Integrated Molecular Docking and Dynamic Simulations Reveal Glycyrrhizic Acid Alleviates Allergic Rhinitis in Rats by...

Allergic rhinitis (AR) is a prevalent chronic inflammatory nasal disorder with suboptimal current therapies. Glycyrrhizic acid (GA), a bioactive triterpenoid from Glycyrrhiza uralensis, exerts well-documented antiinflammatory effects, and preliminary evidence indicates its efficacy in alleviating airway inflammation in AR models. However, two critical knowledge gaps remain unaddressed: whether GA directly binds to core proteins of the toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB)/IL-1β inflammatory pathway, and whether this binding mediates GA's therapeutic effects in AR have not been systematically verified by integrated computational and in vivo experiments.

An ovalbumin (OVA)-induced AR rat model was established. GA was administered intranasally for seven consecutive days. Behavioral observations, histopathological examination, and serum cytokine detection were performed to evaluate AR-related symptoms and immune imbalance. Molecular docking was employed to assess the binding affinity between GA and four key proteins in the TLR4 pathway (TLR4, myeloid differentiation primary response 88 [MyD88], NF-κB, and IL-1β). About 100 ns molecular dynamics (MD) simulations were further conducted to validate the stability of the GA-protein complexes. Immunohistochemistry and RT-qPCR were used to verify the expression of pathway-related proteins and cytokines in nasal mucosal tissues.

GA significantly reduced sneezing, rhinorrhea, and nasal mucosal pathological damage in AR rats. It restored the T helper 1 (Th1)/Th2 immune balance by suppressing Th2 cytokines (IL-4 and IL-13) and enhancing Th1 cytokines (interferon-gamma [IFN-γ] and IL-2). Molecular docking results showed that GA bound strongly to all four target proteins, with the highest affinity for IL-1β (-9.3 kcal/mol) and TLR4 (-7.6 kcal/mol). MD simulations confirmed the stable conformational dynamics of the GA-IL-1β and GA-TLR4 complexes. In vivo experiments further demonstrated that GA significantly downregulated the expression of TLR4, MyD88, NF-κB, and IL-1β in nasal mucosa and reduced the levels of downstream proinflammatory cytokines (TNF-α and IL-6).

GA alleviates AR symptoms by directly binding to core proteins of the TLR4/NF-κB/IL-1β pathway, inhibiting pathway activation, restoring Th1/Th2 immune balance, and suppressing inflammatory responses. This study provides structural and functional evidence supporting GA as a promising targeted therapeutic candidate for AR.