Nitro-oleic acid inhibits firing and activates TRPV1- and TRPA1-mediated inward currents in dorsal root ganglion neurons from adult male rats

• Published in: The Journal of pharmacology and experimental therapeutics Vol. 333; no. 3; pp. 883 - 895
• Main Authors: Sculptoreanu, A, Kullmann, F A, Artim, D E, Bazley, F A, Schopfer, F, Woodcock, S, Freeman, B A, de Groat, W C
• Format: Journal Article
• Language: English
• Published: United States The American Society for Pharmacology and Experimental Therapeutics 01.06.2010
• Subjects: Action Potentials - drug effects; Animals; Ankyrins; Anti-Inflammatory Agents - pharmacology; Calcium Channels - drug effects; Calcium Channels - metabolism; Calcium Signaling - drug effects; Cell Separation; Cellular and Molecular; Electrophysiology; Ganglia, Spinal - cytology; Ganglia, Spinal - drug effects; Image Processing, Computer-Assisted; Male; Membrane Potentials - drug effects; Neurons, Afferent - drug effects; Nitric Oxide - physiology; Nociceptors - drug effects; Oleic Acids - pharmacology; Patch-Clamp Techniques; Rats; Sodium Channel Agonists; Sodium Channels - drug effects; TRPA1 Cation Channel; TRPC Cation Channels; TRPV Cation Channels - agonists; TRPV Cation Channels - metabolism
• ISSN: 0022-3565; 1521-0103
• DOI: 10.1124/jpet.109.163154

Nitro-oleic acid (OA-NO(2)), an electrophilic fatty acid by-product of nitric oxide and nitrite reactions, is present in normal and inflamed mammalian tissues at up to micromolar concentrations and exhibits anti-inflammatory signaling actions. The effects of OA-NO(2) on cultured dorsal root ganglion (DRG) neurons were examined using fura-2 Ca(2+) imaging and patch clamping. OA-NO(2) (3.5-35 microM) elicited Ca(2+) transients in 20 to 40% of DRG neurons, the majority (60-80%) of which also responded to allyl isothiocyanate (AITC; 1-50 microM), a TRPA1 agonist, and to capsaicin (CAPS; 0.5 microM), a TRPV1 agonist. The OA-NO(2)-evoked Ca(2+) transients were reduced by the TRPA1 antagonist 2-(1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydro-7H-purin-7-yl)-N-(4-isopropylphenyl) acetamide (HC-030031; 5-50 microM) and the TRPV1 antagonist capsazepine (10 microM). Patch-clamp recording revealed that OA-NO(2) depolarized and induced inward currents in 62% of neurons. The effects of OA-NO(2) were elicited by concentrations >or=5 nM and were blocked by 10 mM dithiothreitol. Concentrations of OA-NO(2) >or=5 nM reduced action potential (AP) overshoot, increased AP duration, inhibited firing induced by depolarizing current pulses, and inhibited Na(+) currents. The effects of OA-NO(2) were not prevented or reversed by the NO-scavenger carboxy-2-phenyl-4,4,5,5-tetramethylimidazolineoxyl-1-oxyl-3-oxide. A large percentage (46-57%) of OA-NO(2)-responsive neurons also responded to CAPS (0.5 microM) or AITC (0.5 microM). OA-NO(2) currents were reduced by TRPV1 (diarylpiperazine; 5 microM) or TRPA1 (HC-030031; 5 microM) antagonists. These data reveal that endogenous OA-NO(2) generated at sites of inflammation may initially activate transient receptor potential channels on nociceptive afferent nerves, contributing to the initiation of afferent nerve activity, and later suppresses afferent firing.