title: Human organic cation transporters 1 (SLC22A1), 2 (SLC22A2), and 3 (SLC22A3) as disposition pathways for fluoroquinolone antimicrobials.
abstract: Fluoroquinolones (FQs) are important antimicrobials that exhibit activity against a wide range of bacterial pathogens and excellent tissue permeation. They exist as charged molecules in biological fluids, and thus, their disposition depends heavily on active transport and facilitative diffusion. A recent review of the clinical literature indicated that tubular secretion and reabsorption are major determinants of their half-life in plasma, efficacy, and drug-drug interactions. In particular, reported in vivo interactions between FQs and cationic drugs affecting renal clearance implicated organic cation transporters (OCTs). In this study, 13 FQs, ciprofloxacin, enoxacin, fleroxacin, gatifloxacin, levofloxacin, lomefloxacin, moxifloxacin, norfloxacin, ofloxacin, pefloxacin, prulifloxacin, rufloxacin, and sparfloxacin, were screened for their ability to inhibit transport activity of human OCT1 (hOCT1) (SLC22A1), hOCT2 (SLC22A2), and hOCT3 (SLC22A3). All, with the exception of enoxacin, significantly inhibited hOCT1-mediated uptake under initial test conditions. None of the FQs inhibited hOCT2, and only moxifloxacin inhibited hOCT3 (~30%), even at a 1,000-fold excess. Gatifloxacin, moxifloxacin, prulifloxacin, and sparfloxacin were determined to be competitive inhibitors of hOCT1. Inhibition constants (K(i)) were estimated to be 250 ± 18 μM, 161 ± 19 μM, 136 ± 33 μM, and 94 ± 8 μM, respectively. Moxifloxacin competitively inhibited hOCT3-mediated uptake, with a K(i) value of 1,598 ± 146 μM. Despite expression in enterocytes (luminal), hepatocytes (sinusoidal), and proximal tubule cells (basolateral), hOCT3 does not appear to contribute significantly to FQ disposition. However, hOCT1 in the sinusoidal membrane of hepatocytes, and potentially the basolateral membrane of proximal tubule cells, is likely to play a role in the disposition of these antimicrobial agents.
authors.affiliation: Department of Pharmaceutics, Virginia Commonwealth University, Richmond, Virginia, USA.
authors.forename: Aditi
authors.initials: A
authors.lastname: Mulgaonkar
authors.forename: Jürgen
authors.initials: J
authors.lastname: Venitz
authors.forename: Dirk
authors.initials: D
authors.lastname: Gründemann
authors.forename: Douglas H
authors.initials: DH
authors.lastname: Sweet
mesh_terms: D000890:Anti-Infective Agents / Q000378:metabolism*; D001693:Biological Transport, Active; D004347:Drug Interactions; D020895:Enterocytes / Q000378:metabolism; D024841:Fluoroquinolones / Q000378:metabolism*; D057809:HEK293 Cells; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D027701:Organic Cation Transport Proteins / Q000378:metabolism*; D027702:Organic Cation Transporter 1 / Q000378:metabolism*; D000075102:Organic Cation Transporter 2; D000099254:Organic Cation Transporter 3
chemical_list: D000890:Anti-Infective Agents; D024841:Fluoroquinolones; D027701:Organic Cation Transport Proteins; D027702:Organic Cation Transporter 1; D000075102:Organic Cation Transporter 2; D000099254:Organic Cation Transporter 3; C491013:SLC22A2 protein, human
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