Department of Anesthesiology and Center for Shock, Trauma, and Anesthesiology Research (STAR), University of Maryland , School of Medicine, Baltimore, Maryland.
J Neurotrauma. 2018 Oct 15;35(20):2462-2481. doi: 10.1089/neu.2017.5572. Epub 2018 Jul 10.
Angiopoietin-1 (Ang-1) is a well-known endothelial growth factor, but its effects on neurons have yet to be elucidated. We show that Ang-1 is rapidly downregulated in the injured brain after controlled cortical impact (CCI), a mouse experimental traumatic brain injury (TBI) model and in etoposide-induced neuronal apoptosis in vitro. Ang-1 treatment inhibits etoposide-induced upregulation of proapoptotic B-cell lymphoma 2 (Bcl-2) family members Noxa, p53 upregulated modulator of apoptosis (Puma), Bcl-2 interacting mediator of cell death (Bim), and Bcl-2-associated X protein (Bax); reduces markers of caspase-dependent (cytochrome c release/caspase activation) and caspase-independent (apoptosis-inducing factor release) pathways; and limits neuronal cell death. Ang-1 treatment phosphorylates receptors Tunica interna endothelial cell kinase 2 (Tie2), and β1-integrin and limits the etoposide-induced decrease in protein kinase B (Akt) activity. Blocking Tie2 and β1-integrin signaling reduces Ang-1 neuroprotective effects. After both TBI and etoposide treatment microRNA (miR)-711 are upregulated, consistent with its putative role as a negative regulator of Ang-1. We show that miR-711 directly targets the Ang-1 messenger RNA (mRNA), decreasing Ang-1 expression. Increased levels of miR-711 and Ang-1 mRNA are found in the RNA-induced silencing complex complex site of miR-mediated degradation of target mRNAs after etoposide treatment and the miR-711mimic downregulates Ang-1. Administration of miR-711 inhibitor elevates Ang-1 after TBI whereas Ang-1 administration increases Akt activation; reduces Puma, Noxa, Bim, and Bax levels; and attenuates caspase-dependent and -independent neuronal apoptosis 24 h after TBI. Ang-1 also attenuates neuronal degeneration, increases gene expression of molecules that maintain blood-brain barrier integrity, and reduces post-traumatic lesion volume/edema 24 h after TBI. Although we only observed short-term neuroprotective effects after Ang-1 administration, miR-711-dependent downregulation of Ang-1, followed by Akt pathway inhibition, may play a role in neuronal cell death after neuronal injury in vitro and after experimental TBI.
血管生成素 1（Ang-1）是一种众所周知的内皮生长因子，但它对神经元的影响尚未阐明。我们发现，在受控皮质撞击（CCI）后，即小鼠实验性创伤性脑损伤（TBI）模型和依托泊苷诱导的体外神经元细胞凋亡中，Ang-1 在损伤的大脑中迅速下调。Ang-1 治疗可抑制依托泊苷诱导的促凋亡 B 细胞淋巴瘤 2（Bcl-2）家族成员 Noxa、p53 上调凋亡调节剂（Puma）、Bcl-2 相互作用的细胞死亡介体（Bim）和 Bcl-2 相关 X 蛋白（Bax）的上调；降低 caspase 依赖性（细胞色素 c 释放/半胱天冬酶激活）和 caspase 非依赖性（凋亡诱导因子释放）途径的标志物；并限制神经元细胞死亡。Ang-1 治疗可使内皮层激酶 2（Tie2）和 β1-整联蛋白受体磷酸化，并限制依托泊苷诱导的蛋白激酶 B（Akt）活性降低。阻断 Tie2 和 β1-整联蛋白信号可降低 Ang-1 的神经保护作用。在 TBI 和依托泊苷治疗后，microRNA（miR）-711 均上调，与其作为 Ang-1 的负调节剂的作用一致。我们发现，miR-711 可直接靶向 Ang-1 信使 RNA（mRNA），降低 Ang-1 表达。在依托泊苷处理后，miR 介导的靶 mRNA 降解的 RNA 诱导沉默复合物部位发现 miR-711 和 Ang-1 mRNA 水平升高，而 miR-711 模拟物下调 Ang-1。TBI 后给予 miR-711 抑制剂可增加 Ang-1，而 Ang-1 给药可增加 Akt 激活；降低 Puma、Noxa、Bim 和 Bax 水平；并减轻 TBI 后 24 小时 caspase 依赖性和非依赖性神经元凋亡。Ang-1 还可减轻神经元变性，增加维持血脑屏障完整性的分子的基因表达，并减少 TBI 后 24 小时的创伤后病变体积/水肿。尽管我们仅在 Ang-1 给药后观察到短期神经保护作用，但 Ang-1 依赖性下调，随后 Akt 途径抑制，可能在体外神经元损伤和实验性 TBI 后神经元细胞死亡中发挥作用。
