Dickkopf1 is a novel endogenous ligand for priming NLRP3 inflammasome in macrophages via TLR4

Dickkopf1 (DKK1) is a quintessential Wnt antagonist and immunomodulator in various inflammatory diseases. The underlying molecular mechanisms of DKK1-mediated immunomodulation remain elusive. Here, we identified TLR4 as a new receptor for DKK1, activating NFκB-mediated gene expression. Subsequently, this event resulted in pyroptosis via the NLRP3 inflammasome in human and mouse macrophages. DKK1 employed TLR4 to initiate the NFκB signaling cascade via MyD88. Activation of the MyD88-TAK1-NFκΒ pathway by DKK1 increased the expression of HIF1α, NFκB, and NLRP3 proteins. Unlike LPS, DKK1 did not induce IRAK4 phosphorylation, while the interaction between MyD88 and IRAK4 was maintained for downstream signaling activation. DKK1 did not induce IRF3 phosphorylation in the nucleus and failed to induce IFNB gene expression, indicating that LPS signaling is differentially regulated. DKK1 primed macrophages via TLR4-MyD88, resulting in NFκB pathway activation that mediates NLRP3 inflammasome-mediated pyroptosis via caspase-1 and gasdermin D maturation with various NLRP3 inflammasome activators, including nigericin. Our results demonstrated that DKK1 is a novel endogenous priming ligand that differentially augments the NFκB pathway activation via TLR4 and primes mouse and human macrophages for NLRP3 inflammasome activation.