五味子乙素对染矽尘大鼠肺组织转化生长因子β1信号转导通路分子mRNA表达的影响

目的 观察五味子乙素(sehisandrin B,Sch-B)对染矽尘大鼠肺组织转化生长因子β1(TGF-β1)信号通路分子mRNA表达的影响,探讨其防治矽肺纤维化的作用及机制.方法 将96只Wistar大鼠随机分为对照组、染矽尘组、Sch-B干预组,每组32只,气管暴露法一次性染尘建立大鼠矽肺模型,染矽尘组和Sch-B干预组每只大鼠气管内注入1 ml(50 mg/ml)SiO2混悬液,对照组注入1 ml灭菌生理盐水.染尘后第1天开始灌胃干预,Sch-B组给予Sch-B(80mg·kg-1/d-1),染矽尘组和对照组给予等体积的橄榄油.不同处理3、7、14和28 d后,各组处死8只大鼠,对肺组织HE染色观察病理改变;用反转录-聚合酶链式反应(RT-PCR)法测定大鼠肺组织中TGF-β1、转化生长因子βⅡ型受体(TGF-βRⅡ)和Smad4基因表达.结果 染矽尘组肺损伤明显,在3和7 d时表现为明显的肺泡炎,可见肺泡间隔水肿,大量炎性细胞浸润,在14d时,肺泡间隔明显增宽,成纤维细胞和胶原基质明显增多;在28 d时,肺泡结构破坏,肺泡壁明显增厚,肺组织以胶原沉积和肺纤维化改变为主.Sch-B组肺泡炎和肺纤维化程度均较染矽尘组明显减轻.染矽尘组3、7、14、28 d时大鼠肺内TGF-β1、TGF-βRⅡ和Smad4的mRNA表达(TGF-β1:1.03±0.31、1.33±0.39、1.08±0.26、0.82±0.16,TGF-βRⅡ:0.65±0.11、0.80±0.16、0.83±0.24、0.62±0.15,Smad4:0.87±0.15、0.68±0.11、0.78±0.19、0.30±0.08)均明显高于对照组(TGF-β1:0.59±0.22、0.55±0.25、0.56±0.20、0.55±0.12,TGR-βRⅡ:0.28±0.13、0.31 ±0.15、0.34±0.15、0.27±0.09,Smad4:0.23±0.11、0.40±0.12、0.39±0.12、0.18±0.06),差异均有统计学意义(P＜0.01或P＜0.05),其中TGF-β1在第7天时达高峰后开始下降.Sch-B干预组各时间点TGF-β1和Smad4(TGF-β1:0.68±0.28、0.88±0.25、0.75±0.11、0.61±0.14,Smad4:0.25±0.12、0.45±0.09、0.44±0.07、0.21±0.04)均低于染矽尘组,差异有统计学意义(P＜0.01或P＜0.05).与染矽尘组相比,Sch-B干预组TGF-βRⅡmRNA表达无明显改变,差异无统计学意义(P＞0.05).结论 Sch-B能减轻染矽尘大鼠肺组织的纤维化程度,其作用机制可能是通过抑制TGF-β1和Smad4的mRNA表达上调,从而干扰TGF-β1/Smad4信号通路对靶基因的激活来实现的.

Abstract：

Objective To investigate the effects of schisandrin B (Sch-B) on expression of transforming growth factor-β1 (TGF-β1) and signal transduction molecule mRNA in rat lungs exposed to SiO2,and explore the intervention mechanism of Sch-B on pulmonary fibrosis induced by SiO2. Methods Ninety six Wistar rats were randomly divided into control (normal saline) group, SiO2 group and SiO2 plus Sch-B group.The rats were exposed to SiO2 by direct tracheal instillation to establish the silicotic animal models. SiO2 group and SiO2 plus Sch-B group were treated with 1ml SiO2 (50 mg/ml) for each rat From the first day after model establishment, SiO2 plus Sch-B group were orally given Sch-B (80 mg/kg) a day, control group and silica group were orally given olive oil. On the 3rd, 7th,14th and 28th days after treatment, 8 rats in each group were sacrificed and samples were collected. The histo-pathological examination of lung was performed by HE staining. The expression levels of TGF-β1 、TGFβR Ⅱ and Smad4 mRNA in the lung tissues were detected by RT-PCR. Results The results of histo-pathological examination showed that in SiO2 group, lung tissues were injured obviously; the alveolar inflammation with alveolus interval edema and inflammation cell infiltration appeared on the 3rd and 7th days; the alveolus interval became thicker, became thicker, fibroblast and collagen matiix increased markedly on 14th day; the alveolar structure was damaged, alveolar wall thickened obviously,collagen aggradation and pulmonary fibrosis displayed on 28th day. The alveolar inflammation and pulmonary fibrosis in SiO2 plus Sch-B group were significantly less than those in SiO2 group. The expressions levels of TGF-β1、TGFβR Ⅱ and Smad4 mRNA (TGF-β1: 1.03±0.31 、1.33±0.39、1.08±0.26、0.82±0.16,TGF-βR Ⅱ:0.65 ±0.11、0.80 ±0.16、0.83 ±0.24、0.62 ±0.15, Smad4: 0.87 ±0. 15、0.68 ±0.11、0.78 ±0.19、0.30 ±0.08) in SiO2group were significantly higher than those in the control group (TGF-β1:0.59±0.22、0.55 ±0.25、0.56±0.20、0.55 ±0.12,TGR-βR Ⅱ:0.28 ±0.13、0.31 ±0. 15、0.34 ±0.15、0.27 ±0.09,Smad4:0.23 ±0.11、0.40 ±0. 12、0.39 ±0.12、0.18±0.06)(P＜0.01 or P＜0.05), but the expression level of TGF-β1 mRNA was the highest on the 7th day. The expression levels of TGF-β1 and Smad4 mRNA (TGF-β1: 0.68 ±0.28、0.88 ±0.25、0.75 ±0.11、0.61 ±0. 14,Smad4:0.25 ±0.12、0.45 ±0.09、0.44 ±0.07、0.21 ±0.04) in SiO2 plus Sch-B group were significantly lower than those in SiO2 group (P＜0.01 or P＜0.05),but there were no significant differences of the TGFβR Ⅱ mRNA expression levels between SiO2 group and SiO2 plus Sch-B group. Conclusion Sch-B can reduce the pulmonary fibrosis induced by SiO2 through inhibition of the mRNA express of TGF-β1 and Smad4 in the lung tissue, modulating the TGF-β1/Smad4 signal transduction pathway and inhibiting the target gene activation.