Role of ACAT1 in Pathological Retinal Neovascularization

项目总结 对小鼠氧诱导视网膜病变(OIR)模型的研究表明，巨噬细胞- 诱导的血管生成在病理性视网膜新生血管(RNV)中起着关键作用，但 机制尚不清楚。我们建议研究胆固醇的表达/活性 代谢酶ACAT(酰基辅酶A：胆固醇酰基转移酶，也称为甾醇 O-酰基转移酶)作为治疗RNV的新靶点。ACAT有两种亚型：ACAT1 和ACAT2。ACAT1在巨噬细胞或巨噬细胞中广泛表达和上调 巨噬细胞/小胶质细胞与动脉粥样硬化和阿尔茨海默病有关， 分别进行了分析。ACAT2主要在肠道和肝脏表达。我们将在年重点关注ACAT1 这个项目。在缺血/缺氧期间，巨噬细胞暴露在氧化水平增加的环境中 低密度脂蛋白胆固醇(OxLDLc)。它被低密度脂蛋白受体(LDLR)内化 增加ACAT1的活性，ACAT1将胆固醇酯化形成胆固醇酯(CE)。 CE增加促进炎性巨噬细胞表型，其特征是增加 炎症信号放大因子TREM-1的表达(触发受体在 髓系细胞-1)、巨噬细胞集落刺激因子、血管内皮生长因子和肿瘤坏死因子α。我们的预赛 在小鼠OIR模型中的研究表明，脂质堆积、LDLR表达显著增加 和CE在RNV区域的形成，表明血脂异常和ACAT活性起关键作用 在RNV。此外，LDLR缺失或ACAT抑制可预防RNV并减少 TREM-1、MCSF和VEGF的表达。此外，巨噬细胞的体外低氧处理 显著增加其TREM-1、MCSF和VEGF的表达。基于这些结果，我们的 中心假说是低密度脂蛋白诱导ACAT1和CE形成驱动增加 OIR小鼠模型中巨噬细胞的激活和病理性RNV(图1)。我们的目标 将通过确定1)抑制ACAT1是否在体内预防RNV来检验这一假说，2) 髓系细胞中ACAT1基因的缺失可阻止活体RNV和M-Φ诱导的血管生成 在试管中。

PROJECT SUMMARY Studies in the mouse model of oxygen-induced retinopathy (OIR) have shown that macrophage- induced angiogenesis has a critical role in pathological retinal neovascularization (RNV) but the mechanisms are not yet known. We propose to investigate expression/activity of the cholesterol metabolizing enzyme ACAT (acyl-Coenzyme A: cholesterol acyltransferase, also known as sterol O-acyltranserase) as a novel therapeutic target for RNV. There are two isoforms of ACAT: ACAT1 and ACAT2. ACAT1 is widely expressed and its upregulation in macrophages or macrophage/microglia has been implicated in atherosclerosis and Alzheimer's disease, respectively. ACAT2 is mainly expressed in the intestines and liver. We will focus on ACAT1 in this project. During ischemia/hypoxia, macrophages are exposed to increased levels of oxidized low density lipoprotein cholesterol (oxLDLc). Its internalization by the LDL receptor (LDLR) increases activity of ACAT1, which esterifies cholesterol to form cholesterol esters (CE). Increases in CE promote an inflammatory macrophage phenotype characterized by increased expression of the amplifier of inflammatory signaling TREM-1 (triggering receptor expressed in myeloid cells-1), MCSF (macrophage colony stimulating factor), VEGF and TNFα. Our preliminary studies in the mouse OIR model show marked increases in lipid accumulation, LDLR expression and CE formation in areas of RNV suggesting that dyslipidemia and ACAT activity play a key role in RNV. Furthermore, LDLR deletion or ACAT inhibition prevented RNV and decreased expression of TREM-1, MCSF and VEGF. Moreover, hypoxia treatment of macrophages in vitro significantly increased their expression of TREM-1, MCSF and VEGF. Based on these results our central hypothesis is that LDLc-induced increases in ACAT1 and CE formation drive macrophage activation and pathological RNV in the mouse model of OIR (Fig. 1). Our aims will test this hypothesis by determining whether 1) Inhibition of ACAT1 prevents RNV in vivo, 2) Deletion of ACAT1 in myeloid derived cells prevents RNV in vivo and MΦ -induced angiogenesis in vitro.