Identification of Natural Compounds Triggering MRGPRX2-Mediated Calcium Flux and Degranulation in RBL-2H3 Cells.

Natural compounds have experienced increasing clinical application, but their association with rapid-onset anaphylactoid reactions (ARs) present a significant challenge to their safe use. These ARs, clinically resembling Type I hypersensitivity, are non-IgE-mediated and involve direct mast cell activation, primarily through the human Mas-related G protein-coupled receptor X2 (MRGPRX2). We computationally screened a natural compound library for MRGPRX2 activation. A human MRGPRX2-expressing cell model was established. Cell viability assays (0-80 μM) were performed to determine appropriate drug concentrations. Compared to the controls, Baohuoside I (10 μM), along with Kaempferol-3-O-rutinoside, Epigallocatechin gallate (EGCG), Isochlorogenic Acid B, Baicalin, Andrographolide, Isorhamnetin, and Dehydroandrographolide (all at 20 μM), significantly increased intracellular calcium flux (p < 0.05) and boosted tryptase and β-hexosaminidase secretion (ELISA) (p < 0.05) in mast cells. Furthermore, the degranulation induced by these compounds was inhibited by the MRGPRX2 inhibitor Z3578 at 20 μM. Neutral red staining was employed to observe cellular morphological changes. Specific compounds capable of mediating ARs through MRGPRX2 activation on mast cells were identified. This contributes to safer and more effective drug use by elucidating the potential triggers of ARs.