Genetics of Smoke-Altered LTA4H in COPD

 描述(申请人提供)：在慢性阻塞性肺疾病持续炎症的病理中的一个关键分子是胶原片段Pro-甘氨酸-Pro(PGP)。从CCRN大环内酯类试验中，我们发现Pgp水平显著下降，与阿奇霉素减少COPD恶化频率的能力一致。据我们所知，PGP是研究中唯一显示出如此深刻反应的生物标志物。最近，我们的实验室证明Pgp受到白三烯A4水解酶(LTA4H)的负调控。LTA4H是一种独特的同时具有水解酶和氨基肽酶催化位点的酶。虽然众所周知，LTA4H的水解酶位置可以催化白三烯A4转化为白三烯B4(一种PMN趋化剂)，但氨基肽酶活性的底物尚不清楚。在2010年的一篇关键科学论文中，我们的团队证明了氨基肽酶活性可以降解PGP，从而减少中性粒细胞(PMN)炎症。因此，LTA4H在基线上既是促炎(水解酶)又是抗炎(氨基肽酶)，在炎症反应中起着关键作用。香烟烟雾可以上调LTA4H的总量，并对LTA4H的氨基肽酶进行化学修饰和失活，但不能使水解酶活性降低，从而使LTB4的生成保持不变，同时允许PGP炎症水平的慢性积累。因此，这种酶的数量和活性的调节可能在COPD相关的呼吸道炎症中起着至关重要的作用。事实上，我们发现，与非肺部疾病组相比，吸烟和COPD组的LTA4H氨基肽酶活性显著增加，但LTA4H氨基肽酶活性降低，尽管这些组中的每一组都存在显著的差异性，表明环境和遗传之间的相互作用可能在COPD疾病进展中发挥关键作用。事实上，以前的遗传分析已经揭示了LTA4H启动子和编码区的许多多态性，这些多态性与包括COPD在内的各种炎症性疾病有关。在这项将LTA4H蛋白水平和酶活性的变化归因于相关SNPs的建议中，我们将检查LTA4H可能启动子区的遗传变异，以确定在体外和体内对LTA4H蛋白水平的影响。我们还将探讨LTA4H编码区的SNPs对其活性的作用。这一提议的总体假设是，表达的可变性 LTA4H的酶活性影响COPD易感性和相关表型，因此影响LTA4H表达和氨基肽酶功能的遗传变异影响COPD相关表型。这样的人体研究现在才有可能归功于COPDgene计划，该计划的更新为进行这些范式建立研究提供了一个时间敏感的窗口。

 DESCRIPTION (provided by applicant): A key molecule in the pathology of ongoing inflammation in COPD is the collagen fragment proline-glycine- proline (PGP). From the CCRN Macrolide trial, we found that PGP levels markedly declined in concert with azithromycin's ability to reduce COPD exacerbation frequency. To our knowledge, PGP was the only biomarker studied that showed such a profound response. More recently, our laboratory has demonstrated that PGP is negatively regulated by leukotriene A4 hydrolase (LTA4H). LTA4H is a unique enzyme which possesses both a hydrolase and aminopeptidase catalytic site. Although the hydrolase site of LTA4H is well- known to catalyze the conversion of leukotriene A4 into leukotriene B4 (a PMN chemoattractant), the substrate of the aminopeptidase activity was unknown. In a pivotal Science paper in 2010, our group demonstrated that the aminopeptidase activity degrades PGP, thereby leading to less neutrophilic (PMN) inflammation. As such, LTA4H is both pro-inflammatory (hydrolase) and anti-inflammatory (aminopeptidase) at baseline serving as a critical pivot in inflammatory responses. Cigarette smoke can upregulate the total amount of LTA4H as well as chemically modify and inactivate LTA4H's aminopeptidase but not hydrolase activity thus leaving LTB4 generation intact while allowing for chronic accumulation of inflammatory levels of PGP. Therefore, the regulation of this enzyme's amount and activities may have a crucial role in airway inflammation associated with COPD. In fact, we found marked elevation in amount but reduction in LTA4H aminopeptidase activity in smoking and COPD cohorts compared to non-lung disease cohorts although there was notable variability in each of these groups suggesting that the interaction between environment and genetics may play a key feature in COPD disease progression. In fact, previous genetic analyses have revealed a number of polymorphisms in the promoter and coding regions of LTA4H that showed associations with a variety of inflammatory disorders including COPD. In this proposal to assign alterations in LTA4H protein levels and enzyme activity to associated SNPs, we will examine genetic variation in the putative promoter region of LTA4H to determine impact on LTA4H protein levels both in vitro and in vivo. We will also explore the role of SNPs in the coding regio of LTA4H on its activity. The overall hypothesis of this proposal is that variability in expression and enzymatic activity of LTA4H impacts COPD susceptibility and related phenotypes, thus genetic variation affecting LTA4H expression and aminopeptidase function impacts COPD-related phenotypes. Such human studies are only now possible as a result of the COPDGene program, the renewal of which provides a time-sensitive window to conduct these paradigm establishing studies.