Icariin Activates Autophagy via Down-Regulation of the NF-κB Signaling-Mediated Apoptosis in Chondrocytes.

Bobin Mi,Liangcong Hu,Guohui Liu,Wu Zhou,Junqing Wang,Yi Liu,Adriana C Panayi,Jing Liu

doi:10.3389/fphar.2018.00605

Abstract

Osteoarthritis (OA) is a common chronic and degenerative joint condition that is mainly characterized by cartilage degradation, osteophyte formation, and joint stiffness. The NF-κB signaling pathway in inflammation, autophagy, and apoptosis plays a prominent role in the progression of OA. Icariin, a prenylated flavonol glycoside extracted from Epimedium, have been proven to exert anti-osteoporotic and anti-inflammatory effects in OA. However, the action mechanisms of its effect on chondrocytes have yet to be elucidated. In the present study, we demonstrated that the in vitro therapeutic effects of icariin on rat chondrocytes in a dose-dependent manner. We found that TNF-α induced the production of IL-1, IL-6, IL-12, reactive oxygen species (ROS), nitric oxide (NO), Caspase-3, and Caspase-9 in chondrocytes. We also provided evidence that TNF-α inhibited autophagy markers (Atg 5, Atg 7) and prevented LC3 I translate to LC3 II. Furthermore, TNF-α induced matrix metalloproteinase (MMP)3 and MMP9 expression. The negative effects of TNF-α on chondrocytes can be partially blocked by treating with icariin or ammonium pyrrolidinedithiocarbamate (PDTC, an NF-κB inhibitor). The present study data also suggested that icariin suppressed both TNF-α-stimulated p65 nuclear translocation and IκBα protein degradation. These results indicated that icariin protected against OA by suppressing inflammatory cytokines and apoptosis, through activation of autophagy via NF-κB inhibition. In conclusion, icariin appears to favorably modulate autophagy and apoptosis in chondrocytes making it a promising compound for cartilage tissue engineering in the treatment of OA.

Highlights

Osteoarthritis (OA) is a chronic degenerative joint disease that occurs mostly in the elderly (GlynJones et al, 2015)
To determine whether icariin was toxic to chondrocytes, Cell Counting Kit-8 (CCK8) assay was used after the cells had been treated with increasing concentration of icariin (0, 3, 5, 7, 10, 20 μM) for 24, 48, and 72 h
We found that TNF-α induced the production of IL-1, IL-6, and IL-12 in chondrocytes

Summary

Introduction

Osteoarthritis (OA) is a chronic degenerative joint disease that occurs mostly in the elderly (GlynJones et al, 2015). The capacity of chondrocytes to regenerate normal cartilage matrix architecture declines with aging, resulting in cartilage degradation and erosion. In the cases of OA, various changes occur in the cartilage including inflammation, oxidative stress, loss of cartilage matrix, autophagy, and apoptosis. During the progression of OA, the increased expression of inflammatory cytokines (such as TNF-α and IL-1β) in articular cartilage and synovium contribute to the degradation and erosion of cartilage (Raman et al, 2018). Autophagy and apoptosis occur in the progression of OA. More and more evidences suggest that increased chondrocyte apoptosis induces cartilage degeneration in OA (Kobayashi et al, 2016). Activation of autophagy and inhibition of apoptosis in chondrocytes may limit OA progress

Methods

Results

Conclusion