1
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Aldfer MM, Hulpia F, van Calenbergh S, De Koning HP. Mapping the transporter-substrate interactions of the Trypanosoma cruzi NB1 nucleobase transporter reveals the basis for its high affinity and selectivity for hypoxanthine and guanine and lack of nucleoside uptake. Mol Biochem Parasitol 2024; 258:111616. [PMID: 38401850 DOI: 10.1016/j.molbiopara.2024.111616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2023] [Revised: 02/19/2024] [Accepted: 02/20/2024] [Indexed: 02/26/2024]
Abstract
Trypanosoma cruzi is a protozoan parasite and the etiological agent of Chagas disease, a debilitating and sometimes fatal disease that continues to spread to new areas. Yet, Chagas disease is still only treated with two related nitro compounds that are insufficiently effective and cause severe side effects. Nucleotide metabolism is one of the known vulnerabilities of T. cruzi, as they are auxotrophic for purines, and nucleoside analogues have been shown to have genuine promise against this parasite in vitro and in vivo. Since purine antimetabolites require efficient uptake through transporters, we here report a detailed characterisation of the T. cruzi NB1 nucleobase transporter with the aim of elucidating the interactions between TcrNB1 and its substrates and finding the positions that can be altered in the design of novel antimetabolites without losing transportability. Systematically determining the inhibition constants (Ki) of purine analogues for TcrNB1 yielded their Gibbs free energy of interaction, ΔG0. Pairwise comparisons of substrate (hypoxanthine, guanine, adenine) and analogues allowed us to determine that optimal binding affinity by TcrNB1 requires interactions with all four nitrogen residues of the purine ring, with N1 and N9, in protonation state, functioning as presumed hydrogen bond donors and unprotonated N3 and N7 as hydrogen bond acceptors. This is the same interaction pattern as we previously described for the main nucleobase transporters of Trypanosoma brucei spp. and Leishmania major and makes it the first of the ENT-family genes that is functionally as well as genetically conserved between the three main kinetoplast pathogens.
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Affiliation(s)
- Mustafa M Aldfer
- School of Infection and Immunity, Sir Graeme Davies Building, 120 University Place, University of Glasgow, GlasgowG12 8TA, UK
| | - Fabian Hulpia
- Laboratory for Medicinal Chemistry (Campus Heymans), Ghent University, Ottergemsesteenweg 460, 9000 Gent, Belgium
| | - Serge van Calenbergh
- Laboratory for Medicinal Chemistry (Campus Heymans), Ghent University, Ottergemsesteenweg 460, 9000 Gent, Belgium
| | - Harry P De Koning
- School of Infection and Immunity, Sir Graeme Davies Building, 120 University Place, University of Glasgow, GlasgowG12 8TA, UK.
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2
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Timm BL, da Gama ANS, Batista MM, Batista DDGJ, Boykin DW, De Koning HP, Correia Soeiro MDN. Arylimidamides Have Potential for Chemoprophylaxis against Blood-Transmitted Chagas Disease. Pathogens 2023; 12:pathogens12050701. [PMID: 37242371 DOI: 10.3390/pathogens12050701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 04/28/2023] [Accepted: 05/11/2023] [Indexed: 05/28/2023] Open
Abstract
Chagas disease (CD) affects over 6 million people worldwide and can be transmitted iatrogenically. Crystal violet (CV) was previously used for pathogen reduction but has harmful side-effects. In the present study, three arylimidamides (AIAs) and CV were used to sterilize mice blood samples experimentally contaminated with bloodstream trypomastigotes (BT) of Trypanosoma cruzi, at non hemolytic doses. All AIAs were not toxic to mouse blood cells until the highest tested concentration (96 µM). The previous treatment of BT with the AIAs impaired the infection establishment of cardiac cell cultures. In vivo assays showed that pre-incubation of mouse blood samples with the AIAs and CV (96 µM) significantly suppressed the parasitemia peak, but only the AIA DB1831 gave ≥90% animal survival, while vehicle treated samples reached 0%. Our findings support further studies regarding the potential use of AIAs for blood bank purposes.
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Affiliation(s)
- Bruno Lisboa Timm
- Laboratório de Biologia Celular, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro 21045-900, Brazil
| | | | - Marcos Meuser Batista
- Laboratório de Biologia Celular, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro 21045-900, Brazil
| | - Denise da Gama Jaén Batista
- Laboratório de Biologia Celular, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro 21045-900, Brazil
| | - David W Boykin
- Department of Chemistry, Georgia State University, Atlanta, GA 30303, USA
| | - Harry P De Koning
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G43 2DX, UK
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3
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Ungogo MA, Aldfer MM, Natto MJ, Zhuang H, Chisholm R, Walsh K, McGee M, Ilbeigi K, Asseri JI, Burchmore RJS, Caljon G, Van Calenbergh S, De Koning HP. Cloning and Characterization of Trypanosoma congolense and T. vivax Nucleoside Transporters Reveal the Potential of P1-Type Carriers for the Discovery of Broad-Spectrum Nucleoside-Based Therapeutics against Animal African Trypanosomiasis. Int J Mol Sci 2023; 24:ijms24043144. [PMID: 36834557 PMCID: PMC9960827 DOI: 10.3390/ijms24043144] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Revised: 02/01/2023] [Accepted: 02/02/2023] [Indexed: 02/09/2023] Open
Abstract
African Animal Trypanosomiasis (AAT), caused predominantly by Trypanosoma brucei brucei, T. vivax and T. congolense, is a fatal livestock disease throughout Sub-Saharan Africa. Treatment options are very limited and threatened by resistance. Tubercidin (7-deazaadenosine) analogs have shown activity against individual parasites but viable chemotherapy must be active against all three species. Divergence in sensitivity to nucleoside antimetabolites could be caused by differences in nucleoside transporters. Having previously characterized the T. brucei nucleoside carriers, we here report the functional expression and characterization of the main adenosine transporters of T. vivax (TvxNT3) and T. congolense (TcoAT1/NT10), in a Leishmania mexicana cell line ('SUPKO') lacking adenosine uptake. Both carriers were similar to the T. brucei P1-type transporters and bind adenosine mostly through interactions with N3, N7 and 3'-OH. Expression of TvxNT3 and TcoAT1 sensitized SUPKO cells to various 7-substituted tubercidins and other nucleoside analogs although tubercidin itself is a poor substrate for P1-type transporters. Individual nucleoside EC50s were similar for T. b. brucei, T. congolense, T. evansi and T. equiperdum but correlated less well with T. vivax. However, multiple nucleosides including 7-halogentubercidines displayed pEC50>7 for all species and, based on transporter and anti-parasite SAR analyses, we conclude that nucleoside chemotherapy for AAT is viable.
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Affiliation(s)
- Marzuq A. Ungogo
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
- Department of Veterinary Pharmacology and Toxicology, Ahmadu Bello University, Zaria 810107, Kaduna State, Nigeria
- Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian EH25 9RG, UK
| | - Mustafa M. Aldfer
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
| | - Manal J. Natto
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
| | - Hainan Zhuang
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
| | - Robyn Chisholm
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
| | - Katy Walsh
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
| | - MarieClaire McGee
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
| | - Kayhan Ilbeigi
- Laboratory of Microbiology, Parasitology and Hygiene (LMPH), University of Antwerp, B-2610 Wilrijk, Belgium
| | - Jamal Ibrahim Asseri
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
| | - Richard J. S. Burchmore
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
| | - Guy Caljon
- Laboratory of Microbiology, Parasitology and Hygiene (LMPH), University of Antwerp, B-2610 Wilrijk, Belgium
| | - Serge Van Calenbergh
- Laboratory for Medicinal Chemistry (Campus Heymans), Ghent University, B-9000 Gent, Belgium
| | - Harry P. De Koning
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
- Correspondence:
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4
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Fiuza LFDA, Batista DGJ, Girão RD, Hulpia F, Finamore-Araújo P, Aldfer MM, Elmahallawy EK, De Koning HP, Moreira O, Van Calenbergh S, Soeiro MDNC. Phenotypic Evaluation of Nucleoside Analogues against Trypanosoma cruzi Infection: In Vitro and In Vivo Approaches. Molecules 2022; 27:molecules27228087. [PMID: 36432189 PMCID: PMC9695592 DOI: 10.3390/molecules27228087] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 11/07/2022] [Accepted: 11/08/2022] [Indexed: 11/23/2022] Open
Abstract
Chagas disease, caused by Trypanosoma cruzi (T. cruzi), is a serious public health problem. Current treatment is restricted to two drugs, benznidazole and nifurtimox, displaying serious efficacy and safety drawbacks. Nucleoside analogues represent a promising alternative as protozoans do not biosynthesize purines and rely on purine salvage from the hosts. Protozoan transporters often present different substrate specificities from mammalian transporters, justifying the exploration of nucleoside analogues as therapeutic agents. Previous reports identified nucleosides with potent trypanocidal activity; therefore, two 7-derivatized tubercidins (FH11706, FH10714) and a 3′-deoxytubercidin (FH8513) were assayed against T. cruzi. They were highly potent and selective, and the uptake of the tubercidin analogues appeared to be mediated by the nucleoside transporter TcrNT2. At 10 μM, the analogues reduced parasitemia >90% in 2D and 3D cardiac cultures. The washout assays showed that FH10714 sterilized the infected cultures. Given orally, the compounds did not induce noticeable mouse toxicity (50 mg/kg), suppressed the parasitemia of T. cruzi-infected Swiss mice (25 mg/kg, 5 days) and presented DNA amplification below the limit of detection. These findings justify further studies with longer treatment regimens, as well as evaluations in combination with nitro drugs, aiming to identify more effective and safer therapies for Chagas disease.
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Affiliation(s)
- Ludmila F. de A. Fiuza
- Laboratório de Biologia Celular, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Av. Brasil, 4365 Manguinhos, Rio de Janeiro 21040-360, Brazil
| | - Denise G. J. Batista
- Laboratório de Biologia Celular, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Av. Brasil, 4365 Manguinhos, Rio de Janeiro 21040-360, Brazil
| | - Roberson D. Girão
- Laboratório de Biologia Celular, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Av. Brasil, 4365 Manguinhos, Rio de Janeiro 21040-360, Brazil
| | - Fabian Hulpia
- Laboratory for Medicinal Chemistry (Campus Heymans), Ghent University, Ottergemsesteenweg 460, B-9000 Ghent, Belgium
| | - Paula Finamore-Araújo
- Laboratório de Virologia Molecular, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, Rio de Janeiro 20000-000, Brazil
| | - Mustafa M. Aldfer
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow 62694, UK
| | - Ehab Kotb Elmahallawy
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow 62694, UK
- Department of Zoonoses, Faculty of Veterinary Medicine, Sohag University, Sohag 82524, Egypt
| | - Harry P. De Koning
- School of Infection and Immunity, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow 62694, UK
| | - Otacílio Moreira
- Laboratório de Virologia Molecular, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, Rio de Janeiro 20000-000, Brazil
| | - Serge Van Calenbergh
- Laboratory for Medicinal Chemistry (Campus Heymans), Ghent University, Ottergemsesteenweg 460, B-9000 Ghent, Belgium
| | - Maria de Nazaré C. Soeiro
- Laboratório de Biologia Celular, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Av. Brasil, 4365 Manguinhos, Rio de Janeiro 21040-360, Brazil
- Correspondence: ; Tel.: +55-21-2562-1368
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5
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Natto MJ, Miyamoto Y, Munday JC, AlSiari TA, Al-Salabi MI, Quashie NB, Eze AA, Eckmann L, De Koning HP. Comprehensive characterization of purine and pyrimidine transport activities in Trichomonas vaginalis and functional cloning of a trichomonad nucleoside transporter. Mol Microbiol 2021; 116:1489-1511. [PMID: 34738285 PMCID: PMC8688338 DOI: 10.1111/mmi.14840] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2021] [Revised: 10/30/2021] [Accepted: 10/30/2021] [Indexed: 11/30/2022]
Abstract
Trichomoniasis is a common and widespread sexually-transmitted infection, caused by the protozoan parasite Trichomonas vaginalis. T. vaginalis lacks the biosynthetic pathways for purines and pyrimidines, making nucleoside metabolism a drug target. Here we report the first comprehensive investigation into purine and pyrimidine uptake by T. vaginalis. Multiple carriers were identified and characterized with regard to substrate selectivity and affinity. For nucleobases, a high-affinity adenine transporter, a possible guanine transporter and a low affinity uracil transporter were found. Nucleoside transporters included two high affinity adenosine/guanosine/uridine/cytidine transporters distinguished by different affinities to inosine, a lower affinity adenosine transporter, and a thymidine transporter. Nine Equilibrative Nucleoside Transporter (ENT) genes were identified in the T. vaginalis genome. All were expressed equally in metronidazole-resistant and -sensitive strains. Only TvagENT2 was significantly upregulated in the presence of extracellular purines; expression was not affected by co-culture with human cervical epithelial cells. All TvagENTs were cloned and separately expressed in Trypanosoma brucei. We identified the main broad specificity nucleoside carrier, with high affinity for uridine and cytidine as well as purine nucleosides including inosine, as TvagENT3. The in-depth characterization of purine and pyrimidine transporters provides a critical foundation for the development of new anti-trichomonal nucleoside analogues.
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Affiliation(s)
- Manal J. Natto
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Yukiko Miyamoto
- Department of Medicine, University of California, San Diego, La Jolla, California 92093, United States
| | - Jane C. Munday
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Tahani A. AlSiari
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Mohammed I. Al-Salabi
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Neils B. Quashie
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
- Centre for Tropical Clinical Pharmacology and Therapeutics, University of Ghana Medical School, University of Ghana
| | - Anthonius A. Eze
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
- Current affiliation: Department of Medical Biochemistry, Faculty of Basic Medical Sciences, College of Medicine, University of Nigeria, Enugu Campus, Enugu, Nigeria
| | - Lars Eckmann
- Department of Medicine, University of California, San Diego, La Jolla, California 92093, United States
| | - Harry P. De Koning
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
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6
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Alotaibi A, Ebiloma GU, Williams R, Alfayez IA, Natto MJ, Alenezi S, Siheri W, AlQarni M, Igoli JO, Fearnley J, De Koning HP, Watson DG. Activity of Compounds from Temperate Propolis against Trypanosoma brucei and Leishmania mexicana. Molecules 2021; 26:molecules26133912. [PMID: 34206940 PMCID: PMC8272135 DOI: 10.3390/molecules26133912] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Revised: 06/17/2021] [Accepted: 06/18/2021] [Indexed: 11/16/2022] Open
Abstract
Ethanolic extracts of samples of temperate zone propolis, four from the UK and one from Poland, were tested against three Trypanosoma brucei strains and displayed EC50 values < 20 µg/mL. The extracts were fractionated, from which 12 compounds and one two-component mixture were isolated, and characterized by NMR and high-resolution mass spectrometry, as 3-acetoxypinobanksin, tectochrysin, kaempferol, pinocembrin, 4′-methoxykaempferol, galangin, chrysin, apigenin, pinostrobin, cinnamic acid, coumaric acid, cinnamyl ester/coumaric acid benzyl ester (mixture), 4′,7-dimethoxykaempferol, and naringenin 4′,7-dimethyl ether. The isolated compounds were tested against drug-sensitive and drug-resistant strains of T. brucei and Leishmania mexicana, with the highest activities ≤ 15 µM. The most active compounds against T. brucei were naringenin 4′,7 dimethyl ether and 4′methoxy kaempferol with activity of 15–20 µM against the three T. brucei strains. The most active compounds against L. mexicana were 4′,7-dimethoxykaempferol and the coumaric acid ester mixture, with EC50 values of 12.9 ± 3.7 µM and 13.1 ± 1.0 µM. No loss of activity was found with the diamidine- and arsenical-resistant or phenanthridine-resistant T. brucei strains, or the miltefosine-resistant L. mexicana strain; no clear structure activity relationship was observed for the isolated compounds. Temperate propolis yields multiple compounds with anti-kinetoplastid activity.
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Affiliation(s)
- Adullah Alotaibi
- Strathclyde Institute of Pharmacy and Biomedical Science, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, UK; (A.A.); (S.A.); (J.O.I.)
| | - Godwin U. Ebiloma
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK; (G.U.E.); (I.A.A.); (M.J.N.)
- School of Health and Life Sciences, Teesside University, Middlesbrough TS1 3BX, UK
| | - Roderick Williams
- IBEHR, School of Health and Life Science, University of the West of Scotland, High Street, Paisley PA1 2BE, UK;
| | - Ibrahim A. Alfayez
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK; (G.U.E.); (I.A.A.); (M.J.N.)
- Qassim Health Cluster, Ministry of Health, Buraydah 52367, Saudi Arabia
- Department of Pharmaceutical Chemistry, College of Clinical Pharmacy, Imam Abdulrahman Bin Faisal University, Dammam 31441, Saudi Arabia;
| | - Manal J. Natto
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK; (G.U.E.); (I.A.A.); (M.J.N.)
| | - Sameah Alenezi
- Strathclyde Institute of Pharmacy and Biomedical Science, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, UK; (A.A.); (S.A.); (J.O.I.)
| | - Weam Siheri
- Department of Pharmacognosy and Natural Products, Faculty of Pharmacy, University of Tripoli, Tripoli 50676, Libya;
| | - Malik AlQarni
- Department of Pharmaceutical Chemistry, College of Clinical Pharmacy, Imam Abdulrahman Bin Faisal University, Dammam 31441, Saudi Arabia;
| | - John O. Igoli
- Strathclyde Institute of Pharmacy and Biomedical Science, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, UK; (A.A.); (S.A.); (J.O.I.)
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK; (G.U.E.); (I.A.A.); (M.J.N.)
- Department of Chemistry, University of Agriculture, Makurdi PMB 2373, Nigeria
| | | | - Harry P. De Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK; (G.U.E.); (I.A.A.); (M.J.N.)
- Correspondence: (H.P.D.K.); (D.G.W.)
| | - David G. Watson
- Strathclyde Institute of Pharmacy and Biomedical Science, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, UK; (A.A.); (S.A.); (J.O.I.)
- Correspondence: (H.P.D.K.); (D.G.W.)
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7
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De Araújo JS, da Silva PB, Batista MM, Peres RB, Cardoso-Santos C, Kalejaiye TD, Munday JC, De Heuvel E, Sterk GJ, Augustyns K, Salado IG, Matheeussen A, De Esch I, De Koning HP, Leurs R, Maes L, Soeiro MDNC. Evaluation of phthalazinone phosphodiesterase inhibitors with improved activity and selectivity against Trypanosoma cruzi. J Antimicrob Chemother 2021; 75:958-967. [PMID: 31860098 DOI: 10.1093/jac/dkz516] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 10/15/2019] [Accepted: 11/08/2019] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND Chagas' disease, caused by the protozoan parasite Trypanosoma cruzi, needs urgent alternative therapeutic options as the treatments currently available display severe limitations, mainly related to efficacy and toxicity. OBJECTIVES As phosphodiesterases (PDEs) have been claimed as novel targets against T. cruzi, our aim was to evaluate the biological aspects of 12 new phthalazinone PDE inhibitors against different T. cruzi strains and parasite forms relevant for human infection. METHODS In vitro trypanocidal activity of the inhibitors was assessed alone and in combination with benznidazole. Their effects on parasite ultrastructural and cAMP levels were determined. PDE mRNA levels from the different T. cruzi forms were measured by quantitative reverse transcription PCR. RESULTS Five TcrPDEs were found to be expressed in all parasite stages. Four compounds displayed strong effects against intracellular amastigotes. Against bloodstream trypomastigotes (BTs), three were at least as potent as benznidazole. In vitro combination therapy with one of the most active inhibitors on both parasite forms (NPD-040) plus benznidazole demonstrated a quite synergistic profile (xΣ FICI = 0.58) against intracellular amastigotes but no interaction (xΣ FICI = 1.27) when BTs were assayed. BTs treated with NPD-040 presented disrupted Golgi apparatus, a swollen flagellar pocket and signs of autophagy. cAMP measurements of untreated parasites showed that amastigotes have higher ability to efflux this second messenger than BTs. NPD-001 and NPD-040 increase the intracellular cAMP content in both BTs and amastigotes, which is also released into the extracellular milieu. CONCLUSIONS The findings demonstrate the potential of PDE inhibitors as anti-T. cruzi drug candidates.
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Affiliation(s)
| | | | - Marcos Meuser Batista
- Laboratório de Biologia Celular, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil
| | - Raiza Brandão Peres
- Laboratório de Biologia Celular, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil
| | - Camila Cardoso-Santos
- Laboratório de Biologia Celular, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil
| | - Titilola D Kalejaiye
- Institute of Infection, Immunity & Inflammation, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK
| | - Jane C Munday
- Institute of Infection, Immunity & Inflammation, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK
| | - Erik De Heuvel
- Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines & Systems, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Geert Jan Sterk
- Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines & Systems, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Koen Augustyns
- Laboratory of Medicinal Chemistry, University of Antwerp, Antwerp, Belgium
| | - Irene G Salado
- Laboratory of Medicinal Chemistry, University of Antwerp, Antwerp, Belgium
| | - An Matheeussen
- Laboratory for Microbiology, Parasitology and Hygiene (LMPH), University of Antwerp, Antwerp, Belgium
| | - Iwan De Esch
- Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines & Systems, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Harry P De Koning
- Institute of Infection, Immunity & Inflammation, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK
| | - Rob Leurs
- Medicinal Chemistry, Amsterdam Institute for Molecules, Medicines & Systems, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Louis Maes
- Laboratory for Microbiology, Parasitology and Hygiene (LMPH), University of Antwerp, Antwerp, Belgium
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8
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Alkhaldi AA, Abdelgawad MA, Youssif BG, El-Gendy AO, De Koning HP. Synthesis, antimicrobial activities and GAPDH docking of novel 1, 2, 3-triazole derivatives. TROP J PHARM RES 2021. [DOI: 10.4314/tjpr.v18i5.27] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Purpose: To synthesize new triazole derivatives in order to overcome the problem of side effects of antimicrobial agents and microbial resistance, while broadening the spectrum of antimicrobial activity.
Methods: The starting triazole, compound 1, was prepared through click chemistry and reacted with chloroacetyl chloride to yield compound II. Triazole 1 was reacted with acids and aldehydes to produce oxadiazole (III) and azomethine (IV) which cyclized in acetic anhydride to give a new acetylated oxadiazole (V). Minimum inhibitory concentration (MIC) and resorufin assays were used for antibacterial and anti-parasitic screening, respectively. Compounds II and IVb were subjected to molecular docking studies using glyceraldehyde-3-phosphate dehydrogenase (GAPDH) Molecular Operating Environment (MOE) program.
Results: Novel oxazole-triazole derivative (III) showed high activity against Pseudomonas aeruginosa and moderate activity against Staphylococcus epidermidis, whereas compound IVc showed moderate activity against Staphylococcus epidermidis. Chloro-acetyl-triazole II and 2-hydroxyphenyl-triazole Schiff base (Ivb) showed pronounced activity against the kinetoplastid parasites, Leishmania major, Leishmania mexicana and Trypanosoma brucei.
Conclusion: The new synthesized triazoles represent a new antimicrobial scaffold and identifies potential new lead compounds for follow-up and for further mechanistic studies.
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9
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Carruthers LV, Munday JC, Ebiloma GU, Steketee P, Jayaraman S, Campagnaro GD, Ungogo MA, Lemgruber L, Donachie AM, Rowan TG, Peter R, Morrison LJ, Barrett MP, De Koning HP. Diminazene resistance in Trypanosoma congolense is not caused by reduced transport capacity but associated with reduced mitochondrial membrane potential. Mol Microbiol 2021; 116:564-588. [PMID: 33932053 DOI: 10.1111/mmi.14733] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 04/14/2021] [Accepted: 04/27/2021] [Indexed: 01/27/2023]
Abstract
Trypanosoma congolense is a principal agent causing livestock trypanosomiasis in Africa, costing developing economies billions of dollars and undermining food security. Only the diamidine diminazene and the phenanthridine isometamidium are regularly used, and resistance is widespread but poorly understood. We induced stable diminazene resistance in T. congolense strain IL3000 in vitro. There was no cross-resistance with the phenanthridine drugs, melaminophenyl arsenicals, oxaborole trypanocides, or with diamidine trypanocides, except the close analogs DB829 and DB75. Fluorescence microscopy showed that accumulation of DB75 was inhibited by folate. Uptake of [3 H]-diminazene was slow with low affinity and partly but reciprocally inhibited by folate and by competing diamidines. Expression of T. congolense folate transporters in diminazene-resistant Trypanosoma brucei brucei significantly sensitized the cells to diminazene and DB829, but not to oxaborole AN7973. However, [3 H]-diminazene transport studies, whole-genome sequencing, and RNA-seq found no major changes in diminazene uptake, folate transporter sequence, or expression. Instead, all resistant clones displayed a moderate reduction in the mitochondrial membrane potential Ψm. We conclude that diminazene uptake in T. congolense proceed via multiple low affinity mechanisms including folate transporters; while resistance is associated with a reduction in Ψm it is unclear whether this is the primary cause of the resistance.
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Affiliation(s)
- Lauren V Carruthers
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Jane C Munday
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Godwin U Ebiloma
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.,School of Health and Life Sciences, Teesside University, Middlesbrough, UK
| | - Pieter Steketee
- Roslin Institute, Royal (Dick) School of Veterinary Sciences, University of Edinburgh, Edinburgh, UK
| | - Siddharth Jayaraman
- Roslin Institute, Royal (Dick) School of Veterinary Sciences, University of Edinburgh, Edinburgh, UK
| | - Gustavo D Campagnaro
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Marzuq A Ungogo
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Leandro Lemgruber
- Glasgow Imaging Facility, Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Anne-Marie Donachie
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Tim G Rowan
- Global Alliance for Livestock Veterinary Medicine, Pentlands Science Park, Edinburgh, UK
| | - Rose Peter
- Global Alliance for Livestock Veterinary Medicine, Pentlands Science Park, Edinburgh, UK
| | - Liam J Morrison
- Roslin Institute, Royal (Dick) School of Veterinary Sciences, University of Edinburgh, Edinburgh, UK
| | - Michael P Barrett
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.,Wellcome Centre for Integrative Parasitology, University of Glasgow, Glasgow, UK
| | - Harry P De Koning
- Institute of Infection, Immunity and Inflammation, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
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10
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Anyam JV, Daikwo PE, Ungogo MA, Nweze NE, Igoli NP, Gray AI, De Koning HP, Igoli JO. Two New Antiprotozoal Diterpenes From the Roots of Acacia nilotica. Front Chem 2021; 9:624741. [PMID: 33968894 PMCID: PMC8097170 DOI: 10.3389/fchem.2021.624741] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 01/29/2021] [Indexed: 11/13/2022] Open
Abstract
The powdered roots of the medicinal plant Acacia nilotica were extracted with hexane and ethyl acetate, and the extracts were subjected to column chromatography for the isolation of potentially bioactive compounds and their screening against kinetoplastid pathogens. NMR and HREI mass spectrometric analyses identified two new diterpenes, characterized as 16, 19-dihydroxycassa-12-en-15-one (Sandynone, 1) and (5S, 7R, 8R, 9R, 10S, 13Z, 17S)-7,8:7,17:16,17-triepoxy-7,8-seco-cassa-13-ene (niloticane B, 2). The previously reported (5S,7R,8R,9R,10S) -(-)-7,8-seco-7, 8-oxacassa-13,15-diene-7,17-diol (3), (5S,7R,8R,9R,10S) -(-)-7,8-seco-7, 8-oxacassa-13,15-dien-7-ol-17-al (4), and (5S,7R,8R,9R,10S) -(-)-7,8-seco-7, 8-oxacassa-13,15-dien-7-ol (5) a, mixture of stigmasterol (6a) and sitosterol (6b), and lupeol (7) were also isolated. Several column fractions displayed significant activity against a panel of Trypanosoma and Leishmania spp., and from the most active fraction, compound 4 was isolated with high purity. The compound displayed high activity, particularly against T. brucei, T. evansi, and L. mexicana (0.88-11.7 µM) but only a modest effect against human embryonic kidney cells and no cross-resistance with the commonly used melaminophenyl arsenical and diamidine classes of trypanocides. The effect of compound 4 against L. mexicana promastigotes was irreversible after a 5-h exposure, leading to the sterilization of the culture between 24 and 48 h.
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Affiliation(s)
- John V Anyam
- Phytochemistry Research Group, Department of Chemistry, University of Agriculture, Makurdi, Nigeria
| | - Priscilla E Daikwo
- Phytochemistry Research Group, Department of Chemistry, University of Agriculture, Makurdi, Nigeria
| | - Marzuq A Ungogo
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom.,Department of Veterinary Pharmacology and Toxicology, Ahmadu Bello University, Zaria, Nigeria
| | - Nwakaego E Nweze
- Department of Veterinary Medicine, Faculty of Veterinary Medicine, University of Nigeria, Nsukka, Nigeria
| | | | - Alexander I Gray
- Strathclyde Institute of Pharmacy and Biomedical Science, University of Strathclyde, Glasgow, United Kingdom
| | - Harry P De Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - John O Igoli
- Phytochemistry Research Group, Department of Chemistry, University of Agriculture, Makurdi, Nigeria
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11
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Ebiloma GU, Ichoron N, Siheri W, Watson DG, Igoli JO, De Koning HP. The Strong Anti-Kinetoplastid Properties of Bee Propolis: Composition and Identification of the Active Agents and Their Biochemical Targets. Molecules 2020; 25:E5155. [PMID: 33167520 PMCID: PMC7663965 DOI: 10.3390/molecules25215155] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/01/2020] [Accepted: 11/03/2020] [Indexed: 12/12/2022] Open
Abstract
The kinetoplastids are protozoa characterized by the presence of a distinctive organelle, called the kinetoplast, which contains a large amount of DNA (kinetoplast DNA (kDNA)) inside their single mitochondrion. Kinetoplastids of medical and veterinary importance include Trypanosoma spp. (the causative agents of human and animal African Trypanosomiasis and of Chagas disease) and Leishmania spp. (the causative agents of the various forms of leishmaniasis). These neglected diseases affect millions of people across the globe, but drug treatment is hampered by the challenges of toxicity and drug resistance, among others. Propolis (a natural product made by bees) and compounds isolated from it are now being investigated as novel treatments of kinetoplastid infections. The anti-kinetoplastid efficacy of propolis is probably a consequence of its reported activity against kinetoplastid parasites of bees. This article presents a review of the reported anti-kinetoplastid potential of propolis, highlighting its anti-kinetoplastid activity in vitro and in vivo regardless of geographical origin. The mode of action of propolis depends on the organism it is acting on and includes growth inhibition, immunomodulation, macrophage activation, perturbation of the cell membrane architecture, phospholipid disturbances, and mitochondrial targets. This gives ample scope for further investigations toward the rational development of sustainable anti-kinetoplastid drugs.
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Affiliation(s)
- Godwin U. Ebiloma
- School of Health and Life Sciences, Teesside University, Middlesbrough TS1 3BX, UK;
| | - Nahandoo Ichoron
- Phytochemistry Research Group, Department of Chemistry, University of Agriculture, Makurdi 2373, Nigeria; (N.I.) (J.O.I.)
| | - Weam Siheri
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G1 1XQ, UK; (W.S.), (D.G.W.)
| | - David G. Watson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G1 1XQ, UK; (W.S.), (D.G.W.)
| | - John O. Igoli
- Phytochemistry Research Group, Department of Chemistry, University of Agriculture, Makurdi 2373, Nigeria; (N.I.) (J.O.I.)
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G1 1XQ, UK; (W.S.), (D.G.W.)
| | - Harry P. De Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, UK
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12
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Alghamdi AH, Munday JC, Campagnaro GD, Gurvic D, Svensson F, Okpara CE, Kumar A, Quintana J, Martin Abril ME, Milić P, Watson L, Paape D, Settimo L, Dimitriou A, Wielinska J, Smart G, Anderson LF, Woodley CM, Kelly SPY, Ibrahim HM, Hulpia F, Al-Salabi MI, Eze AA, Sprenger T, Teka IA, Gudin S, Weyand S, Field M, Dardonville C, Tidwell RR, Carrington M, O'Neill P, Boykin DW, Zachariae U, De Koning HP. Positively selected modifications in the pore of TbAQP2 allow pentamidine to enter Trypanosoma brucei. eLife 2020; 9:56416. [PMID: 32762841 PMCID: PMC7473772 DOI: 10.7554/elife.56416] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Accepted: 08/06/2020] [Indexed: 11/25/2022] Open
Abstract
Mutations in the Trypanosoma brucei aquaporin AQP2 are associated with resistance to pentamidine and melarsoprol. We show that TbAQP2 but not TbAQP3 was positively selected for increased pore size from a common ancestor aquaporin. We demonstrate that TbAQP2’s unique architecture permits pentamidine permeation through its central pore and show how specific mutations in highly conserved motifs affect drug permeation. Introduction of key TbAQP2 amino acids into TbAQP3 renders the latter permeable to pentamidine. Molecular dynamics demonstrates that permeation by dicationic pentamidine is energetically favourable in TbAQP2, driven by the membrane potential, although aquaporins are normally strictly impermeable for ionic species. We also identify the structural determinants that make pentamidine a permeant although most other diamidine drugs are excluded. Our results have wide-ranging implications for optimising antitrypanosomal drugs and averting cross-resistance. Moreover, these new insights in aquaporin permeation may allow the pharmacological exploitation of other members of this ubiquitous gene family. African sleeping sickness is a potentially deadly illness caused by the parasite Trypanosoma brucei. The disease is treatable, but many of the current treatments are old and are becoming increasingly ineffective. For instance, resistance is growing against pentamidine, a drug used in the early stages in the disease, as well as against melarsoprol, which is deployed when the infection has progressed to the brain. Usually, cases resistant to pentamidine are also resistant to melarsoprol, but it is still unclear why, as the drugs are chemically unrelated. Studies have shown that changes in a water channel called aquaglyceroporin 2 (TbAQP2) contribute to drug resistance in African sleeping sickness; this suggests that it plays a role in allowing drugs to kill the parasite. This molecular ‘drain pipe’ extends through the surface of T. brucei, and should allow only water and a molecule called glycerol in and out of the cell. In particular, the channel should be too narrow to allow pentamidine or melarsoprol to pass through. One possibility is that, in T. brucei, the TbAQP2 channel is abnormally wide compared to other members of its family. Alternatively, pentamidine and melarsoprol may only bind to TbAQP2, and then ‘hitch a ride’ when the protein is taken into the parasite as part of the natural cycle of surface protein replacement. Alghamdi et al. aimed to tease out these hypotheses. Computer models of the structure of the protein were paired with engineered changes in the key areas of the channel to show that, in T. brucei, TbAQP2 provides a much broader gateway into the cell than observed for similar proteins. In addition, genetic analysis showed that this version of TbAQP2 has been actively selected for during the evolution process of T. brucei. This suggests that the parasite somehow benefits from this wider aquaglyceroporin variant. This is a new resistance mechanism, and it is possible that aquaglyceroporins are also larger than expected in other infectious microbes. The work by Alghamdi et al. therefore provides insight into how other germs may become resistant to drugs.
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Affiliation(s)
- Ali H Alghamdi
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Jane C Munday
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | | | - Dominik Gurvic
- Computational Biology Centre for Translational and Interdisciplinary Research, University of Dundee, Dundee, United Kingdom
| | - Fredrik Svensson
- IOTA Pharmaceuticals Ltd, St Johns Innovation Centre, Cambridge, United Kingdom
| | - Chinyere E Okpara
- Department of Chemistry, University of Liverpool, Liverpool, United Kingdom
| | - Arvind Kumar
- Chemistry Department, Georgia State University, Atlanta, United States
| | - Juan Quintana
- School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | | | - Patrik Milić
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Laura Watson
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Daniel Paape
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Luca Settimo
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Anna Dimitriou
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Joanna Wielinska
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Graeme Smart
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Laura F Anderson
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | | | - Siu Pui Ying Kelly
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Hasan Ms Ibrahim
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Fabian Hulpia
- Laboratory for Medicinal Chemistry, University of Ghent, Ghent, Belgium
| | - Mohammed I Al-Salabi
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Anthonius A Eze
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Teresa Sprenger
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Ibrahim A Teka
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Simon Gudin
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Simone Weyand
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Mark Field
- School of Life Sciences, University of Dundee, Dundee, United Kingdom.,Institute of Parasitology, Biology Centre, Czech Academy of Sciences, Ceske Budejovice, Czech Republic
| | | | - Richard R Tidwell
- Department of Pathology and Lab Medicine, University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Mark Carrington
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
| | - Paul O'Neill
- Department of Chemistry, University of Liverpool, Liverpool, United Kingdom
| | - David W Boykin
- Chemistry Department, Georgia State University, Atlanta, United States
| | - Ulrich Zachariae
- Computational Biology Centre for Translational and Interdisciplinary Research, University of Dundee, Dundee, United Kingdom
| | - Harry P De Koning
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
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13
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P De Koning H. The Drugs of Sleeping Sickness: Their Mechanisms of Action and Resistance, and a Brief History. Trop Med Infect Dis 2020; 5:E14. [PMID: 31963784 PMCID: PMC7157662 DOI: 10.3390/tropicalmed5010014] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 01/15/2020] [Accepted: 01/16/2020] [Indexed: 12/17/2022] Open
Abstract
With the incidence of sleeping sickness in decline and genuine progress being made towards the WHO goal of eliminating sleeping sickness as a major public health concern, this is a good moment to evaluate the drugs that 'got the job done': their development, their limitations and the resistance that the parasites developed against them. This retrospective looks back on the remarkable story of chemotherapy against trypanosomiasis, a story that goes back to the very origins and conception of chemotherapy in the first years of the 20 century and is still not finished today.
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Affiliation(s)
- Harry P De Koning
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow G12 8TA, UK
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14
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Eze AA, Igoli J, Gray AI, Skellern GG, De Koning HP. The individual components of commercial isometamidium do not possess stronger trypanocidal activity than the mixture, nor bypass isometamidium resistance. Int J Parasitol Drugs Drug Resist 2019; 9:54-58. [PMID: 30685630 PMCID: PMC6356087 DOI: 10.1016/j.ijpddr.2019.01.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 01/17/2019] [Accepted: 01/20/2019] [Indexed: 11/15/2022]
Abstract
The four components present in the trypanocidal treatment Samorin, the commercially available formulation of isometamidium, were separated and purified by column chromatography. These compounds as well as the Samorin mixture and the other phenanthridine trypanocide, homidium, were tested on Trypanosoma congolense and wild type, diamidine- and isometamidium-resistant Trypanosoma brucei brucei strains using an Alamar blue drug sensitivity assay. EC50 values obtained suggest that M&B4180A (2) was the most active of the components, followed by M&B38897 (1) in all the strains tested, whereas M&B4596 (4) was inactive. Samorin was found to be significantly more active than any of the individual components alone, against T. congolense and all three T. b, brucei strains. Samorin and all its active constituents displayed reduced activity against the previously characterised isometamidium-resistant strain ISMR1.
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Affiliation(s)
- Anthonius A Eze
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom; Medical Biochemistry Department, Faculty of Basic Medical Sciences, College of Medicine, University of Nigeria, Enugu Campus, Enugu, Nigeria
| | - John Igoli
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK; Department of Chemistry, College of Science, University of Agriculture, Makurdi, Nigeria
| | - Alexander I Gray
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Graham G Skellern
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Harry P De Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom.
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15
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Botros SS, William S, Sabra ANA, El-Lakkany NM, Seif El-Din SH, García-Rubia A, Sebastián-Pérez V, Blaazer AR, de Heuvel E, Sijm M, Zheng Y, Salado IG, Munday JC, Maes L, de Esch IJP, Sterk GJ, Augustyns K, Leurs R, Gil C, De Koning HP. Screening of a PDE-focused library identifies imidazoles with in vitro and in vivo antischistosomal activity. Int J Parasitol Drugs Drug Resist 2019; 9:35-43. [PMID: 30669086 PMCID: PMC6350229 DOI: 10.1016/j.ijpddr.2019.01.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 01/10/2019] [Accepted: 01/13/2019] [Indexed: 01/10/2023]
Abstract
We report the evaluation of 265 compounds from a PDE-focused library for their antischistosomal activity, assessed in vitro using Schistosoma mansoni. Of the tested compounds, 171 (64%) displayed selective in vitro activity, with 16 causing worm hypermotility/spastic contractions and 41 inducing various degrees of worm killing at 100 μM, with the surviving worms displaying sluggish movement, worm unpairing and complete absence of eggs. The compounds that did not affect worm viability (n = 72) induced a complete cessation of ovipositing. 82% of the compounds had an impact on male worms whereas female worms were barely affected. In vivo evaluation in S. mansoni-infected mice with the in vitro 'hit' NPD-0274 at 20 mg/kg/day orally for 5 days resulted in worm burden reductions of 29% and intestinal tissue egg load reduction of 35% at 10 days post-treatment. Combination of praziquantel (PZQ) at 10 mg/kg/day for 5 days with NPD-0274 or NPD-0298 resulted in significantly higher worm killing than PZQ alone, as well as a reduction in intestinal tissue egg load, disappearance of immature eggs and an increase in the number of dead eggs.
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Affiliation(s)
- Sanaa S Botros
- Pharmacology Department, Theodor Bilharz Research Institute, Warrak El-Hadar, Imbaba, P.O. Box 30, Giza, 12411, Egypt
| | - Samia William
- Parasitology Department, Theodor Bilharz Research Institute, Warrak El-Hadar, Imbaba, P.O. Box 30, Giza, 12411, Egypt
| | - Abdel-Nasser A Sabra
- Pharmacology Department, Theodor Bilharz Research Institute, Warrak El-Hadar, Imbaba, P.O. Box 30, Giza, 12411, Egypt
| | - Naglaa M El-Lakkany
- Pharmacology Department, Theodor Bilharz Research Institute, Warrak El-Hadar, Imbaba, P.O. Box 30, Giza, 12411, Egypt
| | - Sayed H Seif El-Din
- Pharmacology Department, Theodor Bilharz Research Institute, Warrak El-Hadar, Imbaba, P.O. Box 30, Giza, 12411, Egypt
| | | | | | - Antoni R Blaazer
- Medicinal Chemistry Vrije Universiteit Amsterdam (VUA), the Netherlands
| | - Erik de Heuvel
- Medicinal Chemistry Vrije Universiteit Amsterdam (VUA), the Netherlands
| | - Maarten Sijm
- Medicinal Chemistry Vrije Universiteit Amsterdam (VUA), the Netherlands
| | - Yang Zheng
- Medicinal Chemistry Vrije Universiteit Amsterdam (VUA), the Netherlands
| | | | - Jane C Munday
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, G12 8TA, UK
| | | | - Iwan J P de Esch
- Medicinal Chemistry Vrije Universiteit Amsterdam (VUA), the Netherlands
| | - Geert J Sterk
- Medicinal Chemistry Vrije Universiteit Amsterdam (VUA), the Netherlands
| | | | - Rob Leurs
- Medicinal Chemistry Vrije Universiteit Amsterdam (VUA), the Netherlands
| | - Carmen Gil
- Centro de Investigaciones Biológicas (CIB-CSIC), Madrid, Spain
| | - Harry P De Koning
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, G12 8TA, UK.
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16
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Ebiloma GU, Katsoulis E, Igoli JO, Gray AI, De Koning HP. Multi-target mode of action of a Clerodane-type diterpenoid from Polyalthia longifolia targeting African trypanosomes. Sci Rep 2018; 8:4613. [PMID: 29545637 PMCID: PMC5854603 DOI: 10.1038/s41598-018-22908-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Accepted: 02/19/2018] [Indexed: 11/09/2022] Open
Abstract
Natural products have made remarkable contributions to drug discovery and therapy. In this work we exploited various biochemical approaches to investigate the mode of action of 16-α-hydroxy-cleroda-3,13 (14)-Z-dien-15,16-olide (HDK-20), which we recently isolated from Polyalthia longifolia, on Trypanosoma brucei bloodstream trypomastigotes. HDK20 at concentrations ≥ EC50 (0.4 μg/ml) was trypanocidal, with its effect irreversible after only a brief exposure time (<1 h). Fluorescence microscopic assessment of DNA configuration revealed severe cell cycle defects after 8 h of incubation with the compound, the equivalent of a single generation time. This was accompanied by DNA fragmentation as shown by Terminal deoxynucleotidyl transferase dUTP Nick-End Labelling (TUNEL) assays. HDK-20 also induced a fast and profound depolarisation of the parasites’ mitochondrial membrane potential and depleted intracellular ATP levels of T. brucei. Overall, HDK20 showed a multi-target mechanism of action, which provides a biochemical explanation for the promising anti-trypanosomatid activity in our previous report.
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Affiliation(s)
- Godwin U Ebiloma
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.,Department of Biochemistry, Faculty of Natural Sciences, Kogi State University, Anyigba, Nigeria
| | - Evangelos Katsoulis
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - John O Igoli
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK.,Department of Chemistry, College of Science, University of Agriculture, Makurdi, Nigeria
| | - Alexander I Gray
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Harry P De Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK.
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17
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Campagnaro GD, Alzahrani KJ, Munday JC, De Koning HP. Trypanosoma brucei bloodstream forms express highly specific and separate transporters for adenine and hypoxanthine; evidence for a new protozoan purine transporter family? Mol Biochem Parasitol 2018; 220:46-56. [DOI: 10.1016/j.molbiopara.2018.01.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 01/10/2018] [Accepted: 01/19/2018] [Indexed: 10/18/2022]
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18
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Eze AA, Gould MK, Munday JC, Tagoe DNA, Stelmanis V, Schnaufer A, De Koning HP. Reduced Mitochondrial Membrane Potential Is a Late Adaptation of Trypanosoma brucei brucei to Isometamidium Preceded by Mutations in the γ Subunit of the F1Fo-ATPase. PLoS Negl Trop Dis 2016; 10:e0004791. [PMID: 27518185 PMCID: PMC4982688 DOI: 10.1371/journal.pntd.0004791] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2016] [Accepted: 05/30/2016] [Indexed: 11/19/2022] Open
Abstract
Background Isometamidium is the main prophylactic drug used to prevent the infection of livestock with trypanosomes that cause Animal African Trypanosomiasis. As well as the animal infective trypanosome species, livestock can also harbor the closely related human infective subspecies T. b. gambiense and T. b. rhodesiense. Resistance to isometamidium is a growing concern, as is cross-resistance to the diamidine drugs diminazene and pentamidine. Methodology/Principal Findings Two isometamidium resistant Trypanosoma brucei clones were generated (ISMR1 and ISMR15), being 7270- and 16,000-fold resistant to isometamidium, respectively, which retained their ability to grow in vitro and establish an infection in mice. Considerable cross-resistance was shown to ethidium bromide and diminazene, with minor cross-resistance to pentamidine. The mitochondrial membrane potentials of both resistant cell lines were significantly reduced compared to the wild type. The net uptake rate of isometamidium was reduced 2-3-fold but isometamidium efflux was similar in wild-type and resistant lines. Fluorescence microscopy and PCR analysis revealed that ISMR1 and ISMR15 had completely lost their kinetoplast DNA (kDNA) and both lines carried a mutation in the nuclearly encoded γ subunit gene of F1 ATPase, truncating the protein by 22 amino acids. The mutation compensated for the loss of the kinetoplast in bloodstream forms, allowing near-normal growth, and conferred considerable resistance to isometamidium and ethidium as well as significant resistance to diminazene and pentamidine, when expressed in wild type trypanosomes. Subsequent exposure to either isometamidium or ethidium led to rapid loss of kDNA and a further increase in isometamidium resistance. Conclusions/Significance Sub-lethal exposure to isometamidium gives rise to viable but highly resistant trypanosomes that, depending on sub-species, are infective to humans and cross-resistant to at least some diamidine drugs. The crucial mutation is in the F1 ATPase γ subunit, which allows loss of kDNA and results in a reduction of the mitochondrial membrane potential. Isometamidium is the only prophylactic treatment of Animal African Trypanosomiasis, a wasting disease of livestock and domestic animals in sub-Saharan Africa. Unfortunately resistance threatens the continued utility of this drug after decades of use. Not only does this disease have severe impacts on agriculture, but some subspecies of Trypanosoma brucei are human-infective as well (causing sleeping sickness) and there is concern that cross-resistance with trypanocides of the diamidine class could further undermine treatment of both veterinary and human infections. It is therefore essential to understand the mechanism of isometamidium resistance and the likelihood for cross-resistance with other first-line trypanocides. Here, we report that isometamidium resistance can be caused by a mutation in an important mitochondrial protein, the γ subunit of the F1 ATPase, and that this mutation alone is sufficient for high levels of resistance, cross-resistance to various drugs, and a strongly reduced mitochondrial membrane potential. This report will for the first time enable a structural assessment of isometamidium resistance genes in T. brucei spp.
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Affiliation(s)
- Anthonius A. Eze
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Matthew K. Gould
- Institute for Immunology and Infection Research and Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Jane C. Munday
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Daniel N. A. Tagoe
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, United Kingdom
| | - Valters Stelmanis
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Achim Schnaufer
- Institute for Immunology and Infection Research and Centre for Immunity, Infection and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Harry P. De Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- * E-mail:
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Imamura H, Downing T, Van den Broeck F, Sanders MJ, Rijal S, Sundar S, Mannaert A, Vanaerschot M, Berg M, De Muylder G, Dumetz F, Cuypers B, Maes I, Domagalska M, Decuypere S, Rai K, Uranw S, Bhattarai NR, Khanal B, Prajapati VK, Sharma S, Stark O, Schönian G, De Koning HP, Settimo L, Vanhollebeke B, Roy S, Ostyn B, Boelaert M, Maes L, Berriman M, Dujardin JC, Cotton JA. Evolutionary genomics of epidemic visceral leishmaniasis in the Indian subcontinent. eLife 2016; 5. [PMID: 27003289 PMCID: PMC4811772 DOI: 10.7554/elife.12613] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 02/15/2016] [Indexed: 12/25/2022] Open
Abstract
Leishmania donovani causes visceral leishmaniasis (VL), the second most deadly vector-borne parasitic disease. A recent epidemic in the Indian subcontinent (ISC) caused up to 80% of global VL and over 30,000 deaths per year. Resistance against antimonial drugs has probably been a contributing factor in the persistence of this epidemic. Here we use whole genome sequences from 204 clinical isolates to track the evolution and epidemiology of L. donovani from the ISC. We identify independent radiations that have emerged since a bottleneck coincident with 1960s DDT spraying campaigns. A genetically distinct population frequently resistant to antimonials has a two base-pair insertion in the aquaglyceroporin gene LdAQP1 that prevents the transport of trivalent antimonials. We find evidence of genetic exchange between ISC populations, and show that the mutation in LdAQP1 has spread by recombination. Our results reveal the complexity of L. donovani evolution in the ISC in response to drug treatment. DOI:http://dx.doi.org/10.7554/eLife.12613.001 The parasite Leishmania donovani causes a disease called visceral leishmaniasis that affects many of the world's poorest people. Around half a million new cases develop every year, but health authorities lack safe and effective drugs to treat them. Up to 80% of these cases occur in the Indian subcontinent, where devastating epidemics have occurred in the last decades. One reason these epidemics continue to occur is that the parasites develop genetic mutations allowing them to adapt to and resist the drugs used to kill them. As there are few existing drugs that can kill L. donovani, it is crucial to understand how drug resistance emerges and spreads among parasite populations. Imamura, Downing, Van den Broeck et al. have now investigated the history of visceral leishmaniasis epidemics by characterising the complete genetic sequence – or genome – of 204 L. donovani parasite samples. This revealed that the majority of parasites in the Indian subcontinent first appeared in the nineteenth century, matching the first historical records of visceral leishmaniasis epidemics. The genomes show that most of the parasites are genetically similar and can be clustered into several closely related groups. These groups first appeared in the 1960s following the end of a regional campaign to eradicate malaria. The most common parasite group is particularly resistant to drugs called antimonials, which were the main treatment for leishmaniasis until recently. These parasites have a small genetic change that scrambles most of a protein known to be involved in the uptake of antimonials. Parasites may also be able to develop resistance to drugs through additional mechanisms that allow them to produce many copies of the same gene. These mechanisms could allow the parasites to rapidly adapt to new drugs or changes in the populations it infects. The work of Imamura et al. looks only at parasites isolated from patients then grown in the laboratory, so further research is now needed to explore how variable the Leishmania genome is in both of the parasite’s hosts: humans and sandflies. Imamura et al.’s study reveals how L. donovani has spread throughout the Indian subcontinent in fine detail. The genome data can be used to create simple molecular tools that could form an "early warning system" to track the success of disease control programs and to determine how well the current drugs are working. DOI:http://dx.doi.org/10.7554/eLife.12613.002
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Affiliation(s)
- Hideo Imamura
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Tim Downing
- Wellcome Trust Sanger Institute, Hinxton, United Kingdom.,School of Maths, Applied Maths and Statistics, National University of Ireland Galway, Galway, Ireland
| | | | | | - Suman Rijal
- BP Koirala Institute of Health Sciences, Dharan, Nepal
| | - Shyam Sundar
- Department of Medicine, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
| | - An Mannaert
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Manu Vanaerschot
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Maya Berg
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Géraldine De Muylder
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Franck Dumetz
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Bart Cuypers
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | - Ilse Maes
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium
| | | | - Saskia Decuypere
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.,Telethon Kids Institute, University of Western Australia, Perth, Australia
| | - Keshav Rai
- BP Koirala Institute of Health Sciences, Dharan, Nepal
| | | | | | | | - Vijay Kumar Prajapati
- Department of Medicine, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
| | - Smriti Sharma
- Department of Medicine, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
| | - Olivia Stark
- Institut für Mikrobiologie und Hygiene, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Gabriele Schönian
- Institut für Mikrobiologie und Hygiene, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Harry P De Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
| | - Luca Settimo
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom.,Department of Chemistry and Chemical Biology, Northeastern University, Boston, United States
| | - Benoit Vanhollebeke
- Laboratory of Molecular Parasitology, Université Libre de Bruxelles, Gosselies, Belgium
| | - Syamal Roy
- Department of Infectious Diseases and Immunology, Council of Scientific and Industrial Research, Indian Institute of Chemical Biology, Kolkata, India
| | - Bart Ostyn
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
| | - Marleen Boelaert
- Department of Public Health, Institute of Tropical Medicine, Antwerp, Belgium
| | - Louis Maes
- Department of Biomedical Sciences, Faculty of Pharmaceutical, Biomedical and Veterinary Sciences, University of Antwerp, Antwerp, Belgium
| | | | - Jean-Claude Dujardin
- Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.,Department of Biomedical Sciences, Faculty of Pharmaceutical, Biomedical and Veterinary Sciences, University of Antwerp, Antwerp, Belgium
| | - James A Cotton
- Wellcome Trust Sanger Institute, Hinxton, United Kingdom
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20
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Omar RMK, Igoli J, Gray AI, Ebiloma GU, Clements C, Fearnley J, Ebel RAE, Zhang T, De Koning HP, Watson DG. Chemical characterisation of Nigerian red propolis and its biological activity against Trypanosoma Brucei. Phytochem Anal 2016; 27:107-115. [PMID: 26662866 DOI: 10.1002/pca.2605] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 11/03/2015] [Accepted: 11/08/2015] [Indexed: 06/05/2023]
Abstract
INTRODUCTION A previous study showed the unique character of Nigerian red propolis from Rivers State, Nigeria (RSN), with regards to chemical composition and activity against Trypanosoma brucei in comparison with other African propolis. OBJECTIVE To carry out fractionation and biological testing of Nigerian propolis in order to isolate compounds with anti-trypanosomal activity. To compare the composition of the RSN propolis with the composition of Brazilian red propolis. METHODOLOGY Profiling was carried out using HPLC-UV-ELSD and HPLC-Orbitrap-FTMS on extracts of two samples collected from RSN with data extraction using MZmine software. Isolation was carried out by normal phase and reversed phase MPLC. Elucidation of the compounds with a purity > 95% was performed by 1D/2D NMR HRMS and HRLC-MS(n) . RESULTS Ten phenolic compounds were isolated or in the case of liquiritigenin partially purified. Data for nine of these correlated with literature reports of known compounds i.e. one isoflavanone, calycosin (1); two flavanones, liquiritigenin (2) and pinocembrin (5); an isoflavan, vestitol (3); a pterocarpan, medicarpin (4); two prenylflavanones, 8-prenylnaringenin (7) and 6-prenylnaringenin (8); and two geranyl flavonoids, propolin D (9) and macarangin (10). The tenth was elucidated as a previously undescribed dihydrobenzofuran (6). The isolated compounds were tested against Trypanosoma brucei and displayed moderate to high activity. Some of the compounds tested had similar activity against wild type T. brucei and two strains displaying pentamidine resistance. CONCLUSION Nigerian propolis from RSN has some similarities with Brazilian red propolis. The propolis displayed anti-trypanosomal activity at a potentially useful level.
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Affiliation(s)
- Ruwida M K Omar
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 27 Taylor Street, Glasgow, G4 0NR, UK
| | - John Igoli
- Phytochemistry Research Group, Department of Chemistry, University of Agriculture, Makurdi, Nigeria
| | - Alexander I Gray
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 27 Taylor Street, Glasgow, G4 0NR, UK
| | - Godwin Unekwuojo Ebiloma
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
| | - Carol Clements
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 27 Taylor Street, Glasgow, G4 0NR, UK
| | | | - Ru Angeli Edrada Ebel
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 27 Taylor Street, Glasgow, G4 0NR, UK
| | - Tong Zhang
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 27 Taylor Street, Glasgow, G4 0NR, UK
| | - Harry P De Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
| | - David G Watson
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 27 Taylor Street, Glasgow, G4 0NR, UK
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21
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Munday JC, Tagoe DNA, Eze AA, Krezdorn JAM, Rojas López KE, Alkhaldi AAM, McDonald F, Still J, Alzahrani KJ, Settimo L, De Koning HP. Functional analysis of drug resistance-associated mutations in the Trypanosoma brucei adenosine transporter 1 (TbAT1) and the proposal of a structural model for the protein. Mol Microbiol 2015; 96:887-900. [PMID: 25708978 PMCID: PMC4755147 DOI: 10.1111/mmi.12979] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/21/2015] [Indexed: 02/01/2023]
Abstract
The Trypanosoma brucei aminopurine transporter P2/TbAT1 has long been implicated in the transport of, and resistance to, the diamidine and melaminophenyl arsenical classes of drugs that form the backbone of the pharmacopoeia against African trypanosomiasis. Genetic alterations including deletions and single nucleotide polymorphisms (SNPs) have been observed in numerous strains and clinical isolates. Here, we systematically investigate each reported mutation and assess their effects on transporter function after expression in a tbat1−/−T. brucei line. Out of a set of six reported SNPs from a reported ‘resistance allele’, none significantly impaired sensitivity to pentamidine, diminazene or melarsoprol, relative to the TbAT1‐WT allele, although several combinations, and the deletion of the codon for residue F316, resulted in highly significant impairment. These combinations of SNPs, and ΔF316, also strongly impaired the uptake of [3H]‐adenosine and [3H]‐diminazene, identical to the tbat1−/− control. The TbAT1 protein model predicted that residues F19, D140 and F316 interact with the substrate of the transporter. Mutation of D140 to alanine resulted in an inactive transporter, whereas the mutation F19A produced a transporter with a slightly increased affinity for [3H]‐diminazene but reduced the uptake rate. The results presented here validate earlier hypotheses of drug binding motifs for TbAT1.
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Affiliation(s)
- Jane C Munday
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK.,Wellcome Trust Centre for Molecular Parasitology, University of Glasgow, Glasgow, UK
| | - Daniel N A Tagoe
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK.,Department of Laboratory Technology, University of Cape Coast, Cape Coast, Ghana
| | - Anthonius A Eze
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK.,Department of Medical Biochemistry, College of Medicine, University of Nigeria, Enugu Campus, Enugu, Nigeria
| | - Jessica A M Krezdorn
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
| | - Karla E Rojas López
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
| | - Abdulsalam A M Alkhaldi
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK.,Department of Biology, College of Science, Aljouf University, Sakaka, Saudi Arabia
| | - Fiona McDonald
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
| | - Jennifer Still
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
| | - Khalid J Alzahrani
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK.,Faculty of Medical Sciences, Taif University, Taif, Saudi Arabia
| | - Luca Settimo
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK.,Department of Chemistry and Chemical Biology, 417 Egan Research Center, Northeastern University, 360 Huntington Avenue, Boston, MA, 02115, USA
| | - Harry P De Koning
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, G12 8TA, UK
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Dardonville C, Alkhaldi AAM, De Koning HP. SAR Studies of Diphenyl Cationic Trypanocides: Superior Activity of Phosphonium over Ammonium Salts. ACS Med Chem Lett 2015; 6:151-5. [PMID: 25699142 DOI: 10.1021/ml500408d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2014] [Accepted: 12/10/2014] [Indexed: 11/29/2022] Open
Abstract
In previous studies, we have shown that phosphonium salt diphenyl derivatives are attractive antitrypanosomal hit compounds with EC50 values against Trypanosoma brucei in the nanomolar range. To evaluate the role of the cationic center on the trypanocidal activity and extend the structure-activity relationship (SAR) of this series, trialkylammonium, pyridinium, and quinolinium salt analogues were synthesized and evaluated in vitro against T. b. brucei. Similar SARs were observed with ammonium and phosphonium salts showing that charge dispersion and lipophilic groups around the cationic center are crucial to obtain submicromolar activities. The new compounds were equally effective against wild type (T. b. brucei s427) and resistant strains (TbAT1-KO and TbB48) of trypanosomes indicating that the P2 and high affinity pentamidine transporters (HAPT) are not essential to their trypanocidal action. Similarly to phosphonium salt derivatives, diffusion seems to be the main route of entry into trypanosomes.
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Affiliation(s)
| | - Abdulsalam A. M. Alkhaldi
- Institute
of Infection, Immunity and Inflammation, College of Medical, Veterinary
and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- Department
of Biology, College of Science, Aljouf University, Sakaka, Saudi Arabia
| | - Harry P. De Koning
- Institute
of Infection, Immunity and Inflammation, College of Medical, Veterinary
and Life Sciences, University of Glasgow, Glasgow, United Kingdom
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23
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Munday JC, Eze AA, Baker N, Glover L, Clucas C, Aguinaga Andrés D, Natto MJ, Teka IA, McDonald J, Lee RS, Graf FE, Ludin P, Burchmore RJS, Turner CMR, Tait A, MacLeod A, Mäser P, Barrett MP, Horn D, De Koning HP. Trypanosoma brucei aquaglyceroporin 2 is a high-affinity transporter for pentamidine and melaminophenyl arsenic drugs and the main genetic determinant of resistance to these drugs. J Antimicrob Chemother 2013; 69:651-63. [PMID: 24235095 PMCID: PMC3922157 DOI: 10.1093/jac/dkt442] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Objectives Trypanosoma brucei drug transporters include the TbAT1/P2 aminopurine transporter and the high-affinity pentamidine transporter (HAPT1), but the genetic identity of HAPT1 is unknown. We recently reported that loss of T. brucei aquaglyceroporin 2 (TbAQP2) caused melarsoprol/pentamidine cross-resistance (MPXR) in these parasites and the current study aims to delineate the mechanism by which this occurs. Methods The TbAQP2 loci of isogenic pairs of drug-susceptible and MPXR strains of T. brucei subspecies were sequenced. Drug susceptibility profiles of trypanosome strains were correlated with expression of mutated TbAQP2 alleles. Pentamidine transport was studied in T. brucei subspecies expressing TbAQP2 variants. Results All MPXR strains examined contained TbAQP2 deletions or rearrangements, regardless of whether the strains were originally adapted in vitro or in vivo to arsenicals or to pentamidine. The MPXR strains and AQP2 knockout strains had lost HAPT1 activity. Reintroduction of TbAQP2 in MPXR trypanosomes restored susceptibility to the drugs and reinstated HAPT1 activity, but did not change the activity of TbAT1/P2. Expression of TbAQP2 sensitized Leishmania mexicana promastigotes 40-fold to pentamidine and >1000-fold to melaminophenyl arsenicals and induced a high-affinity pentamidine transport activity indistinguishable from HAPT1 by Km and inhibitor profile. Grafting the TbAQP2 selectivity filter amino acid residues onto a chimeric allele of AQP2 and AQP3 partly restored susceptibility to pentamidine and an arsenical. Conclusions TbAQP2 mediates high-affinity uptake of pentamidine and melaminophenyl arsenicals in trypanosomes and TbAQP2 encodes the previously reported HAPT1 activity. This finding establishes TbAQP2 as an important drug transporter.
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Affiliation(s)
- Jane C Munday
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
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24
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Ali JAM, Creek DJ, Burgess K, Allison HC, Field MC, Mäser P, De Koning HP. Pyrimidine salvage in Trypanosoma brucei bloodstream forms and the trypanocidal action of halogenated pyrimidines. Mol Pharmacol 2012. [PMID: 23188714 DOI: 10.1124/mol.112.082321] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
African trypanosomes are capable of both pyrimidine biosynthesis and salvage of preformed pyrimidines from the host. However, uptake of pyrimidines in bloodstream form trypanosomes has not been investigated, making it difficult to judge the relative importance of salvage and synthesis or to design a pyrimidine-based chemotherapy. Detailed characterization of pyrimidine transport activities in bloodstream form Trypanosoma brucei brucei found that these cells express a high-affinity uracil transporter (designated TbU3) that is clearly distinct from the procyclic pyrimidine transporters. This transporter had low affinity for uridine and 2'deoxyuridine and was the sole pyrimidine transporter expressed in these cells. In addition, thymidine was taken up inefficiently through a P1-type nucleoside transporter. Of importance, the anticancer drug 5-fluorouracil was an excellent substrate for TbU3, and several 5-fluoropyrimidine analogs were investigated for uptake and trypanocidal activity; 5F-orotic acid, 5F-2'deoxyuridine displayed activity in the low micromolar range. The metabolism and mode of action of these analogs was determined using metabolomic assessments of T. brucei clonal lines adapted to high levels of these pyrimidine analogs, and of the sensitive parental strains. The analysis showed that 5-fluorouracil is incorporated into a large number of metabolites but likely exerts toxicity through incorporation into RNA. 5F-2'dUrd and 5F-2'dCtd are not incorporated into nucleic acids but act as prodrugs by inhibiting thymidylate synthase as 5F-dUMP. We present the most complete model of pyrimidine salvage in T. brucei to date, supported by genome-wide profiling of the predicted pyrimidine biosynthesis and conversion enzymes.
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Affiliation(s)
- Juma A M Ali
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TA, United Kingdom
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25
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Paine MF, Wang MZ, Generaux CN, Boykin DW, Wilson WD, De Koning HP, Olson CA, Pohlig G, Burri C, Brun R, Murilla GA, Thuita JK, Barrett MP, Tidwell RR. Diamidines for human African trypanosomiasis. Curr Opin Investig Drugs 2010; 11:876-883. [PMID: 20721830] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Aromatic diamidines are potent trypanocides. Pentamidine, a diamidine, has been used for more than 60 years to treat human African trypanosomiasis (HAT); however, the drug must be administered parenterally and is active against first-stage HAT only, prior to the parasites causing neurological deterioration through invasion of the CNS. A major research effort to design novel diamidines has led to the development of orally active prodrugs and, remarkably, a new generation of compounds that can penetrate the CNS. In this review, progress in the development of diamidines for the treatment of HAT is discussed.
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Affiliation(s)
- Mary F Paine
- University of North Carolina at Chapel Hill, Eshelman School of Pharmacy, Campus Box 7569, and Department of Pathology and Laboratory Medicine, Campus Box 7525, Chapel Hill, NC 27599, USA
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Biagini GA, Pasini EM, Hughes R, De Koning HP, Vial HJ, O'Neill PM, Ward SA, Bray PG. Characterization of the choline carrier of Plasmodium falciparum: a route for the selective delivery of novel antimalarial drugs. Blood 2004; 104:3372-7. [PMID: 15205262 DOI: 10.1182/blood-2004-03-1084] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
New drugs are urgently needed to combat the growing problem of drug resistance in Plasmodium falciparum malaria. The infected erythrocyte is a multicompartmental system, and its transporters are of interest as drug targets in their own right and as potential routes for the delivery of antimalarial drugs. Choline is an important nutrient that penetrates infected erythrocyte membranes through the endogenous carrier and through parasite-induced permeability pathways, but nothing is known about its transport into the intracellular parasite. Here we present the first characterization of choline transport across the parasite membrane. Transport exhibits Michaelis-Menten kinetics with an apparent Km of 25.0 ± 3.5 μM for choline. The carrier is inhibitor-sensitive, temperature-dependent, and Na+-independent, and it is driven by the proton-motive force. Highly active bis-amidine and bis-quaternary ammonium compounds are also known to penetrate the host erythrocyte membrane through parasite-induced permeability pathways. Here, we demonstrate that the parasite choline transporter mediates the delivery of these compounds to the intracellular parasite. Thus, the induced permeability pathways in the host erythrocyte membrane and the parasite choline transporter described here form a cooperative transport system that shows great promise for the selective targeting of new agents for the chemotherapy of malaria. (Blood. 2004;104: 3372-3377)
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Affiliation(s)
- Giancarlo A Biagini
- Molecular and Biochemical Parasitology Group, Liverpool School of Tropical Medicine, England
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De Koning HP, Al-Salabi MI, Cohen AM, Coombs GH, Wastling JM. Identification and characterisation of high affinity nucleoside and nucleobase transporters in Toxoplasma gondii. Int J Parasitol 2003; 33:821-31. [PMID: 12865082 DOI: 10.1016/s0020-7519(03)00091-2] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The protozoan parasite Toxoplasma gondii depends upon salvaging the purines that it requires. We have re-analysed purine transport in T. gondii and identified novel nucleoside and nucleobase transporters. The latter transports hypoxanthine (TgNBT1; K(m)=0.91+/-0.19 microM) and is inhibited by guanine and xanthine: it is the first high affinity nucleobase transporter to be identified in an apicomplexan parasite. The previously reported nucleoside transporter, TgAT1, is low affinity with K(m) values of 105 and 134 microM for adenosine and inosine, respectively. We have now identified a second nucleoside transporter, TgAT2, which is high affinity and inhibited by adenosine, inosine, guanosine, uridine and thymidine (K(m) values 0.28-1.5 microM) as well as cytidine (K(i)=32 microM). TgAT2 also recognises several nucleoside analogues with therapeutic potential. We have investigated the basis for the broad specificity of TgAT2 and found that hydrogen bonds are formed with the 3' and 5' hydroxyl groups and that the base groups are bound through H-bonds with either N3 of the purine ring or N(3)H of the pyrimidine ring, and most probably pi-pi-stacking as well. The identification of these high affinity purine nucleobase and nucleoside transporters reconciles for the first time the low abundance of free nucleosides and nucleobases in the intracellular environment with the efficient purine salvage carried out by T. gondii.
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Affiliation(s)
- Harry P De Koning
- Division of Infection and Immunity, Institute of Biomedical and Life Sciences, University of Glasgow, Joseph Black Building, Glasgow G12 8QQ, UK.
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Al-Salabi MI, Wallace LJM, De Koning HP. A Leishmania major nucleobase transporter responsible for allopurinol uptake is a functional homolog of the Trypanosoma brucei H2 transporter. Mol Pharmacol 2003; 63:814-20. [PMID: 12644582 DOI: 10.1124/mol.63.4.814] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Nucleobase transporters play an important role in the physiology of protozoan parasites, because these organisms are purine auxotrophs and rely entirely on salvage of these vital compounds. Purine transporters have also been shown to mediate the uptake of important antiparasitic drugs. In the current study, we investigated the uptake of [(3)H]adenine, [(3)H]hypoxanthine, and [(3)H]allopurinol, an antileishmanial hypoxanthine analog, by Leishmania major. These compounds were all taken up by a single high-affinity transporter, LmNBT1, with K(m) values of 4.6 +/- 0.9, 0.71 +/- 0.07, and 54 +/- 3 microM, respectively. Guanine and xanthine fully inhibited [(3)H]adenine transport, with K(i) values of 2.8 +/- 0.7 and 23 +/- 8 microM. Using purine analogs, an inhibitor profile for LmNBT1 was obtained, which allowed the construction of a quantitative model for the interactions between the transporter binding site and the permeant. The model predicts that hypoxanthine was bound through hydrogen bonds to N(1)H, N3, N7, and N(9)H of the purine ring, with a total Gibbs free energy of -39.5 kJ/mol. The interactions with adenine were similar, except for a weak hydrogen bond to N1 (unprotonated in adenine). The predicted mode of substrate binding for LmNBT1 was almost identical to that for the Trypanosoma brucei H2 (TbH2) transporter. It is proposed that the architecture of their respective binding sites is very similar and that LmNBT1 can be named a functional homolog of TbH2.
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Affiliation(s)
- Mohammed I Al-Salabi
- Institute of Biomedical and Life Sciences, Division of Infection and Immunity, Joseph Black Building, University of Glasgow, Glasgow, United Kingdom
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Wallace LJM, Candlish D, De Koning HP. Different substrate recognition motifs of human and trypanosome nucleobase transporters. Selective uptake of purine antimetabolites. J Biol Chem 2002; 277:26149-56. [PMID: 12004061 DOI: 10.1074/jbc.m202835200] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The therapeutic index of antimetabolites such as purine analogues is in large part determined by the extent to which it is selectively accumulated by the target cell. In the current study we have compared the transport of purine nucleobase analogues by the H2 transporter of bloodstream form Trypanosoma brucei brucei and the equilibrative nucleobase transporter of human erythrocytes. The H2 transporter forms hydrogen bonds with hypoxanthine at positions N3, N7, N(1)H, and N(9)H of the purine ring, with apparent Delta G(0) of 7.7-12.6 kJ/mol. The transporter also appears to H-bond with the amine group of adenine. The human transporter forms hydrogen bonds that form to (6)NH(2) and N1 of adenine. An H-bond is also formed with N3 and the 6-keto and amine groups of guanine but not with the protonated N1, thus explaining the low affinity for hypoxanthine. N7 and N9 do not directly interact with the human transporter in the form of H-bonds, and it is proposed that pi-pi stacking interactions contribute significantly to permeant binding. The potential for selective uptake of antimetabolites by the parasite transporter was demonstrated.
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Affiliation(s)
- Lynsey J M Wallace
- Institute of Biomedical and Life Sciences, Division of Infection and Immunity, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
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