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Updated: Jan 3, 2026
Fast and Specific Assessment of the Halogenating Peroxidase Activity in Leukocyte-enriched Blood Samples
Published on: July 28, 2016
The effect of myeloperoxidase isoforms on biophysical properties of red blood cells
Ekaterina V Shamova1, Irina V Gorudko2, Daria V Grigorieva2
1Belarusian State University, Minsk, Belarus. shamova@tut.by.
Abstract:
Myeloperoxidase (MPO), an oxidant-producing enzyme, stored in azurophilic granules of neutrophils has been recently shown to influence red blood cell (RBC) deformability leading to abnormalities in blood microcirculation. Native MPO is a homodimer, consisting of two identical protomers (monomeric MPO) connected by a single disulfide bond but in inflammatory foci as a result of disulfide cleavage monomeric MPO (hemi-MPO) can also be produced. This study investigated if two MPO isoforms have distinct effects on biophysical properties of RBCs. We have found that hemi-MPO, as well as the dimeric form, bind to the glycophorins A/B and band 3 protein on RBC's plasma membrane, that lead to reduced cell resistance to osmotic and acidic hemolysis, reduction in cell elasticity, significant changes in cell volume, morphology, and the conductance of RBC plasma membrane ion channels. Furthermore, we have shown for the first time that both dimeric and hemi-MPO lead to phosphatidylserine (PS) exposure on the outer leaflet of RBC membrane. However, the effects of hemi-MPO on the structural and functional properties of RBCs were lower compared to those of dimeric MPO. These findings suggest that the ability of MPO protein to influence RBC's biophysical properties depends on its conformation (dimeric or monomeric isoform). It is intriguing to speculate that hemi-MPO appearance in blood during inflammation can serve as a regulatory mechanism addressed to reduce abnormalities on RBC response, induced by dimeric MPO.
Insights
Myeloperoxidase (MPO) affects red blood cell (RBC) properties. Both dimeric and monomeric MPO bind RBCs, altering their function, but dimeric MPO has a stronger impact.
Area of Science:
- Biochemistry
- Hematology
- Cell Biology
Background:
- Myeloperoxidase (MPO) is an enzyme in neutrophils known to affect red blood cell (RBC) deformability and microcirculation.
- MPO exists as a homodimer, but monomeric MPO (hemi-MPO) can form during inflammation.
Purpose of the Study:
- To investigate the distinct effects of dimeric and monomeric MPO isoforms on the biophysical properties of RBCs.
Main Methods:
- Studied the binding of MPO isoforms to RBC membrane proteins (glycophorins A/B, band 3).
- Assessed changes in RBC resistance to hemolysis, elasticity, volume, morphology, and ion channel conductance.
- Quantified phosphatidylserine (PS) exposure on the RBC membrane.
Main Results:
- Both dimeric and hemi-MPO bind to RBCs, reducing cell resistance, elasticity, and altering volume, morphology, and ion channel conductance.
- Both MPO forms induce phosphatidylserine exposure on the RBC membrane.
- Hemi-MPO exhibited lower impact on RBC structural and functional properties compared to dimeric MPO.
Conclusions:
- The conformation of MPO (dimeric vs. monomeric) influences its effect on RBC biophysical properties.
- Hemi-MPO may act as a regulatory mechanism to mitigate RBC abnormalities induced by dimeric MPO during inflammation.
