A Role for High Mobility Group Box 1 (HMGB1) Release in the Pathogenesis of Gastroesophageal Reflux Disease.

BACKGROUND: Many gastroesophageal reflux disease (GORD) patients have heartburn symptoms despite PPI treatment, potentially via esophageal mucosa exposure to weakly acidic bile salts, leading to oxidative stress. High mobility group box 1 (HMGB1) is a nuclear protein secreted during oxidative stress that binds to receptors including TLR2, TLR4, and RAGE, inducing inflammatory signaling. We describe the release and potential downstream effects of HMGB1 in GORD. METHODS: Esophageal biopsies were obtained from healthy controls (HC), functional heartburn (FH), non-erosive reflux disease (NERD), and erosive reflux disease (ERD) patients. Biopsies were analyzed by RNA-sequencing, and the expression of TLR2, TLR4, and RAGE was assessed with immunohistochemistry. NE-1 cells were challenged with pH 5 media and/or 500 μM deoxycholate (DCA), with/without 2-h 5 or 50 μM curcumin pre-treatment. HMGB1 translocation was measured with immunofluorescence and release with ELISA. RESULTS: HMGB1, alongside 12 additional oxidative stress-associated genes, is over-expressed in NERD and ERD patients compared to HC (adjusted p < 0.05). Weakly acidic bile salt (pH 5 + DCA) stimulated HMGB1 translocation (p < 0.0001) and release from NE-1 cells (p < 0.001), but ameliorated with curcumin pre-treatment. ERD biopsies had increased DAPI+TLR4+ cells (p < 0.05) and TLR4 fluorescence intensity (p < 0.05), compared to HC. RAGE was expressed on CD45+ cells, and the number of RAGE+CD45+ cells was higher in ERD compared to HC (p < 0.05). CONCLUSIONS: Release of HMGB1 from esophageal epithelial cells by weakly acidic bile salts, inhibited by curcumin, and increased expression of TLR4 and RAGE in ERD mucosa suggest this pathway has a role in GORD. Modulating HMGB1 activity may be a strategy for treating recurrent symptoms.