Toll-like receptor signaling in pathogenesis of pulmonary hypertension

描述（由申请人提供）： 6.摘要肺动脉高压（PAH）是导致肺和心脏疾病患者发病率和死亡率的重要因素，是退伍军人群体的重要健康问题。缺氧诱导PAH，其包括肺动脉的结构重构。近年来研究发现，Toll样受体4（TLR 4）缺陷的小鼠易发生致死性氧化性肺损伤和肺气肿。与TLR 4缺陷在肺部疾病的发展中很重要的这些观察结果一致，我们发现TLR 4-而不是TLR 2-缺陷小鼠自发地发展PAH。此外，缺氧诱导PAH的野生型和TLR 2-/-小鼠，但没有增强PAH自发发展的TLR 4-/-小鼠，这表明TLR 4在维持正常的肺血管系统和缺氧诱导PAH通过TLR 4的重要作用。该提案的重点是了解TLR 4及其信号通路在调节PAH发展中的作用。血管重塑是PAH发病机制中的关键步骤。在细胞水平，血管重塑与平滑肌细胞（SMC）增殖增加有关。初步研究发现，低氧抑制肺动脉平滑肌细胞TLR 4的表达，诱导NOX 1和NOX 4的表达。另一方面，来自TLR 4-/-小鼠的SMC表现出细胞内活性氧（ROS）的产生增加以及NOX 4和NOX 1的表达增加。NOX 4是SMC中产生ROS的主要NADPH氧化酶。增加的NOX 4促进SMC增殖，并且抑制NOX 4减少ROS的产生和SMC增殖。因此，我们推测缺氧抑制TLR 4通过激活NADPH氧化酶信号促进PAH，增加SMC增殖和血管重塑。将追求两个具体目标来检验假设：具体目标1：表征TLR 4信号在调节小鼠PAH中的功能作用。TLR 4的表达，其功能结构域及其衔接蛋白，MyD 88，在调节自发性和缺氧诱导的PAH的发展的作用将被表征。具体目标2：阐明负责TLR 4调节PAH的分子机制。将确定TLR 4信号和NADPH氧化酶介导的氧化还原信号通路在调节SMC增殖和血管重塑中的相互作用。 我们的研究将确定TLR 4信号在PAH发病机制中调节SMC增殖和血管重塑的重要新功能，这将拓宽我们对肺血管系统中先天免疫和氧化应激信号之间串扰的认识。确定TLR信号级联在PAH发病机制中的分子机制可能会导致预防或干预PAH以及可能由慢性氧化应激和血管重塑引起的其他疾病的新策略。这种疾病影响了许多退伍军人，拟议的研究将有助于提高他们的生活质量。

DESCRIPTION (provided by applicant): 6. ABSTRACT Pulmonary arterial hypertension (PAH) contributes to the morbidity and mortality of patients with lung and heart diseases, important health problems in the Veteran's population. Hypoxia induces PAH, which comprises structural remodeling of pulmonary arteries. Recently studies have found that mice deficient in Toll- like receptor 4 (TLR4) are susceptible to lethal oxidant lung injury and emphysema. Consistent with these observations that TLR4 deficiency is important in the development of lung diseases, we found that TLR4-, not TLR2-deficient mice spontaneously developed PAH. Further, hypoxia induced PAH in wild type and TLR2-/- mice, but did not enhance PAH spontaneously developed in TLR4-/- mice, suggesting that TLR4 plays an important role in maintaining normal pulmonary vasculature and hypoxia induces PAH via TLR4. This proposal is focused on understanding the role of TLR4 and its signaling pathways in regulating the development of PAH. Vascular remodeling represents a key step in the pathogenesis of PAH. At the cellular level, vascular remodeling is associated withincreased proliferation of smooth muscle cells (SMC). Preliminary studies found that hypoxia inhibited the expression of TLR4, and induced the expression of NOX1 and NOX4 in pulmonary artery SMC. On the other hand, SMC derived from TLR4-/- mice exhibited increased production of intracellular reactive oxygen species (ROS) and increased expression of NOX4 and NOX1. NOX4 is the predominant NADPH oxidase in SMC that produce ROS. Increased NOX4 promotes SMC proliferation, and inhibition of NOX4 reduces production of ROS and SMC proliferation. Therefore, we hypothesize that inhibition of TLR4 by hypoxia promotes PAH by activating NADPH oxidase signaling that increases SMC proliferation and vascular remodeling. Two specific aims will be pursued to test the hypothesis: Specific Aim 1: Characterize the functional role of TLR4 signals in regulation of PAH in mice. The role of TLR4 expression, its functional domain and its adaptor protein, MyD88, in regulating the development of spontaneous and hypoxia-induced PAH will be characterized. Specific Aim 2: Delineate the molecular mechanisms responsible for TLR4 regulation of PAH. The cross talk between TLR4 signals and the NADPH oxidase-mediated redox signaling pathways in regulating SMC proliferation and vascular remodeling will be determined. Our studies will define an important novel function of TLR4 signaling in regulating SMC proliferation and vascular remodeling in the pathogenesis of PAH, which will broaden our knowledge on the crosstalk between innate immunity and oxidative stress signals in the pulmonary vasculature. Determination of the molecular mechanisms responsible for TLR signaling cascade in the pathogenesis of PAH might lead to novel strategies to prevent or intervene PAH, and possibly other diseases induced by chronic oxidative stress and vascular remodeling. Such disorders affect many veterans, the proposed studies will help to improve quality of their life.