Polymyxin B and polymyxin E induce anaphylactoid response through mediation of Mas-related G protein-coupled receptor X2.

Polymyxin B (PMB) and polymyxin E (PME) are cyclic, peptide antibiotics which derived from various species of Paenibacillus (Bacillus) polymyxa. They are decapeptide antibiotics with an antimicrobial spectrum that includes Gram-negative bacteria, and reused as therapeutic agents due to the emergence of multidrug-resistant (MDR) Gram-positive bacteria. PMB or PME-induced anaphylactoid reactions in the clinic have been documented. However, the mechanism underlying anaphylactoid reaction induced by polymyxin has not yet been reported. Here, we report that human Mas-related G protein-coupled receptor X2 (MRGPRX2) and its mouse homologue Mas-related G protein-coupled receptor B2 (MrgprB2) are the receptors mediating the anaphylactoid response provoked by PMB and PME. We firstly investigated the anaphylactoid reactions induced by PMB and PME in LAD2 cells in vitro and in vivo, and found that treatment with PMB and PME led to significant release of mast cell granules such as histamine and β-hexosaminidase, secretion of pro-inflammatory cytokines, such as TNF-α and PGD2, and provocation of calcium flux in LAD2 cells. Furthermore, treatment with PMB and PME led to reduced release of β-hexosaminidase in MRGPRX2 knockdown-LAD2 cells, and obvious increased calcium release in MRGPRX2 overexpressing HEK293 cells, which suggested that MRGPRX2 are involved in mast cell activation provoked by PMB or PME. In vivo, MRGPRB2 knockout mice exhibited lower pseudo-allergic reactions than wild type mice. Activation of MrgprB2 also triggers increased capillary permeability and paw swelling. Our results elucidated the role of MRGPRX2 in PMB and PME-induced anaphylactoid response and suggested that MRGPRX2 as a potential therapeutic target to control the anaphylactoid reactions which triggered by PMB or PME.