Cisplatin-induced downregulation of OCTN2 affects carnitine wasting.
Cisplatin-induced downregulation of OCTN2 affects carnitine wasting.
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DOI：
10.1158/1078-0432.ccr-10-1239
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发表时间：
2010-10-01
期刊：
影响因子：
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通讯作者：
Sparreboom A
中科院分区：
文献类型：
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作者：
Lancaster CS;Hu C;Franke RM;Filipski KK;Orwick SJ;Chen Z;Zuo Z;Loos WJ;Sparreboom A
肉碱是线粒体脂肪酸氧化的重要辅助因子，被腔转运蛋白OCTN2(SLC22A5)主动重吸收。由于肾毒性药物顺铂导致人类尿中肉碱的丢失，我们推测顺铂可能会影响OCTN2的功能。用或不用顺铂的小鼠的尿液中测定肉碱和乙酰肉碱的排泄。肉碱在OCT1或OCT2细胞中的转运被评估。用小鼠基因芯片芯片分析顺铂治疗对基因表达的影响，并用qRT-PCR进行验证。在野生型小鼠中，基线时尿肉碱排泄量是缺乏基底侧向顺铂转运体Oct1和Oct2[Oct1/2(−/−)小鼠]的小鼠的约3倍，表明肉碱本身经历了基底侧向摄取进入肾脏。在转基因细胞中证实了OCT2转运肉碱，而不是OCT1转运。我们还发现，顺铂引起野生型小鼠尿中肉碱和乙酰肉碱的排泄增加，但在Oct1/2(−/−)小鼠中没有，这表明顺铂的肾小管转运是这一现象的先决条件。顺铂不直接抑制OCTN_2对肉碱的转运，但下调野生型小鼠肾脏中转录因子PPAR-α的多个靶基因，包括SLC22A5，而OCT1/2(−/−)小鼠不存在。我们的研究表明，Oct1和Oct2在顺铂相关的肉碱稳态紊乱中起着关键作用。我们推测，这种现象是由PPAR-α失活引发的，并导致肉碱穿梭基因的解除调控。
Carnitine is an essential cofactor for mitochondrial fatty acid oxidation that is actively reabsorbed by the luminal transporter Octn2 (Slc22a5). Since the nephrotoxic agent cisplatin causes urinary loss of carnitine in humans, we hypothesized that cisplatin may affect Octn2 function. Excretion of carnitine and acetylcarnitine was measured in urine collected from mice with or without cisplatin administration. The transport of carnitine was assessed in cells that were transfected with OCT1 or OCT2. The effect of cisplatin treatment on gene expression was analyzed using a mouse GeneChip array and validated using qRT-PCR. In wildtype mice, urinary carnitine excretion at baseline was about ~3 fold higher than in mice lacking the basolateral cisplatin transporters Oct1 and Oct2 [Oct1/2(−/−) mice], indicating that carnitine itself undergoes basolateral uptake into the kidney. Transport of carnitine by OCT2, but not OCT1, was confirmed in transfected cells. We also found that cisplatin caused an increase in the urinary excretion of carnitine and acetylcarnitine in wildtype mice but not in Oct1/2(−/−) mice, suggesting that tubular transport of cisplatin is a prerequisite for this phenomenon. Cisplatin did not directly inhibit the transport of carnitine by Octn2, but downregulated multiple target genes of the transcription factor Ppar-α, including Slc22a5, in kidney of wildtype mice that were absent in Oct1/2(−/−) mice. Our study demonstrates a pivotal role of Oct1 and Oct2 in cisplatin-related disturbances in carnitine homeostasis. We postulate that this phenomenon is triggered by deactivation of Ppar-α and leads to deregulation of carnitine-shuttle genes.