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Morales-Luna L, Vázquez-Bautista M, Martínez-Rosas V, Rojas-Alarcón MA, Ortega-Cuellar D, González-Valdez A, Pérez de la Cruz V, Arreguin-Espinosa R, Rodríguez-Bustamante E, Rodríguez-Flores E, Hernández-Ochoa B, Gómez-Manzo S. Fused Enzyme Glucose-6-Phosphate Dehydrogenase::6-Phosphogluconolactonase (G6PD::6PGL) as a Potential Drug Target in Giardia lamblia, Trichomonas vaginalis, and Plasmodium falciparum. Microorganisms 2024; 12:112. [PMID: 38257939 PMCID: PMC10819308 DOI: 10.3390/microorganisms12010112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2023] [Revised: 01/01/2024] [Accepted: 01/03/2024] [Indexed: 01/24/2024] Open
Abstract
Several microaerophilic parasites such as Giardia lamblia, Trichomonas vaginalis, and Plasmodium falciparum are major disease-causing organisms and are responsible for spreading infections worldwide. Despite significant progress made in understanding the metabolism and molecular biology of microaerophilic parasites, chemotherapeutic treatment to control it has seen limited progress. A current proposed strategy for drug discovery against parasitic diseases is the identification of essential key enzymes of metabolic pathways associated with the parasite's survival. In these organisms, glucose-6-phosphate dehydrogenase::6-phosphogluconolactonase (G6PD:: 6PGL), the first enzyme of the pentose phosphate pathway (PPP), is essential for its metabolism. Since G6PD:: 6PGL provides substrates for nucleotides synthesis and NADPH as a source of reducing equivalents, it could be considered an anti-parasite drug target. This review analyzes the anaerobic energy metabolism of G. lamblia, T. vaginalis, and P. falciparum, with a focus on glucose metabolism through the pentose phosphate pathway and the significance of the fused G6PD:: 6PGL enzyme as a therapeutic target in the search for new drugs.
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Affiliation(s)
- Laura Morales-Luna
- Laboratorio de Bioquímica Genética, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico; (L.M.-L.); (M.V.-B.); (V.M.-R.); (M.A.R.-A.)
- Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico
| | - Montserrat Vázquez-Bautista
- Laboratorio de Bioquímica Genética, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico; (L.M.-L.); (M.V.-B.); (V.M.-R.); (M.A.R.-A.)
- Programa de Posgrado en Biomedicina y Biotecnología Molecular, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City 11340, Mexico
| | - Víctor Martínez-Rosas
- Laboratorio de Bioquímica Genética, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico; (L.M.-L.); (M.V.-B.); (V.M.-R.); (M.A.R.-A.)
- Programa de Posgrado en Biomedicina y Biotecnología Molecular, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City 11340, Mexico
| | - Miriam Abigail Rojas-Alarcón
- Laboratorio de Bioquímica Genética, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico; (L.M.-L.); (M.V.-B.); (V.M.-R.); (M.A.R.-A.)
- Programa de Posgrado en Biomedicina y Biotecnología Molecular, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City 11340, Mexico
| | - Daniel Ortega-Cuellar
- Laboratorio de Nutrición Experimental, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico;
| | - Abigail González-Valdez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico;
| | - Verónica Pérez de la Cruz
- Neurobiochemistry and Behavior Laboratory, National Institute of Neurology and Neurosurgery “Manuel Velasco Suárez”, Mexico City 14269, Mexico;
| | - Roberto Arreguin-Espinosa
- Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico; (R.A.-E.); (E.R.-B.); (E.R.-F.)
| | - Eduardo Rodríguez-Bustamante
- Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico; (R.A.-E.); (E.R.-B.); (E.R.-F.)
- Departamento de Bioingeniería, Escuela de Ingeniería y Ciencias, Tecnológico de Monterrey, Monterrey 64849, Mexico
| | - Eden Rodríguez-Flores
- Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico; (R.A.-E.); (E.R.-B.); (E.R.-F.)
| | - Beatriz Hernández-Ochoa
- Laboratorio de Inmunoquímica, Hospital Infantil de México Federico Gómez, Secretaría de Salud, Mexico City 06720, Mexico
| | - Saúl Gómez-Manzo
- Laboratorio de Bioquímica Genética, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico; (L.M.-L.); (M.V.-B.); (V.M.-R.); (M.A.R.-A.)
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Saleh M, Mostafa YA, Kumari J, Thabet MM, Sriram D, Kandeel M, Abdu-Allah HHM. New nitazoxanide derivatives: design, synthesis, biological evaluation, and molecular docking studies as antibacterial and antimycobacterial agents. RSC Med Chem 2023; 14:2714-2730. [PMID: 38107181 PMCID: PMC10718594 DOI: 10.1039/d3md00449j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Accepted: 10/05/2023] [Indexed: 12/19/2023] Open
Abstract
A new series inspired by combining fragments from nitazoxanide (NTZ) and 4-aminosalicylic acid (4-ASA) was synthesized and screened for in vitro antibacterial and antimycobacterial activities. The majority showed higher antibacterial potency than NTZ against all the screened strains, notably, 5f, 5j, 5n and 5o with MICs of 0.87-9.00 μM. Compounds 5c, 5n and 5o revealed higher potency than ciprofloxacin against K. pneumoniae, while 5i was equipotent. For E. faecalis, 3b, 5j, and 5k showed higher potency than ciprofloxacin. 5j was more potent against P. aeruginosa than ciprofloxacin, while 5n was more potent against S. aureus with an MIC of 0.87 μM. 5f showed equipotency to ciprofloxacin against H. pylori with an MIC of 1.74 μM. Compounds 3a and 3b (4-azidoNTZ, MIC 4.47 μM) are 2 and 5-fold more potent against Mycobacterium tuberculosis (Mtb H37Rv) than NTZ (MIC 20.23 μM) and safer. 4-Azidation and/or acetylation of NTZ improve both activities, while introducing 1,2,3-triazoles improves the antibacterial activity. Molecular docking studies within pyruvate ferredoxin oxidoreductase (PFOR), glucosamine-6-phosphate synthase (G6PS) and dihydrofolate reductase (DHFR) active sites were performed to explore the possible molecular mechanisms of actions. Acceptable drug-likeness properties were found. This study may shed light on further rational design of substituted NTZ as broad-spectrum more potent antimicrobial candidates.
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Affiliation(s)
- Mahmoud Saleh
- Pharmaceutical Organic Chemistry Department, Faculty of Pharmacy, Assiut University Assiut 71526 Egypt
| | - Yaser A Mostafa
- Pharmaceutical Organic Chemistry Department, Faculty of Pharmacy, Assiut University Assiut 71526 Egypt
| | - Jyothi Kumari
- Department of Pharmacy, Birla Institute of Technology & Science-Pilani Hyderabad Campus, Jawahar Nagar Hyderabad-500 078 India
| | - Momen M Thabet
- Microbiology and Immunology Department, Faculty of Pharmacy, South Valley University Qena 83523 Egypt
| | - Dharmarajan Sriram
- Department of Pharmacy, Birla Institute of Technology & Science-Pilani Hyderabad Campus, Jawahar Nagar Hyderabad-500 078 India
| | - Mahmoud Kandeel
- Department of Biomedical Sciences, College of Veterinary Medicine, King Faisal University 31982 Al-Ahsa Saudi Arabia
- Department of Pharmacology, Faculty of Veterinary Medicine, Kafrelsheikh University 33516 Kafrelsheikh Egypt
| | - Hajjaj H M Abdu-Allah
- Pharmaceutical Organic Chemistry Department, Faculty of Pharmacy, Assiut University Assiut 71526 Egypt
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Martínez-Rosas V, Hernández-Ochoa B, Morales-Luna L, Ortega-Cuellar D, González-Valdez A, Arreguin-Espinosa R, Rufino-González Y, Calderón-Jaimes E, Castillo-Rodríguez RA, Wong-Baeza C, Baeza-Ramírez I, Pérez de la Cruz V, Vidal-Limón A, Gómez-Manzo S. Nitazoxanide Inhibits the Bifunctional Enzyme GlG6PD::6PGL of Giardia lamblia: Biochemical and In Silico Characterization of a New Druggable Target. Int J Mol Sci 2023; 24:11516. [PMID: 37511272 PMCID: PMC10380810 DOI: 10.3390/ijms241411516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 07/08/2023] [Accepted: 07/12/2023] [Indexed: 07/30/2023] Open
Abstract
Giardiasis, which is caused by Giardia lamblia infection, is a relevant cause of morbidity and mortality worldwide. Because no vaccines are currently available to treat giardiasis, chemotherapeutic drugs are the main options for controlling infection. Evidence has shown that the nitro drug nitazoxanide (NTZ) is a commonly prescribed treatment for giardiasis; however, the mechanisms underlying NTZ's antigiardial activity are not well-understood. Herein, we identified the glucose-6-phosphate::6-phosphogluconate dehydrogenase (GlG6PD::6PGL) fused enzyme as a nitazoxanide target, as NTZ behaves as a GlG6PD::6PGL catalytic inhibitor. Furthermore, fluorescence assays suggest alterations in the stability of GlG6PD::6PGL protein, whereas the results indicate a loss of catalytic activity due to conformational and folding changes. Molecular docking and dynamic simulation studies suggest a model of NTZ binding on the active site of the G6PD domain and near the structural NADP+ binding site. The findings of this study provide a novel mechanistic basis and strategy for the antigiardial activity of the NTZ drug.
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Affiliation(s)
- Víctor Martínez-Rosas
- Laboratorio de Bioquímica Genética, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico
- Programa de Posgrado en Biomedicina y Biotecnología Molecular, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City 11340, Mexico
| | - Beatriz Hernández-Ochoa
- Laboratorio de Inmunoquímica, Hospital Infantil de México Federico Gómez, Secretaría de Salud, Mexico City 06720, Mexico
| | - Laura Morales-Luna
- Laboratorio de Bioquímica Genética, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico
- Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico
| | - Daniel Ortega-Cuellar
- Laboratorio de Nutrición Experimental, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico
| | - Abigail González-Valdez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico
| | - Roberto Arreguin-Espinosa
- Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico
| | - Yadira Rufino-González
- Laboratorio de Parasitología Experimental, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico
| | - Ernesto Calderón-Jaimes
- Laboratorio de Inmunoquímica, Hospital Infantil de México Federico Gómez, Secretaría de Salud, Mexico City 06720, Mexico
| | | | - Carlos Wong-Baeza
- Laboratorio de Biomembranas, Departamento de Bioquímica, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City 11340, Mexico
| | - Isabel Baeza-Ramírez
- Laboratorio de Biomembranas, Departamento de Bioquímica, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City 11340, Mexico
| | - Verónica Pérez de la Cruz
- Neurobiochemistry and Behavior Laboratory, National Institute of Neurology and Neurosurgery "Manuel Velasco Suárez", Mexico City 14269, Mexico
| | - Abraham Vidal-Limón
- Red de Estudios Moleculares Avanzados, Clúster Científico y Tecnológico BioMimic®, Instituto de Ecología A.C. (INECOL), Carretera Antigua a Coatepec 351, El Haya, Xalapa 91073, Mexico
| | - Saúl Gómez-Manzo
- Laboratorio de Bioquímica Genética, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico
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Benchimol M, Gadelha AP, de Souza W. Ultrastructural Alterations of the Human Pathogen Giardia intestinalis after Drug Treatment. Pathogens 2023; 12:810. [PMID: 37375500 DOI: 10.3390/pathogens12060810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 06/04/2023] [Accepted: 06/05/2023] [Indexed: 06/29/2023] Open
Abstract
This review presents the main cell characteristics altered after in vitro incubation of the parasite with commercial drugs used to treat the disease caused by Giardia intestinalis. This important intestinal parasite primarily causes diarrhea in children. Metronidazole and albendazole are the primary compounds used in therapy against Giardia intestinalis. However, they provoke significant side effects, and some strains have developed resistance to metronidazole. Benzimidazole carbamates, such as albendazole and mebendazole, have shown the best activity against Giardia. Despite their in vitro efficacy, clinical treatment with benzimidazoles has yielded conflicting results, demonstrating lower cure rates. Recently, nitazoxanide has been suggested as an alternative to these drugs. Therefore, to enhance the quality of chemotherapy against this parasite, it is important to invest in developing other compounds that can interfere with key steps of metabolic pathways or cell structures and organelles. For example, Giardia exhibits a unique cell structure called the ventral disc, which is crucial for host adhesion and pathogenicity. Thus, drugs that can disrupt the adhesion process hold promise for future therapy against Giardia. Additionally, this review discusses new drugs and strategies that can be employed, as well as suggestions for developing novel drugs to control the infection caused by this parasite.
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Affiliation(s)
- Marlene Benchimol
- BIOTRANS-CAXIAS, Universidade do Grande Rio. UNIGRANRIO, Rio de Janeiro 96200-000, Brazil
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
- Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens e Centro Nacional de Biologia Estrutural e Bioimagens, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
| | - Ana Paula Gadelha
- Diretoria de Metrologia Científica, Instituto Nacional de Metrologia, Qualidade e Tecnologia (INMETRO), Rio de Janeiro 25259-020, Brazil
| | - Wanderley de Souza
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
- Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens e Centro Nacional de Biologia Estrutural e Bioimagens, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
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Pimviriyakul P, Kapaothong Y, Tangsupatawat T. Heterologous Expression and Characterization of a Full-length Protozoan Nitroreductase from Leishmania orientalis isolate PCM2. Mol Biotechnol 2023; 65:556-569. [PMID: 36042106 DOI: 10.1007/s12033-022-00556-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 08/22/2022] [Indexed: 11/25/2022]
Abstract
Leishmaniasis, a parasitic disease found in parts of the tropics and subtropics, is caused by Leishmania protozoa infection. Nitroreductases (NTRs), enzymes involved in nitroaromatic prodrug activation, are attractive targets for leishmaniasis treatment development. In this study, a full-length recombinant NTR from the Leishmania orientalis isolate PCM2 (LoNTR), which causes severe leishmaniasis in Thailand, was successfully expressed in soluble form using chaperone co-expression in Escherichia coli BL21(DE3). The purified histidine-tagged enzyme (His6-LoNTR) had a subunit molecular mass of 36 kDa with no cofactor bound; however, the addition of exogenous flavin (either FMN or FAD) readily increased its enzyme activity. Bioinformatics analysis found that the unique N-terminal sequences of LoNTR is only present in Leishmania where the addition of this region might result in the loss of flavin binding. Either NADH or NADPH can serve as an electron donor to transfer electrons to nitrofurazone; however, NADPH was preferred. Molecular oxygen was identified as an additional electron acceptor resulting in wasteful electrons from NADPH for the main catalysis. Steady-state kinetic experiments revealed a ping-pong mechanism for His6-LoNTR with Km,NADPH, Km,NFZ, and kcat of 28 µM, 68 µM, and 0.84 min-1, respectively. Besides nitroreductase activity, His6-LoNTR also has the ability to reduce quinone derivatives. The properties of full-length His6-LoNTR were different from previously reported protozoa and bacterial NTRs in many respects. This study provides information of NTR catalysis to be developed as a potential future therapeutic target to treat leishmaniasis.
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Affiliation(s)
- Panu Pimviriyakul
- Department of Biochemistry, Faculty of Science, Kasetsart University, Chatuchak, Bangkok, 10900, Thailand.
| | - Yuvarun Kapaothong
- Department of Biochemistry, Faculty of Science, Kasetsart University, Chatuchak, Bangkok, 10900, Thailand
| | - Theerapat Tangsupatawat
- Department of Biochemistry, Faculty of Science, Kasetsart University, Chatuchak, Bangkok, 10900, Thailand
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Saghaug CS, Gamlem AL, Hauge KB, Vahokoski J, Klotz C, Aebischer T, Langeland N, Hanevik K. Genetic diversity in the metronidazole metabolism genes nitroreductases and pyruvate ferredoxin oxidoreductases in susceptible and refractory clinical samples of Giardia lamblia. Int J Parasitol Drugs Drug Resist 2022; 21:51-60. [PMID: 36682328 PMCID: PMC9871439 DOI: 10.1016/j.ijpddr.2022.12.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 11/30/2022] [Accepted: 12/20/2022] [Indexed: 12/24/2022]
Abstract
The effectiveness of metronidazole against the tetraploid intestinal parasite Giardia lamblia is dependent on its activation/inactivation within the cytoplasm. There are several activating enzymes, including pyruvate ferredoxin reductase (PFOR) and nitroreductase (NR) 1 which metabolize metronidazole into toxic forms, while NR2 on the other hand inactivates it. Metronidazole treatment failures have been increasing rapidly over the last decade, indicating genetic resistance mechanisms. Analyzing genetic variation in the PFOR and NR genes in susceptible and refractory Giardia isolates may help identify potential markers of resistance. Full length PFOR1, PFOR2, NR1 and NR2 genes from clinical culturable isolates and non-cultured clinical Giardia assemblage B samples were cloned, sequenced and single nucleotide variants (SNVs) were analyzed to assess genetic diversity and alleles. A similar ratio of amino acid changing SNVs per gene length was found for the NRs; 4.2% for NR1 and 6.4% for NR2, while the PFOR1 and PFOR2 genes had less variability with a ratio of 1.1% and 1.6%, respectively. One of the samples from a refractory case had a nonsense mutation which caused a truncated NR1 gene in one out of six alleles. Further, we found three NR2 alleles with frameshift mutations, possibly causing a truncated protein in two susceptible isolates. One of these isolates was homozygous for the affected NR2 allele. Three nsSNVs with potential for affecting protein function were found in the ferredoxin domain of the PFOR2 gene. The considerable variation and discovery of mutations possibly causing dysfunctional NR proteins in clinical Giardia assemblage B isolates, reveal a potential for genetic link to metronidazole susceptibility and resistance.
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Affiliation(s)
- Christina S Saghaug
- Department of Clinical Science, University of Bergen, Bergen, Norway; Norwegian National Advisory Unit on Tropical Infectious Diseases, Department of Medicine, Haukeland University Hospital, Bergen, Norway.
| | - Astrid L Gamlem
- Department of Clinical Science, University of Bergen, Bergen, Norway
| | - Kirsti B Hauge
- Department of Clinical Science, University of Bergen, Bergen, Norway
| | - Juha Vahokoski
- Department of Clinical Science, University of Bergen, Bergen, Norway; Department of Medicine, Haukeland University Hospital, Bergen, Norway
| | - Christian Klotz
- Department of Infectious Diseases, Unit 16 Mycotic and Parasitic Agents and Mycobacteria, Robert Koch-Institute, Berlin, Germany
| | - Toni Aebischer
- Department of Infectious Diseases, Unit 16 Mycotic and Parasitic Agents and Mycobacteria, Robert Koch-Institute, Berlin, Germany
| | - Nina Langeland
- Department of Clinical Science, University of Bergen, Bergen, Norway; Norwegian National Advisory Unit on Tropical Infectious Diseases, Department of Medicine, Haukeland University Hospital, Bergen, Norway
| | - Kurt Hanevik
- Department of Clinical Science, University of Bergen, Bergen, Norway; Norwegian National Advisory Unit on Tropical Infectious Diseases, Department of Medicine, Haukeland University Hospital, Bergen, Norway
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Morales-Luna L, Hernández-Ochoa B, Martínez-Rosas V, Navarrete-Vázquez G, Ortega-Cuellar D, Rufino-González Y, González-Valdez A, Arreguin-Espinosa R, Franco-Vásquez AM, Pérez de la Cruz V, Enríquez-Flores S, Martínez-Conde C, Canseco-Ávila LM, Gómez-Chávez F, Gómez-Manzo S. Giardia lamblia G6PD::6PGL Fused Protein Inhibitors Decrease Trophozoite Viability: A New Alternative against Giardiasis. Int J Mol Sci 2022; 23:ijms232214358. [PMID: 36430836 PMCID: PMC9697976 DOI: 10.3390/ijms232214358] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 11/08/2022] [Accepted: 11/14/2022] [Indexed: 11/22/2022] Open
Abstract
Treatments to combat giardiasis have been reported to have several drawbacks, partly due to the drug resistance and toxicity of current antiparasitic agents. These constraints have prompted many researchers to investigate new drugs that act against protozoan parasites. Enzyme inhibition is an important means of regulating pathogen metabolism and has recently been identified as a significant alternative target in the search for new treatments. Glucose-6-phosphate dehydrogenase and 6-phosphogluconolactonase (G6PD::6PGL) is a bifunctional enzyme involved in the pentose phosphate pathway (PPP) in Giardia lamblia (G. lamblia). The G. lamblia enzyme is unusual since, unlike the human enzyme, it is a fused enzyme. Here, we show, through inhibition assays, that an in-house chemical library of 120 compounds and four target compounds, named CNZ-7, CNZ-8, CMC-1, and FLP-2, are potent inhibitors of the G. lamblia G6PD::6PGL fused enzyme. With a constant (k2) of 2.3, 3.2, and 2.8 M−1 s−1, respectively, they provoke alterations in the secondary and tertiary protein structure and global stability. As a novel approach, target compounds show antigiardial activity, with IC50 values of 8.7, 15.2, 15.3, and 24.1 µM in trophozoites from G. lamblia. Moreover, these compounds show selectivity against G. lamblia, since, through counter-screening in Caco-2 and HT29 human cells, they were found to have low toxicity. This finding positions these compounds as a potential and attractive starting point for new antigiardial drugs.
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Affiliation(s)
- Laura Morales-Luna
- Laboratorio de Bioquímica Genética, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico
- Posgrado en Ciencias Biológicas, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico
| | - Beatriz Hernández-Ochoa
- Laboratorio de Inmunoquímica, Hospital Infantil de México Federico Gómez, Secretaría de Salud, Mexico City 06720, Mexico
| | - Víctor Martínez-Rosas
- Laboratorio de Bioquímica Genética, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico
- Programa de Posgrado en Biomedicina y Biotecnología Molecular, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City 11340, Mexico
| | - Gabriel Navarrete-Vázquez
- Facultad de Farmacia, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, Chamilpa, Cuernavaca 62209, Mexico
| | - Daniel Ortega-Cuellar
- Laboratorio de Nutrición Experimental, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico
| | - Yadira Rufino-González
- Laboratorio de Parasitología Experimental, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico
| | - Abigail González-Valdez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico
| | - Roberto Arreguin-Espinosa
- Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico
| | - Adrián Marcelo Franco-Vásquez
- Departamento de Química de Biomacromoléculas, Instituto de Química, Universidad Nacional Autónoma de México, Mexico City 04510, Mexico
| | - Verónica Pérez de la Cruz
- Neurobiochemistry and Behavior Laboratory, National Institute of Neurology and Neurosurgery “Manuel Velasco Suárez”, Mexico City 14269, Mexico
| | - Sergio Enríquez-Flores
- Laboratorio de Biomoléculas y Salud Infantil, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico
| | - Carlos Martínez-Conde
- Facultad de Farmacia, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, Chamilpa, Cuernavaca 62209, Mexico
| | - Luis Miguel Canseco-Ávila
- Facultad de Ciencias Químicas, Campus IV, Universidad Autónoma de Chiapas, Tapachula City 30700, Mexico
| | - Fernando Gómez-Chávez
- Laboratorio de Enfermedades Osteoarticulares e Inmunológicas, Sección de Estudios de Posgrado e Investigación, Escuela Nacional de Medicina y Homeopatía, Instituto Politécnico Nacional, Mexico City 07320, Mexico
| | - Saúl Gómez-Manzo
- Laboratorio de Bioquímica Genética, Instituto Nacional de Pediatría, Secretaría de Salud, Mexico City 04530, Mexico
- Correspondence: ; Tel.: +52-55-1084-0900 (ext. 1442)
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Stevens AJ, Abraham R, Young KA, Russell CC, McCluskey SN, Baker JR, Rusdi B, Page SW, O'Handley R, O'Dea M, Abraham S, McCluskey A. Antigiardial Activity of Novel Guanidine Compounds. ChemMedChem 2022; 17:e202200341. [PMID: 36085254 PMCID: PMC9828538 DOI: 10.1002/cmdc.202200341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2022] [Revised: 08/31/2022] [Indexed: 01/12/2023]
Abstract
From four focused compound libraries based on the known anticoccidial agent robenidine, 44 compounds total were synthesised and screened for antigiardial activity. All active compounds were counter-screened for antibiotic and cytotoxic action. Of the analogues examined, 21 displayed IC50 <5 μM, seven with IC50 <1.0 μM. Most active were 2,2'-bis{[4-(trifluoromethoxy)phenyl]methylene}carbonimidic dihydrazide hydrochloride (30), 2,2'-bis{[4-(trifluoromethylsulfanyl)phenyl]methylene}carbonimidic dihydrazide hydrochloride (32), and 2,2'-bis[(2-bromo-4,5-dimethoxyphenyl)methylene]carbonimidic dihydrazide hydrochloride (41) with IC50 =0.2 μM. The maximal observed activity was a 5 h IC50 value of 0.2 μM for 41. The clinically used metronidazole was inactive at this timepoint at a concentration of 25 μM. Robenidine off-target effects at bacteria and cell line toxicity were removed. Analogue 41 was well tolerated in mice treated orally (100 mg/kg). Following 5 h treatment with 41, no Giardia regrowth was noted after 48 h.
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Affiliation(s)
- Andrew J. Stevens
- School of Environmental & Life SciencesThe University of NewcastleUniversity DriveCallaghanNSW 2308Australia
| | - Rebecca Abraham
- Antimicrobial resistance and Infectious Diseases Laboratory, Harry butler InstituteMurdoch University90 South StreetMurdochWA 6150Australia,School of Animal and Veterinary SciencesUniversity of Adelaide, Roseworthy CampusMudla Wirra RoadRoseworthySA 5371Australia
| | - Kelly A. Young
- School of Environmental & Life SciencesThe University of NewcastleUniversity DriveCallaghanNSW 2308Australia
| | - Cecilia C. Russell
- School of Environmental & Life SciencesThe University of NewcastleUniversity DriveCallaghanNSW 2308Australia
| | - Siobhann N. McCluskey
- School of Environmental & Life SciencesThe University of NewcastleUniversity DriveCallaghanNSW 2308Australia
| | - Jennifer R. Baker
- School of Environmental & Life SciencesThe University of NewcastleUniversity DriveCallaghanNSW 2308Australia
| | - Bertha Rusdi
- Antimicrobial resistance and Infectious Diseases Laboratory, Harry butler InstituteMurdoch University90 South StreetMurdochWA 6150Australia
| | | | - Ryan O'Handley
- School of Animal and Veterinary SciencesUniversity of Adelaide, Roseworthy CampusMudla Wirra RoadRoseworthySA 5371Australia
| | - Mark O'Dea
- Antimicrobial resistance and Infectious Diseases Laboratory, Harry butler InstituteMurdoch University90 South StreetMurdochWA 6150Australia
| | - Sam Abraham
- Antimicrobial resistance and Infectious Diseases Laboratory, Harry butler InstituteMurdoch University90 South StreetMurdochWA 6150Australia
| | - Adam McCluskey
- School of Environmental & Life SciencesThe University of NewcastleUniversity DriveCallaghanNSW 2308Australia
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9
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Benchimol M, Gadelha AP, de Souza W. Unusual Cell Structures and Organelles in Giardia intestinalis and Trichomonas vaginalis Are Potential Drug Targets. Microorganisms 2022; 10:2176. [PMID: 36363768 PMCID: PMC9698047 DOI: 10.3390/microorganisms10112176] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Revised: 10/28/2022] [Accepted: 10/31/2022] [Indexed: 09/29/2023] Open
Abstract
This review presents the main cell organelles and structures of two important protist parasites, Giardia intestinalis, and Trichomonas vaginalis; many are unusual and are not found in other eukaryotic cells, thus could be good candidates for new drug targets aimed at improvement of the chemotherapy of diseases caused by these eukaryotic protists. For example, in Giardia, the ventral disc is a specific structure to this parasite and is fundamental for the adhesion and pathogenicity to the host. In Trichomonas, the hydrogenosome, a double membrane-bounded organelle that produces ATP, also can be a good target. Other structures include mitosomes, ribosomes, and proteasomes. Metronidazole is the most frequent compound used to kill many anaerobic organisms, including Giardia and Trichomonas. It enters the cell by passive diffusion and needs to find a highly reductive environment to be reduced to the nitro radicals to be active. However, it provokes several side effects, and some strains present metronidazole resistance. Therefore, to improve the quality of the chemotherapy against parasitic protozoa is important to invest in the development of highly specific compounds that interfere with key steps of essential metabolic pathways or in the functional macromolecular complexes which are most often associated with cell structures and organelles.
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Affiliation(s)
- Marlene Benchimol
- Laboratorio de Ultraestrutura Celular Hertha Meyer, Centro de Ciêcias da Saúde, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Cidade Universitaria, Rio de Janeiro 96200-000, Brazil
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
- Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens e Centro Nacional de Biologia Estrutural e Bioimagens, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
| | - Ana Paula Gadelha
- Diretoria de Metrologia Aplicada as Ciências da Vida, Instituto Nacional de Metrologia, Qualidade e Tecnologia (INMETRO), Rio de Janeiro 25250-020, Brazil
| | - Wanderley de Souza
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
- Instituto Nacional de Ciência e Tecnologia em Biologia Estrutural e Bioimagens e Centro Nacional de Biologia Estrutural e Bioimagens, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-901, Brazil
- CMABio, Escola Superior de Saúde, Universidade do Estado do Amazonas-UEA, Manaus 69850-000, Brazil
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10
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Müller J, Boubaker G, Imhof D, Hänggeli K, Haudenschild N, Uldry AC, Braga-Lagache S, Heller M, Ortega-Mora LM, Hemphill A. Differential Affinity Chromatography Coupled to Mass Spectrometry: A Suitable Tool to Identify Common Binding Proteins of a Broad-Range Antimicrobial Peptide Derived from Leucinostatin. Biomedicines 2022; 10:biomedicines10112675. [PMID: 36359195 PMCID: PMC9687860 DOI: 10.3390/biomedicines10112675] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 10/10/2022] [Accepted: 10/20/2022] [Indexed: 11/28/2022] Open
Abstract
Leucinostatins are antimicrobial peptides with a broad range of activities against infectious agents as well as mammalian cells. The leucinostatin-derivative peptide ZHAWOC_6027 (peptide 6027) was tested in vitro and in vivo for activity against the intracellular apicomplexan parasite Toxoplasma gondii. While highly efficacious in vitro (EC50 = 2 nM), subcutaneous application of peptide 6027 (3 mg/kg/day for 5 days) in mice experimentally infected with T. gondii oocysts exacerbated the infection, caused mild clinical signs and elevated cerebral parasite load. Peptide 6027 also impaired the proliferation and viability of mouse splenocytes, most notably LPS-stimulated B cells, in vitro. To identify common potential targets in Toxoplasma and murine splenocytes, we performed differential affinity chromatography (DAC) with cell-free extracts from T. gondii tachyzoites and mouse spleens using peptide 6027 or an ineffective analogue (peptide 21,358) coupled to N-hydroxy-succinimide sepharose, followed by mass spectrometry. Proteins specifically binding to peptide 6027 were identified in eluates from the peptide 6027 column but not in peptide 21,358 nor the mock column eluates. In T. gondii eluates, 269 proteins binding specifically to peptide 6027 were identified, while in eluates from mouse spleen extracts 645 proteins specifically binding to this peptide were detected. Both datasets contained proteins involved in mitochondrial energy metabolism and in protein processing and secretion. These results suggest that peptide 6027 interacts with common targets in eukaryotes involved in essential pathways. Since this methodology can be applied to various compounds as well as target cell lines or organs, DAC combined with mass spectrometry and proteomic analysis should be considered a smart and 3R-relevant way to identify drug targets in pathogens and hosts, thereby eliminating compounds with potential side effects before performing tedious and costly safety and efficacy assessments in animals or humans.
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Affiliation(s)
- Joachim Müller
- Institute of Parasitology, Vetsuisse Faculty, University of Bern, Länggass-Strasse 122, 3012 Bern, Switzerland
| | - Ghalia Boubaker
- Institute of Parasitology, Vetsuisse Faculty, University of Bern, Länggass-Strasse 122, 3012 Bern, Switzerland
| | - Dennis Imhof
- Institute of Parasitology, Vetsuisse Faculty, University of Bern, Länggass-Strasse 122, 3012 Bern, Switzerland
| | - Kai Hänggeli
- Institute of Parasitology, Vetsuisse Faculty, University of Bern, Länggass-Strasse 122, 3012 Bern, Switzerland
| | - Noé Haudenschild
- Institute of Parasitology, Vetsuisse Faculty, University of Bern, Länggass-Strasse 122, 3012 Bern, Switzerland
| | - Anne-Christine Uldry
- Proteomics and Mass Spectrometry Core Facility, Department for BioMedical Research (DBMR), University of Bern, 3012 Bern, Switzerland
| | - Sophie Braga-Lagache
- Proteomics and Mass Spectrometry Core Facility, Department for BioMedical Research (DBMR), University of Bern, 3012 Bern, Switzerland
| | - Manfred Heller
- Proteomics and Mass Spectrometry Core Facility, Department for BioMedical Research (DBMR), University of Bern, 3012 Bern, Switzerland
| | - Luis-Miguel Ortega-Mora
- SALUVET, Animal Health Department, Faculty of Veterinary Sciences, Complutense University of Madrid, Ciudad Universitaria, 28040 Madrid, Spain
| | - Andrew Hemphill
- Institute of Parasitology, Vetsuisse Faculty, University of Bern, Länggass-Strasse 122, 3012 Bern, Switzerland
- Correspondence:
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11
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Santos HLC, Rebello KM. An Overview of Mucosa-Associated Protozoa: Challenges in Chemotherapy and Future Perspectives. Front Cell Infect Microbiol 2022; 12:860442. [PMID: 35548465 PMCID: PMC9084232 DOI: 10.3389/fcimb.2022.860442] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Accepted: 03/29/2022] [Indexed: 11/13/2022] Open
Abstract
Parasitic infections caused by protozoans that infect the mucosal surfaces are widely neglected worldwide. Collectively, Entamoeba histolytica, Giardia lamblia, Cryptosporidium spp. and Trichomonas vaginalis infect more than a billion people in the world, being a public health problem mainly in developing countries. However, the exact incidence and prevalence data depend on the population examined. These parasites ultimately cause pathologies that culminate in liver abscesses, malabsorption syndrome, vaginitis, and urethritis, respectively. Despite this, the antimicrobial agents currently used to treat these diseases are limited and often associated with adverse side effects and refractory cases due to the development of resistant parasites. The paucity of drug treatments, absence of vaccines and increasing problems of drug resistance are major concerns for their control and eradication. Herein, potential candidates are reviewed with the overall aim of determining the knowledge gaps and suggest future perspectives for research. This review focuses on this public health problem and focuses on the progress of drug repositioning as a potential strategy for the treatment of mucosal parasites.
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Affiliation(s)
- Helena Lucia Carneiro Santos
- Laboratório de Estudos Integrados em Protozoologia, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz (FIOCRUZ), Rio de Janeiro, Brazil
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12
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Synthesis and antiplasmodial assessment of nitazoxanide and analogs as new antimalarial candidates. Med Chem Res 2022; 31:426-435. [PMID: 35106047 PMCID: PMC8794615 DOI: 10.1007/s00044-021-02843-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 12/16/2021] [Indexed: 10/26/2022]
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13
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Prathapan P. A determination of pan-pathogen antimicrobials? MEDICINE IN DRUG DISCOVERY 2022; 14:100120. [PMID: 35098103 PMCID: PMC8785259 DOI: 10.1016/j.medidd.2022.100120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2021] [Revised: 01/01/2022] [Accepted: 01/17/2022] [Indexed: 11/29/2022] Open
Abstract
While antimicrobial drug development has historically mitigated infectious diseases that are known, COVID-19 revealed a dearth of ‘in-advance’ therapeutics suitable for infections by pathogens that have not yet emerged. Such drugs must exhibit a property that is antithetical to the classical paradigm of antimicrobial development: the ability to treat infections by any pathogen. Characterisation of such ‘pan-pathogen’ antimicrobials requires consolidation of drug repositioning studies, a new and growing field of drug discovery. In this review, a previously-established system for evaluating repositioning studies is used to highlight 4 therapeutics which exhibit pan-pathogen properties, namely azithromycin, ivermectin, niclosamide, and nitazoxanide. Recognition of the pan-pathogen nature of these antimicrobials is the cornerstone of a novel paradigm of antimicrobial development that is not only anticipatory of pandemics and bioterrorist attacks, but cognisant of conserved anti-infective mechanisms within the host-pathogen interactome which are only now beginning to emerge. Ultimately, the discovery of pan-pathogen antimicrobials is concomitantly the discovery of a new class of antivirals, and begets significant implications for pandemic preparedness research in a world after COVID-19.
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Affiliation(s)
- Praveen Prathapan
- New Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, United Kingdom
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14
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Abstract
PURPOSE OF REVIEW Giardiasis remains a common cause of diarrhea and intestinal enteropathy globally. Here we give an overview of clinical treatment studies and discuss potential mechanisms and molecular targets for in-vitro testing of drug resistance. RECENT FINDINGS Giardia is a cause of disease both in diarrheal and nondiarrheal cases. The prevalence of treatment refractory giardiasis is increasing. Recent studies reveal 5-nitroimidazole refractory infection occurs in up to 50% of cases. Mechanisms of drug resistance are not known. Placebo controlled studies of drug efficacy, taking the self-limiting course of giardiasis into account, has not been reported. No randomized controlled trials of treatment of refractory infection have been performed the last 25 years. Based on the clinical studies reported, combination treatment with a 5-nitroimidazole and a benzimidazole is more effective than repeated courses of 5-nitroimidazole or monotherapies in refractory cases. Quinacrine is effective in refractory cases, but potentially severe side effects limit its use. SUMMARY A combination of a 5-nitroimidazole and albendazole or mebendazole, and quinacrine monotherapy, are rational choices in nitroimidazole refractory infections, but randomized controlled studies are needed. Further research into more recent clinical isolates is necessary to uncover mechanisms for the increase in metronidazole refractory giardiasis observed during the last decade.
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15
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Salah EB, Barrera C, Mosbahi S, Gottstein B, Siles-Lucas M, Belhassen S, Nouri A, Babba H, Millon L, Sakly W. Promising proteins detected by Western blot from Echinococcus granulosus protoscoleces for predicting early post-surgical outcomes in CE-affected Tunisian children. Parasit Vectors 2021; 14:180. [PMID: 33781311 PMCID: PMC8008569 DOI: 10.1186/s13071-021-04679-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Accepted: 03/11/2021] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Cystic echinococcosis (CE) affects predominantly young patients in highly endemic areas. Improved serological methods are needed for the follow-up of CE cases, especially given the high rates of post-surgical relapse that require detection as soon as possible. METHODS We designed a study to investigate the value of antigenic proteins extracted from Echinococcus granulosus (E. granulosus) protoscoleces, and of recombinant B2t and 2B2t proteins, for assessing the efficacy of surgical treatment carried out on CE-affected children. This study was performed on 278 plasma samples collected from 59 Tunisian children surgically treated for CE and monitored for 3 years post-surgery. The patients were classified according to post-surgical outcomes into a "non-relapsed" (NRCE) and a "relapsed" (RCE) group. We performed in-house ELISAs to measure anti-B2t and anti-2B2t IgG and immunoblotting for the detection of IgG against SDS-PAGE-resolved E. granulosus protoscoleces-specific antigens. The Wilcoxon test was applied to assess anti-B2t and anti-2B2t IgG levels. We applied the Cochran Q test to compare the distribution of immunoblotting antigenic bands between 1-month and 1-year post-surgery. RESULTS The probability of being "relapse-free" when a decrease in antibody titers occurred between 1 month and 1 year post-surgery was 81% and 75%, respectively, for anti-B2t and anti-2B2t IgG. We identified five protoscolex protein bands of 20, 26/27, 30, 40 and 46 kDa as highly immunoreactive by immunoblot for both RCE and NRCE patients at 1 month post-surgery, and significantly lower immunoreactivity after 1 year (p < 10-4) for NRCE compared to RCE patients. The proteins at 26/27 and 40 kDa displayed the best performance in predicting the outcome, with an 84% probability of being relapse-free when the reactivity against the 40 kDa antigen, the doublet at 26/27 kDa, or both was absent or disappeared between 1 month and 1 year post-surgery, and a 93% probability of being relapsed when both bands remained reactive or increased in intensity between the two time points. CONCLUSIONS The B2t protein could be useful for the prediction of CE early post-surgical outcomes. The proteins of E. granulosus protoscoleces, especially the doublet P26/27 and P40, could be promising predictive biomarkers for the post-surgical follow-up of CE cases as well.
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Affiliation(s)
- Eya Ben Salah
- Département de Biologie Clinique B, Faculté de Pharmacie, Laboratoire de Parasitologie-Mycologie Médicale Et Moléculaire, LR12ES08, Université de Monastir, 1 Rue Avicenne, 5000, Monastir, Tunisie
| | - Coralie Barrera
- Department of Parasitology Mycology, University Hospital of Besançon, UMR/CNRS 6249 Chrono-Environnement Research Team, University of Bourgogne- Franche-Comté, Besançon, France
| | - Sana Mosbahi
- Pediatric Surgery Department, Fattouma Bourguiba Hospital, Medical School , Monastir, Tunisia
| | - Bruno Gottstein
- Institute for Infectious Diseases, Faculty of Medicine, University of Bern, 3001, Bern, Switzerland
| | - Mar Siles-Lucas
- Instituto de Recursos Naturales Y Agrobiología de Salamanca (IRNASA-CSIC), 37008, Salamanca, España
| | - Samia Belhassen
- Pediatric Surgery Department, Fattouma Bourguiba Hospital, Medical School , Monastir, Tunisia
| | - Abdellatif Nouri
- Pediatric Surgery Department, Fattouma Bourguiba Hospital, Medical School , Monastir, Tunisia
| | - Hamouda Babba
- Département de Biologie Clinique B, Faculté de Pharmacie, Laboratoire de Parasitologie-Mycologie Médicale Et Moléculaire, LR12ES08, Université de Monastir, 1 Rue Avicenne, 5000, Monastir, Tunisie
| | - Laurence Millon
- Department of Parasitology Mycology, University Hospital of Besançon, UMR/CNRS 6249 Chrono-Environnement Research Team, University of Bourgogne- Franche-Comté, Besançon, France
| | - Wahiba Sakly
- Département de Biologie Clinique B, Faculté de Pharmacie, Laboratoire de Parasitologie-Mycologie Médicale Et Moléculaire, LR12ES08, Université de Monastir, 1 Rue Avicenne, 5000, Monastir, Tunisie.
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16
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Nitroreductase Activites in Giardia lamblia: ORF 17150 Encodes a Quinone Reductase with Nitroreductase Activity. Pathogens 2021; 10:pathogens10020129. [PMID: 33513906 PMCID: PMC7912051 DOI: 10.3390/pathogens10020129] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/12/2021] [Accepted: 01/22/2021] [Indexed: 02/05/2023] Open
Abstract
The intestinal diplomonadid Giardia lamblia is a causative agent of persistent diarrhea. Current treatments are based on nitro drugs, especially metronidazole. Nitro compounds are activated by reduction, yielding toxic intermediates. The enzymatic systems responsible for this activation are not completely understood. By fractionating cell free crude extracts by size exclusion chromatography followed by mass spectrometry, enzymes with nitroreductase (NR) activities are identified. The protein encoded by ORF 17150 found in two pools with NR activities is overexpressed and characterized. In pools of fractions with main NR activities, previously-known NRs are identified, as well as a previously uncharacterized protein encoded by ORF 17150. Recombinant protein 17150 is a flavoprotein with NADPH-dependent quinone reductase and NR activities. Besides a set of previously identified NRs, we have identified a novel enzyme with NR activity.
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Riches A, Hart CJS, Trenholme KR, Skinner-Adams TS. Anti- Giardia Drug Discovery: Current Status and Gut Feelings. J Med Chem 2020; 63:13330-13354. [PMID: 32869995 DOI: 10.1021/acs.jmedchem.0c00910] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Giardia parasites are ubiquitous protozoans of global importance that impact a wide range of animals including humans. They are the most common enteric pathogen of cats and dogs in developed countries and infect ∼1 billion people worldwide. While Giardia infections can be asymptomatic, they often result in severe and chronic diseases. There is also mounting evidence that they are linked to postinfection disorders. Despite growing evidence of the widespread morbidity associated with Giardia infections, current treatment options are limited to compound classes with broad antimicrobial activity. Frontline anti-Giardia drugs are also associated with increasing drug resistance and treatment failures. To improve the health and well-being of millions, new selective anti-Giardia drugs are needed alongside improved health education initiatives. Here we discuss current treatment options together with recent advances and gaps in drug discovery. We also propose criteria to guide the discovery of new anti-Giardia compounds.
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Affiliation(s)
- Andrew Riches
- Commonwealth Scientific and Industrial Research Organization, Biomedical Manufacturing, Clayton, Victoria 3168, Australia
| | - Christopher J S Hart
- Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland 4111, Australia
| | - Katharine R Trenholme
- QIMR Berghofer Medical Research Institute, 300 Herston Road, Brisbane, Queensland 4029, Australia.,School of Medicine, University of Queensland, Brisbane, Queensland 4029, Australia
| | - Tina S Skinner-Adams
- Griffith Institute for Drug Discovery, Griffith University, Nathan, Queensland 4111, Australia
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18
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Drug resistance in Giardia: Mechanisms and alternative treatments for Giardiasis. ADVANCES IN PARASITOLOGY 2020; 107:201-282. [PMID: 32122530 DOI: 10.1016/bs.apar.2019.11.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The use of chemotherapeutic drugs is the main resource against clinical giardiasis due to the lack of approved vaccines. Resistance of G. duodenalis to the most used drugs to treat giardiasis, metronidazole and albendazole, is a clinical issue of growing concern and yet unknown impact, respectively. In the search of new drugs, the completion of the Giardia genome project and the use of biochemical, molecular and bioinformatics tools allowed the identification of ligands/inhibitors for about one tenth of ≈150 potential drug targets in this parasite. Further, the synthesis of second generation nitroimidazoles and benzimidazoles along with high-throughput technologies have allowed not only to define overall mechanisms of resistance to metronidazole but to screen libraries of repurposed drugs and new pharmacophores, thereby increasing the known arsenal of anti-giardial compounds to some hundreds, with most demonstrating activity against metronidazole or albendazole-resistant Giardia. In particular, cysteine-modifying agents which include omeprazole, disulfiram, allicin and auranofin outstand due to their pleiotropic activity based on the extensive repertoire of thiol-containing proteins and the microaerophilic metabolism of this parasite. Other promising agents derived from higher organisms including phytochemicals, lactoferrin and propolis as well as probiotic bacteria/fungi have also demonstrated significant potential for therapeutic and prophylactic purposes in giardiasis. In this context the present chapter offers a comprehensive review of the current knowledge, including commonly prescribed drugs, causes of therapeutic failures, drug resistance mechanisms, strategies for the discovery of new agents and alternative drug therapies.
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19
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Müller J, Müller N. Nitroreductases of bacterial origin in Giardia lamblia: Potential role in detoxification of xenobiotics. Microbiologyopen 2019; 8:e904. [PMID: 31343119 PMCID: PMC7938412 DOI: 10.1002/mbo3.904] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 06/19/2019] [Accepted: 06/19/2019] [Indexed: 11/05/2022] Open
Abstract
The anaerobic parasite Giardia lamblia, causative agent of persistent diarrhea, contains a family of nitroreductase genes most likely acquired by lateral transfer from anaerobic bacteria or archaebacteria. Two of these nitroreductases, containing a ferredoxin domain at their N-terminus, NR1, and NR2, have been characterized previously. Here, we present the characterization of a third member of this family, NR3. In functional assays, recombinant NR1 and NR3 reduced quinones like menadione and the antibiotic tetracycline, and-to much lesser extents-the nitro compound dinitrotoluene. Conversely, recombinant NR2 had no activity on tetracycline. Escherichia coli expressing NR3 were less susceptible to tetracycline, but more susceptible to the nitro compound metronidazole under semi-aerobic growth conditions. G. lamblia overexpressing NR1 and NR3, but not lines overexpressing NR2, are more susceptible to the nitro drug nitazoxanide. These findings suggest that NR3 is an active quinone reductase with a mode of action similar to NR1, but different from NR2. The biological function of this family of enzymes may reside in the use of xenobiotics as final electron acceptors. Thereby, these enzymes may provide at least two evolutionary advantages namely a higher potential to recycle NAD(P) as electron acceptors for the (fermentative) energy and intermediary metabolism, and the possibility to inactivate toxic xenobiotics produced by microorganisms living in concurrence inside the intestinal habitat.
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Affiliation(s)
- Joachim Müller
- Vetsuisse Faculty, Institute of Parasitology, University of Berne, Berne, Switzerland
| | - Norbert Müller
- Vetsuisse Faculty, Institute of Parasitology, University of Berne, Berne, Switzerland
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20
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Saghaug CS, Klotz C, Kallio JP, Brattbakk HR, Stokowy T, Aebischer T, Kursula I, Langeland N, Hanevik K. Genetic variation in metronidazole metabolism and oxidative stress pathways in clinical Giardia lamblia assemblage A and B isolates. Infect Drug Resist 2019; 12:1221-1235. [PMID: 31190910 PMCID: PMC6519707 DOI: 10.2147/idr.s177997] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Accepted: 01/16/2019] [Indexed: 12/12/2022] Open
Abstract
Purpose: Treatment-refractory Giardia cases have increased rapidly within the last decade. No markers of resistance nor a standardized susceptibility test have been established yet, but several enzymes and their pathways have been associated with metronidazole (MTZ) resistant Giardia. Very limited data are available regarding genetic variation in these pathways. We aimed to investigate genetic variation in metabolic pathway genes proposed to be involved in MTZ resistance in recently acquired, cultured clinical isolates. Methods: Whole genome sequencing of 12 assemblage A2 and 8 assemblage B isolates was done, to decipher genomic variation in Giardia. Twenty-nine genes were identified in a literature search and investigated for their single nucleotide variants (SNVs) in the coding/non-coding regions of the genes, either as amino acid changing (non-synonymous SNVs) or non-changing SNVs (synonymous). Results: In Giardia assemblage B, several genes involved in MTZ activation or oxidative stress management were found to have higher numbers of non-synonymous SNVs (thioredoxin peroxidase, nitroreductase 1, ferredoxin 2, NADH oxidase, nitroreductase 2, alcohol dehydrogenase, ferredoxin 4 and ferredoxin 1) than the average variation. For Giardia assemblage A2, the highest genetic variability was found in the ferredoxin 2, ferredoxin 6 and in nicotinamide adenine dinucleotide phosphate (NADPH) oxidoreductase putative genes. SNVs found in the ferredoxins and nitroreductases were analyzed further by alignment and homology modeling. SNVs close to the iron-sulfur cluster binding sites in nitroreductase-1 and 2 and ferredoxin 2 and 4 could potentially affect protein function. Flavohemoprotein seems to be a variable-copy gene, due to higher, but variable coverage compared to other genes investigated. Conclusion: In clinical Giardia isolates, genetic variability is common in important genes in the MTZ metabolizing pathway and in the management of oxidative and nitrosative stress and includes high numbers of non-synonymous SNVs. Some of the identified amino acid changes could potentially affect the respective proteins important in the MTZ metabolism.
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Affiliation(s)
- Christina S Saghaug
- Department of Clinical Science, University of Bergen, Bergen, Hordaland, Norway.,Norwegian National Advisory Unit on Tropical Infectious Diseases, Department of Medicine, Haukeland University Hospital, Bergen, Hordaland, Norway
| | - Christian Klotz
- Department of Infectious Diseases, Unit 16 Mycotic and Parasitic Agents and Mycobacteria, Robert Koch-Institute, Berlin, Germany
| | - Juha P Kallio
- Department of Biomedicine, University of Bergen, Bergen, Hordaland, Norway
| | - Hans-Richard Brattbakk
- Department of Clinical Science, University of Bergen, Bergen, Hordaland, Norway.,Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Hordaland, Norway
| | - Tomasz Stokowy
- Department of Clinical Science, University of Bergen, Bergen, Hordaland, Norway.,Center for Medical Genetics and Molecular Medicine, Haukeland University Hospital, Bergen, Hordaland, Norway
| | - Toni Aebischer
- Department of Infectious Diseases, Unit 16 Mycotic and Parasitic Agents and Mycobacteria, Robert Koch-Institute, Berlin, Germany
| | - Inari Kursula
- Department of Biomedicine, University of Bergen, Bergen, Hordaland, Norway.,Biocenter Oulu and Faculty of Biochemistry and Molecular Medicine, University of Oulu, Oulu, Finland
| | - Nina Langeland
- Department of Clinical Science, University of Bergen, Bergen, Hordaland, Norway.,Norwegian National Advisory Unit on Tropical Infectious Diseases, Department of Medicine, Haukeland University Hospital, Bergen, Hordaland, Norway.,Department of Medicine, Haraldsplass Deaconess Hospital, Bergen, Hordaland, Norway
| | - Kurt Hanevik
- Department of Clinical Science, University of Bergen, Bergen, Hordaland, Norway.,Norwegian National Advisory Unit on Tropical Infectious Diseases, Department of Medicine, Haukeland University Hospital, Bergen, Hordaland, Norway
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Stairs CW, Kokla A, Ástvaldsson Á, Jerlström-Hultqvist J, Svärd S, Ettema TJG. Oxygen induces the expression of invasion and stress response genes in the anaerobic salmon parasite Spironucleus salmonicida. BMC Biol 2019; 17:19. [PMID: 30823887 PMCID: PMC6397501 DOI: 10.1186/s12915-019-0634-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Accepted: 02/06/2019] [Indexed: 01/01/2023] Open
Abstract
Background Spironucleus salmonicida is an anaerobic parasite that can cause systemic infections in Atlantic salmon. Unlike other diplomonad parasites, such as the human pathogen Giardia intestinalis, Spironucleus species can infiltrate the blood stream of their hosts eventually colonizing organs, skin and gills. How this presumed anaerobe can persist and invade oxygenated tissues, despite having a strictly anaerobic metabolism, remains elusive. Results To investigate how S. salmonicida response to oxygen stress, we performed RNAseq transcriptomic analyses of cells grown in the presence of oxygen or antioxidant-free medium. We found that over 20% of the transcriptome is differentially regulated in oxygen (1705 genes) and antioxidant-depleted (2280 genes) conditions. These differentially regulated transcripts encode proteins related to anaerobic metabolism, cysteine and Fe-S cluster biosynthesis, as well as a large number of proteins of unknown function. S. salmonicida does not encode genes involved in the classical elements of oxygen metabolism (e.g., catalases, superoxide dismutase, glutathione biosynthesis, oxidative phosphorylation). Instead, we found that genes encoding bacterial-like oxidoreductases were upregulated in response to oxygen stress. Phylogenetic analysis revealed some of these oxygen-responsive genes (e.g., nadh oxidase, rubrerythrin, superoxide reductase) are rare in eukaryotes and likely derived from lateral gene transfer (LGT) events into diplomonads from prokaryotes. Unexpectedly, we observed that many host evasion- and invasion-related genes were also upregulated under oxidative stress suggesting that oxygen might be an important signal for pathogenesis. Conclusion While oxygen is toxic for related organisms, such as G. intestinalis, we find that oxygen is likely a gene induction signal for host invasion- and evasion-related pathways in S. salmonicida. These data provide the first molecular evidence for how S. salmonicida could tolerate oxic host environments and demonstrate how LGT can have a profound impact on the biology of anaerobic parasites. Electronic supplementary material The online version of this article (10.1186/s12915-019-0634-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Courtney W Stairs
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden.
| | - Anna Kokla
- Present Address: Department of Plant Biology, Swedish University of Agricultural Sciences (SLU), Almas Allé 5, BioCentrum, room D-444, Uppsala, Sweden
| | - Ásgeir Ástvaldsson
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Jon Jerlström-Hultqvist
- Present Address: Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Canada
| | - Staffan Svärd
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Thijs J G Ettema
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden.,Laboratory of Microbiology, Department of Agrotechnology and Food Sciences, Wageningen University, Stippeneng 4, 6708WE, Wageningen, The Netherlands
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22
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Emery SJ, Baker L, Ansell BRE, Mirzaei M, Haynes PA, McConville MJ, Svärd SG, Jex AR. Differential protein expression and post-translational modifications in metronidazole-resistant Giardia duodenalis. Gigascience 2018; 7:4931738. [PMID: 29688452 PMCID: PMC5913674 DOI: 10.1093/gigascience/giy024] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 03/06/2018] [Indexed: 01/20/2023] Open
Abstract
Background Metronidazole (Mtz) is the frontline drug treatment for multiple anaerobic pathogens, including the gastrointestinal protist, Giardia duodenalis. However, treatment failure is common and linked to in vivo drug resistance. In Giardia, in vitro drug-resistant lines allow controlled experimental interrogation of resistance mechanisms in isogenic cultures. However, resistance-associated changes are inconsistent between lines, phenotypic data are incomplete, and resistance is rarely genetically fixed, highlighted by reversion to sensitivity after drug selection ceases or via passage through the life cycle. Comprehensive quantitative approaches are required to resolve isolate variability, fully define Mtz resistance phenotypes, and explore the role of post-translational modifications therein. Findings We performed quantitative proteomics to describe differentially expressed proteins in 3 seminal Mtz-resistant lines compared to their isogenic, Mtz-susceptible, parental line. We also probed changes in post-translational modifications including protein acetylation, methylation, ubiquitination, and phosphorylation via immunoblotting. We quantified more than 1,000 proteins in each genotype, recording substantial genotypic variation in differentially expressed proteins between isotypes. Our data confirm substantial changes in the antioxidant network, glycolysis, and electron transport and indicate links between protein acetylation and Mtz resistance, including cross-resistance to deacetylase inhibitor trichostatin A in Mtz-resistant lines. Finally, we performed the first controlled, longitudinal study of Mtz resistance stability, monitoring lines after cessation of drug selection, revealing isolate-dependent phenotypic plasticity. Conclusions Our data demonstrate understanding that Mtz resistance must be broadened to post-transcriptional and post-translational responses and that Mtz resistance is polygenic, driven by isolate-dependent variation, and is correlated with changes in protein acetylation networks.
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Affiliation(s)
- Samantha J Emery
- Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Melbourne, VIC, Australia
| | - Louise Baker
- Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Melbourne, VIC, Australia.,Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Melbourne, VIC, Australia
| | - Brendan R E Ansell
- Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Melbourne, VIC, Australia.,Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Melbourne, VIC, Australia
| | - Mehdi Mirzaei
- Chemistry and Biomolecular Sciences, Faculty of Science, Macquarie University, North Ryde, NSW, Australia.,Australian Proteome Analysis Facility, Macquarie University, North Ryde, NSW, Australia
| | - Paul A Haynes
- Chemistry and Biomolecular Sciences, Faculty of Science, Macquarie University, North Ryde, NSW, Australia
| | - Malcom J McConville
- Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, VIC, Australia
| | - Staffan G Svärd
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Aaron R Jex
- Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical Research, Melbourne, VIC, Australia.,Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Melbourne, VIC, Australia
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Abstract
The 5-nitroimidazole drug metronidazole has remained the drug of choice in the treatment of anaerobic infections, parasitic as well as bacterial, ever since its development in 1959. In contrast to most other antimicrobials, it has a pleiotropic mode of action and reacts with a large number of molecules. Importantly, metronidazole, which is strictly speaking a prodrug, needs to be reduced at its nitro group in order to become toxic. Reduction of metronidazole, however, only takes place under very low concentrations of oxygen, explaining why metronidazole is exclusively toxic to microaerophilic and anaerobic microorganisms. In general, resistance rates amongst the pathogens treated with metronidazole have remained low until the present day. Nevertheless, metronidazole resistance does occur, and for the treatment of some pathogens, especially Helicobacter pylori, metronidazole has become almost useless in some parts of the world. This review will give an account on the current status of research on metronidazole's mode of action, metronidazole resistance in eukaryotes and prokaryotes, and on other 5-nitroimidazoles in use.
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Effects of (1 E,4 E)-2-Methyl-1,5-bis(4-nitrophenyl)penta-1,4-dien-3-one on Trypanosoma cruzi and Its Combinational Effect with Benznidazole, Ketoconazole, or Fluconazole. BIOMED RESEARCH INTERNATIONAL 2017; 2017:7254193. [PMID: 28620619 PMCID: PMC5460392 DOI: 10.1155/2017/7254193] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Revised: 11/25/2016] [Accepted: 01/10/2017] [Indexed: 01/09/2023]
Abstract
This study reports the activity induced by (1E,4E)-2-methyl-1,5-bis(4-nitrophenyl)penta-1,4-dien-3-one (A3K2A3) against Trypanosoma cruzi. This compound showed trypanocidal activity against the multiplicative epimastigote and amastigote forms of this protozoan, with IC50 values of 1.99 ± 0.17 and 1.20 ± 0.16 μM, respectively, and EC50 value of 15.57 ± 0.34 μM against trypomastigotes. The combination of A3K2A3 with benznidazole or ketoconazole demonstrated strong synergism, increasing effectiveness against trypomastigotes or epimastigotes of T. cruzi. In addition, the drug combination of A3K2A3 with benznidazole or ketoconazole on LLCMK2 cells demonstrated an antagonist effect, which resulted in greater protection of the cells from drug damage. The combination of the compound with fluconazole was not effective. Transmission and scanning electron micrographs showed changes on parasites, mainly in the cytoplasmatic membrane, nucleus, mitochondrion, and Golgi complex, and a large increase in the number of autophagosome-like structures and lipid-storage bodies, accompanied by volume reduction and rounding of the parasite. A3K2A3 might be a promising compound against T. cruzi.
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25
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Ansell BRE, Baker L, Emery SJ, McConville MJ, Svärd SG, Gasser RB, Jex AR. Transcriptomics Indicates Active and Passive Metronidazole Resistance Mechanisms in Three Seminal Giardia Lines. Front Microbiol 2017; 8:398. [PMID: 28367140 PMCID: PMC5355454 DOI: 10.3389/fmicb.2017.00398] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Accepted: 02/27/2017] [Indexed: 12/13/2022] Open
Abstract
Giardia duodenalis is an intestinal parasite that causes 200-300 million episodes of diarrhoea annually. Metronidazole (Mtz) is a front-line anti-giardial, but treatment failure is common and clinical resistance has been demonstrated. Mtz is thought to be activated within the parasite by oxidoreductase enzymes, and to kill by causing oxidative damage. In G. duodenalis, Mtz resistance involves active and passive mechanisms. Relatively low activity of iron-sulfur binding proteins, namely pyruvate:ferredoxin oxidoreductase (PFOR), ferredoxins, and nitroreductase-1, enable resistant cells to passively avoid Mtz activation. Additionally, low expression of oxygen-detoxification enzymes can allow passive (non-enzymatic) Mtz detoxification via futile redox cycling. In contrast, active resistance mechanisms include complete enzymatic detoxification of the pro-drug by nitroreductase-2 and enhanced repair of oxidized biomolecules via thioredoxin-dependent antioxidant enzymes. Molecular resistance mechanisms may be largely founded on reversible transcriptional changes, as some resistant lines revert to drug sensitivity during drug-free culture in vitro, or passage through the life cycle. To comprehensively characterize these changes, we undertook strand-specific RNA sequencing of three laboratory-derived Mtz-resistant lines, 106-2ID10, 713-M3, and WB-M3, and compared transcription relative to their susceptible parents. Common up-regulated genes encoded variant-specific surface proteins (VSPs), a high cysteine membrane protein, calcium and zinc channels, a Mad-2 cell cycle regulator and a putative fatty acid α-oxidase. Down-regulated genes included nitroreductase-1, putative chromate and quinone reductases, and numerous genes that act proximal to PFOR. Transcriptional changes in 106-2ID10 diverged from those in 713-r and WB-r (r ≤ 0.2), which were more similar to each other (r = 0.47). In 106-2ID10, a nonsense mutation in nitroreductase-1 transcripts could enhance passive resistance whereas increased transcription of nitroreductase-2, and a MATE transmembrane pump system, suggest active drug detoxification and efflux, respectively. By contrast, transcriptional changes in 713-M3 and WB-M3 indicated a higher oxidative stress load, attributed to Mtz- and oxygen-derived radicals, respectively. Quantitative comparisons of orthologous gene transcription between Mtz-resistant G. duodenalis and Trichomonas vaginalis, a closely related parasite, revealed changes in transcripts encoding peroxidases, heat shock proteins, and FMN-binding oxidoreductases, as prominent correlates of resistance. This work provides deep insight into Mtz-resistant G. duodenalis, and illuminates resistance-associated features across parasitic species.
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Affiliation(s)
- Brendan R. E. Ansell
- Faculty of Veterinary and Agricultural Sciences, The University of MelbourneMelbourne, VIC, Australia
| | - Louise Baker
- Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical ResearchMelbourne, VIC, Australia
| | - Samantha J. Emery
- Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical ResearchMelbourne, VIC, Australia
| | - Malcolm J. McConville
- Bio21 Molecular Science and Biotechnology Institute, The University of MelbourneMelbourne, VIC, Australia
| | - Staffan G. Svärd
- Department of Cell and Molecular Biology, Uppsala UniversityUppsala, Sweden
| | - Robin B. Gasser
- Faculty of Veterinary and Agricultural Sciences, The University of MelbourneMelbourne, VIC, Australia
| | - Aaron R. Jex
- Faculty of Veterinary and Agricultural Sciences, The University of MelbourneMelbourne, VIC, Australia
- Population Health and Immunity Division, Walter and Eliza Hall Institute of Medical ResearchMelbourne, VIC, Australia
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26
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Valladares-Méndez A, García-Flores M, Navarrete-Vázquez G, Orozco-Castellanos LM, Hernandez-Nuñez E, Rivera-Leyva JC. Physicochemical characterization of two new Nitazoxanide analogs with antiparasitic activity. Med Chem Res 2016. [DOI: 10.1007/s00044-016-1749-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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27
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Divergent Transcriptional Responses to Physiological and Xenobiotic Stress in Giardia duodenalis. Antimicrob Agents Chemother 2016; 60:6034-45. [PMID: 27458219 DOI: 10.1128/aac.00977-16] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 07/19/2016] [Indexed: 12/22/2022] Open
Abstract
Understanding how parasites respond to stress can help to identify essential biological processes. Giardia duodenalis is a parasitic protist that infects the human gastrointestinal tract and causes 200 to 300 million cases of diarrhea annually. Metronidazole, a major antigiardial drug, is thought to cause oxidative damage within the infective trophozoite form. However, treatment efficacy is suboptimal, due partly to metronidazole-resistant infections. To elucidate conserved and stress-specific responses, we calibrated sublethal metronidazole, hydrogen peroxide, and thermal stresses to exert approximately equal pressure on trophozoite growth and compared transcriptional responses after 24 h of exposure. We identified 252 genes that were differentially transcribed in response to all three stressors, including glycolytic and DNA repair enzymes, a mitogen-activated protein (MAP) kinase, high-cysteine membrane proteins, flavin adenine dinucleotide (FAD) synthetase, and histone modification enzymes. Transcriptional responses appeared to diverge according to physiological or xenobiotic stress. Downregulation of the antioxidant system and α-giardins was observed only under metronidazole-induced stress, whereas upregulation of GARP-like transcription factors and their subordinate genes was observed in response to hydrogen peroxide and thermal stressors. Limited evidence was found in support of stress-specific response elements upstream of differentially transcribed genes; however, antisense derepression and differential regulation of RNA interference machinery suggest multiple epigenetic mechanisms of transcriptional control.
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28
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Ashour DS, Abou Rayia DM, Saad AE, El-Bakary RH. Nitazoxanide anthelmintic activity against the enteral and parenteral phases of trichinellosis in experimentally infected rats. Exp Parasitol 2016; 170:28-35. [PMID: 27585500 DOI: 10.1016/j.exppara.2016.08.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Revised: 08/14/2016] [Accepted: 08/29/2016] [Indexed: 12/26/2022]
Abstract
Most of the drugs used for the treatment of trichinellosis show a limited bioavailability and a high degree of resistance. Therefore, this study aimed to characterize the anthelmintic potential activity of nitazoxanide (NTZ) in a rat model of experimental trichinellosis. Animals were divided into three groups; group I, infected and non-treated; group II, received NTZ for three days post-infection (dpi) and group III, received NTZ 30 dpi for 14 consecutive days. Treatment efficacy was assessed by Trichinella spiralis adult and larval counts, histopathological studies of the small intestine and muscles and inducible nitric oxide synthase (iNOS) expression in the small intestine. T. spiralis adult count was reduced in NTZ -treated group (66.6%) and the larval count decreased to 68.7 and 76.7% in the early and late treatment, respectively. The infected non-treated rats showed massive inflammatory cellular infiltration in the small intestines and muscles. This inflammatory response was minor in the treated groups and was accompanied by a decrease in iNOS expression. Moreover, in group III, the larvae were replaced by homogenized substance with some destructive changes in the capsule. In conclusion, NTZ showed a promising activity against enteral and more effect in parenteral phases of trichinellosis.
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Affiliation(s)
- Dalia S Ashour
- Medical Parasitology Department, Faculty of Medicine, Tanta University, Egypt.
| | - Dina M Abou Rayia
- Medical Parasitology Department, Faculty of Medicine, Tanta University, Egypt
| | - Abeer E Saad
- Medical Parasitology Department, Faculty of Medicine, Tanta University, Egypt
| | - Reda H El-Bakary
- Histology Department, Faculty of Medicine, Tanta University, Egypt
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29
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Introducing nitazoxanide as a promising alternative treatment for symptomatic to metronidazole-resistant giardiasis in clinical isolates. ASIAN PAC J TROP MED 2016; 9:887-892. [PMID: 27633304 DOI: 10.1016/j.apjtm.2016.07.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 06/16/2016] [Accepted: 07/01/2016] [Indexed: 11/21/2022] Open
Abstract
OBJECTIVE To identify the frequencies (F) of ferredoxin and nitroreductase mutations on Iranian clinical isolates of Giardia lamblia in order to predict whether the nitazoxanide can be prescribed as suitable drug for symptomatic to metronidazole-resistant giardiasis. METHODS Forty Giardia lamblia isolates as of 38 symptomatic and two metronidazole-resistant patients were collected from Iran. DNAs were extracted and amplified by targeting ferredoxin and GlNR genes. The amplicons were directly sequenced to determine gene mutations. RESULTS The various amino acid substitutions (F: 20%, Haplotype diversity: 0.891, Tajima's D: -0.44013) were identified by analyzing ferredoxin gene in four symptomatic and two resistant isolates. Only two haplotypes (F: 5%, HD: 0.345; Tajima's D: 0.77815) characterized in metronidazole-resistant isolates of GlNR, however, no point mutations was found in symptomatic isolates. CONCLUSIONS Non-synonymous mutations of ferredoxin oxidoreductase gene reduce translational regulatory protein's binding affinity which concludes reduction of ferredoxin expression and its activity. This leads to decrease in metronidazole drug delivery into the cells. Mutations in these isolates may lead to their resistance to metronidazole. No to low synonymous mutations of GlNR demonstrates that nitazoxanide can be prescribed as promising alternative treatment for symptomatic to metronidazole-resistant giardiasis in Iranian clinical isolates.
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30
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Leitsch D, Müller J, Müller N. Evaluation of Giardia lamblia thioredoxin reductase as drug activating enzyme and as drug target. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2016; 6:148-153. [PMID: 27485086 PMCID: PMC4971154 DOI: 10.1016/j.ijpddr.2016.07.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 07/21/2016] [Indexed: 12/11/2022]
Abstract
The antioxidative enzyme thioredoxin reductase (TrxR) has been suggested to be a drug target in several pathogens, including the protist parasite Giardia lamblia. TrxR is also believed to catalyse the reduction of nitro drugs, e.g. metronidazole and furazolidone, a reaction required to render these compounds toxic to G. lamblia and other microaerophiles/anaerobes. It was the objective of this study to assess the potential of TrxR as a drug target in G. lamblia and to find direct evidence for the role of this enzyme in the activation of metronidazole and other nitro drugs. TrxR was overexpressed approximately 10-fold in G. lamblia WB C6 cells by placing the trxR gene behind the arginine deiminase (ADI) promoter on a plasmid. Likewise, a mutant TrxR with a defective disulphide reductase catalytic site was strongly expressed in another G. lamblia WB C6 cell line. Susceptibilities to five antigiardial drugs, i.e. metronidazole, furazolidone, nitazoxanide, albendazole and auranofin were determined in both transfectant cell lines and compared to wildtype. Further, the impact of all five drugs on TrxR activity in vivo was measured. Overexpression of TrxR rendered G. lamblia WB C6 more susceptible to metronidazole and furazolidone but not to nitazoxanide, albendazole, and auranofin. Of all five drugs tested, only auranofin had an appreciably negative effect on TrxR activity in vivo, albeit to a much smaller extent than expected. Overexpression of TrxR and mutant TrxR had hardly any impact on growth of G. lamblia WB C6, although the enzyme also exerts a strong NADPH oxidase activity which is a source of oxidative stress. Our results constitute first direct evidence for the notion that TrxR is an activator of metronidazole and furazolidone but rather question that it is a relevant drug target of presently used antigiardial drugs.
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Affiliation(s)
- David Leitsch
- Institute of Parasitology, Vetsuisse Faculty, University of Bern, Länggassstrasse 122, CH-3012, Bern, Switzerland; Institute of Specific Prophylaxis and Tropical Medicine, Medical University of Vienna, Kinderspitalgasse 15, A-1090, Vienna, Austria.
| | - Joachim Müller
- Institute of Parasitology, Vetsuisse Faculty, University of Bern, Länggassstrasse 122, CH-3012, Bern, Switzerland
| | - Norbert Müller
- Institute of Parasitology, Vetsuisse Faculty, University of Bern, Länggassstrasse 122, CH-3012, Bern, Switzerland
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Lescano SAZ, Santos SVD, Assis JML, Chieffi PP. EFFICACY OF NITAZOXANIDE AGAINST Toxocara canis: LARVAL RECOVERY AND HUMORAL IMMUNE RESPONSE IN EXPERIMENTALLY INFECTED MICE. Rev Inst Med Trop Sao Paulo 2016; 57:337-41. [PMID: 26422159 PMCID: PMC4616920 DOI: 10.1590/s0036-46652015000400011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The efficacy of nitazoxanide (NTZ) against toxocariasis was investigated in an experimental murine model and results were compared to those obtained using mebendazole. Sixty male BALB/c mice, aged six to eight weeks-old, were divided into groups of 10 each; fifty were orally infected with 300 larvaed eggs of T. canisand grouped as follows, G I: infected untreated mice; G II: infected mice treated with MBZ (15 mg/kg/day) 10 days postinfection (dpi); G III: infected mice treated with NTZ (20 mg/kg/day) 10 dpi; G IV: infected mice treated with MBZ 60 dpi; G V: infected mice treated with NTZ 60 dpi; GVI: control group comprising uninfected mice. Mice were bled via retro-orbital plexus on four occasions between 30 and 120 dpi. Sera were processed using the ELISA technique to detect IgG anti- Toxocaraantibodies. At 120 dpi, mice were sacrificed for larval recovery in the CNS, liver, lungs, kidneys, eyes and carcass. Results showed similar levels of anti- ToxocaraIgG antibodies among mice infected but not submitted to treatment and groups treated with MBZ or NTZ, 10 and 60 dpi. Larval recovery showed similar values in groups treated with NTZ and MBZ 10 dpi. MBZ showed better efficacy 60 dpi, with a 72.6% reduction in the parasite load compared with NTZ, which showed only 46.5% reduction. We conclude that administration of these anthelmintics did not modify the humoral response in experimental infection by T. canis. No parasitological cure was observed with either drug; however, a greater reduction in parasite load was achieved following treatment with MBZ.
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32
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Antioxidant defence systems in the protozoan pathogen Giardia intestinalis. Mol Biochem Parasitol 2016; 206:56-66. [DOI: 10.1016/j.molbiopara.2015.12.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 11/26/2015] [Accepted: 12/01/2015] [Indexed: 01/03/2023]
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Validation of housekeeping genes as an internal control for gene expression studies in Giardia lamblia using quantitative real-time PCR. Gene 2016; 581:21-30. [PMID: 26778241 DOI: 10.1016/j.gene.2016.01.018] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Revised: 01/12/2016] [Accepted: 01/13/2016] [Indexed: 02/06/2023]
Abstract
The analysis of transcript levels of specific genes is important for understanding transcriptional regulation and for the characterization of gene function. Real-time quantitative reverse transcriptase PCR (RT-qPCR) has become a powerful tool to quantify gene expression. The objective of this study was to identify reliable housekeeping genes in Giardia lamblia. Twelve genes were selected for this purpose, and their expression was analyzed in the wild type WB strain and in two strains with resistance to nitazoxanide (NTZ) and metronidazole (MTZ), respectively. RefFinder software analysis showed that the expression of the genes is different in the three strains. The integrated data from the four analyses showed that the NADH oxidase (NADH) and aldolase (ALD) genes were the most steadily expressed genes, whereas the glyceraldehyde-3-phosphate dehydrogenase gene was the most unstable. Additionally, the relative expression of seven genes were quantified in the NTZ- and MTZ-resistant strains by RT-qPCR, using the aldolase gene as the internal control, and the results showed a consistent differential pattern of expression in both strains. The housekeeping genes found in this work will facilitate the analysis of mRNA expression levels of other genes of interest in G. lamblia.
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Evaluating 5-Nitrothiazoles as Trypanocidal Agents. Antimicrob Agents Chemother 2015; 60:1137-40. [PMID: 26596950 DOI: 10.1128/aac.02006-15] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2015] [Accepted: 11/16/2015] [Indexed: 11/20/2022] Open
Abstract
The growth-inhibitory properties of a 5-nitrothiazole series were evaluated against Trypanosoma brucei. A subset of related compounds displayed the greatest potency toward the parasite while exhibiting little cytotoxic effect on mammalian cells, with this antiparasitic activity dependent on expression of a type I nitroreductase by the trypanosome. We conclude that the 5-nitrothiazole class of nitroheterocyclic drugs may represent a new lead in the treatment of human African trypanosomiasis.
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Azam A, Peerzada MN, Ahmad K. Parasitic diarrheal disease: drug development and targets. Front Microbiol 2015; 6:1183. [PMID: 26617574 PMCID: PMC4621754 DOI: 10.3389/fmicb.2015.01183] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2015] [Accepted: 10/12/2015] [Indexed: 12/23/2022] Open
Abstract
Diarrhea is the manifestation of gastrointestinal infection and is one of the major causes of mortality and morbidity specifically among the children of less than 5 years age worldwide. Moreover, in recent years there has been a rise in the number of reports of intestinal infections continuously in the industrialized world. These are largely related to waterborne and food borne outbreaks. These occur by the pathogenesis of both prokaryotic and eukaryotic organisms like bacteria and parasites. The parasitic intestinal infection has remained mostly unexplored and under assessed in terms of therapeutic development. The lack of new drugs and the risk of resistance have led us to carry out this review on drug development for parasitic diarrheal diseases. The major focus has been depicted on commercially available drugs, currently synthesized active heterocyclic compounds and unique drug targets, that are vital for the existence and growth of the parasites and can be further exploited for the search of therapeutically active anti-parasitic agents.
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Affiliation(s)
- Amir Azam
- Medicinal Chemistry Laboratory, Department of Chemistry, Jamia Millia IslamiaNew Delhi, India
| | - Mudasir N. Peerzada
- Medicinal Chemistry Laboratory, Department of Chemistry, Jamia Millia IslamiaNew Delhi, India
| | - Kamal Ahmad
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia IslamiaNew Delhi, India
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Abstract
The microaerophilic parasite Giardia lamblia is a causative agent of dysentery affecting hundreds of millions of people around the globe every year. The symptoms of the disease, commonly referred to as giardiasis, are diarrhea, nausea, and malabsorption. Treatment of giardiasis is exclusively based on chemotherapy with antigiardial drugs, including metronidazole, albendazole, and nitazoxanide. In this review, all drugs currently used in the treatment of Giardia infections are discussed with a special emphasis on treatment failure and drug resistance.
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Ansell BRE, McConville MJ, Ma'ayeh SY, Dagley MJ, Gasser RB, Svärd SG, Jex AR. Drug resistance in Giardia duodenalis. Biotechnol Adv 2015; 33:888-901. [PMID: 25922317 DOI: 10.1016/j.biotechadv.2015.04.009] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Revised: 04/21/2015] [Accepted: 04/21/2015] [Indexed: 02/07/2023]
Abstract
Giardia duodenalis is a microaerophilic parasite of the human gastrointestinal tract and a major contributor to diarrheal and post-infectious chronic gastrointestinal disease world-wide. Treatment of G. duodenalis infection currently relies on a small number of drug classes. Nitroheterocyclics, in particular metronidazole, have represented the front line treatment for the last 40 years. Nitroheterocyclic-resistant G. duodenalis have been isolated from patients and created in vitro, prompting considerable research into the biomolecular mechanisms of resistance. These compounds are redox-active and are believed to damage proteins and DNA after being activated by oxidoreductase enzymes in metabolically active cells. In this review, we explore the molecular phenotypes of nitroheterocyclic-resistant G. duodenalis described to date in the context of the protist's unusual glycolytic and antioxidant systems. We propose that resistance mechanisms are likely to extend well beyond currently described resistance-associated enzymes (i.e., pyruvate ferredoxin oxidoreductases and nitroreductases), to include NAD(P)H- and flavin-generating pathways, and possibly redox-sensitive epigenetic regulation. Mechanisms that allow G. duodenalis to tolerate oxidative stress may lead to resistance against both oxygen and nitroheterocyclics, with implications for clinical control. The present review highlights the potential for systems biology tools and advanced bioinformatics to further investigate the multifaceted mechanisms of nitroheterocyclic resistance in this important pathogen.
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Affiliation(s)
- Brendan R E Ansell
- Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Cnr Park Dr and Flemington Rd, Parkville, VIC 3010, Australia.
| | - Malcolm J McConville
- Bio21 Institute, University of Melbourne, 30 Flemington Rd, Parkville, VIC 3010, Australia
| | - Showgy Y Ma'ayeh
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Box 596, SE-751 24 Uppsala, Sweden
| | - Michael J Dagley
- Bio21 Institute, University of Melbourne, 30 Flemington Rd, Parkville, VIC 3010, Australia
| | - Robin B Gasser
- Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Cnr Park Dr and Flemington Rd, Parkville, VIC 3010, Australia
| | - Staffan G Svärd
- Department of Cell and Molecular Biology, Biomedical Center, Uppsala University, Box 596, SE-751 24 Uppsala, Sweden
| | - Aaron R Jex
- Faculty of Veterinary and Agricultural Sciences, University of Melbourne, Cnr Park Dr and Flemington Rd, Parkville, VIC 3010, Australia
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Comparative characterisation of two nitroreductases from Giardia lamblia as potential activators of nitro compounds. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2015; 5:37-43. [PMID: 27099829 PMCID: PMC4813764 DOI: 10.1016/j.ijpddr.2015.03.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/05/2015] [Revised: 03/12/2015] [Accepted: 03/16/2015] [Indexed: 11/23/2022]
Abstract
G. lamblia has two nitroreductases with substrate specificities not only for nitro compounds, but also for quinones. GlNR1 rather activates nitro drugs by forming toxic intermediates, GlNR2 rather inactivates them.
Giardia lamblia is a protozoan parasite that causes giardiasis, a diarrhoeal disease affecting humans and various animal species. Nitro drugs such as the nitroimidazole metronidazole and the nitrothiazolide nitazoxanide are used for treatment of giardiasis. Nitroreductases such as GlNR1 and GlNR2 may play a role in activation or inactivation of these drugs. The aim of this work is to characterise these two enyzmes using functional assays. For respective analyses recombinant analogues from GlNR1 and GlNR2 were produced in Escherichia coli. E. coli expressing GlNR1 and GlNR2 alone or together were grown in the presence of nitro compounds. Furthermore, pull-down assays were performed using HA-tagged GlNR1 and GlNR2 as baits. As expected, E. coli expressing GlNR1 were more susceptible to metronidazole under aerobic and semi-aerobic and to nitazoxanide under semi-aerobic growth conditions whereas E. coli expressing GlNR2 were susceptible to neither drug. Interestingly, expression of both nitroreductases gave the same results as expression of GlNR2 alone. In functional assays, both nitroreductases had their strongest activities on the quinone menadione (vitamin K3) and FAD, but reduction of nitro compounds including the nitro drugs metronidazole and nitazoxanide was clearly detected. Full reduction of 7-nitrocoumarin to 7-aminocoumarin was preferentially achieved with GlNR2. Pull-down assays revealed that GlNR1 and GlNR2 interacted in vivo forming a multienzyme complex. These findings suggest that both nitroreductases are multifunctional. Their main biological role may reside in the reduction of vitamin K analogues and FAD. Activation by GlNR1 or inactivation by GlNR2 of nitro drugs may be the consequence of a secondary enzymatic activity either yielding (GlNR1) or eliminating (GlNR2) toxic intermediates after reduction of these compounds.
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El-Taweel HA. Understanding drug resistance in human intestinal protozoa. Parasitol Res 2015; 114:1647-59. [DOI: 10.1007/s00436-015-4423-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2014] [Accepted: 03/05/2015] [Indexed: 01/07/2023]
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Navarrete-Vázquez G, Chávez-Silva F, Colín-Lozano B, Estrada-Soto S, Hidalgo-Figueroa S, Guerrero-Álvarez J, Méndez ST, Reyes-Vivas H, Oria-Hernández J, Canul-Canché J, Ortiz-Andrade R, Moo-Puc R. Synthesis of nitro(benzo)thiazole acetamides and in vitro antiprotozoal effect against amitochondriate parasites Giardia intestinalis and Trichomonas vaginalis. Bioorg Med Chem 2015; 23:2204-10. [PMID: 25801157 DOI: 10.1016/j.bmc.2015.02.059] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2015] [Revised: 02/17/2015] [Accepted: 02/26/2015] [Indexed: 01/03/2023]
Abstract
We synthesized four 5-nitrothiazole (1-4) and four 6-nitrobenzothiazole acetamides (5-8) using an easy two step synthetic route. All compounds were tested in vitro against amitochondriate parasites Giardia intestinalis and Trichomonas vaginalis, showing excellent antiprotozoal effects. IC₅₀'s of the most potent compounds range from nanomolar to low micromolar order, being more active than their drugs of choice. Compound 1 (IC₅₀=122 nM), was 44-times more active than Metronidazole, and 10-fold more effective than Nitazoxanide against G. intestinalis and showed good trichomonicidal activity (IC₅₀=2.24 μM). This compound did not display in vitro cytotoxicity against VERO cells. The in vitro inhibitory effect of compounds 1-8 and Nitazoxanide against G. intestinalis fructose-1,6-biphosphate aldolase (GiFBPA) was evaluated as potential drug target, showing a clear inhibitory effect over the enzyme activity. Molecular docking of compounds 1, 4 and Nitazoxanide into the ligand binding pocket of GiFBPA, revealed contacts with the active site residues of the enzyme. Ligand efficiency metrics of 1 revealed optimal combinations of physicochemical and antiprotozoal properties, better than Nitazoxanide.
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Affiliation(s)
- Gabriel Navarrete-Vázquez
- Facultad de Farmacia, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos 62209, Mexico.
| | - Fabiola Chávez-Silva
- Facultad de Farmacia, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos 62209, Mexico
| | - Blanca Colín-Lozano
- Facultad de Farmacia, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos 62209, Mexico
| | - Samuel Estrada-Soto
- Facultad de Farmacia, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos 62209, Mexico
| | - Sergio Hidalgo-Figueroa
- Facultad de Farmacia, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos 62209, Mexico; Laboratorio de Farmacología, Depto. Ciencias de la Salud, Universidad Autónoma Metropolitana-Iztapalapa, 09340 México, D.F., Mexico
| | - Jorge Guerrero-Álvarez
- Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos 62209, Mexico
| | - Sara T Méndez
- Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, 04530 México, D.F., Mexico
| | - Horacio Reyes-Vivas
- Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, 04530 México, D.F., Mexico
| | - Jesús Oria-Hernández
- Laboratorio de Bioquímica-Genética, Instituto Nacional de Pediatría, Secretaría de Salud, 04530 México, D.F., Mexico
| | | | - Rolffy Ortiz-Andrade
- Facultad de Química, Universidad Autónoma de Yucatán, Mérida, Yucatán 97150, Mexico
| | - Rosa Moo-Puc
- Unidad de Investigación Médica Yucatán, IMSS Mérida, Yucatán 97000, Mexico
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Somvanshi VS, Ellis BL, Hu Y, Aroian RV. Nitazoxanide: nematicidal mode of action and drug combination studies. Mol Biochem Parasitol 2014; 193:1-8. [PMID: 24412397 PMCID: PMC3972318 DOI: 10.1016/j.molbiopara.2013.12.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Revised: 12/03/2013] [Accepted: 12/17/2013] [Indexed: 11/18/2022]
Abstract
Intestinal nematodes or roundworms (aka soil-transmitted helminths or STHs) cause great disease. They infect upwards of two billion people, leading to high morbidity and a range of health problems, especially in infected children and pregnant women. Development of resistance to the two main classes of drugs used to treat intestinal nematode infections of humans has been reported. To fight STH infections, we need new and more effective drugs and ways to improve the efficacy of the old drugs. One promising alternative drug is nitazoxanide (NTZ). NTZ, approved for treating human protozoan infections, was serendipitously shown to have therapeutic activity against STHs. However, its mechanism of action against nematodes is not known. Using the laboratory nematode Caenorhabditis elegans, we show that NTZ acts on the nematodes through avr-14, an alpha-type subunit of a glutamate-gated chloride ion channel known for its role in ivermectin susceptibility. In addition, a forward genetic screen to select C. elegans mutants resistant to NTZ resulted in isolation of two NTZ resistant mutants that are not in avr-14, suggesting that additional mechanisms are involved in resistance to NTZ. We found that NTZ combines synergistically with other classes of anthelmintic drugs, i.e. albendazole and pyrantel, making it a good candidate for further studies on its use in drug combination therapy of STH infections. Given NTZ acts against a wide range of nematode parasites, our findings also validate avr-14 as an excellent target for pan-STH therapy.
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Affiliation(s)
- Vishal S Somvanshi
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA, USA
| | - Brian L Ellis
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA, USA
| | - Yan Hu
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA, USA
| | - Raffi V Aroian
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California San Diego, La Jolla, CA, USA.
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Müller J, Schildknecht P, Müller N. Metabolism of nitro drugs metronidazole and nitazoxanide in Giardia lamblia: characterization of a novel nitroreductase (GlNR2). J Antimicrob Chemother 2013; 68:1781-9. [PMID: 23580565 DOI: 10.1093/jac/dkt106] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVES The protozoan parasite Giardia lamblia causes giardiasis, a persistent diarrhoea. Nitro drugs such as the nitroimidazole metronidazole and the nitrothiazolide nitazoxanide are used for the treatment of giardiasis. Nitroreductases may play a role in activating these drugs. G. lamblia contains two nitroreductases, GlNR1 and GlNR2. The aim of this work was to elucidate the role of GlNR2. METHODS Expression of GlNR2 was analysed by reverse transcription PCR. Recombinant GlNR2 was overexpressed in G. lamblia and drug susceptibility was analysed. Recombinant GlNR2 was subjected to functional assays. Escherichia coli expressing full-length or truncated GlNR1 and GlNR2 were grown in the presence of nitro compounds. Using E. coli reporter strains for nitric oxide and DNA damage responses, we analysed whether GlNR1 and GlNR2 elicited the respective responses in the presence, or absence, of the drugs. RESULTS G. lamblia trophozoites overexpressing GlNR2 were less susceptible to both nitro drugs as compared with control trophozoites. GlNR2 was a functional nitroreductase when expressed in E. coli. E. coli expressing GlNR1 was more susceptible to metronidazole under aerobic and semi-aerobic and to nitazoxanide under semi-aerobic growth conditions. E. coli expressing GlNR2 was not susceptible to either drug. In reporter strains, GlNR1, but not GlNR2, elicited nitric oxide and DNA repair responses, even in the absence of nitro drugs. CONCLUSIONS These findings suggest that GlNR2 is an active nitroreductase with a mode of action different from that of GlNR1. Thus, susceptibility to nitro drugs may depend not only on activation, but also on inactivation of the drugs by specific nitroreductases.
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Affiliation(s)
- Joachim Müller
- Institute of Parasitology, Vetsuisse Faculty, University of Berne, Länggass-Strasse 122, CH-3012 Berne, Switzerland
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Müller J, Hemphill A. New approaches for the identification of drug targets in protozoan parasites. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2013; 301:359-401. [PMID: 23317822 DOI: 10.1016/b978-0-12-407704-1.00007-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Abstract
Antiparasitic chemotherapy is an important issue for drug development. Traditionally, novel compounds with antiprotozoan activities have been identified by screening of compound libraries in high-throughput systems. More recently developed approaches employ target-based drug design supported by genomics and proteomics of protozoan parasites. In this chapter, the drug targets in protozoan parasites are reviewed. The gene-expression machinery has been among the first targets for antiparasitic drugs and is still under investigation as a target for novel compounds. Other targets include cytoskeletal proteins, proteins involved in intracellular signaling, membranes, and enzymes participating in intermediary metabolism. In apicomplexan parasites, the apicoplast is a suitable target for established and novel drugs. Some drugs act on multiple subcellular targets. Drugs with nitro groups generate free radicals under anaerobic growth conditions, and drugs with peroxide groups generate radicals under aerobic growth conditions, both affecting multiple cellular pathways. Mefloquine and thiazolides are presented as examples for antiprotozoan compounds with multiple (side) effects. The classic approach of drug discovery employing high-throughput physiological screenings followed by identification of drug targets has yielded the mainstream of current antiprotozoal drugs. Target-based drug design supported by genomics and proteomics of protozoan parasites has not produced any antiparasitic drug so far. The reason for this is discussed and a synthesis of both methods is proposed.
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Affiliation(s)
- Joachim Müller
- Institute of Parasitology, University of Berne, Berne, Switzerland.
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Targeting the substrate preference of a type I nitroreductase to develop antitrypanosomal quinone-based prodrugs. Antimicrob Agents Chemother 2012; 56:5821-30. [PMID: 22948871 DOI: 10.1128/aac.01227-12] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nitroheterocyclic prodrugs are used to treat infections caused by Trypanosoma cruzi and Trypanosoma brucei. A key component in selectivity involves a specific activation step mediated by a protein homologous with type I nitroreductases, enzymes found predominantly in prokaryotes. Using data from determinations based on flavin cofactor, oxygen-insensitive activity, substrate range, and inhibition profiles, we demonstrate that NTRs from T. cruzi and T. brucei display many characteristics of their bacterial counterparts. Intriguingly, both enzymes preferentially use NADH and quinones as the electron donor and acceptor, respectively, suggesting that they may function as NADH:ubiquinone oxidoreductases in the parasite mitochondrion. We exploited this preference to determine the trypanocidal activity of a library of aziridinyl benzoquinones against bloodstream-form T. brucei. Biochemical screens using recombinant NTR demonstrated that several quinones were effective substrates for the parasite enzyme, having K(cat)/K(m) values 2 orders of magnitude greater than those of nifurtimox and benznidazole. In tests against T. brucei, antiparasitic activity mirrored the biochemical data, with the most potent compounds generally being preferred enzyme substrates. Trypanocidal activity was shown to be NTR dependent, as parasites with elevated levels of this enzyme were hypersensitive to the aziridinyl agent. By unraveling the biochemical characteristics exhibited by the trypanosomal NTRs, we have shown that quinone-based compounds represent a class of trypanocidal compound.
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Shahiduzzaman M, Daugschies A. Therapy and prevention of cryptosporidiosis in animals. Vet Parasitol 2012; 188:203-14. [DOI: 10.1016/j.vetpar.2012.03.052] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Revised: 03/26/2012] [Accepted: 03/28/2012] [Indexed: 11/16/2022]
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Cañete R, Rodríguez P, Mesa L, Brito K, Prior A, Guilhem D, Novaes MRCG. Albendazole versus metronidazole in the treatment of adult giardiasis: a randomized, double-blind, clinical trial. Curr Med Res Opin 2012; 28:149-54. [PMID: 22114904 DOI: 10.1185/03007995.2011.637915] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
BACKGROUND Albendazole (ABZ) is a benzimidazole carbamate compound currently in use for human medical practice against enterobiasis and soil-transmitted helminthiasis (STH); However, its spectrum of activity is broad and goes beyond these infections. OBJECTIVE This study compares the efficacy and safety of ABZ versus metronidazole (MTZ) in human giardiasis. RESEARCH DESIGN AND METHODS A randomized, double-blind, clinical trial was carried out at the Centre of Hygiene, Epidemiology and Microbiology in Matanzas City, Cuba. Adult patients with confirmed symptomatic G. duodenalis mono-infection were randomly assigned to receive either ABZ [400 mg daily (n = 75)] or MTZ [250 mg t.i.d. (n = 75)], both for 5 days. Follow-up fecal samples were obtained at 3, 5, 7 days after treatment end. RESULTS The efficacy was similar for both treatment groups: ABZ (82.6%) and MTZ (85.3%); p > 0.05. Side-effects including bitter taste, headache, vomiting and dizziness were significantly higher in the MTZ group. Abdominal pain was significantly higher in ABZ group. CONCLUSION ABZ was found as effective as MTZ in the treatment of G. duodenalis infections in adult patients from Cuba and could be a useful drug in areas where co-infection with STH infections is common.
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Roy KK, Singh S, Sharma SK, Srivastava R, Chaturvedi V, Saxena AK. Synthesis and biological evaluation of substituted 4-arylthiazol-2-amino derivatives as potent growth inhibitors of replicating Mycobacterium tuberculosis H₃₇Rv. Bioorg Med Chem Lett 2011; 21:5589-93. [PMID: 21783364 DOI: 10.1016/j.bmcl.2011.06.076] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Revised: 06/15/2011] [Accepted: 06/17/2011] [Indexed: 11/30/2022]
Abstract
In search of potential therapeutics for tuberculosis, we describe herein synthesis and biological evaluation of some substituted 4-arylthiazol-2-amino derivatives as modified analogues of the antiprotozoal drug Nitazoxanide (NTZ), which has recently been reported as potent inhibitor of Mtb H(37)Rv (Mtb MIC=52.12 μM) with an excellent ability to evade resistance. Among the synthesized derivatives, the two compounds 7a (MIC=15.28 μM) and 7c (MIC=17.03 μM) have exhibited about three times better Mtb growth inhibitory activity over NTZ and are free from any cytotoxicity (Vero CC(50) of 244 and 300 μM respectively). These two compounds represent promising leads for further optimization.
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Affiliation(s)
- Kuldeep K Roy
- Division of Medicinal and Process Chemistry, Central Drug Research Institute, CSIR, Lucknow 226 001, India
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Stachulski AV, Pidathala C, Row EC, Sharma R, Berry NG, Iqbal M, Bentley J, Allman SA, Edwards G, Helm A, Hellier J, Korba BE, Semple JE, Rossignol JF. Thiazolides as novel antiviral agents. 1. Inhibition of hepatitis B virus replication. J Med Chem 2011; 54:4119-32. [PMID: 21553812 DOI: 10.1021/jm200153p] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
We report the syntheses and activities of a wide range of thiazolides [viz., 2-hydroxyaroyl-N-(thiazol-2-yl)amides] against hepatitis B virus replication, with QSAR analysis of our results. The prototypical thiazolide, nitazoxanide [2-hydroxybenzoyl-N-(5-nitrothiazol-2-yl)amide, NTZ] 1 is a broad spectrum antiinfective agent effective against anaerobic bacteria, viruses, and parasites. By contrast, 2-hydroxybenzoyl-N-(5-chlorothiazol-2-yl)amide 3 is a novel, potent, and selective inhibitor of hepatitis B replication (EC(50) = 0.33 μm) but is inactive against anaerobes. Several 4'- and 5'-substituted thiazolides show good activity against HBV; by contrast, some related salicyloylanilides show a narrower spectrum of activity. The ADME properties of 3 are similar to 1; viz., the O-acetate is an effective prodrug, and the O-aryl glucuronide is a major metabolite. The QSAR study shows a good correlation of observed EC(90) for intracellular virions with thiazolide structural parameters. Finally we discuss the mechanism of action of thiazolides in relation to the present results.
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Affiliation(s)
- Andrew V Stachulski
- Robert Robinson Laboratories, Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, UK.
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Leitsch D, Burgess AG, Dunn LA, Krauer KG, Tan K, Duchêne M, Upcroft P, Eckmann L, Upcroft JA. Pyruvate:ferredoxin oxidoreductase and thioredoxin reductase are involved in 5-nitroimidazole activation while flavin metabolism is linked to 5-nitroimidazole resistance in Giardia lamblia. J Antimicrob Chemother 2011; 66:1756-65. [PMID: 21602576 DOI: 10.1093/jac/dkr192] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
OBJECTIVES The mechanism of action of, and resistance to, metronidazole in the anaerobic (or micro-aerotolerant) protozoan parasite Giardia lamblia has long been associated with the reduction of ferredoxin (Fd) by the enzyme pyruvate:ferredoxin oxidoreductase (PFOR) and the subsequent activation of metronidazole by Fd to toxic radical species. Resistance to metronidazole has been associated with down-regulation of PFOR and Fd. The aim of this study was to determine whether the PFOR/Fd couple is the only pathway involved in metronidazole activation in Giardia. METHODS PFOR and Fd activities were measured in extracts of highly metronidazole-resistant (MTR(r)) lines and activities of recombinant G. lamblia thioredoxin reductase (GlTrxR) and NADPH oxidase were assessed for their involvement in metronidazole activation and resistance. RESULTS We demonstrated that several lines of highly MTR(r) G. lamblia have fully functional PFOR and Fd indicating that PFOR/Fd-independent mechanisms are involved in metronidazole activation and resistance in these cells. Flavin-dependent GlTrxR, like TrxR of other anaerobic protozoa, reduces 5-nitroimidazole compounds including metronidazole, although expression of TrxR is not decreased in MTR(r) Giardia. However, reduction of flavins is suppressed in highly MTR(r) cells, as evidenced by as much as an 80% decrease in NADPH oxidase flavin mononucleotide reduction activity. This suppression is consistent with generalized impaired flavin metabolism in highly MTR(r) Trichomonas vaginalis. CONCLUSIONS These data add to the mounting evidence against the dogma that PFOR/Fd is the only couple with a low enough redox potential to reduce metronidazole in anaerobes and point to the multi-factorial nature of metronidazole resistance.
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Affiliation(s)
- David Leitsch
- Institute of Specific Prophylaxis and Tropical Medicine, Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Vienna, Austria
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Identification of a host cell target for the thiazolide class of broad-spectrum anti-parasitic drugs. Exp Parasitol 2011; 128:145-50. [PMID: 21335006 DOI: 10.1016/j.exppara.2011.02.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Revised: 02/01/2011] [Accepted: 02/02/2011] [Indexed: 01/22/2023]
Abstract
The thiazolide nitazoxanide (NTZ) and some derivatives exhibit considerable in vitro activities against a broad range of parasites, including the apicomplexans Neospora caninum and Toxoplasma gondii tachyzoites. In order to identify potential molecular targets for this compound in both parasites, RM4847 was coupled to epoxy-agarose and affinity chromatography was performed. A protein of approximately 35 kDa was eluted upon RM4847-affinity-chromatography from extracts of N. caninum-infected human foreskin fibroblasts (HFF) and non-infected HFF, but no protein was eluted when affinity chromatography was performed with T. gondii or N. caninum tachyzoite extracts. Mass spectrometry analysis identified the 35 kDa protein as human quinone reductase NQO1 (P15559; QR). Within 8h after infection of HFF with N. caninum tachyzoites, QR transcript expression levels were notably increased, but no such increase was observed upon infection with T. gondii tachyzoites. Treatment of non-infected HFF with RM4847 did also lead to an increase of QR transcript levels. The enzymatic activity of 6-histidine-tagged recombinant QR (recQR) was assayed using menadione as a substrate. The thiazolides NTZ, tizoxanide and RM4847 inhibited recQR activity on menadione in a concentration-dependent manner. Moreover, a small residual reducing activity was observed when these thiazolides were offered as substrates.
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