Role of PTEN in Vascular Lesion Formation

描述(申请人提供)：再狭窄的特征是动脉内膜中的平滑肌细胞(SMC)通过中膜来源的SMC的去分化、迁移和增殖而积聚。炎症反应的特点是骨髓来源和/或循环中的炎性细胞和祖细胞重新聚集到受损的血管，也是导致再狭窄的原因之一。几种趋化因子包括MCP-1/JE、SDF-1a、IL-6和CXCL1/KC在SMC损伤后迅速被诱导，并通过募集炎性细胞和血管前体细胞参与重塑过程。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既是损伤反应的中介者，又是损伤反应的效应者。然而，在SMC中激活的反应损伤的潜在分子程序还没有明确的定义。我们以前的工作表明，SMC特异性PTEN失活是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。我们建立了可诱导的SMC特异性PTEN突变小鼠(PTEN Iko)，并发现与对照组相比，PTEN Iko小鼠主要血管中的总PTEN显著减少，同时伴随着颈动脉损伤后磷酸化Akt水平的增加和新生内膜形成的增加。PTEN基因缺陷的SMC在基础条件下表现为自分泌生长表型，并表达与实验性损伤后SMC相似的细胞因子/趋化因子。初步研究表明，PTEN缺失可激活转录因子NF1b和HIF-1a，抑制NF1b或HIF-1a可阻断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，SMC中核受体PPAR？的激活上调了PTEN，因此我们的研究将检验PPAR？激活抑制SMC增殖，通过上调SMC PTEN调节抗炎反应。总之，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，通过产生一系列趋化物质来推动病理性血管重构，这些趋化物质通过旁分泌机制招募炎症/前体细胞，并促进自分泌的SMC增殖反应。因此，SMC PTEN信号的恢复有望逆转血管损伤引起的一连串事件。我们将确定PTEN缺失对培养的PTEN缺失的SMC产生前体/炎性细胞介质的影响和作用机制，并评估小鼠SMC特异性PTEN缺失对趋化因子诱导的SMC增殖和实验性血管损伤后新生内膜形成过程中前体细胞和炎症细胞的募集的相对贡献。在第二个目标中，我们将确定PPAR？激动剂上调PTEN和SMC的生物学功能，确定PTEN调节在介导PPAR保护作用中的作用？抗损伤诱导的血管重塑的激动剂。 与公共卫生相关：心脏病并发症仍然是西方社会的主要死亡原因。虽然血管成形术/支架部署和移植物移植已被广泛用于治疗动脉粥样硬化，但这些手术中有很大一部分是由于术后再狭窄而失败的，其特征是显著的细胞生长和炎症反应导致血管阻塞。因此，为了确定调节这些过程以减少介入后血管闭塞的潜在机制，人们付出了大量的努力。我们的研究旨在测试一种由血管细胞表达的蛋白质PTEN在积极阻止一系列趋化因子的表达方面的作用和作用机制，这些趋化因子家族本来可以促进血管细胞的生长和血管干预后的炎症反应。

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.