The role of MicroRNAs miR-200b and miR-200c in TLR4 signaling and NF-κB activation

• Published in: Innate immunity (London, England) Vol. 18; no. 6; pp. 846 - 855
• Main Authors: Wendlandt, Erik B, Graff, Joel W, Gioannini, Theresa L, McCaffrey, Anton P, Wilson, Mary E
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01.12.2012
• Subjects: adaptor proteins; Chemokine CXCL9 - genetics; Chemokine CXCL9 - metabolism; Cytokines; Data processing; Down-Regulation; HEK293 Cells; Host-Pathogen Interactions; Humans; Immunity, Innate - genetics; Inflammation; Interleukin 6; Interleukin-6 - genetics; Interleukin-6 - metabolism; Intracellular signalling; IRAK protein; Lipopolysaccharides - immunology; MicroRNAs - genetics; MicroRNAs - metabolism; miRNA; Monocytes; Monocytes - immunology; MyD88 protein; Myeloid Differentiation Factor 88 - genetics; Myeloid Differentiation Factor 88 - metabolism; NF- Kappa B protein; NF-kappa B - genetics; NF-kappa B - metabolism; Pathogens; Plasmids; Signal transduction; Signal Transduction - genetics; Signal Transduction - immunology; TLR4 protein; Toll-Like Receptor 4 - agonists; Toll-Like Receptor 4 - genetics; Toll-Like Receptor 4 - metabolism; Toll-like receptors; Transcriptional Activation - genetics; Transfection; Transgenes - genetics; Tumor necrosis factor- alpha; Tumor Necrosis Factor-alpha - genetics; Tumor Necrosis Factor-alpha - metabolism; microRNAs; pro-inflammatory response; Toll-like receptor; gene expression; Macrophage
• ISSN: 1753-4259; 1753-4267
• DOI: 10.1177/1753425912443903

Recognition of microbial products by members of the Toll-like receptor (TLR) family initiates intracellular signaling cascades that result in NF-κB activation and subsequent production of inflammatory cytokines. We explored the potential roles of microRNAs (miRNAs) in regulating TLR pathways. A target analysis approach to the TLR4 pathway adaptor molecules identified several putative targets of miR-200a, miR-200b and miR-200c. miRNA mimics were co-transfected with a NF-κB activity reporter plasmid into HEK293 cells stably expressing TLR4 (HEK293-TLR4). Mimics of both miR-200b and miR-200c, but not miR-200a, decreased NF-κB reporter activity in either untreated cells or in cells treated with endotoxin:MD2 as a TLR4 agonist. Transfection of HEK293-TLR4 cells with miR-200b or miR-200c significantly decreased expression of MyD88, whereas TLR4, IRAK-1 and TRAF-6 mRNAs were unaffected. When miR-200b or miR-200c mimics were transfected into the differentiated monocytic THP-1 cell line, the abundance of MyD88 transcripts, as well as LPS-induced expression of the pro-inflammatory molecules IL-6, CXCL9 and TNF-α were diminished. These data define miRNAs miR-200b and miR-200c as factors that modify the efficiency of TLR4 signaling through the MyD88-dependent pathway and can thus affect host innate defenses against microbial pathogens.