Moraes Theo J, Martin Raiza, Plumb Jonathan D, Vachon Eric, Cameron Cheryl M, Danesh Ali, Kelvin David J, Ruf Wolfram, Downey Gregory P
Academic Affairs, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, CO 80206, USA.
Am J Physiol Lung Cell Mol Physiol. 2008 Feb;294(2):L368-77. doi: 10.1152/ajplung.00036.2007. Epub 2007 Dec 14.
Proteinases can influence lung inflammation by various mechanisms, including via cleavage and activation of protease-activated receptors (PAR) such as PAR2. In addition, proteinases such as neutrophil and/or Pseudomonas-derived elastase can disarm PAR2 resulting in loss of PAR2 signaling. Currently, the role of PAR2 in host defense against bacterial infection is not known. Using a murine model of acute Pseudomonas aeruginosa pneumonia, we examined differences in the pulmonary inflammatory response between wild-type and PAR2(-/-) mice. Compared with wild-type mice, PAR2(-/-) mice displayed more severe lung inflammation and injury in response to P. aeruginosa infection as indicated by higher bronchoalveolar lavage fluid neutrophil numbers, protein concentration, and TNF-alpha levels. By contrast, IFN-gamma levels were markedly reduced in PAR2(-/-) compared with wild-type mice. Importantly, clearance of P. aeruginosa was diminished in PAR2(-/-) mice. In vitro testing revealed that PAR2(-/-) neutrophils killed significantly less bacteria than wild-type murine neutrophils. Further, both neutrophils and macrophages from PAR2(-/-) mice displayed significantly reduced phagocytic efficiency compared with wild-type phagocytes. Stimulation of PAR2 on macrophages using a PAR2-activating peptide resulted in enhanced phagocytosis directly implicating PAR2 signaling in the phagocytic process. We conclude that genetic deletion of PAR2 is associated with decreased clearance of P. aeruginosa. Our data suggest that a deficiency in IFN-gamma production and impaired bacterial phagocytosis are two potential mechanisms responsible for this defect.
蛋白酶可通过多种机制影响肺部炎症，包括通过切割和激活蛋白酶激活受体（PAR），如PAR2。此外，诸如中性粒细胞和/或铜绿假单胞菌衍生的弹性蛋白酶等蛋白酶可使PAR2失活，导致PAR2信号传导丧失。目前，PAR2在宿主抵抗细菌感染中的作用尚不清楚。我们使用急性铜绿假单胞菌肺炎小鼠模型，研究了野生型和PAR2（-/-）小鼠肺部炎症反应的差异。与野生型小鼠相比，PAR2（-/-）小鼠在感染铜绿假单胞菌后表现出更严重的肺部炎症和损伤，这表现为支气管肺泡灌洗液中中性粒细胞数量、蛋白质浓度和TNF-α水平更高。相比之下，PAR2（-/-）小鼠的IFN-γ水平明显低于野生型小鼠。重要的是，PAR2（-/-）小鼠清除铜绿假单胞菌的能力下降。体外试验表明，PAR2（-/-）中性粒细胞杀死的细菌明显少于野生型小鼠中性粒细胞。此外，与野生型吞噬细胞相比，PAR2（-/-）小鼠的中性粒细胞和巨噬细胞吞噬效率均显著降低。使用PAR2激活肽刺激巨噬细胞上的PAR2导致吞噬作用增强，这直接表明PAR2信号传导参与吞噬过程。我们得出结论，PAR2基因缺失与铜绿假单胞菌清除能力下降有关。我们的数据表明，IFN-γ产生不足和细菌吞噬受损是导致这一缺陷的两个潜在机制。
