Verhulst Anja, Sun Shuting, McKenna Charles E, D'Haese Patrick C
Laboratory of Pathophysiology, University of Antwerp, Antwerp, Belgium.
Department of Chemistry, University of Southern California, Los Angeles, California, United States of America.
PLoS One. 2015 Mar 10;10(3):e0121861. doi: 10.1371/journal.pone.0121861. eCollection 2015.
Zoledronic acid, a highly potent nitrogen-containing bisphosphonate used for the treatment of pathological bone loss, is excreted unmetabolized via the kidney if not bound to the bone. In cancer patients receiving high doses of the compound renal excretion may be associated with acute tubular necrosis. The question of how zoledronic acid is internalized by renal tubular cells has not been answered until now. In the current work, using a primary human tubular cell culture system, the pathway of cellular uptake of zoledronic acid (fluorescently/radiolabeled) and its cytotoxicity were investigated. Previous studies in our laboratory have shown that this primary cell culture model consistently mimics the physiological characteristics of molecular uptake/transport of the epithelium in vivo. Zoledronic acid was found to be taken up by tubular cells via fluid-phase-endocytosis (from apical and basolateral side) as evidenced by its co-localization with dextran. Cellular uptake and the resulting intracellular level was twice as high from the apical side compared to the basolateral side. Furthermore, the intracellular zoledronic acid level was found to be dependent on the administered concentration and not saturable. Cytotoxic effects however, were only seen at higher administration doses and/or after longer incubation times. Although zoledronic acid is taken up by tubular cells, no net tubular transport could be measured. It is concluded that fluid-phase-endocytosis of zoledronic acid and cellular accumulation at high doses may be responsible for the acute tubular necrosis observed in some cancer patients receiving high doses of the compound.
唑来膦酸是一种用于治疗病理性骨质流失的高效含氮双膦酸盐，如果未与骨骼结合，它会未经代谢通过肾脏排泄。在接受高剂量该化合物的癌症患者中，肾脏排泄可能与急性肾小管坏死有关。到目前为止，唑来膦酸如何被肾小管细胞内化的问题尚未得到解答。在当前的研究中，使用原代人肾小管细胞培养系统，研究了唑来膦酸（荧光/放射性标记）的细胞摄取途径及其细胞毒性。我们实验室之前的研究表明，这种原代细胞培养模型始终如一地模拟了体内上皮细胞分子摄取/转运的生理特征。发现唑来膦酸通过液相内吞作用（从顶端和基底外侧）被肾小管细胞摄取，这一点通过它与葡聚糖的共定位得到证明。与基底外侧相比，从顶端摄取的细胞摄取量和由此产生的细胞内水平高出两倍。此外，发现细胞内唑来膦酸水平取决于给药浓度且不饱和。然而，细胞毒性仅在较高给药剂量和/或较长孵育时间后才出现。尽管唑来膦酸被肾小管细胞摄取，但未检测到净肾小管转运。得出的结论是，唑来膦酸的液相内吞作用和高剂量下的细胞蓄积可能是一些接受高剂量该化合物的癌症患者中观察到的急性肾小管坏死的原因。
