[Retinoic acid diminished the expression of lung tissue matrix metalloproteinase-2 and matrix metalloproteinase-9 in hyperoxia-exposed premature rats through regulating mitogen-activated protein kinases].
OBJECTIVE
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).


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Li
Wen-bin
WB
Department of Pediatrics, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
Chang
Li-wen
LW
Rong
Zhi-hui
ZH
Liu
Han-chu
HC
Zhang
Qian-shen
QS
Chen
Hong-bing
HB
Zhu
Hua-Ping
HP
Lu
Hong-yan
HY
Wang
Hua
H
D000818:Animals; D000831:Animals, Newborn; D004195:Disease Models, Animal; D005260:Female; D018496:Hyperoxia / Q000150:complications; D008168:Lung / Q000187:drug effects* / Q000378:metabolism; D055370:Lung Injury / Q000209:etiology / Q000378:metabolism; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014212:Tretinoin / Q000494:pharmacology*
D014212:Tretinoin; D020928:Mitogen-Activated Protein Kinases; D020778:Matrix Metalloproteinase 2; C522363:Mmp2 protein, rat; D020780:Matrix Metalloproteinase 9