title: Histone deacetylase inhibitors prevent p53-dependent and p53-independent Bax-mediated neuronal apoptosis through two distinct mechanisms.
abstract: Pharmacological manipulation of protein acetylation levels by histone deacetylase (HDAC) inhibitors represents a novel therapeutic strategy to treat neurodegeneration as well as cancer. However, the molecular mechanisms that determine how HDAC inhibition exerts a protective effect in neurons as opposed to a cytotoxic action in tumor cells has not been elucidated. We addressed this issue in cultured postnatal mouse cortical neurons whose p53-dependent and p53-independent intrinsic apoptotic programs require the proapoptotic multidomain protein, Bax. Despite promoting nuclear p53 accumulation, Class I/II HDAC inhibitors (HDACIs) protected neurons from p53-dependent cell death induced by camptothecin, etoposide, heterologous p53 expression or the MDM2 inhibitor, nutlin-3a. HDACIs suppressed p53-dependent PUMA expression, a critical signaling intermediate linking p53 to Bax activation, thus preventing postmitochondrial events including cleavage of caspase-9 and caspase-3. In human SH-SY5Y neuroblastoma cells, however, HDACIs were not able to prevent p53-dependent cell death. Moreover, HDACIs also prevented caspase-3 cleavage in postnatal cortical neurons treated with staurosporine, 3-nitropropionic acid and a Bcl-2 inhibitor, all of which require the presence of Bax but not p53 to promote apoptosis. Although these three toxic agents displayed a requirement for Bax, they did not promote PUMA induction. These results demonstrate that HDACIs block Bax-dependent cell death by two distinct mechanisms to prevent neuronal apoptosis, thus identifying for the first time a defined molecular target for their neuroprotective actions.
authors.affiliation: Department of Neurological Surgery, University of Washington School of Medicine, Seattle, Washington 98195-6470, USA.
authors.forename: Takuma
authors.initials: T
authors.lastname: Uo
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Veenstra
authors.forename: Richard S
authors.initials: RS
authors.lastname: Morrison
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000502:physiology; D015153:Blotting, Western; D053148:Caspase 3 / Q000378:metabolism; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005455:Fluorescent Antibody Technique; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D047468:Immunoprecipitation; D009474:Neurons / Q000187:drug effects*; D018696:Neuroprotective Agents / Q000494:pharmacology; D010957:Plasmids / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014162:Transfection; D016159:Tumor Suppressor Protein p53 / Q000037:antagonists & inhibitors*; D051028:bcl-2-Associated X Protein / Q000037:antagonists & inhibitors*
chemical_list: D051017:Apoptosis Regulatory Proteins; C438378:BBC3 protein, human; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D018696:Neuroprotective Agents; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D053148:Caspase 3