Crebinostat: A novel cognitive enhancer that inhibits histone deacetylase activity and modulates chromatin-mediated neuroplasticity

Abstract

Long-term memory formation is known to be critically dependent upon de novo gene expression in the brain. As a consequence, pharmacological enhancement of the transcriptional processes mediating long-term memory formation provides a potential therapeutic strategy for cognitive disorders involving aberrant neuroplasticity. Here we focus on the identification and characterization of small molecule inhibitors of histone deacetylases (HDACs) as enhancers of CREB (cAMP response element-binding protein)-regulated transcription and modulators of chromatin-mediated neuroplasticity. Using a CREB reporter gene cell line, we screened a library of small molecules structurally related to known HDAC inhibitors leading to the identification of a probe we termed crebinostat that produced robust activation of CREB-mediated transcription. Further characterization of crebinostat revealed its potent inhibition of the deacetylase activity of recombinant class I HDACs 1, 2, 3, and class IIb HDAC6, with weaker inhibition of the class I HDAC8 and no significant inhibition of the class IIa HDACs 4, 5, 7, and 9. In cultured mouse primary neurons, crebinostat potently induced acetylation of both histone H3 and histone H4 as well as enhanced the expression of the CREB target gene Egr1 (early growth response 1). Using a hippocampus-dependent, contextual fear conditioning paradigm, mice systemically administered crebinostat for a ten day time period exhibited enhanced memory. To gain insight into the molecular mechanisms of memory enhancement by HDAC inhibitors, whole genome transcriptome profiling of cultured mouse primary neurons treated with crebinostat, combined with bioinformatic analyses of CREB-target genes, was performed revealing a highly connected protein-protein interaction network reflecting modules of genes important to synaptic structure and plasticity. Consistent with these findings, crebinostat treatment increased the density of synapsin-1 punctae along dendrites in cultured neurons. Finally, crebinostat treatment of cultured mouse primary neurons was found to upregulate Bdnf (brain-derived neurotrophic factor) and Grn (granulin) and downregulate Mapt (tau) gene expression—genes implicated in aging-related cognitive decline and cognitive disorders. Taken together, these results demonstrate that crebinostat provides a novel probe to modulate chromatin-mediated neuroplasticity and further suggests that pharmacological optimization of selective of HDAC inhibitors may provide an effective therapeutic approach for human cognitive disorders.

Epigenetic regulation of memory formation and maintenance

“…Using fear conditioning as a model of associative learning, Miller and Sweatt (2007) found that DNA methylation was rapidly altered 1 h after training and that the changes in DNA methylation returned to baseline within 24 h. Also using fear conditioning, it was found that histone acetylation, phosphorylation, and methylation followed a similar temporal pattern (Levenson et al 2004;Chwang et al 2006;Miller et al 2008;Gupta et al 2010;Gupta-Agarwal et al 2012). Consistent with a role for epigenetic mechanisms in initial memory consolidation, the administration of DNMT inhibitors impaired fear memory and HDAC inhibitors improved fear memory (Miller and Sweatt 2007;Lubin et al 2008;Miller et al 2008;Monsey et al 2011;Fass et al 2013) only if administered during the restricted consolidation window shortly after training. Neither drug was effective at reversing memory if administered 6 h after training (Miller et al 2008;Monsey et al 2011).…”

Treatment of Niemann–Pick Type C Disease by Histone Deacetylase Inhibitors

“…Its lack of HDAC isoform selectivity likely leads to changes in expression of a large number of genes that have no relevance to NPC. Although there is evidence of some penetration of the blood-brain barrier by vorinostat, other HDACi have measurably superior penetration [109][110][111][112].…”

Novel Protective Effects of Histone Deacetylase Inhibition on Stroke and White Matter Ischemic Injury

“…Addition of VPA to cultured rat cortical neurons induces BDNF messenger RNA [34] and induces vascular endothelial growth factor, angiogenesis, and neurogenesis in vivo [35,36]. In a screen of small molecules structurally related to known HDAC inhibitors a compound referred to as crebinostat, for its ability to concomitantly activate cyclic adenosine monophosphate response element binding-mediated transcription, was identified [37]. Crebinostat expressed potent inhibition of the deacetylase activity of recombinant class I HDACs 1, 2, 3, and class IIb HDAC6.…”