Inhibition of OCTN2-mediated transport of carnitine by etoposide.
Inhibition of OCTN2-mediated transport of carnitine by etoposide.
复制标题
DOI：
10.1158/1535-7163.mct-11-0980
复制
发表时间：
2012-04
影响因子：
5.7
通讯作者：
Sparreboom A
中科院分区：
文献类型：
--
作者：
Hu C;Lancaster CS;Zuo Z;Hu S;Chen Z;Rubnitz JE;Baker SD;Sparreboom A
OCTN 2是一种双功能转运蛋白，以钠依赖性方式重吸收过滤的肉毒碱，并作为质子反向转运机制将有机阳离子分泌到尿液中。我们假设，通过抗癌药物抑制OCTN 2可以影响肉毒碱的再吸收。使用用人OCTN 2（hOCTN 2）或小鼠Octn 2（mOctn 2）转染的细胞评估抗癌药物对OCTN 2介导的转运抑制。在给药依托泊苷之前和之后，在从小鼠和儿科癌症患者收集的尿液中测量肉毒碱和乙酰肉毒碱的排泄。27种测试药物中的5种（50-100 µM）可抑制hOCTN 2介导的肉毒碱摄入42-85%（P<0.001）。在这些抑制剂中，依托泊苷本身是hOCTN 2和mOctn 2的转运底物。依托泊苷摄取hOCTN 2逆转过量肉毒碱的存在下。这种竞争性抑制机制在计算机分子对接分析中得到证实。此外，依托泊苷抑制肾脏细胞中肉毒碱的跨细胞顶侧至基底侧通量。依托泊苷还与小鼠（~1.5倍）和癌症患者（~2.4倍）中肉毒碱的显著尿液损失相关。总的来说，这些研究结果表明，依托泊苷可以抑制hOCTN 2功能，潜在地干扰肉毒碱稳态，并且这种现象可以导致治疗相关的毒性。
OCTN2 is a bifunctional transporter that reabsorbs filtered carnitine in a sodium dependent manner and secretes organic cations into urine as a proton antiport mechanism. We hypothesized that inhibition of OCTN2 by anticancer drugs can influence carnitine resorption. OCTN2-mediated transport inhibition by anticancer drugs was assessed using cells transfected with human OCTN2 (hOCTN2) or mouse Octn2 (mOctn2). Excretion of carnitine and acetylcarnitine was measured in urine collected from mice and pediatric cancer patients before and after administration of etoposide. Five of 27 tested drugs (50–100 µM) inhibited hOCTN2-mediated carnitine uptake by 42–85% (P<0.001). Of these inhibitors, etoposide was itself a transported substrate of hOCTN2 and mOctn2. Etoposide uptake by hOCTN2 was reversed in the presence of excess carnitine. This competitive inhibitory mechanism was confirmed in an in silico molecular docking analysis. In addition, etoposide inhibited the transcellular apical-to-basolateral flux of carnitine in kidney cells. Etoposide was also associated with a significant urinary loss of carnitine in mice (~1.5-fold) and cancer patients (~2.4-fold). Collectively, these findings indicate that etoposide can inhibit hOCTN2 function, potentially disturb carnitine homeostasis, and that this phenomenon can contribute to treatment-related toxicities.