Inhibition Of Parasite Growth Research Articles

Effect of Titanium Dioxide Nanoparticles (Tio2NPs) on Entamoeba gingivalis in vitro

The effect of Titanium Dioxide Nanoparticals (Tio2NPs) on Entamoeba gingivalis in vitro were studied,which isolated from gums in gingivitis patients who attended the periodontal disease department at the Faculty Dentistry of Mosul University for the period from 1/4/2018 to 31/7/2018. In our study three different concentrations of (Tio2NPs) were prepared as the following order: (0.1, 0.01, 0.001) mg/ml and evaluated the effect of these different concentrations through (2,4,6) hours. Results showed that time factor and the increasing of the appositive effect on the parasite killing and the highest concentration (0.1mg/ml) had a role in inhibition of parasite growth and reduced parasite survival rate to (3.60±0.953) compared to the other concentrations. Also in this present study we found the concentration (0.1 mg/ml) was the highest inhibition of parasite (86.73%) in the time period at (6 hours) compared to other concentrations and periods time which showed slight differences between them.

Effect of some Materials and Drugs on Entamoeba gingivalis Culture

The aim of this study was to investigate the effects of some materials and drugs on Entamoeba gingivalis culture which was isolated from gums in gingivitis patients who attended to the periodental disease department at the college of Dentistry/ Mosul University, at the period from August to October 2018. Five different concentrations of Flagyl, Ketamine, Bowsella and Apignein were prepared then added to the culture media of the parasite at three periods (2, 4, 6) hours. as (0.0001, 0.0002, 0.0004, 0.0008, 0.0016) microgram/ml. Statistical analysis showed that there were significant difference between concentrations and time which showed that best concentrations were 0.0016 mg/ml for Flagyl, Ketamine, Apignein which inhibit parasite growth as (0.0, 4.73j, 9.53g) respectively also reduced parasite survival rate at (100%, 72.81%, 54.4%) respectively in the time period at (6 hours) while Bowsella at 0.0008 mg/ml inhibition of parasite growth to (5.47l) also reduced parasite survival rate to (72.04%) compared together concentrations and time periods (2, 4) hours which showed slight differences between them.

Natural Product Inspired Novel Indole based Chiral Scaffold Kills Human Malaria Parasites via Ionic Imbalance Mediated Cell Death

Natural products offer an abundant source of diverse novel scaffolds that inspires development of next generation anti-malarials. With this vision, a library of scaffolds inspired by natural biologically active alkaloids was synthesized from chiral bicyclic lactams with steps/scaffold ratio of 1.7:1. On evaluation of library of scaffolds for their growth inhibitory effect against malaria parasite we found one scaffold with IC50 in low micro molar range. It inhibited parasite growth via disruption of Na+ homeostasis. P-type ATPase, PfATP4 is responsible for maintaining parasite Na+ homeostasis and is a good target for anti-malarials. Molecular docking with our scaffold showed that it fits well in the binding pocket of PfATP4. Moreover, inhibition of Na+-dependent ATPase activity by our potent scaffold suggests that it targets parasite by inhibiting PfATP4, leading to ionic imbalance. However how ionic imbalance attributes to parasite’s death is unclear. We show that ionic imbalance caused by scaffold 7 induces autophagy that leads to onset of apoptosis in the parasite evident by the loss of mitochondrial membrane potential (ΔΨm) and DNA degradation. Our study provides a novel strategy for drug discovery and an insight into the molecular mechanism of ionic imbalance mediated death in malaria parasite.

Diketopiperazine alkaloids produced by the endophytic fungus Penicillium citrinum and evaluation of their antileishmanial activity

Chromatographic fractionation of the antileishmanial extract obtained from fermentation of the endophytic fungus Penicillium citrinum, isolated from leaves of Ageratum myriadenia, yielded three diketopiperazine alkaloids; cyclo(L-Pro-L-Leu) (1), cyclo-(L-Pro-L-Phe) (2) and tryprostatin B (3). The structures of these compounds were established on the basis of spectroscopic methods and comparison with the literature. Compounds 1 and 2 were active against both amastigote-like forms of Leishmania (Leishmania) amazonensis and intracelular amastigotes of L. (Leishmania) infantum with approximately 50% of parasite growth inhibition at 100 μM. None of the compounds were considered toxic against human leukemia monocyte cell line (THP-1) at 100 μM. It is the first report about isolation of these diketopiperazines from P. citrinum and their antileishmanial potential against L. (L.) infantum. Key words: Microfungi, natural products, in vitro, Leishmania, amphotericin B, cytotoxic activity.

Nitric oxide-loaded chitosan nanoparticles as an innovative antileishmanial platform

Leishmaniasis is a neglected tropical disease that demands for new therapeutic strategies due to adverse side effects and resistance development promoted by current drugs. Nitric oxide (NO)-donors show potential to kill Leishmania spp. but their use is limited because of their instability. In this work, we synthesize, characterize, and encapsulate S-nitroso-mercaptosuccinic acid into chitosan nanoparticles (NONPs) and investigate their activity on promastigotes and intracellular amastigotes of Leishmania (Leishmania) amazonensis. Cytotoxicity on macrophages was also evaluated. We verified that NONPs reduced both forms of the parasite in a single treatment. We also noticed reduction of parasitophorous vacuoles as an evidence of inhibition of parasite growth and resolution of infection. No substantial cytotoxicity was detected on macrophages. NONPs were able to provide a sustained parasite killing for both L. (L.) amazonensis infective stages with no toxicity on macrophages, representing a promising nanoplatform for cutaneous leishmaniasis.

Chemical Genomic Profiling Unveils the in Vitro and in Vivo Antiplasmodial Mechanism of Açaí (Euterpe oleracea Mart.) Polyphenols.

Malaria remains a major detrimental parasitic disease in the developing world, with more than 200 million cases annually. Widespread drug-resistant parasite strains push for the development of novel antimalarial drugs. Plant-derived natural products are key sources of antimalarial molecules. Euterpe oleracea Martius (“açaí”) originates from Brazil and has anti-inflammatory and antineoplasic properties. Here, we evaluated the antimalarial efficacy of three phenolic fractions of açaí; total phenolics (1), nonanthocyanin phenolics (2), and total anthocyanins (3). In vitro, fraction 2 moderately inhibited parasite growth in chloroquine-sensitive (HB3) and multiresistant (Dd2) Plasmodium falciparum strains, while none of the fractions was toxic to noncancer cells. Despite the limited activity in vitro, the oral treatment with 20 mg/kg of fraction 1 reduced parasitemia by 89.4% in Plasmodium chabaudi-infected mice and prolonged survival. Contrasting in vitro and in vivo activities of 1 suggest key antiplasmodial roles for polyphenol metabolites rather than the fraction itself. Finally, we performed haploinsufficiency chemical genomic profiling (HIP) utilizing heterozygous Saccharomyces cerevisiae deletion mutants to identify molecular mechanisms of açaí fractions. HIP results indicate proteostasis as the main cellular pathway affected by fraction 2. These results open avenues to develop açaí polyphenols as potential new antimalarial candidates.

Serologic Markers of Previous Malaria Exposure and Functional Antibodies Inhibiting Parasite Growth Are Associated With Parasite Kinetics Following a Plasmodium falciparum Controlled Human Infection.

BackgroundWe assessed the impact of exposure to Plasmodium falciparum on parasite kinetics, clinical symptoms, and functional immunity after controlled human malaria infection (CHMI) in 2 cohorts with different levels of previous malarial exposure.MethodsNine adult males with high (sero-high) and 10 with low (sero-low) previous exposure received 3200 P. falciparum sporozoites (PfSPZ) of PfSPZ Challenge by direct venous inoculation and were followed for 35 days for parasitemia by thick blood smear (TBS) and quantitative polymerase chain reaction. Endpoints were time to parasitemia, adverse events, and immune responses.ResultsTen of 10 (100%) volunteers in the sero-low and 7 of 9 (77.8%) in the sero-high group developed parasitemia detected by TBS in the first 28 days (P = .125). The median time to parasitemia was significantly shorter in the sero-low group than the sero-high group (9 days [interquartile range {IQR} 7.5–11.0] vs 11.0 days [IQR 7.5–18.0], respectively; log-rank test, P = .005). Antibody recognition of sporozoites was significantly higher in the sero-high (median, 17.93 [IQR 12.95–24] arbitrary units [AU]) than the sero-low volunteers (median, 10.54 [IQR, 8.36–12.12] AU) (P = .006). Growth inhibitory activity was significantly higher in the sero-high (median, 21.8% [IQR, 8.15%–29.65%]) than in the sero-low group (median, 8.3% [IQR, 5.6%–10.23%]) (P = .025).ConclusionsCHMI was safe and well tolerated in this population. Individuals with serological evidence of higher malaria exposure were able to better control infection and had higher parasite growth inhibitory activity.Clinical Trials RegistrationNCT03496454.

An ImmunoPEGliposome for Targeted Antimalarial Combination Therapy at the Nanoscale.

Combination therapies, where two drugs acting through different mechanisms are administered simultaneously, are one of the most efficient approaches currently used to treat malaria infections. However, the different pharmacokinetic profiles often exhibited by the combined drugs tend to decrease treatment efficacy as the compounds are usually eliminated from the circulation at different rates. To circumvent this obstacle, we have engineered an immunoliposomal nanovector encapsulating hydrophilic and lipophilic compounds in its lumen and lipid bilayer, respectively. The antimalarial domiphen bromide has been encapsulated in the liposome membrane with good efficiency, although its high IC50 of ca. 1 µM for living parasites complicates its use as immunoliposomal therapy due to erythrocyte agglutination. The conjugation of antibodies against glycophorin A targeted the nanocarriers to Plasmodium-infected red blood cells and to gametocytes, the sole malaria parasite stage responsible for the transmission from the human to the mosquito vector. The antimalarials pyronaridine and atovaquone, which block the development of gametocytes, have been co-encapsulated in glycophorin A-targeted immunoliposomes. The co-immunoliposomized drugs have activities significantly higher than their free forms when tested in in vitro Plasmodium falciparum cultures: Pyronaridine and atovaquone concentrations that, when encapsulated in immunoliposomes, resulted in a 50% inhibition of parasite growth had no effect on the viability of the pathogen when used as free drugs.

Ethyl acetate Fraction of Garcinia Mangostana L Rind Study as Antimalaria and Antioxidant in Plasmodium berghei Inoculated Mice.

BACKGROUND:Drug resistance to malaria is still a problem in various regions, and there have even been developments in resistance to the ACTs (artemisinin-based combination therapies) as standard antimalarial drugs included to artemisinin’s partner drugs. Ethyl acetate fraction of G. mangostana L rind, containing xanthones as an antioxidant, has antimalarial activity in vitro which has a synergistic effect with artemisinin. That’s why the activities of this fraction are needed to be studied in vivo.AIM:To explore the antimalarial and antioxidant activity of ethyl acetate fraction of Garcinia mangostana L rind in mice.METHODS:This was a complete randomised design true experimental study. Six groups of mice: a healthy mice group and 5 groups of Plasmodium berghei inoculated mice treated with various doses of the sample for 3 days compared to artemisinin. Parasitemia and total antioxidant status were examined and analysed using ANOVA, and probit analysis were done.RESULTS:The parasitemia level in all of the treatment groups were lower than the positive control group without treatment (p < 0.01) and the parasitemia level was the lowest in artemisinin group which was not significantly different from the 100 mg/kg body weight dose group (p > 0.05). The parasitemia level in 20 and 4 mg/kg body weight dose groups were higher than the artemisinin group (p < 0.01). Parasite growth inhibition rate from the highest to the lowest consecutively was: artemisinin, 100 mg/kg body weight, 20 mg/kg body weight, 4 mg/kg body weight, and positive control group (p < 0.05) and ED50 was 3.396 mg/kg body weight. Total antioxidant status was the highest in 20 mg/ kg body weight dose and higher than the negative control group (p < 0.05) while the lowest total antioxidant status was in the positive control group.CONCLUSION:Ethyl acetate fraction of G. mangostana L rind potentially showed antimalarial and antioxidant activity in vivo. Further study is needed to explore the detail of its mechanism of action and its quantitative phytochemical analysis to find the leading compound in it.

Bioprospection for antiplasmodial activity, and identification of bioactive metabolites of native plants species from the Mata Atlântica biome, Brazil

A total of 33 extracts of eleven different plants species from Mata Atlântica biome, Brazil, and different fractions of the bioactive extracts were evaluated against chloroquine-resistant Plasmodium falciparum W2 strain by PfLDH method and cytotoxicity to HepG2 cells by the MTT assay, and chemically characterized by LC-DAD-ESI-MS/MS analysis. The results allowed the identification of Alchornea glandulosa, Miconia latecrenata, and Psychotria suterella as the most active plant species. Different flavonoids and tannins in Alchornea glandulosa and Miconia latecrenata besides alkaloids in Psychotria suterella were identified. Bioguided fractionation of A. glandulosa and M. latecrenata leaves extracts led to fractions exhibiting high parasite growth inhibition. Seven known alkaloids were identified in the P. suterella extract, and of these, only 5-carboxystrictosidine had been assayed for antiplasmodial activity what points to this species as the most promising among the eleven one assayed.

Modelling pathogen load dynamics to elucidate mechanistic determinants of host-Plasmodium falciparum interactions.

SummaryDuring infection, increasing pathogen load stimulates both protective and harmful aspects of the host response. The dynamics of this interaction are hard to quantify in humans, but doing so could improve understanding of mechanisms of disease and protection. We sought to model the contributions of parasite multiplication rate and host response to observed parasite load in individual subjects with Plasmodium falciparum malaria, using only data obtained at the time of clinical presentation, and then to identify their mechanistic correlates. We predicted higher parasite multiplication rates and lower host responsiveness in severe malaria cases, with severe anemia being more insidious than cerebral malaria. We predicted that parasite growth-inhibition was associated with platelet consumption, lower expression of CXCL10 and type-1 interferon-associated genes, but increased cathepsin G and matrix metallopeptidase 9 expression. We found that cathepsin G and matrix metallopeptidase 9 directly inhibit parasite invasion into erythrocytes. Parasite multiplication rate was associated with host iron availability and higher complement factor H levels, lower expression of gametocyte-associated genes but higher expression of translation-associated genes in the parasite. Our findings demonstrate the potential of using explicit modelling of pathogen load dynamics to deepen understanding of host-pathogen interactions and identify mechanistic correlates of protection.

Repurposing Glyburide as Antileishmanial Agent to Fight Against Leishmaniasis

Leishmaniasis is caused by a protozoan parasite, Leishmania. It is common in more than 98 countries throughout the world. Due to insufficient availability of antileishmanial chemotherapeutics, it is an urgent need to search for new molecules which have better efficacy, low toxicity and are available at low cost. There is a high rate of diabetic cases throughout the world that is why we planned to test the antileishmanial activity of glyburide, an effective sugar lowering drug used for the treatment of diabetes. In this study, glyburide showed a significant decrease in the parasite growth and survival in vitro in a dose-dependent manner. Anti-leishmanial activity of glyburide was checked by culturing Leishmania donovani promastigotes in the presence of glyburide in a dose and time dependent manner. Docking study against Leishmania donovani-Trypanothione synthetase (LdTrySyn) protein was performed using Autodock Vina tool. Growth reversibility assay shows that growth of treated parasite was not reversed when transferred to fresh culture media after 7 days. Moreover, docking studies show efficient interactions of glyburide with key residues in the catalytic site of Leishmania donovani- Trypanothione synthetase (LdTrySyn), a very important leishmanial enzyme involved in parasite's survival by detoxification of Nitric Oxide (NO) species, generated by the mammalian host as a defense molecule. Thus this study proves that the drug-repurposing is a beneficial strategy for identification of new and potent antileishmanial molecules. The results suggest that glyburide binds to LdTrySyn and inhibits its activity which further leads to the altered parasite morphology and inhibition of parasite growth. Glyburide may also be used in combination with other anti-leishmanial drugs to potentiate the response of the chemotherapy. Overall this study provides information about combination therapy as well as a single drug treatment for the infected patients suffering from diabetes. This study also provides raw information for further in vivo disease model studies to confirm the hypothesis.

Identification of druggable small molecule antagonists of the Plasmodium falciparum hexose transporter PfHT and assessment of ligand access to the glucose permeation pathway via FLAG-mediated protein engineering.

Although the Plasmodium falciparum hexose transporter PfHT has emerged as a promising target for anti-malarial therapy, previously identified small-molecule inhibitors have lacked promising drug-like structural features necessary for development as clinical therapeutics. Taking advantage of emerging insight into structure/function relationships in homologous facilitative hexose transporters and our novel high throughput screening platform, we investigated the ability of compounds satisfying Lipinksi rules for drug likeness to directly interact and inhibit PfHT. The Maybridge HitFinder chemical library was interrogated by searching for compounds that reduce intracellular glucose by >40% at 10 μM. Testing of initial hits via measurement of 2-deoxyglucose (2-DG) uptake in PfHT over-expressing cell lines identified 6 structurally unique glucose transport inhibitors. WU-1 (3-(2,6-dichlorophenyl)-5-methyl-N-[2-(4-methylbenzenesulfonyl)ethyl]-1,2-oxazole-4-carboxamide) blocked 2-DG uptake (IC50 = 5.8 ± 0.6 μM) with minimal effect on the human orthologue class I (GLUTs 1–4), class II (GLUT8) and class III (GLUT5) facilitative glucose transporters. WU-1 showed comparable potency in blocking 2-DG uptake in freed parasites and inhibiting parasite growth, with an IC50 of 6.1 ± 0.8 μM and EC50 of 5.5 ± 0.6 μM, respectively. WU-1 also directly competed for N-[2-[2-[2-[(N-biotinylcaproylamino)ethoxy)ethoxyl]-4-[2-(trifluoromethyl)-3H-diazirin-3-yl]benzoyl]-1,3-bis(mannopyranosyl-4-yloxy)-2-propylamine (ATB-BMPA) binding and inhibited the transport of D-glucose with an IC50 of 5.9 ± 0.8 μM in liposomes containing purified PfHT. Kinetic analysis revealed that WU-1 acts as a non-competitive inhibitor of zero-trans D-fructose uptake. Decreased potency for WU-1 and the known endofacial ligand cytochalasin B was observed when PfHT was engineered to contain an N-terminal FLAG tag. This modification resulted in a concomitant increase in affinity for 4,6-O-ethylidene-α-D-glucose, an exofacially directed transport antagonist, but did not alter the Km for 2-DG. Taken together, these data are consistent with a model in which WU-1 binds preferentially to the transporter in an inward open conformation and support the feasibility of developing potent and selective PfHT antagonists as a novel class of anti-malarial drugs.

Internalization of Erythrocyte Acylpeptide Hydrolase Is Required for Asexual Replication of Plasmodium falciparum.

The human malaria parasite Plasmodium falciparum causes disease as it replicates within the host's erythrocytes. We have found that an erythrocyte serine hydrolase, acylpeptide hydrolase (APEH), accumulates within developing asexual parasites. Internalization of APEH was associated with a proteolytic event that reduced the size of the catalytic polypeptide from 80 to 55 kDa. A triazole urea APEH inhibitor, termed AA74-1, was employed to characterize the role of parasite-internalized APEH. In cell lysates, AA74-1 was a potent and highly selective inhibitor of both host erythrocyte and parasite-internalized APEH. When added to cultures of ring-stage parasites, AA74-1 was a poor inhibitor of replication over one asexual replication cycle; however, its potency increased dramatically after a second cycle. This enhancement of potency was not abrogated by the addition of exogenous isopentenyl pyrophosphate, the sole essential product of apicoplast metabolism. High-potency inhibition of parasite growth could be effected by adding AA74-1 to schizont-stage parasites, which resulted in parasite death at the early trophozoite stage of the ensuing replication cycle. Analysis of APEH inhibition in intact cultured cells revealed that host erythrocyte APEH, but not the parasite-internalized APEH pool, was inhibited by exogenous AA74-1. Our data support a model for the mode of parasiticidal activity of AA74-1 whereby sustained inactivation of host erythrocyte APEH is required prior to merozoite invasion and during parasite asexual development. Together, these findings provide evidence for an essential catalytic role for parasite-internalized APEH.IMPORTANCE Nearly half a million deaths were attributed to malaria in 2017. Protozoan parasites of the genus Plasmodium cause disease in humans while replicating asexually within the host's erythrocytes, with P. falciparum responsible for most of the mortality. Understanding how Plasmodium spp. have adapted to their unique host erythrocyte environment is important for developing malaria control strategies. Here, we demonstrate that P. falciparum coopts a host erythrocyte serine hydrolase termed acylpeptide hydrolase. By showing that the parasite requires acylpeptide hydrolase activity for replication, we expand our knowledge of host cell factors that contribute to robust parasite growth.

Screening of the pathogen box for the identification of anti-Acanthamoeba agents

Acanthamoeba are free living amoeba that have been isolated from different environments like soil, water, air dust. Moreover, they are also able to act as opportunist pathogens, mainly causing a fatal encephalitis and also keratitis in both human and animals. This study was aimed to evaluate the activity of the Medicines for Malaria Venture (MMV) compounds against the trophozoite stage of Acanthamoeba castellanii Neff. Sixteen compounds showed ≥90% inhibition of parasite growth in the initial screen (10 μM). Those set were further evaluated to determine the inhibitor concentration that inhibit the 50% of the initial population and cytotoxicity against murine macrophages. Among the compounds included in the pathogen box, pentamidine and posaconazole were the most effective against this parasite with an of IC50 of 0.567 ± 0.04 and 0.630 ± 0.11, respectively.

Salivary IgA: A biomarker for resistance to Teladorsagia circumcincta and a new estimated breeding value

Teladorsagia circumcincta is the dominant nematode of sheep in cool, temperate climates. Faecal nematode egg counts (FEC) are widely used to identify the intensity of infection and as a measure of host resistance to nematodes. However due to density-dependent effects on worm fecundity the relationship between FEC and worm burden is not linear. In addition collecting FEC data is challenging on a practical level and there is a need for more reliable markers of resistance. There are two major known mechanisms of immunity to T. circumcincta: IgE against third stage larvae (L3) and IgA against fourth stage larvae (L4), which inhibits parasite growth. In this study salivary IgA responses were measured in over 5000 animals against L3 antigen by Enzyme Linked Immunosorbent Assay (ELISA). Antigen-specific IgA levels were negatively correlated with FEC (r=−0.26, SE = 0.02) and were heritable (h2 = 0.16, SE = 0.04) indicating that they can be used to identify resistant animals suitable for inclusion in selective breeding programs. Antigen-specific IgA responses were not negatively correlated with muscle depth. Our analyses indicate that selection for T. circumcincta L3 antigen-specific IgA is possible without impacting on the production traits for the Lleyn breed.

Indole-3-glyoxyl tyrosine: synthesis and antimalarial activity against Plasmodium falciparum.

More than 40% of the world's population, across 105 countries, live in malaria endemic areas. It is estimated that about 500million cases of malaria and half a million deaths occur per year. Herein, we demonstrate the biological activity of indole-3-glyoxyl tyrosine against Plasmodium falciparum, which is the causal agent of the most virulent form of malaria in humans. We developed an efficient synthesis of indole-3-glyoxyl tyrosine derivatives, which were then used as key intermediates in the synthesis of functionalized indole-3-glyoxyl biphenyl tyrosines. In biological testing, the compounds exhibited a parasite growth inhibition of over 85%. A cell viability assay showed low cytotoxicity against human cells, with no significant changes in cell viability, making these compounds potential antimalarials.

Chemical composition, antioxidant, anti-lipooxygenase, antimicrobial, anti-parasite and cytotoxic activities of Polyalthia longifolia seed oil

This work investigates the chemical compositions of Polyalthia longifolia Thw. seed oil with the associated antioxidant, anti-inflammatory, anti-parasite and cytotoxicity potentials. The oil of P. longifolia seed obtained by soxhlet extraction was trans-esterified and the fatty acid profile characterized using gas chromatography mass spectrometry (GC–MS). The antioxidant activity was evaluated using DPPH and ABTS assays. The anti-bacterial and anti-fungi properties of the oil were determine on clinical isolates of the organisms using agar diffusion method. The anti-inflammatory activities, cytotoxicity and anti-parasite potential were evaluated using lipooxygenase, mammalian cell and Toxoplasma gondii assays respectively. P. longifolia seed was observed to contain oleic (30.31%), linoleic acid (19.27%) and palmitic acid (15.11%) as the major fatty acids with low proportion of tricosylic acid (6.10) and stearic acid (5.56%). The oil had significant anti-lipooxygenase activity (IC50 = 0.70 ± 0.02 µg/mL) comparable to indomethacin (IC50 = 0.53 ± 0.07 µg/mL). The DPPH (IC50 = 55.91 ± 31.18 µg/mL) and ABTS (IC50 = 16.89 ± 15.50 µg/mL) antioxidant activity of the oil was lower to the ascorbic acid (IC50 = 0.34 ± 0.04 and 0.54 ± 0.04 µg/mL). The oil also showed activities against all the tested bacteria and fungi. The highest inhibition was recorded against S. aureus (17 ± 1 mm) at concentration 200 mg/mL. Further, the oils showed strong potential to restrict growth of Toxoplasma gondii in vitro, but the parasite growth inhibition was mildly abated in the presence of α-tocopherol. The seed oil of the underutilized P. longifolia possesses essential fatty acids which could be responsible for the numerous biological potentials which include anti-lipooxygenase, antioxidant, anti-inflammatory, anti-parasite, anti-microbial and cytotoxic activities. The incorporation of the natural oil into pharmaceuticals or cosmetics may enhance antioxidant, anti-inflammatory, antimicrobial and cytotoxicity potential of such products.

Tryptophan-kynurenine pathway attenuates \u03b2-catenin-dependent pro-parasitic role of STING-TICAM2-IRF3-IDO1 signalosome in Toxoplasma gondii infection

Recent studies have documented the diverse role of host immunity in infection by the protozoan parasite, Toxoplasma gondii. However, the contribution of the β-catenin pathway in this process has not been explored. Here, we show that AKT-mediated phosphorylated β-catenin supports T. gondii multiplication which is arrested in the deficiency of its phosphorylation domain at S552 position. The β-catenin-TCF4 protein complex binds to the promoter region of IRF3 gene and initiates its transcription, which was also abrogated in β-catenin knockout cells. TBK-independent phosphorylation of STING(S366) and its adaptor molecule TICAM2 by phospho-AKT(T308S473) augmented downstream IRF3-dependent IDO1 transcription, which was also dependent on β-catenin. But, proteasomal degradation of IDO1 by its tyrosine phosphorylation (at Y115 and Y253) favoured parasite replication. In absence of IDO1, tryptophan was catabolized into melatonin, which supressed cellular reactive oxygen species (ROS) and boosted parasite growth. Conversely, when tyrosine phosphorylation was abolished by phosphosite mutations, IDO1 escaped its ubiquitin-mediated proteasomal degradation system (UPS) and the stable IDO1 prevented parasite replication by kynurenine synthesis. We propose that T. gondii selectively utilizes tryptophan to produce the antioxidant, melatonin, thus prolonging the survival of infected cells through functional AKT and β-catenin activity for better parasite replication. Stable IDO1 in the presence of IFN-γ catabolized tryptophan into kynurenine, promoting cell death by suppressing phospho-AKT and phospho-β-catenin levels, and circumvented parasite replication. Treatment of infected cells with kynurenine or its analogue, teriflunomide suppressed kinase activity of AKT, and phosphorylation of β-catenin triggering caspase-3 dependent apoptosis of infected cells to inhibit parasite growth. Our results demonstrate that β-catenin regulate phosphorylated STING-TICAM2-IRF3-IDO1 signalosome for a cell-intrinsic pro-parasitic role. We propose that the downstream IRF3-IDO1-reliant tryptophan catabolites and their analogues can act as effective immunotherapeutic molecules to control T. gondii replication by impairing the AKT and β-catenin axis.

In Vitro Assessment of Antiplasmodial Activity and Cytotoxicity of Polyalthia longifolia Leaf Extracts on Plasmodium falciparum Strain NF54.

Background Malaria is one of the most important life-threatening infectious diseases in the tropics. In spite of the effectiveness of artemisinin-based combination therapy, reports on reduced sensitivity of the parasite to artemisinin in Cambodia and Thailand warrants screening for new potential antimalarial drugs for future use. Ghanaian herbalists claim that Polyalthia longifolia has antimalarial activity. Therefore, antiplasmodial activity, cytotoxic effects, and antioxidant and phytochemical properties of P. longifolia leaf extract were investigated in this study. Methodology/Principal Findings Aqueous, 70% hydroethanolic and ethyl acetate leaf extracts were prepared using standard procedures. Antiplasmodial activity was assessed in vitro by using chloroquine-sensitive malaria parasite strain NF54. The SYBR® Green and tetrazolium-based calorimetric assays were used to measure parasite growth inhibition and cytotoxicity, respectively, after extract treatment. Total antioxidant activity was evaluated using a free radical scavenging assay. Results obtained showed that extracts protected red blood cells against Plasmodium falciparum mediated damage. Fifty percent inhibitory concentration (IC50) values were 24.0±1.08 μg/ml, 22.5±0.12 μg/ml, and 9.5±0.69 μg/ml for aqueous, hydroethanolic, and ethyl acetate extracts, respectively. Flavonoids, tannins, and saponins were present in the hydroethanolic extract, whereas only the latter was observed in the aqueous extract. Aqueous and hydroethanolic extracts showed stronger antioxidant activities compared to the ethyl acetate extract. Conclusions/Significance The extracts of P. longifolia have antiplasmodial properties and low toxicities to human red blood cells. The extracts could be developed as useful alternatives to antimalarial drugs. These results support claims of the herbalists that decoctions of P. longifolia are useful antimalarial agents.