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1.
Blood coagulation plays a key role among numerous mediating systems that are activated in inflammation. Receptors of the PAR family serve as sensors of serine proteinases of the blood clotting system in the target cells involved in inflammation.Activation of PAR-1 by thrombin and of PAR-2 by factor Xa leads to a rapid expression and exposure on the membrane of endothelial cells of both adhesive proteins that mediate an acute inflammatory reaction and of the tissue factor that initiates the blood coagulation cascade. Certain other receptors (EPR-1, thrombomodulin, etc.), which can modulate responses of the cells activated by proteinases through PAR receptors, are also involved in the association of coagulation and inflammation together with the receptors of the PAR family. The presence of PAR receptors on mast cells is responsible for their reactivity to thrombin and factor Xa and defines their contribution to the association of inflammation and blood clotting processes.  相似文献   

2.
Thrombin-induced degranulation of cultured bone marrow-derived mast cells   总被引:6,自引:0,他引:6  
This study was undertaken to determine if a plasma protease such as thrombin, a highly specific procoagulant enzyme that has numerous effects on platelets, endothelial cells, and smooth muscle cells, could mediate mast cell activation processes. Our results indicate that at near physiologic levels, thrombin can rapidly trigger mast cell degranulation without activating the 5-lipoxygenase system.  相似文献   

3.

Background  

In general, inflammation plays a role in most bladder pathologies and represents a defense reaction to injury that often times is two edged. In particular, bladder neurogenic inflammation involves the participation of mast cells and sensory nerves. Increased mast cell numbers and tryptase release represent one of the prevalent etiologic theories for interstitial cystitis and other urinary bladder inflammatory conditions. The activity of mast cell-derived tryptase as well as thrombin is significantly increased during inflammation. Those enzymes activate specific G-protein coupled proteinase-activated receptors (PAR)s.  相似文献   

4.
It is suggested that mast cells contribute to cell recruitment in inflammation through the upregulation of endothelial adhesion molecules. P-selectin and intercellular adhesion molecule(ICAM)-1 are two key adhesion molecules that have been associated indirectly with mast cell activity. The canine C2 mastocytoma cell line and primary cultures of canine carotid endothelial cells were used to establish a new in vitro model to help study the interaction between mast cells and endothelial cells. Carotid endothelial cells were incubated with mast cell mediators to uncover their effect on endothelial ICAM-1 and P-selectin expression. To assess the relative contributions of tumour necrosis factor (TNF)-alpha and histamine to such effect, an H1 antihistamine and a TNF-alpha blocking antibody were used. Prior to activation by mast cell mediators, P-selectin was expressed only within the cytoplasm, and ICAM-1 was constitutively expressed on the surface of the canine carotid endothelial cells. Both adhesion molecules were enhanced significantly and strongly upon mast cell activation at various time points. Unstored TNF-alpha was fully responsible for ICAM-1 upregulation. P-selectin was up-regulated by both preformed and newly synthesized mast cell mediators, but neither histamine nor TNF-alpha accounted for such an effect. Therefore,a new model is proposed in which the pro-inflammatory effect of mast cells on endothelial cells can be studied in vitro.In this model, it has been demonstrated that only TNF-alpha accounts for the overexpression of ICAM-1 induced by mast cells, and that mast cells up-regulate P-selectin expression through a histamine-independent mechanism.  相似文献   

5.
The mononuclear inflammatory response to Sindbis virus infection of the central nervous system is analogous to the cutaneous delayed-type hypersensitivity reaction. It is dependent on sensitized T cells for initiation, but many of the cells present are nonsensitized bone marrow-derived cells. Tissue mast cells have been shown to be important for the development of the delayed-type hypersensitivity reaction in the skin where capillary endothelial cells are joined by tight junctions. To determine whether mast cells are also important for the development of an immune-mediated inflammatory response across the endothelial tight junctions of the blood-brain barrier, the development of mononuclear inflammation in the central nervous system of reserpine-treated mice and mast cell-deficient mice (WBB6F1-W/Wv) was studied after infection with Sindbis virus. Three central nervous system compartments, the cerebrospinal fluid, the meninges, and the brain parenchyma, were evaluated for inflammation by counting the number of cells present, by grading the histopathologic lesions, and by labeling infiltrating cells with 125IUDR. By all parameters inflammation was reduced when mice were treated with reserpine or were deficient in mast cells. Antigen-specific humoral and cellular immune responses were depressed and virus clearance delayed in reserpine-treated mice, but not in mast cell deficient mice. It is concluded that the vasoactive amines released by mast cells in the central nervous system play a facilitating role in the development of the inflammatory response to Sindbis virus.  相似文献   

6.
Vascular endothelium is a key regulator of homeostasis. In physiological conditions it mediates vascular dilatation, prevents platelet adhesion, and inhibits thrombin generation. However, endothelial dysfunction caused by physical injury of the vascular wall, for example during balloon angioplasty, acute or chronic inflammation, such as in atherothrombosis, creates a proinflammatory environment which supports leukocyte transmigration toward inflammatory sites. At the same time, the dysfunction promotes thrombin generation, fibrin deposition, and coagulation. The serine protease thrombin plays a pivotal role in the coagulation cascade. However, thrombin is not only the key effector of coagulation cascade; it also plays a significant role in inflammatory diseases. It shows an array of effects on endothelial cells, vascular smooth muscle cells, monocytes, and platelets, all of which participate in the vascular pathophysiology such as atherothrombosis. Therefore, thrombin can be considered as an important modulatory molecule of vascular homeostasis. This review summarizes the existing evidence on the role of thrombin in vascular inflammation.  相似文献   

7.
Activation of mouse bone marrow-derived mast cells (BMMC) by thrombin (0.05-0.5 U/million cells) resulted in a concentration-dependent release of histamine, which levelled off by 0.1 U thrombin. Rat peritoneal mast cells (RMC) were not stimulated by thrombin, though in control experiments, both types of mast cells degranulated upon exposure to IgE-antigen. Pretreatment of thrombin with 0.2 mM diisopropylfluorophosphate (DFP), a specific serine protease inhibitor, resulted in 90% loss of thrombin degranulation and coagulant activity. Fluorescently labelled thrombin (FITC-thrombin) specifically bound to the BMMC surface, as measured by fluorescence cytometry. Pre-exposure of the BMMC to 20-fold excess of unlabelled thrombin prior to incubation with FITC-thrombin, prevented the binding of the labelled-thrombin to the cells. Incubation of thrombin with DFP or with antithrombin III (AT-III) resulted in losses of procoagulant and of BMMC degranulatory activities. DFP treatment of FITC-thrombin had no effect on the binding of the labelled enzyme to the cell surface. However, preincubation of the FITC-thrombin with AT-III prevented thrombin binding to the BMMC. Thus, the binding and the catalytic regions of the thrombin molecule are operationally distinct from one another. Kinetic analysis of the BMMC exposed to 0.5 U thrombin revealed a transient rise in intracellular cAMP, which peaked by 15 sec and was not measurable after 1 min. This suggests that differential activation of mast cells can occur at sites of tissue injury.  相似文献   

8.
9.
Mast cells become activated in multiple diseases wherein thrombin generation is often clinically apparent, but the effect of thrombin on cytokine release by mast cells remains unexplored. Thus, we examined IL-6 and TNFalpha release by thrombin-challenged mast cells. Thrombin and the protease-activated receptor (PAR)-1 peptide TRAP(14) induced these cells to secrete IL-6 in a dose-dependent fashion. Mast cells secreted > or =2800 pg IL-6/10(6) cells over 24 h, but only low levels of serotonin and no significant TNFalpha. Furthermore, at near-background levels of allergen, threshold doses of alpha-thrombin synergistically enhanced the IL-6 response (by up to 100-fold), but high-dose costimulation led to a simple additive response. Both the PI(3)- and sphingosine-kinase signaling pathways contributed importantly to the thrombin response. Our data thus clearly demonstrate that low-level thrombin and FcepsilonRI signaling can synergize to augment mast cell IL-6 responses, and that thrombin also differentially induces cytokine secretion by mast cells.  相似文献   

10.
The protein C anticoagulant pathway regulates thrombin formation. The pathway is triggered when thrombin binds to the endothelial cell proteoglycan, thrombomodulin. Unlike thrombin, this complex is a potent activator of the protein C zymogen, but it cannot clot blood. Activated protein C binds to protein S on cell surfaces where it proteolytically inactivates coagulation factors Va and VIIIa. Activated protein C also binds to a newly identified endothelial protein C receptor. Congenital deficiencies in this pathway are associated with thrombotic disease, and inflammation can cause acquired deficiencies. Activated protein C appears to inhibit inflammation. Thus, this pathway modulates both coagulation and inflammation.  相似文献   

11.
Disruption of endothelial barrier is a critical pathophysiological factor in inflammation. Thrombin exerts a variety of cellular effects including inflammation and apoptosis through activation of the protease activated receptors (PARs). The activation of PAR‐1 by thrombin is known to have a bimodal effect in endothelial cell permeability with a low concentration (pM levels) eliciting a barrier protective and a high concentration (nM levels) eliciting a barrier disruptive response. It is not known whether this PAR‐1‐dependent activity of thrombin is a unique phenomenon specific for the in vitro assay or it is part of a general anti‐inflammatory effect of low concentrations of thrombin that may have a physiological relevance. Here, we report that low concentrations of thrombin or of PAR‐1 agonist peptide induced significant anti‐inflammatory activities. However, relatively high concentration of thrombin or of PAR‐1 agonist peptide showed pro‐inflammatory activities. By using function‐blocking anti‐PAR‐1 antibodies and PI3 kinase inhibitor, we show that the direct anti‐inflammatory effects of low concentrations of thrombin are dependent on the activation of PAR‐1 and PI3 kinase. These results suggest a role for cross communication between PAR‐1 activation and PI3 kinase pathway in mediating the cytoprotective effects of low concentrations of thrombin in the cytokine‐stimulated endothelial cells. J. Cell. Physiol. 219: 744–751, 2009. © 2009 Wiley‐Liss, Inc.  相似文献   

12.
Laminin promotes mast cell attachment   总被引:4,自引:0,他引:4  
Tissue mast cells often localize in close proximity to the basement membrane of endothelial cells and increase at sites of inflammation. The reason for this unique tissue distribution is unknown. We report here that both the murine mast cell line PT18 and mouse bone marrow-derived mast cells possess functional receptors for laminin, and exhibit adhesion, spreading and redistribution of histamine-containing granules on a laminin substratum. This adherence is enhanced in the presence of purified IL-3 and can be inhibited by antibodies to laminin and by antibodies to laminin receptors. Northern analysis showed a high level of mRNA for a 32-kDa laminin receptor in PT18 mast cells. Mouse bone marrow-derived cultures initially exhibited a low level of the mRNA expression. However, the expression of the laminin receptor mRNA is induced rapidly within 1 wk of culture with IL-3. Thus, mast cells exhibit functional laminin receptors that may explain the tissue distribution of mast cells and their accumulation at sites of tissue injury.  相似文献   

13.
Human endothelial cell thrombin receptors were functionally expressed in Xenopus laevis oocytes by injection of RNA extracted from human umbilical vein endothelial cells. Oocytes injected with endothelial cell RNA responded to thrombin with a Ca2(+)-dependent depolarizing current whose size depended on the amount of RNA injected. In oocytes expressing thrombin receptors, thrombin caused homologous but not heterologous desensitization. Both the catalytic and anion-binding exosites of thrombin were necessary to elicit depolarizing currents. Thus, Xenopus laevis oocytes injected with mRNA from human endothelial cells express Ca2(+)-dependent thrombin receptors which share many common features with thrombin receptors on intact endothelial cells. Xenopus oocytes may, therefore, be used as a screening system in the expression cloning of the endothelial cell thrombin receptor.  相似文献   

14.
Mast cells are well known for their role in allergic and anaphylactic reactions, as well as their involvement in acquired and innate immunity. Increasing evidence now implicates mast cells in inflammatory diseases where they are activated by non-allergic triggers, such as neuropeptides and cytokines, often exerting synergistic effects as in the case of IL-33 and neurotensin. Mast cells can also release pro-inflammatory mediators selectively without degranulation. In particular, IL-1 induces selective release of IL-6, while corticotropin-releasing hormone secreted under stress induces the release of vascular endothelial growth factor. Many inflammatory diseases involve mast cells in cross-talk with T cells, such as atopic dermatitis, psoriasis and multiple sclerosis, which all worsen by stress. How mast cell differential responses are regulated is still unresolved. Preliminary evidence suggests that mitochondrial function and dynamics control mast cell degranulation, but not selective release. Recent findings also indicate that mast cells have immunomodulatory properties. Understanding selective release of mediators could explain how mast cells participate in numerous diverse biologic processes, and how they exert both immunostimulatory and immunosuppressive actions. Unraveling selective mast cell secretion could also help develop unique mast cell inhibitors with novel therapeutic applications. This article is part of a Special Issue entitled: Mast cells in inflammation.  相似文献   

15.
Mast cells are well known for their role in allergic and anaphylactic reactions, as well as their involvement in acquired and innate immunity. Increasing evidence now implicates mast cells in inflammatory diseases where they are activated by non-allergic triggers, such as neuropeptides and cytokines, often exerting synergistic effects as in the case of IL-33 and neurotensin. Mast cells can also release pro-inflammatory mediators selectively without degranulation. In particular, IL-1 induces selective release of IL-6, while corticotropin-releasing hormone secreted under stress induces the release of vascular endothelial growth factor. Many inflammatory diseases involve mast cells in cross-talk with T cells, such as atopic dermatitis, psoriasis and multiple sclerosis, which all worsen by stress. How mast cell differential responses are regulated is still unresolved. Preliminary evidence suggests that mitochondrial function and dynamics control mast cell degranulation, but not selective release. Recent findings also indicate that mast cells have immunomodulatory properties. Understanding selective release of mediators could explain how mast cells participate in numerous diverse biologic processes, and how they exert both immunostimulatory and immunosuppressive actions. Unraveling selective mast cell secretion could also help develop unique mast cell inhibitors with novel therapeutic applications. This article is part of a Special Issue entitled: Mast cells in inflammation.  相似文献   

16.
PURPOSE OF REVIEW: A novel link between inflammation and acute coronary syndromes is emerging, in that infiltrating inflammatory cells may convert a clinically silent coronary plaque into a dangerous and potentially lethal plaque. The majority of acute atherothrombotic events now relate to erosion or rupture of such unstable plaques. Here we summarize the molecular mechanisms by which activated mast cells may contribute to plaque erosion or rupture. RECENT FINDINGS: In-vitro experiments have revealed a multitude of paracrine effects exerted by activated mast cells. By secreting heparin proteoglycans and chymase, activated mast cells efficiently inhibit the proliferation of smooth muscle cells in vitro, and reduce their ability to produce collagen by a transforming growth factor beta-dependent and -independent mechanism. Mast cell chymase and tryptase are capable of activating matrix metalloproteinases types 1 and 3, causing degradation of the extracellular matrix component, collagen, necessary for the stability of the plaque. Activated mast cells also secrete matrix metalloproteinases types 1 and 9 themselves. Furthermore, chymase induces SMC apoptosis by degrading fibronectin, a pericellular matrix component necessary for SMC adhesion and survival, with the subsequent disruption of focal adhesions and loss of outside-in survival signaling. By secreting chymase and tumour necrosis factor alpha, activated mast cells also induce endothelial cell apoptosis. SUMMARY: Locally activated mast cells may participate in the weakening of atherosclerotic plaques by secreting heparin proteoglycans, chymase, and cytokines, which affect the growth, function and death of arterial endothelial cells and smooth muscle cells, thereby predisposing to plaque erosion or rupture.  相似文献   

17.
The interaction of bovine alpha-thrombin with peritoneal mast cells was studied using FITC-labeled enzyme. Thrombin was modified with FITC in the presence of heparin and was separated from heparin and free FITC by gel-filtration at HPLC yielding FITC-labeled alpha-thrombin with intact additional recognition binding site for high molecular substrates and cell receptors. Equilibrium studies have shown that the binding of thrombin to peritoneal mast cells is active independent, rapid, specific, saturable and reversible. Equilibrium between bound and free thrombin is attained within I min and Scatchard analysis indicates a population of approximately 54 x 10(3) sites/cell with a dissociation constant of 1.3 x 10(-9) M. FITC-labeled alpha-thrombin binds to peritoneal mast cells in a temperature-dependent manner with optimum at 37 degrees C. These results indicate that FITC-labeled alpha-thrombin binds to peritoneal mast cells with high affinity.  相似文献   

18.
Intracellular ascorbate (vitamin C) has previously been shown to tighten the endothelial barrier and maintain barrier integrity during acute inflammation in vitro. However, the downstream effectors of ascorbate in the regulation of endothelial permeability remain unclear. In this study, we evaluated ascorbate as a mediator of thrombin-induced barrier permeabilization in human umbilical vein endothelial cells and their immortalized hybridoma line, EA.hy926. We found that the vitamin fully prevented increased permeability to the polysaccharide inulin by thrombin in a dose-dependent manner, and it took effect both before and after subjection to thrombin. Thrombin exposure consumed intracellular ascorbate but not the endogenous antioxidant GSH. Likewise, the antioxidants dithiothreitol and tempol did not reverse permeabilization. We identified a novel role for ascorbate in preserving cAMP during thrombin stimulation, resulting in two downstream effects. First, ascorbate maintained the cortical actin cytoskeleton in a Rap1- and Rac1-dependent manner, thus preserving stable adherens junctions between adjacent cells. Second, ascorbate prevented actin polymerization and formation of stress fibers by reducing the activation of RhoA and phosphorylation of myosin light chain. Although ascorbate and thrombin both required calcium for their respective effects, ascorbate did not prevent thrombin permeabilization by obstructing calcium influx. However, preservation of cAMP by ascorbate was found to depend on both the production of nitric oxide by endothelial nitric-oxide synthase, which ascorbate is known to activate, and the subsequent generation cGMP by guanylate cyclase. Together, these data implicate ascorbate in the prevention of inflammatory endothelial barrier permeabilization and explain the underlying signaling mechanism.  相似文献   

19.
The status of the mast cell population was studied and compared after administration of trypsin or alpha-thrombin in similar molar concentrations. Morphometry disclosed a substantial shift of the mast cell population towards light, heparin-free cells within one minute after alpha-thrombin administration. The index of mast cell saturation with heparin dropped below 1. The maximal heparin secretion was observed at the 5th minute of experiment. The morphometric criteria of the mast cell population returned to basal level in 120 minutes. These data along with a significant increase in the level of complex heparin compounds and plasma thrombin time indicate heparin release as a result of the effector action of the anticoagulation system. No changes were observed in the activity of complex heparin compounds and in thrombin time after intravenous injection of trypsin. It is suggested that high heparin secretion by mast cells may serve as criterion of the active status of the anticoagulation system.  相似文献   

20.
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