Clarithromycin Accumulation by Phagocytes and Its Effect on Killing of Aggregatibacter actinomycetemcomitans

• Published in: Journal of periodontology (1970) 2011-03, Vol.82 (3), p.497-504
• Main Authors: Iskandar, Irma, Walters, John D.
• Format: Article
• Language: English
• Subjects: Aggregatibacter actinomycetemcomitans - drug effects; Anti-Bacterial Agents - pharmacokinetics; Anti-Bacterial Agents - pharmacology; Antibacterial agents; Antibiotics. Antiinfectious agents. Antiparasitic agents; Biological and medical sciences; Biological Transport, Active; Clarithromycin - pharmacokinetics; Clarithromycin - pharmacology; Facial bones, jaws, teeth, parodontium: diseases, semeiology; Granulocyte precursor cells; HL-60 Cells - metabolism; HL-60 Cells - microbiology; Humans; Hydrogen-Ion Concentration; Kinetics; macrolides; Medical sciences; neutrophils; Neutrophils - metabolism; Neutrophils - microbiology; Non tumoral diseases; Otorhinolaryngology. Stomatology; periodontitis; Phagocytosis; Pharmacology. Drug treatments; Time Factors
• ISSN: 0022-3492; 1943-3670
• DOI: 10.1902/jop.2010.100221

Background: Clarithromycin inhibits several periodontal pathogens and is concentrated inside gingival fibroblasts and epithelial cells by an active transporter. We hypothesized that polymorphonuclear leukocytes (PMNs) and less mature myeloid cells possess a similar transporter for clarithromycin. It is feasible that clarithromycin accumulation inside PMNs could enhance their ability to kill Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans). Methods: To test the first hypothesis, purified PMNs and cultured HL‐60 cells were incubated with [3H]‐clarithromycin. Clarithromycin transport was assayed by measuring changes in cell‐associated radioactivity over time. The second hypothesis was examined with PMNs loaded by incubation with clarithromycin (5 μg/ml). Opsonized bacteria were incubated at 37°C with control and clarithromycin‐loaded PMNs. Results: Mature human PMNs, HL‐60 cells differentiated into granulocytes, and undifferentiated HL‐60 cells all took up clarithromycin in a saturable manner. The kinetics of uptake by all yielded linear Lineweaver‐Burk plots. HL‐60 granulocytes transported clarithromycin with a Km of ≈250 μg/ml and a Vmax of 473 ng/min/106 cells, which were not significantly different from the values obtained with PMNs. At steady state, clarithromycin levels inside HL‐60 granulocytes and PMNs were 28‐ to 71‐fold higher than extracellular levels. Clarithromycin‐loaded PMNs killed significantly more A. actinomycetemcomitans and achieved shorter half‐times for killing than control PMNs when assayed at a bacteria‐to‐PMN ratio of 100:1 (P