早产鼠高氧暴露后肺组织血管内皮生长因子和一氧化氮合酶的动态变化及相互关系

Dynamic changes in vascular endothelial growth factor and endothelial nitric oxide synthase in lungs of premature rats after hyperoxia exposure

摘要:

目的：最近研究表明，血管内皮生长因子（VEGF）及内皮型一氧化氮合酶(eNOS)功能的缺失，在支气管肺发育不良（BPD）发病机制中发挥了重要的作用。该文通过动态观察持续中浓度高氧暴露（60％O2）对早产大鼠肺内VGEF蛋白及mRNA和eNOS蛋白及mRNA表达的影响，探讨BPD的发病机制。方法：将21 d 孕早产鼠随机分为高氧暴露组(简称高氧组) 和空气对照组(简称空气组) ，分别置于常压高氧仓中（60％O2）和正常空气中暴露。分别于生后1，4，7，11，14 d每组各处死6只大鼠，留取肺组织标本。苏木精-伊红染色观察病理改变，免疫组化检测VEGF和eNOS蛋白表达，逆转录-聚合酶链反应方法检测VEGF和eNOS mRNA表达。结果：早产鼠高氧暴露4 d后出现肺泡间隔减少，微血管发育异常，间质纤维化，且病变随着高氧暴露时间的延长而加重。高氧组大鼠第4，7天时肺组织VEGF蛋白表达明显低于相应空气对照组(P< 0. 05), VEGF mRNA表达亦显著减少(P< 0. 05)。随着暴露时间的延长，VEGF蛋白和mRNA进行性降低。高氧组大鼠在高氧暴露过程中肺组织eNOS蛋白和mRNA表达亦随着暴露时间的延长而降低。结论：高氧暴露导致早产鼠肺组织VEGF和eNOS表达持续性减少，微血管发育异常和肺泡化受阻。这些由高氧暴露诱导产生的BPD样损害，可能与VEGF和eNOS的表达下调有关，且二者之间存在着密切的联系。［中国当代儿科杂志，2007，9（5）：473-478］

Abstract:

OBJECTIVE: Recent studies suggest that the disruption of vascular endothelial growth factor (VEGF) and endothelial nitric oxide synthase (eNOS) functions plays a pivotal role in the pathogenesis of bronchopulmonary dysplasia (BPD). The aim of this study was to investigate the changes of VEGF and eNOS expression in the lungs of premature rats exposed to moderate hyperoxia in order to explore possible relationships with BPD. METHODS: Premature rats delivered by hysterotomy at 21 days gestation were randomly continuously exposed to moderate hyperoxia (60% FiO2) and room air. The rats were sacrificed at 1, 4, 7, 11 and 14 days of exposure (6 rats at each time point). Lung sections were stained with hematoxylin and eosin for histological examination. Expression of VEGF and eNOS proteins and mRNA were assayed using immunohistochemistry and RT-PCR. RESULTS: After 4 days of hyperoxia, lungs developed interstitial fibrosis, abnormal vascular patterns and decreased alveolar septation. These changes became more obvious with more prolonged hyperoxia exposure. The expression of VEGF protein after 4 and 7 days of exposure decreased significantly in the hyperoxia group compared with controls. The expression of VEGF mRNA in the hyperoxia group was also lower after 4 and 7 days of exposure. Both VEGF protein and mRNA levels decreased with increasing hyperoxia exposure time. The expressions of eNOS protein and mRNA also progressively decreased with increasing hyperoxia exposure. CONCLUSIONS: Hyperoxia caused progressive reduction in lung VEGF and eNOS expression as well as abnormalities of lung structures, including decreased vascular growth and impaired alveolarization. These histologic changes are similar to those of BPD. The data support a link between BPD and decreased expression of VEGF and eNOS.