The Inverse Agonist DG172 Triggers a PPARβ/δ-Independent Myeloid Lineage Shift and Promotes GM-CSF/IL-4-Induced Dendritic Cell Differentiation

The stilbene derivative (Z)-2-(2-bromophenyl)-3-{[4-(1-methylpiperazine)amino]phenyl}acrylonitrile (DG172) was developed as a highly selective inhibitory peroxisome proliferator-activated receptor (PPAR)β/δ ligand. Here, we describe a novel PPARβ/δ-independent, yet highly specific, effect of DG172 on the differentiation of bone marrow cells (BMCs). DG172 strongly augmented granulocyte-macrophage-colony-stimulating factor (GM-CSF)-induced differentiation of primary BMCs from Ppard null mice into two specific populations, characterized as mature (CD11c^hiMHCII^hi) and immature (CD11c^hiMHCII^lo) dendritic cells (DCs). IL-4 synergized with DG172 to shift the differentiation from MHCII^lo cells to mature DCs in vitro. The promotion of DC differentiation occurred at the expense of differentiation to granulocytic Gr1⁺Ly6B⁺ cells. In agreement with these findings, transcriptome analyses showed a strong DG172-mediated repression of genes encoding neutrophilic markers in both differentiating wild-type and Ppard null cells, while macrophage/DC marker genes were up-regulated. DG172 also inhibited the expression of transcription factors driving granulocytic differentiation (Cebpe, Gfi1, and Klf5), and increased the levels of transcription factors promoting macrophage/DC differentiation (Irf4, Irf8, Spib, and Spic). DG172 exerted these effects only at an early stage of BMC differentiation induced by GM-CSF, did not affect macrophage-colony-stimulating factor–triggered differentiation to macrophages and had no detectable PPARβ/δ-independent effect on other cell types tested. Structure-function analyses demonstrated that the 4-methylpiperazine moiety in DG172 is required for its effect on DC differentiation, but is dispensable for PPARβ/δ binding. Based on these data we developed a new compound, (Z)-2-(4-chlorophenyl)-3-[4-(4-methylpiperazine-1-yl)phenyl]acrylonitrile (DG228), which enhances DC differentiation in the absence of significant PPARβ/δ binding.