title: Mass spectrometric identification of isocyanate-induced modifications of keratins in human skin.
abstract: In the current paper we show that exposure of human callus to isocyanates leads to covalent modifications within keratin proteins. Mass spectrometric analyses of pronase digests of keratin isolated from exposed callus show that both mono- and di-adducts (for di-isocyanates) are predominantly formed on the ε-amino group of lysine. In addition, numerous modified tryptic keratin fragments were identified, demonstrating rather random lysine modification. Interestingly, preliminary experiments demonstrate that in case of MDI a similar lysine di-adduct was formed with lung elastin. Our data support the hypothesis that skin sensitization through antigenic modifications of skin proteins by isocyanates could play a role in occupational isocyanate-induced asthma. It is further envisaged that the elucidated adducts will also have great potential for use as biomarkers to assess skin exposure to isocyanates. Advantageously, the various lysine adducts display the presence of a characteristic daughter fragment at m/z 173.1 [lysine-NCO](+), enabling generic and rapid screening for exposure to isocyanates.
authors.affiliation: TNO, Department of CBRN Protection, P.O. Box 45, 2280 AA Rijswijk, The Netherlands.
authors.forename: Albert G
authors.initials: AG
authors.lastname: Hulst
authors.affiliation: TNO, Department of CBRN Protection, P.O. Box 45, 2280 AA Rijswijk, The Netherlands; Section of Molecular Toxicology, AIMMS, VU University, Amsterdam, The Netherlands.
authors.forename: Daan R W
authors.initials: DR
authors.lastname: Verstappen
authors.affiliation: TNO, Department of CBRN Protection, P.O. Box 45, 2280 AA Rijswijk, The Netherlands.
authors.forename: Debora
authors.initials: D
authors.lastname: van der Riet-Van Oeveren
authors.affiliation: Section of Molecular Toxicology, AIMMS, VU University, Amsterdam, The Netherlands.
authors.forename: Nico P E
authors.initials: NP
authors.lastname: Vermeulen
authors.affiliation: TNO, Department of CBRN Protection, P.O. Box 45, 2280 AA Rijswijk, The Netherlands. Electronic address: daan.noort@tno.nl.
authors.forename: Daan
authors.initials: D
authors.lastname: Noort
mesh_terms: D000595:Amino Acid Sequence; D066241:Carbon-13 Magnetic Resonance Spectroscopy; D002853:Chromatography, Liquid; D006801:Humans; D017953:Isocyanates / Q000494:pharmacology*; D007633:Keratins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D066244:Proton Magnetic Resonance Spectroscopy; D012867:Skin / Q000187:drug effects* / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D017953:Isocyanates; D007633:Keratins
keywords: Adducts; Biomarkers; Exposure assessment; Isocyanates; Keratin; Skin