Kruppel-like factor 4 contributes to high phosphate-induced phenotypic switching of vascular smooth muscle cells into osteogenic cells.
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.
Apheresis and Dialysis Center, School of Medicine, Keio University, Tokyo 160-8582, Japan. tayoshida-npr@umin.ac.jp
Tadashi
T
Yoshida
Maho
M
Yamashita
Matsuhiko
M
Hayashi
D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000943:Antigens, Differentiation / Q000378:metabolism; D001013:Aorta, Thoracic / Q000378:metabolism / Q000473:pathology; D054338:Cell Transdifferentiation; D002478:Cells, Cultured; D050659:Core Binding Factor Alpha 1 Subunit / Q000378:metabolism; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000473:pathology*; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D010006:Osteoblasts / Q000378:metabolism*; D010641:Phenotype; D010710:Phosphates / Q000502:physiology*; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011499:Protein Processing, Post-Translational; D034622:RNA Interference; D051381:Rats; D017207:Rats, Sprague-Dawley; D014511:Uremia / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology; D061205:Vascular Calcification / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology; D050807:ets-Domain Protein Elk-1 / Q000378:metabolism
D000199:Actins; D000943:Antigens, Differentiation; D050659:Core Binding Factor Alpha 1 Subunit; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; D010710:Phosphates; D050807:ets-Domain Protein Elk-1; C000715469:Klf4 protein, rat; C493717:Runx2 protein, rat; C498862:Acta2 protein, rat