title: Hexamethylene diisocyanate (HDI) vapor reactivity with glutathione and subsequent transfer to human albumin.
abstract: BACKGROUND
  Airway fluid glutathione (GSH) reactivity with inhaled vapors of diisocyanate, a common occupational allergen, is postulated to be a key step in exposure-induced asthma pathogenesis.
  
  
  METHODS
  A mixed (vapor/liquid) phase exposure system was used to model the in vivo reactivity of inhaled HDI vapor with GSH in the airway fluid. HDI-GSH reaction products, and their capacity to transfer HDI to human albumin, were characterized through mass spectrometry and serologic assays, using HDI-specific polyclonal rabbit serum.
  
  
  RESULTS
  HDI vapor exposure of 10mM GSH solutions resulted in primarily S-linked, bis(GSH)-HDI reaction products. In contrast, lower GSH concentrations (100μM) resulted in mainly mono(GSH)-HDI conjugates, with varying degrees of HDI hydrolysis, dimerization and/or intra-molecular cyclization, depending upon the presence/absence of H2PO4(-)/HPO4(2-) and Na(+)/Cl(-) ions. The ion composition and GSH concentration of the fluid phase, during HDI vapor exposure, strongly influenced the transfer of HDI from GSH to albumin, as did the pH and duration of the carbamoylating reaction. When carbamoylation was performed overnight at pH 7, 25 of albumin's lysines were identified as potential sites of conjugation with partially hydrolyzed HDI. When carbamoylation was performed at pH 9, more rapid (within 3h) and extensive modification was observed, including additional lysine sites, intra-molecular cross-linkage with HDI, and novel HDI-GSH conjugation.
  
  
  CONCLUSIONS
  The data define potential mechanisms by which the levels of GSH, H2PO4(-)/HPO4(2-), and/or other ions (e.g. H(+)/OH(-), Na(+), Cl(-)) affect the reactivity of HDI vapor with self-molecules in solution (e.g. airway fluid), and thus, might influence the clinical response to HDI respiratory tract exposure.
authors.affiliation: Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA. adam.wisnewski@yale.edu
authors.forename: Adam V
authors.initials: AV
authors.lastname: Wisnewski
authors.forename: Morgen
authors.initials: M
authors.lastname: Mhike
authors.forename: Justin M
authors.initials: JM
authors.lastname: Hettick
authors.forename: Jian
authors.initials: J
authors.lastname: Liu
authors.forename: Paul D
authors.initials: PD
authors.lastname: Siegel
mesh_terms: D000418:Albumins; D000485:Allergens / Q000737:chemistry*; D003485:Cyanates / Q000737:chemistry*; D005978:Glutathione / Q000737:chemistry*; D006801:Humans; D017953:Isocyanates; D014835:Volatilization
chemical_list: D000418:Albumins; D000485:Allergens; D003485:Cyanates; D017953:Isocyanates; C015262:1,6-hexamethylene diisocyanate; D005978:Glutathione