Wednesday, April 17, 2024
4/17/2024
Project Summary/Abstract Migraine is a painful, chronic neurological disorder that represents the second most disabling illness worldwide. Two of the mechanisms that to contribute to migraine pain are immune cell activation and calcitonin gene-related peptide (CGRP) signaling. This proposal investigates the connection between these two mechanisms. Cortical spreading depression (CSD), thought to underlie the aura that precedes migraine attack in a subpopulation of migraineurs, is associated with increased meningeal macrophage activation. Macrophages can activate meningeal primary afferent neurons and promote migraine pain through release of pro-inflammatory cytokines, which are increased in patient cerebrospinal fluid (CSF) during migraine. CSD also increases CGRP synthesis and release, and single-cell RNA sequencing data support the expression of CGRP receptor subunit mRNA in mouse meningeal immune cells. Elevated CGRP in patient plasma and CSF and the efficacy of CGRP receptor antagonists as migraine therapies support the central role of CGRP in the development of migraine pain. However, the mechanism of action of these drugs is incompletely understood. Given the effect of CSD on immune cell activation and CGRP release, the presence of CGRP receptor on immune cells, and the use of CGRP receptor antagonists to treat migraine, I hypothesize that the efficacy of CGRP receptor antagonists is mediated by their ability to inhibit the activation of pro-inflammatory macrophages in the meninges. In a set of experiments described under three specific aims, I will use anatomical (Aim 1), functional (Aim 2), and behavioral (Aim 3) approaches to test my hypothesis in the context of a minimally invasive model of migraine with aura (optogenetic spreading depression, OSD). I will characterize OSD-dependent changes in CGRP receptor expression in meningeal immune cells using fluorescent in situ hybridization and RT-qPCR (Aim 1). I will assess the ability of CGRP receptor antagonists to prevent OSD-induced changes in macrophage morphology and phenotype consistent with activation using real-time in vivo two-photon microscopy (Aim 2A) and flow cytometry (Aim 2B). Finally, I will assess the contribution of macrophage CGRP receptors to OSD- induced pain behavior using a selective depletion strategy (Aim 3). The outcomes of these experiments may not only reveal a mechanism underlying the therapeutic efficacy of CGRP antagonists but potentially novel targets and mechanisms to improve existing migraine therapies. In completing this proposal, I will develop valuable technical skills and receive rigorous intellectual training necessary to becoming an independent investigator, and I have assembled a team of expert scientist and clinician mentors to help ensure my success. Thus, this fellowship will allow me to achieve my long-term goal of becoming an academic neurologist-scientist working at the intersection of pain research and clinical neurology.
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