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

Glutathione conjugation of sesquimustard: in vitro investigation of potential biomarkers

Sesquimustard (Q) is a powerful blistering agent that contains additional sulfur atoms. Sulfur mustard causes covalent bonding by alkylating nucleophilic groups of biologically important macromolecules such as lipids, proteins, DNA, or RNA. Most cells maintain relatively high amounts of a unique tripeptide called glutathione (GSH) (γ-glutamyl-cysteinyl glycine), which possesses a free thiol group, to prevent unwanted reactions caused by reactive chemical entities. Moreover, these thiol groups on cysteines (Cys) are the main target for alkylation. Although Q is the most potent vesicant among sulfur mustards, research studies identifying biomarkers of Q are very limited. Therefore, here in this study, we aimed to identify the GSH and Cys conjugates of Q using mass spectrometric methods and to observe the formation of these conjugates in HaCat cell culture following exposure to different doses. We identified four different conjugates of Q, which are bis-glutathionyl ethylthioethylthioethyl conjugate (GSH-ETETE-GSH), hydroxyethylthioethylthioethyl glutathione conjugate (HETETE-GSH), bis-cysteinyl ethylthioethylthioethyl conjugate (Cys-ETETE-Cys), and hydroxyethylthioethylthioethyl cysteine conjugate (HETETE-Cys). The identity of the conjugates was elucidated using liquid chromatography-high-resolution mass spectrometry (LC-HRMS). We also investigated changes in conjugate formation with exposure concentration and time elapsed after exposure in the cell culture. After exposure, GSH conjugates decreased until 1st hour, while Cys conjugates increased until 6th hour. We also observed that conjugate formation depended on the concentration of Q. This is the first study to elucidate the conjugates of Q dependent on GSH conjugation. As biomarkers are essential tools for evaluating exposure to Q, this study contributes to the limited number of studies identifying biomarkers for Q.

Unambiguous identification of γ-aminobutyric acid adducts as novel plant biomarkers and their ultra-sensitive detection by UPLC-MS/MS for retrospective analyses of nitrogen mustards exposure

Plants are widely existing in the environments and have been considered as potential sentinel species of toxic chemicals' exposure. In this study, the deadly toxic chemicals of three nitrogen mustards (NMs, including NH1, NH2 and NH3) were selected as the investigated targets. First, the reactivities of common endogenous plant components with NMs were examined in vitro. Then, the model plant Nicotiana benthamiana Domin was exposed to NMs. Three γ-aminobutyric acid-nitrogen mustard adducts (GABA-NMs) were identified in the living plant by high resolution mass spectrometry and comparison with the synthesized references. A sensitive detection method with the limits of quantification of 0.0500 ng mL-1 was developed using ultrahigh performance liquid chromatography-triple quadrupole mass spectrometry. The GABA-NMs could be detected after 120 days of the exposure and even in the dead leaves without obvious decrease. Furthermore, 20 different plant species grown in diverse climate zones were exposed to HN1, and the adduct of GABA-HN1 was identified in all the leaves. The results showed the good universality and specificity of GABA-NMs as plant biomarkers for NMs exposure. This work provides a new approach for the pollution investigation of toxic chemicals through analysing biomarkers in plant materials.