OP0007 Growth differentiation factor 11 attenuates inflamatory arthritis through antagonising nf-Κb signalling pathway
Authors: Y. Zhao, W. Li, K. Vasilev
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> It is well established that the tumour necrosis factor-α (TNF-α) plays a dominant role in rheumatoid arthritis (RA)<sup>1</sup> and other arthritis models.<sup>2 3</sup> Growth Differentiation Factor 11 (GDF11) is recently reported to be closely associated with various inflammatory diseases. However, whether GDF11 interacts with TNF-α and plays a role in RA still remains unknown. <h3>Objectives</h3> To investigate the potential role of GDF11 in development of RA, and to testify the underlying mechanisms involved. <h3>Methods</h3> NF-κB-luciferase transgenic mice (Balb/c strain), DBA-1 mice, micro-CT, <i>in vivo</i> imaging system (IVIS), mice bone marrow-derived macrophages (BMDM), cell immunostaining, collagen induced arthritis model (CIA), collagen antibody induced arthritis model (CAIA), GDF11 recombinant protein, co-immunoprecipitation Co-IP, Western blot, real time PCR, Histology, immunohistochemistry, unpaired t-tests (Mann-Whitney), paired t-tests, and ANOVA. <h3>Results</h3> The interaction between GDF11 and TNFR1/TNFR2 in BMDM was implied by co-immunoprecipitation (Co-IP) (figure 1A-B). BMDM cells were cultured with stimulation of 10 ng/ml TNF-α, in the presence or absence of 10 µg/ml GDF11. Inflammation-associated cytokines, including IL-1β, IL-6 and inducible nitric oxide synthase (iNOS) were assessed at 12 hour time point through real time PCR (figure 1C-1E), and expression level of IL-1β was assayed through ELISA at 72 hour time point (figure 1F). As a result, GDF11 suppressed TNF-α-induced expression of inflammatory cytokines. Every experiment was repeated for three times. Collagen-induced arthritis (CIA) mice model was established in DBA-1 mice, and intraperitoneal injection of GDF11 attenuated clinical score (figure 2A), synovitis, pannus and bone erosion (figure 2B-2D) compared with PBS control group (n=7 for each group). Representative pictures of the paw (figure 2E), micro-CT (figure 2F) as well as HE staining (figure 2G) revealed that GDF11 greatly suppressed joint destruction in CIA model. In addition, GDF11 inhibited TNF-α-induced expression of biomarkers for activation of NF-κB signalling pathway, including NF-κB2 (figure 3A), phosphorylation of IκBα (figure 3B) and nuclear translocation of p65 (figure 3C) in BMDM, which were tested through real time PCR, Western blot and cell immunostaining, respectively. To testify the function of GDF11 in activation of NF-κB signalling pathway <i>in vivo</i>, p-IκBα expression was detected through immunohistochemistry in CIA model, and GDF11 diminished phosphorylation of IκBα (figure 4A) compared with PBS group (n=5). Moreover, CAIA arthritis model was established in BALB/C strain-based NF-κB luciferase mice, and GDF11 markedly repressed intensity of bioluminescence signal in the paws of CAIA model (figure 4B-4C). The values are the mean ±SD. *p&lt;0.05, **p&lt;0.01 and ***p&lt;0.005 vs control group. <h3>Conclusions</h3> These results reveal GDF11 as potential antagonist for inflammatory function of TNF-α. Besides, GDF11 displays promising protective function in inflammatory arthritis mice models. In conclusion, GDF11 may shed light on treatment of inflammatory arthritis and provide a potential therapeutic instrument for RA in the future. <h3>References</h3> [1] Tang, et al. <i>Science</i>2011. [2] Zhao, et al. Ann Rheum Dis2015. [3] Lai, et al. Ann Rheum Dis2014. <h3>Acknowledgements</h3> This work was supported by the National Natural Science Foundation of China (Grant No. 81501880). <h3>Disclosure of Interest</h3> None declared