title: TRPA1 contributes to specific mechanically activated currents and sensory neuron mechanical hypersensitivity.
abstract: The mechanosensory role of TRPA1 and its contribution to mechanical hypersensitivity in sensory neurons remains enigmatic. We elucidated this role by recording mechanically activated currents in conjunction with TRPA1 over- and under-expression and selective pharmacology. First, we established that TRPA1 transcript, protein and functional expression are more abundant in smaller-diameter neurons than larger-diameter neurons, allowing comparison of two different neuronal populations. Utilising whole cell patch clamping, we applied calibrated displacements to neurites of dorsal root ganglion (DRG) neurons in short-term culture and recorded mechanically activated currents termed intermediately (IAMCs), rapidly (RAMCs) or slowly adapting (SAMCs). Trpa1 deletion (–/–) significantly reduced maximum IAMC amplitude by 43% in small-diameter neurons compared with wild-type (+/+) neurons. All other mechanically activated currents in small- and large-diameter Trpa1−/− neurons were unaltered. Seventy-three per cent of Trpa1+/+ small-diameter neurons responding to the TRPA1 agonist allyl-isothiocyanate (AITC) displayed IAMCs to neurite displacement, which were significantly enhanced after AITC addition. The TRPA1 antagonist HC-030031 significantly decreased Trpa1+/+ IAMC amplitudes, but only in AITC responsive neurons. Using a transfection system we also showed TRPA1 over-expression in Trpa1+/+ small-diameter neurons increases IAMC amplitude, an effect reversed by HC-030031. Furthermore, TRPA1 introduction into Trpa1−/− small-diameter neurons restored IAMC amplitudes to Trpa1+/+ levels, which was subsequently reversed by HC-030031. In summary our data demonstrate TRPA1 makes a contribution to normal mechanosensation in a specific subset of DRG neurons. Furthermore, they also provide new evidence illustrating mechanisms by which sensitisation or over-expression of TRPA1 enhances nociceptor mechanosensitivity. Overall, these findings suggest TRPA1 has the capacity to tune neuronal mechanosensitivity depending on its degree of activation or expression.
authors.affiliation: Nerve-Gut Research Laboratory, Department of Gastroenterology and Hepatology, Hanson Institute, Royal Adelaide Hospital, Adelaide, South Australia, Australia 5000. stuart.brierley@adelaide.edu.au
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Brierley
authors.forename: Joel
authors.initials: J
authors.lastname: Castro
authors.forename: Andrea M
authors.initials: AM
authors.lastname: Harrington
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Hughes
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Page
authors.forename: Grigori Y
authors.initials: GY
authors.lastname: Rychkov
authors.forename: L Ashley
authors.initials: LA
authors.lastname: Blackshaw
mesh_terms: D000083:Acetanilides / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D000818:Animals; D002478:Cells, Cultured; D005727:Ganglia, Spinal / Q000187:drug effects / Q000502:physiology*; D006930:Hyperalgesia / Q000503:physiopathology*; D017879:Isothiocyanates / Q000494:pharmacology; D040542:Mechanotransduction, Cellular / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018408:Patch-Clamp Techniques / Q000379:methods; D011687:Purines / Q000494:pharmacology; D011984:Sensory Receptor Cells / Q000187:drug effects / Q000502:physiology*; D000074025:TRPA1 Cation Channel; D050051:Transient Receptor Potential Channels / Q000819:agonists / Q000037:antagonists & inhibitors / 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; D000083:Acetanilides; D017879:Isothiocyanates; D011687:Purines; D000074025:TRPA1 Cation Channel; D050051:Transient Receptor Potential Channels; C475685:Trpa1 protein, mouse; C004471:allyl isothiocyanate