Dexamethasone induces caspase activation in murine osteoblastic MC3T3-E1 cells

• Published in: Biochimica et biophysica acta 2003-09, Vol.1642 (1-2), p.79-85
• Main Authors: Chua, Chu Chang, Chua, Balvin H.L., Chen, Zhongyi, Landy, Cathy, Hamdy, Ronald C.
• Format: Article
• Language: English
• Subjects: Animals; Apoptosis; Apoptosis - drug effects; Apoptosis - physiology; bcl-X Protein; Caspase; Caspases - genetics; Cytochrome c Group - drug effects; Cytochrome c Group - metabolism; Dexamethasone; Dexamethasone - pharmacology; Enzyme Induction - drug effects; Gene Expression Regulation, Enzymologic - drug effects; Gene Expression Regulation, Enzymologic - genetics; Lamin Type A - drug effects; Lamin Type A - metabolism; Mice; Osteoblast; Osteoblasts - drug effects; Osteoblasts - enzymology; Osteoporosis - chemically induced; Osteoporosis - enzymology; Osteoporosis - genetics; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerases; Proteins - drug effects; Proteins - metabolism; Proto-Oncogene Proteins c-bcl-2 - drug effects; Proto-Oncogene Proteins c-bcl-2 - metabolism; Reaction Time - drug effects; Reaction Time - physiology; RNA, Messenger - drug effects; RNA, Messenger - metabolism; Transcriptional Activation; Up-Regulation - drug effects; Up-Regulation - genetics
• ISSN: 0167-4889; 0006-3002; 1879-2596
• DOI: 10.1016/S0167-4889(03)00100-9

Glucocorticoids are widely used as anti-inflammatory and chemotherapeutic agents. However, prolonged use of glucocorticoids leads to osteoporosis. This study was designed to examine the mechanism of dexamethasone (DEX)-induced apoptosis in murine osteoblastic MC3T3-E1 cells. Total RNA was extracted from MC3T3-E1 cells treated with 10−7 M DEX for 6 h. DEX exerted a variety of effects on apoptotic gene expression in osteoblasts. Ribonuclease protection assays (RPA) revealed that DEX upregulated mRNA levels of caspases-1, -3, -6, -8, -11, -12, and bcl-XL. Western blot analysis showed enhanced processing of these caspases, with the appearance of their activated enzymes 8 h after DEX treatment. In addition, DEX also induced the activation of caspase-9. DEX elevated the levels of cleaved poly(ADP-ribose) polymerase and lamin A, a caspase-3 and a caspase-6 substrate, respectively. Expression of bcl-XL protein level was upregulated by DEX. Cytochrome c release was detected in the cytosol of DEX-treated cells. Furthermore, caspase-3 enzyme activity was elevated by 2-fold after DEX treatment for 7 h. Finally, early apoptotic cells were detected in cells treated with DEX for 3 h. Our results demonstrate that DEX-induced apoptosis involves gene activation of a number of caspases.