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The American Journal of Pathology Dec 2000Functional inhibition of tissue factor (TF) has been shown to improve coronary blood flow after myocardial ischemia/reperfusion (I/R) injury. TF initiates the...
Functional inhibition of tissue factor (TF) has been shown to improve coronary blood flow after myocardial ischemia/reperfusion (I/R) injury. TF initiates the coagulation protease cascade, resulting in the generation of the serine protease thrombin and fibrin deposition. Thrombin can also contribute to an inflammatory response by activating various cell types, including vascular endothelial cells. We used a rabbit coronary ligation model to investigate the role of TF in acute myocardial I/R injury. At-risk areas of myocardium showed increased TF expression in the sarcolemma of cardiomyocytes, which was associated with a low level of extravascular fibrin deposition. Functional inhibition of TF activity with an anti-rabbit TF monoclonal antibody administered either 15 minutes before or 30 minutes after coronary ligation reduced infarct size by 61% (P = 0.004) and 44% (P = 0.014), respectively. Similarly, we found that inhibition of thrombin with hirudin reduced infarct size by 59% (P = 0.014). In contrast, defibrinogenating the rabbits with ancrod had no effect on infarct size, suggesting that fibrin deposition does not significantly contribute to infarct size. Functional inhibition of thrombin reduced chemokine expression and inhibition of either TF or thrombin reduced leukocyte infiltration. We propose that cardiomyocyte TF initiates extravascular thrombin generation, which enhances inflammation and injury during myocardial I/R.
Topics: Animals; Antibodies, Monoclonal; Antithrombins; Cell Movement; Chemokines; Fibrin; Fibrinogen; Hirudins; Microscopy, Electron; Myocardial Infarction; Myocardial Ischemia; Myocardial Reperfusion Injury; Myocarditis; Myocardium; Neutrophils; Rabbits; Thrombin; Thromboplastin
PubMed: 11106558
DOI: 10.1016/S0002-9440(10)64824-9 -
Blood Oct 2000Ancrod is a purified fraction of venom from the Malayan pit viper, Calloselasma rhodostoma, currently under investigation for treatment of acute ischemic stroke....
Ancrod is a purified fraction of venom from the Malayan pit viper, Calloselasma rhodostoma, currently under investigation for treatment of acute ischemic stroke. Treatment with ancrod leads to fibrinogen depletion. The present study investigated the mechanisms leading to the reduction of plasma fibrinogen concentration. Twelve healthy volunteers received an intravenous infusion of 0.17 U/kg body weight of ancrod for 6 hours. Blood samples were drawn and analyzed before and at various time points until 72 hours after start of infusion. Ancrod releases fibrinopeptide A from fibrinogen, leading to the formation of desAA-fibrin monomer. In addition, a considerable proportion of desA-profibrin is formed. Production of desA-profibrin is highest at low concentrations of ancrod, whereas desA-profibrin is rapidly converted to desAA-fibrin at higher concentrations of ancrod. Both desA-profibrin and desAA-fibrin monomers form fibrin complexes. A certain proportion of complexes carries exposed fibrin polymerization sites E(A), indicating that the terminal component of the protofibril is a desAA-fibrin monomer unit. Soluble fibrin complexes potentiate tissue-type plasminogen activator-induced plasminogen activation. Significant amounts of plasmin are formed when soluble fibrin in plasma reaches a threshold concentration, leading to the proteolytic degradation of fibrinogen and fibrin. In the present setting, high concentrations of soluble fibrin are detected after 1 hour of ancrod infusion, whereas a rise in fibrinogen and fibrin degradation products, and plasmin-alpha(2)-plasmin inhibitor complex levels is first detected after 2 hours of ancrod infusion. Ancrod treatment also results in the appearance of cross-inked fibrin degradation product D-dimer in plasma. (Blood. 2000;96:2793-2802)
Topics: Adult; Ancrod; Biopolymers; Calcium Chloride; Chromatography, Gel; Enzyme Activation; Factor XIII; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Fibrinolysin; Fibrinolysis; Fibrinolytic Agents; Fibrinopeptide A; Hirudins; Humans; Infusions, Intravenous; Macromolecular Substances; Male; Middle Aged; Peptide Fragments; Plasminogen; Recombinant Proteins; Solubility; Thrombin; Tissue Plasminogen Activator; alpha-2-Antiplasmin
PubMed: 11023513
DOI: No ID Found -
The Journal of Thoracic and... Aug 2000
Topics: Ancrod; Anticoagulants; Aprotinin; Cardiopulmonary Bypass; Chondroitin Sulfates; Coronary Disease; Dermatan Sulfate; Drug Combinations; Heparin; Heparitin Sulfate; Humans; Serine Proteinase Inhibitors; Thrombocytopenia; Thrombosis; Treatment Failure
PubMed: 10917979
DOI: 10.1067/mtc.2000.108285 -
European Journal of Biochemistry Feb 2000Kinetics for the hydrolysis of the chromogenic active-site titrant N alpha-(N,N-dimethylcarbamoyl)-alpha-azaornithine p-nitrophenyl ester (Dmc-azaOrn-ONp) catalysed by... (Comparative Study)
Comparative Study
Kinetics for the hydrolysis of the chromogenic active-site titrant N alpha-(N,N-dimethylcarbamoyl)-alpha-azaornithine p-nitrophenyl ester (Dmc-azaOrn-ONp) catalysed by bovine beta-trypsin, bovine alpha-thrombin, bovine Factor Xa, human alpha-thrombin, human Factor Xa, human Lys77-plasmin, human urinary kallikrein, Mr 33 000 and Mr 54 000 species of human urokinase, porcine pancreatic beta-kallikrein-A and -B and Ancrod (the coagulating serine proteinase from the Malayan pit viper Agkistrodon rhodostoma venom) have been obtained between pH 6.0 and 8.0, at 21.0 degrees C, and analysed in parallel with those for the enzymatic cleavage of N alpha-(N,N-dimethylcarbamoyl)-alpha-azalysine p-nitrophenyl ester (Dmc-azaLys-ONp). The enzyme kinetics are consistent with the minimum three-step catalytic mechanism of serine proteinases, the rate-limiting step being represented by the deacylation process. Bovine beta-trypsin kinetics are modulated by the acid-base equilibrium of the His57 catalytic residue (pKa approximately 6.9). Dmc-azaOrn-ONp and Dmc-azaLys-ONp bind stoichiometrically to the serine proteinase active site, and allow the reliable determination of the active enzyme concentration between 1.0 x 10-6 M and 3.0 x 10-4 M. The affinity and the reactivity for Dmc-azaOrn-ONp (expressed by Ks and k+2/Ks, respectively) of the serine proteinases considered are much lower than those for Dmc-azaLys-ONp. The very different affinity and reactivity properties for Dmc-azaOrn-ONp and Dmc-azaLys-ONp have been related to the different size of the ornithine/lysine side chains, and to the ensuing different positioning of the active-site titrants upon binding to the enzyme catalytic centre (i.e. to P1-S1 recognition). These data represent the first detailed comparative investigation on the catalytic properties of serine proteinases towards an ornithine derivative (i. e. Dmc-azaOrn-ONp).
Topics: Animals; Aza Compounds; Binding Sites; Catalytic Domain; Histidine; Humans; Hydrogen-Ion Concentration; Hydrolysis; Kinetics; Lysine; Models, Molecular; Ornithine; Serine Endopeptidases; Serine Proteinase Inhibitors; Titrimetry
PubMed: 10672036
DOI: 10.1046/j.1432-1327.2000.01120.x -
Medicine May 1998We analyzed the clinical and laboratory characteristics of 50 patients with catastrophic antiphospholipid syndrome (APS) (5 from our clinics and 45 from a MEDLINE... (Review)
Review
We analyzed the clinical and laboratory characteristics of 50 patients with catastrophic antiphospholipid syndrome (APS) (5 from our clinics and 45 from a MEDLINE computer-assisted review of the literature from 1992 through 1996). Thirty-three (66%) patients were female and 17 (34%) were male. Twenty-eight (56%) patients had primary APS, 15 (30%) had defined systemic lupus erythematosus (SLE), 6 (12%) had "lupus-like" syndrome, and 1 (2%) had rheumatoid arthritis. Mean age of patients in this series was 38 +/- 14 years (range, 11-74 yr). Three (6%) patients developed the clinical picture of catastrophic APS under the age of 15 years, and 11 (22%) were 50 years old or more. In 11 (22%) patients, precipitating factors contributed to the development of catastrophic APS (infections in 3, drugs in 3, minor surgical procedures in 3, anticoagulation withdrawal in 2, and hysterectomy in 1). The presentation of the acute multi-organ failure was usually complex, involving multiple organs simultaneously or in a very short period of time. The majority of patients manifested microangiopathy--that is, occlusive vascular disease affecting predominantly small vessels of organs, particularly kidney, lungs, brain, heart, and liver--with a minority of patients experiencing only large vessel occlusions. Thrombocytopenia was reported in 34 (68%) patients, hemolytic anemia in 13 (26%), disseminated intravascular coagulation in 14 (28%), and schistocytes in 7 (14%). The following antibodies were detected: lupus anticoagulant (94%), anticardiolipin antibodies (94%), anti-dsDNA (87% of patients with SLE), antinuclear antibodies (58%), anti-Ro/SS-A (8%), anti-RNP (8%), and anti-La/SS-B (2%). Anticoagulation was used in 70% of the patients, steroids in 70%, plasmapheresis in 40%, cyclophosphamide in 34%, intravenous gammaglobulins in 16%, and splenectomy in 4%. Most patients, however, received a combination of nonsurgical therapies. Death occurred in 25 of the 50 (50%) patients. In most, cardiac problems seemed to be the major cause of death. In several of these, respiratory failure was also present, usually due to acute respiratory distress syndrome and diffuse alveolar hemorrhage. Among the 20 patients who received the combination of anticoagulation, steroids, and plasmapheresis or intravenous gammaglobulins, recovery occurred in 14 (70%) patients. The use of ancrod and defibrotide appeared to be effective in the 2 respective patients in whom they were used.
Topics: Adolescent; Adult; Aged; Antibodies, Antinuclear; Antiphospholipid Syndrome; Biopsy; Child; Diagnosis, Differential; Female; Humans; Immunoglobulin G; Immunoglobulin M; Kidney; Lung; Male; Middle Aged; Platelet Count; Risk Factors
PubMed: 9653431
DOI: 10.1097/00005792-199805000-00005 -
The Journal of Clinical Investigation Jul 1998In rheumatoid arthritis, synovial expression of urokinase (uPA) activity is greatly increased (Busso, N., V. Péclat, A. So, and A. -P. Sappino. 1997. Ann. Rheum. Dis....
In rheumatoid arthritis, synovial expression of urokinase (uPA) activity is greatly increased (Busso, N., V. Péclat, A. So, and A. -P. Sappino. 1997. Ann. Rheum. Dis. 56:550- 557). We report the same effect in murine antigen-induced arthritis. uPA-mediated plasminogen activation in arthritic joints may have deleterious effects via degradation of cartilage and bone matrix proteins as well as beneficial effects via fibrin degradation. We evaluated these contrasting effects in vivo by analyzing the phenotype of uPA-deficient (uPA-/-) and control mice during antigen-induced arthritis. Joint inflammation was comparable in both groups up to day 3 and subsequently declined in control mice, remaining significantly elevated in uPA-/- mice on days 10 and 30 after arthritis onset. Likewise, synovial thickness was markedly increased in uPA-deficient mice persisting for up to 2 mo, whereas it subsided in control animals. Bone erosion was exacerbated in uPA-/- mice on day 30. By contrast, no difference in articular cartilage proteoglycan content was found between both groups. Significantly increased accumulation of fibrin was observed by day 30 in arthritic joints of uPA-/- mice. We hypothesized that synovial fibrin deposition plays a role in joint inflammation. Accordingly, defibrinogenation of uPA-/- mice by ancrod significantly decreased the sustained joint inflammation. All the above observations were reproducible in plasminogen-deficient (Pln-/-) mice. In conclusion, synovial fibrin deposition plays a role as a nonimmunological mechanism which sustains chronic arthritis.
Topics: Animals; Antigens; Arthritis; Fibrin; Fibrinogen; Interleukin-1; Mice; Mice, Inbred C57BL; Synovial Membrane; Urokinase-Type Plasminogen Activator
PubMed: 9649555
DOI: 10.1172/JCI2312 -
The Annals of Pharmacotherapy Jan 1998To highlight the importance of heparin-induced thrombocytopenia (HIT), a potentially fatal adverse effect of heparin therapy.
OBJECTIVE
To highlight the importance of heparin-induced thrombocytopenia (HIT), a potentially fatal adverse effect of heparin therapy.
CASE SUMMARY
There are two types of HIT with distinct etiology. Type 1 HIT is a relatively mild thrombocytopenia of early onset that generally resolves with ongoing heparin therapy. Clinical complications are uncommon. Type 2 HIT, which is more severe, is the main focus of this report. Five patients receiving heparin therapy developed type 2 HIT, which in some cases resulted in complications that required limb amputation, or eventuated in death.
DISCUSSION
In a patient receiving heparin therapy, the development of thrombocytopenia should alert the caregiver to the possible development of HIT. Prompt management of HIT can help prevent complications. HIT usually manifests 5-8 days after starting heparin therapy. The platelet count usually decreases to less than 100 x 10(3)/mm3. It generally normalizes within 5-7 days after discontinuing heparin therapy. In spite of the thrombocytopenia, thrombosis or disseminated intravascular coagulation can occur. The management may be subdivided into three clinical situations: mild-to-moderate asymptomatic thrombocytopenia, severe thrombocytopenia with a platelet count of less than 50 x 10(3)/mm3, and thrombosis or embolism complicating HIT.
CONCLUSIONS
Heparin-induced thrombocytopenia is an uncommon but potentially serious, and sometimes lethal, complication of heparin therapy. Therefore, it is important to be aware of the possibility of the development of HIT with heparin therapy, to recognize it early, and to manage it appropriately before the manifestation of adverse effects.
Topics: Adult; Aged; Ancrod; Anticoagulants; Fatal Outcome; Female; Gangrene; Heparin; Humans; Male; Serotonin; Thrombocytopenia; Thromboembolism
PubMed: 9475822
DOI: 10.1345/aph.16388 -
Journal of Vascular Surgery Dec 1997Digital gangrene was observed in a patient who had angiographic findings of digital arterial occlusion. The patient's blood showed a marked red blood cell aggregation... (Review)
Review
Digital gangrene was observed in a patient who had angiographic findings of digital arterial occlusion. The patient's blood showed a marked red blood cell aggregation with rouleaux formation in long chains, which could not be dispersed at shear rates up to 200 sec-1. Studies of the patient's blood revealed the presence of an abnormal fibrinogen capable of aggregating normal red blood cells. This fibrinogen was found by Raman spectroscopy to have an increased alpha-helical content, whereas the beta-sheet content was decreased. Defibrinogenation therapy with ancrod resulted in a dramatic symptomatic relief. The disappearance of the abnormal fibrinogen 6 months later and an absence of a family history indicate that this dysfibrinogenemia was acquired.
Topics: Arterial Occlusive Diseases; Erythrocyte Aggregation; Fibrinogen; Fingers; Gangrene; Humans; Male; Middle Aged
PubMed: 9423724
DOI: 10.1016/s0741-5214(97)70021-1 -
Journal of Biochemistry May 1996A thrombin-like enzyme, calobin, has been purified to homogeneity from the venom of Agkistrodon caliginosus by a procedure involving Bio-Gel P-100, Mono S, and Pro-RPC....
A thrombin-like enzyme, calobin, has been purified to homogeneity from the venom of Agkistrodon caliginosus by a procedure involving Bio-Gel P-100, Mono S, and Pro-RPC. The enzyme was identified as a monomer with a molecular weight of 34,000 on SDS-PAGE, and its isoelectric point was 6.2. Calobin acted on fibrinogen to form fibrin with a specific activity of 226 NIH equivalent units, and also exhibited arginine esterase activity. The enzyme predominantly cleaved the alpha-chain of fibrinogen with little degradation of the beta-chain. It contained abundant asparagine/aspartic acid residues, but very few tyrosine or methionine residues. The proteolytic activity of the enzyme with TAME as a substrate was higher than that of thrombin. However, it showed neither lysine esterase nor caseinolytic activity. The enzyme activity was strongly inhibited by PMSF, and moderately by benzamidine and soybean trypsin inhibitor, indicating it is a serine protease. On the other hand, the enzyme activity was not inhibited by hirudin or aprotinin. cDNA (1.6 kb) for calobin has been cloned from an A. caliginosus cDNA library. The cDNA sequence indicates that calobin is synthesized as a pre-zymogen of 262 amino acids, including a putative secretory signal peptide of 18 amino acids and a proposed zymogen peptide of 6 amino acid residues. The cDNA sequence encodes a 238-amino acid residue molecule exhibiting strong amino acid sequence homology to those of ancrod, batroxobin, and flavoxobin isolated from other snake venoms. Calobin contains 12 cysteine residues. As judged on alignment of the amino acid sequences of other thrombin-like enzymes (batroxobin, ancrod, and flavoxobin), calobin constitute the formation of six disulfide bridges. Amino acid residues, His43, Asp88, and Ser182, which are thought to be the catalytic active site are highly conserved. As calobin is a glycoprotein, its possible glycosylation site, Asn-X-Thr, is located at amino acid residues 81-83.
Topics: Agkistrodon; Amino Acid Sequence; Animals; Base Sequence; Cloning, Molecular; Crotalid Venoms; Isoelectric Point; Molecular Sequence Data; Molecular Weight; Platelet Aggregation; Rats; Sequence Homology, Amino Acid; Serine Endopeptidases; Substrate Specificity; Thrombin
PubMed: 8797081
DOI: 10.1093/oxfordjournals.jbchem.a021319 -
European Journal of Biochemistry Apr 1996The thrombin-like serine protease ancrod from the Malayan pit viper Agkistrodon rhodostoma was expressed in mouse epithelial cells (C127). Oligosaccharide constituents...
The thrombin-like serine protease ancrod from the Malayan pit viper Agkistrodon rhodostoma was expressed in mouse epithelial cells (C127). Oligosaccharide constituents were liberated from tryptic glycopeptides by treatment with peptide-N4-(N-acetyl-beta-glucosaminyl) asparagine amidase F. Neutral oligosaccharide alditols obtained after reduction and enzymic desialylation were separated by two-dimensional HPLC and characterized by methylation analysis, liquid secondary-ion mass spectrometry, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and sequential degradation with exoglycosidases. In contrast to natural ancrod, the recombinant glycoprotein carries exclusively diantennary, triantennary and tetraantennary N-glycans with Gal beta 4 GlcNAc beta (type-2) antennae which were, in part, further substituted by host-cell-specific structural elements such as Gal alpha 3 residues or N-acetyllactosamine repeats. As a characteristic feature, a substantial proportion of the oligosaccharides bears a GalNAc beta 4Glc-NAc antenna. Studies at the level of individual N-glycosylation sites demonstrated that glycans with N, N'-diacetyllactosediamine units are not specifically attached but occur at all sites in varying amounts. Hence, the putative recognition signal (Pro70-Lys-Lys) for glycoprotein hormone N-acetylgalactosaminyltransferase, present in this glycoprotein in close proximity to Asn79, does not convey site-specific transfer of GalNAc residues in these cells.
Topics: Agkistrodon; Ancrod; Animals; Carbohydrate Sequence; Carbohydrates; Cell Line; Cloning, Molecular; Glycosylation; Mice; Molecular Sequence Data; Polysaccharides; Recombinant Proteins; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
PubMed: 8620863
DOI: 10.1111/j.1432-1033.1996.0113n.x