Elk‐1‐mediated 15‐Lipoxygenase Expression is Required for Hypoxia‐induced Pulmonary Vascular Adventitial Fibroblast Dynamics

Abstract 15-Lipoxygenase (15-LO) is an important factor in the pathogenesis of pulmonary artery hypertension (PAH). However, the role of 15-LO in the adventitia of the pulmonary arterial wall is unclear. The aim of the present study was to explore the role of 15-LO in the modulation of pulmonary adventitial fibroblast (PAF) dynamics. Rats were exposed to normoxic or hypoxic (fraction of inspired O2 = 0.12) treatments for 7 days. PAF proliferation and cell cycle alterations were measured by MTT assay, cell immunofluorescence, flow cytometry, and Western blot analysis. The 15-LO promoter was analyzed by luciferase reporter and ChIP assays. Our results showed that hypoxia induced 15-LO expression in PAFs both in vivo and in vitro. In addition, hypoxia stimulated JNK phosphorylation in PAFs. Blocking 15-LO or JNK suppressed 15-LO-induced PAF proliferation and cell cycle alterations. The inhibition of p27(kipl) by gene silencing attenuated 15-LO-induced PAF proliferation and cell cycle alterations. Furthermore, JNK inhibition or Elk-1 knockdown suppressed hypoxia-induced 15-LO expression in PAFs. Luciferase reporter and ChIP assays revealed that the 15-LO promoter contains Elk-1 binding sites and also that Elk-1 increased the hypoxia-induced activity of the 15-LO promoter. These results suggest that hypoxia promotes changes in the cellular dynamics of PAFs by inducing 15-LO expression, which leads to vascular adventitial remodeling. The modulation of p27(kipl) expression by 15-LO enhances PAF proliferation and cell cycle alterations. Furthermore, the JNK-dependent increase in Elk-1 signaling is required for hypoxia-induced 15-LO expression in PAFs. This article is protected by copyright. All rights reserved.