Extracellular ATP: potential regulator of hypoxia-induced vasa vasorum neovascula

描述(申请人提供)：病理性血管重塑是体循环和肺循环血管疾病的关键组成部分，常常危及生命。在缺氧性肺动脉高压的新生儿模型中，我们已经证明了缺氧性肺动脉(PA)重构与血管网络密度的显著增加有关。观察到的血管密度增加表明，新生血管过程可能有助于肺血管重塑和高血压的进展。我们研究的长期目标是评估在缺氧性肺血管重塑中介导血管新生的确切的细胞机制和内源性分子因素。细胞外腺嘌呤核苷酸越来越被认为是重要的血管功能调节因子。由于在PA外膜内，许多血管和血细胞可以对低氧作出反应，因此可以推测，在缺氧的血管微环境中，细胞外的ATP可能是参与低氧诱导的PA外膜新生血管的信号分子。我们在体外的初步研究表明，从PA外膜分离的血管内皮细胞(VVEC)对细胞外ATP有明显的增殖反应。反过来，低氧被发现是一种强有力的ATP释放诱导剂。因此，我们推测细胞外ATP可能作为一种自分泌/旁分泌因子在刺激缺氧诱导的血管内皮细胞血管生成反应中起作用。以培养的血管内皮细胞为模型系统，本研究的目的是：(1)确定在低氧和ATP诱导的VVEC血管生成反应中起关键作用的细胞外ATP和细胞内信号转导通路的血管生成能力；(2)阐明缺氧诱导VVEC释放ATP的细胞内机制；(3)检测内源性释放的ATP在介导VEC缺氧效应中发挥自分泌作用的可能性。最终，这项研究计划致力于将嘌呤能信号的基本问题转化为低氧诱导的血管生成这一临床相关问题。血管内皮细胞的血管生成表型，包括嘌呤能受体和耦合的信号通路，将为旨在抑制血管壁病理性血管生成的治疗策略提供独特的靶点。 公共卫生相关性：病理性血管重塑是体循环和肺循环血管疾病的关键组成部分，常常危及生命。越来越多的实验数据表明，血管扩张可能参与了缺氧性肺血管重构与肺动脉高压的关系。因此，我们研究的长期目标是评估介导血管新生的确切细胞机制和内源性分子因素。具体地说，利用从慢性低氧动物肺外膜分离的血管内皮细胞(VVEC)，我们将检验细胞外ATP可能在刺激低氧诱导的VVEC血管生成反应中作为自分泌/旁分泌因子的假设。

DESCRIPTION (provided by applicant): Pathological vascular remodeling is a key component and frequently life-threatening consequence, of vascular diseases in both the systemic and pulmonary circulation. In a neonatal model of hypoxic pulmonary hypertension, we have demonstrated that hypoxia-induced pulmonary artery (PA) remodeling is associated with marked increases in the density of vasa vasorum network. The observed increases in vasa density suggests that neovascularization process may contribute to the progression of pulmonary vascular remodeling and hypertension. The long-term goal of our studies is to evaluate the precise cellular mechanisms and endogenous molecular factors that mediate vasa vasorum neovascularization in hypoxia-induced pulmonary vascular remodeling. Extracellular adenine nucleotides are increasingly recognized as important regulators of vascular functions. Since within the PA adventitial compartment, ATP can be released from a number of vascular and blood cells in response to hypoxia, it could be expected that in the hypoxic vessel microenvironment, extracellular ATP may be the signaling molecules involved in the hypoxia-induced PA adventitial neovascularization. Our preliminary studies in vitro have demonstrated that vasa vasorum endothelial cells (VVEC) isolated from PA adventitia are distinct in their dramatic proliferative responses to extracellular ATP. In turn, hypoxia was found to be a potent inducer of ATP release. Therefore, we hypothesized that extracellular ATP may act as an autocrine/paracrine factor in stimulating hypoxia-induced angiogenic responses in VVEC. Using cultured vasa vasorum endothelial cell as a model system, the specific aims are proposed to (i) determine the angiogenic capacity of extracellular ATP and intracellular signaling pathways that play critical roles in hypoxia- and ATP-induced angiogenic responses in VVEC; (ii) elucidate the intracellular mechanisms through which hypoxia induces ATP release from VVEC; (iii) test the possibility that endogenously released ATP plays an autocrine role in mediating the effects of hypoxia in VVEC. Ultimately, this research proposal aspires to translate fundamental questions of purinergic signaling to the clinically relevant problem of hypoxia-induced angiogenesis. The characterization of an angiogenic phenotype of VVEC, including purinergic receptors and coupled signaling pathways, will provide unique targets for therapeutic strategies aimed at inhibiting pathologic angiogenesis in blood vessel wall. PUBLIC HEALTH RELEVANCE: Pathological vascular remodeling is a key component and frequently life-threatening consequence of vascular diseases in both the systemic and pulmonary circulation. An increasing body of experimental data suggest that vasa vasorum expansion may contribute to hypoxia-induced pulmonary vascular remodeling associated with pulmonary arterial hypertension. Therefore, the long-term goal of our studies is to evaluate the precise cellular mechanisms and endogenous molecular factors that mediate vasa vasorum neovascularization. Specifically, using cultured vasa vasorum endothelial cells (VVEC) isolated from pulmonary adventitia of chronically hypoxic animals, we will test the hypothesis that extracellular ATP may act as an autocrine/paracrine factor in stimulating hypoxia-induced angiogenic responses in VVEC.