P096 The anti-inflammatory effects of niclosamide on cytokines produced by PBMCs derived from IBD patients

Abstract

Background: Even after considerable progress in IBD therapies, at least half of the treated patients fail to reach remission. Monoclonal antibody therapies are associated with immunogenicity. Niclosamide is a salicylide which has been used as an anti-helminthic drug and minimally absorbed from the gastrointestinal tract. It has been shown to have anti-inflammatory properties and is currently repurposed for use in head and neck cancer. We aimed to study its effects on immune cells ex vivo and potential for repurposing in IBD. Methods: Peripheral blood mononuclear cells (PBMCs) from the bloods of 6 IBD patients were cultured with or without stimulation with 0.5 μg/ml anti-CD3 (clone OKT3). Niclosamide was prepared in dimethyl sulfoxide (DMSO) and diluted into culture medium at 0.25 μM and 0.5 μM. Effect of niclosamide upon cell survival and T-cell activation was measured at 1 day by flow cytometry analysis of activation markers CD69, CD25, and CTLA-4. At 6 days, cells were re-stimulated with PMA and ionomycin in the presence of Brefeldin A and expression of cytokines IL-17A, TNFα, IFNγ and IL-2 measured by flow cytometry. Data were analysed by Flowjo and significance tested by Friedman Analysis. Results: Niclosamide was not toxic to cells at the concentrations tested and did not alter the frequencies of CD4+ and CD8+ T cells, CD19+ B cells or CD14+ monocytes in unstimulated cells. However, niclosamide reduced CD4 and CD8 T-cell activation indicated by a significant decrease in the frequency of CD4+ cells expressing CTLA-4 and CD25 and CD69 and CD25 by CD8+ cells (Figure 1A). This resulted in a significant decrease in T-cell number at 6 days (p = 0.0120). Furthermore, it significantly inhibited expression of proinflammatory cytokines IL-17, IFNγ, TNFα and IL-2 by CD4 and CD8+ T cells (Figure 1B). Conclusions: Our results suggest a strong anti-inflammatory action of niclosamide when tested on T cells from IBD patients with no significant cell toxicity seen at concentrations used. The significant reduction in cytokine levels known to be involved in IBD make it a potential drug that could be used for treatment of IBD in the future.