title: High-phosphate-induced calcification is related to SM22α promoter methylation in vascular smooth muscle cells.
abstract: Hyperphosphatemia is closely related to vascular calcification in patients with chronic kidney disease. Vascular smooth muscle cells (VSMCs) exposed to high phosphate concentrations in vitro undergo phenotypic transition to osteoblast-like cells. Mechanisms underlying this transdifferentiation are not clear. In this study we used two in vitro models, human aortic smooth muscle cells and rat aortic rings, to investigate the phenotypic transition of VSMCs induced by high phosphate. We found that high phosphate concentration (3.3 mmol/L) in the medium was associated with increased DNA methyltransferase activity and methylation of the promoter region of SM22α. This was accompanied by loss of the smooth muscle cell-specific protein SM22α, gain of the osteoblast transcription factor Cbfa1, and increased alkaline phosphatase activity with the subsequent in vitro calcification. The addition of a demethylating agent (procaine) to the high-phosphate medium reduced DNA methyltransferase activity and prevented methylation of the SM22α promoter, which was accompanied by an increase in SM22α expression and less calcification. Additionally, downregulation of SM22α, either by siRNA or by a methyl group donor (S-adenosyl methionine), resulted in overexpression of Cbfa1. In conclusion, we demonstrate that methylation of SM22α promoter is an important event in vascular smooth muscle cell calcification and that high phosphate induces this epigenetic modification. These findings uncover a new insight into mechanisms by which high phosphate concentration promotes vascular calcification.
authors.affiliation: Department of Medicina y Cirugia Animal, Universidad de Cordoba, Cordoba, Spain.
authors.forename: Addy
authors.initials: A
authors.lastname: Montes de Oca
authors.forename: Juan A
authors.initials: JA
authors.lastname: Madueño
authors.forename: Julio M
authors.initials: JM
authors.lastname: Martinez-Moreno
authors.forename: Fatima
authors.initials: F
authors.lastname: Guerrero
authors.forename: Juan
authors.initials: J
authors.lastname: Muñoz-Castañeda
authors.forename: Marien E
authors.initials: ME
authors.lastname: Rodriguez-Ortiz
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Mendoza
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Almaden
authors.forename: Ignacio
authors.initials: I
authors.lastname: Lopez
authors.forename: Mariano
authors.initials: M
authors.lastname: Rodriguez
authors.forename: Escolastico
authors.initials: E
authors.lastname: Aguilera-Tejero
mesh_terms: D000818:Animals; D001483:Base Sequence; D002114:Calcinosis / Q000150:complications*; D019175:DNA Methylation; D017931:DNA Primers; D006801:Humans; D008840:Microfilament Proteins / Q000235:genetics*; D009124:Muscle Proteins / Q000235:genetics*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D051381:Rats
chemical_list: D017931:DNA Primers; D008840:Microfilament Proteins; D009124:Muscle Proteins; C051615:transgelin