Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P15088 (mast cell)
 14,925 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Snake envenomation employs three well integrated strategies: prey immobilization via hypotension, prey immobilization via paralysis, and prey digestion. Purines (adenosine, guanosine and inosine) evidently play a central role in the envenomation strategies of most advanced snakes. Purines constitute the perfect multifunctional toxins, participating simultaneously in all three envenomation strategies. Because they are endogenous regulatory compounds in all vertebrates, it is impossible for any prey organism to develop resistance to them. Purine generation from endogenous precursors in the prey explains the presence of many hitherto unexplained enzyme activities in snake venoms: 5'-nucleotidase, endonucleases (including ribonuclease), phosphodiesterase, ATPase, ADPase, phosphomonoesterase, and NADase. Phospholipases A(2), cytotoxins, myotoxins, and heparinase also participate in purine liberation, in addition to their better known functions. Adenosine contributes to prey immobilization by activation of neuronal adenosine A(1) receptors, suppressing acetylcholine release from motor neurons and excitatory neurotransmitters from central sites. It also exacerbates venom-induced hypotension by activating A(2) receptors in the vasculature. Adenosine and inosine both activate mast cell A(3) receptors, liberating vasoactive substances and increasing vascular permeability. Guanosine probably contributes to hypotension, by augmenting vascular endothelial cGMP levels via an unknown mechanism. Novel functions are suggested for toxins that act upon blood coagulation factors, including nitric oxide production, using the prey's carboxypeptidases. Leucine aminopeptidase may link venom hemorrhagic metalloproteases and endogenous chymotrypsin-like proteases with venom L-amino acid oxidase (LAO), accelerating the latter. The primary function of LAO is probably to promote prey hypotension by activating soluble guanylate cyclase in the presence of superoxide dismutase. LAO's apoptotic activity, too slow to be relevant to prey capture, is undoubtedly secondary and probably serves principally a digestive function. It is concluded that the principal function of L-type Ca(2+) channel antagonists and muscarinic toxins, in Dendroaspis venoms, and acetylcholinesterase in other elapid venoms, is to promote hypotension. Venom dipeptidyl peptidase IV-like enzymes probably also contribute to hypotension by destroying vasoconstrictive peptides such as Peptide YY, neuropeptide Y and substance P. Purines apparently bind to other toxins which then serve as molecular chaperones to deposit the bound purines at specific subsets of purine receptors. The assignment of pharmacological activities such as transient neurotransmitter suppression, histamine release and antinociception, to a variety of proteinaceous toxins, is probably erroneous. Such effects are probably due instead to purines bound to these toxins, and/or to free venom purines.
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PMID:Ophidian envenomation strategies and the role of purines. 1173 31

Mast cells are key regulators in allergy and inflammation, and release histamine upon clustering of their IgE receptors. Here we demonstrate that murine mast cell responses are exacerbated in vitro and in vivo by autocrine signals through G protein-coupled receptors (GPCRs) and require functional phosphoinositide 3-kinase gamma (PI3Kgamma). Adenosine, acting through the A(3) adenosine receptor (A(3)AR) as well as other agonists of G(alphai)-coupled GPCRs, transiently increased PtdIns(3,4,5)P(3) exclusively via PI3Kgamma. PI3Kgamma-derived PtdIns(3,4,5)P(3) was instrumental for initiating a sustained influx of external Ca(2+) and degranulation. Mice lacking PI3Kgamma did not form edema after intradermal injection of adenosine and when challenged by passive systemic anaphylaxis. PI3Kgamma thus relays inflammatory signals through various G(i)-coupled receptors and is central to mast cell function.
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PMID:Phosphoinositide 3-kinase gamma is an essential amplifier of mast cell function. 1191 28

Adenosine administration by inhalation elicits concentration-related bronchoconstriction in subjects with asthma and chronic obstructive pulmonary disease (COPD). The mechanisms of adenosine-induced bronchoconstriction appear to involve a selective interaction with activated mast cells with subsequent release of preformed and newly-formed mediators. Further evidence linking adenosine signalling to asthma and COPD comes from the finding that many cell types that play important roles in the exacerbation of these conditions express adenosine receptors and demonstrate relevant effects through stimulation of these receptors. Therefore, blockade of these receptors may be a valuable approach to the treatment of asthma and chronic obstructive pulmonary disease. Promising adenosine-receptor targets for novel therapeutics of asthma and chronic obstructive pulmonary disease have recently been identified in a number of inflammatory cell types, including mast cells, eosinophils, lymphocytes, neutrophils, and macrophages. The recent characterisation of the A2B receptors indicates the human lung mast cell as one of the most strategic cellular targets.
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PMID:Adenosine-receptor subtypes: their relevance to adenosine-mediated responses in asthma and chronic obstructive pulmonary disease. 1221 85

Chronic inflammation and allergy involve the activation of tissue-resident cells and, later on, the invasion of effector cells. We have previously shown that the loss of phosphoinositide 3-kinase (PI3K) gamma impairs chemokine-dependent migration of neutrophils and macrophages both in vitro and in vivo. On the other hand, PI3K gamma is not required either during phagocytic processes or in the activation of bactericidal activities like granule secretion and particle-mediated respiratory burst in neutrophils. Tissue mast cells are key regulators in allergy and inflammation and release histamine upon clustering of their IgE receptors. We have demonstrated that murine mast cell responses are exacerbated in vitro and in vivo by autocrine signals, and require functional PI3K gamma. Adenosine, acting through the A(3) adenosine receptor, as well as other agonists of G(alpha i)-coupled receptors, transiently increased PtdIns(3,4,5) P (3) exclusively via PI3K gamma. PI3K gamma-derived PtdIns(3,4,5) P (3) was instrumental for initiation of a sustained influx of external Ca(2+) and degranulation. Mice that lacked PI3K gamma did not form oedema when challenged by passive systemic anaphylaxis. PI3K gamma thus relays inflammatory signals through various GPCRs, and is thus central to mast cell function. Taken together, this suggests that pharmaceutical targeting of PI3K gamma might alleviate inflammation at both early and late stages of the allergic response.
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PMID:Phosphoinositide 3-kinase gamma: a key modulator in inflammation and allergy. 1254 1

Adenosine is released during tissue injury, ischemia and tumor growth, and promotes angiogenesis. Because mast cells accumulate in the proximity of new blood vessel development, we examined if they may contribute to adenosine-induced angiogenesis. We found that HMC-1 human mast cells express A2A, A2B, and A3 adenosine receptors. The adenosine agonist NECA (100 micromol/L) increased interleukin-8 (IL-8), vascular endothelial growth factor (VEGF), and angiopoietin-2 mRNA expression. NECA-induced secretion of IL-8 and VEGF was verified by ELISA. A2B receptors mediate VEGF and IL-8 secretion because neither CGS21680 (selective A2A agonist) nor IB-MECA (selective A3 agonist) produced this effect, and it was inhibited by the selective A2B antagonist IPDX but not by the selective A2A antagonist SCH58261 or the selective A3 antagonist MRS1191. In contrast, the selective A3 agonist IB-MECA (EC50 1 nmol/L) stimulated angiopoietin-2 expression. Conditioned media from NECA-activated HMC-1 stimulated human umbilical vein endothelial cell proliferation and migration, and induced capillary tube formation. Capillary formation induced by mast cell-conditioned media was maximal if both HMC-1 A2B and A3 receptors were activated, whereas activation of A2B receptor alone was less effective. Thus, adenosine A2B and A3 receptors act in a functional cooperative fashion to promote angiogenesis by a paracrine mechanism involving the differential expression and secretion of angiogenic factors from human mast cells.
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PMID:Mast cell-mediated stimulation of angiogenesis: cooperative interaction between A2B and A3 adenosine receptors. 1260 Aug 79

Mice rendered adenosine deaminase-deficient manifest an 'asthma' phenotype in the lungs that includes mast cell degranulation, eosinophilia, mucus hypersecretion and bronchial hyperresponsiveness. These changes can be reversed by enzyme therapy with adenosine deaminase, and attenuated by theophylline. Theophylline also blocks the pro-inflammatory effects of adenosine in allergen-challenged mice. Adenosine A(2A) receptors are an essential part of the physiological negative feedback mechanism for limitation and termination of both tissue-specific and systemic inflammatory responses. In recent clinical studies, increases in plasma adenosine have been shown to accompany exercise-induced asthma, and adenosine concentrations in exhaled breath condensate are increased in asthmatics. These new data provide support for a key role for adenosine in asthma, which has become increasingly persuasive in recent years. The evidence is now convincing, and the time has come for the asthma community to give its full support to the design and evaluation of molecules that mimic or block the biological effects of adenosine as potential novel therapeutics for this condition.
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PMID:The case for a role for adenosine in asthma: almost convincing? 1281 Jan 90

Adenosine-induced bronchoconstriction is a well-recognized feature of atopic asthma. Adenosine acts through four different G protein-coupled receptors to produce a myriad of physiological effects. To examine the contribution of the A(3) adenosine receptor to adenosine-induced bronchoconstriction and to assess the contribution of mast cells to this process, we quantified airway responsiveness to aerosolized adenosine in wild-type, A(3) receptor-deficient, and mast cell-deficient mice. Compared with the robust airway responses elicited by adenosine in wild-type mice, both A(3)-deficient and mast cell-deficient mice exhibited a significantly attenuated response compared with their respective wild-type controls. Histological examination of the airways 4 h after adenosine exposure revealed extensive degranulation of airway mast cells as well as infiltration of neutrophils in wild-type mice, whereas these findings were much diminished in A(3)-deficient mice and were not different from those in PBS-treated controls. These data indicate that the airway responses to aerosolized adenosine in mice occur largely through A(3) receptor activation and that mast cells contribute significantly to these responses, but that activation of additional adenosine receptors on a cell type(s) other than mast cells also contributes to adenosine-induced airway responsiveness in mice. Finally, our findings indicate that adenosine exposure can result in A(3)-dependent airway inflammation, as reflected in neutrophil recruitment, as well as alterations in airway function.
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PMID:Identification of A3 receptor- and mast cell-dependent and -independent components of adenosine-mediated airway responsiveness in mice. 1281 15

Adenosine has been implicated to play a role in asthma in part through its ability to influence mediator release from mast cells. Most physiological roles of adenosine are mediated through adenosine receptors; however, the mechanisms by which adenosine influences mediator release from lung mast cells are not understood. We established primary murine lung mast cell cultures and used real-time RT-PCR and immunofluorescence to demonstrate that the A(2A), A(2B), and A(3) adenosine receptors are expressed on murine lung mast cells. Studies using selective adenosine receptor agonists and antagonists suggested that activation of A(3) receptors could induce mast cell histamine release in association with increases in intracellular Ca(2+) that were mediated through G(i) and phosphoinositide 3-kinase signaling pathways. The function of A(3) receptors in vivo was tested by exposing mice to the A(3) receptor agonist, IB-MECA. Nebulized IB-MECA directly induced lung mast cell degranulation in wild-type mice while having no effect in A(3) receptor knockout mice. Furthermore, studies using adenosine deaminase knockout mice suggested that elevated endogenous adenosine induced lung mast cell degranulation by engaging A(3) receptors. These results demonstrate that the A(3) adenosine receptor plays an important role in adenosine-mediated murine lung mast cell degranulation.
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PMID:Activation of murine lung mast cells by the adenosine A3 receptor. 1281 16

Adenosine is an endogenous nucleoside that is released under pathological conditions and interacts with four G-protein-coupled receptor subtypes. These receptors are widely distributed throughout the body. They are involved in many central and peripheral processes, including immunological and inflammatory responses. In inflammatory and asthmatic conditions, the extracellular concentration of adenosine increases in the airway tissue. It enhances mast cell degranulation and bronchoconstriction, but may also inhibit eosinophil or lymphocyte function or modulate reactive oxygen species generation in neutrophils. Despite a large number of studies clearly indicating the effects of adenosine in vitro, many aspects of the mechanisms involved in the adenosine-mediated responses are still unclear, and our knowledge is limited in understanding the complex multifactorial interactions occurring in the whole body. The discovery of adenosine receptor compounds acting with increasing selectivity will bring new approaches to the use of adenosine receptor agonists and antagonists and may clarify some of the current uncertainties. On the basis of our present knowledge, the development of adenosine A(2A)- or (A3)-receptor agonists as antiinflammatory agents or A(2B)-receptor antagonists as inhibitors of mast cell degranulation for the treatment of asthma holds promise.
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PMID:Therapy of bronchial asthma with adenosine receptor agonists or antagonists. 1281

Adenosine, when given by inhalation, initiates the narrowing of airways in subjects with asthma or chronic obstructive pulmonary disease (COPD). The underlying mechanism of this narrowing appears to involve the stimulation of specific mast cell surface adenosine receptors with the subsequent release of mediators and contraction of airway smooth muscle. Although methacholine and histamine have become gold standards as bronchial provocants used to quantify bronchial hyperresponsiveness, the airways response to the indirect stimulus adenosine more closely reflects bronchial inflammation. This distinctive feature of adenosine could be exploited to enable superior diagnostic discrimination between asthma and COPD, allow better monitoring of disease activity and progression, and improve the individual adjustment of long-term asthma management with topical glucocorticosteroids. In this article, we review recent developments in this area of rapidly evolving clinical research, focusing on the putative role of adenosine as a mediator of airway inflammation and as a useful bronchoprovocant in several clinical and research applications.
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PMID:Research applications and implications of adenosine in diseased airways. 1291 50


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