Pulse Inhibition of Histone Deacetylases Induces Complete Resistance to Oxidative Death in Cortical Neurons without Toxicity and Reveals a Role for Cytoplasmic p21waf1/cip1 in Cell Cycle-Independent Neuroprotection

Burke Medical Research Institute, White Plains, New York 10605, USA.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.34). 02/2008; 28(1):163-76. DOI: 10.1523/JNEUROSCI.3200-07.2008
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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).

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Available from: M. Flint Beal,
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    • "It seems that lower HDAC2 expression in our cells and possibly also lower HDAC activity may play a role in histone hyperacetylation and may be due to oxidative stress associated with CYP2E1 expression. On the other hand, it was shown that HDAC inhibitors protect neuronal cells from oxidative stress-induced damages (Langley et al. 2008) and against in vitro cytotoxicity (Kang et al. 2005), and it appear that such mechanism may be extended to other diseases that share both oxidative stress and inflammation. Our data confirm that HDAC inhibitors may act as antioxidants, since TSA significantly reduced oxidative stress induced by AA. "
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    ABSTRACT: The aim of this work was to assess the role of ethanol-derived acetate and acetate-mediated histone acetylation in arachidonic acid-induced stress in HepG2 cells and cells overexpressing CYP2E1. Cells were grown for 7 days with 1 mM sodium acetate or 100 mM ethanol; their acetylated histone proteins and histone deacetylase 2 expression was quantified using Western blot. Ethanol- or acetate-pretreated cells were also treated for 24 h with 60 μM arachidonic acid to induce oxidative stress. Cytotoxicity was estimated by lactate dehydrogenase release, 3-[4,5-dimethylthiazolyl-2] 2,5-diphenyltetrazolium bromide test, and by DNA damage, while oxidative stress was quantified using dichlorofluorescein diacetate. Cells grown with ethanol or acetate had increased acetylated histone H3 levels in both cell types and elevated acetylated histone H4 levels in cells overexpressing CYP2E1 but not in naïve cells. In cells overexpressing CYP2E1 grown with ethanol, expression of histone deacetylase 2 was reduced by about 40 %. Arachidonic acid altered cell proliferation and was cytotoxic mostly to cells engineered to overexpress CYP2E1 but both effects were significantly lower in cells pretreated with ethanol or acetate. Cytotoxicity was also significantly decreased by 4-methylpyrazole-a CYP2E1 inhibitor and by trichostatin-an inhibitor of histone deacetylases. In cells pretreated with acetate or ethanol, the oxidative stress induced by arachidonic acid was also significantly lower. Our data indicate that histone hyperacetylation may in some extent protect the cells against oxidative stress. It is possible that acetate may act as an antioxidant at histone level. This mechanism may be relevant to alcohol-induced liver injury.
    Archiv für Experimentelle Pathologie und Pharmakologie 11/2013; 387(3). DOI:10.1007/s00210-013-0942-4 · 2.47 Impact Factor
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    • "The ischemic injury also reduces the H3 histone acetylation, as previously shown (Faraco et al., 2006). Prompted by the findings that deacetylation of RelA K310 by the sirtuin 1 activator resveratrol (30 μM) increases neuronal resistance to OGD (Lanzillotta et al., 2010) and inhibition of HDAC activity by restoring histone acetylation reduces post-ischemic brain injuries (Faraco et al., 2006; Kim et al., 2007, 2009; Langley et al., 2008), we investigated the neuroprotective effect of resveratrol in combination with MS-275, a class I HDAC inhibitor. We show that post-ischemic administration of individual drugs, which are already used in various clinical trials, decreases the infarct volume. "
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    Neurobiology of Disease 08/2012; 49C(1):177-189. DOI:10.1016/j.nbd.2012.08.018 · 5.08 Impact Factor
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    • "Given the growing number of non-histone HDAC targets been discovered, old assumptions based on mechanisms solely surrounding histone acetylation status are being challenged [48]. Moreover, the pleiotropic effects of HDAC inhibition and neurotoxicity of sustained strong inhibition raise the question as to their suitability for treating chronic neurodegenerative disease [49], particularly given the documented adverse side-effects of HDAC inhibitors after short-term therapy in cancer patients [50]. In order to find more selective and tolerable inhibitors of HDAC effects, future strategies may be to use peptides or molecules designed to disrupt interactions between HDACs and key targets relevant to neuroprotection. "
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    ABSTRACT: The transcriptional corepressor SMRT controls neuronal responsiveness of several transcription factors and can regulate neuroprotective and neurogenic pathways. SMRT is a multi-domain protein that complexes with HDAC3 as well as being capable of interactions with HDACs 1, 4, 5 and 7. We previously showed that in rat cortical neurons, nuclear localisation of SMRT requires histone deacetylase activity: Inhibition of class I/II HDACs by treatment with trichostatin A (TSA) causes redistribution of SMRT to the cytoplasm, and potentiates the activation of SMRT-repressed nuclear receptors. Here we have sought to identify the HDAC(s) and region(s) of SMRT responsible for anchoring it in the nucleus under normal circumstances and for mediating nuclear export following HDAC inhibition. We show that in rat cortical neurons SMRT export can be triggered by treatment with the class I-preferring HDAC inhibitor valproate and the HDAC2/3-selective inhibitor apicidin, and by HDAC3 knockdown, implicating HDAC3 activity as being required to maintain SMRT in the nucleus. HDAC3 interaction with SMRT's deacetylation activation domain (DAD) is known to be important for activation of HDAC3 deacetylase function. Consistent with a role for HDAC3 activity in promoting SMRT nuclear localization, we found that inactivation of SMRT's DAD by deletion or point mutation triggered partial redistribution of SMRT to the cytoplasm. We also investigated whether other regions of SMRT were involved in mediating nuclear export following HDAC inhibition. TSA- and valproate-induced SMRT export was strongly impaired by deletion of its repression domain-4 (RD4). Furthermore, over-expression of a region of SMRT containing the RD4 region suppressed TSA-induced export of full-length SMRT. Collectively these data support a model whereby SMRT's RD4 region can recruit factors capable of mediating nuclear export of SMRT, but whose function and/or recruitment is suppressed by HDAC3 activity. Furthermore, they underline the fact that HDAC inhibitors can cause reorganization and redistribution of corepressor complexes.
    PLoS ONE 06/2011; 6(6):e21056. DOI:10.1371/journal.pone.0021056 · 3.23 Impact Factor
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