HMGB1 Facilitated Macrophage Reprogramming towards a Proinflammatory M1-like Phenotype in Experimental Autoimmune Myocarditis Development

Macrophages can be reprogramming, such as the classical activated macrophage, M1 or alternative activated macrophages, M2 phenotype following the milieu danger signals, especially inflammatory factors. Macrophage reprogramming is now considered as a key determinant of disease development and/or regression. Experimental autoimmune myocarditis (EAM) is characterized by monocytes/macrophage infiltration, Th17 cells activation and inflammatory factors producing such as high mobility group box 1 (HMGB1). Whether infiltrated macrophages could be reprogramming in EAM? HMGB1 was associated with macrophage reprogramming? Our results clearly demonstrated that infiltrated macrophage was reprogrammed towards a proinflammatory M1-like phenotype and cardiac protection by monocytes/macrophages depletion or HMGB1 blockade in EAM; in vitro, HMGB1 facilitated macrophage reprogramming towards M1-like phenotype dependent on TLR4-PI3Kγ-Erk1/2 pathway; furthermore, the reprogramming M1-like macrophage promoted Th17 expansion. Therefore, we speculated that HMGB1 contributed EAM development via facilitating macrophage reprogramming towards M1-like phenotype except for directly modulating Th17 cells expansion.