Department of Nephrology and Hypertension, Hannover Medical School, Hannover, Germany.
Department of Cardiothoracic, Transplantation and Vascular Surgery, Hannover Medical School, Hannover, Germany.
Crit Care Med. 2018 Sep;46(9):e928-e936. doi: 10.1097/CCM.0000000000003269.
Tie2 is a tyrosine kinase receptor expressed by endothelial cells that maintains vascular barrier function. We recently reported that diverse critical illnesses acutely decrease Tie2 expression and that experimental Tie2 reduction suffices to recapitulate cardinal features of the septic vasculature. Here we investigated molecular mechanisms driving Tie2 suppression in settings of critical illness.
Laboratory and animal research, postmortem kidney biopsies from acute kidney injury patients and serum from septic shock patients.
Research laboratories and ICU of Hannover Medical School, Harvard Medical School, and University of Groningen.
Deceased septic acute kidney injury patients (n = 16) and controls (n = 12) and septic shock patients (n = 57) and controls (n = 22).
Molecular biology assays (Western blot, quantitative polymerase chain reaction) + in vitro models of flow and transendothelial electrical resistance experiments in human umbilical vein endothelial cells; murine cecal ligation and puncture and lipopolysaccharide administration.
We observed rapid reduction of both Tie2 messenger RNA and protein in mice following cecal ligation and puncture. In cultured endothelial cells exposed to tumor necrosis factor-α, suppression of Tie2 protein was more severe than Tie2 messenger RNA, suggesting distinct regulatory mechanisms. Evidence of protein-level regulation was found in tumor necrosis factor-α-treated endothelial cells, septic mice, and septic humans, all three of which displayed elevation of the soluble N-terminal fragment of Tie2. The matrix metalloprotease 14 was both necessary and sufficient for N-terminal Tie2 shedding. Since clinical settings of Tie2 suppression are often characterized by shock, we next investigated the effects of laminar flow on Tie2 expression. Compared with absence of flow, laminar flow induced both Tie2 messenger RNA and the expression of GATA binding protein 3. Conversely, septic lungs exhibited reduced GATA binding protein 3, and knockdown of GATA binding protein 3 in flow-exposed endothelial cells reduced Tie2 messenger RNA. Postmortem tissue from septic patients showed a trend toward reduced GATA binding protein 3 expression that was associated with Tie2 messenger RNA levels (p < 0.005).
Tie2 suppression is a pivotal event in sepsis that may be regulated both by matrix metalloprotease 14-driven Tie2 protein cleavage and GATA binding protein 3-driven flow regulation of Tie2 transcript.
Tie2 是一种在血管内皮细胞中表达的酪氨酸激酶受体，它维持着血管屏障功能。我们最近报道，多种严重疾病会使 Tie2 表达急剧下降，而实验性 Tie2 减少足以重现败血症血管的主要特征。在这里，我们研究了在危重疾病情况下导致 Tie2 抑制的分子机制。
实验室和动物研究，急性肾损伤患者的肾活检组织和败血症性休克患者的血清。
汉诺威医学院、哈佛医学院和格罗宁根大学的研究实验室和 ICU。
死亡的败血症性急性肾损伤患者（n = 16）和对照组（n = 12）和败血症性休克患者（n = 57）和对照组（n = 22）。
分子生物学检测（Western blot、定量聚合酶链反应）+体外人脐静脉内皮细胞流动和跨内皮电阻实验模型；小鼠盲肠结扎和穿孔及脂多糖给药。
我们观察到小鼠盲肠结扎和穿孔后 Tie2 信使 RNA 和蛋白迅速减少。在暴露于肿瘤坏死因子-α的培养内皮细胞中，Tie2 蛋白的抑制比 Tie2 信使 RNA 更严重，表明存在不同的调节机制。在肿瘤坏死因子-α处理的内皮细胞、败血症小鼠和败血症患者中都发现了蛋白水平调节的证据，这三者都显示 Tie2 的可溶性 N 端片段升高。基质金属蛋白酶 14 既是必需的，也是充分的，可用于 Tie2 的 N 端脱落。由于 Tie2 抑制的临床情况通常伴有休克，我们接下来研究了层流对 Tie2 表达的影响。与没有流动相比，层流诱导 Tie2 信使 RNA 和 GATA 结合蛋白 3 的表达。相反，败血症肺表现出 GATA 结合蛋白 3 的减少，而在暴露于层流的内皮细胞中敲低 GATA 结合蛋白 3 会减少 Tie2 信使 RNA。来自败血症患者的尸检组织显示 GATA 结合蛋白 3 的表达减少趋势，这与 Tie2 信使 RNA 水平相关（p < 0.005）。
Tie2 抑制是败血症中的一个关键事件，它可能受到基质金属蛋白酶 14 驱动的 Tie2 蛋白裂解和 GATA 结合蛋白 3 驱动的 Tie2 转录的层流调节的共同调控。
