Abstract
HDAC inhibitors (HDACIs) induce irreversible cell cycle arrest and senescence in mouse
embryonic fibroblasts transformed with E1A and c-Ha-Ras oncogenes (E1A+Ras cell line).
The aging rate has been associated with the production of high levels of Reactive
Oxygen Species (ROS). Specific increases of ROS level have been demonstrated as potentially
critical for induction and maintenance of cell senescence process. It's known that
HDACs regulate the ROS-dependent FoxO factors, which are responsible for cell growth,
proliferation, and longevity. The characteristic ROS increase during aging may be
responsible for the decreased HDAC activity, which facilitates the senescent-like
phenotype. The objective of this study was to investigate the impact of FoxO transcription
factors on HDACIs-induced senescence of E1A+Ras oncogenes transformed cells. This
study shows the specific time-dependent effect of HDACI sodium butyrate treatment
on FoxO proteins in E1A+Ras cells. Indeed, short-term treatment with NaB results in
FoxO activation, which takes place through nuclear translocation, and accompanied
by accumulation of such ROS scavengers as MnSOD and SOD2. However, prolonged treatment
leads to extensive FoxO degradation and increased intracellular levels of ROS. This
degradation is connected with NaB-induced activation of Akt kinase. All of these findings
establish that one of the possible mechanism involved in NaB-induced senescence of
transformed cells is mediated through down-regulation of FoxO transcription factors
and ROS accumulation.
Keywords
histone deacetylase inhibitor (HDACi) - sodium butyrate - FoxO - oxidative stress
- ROS - Akt - nuclear shuttling