Sustained expression of lipocalin-type prostaglandin D synthase in the antisense direction positively regulates adipogenesis in cloned cultured preadipocytes.

ABSTRACT

Adipocytes express preferentially lipocalin-type prostaglandin (PG)D synthase (L-PGDS) that is responsible for the biosynthesis of PGD(2) and other related prostanoids with pro-adipogenic or anti-adipogenic effects. To evaluate the role of L-PGDS in cultured adipocytes and the precursor cells, we attempted to interfere the intracellular expression of L-PGDS in cultured 3T3-L1 preadipocytes by stable transfection with a mammalian expression vector having the full-length cDNA of L-PGDS oriented in the antisense direction. The cloned transfectants with antisense L-PGDS exhibited the reduction in the transcript and protein levels of L-PGDS, resulting in the significant inhibition of the PGD(2) synthesis from exogenous and endogenous arachidonic acid. By contrast, the synthesis of PGE(2) was not influenced appreciably, indicating no interfering effects on cyclooxygenases and PGE synthases. The stable transfection with antisense L-PGDS induced markedly the stimulation of fat storage in cultured adipocytes during the maturation phase. In addition, the spontaneous accumulation of fats occurred in the transfectants with antisense L-PGDS without undergoing the stimulation with inducing factors. The gene expression studies revealed the enhanced expression of adipocyte-specific markers in the transfectants with antisense L-PGDS, indicating the up-regulation of adipogenesis program. The stimulated adipogenesis was significantly reversed by anti-adipogenic prostanoids including PGE(2) and PGF(2α), while the storage of fats was additionally enhanced by pro-adipogenic 15-deoxy- Δ(12,14)-prostaglandin J(2). These results suggest that the stably reduced expression levels of L-PGDS regulates positively adipogenesis program in a cellular mechanism independent of pro-adipogenic action of PGJ(2) series.