Baicalin regulates Treg/Th17 cell imbalance by inhibiting autophagy in allergic rhinitis.

Background: Baicalin has many biological properties such as anti-oxidation and anti-allergy. The current study aimed to explore the effect of Baicalin on allergic rhinitis (AR) and its potential mechanism of action.

Methods: Peripheral blood mononuclear cells (PBMCs) were isolated by density gradient centrifugation. Expression levels of Th17 and Treg cells-related proteins in nasal mucosa and peripheral blood cells were detected by real-time quantitative PCR, flow cytometry and Western blot. The mice were randomly divided into Control, ovalbumin (OVA), l-Baicalin, H-Baicalin, DSGC, 3-MA, and H-Baicalin + Rapa groups. Changes of allergic rhinitis conditions and eosinophil infiltration of the mice were detected and scored by Diff-Quik staining, and histological changes were observed by Hematoxylin & Eosin (H&E) staining and Periodate Schiff (PAS) staining. Serological changes, expression levels of interleukin-17A (IL-17A), interleukin-10 (IL-10), eosinophilic cationic protein (ECP) and anti-OVA-specific antibodies were detected by Enzyme-linked immunosorbent assay (ELISA).

Results: Clinical case analysis found that AR patients had a Th17/Treg imbalance and activated autophagy, however, Baicalin restored Th17/Treg cell balance and inhibited autophagy in vitro. in vivo experiments demonstrated that Baicalin inhibited OVA-induced allergic nasal symptoms and the activation of autophagy pathway, which was the same as the regulation of 3-MA, while Rapa could weaken the effects of H-baicalin. Moreover, Baicalin reduced the infiltration of different inflammatory cells of the nasal lavage fluid, prevented the damages to epithelial cells, and improved nasal mucosal thickness and mucus secretion. In addition, Baicalin regulated the balance of mouse anti-OVA-specific antibody levels and expressions of Th17/Treg-associated cytokines.

Conclusion: Our study revealed that Baicalin can be used to treat AR, and the effect is realized through inhibiting autophagy to regulate Th17/Treg cell differentiation.