Beta‑2 Adrenergic Agonists Are Substrates and Inhibitors of Human Organic Cation Transporter 1

• Published in: Molecular pharmaceutics 2015-08, Vol.12 (8), p.2633-2641
• Main Authors: Salomon, Johanna J, Hagos, Yohannes, Petzke, Sören, Kühne, Annett, Gausterer, Julia C, Hosoya, Ken-ichi, Ehrhardt, Carsten
• Format: Article
• Language: English
• Subjects: Adrenergic beta-2 Receptor Agonists - metabolism; Adrenergic beta-2 Receptor Agonists - pharmacokinetics; Adrenergic beta-2 Receptor Agonists - pharmacology; Albuterol - metabolism; Albuterol - pharmacokinetics; Albuterol - pharmacology; Biological Transport; Cells, Cultured; Epithelial Cells - drug effects; Epithelial Cells - metabolism; Formoterol Fumarate - metabolism; Formoterol Fumarate - pharmacokinetics; Formoterol Fumarate - pharmacology; HEK293 Cells; Humans; Organic Cation Transporter 1 - antagonists & inhibitors; Organic Cation Transporter 1 - genetics; Organic Cation Transporter 1 - metabolism; Respiratory Mucosa - drug effects; Respiratory Mucosa - metabolism; Respiratory Tract Absorption; Salmeterol Xinafoate - metabolism; Salmeterol Xinafoate - pharmacokinetics; Salmeterol Xinafoate - pharmacology; Transfection
• ISSN: 1543-8384; 1543-8392
• DOI: 10.1021/mp500854e

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.