A Generic LC-MS/MS Exposome Method for the Determination Of
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A generic LC-MS/MS exposome method for the determination of xenoestrogens in biological matrices Karin Preindl1, Dominik Braun1, Georg Aichinger1, Sabina Sieri2, Mingliang Fang3, Doris Marko1, Benedikt Warth1* 1University of Vienna, Faculty of Chemistry, Department of Food Chemistry and Toxicology, Währingerstraße 38, 1090 Vienna, Austria 2Epidemiology and Prevention Unit, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy 3Nanyang Technological University, School of Civil and Environmental Engineering, 50 Nanyang Avenue, Singapore 639798, Singapore ABSTRACT: We are constantly exposed to a variety of environmental contaminants and hormones including those mimicking endogenous estrogens. These highly heterogeneous molecules are collectively re- ferred to as xenoestrogens and hold the potential to affect and alter the delicate hormonal balance of the human body. To monitor exposure and investigate potential health implications, comprehensive analytical methods covering all major xenoestrogen classes are urgently needed but still not available. Herein, we describe an LC-MS/MS method for the simultaneous determination of multiple classes of endogenous as well as exogenous estrogens in human urine, serum and breast milk to enable proper exposure and risk assessment. In total, 75 analytes were included, whereof a majority was successfully in-house validated in the three matrices. Extraction recoveries of validated analytes ranged from 71% to 110% and limits of quantification from 0.015 to 5 µg/L, 0.03 to 14 µg/L, and 0.03 to 4.6 µg/L in urine, serum and breast milk, respec- tively. The applicability of the novel method was demonstrated in proof-of-principle experiments by analyzing urine from Austrian, and breast milk from Austrian and Nigerian individuals. Thereby, we proved the methods’ feasibility to identify and quantify different classes of xenoestrogens simultaneously. The results illustrate the general importance of multi-class exposure assessment in the context of the expo- some paradigm. Specifically, they highlight the need for estimating total estrogenic burden rather than single analyte or chemical class meas- urements and its potential impact in endocrine disruption and hormone related diseases including cancers. The human endocrine system is an important signaling system caused by differing time windows of exposure or the applied, rather which regulates organ communication and behavior. In recent targeted, single class human biomonitoring (HBM) approaches years, attention has been drawn to the so-called endocrine disrupt- which did not consider mixture effects. Exposure to xenoestrogens ing chemicals (EDCs), compounds not produced by the body itself may also be a risk factor for hormone-related cancers including that can disturb the hormonal balance in various ways.1 One class those of breast and the reproductive tract, especially during the of EDCs are xenoestrogens, small molecules imitating or interfer- sensitive, early developmental stages.11-13 ing with endogenous estrogens, the most important female sex 2 The proper assessment of combinatory effects of multiple xenoes- hormones. Xenoestrogens are a highly diverse group of chemicals trogens are a current key challenge. Numerous studies investigating and can be produced either naturally, e.g. by plant (phytoestrogens) the potency of individual compounds or compound classes have and fungi (mycoestrogens), or synthetically as pesticides, plasticiz- 3 been published, while data on estrogenic mixtures is scarce. There ers, personal care product additives and other industrial chemicals. is a growing body of evidence that xenoestrogen combinations, In the past, research efforts typically focused on single representa- even at very low concentrations, can have potentiating14-17 and/or tives such as bisphenol A (BPA) and substance classes including antagonizing effects.18 Because of the variety of different structural parabens or phthalates. As a result, these chemicals may be banned classes, routes of exposure are divers; they may be inhaled through and replaced by less investigated analogues for which similar or 4 the ambient air, ingested via contaminated food or absorbed by the even more potent toxicological effects cannot be ruled out. skin. Due to these multiple exposure scenarios HBM is the best A suspected adverse health effect of xenoestrogens is reduced option for proper exposure assessment and should lead towards a fertility. It has been shown that high urinary concentrations of more comprehensive, exposome-scale assessment of environmental BPA, parabens and phthalate metabolites reduce positive outcomes risk factors in the etiology of chronic disease.19-20 of in vitro fertilization.5 A high uptake of phytoestrogens has been 6-8 To correlate exposure with potential health implications, ad- associated with negative effects on male fertility in some studies, vanced analytical assays for a simultaneous measurement of the while not in others.9-10 These controversial outcomes might be 1 different classes of xenoestrogens are essential, yet not readily achieve chromatographic separation. The column compartment and available. To date, the majority of multi-analyte methods focus on the autosampler were maintained at 40 °C and at 10 °C, respective- 21-23 single classes and the few existing multi-class methods typical- ly. LC-MS grade water with 0.3 mM ammonium fluoride (NH4F) ly contain no more than two different classes of xenoestrogens.24-28 as additive (eluent A) and acetonitrile (eluent B) were used as mo- The development of a method covering multiple classes of xenoes- bile phases. Aqueous ammonium fluoride solutions have to be trogens is a challenging task due to the diverse chemical properties handled with care as HF may outgas. Although, the NH4F concen- and low biological concentrations of such exposures. Single ana- tration in the eluent was very low, contact with acids (e.g. from lyte/class methods are not practical in large-scale epidemiological previously used eluent additives in the waste) was prevented. The studies involving the measurement of thousands of samples as system was operated at a flow rate of 0.4 mL/min with following proposed for future exposome-wide association studies (EWAS). gradient: 0-1 min: 5% B; rise to 18% B until min 1.8 and to 35% B Currently, a targeted multi-class method constitutes the most feasi- until min 4.2; rise to 48% B until min 13 and to 90% B until ble approach for the implementation of this challenging task. Ad- min 14; flush with 98% B from min 15.8 to min 17.6; re-equilibrate vantages of the targeted approach compared to non-targeted LC- with 5% B from min 17.7 to min 20. Multiple reaction monitoring HRMS screening, are the increased sensitivity and the improved (MRM) experiments were performed in positive and negative elec- ability to perform quantitative measurements. This work addresses trospray ionization (ESI) mode using fast polarity switching. The the need for a broad, quantitative LC-MS/MS method covering a detailed settings are described in the Supporting Information. multitude of estrogenic compounds in three relevant biological Quantification and data evaluation. To account for matrix ef- fluids. Following in-house validation, the method was applied to fects and potential retention time deviations in the different matri- biological samples for assessing early-life xenoestrogen exposures ces, matrix-matched reference standards were prepared by re- in first proof-of-principle experiments. solving evaporated ‘blank’ samples of urine, serum and breast milk EXPERIMENTAL SECTION with 200 µL (urine and serum) or 250 µL (breast milk) with solvent standards of six different concentrations. For quantification, the Chemicals and reagents. In this study, 75 analytes, 61 xenoes- fragment ion with the highest signal to noise ratio was chosen. A trogens and 14 endogenous estrogens, were included. Detailed second fragment ion was obtained for confirmation and ion ratio information regarding analytes and suppliers are provided in Table determination (Table S2). Methyl-, ethyl-, propyl-, butylparaben, S1 and Figures S2-S6. genistein, mono-n-butyl phthalate (MBP), perfluoroctanoic acid Sample collection. For validation experiments of human serum, (PFOA) and perfluoroctanesulfonic acid (PFOS) were evaluated by pooled male AB plasma derived serum was used (USA origin; internal standards in all matrices. Zearalenone (ZEN) and estradiol Sigma Aldrich, Vienna, Austria). For urine, a pooled sample was (E2) were evaluated by internal standard calibration in urine and obtained from a female volunteer who avoided foodstuff and bev- serum. 4-tert-octylphenol (4tOP) was evaluated by internal stand- erages stored in plastic containers, foods rich in phytoestrogens, ard calibration in serum and mono-2-ethylhexyl phthalate (MEHP) and cosmetics containing parabens for two days prior to sample was evaluated by internal standard calibration in urine. Data evalu- collection. For breast milk validation experiments, anonymized ation was carried out with TraceFinder™ software (version 4.1, pooled breast milk was provided by the Semmelweis Women’s Thermo Scientific). Linear calibration curves were created using 29 Clinic in Vienna, Austria, as previously reported. Urine and breast 1/x weighing. In case of ‘blank’ matrix contamination (not all milk were stored at -20 °C, serum at -80 °C until analysis. pooled samples for validation purpose were true blanks as the high To evaluate the applicability of the developed method, four urine