23127-40-4Relevant articles and documents
Acrolein mercapturates: Synthesis, characterization, and assessment of their role in the bladder toxicity of cyclophosphamide
Ramu,Fraiser,Mamiya,Ahmed,Kehrer
, p. 515 - 524 (2007/10/03)
Acrolein is the metabolite of cyclophosphamide (CP) believed to be involved in the bladder toxicity associated with this anticancer drug. The mechanism by which this extremely reactive intermediate is delivered to the bladder is not known. Glutathione (GSH) readily conjugates with acrolein, and the acrolein mercapturate S-(3-hydroxypropyl)-N-acetylcysteine (3- hydroxyPrMCA) has been found in the urine of animals and man given CP. The objectives of this study were to prepare and characterize synthetic standards of the GSH acrolein adduct (3-oxopropyl)glutathione (3-oxoPrGSH), the acrolein mercapturates S-(3-oxopropyl)-N-acetylcysteine (3-oxoPrMCA) and 3- hydroxyPrMCA, and the S-oxidation product of 3-oxoPrMCA (3-oxoPrMCAS-oxide). In addition, the release of acrolein from, and the bladder toxicity of, these conjugates was determined. 3-OxoPrGSH and 3-oxoPrMCA were prepared with a 99% yield by condensing acrolein with GSH and N-acetylcysteine, respectively. 3- HydroxyPrMCA was prepared with a 63% yield by refluxing 3-chloropropanol and N-acetylcysteine in a basic medium. Oxidation of 3-oxoPrMCA with H2O2 was used to prepare 3-oxoPrMCA S-oxide. By decreasing the reaction time to 1 h, and adjusting the ratio of 3-oxoPrMCA to H2O2, the yield of 3-oxoPrMCA S- oxide was increased to 96%. The anhydrous aldehyde, 3-oxoPrMCA, afforded characteristic aldehydic proton resonances (1H NMR) in deuterated dimethyl sulfoxide. New resonances were observed in deuterated water, indicating a 75% hydration of the aldehyde to the corresponding geminal diol. This phenomenon was enhanced with 3-oxoPrMCA S-oxide where ~100% hydration of the aldehyde to the corresponding geminal diol was observed. When incubated at 25°C in 100 mM potassium phosphate buffer containing 1 M KCl, pH 8.0, 3-oxoPrMCA released ~6% and 3-oxoPrMCA S-oxide released ~16-18% of the theoretical maximum yield of acrolein after 30 min, as indicated by an increase in absorbance at 210 nm and confirmed by trapping this aldehyde as a semicarbazone. There was less than a 2% yield of acrolein from 3-hydroxyPrMCA or 3-oxoPrGSH under similar conditions. At pH 7.4 the release of acrolein from 3-oxoPrMCA and 3-oxoPrMCA S-oxide was decreased by 50%. An assay where aldehydes are reacted with m-aminophenol in acid media produced fluorescence consistent with 72%, 46%, 23%, and 1% yields of acrolein from 3-oxoPrMCA S- oxide, 3-oxoPrMCA, 3-oxoPrGSH, and 3-hydroxyPrMCA, respectively. These yields were unaffected by incubation in buffer for up to 2 h. Acrolein, 3-oxoPrMCA S-oxide, 3-oxoPrMCA and 3-oxoPrGSH, but not 3-hydroxyPrMCA, damaged the bladder dose-dependently when instilled intravesically in mice at concentrations of 10-20 mM. Potency was acrolein > 3-oxoPrMCA S-oxide > 3- oxoPrMCA > 3-oxoPrGSH. These data support the possibility that a mercapturic acid may be involved in the bladder toxicity of CP.
Identification of N-Acetylcysteine Conjugates of 1,2-Dibromo-3-chloropropane: Evidence for Cytochrome P450 and Glutathione Mediated Bioactivation Pathways
Weber, Gregory L.,Steenwyk, Rick C.,Nelson, Sidney D.,Pearson, Paul G.
, p. 560 - 573 (2007/10/03)
The haloalkane 1,2-dibromo-3-chloropropane (DBCP) is a carcinogen, mutagen, nephrotoxin, and testicular toxin. The identification of N-acetylcysteine conjugates of DBCP provides information on GSH mediated and cytochrome P450 mediated bioactivation pathways in the expression of DBCP-induced toxicities. N-Acetylcysteine conjugates excreted in the urine of male Sprague-Dawley rats administered DBCP, C1D2-DBCP, C2D1-DBCP, C3D2-DBCP, or D5-DBCP (80 mg/kg) were purified by reverse-phase HPLC as their methyl ester derivatives and characterized by fast atom bombardment tandem mass spectrometry. These metabolites were also converted to tert-butyldimethylsilyl ether derivatives and analyzed by gas chromatography-mass spectrometry (GC-MS) to facilitate the identification of N-acetyl-S-(2,3-dihydroxypropyl)cysteine (Ia), an apparent regioisomer of Ia, 2-(S-(N-acetylcysteinyl))-1,3-propanediol (Ib), N-acetyl-S-(3-hydroxypropyl)cysteine (IIa), and N-acetyl-S-(3-chloro-2-hydroxypropyl)cysteine (III). Metabolites Ia, Ib, and III displayed quantitative retention of deuterium, an observation consistent with the formation of episulfonium ion intermediate(s) in their biogenesis. Mercapturate IIa retained three atoms of deuterium from D5-DBCP, and two atoms of deuterium from the dideuterio analogs (C1D2-DBCP and C3D2-DBCP), thus invoking P450 mediated formation of 2-bromoacrolein (2-BA) as an intermediate in the biogenesis of IIa. A mechanism is proposed in which conjugate addition of GSH to 2-BA, subsequent episulfonium ion formation, and addition of GSH afford 1,2-(diglutathion-S-yl)propanal. Glutathione mediated reduction is invoked to afford S-(3-hydroxypropyl)GSH which would be excreted in the urine as IIa. The quantitative retention of deuterium from C1D2-DBCP or C3D2-DBCP was indicative of isotopically sensitive branching of P450 metabolism at either C1 or C3 to afford 2-BA. C2D1-DBCP showed a 30 percent retention of 1 deuterium atom in IIa; the loss of the deuterium is consistent with 2-BA formation, whereas the retention of one deuterium atom is indicative of the formation of metabolite IIa through GSH conjugation of either 2,3-dibromopropanal or 2-bromo-3-chloropropanal. These data indicate that IIa is a marker metabolite for the potent direct-acting mutagen, 2-BA, or its metabolic precursors 2,3-dibromopropanal or 2-bromo-3-chloropropanal. Therefore, evidence has been presented for bioactivation of DBCP by glutathione and cytochrome P450 mediated mechanisms.
