Amoebicidal Activity of Caffeine and Maslinic Acid by the Induction of Programmed Cell Death in Acanthamoeba

Cinnamic acid and lactobionic acid based nanoformulations as a potential antiamoebic therapeutics

Acanthamoeba castellanii causes granulomatous amoebic encephalitis, an uncommon but severe brain infection and sight-threatening Acanthamoeba keratitis. Most of the currently used anti-amoebic treatments are not always effective, due to persistence of the cyst stage, and recurrence can occur. Here in this study we synthesize cinnamic acid and lactobionic acid-based magnetic nanoparticles (MNPs) using co-precipitation technique. These nanoformulations were characterized by Fourier transform infrared spectroscopy and Atomic form microscopy. The drugs alone (Hesperidin, Curcumin and Amphotericin B), magnetic NPs alone, and drug-loaded nano-formulations were evaluated at a concentration of 100 μg/mL for antiamoebic activity against a clinical isolate of A. castellanii. Amoebicidal assays revealed that drugs and conjugation of drugs and NPs further enhanced amoebicidal effects of drug-loaded nanoformulations. Drugs and drug-loaded nanoformulations inhibited both encystation and excystation of amoebae. In addition, drugs and drug-loaded nanoformulations inhibited parasite binding capability to the host cells. Neither drugs nor drug-loaded nanoformulations showed cytotoxic effects against host cells and considerably reduced parasite-mediated host cell death. Overall, these findings imply that conjugation of medically approved drugs with MNPs produce potent anti-Acanthamoebic effects, which could eventually lead to the development of therapeutic medications.

Recent Advances Regarding the Molecular Mechanisms of Triterpenic Acids: A Review (Part II)

Triterpenic acids are a widespread class of phytocompounds which have been found to possess valuable therapeutic properties such as anticancer, anti-inflammatory, hepatoprotective, cardioprotective, antidiabetic, neuroprotective, lipolytic, antiviral, and antiparasitic effects. They are a subclass of triterpenes bearing a characteristic lipophilic structure that imprints unfavorable in vivo properties which subsequently limit their applications. The early investigation of the mechanism of action (MOA) of a drug candidate can provide valuable information regarding the possible side effects and drug interactions that may occur after administration. The current paper aimed to summarize the most recent (last 5 years) studies regarding the MOA of betulinic acid, boswellic acid, glycyrrhetinic acid, madecassic acid, moronic acid, and pomolic acid in order to provide scientists with updated and accessible material on the topic that could contribute to the development of future studies; the paper stands as the sequel of our previously published paper regarding the MOA of triterpenic acids with therapeutic value. The recent literature published on the topic has highlighted the role of triterpenic acids in several signaling pathways including PI3/AKT/mTOR, TNF-alpha/NF-kappa B, JNK-p38, HIF-α/AMPK, and Grb2/Sos/Ras/MAPK, which trigger their various biological activities.

Novel Plant-Based Metabolites as Disinfectants against Acanthamoeba castellanii

Due to global warming, coupled with global water shortages and the reliance of the public on household water tanks, especially in developing countries, it is anticipated that infections caused by free-living amoebae such as Acanthamoeba will rise. Thus, the development of novel disinfectant(s) which can target pathogenic free-living amoebae effectively is warranted. Herein, we extracted and isolated several plant-based secondary metabolites as novel disinfectants for use against pathogenic Acanthamoeba. The identity of the compounds was confirmed by nuclear magnetic resonance and tested for antiamoebic activities against clinical isolate of A. castellanii, belonging to the T4 genotype. Amoebicidal assays revealed that the compounds tested showed antiamoebic properties. Betulinic acid and betulin exhibited parasite killing of more than 65%. When tested against the cyst stage, betulinic acid, betulin, and vanillic acid inhibited both encystation and excystation processes. Furthermore, the plant-based metabolites significantly inhibited the binding capability of A. castellanii to host cells. Finally, most of the tested compounds displayed minimal cytotoxic activities against human cells and noticeably perturbed amoeba-mediated host cell cytotoxicity. Notably, both alkaloid and betulinic acid showed 20% cytotoxic effects, whereas betulin and lupeol had cytotoxic effects of 24% and 30%, respectively. Overall, our findings indicate that plant-based natural compounds demonstrate anti-Acanthamoebic properties, and they have potential candidates for water disinfectants or contact lens disinfecting solutions, as well as possible therapeutic drugs against Acanthamoeba infections.

Antiproliferation and Antiencystation Effect of Class II Histone Deacetylase Inhibitors on Acanthamoeba castellanii

Acanthamoeba is a ubiquitous and free-living protozoan pathogen responsible for causing Acanthamoeba keratitis (AK), a severe corneal infection inflicting immense pain that can result in permanent blindness. A drug-based treatment of AK has remained arduous because Acanthamoeba trophozoites undergo encystment to become highly drug-resistant cysts upon exposure to harsh environmental conditions such as amoebicidal agents (e.g., polyhexanide, chloroquine, and chlorohexidine). As such, drugs that block the Acanthamoeba encystation process could result in a successful AK treatment. Histone deacetylase inhibitors (HDACi) have recently emerged as novel therapeutic options for treating various protozoan and parasitic diseases. Here, we investigated whether novel HDACi suppress the proliferation and encystation of Acanthamoeba. Synthetic class II HDACi FFK29 (IIa selective) and MPK576 (IIb selective) dose-dependently decreased the viability of Acanthamoeba trophozoites. While these HDACi demonstrated a negligible effect on the viability of mature cysts, Acanthamoeba encystation was significantly inhibited by these HDACi. Apoptosis was slightly increased in trophozoites after a treatment with these HDACi, whereas cysts were unaffected by the HDACi exposure. The viability of human corneal cells was not affected by HDACi concentrations up to 10 μmol/L. In conclusion, these synthetic HDACi demonstrated potent amoebicidal effects and inhibited the growth and encystation of Acanthamoeba, thus highlighting their enormous potential for further development.

Anti-Inflammatory Activity of Three Triterpene from Hippophae rhamnoides L. in Lipopolysaccharide-Stimulated RAW264.7 Cells

Oleanolic acid (OA), asiatic acid (AA), and maslinic acid (MA) are ubiquitous isomeric triterpene phytochemicals with many pharmacological effects. To improve their application value, we used lipopolysaccharide (LPS) to induce RAW264.7 cells and studied the differences in the anti-inflammatory effects of the triterpenes according to their structural differences. MTT, Griess, and immunofluorescence assays, ELISA, flow cytometry, and Western blotting, were performed. The release of LPS-induced pro-inflammatory mediators, such as nitric oxide (NO), inducible nitric oxide synthase (iNOS), and interleukin (IL-6), was significantly inhibited by OA, AA, and MA at the same concentration, and AA and MA promoted the production of anti-inflammatory factor IL-10. OA, AA, and MA inhibited LPS-induced NF-κB nuclear translocation in RAW264.7 cells. OA and AA inhibited the phosphorylation of ERK1/2, P38, and JNK1/2 in LPS-stimulated RAW264.7 cells. Moreover, OA increased LPS-induced Nrf2 expression and decreased Keap1 expression in RAW264.7 cells. OA, AA, and MA inhibited LPS-stimulated intracellular reactive oxygen species (ROS) production and alleviated mitochondrial membrane potential depletion. Overall, our data suggested that OA, AA, and MA exhibited significant anti-inflammatory effects in vitro. In particular, OA and AA take effects through the MAPKs, NF-κB, and Nrf2 signaling pathways.

Cationic Surfactant-Natural Clay Complex as a Novel Agent Against Acanthamoeba castellanii Belonging to the T4 Genotype

BACKGROUND

Acanthamoeba is a protozoan pathogen that is widely distributed in the environment. Given the opportunity, it can cause a serious eye infection known as Acanthamoeba keratitis as well as a fatal brain infection known as granulomatous amoebic encephalitis. Inappropriate use of contact lenses can contribute to contracting Acanthamoeba keratitis, and contact lens disinfectants are not always effective in eradicating Acanthamoeba. Therefore, there is a need to develop novel antimicrobial agents with efficient antiamoebic properties.

OBJECTIVE

In this study, we tested octadecyltrimethylammonium (ODTMA)-clay (montmorillonite) complex as a novel antiamoebic agent.

METHODS

Using A. castellanii belonging to the T4 genotype of keratitis origin, amobicidal assays were performed to determine the effects of ODTMA-cay complex on the viability of parasites at various concentrations ranging from 10 to 100 μg. Adhesion and cytopathogenicity assays were performed to investigate ODTMA effects on A. castellanii-mediated binding and damage to human cells. Encystation and excystation assays were conducted to establish ODTMA-mediated inhibitory effects against the cyst stage of A. castellanii.

RESULTS

Using cell survival assays, the results revealed that ODTMA-clay complex exhibited amobicidal activity against keratitis-causing A. castellanii in a dose-dependent manner. Pretreatment of A. castellanii with ODTMA-clay complex inhibited parasite adhesion to as well as parasite-mediated human cell damage. Using encystation and excystation assays, it was revealed that ODTMA-clay complex inhibited A. castellanii cysts at 100 μg (P<0.05).

CONCLUSION

To the best of our knowledge, for the first time, it was shown that ODTMA-clay complex exhibited anti-Acanthamoebic activities. The possibility of adding ODTMA-clay in a contact lens cleaning solution to formulate effective disinfectants is discussed further.

Advances in Research on the Preparation and Biological Activity of Maslinic Acid

Maslinic acid, a pentacyclic triterpene acid, is mainly isolated from olives. Maslinic acid and its derivatives exhibit a broad range of biological properties, such as anti-inflammatory, anticancer, anti-diabetic, antimicrobial, neuroprotective and hepatoprotective activities. In this minireview, the progress of research on maslinic acid with regard to its bioactivities, extraction, semisynthetic preparation and patents is reported. The relationships between the structure and the activity of maslinic acid and its derivatives are also discussed.

Pharmacoinformatics approaches in the discovery of drug-like antimicrobials of plant origin

Medicinal plants have served as an important source for addressing the ailments of humans and animals alike. The emergence of advanced technologies in the field of drug discovery and development has helped in isolating various bioactive phytochemicals and developing them as drugs. Owing to their significant pharmacological benefits and minimum adverse effects, they not only serve as good candidates for therapeutics themselves but also help in the identification and development of related drug like molecules against various metabolic and infectious diseases. The ever-increasing diversity, severity and incidence of infectious diseases has resulted in an exaggerated mortality and morbidity levels. Geno-proteomic mutations in microbes, irrational prescribing of antibiotics, antimicrobial resistance and human population explosion, all call for continuous efforts to discover and develop alternated therapeutic options against the microbes. This review article describes the pharmacoinformatics tools and methods which are currently used in the discovery of bioactive phytochemicals, thus making the process more efficient and effective. The pharmacological aspects of the drug discovery and development process have also been reviewed with reference to the in silico activities. Communicated by Ramaswamy H. Sarma.

Repurposing of Drugs Is a Viable Approach to Develop Therapeutic Strategies against Central Nervous System Related Pathogenic Amoebae

Brain-eating amoebae including Acanthamoeba spp., Naegleria fowleri, and Balamuthia mandrillaris cause rare infections of the central nervous system that almost always result in death. The high mortality rate, lack of interest for drug development from pharmaceutical industries, and no available effective drugs present an alarming challenge. The current drugs employed in the management and therapy of these devastating diseases are amphotericin B, miltefosine, chlorhexidine, pentamidine, and voriconazole which are generally used in combination. However, clinical evidence shows that these drugs have limited efficacy and high host cell cytotoxicity. Repurposing of drugs is a practical approach to utilize commercially available, U.S. Food and Drug Administration approved drugs for one disease against rare diseases caused by brain-eating amoebae. In this Perspective, we highlight some of the success stories of drugs repositioned against neglected parasitic diseases and identify future potential for effective and sustainable drug development against brain-eating amoebae infections.

Novel Oleanolic and Maslinic Acid Derivatives as a Promising Treatment against Bacterial Biofilm in Nosocomial Infections: An in Vitro and in Vivo Study

Oleanolic acid (OA) and maslinic acid (MA) are pentacyclic triterpenic compounds that abound in industrial olive oil waste. These compounds have renowned antimicrobial properties and lack cytotoxicity in eukaryotic cells as well as resistance mechanisms in bacteria. Despite these advantages, their antimicrobial activity has only been tested in vitro, and derivatives improving this activity have not been reported. In this work, a set of 14 OA and MA C-28 amide derivatives have been synthesized. Two of these derivatives, MA-HDA and OA-HDA, increase the in vitro antimicrobial activity of the parent compounds while reducing their toxicity in most of the Gram-positive bacteria tested, including a methicillin-resistant Staphylococcus aureus-MRSA. MA-HDA also shows an enhanced in vivo efficacy in a Galleria mellonella invertebrate animal model of infection. A preliminary attempt to elucidate their mechanism of action revealed that these compounds are able to penetrate and damage the bacterial cell membrane. More significantly, their capacity to reduce antibiofilm formation in catheters has also been demonstrated in two sets of conditions: a static and a more challenged continuous-flow S. aureus biofilm.

G418 induces programmed cell death in Acanthamoeba through the elevation of intracellular calcium and cytochrome c translocation

Acanthamoeba is a widely distributed opportunistic parasite which causes a vision-threatening keratitis and a life-threatening encephalitis. The cyst stage of this amoeba is especially resistant to currently used therapeutics and so alternative agents are urgently required. Growing evidence supports the existence of a programmed cell death system (PCD) in Acanthamoeba and while some features are shared by higher eukaryote cells, others differ. It is hoped that by understanding these differences we can exploit them as targets for novel drug intervention to activate PCD pathways in the amoebae but not the invaded human tissue. Here, we use the aminoglycoside G418 to activate PCD in Acanthamoeba. This drug caused a shape change in the treated amoebae. Cells rounded up and contracted, and after 6 h fragments of cells resembling the ‘apoptotic bodies’ of vertebrate cells were observed. G418 causes an increase in intracellular calcium from a resting level of 24 nM to 60 nM after 6 h of treatment. Mitochondrial function as assayed by the ΔΨ_m reporting dye JC-1 and CTC a redox dye becomes inhibited during treatment and we have found that cytochrome c is released from the mitochondria. Cells stained with Hoechst showed first an alteration in chromatin structure and then a vesiculation of the nucleus with G418 treatment, although we found no obvious breakdown in genomic DNA in the early stages of PCD.