Rational design and simple chemistry yield a superior, neuroprotective HDAC6 inhibitor, tubastatin A

Abstract

Structure-based drug design combined with homology modeling techniques were used to develop potent inhibitors of HDAC6 that display superior selectivity for the HDAC6 isozyme compared to other inhibitors. These inhibitors can be assembled in a few synthetic steps, and thus are readily scaled up for in vivo studies. An optimized compound from this series, designated Tubastatin A, was tested in primary cortical neuron cultures in which it was found to induce elevated levels of acetylated alpha-tubulin, but not histone, consistent with its HDAC6 selectivity. Tubastatin A also conferred dose-dependent protection in primary cortical neuron cultures against glutathione depletion-induced oxidative stress. Importantly, when given alone at all concentrations tested, this hydroxamate-containing HDAC6-selective compound displayed no neuronal toxicity, thus, forecasting the potential application of this agent and its analogues to neurodegenerative conditions.

Figure 1

Top-down view of active site for homology models of HDAC1 (top) and HDAC6 (bottom). Distances between boundaries of the catalytic channel rim are shown with orange arrows. Letters A–D denote four boundary areas surrounding the channel rim.

Figure 2

Comparison of histone and α-tubulin hyperacetylation for TSA, Tubastatin A, and Tubacin.

Figure 3

HCA oxidative stress assay: neurons were treated with Tubastatin A, with or without addition of HCA. Viability was assessed after 24 h by MTT assay. Yellow bars: Tubastatin A alone; Blue bars: Tubastatin A + HCA. *, significant increase in survival relative to HCA-treated control, P < 0.01, by two-way ANOVA followed by Bonferroni post-tests.