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Oscanoa TJ, Romero-Ortuno R, Carvajal A, Savarino A. A pharmacological perspective of chloroquine in SARS-CoV-2 infection: An old drug for the fight against a new coronavirus? Int J Antimicrob Agents 2020; 56:106078. [PMID: 32629115 PMCID: PMC7334645 DOI: 10.1016/j.ijantimicag.2020.106078] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 06/24/2020] [Accepted: 06/28/2020] [Indexed: 02/06/2023]
Abstract
The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is having serious consequences on health and the economy worldwide. All evidence-based treatment strategies need to be considered to combat this new virus. Drugs need to be considered on scientific grounds of efficacy, safety and cost. Chloroquine (CQ) and hydroxychloroquine (HCQ) are old drugs used in the treatment of malaria. Moreover, their antiviral properties have been previously studied, including against coronaviruses, where evidence of efficacy has been found. In the current race against time triggered by the COVID-19 pandemic, the search for new antivirals is very important. However, consideration should be given to old drugs with known anti-coronavirus activity, such as CQ and HCQ. These could be integrated into current treatment strategies while novel treatments are awaited, also in light of the fact that they display an anticoagulant effect that facilitates the activity of low-molecular-weight heparin, aimed at preventing acute respiratory distress syndrome (ARDS)-associated thrombotic events. The safety of CQ and HCQ has been studied for over 50 years, however recently published data raise concerns for cardiac toxicity of CQ/HCQ in patients with COVID-19. This review also re-examines the real information provided by some of the published alarming reports, although concluding that cardiac toxicity should in any case be stringently monitored in patients receiving CQ/HCQ.
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Affiliation(s)
- Teodoro J Oscanoa
- Department of Pharmacology, Facultad de Medicina, Universidad Nacional Mayor de San Marcos, Lima, Peru, and Drug Safety Research Center, Facultad de Medicina Humana, Universidad de San Martín de Porres, Hospital Almenara, ESSALUD, Lima, Peru.
| | - Roman Romero-Ortuno
- Discipline of Medical Gerontology, Mercer's Institute for Successful Ageing, St James's Hospital, Dublin, Ireland, and Global Brain Health Institute, Trinity College Dublin, Dublin, Ireland
| | - Alfonso Carvajal
- Centro de Estudios sobre la Seguridad de los Medicamentos (CESME), Universidad de Valladolid, Valladolid, Spain
| | - Andrea Savarino
- Department of Infectious Diseases, Istituto Superiore di Sanità, Rome, Italy
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Reiling SJ, Rohrbach P. Uptake of a fluorescently tagged chloroquine analogue is reduced in CQ-resistant compared to CQ-sensitive Plasmodium falciparum parasites. Malar J 2019; 18:342. [PMID: 31590674 PMCID: PMC6781371 DOI: 10.1186/s12936-019-2980-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 09/28/2019] [Indexed: 11/11/2022] Open
Abstract
Background Chloroquine (CQ) was the drug of choice for decades in the treatment of falciparum malaria until resistance emerged. CQ is suggested to accumulate in the parasite’s digestive vacuole (DV), where it unfolds its anti-malarial properties. Discrepancies of CQ accumulation in CQ-sensitive (CQS) and CQ-resistant (CQR) strains are thought to play a significant role in drug susceptibility. Analysis of CQ transport and intracellular localization using a fluorescently tagged CQ analogue could provide much needed information to distinguish susceptible from resistant parasite strains. The fluorescently tagged CQ analogue LynxTag-CQ™GREEN (CQGREEN) is commercially available and was assessed for its suitability. Methods IC50 values were determined for both CQ and CQGREEN in two CQS and two CQR Plasmodium falciparum strains. Buffer solutions with varying pH were used to determine pH-dependent localization of CQGREEN in infected red blood cells. Before CQS or CQR parasites were exposed to different pH buffers, they were pre-loaded with varying concentrations of CQGREEN for up to 7 h. Intracellular accumulation was analysed using live cell confocal microscopy. CQGREEN uptake rates were determined for the cytosol and DV in the presence and absence of verapamil. Results In CQS strains, twofold higher IC50 values were determined for the CQGREEN analogue compared to CQ. No significant differences in IC50 values were observed in CQR strains. Addition of verapamil reversed drug resistance of CQR strains to both CQ and CQGREEN. Live cell imaging revealed that CQGREEN fluorescence was mainly seen in the cytosol of most parasites, independent of the concentration used. Incubation periods of up to 7 h did not influence intracellular localization of CQGREEN. Nevertheless, CQGREEN uptake rates in CQR strains were reduced by 50% compared to CQS strains. Conclusion Although fluorescence of CQGREEN was mainly seen in the cytosol of parasites, IC50 assays showed comparable efficacy of CQGREEN and CQ in parasite killing of CQS and CQR strains. Reduced uptake rates of CQGREEN in CQR strains compared to CQS strains indicate parasite-specific responses to CQGREEN exposure. The data contains valuable information when CQGREEN is used as an analogue for CQ.
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Affiliation(s)
- Sarah J Reiling
- Institute of Parasitology, McGill University, Ste. Anne de Bellevue, Montreal, QC, H9X-3V9, Canada
| | - Petra Rohrbach
- Institute of Parasitology, McGill University, Ste. Anne de Bellevue, Montreal, QC, H9X-3V9, Canada.
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Woodland JG, Hunter R, Smith PJ, Egan TJ. Chemical Proteomics and Super-resolution Imaging Reveal That Chloroquine Interacts with Plasmodium falciparum Multidrug Resistance-Associated Protein and Lipids. ACS Chem Biol 2018; 13:2939-2948. [PMID: 30208272 DOI: 10.1021/acschembio.8b00583] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
It is well established that chloroquine, a quinoline antimalarial, inhibits hemozoin formation in the malaria parasite. Counterintuitively, this archetypal antimalarial is also used in the treatment of diseases in which hemozoin biocrystallization does not play a role. Hence, we decided to investigate whether chloroquine possesses binding targets other than Fe(III) protoporphyrin IX in blood stage Plasmodium falciparum parasites and whether these are related to sites of accumulation within the parasite other than the digestive vacuole. A 7-nitrobenz-2-oxa-1,3-diazole (NBD)-labeled fluorescent derivative of chloroquine, especially sensitive to regions outside the digestive vacuole and retaining the antiplasmodial pharmacophore, was synthesized to investigate subcellular localization in the parasite. Super-resolution microscopy revealed association with membranes including the parasite plasma membrane, the endoplasmic reticulum, and possibly also the mitochondrion. A drug-labeled affinity matrix was then prepared to capture protein binding targets of chloroquine. SDS-PAGE revealed a single prominent band between 200 and 250 kDa from the membrane-associated fraction. Subsequent proteomic analysis revealed that this band corresponded to P. falciparum multidrug resistance-associated protein (PfMRP1). Intrigued by this finding, we demonstrated pull-down of PfMRP1 by matrices labeled with Cinchona alkaloids quinine and quinidine. While PfMRP1 has been implicated in resistance to quinolines and other antimalarials, this is the first time that these drugs have been found to bind directly to this protein. Based on previous reports, PfMRP1, the only prominent protein found to bind to quinolines in this work, is likely to modulate the activity of these antimalarials in P. falciparum rather than act as a drug target.
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Affiliation(s)
- John G. Woodland
- Department of Chemistry, University of Cape Town, Private Bag, Rondebosch, Cape Town 7701, South Africa
| | - Roger Hunter
- Department of Chemistry, University of Cape Town, Private Bag, Rondebosch, Cape Town 7701, South Africa
| | | | - Timothy J. Egan
- Department of Chemistry, University of Cape Town, Private Bag, Rondebosch, Cape Town 7701, South Africa
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Reiling SJ, Krohne G, Friedrich O, Geary TG, Rohrbach P. Chloroquine exposure triggers distinct cellular responses in sensitive versus resistant Plasmodium falciparum parasites. Sci Rep 2018; 8:11137. [PMID: 30042399 PMCID: PMC6057915 DOI: 10.1038/s41598-018-29422-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 07/06/2018] [Indexed: 11/25/2022] Open
Abstract
Chloroquine (CQ) treatment failure in Plasmodium falciparum parasites has been documented for decades, but the pharmacological explanation of this phenotype is not fully understood. Current concepts attribute CQ resistance to reduced accumulation of the drug at a given external CQ concentration ([CQ]ex) in resistant compared to sensitive parasites. The implication of this explanation is that the mechanisms of CQ-induced toxicity in resistant and sensitive strains are similar once lethal internal concentrations have been reached. To test this hypothesis, we investigated the mechanism of CQ-induced toxicity in CQ-sensitive (CQS) versus CQ-resistant (CQR) parasites by analyzing the time-course of cellular responses in these strains after exposure to varying [CQ]ex as determined in 72 h toxicity assays. Parasite killing was delayed in CQR parasites for up to 10 h compared to CQS parasites when exposed to equipotent [CQ]ex. In striking contrast, brief exposure (1 h) to lethal [CQ]ex in CQS but not CQR parasites caused the appearance of hitherto undescribed hemozoin (Hz)-containing compartments in the parasite cytosol. Hz-containing compartments were very rarely observed in CQR parasites even after CQ exposures sufficient to cause irreversible cell death. These findings challenge current concepts that CQ killing of malaria parasites is solely concentration-dependent, and instead suggest that CQS and CQR strains fundamentally differ in the consequences of CQ exposure.
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Affiliation(s)
- Sarah J Reiling
- Institute of Parasitology, McGill University, Ste. Anne de Bellevue (Montréal), Québec, Canada
| | - Georg Krohne
- Theodor Boveri Institute, Biocenter, University of Würzburg, Würzburg, Germany
| | - Oliver Friedrich
- Institute of Medical Biotechnology, Friedrich-Alexander University of Erlangen-Nürnberg, Erlangen, Germany
| | - Timothy G Geary
- Institute of Parasitology, McGill University, Ste. Anne de Bellevue (Montréal), Québec, Canada
| | - Petra Rohrbach
- Institute of Parasitology, McGill University, Ste. Anne de Bellevue (Montréal), Québec, Canada.
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Jida M, Sanchez CP, Urgin K, Ehrhardt K, Mounien S, Geyer A, Elhabiri M, Lanzer M, Davioud-Charvet E. A Redox-Active Fluorescent pH Indicator for Detecting Plasmodium falciparum Strains with Reduced Responsiveness to Quinoline Antimalarial Drugs. ACS Infect Dis 2017; 3:119-131. [PMID: 28183182 DOI: 10.1021/acsinfecdis.5b00141] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Mutational changes in the Plasmodium falciparum chloroquine resistance transporter (PfCRT) have been associated with differential responses to a wide spectrum of biologically active compounds including current and former quinoline and quinoline-like antimalarial drugs. PfCRT confers altered drug responsiveness by acting as a transport system, expelling drugs from the parasite's digestive vacuole where these drugs exert, at least part of, their antiplasmodial activity. To preserve the efficacy of these invaluable drugs, novel functional tools are required for epidemiological surveys of parasite strains carrying mutant PfCRT variants and for drug development programs aimed at inhibiting or circumventing the action of PfCRT. Here we report the synthesis and characterization of a pH-sensitive fluorescent chloroquine analogue consisting of 7-chloro-N-{2-[(propan-2-yl)amino]ethyl}quinolin-4-amine functionalized with the fluorochrome 7-nitrobenzofurazan (NBD) (henceforth termed Fluo-CQ). In the parasite, Fluo-CQ accumulates in the digestive vacuole, giving rise to a strong fluorescence signal but only in parasites carrying the wild type PfCRT. In parasites carrying the mutant PfCRT, Fluo-CQ does not accumulate. The differential handling of the fluorescent probe, combined with live cell imaging, provides a diagnostic tool for quick detection of those P. falciparum strains that carry a PfCRT variant associated with altered responsiveness to quinoline and quinoline-like antimalarial drugs. In contrast to the accumulation studies, chloroquine (CQ)-resistant parasites were observed cross-resistant to Fluo-CQ when the chemical probe was tested in various CQ-sensitive and -resistant parasite strains. NBD derivatives were found to act as redox cyclers of two essential targets, using a coupled assay based on methemoglobin and the NADPH-dependent glutathione reductase (GRs) from P. falciparum. This redox activity is proposed to contribute to the dual action of Fluo-CQ on redox equilibrium and methemoglobin reduction via PfCRT-mediated drug efflux in the cytosol and then continuous redox-dependent shuttling between food vacuole and cytosol. Taking into account these physicochemical characteristics, a model was proposed to explain Fluo-CQ antimalarial effects involving the contribution of PfCRT-mediated transport, methemoglobin reduction, hematin binding, and NBD reduction activity catalyzed by PfGR in CQ-resistant versus CQ-sensitive parasites. Therefore, introduction of NBD fluorophore in drugs is not inert and should be taken into account in drug transport and imaging studies.
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Affiliation(s)
- Mouhamad Jida
- UMR 7509 Centre National de la Recherche Scientifique and University of Strasbourg, European School of Chemistry, Polymers and Materials (ECPM), 25 rue Becquerel, F-67087 Strasbourg, France
| | - Cecilia P. Sanchez
- Zentrum
für Infektiologie, Parasitologie, Universität Heidelberg, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
| | - Karène Urgin
- UMR 7509 Centre National de la Recherche Scientifique and University of Strasbourg, European School of Chemistry, Polymers and Materials (ECPM), 25 rue Becquerel, F-67087 Strasbourg, France
| | - Katharina Ehrhardt
- UMR 7509 Centre National de la Recherche Scientifique and University of Strasbourg, European School of Chemistry, Polymers and Materials (ECPM), 25 rue Becquerel, F-67087 Strasbourg, France
- Zentrum
für Infektiologie, Parasitologie, Universität Heidelberg, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
| | - Saravanan Mounien
- UMR 7509 Centre National de la Recherche Scientifique and University of Strasbourg, European School of Chemistry, Polymers and Materials (ECPM), 25 rue Becquerel, F-67087 Strasbourg, France
| | - Aurelia Geyer
- UMR 7509 Centre National de la Recherche Scientifique and University of Strasbourg, European School of Chemistry, Polymers and Materials (ECPM), 25 rue Becquerel, F-67087 Strasbourg, France
| | - Mourad Elhabiri
- UMR 7509 Centre National de la Recherche Scientifique and University of Strasbourg, European School of Chemistry, Polymers and Materials (ECPM), 25 rue Becquerel, F-67087 Strasbourg, France
| | - Michael Lanzer
- Zentrum
für Infektiologie, Parasitologie, Universität Heidelberg, Im Neuenheimer Feld 324, 69120 Heidelberg, Germany
| | - Elisabeth Davioud-Charvet
- UMR 7509 Centre National de la Recherche Scientifique and University of Strasbourg, European School of Chemistry, Polymers and Materials (ECPM), 25 rue Becquerel, F-67087 Strasbourg, France
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Evolution of Fitness Cost-Neutral Mutant PfCRT Conferring P. falciparum 4-Aminoquinoline Drug Resistance Is Accompanied by Altered Parasite Metabolism and Digestive Vacuole Physiology. PLoS Pathog 2016; 12:e1005976. [PMID: 27832198 PMCID: PMC5104409 DOI: 10.1371/journal.ppat.1005976] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Accepted: 10/03/2016] [Indexed: 11/19/2022] Open
Abstract
Southeast Asia is an epicenter of multidrug-resistant Plasmodium falciparum strains. Selective pressures on the subcontinent have recurrently produced several allelic variants of parasite drug resistance genes, including the P. falciparum chloroquine resistance transporter (pfcrt). Despite significant reductions in the deployment of the 4-aminoquinoline drug chloroquine (CQ), which selected for the mutant pfcrt alleles that halted CQ efficacy decades ago, the parasite pfcrt locus is continuously evolving. This is highlighted by the presence of a highly mutated allele, Cam734 pfcrt, which has acquired the singular ability to confer parasite CQ resistance without an associated fitness cost. Here, we used pfcrt-specific zinc-finger nucleases to genetically dissect this allele in the pathogenic setting of asexual blood-stage infection. Comparative analysis of drug resistance and growth profiles of recombinant parasites that express Cam734 or variants thereof, Dd2 (the most common Southeast Asian variant), or wild-type pfcrt, revealed previously unknown roles for PfCRT mutations in modulating parasite susceptibility to multiple antimalarial agents. These results were generated in the GC03 strain, used in multiple earlier pfcrt studies, and might differ in natural isolates harboring this allele. Results presented herein show that Cam734-mediated CQ resistance is dependent on the rare A144F mutation that has not been observed beyond Southeast Asia, and reveal distinct impacts of this and other Cam734-specific mutations on CQ resistance and parasite growth rates. Biochemical assays revealed a broad impact of mutant PfCRT isoforms on parasite metabolism, including nucleoside triphosphate levels, hemoglobin catabolism and disposition of heme, as well as digestive vacuole volume and pH. Results from our study provide new insights into the complex molecular basis and physiological impact of PfCRT-mediated antimalarial drug resistance, and inform ongoing efforts to characterize novel pfcrt alleles that can undermine the efficacy of first-line antimalarial drug regimens. Point mutations in the Plasmodium falciparum chloroquine resistance transporter (PfCRT) earlier thwarted the clinical efficacy of chloroquine, the former gold standard, and constitute a major determinant of parasite susceptibility to antimalarial drugs. Recently, we reported that the highly mutated Cambodian PfCRT isoform Cam734 is fitness-neutral in terms of parasite growth, unlike other less fit isoforms such as Dd2 that are outcompeted by wild-type parasites in the absence of CQ pressure. Using pfcrt-specific zinc-finger nucleases to genetically dissect the Cam734 allele, we report that its unique constituent mutations directly contribute to CQ resistance and collectively offset fitness costs associated with intermediate mutational steps. We also report that these mutations can contribute to resistance or increased sensitivity to multiple first-line partner drugs. Using isogenic parasite lines, we provide evidence of changes in parasite metabolism associated with the Cam734 allele compared to Dd2. We also observe a close correlation between CQ inhibition of hemozoin formation and parasite growth, and provide evidence that Cam734 PfCRT can modulate drug potency depending on its membrane electrochemical gradient. Our data highlight the capacity of PfCRT to evolve new states of antimalarial drug resistance and to offset associated fitness costs through its impact on parasite physiology and hemoglobin catabolism.
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Abstract
Although efforts to understand the basis for inter-strain phenotypic variation in the most virulent malaria species, Plasmodium falciparum, have benefited from advances in genomic technologies, there have to date been few metabolomic studies of this parasite. Using 1H-NMR spectroscopy, we have compared the metabolite profiles of red blood cells infected with different P. falciparum strains. These included both chloroquine-sensitive and chloroquine-resistant strains, as well as transfectant lines engineered to express different isoforms of the chloroquine-resistance-conferring pfcrt (P. falciparum chloroquine resistance transporter). Our analyses revealed strain-specific differences in a range of metabolites. There was marked variation in the levels of the membrane precursors choline and phosphocholine, with some strains having >30-fold higher choline levels and >5-fold higher phosphocholine levels than others. Chloroquine-resistant strains showed elevated levels of a number of amino acids relative to chloroquine-sensitive strains, including an approximately 2-fold increase in aspartate levels. The elevation in amino acid levels was attributable to mutations in pfcrt. Pfcrt-linked differences in amino acid abundance were confirmed using alternate extraction and detection (HPLC) methods. Mutations acquired to withstand chloroquine exposure therefore give rise to significant biochemical alterations in the parasite. The metabolite profiles of red blood cells infected with different malaria parasite strains were compared. Amino acid profiles varied with the chloroquine resistance status of the strain, and this was linked specifically to mutations in the parasite's chloroquine resistance transporter.
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Characterization of the commercially-available fluorescent chloroquine-BODIPY conjugate, LynxTag-CQGREEN, as a marker for chloroquine resistance and uptake in a 96-well plate assay. PLoS One 2014; 9:e110800. [PMID: 25343249 PMCID: PMC4208776 DOI: 10.1371/journal.pone.0110800] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 09/18/2014] [Indexed: 11/24/2022] Open
Abstract
Chloroquine was a cheap, extremely effective drug against Plasmodium falciparum until resistance arose. One approach to reversing resistance is the inhibition of chloroquine efflux from its site of action, the parasite digestive vacuole. Chloroquine accumulation studies have traditionally relied on radiolabelled chloroquine, which poses several challenges. There is a need for development of a safe and biologically relevant substitute. We report here a commercially-available green fluorescent chloroquine-BODIPY conjugate, LynxTag-CQGREEN, as a proxy for chloroquine accumulation. This compound localized to the digestive vacuole of the parasite as observed under confocal microscopy, and inhibited growth of chloroquine-sensitive strain 3D7 more extensively than in the resistant strains 7G8 and K1. Microplate reader measurements indicated suppression of LynxTag-CQGREEN efflux after pretreatment of parasites with known reversal agents. Microsomes carrying either sensitive- or resistant-type PfCRT were assayed for uptake; resistant-type PfCRT exhibited increased accumulation of LynxTag-CQGREEN, which was suppressed by pretreatment with known chemosensitizers. Eight laboratory strains and twelve clinical isolates were sequenced for PfCRT and Pgh1 haplotypes previously reported to contribute to drug resistance, and pfmdr1 copy number and chloroquine IC50s were determined. These data were compared with LynxTag-CQGREEN uptake/fluorescence by multiple linear regression to identify genetic correlates of uptake. Uptake of the compound correlated with the logIC50 of chloroquine and, more weakly, a mutation in Pgh1, F1226Y.
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Patzewitz EM, Salcedo-Sora JE, Wong EH, Sethia S, Stocks PA, Maughan SC, Murray JAH, Krishna S, Bray PG, Ward SA, Müller S. Glutathione transport: a new role for PfCRT in chloroquine resistance. Antioxid Redox Signal 2013; 19:683-95. [PMID: 23256874 PMCID: PMC3739961 DOI: 10.1089/ars.2012.4625] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
AIMS Chloroquine (CQ) kills Plasmodium falciparum by binding heme, preventing its detoxification to hemozoin in the digestive vacuole (DV) of the parasite. CQ resistance (CQR) is associated with mutations in the DV membrane protein P. falciparum chloroquine resistance transporter (PfCRT), mediating the leakage of CQ from the DV. However, additional factors are thought to contribute to the resistance phenotype. This study tested the hypothesis that there is a link between glutathione (GSH) and CQR. RESULTS Using isogenic parasite lines carrying wild-type or mutant pfcrt, we reveal lower levels of GSH in the mutant lines and enhanced sensitivity to the GSH synthesis inhibitor l-buthionine sulfoximine, without any alteration in cytosolic de novo GSH synthesis. Incubation with N-acetylcysteine resulted in increased GSH levels in all parasites, but only reduced susceptibility to CQ in PfCRT mutant-expressing lines. In support of a heme destruction mechanism involving GSH in CQR parasites, we also found lower hemozoin levels and reduced CQ binding in the CQR PfCRT-mutant lines. We further demonstrate via expression in Xenopus laevis oocytes that the mutant alleles of Pfcrt in CQR parasites selectively transport GSH. INNOVATION We propose a mechanism whereby mutant pfcrt allows enhanced transport of GSH into the parasite's DV. The elevated levels of GSH in the DV reduce the level of free heme available for CQ binding, which mediates the lower susceptibility to CQ in the PfCRT mutant parasites. CONCLUSION PfCRT has a dual role in CQR, facilitating both efflux of harmful CQ from the DV and influx of beneficial GSH into the DV.
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Affiliation(s)
- Eva-Maria Patzewitz
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
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Alcantara LM, Kim J, Moraes CB, Franco CH, Franzoi KD, Lee S, Freitas-Junior LH, Ayong LS. Chemosensitization potential of P-glycoprotein inhibitors in malaria parasites. Exp Parasitol 2013; 134:235-43. [PMID: 23541983 DOI: 10.1016/j.exppara.2013.03.022] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Revised: 03/05/2013] [Accepted: 03/17/2013] [Indexed: 01/24/2023]
Abstract
Members of the ATP-binding cassette (ABC)-type transporter superfamily have been implicated in multidrug resistance in malaria, and various mechanistic models have been postulated to explain their interaction with diverse antimalarial drugs. To gain insight into the pharmacological benefits of inhibiting ABC-type transporters in malaria chemotherapy, we investigated the in vitro chemosensitization potential of various P-glycoprotein inhibitors. A fluorescent chloroquine derivative was synthesized and used to assess the efflux dynamics of chloroquine in MDR and wild type Plasmodium falciparum parasites. This novel BODIPY-based probe accumulated in the digestive vacuole (DV) of CQ-sensitive parasites but less so in MDR cells. Pre-exposure of the MDR parasites to non-cytocidal concentrations of unlabeled chloroquine resulted in a diffused cytoplasmic retention of the probe whereas a similar treatment with the CQR-reversing agent, chlorpheniramine, resulted in DV accumulation. A diffused cytoplasmic distribution of the probe was also obtained following treatment with the P-gp specific inhibitors zosuquidar and tariquidar, whereas treatments with the tyrosine kinase inhibitors gefitinib or imatinib produced a partial accumulation within the DV. Isobologram analyses of the interactions between these inhibitors and the antimalarial drugs chloroquine, mefloquine, and artemisinin revealed distinct patterns of drug synergism, additivity and antagonism. Taken together, the data indicate that competitive tyrosine kinase and noncompetitive P-glycoprotein ATPase-specific inhibitors represent two new classes of chemosensitizing agents in malaria parasites, but caution against the indiscriminate use of these agents in antimalarial drug combinations.
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Affiliation(s)
- Laura M Alcantara
- Center for Neglected Diseases Drug Discovery, Institut Pasteur Korea, Sampyeong-dong 696, Bundang-gu, Seongnam-si, Gyeonggi-do 463-400, Republic of Korea
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11
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Abstract
A wide range of drug transport studies using intact infected red blood cells, isolated malarial parasites, heterologous expression systems, and purified protein, combined with elegant genetic experiments, have suggested that chloroquine transport by the Plasmodium falciparum chloroquine resistance transporter (PfCRT) is a key aspect of the molecular mechanism of quinoline antimalarial drug resistance. However, many questions remain. This short review summarizes data that have led to drug channel versus drug pump hypotheses for PfCRT and suggests ways in which recent contrasting interpretations might be reconciled.
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Affiliation(s)
- Paul D Roepe
- Department of Chemistry, Department of Biochemistry and Cellular and Molecular Biology, Georgetown University, Washington, DC 20057, United States.
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12
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Müller IB, Hyde JE. Antimalarial drugs: modes of action and mechanisms of parasite resistance. Future Microbiol 2010; 5:1857-73. [DOI: 10.2217/fmb.10.136] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Malaria represents one of the most serious threats to human health worldwide, and preventing and curing this parasitic disease still depends predominantly on the administration of a small number of drugs whose efficacy is continually threatened and eroded by the emergence of drug-resistant parasite populations. This has an enormous impact on the mortality and morbidity resulting from malaria infection, especially in sub-Saharan Africa, where the lethal human parasite species Plasmodium falciparum accounts for approximately 90% of deaths recorded globally. Successful treatment of uncomplicated malaria is now highly dependent on artemisinin-based combination therapies. However, the first cases of artemisinin-resistant field isolates have been reported recently and potential replacement antimalarials are only in the developmental stages. Here, we summarize recent progress in tackling the problem of parasite resistance and discuss the underlying molecular mechanisms that confer resistance to current antimalarial agents as far as they are known, understanding of which should assist in the rational development of new drugs and the more effective deployment of older ones.
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Affiliation(s)
- Ingrid B Müller
- Department of Biochemistry, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - John E Hyde
- Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
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13
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Exploiting the therapeutic potential of Plasmodium falciparum solute transporters. Trends Parasitol 2010; 26:284-96. [DOI: 10.1016/j.pt.2010.03.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2009] [Revised: 03/02/2010] [Accepted: 03/05/2010] [Indexed: 01/16/2023]
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14
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Cabrera M, Paguio MF, Xie C, Roepe PD. Reduced digestive vacuolar accumulation of chloroquine is not linked to resistance to chloroquine toxicity. Biochemistry 2009; 48:11152-4. [PMID: 19883122 DOI: 10.1021/bi901765v] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Chloroquine (CQ) accumulation studies in live malaria parasites are typically conducted at low nanomolar CQ concentrations, and definition of CQ resistance (CQR) has been via growth inhibition assays versus low-dose CQ (i.e., via IC(50) ratios). These data have led to the nearly universally accepted idea that reduced parasite CQ accumulation is the underlying basis of CQR. Surprisingly, when quantifying CQR via cytocidal CQ activity and examining CQ accumulation at medically relevant LD(50) doses, we find reduced CQ accumulation is not the underlying cause of CQR.
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Affiliation(s)
- Mynthia Cabrera
- Department of Chemistry, Georgetown University, 37th and O Streets NW, Washington, DC 20057, USA
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Paguio MF, Cabrera M, Roepe PD. Chloroquine transport in Plasmodium falciparum. 2. Analysis of PfCRT-mediated drug transport using proteoliposomes and a fluorescent chloroquine probe. Biochemistry 2009; 48:9482-91. [PMID: 19725576 DOI: 10.1021/bi901035j] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Mutations in the PfCRT protein cause chloroquine resistance (CQR), and earlier studies from our laboratory using plasma membrane inside-out vesicles (ISOV) prepared from yeast expressing recombinant PfCRT [Zhang, H., et al. (2004) Biochemistry 43, 8290-8296] suggested that the putative transporter mediates downhill facilitated diffusion of charged chloroquine (CQ). However, more recent experiments with a fluorescent CQ probe (NBD-CQ) presented in the accompanying paper (DOI 10.1021/bi901034r ) indicated that the CQR phenotype in live parasites is associated with a reduced rate of ATP-dependent CQ uptake into the digestive vacuole (DV). An altered rate constant for uptake has multiple interpretations. To further investigate this phenomenon, PfCRT proteins found in chloroquine-sensitive (CQS) and CQR strains of Plasmodium falciparum were purified from yeast engineered to express "yeast optimized" pfcrt genes, reconstituted into proteoliposomes (PL), and efflux of NBD-CQ was measured from these PL. A membrane-impermeant quencher was used to distinguish intra-PL NBD-CQ from extra-PL NBD-CQ vs time as well as resolve initial rates and rate constants for efflux. Efflux was investigated at a range of NBD-CQ concentrations, in the presence vs absence of pH gradients (DeltapH) and transmembrane potentials (DeltaPsi). Explicit turnover numbers for apparent PfCRT-mediated transport were then calculated under these conditions. Our data are consistent with a model wherein PfCRT catalyzes electrochemically downhill diffusion of NBD-CQ out of the DV, in response to DeltaPsi or DeltapH, at a rate that can partially compete with the ATP-dependent uptake of NBD-CQ by CQS parasites described in the previous paper. These data allow us to propose a refined model for altered CQ accumulation in CQR malarial parasites.
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Affiliation(s)
- Michelle F Paguio
- Department of Chemistry, Georgetown University, NW, Washington, DC 20057, USA
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