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The effects of IL-1 on mitogen-activated protein kinases in rabbit articular chondrocytes
P A Scherle1, M A Pratta, W S Feeser
1Inflammatory Diseases Research, The DuPont Merck Pharmaceutical Company, Wilmington, Delaware 19880, USA.
Abstract:
IL-1-activated chondrocytes express a large number of genes which contribute to cartilage degradation. The signaling pathways activated in response to IL-1 in these cells are not well-defined. We examined the effects of IL-1 and other stimuli on the mitogen activated protein kinase (MAPK) pathways in rabbit articular chondrocytes. We demonstrate that IL-1 activates three MAPKs, ERK, JNK and p38, in a time and dose-dependent manner. Activation is maximal by 15 minutes and returns to baseline levels by 1 hour. Maximal activation of ERK and p38 occurs with 1 ng/ml IL-1 whereas activation of JNK requires 10-fold higher levels. In contrast to IL-1, the PKC activator, PDBu preferentially activates ERK while TNF alpha preferentially activates JNK. LPS and TGF beta fail to stimulate any of the kinases examined. These results suggest that activation of the various MAPK pathways is important in the response of chondrocytes to IL-1, cytokines and growth factors.
Insights
Interleukin-1 (IL-1) activates multiple mitogen-activated protein kinase (MAPK) pathways, including ERK, JNK, and p38, in chondrocytes, influencing cartilage degradation. These pathways are crucial for cellular responses to IL-1 and other signaling molecules.
Area of Science:
- Cell Biology
- Biochemistry
- Immunology
Background:
- Chondrocytes play a key role in cartilage homeostasis and degradation.
- Interleukin-1 (IL-1) is a critical mediator in inflammatory conditions affecting cartilage.
- The specific signaling pathways activated by IL-1 in chondrocytes remain incompletely understood.
Purpose of the Study:
- To investigate the effects of IL-1 on mitogen-activated protein kinase (MAPK) pathways in rabbit articular chondrocytes.
- To compare the activation patterns of different MAPK pathways (ERK, JNK, p38) by IL-1 and other stimuli.
- To elucidate the role of MAPK signaling in chondrocyte responses to inflammatory and growth factor stimuli.
Main Methods:
- Primary rabbit articular chondrocytes were treated with IL-1, PDBu, TNF-alpha, LPS, and TGF-beta.
- Mitogen-activated protein kinase (MAPK) activation (ERK, JNK, p38) was assessed using Western blotting.
- Time- and dose-dependent effects of IL-1 on MAPK activation were analyzed.
Main Results:
- IL-1 induced a time- and dose-dependent activation of ERK, JNK, and p38 MAPKs in chondrocytes.
- Maximal MAPK activation by IL-1 occurred within 15 minutes, returning to baseline by 1 hour.
- Different stimuli showed distinct MAPK activation profiles: PDBu preferentially activated ERK, while TNF-alpha preferentially activated JNK. LPS and TGF-beta did not activate these kinases.
Conclusions:
- IL-1 activates multiple MAPK signaling pathways in articular chondrocytes, contributing to cartilage's response to inflammatory stimuli.
- The differential activation of ERK, JNK, and p38 by various factors highlights the complexity of chondrocyte signaling.
- MAPK pathways are integral to the cellular response of chondrocytes to IL-1, cytokines, and growth factors, impacting cartilage degradation processes.