MEK/ERK and signal transducer and activator of transcription signaling pathways modulate oncostatin M-stimulated CCL2 expression in human osteoblasts through a common transcription factor.
OBJECTIVE
To analyze the effects of oncostatin M (OSM), a gp130-type cytokine, on CCL2 expression in MG-63 cells, a human osteosarcoma cell line with a characteristic osteoblastic phenotype, and to investigate the signaling pathway involved.


METHODS
The expression of messenger RNA (mRNA) for CCL2 and c-Fos was analyzed by Northern blotting. Amounts of CCL2 released into the supernatant were measured by enzyme-linked immunosorbent assay. Western blotting was used to examine the activation of MAPK signaling pathways. Interactions between activator protein 1 (AP-1) and DNA were evaluated by electrophoretic mobility shift assay.


RESULTS
OSM stimulated CCL2 expression at both the mRNA and the protein levels. Cyclooxygenase 2 (COX-2) was also induced by OSM. However, the up-regulation of CCL2 mRNA was COX-2-independent but required tyrosine kinase and protein kinase C (PKC). OSM stimulated the phosphorylation of MEK-1/2 and ERK-1/2 but not p38 and JNK. A transient elevation of c-Fos mRNA was induced by OSM, but PD 98059 (MEK inhibitor), fludarabine (signal transducer and activator of transcription 1 [STAT-1] inhibitor), and piceatannol (STAT-3 and STAT-5 inhibitor) abolished this effect. Electrophoretic mobility shift assay revealed that OSM stimulated AP-1-DNA binding, which was also abolished by PD 98059, fludarabine, and piceatannol. Supershift study further confirmed the role of c-Fos in the above interaction. PD 98059, fludarabine, piceatannol, and curcumin (AP-1 inhibitor) inhibited the OSM-induced expression of CCL2.


CONCLUSIONS
OSM induces CCL-2 expression in osteoblasts. Activation of the MEK/ERK and STAT pathways, which leads to c-Fos expression and AP-1-DNA binding, is involved in the process. The signaling requires tyrosine kinase and PKC but not COX-2.
Lin
Sze-Kwan
SK
National Taiwan University Hospital, Taipei, Taiwan.
Kok
Sang-Heng
SH
Yeh
Flora Tzu-Chin
FT
Kuo
Mark Yen-Ping
MY
Lin
Ching-Chuan
CC
Wang
Chih-Chiang
CC
Goldring
Steven R
SR
Hong
Chi-Yuan
CY
D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000378:metabolism*; D051546:Cyclooxygenase 2; D004247:DNA / Q000502:physiology; D004268:DNA-Binding Proteins / Q000502:physiology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D008565:Membrane Proteins; D008894:Milk Proteins; D020929:Mitogen-Activated Protein Kinase Kinases / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D053683:Oncostatin M; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D047428:Protein Kinase Inhibitors; D050794:STAT1 Transcription Factor; D050796:STAT3 Transcription Factor; D050799:STAT5 Transcription Factor; D015398:Signal Transduction / Q000502:physiology*; D015534:Trans-Activators / Q000502:physiology*; D018808:Transcription Factor AP-1 / Q000502:physiology; D014157:Transcription Factors / Q000502:physiology
D018932:Chemokine CCL2; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D007527:Isoenzymes; D008565:Membrane Proteins; D008894:Milk Proteins; C508351:OSM protein, human; D010455:Peptides; D047428:Protein Kinase Inhibitors; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D018808:Transcription Factor AP-1; D014157:Transcription Factors; D053683:Oncostatin M; D004247:DNA; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D020928:Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases