Reaction products of hexamethylene diisocyanate vapors with “self” molecules in the airways of rabbits exposed via tracheostomy

Abstract

1. Hexamethylenediisocyanate (HDI) is a widely used aliphatic diisocyanate and a well-recognized cause of occupational asthma.

2. “Self” molecules (peptides/proteins) in the lower airways, susceptible to chemical reactivity with HDI, have been hypothesized to play a role in asthma pathogenesis and/or chemical metabolism, but remain poorly characterized.

3. This study employed unique approaches to identify and characterize “self” targets of HDI reactivity in the lower airways. Anesthetized rabbits free breathed through a tracheostomy tube connected to chambers containing either, O₂, or O₂ plus ∼200 ppb HDI vapors. Following 60 minutes of exposure, the airways were lavaged and the fluid was analyzed by LC-MS and LC-MS/MS.

4. The low-molecular weight (<3 kDa) fraction of HDI exposed, but not control rabbit bronchoalveolar lavage (BAL) fluid identified 783.26 and 476.18 m/z [M+H]⁺ ions with high energy collision-induced dissociation (HCD) fragmentation patterns consistent with bis glutathione (GSH)-HDI and mono(GSH)-HDI. Proteomic analyses of the high molecular weight (>3 kDa) fraction of exposed rabbit BAL fluid identified HDI modification of specific lysines in uteroglobin (aka clara cell protein) and albumin.

5. In summary, this study utilized a unique approach to chemical vapor exposure in rabbits, to identify HDI reaction products with “self” molecules in the lower airways.

Keywords:

• Exposure
• glutathione
• hexamethylene diisocyanate
• tracheostomy

Acknowledgements

We would like to acknowledge Dr. Terence Wu for his expert assistance with LC-MS and LC-MS/MS studies, Deborah Caruso from Yale Veterinary Care Services, Heidi Voegeli and Partha Krishnan from the Yale Environmental Health & Safety Office, and Claudia Swanson from Yale’s Institutional Animal Care and Use Committee. We would also like to acknowledge Ms. Karen Liu for her computer-generated schematic representation of the experimental rabbit exposure system (Figure 1).

Declaration of interest

No potential conflict of interest was reported by the authors.

The work was supported by a gift from the American Chemistry Council and the Centers for Disease Control / National Institute of Occupational Safety and Health (OH010438 and OH10941).

Supplementary material available online