Related Experiment Videos
The new ketolide HMR3647 accumulates in the azurophil granules of human polymorphonuclear cells
C Miossec-Bartoli1, L Pilatre, P Peyron
1Hoechst Marion Roussel, 93235 Romainville Cedex, France. christine.miossec@hmrag.com
Abstract:
HMR3647 is a semisynthetic representative of a new group of drugs, the ketolides, derived from erythromycin A. Since macrolides have been shown to accumulate in human polymorphonuclear cells (PMNs), we have investigated the ability of the molecule HMR3647 to enter human PMNs as well as other cell types, such as peripheral blood mononuclear cells and cell lines of hematopoietic and nonhematopoietic origin. In these experiments, HMR3647 was compared to erythromycin A, azithromycin, clarithromycin, and roxithromycin. Our results show that HMR3647 is specifically trapped in PMNs, where it is concentrated up to 300 times. In addition, it is poorly released by these cells, 80% of the compound remaining cell associated after 2 h in fresh medium. By contrast, it is poorly internalized and quickly released by the other cell types studied. This differs from the results obtained with the macrolide molecules, which behaved similarly in the different cells studied. In addition, subcellular fractionation of PMNs allowed us to identify the intracellular compartment where HMR3647 was trapped. In PMNs, more than 75% of the molecule was recovered in the azurophil granule fraction. Similarly, in NB4 cells differentiated into PMN-like cells, almost 60% of the molecules accumulated in the azurophil granule fraction. In addition, when HMR3647 was added to disrupted PMNs, 63% accumulated in the azurophil granules. Therefore, this study shows that the ketolide HMR3647 specifically accumulates in PMN azurophil granules, thus favoring its delivery to bacteria phagocytosed in these cells.
Insights
The novel ketolide HMR3647 selectively accumulates in human polymorphonuclear cells (PMNs), concentrating within azurophil granules. This targeted delivery enhances its efficacy against phagocytosed bacteria.
Area of Science:
- Pharmacology
- Cell Biology
- Drug Discovery
Background:
- Macrolide antibiotics are known to accumulate in human polymorphonuclear cells (PMNs).
- Ketolides represent a new class of macrolide-derived antibiotics, with HMR3647 being a key example.
- Understanding drug-cell interactions is crucial for optimizing antibiotic therapy.
Purpose of the Study:
- To investigate the cellular uptake and intracellular localization of the ketolide HMR3647 in human PMNs and other cell types.
- To compare the cellular behavior of HMR3647 with existing macrolides (erythromycin A, azithromycin, clarithromycin, roxithromycin).
- To identify the specific intracellular compartment responsible for HMR3647 accumulation in PMNs.
Main Methods:
- Cellular uptake studies using human PMNs, peripheral blood mononuclear cells, and hematopoietic/non-hematopoietic cell lines.
- Comparison of HMR3647 with four macrolide antibiotics.
- Subcellular fractionation of PMNs to determine intracellular drug localization.
- Experiments with disrupted PMNs to confirm granule association.
Main Results:
- HMR3647 demonstrated specific and significant accumulation in human PMNs, reaching concentrations up to 300 times higher than in other cell types.
- The compound exhibited poor release from PMNs, with 80% remaining cell-associated after 2 hours.
- Over 75% of internalized HMR3647 in PMNs was localized within the azurophil granule fraction, a finding consistent in differentiated NB4 cells and disrupted PMNs.
Conclusions:
- The ketolide HMR3647 exhibits unique cellular accumulation properties, specifically targeting PMN azurophil granules.
- This selective accumulation mechanism suggests enhanced delivery of HMR3647 to bacteria phagocytosed within PMNs.
- HMR3647's distinct intracellular localization differentiates it from traditional macrolides and may contribute to its therapeutic potential.