scholarly journals Activation of Melanin Synthesis in Alternaria infectoria by Antifungal Drugs

2015 ◽  
Vol 60 (3) ◽  
pp. 1646-1655 ◽  
Author(s):  
Chantal Fernandes ◽  
Rafael Prados-Rosales ◽  
Branca M. A. Silva ◽  
Antonio Nakouzi-Naranjo ◽  
Mónica Zuzarte ◽  
...  
Keyword(s):  
Cell Walls ◽  
Therapeutic Potential ◽  
Morphological Changes ◽  
Antifungal Drugs ◽  
Protective Mechanism ◽  
Melanin Synthesis ◽  
Melanin Production ◽  
Minimum Effective Concentration ◽  
Content Type ◽  
Alternaria Infectoria

The importance ofAlternariaspecies fungi to human health ranges from their role as etiological agents of serious infections with poor prognoses in immunosuppressed individuals to their association with respiratory allergic diseases. The present work focuses onAlternaria infectoria, which was used as a model organism of the genus, and was designed to unravel melanin production in response to antifungals. After we characterized the pigment produced byA. infectoria, we studied the dynamics of 1,8-dihydroxynaphthalene (DHN)-melanin production during growth, the degree of melanization in response to antifungals, and how melanization affected susceptibility to several classes of therapeutic drugs. We demonstrate thatA. infectoriaincreased melanin deposition in cell walls in response to nikkomycin Z, caspofungin, and itraconazole but not in response to fluconazole or amphotericin B. These results indicate thatA. infectoriaactivates DHN-melanin synthesis in response to certain antifungal drugs, possibly as a protective mechanism against these drugs. Inhibition of DHN-melanin synthesis by pyroquilon resulted in a lower minimum effective concentration (MEC) of caspofungin and enhanced morphological changes (increased hyphal balloon size), characterized by thinner and less organizedA. infectoriacell walls. In summary,A. infectoriasynthesizes melanin in response to certain antifungal drugs, and its susceptibility is influenced by melanization, suggesting the therapeutic potential of drug combinations that affect melanin synthesis.

scholarly journals Melanin Externalization in Candida albicans Depends on Cell Wall Chitin Structures

2010 ◽  
Vol 9 (9) ◽  
pp. 1329-1342 ◽  
Author(s):  
Claire A. Walker ◽  
Beatriz L. Gómez ◽  
Héctor M. Mora-Montes ◽  
Kevin S. Mackenzie ◽  
Carol A. Munro ◽  
...  
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Fungal Pathogen ◽  
Cell Walls ◽  
Chitin Synthesis ◽  
Melanin Production ◽  
Content Type ◽  
Encoding Gene ◽  
Chitinase Genes

ABSTRACT The fungal pathogen Candida albicans produces dark-pigmented melanin after 3 to 4 days of incubation in medium containing l-3,4-dihydroxyphenylalanine (l-DOPA) as a substrate. Expression profiling of C. albicans revealed very few genes significantly up- or downregulated by growth in l-DOPA. We were unable to determine a possible role for melanin in the virulence of C. albicans. However, we showed that melanin was externalized from the fungal cells in the form of electron-dense melanosomes that were free or often loosely bound to the cell wall exterior. Melanin production was boosted by the addition of N-acetylglucosamine to the medium, indicating a possible association between melanin production and chitin synthesis. Melanin externalization was blocked in a mutant specifically disrupted in the chitin synthase-encoding gene CHS2. Melanosomes remained within the outermost cell wall layers in chs3Δ and chs2Δ chs3Δ mutants but were fully externalized in chs8Δ and chs2Δ chs8Δ mutants. All the CHS mutants synthesized dark pigment at equivalent rates from mixed membrane fractions in vitro, suggesting it was the form of chitin structure produced by the enzymes, not the enzymes themselves, that was involved in the melanin externalization process. Mutants with single and double disruptions of the chitinase genes CHT2 and CHT3 and the chitin pathway regulator ECM33 also showed impaired melanin externalization. We hypothesize that the chitin product of Chs3 forms a scaffold essential for normal externalization of melanosomes, while the Chs8 chitin product, probably produced in cell walls in greater quantity in the absence of CHS2, impedes externalization.

scholarly journals Mitogen-Activated Protein Kinase Cross-Talk Interaction Modulates the Production of Melanins in Aspergillus fumigatus

mBio ◽  
2019 ◽  
Vol 10 (2) ◽  
Author(s):  
Adriana Oliveira Manfiolli ◽  
Filipe Silva Siqueira ◽  
Thaila Fernanda dos Reis ◽  
Patrick Van Dijck ◽  
Sanne Schrevens ◽  
...  
Keyword(s):  
Cell Wall ◽  
Aspergillus Fumigatus ◽  
Cross Talk ◽  
Pathogenic Fungus ◽  
Antifungal Drugs ◽  
Mitogen Activated Protein Kinase ◽  
Melanin Production ◽  
Content Type ◽  
Mitogen Activated Protein ◽  
Salvage Pathways

ABSTRACT The pathogenic fungus Aspergillus fumigatus is able to adapt to extremely variable environmental conditions. The A. fumigatus genome contains four genes coding for mitogen-activated protein kinases (MAPKs), which are important regulatory knots involved in diverse cellular responses. From a clinical perspective, MAPK activity has been connected to salvage pathways, which can determine the failure of effective treatment of invasive mycoses using antifungal drugs. Here, we report the characterization of the Saccharomyces cerevisiae Fus3 ortholog in A. fumigatus, designated MpkB. We demonstrate that MpkB is important for conidiation and that its deletion induces a copious increase of dihydroxynaphthalene (DHN)-melanin production. Simultaneous deletion of mpkB and mpkA, the latter related to maintenance of the cell wall integrity, normalized DHN-melanin production. Localization studies revealed that MpkB translocates into the nuclei when A. fumigatus germlings are exposed to caspofungin stress, and this is dependent on the cross-talk interaction with MpkA. Additionally, DHN-melanin formation was also increased after deletion of genes coding for the Gα protein GpaA and for the G protein-coupled receptor GprM. Yeast two-hybrid and coimmunoprecipitation assays confirmed that GpaA and GprM interact, suggesting their role in the MpkB signaling cascade. IMPORTANCE Aspergillus fumigatus is the most important airborne human pathogenic fungus, causing thousands of deaths per year. Its lethality is due to late and often inaccurate diagnosis and the lack of efficient therapeutics. The failure of efficient prophylaxis and therapy is based on the ability of this pathogen to activate numerous salvage pathways that are capable of overcoming the different drug-derived stresses. A major role in the protection of A. fumigatus is played by melanins. Melanins are cell wall-associated macromolecules classified as virulence determinants. The understanding of the various signaling pathways acting in this organism can be used to elucidate the mechanism beyond melanin production and help to identify ideal drug targets.

scholarly journals Unravelling the Role of Melanin in Cd and Zn Tolerance and Accumulation of Three Dark Septate Endophytic Species

2020 ◽  
Vol 8 (4) ◽  
pp. 537
Author(s):  
Charlotte Berthelot ◽  
Asfaw Zegeye ◽  
Dalia A. Gaber ◽  
Michel Chalot ◽  
Philipp Franken ◽  
...  
Keyword(s):  
Trace Element ◽  
Cell Walls ◽  
Functional Trait ◽  
Dark Septate Endophytes ◽  
Melanin Synthesis ◽  
Melanin Production ◽  
Cd Accumulation ◽  
Series Of Experiments ◽  
Zn Tolerance

Dark septate endophytes (DSEs) are often trace element (TE)-tolerant fungi and are abundant in TE-polluted environments. The production of melanin, a black polymer found in cell walls, was hypothesized by several authors to play a role in the TE tolerance of DSEs. To test this hypothesis, we established a series of experiments using albino strains and melanin inhibitors and examined the responses to Cd and Zn. Six DSEs belonging to genera Cadophora sp., Leptodontidium sp. and Phialophora mustea, were evaluated. The strains mainly produced 1,8-dihydroxynaphthalene (DHN) melanin whereas 3,4-dihydroxyphenylalanin melanin was also synthetized. Cd and Zn decreased melanin synthesis in most of the strains. A reduction in melanin concentration in hyphae through the use of tricyclazole, an inhibitor of DHN-melanin synthesis, did not reduce the tolerance of the strains to Cd and Zn. Similarly, albino mutants of Leptodontidium sp. were not more sensitive to Cd and Zn than the WT strain. Moreover, tricyclazole-treated colonies accumulated less Cd but more Zn compared to untreated colonies. The Cd and Zn contents of Leptodontidium albino strains were variable and similar to that of the WT. The results suggest that melanin production is not an important functional trait that contributes to Cd and Zn tolerance, but might contribute to Cd accumulation.

scholarly journals Jerveratrum-Type Steroidal Alkaloids Inhibit β-1,6-Glucan Biosynthesis in Fungal Cell Walls

2022 ◽  
Author(s):  
Karen Kubo ◽  
Kaori Itto-Nakama ◽  
Shinsuke Ohnuki ◽  
Yoko Yashiroda ◽  
Sheena C. Li ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Cell Walls ◽  
Therapeutic Agents ◽  
Antifungal Drugs ◽  
Steroidal Alkaloids ◽  
Fungal Cell ◽  
Content Type ◽  
Fungal Cell Walls

Non- Candida albicans Candida species (NCAC) are on the rise as a cause of mycosis. Many antifungal drugs are less effective against NCAC, limiting the available therapeutic agents.

scholarly journals Paradoxical Growth of Candida albicans in the Presence of Caspofungin Is Associated with Multiple Cell Wall Rearrangements and Decreased Virulence

2013 ◽  
Vol 58 (2) ◽  
pp. 1071-1083 ◽  
Author(s):  
Cristina Rueda ◽  
Manuel Cuenca-Estrella ◽  
Oscar Zaragoza
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Galleria Mellonella ◽  
Morphological Changes ◽  
Antifungal Drugs ◽  
Proinflammatory Response ◽  
Content Type ◽  
Multiple Cell ◽  
Fungal Adaptation ◽  
Paradoxical Growth

ABSTRACTIn the last decade, echinocandins have emerged as an important family of antifungal drugs because of their fungicidal activity againstCandidaspp. Echinocandins inhibit the enzyme β-1,3-d-glucan synthase, encoded by theFKSgenes, and resistance to echinocandins is associated with mutations in this gene. In addition, echinocandin exposure can produce paradoxical growth, defined as the ability to grow at high antifungal concentrations but not at intermediate concentrations. In this work, we have demonstrated that paradoxical growth ofCandida albicansin the presence of caspofungin is not due to antifungal degradation or instability. Media with high caspofungin concentrations recovered from wells whereC. albicansshowed paradoxical growth inhibited the growth of aCandida kruseireference strain. Cells exhibiting paradoxical growth at high caspofungin concentrations showed morphological changes such as enlarged size, abnormal septa, and absence of filamentation. Chitin content increased from the MIC to high caspofungin concentrations. Despite the high chitin levels, around 23% of cells died after treatment with caspofungin, indicating that chitin is required but not sufficient to protect the cells from the fungicidal effect of caspofungin. Moreover, we found that after paradoxical growth, β-1,3-glucan was exposed at the cell wall surface. Cells grown at high caspofungin concentrations had decreased virulence in the invertebrate hostGalleria mellonella. Cells grown at high caspofungin concentrations also induced a proinflammatory response in murine macrophages compared to control cells. Our work highlights important aspects about fungal adaptation to caspofungin, and although this adaptation is associated with reduced virulence, the clinical implications remain to be elucidated.

scholarly journals Dectin-1-Targeted Antifungal Liposomes Exhibit Enhanced Efficacy

mSphere ◽  
2019 ◽  
Vol 4 (1) ◽  
Author(s):  
Suresh Ambati ◽  
Aileen R. Ferarro ◽  
S. Earl Kang ◽  
Jianfeng Lin ◽  
Xiaorong Lin ◽  
...  
Keyword(s):  
Invasive Aspergillosis ◽  
Cell Walls ◽  
Fungal Pathogens ◽  
Antifungal Drugs ◽  
Beta Glucan ◽  
Fungal Cell ◽  
Content Type ◽  
Current Therapies ◽  
Mammalian Protein ◽  
Fungal Cell Walls

The fungus Aspergillus fumigatus causes pulmonary invasive aspergillosis resulting in nearly 100,000 deaths each year. Patients are often treated with antifungal drugs such as amphotericin B (AmB) loaded into liposomes (AmB-LLs), but all antifungal drugs, including AmB-LLs, have serious limitations due to human toxicity and insufficient fungal cell killing. Even with the best current therapies, 1-year survival among patients with invasive aspergillosis is only 25 to 60%. Hence, there is a critical need for improved antifungal therapeutics. Dectin-1 is a mammalian protein that binds to beta-glucan polysaccharides found in nearly all fungal cell walls. We coated AmB-LLs with Dectin-1 to make DEC-AmB-LLs. DEC-AmB-LLs bound strongly to fungal cells, while AmB-LLs had little affinity. DEC-AmB-LLs killed or inhibited A. fumigatus 10 times more efficiently than untargeted liposomes, decreasing the effective dose of AmB. Dectin-1-coated drug-loaded liposomes targeting fungal pathogens have the potential to greatly enhance antifungal therapeutics.

scholarly journals CD4+T Cells Mediate the Protective Effect of the Recombinant Asp f3-Based Anti-Aspergillosis Vaccine

2011 ◽  
Vol 79 (6) ◽  
pp. 2257-2266 ◽  
Author(s):  
Diana Diaz-Arevalo ◽  
Karine Bagramyan ◽  
Teresa B. Hong ◽  
James I. Ito ◽  
Markus Kalkum
Keyword(s):  
T Cells ◽  
Fungal Pathogen ◽  
Cell Walls ◽  
Hematopoietic Cell ◽  
Protective Mechanism ◽  
Antifungal Effect ◽  
Content Type ◽  
Mortality And Morbidity ◽  
Cell Transplants ◽  
Immunosuppressed Mice

ABSTRACTThe mortality and morbidity caused by invasive aspergillosis present a major obstacle to the successful treatment of blood cancers with hematopoietic cell transplants. Patients who receive hematopoietic cell transplants are usually immunosuppressed for extended periods, and infection with the ubiquitous moldAspergillus fumigatusis responsible for most cases of aspergillosis. Previously, we demonstrated that vaccination with recombinant forms of theA. fumigatusprotein Asp f3 protected cortisone acetate-immunosuppressed mice from experimentally induced pulmonary aspergillosis. Here, we investigated the vaccine's protective mechanism and evaluated in particular the roles of antibodies and T cells. After vaccination, Asp f3-specific preinfection IgG titers did not significantly differ between surviving and nonsurviving mice, and passive transfer of anti-Asp f3 antibodies did not protect immunosuppressed recipients from aspergillosis. We experimentally confirmed Asp f3's predicted peroxisomal localization inA. fumigatushyphae. We found that fungal Asp f3 is inaccessible to antibodies, unless both cell walls and membranes have been permeabilized. Antibody-induced depletion of CD4+T cells reduced the survival of recombinant Asp f3 (rAsp f3)-vaccinated mice to nonimmune levels, and transplantation of purified CD4+T cells from rAsp f3-vaccinated mice into nonimmunized recipients transferred antifungal protection. In addition, residues 60 to 79 and 75 to 94 of Asp f3 contain epitopes that induce proliferation of T cells from vaccinated survivors. Vaccine-primed CD4+T cells are not expected to clear the fungal pathogen directly; however, they may locally activate immunosuppressed phagocytes that elicit the antifungal effect.

scholarly journals In VitroActivity of Isavuconazole against Rasamsonia Species

2016 ◽  
Vol 60 (11) ◽  
pp. 6890-6891 ◽  
Author(s):  
J. Steinmann ◽  
S. Dittmer ◽  
J. Houbraken ◽  
J. Buer ◽  
P.-M. Rath
Keyword(s):  
Species Complex ◽  
Antifungal Agents ◽  
Effective Concentration ◽  
Antifungal Drugs ◽  
The Novel ◽  
Large Collection ◽  
Minimum Effective Concentration ◽  
Content Type

ABSTRACTThein vitrosusceptibilities to the novel triazole isavuconazole and six other antifungal agents of a large collection ofRasamsoniaisolates (n= 47) belonging to seven species were determined. Isavuconazole and voriconazole had noin vitroactivity (MIC, >32 mg/liter) against isolates of theRasamsoniaargillaceaspecies complex. The echinocandins were the most potent antifungal drugs against all of the isolates tested (minimum effective concentration, ≤0.19 mg/liter).

scholarly journals The Antifungal Drug Isavuconazole Is both Amebicidal and Cysticidal against Acanthamoeba castellanii

2020 ◽  
Vol 64 (5) ◽  
Author(s):  
Brian Shing ◽  
Seema Singh ◽  
Larissa M. Podust ◽  
James H. McKerrow ◽  
Anjan Debnath
Keyword(s):  
Morphological Changes ◽  
Unmet Need ◽  
Acanthamoeba Castellanii ◽  
Recurrent Infection ◽  
Cost Effective ◽  
Antifungal Drugs ◽  
Content Type ◽  
Viability Assay ◽  
Rapid Action ◽  
Drug Concentrations

ABSTRACT Current treatments for Acanthamoeba keratitis rely on a combination of chlorhexidine gluconate, propamidine isethionate, and polyhexamethylene biguanide. These disinfectants are nonspecific and inherently toxic, which limits their effectiveness. Furthermore, in 10% of cases, recurrent infection ensues due to the difficulty in killing both trophozoites and double-walled cysts. Therefore, development of efficient, safe, and target-specific drugs which are capable of preventing recurrent Acanthamoeba infection is a critical unmet need for averting blindness. Since both trophozoites and cysts contain specific sets of membrane sterols, we hypothesized that antifungal drugs targeting sterol 14-demethylase (CYP51), known as conazoles, would have deleterious effects on A. castellanii trophozoites and cysts. To test this hypothesis, we first performed a systematic screen of the FDA-approved conazoles against A. castellanii trophozoites using a bioluminescence-based viability assay adapted and optimized for Acanthamoeba. The most potent drugs were then evaluated against cysts. Isavuconazole and posaconazole demonstrated low nanomolar potency against trophozoites of three clinical strains of A. castellanii. Furthermore, isavuconazole killed trophozoites within 24 h and suppressed excystment of preformed Acanthamoeba cysts into trophozoites. The rapid action of isavuconazole was also evident from the morphological changes at nanomolar drug concentrations causing rounding of trophozoites within 24 h of exposure. Given that isavuconazole has an excellent safety profile, is well tolerated in humans, and blocks A. castellanii excystation, this opens an opportunity for the cost-effective repurposing of isavuconazole for the treatment of primary and recurring Acanthamoeba keratitis.

scholarly journals Modulation of Morphogenesis in Candida albicans by Various Small Molecules

2011 ◽  
Vol 10 (8) ◽  
pp. 1004-1012 ◽  
Author(s):  
Julie Shareck ◽  
Pierre Belhumeur
Keyword(s):  
Candida Albicans ◽  
Small Molecules ◽  
Histone Deacetylase Inhibitors ◽  
Therapeutic Potential ◽  
Antifungal Drugs ◽  
Pathogenic Yeast ◽  
Content Type ◽  
Life Threatening ◽  
Experimental Findings ◽  
Cell Cycle Inhibitors

ABSTRACTThe pathogenic yeastCandida albicans, a member of the mucosal microbiota, is responsible for a large spectrum of infections, ranging from benign thrush and vulvovaginitis in both healthy and immunocompromised individuals to severe, life-threatening infections in immunocompromised patients. A striking feature ofC. albicansis its ability to grow as budding yeast and as filamentous forms, including hyphae and pseudohyphae. The yeast-to-hypha transition contributes to the overall virulence ofC. albicansand may even constitute a target for the development of antifungal drugs. Indeed, impairing morphogenesis inC. albicanshas been shown to be a means to treat candidiasis. Additionally, a large number of small molecules such as farnesol, fatty acids, rapamycin, geldanamycin, histone deacetylase inhibitors, and cell cycle inhibitors have been reported to modulate the yeast-to-hypha transition inC. albicans. In this minireview, we take a look at molecules that modulate morphogenesis in this pathogenic yeast. When possible, we address experimental findings regarding their mechanisms of action and their therapeutic potential. We discuss whether or not modulating morphogenesis constitutes a strategy to treatCandidainfections.

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