Charité-Universitätsmedizin Berlin, corporate of Freie Universität Berlin, Department of Experimental Neurosurgery, Humbold-Universität zu Berlin, and Berlin Institute of Health, Charitéplatz 1, 10117, Berlin, Germany.
Neuroscience Research Center, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, 10117, Berlin, Germany.
Transl Stroke Res. 2018 Dec;9(6):631-642. doi: 10.1007/s12975-018-0614-2. Epub 2018 Feb 10.
Compromised blood-brain barrier (BBB) by dysregulation of cellular junctions is a hallmark of many cerebrovascular disorders due to the pro-inflammatory cytokines action. Interleukin 6 (IL6) is implicated in inflammatory processes and in secondary brain injury after subarachnoid hemorrhage (SAH) but its role in the maintenance of cerebral endothelium still requires a precise elucidation. Although IL6 has been shown to exert pro-inflammatory action on brain microvascular endothelial cells (ECs), the expression of one of the IL6 receptors, the IL6R is controversially discussed. In attempt to reach more clarity in this issue, we present here an evident baseline expression of the IL6R in BBB endothelium in vivo and in an in vitro model of the BBB, the cEND cell line. A significantly increased expression of IL6R and its ligand was observed in BBB capillaries 2 days after experimental SAH in mice. In vitro, we saw IL6 administration resulting in an intracellular and extracellular elevation of IL6 protein, which was accompanied by a reduced expression of tight and adherens junctions, claudin-5, occludin, and vascular-endothelial (VE-) cadherin. By functional assays, we could demonstrate IL6-incubated brain ECs to lose their endothelial integrity that can be attenuated by inhibiting the IL6R. Blockade of the IL6R by a neutralizing antibody has reconstituted the intercellular junction expression to the control level and caused a restoration of the transendothelial electrical resistance of the cEND cell monolayer. Our findings add depth to the current understanding of the involvement of the endothelial IL6R in the loss of EC integrity implicating potential therapy options.
细胞连接的失调导致血脑屏障（BBB）受损，是许多血管性脑疾病的标志，这与促炎细胞因子的作用有关。白细胞介素 6（IL6）参与炎症过程和蛛网膜下腔出血（SAH）后的继发性脑损伤，但它在维持脑内皮中的作用仍需要更精确的阐明。尽管 IL6 已被证明对脑微血管内皮细胞（EC）具有促炎作用，但 IL6 受体之一的 IL6R 的表达存在争议。为了在这个问题上取得更清晰的认识，我们在此展示了体内 BBB 内皮和体外 BBB 模型（cEND 细胞系）中 IL6R 的明显基础表达。在实验性 SAH 后 2 天，在小鼠的 BBB 毛细血管中观察到 IL6R 和其配体的表达显著增加。在体外，我们发现 IL6 给药导致细胞内和细胞外 IL6 蛋白升高，同时紧密连接和黏附连接、claudin-5、occludin 和血管内皮（VE）钙黏蛋白的表达减少。通过功能测定，我们可以证明 IL6 孵育的脑 EC 失去了内皮完整性，而通过抑制 IL6R 可以减轻这种损伤。中和抗体阻断 IL6R 可将细胞间连接的表达恢复到对照水平，并恢复 cEND 细胞单层的跨内皮电阻。我们的研究结果加深了对内皮 IL6R 参与 EC 完整性丧失的认识，这暗示了潜在的治疗选择。
