Sex differences in the expression of calcitonin gene-related peptide receptor components in the spinal trigeminal nucleus

Yadong Ji,Alexandra Rizk,Pamela Voulalas,Hanan Aljohani,Simon Akerman,Gregory Dussor,Asaf Keller,Radi Masri

doi:10.1016/j.ynpai.2019.100031

Abstract

Background and purposeCalcitonin gene-related peptide (CGRP) plays an important role in migraine pathophysiology. CGRP acts primarily by activating a receptor composed of 3 proteins: calcitonin receptor-like receptor (CLR), receptor activity-modifying protein 1 (RAMP1), and receptor component protein (RCP). We tested the hypothesis that sex differences exist in protein levels of two key components of this CGRP receptor: CLR and RCP. MethodsWe used specific antibodies to assess baseline protein levels of CLR and RCP in the spinal trigeminal nucleus caudalis (SpVc) and upper cervical spinal cord of both male and female rats. We also tested if manipulations that knock-down the expression of RCP in SpVc, using locally-mediated gene transfer of short hairpin RNA (shRNA), ameliorate pain in an animal model of intracranial migraine-like pain induced by chemical noxious stimulation of the meninges. To assess pain, we used tests of ongoing pain (rat face grimace test and freezing behavior) and tests of facial mechanical hypersensitivity and allodynia. ResultsThere was no difference in CLR levels between male and female animals (p > 0.11) in SpVc and the upper cervical cord. However, female animals exhibited greater baseline levels of RCP (up to 3-fold higher) compared to males (p < 0.002). The knock-down of RCP expression in SpVc attenuated mechanical facial allodynia induced by chemical noxious stimulation of the meninges, but had little effect on ongoing pain behaviors in female and male animals. ConclusionsRCP is an integral component of the CGRP receptor and may play a key role in mediating CGRP induced central sensitization after noxious stimulation of the meninges. RCP expression in the SpVc and upper cervical cord is sexually dimorphic, with higher levels of expression in females. This dimorphism may be related to the increased incidence of migraines in females–a hypothesis that should be tested in the future.

Highlights

Migraine afflicts hundreds of millions of individuals worldwide, with a pronounced sex difference as migraine is 3 times more prevalent in females than males (Lipton and Stewart, 1998)
We test the null hypothesis that there is no difference in protein expression of Calcitonin gene-related peptide (CGRP) receptor components in the spinal trigeminal nucleus caudalis (SpVc) and upper cervical spinal cord between male and female rats
We tested if there are sex differences in the expression of calcitonin receptor-like receptor (CLR) and receptor component protein (RCP)—two key components of the CGRP receptor—in the brainstem containing SpVC

Summary

Introduction

Migraine afflicts hundreds of millions of individuals worldwide, with a pronounced sex difference as migraine is 3 times more prevalent in females than males (Lipton and Stewart, 1998). We tested if manipulations that knock-down the expression of RCP in SpVc, using locally-mediated gene transfer of short hairpin RNA (shRNA), ameliorate pain in an animal model of intracranial migraine-like pain induced by chemical noxious stimulation of the meninges. Results: There was no difference in CLR levels between male and female animals (p > 0.11) in SpVc and the upper cervical cord. The knock-down of RCP expression in SpVc attenuated mechanical facial allodynia induced by chemical noxious stimulation of the meninges, but had little effect on ongoing pain behaviors in female and male animals. RCP expression in the SpVc and upper cervical cord is sexually dimorphic, with higher levels of expression in females This dimorphism may be related to the increased incidence of migraines in females–a hypothesis that should be tested in the future

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Conclusion