NF‐κB‐dependent IL‐8 induction by prostaglandin E2 receptors EP1 and EP4

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). Experimental Approach IL‐8 mRNA and protein induction and IL‐8 promoter and NF‐κB activation were assessed in EP expressing HEK cells. Key Results 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.