Characterisation of the cannabinoid receptor system in synovial tissue and fluid in patients with osteoarthritis and rheumatoid arthritis.
BACKGROUND
Cannabis-based medicines have a number of therapeutic indications, including anti-inflammatory and analgesic effects. The endocannabinoid receptor system, including the cannabinoid receptor 1 (CB1) and receptor 2 (CB2) and the endocannabinoids, are implicated in a wide range of physiological and pathophysiological processes. Pre-clinical and clinical studies have demonstrated that cannabis-based drugs have therapeutic potential in inflammatory diseases, including rheumatoid arthritis (RA) and multiple sclerosis. The aim of this study was to determine whether the key elements of the endocannabinoid signalling system, which produces immunosuppression and analgesia, are expressed in the synovia of patients with osteoarthritis (OA) or RA.


METHODS
Thirty-two OA and 13 RA patients undergoing total knee arthroplasty were included in this study. Clinical staging was conducted from x-rays scored according to Kellgren-Lawrence and Larsen scales, and synovitis of synovial biopsies was graded. Endocannabinoid levels were quantified in synovial fluid by liquid chromatography-mass spectrometry. The expression of CB1 and CB2 protein and RNA in synovial biopsies was investigated. Functional activity of these receptors was determined with mitogen-activated protein kinase assays. To assess the impact of OA and RA on this receptor system, levels of endocannabinoids in the synovial fluid of patients and non-inflamed healthy volunteers were compared. The activity of fatty acid amide hydrolase (FAAH), the predominant catabolic endocannabinoid enzyme, was measured in synovium.


RESULTS
CB1 and CB2 protein and RNA were present in the synovia of OA and RA patients. Cannabinoid receptor stimulation of fibroblast-like cells from OA and RA patients produced a time-dependent phosphorylation of extracellular signal-regulated kinase (ERK)-1 and ERK-2 which was significantly blocked by the CB1 antagonist SR141716A. The endocannabinoids anandamide (AEA) and 2-arachidonyl glycerol (2-AG) were identified in the synovial fluid of OA and RA patients. However, neither AEA nor 2-AG was detected in synovial fluid from normal volunteers. FAAH was active in the synovia of OA and RA patients and was sensitive to inhibition by URB597 (3'-(aminocarbonyl) [1,1'-biphenyl]-3-yl)-cyclohexylcarbamate).


CONCLUSIONS
Our data predict that the cannabinoid receptor system present in the synovium may be an important therapeutic target for the treatment of pain and inflammation associated with OA and RA.
Richardson
Denise
D
Centre for Analytical Bioscience, School of Pharmacy, University of Nottingham, Nottingham, NG7 2RD, UK. denise.richardson@pfizer.com
Pearson
Richard G
RG
Kurian
Nisha
N
Latif
M Liaque
ML
Garle
Michael J
MJ
Barrett
David A
DA
Kendall
David A
DA
Scammell
Brigitte E
BE
Reeve
Alison J
AJ
Chapman
Victoria
V
D000368:Aged; D000581:Amidohydrolases / Q000032:analysis / Q000378:metabolism; D001095:Arachidonic Acids / Q000032:analysis / Q000378:metabolism; D001172:Arthritis, Rheumatoid / Q000378:metabolism*; D015153:Blotting, Western; D002478:Cells, Cultured; D002853:Chromatography, Liquid; D016207:Cytokines / Q000032:analysis / Q000378:metabolism; D063388:Endocannabinoids; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D005989:Glycerides / Q000032:analysis / Q000378:metabolism; D006801:Humans; D007719:Knee Joint / Q000378:metabolism; D008297:Male; D013058:Mass Spectrometry; D008875:Middle Aged; D019950:Mitogen-Activated Protein Kinase 1 / Q000032:analysis / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000032:analysis / Q000378:metabolism; D010003:Osteoarthritis / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010880:Piperidines / Q000494:pharmacology; D053284:Polyunsaturated Alkamides / Q000032:analysis / Q000378:metabolism; D011720:Pyrazoles / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D043884:Receptor, Cannabinoid, CB1 / Q000378:metabolism*; D043885:Receptor, Cannabinoid, CB2 / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000077285:Rimonabant; D013582:Synovial Fluid / Q000737:chemistry / Q000378:metabolism; D013583:Synovial Membrane / Q000378:metabolism*; D000099252:Fatty Acid Amide Hydrolases
D000581:Amidohydrolases; D001095:Arachidonic Acids; D016207:Cytokines; D063388:Endocannabinoids; D005989:Glycerides; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D010880:Piperidines; D053284:Polyunsaturated Alkamides; D011720:Pyrazoles; D012333:RNA, Messenger; D043884:Receptor, Cannabinoid, CB1; D043885:Receptor, Cannabinoid, CB2; D000077285:Rimonabant; D000099252:Fatty Acid Amide Hydrolases; C094503:glyceryl 2-arachidonate; C078814:anandamide