1: Antimicrob Agents Chemother.  2004 Aug;48(8):2853-60.  

Cellular pharmacokinetics and pharmacodynamics of the glycopeptide antibiotic
oritavancin (LY333328) in a model of J774 mouse macrophages.

Van Bambeke F, Carryn S, Seral C, Chanteux H, Tyteca D, Mingeot-Leclercq MP,
Tulkens PM.

Unite de Pharmacologie Cellulaire et Moleculaire, Universite Catholique de
Louvain, Brussels, Belgium. vanbambeke@facm.ucl.ac.be

The intracellular pharmacokinetics and pharmacodynamics of oritavancin
(LY333328) were studied in cultured cells. Oritavancin was avidly accumulated by
J774 and THP-1 macrophages and rat fibroblasts and to a lesser extent by LLC-PK1
and Caco-2 cells. In J774 macrophages, the level of accumulation reached a
plateau (at 370-fold the extracellular concentration) within 24 h and was partly
defeated by a rise in serum protein levels. Efflux was incomplete (with a
plateau at two-thirds of the original level at 6 h). In short-term kinetic
studies, oritavancin uptake was linear for up to 4 h (as was the case for
horseradish peroxidase and small latex beads, used as markers of the fluid phase
and adsorptive endocytosis, respectively), which was in contrast to azithromycin
and chloroquine uptake (which accumulate in cells by diffusion and segregation).
The rates of clearance of oritavancin and latex beads were comparable (150 and
120 microl x mg of protein(-1) x h(-1), respectively) and were approximately 200
times higher than that of horseradish peroxidase. Oritavancin accumulation was
partially reduced by monensin but was unaffected by acidic pH (these conditions
abolished chloroquine accumulation). Cell-associated oritavancin was found in
lysosomal fractions after homogenization of J774 macrophages and fractionation
by isopycnic centrifugation. Oritavancin was bactericidal against intracellular
Staphylococcus aureus (phagolysosomal infection) but was unable to control the
intracellular growth of Listeria monocytogenes (cytosolic infection), even
though its cellular concentration largely exceeded the MIC (0.02 mg/liter) and
minimal bactericidal concentration (2 mg/liter). We conclude that oritavancin
enters cells by adsorptive endocytosis (favored by its lipophilic side chain
and/or the presence of three protonatable amines), which drives it to lysosomes,
where it exerts antibiotic activity.

PMID: 15273091 [PubMed - in process]