Monoacylglycerols activate TRPV1--a link between phospholipase C and TRPV1

PLoS One. 2013 Dec 2;8(12):e81618. doi: 10.1371/journal.pone.0081618. eCollection 2013.

Abstract

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.

MeSH terms

  • Animals
  • Arachidonic Acids / biosynthesis
  • Benzodioxoles / pharmacology
  • Endocannabinoids / biosynthesis
  • Female
  • Ganglia, Spinal / cytology
  • Ganglia, Spinal / drug effects
  • Ganglia, Spinal / metabolism
  • Glycerides / biosynthesis
  • HEK293 Cells
  • Humans
  • Male
  • Mice
  • Monoglycerides / biosynthesis
  • Monoglycerides / metabolism*
  • Nociception / drug effects
  • Piperidines / pharmacology
  • Rats
  • Sensory Receptor Cells / cytology
  • Sensory Receptor Cells / drug effects
  • Sensory Receptor Cells / metabolism
  • TRPV Cation Channels / metabolism*
  • Type C Phospholipases / metabolism*

Substances

  • Arachidonic Acids
  • Benzodioxoles
  • Endocannabinoids
  • Glycerides
  • JZL 184
  • Monoglycerides
  • Piperidines
  • TRPV Cation Channels
  • TRPV1 protein, human
  • TRPV1 protein, mouse
  • Trpv1 protein, rat
  • glyceryl 2-arachidonate
  • Type C Phospholipases

Grants and funding

This work was supported by the Swedish Research Council, the School of Pharmaceutical Sciences (FLÄK), Lund University, the UK Medical Research Council and by grants from the Spanish government (BFU2009-07835 and CONSOLIDER-INGENIO 2010 CSD2007-0023). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.