A Novel C1-Esterase Inhibitor Oxygenator Coating Prevents FXII Activation in Human Blood.

The limited hemocompatibility of currently used oxygenator membranes prevents long-term use of artificial lungs in patients with lung failure. To improve hemocompatibility, we developed a novel covalent C1-esterase inhibitor (C1-INH) coating. Besides complement inhibition, C1-INH also prevents FXII activation, a very early event of contact phase activation at the crossroads of coagulation and inflammation. Covalently coated heparin, as the current anticoagulation gold standard, served as control. Additionally, a combination of both coatings (C1-INH/heparin) was established. The coatings were tested for their hemocompatibility by dynamic incubation with freshly drawn human whole blood. The analysis of various blood and plasma parameters revealed that C1-INH-containing coatings were able to markedly reduce FXIIa activity compared to heparin coating. Combined C1-INH/heparin coatings yielded similarly low levels of thrombin-antithrombin III complex formation as heparin coating. In particular, adhesion of monocytes and platelets as well as the diminished formation of fibrin networks were observed for combined coatings. We could show for the first time that a covalent coating with complement inhibitor C1-INH was able to ameliorate hemocompatibility. Thus, the early inhibition of the coagulation cascade is likely to have far-reaching consequences for the other cross-reacting plasma protein pathways.

New agents for thromboprotection. A role for factor XII and XIIa inhibition.

Blood coagulation is essential for hemostasis, however excessive coagulation can lead to thrombosis. Factor XII starts the intrinsic coagulation pathway and contact-induced factor XII activation provides the mechanistic basis for the diagnostic aPTT clotting assay. Despite its function for fibrin formation in test tubes, patients and animals lacking factor XII have a completely normal hemostasis. The lack of a bleeding tendency observed in factor XII deficiency states is in sharp contrast to deficiencies of other components of the coagulation cascade and factor XII has been considered to have no function for coagulation in vivo. Recently, experimental animal models showed that factor XII is activated by an inorganic polymer, polyphosphate, which is released from procoagulant platelets and that polyphosphate-driven factor XII activation has an essential role in pathologic thrombus formation. Cumulatively, the data suggest to target polyphosphate, factor XII, or its activated form factor XIIa for anticoagulation. As the factor XII pathway specifically contributes to thrombosis but not to hemostasis, interference with this pathway provides a unique opportunity for safe anticoagulation that is not associated with excess bleeding. The review summarizes current knowledge on factor XII functions, activators and inhibitors.

Oversulfated chondroitin sulfate inhibits the complement classical pathway by potentiating C1 inhibitor.

Oversulfated chondroitin sulfate (OSCS) has become the subject of multidisciplinary investigation as a non-traditional contaminant in the heparin therapeutic preparations that were linked to severe adverse events. In this study, it was found that OSCS inhibited complement fixation on bacteria and bacterial lysis mediated by the complement classical pathway. The inhibition of complement by OSCS is not due to interference with antibody/antigen interaction or due to consumption of C3 associated with FXII-dependent contact system activation. However, OSCS complement inhibition is dependent on C1 inhibitor (C1inh) since the depletion of C1inh from either normal or FXII-deficient complement plasma prevents OSCS inhibition of complement activity. Surface plasmon resonance measurements revealed that immobilized C1inhibitor bound greater than 5-fold more C1s in the presence of OSCS than in presence of heparin. Although heparin can also inhibit complement, OSCS and OSCS contaminated heparin are more potent inhibitors of complement. Furthermore, polysulfated glycosaminoglycan (PSGAG), an anti-inflammatory veterinary medicine with a similar structure to OSCS, also inhibited complement in the plasma of dogs and farm animals. This study provides a new insight that in addition to the FXII-dependent activation of contact system, oversulfated and polysulfated chondroitin-sulfate can inhibit complement activity by potentiating the classical complement pathway regulator C1inh. This effect on C1inh may play a role in inhibiting inflammation as well as impacting bacterial clearance.

The effects of aspirin and nonselective beta blockade on the acute prothrombotic response to psychosocial stress in apparently healthy subjects.

We hypothesized that the 2 cardiovascular drugs aspirin and propranolol attenuate the prothrombotic response to acute psychosocial stress relative to placebo medication. We randomized 56 healthy subjects, double-blind, to 5-day treatment with an oral dose of either 100 mg of aspirin plus 80 mg of propranolol combined, single aspirin, single propranolol, or placebo medication. Thereafter, subjects underwent a 13-minute psychosocial stressor. Plasma levels of von Willebrand factor antigen (VWF:Ag), fibrinogen, coagulation factor VII (FVII:C) and XII (FXII:C) activity, and D-dimer were determined in blood samples collected immediately pre- and post-stress and 45 minutes post-stress. The stress-induced changes in prothrombotic measures were adjusted for gender, age, body mass index, mean arterial blood pressure, smoking status, and sleep quality. There was an increase in VWF:Ag levels from immediately pre-stress to 45 minutes post-stress in the placebo group relative to the 3 subject groups with verum medication (P's

Changes of plasma activated Factor XII type A (XIIaA) concentrations following percutaneous coronary intervention (PCI).

BACKGROUND: Recent research has demonstrated that in-vivo XIIa exists in a number of different types and that treatment with tenecteplase increases the plasma concentration of XIIaA. Only limited data exist on changes in activated Factor XII (XIIa) levels following mechanical revascularisation, such as percutaneous coronary intervention (PCI). METHODS: Citrated blood samples were obtained from 31 PCI-treated patients admitted with ST-elevation myocardial infarction (STEMI) and 20 patients undergoing elective PCI. Samples were taken immediately before the invasive procedure, 30-90 min after PCI and (in patients undergoing primary PCI) 4-6 days following intervention. Additional samples were taken after angiography, just prior to the follow-on PCI procedure, in 16 of the patients undergoing elective PCI, to investigate possible effects of contrast fluid and heparin. XIIa measurements were performed using 2 ELISA assays designed to preferentially measure different types of XIIa; XIIaA and XIIaR. RESULTS: In the group undergoing primary PCI, XIIaA showed a significant increase from 68 (48-93) pM in the pre-treatment sample to 100 (75-123) pM [median and 25- and 75% percentiles] in the 30-90-min post-treatment sample (p < 0.001), returning to pre-intervention levels by day 4-6. A similar increase in XIIaA was obtained in patients undergoing elective PCI. In contrast, no significant changes in XIIaR concentration were observed. Whilst XIIaA concentrations remained unchanged in 6 non-heparinised patients undergoing elective coronary angiography, XIIaA levels rose significantly from 56 (51-75) pM to 98 (71-125) pM [median and 25- and 75% percentiles], (p < 0.01) in 10 patients after the addition of heparin. CONCLUSION: A significant short-lasting increase in specific types of XIIa (namely XIIaA) was observed following PCI. These increases are most likely induced by the concomitant treatment with heparin.

Heparin modulation of human plasma kallikrein on different substrates and inhibitors.

The interplay of different proteases and glycosaminoglycans is able to modulate the activity of the enzymes and to affect their structures. Human plasma kallikrein (huPK) is a proteolytic enzyme involved in intrinsic blood clotting, the kallikrein-kinin system and fibrinolysis. We investigated the effect of heparin on the action, inhibition and secondary structure of huPK. The catalytic efficiency for the hydrolysis of substrates by huPK was determined by Michaelis-Menten kinetic plots: 5.12x10(4) M-1 s-1 for acetyl-Phe-Arg-p-nitroanilide, 1.40x10(5) M-1 s-1 for H-D-Pro-Phe-Arg-p-nitroanilide, 2.25x10(4) M-1 s-1 for Abz-Gly-Phe-Ser-Pro-Phe-Arg-Ser-Ser-Arg-Gln-EDDnp, 4.24x10(2)M-1 s-1 for factor XII and 5.58x10(2) M-1 s-1 for plasminogen. Heparin reduced the hydrolysis of synthetic substrates (by 2.0-fold), but enhanced factor XII and plasminogen hydrolysis (7.7- and 1.4-fold, respectively). The second-order rate constants for inhibition of huPK by antithrombin and C1-inhibitor were 2.40x10(2) M-1 s-1 and 1.70x10(4) M-1 s-1, respectively. Heparin improved the inhibition of huPK by these inhibitors (3.4- and 1.4-fold). Despite the fact that huPK was able to bind to a heparin-Sepharose matrix, its secondary structure was not modified by heparin, as monitored by circular dichroism. These actions may have a function in the control or maintenance of some pathophysiological processes in which huPK participates.

Folate deficiency-induced hyperhomocysteinemia attenuates, and folic acid supplementation restores, the functional activities of rat coagulation factors XII, X, and II.

Hyperhomocysteinemia (HH) constitutes a risk marker for thrombosis, but the pathophysiological mechanisms in thrombus formation are still unresolved. We investigated the influence of HH on single coagulation factor functions and evaluated the platelet GpIIb/IIIa receptor function in HH-induced changes in whole-blood coagulation profiles (WBCP). Three groups of 12 rats were investigated: control rats, folate deficient-HH (FD-HH) rats, and treated rats. Plasma total homocysteine was 7.1 micromol/L in controls, 31.3 micromol/L in FD-HH rats, and 7.6 micromol/L in treated rats. Factor (F) II:C, FX:C, and FXII:C were reduced in FD-HH rats compared with controls and normalized in treated rats (P < 0.05). FVII:C activity did not differ among the groups. Factor VIII:C activity was greater in FD-HH rats than in controls (P < 0.05). Blockage of the platelet GpIIb/IIIa receptor by Integrilin (Schering-Plough A/S) did not abolish the FD-HH-induced increase in whole-blood coagulation velocity, irrespective of the dosage of Integrilin. In conclusion, FD-HH reduced the functional activities of FXII:C, FX:C and FII:C, whereas FVII:C was unchanged and FVIII:C increased. These findings may partially explain the prolonged initiation phase of WBCP in FD-HH rats. The changes in single coagulation factor functions and WBCPs in FD-HH rats were reversed by treatment with folic acid.

Role of bradykinin B2-receptor in the sympathoadrenal effects of 'new pressor protein' related to human blood coagulation factor XII fragment.

BACKGROUND: Human plasma new pressor protein (NPP) increases blood pressure, heart rate and plasma adrenal medullary catecholamines in bioassay rats - all potentiated by angiotensin-converting enzyme (ACE) inhibition. High plasma NPP activity has been found in haemodialysis patients with hypertension. OBJECTIVE: To investigate whether the bradykinin B2-receptor mediates the effects of NPP. METHODS AND RESULTS: Male Wistar bioassay rats were anaesthetized with inactin, ganglion blocked with pentolinium and injected intravenously (i.v.) with human NPP (20 microl plasma equivalent) or bradykinin (100 ng/kg). Both NPP and bradykinin increased systolic (SBP) and diastolic (DBP) blood pressures, heart rate and plasma adrenaline and noradrenaline concentrations. All these responses were potentiated by the ACE inhibitor, captopril (10 mg/kg i.v.), but not by antagonism of the angiotensin II type 1 receptor with losartan (10 mg/kg i.v.). Administration of the bradykinin B2-receptor antagonist, HOE-140 (20 microg/kg i.v.), significantly attenuated the peak NPP responses as follows: SBP from 58 +/- 3 to 40 +/- 4 mmHg (decrease of 30%; P < 0.05); DBP from 22 +/- 4 to 10 +/- 1 mmHg (decrease of 55%; P < 0.05); heart rate from 124 +/- 8 to 28 +/-6 beats/min (decrease of 77%; P < 0.05); plasma adrenaline from 14297 +/- 2477 to 3318 +/- 1105 pg/ml (decrease of 77%; P < 0.05) and noradrenaline from 505 +/- 66 to 77 +/-29 pg/ml (decrease of 85%; P < 0.05). CONCLUSIONS: The haemodynamic and sympathoadrenal effects of NPP involve substantial mediation by the bradykinin B2-receptor, in addition to other mechanisms.

The implementation of factor analysis for the evaluation of selected blood parameter changes induced by hyperbaric exposure.

This paper discusses the application of factor analysis when used to compare selected blood parameter (a three-parameter smear, hematocrit, C3c, C4, IgG, IgA, IgM, CRP, fibrinogen and the level of factor XII) properties, just before, and after exposure to pressure changes, and 24-hours after the completion of decompression. To-date the most popular method of statistical analysis was based only on investigation of the significance of the separated individual parameters. This factor analysis that has not been applied previously in the analysis of such problems, enabled the neutral hierarchic evaluation of the significant parameter changes within their chosen range, and mutual relationships. It seems that the application of this method is purposeful and it can be an objective tool for evaluating the significance of changes in blood constituency induced by pressure.

[Contact phase activation can occur with certain types of activated carbon]. / Attivazione della fase contatto, durante emodiafiltrazione con la tecnica HFR, può verificarsi con alcuni tipi di carbone attivato.

HFR is an integrated hemodiafiltration system that utilizes a double chamber filter to separate convection from diffusion. The ultrafiltrate is regenerated by passage through a sorbent cartridge made up of resin and activated carbon. A small percentage of patients using this technique had gastrointestinal symptoms that included nausea/vomiting, diarrhea and/or stomach cramps approximately 1-2 hours after the start of HFR. We undertook a series of investigations to try and elucidate the cause of these reactions. Since the majority of the patients were taking ACE inhibitors, attention was focused on contact phase activation. Healthy and uremic plasma were incubated with different components of the HFR circuit. The activated carbon caused a moderate activation of factor XII and production of kallikrein, while there was no activation for the lines, double filter or resin. Patients taking ACE inhibitors may be at risk for treatments involved with contact phase activation as ACE inhibitors also block the degradation of bradykinin. A new sorbent cartridge has now been developed that contains only resin.

Glycosaminoglycans affect the interaction of human plasma kallikrein with plasminogen, factor XII and inhibitors.

Human plasma kallikrein, a serine proteinase, plays a key role in intrinsic blood clotting, in the kallikrein-kinin system, and in fibrinolysis. The proteolytic enzymes involved in these processes are usually controlled by specific inhibitors and may be influenced by several factors including glycosaminoglycans, as recently demonstrated by our group. The aim of the present study was to investigate the effect of glycosaminoglycans (30 to 250 micro/ml) on kallikrein activity on plasminogen and factor XII and on the inhibition of kallikrein by the plasma proteins C1-inhibitor and antithrombin. Almost all available glycosaminoglycans (heparin, heparan sulfate, bovine and tuna dermatan sulfate, chondroitin 4- and 6-sulfates) reduced (1.2 to 3.0 times) the catalytic efficiency of kallikrein (in a nanomolar range) on the hydrolysis of plasminogen (0.3 to 1.8 microM) and increased (1.9 to 7.7 times) the enzyme efficiency in factor XII (0.1 to 10 microM) activation. On the other hand, heparin, heparan sulfate, and bovine and tuna dermatan sulfate improved (1.2 to 3.4 times) kallikrein inhibition by antithrombin (1.4 microM), while chondroitin 4- and 6-sulfates reduced it (1.3 times). Heparin and heparan sulfate increased (1.4 times) the enzyme inhibition by the C1-inhibitor (150 nM).

Anti-c5a ameliorates coagulation/fibrinolytic protein changes in a rat model of sepsis.

Sepsis and trauma are the two most common causes of disseminated intravascular coagulation and multiple organ dysfunction syndrome. Both disseminated intravascular coagulation and the systemic inflammatory response syndrome often lead to multiple organ dysfunction syndrome. The current studies have evaluated the relationship between the anaphylatoxin, C5a, and changes in the coagulation/fibrinolytic systems during the cecal ligation and puncture (CLP) model of sepsis in rats. CLP animals treated with anti-C5a had a much improved number of survivors (63%) compared to rats treated with pre-immune IgG (31%). In CLP rats treated with pre-immune IgG there was clearly increased procoagulant activity with prolongation of the activated partial thromboplastin time and prothrombin time, reduced platelet counts, and increased levels of plasma fibrinogen. Evidence for thrombin formation was indicated by early consumption of factor VII:C, subsequent consumption of factors XI:C and IX:C and anti-thrombin and increased levels of the thrombin-anti-thrombin complex and D-dimer. Limited activation of fibrinolysis was indicated by reduced plasma levels of plasminogen and increased levels of tissue plasminogen activator and plasminogen activator inhibitor. Most of these parameters were reversed in CLP rats that had been treated with anti-C5a. Production of C5a during sepsis may directly or indirectly cause hemostatic defects that can be reduced by blockade of C5a.

Changes of selected morphotic parameters and blood plasma proteins in blood of divers after a single short-time operational heliox exposure.

In the Polish Navy, deep-water dives, performed for the needs of the maritime industry, are conducted using our own national technology and trimix as a breathing medium. In this paper are presented the results obtained during a short-time deep-water diving test using the principles of US Navy technology, combined with the use of diving equipment type AF-2 and heliox-type breathing mixture in the open circuit. In the performed examinations changes in clinical parameters were assessed viz.: blood morphology, hematocrit level, concentration of C3c, C4, IgG, IgA, IgM, CRP, concentration of fibrinogen and factor XII level, obtained 30 minutes prior to commencement, immediately after completion, and 24 hours after termination of the exposure. The results thus generated were subjected to a preliminary analysis by the description of trends observed. It was revealed that the diving technology employed did not generate substantial changes in the examined parameters of blood in divers, and the increase of neutrophils, blood platelets and fibrinogen concentration in the blood plasma immediately after diving is of temporary character, being a typical reaction observed during diving.

Effects of diets containing olive oil, sunflower oil, or rapeseed oil on the hemostatic system.

Various studies have already shown that the fatty acid composition of dietary fat has different effects on hemostasis and platelet function. However, knowledge on this topic is incomplete. In the present study, fifty-eight healthy students received either a 4-week rapeseed oil [high content of monounsaturated fatty acids (MUFA) and high n-3/n-6 PUFA ratio], an olive oil (high content of MUFA, low n-3/n-6 PUFA ratio) or a sunflower oil (low content of MUFA, low n-3/n-6 PUFA ratio) diet. In each group, effects on hemostatic parameters were compared with a wash-in diet rich in saturated fatty acids with respect to intermediate-time effects on the hemostatic system and platelet function. With the olive oil diet, a reduction of coagulation factors VIIc, XIIc, XIIa, and Xc was found, whereas sunflower oil led to lower values of coagulation factors XIIc, XIIa, and IXc. In all study groups levels of plasmin-alpha2-antiplasmin were lower in week 4 than at baseline. Lower fibrinogen binding on platelets was found after the sunflower oil diet, whereas expression of CD62 and spontaneous platelet aggregation were slightly higher after the olive oil diet. However, given the major differences in the fatty acid compositions of the diets, the differences between the groups with respect to hemostasis tended to be small. Therefore, the clinical significance of the present findings remains to be evaluated.

Factor XII-dependent contact activation on endothelial cells and binding proteins gC1qR and cytokeratin 1.

Although proteins of the kinin-forming pathway are bound along the surface of endothelial cells, the mechanism of activation of this proteolytic cascade is unclear. Endothelial cell surface proteins, gC1qR and cytokeratin 1, are capable of binding Factor XII and high molecular weight kininogen (HK) in a zinc-dependent reaction thus we considered the possibility that these proteins might catalyze initiation of the cascade. Incubation of Factor XII, prekallikrein, and HK with gC1qR or cytokeratin 1 leads to a zinc-dependent and Factor XII-dependent conversion of prekallikrein to kallikrein. We also demonstrate that normal plasma is capable of activating upon interaction with the cells whereas plasma deficient in Factor XII, prekallikrein and HK do not activate. Normal plasma activation was inhibitable by antibody to gC1qR and cytokeratin 1. Thus, gC1qR and cytokeratin 1, represent potential initiating surfaces for activation of the plasma kinin-forming cascade and may do so as a result of their expression along cell surfaces.

Studies of adsorption, activation, and inhibition of factor XII on immobilized heparin.

The aim of the present investigation was to clarify whether immobilized heparin does, as previously suggested, prevent triggering of the plasma contact activation system. Purified FXII in the absence or presence of antithrombin and/or C1 esterase inhibitor as well as plasma was exposed for 1 to 600 seconds to a surface modified by end-point immobilization of heparin. With purified reagents, a process including surface adsorption and activation of FXII occurred within 1 second. In the presence of antithrombin, the resulting surface-bound alpha-FXIIa was inhibited within that time. Likewise, the adsorption of native FXII from plasma was a rapid process. However, the inhibition of surface-bound alpha-FXIIa was slightly slower than with purified components. Nevertheless, neither beta-FXIIa nor FXIa were found in the plasma phase. Exposure of a surface prepared from heparin molecules, lacking antithrombin binding properties, to plasma resulted in surface-bound alpha-FXIIa within 1 second. In the liquid phase, beta-FXIIa was detected after 2.5 seconds and, 12 seconds later, FXIIa and FXIa in complex with the C1 esterase inhibitor appeared. Addition of heparin to plasma prior to surface exposure did not prevent activation of surface-bound FXII, nor did it increase the beta-FXIIa inhibition rate and prevent FXI activation in plasma, although beta-FXIIa and FXIa-AT complex formation occurred. It is concluded that surface-immobilized heparin, unlike heparin in solution, effectively inhibits the initial contact activation enzymes by an antithrombin-mediated mechanism, thereby suppressing the triggering of the intrinsic plasma coagulation pathway.

Heparin coating of extracorporeal circuits inhibits contact activation during cardiac operations.

OBJECTIVE: Heparin coating reduces complement activation on the surface of extracorporeal circuits. In this study we investigated its effect on activation of the contact system in 30 patients undergoing coronary artery bypass grafting with the use of a heparin-coated (Duraflo II, Baxter Healthcare Corp., Edwards Division, Santa Ana, Calif.; n = 15) or an uncoated extracorporeal circuit (n = 15). METHODS: Plasma markers that reflect activation of contact (kallikrein-C1-inhibitor complexes), coagulation (prothrombin fragments F1 + 2), or fibrinolytic (plasmin-alpha 2-antiplasmin complexes) systems were determined before and during the operation. The generation of kallikrein-C1-inhibitor complexes was reduced by 62% (p = 0.06) after the onset of cardiopulmonary bypass and by 43% (p = 0.026) after the cessation of bypass in the group in which a heparin-coated circuit was used compared with the group in which the circuit was uncoated. Generation was reduced by 58% (p = 0.06) when the ratio of kallikrein-C1-inhibitor to prekallikrein after onset of bypass was considered. We detected significant increases in F1 + 2 levels in both groups and increases in plasmin-alpha 2-antiplasmin complexes in the heparin-coated group at cessation of bypass, but no intergroup differences were observed. Thus use of heparin-coated extracorporeal circuits during cardiac operations reduces formation of kallikrein-C1-inhibitor complexes when compared with use of uncoated circuits. The heparin coating is not accompanied by similar reductions in coagulation or fibrinolysis, suggesting that thrombin and plasmin formation during cardiopulmonary bypass occurs mainly independently of the contact system activation.

Randomized placebo-controlled study of the effects of simvastatin on haemostatic variables, lipoproteins and free fatty acids. The Oxford Cholesterol Study Group.

The Oxford Cholesterol Study is a randomized placebo-controlled trial designed primarily to assess the effects of simvastatin on blood cholesterol levels and side-effects in preparation for a large, long-term trial of the effects of cholesterol-lowering drug therapy on mortality. At present there is only limited evidence from randomized comparisons of the effects of HMG-CoA reductase inhibitors, such as simvastatin, on thrombogenic, as distinct from atherogenic, pathways in coronary heart disease. The present sub-study was carried out to assess the effects of simvastatin on a range of haemostatic variables, as well as on free fatty acids and on lipoprotein fractions not studied in detail previously. At an average of about 2 years after starting study treatment, non-fasting blood samples were obtained from a sequential sample of 162 participants who had been randomly allocated to receive 40 mg (54 patients) or 20 mg (57 patients) daily simvastatin or matching placebo treatment (51 patients). Only patients who reported taking their study treatment and who were not known to be diabetic or to be taking some other lipid lowering treatment were to be included. The principal comparisons were to be of those allocated simvastatin (i.e. 20 and 40 mg doses combined) vs those allocated placebo. Among patients allocated simvastatin, marginally significant lower factor VII antigen levels (12.10% +/- 6.08 of standard; 2P < 0.05) and non-significantly lower factor VII coagulant activity (8.24% +/- 4.99 of standard) and fibrinogen concentrations (0.10 +/- 0.08 g. l-1) were observed. In contrast, plasminogen activator inhibitor activity was significantly higher (2.62 +/- 1.03 IU; 2P < 0.01) among patients allocated simvastatin. No significant differences were seen in the other haemostatic factors studied (e.g. prothrombin fragment 1.2, factor XII and C1 inhibitor). Total free fatty acid concentration was marginally significantly reduced (2P = 0.02) with simvastatin, but none of the reductions in individual free fatty acids was significant. Lipoprotein fractions were only measured among patients allocated 40 mg daily simvastatin or placebo. Compared with placebo, simvastatin produced significant decreases not only in LDL cholesterol (1.74 +/- 0.15 mmol.1(-1): 2P < 0.0001) but also in VLDL cholesterol (0.28 +/- 0.08 mmol.1(-1); 2P < 0.001) and IDL cholesterol (0.17 +/- 0.03 mmol.1(-1); 2P < 0.0001). There were also lower triglyceride levels associated with LDL (0.07 +/- 0.01 mmol.1(-1); 2P < 0.0001), IDL (0.03 +/- 0.01 mmol.1(-1); 2P < 0.01) and VLDL (0.27 +/- 0.14; 2P = 0.05). The effects of simvastatin on haemostatic variables appear to be far less marked than its lipid effects. Given the associations of haemostatic factors with coronary heart disease incidence, larger randomized comparisons of the HMG-CoA reductase inhibitors (and of the newer fibrates which may produce greater effects) are needed to provide more reliable estimates of the extent to which they influence these variables.

Homozygous type I plasminogen deficiency.

Homozygous type I plasminogen (Plg) deficiency has not been described in human subjects so far. Ligneous conjunctivitis is a rare and unusual form of chronic pseudomembranous conjunctivitis of unknown etiology. Here we report for the first time on homozygous type I Plg deficiency in three unrelated female patients who suffered from ligneous conjunctivitis and additional pseudomembranous lesions of other mucous membranes. The disease is caused by massive fibrin depositions within the "extravascular space" of mucous membranes because of absent clearance by plasmin. Infusions of albumin, fresh frozen plasma, or Lys-plasminogen (Lys-Plg) into two of the three patients revealed normal Plg activation capacity in these patients. The absence of fibrinolytic activity could therefore be shown to be due to Plg deficiency. Similar studies in the third patient have not been completed. In the two patients studied so far, infusions of Lys-Plg resulted in prompt and adequate Plg recovery with a short half-life and high amounts of plasmin-antiplasmin complexes and D-dimer. One patient additionally revealed an inherited partial factor XII deficiency. Functionally, this factor XII deficiency did not interfere with Plg activation. However, there may be a pathway of Plg activation in this patient via the prekallikrein C1-INH system.

Explicit constants for the dextran-sulfate-mediated activation and autoactivation of purified human factor XII (Hageman factor).

The autoactivation kinetics of purified factor XII (FXII) in the presence of dextran sulfate of 500000 Da was reexamined assuming the existence of two preceding activation steps. Kinetics were numerically simulated by using rate and equilibrium constants related to surface-bound species. Relevant feature parameters related to the polymer (number of binding sites and concentration, dissociation constant of FXII from the surface) and the zymogen (concentration. Michaelis-Menten constant of the autoactivation reaction, catalytic rate constant) were accordingly introduced in the mechanisms. Depending on the rate-limiting step i.e. whether the polymer or FXII predominates, numerical simulation analysis led to obtain for the observed autoactivation rate constant (kobs) two explicit expressions which included the contributing variables. One of the two proposed models was in good accordance with the experimental data obtained in this study and with others published previously. We were able to estimate the mean number of the FXII-activating sites supported by the polymer chains (220) and the equilibrium dissociation constant of FXII from the surface (1 microM). Further treatment led us to determine surface-concentration-independent constants (K(m) = 2510 nM and kcat = 0.01 s-1), as well as the rate constant (k1 = 1.6 x 10(-4) s-1) of the postulated first-order activation rate aimed at explaining the formation of the first trace amounts of FXIIa via an intramolecular mechanism. Overall, the treatment applied to the dextran sulfate case offers a quantitative tool by which data determined in the presence of other activating materials can be rationalized.