Inhibitory function of Shikonin on MRGPRX2-mediated pseudo-allergic reactions induced by the secretagogue.

BACKGROUND

Mast cells (MCs) are crucial effectors in allergic disorders by secreting inflammatory mediators. The Mas-related G-protein-coupled receptor X2 (Mrgprx2) was shown to have a key role in IgE-independent allergic reactions. Therefore, potential drug candidates that directly target Mrgprx2 could be used to treat pseudo-allergic diseases. Shikonin, an active ingredient derived from Lithospermum erythrorhizon Sieb. et Zucc has been used for its anti-inflammatory properties since ancient China.

PURPOSE

To investigate the inhibitory effects of Shikonin on IgE-independent allergy both in vitro and in vivo, as well as the mechanism underlying its effects.

METHODS/STUDY DESIGNS: The anti-anaphylactoid activity of Shikonin was evaluated in PCA and systemic anaphylaxis models, Calcium imaging was used to assess intracellular Ca mobilization. The release of cytokines and chemokines was measured using enzyme immunoassay kits. Western blot analysis was conducted to investigate the molecules of PLCγ-PKC-IP3 signaling pathway. The analytical method of surface plasmon resonance was employed to study the interaction between Shikonin and potential target protein Mrgprx2.

RESULTS

Shikonin can suppress compound 48/80 (C48/80)-induced PCA, active systemic anaphylaxis, and MCs degranulation in mice in a dose-dependent manner. In addition, Shikonin reduced C48/80-induced calcium flux and suppressed LAD2 cell degranulation via PLCγ-PKC-IP3 signaling pathway. Moreover, Shikonin was found to inhibit C48/80-induced Mrgprx2 expression in HEK cells, displaying specific interactions with the Mrgprx2 protein.

CONCLUSION

Shikonin could be a potential antagonist of Mrgprx2, thereby inhibiting pseudo-allergic reactions through Ca mobilization.