Furthermore, we examined the effect of the PGE2-EP4 receptor pathway on the activation of MAPK and NF-κB signaling in E. coli-infected BMDM, performed through Western blotting, indicated that Grapiprant treatment significantly reduced the phosphorylation of ERK, p38, and p65 compared to the E. coli infection group (Figures 6F–I, P < 0.01), indicating that the PGE2-EP4 pathway modulates these keys signaling pathways in the inflammatory response. The gene discussed is PTGER4; the disease is escherichia coli infection.