title: High affinity capture and concentration of quinacrine in polymorphonuclear neutrophils via vacuolar ATPase-mediated ion trapping: comparison with other peripheral blood leukocytes and implications for the distribution of cationic drugs.
abstract: Many cationic drugs are concentrated in acidic cell compartments due to low retro-diffusion of the protonated molecule (ion trapping), with an ensuing vacuolar and autophagic cytopathology. In solid tissues, there is evidence that phagocytic cells, e.g., histiocytes, preferentially concentrate cationic drugs. We hypothesized that peripheral blood leukocytes could differentially take up a fluorescent model cation, quinacrine, depending on their phagocytic competence. Quinacrine transport parameters were determined in purified or total leukocyte suspensions at 37 °C. Purified polymorphonuclear leukocytes (PMNLs, essentially neutrophils) exhibited a quinacrine uptake velocity inferior to that of lymphocytes, but a consistently higher affinity (apparent KM 1.1 vs. 6.3 μM, respectively). However, the vacuolar (V)-ATPase inhibitor bafilomycin A1 prevented quinacrine transport or initiated its release in either cell type. PMNLs capture most of the quinacrine added at low concentrations to fresh peripheral blood leukocytes compared with lymphocytes and monocytes (cytofluorometry). Accumulation of the autophagy marker LC3-II occurred rapidly and at low drug concentrations in quinacrine-treated PMNLs (significant at ≥2.5 μM, ≥2 h). Lymphocytes contained more LAMP1 than PMNLs, suggesting that the mass of lysosomes and late endosomes is a determinant of quinacrine uptake Vmax. PMNLs, however, exhibited the highest capacity for pinocytosis (uptake of fluorescent dextran into endosomes). The selectivity of quinacrine distribution in peripheral blood leukocytes may be determined by the collaboration of a non-concentrating plasma membrane transport mechanism, tentatively identified as pinocytosis in PMNLs, with V-ATPase-mediated concentration. Intracellular reservoirs of cationic drugs are a potential source of toxicity (e.g., loss of lysosomal function in phagocytes).
authors.affiliation: Centre de recherche en rhumatologie et immunologie, CHU de Québec, and Department of Microbiology-Infectious Diseases and Immunology, Faculty of Medicine, Laval University, Québec, QC, G1V 4G2 Canada.
authors.forename: Caroline
authors.initials: C
authors.lastname: Roy
authors.forename: Valérie
authors.initials: V
authors.lastname: Gagné
authors.forename: Maria J G
authors.initials: MJ
authors.lastname: Fernandes
authors.forename: François
authors.initials: F
authors.lastname: Marceau
mesh_terms: D001343:Autophagy / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000097:blood / Q000493:pharmacokinetics / Q000494:pharmacology; D006801:Humans; D015151:Immunoblotting; D007700:Kinetics; D007962:Leukocytes / Q000201:enzymology / Q000378:metabolism*; D018942:Macrolides / Q000097:blood / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D009504:Neutrophils / Q000201:enzymology / Q000378:metabolism*; D010873:Pinocytosis / Q000502:physiology; D011796:Quinacrine / Q000097:blood*; D012044:Regression Analysis; D025262:Vacuolar Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000097:blood*
chemical_list: D004791:Enzyme Inhibitors; D018942:Macrolides; C040929:bafilomycin A1; D025262:Vacuolar Proton-Translocating ATPases; D011796:Quinacrine