MyD88, IRAK1 and TRAF6 knockdown in human chondrocytes inhibits interleukin-1-induced matrix metalloproteinase-13 gene expression and promoter activity by impairing MAP kinase activation.
Interleukin-1 (IL-1) is the major prototypic proinflammatory cytokine that stimulates degradation of cartilage in arthritis by inducing prominent collagen II-degrading matrix metalloproteinase-13 (MMP-13). Nothing is known about the involvement of adaptor proteins, MyD88, IRAK1 and TRAF6 in MMP-13 regulation. Here we investigated for the first time the role of these proteins in IL-1-regulated MMP-13 expression in chondrocytes. MyD88 homodimerization inhibitory peptide diminished the expression of MMP-13 gene, promoter activity, phosphorylation of mitogen-activated protein kinases (MAPKs), c-Jun and activating protein 1 (AP-1) activity. Knockdown of MyD88, IRAK1 and TRAF6 by RNA interference (RNAi) drastically down-regulated the expression of IL-1-induced MMP-13 mRNA and protein levels and MMP-13 promoter-driven luciferase activity. Non-specific control siRNA had no effect. Mechanisms of MMP-13 inhibition involved reduced phosphorylation of ERK, p38, JNK and c-Jun as well as AP-1 transcription factor binding activity. The genetic evidence presented here demonstrates that MyD88, IRAK1 and TRAF6 proteins are crucial early mediators for the IL-1-induced MMP-13 regulation through MAPK pathways and AP-1 activity. These proteins could constitute important therapeutic targets for arthritis-associated cartilage loss by MMP-13.
Ahmad
Rasheed
R
Department of Medicine, University of Montreal and Research Centre of CHUM Notre-Dame Hospital, Montreal, Quebec, Canada H2L 4M1.
Sylvester
Judith
J
Zafarullah
Muhammad
M
D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D019281:Dimerization; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D053592:Interleukin-1 Receptor-Associated Kinases / Q000235:genetics / Q000378:metabolism*; D053583:Interleukin-1beta / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D020935:MAP Kinase Signaling System; D053509:Matrix Metalloproteinase 13 / Q000235:genetics / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D053594:Myeloid Differentiation Factor 88 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000187:drug effects; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D048029:TNF Receptor-Associated Factor 6 / Q000235:genetics / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D053583:Interleukin-1beta; C507779:MYD88 protein, human; D053594:Myeloid Differentiation Factor 88; D010455:Peptides; D016755:Proto-Oncogene Proteins c-jun; D034741:RNA, Small Interfering; D048029:TNF Receptor-Associated Factor 6; D018808:Transcription Factor AP-1; C507768:IRAK1 protein, human; D053592:Interleukin-1 Receptor-Associated Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D053509:Matrix Metalloproteinase 13