Li Wen-bin, Chang Li-wen, Rong Zhi-hui, Liu Han-chu, Zhang Qian-shen, Chen Hong-bing, Zhu Hua-Ping, Lu Hong-yan, Wang Hua
Department of Pediatrics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
Zhonghua Er Ke Za Zhi. 2008 May;46(5):347-53.
To further investigate the protective effect of retinoic acid (RA) on hyperoxia induced lung injury and the role of RA as a modulator on mitogen-activated protein kinases (MAPKs).
Establishment of hyperoxia (85%) induced lung injury model of premature Sprague-Dawley (SD) rats: 21 d gestational age SD rat's fetuses (term = 22 d) were delivered by hysterectomy. Within 12 - 24 h after birth, the premature rat pups were randomly divided into 4 groups: Group I, air-exposed control group; Group II, hyperoxia-exposed group; Group III, air plus RA-exposed group, Group IV, hyperoxia plus RA-exposed group. Group I and III were remained in room air, and group II and IV were placed in 85% oxygen. The pups in Group III and IV were injected with RA (500 microg/kg, every day) intraperitoneally. The entire lung tissues of premature rat pups were collected at 4 d, 7 d and 14 d. The mRNA levels of MMP-2 and MMP-9 were detected by semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). MMP-2 and MMP-9 activities were measured by zymography. Western blot was used to detect phosphorylated and total nonphosphorylated form of ERKs, JNKs and p38.
Exposure to oxygen for 4 d, 7 d, and 14 d resulted in increased mRNA levels of MMP-2 and MMP-9 compared with air-exposed control group (P < 0.01 for all). The mean protein levels of active MMP-2 and pro/active MMP-9 after exposure to O2 were higher than air control groups on each experimental day (P < 0.01 or < 0.05). The phosphorylated ERK1/2, JNK1/2 and p38 proteins in hyperoxia-exposed group increased markedly compared with air-exposed control group (P < 0.01 for all). The pups treated with RA in the hyperoxic environment expressed significantly lower mRNA levels of MMP-2 and MMP-9 than the hyperoxic control pups on each experimental day (P < 0.05 for all). The levels of active MMP-2 and pro/active MMP-9 decreased to a different degree after RA treatment in hyperoxia exposure rat pups. In addition, RA treatment led to a decrease of p-JNK1/2 and p-38 (P < 0.01 for all) protein levels and a further elevation of p-ERK1/2 compared with hyperoxia-exposed group.
Hyperoxia exposure elevated the expression of MMP-2 and MMP-9 markedly, which played a role in oxygen-induced lung injury. RA could have a protective effect on hyperoxia induced lung injury by decreasing active levels of JNK and p38, which subsequently reduce the expression and activation of MMP-2 and MMP-9.
进一步研究视黄酸（RA）对高氧诱导的肺损伤的保护作用以及RA作为丝裂原活化蛋白激酶（MAPKs）调节剂的作用。
建立高氧（85%）诱导的早产Sprague-Dawley（SD）大鼠肺损伤模型：通过子宫切除术娩出孕21天（足月为22天）的SD大鼠胎儿。出生后12 - 24小时内，将早产幼鼠随机分为4组：I组，空气暴露对照组；II组，高氧暴露组；III组，空气加RA暴露组；IV组，高氧加RA暴露组。I组和III组置于室内空气中，II组和IV组置于85%氧气环境中。III组和IV组幼鼠腹腔注射RA（500μg/kg，每日）。在4天、7天和14天收集早产幼鼠的全肺组织。采用半定量逆转录聚合酶链反应（RT-PCR）检测MMP-2和MMP-9的mRNA水平。通过酶谱法测定MMP-2和MMP-9的活性。采用蛋白质印迹法检测细胞外信号调节激酶（ERK）、应激活化蛋白激酶（JNK）和p38的磷酸化及总非磷酸化形式。
与空气暴露对照组相比，暴露于氧气4天、7天和14天后，MMP-2和MMP-9的mRNA水平升高（均P < .01）。在每个实验日，暴露于氧气后活性MMP-2和前体/活性MMP-9的平均蛋白水平均高于空气对照组（P < 0.01或< 0.05）。与空气暴露对照组相比，高氧暴露组中磷酸化的ERK1/2、JNK1/2和p38蛋白显著增加（均P < 0.01）。在每个实验日，高氧环境中用RA处理的幼鼠MMP-2和MMP-9的mRNA水平均显著低于高氧对照幼鼠（均P < 0.05）。高氧暴露大鼠幼鼠经RA处理后，活性MMP-2和前体/活性MMP-9水平有不同程度下降。此外，与高氧暴露组相比，RA处理导致p-JNK1/2和p-38蛋白水平降低（均P < 0.01），p-ERK1/2进一步升高。
高氧暴露显著升高MMP-2和MMP-9的表达，其在氧诱导的肺损伤中起作用。RA可通过降低JNK和p38的活性水平对高氧诱导的肺损伤产生保护作用，进而降低MMP-2和MMP-9的表达及活化。
