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Synergistic induction of monocyte chemoattractant protein-1 (MCP-1) by platelet-derived growth factor and
M Goppelt-Struebe1, M Stroebel
1Medizinische Klinik IV, Universität Erlangen-Nürnberg, Germany.
Abstract:
Monocyte chemoattractant protein-1 (MCP-1) plays an important role in the recruitment of monocytic cells to the site of inflammation. Resting mesangial cells express barely detectable levels of MCP-1 mRNA. Treatment of rat mesangial cells with platelet products PDGF-AB, PDGF-BB or serotonin transiently induced MCP-1 expression with a maximum after 2 to 4 h and a decline to baseline after 6 to 8 h. Different kinetics were observed with interleukin-1 beta (IL-1 beta), which induced a long lasting elevation of MCP-1 mRNA for more than 20 h. Together, PDGF and IL-1 beta synergistically induced MCP-1 expression. The effect was most obvious after 16 to 20 h, when induction by PDGF alone had already faded, but still PDGF strongly enhanced IL-1 beta-induced MCP-1 mRNA expression. MCP-1 mRNA levels were regulated by changes in the stability of the mRNA: inhibition of protein synthesis by cycloheximide by itself induced MCP-1 mRNA expression and led to superinduction in the presence of PDGF. Message stabilization also contributed to the synergistic action of PDGF and IL-1 beta: the apparent half life of MCP-1 mRNA determined in the presence of actinomycin D was prolonged when both stimuli were added together. We could thus show that in mesangial cells different types of cytokines and growth factors synergize to enhance MCP-1, the secretion of which could lead to the recruitment of monocytic cells into the inflamed mesangium.
Insights
Platelet-derived growth factor (PDGF) and interleukin-1 beta (IL-1 beta) synergistically increase monocyte chemoattractant protein-1 (MCP-1) in mesangial cells. This synergistic effect enhances MCP-1 mRNA stability, potentially recruiting monocytic cells to inflamed tissues.
Area of Science:
- Cell Biology
- Immunology
- Molecular Biology
Background:
- Monocyte chemoattractant protein-1 (MCP-1) is crucial for recruiting monocytes to inflammatory sites.
- Resting mesangial cells exhibit minimal MCP-1 mRNA expression.
Purpose of the Study:
- To investigate the regulation of MCP-1 expression in rat mesangial cells by various growth factors and cytokines.
- To elucidate the mechanisms underlying the synergistic induction of MCP-1 by PDGF and IL-1 beta.
Main Methods:
- Treatment of rat mesangial cells with platelet-derived growth factor (PDGF-AB, PDGF-BB), serotonin, and interleukin-1 beta (IL-1 beta).
- Analysis of MCP-1 mRNA levels using quantitative methods.
- Assessment of mRNA stability using cycloheximide (protein synthesis inhibitor) and actinomycin D (transcription inhibitor).
Main Results:
- PDGF and serotonin induced transient MCP-1 expression (peak 2-4h, baseline 6-8h).
- IL-1 beta caused a sustained elevation of MCP-1 mRNA (>20h).
- PDGF and IL-1 beta synergistically induced MCP-1, particularly at later time points (16-20h), by stabilizing MCP-1 mRNA.
Conclusions:
- Mesangial cells utilize mRNA stabilization as a key mechanism for regulating MCP-1 expression.
- Synergistic action of PDGF and IL-1 beta on MCP-1 mRNA stability enhances the inflammatory response.
- Understanding these pathways is vital for targeting inflammatory processes involving mesangial cells and monocytic infiltration.