Bupivacaine‐induced cellular entry of QX‐314 and its contribution to differential nerve block

Abstract

BACKGROUND AND PURPOSESelective nociceptor fibre block is achieved by introducing the cell membrane impermeant sodium channel blocker lidocaine N-ethyl bromide (QX-314) through transient receptor potential V1 (TRPV1) channels into nociceptors. We screened local anaesthetics for their capacity to activate TRP channels, and characterized the nerve block obtained by combination with QX-314. EXPERIMENTAL APPROACHWe investigated TRP channel activation in dorsal root ganglion (DRG) neurons by calcium imaging and patch-clamp recordings, and cellular QX-314 uptake by MS. To characterize nerve block, compound action potential (CAP) recordings from isolated nerves and behavioural responses were analysed. KEY RESULTSOf the 12 compounds tested, bupivacaine was the most potent activator of ruthenium red-sensitive calcium entry in DRG neurons and activated heterologously expressed TRPA1 channels. QX-314 permeated through TRPA1 channels and accumulated intracellularly after activation of these channels. Upon sciatic injections, QX-314 markedly prolonged bupivacaine's nociceptive block and also extended (to a lesser degree) its motor block. Bupivacaine's blockade of C-, but not A-fibre, CAPs in sciatic nerves was extended by co-application of QX-314. Surprisingly, however, this action was the same in wild-type, TRPA1-knockout and TRPV1/TRPA1-double knockout mice, suggesting a TRP-channel independent entry pathway. Consistent with this, high doses of bupivacaine promoted a non-selective, cellular uptake of QX-314. CONCLUSIONS AND IMPLICATIONSBupivacaine, combined with QX-314, produced a long-lasting sensory nerve block. This did not require QX-314 permeation through TRPA1, although bupivacaine activated these channels. Regardless of entry pathway, the greatly extended duration of block produced by QX-314 and bupivacaine may be clinically useful.

Effects of Liposomes Charge on Extending Sciatic Nerve Blockade of N-ethyl Bromide of Lidocaine in Rats

“…The negative control, Saline, did not elicit any detectable analgesia or muscle strength deficits. Peri-sciatic injection of 0.5% bupivacaine, the positive control, produced effective sensory and motor blockade that lasted for 4.0 ± 0.8 h and 3.6 ± 1.3 h, respectively, consistent with literature14. 25 mmol/L QX-314 resulted in slow-onset, short-lasting nerve blockades (sensory blockade: 2.9 ± 1.1 h, motor blockade: 2.5 ± 0.8 h; Fig.…”

“…Human embryonic kidney 293 cells (HEK293) were used to investigate cellular entry of QX-31414. Test solutions were initially prepared as in animal experiments, then 1:50 diluted with PBS.…”

Transient Receptor Potential Channels as Drug Targets: From the Science of Basic Research to the Art of Medicine

“…It is hoped that this innovative approach may tame hyperactive TRPV1 in diseased tissues and spare normal nociception. Of note, in combination with bupivacaine, QX-314 can be also used to selectively block TRPA1-expressing neurons (Brenneis et al, 2014). Indeed, as discussed later, QX-314 was used to silence neuronal pathways conducting itch .…”

Structure and Function of the ThermoTRP Channel Pore

“…The QX-314/channel interaction occurs only at the intracellular side of the Na channel protein. Encouraging results suggest that selective inhibition of nociceptive neurons through the TRPV1 portal may be possible (Binshtok, Bean, & Woolf, 2007;Brenneis et al, 2014).…”