Cannabinoid receptor 1 suppresses transient receptor potential vanilloid 1-induced inflammatory responses to corneal injury

Cell Signal. 2013 Feb;25(2):501-11. doi: 10.1016/j.cellsig.2012.10.015. Epub 2012 Nov 8.

Abstract

Cannabinoid receptor type 1 (CB1)-induced suppression of transient receptor potential vanilloid type 1 (TRPV1) activation provides a therapeutic option to reduce inflammation and pain in different animal disease models through mechanisms involving dampening of TRPV1 activation and signaling events. As we found in both mouse corneal epithelium and human corneal epithelial cells (HCEC) that there is CB1 and TRPV1 expression colocalization based on overlap of coimmunostaining, we determined in mouse corneal wound healing models and in human corneal epithelial cells (HCEC) if they interact with one another to reduce TRPV1-induced inflammatory and scarring responses. Corneal epithelial debridement elicited in vivo a more rapid wound healing response in wildtype (WT) than in CB1(-/-) mice suggesting functional interaction between CB1 and TRPV1. CB1 activation by injury is tenable based on the identification in mouse corneas of 2-arachidonylglycerol (2-AG) with tandem LC-MS/MS, a selective endocannabinoid CB1 ligand. Suppression of corneal TRPV1 activation by CB1 is indicated since following alkali burning, CB1 activation with WIN55,212-2 (WIN) reduced immune cell stromal infiltration and scarring. Western blot analysis of coimmunoprecipitates identified protein-protein interaction between CB1 and TRPV1. Other immunocomplexes were also identified containing transforming growth factor kinase 1 (TAK1), TRPV1 and CB1. CB1 siRNA gene silencing prevented suppression by WIN of TRPV1-induced TAK1-JNK1 signaling. WIN reduced TRPV1-induced Ca(2+) transients in fura2-loaded HCEC whereas pertussis toxin (PTX) preincubation obviated suppression by WIN of such rises caused by capsaicin (CAP). Whole cell patch clamp analysis of HCEC showed that WIN blocked subsequent CAP-induced increases in nonselective outward currents. Taken together, CB1 activation by injury-induced release of endocannabinoids such as 2-AG downregulates TRPV1 mediated inflammation and corneal opacification. Such suppression occurs through protein-protein interaction between TRPV1 and CB1 leading to declines in TRPV1 phosphorylation status. CB1 activation of the GTP binding protein, G(i/o) contributes to CB1 mediated TRPV1 dephosphorylation leading to TRPV1 desensitization, declines in TRPV1-induced increases in currents and pro-inflammatory signaling events.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arachidonic Acids / metabolism
  • Benzoxazines / pharmacology
  • Calcium / metabolism
  • Calcium Channel Blockers / pharmacology
  • Cell Line
  • Disease Models, Animal
  • Endocannabinoids / metabolism
  • Epithelial Cells / drug effects
  • Epithelial Cells / physiology
  • Epithelium, Corneal / cytology
  • Epithelium, Corneal / injuries*
  • Epithelium, Corneal / metabolism
  • Glycerides / metabolism
  • Humans
  • Immunity, Innate / drug effects
  • MAP Kinase Kinase Kinases / metabolism
  • Mice
  • Mice, Knockout
  • Mitogen-Activated Protein Kinase 8 / metabolism
  • Morpholines / pharmacology
  • Naphthalenes / pharmacology
  • Patch-Clamp Techniques
  • Pertussis Toxin / pharmacology
  • Protein Binding
  • RNA Interference
  • RNA, Small Interfering / metabolism
  • Receptor, Cannabinoid, CB1 / antagonists & inhibitors
  • Receptor, Cannabinoid, CB1 / genetics
  • Receptor, Cannabinoid, CB1 / metabolism*
  • Signal Transduction
  • TRPV Cation Channels / antagonists & inhibitors
  • TRPV Cation Channels / metabolism*
  • Wound Healing / drug effects

Substances

  • Arachidonic Acids
  • Benzoxazines
  • Calcium Channel Blockers
  • Endocannabinoids
  • Glycerides
  • Morpholines
  • Naphthalenes
  • RNA, Small Interfering
  • Receptor, Cannabinoid, CB1
  • TRPV Cation Channels
  • TRPV1 protein, human
  • Win 55212-2
  • glyceryl 2-arachidonate
  • Pertussis Toxin
  • Mitogen-Activated Protein Kinase 8
  • MAP Kinase Kinase Kinases
  • MAP kinase kinase kinase 7
  • Calcium