Physiological mechanisms in coagulation and fibrinolysis

Effects of lipopolysaccharide on human endothelial cells in culture

Lipopolysaccharide (LPS) in concentrations up to 10 micrograms/ml did not induce detectable direct cytotoxicity in human umbilical vein, pulmonary artery, or pulmonary vein endothelial cells. By contrast, significant cytotoxicity was observed in bovine aortic endothelial cells exposed to LPS 0.01 micrograms/ml. Transmission electron microscopy of human umbilical vein cells exposed to LPS 10 micrograms/ml for 4 days revealed no significant ultrastructural abnormalities compared to control cells. Whereas human umbilical vein endothelial cell cytotoxicity was observed when neutrophils were stimulated with phorbol myristate acetate, LPS-stimulated neutrophils did not induce significant cytotoxicity even in the presence of fresh human serum as a complement source. Moreover, human umbilical vein endothelial cell factor VIII-antigen and fibronectin release, angiotensin-converting enzyme activity, and PGI2 release were unaffected by a 24-hour exposure to LPS. Cytotoxicity, however, was produced when human umbilical vein endothelial cells were coincubated with LPS and cycloheximide. The proliferation of human umbilical vein endothelial cells was also inhibited after prolonged, continuous exposure to LPS 10 micrograms/ml. We conclude that LPS with or without complement or neutrophils does not induce significant human endothelial cell lysis or detachment. Moreover, brief exposure to LPS has minimal, direct effect on several functions of human endothelial cells in vitro.

A family with reduced plasminogen activator activity in blood associated with recurrent venous thrombosis

6 members of a family with a tendency to thrombosis and defective fibrinolysis were examined. After stimulation of plasminogen activator release from the vessel wall by local venous occlusion or by submaximal physical exercise, they had a lower plasminogen activator activity in blood than a healthy control group (P less than 0.01). 5 of the examined members suffered from recurrent venous thrombosis. The defect appeared to be autosomal dominant.

Deficiencies of protein C, an inhibitor of blood coagulation

Protein C is a vitamin-K-dependent plasma glycoprotein that when activated inhibits coagulation by selectively inactivating the active forms of factor V and factor VIII. A specific antiserum to protein C has been raised, and plasma protein C levels have been measured by means of an electroimmunoassay in several physiological and pathological conditions. In 60 healthy adults there were no differences in protein C related to age or sex; protein C levels ranged from 72 to 139% of values in a normal plasma pool. Low levels were found in 12 healthy full-term newborn infants; the levels in 20 women in the last trimester of normal pregnancy were no different from those in healthy non-pregnant women. In 58 patients with chronic liver diseases protein C levels were lower than those in healthy subjects, in degrees roughly proportional to the severity of the disease. Protein C levels were very low in 21 patients with the disseminated intravascular coagulation syndrome, particularly in those who had evidence of consumption coagulopathy. Very low levels were also found, however, in 20 patients with adult respiratory distress syndrome without consumption coagulopathy. Acquired defects of protein C developed after surgery in the patients operated on for malignancies, after major abdominal operations for benign conditions, and also after relatively minor procedures such as appendicectomy and hernia repair. These findings indicate that protein C deficiencies occur in several conditions associated with increased tendency to thrombosis.

Profound sensorineural hearing loss in polyarteritis nodosa. An atypical case of Cogan's syndrome

Parameters of importance for the development of thrombosis were investigated in a patient with polyarteritis nodosa (PAN) and profound sensorineural hearing loss. During the acute phase, platelet hyperaggregability, shortened platelet survival, and decreased fibrinolytic activity were found. The possibility is discussed that the etiology of the acoustico-vestibular symptoms in this patient could be an inner ear thromboembolic disorder. It is suggested that platelet functions and fibrinolytic activity should be investigated in patients with acoustico-vestibular symptoms and PAN or other systemic diseases. If abnormalities are found, specific platelet inhibitory and/or fibrinolysis-increasing treatment should be considered as an addition to the conventional medical treatment.

The effect of L-asparaginase on antithrombin, plasminogen, and plasma coagulation during therapy for acute lymphoblastic leukemia

Hemostatic function was studied sequentially in 12 children receiving L-asparaginase, vincristine, and prednisone as remission induction chemotherapy for acute lymphoblastic leukemia. The three-week period of L-asparaginase therapy was characterized by progressive decreases in plasma antithrombin, plasminogen, and fibrinogen concentrations, and by progressive increases in plasma clotting times (prothrombin time, partial thromboplastin time, thrombin time). Platelet counts rose rapidly during the third and fourth weeks of therapy as bone marrow remission was achieved. Factor V levels increased steadily during a five-week period, perhaps related to vincristine or prednisone therapy. Recent reports of thrombosis and hemorrhage in children and adults receiving L-asparaginase may be explained by this complex set of abnormalities in coagulation and coagulation control.

Oral contraceptives, clotting factors, and thrombosis

Oral contraceptives (OCs) raise the plasma levels of some clotting factors, especially factor VII. Until recently, however, there has been no evidence for a relationship between high levels of clotting factor and the onset of clinically manifest vascular disease. It has not been established, on a preliminary basis, that high levels of factors VII and VIII and of fibrinogen in men are associated with an increased risk of death from cardiovascular disease. There is a strong relationship between OC estrogen dose and the level of factor VII, a clotting factor with a number of other characteristics, suggesting that high levels would be thrombogenic. A strong relationship also exists between OC estrogen dose and the risk of thromboembolism. The thrombotic effects of OC are probably mediated, at least partly, through their effects on the coagulation system.

Bleeding time and scoliosis

Collagen abnormalities in idiopathic scoliosis are on record. Since there is a correlation between the platelet aggregating power of the collagen and the bleeding time in patients with scoliosis, the bleeding time was studied in 195 cases with scoliosis and in 318 controls. The bleeding time was longer in the females, especially in those with idiopathic scoliosis (n = 149). Patients with paralytic scoliosis (n = 5) also had a significantly longer bleeding time than non-scoliotic controls. The patients with congenital scoliosis (n = 13) did not differ significantly from the controls or from patients with idiopathic scoliosis. The bleeding time in idiopathic scoliosis did not vary with age or magnitude of the scoliosis. Our data support the view that collagen abnormalities play a role not only in the aetiology of idiopathic scoliosis, but also in other forms of scoliosis.

Effect of captopril on inactive renin and contact phase of coagulation system

It has been suggested that a Factor XII-plasma Prekallikrein dependent pathway might play an important role in the activation of inactive renin. Since Captopril has the potential to affect the kinin-kallikrein system, we have studied in a group of 16 patients with essential hypertension its acute effect both on the levels of active, inactive and total renin, and on the contact phase of the coagulation system. Our results show that a single dose of Captopril (25 mg) induces a rapid and persistent increase of active and total renin, while inactive renin tends to decrease. Together with blood pressure, plasma Prekallikrein(PK), Factor XII(FXII) and Factor XI(FXI) concomitantly decrease, although not significantly, and their values seem to return to basal levels soonafter. However, no correlation was found at any time between the levels of any of these coagulation factors, including PK, and those of inactive, active or the ratio inactive/total renin. In spite of that, it is still possible that an activation of PK, which is likely to occur under Captopril administration, may affect at least the conversion of vessel-bound prorenin rather than the circulating form.

Intracranial bleeding during therapy with L-asparaginase in childhood acute lymphocytic leukemia

Two patients developed clinical features of intracranial bleeding--which were confirmed by computerized axial tomograms--during their induction therapy for acute lymphocytic leukemia. Coagulation studies showed clotting abnormalities including severe hypofibrinogenemia. These findings most probably were related to the effect of L-asparaginase which was part of the treatment protocol. Central nervous system leukemia, intrathecal chemotherapy, cranial irradiation, extreme leukocytosis, or thrombopenia at the time of diagnosis or day of stroke did not appear to be predisposing factors in these cases.

Effects of diet and gliclazide on the haemostatic system of non-insulin-dependent diabetics

The effect of the sulphonylurea gliclazide on tests of haemostatic function was studied in 14 newly diagnosed non-insulin-dependent diabetics. After two months' treatment with diet alone 11 of the 14 were given gliclazide; the three others remained on dietary treatment. Compared with pretreatment values, significant reductions in platelets retention, factor VIII-related antigen, factor VIII coagulant activity, and plasma heparin neutralising activity accompanied a fall in the plasma glucose concentration due to either diet alone or diet and gliclazide. The beneficial effects of gliclazide on platelet abnormalities seem likely to be due to its hypoglycaemic action rather than to any direct effect on haemostatic function.

Alterations of factor VIII von Willebrand factor in clinical conditions associated with an increase in its plasma concentration

Factor VIII-related antigen (VIIIR:Ag) was consistently higher than factor-VIII procoagulant activity (VIII:C) in 57 patients with clinical conditions characterized by acute-phase reactions. Two different methods for measuring VIII:C (one- and two-stage assays) and VIIIR:Ag (electroimmunodiffusion and immunoradiometric assay) gave concordant results in the majority of cases. In 43% of plasma samples, crossed immunoelectrophoresis in agarose gel was characterized by the appearance of an additional, fast-moving precipitin peak which was immunologically identical with the major, slower-moving VIIIR:Ag peak. The fast-moving peak was detected in all the patients with clinical conditions typically associated with increased plasma proteolysis (DIC, acute pancreatitis, during thrombolytic therapy). It was present in a smaller proportion of cases with liver and renal failure and malignancies and in the post-operative period. The additional VIIIR:Ag peak is thought to be the result of in vivo factor VIII/von Willebrand factor fragmentation by proteolytic enzymes.

Haemostatic changes in diabetic coma

Diabetic coma is frequently associated with thromboembolic complications. A prospective study was undertaken of the haemostatic changes occurring in 15 patients (12 with ketoacidosis, three with the hyperosmolar syndrome) during diabetic coma. When compared with the results after stabilization of the diabetes, ketoacidosis was associated with significantly higher levels of factor VIII coagulant activity, factor VIII-related antigen and fibrin degradation products, a shorter partial thromboplastin time and reduced concentrations of antithrombin III. These results suggest that in uncomplicated ketoacidosis, haematological changes occur which may reflect vascular endothelial damage and intravascular fibrin deposition. Out of three deaths, two patients (both with the hyperosmolar syndrome) had evidence of disseminated intravascular coagulation. To reduce further the mortality and morbidity from diabetic coma, controlled clinical trials of anticoagulant and antiplatelet drugs may be indicated.

Relationships between metabolic and hemostatic variables in uncomplicated diabetes

Several metabolic (HbA1, HDL-C, triglycerides) and hemostatic (VIIIR: Ag, VIII:C, B-TG variables were investigated in 35 non-obese, insulin-dependent diabetics without clinically evident vascular complications. B-TG was high but did not correlate with other metabolic and hemostatic parameters, suggesting that elevated B-TG in diabetes might be an expression of in vitro platelet activation. VIIIR: Ag and the ratio of VIIIR: Ag to VIII: C were markedly increased. There was a significant correlation of the HbA1 and HDL-C levels with VIIIR: Ag, indicating that VIIIR:Ag is another reflection of metabolic control in diabetes. Additional pathogenic mechanisms, however, appear to be involved in causing the changes in VIIIR: Ag in diabetes.

Haematological stress syndrome in atherosclerosis

Forty patients with atherosclerotic peripheral vascular disease, as compared to 29 healthy controls, showed a significant increase in platelet number and activity, a neutrophil leucocytosis, and a raised level of several acute-phase reactant proteins (fibrinogen, antithrombin III, factor VIII, and serum globulin). The hyperproteinaemia was associated with increases in plasma-, serum-, and blood-viscosity and is the likely cause of the hyperviscosity of vascular disease. These multiple haemostatic abnormalities closely resemble the non-specific, haematological stress-syndrome response to acute and chronic inflammatory disorders. In atherosclerosis also they may represent a non-specific, secondary response and neither be of aetiological significance nor reflect continuing low-grade intravascular coagulation.

Synthesis and release of factor VIII by cultured human endothelial cells

Endothelial cells (ECs) derived from human umbilical veins were cultured in order to study the physiological control of factor VIII synthesis and release. The culture media were studied from multiple replicate cultures at confluence. Factor VIII related antigen (VIIIR:Ag) and factor VIII coagulant antigen (VIII:CAg) were measured by sensitive immunoradiometric assays. De novo synthesis of factor VIII related protein (VIII:R) was quantitated by incorporation of labelled amino acids into specific protein subunits. The following agents were added to the culture medium in a range of concentrations from physiological to pharmacological: adrenaline, 5 hydroxytryptamine, 2,3-DPG, cyclic AMP, thyroxine, hydrocortisone, and human growth hormone. None of them had any effect at any concentration on the rate of accumulation of VIIIR:Ag in the culture medium. Addition of exogenous factor VIII had no effect on do novo synthesis of VIII:R. VIII:CAg was found to be stable under the conditions of culture but none was released from the ECs. Long-term monocyte cultures also failed to release VIII:CAg. It appears that VIII:R is a constitutive gene product of umbilical vein endothelial cells and that VIII:CAg is not made by these cells.

Thrombotic and hemorrhagic strokes complicating early therapy for childhood acute lymphoblastic leukemia

Sudden cerebrovascular insults occurred during or immediately following remission induction therapy in 4 children with acute lymphoblastic leukemia. In 3, cerebral infarction was due to thrombosis. In the fourth, an intracerebral hematoma developed representing either frank hemorrhaging or a hemorrhagic infarction. None of the patients had central nervous system leukemia or extreme leukocytosis at the time of diagnosis. Symptoms were obtundation, hemiparesis, seizures, and headache. The induction chemotherapy included L-asparaginase which causes deficiencies of antithrombin, plasminogen, fibrinogen, and factors IX and XI. These hemostatic abnormalities may explain the thromboses and bleeding observed in these children.

Haemostatic function and cardiovascular death: early results of a prospective study

Components of the haemostatic system which may be involved in the pathogenesis of ischaemic heart disease (IHD) were measured in the Northwick Park Heart Study. Of 1510 white men aged 40-64 at recruitment, 49 have since died. 27 died from cardiovascular disease (IHD in all but 3), 18 from cancer, and 4 from other causes. The mean recruitment levels of factor VIIc, factor VIIIc, and fibrinogen were significantly higher in those who died of cardiovascular disease than in those who survived. The independent associations of factor VIIc and fibrinogen with cardiovascular death were at least as strong as the association of blood cholesterol with cardiovascular death. A clustering of two or three high clotting-factor values (factor VIIc, factor VIIIc, and fibrinogen) was present at recruitment in 63% of those who died of cardiovascular disease, compared with 23% of those who survived. The clotting-factor results appeared to be specific for cardiovascular disease: there was no evidence that high levels of factor VIIc, factor VIIIc, and fibrinogen were associated with death from cancer. The general epidemiology of factor VIIc, factor VIIIc, and fibrinogen is consistent with their having a role in the pathogenesis of IHD.

Comparison of three methods for the estimation of plasma antithrombin

Plasma antithrombin levels were measured by clotting, immunological, and amidolytic methods on two groups of subjects: 20 normal individuals and nine patients studied serially post-operatively (hip replacement). The postoperative patients were observed for the emergence of deep-vein thrombosis using 125I-fibrinogen uptake measurements (FUT). The three methods gave similar ranges for the normal subjects, were reproducible (cv less than 5%), and detected early postoperative reduction of antithrombin levels. All three methods failed to show any significant differences in preoperative antithrombin levels between the positive and negative FUT groups. Correlation studies were performed on the pooled data from the normal and postoperative group (range 60-130% of normal; 100 samples). The best correlation (r = 0.75; P less than 0.01) was achieved with the chromogenic kit assay method versus the Mancini immunoassay technique. The thrombin agarose (total antithrombin) gel diffusion technique correlated less well with the chromogenic (r = 0.65; P less than 0.01) and Mancini immunoassay (r = 0.45; P less than 0.01) methods. It is concluded that the chromogenic kit method gives a rapid, reproducible, and specific measurement of antithrombin III. The thrombin agarose diffusion method, though not specific for antithrombin III, is a cheap and simple method to perform. The potential of the three methods for detecting the prethrombotic stage and early thrombosis is discussed.

Physical conditioning augments the fibrinolytic response to venous occlusion in healthy adults

The effects of a 10-week physical-conditioning program on fibrinolytic activity at rest and after stimulation by venous occlusion were studied in 69 healthy adults 25 to 69 years old. Physical conditioning was documented by treadmill performance, and fibrinolysis was measured with a newly developed radioenzymatic assay. Whereas fibrinolysis declined at rest from 16.2 +/- 1.3 to 11.4 +/- 0.8 units (mean +/- S.E.M.) (P = 0.0017), the increment in fibrinolysis produced by venous occlusion was increased from 21.7 +/- 2.9 to 33.8 +/- 4.7 units (P = 0.0037). This augmentation was most marked in women, persons with low initial levels of stimulated fibrinolysis, and persons with low initial physical fitness. We conclude that physical conditioning can enhance the augmentation of fibrinolytic activity that occurs in response to venous occlusion. Enhanced fibrinolysis in response to thrombotic stimuli could be an important mechanism in the beneficial effect of habitual physical activity on the risk of cardiovascular disease.

Coagulation activation and hyperviscosity in infection

A serial study of coagulation activation and whole-blood viscosity was performed on 37 patients with local or systemic bacterial infection, malaria, or a viral infection. Thrombocytopenia, without consumption of coagulation factors, was the main feature of benign tertian malaria and viral infection, whereas in septicaemia and malignant tertian malaria it was associated with activation of coagulation and fibrinolysis. Patients with evidence of intravascular coagulation showed the highest levels of factor VIII related antigen which did not correlate with fibrinogen and probably reflected vascular endothelial cell damage rather than an acute-phase protein reaction. Hyperviscosity, which has been implicated in the pathogenesis of endotoxic shock and cerebral malaria, occurred in parallel with the acute-phase rise in plasma fibrinogen. There was, however, no evidence to implicate hyperviscosity as a major causative factor in the pathogenesis of septic shock or severe infective illness.