to the system. When the platelets were activated before testing, their effects on the tests were increased. Microparticles that formed during platelet activation may have contributed to these effects.

Diagnostic value of family histories of thrombosis to identify children with thrombophilia

Thrombophilia screening is a time-consuming and expensive procedure. Information about thromboembolism among relatives may be a simple method to identify those at risk of having thrombophilia. In a cross-sectional clinical study the authors have investigated the role of such family histories to detect children with thrombophilia. In 202 children a family history of venous or arterial thromboembolism was recorded. The participants were either children with congenital heart defects at the time of a scheduled cardiac catheterization (n=134) or children with newly diagnosed cancer (n=68). Questions were answered, on the spot, by the parents, at the same time as blood samples for thrombophilia screening were taken. Questions about family history of thromboembolism were completed in 184 children, of whom 114 children (62%) were positive, and 35 of these had relatives with venous thromboembolic events. Only one child had an affected first-degree relative. Thrombophilic alterations were observed in 60 children (30%), and 25 of these were defined as inherited. A positive family history of venous origin increased the relative risk of a child having inherited thrombophilia to 2.35 (95% confidence interval 1.1--5.2). Information about familial arterial thromboembolism was not useful in spotting children with prothrombotic risk factors. These results indicate that questioning about family history of venous thromboembolism may identify children with genetic thrombophilia, but the association is not strong. The authors encourage similar larger-scale studies to enlighten the issue fully.