PPARβ/δ调节nNOS对肺型氧中毒保护作用的研究

When administering supplemental oxygen to treat hypoxemia diseases,hyperoxic acute lung injury(HALI) by overexposure may be present. Prolonged exposure to hyperoxia leads to the generation of excessive reactive oxygen species(ROS),which cause acute lung injury. However, until now, there were no effective therapeutic strategies for treat HALI patients. We detected the expression of peroxisome proliferator-activated receptor β/δ(PPAR-β/δ)were up-regulated in lungs of mice which suffered with HALI through gene chip technology.Then we investigated the role of PPAR-beta/delta activation in pulmonary oxygen toxicity, through the use of PPARβ/δ agonist and antagonist in vivo. We found treatment with agonist significantly reduced the (1) Histological evidence of lung injury,(2) MPO activity,(3) proinflammatory cytokines (TNF-α, IL-1β,IFN-γ),(4) PAR formation, and (5) apoptosis (caspase-3, and TUNEL).While PPAR-β/δantagonist,GSK0660 significantly blocked the effect of the agonist and thus abolished the protective .effect. Thus, based on these findings, we propose that PPAR-β/δ may play a role in the pathology of pulmonary type of oxygen toxicity. We also found PPAR-β/δ activation can elevate the expression of nNOS in lung, and when compared with the WT+GSK group, the lung injury in nNOS-/-+GSK was obviously decreased. some studies had proved that nNOS play an important role in the pathogenesis of HALI.So, in this study，we designed this study to explore if PPARβ/δ could protect against oxidative lung injury via up-regulation ..

机体持续暴露于氧气中，易导致肺型氧中毒（pulmonary oxygen toxicity，POT），严重影响呼吸衰竭病人的预后。目前对POT缺乏有效防治方法。本课题组在前期通过cDNA芯片对POT小鼠肺组织进行表达谱分析，发现过氧化物酶增殖物激活受体β/δ（PPAR-β/δ）上调。经体内采用激动剂、阻滞剂干预后，证实PPAR-β/δ通路的激活对POT具有保护作用,同时发现PPAR-β/δ激活后可下调肺组织中神经元型一氧化氮合酶（nNOS）的表达。nNOS代谢过程中产生的氧自由基产物是导致POT发病的主要原因之一。因此我们设想nNOS可能是PPAR-β/δ在POT中发挥作用的重要调控因子。我们拟先在体外采用基因敲减技术明确两者在氧中毒肺上皮细胞中的关联，再从转录调控及非基因组效应来探讨PPAR-β/δ对nNOS的调节机制，最后采用基因敲除鼠体内验证。从而为肺型氧中毒提供新的临床治疗靶点。

潜水作业、高压氧治疗及呼吸机辅助支持治疗时，可导致肺型氧中毒的发生。目前对肺型氧中毒的发病机制尚未完全明确，且针对肺型氧中毒缺乏有效的防治方法。本课题通过体外实验证实PPAR-β/δ活化可通过下调nNOS，降低高氧对A549细胞的损伤，减少细胞凋亡、促进增殖及降低炎症因子分泌；体内研究首先建立了不同压力氧气暴露致肺型氧中毒的动物模型，探讨了高分压氧导致的肺型氧中毒与常压氧导致的肺型氧中毒的不同的发病特点。证实了PPAR-β/δ激活可减轻高压氧导致的肺损伤：降低肺组织湿/干比、病理评分及支气管肺泡灌洗液的蛋白含量；增高肺组织中抗氧化酶GPx 和SOD 的活性；降低肺组织中炎性因子及凋亡蛋白的表达；可通过降低pERK/ERK、NF-κB DNA 的结合活性及上调Bcl-2/Bax 的比例来降低肺损伤。同时通过采用C57BL/6 来源NOS1、NOS3 基因敲除小鼠和野生型健康C57BL/6 小鼠作为实验对象，证实敲除nNOS 基因可拮抗PPAR-β/δ 拮抗剂对肺型氧中毒的恶化作用。在该实验的基础上，提出了预防性使用辛伐他汀对肺型氧中毒的保护作用及机制研究。

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