Expression of Occludin in lung tissues of newborn rats with bronchopulmonary dysplasia and its influence on pulmonary epithelial permeability / 中华实用儿科临床杂志

ABSTRACT

Objective To explore the dynamic changes of Occludin gene and protein levels in lung tissues of newborn rats with hyperoxia-induced bronchopulmonary dysplasia (BPD) in the early phase and its effect on pulmonary epithelial permeability.Methods One hundred and sixty newborn Wistar rats were randomly assigned to hyperoxia group (900 mL/L oxygen)and normoxia group (210 mL/L oxygen) according to different oxygen concentrations,80rats in each group.Rats were sacrificed and lung tissues were removed on 1,3,5,7 d after treatment.Bronchoalveolar lavage fluid (BALF)serum FD4 ratio was detected;location and expression of Occludin were examined by immunofluorescence staining and Western blot; messenger RNA (mRNA) was studied by reverse transcription-PCR.Results There was no obvious difference in the BALF and serum FD4 ratio (1.533 ±0.122 vs 1.575 ± 0.140,P ＞ 0.05) between the hyperoxia group and the normoxia group on the first day.After 3 days of hyperoxia exposure,the ratio of FD4between BALF and serum was significantly higher than that in the normoxia group(1.365 ±0.159 vs 1.615 ±0.196,P ＜ 0.05).And after 5 or 7 days of hyperoxia exposure,the ratio of FD4 between BALF and serum was dramatically increased(1.245 ±0.152 vs 3.211 ±0.799,1.178 ± 0.594 vs 5.15 ± 0.967,all P ＜ 0.01).On the 7 day,immunofluorescence staining showed Occludin distribllted in a consecutive line along lung epithelial cell membrane in the normoxia group,while in the hyperoxia group Occludin was distributed in a discontinuous line and lacking intensity.There was no obvious difference in Occludin mRNA level between the hyperoxia group and normoxia group on the first day(2.15 ±0.33 vs 2.23 ± 0.39,P ＞ 0.05).Compared to the normoxia group,the decrease in Occludin mRNA level was statistically significant after 3 or 5 days of hyperoxia exposure(2.46 ± 0.27 vs 2.00 ± 0.19,2.62 ± 0.28 vs 2.15 ± 0.20,all P ＜ 0.05),and after 7 days of hyperoxia exposure,the Occludin mRNA level dramatically declined (3.08 ± 0.43 vs 2.01 ±0.34,P ＜0.01).There was no obvious difference in Occludin protein level between the hyperoxia group and normoxia group on the 1 st and the 3th day(1.00 ± 0.05 vs 1.05 ± 0.03,1.24 ± 0.06 vs 1.17 ± 0.04,all P ＞ 0.05).Compared to the normoxia groups,the decrease in Occludin protein level was statistically significant after 5 days of hyperoxia exposure (1.03 ± 0.04 vs 0.93 ± 0.05,P ＜ 0.05),and after 7 days of hyperoxia exposure,the Occludin protein level dramatically declined(0.96 ± 0.14 vs 0.65 ± 0.07,P ＜ 0.01).There was a significantly negative correlation between Occludin protein expression and pulmonary epithelial permeability after hyperoxia exposure (r =-0.755,P ＜0.01).Conclusions Downregulation of Occludin hyperoxia-induced may lead to the increase of pulmonary epithelial paracellular permeability,which participates in the development of pulmonary edema in the early phase of BPD induced by hyperoxia.