In vitro investigation of how the endocannabinoid system modulates inflammation and pain pathways involved in arthritis

Abstract

Rheumatoid arthritis (RA) is an autoinflammatory disease characterised by pain and chronically inflamed joints. Clinical features in RA include a loss of immune tolerance to citrullinated peptides, which leads to increased levels of T helper 17 (Th17) cells and pro-inflammatory cytokines in the blood circulation. The endocannabinoid system (ES) is mainly found in the nervous and immune systems and thus represents a potential therapeutic target. However, the mechanisms underpinning the relationship between inflammation, pain signalling and the ES are still poorly understood in RA.

Inflamed PBMCs were treated with phytocannabinoid compounds and terpenes prior to flow cytometry analysis of regulatory T (Treg) cells and Th17 responses. In addition, cytokine profiles were analysed by qRT-PCR, ELISA and Luminex assays. These assays showed that GL1b and GL7a can suppress interleukin 6 (IL-6), IL-17A, IL-16, interferon gamma-induced protein 10 (IP-10) and tumour necrosis factor alpha (TNF-α), with inhibition of T cells, forkhead box P3 (FOXP3), retinoic acid receptor-related orphan receptor C (RORC) and nuclear factor kappa-light-chain-enhancer of activated B cells p105 subunit (NF-κB1) expression.

Subsequently, a neuroblastoma cell line (SH-SY5Y) and two sources of human induced pluripotent stem cell-derived sensory neurons (huiPSC-SN) were characterised for phytocannabinoids treatments. These cellular models have provided insights into pro-inflammatory cytokine-mediated pathways and analgesic properties through regulation of cannabinoid receptor 1 (CB1), transient receptor potential cation channel vanilloid 2 (TRPV2), tropomyosin receptor kinase A (TrkA), 5-hydroxytryptamine receptor 1A (HTR1A) and NF-κB1 expression.

Extensive analysis of GL1b and GL7a treatments has indicated that both phytocannabinoids modulate IL-17A, IL-6, IL-3 and chemokine (C-X-C motif) ligand 13 (CXCL13) through the Janus kinases and signal transducer and activator of transcription proteins (JAK-STAT) pathway with low cytotoxicity in the in vitro models. Therefore, phytocannabinoids, especially GL1b, represent potential alternative medicines for treating RA, particularly in non-responders to disease-modifying anti-rheumatic drugs (DMARDs) or RA patients experiencing severe adverse reactions.

Thesis is embargoed until 31st January 2024

Date of Award	Jan 2022
Original language	English
Sponsors	Department for the Economy & GreenLight Pharmaceuticals Ltd
Supervisor	David Gibson (Supervisor), Steven Watterson (Supervisor) & Elaine Murray (Supervisor)