Prostaglandin E 2 and an EP4 receptor agonist inhibit LPS-Induced monocyte chemotactic protein 5 production and secretion in mouse cardiac fibroblasts via Akt and NF-κB signaling.

Background: Prostaglandin E2 (PGE ₂ ) signals through 4 separate G-protein coupled receptor sub-types to elicit a variety of physiologic and pathophysiological effects. We have previously reported that mice lacking the EP4 receptor in the cardiomyocytes develop heart failure with a phenotype of dilated cardiomyopathy. Also, these mice have increased levels of chemokines, like MCP-5, in their left ventricles. We have recently reported that overexpression of the EP4 receptor could improve cardiac function in the myocardial infarction model. Furthermore, we showed that overexpression of EP4 had an anti-inflammatory effect in the whole left ventricle. It has also been shown that PGE ₂ can antagonize lipopolysaccharide-induced secretion of chemokines/cytokines in various cell types. We therefore hypothesized that PGE ₂ inhibits lipopolysaccharide (LPS)-induced MCP-5 secretion in adult mouse cardiac fibroblasts via its EP4 receptor.
Methods and Results: Our hypothesis was tested using isolated mouse adult ventricular fibroblasts (AVF) treated with LPS. Pre-treatment of the cells with PGE ₂ and the EP4 agonist CAY10598 resulted in reductions of the pro-inflammatory response induced by LPS. Specifically, we observed reductions in MCP-5 secretion. Western blot analysis showed reductions in phosphorylated Akt and IκBα indicating reduced NF-κB activation. The anti-inflammatory effects of PGE ₂ and EP4 agonist signaling appeared to be independent of cAMP, p-44/42, or p38 pathways.
Conclusion: Exogenous treatment of PGE ₂ and the EP4 receptor agonist blocked the pro-inflammatory actions of LPS. Mechanistically, this was mediated via reduced Akt phosphorylation and inhibition of NF-κB.
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