CREB: Molecular determinant of pulmonary hypertension

描述（由申请人提供）： 肺动脉高压的特征在于动脉壁结构的深刻变化，这在很大程度上是由于平滑肌细胞的增殖。对心肺系统的损伤通过多种机制引起SMC表型的变化，包括内皮细胞和血小板产生增殖和炎性细胞因子。本研究的长期目标是明确细胞因子血小板源性生长因子-BB（PDGF-BB）调节肺动脉（PA）SMC增殖的分子机制。 以前，我们报告说，水平的转录因子，cAMP-反应元件结合蛋白（CREB）减少增殖SMC在PA从高血压，新生牛，或在培养的SMC与PDGF-BB治疗。 我们还表明，异位表达的组成型活性CREB亚型在SMC抑制基础和PDGF诱导的体外生长，而显性负CREB亚型增强增殖。PDGF似乎在基因转录水平上调节CREB含量。有趣的是，PPARg激动剂增加CREB含量，并在体外和啮齿动物糖尿病血管疾病模型中阻断SMC增殖。最近的初步研究表明CREB调节SMC中cyclin D1和Cdk-4的表达。基于这些结果，我们假设PDGF-BB通过相关的信号通路和转录因子调节SMC增殖， 控制CREB基因转录，进而控制调控细胞周期进入和进展的因子如细胞周期蛋白D1和Cdk-4的表达。为了解决这一假设，我们设计了三个特定目的：1）鉴定响应于PDGF-BB调节CREB基因转录的细胞内信号传导途径和转录因子，2）证明CREB诱导的细胞周期蛋白D1和Cdk 4的变化调节SMC增殖，3）证明PPAR激动剂增加CREB含量并防止暴露于缺氧条件的新生奶牛的血管重塑。 尽管环核苷酸和PKA在控制SMC增殖中的作用已得到证实，但CREB并没有广泛参与SMC功能，因此这些研究具有重要意义。同样，CREB活性的调节传统上被视为磷酸化状态的函数，而不是CREB含量的变化。确定CREB在SMC中的表达和调节对于开发其参与控制SMC增殖的综合模型至关重要。拟议的研究应该为控制SMC生长的基因转录事件提供新的见解，并可能为旨在预防或治疗PH和相关疾病的新疗法确定目标。

DESCRIPTION (provided by applicant): Pulmonary hypertension is characterized by profound changes in the structure of the arterial wall due in large part, to the proliferation of smooth muscle cells. Insults to the cardiopulmonary system elicit changes in SMC phenotype through a variety of mechanisms including the production of proliferative and inflammatory cytokines by endothelial cells and platelets. The long-term goals of our research are to define the molecular mechanisms by which the cytokine, Platelet-derived Growth Factor-BB (PDGF-BB) regulates pulmonary artery (PA) SMC proliferation. Previously, we reported that levels of the transcription factor, cAMP-Response Element Binding Protein (CREB) are reduced in proliferating SMCs in PAs from hypertensive, neonatal cows, or in cultured SMCs treated with PDGF-BB. We also demonstrated that ectopic expression of constitutively active CREB isoforms in SMCs inhibits basal and PDGF-induced growth in vitro, whereas dominant negative CREB isoforms enhanced proliferation. PDGF appears to regulate CREB content at the level of gene transcription. Interestingly, PPARg agonists increased CREB content and blocked SMC proliferation in vitro and in rodent models of diabetic vascular disease. Recent preliminary studies indicate that CREB modulates cyclin D1 and Cdk-4 expression in SMCs. Based on these results, we hypothesize that PDGF-BB regulates SMC proliferation via associated signaling pathways and transcription factors that control CREB gene transcription, which in turn controls the expression of factors that govern cell cycle entry and progression like cyclin D1 and Cdk-4. To address this hypothesis we have designed three Specific Aims to 1) identify the intracellular signaling pathways and transcription factors that regulate CREB gene transcription in response to PDGF-BB, 2) demonstrate that CREB-induced changes in cyclin D1 and Cdk4 regulates SMC proliferation, and 3) demonstrate that PPAR agonists increase CREB content and prevent vascular remodeling in neonatal cows exposed to hypoxic conditions. These studies are significant since CREB has not been widely implicated in SMC function, in spite of the well-established role of cyclic nucleotides and PKA in controlling SMC proliferation. Likewise, the regulation of CREB activity has traditionally been viewed as a function of phosphorylation status rather than changes in CREB content. Defining the expression and regulation of CREB in SMCs is crucial to developing a comprehensive model for its participation in controlling SMC proliferation. The proposed studies should provide new insights into the gene transcription events that control SMC growth and perhaps identify targets for new therapies designed to prevent or treat PH and related diseases.