多聚鸟嘌呤核苷酸对矽尘致大鼠肺纤维化干预作用及机制研究

Intervention effect and mechanism of polyguanylic acid on pulmonary fibrosis in silica-exposed rats

目的观察多聚鸟嘌呤核苷酸(Poly G)对染矽尘大鼠肺纤维化的干预作用,并探讨其作用机制。方法无特定病原体级健康成年雄性SD大鼠随机分为对照组、矽肺模型组和4个干预组(即干预1、2、3、4次组),每组5只。除对照组外,其余5组大鼠均以非暴露式气管插管法一次性予质量浓度为50.0 g/L的矽尘混悬液1.0 m L造模,4个干预组大鼠分别于造模后第1~21天内腹腔注射1、2、3、4次剂量为2.5 mg/kg体质量的Poly G。造模后28 d处死大鼠,观察肺部组织病理学改变情况,以Ashcroft评分法评估肺纤维化程度,以蛋白免疫印迹法测定肺组织内胶原样结构巨噬细胞受体(MARCO)、转化生长因子-β1(TGF-β1)、E-钙黏蛋白(E-cad)、波形蛋白(Vimentin)和α-平滑肌肌动蛋白(α-SMA)的蛋白相对表达水平。结果矽肺模型组大鼠肺泡腔内有大量尘细胞聚集,肺间质内出现弥漫性的胶原沉积,说明矽肺造模成功;干预1次组大鼠肺泡结构基本完整,肺纤维化程度较矽肺模型组明显减轻。与对照组比较,矽肺模型组大鼠肺组织Ashcroft评分和MARCO、TGF-β1、Vimentin、α-SMA的蛋白相对表达水平均升高(P<0.05),E-cad相对表达水平下降(P<0.05);与矽肺模型组比较,干预1次组大鼠肺组织的TGF-β1、Vimentin和α-SMA的蛋白相对表达水平均下降(P<0.05),E-cad相对表达水平升高(P<0.05)。Poly G干预次数与大鼠肺组织的Ashcroft评分和MARCO、TGF-β1、E-cad、Vimentin、α-SMA的蛋白相对表达水平之间均无剂量-效应关系。结论 Poly G可改善矽尘所致的大鼠肺组织炎症和纤维化,以在造模后第1天进行一次性干预(2.5 mg/kg体质量,腹腔注射)效果较好,其机制可能与低剂量Poly G抑制上皮间质转化的进程从而减少胶原合成有关。

Objective To observe the intervention effect of polyguanylic acid（ Poly G） on silicosis fibrosis in rats and to explore its possible mechanism. Methods Specific pathogen free adult male SD rats were randomly divided into 6 groups：control group,silicosis model group and 4 intervention groups（ intervention group 1,2,3 and 4）,with 5 rats in each group. Except for the control group,the other 5 groups were treated with 1. 0 mL silica suspension（ 50. 0 g / L mass concentration） by intratracheal intubation,four intervention group was given by intraperitoneal injection of 1,2,3 and 4doses of Poly G at 2. 5 mg / kg body weight after establishing the model for 1 to 21 days. All rats were sacrificed 28 days after silicosis model establishment. Lung pathological changes were observed and the pulmonary fibrosis was evaluated by Ashcroft scores. The expression of Macrophage receptor with collagenous structure（ MARCO）,transforming growth factor-β1（ TGF-β1）,E-cadherin,Vimentin and α-smooth muscle actin（ α-SMA） protein were detected by western blot.Results In the model group,a large number of dust cell aggregates were found in the alveolar cavity and diffuse collagen deposition appeared in the pulmonary interstitial,indicating that silicosis model was successfully constructed. The alveolar structure of the single dose intervention group was integral and the degree of fibrosis was significantly less than that of the silicosis model group. Compared with the control group,MARCO,TGF-β1,Vimentin and α-SMA expression levels of silicosis model group were increased,the expression level of E-cadherin decreased, the difference was statistically significant（ P〈0. 05）. Compared with the silicosis model group,TGF-β1,Vimentin and α-SMA expression levels of single dose intervention group decreased,E-cadherin expression level increased,the difference was statistically significant（ P〈0. 05）. The dose-response relationship could not perceived between the Poly G intervention times and the Ashcroft scores or the protein expression levels of MARCO,TGF-β1,E-cadherin,Vimentin and α-SMA respectively. Conclusion Poly G can effectively reduce lung inflammation and fibrosis in rats. The effect of single dose intervention（ 2. 5 mg / kg body weight,intraperitoneal injection） at the first day after silica exposure is the best. The mechanism of action may be related to the low-does Ply G which can inhibit the epithelial-mesenchymal transition and then result in the decrease of collagen synthesis.