EP2 Receptor Blockade Decreases the Incidence and Severity of Experimental Necrotizing Enterocolitis
Author(s):
Jamie Golden, Children's Hospital Los Angeles; Laura Illingworth, Children's Hospital Los Angeles; Patil Kavarian, Children's Hospital Los Angeles; Jordan Bowling, Children's Hospital Los Angeles; Brandon Bowling, Children's Hospital Los Angeles; Mubina Isani, Children's Hospital Los Angeles; Oswaldo Escobar, Children's Hospital Los Angeles; Joanna Lim, Children's Hospital Los Angeles; Christopher P. Gayer; Anatoly Grishin; Henri Ford, Children's Hospital of LA, University of SC
Background: Low levels of cyclooxygenase-2 (COX-2) and its product, prostaglandin E2 (PGE2), play a critical role in intestinal homeostasis while high levels of COX-2 and PGE have been implicated in the pathogenesis of necrotizing enterocolitis (NEC). PGE2 acts on 4 EP receptors (EP1-EP4) leading to differential downstream effects. Modulation of COX-2 and PGE2 levels may be a potential treatment for NEC; yet global inhibition of COX-2 may be detrimental for intestinal barrier function. Previous work in our lab has shown that COX-2 can be induced by PGE2 via EP2 receptor activation in vitro likely contributing to the high levels of COX-2 and runaway inflammation seen in NEC.
Hypothesis: We hypothesized that selective EP2 inhibition, but not global inhibition of COX-2, would decrease the incidence and severity of experimental NEC.
Methods: Neonatal rat pups were subjected to a regimen of formula feeding and hypoxia three times daily for 4 days. Formula contained a known NEC pathogen, Cronobacter muytjensii (CM), at 10^7 CFU with or without the COX-2 inhibitor, Celecoxib 0.1mg/kg/day, or EP2 antagonist PF-04418948 10mg/kg/day. Terminal ileum was harvested on day of life 4 for NEC scoring, real time PCR analysis, and histological staining. A score of 2 or greater was considered NEC.
Results: Treatment with a COX-2 inhibitor increased mean NEC score from 1.2 to 1.4 and increased the incidence of NEC from 40% to 57% compared with CM controls. However, treatment with an EP2 antagonist decreased mean NEC score from 1.5 to 1 (p<0.05) and decreased the incidence of NEC from 58% to 24% (p<0.05) compared with CM controls. Treatment with an EP2 antagonist decreased COX-2 protein expression as seen on histologic staining and decreased COX-2 mRNA expression to 0.37 fold control levels (p<0.05).
Conclusions: EP2 receptor inhibition, but not COX-2 inhibition, decreases the incidence and severity of experimental NEC. An EP2 receptor antagonist also decreases COX-2 protein expression and mRNA expression in terminal ileal samples. This suggests that blocking specific downstream effects of COX-2 and PGE2 via EP2 may inhibit the inflammatory cascade seen in NEC while maintaining the homeostatic properties of COX-2. Treatment with an EP2 receptor antagonist may have important therapeutic implications in the treatment of NEC.