Synergistic Induction of Endothelin-1 by Tumor Necrosis Factor α and Interferon γ Is due to Enhanced NF-κB Binding and Histone Acetylation at Specific κB Sites

Endothelin-1 (ET-1) is a potent vasoconstrictor and co-mitogen for vascular smooth muscle and is implicated in pulmonary vascular remodeling and the development of pulmonary arterial hypertension. Vascular smooth muscle is an important source of ET-1. Here we demonstrate synergistic induction of preproET-1 message RNA and release of mature peptide by a combination of tumor necrosis factor α (TNFα) and interferon γ (IFNγ) in primary human pulmonary artery smooth muscle cells. This induction was prevented by pretreatment with the histone acetyltransferase inhibitor anacardic acid. TNFα induced a rapid and prolonged pattern of nuclear factor (NF)-κB p65 subunit activation and binding to the native preproET-1 promoter. In contrast, IFNγ induced a delayed activation of interferon regulatory factor-1 without any effect on NF-κB p65 nuclear localization or consensus DNA binding. However, we found cooperative p65 binding and histone H4 acetylation at distinct κB sites in the preproET-1 promoter after stimulation with both TNFα and IFNγ. This was associated with enhanced recruitment of RNA polymerase II to the ATG start site and read-through of the ET-1 coding region. Understanding such mechanisms is crucial in determining the key control points in ET-1 release. This has particular relevance to developing novel treatments targeted at the inflammatory component of pulmonary vascular remodeling.