Identifying Functional MicroRNAs in Macrophages with Polarized Phenotypes

• Published in: The Journal of biological chemistry 2012-06, Vol.287 (26), p.21816-21825
• Main Authors: Graff, Joel W., Dickson, Anne M., Clay, Gwendolyn, McCaffrey, Anton P., Wilson, Mary E.
• Format: Article
• Language: English
• Subjects: Activation; Cell Differentiation; Cell Line, Tumor; Chemokines; Chemokines - metabolism; Cytokine; Cytokines - metabolism; Gene Expression; Gene Expression Regulation, Neoplastic; HEK293 Cells; Humans; Immunology; Inflammation; Interferon-gamma - metabolism; Leukocytes - cytology; Lipopolysaccharide (LPS); Lipopolysaccharides - metabolism; Macrophages; Macrophages - cytology; Macrophages - metabolism; MicroRNA; MicroRNAs - metabolism; Monocytes - metabolism; Phenotype
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M111.327031

Macrophages respond to external stimuli with rapid changes in expression of many genes. Different combinations of external stimuli lead to distinct polarized activation patterns, resulting in a spectrum of possible macrophage activation phenotypes. MicroRNAs (miRNAs) are small, noncoding RNAs that can repress the expression of many target genes. We hypothesized that miRNAs play a role in macrophage polarization. miRNA expression profiles were determined in monocyte-derived macrophages (MDMs) incubated in conditions causing activation toward M1, M2a, M2b, or M2c phenotypes. One miRNA guide strand and seven miRNA passenger strands were significantly altered. Changes were confirmed in MDMs from six separate donors. The amplitude of miRNA expression changes in MDMs was smaller than described studies of monocytes responding to inflammatory stimuli. Further investigation revealed this correlated with higher basal miRNA expression in MDMs compared with monocytes. The regulation of M1- and M2b-responsive miRNAs (miR-27a, miR-29b, miR-125a, miR-146a, miR-155, and miR-222) was similar in differentiated THP-1 cells and primary MDMs. Studies in this model revealed cross-talk between IFNγ- and LPS-associated pathways regulating miRNA expression. Furthermore, expression of M1-associated transcripts was increased in THP-1 cells transfected with mimics of miR-29b, miR-125a-5p, or miR-155. The apparent inflammatory property of miR-29b and miR-125a-5p can be at least partially explained by repression of TNFAIP3, a negative regulator of NF-κB signaling. Overall, these data suggest miRNAs can contribute to changes in macrophage gene expression that occur in different exogenous activating conditions. Macrophages that respond to external stimuli assume a spectrum of activation states. Expression of several miRNAs was altered significantly in different macrophage activation states. Functional activities on cytokine/chemokine expression were shown. miRNAs influenced macrophage differentiation toward distinct activation patterns. Profiling miRNA guide and passenger strands can reveal miRNA changes in differentiated cells responding to acute stimuli.