title: TRPA1 mediates trigeminal neuropathic pain in mice downstream of monocytes/macrophages and oxidative stress.
abstract: Despite intense investigation, the mechanisms of the different forms of trigeminal neuropathic pain remain substantially unidentified. The transient receptor potential ankyrin 1 channel (encoded by TRPA1) has been reported to contribute to allodynia or hyperalgesia in some neuropathic pain models, including those produced by sciatic nerve constriction. However, the role of TRPA1 and the processes that cause trigeminal pain-like behaviours from nerve insult are poorly understood. The role of TRPA1, monocytes and macrophages, and oxidative stress in pain-like behaviour evoked by the constriction of the infraorbital nerve in mice were explored. C57BL/6 and wild-type (Trpa1(+/+)) mice that underwent constriction of the infraorbital nerve exhibited prolonged (20 days) non-evoked nociceptive behaviour and mechanical, cold and chemical hypersensitivity in comparison to sham-operated mice (P < 0.05-P < 0.001). Both genetic deletion of Trpa1 (Trpa1(-/-)) and pharmacological blockade (HC-030031 and A-967079) abrogated pain-like behaviours (both P < 0.001), which were abated by the antioxidant, α-lipoic acid, and the nicotinamide adenine dinucleotide phosphate oxidase inhibitor, apocynin (both P < 0.001). Nociception and hypersensitivity evoked by constriction of the infraorbital nerve was associated with intra- and perineural monocytic and macrophagic invasion and increased levels of oxidative stress by-products (hydrogen peroxide and 4-hydroxynonenal). Attenuation of monocyte/macrophage increase by systemic treatment with an antibody against the monocyte chemoattractant chemokine (C-C motif) ligand 2 (CCL2) or the macrophage-depleting agent, clodronate (both P < 0.05), was associated with reduced hydrogen peroxide and 4-hydroxynonenal perineural levels and pain-like behaviours (all P < 0.01), which were abated by perineural administration of HC-030031, α-lipoic acid or the anti-CCL2 antibody (all P < 0.001). The present findings propose that, in the constriction of the infraorbital nerve model of trigeminal neuropathic pain, pain-like behaviours are entirely mediated by the TRPA1 channel, targeted by increased oxidative stress by-products released from monocytes and macrophages clumping at the site of nerve injury.
authors.affiliation: Laboratory of Cellular and Molecular Biology, Graduate Program in Health Sciences, University of the Extreme South of Santa Catarina (UNESC), Criciúma 88806-000, SC, Brazil.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Trevisan
authors.affiliation: Department of Health Sciences, Clinical Pharmacology and Oncology Unit, University of Florence, Florence 50139, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Benemei
authors.affiliation: Department of Health Sciences, Clinical Pharmacology and Oncology Unit, University of Florence, Florence 50139, Italy.
authors.forename: Serena
authors.initials: S
authors.lastname: Materazzi
authors.affiliation: Department of Health Sciences, Clinical Pharmacology and Oncology Unit, University of Florence, Florence 50139, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: De Logu
authors.affiliation: Department of Health Sciences, Clinical Pharmacology and Oncology Unit, University of Florence, Florence 50139, Italy.
authors.forename: Gaetano
authors.initials: G
authors.lastname: De Siena
authors.affiliation: Department of Health Sciences, Clinical Pharmacology and Oncology Unit, University of Florence, Florence 50139, Italy.
authors.forename: Camilla
authors.initials: C
authors.lastname: Fusi
authors.affiliation: Department of Pharmacology, Federal University of Santa Catarina (UFSC), Florianópolis 88040-900, SC, Brazil.
authors.forename: Mateus
authors.initials: M
authors.lastname: Fortes Rossato
authors.affiliation: Department of Health Sciences, Clinical Pharmacology and Oncology Unit, University of Florence, Florence 50139, Italy.
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Coppi
authors.affiliation: Department of Health Sciences, Clinical Pharmacology and Oncology Unit, University of Florence, Florence 50139, Italy.
authors.forename: Ilaria Maddalena
authors.initials: IM
authors.lastname: Marone
authors.affiliation: Department of Health Sciences, Clinical Pharmacology and Oncology Unit, University of Florence, Florence 50139, Italy Department of Pharmacology, Federal University of Santa Catarina (UFSC), Florianópolis 88040-900, SC, Brazil.
authors.forename: Juliano
authors.initials: J
authors.lastname: Ferreira
authors.affiliation: Department of Health Sciences, Clinical Pharmacology and Oncology Unit, University of Florence, Florence 50139, Italy geppetti@unifi.it.
authors.forename: Pierangelo
authors.initials: P
authors.lastname: Geppetti
authors.affiliation: Department of Health Sciences, Clinical Pharmacology and Oncology Unit, University of Florence, Florence 50139, Italy.
authors.forename: Romina
authors.initials: R
authors.lastname: Nassini
mesh_terms: D000083:Acetanilides / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000098:Acetophenones / Q000494:pharmacology; D000818:Animals; D018932:Chemokine CCL2 / Q000037:antagonists & inhibitors; D004002:Clodronic Acid / Q000494:pharmacology; D006930:Hyperalgesia / Q000378:metabolism / Q000503:physiopathology*; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009000:Monocytes / Q000187:drug effects* / Q000378:metabolism; D009437:Neuralgia / Q000378:metabolism / Q000503:physiopathology*; D018384:Oxidative Stress / Q000187:drug effects*; D010091:Oximes / Q000037:antagonists & inhibitors / Q000494:pharmacology; D011687:Purines / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000074025:TRPA1 Cation Channel; D008063:Thioctic Acid / Q000494:pharmacology; D050051:Transient Receptor Potential Channels / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*
chemical_list: C552888:2-(1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydro-7H-purin-7-yl)-N-(4-isopropylphenyl)acetamide; C560402:A 967079; D000083:Acetanilides; D000098:Acetophenones; C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D010091:Oximes; D011687:Purines; D000074025:TRPA1 Cation Channel; D050051:Transient Receptor Potential Channels; C475685:Trpa1 protein, mouse; D004002:Clodronic Acid; D008063:Thioctic Acid; C056165:acetovanillone
keywords: 4-hydroxynonenal; CCL2; CION; NADPH oxidase; hydrogen peroxide