Session Type: Abstract Submissions (ACR)
Background/Purpose: Endocannabinoids are immunomodulatory lipid compounds that act on cannabinoid receptors type 1 and 2 but also on transient receptor potential (TRP) channels. Their action is terminated by FAAH, one major enzyme responsible for endocannabinoid degradation. COX-2, however, also degrades endocannabinoids, and products from this reaction are pro-inflammatory. This study studied a potential mode of action for the anti-inflammatory effects of endocannabinoids in synovial fibroblasts from RA and OA donors. Furthermore it is investigated how pro-inflammatory cytokines alter the responsiveness of synovial fibroblasts to (endo)cannabinoid ligands.
Methods: MMP-3 and cytokines were detected by ELISA. ERK 1/2, p38, CREB and cjun phosphorylation was assessed by proteome profiler analysis and cell-based ELISA. Cannabinoid receptors 1 and 2, TRPA1, TRPV1, and COX-2 were detected by western blotting and cell-based ELISA. The XCELLigence system was used to determine EC50 values for CB1/CB2/TRPV1/TRPA1 with/without cytokine stimulation.
Results: The endocannabinoid arachidonylethanolamide (anandamide, AEA) and related eicosanoids palmitoylethanolamide (PEA), oleoylethanolamide (OEA) and N-arachidonylglycine (NAGly) reduced TNF induced production of IL-6, IL-8 and MMP-3. The effects of AEA, PEA and OEA were significantly enhanced by addition of the COX-2 inhibitor nimesulide but not by FAAH inhibiton. The effects of all compounds tested were not inhibited by CB1 or CB2 antagonism but were blocked by TRPV1 and TRPA1 antagonists in RASFs and OASFs. In the case of AEA, COX-2 inhibition reversed the effects of TRPA1 antagonism. Quantification of CB1, CB2, COX-2, TRPV1 and TRPA1 revealed a significant stimulatory influence of pro-inflammatory cytokines and hypoxia on observed protein levels. Furthermore, high AEA concentrations (>1µM) induced cell death only when combined with the intracellular calcium chelating agent BAPTA-AM. Analysis of intracellular signaling pathways revealed an inhibitory effect of AEA on p38 and ERK1/2 phosphorylation after TNF stimulation.
Conclusion: Under hypoxic conditions, Endocannabinoids promote an anti-inflammatory phenotype in RASFs and OASFs by activating/desensitizing TRPV1 and TRPA1. As a consequence, MAP kinase signaling is reduced as demonstrated after AEA treatment. Furthermore, COX-2 and FAAH inhibition are necessary to fully exploit the therapeutic potential of endocannabinoids. This might be important in RA where low oxygen and abundant cytokine expression up-regulate COX-2 in the joint. In addition, pro-inflammatory cytokines increase the efficacy of endocannabinoids due to upregulation of target receptors.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/anandamide-and-related-eicosanoids-decrease-the-production-of-pro-inflammatory-cytokines-in-synovial-fibroblasts-by-a-cox-2-dependent-mechanism-involvement-of-calcium-and-trp-channels/