Alteration of sugar chains on α 1-acid glycoprotein secreted following cytokine stimulation of HuH-7 cells in vitro

Abstract

In inflammation, hepatocytes secrete several proteins into serum, the so-called acute phase proteins. In addition to increased serum levels of α 1-acid glycoprotein (AGP), there are also changes in the composition of its sugar chains. To investigate the cytokine-stimulated alteration of sugar chains on AGP, we cultured the human hepatoma cell line HuH-7 cells in serum-free medium (IS-RPMI) with and without IL-1β and IL-6, and analyzed AGP secretion into the medium. AGP was increased during stimulation with both IL-1β and IL-6, although the effect of IL-1β was more pronounced. Lectin-binding assay for secreted AGP also indicated significant increases in the binding activities to Aleuria aurantia lectin (AAL), Sambucus sieboldiana agglutinin (SSA), and concanavalin-A (ConA). In particular, AAL binding activity increased with higher expression of the sialyl Lewis X (sLe X) antigen, NeuAc α2–3 Gal β1–4 (Fuc α1–3) GlcNAc-R. Thus, the increase in AGP fucosylation may be correlated with the increase of sLe X. The present results indicate that the serum-free culture of HuH-7 cells provides a useful model for investigating the secretion of proteins from hepatocytes, and the effects of cytokines on the changes in sugar chains of glycoproteins in vitro.