Regulatory mechanisms of uncoupling protein 2 (an anti-obesity molecule) expression: the application to preventive medicine

3周运动训练可降低小鼠腹腔巨噬细胞β_2肾上腺素能受体(β_2AR)基因的稳态表达水平。运动小鼠和安静对照组小鼠腹腔巨噬细胞经脂多糖刺激后，白介素12mRNA和蛋白表达均显著高于对照组。为了确定IL-12的增加是否与β_2AR的表达降低有关，我们将含有β_2AR的真核表达载体导入巨噬细胞系RAW264，建立了高表达β_2AR的细胞系(RAWAR)。经脂多糖刺激后，RAWAR细胞中IL-12mRNA和蛋白的表达显著低于单纯载体(RAWvec)的RAW264细胞。此外，当四环素抑制物调控的哺乳动物表达系统下调β_2AR在RAWAR细胞中的表达时，IL-12mRNA和蛋白的表达在脂多糖刺激后趋于恢复到RAWEAC细胞中的水平。这些结果表明，内毒素刺激后巨噬细胞产生IL-12受β_2AR表达水平的调节，提示运动训练下调β_2AR表达可改善IL-12诱导的1型辅助性T细胞(Th1)细胞免疫反应。解偶联蛋白1(UCP1)是解偶联蛋白家族的成员之一，在脂肪组织中的表达受β_3AR的调节。我们先前已经证明，UCP2的表达受巨噬细胞内脂多糖刺激的调节。UCP2和β_2AR主要在巨噬细胞中表达，提示β_2AR对UCP_2表达的调控系统与内毒素诱导的信号转导级联反应之间存在交互作用。

Three-week exercise training decreased the steady state level of β_2-adrenergic receptor (β_2AR) mRNA in peritoneal macrophages from BALB/c mice. When peritoneal macrophages from both exercise-trained and sedentary control mice were stimulated with lipopolysaccharide (LPS), interleukin (IL)-12 mRNA and protein expression was markedly higher in trained mice than in control mice. To determine whether enhanced production of IL-12 was associated with decreased expression of β_2AR, we transfected the macrophage cell line, RAW264, with an eukaryotic expression vector containing β_2ar cDNA, establishing a cell line overexpressing β_2AR (RAWar). Following LPS stimulation, IL-12 mRNA and protein expression was significantly lower in RAWar cells than in RAW264 cells transfected with vector alone (RAWvec). Furthermore, when the expression of transfected β_2AR in RAWar cells was down-regulated by a tetracycline repressor-regulated mammalian expression system, expression of IL-12 mRNA and protein following LPS stimulation tended to return to the levels in RAWvec cells. These findings indicate that macrophage production of IL-12 following LPS stimulation is regulated by the expression level of β_2AR, suggesting that the down-regulation of β_2AR expression associated with exercise training improves IL-12-induced type 1 helper T (Th 1) cell-mediated immune responses.The expression of uncoupling protein 1 (UCP 1), a member of the UCP family, is known to be regulated by β_3AR in adipose tissues. We previously demonstrated that UCP2 expression is regulated by LPS stimulation in macrophages. UCP2 and β_2AR are dominantly expressed in macrophages, suggesting the cross-talk between the regulatory system of UCP 2 expression by β_2AR and the LPS induced signal transduction cascade.