Effect and mechanism of magnesium on vascular calcification induced by hyperphosphate

Abstract

Objective To explore the effect and mechanism of magnesium on calcification induced by hyperphosphate. Methods Vascular smooth muscle cells (VSMCs) were primarily cultured in vitro and induced calcification by β-glycerophosphate (β-GP). VSMCs were randomly divided into control group, high phosphorus group (10 mmol/L β-GP), magnesium intervention group(10 mmol/L β-GP+3 mmol/L MgSO4) and 2-aminoethoxy-diphenylborate (2-APB, an inhibitor of magnesium transporter) intervention group(10 mmol/L β-GP+3 mmol/L MgSO4+10-4 mol/L 2-APB). Calcium deposition and alkaline phosphatase (ALP) activity were measured by alizarin red staining, quantification of calcium and enzyme linked immunosorbent assay. RT-PCR and Western blotting were used to observe the expression of core binding factor α-1 (Cbfα-1) mRNA and protein, respectively. In vivo, male Sprague-Dawley rats (n=24) were randomly divided into control group (methylcellulose+high phosphorous diet), vascular calcification group (adenine suspension+high phosphorous diet), high magnesium intervention group(adenine suspension+high phosphorous and magnesium diet). The aortic pulse wave velocity (PWV) was measured, and vascular calcification was determined by von Kossa stain and quantification of calcium. Cbfα-1 in aortic was measured by immunohistochemistry. Results In vitro, compared with high phosphorus group, calcification, ALP activity (P<0.05) and Cbfα-1 expression in VSMCs were significantly decreased in magnesium intervention group after incubation for 14 days, but the addition of 2-APB might inhibit the protective effect of magnesium on VSMCs. Dynamic observation of Cbfα-1 showed that magnesium significantly inhibited the expression of Cbfα-1 (P<0.05) on the third day and the inhibitory role was obviously increased in a time-dependent manner. Consistent with the findings in vitro, the aortic PWV, calcification were all significantly reduced (P<0.05) in high magnesium intervention group with high serum magnesium level, when compared with vascular calcification group. Immunohistochemistry showed that hypermagnesemia down-regulated obviously the expression of Cbfα-1 induced by hyperphosphatemia(P<0.05). Conclusion Magnesium protects against vascular calcification by inhibiting osteogenic differentiation of VSMCs. Key words: Magnesium; Calcification; Chronic renal failure; β-glycerophosphate; Core binding factor alpha 1