Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins Medical Institutions, Baltimore, MD 21224, USA.
Am J Physiol Lung Cell Mol Physiol. 2011 Aug;301(2):L161-70. doi: 10.1152/ajplung.00073.2011. Epub 2011 May 13.
Phosphodiesterase 2A (PDE2A) is stimulated by cGMP to hydrolyze cAMP, a potent endothelial barrier-protective molecule. We previously found that lung PDE2A contributed to a mouse model of ventilator-induced lung injury (VILI). The purpose of the present study was to determine the contribution of PDE2A in a two-hit mouse model of 1-day intratracheal (IT) LPS followed by 4 h of 20 ml/kg tidal volume ventilation. Compared with IT water controls, LPS alone (3.75 μg/g body wt) increased lung PDE2A mRNA and protein expression by 6 h with a persistent increase in protein through day 4 before decreasing to control levels on days 6 and 10. Similar to the PDE2A time course, the peak in bronchoalveolar lavage (BAL) neutrophils, lactate dehydrogenase (LDH), and protein concentration also occurred on day 4 post-LPS. IT LPS (1 day) and VILI caused a threefold increase in lung PDE2A and inducible nitric oxide synthase (iNOS) and a 24-fold increase in BAL neutrophilia. Compared with a control adenovirus, PDE2A knockdown with an adenovirus expressing a short hairpin RNA administered IT 3 days before LPS/VILI effectively decreased lung PDE2A expression and significantly attenuated BAL neutrophilia, LDH, protein, and chemokine levels. PDE2A knockdown also reduced lung iNOS expression by 53%, increased lung cAMP by nearly twofold, and improved survival from 47 to 100%. We conclude that in a mouse model of LPS/VILI, a synergistic increase in lung PDE2A expression increased lung iNOS and alveolar inflammation and contributed significantly to the ensuing acute lung injury.
磷酸二酯酶 2A（PDE2A）受 cGMP 刺激水解 cAMP，cAMP 是一种有效的内皮屏障保护分子。我们之前发现肺 PDE2A 有助于呼吸机诱导性肺损伤（VILI）的小鼠模型。本研究的目的是确定 PDE2A 在一天内经气管内（IT）给予 LPS 后再进行 4 小时 20ml/kg 潮气量通气的双打击小鼠模型中的作用。与 IT 水对照组相比，单独给予 LPS（3.75μg/g 体重）可在 6 小时内增加肺 PDE2A mRNA 和蛋白表达，其蛋白表达持续增加至第 4 天，然后在第 6 天和第 10 天降至对照水平。与 PDE2A 时间进程相似，支气管肺泡灌洗液（BAL）中性粒细胞、乳酸脱氢酶（LDH）和蛋白浓度的峰值也出现在 LPS 后第 4 天。IT LPS（1 天）和 VILI 导致肺 PDE2A 和诱导型一氧化氮合酶（iNOS）增加三倍，并使 BAL 中性粒细胞增加 24 倍。与对照腺病毒相比，在 LPS/VILI 前 3 天经 IT 给予表达短发夹 RNA 的腺病毒下调 PDE2A 可有效降低肺 PDE2A 表达，并显著减轻 BAL 中性粒细胞增多、LDH、蛋白和趋化因子水平。PDE2A 下调还使肺 iNOS 表达减少 53%，肺 cAMP 增加近两倍，并使存活率从 47%提高到 100%。我们的结论是，在 LPS/VILI 的小鼠模型中，肺 PDE2A 表达的协同增加增加了肺 iNOS 和肺泡炎症，并对随后的急性肺损伤有重要贡献。
