Identification of human lung and skin proteins conjugated with hexamethylene diisocyanate in vitro and in vivo

Diiisocyanates are asthma-causing chemicals used in the commercial producti on of polyurethane. We have previously shown that human lung epithelial cel l proteins can become conjugated with hexamethylene diisocyanate (HDI) and may be biologically important in diisocyanate-induced asthma. The objective of this study was to identify specific human lung and skin proteins that b ecome conjugated with diisocyanate after in vitro and in vivo exposure. Fol lowing in vitro exposure of human airway epithelial cells (A549), keratin 1 8, the 78-kD glucose-regulated protein, trans-1,2-dihyrobenzene-1,2-diol de hydrogenase, and actin were identified as prominent diisocyanate-conjugated proteins through use of a combination of immunocytochemical and mass spect rometric techniques. Following in vivo inhalation of an HDI aerosol, kerati n 18 was also identified as the predominant diisocyanate-conjugated protein in human endobronchial biopsy samples, whereas albumin was the predominant diisocyanate-conjugated protein in bronchoalveolar lavage fluid. Keratin w as also identified as a predominant diisocyanate-conjugated protein in huma n skin biopsy samples after epicutaneous exposure to liquid-phase HDI, alth ough the major skin diisocyanate-conjugated protein (56-kD) differed from t he predominant lung diisocyanate-conjugated keratin (47-kD). The data from this study identify keratin and other proteins as potential "carriers" for diisocyanates in vivo, and suggest that HDI conjugation of these proteins m ay play a role in the pathogenesis of diisocyanate-induced asthma.