Table2_Pharmacological blockade of the mast cell MRGPRX2 receptor supports investigation of its relevance in skin disorders.pdf

IntroductionBecause MRGPRX2 is now recognized as the mast cell receptor for basic secretagogues, there is currently a tremendous interest in whether MRGRPX2 could play an important role in various pruritic dermatoses such as chronic spontaneous urticaria. Therefore, we sought to identify new potent and selective antagonists to pharmacologically characterize the biological role of MRGPRX2.MethodsVarious relevant in vitro, ex vivo, and in vivo model systems were used to investigate the role of MRGPRX2. This included the study of freshly isolated human skin mast cells and human basophils as well as an ex vivo human skin microdialysis preparation. The additivity of MRGPRX2 and FcεR1-mediated degranulation was also investigated. Human MRGPRX2 knock-in mice were generated to interrogate pharmacokinetic/pharmacodynamic relationships because both antagonists studied were shown to be human specific.ResultsTwo novel and structurally distinct MRGPRX2 antagonists were identified with one, Compound B, being orally active and demonstrating high potency in blocking Substance P–mediated degranulation using freshly isolated human skin mast cells with half maximal inhibitory concentration (IC50) at 0.42 nM. Compound B also potently blocked Substance P–stimulated histamine release from resident mast cells in a human skin explant setup as well as blocking itch in an established behavioral scratching model using MRGPRX2 knock-in mice. Unlike human mast cells, Substance P failed to elicit a functional response in human basophils.ConclusionThese data fully support the investigation of MRGPRX2 receptor antagonists in mast cell–driven allergic skin disorders such as chronic spontaneous urticaria.

引言：鉴于MRGPRX2现已被确认为基本分泌剌激剂的肥大细胞受体，目前对于MRGPRX2在诸如慢性自发性荨麻疹等瘙痒性皮炎中是否可能发挥重要作用，产生了极大的兴趣。因此，本研究旨在寻找新的强力且具有选择性的拮抗剂，以药理学方式表征MRGPRX2的生物作用。方法：本研究采用了多种相关的体外、离体和体内模型系统来探究MRGPRX2的作用，包括新鲜分离的人体皮肤肥大细胞和人体嗜碱性粒细胞的研究，以及离体人体皮肤微透析制备。同时，还研究了MRGPRX2与FcεR1介导的脱颗粒的叠加性。通过构建人MRGPRX2敲入小鼠，以研究药代动力学/药效学关系，因为所研究的两种拮抗剂均已被证实具有人类特异性。结果：鉴定出两种新型且结构独特的MRGPRX2拮抗剂，其中之一，化合物B，具有口服活性，并且在对新鲜分离的人体皮肤肥大细胞进行Substance P介导的脱颗粒抑制实验中表现出高效性，其半数最大抑制浓度（IC50）为0.42 nM。化合物B还能有效地抑制人体皮肤移植模型中驻留肥大细胞受到Substance P刺激后释放组胺，以及通过MRGPRX2敲入小鼠模型阻断瘙痒行为。与人体肥大细胞不同，Substance P未能引起人体嗜碱性粒细胞的功能性反应。结论：这些数据充分支持了对MRGPRX2受体拮抗剂在肥大细胞驱动型过敏性皮肤疾病，如慢性自发性荨麻疹中的研究。