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）是一种严重的，危及生命的反应，在成人患者受伤或急性感染的肺部。就ARDS而言，机械通气可以是一种挽救生命的治疗，同时提供足够的肺气体交换，但它也可能对肺组织产生有害影响，从而使ARDS恶化。ARDS的恶化是由机械通气的肺部后果引起的，其被称为呼吸机诱导的肺损伤（VILI）。尽管重症监护医学得到了广泛的发展，但VILI仍然是ARDS死亡率的重要原因。在患有严重ARDS的患者中，吸入一氧化氮（iNO）可以具有潜在的益处，同时改善全身动脉氧合并介导抗炎作用，但到目前为止没有改变存活率。NO的作用是由产生第二信使环磷酸鸟苷（cGMP）的酶的活化介导的。已知cGMP浓度增加可抑制白细胞粘附，从而介导NO的抗炎作用。cGMP的作用受磷酸二酯酶（PDE）限制，磷酸二酯酶是特异性水解cGMP的酶。一种PDE同种型PDE 9在免疫细胞中高度表达。从最近的动物研究中，我们了解到，NO供体化合物与BAY 73 -6691对PDE 9的抑制的组合显示出协同抗炎作用。综上所述，在本研究中有两个关键问题需要解决：1）BAY 73 -6691和NO供体化合物的组合是否可能调节分离的中性粒细胞的细胞特性？2)BAY 73 -6691和iNO的组合是否改善了模拟ARDS临床事实的VILI小鼠模型中的炎症反应和肺力学？在我们研究的第一部分中，我们将确定BAY 73-6691单独和与NO供体化合物组合对鼠嗜中性粒细胞的cGMP水平和细胞因子产生的体外作用。在我们研究的第二部分中，我们将检查BAY 73-6691单独和与iNO（5 ppm）组合对VILI小鼠模型中的炎性标志物和肺顺应性的影响。总的来说，我们预期在用BAY 73-6691和iNO处理的小鼠中发现更高的存活率，这是由于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.