Obesity and immune system -with enphasis on macrophages-

已经提出解偶联蛋白2（UCP-2）通过降低线粒体膜电位来限制活性氧（ROS）的产生。虽然活性氧参与巨噬细胞内脂多糖（LPS）刺激后诱导型一氧化氮合酶（NOS II）基因表达的细胞信号传导，但UCP-2在调节对LPS的反应中的作用尚未阐明。LPS刺激后，巨噬细胞UCP 2的表达减少。在巨噬细胞系RAW 264细胞中研究了LPS下调UCP-2的生理后果和调节机制。UCP-2基因转染RAW 264细胞后，UCP-2基因的过表达显著降低了细胞内ROS的产生，且UCP-2基因转染细胞内NO的合成、NOS Ⅱ蛋白、NOS Ⅱ mRNA和NOS Ⅱ启动子活性均明显低于LPS刺激的对照细胞。 ...更多信息 在单独用载体转染的亲代RAW 264或RAW 264细胞中。报告基因分析表明，UCP-2基因的第二内含子区域存在一个增强子元件，UCP-2基因的表达不是受7.3kb启动子区的调控，而是受UCP-2基因5 '端含有两个内含子的区域的调控。第二内含子的缺失导致转录活性降低，并消除了LPS相关的负调控。此外，转染UCP-2基因组DNA的表达载体可抑制转染UCP-2的mRNA表达，而转染UCP-2无内含子cDNA的表达载体可显著增加转染UCP-2的mRNA表达。这些结果表明，LPS刺激的信号通过中断内含子增强子的功能来抑制UCP-2的表达，导致细胞内ROS的上调，从而激活NOS II表达的信号转导级联，这可能是为了确保细胞对微生物攻击的快速和充分的反应。少

It has been proposed that uncoupling protein 2 (UCP-2) limits production of reactive oxygen species (ROS) by decreasing the mitochondrial membrane potential. Although reactive oxygen species are involved in cellular signaling for inducible nitric oxide synthase (NOS II) gene expression following lipopolysaccharide (LPS) stimulation in macrophages, the role of UCP-2 in the regulation of the response to LPS has not been elucidated. The expression of UCP2 was reduced in macrophages following stimulation with LPS. The physiological consequence and the regulatory mechanisms of the UCP-2 down-regulation by LPS were investigated in a macrophage cell line, RAW264 cells. UCP-2 overexpression in RAW264 cells transfected with eukaryotic expression vector containing ucp-2 cDNA markedly reduced the production of ROS, Furthermore, in the UCP-2 transfectant, NO synthesis, NOS II protein, NOS II mRNA, and NOS II promoter activity were definitely decreased following LPS stimulation compared with those … More in parental RAW264 or RAW264 cells transfected with the vector alone. Reporter assays suggested that an enhancer element was located in the region of the second intron of UCP-2 gene and that the UCP-2 expression was down-regulated not by the 7.3 kb promoter region but by the 5'-region of UCP-2 gene containing two introns. Deletion of the second intron resulted in the low transcriptional activities and abolishment of the LPS-associated negative regulation. In addition, the mRNA expression of transfected UCP-2 was suppressed in RAW264 cells transfected with expression vector containing UCP-2 genomic DNA, but was markedly increased in cells transfected with the vector containing UCP-2 intronless cDNA. These findings suggest that the LPS stimulated signals suppress UCP-2 expression by interrupting the function of intronic enhancer, leading to an up-regulation of intracellular ROS which activate the signal transduction cascade of NOS II expression, probably to ensure rapid and sufficient cellular responses to a microbial attack. Less