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 H(2)O(2) as an oxidizing agent. Abbreviations: Albumin (HSA); non-glycated mercaptoalbumin (HSA-SH); glycated mercaptoalbumin (HSA-Glc); cysteinylated albumin (HSA-Cys); sum of glycated and non-glycated mercaptoalbumin (HSA-SHt); end stage renal diseases (ESRD); hemodialysis (HD); reactive carbonyl species (RCS); 4-hydroxy-trans-2-nonenal (HNE).