Alpha-Adrenoceptors in Vascular Wall Growth

描述（由申请人提供）：在过去的十年中，该基金支持的工作发现，去甲肾上腺素（NE）在体外和体内诱导平滑肌细胞（SMCs）和外层成纤维细胞的生长。这种生长因子样活性得到了其他人的证实，即使在交感神经张力的基线水平下，在经历病理性（如球囊损伤）和适应性生理环境（如血流重塑）肥厚变化的动脉中也会得到加强。负责的11-肾上腺素受体（AR）类型不同于通常介导收缩的类型。在之前的资助期间的主要发现是：(1)肾上腺素能诱导的生长可推广到除损伤外的其他情况，例如肺动脉高压的内膜增生、侧支壁增厚和低流量诱导的负（内向）肥厚重塑（FINR）。(2)鉴定出关键信号元件：11-AR、NAD(P) h -氧化酶、ROS/H2O2、pro-HB-EGF-cleavage、HB-EGF、EGFR、Raf1、MEK、ERK1/2、细胞肥大、增殖迁移、胶原积累、内膜、中膜和外膜增厚。这些发现不仅与疾病有潜在的相关性，而且还与SMCs和外基质成纤维细胞中存在的特定11- AR亚型具有一定的功能，而这些亚型到目前为止还没有被赋予功能。最近出现了对这种人类机制的可能支持；用11A-AR拮抗剂慢性治疗前列腺肥大可使动脉粥样硬化引起的缺血性心脏病的症状减少72%（见第4节）。因此，现在重要的是确定这种营养途径是否存在于人类血管中，以及它是否有助于或恶化动脉粥样硬化（目的1和2）。虽然HB-EGF是上皮生长、伤口愈合和癌症的主要调节因子，但对其在血管壁细胞中的作用知之甚少。与上述发现相补充的是，我们对Aim III的初步研究已经获得了有趣的证据，表明HB-EGF可能在血管壁生长中起着一般的信号联系作用。例如，我们发现HB-EGF是肾上腺素能生长和FINR（一种具有动脉粥样硬化共同特征的模型）所必需的。虽然内皮细胞、SMCs和巨噬细胞在体外释放HB-EGF，但它们在体内是否释放HB-EGF尚不清楚（Aim III）。这些研究是Aim IV的必要条件，它将检验ROSAEHB-EGF信号在动脉粥样硬化中很重要的新假设。这些研究继续该项目的长期目标，以更好地了解适应性条件和血管疾病中血管壁生长和重塑的调节。公共卫生相关性：虽然儿茶酚胺（肾上腺素和去甲肾上腺素）的急性增加有利于在运动和紧张情况下收缩血管和加强心脏活动，但持续高水平是由血管疾病的危险因素引起的（例如，慢性压力、衰老、高盐饮食、糖尿病、肥胖、吸烟、男性、高血压和久坐不动的生活方式）。该项目旨在扩展我们之前在啮齿动物中的研究，这些研究表明，儿茶酚胺的慢性增加具有生长因子样（营养）作用，可能导致或加重血管疾病（例如，动脉粥样硬化，动脉硬化，再狭窄和旁路移植失败），从而可能导致新的治疗方法来阻断人类血管疾病的这一途径。因此，我们将研究人类血管：1)检查儿茶酚胺是否有营养，特别是那些有血管疾病早期迹象的血管；2)确定负责的细胞信号传导机制；3)在大鼠和小鼠身上进行研究，以更好地了解信号传导机制（特别是HB-EGF），测试儿茶酚胺和HB-EGF是否会加重实验性动脉粥样硬化，并看看我们是否可以通过阻断这些信号传导成分来减轻动物模型中的疾病。

DESCRIPTION (provided by applicant): In the past decade, work supported by this grant has found that norepinephrine (NE) induces growth of smooth muscle cells (SMCs) and adventitial fibroblasts in vitro and in vivo. This growth factor-like activity, con- firmed by others, is accentuated in arteries undergoing hypertrophic changes in pathologic (e.g., balloon injury) and adaptive physiologic settings (e.g., flow remodeling), even at baseline levels of sympathetic tone. The responsible 11-adrenoceptor (AR) type differs from the one that generally mediates constriction. Major findings during the previous grant period were: (1) Adrenergic-induced growth is generalized to other settings besides injury, e.g., intimal hyperplasia in pulmonary hypertension, collateral wall thickening, and low-Flow Induced Negative (inward) hypertrophic Remodeling (FINR). (2) The key signaling elements were identified: 11-AR AE NAD(P)H-oxidase AE ROS/H2O2 AE pro-HB-EGF-cleavage AE HB-EGF AE EGFR AE Raf1 AE MEK AE ERK1/2 AE cell hypertrophy, proliferation and migration, collagen accumulation, thickening of intima, media and adventitia. Not only do these findings have potential relevance to disease, but they also attach a function to particular 11- AR subtypes present on SMCs and adventitial fibroblasts that until now had not been ascribed a function. Possible support for this mechanism in humans has recently appeared; chronic treatment of prostatic hypertrophy with an 11A-AR antagonist was accompanied by a 72% reduction in the development of symptoms of atherosclerosis-induced ischemic heart disease (reviewed in Section 4). Thus, it is now important to determine if this trophic pathway exists in human vessels and if it contributes to or worsens atherogenesis (Aims I & II). Although HB-EGF is a major regulator of epithelial growth, wound healing and cancer, little is known about its role in vascular wall cells. Complimenting the above findings, our preliminary work for Aim III has obtained intriguing evidence that HB-EGF may serve as a general signaling nexus in vascular wall growth. For example, we find HB-EGF is required for both adrenergic growth and FINR-- a model with some features common to atherogenesis. While ECs, SMCs and macrophages release HB-EGF in vitro, whether they do in vivo is un- known (Aim III). These studies are requisite to Aim IV which will test the novel hypothesis that ROSAEHB-EGF signaling is important in atherosclerosis. These studies continue the long-term goal of this project to better understand the regulation of vascular wall growth and remodeling in adaptive conditions and vascular disease. PUBLIC HEALTH RELEVANCE: While acute increases in catecholamines (adrenalin and noradrenaline) act beneficially to constrict blood vessels and strengthen the heart's activity in exercise and stressful situations, continuously high levels are induced by risk factors for vascular disease (e.g., chronic stress, aging, high salt diet, diabetes, obesity, smoking, male sex, hypertension, and sedentary lifestyle). This project seeks to extend our previous investigations in rodents, which have shown that chronic increases in catecholamines have growth factor-like (trophic) actions that may contribute to or worsen vascular disease (e.g., atherosclerosis, arteriosclerosis, restenosis and bypass graft failure), into studies that may lead to new treatments to block this pathway in human vascular disease. Thus, we will study human vessels to: 1) examine if catecholamines are trophic, especially those with early signs of vascular disease, 2) identify the responsible cellular signaling mechanisms, and 3) also conduct studies in rats and mice to better understand the signaling mechanisms (in particular HB- EGF), test whether catecholamines and HB-EGF worsen experimental atherosclerosis, and see if we can lessen disease in animal models by blocking these signaling components.