Inhibition of TNFalpha gene transcription in macrophages

巨噬细胞中 TNFα 基因转录的抑制

• 批准号: 6763823
• 负责人: PETER JOHNSON
• 金额: --
• 依托单位: DIVISION OF BASIC SCIENCES - NCI
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6763823
• 关键词: antiinflammatory agents; autocrine; biological signal transduction; gene expression; gene induction /repression; genetic promoter element; genetic regulation; genetic transcription; immune tolerance /unresponsiveness; inhibitor /antagonist; interleukin 10; interleukin 4; lipopolysaccharides; macrophage; molecular cloning; nuclear factor kappa beta; protein purification; protein structure function; tissue /cell culture; transcription factor; transforming growth factors; tumor necrosis factor alpha

The proinflammatory cytokine, tumor necrosis factor-a (TNFa), is expressed primarily in macrophages in response to bacterial products such as lipopolysaccharide (LPS). Induction of TNFa gene transcription by LPS is regulated by several transcription factors, including NF-kB. Athough TNFa plays an important protective function in animals by mediating inflammatory and immune responses, deregulated production of TNFa is associated with several serious diseases, including septic shock and rheumatoid arthritis. Therefore, it is important to determine the mechanisms that limit TNFa production during conditions of infection or injury. We have identified an activity, termed TNFa-inhibiting factor (TIF), that is secreted by macrophages in response to LPS stimulation and that negatively regulates LPS-induced transcription of the TNFa gene. Inhibition of TNFa expression by TIF is accompanied by selective induction of the p50 subunit of NF-kB as well as BCL-3, an IkappaB related protein that associates with p50 homodimers. The NF-kB p50 protein lacks transactivation domains and can inhibit transcription of certain NF-kB regulated genes. We found that overexpression of BCL-3 or p50 repressed LPS-dependent activation of the TNFa promoter and that p50 homodimers bind selectively to two sites in the TNFa promoter. These findings indicate that increased expression of NF-kB p50 and BCL-3 contributes to the repression of TNFa gene transcription. We postulate that TIF functions as a negative autocrine signal that attenuates TNFa expression in activated macrophages and that the effects of TIF are mediated, at least in part, by induction of NF-kB p50. TIF appears to be distinct from several known TNFa-inhibiting factors (IL-4, IL-10, and TGFb) and thus may represent a novel anti-inflammatory cytokine. Our current efforts involve purifying the TIF protein, cloning the TIF gene, and elucidating the signaling pathway by which TIF down-regulates TNFa gene transcription.

促炎细胞因子，肿瘤坏死因子-A（TNFA），主要在巨噬细胞中表达，响应细菌产物，例如脂多糖（LPS）。 LPS诱导TNFA基因转录受到包括NF-KB在内的几种转录因子的调节。 Athough TNFA通过介导炎症和免疫反应在动物中起着重要的保护作用，TNFA的失调产生与几种严重的疾病有关，包括败血性休克和类风湿关节炎。因此，确定在感染或损伤条件下限制TNFA产生的机制很重要。 我们已经确定了一种被称为TNFA抑制因子（TIF）的活性，该活性是巨噬细胞对LPS刺激的响应而分泌的，并且对LPS诱导的TNFA基因的转录负调节。通过TIF抑制TNFA表达，伴随着NF-KB的P50亚基以及与P50同型二聚体相关的IKAPPAB相关蛋白BCl-3的P50亚基。 NF-KB p50蛋白缺乏反式激活结构域，可以抑制某些NF-KB调节基因的转录。我们发现，Bcl-3或P50的过表达抑制了TNFA启动子的LPS依赖性激活，并且P50同型二聚体选择性地与TNFA启动子中的两个位点结合。这些发现表明，NF-KB P50和BCl-3的表达增加有助于抑制TNFA基因转录。我们假设TIF充当负自分泌信号，可减弱活化巨噬细胞中TNFA的表达，并且TIF的作用至少部分通过诱导NF-KB P50介导。 TIF似乎与几种已知的TNFA抑制因子（IL-4，IL-10和TGFB）不同，因此可能代表一种新型的抗炎细胞因子。我们目前的工作涉及纯化TIF蛋白，克隆TIF基因，并阐明TIF下调TNFA基因转录的信号传导途径。