Zhou Guo-Kun, Xu Wen-Jing, Lu Yi, Zhou Yan, Feng Chen-Zhang, Zhang Jiang-Tao, Sun Shi-Yu, Wang Ruo-Meng, Liu Tong, Wu Bin
Institute of Pain Medicine and Special Environmental Medicine, Nantong University, Nantong, Jiangsu, China.
Jiangsu Key Laboratory of Neuropsychiatric Diseases, Institute of Neuroscience, Soochow University, Suzhou, China.
Front Mol Neurosci. 2023 Mar 1;16:1086285. doi: 10.3389/fnmol.2023.1086285. eCollection 2023.
Itch is a common symptom of many skin and systemic diseases. Identifying novel endogenous itch mediators and the downstream signaling pathways involved will contribute to the development of new strategies for the treatment of chronic itch. In the present study, we adopted behavioral testing, patch clamp recording and metabonomics analysis to investigate the role of agmatine in itch and the underlying mechanism.
Behavioral analysis was used to evaluate the establishing of acute and chronic itch mice model, and to test the effects of different drugs or agents on mice itch behavior. Western blotting analysis was used to test the effect of agmatine on phosphorylation of ERK (p-ERK) expression in the spinal cord. Patch clamp recording was used to determine the effect agmatine on the excitability of DRG neurons and the role of ASIC3. Finally, the metabonomics analysis was performed to detect the concentration of agmatine in the affected skin under atopic dermatitis or psoriasis conditions.
We fused a mouse model and found that an intradermal injection of agmatine (an endogenous polyamine) into the nape of the neck or cheek induced histamine-independent scratching behavior in a dose-dependent manner. In addition, the ablation of nociceptive C-fibers by resiniferatoxin (RTX) abolished agmatine-induced scratching behavior. However, agmatine-induced itch was not affected by the pharmacological inhibition of either transient receptor potential vanilloid 1 (TRPV1) or transient receptor potential ankyrin 1 (TRPA1); similar results were obtained from TRPV1 or TRPA1 mice. Furthermore, agmatine-induced itch was significantly suppressed by the administration of acid-sensing ion channel 3 (ASIC3) inhibitors, APETx2 or amiloride. Agmatine also induced the upregulation of p-ERK in the spinal cord; this effect was inhibited by amiloride. Current clamp recording showed that the acute perfusion of agmatine reduced the rheobase and increased the number of evoked action potentials in acute dissociated dorsal root ganglion (DRG) neurons while amiloride reversed agmatine-induced neuronal hyperexcitability. Finally, we identified significantly higher levels of agmatine in the affected skin of a mouse model of atopic dermatitis (AD) when compared to controls, and the scratching behavior of AD mice was significantly attenuated by blocking ASIC3.
Collectively, these results provide evidence that agmatine is a novel mediator of itch and induces itch via the activation of ASIC3. Targeting neuronal ASIC3 signaling may represent a novel strategy for the treatment of itch.
瘙痒是许多皮肤和全身性疾病的常见症状。识别新的内源性瘙痒介质及其下游信号通路将有助于开发治疗慢性瘙痒的新策略。在本研究中，我们采用行为测试、膜片钳记录和代谢组学分析来研究胍丁胺在瘙痒中的作用及其潜在机制。
行为分析用于评估急性和慢性瘙痒小鼠模型的建立，并测试不同药物或试剂对小鼠瘙痒行为的影响。蛋白质免疫印迹分析用于检测胍丁胺对脊髓中细胞外信号调节激酶（p-ERK）磷酸化表达的影响。膜片钳记录用于确定胍丁胺对背根神经节（DRG）神经元兴奋性的影响以及酸敏感离子通道3（ASIC3）的作用。最后，进行代谢组学分析以检测特应性皮炎或银屑病条件下受累皮肤中胍丁胺的浓度。
我们建立了一个小鼠模型，发现将胍丁胺（一种内源性多胺）皮内注射到颈部或脸颊可诱导组胺非依赖性搔抓行为，且呈剂量依赖性。此外，树脂毒素（RTX）对伤害性C纤维的消融消除了胍丁胺诱导的搔抓行为。然而，胍丁胺诱导的瘙痒不受瞬时受体电位香草酸亚型1（TRPV1）或瞬时受体电位锚蛋白1（TRPA1）的药理学抑制影响；从TRPV1或TRPA1基因敲除小鼠获得了类似结果。此外，给予酸敏感离子通道3（ASIC3）抑制剂APETx2或阿米洛利可显著抑制胍丁胺诱导的瘙痒。胍丁胺还诱导脊髓中p-ERK上调；这种作用被阿米洛利抑制。电流钳记录显示，急性灌流胍丁胺降低了急性分离的背根神经节（DRG）神经元的阈强度并增加了诱发动作电位的数量，而阿米洛利逆转了胍丁胺诱导的神经元兴奋性过高。最后，我们发现与对照组相比，特应性皮炎（AD）小鼠模型受累皮肤中胍丁胺水平显著更高，并且阻断ASIC3可显著减轻AD小鼠的搔抓行为。
总体而言，这些结果提供了证据表明胍丁胺是一种新的瘙痒介质，并通过激活ASIC3诱导瘙痒。靶向神经元ASIC3信号通路可能代表一种治疗瘙痒的新策略。
