Nonylphenol induces bronchial epithelial apoptosis via Fas-mediated pathway and stimulates bronchial epithelium to secrete IL-6 and IL-8, causing bronchial smooth muscle proliferation and migration

Abstract

Features of airway remodelling have been described using tissue obtained from fatal cases of asthma and bronchial biopsies from mildly, moderately and severely asthmatic patients. Epithelial detachment and smooth muscle mass enhancement are common features of asthmatic bronchial tissue. This study is the first to investigate the inhibitory effect of nonylphenol (NP) on human bronchial epithelial cell lines BEAS-2B and HBE135-E6E7 (HBE). The results show that NP inhibits bronchial epithelial proliferation via the Fas/Fas ligand apoptotic system. We also treated BEAS-2B and HBE with NP and harvested the condition medium (CM), which was then added to bronchial smooth muscle cells (BSMC). Cultures of BSMC with NP-BEAS-2B-CM and NP-HBE-CM increased BSMC proliferation and migration. Exposure of BEAS-2B and HBE to NP caused epithelial cells to produce inflammatory cytokines IL-6 and IL-8, which subsequently induced BSMC proliferation and migration. Depleting both IL-6 and IL-8 completely reversed the effect of NP-BEAS-2B-CM- and NP-HBE-CM-mediated BSMC proliferation and migration, suggesting that this effect is a synergistic influence of IL-6 and IL-8. This study is the first to demonstrate that NP not only induces bronchial epithelial apoptosis via the Fas-mediated pathway but also stimulates the bronchial epithelium to secrete IL-6 and IL-8, which cause bronchial smooth muscle proliferation and migration - major features in asthma remodelling.