Profiling of sulfoconjugates in urine by using precursor ion and neutral loss scans in tandem mass spectrometry. Application to the investigation of heavy metal toxicity in rats

Abstract

This paper reports a liquid chromatographic/electrospray ionization mass spectrometric (LC/ESI-MS) method for profiling a wide range of structurally different sulfoconjugated compounds in urine and its application to the characterization of biomarkers for heavy metal toxicity in rat urine. Sulfoconjugates were first isolated by solid-phase extraction and the LC separation was performed on a reversed-phase column. Sulfoconjugates were detected in a triple-quadrupole mass spectrometer by simultaneously monitoring constant losses of 80 u (or 80 Th for doubly charged ions), precursors of m/z 80 (SO(3) (-*)) and precursors of m/z 97 (HSO4-). The ESI-MS detection conditions were optimized on dehydroepiandrosterone sulfate and estradiol sulfate and tested on other sulfoconjugates. The analysis of urine samples from humans and rats by using the developed method allowed the detection of about 15 peaks in each mode of detection. It was then applied to the investigation of heavy metal toxicity in rats. Comparative analysis of the chromatographic fingerprints of urine from control and uranium- and cadmium-treated rats showed several variations in the chromatographic pattern of the sulfoconjugates. Diagnostic m/z ratios were confirmed by analyzing individual urine samples and one of the observed variations seemed to be specific to uranium toxicity. The ion responsible for this variation has been identified as 4-ethylphenol sulfate by comparison of its chromatographic retention time and collision-induced dissociation mass spectra (MS(2) and MS(3) performed on a quadrupole ion trap instrument) with those of the synthesized compound.

Detection and Characterization of Metabolites in Biological Matrices Using Mass Defect Filtering of Liquid Chromatography/High Resolution Mass Spectrometry Data

“…The detection of conjugates (e.g., glucuronide and sulfate) can usually be accomplished with a NL analysis because these con-jugates often undergo common cleavages to generate specific neutral fragments under collision-induced dissociation conditions (Baillie and Davis, 1993;Lafaye et al, 2004). PI scanning can also be used to search for metabolites with common product ions that can be predicted from the patterns of the parent drug product ions (Xia et al, 2003;Liu and Hop, 2005).…”

LC–MS-based metabonomics analysis

“…The authors utilized the MS/MS capability of this instrument to derive structural information for specific metabolites. Then they reported a LC/ESI-MS method for profiling a wide range of structurally different sulfoconjugated compounds in urine and its application in the characterization of biomarkers for heavy metal toxicity in rat urine [103]. Comparative analysis of the chromatographic fingerprints of urine from control and uranium-and cadmium-treated rats showed several variations in the chromatographic pattern of the sulfoconjugates.…”

Metabolite profiling in human urine by LC–MS/MS: Method optimization and application for glucuronides from dextromethorphan metabolism

“…Another group has developed a method for profiling sulfoconjugates in human urine and compared the neutral loss of 80 with precursor ion scanning of m/z 80 (SO 3 − ) and m/z 97 (HSO 4 − ). The method was applied to the characterization of urinary biomarkers for heavy metal toxicity in rats [41]. The same authors used a quadrupole ion trap for metabolite profiling of rat urine for various chemical families, including carboxylic acids, amines, sulfated compounds, glucuronides and glycosides, based on information-dependent acquisition of product ion spectra [42].…”