Aa Ltx Induced Cell Death

Aa Ltx 诱导细胞死亡

• 批准号: 6891030
• 负责人: Edward Thomas Lally
• 金额: $ 35.66万
• 依托单位: UNIVERSITY OF PENNSYLVANIA
• 依托单位国家: 美国
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-07-01 至 2008-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6891030
• 关键词: Actinobacillus actinomycetemcomitans; BCL2 gene /protein; actin binding protein; apoptosis; bacterial cytopathogenic effect; bacterial toxins; calcium flux; calpain; cell component structure /function; confocal scanning microscopy; cyclodextrins; cytolysis; endoplasmic reticulum; immunoprecipitation; membrane permeability; membrane potentials; mitochondria; necrosis; nuclear membrane; periodontitis; phosphorylation; protease inhibitor

DESCRIPTION: Actinobacillus actinomycetemcomitans is a facultative anaerobe that has been implicated in a variety of periodontal diseases. Its presence is most closely associated with localized juvenile periodontitis (LJP) where it is believed to be the etiologic agent. The role this organism plays in other periodontal diseases, however, is not entirely clear. While A. actinomycetemcomitans produces a number of virulence factors, a leukotoxin (Ltx) appears to be most associated with enabling this organism to establish an ecological niche and thereby achieve its pathogenic potential. This concept is supported by an increasing number of clinical studies that demonstrate a reproducible ability to culture strains with the high leukotoxic phenotype from patients with active LJP. The mechanism by which A. actinomycetemcomitans Ltx kills target cells is ambiguous since two mechanisms of eukaryotic cell death have been identified: necrosis and apoptosis. High concentrations (> 104 M) of Ltx induce very rapid target cell death with little morphologic or cytometric evidence of apoptosis. Nevertheless, cells exposed to low concentrations of Ltx exhibit an alteration in mitochondrial transmembrane permeability that is followed by: 1) dissipation of the mitochondrial transmembrane potential, 2) release of apoptosis-inducing factors, 3) generation of reactive-oxygen radicals, and 4) depletion of ATP stores. The earliest change that we have observed following the addition of Ltx to susceptible cells is a rise in intracellular calcium [Ca2+]; which is both immediate (within 10 sec) and sustained. The Ltx-induced Ca 2+ influx and apoptosis exhibit an identical dose-dependence and point to a mechanistic connection linking of Ca 2+ influx and the onset of apoptosis. The ability of a mAb to neutralize the cytolytic activity of the Ltx and to inhibit the [Ca 2+]; changes are a strong indication that the reaction begins with Ltx. The proposed investigations are designed to increase our understanding of Ltx cytolysis by: 1) exploring early steps that result in Ltx-induced [Ca2+] c increases in target cells; 2) identifying the origin(s) of the increased [Ca2+] c seen in Ltx-treated cells; 3) defining effects Ltx-induced [Ca 2+] c increases have on cellular organelles and 4) characterizing the function of the endoplasmic reticulum in Ltx-treated cells.

描述：放线杆菌静脉菌群是一种辅助厌氧菌，与多种牙周疾病有关。它的存在与局部幼年牙周炎（LJP）最密切相关，该牙周炎被认为是病因学剂。但是，该生物体在其他牙周疾病中的作用尚不完全清楚。尽管A.放线菌co虫产生了许多毒力因子，但白细胞毒素（LTX）似乎与使该生物体建立生态位的生态位并从而达到其致病潜力最相关。这个概念得到了越来越多的临床研究的支持，这些研究表明，活性LJP患者具有高白细胞毒性表型培养菌株的可再现能力。 A.放线菌Cytemcomitans LTX杀死靶细胞的机制是模棱两可的，因为已经确定了两种真核细胞死亡的机制：坏死和凋亡。 LTX的高浓度（> 104 m）诱导非常快速的靶细胞死亡，几乎没有形态学或细胞凋亡的证据。然而，暴露于低浓度LTX的细胞表现出线粒体跨膜通透性的改变，其次是：1）线粒体跨膜电位的耗散，2）释放凋亡诱导因子，3）3）产生活性氧自由基的产生，以及4）DEPLETERION的生成。将LTX添加到易感细胞中后，我们观察到的最早的变化是细胞内钙[Ca2+]的升高。这既是立即（在10秒内）并持续的。 LTX诱导的Ca 2+涌入和凋亡表现出相同的剂量依赖性，并指向Ca 2+涌入和凋亡发作的机械连接。 mAb中和LTX的溶细胞活性并抑制[Ca 2+]的能力；变化是强烈的指示反应从LTX开始。拟议的研究旨在通过以下方式提高我们对LTX细胞溶解的理解：1）探索导致LTX诱导的[Ca2+] C的早期步骤增加靶细胞的[Ca2+] C增加； 2）确定在LTX处理的​​细胞中看到的[Ca2+] C增加的来源； 3）定义效应LTX诱导的[Ca 2+] C增加对细胞细胞器的增加和4）表征内质网中LTX处理细胞中内质网的功能。