Detection of glutathione conjugates of amiodarone and its reactive diquinone metabolites in rat bile using mass spectrometry tools

Abstract

This study confirmed generation of reactive metabolites of amiodarone for the first time, as was hypothesised earlier by various research groups. Also, the responsible toxicophore was identified to be a benzofuran moiety liable to form reactive diquinone species. However, the results need to be further confirmed in human subjects. Copyright © 2016 John Wiley & Sons, Ltd.

Permeabilized Cryopreserved Human Hepatocytes as an Exogenous Metabolic System in a Novel Metabolism-Dependent Cytotoxicity Assay for the Evaluation of Metabolic Activation and Detoxification of Drugs Associated with Drug-Induced Liver Injuries: Results with Acetaminophen, Amiodarone, Cyclophosphamide, Ketoconazole, Nefazodone, and Troglitazone

“…NADPH/NAD+ enhancement of amiodarone cytotoxicity is consistent with previous findings that CYP3A4 induction by rifampin resulted in its higher cytotoxicity in cultured human hepatocytes and that cytotoxicity in HepG2 cells was enhanced via supplementation with exogenous CYP3A4 supersomes (Zahno et al, 2011). GSH attenuation of amiodarone cytotoxicity is consistent with the detection of its reactive metabolites in rat bile (Parmar et al, 2016) and upon incubation with human and rat liver homogenates (Ramesh Varkhede et al, 2014). The lack of effects of UDPGA and PAPS on amiodarone in MDCA suggest that the cytotoxic metabolites of amiodarone are not significantly detoxified by glucuronidation and sulfation.…”

Investigating protein thiol chemistry associated with dehydroascorbate, homocysteine and glutathione using mass spectrometry

“…This was confirmed by product ions formed with neutral loss of γ‐Glu (129 Da) from GSH. Loss of γ‐Glu is commonly observed when GSH or glutationylated peptides are subjected to CID 57,58 . MS/MS of the [M + 3H] 3+ ion for peptide 77 Asp‐Arg 97 with one and two GS adducts ( m / z 833.7117 and 935.4065, respectively) gave almost identical spectra and confirmed the peptide's identity (Figures 2B and 2C).…”

Discovery of Modified Metabolites, Secondary Metabolites, and Xenobiotics by Structure-Oriented LC–MS/MS

“…37,94 Analysis of GSH-trapped reactive metabolites via CNL monitoring of the pyroglutamic acid moiety (129 Da) 32,95 and PI monitoring of the γ-glutamyldehydroalanyl-glycine fragment in negative ion mode (272 m/ z) 96,97 have been employed to measure reactive metabolites in urine derived from xenobiotics, 32 cigarette smoke, 98,99 and drug-induced toxicity. 37,40,[95][96][97]100 Further transformation of GSH via transpeptidase cleavage and subsequent acetylation produces mercapturic acids-conjugates that are commonly assessed via CNL monitoring to evaluate reactive metabolite exposure. 34,44,45,101 Biomonitoring of phase II metabolites produced through glucuronidation 50,83,101,102 and sulfation 48,49 processes are routinely monitored through CNL and PI approaches.…”

“…There are a multitude of applications of CNL and PI monitoring in the fields of toxicology, pharmacology, and drug discovery. Xenobiotics, endogenous chemicals, and drug intermediaries are reported to react with DNA, proteins, and host metabolic processes in living organisms. − The reactive tendency of these toxins impedes the ability to monitor their concentration in biological systems directly, but the analysis of the adducted and trapped byproducts is commonly employed to monitor for exposures. , Analysis of GSH-trapped reactive metabolites via CNL monitoring of the pyroglutamic acid moiety (129 Da) , and PI monitoring of the γ-glutamyl-dehydroalanyl-glycine fragment in negative ion mode (272 m / z ) , have been employed to measure reactive metabolites in urine derived from xenobiotics, cigarette smoke, , and drug-induced toxicity. ,,− , Further transformation of GSH via transpeptidase cleavage and subsequent acetylation produces mercapturic acids-conjugates that are commonly assessed via CNL monitoring to evaluate reactive metabolite exposure. ,,, Biomonitoring of phase II metabolites produced through glucuronidation ,,, and sulfation , processes are routinely monitored through CNL and PI approaches. Chemical detoxification is finite with nontrivial levels of various reactive metabolites interacting with host systems by means of covalent modification.…”