IRF5 and IRF5 Disease-Risk Variants Increase Glycolysis and Human M1 Macrophage Polarization by Regulating Proximal Signaling and Akt2 Activation.

Interferon regulatory factor 5 (IRF5) regulates inflammatory M1 macrophage polarization, and disease-associated IRF5 genetic variants regulate pattern-recognition-receptor (PRR)-induced cytokines. PRR-stimulated macrophages and M1 macrophages exhibit enhanced glycolysis, a central mediator of inflammation. We find that IRF5 is needed for PRR-enhanced glycolysis in human macrophages and in mice in vivo. Upon stimulation of the PRR nucleotide binding oligomerization domain containing 2 (NOD2) in human macrophages, IRF5 binds RIP2, IRAK1, and TRAF6. IRF5, in turn, is required for optimal Akt2 activation, which increases expression of glycolytic pathway genes and HIF1A as well as pro-inflammatory cytokines and M1 polarization. Furthermore, pro-inflammatory cytokines and glycolytic pathways co-regulate each other. Rs2004640/rs2280714 TT/TT IRF5 disease-risk-carrier cells demonstrate increased IRF5 expression and increased PRR-induced Akt2 activation, glycolysis, pro-inflammatory cytokines, and M1 polarization relative to GG/CC carrier macrophages. Our findings identify that IRF5 disease-associated polymorphisms regulate diverse immunological and metabolic outcomes and provide further insight into mechanisms contributing to the increasingly recognized important role for glycolysis in inflammation.