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Background: The rapid spread of drug-resistant strains of protozoan parasites required the urgent need for new effective drugs. Natural products offer a variety of chemical structures, which make them a valuable source of lead compounds for the development of such new drugs. Cerrado is the second largest biome in Brazil and has the richest flora of all the world savannahs. We selected Qualea grandiflora, a plant species known for its proprieties in folk medicine and its antibacterial activity. Objective: However, its antiprotozoal activity was not yet explored. Materials and Methods: We investigated the activities of fractions from the ethyl acetate extract of Q. grandiflora leaves against human life forms of Plasmodium falciparum, Trypanosoma cruzi, and Trypanosoma brucei gambiense, and for its cytotoxicity upon the rat L6-myoblast cell line. Ten fractions were produced by ethyl acetate:hexane chromatography. Results and Conclusion: The fractions showed no cytotoxicity against L-6 cells (IC50 > 100 µg/mL) and no hemolysis propriety. Three fractions had a moderate activity against P. falciparum, anyone was active against T. cruzi but four fractions demonstrated a high activity against bloodstream forms of T. brucei gambiense (8.0< IC50 <15 µg/mL). Identification and characterization of the active compounds are currently under investigation. [ABSTRACT FROM AUTHOR]

The threatened Brazilian Cerrado biome is an important biodiversity hotspot but still few explored that constitutes a potential reservoir of molecules to treat infectious diseases. We selected eight Cerrado plant species for screening against the erythrocytic stages of Plasmodium falciparum, human intracellular stages of Trypanosoma cruzi and bloodstream forms of T. brucei gambiense, and for their cytotoxicity upon the rat L6-myoblast cell line. Bioassays were performed with 37 hexane, ethyl acetate and ethanol extracts prepared from different plant organs. Activities against parasites were observed for 24 extracts: 9 with anti-P. falciparum, 4 with anti-T. cruzi and 11 with anti-T. brucei gambiense activities. High anti-protozoal activity (IC50 values < 10 μg/mL) without obvious cytotoxicity to L6 cells was observed for eight extracts from plants: Connarus suberosus, Blepharocalyx salicifolius, Psidium laruotteanum and Myrsine guianensis. Overall, studies of plant extracts will contribute to increase the biodiversity knowledge essential for Cerrado conservation and sustainable development. [ABSTRACT FROM AUTHOR]

Radikale Wirkung: Ferroquin ist ein Ferrocen ‐ basiertes Analogon des Antimalariamittels Chloroquin. Wie Fluoreszenzsonden in infizierten roten Blutzellen zeigen, läuft zusätzlich zum primären Mechanismus der Chinolinwirkung noch ein anderer Mechanismus ab. Er beruht auf der Bildung von HO. in der sauren und oxidierenden Umgebung der Verdauungsvakuole des Malariaparasiten und könnte bewirken, dass mit Ferroquin eine Reinvasion verhindert werden kann. [ABSTRACT FROM AUTHOR]

Background: The relationship between malaria and obesity are largely unknown. This is partly due to the fact that malaria occurs mainly in tropical areas where, until recently, obesity was not prevalent. It now appears, however, that obesity is emerging as a problem in developing countries. To investigate the possible role of obesity on the host-parasite response to malarial infection, this study applied a murine model, which uses the existence of genetically well characterized obese mice. Methods: The receptivity of obese homozygous ob/ob mice was compared to the receptivity of control heterozygous ob/+ lean mice after a single injection of Plasmodium berghei ANKA sporozoites. Both parasitaemia and mortality in response to infection were recorded. Results: The control mice developed the expected rapid neurological syndromes associated with the ANKA strain, leading to death after six days, in absence of high parasitaemia. The obese mice, on the other hand, did not develop cerebral malaria and responded with increasing parasitaemia, which produced severe anemia leading to death 18-25 days after injection. Conclusion: The observed major differences in outward symptoms for malarial infection in obese versus control mice indicate a link between obesity and resistance to the infection which could be addressed by malariologists studying human malaria. [ABSTRACT FROM AUTHOR]

Abstract: Four new ether diglycosides (1–4), named matayosides A–D, were isolated from the root bark of Matayba guianensis, a plant exhibiting in vitro antiplasmodial activity. They were identified as hexadecyl-[O-2,3,4-tri-O-acetyl-α-l-rhamnopyranosyl-(1→2)]-6-O-palmitoyl-β-d-glucopyranoside, hexadecyl-[O-2,3,4-tri-O-acetyl-α-l-rhamnopyranosyl-(1→2)]-4,6-di-O-acetyl-β-d-glucopyranoside, hexadecyl-[O-2,3,4-tri-O-acetyl-α-l-rhamnopyranosyl-(1→2)]-3,6-di-O-acetyl-β-d-glucopyranoside and hexadecyl-[O-2,3,4-tri-O-acetyl-α-l-rhamnopyranosyl-(1→2)]-6-O-acetyl-β-d-glucopyranoside, respectively. Their structures were established using one- and two-dimensional NMR techniques, mass spectrometry (MS) and MS/MS experiments. The compounds were found to inhibit the growth of Plasmodium falciparum in vitro with IC50 values ranging from 2.5 to 8.9μg/mL. [Copyright &y& Elsevier]

Background: Sphingolipids are key molecules regulating many essential functions in eukaryotic cells and ceramide plays a central role in sphingolipid metabolism. A sphingolipid metabolism occurs in the intraerythrocytic stages of Plasmodium falciparum and is associated with essential biological processes. It constitutes an attractive and potential target for the development of new antimalarial drugs. Methods: The anti-Plasmodium activity of a series of ceramide analogs containing different linkages (amide, methylene or thiourea linkages) between the fatty acid part of ceramide and the sphingoid core was investigated in culture and compared to the sphingolipid analog PPMP (d,1-threo-1-phenyl-2-palmitoylamino-3-morpholino-1-propanol). This analog is known to inhibit the parasite sphingomyelin synthase activity and block parasite development by preventing the formation of the tubovesicular network that extends from the parasitophorous vacuole to the red cell membrane and delivers essential extracellular nutrients to the parasite. Results: Analogs containing methylene linkage showed a considerably higher anti-Plasmodium activity (IC50 in the low nanomolar range) than PPMP and their counterparts with a natural amide linkage (IC50 in the micromolar range). The methylene analogs blocked irreversibly P. falciparum development leading to parasite eradication in contrast to PPMP whose effect is cytostatic. A high sensitivity of action towards the parasite was observed when compared to their effect on the human MRC-5 cell growth. The toxicity towards parasites did not correlate with the inhibition by methylene analogs of the parasite sphingomyelin synthase activity and the tubovesicular network formation, indicating that this enzyme is not their primary target. Conclusions: It has been shown that ceramide analogs were potent inhibitors of P. falciparum growth in culture. Interestingly, the nature of the linkage between the fatty acid part and the sphingoid core considerably influences the antiplasmodial activity and the selectivity of analogs when compared to their cytotoxicity on mammalian cells. By comparison with their inhibitory effect on cancer cell growth, the ceramide analogs might inhibit P. falciparum growth through modulation of the endogenous ceramide level. [ABSTRACT FROM AUTHOR]

We previously showed that injection of recombinant human group IIA secreted phospholipase A 2 (hGIIA sPLA 2) to Plasmodium chabaudi -infected mice lowers parasitaemia by 20%. Here, we show that transgenic (TG) mice overexpressing hGIIA sPLA 2 have a peak of parasitaemia about 30% lower than WT littermates. During infection, levels of circulating sPLA 2 , enzymatic activity and plasma lipid peroxidation were maximal at day-14, the peak of parasitaemia. Levels of hGIIA mRNA increased in liver but not in spleen and blood cells, suggesting that liver may contribute as a source of circulating hGIIA sPLA 2. Before infection, baseline levels of leukocytes and pro-inflammatory cytokines were higher in TG mice than WT littermates. Upon infection, the number of neutrophils, lymphocytes and monocytes increased and were maximal at the peak of parasitaemia in both WT and TG mice, but were higher in TG mice. Similarly, levels of the Th1 cytokines IFN-γ and IL-2 increased in WT and TG mice, but were 7.7- and 1.7-fold higher in TG mice. The characteristic shift towards Th2 cytokines was observed during infection in both WT and TG mice, with increased levels of IL-10 and IL-4 at day-14. The current data are in accordance with our previous in vitro findings showing that hGIIA kills parasites by releasing toxic lipids from oxidized lipoproteins. They further show that hGIIA sPLA 2 is induced during mouse experimental malaria and has a protective in vivo role, lowering parasitaemia by likely releasing toxic lipids from oxidized lipoproteins but also indirectly by promoting a more sustained innate immune response. [Display omitted] • Mice overexpressing hGIIA sPLA 2 (TG) are more resistant to Plasmodium infection. • Infected TG mice have high levels of hGIIA and oxidized lipoproteins. • Infected TG mice have high levels of host defence pro-inflammatory cytokines. • Likely mechanism 1: hGIIA releases parasiticidal lipids from oxidized lipoproteins. • Likely mechanism 2: hGIIA boosts host innate immunity against Plasmodium. [ABSTRACT FROM AUTHOR]

In our search for new protein farnesyltransferase inhibitors with improved antiparasitic activities, we modified our previously developed 3-arylthiophene series of inhibitors by replacing the thio iso propyl group by different substituted imidazolylmethanamino moieties. Twenty four new derivatives were synthesized and evaluated against human and parasite farnesyltransferases, and their anti-parasitic activity was determined against Plasmodium falciparum , Trypanosoma brucei , Trypanosoma cruzi , and Leishmania donovani . Introduction of a N-p -substituted-benzylimidazole led to significantly increase the inhibition of parasite proliferation in the submicromolar range. The structure of the best inhibitors was parasite dependent. Three compounds possess IC 50 values at the same range as the reference miltefosine against L. donovani proliferation and other new derivatives display high level of anti-trypanosomal activity against T. cruzi , higher or in the same order of magnitude as the reference compounds benznidazole and nifurtimox. [ABSTRACT FROM AUTHOR]

Abstract: Protein farnesyltransferase (FTase) has recently appeared as a new target of parasitic diseases, a field poor in drugs in development. With the aim of creating new bisubstrate inhibitors of FTase, new farnesyl pyrophosphate analogues have been studied. Farnesyl analogues with a malonic acid function exhibited the best inhibitory activity on FTase. This group was introduced into our imidazole-containing model leading to new compounds with submicromolar activities. Kinetic experiments have been realized to determine their binding mode to the enzyme. [Copyright &y& Elsevier]

Abstract: A series of new piperazine derivatives of ursolic acid was synthesized and tested against Plasmodium falciparum strains. They were also tested on their cytotoxicity effects upon MRC-5 cells. Seven new piperazinyl analogues showed significant activity in the nanomolar range (IC50 =78–167nM) against Plasmodium falciparum CQ-resistant strain FcB1. A possible mechanism of interaction implicating binding of these compounds to β-hematin was supported by in vitro tests. Moreover, the importance of the hydrophilic framework attached at the terminal nitrogen atom of the bis-(3-aminopropyl)piperazine joined to the triterpene ring was also explored through molecular dynamic simulations. [Copyright &y& Elsevier]

Abstract: Dynamin superfamily members are large GTPases conserved through evolution mainly described as mechanochemical enzymes involved in membrane scission events. The Plasmodium falciparum dynamin-2 (Pfdyn2) gene was cloned from the FcB1 strain. PfDYN2 belongs to the dynamin-like protein subgroup of the dynamin superfamily since it possesses a large GTPase domain together with the conserved dynamin_M and GED domains. Recombinant PfDYN2 was able to bind GTP, to hydrolyze GTP into GDP and to self-associate in low-salt conditions. PfDYN2 expression was restricted to schizonts where it localized in punctuate structures within the parasite cytoplasm. PfDYN2 partly co-localized with markers of the parasite endoplasmic reticulum, Golgi apparatus and apicoplast, suggesting it could be implicated in vesicular trafficking and/or organelle fission events known to occur during the last hours of the parasite development in erythrocytes. PfDYN2 and the previously described PfDYN1 are the only two dynamin superfamily members identified in the P. falciparum genome and the available data suggest that this situation is conserved in the Apicomplexa phylum. [Copyright &y& Elsevier]

Abstract: We have previously reported the isolation of a 52,000 M r protein (Pf52) displaying consensus sequences for thiol:disulfide oxidoreductases. Pf52 therefore represents the plasmodial protein disulfide isomerase (PDI). It has been renamed PfPDI and correlates to MAL8P1.17 in the annotated genome of P. falciparum (3D7 strain). Antibodies were raised against recombinant (His)6-tagged forms of PfPDI devoid of its signal peptide sequence, demonstrating a major co-localization of PfPDI with endoplasmic reticulum-resident proteins, PfBIP and PfERC, but not with the Golgi marker PfERD2. Recombinant PfPDI displayed typical biochemical functions of PDIs: oxidase/isomerase and reductase activities, as well as a chaperone-like behavior on the denaturated protein rhodanese. These activities were comparable to those measured for the purified native bovine PDI and the human recombinant PDI. The antiplasmodial compound DS61 does inhibit the recombinant PfPDI oxidase/isomerase activity but not that of the human recombinant PDI, suggesting structural differences between both enzymes. However, a discrepancy between the inhibitory activity of DS61 on the recombinant PfPDI (IC50 of 430μM) and its in vitro antiplasmodial activity (IC50 of 0.1μM) was observed, suggesting that PfPDI is not the only target of DS61. Taking into account its biochemical properties and its intracellular localization, the involvement of PfPDI in the parasite protein folding is discussed, as well as its potential for the development of alternative antimalarial chemotherapy strategies. [Copyright &y& Elsevier]

Abstract: Malaria is a major global public health problem and the alarming spread of drug resistance and limited number of effective drugs now available underline how important it is to discover new antimalarial compounds. An ethnopharmacological investigation was undertaken of medicinal plants traditionally used to treat malaria in the South Vietnam. Forty-nine plants were identified, 228 extracts were prepared and tested for their in vitro activity against Plasmodium falciparum, and assessed for any cytotoxicity against the human cancer cell line HeLa and the embryonic lung MRC5 cell line. In a first screening at a concentration of 10μg/ml, 92 extracts from 46 plants showed antiplasmodial activity (parasite growth inhibition >30%). The IC50 values of the most active extracts were determined as well as their selectivity towards Plasmodium falciparum in comparison to their cytotoxic effects against the human cell lines. Six plants showed interesting antiplasmodial activity (IC50 ranging from 0.4 to 8.6μg/ml) with a good selectivity: two Menispermaceae, Arcangelisia flava (L.) Merr. and Fibraurea tinctoria Lour., and also Harrisonia perforata (Blanco) Merr. (Simaroubaceae), Irvingia malayana Oliv. ex Benn. (Irvingiaceae), Elaeocarpus kontumensis Gagn. (Elaeocarpaceae) and Anneslea fragrans Wall. (Theaceae). [Copyright &y& Elsevier]

Abstract: A library of acylhydrazone iron chelators was synthesized and tested for its ability to inhibit the growth of a chloroquine-resistant strain of Plasmodium falciparum. Some of these new compounds are significantly more active than desferrioxamine DFO, the iron chelator in widespread clinical use and also than the most effective chelators. [Copyright &y& Elsevier]

The antimalarial activity of 22 xanthones against chloroquino-resistant strains of Plasmodium falciparum was evaluated. Natural caloxanthone C (1), demethylcalabaxanthone (2), calothwaitesixanthone (3), calozeyloxanthone (4), dombakinaxanthone (5), macluraxanthone (6), and 6-deoxy-γ-mangostin (7) were isolated from Calophyllum caledonicum. 1,6-dihydroxyxanthone (8), pancixanthone A (9), isocudraniaxanthone B (10), isocudraniaxanthone A (11), 2-deprenylrheediaxanthone B (12) and 1,4,5-trihydroxyxanthone (13) were isolated from Garcinia vieillardii. Moreover, synthetic compounds (14–22) are analogues or intermediates of xanthones purified from Calophyllum caledonicum (Oger J.M., Morel C., Hélesbeux J.J., Litaudon M., Séraphin D., Dartiguelongue C., Larcher G., Richomme P., Duval O. 2003. First 2-Hydroxy-3-Methylbut-3-Enyl substituted xanthones isolated from Plants: structure elucidation, synthesis and antifungal activity. Natural Product Research 17(3), 195–199; Hélesbeux J.J., Duval O., Dartiguelongue C., Séraphin D., Oger J.M., Richomme P., 2004. Synthesis of 2-hydroxy-3-methylbut-3-enyl substituted coumarins and xanthones as natural products. Application of the Schenck ene reaction of singlet oxygen with ortho-prenylphenol precursors. Tetrahedron 60(10), 2293–2300). The relationship between antimalarial activity and molecular structure of xanthones has also been explored. The most potent xanthones (2), (3) and (7) (IC50 = c.a. 1.0 μg/mL) are 1,3,7 trioxygenated and prenylated on the positions 2 and 8. [Copyright &y& Elsevier]

Plasmodium blood stages, responsible for human to vector transmission, termed gametocytes, are the precursor cells that develop into gametes in the mosquito. Male gametogenesis works as a bottleneck for the parasite life cycle, where, during a peculiar and rapid exflagellation, a male gametocyte produces 8 intracellular axonemes that generate by budding 8 motile gametes. Understanding the molecular mechanisms of gametogenesis is key to design strategies for controlling malaria transmission. In the rodent P. berghei , the microtubule-based motor kinesin-8B (PbKIN8B) is essential for flagellum assembly during male gametogenesis and its gene disruption impacts on completion of the parasitic life cycle. In efforts to improve our knowledge about male gametogenesis, we performed an iTRAQ-based quantitative proteomic comparison of P. berghei mutants with disrupted kinesin-8B gene (Δ Pbkin8B) and wild type parasites. During the 15 min of gametogenesis, Δ Pbkin8B parasites exhibited important motor protein dysregulation that suggests an essential role of PbKIN8B for the correct interaction or integration of axonemal proteins within the growing axoneme. The energy metabolism of Δ Pbkin8B mutants was further affected, as well as the response to stress proteins, protein synthesis, as well as chromatin organisation and DNA processes, although endomitoses seemed to occur. Malaria continues to be a global scourge, mainly in subtropical and tropical areas. The disease is caused by parasites from the Plasmodium genus. Plasmodium life cycle alternates between female Anopheles mosquitoes and vertebrate hosts through bites. Gametocytes are the parasite blood forms responsible for transmission from vertebrates to vectors. Inside the mosquito midgut, after stimulation, male and female gametocytes transform into gametes resulting in fertilization. During male gametogenesis, one gametocyte generates eight intracytoplasmic axonemes that generate, by budding, flagellated motile gametes involving a process termed exflagellation. Sexual development has a central role in ensuring malaria transmission. However, molecular data on male gametogenesis and particularly on intracytoplasmic axoneme assembly are still lacking. Since rodent malaria parasites permit the combination of in vivo and in vitro experiments and reverse genetic studies, our group investigated the molecular events in rodent P. berghei gametogenesis. The P. berghei motor ATPase kinesin-8B is proposed as an important component for male gametogenesis. We generated Pbkin 8B gene-disrupted gametocytes (Δ Pbkin8B) that were morphologically similar to the wild- type (WT) parasites. However, in mutants, male gametogenesis is impaired, male gametocytes are disabled in their ability to assemble axonemes and to exflagellate to release gametes, reducing fertilization drastically. Using a comparative quantitative proteomic analysis, we associated the nonfunctional axoneme of the mutants with the abnormal differential expression of proteins essential to axoneme organisation and stability. We also observed a differential dysregulation of proteins involved in protein biosynthesis and degradation, chromatin organisation and DNA processes in Δ Pbkin8B parasites, although DNA condensation, mitotic spindle formation and endomitoses seem to occur. This is the first functional proteomic study of a kinesin gene-disrupted Plasmodium parasite providing new insights into Plasmodium male gametogenesis. Unlabelled Image • First functional proteomic analysis of kinesin8B gene-disrupted Plasmodium parasites. • 148 and 61 proteins restrictedly detected in Δ Pbkin8B and WT parasites, respectively. • Absence of PbKIN8B results in abundance dysregulation of axonemal-associated proteins during gametogenesis. • PBKIN8B role for the correct interaction of axonemal proteins within the growing axoneme. [ABSTRACT FROM AUTHOR]