title: Identification of novel reaction products of methylene-bis-phenylisocyanate ("MDI") with oxidized glutathione in aqueous solution and also during incubation of MDI with a murine hepatic S9 fraction.
abstract: Methylene diphenyl diisocyanate (MDI) is an important industrial chemical and asthmagenic respiratory sensitizer, however its metabolism remains unclear. In this study we used LC-MS and LC-MS/MS to identify novel reaction products of MDI with oxidized glutathione (GSSG), including an 837m/z [M+H](+) ion corresponding to GSSG bound (via one of its N-termini) to partially hydrolyzed MDI, and an 863m/z [M+H](+) ion corresponding to GSSG cross-linked by MDI (via its two γ-glutamate N-termini) [corrected]. Further studies with heavy isotope labeled and native reduced glutathione (GSH) identified an [M+H](+) ion corresponding to previously described mono(GSH)-MDI, and evidence for "oligomeric" GSH-MDI conjugates. This study also investigated transformational changes in MDI after incubation with an S9 fraction prepared from murine liver. LC-MS analyses of the S9 reaction products revealed the formation of [M+H](+) ions with m/z's and retention times identical to the newly described GSSG-MDI (837 and 863) conjugates and the previously described mono(GSH)-MDI conjugate. Together the data identify novel biological transformations of MDI, which could have implications for exposure-related health effects, and may help target future in vivo studies of metabolism.
authors.affiliation: Department of Medicine, Yale University School of Medicine, New Haven, CT 06524, USA. Electronic address: adam.wisnewski@yale.edu.
authors.forename: A V
authors.initials: AV
authors.lastname: Wisnewski
authors.affiliation: Department of Medicine, Yale University School of Medicine, New Haven, CT 06524, USA.
authors.forename: J
authors.initials: J
authors.lastname: Liu
authors.affiliation: Department of Medicine, Yale University School of Medicine, New Haven, CT 06524, USA.
authors.forename: A F
authors.initials: AF
authors.lastname: Nassar
mesh_terms: D000485:Allergens / Q000378:metabolism*; D000818:Animals; D005978:Glutathione / Q000378:metabolism; D019803:Glutathione Disulfide / Q000378:metabolism*; D017953:Isocyanates / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008297:Male; D008810:Mice, Inbred C57BL; D012996:Solutions; D001559:Benzhydryl Compounds
chemical_list: D000485:Allergens; D005978:Glutathione; D019803:Glutathione Disulfide; D017953:Isocyanates; D012996:Solutions; C005969:4,4'-diphenylmethane diisocyanate; D001559:Benzhydryl Compounds
keywords: Asthma; Diisocyanate; Glutathione; Oxidized; Reduced; S9