MRGPRX2 and Immediate Drug Hypersensitivity: Insights from Cultured Human Mast Cells.

BACKGROUND AND OBJECTIVE: Mast cell (MC) degranulation via activation of the Mas-related G protein-coupled receptor X2 (MRGPRX2) is held to be of key importance for immediate drug hypersensitivity (IDH). However, data in humans are limited to observations in specific cell lines. Objective: To study the usefulness of silencing MRGPRX2 in human MCsto further unveil the MRGPRX2 pathway in IDH.

METHODS: MCs were cultured out of CD34+ve progenitor cells obtained from peripheral blood (PBCMCs) and incubated with substance P as positive control, rocuronium, moxifloxacin, morphine oramoxicillin. Immunophenotyping of the cells included flow cytometric and microscopic analyses of the expression of CD117, CD203c and MRGPRX2. Intracellular calcium was measured using Fluo-4. Degranulation was analyzed by quantification of CD63expression. For MRGPRX2 silencing, MCs were electroporated with Dicer-substrate silencing RNAs.

RESULTS: Incubation of MCs with substance P, morphine and moxifloxacin increased intracellular calcium levels and triggered MC degranulation, which, for the drugs, is almost completely abolished by selective MRGPRX2 silencing. Despite an increase in intracellular calcium in MRGPRX2+ve cells, incubation with non-toxic concentrations of rocuronium does not result in degranulation of PBCMCs, whereas amoxicillin has no effect on PBCMCs.

CONCLUSION: The use of MRGPRX2 silencing inhuman MCs can provide important insights into the role of MRGPRX2 in the pathogenesis of IDH.As induction of calcium signals does not necessarily translate into a secretory response, measurement of the degranulation reaction seems more meaningful in the context of drug testing.