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Structural changes of mitochondria related to apoptosis: swelling and megamitochondria formation

T Wakabayashi1

  • 1Department of Cell Biology and Molecular Pathology, Nagoya University School of Medicine, Japan. twakaba@tsuru.med.nagoya-u.ac.jp

Acta Biochimica Polonica
|November 5, 1999
PubMed

Insights

Free radicals trigger megamitochondria formation, a key step in apoptosis. Swollen megamitochondria release factors like cytochrome c, leading to cell death.

Area of Science:

  • Cell Biology
  • Biochemistry
  • Toxicology

Background:

  • Free radicals are implicated in cellular damage and apoptosis.
  • Mitochondrial dynamics play a crucial role in cell fate.
  • Megamitochondria, enlarged mitochondria formed by fusion, have been observed in various cellular contexts.

Purpose of the Study:

  • To investigate the role of megamitochondria formation in free radical-induced apoptosis.
  • To elucidate the functional and morphological changes associated with megamitochondria during apoptosis.
  • To propose a hypothesis linking megamitochondria to the mechanism of free radical-mediated cell death.

Main Methods:

  • Induction of megamitochondria formation using free radical-generating chemicals in cultured cells.
  • Detailed morphological and functional analysis of megamitochondria.
  • Assessment of mitochondrial membrane potential, oxygen consumption, ATP synthesis, and release of apoptotic factors (cytochrome c, apoptosis-inducing factor).

Main Results:

  • Chemical induction of free radicals led to megamitochondria formation followed by apoptotic changes.
  • Megamitochondria exhibited altered morphology (swelling) and decreased function (reduced oxygen consumption and ATP synthesis).
  • Release of cytochrome c and apoptosis-inducing factor from swollen megamitochondria into the cytoplasm was observed, correlating with apoptotic events.

Conclusions:

  • Megamitochondria formation is a potential prerequisite for free radical-mediated apoptosis.
  • Free radical-induced mitochondrial membrane modification leads to fusion (megamitochondria), swelling, and subsequent release of apoptotic factors.
  • This process highlights a novel pathway linking oxidative stress, mitochondrial dysfunction, and programmed cell death.

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