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Kobpornchai P, Imwong M, Kulkeaw K. Trio fluorophore-based phenotypic assay for the detection of artemisinin-induced growth-arrested Plasmodium falciparum in human erythrocytes. Sci Rep 2024; 14:1802. [PMID: 38245618 PMCID: PMC10799909 DOI: 10.1038/s41598-024-52414-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2023] [Accepted: 01/18/2024] [Indexed: 01/22/2024] Open
Abstract
Artemisinin combination therapy remains effective for the treatment of falciparum malaria. However, Plasmodium falciparum can escape the effects of artemisinin by arresting their growth. The growth-arrested parasites cannot be distinguished from nonviable parasites with standard microscopy techniques due to their morphological similarities. Here, we demonstrated the efficacy of a new laboratory assay that is compatible with the artemisinin susceptibility test. As a result of the differential cell permeabilities of two DNA-binding fluorophores, growth-arrested P. falciparum can be distinguished from parasites killed by artemisinin, since the latter lose cell membrane permeability. This fluorescence-based assay increased the sensitivity and specificity of the ring survival assay in the assessment of artemisinin susceptibility. When combined with a third fluorophore-conjugated anti-human leukocyte antibody, this trio fluorophore assay became more useful in identifying growth-arrested parasites in mock human blood samples. This novel assay is a simple and rapid technique for monitoring artemisinin resistance with greater sensitivity and accuracy compared with morphology-based observations under a light microscope.
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Affiliation(s)
- Porntida Kobpornchai
- Siriraj Integrative Center for Neglected Parasitic Diseases, Department of Parasitology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, 10700, Thailand
- Siriraj-Long Read Lab, Department of Bioinformatics, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, 10700, Thailand
| | - Mallika Imwong
- Department of Molecular Tropical Medicine and Genetics, Faculty of Tropical Medicine, Mahidol University, Bangkok, 10700, Thailand
| | - Kasem Kulkeaw
- Siriraj Integrative Center for Neglected Parasitic Diseases, Department of Parasitology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, 10700, Thailand.
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2
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Lin M, Song X, Zuo R, Zheng Y, Hu S, Gao S, Chen L, Zhu Y, Xu X, Liu M, Zhang J, Jiang S, Guo D. Nano-encapsulation of halofuginone hydrobromide enhances anticoccidial activity against Eimeria tenella in chickens. Biomater Sci 2023; 11:1725-1738. [PMID: 36648120 DOI: 10.1039/d2bm01543a] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Coccidiosis is a worldwide epidemic intestinal disease with high incidence, which causes huge economic losses. Halofuginone hydrobromide (HF) is widely applied as an effective anticoccidial drug in the poultry industry. However, its therapeutic efficacy is severely restrained due to toxic effects, poor aqueous solubility and low permeability. Nanotechnology can improve the biological effect of drugs, and thus, reduce administered doses and toxic effects. The objective of this study was to investigate the therapeutic and preventive potential of novel HF-loaded D-α-tocopherol polyethylene glycol 1000 succinate (TPGS) polymer micelles (HTPM) for preventing coccidiosis in chickens. The HTPM were approximately spherical with a hydrodynamic diameter of 12.65 ± 0.089 nm, a zeta potential of 8.03 ± 0.242 mV, a drug loading of 14.04 ± 0.12%, and an encapsulation efficiency of 71.1 ± 4.15%. HF was encapsulated in the polymer micelles through interactions with TPGS, as characterized by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. Cellular take up assays showed that TPGS polymer micelles could enhance drug internalization to alleviate intestinal apoptosis induced by coccidiosis and promote the necrosis of second-generation merozoites of E. tenella. Notably, clinical trials proved that 1.5 mg L-1 HTPM had a stronger anticoccidial effect on E. tenella than that of 3 mg kg-1 HF premix. Amplicon sequencing identified that HTPM could alleviate coccidiosis by restoring the structure of the gut microbiome. These findings indicated that the anticoccidial efficacy of HF was significantly enhanced after being encapsulated in polymer micelles, and further demonstrated the potential protective application of nano-encapsulating anticoccidial drugs as a promising approach to control coccidiosis in poultry. In summary, HTPM hold huge potential as an effective therapeutic agent for coccidiosis.
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Affiliation(s)
- Mengjuan Lin
- Engineering Center of Innovative Veterinary Drugs, Center for Veterinary Drug Research and Evaluation, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China. .,MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China
| | - Xinhao Song
- Engineering Center of Innovative Veterinary Drugs, Center for Veterinary Drug Research and Evaluation, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China. .,MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China
| | - Runan Zuo
- Engineering Center of Innovative Veterinary Drugs, Center for Veterinary Drug Research and Evaluation, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China. .,MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China
| | - Yuling Zheng
- Engineering Center of Innovative Veterinary Drugs, Center for Veterinary Drug Research and Evaluation, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China. .,MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China
| | - Shiheng Hu
- Engineering Center of Innovative Veterinary Drugs, Center for Veterinary Drug Research and Evaluation, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China. .,MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China
| | - Shasha Gao
- Engineering Center of Innovative Veterinary Drugs, Center for Veterinary Drug Research and Evaluation, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China. .,MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China
| | - Lu Chen
- Engineering Center of Innovative Veterinary Drugs, Center for Veterinary Drug Research and Evaluation, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China. .,MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China
| | - Yuan Zhu
- Engineering Center of Innovative Veterinary Drugs, Center for Veterinary Drug Research and Evaluation, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China. .,MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China
| | - Xiaolin Xu
- Engineering Center of Innovative Veterinary Drugs, Center for Veterinary Drug Research and Evaluation, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China. .,MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China
| | - Moxin Liu
- Engineering Center of Innovative Veterinary Drugs, Center for Veterinary Drug Research and Evaluation, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China. .,MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China
| | - Junren Zhang
- Engineering Center of Innovative Veterinary Drugs, Center for Veterinary Drug Research and Evaluation, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China. .,MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China
| | - Shanxiang Jiang
- Engineering Center of Innovative Veterinary Drugs, Center for Veterinary Drug Research and Evaluation, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China. .,MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China
| | - Dawei Guo
- Engineering Center of Innovative Veterinary Drugs, Center for Veterinary Drug Research and Evaluation, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China. .,MOE Joint International Research Laboratory of Animal Health and Food Safety, College of Veterinary Medicine, Nanjing Agricultural University, 1 Weigang, Nanjing 210095, China
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3
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Singh V, Hada RS, Jain R, Vashistha M, Kumari G, Singh S, Sharma N, Bansal M, Poonam, Zoltner M, Caffrey CR, Rathi B, Singh S. Designing and development of phthalimides as potent anti-tubulin hybrid molecules against malaria. Eur J Med Chem 2022; 239:114534. [PMID: 35749989 DOI: 10.1016/j.ejmech.2022.114534] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 06/06/2022] [Accepted: 06/11/2022] [Indexed: 11/03/2022]
Abstract
Constant emergence of drug-resistant Plasmodium falciparum warrants urgent need for effective and inexpensive drugs. Herein, phthalimide (Pht) analogs possessing the bioactive scaffolds, benzimidazole and 1,2,3-triazole, were evaluated for in vitro and in vivo anti-plasmodial activity without any apparent hemolysis, or cytotoxicity. Analogs 4(a-e) inhibited the growth of 3D7 and RKL-9 strains at submicromolar concentrations. Defects were observed during parasite egress from or invasion of the red blood cells. Mitochondrial membrane depolarization was measured as one of the causes of cell death. Phts 4(a-e) in combination with artemisinin exhibited two-to three-fold increased efficacy. Biophysical and biochemical analysis suggest that Pht analogs mediate plasmodial growth inhibition by interacting with tubulin protein of the parasite. Lastly, Phts 4(a-e) significantly decreased parasitemia and extended host survival in murine model Plasmodium berghei ANKA infection. Combined, the data indicate that Pht analogs should be further explored, which could offer novel value to the antimalarial drug development pipeline.
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Affiliation(s)
- Vigyasa Singh
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Rahul Singh Hada
- Department of Life Sciences, Shiv Nadar University, Gautam Buddha Nagar, UP, 201314, India
| | - Ravi Jain
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Manu Vashistha
- Advanced Instrumentation Research Facility, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Geeta Kumari
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, 110067, India
| | - Snigdha Singh
- Laboratory for Translational Chemistry and Drug Discovery, Department of Chemistry, Hansraj College, University of Delhi, Delhi, 110007, India
| | - Neha Sharma
- Laboratory for Translational Chemistry and Drug Discovery, Department of Chemistry, Hansraj College, University of Delhi, Delhi, 110007, India
| | - Meenakshi Bansal
- Laboratory for Translational Chemistry and Drug Discovery, Department of Chemistry, Hansraj College, University of Delhi, Delhi, 110007, India
| | - Poonam
- Department of Chemistry, Miranda House, University of Delhi, Delhi, 110007, India; Delhi School of Public Health, Institute of Eminence, University of Delhi, Delhi, 110007, India
| | - Martin Zoltner
- Drug Discovery and Evaluation Unit, Department of Parasitology, Faculty of Science, Charles University, BIOCEV, Vestec, Czech Republic
| | - Conor R Caffrey
- Center for Discovery and Innovation in Parasitic Diseases, Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA
| | - Brijesh Rathi
- Laboratory for Translational Chemistry and Drug Discovery, Department of Chemistry, Hansraj College, University of Delhi, Delhi, 110007, India; Delhi School of Public Health, Institute of Eminence, University of Delhi, Delhi, 110007, India.
| | - Shailja Singh
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi, 110067, India.
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4
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Ding L, Wen Y, Zhang X, Zhao F, Lv K, Shi JH, Shen S, Pan X. Transcriptional network constituted of CBP, Ku70, NOX2, and BAX prevents the cell death of necrosis, paraptosis, and apoptosis in human melanoma. Cell Death Discov 2021; 7:40. [PMID: 33637687 PMCID: PMC7910564 DOI: 10.1038/s41420-021-00417-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2020] [Revised: 01/03/2021] [Accepted: 02/03/2021] [Indexed: 11/20/2022] Open
Abstract
CREB-binding protein (CBP) is an acetyltransferase known to play multiple roles in the transcriptions of genes involving oxidative metabolism, cell cycle, DNA damage checkpoints, and cell death. In this study, CBP was found to positively regulate the expression of Ku70, and both CBP and Ku70 were found to negatively regulate the expression of NOX2, therefore, mitigating the intracellular ROS in human melanoma. Knocking down CBP or Ku70 induced necrotic and paraptotic cell death as indicated by high-level intracellular ROS, cytoplasmic vacuolization, and cell cycle arrest in the S phase. In addition, chromosomal condensations were also observed in the cells proceeding necrotic and paraptotic cell death, which was found to be related to the BAX-associated intrinsic pathway of apoptotic cell death, when Ku70 was decreased either by CBP depletion or by Ku70 depletion directly. Our results, therefore, supported the idea that CBP, Ku70, BAX, and NOX2 have formed a transcriptional network in the prevention of cell death of necrosis, paraptosis, and apoptosis in human melanoma.
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Affiliation(s)
- Liang Ding
- School of Medicine, Hebei University, Baoding, 071002, China
| | - Yalei Wen
- School of Medicine, Hebei University, Baoding, 071002, China
| | - Xin Zhang
- School of Medicine, Hebei University, Baoding, 071002, China
| | - Fang Zhao
- School of Medicine, Hebei University, Baoding, 071002, China
| | - Kenao Lv
- School of Life Science, Beijing Institute of Technology, Beijin, 100081, China
| | - Jian-Hong Shi
- Central Laboratory, Affiliated Hospital of Hebei University, Baoding, 071002, China
| | - Shigang Shen
- School of Chemistry and environmental Science, Hebei University, Baodin, 071002, China
| | - Xuefeng Pan
- School of Medicine, Hebei University, Baoding, 071002, China. .,School of Life Science, Beijing Institute of Technology, Beijin, 100081, China. .,School of Chemistry and environmental Science, Hebei University, Baodin, 071002, China.
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5
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High-Content Screening of the Medicines for Malaria Venture Pathogen Box for Plasmodium falciparum Digestive Vacuole-Disrupting Molecules Reveals Valuable Starting Points for Drug Discovery. Antimicrob Agents Chemother 2018; 62:AAC.02031-17. [PMID: 29311064 DOI: 10.1128/aac.02031-17] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 12/20/2017] [Indexed: 02/06/2023] Open
Abstract
Plasmodium falciparum infections leading to malaria have severe clinical manifestations and high mortality rates. Chloroquine (CQ), a former mainstay of malaria chemotherapy, has been rendered ineffective due to the emergence of widespread resistance. Recent studies, however, have unveiled a novel mode of action in which low-micromolar levels of CQ permeabilized the parasite's digestive vacuole (DV) membrane, leading to calcium efflux, mitochondrial depolarization, and DNA degradation. These phenotypes implicate the DV as an alternative target of CQ and suggest that DV disruption is an attractive target for exploitation by DV-disruptive antimalarials. In the current study, high-content screening of the Medicines for Malaria Venture (MMV) Pathogen Box (2015) was performed to select compounds which disrupt the DV membrane, as measured by the leakage of intravacuolar Ca2+ using the calcium probe Fluo-4 AM. The hits were further characterized by hemozoin biocrystallization inhibition assays and dose-response half-maximal (50%) inhibitory concentration (IC50) assays across resistant and sensitive strains. Three hits, MMV676380, MMV085071, and MMV687812, were shown to demonstrate a lack of CQ cross-resistance in parasite strains and field isolates. Through systematic analyses, MMV085071 emerged as the top hit due to its rapid parasiticidal effect, low-nanomolar IC50, and good efficacy in triggering DV disruption, mitochondrial degradation, and DNA fragmentation in P. falciparum These programmed cell death (PCD)-like phenotypes following permeabilization of the DV suggests that these compounds kill the parasite by a PCD-like mechanism. From the drug development perspective, MMV085071, which was identified to be a potent DV disruptor, offers a promising starting point for subsequent hit-to-lead generation and optimization through structure-activity relationships.
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6
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Chou ES, Abidi SZ, Teye M, Leliwa-Sytek A, Rask TS, Cobbold SA, Tonkin-Hill GQ, Subramaniam KS, Sexton AE, Creek DJ, Daily JP, Duffy MF, Day KP. A high parasite density environment induces transcriptional changes and cell death in Plasmodium falciparum blood stages. FEBS J 2018; 285:848-870. [PMID: 29281179 DOI: 10.1111/febs.14370] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2016] [Revised: 12/01/2017] [Accepted: 12/20/2017] [Indexed: 12/17/2022]
Abstract
Transient regulation of Plasmodium numbers below the density that induces fever has been observed in chronic malaria infections in humans. This species transcending control cannot be explained by immunity alone. Using an in vitro system we have observed density dependent regulation of malaria population size as a mechanism to possibly explain these in vivo observations. Specifically, Plasmodium falciparum blood stages from a high but not low-density environment exhibited unique phenotypic changes during the late trophozoite (LT) and schizont stages of the intraerythrocytic cycle. These included in order of appearance: failure of schizonts to mature and merozoites to replicate, apoptotic-like morphological changes including shrinking, loss of mitochondrial membrane potential, and blebbing with eventual release of aberrant parasites from infected erythrocytes. This unique death phenotype was triggered in a stage-specific manner by sensing of a high-density culture environment. Conditions of glucose starvation, nutrient depletion, and high lactate could not induce the phenotype. A high-density culture environment induced rapid global changes in the parasite transcriptome including differential expression of genes involved in cell remodeling, clonal antigenic variation, metabolism, and cell death pathways including an apoptosis-associated metacaspase gene. This transcriptional profile was also characterized by concomitant expression of asexual and sexual stage-specific genes. The data show strong evidence to support our hypothesis that density sensing exists in P. falciparum. They indicate that an apoptotic-like mechanism may play a role in P. falciparum density regulation, which, as in yeast, has features quite distinguishable from mammalian apoptosis. DATABASE Gene expression data are available in the GEO databases under the accession number GSE91188.
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Affiliation(s)
- Evelyn S Chou
- Bio21 Institute for Molecular Science and Biotechnology and School of BioSciences, University of Melbourne, Parkville, VIC., Australia
| | - Sabia Z Abidi
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Marian Teye
- Department of Microbiology, Division of Medical Parasitology, New York University School of Medicine, NY, USA
| | - Aleksandra Leliwa-Sytek
- Department of Microbiology, Division of Medical Parasitology, New York University School of Medicine, NY, USA
| | - Thomas S Rask
- Department of Microbiology, Division of Medical Parasitology, New York University School of Medicine, NY, USA
| | - Simon A Cobbold
- Bio21 Institute for Molecular Science and Biotechnology and School of BioSciences, University of Melbourne, Parkville, VIC., Australia
| | - Gerry Q Tonkin-Hill
- Walter and Eliza Hall Institute of Medical Research, Parkville, VIC., Australia
| | - Krishanthi S Subramaniam
- Department of Parasitology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, UK
| | - Anna E Sexton
- Drug Delivery Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC., Australia
| | - Darren J Creek
- Drug Delivery Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC., Australia
| | - Johanna P Daily
- Department of Medicine, Department of Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Michael F Duffy
- Bio21 Institute for Molecular Science and Biotechnology and School of BioSciences, University of Melbourne, Parkville, VIC., Australia
| | - Karen P Day
- Bio21 Institute for Molecular Science and Biotechnology and School of BioSciences, University of Melbourne, Parkville, VIC., Australia
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7
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Plasmodium falciparum exhibits markers of regulated cell death at high population density in vitro. Parasitol Int 2016; 65:715-727. [DOI: 10.1016/j.parint.2016.07.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2016] [Revised: 07/13/2016] [Accepted: 07/14/2016] [Indexed: 11/22/2022]
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8
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Vieira WA, Coetzer TL. Localization and interactions of Plasmodium falciparum SWIB/MDM2 homologues. Malar J 2016; 15:32. [PMID: 26791088 PMCID: PMC4721021 DOI: 10.1186/s12936-015-1065-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2015] [Accepted: 12/22/2015] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND Malaria remains a global health problem and the majority of deaths are caused by Plasmodium falciparum parasites. Due to the rapid emergence of drug-resistant strains, novel avenues of research on the biology of the parasite are needed. The massive proliferation of asexual, intra-erythrocytic parasites every 48 h could kill the human host prior to transmission of slow-developing gametocytes to the mosquito vector. A self-induced P. falciparum programmed cell death mechanism has been hypothesized to maintain this balance between the parasite and its two hosts, but molecular participants of the cell death pathway in P. falciparum have not been characterized. Proteins with SWIB/MDM2 domains play a key role in metazoan programmed cell death and this study provides the first evaluation of two parasite SWIB/MDM2 homologues, PF3D7_0518200 (PfMDM2) and PF3D7_0611400 (PfSWIB). METHODS The function of these proteins was assessed by predicting their structural topology with the aid of bioinformatics and determining their location within live transgenic parasites, expressing green fluorescent protein-tagged PfMDM2 and PfSWIB under normal and elevated temperatures, which mimic fever and which are known to induce a programmed cell death response. Additionally, P. falciparum phage display library technology was used to identify binding partners for the two parasite SWIB/MDM2 domains. RESULTS Structural features of the SWIB/MDM2 domains of PfMDM2 and PfSWIB, suggested that they are chromatin remodelling factors. The N-terminal signal sequence of PfMDM2 directed the protein to the mitochondrion under both normal and heat stress conditions. Plasmodium falciparum phage display library technology revealed that the C-terminal SWIB/MDM2 domain of PfMDM2 interacted with a conserved protein containing a LisH domain. PfSWIB localized to the cytoplasm under normal growth conditions, while approximately 10% of the heat-stressed trophozoite-stage parasites presented a rapid but short-lived nuclear localization pattern. Two PfSWIB binding partners, a putative Aurora-related kinase and a member of the inner membrane complex, were identified. CONCLUSION These novel data provide insight into the function of two parasite SWIB/MDM2 homologues and suggest that PfMDM2 plays a role within the mitochondrion and that PfSWIB is involved in a stage-specific, heat-stress, response pathway.
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Affiliation(s)
- Warren Antonio Vieira
- Wits Research Institute for Malaria, Wits Medical School, 7 York Road Parktown, Johannesburg, 2193, South Africa. .,Plasmodium Molecular Research Unit, Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
| | - Thérèsa L Coetzer
- Wits Research Institute for Malaria, Wits Medical School, 7 York Road Parktown, Johannesburg, 2193, South Africa. .,Plasmodium Molecular Research Unit, Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa. .,National Health Laboratory Service, Johannesburg, South Africa.
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9
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Maduramicin Rapidly Eliminates Malaria Parasites and Potentiates the Gametocytocidal Activity of the Pyrazoleamide PA21A050. Antimicrob Agents Chemother 2015; 60:1492-9. [PMID: 26711768 DOI: 10.1128/aac.01928-15] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2015] [Accepted: 12/08/2015] [Indexed: 12/23/2022] Open
Abstract
New strategies targeting Plasmodium falciparum gametocytes, the sexual-stage parasites that are responsible for malaria transmission, are needed to eradicate this disease. Most commonly used antimalarials are ineffective against P. falciparum gametocytes, allowing patients to continue to be infectious for over a week after asexual parasite clearance. A recent screen for gametocytocidal compounds demonstrated that the carboxylic polyether ionophore maduramicin is active at low nanomolar concentrations against P. falciparum sexual stages. In this study, we showed that maduramicin has an EC50 (effective concentration that inhibits the signal by 50%) of 14.8 nM against late-stage gametocytes and significantly blocks in vivo transmission in a mouse model of malaria transmission. In contrast to other reported gametocytocidal agents, maduramicin acts rapidly in vitro, eliminating gametocytes and asexual schizonts in less than 12 h without affecting uninfected red blood cells (RBCs). Ring stage parasites are cleared by 24 h. Within an hour of drug treatment, 40% of the normally crescent-shaped gametocytes round up and become spherical. The number of round gametocytes increases to >60% by 2 h, even before a change in membrane potential as monitored by MitoProbe DiIC1 (5) is detectable. Maduramicin is not preferentially taken up by gametocyte-infected RBCs compared to uninfected RBCs, suggesting that gametocytes are more sensitive to alterations in cation concentration than RBCs. Moreover, the addition of 15.6 nM maduramicin enhanced the gametocytocidal activity of the pyrazoleamide PA21A050, which is a promising new antimalarial candidate associated with an increase in intracellular Na(+) concentration that is proposed to be due to inhibition of PfATP4, a putative Na(+) pump. These results underscore the importance of cation homeostasis in sexual as well as asexual intraerythrocytic-stage P. falciparum parasites and the potential of targeting this pathway for drug development.
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10
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Zhang Y, Zheng MX, Xu ZY, Xu HC, Cui XZ, Yang SS, Zhao WL, Li S, Lv QH, Bai R. Relationship between Eimeria tenella development and host cell apoptosis in chickens. Poult Sci 2015; 94:2970-9. [PMID: 26467006 DOI: 10.3382/ps/pev293] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2015] [Accepted: 08/19/2015] [Indexed: 01/18/2023] Open
Abstract
Coccidiosis causes considerable economic losses in the poultry industry. At present, the pathology of coccidiosis is preventable with anticoccidials and vaccination, although at considerable cost to the international poultry industry. The purpose of the present study was to elucidate the relationship between Eimeria tenella development and host cell apoptosis in chickens, which provides a theoretical basis for further study of the injury mechanism of E. tenella and the prevention and treatment of coccidiosis. Cecal epithelial cells from chick embryo were used as host cells in vitro. In addition, flow cytometry, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick-end labeling, and histopathological assays were used to detect the dynamic changes in E. tenella infection rates, DNA injury rates, and apoptosis rates in groups treated with and without the caspase-9 inhibitor Z-LEHD-FMK. Following E. tenella infection, we demonstrated that untreated cells had less apoptosis at 4 h and, inversely, more apoptosis at 24 to 120 h compared with control cells. Furthermore, after the application of Z-LEHD-FMK, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assays, and translation of phosphatidyl serines to the host cell plasma membrane surface, the treated group chick embryo cecal epithelial cells exhibited decreased apoptosis and DNA injuries (P<0.01) at 24 to 120 h. However, light microscopy showed that E. tenella infection rates of treated cells were higher (P<0.01) than untreated cells during the whole experimental period. Together, these observations suggest that E. tenella can protect host cells from apoptosis at early stages of development but can promote apoptosis during the middle to late stages. In addition, the inhibition of host cell apoptosis can be beneficial to the intracellular growth and development of E. tenella.
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Affiliation(s)
- Yan Zhang
- College of Animal Science and Technology, Shanxi Agricultural University, Taigu, 030801, China
| | - Ming-xue Zheng
- College of Animal Science and Technology, Shanxi Agricultural University, Taigu, 030801, China
| | - Zhi-yong Xu
- College of Animal Science and Technology, Shanxi Agricultural University, Taigu, 030801, China College of Animal Science, Henan Institute of Science and Technology, Xinxiang, 453003, China
| | - Huan-cheng Xu
- College of Animal Science and Technology, Shanxi Agricultural University, Taigu, 030801, China
| | - Xiao-zhen Cui
- College of Animal Science and Technology, Shanxi Agricultural University, Taigu, 030801, China
| | - Sha-sha Yang
- College of Animal Science and Technology, Shanxi Agricultural University, Taigu, 030801, China
| | - Wen-long Zhao
- College of Animal Science and Technology, Shanxi Agricultural University, Taigu, 030801, China
| | - Shan Li
- College of Animal Science and Technology, Shanxi Agricultural University, Taigu, 030801, China
| | - Qiang-hua Lv
- College of Animal Science and Technology, Shanxi Agricultural University, Taigu, 030801, China
| | - Rui Bai
- College of Animal Science and Technology, Shanxi Agricultural University, Taigu, 030801, China
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11
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Engelbrecht D, Coetzer TL. Sunlight inhibits growth and induces markers of programmed cell death in Plasmodium falciparum in vitro. Malar J 2015; 14:378. [PMID: 26419629 PMCID: PMC4588498 DOI: 10.1186/s12936-015-0867-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 08/22/2015] [Indexed: 12/20/2022] Open
Abstract
Background Plasmodium falciparum is responsible for the majority of global malaria deaths. During the pathogenic blood stages of infection, a rapid increase in parasitaemia threatens the survival of the host before transmission of slow-maturing sexual parasites to the mosquito vector to continue the life cycle. Programmed cell death (PCD) may provide the parasite with the means to control its burden on the host and thereby ensure its own survival. Various environmental stress factors encountered during malaria may induce PCD in P. falciparum. This study is the first to characterize parasite cell death in response to natural sunlight. Methods The 3D7 strain of P. falciparum was cultured in vitro in donor erythrocytes. Synchronized and mixed-stage parasitized cultures were exposed to sunlight for 1 h and compared to cultures maintained in the dark, 24 h later. Mixed-stage parasites were also subjected to a second one-hour exposure at 24 h and assessed at 48 h. Parasitaemia was measured daily by flow cytometry. Biochemical markers of cell death were assessed, including DNA fragmentation, mitochondrial membrane polarization and phosphatidylserine externalization. Results Sunlight inhibited P. falciparum growth in vitro. Late-stage parasites were more severely affected than early stages. However, some late-stage parasites survived exposure to sunlight to form new rings 24 h later, as would be expected during PCD whereby only a portion of the population dies. DNA fragmentation was observed at 24 and 48 h and preceded mitochondrial hyperpolarization in mixed-stage parasites at 48 h. Mitochondrial hyperpolarization likely resulted from increased oxidative stress. Although data suggested increased phosphatidylserine externalization in mixed-stage parasites, results were not statistically significant. Conclusion The combination of biochemical markers and the survival of some parasites, despite exposure to a lethal stimulus, support the occurrence of PCD in P. falciparum.
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Affiliation(s)
- Dewaldt Engelbrecht
- Department of Molecular Medicine and Haematology, Faculty of Health Sciences, School of Pathology, Wits Medical School, Wits Research Institute for Malaria, University of the Witwatersrand, 7th floor, 7 York Road, Parktown, Johannesburg, 2193, South Africa.
| | - Thérèsa Louise Coetzer
- Department of Molecular Medicine and Haematology, Faculty of Health Sciences, School of Pathology, Wits Medical School, Wits Research Institute for Malaria, University of the Witwatersrand, 7th floor, 7 York Road, Parktown, Johannesburg, 2193, South Africa. .,National Health Laboratory Service, Johannesburg, South Africa.
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12
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Durand PM, Choudhury R, Rashidi A, Michod RE. Programmed death in a unicellular organism has species-specific fitness effects. Biol Lett 2014; 10:20131088. [PMID: 24573154 DOI: 10.1098/rsbl.2013.1088] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Programmed cell death (PCD) is an ancient phenomenon and its origin and maintenance in unicellular life is unclear. We report that programmed death provides differential fitness effects that are species specific in the model organism Chlamydomonas reinhardtii. Remarkably, PCD in this organism not only benefits others of the same species, but also has an inhibitory effect on the growth of other species. These data reveal that the fitness effects of PCD can depend upon genetic relatedness.
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Affiliation(s)
- Pierre M Durand
- Department of Molecular Medicine and Sydney Brenner Institute for Molecular Biosciences, University of the Witwatersrand, , 7 York Road, Johannesburg 2193, South Africa
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13
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Turning up the heat: heat stress induces markers of programmed cell death in Plasmodium falciparum in vitro. Cell Death Dis 2013; 4:e971. [PMID: 24357802 PMCID: PMC3877572 DOI: 10.1038/cddis.2013.505] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 11/14/2013] [Accepted: 11/14/2013] [Indexed: 11/09/2022]
Abstract
Malaria is characterised by cyclical febrile episodes that result from the rupture of mature schizont-infected erythrocytes releasing merozoites. In patients infected with Plasmodium falciparum, fever may reach peak temperatures as high as 41 °C. Febrile episodes typically have a deleterious effect on parasites and probably benefit the host by aiding parasite clearance; however, the parasite may also gain advantage from limiting its burden on the host and prolonging infection to ensure development and transmission of slow-maturing gametocytes. Programmed cell death (PCD) may provide the parasite with a mechanism of self-limitation, although the occurrence and phenotype of PCD in the erythrocytic stages remain controversial due to conflicting data. This study aimed to characterise the cell death phenotype of P. falciparum in response to in vitro heat stress. A variety of biochemical markers of PCD, including DNA fragmentation, mitochondrial dysregulation and phosphatidylserine externalisation, as well as morphological studies of Giemsa-stained thin smears and real-time microscopy were utilised to characterise the phenotype. Heat stress decreased P. falciparum growth and development in vitro. Late-stage parasites were more susceptible, although early stages were more affected than expected. Early-stage parasites exposed to 41 °C exhibited markers of an apoptosis-like PCD phenotype, including DNA fragmentation and mitochondrial depolarisation. Heat-stressed late-stage parasites showed no significant DNA fragmentation or mitochondrial dysregulation; however, cytoplasmic vacuolisation was suggestive of an autophagy-like form of PCD. Our results therefore showed that biochemical and morphological markers of PCD varied with intra-erythrocytic parasite development and that P. falciparum exhibited facets of both apoptosis- and autophagy-like phenotypes after exposure to febrile temperatures, which may reflect a unique PCD phenotype.
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14
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Orellana MV, Pang WL, Durand PM, Whitehead K, Baliga NS. A role for programmed cell death in the microbial loop. PLoS One 2013; 8:e62595. [PMID: 23667496 PMCID: PMC3648572 DOI: 10.1371/journal.pone.0062595] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Accepted: 03/25/2013] [Indexed: 12/03/2022] Open
Abstract
The microbial loop is the conventional model by which nutrients and minerals are recycled in aquatic eco-systems. Biochemical pathways in different organisms become metabolically inter-connected such that nutrients are utilized, processed, released and re-utilized by others. The result is that unrelated individuals end up impacting each others' fitness directly through their metabolic activities. This study focused on the impact of programmed cell death (PCD) on a population's growth as well as its role in the exchange of carbon between two naturally co-occurring halophilic organisms. Flow cytometric, biochemical, ¹⁴C radioisotope tracing assays, and global transcriptomic analyses show that organic algal photosynthate released by Dunalliela salina cells undergoing PCD complements the nutritional needs of other non-PCD D. salina cells. This occurs in vitro in a carbon limited environment and enhances the growth of the population. In addition, a co-occurring heterotroph Halobacterium salinarum re-mineralizes the carbon providing elemental nutrients for the mixoheterotrophic chlorophyte. The significance of this is uncertain and the archaeon can also subsist entirely on the lysate of apoptotic algae. PCD is now well established in unicellular organisms; however its ecological relevance has been difficult to decipher. In this study we found that PCD in D. salina causes the release of organic nutrients such as glycerol, which can be used by others in the population as well as a co-occurring halophilic archaeon. H. salinarum also re-mineralizes the dissolved material promoting algal growth. PCD in D. salina was the mechanism for the flow of dissolved photosynthate between unrelated organisms. Ironically, programmed death plays a central role in an organism's own population growth and in the exchange of nutrients in the microbial loop.
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Affiliation(s)
- Mónica V. Orellana
- Institute for Systems Biology, Seattle, Washington, United States of America
- Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, Washington, United States of America
| | - Wyming L. Pang
- Institute for Systems Biology, Seattle, Washington, United States of America
- Genomatica, Inc., San Diego, California, United States of America
| | - Pierre M. Durand
- Department of Molecular Medicine, University of the Witwatersrand and National Health Laboratory Service, Parktown, South Africa
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona, United States of America
| | - Kenia Whitehead
- Institute for Systems Biology, Seattle, Washington, United States of America
- Integral Consulting Inc., Seattle, Washington, United States of America
| | - Nitin S. Baliga
- Institute for Systems Biology, Seattle, Washington, United States of America
- Department of Microbiology, University of Washington, Seattle, Washington, United States of America
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15
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Taylor-Brown E, Hurd H. The first suicides: a legacy inherited by parasitic protozoans from prokaryote ancestors. Parasit Vectors 2013; 6:108. [PMID: 23597031 PMCID: PMC3640913 DOI: 10.1186/1756-3305-6-108] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Accepted: 04/05/2013] [Indexed: 12/23/2022] Open
Abstract
It is more than 25 years since the first report that a protozoan parasite could die by a process resulting in a morphological phenotype akin to apoptosis. Since then these phenotypes have been observed in many unicellular parasites, including trypanosomatids and apicomplexans, and experimental evidence concerning the molecular pathways that are involved is growing. These observations support the view that this form of programmed cell death is an ancient one that predates the evolution of multicellularity. Here we review various hypotheses that attempt to explain the origin of apoptosis, and look for support for these hypotheses amongst the parasitic protists as, with the exception of yeast, most of the work on death mechanisms in unicellular organisms has focussed on them. We examine the role that addiction modules may have played in the original eukaryote cell and the part played by mitochondria in the execution of present day cells, looking for examples from Leishmania spp. Trypanosoma spp. and Plasmodium spp. In addition, the expanding knowledge of proteases, nucleases and other molecules acting in protist execution pathways has enabled comparisons to be made with extant Archaea and bacteria and with biochemical pathways that evolved in metazoans. These comparisons lend support to the original sin hypothesis but also suggest that present-day death pathways may have had multifaceted beginnings.
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16
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Eickel N, Kaiser G, Prado M, Burda PC, Roelli M, Stanway RR, Heussler VT. Features of autophagic cell death in Plasmodium liver-stage parasites. Autophagy 2013; 9:568-80. [PMID: 23388496 DOI: 10.4161/auto.23689] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Analyzing molecular determinants of Plasmodium parasite cell death is a promising approach for exploring new avenues in the fight against malaria. Three major forms of cell death (apoptosis, necrosis and autophagic cell death) have been described in multicellular organisms but which cell death processes exist in protozoa is still a matter of debate. Here we suggest that all three types of cell death occur in Plasmodium liver-stage parasites. Whereas typical molecular markers for apoptosis and necrosis have not been found in the genome of Plasmodium parasites, we identified genes coding for putative autophagy-marker proteins and thus concentrated on autophagic cell death. We characterized the Plasmodium berghei homolog of the prominent autophagy marker protein Atg8/LC3 and found that it localized to the apicoplast. A relocalization of PbAtg8 to autophagosome-like vesicles or vacuoles that appear in dying parasites was not, however, observed. This strongly suggests that the function of this protein in liver-stage parasites is restricted to apicoplast biology.
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Affiliation(s)
- Nina Eickel
- Institute of Cell Biology, University of Bern, Bern, Switzerland
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18
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Matthews H, Ali M, Carter V, Underhill A, Hunt J, Szor H, Hurd H. Variation in apoptosis mechanisms employed by malaria parasites: the roles of inducers, dose dependence and parasite stages. Malar J 2012; 11:297. [PMID: 22929459 PMCID: PMC3489549 DOI: 10.1186/1475-2875-11-297] [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: 06/07/2012] [Accepted: 08/24/2012] [Indexed: 12/14/2022] Open
Abstract
Background Plasmodium berghei ookinetes exhibit an apoptotic phenotype when developing within the mosquito midgut lumen or when cultured in vitro. Markers of apoptosis increase when they are exposed to nitric oxide or reactive oxygen species but high concentrations of hydrogen peroxide cause death without observable signs of apoptosis. Chloroquine and other drugs have been used to induce apoptosis in erythrocytic stages of Plasmodium falciparum and to formulate a putative pathway involving cysteine protease activation and mitochondrial membrane permeabilization; initiated, at least in the case of chloroquine, after its accumulation in the digestive vacuole causes leakage of the vacuole contents. The lack of a digestive vacuole in ookinetes prompted the investigation of the effect of chloroquine and staurosporine on this stage of the life cycle. Finally, the suggestion that apoptosis may have evolved as a strategy employed by ookinetes to increase the fitness of surviving parasites was explored by determining whether increasing the ecological triggers parasite density and nutrient depletion induced apoptosis. Methods Ookinetes were grown in culture then either exposed to hydrogen peroxide, chloroquine or staurosporine, or incubated at different densities and in different media. The proportion of ookinetes displaying positive markers for apoptosis in treated samples was compared with controls and results were analyzed using analysis of variance followed by a Turkey’s test, or a Kruskal-Wallis test as appropriate. Results Hydrogen peroxide below 50 μM triggered apoptosis but cell membranes were rapidly compromised by higher concentrations, and the mode of death could not be defined. Both chloroquine and staurosporine cause a significant increase in ookinetes with condensed chromatin, caspase-like activity and, in the case of chloroquine, phosphatidylserine translocation and DNA fragmentation (not investigated for staurosporine). However, mitochondrial membrane potential remained intact. No relationship between ookinete density and apoptosis was detected but nutrient depletion significantly increased the proportion of ookinetes with chromatin condensation in four hours. Conclusions It is proposed that both a mitochondrial and an amitochondrial apoptotic pathway may be involved, dependent upon the trigger that induces apoptosis, and that pathways may differ between erythrocytic stages and ookinetes, or between rodent and human malaria parasites.
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Affiliation(s)
- Holly Matthews
- Centre for Applied Entomology and Parasitology, Institute for Science and Technology in Medicine, School of Life Sciences, Keele University, Keele, Staffordshire, ST5 5BG, UK
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19
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Sinai AP, Roepe PD. Autophagy in Apicomplexa: a life sustaining death mechanism? Trends Parasitol 2012; 28:358-64. [PMID: 22819059 DOI: 10.1016/j.pt.2012.06.006] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Revised: 06/25/2012] [Accepted: 06/26/2012] [Indexed: 12/15/2022]
Abstract
Programmed cell death (PCD) pathways remain understudied in parasitic protozoa in spite of the fact that they provide potential targets for the development of new therapy. The best understood PCD pathway in higher eukaryotes is apoptosis although emerging evidence also points to autophagy as a mediator of death in certain physiological contexts. Bioinformatic analyses coupled with biochemical and cell biological studies suggest that parasitic protozoa possess the capacity for PCD including a primordial form of apoptosis. Recent work in Toxoplasma and emerging data from Plasmodium suggest that autophagy-related processes may serve as an additional death promoting pathway in Apicomplexa. Detailed mechanistic studies into the molecular basis for PCD in parasitic protozoa represent a fertile area for investigation and drug development.
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Affiliation(s)
- Anthony P Sinai
- Department of Microbiology, Immunology and Molecular Genetics, University of Kentucky College of Medicine, Lexington, KY 40526, USA.
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20
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Ch'ng JH, Renia L, Nosten F, Tan KSW. Can we teach an old drug new tricks? Trends Parasitol 2012; 28:220-4. [PMID: 22445323 DOI: 10.1016/j.pt.2012.02.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Revised: 02/07/2012] [Accepted: 02/08/2012] [Indexed: 11/19/2022]
Abstract
Although resistance to chloroquine (CQ) has relegated it from modern chemotherapeutic strategies to treat Plasmodium falciparum malaria, new evidence suggests that higher doses of the drug may exert a different killing mechanism and offers this drug a new lease of life. Whereas the established antimalarial mechanisms of CQ are usually associated with nanomolar levels of the drug, micromolar levels of CQ trigger a distinct cell death pathway involving the permeabilization of the digestive vacuole of the parasite and a release of hydrolytic enzymes. In this paper, we propose that this pathway is a promising antimalarial strategy and suggest that revising the CQ treatment regimen may elevate blood drug levels to trigger this pathway without increasing the incidence of adverse reactions.
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Affiliation(s)
- Jun-Hong Ch'ng
- Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
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