Endogenous Unsaturated C18 N-Acylethanolamines Are Vanilloid Receptor (TRPV1) Agonists

Abstract

The endogenous C18 N-acylethanolamines (NAEs) N-linolenoylethanolamine (18:3 NAE), N-linoleoylethanolamine (18:2 NAE), N-oleoylethanolamine (18:1 NAE), and N-stearoylethanolamine (18:0 NAE) are structurally related to the endocannabinoid anandamide (20:4 NAE), but these lipids are poor ligands at cannabinoid CB 1 receptors. Anandamide is also an activator of the transient receptor potential (TRP) vanilloid 1 (TRPV 1 ) on primary sensory neurons. Here we show that C18 NAEs are present in rat sensory ganglia and vascular tissue. With the exception of 18:3 NAE in rat sensory ganglia, the levels of C18 NAEs are equal to or substantially exceed those of anandamide. At submicromolar concentrations, 18:3 NAE, 18:2 NAE, and 18:1 NAE, but not 18:0 NAE and oleic acid, activate native rTRPV 1 on perivascular sensory nerves. 18:1 NAE does not activate these nerves in TRPV 1 gene knock-out mice. Only the unsaturated C18 NAEs elicit whole cell currents and fluorometric calcium responses in HEK293 cells expressing hTRPV 1 . Molecular modeling revealed a low energy cluster of U-shaped unsaturated NAE conformers, sharing several pharmacophoric elements with capsaicin. Furthermore, one of the two major low energy conformational families of anandamide also overlaps with the cannabinoid CB 1 receptor ligand HU210, which is in line with anandamide being a dual activator of TRPV 1 and the cannabinoid CB 1 receptor. This study shows that several endogenous non-cannabinoid NAEs, many of which are more abundant than anandamide in rat tissues, activate TRPV 1 and thus may play a role as endogenous TRPV 1 modulators. Long chain C18 N-acylethanolamines (NAEs)2 are a group of bioactive lipids generated following hydrolysis of membrane N-acylphosphatidylethanolamine (NAPE) lipids, a reaction catalyzed by phospholipase D-like enzymes (1-4). In 1992, one member of this group, anandamide (N-arachidonoylethanolamine), was identified as a ligand for the central cannabinoid CB 1 receptor (5). This receptor is also present on a subpopulation of primary sensory neurons, which express the vanilloid receptor (TRPV 1 ), a marker of nociceptive sensory neurons (6 -8). TRPV 1 is a heat-activated cation channel, belonging to the transient receptor potential (TRP) superfamily of cation channels (9), of which TRPV 2 , TRPM 8 (the menthol receptor), and TRPA 1 (ANKTM 1 ) are also temperature-sensitive and present on primary sensory neurons (10 -14). Activation of TRPV 1 and TRPA 1 , e.g. by the pungent ingredients in hot chili pepper (capsaicin) and mustard (isothiocyanates), causes acute pain and local release of inflammatory neuropeptides (6, 14 -16). Other mediators of inflammation, such as bradykinin, prostaglandin E 2 , or nerve growth factor, promote TRPV 1 and TRPA 1 activation via multiple signaling pathways, which is consistent with TRPV 1 and TRPA 1 being essential for the development of inflammation-induced hyperalgesia (14 -19).Since our discovery that anandamide directly activates TRPV 1 (20), this lipid has emerged as a potential mediator of i...

Functional Analysis of the Purified Anandamide-generating Phospholipase D as a Member of the Metallo-β-lactamase Family

“…14 C]linoleoyl-sn-glycero-3-phosphoethanolamine (2.04 GBq/ mmol), 1-palmitoyl-2-[ 14 C]linoleoyl-sn-glycero-3-phosphocholine (4.11 GBq/mmol), [1][2][3][4][5][6][7][8][9][10][11][12][13][14] C]arachidonic acid (2.07 GBq/mmol), [1][2][3][4][5][6][7][8][9][10][11][12][13][14] C]oleic acid (2.22 GBq/mmol), [1][2][3][4][5][6][7][8][9][10][11][12][13][14] C]stearic acid (2.15 GBq/mmol), [1][2][3][4][5][6][7][8][9]…”

“…On the other hand, cannabinoid receptor-inactive N-palmitoylethanolamine is known to be an anti-inflammatory substance (8,9), N-oleoylethanolamine is known as an anorexic mediator (10), and N-stearoylethanolamine is known as a pro-apoptotic (11) and anorexic mediator (12). Furthermore, unsaturated C18 NAEs were recently reported to activate transient receptor potential vanilloid 1 (13). Noticeably, NAEs markedly increase in a variety of animal models of tissue degeneration (2, 14 -16).…”

The Endocannabinoid System and its Modulation by Phytocannabinoids

“…Nevertheless, the abovementioned thermo-TRPs, especially in the absence of other strong and specific exogenous/xenobiotic modulators, are now considered by all means bona fide "ionotropic cannabinoid receptors", whereas CB 1 R and CB 2 R would thus be defined as "metabotropic cannabinoid receptors" [3,17,18]. Importantly, several "endocannabinoid-like" mediators, such as, on the one hand, the anandamide congeners N-palmitoylethanolamine, N-oleoylethanolamine, and N-linoleoylethanolamine, as well as several N-acyl-dopamines and N-acyl-taurines, as direct or indirect activators [11,[19][20][21][22], and, on the other hand, some N-acyl-serotonins, as competitive antagonists [23,24], have been shown to interact with TRPV1 in in vitro and in vivo studies.…”

N-Acylethanolamine Metabolism Interacts with Abscisic Acid Signaling inArabidopsis thalianaSeedlings

“…In mammalian systems, the metabolism of NAEs is part of the endocannabinoid signaling system wherein NAEs bind to and activate G protein-coupled cannabinoid receptors, which in turn regulate a wide array of physiological and behavioral processes (Howlett et al, 2004). Recently, additional cellular targets of endocannabinoid lipids have been discovered, including ion channels (Movahed et al, 2005;Oz et al, 2005) and transcription factors (LoVerme et al, 2006).…”