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P031. Induction of an M2 macrophage phenotype by the HDAC inhibitor ITF2357

M. Wetzel1, M. Gerling1, R. Glauben1, T. Stroh1, U. Erben2, M. Zeitz1, B. Siegmund1

1Charité – Universitaetsmedizin Berlin, Medical Clinic I, Berlin, Germany; 2Charité – Universitaetsmedizin Berlin, RCIS, Berlin, Germany

Background: In murine colitis models, the histone deacetylase (HDAC) inhibitor ITF2357, which currently undergoes clinical trials, ameliorates disease activity and can prevent colitis-associated carcinogenesis. Recently, HDAC inhibitors (trichostatin A and valproic acid) were shown to markedly alter macrophage phenotypes. We sought to study the effect of ITF2357 on murine macrophages, hypothesizing that an alteration of the macrophage phenotype might partially explain the diverse effects of this agent.

Methods: Bone marrow derived macrophages (BMDMs) were harvested from femurs of C57BL/6 mice. Cells were cultured with rmM-CSF. BMDMs (F4/80+/CD11b+) were treated with ITF2357 in dosages of 0 to 200 nM and stimulated with lipopolysaccharide. Cytokine expression was assessed by a multiplex bead assay. Fluorescent latex spheres were used to investigate phagocytosis activity. Finally, BMDMs were co-cultured with T‑cells of OT-II C57BL/6 mice with either recombinant OVA323–329-peptide or ovalbumin. To determine proliferative response, T‑cells were stained with carboxyfluorescein diacetate succinimidyl ester (CFDA-SE) and subjected to FACS analysis.

Results: ITF2357 treatment lead to a dose-dependent down regulation of tumor necrosis factor alpha (TNFα), interleukin (IL)‑6, IL‑12p70, and IL‑10 secretion by BMDMs. TLR4-dependent CD126 (IL‑6 receptor) up regulation was significantly impaired by ITF2357, while expression of the signaling transducer CD130 was unchanged. ITF2357 reduced the ability of antigen-specific, MHC-II-dependent T‑cell activation, while not impairing antigen processing. Phagocytotic activity of BMDMs was significantly reduced.

Conclusions: Our results demonstrate a pronounced impact of ITF2357 on the phenotype of BMDMs, leading to impaired IL‑6 signaling on the levels of the IL‑6 receptor and secreted IL‑6. Together with an impairment of MHC-II dependent activation of T‑cells and diminished phagocytotic activity, our results suggest the induction of an M2-like phenotype by therapeutic levels of ITF2357. This alteration of the macrophage phenotype might impact on other central macrophage functions such as wound healing, which warrants further investigation in vivo.