Effects of bergapten on damages of osteocytes MLO-Y4 induced by TCP wear particles and its mechanism

Abstract

To study the effects of bergapten (BP) on damages of osteocytes MLO-Y4 induced by tricalcium phosphate (TCP) wear particles and its mechanism. ;Methods: MLO-Y4 cells were treated with TCP wear particles for 48 h to establish the model of osteocytes injuries in vitro. The MLO-Y4 cells were divided into the following five groups: control group, TCP wear particles treated (0.1 mg/ml) group, bergapten (1, 5 and 20 μmol/L) treated groups. MTT assay and Calcein-AM staining were used to determine the viability of MLO-Y4 cells; Hoechst 33342 staining and the flow cytometry were applied to detect the apoptosis of MLO-Y4; real-time PCR was performed to examine the mRNA levels of dentin matrix protein1 (DMP-1), sclerostin (SOST) and fibroblast growth factor23 (FGF23); Western blot was performed to examine protein expressions of glucose-regulated protein 78 (GRP78), protein kinase R-like ER kinase (PERK) phospho-PERK (p-PERK), eukaryotic initiation factor 2α (eIF2α), phospho-eIF2α (p-eIF2α), activating transcription factor 4 (AFT4), C/EBP homologous protein (CHOP) and caspase-3 in MLO-Y4 cells. ;Results: Compared with control group, the MLO-Y4 viability and DMP-1 mRNA level in TCP group were decreased significantly (P＜0.05), while the percentage of apoptosis and mRNA levels of SOST and FGF23 were obviously increased (P＜0.05), and protein expressions of GRP78, AFT4, CHOP, p-PERK/PERK and p-eIF2α/eIF2α were up-regulated significantly in MLO-Y4 cells (P＜0.05). Compared with TCP group, the damages of MLO-Y4 and cell apoptosis in bergapten treated groups were decrease obviously (P＜0.05), the expressions of GRP78, AFT4, CHOP, p-PERK/PERK and p-eIF2α/eIF2α were down-regulated remarkably (P＜0.05). ;Conclusion: Bergapten can inhibit osteocytes damages induced by TCP wear particles, which may be related to reducing ER stress and PERK pathway activation.