Human serum albumin cysteinylation is increased in end stage renal disease patients and reduced by hemodialysis: mass spectrometry studies

Abstract

The aim of the present work was to monitor the covalent modifications of human serum albumin (HSA) in end stage renal diseases (ESRD) non-diabetic patients, before and after hemodialysis (HD), by direct infusion electrospray mass spectrometry (ESI-MS). Human serum samples were collected from healthy subjects (n = 10, 20–60 yr) and age-matched ESRD patients (n = 8) before and after HD, purified by affinity chromatography and analyzed by a triple-quadrupole mass spectrometer. The deconvoluted spectra from healthy subjects were all characterized by three peaks attributed to non-glycated mercaptoalbumin (HSA-SH) and to the corresponding adducts with cysteine (HSA-Cys) and glucose (HSA-Glc); relative contents: mercaptoalbumin in both glycated and non-glycated form, HSA-SHt (74 ± 6%), HSA-Cys (26 ± 5%) and HSA-Glc (24 ± 3%). HSA isolated from ESRD patients before HD was characterized by a significant reduction of HSA-SHt (42 ± 7%), and by a concomitant increase of the HSA-Cys adduct (58 ± 7%). Hemodialysis significantly reduced the cysteinylated form (37 ± 7%) and restored HSA-SHt (63 ± 8%) in all the ESRD patients. The mechanism of thiol oxidation and cysteinylation was then studied by mass spectrometry, using LQQCPF as a model peptide and H₂O₂ as an oxidizing agent.

Keywords::

• end
• stage renal diseases
• albumin
• Cys34
• cysteinylation
• mass spectrometry
• hemodialysis
• oxidative damage

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

This work was supported by Regione Lombardia (Technological and Scientific Cooperation Agreement, ID SAL-60, Ref n. 16749).

KJ Yeum has been supported in part by the BioGreen 21 Program (Code #20070301034009), Rural Development Administration, Korea and US Department of Agriculture, under Agreement 58-1950-7-707. The contents of this publication do not necessarily reflect the views or policies of the US Department of Agriculture, nor does mention of trade names, commercial products, or organizations imply endorsement by the US Government.