Thymoquinone Induced Leishmanicidal Effect via Programmed Cell Death in Leishmania donovani

Antiparasitic and Antifungal Activities of Cetyl-Maritima, a New N-Cetyl-Modified Maritima Derivative

Background/Objectives: New drugs are urgently needed for the treatment of neglected tropical diseases including leishmaniasis and eumycetoma, as well as globally occurring parasitic diseases such as toxoplasmosis. Fragrances, both natural and synthetic, were shown to be a rich source for the development of new anti-infectives and warrant deeper investigations. Exemplarily, we synthetically optimized the fragrance 4-(4,8-dimethyl-3,7-nonadienyl)-pyridine, a.k.a. Maritima, a pyridine derivative with marine odor. Methods: A new cationic N-cetyl-modified derivative of Maritima (dubbed Cetyl-Maritima), obtained by alkylation of Maritima, was tested for its activity against Madurella mycetomatis (M. mycetomatis) fungi, as well as against Toxoplasma gondii (T. gondii) and Leishmania major (L. major) protozoal parasites. Results: Cetyl-Maritima was found to be more strongly antifungal than the parent Maritima and a known antibiotic cetylpyridinium salt. Cetyl-Maritima also showed a similar activity against T. gondii parasites and, most notably, exhibited sub-micromolar activity against L. major amastigotes. Conclusions: The considerable antileishmanial activity of Cetyl-Maritima might lead to the development of a new potent and cost-effective drug candidate for the therapy of leishmaniasis and other infectious diseases caused by kinetoplastid parasites.

Identification of novel anti-leishmanials targeting glutathione synthetase of the parasite: a drug repurposing approach

Drug repurposing has emerged as an effective strategy against infectious diseases such as visceral leishmaniasis. Here, we evaluated four FDA-approved drugs-valrubicin, ciclesonide, deflazacort, and telithromycin-for their anti-leishmanial activity on Leishmania donovani parasites, especially their ability to target the enzyme glutathione synthetase (LdGS), which enables parasite survival under oxidative stress in host macrophages. Valrubicin and ciclesonide exhibited superior inhibitory effects compared to deflazacort and telithromycin, inhibiting the promastigotes at very low concentrations, with IC50 values of 1.09 ± 0.09 μm and 2.09 ± 0.09 μm, respectively. Subsequent testing on amastigotes revealed the IC50 values of 1.74 ± 0.05 μm and 3.32 ± 0.21 μm for valrubicin and ciclesonide, respectively. Molecular and cellular level analysis further elucidated the mechanisms underlying the anti-leishmanial activity of valrubicin and ciclesonide.

Repurposing FDA approved drugs against Sterol C-24 methyltransferase of Leishmania donovani: A dual in silico and in vitro approach

Leishmaniasis is a disease caused by the parasite Leishmania donovani affecting populations belonging to developing countries. The present study explores drug repurposing as an innovative strategy to identify new uses for approved clinical drugs, reducing the time and cost required for drug discovery. The three-dimensional structure of Leishmania donovani Sterol C-24 methyltransferase (LdSMT) was modeled and 1615 FDA-approved drugs from the ZINC database were computationally screened to identify the potent leads. Fulvestrant, docetaxel, indocyanine green, and iohexol were shortlisted as potential leads with the highest binding affinity and fitness scores for the concerned pathogenic receptor. Molecular dynamic simulation studies showed that the macromolecular complexes of indocyanine green and iohexol with LdSMT remained stable throughout the simulation and can be further evaluated experimentally for developing an effective drug. The proposed leads have further demonstrated promising safety profiles during cytotoxicity analysis on the J774.A1 macrophage cell line. Mechanistic analysis with these two drugs also revealed significant morphological alterations in the parasite, along with reduced intracellular parasitic load. Overall, this study demonstrates the potential of drug repurposing in identifying new treatments for leishmaniasis and other diseases affecting developing countries, highlighting the importance of considering approved clinical drugs for new applications.

Simultaneous Application of Thymoquinone and Hydroxychloroquine Suppresses Autophagy and Disrupts the Autophagosomal Trench Engulfed Leishmania major

Background

Leishmaniasis is a vector-borne disease prevalent in 98 countries worldwide. The current treatment has shortcomings, including drug resistance and adverse effects, highlighting the need for novel medications and treatment strategies. This study aimed to investigate the anti-leishmanial effect of thymoquinone (TQ) during the regulation of autophagy in the macrophage cell line (RAW 264.7).

Methods

After culturing the macrophage cell line, an MTT assay was performed to assess the cytotoxicity effects of the agents at different concentrations of TQ, HCQ (hydroxychloroquine), MET (metformin), and GLU (glucantime). The study groups included PBS, GLU, TQ, TQ + MET, GLU + MET, TQ + HCQ, GLU + HCQ, HCQ, and MET. The cells were then infected with L. major and treated with TQ, while autophagy was regulated using HCQ and MET. Subsequently, the infection index, the number of amastigote loads, and the fold change in the expression of specific autophagy-related genes (LC3, P62, and Beclin) in the treatment groups were evaluated.

Results

There was a significant decrease in the percentage of the infected macrophages treated with TQ and also the autophagy inhibitor HCQ compared to the control group. Macrophages treated with HCQ + TQ showed a significant reduction in the infection index and amastigote load compared to the TQ-treated group. Additionally, using HCQ as an autophagy inhibitor, along with TQ or GLU, enhanced the clearance of parasites and reduced the infection index of macrophages.

Conclusion

Downregulating autophagy could be a promising approach for Leishmania therapy, by which the leishmanicidal effect of TQ and GLU will be enhanced.

Anhydroparthenin as a dual-target inhibitor against Sterol C-24 methyltransferase and Sterol 14-α demethylase of Leishmania donovani: A comprehensive in vitro and in silico study

Parthenium hysterophorus plant has a diverse chemical profile and immense bioactive potential. It exhibits excellent pharmacological properties such as anti-cancer, anti-inflammatory, anti-malarial, microbicidal, and anti-trypanosomal. The present study aims to evaluate the anti-leishmanial potential and toxicological safety of anhydroparthenin isolated from P. hysterophorus. Anydroparthenin was extracted from the leaves of P. hysterophorus and characterized through detailed analysis of 1H, 13C NMR, and HRMS. Dye-based in vitro and ex vivo assays confirmed that anhydroparthenin significantly inhibited both promastigote and amastigote forms of the Leishmania donovani parasites. Both the cytotoxicity experiment and hemolytic assay revealed its non-toxic nature and safety index in the range of 10 to 15. Further, various mechanistic assays suggested that anhydroparthenin led to the generation of oxidative stress, intracellular ATP depletion, alterations in morphology and mitochondrial membrane potential, formation of intracellular lipid bodies, and acidic vesicles, ultimately leading to parasite death. As a dual targeting approach, computational studies and sterol quantification assays confirmed that anhydroparthenin inhibits the Sterol C-24 methyl transferase and Sterol 14-α demethylase proteins involved in the ergosterol biosynthesis in Leishmania parasites. These results suggest that anhydroparthenin could be a promising anti-leishmanial molecule and can be developed as a novel therapeutic stratagem against leishmaniasis.

Thymoquinone Effect on Leishmania tropica/infantum and Leishmania-Infected Macrophages

INTRODUCTION

Leishmania is a parasitic protozoan that tries to enter and amplify within macrophages. Macrophage cells are also immune defense cells that phagocyte many microbes like bacteria, fungi, as well as parasites like Leishmania spp. However, they are unable to kill this parasite that resides in the phagosomes of contaminated macrophages and multiplies in these macrophages, leading to the destruction of contaminated macrophages and the emerging of Leishmania wounds. A large number of current therapies for Leishmania cure have adverse effects, or parasites have developed resistance to some of these therapies, so a better therapy for the cure of Leishmania is required. Thymoquinone is one of the Nigella Sativa ingredients with numerous biological effects, such as antioxidant as well as antimicrobial effects on a variety of microbes, namely fungi, bacteria, as well as parasites like Leishmania spp. The impacts of Thymoquinone on Leishmania tropica and Leishmania infantum, as well as Leishmania-infected macrophages, were examined in this study.

METHODS

The impact of various Thymoquinone dosages on L. tropica and L. infantum promastigotes and amastigotes was examined in vitro. Flow cytometry, as well as MTT, was also applied to examine the cytotoxic activity of Thymoquinone on promastigotes of L. tropica and L. infantum, as well as the incidence of apoptosis. The amastigote assay is also utilized to calculate the % of contaminated macrophages as well as the number of the present parasites in each macrophage.

RESULTS

The percentage of macrophages contaminated with L. tropica and L. infantum amastigotes after medicating with 20 μM of Thymoquinone was 23% and 19%, respectively. Also, after medicating with 10 μM of Thymoquinone, these percentages were 32% and 31%, respectively. Flow cytometry indicated that Thymoquinone caused 33.9% and 31.4% apoptosis in L. tropica and L. infantum, respectively. As determined by the promastigote assay, the inhibitory concentration (IC50) of Thymoquinone for L. tropica and L. infantum was 9.49 μM and 12.66 μM, respectively. The results of the promastigote and amastigote assay show that with an increase in Thymoquinone doses, its ability to kill Leishmania parasites increases, too.

CONCLUSION

According to the results of the study, Thymoquinone has a potentially lethal impact on L. tropica and L. infantum promastigotes as well as amastigotes (within leishmania contaminated macrophages).

Exploring the Potential of Thymoquinone-Stabilized Selenium Nanoparticles: In HEC1B Endometrial Cancer Cells Revealing Enhanced Anticancer Efficacy

The aim of this research is to examine the potential anticancer properties of thymoquinone (TQ)-encapsulated selenium nanoparticles (TQ-SeNPs) in HEC1B endometrial carcinoma cells. TQ-SeNPs were synthesized, and their size, morphology, and elemental analysis were characterized. Morphological changes were examined by using scanning electron microscopy (SEM). The cytotoxicity and viability of nanothymoquinone were assessed by the XTT (2,3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5 carboxanilide) assay. Gene expressions and protein levels of the mitogen-activated protein kinase (MAPK) signaling pathway were analyzed by real-time PCR and enzyme-linked immunosorbent assay (ELISA), respectively. The decrease in the viability of HEC1B endometrial carcinoma cells was observed in a time- and dose-dependent manner. HEC-1B cells were treated with TQ-SeNP at 40-640 μg/mL concentrations and time intervals, and their viability was assessed by XTT assay. IC50 doses of TQ-SeNP in HEC1B cells were detected as 526.45 μg/mL at 48th hour. ELISA indicated that TQ-SeNP treatment reduced the level of p38 MAPK. ERK2, MEK2, and NFKB (p65) mRNA expressions were decreased in the dose group administered TQ-SeNP at the 48th hour compared to that in the control group. However, it was not significant. The novel nanoparticle showed an antiproliferative effect in endometrial cancer cells. However, further studies are needed to increase the anticancer activity of the cell in the TQ-SeNP interaction.

Novel chemical scaffold as potential drug against Leishmania donovani: Integrated computational and experimental approaches

In this study, we have screened a large number of Food and Drug Administration-approved compounds for novel anti-leishmanial molecules targeting the citrate synthase enzyme of the parasite. Based on their docking and molecular dynamic simulation statistics, five compounds were selected. These compounds followed Lipinski's rule of five. Additionally, in vitro, antileishmanial and cytotoxicity studies were performed. The three compounds, Abemaciclib, Bazedoxifene, and Vorapaxar, had shown effective anti-leishmanial activities with IC50 values of 0.92 ± 0.02, 0.65 ± 0.09, and 6.1 ± 0.91 against Leishmania donovani promastigote and with EC50 values of 1.52 ± 0.37, 2.11 ± 0.38, 10.4 ± 1.27 against intramacrophagic amastigote without significantly harming macrophage cells. Among them, from in silico and antileishmanial activities studies, Abemaciclib had been selected based on their less binding energy, good antileishmanial activities, and also a significant difference in their binding energy with human citrate synthase for cell death mechanistic studies using flow cytometry and a DNA fragmentation assay. The action of this compound resulted in an increased reactive oxygen species production, depolarization of mitochondrial membrane potential, DNA damage, and an increase in the sub-G1 cell population. These properties are the hallmarks of apoptosis which were further confirmed by apoptotic assay. Based on the above result, this anticancer compound Abemaciclib could be employed as a potential treatment option for leishmaniasis after further confirmation.

Antiprotozoal Activity of Thymoquinone (2-Isopropyl-5-methyl-1,4-benzoquinone) for the Treatment of Leishmania major-Induced Leishmaniasis: In Silico and In Vitro Studies

Leishmaniasis, a neglected tropical parasitic disease (NTPD), is caused by various Leishmania species. It transmits through the bites of the sandfly. The parasite is evolving resistance to commonly prescribed antileishmanial drugs; thus, there is an urgent need to discover novel antileishmanial drugs to combat drug-resistant leishmaniasis. Thymoquinone (2-isopropyl-5-methyl-1,4-benzoquinone; TQ), a primary pharmacologically active ingredient of Nigella sativa (black seed) essential oil, has been reported to possess significant antiparasitic activity. Therefore, the present study was designed to investigate the in vitro and in silico antileishmanial activity of TQ against various infectious stages of Leishmania major (L. major), i.e., promastigotes and amastigotes, and its cytotoxicity against mice macrophages. In silico molecular dockings of TQ were also performed with multiple selected target proteins of L. major, and the most preferred antileishmanial drug target protein was subjected to in silico molecular dynamics (MD) simulation. The in vitro antileishmanial activity of TQ revealed that the half-maximal effective concentration (EC₅₀), half-maximal cytotoxic concentration (CC₅₀), and selectivity index (SI) values for promastigotes are 2.62 ± 0.12 μM, 29.54 ± 0.07 μM, and 11.27, while for the amastigotes, they are 17.52 ± 0.15 μM, 29.54 ± 0.07 μM, and 1.69, respectively. The molecular docking studies revealed that squalene monooxygenase is the most preferred antileishmanial drug target protein for TQ, whereas triosephosphate isomerase is the least preferred. The MD simulation revealed that TQ remained stable in the binding pocket throughout the simulation. Additionally, the binding energy calculations using Molecular Mechanics Generalized-Born Surface Area (MMGBSA) indicated that TQ is a moderate binder. Thus, the current study shows that TQ is a promising antileishmanial drug candidate that could be used to treat existing drug-resistant leishmaniasis.