The production of chemokine stromal cell-derived factor(SDF)-1 is significantly higher in synovial fluid of patients with osteoarthritis and rheumatoid arthritis. Matrix metalloproteinase (MMP)-13 may contribute to the breakdown of articular cartilage during arthritis.
Here, we found that SDF-1α increased the secretion of MMP-13 in cultured human chondrocytes, as shown by reverse transcriptase-polymerase chain reaction, Western blot, and zymographic analysis. SDF-1α also increased the surface expression of CXCR4 receptor in human chondrocytes. CXCR4-neutralizing antibody, CXCR4-specific inhibitor[1-[[4-(1,4,8,11-tetrazacyclotetradec-1-ylmethyl) phenyl]methyl]-1,4,8,11-tetrazacyclotetradecane (AMD3100)], orsmall interfering RNA against CXCR4 inhibited the SDF-1α-induced increase of MMP-13 expression.
The transcriptional regulation of MMP-13 by SDF-1α was mediated by phosphorylation of extracellular signal-regulated kinases (ERK) and activation of the activator protein (AP)-1 components of c-Fos and c-Jun. The binding of c-Fos and c-Jun to the activator protein(AP-1) element on the MMP-13 promoter and the increase in luciferase activity was enhanced by SDF-1α. Cotransfection with dominant-negative mutant of ERK2 or c-Fos and c-Jun antisense oligonucleotide inhibited the potentiating action of SDF-1α on MMP-13 promoter activity.
Taken together, our results provide evidence that SDF-1α acts through CXCR4 to activate ERK and the downstream transcription factors (c-Fos and c-Jun), resulting in the activation of AP-1 on the MMP-13 promoter and contributing cartilage destruction during arthritis.
