Stable expression of lipocalin-type prostaglandin D synthase in cultured preadipocytes impairs adipogenesis program independently of endogenous prostanoids

Lipocalin-type prostaglandin D synthase (L-PGDS) expressed preferentially in adipocytes is responsible for the synthesis of PGD 2 and its non-enzymatic dehydration products, PGJ 2 series, serving as pro-adipogenic factors. However, the role of L-PGDS in the regulation of adipogenesis is complex because of the occurrence of several derivatives from PGD 2 and their distinct receptor subtypes as well as other functions such as a transporter of lipophilic molecules. To manipulate the expression levels of L-PGDS in cultured adipocytes, cultured preadipogenic 3T3-L1 cells were transfected stably with a mammalian expression vector having cDNA encoding murine L-PGDS oriented in the sense direction. The isolated cloned stable transfectants with L-PGDS expressed higher levels of the transcript and protein levels of L-PGDS, and synthesized PGD 2 from exogenous arachidonic acid at significantly higher levels. By contrast, the synthesis of PGE 2 remained unchanged, indicating no influence on the reactions of cyclooxygenase (COX) and PGE synthase. Furthermore, the ability of those transfectants to synthesize Δ 12-PGJ 2 increased more greatly during the maturation phase. The sustained expression of L-PGDS in cultured stable transfectants hampered the storage of fats during the maturation phase of adipocytes, which was accompanied by the reduced gene expression of adipocyte-specific markers reflecting the down-regulation of the adipogenesis program. The suppressed adipogenesis was not rescued by either exogenous aspirin or peroxisome proliferator-activated receptor γ (PPARγ) agonists including troglitazone and Δ 12-PGJ 2. Taken together, the results indicate the negative regulation of the adipogenesis program by the enhanced expression of L-PGDS through a cellular mechanism involving the interference of the PPARγ signaling pathway without the contribution of endogenous pro-adipogenic prostanoids. ► Cultured preadipocytes were transfected with sense lipocalin-type PGD synthase. ► The cloned transfectants had a higher ability to synthesize PGD 2 and PGJ 2 series. ► The sustained expression of sense L-PGDS hampered the storage of fats. ► Adipogenesis program was suppressed independently of endogenous prostanoids.