Abstract: Objectives To clarify whether NLRP3 inflammasome can modulate macrophage phagocytic capacity towards red blood cells (RBCs) and regulate macrophage subtype polarization. Methods THP-1 cells with low expression of NLRP3 (ID3 THP-1), cells transfected with an empty vector (shNC THP-1), and wild-type THP-1 cells were used as macrophage models. These cells were incubated with untreated RBCs, water bath-aged RBCs, and IgG-opsonized RBCs, respectively. Flow cytometry was used to detect the phagocytic rate of THP-1 cells to different RBC types and to measure the expression of M1 subtype markers (CD16 and CD86), and M2 subtype markers (CD163 and CD206) on THP-1 cells. Results ID3 THP-1 with reduced NLRP3 expression exhibited significantly downregulated phagocytic capacity towards RBCs. Aged RBCs induced the differentiation of THP-1 cells into the M1 subclass while inhibiting their differentiation into the M2 subclass. Decreased expression of the NLRP3 inflammasome in THP-1 cells led to a downregulation of their ability to differentiate into the M1 subclass following RBC phagocytosis, accompanied by their enhanced capacity to differentiate into the M2 subclass. Conclusion NLRP3 inflammasome can serve as a pivotal regulatory target, governing macrophage phagocytosis of RBCs and their subsequent subclass differentiation.

Key words: Macrophage, Aged RBCs, Phagocytosis, Macrophage polarization