Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
J Neurosci. 2011 May 18;31(20):7563-7. doi: 10.1523/JNEUROSCI.1192-11.2011.
Chronic itch accompanying many dermatological, neurological, and systemic diseases is unresponsive to antihistamines. Our knowledge of endogenous chemicals that evoke histamine-independent itch and their molecular targets is very limited. Recently it was demonstrated in behavioral and cellular experiments that bovine adrenal medulla 8-22 peptide (BAM8-22), a proteolytically cleaved product of proenkephalin A, is a potent activator of Mas-related G-protein-coupled receptors (Mrgprs), MrgprC11 and hMrgprX1, and induces scratching in mice in an Mrgpr-dependent manner. To study the sensory qualities that BAM8-22 evokes in humans, we tested the volar forearm of 15 healthy volunteers with heat-inactivated cowhage spicules previously soaked in the peptide. BAM8-22 produced itch in each subject, usually accompanied by sensations of pricking/stinging and burning. The sensations were occasionally accompanied by one or more mechanically evoked dysesthesias, namely alloknesis, hyperknesis, and/or hyperalgesia, but no wheal or neurogenic flare in the skin surrounding the application site. The inactive truncated peptide BAM8-18 produced weak or no sensations. Pretreatment of the tested skin with an antihistamine cream (doxepin) inhibited histamine-induced sensations, dysesthesias, and skin reactions but not the sensations and dysesthesias evoked by BAM8-22. We show that BAM8-22 produces itch and nociceptive sensations in humans in a histamine-independent manner. Thus, BAM8-22 may be an endogenous itch mediator that activates, in humans, MrgprX1, a novel target for potential anti-itch treatments.
许多皮肤病学、神经病学和系统性疾病都伴有慢性瘙痒,而抗组胺药对此并无作用。我们对引起非组胺依赖性瘙痒的内源性化学物质及其分子靶点知之甚少。最近的行为学和细胞实验表明,牛肾上腺髓质 8-22 肽(BAM8-22)是前啡肽 A 的蛋白水解产物,是 Mas 相关 G 蛋白偶联受体(Mrgprs)、MrgprC11 和 hMrgprX1 的有效激活剂,并以 Mrgpr 依赖的方式诱导小鼠搔抓。为了研究 BAM8-22 在人类中引起的感觉特性,我们用先前浸泡在肽中的热灭活牛痘刺测试了 15 名健康志愿者的前臂掌侧。BAM8-22 引起了每位受试者的瘙痒,通常伴有刺痛/刺痛和灼热感。这些感觉偶尔伴有一种或多种机械诱发的感觉异常,即异感、超敏和/或痛觉过敏,但在应用部位周围的皮肤周围没有风团或神经源性红斑。无活性的截断肽 BAM8-18 产生微弱或无感觉。用抗组胺乳膏(多虑平)预处理测试皮肤可抑制组胺引起的感觉、感觉异常和皮肤反应,但不能抑制 BAM8-22 引起的感觉和感觉异常。我们表明,BAM8-22 以非组胺依赖性方式在人类中产生瘙痒和疼痛感觉。因此,BAM8-22 可能是一种内源性瘙痒介质,它在人类中激活 MrgprX1,这是一种潜在抗瘙痒治疗的新靶点。