Role of the endogenous gasotransmitter H2S in ETS-mediated airway disease

 描述（由申请人提供）：环境烟草烟雾（ETS）是一种复杂的气体和颗粒混合物，包括来自燃烧的香烟、雪茄或烟斗尖端的烟雾（侧流烟雾，SS）和呼出的主流烟雾（MS）。它是不吸烟者不自觉地吸入，在香烟熄灭后在空气中逗留数小时，并可诱发或加剧各种肺部疾病，从癌症到呼吸道感染，慢性阻塞性肺病（COPD）和哮喘（4;5）。尽管发达国家的吸烟率有所下降，尽管有证据表明ETS对健康有严重影响，但ETS的暴露仍然很普遍。呼吸道合胞病毒（Respiratory syncytial virus，RSV）是引起儿童急性下呼吸道感染（毛细支气管炎）的最重要的病毒病原体，也是儿童哮喘的易感因素。暴露于ETS是发生严重RSV感染的已知风险因素，但决定ETS/RSV感染共病的机制在很大程度上尚不清楚。毛细支气管炎的严重程度由气道中较高水平的病毒复制驱动，如在RSV感染前暴露于SHTS的新生小鼠的研究中所示。硫化氢（H2S）是半胱氨酸代谢产生的内源性气体递质，主要通过胱硫醚γ-裂解酶（CSE）和胱硫醚-β-合成酶（CBS）两种酶的活性产生，其中CSE是肺组织中主要的硫化氢形成酶。吸烟者血清中H2S水平较低，与COPD患者气道阻塞的严重程度呈负相关。我们实验室最近的研究发现了H2S在气道上皮细胞和肺中作为抗病毒介质的一种以前未被认识的功能。我们提出的假设是，暴露于ETS抑制内源性H2S生成酶CSE的表达，导致肺中H2S水平的相对缺陷，从而增强病毒复制。在这个探索性的项目中将追求两个目标。目的1将检验内源性H2S生成CSE酶是暴露于ETS的儿童严重细支气管炎的关键决定因素这一假设。具体而言，我们将检验以下主要假设：暴露于ETS的RSV感染受试者中CSE的表达降低，导致H2S产生降低、病毒复制增强和疾病严重程度增加。目的2将检验CSE过表达或直接H2S在小鼠肺中增加的产生将钝化RSV复制并影响抗病毒应答的假设。为了验证这一假设，我们将通过复制缺陷型重组腺病毒介导的基因转移或通过使用新型水溶性H2S供体GYY 4137，通过CSE在肺中过表达来增加H2S的产生。我们在RSV和ETS翻译研究方面的经验是追求这一创新项目的理想选择。通过确定治疗原发性呼吸道病毒感染或与暴露于ETS相关的慢性潜在肺部疾病加重的新策略，这些结果将具有重要的治疗意义。

 DESCRIPTION (provided by applicant): Environmental tobacco smoke (ETS) is a complex mixture of gases and particles that include smoke from the burning cigarette, cigar, or pipe tip (side-stream smoke, SS) and exhaled mainstream smoke (MS). It is involuntarily inhaled by nonsmokers, lingers in the air for hours after cigarettes have been extinguished, and can induce or exacerbate a wide range of lung diseases, from cancer to respiratory infections, chronic obstructive pulmonary disease (COPD) and asthma (4;5). Exposure to ETS continues to be common despite a decline in smoking in developed countries and despite evidence of serious health effects. Respiratory syncytial virus (RSV) is the single most important viral pathogen causing acute lower respiratory-tract infections (bronchiolitis) in children and predisposing to th development of childhood asthma. Exposure to ETS is a known risk factor for the development of severe RSV infections, yet the mechanisms that determine ETS/RSV infection co-morbidity are largely unknown. Severity of bronchiolitis is driven by higher level of viral replication in th airways, as shown in studies of neonatal mice exposed to SHTS prior to RSV infection. Hydrogen sulfide (H2S) is a gasotransmitter which is endogenously generated from cysteine metabolism mainly by the activity of two enzymes, cystathionine gamma-lyase (CSE) and cystathionine-beta-synthase (CBS), with CSE being the main H2S-forming enzyme in lung tissue. Lower levels of H2S have been demonstrated in serum of smokers, and negatively correlate with the severity of airway obstruction in patients with COPD. Recent investigations in our laboratory have discovered a previously unrecognized function of H2S as antiviral mediator in airway epithelial cells and in the lung. We propose the hypothesis that exposure to ETS inhibits the expression of the endogenous H2S-generating enzyme CSE, causing a relative defect in H2S levels in the lung, resulting in enhanced viral replication. Two Aims will be pursued in this exploratory project. Aim 1 will test the hypothesis that the endogenous H2S-generating CSE enzyme is a critical determinant of severe bronchiolitis in children exposed to ETS. Specifically, we will test the primary hypothesis that expression of CSE is reduced in RSV- infected subjects who are exposed to ETS, resulting in lower H2S production, enhanced viral replication and greater severity of illness. In Aim 2 will test the hypothesis that CSE overexpression or direct H2S increased production in lungs of mice will blunt RSV replication and affect antiviral responses. To test this hypothesis, we will increase H2S production by CSE overexpression in the lung by replication deficient recombinant adenovirus-mediated gene transfer or by the use of GYY4137, a novel water-soluble H2S donor. Our experience with translational studies of RSV and ETS is ideal to pursue this innovative project. The results should have important therapeutic implications by identifying new strategies to treat primary respiratory viral infections or exacerbations of chronic underlying lung diseases that are associated with exposure to ETS.