Recent innovative advances in the discovery of selective HDAC6 inhibitors

Histone Deacetylation in Alzheimer's Diseases (AD); Hope or Hype

Histone acetylation is the process by which histone acetyltransferases (HATs) add an acetyl group to the N-terminal lysine residues of histones, resulting in a more open chromatin structure. Histone acetylation tends to increase gene expression more than methylation does. In the central nervous system (CNS), histone acetylation is essential for controlling the expression of genes linked to cognition and learning. Histone deacetylases (HDACs), "writing" enzymes (HATs), and "reading" enzymes with bromodomains that identify and localize to acetylated lysine residues are responsible for maintaining histone acetylation. By giving animals HDAC inhibitors (HDACis), it is possible to intentionally control the ratios of "writer" and "eraser" activity, which will change the acetylation of histones. In addition to making the chromatin more accessible, these histone acetylation alterations re-allocate the targeting of "readers," including the transcriptional co-activators, cAMP response element-binding protein (CBP), and bromodomain-containing protein 4 (Brd4) in the CNS. Conclusive evidence has shown that HDACs slow down the progression of Alzheimer's disease (AD) by reducing the amount of histone acetylation, decreasing the activity of genes linked to memory, supporting cognitive decline and Amyloid beta (Aβ) protein accumulation, influencing aberrant tau phosphorylation, and promoting the emergence of neurofibrillary tangles (NFTs). In this review, we have covered the therapeutic targets and functions of HDACs that might be useful in treating AD.

Design, Synthesis, and Antiproliferative Activity of Selective Histone Deacetylases 6 Inhibitors Containing a Tetrahydropyridopyrimidine Scaffold

The development of selective histone deacetylase 6 inhibitors (sHDAC6is) is being recognized as a therapeutic approach for cancers. In this paper, we designed a series of novel tetrahydropyridopyrimidine derivatives as sHDAC6 inhibitors. The most potent compound, 8-(2, 4-bis(3-methoxyphenyl)-5, 8-dihydropyrido [3, 4-d]pyrimidin-7(6H)-yl)-N-hydroxy-8-oxooctanamide (8f), inhibited HDAC6 with IC50 of 6.4 nM, and showed > 48-fold selectivity over other subtypes. In Western blot assay, 8f elevated the levels of acetylated α-tubulin in a dose-dependent manner. In vitro, 8f inhibited RPMI-8226, HL60, and HCT116 tumor cells with IC50 of 2.8, 3.20, and 3.25 μM, respectively. Moreover, 8f showed good antiproliferative activity against a panel of tumor cells.

Recent advances in HDAC-targeted imaging probes for cancer detection

Histone Deacetylases (HDACs) are abnormally high expressed in various cancers and play a crucial role in regulating gene expression. While HDAC-targeted inhibitors have been rapidly developed and approved in the last twenty years, noninvasive monitoring and visualizing the expression levels of HDACs in tumor tissues might help to early diagnosis in cancer and predict the response to HDAC-targeted cancer therapy. In this review, we summarize the recent advancements in the development of HDAC-targeted probes and their applications in cancer imaging and image-guided surgery. We also discuss the design strategies, advantages and disadvantages of these probes. We hope that this review will provide guidance for the design of HDAC-targeted imaging probes and clinical applications in future.