Salomon Johanna J, Hagos Yohannes, Petzke Sören, Kühne Annett, Gausterer Julia C, Hosoya Ken-ichi, Ehrhardt Carsten
†School of Pharmacy and Pharmaceutical Sciences and Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin 2, Ireland.
‡Zentrum für Physiologie und Pathophysiologie, Georg-August-Universität, 37073 Göttingen, Germany.
Mol Pharm. 2015 Aug 3;12(8):2633-41. doi: 10.1021/mp500854e. Epub 2015 Mar 18.
Beta-2-adrenergic agonists are first line therapeutics in the treatment of asthma and chronic obstructive pulmonary disease (COPD). Upon inhalation, bronchodilation is achieved after binding to β2-receptors, which are primarily localized on airway smooth muscle cells. Given that β2-adrenergic agonists chemically are bases, they carry net positive charge at physiologic pH value in the lungs (i.e., pH 7.4). Here, we studied whether β2-agonists interact with organic cation transporters (OCT) and whether this interaction exerted an influence on their passage across the respiratory epithelium to their target receptors. [14C]-TEA uptake into proximal (i.e., Calu-3) and distal (i.e., A549 and NCI-H441) lung epithelial cells was significantly reduced in the presence of salbutamol sulfate, formoterol fumarate, and salmeterol xinafoate in vitro. Expression of all five members of the OCT/N family has been confirmed in human pulmonary epithelial cells in situ and in vitro, which makes the identification of the transporter(s) responsible for the β2-agonist interaction challenging. Thus, additional experiments were carried out in HEK-293 cells transfected with hOCT1-3. The most pronounced inhibition of organic cation uptake by β2-agonists was observed in hOCT1 overexpressing HEK-293 cells. hOCT3 transfected HEK-293 cells were affected to a lesser extent, and in hOCT2 transfectants only marginal inhibition of organic cation uptake by β2-agonists was observed. Bidirectional transport studies across confluent NCI-H441 cell monolayers revealed a net absorptive transport of [3H]-salbutamol, which was sensitive to inhibition by the OCT1 modulator, verapamil. Accordingly, salbutamol uptake into hOCT1 overexpressing HEK-293 cells was time- and concentration-dependent and could be completely blocked by decynium-22. Taken together, our data suggest that β2-agonists are specific substrates and inhibitors of OCT1 in human respiratory epithelial cells and that this transporter might play a role in the pulmonary disposition of drugs of this class.
β2肾上腺素能激动剂是治疗哮喘和慢性阻塞性肺疾病（COPD）的一线药物。吸入后，与主要位于气道平滑肌细胞上的β2受体结合后可实现支气管扩张。鉴于β2肾上腺素能激动剂在化学上属于碱类，它们在肺部生理pH值（即pH 7.4）下带净正电荷。在此，我们研究了β2激动剂是否与有机阳离子转运体（OCT）相互作用，以及这种相互作用是否会影响它们穿过呼吸道上皮到达其靶受体的过程。在体外，当存在硫酸沙丁胺醇、富马酸福莫特罗和昔萘酸沙美特罗时，[14C] -TEA进入近端（即Calu-3）和远端（即A549和NCI-H441）肺上皮细胞的摄取显著减少。OCT/N家族的所有五个成员在人肺上皮细胞原位和体外均已得到证实，这使得确定负责β2激动剂相互作用的转运体具有挑战性。因此，在用hOCT1 - 3转染的HEK - 293细胞中进行了额外的实验。在过表达hOCT1的HEK - 293细胞中观察到β2激动剂对有机阳离子摄取的抑制最为明显。hOCT3转染的HEK - 293细胞受到的影响较小，而在hOCT2转染细胞中仅观察到β2激动剂对有机阳离子摄取的轻微抑制。跨汇合的NCI - H441细胞单层的双向转运研究显示[3H] - 沙丁胺醇的净吸收转运，其对OCT1调节剂维拉帕米的抑制敏感。因此，沙丁胺醇进入过表达hOCT1的HEK - 293细胞的摄取是时间和浓度依赖性的，并且可以被癸鎓-22完全阻断。综上所述，我们的数据表明β2激动剂是人类呼吸道上皮细胞中OCT1的特异性底物和抑制剂，并且该转运体可能在这类药物的肺部处置中发挥作用。
