Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.37 (neutrophil elastase)
 4,078 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Protease-activated receptors (PARs) mediate cell activation after proteolytic cleavage of their extracellular amino terminus. We have reported earlier that primary cultures of rat brain capillary endothelial (RBCE) cells express at least two receptors for thrombin: PAR-1 and PAR-3. In the present study we show that PAR-2 activation by trypsin or by the PAR-2 agonist peptide (SLIGRL) evokes [Ca(2+) ](i) signal in RBCE cells. Taking advantage of RBCE cells expressing PAR-1 and PAR-2, we show that trypsin activates both receptors. The relative agonist activity of trypsin and thrombin on PARs of RBCE cells compared with that of SLIGRL were 112% and 48%, respectively, whereas the potency of trypsin was 10(5) -fold higher than that of SLIGRL. Because under pathological conditions other proteases such as plasmin or leukocyte elastase may reach the cells of the blood-brain barrier, we investigated the effect of these proteases on RBCE cells. Elastase evoked a small increase in [Ca(2+) ](i) but preincubation of cells with elastase dose-dependently reduced the trypsin-induced [Ca(2+) ](i) signal. Plasmin had a 30% inhibitory effect on the trypsin-induced response, and reduced the SLIGRL signal by 20%. It is concluded that PAR-2 is functional in brain capillary endothelium, and that the main fibrinolytic proteases, plasmin and elastase, may regulate PAR-2 signalling under pathological conditions.
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PMID:Protease-activated receptor-2 (PAR-2) in brain microvascular endothelium and its regulation by plasmin and elastase. 1194 37

Activated human polymorphonuclear neutrophils at inflammatory sites release the chymotrypsin-like protease cathepsin G, together with elastase and proteinase 3 (myeloblastin), from their azurophil granules. The low activity of cathepsin G on synthetic substrates seriously impairs studies designed to clarify its role in tissue inflammation. We have solved this problem by producing new peptide substrates with intramolecularly quenched fluorescence. These substrates were deduced from the sequence of putative protein targets of cathepsin G, including the reactive loop sequence of serpin inhibitors and the N-terminal domain of the protease-activated receptor of thrombin, PAR-1. Two substrates were selected, Abz-TPFSGQ-EDDnp and Abz-EPFWEDQ-EDDnp, that are cleaved very efficiently by cathepsin G but not by neutrophil elastase or proteinase 3, with specificity constants (k(cat)/K(m)) in the 10(5) M(-1).s(-1) range. They can be used to measure subnanomolar concentrations of free enzyme in vitro and at the surface of neutrophils purified from fresh human blood. Purified neutrophils express 0.02-0.7 pg of cathepsin G/cell (n=15) at their surface. This means that about 10(4) purified cells may be enough to record cathepsin G activity within minutes. This may be most important for investigating the role of cathepsin G as an inflammatory agent, especially in bronchoalveolar lavage fluids from patients with pulmonary inflammatory disorders.
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PMID:Measurement of free and membrane-bound cathepsin G in human neutrophils using new sensitive fluorogenic substrates. 1208 7

Neutrophils and mononuclear cells are implicated in the pathogenesis of several inflammatory conditions including chronic obstructive pulmonary disease (COPD). Neutrophil-derived serine proteases, such as cathepsin G (CG) and neutrophil elastase (NE), may interact with mononuclear cells via protease-activated receptors (PARs) which are seven-transmembrane G protein-coupled receptors activated by proteolytic cleavage of the extracellular N-terminus, and which, on activation, induce the release of several mediators and cytokines. We determined whether CG and NE could affect PAR-1 expression and function in mononuclear cells. Human blood mononuclear cells were isolated from 20 healthy donors. Surface and intracellular receptor expression and calcium mobilisation (using the calcium chelator, FLUO3-AM) were studied by fluorescence-assisted cell sorting (FACS analysis). Positive controls, i.e. thrombin (0.1-100 mU/ml) and the PAR-1-activating peptide SFLLRN (100 microM) induced a rapid and transient intemalisation of PAR-1 in monocytes and lymphocytes. CG but not NE had a similar effect. By contrast, in monocytes intracellular calcium mobilisation was induced by thrombin and SFLLRN but not by CG and NE. Thus, CG can induce intracellular PAR-1 sequestration without activation of the receptor, and may act as an antagonist and prevent subsequent activation of PAR-1 in mononuclear cells. These findings may be of relevance to the pathogenesis of COPD.
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PMID:Regulation of protease-activated receptor-1 in mononuclear cells by neutrophil proteases. 1264 29

Protease-activated receptors (PARs) compose a family of G protein-coupled receptors activated by proteolysis with exposure of their tethered ligand. Recently, we reported that a neutrophil-derived serine proteinase, proteinase 3 (PR3), activated human oral epithelial cells through PAR-2. The present study examined whether other neutrophil serine proteinases, human leukocyte elastase (HLE), and cathepsin G (Cat G) activate nonepithelial cells, human gingival fibroblasts (HGF). HLE and Cat G as well as PR3 activated HGF to produce IL-8 and monocyte chemoattractant protein 1. Human oral epithelial cells but not HGF express mRNA and protein of secretory leukocyte protease inhibitor, an inhibitor of HLE and Cat G, and recombinant secretory leukocyte protease inhibitor clearly inhibited the activation of HGF induced by HLE and Cat G but not by PR3. HGF express PAR-1 and PAR-2 mRNA in the cells and the proteins on the cell surface. HLE and Cat G cleaved the peptide corresponding to the N terminus of PAR-2 with exposure of its tethered ligand. Treatment with trypsin, an agonist for PAR-2, and a synthetic PAR-2 agonist peptide induced intracellular Ca(2+) mobilization and rendered cells refractory to subsequent stimulation with HLE and Cat G. The production of cytokine induced by HLE and Cat G and the PAR-2 agonist peptide was completely abolished by inhibition of phospholipase C. These findings suggest that neutrophil serine proteinases have equal ability to activate human nonepithelial cells through PAR-2 to produce inflammatory cytokines and may control a number of inflammatory processes such as periodontitis.
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PMID:Neutrophil serine proteinases activate human nonepithelial cells to produce inflammatory cytokines through protease-activated receptor 2. 2030 34

Apoptosis of distal lung epithelial cells plays a pivotal role in the pathogenesis of acute lung injury. In this context, proteinases, either circulating or leukocyte-derived, may contribute to epithelial apoptosis and lung injury. We hypothesized that apoptosis of lung epithelial cells induced by leukocyte elastase is mediated via the proteinase activated receptor (PAR)-1. Leukocyte elastase, thrombin, and PAR-1-activating peptide, but not the control peptide, induced apoptosis in human airway and alveolar epithelial cells as assessed by increases in cytoplasmic histone-associated DNA fragments and TUNEL staining. These effects were largely prevented by a specific PAR-1 antagonist and by short interfering RNA directed against PAR-1. To ascertain the mechanism of epithelial apoptosis, we determined that PAR-1AP, thrombin, and leukocyte elastase dissipated mitochondrial membrane potential, induced translocation of cytochrome c to the cytosol, enhanced cleavage of caspase-9 and caspase-3, and led to JNK activation and Akt inhibition. In concert, these observations provide strong evidence that leukocyte elastase mediates apoptosis of human lung epithelial cells through PAR-1-dependent modulation of the intrinsic apoptotic pathway via alterations in mitochondrial permeability and by modulation of JNK and Akt.
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PMID:Proteinase-activated receptor-1 mediates elastase-induced apoptosis of human lung epithelial cells. 1610 73