Xu Li, Nishimura Kohji, Jisaka Mitsuo, Nagaya Tsutomu, Yokota Kazushige
Department of Life Science and Biotechnology, Shimane University, Nishikawatsu-cho, Matsue, Shimane 690-8504, Japan.
Biochim Biophys Acta. 2006 Apr;1761(4):434-44. doi: 10.1016/j.bbalip.2006.03.017. Epub 2006 Mar 29.
Several types of prostaglandin (PG)s are synthesized in adipocytes and involved differently in the control of adipogenesis. To elucidate how the PG synthesis is regulated at different stages in the life cycle of adipocytes, we examined the gene expression of arachidonate cyclooxygenase (COX) pathway leading to the delayed synthesis of PGE2 and PGF2alpha and their roles in adipogenesis after exposure of cultured cells to phorbol 12-myristate 13-acetate (PMA), which is a useful system for monitoring mitogen-induced changes. While the expression of COX-1 remained constitutive, mRNA and protein levels of COX-2 were up-regulated by treatment with PMA. Preadipocytes exhibited higher gene expression of cytosolic phospholipase A2alpha (cPLA2alpha) and PGF synthase. In contrast, three isoforms of PGE synthase are expressed constitutively during all phases. The delayed synthesis of PGE2 and PGF2alpha following the stimulation for 24 with a mixture of PMA and calcium ionophore A23187 was the highest in preadipocytes, reflecting the increased expression levels of cPLA2alpha and COX-2. Cultured cells treated with PMA during the differentiation phase and then exposed to the maturation medium, or cells treated with PMA in the maturation medium after the differentiation phase showed the suppression of adipogenesis in adipocytes. The attenuating effect of PMA was additionally enhanced when the cell were treated along with A32187 during the differentiation phase, suggesting the involvement of endogenous PGs. The cells at the stages of the differentiation and maturation phases were highly sensitive to exogenous PGE2 and PGF2alpha, respectively, resulting in the marked suppression of the stored fats in adipocytes. Taken together, these results provided the evidence for the distinct gene expression of isoformic enzymes in the COX pathway leading to the synthesis of PGE2 and PGF2alpha and the specific action of these prostanoids at different cycle stages of adipocytes.
几种前列腺素（PG）在脂肪细胞中合成，并在脂肪生成的控制中发挥不同作用。为了阐明在脂肪细胞生命周期的不同阶段PG合成是如何被调控的，我们检测了花生四烯酸环氧化酶（COX）途径的基因表达，该途径导致PGE2和PGF2α的延迟合成，以及在培养细胞暴露于佛波酯12 - 肉豆蔻酸酯13 - 乙酸酯（PMA）后它们在脂肪生成中的作用，PMA是监测有丝分裂原诱导变化的有用体系。虽然COX - 1的表达保持恒定，但COX - 2的mRNA和蛋白质水平经PMA处理后上调。前脂肪细胞表现出更高的胞质磷脂酶A2α（cPLA2α）和PGF合酶基因表达。相比之下，PGE合酶的三种同工型在所有阶段均持续表达。用PMA和钙离子载体A23187混合物刺激24小时后，PGE2和PGF2α的延迟合成在前脂肪细胞中最高，反映了cPLA2α和COX - 2表达水平的增加。在分化阶段用PMA处理然后暴露于成熟培养基的培养细胞，或在分化阶段后在成熟培养基中用PMA处理的细胞，显示脂肪细胞中脂肪生成受到抑制。当细胞在分化阶段与A32187一起处理时，PMA的减弱作用进一步增强，提示内源性PG参与其中。处于分化和成熟阶段的细胞分别对外源性PGE2和PGF2α高度敏感，导致脂肪细胞中储存脂肪的显著抑制。综上所述，这些结果为COX途径中导致PGE2和PGF2α合成的同工酶的不同基因表达以及这些前列腺素在脂肪细胞不同周期阶段的特定作用提供了证据。
