Antischistosomal Activity Research Articles

Schistosoma mansoni: Antischistosomal activity of the four optical isomers and the two racemates of mefloquine on schistosomula and adult worms in vitro and in vivo

Recent studies have shown that mefloquine (MQ) reveals interesting antischistosomal properties. We examined the antischistosomal activities of the erythro and threo isomers and racemates of MQ on newly transformed schistosomula (NTS) and adult Schistosoma mansoni in vitro and in mice harbouring adult S. mansoni. The in vitro effects in the presence and absence of haemin were monitored by means of microcalorimetry, scanning electron microscopy and phenotypic evaluation. Incubation of NTS with the erythro derivatives at concentrations of 3 μg/ml and above resulted in convulsions, granularity, decrease in heat flow, and death while NTS incubated with the threo derivatives were only affected at high concentrations (100 μg/ml). Extensive tegumental alterations, decrease in metabolic activity, viability, and death were observed when adult schistosomes had been exposed to 10 μg/ml of the erythro compounds. Moderate tegumental and viability changes but reduced heat production rates were observed with the threo derivatives at 10 μg/ml. In the presence of haemin, all MQ derivatives showed pronounced antischistosomal properties against adult S. mansoni in vitro. In vivo, MQ derivatives achieved statistically significant total and female worm burden reductions ranging between 65.4% and 100%. The highest total worm burden reductions of 93.4% and 90.2% were observed following treatment with the erythro and threo racemates, respectively. In conclusion, the optical isomers and racemates of MQ show only moderate stereoselectivity, in particular in vivo. Our results may enhance our understanding of the mechanism of action and therapeutic profile of MQ derivates on schistosomes.

Evaluation of the in vivo activity of different concentrations of <i>Clerodendrum umbellatum</i> poir against <i>Schistosoma mansoni</i> infection in mice

Clerodendrum umbellatum Poir (Verbenaceae) is traditionally used in Cameroon for the treatment of many diseases including intestinal helminthiasis. This study was undertaken to assess the in vivo antischistosomal activity of its leaves aqueous extract on a Schistosoma mansoni mice model and to determine the most effective dose of this extract. Mice showing a patent infection of S. mansoni were daily treated with C. umbellatum leaves aqueous extract at the doses of 40, 80 or 160 mg/kg body weight for 14 days. Seven days after administration of the extract, schistosomicidal activity was evaluated on the liver and spleen weights, faecal eggs releasing, liver egg count and worm burden. Treatment using C. umbellatum leaves aqueous extract resulted in an important reduction in faecal egg output by 75.49% and 85.14% for 80 mg/kg and 160 mg/kg of the extract respectively. These reduction rates did not differ significantly from the 100% obtained in the group of infected mice treated with 100 mg/kg of praziquantel. C. umbellatum leaves aqueous extract was lethal to S. mansoni worm. A 100% reduction rate was recorded in the group of infected mice treated with 160 mg/kg of the extract, as well as in praziquantel-treated mice. An amelioration of the hepatosplenomegaly was noticed in both the extract-treated mice and the praziquantel-treated mice. From these results, we can conclude that C. umbellatum leaves aqueous extract demonstrated schistosomicidal properties in S. mansoni model at doses of at least 80 mg/kg body weight.

Development and Validation of a Quantitative, High-Throughput, Fluorescent-Based Bioassay to Detect Schistosoma Viability

BackgroundSchistosomiasis, caused by infection with the blood fluke Schistosoma, is responsible for greater than 200,000 human deaths per annum. Objective high-throughput screens for detecting novel anti-schistosomal targets will drive ‘genome to drug’ lead translational science at an unprecedented rate. Current methods for detecting schistosome viability rely on qualitative microscopic criteria, which require an understanding of parasite morphology, and most importantly, must be subjectively interpreted. These limitations, in the current state of the art, have significantly impeded progress into whole schistosome screening for next generation chemotherapies.Methodology/Principal FindingsWe present here a microtiter plate-based method for reproducibly detecting schistosomula viability that takes advantage of the differential uptake of fluorophores (propidium iodide and fluorescein diacetate) by living organisms. We validate this high-throughput system in detecting schistosomula viability using auranofin (a known inhibitor of thioredoxin glutathione reductase), praziquantel and a range of small compounds with previously-described (gambogic acid, sodium salinomycin, ethinyl estradiol, fluoxetidine hydrochloride, miconazole nitrate, chlorpromazine hydrochloride, amphotericin b, niclosamide) or suggested (bepridil, ciclopirox, rescinnamine, flucytosine, vinblastine and carbidopa) anti-schistosomal activities. This developed method is sensitive (200 schistosomula/well can be assayed), relevant to industrial (384-well microtiter plate compatibility) and academic (96-well microtiter plate compatibility) settings, translatable to functional genomics screens and drug assays, does not require a priori knowledge of schistosome biology and is quantitative.Conclusions/SignificanceThe wide-scale application of this fluorescence-based bioassay will greatly accelerate the objective identification of novel therapeutic lead targets/compounds to combat schistosomiasis. Adapting this bioassay for use with other parasitic worm species further offers an opportunity for great strides to be made against additional neglected tropical diseases of biomedical and veterinary importance.

Bioimmunological responses to Schistosoma mansoni and Fasciola gigantica worm homogenates either with or without saponin

In this study, we evaluated the biochemical, immunological, histopathological and antischistosomal activities of Schistosoma mansoni or Fasciola gigantica worm homogenates mixed either with or without saponin that was extracted from Atriplex nummularia. The immunization schedule was based on subcutaneous administration of two doses (50 microg /100 microl PBS) of each homogenate with time intervals of 15 days. After 15 days of the last homogenate inoculation, all mice were challenged with 100 Schistosoma mansoni cercariae and sacrificed after two months. Free radical scavengers and liver function enzymes were determined in mice liver. Worm counting and the histopathological picture of the liver were also done. Immunization with Schistosoma or Fasciola worm homogenates, mixed either with or without saponin, recorded an amelioration of the free radical scavenger levels, liver function enzymes and reduction in worm burden, as well as improvement of the histological feature of the liver, the number and size of granuloma, evidence of increased immune reaction manifested by a lymphocytic cuff surrounding the granuloma, diminution of its fibrotic and collagen content, and destruction of Schistosoma ova. Fasciola or Schistosoma worm antigens mixed with or without saponin succeeded to eliminate the product of oxidative stress and assistance in immune-mediated destruction of eggs that ameliorate the histopathological picture of the liver cells and preserve its function.

Praziquantel analogs with activity against juvenile Schistosoma mansoni

Six amide and four urea derivatives of praziquantel were synthesized and tested for antischistosomal activity against juvenile and adults stages of Schistosoma mansoni in infected mice. Only one of these had significant activity against adult worms, but, unlike praziquantel, six of these had low to modest activity against juvenile worms. A praziquantel ketone derivative had the best combination of activity against juveniles and adults, but it had no effect on the motility of adult S. mansoni in ex vivo culture. Cytochrome P450 metabolic stability data support the hypothesis that the major trans-cyclohexanol metabolite of praziquantel plays an important role in the antischistosomal activity of this drug.

Evaluation of Antinociceptive and Anti-Inflammatory Activities of a New Triterpene Saponin from Bauhinia variegata Leaves

A new triterpene saponin, named as 23-hydroxy-3alpha-[O-alpha-L-1C4-rhamnopyranosyl-(1"-->4')-O-alpha-L-4C1-arabinopyranosyl-oxy]olean-12-en-28-oic acid O-alpha-L-1C4-rhamnopyranosyl-(1""'-->4"")-O-beta-D-4C1-glucopyranosyl-(1""-->6"')-O-beta-D-4C1-glucopyranosyl ester (9), was isolated from the leaves of Bauhinia variegata Linn. In addition, six flavonoid compounds along with two cinnamic acid derivatives were isolated and identified based on their chromatographic properties, and chemical and spectral data (ESI-high resolution-MSn, 1H NMR, 13C NMR, 1H-1H COSY, HSQC, and HMBC). Compound 9 was found to be nontoxic (LD50) and to have significant anti-inflammatory and antinociceptive activities. It also showed a slight antischistosomal activity.

Antischistosomal activity of hexadecyloxypropyl cyclic 9-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]adenine and other alkoxyalkyl esters of acyclic nucleoside phosphonates assessed by schistosome worm killing in vitro.

9-(S)-[3-Hydroxy-2-(phosphonomethoxy)propyl]adenine [(S)-HPMPA] has been reported to have antischistosomal activity. Ether lipid esters of (S)-HPMPA and cidofovir (CDV) have greatly increased activities in antiviral assays and in lethal animal models of poxvirus diseases. To see if ether lipid esters of CDV and (S)-HPMPA enhance antischistosomal activity, we tested their alkoxyalkyl esters using Schistosoma mansoni worm killing in vitro. Hexadecyloxypropyl (HDP)-cyclic-(S)-HPMPA and HDP-cyclic-CDV exhibited significant in vitro antischistosomal activities and may offer promise alone or in combination with praziquantel.

Antiviral and Antischistosomal Evaluation of Newly Synthesized Thioglycosides and their Acyclic Analogues

The pyrimidine thione derivatives 2a-d were prepared by the reaction of thiourea, ethyl cyanoacetate and several aromatic aldehydes. The acyclic thioglycosides 4a-7d were prepared by the reaction of the synthesized pyrimidine thiones 2a-d with different alkyl halides, whereas the reaction of 2a-d with 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl bromide afforded the cyclic thioglycosides 8a-d whose deprotection afforded 9a-d. The obtained compounds were tested for their antischistosomal and antiviral activity against hepatitis B virus (HBV). Compounds 5a, 5d, 7a showed high activity against HBV using the MTT assay; moreover compounds 5c, 6d, 7a, 9a, 9c exhibited high activity as antischistosomal agents.

In vitro antischistosomal activities of phenylpropanoids and lignans against Schistosoma mansoni adult worms

In vitro antischistosomal activities of phenylpropanoids and lignans against Schistosoma mansoni adult worms

Synthesis of oxadiazole-2-oxide analogues as potential antischistosomal agents

The synthesis of several 1,2,5-oxadiazole-2-oxide (Furoxan) analogues is described herein. These compounds were prepared in an effort to probe the SAR around the phenyl substituent and oxadiazole core for our studies toward thioredoxin-glutathione reductase (TGR) inhibition and antischistosomal activity.

Association of oxamniquine praziquantel and clonazepam in experimental Schistosomiasis mansoni

The antischistosomal activity of clonazepam, when administered alone or in association with oxamniquine and praziquantel, was experimentally evaluated in mice infected with Schistosoma mansoni. The animals were treated 45 days post-infection with a single dose, by oral route, according to three treatment schedules: clonazepam 25 mg/kg and sacrificed 15 min, 1h or 4 h after treatment; clonazepam 1.0, 2.5 or 10.0 mg/kg and sacrificed 15 days post-treatment or with the dose of 10 mg/kg in association with oxamniquine 50 mg/kg or praziquantel 200 mg/kg, single dose, orally, every schedule with a control group. The efficacy of the drugs in vivo was assessed by means of worm counts and their distribution in mesentery and liver, mortality and oogram changes. In the chemotherapeutic schedules used, clonazepam did not present antischistosomal activity and the result of the association of this drug with oxamniquine or praziquantel was not significantly different from the one obtained when these two last drugs were administered alone. In the in vitro experiments, the worms exposed to 0.6 mg/mL clonazepam remained motionless throughout the 8-day-period of observation, without egg-laying, whereas the worms of the control group showed normal movements, egg-laying and hatching of miracidia on the last day of observation. The results obtained in the present study confirm the action of clonazepam on S. mansoni adult worm, in vitro, causing total paralysis of males and females. However, no additive or synergistic effects were observed when clonazepam were used in association with oxamniquine or praziquantel.

Schistosomicidal activity of the antimalarial drug, mefloquine, in Schistosoma mansoni-infected mice

Therapeutic effects of racemic mefloquine were assessed in Schistosoma mansoni-infected mice, and evaluated by recording worm burden, the status of egg maturation and viability, and intestinal mast cell recruitment. Age-matched mice were divided into four groups, of which two were infected. At 8 weeks postinfection, one group of infected and one group of uninfected mice were treated with a single dose of mefloquine (150 mg/kg). Ten days after treatment, all animals were killed. Mefloquine at 150 mg/kg had no effect on worm burden, but significantly reduced the number of eggs in the first three developmental egg stages. Analysis of intestinal mast cell numbers showed that mefloquine induced mastocytosis both in infected and control animals. In conclusion, mefloquine significantly reduces egg production in S. mansoni-infected mice, suggesting a therapeutic potency in schistosomiasis therapy. Mefloquine also exerts a significant proinflammatory effect on the intestine. Through its effect on egg production, mefloquine may be a cause of silent schistosomiasis in travelers using mefloquine for malaria chemoprophylaxis. Further study of the anti-schistosomal activity of mefloquine is warranted, as its activity against other helminths.

The effect of antioxidant properties of aqueous garlic extract and Nigella sativa as anti-schistosomiasis agents in mice

The aim of this study was to assess the antioxidant and anti-schistosomal activities of the garlic extract (AGE) and Nigella sativa oil (NSO) on normal and Schistosoma mansoni-infected mice. AGE (125 mg kg-1, i.p.) and NSO (0.2 mg kg-1, i.p.) were administrated separately or in combination for successive 28 days, starting from the 1st day post infection (pi). All mice were sacrificed at weeks 7 pi. Hematological and biochemical parameters including liver and kidney functions were measured to assess the progress of anemia, and the possibility of the tissue damage. Serum total protein level, albumin, globulin and cholesterol were also determined. Malondialdehyde (MDA) and glutathione (GSH) levels were determined in the liver tissues as biomarkers for oxidative and reducing status, respectively. The possible effect of the treatment regimens on Schistosoma worms was evaluated by recording percentage of the recovered worms, tissue egg and oogram pattern. Result showed that, protection with AGE and NSO prevented most of the hematological and biochemical changes and markedly improved the antioxidant capacity of schistosomiasis mice compared to the infected-untreated ones. In addition, remarkable reduction in worms, tissue eggs and alteration in oogram pattern were recorded in all the treated groups. The antioxidant and antischistosomal action of AGE and NSO was greatly diverse according to treatment regimens. These data point to these compounds as promising agents to complement schistosomiasis specific treatment.

Thiation of new 5-(2-aryl-2-oxoethyl)-2,4-dioxo-1, 3-thiazolidines

The hitherto unknown 5-(2-aryl-2-oxoethyl)-3-substituted-2,4-dioxo-1,3-thiazolidines 2 and 5-(2-aryl-2-oxoethylidene)-3-aryl-2,4-dioxo-1,3-thiazolidines 4 have been prepared from their 2-thioxo- homologues 1 and 3, respectively, via treatment with CrO3. Compound 4 has also been obtained by treating 1 and/or 2 with bromine at different experimental conditions. Thiation of 2 and/or 4, gave a mixture of 3,5-di-substituted-2,3-dihydro-2-oxothieno[2,3-d]thiazoles 5 and the respective 2-thioxo derivatives 6. Reactions of hydrazine hydrate with 1c, d, were carried out at room temperature as well as under reflux, affording di-(3-oxo-6-aryl-4,5-dihydropyridazin)disulfides 7c, d and di-(3-oxo-6-arylpyridazin)disulfides 8c, d, respectively, together with 4-arylthiosemi carbazides 9c, d, under both conditions. Structures of the above products have been elucidated based on their microanalytical and spectroscopic data. Compound 2e exhibited pronounced antischistosomal activity.

The antischistosomal efficacies of artesunate–sulfamethoxypyrazine–pyrimethamine and artemether–lumefantrine administered as treatment for uncomplicated,Plasmodium falciparummalaria

Although artemisinin and its derivatives are widely used for the treatment of malaria, they also have antischistosomal activity. In a small study in eastern Sudan, the effects of the treatment of uncomplicated, Plasmodium falciparum malaria with artesunate-sulfamethoxypyrazine-pyrimethamine (AS-SMP) and artemether-lumefantrine (AT-LU) on co-infections with Schistosoma mansoni were therefore investigated. Faecal samples from 14 of the 306 patients screened on presentation, at the start of a clinical trial of antimalarial treatment, were found to contain Schistosoma mansoni eggs. For the treatment of their malaria, the 14 egg-positive cases, who were aged 6-40 years (mean = 13.7 years), were each subsequently treated with three tablets of a fixed combination of AS-SMP, with a 12-h (six patients) or 24-h interval (five patients) between each tablet, or with six doses of AT-LU given over 3 days. When checked 28 and 29 days after the initiation of treatment, all 14 patients were found stool-negative for schistosome eggs. These results indicate that AS-SMP and AT-LU are currently very effective treatments not only for uncomplicated, P. falciparum malaria but also for S. mansoni infections.

Antischistosomal and Antimicrobial Activities of Some Egyptian Plant Species

On the bases of ethnomedicinal and random plant collection approaches for searching out new pharmacologically bioactive agents, 45 Egyptian plant species belonging to 25 families were collected, and methanol extracts (52) were assayed in vitro for their antischistosomal and antimicrobial activities. Only extracts of Curcuma longa L. (Zingiberaceae) and Nerium oleander L. (Apocynaceae) were lethal to Schistosoma mansoni worms after a 24-h incubation period in a culture medium at concentration up to 100 μ g/mL. The different successive organic extracts of C. longa showed variable activities and the greatest activity was exhibited by the chloroform extract (EC50 = 28.92 and 31.58 μ g/mL against male and female worms, respectively). On the other hand, the antimicrobial potency of the methanol extracts were tested using the disk diffusion method against three bacteria and two fungi species: Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Candida albicans. Three plants, Chamomilla recutita L. (Asteraceae), Buddleja hybrida Lour. (Buddlejaceae), and Glinus lotoides L. (Molluginaceae), showed the highest antimicrobial potency. Also, antimicrobial screening of the different organic solvent extracts of these three plants was investigated by measuring the diameter of inhibition zone. Finally, the active extracts were subjected to preliminary phytochemical analysis using chemical tests and thin-layer and paper chromatography to explore the major classes of natural products that may be responsible for their activity.

The anti-schistosomal drug praziquantel is an adenosine antagonist

The mechanism of action of praziquantel (PZQ), the drug of choice against schistosomiasis, is still unclear. Since exposure of schistosomes to the drug is associated with calcium influx and muscular contraction, calcium channels have been suggested as the target, although direct combination of PZQ with their subunits was never demonstrated. We report a hitherto unknown effect of PZQ, namely the inhibition of nucleoside uptake, as observed in living worms using radio-isotope labelled adenosine and uridine. This effect is clearly seen in schistosomes but is absent in mammalian cells in culture. Moreover it is a specific pharmacological effect seen exclusively with the active levo-R(-)stereo isomer of the drug, and is shared by at least one benzodiazepine having antischistosomal activity. This novel effect acquires significance given that schistosomes cannot synthesize purine nucleosides de novo. A possible relationship between this novel effect and the known action of PZQ on calcium channels is discussed, since adenosine is known to bind to specific receptors and to behave as an indirect antagonist of calcium release in mammalian cells. If calcium channels were correlated with adenosine receptors also in schistosomes, as they are in mammals, this would support the hypothesis that PZQ-induced calcium influx may be correlated to adenosine receptor blockade.

Large-scale in Vitro. Screening of Egyptian Native and Cultivated Plants for Schistosomicidal Activity

In vitro. bioassay screening of 346 methanol extracts originated from 281 native and cultivated plant species growing in Egypt, and related to 81 families, was carried out for schistosomicidal activity. The extracts were bioassayed at 100 µg/mL on viable Schistosoma mansoni. mature worms in culture medium. Viability of worms was examined after exposure for 24 h, and mortality determined. Negative (DMSO) and positive (praziquantel) controls were used. Of the tested plant extracts, 72 were found to possess reproducible in vitro. antischistosomal activity. These active extracts were further subjected to determination of their LC50 and LC90 values. Strong antischistosomal activity was found in the extracts of 15 species (possessing LC50 ≤ 15 µg/mL), viz. Agave americana. L. var. marginata. Trel. (Agavaceae), A. lophantha. Schiede (Agavaceae), Furcraea selloa. C.Koch. (Agavaceae), Calotropis procera. (Aiton) W.T.Aiton (Asclepiadaceae), Pergularia tomentosa. L. (Asclepiadaceae), Asclepias sinaica. (Boiss.) Muschl. (Asclepiadaceae), Alkanna orientalis. (L.) Boiss. (Boraginaceae), Khaya grandifoliola. DC. (Meliaceae), Swietenia mahogani. (L.) Jacq. (Meliaceae), Pimenta racemosa. (Mill.) J.W.Moore (Myrtaceae), Pinus canariensis. C.Sm. (Pinaceae), Verbascum sinaiticum. L. (Scrophulariaceae), Solanum elaeagnifolium. Cav. (Solanaceae), S. nigrum. L. (Solanaceae), and Brachychiton rupestris. (Lindl.) K.Schum. (Sterculiaceae). These 15 species could represent promising bioactive sources that deserve further investigation, with the aim of finding novel antischistosomal agents. The current study represents the first report on a systematic screening of schistosomicidal activity utilizing a large number of plant species.

Modulation of the antioxidant defence in different developmental stages of Schistosoma mansoni by praziquantel and artemether

Human schistosomiasis is a chronic and debilitating parasitic disease caused by parasitic trematode worms (schistosomes). Praziquantel (PZQ) is the drug of choice as it is active against all Schistosoma species, can be administered easily, has high cure and egg reduction rates, with no or only mild side effects. Rapid re-infection following treatment and the concerns about PZQ resistance has led to the search for new drugs to treat schistosomiasis. Significant progress has been made with artemisinin derivatives (e.g., artemether [ART]) that are used for chemoprophylaxis. This present study aims to look at the effects of ART and PZQ on the antioxidant defence of immature (three-week-old) and mature (six-week-old) stages of S. mansoni. The possible development of time- or concentration-dependent changes in oxidative stress is assessed by incubation with different sublethal drug concentrations (50, 75, 100 ng/mL for both ART and PZQ) and different time periods (one and three hours). The results indicated a time- and concentration-dependent depletion of glutathione (GSH), which was greater in the immature worms after incubation with ART. On addition of ART to the incubation medium of mature and immature worms, elevation in lipid peroxidation (TBARS) level was observed, which was time- and concentration-dependent, and more prominent in the immature schistosomes. Addition of PZQ to the incubation medium containing the immature schistosomes did not have a significant effect on TBARS level, except after three hours’ incubation with the highest concentration used; however, a significant rise was seen in the mature worms. The PZQ had no effect on the activities of superoxide dismutase (SOD), glutathione peroxidase (tGPx, sGPx and nGPx) and glutathione transferase (GST) in mature or immature worms. While ART induced SOD activity in mature worms, it induced tGPx, nGPx and GST activities in a time- and concentration-dependent manner in both mature and immature worms. Activation was more prominent in the immature schistosomes. The results of the present study indicate that the immature schistosomes are more prone to oxidative killing, which probably participates in the mechanism of antischistosomal action of ART against the immature stage of S. mansoni. The results suggest that the mechanism of schistosomicidal action of PZQ is probably not substantially dependent on oxidative stress or oxidative killing.

Characterization and partial purification of cystatins from Malian medicinal plants

Cysteine proteases (CPs) expressed by Schistosoma mansoni (Sm) participate in the hydrolysis of host hemoglobin [1]. Cystatins are proteinaceous CP inhibitors (CPIs) present in humans as well as in plants. Two Malian medicinal plants used against schistosomiasis, Securidaca longepedunculata Fres (root: SR and leaf: SL) and Stylosanthes erecta Beauv. (aerial part: SE), were investigated for presence of cystatins. Cystatins were purified by extraction of powdered plant material with Tris-HCl, followed by affinity chromatography, gel filtration (GF) and anion exchange chromatography (AEC). S. mansoni CPs activity and protease inhibitory assays were performed using fluorogenic substrates according to [2]. High papain inhibition observed in all crude extracts indicated presence of CPIs. The papain inhibitory activity in the three extracts eluted into one single peak each, after affinity chromatography. These fractions were resolved by GF into papain inhibitory activities consistent with the presence of cystatins. SmCP activities were also inhibited by these cystatins. The strongest papain and SmCPs inhibitory activities were observed in SR. After AEC, one papain inhibitory peak which weakly inhibited SmCP was obtained from SR. On SDS-PAGE (under reduction), this peak appeared as a single 88kDa- band. The purified cystatins were characterized with respect to their papain and SmCPs inhibitory activities and by Mr. Cystatins with strong papain and moderate SmCPs inhibitory activity are isolated from the extracts and could participate into the antischistosomal activity of the studied plants.