Neutrophil extracellular traps promote M1 macrophage polarization in gouty inflammation via targeting hexokinase-2.

Peptidylarginine deiminase 4 (PAD4)-dependent neutrophil extracellular trap (NET) formation is a new neutrophil death mechanism. Increased NET formation has been demonstrated to be associated with gouty inflammation. Macrophages release proinflammatory mediators and chemokines in acute gouty inflammation and subsequently lead to inflammatory cascades. However, whether NETs regulate macrophage function and polarization and further contribute to gout development remains unclear. Herein, we investigated the relationship between monosodium urate (MSU) crystal-induced NETs and macrophages and the associated mechanisms in gouty inflammation. Elevated NET formation and CD86 macrophage infiltration were observed in human gouty arthritis (GA). In vitro, MSU crystal-induced NETs or NET-associated histone H3 treatments modulated nod-like receptor protein 3 (NLRP3) inflammasome activation, M1 polarization, and metabolic changes in macrophages. These effects were eliminated by hexokinase-2 (HK-2) silencing. Moreover, NET formation and inflammation were significantly reduced in PAD4-/- GA mice. Pharmacological inhibition of NET formation with Cl-Amidine or NET degradation with DNase Ⅰ significantly reduced M1 polarization of macrophages and ameliorated inflammation in GA mice. In sum, MSU crystal-induced NETs promote M1 polarization and NLRP3 activation in macrophages via targeting HK-2. Cell-free DNA and histone H3 may be the driving elements behind the NET-induced M1 macrophage polarization, NLRP3 activation, and metabolic changes. Targeting NETs could be a potential therapeutic strategy for gout flare.