title: Regulation of TLR2-mediated tolerance and cross-tolerance through IRAK4 modulation by miR-132 and miR-212.
abstract: Innate immune response is the first defense against pathogens via recognition by various conserved pattern recognition receptors, such as TLRs, to initiate a rapid and strong cytokine alarm. TLR signaling-mediated cytokine production must be properly regulated to prevent pathological conditions deriving from overproduction of cytokines. In this study, the role of specific microRNAs in TLR-signaling pathway was investigated to reveal the cross-interaction and -regulation in the MyD88 pathway. In peptidoglycan (PGN)/TLR2-stimulated THP-1 monocytes, PBMCs, and primary macrophages showed rapid and dramatic miR-132 and miR-212 (miR-132/-212) upregulation. This newly identified response appeared earlier in time than the characteristic miR-146a response in LPS-TLR4 stimulation. The rapid induction of miR-132/-212 was transcription factor CREB dependent, and the sustained expression of miR-132/-212 was responsible for inducing tolerance to subsequent PGN challenge. Cross-tolerance was observed by TLR5 ligand flagellin and heat-killed or live bacteria resulting from miR-132/-212 upregulation. Mechanistically, IRAK4 was identified and validated as a target of miR-132/-212 by luciferase reporter assay and seed-sequence mutagenesis of the reporter. Transfection of miR-132 or miR-212 alone mimicked PGN tolerance in monocytes, whereas transfected specific miRNA inhibitors tampered the tolerance effect. During bacterial infection, PGN-mediated TLR2 signaling induces miR-132/-212 to downregulate IRAK4, an early component in the MyD88-dependent pathway, whereas LPS/TLR4-induced miR-146a downregulates downstream components of the same MyD88-dependent pathway. The identification of miR-132/-212 and miR-146a together to prevent damaging consequences from the overproduction of proinflammatory cytokines by targeting a common signaling pathway is significant and will provide insights into future design and development of therapeutics.
authors.affiliation: Department of Oral Biology, University of Florida, Gainesville, FL 32610, USA.
authors.forename: Md A
authors.initials: MA
authors.lastname: Nahid
authors.forename: Bing
authors.initials: B
authors.lastname: Yao
authors.forename: Paul R
authors.initials: PR
authors.lastname: Dominguez-Gutierrez
authors.forename: Lakshmyya
authors.initials: L
authors.lastname: Kesavalu
authors.forename: Minoru
authors.initials: M
authors.lastname: Satoh
authors.forename: Edward K L
authors.initials: EK
authors.lastname: Chan
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000276:immunology; D002478:Cells, Cultured / Q000276:immunology; D017362:Cyclic AMP Response Element-Binding Protein / Q000276:immunology; D005260:Female; D005408:Flagellin / Q000276:immunology / Q000494:pharmacology; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D007108:Immune Tolerance / Q000276:immunology*; D053592:Interleukin-1 Receptor-Associated Kinases / Q000276:immunology*; D008070:Lipopolysaccharides / Q000276:immunology; D008074:Lipoproteins / Q000494:pharmacology; D008262:Macrophage Activation; D017737:Macrophages, Peritoneal / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D035683:MicroRNAs / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000276:immunology*; D009000:Monocytes / Q000276:immunology*; D053594:Myeloid Differentiation Factor 88 / Q000276:immunology; D010457:Peptidoglycan / Q000276:immunology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction / Q000276:immunology*; D051195:Toll-Like Receptor 2 / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; C115163:CREB1 protein, human; C492004:Creb1 protein, mouse; D017362:Cyclic AMP Response Element-Binding Protein; D008070:Lipopolysaccharides; D008074:Lipoproteins; C547077:MIRN132 microRNA, human; C546976:MIRN132 microRNA, mouse; C551411:MIRN212 microRNA, human; C554518:MIRN212 microRNA, mouse; C507779:MYD88 protein, human; D035683:MicroRNAs; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; D010457:Peptidoglycan; D034741:RNA, Small Interfering; C495342:TLR2 protein, human; C493486:Tlr2 protein, mouse; D051195:Toll-Like Receptor 2; D014409:Tumor Necrosis Factor-alpha; D005408:Flagellin; C507773:IRAK4 protein, human; D053592:Interleukin-1 Receptor-Associated Kinases; C507774:Irak4 protein, mouse