Background:
Current treatments for arthritis are either too addictive (opioids), have poor analgesic efficacy (paracetamol) or are toxic (dMARDs) indicating a need for alternative treatments. The cannabinoids include Cannabis plant extracts (phytocannabinoids) and endogenously produced cannabinoids (endocannabinoids) which have shown analgesic and anti-inflammatory effects in various studies. Within arthritic joints, cannabinoid receptors are expressed on fibroblast-like synoviocytes (FLS) and immune cells which produce inflammatory cytokines. Cannabinoid receptors are also expressed on nociceptive neurons transmitting pain signals. Therefore, the aim of this study was to investigate the anti-inflammatory and analgesic potential of the phytocannabinoids, cannabidiol (CBD), novel CB123 and endocannabinoids, oleoylethanolamide (OEA) and palmitoylethanolamide (PEA) in an arthritis rat model.
Methods:
Arthritic rats were randomly assigned to either the cyclosporin clinical control (10 mg/kg), OEA and PEA (10 mg/kg), CBD and CB123 (20 mg/kg) and treated over six days. Healthy and disease controls were also included. Joint swelling was measured as a clinical outcome for inflammation and paw pressure for pain. In in vitro studies, human rheumatoid arthritis FLS were stimulated with TNF-α alone or in the presence of OEA, PEA, CBD or CBG. Resulting cytokine gene expression was measured by real-time qPCR.
Results:
Joint swelling significantly reduced from induction of arthritis until the final day of treatment for cyclosporin, OEA, CBD and CB123. Paw pressure significantly improved from induction of arthritis until the final day of treatment for cyclosporin, PEA, CBD and CB123.
Conclusions:
The data exhibits the therapeutic potential of cannabinoids in alleviating inflammatory arthritic pain.