Role of the sodium-dependent phosphate cotransporter, Pit-1, in vascular smooth muscle cell calcification
Role of the sodium-dependent phosphate cotransporter, Pit-1, in vascular smooth muscle cell calcification
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DOI：
10.1161/01.res.0000216409.20863.e7
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发表时间：
2006-04-14
影响因子：
20.1
通讯作者：
Giachelli, CM
中科院分区：
文献类型：
--
作者：
Li, XW;Yang, HY;Giachelli, CM
血管钙化与心血管病发病率和死亡率相关。高磷血症是血管钙化的重要原因。我们以前的研究表明，高磷酸盐诱导平滑肌细胞（SMC）在体外钙化。磷酸盐转运抑制膦甲酸阻断磷酸盐诱导的钙化，牵连钠依赖性磷酸盐协同转运蛋白在这个过程中。在本研究中，我们研究了III型钠依赖性磷酸盐协同转运蛋白Pit-1在体外SMC钙化中的作用。利用逆转录病毒系统建立了稳定表达Pit-1小干扰双链RNA（SMC-iRNA）的人SMC。与对照转导细胞（SMC-CT）相比，SMC-iRNA降低了Pit-1 mRNA和蛋白水平以及钠依赖性磷酸盐转运活性（分别为2.9和9.78 nmol/mg蛋白/30分钟）。此外，与SMC-CT相比，在所有检查的时间点，磷酸盐诱导的SMC钙化在SMC-iRNA中被显著抑制。Pit-1的过表达恢复了Pit-1缺陷细胞的磷酸盐摄取和磷酸盐诱导的钙化。从机制上讲，虽然Pit-1介导的SMC钙化与细胞凋亡或细胞衍生的囊泡无关，但Pit-1敲低细胞中磷酸盐摄取的抑制阻断了成骨标志物Cbfa-1和骨桥蛋白的诱导。我们的研究结果表明，通过Pit-1的磷酸盐摄取是至关重要的SMC钙化和表型调制，以应对磷酸盐升高。
Vascular calcification is associated with cardiovascular morbidity and mortality. Hyperphosphatemia is an important contributor to vascular calcification. Our previous studies demonstrated that elevated phosphate induces calcification of smooth muscle cells (SMC) in vitro. Inhibition of phosphate transport by phosphonoformic acid blocked phosphate-induced calcification, implicating sodium-dependent phosphate cotransporters in this process. In the present study, we have investigated the role of the type III sodium-dependent phosphate cotransporter, Pit-1, in SMC calcification in vitro. Human SMC stably expressing Pit-1 small interfering double-stranded RNA (SMC-iRNA) were established using a retroviral system. SMC-iRNA had decreased Pit-1 mRNA and protein levels and sodium-dependent phosphate transport activity compared with the control transduced cells (SMC-CT) (2.9 versus 9.78 nmol/mg protein per 30 minutes, respectively). Furthermore, phosphate-induced SMC calcification was significantly inhibited in SMC-iRNA compared with SMC-CT at all time points examined. Overexpression of Pit-1 restored phosphate uptake and phosphate-induced calcification in Pit-1 deficient cells. Mechanistically, although Pit-1-mediated SMC calcification was not associated with apoptosis or cell-derived vesicles, inhibition of phosphate uptake in Pit-1 knockdown cells blocked the induction of the osteogenic markers Cbfa-1 and osteopontin. Our results indicate that phosphate uptake through Pit-1 is essential for SMC calcification and phenotypic modulation in response to elevated phosphate.