KLF4 and Myeloid Cell Biology

描述（由申请人提供）：代谢综合征（MetS）是一系列生物化学和物理紊乱，困扰着全世界近20-25%的个体。越来越多的人认识到，慢性炎症是一个统一的潜在机制，不仅是MetS的发展，也是随后发展的动脉粥样硬化性血栓性心血管疾病-这些个体发病率和死亡率的主要来源。最近的研究强调了单核细胞/巨噬细胞谱系在MetS及其后果（如动脉粥样硬化血栓形成）的发展中的重要作用。单核/巨噬细胞谱系的细胞表现出显著的可塑性，使它们能够调节其表型，有效地响应环境信号并改变其表型。为了简单起见，我们建立了一个模型系统，将炎性巨噬细胞划分为M1，抗炎巨噬细胞划分为M2。这两个亚群的平衡被认为对生理和病理炎症反应有重要影响，但它们的物种形成和功能的分子决定因素仍然知之甚少。kruppel样因子（KLFs）是锌指转录因子，涉及广泛的生物过程，包括造血生物学。尽管本课题组和其他研究人员先前的研究表明KLF4与髓细胞生物学有关，但其体内生理相关性尚未得到阐明。根据我们的初步研究，KLF4的表达在M2群体中被确定，在M1巨噬细胞中被强烈降低——这些观察结果在体内的人类炎症范式中得到了概括。功能获得和功能丧失研究表明，KLF4促进M2遗传程序并抑制M1靶基因。携带骨髓特异性KLF4缺失的小鼠表现出特征性的M1表型，这被增强的杀菌活性所证明。此外，在高脂肪饮食（HFD）的反应中，这些动物出现了许多与MetS一致的特征，包括肥胖、血脂异常、胰岛素抵抗和促动脉粥样硬化/促血栓形成状态。这些观察结果为KLF4是控制巨噬细胞亚群规范和功能的上游分子开关这一中心假设提供了基础。为了更好地了解KLF4在巨噬细胞极化和功能中的确切作用，我们提出了三个目标。在Aim 1中，我们将描述髓细胞中KLF4表达的上游机制。在Aim 2中，我们将确定KLF4调节M1/M2表型能力的分子基础。在Aim 3中，研究将确定髓系KLF4表达改变对胰岛素抵抗和动脉粥样硬化血栓形成的影响。总的来说，这些研究将阐明KLF4介导的M2表型极化的分子基础，以及KLF4充足和缺乏对胰岛素抵抗和动脉粥样硬化血栓形成的功能影响。

DESCRIPTION (provided by applicant): The metabolic syndrome (MetS) is a constellation of biochemical and physical derangements that afflicts nearly 20-25% of individuals worldwide. It is increasingly appreciated that chronic inflammation is a unifying underlying mechanism not only for the development of MetS but also for the subsequent development of atherothrombotic cardiovascular disease - the primary source of morbidity and mortality in these individuals. Recent studies highlight an essential role for cells of the monocyte/macrophage lineage in the development of MetS and its consequences such as atherothrombosis. Cells of the monocyte/macrophages lineage exhibit remarkable plasticity that allows them to modulate their phenotype and efficiently respond to environmental signals and change their phenotype. For purposes of simplicity, a model system that classifies inflammatory macrophages as M1 and anti-inflammatory macrophages as M2 macrophages has been developed. The balance of these two subsets is thought to critically influence the physiologic and pathologic inflammatory response yet the molecular determinants of their speciation and function remain poorly understood. Kruppel-like factors (KLFs) are zinc-finger transcription factors implicated in a wide spectrum of biological processes including hematopoietic biology. Although previous studies by our group and others implicated KLF4 in myeloid cell biology, the in vivo physiological relevance has not been elucidated. Based on our preliminary studies, KLF4 expression is identified with the M2 population and strongly reduced in M1 macrophages - observations that are recapitulated in human inflammatory paradigms in vivo. Gain and loss-of-function studies reveal that KLF4 promotes an M2 genetic program and inhibits M1 target genes. Mice bearing myeloid-specific deletion of KLF4 exhibit a characteristic M1 phenotype as evidenced by enhanced bactericidal activity. Further, in response to a high fat diet (HFD), these animals develop numerous features consistent with MetS including obesity, dyslipidemia, insulin resistance, and a pro-atherogenic/pro-thrombotic state. These observations provide the foundation for the central hypothesis that KLF4 is an upstream molecular switch governing macrophage subset specification and function. To better understand the precise role of KLF4 in macrophage polarization and function, three aims are proposed. In Aim 1, we will delineate the upstream mechanisms governing KLF4 expression in myeloid cells. In Aim 2, we will determine the molecular basis for KLF4's ability to regulate the M1/M2 phenotype. In Aim 3, studies will determine the effect of altered myeloid KLF4 expression on insulin resistance and atherothrombosis. Collectively, these studies will elucidate the molecular basis for KLF4-mediated polarization towards the M2 phenotype and the functional consequences of KLF4 sufficiency and deficiency on insulin resistance and atherothrombosis.