Functional Analysis of Mrgpr Family in itch sensation

Mrgpr家族在痒觉中的功能分析

• 批准号: 10360966
• 负责人: Xinzhong Dong
• 金额: $ 61.99万
• 依托单位: JOHNS HOPKINS UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-02-07 至 2026-01-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10360966
• 关键词: Adenine; Afferent Neurons; Agonist; Allergens; Allergic Contact Dermatitis; American; Anticonvulsants; Antihistamines; Behavioral Model; Bile Acids; Bilirubin; Binding; Biological Assay; Cholestasis; Chronic Kidney Failure; Clinical; Complex; Data; Development; Dinitrochlorobenzene; Disease; Electrophysiology (science); Family; Funding; G-Protein-Coupled Receptors; GTP-Binding Protein alpha Subunits, Gs; Goals; Hemodialysis; Histamine; Homologous Gene; Human; Image; In Vitro; Inflammation; Injections; Irritant Dermatitis; Kidney Diseases; Kidney Failure; Knockout Mice; Knowledge; Lead; Life; Mediating; Mediator of activation protein; Modeling; Molecular; Mus; Neurons; Oxazolone; Pathogenesis; Pathologic; Pathway interactions; Patients; Peptides; Pharmaceutical Preparations; Pharmacology; Phenytoin; Plasma; Play; Pruritus; Quality of life; Research; Rhus radicans; Role; Sampling; Skin; Spinal Ganglia; Stimulus; Symptoms; Testing; Therapeutic; afferent nerve; antagonist; associated symptom; bile duct; chronic itch; disabling symptom; in vivo; insight; interdisciplinary approach; mast cell; member; mortality; mouse genetics; mouse model; neuropeptide FF; novel; patient screening; pruriceptive neurons; receptor; side effect; skin disorder; solute; wasting

Project Summary The goal of our research is to understand the cellular and molecular mechanisms of chronic itch, a disease that interferes with normal daily activity and can have serious clinical consequences. Many pathological conditions can lead to chronic itch such as localized skin diseases or more systemic conditions like cholestasis and kidney failure. Itch can also be a side effect of many therapeutic drugs. Current therapies including antihistamines are ineffective in most chronic itch conditions suggesting the involvement of histamine independent pathways. A major hurdle in understanding histamine-independent itch is the lack of knowledge about the receptors directly activated by non-histaminergic stimuli. Primary sensory neurons in dorsal root ganglia (DRG) play an essential role in detecting itch. Our lab has identified members of a G protein-coupled receptor (GPCR) Mrgpr family that are specifically expressed in DRG and function as itch receptors. Recently we showed that MrgprA1 in mice and its human homologue MRGPRX4 function as novel itch receptors, detecting bilirubin and bile acids (BAs). More importantly, we demonstrated that MrgprA1/X4 play an essential role for mediating cholestatic pruritus (itch), a condition resulting in elevated bilirubin and BAs due to bile duct blockage. Our preliminary data suggest that MrgprA1 are novel receptors for various therapeutic drugs and mediates drug-induced itch side effect. Preliminary data show that MrgprA1 also contributes to allergic contact dermatitis (ACD). Furthermore, previous studies and our preliminary data suggest BAs are also mediators for uremic pruritus. In this proposal, we will take a multidisciplinary approach to test the hypothesis that MrgprA1/X4 are itch receptors and mediate itch caused by different disease conditions including medication caused itch side effect, ACD, and kidney disease which dramatically impact the quality of patient's life and the underlying mechanisms remain unclear. In Aim I, we will test the hypothesis that some of drugs with itch side effect are pruritogens themselves by directly activating pruriceptive (itch sensing) neurons via MrgprA1 using mouse genetics, pharmacology, in vitro Ca2+ imaging, electrophysiology, and in vivo DRG imaging. In Aim II, we will test the hypothesis that MrgprA1 in sensory nerves and its peptide agonist NPFF released from nearby mast cells in the skin contributes to ACD itch using different ACD mouse models combined with mouse genetics and pharmacological approaches. In addition, we will determine whether pruriceptive neurons are activated under ACD conditions and if so whether MrgprA1 and NPFF mediate the activation using in vivo DRG GCaMP imaging. In Aim III, we will employ two uremic itch mouse models, an adenine-induced or a uremic itch patient plasma injection model to test the hypothesis that BAs mediate uremic itch by activating MRGPRX4 expressed in mouse DRG neurons. Moreover, we will identify other itch mediators present in patient plasma who are receiving hemodialysis due to kidney failure. The results of this project will provide insight into key itch mechanisms and open the door for the development of novel itch therapeutics.

项目摘要 我们研究的目的是了解慢性瘙痒的细胞和分子机制，这种疾病是一种疾病 干扰日常活动正常，可能会带来严重的临床后果。许多病理条件 可能导致慢性瘙痒，例如局部皮肤疾病或更多的全身性疾病，例如胆汁淤积和 肾衰竭。瘙痒也可能是许多治疗药物的副作用。当前疗法包括 抗组胺药在大多数慢性瘙痒状况中无效，表明组胺参与 独立途径。理解独立于组胺的瘙痒的主要障碍是缺乏知识 关于直接被非希斯胺能刺激激活的受体。背根中的主要感觉神经元 神经节（DRG）在检测瘙痒中起着至关重要的作用。我们的实验室已经确定了G蛋白耦合的成员 受体（GPCR）MRGPR家族在DRG中特异性表达并充当瘙痒受体。最近 我们表明，小鼠及其人类同源物MRGPRX4的MRGPRA1充当新型瘙痒受体， 检测胆红素和胆汁酸（BAS）。更重要的是，我们证明了MRGPRA1/X4发挥着必不可少的 介导胆固性瘙痒（ITCH）的作用，这种疾病导致胆红素升高和BAS，胆管导致BAS 阻塞。我们的初步数据表明，MRGPRA1是各种治疗药物的新型受体， 介导药物引起的瘙痒副作用。初步数据表明，MRGPRA1也有助于过敏反应 皮炎（ACD）。此外，以前的研究和我们的初步数据表明，BAS也是中介者 尿毒症瘙痒。在此提案中，我们将采用一种多学科的方法来检验以下假设 MRGPRA1/X4是瘙痒受体，并介导由不同疾病（包括药物）引起的瘙痒 引起瘙痒性副作用，ACD和肾脏疾病，这极大地影响了患者的生活质量和 潜在机制尚不清楚。在AIM I中，我们将检验以下假设：一些有瘙痒一面的药物 效果是通过使用MRGPRA1直接激活培养基（瘙痒感应）神经元的效果。 小鼠遗传学，药理学，体外CA2+成像，电生理学和体内DRG成像。在AIM II中， 我们将检验以下假设：感觉神经中的MRGPRA1及其肽激动剂NPFF从附近释放 皮肤中的肥大细胞使用不同的ACD小鼠模型有助于ACD瘙痒 遗传学和药理方法。此外，我们将确定牙齿神经元是否是 在ACD条件下激活，如果是MRGPRA1和NPFF，使用体内介导激活 DRG GCAMP成像。在AIM III中，我们将采用两种尿毒症小鼠模型，一个腺嘌呤诱导或 尿毒症瘙痒患者血浆注射模型，以测试BAS通过激活介导尿毒症瘙痒的假设 MRGPRX4在小鼠DRG神经元中表达。此外，我们将确定存在于 由于肾衰竭而接受血液透析的患者血浆。该项目的结果将提供 深入了解关键瘙痒机制，并为开发新颖的瘙痒疗法打开大门。