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Accumulation of clarithromycin in macrophages infected with Mycobacterium avium
N Mor1, J Vanderkolk, L Heifets
1Department of Medicine, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206.
Abstract:
Clarithromycin is known to accumulate in polymorphonuclear leukocytes, but no accumulation studies with macrophages have been reported. We exposed J774 macrophages, grown for 4-6 days, to clarithromycin 3.0 micrograms/ml for 2 hours. The cells were separated from the extracellular fluid, and the concentration of clarithromycin was determined in an agar diffusion bioassay. The accumulation of clarithromycin was 15.8-fold greater in the cells than it was in the extracellular fluid when the test was performed with noninfected cells, and 17.3-fold greater for cells infected with Mycobacterium avium. However, the ratio was substantially lower, only 3.7 for dead macrophages, suggesting that intracellular accumulation is probably an active process. These data may clarify the nature of the activity of clarithromycin against M. avium in macrophages.
Insights
Clarithromycin accumulates significantly in macrophages, especially when infected with Mycobacterium avium. This intracellular accumulation appears to be an active process, clarifying its therapeutic action.
Area of Science:
- Pharmacology
- Cell Biology
- Immunology
Background:
- Clarithromycin is known to accumulate in polymorphonuclear leukocytes.
- No prior studies investigated clarithromycin accumulation in macrophages.
Purpose of the Study:
- To investigate the intracellular accumulation of clarithromycin in J774 macrophages.
- To determine if Mycobacterium avium infection affects clarithromycin accumulation.
- To explore the mechanism of clarithromycin accumulation in macrophages.
Main Methods:
- J774 macrophages were exposed to clarithromycin (3.0 µg/ml) for 2 hours.
- Clarithromycin concentration was measured in both cells and extracellular fluid using an agar diffusion bioassay.
- Accumulation was assessed in noninfected, Mycobacterium avium-infected, and dead macrophages.
Main Results:
- Clarithromycin accumulated 15.8-fold higher in noninfected macrophages compared to extracellular fluid.
- Accumulation increased to 17.3-fold in Mycobacterium avium-infected macrophages.
- Accumulation was significantly lower (3.7-fold) in dead macrophages, indicating an active process.
Conclusions:
- Intracellular accumulation of clarithromycin in macrophages is likely an active, energy-dependent process.
- This accumulation is enhanced in macrophages infected with Mycobacterium avium.
- Findings may elucidate the mechanism of clarithromycin's activity against Mycobacterium avium within macrophages.