Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.69 (APC)
 16,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We investigated the effect of activated protein C (APC) on lipopolysaccharide (LPS)-induced pulmonary vascular injury in rats to investigate the possible usefulness of APC as a treatment for adult respiratory distress syndrome. Intravenously administered LPS (5 mg/kg) significantly increased pulmonary vascular permeability. APC prevented the LPS-induced increase in pulmonary vascular permeability observed at 6 hours. Heparin plus antithrombin III (ATIII) and active site-blocked factor Xa (DEGR-Xa), a selective inhibitor of thrombin generation, inhibited LPS-induced coagulopathy but did not prevent LPS-induced pulmonary vascular injury. LPS-induced pulmonary vascular injury was significantly attenuated in rats with nitrogen mustard-induced leukocytopenia and in rats treated with ONO-5046, a potent granulocyte elastase inhibitor. Administration of LPS also increased pulmonary accumulation of leukocytes, as evaluated by measurement of myeloperoxidase activity in the lungs. APC significantly reduced LPS-induced increases in pulmonary accumulation of leukocytes at 1 hour. Neither ATIII plus heparin nor DEGR-Xa inhibited leukocyte accumulation. Active site-blocked APC (DIP-APC) prevented neither the LPS-induced pulmonary accumulation of leukocytes nor the LPS-induced increase in pulmonary vascular permeability. These results suggest that the mechanism of APC inhibition of LPS-induced pulmonary vascular injury was independent of its anticoagulant activity and was related to its ability to inhibit accumulation of leukocytes. In addition, these findings suggest that the serine protease activity of APC may be essential to its inhibitory effect on LPS-induced pulmonary accumulation of leukocytes and subsequent pulmonary vascular injury.
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PMID:Activated protein C attenuates endotoxin-induced pulmonary vascular injury by inhibiting activated leukocytes in rats. 855 86

Heparin is still the most commonly used anticoagulant in cardiac surgery necessitating cardiopulmonary bypass. In recent years, endothelial-related coagulation (e.g. thrombomodulin/protein C-system) has enlarged our knowledge of the regulation of haemostasis. In a controlled randomised study, the influence of different regimens of anticoagulation on the thrombomodulin/protein C-system was studied. Sixty patients undergoing elective coronary artery bypass grafting were randomly allocated into four groups (n = 15) to receive: 300 IU.kg-1 of heparin before bypass; 600 IU.kg-1 of heparin; 300 IU.kg-1 of heparin as bolus followed by a continuous infusion of 10 000 IU.h-1 until the end of bypass; or 600 IU.kg-1 of heparin plus 'high dose' aprotinin (2 million IU of aprotinin before bypass, 500 000 IU.h-1 until the end of the operation and 2 million IU added to the bypass pump prime). Grouping was blinded for the surgeon and the anaesthetist. Plasma concentrations of thrombomodulin, protein C and (free) protein S as well as thrombin/antithrombin III were measured by enzyme-linked-immunosorbent assays after induction of anaesthesia, during and after bypass, at the end of surgery, 5 h after bypass, and on the first postoperative day. Activated clotting time was significantly longer during bypass in group 2 (566 (60)s) and group 4 (655 (59)s), whereas standard coagulation parameters showed no differences between the four groups. Blood loss and use of homologous blood and blood products were highest in groups 2 and 3. Thrombomodulin plasma levels were similar (and normal) at baseline (< 40 ng.l-1), decreased during bypass and reached baseline values postoperatively without showing significant group differences. Protein C did not show any differences among the groups within the investigation period. 'Free' protein S plasma levels were most reduced in group 1 (from 68 (8)% to 48 (9)% after bypass). Thrombin/antithrombin III plasma concentrations increased most in groups 1 (to 69 (14) micrograms.l-1 after bypass) and 2 (to 48 (7) micrograms.l-1 after bypass), whereas they remained significantly lower in groups 3 and 4. The thrombomodulin/protein C-system was not significantly influenced by the regimen of anticoagulation. Administration of 'high-dose' heparin was associated with the highest blood loss, which could not be related to endothelial-associated coagulation.
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PMID:The effect of the anticoagulation regimen on endothelial-related coagulation in cardiac surgery patients. 2648 76

Tryptase (EC 3.4.21.59), the major secretory product of human mast cells, has become widely used as a biochemical marker for mast cells and mast cell activation, and is attracting attention as a mediator of allergic disease. However, there is little information available on the properties, or even the presence, of this protease in commonly used species of laboratory animals. We, here, report the demonstration and characterisation of this enzyme in the guinea pig lung. Tryptic activity resistant to alpha 1-proteinase inhibitor and soybean trypsin inhibitor was detected in sections of guinea pig lung tissue with the histochemical substrate Z-Gly-Pro-Arg-MNA. It was localised to mast cells and appeared to be present in all mast cells staining with Alcian Blue. A tryptic protease was purified 2400-fold from whole lung tissue by high salt extraction, cetylpyridinium chloride precipitation, heparin agarose chromatography, and gel filtration. This enzyme was found to be multimeric with a subunit of 38 kDa and a native molecular mass of 860 +/- 100 kDa. Inhibitor studies identified it as a serine protease. Like human tryptase, it was inhibited by leupeptin, benzamidine, and APC 366 (N-(1-hydroxy-2- naphthoyl)-L-arginyl(-L-prolinamide hydrochloride), but not by alpha 1-proteinase inhibitor, soybean trypsin inhibitor, or antithrombin III. Its response to changes in pH and ionic strength was similar to that of human tryptase. Differences between the guinea pig and human enzymes were seen in activity toward a panel fo 10 tryptic p_nitroanilide peptide substrates. Kinetic constants were determined for two of these: with L-Pyr-Pro-Arg-pNA the guinea pig tryptase had a similar Km but a 5-fold lower kcat than human tryptase, and with L-Pyr-Gly-Arg-pNA the guinea pig enzyme had a 10-fold lower Km and a 30% greater kcat than human counterpart. Heparin stabilised guinea pig tryptase, but did not alter its kinetic parameters as it did with human tryptase, decreasing the Km towards both substrates. The presence of a protease with similarities to human tryptase in the mast cells of guinea pigs suggests that this species may be an appropriate model to investigate the actions to tryptase in vivo, provided cognizance is taken of the differences that do exist.
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PMID:Guinea pig lung tryptase. Localisation to mast cells and characterisation of the partially purified enzyme. 869 58

A proper laboratory diagnosis of inherited thrombophilia due to defects of the coagulation system may be obtained only by a stringent definition of the diagnostic reference ranges taking into account the influence exerted by major physiological variables. To this purpose, we analyzed the data for Protein C, Antithrombin III, Heparin-Cofactor II and plasminogen coming from the first 4,000 subjects enrolled in the VITA Project. This is the first study that allows the establishment of reference ranges in a non-selected, active population using stringent standardization of clinical and laboratory measurements and multivariable regression techniques for data analysis. Serum triglycerides and total cholesterol, together with plasma fibrinogen were found to influence the functional plasma level of the four considered proteins. Menopause increased AT-III concentration, while pill use increased Heparin-Cofactor II and plasminogen. PT and PTT ratio, gender, age, smoking, body-mass index, HDL cholesterol and blood group had minor effects. The effect of these variables should be taken into account for both clinical and epidemiologic purposes, using appropriate reference ranges or covariance analysis for adjustment.
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PMID:The VITA Project: population-based distributions of protein C, antithrombin III, heparin-cofactor II and plasminogen--relationship with physiological variables and establishment of reference ranges. 886 36

Resistance to the activation of protein C is a recently discovered constitutional anomaly of coagulation which is responsible for thromboembolic events in young subjects. We report a case in a 26 year old man who presented with pulmonary embolus. Laboratory data was characterised by an absence of any lengthening of the activated cephaline time after adding purified activated exogenous Protein C. The confirmation of this anomaly is provided by the evidence of a mutation Arg 506 to Gln of Factor 5. The outcome is favourable with treatment by Heparin then by anti-Vitamin K.
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PMID:[Pulmonary embolism disclosing activated protein C resistance]. 899 81

Bilateral renal vein thrombosis and venous sinus thrombosis were diagnosed within 3 weeks of birth in a full-term neonate. Heterozygosity for a factor V mutation leading to resistance against the anticoagulatory properties of activated protein C was found. Heparin therapy led to resolution of the thrombotic manifestations. With long-term oral anticoagulation, no relapse or other thrombotic event occurred during infancy.
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PMID:Bilateral renal vein thrombosis and venous sinus thrombosis in a neonate with factor V mutation (FV Leiden). 947 20

There is growing evidence on the superior efficacy and safety of low molecular weight heparins (LMWHs) over unfractionated heparin (UFH) for the treatment of both venous and arterial thromboembolism. Heparin exerts its function by potentiating antithrombin and by mobilizing tissue factor pathway inhibitor (TFPI) into the circulation. The present study was conducted to compare the effect of subcutaneous LMWH and infusion of UFH on these two anticoagulants in plasma. Eighteen healthy male volunteers were randomly allocated to therapy with continuous intravenous (iv) UFH (n=6) (initial infusion rate 450 IU/kg/day) or low molecular weight heparin (LMWH) (enoxaparin, 1.5 mg/kg/day) subcutaneously (sc) once daily for 72 hours. Free TFPI antigen, measured by a solid-phase two-site enzyme immunoassay, and antithrombin and protein C activities, measured by chromogenic assays, were assessed in plasma samples before, during, and after anticoagulant treatment. Infusion of UFH, but not subcutaneous LMWH, was found to attenuate the antithrombotic defense by a selective decrease of both circulating antithrombin (-21+/-7%, p<0.0001) and of free and endothelial-bound TFPI. The changes in antithrombin and TFPI by LMWH and UFH were statistically different between groups (p<0.001). The differential effect of UFH and LMWH on antithrombin and TFPI may explain the superior efficacy of subcutaneous LMWH compared with conventional intravenous UFH for treatment of both arterial and venous thrombosis.
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PMID:Differential effects of low molecular weight heparin and unfractionated heparin on circulating levels of antithrombin and tissue factor pathway inhibitor (TFPI): a possible mechanism for difference in therapeutic efficacy. 973 20

Heparin induced thrombocytopenia is encountered in clinical practice as type I and type II. Heparin induced thrombocytopenia type II is one of the most serious complications of heparin treatment. Its incidence is between 0.5-5% of all patients treated with heparins. Contrary to type I which is most probably caused by simple interaction of heparin with platelets, in type II factors of the immune system are involved. The laboratory diagnosis is complicated and negative, in vitro tests do not rule out the diagnosis in vivo. The latter is assessed most frequently per exclusionem when there is a marked drop of platelets associated with the clinical picture of thrombotic complications. Heparin must then be immediately discontinued and at the same time usually alternative antithrombotic treatment is necessary. Low-molecular heparins are contraindicated by the majority of authors because of possible immunological cross reactions, and coumarins are also unsuitable as drugs of first choice because of their late onset of effect and initial drop of protein C. Ideal preparations are most probably direct thrombin inhibitors (recombinant hirudin and its analogues, oligopetides). Anti-thrombocyte drugs can be used, possibly the defibrination enzyme ancrode (Arwin).
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PMID:[Heparin-induced thrombocytopenia]. 982 74

Inhibition of activated protein C (APC) by protein C inhibitor (PCI) is stimulated by heparin, whereas inhibition by alpha1-antitrypsin (AAT) is heparin-independent. Three lysine residues located in a positively charged cluster in the serine protease domain of protein C (PC) were mutated to probe their involvement in the heparin stimulation of inhibition by PCI. These mutations were selected after analysis of the three-dimensional structure of APC and of molecular models for PCI and the APC-PCI complex. A double mutant, K62[217]N/K63[218]D, a single mutant, K86[241]S, and wild-type PC were expressed in embryonic human kidney 293 cells. Heparin stimulated the rate of inhibition of wt-APC by PCI approximately 400-fold, with second order rate constants (k2) in the absence and presence of heparin of 0.72 x 10(3) M(-1)s(-1) and 2.87 x 10(5) M(-1)s(-1), respectively. In contrast, heparin only yielded a 52-fold stimulation of the rate of inhibition of the double mutant APC by PCI as the rate constants in the absence and presence of heparin were k2 = 2.44 x 10(3) M(-1)s(-1) and k2 = 1.26 x 10(5)M(-1)s(-1), respectively. The double mutant K62N/K63D eluted at approximately 10% lower NaCl concentration from a heparin Sepharose column than the K86S mutant or wt-APC. These data suggest K62 and K63 in APC to be part of a heparin binding site which is important for heparin-mediated stimulation of inhibition of APC by PCI.
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PMID:Involvement of Lys 62(217) and Lys 63(218) of human anticoagulant protein C in heparin stimulation of inhibition by the protein C inhibitor. 1045 57

Accelerated thrombin generation is central to the development of hemostatic abnormalities during cardiopulmonary bypass (CPB) that are associated with both thromboembolic complications and serious, abnormal bleeding. Thrombin not only converts fibrinogen to fibrin, but also activates platelets and coagulation factors V, VIII, and XI and causes release of von Willebrand factor from vascular endothelium. Thrombin can also downregulate the hemostatic system by inducing formation of platelet inhibitory agents, such as nitric oxide and prostacyclin, and release of tissue plasminogen activator, facilitating activation of protein C, and releasing tissue factor pathway inhibitor. Excessive thrombin activity may also result in substantial consumption of platelets, fibrinogen, and labile coagulation factors and abnormal bleeding. Elevated tissue plasminogen activator levels secondary to activation of the contact system and surgery catalyze the formation of plasmin, which also consumes or internalizes platelet glycoprotein receptors and coagulation factors V, VIII, and fibrinogen. Heparin can reduce the generation of and mediate neutralization of excessive and CPB-associated thrombin activity. Heparin anticoagulation is commonly monitored with the activated clotting time (ACT). However, the ACT may be prolonged by factors other than heparin during CPB, such as hemodilution and hypothermia, and therefore may not accurately reflect the extent of anticoagulation by heparin. Aprotinin, a nonspecific serine protease inhibitor used with CPB, can also prolong celite-based ACT values, rendering it less reliable for monitoring heparin anticoagulation. Therefore, several alternative anticoagulation strategies have been recommended when aprotinin is used, such as a higher celite ACT trigger (>750 seconds), monitoring of whole blood heparin concentrations (eg, >2.7 U/mL), or administration of heparin based on a CPB duration-dependent, fixed-dose regimen. Administration of heparin doses higher than those generally recommended, as guided by predetermined, patient-specific whole blood heparin concentration measurements during bypass, can reduce excessive thrombin-mediated consumption of platelets and coagulation factors as well as post-CPB blood loss and blood component transfusions. New modalities of improving suppression of excess thrombin generation during CPB include use of heparin-bonded CPB circuits, heparin cofactor II or related analogs, supplemental antithrombin III, direct thrombin inhibitors (eg, hirudin, argatroban), and inhibitors of the contact and tissue factor pathways. The safety and efficacy of these approaches remains to be established by additional, appropriately powered, prospective studies.
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PMID:Anticoagulation and anticoagulation reversal with cardiac surgery involving cardiopulmonary bypass: an update. 1046 45


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