Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.5 (thrombin)
 33,306 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

When human citrated plasma is dialysed against a phosphate buffer containing Ca++, citrate anions are removed, thrombin is generated and soluble fibrinogen derivatives (fibrin monomers and/or soluble fibrin polymers) are formed. These derivatives are able to combine with human or bovine elastin to form a very stable addition product or adduct. The formation of the adduct is dependent on time, Ca++ and thrombin concentrations.
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PMID:Soluble fibrinogen derivatives generated by thrombin: affinity for elastin. 373 60

In isolated rabbit lungs standardized amounts of edema were induced. Stimulation with the Ca ionophore A23187, leukotriene C4, Pseudomonas aeruginosa cytotoxin and human serum (activated complement) all resulted in protein leakage into the alveolar space with no change in the total phospholipid content. The pressure-volume characteristics of the lungs and the characteristics of the lavage surfactant (Wilhelmy balance) were markedly altered, correlating to the lavage protein content. The surfactant alterations were reproduced by addition of perfusion fluid protein to control surfactant in vitro. All changes were far less expressed or even missing in isolated lungs developing the same amount of edema due to omittance of proteins from the perfusion liquid. Different proteins added to control surfactant in the Wilhelmy balance showed a marked rank order of potency in interfering with surfactant function: immunoglobulins G and M and elastin less than albumin less than fibrinogen less than fibrin monomers. The fibrin monomer effect was reproduced by addition of thrombin to a surfactant fibrinogen mixture and was partly reversed by subsequent incubation with plasmin. In conclusion, high-permeability edema induced by different means results in alterations of lung mechanics and surface activity of lavaged surfactant, presumably due to protein surfactant interaction. Among different proteins, fibrin monomers are especially effective in interfering with surfactant function.
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PMID:Alteration of surfactant function due to protein leakage: special interaction with fibrin monomer. 383 43

Soluble elastin, prepared from insoluble elastin by treatment with oxalic acid or elastase, was found to inhibit the formation of thromboxane B2 both from [1-14C]arachidonic acid added to washed platelets and from [1-14C]arachidonic acid in prelabeled platelets on stimulation with thrombin. In both systems, the formation of 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) was accelerated. Oxalic acid-treated soluble elastin at 1 and 10 mg/ml inhibited the formation of thromboxane B2 from exogenously supplied arachidonic acid 21 and 59%, respectively, and the formation of thromboxane B2 in prelabeled platelets stimulated by thrombin 44 and 94%, respectively. These concentrations of elastin increased the formation of 12-HETE from exogenously supplied arachidonic acid about 3.4- and 7.3-times, respectively. Almost all the added arachidonic acid was converted to metabolites. In prelabeled platelets, soluble elastin at 1 and 10 mg/ml increased the formation of 12-HETE stimulated by thrombin about 1.3- and 2.8-times, respectively, and inhibited the thrombin-induced total productions of thromboxane B2 (12-hydroxy-5,8,10-heptadecatrienoic acid (12-HETE) and free arachidonic acid by 26 and 25%, respectively. Elastase-treated digested elastin also inhibited the formation of thromboxane B2 and stimulated the formation of 12-HETE in prelabeled platelets stimulated by thrombin. This inhibitory action of elastin was not replaced by desmosine. The level of cAMP in platelets was not affected by soluble elastin. Soluble elastin was also found to inhibit platelet aggregation induced by thrombin. However, the inhibitory action of soluble elastin on platelet aggregation cannot be explained by inhibition of thromboxane B2 formation by the elastin.
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PMID:Inhibitory action of soluble elastin on thromboxane B2 formation in blood platelets. 632 Sep 5

Platelets do not adhere to surfaces to which flowing blood is normally exposed in vivo. When the lining of a blood vessel is altered or damaged, however, platelets do adhere to the injured site. Platelet adhesion is one of the first events in the formation of hemostatic plugs and thrombi, and plays a part in the development of atherosclerotic lesions. Other surfaces to which platelets adhere include particulate matter in the blood stream, bacteria and other microorganisms, the artificial surfaces of prosthetic devices, and some altered cells in the blood, particularly macrophages. The majority of investigators have studied the interaction of platelets with the subendothelium of normal vessels of young animals, or with isolated vessel wall constituents such as collagen. There are very few studies of platelet adhesion to repeatedly damaged or diseased blood vessels, although it is generally assumed that platelets interact with the connective tissue, fibrin, and cholesterol crystals in atherosclerotic lesions. Underlying the endothelium of blood vessel is the basement membrane, which has been shown to contain type IV collagen, elastin with its associated microfibrils, von Willebrand Factor, fibronectin, thrombospondin, laminin, and heparan sulfate. If only the endothelium is removed, the main structure exposed is the basement membrane with its associated proteins, but deeper injuries expose fibrillar type III collagen and microfibrils. In most studies in which large arteries have been injured by passage of a balloon catheter, basement membrane, type III collagen and the microfibrils around elastin have been exposed. Platelets do not react strongly with basement membrane and the type IV collagen in it is relatively inert. In contrast, platelets adhere firmly to type III (and type I) collagen and spread on it. Although in vitro studies have shown that platelets can interact with collagen in artificial media without plasma proteins, investigations of platelet adhesion at high shear rates indicate that von Willebrand Factor is necessary for firm platelet adhesion under these conditions. Fibronectin and thrombospondin may also have a role in platelet adhesion. However, platelets do not bind von Willebrand Factor or fibronectin until the platelets have been stimulated to release their granule contents, so these binding sites probably do not become available until the platelets have interacted with collagen or another release-inducing agent such as thrombin.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Platelet adhesion. 639 67

Cyclic mechanical strain (1 Hz) causes a mitogenic response in neonatal rat vascular smooth muscle cells due to production and secretion of PDGF. In this study, the mechanism for sensing mechanical strain was investigated. Silicone elastomer strain plates were coated at varying densities with elastin, laminin, type I collagen, fibronectin, or vitronectin. Strain was applied by cyclic application of a vacuum under the dishes. Cells adhered, spread, and proliferated on each matrix protein, but the mitogenic response to strain was matrix dependent. Strain increased DNA synthesis in cells on collagen, fibronectin, or vitronectin, but not in cells on elastin or laminin. When strain was applied on matrices containing both laminin and vitronectin, the mitogenic response to strain depended upon the vitronectin content of the matrix. Fibronectin, in soluble form (0-50 micrograms/ml), and the integrin binding peptide GRGDTP (100 micrograms/ml) both blocked the mitogenic response to mechanical strain in cells grown on immobilized collagen. Neither soluble laminin nor the inactive peptide GRGESP blocked the response to strain. GRGDTP did not alter the mitogenic response to exogenous PDGF or alpha-thrombin but did prevent the secretion of PDGF in response to strain. Furthermore, GRGDTP, but not GRGESP, prevented strain-induced expression of a PDGF-A chain promoter 890 bp-chloramphenicol acetyltransferase construct that was transiently transfected into vascular smooth muscle cells. Finally, the response to strain was abrogated by antibodies to both beta 3 and alpha v beta 5 integrins but not by an antibody to beta 1 integrins. Thus interaction between integrins and specific matrix proteins is responsible for sensing mechanical strain in vascular smooth muscle cells.
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PMID:Mechanical strain of rat vascular smooth muscle cells is sensed by specific extracellular matrix/integrin interactions. 759 24

Human lung macrophages express all four of the known lysosomal thiol proteases: cathepsins B, H, L, and S. These enzymes share a similar size and targeting mechanism for lysosomal accumulation and all have relatively indiscriminate substrate specificity in comparison with such highly selective serine proteases as urokinase or thrombin. These enzymes do have distinctive properties: only cathepsin B has C-terminal dipeptidase activity, only cathepsin H has potent aminopeptidase activity, and only cathepsin L and S are elastolytic. Cathepsin S is unique in that it is stable at neutral pH; indeed, at neutral pH it has elastolytic activity roughly comparable with that of neutrophil elastase. Recent studies of the differential expression of these cathepsins suggest they not only cooperate in terminal degradation of endocytized protein but also have specific functions such as proenzyme activation, antigen processing, and tissue remodeling, especially bone matrix resorption. Lysates of lung macrophages degrade elastin at neutral pH, suggesting that necrosis of macrophages at sites of macrophage accumulation, e.g., caseation necrosis, could contribute to tissue destruction. Tissue destruction and remodeling by thiol proteases expressed by live macrophages, however, is limited by tight compartmentalization of cathepsins to lysosomes. Nonetheless, macrophages accumulate at sites of known injury in cigarette smokers. Because these cells contain potent elastases, and because lysosomal enzyme release and cell surface acidification are regulated events, dysregulation of thiol protease expression in stimulated macrophages may contribute to the injury observed in cigarette smokers with non-alpha-1-protease inhibitor-type emphysema.
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PMID:The role of thiol proteases in tissue injury and remodeling. 795 52

Derivatives of benzisothiazolinone 1,1-dioxide (saccharin) N-acetylated with aliphatic and aromatic substituted aliphatic acyl groups were prepared. The inhibitory activity of the compounds was assayed against human leucocyte elastase (EC 3.4.21.37) and several other proteases. The IC50 values for inhibition of the human leucocyte elastase decreased with increasing length of the acyl residue, and reached a minimum value at C16 (2 microM). This phenomenon and the decrease of the inhibition by surfactants or by saturation of the enzyme with palmitic acid, indicates that in addition to acylation, hydrophobic interactions are also involved in the inhibition of this proteinase by compounds substituted with acyl groups containing at least 12 carbon atoms. The inhibitory activity of N-palmitoyl-benzisothiazolinone 1,1-dioxide (palmitoyl-saccharin) is about 14 times higher toward human leucocyte elastase than for thrombin (EC 3.4.21.5), and several hundred times, compared to porcine pancreatic elastase (EC 3.4.21.36) and to plasmin (EC 3.4.21.7). Fatty acylated saccharin derivatives were seen to bind in a saturable fashion to insoluble elastin, and decreased the susceptibility of this protein to hydrolysis by human leucocyte elastase.
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PMID:Inhibition of human leucocyte elastase by fatty acyl-benzisothiazolinone, 1,1-dioxide conjugates (fatty acyl-saccharins). 849 48

Thrombin generated at sites of vascular injury not only participates in the coagulation cascade but can signal other events related to development and complication of atherosclerotic plaques. We investigated here a novel non-thrombotic action of thrombin: the possibility that this protease influences the expression or activation of matrix metalloproteinases (MMPs) produced by vascular smooth muscle cells (SMCs). Matrix-degrading proteinases likely contribute to several aspects of vascular lesion development. Vascular SMCs constitutively elaborate the zymogen form of gelatinase A (MMP-2), found in cell supernatants complexed with its inhibitor, the tissue inhibitor of metalloproteinases (TIMP)-2. When activated, MMP-2 digests collagens and elastin and may thus promote cell migration and vascular remodeling. Analysis of culture supernatants harvested from either human or rabbit vascular SMCs by gelatin zymography revealed that compared with supernatants of unstimulated SMCs, media conditioned by thrombin-stimulated cells contained increased amounts of proteolytically processed MMP-2, suggesting activation of this MMP. Further experiments tested whether thrombin directly activates MMP-2. In cell-free experiments, when added to medium harvested from unstimulated SMCs, alpha-thrombin increased in a dose- and time-dependent manner the amount of proteolytically processed MMP-2, as shown by zymography and by Western blotting with specific antibodies. Thrombin cleaved pro-MMP-2 within 4 hours, even when the gelatinase was bound with its inhibitor, TIMP-2. Thrombin treatment rendered culture media of unstimulated SMCs able to degrade collagen type IV, consistent with generation of active MMP-2. Addition of inhibitors of either thrombin or MMPs decreased this type IV collagenolytic activity, but thrombin in the absence of SMC-conditioned medium containing pro-MMP-2 exhibited only minimal collagenolysis. Our results suggest that at sites of vascular injury, thrombin may activate locally produced MMP-2 and thereby facilitate cell migration and proliferation. In the case of complicated atherosclerotic plaques, episodes of intraplaque hemorrhage or plaque disruption with thrombosis may promote plaque instability by increasing local matrix-degrading activity.
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PMID:Thrombin promotes activation of matrix metalloproteinase-2 produced by cultured vascular smooth muscle cells. 910 66

The thrombospondins are a family of extracellular calcium-binding proteins that modulate cellular phenotype. Thrombospondin-1 (TSP-1) reportedly regulates cellular attachment, proliferation, migration, and differentiation in vitro. To explore its function in vivo, we have disrupted the TSP-1 gene by homologous recombination in the mouse genome. Platelets from these mice are completely deficient in TSP-1 protein; however, thrombin-induced platelet aggregation is not diminished. TSP-1-deficient mice display a mild and variable lordotic curvature of the spine that is apparent from birth. These mice also display an increase in the number of circulating white blood cells, with monocytes and eosinophils having the largest percent increases. The brain, heart, kidney, spleen, stomach, intestines, aorta, and liver of TSP-1-deficient mice showed no major abnormalities. However, consistent with high levels of expression of TSP-1 in lung, we observe abnormalities in the lungs of mice that lack the protein. Although normal at birth, histopathological analysis of lungs from 4-wk-old TSP-1-deficient mice reveals extensive acute and organizing pneumonia, with neutrophils and macrophages. The macrophages stain for hemosiderin, indicating that diffuse alveolar hemorrhage is occurring. At later times, the number of neutrophils decreases and a striking increase in the number of hemosiderin-containing macrophages is observed associated with multiple-lineage epithelial hyperplasia and the deposition of collagen and elastin. A thickening and ruffling of the epithelium of the airways results from increasing cell proliferation in TSP-1-deficient mice. These results indicate that TSP-1 is involved in normal lung homeostasis.
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PMID:Thrombospondin-1 is required for normal murine pulmonary homeostasis and its absence causes pneumonia. 948 68

Abciximab (c7E3 Fab, ReoPro), a platelet glycoprotein (GP) IIb/IIIa inhibitor, decreases acute ischemic complications after percutaneous coronary interventions. Recently, abciximab was shown to decrease thrombin generation in vitro in a static system. To assess whether abciximab can decrease fibrin formation in blood from patients, we quantified both platelet thrombi and fibrin deposition by using an ex vivo flow chamber model. We prospectively studied 18 consecutive patients who underwent percutaneous interventions for unstable coronary syndromes. Blood was perfused directly from the patient through an ex vivo perfusion chamber at a high shear rate, thus mimicking mildly stenosed coronary arteries. Perfusion chamber studies were performed when patients were being treated with heparin plus aspirin before the procedure (baseline) and then repeated after the procedure, when patients were on either aspirin plus heparin alone (group 1, no abciximab, control) or aspirin plus heparin plus abciximab (group 2, abciximab treated). Each patient served as his or her own control. Specimens were stained with combined Masson's trichrome-elastin and antibodies specific for fibrinogen, fibrin, and platelet GP IIIa. Total thrombus area and areas occupied by platelet aggregates and fibrin layers were quantified by planimetry. Group 1 demonstrated no significant change in thrombus area before versus after the procedure; in contrast, treatment with abciximab reduced total thrombus area by 48% in group 2 (after the procedure versus baseline, P=0.01). This decline was due to significant reductions in both platelet aggregates (55%, P=0.005) and fibrin layers (45%, P=0.03). The addition of abciximab to heparin and aspirin in patients undergoing coronary interventions significantly decreases ex vivo thrombus formation on an injured vascular surface. Treatment with abciximab appears to reduce both the platelet and the fibrin thrombus components. This finding supports a potential role for GP IIb/IIIa receptor blockade in decreasing fibrin formation in addition to inhibition of platelet aggregation. Thus, potent inhibitors of GP IIb/IIIa may also act as anticoagulants.
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PMID:Administration of abciximab during percutaneous coronary intervention reduces both ex vivo platelet thrombus formation and fibrin deposition: implications for a potential anticoagulant effect of abciximab. 971 43


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