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Patra J, Rana D, Arora S, Pal M, Mahindroo N. Falcipains: Biochemistry, target validation and structure-activity relationship studies of inhibitors as antimalarials. Eur J Med Chem 2023; 252:115299. [PMID: 36996716 DOI: 10.1016/j.ejmech.2023.115299] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Revised: 03/04/2023] [Accepted: 03/17/2023] [Indexed: 03/29/2023]
Abstract
Malaria is a tropical disease with significant morbidity and mortality burden caused by Plasmodium species in Africa, the Middle East, Asia, and South America. Pathogenic Plasmodium species have lately become increasingly resistant to approved chemotherapeutics and combination therapies. Therefore, there is an emergent need for identifying new druggable targets and novel chemical classes against the parasite. Falcipains, cysteine proteases required for heme metabolism in the erythrocytic stage, have emerged as promising drug targets against Plasmodium species that infect humans. This perspective discusses the biology, biochemistry, structural features, and genetics of falcipains. The efforts to identify selective or dual inhibitors and their structure-activity relationships are reviewed to give a perspective on the design of novel compounds targeting falcipains for antimalarial activity evaluating reasons for hits and misses for this important target.
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Affiliation(s)
- Jeevan Patra
- School of Health Sciences and Technology, University of Petroleum and Energy Studies, Energy Acres, Bidholi, Via Prem Nagar, Uttarakhand, 248007, India
| | - Devika Rana
- School of Pharmaceutical Sciences, Shoolini University of Biotechnology and Management Sciences, Bajhol, Solan, Himachal Pradesh, 173229, India
| | - Smriti Arora
- School of Health Sciences and Technology, University of Petroleum and Energy Studies, Energy Acres, Bidholi, Via Prem Nagar, Uttarakhand, 248007, India
| | - Mintu Pal
- Department of Pharmacology, All India Institute of Medical Sciences (AIIMS), Bathinda, Punjab, 151001, India
| | - Neeraj Mahindroo
- School of Health Sciences and Technology, University of Petroleum and Energy Studies, Energy Acres, Bidholi, Via Prem Nagar, Uttarakhand, 248007, India; School of Health Sciences and Technology, Dr. Vishwanath Karad MIT World Peace University, 124 Paud Road, Kothrud, Pune, Maharashtra, 411038, India.
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2
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Kasozi KI, MacLeod ET, Ntulume I, Welburn SC. An Update on African Trypanocide Pharmaceutics and Resistance. Front Vet Sci 2022; 9:828111. [PMID: 35356785 PMCID: PMC8959112 DOI: 10.3389/fvets.2022.828111] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Accepted: 01/12/2022] [Indexed: 12/22/2022] Open
Abstract
African trypanosomiasis is associated with Trypanosoma evansi, T. vivax, T. congolense, and T. brucei pathogens in African animal trypanosomiasis (AAT) while T. b gambiense and T. b rhodesiense are responsible for chronic and acute human African trypanosomiasis (HAT), respectively. Suramin sodium suppresses ATP generation during the glycolytic pathway and is ineffective against T. vivax and T. congolense infections. Resistance to suramin is associated with pathogen altered transport proteins. Melarsoprol binds irreversibly with pyruvate kinase protein sulfhydryl groups and neutralizes enzymes which interrupts the trypanosome ATP generation. Melarsoprol resistance is associated with the adenine-adenosine transporter, P2, due to point mutations within this transporter. Eflornithine is used in combination with nifurtimox. Resistance to eflornithine is caused by the deletion or mutation of TbAAT6 gene which encodes the transmembrane amino acid transporter that delivers eflornithine into the cell, thus loss of transporter protein results in eflornithine resistance. Nifurtimox alone is regarded as a poor trypanocide, however, it is effective in melarsoprol-resistant gHAT patients. Resistance is associated with loss of a single copy of the genes encoding for nitroreductase enzymes. Fexinidazole is recommended for first-stage and non-severe second-stage illnesses in gHAT and resistance is associated with trypanosome bacterial nitroreductases which reduce fexinidazole. In AAT, quinapyramine sulfate interferes with DNA synthesis and suppression of cytoplasmic ribosomal activity in the mitochondria. Quinapyramine sulfate resistance is due to variations in the potential of the parasite's mitochondrial membrane. Pentamidines create cross-links between two adenines at 4–5 pairs apart in adenine-thymine-rich portions of Trypanosoma DNA. It also suppresses type II topoisomerase in the mitochondria of Trypanosoma parasites. Pentamidine resistance is due to loss of mitochondria transport proteins P2 and HAPT1. Diamidines are most effective against Trypanosome brucei group and act via the P2/TbAT1 transporters. Diminazene aceturate resistance is due to mutations that alter the activity of P2, TeDR40 (T. b. evansi). Isometamidium chloride is primarily employed in the early stages of trypanosomiasis and resistance is associated with diminazene resistance. Phenanthridine (homidium bromide, also known as ethidium bromide) acts by a breakdown of the kinetoplast network and homidium resistance is comparable to isometamidium. In humans, the development of resistance and adverse side effects against monotherapies has led to the adoption of nifurtimox-eflornithine combination therapy. Current efforts to develop new prodrug combinations of nifurtimox and eflornithine and nitroimidazole fexinidazole as well as benzoxaborole SCYX-7158 (AN5568) for HAT are in progress while little comparable progress has been done for the development of novel therapies to address trypanocide resistance in AAT.
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Affiliation(s)
- Keneth Iceland Kasozi
- Infection Medicine, Deanery of Biomedical Sciences, College of Medicine and Veterinary Medicine, The University of Edinburgh, Edinburgh, United Kingdom
- School of Medicine, Kabale University, Kabale, Uganda
- *Correspondence: Keneth Iceland Kasozi ;
| | - Ewan Thomas MacLeod
- Infection Medicine, Deanery of Biomedical Sciences, College of Medicine and Veterinary Medicine, The University of Edinburgh, Edinburgh, United Kingdom
| | - Ibrahim Ntulume
- School of Biosecurity Biotechnical and Laboratory Sciences, College of Medicine and Veterinary Medicine, Makerere University, Kampala, Uganda
| | - Susan Christina Welburn
- Infection Medicine, Deanery of Biomedical Sciences, College of Medicine and Veterinary Medicine, The University of Edinburgh, Edinburgh, United Kingdom
- Zhejiang University-University of Edinburgh Joint Institute, Zhejiang University, Hangzhou, China
- Susan Christina Welburn
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3
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Ettari R, Previti S, Di Chio C, Zappalà M. Falcipain-2 and Falcipain-3 Inhibitors as Promising Antimalarial Agents. Curr Med Chem 2021; 28:3010-3031. [PMID: 32744954 DOI: 10.2174/0929867327666200730215316] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 07/01/2020] [Accepted: 07/11/2020] [Indexed: 11/22/2022]
Abstract
Malaria remains a serious problem in global public health, particularly widespread in South America and in tropical regions of Africa and Asia. Chemotherapy is actually the only way to treat this poverty-related disease, since an effective vaccine is not currently available. However, the onset of resistance to the most common antimalarial drugs sometimes makes the current therapeutic regimen problematic. Therefore, the identification of new targets for a new drug discovery process is an urgent priority. In this context, falcipain-2 and falcipain- 3 of P. falciparum represent the key enzymes in the life-cycle of the parasite. Both falcipain- 2 and falcipain-3 are involved in hemoglobin hydrolysis, an essential pathway to provide free amino acids for the parasite metabolic needs. In addition, falcipain-2 is involved in cleaving ankirin and band 4.1 protein, which are cytoskeletal elements essential for the stability of the red cell membrane. This review article is focused on the most recent and effective inhibitors of falcipain-2 and falcipain-3, with particular attention to peptide, peptidomimetic or nonpeptide inhibitors, which targeted one or both the malarial cysteine proteases, endowed with a consistent activity against P. falciparum.
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Affiliation(s)
- Roberta Ettari
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Annunziata, 98168 Messina, Italy
| | - Santo Previti
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Annunziata, 98168 Messina, Italy
| | - Carla Di Chio
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Annunziata, 98168 Messina, Italy
| | - Maria Zappalà
- Department of Chemical, Biological, Pharmaceutical and Environmental Sciences, University of Messina, Viale Annunziata, 98168 Messina, Italy
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4
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Duschak VG. Major Kinds of Drug Targets in Chagas Disease or American Trypanosomiasis. Curr Drug Targets 2019; 20:1203-1216. [PMID: 31020939 DOI: 10.2174/1389450120666190423160804] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 04/12/2019] [Accepted: 04/12/2019] [Indexed: 11/22/2022]
Abstract
American Trypanosomiasis, a parasitic infection commonly named Chagas disease, affects millions of people all over Latin American countries. Presently, the World Health Organization (WHO) predicts that the number of international infected individuals extends to 7 to 8 million, assuming that more than 10,000 deaths occur annually. The transmission of the etiologic agent, Trypanosoma cruzi, through people migrating to non-endemic world nations makes it an emergent disease. The best promising targets for trypanocidal drugs may be classified into three main groups: Group I includes the main molecular targets that are considered among specific enzymes involved in the essential processes for parasite survival, principally Cruzipain, the major antigenic parasite cysteine proteinase. Group II involves biological pathways and their key specific enzymes, such as Sterol biosynthesis pathway, among others, specific antioxidant defense mechanisms, and bioenergetics ones. Group III includes the atypical organelles /structures present in the parasite relevant clinical forms, which are absent or considerably different from those present in mammals and biological processes related to them. These can be considered potential targets to develop drugs with extra effectiveness and fewer secondary effects than the currently used therapeutics. An improved distinction between the host and the parasite targets will help fight against this neglected disease.
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Affiliation(s)
- Vilma G Duschak
- National Council of Scientific and Technical Reasearch (CONICET) Researcher, Area of Protein Biochemistry and Parasite Glycobiology, Research Department, National Institute of Parasitology (INP), "Dr. Mario Fatala Chaben", ANLIS-Malbran, National Health Secretary, Av. Paseo Colon 568, Lab 506, Ciudad Autonoma de Buenos Aires (1063), Buenos Aires, Argentina
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5
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Arora K, Rai AK. Dependence of Leishmania parasite on host derived ATP: an overview of extracellular nucleotide metabolism in parasite. J Parasit Dis 2019; 43:1-13. [PMID: 30956439 PMCID: PMC6423245 DOI: 10.1007/s12639-018-1061-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2018] [Accepted: 11/24/2018] [Indexed: 12/29/2022] Open
Affiliation(s)
- Kashika Arora
- Department of Biotechnology, Motilal Nehru National Institute of Technology (MNNIT) Allahabad, Allahabad, 211004 U.P. India
- Present Address: Biomedical Research Center, Ghent University Global Campus, Incheon, 21985 South Korea
| | - Ambak Kumar Rai
- Department of Biotechnology, Motilal Nehru National Institute of Technology (MNNIT) Allahabad, Allahabad, 211004 U.P. India
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6
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Rojas R, Segovia C, Trombert AN, Santander J, Manque P. The effect of tunicamycin on the glucose uptake, growth, and cellular adhesion in the protozoan parasite Crithidia fasciculata. Curr Microbiol 2014; 69:541-8. [PMID: 24894907 DOI: 10.1007/s00284-014-0620-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 04/08/2014] [Indexed: 01/17/2023]
Abstract
Crithidia fasciculata represents a very interesting model organism to study biochemical, cellular, and genetic processes unique to members of the family of the Trypanosomatidae. Thus, C. fasciculata parasitizes several species of insects and has been widely used to test new therapeutic strategies against parasitic infections. By using tunicamycin, a potent inhibitor of glycosylation in asparaginyl residues of glycoproteins (N-glycosylation), we demonstrate that N-glycosylation in C. fasciculata cells is involved in modulating glucose uptake, dramatically impacting growth, and cell adhesion. C. fasciculata treated with tunicamycin was severely affected in their ability to replicate and to adhere to polystyrene substrates and losing their ability to aggregate into small and large groups. Moreover, under tunicamycin treatment, the parasites were considerably shorter and rounder and displayed alterations in cytoplasmic vesicles formation. Furthermore, glucose uptake was significantly impaired in a tunicamycin dose-dependent manner; however, no cytotoxic effect was observed. Interestingly, this effect was reversible. Thus, when tunicamycin was removed from the culture media, the parasites recovered its growth rate, cell adhesion properties, and glucose uptake. Collectively, these results suggest that changes in the tunicamycin-dependent glycosylation levels can influence glucose uptake, cell growth, and adhesion in the protozoan parasite C. fasciculata.
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Affiliation(s)
- Robert Rojas
- Nucleus for Microbiology and Immunity, Center for Genomics and Bioinformatics, Faculty of Sciences, Universidad Mayor, Campus Huechuraba, Camino La Pirámide 5750, Huechuraba, Santiago, Chile,
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7
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Austrup J, Ntais P, Christodoulou V, Dedet JP, Pratlong F, Antoniou M. Frequency of MDR1-related p-gp overexpression in Greek Leishmania isolates. Parasitol Res 2014; 113:1225-32. [PMID: 24504599 DOI: 10.1007/s00436-014-3761-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Accepted: 01/10/2014] [Indexed: 11/29/2022]
Abstract
In this work, we investigated Greek Leishmania isolates (n = 70) for their individual MDR1-gene-related p-gp (belonging to the ABC-B subfamily of permeases) expression levels by means of flow cytometric analysis of Rhodamine 123 extrusion kinetics. Of all used isolates, 5.71% express this drug-extruding ABC-transporter at alarming levels and are distributed widely over the country. Some 33% of all examined isolates originated on the island of Crete though none of the strains showed vastly elevated p-gp extrusion activity, indicating a reasonable implementation of anti-leishmanial compounds in this part of the country. Compared to isolates obtained from canine tissue, human Leishmania isolates were superior both in size and in subcellular differentiation in flow cytometry. Furthermore, a specific t test confirmed verapamil hydrochloride to be a highly potent p-gp reversal agent with p < 0.0001. In a second test series, the loading of Leishmania with Rhodamine 123 was moreover reduced when occurring under influence of verapamil hydrochloride, a known p-gp reversal agent, indicating an ATP-dependant influx of the fluorescent dye and therewith the drug itself. In a final, third experiment series, it was shown that Sb(V) does not act upon the promastigote form of Leishmania.
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Affiliation(s)
- Johannes Austrup
- Center of Anatomy, Institute II, Laboratory for Medical and Molecular Parasitology, Medical School, University of Cologne, Cologne, Germany,
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8
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Ettari R, Tamborini L, Angelo IC, Micale N, Pinto A, De Micheli C, Conti P. Inhibition of Rhodesain as a Novel Therapeutic Modality for Human African Trypanosomiasis. J Med Chem 2013; 56:5637-58. [DOI: 10.1021/jm301424d] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Roberta Ettari
- Dipartimento
di Scienze Farmaceutiche, Università degli Studi di Milano, Via Mangiagalli
25, 20133 Milano, Italy
| | - Lucia Tamborini
- Dipartimento
di Scienze Farmaceutiche, Università degli Studi di Milano, Via Mangiagalli
25, 20133 Milano, Italy
| | - Ilenia C. Angelo
- Dipartimento di Scienze del
Farmaco e Prodotti per la Salute, Università degli Studi di Messina, Viale Annunziata, 98168 Messina, Italy
| | - Nicola Micale
- Dipartimento di Scienze del
Farmaco e Prodotti per la Salute, Università degli Studi di Messina, Viale Annunziata, 98168 Messina, Italy
| | - Andrea Pinto
- Dipartimento
di Scienze Farmaceutiche, Università degli Studi di Milano, Via Mangiagalli
25, 20133 Milano, Italy
| | - Carlo De Micheli
- Dipartimento
di Scienze Farmaceutiche, Università degli Studi di Milano, Via Mangiagalli
25, 20133 Milano, Italy
| | - Paola Conti
- Dipartimento
di Scienze Farmaceutiche, Università degli Studi di Milano, Via Mangiagalli
25, 20133 Milano, Italy
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9
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Caradonna KL, Engel JC, Jacobi D, Lee CH, Burleigh BA. Host metabolism regulates intracellular growth of Trypanosoma cruzi. Cell Host Microbe 2013; 13:108-17. [PMID: 23332160 DOI: 10.1016/j.chom.2012.11.011] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Revised: 09/08/2012] [Accepted: 11/12/2012] [Indexed: 11/15/2022]
Abstract
Metabolic coupling of intracellular pathogens with host cells is essential for successful colonization of the host. Establishment of intracellular infection by the protozoan Trypanosoma cruzi leads to the development of human Chagas' disease, yet the functional contributions of the host cell toward the infection process remain poorly characterized. Here, a genome-scale functional screen identified interconnected metabolic networks centered around host energy production, nucleotide metabolism, pteridine biosynthesis, and fatty acid oxidation as key processes that fuel intracellular T. cruzi growth. Additionally, the host kinase Akt, which plays essential roles in various cellular processes, was critical for parasite replication. Targeted perturbations in these host metabolic pathways or Akt-dependent signaling pathways modulated the parasite's replicative capacity, highlighting the adaptability of this intracellular pathogen to changing conditions in the host. These findings identify key cellular process regulating intracellular T. cruzi growth and illuminate the potential to leverage host pathways to limit T. cruzi infection.
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Affiliation(s)
- Kacey L Caradonna
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, 665 Huntington Avenue, Building I, Room 817, Boston, MA 02115, USA
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10
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On the evolution of hexose transporters in kinetoplastid Protozoans [corrected]. PLoS One 2012; 7:e36303. [PMID: 22567148 PMCID: PMC3342237 DOI: 10.1371/journal.pone.0036303] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 04/02/2012] [Indexed: 11/24/2022] Open
Abstract
Glucose, an almost universally used energy and carbon source, is processed through several well-known metabolic pathways, primarily glycolysis. Glucose uptake is considered to be the first step in glycolysis. In kinetoplastids, a protozoan group that includes relevant human pathogens, the importance of glucose uptake in different phases of the life cycles is well established, and hexose transporters have been proposed as targets for therapeutic drugs. However, little is known about the evolutionary history of these hexose transporters. Hexose transporters contain an intracellular N- and C- termini, and 12 transmembrane spans connected by alternate intracellular and extracellular loops. In the present work we tested the hypothesis that the evolutionary rate of the transmembrane span is different from that of the whole sequence and that it is possible to define evolutionary units inside the sequence. The phylogeny of whole molecules was compared to that of their transmembrane spans and the loops connecting the transmembrane spans. We show that the evolutionary units in these proteins primarily consist of clustered rather than individual transmembrane spans. These analyses demonstrate that there are evolutionary constraints on the organization of these proteins; more specifically, the order of the transmembrane spans along the protein is highly conserved. Finally, we defined a signature sequence for the identification of kinetoplastid hexose transporters.
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11
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Miguel DC, Ferraz ML, Alves RDO, Yokoyama-Yasunaka JKU, Torrecilhas AC, Romanha AJ, Uliana SRB. The anticancer drug tamoxifen is active against Trypanosoma cruzi in vitro but ineffective in the treatment of the acute phase of Chagas disease in mice. Mem Inst Oswaldo Cruz 2011; 105:945-8. [PMID: 21120371 DOI: 10.1590/s0074-02762010000700021] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Accepted: 09/01/2010] [Indexed: 11/21/2022] Open
Abstract
The activity of the antineoplastic drug tamoxifen was evaluated against Trypanosoma cruzi. In vitro activity was determined against epimastigote, trypomastigote and amastigote forms of CL14, Y and Y benznidazole resistant T. cruzi strains. Regardless of the strain used, the drug was active against all life-cycle stages of the parasite with a half maximal effective concentration ranging from 0.7-17.9 µM. Two experimental models of acute Chagas disease were used to evaluate the in vivo efficacy of treatment with tamoxifen. No differences in parasitemia and mortality were observed between control mock-treated and tamoxifen-treated mice.
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Affiliation(s)
- Danilo Ciccone Miguel
- Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, SP, Brasil
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12
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Singh A, Mandal D. A novel sucrose/H+ symport system and an intracellular sucrase in Leishmania donovani. Int J Parasitol 2011; 41:817-26. [PMID: 21515279 DOI: 10.1016/j.ijpara.2011.03.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 02/09/2011] [Accepted: 03/01/2011] [Indexed: 10/18/2022]
Abstract
The flagellated form of pathogenic parasitic protozoa Leishmania, resides in the alimentary tract of its sandfly vector, where sucrose serves as a major nutrient source. In this study we report the presence of a sucrose transport system in Leishmania donovani promastigotes. The kinetics of sucrose uptake in promastigotes are biphasic in nature with both high affinity K(m) (K(m) of ∼ 75 μM) and low affinity K(m) (K(m)∼ 1.38 mM) components. By contrast the virulent amastigotes take up sucrose via a low affinity process with a K(m) of 2.5mM. The transport of sucrose into promastigotes leads to rapid intracellular acidification, as indicated by changes in the fluorescence of the pH indicator 2',7'-bis-(2-carboxyethyl)-5-(6) Carboxyfluorescein (BCECF). In experiments with right side-out plasma membrane vesicles derived from L. donovani promastigotes, an artificial pH gradient was able to drive the active accumulation of sucrose. These data are consistent with the operation of a H(+)-sucrose symporter. The symporter was shown to be independent of Na(+) and to be insensitive to cytochalasin B, to the flavonoid phloretin and to the Na(+)/K(+) ATPase inhibitor ouabain. However, the protonophore carbonylcyanide P- (trifluromethoxy) phenylhydrazone (FCCP) and a number of thiol reagents caused significant inhibition of sucrose uptake. Evidence was also obtained for the presence of a stable intracellular pool of the sucrose splitting enzyme, sucrase, in promastigote stage parasites. The results are consistent with the hypothesis that L. donovani promastigotes take up sucrose via a novel H(+)-sucrose symport system and that, on entering the cell, the sucrose is hydrolysed to its component monosaccharides by an intracellular sucrase, thereby providing an energy source for the parasites.
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Affiliation(s)
- Arpita Singh
- Division of Infectious Diseases and Immunology, Indian Institute of Chemical Biology, West Bengal, India
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13
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Jacobs RT, Nare B, Phillips MA. State of the art in African trypanosome drug discovery. Curr Top Med Chem 2011; 11:1255-74. [PMID: 21401507 PMCID: PMC3101707 DOI: 10.2174/156802611795429167] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Accepted: 11/25/2010] [Indexed: 11/22/2022]
Abstract
African sleeping sickness is endemic in sub-Saharan Africa where the WHO estimates that 60 million people are at risk for the disease. Human African trypanosomiasis (HAT) is 100% fatal if untreated and the current drug therapies have significant limitations due to toxicity and difficult treatment regimes. No new chemical agents have been approved since eflornithine in 1990. The pentamidine analog DB289, which was in late stage clinical trials for the treatment of early stage HAT recently failed due to toxicity issues. A new protocol for the treatment of late-stage T. brucei gambiense that uses combination nifurtomox/eflornithine (NECT) was recently shown to have better safety and efficacy than eflornithine alone, while being easier to administer. This breakthrough represents the only new therapy for HAT since the approval of eflornithine. A number of research programs are on going to exploit the unusual biochemical pathways in the parasite to identify new targets for target based drug discovery programs. HTS efforts are also underway to discover new chemical entities through whole organism screening approaches. A number of inhibitors with anti-trypanosomal activity have been identified by both approaches, but none of the programs are yet at the stage of identifying a preclinical candidate. This dire situation underscores the need for continued effort to identify new chemical agents for the treatment of HAT.
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Affiliation(s)
- Robert T. Jacobs
- SCYNEXIS, Inc., Research Triangle Park, North Carolina 27709-2878
| | - Bakela Nare
- SCYNEXIS, Inc., Research Triangle Park, North Carolina 27709-2878
| | - Margaret A. Phillips
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park Rd, Dallas, Texas 75390-9041
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14
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Barratt JLN, Harkness J, Marriott D, Ellis JT, Stark D. Importance of nonenteric protozoan infections in immunocompromised people. Clin Microbiol Rev 2010; 23:795-836. [PMID: 20930074 PMCID: PMC2952979 DOI: 10.1128/cmr.00001-10] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
There are many neglected nonenteric protozoa able to cause serious morbidity and mortality in humans, particularly in the developing world. Diseases caused by certain protozoa are often more severe in the presence of HIV. While information regarding neglected tropical diseases caused by trypanosomatids and Plasmodium is abundant, these protozoa are often not a first consideration in Western countries where they are not endemic. As such, diagnostics may not be available in these regions. Due to global travel and immigration, this has become an increasing problem. Inversely, in certain parts of the world (particularly sub-Saharan Africa), the HIV problem is so severe that diseases like microsporidiosis and toxoplasmosis are common. In Western countries, due to the availability of highly active antiretroviral therapy (HAART), these diseases are infrequently encountered. While free-living amoebae are rarely encountered in a clinical setting, when infections do occur, they are often fatal. Rapid diagnosis and treatment are essential to the survival of patients infected with these organisms. This paper reviews information on the diagnosis and treatment of nonenteric protozoal diseases in immunocompromised people, with a focus on patients infected with HIV. The nonenteric microsporidia, some trypanosomatids, Toxoplasma spp., Neospora spp., some free-living amoebae, Plasmodium spp., and Babesia spp. are discussed.
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Affiliation(s)
- J L N Barratt
- Department of Microbiology, St. Vincent's Hospital, Darlinghurst 2010, NSW, Australia.
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Abstract
The molecular mechanisms of K(+) homeostasis are only poorly understood for protozoan parasites. Trypanosoma brucei subsp. parasites, the causative agents of human sleeping sickness and nagana, are strictly extracellular and need to actively concentrate K(+) from their hosts' body fluids. The T. brucei genome contains two putative K(+) channel genes, yet the trypanosomes are insensitive to K(+) antagonists and K(+) channel-blocking agents, and they do not spontaneously depolarize in response to high extracellular K(+) concentrations. However, the trypanosomes are extremely sensitive to K(+) ionophores such as valinomycin. Surprisingly, T. brucei possesses a member of the Trk/HKT superfamily of monovalent cation permeases which so far had only been known from bacteria, archaea, fungi, and plants. The protein was named TbHKT1 and functions as a Na(+)-independent K(+) transporter when expressed in Escherichia coli, Saccharomyces cerevisiae, or Xenopus laevis oocytes. In trypanosomes, TbHKT1 is expressed in both the mammalian bloodstream stage and the Tsetse fly midgut stage; however, RNA interference (RNAi)-mediated silencing of TbHKT1 expression did not produce a growth phenotype in either stage. The presence of HKT genes in trypanosomatids adds a further piece to the enigmatic phylogeny of the Trk/HKT superfamily of K(+) transporters. Parsimonial analysis suggests that the transporters were present in the first eukaryotes but subsequently lost in several of the major eukaryotic lineages, in at least four independent events.
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Abstract
SUMMARYLeishmania spp. are sandfly-transmitted protozoa parasites that cause a spectrum of diseases in humans. Many enzymes involved in Leishmania central carbon metabolism differ from their equivalents in the mammalian host and are potential drug targets. In this review we summarize recent advances in our understanding of Leishmania central carbon metabolism, focusing on pathways of carbon utilization that are required for growth and pathogenesis in the mammalian host. While Leishmania central carbon metabolism shares many features in common with other pathogenic trypanosomatids, significant differences are also apparent. Leishmania parasites are also unusual in constitutively expressing most core metabolic pathways throughout their life cycle, a feature that may allow these parasites to exploit a range of different carbon sources (primarily sugars and amino acids) rapidly in both the insect vector and vertebrate host. Indeed, recent gene deletion studies suggest that mammal-infective stages are dependent on multiple carbon sources in vivo. The application of metabolomic approaches, outlined here, are likely to be important in defining aspects of central carbon metabolism that are essential at different stages of mammalian host infection.
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Abstract
Glucose and related hexoses play central roles in the biochemistry and metabolism of single-cell parasites such as Leishmania, Trypanosoma, and Plasmodium that are the causative agents of leishmaniasis, African sleeping sickness, and malaria. Glucose transporters and the genes that encode them have been identified in each of these parasites and their functional properties have been scrutinized. These transporters are related in sequence and structure to mammalian facilitative glucose transporters of the SLC2 family, but they are nonetheless quite divergent in sequence. Hexose transporters have been shown to be essential for the viability of the infectious stage of each of these parasites and thus may represent targets for development of novel anti-parasitic drugs. The study of these transporters also illuminates many aspects of the basic biology of Leishmania, trypanosomes, and malaria parasites.
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Glucose uptake in the mammalian stages of Trypanosoma cruzi. Mol Biochem Parasitol 2009; 168:102-8. [PMID: 19631694 DOI: 10.1016/j.molbiopara.2009.07.006] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Revised: 07/14/2009] [Accepted: 07/15/2009] [Indexed: 02/06/2023]
Abstract
Trypanosoma cruzi, the agent of Chagas' disease, alternates between different morphogenetic stages that face distinct physiological conditions in their invertebrate and vertebrate hosts, likely in the availability of glucose. While the glucose transport is well characterized in epimastigotes of T. cruzi, nothing is known about how the mammalian stages acquire this molecule. Herein glucose transport activity and expression were analyzed in the three developmental stages present in the vertebrate cycle of T. cruzi. The infective trypomastigotes showed the highest transport activity (V(max)=5.34+/-0.54 nmol/min per mg of protein; K(m)=0.38+/-0.01 mM) when compared to intracellular epimastigotes (V(max)=2.18+/-0.20 nmol/min per mg of protein; K(m)=0.39+/-0.01 mM). Under the conditions employed no transport activity could be detected in amastigotes. The gene of the glucose transporter is expressed at the mRNA level in trypomastigotes and in intracellular epimastigotes but not in amastigotes, as revealed by real-time PCR. In both trypomastigotes and intracellular epimastigotes protein expression could be detected by Western blot with an antibody raised against the glucose transporter correlating well with the transport activity measured experimentally. Interestingly, anti-glucose transporter antibodies showed a strong reactivity with glycosome and reservosome organelles. A comparison between proline and glucose transport among the intracellular differentiation forms is presented. The data suggest that the regulation of glucose transporter reflects different energy and carbon requirements along the intracellular life cycle of T. cruzi.
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Host-derived glucose and its transporter in the obligate intracellular pathogen Toxoplasma gondii are dispensable by glutaminolysis. Proc Natl Acad Sci U S A 2009; 106:12998-3003. [PMID: 19617561 DOI: 10.1073/pnas.0903831106] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Toxoplasma gondii, as an obligate intracellular and promiscuous pathogen of mammalian cells, utilizes host sugars for energy and to generate glycoconjugates that are important to its survival and virulence. Here, we report that T. gondii glucose transporter (TgGT1) is proficient in transporting mannose, galactose, and fructose besides glucose, and serves as a major hexose transporter at its plasma membrane. Toxoplasma harbors 3 additional putative sugar transporters (TgST1-3), of which TgST2 is expressed at its surface, whereas TgST1 and TgST3 are intracellular. Surprisingly, TgGT1 and TgST2 are nonessential to the parasite as their ablations inflict only a 30% or no defect in its intracellular growth, respectively. Indeed, Toxoplasma can also tolerate the deletion of both genes while incurring no further growth phenotype. Unlike Deltatgst2, the modest impairment in Deltatggt1 and Deltatggt1/Deltatgst2 mutants is because of a minor delay in their intracellular replication, which is a direct consequence of the abolished import of glucose. The Deltatggt1 displays an attenuated motility in defined minimal media that is rescued by glutamine. TgGT1-complemented parasites show an entirely restored growth, motility, and sugar import. The lack of exogenous glucose in Deltatggt1 culture fails to accentuate its intrinsic growth defect and prompts it to procure glutamine to sustain its metabolism. Unexpectedly, in vivo virulence of Deltatggt1 in mice remains unaffected. Taken together, our data demonstrate that glucose is nonessential for T. gondii tachyzoites, underscore glutamine is a complement substrate, and provide a basis for understanding the adaptation of T. gondii to diverse host cells.
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Cavalli A, Bolognesi ML. Neglected Tropical Diseases: Multi-Target-Directed Ligands in the Search for Novel Lead Candidates against Trypanosoma and Leishmania. J Med Chem 2009; 52:7339-59. [DOI: 10.1021/jm9004835] [Citation(s) in RCA: 172] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Andrea Cavalli
- Department of Pharmaceutical Sciences, Alma Mater Studiorum, University of Bologna, Via Belmeloro 6, 40126 Bologna, Italy
- Department of Drug Discovery and Development, Italian Institute of Technology, Via Morego 30, 16163 Genova, Italy
| | - Maria Laura Bolognesi
- Department of Pharmaceutical Sciences, Alma Mater Studiorum, University of Bologna, Via Belmeloro 6, 40126 Bologna, Italy
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Magdaleno A, Ahn IY, Paes LS, Silber AM. Actions of a proline analogue, L-thiazolidine-4-carboxylic acid (T4C), on Trypanosoma cruzi. PLoS One 2009; 4:e4534. [PMID: 19229347 PMCID: PMC2645137 DOI: 10.1371/journal.pone.0004534] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2008] [Accepted: 01/07/2009] [Indexed: 12/18/2022] Open
Abstract
It is well established that L-proline has several roles in the biology of trypanosomatids. In Trypanosoma cruzi, the etiological agent of Chagas' disease, this amino acid is involved in energy metabolism, differentiation processes and resistance to osmotic stress. In this study, we analyzed the effects of interfering with L-proline metabolism on the viability and on other aspects of the T. cruzi life cycle using the proline analogue L- thiazolidine-4-carboxylic acid (T4C). The growth of epimastigotes was evaluated using different concentrations of T4C in standard culture conditions and at high temperature or acidic pH. We also evaluated possible interactions of this analogue with stress conditions such as those produced by nutrient starvation and oxidative stress. T4C showed a dose-response effect on epimastigote growth (IC(50) = 0.89+/-0.02 mM at 28 degrees C), and the inhibitory effect of this analogue was synergistic (p<0.05) with temperature (0.54+/-0.01 mM at 37 degrees C). T4C significantly diminished parasite survival (p<0.05) in combination with nutrient starvation and oxidative stress conditions. Pre-incubation of the parasites with L-proline resulted in a protective effect against oxidative stress, but this was not seen in the presence of the drug. Finally, the trypomastigote bursting from infected mammalian cells was evaluated and found to be inhibited by up to 56% when cells were treated with non-toxic concentrations of T4C (between 1 and 10 mM). All these data together suggest that T4C could be an interesting therapeutic drug if combined with others that affect, for example, oxidative stress. The data also support the participation of proline metabolism in the resistance to oxidative stress.
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Affiliation(s)
- Anahí Magdaleno
- Departamento de Parasitología, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Il-Young Ahn
- Departamento de Parasitología, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Lisvane Silva Paes
- Departamento de Parasitología, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Ariel M. Silber
- Departamento de Parasitología, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
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