Browsing by Author "Wu, Kuen-Yuh"

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In vivo formation of N7- guanine DNA adduct by safrole 2 ',3 '-oxide in mice
(2012-09-18)
Shen, Li-Ching
;
Chiang, Su-Yin
;
Lin, Ming-Huan
;
Chung, Wen-Sheng
;
Wu, Kuen-Yuh
Safrole, a naturally occurring product derived from spices and herbs, has been shown to be associated with the development of hepatocellular carcinoma in rodents. Safrole 2',3'-oxide (SFO), an electrophilic metabolite of safrole, was shown to react with DNA bases to form detectable DNA adducts in vitro, but not detected in vivo. Therefore, the objective of this study was to investigate the formation of N7-(3-benzo[1,3] dioxol-5-yl-2-hydroxypropyl) guanine ( N7 gamma-SFO-Gua) resulting from the reaction of SFO with the most nucleophilic site of guanine in vitro and in vivo with a newly developed isotope-dilution high performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) method. N7 gamma-SFO-Gua and [N-15(5)]-N7-(3-benzo[1,3] dioxol-5-yl-2-hydroxypropyl) guanine ([N-15(5)]-N7 gamma-SFO-Gua) were first synthesized, purified, and characterized. The HPLC-ESI-MS/MS method was developed to measure N7 gamma-SFO-Gua in calf thymus DNA treated with 60 mu mol of SFO for 72 h and in urine samples of mice treated with a single dose of SFO (30 mg/kg body weight, intraperitoneally). In calf thymus DNA, the level of N7 gamma-SFO-Gua was 2670 adducts per 106 nucleotides. In urine of SFO-treated mice, the levels of N7 gamma- SFO-Gua were 1.02 +/- 0.14 ng/mg creatinine (n = 4) on day 1, 0.73 +/- 0.68 ng/mg creatinine (n = 4) on day 2, and below the limit of quantitation on day 3. These results suggest that SFO can cause in vivo formation of N7 gamma-SFO-Gua, which may then be rapidly depurinated from the DNA backbone and excreted through urine. (c) 2012 Elsevier Ireland Ltd. All rights reserved.
Potential Association of Urinary N7-(2-Carbamoyl-2-hydroxyethyl) Guanine with Dietary Acrylamide Intake of Smokers and Nonsmokers
(2015-01-01)
Huang, Chih-Chun Jean
;
Wu, Chia-Fang
;
Shih, Wei-Chung
;
Luo, Yu-Syuan
;
Chen, Ming-Feng
Acrylamide (AA), a rodent carcinogen, is widely used in industry and present in cigarette smoke as well as in foods processed at high temperatures. The metabolic activation of AA to glycidamide (GA) could be critical for AA carcinogenicity since GA causes DNA adduct formation in vivo. N7-(2-carbamoyl-2-hydroxyethyl) guanine (N7-GAG), the most abundant DNA adduct of AA, is subjected to spontaneous and enzymatic depurination and excreted through urine. Urinary N7-GAG analysis can confirm AA genotoxicity and identify active species of AA metabolites in humans, thereby serving as a risk-associated biomarker for molecular epidemiology studies. This study aimed to develop an isotope-dilution solid-phase extraction liquid chromatography tandem mass spectrometry method to comparatively analyze urinary N7-GAG levels in nonsmokers and smokers. Urinary N-acetyl-S-(propionamide)-cysteine (AAMA), a metabolite of AA, was also analyzed as a biomarker for current AA exposure. Urinary N7-GAG was quantified by monitoring m/z 239 ? 152 for N7-GAG and m/z 242 ? 152 for C-13(3)-labeled N7-GAG under positive electron spray ionization and multiple reaction mode. The median urinary N7-GAG level was 0.93 mu g/g creatinine in nonsmokers (n = 33) and 1.41 mu g/g creatinine in smokers (n = 30). Multiple linear regression analysis of data revealed that N7-GAG levels were only significantly associated with AAMA levels. These results demonstrate that urinary N7-GAG of nonsmokers and smokers is significantly associated with a very low level of dietary AA intake, assessed by analyzing urinary AAMA.
Study of urinary 2-{[2-(acetylamino-2-carboxyethyl]sulfanyl}butanedioic acid, a mercapturic acid of rats treated with maleic acid
(2015-08-05)
Luo, Yu-Syuan
;
Tsai, Hsin-Yun
;
Chen, Hsin-Chang
;
Wu, Charlene
;
Shen, Li-Ching
Maleic anhydride was reported illegally adulterated into starch to prepare traditional foods for decades in Taiwan. Maleic acid (MA), hydrolyzed from maleic anhydride, could cause kidney damages to animals. The potential health effects due to long-term MA exposures through food consumption have been of great concerns. Assessment of the dietary MA exposures could be very difficult and complicated. One of the alternatives is to analyze an MA-specific biomarker to assess the daily total MA intake. Therefore, this paper aimed to study the mercapturic acid of MA, 2-{[2-(acetylamino)-2-carboxyethyl]sulfanyl} butanedioic acid (MAMA), with our newly-developed isotope-dilution online solid-phase extraction liquid chromatography tandem mass spectrometry (ID-SPE-LC-MS/MS) method. MAMA was first synthesized, purified, and characterized with NMR to reveal two diastereomers and used for developing the analytical method. The method was validated to reveal excellent sensitivity with a LOD at 16.3 ng/mL and a LOQ at 20.6 ng/mL and used to analyze MAMA in urine samples collected from Sprague-Dawley rats treated with a single dose of 0 mg/kg, 6 mg/kg, and 60 mg/kg (n = 5) of MA through gavage. Our results show dose-dependent increases in urinary MAMA contents, and 70% MAMA was excreted within 12 h with no gender differences (p > 0.05). A half life of urinary MAMA was estimated at 6.8 h for rat. The formation of urinary MAMA validates it as a chemically-specific biomarker for current MA exposure. Future study of MA metabolism in vivo will elucidate mechanisms of MAMA formation, and analysis of this marker in epidemiology studies could help to shed light on the causal effects of MA on human. (C) 2015 Elsevier Ireland Ltd. All rights reserved.
Synthesis and Characterization of Adducts Formed in the Reactions of Safrole 2',3'-Oxide with 2'-Deoxyadenosine, Adenine, and Calf Thymus DNA
(2012-02-01)
Shen, Li-Ching
;
Chiang, Su-Yin
;
Ho, I-Ting
;
Wu, Kuen-Yuh
;
Chung, Wen-Sheng
Safrole (1) is a natural product found in herbs and spices. Upon uptake, it can be metabolized to safrole 2',3'-oxide [(+/-)-SFO, 2], which can react with DNA bases to form DNA adducts. The reactions of 2 with 2'-deoxyadenosine (3) and adenine (8) under physiological conditions (pH 7.4, 37 degrees C) were carried out to characterize its possible adducts with adenine. Four adducts were isolated by reverse-phase liquid chromatography and their structures were characterized by UV/Vis, 1H and 13C NMR spectroscopy and MS. The reaction of 2 with 3 produced two regioisomers, N1?-SFO-dAdo (4) and N6?-SFO-dAdo (5), in 4.24.5?% yield, and the reaction of 2 with 8 generated N3?-SFO-Ade (9) and N9?-SFO-Ade (10) in 1.02.4?% yield. Using HPLCESI-MS/MS, we traced the amounts of the four adducts formed when calf thymus DNA (10 mg) was treated with 2 (60 mu mol) and the levels of 4, 5, and 9 were determined to be 2000, 170, and 660 adducts per 106 nucleotides, respectively. Adduct 10 was not detected under these conditions. These results suggested that stable DNA adducts of 2 were formed in vitro, and further studies on the formation of these DNA adducts in vivo may help to elucidate their role in safrole carcinogenicity.
Synthesis, characterization and analysis of the acrylamide- and glycidamide-glutathione conjugates
(2015-07-25)
Luo, Yu-Syuan
;
Long, Tai-Ying
;
Shen, Li-Ching
;
Huang, Shou-Ling
;
Chiang, Su-Yin
Acrylamide (AA) is reported present in high-temperature-processed food and classified as a possible human carcinogen. In vivo metabolic activation of AA by CYP 2E1 to glycidamide (GA) may play an important role on AA carcinogenicity. AA and GA can be detoxified by glutathione-S-transferase to form AA and isomeric GA glutathione conjugates (M-, GA2- and GA3-GSH, respectively), which can be further metabolized to mercapturic acids (MAs). Although many studies analyzed MAs in urine of rodents and humans, few studies have characterized and analyzed the GSH conjugates. The objectives of this study were to synthesize, purify, and characterize AA-GSH, GA2-GSH, GA3-GSH, (C-13(3))-AA-GSH, (C-13(3))-GA2-GSH, and (C-13(3))-GA3-GSH to develop an isotope-dilution liquid chromatography tandem mass spectrometry (LC-MS/MS) method to analyze AA- and GA-GSHs in blood of rats treated with AA. After purification and characterization of these conjugates, the LC-MS/MS method was developed and validated. This method reveals a limit of detection (S/N= 3) at 0.017 and a limit of quantitation (S/N = 10) at 0.05 ng/mL of serum for AA-GSH, 0.075 and 0.25 ng/mL for GA2-GSH, and 0.15 and 0.5 ng/mL for GA3-GSH. Analyzed with this method, AA-GSH, GA2-GSH and GA3-GSH were 1651.1 +/- 374.5, 18.4 +/- 6.3 and 75.3 +/- 31.3 ng/mL in blood of male rats at 2 h after treatment with 5 mg/kg bw of AA by ip injection. These results showed that the LC-MS/MS method was successfully developed to analyze AA-GSH, GA2-GSH and GA3-GSH with satisfying sensitivity of AA and GA which were conjugated by glutathione in vivo. (C) 2015 Elsevier Ireland Ltd. All rights reserved.