Histone deacetylase (HDAC) inhibitors have shown enormous promise for treating various disease states, presumably due to their ability to modulate acetylation of histone and non-histone proteins. Many of these inhibitors contain functional groups capable of strongly chelating metal ions. We demonstrate that several members of one such class of compounds, the hydroxamate-based HDAC inhibitors, can protect neurons from oxidative stress via an HDAC-independent mechanism. This previously unappreciated antioxidant mechanism involves the in situ formation of hydroxamate-iron complexes that catalyze the decomposition of hydrogen peroxide in a manner reminiscent of catalase. We demonstrate that while many hydroxamate-containing HDAC inhibitors display a propensity for binding iron, only a subset form active catalase mimetics capable of protecting neurons from exogenous H2O2. In addition to their impact on stroke and neurodegenerative disease research, these results highlight the possibility that HDAC-independent factors might play a role in the therapeutic effects of hydroxamate-based HDAC inhibitors.

Despite being extensively characterized structurally and biochemically, the functional role of histone deacetylase 8 (HDAC8) has remained largely obscure due in part to a lack of known cellular substrates. Herein, we describe an unbiased approach using chemical tools in conjunction with sophisticated proteomics methods to identify novel non-histone nuclear substrates of HDAC8, including the tumor suppressor ARID1A. These newly discovered substrates of HDAC8 are involved in diverse biological processes including mitosis, transcription, chromatin remodeling, and RNA splicing and may help guide therapeutic strategies that target the function of HDAC8.