Mast Cells

Mast cells have been considered for many years to participate specifically in allergic reactions through the release of cytokines, chemokines, proteases, leukotrienes, and bioactive polyamines. Emerging roles for mast cells have been identified recently, which highlight their relevance in both innate and adaptive immunity. Mast cells play a role in many different processes, including clearance of enteric pathogens, food allergies, visceral hypersensitivity, and intestinal cancer. The activation of mast cells can initiate inflammatory reactions that are life-saving in some circumstances (eg, nematode infection) but life-threatening in others (eg, allergy). In recent years, mast cells, their products, and the mechanisms by which mast cell activity can be regulated by the microenvironment are a major area of investigation. The purpose of this review article is to summarize and highlight the latest findings in mast cell biology associated with intestinal homeostasis and pathologies.     

The Role of Eosinophils and Mast Cells in Intestinal Functional Disease

Functional gastrointestinal disorders (FGIDs) are common and currently defined by a symptom-based classification with no discernable pathology. In functional dyspepsia (FD), the duodenum is now implicated as a key area where symptoms originate.This is attributed to immune activation with increasing evidence indicating a role for duodenal eosinophilia. In irritable bowel syndrome (IBS), mastocytosis has been documented throughout the small and large intestine. Eosinophils and mast cells are an important link between innate and adaptive immunity, and are important in allergic type TH2 inflammation. Eosinophils may give rise to symptoms due to release of preformed cytokine proteins, which trigger neural excitation, muscle spasm, and pain. The close relationship of mast cells to nerves in IBS may similarly give rise to symptoms. Genetic studies also support of the role of innate immunity in FGIDs. The data supporting a prime role for eosinophils and mast cells in subsets of FD and IBS has become credible, and these data should be used to implement advances in diagnosis and therapeutic trials.     

Characterization of N-Linked Oligosaccharides Attached to Human Renin Expressed in COS Cells

ABSTRACT

To study the role of N-linked oligosaccharides attached to human renin, we generated three kinds of glycosylation-deficient renins in which one or both of two putative N-glycosylation sites was eliminated by amino acid replacement using site-directed mutagenesis. Examination of the three mutant renins (Asn-5 to Ala, Asn-75 to Ala, and both Asn-5 and -75 to Ala) expressed in COS cells demonstrated that both putative sites were certainly glycosylated with heterologous N-linked oligosaccharides. Moreover, the oligosaccharide chain attached at Asn-5 was different from that attached at Asn-75 in its molecular size. In addition, the secreted amount of the three mutant renins were different from one another, although the mutant and wild-type renins had practically the same specific activity. Our results suggest that the N-linked oligosaccharides have no effect on the enzymatic activity, but play an important role in stable secretion of human renin.     

Mast Cells and Anaphylaxis

For half a century, it has been known that the mast cell is the cell responsible for the majority of anaphylactic events. Its mediators, taken as a whole, are capable of producing all of the clinical manifestations of these events. With the discovery of immunoglobulin E (IgE), it was originally felt that the vast majority of anaphylactic episodes were due to antigen coupling with two cell-bound IgE molecules. More recently it has been learned that many episodes are produced by direct activation of mast cells, not involving antigen binding to IgE, and that monomeric IgE under certain conditions can also cause degranulation. Of note—in regard to antigen independent degranulation—are recent reports that the human G-protein-coupled receptor, MRGPRX2, may be the receptor for many drugs and cationic proteins capable of producing direct mast cell degranulation and anaphylactic events.     

功能性消化不良患者胃粘膜肥大细胞的增加

目的:探讨胃粘膜肥大细胞(MC)与功能性消化不良(FD)之间的关系。方法:对15例健康自愿者和34例FD患者进行研究。每例胃镜下取胃窦粘膜2块,用免疫组化方法染色MC并计数。结果:34例FD患者胃粘膜MC数明显多于健康对照者(19.48/HSP±3.14/HSP与16.07/HSP±2.13/HSP,P<0.05),其中12例(35.3%)FD患者MC数超过正常人上限。且MC数与幽门螺杆菌( H.pylori)。胃粘膜炎症有明显关系。结论:FD患者胃粘膜MC数增多,可能参与了FD的发病。     

Structural and Functional Characterization of Isolated Pancreatic Exocrine Cells

Viable isolated exocrine cells have been obtained from guinea-pig pancreas by a tissue dissociation procedure using crude collagenase (EC 3.4.4.19) and hyaluronidase (EC 3.2.1.35), chelation of divalent cations, and mild shearing forces. Cell yields are 50-60%, based on recovered DNA, and about 90% of the population consists of exocrine cells which, although rounded up, retain their in situ polarity with regard to regional distribution of zymogen granules and specialization of the former luminal plasmalemma. The isolated cells incorporate labeled amino acids into proteins at linear rates for at least 4 hr at levels comparable to pancreatic slices in vitro; more than 95% of the exocrine cell population is active in this process, as shown by autoradiography. In response to secretogogues at optimal doses (100 muM carbamylcholine; 0.1 muM pancreozymin, or 0.01 muM caerulein), the cells discharge up to 30% of their content of pulse-labeled secretory proteins to the medium over a 3-hr period; in the same time, the controls release about 5% of their content. The results indicate that isolated exocrine cells are capable of synthesizing the processing secretory proteins, and of responding directly to cholinergic and peptidic secretogogues.     

大鼠肠黏膜肥大细胞生长抑素和血管活性肠肽受体mRNA的表达

背景：已知胃肠多肽生长抑素(SST)和血管活性肠肽(VIP)可调节肠黏膜肥大细胞(IMMC)的生物学活性。多数胃肠多肽对IMMC活性的调节作用可能与其受体途径有关。目的：探讨大鼠IMMC上是否有SST受体(SSTR)和VIP受体(VIPR)mRNA表达，确定SST和VIP调节IMMC活性的分子机制。方法：采用胶原酶消化法分离大鼠小肠IMMC，Percoll不连续密度梯度离心法纯化，逆转录聚合酶链反应(RT-PCR)观察IMMC上SSTR-1、SSTR-3和VIPR-1、VIPR-2mRNA的表达。结果：大鼠IMMC上有SSTR-1和VIPR-2 mRNA表达，其电泳条带分别位于1183bp和494bp，但无SSTR-3和VIPR-1mRNA表达。结论：大鼠IMMC可表达SSTR-1和VIPR-2基因，SST和VIP对IMMC活性的调节作用可能是通过其相应受体SSTR-1和VIPR-2途径实现的。     

Origin of Basophils and Mast Cells

Basophils and mast cells are major players in the progression of allergic disorders. Although both cell types originate from hematopoietic stem cells, their lineage commitment pathways and mechanisms have been unsolved issues in hematology. Recent advances in the multicolor FACS system enable the prospective isolation of progenitor populations whose readouts are restricted to basophil and/or mast cell lineages. These newly-isolated progenitor subsets are helpful to understand the developmental machinery of basophil and mast cell lineages, leading to the possible exploitation of a novel therapeutic strategy for allergic and autoimmune disorders. In this review, we summarize the recent progress in our understanding of the basophil/mast cell ontogeny on a cellular basis.     

Characterization of Mast Cell Activation Syndrome

Background

Mast cell activation syndrome (MCAS), a recently recognized nonneoplastic mast cell disease driving chronic multisystem inflammation and allergy, appears prevalent and thus important. We report the first systematic characterization of a large MCAS population.

Functional ENaC Channels Expressed in Endothelial Cells: a New Candidate for Mediating Shear Force

Endothelial cells (ECs) are regulated not only by circulating hormones, but also by mechanical stresses, such as shear force. Ion channels in ECs can signal rapid changes of shear forces and are involved in controling EC permeability, proliferation, and angiogenesis. In this study, we employed patch clamping and molecular biology approaches to clarify whether the epithelial sodium channel (ENaC) is functionally expressed in ECs. The α‐subunit of the ENaC was expressed in cultured human ECs and in intact ECs from a variety of rat arteries. In either inside‐ or outside‐out current recordings, inward currents with a conductance of 4.83 pS were detected in cultured human ECs, where these were sensitive to micromolar amiloride. The right shift of the I‐V curve in the condition of low cytoplasmic Na⁺ implicated that these currents were carried by Na⁺. The currents were mediated by ENaC channels, as confirmed by ENaC knockdown experiments. However, the activity of ENaC was nearly absent in intact ECs, because its activity was greatly inhibited by cellular molecules, partly due to 11,12‐epoxyeicosatrienoic acid. In the outside‐out configuration, laminar flow directly enhanced ENaC opening probability, suggesting a potential role for ENaC in mediating shear force signaling events.     

肥大细胞与缺血性心脏病

心脏中存在肥大细胞。在心肌缺血状态下,心脏肥大细胞密度增多并处于功能活跃状态。肥大细胞通过释放细胞因子、炎症介质、蛋白酶等内容物,参与动脉粥样硬化、心肌梗死、充血性心力衰竭等疾病的病理过程。现就当前对肥大细胞与缺血性心脏病关系的相关研究进行综述。     

Proton Pump Inhibitors Reduce Duodenal Eosinophilia,Mast Cells,and Permeability in Patients With Functional Dyspepsia

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Ethanol, Flunitrazepam, and Pentobarbital Modulation of GABAA Receptors Expressed in Mammalian Cells and Xenopus Oocytes

GABA_A receptors composed of human α1β2γ2L, α1β2γ2S, α1 β3γ2S, α6β3γ2S, and αβ3γ3 subunits as well as bovine α1 β1 γ2L and α1β1 subunits were stably expressed in mammalian L(tk^?) cells and transiently expressed in Xenopus oocytes. Effects of muscimol, ethanol, flunitrazepam, and pentobarbital on receptor function were compared for the two expression systems using a ³⁶CI^? flux assay for cells and an electrophysiological assay for oocytes. Muscimol activated all receptors in both expression systems but was more potent for L(tk^?) cells than oocytes; this difference ranged from 2.6–to 26–fold, depending upon subunit composition. The most pronounced differences between receptors and expression systems were found for ethanol. In L(tk^?) cells, low (5–50 mM) concentrations of ethanol potentiated muscimol responses only with receptors containing the γ2L subunit. In oocytes, concentrations of 30–100 mM produced small enhancements for most subunit combinations. Flunitrazepam enhanced muscimol responses for all receptors except α6β3γ2S and α1β1, and this enhancement was similar for both expression systems. Pentobarbital also enhanced muscimol responses for all receptors, and this enhancement was similar for L(tk^?) cells and oocytes, except for α6β3γ2S where the pentobarbital enhancement was much greater in oocytes than cells. The α6β3γ2S receptors were also distinct in that pentobarbital produced direct activation of chloride channels in both expression systems. Thus, the type of expression/assay system markedly affects the actions of ethanol on GABA_A receptors and also influences the actions of muscimol and pentobarbital on this receptor. Differences between these expression systems may reflect posttranslational modifications of receptor subunits.