OHRI/University of Ottawa, 451 Smyth Road, Ottawa, K1H 8M5 Ontario, Canada.
Hypertension. 2010 Sep;56(3):453-62. doi: 10.1161/HYPERTENSIONAHA.110.152058. Epub 2010 Aug 9.
Arterial calcification, common in vascular diseases, involves vascular smooth muscle cell (VSMC) transformation to an osteoblast phenotype. Clinical studies suggest that magnesium may prevent this, but mechanisms are unclear. We assessed whether increasing magnesium levels reduce VSMC calcification and differentiation and questioned the role of the Mg(2+) transporter, transient receptor potential melastatin (TRPM)7 cation channels in this process. Rat VSMCs were exposed to calcification medium in the absence and presence of magnesium (2.0 to 3.0 mmol/L) or 2-aminoethoxy-diphenylborate (2-APB) (TRPM7 inhibitor). VSMCs from mice with genetically low (MgL) or high-normal (MgH) Mg(2+) were also studied. Calcification was assessed by von Kossa staining. Expression of osteocalcin, osteopontin, bone morphogenetic protein (BMP)-2, BMP-4, BMP-7, and matrix Gla protein and activity of TRPM7 (cytosol:membrane translocation) were determined by immunoblotting. Calcification medium induced osteogenic differentiation, reduced matrix Gla protein content, and increased expression of the sodium-dependent cotransporter Pit-1. Magnesium prevented calcification and decreased osteocalcin expression and BMP-2 activity and increased expression of calcification inhibitors, osteopontin and matrix Gla protein. TRPM 7 activation was decreased by calcification medium, an effect reversed by magnesium. 2-APB recapitulated the VSMC osteoblastic phenotype in VSMCs. Osteocalcin was increased by calcification medium in VSMCs and intact vessels from MgL but not MgH, whereas osteopontin was increased in MgH, but not in MgL mice. Magnesium negatively regulates vascular calcification and osteogenic differentiation through increased/restored TRPM7 activity and increased expression of anticalcification proteins, including osteopontin, BMP-7, and matrix Gla protein. New molecular insights are provided whereby magnesium could protect against VSMC calcification.
动脉钙化常见于血管疾病，涉及血管平滑肌细胞（VSMC）向成骨细胞表型的转化。临床研究表明，镁可能预防这种情况，但机制尚不清楚。我们评估了增加镁水平是否会减少 VSMC 钙化和分化，并探讨了镁（2+）转运体，瞬时受体电位 melastatin（TRPM）7 阳离子通道在这一过程中的作用。将大鼠 VSMC 暴露于钙化培养基中，在不存在和存在镁（2.0 至 3.0mmol/L）或 2-氨基乙氧基-二苯硼酸盐（2-APB）（TRPM7 抑制剂）的情况下。还研究了具有遗传低（MgL）或高正常（MgH）[Mg（2+）]（i）的小鼠的 VSMC。通过 von Kossa 染色评估钙化。通过免疫印迹法测定骨钙蛋白、骨桥蛋白、骨形成蛋白（BMP）-2、BMP-4、BMP-7 和基质 Gla 蛋白的表达以及 TRPM7 的活性（细胞质：膜易位）。钙化培养基诱导成骨分化，降低基质 Gla 蛋白含量，增加钠依赖性共转运蛋白 Pit-1 的表达。镁可防止钙化，降低骨钙蛋白表达和 BMP-2 活性，并增加钙化抑制剂骨桥蛋白和基质 Gla 蛋白的表达。钙培养基激活 TRPM7，镁可逆转该作用。2-APB 可在 VSMC 中重现 VSMC 成骨表型。在 VSMC 和完整血管中，钙化培养基增加了 MgL 但不是 MgH 的骨钙蛋白，而在 MgH 中增加了骨桥蛋白，但在 MgL 中没有增加。镁通过增加/恢复 TRPM7 活性和增加抗钙化蛋白（包括骨桥蛋白、BMP-7 和基质 Gla 蛋白）的表达来负调控血管钙化和成骨分化。提供了新的分子见解，表明镁可以预防 VSMC 钙化。
