title: Role of TRPA1 in cortical spreading depression-associated migraine pathophysiology
Creators: name: Jiang, Liwen
Publisher: name: University of Liverpool Repository
Year: 2027

description: Introduction: Migraine is a neurovascular disorder, ranking as the 2nd most prevalent and 6th most disabling disease. The transient receptor potential ankyrin 1 (TRPA1), a cation channel that is sensitive to stress, has been proposed as a potential target for migraine therapy in that the channel activation triggers mechanical allodynia, alters cerebral blood flow changes and causes headache in patients. However, how TRPA1 regulates cortical spreading depression (CSD), one of the key pathophysiological features of migraine with aura, that is also known to subsequently lead to peripheral sensitizations, is not fully known. Albeit our groups’ data show that TRPA1 regulates cortical susceptibility to CSD in vitro, little is known about whether and how TRPA1 contributes to CSD-associated migraine pathogenesis. Aim: This Ph.D. project aims to explore the role of TRPA1 in regulating cortical susceptibility to CSD in vivo and CSD-associated oxidative stress, neuroinflammation, changes in cerebral blood flow (CBF) as well as activation of meninges and associated vasculature (MAV). The TRPA1 downstream signaling in mediating CSD involving calcitonin gene-related peptide (CGRP) and Src family kinases (SFK), two key intracellular signals that can regulate cortical susceptibility to CSD are also explored. Methods: Multi-disciplinary methods were applied: Electrophysiology for high potassium-induced CSD induction and recording both in rats and mice; Intrinsic optic signal imaging for CSD recording in the mouse brain slice; Immunohistochemistry, western blot and enzyme-linked immunosorbent assay for protein detection; Real-time quantitative PCR for gene expression analysis; Laser Doppler Flowmetry for monitoring CBF changes. Results: The data first displayed that knockout of TRPA1 showed lowered cortical susceptibility to CSD in mice; Consistently, pharmacological deactivation of TRPA1 via pre-intracerebroventricular (i.c.v.) injection of anti-TRPA1 antibody reduced cortical susceptibility to CSD in rats. Additionally, pretreatment of the anti-TRPA1 antibody into contralateral i.c.v. reduced malondialdehyde level and interleukin-1β gene and protein expression 10 minutes after CSD in ipsilateral cerebral cortices of rats. Unexpectedly, no changes in CSD-associated CBF were observed in TRPA1 knockout mice when comparing with wild type. Furthermore, RNA-seq analysis showed that pretreatment of anti-TRPA1 antibody was able to counteract changes in CSD-induced gene expression profile to a large extent (878 genes), which took 78% of those altered by CSD. These genes were largely related to pathways in synaptic transmission, ion transport and neuroinflammation such as Plp1, Oxt, Grin2a, Gabra2, Avp and Gjd2, suggesting TRPA1 contributes to MAV activation in CSD-associated migraine. Further investigation on downstream signaling of TRPA1 showed that both CGRP and SFK activity were involved in TRPA1-mediated CSD. Conclusion: These data demonstrate that TRPA1 activation facilitates cortical susceptibility to CSD and subsequent central sensitization and MAV activation. The underlying mechanism of TRPA1-mediated CSD involves SFK activity and CGRP. The novel TRPA1 signaling underlying CSD-associated pathophysiology provides a future therapeutic direction especially for migraine with aura.