Abstract
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 alpha (TNFalpha) and interferon gamma (IFNgamma) in primary human pulmonary artery smooth muscle cells. This induction was prevented by pretreatment with the histone acetyltransferase inhibitor anacardic acid. TNFalpha induced a rapid and prolonged pattern of nuclear factor (NF)-kappaB p65 subunit activation and binding to the native preproET-1 promoter. In contrast, IFNgamma induced a delayed activation of interferon regulatory factor-1 without any effect on NF-kappaB p65 nuclear localization or consensus DNA binding. However, we found cooperative p65 binding and histone H4 acetylation at distinct kappaB sites in the preproET-1 promoter after stimulation with both TNFalpha and IFNgamma. 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.
Highlights
Endothelial cells are thought to be the main source of ET-1 release, several groups including our own have shown that ET-1 can be released from the more numerous vascular smooth muscle cells [5,6,7,8,9,10]
Pulmonary vascular smooth muscle cells are an important source of mitogenic factors, which contribute to the development of pulmonary arterial hypertension
We demonstrate that enhanced histone acetylation and RNA polymerase II recruitment occurs at selective nuclear factor (NF)-B sites in the preproET-1 promoter after cooperative p65 recruitment to these sites in the native promoter and that this is associated with enhanced gene transcription
Summary
Endothelial cells are thought to be the main source of ET-1 release, several groups including our own have shown that ET-1 can be released from the more numerous vascular smooth muscle cells [5,6,7,8,9,10]. In many cell types cytokines mediate their biological effects at least in part by the activation of the nuclear factor B (NF-B) pathway [16], and a role for NF-B in pulmonary arterial hypertension has been proposed [17]. We have shown previously that a combination of TNF␣ and interferon ␥ (IFN␥) stimulates human pulmonary artery smooth muscle (HPASM) cells to release ET-1 [18]. We were interested in the role of histone acetylation in the epigenetic control of the ET-1 production. Understanding these novel mechanisms will allow a greater understanding of the pathogenesis of vascular remodeling in pulmonary vessels and aid in the development of new treatment strategies aimed at blocking synthesis of ET-1
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