N-乙酰基-丝氨酰-天门冬氨酰-赖氨酰-脯氨酸对人肺泡Ⅱ型上皮细胞向肌成纤维细胞转化的调节作用

N-acetyl-seryl-aspartly-lysyl-proline regulates the transition from human type Ⅱ alveolar epithelial cells to myofibroblasts

目的：探讨N-乙酰基-丝氨酰-天门冬氨酰-赖氨酰-脯氨酸（Ac-SDKP）是否通过对转化生长因子-β1（TGF-β1）介导的ROCK/SRF/α-SMA信号转导通路活化的调节,阻抑肺泡Ⅱ型上皮细胞向间质细胞转化,即上皮-间质转化（EMT）,进而发挥其抗（矽）肺纤维化的作用.方法：培养人A549肺泡Ⅱ型上皮细胞株,免疫细胞化学显色检测角蛋白、波形蛋白及α-平滑肌肌动蛋白（α-SMA）的表达；免疫印迹检测E-钙黏蛋白（E-cad）、波形蛋白及Rho相关卷曲蛋白激酶（ROCK）、血清反应因子（SRF）、α-SMA及Ⅰ型、Ⅲ型胶原蛋白表达；Real-Time PCR检测ROCK、SRF、α-SMA的表达情况.结果：在TGF-β1的诱导下,上皮细胞向肌成纤维细胞的形态改变,伴随着上皮标志物角蛋白、E-cad降低,而间质细胞标志物波形蛋白增高,α-SMA表达并增多.与对照组相比,TGF-β1诱导刺激组ROCK、SRF、α-SMA蛋白和基因表达水平上调,Ⅰ型、Ⅲ型胶原蛋白表达上调.给予ROCK阻滞剂Y-27632、Ac-SDKP干预后,ROCK、SRF、α-SMA及Ⅰ型、Ⅲ型胶原表达显著降低.结论：Ac-SDKP通过阻断TGF-β1介导的ROCK/SRF/α-SMA信号转导通路,阻抑肺泡Ⅱ型上皮细胞向肌成纤维细胞的转化及胶原的合成,进而发挥其抗（矽）肺纤维化的作用.

Objective： To investigate whether Ac-SDKP can regulate the ROCK/SRF/-SMA pathway mediated by TGF-I81 on EMT and play the role of anti-（Si） pulmonary fibrosis. Methods： Human type Ⅱ alveolar epithelial cells （A549） were used in the experiment. The evidence of EMT was assessed by morphology under a phase-contrast microscope. The expressions of the phenotype markers of the epithelial cells cytokeratin and mesenchymal marker vimentin, a-SMA were identified by immunocytochemistry. The expressions of E-cad, vimentin, ROOK, SRF a-SMA protein and type Ⅰ , type m collagen were measured by Western blotting. ROOK, SRF a-SMA were also evaluated by measuring mRNA level using real-time PCR. Results： The process of EMT induced by TGF-β1 was accompanied by morphological alteration and the expression of the fibroblast phenotypie marker vimentin and myofibroblast phenotypic marker a-SMA, concomitant with a down-regulation of the epithelial phenotypic markers E-cad and cytokeratin. Compared with the control group, the expressions of ROOK, SRF, a-SMA on the level of both protein expression and gene detection increased significantly after the stimulation of TGF-~31. Collagen I and Collagen 1]I were up-regulated too. While they were decreased significantly in Y-27632 （ROOK blockers） treating group and Ae-SDKP group. Conclusion： Our study shows that TGF-β1 induces A549 alveolar epithelial cells to undergo EMT via Rho/ROCK pathway activation. Ac-SDKP, similar to Y-27632, can inhibit the process of differentiation from epithelial cells to myofibroblasts by blocking TGF-β1 which induces ROOK/SRF/a-SMA signal transduction pathway, decreases the expressions of type I and type Ⅲ collagen and enhances its anti-silieotic effects.