Kumar Ajay, Lin Zhiyong, SenBanerjee Sucharita, Jain Mukesh K
Program in Cardiovascular Transcriptional Biology, Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, 75 Francis St. TH1127, Boston, Massachusetts 02115, USA.
Mol Cell Biol. 2005 Jul;25(14):5893-903. doi: 10.1128/MCB.25.14.5893-5903.2005.
Activation of the endothelium by inflammatory cytokines is a key event in the pathogenesis of vascular disease states. Proinflammatory cytokines repress the expression of KLF2, a recently identified transcriptional inhibitor of the cytokine-mediated activation of endothelial cells. In this study the molecular basis for the cytokine-mediated inhibition of KLF2 is elucidated. Tumor necrosis factor alpha (TNF-alpha) potently inhibited KLF2 expression. This effect was completely abrogated by a constitutively active form of IkappaBalpha, as well as treatment with trichostatin A, implicating a role for the NF-kappaB pathway and histone deacetylases. Overexpression studies coupled with observations with p50/p65 null cells support an essential role for p65. A combination of promoter deletion and mutational analyses, chromatin immunoprecipitation assays, and co-immunoprecipitation studies indicates that p65 and histone deacetylases 4 cooperate to inhibit the ability of MEF2 factors to induce the KLF2 promoter. These studies identify a novel mechanism by which TNF-alpha can inhibit endothelial gene expression. Furthermore, the inhibition of MEF2 function by p65 and HDAC4 has implications for other cellular systems where these factors are operative.
炎症细胞因子激活内皮细胞是血管疾病发病机制中的关键事件。促炎细胞因子会抑制KLF2的表达，KLF2是最近发现的一种细胞因子介导的内皮细胞激活的转录抑制剂。在本研究中，阐明了细胞因子介导的KLF2抑制的分子基础。肿瘤坏死因子α（TNF-α）强烈抑制KLF2的表达。组成型活性形式的IkappaBalpha以及曲古抑菌素A处理可完全消除这种作用，这暗示了NF-kappaB途径和组蛋白脱乙酰酶的作用。过表达研究以及对p50/p65缺失细胞的观察结果支持p65的重要作用。启动子缺失和突变分析、染色质免疫沉淀测定以及免疫共沉淀研究的结合表明，p65和组蛋白脱乙酰酶4协同抑制MEF2因子诱导KLF2启动子的能力。这些研究确定了TNF-α抑制内皮基因表达的新机制。此外，p65和HDAC4对MEF2功能的抑制作用对这些因子起作用的其他细胞系统具有影响。
