Abstract
Introduction The efficient clearance of bacteria by macrophages is crucial for the timely resolution of inflammation. In this study, we investigated the role of microRNA-21 (miR-21)-induced phagocytosis and its intracellular signaling pathways in human macrophages in vitro. Methods Human peripheral blood mononuclear cells (PBMCs) were isolated from whole blood collected from 15 healthy volunteers. Differentiated human macrophages were incubated with lipopolysaccharide (LPS) to determine the time course of changes in phagocytic activity and miR-21 expression. The expression of candidate genes targeted by miR-21 and its downstream effectors was quantitatively assessed. The effects of miR-21 modulation were also examined via transfection with miR-21 mimics and inhibitors. Results Incubation of human macrophages with LPS upregulated both phagocytosis and miR-21 expression. Notably, changing miR-21 expression levels using miR-21 mimics or inhibitors led to significant and opposite changes in the expression of its downstream effectors. miR-21 induction in macrophages downregulated PDCD4 and PTEN, promoted the phosphorylation of Akt and the production of the anti-inflammatory cytokine IL-10, and facilitated phagocytosis. Conclusion This study directly confirms that LPS upregulates macrophage phagocytosis and miR-21 expression. Elevated miR-21 levels in macrophages enhanced phagocytosis, contributing to an anti-inflammatory phenotype. These findings underscore the importance of miR-21 in resolving inflammation.