大鼠油酸性急性肺损伤初期水通道蛋白4在肺水代谢的实验研究

Role of AQP-4 in pulmonary water metabolism in rats in early stage of oleic acid-induced acute lung injury

目的测定油酸造成急性肺损伤(ALI)初期损伤程度及肺泡Ⅱ型上皮细胞(ATⅡ)上水通道蛋白4(AQP-4)的表达量以评估病理状态下ATⅡ细胞水通道水转运能力的状况。方法血气分析、观察肺组织病理学、用重力法测定血管外肺水(EVLW)含量检测早期肺损伤的程度;急性分离纯化大鼠油酸ALI模型的ATⅡ细胞,显微镜及电子显微镜观察形态病理变化;免疫组化了解肺组织AQP-4的表达,采用逆转录-聚合酶链反应(RT-PCR)检测肺泡Ⅱ型上皮细胞AQP-4的m-RNA表达的情况。结果血气分析、光镜下肺损伤评分及EVLW油酸组严重程度显著高于对照组,显微镜下肺泡Ⅱ型上皮细胞的数量较对照组无明显减少,但电镜下细胞的超微结构改变,板层小体排空,线粒体损伤等改变;肺组织免疫组化观察到AQP-4明显表达增强,肺泡Ⅱ型上皮细胞AQP-4的m-RNA表达增多,AQP-4由胞浆向胞膜转运,胞膜的表达增多(P<0.05)。结论在肺损伤初期就有了肺损伤水肿的病理生理的改变,AQP-4在肺泡Ⅱ型上皮细胞上m-RNA及细胞膜的表达上调,很大程度调节肺泡腔及肺泡上皮细胞的水转运,在钠通道功能下降的情况下发挥了重要的代偿作用。

Objective To evaluate the capacity of alveolar type Ⅱ （AT Ⅱ） cells for water and sodium transport in rats with early-stage oleic acid-induced acute lung injury （ALI）/acute respiratory distress syndrome （ARDS）. Methods AT Ⅱ cells were isolated and purified from rats with ALI/ARDS induced by oleic acid, and their morphology was observed using electron microscopy and optical microscopy. The extravascular hmg water （EVLW） content in the rats was measured by gravimetric method. The distribution of aquaporin-4 （AQP-4） on the cell membrane was observed with immtmohistochemistry, and the expression ofAQP-4 mRNA was detected with RT-PCR. Results Microscopic examination and blood gas analysis indicated severe injury of the lung tissues in ALI group. Smith lung injury score and EVLW in ALI group were significantly higher in ALI group than in the control group （P〈0.05）. Immunohistochemistry identified intensified AQP-4 expression in rat hmg tissues and RT-PCR also demonstrated increased AQP-4 mRNA expression as compared with the control group. The level of APQ-4 whole-cell currents was decreased in AT Ⅱ cell membrane and increased in cytoplasm in ALI group （P〈0.05）. Conclusions Pathophysiological changes occurs in early stage of oleic acid-induced AMI, and AQP-4 mRNA expression is up-regulated on the AT Ⅱ cell membrane to regulate the exchange of fluid between the alveolar space and alveolar epithelium barrier and play an important compensational role in pulmonary liquid clearance in the event of sodium transport damages in ALI.