Department of Life Science and Biotechnology, Shimane University, 1060 Nishikawatsu-cho, Matsue, Shimane 690-8504, Japan.
Exp Cell Res. 2012 Feb 15;318(4):408-15. doi: 10.1016/j.yexcr.2011.11.003. Epub 2011 Nov 9.
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.
脂氧素型前列腺素 D 合酶（L-PGDS）在脂肪细胞中优先表达，负责合成 PGD（2）及其非酶脱水产物 PGJ（2）系列，作为促脂肪生成因子。然而，由于 PGD（2）的几种衍生物及其不同的受体亚型以及其他功能（如脂溶性分子的转运体）的存在，L-PGDS 在调节脂肪生成中的作用是复杂的。为了操纵培养的脂肪细胞中 L-PGDS 的表达水平，用编码鼠 L-PGDS 的哺乳动物表达载体稳定转染培养的前脂肪细胞 3T3-L1 细胞，该载体定向为有义方向。分离的具有 L-PGDS 表达的克隆稳定转染子表达更高水平的转录物和 L-PGDS 蛋白水平，并从外源性花生四烯酸以显著更高的水平合成 PGD（2）。相比之下，PGE（2）的合成保持不变，表明对环加氧酶（COX）和 PGE 合酶的反应没有影响。此外，这些转染子在成熟阶段合成 Δ（12）-PGJ（2）的能力增加得更大。培养的稳定转染子中 L-PGDS 的持续表达阻碍了脂肪细胞成熟阶段脂肪的储存，这伴随着反映脂肪生成程序下调的脂肪细胞特异性标记物的基因表达降低。外源阿司匹林或过氧化物酶体增殖物激活受体 γ（PPARγ）激动剂（包括曲格列酮和 Δ（12）-PGJ（2））均不能挽救被抑制的脂肪生成。总之，这些结果表明，通过涉及干扰 PPARγ 信号通路的细胞机制，增强 L-PGDS 的表达对脂肪生成程序具有负调节作用，而没有内源性促脂肪生成前列腺素的贡献。
