Exuberant expression of chemokine genes by adult human articular chondrocytes in response to IL-1β

SummaryObjectiveTo provide a more complete picture of the effect of interleukin-1 beta (IL-1β) on adult human articular chondrocyte gene expression, in contrast to the candidate gene approach.DesignChondrocytes from human knee cartilage were cultured in medium containing IL-1β. Changes in gene expression were analyzed by microarray and reverse transcriptase-polymerase chain reaction analysis. The ability of transforming growth factor beta-1 (TGF-β1), fibroblast growth factor (FGF)-18, and bone morphogenetic protein 2 (BMP-2) to alter the effects of IL-1β was analyzed. Computational analysis of the promoter regions of differentially expressed genes for transcription factor binding motifs was performed.ResultsIL-1β-treated human chondrocytes showed significant increases in the expression of granulocyte colony stimulating factor-3, endothelial leukocyte adhesion molecule 1 and leukemia inhibitory factor as well as for a large group of chemokines that include CXCL1, CXCL2, CXCL3, CXCL5, CXCL6, CXCL8, CCL2, CCL3, CCL4, CCL5, CCL8, CCL20, CCL3L1, CX3CL1 and the cytokine IL-6. As expected, the mRNA for matrix metalloproteinase (MMP)-13 and BMP-2 also increased while mRNA for the matrix genes COL2A1 and aggrecan was down-regulated. A subset of chemokines increased rapidly at very low levels of IL-1β. The phenotype induced by IL-1β was partially reversed by TGF-β1, but not by BMP-2. In the presence of IL-1β, FGF-18 increased expression of ADAMTS-4, aggrecan, BMP-2, COL2A1, CCL3, CCL4, CCL20, CXCL1, CXCL3, CXCL6, IL-1β, IL-6, and IL-8 and decreased ADAMTS-5, MMP-13, CCL2, and CCL8. Computational analysis revealed a high likelihood that the most up-regulated chemokines are regulated by the transcription factors myocyte enhancer binding factor-3 (MEF-3), CCAAT/enhancer binding protein (C/EBP) and nuclear factor-kappa B (NF-κB).ConclusionIL-1β has a diverse effect on gene expression profile in human chondrocytes affecting matrix genes as well as chemokines and cytokines. TGF-β1 has the ability to antagonize some of the phenotype induced by IL-1β