Birgit Svensson

Tissue-factor pathway inhibitor and lipoproteins. Evidence for association with and regulation by LDL in human plasma.

Tissue-factor pathway inhibitor (TFPI) is a potent inhibitor of extrinsic coagulation, which is mainly associated with lipoproteins in circulating blood. Gel filtration of human plasma confirmed the presence of three peaks in which approximately 10%, 70%, and 20% of total TFPI activity was retained. Precipitation of very-low-density lipoproteins and low-density lipoproteins (LDLs) in plasma by polyethylene glycol almost completely abolished peaks and I and II. LDL isolated by ultracentrifugation revealed two peaks of TFPI after gel filtration that coeluted with peaks I and II, respectively, from gel filtration of total plasma. TFPI activity in peaks I and II was also precipitated by anti-apolipoprotein B antibodies. Fourteen patients with familial hypercholesterolemia had higher plasma TFPI activity than did age- and sex-matched normolipemic control subjects (1.45 +/- 0.27 U/mL versus 0.80 +/- 0.09 U/mL, P < .001). Plasma TFPI was correlated with LDL cholesterol (r = .73, P < .001) and apolipoprotein B (r = .69, P < .001). No association was found with high-density lipoprotein cholesterol or apolipoprotein A-I. In a double-blind, placebo-controlled trial among the familial hypercholesterolemia patients, lovastatin alone or in combination with fish oil concentrate lowered plasma TFPI in parallel with LDL cholesterol. Gel filtration of plasma from these patients demonstrated a specific drop in apolipoprotein B-TFPI complexes, whereas TFPI not associated with lipoproteins was unchanged. This study demonstrated that plasma TFPI was associated with and regulated by LDL in plasma from healthy subjects and patients with familial hypercholesterolemia.

Atorvastatin and omega-3 fatty acids protect against activation of the coagulation system in patients with combined hyperlipemia

Summary.  Activation of factor (F)VII by tissue factor may represent a critical event during plaque rupture in acute coronary syndromes. Patients with combined hyperlipemia are at high risk for developing coronary heart disease and their tendency to thrombosis may be accelerated during postprandial hyperlipemia. In the present double‐blind, placebo‐controlled parallel study, 42 patients with combined hyperlipemia and serum triglycerides between 2.0 and 15.0 mmol L−1 and serum cholesterol >5.3 mmol L−1 at the end of a 3‐month dietary run‐in period were treated with atorvastatin at 10 mg day−1 for at least 10 weeks. During the last 5 weeks the patients were randomized into two groups receiving 1.68 g day−1 omega‐3 fatty acids (ω‐3 FA) or placebo (corn oil). The fasting levels of FVII antigen (FVII‐Ag) and FVII coagulant activity (FVII:C) were high compared with healthy males. The fasting levels of activated FVII (FVIIa) and FVII‐Ag correlated both to serum triglycerides and apolipoprotein A1 (apoA1). FVIIa and FVII:C increased during postprandial hyperlipemia. This increase of FVIIa correlated to the fasting triglyceride and apoA1 levels, but not to the degree of postprandial hypertriglyceridemia. The concentrations of fasting FVIIa in these patients were reduced in parallel with a reduction of fasting triglycerides by treatment with atorvastatin + placebo. This treatment also reduced the postprandial level of FVIIa. ω‐3 FA in addition to atorvastatin further reduced FVIIa concentrations, fasting and postprandially, and also significantly reduced FVII:C and FVII‐Ag during postprandial hyperlipemia. Prothrombin fragment 1 + 2 (F1 + 2) increased during postprandial hyperlipemia. This increase was significantly reduced after treatment with atorvastatin plus ω‐3 FA. The increase of F1 + 2 measured as incremental area under the curve (iAUC) during postprandial hyperlipemia correlated to the fasting levels of FVIIa, FVII:C and FVII‐Ag and also to the levels of these factors during postprandial lipemia. In conclusion, patients with combined hyperlipemia are at risk for activation of the coagulation system, particularly during postprandial lipemia. This activation may be significantly reduced by statins and ω‐3 FA.

The effects of albumin bound fatty acids on the platelet inhibitory function of human endothelial cells

Abstract. This study was carried out to evaluate the effects of albumin‐bound fatty acids on the anti‐platelet effects of endothelial cells. Primary cultures of human endothelial cells (ECM), grown in confluent monolayers, were incubated with plasma or growth medium enriched with albumin‐bound fatty acids (FA) for 2–20 h. The effects of ECM on ADP‐induced platelet aggregation (PA) and collagen‐induced PA and prostaglandin synthesis in platelet‐rich plasma were tested.

Inhibition of exercise-induced shortening of bleeding time by fish oil in familial hypercholesterolemia (type IIa).

Fourteen patients suffering from familial hypercholesterolemia (type IIa) participated in a double-blind, placebo-controlled trial that evaluated the effects of fish oil ethyl ester (K-85, 5.7 g/day) or a hydroxymethylglutaryl coenzyme A reductase inhibitor (lovastatin, 40 mg/day) alone or in combination on lipid metabolism and bleeding time at rest and after standardized exercise. Lovastatin treatment reduced total cholesterol (-27%), low density lipoprotein cholesterol (-37%), and triglycerides (-18%), whereas high density lipoprotein cholesterol increased significantly (14%). K-85 affected total (-4%), low density lipoprotein (-9%), and high density lipoprotein (+7%) cholesterol insignificantly, whereas the triglyceride level decreased by 24% (p < 0.001). The combined regimen caused an additive decrease in the triglyceride level (41%), which differed significantly (p < 0.01) from that gained by lovastatin alone. Under basal conditions the bleeding time was not influenced by the different interventions....

Female sex hormones and platelet/endothelial cell interactions.

The effects of estradiol and progesterone added to the growth medium of human umbilical vein endothelial cells for 72 h on the formation and release of prostacyclin were investigated. The influence on collagen-induced platelet aggregation and on the platelet formation of thromboxane A2 following aggregation, of the growth medium collected before and after thrombin stimulation of the endothelial cells, was studied simultaneously. Under basal conditions, endothelial cells grown with progesterone released significantly less prostacyclin into the growth medium than did controls (p

The simultaneous effect of albumin bound fatty acids on platelets and endothelial cells.

Abstract Platelet rich plasma (PRP) added albumin bound fatty acids (stearic acid, oleic acid, linoleic acid) (LA), α-linolenic acid, di-homo-γ-`linolenic (DHLA) and arachidonic acid (AA), ratio 2, were preincubated with and without endothelial cell monolayers (ECM), prepared from human umbilical veins, for 90 min at room temperature. Aliquots of PRP were then exposed to ADP and collagen, and platelet aggregation (PA) and malondialdehyde(MDA) production after collagen-induced PA were measured. DHLA inhibited PA in PRP, and in PRP incubated with ECM, whereas LA and AA were inhibitory only after preincubation with ECM. MDA production only partially followed PA. When PRP were incubated with albumin bound FA and then added prostacyclin (PGI2) or 6-keto-PGFlα (20 nmol/1) before exposure to the aggregating agents, PGI2 regularly inhibited PA. Only PRP incubated with DHLA showed a significant less aggregation than PRP incubated with albumin or the other FA. This study shows that the effects of the linoleate sequence of fatty acids on platelets and endothelial cells are different than on platelets in the absence of endothelial cells. This probably reflects the two cell types different ability to convert and metabolize the various FA to platelet activity prostaglandins and thromboxanes, and may be of significance for the influence of albumin bound FA on the thrombosis mechanism.

The bleeding time in women: An influence of the sex hormones?

A sex difference in the bleeding time has been reported. To investigate the effects of the different sex hormones, the bleeding time (BT) and hemostatic factors related to it were measured in 209 healthy women: 50 pregnant, 113 menstruating and 46 post‐menopausal. The serum levels of estrogens, progesterone and testosterone were distributed as expected for the different groups. There were no significant differences in the BT between any of the groups. No correlations between the BT and female or male sex hormones were found. The findings indicate that although sex hormone mediated effects on platelet/endothelial cell interactions may exist, they do not become evident within the physiological variations in the BT of healthy women.

Reduction of factor FVIIa activity during heparin therapy. Evidence for assay interactions with tissue factor pathway inhibitor and antithrombin.

Heparin is known to exert its antithrombotic effects by accelerating the effect of antithrombin (AT) and by mobilizing tissue factor pathway inhibitor (TFPI) into the circulation from vascular endothelium. Heparin treatment has been reported to decrease FVIIa activity by 40%; this was suggested as a new antithrombotic action of heparins. The present study was conducted to investigate whether the apparent reduction in FVIIa activity induced by unfractionated heparin (UFH) infusion in vivo is due to interactions between AT and TFPI with the FVIIa assay or due to an actual decrease in FVIIa. Blocking plasma TFPI in affinity purified anti-TFPI IgG caused a 25% increase in plasma FVIIa activity (Staclot VII - rTF, Diagnostica Stago, Aswiéres-sur-Seine, France). In vitro heparinization of plasma caused a dose-dependent decrease in FVIIa (up to 56 +/- 8%) at high heparin concentrations (1.0-5.0 IU/mL UFH), a reduction abolished by Hexadimethine Bromide (HDB) to neutralize heparin-induced activation of AT. Thus, heparin-induced activation of AT is apparently responsible for decreased FVIIa under in vitro conditions. Bolus injection followed by continuous infusion of heparin to healthy volunteers was accompanied by a prompt 50% reduction in FVIIa activity, which was sustained throughout heparin infusion and normalized within 24 hours after discontinuation of treatment. Addition of anti-TFPI IgG to postheparin plasma reversed the heparin-induced reduction in FVIIa by approximately 50%, and combined pretreatment of postheparin plasma with anti-TFPI IgG and HDB brought FVIIa to preheparin levels. The present study shows that the FVIIa assay is sensitive to TFPI and AT, especially during heparin treatment, and thereby indicates that the heparin-induced decrease in FVIIa is affected by interactions between TFPI and AT with the FVIIa assay.

Inhibition of stress-induced shortening of bleeding time by fish oil in familial hypercholesterolemia (type IIa)

Fourteen patients suffering from familial hypercholesterolemia (type IIa) participated in a double-blind, placebo-controlled trial that evaluated the effects of fish oil ethyl ester (K-85, 5.7 g/day) or a hydroxymethylglutaryl coenzyme A reductase inhibitor (lovastatin, 40 mg/day) alone or in combination on lipid metabolism and bleeding time at rest and after standardized exercise. Lovastatin treatment reduced total cholesterol (-27%), low density lipoprotein cholesterol (-37%), and triglycerides (-18%), whereas high density lipoprotein cholesterol increased significantly (14%). K-85 affected total (-4%), low density lipoprotein (-9%), and high density lipoprotein (+7%) cholesterol insignificantly, whereas the triglyceride level decreased by 24% (p < 0.001). The combined regimen caused an additive decrease in the triglyceride level (41%), which differed significantly (p < 0.01) from that gained by lovastatin alone. Under basal conditions the bleeding time was not influenced by the different interventions. Standardized exercise shortened the bleeding time by 19% (p < 0.001) and 16% (p < 0.001) before intervention and after lovastatin treatment, respectively. After K-85 alone or in combination with lovastatin, the exercise-induced shortening of the bleeding time was totally inhibited, which may reflect a favorable influence of fish oil on the platelet-vessel wall interaction in these high-risk patients.

Female sex hormones and platelet/endothelial cell interactions

The effects of estradiol and progesterone added to the growth medium of human umbilical vein endothelial cells for 72 h on the formation and release of prostacyclin were investigated. The influence on collagen-induced platelet aggregation and on the platelet formation of thromboxane A2 following aggregation, of the growth medium collected before and after thrombin stimulation of the endothelial cells, was studied simultaneously. Under basal conditions, endothelial cells grown with progesterone released significantly less prostacyclin into the growth medium than did controls (p less than 0.05). Following thrombin stimulation, endothelial cells grown with estradiol (p less than 0.05) or a combination of estradiol and progesterone (p less than 0.01) contained significantly less prostacyclin than controls. No significant effects on the platelet aggregation or platelet thromboxane formation could be found. This study indicates a lowering effect of both female sex hormones on the endothelial cell prostacyclin formation and release. This may be of significance for the increased risk of vascular disease in pregnant women and oral contraceptive users, but can hardly explain the consequences of the hormonal loss occurring at the menopause.