Potent Histone Deacetylase 6 Inhibitors Research Articles

Novel HDAC6 Inhibitors Increase Tubulin Acetylation and Rescue Axonal Transport of Mitochondria in a Model of Charcot-Marie-Tooth Type 2F.

Disruption of axonal transport causes a number of rare, inherited axonopathies and is heavily implicated in a wide range of more common neurodegenerative disorders, many of them age-related. Acetylation of α-tubulin is one important regulatory mechanism, influencing microtubule stability and motor protein attachment. Of several strategies so far used to enhance axonal transport, increasing microtubule acetylation through inhibition of the deacetylase enzyme histone deacetylase 6 (HDAC6) has been one of the most effective. Several inhibitors have been developed and tested in animal and cellular models, but better drug candidates are still needed. Here we report the development and characterization of two highly potent HDAC6 inhibitors, which show low toxicity, promising pharmacokinetic properties, and enhance microtubule acetylation in the nanomolar range. We demonstrate their capacity to rescue axonal transport of mitochondria in a primary neuronal culture model of the inherited axonopathy Charcot-Marie-Tooth Type 2F, caused by a dominantly acting mutation in heat shock protein beta 1.

Histone deacetylase 6 inhibitor tubastatin A attenuates angiotensin II-induced hypertension by preventing cystathionine γ-lyase protein degradation

Cystathionine γ-lyase (CSEγ) is a hydrogen sulfide (H2S)-producing enzyme. Endothelial H2S production can mediate vasodilatory effects, contributing to the alleviation of hypertension (high blood pressure). Recent studies have suggested a role of histone deacetylase 6 (HDAC6) in hypertension, although its underlying mechanisms are poorly understood. Here, we addressed the potential regulation of CSEγ by HDAC6 in angiotensin II (AngII)-induced hypertension and its molecular details focusing on CSEγ posttranslational modification. Treatment of mice with a selective HDAC6 inhibitor tubastatin A (TubA) alleviated high blood pressure and vasoconstriction induced by AngII. Cotreatment of the aorta and human aortic endothelial cells with TubA recovered AngII-mediated decreased H2S levels. AngII treatment upregulated HDAC6 mRNA and protein expression, but conversely downregulated CSEγ protein. Notably, potent HDAC6 inhibitors and HDAC6 siRNA as well as a proteasomal inhibitor increased CSEγ protein levels and blocked the downregulatory effect of AngII on CSEγ. In contrast, other HDAC isoforms-specific inhibitors and siRNAs did not show such blocking effects. Transfected CSEγ protein levels were also reciprocally regulated by AngII and TubA, and were reduced by wild-type, but not by deacetylase-deficient, HDAC6. Moreover, TubA significantly increased both protein stability and K73 acetylation level of CSEγ. Consistent with these results, AngII induced CSEγ ubiquitination and degradation, which was inhibited by TubA. Our results indicate that AngII promoted HDAC6-dependent deacetylation of CSEγ at K73 residue, leading to its ubiquitin-mediated proteolysis, which underlies AngII-induced hypertension. Overall, this study suggests that upregulation of CSEγ and H2S through HDAC6 inhibition may be considered as a valid strategy for preventing the progression of hypertension.

Structure-Based Drug Designing Recommends HDAC6 Inhibitors To Attenuate Microtubule-Associated Tau-Pathogenesis.

Protein acetylation and deacetylation play vital roles in the structural and physiological behavior of target proteins. Histone deacetylase 6 (HDAC6) remains a key therapeutic target in several chronic diseases such as cancer, neurodegenerative, and hematological diseases. In tau-pathogenesis, HDAC6 tightly regulates microtubule-associated tau physiology, and its inhibition suppresses Alzheimer's phenotype. To this end, the current study has identified novel HDAC6 inhibitors by structure-based drug designing method. A pharmacophore was generated from HDAC6 in complex with trichostatin A. The selected pharmacophore had five features including two hydrogen bond donors, one hydrogen bond acceptor, and two hydrophobic features. Pharmacophore validation obtained the highest GH score of 0.80. By applying Lipinski's rule of five and ADMET Descriptors, a drug-like database of 29 183 molecules was generated from the Zinc Natural Product Database. The validated pharmacophore screened 841 drug-like molecules and was subsequently subjected to molecular docking in the active site of HDAC6. Molecular docking identified 11 hits, where they showed the highest ChemPLP score (>90.00), stable conformation, and hydrogen-bond interactions with catalytic residues of HDAC6. Finally, molecular dynamics simulation identified three molecules as potent HDAC6 inhibitors with stable root-mean-square deviation and the highest number of hydrogen bonds with the catalytic residues of HDAC6. Overall, we recommend three novel inhibitors of HDAC6, capable of suppressing the microtubule-associated tau-pathogenesis.

Design and biological evaluation of tetrahydro-β-carboline derivatives as highly potent histone deacetylase 6 (HDAC6) inhibitors

Various diseases are related to epigenetic modifications. Histone deacetylases (HDACs) and histone acetyl transferases (HATs) determine the pattern of histone acetylation, and thus are involved in the regulation of gene expression. First generation histone deacetylase inhibitors (HDACi) are unselective, hinder all different kinds of zinc dependent HDACs and additionally cause several side effects. Subsequently, selective HDACi are gaining more and more interest. Especially, selective histone deacetylase 6 inhibitors (HDAC6i) are supposed to be less toxic. Here we present a successful optimization study of tubastatin A, the synthesis and biological evaluation of new inhibitors based on hydroxamic acids linked to various tetrahydro-β-carboline derivatives. The potency of our selective HDAC6 inhibitors, exhibiting IC50 values in a range of 1–10 nM towards HDAC6, was evaluated with the help of a recombinant human HDAC6 enzyme assay. Selectivity was proofed in cellular assays by the hyperacetylation of surrogate parameter α-tubulin in the absence of acetylated histone H3 analyzed by Western Blot. We show that all synthesized compounds, with varies modifications of the rigid cap group, were selective and potent HDAC6 inhibitors.