糖皮质激素及其受体在脂多糖所致大鼠急性肺损伤后肺纤维化中的作用

The roles of glucocorticoid and glucoorticoid receptor in the pulmonary fibrosis caused by acute lung injury induced by lipopolysaccharide in rats

目的探讨糖皮质激素及其受体在大鼠急性肺损伤(ALI)后肺纤维化中的作用及地塞米松对其的影响。方法将60只大鼠随机分为正常对照组(NS组,n=10)、模型组(ALI组,n=30)和地塞米松干预组(Dex组,n=20),ALI组和Dex组通过腹腔注射脂多糖(5mg.kg-1.d-1×3d)制备大鼠ALI后肺纤维化模型,Dex组第4d开始每日8:00AM给予地塞米松(5mg/kg)腹腔注射,NS组以等量生理盐水代替。ALI组分别于制模后第3,7和14d,Dex组分别于第7和14d各随机处死10只。处死前进行动脉血气分析和肺功能检测。处死后留取标本观察肺组织病理形态改变,测定肺损伤指标[肺湿/干重比值,支气管肺泡灌洗液(BALF)中细胞数和蛋白含量],通过检测肺组织中羟脯氨酸含量、BALF中N-末端Ⅰ型前胶原肽(PINP)及N-末端Ⅲ型前胶原肽(PIIINP)水平评价纤维化程度,采用免疫组化法观察肺组织内糖皮质激素受体(GR)的表达。结果与NS组比较,ALI组上述肺损伤指标均明显升高,并出现明显的纤维化改变(羟脯氨酸含量、PINP水平升高),肺组织内GR表达减少。Dex组肺损伤指标及纤维化程度均明显下降,与ALI组比较差异有统计学意义(P<0.05,P<0.01),GR表达增加。结论地塞米松对脂多糖所致大鼠ALI后肺纤维化有一定的抑制作用,对GR表达的上调可能是其发挥抗纤维化作用的机制之一。

Objective To investigate the role of glucocorticoid（GC） and glucocorticoid receptor（GR） in the pulmonary fibrosis caused by lipopolysaccharide（LPS）-induced acute lung injury（ALI）. Methods Sixty rats were randomly divided into three groups, ie. a control group（ n = 10）, an ALl group（ n = 30）, and a dexamethasone（Dex） treatment group（ n = 20）. ALl was induced by intraperitoneal injection of LPS（5 mg/kg） for 3 days in the ALl and Dex groups. Then the rats in the Dex group were treated with intrapefitoneal injection of Dex（5 mg/kg） at 8：00 AM every day from the 4th day on. Ten rats in each group were randomly sacrificed on the 3th, 7th and 14th day respectively. Blood analysis, airway resistance and compliance were measured before sacrificed. Histological examination was performed with HE and VP staining. The protein concentration, total and differential ceils counts in bronchoalveolar lavage fluid（BALF） and lung wet-dry weight ratio were examined. The levels of hydroxyproline and procoilagen aminoterminal propeptide type Ⅰand Ⅲ （ PINP and PIIINP） in lung tissue were measured by digestion method and ELISA respectively. The GR expression in lung tissue was detected by i mmunohistochemistry. Results The lung resistance of the dexamethasone-treated rats was significantly decreased in comparison with the ALl group on the 7th day[（0.49 ± 0.11）kPa· mL^-1· s^-1 vs （0.59 ± 0.08）kPa·mL^-1·s^-1,P 〈0.05] and on the 14th day[（0.59± 0.07）kPa·mL^-1·s^-1 vs（0.68±0.25）kPa·mL^-1·s^-1, P 〈 0.05 ]. PINP in BALF decreased significantly after dexamethasone administration [ （74.13 ± 2.27 ）pg/mL vs （90.73± 3.29）pg/mL, P 〈 0.01 ]. The dexamethasone-treated animals showed alleviated pulmonary fibrosis compared to the ALl group as shown by histology and hydroxyproline content [（264.41 ± 8.41） mg,/g vs （293.80 ± 26.85） mg,/g, P 〈 0.05 ]. The GR level was significantly increased in the dexamethasone-treated rots in comparison with the ALl group. Conclusions The results suggest that an early treatment with dexamethasone may be useful in inhibiting pulmonary fibrosis of LPS-induced ALl. It is possible that the dexamethasone treatment suppresses lung fibrosis by upregulating the GR expression in lung.