Abstract | OBJECTIVE: METHODS: Bovine articular chondrocytes were stimulated with sphingomyelinase (SMase) to increase levels of endogenous ceramide. Components of the ERK pathway were inhibited by Raf-1 kinase inhibitor and the MEK inhibitor, PD98059. Cell extracts were analyzed by Western blotting for ERK-1/2, SOX9, c-Fos, and type II collagen, and the level of c-fos messenger RNA ( mRNA) was analyzed by quantitative polymerase chain reaction. Localization of ERK-1/2, SOX9, and c-Fos was assessed by immunocytochemistry and confocal microscopy. RESULTS: SMase treatment of chondrocytes caused sustained phosphorylation of ERK-1/2 throughout the cytoplasm and nucleus that was reduced by inhibitors of Raf-1 kinase and MEK-1/2. SMase treatment of chondrocytes also induced translocation of c-Fos to the nucleus and phospho-SOX9 to the cytoplasm and increased expression of c-fos mRNA. Type II collagen expression, which was down-regulated by SMase treatment, was restored by the MEK-1/2 inhibitor, PD98059. CONCLUSION: SMase down-regulates type II collagen in articular chondrocytes via activation of the ERK signaling cascade, redistribution of SOX9, and recruitment of c-Fos. This new mechanism for cartilage degradation provides potential targets for future treatment of arthritic disease.
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Authors | S J Gilbert, E J Blain, V C Duance, D J Mason |
Journal | Arthritis and rheumatism
(Arthritis Rheum)
Vol. 58
Issue 1
Pg. 209-20
(Jan 2008)
ISSN: 0004-3591 [Print] United States |
PMID | 18163502
(Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
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Chemical References |
- Collagen Type II
- Culture Media
- High Mobility Group Proteins
- Proto-Oncogene Proteins c-fos
- RNA, Messenger
- SOX9 Transcription Factor
- Transcription Factors
- Proto-Oncogene Proteins c-raf
- Mitogen-Activated Protein Kinase 1
- Mitogen-Activated Protein Kinase 3
- MAP Kinase Kinase 1
- MAP Kinase Kinase 2
- Sphingomyelin Phosphodiesterase
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Topics |
- Animals
- Cartilage, Articular
(cytology, metabolism)
- Cattle
- Cells, Cultured
- Chondrocytes
(cytology, drug effects, enzymology)
- Collagen Type II
(metabolism)
- Culture Media
- Down-Regulation
(physiology)
- Genes, Immediate-Early
(physiology)
- High Mobility Group Proteins
(metabolism)
- MAP Kinase Kinase 1
(metabolism)
- MAP Kinase Kinase 2
(metabolism)
- MAP Kinase Signaling System
(drug effects, physiology)
- Mitogen-Activated Protein Kinase 1
(metabolism)
- Mitogen-Activated Protein Kinase 3
(metabolism)
- Proto-Oncogene Proteins c-fos
(genetics)
- Proto-Oncogene Proteins c-raf
(metabolism)
- RNA, Messenger
(metabolism)
- SOX9 Transcription Factor
- Sphingomyelin Phosphodiesterase
(metabolism, pharmacology)
- Transcription Factors
(metabolism)
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