Leukemia inhibitory factor, interferon gamma and dexamethasone regulate N-glycosylation of alpha 1-protease inhibitor in human hepatoma cells.

Hepatocytes respond to inflammatory stimuli by changing the synthesis and N-glycosylation of acute phase plasma proteins (APP). So far, interleukin (IL) 6, transforming growth factor beta (TGF beta), tumor necrosis factor alpha (TNF) and IL-1 have been found to control N-glycosylation patterns of APP. Cytokines either increased (type I) or decreased (type II) the ratio of bi-relative to more branched N-glycans on APP. In this study, we describe the effect of leukemia inhibitory factor (LIF), interferon gamma (INF gamma) and dexamethasone (dex) on production of alpha 1-protease inhibitor (PI) and alpha 1-antichymotrypsin (ACT) and on glycosylation of PI in the human hepatoma cell line HepG2. Cytokines and dex were used separately and in various combinations including also IL-6 and TGF beta. Production of the antiproteases was quantitated by immunoelectrophoresis of the proteins accumulated in the culture medium. Glycosylation pattern of PI was assessed by crossed immunoaffinity electrophoresis (CIAE) with Concanavalin A (Con A) as a ligand. The production of ACT and PI was increased by LIF, decreased by INF gamma and unaffected by dex. LIF and INF gamma each like IL-6, decreased PI-Con A reactivity while dex like TGF beta enhanced PI-Con A reactivity. Combination of dex with LIF yielded additive effects while combination of dex with either INF gamma, L-6 or TGF beta acted synergistically on PI-Con A reactivity. Combinations of multiple cytokines and dex produced additive, inhibitory or synergistic effects. The type of glycosylation profile of PI secreted by HepG2 cells depended on the composition and amounts of interacting cytokines and dex.