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Is the uptake of pefloxacin in human blood monocytes a simple diffusion process?
1Centre Hospitalier Lyon Sud, Service de Biochimie, Pierre Bénite, France.
Abstract:
Effective therapy of infections caused by facultative intracellular micro-organisms, which persist after ingestion by mononuclear phagocytic cells, requires antibiotics which inactivate these intraphagocytic bacteria. A previous study demonstrated that intracellular concentrations of normethylpefloxacin, Ci, were the result of simple diffusion and an active efflux involving organic anion transporters. In our work, we studied pefloxacin transport in human monocytes. A kinetic approach was followed to establish the processes involved. Extracellular concentrations, Ce, corresponding to in-vivo pharmacological levels of the drug were used. Uptake of the antibiotic was assessed principally by HPLC. Pefloxacin was accumulated by the cells (Ci/Ce = 3). The uptake was rapid, non saturable, reversible and temperature dependent. At 4 degrees C, the Ci/Ce was equal to 1. At high temperatures, an active and initial process appeared that was not visible at lower temperatures and disappeared in presence of energetic metabolism inhibitor: At 42 degrees C, NaCN and 2.4 DNP (1 mM) reduced the initial transport but they had no significant effect on the subsequent curve.
Insights
Pefloxacin uptake by human monocytes involves active transport at higher temperatures, indicating a complex cellular mechanism for this antibiotic. This finding is crucial for understanding effective intracellular bacterial infection therapies.
Area of Science:
- Pharmacology
- Cell Biology
- Microbiology
Background:
- Effective treatment of intracellular bacterial infections requires antibiotics that target bacteria within host cells.
- Previous research suggested pefloxacin intracellular accumulation involves diffusion and active efflux via organic anion transporters.
Purpose of the Study:
- To investigate the transport mechanisms of pefloxacin in human monocytes.
- To characterize the kinetics of pefloxacin uptake and intracellular accumulation.
Main Methods:
- Human monocytes were used to study pefloxacin transport.
- A kinetic approach with varying extracellular concentrations (Ce) was employed.
- High-performance liquid chromatography (HPLC) was used to measure intracellular pefloxacin concentrations (Ci).
Main Results:
- Pefloxacin accumulated within monocytes, with an intracellular to extracellular ratio (Ci/Ce) of 3.
- Uptake was rapid, non-saturable, reversible, and temperature-dependent.
- An active transport process was observed at higher temperatures (e.g., 42°C), which was inhibited by metabolic inhibitors (NaCN, 2.4 DNP).
Conclusions:
- Pefloxacin transport into human monocytes is a complex process involving both passive diffusion and active mechanisms.
- Temperature and cellular energy metabolism significantly influence pefloxacin uptake.
- Understanding these transport dynamics is vital for optimizing antibiotic therapy against intracellular pathogens.