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Fulltext Galactose as novel target against Acanthamoeba cysts

Anwar A, Khan NA, Siddiqui R

PLoS Negl Trop Dis, 2019 07;13(7):e0007385.
PMID: 31348789 DOI: 10.1371/journal.pntd.0007385
Matched MeSH terms: Acanthamoeba/drug effects*
Anti-amoebic potential of azole scaffolds and nanoparticles against pathogenic Acanthamoeba

Walvekar S, Anwar A, Anwar A, Sridewi N, Khalid M, Yow YY, et al.

Acta Trop, 2020 Nov;211:105618.
PMID: 32628912 DOI: 10.1016/j.actatropica.2020.105618

Acanthamoeba spp. are free living amoeba (FLA) which are widely distributed in nature. They are opportunistic parasites and can cause severe infections to the eye, skin and central nervous system. The advances in drug discovery and modifications in the chemotherapeutic agents have shown little improvement in morbidity and mortality rates associated with Acanthamoeba infections. The mechanism-based process of drug discovery depends on the molecular drug targets present in the signaling pathways in the genome. Synthetic libraries provide a platform for broad spectrum of activities due to their desired structural modifications. Azoles, originally a class of synthetic anti-fungal drugs, disrupt the fungal cell membrane by inhibiting the biosynthesis of ergosterol through the inhibition of cytochrome P450 dependent 14α-lanosterol, a key step of the sterol pathway. Acanthamoeba and fungi share the presence of similar sterol intermediate, as ergosterol is also the major end-product in the sterol biosynthesis in Acanthamoeba. Sterols present in the eukaryotic cell membrane are one of the most essential lipids and exhibit important structural and signaling functions. Therefore, in this review we highlight the importance of specific targeting of ergosterol present in Acanthamoebic membrane by azole compounds for amoebicidal activity. Previously, azoles have also been repurposed to report antimicrobial, antiparasitic and antibacterial properties. Moreover, by loading the azoles into nanoparticles through advanced techniques in nanotechnology, such as physical encapsulation, adsorption, or chemical conjugation, the pharmacokinetics and therapeutic index of the drugs can be significantly improved. The current review proposes an important strategy to target Acanthamoeba using synthetic libraries of azoles and their conjugated nanoparticles for the first time.

Matched MeSH terms: Acanthamoeba/drug effects*
Fulltext In vitro drug susceptibility of Acanthamoeba castellani to chloroquine, ivermectin and fungizon

Rain AN, Radzan T, Sajiri S, Mak JW

Southeast Asian J. Trop. Med. Public Health, 1996 Jun;27(2):319-24.
PMID: 9279996

In vitro sensitivity of Acanthamoeba castellani was tested to three drugs: Chloroquine, ivermectin and fungizone (amphotericin B). Sensitivity was demonstrated to the latter two compounds but not to chloroquine. Thus ivermectin and amphotericin B show promise as therapeutic agents against this parasite.

Matched MeSH terms: Acanthamoeba/drug effects*
Fulltext Novel insights into the potential role of ion transport in sensory perception in Acanthamoeba

Siddiqui R, Roberts SK, Ong TYY, Mungroo MR, Anwar A, Khan NA

Parasit Vectors, 2019 Nov 14;12(1):538.
PMID: 31727139 DOI: 10.1186/s13071-019-3785-0

BACKGROUND: Acanthamoeba is well known to produce a blinding keratitis and serious brain infection known as encephalitis. Effective treatment is problematic, and can continue up to a year, and even then, recurrence can ensue. Partly, this is due to the capability of vegetative amoebae to convert into resistant cysts. Cysts can persist in an inactive form for decades while retaining their pathogenicity. It is not clear how Acanthamoeba cysts monitor environmental changes, and determine favourable conditions leading to their emergence as viable trophozoites.
METHODS: The role of ion transporters in the encystation and excystation of Acanthamoeba remains unclear. Here, we investigated the role of sodium, potassium and calcium ion transporters as well as proton pump inhibitors on A. castellanii encystation and excystation and their effects on trophozoites.
RESULTS: Remarkably 3',4'-dichlorobenzamil hydrochloride a sodium-calcium exchange inhibitor, completely abolished excystation of Acanthamoeba. Furthermore, lanthanum oxide and stevioside hydrate, both potassium transport inhibitors, resulted in the partial inhibition of Acanthamoeba excystation. Conversely, none of the ion transport inhibitors affected encystation or had any effects on Acanthamoeba trophozoites viability.
CONCLUSIONS: The present study indicates that ion transporters are involved in sensory perception of A. castellanii suggesting their value as potential therapeutic targets to block cellular differentiation that presents a significant challenge in the successful prognosis of Acanthamoeba infections.

Matched MeSH terms: Acanthamoeba/drug effects*
CONJUGATION WITH SILVER NANOPARTICLES ENHANCES ANTI-ACANTHAMOEBIC ACTIVITY OF KAPPAPHYCUS ALVAREZII

Walvekar S, Anwar A, Anwar A, Lai NJY, Yow YY, Khalid M, et al.

J Parasitol, 2021 07 01;107(4):537-546.
PMID: 34265050 DOI: 10.1645/21-41

Nanomedicine has the potential in enhancing the efficacy and bioavailability of anti-infective agents. Here we determined whether conjugation of the Malaysian cultivated seaweed Kappaphycus alvarezii with silver-conjugated nanoparticles enhanced anti-acanthamoebic properties. Silver-conjugated K. alvarezii were successfully synthesized, followed by characterization with Fourier transform infrared spectroscopy, ultraviolet-visible spectrophotometry, and transmission electron microscopy. Amoebicidal effects were evaluated against Acanthamoeba castellanii, and cytotoxicity assays were performed using HaCaT cells. Viability assays revealed that silver nanoparticles conjugated with K. alvarezii extract exhibited significant antiamoebic properties (P < 0.05). Nano-conjugates induced the production of reactive oxygen species. Importantly, silver-conjugated extract inhibited amoeba-mediated host cell damage as established by lactate dehydrogenase release. Neither the nano-conjugates nor the extract showed cytotoxicity against human cells in vitro. Liquid chromatography and mass spectroscopy revealed several molecules, including 2,6-nonadien-1-ol, N-desmethyl trifluoperazine, dulciol B, lucidumol A, acetoxolone, 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-(octyloxy)phenol, C16 sphinganine, 22-tricosenoic acid, and β-dihydrorotenone, of which dulciol B and C16 sphinganine are known to possess antimicrobial activities. In summary, marine organisms are an important source of bioactive molecules with anti-acanthamoebic properties that can be enhanced by conjugating with silver nanoparticles. Natural products combined with nanotechnology using multifunctional nanoparticle complexes can deliver therapeutic agents effectively and hold promise in the development of new formulations of anti-acanthamoebic agents.

Matched MeSH terms: Acanthamoeba/drug effects*
Fulltext Combating Acanthamoeba spp. cysts: what are the options?

Anwar A, Khan NA, Siddiqui R

Parasit Vectors, 2018 01 09;11(1):26.
PMID: 29316961 DOI: 10.1186/s13071-017-2572-z

Acanthamoeba spp. are protist pathogens and causative agents of serious infections including keratitis and granulomatous amoebic encephalitis. Its ability to convert into dormant and highly resistant cysts form limits effectiveness of available therapeutic agents and presents a pivotal challenge for drug development. During the cyst stage, Acanthamoeba is protected by the presence of hardy cyst walls, comprised primarily of carbohydrates and cyst-specific proteins, hence synthesis inhibition and/or degradation of cyst walls is of major interest. This review focuses on targeting of Acanthamoeba cysts by identifying viable therapeutic targets.

Matched MeSH terms: Acanthamoeba/drug effects*
Fulltext Anti-amoebic properties of carbonyl thiourea derivatives

Ibrahim MA, Yusof MS, Amin NM

Molecules, 2014 Apr 22;19(4):5191-204.
PMID: 24759076 DOI: 10.3390/molecules19045191

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.

Matched MeSH terms: Acanthamoeba/drug effects*
Fulltext PLGA nanoparticles loaded with Gallic acid- a constituent of Leea indica against Acanthamoeba triangularis

Mahboob T, Nawaz M, de Lourdes Pereira M, Tian-Chye T, Samudi C, Sekaran SD, et al.

Sci Rep, 2020 06 02;10(1):8954.
PMID: 32488154 DOI: 10.1038/s41598-020-65728-0

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.

Matched MeSH terms: Acanthamoeba/drug effects
Anti-amoebic activity of acyclic and cyclic-samarium complexes on Acanthamoeba

Kusrini E, Hashim F, Gunawan C, Mann R, Azmi WNNWN, Amin NM

Parasitol Res, 2018 May;117(5):1409-1417.
PMID: 29532220 DOI: 10.1007/s00436-018-5814-x

This work investigated the anti-amoebic activity of two samarium (Sm) complexes, the acyclic complex [bis(picrato)(pentaethylene glycol)samarium(III)] picrate-referred to as [Sm(Pic)2(EO5)](Pic)-and the cyclic complex [bis(picrato)(18-crown-6)samarium(III)] picrate-referred to as [Sm(Pic)2(18C6)](Pic). Both Sm complexes caused morphological transformation of the protozoa Acanthamoeba from its native trophozoite form carrying a spine-like structure called acanthopodia, to round-shaped cells with loss of the acanthopodia structure, a trademark response to environmental stress. Further investigation, however, revealed that the two forms of the Sm complexes exerted unique cytotoxicity characteristics. Firstly, the IC50 of the acyclic complex (0.7 μg/mL) was ~ 10-fold lower than IC50 of the cyclic Sm complex (6.5 μg/mL). Secondly, treatment of the Acanthamoeba with the acyclic complex caused apoptosis of the treated cells, while the treatment with the cyclic complex caused necrosis evident by the leakage of the cell membrane. Both treatments induced DNA damage in Acanthamoeba. Finally, a molecular docking simulation revealed the potential capability of the acyclic complex to form hydrogen bonds with profilin-a membrane protein present in eukaryotes, including Acanthamoeba, that plays important roles in the formation and degradation of actin cytoskeleton. Not found for the cyclic complex, such potential interactions could be the underlying reason, at least in part, for the much higher cytotoxicity of the acyclic complex and also possibly, for the observed differences in the cytotoxicity traits. Nonetheless, with IC50 values of

Matched MeSH terms: Acanthamoeba/drug effects*
Fulltext The Development of Drugs against Acanthamoeba Infections

Siddiqui R, Aqeel Y, Khan NA

Antimicrob Agents Chemother, 2016 11;60(11):6441-6450.
PMID: 27600042 DOI: 10.1128/AAC.00686-16

For the past several decades, there has been little improvement in the morbidity and mortality associated with Acanthamoeba keratitis and Acanthamoeba encephalitis, respectively. The discovery of a plethora of antiacanthamoebic compounds has not yielded effective marketed chemotherapeutics. The rate of development of novel antiacanthamoebic chemotherapies of translational value and the lack of interest of the pharmaceutical industry in developing such chemotherapies have been disappointing. On the other hand, the market for contact lenses/contact lens disinfectants is a multi-billion-dollar industry and has been successful and profitable. A better understanding of drugs, their targets, and mechanisms of action will facilitate the development of more-effective chemotherapies. Here, we review the progress toward phenotypic drug discovery, emphasizing the shortcomings of useable therapies.

Matched MeSH terms: Acanthamoeba/drug effects*
Future Priorities in Tackling Infections Due to Brain-Eating Amoebae

Khan NA, Anwar A, Siddiqui R

ACS Chem Neurosci, 2017 11 15;8(11):2355.
PMID: 28933530 DOI: 10.1021/acschemneuro.7b00343

Brain-eating amoebae (Acanthamoeba spp., Balamuthia mandrillaris, and Naegleria fowleri) can cause opportunistic infections involving the central nervous system. It is troubling that the mortality rate is more than 90% despite advances in antimicrobial chemotherapy over the last few decades. Here, we describe urgent key priorities for improving outcomes from infections due to brain-eating amoebae.

Matched MeSH terms: Acanthamoeba/drug effects
Acanthamoebicidal activity of periglaucine A and betulinic acid from Pericampylus glaucus (Lam.) Merr. in vitro

Mahboob T, Azlan AM, Shipton FN, Boonroumkaew P, Nor Azman NS, Sekaran SD, et al.

Exp Parasitol, 2017 Dec;183:160-166.
PMID: 28916456 DOI: 10.1016/j.exppara.2017.09.002

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 Acanthamoeba infection. Periglaucine A could also be of value for the treatment of Acanthamoeba infection.

Matched MeSH terms: Acanthamoeba/drug effects*