High-phosphate-induced calcification is related to SM22α promoter methylation in vascular smooth muscle cells.
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.
Montes de Oca
Addy
A
Department of Medicina y Cirugia Animal, Universidad de Cordoba, Cordoba, Spain.
Madueño
Juan A
JA
Martinez-Moreno
Julio M
JM
Guerrero
Fatima
F
Muñoz-Castañeda
Juan
J
Rodriguez-Ortiz
Marien E
ME
Mendoza
Francisco J
FJ
Almaden
Yolanda
Y
Lopez
Ignacio
I
Rodriguez
Mariano
M
Aguilera-Tejero
Escolastico
E
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
D017931:DNA Primers; D008840:Microfilament Proteins; D009124:Muscle Proteins; C051615:transgelin