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Detection of reactive metabolites using isotope-labeled glutathione trapping and simultaneous neutral loss and precursor ion scanning with ultra-high-pressure liquid chromatography triple quadruple mass spectrometry.

ABSTRACT: Metabolic activation of drugs to electrophilic species is responsible for over 60% of black box warnings and drug withdrawals from the market place in the United States. Reactive metabolite trapping using glutathione (GSH) and analysis using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) or HPLC with high resolution mass spectrometry (mass defect filtering) have enabled screening for metabolic activation to become routine during drug development. However, current MS-based approaches cannot detect all GSH conjugates present in complex mixtures, especially those present in extracts of botanical dietary supplements. To overcome these limitations, a fast triple quadrupole mass spectrometer-based approach was developed that can detect positively and negatively charged GSH conjugates in a single analysis without the need for advanced knowledge of the elemental compositions of potential conjugates and while avoiding false positives. This approach utilized UHPLC instead of HPLC to shorten separation time and enhance sensitivity, incorporated stable-isotope labeled GSH to avoid false positives, and used fast polarity switching electrospray MS/MS to detect GSH conjugates that form positive and/or negative ions. The general new method was then used to test the licorice dietary supplement Glycyrrhiza glabra, which was found to form multiple GSH conjugates upon metabolic activation. Among the GSH conjugates found in the licorice assay were conjugates with isoliquiritigenin and glabridin, which is an irreversible inhibitor of cytochrome P450 enzymes.

SUBMITTER: Huang K

PROVIDER: S-EPMC4487545 | biostudies-literature | 2015 Apr

REPOSITORIES: biostudies-literature

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Detection of reactive metabolites using isotope-labeled glutathione trapping and simultaneous neutral loss and precursor ion scanning with ultra-high-pressure liquid chromatography triple quadruple mass spectrometry.

Huang Ke K Huang Lingyi L van Breemen Richard B RB

Analytical chemistry 20150325 7

Metabolic activation of drugs to electrophilic species is responsible for over 60% of black box warnings and drug withdrawals from the market place in the United States. Reactive metabolite trapping using glutathione (GSH) and analysis using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) or HPLC with high resolution mass spectrometry (mass defect filtering) have enabled screening for metabolic activation to become routine during drug development. However, current MS ...[more]

PMID: 25774910

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Project description:BackgroundPlant glutathione S-transferases (GSTs, EC 2.5.1.18) are multifunctional enzymes involved in heavy metal cellular detoxification by conjugating the tripeptide (g-Glu-Cys-Gly) glutathione to heavy metals. Previous studies demonstrated that individual rice GSTs were differentially induced by heavy metal exposure at the mRNA transcript level. However, little information is available concerning changes in protein concentration of rice GSTs under heavy metal stress. Because the correlation between changes in protein concentration and gene expression under abiotic stress is poor, direct determination of rice GSTs protein concentrations during cadmium (Cd) exposure is a more effective and reliable approach to explore possible mechanisms of rice Cd translocation and accumulation.ResultsThis study established an optimized and advanced liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based targeted proteomics assay for quantification of OsGSTF14 and OsGSTU6 proteins in Cd-stressed rice roots. The tryptic signature peptides were chosen as surrogate analytes and winged peptides containing the isotope-labeled signature peptides were used as the internal standards. The signature peptides exhibited good linearity in the range of 0.6-60 and 0.3-30 nM, respectively. The limit of detection and limit of quantification were 4.5 and 14.5 µg/g for OsGSTF14, respectively, and 2.1 and 7.0 µg/g for OsGSTU6. The spiking recoveries rates at low, medium and high levels were in the range of 72.5-93.4%, with intra- and inter-day precisions of 5.5-9.1 and 4.2-10.2%, respectively.ConclusionsThe assay successfully quantified the temporal and dose responses of OsGSTF14 and OsGSTU6 proteins in Cd-stressed rice roots, with good accuracy, precision and high-throughput. This assay will have significant application in developing quantification methods of other proteins in Cd-stressed rice, which may provide more insight into the mechanisms of Cd translocation and accumulation in rice.

Project description:Rice is an important cereal that is consumed as both an energy and protein source by a large proportion of the population worldwide. However, clinical studies have found that rice grains are responsible for cases of severe asthma, eczema, and atopic dermatitis in some adult patients. Several allergenic proteins have been identified and biochemically and immunochemically characterized from rice grains. These include α-amylase/trypsin inhibitors, glyoxalase Ⅰ, and α-globulin. In this study, we proposed an approach for the simultaneous quantification of three allergenic proteins in rice and its products, based on a stable isotope-labeled signature peptide standard and liquid chromatography-tandem mass spectrometry. Samples of rice and products were extracted by a salt solution, hydrolyzed by Lys-C and Trypsin, and purified by C18-SD. The linear ion trap-high resolution mass spectrometry (LTQ-Orbitrap) and Protein Discovery software were used to acquire and identify allergenic proteins in rice samples. In present study, three proteins including seed allergenic protein RAG2, glyoxalase Ⅰ, and 19 kDa globulin were identified. To establish a stable quantitative detection method, the signature peptides selected from the identified enzymatic hydrolysis peptides must have greater abundance and higher specificity as characteristic peptides. Three corresponding signature peptides in rice were screened based on the principles of previous study, and were validated through comparisons of the basic local alignment search tool (BLAST) with the NCBI and UniProt databases. The three signature peptides were successively eluted by liquid chromatography and separated on a Poroshell column. They were then detected by positive electrospray ionization (ESI+) in multiple reaction monitoring mode and quantified by an isotope dilution method. To achieve an improvement in the detection sensitivity and specificity, mass spectrometry parameters, such as the collision energy of three ion pairs of each peptide, were optimized. Three recombinant allergenic proteins and the winged stable isotope-labeled signature peptide standard were synthesized. These were then used to compare the effects of different enzymatic conditions, including hydrolysis solvents containing sodium dodecyl sulfate (SDS) with different contents, as well as the enzymes and their amounts, on the digestion efficiency. The data showed that the digestion efficiency of the three proteins could be improved to 65.7%-97.3% when 1 g/L of the SDS-containing hydrolysis solvent, and the combined digestion strategy of Lys-C and Trypsin, were adopted in the enzymatic process. These results indicate the following inferences: a small amount of SDS (1 g/L) in the enzymatic hydrolysis system is beneficial to complete protein denaturation, a Lys-C and Trypsin combined digestion strategy can complement the shortcomings of the two enzymes and improve the digestion efficiency, and the recoveries of the three proteins was not significantly increased by increasing the amount of enzyme when the ratio of protein to enzyme reached more than 20∶1. The method displayed good linearity in the range of 1-200 nmol/L with the correlation coefficients greater than 0.9972. The limits of detection and limits of quantification of the three proteins were 3 mg/kg and 10 mg/kg, respectively. The average recoveries of the three proteins spiked at three levels in different matrices ranging between 80.6%-103.7%, with the intra-day and inter-day precision less than 11.5%. Due to its high stability, excellent sensitivity, and simple operation, this method presents a wide range of application prospects in the analysis of the three allergenic proteins in different rice and rice food products.

Dataset Information

Detection of reactive metabolites using isotope-labeled glutathione trapping and simultaneous neutral loss and precursor ion scanning with ultra-high-pressure liquid chromatography triple quadruple mass spectrometry.

Publications

Detection of reactive metabolites using isotope-labeled glutathione trapping and simultaneous neutral loss and precursor ion scanning with ultra-high-pressure liquid chromatography triple quadruple mass spectrometry.

Similar Datasets

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