NF-κB-dependent IL-8 induction by prostaglandin E2 receptors EP1 and EP4
- The first two authors contributed equally to the paper.
Background and Purpose
Recent studies suggested a role for PGE2 in the expression of the chemokine IL-8. PGE2 signals via four different GPCRs, EP1-EP4. The role of EP1 and EP4 receptors for IL-8 induction was studied in HEK293 cells, overexpressing EP1 (HEK-EP1), EP4 (HEK-EP4) or both receptors (HEK-EP1 + EP4).
IL-8 mRNA and protein induction and IL-8 promoter and NF-κB activation were assessed in EP expressing HEK cells.
In HEK-EP1 and HEK-EP1 + EP4 but not HEK or HEK-EP4 cells, PGE2 activated the IL-8 promoter and induced IL-8 mRNA and protein synthesis. Stimulation of HEK-EP1 + EP4 cells with an EP1-specific agonist activated IL-8 promoter and induced IL-8 mRNA and protein, whereas a specific EP4 agonist neither activated the IL-8 promoter nor induced IL-8 mRNA and protein synthesis. Simultaneous stimulation of HEK- EP1 + EP4 cells with both agonists activated IL-8 promoter and induced IL-8 mRNA to the same extent as PGE2. In HEK-EP1 + EP4 cells, PGE2-mediated IL-8 promoter activation and IL-8 mRNA induction were blunted by inhibition of IκB kinase. PGE2 activated NF-κB in HEK-EP1, HEK-EP4 and HEK-EP1 + EP4 cells. In HEK-EP1 + EP4 cells, simultaneous activation of both receptors was needed for maximal PGE2-induced NF-κB activation. PGE2-stimulated NF-κB activation by EP1 was blocked by inhibitors of PLC, calcium-signalling and Src-kinase, whereas that induced by EP4 was only blunted by Src-kinase inhibition.
Conclusions and Implications
These findings suggest that PGE2-mediated NF-κB activation by simultaneous stimulation of EP1 and EP4 receptors induces maximal IL-8 promoter activation and IL-8 mRNA and protein induction.