Collapse of the inner mitochondrial transmembrane potential is not required for apoptosis of HL60 cells

Exp Cell Res. 1999 Aug 25;251(1):166-74. doi: 10.1006/excr.1999.4527.

Abstract

Apoptotic cell death involves a series of morphological and biochemical changes orchestrated by activated proteases belonging to the caspase family. Recent studies have suggested that the activation of this process of execution is dependent upon events associated with the loss of mitochondrial inner transmembrane potential (Deltapsi(m)), as a consequence of the formation of the permeability transition (PT) pore. This has led to the proposal that mitochondrial depolarization represents a central irreversible checkpoint in the apoptotic program. Here, we present evidence that HL-60 cells undergo apoptosis in response to the cytotoxic insults of actinomycin-D, etoposide, and staurosporine without showing significant changes in Deltapsi(m). Instead, the loss of Deltapsi(m) could be detected only later in the cell death pathway. In addition, the uncoupling agent CCCP produced an early mitochondrial depolarization in HL-60s but these cells showed few signs of apoptosis up to 8 h after the insult. Furthermore, examination of these cells in response to staurosporine revealed the release of mitochondrial cytochrome c into the cytosol over time, corresponding to caspase activation irrespective of mitochondrial depolarization. In summary, our data suggest that the collapse of Deltapsi(m) as a consequence of PT is not a universal early marker for apoptosis and, moreover, it is not part of the central apoptotic machinery.

Publication types

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

MeSH terms

  • Apoptosis* / drug effects
  • Carbonyl Cyanide m-Chlorophenyl Hydrazone / pharmacology
  • Caspase 3
  • Caspases / metabolism
  • Cell Nucleus / drug effects
  • Cell Nucleus / genetics
  • Cell Nucleus / metabolism
  • Cell Size / drug effects
  • Cytochrome c Group / metabolism
  • DNA Fragmentation / drug effects
  • Dactinomycin / pharmacology
  • Enzyme Activation / drug effects
  • Etoposide / pharmacology
  • Fluorescent Dyes
  • HL-60 Cells
  • Humans
  • Intracellular Membranes / drug effects
  • Intracellular Membranes / physiology*
  • Jurkat Cells
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology*
  • Mitochondria / drug effects
  • Mitochondria / enzymology
  • Mitochondria / metabolism
  • Mitochondria / physiology*
  • Oxidative Phosphorylation / drug effects
  • Phosphatidylserines / metabolism
  • Poly(ADP-ribose) Polymerases / metabolism
  • Staurosporine / pharmacology

Substances

  • Cytochrome c Group
  • Fluorescent Dyes
  • Phosphatidylserines
  • Dactinomycin
  • Carbonyl Cyanide m-Chlorophenyl Hydrazone
  • Etoposide
  • Poly(ADP-ribose) Polymerases
  • CASP3 protein, human
  • Caspase 3
  • Caspases
  • Staurosporine