Connecting glutathione with immune responses to occupational methylene diphenyl diisocyanate exposure.

Abstract

Methylene diphenyl diisocyanate (MDI) is among the leading chemical causes of occupational asthma world-wide, however, the mechanisms of disease pathogenesis remain unclear. This study tests the hypothesis that glutathione (GSH) reacts with MDI to form quasi-stable conjugates, capable of mediating the formation of MDI-conjugated "self" protein antigens, which may participate in pathogenic inflammatory responses. To test this hypothesis, an occupationally relevant dose of MDI (0.1%w/v) was reacted with varying concentrations of GSH (10μM-10mM), and the reaction products were characterized with regard to mass/structure, and ability to carbamoylate human albumin, a major carrier protein for MDI in vivo. LC-MS/MS analysis of GSH-MDI reaction products identified products possessing the exact mass of previously described S-linked bis(GSH)-MDI and its partial hydrolysis product, as well as novel cyclized GSH-MDI structures. Upon co-incubation of GSH-MDI reaction products with human albumin, MDI was rapidly transferred to specific lysines of albumin, and the protein's native conformation/charge was altered, based on electrophoretic mobility. Three types of modification were observed, intra-molecular MDI cross-linking, addition of partially hydrolyzed MDI, and addition of "MDI-GSH", where MDI's 2nd NCO had reacted with GSH's "N-terminus". Importantly, human albumin carbamoylated by GSH-MDI was specifically recognized by serum IgG from MDI exposed workers, with binding dependent upon the starting GSH concentration, pH, and NaCl levels. Together, the data define a non-enzymatic, thiol-mediated transcarbamoylating mechanism by which GSH may promote immune responses to MDI exposure, and identify specific factors that might further modulate this process.

• Authors: Adam V Wisnewski, Jian Liu, Carrie A Redlich
• Journal: Chemico-biological interactions (Chem Biol Interact) Vol. 205 Issue 1 Pg. 38-45 (Sep 05 2013) ISSN: 1872-7786 [Electronic] Ireland
• PMID: 23791970 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)
• Copyright: Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Chemical References

• Albumins
• Allergens
• Benzhydryl Compounds
• Isocyanates
• methylenediphenyl diisocyanate-glutathione adduct
• 4,4'-diphenylmethane diisocyanate
• Glutathione

Topics

• Adult
• Albumins (immunology, metabolism)
• Allergens (adverse effects, immunology, metabolism)
• Asthma, Occupational (etiology, immunology, metabolism)
• Benzhydryl Compounds (adverse effects, immunology, metabolism)
• Case-Control Studies
• Female
• Glutathione (adverse effects, analogs & derivatives, immunology, metabolism)
• Humans
• Isocyanates (adverse effects, immunology, metabolism)
• Male
• Middle Aged
• Occupational Exposure
• Tandem Mass Spectrometry