The vanilloid receptor TRPV1 is activated and sensitized by local anesthetics in rodent sensory neurons
Andreas Leffler, … , Peter W. Reeh, Carla Nau
Andreas Leffler, … , Peter W. Reeh, Carla Nau
Published January 2, 2008
Citation Information: J Clin Invest. 2008;118(2):763-776. https://doi.org/10.1172/JCI32751.
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The vanilloid receptor TRPV1 is activated and sensitized by local anesthetics in rodent sensory neurons

Abstract

Local anesthetics (LAs) block the generation and propagation of action potentials by interacting with specific sites of voltage-gated Na+ channels. LAs can also excite sensory neurons and be neurotoxic through mechanisms that are as yet undefined. Nonspecific cation channels of the transient receptor potential (TRP) channel family that are predominantly expressed by nociceptive sensory neurons render these neurons sensitive to a variety of insults. Here we demonstrated that the LA lidocaine activated TRP channel family receptors TRPV1 and, to a lesser extent, TRPA1 in rodent dorsal root ganglion sensory neurons as well as in HEK293t cells expressing TRPV1 or TRPA1. Lidocaine also induced a TRPV1-dependent release of calcitonin gene–related peptide (CGRP) from isolated skin and peripheral nerve. Lidocaine sensitivity of TRPV1 required segments of the putative vanilloid-binding domain within and adjacent to transmembrane domain 3, was diminished under phosphatidylinositol 4,5-bisphosphate depletion, and was abrogated by a point mutation at residue R701 in the proximal C-terminal TRP domain. These data identify TRPV1 and TRPA1 as putative key elements of LA-induced nociceptor excitation. This effect is sufficient to release CGRP, a key component of neurogenic inflammation, and warrants investigation into the role of TRPV1 and TRPA1 in LA-induced neurotoxicity.

Authors

Andreas Leffler, Michael J. Fischer, Dietlinde Rehner, Stephanie Kienel, Katrin Kistner, Susanne K. Sauer, Narender R. Gavva, Peter W. Reeh, Carla Nau

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Figure 2

Lidocaine activates and blocks recombinant rTRPV1 expressed in HEK293t cells.

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Lidocaine activates and blocks recombinant rTRPV1 expressed in HEK293t c...
(A) Representative responses to 1, 3, 10, 30, and 100 mM lidocaine of HEK293t cells transiently expressing rTRPV1. The holding potential (Vh) was –60 mV. Various concentrations of lidocaine were applied for about 10 s. Only 1 concentration per cell was applied. (B) Concentration-response curve for lidocaine. Each data point represents mean peak current amplitudes evoked by 1, 3, 10, 30, or 100 mM lidocaine in 11 independent cells each. The line represents a fit of the data to the Hill equation. (C) Outward currents evoked by 3, 10, and 30 mM lidocaine in a HEK293t cell held at +60 mV. Lidocaine was applied for about 10 s in intervals of 2 min. (D) Representative ramp currents of TRPV1 in control solution, in 30 mM lidocaine, and in 30 nM capsaicin (n = 8). Cells were held at –60 mV, and currents were measured during 500-ms-long voltage ramps from –100 to +100 mV. Note the typical outward rectification of TRPV1 at 30 mM lidocaine and 30 nM capsaicin. (E) Representative capsaicin-evoked inward currents blocked by lidocaine. Increasing concentrations of lidocaine were coapplied with capsaicin after currents were evoked by a supramaximal concentration of capsaicin (10 μM). Cells were held at –60 mV, and experiments were performed in a Ca2+-free extracellular solution in order to avoid desensitization. (F) Dose-response curve for lidocaine-induced block of TRPV1 inward (Vh, –60 mV) and outward (Vh, +60 mV) currents evoked by capsaicin. The fractional block was plotted against the lidocaine concentration. Lines represent fits of the data to the Hill equation. The IC50 values were 45 ± 7 mM (n = 4) at –60 mV and 16 ± 17 mM (n = 4) at +60 mV. (G–I) Effect of the noncompetitive TRPV1 antagonist ruthenium red (RR, 5 μM; G), the competitive TRPV1 antagonist capsazepine (CPZ, 10 μM; H), and the highly selective TRPV1 antagonist BCTC (100 nM; I) on lidocaine-evoked currents in HEK293t cells expressing TRPV1. The substances were coapplied with 15 mM lidocaine after currents evoked by 15 mM lidocaine had reached steady state.