ESPN 54th Annual Meeting

ESPN 2022


 
Profound conformational changes of serum albumin in children with nephrotic syndrome detected by light scattering and electron paramagnetic resonance (EPR) spectroscopy
PETER HOYER 1 HALEH HAERI 2 JANA EISERMANN 3 HEIKE SCHIMM 2 ANJA B√úSCHER 1 DARIUSH HINDERBERGER 2

1- UNIVERSITY DUISBURG - ESSEN, KINDERHEILKUNDE II, ESSEN, GERMANY
2- INSTITUTE OF CHEMISTRY, PHYSICAL CHEMISTRY - COMPLEX SELF-ORGANIZING SYSTEMS, MARTIN LUTHER UNIVERSITY (MLU) HALLE-WITTENBERG, GERMANY
3- DEPARTMENT OF CHEMISTRY - MOLECULAR SCIENCES RESEARCH HUB, IMPERIAL COLLEGE LONDON, LONDON, UNITED KINGDOM
 
Introduction:

Molecular characteristics of the most abundant serum protein, albumin, in patients with nephrotic syndrome (NS) has not be in the focus of recent research. The observation of a patient with NS, refractory to all therapeutic interventions, before and after kidney transplantation clearly points toward malfunction of human serum albumin (HAS) as a remission could repeatedly be achieved by extremely high albumin infusion.

Material and methods:

After excluding a mutation in the albumin encoding gene, we set out to characterize the molecular physicochemical properties of serum albumin in patients with MCNS and FSGS by employing dynamic light scattering (DLS), electrophoretic light scattering (ELS), and electron paramagnetic resonance (EPR) spectroscopy. An EPR-active stearic acid (16-DSA) was added to serum samples in in HSA:16-DSA ratios of 1:2, 1:4, and 1:6, probing mainly the high affinity (1:2) or globally up to almost all fatty acid binding sites of albumin.

Results:

EPR spectroscopy has shown that fatty acids binding behavior to HSA is significantly different in diseased and healthy HSA [1, 2]. We found changes in the local environment and binding capacity of HSA in NS patients, especially pronounced in the patient with steroid resistant type of NS. These changes are correlated with variations of HSA surface potential/charge as investigated by DLS/ELS.

Conclusions:

Our results show profound functional changes in serum albumin from patients with NS, like an increased hydrodynamic radius, a less negative surface potential and lower binding affinity to 16-DSA even at 1:2 ratio. Whether these changes are caused by other serum factors, loss of the binding capacity of podocyte toxic factors, or if albumin with less negative surface potential is prone to filtering through the glomerular basement membrane are subject to further research.

[1] Haeri,H.H. et al. (2019) Fatty Acid Binding to Human Serum Albumin in Blood Serum Characterized by EPR Spectroscopy. ChemistryOpen, 8, 650 - 656.
[2] Haeri H.H. et al. (2020) Identification of Patients with Pancreatic Cancer by Electron Paramagnetic Resonance Spectroscopy of Fatty Acid Binding to Human Serum Albumin. ACS Pharmacol Transl Sci. 3(6):1188-1198.