Presence of N-acetylneuraminic acid in the lung during postnatal development

Abstract

Sialic acids, particularly N-acetylneuraminic acid (Neu5Ac), are present as terminal components of rich and complex oligosaccharide chains, which are termed glycans, and are exhibited on the cell surfaces, especially on epithelial cells. Crucial in the ‘social behavior’ of the cell, sialic acids play vital roles in many physiological and pathological phenomena. The aim of the present study was to separate, identify, and quantify Neu5Ac in purified lung membranes from 4-, 14-, and 21-day-old animals, followed by the statistical analysis of these results with our previously reported data (0-day-old and adult results). Complementary, ultrastructural methodologies were used. The differences in the Neu5Ac values obtained across the examined postnatal-lung development relevant ages studied were found to be statistically significant. A substantial increase in the mean level of this compound was found during the period of ‘bulk’ alveolarization, which takes place from postnatal day 4 to 14 (P4-P14). The comparison of the mean levels of Neu5Ac, during microvascular maturation (mainly between P12 and P21), reveals that the difference, although statistically significant, is the least significant difference among all the pair-wise differences between the developmental stages. The presence of sub-terminal N-acetylgalactosamine (GalNAc)/Galactose (Gal) residues with terminal sialic acids on the bronchioloalveolar cell surfaces was confirmed using lung ultra-thin sections of adult and 0-day-old animals. These results showed that, although Neu5Ac levels increase throughout postnatal lung development, this sialic acid was substantially added to epithelial cell surfaces during the “bulk” alveolarization period, while its presence was less important during the microvascular maturation period. Bearing in mind that sialic acids are negatively charged and create charge repulsions between adjacent cells, we hypothesized that they can substantially contribute to postnatal alveolar formation and maturation.

Quantification of free sialic acids, Effect of EHF therapy in pulmonary edema: a possible alternative in the fight against COVID-19

“…In the lungs, sialic acids are found on the plasma membranes of the epithelium of the bronchi, bronchioles and alveoli. They are also found in endothelial cells of the pulmonary artery and capillaries 13,14,15,16 . EHF therapy is a physiotherapeutic method, translated from Russian as "Extremely high-frequency (EHF) therapy" 17 .…”

“…They exhibit a very great structural diversity such as acetylated, alkylated, phosphate, sulphated or methylated sialic acids, 10 Nowadays, more than 80 derivatives of neuraminic acid have been described 11 . At present, all the functions of sialic acids are not yet known 12 , however, they have been found to be important building blocks for the body, as they are involved in various biological processes, such as blood cell renewal, neural development and the functioning of the immune system 8, 10,13 . Sialic acids frequently attach to the terminal surface of glycan chains expressed on oligosaccharides, polysaccharides, glycoproteins, gangliosides and lipopolysaccharides on the surface of many cells, prokaryotes and eukaryotes, but some members of the sialic acid family are found only in free form 8,10,12,13 .…”

“…At present, all the functions of sialic acids are not yet known 12 , however, they have been found to be important building blocks for the body, as they are involved in various biological processes, such as blood cell renewal, neural development and the functioning of the immune system 8, 10,13 . Sialic acids frequently attach to the terminal surface of glycan chains expressed on oligosaccharides, polysaccharides, glycoproteins, gangliosides and lipopolysaccharides on the surface of many cells, prokaryotes and eukaryotes, but some members of the sialic acid family are found only in free form 8,10,12,13 . In the lungs, sialic acids are found on the plasma membranes of the epithelium of the bronchi, bronchioles and alveoli.…”