Isosalvianolic acid C-induced pseudo-allergic reactions via the mast cell specific receptor MRGPRX2

Pseudo-allergic reactions occurred in patients administered drugs for the first time, seriously threaten man's survival. Due to the frequent reports of pseudo-allergic reactions to Danshen injection, in our previous study, isosalvianolic acid C in Danshen injection was found to trigger off mast cell degranulation. However, the direct involvement and the mechanisms underlying pseudo-allergic reactions have not been elucidated. In this study, the pseudo-allergic reactions induced by isosalvianolic acid C were confirmed by an ear swelling assay, a hindpaw swelling and extravasation assay in vivo and mast cell degranulation assays in vitro. We also evaluated whether the pseudo-allergic effect is related to MRGPRX2, Isosalvianolic acid C induced Ca²⁺ mobilization was verified as MRGPRX2-related by Ca²⁺ imaging using mouse peritoneal mast cells (both wild-type and MrgprB2 knockout mice), MRGPRX2-expressing HEK293 and MrgprB2-expressing HEK293 cells. MRGPRX2-related pseudo-allergic reactions induced by Isosalvianolic acid C were further confirmed by MrgprB2 knockout mice and MRGPRX2 knockdown mast cells both exhibited reduced isosalvianolic acid C-induced pseudo-allergic effects. Furthermore, both the frontal analysis and molecular docking assays showed that isosalvianolic acid C has a considerable affinity with MRGPRX2. Based on the above experiments, the western blot analyses were conducted, the results indicated that isosalvianolic acid C induced Ca²⁺ mobilization and degranulation via the activation of PLC-γ and IP3R, and releasing chemokines via the activation of PLC-γ, PKC and P38. This study should alarm many clinicians that medicines containing isosalvianolic acid C might induce pseudo-allergic reactions, and it may provide guidance on safe dosage of these medicines in the process of production and use.