Inhibition of Toxoplasma gondii Growth by Dihydroquinine and Its Mechanisms of Action

Mitochondrial dysfunction induced by bedaquiline as an anti-Toxoplasma alternative

Toxoplasma gondii is a zoonotic parasite that infects one-third of the world's population and nearly all warm-blooded animals. Due to the complexity of T. gondii's life cycle, available treatment options have limited efficacy. Thus, there is an urgent need to develop new compounds or repurpose existing drugs with potent anti-Toxoplasma activity. This study demonstrates that bedaquiline (BDQ), an FDA-approved diarylquinoline antimycobacterial drug for the treatment of tuberculosis, potently inhibits the tachyzoites of T. gondii. At a safe concentration, BDQ displayed a dose-dependent inhibition on T. gondii growth with a half-maximal effective concentration (EC50) of 4.95 μM. Treatment with BDQ significantly suppressed the proliferation of T. gondii tachyzoites in the host cell, while the invasion ability of the parasite was not affected. BDQ incubation shrunk the mitochondrial structure and decreased the mitochondrial membrane potential and ATP level of T. gondii parasites. In addition, BDQ induced elevated ROS and led to autophagy in the parasite. By transcriptomic analysis, we found that oxidative phosphorylation pathway genes were significantly disturbed by BDQ-treated parasites. More importantly, BDQ significantly reduces brain cysts for the chronically infected mice. These results suggest that BDQ has potent anti-T. gondii activity and may impair its mitochondrial function by affecting proton transport. This study provides bedaquiline as a potential alternative drug for the treatment of toxoplasmosis, and our findings may facilitate the development of new effective drugs for the treatment of toxoplasmosis.

Rottlerin impairs early and late steps of Toxoplasma gondii infection in human trophoblast cells and villous explants

Congenital toxoplasmosis, caused by the opportunistic protozoan parasite T. gondii, can cause stillbirths, miscarriages and fetal abnormalities, as well as encephalitis and chorioretinitis in newborns. Available treatment options rely on antiparasitic drugs that have been linked to serious side effects, high toxicity and the development of drug-resistant parasites. The search for alternative therapeutics to treat this disease without acute toxicity for the mother and child is essential for the advancement of current therapeutic procedures. The present study aimed to unravel the mode of the anti-T. gondii action of Rottlerin, a natural polyphenol with multiple pharmacological properties described. Herein, we further assessed the antiparasitic activity of Rottlerin against T. gondii infection on the human trophoblastic cells (BeWo cells) and, for the first time, on human villous explants. We found that non-cytotoxic doses of Rottlerin impaired early and late steps of parasite infection with an irreversible manner in BeWo cells. Rottlerin caused parasite cell cycle arrest in G1 phase and compromised the ability of tachyzoites to infect new cells, thus highlighting the possible direct action on parasites. An additional and non-exclusive mechanism of action of Rottlerin involves the modulation of host cell components, by affecting lipid droplet formation, mitochondrial function and upregulation of the IL-6 and MIF levels in BeWo cells. Supporting our findings, Rottlerin also controlled T. gondii proliferation in villous explants with low toxicity and reduced the IL-10 levels, a cytokine associated with parasite susceptibility. Collectively, our results highlighted the potential use of Rottlerin as a promising tool to prevent and/or treat congenital toxoplasmosis.

Quercetin inhibits Toxoplasma gondii tachyzoite proliferation and acts synergically with azithromycin

Quercetin (QUE) is a natural polyphenol known to have numerous pharmacological properties against infectious and non-infectious diseases. Azithromycin (AZ) is an antibiotic that belongs to the azalide class of antimicrobials and an antiparasitic that is known to be effective in combination with clindamycin against pyrimethamine/sulfadiazine-resistant Toxoplasma gondii tachyzoites in clinical settings. Both compounds are known to target protein synthesis and have anti-inflammatory properties. However, little is known about QUE and AZ synergistic interaction against T. gondii growth. Here, we report for the first time the effects of the combination of QUE and AZ on T. gondii growth. The 50% inhibitory concentration (IC50) for QUE at 72 h of interaction was determined to be 0.50 µM, whereas AZ gave an IC50 value of 0.66 µM at 72 h of interaction with parasites. Combination testing of QUE and AZ in a ratio of 2:1 (QUE:AZ) showed an IC50 value of 0.081 µM. Interestingly, a fractional inhibitory index value of 0.28 was observed, indicating a strong synergy. QUE was also found to upregulate the generation of reactive oxygen species and cause dysfunction of the mitochondria membrane of both intracellular and extracellular T. gondii tachyzoites. Overall, the results indicate that QUE is a novel lead capable of synergizing with AZ for inhibiting T. gondii growth and may merit future investigation in vivo for possible combination drug development.

BjussuLAAO-II, an l-amino acid oxidase from Bothrops jararacussu snake venom, impairs Toxoplasma gondii infection in human trophoblast cells and villous explants from the third trimester of pregnancy

One-third of the world's population is estimated to be affected by toxoplasmosis. Pregnancy-related Toxoplasma gondii infection can cause vertical transmission, infect the fetus, and cause miscarriage, stillbirth, and fetal death. The current study showed that both human trophoblast cells (BeWo lineage) and human explant villous were resistant to T. gondii infection after incubation with BjussuLAAO-II, an l-amino acid oxidase isolated from Bothrops jararacussu. Almost 90% of the parasite's ability to proliferate in BeWo cells was decreased by the toxin at 1.56 μg/mL and showed an irreversible anti-T. gondii effect. Also, BjussuLAAO-II impaired the key events of adhesion and invasion of T. gondii tachyzoites in BeWo cells. BjussuLAAO-II antiparasitic properties were associated with the intracellular production of reactive oxygen species and hydrogen peroxide, since the presence of catalase restored the parasite's growth and invasion. In addition, T. gondii growth in human villous explants was decreased to approximately 51% by the toxin treatment at 12.5 μg/mL. Furthermore, BjussuLAAO-II treatment altered IL-6, IL-8, IL-10 and MIF cytokines levels, assuming a pro-inflammatory profile in the control of T. gondii infection. This study contributes to the potential use of a snake venom l-amino acid oxidase for the development of agents against congenital toxoplasmosis and the discovery of new targets in parasites and host cells.

Anti-Toxoplasma gondii activity of Trametes versicolor (Turkey tail) mushroom extract

Toxoplasma gondii (T. gondii) infection continues to rise globally in humans and animals with high socioeconomic and public health challenges. Current medications used against T. gondii infection are limited in efficacy, safety, and affordability. This research was conducted to assess the higher fungi extract effect on T. gondii tachyzoites growth in vitro and possibly decipher its mechanism of action. Furthermore, we evaluated the extract's effect on human foreskin fibroblast viability. The methanol extracts of Turkey tail (TT) mushroom was tested against T. gondii tachyzoites growth using an RH-RFP type I strain that expresses red fluorescent protein throughout culture in a dose-dependent manner using a fluorescent plate reader. Similarly, we tested the effect of the extract on host cell viability. We observed that TT extract inhibited tachyzoites growth with a 50% minimum inhibitory concentration (IC_50s), IC₅₀ = 5.98 ± 1.22 µg/mL, and 50% cytotoxic concentration (CC_50s), CC₅₀ ≥ 100 µg/mL. It was discovered that TT extract induced strong mitochondria superoxide and  reactive oxygen species production and disrupted mitochondria membrane potential in T. gondii tachyzoites. Additionally, scanning electron microscopy depicted that TT extract and pyrimethamine (PY) caused a morphological deformation of tachyzoites in vitro. In conclusion, TT methanol extract made up of phytosterols, bioactive sphingolipids, peptides, phenolic acids, and lactones could be a promising source of new compounds for the future development of anti-Toxoplasma gondii drugs. Extracts were non-cytotoxic, even at higher concentrations.

In Vitro Evaluation Reveals Effect and Mechanism of Artemether against Toxoplasma gondii

Due to the limited effectiveness of existing drugs for the treatment of toxoplasmosis, there is a dire need for the discovery of new therapeutic options. Artemether is an important drug for malaria and several studies have indicated that it also exhibits anti-T. gondii activity. However, its specific effect and mechanisms are still not clear. To elucidate its specific role and potential mechanism, we first evaluated its cytotoxicity and anti-Toxoplasma effect on human foreskin fibroblast cells, and then analyzed its inhibitory activity during T. gondii invasion and intracellular proliferation. Finally, we examined its effect on mitochondrial membrane potential and reactive oxygen species (ROS) in T. gondii. The CC50 value of artemether was found to be 866.4 μM, and IC50 was 9.035 μM. It exhibited anti-T. gondii activity and inhibited the growth of T. gondii in a dose-dependent manner. We also found that the inhibition occurred primarily in intracellular proliferation, achieved by reducing the mitochondrial membrane integrity of T. gondii and stimulating ROS production. These findings suggest that the mechanism of artemether against T. gondii is related to a change in the mitochondrial membrane and the increase in ROS production, which may provide a theoretical basis for optimizing artemether derivatives and further improving their anti-Toxoplasma efficacy.

Evaluation of the Combined Effect of Artemisinin and Ferroptosis Inducer RSL3 against Toxoplasma gondii

Toxoplasma gondii is a widespread intracellular pathogen that infects humans and a variety of animals. Dihydroartemisinin (DHA), an effective anti-malarial drug, has potential anti-T. gondii activity that induces ferroptosis in tumor cells, but the mechanism by which it kills T. gondii is not fully understood. In this study, the mechanism of DHA inhibiting T. gondii growth and its possible drug combinations are described. DHA potently inhibited T. gondii with a half-maximal effective concentration (EC₅₀) of 0.22 μM. DHA significantly increased the ROS level of parasites and decreased the mitochondrial membrane potential, which could be reversed by ferroptosis inhibitors (DFO). Moreover, the ferroptosis inducer RSL3 inhibited T. gondii with an EC₅₀ of 0.75 μM. In addition, RSL3 enhanced the DHA-induced ROS level, and the combination of DHA and RSL3 significantly increased the anti-Toxoplasma effect as compared to DHA alone. In summary, we found that DHA-induced ROS accumulation in tachyzoites may be an important cause of T. gondii growth inhibition. Furthermore, we found that the combination of DHA and RSL3 may be an alternative to toxoplasmosis. These results will provide a new strategy for anti-Toxoplasma drug screening and clinical medication guidance.

Hydroquinine Possesses Antibacterial Activity, and at Half the MIC, Induces the Overexpression of RND-Type Efflux Pumps Using Multiplex Digital PCR in Pseudomonas aeruginosa

Hydroquinine is an organic compound that is closely related to quinine-derivative drugs and contains anti-malarial and anti-arrhythmia activities. It has been also found in abundance in some natural extracts that possess antibacterial properties. However, there is little evidence demonstrating the antibacterial effect of hydroquinine. Therefore, we aimed to investigate the antibacterial properties of hydroquinine using broth microdilution methods. In addition, we evaluated the transcriptional responses of P. aeruginosa to hydroquinine-induced stress using RNA sequencing with transcriptomic analysis and validated the results using PCR-based methods. The MIC and MBC values of hydroquinine against all eight bacterial strains investigated ranged from 650 to 2500 and from 1250 to 5000 µg/mL, respectively. Transcriptomic analysis demonstrated that RND efflux pump transcripts were overexpressed (4.90−9.47 Log2 fold change). Using mRT-dPCR and RT-qPCR, we identified that mRNA levels of mexD and mexY genes were overexpressed in response to just half the MIC of hydroquinine in P. aeruginosa. In conclusion, we uncover the antimicrobial potential of hydroquinine as well as identify changes in gene expression that may contribute to bacterial resistance. Further work will be required to explore the efficacy and potential use of hydroquinine in the clinic.

Decellularized Avian Cartilage, a Promising Alternative for Human Cartilage Tissue Regeneration

Articular cartilage defects, and subsequent degeneration, are prevalent and account for the poor quality of life of most elderly persons; they are also one of the main predisposing factors to osteoarthritis. Articular cartilage is an avascular tissue and, thus, has limited capacity for healing and self-repair. Damage to the articular cartilage by trauma or pathological causes is irreversible. Many approaches to repair cartilage have been attempted with some potential; however, there is no consensus on any ideal therapy. Tissue engineering holds promise as an approach to regenerate damaged cartilage. Since cell adhesion is a critical step in tissue engineering, providing a 3D microenvironment that recapitulates the cartilage tissue is vital to inducing cartilage regeneration. Decellularized materials have emerged as promising scaffolds for tissue engineering, since this procedure produces scaffolds from native tissues that possess structural and chemical natures that are mimetic of the extracellular matrix (ECM) of the native tissue. In this work, we present, for the first time, a study of decellularized scaffolds, produced from avian articular cartilage (extracted from Gallus Gallus domesticus), reseeded with human chondrocytes, and we demonstrate for the first time that human chondrocytes survived, proliferated and interacted with the scaffolds. Morphological studies of the decellularized scaffolds revealed an interconnected, porous architecture, ideal for cell growth. Mechanical characterization showed that the decellularized scaffolds registered stiffness comparable to the native cartilage tissues. Cell growth inhibition and immunocytochemical analyses showed that the decellularized scaffolds are suitable for cartilage regeneration.