Objective To observe the expressions of long noncoding RNA (IncRNA)metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and nuclear factor etythroid-2 related factor 2 (Nrf2) in lung tissues of hyperoxia-exposed premature neonatal rats,and explore the role of MALAT1 and Nrf2 in hyperoxia-induced lung injury.Methods Pregnant Sprague-Dawley (SD) rats were given cesarean section on the 21st day of gestation.After feeding for 24 h,a total of 80 premature rats were randomly divided into the air group and hyperoxia group.The rats in the air group were fed in the indoor environment[fraction of inspiration O2 (FiO2) =210 mL/L] and those in the hyperoxia group were fed in a high-oxygen box (FiO2 ＞ 850 mL/L).Eight premature rats from each group were sacrificed and lung tissue samples were collected at 5 experimental time points (1st,4th,7th,10th,14th day),respectively.Hematoxylin-eosin staining was used to observe pathological changes in lung tissues.Real-time quantitative polymerase chain reaction (qPCR) and Western blot were used to detect the expression level of MALAT1and Nrf2.Results Compared with the air group,the degree of alveolarization in lung tissues of the hyperoxia group rats was reduced,and radial alveolar count (RAC) decreased on the 1st day,but there was no significant difference between 2 groups (P ＞0.05),when they decreased on the 4th(3.14 ± 0.23),7th(5.25 ± 0.38),10th (4.41 ± 0.44),14th (3.41 ± 0.13) day of exposure,the differences were statistically significant (all P ＜ 0.05).Compared with the air group,the RNA expression of MALAT1 of hyperoxia group preterm rats decreased after the 1 st day(0.527 ± 0.124) of exposure,increased after the 4th (0.538 ±0.128),7th (0.748 ±0.071) day,decreased after the 10th (0.519 ± 0.081)day,and the differences were statistically significant (all P ＜ 0.05),but it continually became weak on the 14th day,but there was no significant difference between 2 groups (P ＞ 0.05).Compared with the air group,the mRNA expression of Nrf2 of hyperoxia group preterm rats decreased after the 1st day(0.791 ± 0.031) of exposure,increased after the 4th (0.977 ± 0.189),7 th (1.369 ± 0.100),10th (1.094 ± 0.104) day,and the differences were statistically significant (all P ＜ 0.05),and it decreased after the 14th day,but there was no significant difference between 2 groups (P ＞0.05).The hyperoxia group had significantly higher expression of free Nrf2 protein and lower expression of Nrf2-Keapl protein than those of the air group at all time points.Within the hyperoxia group,the RNA expression of MALAT1 was positively correlated with RAC and Nrf2 (r =0.517,0.533,all P ＜ 0.001).Conclusions Lung injury is gradually aggravated over the time of hyperoxia exposure.The level of lncRNA MALAT1 is associated with the severity of lung injury and the level of Nrf2 mRNA,suggesting that IncRNA MALAT1 and the Nrf2 target gene signaling pathway might be involved in the development of hyperoxia-induced lung injury in neonatal premature rats together.%目的 观察高体积分数氧(高氧)暴露下新生早产大鼠肺组织的长链非编码RNA (IncRNA)转移相关肺腺癌转录本1(MALATl)和核转录相关因子-2(Nrf2)的动态表达,探讨MALAT1和Nrf2的表达变化在高氧肺损伤中的作用.方法 孕21 d SD大鼠行剖宫产,80只早产大鼠喂养24 h后按随机数字表法分为空气组和高氧组.空气组早产大鼠置于室内空气中饲养[吸入氧体积分数(FiO2)=210 mL/L],高氧组早产大鼠置于常压氧箱(FiO2 ＞850 mL/L)中饲养,2组新生早产大鼠分别于空气或高氧暴露后第1、4、7、10、14天处死并收集肺组织标本.采用苏木精-伊红染色法观察新生早产大鼠肺组织病理变化;采用实时定量聚合酶链反应(qPCR)及Western blot技术分别检测MALAT1、Nrf2的RNA和蛋白表达水平.结果 与空气组比较,高氧组新生早产大鼠肺组织肺泡化程度降低,辐射状肺泡计数(RAC)在第1天减少,但差异无统计学意义(P＞0.05),第4天[(3.14±0.23)个]、第7天[(5.25±0.38)个]、第10天[(4.4l±0.44)个]、第14天[(3.41±0.13)个]均显著减少,差异均有统计学意义(均P ＜0.05).与空气组比较,高氧组新生早产大鼠肺组织中MALAT1的RNA相对表达量在第1天(0.527±0.124)显著减弱,第4天(0.538±0.128)、第7天(0.748±0.071)均显著增强,第10天(0.519 ±0.081)显著减弱,差异均有统计学意义(均P＜0.05),第14天时减弱,但差异无统计学意义(P＞0.05).与空气组比较,高氧组新生早产大鼠肺组织中Nrf2 mRNA的表达在第1天(0.791±0.031)显著减弱,第4天(0.977±0.189)、第7天(1.369 ±0.100)、第10天(1.094 ±0.104)均显著增强,差异均有统计学意义(均P＜0.05),第14天表达减弱,但差异无统计学意义(P＞0.05).与空气组比较,高氧组新生早产大鼠肺组织中游离态Nrf2蛋白在各时间点表达均增强,Nrf2-Keapl结合型蛋白在各时间点表达均减弱.高氧作用下,MALAT1表达与RAC、Nrf2均呈正相关(r=0.517、0.533,均P＜0.001).结论 肺组织损伤程度随高氧暴露时间延长逐渐加重,MALAT1表达与肺损伤程度及Nrf2水平具有相关性,提示MALAT1与Nrf2相关信号通路可能共同参与新生早产大鼠高氧肺损伤的发病过程.
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