Krüppel-like Factor 4 Contributes to High Phosphate-induced Phenotypic Switching of Vascular Smooth Muscle Cells into Osteogenic Cells*
Krüppel-like Factor 4 Contributes to High Phosphate-induced Phenotypic Switching of Vascular Smooth Muscle Cells into Osteogenic Cells*
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DOI：
10.1074/jbc.m112.361360
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发表时间：
2012-06
期刊：
影响因子：
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通讯作者：
Tadashi Yoshida;Maho Yamashita;M. Hayashi
中科院分区：
文献类型：
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作者：
Tadashi Yoshida;Maho Yamashita;M. Hayashi
背景：阐明控制血管钙化的分子机制对慢性肾脏疾病患者至关重要。结果：高磷诱导SMC表达KLF4。KLF4基因敲除可减弱高磷诱导的SMC向成骨细胞的表型转换。结论：KLF4参与了高磷诱导的SMC向成骨细胞的转化。意义：控制KLF4可能成为治疗血管钙化的新靶点。慢性肾脏疾病的高磷血症与血管钙化高度相关。以往的研究表明，高磷诱导的血管平滑肌细胞向成骨细胞的表型转换在钙化过程中起着重要作用。在本研究中，我们确定了Krüppel样因子4(Klf4)和磷酸化的Elk-1是否参与了这一过程，它们是由动脉内膜致动脉粥样硬化刺激激活的SMC分化标志基因的转录抑制因子。将大鼠主动脉平滑肌细胞培养在磷酸盐浓度正常(0.9 mm o l/L)和高浓度(4.5 m o l/L)的培养液中。结果表明，高浓度磷酸盐可诱导SMC钙化。此外，高磷降低了平滑肌细胞分化标志基因α-肌动蛋白和SM22α的表达，而增加了成骨基因Runx2和骨桥蛋白的表达。高磷也能诱导KLF4的表达，尽管它不能使ELK-1磷酸化。作为对高磷的响应，KLF4选择性地结合到SMC分化标记基因的启动子区域。重要的是，siRNA介导的KLF4基因敲除减弱了高磷诱导的SMC分化标志基因的抑制，以及成骨基因表达和钙沉积的增加。KLF4在腺嘌呤尿毒症大鼠钙化的主动脉中也有明显的诱导。这些结果为KLF4介导高磷诱导的SMC向成骨细胞转化提供了新的证据。
Background: Elucidation of molecular mechanisms controlling vascular calcification is critical for chronic kidney disease patients. Results: High phosphate induced Klf4 expression in SMCs. Klf4 knockdown attenuated high phosphate-induced SMC phenotypic switching into osteogenic cells. Conclusion: Results suggest that Klf4 contributes to high phosphate-induced conversion of SMCs into osteogenic cells. Significance: Control of Klf4 might be a novel therapeutic target for vascular calcification. Hyperphosphatemia in chronic kidney disease is highly associated with vascular calcification. Previous studies have shown that high phosphate-induced phenotypic switching of vascular smooth muscle cells (SMCs) into osteogenic cells plays an important role in the calcification process. In the present study, we determined whether Krüppel-like factor 4 (Klf4) and phosphorylated Elk-1, transcriptional repressors of SMC differentiation marker genes activated by intimal atherogenic stimuli, contributed to this process. Rat aortic SMCs were cultured in the medium with normal (0.9 mmol/liter) or high (4.5 mmol/liter) phosphate concentration. Results showed that high phosphate concentration induced SMC calcification. Moreover, high phosphate decreased expression of SMC differentiation marker genes including smooth muscle α-actin and SM22α, whereas it increased expression of osteogenic genes, such as Runx2 and osteopontin. High phosphate also induced Klf4 expression, although it did not phosphorylate Elk-1. In response to high phosphate, Klf4 selectively bound to the promoter regions of SMC differentiation marker genes. Of importance, siRNA-mediated knockdown of Klf4 blunted high phosphate-induced suppression of SMC differentiation marker genes, as well as increases in expression of osteogenic genes and calcium deposition. Klf4 was also induced markedly in the calcified aorta of adenine-induced uremic rats. Results provide novel evidence that Klf4 mediates high phosphate-induced conversion of SMCs into osteogenic cells.