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Protein kinase C and chondrocyte activation.
K I Hulkower1, H I Georgescu, C H Evans
1Ferguson Laboratory for Orthopaedic Research, University of Pittsburgh School of Medicine, PA 15261.
Agents and Actions
|June 1, 1989
Summary
Protein kinase C (PKC) is unlikely to mediate interleukin-1 (IL-1) induction of chondrocyte metalloproteinases. However, PKC may modulate enzyme activity post-induction and regulate prostaglandin E2 (PGE2) synthesis.
Area of Science:
- Biochemistry
- Cell Biology
- Immunology
Background:
- Interleukin-1 (IL-1) stimulates chondrocytes to produce matrix-degrading enzymes and prostaglandin E2 (PGE2).
- Protein kinase C (PKC) is a signaling pathway implicated in cellular responses.
- Understanding IL-1 signaling in chondrocytes is crucial for cartilage biology and disease.
Purpose of the Study:
- To investigate the role of PKC in IL-1-induced chondrocyte activation.
- To elucidate the signal transduction mechanisms involved in chondrocyte response to IL-1.
Main Methods:
- Chondrocytes were treated with IL-1, phorbol myristate acetate (PMA), and PKC inhibitors (sphingosine, staurosporin).
- Synthesis of collagenase, gelatinase, and PGE2 was measured.
- PKC activity was assessed by protein phosphorylation.
Main Results:
- IL-1 significantly increased metalloproteinase and PGE2 synthesis.
- PMA alone had minimal effect on metalloproteinases but enhanced PGE2.
- PKC inhibitors blocked PMA's synergistic effect on enzyme induction with high-dose IL-1 but enhanced induction with low-dose IL-1.
- PKC inhibitors reduced PMA-induced PGE2 but enhanced IL-1-induced PGE2.
- PMA, not IL-1, increased phosphorylation of an 80 kDa protein associated with PKC.
Conclusions:
- PKC is unlikely to be directly involved in IL-1-induced metalloproteinase production.
- PKC may modulate metalloproteinase activity after induction by IL-1.
- PKC might regulate PGE2 synthesis in chondrocytes, warranting further study.