观察黄芩苷对博来霉素诱导肺纤维化小鼠的保护作用及其机制。

将18只小鼠分为对照组、博来霉素组和黄芩苷组，每组6只。博来霉素组和黄芩苷组小鼠给予博来霉素（5 mg/kg）气管内给药以建立小鼠肺纤维化模型，对照组小鼠给予等量等渗NaCl溶液。建模后3 d黄芩苷组小鼠给予黄芩苷（25 g/kg）隔天腹腔注射，对照组和博来霉素组小鼠分别于相同时间点腹腔注射等量等渗NaCl溶液，均持续25 d。建模28 d后处死小鼠取肺组织，采用苏木素-伊红（HE）染色及Masson染色观察小鼠肺组织炎症和纤维化情况，并比较各组小鼠间肺组织纤维化评分及羟脯氨酸含量；采用实时荧光定量PCR（qPCR）检测纤维胶原蛋白基因[Collagen 1a1信使RNA（mRNA）、Collagen 3a1 mRNA]，Wnt3a/β-catenin信号通路相关基因[Wnt3a mRNA、基质金属蛋白酶3（MMP-3）mRNA、MMP-9 mRNA和Cyclin D1 mRNA]表达水平；采用Western-blotting检测上皮细胞-间充质细胞转分化（EMT）相关蛋白[Vimentin、α-平滑肌肌动蛋白（α-SMA）]和β-catenin蛋白的表达水平。

光镜下观察发现，对照组小鼠肺组织结构完整，未见炎症细胞浸润；博来霉素组小鼠肺组织结构破坏，炎症细胞浸润，呈弥漫性肺纤维化改变；而黄芩苷组小鼠肺组织炎症细胞浸润及肺纤维化程度较博来霉素组小鼠均明显减轻。3组小鼠间肺纤维化评分、羟脯氨酸含量、Collagen 1a1 mRNA、Collagen 3a1 mRNA、Wnt3a mRNA、MMP-3 mRNA、MMP-9 mRNA、Cyclin D1 mRNA、Vimentin、α-SMA及β-catenin蛋白的比较，差异均有统计学意义（F = 12.012、8.414、46.224、30.179、85.912、125.435、19.521、40.247、72.731、58.169、70.471，P均< 0.001）。且进一步两两比较发现，博来霉素组小鼠上述指标较对照组均明显升高，而黄芩苷组小鼠上述指标较博来霉素组小鼠均显著降低（P均< 0.05）。

黄芩苷对于博来霉素诱导的肺纤维化小鼠具有保护作用，该保护作用与抑制Wnt3a/β-catenin信号通路和EMT相关蛋白的活化有关。

To observe the protective effect of baicalin on bleomycin-induced pulmonary fibrosis in mice and its mechanism.

Totally 18 mice were divided into a control group, a bleomycin group and a baicalin group, with 6 mice in the each group. Mice in the bleomycin group and baicalin group were intratracheally administered with bleomycin (5 mg/kg) to establish a model of pulmonary fibrosis, and those in the control group were given the same volume of isotonic NaCl solution. Three days after modeling, mice in the baicalin group were intraperitoneally injected with baicalin (25 g/kg), while those in the control group and bleomycin group were given the same volume of isotonic NaCl solution every other day for 25 days. Then mice were sacrificed after 28 days of modeling. The hatmatoxylin-eosin (HE) staining and Masson staining were used to observe the severity of inflammation and fibrosis in the lung tissue. The pulmonary fibrosis score and hydroxyproline content were compared among the three groups. The messenger RNA (mRNA) expression levels of fibrilagen (Collagen 1a1, Collagen 3a1) and Wnt3a/β-catenin signal pathway related proteins [Wnt3a, matrix metalloproteinases-3 (MMP-3), MMP-9, Cyclin D1] were detected by real-time quantitative PCR (qPCR), and the expression levels of epithelial-mesenchymal transition (EMT) related proteins [Vimentin, alpha-smooth muscle actin (α-SMA)] and β-catenin were examined by Western-blotting.

Under the light microscope, the lung tissue was structurally intact and no inflammatory cell infiltration was observed in the control group; the lung tissue was structurally destroyed and inflammatory cells infiltrated, presenting diffuse pulmonary fibrosis in the bleomycin group; the inflammatory cell infiltration and pulmonary fibrosis in the baicalin group significantly reduced as compared with those in the bleomycin group. The pulmonary fibrosis score, hydroxyproline content, Collagen 1a1 mRNA, Collagen 3a1 mRNA, Wnt3a mRNA, MMP-3 mRNA, MMP-9 mRNA, Cyclin D1 mRNA, Vimentin, α-SMA and β-catenin all showed significant differences among the three groups (F = 12.012, 8.414, 46.224, 30.179, 85.912, 125.435, 19.521, 40.247, 72.731, 58.169, 70.471; all P < 0.001). Further pairwise comparison revealed that the above indicators in the bleomycin group were significantly higher than those in the control group, and the above indicators in the baicalin group were significantly lower than those in the bleomycin group (both P < 0.05).

Baicalin has protective effect on bleomycin-induced pulmonary fibrosis in mice, which may be related to the inhibition of Wnt3a/β-catenin signaling pathway and activation of EMT proteins.