Inhibitory effects of (-)-epigallocatechin-3-gallate from green tea on the growth of Babesia parasites

In vitro anti-Trichomonas gallinae effects of Ziziphus vulgaris L. and Camellia sinensis (L.) Kuntze extracts

BACKGROUND

Trichomonas gallinae is a parasite that causes canker and severe loss and death, especially in young pigeons. Metronidazole (MTZ) is the recommended drug for treating avian trichomoniasis. Due to drug resistance, non-chemical alternatives, such as medicinal plant extracts, are also considered possible therapies for this disease.

OBJECTIVES

This study compares the antitrichomonal effects of MTZ with extracts of Camellia sinensis and Ziziphus vulgaris on T. gallinae in vitro.

METHODS

Samples of T. gallinae were taken from infected pigeons. Multi-well plates with different concentrations (5, 10, 25, 50 and 100 µg/mL) of plant extracts were used for the in vitro study.

RESULTS

The minimum inhibitory concentration (MIC) of C. sinensis extract was 25 µg/mL over 24 h, compared to 50 µg/mL for MTZ. The MIC value of the Z. vulgaris extracts was 50 µg/mL.

CONCLUSIONS

The results suggest that the extracts of Z. vulgaris and C. sinensis, as potential natural agents, could have anti-avian trichomoniasis properties. This study also shows that MTZ, C. sinensis and Z. vulgaris are equally effective in preventing the growth of T. gallinae trophozoites in the culture.

Physiological Effects of Green-Colored Food-Derived Bioactive Compounds on Cancer

Green-colored foods, such as broccoli, sprouts, soybean, and green leafy vegetables are considered one of the representative healthy foods for containing various functional ingredients that can combat chronic diseases, including diabetes, obesity, and cancer. Herein, we reviewed the anti-cancer activities and the underlying mechanisms of some important bioactive compounds, such as sulforaphane, catechins, chlorophyll, isoflavone, indole dervatives, and lutein, present in green-colored foods. In vivo and clinical studies suggest that sulforaphane, a sulfur-containing compound found in cruciferous vegetables, can ameliorate prostate and breast cancer symptoms by arresting cell-cycle progression and modulating Ki67 and HDAC expression. A green tea compound, known as epigallocatechin-3-gallate (EGCG), has shown remarkable anti-cancer effects against prostate cancer and lung adenocarcinoma in human trials through its antioxidative defense and immunomodulatory functions. Chlorophyll, a natural pigment found in all green plants, can regulate multiple cancer-related genes, including cyclin D1, CYP1A, CYP1B1, and p53. Epidemiological studies indicate that chlorophyll can substantially reduce aflatoxin level and can mitigate colon cancer in human subjects. Remarkably, the consumption of soy isoflavone has been found to be associated with the lower incidence and mortality of breast and prostate cancers in East Asia and in Canada. In vivo and in vitro data point out that isoflavone has modulatory effects on estrogen and androgen signaling pathways and the expression of MAPK, NfκB, Bcl-2, and PI3K/AKT in different cancer models. Other green food bioactive compounds, such as indole derivatives and lutein, also exhibited suppressing effects in rodent models of lung, liver, stomach, cervical, and prostate cancers. In addition, some micronutrients, such as folate, riboflavin, retinoic acid, and vitamin D3 present in green foods, also showed potential cancer suppressing effects. Taken together, these data suggest potential chemopreventive functions of the bioactive compounds from green-colored foods. This paper could be beneficial for further research on the anti-carcinogenic effects of green-colored food-derived compounds, in order to develop green chemotherapeutics for cancers.

The antimicrobial and immunomodulatory effects of Ionophores for the treatment of human infection

Ionophores are a diverse class of synthetic and naturally occurring ion transporter compounds which demonstrate both direct and in-direct antimicrobial properties against a broad panel of bacterial, fungal, viral and parasitic pathogens. In addition, ionophores can regulate the host-immune response during communicable and non-communicable disease states. Although the clinical use of ionophores such as Amphotericin B, Bedaquiline and Ivermectin highlight the utility of ionophores in modern medicine, for many other ionophore compounds issues surrounding toxicity, bioavailability or lack of in vivo efficacy studies have hindered clinical development. The antimicrobial and immunomodulating properties of a range of compounds with characteristics of ionophores remain largely unexplored. As such, ionophores remain a latent therapeutic avenue to address both the global burden of antimicrobial resistance, and the unmet clinical need for new antimicrobial therapies. This review will provide an overview of the broad-spectrum antimicrobial and immunomodulatory properties of ionophores, and their potential uses in clinical medicine for combatting infection.

Catechins as Model Bioactive Compounds for Biomedical Applications

Research regarding polyphenols has gained prominence over the years because of their potential as pharmacological nutrients. Most polyphenols are flavanols, commonly known as catechins, which are present in high amounts in green tea. Catechins are promising candidates in the field of biomedicine. The health benefits of catechins, notably their antioxidant effects, are related to their chemical structure and the total number of hydroxyl groups. In addition, catechins possess strong activities against several pathogens, including bacteria, viruses, parasites, and fungi. One major limitation of these compounds is low bioavailability. Catechins are poorly absorbed by intestinal barriers. Some protective mechanisms may be required to maintain or even increase the stability and bioavailability of these molecules within living organisms. Moreover, novel delivery systems, such as scaffolds, fibers, sponges, and capsules, have been proposed. This review focuses on the unique structures and bioactive properties of catechins and their role in inflammatory responses as well as provides a perspective on their use in future human health applications.

In Vitro Growth- and Encystation-Inhibitory Efficacies of Matcha Green Tea and Epigallocatechin Gallate Against Acanthameoba Castellanii

We examined the inhibitory effect of matcha green tea (Camellia sinensis) and epigallocatechin gallate (EGCg; the most abundant catechin in tea) on the vegetative growth and encystation of Acanthamoeba castellanii T4 genotype. The sulforhodamine B (SRB) stain-based colorimetric assay and hemocytometer counting were used to determine the reduction in A. castellanii trophozoite proliferation and encystation, in response to treatment with C. sinensis or EGCg. Fourier transform infrared (FTIR) microscopy was used to analyze chemical changes in the trophozoites and cysts due to C. sinensis treatment. Hot brewed and cold brewed matcha inhibited the growth of trophozoites by >40% at a 100 % concentration. EGCg at concentrations of 50 to 500 µM significantly inhibited the trophozoite growth compared to control. Hot brewed matcha (100% concentration) also showed an 87% reduction in the rate of encystation compared to untreated control. Although 500 µM of EGCg increased the rate of encystation by 36.3%, 1000 µM reduced it by 27.7%. Both percentages were not significant compared to control. C. sinensis induced more cytotoxicity to Madin Darby canine kidney cells compared to EGCg. FTIR chemical fingerprinting analysis showed that treatment with brewed matcha significantly increased the levels of glycogen and carbohydrate in trophozoites and cysts.

In vitro activity of Camellia sinensis (green tea) against trophozoites and cysts of Acanthamoeba castellanii

The effect of Camellia sinensis (green tea) on the growth of Acanthamoeba castellanii trophozoites was examined using a microplate based-Sulforhodamine B (SRB) assay. C. sinensis hot and cold brews at 75% and 100% concentrations significantly inhibited the growth of trophozoites. We also examined the structural alterations in C. sinensis-treated trophozoites using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). This analysis showed that C. sinensis compromised the cell membrane integrity and caused progressive destruction of trophozoites. C. sinensis also significantly inhibited the parasite's ability to form cysts in a dose-dependent manner and reduced the rate of excystation from cysts to trophozoites. C. sinensis exhibited low cytotoxic effects on primary corneal stromal cells. However, cytotoxicity was more pronounced in SV40-immortalized corneal epithelial cells. Chromatographic analysis showed that both hot and cold C. sinensis brews contained the same number and type of chemical compounds. This work demonstrated that C. sinensis has anti-acanthamoebic activity against trophozoite and cystic forms of A. castellanii. Further studies are warranted to identify the exact substances in C. sinensis that have the most potent anti-acanthamoebic effect.

Myrrh Oil in Vitro Inhibitory Growth on Bovine and Equine Piroplasm Parasites and Babesia microti of Mice

The present experimental study was conducted for the assessment of the efficacy of in vitro inhibition of myrrh oil on the propagation of Babesia bovis, B. divergens, B. bigemina, Theileria equi, and B. caballi and in vivo efficacy on B. microti in mice through fluorescence assay based on SYBR green I. The culture of B. divergens B. bovis and was used to evaluate the in vitro possible interaction between myrrh oil and other commercial compound, such as pyronaridine tetraphosphate (PYR), diminazene aceturate (DA), or luteolin. Nested-polymerase chain reaction protocol using primers of the small-subunit rRNA of B. microti was employed to detect any remnants of DNA for studied parasitic species either in blood or tissues. Results elucidated that; Myrrh oil significantly inhibit the growth at 1% of parasitic blood level for all bovine and equine piroplasm under the study. Parasitic regrowth was inhibited subsequently by viability test at 2 µg/mL for B. bigemina and B. bovis, and there was a significant improvement in the in vitro growth inhibition by myrrh oil when combined with DA, PYR, and luteolin. At the same time; mice treated with a combination of myrrh oil/DA showed a higher inhibition in emitted fluorescence signals than the group that challenged with 25 mg/kg of diminazene aceturate at 10 and 12 days post-infection. In conclusion, this study has recommended the myrrh oil to treat animal piroplasmosis, especially in combination with low doses of DA.

Assay methods for in vitro and in vivo anti-Babesia drug efficacy testing: Current progress, outlook, and challenges

Absence of an effective high-throughput drug-screening system for Babesia parasites is considered one of the main causes for the presence of a wide gap in the treatment of animal babesiosis when compared with other hemoprotozoan diseases, such as malaria. Recently, a simple, accurate, and automatic fluorescence assay was established for large-scale anti-Babesia (B. bovis, B. bigemina, B. divergens, B. caballi and T. equi) drug screening. Such development will facilitate anti-Babesia drug discovery, especially in the post-genomic era, which will bring new chemotherapy targets with the completion of the Babesia genome sequencing project currently in progress. In this review, we present the current progress in the various assays for in vitro and in vivo anti-Babesia drug testing, as well as the challenges, highlighting new insights into the future of anti-Babesia drug screening.

Inhibitory effects of Syzygium aromaticum and Camellia sinensis methanolic extracts on the growth of Babesia and Theileria parasites

Currently, chemotherapeutics against piroplasmosis are also associated with toxicity and the emergence of drug-resistant parasites. Therefore, the discovery of new drug compounds is necessary for the effective control of bovine and equine piroplasms. Syzygium aromaticum (clove) and Camellia sinensis (green tea) have several documented medicinal properties. In the present study, the growth-inhibiting effects of S. aromaticum and C. sinensis methanolic extracts were evaluated in vitro and in vivo. The half-maximal inhibitory concentration (IC₅₀) values for methanolic S. aromaticum against Babesia bovis, B. bigemina, B. divergens, B. caballi, and Theileria equi were 109.8 ± 3.8, 8.7 ± 0.09, 76.4 ± 4.5, 19.6 ± 2.2, and 60 ± 7.3 μg/ml, respectively. Methanolic C. sinensis exhibited IC₅₀ values of 114 ± 6.1, 71.3 ± 3.7, 35.9 ± 6.8, 32.7 ± 20.3, and 60.8 ± 7.9 μg/ml against B. bovis, B. bigemina, B. divergens, B. caballi, and T. equi, respectively. The toxicity assay on Madin-Darby bovine kidney (MDBK), mouse embryonic fibroblast (NIH/3T3), and human foreskin fibroblast (HFF) cell lines showed that methanolic S. aromaticum and methanolic C. sinensis affected only the viability of the MDBK cell line with half-maximal effective concentrations (EC₅₀) of 894.7 ± 4.9 and 473.7 ± 7.4 μg/ml, respectively, while the viability of NIH/3T3 and HFF cell lines was not affected even at 1000 μg/ml. In the in vivo experiment, methanolic S. aromaticum and methanolic C. sinensis oral treatments at 150 mg/kg inhibited the growth of Babesia microti in mice by 69.2% and 42.4%, respectively. These findings suggest that methanolic S. aromaticum and methanolic C. sinensis extracts have the potential as alternative remedies for treating piroplasmosis.

Evaluation of the in vitro and in vivo inhibitory effect of thymoquinone on piroplasm parasites

BACKGROUND

Developing new antibabesial drugs with a low toxic effect to the animal and with no resistance from Babesia parasites is in urgent demand. In this concern, the antimalarial, anticancer and antioxidant effect of thymoquinone (TQ), a phytochemical compound found in the plant Nigella sativa, has been reported. Therefore, in the present study, the antibabesial effect of this compound was evaluated on the growth of piroplasm parasites.

RESULTS

Significant inhibition (P < 0.05) of the in vitro growth of piroplasm parasites were observed after treatment by TQ with IC₅₀ values of 35.41 ± 3.60, 7.35 ± 0.17, 0.28 ± 0.016, 74.05 ± 4.55 and 67.33 ± 0.94 μM for Babesia bovis, Babesia bigemina, Babesia divergens, Theileria equi and Babesia caballi, respectively. The in vitro inhibitory effect of TQ was significantly enhanced (P < 0.05) when used in combination with either diminazene aceturate on bovine Babesia and equine Babesia and Theileria cultures. In B. microti-infected mice, oral and intraperitoneal administrations of TQ showed significant (P < 0.05) inhibition of parasite growth at a dose of 70 mg/kg and 50 mg/kg, respectively, compared to the control group.

CONCLUSIONS

The obtained results indicate that thymoquinone might be a promising medicinal compound for use in the treatment of animal piroplasmosis.

2'-Hydroxyflavanone activity in vitro and in vivo against wild-type and antimony-resistant Leishmania amazonensis

Background

To overcome the current problems in leishmaniasis chemotherapy, natural products have become an interesting alternative over the past few decades. Flavonoids have been studied as promising family of compounds for leishmaniasis treatment. 2’-Hydroxyflavanone (2HF) is a flavanone, a class of flavonoid that has shown promising results in cancer studies. In this study, we demonstrated the effects of 2HF in vitro and in vivo against wild-type and antimony-resistant Leishmania amazonensis promastigotes.

Methodology/Principal findings

2HF was effective against promastigotes and the intracellular amastigote form, decreasing the infection index in macrophages infected with wild-type and antimony-resistant promastigotes, but it was not toxic to macrophages. In silico analysis indicated 2HF as a good oral candidate for leishmaniasis treatment. In vivo, 2HF was able to reduce the lesion size and parasite load in a murine model of cutaneous leishmaniasis using wild-type and antimony-resistant promastigotes, demonstrating no cross-resistance with antimonials.

Conclusions/Significance

Taken together, these results suggest 2HF as a potential candidate for leishmaniasis chemotherapy for cutaneous leishmaniasis caused by both wild-type and antimony-resistant Leishmania species by oral administration. Furthermore, studies should be conducted to determine the ideal dose and therapeutic regimen.

Leishmaniasis is a parasitic disease endemic to 98 countries, affecting more than 12 million people globally, and there are more than 350 million people in risk areas. Although there are many drugs available as alternatives for leishmaniasis treatment, they remain mostly ineffective, expensive and longstanding, in addition to generating side effects and resistance. Antimonial resistance is currently one of the biggest obstacles in leishmaniasis chemotherapy. Due to the poor chemotherapy scenario and the need for a drug able to overcome resistance problems and therapeutic failures, natural products have become an important alternative for leishmaniasis treatment. Here, we evaluated the antileishmanicidal activity of 2HF in vitro and in vivo against wild-type and antimony-resistant L. amazonensis cells. 2HF inhibited the cellular proliferation of promastigotes and the intracellular amastigote form in a dose-dependent manner in both wild-type and antimony-resistant cells. Furthermore, 2HF reduced the lesion size and parasitic load in a murine model of cutaneous leishmaniasis using wild-type and antimony-resistant promastigotes without altering hematological parameters and serological toxicology markers. This is the first time that the activity of a flavonoid on the antimony-resistant L. amazonensis has been demonstrated in vitro and in vivo by the oral route.

Green Tea Catechins: Their Use in Treating and Preventing Infectious Diseases

Green tea is one of the most popular drinks consumed worldwide. Produced mainly in Asian countries from the leaves of the Camellia sinensis plant, the potential health benefits have been widely studied. Recently, researchers have studied the ability of green tea to eradicate infectious agents and the ability to actually prevent infections. The important components in green tea that show antimicrobial properties are the catechins. The four main catechins that occur in green tea are (-)-epicatechin (EC), (-)-epicatechin-3-gallate (ECG), (-)-epigallocatechin (EGC), and (-)-epigallocatechin-3-gallate (EGCG). Of these catechins, EGCG and EGC are found in the highest amounts in green tea and have been the subject of most of the studies. These catechins have been shown to demonstrate a variety of antimicrobial properties, both to organisms affected and in mechanisms used. Consumption of green tea has been shown to distribute these compounds and/or their metabolites throughout the body, which allows for not only the possibility of treatment of infections but also the prevention of infections.

Green tea (Camellia sinensis) and l-theanine: Medicinal values and beneficial applications in humans-A comprehensive review

Green tea (Camellia sinensis) is a famous herb, and its extract has been extensively used in traditional Chinese medicinal system. In this context, several studies have revealed its health benefits and medicinal potentialities for several ailments. With ever increasing scientific knowledge, search for safer, potential and novel type of health-related supplements quest, scientists are re-directing their research interests to explore natural resources i.e. medicinal herbs/plant derived compounds. Green tea consumption has gained a special attention and popularity in the modern era of changing lifestyle. The present review is aimed to extend the current knowledge by highlighting the importance and beneficial applications of green tea in humans for safeguarding various health issues. Herein, we have extensively reviewed, analyzed, and compiled salient information on green tea from the authentic published literature available in PubMed and other scientific databases. Scientific literature evidenced that owing to the bioactive constituents including caffeine, l-theanine, polyphenols/flavonoids and other potent molecules, green tea has many pharmacological and physiological functions. It possesses multi-beneficial applications in treating various disorders of humans. This review also provides in-depth insights on the medicinal values of green tea which will be useful for researchers, medical professionals, veterinarians, nutritionists, pharmacists and pharmaceutical industry. Future research emphasis and promotional avenues are needed to explore its potential therapeutic applications for designing appropriate pharmaceuticals, complementary medicines, and effective drugs as well as popularize and propagate its multidimensional health benefits.

Performance and consistency of a fluorescence-based high-throughput screening assay for use in Babesia drug screening in mice

In this study, we evaluated the validity of a fluorescence-based assay using SYBR Green I (SG I) stain for screening antibabesial compounds against B. microti in mice. Two different hematocrits (HCTs; 2.5% and 5%) were used. Correlating relative fluorescence units (RFUs) with parasitemia showed significant linear relationships with R² values of 0.97 and 0.99 at HCTs of 2.5% and 5%, respectively. Meanwhile, the Z′ factors in a high-throughput screening (HTS) assay were within the permissible limit (≥0.5) at 2.5% HCT and lower than this value at 5% HCT. Taken together, the highest signal-to-noise (S/N) ratios were obtained at 2.5% HCT; therefore, we concluded that 2.5% was the best HCT for applying fluorescence assay in antibabesial drug screening in mice. Additionally, positive control mice and those treated with diminazene aceturate, pyronaridine tetraphosphate, and an allicin/diminazene aceturate combination showed peak parasitemia and fluorescence values on the same day post-inoculation. Moreover, using different concentrations of SG I revealed that the optimal concentration was 2x. In summary, considering that all experiments were applied under optimal laboratory conditions, fluorescence assay at 2.5% HCT using 2x SG I for B. microti parasite offers a novel approach for drug screening in mice.

Large-scale drug screening against Babesia divergens parasite using a fluorescence-based high-throughput screening assay

The validation of a fluorescence-based high-throughput screening (HTS) assay for determining the efficacies of large chemical libraries against Babesia divergens (bovine strain) in in vitro cultures was evaluated in this study. Hematocrits (HCTs) of 2.5%, 5%, and 10% were used for the in vitro culture at 1% parasitemia without daily replacement of the medium. Linearity and HTS assay results revealed that the best HCTs were 5% and 10%. The obtained IC50 values of diminazene aceturate, either by fluorescence-based HTS assay with and without daily replacement of medium or by fluorescence- and microscopy-based methods, did not differ significantly at 5% HCT. Actinonin and chloroquine diphosphate were the most effective drugs against the in vitro growth of B. divergens, followed by pyronaridine tetraphosphate- and luteolin-treated cultures. On contrary, tetracycline hydrochloride and (-)-epigallocatechin-3-gallate from green tea exhibited poor activity as compared with diminazene aceturate (positive control drug). The data indicated that 5% HCT without daily replacement of the culture medium mixed with bovine serum in vitro using a fluorescence-based HTS assay creates the best conditions for large-scale drug screening against B. divergens that infect cattle.

Clofazimine Inhibits the Growth of Babesia and Theileria Parasites In Vitro and In Vivo

The present study evaluated the growth-inhibitory effects of clofazimine, currently used for treating leprosy, against Babesia bovis, B. bigemina, B. caballi, and Theileria equi in in vitro culture and against Babesia microti in mice. The 50% inhibitory concentrations (IC50s) of clofazimine against the in vitro growth of B. bovis, B. bigemina, B. caballi, and T. equi were 4.5, 3, 4.3, and 0.29 μM, respectively. In mice infected with B. microti, treatment with 20 mg/kg of body weight of clofazimine administered orally resulted in a significantly lower peak parasitemia (5.3%) than that in the control group (45.9%), which was comparable to the subcutaneous administration of 25 mg/kg diminazene aceturate, the most widely used treatment for animal piroplasmosis. Although slight anemia was observed in both clofazimine- and diminazene aceturate-treated infected mice, the level and duration of anemia were lower and shorter, respectively, than those in untreated infected mice. Using blood transfusions and PCR, we also examined whether clofazimine completely killed B. microti On day 40 postinfection, when blood analysis was performed, parasites were not found in blood smears; however, the DNA of B. microti was detected in the blood of clofazimine-treated animals and in several tissues of clofazimine- and diminazene aceturate-treated mice by PCR. The growth of parasites was observed in mice after blood transfusions from clofazimine-treated mice. In conclusion, clofazimine showed excellent inhibitory effects against Babesia and Theileria in vitro and in vivo, and further study on clofazimine is required for the future development of a novel chemotherapy with high efficacy and safety against animal piroplasmosis and, possibly, human babesiosis.

Evaluation of in vitro inhibitory effect of enoxacin on Babesia and Theileria parasites

Enoxacin is a broad-spectrum 6-fluoronaphthyridinone antibacterial agent (fluoroquinolones) structurally related to nalidixic acid used mainly in the treatment of urinary tract infections and gonorrhea. Also it has been shown recently that it may have cancer inhibiting effect. The primary antibabesial effect of Enoxacin is due to inhibition of DNA gyrase subunit A, and DNA topoisomerase. In the present study, enoxacin was tested as a potent inhibitor against the in vitro growth of bovine and equine Piroplasms. The in vitro growth of five Babesia species that were tested was significantly inhibited (P < 0.05) by micro molar concentrations of enoxacin (IC50 values = 33.5, 15.2, 7.5 and 23.2 μM for Babesia bovis, Babesia bigemina, Babesia caballi, and Theileria equi, respectively). Enoxacin IC50 values for Babesia and Theileria parasites were satisfactory as the drug is potent antibacterial drug with minimum side effects. Therefore, enoxacin might be used for treatment of Babesiosis and Theileriosis especially in case of mixed infections with bacterial diseases or incase of animal sensitivity against diminazin toxicity.

Inhibitory effect of allicin on the growth of Babesia and Theileria equi parasites

Allicin is an active ingredient of garlic that has antibacterial, antifungal, antiviral, and antiprotozoal activity. However, the inhibitory effects of allicin on Babesia parasites have not yet been examined. In the present study, allicin was tested as a potent inhibitor against the in vitro growth of bovine and equine Babesia parasites and the in vivo growth of Babesia microti in a mouse model. The in vitro growth of Babesia bovis, Babesia bigemina, Babesia caballi, or Theileria equi was inhibited by allicin in a dose-dependent manner and had IC50 values of 818, 675, 470, and 742 μM, respectively. Moreover, allicin significantly inhibited (P < 0.001) invasion of B. bovis, B. bigemina, B. caballi, and T. equi into the host erythrocyte. Furthermore, mice treated with 30 mg/kg of allicin for 5 days significantly (P < 0.05) reduced the parasitemia of B. microti over the period of the study. To further examine the potential synergism of allicin with diminazene aceturate, growth inhibitory assays were performed in vitro and in vivo. Interestingly, combinations of diminazene aceturate with allicin synergistically potentiated its inhibitory effects in vitro and in vivo. These results indicate that allicin might be beneficial for the treatment of babesiosis, particularly when used in combination with diminazene aceturate.

Babesia bovis dihydroorotate dehydrogenase (BboDHODH) is a novel molecular target of drug for bovine babesiosis

The emergence of drug resistance and adverse side effects of current bovine babesiosis treatment suggest that the search of new drug targets and development of safer and effective compounds are required. This study focuses on dihydroorotate dehydrogenase (DHODH), the fourth enzyme of pyrimidine biosynthesis pathway as a potential drug target for bovine babesiosis. Recombinant Babesia bovis DHODH protein (rBboDHODH) was produced in Escherichia coli and used for characterization and measurement of enzymatic activity. Furthermore, the effects of DHODH inhibitors were evaluated in vitro. The recombinant B. bovis DHODH histidine fusion protein (rBboDHODH) had 42.4-kDa molecular weight and exhibited a specific activity of 475.7 ± 245 Unit/mg, a K_m = 276.2 µM for L-dihydroorotate and a K_m= 94.41 µM for decylubiquinone. A 44-kDa band of native BboDHODH was detected by Western blot analysis and found in parasites mitochondria using a confocal microscope. Among DHODH inhibitors, atovaquone (ATV) and leflunomide (LFN) significantly inhibited the activity of rBboDHODH as well as the growth of B. bovis in vitro. The half maximal inhibitory concentration (IC₅₀) of ATV and LFN was 2.38 ± 0.53 nM and 52.41 ± 11.47 µM, respectively. These results suggest that BboDHODH might be a novel target for development of new drug for treatment of B. bovis infection.

Evaluation of the In Vitro Efficacy of Artemisia annua, Rumex abyssinicus, and Catha edulis Forsk Extracts in Cancer and Trypanosoma brucei Cells

The current drugs against sleeping sickness are derived from cancer chemotherapeutic approaches. Herein, we aimed at evaluating the in vitro effect of alcoholic extracts of Artemisia annua (AMR), Rumex abyssinicus (RMA), and Catha edulis Forsk (CEF) on proliferation/viability of 1321N1 astrocytoma, MCF-7 breast cancer, THP-1 leukemia, and LNCaP, Du-145, and PC-3 prostate cancer cells and on Trypanosoma brucei cells. Proliferation of tumor cells was evaluated by WST-1 assay and viability/behaviour of T. brucei by cell counting and light microscopy. CEF was the most efficient growth inhibitor in comparison to AMR and RMA. Nevertheless, in LNCaP and THP-1 cells, all extracts significantly inhibited tumor growth at 3 μg/mL. All extracts inhibited proliferation of T. brucei cells in a concentration-dependent manner. Microscopic analysis revealed that 95% of the T. brucei cells died when exposed to 33 μg/mL CEF for 3 hrs. Similar results were obtained using 33 μg/mL AMR for 6 hrs. In case of RMA, however, higher concentrations were necessary to obtain similar effects on T. brucei. This demonstrates the antitumor efficacy of these extracts as well as their ability to dampen viability and proliferation of T. brucei, suggesting a common mechanism of action on highly proliferative cells, most probably by targeting cell metabolism.

Evaluation of in vitro and in vivo inhibitory effects of fusidic acid on Babesia and Theileria parasites

Fusidic acid known to has antibacterial, antifungal, and antimalarial activities. Fusidic acid blocks translation elongation factor G gene in Plasmodium falciparum. In the present study, the inhibitory effects of fusidic acid on the in vitro growth of bovine and equine Babesia parasites were evaluated. The inhibitory effect of fusidic acid on the in vivo growth of Babesia microti was also assessed. The in vitro growth of four Babesia species that were tested was significantly inhibited (P<0.05) by micromolar concentrations of fusidic acid (IC(50) values=144.8, 17.3, 33.3, and 56.25 μM for Babesia bovis, Babesia bigemina, Babesia caballi, and Theileria equi, respectively). Combinations of fusidic acid with diminazene aceturate synergistically potentiated its inhibitory effects in vitro on B. bovis and B. caballi. In B. microti-infected mice, fusidic acid caused significant (P<0.05) inhibition of the growth of B. microti at the dose of 500 mg/kg BW relative to control group. These results indicate that fusidic acid might be incorporated in treatment of babesiosis.

Inhibitory effects of pepstatin A and mefloquine on the growth of Babesia parasites

We evaluated the inhibitory effects of pepstatin A and mefloquine on the in vitro and in vivo growths of Babesia parasites. The in vitro growth of Babesia bovis, B. bigemina, B. caballi, and B. equi was significantly inhibited (P < 0.05) by micromolar concentrations of pepstatin A (50% inhibitory concentrations = 38.5, 36.5, 17.6, and 18.1 μM, respectively) and mefloquine (50% inhibitory concentrations = 59.7, 56.7, 20.7, and 4 μM, respectively). Furthermore, both reagents either alone at a concentration of 5 mg/kg or in combinations (2.5/2.5 and 5/5 mg/kg) for 10 days significantly inhibited the in vivo growth of B. microti in mice. Mefloquine treatment was highly effective and the combination treatments were less effective than other treatments. Therefore, mefloquine may antagonize the actions of pepstatin A against babesiosis and aspartic proteases may play an important role in the asexual growth cycle of Babesia parasites.

Cloning and characterization of histone deacetylase from Babesia bovis

The effect of inhibitors of histone deacetylase (HDAC) on Apicomplexa has been previously reported with the discovery of apicidin, a cyclic tetrapeptide having broad-spectrum antiparasitic activity. In the current study, we expressed Babesia bovis (B. bovis) recombinant-HDAC 3 (rBbHDAC3) as a GST-fusion protein in Escherichia coli (E. coli) and found that it was antigenic. An antiserum against the recombinant protein was generated in mice. The mice serum demonstrated the presence of HDAC in B. bovis by a Western blot assay. The murine anti-rBbHDAC3 reacted with B. bovis, Babesia bigemina (B. bigemina), Theileria equi (T. equi), and Babeisa caballi (B. caballi) merozoites in the indirect fluorescent antibody test (IFAT). Furthermore, the HDAC-enzymatic activity of the rBbHDAC3 protein was evaluated by a colorimetric assay. The enzymatic activity of rBbHDAC3 was inhibited by 100 ng/ml of apicidin, and the inhibitory effect of apicidin was dose-dependent. The inhibition of BbHDAC3 by apicidin was confirmed by Western blot, IFAT, and reverse transcription-polymerase chain reaction (RT-PCR). Finally, apicidin potentially inhibited the in vitro growth of Babesia parasites. The lower IC(50) values of apicidin against apicomplexan parasites than those of mammalian cells point to HDAC as an excellent drug target. The findings of the present study indicate that BbHDAC3 is a potential target for apicidin and might be a promising target for the development of novel anti-babesial drugs.

Apicoplast-targeting antibacterials inhibit the growth of Babesia parasites

The apicoplast housekeeping machinery, specifically apicoplast DNA replication, transcription, and translation, was targeted by ciprofloxacin, thiostrepton, and rifampin, respectively, in the in vitro cultures of four Babesia species. Furthermore, the in vivo effect of thiostrepton on the growth cycle of Babesia microti in BALB/c mice was evaluated. The drugs caused significant inhibition of growth from an initial parasitemia of 1% for Babesia bovis, with 50% inhibitory concentrations (IC(50)s) of 8.3, 11.5, 12, and 126.6 μM for ciprofloxacin, thiostrepton, rifampin, and clindamycin, respectively. The IC(50)s for the inhibition of Babesia bigemina growth were 15.8 μM for ciprofloxacin, 8.2 μM for thiostrepton, 8.3 μM for rifampin, and 206 μM for clindamycin. The IC(50)s for Babesia caballi were 2.7 μM for ciprofloxacin, 2.7 μM for thiostrepton, 4.7 μM for rifampin, and 4.7 μM for clindamycin. The IC(50)s for the inhibition of Babesia equi growth were 2.5 μM for ciprofloxacin, 6.4 μM for thiostrepton, 4.1 μM for rifampin, and 27.2 μM for clindamycin. Furthermore, an inhibitory effect was revealed for cultures with an initial parasitemia of either 10 or 7% for Babesia bovis or Babesia bigemina, respectively. The three inhibitors caused immediate death of Babesia bovis and Babesia equi. The inhibitory effects of ciprofloxacin, thiostrepton, and rifampin were confirmed by reverse transcription-PCR. Thiostrepton at a dose of 500 mg/kg of body weight resulted in 77.5% inhibition of Babesia microti growth in BALB/c mice. These results implicate the apicoplast as a potential chemotherapeutic target for babesiosis.

The dietary bioflavonoid quercetin synergizes with epigallocathechin gallate (EGCG) to inhibit prostate cancer stem cell characteristics, invasion, migration and epithelial-mesenchymal transition

Background

Much attention has been recently focused on the role of cancer stem cells (CSCs) in the initiation and progression of solid malignancies. Since CSCs are able to proliferate and self-renew extensively due to their ability to express anti-apoptotic and drug resistant proteins, thus sustaining tumor growth. Therefore, the strategy to eradicate CSCs might have significant clinical implications. The objectives of this study were to examine the molecular mechanisms by which epigallocathechin gallate (EGCG) inhibits stem cell characteristics of prostate CSCs, and synergizes with quercetin, a major polyphenol and flavonoid commonly detected in many fruits and vegetables.

Results

Our data indicate that human prostate cancer cell lines contain a small population of CD44⁺CD133⁺ cancer stem cells and their self-renewal capacity is inhibited by EGCG. Furthermore, EGCG inhibits the self-renewal capacity of CD44⁺α2β1⁺CD133⁺ CSCs isolated from human primary prostate tumors, as measured by spheroid formation in suspension. EGCG induces apoptosis by activating capase-3/7 and inhibiting the expression of Bcl-2, survivin and XIAP in CSCs. Furthermore, EGCG inhibits epithelial-mesenchymal transition by inhibiting the expression of vimentin, slug, snail and nuclear β-catenin, and the activity of LEF-1/TCF responsive reporter, and also retards CSC's migration and invasion, suggesting the blockade of signaling involved in early metastasis. Interestingly, quercetin synergizes with EGCG in inhibiting the self-renewal properties of prostate CSCs, inducing apoptosis, and blocking CSC's migration and invasion. These data suggest that EGCG either alone or in combination with quercetin can eliminate cancer stem cell-characteristics.

Conclusion

Since carcinogenesis is a complex process, combination of bioactive dietary agents with complementary activities will be beneficial for prostate cancer prevention and/ortreatment.