Diebel Mark E, Martin Jonathan V, Liberati David M, Diebel Lawrence N
From the Michael and Marian Ilitch Department of General Surgery (M.E.D., J.V.M., D.M.L., L.N.D.), Wayne State University, Detroit, MI.
J Trauma Acute Care Surg. 2018 Jan;84(1):75-80. doi: 10.1097/TA.0000000000001726.
The endothelial glycocalyx (GCX) plays an important role in vascular barrier function. Damage to the GCX occurs due to a variety of causes including hypoxia, ischemia-reperfusion, stress-related sympathoadrenal activation, and inflammation. Tranexamic acid (TXA) may prevent GCX degradation. The therapeutic window for TXA administration and the mechanism of action has been under review. Membrane-anchored proteases (sheddases) are key components in endothelial cell biology including the regulation of vascular permeability. The effect of TXA administration on stress-related GCX damage, and the role of sheddases in this process was studied in a cell-based model.
Confluent human umbilical vein endothelial cells (HUVEC) were exposed to hydrogen peroxide and/or epinephrine (EPI) to stimulate postshock reperfusion. TXA was added at various times after hydrogen peroxide (H2O2) and/or EPI exposure. GCX degradation was indexed by syndecan-1 and hyaluronic acid release. Activation of endothelial sheddases was indexed by A Disintegrin and Metalloproteinase-17 and matrix metalloproteinase-9 activity in culture supernatants.
Exposure of HUVEC to either/both EPI and H2O2 resulted in a cellular stress and GCX disruption demonstrated by increased levels of syndecan-1 shedding, hyaluronic acid release, tumor necrosis factor-α release. Shedding of these GCX components was associated with increased activity of both A Disintegrin and Metalloproteinase-17 and matrix metalloproteinase. Disruption of the GCX was further demonstrated via fluorescent imaging, which demonstrated disruption after exposure to either/both H2O2 and EPI. Early administration of either TXA or doxycycline resulted in preservation of the GCX. Late administration of TXA had no effect, whereas doxycycline had some residual protective effect.
Tranexamic acid as a serine protease inhibitor prevented GCX degradation via inhibition of endothelial sheddase activation. This effect was not apparent when TXA was administered greater than 60 minutes after "simulated" reperfusion. Our study supports the clinical practice of early TXA administration in the severely injured patient.
内皮糖萼（GCX）在血管屏障功能中起重要作用。GCX因多种原因受损，包括缺氧、缺血再灌注、应激相关的交感肾上腺激活和炎症。氨甲环酸（TXA）可能预防GCX降解。TXA给药的治疗窗和作用机制一直在研究中。膜锚定蛋白酶（脱落酶）是内皮细胞生物学的关键成分，包括调节血管通透性。在基于细胞的模型中研究了TXA给药对应激相关GCX损伤的影响以及脱落酶在此过程中的作用。
将汇合的人脐静脉内皮细胞（HUVEC）暴露于过氧化氢和/或肾上腺素（EPI）以刺激休克后再灌注。在过氧化氢（H2O2）和/或EPI暴露后的不同时间添加TXA。通过syndecan-1和透明质酸释放来衡量GCX降解。通过培养上清液中解整合素和金属蛋白酶-17以及基质金属蛋白酶-9的活性来衡量内皮脱落酶的激活。
HUVEC暴露于EPI和/或H2O2导致细胞应激和GCX破坏，表现为syndecan-1脱落、透明质酸释放、肿瘤坏死因子-α释放水平增加。这些GCX成分的脱落与解整合素和金属蛋白酶-17以及基质金属蛋白酶的活性增加有关。通过荧光成像进一步证明了GCX的破坏，该成像显示在暴露于H2O2和/或EPI后发生破坏。早期给予TXA或强力霉素可保留GCX。晚期给予TXA无效，而强力霉素有一些残余保护作用。
氨甲环酸作为一种丝氨酸蛋白酶抑制剂，通过抑制内皮脱落酶激活来预防GCX降解。在“模拟”再灌注后60分钟以上给予TXA时，这种作用不明显。我们的研究支持在严重受伤患者中早期给予TXA的临床实践。
