Abstract
The antiprotozoal agent quinacrine is a lipophilic cationic drug highly distributed to tissues. It has been used in the present experiments to examine whether the vacuolar and autophagic cytopathology induced by organic amines is independent from the therapeutic class. Furthermore, we tested the presence of the concentrated cationic drug itself in the enlarged vacuoles by exploiting the intense green fluorescence of quinacrine. Finally, the influence of lipophilicity on the apparent affinity of amine pseudotransport has been addressed by comparing quinacrine to another substituted triethylamine, procainamide. Quinacrine was concentration-dependently taken up by human smooth muscle cells (cytosolic granular-vacuolar morphology at and above 25 nM; in cell extracts, uptake nearly maximal in 2 h, apparent Km of 8.7 μM). The vacuolar (V)-ATPase inhibitor bafilomycin A1 prevented quinacrine uptake by cells or released the cell-associated drug in preloaded cells. The lipidated (II) form of microtubule-associated protein light chain 3 accumulated at and above a quinacrine concentration of 2.5 μM (4 h), indicating the conserved macroautophagic nature of the vacuolar cytopathology, although vacuole size was modest. The enlarged vacuoles containing quinacrine excluded cherry fluorescent protein; many vacuoles were lined with cherry fluorescent protein-conjugated Rab7, a GTPase associated with late endosomes/lysosomes. Taken together, these results are compatible with the transition of quinacrine-concentrating vacuoles toward an autophagolysosome identity. Quinacrine is concentrated in cells via V-ATPase-mediated ion trapping with an apparent affinity ∼500-fold higher than that of the less lipophilic drug procainamide, and, despite the small size of ensuing vacuoles, the macroautophagic signature of this cytopathology was observed.
Footnotes
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This study was supported by the Canadian Institutes of Health Research [Grant MOP-74448]; Canada Graduate Scholarships Doctoral Award (to G.M.); and Fonds de la Recherche en Santé du Québec, QC, Canada (Studentship Award to M.-T.B.).
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Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
doi:10.1124/dmd.109.028480
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- V
- vacuolar
- LC3
- microtubule-associated protein light chain 3
- cherryFP
- cherry fluorescent protein
- OCT
- organic cation transporter
- FR 167356
- 2,6-dichloro-N-[3-(1-hydroxy-1-methylethyl)-2-methyl-7-benzofuranyl] benzamide.
- Received May 14, 2009.
- Accepted September 18, 2009.
- Copyright © 2009 by The American Society for Pharmacology and Experimental Therapeutics
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