Activation of TRPA1 by membrane permeable local anesthetics

Mol Pain. 2011 Aug 23;7:62. doi: 10.1186/1744-8069-7-62.

Abstract

Background: Low concentrations of local anesthetics (LAs) suppress cellular excitability by inhibiting voltage-gated Na⁺ channels. In contrast, LAs at high concentrations can be excitatory and neurotoxic. We recently demonstrated that LA-evoked activation of sensory neurons is mediated by the capsaicin receptor TRPV1, and, to a lesser extent by the irritant receptor TRPA1. LA-induced activation and sensitization of TRPV1 involves a domain that is similar, but not identical to the vanilloid-binding domain. Additionally, activation of TRPV1 by LAs involves PLC and PI(4,5)P₂-signalling. In the present study we aimed to characterize essential structural determinants for LA-evoked activation of TRPA1.

Results: Recombinant rodent and human TRPA1 were expressed in HEK293t cells and investigated by means of whole-cell patch clamp recordings. The LA lidocaine activates TRPA1 in a concentration-dependent manner. The membrane impermeable lidocaine-derivative QX-314 is inactive when applied extracellularly. Lidocaine-activated TRPA1-currents are blocked by the TRPA1-antagonist HC-030031. Lidocaine is also an inhibitor of TRPA1, an effect that is more obvious in rodent than in human TRPA1. This species-specific difference is linked to the pore region (transmembrane domain 5 and 6) as described for activation of TRPA1 by menthol. Unlike menthol-sensitivity however, lidocaine-sensitivity is not similarly determined by serine- and threonine-residues within TM5. Instead, intracellular cysteine residues known to be covalently bound by reactive TRPA1-agonists seem to mediate activation of TRPA1 by LAs.

Conclusions: The structural determinants involved in activation of TRPA1 by LAs are disparate from those involved in activation by menthol or those involved in activation of TRPV1 by LAs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anesthetics, Local / pharmacology*
  • Animals
  • Ankyrins / metabolism
  • Calcium / pharmacology
  • Calcium Channels / metabolism
  • Cell Membrane Permeability / drug effects*
  • HEK293 Cells
  • Humans
  • Intracellular Space / drug effects
  • Intracellular Space / metabolism
  • Ion Channel Gating / drug effects*
  • Lidocaine / analogs & derivatives
  • Lidocaine / pharmacology
  • Mice
  • Mustard Plant
  • Mutant Proteins / metabolism
  • Nerve Tissue Proteins / metabolism
  • Plant Oils / pharmacology
  • Rats
  • TRPA1 Cation Channel
  • TRPC Cation Channels
  • TRPM Cation Channels / metabolism
  • Transient Receptor Potential Channels / metabolism*

Substances

  • Anesthetics, Local
  • Ankyrins
  • Calcium Channels
  • Mutant Proteins
  • Nerve Tissue Proteins
  • Plant Oils
  • TRPA1 Cation Channel
  • TRPA1 protein, human
  • TRPC Cation Channels
  • TRPM Cation Channels
  • Transient Receptor Potential Channels
  • Trpa1 protein, mouse
  • Trpa1 protein, rat
  • Trpm8 protein, rat
  • QX-314
  • Lidocaine
  • Calcium
  • mustard oil