Activation of LXRs using the synthetic agonist GW3965 represses the production of pro-inflammatory cytokines by murine mast cells

BackgroundThe activation of liver X receptor (LXR) α or LXRβ negatively regulates the expression of pro-inflammatory genes in mammalian cells. We recently reported that 25-hydroxycholesterol, a representative LXR-activating oxysterol, suppresses IL-6 production in mouse mast cells (MCs) following its engagement of the high-affinity IgE receptor (FcεRI). This finding suggests that murine MCs express functional LXRs; however, the mechanisms underlying the LXR-dependent repression of the MC-mediated production of pro-inflammatory cytokines, including IL-6, are poorly understood. Therefore, we employed the synthetic LXR ligand GW3965 to examine the functions of LXRα and LXRβ in the production of pro-inflammatory cytokines by murine bone marrow-derived MCs (BMMCs).MethodsWe prepared BMMCs from wild-type (WT), LXRα−/−, and LXRα/β−/− mice. Each group of BMMCs was pretreated with GW3965 and then stimulated with IgE+antigen (Ag) or lipopolysaccharide (LPS). Cytokine production was then analyzed using specific ELISA kits.ResultsThe activation of LXRs by GW3965 significantly attenuated the production of IL-1α and IL-1β, but not of IL-6, in the WT and LXRα−/− BMMCs stimulated with IgE+Ag. However, GW3965 treatment decreased the production of IL-1α, IL-1β, and IL-6 in WT and LXRα−/− BMMCs upon stimulation with LPS, while the GW3965-mediated suppression of cytokine production was nearly absent from the LXRα/β−/− BMMCs.ConclusionsThese findings demonstrate, for the first time, that the activation of LXRs by GW3965 attenuates the antigen- or LPS-induced production of pro-inflammatory cytokines, such as IL-1α and IL-1β, in murine MCs and that LXRβ plays an important role in the LXR-mediated repression of cytokine production.