THU0056 14–3–3 is a molecular switch regulating macrophage polarisation in inflammatory arthritis
Authors: W. Fu, A. Hettinghouse, C. Liu
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Functional heterogeneity is a hallmark of macrophages, which can classified into 2 major phenotypes with opposite role in inflammation termed M1 (inflammatory or classically activated) macrophages and M2 (alternatively activated) macrophages. In addition, M1-M2 polarisation of macrophages is a highly dynamic process and the phenotype of polarised macrophages can be switched under physiological and pathological conditions. Progranulin (PGRN), a multiple functional growth factor, binds to TNF receptor 2 (TNFR2) and activates the protective and anti-inflammatory pathway in inflammatory arthritis. In addition, 14–3–3e was identified as a component of PGRN/TNFR2 complexes in Raw264.7 macrophages. <h3>Objectives</h3> In this study, we examined whether 14–3–3e regulated macrophage polarisation and if so, whether this was important for PGRN's anti-inflammatory action in inflammatory arthritis. <h3>Methods</h3> LysMCre and14–3–3ε F/F mouse line was obtained from Jackson Laboratory. <h3>Results</h3> <b>: 14–3–3e regulates macrophage polarisation<i>in vitro</i>.</b> We found that 14–3–3e deficiency enhanced M1 while inhibited M2 polarisation (figure<b> 1a, b</b>). Interestingly, PGRN showed reverse effects on macrophage polarisation. In addition, PGRN's effects were largely lost in 14–3–3e deficient BMDMs (figure<b> 1a, b</b>). Together, these data indicate that 14–3–3e is a critical downstream mediator of PGRN regulation of macrophage polarisation. <b>Macrophage-specific 14–3–3e contributes to control of inflammatory arthritis and is critical for PGRN's anti-inflammatory action.</b> We then explored the role of macrophage-specific 14–3–3e in inflammatory arthritis and whether PGRN's anti-inflammatory activity depended on 14–3–3e <i>in vivo</i>. We established CIA in 14–3–3eF/F (serve as WT) and 14–3–3eΔ/Δ mice, followed by i.p. injection of recombinant PGRN. The clinical arthritis score demonstrated that 14–3–3eΔ/Δ mice displayed increased severity of CIA compared with WT CIA. In addition, PGRN's protective effects against inflammatory arthritis was compromised in 14–3–3eΔ/Δ mice (figure<b> 1c</b>), suggesting that 14–3–3e is critical downstream mediator of PGRN's anti-inflammatory effects. In addition, FACS analysis showed that total numbers of F4/80 cells were not different in all WT and knockout CIA mice. However, analysis of CD45 +CD11b+cell population in spleen demonstrated a significant increase in mean fluorescence intensity (MFI) of iNOS and a significant decrease of CD206 +cells in PBS treated 14–3–3eΔ/Δ CIA mice as compared with PBS treated WT CIA mice; moreover, there was a significant decrease of iNOS MFI while a dramatic increase of CD206 +cells in PGRN-treated WT mice compared to that in PBS-treated mice. Further PGRN-mediated effects on macrophage polarisation was lost in 14–3–3eΔ/Δ CIA mice (<b>Fig 1d, e</b>). Cellectively, these results indicate that PGRN skews macrophage toward M2 polarisation to resolve inflammation and this effect depends on 14–3–3ε. <h3>Conclusions</h3> Both <i>in vitro</i> and <i>in vivo</i> results indicate that 14–3–3ε is a key molecule regulating macrophage polarisation which plays an important role in inflammatory arthritis, and it is an essential component for PGRN/TNFR2 mediated protective effect against inflammatory arthritis. <h3>Disclosure of Interest</h3> None declared