1: Antimicrob Agents Chemother. 2009 Jun;53(6):2410-6. Epub 2009 Mar 23.

Identification of the efflux transporter of the fluoroquinolone antibiotic
ciprofloxacin in murine macrophages: studies with ciprofloxacin-resistant cells.

Marquez B, Caceres NE, Mingeot-Leclercq MP, Tulkens PM, Van Bambeke F.

Unité de Pharmacologie Cellulaire et Moléculaire, Louvain Drug Research
Institute, UCL 7370 Avenue Mounier 73, B-1200 Brussels, Belgium.

Ciprofloxacin, the most widely used totally synthetic antibiotic, is subject to
active efflux mediated by a MRP-like transporter in wild-type murine J774
macrophages. To identify the transporter among the seven potential Mrps, we used 
cells made resistant to ciprofloxacin obtained by long-term exposure to
increasing drug concentrations (these cells show less ciprofloxacin accumulation 
and provide a protected niche for ciprofloxacin-sensitive intracellular Listeria 
monocytogenes). In the present paper, we first show that ciprofloxacin-resistant 
cells display a faster efflux of ciprofloxacin which is inhibited by gemfibrozil 
(an unspecific MRP inhibitor). Elacridar, at a concentration known to inhibit
P-glycoprotein and breast cancer resistance protein (BCRP), only slightly
increased ciprofloxacin accumulation, with no difference between resistant and
wild-type cells. Analysis at the mRNA (real-time PCR) and protein (Western
blotting) levels revealed an overexpression of Mrp2 and Mrp4. Mrp4 transcripts,
however, were overwhelmingly predominant (45% [wild-type cells] to 95%
[ciprofloxacin-resistant cells] of all Mrp transcripts tested [Mrp1 to Mrp7]).
Silencing of Mrp2 and Mrp4 with specific small interfering RNAs showed that only 
Mrp4 is involved in ciprofloxacin transport in both ciprofloxacin-resistant and
wild-type cells. The study therefore identifies Mrp4 as the most likely
transporter of ciprofloxacin in murine macrophages but leaves open a possible
common upregulation mechanism for both Mrp4 and Mrp2 upon chronic exposure of
eukaryotic cells to this widely used antibiotic.

PMID: 19307362 [PubMed - in process]

Related Links

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