Oxidative Stress Induces Chondrocyte Apoptosis through Caspase-Dependent and Caspase-Independent Mitochondrial Pathways and the Antioxidant Mechanism of Angelica Sinensis Polysaccharide

Abstract

Introduction: Chondrocyte apoptosis is considered one of the pathogenic factors of osteoarthritis (OA), but its importance in the pathogenesis of OA remains unclear. Recent research adds progress to the knowledge that the mitochondrial signaling pathway mediates chondrocyte apoptosis in OA.

Method: Rat chondrocyte exposed to H₂O₂ was used as the experimental oxidative stress model. Chondrocyte viability was tested by cell counting kit-8 (CCK-8) assay. Cell apoptosis and ROS were tested by flow cytometry. Contents of malondialdehyde (MDA), catalase (CAT), caspase-3, caspase-9, cytochrome C, superoxide dismutase (SOD)-2, and adenosine triphosphate (ATP) were evaluated by biochemical detection. The expressions of related genes and proteins were assessed by quantitative polymerase chain reaction (qPCR) and western blot.

Results: H₂O₂ provokes oxidative stress and decreases the viability of chondrocyte, which leads to the release of cytochrome C and inhibition of SOD-2 activity. The damage of mitochondrion disturbs the energy metabolism of chondrocyte and eventually induces chondrocyte apoptosis through the mitochondrial pathway. Furthermore, pretreated with anglicasinensis polysaccharide (ASP) or caspase inhibitors increase the expression of Bcl-2 and Bcl-xL but do not work for the expression of Bax and Bad.

Conclusion: Oxidative stress induces chondrocyte apoptosis through caspase-dependent and caspase-independent mitochondrial pathways. ASP protects chondrocyte from H₂O₂-induced oxidative stress and subsequent cell injury through its antioxidant effect by inhibiting the caspase pathway.