PF-04418948

Inflammatory bowel diseases (IBDs) are characterized by unrestrained innate and adaptive immune responses and compromised intestinal epithelial barrier integrity. Regulatory T (T_reg) cells are crucial for maintaining self-tolerance and immune homeostasis in intestinal tissues. Prostaglandin E₂ (PGE₂), a bioactive lipid compound derived from arachidonic acid, can modulate T cell functions in a receptor subtype-specific manner. However, whether PGE₂ regulates T_reg cell function and contributes to IBD pathogenesis remains unclear. Here, we found that the PGE₂ receptor subtype 2 (EP2) is highly expressed in T_reg cells. T_reg cell-specific deletion of EP2 resulted in increased T_reg cell numbers, and enhanced granzyme B(GzmB) expression and immunosuppressive capacity of T_reg cells in mice. Adoptive transfer of EP2-deficient T_reg cells attenuated naïve CD4⁺ T cell transfer-induced colitis in Rag1^-/- mice. Mice with EP2-deficient T_reg cells were protected from 2,4,6-trinitrobenzene sulfonic acid (TNBS)- and dextran sodium sulfate (DSS)-induced colitis. Pharmacological blockage of EP2 with PF-04418948 markedly alleviated DSS-induced colitis in mice in a T_reg-dependent manner. Mechanistically, activation of EP2 suppressed T_reg cell function, at least in part, through reduction of GzmB expression via PKA-mediated inhibition of NF-κB signaling. Thus, we identified the PGE₂/EP2 axis as a key negative modulator of T_reg cell function, suggesting EP2 inhibition as a potential therapeutic strategy for IBD treatment.

The inflammatory mediator prostaglandin E₂ (PGE₂) binds to G_s-coupled EP2 and EP4 receptors. These receptors are located in the locus coeruleus (LC), the principal noradrenergic nucleus in the brain, but their functional role remains unknown. In this study, the PGE₂ EP2 and EP4 receptors in LC cells from male rat brain slices were pharmacologically characterized by single-unit extracellular electrophysiology. The EP2 receptor agonists butaprost (0.01-10 μM) and treprostinil (0.03-10 µM) and the EP4 receptor agonists rivenprost (0.01 nM-1 µM) and TCS2510 (0.20 nM-2 µM) increased the firing rate of LC neurons in a concentration-dependent manner. The EP2 receptor antagonist PF-04418948 (10 nM) hindered the excitatory effect of butaprost and treprostinil while the EP4 receptor antagonist L-161,982 (30 and 300 nM) blocked the excitatory effect caused by rivenprost and TCS2510. The effects of butaprost and rivenprost were prevented by extracellular sodium replacement but were not modified by the protein kinase A (PKA) activator 8-Br-cAMP (1 mM) or the inhibitor H-89 (10 μM). However, the G_βγ subunit blocker gallein (20 μM) hindered the stimulatory effect of butaprost while the G_αs subunit inhibitor NF449 (10 µM) prevented that of rivenprost. Finally, rivenprost-induced stimulation (30 nM) was not occluded by butaprost (1 µM). In conclusion, activation of EP2 and EP4 receptors excites LC noradrenergic neurons through sodium-dependent currents via different G protein subunits in male rat brain slices. EP2 and EP4 in the LC may constitute pharmacological targets for the treatment of pain, fever, drug addiction, anxiety and neuroinflammatory diseases.