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Cyclooxygenase 2 expression by endothelin-1-stimulated mouse resident peritoneal macrophages in vitro
K Shimada1, Y Yonetani, T Kita
1Department of Pharmacology, Nara Medical University, Kashihara, Japan. keijishi@nmugw.cc.naramed-u.ac.jp
Abstract:
Macrophages have been shown to produce endothelin and to play a role in the pathogenesis of neural damage after cerebral ischemia or vasospasm after subarachnoid hemorrhage. Cyclooxygenase 2 is induced during inflammation following brain insult and participates in inflammation-mediated neurotoxicity. However, it has not yet been established how endothelin-1 acts on cyclooxygenase 2 expression in macrophages. In the present study, we examined the effects of endothelin-1 on cyclooxygenase 2 expression and prostaglandin E2 production, and the effects of endothelin ET(A) and ET(B) receptor antagonists. Stimulation by endothelin-1 ranging from 10(-11) to 10(-9) M time and dose dependently increased the production of prostaglandin E2 and the expression of cyclooxygenase 2 protein without changing that of cyclooxygenase 1 protein, an effect which was inhibited by dexamethasone, nonsteroidal anti-inflammatory drugs and the selective endothelin ET(B) receptor antagonist, BQ788 (N-cis-2,6-dimethylpiperidinocarbonyl-L-gamma-methyl-leucyl-D-L-me thoxycarbonyl-tryptophanyl-D-norleucine). The selective endothelin ET(A) receptor antagonist, BQ123 [cyclo (D-Trp-D-Asp-Pro-D-Val-Leu)] also inhibited these reactions, but its potency was less than that of the selective endothelin ET(B) receptor antagonist. Endothelin ET(A) and ET(B) receptor antagonists had no effects on cyclooxygenase 2 protein expression and prostaglandin E2 production in lipopolysaccharide-stimulated macrophages. We conclude that endothelin-1 increases cyclooxygenase 2 protein expression and prostaglandin E2 production via mainly endothelin ET(B) receptors and partly endothelin ET(A) receptors in macrophages; however, lipopolysaccharide increases both cyclooxygenase 2 protein expression and prostaglandin E2 production in pacrophages without involving endothelin ET(A) or ET(B) receptor-mediated processes.
Insights
Endothelin-1 increases cyclooxygenase 2 (COX-2) and prostaglandin E2 in macrophages, primarily via ET(B) receptors. Lipopolysaccharide stimulation of COX-2 and prostaglandin E2 bypasses these endothelin receptors.
Area of Science:
- Neuroscience
- Immunology
- Pharmacology
Background:
- Macrophages play a role in neural damage after cerebral ischemia and subarachnoid hemorrhage.
- Cyclooxygenase 2 (COX-2) is induced during brain inflammation and contributes to neurotoxicity.
Purpose of the Study:
- To investigate the effect of endothelin-1 (ET-1) on cyclooxygenase 2 (COX-2) expression and prostaglandin E2 (PGE2) production in macrophages.
- To determine the roles of endothelin ET(A) and ET(B) receptors in ET-1-mediated COX-2 and PGE2 regulation.
Main Methods:
- Macrophages were stimulated with varying concentrations of endothelin-1.
- The expression of COX-2 and COX-1 proteins was analyzed.
- Prostaglandin E2 production was measured.
- The effects of selective endothelin ET(A) and ET(B) receptor antagonists (BQ123 and BQ788) were assessed.
- Macrophage responses to lipopolysaccharide were examined in the presence of receptor antagonists.
Main Results:
- Endothelin-1 dose- and time-dependently increased prostaglandin E2 production and cyclooxygenase 2 protein expression, but not cyclooxygenase 1.
- Dexamethasone, NSAIDs, and the selective endothelin ET(B) receptor antagonist BQ788 inhibited these ET-1-induced effects.
- The selective endothelin ET(A) receptor antagonist BQ123 also inhibited these reactions, albeit with lower potency than BQ788.
- Endothelin receptor antagonists did not affect cyclooxygenase 2 protein expression or prostaglandin E2 production in lipopolysaccharide-stimulated macrophages.
Conclusions:
- Endothelin-1 upregulates cyclooxygenase 2 protein expression and prostaglandin E2 production in macrophages predominantly through endothelin ET(B) receptors and partly through endothelin ET(A) receptors.
- Lipopolysaccharide-induced cyclooxygenase 2 and prostaglandin E2 production in macrophages occurs independently of endothelin ET(A) or ET(B) receptor signaling.