Involvement of the constitutive prostaglandin E synthase cPGES/p23 in expression of an initial prostaglandin E2 inactivating enzyme, 15-PGDH.

We previously showed that cytosolic prostaglandin (PG) E synthase (cPGES/p23) which isomerizes PGH(2) to PGE(2), is essential for fetal mouse development. Embryonic fibroblasts derived from cPGES/p23 knockout mice generated higher amounts of PGE(2) in culture supernatants than wild-type-derived cells. In order to elucidate this apparent conflict that absence of PGE(2) synthetic enzyme caused facilitation of PGE(2) biosynthesis, we examined expression of the PGE(2) degrading enzyme in embryonic fibroblasts. We report here that embryonic fibroblasts deficient in cPGES/p23 decreased the expression of the PGE(2) degrading enzyme, 15-hydroxyprostaglandin dehydrogenase (15-PGDH), which catalyzes the inactivating conversion of the PGE(2) 15-OH to a 15-keto group, compared with that of wild-type. In addition, rat fibroblastic 3Y1 cells harboring cPGES/p23 siRNA exhibited lower 15-PGDH expression than mock-transfected cells. Furthermore, forcible expression of cPGES/p23 in 3Y1 cells resulted in facilitation of 15-PGDH promoter activity. These results suggest that the PGE(2)-inactivating pathway is controlled by the PGE(2) biosynthetic enzyme, cPGES/p23.