51
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Schroeder JH, McCarthy D, Szestak T, Cook DA, Taylor MJ, Craig AG, Lawson C, Lawrence RA. Brugia malayi microfilariae adhere to human vascular endothelial cells in a C3-dependent manner. PLoS Negl Trop Dis 2017; 11:e0005592. [PMID: 28481947 PMCID: PMC5436873 DOI: 10.1371/journal.pntd.0005592] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 05/18/2017] [Accepted: 04/23/2017] [Indexed: 01/17/2023] Open
Abstract
Brugia malayi causes the human tropical disease, lymphatic filariasis. Microfilariae (Mf) of this nematode live in the bloodstream and are ingested by a feeding mosquito vector. Interestingly, in a remarkable co-evolutionary adaptation, Mf appearance in the peripheral blood follows a circadian periodicity and reaches a peak when the mosquito is most likely to feed. For the remaining hours, the majority of Mf sequester in the lung capillaries. This circadian phenomenon has been widely reported and is likely to maximise parasite fitness and optimise transmission potential. However, the mechanism of Mf sequestration in the lungs remains largely unresolved. In this study, we demonstrate that B. malayi Mf can, directly adhere to vascular endothelial cells under static conditions and under flow conditions, they can bind at high (but not low) flow rates. High flow rates are more likely to be experienced diurnally. Furthermore, a non-periodic nematode adheres less efficiently to endothelial cells. Strikingly C3, the central component of complement, plays a crucial role in the adherence interaction. These novel results show that microfilariae have the ability to bind to endothelial cells, which may explain their sequestration in the lungs, and this binding is increased in the presence of inflammatory mediators.
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Affiliation(s)
- Jan-Hendrik Schroeder
- Royal Veterinary College, Department of Comparative Biomedical Sciences, Royal College Street, London, United Kingdom
| | | | - Tadge Szestak
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Darren A. Cook
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Mark J. Taylor
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Alister G. Craig
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom
| | - Charlotte Lawson
- Royal Veterinary College, Department of Comparative Biomedical Sciences, Royal College Street, London, United Kingdom
| | - Rachel A. Lawrence
- Royal Veterinary College, Department of Comparative Biomedical Sciences, Royal College Street, London, United Kingdom
- * E-mail:
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52
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Soni R, Sharma D, Rai P, Sharma B, Bhatt TK. Signaling Strategies of Malaria Parasite for Its Survival, Proliferation, and Infection during Erythrocytic Stage. Front Immunol 2017; 8:349. [PMID: 28400771 PMCID: PMC5368685 DOI: 10.3389/fimmu.2017.00349] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Accepted: 03/10/2017] [Indexed: 12/22/2022] Open
Abstract
Irrespective of various efforts, malaria persist the most debilitating effect in terms of morbidity and mortality. Moreover, the existing drugs are also vulnerable to the emergence of drug resistance. To explore the potential targets for designing the most effective antimalarial therapies, it is required to focus on the facts of biochemical mechanism underlying the process of parasite survival and disease pathogenesis. This review is intended to bring out the existing knowledge about the functions and components of the major signaling pathways such as kinase signaling, calcium signaling, and cyclic nucleotide-based signaling, serving the various aspects of the parasitic asexual stage and highlighted the Toll-like receptors, glycosylphosphatidylinositol-mediated signaling, and molecular events in cytoadhesion, which elicit the host immune response. This discussion will facilitate a look over essential components for parasite survival and disease progression to be implemented in discovery of novel antimalarial drugs and vaccines.
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Affiliation(s)
- Rani Soni
- Department of Biotechnology, School of Life sciences, Central University of Rajasthan , Ajmer , India
| | - Drista Sharma
- Department of Biotechnology, School of Life sciences, Central University of Rajasthan , Ajmer , India
| | - Praveen Rai
- Department of Biotechnology, School of Life sciences, Central University of Rajasthan , Ajmer , India
| | - Bhaskar Sharma
- Department of Biotechnology, School of Life sciences, Central University of Rajasthan , Ajmer , India
| | - Tarun K Bhatt
- Department of Biotechnology, School of Life sciences, Central University of Rajasthan , Ajmer , India
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53
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Nunes RR, Costa MDS, Santos BDR, Fonseca ALD, Ferreira LS, Chagas RCR, Silva AMD, Varotti FDP, Taranto AG. Successful application of virtual screening and molecular dynamics simulations against antimalarial molecular targets. Mem Inst Oswaldo Cruz 2016; 111:721-730. [PMID: 27982302 PMCID: PMC5146734 DOI: 10.1590/0074-02760160207] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 08/23/2016] [Indexed: 11/22/2022] Open
Abstract
The main challenge in the control of malaria has been the emergence of drug-resistant parasites. The presence of drug-resistant Plasmodium sp. has raised the need for new antimalarial drugs. Molecular modelling techniques have been used as tools to develop new drugs. In this study, we employed virtual screening of a pyrazol derivative (Tx001) against four malaria targets: plasmepsin-IV, plasmepsin-II, falcipain-II, and PfATP6. The receiver operating characteristic curves and area under the curve (AUC) were established for each molecular target. The AUC values obtained for plasmepsin-IV, plasmepsin-II, and falcipain-II were 0.64, 0.92, and 0.94, respectively. All docking simulations were carried out using AutoDock Vina software. The ligand Tx001 exhibited a better interaction with PfATP6 than with the reference compound (-12.2 versus -6.8 Kcal/mol). The Tx001-PfATP6 complex was submitted to molecular dynamics simulations in vacuum implemented on an NAMD program. The ligand Tx001 docked at the same binding site as thapsigargin, which is a natural inhibitor of PfATP6. Compound TX001 was evaluated in vitro with a P. falciparum strain (W2) and a human cell line (WI-26VA4). Tx001 was discovered to be active against P. falciparum (IC50 = 8.2 µM) and inactive against WI-26VA4 (IC50 > 200 µM). Further ligand optimisation cycles generated new prospects for docking and biological assays.
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Affiliation(s)
- Renata Rachide Nunes
- Universidade Federal de São João Del-Rei, Laboratório de Química Farmacêutica Medicinal, Divinópolis, MG, Brasil.,Universidade Federal de São João Del-Rei, Núcleo de Pesquisa em Química Biológica, Divinópolis, MG, Brasil
| | - Marina Dos Santos Costa
- Centro Federal de Educação Tecnológica de Minas Gerais, Departamento de Informática, Gestão e Design, Divinópolis, MG, Brasil
| | - Bianca Dos Reis Santos
- Centro Federal de Educação Tecnológica de Minas Gerais, Departamento de Informática, Gestão e Design, Divinópolis, MG, Brasil
| | - Amanda Luisa da Fonseca
- Universidade Federal de São João Del-Rei, Núcleo de Pesquisa em Química Biológica, Divinópolis, MG, Brasil
| | - Lorena Sales Ferreira
- Universidade Federal de São João Del-Rei, Laboratório de Compostos Bioativos e Catalíticos, Divinópolis, MG, Brasil
| | - Rafael Cesar Russo Chagas
- Universidade Federal de São João Del-Rei, Laboratório de Compostos Bioativos e Catalíticos, Divinópolis, MG, Brasil
| | - Alisson Marques da Silva
- Centro Federal de Educação Tecnológica de Minas Gerais, Departamento de Informática, Gestão e Design, Divinópolis, MG, Brasil
| | - Fernando de Pilla Varotti
- Universidade Federal de São João Del-Rei, Núcleo de Pesquisa em Química Biológica, Divinópolis, MG, Brasil
| | - Alex Gutterres Taranto
- Universidade Federal de São João Del-Rei, Laboratório de Química Farmacêutica Medicinal, Divinópolis, MG, Brasil
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54
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Bennardo M, Alibhai F, Tsimakouridze E, Chinnappareddy N, Podobed P, Reitz C, Pyle WG, Simpson J, Martino TA. Day-night dependence of gene expression and inflammatory responses in the remodeling murine heart post-myocardial infarction. Am J Physiol Regul Integr Comp Physiol 2016; 311:R1243-R1254. [PMID: 27733386 DOI: 10.1152/ajpregu.00200.2016] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 10/05/2016] [Accepted: 10/05/2016] [Indexed: 01/10/2023]
Abstract
Diurnal or circadian rhythms are fundamentally important for healthy cardiovascular physiology and play a role in timing of onset and tolerance to myocardial infarction (MI) in patients. Whether time of day of MI triggers different molecular and cellular responses that can influence myocardial remodeling is not known. This study was designed to test whether time of day of MI triggers different gene expression, humoral, and innate inflammatory responses that contribute to cardiac repair after MI. Mice were infarcted by left anterior descending coronary artery ligation (MI model) within a 2-h time window either shortly after lights on or lights off, and the early remodeling responses at 8 h postinfarction were examined. We found that sleep-MI preferentially triggers early expression of genes associated with inflammatory responses, whereas wake-MI triggers more genes associated with metabolic pathways and transcription/translation, by microarray analyses. Homozygous clock mutant mice exhibit altered diurnal gene expression profiles, consistent with their cycling before onset of MI. In the first 8 h, crucial for innate immune responses to MI, there are also significant differences in sleep-MI and wake-MI serum cytokine responses and in neutrophil infiltration to infarcted myocardium. By 1-wk post-MI, there are differences in survivorship between the sleep and wake MI mice that could be explained by the different molecular and cellular responses. Our whole body physiology, tissues, and cells exhibit endogenous daily rhythms, and understanding their role in triggering effective responses after MI could lead to new strategies to benefit patients with cardiovascular disease.
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Affiliation(s)
- Michael Bennardo
- Centre for Cardiovascular Investigations, Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada; and
| | - Faisal Alibhai
- Centre for Cardiovascular Investigations, Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada; and
| | - Elena Tsimakouridze
- Centre for Cardiovascular Investigations, Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada; and
| | - Nirmala Chinnappareddy
- Centre for Cardiovascular Investigations, Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada; and
| | - Peter Podobed
- Centre for Cardiovascular Investigations, Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada; and
| | - Cristine Reitz
- Centre for Cardiovascular Investigations, Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada; and
| | - W Glen Pyle
- Centre for Cardiovascular Investigations, Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada; and
| | - Jeremy Simpson
- Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario, Canada
| | - Tami A Martino
- Centre for Cardiovascular Investigations, Department of Biomedical Sciences, University of Guelph, Guelph, Ontario, Canada; and
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55
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Lima WR, Tessarin-Almeida G, Rozanski A, Parreira KS, Moraes MS, Martins DC, Hashimoto RF, Galante PAF, Garcia CRS. Signaling transcript profile of the asexual intraerythrocytic development cycle of Plasmodium falciparum induced by melatonin and cAMP. Genes Cancer 2016; 7:323-339. [PMID: 28050233 PMCID: PMC5115173 DOI: 10.18632/genesandcancer.118] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
According to the World Health Organization (WHO), Plasmodium falciparum is the deadliest parasite among all species. This parasite possesses the ability to sense molecules, including melatonin (MEL) and cAMP, and modulate its cell cycle accordingly. MEL synchronizes the development of this malaria parasite by activating several cascades, including the generation of the second messenger cAMP. Therefore, we performed RNA sequencing (RNA-Seq) analysis in P. falciparum erythrocytic stages (ring, trophozoite and schizont) treated with MEL and cAMP. To investigate the expression profile of P. falciparum genes regulated by MEL and cAMP, we performed RNA-Seq analysis in three P. falciparum strains (control, 3D7; protein kinase 7 knockout, PfPK7-; and PfPK7 complement, PfPK7C). In the 3D7 strain, 38 genes were differentially expressed upon MEL treatment; however, none of the genes in the trophozoite (T) stage PfPK7- knockout parasites were differentially expressed upon MEL treatment for 5 hours compared to untreated controls, suggesting that PfPK7 may be involved in the signaling leading to differential gene expression. Moreover, we found that MEL modified the mRNA expression of genes encoding membrane proteins, zinc ion-binding proteins and nucleic acid-binding proteins, which might influence numerous functions in the parasite. The RNA-Seq data following treatment with cAMP show that this molecule modulates different genes throughout the intraerythrocytic cycle, namely, 75, 101 and 141 genes, respectively, in the ring (R), T and schizont (S) stages. Our results highlight P. falciparum's perception of the external milieu through the signaling molecules MEL and cAMP, which are able to drive to changes in gene expression in the parasite.
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Affiliation(s)
- Wânia Rezende Lima
- Departamento de Fisiologia, Instituto de Biociências, Universidade de Sao Paulo, Sao Paulo, Brazil.,Instituto de Ciências Exatas e Naturais (ICEN)- Medicina, Universidade Federal do Mato Grosso - Campus Rondonópolis, Brazil
| | | | - Andrei Rozanski
- Centro de Oncologia Molecular, Hospital Sírio-Libanês, Sao Paulo, Brazil
| | - Kleber S Parreira
- Departamento de Imunologia e Parasitologia, Instituto de Ciências Biomédicas, Universidade Federal de Uberlândia, Brazil
| | - Miriam S Moraes
- Departamento de Fisiologia, Instituto de Biociências, Universidade de Sao Paulo, Sao Paulo, Brazil
| | - David C Martins
- Centro de Matemática, Computação e Cognição, Universidade Federal do ABC, São Paulo, Brazil
| | - Ronaldo F Hashimoto
- Departamento de Ciência da Computação, Instituto de Matemática e Estatística, Universidade de São Paulo, São Paulo, Brazil
| | - Pedro A F Galante
- Centro de Oncologia Molecular, Hospital Sírio-Libanês, Sao Paulo, Brazil
| | - Célia R S Garcia
- Departamento de Fisiologia, Instituto de Biociências, Universidade de Sao Paulo, Sao Paulo, Brazil
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56
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Jockers R, Delagrange P, Dubocovich ML, Markus RP, Renault N, Tosini G, Cecon E, Zlotos DP. Update on melatonin receptors: IUPHAR Review 20. Br J Pharmacol 2016; 173:2702-25. [PMID: 27314810 DOI: 10.1111/bph.13536] [Citation(s) in RCA: 272] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 05/15/2016] [Accepted: 05/19/2016] [Indexed: 02/06/2023] Open
Abstract
Melatonin receptors are seven transmembrane-spanning proteins belonging to the GPCR superfamily. In mammals, two melatonin receptor subtypes exist - MT1 and MT2 - encoded by the MTNR1A and MTNR1B genes respectively. The current review provides an update on melatonin receptors by the corresponding subcommittee of the International Union of Basic and Clinical Pharmacology. We will highlight recent developments of melatonin receptor ligands, including radioligands, and give an update on the latest phenotyping results of melatonin receptor knockout mice. The current status and perspectives of the structure of melatonin receptor will be summarized. The physiological importance of melatonin receptor dimers and biologically important and type 2 diabetes-associated genetic variants of melatonin receptors will be discussed. The role of melatonin receptors in physiology and disease will be further exemplified by their functions in the immune system and the CNS. Finally, antioxidant and free radical scavenger properties of melatonin and its relation to melatonin receptors will be critically addressed.
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Affiliation(s)
- Ralf Jockers
- Inserm, U1016, Institut Cochin, Paris, France.,CNRS UMR 8104, Paris, France.,University Paris Descartes, Paris, France
| | | | - Margarita L Dubocovich
- Department Pharmacology and Toxicology, Jacobs School of Medicine and Biomedical Science, University at Buffalo (SUNY), Buffalo, USA
| | - Regina P Markus
- Institute of Biosciences, University of São Paulo, São Paulo, Brazil
| | | | - Gianluca Tosini
- Neuroscience Institute and Department of Pharmacology and Toxicology, Morehouse School of Medicine, Atlanta, GA, USA
| | - Erika Cecon
- Inserm, U1016, Institut Cochin, Paris, France.,CNRS UMR 8104, Paris, France.,University Paris Descartes, Paris, France
| | - Darius P Zlotos
- Department of Pharmaceutical Chemistry, The German University in Cairo, New Cairo City, Cairo, Egypt
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57
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Heath-Heckman EAC. The Metronome of Symbiosis: Interactions Between Microbes and the Host Circadian Clock. Integr Comp Biol 2016; 56:776-783. [PMID: 27371387 DOI: 10.1093/icb/icw067] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The entrainment of circadian rhythms, physiological cycles with a period of about 24 h, is regulated by a variety of mechanisms, including nonvisual photoreception. While circadian rhythms have been shown to be integral to many processes in multicellular organisms, including immune regulation, the effect of circadian rhythms on symbiosis, or host-microbe interactions, has only recently begun to be studied. This review summarizes recent work in the interactions of both pathogenic and mutualistic associations with host and symbiont circadian rhythms, focusing specifically on three mutualistic systems in which this phenomenon has been best studied. One important theme taken from these studies is the fact that mutualisms are profoundly affected by the circadian rhythms of the host, but that the microbial symbionts in these associations can, in turn, manipulate host rhythms. The interplay between circadian rhythms and symbiosis is a promising new field with effects that should be kept in mind when designing future studies across biology.
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58
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Daily Rhythms in Mosquitoes and Their Consequences for Malaria Transmission. INSECTS 2016; 7:insects7020014. [PMID: 27089370 PMCID: PMC4931426 DOI: 10.3390/insects7020014] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/22/2015] [Revised: 03/25/2016] [Accepted: 04/06/2016] [Indexed: 11/16/2022]
Abstract
The 24-h day involves cycles in environmental factors that impact organismal fitness. This is thought to select for organisms to regulate their temporal biology accordingly, through circadian and diel rhythms. In addition to rhythms in abiotic factors (such as light and temperature), biotic factors, including ecological interactions, also follow daily cycles. How daily rhythms shape, and are shaped by, interactions between organisms is poorly understood. Here, we review an emerging area, namely the causes and consequences of daily rhythms in the interactions between vectors, their hosts and the parasites they transmit. We focus on mosquitoes, malaria parasites and vertebrate hosts, because this system offers the opportunity to integrate from genetic and molecular mechanisms to population dynamics and because disrupting rhythms offers a novel avenue for disease control.
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59
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Cruz LN, Wu Y, Ulrich H, Craig AG, Garcia CRS. Tumor necrosis factor reduces Plasmodium falciparum growth and activates calcium signaling in human malaria parasites. Biochim Biophys Acta Gen Subj 2016; 1860:1489-97. [PMID: 27080559 PMCID: PMC4876768 DOI: 10.1016/j.bbagen.2016.04.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 03/08/2016] [Accepted: 04/04/2016] [Indexed: 12/29/2022]
Abstract
Background Plasmodium has a complex biology including the ability to interact with host signals modulating their function through cellular machinery. Tumor necrosis factor (TNF) elicits diverse cellular responses including effects in malarial pathology and increased infected erythrocyte cytoadherence. As TNF levels are raised during Plasmodium falciparum infection we have investigated whether it has an effect on the parasite asexual stage. Methods Flow cytometry, spectrofluorimetric determinations, confocal microscopy and PCR real time quantifications were employed for characterizing TNF induced effects and membrane integrity verified by wheat germ agglutinin staining. Results TNF is able to decrease intracellular parasitemia, involving calcium as a second messenger of the pathway. Parasites incubated for 48 h with TNF showed reduced erythrocyte invasion. Thus, TNF induced rises in intracellular calcium concentration, which were blocked by prior addition of the purinergic receptor agonists KN62 and A438079, or interfering with intra- or extracellular calcium release by thapsigargin or EGTA (ethylene glycol tetraacetic acid). Importantly, expression of PfPCNA1 which encodes the Plasmodium falciparum Proliferating-Cell Nuclear Antigen 1, decreased after P. falciparum treatment of TNF (tumor necrosis factor) or 6-Bnz cAMP (N6-benzoyladenosine-3′,5′-cyclic monophosphate sodium salt). Conclusions This is potentially interesting data showing the relevance of calcium in downregulating a gene involved in cellular proliferation, triggered by TNF. General significance The data show that Plasmodium may subvert the immunological system and use TNF for the control of its proliferation within the vertebrate host. TNF is able to decrease parasitemia in P. falciparum‐infected RBCs. TNF induced rises in intracellular calcium concentration, which were blocked by the purinergic receptor agonists KN62 and A438079. Interfering with intra‐ or extracellular calcium release by thapsigargin or EGTA also block TNF‐induce calcium release in P. falciparum. Expression of the P. falciparum Proliferating‐Cell Nuclear Antigen 1 (PfPCNA1) decreased after P. falciparum treatment with TNF or 6‐Bnz cAMP. The data show that Plasmodium may subvert the immunological system and use TNF for the control of its proliferation within the vertebrate host.
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Affiliation(s)
- Laura N Cruz
- Department of Physiology, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, travessa 14, n321, CEP 05508-900 São Paulo, SP, Brazil
| | - Yang Wu
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Henning Ulrich
- Department of Biochemistry, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Alister G Craig
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Célia R S Garcia
- Department of Physiology, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, travessa 14, n321, CEP 05508-900 São Paulo, SP, Brazil.
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60
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Wu Y, Cruz LN, Szestak T, Laing G, Molyneux GR, Garcia CRS, Craig AG. An external sensing system in Plasmodium falciparum-infected erythrocytes. Malar J 2016; 15:103. [PMID: 26893139 PMCID: PMC4759932 DOI: 10.1186/s12936-016-1144-6] [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] [Received: 12/04/2015] [Accepted: 02/04/2016] [Indexed: 11/17/2022] Open
Abstract
Background A number of experiments have previously indicated that Plasmodium falciparum-infected erythrocytes (pRBC) were able to sense host environment. The basis of this ability to detect external cues is not known but in screening signalling molecules from pRBC using commercial antibodies, a 34 kDa phosphorylated molecule that possesses such ability was identified. Methods The pRBC were exposed to different culture conditions and proteins were extracted for 1D or 2D gel electrophoresis followed by Western blot. The localization of 34 kDa protein was examined by biochemical fractionation followed by Western blot. High-resolution mass spectrometric analysis of immune precipitants was used to identify this protein and real-time quantitative reverse transcriptase polymerase chain reaction was used for detecting mRNA expression level. Results The 34 kDa protein was called PfAB4 has immediate responses (dephosphorylation and rapid turnover) to host environmental stimuli such as serum depletion, osmolality change and cytokine addition. PfAB4 is expressed constitutively throughout the erythrocytic lifecycle with dominant expression in trophozoites 30 h post-infection. Tumour necrosis factor (TNF) treatment induced a transient detectable dephosphorylation of PfAB4 in the ItG strain (2 min after addition) and the level of expression and phosphorylation returned to normal within 1–2 h. PfAB4 localized dominantly in pRBC cytoplasm, with a transient shift to the nucleus under TNF stimulation as shown by biochemical fractionation. High-resolution mass spectrometric analysis of immune precipitants of AB4 antibodies revealed a 34 kDa PfAB4 component as a mixture of proliferating cellular nuclear antigen-1 (PCNA1) and exported protein-2 (EXP2), along with a small number of other inconsistently identified peptides. Different parasite strains have different PfAB4 expression levels, but no significant association between mRNA and PfAB4 levels was seen, indicating that the differences may be at the post-transcriptional, presumably phosphorylation, level. A triple serine phosphorylated PCNA1 peptide was identified from the PfAB4 high expression strain only, providing further evidence that the identity of PfAB4 is PCNA1 in P.falciparum. Conclusion A protein element in the human malaria parasite that responds to external cues, including the pro-inflammatory cytokine TNF have been discovered. Treatment results in a transient change in phosphorylation status of the response element, which also migrates from the parasite cytoplasm to the nucleus. The response element has been identified as PfPCNA1. This sensing response could be regulated by a parasite checkpoint system and be analogous to bacterial two-component signal transduction systems. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1144-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Yang Wu
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Laura N Cruz
- Department of Physiology, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil.
| | - Tadge Szestak
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Gavin Laing
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Gemma R Molyneux
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Celia R S Garcia
- Department of Physiology, Instituto de Biociências, Universidade de São Paulo, São Paulo, São Paulo, Brazil.
| | - Alister G Craig
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, UK.
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61
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Brochet M, Billker O. Calcium signalling in malaria parasites. Mol Microbiol 2016; 100:397-408. [PMID: 26748879 DOI: 10.1111/mmi.13324] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/05/2016] [Indexed: 12/24/2022]
Abstract
Ca(2+) is a ubiquitous intracellular messenger in malaria parasites with important functions in asexual blood stages responsible for malaria symptoms, the preceding liver-stage infection and transmission through the mosquito. Intracellular messengers amplify signals by binding to effector molecules that trigger physiological changes. The characterisation of some Ca(2+) effector proteins has begun to provide insights into the vast range of biological processes controlled by Ca(2+) signalling in malaria parasites, including host cell egress and invasion, protein secretion, motility and cell cycle regulation. Despite the importance of Ca(2+) signalling during the life cycle of malaria parasites, little is known about Ca(2+) homeostasis. Recent findings highlighted that upstream of stage-specific Ca(2+) effectors is a conserved interplay between second messengers to control critical intracellular Ca(2+) signals throughout the life cycle. The identification of the molecular mechanisms integrating stage-transcending mechanisms of Ca(2+) homeostasis in a network of stage-specific regulator and effector pathways now represents a major challenge for a meaningful understanding of Ca(2+) signalling in malaria parasites.
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Affiliation(s)
- Mathieu Brochet
- Faculty of Medicine, Department of Microbiology and Molecular Medicine, University of Geneva, 1 Rue Michel-Servet, CH-1211 Geneva 4, Switzerland.,UMR5235 CNRS-Université Montpellier 2, 34095, Montpellier, France
| | - Oliver Billker
- Wellcome Trust Sanger Institute, Malaria Programme, CB10 1SA, Hinxton, UK
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62
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Budu A, Gomes MM, Melo PM, El Chamy Maluf S, Bagnaresi P, Azevedo MF, Carmona AK, Gazarini ML. Calmidazolium evokes high calcium fluctuations in Plasmodium falciparum. Cell Signal 2015; 28:125-135. [PMID: 26689736 DOI: 10.1016/j.cellsig.2015.12.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 11/30/2015] [Accepted: 12/07/2015] [Indexed: 10/22/2022]
Abstract
Calcium and calmodulin (CaM) are important players in eukaryote cell signaling. In the present study, by using a knockin approach, we demonstrated the expression and localization of CaM in all erythrocytic stages of Plasmodium falciparum. Under extracellular Ca(2+)-free conditions, calmidazolium (CZ), a potent CaM inhibitor, promoted a transient cytosolic calcium ([Ca(2+)]cyt) increase in isolated trophozoites, indicating that CZ mobilizes intracellular sources of calcium. In the same extracellular Ca(2+)-free conditions, the [Ca(2+)]cyt rise elicited by CZ treatment was ~3.5 fold higher when the endoplasmic reticulum (ER) calcium store was previously depleted ruling out the mobilization of calcium from the ER by CZ. The effects of the Ca(2+)/H(+) ionophore ionomycin (ION) and the Na(+)/H(+) ionophore monensin (MON) suggest that the [Ca(2+)]cyt-increasing effect of CZ is driven by the removal of Ca(2+) from at least one Ca(2+)-CaM-related (CaMR) protein as well as by the mobilization of Ca(2+) from intracellular acidic calcium stores. Moreover, we showed that the mitochondrion participates in the sequestration of the cytosolic Ca(2+) elicited by CZ. Finally, the modulation of membrane Ca(2+) channels by CZ and thapsigargin (THG) was demonstrated. The opened channels were blocked by the unspecific calcium channel blocker Co(2+) but not by 2-APB (capacitative calcium entry inhibitor) or nifedipine (L-type Ca(2+) channel inhibitor). Taken together, the results suggested that one CaMR protein is an important modulator of calcium signaling and homeostasis during the Plasmodium intraerythrocytic cell cycle, working as a relevant intracellular Ca(2+) reservoir in the parasite.
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Affiliation(s)
- Alexandre Budu
- Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, SP, Brazil
| | - Mayrim M Gomes
- Departamento de Biociências, Universidade Federal de São Paulo, Santos, SP, Brazil
| | - Pollyana M Melo
- Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, SP, Brazil
| | - Sarah El Chamy Maluf
- Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, SP, Brazil
| | - Piero Bagnaresi
- Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, SP, Brazil
| | - Mauro F Azevedo
- Instituto de Ciências Biomédicas, Universidade de São Paulo, SP, Brazil
| | - Adriana K Carmona
- Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, SP, Brazil.
| | - Marcos L Gazarini
- Departamento de Biociências, Universidade Federal de São Paulo, Santos, SP, Brazil.
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63
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Laranjeira-Silva MF, Zampieri RA, Muxel SM, Floeter-Winter LM, Markus RP. Melatonin attenuates Leishmania (L.) amazonensis infection by modulating arginine metabolism. J Pineal Res 2015; 59:478-87. [PMID: 26383232 DOI: 10.1111/jpi.12279] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Accepted: 09/11/2015] [Indexed: 01/08/2023]
Abstract
Acute inflammatory responses induced by bacteria or fungi block nocturnal melatonin synthesis by rodent pineal glands. Here, we show Leishmania infection does not impair daily melatonin rhythm in hamsters. Remarkably, the attenuated parasite burden and lesion progression in hamsters infected at nighttime was impaired by blockage of melatonin receptors with luzindole, whereas melatonin treatment during the light phase attenuated Leishmania infection. In vitro studies corroborated in vivo observations. Melatonin treatment reduced macrophage expression of Cat-2b, Cat1, and ArgI, genes involved in arginine uptake and polyamine synthesis. Indeed, melatonin reduced macrophage arginine uptake by 40%. Putrescine supplementation reverted the attenuation of infectivity by melatonin indicating that its effect was due to the arrest of parasite replication. This study shows that the Leishmania/host interaction varies in a circadian manner according to nocturnal melatonin pineal synthesis. Our results provide new data regarding Leishmania infectiveness and show new approaches for applying agonists of melatonin receptors in Leishmaniasis therapy.
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Affiliation(s)
| | | | - Sandra M Muxel
- Institute of Biosciences, University of São Paulo, São Paulo, Brazil
| | | | - Regina P Markus
- Institute of Biosciences, University of São Paulo, São Paulo, Brazil
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64
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Martinez-Bakker M, Helm B. The influence of biological rhythms on host-parasite interactions. Trends Ecol Evol 2015; 30:314-26. [PMID: 25907430 DOI: 10.1016/j.tree.2015.03.012] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 02/22/2015] [Accepted: 03/12/2015] [Indexed: 01/09/2023]
Abstract
Biological rhythms, from circadian control of cellular processes to annual cycles in life history, are a main structural element of biology. Biological rhythms are considered adaptive because they enable organisms to partition activities to cope with, and take advantage of, predictable fluctuations in environmental conditions. A flourishing area of immunology is uncovering rhythms in the immune system of animals, including humans. Given the temporal structure of immunity, and rhythms in parasite activity and disease incidence, we propose that the intersection of chronobiology, disease ecology, and evolutionary biology holds the key to understanding host-parasite interactions. Here, we review host-parasite interactions while explicitly considering biological rhythms, and propose that rhythms: influence within-host infection dynamics and transmission between hosts, might account for diel and annual periodicity in host-parasite systems, and can lead to a host-parasite arms race in the temporal domain.
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Affiliation(s)
- Micaela Martinez-Bakker
- Department of Ecology & Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Barbara Helm
- Institute for Biodiversity, Animal Health, and Comparative Medicine, University of Glasgow, Glasgow, UK
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65
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Koyama FC, Azevedo MF, Budu A, Chakrabarti D, Garcia CRS. Melatonin-induced temporal up-regulation of gene expression related to ubiquitin/proteasome system (UPS) in the human malaria parasite Plasmodium falciparum. Int J Mol Sci 2014; 15:22320-30. [PMID: 25479077 PMCID: PMC4284710 DOI: 10.3390/ijms151222320] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2014] [Revised: 09/11/2014] [Accepted: 10/16/2014] [Indexed: 12/24/2022] Open
Abstract
There is an increasing understanding that melatonin and the ubiquitin/ proteasome system (UPS) interact to regulate multiple cellular functions. Post-translational modifications such as ubiquitination are important modulators of signaling processes, cell cycle and many other cellular functions. Previously, we reported a melatonin-induced upregulation of gene expression related to ubiquitin/proteasome system (UPS) in Plasmodium falciparum, the human malaria parasite, and that P. falciparum protein kinase 7 influences this process. This implies a role of melatonin, an indolamine, in modulating intraerythrocytic development of the parasite. In this report we demonstrate by qPCR analysis, that melatonin induces gene upregulation in nine out of fourteen genes of the UPS, consisting of the same set of genes previously reported, between 4 to 5 h after melatonin treatment. We demonstrate that melatonin causes a temporally controlled gene expression of UPS members.
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Affiliation(s)
- Fernanda C Koyama
- Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São, São Paulo 05508-900, Brazil.
| | - Mauro F Azevedo
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo 05508-090, Brazil.
| | - Alexandre Budu
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo 05508-090, Brazil.
| | - Debopam Chakrabarti
- Burnett School of Biomedical Sciences, University of Central Florida, Orlando, FL 32826, USA.
| | - Célia R S Garcia
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo 05508-090, Brazil.
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Abstract
Melatonin (N-acetyl-5-methoxytryptamine) is widely known as "the darkness hormone". It is a major chronobiological regulator involved in circadian phasing and sleep-wake cycle in humans. Numerous other functions, including cyto/neuroprotection, immune modulation, and energy metabolism have been ascribed to melatonin. A variety of studies have revealed a role for melatonin and its receptors in different pathophysiological conditions. However, the suitability of melatonin as a drug is limited because of its short half-life, poor oral bioavailability, and ubiquitous action. Due to the therapeutic potential of melatonin in a wide variety of clinical conditions, the development of new agents able to interact selectively with melatonin receptors has become an area of great interest during the last decade. Therefore, the field of melatonergic receptor agonists comprises a great number of structurally different chemical entities, which range from indolic to nonindolic compounds. Melatonergic agonists are suitable for sleep disturbances, neuropsychiatric disorders related to circadian dysphasing, and metabolic diseases associated with insulin resistance. The results of preclinical studies on animal models show that melatonin receptor agonists can be considered promising agents for the treatment of central nervous system-related pathologies. An overview of recent advances in the field of investigational melatonergic drugs will be presented in this review.
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Affiliation(s)
- Alessia Carocci
- Department of Pharmacy–Drug Sciences, University of Bari Aldo Moro, Bari, Italy
| | - Alessia Catalano
- Department of Pharmacy–Drug Sciences, University of Bari Aldo Moro, Bari, Italy
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67
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Vriend J, Reiter RJ. Melatonin and ubiquitin: what's the connection? Cell Mol Life Sci 2014; 71:3409-18. [PMID: 24920061 PMCID: PMC11113875 DOI: 10.1007/s00018-014-1659-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2014] [Revised: 05/09/2014] [Accepted: 05/27/2014] [Indexed: 12/29/2022]
Abstract
Melatonin has been widely studied for its role in photoperiodism in seasonal breeders; it is also a potent antioxidant. Ubiquitin, a protein also widespread in living cells, contributes to many cellular events, although the most well known is that of tagging proteins for destruction by the proteasome. Herein, we suggest a model in which melatonin interacts with the ubiquitin-proteasome system to regulate a variety of seemingly unrelated processes. Ubiquitin, for example, is a major regulator of central activity of thyroid hormone type 2 deiodinase; the subsequent regulation of T3 may be central to the melatonin-induced changes in seasonal reproduction and seasonal changes in metabolism. Both melatonin and ubiquitin also have important roles in protecting cells from oxidative stress. We discuss the interaction of melatonin and the ubiquitin-proteasome system in oxidative stress through regulation of the ubiquitin-activating enzyme, E1. Previous reports have shown that glutathiolation of this enzyme protects proteins from unnecessary degradation. In addition, evidence is discussed concerning the interaction of ubiquitin and melatonin in activation of the transcription factor NF-κB as well as modulating cellular levels of numerous signal transducing factors including the tumor suppressor, p53. Some of the actions of melatonin on the regulatory particle of the proteasome appear to be related to its inhibition of the calcium-dependent calmodulin kinase II, an enzyme which reportedly copurifies with proteasomes. Many of the actions of melatonin on signal transduction are similar to those of a proteasome inhibitor. While these actions of melatonin could be explained by a direct inhibitory action on the catalytic core particle of the proteasome, this has not been experimentally verified. If our hypothesis of melatonin as a general inhibitor of the ubiquitin-proteasome system is confirmed, it is predicted that more examples of this interaction will be demonstrated in a variety of tissues in which ubiquitin and melatonin co-exist. Furthermore, the hypothesis of melatonin as an inhibitor of the ubiquitin-proteasome system will be a very useful model for clinical testing of melatonin.
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Affiliation(s)
- Jerry Vriend
- Department of Human Anatomy and Cell Science, University of Manitoba, 745 Bannatyne Avenue, Winnipeg, MB, R3E 0J9, Canada,
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68
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Synthetic indole and melatonin derivatives exhibit antimalarial activity on the cell cycle of the human malaria parasite Plasmodium falciparum. Eur J Med Chem 2014; 78:375-82. [DOI: 10.1016/j.ejmech.2014.03.055] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Revised: 03/14/2014] [Accepted: 03/16/2014] [Indexed: 11/21/2022]
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69
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Abstract
As it grows and replicates within the erythrocytes of its host the malaria parasite takes up nutrients from the extracellular medium, exports metabolites and maintains a tight control over its internal ionic composition. These functions are achieved via membrane transport proteins, integral membrane proteins that mediate the passage of solutes across the various membranes that separate the biochemical machinery of the parasite from the extracellular environment. Proteins of this type play a key role in antimalarial drug resistance, as well as being candidate drug targets in their own right. This review provides an overview of recent work on the membrane transport biology of the malaria parasite-infected erythrocyte, encompassing both the parasite-induced changes in the membrane transport properties of the host erythrocyte and the cell physiology of the intracellular parasite itself.
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70
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Furuyama W, Enomoto M, Mossaad E, Kawai S, Mikoshiba K, Kawazu SI. An interplay between 2 signaling pathways: melatonin-cAMP and IP3-Ca2+ signaling pathways control intraerythrocytic development of the malaria parasite Plasmodium falciparum. Biochem Biophys Res Commun 2014; 446:125-31. [PMID: 24607908 DOI: 10.1016/j.bbrc.2014.02.070] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Accepted: 02/15/2014] [Indexed: 11/26/2022]
Abstract
Plasmodium falciparum spends most of its asexual life cycle within human erythrocytes, where proliferation and maturation occur. Development into the mature forms of P. falciparum causes severe symptoms due to its distinctive sequestration capability. However, the physiological roles and the molecular mechanisms of signaling pathways that govern development are poorly understood. Our previous study showed that P. falciparum exhibits stage-specific spontaneous Calcium (Ca(2+)) oscillations in ring and early trophozoites, and the latter was essential for parasite development. In this study, we show that luzindole (LZ), a selective melatonin receptor antagonist, inhibits parasite growth. Analyses of development and morphology of LZ-treated P. falciparum revealed that LZ severely disrupted intraerythrocytic maturation, resulting in parasite death. When LZ was added at ring stage, the parasite could not undergo further development, whereas LZ added at the trophozoite stage inhibited development from early into late schizonts. Live-cell Ca(2+) imaging showed that LZ treatment completely abolished Ca(2+) oscillation in the ring forms while having little effect on early trophozoites. Further, the melatonin-induced cAMP increase observed at ring and late trophozoite stage was attenuated by LZ treatment. These suggest that a complex interplay between IP3-Ca(2+) and cAMP signaling pathways is involved in intraerythrocytic development of P. falciparum.
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Affiliation(s)
- Wakako Furuyama
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Masahiro Enomoto
- Princess Margaret Cancer Centre, Department of Medical Biophysics, University of Toronto, M5G1L7 Toronto, Ontario, Canada
| | - Ehab Mossaad
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Satoru Kawai
- Laboratory of Tropical Medicine and Parasitology, Dokkyo Medical University, Mibu, Tochigi 321-0293, Japan
| | - Katsuhiko Mikoshiba
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan
| | - Shin-ichiro Kawazu
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan.
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71
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Isah MB, Ibrahim MA. The role of antioxidants treatment on the pathogenesis of malarial infections: a review. Parasitol Res 2014; 113:801-9. [PMID: 24525759 DOI: 10.1007/s00436-014-3804-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Accepted: 01/28/2014] [Indexed: 11/28/2022]
Abstract
Oxidative damage is one of the most important pathological consequences of malarial infections. It affects vital organs of the body manifesting in changes such as splenomegaly, hepatomegaly, endothelial and cognitive damages. The currently used antimalarials often leave traces of these damages after therapy, as evident in memory impairment after cerebral malaria. Hence, some research investigations have focused attention on the use of antioxidants, alone or in combination with antimalarials, as a viable therapeutic strategy aimed at alleviating plasmodium-induced oxidative stress and its associated complications. However, the practical application of this approach often yields conflicting outcomes because some antimalarials specifically act via induction of oxidative stress. This article critically reviews most of the studies conducted on the potential role of antioxidant therapy in malarial infections. The most frequently investigated antioxidants are vitamins C and E, N-acetylcystein, folate and desferroxamine. Some of the investigations measured the effects of direct administration of the antioxidants on the plasmodium parasites while others performed an adjunctive therapy with standard antimalarials. The therapeutic application of each of the antioxidants in malaria management depends on the targeted aspect of malarial pathology. It is hoped that this article will provide an informed basis for future research activities on the therapeutic role of antioxidants on malarial pathogenesis.
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72
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Koyama FC, Carvalho TLG, Alves E, da Silva HB, de Azevedo MF, Hemerly AS, Garcia CRS. The Structurally Related Auxin and Melatonin Tryptophan-Derivatives and their Roles in Arabidopsis thaliana
and in the Human Malaria Parasite Plasmodium falciparum. J Eukaryot Microbiol 2013; 60:646-51. [DOI: 10.1111/jeu.12080] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 07/25/2013] [Accepted: 07/25/2013] [Indexed: 11/29/2022]
Affiliation(s)
- Fernanda C. Koyama
- Departamento de Parasitologia; Instituto de Ciências Biomédicas; Universidade de São Paulo; 05508-000 São Paulo Brazil
- Departamento de Fisiologia; Instituto de Biociências; Universidade de São Paulo; 05508-090 São Paulo Brazil
| | - Thais L. G. Carvalho
- Laboratório de Biologia Molecular de Plantas; Instituto de Bioquímica Médica; Universidade Federal do Rio de Janeiro; 21941-590 Rio de Janeiro Brazil
| | - Eduardo Alves
- Departamento de Parasitologia; Instituto de Ciências Biomédicas; Universidade de São Paulo; 05508-000 São Paulo Brazil
- Departamento de Fisiologia; Instituto de Biociências; Universidade de São Paulo; 05508-090 São Paulo Brazil
| | - Henrique B. da Silva
- Departamento de Imunologia; Instituto de Ciências Biomédicas; Universidade de São Paulo; 05508-900 São Paulo Brazil
| | - Mauro F. de Azevedo
- Centre for Immunology; Macfarlane Burnet Institute of Medical Research and Public Health; Melbourne Victoria 3004 Australia
| | - Adriana S. Hemerly
- Laboratório de Biologia Molecular de Plantas; Instituto de Bioquímica Médica; Universidade Federal do Rio de Janeiro; 21941-590 Rio de Janeiro Brazil
| | - Célia R. S. Garcia
- Departamento de Fisiologia; Instituto de Biociências; Universidade de São Paulo; 05508-090 São Paulo Brazil
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73
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Lima WR, Holder AA, Garcia CRS. Melatonin signaling and its modulation of PfNF-YB transcription factor expression in Plasmodium falciparum. Int J Mol Sci 2013; 14:13704-18. [PMID: 23839089 PMCID: PMC3742212 DOI: 10.3390/ijms140713704] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2013] [Revised: 06/23/2013] [Accepted: 06/25/2013] [Indexed: 12/15/2022] Open
Abstract
Malaria is one of the most severe tropical infectious diseases. More than 220 million people around the world have a clinical malaria infection and about one million die because of Plasmodium annually. This parasitic pathogen replicates efficiently in its human host making it difficult to eradicate. It is transmitted by mosquito vectors and so far mosquito control programs have not effectively eliminated this transmission. Because of malaria's enormous health and economic impact and the need to develop new control and eventual elimination strategies, a big research effort has been made to better understand the biology of this parasite and its interactions with its vertebrate host. Determination of the genome sequence and organization, the elucidation of the role of key proteins, and cell signaling studies have helped to develop an understanding of the molecular mechanisms that provide the parasite's versatility. The parasite can sense its environment and adapt to benefit its survival, indeed this is essential for it to complete its life cycle. For many years we have studied how the Plasmodium parasite is able to sense melatonin. In this review we discuss the melatonin signaling pathway and its role in the control of Plasmodium replication and development.
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Affiliation(s)
- Wânia Rezende Lima
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo 05508900, Brazil; E-Mail:
| | - Anthony A. Holder
- Division of Parasitology, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK; E-Mail:
| | - Célia R. S. Garcia
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo 05508900, Brazil; E-Mail:
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74
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McQueen PG, Williamson KC, McKenzie FE. Host immune constraints on malaria transmission: insights from population biology of within-host parasites. Malar J 2013; 12:206. [PMID: 23767770 PMCID: PMC3691866 DOI: 10.1186/1475-2875-12-206] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Accepted: 05/30/2013] [Indexed: 02/07/2023] Open
Abstract
Background Plasmodium infections trigger complex immune reactions from their hosts against several life stages of the parasite, including gametocytes. These immune responses are highly variable, depending on age, genetics, and exposure history of the host as well as species and strain of parasite. Although the effects of host antibodies that act against gamete stages in the mosquito (due to uptake in the blood meal) are well documented, the effects of host immunity upon within-host gametocytes are not as well understood. This report consists of a theoretical population biology-based analysis to determine constraints that host immunity impose upon gametocyte population growth. The details of the mathematical models used for the analysis were guided by published reports of clinical and animal studies, incorporated plausible modalities of immune reactions to parasites, and were tailored to the life cycl es of the two most widespread human malaria pathogens, Plasmodium falciparum and Plasmodium vivax. Results For the same ability to bind and clear a target, the model simulations suggest that an antibody attacking immature gametocytes would tend to lower the overall density of transmissible mature gametocytes more than an antibody attacking the mature forms directly. Transmission of P. falciparum would be especially vulnerable to complete blocking by antibodies to its immature forms since its gametocytes take much longer to reach maturity than those of P. vivax. On the other hand, antibodies attacking the mature gametocytes directly would reduce the time the mature forms can linger in the host. Simulation results also suggest that varying the standard deviation in the time necessary for individual asexual parasites to develop and produce schizonts can affect the efficiency of production of transmissible gametocytes. Conclusions If mature gametocyte density determines the probability of transmission, both Plasmodium species, but especially P. falciparum, could bolster this probability through evasion or suppression of host immune responses against the immature gametocytes. However, if the long term lingering of mature gametocytes at low density in the host is also important to ensure transmission, then evasion or suppression of antibodies against the mature stages would bolster probability of transmission as well.
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Affiliation(s)
- Philip G McQueen
- Mathematical and Statistical Computing Laboratory, Division of Computational Bioscience, Center for Information Technology, National Institutes of Health, Bethesda, Maryland, USA.
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75
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Lima WR, Moraes M, Alves E, Azevedo MF, Passos DO, Garcia CRS. The PfNF-YB transcription factor is a downstream target of melatonin and cAMP signalling in the human malaria parasite Plasmodium falciparum. J Pineal Res 2013; 54:145-53. [PMID: 22804732 DOI: 10.1111/j.1600-079x.2012.01021.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Plasmodium falciparum causes the most severe form of malaria and is responsible for the majority of deaths worldwide. The mechanism of cell cycle control within intra-erythrocytic stages has been examined as a potential means of a promising way to identifying how to stop parasite development in red blood cells. Our group determined that melatonin increases parasitemia in P. falciparum and P. chabaudi through a complex signalling cascade. In vertebrates, melatonin controls the expression of transcription factors, leading us to postulate rather that the indoleamine would affect PfNF-YB expression in human malaria parasites. We show here that PfNF-YB transcription factor is highly expressed and colocalized in the nucleus in mature parasites during intra-erythrocytic stages, thus suggesting an important role in cell division. Moreover, we demonstrate for the first time that melatonin and cAMP modulate the PfNF-YB transcription factor expression in P. falciparum at erythrocytic stages. In addition, PfNF-YB is found to be more ubiquitinated in the presence of melatonin. Finally, the proteasome inhibitor bortezomib is able to modulate PfNF-YB expression as well. Taken together, our dada reinforce the role played by melatonin in the cell cycle control of P. falciparum and point this indolamine as a target to develop new antimalarial drugs.
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Affiliation(s)
- Wânia R Lima
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil
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76
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Mideo N, Reece SE, Smith AL, Metcalf CJE. The Cinderella syndrome: why do malaria-infected cells burst at midnight? Trends Parasitol 2013; 29:10-6. [PMID: 23253515 PMCID: PMC3925801 DOI: 10.1016/j.pt.2012.10.006] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 10/31/2012] [Accepted: 10/31/2012] [Indexed: 11/20/2022]
Abstract
An interesting quirk of many malaria infections is that all parasites within a host – millions of them – progress through their cell cycle synchronously. This surprising coordination has long been recognized, yet there is little understanding of what controls it or why it has evolved. Interestingly, the conventional explanation for coordinated development in other parasite species does not seem to apply here. We argue that for malaria parasites, a critical question has yet to be answered: is the coordination due to parasites bursting at the same time or at a particular time? We explicitly delineate these fundamentally different scenarios, possible underlying mechanistic explanations and evolutionary drivers, and discuss the existing corroborating data and key evidence needed to solve this evolutionary mystery.
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77
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Batista R, García PA, Castro MA, Miguel Del Corral JM, Speziali NL, de P Varotti F, de Paula RC, García-Fernández LF, Francesch A, San Feliciano A, de Oliveira AB. Synthesis, cytotoxicity and antiplasmodial activity of novel ent-kaurane derivatives. Eur J Med Chem 2012; 62:168-76. [PMID: 23353738 DOI: 10.1016/j.ejmech.2012.12.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 12/06/2012] [Accepted: 12/07/2012] [Indexed: 10/27/2022]
Abstract
This paper reports on the syntheses and spectrometric characterisation of eleven novel ent-kaurane diterpenoids, including a complete set of (1)H, (13)C NMR and crystallographic data for two novel ent-kaurane diepoxides. Moreover, the antineoplastic cytotoxicity for kaurenoic acid and the majority of ent-kaurane derivatives were assessed in vitro against a panel of fourteen cancer cell lines, of which allylic alcohols were shown to be the most active compounds. The good in vitro antimalarial activity and the higher selectivity index values observed for some ent-kaurane epoxides against the chloroquine-resistant W2 clone of Plasmodium falciparum indicate that this class of natural products may provide new hits for the development of antimalarial drugs.
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Affiliation(s)
- Ronan Batista
- Departamento de Estudos Básicos e Instrumentais, Universidade Estadual do Sudoeste da Bahia, BR 415, Km 03, s/n°, 45.700-000 Itapetinga, Bahia, Brazil
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Stritzke C, Nalaskowski MM, Fanick W, Lin H, Mayr GW. A Plasmodium multi-domain protein possesses multiple inositol phosphate kinase activities. Mol Biochem Parasitol 2012; 186:134-8. [PMID: 23123170 DOI: 10.1016/j.molbiopara.2012.10.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Revised: 09/25/2012] [Accepted: 10/22/2012] [Indexed: 01/08/2023]
Abstract
The synchronization of intraerythrocytic maturation of Plasmodium parasites is an important factor in the malaria infection process. Synchronization is mediated by inositol phosphate (InsP(x))-induced Ca(2+)-release from internal stores. To further investigate the InsP(x) metabolism in these parasites a Plasmodium protein possessing inositol phosphate kinase (IPK) activity was recombinantly expressed, purified and enzymatically characterized for the first time. Its main activity is the conversion of the Ca(2+)-releasing second messenger Ins(1,4,5)P(3) to Ins(1,3,4,5)P(4), an important factor in chromatin remodeling and also in Ca(2+)-release. This protein possesses several additional IPK activities pointing to a potential role as inositol phosphate multikinase. Interestingly, we have also identified three putative subdomains of histone deacetylase in this protein possibly linking InsP(x)- and acetylation-mediated transcription regulation. Furthermore, we examined the inhibitory potential of >40 polyphenolic substances against its kinase activity. Because of the important role of InsP(x)-induced Ca(2+)-release in the development of Plasmodium parasites, IPKs are interesting targets for novel antimalarial approaches.
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Affiliation(s)
- Carina Stritzke
- Department of Biochemistry and Signal Transduction, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany
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79
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Koyama FC, Ribeiro RY, Garcia JL, Azevedo MF, Chakrabarti D, Garcia CRS. Ubiquitin proteasome system and the atypical kinase PfPK7 are involved in melatonin signaling in Plasmodium falciparum. J Pineal Res 2012; 53:147-53. [PMID: 22348509 PMCID: PMC3360131 DOI: 10.1111/j.1600-079x.2012.00981.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We previously reported that melatonin modulates the Plasmodium falciparum erythrocytic cycle by increasing schizont stage population as well as diminishing ring stage population. In addition, the importance of calcium and cAMP in melatonin signaling pathway in P. falciparum was also demonstrated. Nevertheless, the molecular effectors of the indoleamine signaling pathway remain elusive. We now demonstrate by real-time PCR that melatonin treatment up-regulates genes related to ubiquitin/proteasome system (UPS) components and that luzindole, a melatonin receptor antagonist, inhibits UPS transcription modulation. We also show that protein kinase PfPK7, a P. falciparum orphan kinase, plays a crucial role in the melatonin transduction pathway, since following melatonin treatment of P. falciparum parasites where pfpk7 gene is disrupted (pfpk7(-) parasites) (i) the ratio of asexual stages remain unchanged, (ii) the increase in cytoplasmatic calcium in response to melatonin was strongly diminished and (iii) up-regulation of UPS genes did not occur. The wild-type melatonin-induced alterations in cell cycle features, calcium rise and UPS gene transcription were restored by re-introduction of a functional copy of the pfpk7 gene in the pfpk7(-) parasites.
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Affiliation(s)
- Fernanda C Koyama
- Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
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80
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Salcedo-Sora JE, Ward SA, Biagini GA. A yeast expression system for functional and pharmacological studies of the malaria parasite Ca²⁺/H⁺ antiporter. Malar J 2012; 11:254. [PMID: 22853777 PMCID: PMC3488005 DOI: 10.1186/1475-2875-11-254] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2012] [Accepted: 07/23/2012] [Indexed: 12/26/2022] Open
Abstract
Background Calcium (Ca2+) signalling is fundamental for host cell invasion, motility, in vivo synchronicity and sexual differentiation of the malaria parasite. Consequently, cytoplasmic free Ca2+ is tightly regulated through the co-ordinated action of primary and secondary Ca2+ transporters. Identifying selective inhibitors of Ca2+ transporters is key towards understanding their physiological role as well as having therapeutic potential, therefore screening systems to facilitate the search for potential inhibitors are a priority. Here, the methodology for the expression of a Calcium membrane transporter that can be scaled to high throughputs in yeast is presented. Methods The Plasmodium falciparum Ca2+/H+ antiporter (PfCHA) was expressed in the yeast Saccharomyces cerevisiae and its activity monitored by the bioluminescence from apoaequorin triggered by divalent cations, such as calcium, magnesium and manganese. Results Bioluminescence assays demonstrated that PfCHA effectively suppressed induced cytoplasmic peaks of Ca2+, Mg2+ and Mn2+ in yeast mutants lacking the homologue yeast antiporter Vcx1p. In the scalable format of 96-well culture plates pharmacological assays with a cation antiporter inhibitor allowed the measurement of inhibition of the Ca2+ transport activity of PfCHA conveniently translated to the familiar concept of fractional inhibitory concentrations. Furthermore, the cytolocalization of this antiporter in the yeast cells showed that whilst PfCHA seems to locate to the mitochondrion of P. falciparum, in yeast PfCHA is sorted to the vacuole. This facilitates the real-time Ca2+-loading assays for further functional and pharmacological studies. Discussion The functional expression of PfCHA in S. cerevisiae and luminescence-based detection of cytoplasmic cations as presented here offer a tractable system that facilitates functional and pharmacological studies in a high-throughput format. PfCHA is shown to behave as a divalent cation/H+ antiporter susceptible to the effects of cation/H+ inhibitors such as KB-R7943. This type of gene expression systems should advance the efforts for the screening of potential inhibitors of this type of divalent cation transporters as part of the malaria drug discovery initiatives and for functional studies in general. Conclusion The expression and activity of the PfCHA detected in yeast by a bioluminescence assay that follows the levels of cytoplasmic Ca2+ as well as Mg2+ and Mn2+ lend itself to high-throughput and quantitative settings for pharmacological screening and functional studies.
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81
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Enomoto M, Kawazu SI, Kawai S, Furuyama W, Ikegami T, Watanabe JI, Mikoshiba K. Blockage of spontaneous Ca2+ oscillation causes cell death in intraerythrocitic Plasmodium falciparum. PLoS One 2012; 7:e39499. [PMID: 22792177 PMCID: PMC3391199 DOI: 10.1371/journal.pone.0039499] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2012] [Accepted: 05/21/2012] [Indexed: 11/18/2022] Open
Abstract
Malaria remains one of the world’s most important infectious diseases and is responsible for enormous mortality and morbidity. Resistance to antimalarial drugs is a challenging problem in malaria control. Clinical malaria is associated with the proliferation and development of Plasmodium parasites in human erythrocytes. Especially, the development into the mature forms (trophozoite and schizont) of Plasmodium falciparum (P. falciparum) causes severe malaria symptoms due to a distinctive property, sequestration which is not shared by any other human malaria. Ca2+ is well known to be a highly versatile intracellular messenger that regulates many different cellular processes. Cytosolic Ca2+ increases evoked by extracellular stimuli are often observed in the form of oscillating Ca2+ spikes (Ca2+ oscillation) in eukaryotic cells. However, in lower eukaryotic and plant cells the physiological roles and the molecular mechanisms of Ca2+ oscillation are poorly understood. Here, we showed the observation of the inositol 1,4,5-trisphospate (IP3)-dependent spontaneous Ca2+ oscillation in P. falciparum without any exogenous extracellular stimulation by using live cell fluorescence Ca2+ imaging. Intraerythrocytic P. falciparum exhibited stage-specific Ca2+ oscillations in ring form and trophozoite stages which were blocked by IP3 receptor inhibitor, 2-aminoethyl diphenylborinate (2-APB). Analyses of parasitaemia and parasite size and electron micrograph of 2-APB-treated P. falciparum revealed that 2-APB severely obstructed the intraerythrocytic maturation, resulting in cell death of the parasites. Furthermore, we confirmed the similar lethal effect of 2-APB on the chloroquine-resistant strain of P. falciparum. To our best knowledge, we for the first time showed the existence of the spontaneous Ca2+ oscillation in Plasmodium species and clearly demonstrated that IP3-dependent spontaneous Ca2+ oscillation in P. falciparum is critical for the development of the blood stage of the parasites. Our results provide a novel concept that IP3/Ca2+ signaling pathway in the intraerythrocytic malaria parasites is a promising target for antimalarial drug development.
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Affiliation(s)
- Masahiro Enomoto
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, Wako-shi, Saitama, Japan
| | - Shin-ichiro Kawazu
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido, Japan
| | - Satoru Kawai
- Laboratory of Tropical Medicine and Parasitology, Dokkyo Medical University, Mibu, Tochigi, Japan
| | - Wakako Furuyama
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido, Japan
| | - Tohru Ikegami
- Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan
| | - Jun-ichi Watanabe
- Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan
| | - Katsuhiko Mikoshiba
- Laboratory for Developmental Neurobiology, RIKEN Brain Science Institute, Wako-shi, Saitama, Japan
- Japan Science and Technology Agency, International Cooperative Research Project and Solution-Oriented Research for Science and Technology, Calcium Oscillation Project, Saitama, Japan
- * E-mail:
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82
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Cruz LN, Wu Y, Craig AG, Garcia CRS. Signal transduction in Plasmodium-Red Blood Cells interactions and in cytoadherence. AN ACAD BRAS CIENC 2012; 84:555-72. [PMID: 22634746 DOI: 10.1590/s0001-37652012005000036] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 03/09/2012] [Indexed: 12/19/2022] Open
Abstract
Malaria is responsible for more than 1.5 million deaths each year, especially among children (Snow et al. 2005). Despite of the severity of malaria situation and great effort to the development of new drug targets (Yuan et al. 2011) there is still a relative low investment toward antimalarial drugs. Briefly there are targets classes of antimalarial drugs currently being tested including: kinases, proteases, ion channel of GPCR, nuclear receptor, among others (Gamo et al. 2010). Here we review malaria signal transduction pathways in Red Blood Cells (RBC) as well as infected RBCs and endothelial cells interactions, namely cytoadherence. The last process is thought to play an important role in the pathogenesis of severe malaria. The molecules displayed on the surface of both infected erythrocytes (IE) and vascular endothelial cells (EC) exert themselves as important mediators in cytoadherence, in that they not only induce structural and metabolic changes on both sides, but also trigger multiple signal transduction processes, leading to alteration of gene expression, with the balance between positive and negative regulation determining endothelial pathology during a malaria infection.
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Affiliation(s)
- Laura N Cruz
- Departamento de Fisiologia, Instituto de Biociências, Universidade de São Paulo, Brasil
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83
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Generation of second messengers in Plasmodium. Microbes Infect 2012; 14:787-95. [PMID: 22584103 DOI: 10.1016/j.micinf.2012.04.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2011] [Revised: 04/17/2012] [Accepted: 04/18/2012] [Indexed: 02/05/2023]
Abstract
Signalling in malaria parasites is a field of growing interest as its components may prove to be valuable drug targets, especially when one considers the burden of a disease that is responsible for up to 500 million infections annually. The scope of this review is to discuss external stimuli in the parasite life cycle and the upstream machinery responsible for translating them into intracellular responses, focussing particularly on the calcium signalling pathway.
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84
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Abstract
The in vitro cultivation of Plasmodium falciparum is absolutely essential for the molecular dissection of parasite biology and still poses several challenges. The dependence on, and interaction with host red blood cells, the tightly regulated stage-specific expression of proteins, and the parasite peculiar demands on nutrients and gaseous environments are only a few aspects that need to be addressed to successfully cultivate P. falciparum in vitro. In this chapter, we present techniques for normal maintenance of the erythrocytic stages of P. falciparum cultures, their synchronization and the generation of clonal cell lines.
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85
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Mideo N, Reece SE. Plasticity in parasite phenotypes: evolutionary and ecological implications for disease. Future Microbiol 2012; 7:17-24. [DOI: 10.2217/fmb.11.134] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Preventing disease is a major goal of applied bioscience and explaining variation in the harm caused by parasites, and their infectiousness, are major goals of evolutionary biology. The emerging field of evolutionary medicine integrates these two ambitions to inform the development of control strategies that retard or withstand unfavorable parasite evolution. However, as parasites live in hostile and changeable environments – the bodies of other organisms – the success of integrating evolutionary biology with medicine requires a better understanding of how natural selection has solved the problems parasites face. There is increasing appreciation that natural selection shapes parasite strategies to survive in the host and transmit between hosts through facultative (plastic) shifts in parasite traits expressed during infections and in different hosts. This article describes how integrating parasite plasticity into biomedical thinking is central to explaining disease outcomes and transmission patterns, as well as predicting the success of control measures.
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Affiliation(s)
- Nicole Mideo
- Centre for Immunity, Infection & Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, UK
| | - Sarah E Reece
- Institutes of Evolution, Immunity & Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JT, UK
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86
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Kato K, Sugi T, Iwanaga T. Roles of Apicomplexan protein kinases at each life cycle stage. Parasitol Int 2011; 61:224-34. [PMID: 22209882 DOI: 10.1016/j.parint.2011.12.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 12/12/2011] [Accepted: 12/18/2011] [Indexed: 01/21/2023]
Abstract
Inhibitors of cellular protein kinases have been reported to inhibit the development of Apicomplexan parasites, suggesting that the functions of protozoan protein kinases are critical for their life cycle. However, the specific roles of these protein kinases cannot be determined using only these inhibitors without molecular analysis, including gene disruption. In this report, we describe the functions of Apicomplexan protein kinases in each parasite life stage and the potential of pre-existing protein kinase inhibitors as Apicomplexan drugs against, mainly, Plasmodium and Toxoplasma.
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Affiliation(s)
- Kentaro Kato
- Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
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87
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Drug-induced permeabilization of parasite's digestive vacuole is a key trigger of programmed cell death in Plasmodium falciparum. Cell Death Dis 2011; 2:e216. [PMID: 21993392 PMCID: PMC3219093 DOI: 10.1038/cddis.2011.97] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Having previously characterized chloroquine (CQ)-induced programmed cell death (PCD) hallmarks in the malaria parasite Plasmodium falciparum and delineating a pathway linking these features, the roles of non-classical mediators were investigated in this paper. It was shown that the later stages of this pathway are Ca2+-dependent and transcriptionally regulated. Moreover, it was demonstrated for the first time that micromolar concentrations of CQ partially permeabilized the parasite's digestive vacuole (DV) membrane and that this important upstream event appears to precede mitochondrial dysfunction. This permeabilization of the DV occurred without rupture of the DV membrane and was reminiscent of lysosome-mediated cell death in mammalian cells. As such micromolar concentrations of CQ are found in the patient's plasma after initial CQ loading, this alludes to a clinically relevant antimalarial mechanism of the drug which has yet to be recognized. Furthermore, other ‘non-antimalarial' lysosomotropic compounds were also shown to cause DV permeabilization, triggering PCD in both CQ-sensitive and -resistant parasites. These findings present new avenues for antimalarial developments, which induce DV destabilization to kill parasites.
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88
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Bagnaresi P, Nakabashi M, Thomas AP, Reiter RJ, Garcia CRS. The role of melatonin in parasite biology. Mol Biochem Parasitol 2011; 181:1-6. [PMID: 21982826 DOI: 10.1016/j.molbiopara.2011.09.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Revised: 09/21/2011] [Accepted: 09/23/2011] [Indexed: 10/17/2022]
Abstract
Regarded as the circadian hormone in mammals, melatonin is a highly conserved molecule, present in nearly all species. In this review, we discuss the role of this indolamine and its precursors in the cell biology of parasites and the role of the molecule in the physiology of the host. In Plasmodium, melatonin can modulate intracellular concentrations of calcium and cAMP, which in turn can regulate kinase activity and cell cycle. In Trypanosoma infections, modulation of the immune system by melatonin is extremely important in controlling the parasite population. Melatonin also contributes to the inflammatory response to Toxoplasma gondii infection. Thus, there are a number of unique adaptations involving intricate connections between melatonin and the biology of the parasite-host relationship.
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Affiliation(s)
- Piero Bagnaresi
- Departamento de Biofísica, Universidade Federal de São Paulo, São Paulo, Brazil
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89
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Schuck DC, Ribeiro RY, Nery AA, Ulrich H, Garcia CRS. Flow cytometry as a tool for analyzing changes in Plasmodium falciparum cell cycle following treatment with indol compounds. Cytometry A 2011; 79:959-64. [PMID: 22015733 DOI: 10.1002/cyto.a.21136] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Revised: 07/28/2011] [Accepted: 08/04/2011] [Indexed: 11/09/2022]
Abstract
Melatonin and its derivatives modulate the Plasmodium falciparum and Plasmodium chabaudi cell cycle. Flow cytometry was employed together with the nucleic acid dye YOYO-1 allowing precise discrimination between mono- and multinucleated forms of P. falciparum-infected red blood cell. The use of YOYO-1 permitted excellent discrimination between uninfected and infected red blood cells as well as between early and late parasite stages. Fluorescence intensities of schizont-stage parasites were about 10-fold greater than those of ring-trophozoite form parasites. Melatonin and related indolic compounds including serotonin, N-acetyl-serotonin and tryptamine induced an increase in the percentage of multinucleated forms compared to non-treated control cultures. YOYO-1 staining of infected erythrocyte and subsequent flow cytometry analysis provides a powerful tool in malaria research for screening of bioactive compounds.
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Affiliation(s)
- Desirée Cigaran Schuck
- Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
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90
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Abstract
Cyclic nucleotides are so-called intracellular second messenger molecules used by all cells to transform environmental signals into an appropriate response. Interest in the cyclic nucleotides cAMP and cGMP in malaria parasites followed early observations that both molecules might be involved in distinct differentiation events within the sexual phase of the life cycle that is required for transmission of parasites to the mosquito vector. Completed genome sequences combined with biochemical and genetic studies have confirmed the presence of the main enzymatic components of cyclic nucleotide signalling in the parasite. Dissection of their functions is underway and is giving initial insights into some of the cellular processes, which are regulated by these signalling pathways. Malaria parasites occupy terminally differentiated red blood cells for a significant proportion of their life cycle, but although there is some evidence of potential roles for the residual host cell signalling machinery in parasite development, details are few. A major gap in our knowledge is the nature of the cell surface receptors, which might trigger cyclic nucleotide signalling in the parasite.
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Affiliation(s)
- David A Baker
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, UK.
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91
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Abstract
Compared with the impressive progress in understanding signal transduction pathways and mechanisms in mammalian systems, advances in protozoan signalling processes, including cyclic nucleotide metabolism, have been very slow. This is in large part connected to the fact that the components of these pathways are very different in the protozoan parasites, as confirmed by the recently completed genome. For instance, kinetoplastids have no equivalents to the mammalian Class I adenylyl cyclases (ACs) in their genomes nor any of the subunits of the associated G-proteins. The cyclases in kinetoplastid parasites contain a single transmembrane domain, a conserved intracellular catalytic domain and a highly variable extracellular domain - consistent with the expression of multiple receptor-activated cyclases - but no receptor ligands, agonists or antagonists have been identified. Apicomplexan AC and guanylyl cyclase (GC) are even more unusual, potentially being bifunctional, harbouring either a putative ion channel (AC) or a P-type ATPase-like domain (GC) alongside the catalytic region. Phosphodiesterases (PDEs) and cyclic-nucleotide-activated protein kinases are essentially conserved in protozoa, although mostly insensitive to inhibitors of the mammalian proteins. Some of the PDEs have now been validated as promising drug targets. In the following manuscript, we will summarize the existing literature on cAMP and cGMP in protozoa: cyclases, PDEs and cyclic-nucleotide-dependent kinases.
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Affiliation(s)
- Matthew K Gould
- Biomedical Research Centre, Institute of Infection, Immunity & Inflammation, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK
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92
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O'Donnell AJ, Schneider P, McWatters HG, Reece SE. Fitness costs of disrupting circadian rhythms in malaria parasites. Proc Biol Sci 2011; 278:2429-36. [PMID: 21208950 PMCID: PMC3125626 DOI: 10.1098/rspb.2010.2457] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Circadian biology assumes that biological rhythms maximize fitness by enabling organisms to coordinate with their environment. Despite circadian clocks being such a widespread phenomenon, demonstrating the fitness benefits of temporal coordination is challenging and such studies are rare. Here, we tested the consequences--for parasites--of being temporally mismatched to host circadian rhythms using the rodent malaria parasite, Plasmodium chabaudi. The cyclical nature of malaria infections is well known, as the cell cycles across parasite species last a multiple of approximately 24 h, but the evolutionary explanations for periodicity are poorly understood. We demonstrate that perturbation of parasite rhythms results in a twofold cost to the production of replicating and transmission stages. Thus, synchronization with host rhythms influences in-host survival and between-host transmission potential, revealing a role for circadian rhythms in the evolution of host-parasite interactions. More generally, our results provide a demonstration of the adaptive value of circadian rhythms and the utility of using an evolutionary framework to understand parasite traits.
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Affiliation(s)
- Aidan J O'Donnell
- Institute of Evolution, Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh EH9 3JT, UK
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93
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Gazarini ML, Beraldo FH, Almeida FM, Bootman M, Da Silva AM, Garcia CRS. Melatonin triggers PKA activation in the rodent malaria parasite Plasmodium chabaudi. J Pineal Res 2011; 50:64-70. [PMID: 20964707 DOI: 10.1111/j.1600-079x.2010.00810.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Calcium (Ca(2+) ) is a critical regulator of many aspects of the Plasmodium reproductive cycle. In particular, intra-erythrocyte Plasmodium parasites respond to circulating levels of the melatonin in a process mediated partly by intracellular Ca(2+) . Melatonin promotes the development and synchronicity of parasites, thereby enhancing their spread and worsening the clinical implications. The signalling mechanisms underlying the effects of melatonin are not fully established, although both Ca(2+) and cyclic AMP (cAMP) have been implicated. Furthermore, it is not clear whether different strains of Plasmodium use the same, or divergent, signals to control their development. The aim of this study was to explore the signalling mechanisms engaged by melatonin in P. chabaudi, a virulent rodent parasite. Using parasites at the throphozoite stage acutely isolated from mice erythrocytes, we demonstrate that melatonin triggers cAMP production and protein kinase A (PKA) activation. Interestingly, the stimulation of cAMP/PKA signalling by melatonin was dependent on elevation of Ca(2+) within the parasite, because buffering Ca(2+) changes using the chelator BAPTA prevented cAMP production in response to melatonin. Incubation with melatonin evoked robust Ca(2+) signals within the parasite, as did the application of a membrane-permeant analogue of cAMP. Our data suggest that P. chabaudi engages both Ca(2+) and cAMP signalling systems when stimulated by melatonin. Furthermore, there is positive feedback between these messengers, because Ca(2+) evokes cAMP elevation and vice versa. Melatonin more than doubled the observed extent of parasitemia, and the increase in cAMP concentration and PKA activation was essential for this effect. These data support the possibility to use melatonin antagonists or derivates in therapeutic approach.
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Affiliation(s)
- Marcos L Gazarini
- Departamento de Biociências, Universidade Federal de São Paulo, Santos, SP, Brasil
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94
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Cruz LND, Alves E, Leal MT, Juliano MA, Rosenthal PJ, Juliano L, Garcia CRS. FRET peptides reveal differential proteolytic activation in intraerythrocytic stages of the malaria parasites Plasmodium berghei and Plasmodium yoelii. Int J Parasitol 2010; 41:363-72. [PMID: 21168413 DOI: 10.1016/j.ijpara.2010.10.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2010] [Revised: 10/26/2010] [Accepted: 10/27/2010] [Indexed: 11/25/2022]
Abstract
Malaria is still a major health problem in developing countries. It is caused by the protist parasite Plasmodium, in which proteases are activated during the cell cycle. Ca(2+) is a ubiquitous signalling ion that appears to regulate protease activity through changes in its intracellular concentration. Proteases are crucial to Plasmodium development, but the role of Ca(2+) in their activity is not fully understood. Here we investigated the role of Ca(2+) in protease modulation among rodent Plasmodium spp. Using fluorescence resonance energy transfer (FRET) peptides, we verified protease activity elicited by Ca(2+) from the endoplasmatic reticulum (ER) after stimulation with thapsigargin (a sarco/endoplasmatic reticulum Ca(2+)-ATPase (SERCA) inhibitor) and from acidic compartments by stimulation with nigericin (a K(+)/H(+) exchanger) or monensin (a Na(+)/H(+) exchanger). Intracellular (BAPTA/AM) and extracellular (EGTA) Ca(2+) chelators were used to investigate the role played by Ca(2+) in protease activation. In Plasmodium berghei both EGTA and BAPTA blocked protease activation, whilst in Plasmodium yoelii these compounds caused protease activation. The effects of protease inhibitors on thapsigargin-induced proteolysis also differed between the species. Pepstatin A and phenylmethylsulphonyl fluoride (PMSF) increased thapsigargin-induced proteolysis in P. berghei but decreased it in P. yoelii. Conversely, E64 reduced proteolysis in P. berghei but stimulated it in P. yoelii. The data point out key differences in proteolytic responses to Ca(2+) between species of Plasmodium.
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Affiliation(s)
- Laura Nogueira da Cruz
- Department of Parasitology, Instituto de Ciências Biomédicas, Universidade de São Paulo, Av. Prof. Lineu Prestes, 1374 Edifício Biomédicas II, CEP 05508-900, São Paulo, SP, Brazil
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95
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Alves E, Bartlett PJ, Garcia CRS, Thomas AP. Melatonin and IP3-induced Ca2+ release from intracellular stores in the malaria parasite Plasmodium falciparum within infected red blood cells. J Biol Chem 2010; 286:5905-12. [PMID: 21149448 DOI: 10.1074/jbc.m110.188474] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
IP(3)-dependent Ca(2+) signaling controls a myriad of cellular processes in higher eukaryotes and similar signaling pathways are evolutionarily conserved in Plasmodium, the intracellular parasite that causes malaria. We have reported that isolated, permeabilized Plasmodium chabaudi, releases Ca(2+) upon addition of exogenous IP(3). In the present study, we investigated whether the IP(3) signaling pathway operates in intact Plasmodium falciparum, the major disease-causing human malaria parasite. P. falciparum-infected red blood cells (RBCs) in the trophozoite stage were simultaneously loaded with the Ca(2+) indicator Fluo-4/AM and caged-IP(3). Photolytic release of IP(3) elicited a transient Ca(2+) increase in the cytosol of the intact parasite within the RBC. The intracellular Ca(2+) pools of the parasite were selectively discharged, using thapsigargin to deplete endoplasmic reticulum (ER) Ca(2+) and the antimalarial chloroquine to deplete Ca(2+) from acidocalcisomes. These data show that the ER is the major IP(3)-sensitive Ca(2+) store. Previous work has shown that the human host hormone melatonin regulates P. falciparum cell cycle via a Ca(2+)-dependent pathway. In the present study, we demonstrate that melatonin increases inositol-polyphosphate production in intact intraerythrocytic parasite. Moreover, the Ca(2+) responses to melatonin and uncaging of IP(3) were mutually exclusive in infected RBCs. Taken together these data provide evidence that melatonin activates PLC to generate IP(3) and open ER-localized IP(3)-sensitive Ca(2+) channels in P. falciparum. This receptor signaling pathway is likely to be involved in the regulation and synchronization of parasite cell cycle progression.
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Affiliation(s)
- Eduardo Alves
- Department of Pharmacology and Physiology, UMDNJ, New Jersey Medical School, Newark, New Jersey 07103, USA
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96
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In vivo uptake of a haem analogue Zn protoporphyrin IX by the human malaria parasite P. falciparum-infected red blood cells. Cell Biol Int 2010; 34:859-65. [PMID: 20491653 DOI: 10.1042/cbi20090427] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The cellular traffic of haem during the development of the human malaria parasite Plasmodium falciparum, through the stages R (ring), T (trophozoite) and S (schizonts), was investigated within RBC (red blood cells). When Plasmodium cultures were incubated with a fluorescent haem analogue, ZnPPIX (Zn protoporphyrin IX) the probe was seen at the cytoplasm (R stage), and the vesicle-like structure distribution pattern was more evident at T and S stages. The temporal sequence of ZnPPIX uptake by P. falciparum-infected erythrocytes shows that at R and S stages, a time-increase acquisition of the porphyrin reaches the maximum fluorescence distribution after 60 min; in contrast, at the T stage, the maximum occurs after 120 min of ZnPPIX uptake. The difference in time-increase acquisition of the porphyrin is in agreement with a maximum activity of haem uptake at the T stage. To gain insights into haem metabolism, recombinant PfHO (P. falciparum haem oxygenase) was expressed, and the conversion of haem into BV (biliverdin) was detected. These findings point out that, in addition to haemozoin formation, the malaria parasite P. falciparum has evolved two distinct mechanisms for dealing with haem toxicity, namely, the uptake of haem into a cellular compartment where haemozoin is formed and HO activity. However, the low Plasmodium HO activity detected reveals that the enzyme appears to be a very inefficient way to scavenge the haem compared with the Plasmodium ability to uptake the haem analogue ZnPPIX and delivering it to the food vacuole.
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97
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Levano-Garcia J, Dluzewski AR, Markus RP, Garcia CRS. Purinergic signalling is involved in the malaria parasite Plasmodium falciparum invasion to red blood cells. Purinergic Signal 2010; 6:365-72. [PMID: 21437007 DOI: 10.1007/s11302-010-9202-y] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Accepted: 09/30/2010] [Indexed: 10/18/2022] Open
Abstract
UNLABELLED Plasmodium falciparum, the most important etiological agent of human malaria, is endowed with a highly complex cell cycle that is essential for its successful replication within the host. A number of evidence suggest that changes in parasite Ca(2+) levels occur during the intracellular cycle of the parasites and play a role in modulating its functions within the RBC. However, the molecular identification of Plasmodium receptors linked with calcium signalling and the causal relationship between Ca(2+) increases and parasite functions are still largely mysterious. We here describe that increases in P. falciparum Ca(2+) levels, induced by extracellular ATP, modulate parasite invasion. In particular, we show that addition of ATP leads to an increase of cytosolic Ca(2+) in trophozoites and segmented schizonts. Addition of the compounds KN62 and Ip5I on parasites blocked the ATP-induced rise in [Ca(2+)](c). Besides, the compounds or hydrolysis of ATP with apyrase added in culture drastically reduce RBC infection by parasites, suggesting strongly a role of extracellular ATP during RBC invasion. The use of purinoceptor antagonists Ip5I and KN62 in this study suggests the presence of putative purinoceptor in P. falciparum. In conclusion, we have demonstrated that increases in [Ca(2+)](c) in the malarial parasite P. falciparum by ATP leads to the modulation of its invasion of red blood cells. ELECTRONIC SUPPLEMENTARY MATERIAL The online version of this article (doi:10.1007/s11302-010-9202-y) contains supplementary material, which is available to authorized users.
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98
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McQueen PG. Population dynamics of a pathogen: the conundrum of vivax malaria. Biophys Rev 2010; 2:111-120. [PMID: 20730124 PMCID: PMC2920408 DOI: 10.1007/s12551-010-0034-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Accepted: 06/25/2010] [Indexed: 11/27/2022] Open
Abstract
Building a mathematical model of population dynamics of pathogens within their host involves considerations of factors similar to those in ecology, as pathogens can prey on cells in the host. But within the multicellular host, attacked cell types are integrated with other cellular systems, which in turn intervene in the infection. For example, immune responses attempt to sense and then eliminate or contain pathogens, and homeostatic mechanisms try to compensate for cell loss. This review focuses on modeling applied to malarias, diseases caused by single-cell eukaryote parasites that infect red blood cells, with special concern given to vivax malaria, a disease often thought to be benign (if sometimes incapacitating) because the parasite only attacks a small proportion of red blood cells, the very youngest ones. However, I will use mathematical modeling to argue that depletion of this pool of red blood cells can be disastrous to the host if growth of the parasite is not vigorously check by host immune responses. Also, modeling can elucidate aspects of new field observations that indicate that vivax malaria is more dangerous than previously thought.
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Affiliation(s)
- Philip G. McQueen
- Mathematical and Statistical Computing Laboratory, Division of Computational Bioscience, Center for Information Technology, National Institutes of Health, 12 South Drive, Bethesda, MD 20892-5620 USA
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Abstract
One of the most important public health problems in the world today is the emergence and dissemination of drug-resistant malaria parasites. Plasmodium falciparum is the causative agent of the most lethal form of human malaria. New anti-malarial strategies are urgently required, and their design and development require the identification of potential therapeutic targets. However, the molecular mechanisms controlling the life cycle of the malaria parasite are still poorly understood. The published genome sequence of P. falciparum and previous studies have revealed that several homologues of eukaryotic signalling proteins, such as protein kinases, are relatively conserved. Protein kinases are now widely recognized as important drug targets in protozoan parasites. Cyclic AMP-dependent protein kinase (PKA) is implicated in numerous processes in mammalian cells, and the regulatory mechanisms of the cAMP pathway have been characterized. P. falciparum cAMP-dependent protein kinase plays an important role in the parasite's life cycle and thus represents an attractive target for the development of anti-malarial drugs. In this review, we focus on the P. falciparum cAMP/PKA pathway to provide new insights and an improved understanding of this signalling cascade.
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100
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Shapiro HM, Ulrich H. Cytometry in malaria: From research tool to practical diagnostic approach? Cytometry A 2010; 77:500-1. [DOI: 10.1002/cyto.a.20903] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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