Activation of Macrophages by Lipoteichoic Acid

脂磷壁酸激活巨噬细胞

• 批准号: 7895603
• 负责人: DAVID L HASTY
• 金额: $ 31.5万
• 依托单位: UNIVERSITY OF TENNESSEE HEALTH SCI CTR
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-17 至 2012-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7895603
• 关键词: Affect; Animal Model; Antibiotics; Bacteria; Binding Proteins; Blood; Cell Wall; Cells; Chemosensitization; Data; Dendritic Cells; Elements; Environment; Funding; G Cells; Genes; Greater sac of peritoneum; Growth; Hemoglobin; IL6 gene; Immune response; Immune system; In Vitro; Infection; Inflammation Mediators; Inflammatory; Inflammatory Response; Interleukin-6; Laboratories; Life; Ligands; Macrophage Activation; Messenger RNA; Molecular; Mus; Nature; Pathway interactions; Peptidoglycan; Peritoneal Macrophages; Process; Proteins; Repression; Role; Signal Pathway; Signal Transduction; Streptococcus pyogenes; Surface; System; TLR4 gene; Testing; Transcriptional Activation; Translations; Tumor Necrosis Factor-alpha; Up-Regulation; Wild Type Mouse; Work; base; chemokine; cytokine; human TNF protein; in vivo; lipoteichoic acid; macromolecule; macrophage; monocyte; pathogenic bacteria; receptor; research study; response

Because Gram-positive (G+) infections are common and can be life-threatening, it is critical to have a thorough understanding of how these pathogenic bacteria and the various molecules that they release interact with the host immune system. One bacterial component long thought to affect the host inflammatory response is lipoteichoic acid (LTA), a surface component expressed by virtually all G+ bacteria and released into the surrounding environment during bacterial growth and as a result of treatment with some antibiotics. LTA’s role in stimulating cells of the innate immune system, particularly monocytes, dendritic cells and macrophages, is supported by a large body of work. In addition, in vitro experiments from our laboratory and others have shown that, while LTA can stimulate cells of the immune system to initiate a pro-inflammatory response, LTA also has the ability to synergize with host macromolecules to greatly enhance this cytokine response. The experiments outlined in this proposal will examine both the in vitro and in vivo interactions of LTA and one of its synergistic partners, hemoglobin (Hb). The specific aims, revised according to the 2-year ARRA funding limit, are to: 1. Determine how LTA synergizes with the host protein Hb. This aim will focus on understanding the mechanisms by which LTA and Hb synergize to result in a 10-fold potentiation of macrophage cytokine secretion and will specifically focus on understanding the role of TLR4 in this process. We will determine the effects of LTA+Hb stimulation on the recruitment of various receptors to the macrophage surface and define which TLR signaling pathways are utilized to transduce these signals. Further understanding of this process will be obtained by looking at the set of TLR-responsive genes that are transcriptionally activated when macrophages are stimulated by LTA+Hb and comparing these data to the genes activated by LTA alone, both in WT and TLR4-/- macrophages. Finally, we will begin to determine what stimulatory molecule is responsible for the TLR4-dependent nature of this response. 2. Determine the consequences of synergistic interactions of LTA and Hb in vivo. We have recently found that Hb potentiates the the IL-6 and TNF-alpha responses of wildtype mice to LTA, indicating that the phenomenon we have studied in vitro is also operative in vivo. We hypothesize that this increased cytokine response will either impede or exacerbate S. pyogenes infections. We will study the release of cytokines into the blood and peritoneal cavities of mice injected i.p. with LTA in the presence and absence of Hb. Lastly, we will determine whether such pretreatments ameliorate or exacerbate a S. pyogenes infection.

由于革兰氏阳性（G+）感染很常见，并且可能危及生命，因此深入了解这些致病细菌及其释放的各种分子如何与宿主免疫系统相互作用至关重要。长期以来被认为影响宿主炎症反应的一种细菌组分是脂磷壁酸（LTA），这是一种几乎所有G+细菌表达的表面组分，并在细菌生长期间释放到周围环境中，并作为某些抗生素治疗的结果。LTA在刺激先天免疫系统的细胞，特别是单核细胞、树突细胞和巨噬细胞中的作用得到了大量工作的支持。此外，来自我们实验室和其他实验室的体外实验表明，虽然LTA可以刺激免疫系统的细胞启动促炎反应，但LTA还具有与宿主大分子协同作用的能力，从而大大增强这种细胞因子反应。本提案中概述的实验将研究LTA及其协同伙伴之一血红蛋白（Hb）的体外和体内相互作用。根据两年期ARRA资金限额修订的具体目标是：1.确定LTA如何与宿主蛋白质Hb协同作用。这一目标将侧重于了解LTA和Hb协同作用导致巨噬细胞细胞因子分泌增强10倍的机制，并将特别侧重于了解TLR 4在这一过程中的作用。我们将确定LTA+Hb刺激对巨噬细胞表面各种受体的募集的影响，并确定哪些TLR信号传导途径用于抑制这些信号。通过观察当巨噬细胞被LTA+Hb刺激时转录激活的TLR响应基因的集合，并将这些数据与WT和TLR 4-/-巨噬细胞中单独由LTA激活的基因进行比较，将获得对该过程的进一步理解。最后，我们将开始，以确定什么刺激分子是负责这种反应的TLR 4依赖性的性质。2.确定LTA和Hb在体内协同相互作用的后果。我们最近发现Hb增强野生型小鼠对LTA的IL-6和TNF-α反应，这表明我们在体外研究的现象在体内也有效。我们假设这种增加的细胞因子反应会阻碍或加重S。化脓性感染我们将研究在存在和不存在Hb的情况下，腹腔注射LTA的小鼠的血液和腹腔中细胞因子的释放。最后，我们将确定这样的预处理是否改善或加剧S。化脓性感染