LPS诱导大鼠急性肺损伤后早期肺纤维化进展过程中肺组织AT1R/Mas受体表达的动态变化

Dynamic changes in expressions of AT1R and Mas receptors in lung tissues during the development of early pulmonary fibrosis following LPS-induced acute lung injury in rats

目的建立脂多糖(LPS)介导的大鼠急性肺损伤后早期肺纤维化模型并观察其过程中血管紧张素系统主要组分血管紧张素Ⅱ1型受体(AT1R)和Mas受体的变化趋势。方法分别由腹腔和气道内间断3次注射LPS建立大鼠急性肺损伤后早期肺纤维化模型,并于末次注射后第3、7、14和21日处死大鼠,取肺组织及血浆。H-E染色和Masson染色观察肺组织形态结构改变;ELISA试剂盒检测血浆中TGF-β的水平;RT-q PCR及Western blotting检测肺组织中AT1R和Mas m RNA和蛋白表达变化。结果经LPS复合打击后,大鼠肺组织病理改变在第3日以肺部炎症反应为主要表现,而第7日后炎症减弱,肺组织正常形态结构遭到破坏,Masson染色提示胶原纤维沉积逐渐增加,血浆中TGF-β的含量逐渐升高(P<0.01),从而形成早期肺纤维化。另外,随着LPS诱导肺纤维化的发展,AT1R m RNA表达无显著变化,但其蛋白表达在第14日及21日明显增加;肺组织内Mas m RNA表达逐渐增加,至第21日明显升高至对照组的15倍,而Mas受体蛋白的表达在第14日及21日明显下调至对照组的30%(P<0.01)。结论 LPS复合多次打击能有效建立大鼠急性肺损伤后早期肺纤维化模型,且随着肺纤维化发展,AT1R/Mas受体呈上升/下降相反的表达变化。

Objective To construct a rat model of early pulmonary fibrosis follow ing lipopolysaccharide（ LPS）-induced acute lung injury and observe the change trend in major members of renin-angiotensin-system angiotensin Ⅱ type 1 receptor（ AT1R） and M as receptor during lung injury process. Methods A rat m odel of early pulm onary fibrosis follow ing acute lung injury was built by three interm ittent injections of LPS into the abdom en and airw ay. Rats w ere sacrificed 3, 7, 14, and 21 d after last injection. Lung tissues and blood sam ples were harvested. The histom orphological changes in lung tissues were observed with H-E and M asson staining. The plasm a TG F-β level was m easured with ELISA kits. The mRNA and protein expressions of A T1 R and Mas receptors in lung tissues were detected w ith RT-q PCR and Western blotting, respectively. Results The main presentation of histom orphological changes in lung tissues was inflam matory response at day 3 after LPS injections. The inflam m tion was reduced 7 d after LPS injections and the norm al morphology of lung tissues was dam aged. Masson staining revealed increased collagen protein deposition and plasm a TG F-β level（ P 〈0. 01）, which resulted in early pulm onary fibrosis. In addition, with the developm ent of LPS-induced pulm onary fibrosis, the m RNA expression of A T1 R did not change significantly, but the protein expression of A T1 R markedly increased on day 14 and 21. The m RN A expression of Mas in lung tissues increased gradually and w as 15 folds higher than that in the control group on day 21, while the protein expression of Mas significantly decreased to 30% of that in the control group on day 14 and 21（ P 〈0. 01）. Conclusion Repeated LPS injections can effectively construct the rat model of early pulmonary fibrosis follow ing acute lung injury. The expressions of AT1R and M as receptors show opposite changes with the development of pulmonary fibrosis.