title: Magnesium prevents phosphate-induced vascular calcification via TRPM7 and Pit-1 in an aortic tissue culture model.
abstract: Previous clinical and experimental studies have indicated that magnesium may prevent vascular calcification (VC), but mechanistic characterization has not been reported. This study investigated the influence of increasing magnesium concentrations on VC in a rat aortic tissue culture model. Aortic segments from male Sprague-Dawley rats were incubated in serum-supplemented high-phosphate medium for 10 days. The magnesium concentration in this medium was increased to demonstrate its role in preventing VC, which was assessed by imaging and spectroscopy. The mineral composition of the calcification was analyzed using Fourier transform infrared (FTIR) spectroscopic imaging, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) mapping. Magnesium supplementation of high-phosphate medium dose-dependently suppressed VC (quantified as aortic calcium content), and almost ablated it at 2.4 mm magnesium. The FTIR images and SEM-EDX maps indicated that the distribution of phosphate (as hydroxyapatite), phosphorus and Mg corresponded with calcium content in the aortic ring and VC. The inhibitory effect of magnesium supplementation on VC was partially reduced by 2-aminoethoxy-diphenylborate, an inhibitor of TRPM7. Furthermore, phosphate transporter-1 (Pit-1) protein expression was increased in tissues cultured in HP medium and was gradually-and dose dependently-decreased by magnesium. We conclude that a mechanism involving TRPM7 and Pit-1 underpins the magnesium-mediated reversal of high-phosphate-associated VC.
authors.affiliation: Division of Nephrology, Department of Internal Medicine, Wakayama Medical University, Wakayama City, Wakayama, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Sonou
authors.affiliation: Division of Nephrology, Department of Internal Medicine, Wakayama Medical University, Wakayama City, Wakayama, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Ohya
authors.affiliation: Division of Nephrology, Department of Internal Medicine, Wakayama Medical University, Wakayama City, Wakayama, Japan.
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Yashiro
authors.affiliation: Division of Nephrology, Department of Internal Medicine, Wakayama Medical University, Wakayama City, Wakayama, Japan.
authors.forename: Asuka
authors.initials: A
authors.lastname: Masumoto
authors.affiliation: Division of Nephrology, Department of Internal Medicine, Wakayama Medical University, Wakayama City, Wakayama, Japan.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Nakashima
authors.affiliation: Department of Bio- and Material Photonics, Chitose Institute of Science and Technology, Chitose City, Hokkaido, Japan.
authors.forename: Teppei
authors.initials: T
authors.lastname: Ito
authors.affiliation: Division of Nephrology, Department of Internal Medicine, Wakayama Medical University, Wakayama City, Wakayama, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Mima
authors.affiliation: Division of Nephrology, Department of Internal Medicine, Wakayama Medical University, Wakayama City, Wakayama, Japan.
authors.forename: Shigeo
authors.initials: S
authors.lastname: Negi
authors.affiliation: Department of Bio- and Material Photonics, Chitose Institute of Science and Technology, Chitose City, Hokkaido, Japan.
authors.forename: Hiromi
authors.initials: H
authors.lastname: Kimura-Suda
authors.affiliation: Division of Nephrology, Department of Internal Medicine, Wakayama Medical University, Wakayama City, Wakayama, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Shigematsu
mesh_terms: D000818:Animals; D001011:Aorta; D008274:Magnesium / Q000494:pharmacology / Q000627:therapeutic use*; D008297:Male; D008855:Microscopy, Electron, Scanning; D010710:Phosphates; D017207:Rats, Sprague-Dawley; D050611:Sodium-Phosphate Cotransporter Proteins, Type III / Q000378:metabolism*; D013052:Spectrometry, X-Ray Emission; D017550:Spectroscopy, Fourier Transform Infrared; D050053:TRPM Cation Channels / Q000378:metabolism*; D046509:Tissue Culture Techniques; D061205:Vascular Calcification / Q000517:prevention & control*
chemical_list: D010710:Phosphates; C493588:Slc20a1 protein, rat; D050611:Sodium-Phosphate Cotransporter Proteins, Type III; D050053:TRPM Cation Channels; C486584:Trpm7 protein, rat; D008274:Magnesium