Polyamine depletion prevents camptothecin-induced apoptosis by inhibiting the release of cytochrome c

Am J Physiol Cell Physiol. 2002 Jun;282(6):C1290-7. doi: 10.1152/ajpcell.00351.2001.

Abstract

We have shown previously that depletion of polyamines delays apoptosis induced by camptothecin in rat intestinal epithelial cells (IEC-6). Mitochondria play an important role in the regulation of apoptosis in mammalian cells because apoptotic signals induce mitochondria to release cytochrome c. The latter interacts with Apaf-1 to activate caspase-9, which in turn activates downstream caspase-3. Bcl-2 family proteins are involved in the regulation of cytochrome c release from mitochondria. In this study, we examined the effects of polyamine depletion on the activation of the caspase cascade, release of cytochrome c from mitochondria, and expression and translocation of Bcl-2 family proteins. We inhibited ornithine decarboxylase, the first rate-limiting enzyme in polyamine synthesis, with alpha-difluoromethylornithine (DFMO) to deplete cells of polyamines. Depletion of polyamines prevented camptothecin-induced release of cytochrome c from mitochondria and decreased the activity of caspase-9 and caspase-3. The mitochondrial membrane potential was not disrupted when cytochrome c was released. Depletion of polyamines decreased translocation of Bax to mitochondria during apoptosis. The expression of antiapoptotic proteins Bcl-x(L) and Bcl-2 was increased in DFMO-treated cells. Caspase-8 activity and cleavage of Bid were decreased in cells depleted of polyamines. These results suggest that polyamine depletion prevents IEC-6 cells from apoptosis by preventing the translocation of Bax to mitochondria, thus preventing the release of cytochrome c.

MeSH terms

  • Animals
  • Apoptosis*
  • BH3 Interacting Domain Death Agonist Protein
  • Blotting, Western
  • Camptothecin / toxicity*
  • Carrier Proteins / metabolism
  • Caspase 3
  • Caspase 8
  • Caspase 9
  • Caspases / metabolism
  • Cell Line
  • Cytochrome c Group / metabolism*
  • DNA Fragmentation / drug effects
  • Eflornithine / pharmacology
  • Enzyme Inhibitors / pharmacology
  • Epithelial Cells / cytology
  • Epithelial Cells / drug effects
  • Epithelial Cells / metabolism*
  • Intestinal Mucosa / cytology
  • Intestinal Mucosa / drug effects
  • Intestinal Mucosa / metabolism*
  • Mitochondria / drug effects
  • Mitochondria / metabolism
  • Ornithine Decarboxylase Inhibitors
  • Polyamines / metabolism*
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Rats
  • bcl-2-Associated X Protein

Substances

  • BH3 Interacting Domain Death Agonist Protein
  • Bax protein, rat
  • Bid protein, rat
  • Carrier Proteins
  • Cytochrome c Group
  • Enzyme Inhibitors
  • Ornithine Decarboxylase Inhibitors
  • Polyamines
  • Proto-Oncogene Proteins
  • Proto-Oncogene Proteins c-bcl-2
  • bcl-2-Associated X Protein
  • Casp3 protein, rat
  • Casp8 protein, rat
  • Casp9 protein, rat
  • Caspase 3
  • Caspase 8
  • Caspase 9
  • Caspases
  • Camptothecin
  • Eflornithine