Nutrient-sensing GHS-R in macrophage reprogramming and inflamm-aging

项目摘要 衰老与肥胖增加有关，这会在许多人中引发低级别的慢性炎症 组织，称为“炎症老化”。这种新陈代谢引发的炎症，也就是“化炎症”，是基础。 这是许多年龄相关疾病的病理过程，也是衰老的标志。巨噬细胞是主要的 免疫--化炎症的中介物。巨噬细胞由促炎症的M1和抗炎的M2组成 细胞，它经历动态极化到M1和M2状态，以响应环境提示。 巨噬细胞极化在衰老过程中受损，从而导致炎症衰老。巨噬细胞抗- 炎性重编程有可能预防/逆转衰老过程中的化炎症。然而， 巨噬细胞极化的调节机制还不是很清楚。生长激素促分泌剂 受体(GHS-R)是一种已知的营养感受型胃肠激素Ghrelin受体。我们发现，全球GHS- 消融术可预防肥胖、胰岛素抵抗、脂肪组织炎症和非酒精性疾病 老年脂肪性肝炎(NASH)。GHS-R在巨噬细胞中高表达，其表达增加 衰老。相反，GHS-R在肝细胞中检测不到表达，在脂肪细胞中表达非常低。我们的基因 基因敲除研究表明，GHS-R在巨噬细胞中具有细胞自主效应。我们的初步数据显示 提示GHS-R缺失下调了关键的胰岛素信号介质-胰岛素受体底物-2 (IRS2)和巨噬细胞中的蛋白激酶Akt。因此，我们假设GHS-R是一个关键的调节因子。 巨噬细胞在衰老过程中的极化。具体地说，GHS-R激活IRS2-Akt途径以代谢 重新编程巨噬细胞以促进衰老过程中的促炎极化，导致新陈代谢 脂肪组织和肝脏的炎症。揭示GHS-R在脑缺血再灌注损伤中的作用及相关机制 巨噬细胞重编程和化炎症，我们已经产生了髓系特异性的GHS-R基因敲除和 重新表达小鼠。将测试以下全面和相辅相成的具体目标：1.确定 GHS-R在巨噬细胞极化中的作用及其对脂肪和肝脏炎症的影响 衰老(体内研究)；2.通过评估GHS-R在小鼠体内的细胞自主效应来询问细胞机制 巨噬细胞及GHS-R缺陷/再表达巨噬细胞对脂肪细胞的旁分泌作用 肝细胞(体外研究)；3.GHS-R调节巨噬细胞的分子机制 极化。我们推测，在衰老过程中，GHS-R激活胰岛素信号通路，上调合成代谢 糖酵解和下调脂肪酸氧化途径，从而促进促炎极化。这 该提案将阐明在衰老过程中巨噬细胞代谢重新编程的新范式，并将 可能发现一种新的调节机制，将营养传感信号与代谢调节联系起来 巨噬细胞中的通路。这项提案还将为是否将目标定为 巨噬细胞中的GHS-R将是对抗炎症老化的独特而有效的策略。

Project Summary Aging is associated with increased adiposity, that induces low grade chronic inflammation in many tissues, termed “inflamm-aging”. This metabolically-triggered inflammation, aka "meta-inflammation", underlies pathological processes of many age-associated diseases and is a hallmark of aging. Macrophages are a major immune-mediator of meta-inflammation. Macrophages consist of pro-inflammatory M1 and anti-inflammatory M2 cells, which undergo dynamically polarization to either M1 and M2 state in response to environmental cues. Macrophage polarization is impaired in aging, which contributes to inflamm-aging. Macrophage anti- inflammatory reprogramming has potential to prevent/reverse meta-inflammation in aging. However, the regulatory mechanisms of macrophage polarization are not well understood. Growth hormone secretagogue receptor (GHS-R), is a known receptor for nutrient-sensing gut hormone ghrelin. We have found that global GHS- R ablation protects against obesity, insulin resistance, adipose tissue inflammation and nonalcoholic steatohepatitis (NASH) in aging. GHS-R is highly expressed in macrophages and its expression increases in aging. In contrast, GHS-R expression is undetectable in hepatocytes and very low in adipocytes. Our gene knockdown study indicates that GHS-R has cell-autonomous effects in macrophages. Our preliminary data have suggested that GHS-R deletion down-regulates key insulin signaling mediators insulin receptor substrate-2 (IRS2) and protein kinase Akt in macrophages. Hence, we hypothesize that GHS-R is a key regulator of macrophage polarization in aging. Specifically, GHS-R activates the IRS2-Akt pathway to metabolically reprogram macrophages to promote pro-inflammatory polarization during aging, leading to meta- inflammation in adipose tissues and liver. To unravel the roles and pertinent mechanisms of GHS-R in macrophage reprogramming and meta-inflammation, we have generated myeloid-specific GHS-R knockout and re-expressing mice. The following comprehensive and complementary Specific Aims will be tested: 1. Determine the role of GHS-R in macrophage polarization, and its effect on adipose and hepatic meta-inflammation during aging (in vivo studies); 2. Interrogate the cellular mechanisms by assessing cell-autonomous effect of GHS-R in macrophages, and paracrine effect of GHS-R deficient/re-expressing macrophages on adipocytes and hepatocytes (ex vivo studies); 3. Delineate molecular mechanisms by which GHS-R regulates macrophage polarization. We anticipate that during aging, GHS-R activates insulin signaling pathway to upregulate anabolic glycolysis and down-regulate fatty acid oxidation pathways, thus promoting pro-inflammatory polarization. This proposal will shed light on a new paradigm for metabolic reprogramming of macrophages during aging, and will likely uncover a novel regulatory mechanism linking nutrient sensing signaling and metabolic regulatory pathways in macrophages. This proposal will also provide “proof-of-concept” evidence for whether targeting GHS-R in macrophages would be a unique and powerful strategy for combating inflamm-aging.