High-mobility group box 1 protein induces epithelialmesenchymal transition in upper airway epithelial cells

BACKGROUND: In the treatment of rhinosinusitis, nasal polyps are a major problem, and the epithelial-to-mesenchymal transition (EMT) process is considered pivotal in their development. Although various studies have addressed the role of high mobility group box 1 (HMGB1) nuclear protein in this setting, its impact on EMT has yet to be evaluated. Our aim was the pathogenic mechanism of HMGB1 in EMT and EMT-induced upper respiratory nasal polyps. METHODS: We investigated the EMT-related effects of HMGB1 in human nasal epithelial (HNE) cells using western blot analysis, transepithelial-electrical resistance (TEER) testing, wound healing assay, and immunofluorescence. HNE cells were incubated in a low-oxygen environment to evaluate the role of HMGB1 in hypoxia-induced EMT. Further support for our in vitro findings was obtained through murine models. Human nasal polyps and nasal lavage fluid samples were collected for western blotting, immunohistochemistry, and enzyme-linked immunosorbent assay (ELISA). RESULTS: HMGB1 increased mesenchymal markers and decreased epithelial markers in HNE cells. Hypoxia-induced HMGB1 in turn induced EMT, apparently through RAGE signaling. We verified HMGB1-induced EMT in the upper respiratory epithelium of mice by instilling intranasal HMGB1. In testing of human nasal polyps, HMGB1 and mesenchymal markers were heightened, whereas epithelial markers were reduced, compared with tissue controls. CONCLUSION: HMGB1 secretion in nasal epithelium may be a major pathogenic factor in upper respiratory EMT, contributing to nasal polyps.