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Antimicrobial Agents and Chemotherapy, October 2000, p. 2689-2692, Vol. 44, No. 10
Department of Pharmacology, University of
Cape Town Medical School, Observatory 7925, South Africa
Received 28 January 2000/Returned for modification 10 May
2000/Accepted 5 July 2000
Since the discovery of the chloroquine (CQ) resistance reversal
properties of several different, structurally unrelated classes of
compounds, including antidepressants, the way is again open to employ
the aminoquinoline drugs to combat malaria effectively. In this study,
CQ sensitivity was restored to varying extents in vitro in the
CQ-resistant Plasmodium falciparum strain RSA11 by using
the antidepressants amitriptyline, citalopram, oxaprotiline, and
nomifensine. The 50% inhibitory concentrations (IC50) of
CQ were reduced from 360 to as low as 11 nM when antidepressants were
present. These particular antidepressants are highly specific for
blocking the ATP-binding cassette transport protein-mediated reuptake
of different neurotransmitters at the synaptic level. This study was
aimed at determining the extent to which the neurotransmitter reuptake-blocking properties of these antidepressants play a role in
the reversal process. None of the compounds or CQ-antidepressant combinations tested had innate antimalarial activity. No
chemosensitizer or combination showed an increased CQ accumulation or
significant shift in the IC50 in the CQ-sensitive clone
D10. Of the compounds tested, citalopram, a highly specific serotonin
reuptake blocker, produced the largest shift observed in the
IC50 for the resistant isolate RSA11. No particular class
of antidepressant was found to be better than any other at restoring CQ
sensitivity. We conclude that the resistance-reversing properties of
these compounds do not correlate with their activities as reuptake blockers.
0066-4804/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Role of the Neurotransmitter Reuptake-Blocking
Activity of Antidepressants in Reversing Chloroquine Resistance In
Vitro in Plasmodium falciparum
*
Corresponding author. Mailing address: Department of
Pharmacology, University of Cape Town Medical School, Anzio Rd.,
Observatory 7925, South Africa. Phone: 27 21 406-6289. Fax: 27 21 448-1989. E-mail: psmith{at}uctgsh1.uct.ac.za.
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