Prostaglandin E2 alterations during sepsis are partially mediated by endotoxin-induced inhibition of prostaglandin 15-hydroxydehydrogenase.

Prostaglandin E2 (PGE2) is significantly elevated in the plasma of septic or injured patients and is thought to be a component of the resultant immune suppression associated with augmented rates of infection and mortality. Many studies have examined the effect of burn injury and sepsis on PGE2 synthesis. However, the effect of sepsis or burn injury on the expression of prostaglandin 15-hydroxydehydrogenase (PGDH), the key enzyme responsible for PGE2 degradation, has not been explored. The aim of this study was to examine the effect of endotoxin treatment and/or burn injury on the expression of PGDH. Male BDF1 mice were assigned to four groups (n = 4/group): sham, lipopolysaccharide (LPS) (2.5 mg/kg, Escherichia coli LPS, i.p.), burn (15% body surface area scald injury), and burn + LPS (15% body surface area + 2.5 mg/kg LPS, i.p.). Lung tissue was harvested at specific time points after treatment and subsequently was processed for total RNA and protein. Northern and Western blot analyses were used to examine differences in PGDH protein and mRNA expression. Total RNA was probed with the riboprobe for murine PGDH, and the 100,000 g protein fraction was immunoblotted using an rabbit antimurine PGDH antibody. PGDH was expressed in lung at t = 0 in both the saline and LPS-treated animals. A decrease in mRNA expression was initially observed at 2 hours after LPS treatment. The decrease was also significant (p < 0.05) at 3 hours after LPS and maximal decrease in mRNA and protein expression was observed at 6 hours. At 24 hours after LPS administration, the PGDH mRNA and protein expression was still significantly depressed to 49% of control expression. PGDH expression was similar and not statistically different in both burn and burn + LPS treatment at t = 0. At 2 hours after LPS, PGDH mRNA expression in the burn + LPS treatment group had significantly decreased to 47% in comparison with the burn alone group. Maximal decrease in PGDH mRNA and protein expression in lung from burn + LPS was observed at 6 hours after LPS treatment. This change represents a 73% decrease in mRNA in comparison with the time-matched burn control. At 24 hours after LPS administration, PGDH mRNA but not protein expression in the lung from burn + LPS treated mice was still significantly decreased. In summary, LPS treatment alters PGDH mRNA expression at the transcriptional and protein levels. Consequently, sepsis-induced increases in PGE2 levels may not be only due to increased PGE2 synthesis but also due to decreased PGDH expression and, hence, PGE2 degradation.