Anti-amoebic properties of a Malaysian marine sponge Aaptos sp. on Acanthamoeba castellanii

A Narrative Review of Acanthamoeba Isolates in Malaysia: Challenges in Infection Management and Natural Therapeutic Advancements

Acanthamoeba, a free-living amoeba (FLA) found in diverse ecosystems, poses significant health risks globally, particularly in Malaysia. It causes severe infectious diseases, e.g., Acanthamoeba keratitis (AK), primarily affecting individuals who wear contact lenses, along with granulomatous amoebic encephalitis (GAE), a rare but often life-threatening condition among immunocompromised individuals. AK has become increasingly prevalent in Malaysia and is linked to widespread environmental contamination and improper contact lens hygiene. Recent studies highlight Acanthamoeba's capacity to serve as a "Trojan horse" for amoeba-resistant bacteria (ARBs), contributing to hospital-associated infections (HAIs). These symbiotic relationships and the resilience of Acanthamoeba cysts make treatment challenging. Current diagnostic methods in Malaysia rely on microscopy and culture, though molecular procedures like polymerase chain reaction (PCR) are employed for more precise detection. Treatment options remain limited due to the amoeba's cyst resistance to conventional therapies. However, recent advancements in natural therapeutics, including using plant extracts such as betulinic acid from Pericampylus glaucus and chlorogenic acid from Lonicera japonica, have shown promising in vitro results. Additionally, nanotechnology applications, mainly using gold and silver nanoparticles to enhance drug efficacy, are emerging as potential solutions. Further, in vivo studies and clinical trials must validate these findings. This review highlights the requirement for continuous research, public health strategies, and interdisciplinary collaboration to address the growing threat of Acanthamoeba infections in Malaysia while exploring the country's rich biodiversity for innovative therapeutic solutions.

Synthesis, anti-amoebic activity and molecular docking simulation of eugenol derivatives against Acanthamoeba sp

Amoebae of the genus Acanthamoeba can cause diseases such as amoebic keratitis and granulomatous amoebic encephalitis. Until now, treatment options for these diseases have not been fully effective and have several drawbacks. Therefore, research into new drugs is needed for more effective treatment of Acanthamoeba infections. Eugenol, a phenolic aromatic compound mainly derived from cloves, has a variety of pharmaceutical properties. In this study, nine eugenol derivatives (K1-K9), consisting of five new and four known compounds, were synthesized and screened for their antiamoebic properties against Acanthamoeba sp. The structure of these compounds was characterized spectroscopically by Fourier transform infrared (FTIR), Ultraviolet-Visible (UV-Vis), 1H and 13C Nuclear Magnetic Resonance (NMR) and mass spectrometer (MS). The derived molecules were screened for antiamoebic activity by determining IC50 values based on 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and observation of amoeba morphological changes by light and fluorescence microscopy. Most of the tested compounds possessed strong to moderate cytotoxic effects against trophozoite cells with IC50 values ranging from 0.61 to 24.83 μg/mL. Observation of amoebae morphology by light microscopy showed that the compounds caused the transformed cells to be roundish and reduced in size. Furthermore, fluorescence microscopy observation using acridine orange (AO) and propidium iodide (PI) (AO/PI) staining showed that the cells have damaged membranes by displaying a green cytoplasm with orange-stained lysosomes. Acidification of the lysosomal structure indicated disruption of the internal structure of Acanthamoeba cells when treated with eugenol derivatives. The observed biological results were also confirmed by interaction simulations based on molecular docking between eugenol derivatives and Acanthamoeba profilin. These interactions could affect the actin-binding ability of the protein, disrupting the shape and mobility of Acanthamoeba. The overall results of this study demonstrate that eugenol derivatives can be considered as potential drugs against infections caused by Acanthamoeba.

Amoebal Tubulin Cleavage Late during Infection Is a Characteristic Feature of Mimivirus but Not of Marseillevirus

Mimivirus and Marseillevirus infections of Acanthamoeba castellanii, like most other viral infections, induce cytopathic effects (CPE). The details of how they bring about CPE and to what extent and how they modify the host cytoskeletal network are unclear. In this study, we compared the rearrangement of the host cytoskeletal network induced by Mimivirus and Marseillevirus upon infection. We show that while both Mimivirus and Marseillevirus infections of A. castellanii cells cause retraction of acanthopodia and depolymerization of the host actin filament network, the Mimivirus infection also results in characteristic cleavage of the host tubulin, a phenomenon not previously reported with any intracellular pathogens. Furthermore, we show that the amoebal tubulin cleavage during Mimivirus infection is a post-replicative event. Because time-lapse microscopy showed that Mimivirus infection leads to the bursting of cells, releasing the virus, we hypothesize that tubulin cleavage together with actin depolymerization during the later stages of Mimivirus assembly is essential for cell lysis due to apoptotic/necrotic cell death. We also characterize the Mimivirus-encoded gp560, a Zn metalloprotease, however, the purified gp560 protein was unable to cleave the commercially available porcine brain tubulin. While protein synthesis is essential for causing the morphological changes in the case of Mimivirus, the proteins which are packaged in the viral capsid along with the genome are sufficient to induce CPE in the case of Marseillevirus. IMPORTANCE In general, intracellular pathogens target the cytoskeletal network to enable their life cycle inside the host. Pathogen-induced changes in the host cell morphology usually accompany global changes in the cytoskeleton resulting in cytopathic effects. While viruses have been shown to use the host actin cytoskeleton for entry and transport during early infection, the role of microtubules in the viral life cycle is only beginning to emerge. Here, we show that the giant viruses Mimivirus and Marseillevirus both induce depolymerization of the actin filament, Mimivirus also causes a characteristic cleavage of tubulin not previously reported for any intracellular pathogen. Because tubulin cleavage occurs late during infection, we hypothesize that tubulin cleavage aids in cell death and lysis rather than establishing infection. The different strategies used by viruses with similar host niches may help them survive in competition.

Anti-Acanthamoeba activity of a semi-synthetic mangostin derivative and its ability in removal of Acanthamoeba triangularis WU19001 on contact lens

Garcinia mangostana L., also known as the mangosteen tree, is a native medicinal plant in Southeast Asia having a wide variety of pharmacologically active compounds, including xanthonoid mangostin. In this study, we examined the pharmacological activities of the selected semi-synthetic mangostin derivative, namely, amoebicidal activity, encystation inhibition, excystation activity, and removal capacity of adhesive Acanthamoeba from the surface of contact lens (CL). Among the three derivatives, C1 exhibited promising anti-Acanthamoeba activity against Acanthamoeba triangularis WU19001 trophozoites and cysts. SEM images displayed morphological changes in Acanthamoeba trophozoites, including the loss of acanthopodia, pore formation in the cell membrane, and membrane damage. In addition, the treated cyst was shrunken and adopted an irregular flat cyst shape. Under a fluorescence microscope, acridine orange and propidium iodide (AO/PI) staining revealed C1 induced condensation of cytoplasm and chromatin with the loss of cell volume in the treated trophozoites, while calcofluor white staining demonstrated the leakage of cell wall in treated cysts, leading to cell death. Interestingly, at the concentration ranges in which C1 showed the anti-Acanthamoeba effects (IC₅₀ values ranging from 0.035-0.056 mg/mL), they were not toxic to Vero cells. C1 displayed the highest inhibitory effect on A. triangularis encystation at 1/16×MIC value (0.004 mg/mL). While C1 demonstrated the excystation activity at 1/128×MIC value with a high rate of 89.47%. Furthermore, C1 exhibited the removal capacity of adhesive Acanthamoeba from the surface of CL comparable with commercial multipurpose solutions (MPSs). Based on the results obtained, C1 may be a promising lead agent to develop a therapeutic for the treatment of Acanthamoeba infections and disinfectant solutions for CL.

Aspergillus niger trehalase enzyme induced morphological and protein alterations on Acanthamoeba cyst and molecular docking studies

The cytotoxicity of Acanthamoeba is yet to fully illustrate due to recalcitrant of Acanthamoeba during cyst stage. The formation of the trehalose layer at the cyst stage protects the inner components of this opportunist protozoan parasite. Trehalase from the Aspergillus niger (AnTre) activity on the cyst of Acanthamoeba was determined based on AnTre dose-response, morphological and protein changes. The interaction of the AnTre and trehalose was also visualized through docking simulation. Vacuolation of the cyst can be seen when observed under light microscopy. Membrane integrity assessment suggested possible hydrolization of the AnTre enzyme to trehalose membranes which based on acridine orange and propidium iodide staining. Surface morphology based on scanning electron microscopy revealed the formation of bulging structure that was also proved through cross sectioning observed by transmission electron microscopy. Loss of internal structure of the cysts was clearly observed. Other morphological distinction where loss of rigid shape due to the destruction of the endo- and ecto cyst layers. However, the protein profile exhibits change of trehalose layer as responses to AnTre treatment. The observed biological results were also supported by interaction simulation based on molecular docking between trehalose and AnTre enzyme. In conclusion, this enzymatic approach could be developed into selective and effective mechanism to control Acanthamoeba without affecting the host especially mammals due to the absence of trehalose elements in the tissues of mammals.

Ultrastructural Study of Acanthamoeba polyphaga Trophozoites and Cysts Treated In Vitro with Cationic Carbosilane Dendrimers

Cationic carbosilane dendrimers are branched molecules with antimicrobial properties. Their activity has been tested against Acanthamoeba polyphaga, a causative agent of Acanthamoeba keratitis, a severe ocular disease in humans. A. polyphaga trophozoites and cysts were exposed to different noncytotoxic cationic carbosilane dendrimers with proven antiamoebic activity. The effects of treatment on cell surface and cell ultrastructure were examined by scanning and transmission electron microscopy, respectively. Two of the dendrimers tested induced dramatic alterations of cellular ultrastructure in both trophozoites and cysts, including vacuolization, depletion of cytoplasmic contents, and reduced cell size. Additionally, we observed severe alterations of the plasma membrane with membrane blebbing in trophozoites and disruption in cysts. These alterations were also observed with chlorhexidine, a drug used for treatment of Acanthamoeba keratitis. Our results support that these compounds may target membranes, and their action is critical for parasite integrity.

PLGA nanoparticles loaded with Gallic acid- a constituent of Leea indica against Acanthamoeba triangularis

Acanthamoeba, a genus that contains at least 24 species of free-living protozoa, is ubiquitous in nature. Successful treatment of Acanthamoeba infections is always very difficult and not always effective. More effective drugs must be developed, and medicinal plants may have a pivotal part in the future of drug discovery. Our research focused on investigating the in vitro anti- acanthamoebic potential of Leea indica and its constituent gallic acid in different concentrations. Water and butanol fractions exhibited significant amoebicidal activity against trophozoites and cysts. Gallic acid (100 µg/mL) revealed 83% inhibition of trophozoites and 69% inhibition of cysts. The butanol fraction induced apoptosis in trophozoites, which was observed using tunnel assay. The cytotoxicity of the fractions and gallic acid was investigated against MRC-5 and no adverse effects were observed. Gallic acid was successfully loaded within poly (D,L-lactide-co-glycolide) (PLGA) nanoparticles with 82.86% encapsulation efficiency, while gallic acid showed 98.24% in vitro release at 48 hours. Moreover, the gallic acid encapsulated in the PLGA nanoparticles exhibited 90% inhibition against trophozoites. In addition, gallic acid encapsulated nanoparticles showed reduced cytotoxicity towards MRC-5 compared to gallic acid, which evidenced that natural product nanoencapsulation in polymeric nanoparticles could play an important role in the delivery of natural products.

Whole Organism Model to Study Molecular Mechanisms of Differentiation and Dedifferentiation

Cancer recurrence has remained a significant challenge, despite advances in therapeutic approaches. In part, this is due to our incomplete understanding of the biology of cancer stem cells and the underlying molecular mechanisms. The phenomenon of differentiation and dedifferentiation (phenotypic switching) is not only unique to stem cells but it is also observed in several other organisms, as well as evolutionary-related microbes. Here, we propose the use of a primitive eukaryotic unicellular organism, Acanthamoeba castellanii, as a model to study the molecular mechanisms of cellular differentiation and dedifferentiation.

Acanthamoeba in Southeast Asia - Overview and Challenges

Acanthamoeba, one of free-living amoebae (FLA), remains a high risk of direct contact with this protozoan parasite which is ubiquitous in nature and man-made environment. This pathogenic FLA can cause sight-threatening amoebic keratitis (AK) and fatal granulomatous amoebic encephalitis (GAE) though these cases may not commonly be reported in our clinical settings. Acanthamoeba has been detected from different environmental sources namely; soil, water, hot-spring, swimming pool, air-conditioner, or contact lens storage cases. The identification of Acanthamoeba is based on morphological appearance and molecular techniques using PCR and DNA sequencing for clinico-epidemiological purposes. Recent treatments have long been ineffective against Acanthamoeba cyst, novel anti-Acanthamoeba agents have therefore been extensively investigated. There are efforts to utilize synthetic chemicals, lead compounds from medicinal plant extracts, and animal products to combat Acanthamoeba infection. Applied nanotechnology, an advanced technology, has shown to enhance the anti-Acanthamoeba activity in the encapsulated nanoparticles leading to new therapeutic options. This review attempts to provide an overview of the available data and studies on the occurrence of pathogenic Acanthamoeba among the Association of Southeast Asian Nations (ASEAN) members with the aim of identifying some potential contributing factors such as distribution, demographic profile of the patients, possible source of the parasite, mode of transmission and treatment. Further, this review attempts to provide future direction for prevention and control of the Acanthamoeba infection.

Amoebicidal and Amoebistatic Effects of Artemisia argyi Methanolic Extracts on Acanthamoeba castellanii Trophozoites and Cysts

PURPOSE : The present study aimed to investigate the amoebicidal and amoebistatic efects of Artemisia argyi leaf methanolic extract by testing the effects on trophozoites and on cysts. We also determined cytotoxic effect, enzymatic and non-enzymatic antioxidant activities, total phenolic, lavonoid and antioxidative contents of A. argyi.

METHODS

A. argyi was harvested from various geographic sites in Ordu province in Turkey. The fresh leaves were subjected to methanolic extraction. In 100 μl culture, different concentrations of A. argyi methanolic extract (in quantities from 1.2, 2.3, 4.7, 9.4, 18.7, 37.4, 74.8 mg/ml) and the same volume of trophozoite/cyst suspension were mixed for the determination of the amoebicidal activity of the plant extract. Human bronchial epithelial cells were treated with the same concentrations of Artemisia extracts to determine cytotoxic potential.

RESULTS

Total phenolic and lavonoid contents of the extract were calculated as 261 mg gallic acid/g dry extract and 29 mg quercetin/g dry extract, respectively. Total antioxidant activity was also calculated as 367 mg ascorbic acid/g dry extract. The growth of trophozoites stopped in A. argyi methanolic extract with 50% inhibitory concentrations (IC50)/8 h for 37.4 mg/ ml and 74.8 mg/ml extract solution and had stronger amoebicidal activity on the cysts with IC50/72 h. Artemisia showed stronger inhibitory effects on bronchial epithelial cells at the concentrations of 9.4, 18.7, 37.4 and 74.8 mg/ml.

CONCLUSION

The study indicated that A. argyi leaf extract has cytotoxic and anti-amoebic activities.

Polyhexamethylene biguanide and chloroquine induce programmed cell death in Acanthamoeba castellanii

Several chemotherapeutic drugs have been described as amoebicidal agents acting against Acanthamoeba trophozoites and cysts. However, the underlying mechanism of action is poorly characterized. Here, we describe programmed cell death (PCD) in A. castellanii induced by polyhexamethylene biguanide (PHMB) and chloroquine. We used four types of amoebicidal agents including 0.02% PHMB, 0.02% chlorhexidine digluconate, 100 μM chloroquine, and 100 μM 2,6-dichlorobenzonitrile to kill Acanthamoeba trophozoites and cysts. Exposure to PHMB and chloroquine induced cell shrinkage and membrane blebbing in Acanthamoeba, observed microscopically. Externalization of phosphatidyl serine on the membranes of Acanthamoeba was detected by annexin V staining. Apoptotic cell death of Acanthamoeba by PHMB and chloroquine was confirmed by FACS analysis. Nuclear fragmentation of Acanthamoeba was demonstrated by DAPI staining. PHMB induced PCD in trophozoites and cysts, and chloroquine induced PCD in cysts. These findings are discussed to establish the most effective treatment for Acanthamoeba-induced keratitis.

Toxic effects of selected proprietary dry eye drops on Acanthamoeba

Amoebae of the genus Acanthamoeba are ubiquitous protists that have been isolated from many sources such as soils, water and the air. They are responsible for infections including fatal encephalitis and a severe keratitis in humans. To date, there is no satisfactorily effective therapeutic agent against this pathogen and the infections it causes are exacerbated by the existence of a resistant cyst stage produced by this amoeba. As dry eye syndrome is a risk factor for Acanthamoeba keratitis, we aimed to evaluate the anti-Acanthamoeba activity of a variety of proprietary eye drops intended to treat dry eye syndrome. From the nine eye drop formulations tested, "Systane Ultra" was determined to be the most active against all tested Acanthamoeba strains. During our investigations into the mode of action of Systane Ultra, we discovered that it decreases mitochondrial membrane potential and ATP levels, induces chromatin condensation, and increases the permeability of the plasma-membrane.

Acanthamoebicidal activity of periglaucine A and betulinic acid from Pericampylus glaucus (Lam.) Merr. in vitro

Acanthamoeba species are pathogenic protozoa which account for amoebic keratitis, conjunctivitis and granulomatous amoebic encephalitis. These amoebae form cysts which resist drugs and more effective acanthamoebicidal agents are needed. Medicinal plants could be useful in improving the current treatment strategies for Acanthamoeba infections. In the present study, we examined the amoebicidal effects of Pericampylus glaucus (Lam.) Merr., a medicinal plant used for the treatment of conjunctivitis in Malaysia. Pathogenic Acanthamoeba triangularis were isolated from environmental water samples and treated with different concentrations of fractions obtained from Pericampylus glaucus (Lam.) Merr. as well as main constituents for 24-72 h. Chlorhexidine was used as a reference drug. Ethanol fraction of stem showed significant (p < 0.05) inhibition of trophozoites survival. Betulinic acid and periglaucine A from this plant at 100 μg/mL inhibited more than 70% survival of both cysts and trophozoites. The calculated therapeutic index for betulinic acid and periglaucine A was 170 and 1.5 for trophozoites stage and 3.75 and 8.5 for cysts stage. The observed amoebicidal efficacies indicate the beneficial aspects of this plant in the treatment of Acanthamoeba infection. Periglaucine A could also be of value for the treatment of Acanthamoeba infection.

Apoptosis of Acanthamoeba castellanii Trophozoites Induced by Oleic Acid

Acanthamoeba spp. can be parasitic in certain situations and are responsible for serious human infections, including Acanthamoeba keratitis, granulomatous amoebic encephalitis, and cutaneous acanthamoebiasis. We analyzed the fatty acid composition of Acanthamoeba castellanii trophozoites and tested the inhibitory activity of the main fatty acids, oleic acid and arachidonic acid, in vitro. Oleic acid markedly inhibited the growth of A. castellanii, with trophozoite viability of 57.4% at a concentration of 200 μM. Caspase-3 staining and annexin V assays showed that apoptotic death occurred in A. castellanii trophozoites. Quantitative PCR and dot blot analysis showed increased levels of metacaspase and interleukin-1β converting enzyme, which is also an indication of apoptosis. In contrast, arachidonic acid showed negligible inhibition of growth of A. castellanii trophozoites. Stimulated expression of Atg3, Atg8 and LC3A/B genes and monodansylcadaverine labeling suggested that oleic acid induces apoptosis by triggering autophagy of trophozoites.

Evaluation of the anti-Acanthamoeba activity of two commercial eye drops commonly used to lower eye pressure

Efficient treatments against Acanthamoeba Keratitis (AK), remains until the moment, as an issue to be solved due to the existence of a cyst stage which is highly resistant to most chemical and physical agents. In this study, two antiglaucoma eye drops were tested for their activity against Acanthamoeba. Moreover, this study was based on previous data which gave us evidence of a possible link between the absences of Acanthamoeba at the ocular surface in patients treated with beta blockers for high eye pressure both containing timolol as active principle. The amoebicidal activity of the tested eye drops was evaluated against four strains of Acanthamoeba using Alamar blue method. For the most active drug the cysticidal activity against A. castellanii Neff cysts and further experiments studying changes in chromatin condensation levels, in the permeability of the plasmatic membrane, the mitochondrial membrane potential and the ATP levels in the treated amoebic strains were done. Even though both eye drops were active against the different tested strains of Acanthamoeba, statistical analysis revealed that one of them (Timolol Sandoz) was the most effective one against all the tested strains presenting IC_50s ranging from 0.529% ± 0.206 for the CLC 16 strain to 3.962% ± 0.150 for the type strain Acanthamoeba castellanii Neff. Timolol Sandoz 0.50% seems to induce amoebic cell death by damaging the amoebae at the mitochondrial level. Considering its effect, Timolol Sandoz 0.50% could be used in the case of contact lens wearers and patients with glaucoma.

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

Free-living amoebae of the genus Acanthamoeba are the causal agents of a sight-threatening ulceration of the cornea called Acanthamoeba keratitis, as well as the rare but usually fatal disease granulomatous amoebic encephalitis. Although there are many therapeutic options for the treatment of Acanthamoeba infections, they are generally lengthy and/or have limited efficacy. For the best clinical outcome, treatments should target both the trophozoite and the cyst stages, as cysts are known to confer resistance to treatment. In this study, we document the activities of caffeine and maslinic acid against both the trophozoite and the cyst stages of three clinical strains of Acanthamoeba These drugs were chosen because they are reported to inhibit glycogen phosphorylase, which is required for encystation. Maslinic acid is also reported to be an inhibitor of extracellular proteases, which may be relevant since the protease activities of Acanthamoeba species are correlated with their pathogenicity. We also provide evidence for the first time that both drugs exert their anti-amoebal effects through programmed cell death.

Anti-encystment and amoebicidal activity of Lonicera japonica Thunb. and its major constituent chlorogenic acid in vitro

OBJECTIVE

To examine the acanthamoebicidal effects of ethyl acetate, aqueous and butanol fractions of dried flower buds of Lonicera japonica (L. japonica) Thunb. (Flos Lonicerae) in vitro.

METHODS

Acanthamoeba triangularis isolates were obtained from environmental water samples and identified by PCR. They were exposed to ethyl acetate, water and butanol fractions of L. japonica Thunb. at concentrations ranging from 0.5 mg/mL to 1.5 mg/mL. The extracts were evaluated for growth inhibition at 24, 48 and 72 h, respectively. Chlorogenic acid at a concentration of 1 mg/mL was examined for inhibition of encystment.

RESULTS

Ethyl acetate fraction at a concentration of 1.5 mg/mL evoked a significant reduction of trophozoite viability by 48.9% after 24 h, 49.2% after 48 h and 33.7% after 72 h chlorogenic acid, the major active constituent of L. japonica Thunb. at the concentration of 1 mg/mL reduced the cysts/trophozoite ratio by 100% after 24 h, 84.0% after 48 h and 72.3% after 72 h. This phenolic compound at concentration of 1 mg/mL concurrent with 0.6% hydrogen peroxide inhibited hydrogen peroxide-induced encystment by 92.8% at 72 h.

CONCLUSIONS

Results obtained from this study show that ethyl acetate fraction at 1.5 mg/mL is the most potent fraction of L. japonica Thunb. and its major constituent chlorogenic acid showed the remarkable inhibition of encystment at a concentration of 1 mg/mL.

A novel antiamoebic agent against Acanthamoeba sp.--A causative agent for eye keratitis infection

The terbium trinitrate.trihydrate.18-crown ether-6, Tb(NO3)3(OH2)3.(18C6) complex has been characterized by elemental analysis, photoluminescence and single X-ray diffraction. The IC50 values were determined based on MTT assay while light and fluorescence microscopy imaging were employed to evaluate the cellular morphological changes. Alkaline comet assay was performed to analyze the DNA damage. The photoluminescence spectrum of the Tb complex excited at 325 nm displayed seven luminescence peaks corresponding to the (5)D4→(7)F(0, 1, 2, 3, 4, 5, 6) transitions. The cytotoxicity and genotoxicity studies indicated that the Tb(NO3)3(OH2)3.(18C6) complex and its salt form as well as the 18C6 molecule have excellent anti-amoebic activity with very low IC50 values are 7, 2.6 and 1.2 μg/mL, respectively, with significant decrease (p<0.05) in Acanthamoeba viability when the concentration was increased from 0 to 30 μg/mL. The mode of cell death in Acanthamoeba cells following treatment with the Tb complex was apoptosis. This is in contrast to the Tb(NO3)3.6H2O salt- and 18C6 molecule-treated Acanthamoeba, which exhibited necrotic type cells. The percentage of DNA damage following treatment with all the compounds at the IC25 values showed high percentage of type 1 with the % nuclei damage are 14.15±2.4; 46.00±4.2; 36.36±2.4; 45.16±0.6%, respectively for untreated, treated with Tb complex, Tb salt and 18C6 molecule. The work features promising potential of Tb(NO3)3(OH2)3.(18C6) complex as anti-amoebic agent, representing a therapeutic option for Acanthamoeba keratitis infection.

Statins and voriconazole induce programmed cell death in Acanthamoeba castellanii

Members of the genus Acanthamoeba are facultative pathogens of humans, causing a sight-threatening keratitis and a life-threatening encephalitis. In order to treat those infections properly, it is necessary to target the treatment not only to the trophozoite but also to the cyst. Furthermore, it may be advantageous to avoid parasite killing by necrosis, which may induce local inflammation. We must also avoid toxicity of host tissue. Many drugs which target eukaryotes are known to induce programmed cell death (PCD), but this process is poorly characterized in Acanthamoeba. Here, we study the processes of programmed cell death in Acanthamoeba, induced by several drugs, such as statins and voriconazole. We tested atorvastatin, fluvastatin, simvastatin, and voriconazole at the 50% inhibitory concentrations (IC50s) and IC90s that we have previously established. In order to evaluate this phenomenon, we investigated the DNA fragmentation, one of the main characteristics of PCD, with quantitative and qualitative techniques. Also, the changes related to phosphatidylserine exposure on the external cell membrane and cell permeability were studied. Finally, because caspases are key to PCD pathways, caspase activity was evaluated in Acanthamoeba. All the drugs assayed in this study induced PCD in Acanthamoeba. To the best of our knowledge, this is the first study where PCD induced by drugs is described quantitatively and qualitatively in Acanthamoeba.

Anti-amoebic properties of carbonyl thiourea derivatives

Thiourea derivatives display a broad spectrum of applications in chemistry, various industries, medicines and various other fields. Recently, different thiourea derivatives have been synthesized and explored for their anti-microbial properties. In this study, four carbonyl thiourea derivatives were synthesized and characterized, and then further tested for their anti-amoebic properties on two potential pathogenic species of Acanthamoeba, namely A. castellanii (CCAP 1501/2A) and A. polyphaga (CCAP 1501/3A). The results indicate that these newly-synthesized thiourea derivatives are active against both Acanthamoeba species. The IC50 values obtained were in the range of 2.39-8.77 µg·mL⁻¹ (9.47-30.46 µM) for A. castellanii and 3.74-9.30 µg·mL⁻¹ (14.84-31.91 µM) for A. polyphaga. Observations on the amoeba morphology indicated that the compounds caused the reduction of the amoeba size, shortening of their acanthopodia structures, and gave no distinct vacuolar and nuclear structures in the amoeba cells. Meanwhile, fluorescence microscopic observation using acridine orange and propidium iodide (AOPI) staining revealed that the synthesized compounds induced compromised-membrane in the amoeba cells. The results of this study proved that these new carbonyl thiourea derivatives, especially compounds M1 and M2 provide potent cytotoxic properties toward pathogenic Acanthamoeba to suggest that they can be developed as new anti-amoebic agents for the treatment of Acanthamoeba keratitis.

Composition of Archaea in seawater, sediment, and sponges in the Kepulauan Seribu reef system, Indonesia

Coral reefs are among the most diverse and productive ecosystems in the world. Most research has, however, focused on eukaryotes such as corals and fishes. Recently, there has been increasing interest in the composition of prokaryotes, particularly those inhabiting corals and sponges, but these have mainly focused on bacteria. There have been very few studies of coral reef Archaea, despite the fact that Archaea have been shown to play crucial roles in nutrient dynamics, including nitrification and methanogenesis, of oligotrophic environments such as coral reefs. Here, we present the first study to assess Archaea in four different coral reef biotopes (seawater, sediment, and two sponge species, Stylissa massa and Xestospongia testudinaria). The archaeal community of both sponge species and sediment was dominated by Crenarchaeota, while the seawater community was dominated by Euryarchaeota. The biotope explained more than 72% of the variation in archaeal composition. The number of operational taxonomic units (OTUs) was highest in sediment and seawater biotopes and substantially lower in both sponge hosts. No "sponge-specific" archaeal OTUs were found, i.e., OTUs found in both sponge species but absent from nonhost biotopes. Despite both sponge species hosting phylogenetically distinct microbial assemblages, there were only minor differences in Kyoto Encyclopedia of Genes and Genomes (KEGG) functional pathways. In contrast, most functional pathways differed significantly between microbiomes from sponges and nonhost biotopes including all energy metabolic pathways. With the exception of the methane and nitrogen metabolic pathway, all energy metabolic pathways were enriched in sponges when compared to nonhost biotopes.