The challenges and promise of targeting the Liver X Receptors for treatment of inflammatory disease.
- Michael B Fessler
- Pharmacology & therapeutics
Migration of CD4-positive lymphocytes into the vessel wall is a critical step in atherogenesis. Recent data suggest that CD4-positive lymphocytes express the nuclear transcription factors Liver-X-Receptor (LXR) alpha and beta with an effect of LXR activators on TH1-cytokine release from these cells. However, the role of LXR in lymphocyte migration remains currently unexplored. Therefore, the present study investigated whether LXR activation might modulate chemokine-induced migration of these cells. Stimulation of CD4-positive lymphocytes with SDF-1 leads to a 2.5 ± 0.8-fold increase in cell migration (P < 0.05; n = 12). Pretreatment of cells with the LXR activator T0901317 reduces this effect in a concentration-dependent manner to a maximal 0.9 ± 0.4-fold induction at 1 μmol/L T0901317 (P < 0.05 compared to SDF-1-treated cells; n = 12). Similar results were obtained with the LXR activator GW3965. The effect of LXR activators on CD4-positive lymphocyte migration was mediated through an early inhibition of chemokine-induced PI-3 kinase activity as determined by PI-3 kinase activity assays. Downstream, T0901317 inhibited activation of the small GTPase Rac and phosphorylation of the myosin light chain (MLC). Moreover, LXR activator treatment reduced f-actin formation as well as ICAM3 translocation to the uropod of the cell, thus interfering with two important steps in T cell migration. Transfection of CD4-positive lymphocytes with LXRα/β siRNA abolished T0901317 inhibitory effect on MLC phosphorylation and ICAM3 translocation. LXR activation by T0901317 or GW3965 inhibits chemokine-induced migration of CD4-positive lymphocytes. Given the crucial importance of chemokine-induced T cell migration in early atherogenesis, LXR activators may be promising tools to modulate this effect.