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Transforming growth factor beta mediates hepatocyte apoptosis through Smad3 generation of reactive oxygen species

Dalliah Black1, Suzanne Lyman, Ting Qian

  • 1Department of Surgery, 4024 Burnett Womack Building, CB 7050, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.

Biochimie
|October 16, 2007
PubMed

Insights

Transforming growth factor beta (TGFbeta) triggers liver cell death through reactive oxygen species (ROS) and Smad3. Blocking Smad3 prevents TGFbeta-induced apoptosis, revealing a key pathway in liver injury.

Area of Science:

  • Hepatology
  • Cell Biology
  • Molecular Biology

Background:

  • Transforming growth factor beta (TGFbeta) is known to induce hepatocyte apoptosis.
  • The precise molecular mechanisms, particularly the involvement of the Smad pathway, remain unclear.

Purpose of the Study:

  • To investigate the role of Smad3 in TGFbeta-induced hepatocyte apoptosis.
  • To elucidate the signaling pathway involving reactive oxygen species (ROS) and mitochondrial permeability transition (MPT).

Main Methods:

  • Primary hepatocytes were isolated from Smad3 wild-type and knockout mice.
  • Cells were treated with TGFbeta and/or trolox, and assessed for ROS generation, MPT, gene transcription, and apoptosis.
  • Smad3 wild-type and dominant-negative plasmids were used to further investigate Smad3's role.

Main Results:

  • Smad3 knockout hepatocytes showed no TGFbeta-induced ROS generation, MPT, caspase activation, or apoptosis.
  • Dominant-negative Smad3 inhibited TGFbeta-mediated transcription, ROS, MPT, and apoptosis.
  • TGFbeta-induced ROS generation was linked to an NADPH-like oxidase pathway.

Conclusions:

  • TGFbeta-induced hepatocyte apoptosis is dependent on Smad3.
  • Smad3 activation leads to ROS generation, initiating the MPT and caspase activation, ultimately causing apoptosis.
  • This pathway is critical for understanding liver cell death mediated by TGFbeta.

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