ABSTRACT
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-α) potently inhibited KLF2 expression. This effect was completely abrogated by a constitutively active form of IκBα, as well as treatment with trichostatin A, implicating a role for the NF-κB 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 coimmunoprecipitation 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-α 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.
Effects of Ozone Exposure on Nuclear Factor-kappaB Activation and Tumor Necrosis Factor-alpha Expression in Human Nasal Epithelial Cells