An herbal formula inhibits STAT3 signaling and attenuates bone erosion in collagen-induced arthritis rats

• Published in: Phytomedicine (Stuttgart) 2020-09, Vol.76, p.153254-153254, Article 153254
• Main Authors: Chen, Ying-Jie, Wu, Jia-Ying, Leung, Wai-Chung, Liu, Yu-Xi, Fu, Xiu-Qiong, Zhu, Jia-Qian, Wu, Ying, Chou, Ji-Yao, Yin, Cheng-Le, Wang, Ya-Ping, Wang, Xiao-Qi, Bai, Jing-Xuan, Wu, Zheng-Zhi, Yu, Zhi-Ling
• Format: Article
• Language: English
• Subjects: Bone erosion; Lonicera japonica; Osteoclastogenesis; Rheumatoid arthritis; Rosa multiflora; STAT3 signaling
• ISSN: 0944-7113; 1618-095X
• DOI: 10.1016/j.phymed.2020.153254

Receptor activator of NF-κB ligand (RANKL) facilitates differentiation of osteoclast precursors into osteoclasts, resulting in bone erosion in rheumatoid arthritis (RA) patients. Fibroblast-like synoviocytes (FLS) are the main cells for producing RANKL. Signal transducer and activator of transcription 3 (STAT3) signaling is activated in FLS of RA patients (RA-FLS), which has been linked to RANKL production. A two-herb formula (RL) comprising Rosae Multiflorae Fructus and Lonicerae Japonicae Flos is traditionally used for treating RA in China. We have found that a standardized ethanolic extract of RL (RLE for short) alleviates bone erosion in collagen-induced arthritis (CIA) rats. This study aimed to determine whether RLE inhibits RANKL production and osteoclastogenesis in cell and rat models, and to explore the involvement of the STAT3 pathway in this inhibition. A CIA rat model, interleukin-6/soluble interleukin-6 receptor (IL-6/sIL-6R)-stimulated RA-FLS and a co-culture system (IL-6/sIL-6R-stimulated RA-FLS/peripheral blood mononuclear cells) were used to evaluate the effects of RLE. Micro-computed tomography analysis was used to observe bone erosion in CIA rats. Tartrate-resistant acid phosphatase staining was used to evaluate osteoclastogenesis. Western blotting and ELISA assays were employed to examine protein levels. RT-qPCR was used to detect mRNA levels. STAT3-over-activated RA-FLS were used to investigate the involvement of STAT3 signaling in the anti-osteoclastogenic effects of RLE. RLE alleviated bone erosion in joints of CIA rats. In both synovial tissues of CIA rats and IL-6/sIL-6R-stimulated RA-FLS, RLE downregulated the protein level of RANKL. In the co-culture system, RLE significantly and dose-dependently inhibited IL-6/sIL-6R-induced osteoclastogenesis. Mechanistic studies revealed that RLE lowered the protein level of phospho-STAT3 (Tyr705) in synovial tissues of CIA rats. In IL-6/sIL-6R-stimulated RA-FLS, RLE inhibited the activation/phosphorylation of a STAT3 upstream kinase Janus kinase 2 (Tyr1007/1008) and STAT3 (Tyr705), decreased the nuclear localization of STAT3, lowered mRNA levels of STAT3-transcriptionally regulated genes IL-1β and TNF-α. RLE's inhibitory effects on RANKL production in RA-FLS gradually decreased when IL-6/sIL-6R doses increased. Over-activation of STAT3 diminished the inhibitory effects of RLE on RANKL production in IL-6/sIL-6R-stimulated RA-FLS, and attenuated the anti-osteoclastogenic effects of RLE in the co