TSG-6: Novel Regulator of Viral-Induced Hyaluronan Synthesis in Inflamed Airways

描述（由申请人提供）：哮喘是一种气道慢性炎症性疾病，通常伴有气道对各种刺激物（包括过敏原、污染物和病毒）的高反应性增加，导致气道阻塞，从而导致 反复发作的喘息和咳嗽。炎症细胞积聚到气道壁中是哮喘的一个标志性特征，也是导致这种疾病炎症的关键因素之一。我们已经发现这些细胞包埋在由气道脉管系统和支气管周围的平滑肌细胞产生的大量富含透明质酸的细胞外基质中。这种透明质酸（HA）基质是异常的，因为它被来自血液中发现的组分的重链（HC）装饰。这种HC-HA修饰是重要的，因为它产生了一种HA配体，该HA配体对于通过未鉴定的受体与HC-HA结合的炎性细胞是“粘性的”。用HC修饰HA基质是通过酶“肿瘤坏死因子刺激基因-6”（TSG-6）完成的。顾名思义，这种蛋白质的合成是由肿瘤坏死因子-α（TNF-α）诱导的，TNF-α是一种众所周知的哮喘炎症介质。此外，已知TSG-6在多种炎性疾病中发挥作用。在我们的研究过程中，我们发现TSG-6不仅具有用HC修饰HA的酶促能力，而且它显著刺激气道平滑肌细胞（ASMC）合成HA。有趣的是，当单独应用TSG-6时，这种诱导不会发生，而是仅与提供模拟病毒感染的刺激的双链RNA（dsRNA）组合。几十年来，病毒感染和哮喘症状恶化之间的联系已经众所周知，但病毒引发这种病理的机制仍然是一个医学之谜。我们观察到，TSG-6是一个有效的放大器的HA应激反应时，气道平滑肌细胞的病毒模拟物的挑战意味着TSG-6的双重功能可能是一个重要的一部分，病毒感染触发哮喘病理机制。我们的长期目标是了解HC-HA如何指导炎症事件，并将这些知识应用于设计新的治疗方法，以使这些基质恢复到正常状态，并改善慢性炎症性疾病患者的临床结局。我们的假设是，TSG-6通过其酶产物（即HC-HA）与炎症期间诱导的细胞表面受体的接合来放大ASMC的HA合成。我们还假设HC-HA影响嵌入HC-HA基质内的白细胞的行为和活化。我们将在以下具体目标中测试这一假设：（i）识别信号通路，受体 和TSG-6刺激HA合成的配体，（ii）确定HC-HA对单核细胞/巨噬细胞活化的影响，和（iii）评价TSG-6与“活”呼吸道病毒合作放大HA合成的能力。

DESCRIPTION (provided by applicant): Asthma is a chronic inflammatory disease of the airways that is typically accompanied by increased airway hyper-responsiveness to various stimuli, including allergens, pollutants and viruses, resulting in airway obstruction that leads to recurrent episodes of wheezing and coughing. The accumulation of inflammatory cells into the airway wall is a hallmark feature of asthma and is one of the key factors driving inflammation in this disease. We have found that these cells are embedded in an extensive hyaluronan-rich extracellular matrix produced by smooth muscle cells surrounding airway vasculature and bronchi. This hyaluronan (HA) matrix is abnormal in the sense that it is decorated with heavy chains (HCs) derived from a component found in blood. This HC-HA modification is important because it creates an HA ligand that is "sticky" for inflammatory cells which bind to HC-HA via an unidentified receptor(s). The decoration of HA matrices with HCs is accomplished by the enzyme "tumor-necrosis-factor-stimulated-gene-6" (TSG-6). As its name implies, synthesis of this protein is induced by tumor-necrosis-factor-alpha (TNF¿), a well-known mediator of inflammation in asthma. Furthermore, TSG-6 is known to play a role in a variety of inflammatory diseases. Over the course of our investigations, we discovered that TSG-6 not only possesses the enzymatic ability to decorate HA with HCs but that it significantly stimulates HA synthesis by airway smooth muscle cells (ASMCs). Interestingly, this induction did not occur when TSG-6 was applied alone, but rather, only in combination with double-stranded RNA (dsRNA) that provides a stimulus mimicking a viral infection. For decades, the connection between viral infections and the exacerbation of asthmatic symptoms has been well known, but the mechanism whereby viruses trigger this pathology remains a medical mystery. Our observation that TSG-6 is a potent amplifier of the HA stress response by airway smooth muscle cells when challenged by a viral mimetic implies that the dual functionality of TSG-6 may be an important part of the mechanism whereby viral infections trigger asthma pathology. Our long-term goal is to understand how HC-HA directs inflammatory events and to apply this knowledge to design novel therapeutic approaches to restore these matrices to their normal state and improve clinical outcomes in patients with chronic inflammatory diseases. Our hypothesis is that TSG-6 amplifies HA synthesis by ASMCs via engagement of its enzymatic product (i.e. HC-HA) with a cell surface receptor that is induced during inflammation. We also hypothesize that HC-HA influences the behavior and activation of leukocytes embedded within the HC-HA matrix. We will test this hypothesis in the following specific aims: (i) identify the signaling pathways, receptors and ligands whereby TSG-6 stimulates HA synthesis, (ii) determine the effect HC-HA has on monocyte/macrophage activation, and (iii) evaluate the ability of TSG-6 to amplify HA synthesis in cooperation with a "live" respiratory virus.