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USING PHARMACOKINETIC DATA TO INTERPRET METABOLOMIC CHANGES IN CD-1 MICE TREATED WITH TRIAZOLE FUNGICIDES
Citation:
HENDERSON, W. M., J. F. KENNEKE, T. W. COLLETTE, AND S. E. RITGER. USING PHARMACOKINETIC DATA TO INTERPRET METABOLOMIC CHANGES IN CD-1 MICE TREATED WITH TRIAZOLE FUNGICIDES. Presented at Society of Toxicology Annual Meeting, Seattle, WA, March 16 - 20, 2008.
Impact/Purpose:
This task is divided into four major research areas: (1) Development of computational tools and databases for screening-level modeling of the environmental fate of organic chemicals; (2) Metabolism of xenobiotics: Enhancing the development of a metabolic simulator; (3) Metabonomics: The use of advanced analytical tools to identify toxicity pathways; and (4) Software infrastructure to support development and application of transformation/metabolic simulators.
For many chemicals, multiple transformation/metabolic pathways can exist. Consequently, transformation/metabolic simulators must utilize transformation rate data for prioritization of competing pathways. The prioritization process thus requires the integration of reliable rate data. When this data is absent, it is necessary to generate a database with metabolic and transformation rate constants based on: (1) experimentally measured values, including those requiring the use of advanced analytical techniques for measuring metabolic rate constants in vivo and in vitro; (2) rate constants derived from SPARC and mechanistic-based QSAR models; and (3) data mined from the literature and Program Office CBI. A long-term goal of this project is to build this database. This information will be used to enhance the predictive capabilities of the transformation/metabolic simulators. As indicated previously, exposure genomics, which provide early signs of chemical exposure based on changes in gene expression, will be used to guide chemical fate and metabolism studies. The incorporation of exposure genomics into fate studies will provide information concerning (1) the minimal concentrations at which biological events occur; and (2) the identification of biologically relevant chemicals(s) in mixtures.
The capability of categorizing chemicals and their metabolites based on toxicity pathway is imperative to the success of the CompTox Research Program. Metabonomics, which is the multi-parametric measurement of metabolites in living systems due to physiological stimuli and/or genetic modification, provides such a capability. The application of metabonomics to toxicity testing involves the elucidation of changes in metabolic patterns associated with chemical toxicity based on the measurement of component profiles in biofluids, and enables the generation of spectral profiles for a wide range of endogenous metabolites. Metabolic profiles can provide a measure of the real outcome of potential changes as the result of xenobiotic exposure.
Description:
Triazoles are a class of fungicides widely used in both pharmaceutical and agricultural applications. These compounds elicit a variety of toxic effects including disruption of normal metabolic processes such as steroidogenesis. Metabolomics is used to measure dynamic changes in endogenous metabolite levels to help understand the biochemical impacts of exposure to xenobiotics. Understanding exposure pharmacokinetics (i.e., metabolism and distribution), coupled with changes in the endogenous metabolome, will help link parent and metabolically derived chemical interactions with the normal biological processes occurring in vivo. In the first study, male CD-1 mice were orally dosed with triadimefon (TDN; 50 or 115 mg/kg/d), propiconazole (PRO; 75 or 150 mg/kg/d) or myclobutanil (MYC; 75 or 150 mg/kg/d) in 10% glycerol formal for 4 days. Daily urine samples were obtained and tissues collected on days 1, 3, and 5. A second study was conducted to investigate the pharmacokinetic parameters of each triazole, and in this study mice received a single oral bolus dose of each fungicide (TDN, PRO, or MYC) and tissues were excised at 0.25, 0.5, 1, 2, 3, 6, 12 and 24 hrs post-treatment. Serum, liver, gonad and fat were extracted and then analyzed via GC/MS to determine chemical concentration. Absorption and metabolism of the triazole fungicides occurred rapidly in vivo. In general, both the parent compound and its transformation products were no longer detectable by 24 hrs post-treatment. Metabolomic analyses of urine, serum and liver were similarly conducted via GC/MS following a two-step derivatization process. Because these compounds are known to disrupt steroidogenesis, the above method was also used to target steroid levels in serum and liver samples. Ultimately, this research will aid in linking both xenobiotic- and metabolomic- biomarkers following triazole fungicide exposure.