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Mitochondrial respiratory chain complex I is inactivated by NADPH oxidase Nox4

Rafał Kozieł1, Haymo Pircher, Manuela Kratochwil

  • 1Institute for Biomedical Aging Research, Innsbruck University, Rennweg 10, 6020 Innsbruck, Austria.

The Biochemical Journal
|March 22, 2013
PubMed

Insights

NADPH oxidase 4 (Nox4) impairs mitochondrial function in human endothelial cells by inhibiting electron transport chain complex I. This finding reveals a new mechanism linking Nox4 activity to reduced mitochondrial health.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Reactive oxygen species (ROS) generated by NADPH oxidases are crucial for cellular signaling, impacting proliferation, survival, and differentiation.
  • NADPH oxidase 4 (Nox4) is known to induce cellular senescence in human endothelial cells, but its specific intracellular targets were not identified.

Purpose of the Study:

  • To investigate the intracellular targets of Nox4 and elucidate its role in mitochondrial dysfunction within human endothelial cells.

Main Methods:

  • Analysis of mitochondrial morphology and membrane potential following Nox4 depletion.
  • Measurement of hydrogen peroxide (H(2)O(2)) production in mitochondria.
  • High-resolution respirometry and native PAGE to assess mitochondrial electron transport chain complex I activity and subunit concentration.

Main Results:

  • Nox4 depletion led to altered mitochondrial morphology, stabilized mitochondrial membrane potential, and reduced mitochondrial H(2)O(2) production.
  • Nox4 was found to specifically inhibit the activity of mitochondrial electron transport chain complex I.
  • A decrease in the concentration of complex I subunits was observed in association with Nox4 activity.

Conclusions:

  • Sustained Nox4 activity leads to mitochondrial dysfunction in human endothelial cells.
  • Nox4 inhibits mitochondrial electron transport chain complex I activity, suggesting a novel pathway for impaired mitochondrial function.

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