Dexamethasone induces caspase activation in murine osteoblastic MC3T3-E1 cells

Biochim Biophys Acta. 2003 Sep 23;1642(1-2):79-85. doi: 10.1016/s0167-4889(03)00100-9.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Apoptosis / drug effects*
  • Apoptosis / physiology
  • Caspases / genetics*
  • Cytochrome c Group / drug effects
  • Cytochrome c Group / metabolism
  • 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
  • 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
  • RNA, Messenger / drug effects
  • RNA, Messenger / metabolism
  • Reaction Time / drug effects
  • Reaction Time / physiology
  • Transcriptional Activation
  • Up-Regulation / drug effects
  • Up-Regulation / genetics
  • bcl-X Protein

Substances

  • Bcl2l1 protein, mouse
  • Cytochrome c Group
  • Lamin Type A
  • Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • RNA, Messenger
  • bcl-X Protein
  • Dexamethasone
  • Parp1 protein, mouse
  • Poly (ADP-Ribose) Polymerase-1
  • Poly(ADP-ribose) Polymerases
  • Caspases