Human erythrocyte surface fucose expression increases with age and hyperglycemia

Huan Cao,Sonja Wright,Dimitrios Tampakis,Beverley Minter,Stuart M Haslam,Maria Williams,Mark A Vickers,Aristotelis Antonopoulos,Ananyo Bagchi,Irina Laidvee,Robert N Barker

doi:10.12688/wellcomeopenres.16409.1

Abstract

Background: Reactive oxygen species and other free radicals, together with glucose and its metabolites are believed to play important roles in the aging process. The carbohydrate components of glycosylated proteins are important in mediating cell-cell interactions and a role has been suggested for them in the aging process. Erythrocytes are critical cells in the human body, heavily glycosylated and relatively easily available and so are good candidates to yield insights into how patterns of glycosylation change with age and disease. It has been claimed, based on a periodic acid Schiff assay, that human aging is associated with a decline of erythrocyte surface sialic acids. Plant lectins allow for more specific assays for glycans, including determining the linkage of sialic acids and analysis of single cells by flow cytometry. Methods: Plant lectins, including Maackia amurensis lectin II (MAL), binding to α-2,3 linked sialic acids and Sambucus nigra (SNA), α-2,6 sialic acids, were used in flow cytometry and western blot of erythrocyte surface membrane. N-glycomics mass spectrometry determines glycan structures. Donors varying in age and hyperglycemia, as indicated by HbA1c were analysed. Results: Erythrocyte surface sialic acids have no significant associations with donor age. A combination of storage and cellular aging produces a specific loss of α-2,6 sialic acids. By contrast, erythrocyte surface terminal fucoses increase significantly with donor age. In order to determine which aspects of aging are important in determining this change, we investigated whether this novel human aging biomarker is associated with higher plasma glucose values, assessed by glycated hemoglobin (HbA1c) and reactive oxygen species (ROS) generation. Fucose levels were associated with HbA1c levels, but not ROS generation. Conclusion: Our study identifies novel glycan-based biomarkers for human aging and disease. The simplicity of lectin-based assays provide an attractive cellular tool to study aging and disease processes.

Highlights

The main function of erythrocytes is to carry oxygen from the lungs to the rest of the body and remove carbon dioxide as a waste product
In order to determine which aspects of aging are important in determining this change, we investigated whether this novel human aging biomarker is associated with higher plasma glucose values, assessed by glycated hemoglobin (HbA1c) and reactive oxygen species (ROS) generation
Neuraminidase sensitivity observed by lectin flow cytometry but not periodic acid Schiff assay Neuraminidase is an enzyme that removes terminal sialic acids from glycoproteins[31]

Summary

Introduction

The main function of erythrocytes is to carry oxygen from the lungs to the rest of the body and remove carbon dioxide as a waste product. Sialic acids are negatively charged sugars and confer a bulk surface charge causing repulsion between cells, so preventing agglutination[2]. They are important signalling molecules as they are found at the periphery of cell surfaces[3]. Erythrocytes are critical cells in the human body, heavily glycosylated and relatively available and so are good candidates to yield insights into how patterns of glycosylation change with age and disease. It has been claimed, based on a periodic acid Schiff assay, that human aging is associated with a decline of erythrocyte surface sialic acids.

Methods

Results

Discussion

Conclusion