骨形成蛋白-7对MCP-1诱导人肾小管上皮细胞转分化和TGF-β1-Smad 3信号转导的作用

目的探讨骨形成蛋白-7（BMP-7）对单核细胞趋化蛋白-1（MCP-1）诱导体外培养人肾小管上皮细胞转分化的作用,并初步探讨该作用与转化生长因子-β1（TGF-β1）、Smad3表达变化的关系。方法将体外培养HK-2细胞分为以下各组：阴性对照组;阳性对照组：TGF-β1（5ng／ml）处理;MCP-1（0．1,1,10及50ng／ml）组,BMP-7组（0．1,1,10,50ng／ml）;MCP-1（1ng／ml）加BMP-7（50ng／ml）组;MCP-1（1ng／ml）加MCP-1中和抗体（5μg／ml）组。应用半定量RT—PCR方法检测HK-2细胞α-平滑肌肌动蛋白（α—SMA）mRNA表达,ELISA方法测定上清液中Ⅰ型胶原分泌,Western blot方法检测HK-2细胞TGF-β1及Smad3表达。结果MCP-1（0．1,1ng／ml）组HK-2细胞α—SMAmRNA表达较阴性对照组明显增强（P〈0．01）。ELISA方法测定MCP-1（0．1,1ng／ml）组上清液中I型胶原分泌明显高于阴性对照组（P〈0．01）。MCP-1中和抗体与MCP-1（1ng／ml）共同作用24h后。HKC细胞α—SMAmRNA表达几乎被完伞抑制（P〈0．001）,而BMP-7（50ng／ml）与MCP-1（1ng／ml）共同作用24h后HK-2细胞α—SMAmRNA表达仅部分被抑制（P〈0．01）;MCP-1中和抗体或BMP-7（50ng／ml）与MCP-1（1ng／ml）共同作用24h后Ⅰ型胶原分泌较MCP-1（1ng／ml）组明显降低（P〈0．05）。Western blot方法检测显示,MCP-1（1ng／ml）组HK-2细胞TGF-β1及Smad3表达水平均较阴性对照组明显上调（P〈0．01）。MCP-1中和抗体或BMP-7（50ng／ml）与MCP-1（1ng／ml）共同作用24h后,HK-2细胞TGF-β1表达均分别比MCP-1（1ng／mL）单独作用明显下调,以MCP-1中和抗体的作用更强（P〈0．01,P〈0．05）;在MCP-1中和抗体或BMP-7作用24h后,Smad3表达也有类似下调（P〈0．01,P〈0．05）。结论MCP-1能诱导体外培养的HK-2细胞发生转分化,该作用可能与TGF-β1及Smad3表达上调有关。BMP-7能部分抑制MCP-7诱导HK-2细胞转分化,该作用可能与TGF-β1及Smad3表达部分下调有关;间时提示MCP-1诱导的转分化可能涉及非TGF—β依赖的细胞信号传导途径,需进一步研究。

Effect of bone morphogenetic protein-7 on monocyte chemoattractant protein-1 induced epithelial-myofibroblast transition and TGF-beta1-Smad 3 signaling pathway of HKC cells

OBJECTIVE: To examine the effect of Bone Morphogenetic protein-7 (BMP-7) on Monocyte chemoattractant protein-1 (MCP-1) induced epithelial-myofibroblast transition (EMT) in cultured renal proximal tubular cells (HK-2) and the relationship between TGF-beta1-smad 3 expressions and MCP-1 induced EMT. METHODS: The cultured HK-2 cells were divided into six groups: a, negative control, b, treated with TGF-beta1 (5 ng/ml) as positive control, c, treated with MCP-1 (0.1, 1, 10, 50 ng/ml), d, treated with BMP-7 (0.1, 1, 10, 50 ng/ml), e. co-treated with MCP-1 (1 ng/ml) and MCP-1 neutralized antibody (1 ng/ml), f. co-treated with MCP-1 (1 ng/ml) and BMP-7 (50 ng/ml). alpha-Smooth Muscle Actin (alpha-SMA) mRNA expression of HK-2 cells was assessed with RT-PCR. Secretion of type I collagen was assessed with RT-PCR and ELISA, respectively. TGF-beta1 and Smad 3 expressions were assessed with Western blot. RESULTS: alpha-SMA mRNA expression significantly increased in HK-2 cells treated with MCP-1 (0.1, 1 ng/ml) compared with negative controls (5.97 +/- 0.35, 23.36 +/- 1.37 vs. 0.59 +/- 0.38, P < 0.01). alpha-SMA mRNA expression of HK-2 cells concomitantly treated with MCP-1 neutralized antibody or BMP-7 (50 ng/ml) and MCP-1 (1 ng/ml) significantly decreased than that in cells treated with MCP-1 (1 ng/ml) alone (1.93 +/- 0.34, 13.59 +/- 0.38 vs. 36.36 +/- 1.37, P < 0.01). Secretion of type I collagen of the cells treated with MCP-1 (0.1, 1 ng/ml) markedly increased compared with negative control (1751 +/- 34, 1876 +/- 45 vs. 1450 +/- 62; P < 0.01). The secretion of type I collagen of the supernatant were also significantly lower than that in cells treated with MCP-1 (1 ng/ml) alone (1462 +/- 56, 1596 +/- 34 vs. 1876 +/- 45, P < 0.05). The expression of TGF-beta1 and Smad 3 of HK-2 cells treated with MCP-1 (1 ng/ml) were markedly higher than that of negative controls, respectively (36.31 +/- 1.37 vs. 0.75 +/- 0.16, P < 0.01; 56.98 +/- 2.61 vs. 23.05 +/- 1.82, P < 0.01). The expressions of TGF-beta1 and Smad 3 in HK-2 cells treated concomitantly with MCP-1 neutralized antibody or BMP-7 (50 ng/ml) and MCP-1 (1 ng/ml) were markedly decreased than that treated with MCP-1 alone, respectively. (4.61 +/- 0.74, 23.74 +/- 2.14 vs. 36.31 +/- 1.37, P < 0.01; 19.63 +/- 1.65, 37.06 +/- 1.82 vs. 56.98 +/- 2.61, P < 0.01). The expressions of TGF-beta1 and Smad 3 in HK-2 cells treated concomitantly with MCP-1 neutralized antibody or BMP-7 (50 ng/ml) and MCP-1 (1 ng/ml) were markedly decreased than that treated with MCP-1 alone, respectively. (4.61 +/- 0.74, 23.74 +/- 2.14 vs. 36.31 +/- 1.37, P < 0.01; 19.63 +/- 1.65, 37.06 +/- 1.82 vs. 56.98 +/- 2.61, P < 0.01). CONCLUSIONS: The results documented that MCP-1 may induce EMT of HK-2 cells in vitro, and this effect is related to up-regulated expression of TGF-beta1 and Smad 3. BMP-7 may partially inhibit MCP-1-induced EMT and this effect is related to the downregulated expression of TGF-beta1 and Smad 3 of the cells. The results also suggest that MCP-1 induced EMT may involve the TGF-beta1-independent pathway of the cells.