Lysophosphatidylcholine enhances cytokine-induced interferon gamma expression in human T lymphocytes.

Accumulation of substantial numbers of activated T lymphocytes, as well as monocyte/macrophages, in focal areas of arterial intima appears to be a hallmark of atherogenesis. Our previous report demonstrated that lysophosphatidylcholine (lyso-PC), a polar phospholipid component that is increased in atherogenic lipoproteins and atherosclerotic lesions, can upregulate the expression of heparin-binding epidermal growth factor-like growth factor and the interleukin (IL)-2 receptor in cultured human peripheral T lymphocytes. In this study, we show that lyso-PC can also enhance interferon gamma (IFN-gamma) secretion and gene expression in human T lymphocytes. Lyso-PC-induced upregulation of IFN-gamma depended on the presence of IL-2, IL-12, or phytohemagglutinin in culture media and was similarly observed in both CD4+ and CD8+ subsets. Actinomycin D chase by Northern blotting showed that lyso-PC significantly prolonged IFN-gamma mRNA half-lives in human T cells. Transient transfection of IFN-gamma promoter-reporter gene construct in the human T-cell line Jurkat cells demonstrated that lyso-PC stimulated the transcription of IFN-gamma promoter-driven luciferase gene. Analyses of serial deletion mutations of IFN-gamma promoter revealed that the lyso-PC-responsive element is located between base pairs - 102 and -78 of the transcription initiation site of the IFN-gamma gene. Enhanced expression of IFN-gamma in T lymphocytes by lyso-PC may play a crucial role in atherogenesis.