HB-EGF-induced IL-8 secretion from airway epithelium leads to lung fibroblast proliferation and migration

Background We have reported that heparin-binding epidermal growth factor (HB-EGF) is increased in patients with chronic obstructive pulmonary disease (COPD) and associated with collagen deposition, but the mechanisms remain unclear. In the present study, we aimed to investigated the inflammatory cytokines secreted by bronchial epithelial cells following exposure to HB-EGF that promoted proliferation and migration of human lung fibroblast. Methods HB-EGF–induced inflammatory cytokines were assayed in two airway epithelial cells (primary human bronchial epithelial cells [HBECs] and BEAS-2B cells). Moreover, the culture supernatants derived from HB-EGF-treated HBECs and BEAS-2B cells were added to human primary lung fibroblasts. The effect of culture supernatants on proliferation and migration of fibroblasts was assessed. Results IL-8 expression was significantly increased in bronchial epithelial cells treated with HB-EGF, which was at least partially dependent on NF-kB pathways activation. HB-EGF–induced IL-8 was found to further promote lung fibroblasts proliferation and migration, and the effects were attenuated after neutralizing IL-8. Conclusions These findings suggest that HB-EGF may be involved in the pathology of airway fibrosis by induction of IL-8 from airway epithelium, subsequently causing lung fibroblasts proliferation and migration. Thus, inhibition of HBEGF and/or IL-8 production could prevent the development of airway fibrosis by modulating fibroblast activation.

Histone deacetylase 7 mediates endothelin-1-induced connective tissue growth factor expression in human lung fibroblasts through p300 and activator protein-1 activation

Background Histone deacetylase (HDAC) inhibition was reported to ameliorate lung fibrosis in animal models. However, little is known about the underlying mechanism of HDAC7 in the regulation of CTGF production in lung fibroblasts. Methods The role of HDAC7 in CTGF production caused by ET-1 stimulation in WI-38 cells (human lung fibroblast) was examined. We also evaluated the expression of HDAC7 in the lung of ovalbumin-induced airway fibrosis model. Statistical data were shown as mean ± standard error. Results ET-1-stimulated CTGF and α-SMA expression was attenuated by small interfering (si)RNA interference of HDAC7. ET-1 promoted HDAC7 translocation from the cytosol to nucleus. ET-1-stimulated CTGF expression was reduced by the transfection of p300 siRNA. ET-1 induced an increase in p300 activity. Furthermore, the acetylation of c-Jun was time-dependently induced by ET-1 stimulation, which was reduced by transfection of either HDAC7 or p300 siRNA. Both transfection of HDAC7 and p300 siRNA suppressed the ET-1-increased activity of AP-1-luciferase. Moreover, the presence of HDAC7 was required for ET-1-stimulated formation of HDAC7, p300, and AP-1 complex and recruitment to the CTGF promoter region. In an ovalbumin-induced airway fibrosis model, the protein level of HDAC7 was increased in the lung tissue, and the distribution of HDAC7 was colocalized with α-SMA-positive cells in the subepithelial layer of the airway. Conclusions ET-1 activates HDAC7 to initiate AP-1 transcriptional activity by recruiting p300 and eventually promotes the production of CTGF. HDAC7 might play a vital role in airway fibrosis and have the potential to be developed as a therapeutic target.

BET proteins are associated with the induction of small airway fibrosis in COPD

RationaleIn COPD, small airway fibrosis occurs due to increased extracellular matrix (ECM) deposition in and around the airway smooth muscle (ASM) layer. Studies of immune cells and peripheral lung tissue have shown that epigenetic changes occur in COPD but it is unknown whether airway mesenchymal cells are reprogrammed.ObjectivesDetermine if COPD ASM cells have a unique epigenetic response to profibrotic cytokine transforming growth factor β1 (TGF-β1).MethodsPrimary human ASM cells from COPD and non-COPD smoking patients were stimulated with TGF-β1. Gene array analysis performed to identify differences in ECM expression. Airway accumulation of collagen 15α1 and tenascin-C proteins was assessed. Aforementioned ASM cells were stimulated with TGF-β1 ± epigenetic inhibitors with qPCR quantification of COL15A1 and TNC. Global histone acetyltransferase (HAT) and histone deacetylase (HDAC) activity were assessed. chromatin immunoprecipitation (ChIP)-qPCR for histone H3 and H4 acetylation at COL15A1 and TNC promoters was carried out. Effects of bromoterminal and extraterminal domain (BET) inhibitor JQ1(+) on expression and acetylation of ECM target genes were assessed.Measurements and main resultsCOPD ASM show significantly higher COL15A1 and TNC expression in vitro and the same trend for higher levels of collagen 15α1 and tenascin-c deposited in COPD airways in vivo. Epigenetic screening indicated differential response to HDAC inhibition. ChIP-qPCR revealed histone H4 acetylation at COL15A1 and TNC promoters in COPD ASM only. ChIP-qPCR found JQ1(+) pretreatment significantly abrogated TGF-β1 induced histone H4 acetylation at COL15A1 and TNC.ConclusionsBET protein binding to acetylated histones is important in TGF-β1 induced expression of COL15A1 and TNC and maintenance of TGF-β1 induced histone H4 acetylation in cell progeny.