Kawami Masashi, Miyamoto Mioka, Yumoto Ryoko, Takano Mikihisa
Department of Pharmaceutics and Therapeutics, Graduate School of Biomedical & Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
Department of Pharmaceutics and Therapeutics, Graduate School of Biomedical & Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734-8553, Japan.
Drug Metab Pharmacokinet. 2015 Aug;30(4):276-81. doi: 10.1016/j.dmpk.2015.04.005. Epub 2015 May 16.
Methotrexate (MTX), a drug used for the treatment of certain cancers as well as rheumatoid arthritis, sometimes induces serious interstitial lung injury. Although lung toxicity of MTX is related to its accumulation, the information concerning MTX transport in the lungs is lacking. In this study, we investigated the mechanisms underlying MTX influx into human alveolar epithelial cell line A549. MTX influx into A549 cells was time-, pH-, and temperature-dependent and showed saturation kinetics. The influx was inhibited by folic acid with IC50 values of 256.1 μM at pH 7.4 and 1.6 μM at pH 5.5, indicating that the mechanisms underlying MTX influx would be different at these pHs. We then examined the role of two folate transporters in MTX influx, reduced folate carrier (RFC) and proton-coupled folate transporter (PCFT). The expression of RFC and PCFT mRNAs in A549 cells was confirmed by reverse transcription polymerase chain reaction. In addition, MTX influx was inhibited by thiamine monophosphate, an RFC inhibitor, at pH 7.4, and by sulfasalazine, a PCFT inhibitor, at pH 5.5. These results indicated that RFC and PCFT are predominantly involved in MTX influx into A549 cells at pH 7.4 and pH 5.5, respectively.
甲氨蝶呤（MTX）是一种用于治疗某些癌症以及类风湿性关节炎的药物，有时会引发严重的间质性肺损伤。尽管MTX的肺毒性与其蓄积有关，但关于MTX在肺中的转运信息却很缺乏。在本研究中，我们调查了MTX流入人肺泡上皮细胞系A549的潜在机制。MTX流入A549细胞具有时间依赖性、pH依赖性和温度依赖性，并呈现出饱和动力学。在pH 7.4时，叶酸对该流入的抑制作用的半数抑制浓度（IC50）值为256.1 μM，在pH 5.5时为1.6 μM，这表明在这些pH值下MTX流入的潜在机制会有所不同。然后我们研究了两种叶酸转运体，即还原型叶酸载体（RFC）和质子偶联叶酸转运体（PCFT）在MTX流入中的作用。通过逆转录聚合酶链反应证实了A549细胞中RFC和PCFT mRNA的表达。此外，在pH 7.4时，MTX的流入受到RFC抑制剂磷酸硫胺素的抑制，在pH 5.5时受到PCFT抑制剂柳氮磺胺吡啶的抑制。这些结果表明，RFC和PCFT分别在pH 7.4和pH 5.5时主要参与MTX流入A549细胞的过程。
