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Increased cytochrome P-450 activity in Aspergillus fumigatus after xenobiotic exposure
G S Baillie1, C A Hitchcock, F R Burnet
1Division of Infection and Immunity, Glasgow University, UK.
Abstract:
Microsomal fractions were isolated from Aspergillus fumigatus cultures that had been treated with dimethylsulphoxide (DMSO), ethanol, benzopyrene, phenobarbital or naphthalene. All these xenobiotics increased microsomal cytochrome P-450 content. Cytochrome P-450 reductase activity remained unaffected and no alteration in the microsomal protein profile was detectable by SDS PAGE. Benzopyrene, dimethylaniline, hexobarbitol and p-nitroanisole were metabolised by A. fumigatus microsomes, while aniline, ethoxyresorufin and pentoxyresorufin were not. No xenobiotic elicited a more specific oxidation of any of the substrates. A fumigatus microsomes also catalyzed the cell-free biosynthesis of ergosterol and quantitative analysis of assay metabolites showed that exposure to ethanol, benzopyrene or phenobarbitone in vivo resulted in enhanced ergosterol biosynthesis in vitro.
Insights
This study shows that treating Aspergillus fumigatus with xenobiotics increases cytochrome P-450 content and enhances ergosterol biosynthesis. These findings are important for understanding fungal metabolism and drug interactions.
Area of Science:
- Biochemistry
- Mycology
- Pharmacology
Background:
- Aspergillus fumigatus is a fungal pathogen with a complex metabolic system.
- Understanding its response to xenobiotics is crucial for developing targeted therapies.
- Microsomal enzymes, particularly cytochrome P-450, play a key role in xenobiotic metabolism.
Purpose of the Study:
- To investigate the impact of various xenobiotics on Aspergillus fumigatus microsomes.
- To determine the effect of xenobiotic treatment on cytochrome P-450 content and activity.
- To assess the influence of xenobiotics on ergosterol biosynthesis in A. fumigatus.
Main Methods:
- Isolation of microsomal fractions from A. fumigatus cultures treated with xenobiotics (DMSO, ethanol, benzopyrene, phenobarbital, naphthalene).
- Measurement of cytochrome P-450 content and cytochrome P-450 reductase activity.
- Analysis of microsomal protein profiles using SDS-PAGE.
- Assay of xenobiotic metabolism using various substrates.
- Cell-free biosynthesis of ergosterol and quantitative analysis of metabolites.
Main Results:
- Xenobiotic treatment significantly increased microsomal cytochrome P-450 content.
- Cytochrome P-450 reductase activity and microsomal protein profiles remained largely unaffected.
- A. fumigatus microsomes metabolized benzopyrene, dimethylaniline, hexobarbitol, and p-nitroanisole, but not aniline, ethoxyresorufin, or pentoxyresorufin.
- No specific oxidation patterns were observed for any substrate across different xenobiotics.
- Exposure to ethanol, benzopyrene, or phenobarbitone in vivo enhanced in vitro ergosterol biosynthesis.
Conclusions:
- Xenobiotics induce cytochrome P-450 in A. fumigatus, suggesting a role in detoxification or adaptation.
- The fungus exhibits specific xenobiotic metabolism capabilities.
- Pre-exposure to certain xenobiotics can enhance ergosterol biosynthesis, indicating a potential metabolic crosstalk.