Tumor necrosis factor-α up-regulates the expression of β1,4-galactosyltransferase I in primary human endothelial cells by mRNA stabilization

During the course of an inflammatory response, the pro-inflammatory cytokine tumor necrosis factor-alpha (TNF alpha) triggers endothelial cells to increase the expression levels of adhesion molecules that are pivotal for the rolling, adhesion, and transmigration of leukocytes over the endothelial cell wall. Here we show that TNF alpha, in addition, has a regulatory function in the biosynthesis of proper carbohydrate molecules on endothelial cells that constitute ligands for adhesion molecules on leukocytes. Our data show that TNF alpha induced an increase in the expression of beta 1,4-galactosyltransferase-1 (beta 4GalT-1) in primary human umbilical vein endothelial cells in a time- and concentration-dependent manner. The beta 4GalT-1 mRNA up-regulation correlated with an increase in the Golgi expression and catalytic activity of the enzyme. Furthermore, an enhanced incorporation of galactose was observed in newly synthesized glycoproteins. Analysis of the molecular mechanism behind the up-regulation of beta 4GalT-1 showed that the increase in mRNA levels is due to an enhanced stability of the transcripts. These data strongly demonstrate that TNF alpha modulates the glycosylation of endothelial cells by a mechanism that directly enhances the stability of beta 4GalT-1 mRNA transcripts.