title: The role of slow and persistent TTX-resistant sodium currents in acute tumor necrosis factor-α-mediated increase in nociceptors excitability.
abstract: Tetrodotoxin-resistant (TTX-r) sodium channels are key players in determining the input-output properties of peripheral nociceptive neurons. Changes in gating kinetics or in expression levels of these channels by proinflammatory mediators are likely to cause the hyperexcitability of nociceptive neurons and pain hypersensitivity observed during inflammation. Proinflammatory mediator, tumor necrosis factor-α (TNF-α), is secreted during inflammation and is associated with the early onset, as well as long-lasting, inflammation-mediated increase in excitability of peripheral nociceptive neurons. Here we studied the underlying mechanisms of the rapid component of TNF-α-mediated nociceptive hyperexcitability and acute pain hypersensitivity. We showed that TNF-α leads to rapid onset, cyclooxygenase-independent pain hypersensitivity in adult rats. Furthermore, TNF-α rapidly and substantially increases nociceptive excitability in vitro, by decreasing action potential threshold, increasing neuronal gain and decreasing accommodation. We extended on previous studies entailing p38 MAPK-dependent increase in TTX-r sodium currents by showing that TNF-α via p38 MAPK leads to increased availability of TTX-r sodium channels by partial relief of voltage dependence of their slow inactivation, thereby contributing to increase in neuronal gain. Moreover, we showed that TNF-α also in a p38 MAPK-dependent manner increases persistent TTX-r current by shifting the voltage dependence of activation to a hyperpolarized direction, thus producing an increase in inward current at functionally critical subthreshold voltages. Our results suggest that rapid modulation of the gating of TTX-r sodium channels plays a major role in the mediated nociceptive hyperexcitability of TNF-α during acute inflammation and may lead to development of effective treatments for inflammatory pain, without modulating the inflammation-induced healing processes.
authors.affiliation: Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, The Hebrew University Faculty of Medicine, Jerusalem, Israel; and The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University, Jerusalem, Israel.
authors.forename: Sagi
authors.initials: S
authors.lastname: Gudes
authors.affiliation: Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, The Hebrew University Faculty of Medicine, Jerusalem, Israel; and The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University, Jerusalem, Israel.
authors.forename: Omer
authors.initials: O
authors.lastname: Barkai
authors.affiliation: Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, The Hebrew University Faculty of Medicine, Jerusalem, Israel; and The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University, Jerusalem, Israel.
authors.forename: Yaki
authors.initials: Y
authors.lastname: Caspi
authors.affiliation: Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, The Hebrew University Faculty of Medicine, Jerusalem, Israel; and The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University, Jerusalem, Israel.
authors.forename: Ben
authors.initials: B
authors.lastname: Katz
authors.affiliation: Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, The Hebrew University Faculty of Medicine, Jerusalem, Israel; and The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University, Jerusalem, Israel.
authors.forename: Shaya
authors.initials: S
authors.lastname: Lev
authors.affiliation: Department of Medical Neurobiology, Institute for Medical Research Israel-Canada, The Hebrew University Faculty of Medicine, Jerusalem, Israel; and The Edmond and Lily Safra Center for Brain Sciences, The Hebrew University, Jerusalem, Israel alexander.binshtok@ekmd.huji.ac.il.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Binshtok
mesh_terms: D000081:Acetamides; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002478:Cells, Cultured; D003198:Computer Simulation; D004195:Disease Models, Animal; D003576:Electron Transport Complex IV / Q000037:antagonists & inhibitors / Q000378:metabolism; D005727:Ganglia, Spinal / Q000187:drug effects / Q000503:physiopathology; D000078334:Lacosamide; D008297:Male; D008959:Models, Neurological; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D010146:Pain / Q000503:physiopathology; D018408:Patch-Clamp Techniques; D017207:Rats, Sprague-Dawley; D026941:Sodium Channel Blockers / Q000494:pharmacology; D015222:Sodium Channels / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D000081:Acetamides; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D014409:Tumor Necrosis Factor-alpha; D013779:Tetrodotoxin; D000078334:Lacosamide; D003576:Electron Transport Complex IV; D048051:p38 Mitogen-Activated Protein Kinases
keywords: DRG; inflammatory pain; nociceptor; sodium (Na+) current; tumor necrosis factor