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Identification of Intracellular Signaling Events Induced in Viable Cells by Interaction with Neighboring Cells Undergoing Apoptotic Cell Death
09:18

Identification of Intracellular Signaling Events Induced in Viable Cells by Interaction with Neighboring Cells Undergoing Apoptotic Cell Death

Published on: December 27, 2016

Hepatocytes sensitized to tumor necrosis factor-alpha cytotoxicity undergo apoptosis through caspase-dependent and

B E Jones1, C R Lo, H Liu

  • 1Department of Medicine, Marion Bessin Liver Research Center, Albert Einstein College of Medicine, Bronx, New York 10461, USA.

The Journal of Biological Chemistry
|January 5, 2000
PubMed

Insights

Tumor necrosis factor (TNF)-alpha toxicity in hepatocytes is enhanced by blocking NF-kappaB or inhibiting RNA synthesis. These distinct pathways sensitize cells via different mechanisms, diverging below FADD signaling.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Hepatology

Background:

  • Hepatocytes can be sensitized to tumor necrosis factor (TNF)-alpha toxicity through NF-kappaB repression or RNA synthesis inhibition.
  • Understanding the distinct mechanisms of TNF-alpha sensitization is crucial for targeted therapeutic strategies.

Purpose of the Study:

  • To investigate whether NF-kappaB inactivation and RNA synthesis inhibition sensitize hepatocytes to TNF-alpha cytotoxicity via similar or distinct pathways.
  • To elucidate the specific molecular events and signaling cascades involved in TNF-alpha-induced hepatocyte death under these sensitization conditions.

Main Methods:

  • Utilized RALA255-10G hepatocytes infected with Ad5IkappaB (NF-kappaB inhibitor) or treated with actinomycin D (ActD) and TNF-alpha.
  • Assessed cell death, apoptosis, caspase activation, FADD involvement, and mitochondrial cytochrome c release.
  • Employed caspase inhibitors (CrmA) and dominant-negative FADD to dissect signaling pathways.

Main Results:

  • Ad5IkappaB/TNF-alpha induced 44% cell death within 6h via apoptosis with caspase activation.
  • ActD/TNF-alpha induced 37% cell death by 24h, with delayed caspase activation and no early death.
  • While both pathways involved FADD, Ad5IkappaB/TNF-alpha triggered cytochrome c release, unlike ActD/TNF-alpha, indicating divergent downstream events.

Conclusions:

  • NF-kappaB inactivation and RNA synthesis inhibition sensitize hepatocytes to TNF-alpha via distinct pathways diverging below FADD.
  • Actinomycin D-induced sensitization involves a FADD-dependent, caspase-independent apoptotic pathway.
  • These findings highlight the complexity of TNF-alpha-mediated hepatocyte death and offer insights into differential sensitization mechanisms.

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