Effects of combining selective PDE9 inhibition with inhaled nitric oxide on pulmonary gas exchange, mechanics, inflammation and lung injury in a murine model of ventilator induced lung injury.

急性呼吸窘迫综合征(ARDS)是成人患者对肺部损伤或急性感染的一种严重的、危及生命的反应。就ARDS而言，机械通气是一种挽救生命的疗法，同时提供足够的肺气体交换，但它也可能对肺组织产生损害，从而加重ARDS。ARDS的恶化是由机械通气的肺部后果引起的，这种后果被称为呼吸机诱导的肺损伤(VILI)。尽管重症监护药物得到了广泛的发展，VILI仍然对ARDS的死亡率起着重要作用。在严重ARDS患者中，吸入一氧化氮(INO)可以在改善全身动脉氧合和调节抗炎作用的同时具有潜在的好处，但到目前为止还没有改变存活率。NO的作用是通过激活一种产生第二信使环鸟苷一磷酸(CGMP)的酶来实现的。已知增加cGMP浓度可抑制白细胞黏附，从而介导NO的抗炎作用。CGMP的作用受到磷酸二酯酶(PDE)的限制，PDE是一种专门降解cGMP的酶。PDE亚型PDE9在免疫细胞中高表达。从最近的动物研究中我们了解到，NO供体化合物与PDE9与BAY73-6691的抑制显示出协同抗炎作用。总之，这项研究有两个关键问题需要解决：1)BAY73-6691和NO供体化合物联合应用能否调节分离的中性粒细胞的细胞特性？2)BAY73-6691和iNO联合应用是否能够改善模拟ARDS临床事实的VILI小鼠模型的炎症反应和肺力学？在我们研究的第一部分，我们将确定BAY73-6691单独以及与NO供体化合物联合使用对小鼠中性粒细胞cGMP水平和细胞因子产生的影响。在我们研究的第二部分，我们将在VILI的小鼠模型中检测BAY73-6691单独和联合iNO(5ppm)对炎症标志物和肺顺应性的影响。总体而言，我们希望在使用Bay 73-6691和iNO治疗的小鼠中发现更高的存活率，这是因为所提出的协同抗炎作用和对肺力学的有益影响。

Acute respiratory distress syndrome (ARDS) is a severe, life-threatening reaction in adult patients to injuries or acute infections of the lung. Mechanical ventilation can be a life-saving therapy in terms of ARDS while providing adequate pulmonary gas exchange, but it can also have injurious effects on the lung tissue and thus worsening ARDS. The worsening of ARDS is caused by the pulmonary consequences of mechanical ventilation which have been termed ventilator-induced lung injury (VILI). Despite extensive developments of intensive care medicine VILI still contributes importantly to the mortality of ARDS. In patients with severe ARDS inhalation of nitric oxide (iNO) can have a potential benefit while improving systemic arterial oxygenation and mediating anti-inflammatory effects, but so far without altering survival rates. The effects of NO are mediated by the activation of an enzyme which produces the second messenger cyclic guanosine monophosphate (cGMP). Increased concentrations of cGMP are known to inhibit leukocyte adhesion and thus mediating the anti-inflammatory effects of NO. The action of cGMP is limited by phosphodiesterases (PDEs), enzymes which specifically hydrolyze cGMP. One PDE isoform, PDE9, is highly expressed in immune cells. From recent animal studies we learned, that the combination of a NO donor compound and the inhibition of PDE9 with BAY73-6691 showed a synergistic anti-inflammatory effect. To sum up, there are two critical questions to be addressed in this proposed study: 1) Is it possible to modulate cell properties of isolated neutrophil granulocytes with the combination of BAY73-6691 and NO donor compounds? 2) Does the combination of BAY73-6691 and iNO ameliorate inflammatory reactions and lung mechanics in a murine model of VILI which mimics the clinical facts of ARDS? In the first part of our study we will determine the in vitro effects of BAY 73-6691 alone and in combination with NO donor compounds on cGMP levels and cytokine production of murine neutrophils. In the second part of our study, we will examine the effects of BAY 73-6691 alone and in combination with iNO (5ppm) on inflammatory markers and lung compliance in a mouse model of VILI. Overall we expect to find higher survival rates in mice treated with BAY 73-6691 and iNO due to the proposed synergistic anti-inflammatory effect and beneficial impact on lung mechanics.