Diisocyanates are
asthma-causing chemicals used in the commercial production of
polyurethane. We have previously shown that human lung epithelial cell
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 become conjugated with diisocyanate after in vitro and in vivo exposure. Following in vitro exposure of human airway epithelial cells (A549),
keratin 18, the 78-kD
glucose-regulated
protein, trans-1, 2-dihyrobenzene-1,2-diol
dehydrogenase, and actin were identified as prominent diisocyanate-conjugated
proteins through use of a combination of immunocytochemical and mass spectrometric techniques. Following in vivo inhalation of an HDI
aerosol,
keratin 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 was also identified as a predominant diisocyanate-conjugated
protein in human skin biopsy samples after epicutaneous exposure to liquid-phase HDI, although the major skin diisocyanate-conjugated
protein (56-kD) differed from the 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 may play a role in the pathogenesis of diisocyanate-induced
asthma.