Background Th17 cells producing the proinflammatory cytokines IL-17A and IL-22 mediate multiple autoimmune conditions including inflammatory arthritides, and among these ankylosing spondylitis (AS) (1, 2). The role of Th17 cells in AS pathogenesis is supported by the efficacy of an anti-IL-17A antibody, secukinumab, in a clinical trial (3). JAK inhibitors like tofacitinib act on Th17 cells in rheumatoid arthritis (RA) (4). In additon to this a bromodomain inhibitor, JQ1, inhibits Th17 polarization in vitro and ameliorates disease in a murine model of arthritis (1).
Objectives Against the background of restricted therapeutic options besides NSAID and anti-TNF therapy in AS we representatively evaluated the in vitro actions of tofacitinib, a JAK1/3 inhibitor, and JQ1, a BET bromodomain inhibitor, on Th17 responses of patient-derived CD4+ T cells.
Methods Peripheral blood mononuclear cells were isolated from patients with AS, psoriatic arthritis (PSA) and RA and from healthy controls (HC). CD4+ T cells were negatively selected with magnetic beads and cultured in Th17-polarizing conditions (anti-CD2/3/28 beads, recombinant IL-2, IL-1β, IL-6 and IL-23). Cells were treated from day 0 on with either tofacitinib or JQ1. After 3 days IL-17A secretion was measured in the supernatant by ELISA and cells were analyzed for cytotoxic effects with a WST-1 assay. On day 6 of culture cells were stained for intracellular cytokines (IL-17A, IFNγ, IL-22, TNFα) and analyzed by flow cytometry. At the same time point cellular proliferation was assessed by a CFSE assay.
Results Both inhibitors effectively reduced IL-17A secretion from Th17-polarized CD4+ T cells. JQ1 also decreased percentages of total IL-17A+ T cells in all diseases and controls, whereas tofacitinib increased percentages of total IL-17A+ T cells in HC, AS and PSA. In addition a reduction of total IFNγ+ T cells in HC, AS and PSA, and no changes of total IL-22+ or TNFα+ T cells in all groups were observed upon treatment with JQ1. Tofacitinib elevated total IL-22+ T cells in HC, AS and PSA. An inhibitory effect of JQ1 on IL-17A+/IFNγ+ T cells was only obvious in AS. IL-17A+/IL-22+ T cells were not effected by either of the inhibitors. However JQ1 and tofacitinib reduced viability of Th17-polarized CD4+ T cells by about 50% in HC and AS. The effect on proliferation was less remarkable for JQ1 compared to tofacitinib in both groups.
Conclusions Our results indicate that the BET bromodomain inhibitor JQ1 (compared to the JAK1/3 inhibitor tofacitinib) significantly inhibits Th17 responses in CD4+ T cells derived from patients with AS, PSA and RA. This encourages further investigation of JQ1 in animal models and the search for more specific derivates of this compound.
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Bowness, P. et al. Th17 cells expressing KIR3DL2+ and responsive to HLA-B27 homodimers are increased in ankylosing spondylitis. J. Immunol. 186, 2672-2680 (4)
Baeten, D. et al. Anti-interleukin-17A monoclonal antibody secukinumab in treatment of ankylosing spondylitis: a randomised, double-blind, placebo-controlled trial. The Lancet 382, 1705–1713 (23)
Maeshima, K. et al. The JAK inhibitor tofacitinib regulates synovitis through inhibition of interferon-γ and interleukin-17 production by human CD4+ T cells. Arthritis Rheum. 64, 1790-1798 (6)
Acknowledgements JQ1 was generously provided by Knapp S. and Fedorov O. (SGC, University of Oxford) and funding for Hammitzsch A. by the DFG.
Disclosure of Interest A. Hammitzsch Grant/research support: DFG grant, HA 7021/1-1, J. de Wit Grant/research support: Merck, A. Ridley: None declared, M. H. Al-Mossawi Grant/research support: Merck, P. Bowness Grant/research support: Merck