Moldobaeva Aigul, Rentsendorj Otgonchimeg, Jenkins John, Wagner Elizabeth M
Department of Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America.
PLoS One. 2014 Sep 2;9(9):e106092. doi: 10.1371/journal.pone.0106092. eCollection 2014.
The process of leukocyte recruitment to the airways in real time has not been extensively studied, yet airway inflammation persists as a major contributor to lung pathology. We showed previously in vivo, that neutrophils are recruited acutely to the large airways after periods of airway distension imposed by the application of positive end-expiratory pressure (PEEP). Given extensive literature implicating products of nitric oxide synthase (NOS) in lung injury after ventilatory over-distension, we questioned whether similar mechanisms exist in airway post-capillary venules. Yet, endothelial nitric oxide has been shown to be largely anti-inflammatory in other systemic venules. Using intravital microscopy to visualize post-capillary tracheal venules in anesthetized, ventilated mice, the number of adherent leukocytes was significantly decreased in eNOS-/- mice under baseline conditions (2±1 cell/60 min observation) vs wild type (WT) C57BL/6 mice (7±2 cells). After exposure to PEEP (8 cmH2O for 1 min; 5 times), adherent cells increased significantly (29±5 cells) in WT mice while eNOS-/- mice demonstrated a significantly decreased number of adherent cells (11±4 cells) after PEEP. A similar response was seen when thrombin was used as the pro-inflammatory stimulus. In addition, mouse tracheal venular endothelial cells studied in vitro after exposure to cyclic stretch (18% elongation) or thrombin both demonstrated increased p-selectin expression that was significantly attenuated by NG-nitro-L-arginine methyl ester, N-acetylcysteine amide (NACA) and excess BH4. In vivo treatment with the ROS inhibitor NACA or co-factor BH4 abolished completely the PEEP-induced leukocyte adherence. These results suggest that pro-inflammatory stimuli cause leukocyte recruitment to tracheal endothelium in part due to eNOS uncoupling.
白细胞实时募集至气道的过程尚未得到广泛研究，但气道炎症仍然是肺部病理的主要促成因素。我们之前在体内研究中发现，在应用呼气末正压（PEEP）导致气道扩张后，中性粒细胞会急性募集至大气道。鉴于大量文献表明一氧化氮合酶（NOS）的产物与通气过度扩张后的肺损伤有关，我们质疑气道毛细血管后微静脉中是否存在类似机制。然而，内皮型一氧化氮在其他全身微静脉中已被证明具有很大的抗炎作用。通过活体显微镜观察麻醉、通气小鼠的气管毛细血管后微静脉，在基线条件下，eNOS基因敲除小鼠（2±1个细胞/60分钟观察时间）的黏附白细胞数量明显少于野生型（WT）C57BL/6小鼠（7±2个细胞）。暴露于PEEP（8 cmH₂O，持续1分钟；共5次）后，WT小鼠的黏附细胞显著增加（29±5个细胞），而eNOS基因敲除小鼠在PEEP后黏附细胞数量显著减少（11±4个细胞）。当使用凝血酶作为促炎刺激物时，也观察到了类似的反应。此外，体外研究发现，小鼠气管微静脉内皮细胞在暴露于周期性拉伸（18%伸长）或凝血酶后，p-选择素表达均增加，而NG-硝基-L-精氨酸甲酯、N-乙酰半胱氨酸酰胺（NACA）和过量的四氢生物蝶呤可显著减弱这种增加。用活性氧抑制剂NACA或辅助因子四氢生物蝶呤进行体内治疗，可完全消除PEEP诱导的白细胞黏附。这些结果表明，促炎刺激导致白细胞募集至气管内皮，部分原因是eNOS解偶联。
