Occupational exposure to HDI: Progress and challenges in biomarker analysis

Abstract

Abstract1,6-hexamethylene diisocyanate (HDI) is extensively used in the automotive repair industry and is a commonly reported cause of occupational asthma in industrialized populations. However, the exact pathological mechanism remains uncertain. Characterization and quantification of biomarkers resulting from HDI exposure can fill important knowledge gaps between exposure, susceptibility, and the rise of immunological reactions and sensitization leading to asthma. Here, we discuss existing challenges in HDI biomarker analysis including the quantification of N-acetyl-1,6-hexamethylene diamine (monoacetyl-HDA) and N,N′-diacetyl-1,6-hexamethylene diamine (diacetyl-HDA) in urine samples based on previously established methods for HDA analysis. In addition, we describe the optimization of reaction conditions for the synthesis of monoacetyl-HDA and diacetyl-HDA, and utilize these standards for the quantification of these metabolites in the urine of three occupationally exposed workers. Diacetyl-HDA was present in untreated urine at 0.015 -0.060 μg/l. Using base hydrolysis, the concentration range of monoacetyl-HDA in urine was 0.19 -2.2 μg/l, 60-fold higher than in the untreated samples on average. HDA was detected only in one sample after base hydrolysis (0.026 μg/l). In contrast, acid hydrolysis yielded HDA concentrations ranging from 0.36 to 10.1 μg/ l in these three samples. These findings demonstrate HDI metabolism via N-acetylation metabolic pathway and protein adduct formation resulting from occupational exposure to HDI.

Hemoglobin adducts in workers exposed to 1,6-hexamethylene diisocyanate

“…Because monoacetyl-HDA-Hb was only detected in one worker, further statistical investigation of these compounds was not feasible. Additionally, the formation of diacetyl-HDA-Hb adducts would not be anticipated based on the proposed metabolism of HDI (Flack et al 2010b). However, the methods described may be adapted to measure urinary diacetyl-HDA in future studies.…”

“…A portion of the filtrate was dried under nitrogen and a 1 mg/ml solution of the dried product prepared in ethyl acetate. Gas chromatography–mass spectrometry (GC-MS) analysis of the diacetyl-HDA mixture showed the product to be ≥99% pure (Flack et al 2010b). …”

Influence of Genetic Variance on Biomarker Levels After Occupational Exposure to 1,6-Hexamethylene Diisocyanate Monomer and 1,6-Hexamethylene Diisocyanate Isocyanurate

“…Little is known about the pathways involved in the absorption, distribution, metabolism, and elimination (ADME) of isocyanates before asthma pathology develops. Research on protein adducts and asthma risk indicates that GST, NAT, and/or CYP450 gene products may be involved in the biotransformation and metabolism of isocyanates (Flack et al, 2010a), but this still needs to be researched further. The impact of genetics Abbreviations: ADME, Absorption, distribution, metabolism, and elimination; APF, Assigned protection factor; DAVID, Database for Annotation, Visualization and Integrated Discovery; FDR, False discovery rate; GWAS, Genomewide association study; HDA, 1,6-diaminohexane; HDI, 1,6-hexamethylene diisocyanate; LD, linkage disequilibrium; LOD, limit of detection; MAF, minor allele frequency; MDL, method detection limit; PBMCs, peripheral blood mononuclear blood cells; QC, quality control; rsID, reference SNP cluster identification; SNP, single-nucleotide polymorphism; TAHI, trisaminohexyl isocyanurate.…”

“…Little is known about the pathways involved in the absorption, distribution, metabolism, and elimination (ADME) of isocyanates before asthma pathology develops. Research on protein adducts and asthma risk indicates that GST, NAT, and/or CYP450 gene products may be involved in the biotransformation and metabolism of isocyanates ( Flack et al, 2010a ), but this still needs to be researched further. The impact of genetics on isocyanate metabolite levels after occupational exposure has been investigated in a few studies.…”

Factors affecting variability in the urinary biomarker 1,6-hexamethylene diamine in workers exposed to 1,6-hexamethylene diisocyanate

“…Upon acid hydrolysis of the urine sample during analysis, protein adducts formed due to direct reaction with HDI or as a product of HDI metabolism may be broken down and released in the form of HDA. 9–12 Thus, a person's inherent ability to metabolize HDI ( e.g ., metabolic rate, genetic polymorphisms) may be only one contributing factor to the elimination rate of HDA after exposure to HDI. Liu et al .…”