Synergistic induction of matrix metalloproteinase 1 by interleukin-1alpha and oncostatin M in human chondrocytes involves signal transducer and activator of transcription and activator protein 1 transcription factors via a novel mechanism.
OBJECTIVE
To investigate the mechanism of interleukin-1alpha (IL-1alpha) 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-1alpha/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.


CONCLUSIONS
Since no changes in receptor expression were observed, receptor modulation cannot account for the IL-1alpha/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.
Catterall
J B
JB
Department of Rheumatology, School of Clinical Medical Sciences, The Medical School, University of Newcastle upon Tyne, UK. J.B.Catterall@ncl.ac.uk
Carrère
S
S
Koshy
P J
PJ
Degnan
B A
BA
Shingleton
W D
WD
Brinckerhoff
C E
CE
Rutter
J
J
Cawston
T E
TE
Rowan
A D
AD
D002461:Cell Line, Transformed; D019902:Chondrocytes / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000502:physiology; D004357:Drug Synergism; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D020781:Matrix Metalloproteinase 1 / Q000502:physiology*; D053683:Oncostatin M; D010455:Peptides / Q000494:pharmacology*; D016760:Proto-Oncogene Proteins c-fos / Q000502:physiology; D050796:STAT3 Transcription Factor; D015398:Signal Transduction / Q000187:drug effects; D015534:Trans-Activators / Q000502:physiology; D018808:Transcription Factor AP-1 / Q000502:physiology
D004268:DNA-Binding Proteins; D007375:Interleukin-1; C508351:OSM protein, human; D010455:Peptides; D016760:Proto-Oncogene Proteins c-fos; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D018808:Transcription Factor AP-1; D053683:Oncostatin M; D020781:Matrix Metalloproteinase 1