Effect of Bacterial Tolerance on TLR4 Signal Transduction

细菌耐受性对 TLR4 信号转导的影响

• 批准号: 7064266
• 负责人: ANDREI E MEDVEDEV
• 金额: $ 32.63万
• 依托单位: UNIVERSITY OF MARYLAND BALTIMORE
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-05-15 至 2010-01-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7064266
• 关键词: alcohol phosphotransferase; biological signal transduction; clinical research; host organism interaction; human subject; immune response; immune tolerance /unresponsiveness; lipopolysaccharides; microorganism immunology; monocyte; posttranslational modifications; protein protein interaction; receptor expression; septicemia; toll like receptor

DESCRIPTION (provided by applicant): Despite advances of modern medicine, bacterial sepsis remains one of the major threats to human health worldwide. In the U.S.A alone, it affects approximately 750,000 Americans per year, with an associated mortality rate >28%. The lipopolysaccharide (LPS), an outer membrane component of Gram negative bacteria, and various structures of Gram positive bacteria and Mycobacterium tuberculosis, represent the initiating stimuli in the activation of the innate immune response. Effective recognition of these bacterial structures by Toll-like receptors (TLR) expressed on monocytes and macrophages is critical for mounting a strong first line defense and prevention of sepsis. Many patients with sepsis develop a hypoinflammatory state that is manifested by marked inhibition of monocyte functions, including suppressed production of a number of cytokines. This state is highly reminiscent of bacterial tolerance defined as a transient state of cell refractoriness following a prior exposure to bacterial components. Therefore, induction of bacterial tolerance can be used as a model to delineate mechanisms that underlie decreased monocyte responsiveness in patients with sepsis. Despite numerous studies, the molecular mechanisms that underlie induction of bacterial tolerance are still largely unknown. The overall goal of this project is to gain a better understanding of the molecular mechanisms of host responses to microbes. Our objective is to define the role of receptors and signal transducing molecules of the TLR pathway in induction and maintenance of bacterial tolerance in monocytes. The central hypothesis is that induction of bacterial tolerance in human monocytes dramatically alters signal-induced complex formation among key components of the TLR pathway, leading to development of a state of suppressed antibacterial responsiveness. The following Specific Aims are proposed to: 1. Examine post-translational modifications and interactions of key molecules of TLR4 complexes associated with tolerance to TLR4 and TLR2 agonists. 2. Analyze the effect of bacterial tolerance on expression, recruitment, post-translational modifications of key adapter proteins and activation of IRAK-4. 3. Characterize suppressors of TLR-mediated signaling in tolerized cells that interfere with agonist-induced interactions among TLRs, adapter proteins, and IRAK kinases. It is expected that at the completion of this grant, we will have identified key molecular mechanisms responsible for development of bacterial tolerance, and have provided strategies for development of new therapeutic approaches for treatment of patients with bacterial sepsis to target components of the TLR signaling pathway that are compromised in tolerance and sepsis.

描述（由申请人提供）：尽管现代医学取得了进步，细菌性败血症仍然是全世界人类健康的主要威胁之一。仅在美国，每年就有大约 750,000 名美国人受到影响，相关死亡率 >28%。脂多糖（LPS）是革兰氏阴性菌的外膜成分，以及革兰氏阳性菌和结核分枝杆菌的各种结构，代表了先天免疫反应激活的起始刺激。单核细胞和巨噬细胞上表达的 Toll 样受体 (TLR) 有效识别这些细菌结构对于建立强大的一线防御和预防败血症至关重要。许多脓毒症患者会出现低炎症状态，表现为单核细胞功能明显受到抑制，包括多种细胞因子的产生受到抑制。这种状态很容易让人想起细菌耐受性，细菌耐受性被定义为细胞在先前暴露于细菌成分后的短暂不应性状态。因此，细菌耐受性的诱导可以作为模型来描述脓毒症患者单核细胞反应性下降的机制。尽管进行了大量研究，但诱导细菌耐受性的分子机制仍然很大程度上未知。该项目的总体目标是更好地了解宿主对微生物反应的分子机制。我们的目标是确定 TLR 通路的受体和信号转导分子在诱导和维持单核细胞细菌耐受性中的作用。中心假设是，人类单核细胞中细菌耐受性的诱导极大地改变了 TLR 途径关键成分之间信号诱导的复合物形成，导致抗菌反应性受到抑制的状态的发展。提出以下具体目标： 1. 检查与 TLR4 和 TLR2 激动剂耐受相关的 TLR4 复合物关键分子的翻译后修饰和相互作用。 2. 分析细菌耐受性对关键接头蛋白表达、募集、翻译后修饰和 IRAK-4 激活的影响。 3. 表征耐受细胞中 TLR 介导的信号传导抑制因子，这些抑制因子会干扰激动剂诱导的 TLR、衔接蛋白和 IRAK 激酶之间的相互作用。预计在这笔资助完成后，我们将确定导致细菌耐受性发展的关键分子机制，并提供开发新治疗方法的策略，以治疗细菌性脓毒症患者，以 TLR 信号通路的目标成分为目标耐受性和败血症受到损害。