Toll-like receptor signaling in pathogenesis of pulmonary hypertension

描述(由申请人提供)： 6.肺动脉高压(PAH)是退伍军人群体中的重要健康问题，也是心肺疾病患者的发病率和死亡率的重要因素。低氧可导致肺动脉高压，包括肺动脉结构重塑。最近的研究发现，Toll样受体4(TLR4)缺陷的小鼠易患致死性氧化性肺损伤和肺气肿。与TLR4缺乏在肺部疾病发展中的重要性的观察一致，我们发现TLR4-而不是TLR2缺陷的小鼠自发地发生PAH。此外，低氧可诱导野生型和TLR2-/-小鼠的PAH，但不会增加TLR4-/-小鼠自发形成的PAH，提示TLR4在维持正常肺血管中起重要作用，低氧通过TLR4诱导PAH。这一建议的重点是了解TLR4及其信号通路在调节PAH的发展中的作用。血管重塑是PAH发病机制中的关键步骤。在细胞水平上，血管重塑与平滑肌细胞(SMC)的增殖增加有关。初步研究发现，低氧抑制了TLR4的表达，诱导了肺动脉SMC中NOX1和NOX4的表达。另一方面，TLR4-/-小鼠来源的SMC细胞内活性氧(ROS)产生增加，NOX4和NOX1表达增加。NOX4是SMC中产生ROS的主要NADPH氧化酶。增加NOX4促进SMC增殖，抑制NOX4减少ROS的产生和SMC增殖。因此，我们推测，低氧抑制TLR4可能通过激活NADPH氧化酶信号，促进SMC增殖和血管重塑，从而促进PAH。将寻求两个特定的目标来检验这一假说：特定的目标1：表征TLR4信号在小鼠的PAH调节中的功能作用。TLR4的表达、功能结构域及其适配蛋白MyD88在调节自发性和低氧诱导的PAH发展中的作用将被表征。具体目标2：阐明TLR4调控PAH的分子机制。TLR4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串扰将被确定。我们的研究将明确TLR4信号在PAH发病机制中调节SMC增殖和血管重塑中的一个重要新功能，这将拓宽我们对先天免疫和氧化应激信号在肺血管系统中相互作用的认识。确定TLR信号转导通路在PAH发病机制中的作用，可能为预防或干预PAH，以及其他由慢性氧化应激和血管重塑引起的疾病提供新的策略。这种障碍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。 公共卫生相关性： 7.说明：在退伍军人群体中，肺病和心脏病是重要的健康问题，而肺动脉高压是导致其发病率和死亡率的原因。我们发现，Toll样受体4(TLR4)缺陷的小鼠会自发地发生PAH，这与氧化应激增加有关。这一建议将进一步定义TLR4信号在调节PAH进展中的血管重塑中的新功能。本研究将拓宽我们对先天免疫在肺血管氧化应激调节中的作用的认识，这将有助于开发新的治疗方法来预防或治疗PAH。

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. PUBLIC HEALTH RELEVANCE: 7. NARRATIVE: 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. We have found that mice deficient in toll like receptor 4 (TLR4) spontaneously developed PAH, that is associated with increased oxidative stress. This proposal will further define a novel function of TLR4 signaling in regulating vascular remodeling in the progression of PAH. The present studies will broaden our knowledge on the contribution of innate immunity to regulation of oxidative stress in the pulmonary vasculature, which will lead to development of novel therapeutics for prevention or treatment of PAH.