Quantification of urinary N-acetyl-S- (propionamide)cysteine using an on-line clean-up system coupled with liquid chromatography/tandem mass spectrometry

Review of the state of the art of acrylamide human biomonitoring

Human biomonitoring (HBM) is a very useful tool for assessing human exposure to acrylamide (AA). In the framework of the Human Biomonitoring Initiative (HBM4EU) AA was included in its second list of priority substances due to the potential threat to human health. HBM data on AA are scarce, but the use of specific and sensitive biomarkers represents a reliable indicator of exposure. In this review an overview of available knowledge on HBM of AA is provided in terms of: i) preferred exposure biomarkers and matrices for the HBM of AA; ii) analytical methods for determining its biomarkers of exposure in the most used specimens; iii) current HBM data available; and iv) tools for interpreting HBM data for AA in relation to risk assessment. Finally, future trends in this field are discussed.

Exposure assessment of Spanish lactating mothers to acrylamide via human biomonitoring

Acrylamide (AA) is an organic compound classified as "Probably carcinogenic to humans" (Group 2 A) that can be found principally in processed carbohydrate-rich foods and tobacco smoke. In humans, after exposure, AA is rapidly metabolized and excreted in urine, predominantly as N-acetyl-S-(2-carbamoylethyl)-l-cysteine (AAMA), N-acetyl-S-(2-carbamoyl-2-hydroxyethyl)-l-cysteine (GAMA3) and N-Acetyl-3-[(3-amino-3-oxopropyl)sulfinyl]-L-alanine (AAMA-Sul), which can be used as short-term biomarkers of exposure to AA. In this study, the presence of AA metabolites in urine samples of lactating mothers living in Spain (n = 114) was analyzed by "dilute and shoot" and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). All urinary metabolites were detected in 100% of the analyzed samples, with geometric means of 70, 33 and 15 ng ml^-1, for AAMA, AAMA-Sul and GAMA3, respectively. The consumption of coffee, bread and precooked food products were found to be significant predictors of internal exposure to AA. An estimated daily intake (EDI) of AA based on its urinary metabolites was calculated, obtaining mean values between 1.2 and 1.9 μg AA·kg bw^-1·day^-1 in the target population. The risk assessment was evaluated using both reverse and forward dosimetry, showing an average margin of exposure (MOE) of 349 and a hazard quotient (HQ) of 5.5. Therefore, AA exposure should be considered a medium priority for risk assessment follow-up in the Spanish population, since a health concern with respect to non-neoplastic toxicity could not be discarded.

Feasibility of using urinary N7-(2-carbamoyl-2-hydroxyethyl) Guanine as a biomarker for acrylamide exposed workers

Acrylamide (AA), a probable human carcinogen, is a widely-used industrial chemical but is also present in tobacco smoke and carbohydrate-rich foods processed at high temperatures. AA is metabolized to glycidamide (GA) to cause the formation of DNA adducts. N7-(2-carbamoyl-2-hydroxyethyl) guanine (N7-GAG), the most abundant DNA adduct induced by GA, was recently detected in urine of smokers and non-smokers. In this study, we assessed the variability of AA exposure and biomarkers of AA exposure in urine samples repeatedly collected from AA-exposed workers and explored the half-life of N7-GAG. A total of 8 AA-exposed workers and 36 non-exposed workers were recruited. Pre-shift and post-shift urine samples were collected from the exposed group in parallel with personal sampling for eight consecutive days and from the control group on day 1 of the study. Urinary N7-GAG and the mercapturic acids of AA and GA, namely N-acetyl-S-(2-carbamoylethyl)-L-cysteine (AAMA) and N-(R,S)-acetyl-S-(1-carbamoyl-2-hydroxyethyl)-L-cysteine (GAMA) were analyzed using on-line solid phase extraction-liquid chromatography-electrospray ionization/tandem mass spectrometry methods. We found that N7-GAG levels in urine were significantly higher in exposed workers than in controls and that N7-GAG level correlated positively with AAMA and GAMA levels. Results from this study showed that AAMA and GAMA possibly remain the more preferred biomarkers of AA exposure and that N7-GAG levels could be elevated by occupational exposures to AA and serve as a biomarker of AA-induced genotoxicity for epidemiological studies.

High-Throughput Screening Application for the Determination of Enantiomeric Excess Using ESI-MS

Methods for the rapid determination of the enantiomeric excess (ee%) of organic substrates, especially for HTS, are often the “bottleneck” in a process. For this purpose, a new process of entirely automated sample preparation and the determination of ee% using electrospray ionization-mass spectrometry (ESI-MS) has been developed. Various substrates and new auxiliaries were explored to enhance the methodical scope. In combination with a very versatile liquid-handling system (HTS-PAL) and a comprehensive processing equipment, a multitude of standardized reaction vessels can be managed with the presented system. As an example of use, the ee% determination of I-phenylethanole via ESI-MS is compared to state-of-the-art GC analysis. In addition, a HTS suitable data processing network was constructed that allows postrun data manipulation and the automated data transfer to analysis and visualization templates with a maximum amount of automation.

Mercapturic acids: recent advances in their determination by liquid chromatography/mass spectrometry and their use in toxicant metabolism studies and in occupational and environmental exposure studies

This review describes recent selected HPLC/MS methods for the determination of urinary mercapturates that are useful as noninvasive biomarkers in characterizing human exposure to electrophilic industrial chemicals in occupational and environmental studies. High-performance liquid chromatography/mass spectrometry is a sensitive and specific method for analysis of small molecules found in biological fluids. In this review, recent selected mercapturate quantification methods are summarized and specific cases are presented. The biological formation of mercapturates is introduced and their use as indicators of metabolic processing of reactive toxicants is discussed, as well as future trends and limitations in this area of research.

A survey of liquid chromatographic-mass spectrometric analysis of mercapturic acid biomarkers in occupational and environmental exposure monitoring

High-performance liquid chromatography/mass spectrometry (HPLC/MS) is sensitive and specific for targeted quantitative analysis and is readily utilized for small molecules from biological matrices. This brief review describes recent selected HPLC/MS methods for the determination of urinary mercapturic acids (mercapturates) which are useful as biomarkers in characterizing human exposure to electrophilic industrial chemicals in occupational and environmental studies. Electrophilic compounds owing to their reactivity are used in chemical and industrial processes. They are present in industrial emissions, are combustion products of fossil fuels, and are components in tobacco smoke. Their presence in both the industrial and general environments are of concern for human and environmental health. Urinary mercapturates which are the products of metabolic detoxification of reactive chemicals provide a non-invasive tool to investigate human exposure to electrophilic toxicants. Selected recent mercapturate quantification methods are summarized and specific cases are presented. The biological formation of mercapturates is introduced and their use as biomarkers of metabolic processing of electrophilic compounds is discussed. Also, the use of liquid chromatography/tandem mass spectrometry in simultaneous determinations of the mercapturates of multiple parent compounds in a single determination is considered, as well as future trends and limitations in this area of research.

Analysis of urinary N-acetyl-S-(propionamide)-cysteine as a biomarker for the assessment of acrylamide exposure in smokers

Acrylamide, classified by the IARC as a probable human carcinogen (Group 2A), is present in cigarette mainstream smoke and also some high-temperature-processed foods, thus smokers and consumers of certain foods are at risk of acrylamide exposure. The objectives of this study were to analyze N-acetyl-S-(propionamide)-cysteine (NASPC), an acrylamide metabolite, in the urine of smokers and nonsmokers, and to investigate the association between acrylamide exposure and urinary NASPC levels in smokers and nonsmokers in order to validate NASPC as a biomarker for the assessment of acrylamide exposure. Urine samples from 63 male military officers were collected as well as background personal information and smoking habits using questionnaires. Acrylamide exposure from tobacco smoke was represented by self-reported daily cigarette consumption and urinary cotinine levels. NASPC and cotinine were analyzed using our newly developed liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) methods. Our results reveal a statistically significant linear relationship between urinary NASPC and cotinine levels for smokers (Spearman correlation coefficient r=0.402, P=0.028), but insignificantly so for nonsmokers. These results verify our suggestion that urinary NASPC could serve as a sensitive, specific, noninvasive, and easily accessible biomarker for low-dose acrylamide exposure as also exposure to carcinogens in tobacco smoke. Routine monitoring of urinary NASPC could be used to assess human exposures to acrylamide in the living environment and the workplace.

Acrylamide levels in Finnish foodstuffs analysed with liquid chromatography tandem mass spectrometry

Sample clean-up and HPLC with tandem mass spectrometric detection (LC-MS/MS) was validated for the routine analysis of acrylamide in various foodstuffs. The method used proved to be reliable and the detection limit for routine monitoring was sensitive enough for foods and drinks (38 microg/kg for foods and 5 microg/L for drinks). The RSDs for repeatability and day-to-day variation were below 15% in all food matrices. Two hundred and one samples which included more than 30 different types of food and foods manufactured and prepared in various ways were analysed. The main types of food analysed were potato and cereal-based foods, processed foods (pizza, minced beef meat, meat balls, chicken nuggets, potato-ham casserole and fried bacon) and coffee. Acrylamide was detected at levels, ranging from nondetectable to 1480 microg/kg level in solid food, with crisp bread exhibiting the highest levels. In drinks, the highest value (29 microg/L) was found in regular coffee drinks.

Quantitation of mercapturic acids from acrylamide and glycidamide in human urine using a column switching tool with two trap columns and electrospray tandem mass spectrometry

A sensitive and specific electrospray tandem mass spectrometry method using a column switching unit with two trap columns was established to quantify the mercapturates (MAs) of acrylamide (AA) and glycidamide (GA) in human urine. A specially endcapped material was applied for trapping the hydrophilic MAs and a pre-trap column was used to remove lipophilic compounds from the directly injected urine to protect the trap column. The limits of quantitation for AA-MA and GA-MA in urine were 0.5 microg/L and 1 microg/L, respectively. Urine was spiked with deuterated internal standards and injected directly into LC-MS/MS. Urine of smokers (n=13) revealed the highest concentrations of AA-MA and GA-MA in the range of 61-706 microg/L and 5-54 microg/L, respectively. Lower levels for AA-MA (14-102 microg/L) and GA-MA (1-11 microg/L) were detected in non-smokers (n=13).

Urinary mercapturic acids and a hemoglobin adduct for the dosimetry of acrylamide exposure in smokers and nonsmokers

Acrylamide, used in the manufacture of polyacrylamide and grouting agents, is also present in the diet and tobacco smoke. It is a neurotoxin and a probable human carcinogen. Analytical methods were established to determine the mercapturic acids of acrylamide (N-acetyl-S-(2-carbamoylethyl)-L-cysteine, AAMA) and its metabolite glycidamide (N-(R/S)-acetyl-S-(2-carbamoyl-2-hydroxyethyl)-L-cysteine, GAMA) by high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS), as well as the N-terminal valine adduct of acrylamide (N-2-carbamoylethylvaline, AAVal) released by N-alkyl Edman degradation of hemoglobin by gas chromatography-mass spectrometry (GC-MS). Twenty-four-hour urine samples from 60 smokers and 60 nonsmokers were analyzed for AAMA and GAMA, and blood samples were analyzed for AAVal. Smokers excreted 2.5-fold higher amounts of AAMA and 1.7-fold higher amounts of GAMA in their urine and had 3-fold higher levels of AAVal in their blood. All three biomarkers of acrylamide exposure were strongly correlated with the smoking dose as determined by the daily cigarette consumption, nicotine equivalents (the molar sum of nicotine, cotinine, trans-3'-hydroxycotinine, and their respective glucuronides) in urine, salivary cotinine, and carbon monoxide in expired breath. In nonsmokers, a weak but significant correlation between AAMA and the estimated dietary intake of acrylamide was found. It is concluded that all three biomarkers of acrylamide are suitable for the determination of exposure in both smokers and nonsmokers.

Excretion of mercapturic acids of acrylamide and glycidamide in human urine after single oral administration of deuterium-labelled acrylamide

We investigated the human metabolism of AA to the mercapturic acids N-acetyl-S-(2-carbamoylethyl)-L-cysteine (AAMA) and N-(R/S)-acetyl-S-(2-carbamoyl-2-hydroxyethyl)-L: -cysteine (GAMA) which are derived from AA itself and from its oxidative genotoxic metabolite glycidamide (GA), respectively. A healthy male volunteer received a single dose of about 1 mg deuterium-labelled acrylamide (d(3)-AA), representing 13 microg/kg body weight, in drinking water. Urine samples before dosing and within 46 h after the dose were analysed for d(3)-AAMA and d(3)-GAMA by LC-ESI-MS/MS. A first phase of increase in urinary concentration was found to last 18 h with a broad plateau between 8 and 18 h for AAMA, and 22 h for GAMA. Elimination half-lives of both AAMA and GAMA were estimated to be approximately 3.5 h for the first phase and more than 10 h up to few days for the second phase. Total recovery in urine after 24 h was about 51% as the sum of AAMA and GAMA and hereby well in accordance with former studies in rats. After 2 days AAMA, accounting for altogether 52% of the total AA dose, was the major metabolite of AA in humans. GAMA, accounting for 5%, appeared as a minor metabolite of AA. In humans we found a urinary ratio of 0.1 for GAMA/AAMA compared to previously reported values of 0.2 for rats and 0.5 for mice. Therefore, the metabolic fate of AA in humans was more similar to that in rats than in mice as already demonstrated in terms of the haemoglobin adducts. Consequently a genotoxic potency of AA mediated by GA could be supposed to be comparable in rats and humans.