Pulse inhibition of histone deacetylases induces complete resistance to oxidative death in cortical neurons without toxicity and reveals a role for cytoplasmic p21(waf1/cip1) in cell cycle-independent neuroprotection.
Histone deacetylase (HDAC) inhibitors are currently in human clinical trials as antitumor drugs because of their ability to induce cell dysfunction and death in cancer cells. The toxic effects of HDAC inhibitors are also apparent in cortical neurons in vitro, despite the ability of these agents to induce significant protection in the cells they do not kill. Here we demonstrate that pulse exposure of cortical neurons (2 h) in an in vitro model of oxidative stress results in durable neuroprotection without toxicity. Protection was associated with transcriptional upregulation of the cell cycle inhibitor, p21(waf1/cip1), both in this model and in an in vivo model of permanent ischemia. Transgenic overexpression of p21(waf1/cip1) in neurons can mimic the protective effect of HDAC inhibitors against oxidative stress-induced toxicity, including death induced by glutathione depletion or peroxide addition. The protective effect of p21(waf1/cip1) in the context of oxidative stress appears to be unrelated to its ability to act in the nucleus to inhibit cell cycle progression. However, although p21(waf1/cip1) is sufficient for neuroprotection, it is not necessary for HDAC inhibitor neuroprotection, because these agents can completely protect neurons cultured from p21(waf1/cip1)-null mice. Together these findings demonstrate (1) that pulse inhibition of HDACs in cortical neurons can induce neuroprotection without apparent toxicity; (2) that p21(waf1/cip1) is sufficient but not necessary to mimic the protective effects of HDAC inhibition; and (3) that oxidative stress in this model induces neuronal cell death via cell cycle-independent pathways that can be inhibited by a cytosolic, noncanonical action of p21(waf1/cip1).
Langley
Brett
B
Burke Medical Research Institute, White Plains, New York 10605, USA. bcl2002@med.cornell.edu
D'Annibale
Melissa A
MA
Suh
Kyungsun
K
Ayoub
Issam
I
Tolhurst
Aaron
A
Bastan
Birgül
B
Yang
Lichuan
L
Ko
Brian
B
Fisher
Marc
M
Cho
Sunghee
S
Beal
M Flint
MF
Ratan
Rajiv R
RR
D000704:Analysis of Variance; D000818:Animals; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology*; D016923:Cell Death / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D004347:Drug Interactions; D004622:Embryo, Mammalian; D004791:Enzyme Inhibitors / Q000627:therapeutic use; D018698:Glutamic Acid / Q000633:toxicity; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism*; D020244:Infarction, Middle Cerebral Artery / Q000188:drug therapy; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014162:Transfection / Q000379:methods
D050759:Cyclin-Dependent Kinase Inhibitor p21; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D049452:Green Fluorescent Proteins; D018698:Glutamic Acid; D006655:Histone Deacetylases