5-Azacytidine induces toxicity in PC12 cells by apoptosis

Exp Toxicol Pathol. 1997 Aug;49(3-4):201-6. doi: 10.1016/S0940-2993(97)80008-5.


5-Azacytidine (5 Az)is a potent inhibitor of DNA methylation, and it may allow inactive genes to become expressed. In a previous study, we demonstrated that 5 Az administered to the dam induced apoptosis in the brains of fetal mice. In this study, the 5 Az-induced apoptosis was further characterized in differentiated PC 12 cells as a model for neuronal apoptosis. Cell death, determined by the activity of released lactate dehydrogenase (LDH) into the medium, occurred from 24 to 48 hrs after 5 Az treatment. Toxicity for differentiated PC 12 cells was observed on treatment with more than 10(-1) micrograms/ml of 5 Az, and it reached the maximal level at 10 micrograms/ml. Cycloheximide, an inhibitor of protein synthesis, prevented 5 Az toxicity, suggesting that this cell death required protein synthesis which could be related to the activation of a dormant gene(s). Electrophoresis of DNA from 5 Az-treated cells evoked ladder formation, indicating the cleavage of DNA into nucleosomes. Scanning electron microscopy demonstrated bleb formation, the so-called apoptotic bodies on the cell surface. The biochemical and morphological findings indicated that 5 Az-induced cell death occurred in the form of apoptosis. 5 Az-induced cell death was prevented by treatment with cAMP but not by treatment with high K+ or deoxycytidine. These results suggest that a cAMP-sensitive mechanism is involved in 5 Az-induced cell death. PC 12 cells should be of value in elucidating the molecular mechanism of 5 Az-induced neuronal apoptosis.

MeSH terms

  • Animals
  • Antimetabolites, Antineoplastic*
  • Apoptosis*
  • Azacitidine / pharmacology*
  • Bucladesine / pharmacology
  • Cycloheximide / pharmacology
  • DNA Methylation
  • L-Lactate Dehydrogenase / metabolism
  • Microscopy, Electron, Scanning
  • Neurons / cytology
  • Neurons / drug effects*
  • PC12 Cells / drug effects*
  • Protein Synthesis Inhibitors / pharmacology
  • Rats


  • Antimetabolites, Antineoplastic
  • Protein Synthesis Inhibitors
  • Bucladesine
  • Cycloheximide
  • L-Lactate Dehydrogenase
  • Azacitidine