Differential effects of interferon-gamma and -beta on fatty acid turnover, lipid bilayer fluidity and TNF-alpha release in murine macrophage J774.2 cells.

The effects of interferon (IFN)-gamma and IFN-beta on the incorporation of 14C-linoleic acid into J774.2 cell membrane phospholipids were examined. Interferon-gamma induced a statistically significant increase in incorporation of 14C-linoleic acid into all the major phospholipid classes. In contrast, IFN-beta induced a slightly reduced incorporation of this fatty acid into the phospholipids. Neither IFN-gamma nor IFN-beta had any effect on the incorporation of the saturated fatty acid 14C-stearic acid into the cellular phospholipids. Interferon-gamma had no effect on the metabolism of 14C-linoleic acid in the fibroblast cell line L929. Macrophage membrane fluidity was assessed by spin-label ESR spectroscopy after incubation with either IFN-gamma or IFN-beta. Interferon-gamma significantly increased membrane fluidity whereas IFN-beta significantly decreased the fluidity. The findings of this study reveal that IFN-gamma might act on the enzymes controlling the labelling of the sn2 position of phospholipids (linoleic acid) but not the sn1 position (stearic acid), and this increases the polyunsaturated fatty acid content of macrophage membranes. This increase in polyunsaturation is reflected in the increased membrane fluidity. We also conclude that IFN-beta and IFN-gamma have different mechanisms of action on macrophage membrane lipid metabolism.