The role of Kupffer cells in alcohol-induced liver disease

总结 酒精性肝病是一个重要的临床问题。枯否细胞（肝驻留细胞） 巨噬细胞）在酒精性肝病的炎症反应中起关键作用。巨噬 具有促炎M1型和抗炎M2型不同的功能状态。的 控制这种经典极化的机制仍有待阐明。本研究的目的是 1）鉴定在乙醇背景下确定M1相对于M2极化的新型分子开关- 诱导的肝脂肪变性和损伤，以及2）评估枯否细胞作为治疗剂的潜力 目标 内质网（ER）驻留蛋白Nogo-B，也称为内质网蛋白4 B，已经被发现。 参与维持ER结构。在肝脏中，Nogo-B仅限于非实质细胞 包括枯否细胞、肝窦内皮细胞和肝星状细胞，但在 肝细胞我们的初步数据表明，Nogo-B水平与严重性相关， 酒精性肝病患者库普弗细胞中Nogo-B水平与M1呈正相关 极化和负M2极化在人肝标本。在小鼠中， Nogo-B导致肝脏脂肪变性和损伤的水平显著低于野生型（WT）小鼠。 对乙醇饮食的反应来自Nogo-B敲除（KO）小鼠的Kupffer细胞显示出显著的细胞毒性。 M1标志物表达减少，包括诱导型一氧化氮合酶（iNOS）、白细胞介素1β (IL1β）和肿瘤坏死因子α（TNFα），但表现出显著增加的M2标志物，如 CD 163和CD 163 -1，与它们的WT对应物相比。重要的是，iNOS、IL 1 β和TNFα具有 据报道，在酒精或非酒精环境中， 活化B细胞的核因子κ-轻链增强子（NF κ B）。Nogo-B KO枯否细胞 表现出显著增加的ER应力，这是诱导M2极化的因素。基于这些 从人类标本和动物研究的观察，我们假设Nogo-B调节 慢性乙醇对枯否细胞极化和肝脂肪变性/损伤的影响 消耗和Kupffer细胞中Nogo-B的选择性缺失将减少乙醇诱导的肝细胞凋亡。 损伤为了验证这些假设，我们提出了以下三个目标：1）确定机制， 其中Nogo-B促进库普弗细胞响应于慢性乙醇消耗的M1极化，2） 确定Nogo-B缺乏促进Kupffer细胞M2极化的机制， 3）确定枯否细胞中Nogo-B的缺失是否 减少乙醇喂养小鼠的肝脂肪变性和损伤。

SUMMARY Alcohol-induced liver disease is a significant clinical problem. Kupffer cells (liver resident macrophages) play crucial roles in the inflammatory responses of alcoholic liver disease. Macrophages have distinct functional states with pro-inflammatory M1 type and anti-inflammatory M2 type. The mechanisms that govern this classical polarization remain to be elucidated. The goals of this study are to: 1) Identify a novel molecular switch that determines M1 vs. M2 polarization in the context of ethanol- induced hepatic steatosis and injury and 2) Evaluate the potential of Kupffer cells as a therapeutic target. An endoplasmic reticulum (ER) resident protein, Nogo-B, also known as reticulon 4B, has been implicated in maintaining ER structure. In the liver, Nogo-B is restricted to non-parenchymal cells including Kupffer cells, liver sinusoidal endothelial cells and hepatic stellate cells, but not in hepatocytes. Our preliminary data demonstrate that Nogo-B levels correlate with the severity of alcoholic liver disease in patients. Nogo-B levels in Kupffer cells were positively associated with M1 polarization and negatively with M2 polarization in human liver specimens. In mice, the absence of Nogo-B resulted in significantly lower levels of hepatic steatosis and injury than wildtype (WT) mice in response to an ethanol diet. Kupffer cells from Nogo-B knockout (KO) mice showed significantly decreased expression of M1 markers, including inducible nitric oxide synthase (iNOS), interleukin 1β (IL1β) and tumor necrosis factor α (TNFα), but exhibited significantly increased M2 markers, such as CD163 and arginase-1, compared to their WT counterparts. Importantly, iNOS, IL1β and TNFα have been reported to enhance hepatic steatosis in alcoholic or non-alcoholic settings and are induced by nuclear factor kappa-light-chain-enhancer of activated B cells (NFkB). Nogo-B KO Kupffer cells exhibited significantly increased ER stress, a factor that induces M2 polarization. Based on these observations from human specimens and animal studies, we hypothesize that Nogo-B regulates Kupffer cell polarization and facilitates hepatic steatosis/injury in response to chronic ethanol consumption and that selective deletion of Nogo-B in Kupffer cells will reduce ethanol-induced hepatic injury. To test these hypotheses, we propose the following three aims: 1) Determine the mechanism by which Nogo-B facilitates M1 polarization of Kupffer cells in response to chronic ethanol consumption, 2) Determine the mechanism by which lack of Nogo-B facilitates M2 polarization of Kupffer cells in response to chronic ethanol consumption, and 3) Determine whether deletion of Nogo-B in Kupffer cells reduces hepatic steatosis and injury in ethanol-fed mice.