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Pooe K, Thulo M, Makumbe H, Akumadu B, Otun O, Aloke C, Achilonu I. Biophysical description of Bromosulfophthalein interaction with the 28-kDa glutathione transferase from Schistosoma japonicum. Mol Biochem Parasitol 2022; 252:111524. [PMID: 36195242 DOI: 10.1016/j.molbiopara.2022.111524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Revised: 09/12/2022] [Accepted: 09/29/2022] [Indexed: 12/31/2022]
Abstract
Glutathione transferases (GSTs) are major detoxification enzymes vital for the survival and reproduction of schistosomes during infection in humans. Schistosoma encode two GST isoenzymes, the 26- and 28-kDa isoforms, that show different substrate specificities and cellular localisations. Bromosulfophthalein (BSP) has been identified and characterised as a potent 26-kDa Schistosoma japonicum GST (Sj26GST) inhibitor with an anthelmintic potential. This study describes the structure, function, and ligandin properties of the 28-kDa Schistosoma japonicum GST (Sj28GST) towards BSP. Enzyme kinetics show that BSP is a potent enzyme inhibitor, with a specific activity decreases from 60.4 µmol/min/mg to 0.0742 µmol/min/mg and an IC50 in the micromolar range of 0.74 µM. Far-UV circular dichroism confirmed that purified Sj28GST follows a typical GST fold, which is predominantly alpha-helical. Fluorescence spectroscopy suggests that BSP binding occurs at a site distinct from the glutathione-binding site (G-site); however, the binding does not alter the local G-site environment. Isothermal titration calorimetry studies show that the binding of BSP to Sj28GST is exergonic (∆G°= -33 kJ/mol) and enthalpically-driven, with a stoichiometry of one BSP per dimer. The stability of Sj28GST (∆G(H2O) = 4.7 kcal/mol) is notably lower than Sj26GST, owing to differences in the enzyme's dimeric interfaces. We conclude that Sj28GST shares similar biophysical characteristics with Sj26GST based on its kinetic properties and susceptibility to low concentrations of BSP. The study supports the potential benefits of re-purposing BSP as a potential drug or prodrug to mitigate the scourge of schistosomiasis.
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Affiliation(s)
- Kagiso Pooe
- Protein Structure-Function and Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Braamfontein 2050, Johannesburg, South Africa
| | - Monare Thulo
- Protein Structure-Function and Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Braamfontein 2050, Johannesburg, South Africa
| | - Hattie Makumbe
- Protein Structure-Function and Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Braamfontein 2050, Johannesburg, South Africa
| | - Blessing Akumadu
- Protein Structure-Function and Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Braamfontein 2050, Johannesburg, South Africa
| | - Oluwatobin Otun
- Protein Structure-Function and Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Braamfontein 2050, Johannesburg, South Africa
| | - Chinyere Aloke
- Protein Structure-Function and Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Braamfontein 2050, Johannesburg, South Africa
| | - Ikechukwu Achilonu
- Protein Structure-Function and Research Unit, School of Molecular and Cell Biology, Faculty of Science, University of the Witwatersrand, Braamfontein 2050, Johannesburg, South Africa.
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Valli A, Achilonu I. Comparative structural analysis of the human and
Schistosoma
glutathione transferase dimer interface using selective binding of bromosulfophthalein. Proteins 2022; 90:1561-1569. [DOI: 10.1002/prot.26338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Revised: 03/05/2022] [Accepted: 03/14/2022] [Indexed: 11/06/2022]
Affiliation(s)
- Akeel Valli
- Protein Structure‐Function Research Unit, School of Molecular and Cell Biology, Faculty of Science University of the Witwatersrand Johannesburg South Africa
| | - Ikechukwu Achilonu
- Protein Structure‐Function Research Unit, School of Molecular and Cell Biology, Faculty of Science University of the Witwatersrand Johannesburg South Africa
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Panzner U, Excler JL, Kim JH, Marks F, Carter D, Siddiqui AA. Recent Advances and Methodological Considerations on Vaccine Candidates for Human Schistosomiasis. FRONTIERS IN TROPICAL DISEASES 2021. [DOI: 10.3389/fitd.2021.719369] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Schistosomiasis remains a neglected tropical disease of major public health concern with high levels of morbidity in various parts of the world. Although considerable efforts in implementing mass drug administration programs utilizing praziquantel have been deployed, schistosomiasis is still not contained. A vaccine may therefore be an essential part of multifaceted prevention control efforts. In the 1990s, a joint United Nations committee promoting parasite vaccines shortlisted promising candidates including for schistosomiasis discussed below. After examining the complexity of immune responses in human hosts infected with schistosomes, we review and discuss the antigen design and preclinical and clinical development of the four leading vaccine candidates: Sm-TSP-2 in Phase 1b/2b, Sm14 in Phase 2a/2b, Sm-p80 in Phase 1 preparation, and Sh28GST in Phase 3. Our assessment of currently leading vaccine candidates revealed some methodological issues that preclude a fair comparison between candidates and the rationale to advance in clinical development. These include (1) variability in animal models - in particular non-human primate studies - and predictive values of each for protection in humans; (2) lack of consensus on the assessment of parasitological and immunological parameters; (3) absence of reliable surrogate markers of protection; (4) lack of well-designed parasitological and immunological natural history studies in the context of mass drug administration with praziquantel. The controlled human infection model - while promising and unique - requires validation against efficacy outcomes in endemic settings. Further research is also needed on the impact of advanced adjuvants targeting specific parts of the innate immune system that may induce potent, protective and durable immune responses with the ultimate goal of achieving meaningful worm reduction.
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Pooe K, Worth R, Iwuchukwu EA, Dirr HW, Achilonu I. An empirical and theoretical description of Schistosoma japonicum glutathione transferase inhibition by bromosulfophthalein and indanyloxyacetic acid 94. J Mol Struct 2021. [DOI: 10.1016/j.molstruc.2020.128892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Thomas CM, Timson DJ. The Mechanism of Action of Praziquantel: Can New Drugs Exploit Similar Mechanisms? Curr Med Chem 2020; 27:676-696. [DOI: 10.2174/0929867325666180926145537] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Revised: 04/06/2018] [Accepted: 08/20/2018] [Indexed: 11/22/2022]
Abstract
Praziquantel (PZQ) is the drug of choice for treating infection with worms from the
genus Schistosoma. The drug is effective, cheap and has few side effects. However, despite its
use in millions of patients for over 40 years its molecular mechanism of action remains elusive.
Early studies demonstrated that PZQ disrupts calcium ion homeostasis in the worm and
the current consensus is that it antagonises voltage-gated calcium channels. It is hypothesised
that disruption of these channels results in uncontrolled calcium ion influx leading to uncontrolled
muscle contraction and paralysis. However, other experimental studies have suggested
a role for myosin regulatory light chains and adenosine uptake in the drug’s mechanism of
action. Assuming voltage-gated calcium channels do represent the main molecular target of
PZQ, the precise binding site for the drug remains to be identified. Unlike other commonly
used anti-parasitic drugs, there are few definitive reports of resistance to PZQ in the literature.
The lack of knowledge about PZQ’s molecular mechanism(s) undermines our ability to predict
how resistance might arise and also hinder our attempts to develop alternative antischistosomal
drugs which exploit the same target(s). Some PZQ derivatives have been identified
which also kill or paralyse schistosomes in culture. However, none of these are in widespread
clinical use. There is a pressing need for fundamental research into the molecular mechanism(
s) of action of PZQ. Such research would enable new avenues for antischsistosomal
drug discovery.
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Affiliation(s)
- Charlotte M. Thomas
- School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, United Kingdom
| | - David J. Timson
- School of Biological Sciences, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast BT9 7BL, United Kingdom
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Rigouin C, Nylin E, Cogswell AA, Schaumlöffel D, Dobritzsch D, Williams DL. Towards an understanding of the function of the phytochelatin synthase of Schistosoma mansoni. PLoS Negl Trop Dis 2013; 7:e2037. [PMID: 23383357 PMCID: PMC3561135 DOI: 10.1371/journal.pntd.0002037] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 12/13/2012] [Indexed: 11/19/2022] Open
Abstract
Phytochelatin synthase (PCS) is a protease-like enzyme that catalyzes the production of metal chelating peptides, the phytochelatins, from glutathione (GSH). In plants, algae, and fungi phytochelatin production is important for metal tolerance and detoxification. PCS proteins also function in xenobiotic metabolism by processing GSH S-conjugates. The aim of the present study is to elucidate the role of PCS in the parasitic worm Schistosoma mansoni. Recombinant S. mansoni PCS proteins expressed in bacteria could both synthesize phytochelatins and hydrolyze various GSH S-conjugates. We found that both the N-truncated protein and the N- and C-terminal truncated form of the enzyme (corresponding to only the catalytic domain) work through a thiol-dependant and, notably, metal-independent mechanism for both transpeptidase (phytochelatin synthesis) and peptidase (hydrolysis of GSH S-conjugates) activities. PCS transcript abundance was increased by metals and xenobiotics in cultured adult worms. In addition, these treatments were found to increase transcript abundance of other enzymes involved in GSH metabolism. Highest levels of PCS transcripts were identified in the esophageal gland of adult worms. Taken together, these results suggest that S. mansoni PCS participates in both metal homoeostasis and xenobiotic metabolism rather than metal detoxification as previously suggested and that the enzyme may be part of a global stress response in the worm. Because humans do not have PCS, this enzyme is of particular interest as a drug target for schistosomiasis. Schistosomiasis is a chronic, debilitating disease that affects hundreds of millions of people. The treatment of schistosomiasis relies solely on monotherapy with praziquantel and there is concern that drug-resistant parasites will evolve. Therefore, it is imperative to identify new drugs for schistosomiasis treatment. In this study our goal was to characterize the function of the phytochelatin synthase of Schistosoma mansoni, previously suggested as a candidate for drug targeting to control schistosomiasis. Phytochelatin synthase catalyzes the production of metal chelating peptides, the phytochelatins, from glutathione (GSH). In plants, algae, and fungi phytochelatin production is important for metal tolerance and detoxification. PCS proteins also function in the elimination of xenobiotics by processing GSH S-conjugates. We found that SmPCS expressed in bacteria could both synthesize phytochelatins and hydrolyze various GSH S-conjugates. We found the enzyme works through a thiol-dependant and, notably, metal-independent mechanism for both transpeptidase (phytochelatin synthesis) and peptidase (hydrolysis of GSH S-conjugates) activities. The expression of the PCS gene in adult schistosome worms was increased by exposure to a number of metals and xenobiotics. In addition, these treatments were found to increase the expression of other enzymes involved in GSH metabolism. Highest levels of PCS transcripts were localized in the esophageal gland of adult worms. Taken together, these results suggest that S. mansoni PCS participates in both metal homoeostasis and xenobiotic metabolism rather than metal detoxification as previously suggested and that it may be part of a global stress response in the worm.
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Affiliation(s)
- Coraline Rigouin
- Department of Immunology/Microbiology, Rush University Medical Center, Chicago, Illinois, United States of America
| | - Elyse Nylin
- Department of Immunology/Microbiology, Rush University Medical Center, Chicago, Illinois, United States of America
| | - Alexis A. Cogswell
- Department of Immunology/Microbiology, Rush University Medical Center, Chicago, Illinois, United States of America
| | - Dirk Schaumlöffel
- Université de Pau et des Pays de l'Adour/CNRS UMR 5254, Laboratoire de Chimie Analytique Bio-Inorganique et Environnement/IPREM, Hélioparc, Pau, France
| | - Dirk Dobritzsch
- Martin-Luther-Universität Halle-Wittenberg, Institut für Biochemie und Biotechnologie, Abteilung Pflanzenbiochemie, Halle, Saale, Germany
| | - David L. Williams
- Department of Immunology/Microbiology, Rush University Medical Center, Chicago, Illinois, United States of America
- * E-mail:
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New insight into praziquantel against various developmental stages of schistosomes. Parasitol Res 2011; 109:1501-7. [PMID: 21984370 DOI: 10.1007/s00436-011-2670-3] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Accepted: 09/27/2011] [Indexed: 10/17/2022]
Abstract
Praziquantel, due to high efficacy, excellent tolerability, few and transient side effects, simple administration, and competitive cost, is virtually the only drug of choice for treatment of human schistosomiasis. Treatment of schistosomiasis has shown great advances with the introduction of the drug into the therapeutic arsenal in areas that are endemic for the parasite. However, the drug presents various efficacies against different developmental stages of schistosomes, appearing an oddity intermitted mode. The present review article reviews the effects and mechanism of action of praziquantel against schistosomes briefly and suggests the research on this oddity phenomenon.
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Abstract
No major changes have occurred during the past 20 years regarding the therapeutic tools available to the clinician for the treatment of schistosomiasis. If anything, the two drugs (oxamniquine and metrifonate) that are valuable alternatives to the drug of choice (praziquantel) have become more difficult to procure in some African countries. Here, Donato Cioli summarizes some of the most recent and interesting laboratory studies on potential antischistosomal compounds, and then reviews recent developments related to the mechanism of action of praziquantel and to the possible emergence of praziquantel-resistant schistosomes.
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Affiliation(s)
- D Cioli
- Institute of Cell Biology of National Research Council, 43 Viale Marx, 00137 Rome, Italy
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Cvilink V, Lamka J, Skálová L. Xenobiotic metabolizing enzymes and metabolism of anthelminthics in helminths. Drug Metab Rev 2009; 41:8-26. [PMID: 19514969 DOI: 10.1080/03602530802602880] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Anthelminthics remain the only accessible means in the struggle against helminth parasites, which cause significant morbidity and mortality in man and farm animals. The treatment of helminthic infections has become problematic because of frequent drug resistance of helminth parasites. The development of drug resistance can be facilitated by the action of xenobiotic metabolizing enzymes (XMEs). In all organisms, XMEs serve as an efficient defense against the potential negative action of xenobiotics. The activities of XMEs determine both desired and undesired effects of drugs, and the knowledge of drug metabolism is necessary for safe, effective pharmacotherapy. While human and mammalian XMEs have been intensively studied for many years, XMEs of helminth parasites have undergone relatively little investigation, so far. However, many types of XMEs, including oxidases, reductases, hydrolases, transferases, and transporters, have been described in several helminth species. XMEs of helminth parasites may protect these organisms from the toxic effects of anthelminthics. In case of certain anthelminthics, metabolic deactivation was reported in helminth larvae and/or adults. Moreover, if a helminth is in the repeated contact with an anthelminthic, it defends itself against the chemical stress by the induction of biotransformation enzymes or transporters. This induction can represent an advantageous defense strategy of the parasites and may facilitate the drug-resistance development.
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Affiliation(s)
- Viktor Cvilink
- Charles University in Prague, Faculty of Pharmacy in Hradec Králové, Hradec Králové, Czech Republic
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Asojo OA, Homma K, Sedlacek M, Ngamelue M, Goud GN, Zhan B, Deumic V, Asojo O, Hotez PJ. X-ray structures of Na-GST-1 and Na-GST-2 two glutathione S-transferase from the human hookworm Necator americanus. BMC STRUCTURAL BIOLOGY 2007; 7:42. [PMID: 17594497 PMCID: PMC1924862 DOI: 10.1186/1472-6807-7-42] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/09/2007] [Accepted: 06/26/2007] [Indexed: 05/16/2023]
Abstract
BACKGROUND Human hookworm infection is a major cause of anemia and malnutrition of adults and children in the developing world. As part of on-going efforts to control hookworm infection, The Human Hookworm Vaccine Initiative has identified candidate vaccine antigens from the infective L3 larval stages and adult stages of the parasite. Adult stage antigens include the cytosolic glutathione-S-transferases (GSTs). Nematode GSTs facilitate the inactivation and degradation of a variety of electrophilic substrates (drugs) via the nucleophilic addition of reduced glutathione. Parasite GSTs also play significant roles in multi-drug resistance and the modulation of host-immune defense mechanisms. RESULTS The crystal structures of Na-GST-1 and Na-GST-2, two major GSTs from Necator americanus the main human hookworm parasite, have been solved at the resolution limits of 2.4 A and 1.9 A respectively. The structure of Na-GST-1 was refined to R-factor 18.9% (R-free 28.3%) while that of Na-GST-2 was refined to R-factor 17.1% (R-free 21.7%). Glutathione usurped during the fermentation process in bound in the glutathione binding site (G-site) of each monomer of Na-GST-2. Na-GST-1 is uncomplexed and its G-site is abrogated by Gln 50. These first structures of human hookworm parasite GSTs could aid the design of novel hookworm drugs. CONCLUSION The 3-dimensional structures of Na-GST-1 and Na-GST-2 show two views of human hookworm GSTs. While the GST-complex structure of Na-GST-2 reveals a typical GST G-site that of Na-GST-1 suggests that there is some conformational flexibility required in order to bind the substrate GST. In addition, the overall binding cavities for both are larger, more open, as well as more accessible to diverse ligands than those of GSTs from organisms that have other major detoxifying mechanisms. The results from this study could aid in the design of novel drugs and vaccine antigens.
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Affiliation(s)
- Oluwatoyin A Asojo
- Department of Pathology and Microbiology, College of Medicine Nebraska Medical Center, Omaha NE 68198-6495, USA
| | - Kohei Homma
- Department of Pathology and Microbiology, College of Medicine Nebraska Medical Center, Omaha NE 68198-6495, USA
| | - Meghan Sedlacek
- Department of Pathology and Microbiology, College of Medicine Nebraska Medical Center, Omaha NE 68198-6495, USA
| | - Michelle Ngamelue
- Department of Pathology and Microbiology, College of Medicine Nebraska Medical Center, Omaha NE 68198-6495, USA
| | - Gaddam N Goud
- Department of Microbiology, Immunology, and Tropical Medicine, The George Washington University Medical Center, Washington DC, 20037, USA
| | - Bin Zhan
- Department of Microbiology, Immunology, and Tropical Medicine, The George Washington University Medical Center, Washington DC, 20037, USA
| | - Vehid Deumic
- Department of Microbiology, Immunology, and Tropical Medicine, The George Washington University Medical Center, Washington DC, 20037, USA
| | - Oluyomi Asojo
- Department of Pathology and Microbiology, College of Medicine Nebraska Medical Center, Omaha NE 68198-6495, USA
| | - Peter J Hotez
- Department of Microbiology, Immunology, and Tropical Medicine, The George Washington University Medical Center, Washington DC, 20037, USA
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Tallima H, El Ridi R. Praziquantel binds Schistosoma mansoni adult worm actin. Int J Antimicrob Agents 2007; 29:570-5. [PMID: 17341443 DOI: 10.1016/j.ijantimicag.2006.12.018] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2006] [Accepted: 12/28/2006] [Indexed: 11/19/2022]
Abstract
Praziquantel (PZQ) is widely used for the treatment of schistosomiasis. It induces worm muscle contractions and tegumental disruption, followed by exposure of parasite surface membrane antigens to the host immunological defence mechanisms. It may be assumed that PZQ, like cholesterol, is too hydrophobic to traverse the schistosome outer lipid bilayers by passive diffusion and probably requires binding to a surface membrane protein carrier for distribution throughout the worm. However, the PZQ binding site on the schistosome surface and the precise mechanism of action are not yet known. The Claisen condensation reaction was used to bind PZQ on cellulose acetate membranes. Triton-insoluble surface membrane antigens of Schistosoma mansoni adult worms were allowed to bind to the PZQ column. The identity of the bound molecules was examined by amino acid microsequencing and immunogenicity in outbred and inbred mice. The PZQ column was found to bind molecules of 45 kDa selectively from the Triton-insoluble surface membrane antigens of S. mansoni adult worms. Amino acid microsequencing revealed that the 45 kDa species consist predominantly of schistosome actin. This finding was supported by the poor immunogenicity of the 45 kDa molecules in outbred and inbred mice. PZQ was also shown to bind bovine actin but not bovine serum albumin. However, pre-incubation with bovine actin did not impair the effect of PZQ on adult worms in vitro. The study represents an attempt to understand how PZQ distributes across schistosome outer lipid bilayers.
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Affiliation(s)
- Hatem Tallima
- Zoology Department, Faculty of Science, Cairo University, Cairo 12613, Egypt
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Doenhoff MJ, Pica-Mattoccia L. Praziquantel for the treatment of schistosomiasis: its use for control in areas with endemic disease and prospects for drug resistance. Expert Rev Anti Infect Ther 2006; 4:199-210. [PMID: 16597202 DOI: 10.1586/14787210.4.2.199] [Citation(s) in RCA: 139] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Praziquantel became available for the treatment of schistosomiasis and other trematode-inflicted diseases in the 1970s. It was revolutionary because it could be administered orally and had very few unwanted side effects. As a result of marked reductions in the price of praziquantel, the rate at which it is used has accelerated greatly in recent years. For the foreseeable future it will be the mainstay of programs designed to control schistosome-induced morbidity, particularly in sub-Saharan Africa where schistosomiasis is heavily endemic. There is currently no evidence to suggest that any schistosomes have developed resistance to praziquantel as a result of its widespread use. Nevertheless, while resistance may not pose an obvious or immediate threat to the usefulness of praziquantel, complacency and a failure to monitor developments may have serious consequences in the longer term since it will be the only drug that is readily available for large-scale treatment of schistosomiasis.
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Affiliation(s)
- Michael J Doenhoff
- University of Wales Bangor, School of Biological Sciences, Bangor, Gwynedd LL576 2UW, UK.
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Lin YL, He S. Sm22.6 antigen is an inhibitor to human thrombin. Mol Biochem Parasitol 2006; 147:95-100. [PMID: 16499980 DOI: 10.1016/j.molbiopara.2006.01.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2005] [Revised: 12/10/2005] [Accepted: 01/25/2006] [Indexed: 11/18/2022]
Abstract
The physiological role of Schistosomiasis mansoni 22.6 antigen (sm22.6 Ag) and its pathogenic effect on the human host has never been reported. Recombinant sm22.6 Ag is a homogenous polymer under non-denaturing/non-reducing conditions, and an inhibitor to human thrombin. Kinetic and Western blot assays show that the recombinant protein interacts with human thrombin and inhibits proteolytic activity of the protease. Tests of whole blood revealed that coagulation time was significantly delayed (3-5 times longer) in the presence of the recombinant protein at a concentration similar to thrombin in normal blood samples. Kinetic studies revealed that the delayed coagulation time was due to the inhibition of alpha-thrombin proteolytic activity by the parasite protein in an irreversible pattern, and a reversible inhibition to gamma-thrombin. Also, Western blot analysis under non-denaturing/non-reducing conditions showed that sm22.6 Ag binds to both alpha- and gamma-thrombin. Our results strongly suggest that sm22.6 antigen plays a role in down-regulation of coagulation in humans.
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Affiliation(s)
- Ya-Ling Lin
- Department of Parasitology, China Medical University School of Medicine, Taichung, 92 Hseu-shi road, Taichung, Taiwan, ROC
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14
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Jao SC, Chen J, Yang K, Li WS. Design of potent inhibitors for Schistosoma japonica glutathione S-transferase. Bioorg Med Chem 2005; 14:304-18. [PMID: 16275109 DOI: 10.1016/j.bmc.2005.07.077] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2005] [Revised: 07/22/2005] [Accepted: 07/22/2005] [Indexed: 11/18/2022]
Abstract
We implemented both structure-based drug design and the concept of polyvalency to discover a series of potent and unsymmetrical Schistosoma japonicum glutathione S-transferase (SjGST) inhibitors 10-12. This strategy achieved not only an excellent enhancement (10- to 490-fold) in the inhibitory potency, compared to the monofunctional analogues 1-5, but was also an effective modification by selecting a hydrophobic moiety with a flexible linker. The designed compounds with a low micromolar hit demonstrate special values in refining the new generation of SjGST inhibitors. The stoichiometry of the binding is one inhibitor molecule per SjGST monomer via isothermal titration calorimetric measurement.
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Affiliation(s)
- Shu-Chuan Jao
- Institute of Chemistry, Academia Sinica, Taipei 11529, Taiwan
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15
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Yassin Z, Ortiz-Salmerón E, García-Maroto F, Barón C, García-Fuentes L. Implications of the ligandin binding site on the binding of non-substrate ligands to Schistosoma japonicum-glutathione transferase. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2004; 1698:227-37. [PMID: 15134656 DOI: 10.1016/j.bbapap.2003.12.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2003] [Revised: 10/31/2003] [Accepted: 12/01/2003] [Indexed: 10/26/2022]
Abstract
The binding interactions between dimeric glutathione transferase from Schistosoma japonicum (Sj26GST) and bromosulfophthalein (BS) or 8-anilino-1-naphthalene sulfonate (ANS) were characterised by fluorescence spectroscopy and isothermal titration calorimetry (ITC). Both ligands inhibit the enzymatic activity of Sj26GST in a non-competitive form. A stoichiometry of 1 molecule of ligand per mole of dimeric enzyme was obtained for the binding of these ligands. The affinity of BS is higher (K(d)=3.2 microM) than that for ANS (K(d)=195 microM). The thermodynamic parameters obtained by calorimetric titrations are pH-independent in the range of 5.5 to 7.5. The interaction process is enthalpically driven at all the studied temperatures. This enthalpic contribution is larger for the ANS anion than for BS. The strongly favourable enthalpic contribution for the binding of ANS to Sj26GST is compensated by a negative entropy change, due to enthalpy-entropy compensation. DeltaG degrees remains almost invariant over the temperature range studied. The free energy change for the binding of BS to Sj26GST is also favoured by entropic contributions at temperatures below 32 degrees C, thus indicating a strong hydrophobic interaction. Heat capacity change obtained for BS (DeltaC(p) degrees =(-580.3+/-54.2) cal x K(-1) mol(-1)) is twofold larger (in absolute value) than for ANS (DeltaC(p) degrees =(-294.8+/-15.8) cal x K(-1) mol(-1)). Taking together the thermodynamic parameters obtained for these inhibitors, it can be argued that the possible hydrophobic interactions in the binding of these inhibitors to L-site must be accompanied by other interactions whose contribution is enthalpic. Therefore, the non-substrate binding site (designed as ligandin) on Sj26GST may not be fully hydrophobic.
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Affiliation(s)
- Zeyad Yassin
- Department of Physical Chemistry, Biochemistry and Inorganic Chemistry, Faculty of Experimental Sciences, University of Almería, La Cañada de San Urbano, Almería, 04120, Spain
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Xiao SH, You JQ, Gao HF, Mei JY, Jiao PY, Chollet J, Tanner M, Utzinger J. Schistosoma japonicum: effect of artemether on glutathione S-transferase and superoxide dismutase. Exp Parasitol 2002; 102:38-45. [PMID: 12615165 DOI: 10.1016/s0014-4894(02)00145-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Glutathione S-transferase (GST) and superoxide dismutase (SOD) are major antioxidant enzymes of schistosomes that are involved in detoxification processes. To study the effect of artemether on these enzymes, mice infected with adult Schistosoma japonicum, were treated with artemether either at a subcurative (100 mg/kg) or a curative dose (300 mg/kg). Schistosomes were recovered 24-72 h post-treatment separated by sex and used for GST and SOD activity measurements. Female worms showed consistently higher GST inhibitions than males. For instance, 24 h after administration of 100 mg/kg artemether, GST activities of female worms were inhibited by 23.3%, as compared to 12.7% in males. Both activities were significantly lower when compared to worms recovered from untreated mice. Slightly higher inhibitions were observed at the higher dose of artemether, which gradually increased to levels of 52.5-55.1%, 72 h post-treatment. GST inhibitions could be reversed by application of 1,4-dithiothreitol at a concentration of 10 mmol/L. Adding L-cysteine also reduced GST inhibitions, but in female worms, GST activities remained significantly higher than in worms from untreated animals. Administration of 300 mg/kg artemether resulted in significant reductions of SOD activities in both sexes. In conclusion, these results suggest that the inhibition of GST and, to a lesser extent also SOD enzymes, could lead to increased schistosome susceptibility to oxidant attacks and might be linked with the antischistosomal action of artemether.
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Affiliation(s)
- Shu-Hua Xiao
- Institute of Parasitic Diseases, Chinese Centre for Disease Control and Prevention, Shanghai 200025, PR China
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Fallon PG. Schistosome resistance to praziquantel. Drug Resist Updat 1998; 1:236-41. [PMID: 16904406 DOI: 10.1016/s1368-7646(98)80004-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/1998] [Revised: 04/22/1998] [Accepted: 04/22/1998] [Indexed: 10/25/2022]
Abstract
Praziquantel (PZQ) is the drug of choice for the treatment of human schistosomiasis. In 1994, it was first demonstrated that by sustained drug pressure on a Schistosoma mansoni strain in laboratory conditions resistance to PZQ can develop. Studies in Senegal and Egypt, both schistosomiasis endemic areas, have found that there are schistosome strain(s) that are tolerant to PZQ. In this article evidence from laboratory and field studies regarding the existence of PZQ resistance or tolerant schistosome strain(s) will be examined.
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Affiliation(s)
- P G Fallon
- Department of Pathology, University of Cambridge, Cambridge, UK.
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