Ca2+ signalling plays a role in celastrol‐mediated suppression of synovial fibroblasts of rheumatoid arthritis patients and experimental arthritis in rats

Article date: August 2019

By: Vincent Kam Wai Wong, Congling Qiu, Su‐Wei Xu, Betty Yuen Kwan Law, Wu Zeng, Hui Wang, Francesco Michelangeli, Ivo Ricardo De Seabra Rodrigues Dias, Yuan Qing Qu, Tsz Wai Chan, Yu Han, Ni Zhang, Simon Wing Fai Mok, Xi Chen, Lu Yu, Hudan Pan, Sami Hamdoun, Thomas Efferth, Wen Jing Yu, Wei Zhang, Zheng Li, Yuesheng Xie, Riqiang Luo, Quan Jiang, Liang Liu in Volume 176, Issue 16, pages 2922-2944

Background and Purpose

Celastrol exhibits anti‐arthritic effects in rheumatoid arthritis (RA), but the role of celastrol‐mediated Ca2+ mobilization in treatment of RA remains undefined. Here, we describe a regulatory role for celastrol‐induced Ca2+ signalling in synovial fibroblasts of RA patients and adjuvant‐induced arthritis (AIA) in rats.

Experimental Approach

We used computational docking, Ca2+ dynamics and functional assays to study the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase pump (SERCA). In rheumatoid arthritis synovial fibroblasts (RASFs)/rheumatoid arthritis fibroblast‐like synoviocytes (RAFLS), mechanisms of Ca2+‐mediated autophagy were analysed by histological, immunohistochemical and flow cytometric techniques. Anti‐arthritic effects of celastrol, autophagy induction, and growth rate of synovial fibroblasts in AIA rats were monitored by microCT and immunofluorescence staining. mRNA from joint tissues of AIA rats was isolated for transcriptional analysis of inflammatory genes, using siRNA methods to study calmodulin, calpains, and calcineurin.

Key Results

Celastrol inhibited SERCA to induce autophagy‐dependent cytotoxicity in RASFs/RAFLS via Ca2+/calmodulin‐dependent kinase kinase‐β–AMP‐activated protein kinase–mTOR pathway and repressed arthritis symptoms in AIA rats. BAPTA/AM hampered the in vitro and in vivo effectiveness of celastrol. Inflammatory‐ and autoimmunity‐associated genes down‐regulated by celastrol in joint tissues of AIA rat were restored by BAPTA/AM. Knockdown of calmodulin, calpains, and calcineurin in RAFLS confirmed the role of Ca2+ in celastrol‐regulated gene expression.

Conclusion and Implications

Celastrol triggered Ca2+ signalling to induce autophagic cell death in RASFs/RAFLS and ameliorated arthritis in AIA rats mediated by calcium‐dependent/‐binding proteins facilitating the exploitation of anti‐arthritic drugs based on manipulation of Ca2+ signalling.

DOI: 10.1111/bph.14718

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