ALVEOLAR MACROPHAGE PHI REGULATION AND CELL FUNCTION

肺泡巨噬细胞 PHI 调节和细胞功能

基本信息

批准号：
2228163
负责人：
AKHIL BIDANI
金额：
$ 22.89万
依托单位：
UNIVERSITY OF TEXAS MED BR GALVESTON
依托单位国家：
美国
项目类别：
财政年份：
1995
资助国家：
美国
起止时间：
1995-08-01 至 2000-07-31
项目状态：
已结题

项目摘要

Alveolar macrophages play a vital role in the inflammatory response to inhaled pathogens and particulates and, by that, are a crucial element of host defense. Further, they participate in antigen presentation and secrete biologically-active substances that modulate the growth and differentiation of lung cells and interact with other phagocytes. Despite the importance of alveolar macrophages in lung physiology and pathophysiology, there is limited knowledge of the factors that modulate and regulate their crucial effector functions (i.e., scavenger activity and secretory properties). Over the past decade, many studies have shown that intracellular pH (pHi) affects and is affected by cell functions. It is not surprising, therefore, that patterns of pHi regulation are cell- specific and "function-related". We recently identified a novel mechanism for pHi regulation in alveolar macrophages, namely, a plasmalemmal vacuolar-type H+-ATPase (V-ATPase) whose activity is allosterically activated with reductions in pHi. V-ATPase activity persists at low extracellular pH (pH0), where other mechanisms for pHi regulation (e.g., Na+-H+ exchange) may be limited. We postulate that the activity of plasmalemmal V-ATPase preserves pHi and, therefore, the ability of alveolar macrophages to maintain pHi-sensitive functions in regions of acidic pH0 (e.g., tumors and abscesses). The proposed research seeks insight into the links between macrophage effector functions and the activity of plasmalemmal acid-base transporters. Our strategy is to correlate selected markers of macrophage functional competence with the activity of plasmalemmal acid-base transporters. Studies will be conducted to characterize the biophysical determinants of specific acid- base transporters, as a function of pHi and pH0. Tightly coupled to these measurements, quantitative theoretical models of whole cell PHi regulation will be used to characterize the kinetic properties of the constituent acid-base transporters. Hypothesis-driven studies then will be conducted to define the mechanisms underlying the responses of individual acid-base transporters to selected exogenous agonists, namely endotoxin and phorbol esters. Concurrently, the pHi/pH0-sensitivity of selected effector functions (phagocytosis, TNFalpha release, superoxide generation) will be determined using a variety of alternate methods to verify the specificity of the observed effects. These tightly-coupled measurements will clarify and quantify the relationships between pHi regulation and macrophage functional competence in resident alveolar macrophages. The results should provide important insights into the mechanisms that modulate alveolar macrophage functions in health and the derangements associated with pulmonary infections and acute lung injury.

肺泡巨噬细胞在炎症反应中发挥着重要作用吸入的病原体和颗粒物是主机防御。此外，它们参与抗原呈递并分泌调节生长的生物活性物质肺细胞的分化并与其他吞噬细胞相互作用。尽管肺泡巨噬细胞在肺生理学中的重要性病理生理学，对调节因素的了解有限并调节其关键的效应功能（即清道夫活性）和分泌特性）。过去十年来，许多研究表明细胞内 pH (pHi) 影响细胞功能并受细胞功能影响。它因此，pHi 调节模式是细胞调节模式也就不足为奇了。具体的和“功能相关的”。我们最近发现了一种新机制调节肺泡巨噬细胞的 pHi，即质膜液泡型 H+-ATP 酶（V-ATP 酶），其活性是变构的随着 pHi 的降低而被激活。 V-ATP酶活性持续处于低水平细胞外 pH (pH0)，其中其他 pHi 调节机制（例如， Na+-H+交换)可能是有限的。我们假设活动质膜 V-ATP 酶保留 pHi，因此，肺泡巨噬细胞维持 pHi 敏感功能酸性 pH0（例如肿瘤和脓肿）。拟议的研究旨在深入了解巨噬细胞效应器功能与质膜酸碱转运蛋白的活性。我们的策略是将巨噬细胞功能能力的选定标记与质膜酸碱转运蛋白的活性。研究将是进行表征特定酸的生物物理决定因素碱基转运蛋白，作为 pHi 和 pH0 的函数。与这些紧密耦合全细胞 PHi 调节的测量、定量理论模型将用于表征成分的动力学特性酸碱转运蛋白。然后将进行假设驱动的研究定义个体酸碱反应的机制转运至选定的外源激动剂，即内毒素和佛波醇酯类。同时，所选效应器的 pHi/pH0 敏感性功能（吞噬作用、TNFα 释放、超氧化物生成）将使用多种替代方法来确定以验证特异性观察到的效果。这些紧密耦合的测量将澄清并量化 pHi 调节与巨噬细胞之间的关系常驻肺泡巨噬细胞的功能能力。结果应该为调节肺泡的机制提供重要见解巨噬细胞在健康中的功能以及与之相关的紊乱肺部感染和急性肺损伤。