Apoptosis of primary osteoblasts induced by dexamethasone: cellular and molecular mechanisms
Nirong Bao, Jianning Zhao, Yurong Wang, Sujia Wu, Xiaofeng Zeng, Junhua Wang
Department of Orthopaedics, Jinling Hospital, Nanjing, Jiangsu Province, China
Keywords: Apoptosis/drug effects; bone density/drug effects; bone marrow cells/drug effects; glucocorticoids/adverse effects; NFkappa B/metabolism; mice; osteoblasts/metabolism/drug effects.
Abstract
Objectives: We investigated the effect of glucocorticoids on cell viability of osteoblasts and explored the cytological and molecular mechanisms of osteoblast apoptosis induced by glucocorticoids. Materials and methods: Dexamethasone was used to induce apoptosis of primary cultured osteoblast-like cells from skulls of suckling mouse. Surviving rate of osteoblasts, apoptosis rate, activity of caspase-3, and DNA binding activity of nuclear factor-kappa B were assessed using MTT-dye reduction microassay, flow cytometry, colorimetric substrate assay and electrophoretic mobility shift assay. The surviving rates of osteoblasts and fibroblasts were also compared to assess the differences in dexamethasone-induced effects on cells.
Results: Dexamethasone significantly decreased the survival rate of osteoblast-like cells through an apoptotic process, activated cellular caspase-3, and inhibited the activity of nuclear factor-kappa B, in a concentrationand time-dependent manner (p<0.05). However, dexamethasone did not exert any apoptotic effect on fibroblasts.
Conclusion: The results suggest that dexamethasone induces apoptosis of primarily cultured and non-transformed osteoblasts, which is caspase-3 dependent, while nuclear factor-kappa B may play a protective role through inhibition of caspase-3.