Background/Purpose: Rheumatoid arthritis (RA) is a chronic inflammatory disease that cannot be cured and current approaches have some severe side effects. Although the pathogenesis is not completely understood, many studies have suggested that the imbalance between Th17 cells/inflammatory cytokines and suppressive Foxp3+ T regulatory (Treg) cells is associated with the pathogenesis and development in RA progression. IL-2 inducible T cell kinase (ITK) is involved in signaling cascades mediating T-lymphocyte proliferation, differentiation, migration, and pro-inflammatory cytokine production. The small molecule BMS509744 covalently binds ITK and inhibits the kinase activity of ITK. In this study, we explored whether BMS509744 regulates Th17/Treg balance and could be an effective in RA therapy.

Methods: DBA/1J mice were immunized with Collagen II and CFA to induce a CIA model. BMS509744 was injected i.p. into the mice on day 30 after immunization. To exam the effects of BMS509744 on Th17 and Treg differentiation and function, naïve CD4+ T cells were isolated from Foxp3^GFP mice and cultured under Th17 and Treg polarization condition in the absence or presence of BMS509744. Results were analyzed by using Graphpad Prism 7.0 software. Student t test was used to assess statistical significance between two groups and one-way ANOVA were used to assess statistical significance among multi-groups.  p values less than 0.05 were considered as statistically significant difference.

Results: In the CIA model, infusion of BMS509744 effectively reduced the severity of arthritis, decreased the histopathology scores, improved bone destruction and down-regulated the expression of inflammatory factor IFN-γ/IL-17A. In addition, infusion of BMS509744 increased ratios of Treg cells in CIA mice. BMS509744 effectively skews naïve T cells to Treg cells under Th17 differentiation condition, and promotes Treg induction and enhances Treg function under Treg polarization condition, and also increases Foxp3 expression across TCR doses under Th17 condition, these effects can be reversed by Foxo1 inhibitor. Moreover, we found that BMS509744 decreased mTOR and Akt activity, resulting in inhibiting the phosphorylation of foxo1 and foxo1 translocation to the cytoplasm. Foxo1 expressed in nuclear can stabilize Foxp3 and inhibit the expression of IL-17A. At last, Foxo1 inhibitors significantly reversed the therapeutic effects of ITK inhibitors in CIA model and reversed effects of ITK inhibitors on the balance of Th17 and Treg in CIA model.

Conclusion: : ITK inhibitor BMS509744 inhibits the development of CIA by changing the balance between Th17 and Treg cells via mTOR-AKT-Foxo1 signaling. ITK may be an effective RA therapeutic target. 

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/targeting-itk-signaling-ameliorates-collagen-induced-arthritis-via-shifting-the-balance-between-th17-and-regulatory-th17-cells/