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Azithromycin uptake and intracellular accumulation by Toxoplasma gondii-infected macrophages
J Blais1, D Beauchamp, S Chamberland
1Laboratoire et Service d'Infectiologie, Centre de Recherche du Centre Hospitalier de l'Université Laval, Québec, Canada.
Abstract:
The uptake of azithromycin and erythromycin was measured in RAW 264.7 mouse macrophages infected with Toxoplasma gondii to determine whether the activity of macrolides could be correlated with their degree of host cell penetration. Uptake was expressed as the ratio of the intracellular (I) to the extracellular (E) concentrations. After infection, the intracellular accumulation of macrolides was equivalent to that measured in uninfected cells and azithromycin reached an I/E ratio of 105.8 +/- 8.0 in infected macrophages incubated with 20 mg/L of drug. The release of azithromycin from macrophages previously exposed to the drug was enhanced by exposure to Micrococcus luteus and phorbol myristate acetate but not after infection with T. gondii. Azithromycin accumulates readily and remains inside T. gondii-infected macrophages thereby interfering with the growth of the parasite which was confirmed by growth-inhibition experiments and by electron microscopy.
Insights
Azithromycin and erythromycin macrolides effectively penetrate Toxoplasma gondii-infected macrophages. Azithromycin accumulation within these cells inhibits parasite growth, demonstrating its potential as an anti-toxoplasmosis agent.
Area of Science:
- Pharmacology
- Infectious Diseases
- Cell Biology
Background:
- Macrolides are antibiotics with potential anti-parasitic activity.
- Understanding macrolide penetration into host cells is crucial for drug development.
- Toxoplasma gondii is an opportunistic pathogen that infects macrophages.
Purpose of the Study:
- To determine if macrolide activity correlates with host cell penetration.
- To investigate the uptake and retention of azithromycin and erythromycin in Toxoplasma gondii-infected macrophages.
- To assess the effect of azithromycin on T. gondii growth within macrophages.
Main Methods:
- RAW 264.7 mouse macrophages were infected with T. gondii.
- Macrolide uptake was measured using the intracellular (I) to extracellular (E) concentration ratio.
- Azithromycin release was studied after exposure to Micrococcus luteus and phorbol myristate acetate.
- Parasite growth inhibition was confirmed by growth assays and electron microscopy.
Main Results:
- Intracellular accumulation of macrolides in infected macrophages was similar to uninfected cells.
- Azithromycin achieved a high intracellular to extracellular ratio (105.8 +/- 8.0) in infected macrophages.
- T. gondii infection did not enhance azithromycin release from macrophages.
- Azithromycin accumulation inhibited T. gondii growth within macrophages.
Conclusions:
- Azithromycin readily accumulates and is retained within T. gondii-infected macrophages.
- The intracellular presence of azithromycin interferes with T. gondii parasite growth.
- Azithromycin demonstrates potential for treating toxoplasmosis due to its cellular penetration and anti-parasitic effects.