Potential Value of Cellulose Synthesis Inhibitors Combined With PHMB in the Treatment of Acanthamoeba Keratitis

Moon, Eun‐Kyung; Hong, Yeonchul; Chung, Dong‐Il; Goo, Youn‐Kyoung; Kong, Hyun-Hee

doi:10.1097/ico.0000000000000642

Cited by 19 publications

(9 citation statements)

References 24 publications

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“…In relation with the inefficiency of encystment inhibitors to impact the amphotericin B IC 50 increase with time, no obvious expansion of cyst proportion was observed when amoebae were cultured in the presence of the drug. Furthermore, the action of wortmannin and DCB on the inhibition of encystment, and of latrunculin B on actin depolymerization have been previously described in A. castellanii ( Dudley et al., 2007 , Soto-Arrendondo et al., 2014 , Moon et al., 2015 ), suggesting that encystment and actin polymerization are not involved in amphotericin B resilience.…”

Section: Discussionmentioning

confidence: 87%

“…These drugs were also ineffective to modify the amphotericin B IC 50 increase from 3 to 5 days of treatment. Although no obvious increase in cyst proportion was observed when amoebae were cultured in the presence of amphotericin B (data not shown), the involvement of encystment was analyzed by treating Acanthamoeba with wortmannin and dichlorobenzonitrile (DCB), previously described to inhibit this cellular process in A. castellanii ( Dudley et al., 2007 , Moon et al., 2015 ). As shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

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In vitro evaluation of antimicrobial agents on Acanthamoeba sp. and evidence of a natural resilience to amphotericin B

Taravaud

Loiseau

Pomel

2017

International Journal for Parasitology: Drugs and Drug Resistan

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The free-living amoeba (FLA) Acanthamoeba sp. is an opportunistic pathogen that can cause amoebic keratitis (AK) or granulomatous amoebic encephalitis (GAE). While current treatments of AK are long with some relapses, no consensus therapy has been developed for GAE remaining lethal in 90% of the cases. In this context, efficient antiacanthamoebal drugs have to be identified. In this work, 15 drugs used in the treatment of AK or GAE or in other parasitic diseases were evaluated for their in vitro activity on A. castellanii. Hexamidine, voriconazole and clotrimazole exhibited the highest activities with IC50 values at 0.05 μM, 0.40 μM and 0.80 μM, respectively, while rifampicin, metronidazole and cotrimoxazole were inactive. Among 15 drug associations evaluated, no synergistic effect was observed, and one antagonism was determined between hexamidine and chlorhexidine. Interestingly, amphotericin B was the only drug presenting an increase of IC50 as a function of treatment duration. The amoebae susceptibility to amphotericin B cultured in the presence of 250 μM of the drug was similar to the one of a naive control, revealing that no resistant strain could be selected. However, the amoebae susceptibility always returned to an initial level at each passage. This natural and non-acquired adaptation to amphotericin B, qualified as resilience, was observed in several strains of A. castellanii and A. polyphaga. Using a pharmacological approach with effectors of different cellular mechanisms or transports, and an ultrastructural analysis of amphotericin B-treated amoebae, the involvement of several mitochondria-dependent pathways as well as multidrug resistant transporters was determined in amphotericin B resilience. Based on the observations from this study, the relevance of using amphotericin B in GAE treatments may be reconsidered, while the use of some other drugs, such as rifampicin or cotrimoxazole, is not relative to intrinsic antiacanthamoebal activity.

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Section: Discussionmentioning

confidence: 87%

Section: Resultsmentioning

confidence: 99%

In vitro evaluation of antimicrobial agents on Acanthamoeba sp. and evidence of a natural resilience to amphotericin B

Taravaud

Loiseau

Pomel

2017

International Journal for Parasitology: Drugs and Drug Resistan

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“…Cellulose is the main component of the cyst wall [ 9 ]. Cellulose synthesis inhibitor 2, 6-dichlorobenzonitrile (DCB) blocked the encystment of Acanthamoeba and improved the anti-amoebic effects [ 7 , 10 ]. In this study, we tested whether DCB can enhance the amoebicidal effects of the MPDS against Acanthamoeba , especially the cysts.…”

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confidence: 99%

Effect of 2, 6-Dichlorobenzonitrile on Amoebicidal Activity of Multipurpose Contact Lens Disinfecting Solutions

et al. 2018

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Multipurpose contact lens disinfecting solutions (MPDS) are widely used to cleanse and disinfect microorganisms. However, disinfection efficacy of these MPDS against Acanthamoeba cyst remain insufficient. 2, 6-dichlorobenzonitrile (DCB), a cellulose synthesis inhibitor, is capable of increasing the amoebical effect against Acanthamoeba by inhibiting its encystation. In this study, we investigated the possibility of DCB as a disinfecting agent to improve the amoebicidal activity of MPDS against Acanthamoeba cyst. Eight commercial MPDS (from a to h) were assessed, all of which displayed insufficient amoebicidal activity against the mature cysts. Solution e, f, and h showed strong amoebicidal effect on the immature cysts. Amoebicidal efficacy against mature cysts remained inadequate even when the 8 MPDS were combined with 100 μM DCB. However, 4 kinds of MPDS (solution d, e, f, and h) including 100 μM DCB demonstrated strong amoebicidal activity against the immature cysts. The amoebicidal activity of solution d was increased by addition of DCB. Cytotoxicity was absent in human corneal epithelial cells treated with either DCB or mixture of DCB with MPDS. These results suggested that DCB can enhance the amoebicical activity of MPDS against Acanthamoeba immature cyst in vitro.

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“…Recent studies have shown that cellulose fibrils exist in both cyst walls, and cellulose synthesis has been suggested as an important target for the treatment of Acanthamoeba infections [74]. Previous research on cellulose synthesis inhibitors and the knockdown of Acanthamoeba cellulose synthase has found that cellulose is essential to the formation of cyst walls during encystation [17,75]. It is known that the transcriptional levels of cellulose synthase are upregulated during the encystation process [76].…”

Section: Discussionmentioning

confidence: 99%

The role of the Acanthamoeba castellanii Sir2-like protein in the growth and encystation of Acanthamoeba

et al. 2020

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Background: The encystation of Acanthamoeba leads to the development of resilient cysts from vegetative trophozoites. This process is essential for the survival of parasites under unfavorable conditions. Previous studies have reported that, during the encystation of A. castellanii, the expression levels of encystation-related factors are upregulated. However, the regulatory mechanisms for their expression during the encystation process remains unknown. Proteins in the sirtuin family, which consists of nicotinamide adenine dinucleotide-dependent deacetylases, are known to play an important role in various cellular functions. In the present study, we identified the Acanthamoeba silent-information regulator 2-like protein (AcSir2) and examined its role in the growth and encystation of Acanthamoeba. Methods: We obtained the full-length sequence for AcSir2 using reverse-transcription polymerase chain reaction. In Acanthamoeba transfectants that constitutively overexpress AcSir2 protein, SIRT deacetylase activity was measured, and the intracellular localization of AcSir2 and the effects on the growth and encystation of trophozoites were examined. In addition, the sirtuin inhibitor salermide was used to determine whether these effects were caused by AcSir2 overexpression Results: AcSir2 was classified as a class-IV sirtuin. AcSir2 exhibited functional SIRT deacetylase activity, localized mainly in the nucleus, and its transcription was upregulated during encystation. In trophozoites, AcSir2 overexpression led to greater cell growth, and this growth was inhibited by treatment with salermide, a sirtuin inhibitor. When AcSir2 was overexpressed in the cysts, the encystation rate was significantly higher; this was also reversed with salermide treatment. In AcSir2-overexpressing encysting cells, the transcription of cellulose synthase was highly upregulated compared with that of control cells, and this upregulation was abolished with salermide treatment. Transmission electron microscope-based ultrastructural analysis of salermide-treated encysting cells showed that the structure of the exocyst wall and intercyst space was impaired and that the endocyst wall had not formed. Conclusions: These results indicate that AcSir2 is a SIRT deacetylase that plays an essential role as a regulator of a variety of cellular processes and that the regulation of AcSir2 expression is important for the growth and encystation of A. castellanii.

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Potential Value of Cellulose Synthesis Inhibitors Combined With PHMB in the Treatment of Acanthamoeba Keratitis

Abstract: The combination of cellulose synthesis inhibitors with low concentrations of PHMB reduced the CPE on HCE cells and improved the amebicidal effect on Acanthamoeba by inhibition of encystation.

Cited by 19 publications

References 24 publications

In vitro evaluation of antimicrobial agents on Acanthamoeba sp. and evidence of a natural resilience to amphotericin B

In vitro evaluation of antimicrobial agents on Acanthamoeba sp. and evidence of a natural resilience to amphotericin B

Effect of 2, 6-Dichlorobenzonitrile on Amoebicidal Activity of Multipurpose Contact Lens Disinfecting Solutions

The role of the Acanthamoeba castellanii Sir2-like protein in the growth and encystation of Acanthamoeba

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