Effects of oxidative damage on selenoprotein gene expression in articular chondrocytes and the mechanism of selenium

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 Na2SeO3+ 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 (OS1, 0.05 mg/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 O 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. Key words: Chondrocytes; Selenoproteins; Sodium selenite