Study on the protective effect of sodium valproic acid on carbonyl cyanide 3-chlorophenylhydrazone-induced oxidative stress injury in osteoblasts

Abstract

To explore the protective effects of sodium valproic acid (VPA) on oxidative stress injury of osteoblasts induced by carbonyl cyanide 3-chlorophenylhydrazone (CCCP) and its mechanism. Osteoblasts were isolated from the skulls of 10 newborn Sprague Dawley rats and cultured by tissue block method, and the 1st generation cells were identified by alkaline phosphatase (ALP) and alizarin red staining. The 3rd generation osteoblasts were cultured with 2-18 μmol/L CCCP for 2-18 minutes, and cell counting kit 8 (CCK-8) was used to detect the cell survival rate. An appropriate inhibitory concentration and culture time were selected for the preparation of osteoblasts oxidative stress injury model based on half maximal concentration principle. The cells were cultured with 0.2- 2.0 mmol/mL VPA for 12-72 hours, and CCK-8 was used to detect cell activity, and appropriate concentration was selected for further treatment. The 3rd generation cells were randomly divided into 4 groups, including blank control group (normal cultured cells), CCCP group (the cells were cultured according to the selected appropriate CCCP concentration and culture time), VPA+CCCP group (the cells were pretreated according to the appropriate VAP concentration and culture time, and then cultured with CCCP), VPA+CCCP+ML385 group (the cells were pretreated with 10 μmol/L Nrf inhibitor ML385 for 2 hours before VPA treatment, and other treatments were the same as VPA+CCCP group). After the above treatment was complete, the cells of 4 groups were taken to detect oxidative stress indicators [reactive oxygen species (ROS), superoxide dismutase (SOD), malondialdehyde (MDA)], cell apoptosis rate, ALP/alizarin red staining, and the relative expressions of osteogenic related proteins [bone morphogenetic protein 2 (BMP-2), RUNX2], anti-apoptotic family protein (Bcl2), apoptotic core protein (Cleaved-Caspase-3, Bax), channel protein (Nrf2) by Western blot. The osteoblasts were successfully extracted. According to the results of CCK-8 assay, the oxidative stress injury model was established by 10 μmol/L CCCP cultured for 10 minutes and 0.8 mmol/mL VPA cultured for 24 hours was selected for subsequent experiments. Compared with blank control group, the activity and mineralization capacity of osteoblasts in CCCP group decreased, the contents of ROS and MDA increased, the activity of SOD decreased, and the apoptosis rate increased. Meanwhile, the relative expressions of BMP-2, RUNX2, and Bcl2 decreased, and the relative expressions of Cleaved-Caspase-3, Nrf2, and Bax increased. The differences were significant ( P<0.05). After further VPA treatment, the oxidative stress damage of osteoblasts in VPA+CCCP group was relieved, and the above indexes showed a recovery trend ( P<0.05). In VPA+CCCP+ML385 group, the above indexes showed an opposite trend ( P<0.05), and the protective effects of VPA were reversed. VPA can inhibit the CCCP-induced oxidative stress injury of osteoblasts and promote osteogenesis via Keap1/Nrf2/Are pathway.