A Group of Cationic Amphiphilic Drugs Activates MRGPRX2 and Induces Scratching Behavior in Mice

Abstract Background Mas gene-related G protein-coupled receptors (MRGPRs) are a GPCR family responsive to various exogenous and endogenous agonists, playing a fundamental role in pain and itch sensation. The primate-specific family member MRGPRX2 and its murine orthologue MRGPRB2 are expressed by mast cells, mediating IgE-independent signaling and pseudo-allergic drug reactions. Objectives Therefore, knowledge about the function and regulation of MRGPRX2/MRGPRB2 is of major importance in prevention of drug hypersensitivity reactions and drug-induced pruritus. Methods To identify novel MRGPR (ant)agonists, we screened a library of pharmacologically active compounds utilizing a high-throughput calcium mobilization assay. Identified hit compounds were analyzed for their pseudo-allergic and pruritogenic effects in mice and human. Results We found a class of commonly used drugs activating MRGPRX2 which consists to a large extent of antidepressants, antiallergic drugs, and antipsychotics. Three-dimensional pharmacophore modeling revealed structural similarities of the identified agonists, classifying them as cationic amphiphilic drugs. Mast cell activation was investigated using the three representatively selected antidepressants clomipramine, paroxetine, and desipramine. Indeed, we could show a concentration-dependent activation and MRGPRX2-dependent degranulation of the human mast cell line LAD2. Furthermore, clomipramine, paroxetine, and desipramine were able to induce degranulation of human skin and murine peritoneal mast cells. These substances elicited dose-dependent scratching behavior upon intradermal injection in C57BL/6 mice but less in MRGPRB2-mutant mice as well as wheal-and-flare reactions upon intradermal injections in humans. Conclusion Our results contribute to the characterization of structure-activity relationships and functionality of MRGPRX2 ligands and facilitate prediction of adverse reactions like drug-induced pruritus to prevent severe drug hypersensitivity reactions.