Role of PTEN in Hypoxia-Induced Vascular Remodeling, Raphael Nemenoff

低氧性肺动脉高压(PAH)的发病机制主要表现为 血管收缩和血管重塑导致肺血管阻力增加 右心衰竭。这些反应的特征是驻留的血管壁细胞的功能变化。 包括平滑肌(SMC)、内皮细胞和成纤维细胞，以及循环祖细胞的招募 和炎性细胞。我们的初步数据表明，低氧导致SMC中Akt的快速激活 肺血管系统。PTEN是PI3-K/Akt/mTOR信号的负调节因子，是PI3-K/Akt/mTOR信号的抑制因子。 SMC增殖。我们已经证明，SMC特异性的靶向PTEN突变小鼠(PTEN KO) 自发性地发展成肺动脉高压。PTEN KO小鼠也表现出血管周围和 血清趋化因子水平，循环中祖细胞的增加，以及祖细胞向主要 血管和肺。PPG中的其他调查人员的工作表明，罗格列酮是一种特定的 核受体激活剂PPARy，减轻低氧诱导的肺血管重构。在……里面 其他系统，PPARy抑制细胞增殖和调节抗炎反应的能力是 在很大程度上是通过上调PTEN的表达和/或活性来实现的。基于这些 集体观察，我们假设肺动脉SMC中PTEN的失活将导致 严重的PAH是对慢性缺氧的反应。这一反应将通过对SMC的直接影响进行中介 SMC的增殖和趋化因子的产生将参与招募 也可能以自分泌的方式作用于SMC本身。 相反，激活PPARy至少可以抑制低氧诱导的肺血管重构 部分是通过上调PTEN的表达。该项目将采用体内和体外方法来 测试一下这个型号。提出了两个具体目标。AIML将使用一种新型的坦帕西芬诱导的PTEN SMC特异性PTEN基因敲除小鼠模型对趋化因子的影响 缺氧诱导的SMC增殖及祖细胞和炎性细胞的募集 肺血管重塑。这个模型将允许内侧SMC和骨髓的命运映射- 派生的祖细胞在PAH发病机制中的作用，提供了关于 这些细胞在肺血管重塑中的作用。体外研究将使用shRNA沉默 PTEN在肺动脉SMC中的表达，以确定介导这些反应的下游效应因子。目标2将 采用类似的策略在体内特异性删除PPARy并与PTEN比较反应 有缺陷的小鼠。体外实验将确定PTEN在介导PPARy效应中的作用。 最后探讨PTEN在罗格列酮和吡格列酮保护作用中的作用。 特征化的PPARy激活剂，将被检验。 相关性(请参阅说明)： 介导低氧诱导PAH的分子通路涉及多种细胞类型。这个项目是 旨在专门审查SMC对这一进程的贡献。新的小鼠模型 信号通路可以以时间依赖的方式操纵，特别是在SMC中将定义角色 SMC的。体外方法将描绘控制生长、表型调节的分子途径 以及这些细胞产生的细胞因子。调节这些通路的药物代表着新的 治疗和预防PAH的治疗药物。

The pathogenesis of hypoxia-induced pulmonary arterial hypertension (PAH) is characterized by vasoconstriction and vascular remodeling contributingto increased pulmonary vascular resistance leading to right heart failure. These responses are characterized by functional changes in resident vascular wall cells including smooth muscle (SMC), endothelial,and fibroblast, as well as recruitment of circulating progenitor and inflammatory cells. Our preliminary data indicatethat hypoxia leads to rapid activation of Akt in SMC of the lung vasculature. PTEN is a negative regulator of PI3-kinase/Akt/mTOR signaling, and an inhibitor of SMC proliferation. We have shown that SMC-specific, targeted PTEN mutant mice (PTEN KO) spontaneously develop pulmonary hypertension. PTEN KO mice also exhibit increased perivascular and serum chemokine levels, increases in circulating progenitor cells, and trafficking of progenitor cells to major vessels and the lung. Work by other investigators in this PPG demonstrated that rosiglitazone, a specific activator of the nuclear receptor PPARy, attenuates hypoxia-induced pulmonary vascular remodeling. In other systems, the ability of PPARy to inhibit cell proliferation and regulate anti-inflammatory responses is mediated, in large part, through the upregulation of PTEN expression and/or activity. Based on these collective observations, we hypothesize that inactivation of PTEN in pulmonary arterial SMC will induce severe PAH in response to chronic hypoxia. This response will be mediated by direct effects on SMC hyperplasia as well as the production of chemokines by SMC which will be involved in the recruitment of progenitor/pro-inflammatory cells and may also act in an autocrine fashion on the SMC themselves. Conversely, activation of PPARy will inhibit hypoxia-induced pulmonary vascular remodeling at least in part through the upregulation of PTEN. This project will employ both in vivo and in vitro approaches to test this model. Two specific aims are proposed. Aiml will use a novel, tampxifen-inducible PTEN knockout mouse model to examine the effects of SMC-specific deletion of PTEN in mice on chemokine- induced SMC hyperplasia and recruitment of progenitor and inflammatory cells during hypoxia-induced pulmonary vascular remodeling. This model will allow fate-mapping of medial SMC and bone marrow- derived progenitor cells during the pathogenesis of PAH, providing clear information regarding the contributions of these cells in pulmonary vascular remodeling. In vitro studies will use shRNA silencing of PTEN in pulmonary artery SMC to define downstream effectors mediating these responses. Aim 2 will employ an analogous strategy to specifically delete PPARy in vivo and compare responses with PTEN deficient mice. In vitro experiments will establish the role of PTEN in mediating the effects of PPARy. Finally, the role of PTEN in mediating the protective effects of rosiglitazone and pioglitazone, two well- characterized PPARy activators, will be examined. RELEVANCE (See instructions): The molecular pathways mediating hypoxia-induced PAH involve multiple cell types. This project is designed to specifically examine the contribution of SMC to this process. Novel mouse models in which signaling pathways can be manipulated in a time-dependent fashion specifically in SMC will define the role of SMC. In vitro approaches will delineate molecular pathways controlling growth, phenotypic modulation and cytokine production by these cells. Pharmacological agents regulating these pathways represent novel therapeutic agents for treatment and prevention of PAH.