title: Using lysine adducts of human serum albumin to investigate the disposition of exogenous formaldehyde in human blood.
abstract: Formaldehyde is a human carcinogen that readily binds to nucleophiles, including proteins and DNA. To investigate whether exogenous formaldehyde produces adducts in extracellular fluids, we characterized modifications to human serum albumin (HSA) following incubation of whole blood, plasma, and saliva with formaldehyde at concentrations of 1, 10 and 100μM. The only HSA locus that showed the presence of formaldehyde modifications was Lys199. A N(6)-Lys adduct with added mass of 12Da, representing a putative intramolecular crosslink, was detected in biological fluids that had been incubated with formaldehyde but not in control fluids. An adduct representing N(6)-Lys formylation was detected in all fluids, but levels did not increase above control values over the tested range of formaldehyde concentrations. An adduct representing N(6)-Lys199 acetylation was also measured in all samples. We then applied the assay to repeated samples of human plasma from 6 nonsmoking volunteer subjects (from Berkeley, CA), and single samples of serum from 15 workers exposed to airborne formaldehyde at about 1.5ppm in a production facility and 15 control workers from Tianjin, China. Although all human plasma/serum samples contained basal levels of the products of N(6)-Lys formylation and acetylation, the putative crosslink product was not detected. Since the putative crosslink was observed in plasma incubated with formaldehyde at 1μM, this suggests that the endogenous concentration of formaldehyde in serum was much lower than reported in the literature. Furthermore, concentrations of the formyl adduct were not higher in workers exposed to formaldehyde at about 1.5ppm than in controls. Follow-up in vitro experiments with gaseous formaldehyde at 1.4ppm detected the putative crosslink in plasma but not whole blood. This combination of results suggests that N(6) formylation occurs within cells with subsequent release of adducted HSA to the systemic circulation. Comparing across human samples, levels of N(6)-Lys199 formyl adducts were present at similar concentrations in subjects from California and China (about 1mmol/mol HSA), but N(6)-Lys199 acetyl adducts were present at higher concentrations in Chinese subjects (0.34 vs. 0.13mmol/mol HSA).
authors.affiliation: Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, CA, United States.
authors.forename: Luca G
authors.initials: LG
authors.lastname: Regazzoni
authors.affiliation: Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, CA, United States.
authors.forename: Hasmik
authors.initials: H
authors.lastname: Grigoryan
authors.affiliation: Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, CA, United States.
authors.forename: Zhiying
authors.initials: Z
authors.lastname: Ji
authors.affiliation: Department of Occupational and Environmental Health, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Xi
authors.initials: X
authors.lastname: Chen
authors.affiliation: Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, CA, United States.
authors.forename: Sarah I
authors.initials: SI
authors.lastname: Daniels
authors.affiliation: Institute of Occupational Health, School of Public Health, Tianjin Bohai Chemical Industry Group Co. Ltd., Tianjin, China.
authors.forename: Deyin
authors.initials: D
authors.lastname: Huang
authors.affiliation: Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, CA, United States.
authors.forename: Sylvia
authors.initials: S
authors.lastname: Sanchez
authors.affiliation: Department of Occupational and Environmental Health, School of Public Health, Tianjin Medical University, Tianjin, China.
authors.forename: Naijun
authors.initials: N
authors.lastname: Tang
authors.affiliation: Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, CA, United States.
authors.forename: Fenna C M
authors.initials: FC
authors.lastname: Sillé
authors.affiliation: California Institute for Quantitative Biosciences and Department of Chemistry, University of California, Berkeley, CA, United States.
authors.forename: Anthony T
authors.initials: AT
authors.lastname: Iavarone
authors.affiliation: California Institute for Quantitative Biosciences and Department of Chemistry, University of California, Berkeley, CA, United States.
authors.forename: Evan R
authors.initials: ER
authors.lastname: Williams
authors.affiliation: Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, CA, United States.
authors.forename: Luoping
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, CA, United States. Electronic address: srappaport@berkeley.edu.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Rappaport
mesh_terms: D000107:Acetylation; D015415:Biomarkers / Q000097:blood; D002140:California; D002274:Carcinogens, Environmental / Q000009:adverse effects / Q000378:metabolism*; D016022:Case-Control Studies; D002681:China; D005260:Female; D005557:Formaldehyde / Q000009:adverse effects / Q000097:blood*; D006801:Humans; D019570:Inhalation Exposure; D008239:Lysine; D008297:Male; D016273:Occupational Exposure; D011485:Protein Binding; D012463:Saliva / Q000378:metabolism; D012709:Serum Albumin / Q000378:metabolism*; D000075462:Serum Albumin, Human; D013997:Time Factors
chemical_list: C422455:ALB protein, human; D015415:Biomarkers; D002274:Carcinogens, Environmental; D012709:Serum Albumin; D005557:Formaldehyde; D008239:Lysine; D000075462:Serum Albumin, Human
keywords: Acetylation; Adducts; Blood; Covalent modification; Formaldehyde; Formylation; Lysine 199; Saliva