Systemic inflammation induces COX-2 mediated prostaglandin D2 biosynthesis in mice spinal cord

Abstract

Although prostaglandin (PG)D 2 is one of the main metabolites of the cyclooxygenase (COX) pathway of arachidonate metabolism in the brain, relatively little is known about the regulation of PGD 2 biosynthesis in the spinal cord during systemic inflammation. Therefore, the present study was aimed at investigating the effect of endotoxin treatment on spinal PGD 2 biosynthesis in BALB/c mice. Spinal inflammatory response to systemic endotoxin was verified by determination of spinal TNFα and IL-1β mRNA. COX-1, COX-2, membrane-bound prostaglandin E synthase-1 (mPGES-1), and lipocalin-type prostaglandin D synthase (L-PGDS) mRNA and protein were determined by RT-PCR and western blot, respectively. The concentrations of immunoreactive PGD 2 and PGE 2 were measured in superfusion media of spinal cord samples in-vitro. Endotoxin treatment (1 mg/kg; 24 h before) enhanced the expression of COX-2, mPGES-1, and L-PGDS mRNA and protein in spinal cord, while there was no significant effect on COX-1 mRNA and protein. In superfusion media of spinal cord samples obtained from endotoxin treated mice, the concentrations of immunoreactive PGE 2 and PGD 2 were higher than in the control group suggesting enhanced spinal PG biosynthesis after endotoxin treatment. Addition of the selective COX-2 inhibitor lumiracoxib (100 nM) to the superfusion medium did not significantly affect PGE 2 or PGD 2 release in spinal cord obtained from non-treated mice. In spinal cord of endotoxin-treated mice, lumiracoxib (100 nM) attenuated PGE 2 and PGD 2 release to values similar to those observed in tissue obtained from non-endotoxin-treated mice. These results show enhanced expression of spinal L-PGDS and increased spinal PGD 2 biosynthesis during systemic inflammation whereby enhanced biosynthesis seems to be dependent primarily on COX-2 activity.