Parasite Killing Research Articles

Amentoflavone isolated from Selaginella sellowii Hieron induces mitochondrial dysfunction in Leishmania amazonensis promastigotes.

Leishmaniasis chemotherapy is a bottleneck in disease treatment. Although available, chemotherapy is limited, toxic, painful, and does not lead to parasite clearance, with parasite resistance also being reported. Therefore, new therapeutic options are being investigated, such as plant-derived anti-parasitic compounds. Amentoflavone is the most common biflavonoid in the Selaginella genus, and its antileishmanial activity has already been described on Leishmania amazonensis intracellular amastigotes but its direct action on the parasite is controversial. In this work we demonstrate that amentoflavone is active on L. amazonensis promastigotes (IC50=28.5±2.0μM) and amastigotes. Transmission electron microscopy of amentoflavone-treated promastigotes showed myelin-like figures, autophagosomes as well as enlarged mitochondria. Treated parasites also presented multiple lipid droplets and altered basal body organization. Similarly, intracellular amastigotes presented swollen mitochondria, membrane fragments in the lumen of the flagellar pocket as well as autophagic vacuoles. Flow cytometric analysis after TMRE staining showed that amentoflavone strongly decreased mitochondrial membrane potential. In silico analysis shows that amentoflavone physic-chemical, drug-likeness and bioavailability characteristics suggest it might be suitable for oral administration. We concluded that amentoflavone presents a direct effect on L. amazonensis parasites, causing mitochondrial dysfunction and parasite killing. Therefore, all results point for the potential of amentoflavone as a promising candidate for conducting advanced studies for the development of drugs against leishmaniasis.

Antimalarial Activity of Ethanol Extract of Kelakai Leaves (Stenochlaena palustris) to Parasitemia and Splenomegaly in BALB/c Mice Infected with Plasmodium berghei ANKA

Introduction: Malaria is one of global health problems. Splenomegaly is one of malaria symptoms. Antimalarial drug resistance had been reported. Alternative treatment is by using traditional medicinal plants such as kelakai (Stenochlaena palustris). Kelakai contains alkaloid and flavonoid which had been reported to have antimalarial activity. The aim of this study was to discover antimalarial activity of ethanol extract of kelakai leaves to parasitemia and splenomegaly of Plasmodium berghei ANKA in infected BALB/c mice.Methods: This study was based on a modified Peter test using BALB/c mice infected with P. berghei ANKA treated with ethanol extract of kelakai leaves, with chloroquine diphosphate as a positive control. The negative control was P. berghei ANKA infected mice without any additional treatment. Administration of ethanol extract of kelakai leaves was performed for 4 days with a serial doses of 100, 10, and 1 mg/kg body weight. The positive control was given chloroquine diphosphate 20 mg/kg body weight. Parasitemia was observed daily prior to the calculation of the percentage of parasite growth and parasite growth inhibition. At the end of the test, the mice were sacrificed and spleens were isolated to measure their sizes. Probit analysis was performed to obtain ED50 to find the effect of extract in parasite killing by 50%. Spearman test was performed to analyze the correlation of doses of extract and splenomegaly.Results: Parasitemia growth inhibition was directly proportional to the dose. Higher parasitemia inhibition was obtained at higher doses and vice versa. Result of probit analysis showed an ED50 was 77.05 mg/kg body weight. Statistical analysis resulted in insignificant correlation between doses and splenomegaly p = 1.0 (significancy < 0.05).Conclusion: Ethanol extract of kelakai leaves possessed good antimalarial activity and there was no correlation between extract doses and splenomegaly in Plasmodium berghei ANKA-infected mice.

Synthetic Perturbations in IL6 Biological Circuit Induces Dynamical Cellular Response.

Macrophage phenotype plays a crucial role in the pathogenesis of Leishmanial infection. Pro-inflammatory cytokines signals through the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway that functions in parasite killing. Suppression of cytokine signaling (SOCS) is a well-known negative feedback regulator of the JAK/STAT pathway. However, change in the expression levels of SOCSs in correlation with the establishment of infection is not well understood. IL6 is a pleotropic cytokine that induces SOCS1 and SOCS3 expression through JAK-STAT signaling. Mathematical modeling of the TLR2 and IL6 signaling pathway has established the immune axis of SOCS1 and SOCS3 functioning in macrophage polarization during the early stage of Leishmania major infection. The ratio has been quantified both in silico and in vitro as 3:2 which is required to establish infection during the early stage. Furthermore, phosphorylated STAT1 and STAT3 have been established as an immunological cross talk between TLR2 and IL6 signaling pathways. Using synthetic biology approaches, peptide based immuno-regulatory circuits have been designed to target the activity of SOCS1 which can restore pro-inflammatory cytokine expression during infection. In a nutshell, we explored the potential of synthetic biology to address and rewire the immune response from Th2 to Th1 type during the early stage of leishmanial infection governed by SOCS1/SOCS3 immune axis.

Prodrugs as new therapies against Chagas disease: in vivo synergy between Trypanosoma cruzi proline racemase inhibitors and benznidazole

Chagas disease, caused by the parasitic protozoan Trypanosoma cruzi, affects approximately 6-7 million people worldwide. There are limited available therapies and they exhibit low efficacy, often high toxicity in chronic cases and some drug resistance. In this study, our objective was to develop ester prodrugs that inhibit proline racemase (TcPRAC), a parasitic enzyme previously identified and characterised as a promising target because of its essential role in the parasite's life cycle and virulence, and to test their activity against T. cruzi. Using structural bioinformatics, we modelled several functional intermediates of the catalytic site between the opened and closed conformations of TcPRAC based on its crystal structures in complex with its competitive inhibitor, pyrrole-2-carboxylic acid. Guided by these intermediates, which were later validated in cocrystals, we designed and evaluated numerous compounds and tested them enzymatically on live parasites and in mice with our quick and straightforward drug screening method, which is based on state-of-the-art bioluminescent T. cruzi parasites injected subcutaneously. Some of our novel compounds specifically inhibited racemase activity, as determined through biochemical assays, and covalently bound to TcPRAC. Furthermore, the corresponding ester prodrugs were effective in killing parasites in vitro. Bioluminescent T. cruzi assays in mice showed that JR1531, a TcPRAC inhibitor prodrug, can kill parasites in living animals, with boosted action when combined with low doses of benznidazole. This approach, based on TcPRAC inhibitor prodrugs in association with low doses of benznidazole, may lead to more effective, specific and non-toxic therapies against Chagas disease.

HIF-α Activation Impacts Macrophage Function during Murine Leishmania major Infection.

Leishmanial skin lesions are characterized by inflammatory hypoxia alongside the activation of hypoxia-inducible factors, HIF-1α and HIF-2α, and subsequent expression of the HIF-α target VEGF-A during Leishmania major infection. However, the factors responsible for HIF-α activation are not known. We hypothesize that hypoxia and proinflammatory stimuli contribute to HIF-α activation during infection. RNA-Seq of leishmanial lesions revealed that transcripts associated with HIF-1α signaling were induced. To determine whether hypoxia contributes to HIF-α activation, we followed the fate of myeloid cells infiltrating from the blood and into hypoxic lesions. Recruited myeloid cells experienced hypoxia when they entered inflamed lesions, and the length of time in lesions increased their hypoxic signature. To determine whether proinflammatory stimuli in the inflamed tissue can also influence HIF-α activation, we subjected macrophages to various proinflammatory stimuli and measured VEGF-A. While parasites alone did not induce VEGF-A, and proinflammatory stimuli only modestly induced VEGF-A, HIF-α stabilization increased VEGF-A during infection. HIF-α stabilization did not impact parasite entry, growth, or killing. Conversely, the absence of ARNT/HIF-α signaling enhanced parasite internalization. Altogether, these findings suggest that HIF-α is active during infection, and while macrophage HIF-α activation promotes lymphatic remodeling through VEGF-A production, HIF-α activation does not impact parasite internalization or control.

HO-3867 Induces ROS-Dependent Stress Response and Apoptotic Cell Death in Leishmania donovani.

Lack of vaccine and increasing chemotherapeutic toxicities currently necessitate the development of effective and safe drugs against various forms of leishmaniases. We characterized the cellular stress induced by a novel curcumin analogue, HO-3867, encapsulated within the phosphatidylcholine-stearylamine (PC-SA) liposome for the first time against Leishmania. The liposomal formulation of HO-3867 (i.e., PC-SA/HO-3867) initiated oxidative stress-induced apoptosis in L. donovani, revealed by altered cell morphology, phosphatidylserine externalization, mitochondrial depolarization, intracellular lipid accumulation, and cell cycle arrest in promastigotes. Liposomal HO-3867 was observed to be a strong apoptosis inducer in L. donovani and L. major in a dose-dependent manner, yet completely safe for normal murine macrophages. Moreover, PC-SA/HO-3867 treatment induced L. donovani metacaspase and PARP1 activation along with downregulation of the Sir2 gene. PC-SA/HO-3867 arrested intracellular L. donovani amastigote burden in vitro, with reactive oxygen species (ROS) and nitric oxide (NO)-mediated parasite killing. These data suggest that liposomal HO-3867 represents a highly promising and non-toxic nanoparticle-based therapeutic platform against leishmaniasis inspiring further preclinical developments.

Anti-Leishmanial Effect of Oral Zinc Sulfate in Acute Cutaneous Leishmaniasis: A Mini-review

Cutaneous Leishmaniasis (CL) is an endemic parasitic infection caused by various Leishmania species, with a specific predisposition of each species into a particular geographical area. Cutaneous lesions can either be a single, limited skin lesion or multiple, large, locally destructions skin lesions. Several therapies are proposed for CL, but severe side effects, high costs, and incomplete efficacy make researchers find replaceable therapies. Since the usage of zinc sulfate as a therapeutic agent has a long history in treating of various dermatological diseases, Zinc plays an essential role in the development and function of innate immunity cells (neutrophils and natural killer cells), which play significant roles in killing parasites. It also has a significant inhibitory effect on key enzymes involved in the carbohydrate metabolism and virulence of L. major and L.tropica. Therefore, its use as an oral therapy for CL might represent a significant addition to the armamentarium of anti-leishmanial medications. This review summarizes and discusses previous and recent findings regarding the therapeutic roles of oral zinc sulfate in cutaneous leishmaniasis therapy.

Keratinocytes and Activation of TREM-1 Pathway in Cutaneous Leishmaniasis Lesions

Triggering Receptor Expressed on Myeloid Cells 1 (TREM-1) amplifies the immune response, operating synergistically with Toll-Like Receptors (TLRs) in the production of inflammatory mediators. TREM-1 signaling depends on the adapter protein DAP12, which results in the activation of NFkB, the expression of inflammatory genes, and the release of antimicrobial peptides, such as Beta-defensin 2. We evaluated the activation of the TREM-1 signaling pathways in Cutaneous Leishmaniasis (CL) caused by Leishmania braziliensis and linage human keratinocytes exposed to these parasites since the host immune response against Leishmania plays a critical role in promoting parasite killing but also participates in inflammation and tissue damage. We analyzed publicly available transcriptome data from the lesions of CL patients. In the CL biopsies, we found increased expression of the molecules involved in the TREM-1 pathway. We then validated these findings with RT-qPCR and immunohistochemistry in newly obtained biopsies. Surprisingly, we found a strong labeling of TREM-1 in keratinocytes, prompting the hypothesis that increased TREM-1 activation may be the result of tissue damage. However, increased TREM-1 expression was only seen in human lineage keratinocytes following parasite stimulation. Moreover, no up-regulation of TREM-1 expression was observed in the skin lesions caused by other non-infectious inflammatory diseases. Together, these findings indicate that L. braziliensis (Lb) induces the expression of the TREM-1 receptor in tissue keratinocytes regardless of tissue damage, suggesting that non-immune skin cells may play a role in the inflammatory response of CL.

Cell-autonomous Toxoplasma killing program requires Irgm2 but not its microbe vacuolar localization.

Interferon-inducible GTPases, such as immunity-related GTPases (IRGs) and guanylate-binding proteins (GBPs), are essential for cell-autonomous immunity against a wide variety of intracellular pathogens including Toxoplasma IRGs comprise regulatory and effector subfamily proteins. Regulatory IRGs Irgm1 and Irgm3 play important roles in anti-Toxoplasma immunity by globally controlling effector IRGs and GBPs. There is a remaining regulatory IRG, called Irgm2, which highly accumulates on parasitophorous vacuole membranes (PVMs). Very little is known about the mechanism of the unique localization on Toxoplasma PVMs. Here, we show that Irgm2 is important to control parasite killing through recruitment of Gbp1 and Irgb6, which does not require Irgm2 localization at Toxoplasma PVMs. Ubiquitination of Irgm2 in the cytosol, but not at the PVM, is also important for parasite killing through recruitment of Gbp1 to the PVM. Conversely, PVM ubiquitination and p62/Sqstm1 loading at later time points post-Toxoplasma infection require Irgm2 localization at the PVM. Irgm2-deficient mice are highly susceptible to Toxoplasma infection. Taken together, these data indicate that Irgm2 selectively controls accumulation of anti-Toxoplasma effectors to the vacuole in a manner dependent or independent on Irgm2 localization at the Toxoplasma PVM, which mediates parasite killing.

A novel nano-anti-malarial induces redox damage and elicits cytokine response to the parasite

Emergence and spread of resistant parasites to the newest chemotherapeutic anti-malarial agents are the biggest challenges against malaria control programs. Therefore, developing a novel effective treatment to reduce the overgrowing burden of multidrug resistant malaria is a pressing need. Herein, we have developed a biocompatible and biodegradable, non-toxic chitosan-tripolyphosphate-chloroquine (CS-TPP CQ) nanoparticle. CS-TPP CQ nanoparticles effectively kill the parasite through redox generation and induction of the pro- and anti-inflammatory cytokines in both sensitive and resistant parasite in vitro. The in vitro observations showed a strong inhibitory effect (p < 0.01) on pro-inflammatory cytokines more specifically on TNF-α and IFN-γ whereas CS-TPP CQ nanoparticles significantly elevated the anti-inflammatory cytokines- IL-10 and TGF-β. In addition, CS-TPP CQ nanoparticle significantly increased NO generation (p < 0.01) and altered the GSH/GSSG ratio 72 h after parasite co-culture with peripheral blood mononuclear cells culminating in the free radical induced parasite killing. CS-TPP CQ nanoparticle had an effective dose of 100 ng/ml against CQ-sensitive parasite lines (p < 0.001) whereas effective dose against CQ-resistant parasite line was 200 ng/ml CS-TPP CQ with an effective duration of 72 h (p < 0.001). Our studies suggest that CS-TPP CQ nanoparticle has a potential to modulate the pro- and anti-inflammatory responses, and to trigger the redox-mediated parasite killing. It can be a novel nano-based futuristic approach towards malaria control.

Constructing an Antiplasmodial Polypeptide in Transgenic Bacteria to Decrease Parasitemia in Plasmodium ‐infected Mosquitoes

Malaria is an infectious disease caused by parasites in the genus Plasmodium, which are transmitted by Anopheles mosquitoes. The long-term goal of this research is to create transgenic bacteria that express antiplasmodial effector proteins which can be introduced to the mosquito through a sugar solution. To test parasite killing efficiency, the mosquitoes will be blood fed on a Plasmodium berghei infected bloodmeal. Efficacy of parasite killing is determined by the number of oocysts present in the mosquito midgut after 19 days. This project aims to construct a polypeptide consisting of multiple antiplasmodial effectors to be expressed within mosquitoes. Previously, we inserted a strong terminator into the plasmid pCG18.Hem. This was achieved by inserting the terminator downstream of the bloodmeal-inducible (BMI) promoter called hemin and the antiplasmodial effector scorpine and is denoted pCG18.Hem.term. Following successful terminator insertion, the current focus of this project is to use pCG18.Hem.term as a backbone to engineer new transgenic plasmids with several different effector proteins. Two plasmids have already been successfully constructed by inserting effector peptides downstream of scorpine; pAVS1 which contains a flexible glycine-serine (Gly-Ser) linker and pAVS2 which contains both the flexible linker and the antiplasmodial effector protein SM1. Next, the focus will be to insert the flexible linker downstream of SM1 and continue inserting other antiplasmodials. This will eventually create an antiplasmodial polypeptide that can be transformed into a bacterial symbiont of mosquitoes fed to mosquitoes via a sugar solution and expressed in the midgut of the mosquito to decrease overall parasitemia.

Cell death effectors are recruited to Toxoplasma gondii parasite vacuoles targeted by interferon-inducible GTPases in infected dendritic cells

Abstract Toxoplasma gondii is an obligate intracellular pathogen whose ability to grow and evade cell autonomous immunity depends on the parasitophorous vacuole membrane (PVM). The PVM forms from the host plasma membrane during invasion and is maintained by parasite effectors. Interferon-inducible GTPases (IIGs) are central in parasite clearance, however, the precise mechanism linking IIG attack of the PVM, parasite killing and inflammatory host cell death is not clear. To identify host and parasite proteins recruited to the PVM, we used Automated Spatially Targeted Optical Micro Proteomics (AutoSTOMP), a novel discovery technique that uses a confocal microscope to visualize and photo-label proteins for identification by LC-MS. Using IFNγ to induce IIG attack of the PVM and the TLR2 ligand Pam3CSK4 to upregulate inflammasome components we examined protein recruitment to the PVM in BMDCs. AutoSTOMP identified over 300 proteins differentially enriched near the PVM of unprimed, TLR2, IFNγ and IFNγ+TLR2 treated BMDCs. To identify candidate regulators of parasite clearance, we selectively purified proteins on the PVMs coated with IIG protein GBP2. We identified the inflammasome components caspase-1 and ASC as well as the apoptotic caspases-3 and -6 on GBP2-coated PVM. This was consistent with the observation that IFNγ priming was sufficient for host cell death and parasite restriction. BMDC death was partially dependent on the Aim2, ASC, Caspase1/11 and gasdermin D, however, blocking the inflammasome didn’t impair parasite restriction. By contrast, iNOS inhibitor, was sufficient to partially rescue parasite growth. In summary, we report a new tool to study the PVM proteome and identify regulators of parasite clearance and host cell death.

Peptide-mediated leishmaniasis management strategy: Tachyplesin emerges as an effective anti-leishmanial peptide against Leishmania donovani

Visceral leishmaniasis is one of the neglected tropical diseases caused by an intracellular parasite, Leishmania donovani. Drug resistance, adverse side effects and long treatment regimes are important limitations in achieving the effective elimination of visceral leishmaniasis. In the absence of any vaccine, chemotherapy remains a viable treatment for leishmaniasis. For effective killing of leishmania parasite, the drug molecule needs to cross the cell membrane. In the present study, marine membrane-active peptide Tachyplesin has been used against Leishmania donovani. Further, the mechanism of action and importance of cysteine amino acids of Tachyplesin in anti-leishmanial activity has been assessed. The cargo-carrying ability of Tachyplesin in L. donovani has been established. Thus, dual-use of Tachyplesin as an anti-leishmanial peptide as well as a cargo delivery vehicle makes the marine peptide an attractive therapeutic target against visceral leishmaniasis.

The Intervention of the Pirfenidone with Pericyst Layer Building of the Hydatid Cyst

Hydatid disease is a zoonosis caused by Echinococcus granulosus larval stage, characterized by developing a fluid-filled hydatid cyst in any part in the body, with a particular liver and lung localization. The released hydatid cyst fluid (HCF) antigens actively induce epithelial to mesenchymal transition (EMT) in the epithelial cells surrounding the mass of the hydatid cyst, result in pericyst layer construction, which plays a vital role in preventing the antiparasitic medications from being reached to the parasite. Therefore, the current study attempted to employ the antifibrotic effect of the Pirfenidone to hinder the induced EMT by HCF antigens. For this reason, the adenocarcinomic human alveolar basal epithelial cells (A549 cell line) was used as a model system to human alveolar epithelial cells type II (AEC II) to assess the effect of the Pirfenidone on the induced EMT by HCF antigens. Different assays used to investigate the EMT induction, then Pirfenidone effect assessed using immunofluorescence assay to detect cytoskeletal markers expression prior to and after treatment. The results reached that the Pirfenidone interrupting the induced EMT in A549 cells, and thus, it may interrupt the EMT and pericyst fibrosis in the same way in the infected tissues, which would facilitate the antiparasitic drugs delivery across the cyst wall and help in parasite killing.

CCR2 Is Dispensable for Disease Resolution but Required for the Restoration of Leukocyte Homeostasis Upon Experimental Malaria-Associated Acute Respiratory Distress Syndrome.

Malaria complications are often lethal, despite efficient killing of Plasmodium parasites with antimalarial drugs. This indicates the need to study the resolution and healing mechanisms involved in the recovery from these complications. Plasmodium berghei NK65-infected C57BL/6 mice develop malaria-associated acute respiratory distress syndrome (MA-ARDS) at 8 days post infection. Antimalarial treatment was started on this day and resulted in the recovery, as measured by the disappearance of the signs of pathology, in >80% of the mice. Therefore, this optimized model represents an asset in the study of mechanisms and leukocyte populations involved in the resolution of MA-ARDS. C-C chemokine receptor type 2 (CCR2) knock-out mice were used to investigate the role of monocytes and macrophages, since these cells are described to play an important role during the resolution of other inflammatory diseases. CCR2 deficiency was associated with significantly lower numbers of inflammatory monocytes in the lungs during infection and resolution and abolished the increase in non-classical monocytes during resolution. Surprisingly, CCR2 was dispensable for the development and the resolution of MA-ARDS, since no effect of the CCR2 knock-out was observed on any of the disease parameters. In contrast, the reappearance of eosinophils and interstitial macrophages during resolution was mitigated in the lungs of CCR2 knock-out mice. In conclusion, CCR2 is required for re-establishing the homeostasis of pulmonary leukocytes during recovery. Furthermore, the resolution of malaria-induced lung pathology is mediated by unknown CCR2-independent mechanisms.

Novel Asaia bogorensis Signal Sequences for Plasmodium Inhibition in Anopheles stephensi.

Mosquitoes vector many pathogens that cause human disease, such as malaria that is caused by parasites in the genus Plasmodium. Current strategies to control vector-transmitted diseases are hindered by mosquito and pathogen resistance, so research has turned to altering the microbiota of the vectors. In this strategy, called paratransgenesis, symbiotic bacteria are genetically modified to affect the mosquito’s phenotype by engineering them to deliver antiplasmodial effector molecules into the midgut to kill parasites. One paratransgenesis candidate is Asaia bogorensis, a Gram-negative, rod-shaped bacterium colonizing the midgut, ovaries, and salivary glands of Anopheles sp. mosquitoes. However, common secretion signals from E. coli and closely related species do not function in Asaia. Here, we report evaluation of 20 native Asaia N-terminal signal sequences predicted from bioinformatics for their ability to mediate increased levels of antiplasmodial effector molecules directed to the periplasm and ultimately outside the cell. We tested the hypothesis that by increasing the amount of antiplasmodials released from the cell we would also increase parasite killing power. We scanned the Asaia bogorensis SF2.1 genome to identify signal sequences from extra-cytoplasmic proteins and fused these to the reporter protein alkaline phosphatase. Six signals resulted in significant levels of protein released from the Asaia bacterium. Three signals were successfully used to drive the release of the antimicrobial peptide, scorpine. Further testing in mosquitoes demonstrated that these three Asaia strains were able to suppress the number of oocysts formed after a blood meal containing P. berghei to a significantly greater degree than wild-type Asaia, although prevalence was not decreased beyond levels obtained with a previously isolated siderophore receptor signal sequence. We interpret these results to indicate that there is a maximum level of suppression that can be achieved when the effectors are constitutively driven due to stress on the symbionts. This suggests that simply increasing the amount of antiplasmodial effector molecules in the midgut is insufficient to create superior paratransgenic bacterial strains and that symbiont fitness must be considered as well.

The anti-parasitic drug miltefosine suppresses activation of human eosinophils and ameliorates allergic inflammation in mice.

Background and PurposeMiltefosine is an alkylphosphocholine drug with proven effectiveness against various types of parasites and cancer cells. Miltefosine is not only able to induce direct parasite killing but also modulates host immunity, for example by reducing the severity of allergies in patients. To date, there are no reports on the effect of miltefosine on eosinophils, central effector cells involved in allergic inflammation.Experimental ApproachWe tested the effect of miltefosine on the activation of human eosinophils and their effector responses in vitro and in mouse models of eosinophilic migration and ovalbumin‐induced allergic lung inflammation.Key ResultsThe addition of miltefosine suppressed several eosinophilic effector reactions such as CD11b up‐regulation, degranulation, chemotaxis and downstream signalling. Miltefosine significantly reduced the infiltration of immune cells into the respiratory tract of mice in an allergic cell recruitment model. Finally, in a model of allergic inflammation, treatment with miltefosine resulted in an improvement of lung function parameters.Conclusion and ImplicationsOur observations suggest a strong modulatory activity of miltefosine in the regulation of eosinophilic inflammation in vitro and in vivo. Our data underline the potential efficacy of miltefosine in the treatment of allergic diseases and other eosinophil‐associated disorders and may raise important questions regarding the immunomodulatory effect of miltefosine in patients treated for leishmania infections.

Anti-parasitic effect of lacquer tree Rhus verniciflua Stokes lignum against Miamiensis avidus (Ciliophora: Scuticociliatida)

Scuticociliatosis is a disease in marine fishes worldwide, especially in olive flounder (Paralichthys olivaceus), and is caused by the ciliate Miamiensis avidus (syn. Philasterides dicentrarchi). To find an effective preventive measure against M. avidus, the usefulness of lignum extract from Rhus verniciflua Stokes (RVS; lacquer tree) was investigated. The maximum anti-parasitic activity and extraction yield for RVS lignum were optimised using response surface methodology with the three-factor–three-level Box–Behnken design model (BBD). The optimised extract (OE) contained major active compounds of gallic acid, fustin, and fisetin at concentrations of 3.07 ± 0.06%, 19.77 ± 0.42%, and 2.52 ± 0.02%, respectively. An in vitro parasite killing study showed that the minimum lethal concentration of OE was 225 ppm, whereas that of individual compounds was 100 ppm for gallic acid, 500 ppm for fustin, and 1000 ppm for fisetin. The in vivo experimental results showed that fish that were fed OE-incorporated feed at 100 mg/kg body weight/day for 1–2 weeks had significant preventive efficacy against M. avidus without any toxic effect. Thus, the OE of RVS lignum can act as an effective and safe natural therapeutic agent to control M. avidus in cultured olive flounder.

Microwave‐assisted synthesis of 2‐styrylquinoline‐4‐carboxylic acid derivatives to improve the toxic effect against Leishmania (Leishmania) amazonensis

The identification of new compounds is urgent to develop safe and efficacious candidates for leishmaniasis treatment, especially from natural products as a potential source of active molecules against neglected tropical parasite diseases. Inspired by the efficacious quinoline alkaloid microbial effects, we have previously reported the synthesis and biological activity of 2‐phenylquinoline‐4‐carboxylic acids and poly‐substituted quinolines against parasites. In this work, a series of eighteen 2‐styryl‐4‐quinolinecarboxylic acids were synthesized under microwave irradiation settings obtaining from good to excellent yields (60%‐90%), shorter reaction times (2 minutes), and eco‐friendly experimental conditions. All these products were evaluated against infective forms of Leishmania (Leishmania) amazonensis, such as promastigotes and intracellular amastigotes, based on cytotoxicity assays, including host macrophage infection assays. Compounds 4 and 5 possessing a 2‐chloro or 4‐chlorostyryl moiety, respectively, were considered the most promising antileishmanial agents due to the parasite killing effect in intracellular forms inside infected macrophages. Thus, our results revealed that the 2‐styryl‐4‐quinolinecarboxylic acid backbone structure was essential for the activity against intracellular pathogens like L. (L.) amazonensis.

Synthesis,in vitroanti-plasmodial potency,in-silico-cum-SPR binding with inhibition ofPfPyridoxal synthase and rapid parasiticidal action by 3,5-bis{(E) arylidene}-N-methyl-4-piperidones

DANMPs have been identified as new pharmacophores that have the ability to targetPfPyridoxal synthase and cause rapid killing of the malaria parasite.