Yu Shuang-Shuang, Jiang Li-Rong, Ling Yan, Qian Zhong-Ming, Zhou Yu-Fu, Li Juan, Ke Ya
Laboratory of Neuropharmacology, Fudan University School of Pharmacy Pudong, China.
School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong Hong Kong, Hong Kong.
Front Pharmacol. 2017 Feb 13;8:60. doi: 10.3389/fphar.2017.00060. eCollection 2017.
Nifedipine was reported to enhance urinary iron excretion in iron overloaded mice. However, it remains unknown how nifedipine stimulates urinary iron excretion in the kidney. We speculated that nifedipine might inhibit the TfR1/ DMT1 (transferrin receptor 1/divalent metal transporter1)-mediated iron uptake by proximal tubule cells in addition to blocking L-type Ca2+ channels, leading to an increase in iron in lumen-fluid and then urinary iron excretion. To test this hypothesis, we investigated the effects of nifedipine on iron content and expression of TfR1, DMT1 and ferroportin1 (Fpn1) in WKPT-0293 Cl.2 cells of the S1 segment of the proximal tubule in rats, using a graphite furnace atomic absorption spectrophotometer and Western blot analysis, respectively. We demonstrated for the first time that nifedipine significantly enhanced iron content as well as TfR1 and DMT1 expression and had no effect on Fpn1 levels in the cells. We also found that ferric ammonium citrate decreased TfR1 levels, increased Fpn1 expression and had no effect on DMT1 content, while co-treatment with nifedipine and FAC increase TfR1 and DMT1 expression and also had no effect on Fpn1 levels. These findings suggest that the nifedipine-induced increase in cell iron may mainly be due to the corresponding increase in TfR1 and DMT1 expression and also imply that the effects of nifedipine on iron transport in proximal tubule cells can not explain the increase in urinary iron excretion.
据报道，硝苯地平可促进铁过载小鼠的尿铁排泄。然而，硝苯地平如何刺激肾脏尿铁排泄仍不清楚。我们推测，硝苯地平除了阻断L型钙通道外，可能还抑制近端小管细胞中TfR1/DMT1（转铁蛋白受体1/二价金属转运体1）介导的铁摄取，导致管腔液中铁含量增加，进而使尿铁排泄增加。为验证这一假设，我们分别使用石墨炉原子吸收分光光度计和蛋白质免疫印迹分析，研究了硝苯地平对大鼠近端小管S1段WKPT-0293 Cl.2细胞中铁含量以及TfR1、DMT1和铁转运蛋白1（Fpn1）表达的影响。我们首次证明，硝苯地平显著提高了细胞内铁含量以及TfR1和DMT1的表达，而对Fpn1水平无影响。我们还发现，柠檬酸铁铵降低了TfR1水平，增加了Fpn1表达，而对DMT1含量无影响，同时硝苯地平和柠檬酸铁铵共同处理增加了TfR1和DMT1表达，对Fpn1水平也无影响。这些发现表明，硝苯地平诱导的细胞内铁增加可能主要归因于TfR1和DMT1表达的相应增加，也意味着硝苯地平对近端小管细胞铁转运的影响无法解释尿铁排泄的增加。
