The Antifungal Action Mode of N-Phenacyldibromobenzimidazoles

Our study aimed to characterise the action mode of N-phenacyldibromobenzimidazoles against C. albicans and C. neoformans. Firstly, we selected the non-cytotoxic most active benzimidazoles based on the structure–activity relationships showing that the group of 5,6-dibromobenzimidazole derivatives are less active against C. albicans vs. 4,6-dibromobenzimidazole analogues (5e–f and 5h). The substitution of chlorine atoms to the benzene ring of the N-phenacyl substituent extended the anti-C. albicans action (5e with 2,4-Cl2 or 5f with 3,4-Cl2). The excellent results for N-phenacyldibromobenzimidazole 5h against the C. albicans reference and clinical isolate showed IC50 = 8 µg/mL and %I = 100 ± 3, respectively. Compound 5h was fungicidal against the C. neoformans isolate. Compound 5h at 160–4 µg/mL caused irreversible damage of the fungal cell membrane and accidental cell death (ACD). We reported on chitinolytic activity of 5h, in accordance with the patterns observed for the following substrates: 4-nitrophenyl-N-acetyl-β-d-glucosaminide and 4-nitrophenyl-β-d-N,N′,N″-triacetylchitothiose. Derivative 5h at 16 µg/mL: (1) it affected cell wall by inducing β-d-glucanase, (2) it caused morphological distortions and (3) osmotic instability in the C. albicans biofilm-treated. Compound 5h exerted Candida-dependent inhibition of virulence factors.

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The newly synthesized thiazole derivatives as potential antifungal compounds against Candida albicans

Applied Microbiology and Biotechnology ◽

10.1007/s00253-021-11477-7 ◽

2021 ◽

Author(s):

Anna Biernasiuk ◽

Anna Berecka-Rycerz ◽

Anna Gumieniczek ◽

Maria Malm ◽

Krzysztof Z. Łączkowski ◽

...

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Antifungal Activity ◽

Cell Membrane ◽

Mode Of Action ◽

Thiazole Derivatives ◽

Fungal Cell ◽

Erythrocyte Lysis ◽

Low Cytotoxicity ◽

High Antifungal Activity

Abstract Recently, the occurrence of candidiasis has increased dramatically, especially in immunocompromised patients. Additionally, their treatment is often ineffective due to the resistance of yeasts to antimycotics. Therefore, there is a need to search for new antifungals. A series of nine newly synthesized thiazole derivatives containing the cyclopropane system, showing promising activity against Candida spp., has been further investigated. We decided to verify their antifungal activity towards clinical Candida albicans isolated from the oral cavity of patients with hematological malignancies and investigate the mode of action on fungal cell, the effect of combination with the selected antimycotics, toxicity to erythrocytes, and lipophilicity. These studies were performed by the broth microdilution method, test with sorbitol and ergosterol, checkerboard technique, erythrocyte lysis assay, and reversed phase thin-layer chromatography, respectively. All derivatives showed very strong activity (similar and even higher than nystatin) against all C. albicans isolates with minimal inhibitory concentration (MIC) = 0.008–7.81 µg/mL Their mechanism of action may be related to action within the fungal cell wall structure and/or within the cell membrane. The interactions between the derivatives and the selected antimycotics (nystatin, chlorhexidine, and thymol) showed additive effect only in the case of combination some of them and thymol. The erythrocyte lysis assay confirmed the low cytotoxicity of these compounds as compared to nystatin. The high lipophilicity of the derivatives was related with their high antifungal activity. The present studies confirm that the studied thiazole derivatives containing the cyclopropane system appear to be a very promising group of compounds in treatment of infections caused by C. albicans. However, this requires further studies in vivo. Key points • The newly thiazoles showed high antifungal activity and some of them — additive effect in combination with thymol. • Their mode of action may be related with the influence on the structure of the fungal cell wall and/or the cell membrane. • The low cytotoxicity against erythrocytes and high lipophilicity of these derivatives are their additional good properties. Graphical abstract

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Spatial Distribution of a Porphyrin-Based Photosensitizer Reveals Mechanism of Photodynamic Inactivation of Candida albicans

Frontiers in Medicine ◽

10.3389/fmed.2021.641244 ◽

2021 ◽

Vol 8 ◽

Author(s):

Thomas Voit ◽

Fabian Cieplik ◽

Johannes Regensburger ◽

Karl-Anton Hiller ◽

Anita Gollmer ◽

...

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Fungal Infections ◽

Cell Envelope ◽

Antimicrobial Photodynamic Therapy ◽

Fungal Cell ◽

Before And After ◽

Antifungal Action ◽

Complete Cell ◽

Further Development

The antimicrobial photodynamic therapy (aPDT) is a promising approach for the control of microbial and especially fungal infections such as mucosal mycosis. TMPyP [5,10,15, 20-tetrakis(1-methylpyridinium-4-yl)-porphyrin tetra p-toluenesulfonate] is an effective photosensitizer (PS) that is commonly used in aPDT. The aim of this study was to examine the localization of TMPyP in Candida albicans before and after irradiation with visible light to get information about the cellular mechanism of antifungal action of the photodynamic process using this PS. Immediately after incubation of C. albicans with TMPyP, fluorescence microscopy revealed an accumulation of the PS in the cell envelope. After irradiation with blue light the complete cell showed red fluorescence, which indicates, that aPDT is leading to a damage in the cell wall with following influx of PS into the cytosol. Incubation of C. albicans with Wheat Germ Agglutinin (WGA) could confirm the cell wall as primary binding site of TMPyP. The finding that the porphyrin accumulates in the fungal cell wall and does not enter the interior of the cell before irradiation makes it unlikely that resistances can emerge upon aPDT. The results of this study may help in further development and modification of PS in order to increase efficacy against fungal infections such as those caused by C. albicans.

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The Chitin Connection

mBio ◽

10.1128/mbio.00056-12 ◽

2012 ◽

Vol 3 (2) ◽

Cited By ~ 20

Author(s):

David L. Goldman ◽

Alfin G. Vicencio

Keyword(s):

Cell Wall ◽

Cell Membrane ◽

Fungal Infections ◽

Allergic Inflammation ◽

Chitinase Activity ◽

Chitin Deacetylase ◽

Fungal Cell ◽

Content Type ◽

Covalently Linked

ABSTRACTChitin, a polymer ofN-acetylglucosamine, is an essential component of the fungal cell wall. Chitosan, a deacetylated form of chitin, is also important in maintaining cell wall integrity and is essential forCryptococcus neoformansvirulence. In their article, Gilbert et al. [N. M. Gilbert, L. G. Baker, C. A. Specht, and J. K. Lodge, mBio 3(1):e00007-12, 2012] demonstrate that the enzyme responsible for chitosan synthesis, chitin deacetylase (CDA), is differentially attached to the cell membrane and wall. Bioactivity is localized to the cell membrane, where it is covalently linked via a glycosylphosphatidylinositol (GPI) anchor. Findings from this study significantly enhance our understanding of cryptococcal cell wall biology. Besides the role of chitin in supporting structural stability, chitin and host enzymes with chitinase activity have an important role in host defense and modifying the inflammatory response. Thus, chitin appears to provide a link between the fungus and host that involves both innate and adaptive immune responses. Recently, there has been increased attention to the role of chitinases in the pathogenesis of allergic inflammation, especially asthma. We review these findings and explore the possible connection between fungal infections, the induction of chitinases, and asthma.

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Structure, Cellular Distribution, Antigenicity, and Biological Functions of Fonsecaea pedrosoi Ceramide Monohexosides

Infection and Immunity ◽

10.1128/iai.73.12.7860-7868.2005 ◽

2005 ◽

Vol 73 (12) ◽

pp. 7860-7868 ◽

Cited By ~ 35

Author(s):

Leonardo Nimrichter ◽

Mariana D. Cerqueira ◽

Eduardo A. Leitão ◽

Kildare Miranda ◽

Ernesto S. Nakayasu ◽

...

Keyword(s):

Cell Wall ◽

Structural Difference ◽

Structural Diversity ◽

Fungal Species ◽

Hydroxyl Group ◽

Current Evidence ◽

Fonsecaea Pedrosoi ◽

Fungal Cell ◽

Long Chain Base ◽

Antifungal Action

ABSTRACT Monohexosylceramides (CMHs, or cerebrosides) have been reported as membrane and cell wall constituents of both pathogenic and nonpathogenic fungi, presenting remarkable differences in their ceramide moiety compared to mammalian CMHs. Current evidence suggests that CMHs are involved in fungal differentiation and growth and contribute to host immune response. Here we describe a structural diversity between cerebrosides obtained from different forms of the human pathogen Fonsecaea pedrosoi. The major CMH species produced by conidial forms displayed the same structure previously demonstrated by our group for mycelia, an N-2′-hydroxyhexadecanoyl-1-β-d-glucopyranosyl-9-methyl-4,8-sphingadienine. However, the major cerebroside species purified from sclerotic cells carries an additional hydroxyl group, bound to its long-chain base. The structural difference between cerebrosides from mycelial and sclerotic cells was apparently not relevant for their antigenicity, since they were both recognized at similar levels by sera from individuals with chromoblastomycosis and a monoclonal antibody to a conserved cerebroside structure. Preincubation of fungal cells with anti-CMH monoclonal antibodies had no effect on the interaction of F. pedrosoi sclerotic cells with murine macrophages. In contrast to what has been described for other fungal species, sclerotic bodies are resistant to the antifungal action of anti-CMH antibodies. Immunofluorescence analysis showed that recognition of sclerotic cells by these antibodies only occurs at cell wall regions in which melanization is not evident. Accordingly, melanin removal with alkali results in an increased reaction of fungal cells with anti-CMH antibodies. Our results indicate that cerebroside expression in F. pedrosoi cells is associated with dimorphism and melanin assembly on the fungal cell wall.

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In vitro antifungal evaluation and structure–activity relationships of a new series of chalcone derivatives and synthetic analogues, with inhibitory properties against polymers of the fungal cell wall

Bioorganic & Medicinal Chemistry ◽

10.1016/s0968-0896(01)00116-x ◽

2001 ◽

Vol 9 (8) ◽

pp. 1999-2013 ◽

Cited By ~ 209

Author(s):

Silvia N López ◽

Marı́a V Castelli ◽

Susana A Zacchino ◽

José N Domı́nguez ◽

Gricela Lobo ◽

...

Keyword(s):

Cell Wall ◽

Fungal Cell Wall ◽

Synthetic Analogues ◽

Fungal Cell ◽

Chalcone Derivatives ◽

Structure Activity Relationships ◽

Structure Activity

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S. cerevisiae Outer and Inner Membranes are Compromised upon Benzyl Alcohol Treatment

International Journal of Membrane Science and Technology ◽

10.15379/2410-1869.2021.08.02.03 ◽

2021 ◽

Vol 8 (2) ◽

pp. 35-39

Author(s):

Ergüden Bengü

Keyword(s):

Cell Wall ◽

Cell Membrane ◽

Yeast Cell ◽

Benzyl Alcohol ◽

Cell Membranes ◽

Antifungal Agents ◽

Fungal Infections ◽

New Drugs ◽

Yeast Cells ◽

Fungal Cell

Although there are innovations in the treatment of diseases caused by fungi and medicines with multiple targets have been developed, the search for a drug with a broad spectrum and without any side effects continues to date. It is generally accepted that determining the cellular target responsible for the toxic effect opens up new possibilities for the development of new drugs. Especially the effects of antifungal agents on the surface components of the fungal cell, on cell wall synthesis and the identification of the target site are crucial in antifungal drug development. Thus studies on the fungal cell membranes in connection with the antifungal agents, aim to develop new strategies for the therapy of fungal infections. Antifungal agents targeting fungal cell wall and cell membrane components have increased in importance in clinical studies. In this study, understanding the mechanism of action of benzyl alcohol, a known membrane fluidizer, and the determination of its cellular targets are aimed. We have shown that in the presence of sorbitol, the osmotic stabilizer, benzyl alcohol becomes less effective against yeast cell. Moreover, benzyl alcohol disrupts cell membrane, causing leakage of ions to the extracellular medium. Nuclear membrane is distorted upon treatment of yeast cells with benzyl alcohol. Thus, we conclude that both outer and inner yeast cell membranes are compromised by the action of benzyl alcohol.

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Mechanism of Action of Antimicrobial Agents

Tutorial Topics in Infection for the Combined Infection Training Programme ◽

10.1093/oso/9780198801740.003.0053 ◽

2019 ◽

Author(s):

Ruaridh Buchanan ◽

Armine Sefton

Keyword(s):

Cell Wall ◽

Cell Membrane ◽

Cellular Structure ◽

Antimicrobial Agents ◽

Cell Integrity ◽

Beta Lactam ◽

Selective Toxicity ◽

Fungal Cell ◽

Lactam Ring ◽

Membrane Target

Antibacterial and antifungal agents aim to kill pathogens, or at the very least incapacitate them. To achieve this aim these agents must have a reasonable degree of toxicity at the cellular level. If this toxicity was equally manifest against all cell types then the drugs would be unusable in patients as the side effect profile would be unacceptably severe. Selective toxicity, whereby the agents are orders of magnitude more toxic to bacteria or fungi than human cells, allows for the safe and effective administration of these agents to patients. There are a number of different mechanisms by which an antimicrobial agent can yield selective toxicity: ● Target a cellular structure that exists only in bacteria/fungi—e.g. the cell wall; ● Target a cellular structure that has a significantly different structure in bacteria/ fungi— e.g. the ribosome; the fungal cell membrane; ● Target cellular enzymes that are significantly different in bacteria/fungi e.g. topoisomerase; ● Target a synthetic pathway that exists only in bacteria e.g. folate synthesis. Broadly, antibacterial drugs can be divided into the following categories: ● Agents that target the cell wall; ● Agents that target the cell membrane; ● Agents that inhibit protein synthesis; ● Agents that inhibit DNA replication/ transcription of RNA; ● Agents that target folate synthesis; ● Agents that directly damage intracellular structures. The cell wall is unique to bacteria, and therefore an ideal target. Disrupting the complex cross-linking process required to produce the cell wall leads to loss of bacterial cell integrity and therefore to cell death. The following classes of antibiotics target the cell wall: The first class to be discovered, and still in many cases the most effective, incorporates the four-membered beta-lactam ring—its homology to d-alanyl-d-alanine allows beta-lactam-containing compounds to bind to cell wall peptidoglycans and act as chain terminators. The beta-lactam ring is fused to a five-membered sulphur-containing ring. Variations in side chains account for the differing pharmacokinetics and spectra of action of the different compounds—for example, the addition of an amino group to benzylpenicillin produces ampicillin.

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The Viscoelastic Properties of the Fungal Cell Wall Allow Traffic of AmBisome as Intact Liposome Vesicles

mBio ◽

10.1128/mbio.02383-17 ◽

2018 ◽

Vol 9 (1) ◽

Cited By ~ 55

Author(s):

Louise Walker ◽

Prashant Sood ◽

Megan D. Lenardon ◽

Gillian Milne ◽

Jon Olson ◽

...

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Cell Membrane ◽

Amphotericin B ◽

Mode Of Action ◽

Viscoelastic Properties ◽

Fungal Cell Wall ◽

Fungal Cell ◽

Pass Through ◽

Cell Wall Porosity

ABSTRACT The fungal cell wall is a critically important structure that represents a permeability barrier and protective shield. We probed Candida albicans and Cryptococcus neoformans with liposomes containing amphotericin B (AmBisome), with or without 15-nm colloidal gold particles. The liposomes have a diameter of 60 to 80 nm, and yet their mode of action requires them to penetrate the fungal cell wall to deliver amphotericin B to the cell membrane, where it binds to ergosterol. Surprisingly, using cryofixation techniques with electron microscopy, we observed that the liposomes remained intact during transit through the cell wall of both yeast species, even though the predicted porosity of the cell wall (pore size, ~5.8 nm) is theoretically too small to allow these liposomes to pass through intact. C. albicans mutants with altered cell wall thickness and composition were similar in both their in vitro AmBisome susceptibility and the ability of liposomes to penetrate the cell wall. AmBisome exposed to ergosterol-deficient C. albicans failed to penetrate beyond the mannoprotein-rich outer cell wall layer. Melanization of C. neoformans and the absence of amphotericin B in the liposomes were also associated with a significant reduction in liposome penetration. Therefore, AmBisome can reach cell membranes intact, implying that fungal cell wall viscoelastic properties are permissive to vesicular structures. The fact that AmBisome can transit through chemically diverse cell wall matrices when these liposomes are larger than the theoretical cell wall porosity suggests that the wall is capable of rapid remodeling, which may also be the mechanism for release of extracellular vesicles. IMPORTANCE AmBisome is a broad-spectrum fungicidal antifungal agent in which the hydrophobic polyene antibiotic amphotericin B is packaged within a 60- to 80-nm liposome. The mode of action involves perturbation of the fungal cell membrane by selectively binding to ergosterol, thereby disrupting membrane function. We report that the AmBisome liposome transits through the cell walls of both Candida albicans and Cryptococcus neoformans intact, despite the fact that the liposome is larger than the theoretical cell wall porosity. This implies that the cell wall has deformable, viscoelastic properties that are permissive to transwall vesicular traffic. These observations help explain the low toxicity of AmBisome, which can deliver its payload directly to the cell membrane without unloading the polyene in the cell wall. In addition, these findings suggest that extracellular vesicles may also be able to pass through the cell wall to deliver soluble and membrane-bound effectors and other molecules to the extracellular space.

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