Capillary electrochromatography-mass spectrometry of kynurenine pathway metabolites

• Type of Material: Article
• Authors: ASMMR Chawdhury, Georgia State University; Shahab A Shamsi, Georgia State University; Andrew Miller, Emory University; Aimin Liu, University of Texas at San Antonio
• Language: English
• Date: 2021-06-05
• Publisher: ELSEVIER
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: © 2021 Published by Elsevier B.V.
• License: Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International
• Final Published Version (URL): http://dx.doi.org/10.1016/j.chroma.2021.462294
• Title of Journal or Parent Work: JOURNAL OF CHROMATOGRAPHY A
• Volume: 1651
• Start Page: 462294
• End Page: 462294
• Grant/Funding Information: National Institutes of Health (1 R21 MH107985–01).
• Keywords: Simultaneous separation; Chemistry, Analytical; ELECTROPHORESIS; Low vs. high inflammation; Capillary electrochromatography-mass spectrometry; RECEPTOR; PROTEIN; Science & Technology; Endogenous plasma quantitation; SEPARATION; Chemistry; Physical Sciences; TRYPTOPHAN; LIQUID-CHROMATOGRAPHIC METHOD; Biochemistry & Molecular Biology; Biochemical Research Methods; QUINOLINIC ACID; CEREBROSPINAL-FLUID; PLASMA; PICOLINIC-ACID; Nine kynurenine pathway metabolites; Life Sciences & Biomedicine; Standard addition-internal standard

Abstract

Few articles are reported for the simultaneous separation and sensitive detection of the kynurenine pathway (KP) metabolites. This work describes a capillary electrochromatography-mass spectrometry (CEC-MS) method using acrylamido-2-methyl-1-propanesulfonic acid (AMPS) functionalized stationary phase. The AMPS column was prepared by first performing silanization of bare silica with gamma-maps, followed by polymerization with AMPS. The CEC-MS/MS methods were established for six upstream and three downstream KP metabolites. The simultaneous separation of all nine KP metabolites is achieved without derivatization for the first time in the open literature. Numerous parameters such as pH and the concentration of background electrolyte, the concentration of the polymerizable AMPS monomer, column length, field strength, and internal pressure were all tested to optimize the separation of multiple KP metabolites. A baseline separation of six upstream metabolites, namely tryptophan (TRP), kynurenine (KYN), 3-hydroxykynurenine (HKYN), kynurenic acid (KA), anthranilic acid (AA), and xanthurenic acid (XA), was possible at pH 9.25 within 26 min. Separation of six downstream and related metabolites, namely: tryptamine (TRPM), hydroxy‑tryptophan (HTRP), hydroxyindole-3 acetic acid (HIAA), 3-hydroxyanthranilic acid (3-HAA), picolinic acid (PA), and quinolinic acid (QA), was achieved at pH 9.75 in 30 min. However, the challenging simultaneous separation of all nine KP metabolites was only accomplished by increasing the column length and simultaneous application of internal pressure and voltage in 114 min. Quantitation of KP metabolites in commercial human plasma was carried out, and endogenous concentration of five KP metabolites was validated. The experimental limit of quantitation ranges from 100 to 10,000 nM (S/N = 8–832, respectively), whereas the experimental limit of detection ranges from 31 to 1000 nM (S/N = 2–16, respectively). Levels of five major KP metabolites, namely TRP, KYN, KA, AA, and QA, and their ratios in patient plasma samples previously screened for inflammatory biomarkers [C-reactive protein (CRP) and tumor necrosis factor-alpha (TNF-α)] was measured. Pairs of the level of metabolites with significant positive correlation were statistically evaluated.