Simultaneous determination of four sulfur mustard–DNA adducts in rabbit urine after dermal exposure by isotope-dilution liquid chromatography–tandem mass spectrometry

Analytical methods based on liquid chromatography for the analysis of albumin adducts involved in retrospective biomonitoring of exposure to mustard agents

The objective of the present review is to list, describe, compare, and critically analyze the main procedures developed in the last 20 years for the analysis of digested alkylated peptides, resulting from the adduction of albumin by different mustard agents, and that can be used as biomarkers of exposure to these chemical agents. While many biomarkers of sulfur mustard, its analogues, and nitrogen mustards can easily be collected in urine such as their hydrolysis products, albumin adducts require blood or plasma collection to be analyzed. Nonetheless, albumin adducts offer a wider period of detectability in human exposed patients than urine found biomarkers with detection up to 25 days after exposure to the chemical agent. The detection of these digested alkylated peptides of adducted albumin constitutes unambiguous proof of exposure. However, their determination, especially when they are present at very low concentration levels, can be very difficult due to the complexity of the biological matrices. Therefore, numerous sample preparation procedures to extract albumin and to recover alkylated peptides after a digestion step using enzymes have been proposed prior to the analysis of the targeted peptides by liquid chromatography coupled to mass spectrometry method with or without derivatization step. This review describes and compares the numerous procedures including a number of different steps for the extraction and purification of adducted albumin and its digested peptides described in the literature to achieve detection limits for biological samples exposed to sulfur mustard, its analogues, and nitrogen mustards in the ng/mL range.

Skin Models Used to Define Mechanisms of Action of Sulfur Mustard

Sulfur mustard (SM) is a threat to both civilian and military populations. Human skin is highly sensitive to SM, causing delayed erythema, edema, and inflammatory cell infiltration, followed by the appearance of large fluid-filled blisters. Skin wound repair is prolonged following blistering, which can result in impaired barrier function. Key to understanding the action of SM in the skin is the development of animal models that have a pathophysiology comparable to humans such that quantitative assessments of therapeutic drugs efficacy can be assessed. Two animal models, hairless guinea pigs and swine, are preferred to evaluate dermal products because their skin is morphologically similar to human skin. In these animal models, SM induces degradation of epidermal and dermal tissues but does not induce overt blistering, only microblistering. Mechanisms of wound healing are distinct in these animal models. Whereas a guinea pig heals by contraction, swine skin, like humans, heals by re-epithelialization. Mice, rats, and rabbits are also used for SM mechanistic studies. However, healing is also mediated by contraction; moreover, only microblistering is observed. Improvements in animal models are essential for the development of therapeutics to mitigate toxicity resulting from dermal exposure to SM.

Urinary Profile of Alkylated DNA Adducts and DNA Oxidative Damage in Sulfur Mustard-Exposed Rats Revealed by Mass Spectrometry Quantification

Alkylation reagents, represented by sulfur mustard (SM), can damage DNA molecules directly as well as lead to oxidative stress, causing DNA lesions indirectly. Correspondingly, two types of biomarkers including alkylated DNA adducts and oxidative DNA adducts are commonly involved in the research of DNA damage evaluation caused by these agents. However, the correlations and differences of the occurrence, duration, severity, and traceability between alkylation and oxidation lesions on the DNA molecular level reflected by these two types of biomarkers have not been systematically studied. A simultaneous determination method for four alkylated DNA adducts, i.e., N7-(2-hydroxyethylthioethyl)2'-guanine (N7-HETEG), O6-(2-hydroxyethylthioethyl)-2'-guanine (O6-HETEG), N3-(2-hydroxyethylthioethyl)-2'-adenine (N3-HETEA), and bis(2-ethyl-N7-guanine)thioether (Bis-G), and the oxidative adduct 8-hydroxy-2'-deoxyguanosine (8-OH-dG) in urine samples by isotope-dilution high-performance liquid chromatography-tandem mass spectrometry (ID-HPLC-MS/MS) was built with a lower limit of detection of 0.02 ng/mL (except Bis-G, 0.05 ng/mL) and a recovery of 79-111%. The profile of these adducts was simultaneously monitored in urine samples after SD rats' dermal exposure to SM in three dose levels (1, 3, and 10 mg/kg). The time-effect and dose-effect experiments revealed that when exposed to SM, DNA alkylation lesions would happen earlier than those of oxidation. For the two types of biomarkers, alkylated DNA adducts showed an obvious dose-effect relationship and could be used as internal exposure dose and effect biomarkers, while 8-OH-dG did not show a correlation with exposure dose, demonstrating that it was more suitable as a biomarker for DNA oxidative lesions but not an indicator for the extent of cytotoxicity and internal exposure.

DNA photoproducts released by repair in biological fluids as biomarkers of the genotoxicity of UV radiation

UV-induced formation of photoproducts in DNA is a major initiating event of skin cancer. Consequently, many analytical tools have been developed for their quantification in DNA. In the present work, we extended our previous liquid chromatography-mass spectrometry method to the quantification of the short DNA fragments containing photoproducts that are released from cells by the repair machinery. We designed a robust protocol including a solid-phase extraction step (SPE), an enzymatic treatment aimed at releasing individual photoproducts, and a liquid chromatography method combining on-line SPE and ultra-high-performance liquid chromatography for optimal specificity and sensitivity. We also added relevant internal standards for a better accuracy. The method was validated for linearity, repeatability, and reproducibility. The limits of detection and quantification were found to be in the fmol range. The proof of concept of the use of excreted DNA repair products as biomarkers of the genotoxicity of UV was obtained first in in vitro studies using cultured HaCat cells and ex vivo on human skin explants. Further evidence was obtained from the detection of pyrimidine dimers in the urine of human volunteers collected after recreational exposure in summer. An assay was designed to quantify the DNA photoproducts released from cells within short fragments by the DNA repair machinery. These oligonucleotides were isolated by solid-phase extraction and enzymatically hydrolyzed. The photoproducts were then quantified by on-line SPE combined with UHPLC-MS/MS with isotopic dilution.

Simultaneous quantification of multiple amino acid adducts from sulfur mustard-modified human serum albumin in plasma at trace exposure levels by ultra-high performance liquid chromatography-triple quadrupole mass spectrometry after propionyl derivatization

Sulfur mustard (HD) is a highly toxic vesicant and is prohibited by the Organisation for the Prohibition of Chemical Weapons (OPCW). HD can modify human serum albumin (HSA) to generate hydroxyethylthioethyl (HETE) adducts, which could be utilized as biomarkers for verifying HD exposure in forensic analysis. Here, five amino acid adducts generated from pronase digestion of HD-exposed human serum albumin (HD-HSA) in plasma were selected as biomarkers to retrospectively detect HD exposure. HD-HSA was precipitated from plasma with acetone, digested by pronase, derivatized with propionic anhydride (PA), and analysed with ultra-high performance liquid chromatography coupled with triple quadrupole mass spectrometry (UHPLC-TQ MS). The limits of detection (LODs) and limits of quantification (LOQs) of the HD exposure concentrations were evaluated as 1.00 ng/mL at S/N≥3 and 3.00 ng/mL at S/N≥10, respectively, which are approximately 60 times lower than those of the reported method. The approach shows good linearity (R²≥0.997) from 3.00 ng/mL to 10.0 µg/mL of HD-exposed human plasma with satisfactory precision and accuracy. The developed approach was applied to analysing samples from the 6^th OPCW Biomedical Proficiency Test (BioPT). The study showed that the developed approach was also suitable for analysing human plasma samples that were exposed to six of HD analogues, which were common impurities in sulfur mustard mixtures. Moreover, the method was successfully applied to plasma from other species, including rabbits, rats and cattle. This study provides a reliable and sensitive tool for the retrospective detection of vesicants exposure based on multiple biomarkers.

A proteomics strategy for the identification of multiple sites in sulfur mustard-modified HSA and screening potential biomarkers for retrospective analysis of exposed human plasma

A major challenge for the unequivocal verification of alleged exposure to sulfur mustard (HD) lies in identifying its multiple modifications on endogenous proteins and utilizing these modified proteins to achieve accurate, sensitive, and rapid detection for retrospective analysis of HD exposure. As the most abundant protein in human plasma, human serum albumin (HSA) can react with many xenobiotics, such as HD, to protect the body from damage. The HSA adducts induced by HD have been used as biomarkers for the verification of HD exposure. In this study, the modification sites on HSA by HD were identified through application of the bottom-up strategy used in proteomics, and 41 modified sites were discovered with seven types of amino acids, of which 3 types were not previously reported. Then, different enzymes, including pepsin, endoproteinase Glu-C, and pronase, were applied to digest HD-HSA to produce adducts with hydroxyethylthioethyl (HETE) groups, which may be used as potential biomarkers for HD exposure. As candidates for retrospective analysis, sixteen adducts were obtained and characterized with ultra-high-pressure liquid chromatography coupled with quadrupole-Orbitrap mass spectrometry (UHPLC-QE Focus MS). These potential biomarkers were evaluated in human plasma that was exposed in vitro to HD and five of its analogues. This study integrated the identification of modification sites through application of the bottom-up strategy of proteomics and screening biomarkers, providing a novel strategy for retrospective detection of the exposure of xenobiotic chemicals.

Evidence for the systemic diffusion of (2-chloroethyl)-ethyl-sulfide, a sulfur mustard analog, and its deleterious effects in brain

Sulfur mustard, a chemical warfare agent known to be a vesicant of skin, readily diffuses in the blood stream and reaches internal organs. In the present study, we used the analog (2-chloroethyl)-ethyl-sulfide (CEES) to provide novel data on the systemic diffusion of vesicants and on their ability to induce brain damage, which result in neurological disorders. SKH-1 hairless mice were topically exposed to CEES and sacrificed at different time until 14 days after exposure. A plasma metabolomics study showed a strong systemic impact following a self-protection mechanism to alleviate the injury of CEES exposure. This result was confirmed by the quantification of specific biomarkers in plasma. Those were the conjugates of CEES with glutathione (GSH-CEES), cysteine (Cys-CEES) and N-acetyl-cysteine (NAC-CEES), as well as the guanine adduct (N7Gua-CEES). In brain, N7Gua-CEES could be detected both in DNA and in organ extracts. Similarly, GSH-CEES, Cys-CEES and NAC-CEES were present in the extracts until day14. Altogether, these results, based on novel exposure markers, confirm the ability of vesicants to induce internal damage following dermal exposure. The observation of alkylation damage to glutathione and DNA in brain provides an additional mechanism to the neurological insult of SM.

Advances in sulfur mustard-induced DNA adducts: Characterization and detection

Sulfur mustard (SM) is a blister chemical warfare agent with severe cytotoxicity and genotoxicity. It can extensively alkylate important macromolecules in organisms, such as proteins, DNA, and lipids, and produce a series of metabolites, among which the characteristic ones can be used as biomarkers. The exact toxicological mechanisms of SM remain unclear but mainly involve the DNA lesions induced by alkylation and oxidative stress caused by glutathione depletion. Various methods have been used to analyze DNA damage caused by SM. Among these methods, liquid chromatography-tandem mass spectrometry (LC-MS/MS) technology stands out and makes it possible to observe damage in view of biomarkers induced by SM. Sample preparation is critical for detection by LC-MS/MS and mainly includes DNA isolation, adduct hydrolysis, and adduct purification. Moreover, optimization of chromatographic conditions, selection of MS transitions, and quantitative strategies are also essential. SM-DNA adducts are generally considered to be N⁷-HETEG, O⁶-HETEG, N⁷-BisG, and N³-HETEA. This article proposes some other possibilities of SM-DNA adducts for the identification of SM genotoxicity.

Alkylated epidermal creatine kinase as a biomarker for sulfur mustard exposure: comparison to adducts of albumin and DNA in an in vivo rat study

Sulfur mustard (SM) is a chemical warfare agent which use is banned under international law and that has been used recently in Northern Iraq and Syria by the so-called Islamic State. SM induces the alkylation of endogenous proteins like albumin and hemoglobin thus forming covalent adducts that are targeted by bioanalytical methods for the verification of systemic poisoning. We herein report a novel biomarker, namely creatine kinase (CK) B-type, suitable as a local biomarker for SM exposure on the skin. Human and rat skin were proven to contain CK B-type by Western blot analysis. Following exposure to SM ex vivo, the CK-adduct was extracted from homogenates by immunomagnetic separation and proteolyzed afterwards. The cysteine residue Cys²⁸² was found to be alkylated by the SM-specific hydroxyethylthioethyl (HETE)-moiety detected as the biomarker tetrapeptide TC(-HETE)PS. A selective and sensitive micro liquid chromatography-electrospray ionization high-resolution tandem-mass spectrometry (µLC-ESI MS/HRMS) method was developed to monitor local CK-adducts in an in vivo study with rats percutaneously exposed to SM. CK-adduct formation was compared to already established DNA- and systemic albumin biomarkers. CK- and DNA-adducts were successfully detected in biopsies of exposed rat skin as well as albumin-adducts in plasma. Relative biomarker concentrations make the CK-adduct highly appropriate as a local dermal biomarker. In summary, CK or rather Cys²⁸² in CK B-type was identified as a new, additional dermal target of local SM exposures. To our knowledge, it is also the first time that HETE-albumin adducts, and HETE-DNA adducts were monitored simultaneously in an in vivo animal study.

Glutathione conjugates of the mercapturic acid pathway and guanine adduct as biomarkers of exposure to CEES, a sulfur mustard analog

Sulfur mustard (SM), a chemical warfare agent, is a strong alkylating compound that readily reacts with numerous biomolecules. The goal of the present work was to define and validate new biomarkers of exposure to SM that could be easily accessible in urine or plasma. Because investigations using SM are prohibited by the Organisation for the Prohibition of Chemical Weapons, we worked with 2-chloroethyl ethyl sulfide (CEES), a monofunctional analog of SM. We developed an ultra-high-pressure liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) approach to the conjugate of CEES to glutathione and two of its metabolites: the cysteine and the N-acetylcysteine conjugates. The N7-guanine adduct of CEES (N7Gua-CEES) was also targeted. After synthesizing the specific biomarkers, a solid-phase extraction protocol and a UHPLC-MS/MS method with isotopic dilution were optimized. We were able to quantify N7Gua-CEES in the DNA of HaCaT keratinocytes and of explants of human skin exposed to CEES. N7Gua-CEES was also detected in the culture medium of these two models, together with the glutathione and the cysteine conjugates. In contrast, the N-acetylcysteine conjugate was not detected. The method was then applied to plasma from mice cutaneously exposed to CEES. All four markers could be detected. Our present results thus validate both the analytical technique and the biological relevance of new, easily quantifiable biomarkers of exposure to CEES. Because CEES behaves very similar to SM, the results are promising for application to this toxic of interest.

A quantitative method to detect human exposure to sulfur and nitrogen mustards via protein adducts

Sulfur and nitrogen mustards are internationally banned vesicants listed as Schedule 1 chemical agents in the Chemical Weapons Convention. These compounds are highly reactive electrophiles that form stable adducts to a variety of available amino acid residues on proteins upon exposure. We present a quantitative exposure assay that simultaneously measures agent specific protein adducts to cysteine for sulfur mustard (HD) and three nitrogen mustards (HN1, HN2, and HN3). Proteinase K was added to a serum or plasma sample to digest protein adducts and form the target analyte, the blister agent bound to the tripeptide cysteine-proline-phenylalanine (CPF). The mustard adducted-tripeptide was purified by solid phase extraction and analyzed using isotope dilution LC-MS/MS. Product ion structures were identified using high-resolution product ion scan data for HD-CPF, HN1-CPF, HN2-CPF, and HN3-CPF. Thorough matrix comparison, analyte recovery, ruggedness, and stability studies were incorporated during method validation to produce a robust method. The method demonstrated long term-stability, precision (RSD < 15%), and intra- and inter-day accuracies > 85% across the reportable range of 3.00-200 ng/mL for each analyte. Compared to previously published assays, this method quantitates both sulfur and nitrogen mustard exposure biomarkers, requires only 10 μL of sample volume, and can use either a liquid sample or dried sample spot.

Therapeutic options to treat mustard gas poisoning - Review

Among the blistering (vesicant) chemical warfare agents (CWA), sulfur mustard is the most important since it is known as the "King of chemical warfare agents". The use of sulfur mustard has caused serious damages in several organs, especially the eyes, skin, respiratory, central and peripheral nervous systems after short and long term exposure, incapacitating and even killing people and troops. In this review, chemical properties, mechanism of actions and their effects on each organ, clinical manifestations, diagnostic evaluation of the actions triage, and treatment of injuries have been described.

A mass spectrometric platform for the quantitation of sulfur mustard-induced nucleic acid adducts as mechanistically relevant biomarkers of exposure

Despite its worldwide ban, the warfare agent sulfur mustard (SM) still represents a realistic threat, due to potential release in terroristic attacks and asymmetric conflicts. Therefore, the rigorous and quantitative detection of SM exposure is crucial for diagnosis, health risk assessment, and surveillance of international law. Alkylation adducts of nucleic acids can serve as valuable toxicologically relevant 'biomarkers of SM exposure'. Here, we developed a robust and versatile bioanalytical platform based on isotope dilution UPLC-MS/MS to quantify major SM-induced DNA and RNA adducts, as well as adducts induced by the monofunctional mustard 2-chloroethyl ethyl sulfide. We synthesized ¹⁵N/¹³C-labeled standards, which allowed absolute quantitation with full chemical specificity and subfemtomole sensitivities. DNA and RNA mono-alkylation adducts and crosslinks were carefully analyzed in a dose- and time-dependent manner in various matrices, including human cancer and primary cells, derived of the main SM-target tissues. Nucleic acid adducts were detected up to 6 days post-exposure, indicating long persistence, which highlights their toxicological relevance and proves their suitability as forensic and medical biomarkers. Finally, we investigated ex vivo-treated rat skin biopsies and human blood samples, which set the basis for the implementation into the method portfolio of Organization for the Prohibition of Chemical Weapons-designated laboratories to analyze authentic samples from SM-exposed victims.

Biological effects of adipocytes in sulfur mustard induced toxicity

Sulphur mustard (2,2'-dichloroethyl sulfide; SM) is a vesicant chemical warfare agent whose mechanism of acute or chronic action is not known with any certainty and to date there is no effective antidote. SM accumulation in adipose tissue (AT) has been originally verified in our previous study. To evaluate the biological effect caused by the presence of abundant SM in adipocyte and assess the biological role of AT in SM poisoning, in vitro and in vivo experiments were performed. High content analysis revealed multi-cytotoxicity in SM exposed cells in a time and dose dependent manner, and adipocytes showed a relative moderate damage compared with non-adipocytes. Cell co-culture model was established and revealed the adverse effect of SM-exposed adipocyte supernatant on the growth of co-cultured cells. The pathological changes in AT from 10mg/kg SM percutaneously exposed rats were checked and inflammation phenomena were observed. The mRNA and protein levels of inflammation-related adipokines secreted from AT in rats exposed to 1, 3 and 10mg/kg doses of SM were determined by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assays. The expressions of proinflammatory and anti-inflammatory adipokines together promoted the inflammation development in the body. The positive correlations between AT and serum adipokine levels were explored, which demonstrated a substantial role of AT in systemic inflammation responding to SM exposure. Thus, AT is not only a target of SM but also a modulator in the SM toxicity.

Accumulation of intact sulfur mustard in adipose tissue and toxicokinetics by chemical conversion and isotope-dilution liquid chromatography-tandem mass spectrometry

Sulfur mustard (SM) is a powerful vesicant and one of the most harmful chemical warfare agents. Although having been studied for a long time, it is still difficult to fully elucidate the mechanisms of SM poisoning, and there is no effective antidote or specific treatment for SM injury. The investigations on toxicokinetics and tissue distribution of SM will help to understand its toxicity and provide a theoretical basis for pretreatment and therapy of SM poisoning. But the metabolic trajectory or fate of intact SM in vivo remains unclear, and there are insufficient experimental data to elucidate, due to its high reactivity and difficulty in biomedical sample analysis. In this paper, a sensitive method for the detection and quantification of intact SM in blood or tissues using isotope-dilution LC-MS/MS coupled with chemical conversion was developed. By transforming highly reactive SM into stable derivative product, the real concentration of intact SM in biological samples was obtained accurately. The toxicokinetics and tissue distribution studies of intact SM in rats were successfully profiled by the novel method after intravenous (10 mg/kg) or cutaneous administration (1, 3 and 10 mg/kg). The SM level in blood with peak time at 30-60 min determined in cutaneous exposure experiment was found much higher than previously reported, and the mean residence time in blood extended to 1-1.5 h. A significant accumulation of intact SM was observed in adipose tissues, including the perirenal fat, epididymal fat, subcutaneous fat and brown fat, in which the concentrations of SM were at least 15 times greater than those in non-adipose tissues in cutaneous exposed rats. The recovery of SM in body fat was calculated as 3.3 % of bioavailable SM (the bioavailability after cutaneous exposure was evaluated as 16 %). Thus, the adipose tissue was important for SM distribution and toxicity, which may pioneer a new model for both the prevention and treatment of SM exposure.

Characterization of nitrogen mustard formamidopyrimidine adduct formation of bis(2-chloroethyl)ethylamine with calf thymus DNA and a human mammary cancer cell line

A robust, quantitative ultraperformance liquid chromatography ion trap multistage scanning mass spectrometric (UPLC/MS(3)) method was established to characterize and measure five guanine adducts formed by reaction of the chemotherapeutic nitrogen mustard (NM) bis(2-chloroethyl)ethylamine with calf thymus (CT) DNA. In addition to the known N7-guanine (NM-G) adduct and its cross-link (G-NM-G), the ring-opened formamidopyrimidine (FapyG) monoadduct (NM-FapyG) and cross-links in which one (FapyG-NM-G) or both (FapyG-NM-FapyG) guanines underwent ring-opening to FapyG units were identified. Authentic standards of all adducts were synthesized and characterized by NMR and mass spectrometry. These adducts were quantified in CT DNA treated with NM (1 μM) as their deglycosylated bases. A two-stage neutral thermal hydrolysis was developed to mitigate the artifactual formation of ring-opened FapyG adducts involving hydrolysis of the cationic adduct at 37 °C, followed by hydrolysis of the FapyG adducts at 95 °C. The limit of quantification values ranged between 0.3 and 1.6 adducts per 10(7) DNA bases when the equivalent of 5 μg of DNA hydrolysate was assayed on column. The principal adduct formed was the G-NM-G cross-link, followed by the NM-G monoadduct; the FapyG-NM-G cross-link adduct; and the FapyG-NM-FapyG was below the limit of detection. The NM-FapyG adducts were formed in CT DNA at a level ∼20% that of the NM-G adduct. NM-FapyG has not been previously quanitified, and the FapyG-NM-G and FapyG-NM-FapyG adducts have not been previously characterized. Our validated analytical method was then applied to measure DNA adduct formation in the MDA-MB-231 mammary tumor cell line exposed to NM (100 μM) for 24 h. The major adduct formed was NM-G (970 adducts per 10(7) bases), followed by G-NM-G (240 adducts per 10(7) bases), NM-FapyG (180 adducts per 10(7) bases), and, last, the FapyG-NM-G cross-link adduct (6.0 adducts per 10(7) bases). These lesions are expected to contribute to NM-mediated toxicity and genotoxicity in vivo.

An improved method for retrospective quantification of sulfur mustard exposure by detection of its albumin adduct using ultra-high pressure liquid chromatography-tandem mass spectrometry

Sulfur mustard (HD) adduct to human serum albumin (ALB) at Cys-34 residue has become an important and long-term retrospective biomarker of HD exposure. Here, a novel, sensitive, and convenient approach for retrospective quantification of HD concentration exposed to plasma was established by detection of the HD-ALB adduct using ultra-high pressure liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) with a novel non-isotope internal standard (IS). The HD-ALB adduct was isolated from HD-exposed plasma with blue Sepharose. The adduct was digested with proteinase K to form sulfur-hydroxyethylthioethyl ([S-HETE])-Cys-Pro-Phe tripeptide biomarker. The tripeptide adduct could be directly analyzed by UHPLC-MS/MS without an additional solid phase extraction (SPE), which was considered as a critical procedure in previous methods. The easily available 2-chloroethyl ethylsulfide (2-CEES) as HD surrogate was first reported to be used as IS in place of traditional d8-HD for quantification of HD exposure. Furthermore, 2-CEES was also confirmed to be a good IS alternative for quantification of HD exposure by investigation of product ion spectra for their corresponding tripeptide adducts which exhibited identical MS/MS fragmentation behaviors. The method was found to be linear between 1.00 and 250 ng•mL(-1) HD exposure (R(2)>0.9989) with precision of <4.50% relative standard deviation (%RSD), accuracy range between 96.5% and 114%, and a calculated limit of detection (LOD) of 0.532 ng•mL(-1). The lowest reportable limit (LRL) is 1.00 ng•mL(-1), over seven times lower than that of the previous method. The entire method required only 0.1 mL of plasma sample and took under 7 h without special sample preparation equipment. It is proven to be a sensitive, simple, and rugged method, which is easily applied in international laboratories to improve the capabilities for the analysis of biomedical samples related to verification of the Chemical Weapon Convention (CWC).

Analysis of different fates of DNA adducts in adipocytes post-sulfur mustard exposure in vitro and in vivo using a simultaneous UPLC-MS/MS quantification method

Sulfur mustard (SM) is a powerful alkylating vesicant that can rapidly penetrate skin, ocular, and lung bronchus mucous membranes and react with numerous nucleophiles in vivo. Although the lesion mechanisms of SM remain unclear, DNA damage is believed to be the most crucial factor in initiating SM-induced toxicity. Four major DNA adducts were identified for retrospective detection and DNA lesion evaluation, namely, N(7)-[2-[(2-hydroxyethyl)thio]-ethyl]guanine (N(7)-HETEG), bis(2-ethyl-N(7)-guanine)thioether (Bis-G), N(3)-(2-hydroxyethylthioethyl)-2'-adenine (N(3)-HETEA), and O(6)-[2-[(2-hydroxyethyl)thio]-ethyl]guanine (O(6)-HETEG). Because of previous observations that the levels of SM-DNA adducts were relatively higher in adipose-rich organs, such as the brain, we focused on the in vitro and in vivo fates of the DNA adducts in exposed adipocytes. A UPLC-MS/MS method developed in our laboratory was used to profile the N(7)-HETEG, Bis-G, and N(3)-HETEA levels in human mature adipocytes (HA-s) that had differentiated from human subcutaneous preadipocytes (HPA-s). This method was also used to profile three other cell lines related to the targeting of major tissues, including human keratinocytes (HaCaT), human hepatocytes (L-02), and human lung fibroblasts (HLF). Long-lasting adduct persistence and a high proportion of Bis-G were found in exposed adipocytes in vitro. The survival properties of exposed adipocytes were also tested. At the same time, the fate of SM-DNA adducts in vivo was characterized using a rat model exposed to 1 and 10 mg/kg doses of SM. The level of DNA adducts in the exposed adipose tissue (AT) was much lower than those in other organs studied in our previous work. The adduct persistence behavior was observed in AT with an extremely high proportion of Bis-G, which was higher than N(7)-HETEG. In light of these results, we suggest that an adipose-rich environment may promote the formation of Bis-G and that adipocyte-specific DNA repair mechanisms may result in adduct persistence and the survival of adipocytes after SM exposure. These conclusions should be further investigated.

Distribution of DNA adducts and corresponding tissue damage of Sprague-Dawley rats with percutaneous exposure to sulfur mustard

Sulfur mustard (SM) is a highly reactive alkylation vesicant and cytotoxic agent that has been recognized as an animal and human carcinogen. Although the exact mechanism of toxicology is vague, DNA alkylation seems to be responsible for the triggering of apoptosis. In this study, after male adult Sprague-Dawley rats were cutaneous exposed to a low concentration of SM at parts-per-million levels, their lungs, livers, pancreases, spleens, marrow, and brains were collected at 11 different time points and analyzed. N7-[2-[(2-hydroxyethyl)thio]-ethyl]guanine (N7-HETEG), N3-[2-[(2-hydroxyethyl)thio]-ethyl]adenine (N3-HETEA), and bis[2-(guanin-7-yl)ethyl]sulfide (Bis-G) as the biomarkers for DNA damage were measured in the vital tissues by isotope dilution ultraperformance liquid chromatography tandem mass spectrometry (ID-UPLC-MS/MS). At the same time, general variations and pathological changes were monitored and detected to evaluate the tissue damage. Time- and dose-dependent data showed that SM had strong permeability and reactivity and that three SM-DNA adducts were detected in all investigated tissues only after 10 min after exposure. Obvious dose-dependency was observed except in the brain and pancreas. Most times to peak (tmax) of all three adducts were less than 3 h, while half-lifetimes (t1/2) were less than 24 h. We also suggested that the lipophilic SM can easily pass through the blood-brain barrier and can be stored in the fatty organs. To the best of our knowledge, the abundant adducts in marrow were found and reported for the first time. The surveillance of N7-HETEG in vivo, which was the most abundant adduct, may be the most efficient indicator to validate SM exposure even without any symptoms. Bis-G can be regarded as a biomarker of effect, which is directly related to the extent of damage. The most abundant Bis-G was found in the most sensitive tissues, marrow, spleen, and lung, which is in good accordance with histopathologic results. General variations and pathological changes were evaluated as well. After cutaneous exposure to SM, the body weights of rats heavily decreased in the first 4 days and were inversely proportional to the applied doses, and then recovered at the last experimental day except for those of the rats at the highest dosing level, in which the relative weights of rat spleens were obviously lost. Moreover, we found remarkable histological changes of the lung and skin, such as encephalemia, at the very beginning of the sampling procedure, and plentiful mononuclear cells in marrow appeared 6 h after exposure. The micronucleus test of marrow cells showed that the micronucleus rate had a positively dose-dependent effect.

Four sulfur mustard exposure cases: Overall analysis of four types of biomarkers in clinical samples provides positive implication for early diagnosis and treatment monitoring

In one event, Chinese male individuals accidentally exposed to unknown chemicals and emerged erythema or blisters on contacted organism derma, then hospitalized. To identify the causative agents, blood, urine and exudate samples were collected from the patients during the therapeutic course. Five established liquid chromatography-mass spectrometry (LC-MS) and gas chromatography (GC)-MS methods were employed to analyze the samples. Here, an overall analysis of four types of sulfur mustard biomarkers, including the hydrolysis/oxidation products, β-lyase metabolites, DNA adducts and hemoglobin adducts, was conducted toward the samples from exposed individuals. The results of all the four types of biomarkers in different biomedical matrices showed high relevance, and verified that this exposure is indeed originated from sulfur mustard. The concentrations of the biomarkers in specimens revealed a good correlation with the severity of the patient's symptom. The concentration-time profile demonstrated that most of the biomarkers quickly achieved maximum at the beginning of the course, and then decreased and kept a detectable level until the 7th day after exposure. The DNA adducts in urine samples still appeared on the 30th day, and the N-terminal valine adducts in hemoglobin could be monitored for over 90 days, which was meaningful for the concurrent study of clinical samples. To the best of our knowledge, this work provides the total analysis and profile of four categories of biomarkers in human specimens for the first time, and the good accordance between concentration and level of burns, between time course and biomarkers will be of great importance for early diagnosis and medical treatment monitoring of sulfur mustard exposure.