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Antigenic changes in human albumin caused by reactivity with the occupational allergen diphenylmethane diisocyanate.

ABSTRACT: Diphenylmethane diisocyanate (MDI), the chemical commonly used as a cross-linking agent in commercial polyurethane production, is a well-recognized cause of asthma. Reaction products between MDI and "self" proteins are hypothesized to act as antigens capable of inducing airway inflammation and asthma; however, such MDI antigens remain incompletely understood. We used a variety of analytical methods to characterize the range of MDI-albumin reaction products that form under physiological conditions. Sites of MDI conjugation on antigenic MDI-albumin products, as defined by serum immunoglobulin G (IgG) from MDI-exposed workers, were determined by high-performance liquid chromatography (HPLC) followed by tandem mass spectrometry (MS/MS). The data identified 14 MDI conjugation sites (12 lysines and 2 asparagines) on human albumin and highlight reaction specificity for the second lysine in dilysine (KK) motifs, and this may be a common characteristic of "immune-sensitizing" chemicals. Several of the MDI conjugation sites are not conserved in albumin from other species, and this may suggest species differences in epitope specificity for self protein (albumin)-isocyanate conjugates. The study also describes new applications of contemporary proteomic methodology for characterizing and standardizing MDI-albumin conjugates destined for use in clinical research.

SUBMITTER: Wisnewski AV

PROVIDER: S-EPMC3106273 | biostudies-literature | 2010 May

REPOSITORIES: biostudies-literature

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Antigenic changes in human albumin caused by reactivity with the occupational allergen diphenylmethane diisocyanate.

Wisnewski Adam V AV Liu Jian J Redlich Carrie A CA

Analytical biochemistry 20100201 2

Diphenylmethane diisocyanate (MDI), the chemical commonly used as a cross-linking agent in commercial polyurethane production, is a well-recognized cause of asthma. Reaction products between MDI and "self" proteins are hypothesized to act as antigens capable of inducing airway inflammation and asthma; however, such MDI antigens remain incompletely understood. We used a variety of analytical methods to characterize the range of MDI-albumin reaction products that form under physiological condition ...[more]

PMID: 20123080

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Project description:4,4'-Methylene diphenyl diisocyanate (herein 4,4'-MDI) is used in the production of polyurethane foams, elastomers, coatings, adhesives and the like for a wide range of commercial products. Occupational exposure to MDI levels above current airborne exposure limits can elicit immune mediated hypersensitivity reactions such as occupational asthma in sensitive individuals. To accurately determine exposure, there has been increasing interest in developing analytical methods to measure internal biomarkers of exposure to MDI. Previous investigators have reported methodologies for measuring MDI diamine metabolites and MDI-Lysine (4,4'-MDI-Lys) adducts. The purpose of this study was to develop and validate an ultra performance liquid chromatography isotope dilution tandem mass spectrometry (UPLC-ID/MS/MS) quantitation method via a signature peptide approach to enable biomonitoring of 4,4'-MDI adducted to human serum albumin (HSA) in plasma. A murine, anti-4,4'-MDI monoclonal IgM antibody was bound to magnetic beads and utilized for enrichment of the MDI adducted HSA. Following enrichment, trypsin digestion was performed to generate the expected 414 site (primary site of adduction) 4,4'-MDI-adducted HSA signature peptide that was quantified by UPLC-ID/MS/MS. An Agilent 6530 UPLC/quadrupole time of flight MS (QTOF) system was utilized for intact adducted protein analysis and an Agilent 6490 UPLC/MS/MS system operated in multiple reaction monitoring (MRM) mode was utilized for quantification of the adducted signature peptide biomarker both for in chemico and worker serum samples. Worker serum samples were initially screened utilizing the previously developed 4,4'-MDI-Lys amino acid method and results showed that 12 samples were identified as quantifiable for 4,4'-MDI-Lys adducts. The signature peptide adduct approach was applied to the 12 worker samples identified as quantifiable for 4,4'-MDI-Lys adducts. Results indicated no positive results were obtained above the quantification limit by the signature peptide approach. If the 414 site of lysine adduction accounted for 100% of the 4,4'-MDI adductions in the signature peptide adduct approach, the three highest quantifiable samples by the 4,4'-MDI-Lys method should have at least been detectable by the signature peptide method. Results show that although the 4,4'-MDI signature peptide approach is more selective, it is 18 times less sensitive than the 4,4'-MDI-Lys method, thus limiting the ability to detect adduct levels relative to the 4,4'-MDI-Lys amino acid method.

Project description:BackgroundIsocyanates, a leading cause of occupational asthma, are known to induce adaptive immune responses; however, innate immune responses, which generally precede and regulate adaptive immunity, remain largely uncharacterized.ObjectiveThe aim of the study was to identify and characterize the cellular, molecular and systemic innate immune responses induced by hexamethylene diisocyanate (HDI).MethodsHuman peripheral blood mononuclear cells (PBMCs) were stimulated in vitro with HDI-albumin conjugates or control antigen, and changes in phenotype, gene and protein expression were characterized by flow cytometry, microarray, Western blot and ELISA. Cell uptake of isocyanate was visualized microscopically using HDI-albumin conjugates prepared with fluorescently labelled albumin. In vivo, human HDI exposure was performed via a specific inhalation challenge, and subsequent changes in PBMCs and serum proteins were measured by flow cytometry and ELISA. Genotypes were determined by PCR.ResultsHuman monocytes take up HDI-albumin conjugates and undergo marked changes in morphology and gene/protein expression in vitro. The most significant (P-values 0.007-0.05) changes in microarray gene expression were noted in lysosomal genes, especially peptidases and proton pumps involved in antigen processing. Chemokines that regulate monocyte/macrophage trafficking (MIF, MCP-1) and pattern-recognition receptors that bind chitin (chitinases) and oxidized low-density lipoprotein (CD68) were also increased following isocyanate-albumin exposure. In vivo, HDI-exposed subjects exhibited a drastic increase in the percentage of PBMCs with the same HDI-albumin responsive phenotype characterized in vitro (HLA-DR(+)/CD11c(+) with altered light scatter properties). An exposure-dependent decrease (46+/-11%; P<0.015) in serum concentrations of chitinase 3-like-1 was also observed in individuals who lack the major (type 1) human chitinase (due to genetic polymorphism), but not in individuals possessing at least one functional chitinase-1 allele.ConclusionsPreviously unrecognized innate immune responses to HDI and HDI-albumin conjugates could influence the clinical spectrum of exposure reactions.

Dataset Information

Antigenic changes in human albumin caused by reactivity with the occupational allergen diphenylmethane diisocyanate.

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Antigenic changes in human albumin caused by reactivity with the occupational allergen diphenylmethane diisocyanate.

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