Refinement of a Methodology for Untargeted Detection of Serum Albumin Adducts in Human Populations.
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ABSTRACT:
SUBMITTER: Preston GW
PROVIDER: S-EPMC5736992 | biostudies-literature |
REPOSITORIES: biostudies-literature
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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.
| S-EPMC4748379 | biostudies-literature
Project description:An important but understudied class of human exposures is comprised of reactive electrophiles that cannot be measured in vivo because they are short-lived. An avenue for assessing these meaningful exposures focuses on adducts from reactions with nucleophilic loci of blood proteins, particularly Cys34 of human serum albumin, which is the dominant scavenger of reactive electrophiles in serum. We developed an untargeted analytical scheme and bioinformatics pipeline for detecting, quantitating, and annotating Cys34 adducts in tryptic digests of human serum/plasma. The pipeline interrogates tandem mass spectra to find signatures of the Cys34-containing peptide, obtains accurate masses of putative adducts, quantitates adduct levels relative to a "housekeeping peptide", and annotates modifications based on a combination of retention time, accurate mass, elemental composition, and database searches. We used the adductomics pipeline to characterize 43 adduct features in archived plasma from healthy human subjects and found several that were highly associated with smoking status, race, and other covariates. Since smoking is a strong risk factor for cancer and cardiovascular disease, our ability to discover adducts that distinguish smokers from nonsmokers with untargeted adductomics indicates that the pipeline is suitable for use in epidemiologic studies. In fact, adduct features were both positively and negatively associated with smoking, indicating that some adducts arise from reactions between Cys34 and constituents of cigarette smoke (e.g., ethylene oxide and acrylonitrile) while others (Cys34 oxidation products and disulfides) appear to reflect alterations in the serum redox state that resulted in reduced adduct levels in smokers.
| S-EPMC5555296 | biostudies-literature
Project description:Metabolism of chemicals from the diet, exposures to xenobiotics, the microbiome, and lifestyle factors (e.g., smoking, alcohol intake) produce electrophiles that react with nucleophilic sites in circulating proteins, notably Cys34 of human serum albumin (HSA). To discover potential risk factors resulting from in utero exposures, we are investigating HSA-Cys34 adducts in archived newborn dried blood spots (DBS) that reflect systemic exposures during the last month of gestation. The workflow includes extraction of proteins from DBS, measurement of hemoglobin (Hb) to normalize for blood volume, addition of methanol to enrich HSA by precipitation of Hb and other interfering proteins, digestion with trypsin, and detection of HSA-Cys34 adducts via nanoflow liquid chromatography-high-resolution mass spectrometry. As proof-of-principle, we applied the method to 49 archived DBS collected from newborns whose mothers either actively smoked during pregnancy or were nonsmokers. Twenty-six HSA-Cys34 adducts were detected, including Cys34 oxidation products, mixed disulfides with low molecular weight thiols (e.g., cysteine, homocysteine, glutathione, cysteinylglycine), and other modifications. Data were normalized with a novel method ("scone") to remove unwanted technical variation arising from HSA digestion, blood volume, DBS age, mass spectrometry analysis, and batch effects. Using an ensemble of linear and nonlinear models, the Cys34 adduct of cyanide was found to consistently discriminate between newborns of smoking and nonsmoking mothers with a mean fold change (smoking/nonsmoking) of 1.31. These results indicate that DBS adductomics is suitable for investigating in utero exposures to reactive chemicals and metabolites that may influence disease risks later in life.
| S-EPMC6461474 | biostudies-literature
Project description: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).
| S-EPMC5555303 | biostudies-literature
Project description:A major challenge in organophosphate (OP) research has been the identification and utilization of reliable biomarkers for the rapid, sensitive, and efficient detection of OP exposure. Although Tyr 411 OP adducts to human serum albumin (HSA) have been suggested to be one of the most robust biomarkers in the detection of OP exposure, the analysis of HSA-OP adduct detection has been limited to techniques using mass spectrometry. Herein, we describe the procurement of two monoclonal antibodies (mAb-HSA-GD and mAb-HSA-VX) that recognized the HSA Tyr 411 adduct of soman (GD) or S-[2-(diisopropylamino)ethyl]-O-ethyl methylphosphonothioate (VX), respectively, but did not recognize nonphosphonylated HSA. We showed that mAb-HSA-GD was able to detect the HSA Tyr 411 OP adduct at a low level (i.e., human blood plasma treated with 180 nM GD) that could not be detected by mass spectrometry. mAb-HSA-GD and mAb-HSA-VX showed an extremely low-level detection of GD adducted to HSA (on the order of picograms). mAb-HSA-GD could also detect serum albumin OP adducts in blood plasma samples from different animals administered GD, including rats, guinea pigs, and monkeys. The ability of the two antibodies to selectively recognize nerve agents adducted to serum albumin suggests that these antibodies could be used to identify biomarkers of OP exposure and provide a new biologic approach to detect OP exposure in animals.
| S-EPMC3558817 | biostudies-other
Project description:Background: Increasing evidence suggests that exposure to air pollution during pregnancy is associated with adverse pregnancy outcomes. However, biomarkers associated with air pollution exposure are widely lacking and often transient. In addition, ascertaining biospecimens during pregnacy to assess the prenatal environment remains largely infeasible. Objectives: To address these challenges, we investigated relationships between air pollution exposure during pregnancy and human serum albumin Cys34 (HSA-Cys34) adducts in newborn dried blood spots (DBS) samples, which captures an integration of perinatal exposures to small reactive molecules in circulating blood. Methods: Newborn DBS were obtained from a state archive for a cohort of 120 children born at one Kaiser Permanente Southern California (KPSC) hospitals in 2007. These children were selected to maximize the range of residential air pollution exposure during the entire pregnancy to PM2.5, PM10, NO2, O3, based on monthly estimates interpolated from regulatory monitoring sites. HSA-Cys34 adducts were selected based on previously reported relationships with air pollution exposure and oxidative stress. Results: Six adducts measured in newborn DBS samples were associated with air pollution exposures during pregnancy; these included direct oxidation products, adducts formed with small thiol compounds, and adducts formed with reactive aldehydes. Two general trends were identified: Exposure to air pollution late in pregnancy (i.e., in the last 30 days) was associated with increased oxidative stress, and exposure to air pollution earlier in pregnancy (i.e., not in the last 30 days) was associated with decreased oxidative stress around the time of birth. Discussion: Air pollution exposure occurring during pregnancy can alter biology and leave measurable impacts on the developing infant captured in the newborn DBS adductome, which represents a promising tool for investigating adverse birth outcomes in population-based studies.
| S-EPMC8733257 | biostudies-literature
Project description:CBDP [2-(2-cresyl)-4H-1-3-2-benzodioxaphosphorin-2-oxide] is a toxic organophosphorus compound. It is generated in vivo from tri-ortho-cresyl phosphate (TOCP), a component of jet engine oil and hydraulic fluids. Exposure to TOCP was proven to occur on board aircraft by finding CBDP-derived phospho-butyrylcholinesterase in the blood of passengers. Adducts on BChE, however, do not explain the toxicity of CBDP. Critical target proteins of CBDP are yet to be identified. Our goal was to facilitate the search for the critical targets of CBDP by determining the range of amino acid residues capable of reacting with CBDP and characterizing the types of adducts formed. We used human albumin as a model protein. Mass spectral analysis of the tryptic digest of CBDP-treated human albumin revealed adducts on His-67, His-146, His-242, His-247, His-338, Tyr-138, Tyr-140, Lys-199, Lys-351, Lys-414, Lys-432, and Lys-525. Adducts formed on tyrosine residues were different from those formed on histidines and lysines. Tyrosines were organophosphorylated by CBDP, while histidine and lysine residues were alkylated. This is the first report of an organophosphorus compound with both phosphorylating and alkylating properties. The o-hydroxybenzyl adduct on histidine is novel. The ability of CBDP to form stable adducts on histidine, tyrosine, and lysine allows one to consider new mechanisms of toxicity from TOCP exposure.
| S-EPMC3427739 | biostudies-literature
Project description:Non-enzymatic glycation of human serum albumin (HSA) is associated with the long-term complications of diabetes. We examined the structure and location of modifications on minimally-glycated HSA and considered their possible impact on the binding of drugs to this protein.Minimally-glycated and normal HSA (used as a control) were digested with trypsin, Glu-C or Lys-C, followed by fractionation of the resulting peptides and their analysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) to determine the structures and locations of glycation adducts.Several specific lysine and arginine residues were identified as modification sites in minimally-glycated HSA. Residues K12, K51, K199, K205, K439 and K538 were found to be modified through the formation of fructosyl-lysine, while the modification of K159 and K286 involved the formation of pyrraline or N(epsilon)-carboxymethyl-lysine, respectively. Lysine K378 was found to give N(epsilon)-carboxyethyl-lysine in some forms of glycated HSA but fructosyl-lysine in other forms. Residues R160 and R472 produced a modification based on N(epsilon)-(5-hydro-4-imidazolon-2-yl)ornithine. Lysine R222 was modified to produce argpyrimidine, N(epsilon)-[5-(2,3,4-trihydroxybutyl)-5-hydro-4-imidazolon-2-yl]ornithine or tetrahydropyrimidine.With the exception of K12, K199, K378, K439 and K525, all of the observed sites of modification for minimally-glycated HSA were new to this current study. The fact that many of these glycation-related modifications are located at or near known drug binding sites on HSA explains why some differences have been previously noted in the binding of certain drugs to normal vs glycated HSA.
| S-EPMC2692699 | biostudies-literature
Project description:Organophosphorus nerve agents inhibit the cholinesterase activity by phosphylation of the active site serine. The resulting phosphylated cholinesterase and adducts on human serum albumin (HSA) are appropriate biomarkers for nerve agents exposure. Several methods have been developed for the detection of nerve agents, including fluoride reactivation or alkaline cleavage. It was previously thought that some nerve agents adducts to HSA could not be detected via fluoride regeneration. In our study, the results showed that tabun (GA) adducts of HSA could be detected by fluoride regeneration. The sample preparation included acetone precipitation, washing and SPE. Deuterated tabun (d5-GA) was applied as the internal standard. The product of regenerated fluorotabun is detected with a good linearity (R2 > 0.997) in the concentration range from 0.02 to 100.0 ng/ml, small relative standard deviation (?6.89%) and favorable recoveries between 94.8 and 106.3%. The established preparation confirmed the fluorotabun was regenerated from the GA-HSA adducts.
| S-EPMC6923783 | biostudies-literature
Project description:Aromatic amines and heterocyclic aromatic amines (HAAs) are a class of structurally related carcinogens that are formed during the combustion of tobacco or during the high temperature cooking of meats. These procarcinogens undergo metabolic activation by N-oxidation of the exocyclic amine group to produce N-hydroxylated metabolites, which are critical intermediates implicated in toxicity and DNA damage. The arylhydroxylamines and their oxidized arylnitroso derivatives can also react with cysteine (Cys) residues of glutathione or proteins to form, respectively, sulfenamide and sulfinamide adducts. However, sulfur-nitrogen linked adducted proteins are often difficult to detect because they are unstable and undergo hydrolysis during proteolytic digestion. Synthetic N-oxidized intermediates of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a carcinogenic HAA produced in cooked meats, and 4-aminobiphenyl, a carcinogenic aromatic amine present in tobacco smoke, were reacted with human serum albumin (SA) and formed labile sulfenamide or sulfinamide adducts at the Cys(34) residue. Oxidation of the carcinogen-modified SA with m-chloroperoxybenzoic acid (m-CPBA) produced the arylsulfonamide adducts, which were stable to heat and the chemical reduction conditions employed to denature SA. The sulfonamide adducts of PhIP and 4-ABP were identified, by liquid chromatography/mass spectrometry, in proteolytic digests of denatured SA. Thus, selective oxidation of arylamine-modified SA produces stable arylsulfonamide-SA adducts, which may serve as biomarkers of these tobacco and dietary carcinogens.
| S-EPMC3621984 | biostudies-literature