高浓度氧对早产鼠肺一氧化氮合酶表达的影响

Effect of Hyperoxia on Nitric Oxide Synthase Expression in the Lung of Preterm Rats

摘要:

目的：明确高浓度氧对早产大鼠肺一氧化氮(nitric oxide, NO)合成及一氧化氮合酶(nitric oxide synthase, NOS)表达的影响，以探讨内源性NO在新生儿高氧肺损伤中的作用。方法：3日龄早产鼠随机分为空气组和高氧组，检测实验3 d及7 d时两组肺湿重/干重比值(W/D)，肺组织病理学改变，支气管肺泡灌洗液中NO含量及诱导型NOS(iNOS)，内皮细胞型NOS(eNOS)在肺内的分布和表达(免疫组织化学方法)。结果：3 d时高氧组表现为急性肺损伤：充血、出血、炎性渗出；7 d时，W/D值高于空气组(5.54±0.41) vs (5.00±0.15)，(P<0.05)，病理改变依然明显。与空气组相比，暴露3 d及7 d时，高氧组灌洗液中的NO含量(17.06±5.86)和(23.75±4.07) μmol/L较空气组(5.59±2.03)和(7.93±2.33) μmol/L明显上升(P均<0.01)。高氧组肺气道和肺泡上皮细胞、炎症细胞iNOS表达强阳性，强度高于空气组(P<0.01)，且高氧7 d组高于3 d组(P<0.01)。与空气组比较，7 d时高氧组气道上皮细胞eNOS表达增加(P<0.05)。结论：高氧可上调早产大鼠肺炎症细胞、上皮细胞NOS的表达，促进NO合成，提示内源性NO介导参与了高氧诱导的肺损伤。

Abstract:

OBJECTIVE: To investigate the role of endogenous nitric oxide (NO) in hyperoxiainduced lung injury, by studying the effect of hyperoxia on NO synthesis and nitric oxide synthase (NOS) expression in the lung of preterm rats. METHODS: Threedayold preterm rats were randomly assigned to a hyperoxia group (90% oxygen) and room air group. After 3 days or 7 days of exposure, the ratio of lung wet weight/dry weight (W/D), lung morphometry, NO content in bronchoalveolar lavage fluid (BALF), and the cellular distribution and expression of endothelial NOS (eNOS) and inducible NOS (iNOS) in the lung were measured. RESULTS: After 3 days of exposure, when compared with the control group, the hyperoxia group showed acute lung injury characterized by the presence of hyperaemia, red cell extravasation, and inflammatory infiltration. After 7 days of exposure, W/D was also increased in the hyperoxia group compared to the controls (5.54±0.41 VS 5.00±0.15, P<0.05), in addition to the pathologic changes. After 3 and 7 days of exposure, the NO content in BALF was significantly elevated in the hyperoxia group compared with that of the air group ［(17.06±5.86) μmol/L vs (5.59±2.03) μmol/L and (23.75±4.07) μmol/L vs (7.93±2.33) μmol/L, respectively, P<0.01］. In the lungs of the hyperoxia group, immunostaining for iNOS was observed in the airway and alveolar epithelium, and in inflammatory cells, to a greater degree than in the air group. The expression of iNOS in rats was stronger after 7 days of hyperoxic exposure than after 3 days. After 7 days of exposure, stronger immunostaining for eNOS in the airway epithelium of the hyperoxia group than of the air group was seen. CONCLUSIONS: Hyperoxia can significantly upregulate the expression of iNOS and eNOS in inflammatory cells and epithelium in the lungs of preterm rats and thus promote NO generation, suggesting that endogenous NO may mediate hyperoxiainduced pulmonary injury.