Role of Monoamine Oxidase A and Diet-Induced Monocyte Dysfunction, Macrophage Reprogramming, and Atherosclerosis

单核细胞和巨噬细胞对于组织稳态是必不可少的，但在代谢紊乱的情况下， 变得功能失调并促进慢性炎症性疾病，包括动脉粥样硬化。但 根本的机制还不清楚。我们发现血液单核细胞长期暴露于 由“西方”式高热量饮食（HCD）引起的营养应激刺激活性氧的形成 活性氧（ROS）和促进蛋白巯基氧化，导致单核细胞功能障碍和重编程 将血液单核细胞转化为促炎、促动脉粥样硬化的表型，对化学引诱物高度敏感。 这些代谢“启动”的血液单核细胞产生重编程和功能障碍的巨噬细胞， 对氧固醇诱导的细胞死亡敏感，具有缺陷的自噬和失调的激活特征。 营养应激引起的单核细胞启动是由H2 O2依赖的S-谷胱甘肽化、失活和 有丝分裂原活化蛋白激酶磷酸酶1（MKP-1）的降解，MKP-1是单核细胞 粘附和迁移以及巨噬细胞功能和可塑性。然而，HCD诱导的H2 O2和 “致敏的”血液单核细胞中的“氧化应激”是未知的。我们现在已经鉴定出单胺氧化酶A（Mao A）和NADPH氧化酶4（Nox 4）作为单核细胞中营养应激诱导的H2 O2的新来源， 巨噬细胞和作为介质的营养应激诱导的单核细胞启动和功能障碍。我们假设 单核细胞中Mao A的诱导对HCD的反应通过促进动脉粥样硬化的发生而加速动脉粥样硬化的发生。 H2 O2产生和MKP-1失活，导致单核细胞启动和重编程，以及 导致单核细胞衍生的巨噬细胞功能失调、过度炎症和促动脉粥样硬化 炎症消退能力受损此外，我们建议通过使硫醇失活， 转移酶谷氧还蛋白1（Grx 1）和破坏巯基氧化还原稳态，Mao A衍生的H2 O2促进了 诱导Nox 4，放大HCD引发的氧化应激反应。为了验证这些假设， 阐明潜在的机制，我们提出以下具体目标： 具体目标1：确定高热量饮食触发诱导Mao A的机制 促进单核细胞功能障碍、巨噬细胞可塑性失调和加速动脉粥样硬化形成。 具体目标2：确定Nox 4对高热量饮食诱导的单核细胞启动的贡献， 巨噬细胞功能障碍和动脉粥样硬化形成。 具体目标3：确定高热量饮食触发单核细胞的分子机制 在代谢健康的人类受试者中的启动和重编程，以及是否以及在多大程度上 这些机制不同于小鼠。

Monocytes and macrophages are essential for tissue homeostasis, but in the context of metabolic disorders they become dysfunctional and promote chronic inflammatory diseases, including atherosclerosis. However, the underlying mechanisms are not well-understood. We showed that chronic exposure of blood monocytes to nutrient stress induced by a “Western”-style high-calorie diet (HCD) stimulates the formation of reactive oxygen species (ROS) and promotes protein thiol oxidation, resulting in monocyte dysfunction and the reprogramming of blood monocytes into a pro-inflammatory, pro-atherogenic phenotype, hyper-sensitive to chemoattractants. These metabolically “primed” blood monocytes give rise to reprogrammed and dysfunctional macrophages, sensitive to oxysterol-induced cell death, with defective autophagy and dysregulated activation profiles. Monocyte priming by nutrient stress is mediated by the H2O2-dependent S-glutathionylation, inactivation and degradation of mitogen-activated protein kinase phosphatase 1 (MKP-1), a master regulator of both monocyte adhesion and migration and macrophage function and plasticity. However, the source of HCD-induced H2O2 and “oxidative stress” in “primed” blood monocytes is not known. We have now identified monoamine oxidase A (Mao A) and NADPH oxidase 4 (Nox4) as novel sources of H2O2 induced by nutrient stress in monocytes and macrophages and as mediators of nutrient stress-induced monocyte priming and dysfunction. We hypothesize that the induction of Mao A in monocytes in response to a HCD accelerates atherogenesis by promoting H2O2 production and the inactivation of MKP-1, resulting in monocyte priming and reprogramming, and giving rise to dysfunctional, hyper-inflammatory and pro-atherogenic monocyte-derived macrophages with impaired inflammation resolving capabilities. Furthermore, we propose that by inactivating the thiol transferase glutaredoxin 1 (Grx1) and disrupting thiol redox homeostasis, Mao A-derived H2O2 promotes the induction of Nox4, amplifying the oxidative stress response triggered by HCD. To test these hypotheses and to elucidate the underlying mechanisms, we propose the following Specific Aims: Specific Aim 1: Determine the mechanisms by which high-calorie diet-triggered induction of Mao A promotes monocyte dysfunction, dysregulates macrophage plasticity, and accelerates atherogenesis. Specific Aim 2: Determine the contribution of Nox4 to high-calorie diet-induced monocyte priming, macrophage dysfunction, and atherogenesis. Specific Aim 3: Determine the molecular mechanisms by which high-calorie diets trigger monocyte priming and reprogramming in metabolically healthy human subjects and whether and to what extent these mechanisms differ from mice.