经泛素-蛋白酶体途径调控的组蛋白乙酰转移酶HBO1降解在COPD肺血管内皮细胞凋亡中的机制研究

Chronic Obstructive Pulmonary Disease (COPD) is a major cause of chronic morbidity and mortality throughout the world. Pulmonary endothelial cell apoptosis plays a crucial role in the pathogenesis of COPD, but the related mechanism remains illusive. Epigenetic modification has been reported to be involved in pulmonary endothelial cell apoptosis recently. It has also been demonstrated that downregulated histone acetylation may be closely related with the cause of COPD. Albeit, the contribution of histone acetylation to pulmonary endothelial cell apoptosis is largely unknown. Histone acetyltransferase HBO1 can regulate cell cycle, proliferation, and transcription through selectively acetylating histone. Our previous research showed that protein expression level of HBO1 was decreased in lung tissue of COPD patients. Besides, HBO1 knockdown ablated H3K14 acetylation and consequently increased apoptotic cells in murine lung epithelial cells. In the meantime, abnormal activation of CSE-induced ubiquitin-proteasome system contributes to the pathogenesis of COPD. E3 ubiquitin ligase is a critical component of ubiquitin-proteasome system. We observed an upregulated protein level of E3 ubiquitin ligase Fbxw in COPD patients and COPD murine models. Moreover, we found that FBXW15 triggered ubiquitin-proteasome pathway to degrade HBO1 directly and specifically. So we hypothesize that FBXW15 regulates pulmonary endothelial cell apoptosis in COPD by degrading HBO1. To prove this hypothesis, we will 1) investigate the mRNA and protein levels of FBXW15 and HBO1, the acetylation level of histone H3K14 in COPD patients lung tissues, COPD murine model lung tissues, and CSE treated pulmonary endothelial cells; and the correlation of their levels to pulmonary endothelial cell apoptosis. 2) determine the role of HBO1 in CSE-induced pulmonary endothelial cell apoptosis. 3) identify the molecular mechanism of ubiquitin-proteasomal degradation of HBO1 in CSE-induced pulmonary endothelial cell apoptosis. 4) using ubiquitination site mutation to regulate HBO1 degradation and then inhibit pulmonary endothelial cell apoptosis, opening a new door for treating COPD. Therefore, execution of these researches will lay the groundwork for the advanced concept regarding a cross-talk among histone acetylation and ubiquitin-proteasome pathway in pulmonary endothelial cell apoptosis of COPD. Completion of this study may present a new therapeutic target for COPD.

肺血管内皮细胞凋亡在慢性阻塞性肺疾病（COPD）的发病机制中起着重要作用，但其确切作用机制不明。组蛋白乙酰转移酶HBO1可通过选择性乙酰化组蛋白位点调节细胞周期、增殖及转录。我们的前期研究证实COPD患者肺组织中HBO1的蛋白表达下降，且在小鼠肺上皮细胞中敲除HBO1基因可去除组蛋白H3K14的乙酰化修饰，导致细胞凋亡增加。同时吸烟所致泛素-蛋白酶体系统导常活化参与COPD病程。我们已发现HBO1可被E3泛素连接酶FBXW15识别并降解。故我们推测FBXW15可能通过降解HBO1参与调控COPD肺血管内皮细胞凋亡。本研究拟从COPD患者、动物和细胞水平观察FBXW15、HBO1表达和H3K14乙酰化水平，探讨HBO1通过组蛋白乙酰化调控COPD肺血管内皮细胞凋亡的作用，并进一步研究泛素-蛋白酶体途径调控HBO1降解的机制，为COPD治疗探索新途径。

慢性阻塞性肺疾病(COPD)已成为全世界发病率和死亡率的主要原因。吸烟是COPD发病中最常见的危险因素。HBO1(与ORC1结合的组蛋白乙酰转移酶)是一种组蛋白乙酰转移酶，参与DNA复制和转录调控等多种生物学过程。然而，HBO1在COPD发病机制中的确切作用尚未被研究。本研究通过免疫组化分析，我们发现慢性阻塞性肺病患者气道上皮和小鼠肺气肿模型中HBO1蛋白水平明显下调。我们还发现HBO1可以减弱香烟烟雾提取物(CSE)诱导的肺气肿小鼠模型中的细胞凋亡和肺气肿程度。在体外，CSE降低了HBO1在蛋白水平上的表达，但在mRNA水平上没有降低。流式细胞检测技术证实，HBO1可抑制CSE干预支气管上皮细胞(HBECs)的凋亡。此外，我们发现HBO1是H3K14乙酰化和BCL-2在气道上皮细胞表达所必需的。这些研究结果表明，HBO1在COPD发病机制中起保护作用，可能为抑制COPD进展提供潜在的治疗靶点。