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Sousa CC, Dziwornu GA, Quadros HC, Araujo-Neto JH, Chibale K, Moreira DRM. Antimalarial Pyrido[1,2- a]benzimidazoles Exert Strong Parasiticidal Effects by Achieving High Cellular Uptake and Suppressing Heme Detoxification. ACS Infect Dis 2022; 8:1700-1710. [PMID: 35848708 DOI: 10.1021/acsinfecdis.2c00326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pyrido[1,2-a]benzimidazoles (PBIs) are synthetic antiplasmodium agents with potent activity and are structurally differentiated from benchmark antimalarials. To study the cellular uptake of PBIs and understand the underlying phenotype of their antiplasmodium activity, their antiparasitic activities were examined in chloroquine (CQ)-susceptible and CQ-resistant Plasmodium falciparum in vitro. Moreover, drug uptake and heme detoxification suppression were examined in Plasmodium berghei-infected mice. The in vitro potency of PBIs is comparable to most 4-aminoquinolines. They have a speed of action in vitro that is superior to that of atovaquone and an ability to kill rings and trophozoites. The antiparasitic effects observed for the PBIs in cell culture and in infected mice are similar in terms of potency and efficacy and are comparable to CQ but with the added advantage of demonstrating equipotency against both CQ susceptible and resistant parasite strains. PBIs have a high rate of uptake by parasite cells and, conversely, a limited rate of uptake by host cells. The mechanism of cellular uptake of the PBIs differs from the ion-trap mechanism typically observed for 4-aminoquinolines, although they share key structural features. The high cellular uptake, attractive parasiticidal profile, and susceptibility of resistant strains to PBIs are desirable characteristics for new antimalarial agents.
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Affiliation(s)
- Caroline C Sousa
- Fundação Oswaldo Cruz (Fiocruz), Instituto Gonçalo Moniz, Salvador, 40296-710 Bahia, Brazil
| | - Godwin Akpeko Dziwornu
- South African Medical Research Council Drug Discovery and Development Research Unit, Department of Chemistry and Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Rondebosch 7701, South Africa
| | - Helenita C Quadros
- Fundação Oswaldo Cruz (Fiocruz), Instituto Gonçalo Moniz, Salvador, 40296-710 Bahia, Brazil
| | | | - Kelly Chibale
- South African Medical Research Council Drug Discovery and Development Research Unit, Department of Chemistry and Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Rondebosch 7701, South Africa
| | - Diogo R M Moreira
- Fundação Oswaldo Cruz (Fiocruz), Instituto Gonçalo Moniz, Salvador, 40296-710 Bahia, Brazil
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2
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Mairet-Khedim M, Leang R, Marmai C, Khim N, Kim S, Ke S, Kauy C, Kloeung N, Eam R, Chy S, Izac B, Mey Bouth D, Dorina Bustos M, Ringwald P, Ariey F, Witkowski B. Clinical and In Vitro Resistance of Plasmodium falciparum to Artesunate-Amodiaquine in Cambodia. Clin Infect Dis 2021; 73:406-413. [PMID: 32459308 PMCID: PMC8326543 DOI: 10.1093/cid/ciaa628] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2019] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Artesunate-amodiaquine is a potential therapy for uncomplicated malaria in Cambodia. METHODS Between September 2016 and January 2017, artesunate-amodiaquine efficacy and safety were evaluated in a prospective, open-label, single-arm observational study at health centers in Mondulkiri, Pursat, and Siem Reap Provinces, Cambodia. Adults and children with microscopically confirmed Plasmodium falciparum malaria received oral artesunate-amodiaquine once daily for 3 days plus single-dose primaquine, with follow-up on days 7, 14, 21, and 28. The primary outcome was day-28 polymerase chain reaction (PCR)-adjusted adequate clinical and parasitological response (ACPR). An amodiaquine parasite survival assay (AQSA) was developed and applied to whole genome sequencing results to evaluate potential amodiaquine resistance molecular markers. RESULTS In 63 patients, day-28 PCR-adjusted ACPR was 81.0% (95% confidence interval [CI], 68.9-88.7). Day 3 parasite positivity rate was 44.4% (28/63; 95% CI, 31.9-57.5). All 63 isolates had the K13(C580Y) marker for artemisinin resistance; 79.4% (50/63) had Pfpm2 amplification. The AQSA resistance phenotype (≥45% parasite survival) was expressed in 36.5% (23/63) of isolates and was significantly associated with treatment failure (P = .0020). Pfmdr1 mutant haplotypes were N86/184F/D1246, and Pfcrt was CVIET or CVIDT at positions 72-76. Additional Pfcrt mutations were not associated with amodiaquine resistance, but the G353V mutant allele was associated with ACPR compared to Pfmdr1 haplotypes harboring F1068L or S784L/R945P mutations (P = .030 and P = .0004, respectively). CONCLUSIONS For uncomplicated falciparum malaria in Cambodia, artesunate-amodiaquine had inadequate efficacy owing to amodiaquine-resistant P. falciparum. Amodiaquine resistance was not associated with previously identified molecular markers.
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Affiliation(s)
- Melissa Mairet-Khedim
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia.,Malaria Translational Research Unit, Institut Pasteur, Paris, France.,Center for Pathophysiology Toulouse-Purpan (CPTP), INSERM, CNRS, University of Toulouse, Toulouse, France
| | - Rithea Leang
- National Center for Parasitology, Entomology and Malaria Control, Phnom Penh, Cambodia
| | - Camille Marmai
- INSERM 1016, Institut Cochin, Université of Paris, Paris, France.,Service de Parasitologie-Mycologie, Hôpital Cochin, Paris, France
| | - Nimol Khim
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia.,Malaria Translational Research Unit, Institut Pasteur, Paris, France
| | - Saorin Kim
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia.,Malaria Translational Research Unit, Institut Pasteur, Paris, France
| | - Sopheakvatey Ke
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia.,Malaria Translational Research Unit, Institut Pasteur, Paris, France
| | - Chhayleang Kauy
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia.,Malaria Translational Research Unit, Institut Pasteur, Paris, France
| | - Nimol Kloeung
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia.,Malaria Translational Research Unit, Institut Pasteur, Paris, France
| | - Rotha Eam
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia.,Malaria Translational Research Unit, Institut Pasteur, Paris, France
| | - Sophy Chy
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia.,Malaria Translational Research Unit, Institut Pasteur, Paris, France
| | - Brigitte Izac
- INSERM 1016, Institut Cochin, Université of Paris, Paris, France.,Service de Parasitologie-Mycologie, Hôpital Cochin, Paris, France
| | | | | | | | - Frederic Ariey
- INSERM 1016, Institut Cochin, Université of Paris, Paris, France.,Service de Parasitologie-Mycologie, Hôpital Cochin, Paris, France
| | - Benoit Witkowski
- Malaria Molecular Epidemiology Unit, Institut Pasteur in Cambodia, Phnom Penh, Cambodia.,Malaria Translational Research Unit, Institut Pasteur, Paris, France
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3
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Ullah I, Gahalawat S, Booshehri LM, Niederstrasser H, Majumdar S, Leija C, Bradford JM, Hu B, Ready JM, Wetzel DM. An Antiparasitic Compound from the Medicines for Malaria Venture Pathogen Box Promotes Leishmania Tubulin Polymerization. ACS Infect Dis 2020; 6:2057-2072. [PMID: 32686409 PMCID: PMC8059355 DOI: 10.1021/acsinfecdis.0c00122] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The few frontline antileishmanial drugs are poorly effective and toxic. To search for new drugs for this neglected tropical disease, we tested the activity of compounds in the Medicines for Malaria Venture (MMV) "Pathogen Box" against Leishmania amazonensis axenic amastigotes. Screening yielded six discovery antileishmanial compounds with EC50 values from 50 to 480 nM. Concentration-response assays demonstrated that the best hit, MMV676477, had mid-nanomolar cytocidal potency against intracellular Leishmania amastigotes, Trypanosoma brucei, and Plasmodium falciparum, suggesting broad antiparasitic activity. We explored structure-activity relationships (SAR) within a small group of MMV676477 analogs and observed a wide potency range (20-5000 nM) against axenic Leishmania amastigotes. Compared to MMV676477, our most potent analog, SW41, had ∼5-fold improved antileishmanial potency. Multiple lines of evidence suggest that MMV676477 selectively disrupts Leishmania tubulin dynamics. Morphological studies indicated that MMV676477 and analogs affected L. amazonensis during cell division. Differential centrifugation showed that MMV676477 promoted partitioning of cellular tubulin toward the polymeric form in parasites. Turbidity assays with purified Leishmania and porcine tubulin demonstrated that MMV676477 promoted leishmanial tubulin polymerization in a concentration-dependent manner. Analogs' antiparasitic activity correlated with their ability to facilitate purified Leishmania tubulin polymerization. Chemical cross-linking demonstrated binding of the MMV676477 scaffold to purified Leishmania tubulin, and competition studies established a correlation between binding and antileishmanial activity. Our studies demonstrate that MMV676477 is a potent antiparasitic compound that preferentially promotes Leishmania microtubule polymerization. Due to its selectivity for and broad-spectrum activity against multiple parasites, this scaffold shows promise for antiparasitic drug development.
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Affiliation(s)
- Imran Ullah
- Department of Pediatrics and Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
| | - Suraksha Gahalawat
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
| | - Laela M. Booshehri
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
| | - Hanspeter Niederstrasser
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
| | - Shreoshi Majumdar
- Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
| | - Christopher Leija
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
| | - James M. Bradford
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
| | - Bin Hu
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
| | - Joseph M. Ready
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
| | - Dawn M. Wetzel
- Department of Pediatrics and Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, United States
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4
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Murithi JM, Owen ES, Istvan ES, Lee MCS, Ottilie S, Chibale K, Goldberg DE, Winzeler EA, Llinás M, Fidock DA, Vanaerschot M. Combining Stage Specificity and Metabolomic Profiling to Advance Antimalarial Drug Discovery. Cell Chem Biol 2019; 27:158-171.e3. [PMID: 31813848 PMCID: PMC7031696 DOI: 10.1016/j.chembiol.2019.11.009] [Citation(s) in RCA: 44] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 10/18/2019] [Accepted: 11/14/2019] [Indexed: 01/08/2023]
Abstract
We report detailed susceptibility profiling of asexual blood stages of the malaria parasite Plasmodium falciparum to clinical and experimental antimalarials, combined with metabolomic fingerprinting. Results revealed a variety of stage-specific and metabolic profiles that differentiated the modes of action of clinical antimalarials including chloroquine, piperaquine, lumefantrine, and mefloquine, and identified late trophozoite-specific peak activity and stage-specific biphasic dose-responses for the mitochondrial inhibitors DSM265 and atovaquone. We also identified experimental antimalarials hitting previously unexplored druggable pathways as reflected by their unique stage specificity and/or metabolic profiles. These included several ring-active compounds, ones affecting hemoglobin catabolism through distinct pathways, and mitochondrial inhibitors with lower propensities for resistance than either DSM265 or atovaquone. This approach, also applicable to other microbes that undergo multiple differentiation steps, provides an effective tool to prioritize compounds for further development within the context of combination therapies.
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Affiliation(s)
- James M Murithi
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA
| | - Edward S Owen
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA
| | - Eva S Istvan
- Department of Medicine, Division of Infectious Diseases, and Department of Molecular Microbiology, Washington University School of Medicine, Saint Louis MO 63130, USA
| | - Marcus C S Lee
- Parasites and Microbes Programme, Wellcome Sanger Institute, Wellcome Genome Campus, Hinxton, Cambridgeshire CB10 1SA, UK
| | - Sabine Ottilie
- School of Medicine, University of California San Diego (UCSD), La Jolla, CA 92093, USA
| | - Kelly Chibale
- Drug Discovery and Development Centre (H3D), University of Cape Town, Rondebosch 7701, South Africa; South African Medical Research Council Drug Discovery and Development Research Unit, Department of Chemistry & Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Rondebosch 7701, South Africa
| | - Daniel E Goldberg
- Department of Medicine, Division of Infectious Diseases, and Department of Molecular Microbiology, Washington University School of Medicine, Saint Louis MO 63130, USA
| | - Elizabeth A Winzeler
- School of Medicine, University of California San Diego (UCSD), La Jolla, CA 92093, USA
| | - Manuel Llinás
- Department of Biochemistry and Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA; Department of Chemistry, Pennsylvania State University, University Park, PA 16802, USA; Huck Center for Malaria Research, Pennsylvania State University, University Park, PA 16802, USA
| | - David A Fidock
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA; Division of Infectious Diseases, Department of Medicine, Columbia University Irving Medical Center, New York, NY 10032, USA.
| | - Manu Vanaerschot
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, NY 10032, USA.
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5
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Valenciano AL, Fernández-Murga ML, Merino EF, Holderman NR, Butschek GJ, Shaffer KJ, Tyler PC, Cassera MB. Metabolic dependency of chorismate in Plasmodium falciparum suggests an alternative source for the ubiquinone biosynthesis precursor. Sci Rep 2019; 9:13936. [PMID: 31558748 PMCID: PMC6763611 DOI: 10.1038/s41598-019-50319-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 09/10/2019] [Indexed: 01/17/2023] Open
Abstract
The shikimate pathway, a metabolic pathway absent in humans, is responsible for the production of chorismate, a branch point metabolite. In the malaria parasite, chorismate is postulated to be a direct precursor in the synthesis of p-aminobenzoic acid (folate biosynthesis), p-hydroxybenzoic acid (ubiquinone biosynthesis), menaquinone, and aromatic amino acids. While the potential value of the shikimate pathway as a drug target is debatable, the metabolic dependency of chorismate in P. falciparum remains unclear. Current evidence suggests that the main role of chorismate is folate biosynthesis despite ubiquinone biosynthesis being active and essential in the malaria parasite. Our goal in the present work was to expand our knowledge of the ubiquinone head group biosynthesis and its potential metabolic dependency on chorismate in P. falciparum. We systematically assessed the development of both asexual and sexual stages of P. falciparum in a defined medium in the absence of an exogenous supply of chorismate end-products and present biochemical evidence suggesting that the benzoquinone ring of ubiquinones in this parasite may be synthesized through a yet unidentified route.
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Affiliation(s)
- Ana Lisa Valenciano
- Department of Biochemistry & Molecular Biology, and Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, Athens, Georgia, 30602, United States
| | - Maria L Fernández-Murga
- Laboratory of Experimental Pathology, Health Research Institute Hospital La Fe, Valencia, 46026, Spain
| | - Emilio F Merino
- Department of Biochemistry & Molecular Biology, and Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, Athens, Georgia, 30602, United States
| | - Nicole R Holderman
- Department of Biochemistry & Molecular Biology, and Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, Athens, Georgia, 30602, United States
| | - Grant J Butschek
- Department of Biochemistry & Molecular Biology, and Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, Athens, Georgia, 30602, United States
| | - Karl J Shaffer
- The Ferrier Research Institute, Victoria University of Wellington, Lower Hutt, New Zealand
| | - Peter C Tyler
- The Ferrier Research Institute, Victoria University of Wellington, Lower Hutt, New Zealand
| | - Maria Belen Cassera
- Department of Biochemistry & Molecular Biology, and Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, Athens, Georgia, 30602, United States.
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6
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Ghavami M, Merino EF, Yao ZK, Elahi R, Simpson ME, Fernández-Murga ML, Butler JH, Casasanta MA, Krai PM, Totrov MM, Slade DJ, Carlier PR, Cassera MB. Biological Studies and Target Engagement of the 2- C-Methyl-d-Erythritol 4-Phosphate Cytidylyltransferase (IspD)-Targeting Antimalarial Agent (1 R,3 S)-MMV008138 and Analogs. ACS Infect Dis 2018; 4:549-559. [PMID: 29072835 DOI: 10.1021/acsinfecdis.7b00159] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Malaria continues to be one of the deadliest diseases worldwide, and the emergence of drug resistance parasites is a constant threat. Plasmodium parasites utilize the methylerythritol phosphate (MEP) pathway to synthesize isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP), which are essential for parasite growth. Previously, we and others identified that the Malaria Box compound MMV008138 targets the apicoplast and that parasite growth inhibition by this compound can be reversed by supplementation of IPP. Further work has revealed that MMV008138 targets the enzyme 2- C-methyl-d-erythritol 4-phosphate cytidylyltransferase (IspD) in the MEP pathway, which converts MEP and cytidine triphosphate (CTP) to cytidinediphosphate methylerythritol (CDP-ME) and pyrophosphate. In this work, we sought to gain insight into the structure-activity relationships by probing the ability of MMV008138 analogs to inhibit PfIspD recombinant enzyme. Here, we report PfIspD inhibition data for fosmidomycin (FOS) and 19 previously disclosed analogs and report parasite growth and PfIspD inhibition data for 27 new analogs of MMV008138. In addition, we show that MMV008138 does not target the recently characterized human IspD, reinforcing MMV008138 as a prototype of a new class of species-selective IspD-targeting antimalarial agents.
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Affiliation(s)
- Maryam Ghavami
- Department of Chemistry and Virginia Tech Center for Drug Discovery, Virginia Tech, Hahn Hall South, 800 West Campus Drive, Blacksburg, Virginia 24061, United States
| | - Emilio F. Merino
- Department of Biochemistry and Virginia Tech Center for Drug Discovery, Virginia Tech, Engel Hall, 340 West Campus Drive, Blacksburg, Virginia 24061, United States
- Department of Biochemistry and Molecular Biology and Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, 120 Green Street, Athens, Georgia 30602, United States
| | - Zhong-Ke Yao
- Department of Chemistry and Virginia Tech Center for Drug Discovery, Virginia Tech, Hahn Hall South, 800 West Campus Drive, Blacksburg, Virginia 24061, United States
| | - Rubayet Elahi
- Department of Biochemistry and Virginia Tech Center for Drug Discovery, Virginia Tech, Engel Hall, 340 West Campus Drive, Blacksburg, Virginia 24061, United States
| | - Morgan E. Simpson
- Department of Biochemistry and Virginia Tech Center for Drug Discovery, Virginia Tech, Engel Hall, 340 West Campus Drive, Blacksburg, Virginia 24061, United States
| | - Maria L. Fernández-Murga
- Department of Biochemistry and Virginia Tech Center for Drug Discovery, Virginia Tech, Engel Hall, 340 West Campus Drive, Blacksburg, Virginia 24061, United States
| | - Joshua H. Butler
- Department of Biochemistry and Molecular Biology and Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, 120 Green Street, Athens, Georgia 30602, United States
| | - Michael A. Casasanta
- Department of Biochemistry and Virginia Tech Center for Drug Discovery, Virginia Tech, Engel Hall, 340 West Campus Drive, Blacksburg, Virginia 24061, United States
| | - Priscilla M. Krai
- Department of Biochemistry and Virginia Tech Center for Drug Discovery, Virginia Tech, Engel Hall, 340 West Campus Drive, Blacksburg, Virginia 24061, United States
| | - Maxim M. Totrov
- Molsoft LLC, 11199 Sorrento Valley Road, San Diego, California 92121, United States
| | - Daniel J. Slade
- Department of Biochemistry and Virginia Tech Center for Drug Discovery, Virginia Tech, Engel Hall, 340 West Campus Drive, Blacksburg, Virginia 24061, United States
| | - Paul R. Carlier
- Department of Chemistry and Virginia Tech Center for Drug Discovery, Virginia Tech, Hahn Hall South, 800 West Campus Drive, Blacksburg, Virginia 24061, United States
| | - Maria Belen Cassera
- Department of Biochemistry and Virginia Tech Center for Drug Discovery, Virginia Tech, Engel Hall, 340 West Campus Drive, Blacksburg, Virginia 24061, United States
- Department of Biochemistry and Molecular Biology and Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, 120 Green Street, Athens, Georgia 30602, United States
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7
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Valverde EA, Romero AH, Acosta ME, Gamboa N, Henriques G, Rodrigues JR, Ciangherotti C, López SE. Synthesis, β-hematin inhibition studies and antimalarial evaluation of new dehydroxy isoquine derivatives against Plasmodium berghei: A promising antimalarial agent. Eur J Med Chem 2018; 148:498-506. [DOI: 10.1016/j.ejmech.2017.10.051] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2017] [Revised: 10/14/2017] [Accepted: 10/16/2017] [Indexed: 10/18/2022]
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8
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Ullah I, Sharma R, Biagini GA, Horrocks P. A validated bioluminescence-based assay for the rapid determination of the initial rate of kill for discovery antimalarials. J Antimicrob Chemother 2017; 72:717-726. [PMID: 27999014 DOI: 10.1093/jac/dkw449] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 09/22/2016] [Indexed: 11/13/2022] Open
Abstract
Objectives A future treatment for uncomplicated malaria will contain at least one component that exerts a rapid rate of kill. We describe here the validation and application of a simple, robust and rapid bioluminescence-based assay for the determination of the initial rate of kill in intra-erythrocytic asexual stages of Plasmodium falciparum . Methods A modification to the concentration-response bioluminescence [here termed bioluminescence relative rate of kill (BRRoK)] assay, utilizing exposure to fold-IC 50 concentrations (0.33× to 9×), was used to monitor the immediate cytocidal effect of 372 open-source compounds for antimalarial drug discovery available through the Medicines for Malaria Venture Malaria Box. Results Antimalarial drugs that exert a rapid cytocidal effect produce a concentration-dependent loss of bioluminescence signal that correlates with available in vitro and in vivo estimates of parasite clearance time and parasite reduction ratio. Following the measurement of IC 50 for the Malaria Box compounds in Dd2 luc , the BRRoK assay was used to identify and rank 372 compounds for their initial cytocidal activity. Fifty-three compounds in the Malaria Box show an initial relative rate of kill greater than that of chloroquine, with 17 of these having an initial relative rate of kill greater than that of dihydroartemisinin. Conclusions The BRRoK assay provides a rapid assay format for the estimation of a key pharmacodynamic property of antimalarial drug action. The simplicity and robustness of the assay suggests it would be readily scalable for high-throughput screening and a critical decision-making tool for antimalarial drug development.
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Affiliation(s)
- Imran Ullah
- Institute for Science and Technology in Medicine, Keele University, Staffordshire ST5 5BG, UK
| | - Raman Sharma
- Research Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Giancarlo A Biagini
- Research Centre for Drugs and Diagnostics, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Paul Horrocks
- Institute for Science and Technology in Medicine, Keele University, Staffordshire ST5 5BG, UK
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9
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Hassett MR, Riegel BE, Callaghan PS, Roepe PD. Analysis of Plasmodium vivax Chloroquine Resistance Transporter Mutant Isoforms. Biochemistry 2017; 56:5615-5622. [PMID: 28898049 DOI: 10.1021/acs.biochem.7b00749] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Chloroquine (CQ) resistance (CQR) in Plasmodium falciparum malaria is widespread and has limited the use of CQ in many regions of the globe. Malaria caused by the related human parasite P. vivax is as widespread as is P. falciparum malaria and has been treated with CQ as extensively as has P. falciparum, suggesting that P. vivax parasites have been selected with CQ as profoundly as have P. falciparum parasites. Indeed, a growing number of clinical reports have presented data suggesting increased P. vivax CQR. Cytostatic (growth inhibitory) CQR for P. falciparum is caused by Plasmodium falciparum chloroquine resistance transporter (PfCRT) mutations, and it has been proposed that mutations in the PvCRT orthologue may simliarly cause P. vivax CQR via increasing CQ transport from the P. vivax digestive vacuole. Here we report the first quantitative analysis of drug transport mediated by all known mutant isoforms of Plasmodium vivax chloroquine resistance transporter (PvCRT) in order to test the protein's potential link to growing P. vivax CQR phenomena. Small, but statistically significant, differences in the transport of CQ and other quinoline antimalarial drugs were found for multiple PvCRT isoforms, relative to wild type PvCRT, suggesting that mutations in PvCRT can contribute to P. vivax CQR and other examples of quinoline antimalarial drug resistance.
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Affiliation(s)
- Matthew R Hassett
- Departments of Chemistry and of Biochemistry & Cellular & Molecular Biology, Georgetown University , 37th and O Streets NW, Washington, D.C. 20057, United States
| | - Bryce E Riegel
- Departments of Chemistry and of Biochemistry & Cellular & Molecular Biology, Georgetown University , 37th and O Streets NW, Washington, D.C. 20057, United States
| | - Paul S Callaghan
- Departments of Chemistry and of Biochemistry & Cellular & Molecular Biology, Georgetown University , 37th and O Streets NW, Washington, D.C. 20057, United States
| | - Paul D Roepe
- Departments of Chemistry and of Biochemistry & Cellular & Molecular Biology, Georgetown University , 37th and O Streets NW, Washington, D.C. 20057, United States
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10
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A Variant PfCRT Isoform Can Contribute to Plasmodium falciparum Resistance to the First-Line Partner Drug Piperaquine. mBio 2017; 8:mBio.00303-17. [PMID: 28487425 PMCID: PMC5424201 DOI: 10.1128/mbio.00303-17] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Current efforts to reduce the global burden of malaria are threatened by the rapid spread throughout Asia of Plasmodium falciparum resistance to artemisinin-based combination therapies, which includes increasing rates of clinical failure with dihydroartemisinin plus piperaquine (PPQ) in Cambodia. Using zinc finger nuclease-based gene editing, we report that addition of the C101F mutation to the chloroquine (CQ) resistance-conferring PfCRT Dd2 isoform common to Asia can confer PPQ resistance to cultured parasites. Resistance was demonstrated as significantly higher PPQ concentrations causing 90% inhibition of parasite growth (IC90) or 50% parasite killing (50% lethal dose [LD50]). This mutation also reversed Dd2-mediated CQ resistance, sensitized parasites to amodiaquine, quinine, and artemisinin, and conferred amantadine and blasticidin resistance. Using heme fractionation assays, we demonstrate that PPQ causes a buildup of reactive free heme and inhibits the formation of chemically inert hemozoin crystals. Our data evoke inhibition of heme detoxification in the parasite’s acidic digestive vacuole as the primary mode of both the bis-aminoquinoline PPQ and the related 4-aminoquinoline CQ. Both drugs also inhibit hemoglobin proteolysis at elevated concentrations, suggesting an additional mode of action. Isogenic lines differing in their pfmdr1 copy number showed equivalent PPQ susceptibilities. We propose that mutations in PfCRT could contribute to a multifactorial basis of PPQ resistance in field isolates. The global agenda to eliminate malaria depends on the continued success of artemisinin-based combination therapies (ACTs), which target the asexual blood stages of the intracellular parasite Plasmodium. Partial resistance to artemisinin, however, is now established in Southeast Asia, exposing the partner drugs to increased selective pressure. Plasmodium falciparum resistance to the first-line partner piperaquine (PPQ) is now spreading rapidly in Cambodia, resulting in clinical treatment failures. Here, we report that a variant form of the Plasmodium falciparum chloroquine resistance transporter, harboring a C101F mutation edited into the chloroquine (CQ)-resistant Dd2 isoform prevalent in Asia, can confer PPQ resistance in cultured parasites. This was accompanied by a loss of CQ resistance. Biochemical assays showed that PPQ, like CQ, inhibits the detoxification of reactive heme that is formed by parasite-mediated catabolism of host hemoglobin. We propose that novel PfCRT variants emerging in the field could contribute to a multigenic basis of PPQ resistance.
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11
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Xie SC, Dogovski C, Hanssen E, Chiu F, Yang T, Crespo MP, Stafford C, Batinovic S, Teguh S, Charman S, Klonis N, Tilley L. Haemoglobin degradation underpins the sensitivity of early ring stage Plasmodium falciparum to artemisinins. J Cell Sci 2015; 129:406-16. [PMID: 26675237 PMCID: PMC4732288 DOI: 10.1242/jcs.178830] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Accepted: 12/02/2015] [Indexed: 11/30/2022] Open
Abstract
Current first-line artemisinin antimalarials are threatened by the emergence of resistant Plasmodium falciparum. Decreased sensitivity is evident in the initial (early ring) stage of intraerythrocytic development, meaning that it is crucial to understand the action of artemisinins at this stage. Here, we examined the roles of iron (Fe) ions and haem in artemisinin activation in early rings using Fe ion chelators and a specific haemoglobinase inhibitor (E64d). Quantitative modelling of the antagonism accounted for its complex dependence on the chemical features of the artemisinins and on the drug exposure time, and showed that almost all artemisinin activity in early rings (>80%) is due to haem-mediated activation. The surprising implication that haemoglobin uptake and digestion is active in early rings is supported by identification of active haemoglobinases (falcipains) at this stage. Genetic down-modulation of the expression of the two main cysteine protease haemoglobinases, falcipains 2 and 3, renders early ring stage parasites resistant to artemisinins. This confirms the important role of haemoglobin-degrading falcipains in artemisinin activation, and shows that changes in the rate of artemisinin activation could mediate high-level artemisinin resistance. Summary: Down-modulation of the expression of haemoglobin-degrading falcipains in P. falciparum renders early ring stage parasites resistant to artemisinins.
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Affiliation(s)
- Stanley C Xie
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Con Dogovski
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Eric Hanssen
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Victoria 3010, Australia Advanced Microscopy Facility, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Francis Chiu
- Monash Institute of Pharmaceutical Sciences, Faculty of Pharmacy and Pharmaceutical Sciences, Melbourne, Victoria 3010, Australia
| | - Tuo Yang
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Maria P Crespo
- Department of Microbiology, University of Valle, 13 #100-00, Cali, Valle del Cauca, Colombia Department of Biomedical Sciences, Santiago de Cali University, 25, Cali, Valle del Cauca, Colombia
| | - Che Stafford
- Walter+Eliza Hall Institute, Department of Medical Biology, The University of Melbourne, Parkville, Victoria 3052, Australia
| | - Steven Batinovic
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Silvia Teguh
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Susan Charman
- Monash Institute of Pharmaceutical Sciences, Faculty of Pharmacy and Pharmaceutical Sciences, Melbourne, Victoria 3010, Australia
| | - Nectarios Klonis
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Leann Tilley
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Melbourne, Victoria 3010, Australia
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12
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Mott BT, Eastman RT, Guha R, Sherlach KS, Siriwardana A, Shinn P, McKnight C, Michael S, Lacerda-Queiroz N, Patel PR, Khine P, Sun H, Kasbekar M, Aghdam N, Fontaine SD, Liu D, Mierzwa T, Mathews-Griner LA, Ferrer M, Renslo AR, Inglese J, Yuan J, Roepe PD, Su XZ, Thomas CJ. High-throughput matrix screening identifies synergistic and antagonistic antimalarial drug combinations. Sci Rep 2015; 5:13891. [PMID: 26403635 PMCID: PMC4585899 DOI: 10.1038/srep13891] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 08/07/2015] [Indexed: 01/22/2023] Open
Abstract
Drug resistance in Plasmodium parasites is a constant threat. Novel therapeutics, especially new drug combinations, must be identified at a faster rate. In response to the urgent need for new antimalarial drug combinations we screened a large collection of approved and investigational drugs, tested 13,910 drug pairs, and identified many promising antimalarial drug combinations. The activity of known antimalarial drug regimens was confirmed and a myriad of new classes of positively interacting drug pairings were discovered. Network and clustering analyses reinforced established mechanistic relationships for known drug combinations and identified several novel mechanistic hypotheses. From eleven screens comprising >4,600 combinations per parasite strain (including duplicates) we further investigated interactions between approved antimalarials, calcium homeostasis modulators, and inhibitors of phosphatidylinositide 3-kinases (PI3K) and the mammalian target of rapamycin (mTOR). These studies highlight important targets and pathways and provide promising leads for clinically actionable antimalarial therapy.
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Affiliation(s)
- Bryan T. Mott
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD
| | - Richard T. Eastman
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD
| | - Rajarshi Guha
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD
| | - Katy S. Sherlach
- Department of Chemistry, Georgetown University, 37th and O St., NW, Washington, DC
| | - Amila Siriwardana
- Department of Chemistry, Georgetown University, 37th and O St., NW, Washington, DC
| | - Paul Shinn
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD
| | - Crystal McKnight
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD
| | - Sam Michael
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD
| | - Norinne Lacerda-Queiroz
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD
| | - Paresma R. Patel
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD
| | - Pwint Khine
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD
| | - Hongmao Sun
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD
| | - Monica Kasbekar
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD
| | - Nima Aghdam
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD
- Department of Chemistry, Georgetown University, 37th and O St., NW, Washington, DC
| | - Shaun D. Fontaine
- Department of Pharmaceutical Chemistry, Small Molecule Discovery Center, University of California, San Francisco, CA
| | - Dongbo Liu
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD
| | - Tim Mierzwa
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD
| | - Lesley A. Mathews-Griner
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD
| | - Marc Ferrer
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD
| | - Adam R. Renslo
- Department of Pharmaceutical Chemistry, Small Molecule Discovery Center, University of California, San Francisco, CA
| | - James Inglese
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD
- National Human Genome Research Institute, National Institutes of Health, Bethesda, MD
| | - Jing Yuan
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD
| | - Paul D. Roepe
- Department of Chemistry, Georgetown University, 37th and O St., NW, Washington, DC
- Department of Biochemistry, Cellular and Molecular Biology and Center for Infectious Diseases, Georgetown University, 37th and O St., NW, Washington, DC
| | - Xin-zhuan Su
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD
| | - Craig J. Thomas
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD
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13
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Romero AH, Acosta ME, Gamboa N, Charris JE, Salazar J, López SE. Synthesis, β-hematin inhibition studies and antimalarial evaluation of dehydroxy isotebuquine derivatives against Plasmodium berghei. Bioorg Med Chem 2015; 23:4755-4762. [DOI: 10.1016/j.bmc.2015.05.040] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2015] [Revised: 05/15/2015] [Accepted: 05/24/2015] [Indexed: 11/29/2022]
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14
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Sherlach KS, Roepe PD. Determination of the cytostatic and cytocidal activities of antimalarial compounds and their combination interactions. ACTA ACUST UNITED AC 2014; 6:237-248. [PMID: 25445179 DOI: 10.1002/9780470559277.ch140125] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Determining the antiplasmodial activity of candidate antimalarial drugs in vitro identifies new therapies for drug-resistant malaria. Importantly though, activity can be either growth-inhibitory (cytostatic) or parasite-kill (cytocidal), or both. The simple methods described here can allow for distinction between these activities, as well as definition of drug interactions between two or more compounds. The latter is important in the definition of novel drug combination therapy for malaria. These methods involve live malarial parasite red blood cell culture, routine pharmacology, high-throughput detection of parasite DNA with fluorescent reporters, and routine mathematical analysis of dose-response curves. The techniques and approaches are accessible to most laboratories and require minimal special equipment beyond a fluorescent plate reader and tissue culture facilities.
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Affiliation(s)
- Katy S Sherlach
- Department of Chemistry and Department of Biochemistry and Cellular and Molecular Biology, Georgetown University, Washington, D.C
| | - Paul D Roepe
- Department of Chemistry and Department of Biochemistry and Cellular and Molecular Biology, Georgetown University, Washington, D.C
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15
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Paulo A, Figueiras M, Machado M, Charneira C, Lavrado J, Santos SA, Lopes D, Gut J, Rosenthal PJ, Nogueira F, Moreira R. Bis-alkylamine Indolo[3,2-b]quinolines as Hemozoin Ligands: Implications for Antimalarial Cytostatic and Cytocidal Activities. J Med Chem 2014; 57:3295-313. [DOI: 10.1021/jm500075d] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Alexandra Paulo
- Instituto
de Investigação do Medicamento (iMed.ULisboa), Faculdade
de Farmácia, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal
| | - Marta Figueiras
- Instituto
de Investigação do Medicamento (iMed.ULisboa), Faculdade
de Farmácia, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal
| | - Marta Machado
- UEI
Malaria, Centro da Malária e Doenças Tropicais, IHMT, Universidade Nova de Lisboa, Rua da Junqueira, 100, P-1349-008 Lisboa, Portugal
| | - Catarina Charneira
- Instituto
de Investigação do Medicamento (iMed.ULisboa), Faculdade
de Farmácia, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal
| | - João Lavrado
- Instituto
de Investigação do Medicamento (iMed.ULisboa), Faculdade
de Farmácia, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal
| | - Sofia A. Santos
- Instituto
de Investigação do Medicamento (iMed.ULisboa), Faculdade
de Farmácia, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal
| | - Dinora Lopes
- UEI
Malaria, Centro da Malária e Doenças Tropicais, IHMT, Universidade Nova de Lisboa, Rua da Junqueira, 100, P-1349-008 Lisboa, Portugal
| | - Jiri Gut
- Department
of Medicine, San Francisco General Hospital, University of California, San Francisco, Box 0811, San Francisco, California 94143, United States
| | - Philip J. Rosenthal
- Department
of Medicine, San Francisco General Hospital, University of California, San Francisco, Box 0811, San Francisco, California 94143, United States
| | - Fátima Nogueira
- UEI
Malaria, Centro da Malária e Doenças Tropicais, IHMT, Universidade Nova de Lisboa, Rua da Junqueira, 100, P-1349-008 Lisboa, Portugal
| | - Rui Moreira
- Instituto
de Investigação do Medicamento (iMed.ULisboa), Faculdade
de Farmácia, Universidade de Lisboa, Av. Prof. Gama Pinto, 1649-003 Lisboa, Portugal
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16
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Roepe PD. To kill or not to kill, that is the question: cytocidal antimalarial drug resistance. Trends Parasitol 2014; 30:130-5. [PMID: 24530127 DOI: 10.1016/j.pt.2014.01.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 01/07/2014] [Accepted: 01/09/2014] [Indexed: 02/03/2023]
Abstract
Elucidating mechanisms of antimalarial drug resistance accelerates development of improved diagnostics and the design of new, effective malaria therapy. Recently, several studies have emphasized that chloroquine (CQ) resistance (CQR) can be quantified in two very distinct ways, depending on whether sensitivity to the growth inhibitory effects or parasite-kill effects of the drug are being measured. It is now clear that these cytostatic and cytocidal CQR phenotypes are not equivalent, and recent genetic, cell biological, and biophysical evidence suggests how the molecular mechanisms may overlap. These conclusions have important implications for elucidating other drug resistance phenomena and emphasize new concepts that are essential for the development of new drug therapy.
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Affiliation(s)
- Paul D Roepe
- Department of Chemistry, Georgetown University, 37th and O Streets NW, Washington DC 20057, USA; Department of Biochemistry and Cellular and Molecular Biology, Georgetown University, 37th and O Streets NW, Washington DC 20057, USA.
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17
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A process similar to autophagy is associated with cytocidal chloroquine resistance in Plasmodium falciparum. PLoS One 2013; 8:e79059. [PMID: 24278114 PMCID: PMC3835802 DOI: 10.1371/journal.pone.0079059] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2013] [Accepted: 09/24/2013] [Indexed: 12/31/2022] Open
Abstract
Resistance to the cytostatic activity of the antimalarial drug chloroquine (CQ) is becoming well understood, however, resistance to cytocidal effects of CQ is largely unexplored. We find that PfCRT mutations that almost fully recapitulate P. falciparum cytostatic CQ resistance (CQRCS) as quantified by CQ IC50 shift, account for only 10–20% of cytocidal CQR (CQRCC) as quantified by CQ LD50 shift. Quantitative trait loci (QTL) analysis of the progeny of a chloroquine sensitive (CQS; strain HB3)×chloroquine resistant (CQR; strain Dd2) genetic cross identifies distinct genetic architectures for CQRCS vs CQRCC phenotypes, including identification of novel interacting chromosomal loci that influence CQ LD50. Candidate genes in these loci are consistent with a role for autophagy in CQRCC, leading us to directly examine the autophagy pathway in intraerythrocytic CQR parasites. Indirect immunofluorescence of RBC infected with synchronized CQS vs CQR trophozoite stage parasites reveals differences in the distribution of the autophagy marker protein PfATG8 coinciding with CQRCC. Taken together, the data show that an unusual autophagy – like process is either activated or inhibited for intraerythrocytic trophozoite parasites at LD50 doses (but not IC50 doses) of CQ, that the pathway is altered in CQR P. falciparum, and that it may contribute along with mutations in PfCRT to confer the CQRCC phenotype.
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18
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Gorka AP, Jacobs LM, Roepe PD. Cytostatic versus cytocidal profiling of quinoline drug combinations via modified fixed-ratio isobologram analysis. Malar J 2013; 12:332. [PMID: 24044530 PMCID: PMC3874740 DOI: 10.1186/1475-2875-12-332] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Accepted: 08/18/2013] [Indexed: 01/13/2023] Open
Abstract
Background Drug combination therapy is the frontline of malaria treatment. There is an ever-accelerating need for new, efficacious combination therapies active against drug resistant malaria. Proven drugs already in the treatment pipeline, such as the quinolines, are important components of current combination therapy and also present an attractive test bank for rapid development of new concepts. Methods The efficacy of several drug combinations versus chloroquine-sensitive and chloroquine-resistant strains was measured using both cytostatic and cytocidal potency assays. Conclusions These screens identify quinoline and non-quinoline pairs that exhibit synergy, additivity, or antagonism using the fixed-ratio isobologram method and find tafenoquine – methylene blue combination to be the most synergistic. Also, interestingly, for selected pairs, additivity, synergy, or antagonism defined by quantifying IC50 (cytostatic potency) does not necessarily predict similar behaviour when potency is defined by LD50 (cytocidal potency). These data further support an evolving new model for quinoline anti-malarials, wherein haem and haemozoin are the principle target for cytostatic activity, but may not be the only target relevant for cytocidal activity.
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Affiliation(s)
- Alexander P Gorka
- Department of Chemistry, Department of Biochemistry, Cellular, & Molecular Biology, and Center for Infectious Disease, Georgetown University, 37th and 'O' Sts, NW, Washington, DC, 20057, USA.
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19
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Hain AUP, Bosch J. Autophagy in Plasmodium, a multifunctional pathway? Comput Struct Biotechnol J 2013; 8:e201308002. [PMID: 24688742 PMCID: PMC3962217 DOI: 10.5936/csbj.201308002] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 07/18/2013] [Accepted: 07/24/2013] [Indexed: 11/23/2022] Open
Abstract
Autophagy is a catabolic process that normally utilizes the lysosome. The far-reaching implications of this system in disease are being increasingly understood. Studying autophagy is complicated by its role in cell survival and programmed cell death and the involvement of the canonical marker of autophagy, Atg8/LC3, in numerous non-autophagic roles. The malaria parasite, Plasmodium, has conserved certain aspects of the autophagic machinery but for what purpose has long remained a mystery. Major advances have recently been gained and suggest a role for Atg8 in apicoplast maintenance, degradation of heme inside the food vacuole, and possibly trafficking of proteins or organelles outside the parasite membrane. Autophagy may also participate in programmed cell death under drug treatment or as a selective tool to limit parasite load. We review the current findings and discuss discrepancies in the field of autophagy in the Plasmodium parasite.
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Affiliation(s)
- Adelaide U P Hain
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins Malaria Research Institute, Baltimore, MD 21205, United States
| | - Jürgen Bosch
- Department of Biochemistry and Molecular Biology, Bloomberg School of Public Health, Johns Hopkins Malaria Research Institute, Baltimore, MD 21205, United States
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20
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Baro NK, Callaghan PS, Roepe PD. Function of resistance conferring Plasmodium falciparum chloroquine resistance transporter isoforms. Biochemistry 2013; 52:4242-9. [PMID: 23688277 PMCID: PMC3703759 DOI: 10.1021/bi400557x] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The function of Plasmodium falciparum chloroquine resistance transporter (PfCRT) can be quantified using a Saccharomyces cerevisiae model system [Baro, N. K., Pooput, C., and Roepe, P. D. (2011) Biochemistry 50, 6701-6710]. We further optimized this system to distinguish PfCRT isoforms found in P. falciparum strains and isolates from across the globe. We created and expressed 13 naturally occurring pfcrt alleles associated with a range of chloroquine resistant (CQR) phenotypes. Using galactose induction of PfCRT, we quantified PfCRT and chloroquine (CQ)-dependent yeast growth inhibition and [3H]CQ transport specifically due to a given PfCRT isoform. Surprisingly, we found poor correlation between these parameters and the CQ IC50 observed in strains of malaria harboring the same isoforms. This suggested that an increased level of CQ transport due to PfCRT mutation is necessary, but not sufficient, for the range of CQ IC50 values observed in globally distributed CQR P. falciparum isolates.
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Affiliation(s)
- Nicholas K. Baro
- Department of Chemistry, Department of Biochemistry and Cellular and Molecular Biology, and Center for Infectious Diseases, Georgetown University, 37th and O Streets, NW Washington, D.C. 20057
| | - Paul S. Callaghan
- Department of Chemistry, Department of Biochemistry and Cellular and Molecular Biology, and Center for Infectious Diseases, Georgetown University, 37th and O Streets, NW Washington, D.C. 20057
| | - Paul D. Roepe
- Department of Chemistry, Department of Biochemistry and Cellular and Molecular Biology, and Center for Infectious Diseases, Georgetown University, 37th and O Streets, NW Washington, D.C. 20057
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21
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Gorka AP, de Dios A, Roepe PD. Quinoline drug-heme interactions and implications for antimalarial cytostatic versus cytocidal activities. J Med Chem 2013; 56:5231-46. [PMID: 23586757 DOI: 10.1021/jm400282d] [Citation(s) in RCA: 132] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Historically, the most successful molecular target for antimalarial drugs has been heme biomineralization within the malarial parasite digestive vacuole. Heme released from catabolized host red blood cell hemoglobin is toxic, so malarial parasites crystallize heme to nontoxic hemozoin. For years it has been accepted that a number of effective quinoline antimalarial drugs (e.g., chloroquine, quinine, amodiaquine) function by preventing hemozoin crystallization. However, recent studies over the past decade have revealed a surprising molecular diversity in quinoline-heme molecular interactions. This diversity shows that even closely related quinoline drugs may have quite different molecular pharmacology. This paper reviews the molecular diversity and highlights important implications for understanding quinoline antimalarial drug resistance and for future drug design.
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Affiliation(s)
- Alexander P Gorka
- Department of Chemistry, Department of Biochemistry, Cellular, and Molecular Biology, and Center for Infectious Diseases, Georgetown University , 37th and O Streets, NW, Washington, D.C. 20057, United States
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22
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Harinantenaina L, Bowman JD, Brodie PJ, Slebodnick C, Callmander MW, Rakotobe E, Randrianaivo R, Rasamison VE, Gorka A, Roepe PD, Cassera MB, Kingston DGI. Antiproliferative and antiplasmodial dimeric phloroglucinols from Mallotus oppositifolius from the Madagascar Dry Forest (1). JOURNAL OF NATURAL PRODUCTS 2013; 76:388-93. [PMID: 23286240 PMCID: PMC3606680 DOI: 10.1021/np300750q] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Bioassay-guided fractionation of an ethanol extract of the leaves and inflorescence of Mallotus oppositifolius collected in Madagascar led to the isolation of the two new bioactive dimeric phloroglucinols mallotojaponins B (1) and C (2), together with the known mallotophenone (3). The structures of the new compounds were determined on the basis of spectroscopic evidence, including their 1D- and 2D-NMR spectra, mass spectrometry, and an X-ray crystal structure. Compounds 1 and 2 showed potent antimalarial activity against chloroquine-resistant Plasmodium falciparum, with IC50 values of 0.75 ± 0.30 and 0.14 ± 0.04 μM, while 3 was inactive in this assay. Compounds 1-3 also displayed strong antiproliferative activity against the A2780 human ovarian cancer cell line (IC50 1.10 ± 0.05, 1.3 ± 0.1 and 6.3 ± 0.4 μM, respectively).
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Affiliation(s)
- Liva Harinantenaina
- Department of Chemistry and Virginia Tech Center for Drug Discovery, M/C 0212, Virginia Tech, Blacksburg, VA 24061, United States
| | - Jessica D. Bowman
- Department of Biochemistry and Virginia Tech Center for Drug Discovery, M/C 0308, Virginia Tech, Blacksburg, VA 24061, United States
| | - Peggy J. Brodie
- Department of Chemistry and Virginia Tech Center for Drug Discovery, M/C 0212, Virginia Tech, Blacksburg, VA 24061, United States
| | - Carla Slebodnick
- Department of Chemistry and Virginia Tech Center for Drug Discovery, M/C 0212, Virginia Tech, Blacksburg, VA 24061, United States
| | | | - Etienne Rakotobe
- Centre National d’Application des Recherches Pharmaceutiques, B.P 702, Antananarivo 101, Madagascar
| | | | - Vincent E. Rasamison
- Centre National d’Application des Recherches Pharmaceutiques, B.P 702, Antananarivo 101, Madagascar
| | - Alexander Gorka
- Department of Chemistry and Lombardi Cancer Center, Georgetown University, 37th and O Streets NW, Washington, DC 20057, United States
| | - Paul D. Roepe
- Department of Chemistry and Lombardi Cancer Center, Georgetown University, 37th and O Streets NW, Washington, DC 20057, United States
| | - Maria B. Cassera
- Department of Biochemistry and Virginia Tech Center for Drug Discovery, M/C 0308, Virginia Tech, Blacksburg, VA 24061, United States
| | - David G. I. Kingston
- Department of Chemistry and Virginia Tech Center for Drug Discovery, M/C 0212, Virginia Tech, Blacksburg, VA 24061, United States
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23
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Altered temporal response of malaria parasites determines differential sensitivity to artemisinin. Proc Natl Acad Sci U S A 2013; 110:5157-62. [PMID: 23431146 DOI: 10.1073/pnas.1217452110] [Citation(s) in RCA: 149] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Reports of emerging resistance to first-line artemisinin antimalarials make it critical to define resistance mechanisms and identify in vitro correlates of resistance. Here we combine unique in vitro experimental and analytical approaches to mimic in vivo drug exposure in an effort to provide insight into mechanisms of drug resistance. Tightly synchronized parasites exposed to short drug pulses exhibit large stage-dependent differences in their drug response that correlate with hemoglobin digestion throughout most of the asexual cycle. As a result, ring-stage parasites can exhibit >100-fold lower sensitivity to short drug pulses than trophozoites, although we identify a subpopulation of rings (2-4 h postinvasion) that exhibits hypersensitivity. We find that laboratory strains that show little differences in drug sensitivity in standard in vitro assays exhibit substantial (>95-fold) difference in sensitivity when exposed to short drug pulses. These stage- and strain-dependent differences in drug sensitivity reflect differential response lag times with rings exhibiting lag times of up to 4 h. A simple model that assumes that the parasite experiences a saturable effective drug dose describes the complex dependence of parasite viability on both drug concentration and exposure time and is used to demonstrate that small changes in the parasite's drug response profile can dramatically alter the sensitivity to artemisinins. This work demonstrates that effective resistance can arise from the interplay between the short in vivo half-life of the drug and the stage-specific lag time and provides the framework for understanding the mechanisms of drug action and parasite resistance.
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Hasenkamp S, Sidaway A, Devine O, Roye R, Horrocks P. Evaluation of bioluminescence-based assays of anti-malarial drug activity. Malar J 2013; 12:58. [PMID: 23394077 PMCID: PMC3571881 DOI: 10.1186/1475-2875-12-58] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 02/03/2013] [Indexed: 11/16/2022] Open
Abstract
Background Transgenic Plasmodium falciparum expressing luciferase offers an attractive bioluminescence-based assay platform for the investigation of the pharmacological properties of anti-malarial drugs. Here a side-by-side comparison of bioluminescence and fluorescence-based assays, utilizing a luciferase reporter cassette that confers a strong temporal pattern of luciferase expression during the S-phase of intraerythrocytic development, is reported. Methods Key assay parameters for a range of commercially available luminogenic substrates are determined and compared to those measured using a Malaria Sybr Green I fluorescence assay. In addition, the short-term temporal effects of anti-malarial compounds are evaluated using both bioluminescent and fluorescent assay platforms. Results The Z’, % coefficient of variation and 50% inhibition concentrations are essentially the same for bioluminescent and fluorescent assays in transgenic parasites generated in both chloroquine-sensitive and -resistant genetic backgrounds. Bioluminescent assays, irrespective of the luminogenic agent employed, do, however, offer significantly enhanced signal-to-noise ratios. Moreover, the bioluminescent assay is more dynamic in terms of determining temporal effects immediately following drug perturbation. Conclusion This study suggests that opportunities for bioluminescence-based assays lie not in the measurement of 50% inhibition concentrations, where the cheaper fluorescence assay performs excellently and is not restricted by the need to genetically modify the parasite clone under investigation. Instead, assays that use the dynamic response of the luciferase reporter for semi-automated screening of additional pharmacological properties, such as relative rate-of-kill and lethal dose estimation, are a more attractive development opportunity.
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Affiliation(s)
- Sandra Hasenkamp
- Institute for Science and Technology in Medicine, Keele University, Staffordshire, UK
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25
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Relative to quinine and quinidine, their 9-epimers exhibit decreased cytostatic activity and altered heme binding but similar cytocidal activity versus Plasmodium falciparum. Antimicrob Agents Chemother 2012; 57:365-74. [PMID: 23114754 DOI: 10.1128/aac.01234-12] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The 9-epimers of quinine (QN) and quinidine (QD) are known to exhibit poor cytostatic potency against P. falciparum (Karle JM, Karle IL, Gerena L, Milhous WK, Antimicrob. Agents Chemother. 36:1538-1544, 1992). We synthesized 9-epi-QN (eQN) and 9-epi-QD (eQD) via Mitsunobu esterification-saponification and evaluated both cytostatic and cytocidal antimalarial activities. Relative to the cytostatic activity of QN and QD, we observed a large decrease in cytostatic activity (higher 50% inhibitory concentration [IC(50)s]) against QN-sensitive strain HB3, QN-resistant strain Dd2, and QN-hypersensitive strain K76I, consistent with previous work. However, we observed relatively small changes in cytocidal activity (the 50% lethal dose), similar to observations with chloroquine (CQ) analogues with a wide range of IC(50)s (see the accompanying paper [A. P. Gorka, J. N. Alumasa, K. S. Sherlach, L. M. Jacobs, K. B. Nickley, J. P. Brower, A. C. de Dios, and P. D. Roepe, Antimicrob. Agents Chemother. 57:356-364, 2013]). Compared to QN and QD, the 9-epimers had significantly reduced hemozoin inhibition efficiency and did not affect pH-dependent aggregation of ferriprotoporphyrin IX (FPIX) heme. Magnetic susceptibility measurements showed that the 9-epimers perturb FPIX monomer-dimer equilibrium in favor of monomer, and UV-visible (VIS) titrations showed that eQN and eQD bind monomer with similar affinity relative to QN and QD. However, unique ring proton shifts in the presence of zinc(II) protoporphyrin IX (ZnPIX) indicate that binding of the 9-epimers to monomeric heme is via a distinct geometry. We isolated eQN- and eQD-FPIX complexes formed under aqueous conditions and analyzed them by mass, fluorescence, and UV-VIS spectroscopies. The 9-epimers produced low-fluorescent adducts with a 2:1 stoichiometry (drug to FPIX) which did not survive electrospray ionization, in contrast to QN and QD complexes. The data offer important insight into the relevance of heme interactions as a drug target for cytostatic versus cytocidal dosages of quinoline antimalarial drugs and further elucidate a surprising structural diversity of quinoline antimalarial drug-heme complexes.
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26
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Cytostatic versus cytocidal activities of chloroquine analogues and inhibition of hemozoin crystal growth. Antimicrob Agents Chemother 2012; 57:356-64. [PMID: 23114783 DOI: 10.1128/aac.01709-12] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
We report an improved, nonhazardous, high-throughput assay for in vitro quantification of antimalarial drug inhibition of β-hematin (hemozoin) crystallization performed under conditions that are more physiological relative to previous assays. The assay uses the differential detergent solubility of crystalline and noncrystalline forms of heme and is optimized via the use of lipid catalyst. Using this assay, we quantify the effect of pH on the crystal growth-inhibitory activities of current quinoline antimalarials, evaluate the catalytic efficiencies of different lipids, and test for a possible correlation between hemozoin inhibition by drugs versus their antiplasmodial activity. Consistent with several previous reports, we found a good correlation between hemozoin inhibition potency versus cytostatic antiplasmodial potency (50% inhibitory concentration) for a series of chloroquine (CQ) analogues. However, we found no correlation between hemozoin inhibition potency and cytocidal antiplasmodial potency (50% lethal dose) for the same drugs, suggesting that cellular targets for these two layers of 4-aminoquinoline drug activity differ. This important concept is also explored further for QN and its stereoisomers in the accompanying paper (A. P. Gorka, K. S. Sherlach, A. C. de Dios, and P. D. Roepe, Antimicrob. Agents Chemother. 57:365-374, 2013).
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27
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Sinai AP, Roepe PD. Autophagy in Apicomplexa: a life sustaining death mechanism? Trends Parasitol 2012; 28:358-64. [PMID: 22819059 DOI: 10.1016/j.pt.2012.06.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Revised: 06/25/2012] [Accepted: 06/26/2012] [Indexed: 12/15/2022]
Abstract
Programmed cell death (PCD) pathways remain understudied in parasitic protozoa in spite of the fact that they provide potential targets for the development of new therapy. The best understood PCD pathway in higher eukaryotes is apoptosis although emerging evidence also points to autophagy as a mediator of death in certain physiological contexts. Bioinformatic analyses coupled with biochemical and cell biological studies suggest that parasitic protozoa possess the capacity for PCD including a primordial form of apoptosis. Recent work in Toxoplasma and emerging data from Plasmodium suggest that autophagy-related processes may serve as an additional death promoting pathway in Apicomplexa. Detailed mechanistic studies into the molecular basis for PCD in parasitic protozoa represent a fertile area for investigation and drug development.
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Affiliation(s)
- Anthony P Sinai
- Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky College of Medicine, Lexington, KY 40526, USA.
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28
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Dinio T, Gorka AP, McGinniss A, Roepe PD, Morgan JB. Investigating the activity of quinine analogues versus chloroquine resistant Plasmodium falciparum. Bioorg Med Chem 2012; 20:3292-7. [PMID: 22512909 PMCID: PMC3345081 DOI: 10.1016/j.bmc.2012.03.042] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Revised: 03/16/2012] [Accepted: 03/21/2012] [Indexed: 11/23/2022]
Abstract
Plasmodium falciparum, the deadliest malarial parasite species, has developed resistance against nearly all man-made antimalarial drugs within the past century. However, quinine (QN), the first antimalarial drug, remains efficacious worldwide. Some chloroquine resistant (CQR) P. falciparum strains or isolates show mild cross resistance to QN, but many do not. Further optimization of QN may provide a well-tolerated therapy with improved activity versus CQR malaria. Thus, using the Heck reaction, we have pursued a structure-activity relationship study, including vinyl group modifications of QN. Certain derivatives show good antiplasmodial activity in QN-resistant and QN-sensitive strains, with lower IC(50) values relative to QN.
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Affiliation(s)
- Theresa Dinio
- Department of Chemistry and Biochemistry, University of North Carolina, Wilmington, Dobo Hall, 601 S. College Road, Wilmington NC 28403
| | - Alexander P. Gorka
- Department of Chemistry, Department of Biochemistry and Cellular and Molecular Biology, and Center for Infectious Disease, Georgetown University, 37 and O Streets, Washington DC 20057
| | - Andrew McGinniss
- Department of Chemistry and Biochemistry, University of North Carolina, Wilmington, Dobo Hall, 601 S. College Road, Wilmington NC 28403
| | - Paul D. Roepe
- Department of Chemistry, Department of Biochemistry and Cellular and Molecular Biology, and Center for Infectious Disease, Georgetown University, 37 and O Streets, Washington DC 20057
| | - Jeremy B. Morgan
- Department of Chemistry and Biochemistry, University of North Carolina, Wilmington, Dobo Hall, 601 S. College Road, Wilmington NC 28403
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29
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Abstract
Nutrient sensing and the capacity to respond to starvation is tightly regulated as a means of cell survival. Among the features of the starvation response are induction of both translational repression and autophagy. Despite the fact that intracellular parasite like Toxoplasma gondii within a host cell predicted to be nutrient rich, they encode genes involved in both translational repression and autophagy. We therefore examined the consequence of starvation, a classic trigger of autophagy, on intracellular parasites. As expected, starvation results in the activation of the translational repression system as evidenced by elevation of phosphorylated TgIF2α (TgIF2α-P). Surprisingly, we also observe a rapid and selective fragmentation of the single parasite mitochondrion that leads irreversibly to parasite death. This profound effect was dependent primarily on the limitation of amino acids and involved signalling by the parasite TOR homologue. Notably, the effective blockade of mitochondrial fragmentation by the autophagy inhibitor 3-methyl adenine (3-MA) suggests an autophagic mechanism. In the absence of a documented apoptotic cascade in T. gondii, the data suggest that autophagy is the primary mechanism of programmed cell death in T. gondii and potentially other related parasites.
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Affiliation(s)
- Debasish Ghosh
- Department of Microbiology, Immunology and Molecular Genetics; University of Kentucky College of Medicine, Lexington KY 40536, USA
| | - Julia L. Walton
- Department of Microbiology, Immunology and Molecular Genetics; University of Kentucky College of Medicine, Lexington KY 40536, USA
| | - Paul D. Roepe
- Departments of Chemistry, Biochemistry and Cellular and Molecular Biology, Georgetown University, Washington DC. 20057, USA
| | - Anthony P. Sinai
- Department of Microbiology, Immunology and Molecular Genetics; University of Kentucky College of Medicine, Lexington KY 40536, USA
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