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Naunyn Schmiedebergs Arch Pharmacol. 2019 Sep 3. doi: 10.1007/s00210-019-01722-2. [Epub ahead of print]

The phospholipase C inhibitor U73122 is a potent agonist of the polymodal transient receptor potential ankyrin type 1 (TRPA1) receptor channel.

Author information

1
Institute for Physiology and Pathophysiology, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany.
2
Department of Anatomy, Physiology and Biophysics, Faculty of Biology, University of Bucharest, Bucharest, Romania.
3
Institute for Physiology and Pathophysiology, Friedrich-Alexander University of Erlangen-Nuremberg, Erlangen, Germany. alex@biologie.kappa.ro.
4
Department of Anatomy, Physiology and Biophysics, Faculty of Biology, University of Bucharest, Bucharest, Romania. alex@biologie.kappa.ro.

Abstract

The aminosteroid U73122 is frequently used as a phospholipase C (PLC) inhibitor and as such was used to investigate PLC-dependent activation and modulation of the transient receptor potential ankyrin type 1 (TRPA1) receptor channel. However, U73122 was recently shown to activate recombinant TRPA1 directly, albeit this interaction was not further explored. Our aim was to perform a detailed characterization of this agonistic action of U73122 on TRPA1. We used Fura-2 calcium microfluorimetry and the patch clamp technique to investigate the effect of U73122 on human and mouse wild type and mutant (C621S/C641S/C665S) TRPA1 expressed in HEK293t cells, as well as native TRPA1 in primary afferent neurons from wild type and TRPV1 and TRPA1 null mutant mice. In addition, we measured calcitonin gene-related peptide (CGRP) release from skin isolated from wild-type and TRPA1 null mutant mice. Human and mouse TRPA1 channels were activated by U73122 in the low nanomolar range. This activation was only partially dependent upon modification of the N-terminal cysteines 621, 641, and 665. U73122 also activated a subpopulation of neurons from wild-type and TRPV1 null mutant mice, but this effect was absent in mice deficient of TRPA1. In addition, U73122 evoked marked calcitonin gene-related peptide (CGRP) release from skin preparations of wild type but not TRPA1 null mutant mice. Our results indicate that U73122 is a potent and selective TRPA1 agonist. This effect should be taken into account when U73122 is used to inhibit PLC in TRPA1-expressing cells, such as primary nociceptors. In addition, U73122 may present a novel lead compound for the development of TRPA1-targeting drugs.

KEYWORDS:

Dorsal root ganglion; Nociceptor; Pain; Signal transduction; TRP channel

PMID:
31482262
DOI:
10.1007/s00210-019-01722-2

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