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Fundamental & Clinical Pharmacology Apr 2023Resistance of malaria parasites to conventionally used antimalarial drugs has necessitated the search for new potent antimalarials, especially those that can also...
Resistance of malaria parasites to conventionally used antimalarial drugs has necessitated the search for new potent antimalarials, especially those that can also ameliorate oxidative stress-mediated secondary complications. This has led to the synthesis of an antimalarial artesunate-procyanidin hybrid compound (PC14), but it has not been evaluated for its antioxidant activity. This study was carried out to evaluate the antioxidant activities of PC14 in the erythrocyte and liver of Plasmodium berghei NK65-infected mice. A hundred mice were randomly divided into 10 equal groups (A-J). Mice in Groups B-J were inoculated with P. berghei NK65 while group A mice were not inoculated. Starting from Day 3 post-inoculation, dimethyl sulfoxide (DMSO) (5%) was administered to mice in Groups A and B (normal and negative controls, respectively), while various doses of chloroquine, artesunate, procyanidin, and PC14 were administered to their respective groups for 3 days. Thereafter, antioxidant parameters were determined in the erythrocyte and liver on Days 6 and 10 post-inoculation. A significant increase (P < 0.05) was observed in malondialdehyde levels in the erythrocyte and liver of negative control on Day 10 post-inoculation compared to normal controls. Significant reduction (P < 0.05) was observed in activities of liver catalase and superoxide dismutase and erythrocyte glutathione peroxidase and glutathione-S-transferase of negative control on Days 6 and 10 compared to normal controls. However, PC14 at various doses significantly (P < 0.05) reversed these alterations. The results suggest that PC14 possesses antioxidant activity, and it enhanced antioxidant defense in the erythrocyte and liver of P. berghei-infected mice.
Topics: Animals; Mice; Antioxidants; Artesunate; Plasmodium berghei; Malaria; Proanthocyanidins; Antimalarials; Liver; Erythrocytes
PubMed: 36308068
DOI: 10.1111/fcp.12846 -
Nature Communications Dec 2023Gametogenesis in Plasmodium spp. occurs within the Anopheles mosquito and is essential for sexual reproduction / differentiation and onwards transmission to mammalian...
Gametogenesis in Plasmodium spp. occurs within the Anopheles mosquito and is essential for sexual reproduction / differentiation and onwards transmission to mammalian hosts. To better understand the 3D organisation of male gametogenesis, we used serial block face scanning electron microscopy (SBF-SEM) and serial-section cellular electron tomography (ssET) of P. berghei microgametocytes to examine key structures during male gamete formation. Our data reveals an elaborate organisation of axonemes coiling around the nucleus in opposite directions forming a central axonemal band in microgametocytes. Furthermore, we discover the nucleus of microgametes to be tightly coiled around the axoneme in a complex structure whose formation starts before microgamete emergence during exflagellation. Our discoveries of the detailed 3D organisation of the flagellated microgamete and the haploid genome highlight some of the atypical mechanisms of axoneme assembly and haploid genome organisation during male gamete formation in the malaria parasite.
Topics: Male; Animals; Plasmodium berghei; Haploidy; Germ Cells; Anopheles; Flagella; Mammals
PubMed: 38092766
DOI: 10.1038/s41467-023-43877-w -
Parasitology Research Feb 2022The search for a novel prophylactic agent against malaria is on the rise due to the negative socio-economic impact of the disease in tropical and subtropical regions of...
The search for a novel prophylactic agent against malaria is on the rise due to the negative socio-economic impact of the disease in tropical and subtropical regions of the world. Sequel to this, we evaluated the in vivo anti-Plasmodium berghei activity of a high-carbohydrate diet as well as the effects of the diet on parasite-associated anemia and organ damage. Mice were fed with either standard or a high-carbohydrate diet for 4 weeks and subsequently infected with chloroquine-sensitive strain of P. berghei. The levels of parasitemia, blood glucose, packed cell volume, and redox sensitive biomarkers of brain and liver tissues were measured. Data from this study showed that high-carbohydrate significantly (p < 0.05) aggravated the multiplication of P. berghei in the animals. Furthermore, our result demonstrated that blood glucose level in P. berghei-infected mice fed with a high-carbohydrate diet was insignificantly (p > 0.05) depleted. Additionally, our findings revealed that high-carbohydrate did not demonstrate a significant (p < 0.05) ameliorative potentials against P. berghei-induced anemia and oxidative stress in the brain and liver tissues. We concluded that high-carbohydrate diet was unable to suppress P. berghei upsurge and accordingly could not mitigate certain pathological alterations induced by P. berghei infection.
Topics: Animals; Antimalarials; Carbohydrates; Malaria; Mice; Oxidative Stress; Parasitemia; Plasmodium berghei
PubMed: 35034199
DOI: 10.1007/s00436-021-07403-5 -
Malaria Journal Nov 2019Tamoxifen is an oestrogen receptor modulator that is widely used for the treatment of early stage breast cancer and reduction of recurrences. Tamoxifen is also used as a...
BACKGROUND
Tamoxifen is an oestrogen receptor modulator that is widely used for the treatment of early stage breast cancer and reduction of recurrences. Tamoxifen is also used as a powerful research tool for controlling gene expression in the context of the Cre/loxP site-specific recombination system in conditional mutant mice.
METHODS
To determine whether the administration of tamoxifen affects Plasmodium growth and/or disease outcome in malaria, in vitro studies assessing the effect of tamoxifen and its active metabolite 4-hydroxytamoxifen on Plasmodium falciparum blood stages were performed. Tamoxifen effects were also evaluated in vivo treating C57/B6 mice infected with Plasmodium berghei (ANKA strain), which is the standard animal model for the study of cerebral malaria.
RESULTS
Tamoxifen and its active metabolite, 4-hydroxytamoxifen, show activity in vitro against P. falciparum (16.7 to 5.8 µM IC50, respectively). This activity was also confirmed in tamoxifen-treated mice infected with P. berghei, which show lower levels of parasitaemia and do not develop signs of cerebral malaria, compared to control mice. Mice treated with tamoxifen for 1 week and left untreated for an additional week before infection showed similar parasitaemia levels and signs of cerebral malaria as control untreated mice.
CONCLUSIONS
Tamoxifen and its active metabolite, 4-hydroxytamoxifen, have significant activity against the human parasite P. falciparum in vitro and the rodent parasite P. berghei in vivo. This activity may be useful for prevention of malaria in patients taking this drug chronically, but also represents a major problem for scientists using the conditional mutagenic Cre/LoxP system in the setting of rodent malaria. Allowing mice to clear tamoxifen before starting a Plasmodium infection allows the use the Cre/LoxP conditional mutagenic system to investigate gene function in specific tissues.
Topics: Animals; Antimalarials; Malaria, Cerebral; Malaria, Falciparum; Mice; Mice, Inbred C57BL; Plasmodium berghei; Plasmodium falciparum; Tamoxifen
PubMed: 31775753
DOI: 10.1186/s12936-019-3012-7 -
The Biochemical Journal Jul 2021During malarial infection, Plasmodium parasites digest human hemoglobin to obtain free amino acids for protein production and maintenance of osmotic pressure. The...
During malarial infection, Plasmodium parasites digest human hemoglobin to obtain free amino acids for protein production and maintenance of osmotic pressure. The Plasmodium M1 and M17 aminopeptidases are both postulated to have an essential role in the terminal stages of the hemoglobin digestion process and are validated drug targets for the design of new dual-target anti-malarial compounds. In this study, we profiled the substrate specificity fingerprints and kinetic behaviors of M1 and M17 aminopeptidases from Plasmodium falciparum and Plasmodium vivax, and the mouse model species, Plasmodium berghei. We found that although the Plasmodium M1 aminopeptidases share a largely similar, broad specificity at the P1 position, the P. falciparum M1 displays the greatest diversity in specificity and P. berghei M1 showing a preference for charged P1 residues. In contrast, the Plasmodium M17 aminopeptidases share a highly conserved preference for hydrophobic residues at the P1 position. The aminopeptidases also demonstrated intra-peptide sequence specificity, particularly the M1 aminopeptidases, which showed a definitive preference for peptides with fewer negatively charged intrapeptide residues. Overall, the P. vivax and P. berghei enzymes had a faster substrate turnover rate than the P. falciparum enzymes, which we postulate is due to subtle differences in structural dynamicity. Together, these results build a kinetic profile that allows us to better understand the catalytic nuances of the M1 and M17 aminopeptidases from different Plasmodium species.
Topics: Aminopeptidases; Animals; Biocatalysis; Humans; Isoenzymes; Kinetics; Leucine; Malaria; Mice; Peptides; Plasmodium; Plasmodium berghei; Plasmodium falciparum; Plasmodium vivax; Protease Inhibitors; Protozoan Proteins; Recombinant Proteins; Species Specificity; Substrate Specificity
PubMed: 34133730
DOI: 10.1042/BCJ20210172 -
Malaria Journal Jul 2021Ascariasis and malaria are highly prevalent parasitic diseases in tropical regions and often have overlapping endemic areas, contributing to high morbidity and mortality...
Concomitant experimental coinfection by Plasmodium berghei NK65-NY and Ascaris suum downregulates the Ascaris-specific immune response and potentiates Ascaris-associated lung pathology.
BACKGROUND
Ascariasis and malaria are highly prevalent parasitic diseases in tropical regions and often have overlapping endemic areas, contributing to high morbidity and mortality rates in areas with poor sanitary conditions. Several studies have previously aimed to correlate the effects of Ascaris-Plasmodium coinfections but have obtained contradictory and inconclusive results. Therefore, the present study aimed to investigate parasitological and immunopathological aspects of the lung during murine experimental concomitant coinfection by Plasmodium berghei and Ascaris suum during larvae ascariasis.
METHODS
C57BL/6J mice were inoculated with 1 × 10 P. berghei strain NK65-NY-infected red blood cells (iRBCs) intraperitoneally and/or 2500 embryonated eggs of A. suum by oral gavage. P. berghei parasitaemia, morbidity and the survival rate were assessed. On the seventh day postinfection (dpi), A. suum lung burden analysis; bronchoalveolar lavage (BAL); histopathology; NAG, MPO and EPO activity measurements; haematological analysis; and respiratory mechanics analysis were performed. The concentrations of interleukin (IL)-1β, IL-12/IL-23p40, IL-6, IL-4, IL-33, IL-13, IL-5, IL-10, IL-17A, IFN-γ, TNF and TGF-β were assayed by sandwich ELISA.
RESULTS
Animals coinfected with P. berghei and A. suum show decreased production of type 1, 2, and 17 and regulatory cytokines; low leukocyte recruitment in the tissue; increased cellularity in the circulation; and low levels of NAG, MPO and EPO activity that lead to an increase in larvae migration, as shown by the decrease in larvae recovered in the lung parenchyma and increase in larvae recovered in the airway. This situation leads to severe airway haemorrhage and, consequently, an impairment respiratory function that leads to high morbidity and early mortality.
CONCLUSIONS
This study demonstrates that the Ascaris-Plasmodium interaction is harmful to the host and suggests that this coinfection may potentiate Ascaris-associated pathology by dampening the Ascaris-specific immune response, resulting in the early death of affected animals.
Topics: Animals; Ascariasis; Ascaris suum; Coinfection; Down-Regulation; Gene Expression Regulation; Immunity, Innate; Lung; Malaria; Male; Mice; Mice, Inbred C57BL; Plasmodium berghei
PubMed: 34210332
DOI: 10.1186/s12936-021-03824-w -
Inorganic Chemistry Sep 2020A small library of "half-sandwich" cyclopentadienylruthenium(II) compounds of the general formula [(η-CR)Ru(PPh)(N-N)][PF], a scaffold hitherto absent from the toolbox...
A small library of "half-sandwich" cyclopentadienylruthenium(II) compounds of the general formula [(η-CR)Ru(PPh)(N-N)][PF], a scaffold hitherto absent from the toolbox of antiplasmodials, was screened for activity against the blood stage of CQ-sensitive 3D7-GFP, CQ-resistant Dd2, and artemisinin-resistant IPC5202 strains and the liver stage of . The best-performing compounds displayed dual-stage activity, with single-digit nanomolar IC values against blood-stage malaria parasites, nanomolar activity against liver-stage parasites, and residual cytotoxicity against HepG2 and Huh7 mammalian cells. The parasitic absorption/distribution of 7-nitrobenzoxadiazole-appended fluorescent compounds and was investigated by confocal fluorescence microscopy, revealing parasite-selective absorption in infected erythrocytes and nuclear accumulation of both compounds. The lead compound impaired asexual parasite differentiation, exhibiting fast parasiticidal activity against both ring and trophozoite stages of a synchronized culture of the 3D7 strain. These results point to cyclopentadienylruthenium(II) complexes as a highly promising chemotype for the development of dual-stage antiplasmodials.
Topics: Antimalarials; Coordination Complexes; Cyclopentanes; Drug Resistance; Erythrocytes; Hep G2 Cells; Humans; Oxadiazoles; Plasmodium berghei; Plasmodium falciparum; Ruthenium
PubMed: 32838513
DOI: 10.1021/acs.inorgchem.0c01795 -
PLoS Biology Jan 2022Anopheles gambiae melanization-based refractoriness to the human malaria parasite Plasmodium falciparum has rarely been observed in either laboratory or natural...
Anopheles gambiae melanization-based refractoriness to the human malaria parasite Plasmodium falciparum has rarely been observed in either laboratory or natural conditions, in contrast to the rodent model malaria parasite Plasmodium berghei that can become completely melanized by a TEP1 complement-like system-dependent mechanism. Multiple studies have shown that the rodent parasite evades this defense by recruiting the C-type lectins CTL4 and CTLMA2, while permissiveness to the human malaria parasite was not affected by partial depletion of these factors by RNAi silencing. Using CRISPR/Cas9-based CTL4 knockout, we show that A. gambiae can mount melanization-based refractoriness to the human malaria parasite, which is independent of the TEP1 complement-like system and the major anti-Plasmodium immune pathway Imd. Our study indicates a hierarchical specificity in the control of Plasmodium melanization and proves CTL4 as an essential host factor for P. falciparum transmission and one of the most potent mosquito-encoded malaria transmission-blocking targets.
Topics: Animals; Anopheles; CRISPR-Cas Systems; Gene Knockout Techniques; Insect Proteins; Lectins, C-Type; Melanins; Plasmodium berghei; Plasmodium falciparum
PubMed: 35025886
DOI: 10.1371/journal.pbio.3001515 -
ACS Infectious Diseases Aug 2022The need for novel antimalarials is apparent given the continuing disease burden worldwide, despite significant drug discovery advances from the bench to the bedside. In...
The need for novel antimalarials is apparent given the continuing disease burden worldwide, despite significant drug discovery advances from the bench to the bedside. In particular, small-molecule agents with potent efficacy against both the liver and blood stages of parasite infection are critical for clinical settings as they would simultaneously prevent and treat malaria with a reduced selection pressure for resistance. While experimental screens for such dual-stage inhibitors have been conducted, the time and cost of these efforts limit their scope. Here, we have focused on leveraging machine learning approaches to discover novel antimalarials with such properties. A random forest modeling approach was taken to predict small molecules with in vitro efficacy versus liver-stage parasites and a lack of human liver cell cytotoxicity. Empirical validation of the model was achieved with the realization of hits with liver-stage efficacy after prospective scoring of a commercial diversity library and consideration of structural diversity. A subset of these hits also demonstrated promising blood-stage efficacy. These 18 validated dual-stage antimalarials represent novel starting points for drug discovery and mechanism of action studies with significant potential for seeding a new generation of therapies.
Topics: Antimalarials; Humans; Malaria; Malaria, Falciparum; Plasmodium berghei; Plasmodium falciparum; Prospective Studies
PubMed: 35894649
DOI: 10.1021/acsinfecdis.2c00189 -
Cell Reports May 2022Intracellular pathogens manipulate host cells to survive and thrive. Cellular sensing and signaling pathways are among the key host machineries deregulated to favor...
Intracellular pathogens manipulate host cells to survive and thrive. Cellular sensing and signaling pathways are among the key host machineries deregulated to favor infection. In this study, we show that liver-stage Plasmodium parasites compete with the host to sequester a host endosomal-adaptor protein (APPL1) known to regulate signaling in response to endocytosis. The enrichment of APPL1 at the parasitophorous vacuole membrane (PVM) involves an atypical Plasmodium Rab5 isoform (Rab5b). Depletion of host APPL1 alters neither the infection nor parasite development; however, upon overexpression of a GTPase-deficient host Rab5 mutant (hRab5_Q79L), the parasites are smaller and their PVM is stripped of APPL1. Infection with the GTPase-deficient Plasmodium berghei Rab5b mutant (PbRab5b_Q91L) in this case rescues the PVM APPL1 signal and parasite size. In summary, we observe a robust correlation between the level of APPL1 retention at the PVM and parasite size during exoerythrocytic development.
Topics: Animals; Endocytosis; GTP Phosphohydrolases; Liver; Parasites; Plasmodium berghei
PubMed: 35649358
DOI: 10.1016/j.celrep.2022.110886