SAT0036 Nicotine promotes mmp-3 and rankl secretion through overexpressed nicotinic acetylcholine receptor Α7 in rheumatoid arthritis fibroblast-like synoviocytes

Background Smoking has been reported not only an established environmental risk factor for developing rheumatoid arthritis (RA), but also a predictor of radiographic progression. Nicotine, the major constituent of cigarette smoke, has been demonstrated inhibitory effect on proinflammatory cytokines through its receptor nicotinic acetylcholine receptor α7 (AChRα7) in RA fibroblast-like synoviocytes (FLS). However, its effects on other function of RA-FLS remain elusive. Objectives To explore the effect of nicotine on matrix metalloproteinases (MMPs) and RANKL expression from RA-FLS and its possible intracellular signalling mechanism. Methods Synovial tissues were obtained from 45 patients with active RA as well as 11 osteoarthritis (OA) and 11 noninflammatory orthopaedic arthropathies (Orth.A) patients for control. The expression of AChRα7 in synovial membrane and cultured FLS were detected by immunohistochemistry staining and Western blot. RA-FLS were treated in vitro with different concentration of nicotine and its effect on RA-FLS viability was evaluated by cell counting kit-8. After nicotine pretreatment on TNF-α stimulated RA-FLS, the expression of MMP-2, MMP-3, MMP-9, TIMP-1, TIMP-2, RANKL, and OPG in culture supernatant were measured by ELISA, while the change of AP-1 pathway including c-Fos and c-Jun were detected by quantitative real-time PCR and Western blot. Results Immunohistochemical analyses showed intense endochylema staining for AChRα7 mainly in lining layer. The percentage of both lining and sublining AChRα7 positive cells were significantly higher in RA than that in OA or Orth.A (figure 1A). Further western blot showed significantly higher expression of AChRα7 in RA-FLS than that in Orth.A-FLS (p=0.003, figure 1B). Nicotine (0.1 µM~50 µM) showed no cytotoxicity on RA-FLS proliferation. Pretreatment with 50 µM nicotine for 24 hours significantly promoted the secretion of MMP-3 and RANKL but inhibited TIMP-1 secretion in TNF-α stimulated RA-FLS (all p Conclusions Nicotine can promote MMP-3 and RANKL expression through overexpressed AChRα7 in RA-FLS which might be involved in the pathogenesis of osteogenesis and bone destruction in RA. Acknowledgements This work was supported by National Natural Science Foundation of China (no. 81471597 and 81671612), Guangdong Natural Science Foundation (no. 2017A030313576 and 2017A030310236) and Fundamental Research Funds for the Central Universities (no. 17ykjc12). Disclosure of Interest None declared