Polysaccharide from Angelica sinensis attenuates SNP-induced apoptosis in osteoarthritis chondrocytes by inducing autophagy via the ERK1/2 pathway

Chao Xu,Su Ni,Ruixia Zhu,Chao Zhuang,Gongyin Zhao,Chenkai Li,Yuji Wang,Andre J Van Wijnen,Liangliang Wang,Shijie Jiang

doi:10.1186/s13075-020-02409-3

Abstract

ObjectiveChondrocyte apoptosis plays a vital role in osteoarthritis (OA) progression. Angelica sinensis polysaccharide (ASP), a traditional Chinese medicine, possesses anti-inflammatory and anti-apoptotic properties in chondrocytes. This study aimed to determine the protective role of ASP on sodium nitroprusside (SNP)-induced chondrocyte apoptosis, and explore the underlying mechanism.MethodHuman primary chondrocytes isolated from the articular cartilage of OA patients were treated with SNP alone or in combination with different doses of ASP. Cell viability and apoptosis were assessed, and apoptosis-related proteins including Bcl-2 and Bax were detected. Autophagy levels were evaluated by light chain 3 (LC3) II immunofluorescence staining, mRFP-GFP-LC3 fluorescence localization, and western blot (LC3II, p62, Beclin-1, Atg5). Meanwhile, activation of the ERK 1/2 pathway was determined by western blot. The autophagy inhibitors, 3-methyladenine (3-MA), chloroquine (CQ), and a specific inhibitor of ERK1/2, SCH772984, were used to confirm the autophagic effect of ASP.ResultsThe results showed that SNP-induced chondrocyte apoptosis was significantly rescued by ASP, whereas ASP alone promoted chondrocyte proliferation. The anti-apoptotic effect of ASP was related to the enhanced autophagy and depended on the activation of the ERK1/2 pathway.ConclusionASP markedly rescued SNP-induced apoptosis by activating ERK1/2-dependent autophagy in chondrocytes, and it made ASP as a potential therapeutic supplementation for OA treatment.

Highlights

Osteoarthritis, a progressive and degenerative disease, is characterized by degeneration of the articular cartilage and osteophyte formation
The results showed that sodium nitroprusside (SNP)-induced chondrocyte apoptosis was significantly rescued by Angelica sinensis polysaccharide (ASP), whereas ASP alone promoted chondrocyte proliferation
SNP dramatically attenuates chondrocyte viability whereas ASP rescues it In order to determine the best dosage and time period of SNP application, OA chondrocytes were incubated with three different concentrations of SNP (0.5, 1, 2 mg/ ml) for three different times, and sterile normal saline was added as a control

Summary

Introduction

Osteoarthritis, a progressive and degenerative disease, is characterized by degeneration of the articular cartilage and osteophyte formation. Many factors, including age, excessive weight bearing, oxidative stress, physiology, and biomechanical environment changes in joints, can result in OA [2]. Degeneration of the cartilage in OA is mainly due to the dramatically decreased self-repair ability of chondrocytes in a pathological status, presenting as low chondrocyte vitality, abnormally high apoptosis, and eventually loss of homeostasis of chondrocyte metabolism [3]. Many studies have reported that various factors could cause chondrocyte apoptosis, such as inflammation, oxidative stress, and mechanical stress [4, 5]. Growing evidence highlights that oxidative stress in chondrocytes is related to metabolic disorder and mitochondrial damage, which leads to massive apoptosis of chondrocytes. A previous study demonstrated that the nitrite levels, a stable end product of nitric oxide (NO) metabolism, are elevated in the serum and cartilage in OA samples. SNP, a NO donor compound, induces chondrocyte apoptosis via mitochondrial-dependent signaling [6]

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