MicroRNA 21 is a homeostatic regulator of macrophage polarization and prevents prostaglandin E2-mediated M2 generation.

Wang Z, Brandt S, Medeiros A, Wang S, Wu H, Dent A, Serezani CH
PLoS One. 2015 10 (2): e0115855

PMID: 25706647 · PMCID: PMC4338261 · DOI:10.1371/journal.pone.0115855

Macrophages dictate both initiation and resolution of inflammation. During acute inflammation classically activated macrophages (M1) predominate, and during the resolution phase alternative macrophages (M2) are dominant. The molecular mechanisms involved in macrophage polarization are understudied. MicroRNAs are differentially expressed in M1 and M2 macrophages that influence macrophage polarization. We identified a role of miR-21 in macrophage polarization, and found that cross-talk between miR-21 and the lipid mediator prostaglandin E2 (PGE2) is a determining factor in macrophage polarization. miR-21 inhibition impairs expression of M2 signature genes but not M1 genes. PGE2 and its downstream effectors PKA and Epac inhibit miR-21 expression and enhance expression of M2 genes, and this effect is more pronounced in miR-21-/- cells. Among potential targets involved in macrophage polarization, we found that STAT3 and SOCS1 were enhanced in miR-21-/- cells and further enhanced by PGE2. We found that STAT3 was a direct target of miR-21 in macrophages. Silencing the STAT3 gene abolished PGE2-mediated expression of M2 genes in miR-21-/- macrophages. These data shed light on the molecular brakes involved in homeostatic macrophage polarization and suggest new therapeutic strategies to prevent inflammatory responses.

MeSH Terms (17)

Acetylcysteine Animals Cell Polarity Cyclic AMP-Dependent Protein Kinases Dinoprostone Erythromycin Female Gene Silencing Homeostasis Macrophage Activation Macrophages Mice Mice, Knockout MicroRNAs STAT3 Transcription Factor Suppressor of Cytokine Signaling 1 Protein Suppressor of Cytokine Signaling Proteins

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