Objective To explore the effects of oxidative damage and selenium on the apoptosis of articular chondrocytes and the expression of selenoprotein genes.Methods C28/I2 chondrocytes were preincubated for 24 h,using sodium selenite (Na2SeO3) or t-butyl hydroperoxide (tBHP) for 24 h.The experiment was divided into six groups,including control group (C,0.00 mg/L Na2,SeO3 + 0.00 μmol/L tBHP),selenium beforehand protection group (S2,0.10 mg/L Na2SeO3),oxidative damage group (O,150.00 μmol/L tBHP),low dose selenium protection group (OS 1,0.05mg/L Na2SeO3 + 150.00 μmol/L tBHP),medium dose selenium protection group (OS2,0.10 mg/L Na2SeO3 + 150.00 μmol/L tBHP),and high dose selenium protection group (OS3,0.15 mg/L Na2SeO3 + 150.00 μmol/L tBHP).After 24 h,Hoechst 33342 staining method was used to observe apoptosis,mRNA expression of glutathione peroxidase 1 (GPX1),GPX4,deiodinase 2 (DIO2),DIO3,selenoprotein P (SEPP1),thioredoxin reductase 1 (TrxR-1) and selenoprotein W(Sel W) was detected by Real-time PCR,both experiments were done three times.Results Apoptotic rates of C,S2,O,OS1,OS2,OS3 groups [(0.78 ± 0.06)％,(13.61 ± 7.11)％,(92.27 ± 3.44)％,(71.38 ± 5.22)％,(44.31 ± 9.16)％,(72.46 ± 4.69)％] were compared between groups,the differences were statistically significant (F =120.10,P ＜ 0.01).The apoptotic rates of O group was significantly higher than that of C group (P ＜ 0.05);compared to O group,the apoptotic rates of OS1,OS2,OS3 groups decreased significantly (P＜ 0.05),OS2 group was the most obvious.DIO2,SEPP1,GPX1,GPX4,TrxR-1,Sel W mRNA levels were compared in the six groups,the differences were statistically significant (F =24.60,14.53,127.60,30.60,637.10,59.64,P ＜ 0.01).Compared to C group (1.00 ± 0.00),the mRNA levels of GPX1 (0.10 ± 0.05),GPX4 (0.43 ± 0.09),TrxR-1 (0.11 ± 0.05) and Sel W (0.72 ± 0.15) in O groups were decreased significantly (P ＜ 0.05);compared to 0 group,the mRNA levels of GPX1 in OS1 (0.20 ± 0.03),OS2 (0.74 ± 0.10),and OS3 (0.30 ± 0.07) were increased significantly (P ＜ 0.05).Conclusion Down-regulated expression of selenoprotein genes are involved in the regulation process of articular cartilage apoptosis caused by oxidative stress,selenium also has a regulatory role in selenoprotein gene expression in articular chondrocytes.