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Agonist-induced up-regulation of platelet-activating factor receptor messenger RNA in human monocytes
H Shirasaki1, I M Adcock, O J Kwon
1Department of Thoracic Medicine, National Heart and Lung Institute, London, UK.
Abstract:
Platelet-activating factor (PAF) is a potent inflammatory mediator and it actions are mediated via specific cell surface receptors which are coupled to G-proteins. PAF stimulates several functions in monocytes and may modulate the expression of its own receptor. To investigate the possible modulation of PAF receptor mRNA expression Northern blot analysis of total RNA from human monocytes was performed using the cDNA of human leukocyte PAF receptor as a probe. Following the addition of 100 nM PAF, there was a 2.0-fold increase in PAF receptor mRNA at 60 minutes after the stimulation, which was inhibited by pretreatment with the PAF receptor antagonist WEB 2086. This increase returned to control level at 120 and 180 min. The increase of PAF receptor mRNA was statistically significant for 10 nM to 1 microM of PAF, while 100 nM of lysoPAF did not increase PAF receptor mRNA levels. These results suggest that PAF receptor expression can be regulated by PAF itself at the transcriptional level.
Insights
Platelet-activating factor (PAF) can increase its own receptor mRNA levels in monocytes. This self-regulation of PAF receptor expression is mediated by PAF itself at the transcriptional level.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Platelet-activating factor (PAF) is a potent inflammatory mediator.
- PAF actions are mediated via specific G-protein coupled cell surface receptors.
- PAF stimulates monocyte functions and may modulate its own receptor expression.
Purpose of the Study:
- To investigate the modulation of PAF receptor mRNA expression in human monocytes.
- To determine if PAF itself regulates its receptor expression at the transcriptional level.
Main Methods:
- Human monocytes were stimulated with varying concentrations of PAF.
- Total RNA was analyzed using Northern blot with a human leukocyte PAF receptor cDNA probe.
- PAF receptor antagonist WEB 2086 was used to inhibit PAF receptor activity.
Main Results:
- 100 nM PAF caused a 2.0-fold increase in PAF receptor mRNA at 60 minutes.
- This increase was inhibited by the PAF receptor antagonist WEB 2086.
- PAF receptor mRNA levels returned to baseline at 120 and 180 minutes, with significant increases observed for PAF concentrations from 10 nM to 1 microM.
Conclusions:
- PAF receptor expression is regulated by PAF itself.
- Regulation occurs at the transcriptional level.
- PAF-induced increase in its own receptor mRNA is transient.