Toxoplasma gondii: A simple high-throughput assay for drug screening in vitro

Application potential of arecoline hydrobromide for anti-Toxoplasma gondii

Although long-term chewing areca nut may cause cancer, it is very feasible to treat human or livestock diseases in a short period of time. In this study, arecoline hydrobromide (AH), which is extracted from Areca catechu, significantly inhibited the proliferation of tachyzoites ofToxoplasma gondii (T. gondii) in vitro and in vivo. Specially,in vivo AH effectively resisted liver damage originate fromT. gondii. Furthemore, the survival and safety evaluation outcome indicated that AH can prolong survival period of mice infected with T. gondii at non-toxic and side-effect dose. Based on these advantages, AH is a candidate compound with great potential for the treatment of T. gondii infection and it may be used clinically in the future.

A novel antibiotic: the antimicrobial effects of CFBSA and its application on electronspun wound dressing

N-chloro-N-fluorobenzenesulfonylamide (CFBSA), was a novel chlorinating reagent, which exhibits potential antibacterial activities. In this study, CFBSA was confirmed as a wide-broad antimicrobial and bactericidal drug against different gram-negative bacteria, gram-positive bacteria and fungi, while it was found to have low cytotoxicity for eukaryotic cells. In addition, microorganism morphology assay and oxidative stress test was used to determine the antimicrobial mechanisms of CFBSA. According to the results, CFBSA probably had a target on cell membrane and killed microorganism by disrupting its cell membrane. Then, CFBSA was first combined with poly(L-lactide-co-caprolactone) (PLCL)/SF via electrospinning and applied in wound dressings. The characterization of different PLCL/SF of CFBSA-loaded nanofibrous mats was investigated by SEM, water contact angle, Fourier transform infrared spectroscopy, cell compatibility and antimicrobial test. CFBSA-loaded PLCL/SF nanofibrous mats showed excellent antimicrobial activities. In order to balance of the biocompatibility and antibacterial efficiency, SP-2.5 was selected as the ideal loading concentration for further application of CFBSA-loaded PLCL/SF. In conclusion, the electrospun CFBSA-loaded PLCL/SF nanofibrous mat with its broad-spectrum antimicrobial and bactericidal activity and good biocompatibility showed enormous potential for wound dressing.

Assessing Acanthamoeba cytotoxicity: comparison of common cell viability assays

Background

In vitro models for studying interactions between Acanthamoeba and host cells are crucial for understanding the pathomechanism of Acanthamoeba and assessing differences between strains and cell types. The virulence of Acanthamoeba strains is usually assessed and monitored by using cell cytotoxicity assays. The aim of the present study was to evaluate and compare the most widely used cytotoxicity assays for their suitability to assess Acanthamoeba cytopathogenicity.

Methods

The viability of human corneal epithelial cells (HCECs) after co-culture with Acanthamoeba was evaluated in phase contrast microscopy.

Results

It was shown that Acanthamoeba is unable to considerably reduce the tetrazolium salt and the NanoLuc® Luciferase prosubstrate to formazan and the luciferase substrate, respectively. This incapacity helped to generate a cell density-dependent signal allowing to accurately quantify Acanthamoeba cytotoxicity. The lactate dehydrogenase (LDH) assay led to an underestimation of the cytotoxic effect of Acanthamoeba on HCECs since their co-incubation negatively affected the lactate dehydrogenase activity.

Discussion

Our findings demonstrate that cell-based assays using the aqueous soluble tetrazolium-formazan, and the NanoLuc® Luciferase prosubstrate products, in contrast to LDH, are excellent markers to monitor the interaction of Acanthamoeba with human cell lines and to determine and quantify effectively the cytotoxic effect induced by the amoebae. Furthermore, our data indicate that protease activity may have an impact on the outcome and thus the reliability of these tests.

Toxoplasma gondii infection: novel emerging therapeutic targets

INTRODUCTION

Toxoplasmosis constitutes a challenge for public health, animal production, and welfare. So far, only a limited panel of drugs has been marketed for clinical applications. In addition to classical screening, the investigation of unique targets of the parasite may lead to the identification of novel drugs.

AREAS COVERED

Herein, the authors describe the methodology to identify novel drug targets in Toxoplasma gondii and review the literature with a focus on the last two decades.

EXPERT OPINION

Over the last two decades, the investigation of essential proteins of T. gondii as potential drug targets has fostered the hope of identifying novel compounds for the treatment of toxoplasmosis. Despite good efficacies in vitro, only a few classes of these compounds are effective in suitable rodent models, and none has cleared the hurdle to applications in humans. This shows that target-based drug discovery is in no way better than classical screening approaches. In both cases, off-target effects and adverse side effects in the hosts must be considered. Proteomics-driven analyses of parasite- and host-derived proteins that physically bind drug candidates may constitute a suitable tool to characterize drug targets, irrespectively of the drug discovery methods.

Evaluation of the anti-Toxoplasma gondii Activity of Hederagenin in vitro and in vivo

Toxoplasma gondii infection is widespread worldwide, not only posing a serious threat to human food safety and animal husbandry, but also endangering human health. The selectivity index was employed to measure anti-T. gondii activity. Hederagenin (HE) exhibited potent anti-T. gondii activity and low cytotoxicity. For this reason, HE was selected for in vivo experiments. HE showed 64.8%±13.1% inhibition for peritoneal tachyzoites in mice, higher than spiramycin 56.8%±6.0%. Biochemical parameters such as alanine aminotransferase, aspartate aminotransferase, glutathione, and malondialdehyde, illustrated that HE was a good inhibitor of T. gondii in vivo. This compound was also effective in relieving T. gondii-induced liver damage. Collectively, it was demonstrated that HE had potential as an anti-T. gondii agent.

Phytochemicals and Potential Therapeutic Targets on Toxoplasma gondii Parasite

Identification of drug target in protozoan T. gondii is an important step in the development of chemotherapeutic agents. Likewise, exploring phytochemical compounds effective against the parasite can lead to the development of new drug agent that can be useful for prophylaxis and treatment of toxoplasmosis. In this review, we searched for the relevant literature on the herbs that were tested against T. gondii either in vitro or in vivo, as well as different phytochemicals and their potential activities on T. gondii. Potential activities of major phytochemicals, such as alkaloid, flavonoid, terpenoids and tannins on various target sites on T. gondii as well as other related parasites was discussed. It is believed that the phytochemicals from natural sources are potential drug candidates for the treatment of toxoplasmosis with little or no toxicity to humans.

Evaluation of ursolic acid derivatives with potential anti-Toxoplasma gondii activity

Toxoplasma gondii is an important pathogen that causes serious public health problems. Currently, therapeutic drugs for toxoplasmosis cause serious side effects, and more effective and novel substances with relatively low toxicity are urgently needed. Ursolic acid (UA) has many properties that can be beneficial to healthcare. In this study, we synthesized eight series of UA derivatives bearing a tetrazole moiety and evaluated their anti-T. gondii activity in vitro using spiramycin as a positive control. Most of the synthesized derivatives exhibited better anti-T. gondii activity in vitro than UA, among which compound 12a exhibited the most potent anti-T. gondii activity. Furthermore, the results of biochemical parameter determination indicated that 12a effectively restored the normal body weight of mice infected with T. gondii, reduced hepatotoxicity, and exerted significant anti-oxidative effects compared with the findings for spiramycin. Additionally, our molecular docking study indicated that the synthesized compounds could act as potential inhibitors of T. gondii calcium-dependent protein kinase 1 (TgCDPK1), with 12a possessing strong affinity for TgCDPK1 via binding to the key amino acids GLU129 and TYR131.

Identification of potential dual -targets anti- toxoplasma gondii compounds through structure-based virtual screening and in-vitro studies

Toxoplasma gondii is the etiologic agent of toxoplasmosis, a disease which can lead to morbidity and mortality of the fetus and immunocompromised individuals. Due to the limited effectiveness or side effects of existing drugs, the search for better drug candidates is still ongoing. In this study, we performed structure-based screening of potential dual-targets inhibitors of active sites of T. gondii drug targets such as uracil phosphoribosyltransferase (UPRTase) and adenosine kinase (AK). First screening of virtual compounds from the National Cancer Institute (NCI) was performed via molecular docking. Subsequently, the hit compounds were tested in-vitro for anti- T. gondii effect using cell viability assay with Vero cells as host to determine cytotoxicity effects and drug selectivities. Clindamycin, as positive control, showed a selectivity index (SI) of 10.9, thus compounds with SI > 10.9 specifically target T. gondii proliferation with no significant effect on the host cells. Good anti- T. gondii effects were observed with NSC77468 (7-ethoxy-4-methyl-6,7-dihydro-5H-thiopyrano[2,3-d]pyrimidin-2-amine) which showed SI values of 25. This study showed that in-silico selection can serve as an effective way to discover potentially potent and selective compounds against T. gondii.

Synthesis, in vitro and in vivo biological evaluation of dihydroartemisinin derivatives with potential anti-Toxoplasma gondii agents

In this study, four series of dihydroartemisinin derivatives were designed, synthesized, and evaluated for anti-toxoplasma gondii activity, and calculated the selectivity index (SI). It was the higher the SI, the better the effect of this compound against Toxoplasma gondii. Our goal was to filter out compounds that were bigger SI than the lead compound. The compound with the highest SI was selected for the anti-toxoplasmosis test in mice in vivo. Among the synthesized compounds, the (3R,5aS,6R,8aS,9R,12R,12aR)-3,6,9-trimethyl-decahydro-12H-3,12-epoxy[1,2]di-oxepino[4,3 -i]isochromen-10-yl-(te-rt-butoxycarbonyl)-l-alaninate (A2) exhibited the most potent anti-T. gondii activity and low cytotoxicity (SI: 6.44), yielding better results than the lead compound DHA (SI: 1.00) and the clinically used positive-control drug spiramycin (SI: 0.72) in vitro. Furthermore, compound A2 had better growth inhibitory effects on T. gondii in vivo than spiramycin did and significantly reduced the number of tachyzoites in the peritoneal cavity of mice (P < 0.01). The evaluation of the data generated in the T. gondii mouse infection model indicates that compound A2 treatment was a good inhibitor of T. gondii in vivo and that it was effective in relieving the liver damage induced by T. gondii. In addition, the results of a docking study revealed that A2 could become a better T. gondii calcium-dependent protein kinase1 (TgCDPK1) inhibitor. For this reason, compound A2 has potential as an anti-parasitic drug. Further studies are required to elucidate the mechanism of the action of compound A2, as well as to develop drug delivery systems for patients.

Synthesis and Biological Evaluation of (+)-Usnic Acid Derivatives as Potential Anti-Toxoplasma gondii Agents

Six series of (+)-usnic acid derivatives were synthesized. The IC₅₀ values of these compounds were determined in T. gondii infected HeLa cells (μM) and in HeLa cells (μM), and their selectivity indexes (SI) were calculated. In vitro, most of the derivatives tested in this study exhibited more anti activity than that of the parent compound (+)-usnic acid and the positive control drugs. Among these derivatives, methyl (E)-(1-(6-acetyl-7,9-dihydroxy-8,9b-dimethyl-1,3-dioxo-3,9b-dihydrodibenzo[b,d]furan-2(1H)-ylidene)ethyl)phenylalaninate (D3) showed the most effective anti-T. gondii activity (selectivity >2.77). In comparison with the clinically used positive control drugs sulfadiazine (selectivity 1.15), pyrimethamine (selectivity 0.89), spiramycin (selectivity 0.72), and the lead compound (+)-usnic acid (selectivity 0.96), D3 showed better results in vitro. Furthermore, D3 and (E)-6-acetyl-7,9-dihydroxy-8,9b-dimethyl-2-(1-(quinolin-6-ylamino)ethylidene)dibenzo[b,d]furan-1,3(2H,9bH)-dione (F3) had greater inhibitory effects on T. gondii (inhibition rates 76.0% and 64.6%) in vivo in comparison to spiramycin (inhibition rate 55.2%); in the peritoneal cavity of mice, the number of tachyzoites was significantly reduced (p < 0.001) in vivo. Additionally, some biochemical parameters were measured and spleen indexes were comprehensively evaluated, and the results indicated that mice treated with both compound D3 and compound F3 showed reduced hepatotoxicity and significantly enhanced antioxidative effects in comparison to the normal group. Granuloma and cyst formation were effected by the inhibition of compound D3 and compound F3 in liver sections. Overall, these results indicated that D3 and F3 for use as anti-T. gondii agents are promising lead compounds.

High-throughput screen of drug repurposing library identifies inhibitors of Sarcocystis neurona growth

The apicomplexan parasite Sarcocystis neurona is the primary etiologic agent of equine protozoal myeloencephalitis (EPM), a serious neurologic disease of horses. Many horses in the U.S. are at risk of developing EPM; approximately 50% of all horses in the U.S. have been exposed to S. neurona and treatments for EPM are 60-70% effective. Advancement of treatment requires new technology to identify new drugs for EPM. To address this critical need, we developed, validated, and implemented a high-throughput screen to test 725 FDA-approved compounds from the NIH clinical collections library for anti-S. neurona activity. Our screen identified 18 compounds with confirmed inhibitory activity against S. neurona growth, including compounds active in the nM concentration range. Many identified inhibitory compounds have well-defined mechanisms of action, making them useful tools to study parasite biology in addition to being potential therapeutic agents. In comparing the activity of inhibitory compounds identified by our screen to that of other screens against other apicomplexan parasites, we found that most compounds (15/18; 83%) have activity against one or more related apicomplexans. Interestingly, nearly half (44%; 8/18) of the inhibitory compounds have reported activity against dopamine receptors. We also found that dantrolene, a compound already formulated for horses with a peak plasma concentration of 37.8 ± 12.8 ng/ml after 500 mg dose, inhibits S. neurona parasites at low concentrations (0.065 μM [0.036-0.12; 95% CI] or 21.9 ng/ml [12.1-40.3; 95% CI]). These studies demonstrate the use of a new tool for discovering new chemotherapeutic agents for EPM and potentially providing new reagents to elucidate biologic pathways required for successful S. neurona infection.

In vitro activity of the interaction between taxifolin (dihydroquercetin) and pyrimethamine against Toxoplasma gondii

Toxoplasmosis is one of the most neglected zoonotic foodborne parasitic diseases that cause public health and socioeconomic concern worldwide. The current drugs used for the treatment of toxoplasmosis have been identified to have clinical limitations. Hence, new drugs are urgently needed to eradicate T.gondii infections globally. Here, an in vitro anti-Toxoplasma gondii activity of taxifolin (dihydroquercetin) and dihydrofolate inhibitor (pyrimethamine) alone and in combination with a fixed concentration of pyrimethamine were investigated against the rapidly proliferating T.gondii RH strain at 48 hr using colorimetric assay. Pyrimethamine showed the highest anti-T. gondii activity with IC_50P of 0.84 μg/ml (p > .05), respectively. The combination of pyrimethamine with dihydroquercetin gave a significant inhibitory activity against tachyzoites in in vitro with IC_50p of 1.39 μg/ml (p < .05). The IC_50p ranges obtained for the individual and the combination of taxifolin with pyrimethamine inhibition of parasite growth were not cytotoxic to the infected HFF and Hek-293 cell lines used. These compounds combination should be investigated further using in vivo model of toxoplasmosis.

Enrofloxacin and Toltrazuril Are Able to Reduce Toxoplasma gondii Growth in Human BeWo Trophoblastic Cells and Villous Explants from Human Third Trimester Pregnancy

Classical treatment for congenital toxoplasmosis is based on combination of sulfadiazine and pyrimethamine plus folinic acid. Due to teratogenic effects and bone marrow suppression caused by pyrimethamine, the establishment of new therapeutic strategies is indispensable to minimize the side effects and improve the control of infection. Previous studies demonstrated that enrofloxacin and toltrazuril reduced the incidence of Neospora caninum and Toxoplasma gondii infection. The aim of the present study was to evaluate the efficacy of enrofloxacin and toltrazuril in the control of T. gondii infection in human trophoblast cells (BeWo line) and in human villous explants from the third trimester. BeWo cells and villous were treated with several concentrations of enrofloxacin, toltrazuril, sulfadiazine, pyrimethamine, or combination of sulfadiazine+pyrimethamine, and the cellular or tissue viability was verified. Next, BeWo cells were infected by T. gondii (2F1 clone or the ME49 strain), whereas villous samples were only infected by the 2F1 clone. Then, infected cells and villous were treated with all antibiotics and the T. gondii intracellular proliferation as well as the cytokine production were analyzed. Finally, we evaluated the direct effect of enrofloxacin and toltrazuril in tachyzoites to verify possible changes in parasite structure. Enrofloxacin and toltrazuril did not decrease the viability of cells and villous in lower concentrations. Both drugs were able to significantly reduce the parasite intracellular proliferation in BeWo cells and villous explants when compared to untreated conditions. Regardless of the T. gondii strain, BeWo cells infected and treated with enrofloxacin or toltrazuril induced high levels of IL-6 and MIF. In villous explants, enrofloxacin induced high MIF production. Finally, the drugs increased the number of unviable parasites and triggered damage to tachyzoite structure. Taken together, it can be concluded that enrofloxacin and toltrazuril are able to control T. gondii infection in BeWo cells and villous explants, probably by a direct action on the host cells and parasites, which leads to modifications of cytokine release and tachyzoite structure.

In Vitro and in Vivo Effects of Nitrofurantoin on Experimental Toxoplasmosis

Toxoplasma gondii is an important opportunistic pathogen that causes toxoplasmosis, which has very few therapeutic treatment options. The most effective therapy is a combination of pyrimethamine and sulfadiazine; however, their utility is limited because of drug toxicity and serious side effects. For these reasons, new drugs with lower toxicity are urgently needed. In this study, the compound, (Z)-1-[(5-nitrofuran-2-yl)methyleneamino]-imidazolidine-2,4-dione (nitrofurantoin), showed anti-T. gondii effects in vitro and in vivo. In HeLa cells, the selectivity of nitrofurantoin was 2.3, which was greater than that of pyrimethamine (0.9). In T. gondii-infected female ICR mice, the inhibition rate of T. gondii growth in the peritoneal cavity was 44.7% compared to the negative control group after 4-day treatment with 100 mg/kg of nitrofurantoin. In addition, hematology indicators showed that T. gondii infection-induced serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, biochemical parameters involved in liver injury, were reduced by nitrofurantoin significantly. Moreover, nitrofurantoin exerted significant effects on the index of antioxidant status, i.e., malondialdehyde (MDA) and glutathione (GSH). The nitrofurantoin-treated group inhibited the T. gondii-induced MDA levels while alleviating the decrease in GSH levels. Thus, nitrofurantoin is a potential anti-T. gondii candidate for clinical application.

Antiparasitic effects of oxymatrine and matrine against Toxoplasma gondii in vitro and in vivo

Toxoplasma gondii (T. gondii) is an important pathogen which can causes serious public health problems. Since the current therapeutic drugs for toxoplasmosis present serious host toxicity, research on effective and new substances of relatively low toxicity is urgently needed. This study was carried out to evaluate the anti-parasitic effect of oxymatrine (OM) and matrine (ME) against T. gondii in vitro and in vivo. In our study, the anti-T. gondii activities of ME and OM were evaluated in vitro using cell counting kit-8 assay, morphological observation and trypan blue exclusion assay. In vivo, mice were sacrificed four days post-infection and ascites were drawn out to determine the extent of tachyzoite proliferation. Viscera indexes and liver biochemical parameters, such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), glutathione (GSH) and malondialdehyde (MDA), were examined to evaluate the toxicity of compounds to mice. As a result, OM and ME showed anti-T. gondii activity but low selectivity toxicity to HeLa cells. Both compounds also significantly decreased the number of tachyzoites in peritoneal cavity and recovered the levels of ALT, AST, GSH and MDA in liver. Moreover, the mice treated with OM or ME achieved better results in viscera index and survival rate than that of spiramycin. These results suggest that OM and ME are likely the sources of new drugs for toxoplasmosis, and further studies will be necessary to compare the efficacy of drug combination, as well as identify its action of mechanism.

Reduction of Toxoplasma gondii Development Due to Inhibition of Parasite Antioxidant Enzymes by a Dinuclear Iron(III) Compound

Toxoplasma gondii, the causative agent of toxoplasmosis, is an obligate intracellular protozoan that can infect a wide range of vertebrate cells. Here, we describe the cytotoxic effects of the dinuclear iron compound [Fe(HPCINOL)(SO4)]2-μ-oxo, in which HPCINOL is the ligand 1-(bis-pyridin-2-ylmethyl-amino)-3-chloropropan-2-ol, on T. gondii infecting LLC-MK2 host cells. This compound was not toxic to LLC-MK2 cells at concentrations of up to 200 μM but was very active against the parasite, with a 50% inhibitory concentration (IC50) of 3.6 μM after 48 h of treatment. Cyst formation was observed after treatment, as indicated by the appearance of a cyst wall, Dolichos biflorus lectin staining, and scanning and transmission electron microscopy characteristics. Ultrastructural changes were also seen in T. gondii, including membrane blebs and clefts in the cytoplasm, with inclusions similar to amylopectin granules, which are typically found in bradyzoites. An analysis of the cell death pathways in the parasite revealed that the compound caused a combination of apoptosis and autophagy. Fluorescence assays demonstrated that the redox environment in the LLC-MK2 cells becomes oxidant in the presence of the iron compound. Furthermore, a reduction in superoxide dismutase and catalase activities in the treated parasites and the presence of reactive oxygen species within the parasitophorous vacuoles were observed, indicating an impaired protozoan response against these radicals. These findings suggest that this compound disturbs the redox equilibrium of T. gondii, inducing cystogenesis and parasite death.

Triazole-based compound as a candidate to develop novel medicines to treat toxoplasmosis

This article reports anti-Toxoplasma gondii activity of 3-(thiophen-2-yl)-1,2,4-triazole-5-thione. The compound displayed significant and reproducible antiparasitic effects at nontoxic concentrations for the host cells, with an experimentally determined 50% inhibitory concentration (IC50) at least 30 times better than that of the known chemotherapeutic agent sulfadiazine. Purine nucleoside phosphorylase was defined as the probable target for anti-Toxoplasma activity of the tested compound. These results provide the foundation for future work to develop a new class of medicines to better treat toxoplasmosis.

Repurposing the open access malaria box to discover potent inhibitors of Toxoplasma gondii and Entamoeba histolytica

Toxoplasmosis and amebiasis are important public health concerns worldwide. The drugs currently available to control these diseases have proven limitations. Therefore, innovative approaches should be adopted to identify and develop new leads from novel scaffolds exhibiting novel modes of action. In this paper, we describe results from the screening of compounds in the Medicines for Malaria Venture (MMV) open access Malaria Box in a search for new anti-Toxoplasma and anti-Entamoeba agents. Standard in vitro phenotypic screening procedures were adopted to assess their biological activities. Seven anti-Toxoplasma compounds with a 50% inhibitory concentration (IC50) of <5 μM and selectivity indexes (SI) of >6 were identified. The most interesting compound was MMV007791, a piperazine acetamide, which has an IC50 of 0.19 μM and a selectivity index of >157. Also, we identified two compounds, MMV666600 and MMV006861, with modest activities against Entamoeba histolytica, with IC50s of 10.66 μM and 15.58 μM, respectively. The anti-Toxoplasma compounds identified in this study belong to scaffold types different from those of currently used drugs, underscoring their novelty and potential as starting points for the development of new antitoxoplasmosis drugs with novel modes of action.

Evaluation of anti-coccidial effects of 1-[4-(4-nitrophenoxy)phenyl]propane-1-one and identification of its potential target proteins in Toxoplasma gondii

Coccidiosis affects many vertebrates worldwide, but treatment with known anti-coccidial drugs causes several adverse side effects. There is a critical need for the development and evaluation of new drugs. The anti-coccidial effect of 1-[4-(4-nitrophenoxy)phenyl]propane-1-one (NPPP), a synthetic compound, was studied in vitro and in vivo. Treatment with NPPP showed anti-Toxoplasma activity in vitro with a lower EC50 value than pyrimethamine. In ICR mice infected with Toxoplasma gondii, oral administration of NPPP for 4 days showed statistically significant anti-Toxoplasma activity with lower numbers of tachyzoite than those of the negative control (p < 0.01). NPPP also exhibited strong anti-Eimeria activity in Eimeria tenella-infected chickens when treated for 4 days with orally administered NPPP at a dose of 100 mg/kg. Potential target proteins of NPPP were analyzed by proteomic profiles of T. gondii tachyzoites. Two hypothetical proteins were identified as possible targets of NPPP, a putative ortholog of vacuolar ATP synthase subunit C and a class I S-adenosylmethionine-dependent methyltransferase. Our data show that the NPPP might be an anti-coccidial drug candidate for clinical application against coccidial infections. Future investigations will focus on identifying the function of proteins regulated by NPPP.

6-trifluoromethyl-2-thiouracil possesses anti-Toxoplasma gondii effect in vitro and in vivo with low hepatotoxicity

Since pyrimethamine, the general therapeutic drug for toxoplasmosis, presents several adverse side effects, the need to develop and evaluate new drugs for the condition is critical. In this study, anti-Toxoplasma gondii activities of 3-[{2-((E)-furan-2-ylmethylene)hydrazinyl}methylene]-1,3-dihydroindol-2-one (ATT-5126) and 6-trifluoromethyl-2-thiouracil (KH-0562) were evaluated in vitro using a 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay and in vivo by measuring amount of the tachyzoites in mice ascites. Biochemical parameters such as lipid peroxidation (LPO), glutathione (GSH), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) were also evaluated in livers of mice at 4 days post-infection. As a result, the ATT-5126 and KH-0562 showed anti-T. gondii activity in vitro. Treatment of ATT-5126 or KH-0562 decreased the amount of tachyzoites in T. gondii infected ICR mice. The relative weight of liver and spleen increased by T. gondii infection were decreased by treatment of ATT-5126 or KH-0562. The levels of LPO, ALT and AST, which are biochemical parameters involved in liver injury, were also significantly recovered by treatment of ATT-5126 or KH-0562 (p<0.05). In particular, the recovered levels by KH-0562 were similar to those of pyrimethamine-treated group (p<0.05). However, the level of GSH, which is an antioxidant indicator, showed insignificant statistics. The results suggest that KH-0562 show anti-T. gondii activities in vitro and in vivo with low hepatotoxicity. Therefore, KH-0562 may be a useful candidate for treating T. gondii infection.

Novel methodology based on biomimetic superhydrophobic substrates to immobilize cells and proteins in hydrogel spheres for applications in bone regeneration

Cell-based therapies for regenerative medicine have been characterized by the low retention and integration of injected cells into host structures. Cell immobilization in hydrogels for target cell delivery has been developed to circumvent this issue. In this work mesenchymal stem cells isolated from Wistar rats bone marrow (rMSCs) were immobilized in alginate beads fabricated using an innovative approach involving the gellification of the liquid precursor droplets onto biomimetic superhydrophobic surfaces without the need of any precipitation bath. The process occurred in mild conditions preventing the loss of cell viability. Furthermore, fibronectin (FN) was also immobilized inside alginate beads with high efficiency in order to mimic the composition of the extracellular matrix. This process occurred in a very fast way (around 5 min), at room temperature, without aggressive mechanical strengths or particle aggregation. The methodology employed allowed the production of alginate beads exhibiting a homogenous rMSCs and FN distribution. Encapsulated rMSCs remained viable and were released from the alginate for more than 20 days. In vivo assays were also performed, by implanting these particles in a calvarial bone defect to evaluate their potential for bone tissue regeneration. Microcomputed tomography and histological analysis results showed that this hybrid system accelerated bone regeneration process. The methodology employed had a dual role by preventing cell and FN loss and avoiding any contamination of the beads or exchange of molecules with the surrounding environment. In principle, the method used for cell encapsulation could be extended to other systems aimed to be used in tissue regeneration strategies.

Induction of sulfadiazine resistance in vitro in Toxoplasma gondii

We induced sulfadiazine resistance in two sulfadiazine sensitive strains of Toxoplasma gondii, RH (Type I) and ME-49 (Type II) in vitro by using drug pressure. At first, sulfadiazine susceptibility of the two sensitive strains and two naturally resistant strains of T. gondii was evaluated on Vero cells using an enzyme-linked immunosorbent assay (ELISA). The IC(50) values of sulfadiazine were 77 μg/mL for RH, 51 μg/mL for ME-49 and higher than 1000 μg/mL for the two natural resistant strains. Secondly, induced resistance of the strains by gradually increase sulfadiazine concentration was verified by this test, which resulted IC(50) values at higher than 1000 μg/mL. In conclusion we developed in vitro two sulfadiazine resistant strains called RH-R(SDZ) and ME-49-R(SDZ). These strains resistant to sulfadiazine would be useful to characterize resistance mechanisms to sulfadiazine.

Modified Field stain - rapid viability test for Trichomonas vaginalis

AIMS

We previously reported that Modified Field Stain (MF) can be used as a rapid stain for diagnosis. In the present study we extend the observation to include the stain as an alternative method to assess viability of the cells.

METHODS AND RESULTS

Six isolates of Trichomonas vaginalis were used to assess the utility of the Modified Field stain as a rapid viability test for T. vaginalis and to compare with 0·4% Trypan Blue dye exclusion test in three conditions; normal in vitro culture growth using Hollander medium, lysed in distilled water and treated with metronidazole. MF stain showed similar growth profile pattern as Trypan Blue dye exclusion for identifying viable cells of T. vaginalis. Although, Trypan Blue dye exclusion test is ready made, rapid and widely used in laboratory as reliable viability assay, however, the limitation using Trypan Blue is the dye was unable to show internal morphological changes during the parasite's transition from being viable to non-viable. On day 3 where cultures peaked the correlation factor of both assays done to assess the viability of parasites harvested from the controls, metronidazole and distilled water treated parasites were more than 0·9 respectively.

CONCLUSIONS

This confirms that MF staining does not only record permanently the morphological changes and retain internal structural details but also provides a reliable and rapid viability assay for the parasites.

SIGNIFICANCE AND IMPACT OF THE STUDY

Therefore, in our study, Modified Field's stain may offer the researchers and laboratory technologists the opportunity to get the result on the same day and the most important thing is the ability to differentiate between viable and non-viable of T. vaginalis under three different conditions (normal culture, drug and distilled water condition). Modified Field's staining method enhanced the morphological identification of T. vaginalis compared to Trypan Blue dye exclusion.

A new alternative in vitro method for quantification of Toxoplasma gondii infectivity

An in vitro method to determine the infectious potency of an unknown suspension of the protozoan parasite Toxoplasma gondii based on kinetics of host cells lysis was developed. Mic1-3KO a mutant strain of T. gondii RH tachyzoites was inoculated in 25-cm² flasks containing a 90% confluent monolayer of human foreskin fibroblasts. Lysis kinetics was monitored for infection ratios ranging from 1∶10⁶ to 1∶10; we defined 10⁶ tachyzoites/ml⁻¹ as the threshold value for parasite egress. Results allowed us to build a calibration curve relating the initial infection ratios to the time needed to reach 10⁶ tachyzoites/ml⁻¹. Finally, we validated the method using a known mixture of dead and live parasites. This method was found to estimate with accuracy the initial ratio of infection of the unknown parasite suspension. This easy-to-use method is reproducible and can be applied to any T. gondii tachyzoite RH strain, genetically modified or not. This method is also suitable for testing promising candidates for an effective live vaccine.

Antimalarial effect of N-acetyl-L-Leucyl-L-leucyl-L-norleucinal by the inhibition of Plasmodium falciparum Calpain

The biological understanding of malaria parasites has increased considerably over the past two decades with the discovery of many potential targets for the development of new antimalarial drugs. Calpain, a cysteine protease of Plasmodium falciparum, is believed to be a central mediator essential for parasitic activity. However, the utility of calpain as a potential anti-malarial target in P. falciparum has not been fully determined. In the present study, we determined the effect of N-acetyl-L-Leucyl-L-leucyl-L-norleucinal (ALLN)-treatment on the expression of calpain in erythrocytic stages of P. falciparum and its usefulness as an antimalarial chemotherapeutic agent. ALLN was shown to have low toxicity to HeLa cells but high toxicity to malaria. ALLN inhibited the expression of calpain in ring, trophozoite and schizont stages when treated for 48 h. Also, after 48 h, samples were characterized by 6.15% and 0% parasitemia without ALLN treatment and with ALLN treatment, respectively. Brightfield and confocal microscopy revealed that ALLN treatment affects merozoite maturation. As ALLN concentration increased from 1 muM to 100 microM, ring stage parasites did not mature into the schizont stage. When ALLN treatment was continued for 48 h, it also significantly inhibited the maturation of ring-stage parasites into trophozoite or schizont stages and survival of malarial parasites. Taken together, these findings suggest that ALLN inhibit the maturation and survival of P. falciparum and calpain expression, and thus has potential utility as an antimalarial chemotherapeutic agent.