Theaflavin-3,3’-Digallate Ameliorates Collagen-Induced Arthritis Through Regulation of Autophagy and Macrophage Polarization

Abstract

Lei Zhang,1,* Wenming Li,1,* Zhenyang Hou,2,* Zhidong Wang,1,* Wei Zhang,1 Xiaolong Liang,1 Zerui Wu,1 Tianhao Wang,1 Xin Liu,1 Xiaole Peng,1 Xing Yang,3 Huilin Yang,1 Dechun Geng1 1Department of Orthopaedics, The First Affiliated Hospital of Soochow University, Suzhou, People’s Republic of China; 2Department of Orthopaedics, Tengzhou City Center People’s Hospital, Tengzhou, People’s Republic of China; 3Orthopedics and Sports Medicine Center, Suzhou Municipal Hospital (North District), Nanjing Medical University Affiliated Suzhou Hospital, Suzhou, People’s Republic of China*These authors contributed equally to this workCorrespondence: Huilin Yang; Dechun Geng, Department of Orthopaedics, The First Affiliated Hospital of Soochow University, Suzhou, People’s Republic of China, Email [email protected]; [email protected]: Previous studies have presented that theaflavin-3,3’-digallate (TFDG), one of natural flavonoids, have protective effects on collagen-induced arthritis (CIA). Besides, it was reported that TFDG could affect inflammatory signaling pathways, like NF-κB, JNK, and so on, to ameliorate inflammation. However, the anti-inflammatory mechanisms mentioned above are common to natural flavonoid products including TFDG. Therefore, this study aimed to further investigate the other mechanisms of TFDG against CIA.Methods: DBA/1 mice (8– 10 weeks) were intravenously injected Freund’s Adjuvant (100μL) at the base of tail and intraperitoneally injected PBS or different dosage of TFDG (1 mg/kg or 10 mg/kg). Then the paw and knee tissues were collected to assess the severity of joint destruction. In vitro experiments, bone marrow macrophages (BMMs) were exposed to TNF-α (10ng/mL) with or without different concentrations of TFDG (0.1μmol/L or 1.0μmol/L). Besides, the targets of TFDG were predicted with docking software and were verified through experiment.Results: TFDG treatment could reduce M1 macrophage (pro-inflammatory) and inflammatory cytokines, such as IL-1, IL− 6 and TNF-α, both in vitro and in vivo. At the same time, the M2 macrophage (alternatively activated) polarization was promoted by TFDG. Animal experiments showed TFDG ameliorated joint destructions. For investigating the mechanisms, the targets of TFDG were predicted by bioinformatics tools. According to predictions, we hypothesized that TFDG could act with BCL-2 to weaken the interaction between BCL-2 and Beclin1. Beclin1 plays a central role in autophagy, and we found that the autophagy level of BMMs was recovered by TFDG. Besides, 3-MA, an autophagy inhibitor, could attenuate the therapeutic effect of TFDG.Conclusion: TFDG protected against collagen-induced arthritis by attenuating the inflammation and promoting anti-inflammatory M2 macrophage polarization through controlling autophagy.Graphical Abstract: Keywords: theaflavin-3,3’-digallate, autophagy, inflammation, macrophage polarization, rheumatoid arthritis

Keywords

• theaflavin-3
• 3'-digallate
• autophagy
• inflammation
• macrophage polarization
• rheumatoid arthritis