title: Molecular mechanisms of sensitization of pain-transducing P2X3 receptors by the migraine mediators CGRP and NGF.
abstract: Migraine headache originates from the stimulation of nerve terminals of trigeminal ganglion neurons that innervate meninges. Characteristic features of migraine pain are not only its delayed onset but also its persistent duration. Current theories propose that endogenous substances released during a migraine attack (the neuropeptide calcitonin gene-related peptide [CGRP] and the neurotrophin nerve growth factor [NGF]) sensitize trigeminal neurons to transmit nociceptive signals to the brainstem, though the mechanisms remain poorly understood. Recent studies indicate that acute, long-lasting sensitization of trigeminal nociceptive neurons occurs via distinct processes involving enhanced expression and function of adenosine triphosphate (ATP)-gated P2X3 receptors known to play a role in chronic pain. In particular, on cultured trigeminal neurons, CGRP (via protein kinase A-dependent signaling) induces a slowly developing upregulation of the ionic currents mediated by P2X3 receptors by enhancing receptor trafficking to the neuronal membrane and activating their gene transcription. Such upregulated receptors acquire the ability to respond repeatedly to extracellular ATP, thus enabling long-lasting signaling of painful stimuli. In contrast, NGF induces rapid, reversible upregulation of P2X3 receptor function via protein kinase C phosphorylation, an effect counteracted by anti-NGF antibodies. The diverse intracellular signaling pathways used by CGRP and NGF show that the sensitization of P2X3 receptor function persists if the action of only one of these migraine mediators is blocked. These findings imply that inhibiting a migraine attack might be most efficient by a combinatorial approach. The different time domains of P2X3 receptor modulation by NGF and CGRP suggest that the therapeutic efficacy of novel antimigraine drugs depends on the time of administration.
authors.affiliation: Neurobiology Sector and Italian Institute of Technology Unit, International School for Advanced Studies (SISSA), 34014 Trieste, Italy.
authors.forename: Rashid
authors.initials: R
authors.lastname: Giniatullin
authors.forename: Andrea
authors.initials: A
authors.lastname: Nistri
authors.forename: Elsa
authors.initials: E
authors.lastname: Fabbretti
mesh_terms: D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D006801:Humans; D008881:Migraine Disorders / Q000188:drug therapy / Q000378:metabolism* / Q000503:physiopathology; D020932:Nerve Growth Factor / Q000378:metabolism*; D009475:Neurons, Afferent / Q000187:drug effects / Q000378:metabolism; D009619:Nociceptors / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000378:metabolism*; D058477:Receptors, Purinergic P2X3; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014276:Trigeminal Nerve / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology
chemical_list: C546407:P2RX3 protein, human; D018048:Receptors, Purinergic P2; D058477:Receptors, Purinergic P2X3; D020932:Nerve Growth Factor; D015740:Calcitonin Gene-Related Peptide