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Identification and Mode of Action of a Plant Natural Product Targeting Human Fungal Pathogens.
- Source :
-
Antimicrobial agents and chemotherapy [Antimicrob Agents Chemother] 2017 Aug 24; Vol. 61 (9). Date of Electronic Publication: 2017 Aug 24 (Print Publication: 2017). - Publication Year :
- 2017
-
Abstract
- Candida albicans is a major cause of fungal diseases in humans, and its resistance to available drugs is of concern. In an attempt to identify novel antifungal agents, we initiated a small-scale screening of a library of 199 natural plant compounds (i.e., natural products [NPs]). In vitro susceptibility profiling experiments identified 33 NPs with activity against C. albicans (MIC <subscript>50</subscript> s ≤ 32 μg/ml). Among the selected NPs, the sterol alkaloid tomatidine was further investigated. Tomatidine originates from the tomato ( Solanum lycopersicum ) and exhibited high levels of fungistatic activity against Candida species (MIC <subscript>50</subscript> s ≤ 1 μg/ml) but no cytotoxicity against mammalian cells. Genome-wide transcriptional analysis of tomatidine-treated C. albicans cells revealed a major alteration (upregulation) in the expression of ergosterol genes, suggesting that the ergosterol pathway is targeted by this NP. Consistent with this transcriptional response, analysis of the sterol content of tomatidine-treated cells showed not only inhibition of Erg6 (C-24 sterol methyltransferase) activity but also of Erg4 (C-24 sterol reductase) activity. A forward genetic approach in Saccharomyces cerevisiae coupled with whole-genome sequencing identified 2 nonsynonymous mutations in ERG6 (amino acids D249G and G132D) responsible for tomatidine resistance. Our results therefore unambiguously identified Erg6, a C-24 sterol methyltransferase absent in mammals, to be the main direct target of tomatidine. We tested the in vivo efficacy of tomatidine in a mouse model of C. albicans systemic infection. Treatment with a nanocrystal pharmacological formulation successfully decreased the fungal burden in infected kidneys compared to the fungal burden achieved by the use of placebo and thus confirmed the potential of tomatidine as a therapeutic agent.<br /> (Copyright © 2017 Dorsaz et al.)
- Subjects :
- Animals
Candidiasis drug therapy
Candidiasis microbiology
Cell Line, Tumor
Drug Resistance, Fungal drug effects
Drug Resistance, Fungal genetics
Ergosterol pharmacology
Female
Fluconazole pharmacology
Genes, Fungal genetics
HeLa Cells
Humans
Mice
Mice, Inbred BALB C
Microbial Sensitivity Tests methods
Saccharomyces cerevisiae genetics
Tomatine analogs & derivatives
Tomatine pharmacology
Antifungal Agents pharmacology
Biological Products pharmacology
Candida albicans drug effects
Plant Extracts pharmacology
Subjects
Details
- Language :
- English
- ISSN :
- 1098-6596
- Volume :
- 61
- Issue :
- 9
- Database :
- MEDLINE
- Journal :
- Antimicrobial agents and chemotherapy
- Publication Type :
- Academic Journal
- Accession number :
- 28674054
- Full Text :
- https://doi.org/10.1128/AAC.00829-17