HDL-Mediated Modulation of CD4+ T Cell Activation Is Related to Changes in the Expression of Genes Involved in Lipid Flux and TCR Signaling

Objectives: We have previously found that HDL modulates CD4+ T cell activation, and that diet-induced remodeling of the HDL proteome and lipidome correlated with changes in HDL immunomodulatory properties. Thus, we further aimed to explore cellular mechanisms of HDL effects, and whether 1) HDL-induced changes in CD4+ T cell activation are due to modulation in the expression of genes involved in T cell activation or HDL-related lipid efflux, and 2) whether these effects are dependent on HDL concentration. Methods: A mixed HDL sample (n =5) was prepared from HDL isolated from young, healthy subjects. Jurkat T cells – a CD4+ T cell line – were incubated with varying concentrations of HDL (50, 150, 300 μg/ml) for 6 hours, then activated via the T cell receptor (TCR) by anti-CD3/CD28 antibodies for 24 hours. Cells were collected measure gene expression by qPCR. Results: We observed concentration-dependent effects of HDL on gene expression. While we previously observed that higher HDL concentrations increased IL-2 secretion in activated T cells, higher HDL concentrations did not alter IL2 mRNA expression. Interestingly, cells treated with 50 μg/ml HDL had suppressed IL2 and CD69 expression. In contrast, mRNA expression of IL2RA, STAT5A, and STAT5B were increased in all activated cells, with greater expression in cells pretreated with the highest concentration of HDL. Interestingly, HDL-dose-dependently increased mRNA expression of ABCG1 and SCARB1 in activated T cells, without impacting expression of ABCA1, which corresponds to our previous observations that high doses of HDL suppress lipid raft formation in activated CD4+ T cells. Conclusions: These findings demonstrate that HDL-mediated modulation of CD4+ T cell activation is associated with differential changes in the expression of genes involved in T cell activation and HDL-related lipid efflux, and that these effects are dependent on HDL concentration. Future studies are warranted to evaluate whether diet-induced changes or metabolic phenotype-specific differences in HDL modulate T cell activation via similar mechanisms. Funding Sources: This study was funded by an Agriculture and Food Research Initiative Grant from the USDA National Institute of Food and Agriculture and pilot funding from the University of Connecticut.