Open AccessSynergistic induction of matrix metalloproteinase 1 by interleukin‐1α and oncostatin M in human chondrocytes involves signal transducer and activator of transcription and activator protein 1 transcription factors via a novel mechanism
Author(s) -
Catterall J. B.,
Carrère S.,
Koshy P. J. T.,
Degnan B. A.,
Shingleton W. D.,
Brinckerhoff C. E.,
Rutter J.,
Cawston T. E.,
Rowan A. D.
Publication year - 2001
Publication title -
arthritis & rheumatism
Language(s) - English
Resource type - Journals
eISSN - 1529-0131
pISSN - 0004-3591
DOI - 10.1002/1529-0131(200110)44:10<2296::aid-art392>3.0.co;2-9
Subject(s) - oncostatin m , stat protein , microbiology and biotechnology , luciferase , transcription factor , activator (genetics) , signal transduction , biology , electrophoretic mobility shift assay , chemistry , receptor , cytokine , stat3 , interleukin 6 , transfection , gene , biochemistry , immunology
Objective To investigate the mechanism of interleukin‐1α (IL‐1α) and oncostatin M (OSM) synergistic regulation of matrix metalloproteinase 1 (MMP‐1) in human chondrocytes. Methods Using an immortalized human chondrocyte cell line (T/C28a4), we investigated regulation of the MMP‐1 gene. Northern blotting and flow cytometric analysis were used to assess changes in receptor, MMP‐1, and c‐ fos expression. Transient transfections using MMP‐1 promoter/luciferase constructs, electrophoretic mobility shift assay, and site‐directed mutagenesis were used to investigate MMP‐1 promoter activation. Results We found no alteration in the expression of receptors used by these cytokines after stimulation with IL‐1α/OSM. Using MMP‐1 promoter/luciferase reporter constructs, we found that the proximal (−517/+63) region of the MMP‐1 promoter was sufficient to support a synergistic activation. A role for activated signal transducers and activators of transcription (STAT‐3) was demonstrated, although no binding of STAT‐3 to the MMP‐1 promoter was found. However, constitutive binding of activator protein 1 (AP‐1) was detected, and changes in c‐ fos expression could modulate promoter activity. Conclusion Since no changes in receptor expression were observed, receptor modulation cannot account for the IL‐1α/OSM synergy observed. Instead, the interplay of various intracellular signaling pathways is a more likely explanation. STAT activation is required, but STAT proteins do not interact directly with the MMP‐1 promoter. We propose that activated STATs stimulate c‐ fos expression, and changes in expression of the AP‐1 components regulate MMP‐1 expression. We highlight a new mechanism for MMP‐1 regulation in human chondrocytes that could provide potential new therapeutic targets.