Chen Neal X, O'Neill Kalisha D, Duan Danxia, Moe Sharon M
Indiana University School of Medicine, and Richard L. Roudebush Veterans Administration Medical Center, Indianapolis, Indiana, USA.
Kidney Int. 2002 Nov;62(5):1724-31. doi: 10.1046/j.1523-1755.2002.00625.x.
Dialysis patients have accelerated atherosclerosis, with extensive calcification of both the intima and media. Cross-sectional studies have implicated hyperphosphatemia in this process, but the mechanism is unclear.
To test the hypothesis that hyperphosphatemia and/or uremia induces vascular calcification, bovine vascular smooth muscle cells (BVSMC) were treated with increasing concentrations of beta-glycerophosphate, a phosphate donor, in the presence or absence of inhibitors for sodium/phosphate (Na/Pi) co-transport (foscarnet) or alkaline phosphatase (levamisole) for 48 hours. BVSMC also were incubated for various times with DMEM plus 15% pooled uremic sera from patients with low (LP) or high serum phosphorus (HP), or from pooled healthy control serum. Calcification in BVSMC was examined by quantitation of calcium deposition. Osteopontin expression and alkaline phosphatase activity were assessed by Western blotting and a colorimetric assay.
beta-glycerophosphate increased osteopontin expression and alkaline phosphatase activity in BVSMC. Inhibition of either alkaline phosphatase activity or Na/Pi co-transport abolished this effect. Compared to incubation with control human serum, BVSMC cultured with uremic sera had increased mineral deposition. Uremic sera also increased alkaline phosphatase activity and osteopontin expression in BVSMC. The addition of beta-glycerophosphate to uremic HP or LP sera did not further augment osteopontin expression. Blocking Na/Pi co-transport or alkaline phosphatase activity only partially inhibited uremic sera-induced osteopontin expression, indicating that other non-Na/Pi co-transport dependent mechanisms also are involved.
beta-glycerophosphate and uremic sera induce calcification and osteopontin expression in BVSMC. The uremic sera-induced osteopontin expression in BVSMC is partially mediated through alkaline phosphatase activity and a Na/Pi co-transporter dependent mechanism. However, other non-Na/Pi dependent mechanisms also contribute to accelerated vascular calcification in patients with ESRD.
透析患者存在动脉粥样硬化加速的情况，内膜和中膜均有广泛钙化。横断面研究表明高磷血症参与了这一过程，但机制尚不清楚。
为验证高磷血症和/或尿毒症诱导血管钙化的假说，在存在或不存在钠/磷酸盐（Na/Pi）共转运抑制剂（膦甲酸钠）或碱性磷酸酶抑制剂（左旋咪唑）的情况下，用浓度递增的β-甘油磷酸钠（一种磷酸盐供体）处理牛血管平滑肌细胞（BVSMC）48小时。BVSMC还分别与含有低血清磷（LP）或高血清磷（HP）患者的混合尿毒症血清、或混合健康对照血清的DMEM一起孵育不同时间。通过定量钙沉积来检测BVSMC中的钙化情况。通过蛋白质印迹法和比色测定法评估骨桥蛋白表达和碱性磷酸酶活性。
β-甘油磷酸钠增加了BVSMC中骨桥蛋白的表达和碱性磷酸酶活性。抑制碱性磷酸酶活性或Na/Pi共转运可消除这种作用。与用对照人血清孵育相比，用尿毒症血清培养的BVSMC矿物质沉积增加。尿毒症血清还增加了BVSMC中的碱性磷酸酶活性和骨桥蛋白表达。向尿毒症HP或LP血清中添加β-甘油磷酸钠并未进一步增加骨桥蛋白表达。阻断Na/Pi共转运或碱性磷酸酶活性仅部分抑制尿毒症血清诱导的骨桥蛋白表达，表明还涉及其他非Na/Pi共转运依赖性机制。
β-甘油磷酸钠和尿毒症血清可诱导BVSMC钙化和骨桥蛋白表达。尿毒症血清诱导BVSMC中骨桥蛋白表达部分是通过碱性磷酸酶活性和Na/Pi共转运体依赖性机制介导的。然而其他非Na/Pi依赖性机制也促成了终末期肾病患者血管钙化的加速。
