Novel cysteine- and albumin-adduct biomarkers to prove human poisoning with the pesticide oxydemeton-S-methyl

Toxicol Lett. 2018 Sep 15:294:122-134. doi: 10.1016/j.toxlet.2018.05.023. Epub 2018 May 17.

Abstract

We herein report on the forensic analysis of plasma samples to prove human poisoning with oxydemeton-S-methyl (ODM), S-(2-(ethylsulfinyl)ethyl)-O,O-dimethyl phosphorothioate. This organophosphorus pesticide is the active ingredient of Metasystox®, that was swallowed by a 77-year-old woman to commit suicide. ODM belongs to the class of dimethyl phosphoryl (DMP) pesticides, contains a 2-(ethylsulfinyl)ethanethiol (ESOET) leaving group and undergoes adduct formation with endogenous molecules as elaborated herein with human serum exposed to pesticides in vitro. A novel bioanalytical micro liquid-chromatography-electrospray ionization tandem high-resolution mass spectrometry method (μLC-ESI MS/HR MS) was developed to target multiple biomarkers of exposure. Following pronase-catalyzed proteolysis of patient plasma and subsequent ultrafiltration, the filtrate was analyzed. Diverse reaction products of ODM as well as of its oxidized biotransformation product demeton-S-methyl sulfone (DSMS), that possesses a 2-(ethylsulfonyl)ethanethiol (ESO2ET) leaving group, were simultaneously detected. Phosphorylated tyrosine residues (Tyr-DMP) derived from human serum albumin (HSA) as well as novel dipeptide-adducts containing the Cys34 residue of HSA coupled to ESOET and ESO2ET via a disulfide bond (ESOET-CysPro and ESO2ET-CysPro) were found. In addition, a related disulfide-product was detected comprising the single amino acid cysteine and ESOET (ESOET-Cys). Whereas Tyr-DMP only proved the intake of any DMP pesticide in general, its simultaneous detection with ESOET-CysPro, ESO2ET-CysPro and ESOET-Cys allowed unambiguous identification of the ingested pesticide. Therefore, the novel biomarkers and the method developed expand the possibilities of forensic investigations of ODM poisoning.

Keywords: Albumin-adducts; Cysteine disulfide-adducts; High-resolution mass spectrometry; Organophosphorus pesticide; Verification analysis.

Publication types

  • Case Reports

MeSH terms

  • Aged
  • Analytic Sample Preparation Methods
  • Biomarkers / blood
  • Biotransformation
  • Chromatography, High Pressure Liquid
  • Cysteine / analogs & derivatives*
  • Cysteine / blood
  • Cysteine / chemistry
  • Dipeptides / chemistry
  • Dipeptides / metabolism
  • Feasibility Studies
  • Female
  • Forensic Toxicology / methods*
  • Germany
  • Humans
  • Molecular Structure
  • Organophosphate Poisoning / blood*
  • Organophosphate Poisoning / diagnosis
  • Organophosphate Poisoning / etiology
  • Organophosphate Poisoning / metabolism
  • Organothiophosphorus Compounds / metabolism
  • Organothiophosphorus Compounds / toxicity*
  • Peptide Fragments / chemistry
  • Peptide Fragments / metabolism
  • Pesticides / metabolism
  • Pesticides / toxicity*
  • Proteolysis
  • Serum Albumin, Human / analysis
  • Serum Albumin, Human / chemistry*
  • Spectrometry, Mass, Electrospray Ionization
  • Suicide
  • Tandem Mass Spectrometry

Substances

  • Biomarkers
  • Dipeptides
  • Organothiophosphorus Compounds
  • Peptide Fragments
  • Pesticides
  • cysteinylproline
  • methyl demeton
  • Cysteine
  • Serum Albumin, Human