1: Antimicrob Agents Chemother.  2004 Jul;48(7):2673-82.  

Active Efflux of Ciprofloxacin from J774 Macrophages through an MRP-Like

Michot JM, Van Bambeke F, Mingeot-Leclercq MP, Tulkens PM.

UCL 7370 Ave. E. Mounier 73 B-1200 Brussels, Belgium. tulkens@facm.ucl.ac.be

The accumulation and efflux kinetics of ciprofloxacin have been examined by
using murine J774 macrophages. Accumulation (at equilibrium) was increased
(three- to fourfold) (i) when cells were incubated with high extracellular drug
concentrations (typically 200 mg/liter) as opposed to clinically meaningful
concentrations (10 mg/liter or lower), (ii) during ATP- depletion and at acid
pH, and (iii) during coincubation with probenecid, gemfibrozil and the
preferential multidrug resistance-related protein (MRP) inhibitor MK571. All
these conditions were also associated with a marked decrease in ciprofloxacin
efflux (half-lives increased from <2 min in controls to up to 10 min). Monensin
(a proton ionophore), verapamil, and the preferential P-glycoprotein (P-gp)
inhibitor GF120918 had no or only minimal effect, while cyclosporin A, which is
not specific for P-gp but also acts on MRP, had an intermediate effect.
Short-term uptake studies showed that the influence of the modulators on the
apparent drug influx was almost immediate (delay of </=1 min). Cells made
resistant to probenecid and showing a marked overexpression of MRP1 (by Western
blot analysis and confocal microscopy) accumulated ciprofloxacin to almost the
same extent as did control cells, but efflux was inhibited less by probenecid,
gemfibrozil, and MK571. We conclude that ciprofloxacin is subject to
constitutive efflux in J774 macrophages through the activity of an MRP-related
transporter which is probably distinct from MRP1. We also suggest that the
cellular accumulation of ciprofloxacin in wild-type cells is constitutively
impaired at therapeutically meaningful concentrations.

PMID: 15215125 [PubMed - in process]