TLR4 induced Wnt3a-Dvl3 restrains the intensity of inflammation and protects against endotoxin-driven organ failure through GSK3ß/ß-catenin signaling.

ABSTRACT

BACKGROUND: Accumulating evidence suggests a regulatory role of Wnt proteins in innate immune responses. However, the effects of Wnt3a signaling on TLR4-mediated inflammatory responses are controversial and the signaling crosstalk between TLR4 and Wnt3a remains uncertain. METHODS: Gain- and Loss- of function approaches were utilized to determine the function of Wnt3a signaling in TLR4-mediated inflammatory responses. Cytokine production at protein and mRNA levels and phosphorylation of signaling molecules were measured by ELISA, qRT-PCR, and Western Blot, respectively. Endotoxemia mouse model was employed to assess the effect of Wnt3a on systemic inflammatory cytokine levels and neutrophil infiltration. RESULTS: LPS stimulation leads to an increase of Wnt3a expression and its downstream molecule, Dvl3, in primary monocytes. Inhibition or silence of Wnt3a or Dvl3 significantly increases the production of pro-inflammatory cytokines (IL-12, IL-6, TNFα), robustly reduces ß-catenin accumulation, and enhances the phosphorylation of NF-κB P65 and its DNA binding activity. These results were confirmed by multiple gain- and loss- of function approaches including specific siRNA and ectopic expression of Dvl3, GSK3ß, and ß-catenin in monocytes. Moreover, in vivo relevance was established in a murine endotoxin model, in which Wnt3a inhibition enhances the inflammatory responses by augmenting the systemic pro-inflammatory cytokine levels and neutrophil infiltration. CONCLUSIONS: TLR4 activation promotes Wnt3a-Dvl3 signaling, which acts as rheostats to restrain the intensity of inflammation through regulating GSK3ß-ß-catenin signaling and NF-κB activity. GENERAL SIGNIFICANCE: Wnt3a-Dvl3-ß-catenin signaling axis could be a potential interventional target for manipulating the direction and intensity of inflammatory responses.