Mechanisms of retinal angiogenesis

描述（由申请人提供）：在了解病理性视网膜血管生成机制的过程中，我们发现除了VEGFA、VEGFB、VEGFC、DLL4和cleaved NOTCH1诱导外，缺氧还以稳健和持续的方式激活小鼠视网膜中的CREB和STAT3。有趣的是，阻断CREB或STAT3均可抑制VEGFC和fgf2诱导的hrmvec中DLL4和裂解的NOTCH1的表达。大量研究表明，NOTCH信号通过调节尖端与柄细胞分化在发育和出生后血管生成中起关键作用。CREB属于碱性/亮氨酸拉链（basic/leucine zipper, bZIP）转录因子家族，能够在基因启动子区域结合公认序列TGAC/GTCA，增强其对多种刺激物（包括细胞因子、生长因子和激素）的表达，参与神经元可塑性、长期记忆和细胞代谢的调节。同样，STAT3属于转录因子家族，其活性受Tyr/Ser磷酸化和乙酰化调节，能够结合基因启动子区域的一致序列TTCCGGGAA，诱导其对多种刺激物（包括细胞因子、生长因子和激素）的表达，参与细胞生长和迁移的调节。虽然大量的数据证明了这些转录因子在许多细胞过程的调节中的重要性，包括细胞增殖、迁移和分化，但它们在病理视网膜血管生成的调节中的作用，特别是与NOTCH信号有关的作用，却一无所知。基于我们新颖的初步观察，我们假设CREB和STAT3通过增强DLL4的表达从而介导NOTCH1信号介导病理性视网膜新生血管。为了解决这一假设，我们将测试以下三个具体目标：验证CREB介导缺氧诱导的病理性视网膜新生血管的假说。目标2。验证STAT3介导缺氧诱导的病理性视网膜新生血管的假说。目标3。为了验证缺氧通过CREB和STAT3诱导DLL4-NOTCH1信号传导导致漏性和非模式病理性视网膜新生血管的假设。本研究将为我们提供NOTCH信号激活在病理视网膜新生中的上游机制的新信息，这些知识将有助于开发针对这种使人衰弱的眼部疾病的治疗药物。

DESCRIPTION (provided by applicant): In understanding the mechanisms of pathological retinal angiogenesis, we have discovered that besides VEGFA, VEGFB, VEGFC, DLL4 and cleaved NOTCH1 induction, hypoxia activates CREB and STAT3 in the mouse retina in a robust and sustained manner. Interestingly enough, blockade of either CREB or STAT3 inhibits VEGFC and FGF2-induced expression of DLL4 and cleaved NOTCH1 in HRMVECs. A large number of studies suggest that NOTCH signaling by modulating the tip versus stalk cell differentiation plays a pivotal role in developmental and postnatal angiogenesis. CREB belongs to a basic/leucine zipper (bZIP) family of transcriptional factors and possess the ability to bind o the consensus sequence TGAC/GTCA in the promoter regions of genes enhancing their expression in response to a wide variety of stimulants, including cytokines, growth factors and hormones and is involved in the regulation of neuronal plasticity, long-term memory and cellular metabolism. Similarly, STAT3, which belongs to a family of transcriptional factors and whose activity is regulated by Tyr/Ser phosphorylation and acetylation, possess the ability to bind to th consensus sequence TTCCGGGAA in the promoter regions of genes inducing their expression in response to a large spectrum of stimulants, including cytokines, growth factors and hormones and is involved in the modulation of cellular growth and migration. While a large body of data demonstrates the importance of these transcriptional factors in the regulation of many cellular processes, including cell proliferation, migration and differentiation, literally nothing is known n regard to their role in the regulation of pathological retinal angiogenesis, particularly in concer with NOTCH signaling. Based on our novel preliminary observations, we hypothesize that CREB and STAT3 via enhancing the expression of DLL4 and thereby NOTCH1 signaling mediates pathological retinal neovascularization. To address this hypothesis, we will test the following three specific aims: Aim 1. To test the hypothesis that CREB mediates hypoxia-induced pathological retinal neovascularization. Aim 2. To test the hypothesis that STAT3 mediates hypoxia-induced pathological retinal neovascularization. Aim 3. To test the hypothesis that hypoxia induces DLL4-NOTCH1 signaling via CREB and STAT3 leading to leaky and non- patterning pathological retinal neovascularization. The execution of the experiments proposed in this grant application should provide us novel information on the upstream mechanisms of NOTCH signaling activation in mediating pathological retinal neovascularization and such knowledge would be useful in the development of therapeutic drugs against this debilitating ocular disease.