Baggio Darciane F, Gambeta Eder, Souza Ivana A, Huang Sun, Zamponi Gerald W, Chichorro Juliana G
Department of Pharmacology, Biological Sciences Sector, Federal University of Parana, Curitiba, PR, Brazil.
Department of Clinical Neuroscience, Hotchkiss Brain Institute and Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
J Headache Pain. 2024 Dec 18;25(1):219. doi: 10.1186/s10194-024-01921-0.
Migraine is a painful neurological syndrome characterized by attacks of throbbing headache, of moderate to severe intensity, which is associated with photo- and phono- sensitivity as well as nausea and vomiting. It affects about 15% of the world's population being 2-3 times more prevalent in females. The calcitonin gene-related peptide (CGRP) is a key mediator in the pathophysiology of migraine, and a significant advance in the field has been the development of anti-CGRP therapies. The trigeminal ganglion (TG) is thought to be an important site of action for these drugs. Moreover, experimental migraine can be induced by CGRP injection in the TG. The signaling pathway induced by CGRP in the TG is not fully understood, but studies suggest that voltage-gated calcium channels contribute to CGRP effects relevant to migraine.
We hypothesised that CGRP injection in the TG enhances Ca3.2 T-type calcium channel currents to contribute to the development of periorbital mechanical allodynia.
A Co-Immunoprecipitation assay in tsA-201 cells revealed that Ca3.2 channels form a complex with RAMP-1, a component of the CGRP receptor. Constitutive CGRPR activity was able to inhibit Ca3.2 channels and induce a depolarizing shift in both activation and inactivation curves. Incubation of TG neurons with CGRP increased T-type current density by ~ 3.6 fold, an effect that was not observed in TG neurons from Ca3.2 knockout mice. Incubation of TG neurons with Z944, a pan T-type channel blocker, resulted in an approximately 80% inhibition of T-type currents. In vivo, this treatment abolished the development of periorbital mechanical allodynia induced by CGRP in male and female mice. Likewise, Ca3.2 knockout mice did not develop periorbital mechanical allodynia after intraganglionic CGRP injection. Finally, we demonstrated that the CGRP effect depends on the activation of its canonical GPCR, followed by protein kinase A activation.
The present study suggests that CGRP modulates Ca3.2 in the TG, an effect possibly mediated by the canonical CGRP receptor and PKA activation. The increase in T-type currents in the TG may represent a contributing factor for the initiation and maintenance of the headache pain during migraine.
偏头痛是一种疼痛性神经综合征，其特征为搏动性头痛发作，强度为中度至重度，伴有对光和声音敏感以及恶心和呕吐。它影响着全球约15%的人口，在女性中的患病率是男性的2至3倍。降钙素基因相关肽（CGRP）是偏头痛病理生理学中的关键介质，该领域的一项重大进展是抗CGRP疗法的开发。三叉神经节（TG）被认为是这些药物的重要作用部位。此外，在TG中注射CGRP可诱发实验性偏头痛。CGRP在TG中诱导的信号通路尚未完全了解，但研究表明电压门控钙通道参与了与偏头痛相关的CGRP效应。
我们假设在TG中注射CGRP会增强Ca3.2 T型钙通道电流，从而导致眶周机械性异常性疼痛的发生。
在tsA - 201细胞中进行的免疫共沉淀试验表明，Ca3.2通道与CGRP受体的一个组成部分RAMP - 1形成复合物。组成型CGRPR活性能够抑制Ca3.2通道，并使激活曲线和失活曲线发生去极化偏移。用CGRP孵育TG神经元可使T型电流密度增加约3.6倍，而在Ca3.2基因敲除小鼠的TG神经元中未观察到这种效应。用泛T型通道阻滞剂Z944孵育TG神经元可使T型电流受到约80%的抑制。在体内，这种治疗消除了CGRP在雄性和雌性小鼠中诱导的眶周机械性异常性疼痛的发生。同样，Ca3.2基因敲除小鼠在神经节内注射CGRP后未出现眶周机械性异常性疼痛。最后，我们证明CGRP的作用取决于其经典GPCR的激活，随后是蛋白激酶A的激活。
本研究表明CGRP在TG中调节Ca3.2，这种效应可能由经典的CGRP受体和PKA激活介导。TG中T型电流的增加可能是偏头痛发作和维持头痛疼痛的一个促成因素。
