Modulation of intracellular machinery by β-glycolipids is associated with alteration of NKT lipid rafts and amelioration of concanavalin-induced hepatitis

The integrity of lipid rafts in cell membranes is important for signal transcluction. Aim: To determine the distinct effects of P-glycolipids on the composition of lipid rafts in natural killer T (NKT) cells and on the level of expression of flotillin-2, leukocyte-specific protein tyrosine kinase (Lck), and STAT1-associated pathways. Methods: The effects of glycolipids were determined by composition analysis of the raft domains, FACS analysis of the distribution patterns for the raft ganglioside, GM1, and fluorescence microscopy of raft patching. To evaluate the effects of the immune environment on glycolipid-associated alteration of lipid rafts, hepatitis was induced by an intravenous injection of concanavalin A (ConA) in mice treated with various glycolipids. Results: The administration of P-glucosylceramide, P-lactosylceramide, and a combination of both significantly altered GM1 content in lymphocyte membranes in an environment-dependent manner. These effects were associated with altered expression levels of flotillin-2, Lck, and STAT1, and with a significant decrease in intrahepatic CD8(+) lymphocyte trapping and the alleviation of ConA-induced hepatitis. The administration of alpha-glycolipids failed to induce similar effects. Conclusions: The alteration in the expression levels of flotillin-2, Lck, and STAT1 that occurs concomitantly with changes in lipid raft composition and structure following the administration of P-glycolipids in ConA-induced hepatitis is microenvironment-dependent and is associated with decreased intrahepatic CD8(+) T lymphocyte trapping and amelioration of immune-mediated hepatitis. (C) 2008 Elsevier Ltd. All rights reserved.