| Objective:Superfluous apoptosis of chondrocytes induced by oxidative stress in osteoarthritis is intimately linked to the reduction of autophagy and the upregulation of endoplasmic reticulum(ER)stress.Quercetin is a potent anti-inflammatory and antioxidant flavonoid which is abundant and ubiquitous in our diet.Quercetin can exert its protective effects by inducing autophagy and eliminating oxygen free radicals in various cells.However,the effect of quercetin involved in oxidative stress-induced chondrocyte apoptosis is still not understood.The objective of this study was to investigate the role of autophagy and ER stress regulated by quercetin in the suppression of oxidative stress-induced chondrocyte apoptosis and the potential mechanism of these effects in oxidative stress-induced rat chondrocytes.Moreover,we explored the effect of quercetin in vivo by the use of a surgically induced rat osteoarthritis model.Methods:TBHP(tert-Butyl hydroperoxide)was used to induce oxidative stress-related apoptosis in rat chondrocytes.CCK-8 assay was performed to study the viability of chondrocytes treated with different concentrations of quercetin with or without TBHP.The apoptosis of chondrocytes was detected by TUNEL staining and flow cytometry.MDC staining and Transmission electron microscopy(TEM)were used to evaluate the level of quercetin-induced chondrocytes autophagy.The expression levels of apoptosis related biomarkers(Cleaved caspase3,Cleaved PARP,Bcl-2),ER stress related biomarkers(CHOP,GRP78,ATF6,PERK,p-PERK,IRE1α,p-IRE1α),autophagy related biomarkers(Beclin1,LC3,P62)and AMPK/SIRT1 signaling pathway associated biomarkers were detected by real-time PCR and Western blotting.In addition,a destabilized medial meniscus(DMM)rat OA model was established to verify the protective effect of quercetin in vivo.Results:TBHP-induced chondrocyte apoptosis,autophagy inhibition and ER stress promotion can be reversed by quercetin.In addition,these protective effects of quercetin were associated with the activation of AMPK/SIRT1 signaling pathway in TBHP-treated chondrocytes.We also found that EX527(a known SIRT1 inhibitor)and Compound C(a known AMPK inhibitor)abrogated the protective effect of quercetin.Meanwhile,quercetin decreased the apoptosis of chondrocytes and ameliorated the degeneration of articular cartilage in DMM rats.Conclusions:Quercetin activates autophagy and inhibits ER stress through AMPK/SIRT1 signaling pathway to ameliorate the development of osteoarthritis in vitro and in vivo.Thus,quercetin is a promising prophylactic and therapeutic drug for OA patients. |
