Astrocyte-endothelial crosstalk after cerebral ischemia and hemorrhage

描述（由申请人提供）：脑缺血和出血后星形胶质细胞-内皮细胞串扰传统上认为反应性星形胶质细胞抑制CNS损伤后的神经元可塑性。但是现在新出现的数据表明，反应性星形胶质细胞也可能具有有益的作用。我们的初步数据表明，（i）反应性星形胶质细胞释放HMGB 1，可以促进血管生成，（ii）下调HMGB 1从反应性星形胶质细胞的释放可能会恶化小鼠局灶性缺血后的神经血管恢复，（iii）HMGB 1可能上调脑内皮细胞上的β受体，（iv）增加的内皮细胞粘附可能通过β-2整合素增强内皮祖细胞的靶向粘附，和（v）HMGB 1可以增加内皮祖细胞的增殖、成熟和血管生成，从而促进中风后的修复。基于这些初步数据，我们假设星形胶质细胞-内皮细胞串扰对于卒中后神经血管恢复是必不可少的：反应性星形胶质细胞释放HMGB 1，其上调脑内皮上的β受体; β受体结合循环内皮祖细胞上的β 2整合素，从而将其拉入恢复中的脑;一旦内皮祖细胞到达，HMGB 1促进其增殖，成熟和血管生成。重要的是，我们认为这一途径可以促进缺血性或出血性中风后的恢复。我们将从三个方面来检验这一假设。在目的1中，我们询问来自刺激的星形胶质细胞的HMGB 1是如何上调脑内皮细胞上的粘附并增强内皮祖细胞的靶向粘附的。在目标2中，我们剖析了HMGB 1增强内皮祖细胞增殖、成熟和血管生成能力的机制。在目标3中，我们将使用小鼠局灶性脑缺血和脑出血模型来证实这些星形胶质细胞-内皮细胞-EPC机制，并表明它们实际上在体内介导神经血管恢复。为了测试我们的途径，我们将使用细胞培养、体内小鼠模型、药理学抑制剂、包括siRNA在内的分子技术、长期神经学结果和体内成像的组合。这项研究应确定一种新的机制，其中反应性星形胶质细胞，脑内皮细胞和循环内皮祖细胞之间的串扰是脑缺血和出血后神经血管恢复的基础。剖析这些细胞-细胞信号通路可能会导致新的治疗方法，促进缺血性和出血性中风后患者的功能恢复。

DESCRIPTION (provided by applicant): Astrocyte-endothelial crosstalk after cerebral ischemia and hemorrhage Reactive astrocytes were traditionally thought to inhibit neuronal plasticity after CNS injury. But emerging data now suggest that reactive astrocytes may also have beneficial actions. Our pilot data suggest that (i) reactive astrocytes release HMGB1 that can promote angiogenesis, (ii) downregulating the release of HMGB1 from reactive astrocytes may worsen neurovascular recovery after focal ischemia in mice, (iii) HMGB1 may upregulate RAGE receptors on cerebral endothelial cells, (iv) increased endothelial RAGE may enhance targeted adhesion of endothelial progenitor cells via beta-2 integrins, and (v) HMGB1 may increase proliferation, maturation and angiogenesis in endothelial progenitor cells, thus promoting repair after stroke. Based on these pilot data, we hypothesize that astrocyte-endothelial crosstalk is essential for neurovascular recovery after stroke: reactive astrocytes release HMGB1 that upregulates RAGE receptor on cerebral endothelium; RAGE binds beta-2 integrins on circulating endothelial progenitor cells thus pulling them into recovering brain; and once endothelial progenitors arrive, HMGB1 promotes their proliferation, maturation and angiogenesis. Importantly, we propose that this pathway can promote recovery after both ischemic or hemorrhagic strokes. We will test this hypothesis in three aims. In Aim 1, we ask how HMGB1 from stimulated astrocytes upregulate RAGE on cerebral endothelial cells and enhance the targeted adhesion of endothelial progenitor cells. In Aim 2, we dissect mechanisms that underlie the ability of HMGB1 to enhance proliferation, maturation and angiogenesis in endothelial progenitor cells. In Aim 3, we will use mouse models of focal cerebral ischemia and intracerebral hemorrhage to confirm these astrocyte-endothelium-EPC mechanisms and show that they actually mediate neurovascular recovery in vivo. To test our pathways, we will use a combination of cell culture, in vivo mouse models, pharmacologic inhibitors, molecular techniques including siRNA, long-term neurological outcomes, and in vivo imaging. This study should define a novel mechanism wherein crosstalk between reactive astrocytes, cerebral endothelium, and circulating endothelial progenitor cells underlie neurovascular recovery after cerebral ischemia and hemorrhage. Dissecting these cell-cell signaling pathways may lead to new therapeutic approaches for promoting functional recovery in patients after ischemic and hemorrhagic strokes.