Dataset Information

Compounds from Sichuan and Melegueta peppers activate, covalently and non-covalently, TRPA1 and TRPV1 channels.

ABSTRACT:

Background and purpose

Oily extracts of Sichuan and Melegueta peppers evoke pungent sensations mediated by different alkylamides [mainly hydroxy-alpha-sanshool (alpha-SOH)] and hydroxyarylalkanones (6-shogaol and 6-paradol). We assessed how transient receptor potential ankyrin 1 (TRPA1) and TRP vanilloid 1 (TRPV1), two chemosensory ion channels, participate in these pungent sensations.

Experimental approach

The structure-activity relationships of these molecules on TRPA1 and TRPV1 was measured by testing natural and synthetic analogues using calcium and voltage imaging on dissociated dorsal root ganglia neurons and human embryonic kidney 293 cells expressing the wild-type channels or specific cysteine mutants using glutathione trapping as a model to probe TRPA1 activation. In addition, using Trpv1 knockout mice, the compounds' aversive responses were measured in a taste brief-access test.

Key results

For TRPA1 activation, the cis C6 double bond in the polyenic chain of alpha-SOH was critical, whereas no structural specificity was required for activation of TRPV1. Both 6-shogaol and 6-paradol were found to activate TRPV1 and TRPA1 channels, whereas linalool, an abundant terpene in Sichuan pepper, activated TRPA1 but not TRPV1 channels. Alkylamides and 6-shogaol act on TRPA1 by covalent bonding whereas none of these compounds activated TRPV1 through such interactions. Finally, TRPV1 mutant mice retained sensitivity to 6-shogaol but were not responsive to alpha-SOH.

Conclusions and implications

The pungent nature of components of Sichuan and Melegueta peppers was mediated via interactions with TRPA1 and TRPV1 channels and may explain the aversive properties of these compounds.

SUBMITTER: Riera CE

PROVIDER: S-EPMC2765304 | biostudies-literature | 2009 Aug

REPOSITORIES: biostudies-literature

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Publications

Compounds from Sichuan and Melegueta peppers activate, covalently and non-covalently, TRPA1 and TRPV1 channels.

Riera C E CE Menozzi-Smarrito C C Affolter M M Michlig S S Munari C C Robert F F Vogel H H Simon S A SA le Coutre J J

British journal of pharmacology 20090708 8

<h4>Background and purpose</h4>Oily extracts of Sichuan and Melegueta peppers evoke pungent sensations mediated by different alkylamides [mainly hydroxy-alpha-sanshool (alpha-SOH)] and hydroxyarylalkanones (6-shogaol and 6-paradol). We assessed how transient receptor potential ankyrin 1 (TRPA1) and TRP vanilloid 1 (TRPV1), two chemosensory ion channels, participate in these pungent sensations.<h4>Experimental approach</h4>The structure-activity relationships of these molecules on TRPA1 and TRPV1 ...[more]

PMID: 19594761

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Project description:The sigma 1 receptor (?1R) and the mu-opioid receptor (MOR) regulate the transient receptor potential (TRP) V1 calcium channel. A series of proteins are involved in the cross-regulation between MORs and calcium channels like the glutamate N-methyl-D-aspartate receptor (NMDAR), including the histidine triad nucleotide-binding protein 1 (HINT1), calmodulin (CaM), and the ?1R. Thus, we assessed whether similar mechanisms also apply to the neural TRP ankyrin member 1 (TRPA1), TRP vanilloid member 1 (TRPV1), and TRP melastatin member 8 (TRPM8). Our results indicate that ?1R and CaM bound directly to cytosolic regions of these TRPs, and this binding increased in the presence of calcium. By contrast, the association of HINT1 with these TRPs was moderately dependent on calcium. The ?1R always competed with CaM for binding to the TRPs, except for its binding to the TRPA1 C-terminal where ?1R binding cooperated with that of CaM. However, ?1R dampened HINT1 binding to the TRPA1 N-terminal. When the effect of ?1R ligands was addressed, the ?1R agonists PRE084 and pregnenolone sulfate enhanced the association of the ?1R with the TRPM8 N-terminal and TRPV1 C-terminal in the presence of physiological calcium, as seen for the ?1R-NMDAR interactions. However, these agonists dampened ?1R binding to the TRPA1 and TRPV1 N-terminal domains, and also to the TRPA1 C-terminal, as seen for ?1R-binding immunoglobulin protein (BiP) interactions in the endoplasmic reticulum (ER). By contrast, the ?1R antagonists progesterone and S1RA reduced the association of ?1R with TRPA1 and TRPV1 C-terminal regions, as seen for the ?1R-NMDAR interactions. Conversely, they enhanced the ?1R interaction with the TRPA1 N-terminal, as seen for ?1R-BiP interactions, whereas they barely affected the association of ?1R with the TRPV1 N-terminal. Thus, depending on the calcium channel and the cytosolic region examined, the ?1R agonists pregnenolone sulfate and PRE084 opposed or collaborated with the ?1R antagonists progesterone and S1RA to disrupt or promote such interactions. Through the use of cloned cytosolic regions of selected TRP calcium channels, we were able to demonstrate that ?1R ligands exhibit biased activity to regulate particular ?1R interactions with other proteins. Since ?1Rs are implicated in essential physiological processes, exploiting such ligand biases may represent a means to develop more selective and efficacious pharmacological interventions.

Project description:Phospholipase C-mediated hydrolysis of phosphatidylinositol 4,5-bisphosphate generates diacylglycerol, inositol 1,4,5-trisphosphate and protons, all of which can regulate TRPV1 activity via different mechanisms. Here we explored the possibility that the diacylglycerol metabolites 2-arachidonoylglycerol and 1-arachidonoylglycerol, and not metabolites of these monoacylglycerols, activate TRPV1 and contribute to this signaling cascade. 2-Arachidonoylglycerol and 1-arachidonoylglycerol activated native TRPV1 on vascular sensory nerve fibers and heterologously expressed TRPV1 in whole cells and inside-out membrane patches. The monoacylglycerol lipase inhibitors methylarachidonoyl-fluorophosphonate and JZL184 prevented the metabolism of deuterium-labeled 2-arachidonoylglycerol and deuterium-labeled 1-arachidonoylglycerol in arterial homogenates, and enhanced TRPV1-mediated vasodilator responses to both monoacylglycerols. In mesenteric arteries from TRPV1 knock-out mice, vasodilator responses to 2-arachidonoylglycerol were minor. Bradykinin and adenosine triphosphate, ligands of phospholipase C-coupled membrane receptors, increased the content of 2-arachidonoylglycerol in dorsal root ganglia. In HEK293 cells expressing the phospholipase C-coupled histamine H1 receptor, exposure to histamine stimulated the formation of 2-AG, and this effect was augmented in the presence of JZL184. These effects were prevented by the diacylglycerol lipase inhibitor tetrahydrolipstatin. Histamine induced large whole cell currents in HEK293 cells co-expressing TRPV1 and the histamine H1 receptor, and the TRPV1 antagonist capsazepine abolished these currents. JZL184 increased the histamine-induced currents and tetrahydrolipstatin prevented this effect. The calcineurin inhibitor ciclosporin and the endogenous "entourage" compound palmitoylethanolamide potentiated the vasodilator response to 2-arachidonoylglycerol, disclosing TRPV1 activation of this monoacylglycerol at nanomolar concentrations. Furthermore, intracerebroventricular injection of JZL184 produced TRPV1-dependent antinociception in the mouse formalin test. Our results show that intact 2-arachidonoylglycerol and 1-arachidonoylglycerol are endogenous TRPV1 activators, contributing to phospholipase C-dependent TRPV1 channel activation and TRPV1-mediated antinociceptive signaling in the brain.

Dataset Information

Compounds from Sichuan and Melegueta peppers activate, covalently and non-covalently, TRPA1 and TRPV1 channels.

Background and purpose

Experimental approach

Key results

Conclusions and implications

Publications

Compounds from Sichuan and Melegueta peppers activate, covalently and non-covalently, TRPA1 and TRPV1 channels.

Similar Datasets

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