60%氧暴露对新生大鼠肺组织细胞凋亡相关基因表达的影响

Effect of 60% oxygen exposure on expression of Bax and Bcl-X_L in lungs of newborn rats

目的探讨中浓度高氧(60%O2)暴露新生大鼠肺损伤模型中细胞凋亡相关基因Bax和Bcl-XL的效应。方法新生足月大鼠随机分为实验组和对照组,每组8只,制备中浓度氧致新生鼠BPD模型,应用HE染色、免疫组织化学和RT-PCR技术,观察生后1、4、7、11和14d肺组织病理改变、Bax及Bcl-XL基因的蛋白和mRNA表达水平。结果高氧组自4d开始出现肺泡发育障碍,至14d单位面积肺泡数明显减少,平均肺泡面积显著增大。高氧组与空气组比较,Bax基因表达1d开始增加,其mRNA水平于11d开始降低至1·0216±0·2597,蛋白表达于14d降低至0·3950±0·0138;Bcl-XL基因mRNA水平1d至14d表达增加,其蛋白表达1d降低至0·3690±0·0399,随后增加,差异有统计学意义。随氧暴露时间延长,高氧组Bax的mRNA及蛋白和Bcl-XL的mRNA表达水平均呈降低趋势,Bcl-XL蛋白表达呈上升趋势。空气组的Bax mRNA水平从11d开始增加,蛋白水平从14d开始增加。空气组Bcl-XLmRNA和蛋白水平1d表达最丰。结论中浓度高氧暴露诱导新生鼠肺细胞凋亡的调节可能和Bax/Bcl-XL基因表达异常有关。在高氧暴露早期,Bax表达增加,促进肺细胞凋亡。肺上皮细胞和血管内皮细胞的凋亡损伤了正常的肺发育。随着氧暴露时间延长,Bax的表达降低,Bcl-XL表达增加。这种变化促进肺修复,新生鼠对高氧形成耐受。本文亦初步揭示了凋亡和氧暴露的时相关系,即高氧暴露早期时肺细胞凋亡效应显著,后期减弱。

Objective To investigate the effect of Bax and Bcl-XL expression in newborn rat with moderate hyperoxic exposure. Methods Hyperoxic lung injury model was established by exposure to 60% O2 in the neonatal period of SD rats. Rats exposed to air were used as control groups, with 8 animals in each group on repeated experiments. The pathology of pulmonary tissues was detected by HE stain. Mean alveolar area and alveolar number per μm^2 were applied to estimate the pathological effects of prolonged hyperoxia in neonatal rats. The expression of Bax and Bcl-XL proteins in lung were detected by immunohistochemistry and the expressions of Bax and Bcl-XL mRNA by RT- PCR. Results In hyperoxia groups, alveolar dysplasia appeared 4 days after hyperoxia, mean alveolar area increased and alveolar number per μmz decreased from the 4th day. Bax and Bcl-XL protein were mainly expressed on bronchiolar epithelial cells and vascular endothelial cells. Compared with control gro.up, the expression of Bax increased from the 1st day after hyperoxia, Bax mRNA decreased from the 11th day （q=8. 4802, P〈0.05） and the level of Bax protein decreased until the 14th day （q =6. 8364, P〈0.05）. The expression of Bcl-XL mRNA augmented from the 1st to 14th day, while the expression of its protein diminished on the 1st day （q=10. 4299, P〈0.05） and then raised up. With the prolonged duration of hyperoxia, the levels of Bax mRNA, its protein and Bcl-XL mRNA degraded, while the level of Bcl-XL protein upgraded. In the air groups, the level of Bax mRNA increased on the 11th day after exposure and the level of its protein increased on the 14th day after exposure. The levels of Bcl-XL mRNA and protein were the highest among the air groups on the 1st day. Conclusions Apoptosis is timely related with oxygen exposure manifested by significant apoptosis early after hypoxic exposure and reduced apoptosis after longer duration.