Monokines regulate glycosylation of acute-phase proteins

Abstract

The acute-phase response to inflammatory stimuli, characterized by increased synthesis of acute-phase proteins (APP), is often accompanied by changes in the glycosylation patterns of some of these proteins. While expression of APP genes in hepatocytes is regulated by monokines, mechanisms governing changes in glycosylation are not known. Exposure of human hepatoma cell line Hep 3B to conditioned medium from LPS-activated human monocytes and to medium from the keratocarcinoma cell line COLO-16 led to increased synthesis of alpha 1 proteinase-inhibitor and ceruloplasmin and to alterations of their glycosylation patterns similar to those seen in human serum in various inflammatory states. IL-1, tumor necrosis factor, and hepatocyte stimulating factor I increased synthesis of ceruloplasmin without alterations in the pattern of its glycosylation. These findings demonstrate that altered glycosylation seen in plasma in some inflammatory states can be explained by the effects of monokines on glycosylation in hepatocytes and that gene expression and glycosylation of some APP during the acute-phase response may be regulated by different mechanisms.