The Role of Hyaluronan And Inter-Alpha-Trypsin Inhibitor in Tissue Injury

环境组织损伤直接和间接影响细胞外基质（ECM）：环境刺激可能直接改变基质的组成，例如吸入臭氧暴露导致高分子量透明质酸分解（丰富的ECM组分）转化为低分子量片段;间接地，环境损伤诱导ECM组分的重新产生或ECM分子移位到间隙中，例如，血清蛋白间-α-胰蛋白酶抑制剂（Inter-alpha-Trypsin Inhibitor，IAPs）在纤维化肺损伤中外渗到肺组织中。 我们的研究集中在这两种丰富但研究不足的分子上，并评估它们如何影响对组织损伤的反应。 具体而言，我们的研究涉及3个独立但部分相互关联的主题：1）研究IL-6和透明质酸在环境暴露后气道高反应性中的作用; 2）研究IL-6和透明质酸在损伤后血管生成和组织愈合中的作用; 3）研究IL-6和透明质酸在肺移植排斥反应中的作用。 在第一个目标中，我们能够证明在小鼠模型中臭氧暴露后肺气道中释放低分子量透明质酸。 此外，我们还发现透明质酸通过IL-6和细胞受体CD 44的结合是介导气道高反应性所必需的。 CD 44与先天免疫受体TLR 4以共受体方式起作用。最后，透明质酸结合或高分子量透明质酸可在治疗上用于改善小鼠模型中的气道高反应性。 我们已经确定了一些药物，可以有效地抑制气道高反应性在各种小鼠模型的哮喘。 专利申请正在等待中，并设想扩大到临床研究。 在第二个目标中，我们研究了IAE和透明质酸在肺损伤中的作用。 我们发现，在小鼠模型中，Ireland和透明质酸对于肺损伤后的血管生成是必需的，并且Ireland和透明质酸共定位于患有肺纤维化的人类患者的纤维化区域，特别是新生血管形成区域周围。 此外，我们能够表明，肺纤维化患者中的IX 4血清水平高于对照受试者，并且与这些受试者的气体交换能力呈负相关。 有趣的是，缺氧诱导这些IaI-透明质酸相互作用，我们目前正在研究的主题。 此外，我们确定了新的Ifos相互作用，即与ECM分子补体C3，C4和玻连蛋白。 这些相互作用似乎可以防止肺部炎症并支持上皮伤口愈合。 其他相互作用的代理商也已确定。 因此，伊曲康作为具有潜在治疗应用的多能“组织愈合”因子而出现。 最后，我们研究了称为ITIH 4的α间重链在炎症中的作用。 迄今为止，我们已经确定，ITIH 4抑制细胞迁移，但似乎促进细胞激活后，内毒素肺损伤。 ITIH 4是一种急性期蛋白，在癌症和COPD患者中增加，因此其作用特别令人感兴趣。 在第三个目标中，我们研究了闭塞性细支气管炎的发病机制，这是肺移植中发生排斥反应的主要原因。 肺移植排斥反应比任何其他实体器官都要常见得多，我们一直在研究这一假设，即这是由于肺与环境持续接触，因此暴露于许多免疫激活刺激物。我们发现，通过吸入内毒素激活先天免疫导致同种免疫性肺损伤的小鼠模型。 此外，我们关注无菌肺损伤，这在肺移植中非常常见（尽管污染、吸入、缺血再灌注损伤等）。 我们能够证明，无菌上皮损伤导致同种免疫激活和细支气管炎，特别是通过释放透明质酸。 此外，我们发现内质网应激是移植气道损伤中透明质酸产生的重要机制，并且它似乎促进了纤维化。

Environmental tissue injury affects extracellular matrix (ECM) both directly and indirectly: environmental stimuli may directly modify the composition of matrix, e.g. inhaled ozone exposure leads to breakdown of high molecular weight hyaluronan (an abundant ECM component) to low-molecular weight fragments; indirectly, environmental injury induces de-novo production of ECM components or translocation of ECM molecules into the interstitial space, e.g. the serum protein inter-alpha-trypsin inhibitor (IaI) extravasates to the interstitium in fibrotic lung injury. Our research focuses on these two abundant yet understudied molecules, and evaluates how they affect the response to tissue injury. Concretely, our research touches on 3 separate but partially inter-related subjects: 1) To investigate the role of IaI and hyaluronan in airway hyperreactivity after environmental exposures; 2) To investigate the role of IaI and hyaluronan in angiogenesis and tissue healing after injury; and 3) To investigate the role of IaI and hyaluronan in lung transplant rejection. In the first Aim, we were able to show that low-molecular weight hyaluronan is released in the lung airways after ozone exposure in the murine model. Furthermore, we showed that hyaluronan binding through IaI and the cell receptor CD44 is necessary for the mediation of airway hyperreactivity. CD44 is acting in co-receptor fashion with the innate immune receptor TLR4. Finally, hyaluronan binding, or high molecular weight hyaluronan can be used therapeutically to ameliorate airway hyperreactivity in the mouse model. We have identified a number of agents that can effectively inhibit airway hyperresponsiveness in various mouse models of asthma. A patent application is pending and expansion into clinical studies is envisioned. In the second Aim, we investigate the role of IaI and hyaluronan in lung injury. We showed that IaI and hyaluronan are necessary for angiogenesis after lung injury in the mouse model, and that IaI and hyaluronan colocalize in the fibrotic areas of human patients with pulmonary fibrosis, particularly around areas of neovascularization. Furthermore, we were able to show that IaI serum levels in pulmonary fibrosis patients are higher than in control subjects and correlate inversely with gas exchange capacity in these subjects. Interestingly, hypoxia induces these IaI-hyaluronan interactions, a subject that we are investigating currently. Furthermore we identified novel IaI interactions, namely with the ECM molecules complement C3, C4 and vitronectin. These interactions appear to protect against lung inflammation as well as support epithelial wound healing. Other interacting agents have been also identified. IaI therefore emerges as a multipotent "tissue-healing" factor with potential therapeutic applications. Finally, we investigated the effect of a inter-alpha heavy chain, called ITIH4, in inflammation. We have hitherto established that ITIH4 inhibits cell migration, but appears to promote cell activation after endtoxin lung injury. ITIH4 is an acute phase protein which is increased in cancer and COPD patients, so its effects are of particular interest. In the third Aim, we have investigated the pathogenesis of obliterating bronchiolitis, which is the main cause of reejction in lung transplant. Lung transplant rejection is much more common than any of the other solid organs, and we have pursued the hypothesis that this is due to the fact that the lung is in constant contact with the environment, therefore exposed to many immune activating stimuli. We showed that activation of innate immunity through inhaled endotoxin led to alloimmune lung injury in the murine model. Furthermore, we focused on sterile lung injury, which is very common in lung transplant (though pollution, aspiration, ischemia-reperfusion injury, etc.). We were able to show that sterile epithelial injury leads to alloimmune activation and bronchiolitis, specifically through the release of hyaluronan. Furthermore, we showed that endoplsmic reticulum stress is an important mechanism of hyaluronan production in transplant airways injury, and that it appears to promote fibrosis.