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Monocyte chemoattractant protein-1-induced activation of p42/44 MAPK and c-Jun in murine peritoneal macrophages: a
1School of Biotechnology, Banaras Hindu University, Varanasi 221005, India. ajit.sodhi@lycos.com
Abstract:
The role of monocyte chemoattractant protein-1 (MCP-1) in mediating the infiltration and activation of monocytes/macrophages into the sites of inflammation or tumor growth is well documented, but the molecular mechanism(s) involved in the process is poorly understood. In the current investigation, we demonstrate activation of the p42/44 MAPK-mediated signal transduction in murine peritoneal macrophages on stimulation with MCP-1 (10-100 ng/ml) in vitro. The p42/44 MAPK activation was determined by studying the expression of the phosphorylated p42/44 MAPK (Thr202/Tyr204) in the MCP-1-treated macrophages. This response was found to be rapid and time dependent, detectable within 5 min of MCP-1 stimulation. PD98058 (5-50 microM), a specific inhibitor of MAPK kinase (MEK) inhibited the p42/44 MAPK phosphorylation, indicating the specificity of the response. Furthermore, the MCP-1-induced phosphorylation of p42/44 MAPK was found to be blocked by pertussis toxin (100 ng/ml), tyrosine kinase inhibitor-genestein (10 ng/ml), PI3K inhibitor-wortmannin (20-200 microM), and anti-CCR2 antibody (2.5 microg/ml). Additionally, phosphorylation of JNK and activation of the transcription factor, c-Jun, were also noted in response to MCP-1 treatment. Lastly, the MCP1-induced p42/44 MAPK activity was correlated with the functional activation of macrophages by demonstrating the dose-specific inhibition of actin polymerization, macrophage-mediated tumor cell cytotoxicity, and tumor necrosis factor-alpha (TNF-alpha) transcription/production afforded by PD98059 in the MCP-1-treated macrophages. Taken together, these data suggest the involvement of the p42/44 MAPK/c-Jun pathway in the signal transduction process, leading to activation of murine peritoneal macrophages.
Insights
Monocyte chemoattractant protein-1 (MCP-1) activates p42/44 MAPK signaling in macrophages, a key step in inflammation and tumor growth. This pathway involves c-Jun and influences macrophage functions like cytotoxicity.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Monocyte chemoattractant protein-1 (MCP-1) is crucial for monocyte/macrophage recruitment to inflammatory and tumor sites.
- The precise molecular mechanisms underlying MCP-1-mediated macrophage activation remain incompletely understood.
Purpose of the Study:
- To elucidate the molecular signaling pathways activated by MCP-1 in murine peritoneal macrophages.
- To investigate the role of p42/44 MAPK signaling in MCP-1-induced macrophage activation.
Main Methods:
- Stimulation of murine peritoneal macrophages with MCP-1 in vitro.
- Assessment of p42/44 MAPK phosphorylation using Western blotting.
- Inhibition studies using specific inhibitors (PD98058, genistein, wortmannin) and pertussis toxin.
- Analysis of JNK phosphorylation, c-Jun activation, and functional macrophage assays (actin polymerization, cytotoxicity, TNF-alpha production).
Main Results:
- MCP-1 rapidly induced p42/44 MAPK phosphorylation in a time-dependent manner.
- This phosphorylation was blocked by MEK inhibitor PD98058, pertussis toxin, genistein, wortmannin, and anti-CCR2 antibody.
- MCP-1 also triggered JNK phosphorylation and c-Jun activation.
- MCP-1-induced macrophage functions, including actin polymerization, tumor cell cytotoxicity, and TNF-alpha production, were inhibited by PD98059.
Conclusions:
- MCP-1 activates macrophages through a signaling cascade involving p42/44 MAPK and c-Jun.
- This pathway is critical for regulating macrophage functional responses relevant to inflammation and tumor immunity.
