Lipoprotein-associated coagulation inhibitor (LACI) is a cofactor for heparin: synergistic anticoagulant action between LACI and sulfated polysaccharides.

Lipoprotein-associated coagulation inhibitor (LACI) is a plasma-derived protein that inhibits tissue factor (TF)/factor VIIa-induced coagulation in a factor Xa-dependent manner. The roles of endogenous plasma LACI and exogenously added LACI and heparin, in the regulation of coagulation, initiated via the intrinsic and extrinsic pathways, were studied using the activated partial thromboplastin time (APTT) and the modified prothrombin time (PT) assays, respectively. Both LACI-depleted plasma and normal plasma have identical APTTs and similar prolongations of the APTT in response to heparin; both are fully anticoagulated (arbitrarily defined as clotting times of greater than 1 hour) at similar concentrations of heparin. These results indicate that heparin is an effective anticoagulant when coagulation is initiated by the intrinsic pathway and that endogenous LACI is not significantly involved in the regulation of this pathway. The PT of normal plasma is only marginally longer than that of LACI-depleted plasma in the absence of heparin, suggesting that endogenous plasma LACI has a very limited capacity to inhibit TF-induced clotting. However, in the presence of heparin, the PTs of LACI-depleted plasma and normal plasma are different. Prolongation of the PT occurred only moderately and linearly with increasing concentrations of heparin in LACI-depleted plasma. In contrast, normal plasma showed a greater extent of PT prolongation in response to heparin and the plasma became fully anticoagulated at a certain threshold concentration of heparin. These results suggest that LACI serves as a cofactor for heparin and thus greatly enhances the inhibition of TF-induced coagulation. LACI-depleted plasma was supplemented with purified recombinant LACI and/or heparin and the effects on TF-induced clotting were studied. A combination of LACI and heparin greatly enhanced anticoagulation compared with LACI or heparin alone. Many sulfated polysaccharides were also found to enhance the LACI-dependent inhibition of TF-induced clotting. By weight, the relative potencies of these compounds are: low molecular weight heparin (mean Mr, 5,100) greater than unfractionated heparin greater than low molecular weight heparin (mean Mr, 3,700) greater than pentosan polysulfate greater than dermatan sulfate greater than dextran sulfate greater than heparan sulfate. Based on the above results, it is concluded that LACI is a cofactor for heparin in the inhibition of TF-induced clotting and that LACI and sulfated polysaccharides act synergistically in whole plasma.     

Purification and properties of heparin-releasable lipoprotein- associated coagulation inhibitor

The lipoprotein-associated coagulation inhibitor (LACI) is present in vivo in at least three different pools: sequestered in platelets, associated with plasma lipoproteins, and released into plasma by intravenous heparin, possibly from vascular endothelium. In this study we have purified the heparin-relesable form of LACI from post-heparin plasma and show that it is structurally different from lipoprotein LACI. The purification scheme uses heparin-agarose chromatography, immunoaffinity chromatography, and size-exclusion chromatography and results in a 185,000-fold purification with a 33% yield. Heparin- releasable LACI (HRL), as analyzed by sodium dodecyl sulfate- polyacrylamide gel electrophoresis, under reducing conditions, appears as a major band at 40 Kd and a minor band at 36 Kd. Immunoblot analysis suggests that the 36-Kd band arises from carboxyl-terminus proteolysis that occurs during the purification. HRL has a specific activity similar to that of HepG2 or lipoprotein LACI. HRL and lipoprotein LACI combine with lipoproteins in vitro while purified HepG2 LACI does not. I125-labeled HRL, injected into a rabbit, is cleared more slowly than I125-labeled HepG2 LACI, which may be due to attachment to lipoproteins in vivo. Preliminary evidence suggests that HRL is associated with vascular endothelium, possibly by attachment to glycosaminoglycans.     

Lipoprotein lipase and hepatic lipase activity after heparin administration in abetalipoproteinemia and hypobetalipoproteinemia

The purpose of this study was to examine whether an absence of triglyceride-rich lipoproteins (chylomicrons and very-low-density lipoproteins) in plasma is associated with any changes in the enzyme activity of lipoprotein lipase or hepatic lipase after heparin administration. To study this, the activities of hepatic lipase and lipoprotein lipase were determined in control subjects, in two patients with heterozygous hypobetalipoproteinemia, and in three patients with phenotypic abetalipoproteinemia after administration of heparin. Both enzymes showed normal activity in the patients with hypobetalipoproteinemia, but showed consistently reduced activity in the patients with abetalipoproteinemia. Hepatic lipase activity in plasma samples from these three patients obtained 15 minutes after intravenous injection of heparin was 55%, 87%, and 46% of that of the controls, whereas corresponding values in plasma samples obtained 30 minutes after heparin were 47%, 70%, and 57%, respectively. Lipoprotein lipase activity in the three patients with abetalipoproteinemia was 46%, 29%, and 34% of that of the controls in the samples obtained 15 minutes after heparin injection, whereas the values obtained after 30 minutes were 53%, 64%, and 47% of that of the controls. We conclude that an inherent absence of triglyceride-rich lipoproteins, as occurs in abetalipoproteinemia, is associated with reduced enzyme activity of both hepatic lipase and lipoprotein lipase in plasma after heparin administration.     

Elevated levels of free tissue factor pathway inhibitor antigen in cases of disseminated intravascular coagulation caused by various underlying diseases.

Tissue factor pathway inhibitor (TFPI) is primarily synthesized by vascular endothelial cells and is found in vivo in association with endothelial cells, lipoproteins, or in free form. Free TFPI is the most potent and important type, because it is released from endothelial cells following an injection of heparin, or as a result of pathological stimuli. In order to study the role of TFPI in disease, the concentration of free form TFPI was measured in the plasma of 114 patients suffering from disseminated intravascular coagulation (DIC), as the result of several underlying diseases. Plasma antigen levels of free TFPI were significantly higher even in those patients not exhibiting DIC than in normal healthy subjects. These levels were even higher among patients exhibiting DIC, especially those with acute promyelocytic leukemia or cancer, receiving continuous heparin drip infusions. A significant correlation was observed between the plasma antigen levels of free form TFPI and those of fibrin/fibrinogen degradation products, and free form TFPI and plasmin inhibitor complex (r = 0.428, P < 0.0001 and r = 0.329, P < 0.0001, respectively) among 114 DIC patients. There were no significant differences between the plasma levels of free TFPI in DIC patients with or without multiple organ failure. It has been suggested that the plasma levels of free TFPI are closely related to the levels of fibrinolysis occurring in DIC patients, although further study is required to clarify the degree to which TFPI is expressed by endothelial cells during DIC.     

Natural anticoagulants, aging, and thromboembolism

—The normal aging process alters blood coagulation system in humans; this may be of great concern in the view of the known association of vascular disease with advancing age. The plasma concentration of several coagulation factors, namely fibrinogen, factor VII, factor VIII, factor IX, high molecular-weight kininogen, and prekallikrein, increase in healthy humans, paralleling the physiological aging process. Plasma parameters of clotting activation in vivo, such as prothrombin fragment 1 + 2, fibrinopeptide A, thrombin–antithrombin III complex, and D-dimer, are positively correlated with age. Nevertheless, among centenarians, biochemical signs of marked hypercoagulability are associated with a healthy state. Natural anticoagulants, including antithrombin III, heparin cofactor II, protein C, protein S, and tissue factor pathway inhibitor, can modulate the reactions of blood coagulation system. The occurrence of menopause is accompanied by a significant increase in antithrombin III plasma level; the mean antithrombin III levels in older women exceed levels in male contemporaries. In healthy elderly subjects heparin cofactor II plasma concentrations are lower than in young subjects, independently of gender. Protein C levels raise with age in both sexes, as well as free protein S levels. In women, statistically significant increases in the plasma concentration of the tissue factor pathway inhibitor have been observed, whereas no significant age-related change has been found in men. The fact that many subjects with congenital defects of natural anticoagulants do not undergo thromboembolic events in young age suggests that in healthy individuals a raise in natural anticoagulants can balance the age-related increase of procoagulant factors.     

The lipoprotein-associated coagulation inhibitor that inhibits the factor VII-tissue factor complex also inhibits factor Xa: insight into its possible mechanism of action

Blood coagulation is initiated when plasma factor VII(a) binds to its essential cofactor tissue factor (TF) and proteolytically activates factors X and IX. Progressive inhibition of TF activity occurs upon its addition to plasma. This process is reversible and requires the presence of VII(a), catalytically active Xa, Ca2+, and another component that appears to be associated with the lipoproteins in plasma, a lipoprotein-associated coagulation inhibitor (LACI). A protein, LACI(HG2), possessing the same inhibitory properties as LACI, has recently been isolated from the conditioned media of cultured human liver cells (HepG2). Rabbit antisera raised against a synthetic peptide based on the N-terminal sequence of LACI(HG2) and purified IgG from a rabbit immunized with intact LACI(HG2) inhibit the LACI activity in human serum. In a reaction mixture containing VIIa, Xa, Ca2+, and purified LACI(HG2), the apparent half-life (t1/2) for TF activity was 20 seconds. The presence of heparin accelerated the initial rate of inhibition threefold. Antithrombin III alpha alone had no effect, but antithrombin III alpha with heparin abrogated the TF inhibition. LACI(HG2) also inhibited Xa with an apparent t1/2 of 50 seconds. Heparin enhanced the rate of Xa inhibition 2.5-fold, whereas phospholipids and Ca2+ slowed the reaction 2.5-fold. Xa inhibition was demonstrable with both chromogenic substrate (S-2222) and bioassays, but no complex between Xa and LACI(HG2) could be visualized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Nondenaturing PAGE, however, showed that LACI(HG2) bound to Xa but not to X or Xa inactivated by diisopropyl fluorophosphate. Thus, LACI(HG2) appears to bind to Xa at or near its active site. Bovine factor Xa lacking its gamma-carboxyglutamic acid-containing domain, BXa(-GD), through treatment with alpha-chymotrypsin, was used to further investigate the Xa requirement for VIIa/TF inhibition by LACI(HG2). LACI(HG2) bound to BXa(-GD) and inhibited its catalytic activity against a small molecular substrate (Spectrozyme Xa), though at a rate approximately sevenfold slower than native BXa. Preincubation of LACI(HG2) with saturating concentrations of BXa(-GD) markedly retarded the subsequent inhibition of BXa. The VII(a)/TF complex was not inhibited by LACI(HG2) in the presence of BXa(-GD), and further, preincubation of LACI(HG2) with BXa(-GD) slowed the inhibition of VIIa/TF after the addition of native Xa. The results are consistent with the hypothesis that inhibition of VII(a)/TF involves the formation of a VIIa-TF-XA-LACI complex that requires the GD of XA.(ABSTRACT TRUNCATED AT 400 WORDS)     

Spectrum of hemostatic derangements, in Budd-Chiari syndrome.

BACKGROUND: Hemostatic abnormalities have been reported in various hepatocellular diseases. We evaluated the hemostatic functions in patients with Budd-Chiari syndrome. METHODS: Biochemical liver function tests, and measurement of prothrombin time, activated partial thromboplastin time, and plasma levels of anti-thrombin III (antigen) and activity of protein C were done in 36 patients with Budd-Chiari syndrome. RESULTS: Liver biochemistry was abnormal in 34 patients. Plasma prothrombin time and activated partial thromboplastin time were prolonged in 17 (47%) and 23 (64%) patients, respectively. Antithrombin III antigen levels and protein C activity were reduced in 15 (50%) and 25 (83%) patients, respectively, among the 30 patients studied. Albumin levels showed significant correlation with coagulation test results, levels of anti-thrombin-III, and protein C activity. CONCLUSION: Hepatic synthesis of coagulation factors and anticoagulants is reduced in Budd-Chiari syndrome; this may play a role in recurrence of thrombosis.     

Decreased plasma tissue factor pathway inhibitor in women taking combined oral contraceptives

Use of combined oral contraceptives (OC) is associated with a significant risk of thrombosis. The mechanisms of this effect are not clearly defined. Tissue factor pathway inhibitor (TFPI) is a circulating anti-coagulant that inhibits the earliest steps in activation of the extrinsic coagulation pathway. It plays a central role in control of coagulation but its contribution to the thrombotic risk associated with OC has not been assessed. Plasma TFPI antigen and activity, factor VIIa, prothrombin fragments 1&2, von Willebrand antigen, fibrinogen, and low density lipoprotein cholesterol were measured by standard assays in women taking OC (aged 16 to 45 years, n = 40) and age-matched women not taking OC (controls, n = 40). Plasma TFPI antigen did not vary significantly across the menstrual cycle in controls. Women on OC had a 25% reduction in plasma TFPI antigen (median 51.0 ng/ml; 95% confidence intervals [CI] 37.5 to 85.5; control 68.0 ng/ml, CI 61.0 to 95.0; P < 0.001) and a 29% reduction in TFPI activity (78.5 U/ml, CI 57.5 to 107.5; control 111.0 U/ml, CI 79.5 to 171.0; P < 0.001) compared to controls. Plasma factor VIIa activity and prothrombin fragments 1&2 were also significantly increased in women using OC (both P < 0.001), indicating activation of the extrinsic coagulation pathway. These results demonstrate that normal cyclic variations in estrogen and/or progesterone do not significantly alter plasma TFPI levels. However, estrogens and/or progestogens in OC result in activation of the extrinsic coagulation pathway and significantly reduce plasma TFPI, its major circulating inhibitor. Reduced plasma TFPI levels may underlie the thrombotic effects of OC.     

Cultured normal human hepatocytes do not synthesize lipoprotein-associated coagulation inhibitor: evidence that endothelium is the principal site of its synthesis.

Human plasma contains a factor Xa-dependent inhibitor of tissue factor/factor VIIa complex termed lipoprotein-associated coagulation inhibitor (LACI). The present study examines the site(s) of LACI synthesis. In this study, cultured hepatocytes isolated from normal human liver were found to be essentially negative in LACI mRNA as revealed by Northern blot analysis using a full-length LACI cDNA as probe. The conditioned media from these cultures were also essentially negative for LACI activity. Similarly, poly(A)+ RNA obtained from normal human liver did not contain detectable LACI mRNA. In contrast, cultured human umbilical vein endothelial cells and human lung tissue (rich in endothelium) both contained abundant amounts of LACI mRNA. Moreover, erythrocyte lysates and culture media from normal monocytes, lymphocytes, or neutrophils did not contain measurable LACI activity; these cells were also negative for LACI mRNA. Platelets, however, contained LACI activity. The likely source of platelet LACI is the megakaryocyte cell since a megakaryocyte cell line (MEG-01) was found to contain LACI mRNA and to secrete small amounts of LACI activity. Additionally, human vascular smooth muscle cells and lung fibroblasts were also found to synthesize only small amounts of LACI. From these observations, we conclude that normal liver does not synthesize LACI and that endothelium is the principal source of plasma LACI. The undegraded LACI synthesized by endothelial cells had a molecular weight of approximately 41,000.     

Rebound thrombin generation after heparin therapy in unstable angina. A randomized comparison between unfractionated and low-molecular-weight heparin

OBJECTIVES: This study compared rebound coagulation in patients with acute coronary syndrome patients after discontinuation of unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH). BACKGROUND: Up to a quarter of patients hospitalized for unstable angina experience recurrent ischemia after discontinuation of UFH or LMWH therapy, which may be the result of rebound coagulation activation and subsequent thrombosis. It is unknown whether UFH and LMWH differ in this respect. METHODS: We randomized 71 patients admitted with unstable angina to intravenous UFH or subcutaneous LMWH (dalteparin) and measured plasma markers of coagulation before, during, and after treatment. RESULTS: A complete series of measurements was obtained in 59 patients. Plasma prothrombin fragment 1+2 (F(1+2)) levels decreased in both groups during treatment. After loss of therapeutic plasma drug levels, F(1+2) increased (within 3 h) to a maximum level at 12 to 24 h that was higher than before or during treatment in both groups (p < 0.0001). In both groups, F(1+2) levels remained higher than pretreatment up to 24 h after discontinuation. Similarly, thrombin-antithrombin (TAT) levels exceeded treatment and pretreatment levels, at a slower rate after dalteparin than after UFH. However, after dalteparin a higher peak value of TAT was observed. CONCLUSIONS: Rebound coagulation activation occurs within hours after discontinuation of both UFH and dalteparin. With both drugs, thrombin generation is significantly greater after treatment than before or during treatment. A longer duration or weaning of treatment, or continuation with another anticoagulant treatment, may reduce rebound coagulation activation and ischemic events.     

Gestational diabetes has no additional effect on plasma thrombin-activatable fibrinolysis inhibitor antigen levels beyond pregnancy

Pregnancy is a prothrombotic condition with increased levels of several circulating coagulation factors. Decreased fibrinolytic activity has been shown in gestational diabetes. Gestational diabetes has been found to be associated with higher plasma plasminogen activator inhibitor-1 (PAI-1) antigen levels than normal pregnancy. The aim of the present study is to investigate the effect of gestational diabetes on plasma thrombin-activatable fibrinolysis inhibitor (TAFI) antigen levels.Plasma TAFI and PAI-1 antigen levels were measured in 26 pregnant women with gestational diabetes, 25 pregnant women with normal glucose tolerance, and age-matched 24 non-pregnant women with no history of gestational diabetes.Increased plasma TAFI antigen levels were found in pregnant women compared to non-pregnant controls. However, no statistically significant difference in TAFI antigen levels was observed between women with gestational diabetes and pregnant controls. Plasma PAI-1 antigen levels were higher in gestational diabetes than pregnant and non-pregnant controls.Our study revealed that pregnancy was associated with elevated plasma TAFI antigen levels. However, no additional effect of gestational diabetes was found on plasma TAFI antigen levels beyond pregnancy. We suggest that pregnancy is associated with enhanced coagulation and impaired fibrinolysis. Despite increased PAI-1 antigen levels associated with gestational diabetes, the effect of gestational diabetes on TAFI antigen levels is lacking.     

Radioimmunoassay of fragment E-related neoantigen: validation studies and clinical application

S ummary. Measurement of fibrinogen-fibrin degradation products (FDP) levels in plasma may provide a direct index of plasmin action, and increased levels of FDP would indicate coagulopathy. We have established an E-neoantigen radioimmunoassay (Eneo RIA) that can determine normal and pathological plasma levels of E-related FDP. The assay employs rabbit antiserum produced against fragment E derived from a plasmin digest of fibrinogen and subsequently absorbed with fibrinogen. The absorbed antiserum contains antibodies which are equally reactive with fibrinogen derived E (Fg-E) and fibrin derived E (Fb-E) but not with fibrinogen at 1 mg/ml. The Eneo RIA was validated by assay parallelism and by recovery experiments. Plasma Eneo immunoreactivities in 14 normals were 4–22 ng/ml (mean 12.7 ng/ml). Plasma Eneo levels in 23 of 24 patients with neoplastic and haematological diseases were elevated above normal (range 27–2027 ng/ml). Unusually high Eneo values were observed with three patients whose diseases were complicated by either disseminated intravascular coagulation (DIC) or deep vein thrombosis. After heparin therapy, the Eneo level of a patient with chronic DIC declined. A pathological plasma was eluted from a Sephadex G-200 column and Eneo immunoreactivity was determined on the eluates. The gel filtration pattern of Eneo indicates that E-related FDP is a family of plasmic fragments derived from crosslinked fibrin.     

Neutral lipid transfer activities in the plasma of patients with abetalipoproteinemia

Plasma lipid transfer proteins stimulate transfer and molecular exchange of cholesteryl esters, phospholipids and triglycerides between individual plasma lipoproteins. To assess whether transfer protein activities are influenced by the inherent absence of apo B-containing lipoproteins, we determined cholesteryl ester and triglyceride transfer activities in the plasma of patients with abetalipoproteinemia (ABL). Transfer activities were measured in plasma fractions of d greater than 1.21 g/ml in 2 patients with abetalipoproteinemia and 12 normal volunteers and were expressed as a percent transfer of labeled lipid from donor high density lipoproteins to acceptor very low density lipoproteins. Cholesteryl ester and triglyceride transfer activities were reduced respectively by 50% and 66% in the plasma of patients with ABL. The addition of the plasma fraction d greater than 1.21 g/ml proteins from abetalipoproteinemic subjects resulted in progressive decreases in cholesteryl ester and triglyceride transfer activities. The reduced activities of these transfer proteins may reflect (at least in part) the presence of an inhibitor(s) which is heat-stable and trypsin-sensitive.     

Relationships between brachial artery flow mediated dilation and carotid artery intima-media thickness in patients with suspected coronary artery disease

The correlation of peripheral endothelial dysfunction and intima-media thickness (IMT) in patients with suspected coronary artery disease (CAD) has been unclear. Inflammation and thrombosis may play a role at early stages of atherosclerosis. Thus, early atherosclerosis was noninvasively examined morphologically by IMT of carotid arteries, and functionally by flow mediated dilation (FMD) of brachial arteries in patients who were suspected of CAD and had undergone coronary angiography. Plasma antigen levels of tumor necrosis factor (TNF)-alpha and interleukin (IL)-6, representative atherogenic cytokines, tissue factor (TF) and tissue factor pathway inhibitor (TFPI), markers of coagulation, and plasma activity level of plasminogen activator inhibitor type-1 (PAI-1), a marker of defective fibrinolysis, were measured. Patients with coronary atherosclerosis in one or more vessels with lesion > or = 50% had significantly reduced FMD compared with those with angiographically normal coronary arteries. Carotid artery IMT increased significantly only in patients with advanced coronary atherosclerosis in one or more vessels with lesion > or = 90%. Plasma antigen levels of IL-6 were significantly increased in patients with reduced FMD (< 5%) compared to those in patients with FMD between 10 and 15%. Plasma antigen levels of TF, total and free TFPI, and PAI-1 activity tended to increase with a reduction in FMD. Thus, (1) FMD was reduced at early stages of CAD while IMT was increased in advanced CAD, and (2) inflammation and thrombosis may play a role in the early stages of the atherosclerotic process.     

Circulating thrombomodulin as a novel endothelial cell marker: comparison of its behavior with von Willebrand factor and tissue-type plasminogen activator.

Circulating thrombomodulin is a novel endothelial cell marker, which may reflect the endothelial injury. Plasma levels of thrombomodulin were quantitated by an enzyme-linked immunosorbent assay (ELISA) in patients with hematological malignancies, liver disease, diabetes mellitus, collagen disease, thrombotic disease, and disseminated intravascular coagulation (DIC), and the thrombomodulin values were compared with those of von Willebrand factor antigen (vWf:Ag) and tissue-type plasminogen activator (t-PA) which are released from stimulated or damaged endothelial cells. The mean plasma concentrations of thrombomodulin in these disease states were elevated as compared with healthy subjects. A relatively high mean thrombomodulin level was observed in DIC, liver disease, and collagen disease. Abnormally high thrombomodulin values (greater than normal mean value + 3 SD) were found in 32.3% of patients with hematological malignancies, 57.7% of patients with liver disease, 39.3% of patients with diabetes mellitus, 30.0% of patients with collagen disease, 23.1% of patients with thrombotic disease, and 69.0% of patients with DIC. Plasma concentrations of both vWf:Ag and t-PA were also elevated in these patients. On the whole, the plasma thrombomodulin concentration was positively correlated with vWf:Ag (r = 0.441, P less than 0.001) and t-PA (r = 0.398, P less than 0.001). These findings indicate that the elevation of plasma thrombomodulin is frequently seen in a variety of diseases and circulating thrombomodulin is possibly useful for evaluating the endothelial damage in selected disease states.     

Regulation of low density lipoprotein receptors by plasma lipoproteins from patients with abetalipoproteinemia.

Despite an absence of low density lipoproteins (LDLs) and chylomicron remnants from plasma, the rates of cholesterol synthesis or the number of LDL receptors expressed on freshly isolated cells from patients with abetalipoproteinemia are not markedly increased. These observations suggest that other lipoprotein particles present in the plasma of patients with abetalipoproteinemia may regulate LDL receptor activity and the rates of cellular cholesterol synthesis in this disorder. In the present report we have studied the effects of lipoprotein fractions from the plasma of normal subjects, patients with abetalipoproteinemia, and a patient with dysbetalipoproteinemia on the binding, internalization, and degradation of 125I-labeled LDL (125I-LDL) by cultured human fibroblasts. LDL from normal subjects or the high density lipoprotein fraction HDL2 from the plasma of patients with abetalipoproteinemia effectively down-regulated LDL receptor activity (greater than 50% inhibition at 20 micrograms of protein per ml). HDL2 from the plasma of patients with abetalipoproteinemia also effectively reduced the binding, internalization, and degradation of 125I-LDL by cultured human fibroblasts. 125I-HDL2 from the plasma of patients with abetalipoproteinemia was bound, internalized, and degraded by cultured human fibroblasts; this process was competitively inhibited by unlabeled normal LDL or HDL2 from abetalipoproteinemic plasma and was 1/6th to 1/8th times as high when 125I-HDL2 was incubated with fibroblasts from a patient with receptor-negative homozygous familial hypercholesterolemia. We conclude that lipoproteins present in the HDL2 fraction of plasma from patients with abetalipoproteinemia (which are relatively rich in apoprotein E) are effective regulators of LDL receptor activity in normal human fibroblasts. These in vitro findings may explain why the in vivo rates of cholesterol synthesis and the number of LDL receptors expressed on freshly isolated cells from patients with abetalipoproteinemia are not markedly increased.     

Methodology and clinical significance of heparin cofactor II. Probable heparin cofactor II deficiency in a patient with cerebrovascular thrombosis

HC II was functionally determined by thrombin inhibition in the presence of heparin in AT III-free plasma prepared by immunoadsorption on anti-AT III-Sepharose 4B column. HC II antigen concentration was assayed using specific antibodies to HC II. Simultaneously, AT III was measured. Plasma levels of HC II and AT III were determined in 110 patients with thrombotic tendency and two patients with obstetric complications and DIC. Highly significant correlations between activity and antigen prove the suitability of the methods. Reduced levels of HC II to about 50% with normal AT III values were repeatedly found in one patient with thrombotic tendency. The course of AT III and HC II during the process of DIC suggests that HC II may function as a thrombin inhibitor reserve when AT III becomes subnormally low.     

Serial studies of protein C and its plasma inhibitor in patients with disseminated intravascular coagulation

This study was undertaken to determine the levels of protein C antigen and activity and protein C inhibitor in sequential plasma samples of disseminated intravascular coagulation (DIC) patients. Our normal range for both protein C antigen and activity is 70 to 130 U/dL, and protein C inhibitor is 65 to 135 U/dL. A decreased level of protein C activity was found in 96% of the plasma samples from individuals with DIC; the protein C antigen was decreased in 73%. The inhibitor of protein C was decreased in all samples. Analysis of serial samples from patients with DIC reveals that protein C activity and antigen and protein C inhibitor decrease progressively during the initial stages of DIC and remain at a low level for 24 to 48 hours before gradually returning toward normal in nonfatal cases. The protein C activity decreases in parallel with protein C inhibitor and is lower than protein C antigen. In a fatal case of DIC, protein C activity and protein C inhibitor rapidly decreased to undetectable levels; however, protein C antigen was gradually decreasing but still detectable at time of death. In DIC, a discrepancy initially occurs between the activity and antigen of protein C, suggesting a complex with the inhibitor or other inactive forms of protein C. Protein C appears to play a major role in the control of DIC.     

Elevated plasma levels of free-form of TFPI antigen in hypercholesterolemic patients

Several studies have previously reported high levels of total tissue factor pathway inhibitor (TFPI) antigen in patients with hypercholesterolemia. The relationship between serum lipid concentrations and total and free-form TFPI antigen in 32 patients with primary type II hypercholesterolemia and 38 age- and gender-matched normolipemic control subjects was studied (Study Group I). Plasma concentrations of total TFPI (tTFPI) antigen, free-form TFPI (fTFPI) antigen, tissue factor antigen, factor VII activity (FVIIc), and prothrombin fragment 1+2 (F1+2) were measured. The median levels of tTFPI, fTFPI, FVIIc, and F1+2 were higher in hyperlipidemic patients compared with those in healthy subjects. The effect of lowering total cholesterol on hypercoagulability in 25 patients with type II hyperlipoproteinemia (Study Group II) were also studied. The median levels of tTFPI, FVIIc, and F1+2 decreased significantly after 6 months of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor therapy in the hypercholesterolemic patients. On the other hand, fTFPI did not change after therapy. Plasma tTFPI was strongly correlated with total cholesterol and low density lipoprotein (LDL)-cholesterol in hyperlipidemic patients. In contrast to the strong correlation between tTFPI and total cholesterol, the correlation between plasma fTFPI and total cholesterol was relatively poor. These results suggest that the activation of the anticoagulant system as well as the activation of the coagulation system may occur in association with hypercholesterolemia. Furthermore, the results of this study may suggest that lowering of total cholesterol in hyperlipidemic patients reduces the thrombin generation in plasma and that down-regulation of LDL does not affect the anticoagulant potency of TFPI in plasma.     

Plasma thrombin-activatable fibrinolysis inhibitor (TAFI) antigen levels in diabetic foot ulcers

Plasma TAFI may participate in arterial thrombosis in cardiovascular diseases (CVD) and may be involved in the mechanism of vascular endothelial damage in diabetic patients. The aim of this study was to investigate the association of plasma TAFI antigen level in the development of diabetic foot ulcer in Type 2 diabetes. The TAFI antigen levels were determined in 50 patients with diabetic foot ulcers and 34 patients without diabetic foot ulcers and 25 healthy individuals. We measured TAFIa/ai antigen in plasma samples with a commercially available ELISA Kit. Diabetic foot ulcer group and diabetic group were similar in terms of mean age and sex distribution. Diabetes duration, retinopathy, neuropathy, macrovascular disease and infection were related to diabetic foot ulcers. HbA1c, HDL-cholesterol and Folic Acid levels were decreased in the diabetic foot ulcer group. TAFI levels were 99.44?±?55.94% in control group, 135.21?±?61.05% in diabetic foot ulcer group, 136.75?±?59.38% in diabetic group and was statistically different (P??0.05). No significant difference in plasma TAFI levels were seen between diabetic foot ulcer stages. TAFI antigen levels are increased in Type 2 diabetic patients, but are not related to diabetic foot ulcer development.