Histone deacetylase inhibitors (HDACIs) activate the prosurvival nuclear factor-κB (NF-κB) pathway by hyperacetylating RelA/p65, whereas the chemopreventive agent
resveratrol inhibits NF-κB by activating the class III
histone deacetylase Sirt1. Interactions between
resveratrol and pan-HDACIs (
vorinostat and
panobinostat) were examined in human
acute myelogenous leukemia (AML) cells. Pharmacologically achievable
resveratrol concentrations (25-50 μM) synergistically potentiated HDACI lethality in AML cell lines and primary AML blasts.
Resveratrol antagonized RelA acetylation and NF-κB activation in HDACI-treated cells. However,
short hairpin RNA Sirt1 knockdown failed to modify HDACI sensitivity, which suggests that factors other than or in addition to
Sirt1 activation contribute to
resveratrol/HDACI interactions. These interactions were associated with
death receptor 5 (DR5) up-regulation and
caspase-8 activation, whereas cells expressing dominant-negative
caspase-8 were substantially protected from
resveratrol/HDACI treatment, which suggests a significant functional role for the extrinsic apoptotic pathway in lethality. Exposure to
resveratrol with HDACI induced sustained
reactive oxygen species (ROS) generation, which was accompanied by increased levels of
DNA double-strand breaks, as reflected in γH2A.X and comet assays. The
free radical scavenger Mn(III)tetrakis(4-benzoic acid)porphyrin
chloride blocked ROS generation, DR5 up-regulation,
caspase-8 activation, DNA damage, and apoptosis, which indicates a primary role for oxidative injury in lethality. Analyses of cell-cycle progression and
5-ethynyl-2'-deoxyuridine incorporation through flow cytometry revealed that
resveratrol induced S-phase accumulation; this effect was abrogated by HDACI coadministration, which suggests that cells undergoing
DNA synthesis may be particularly vulnerable to HDACI lethality. Collectively, these findings indicate that
resveratrol interacts synergistically with HDACIs in AML cells through multiple ROS-dependent actions, including
death receptor up-regulation, extrinsic apoptotic pathway activation, and DNA damage induction. They also raise the possibility that S-phase cells may be particularly susceptible to these actions.