Connecting glutathione with immune responses to occupational methylene diphenyl diisocyanate exposure.
Wisnewski-AV; Liu-J; Redlich-CA
Chem-Biol Interact 2013 Sep; 205(1):38-45
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 (10ÁM-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.
Vapors; Inhalants; Allergens; Exposure-levels; Pathogenesis; Models; In-vivo-studies; In-vivo-study; Serological-techniques; Serology; Animals; Laboratory-animals; Aerosols;
Author Keywords: Hexamethylene diisocyanate (HDI); Vapor; Aliphatic; Albumin; Carbamoylation; Glutathione (GSH)
Adam V. Wisnewski, Yale University School of Medicine, 300 Cedar Street, TAC-S4157, P.O. Box 208057, New Haven, CT 06520-8057
Grant; Cooperative Agreement
Grant-Number-R21-OH-010438; Cooperative-Agreement-Number-U60-OH-009762; M112013
Yale University, New Haven, Connecticut