Tussilagone inhibits MRGPRX2-mediated mast cell degranulation and suppresses pseudo-allergic reactions.

Mas-related G protein-coupled receptor X2 (MRGPRX2) is a crucial target in pseudo-allergic reactions. Tussilagone (Tus), the main bioactive component derived from Tussilago farfara, has anti-inflammatory effects, but its potential inhibitory effects on pseudo-allergic responses remain unclear. This research aimed to evaluate the inhibitory role of Tus on pseudo-allergic reactions and its underlying mechanism. In vivo Systemic pseudo-allergic reactions and passive cutaneous anaphylaxis (PCA) models were established to assess the effects of Tus. In vitro, mast cell (LAD2) degranulation, inflammatory cytokine release, and signaling pathway protein expression were assessed. Calcium influx was measured in MRGPRX2-expressing HEK293 cells. The results showed that Tus significantly attenuated Tween 80- and substance P (SP)-induced systemic pseudo-allergy and PCA reactions. It also suppressed mast cell degranulation and decreased production of tumor necrosis factor-alpha (TNF-α), Interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1). In MRGPRX2-expressing HEK293 cells, Tus suppressed Tween 80- and SP-induced Ca2+ influx. Mechanistically, Tus inhibited tolimidone-induced Lyn kinase activation and suppressed SP-and Tween 80-induced β-hexosaminidase release, exhibiting an inhibitory profile comparable to that of the Lyn/Btk antagonist bosutinib. Additionally, Tus attenuated the phosphorylation levels of MRGPRX2 downstream signal molecules, including Btk, PLCγ1, PKC, p38 MAPK, IκB-α and NF-κB (p65). In conclusion, Tus attenuates SP-and Tween 80-induced mast cell activation and pseudo-allergic reactions by targeting the Lyn/Btk/PLCγ1 and p38/NF-κB pathways, highlighting its therapeutic potential for pseudo-allergy.