Effect of Dexamethasone on the Expression of the alpha 2,3 and alpha 2,6 Sialic Acids in Epithelial Cell Lines

N-acetylneuraminic acid linked to galactose by alpha 2,6 and alpha 2,3 linkages (Sia alpha 2,6 and Sia alpha 2,3) is expressed on glycoconjugates of animal tissues, where it performs multiple biological functions. In addition, these types of sialic acid residues are the main targets for the binding and entry of influenza viruses. Here we used fluorochrome-conjugated Sambuccus nigra, Maackia amurensis, and peanut lectins for the simultaneous detection of Sia alpha 2,3 and Sia alpha 2,6 and galactosyl residues by two-color flow cytometry on A549 cells, a human pneumocyte cell line used for in vitro studies of the infection by influenza viruses, as well as on Vero and MDCK cell lines. The dexamethasone (DEX) glucocorticoid (GC), a widely used anti-inflammatory compound, completely abrogated the expression of Sia alpha 2,3 in A549 cells and decreased its expression in Vero and MDCK cells; in contrast, the expression of Sia alpha 2,6 was increased in the three cell lines. These observations indicate that DEX can be used for the study of the mechanism of sialylation of cell membrane molecules. Importantly, DEX may change the tropism of avian and human/pig influenza viruses and other infectious agents to animal and human epithelial cells.