Increase in the Level of Proinflammatory Cytokine HMGB1 in Nasal Fluids of Patients With Rhinitis and its Sequestration by Glycyrrhizin Induces Eosinophil Cell Death

Abstract

Objectives: The nuclear protein high mobility group protein box 1 (HMGB1) is a proinflammatory mediator that belongs to the alarmin family of proinflammatory mediators, and it has recently emerged as a key player in different acute and chronic immune disorders. Several lines of evidence demonstrate that HMGB1 is actively released extracellularly from immune cells or passively released from necrotic cells. Because of the ability of HMGB1 to sustain chronic inflammation, we investigated whether the protein is present in nasal fluids of patients with different forms of rhinitis.

Methods: HMGB1 levels were evaluated in nasal fluids of healthy subjects or rhinitis patients who were treated or not treated with different treatments.

Results: We report that the level of HMGB1 was significantly increased in nasal fluids of patients with allergic rhinitis, patients with NARES (nonallergic rhinitis with eosinophiliac syndrome), as well as patients with polyps. We also found that a formulation containing the HMGB1-binding compound glycyrrhizin (GLT) reduced the HMGB1 content in nasal fluids of rhinitis patients to an extent similar to that with nasal budesonide treatment. We also found that among the cultured human leukocyte populations, eosinophils released higher amounts of HMGB1. Based on the ability of HMGB1 to sustain eosinophil survival and the ability of GLT to inactivate HMGB1, we report that GLT selectively killed cultured eosinophils and had no effect on neutrophils, macrophages, and lymphocytes.

Conclusion: Collectively, these data underscore the role of HMGB1 in rhinitis pathogenesis and the therapeutic potential of GLT formulations in treatment of chronic inflammatory disorders of the nasal mucosa.

Keywords: Eosinophils; Glycyrrhizin acid; HMGB1 protein; Rhinitis.

Fig. 1. High mobility group protein box 1 (HMGB1) levels in rhinitis patients, plasma levels of glycyrrhizin, glycyrrhetinic acid (GA), and cortisol in patients treated with Narivent (DMG, Rome, Italy) or GLT-containing formulation. (A) HMGB1 content in nasal fluids of healthy subjects and patients with different forms of rhinitis/polyps. (B) Comparison of the HMGB1 content in nasal fluids of healthy subjects or subjects affected by rhinitis. (C) HMGB1 levels in nasal fluids of patients with allergic rhinitis before and after 1 week of treatment with saline, Narivent, or Budesonide. (D) Levels of GLT and GA in subjects treated with acute (i.e., 30 minutes after 1 puff/nostril) or chronic (1 puff/nostril twice a day for 1 week) Narivent administration, or in subjects 30 minutes after ingestion of a GLT-containing formulation. (E) Plasma cortisol concentrations in control subjects or in rhinitis patients who received one week of Narivent treatment (1 puff/nostril twice a day). ^*P<0.05. ^**P<0.01. ^***P<0.001; analysis of variance plus Tukey post hoc test.

Fig. 2. High mobility group protein box 1 (HMGB1) release and effect of glycyrrhizin on survival of different cultured leukocytes. (A) HMGB1 levels in the media of different human leukocyte types purified from peripheral blood and cultured for 12 hours. (B) Effect of GLT on cell survival of different human leukocyte types purified from peripheral blood and cultured for 24 hours. Columns represent the mean±standard error of the mean of at least three experiments conducted in duplicate. ^**P<0.01. ^***P<0.001; analysis of variance plus Tukey post hoc test. PI, propidium Iodide.