Epithelial Heparan Sulfate Contributes to Alveolar Barrier Function and Is Shed during Lung Injury
Epithelial Heparan Sulfate Contributes to Alveolar Barrier Function and Is Shed during Lung Injury
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DOI：
10.1165/rcmb.2017-0428oc
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发表时间：
2018-09-01
影响因子：
6.4
通讯作者：
Schmidt, Eric P.
中科院分区：
文献类型：
--
作者：
Haeger, Sarah M.;Liu, Xinyue;Schmidt, Eric P.
肺上皮糖萼是衬在肺上皮表面的富含碳水化合物的层。虽然已经报道了上皮糖萼的可视化，但其组成和功能仍然未知。使用免疫荧光和质谱，我们确定了硫酸乙酰肝素（HS）和硫酸软骨素在肺上皮糖萼。在体内选择性酶促降解上皮HS，而不是硫酸软骨素，增加肺通透性。使用质谱和凝胶电泳方法，以确定肺损伤过程中上皮HS的命运，我们检测到脱落的20糖长或更大的HS到BAL液intraperheal LPS治疗的小鼠。此外，急性呼吸窘迫综合征患者的临床样本中的空气空间HS与肺泡通透性指数相关，反映了这些发现的临床相关性。内毒素诱导的损伤过程中HS脱落的长度（>= 20 μ m）表明将HS锚定在上皮表面的蛋白聚糖的裂解，而不是HS本身的裂解。我们使用药理学和转基因动物的方法来确定，基质金属蛋白酶部分介导的HS脱落在肺内LPS诱导的肺损伤。尽管在用基质金属蛋白酶抑制剂强力霉素治疗后有肺泡通透性降低的趋势，但这并没有达到统计学意义。这些研究表明，上皮HS有助于肺上皮屏障，其降解足以增加肺通透性。多西环素实现的HS脱落的部分减少不足以挽救上皮屏障功能在肺内愈合LPS诱导的肺损伤;然而，HS脱落的完全衰减是否足以挽救上皮屏障功能仍然未知。
The lung epithelial glycocalyx is a carbohydrate-enriched layer lining the pulmonary epithelial surface. Although epithelial glycocalyx visualization has been reported, its composition and function remain unknown. Using immunofluorescence and mass spectrometry, we identified heparan sulfate (HS) and chondroitin sulfate within the lung epithelial glycocalyx. In vivo selective enzymatic degradation of epithelial HS, but not chondroitin sulfate, increased lung permeability. Using mass spectrometry and gel electrophoresis approaches to determine the fate of epithelial HS during lung injury, we detected shedding of 20 saccharide-long or greater HS into BAL fluid in intratracheal LPS-treated mice. Furthermore, airspace HS in clinical samples from patients with acute respiratory distress syndrome correlated with indices of alveolar permeability, reflecting the clinical relevance of these findings. The length of HS shed during intratracheal LPS-induced injury (>= 20 saccharides) suggests cleavage of the proteoglycan anchoring HS to the epithelial surface, rather than cleavage of HS itself. We used pharmacologic and transgenic animal approaches to determine that matrix metalloproteinases partially mediate HS shedding during intratracheal LPS-induced lung injury. Although there was a trend toward decreased alveolar permeability after treatment with the matrix metalloproteinase inhibitor, doxycycline, this did not reach statistical significance. These studies suggest that epithelial HS contributes to the lung epithelial barrier and its degradation is sufficient to increase lung permeability. The partial reduction of HS shedding achieved with doxycycline is not sufficient to rescue epithelial barrier function during intratracheal LPS-induced lung injury; however, whether complete attenuation of HS shedding is sufficient to rescue epithelial barrier function remains unknown.