Epithelial glycocalyx degradation mediates surfactant dysfunction in acute respiratory distress syndrome

点击翻译按钮获取中文摘要

PROJECT SUMMARY/ABSTRACT Acute respiratory distress syndrome (ARDS), a common cause of respiratory failure in the ICU, is characterized by surfactant dysfunction and impaired lung compliance. Our preliminary data demonstrate that the alveolar epithelial glycocalyx, a layer of glycosaminoglycans that coat the apical surface of the epithelial cells, is damaged in multiple different murine models of ARDS. Additionally, we found that specific enzymatic degradation of the epithelial glycocalyx is sufficient to cause decreased lung compliance and microatelectasis, which appears to be mediated by impaired surfactant function. We have also translated these findings to humans using noninvasively collected airspace fluid obtained from heat moisture exchange filters, which are devices that are used to humidify the airways as part of the usual care of mechanically ventilated patients. Excitingly, we demonstrated that alveolar epithelial glycocalyx degradation, measured by levels of glycosaminoglycans in the airspace fluid, is predictive of duration of mechanical ventilation and degree of hypoxemia. In this proposal, we will determine the mechanisms by which epithelial glycocalyx degradation causes surfactant dysfunction and confirm the translational relevance of these findings in human ARDS patients using noninvasively collected airspace fluid. In Specific Aim 1, we will identify the surfactant protein that binds to the epithelial glycocalyx using heparin affinity chromatography conducted on mouse bronchoalveolar lavage fluid. We will then utilize a heparan sulfate glycoarray to identify the specific heparan sulfate oligosaccharide fragment responsible for this interaction. The functional importance of this interaction will then be tested in mice by administering chemically synthesized surfactant protein-binding oligosaccharides (to competitively displace surfactant from the native alveolar epithelial glycocalyx) and measuring the effects on lung structure and function using design-based stereology, lung mechanics measurements, and constrained sessile drop surfactometry. In Specific Aim 2, we will conduct a pilot observational clinical study in which we will collect both heat moisture exchange filters and advanced lung mechanics data (peak pressure, plateau pressure, driving pressure) from the ventilators of ARDS patients. We will then use this data to test our hypothesis that the quantity of glycosaminoglycans shed into the airspace, measured using a novel point-of-care assay (dimethylmethylene blue), is inversely related to lung compliance in ARDS patients. Given that there are currently no available clinical tests that can predict the course of ARDS, these findings have the potential to become rapidly impactful to patient care in the ICU. This research will be carried out in the highly collaborative Division of Pulmonary Sciences and Critical Care Medicine at the University of Colorado and Denver Health Medical Center. We anticipate that this project will generate data that will both advance the field of translational ARDS research and serve as the foundation for my K08 award application and eventual transition to independent investigator status.