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

 描述(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，包括燃烧的香烟、雪茄或烟斗尖端产生的烟雾(侧流烟雾，SS)和呼出的主流烟雾(MS)。它由非吸烟者不由自主地吸入，在香烟熄灭后在空气中停留数小时，并可诱发或加重多种肺部疾病，从癌症到呼吸道感染、慢性阻塞性肺疾病(COPD)和哮喘(4；5)。尽管发达国家吸烟人数减少，尽管有证据表明ETS对健康有严重影响，但接触ETS的情况仍然很普遍。呼吸道合胞病毒(RSV)是引起儿童急性下呼吸道感染(毛细支气管炎)并易发生儿童哮喘的最重要的病毒病原体。暴露于ETS是发生严重RSV感染的已知危险因素，但决定ETS/RSV感染并存的机制在很大程度上尚不清楚。毛细支气管炎的严重性是由呼吸道内较高水平的病毒复制推动的，正如在RSV感染之前暴露于SHTS的新生小鼠的研究所表明的那样。硫化氢(H_2S)是一种内源性气体递质，主要由半胱氨酸代谢产生，主要通过两种酶--胱硫醚-γ-裂解酶(CSE)和胱硫醚-β-合酶(CBS)的活性产生，CSE是肺组织中主要的H_2S形成酶。吸烟者血清中H_2S水平较低，且与COPD患者的气道阻塞程度呈负相关。我们实验室最近的研究发现，在呼吸道上皮细胞和肺中，硫化氢作为抗病毒介质具有以前未知的功能。我们提出的假设是，暴露在ETS中会抑制内源性硫化氢生成酶CSE的表达，导致肺中硫化氢水平的相对缺陷，从而促进病毒复制。这一探索性项目将追求两个目标。目的1将验证这样的假设，即内源性产生硫化氢的CSE酶是暴露于ETS的儿童严重毛细支气管炎的关键决定因素。具体地说，我们将测试主要假设，即接触ETS的RSV感染者CSE的表达减少，导致硫化氢产生减少，病毒复制增强，病情加重。在Aim 2中，将测试CSE过度表达或导致小鼠肺内过氧化氢产生增加将钝化RSV复制并影响抗病毒反应的假设。为了验证这一假说，我们将通过复制缺陷的重组腺病毒介导的基因转移或使用新型水溶性硫化氢供体GYY4137来增加CSE在肺中的过度表达来增加硫化氢的产生。我们在RSV和ETS的翻译研究方面的经验是进行这一创新项目的理想选择。通过确定新的战略来治疗与暴露于ETS有关的原发呼吸道病毒感染或慢性基础肺部疾病的恶化，这一结果应该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.