Transforming growth factor-beta activates both pro-apoptotic and survival signals in fetal rat hepatocytes

Exp Cell Res. 2004 Jan 1;292(1):209-18. doi: 10.1016/j.yexcr.2003.08.015.

Abstract

Transforming growth factor-beta (TGF-beta) induces apoptosis in fetal rat hepatocytes. However, a subpopulation of these cells survives concomitant with changes in morphology and phenotype, reminiscent of an epithelial mesenchymal transition (EMT) [Exp. Cell Res. 252 (1999) 281-291]. In this work, we have isolated the subpopulation that survives to TGF-beta-induced apoptosis, showing that these cells maintain the response to TGF-beta in terms of Smads activation and growth inhibition. Analyses of the intracellular signals that could impair the apoptotic effects of TGF-beta have indicated that the phosphatidylinositol 3-kinase (PI 3-K)/Akt pathway is activated in these resistant cells. Experiments in fetal rat hepatocytes have shown that TGF-beta is able to transiently activate PI 3-K/Akt by a mechanism independent of protein synthesis but dependent on a tyrosine kinase activity. Pro-apoptotic signals, such as oxidative stress and caspases, contribute to the loss of Akt at later times. Inhibiting PI 3-K sensitizes fetal hepatocytes (FH) to the apoptosis induced by TGF-beta and causes spontaneous death in the resistant cells. In conclusion, TGF-beta, as it is known for other cytokines, could be inducing pro-apoptotic and survival signals in hepatocytes, the balance among them will decide cell fate.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects*
  • Caspase 3
  • Caspases / metabolism
  • Cell Survival
  • Cells, Cultured
  • Enzyme Activation
  • Enzyme Inhibitors / pharmacology
  • Female
  • Fetus
  • Hepatocytes / cytology
  • Hepatocytes / drug effects*
  • Hepatocytes / physiology
  • Humans
  • Oxidative Stress
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphoinositide-3 Kinase Inhibitors
  • Phosphorylation
  • Pregnancy
  • Protein Serine-Threonine Kinases*
  • Protein-Tyrosine Kinases / metabolism
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-akt
  • Rats
  • Rats, Wistar
  • Reactive Oxygen Species / metabolism
  • Recombinant Proteins / pharmacology
  • Signal Transduction*
  • Transforming Growth Factor beta / pharmacology*

Substances

  • Enzyme Inhibitors
  • Phosphoinositide-3 Kinase Inhibitors
  • Proto-Oncogene Proteins
  • Reactive Oxygen Species
  • Recombinant Proteins
  • Transforming Growth Factor beta
  • Protein-Tyrosine Kinases
  • AKT1 protein, human
  • Akt1 protein, rat
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • CASP3 protein, human
  • Casp3 protein, rat
  • Caspase 3
  • Caspases