屋尘螨Derp1介导Mas相关G蛋白偶联受体在慢性瘙痒中的发病机制研究

Chronic pruritus is the main symptom of allergic skin diseases which can be induced by the house dust mite. It has a serious impact on the quality of life. Mast cell plays an important role in the pruritus and the pathogenesis of the histamine-independent is the hot area in recent years. Our previous research demonstrated that Derp1 can induce human mast cell degranulation to release tryptase by activating the Proteinase-activated receptor-2（PAR2） receptor on the surface of mast cells, but the blockade of PAR2 only inhibit part of the cell activation. The other research showed that Mas-related G protein-coupled receptors (Mrgprs) existed on the surface of the mast cell. Derp1 can both activate PARs and Mrgprs. At the same time,our previous research showed that Mrgprs were upregulated in the skin lesion of the histamine-insensitive patients with chronic pruritus. Therefore, we infer that Derp1 can activated the Mrgprs on the mast cell. In this project, we will collect the clinical cases and build the model of the Mrgprs（-/-）mice and the mast cells. Through the change of the mast cell and the Mrgprs/TRPV1 pathway after the Derp1 stimulation, we will prove the “activation of Derp1-Mrgprs-mast cells degranulation”pathway which will reveal a new target of the pathogenesis of chronic pruritus and to provide new theoretical basis for inhibiting pruritus.

慢性瘙痒是过敏性皮肤病的主要症状，屋尘螨是常见诱因，严重影响患者生活质量。肥大细胞是参与慢性瘙痒的关键细胞，其组胺非依赖性致痒机制是近年来研究热点。我们既往研究提示，屋尘螨Derp1可通过蛋白酶激活受体2引起组胺非依赖性肥大细胞活化，而体内外模型中单纯阻断该通路仅能部分（~20%）逆转其细胞活化。近年研究表明，肥大细胞表面存在Mas相关G蛋白偶联受体（Mrgprs），Derp1对于下游PARs与Mrgprs存在交叉激活，我们预实验中发现，临床抗组胺药治疗无效的慢性瘙痒患者，其皮损中肥大细胞高表达Mrgprs。我们推测Derp1可通过Mrgprs引起肥大细胞活化。本研究从临床出发，构建Mrgprs基因敲除小鼠瘙痒模型，研究Derp1刺激下其肥大细胞表型和功能改变，检测Mrgprs/TRPV1信号通路变化，阐明屋尘螨介导Mrgprs在肥大细胞活化中的作用，为慢性瘙痒的治疗提供新的理论依据。

瘙痒是皮肤病最常见的临床症状之一，特应性皮炎、结节性痒疹等慢性炎症性皮肤病伴随的瘙痒感觉最为强烈，迁延不愈，严重影响患者的生活质量。本研究通过转录组测序（RNA-sequencing，RNA-seq）首次解析了痒疹型特应性皮炎（Prurigo nodularis phenotype of atopic dermatitis，PN-AD）的基因表达谱并描绘了不同亚型AD的瘙痒分子图谱。发现PN-AD和非痒疹型特应性皮炎（Non-prurigo nodularis phenotype of atopic dermatitis，NPN-AD）的免疫表型在主体上大致相似，以Th2型免疫为主。lncRNA下调和Th17免疫增强可能在PN-AD的发病机制中有重要意义。NPN-AD中花生四烯酸和谷胱甘肽代谢通路更为活跃，而蛋白聚糖代谢、RAGE受体结合、血管反应和血小板激活、神经突触成熟与修剪等途径在PN-AD中更具代表性。另外，我们发现ADM基因表达升高可能在PN-AD的致痒机制中具有重要意义。与非疾病组皮肤相比，PN-AD皮损而不是NPN-AD皮损中，ADM基因编码的多肽，肾上腺髓质素N端20肽(Proadrenomedullin N-terminal 20 peptide，PAMP)的mRNA和蛋白表达、肥大细胞募集、神经纤维密度均显著增加。体外实验证实， Mas相关G蛋白偶联受体B2亚型（Mas-related G protein-coupled receptor B2，MrgprB2）的表达在不同类型肥大细胞中具有异质性，在小鼠腹腔（Peritoneal mast cells，PMC）来源的原代肥大细胞中高表达而小鼠骨髓来源的原代肥大细胞中低表达。PAMP9-20通过MrgprB2通路引起小鼠PMC的速发相及迟发相免疫应答，介导慢性瘙痒的发生。本课题利用RNA-seq技术，解析伴重度瘙痒的PN-AD和NPN-AD的基因表达谱和信号通路特征，在整体上全面的筛选新型的内源性致痒原和组胺非依赖的痒觉传导通路，拓宽对慢性瘙痒发病机制的认识，为慢性瘙痒的治疗寻找潜在的候选药物靶点。肥大细胞MrgprB2/MRGPRX2通路是独立于经典IgE通路的新型痒觉传导通路，可能是治疗难治性慢性瘙痒的候选药物靶点。