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Inhibitory effect of p38 mitogen-activated protein kinase inhibitors on cytokine release from human macrophages
S J Smith1, P S Fenwick, A G Nicholson
1Airway Disease Section, National Heart and Lung Institute, Imperial College London, London, UK.
Background And Purpose:
Macrophages release cytokines that may contribute to pulmonary inflammation in conditions such as chronic obstructive pulmonary disease. Thus, inhibition of macrophage cytokine production may have therapeutic benefit. p38 MAPK may regulate cytokine production, therefore, the effect of two p38 MAPK inhibitors, SB239063 and SD-282, on the release of TNF-alpha, GM-CSF and IL-8 from human macrophages was investigated.
Experimental Approach:
Cytokine release was measured by ELISA. Immunoblots and mRNA expression studies were performed to confirm p38 MAPK isoform expression and activity. Macrophages were isolated from lung tissue of current smokers, ex-smokers and emphysema patients and exposed to lipopolysaccharide. These cells then released cytokines in a concentration-dependent manner.
Key Results:
SB239063 only inhibited TNF-alpha release (EC50 0.3 +/- 0.1 microM). Disease status had no effect on the efficacy of SB239063. SD-282 inhibited both TNF-alpha and GM-CSF release from macrophages (EC50 6.1 +/- 1.4 nM and 1.8 +/- 0.6 microM respectively) but had no effect on IL-8 release. In contrast, both inhibitors suppressed cytokine production in monocytes.
Conclusions And Implications:
The differential effects of p38 MAPK inhibitors between macrophages and monocytes could not be explained by differences in p38 MAPK isoform expression or activity. However, the stability of TNF-alpha mRNA was significantly increased in macrophages compared to monocytes. These data suggest a differential involvement for p38 MAPK in macrophage cytokine production compared with monocytes. These effects are not due to lack of p38 activation or p38alpha expression in macrophages but may reflect differential effects on the stability of cytokine mRNA.
Insights
Two p38 MAPK inhibitors differentially affected cytokine release in human macrophages, suggesting distinct regulatory roles in pulmonary inflammation. These findings highlight potential therapeutic strategies for inflammatory lung diseases.
Area of Science:
- Immunology
- Cell Biology
- Pharmacology
Background:
- Macrophages contribute to pulmonary inflammation via cytokine release, implicated in diseases like COPD.
- Inhibiting macrophage cytokine production offers a potential therapeutic avenue.
- p38 MAPK (mitogen-activated protein kinase) is a potential regulator of cytokine production.
Purpose of the Study:
- To investigate the effects of two p38 MAPK inhibitors, SB239063 and SD-282, on the release of TNF-alpha, GM-CSF, and IL-8 from human macrophages.
- To explore the role of p38 MAPK in regulating cytokine production in macrophages.
Main Methods:
- Human macrophages isolated from smokers, ex-smokers, and emphysema patients were stimulated with lipopolysaccharide.
- Cytokine release was quantified using ELISA.
- p38 MAPK isoform expression and activity were confirmed via immunoblots and mRNA expression studies.
Main Results:
- SB239063 selectively inhibited TNF-alpha release (EC50 0.3 ± 0.1 μM) from macrophages, irrespective of disease status.
- SD-282 inhibited TNF-alpha and GM-CSF release (EC50 6.1 ± 1.4 nM and 1.8 ± 0.6 μM, respectively) but not IL-8.
- Both inhibitors suppressed cytokine production in monocytes, contrasting with their effects on macrophages.
Conclusions:
- Differential p38 MAPK inhibitor effects between macrophages and monocytes were observed.
- These differences were not attributable to variations in p38 MAPK isoform expression or activity.
- Increased TNF-alpha mRNA stability in macrophages compared to monocytes may explain the differential p38 MAPK involvement in cytokine production.
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