LPS may enhance expression and release of HMGB1 in human nasal epithelial cells in vitro

Chronic rhinosinusitis with nasal polyps is a common disease with still unclear pathophysiologic mechanisms. The airway epithelial barrier has been shown to be involved in different chronic disorders, including rhinitis, nasal polyposis and asthma. High mobility group box 1 (HMGB1), a primarily nuclear protein, is involved in the induction of airway inflammation in patients with chronic rhinosinusitis, allergy, asthma and COPD. Pathogen-derived lipopolysaccharide is widely used as a trigger for inflammation. However, the molecular dialogue between LPS and HMGB1 in the delayed inflammatory processes remains to be explored, and the regulation of HMGB1 release through LPS from epithelial cells has not been extensively studied in patients with chronic rhinosinusitis and nasal polyps. The objective of the present study was to investigate the relocation of HMGB1 in LPS-induced human nasal epithelial cells in vitro. We obtained epithelial cells of nasal polyps from 10 patients requiring surgery for sinusitis at the ENT Department of the Chinese PLA General Hospital. The primary cultured human nasal epithelial (HNE) cells were stimulated with LPS. The expression and translocation of HMGB1 in intracellular and culture supernatants were determined using Western blot and immunofluorescence assay. HMGB1 protein was released in a time-dependent fashion in culture supernatants: in fact, expression of HMGB1 protein in HNE cells showed no significant changes at 0-24 h after exposure to 100 μg/ml LPS, but increased significantly at 48 and 72 hr. Immunofluorescence analysis revealed the transfer of HMGB1 from nuclei to cytoplasm in response to LPS exposure after 24 hr. These data reveal a hitherto unrecognized association between HMGB1 and LPS in human nasal epithelial cells. LPS can affect HMGB1 translocation and release, suggesting the involvement of HMGB1, through inflammatory mediators, in chronic rhinosinusitis with nasal polyps.