A microanalytical capillary electrophoresis mass spectrometry assay for quantifying angiotensin peptides in the brain

Document Type

Journal Article

Publication Date

7-19-2019

Journal

Analytical and Bioanalytical Chemistry

Volume

411

Issue

19

DOI

10.1007/s00216-019-01771-9

Keywords

Angiotensin; Capillary electrophoresis; High-resolution mass spectrometry; Mouse; Nano-liquid chromatography; Parallel reaction monitoring; Paraventricular nucleus; Peptidomics; Renin-angiotensin system; Subfornical organ

Abstract

© 2019, Springer-Verlag GmbH Germany, part of Springer Nature. The renin-angiotensin system (RAS) of the brain produces a series of biologically active angiotensinogen-derived peptides involved in physiological homeostasis and pathophysiology of disease. Despite significant research efforts to date, a comprehensive understanding of brain RAS physiology is lacking. A significant challenge has been the limited set of bioanalytical assays capable of detecting angiotensin (Ang) peptides at physiologically low concentrations (2–15 fmol/g of wet tissue) and sufficient chemical specificity for unambiguous molecular identifications. Additionally, a complex brain anatomy calls for microanalysis of specific tissue regions, thus further taxing sensitivity requirements for identification and quantification in studies of the RAS. To fill this technology gap, we here developed a microanalytical assay by coupling a laboratory-built capillary electrophoresis (CE) nano-electrospray ionization (nano-ESI) platform to a high-resolution mass spectrometer (HRMS). Using parallel reaction monitoring, we demonstrated that this technology achieved confident identification and quantification of the Ang peptides at approx. 5 amol to 300 zmol sensitivity. This microanalytical assay revealed differential Ang peptide profiles between tissues that were micro-sampled from the subfornical organ and the paraventricular nucleus of the hypothalamus, important brain regions involved in thirst and water homeostasis and neuroendocrine regulation to stress. Microanalytical CE-nano-ESI-HRMS extends the analytical toolbox of neuroscience to help better understand the RAS.

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