Background: Tocilizumab is produced by Roche company, using the humanized monoclonal antibody preparation of anti interleukin 6 receptor expressed by mammalian CHO cells, which can effectively block IL-6-mediated signaling in the body and has a good anti-inflammatory effect ^[1] ，Studies have shown that inhibition of IL-6 in a mouse model of bleomycin induced scleroderma delays the progression of skin fibrosis ² .CD38 has been shown to be highly expressed in M1 and promotes the secretion of inflammatory cytokines by macrophages ³

Objectives: Tocilizumab is a monoclonal antibody against IL6 receptor, which could effectively block IL6 mediated signal pathway. In the early stage, we found that there were differences in the expression levels of CD38 ⁺ macrophages in healthy people and systemic sclerosis patients, but there were still few basic research and clinical datas on tocilizumab in systemic sclerosis. Therefore, this study aims to investigate the theraputic effect of tocilizumab on skin fibrosis through inhibiting CD38 ⁺ macrophages in bleomycin-induced systemic sclerosis mice model

Methods: The 8 week old BABL/C mices were randomly divided into control group, model group and tocilizumab group. The mRNA explession of VIMENTIN, TIMP1 and COL1A1 detected by QPCR. Western blot was used to detect the protein expression of α-SMA, TGF-β and col1a1 in skin.The existence of CD38 ⁺ macrophages in BLM Induced Fibrosis Mouse Model was verified by flow cytometry and immunofluorescence

Results: The BLM groups showed skin fibrosis compared with the PBS control group, as well as skin swelling, thickening and increased collagen content. Skins from the BLM group exhibited increased mRNA expression of COL3A, VIMENTIN and TIMP1. In the BLM group, protein expression of the profibrotic markers TGF-β, α-SMA and COL1A1 were also increased in skin tissues. Compared to the PBS group, the expression level of macrophages in the skin of mice was increased after injection of BLM, and the expression level of CD38 ⁺ macrophages in the skin was also increased. At the same time, the expression of macrophages in the peripheral blood and spleen of mice was also increased, and the expression of CD38 ⁺ macrophages in the peripheral blood was increased, but it was decreased in the spleen. After L929 fibroblasts were co-cultured with macrophages, the morphology of the skin changed, and some fibroblasts became myofibroblast cells.The mRNA expression levels of COL1A1, COL3A, TGF-β, and Fibron were increased in L929 fibroblasts after co-culture with macrophages, as was the protein expression of COL1A1 and TGF-β. Furthermore, RAW264.7 cells were stimulated with LPS, and it was found that the mRNA expression levels of IL-6 and CD38 in RAW264.7 cells increased after LPS stimulation, and the protein levels of CD38 also increased. RAW264.7 cells stimulated with LPS were co-cultured with L929 fibroblasts, and we found that LPS-stimulated RAW264.7 cells could increase the mRNA expression levels of COL1A1, COL3A, TGF-β, and Fibron in L929 fibroblasts. The dermal thickness and collagen content induced by BLM were diminished by therapeutic administration of tocilizumab. The skin in the tocilizumab-treated group exhibited decreased mRNA expression of the pro-fibrotic markers COL3A, VIMENTIN, COL1A1 and TIMP1. In the tocilizumab-treated group, protein expression of COL1A1 was also decreased. The expression of α-SMA was also decreased in the tocilizumab-treated group. Compared with the BLM group, the expression level of macrophages in the skin of mice decreased after tocilizumab treatment, and the expression level of CD38 ⁺ macrophages in the skin was also reduced. The expression of macrophages in the peripheral blood and spleen of mice was also reduced, and the expression of CD38 ⁺ macrophages in the peripheral blood was reduced, but there was not change in the spleen

Conclusion: This study proves that tocilizumab can improve skin fibrosis in mice with systemic sclerosis, and the drug may provide a new treatment for autoimmune diseases such as systemic sclerosis

REFERENCES: [1] Liu X Teichtahl AJ Wicks IP Interleukin-6 in rheumatoid arthritis - from the laboratory to the bedside Curr Pharmaceut Des 2015 21(17) 2187e97.

Acknowledgements: NIL.

Disclosure of Interests: None declared.