Calcitonin Gene-Related Peptide-Mediated Enhancement of Purinergic Neuron/Glia Communication by the Algogenic Factor Bradykinin in Mouse Trigeminal Ganglia from Wild-Type and R192Q Ca_v2.1 Knock-In Mice: Implications for Basic Mechanisms of Migraine Pain

Abstract

Within the trigeminal ganglion, crosstalk between neurons and satellite glial cells (SGCs) contributes to neuronal sensitization and transduction of painful stimuli, including migraine pain, at least partly through activation of purinergic receptor mechanisms. We previously showed that the algogenic mediator bradykinin (BK) potentiates purinergic P2Y receptors on SGCs in primary trigeminal cultures. Our present study investigated the molecular basis of this effect in wild-type (WT) mice and Ca V 2.1 ␣1 R192Q mutant knock-in (KI) mice expressing a human mutation causing familial hemiplegic migraine type 1. Single-cell calcium imaging of WT cultures revealed functional BK receptors in neurons only, suggesting a paracrine action by BK to release a soluble mediator responsible for its effects on SGCs. We identified this mediator as the neuropeptide calcitonin gene-related peptide (CGRP), whose levels were markedly increased by BK, while the CGRP antagonist CGRP 8-37 and the anti-migraine drug sumatriptan inhibited BK actions. Unlike CGRP, BK was ineffective in neuron-free SGC cultures, confirming the CGRP neuronal source. P2Y receptor potentiation induced by CGRP in SGCs was mediated via activation of the extracellular signal-regulated kinase 1/2 pathways, and after exposure to CGRP, a significant release of several cytokines was detected. Interestingly, both basal and BK-stimulated CGRP release was higher in KI mouse cultures, where BK significantly upregulated the number of SGCs showing functional UTP-sensitive P2Y receptors. Our findings suggest that P2Y receptors on glial cells might be considered as novel players in the cellular processes underlying migraine pathophysiology and might represent new targets for the development of innovative therapeutic agents against migraine pain.

Nucleotide homeostasis and purinergic nociceptive signaling in rat meninges in migraine-like conditions

“…Specifically, ADP generated large Ca 2+ transients not only in neuron but also in glial cells consistent with previous observations obtained in mouse trigeminal cells [27,40,42]. In glial cells, ADP was even more effective likely due to activation of ADP sensitive P2Y receptors [27,34,35]. These data along with functional expression of P2X7 receptors in SGCs are consistent with intra-ganglion crosstalk between neurons and glial cells likely contributing to long lasting migraine pain [42].…”

“…Noteworthy, these nucleotide-hydrolyzing enzymes are abundantly expressed in the blood vessels such as medial meningeal artery, known to be the strategic sites for pain generation [2,4,33]. It is also likely that substantial ectonucleotidase activities are localized in recently discovered dural lymphatic vessels, generally aligning along the adjacent blood vessels and contributing to the drainage of the cerebrospinal fluid into the periphery [34,35]. More thorough co-staining analysis with different cellspecific markers would be necessary to validate this suggestion.…”

“…The activation of meningeal trigemino-vascular system plays a key role in the initiation of migraine pain [4,35,52]. It was proposed that purinergic signaling have an important role in the initiation and transmission of pain signals [53], including migraine pain [5,42].…”

Identifying local and descending inputs for primary sensory neurons

“…Basbaum and colleagues have observed intraganglion transfer of WGA between DRG neurons (58). Others observed intraganglion release of neuromodulators, such as CGRP and ATP (59)(60)(61). The release of glutamate and other transmitters from DRG neuron somas exposes presynapticlike features on the soma that can be recognized by rabies virus (55).…”

P2Y purinergic receptors: New targets for analgesic and antimigraine drugs

“…The CACNA1A KI mice bear a gain-of-function mutation of the α subunit of the Ca v 2.1 neuronal calcium channel, which is typically detected in families suffering from familial hemiplegic migraine type 1 (FHM1), a severe and genetic form of migraine accompanied by hemiparesis [23]. KI mice show a higher sensitivity to the generation of Cortical Spreading Depression (CSD, the prodromic sign of migraine pain) and also a higher rate of release of pro-algogenic substances (such as CGRP) within the TG [24,25]. Taken together, the biochemical changes observed in purinergic transmission both at the central and the peripheral levels in KI mice could account for the higher susceptibility to migraine triggers in these animals (and, possibly, FHM1 patients) (see also below, Section…”