Role of PTEN in Vascular Lesion Formation

描述（由申请人提供）：动脉再狭窄的特征是平滑肌细胞（SMC）通过中间源性SMC的去分化、迁移和增殖在动脉内膜积累。以骨髓源性和/或循环性炎症和祖细胞向受损血管募集为特征的炎症反应也有助于再狭窄。几种趋化因子，包括MCP-1/JE、SDF-1a、IL-6和CXCL1/KC，在损伤后迅速诱导SMC，并通过募集炎症和血管祖细胞参与重塑过程。其中一些因素也被证明直接影响SMC本身的生物学功能，使SMC成为损伤反应的中介和效应者。然而，SMC在损伤反应中激活的潜在分子程序尚未明确定义。我们之前的工作表明，smc特异性PTEN失活，pi3激酶信号的负调节因子，是驱动血管病变形成的早期触发因素。我们产生了可诱导的smc特异性PTEN突变小鼠（PTEN iKO），并发现与对照组相比，PTEN iKO小鼠在颈动脉损伤后，主要血管中总PTEN显著减少，同时伴随着磷酸化akt水平的增加和新内膜形成的增强。体外缺乏pten的SMC在基础条件下表现出自分泌生长表型，并表达与实验损伤后SMC相似的细胞因子/趋化因子谱。初步数据显示，PTEN缺失激活了转录因子NF？B和HIF-1a；抑制NF？B或HIF-1a阻断了PTEN缺失介导的特异性趋化因子的上调。另一方面，我们的初步数据表明，核受体PPAR？因此，我们的研究将检验PPAR？激活抑制SMC增殖并通过上调SMC PTEN调节抗炎反应。总的来说，我们的初步数据提供了证据，表明SMC PTEN信号的改变是一个关键的启动决定因素，通过产生一系列化学吸引剂，通过旁分泌机制招募炎症/祖细胞，促进自分泌SMC增生反应，从而驱动病理性血管重构。因此，SMC PTEN信号的恢复有望逆转血管损伤带来的级联事件。我们将在Aim 1中确定PTEN缺失对培养的PTEN缺失SMC中祖细胞/炎症细胞介质生成的影响和作用机制，并评估小鼠SMC特异性PTEN缺失对趋化因子诱导的SMC增生以及实验性血管损伤后新生内膜形成过程中祖细胞和炎症细胞募集的相对贡献。在目标二中，我们将确定PPAR的作用。激动剂对PTEN上调和SMC生物学功能的影响，并确定PTEN调节在PPAR保护作用中的作用？抗损伤性血管重构的激动剂。

DESCRIPTION (provided by applicant): Restenosis is characterized by smooth muscle cell (SMC) accumulation in the arterial intima through dedifferentiation, migration, and proliferation of medial-derived SMC. An inflammatory response, characterized by bone marrow-derived and/or circulating inflammatory and progenitor cell recruitment to the injured vessel, also contributes to restenosis. Several chemokines, including MCP-1/JE, SDF-1a, IL-6, and CXCL1/KC, are rapidly induced in SMC following injury and participate in the remodeling process through the recruitment of inflammatory and vascular progenitor cells. Some of these factors have also been shown to directly affect the biological function of the SMC itself placing the SMC as both a mediator and an effector of the injury response. However, the underlying molecular programs activated in SMC in response to injury are not clearly defined. Our previous work indicates SMC-specific PTEN inactivation, a negative regulator of PI3-kinase signaling, is an early trigger driving vascular lesion formation. We generated inducible SMC-specific PTEN mutant mice (PTEN iKO) and found that, compared to controls, PTEN iKO mice exhibit significant reductions of total PTEN in major vessels with accompanying increased phosphoAkt levels and enhanced neointima formation following carotid arterial injury. PTEN-deficient SMC in vitro exhibit an autocrine growth phenotype under basal conditions and express a cytokine/chemokine profile similar to what is observed in SMC following experimental injury. Preliminary data show that PTEN depletion activates the transcription factors, NF?B and HIF-1a; inhibition of NF?B or HIF-1a blocked the upregulation of specific chemokines mediated by PTEN depletion. On the other hand, our preliminary data suggest that activation of the nuclear receptor, PPAR?, in SMC upregulates PTEN, therefore our studies will examine the ability of PPAR? activation to inhibit SMC proliferation and regulate anti-inflammatory responses through the upregulation of SMC PTEN. Overall, our preliminary data provide evidence that an alteration in SMC PTEN signaling serves as a key initiating determinant driving pathological vascular remodeling through the production of a family of chemoattractants that recruit inflammatory/progenitor cells through a paracrine mechanism and promote an autocrine SMC hyperplastic response. Therefore, restoration of SMC PTEN signaling is anticipated to reverse the cascade of events brought on by vascular injury. We will determine the consequences and mechanism of action of PTEN loss on SMC production of progenitor/inflammatory cell mediators in cultured PTEN null SMC and assess the relative contribution of SMC-specific deletion of PTEN in mice on chemokine-induced SMC hyperplasia and recruitment of progenitor and inflammatory cells during neointima formation following experimental vascular injury in Aim One. In Aim Two, we will determine the role of PPAR? agonists on the upregulation of PTEN and biological functions of SMC and determine the role of PTEN regulation in mediating the protective effects of PPAR? agonists against the development of injury-induced vascular remodeling. PUBLIC HEALTH RELEVANCE: Complications of heart disease remain the leading cause of death in Western societies. While angioplasty/stent deployment and graft transplantations have been widely used for the treatment of atherosclerosis, a significant proportion of these procedures fail due to post-procedure restenosis, characterized by significant cell growth and inflammatory responses that lead to vessel blockage. Therefore, a great deal of effort has gone into defining the underlying mechanisms regulating these processes to reduce post-intervention vascular occlusion. Our studies are designed to test the role and mechanisms of action of a protein, PTEN, expressed by vascular cells in actively blocking the expression of a family of chemokines that otherwise promote vascular cell growth and an inflammatory response following vascular interventions.