Two New Pimelic Diphenylamide HDAC Inhibitors Induce Sustained Frataxin Upregulation in Cells from Friedreich's Ataxia Patients and in a Mouse Model

Myriam Rai,C James Chou,Glenn Barnes,James R Rusche,Massimo Pandolfo,Steve Jones,Elisabetta Soragni,Joel M Gottesfeld,Antoni L Andreu

doi:10.1371/journal.pone.0008825

Myriam Rai, C James Chou + Show 7 more

Open Access

https://doi.org/10.1371/journal.pone.0008825

Copy DOI

Abstract

BackgroundFriedreich's ataxia (FRDA), the most common recessive ataxia in Caucasians, is due to severely reduced levels of frataxin, a highly conserved protein, that result from a large GAA triplet repeat expansion within the first intron of the frataxin gene (FXN). Typical marks of heterochromatin are found near the expanded GAA repeat in FRDA patient cells and mouse models. Histone deacetylase inhibitors (HDACIs) with a pimelic diphenylamide structure and HDAC3 specificity can decondense the chromatin structure at the FXN gene and restore frataxin levels in cells from FRDA patients and in a GAA repeat based FRDA mouse model, KIKI, providing an appealing approach for FRDA therapeutics.Methodology/Principal FindingsIn an effort to further improve the pharmacological profile of pimelic diphenylamide HDACIs as potential therapeutics for FRDA, we synthesized additional compounds with this basic structure and screened them for HDAC3 specificity. We characterized two of these compounds, 136 and 109, in FRDA patients' peripheral blood lymphocytes and in the KIKI mouse model. We tested their ability to upregulate frataxin at a range of concentrations in order to determine a minimal effective dose. We then determined in both systems the duration of effect of these drugs on frataxin mRNA and protein, and on total and local histone acetylation. The effects of these compounds exceeded the time of direct exposure in both systems.Conclusions/SignificanceOur results support the pre-clinical development of a therapeutic approach based on pimelic diphenylamide HDACIs for FRDA and provide information for the design of future human trials of these drugs, suggesting an intermittent administration of the drug.

Highlights

Friedreich’s ataxia (FRDA) is the most common of the earlyonset autosomal recessive ataxias in Caucasians
We speculated that histone deacetylase (HDAC) inhibitors (HDACIs) might reverse frataxin gene (FXN) silencing by directly increasing histone acetylation on the FXN gene, leading to chromatin decondensation and active transcription
We found that a commercially available Histone deacetylase inhibitors (HDACIs) (BML-210), and derivatives we have synthesized, relieve repression of the FXN gene in lymphoid cell lines derived from FRDA patients, in primary lymphocytes from donor FRDA patient blood, and in the brain and heart of a mouse model for FRDA [8,9]

Summary

Introduction

Friedreich’s ataxia (FRDA) is the most common of the earlyonset autosomal recessive ataxias in Caucasians. This phenomenon does not occur in all cells, the term ‘‘variegation’’, but leads to an overall downregulation of the involved gene at the tissue and organ level In agreement with this hypothesis, the typical marks of heterochromatin, such as DNA methylation and histone deacetylation, are found near the expanded GAA repeat both in FRDA patients’ cells and in mouse models [6,7,8,9]. Based on these observations, we speculated that histone deacetylase (HDAC) inhibitors (HDACIs) might reverse FXN silencing by directly increasing histone acetylation on the FXN gene, leading to chromatin decondensation and active transcription. Our results support the development of a therapeutic approach based on pimelic diphenylamide HDACIs for FRDA and provide information for the design of future human trials of these drugs [14]

Results

Discussion

Methods