Related Experiment Videos
Effect of forskolin on prostaglandin synthesis by mouse resident peritoneal macrophages
Abstract:
The relationship between cyclic 3',5'-adenosine monophosphate (cAMP) and prostaglandin (PG) synthesis was investigated in the mouse resident peritoneal macrophage. Macrophages were established as monolayer cultures in petri dishes. After addition of various agents, culture media and cells were removed for PG and cAMP analysis by standard radiochromatographic techniques and radioimmunoassay respectively. Forskolin, a potent receptor-independent adenylate cyclase activator, rapidly increased cAMP synthesis within 5 min in a dose related fashion in both non-treated macrophages and macrophages treated with 12-O-tetradecanoylphorbol-13-acetate (TPA). Furthermore, forskolin markedly reduced both 6-keto-PGF1 alpha and PGE2 synthesis induced by TPA and this inhibition was inversely correlated with increases with cAMP generation. In contrast, cholera toxin failed to mimic the inhibitory action of forskolin on PG synthesis even though it induced similar increases in cAMP; however this increase was only evident after a lag period of at least 1 h. Additionally, forskolin, but no cholera toxin inhibited PG synthesis and zymosan phagocytosis when these cells were activated with zymosan particles. These observations, therefore, suggest that a rise in cAMP is not always correlated with a reduction in PG synthesis.
Insights
Elevated cyclic 3
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Cyclic 3',5'-adenosine monophosphate (cAMP) is a key intracellular second messenger.
- Prostaglandins (PGs) are lipid compounds with diverse hormone-like effects.
- The interplay between cAMP and PG synthesis in macrophages is not fully understood.
Purpose of the Study:
- To investigate the relationship between cyclic 3',5'-adenosine monophosphate (cAMP) and prostaglandin (PG) synthesis in mouse resident peritoneal macrophages.
- To determine if increased cAMP levels consistently inhibit PG production.
Main Methods:
- Macrophages were cultured in monolayer.
- Agents like forskolin and cholera toxin were used to modulate cAMP levels.
- Prostaglandin (6-keto-PGF1 alpha, PGE2) and cAMP levels were measured using radiochromatography and radioimmunoassay.
Main Results:
- Forskolin rapidly increased cAMP and inhibited TPA-induced PG synthesis.
- Cholera toxin increased cAMP but did not inhibit PG synthesis.
- Forskolin inhibited zymosan-induced PG synthesis and phagocytosis, but cholera toxin did not.
Conclusions:
- A rapid rise in cAMP induced by forskolin correlates with reduced PG synthesis.
- However, a delayed increase in cAMP from cholera toxin does not inhibit PG synthesis.
- These findings suggest that the correlation between cAMP levels and PG synthesis inhibition is complex and depends on the mechanism of cAMP elevation.