The novel endocannabinoid receptor GPR55 is activated by atypical cannabinoids but does not mediate their vasodilator effects.
OBJECTIVE
Atypical cannabinoids are thought to cause vasodilatation through an as-yet unidentified 'CBx' receptor. Recent reports suggest GPR55 is an atypical cannabinoid receptor, making it a candidate for the vasodilator 'CBx' receptor. The purpose of the present study was to test the hypothesis that human recombinant GPR55 is activated by atypical cannabinoids and mediates vasodilator responses to these agents.


METHODS
Human recombinant GPR55 was expressed in HEK293T cells and specific GTPgammaS activity was monitored as an index of receptor activation. In GPR55-deficient and wild-type littermate control mice, in vivo blood pressure measurement and isolated resistance artery myography were used to determine GPR55 dependence of atypical cannabinoid-induced haemodynamic and vasodilator responses.


RESULTS
Atypical cannabinoids O-1602 and abnormal cannabidiol both stimulated GPR55-dependent GTPgammaS activity (EC50 approximately 2 nM), whereas the CB1 and CB2-selective agonist WIN 55,212-2 showed no effect in GPR55-expressing HEK293T cell membranes. Baseline mean arterial pressure and heart rate were not different between WT and GPR55 KO mice. The blood pressure-lowering response to abnormal cannabidiol was not different between WT and KO mice (WT 20+/-2%, KO 26+/-5% change from baseline), nor was the vasodilator response to abnormal cannabidiol in isolated mesenteric arteries (IC50 approximately 3 micro M for WT and KO). The abnormal cannabidiol vasodilator response was antagonized equivalently by O-1918 in both strains.


CONCLUSIONS
These results demonstrate that while GPR55 is activated by atypical cannabinoids, it does not appear to mediate the vasodilator effects of these agents.
Johns
D G
DG
GlaxoSmithKline, Cardiovascular and Urogenital Center for Excellence in Drug Discovery, Vascular Biology and Thrombosis, King of Prussia, PA 19406, USA. Douglas.G.Johns@gsk.com
Behm
D J
DJ
Walker
D J
DJ
Ao
Z
Z
Shapland
E M
EM
Daniels
D A
DA
Riddick
M
M
Dowell
S
S
Staton
P C
PC
Green
P
P
Shabon
U
U
Bao
W
W
Aiyar
N
N
Yue
T-L
TL
Brown
A J
AJ
Morrison
A D
AD
Douglas
S A
SA
D000818:Animals; D048588:Benzoxazines / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D002185:Cannabidiol / Q000031:analogs & derivatives / Q000494:pharmacology*; D063386:Cannabinoid Receptor Agonists; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D005260:Female; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D009025:Morpholines / Q000494:pharmacology; D009129:Muscle Tonus / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology; D009281:Naphthalenes / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D043882:Receptors, Cannabinoid / Q000235:genetics / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000819:agonists* / Q000235:genetics / Q000378:metabolism; D012118:Resorcinols / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*
C485531:((-)-4-(3-3,4-trans-p-menthadien-(1,8)-yl)-orcinol); D048588:Benzoxazines; D063386:Cannabinoid Receptor Agonists; C524885:GPR55 protein, human; C526692:GPR55 protein, mouse; D009025:Morpholines; D009281:Naphthalenes; D043882:Receptors, Cannabinoid; D043562:Receptors, G-Protein-Coupled; D012118:Resorcinols; D002185:Cannabidiol; D010656:Phenylephrine; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; D011189:Potassium Chloride
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