Histone deacetylase inhibitors: possible implications for neurodegenerative disorders

Is there any therapeutic value for the use of histone deacetylase inhibitors for chronic pain?

Chronic pain is a complex clinical condition that reduces the quality of life for billions of people. In recent years, the role of epigenetic modulation in the control of long-term neuronal plasticity has attracted the attention of pain researchers. The epigenetic mechanisms include covalent modifications of DNA and/or histone proteins. Mounting evidence suggests that the activity of histone deacetylases (HDACs) and levels of histone acetylation are dynamic and that these enzymes modulate pain-related synaptic plasticity. Therefore, HDACs play essential roles in chronic pain development and maintenance. In this mini review, we will discuss the role of HDACs in the pathogenesis of chronic pain and will consider the therapeutic value of HDAC inhibitors in treating chronic pain.

The Effects of Pharmacological Inhibition of Histone Deacetylase 3 (HDAC3) in Huntington's Disease Mice

An important epigenetic modification in Huntington’s disease (HD) research is histone acetylation, which is regulated by histone acetyltransferase and histone deacetylase (HDAC) enzymes. HDAC inhibitors have proven effective in HD model systems, and recent work is now focused on functional dissection of the individual HDAC enzymes in these effects. Histone deacetylase 3 (HDAC3), a member of the class I subfamily of HDACs, has previously been implicated in neuronal toxicity and huntingtin-induced cell death. Hence, we tested the effects of RGFP966 ((E)-N-(2-amino-4-fluorophenyl)-3-(1-cinnamyl-1H-pyrazol-4-yl)acrylamide), a benzamide-type HDAC inhibitor that selectively targets HDAC3, in the N171-82Q transgenic mouse model of HD. We found that RGFP966 at doses of 10 and 25 mg/kg improves motor deficits on rotarod and in open field exploration, accompanied by neuroprotective effects on striatal volume. In light of previous studies implicating HDAC3 in immune function, we measured gene expression changes for 84 immune-related genes elicited by RGFP966 using quantitative PCR arrays. RGFP966 treatment did not cause widespread changes in cytokine/chemokine gene expression patterns, but did significantly alter the striatal expression of macrophage migration inhibitory factor (Mif), a hormone immune modulator associated with glial cell activation, in N171-82Q transgenic mice, but not WT mice. Accordingly, RGFP966-treated mice showed decreased glial fibrillary acidic protein (GFAP) immunoreactivity, a marker of astrocyte activation, in the striatum of N171-82Q transgenic mice compared to vehicle-treated mice. These findings suggest that the beneficial actions of HDAC3 inhibition could be related, in part, with lowered Mif levels and its associated downstream effects.

Fatty acids and their therapeutic potential in neurological disorders

There is little doubt that we are what we eat. Fatty acid supplementation and diets rich in fatty acids are being promoted as ways to a healthier brain. Short chain fatty acids are a product of intestinal microbiota metabolism of dietary fibre; and their derivatives are used as an anti-convulstant. They demonstrated therapeutic potential in neurodegenerative conditions as HDAC inhibitors; and while the mechanism is not well understood, have been shown to lower amyloid β in Alzheimer's Disease in preclinical studies. Medium chain fatty acids consumed as a mixture in dietary oils can induce ketogenesis without the need for a ketogentic diet. Hence, this has the potential to provide an alternative energy source to prevent neuronal cell death due to lack of glucose. Long chain fatty acids are commonly found in the diet as omega fatty acids. They act as an anti-oxidant protecting neuronal cell membranes from oxidative damage and as an anti-inflammatory mediator in the brain. We review which agents, from each fatty acid class, have the most therapeutic potential for neurological disorders (primarily Alzheimer's disease, Parkinson's disease, Autism Spectrum Disorder as well as possible applications to traumatic brain injury), by discussing what is known about their biological mechanisms from preclinical studies.

Histone deacetylase inhibitors reduce WB-F344 oval cell viability and migration capability by suppressing AKT/mTOR signaling in vitro

Histone deacetylase (HDAC) can blockDNA replication and transcription and altered HDAC expression was associated with tumorigenesis. This study investigated the effects of HDAC inhibitors on hepatic oval cells and aimed to delineate the underlying molecular events. Hepatic oval cells were treated with two different HDAC inhibitors, suberoylanilidehydroxamic acid (SAHA) and trichostatin-A (TSA). Cells were subjected to cell morphology, cell viability, cell cycle, and wound healing assays. The expression of proteins related to both apoptosis and the cell cycle, and proteins of the AKT/mammalian target of rapamycin (mTOR) signaling pathway were analyzed by Western blot. The data showed that HDAC inhibitors reduced oval cell viability and migration capability, and arrested oval cells at the G0/G1 and S phases of the cell cycle, in a dose- and time-dependent manner. HDAC inhibitors altered cell morphology and reduced oval cell viability, and downregulated the expression of PCNA, cyclinD1, c-Myc and Bmi1 proteins, while also suppressing AKT/mTOR and its downstream target activity. In conclusion, this study demonstrates that HDAC inhibitors affect oval cells by suppressing AKT/mTOR signaling.

Limited Effect of Chronic Valproic Acid Treatment in a Mouse Model of Machado-Joseph Disease

Machado-Joseph disease (MJD) is an inherited neurodegenerative disease, caused by a CAG repeat expansion within the coding region of ATXN3 gene, and which currently lacks effective treatment. In this work we tested the therapeutic efficacy of chronic treatment with valproic acid (VPA) (200mg/kg), a compound with known neuroprotection activity, and previously shown to be effective in cell, fly and nematode models of MJD. We show that chronic VPA treatment in the CMVMJD135 mouse model had limited effects in the motor deficits of these mice, seen mostly at late stages in the motor swimming, beam walk, rotarod and spontaneous locomotor activity tests, and did not modify the ATXN3 inclusion load and astrogliosis in affected brain regions. However, VPA chronic treatment was able to increase GRP78 protein levels at 30 weeks of age, one of its known neuroprotective effects, confirming target engagement. In spite of limited results, the use of another dosage of VPA or of VPA in a combined therapy with molecules targeting other pathways, cannot be excluded as potential strategies for MJD therapeutics.

4'-O-β-D-glucosyl-5-O-methylvisamminol, an active ingredient of Saposhnikovia divaricata, attenuates high-mobility group box 1 and subarachnoid hemorrhage-induced vasospasm in a rat model

Background

High-mobility group box 1 (HMGB1) was observed to be an important extracellular mediator involved in vascular inflammation associated with subarachnoid hemorrhage (SAH). This study is of interest to examine the efficacy of 4′-O-β-d-glucosyl-5-O-methylvisamminol (4OGOMV), C₂₂H₂₈O₁₀, on the alternation of cytokines and HMGB1 in an animal model.

Methods

A rodent double hemorrhage SAH model was employed. Administration with 4OGOMV was initiated 1 h after animals were subjected to SAH. Basilar arteries (BAs) were harvested and cortexes examined for HMGB1 mRNA, protein expression (Western blot) and monocyte chemoattractant protein-1 (MCP-1) immunostaining. Cerebrospinal fluid samples were collected to examine IL-1β, IL-6, IL-8 and MCP-1 (rt-PCR).

Results

Morphological findings revealed endothelial cell deformity, intravascular elastic lamina torture, and smooth muscle necrosis in the vessels of SAH groups. Correspondently, IL-1β, IL-6 and MCP-1 in the SAH-only and SAH-plus vehicle groups was also elevated. 4OGOMV dose-dependently reduced HMGB1 protein expression when compared with the SAH groups.(p < 0.01) Likewise, 400 μg/kg 4OGOMV reduced IL-1β, MCP-1 and HMGB1 mRNA levels as well as MCP-1(+) monocytes when compared with the SAH groups..

Conclusion

4OGOMV exerts its neuro-protective effect partly through the dual effect of inhibiting IL-6 and MCP-1 activation and also reduced HMGB1 protein, mRNA and MCP-1(+) leukocytes translocation. This study lends credence to validating 4OGOMV as able to attenuate pro-inflammatory cytokine mRNA, late-onset inflammasome, and cellular basis in SAH-induced vasospasm.

Histone Deacetylase Inhibitors Inhibit the Proliferation of Gallbladder Carcinoma Cells by Suppressing AKT/mTOR Signaling

Gallbladder carcinoma is an aggressive malignancy with high mortality mainly due to the limited potential for curative resection and its resistance to chemotherapeutic agents. Here, we show that the histone deacetylase inhibitors (HDACIs) trichostatin-A (TSA) and suberoylanilide hydroxamic acid (SAHA) reduce the proliferation and induce apoptosis of gallbladder carcinoma cells by suppressing the AKT/mammalian target of rapamycin (mTOR) signaling. Gallbladder carcinoma SGC-996 cells were treated with different concentrations of TSA and SAHA for different lengths of time. Cell proliferation and morphology were assessed with MTT assay and microscopy, respectively. Cell cycle distribution and cell apoptosis were analyzed with flow cytometry. Western blotting was used to detect the proteins related to apoptosis, cell cycle, and the AKT/mTOR signaling pathway. Our data showed that TSA and SAHA reduced SGC-996 cell viability and arrested cell cycle at the G1 phase in a dose- and time-dependent manner. TSA and SAHA promoted apoptosis of SGC-996 cells, down-regulated the expression of cyclin D1, c-Myc and Bmi1, and decreased the phosphorylation of AKT, mTOR p70S6K1, S6 and 4E-BP1. Additionally, the mTOR inhibitor rapamycin further reduced the cell viability of TSA- and SAHA-treated SGC-996 cells and the phosphorylation of mTOR, whereas the mTOR activator 1,2-dioctanoyl-sn-glycero-3-phosphate (C8-PA) exerted the opposite influence. Our results demonstrate that histone deacetylase inhibitors (HDACIs) suppress the proliferation of gallbladder carcinoma cell via inhibition of AKT/mTOR signaling. These findings offer a mechanistic rationale for the application of HDACIs in gallbladder carcinoma treatment.

Neurorestoration induced by the HDAC inhibitor sodium valproate in the lactacystin model of Parkinson's is associated with histone acetylation and up-regulation of neurotrophic factors

BACKGROUND AND PURPOSE

Histone hypoacetylation is associated with Parkinson's disease (PD), due possibly to an imbalance in the activities of enzymes responsible for histone (de)acetylation; correction of which may be neuroprotective/neurorestorative. This hypothesis was tested using the anti-epileptic drug sodium valproate, a known histone deacetylase inhibitor (HDACI), utilizing a delayed-start study design in the lactacystin rat model of PD.

EXPERIMENTAL APPROACH

The irreversible proteasome inhibitor lactacystin was unilaterally injected into the substantia nigra of Sprague-Dawley rats that subsequently received valproate for 28 days starting 7 days after lactacystin lesioning. Longitudinal motor behavioural testing, structural MRI and post-mortem assessment of nigrostriatal integrity were used to track changes in this model of PD and quantify neuroprotection/restoration. Subsequent cellular and molecular analyses were performed to elucidate the mechanisms underlying valproate's effects.

KEY RESULTS

Despite producing a distinct pattern of structural re-modelling in the healthy and lactacystin-lesioned brain, delayed-start valproate administration induced dose-dependent neuroprotection/restoration against lactacystin neurotoxicity, characterized by motor deficit alleviation, attenuation of morphological brain changes and restoration of dopaminergic neurons in the substantia nigra. Molecular analyses revealed that valproate alleviated lactacystin-induced histone hypoacetylation and induced up-regulation of brain neurotrophic/neuroprotective factors.

CONCLUSIONS AND IMPLICATIONS

The histone acetylation and up-regulation of neurotrophic/neuroprotective factors associated with valproate treatment culminate in a neuroprotective and neurorestorative phenotype in this animal model of PD. As valproate induced structural re-modelling of the brain, further research is required to determine whether valproate represents a viable candidate for disease treatment; however, the results suggest that HDACIs could hold potential as disease-modifying agents in PD.

Valproic acid attenuates intercellular adhesion molecule-1 and E-selectin through a chemokine ligand 5 dependent mechanism and subarachnoid hemorrhage induced vasospasm in a rat model

BACKGROUND

Up-regulation of regulated upon activation, normal T-cell expressed and secreted (RANTES/CCL5) and adhesion molecules is observed in the serum of animals following experimental subarachnoid hemorrhage (SAH). The present study was to examine the effect of valproic acid (VPA) on RANTES and alternation of adhesion molecules in this model.

METHODS

A rodent SAH model was employed. Animals were randomly assigned into six groups. Basilar artery (BA) was harvested for intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin evaluation (western blotting) and RANTES (rt-PCR). 1 ng CCL5 recombinant protein intrathecal injection was performed in the VPA + SAH groups. (N = 5).

RESULTS

Convoluted internal elastic lamina, distorted endothelial wall, and smooth muscle micro-necrosis was prominently observed in the SAH groups, which is absent in the VPA treatment and the healthy controls. Treatment with VPA dose-dependently reduced the ICAM-1, E-selectin and RANTES level, compared with the SAH group (p <0.01). The administration of CCL5 significantly increased CD45(+) glia and ICAM-1 level in the VPA treatment groups.

CONCLUSION

VPA exerts its anti-vasospastic effect through the dual effect of inhibiting RANTES expression and reduced adhesion molecules. Besides, VPA also decreased CD45(+) cells transmigrated to the vascular wall. The administration of CCL5 significantly reversed the inhibitory effect of this compound on CD45(+) monocytes, E-selectin, and ICAM-1 level. This study also lends credence to support this compound could attenuate SAH induced adhesion molecules and neuro-inflammation in a CCL5 dependent mechanism.

Mechanistic Insights to the Cytotoxicity of Amaryllidaceae Alkaloids

With over 500 individual compounds, the Amaryllidaceae alkaloids represent a large and structurally diverse group of phytochemicals. Coupled to this structural diversity is the significant array of biological properties manifested by many of its members, of which their relevance in motor neuron disease and cancer chemotherapy has attracted considerable attention. To this extent, galanthamine has evolved into a successful commercial drug for Alzheimer's disease since its approval by the FDA in 2001. Concurrently, there have been several positive indicators for the emergence of an anticancer drug from the Amaryllidaceae due to the potency of several of its representatives as cell line specific antiproliferative agents. In this regard, the phenanthridones such as pancratistatin and narciclasine have offered most promise since their advancement into clinical trials, following which there has been renewed interest in the cytotoxic properties of these alkaloids. Given this background, this review seeks to highlight the various mechanisms which have been invoked to corroborate the cytotoxic effects of Amaryllidaceae alkaloids.

Enhancement of Autophagy by Histone Deacetylase Inhibitor Trichostatin A Ameliorates Neuronal Apoptosis After Subarachnoid Hemorrhage in Rats

Trichostatin A (TSA), a pan-histone deacetylase inhibitor, exerts multiple neuroprotective properties. This study aims to examine whether TSA could enhance autophagy, thereby reduce neuronal apoptosis and ultimately attenuate early brain injury (EBI) following subarachnoid hemorrhage (SAH). SAH was performed through endovascular perforation method, and mortality, neurological score, and brain water content were evaluated at 24 h after surgery. Western blot were used for quantification of acetylated histone H3, LC3-II, LC3-I, Beclin-1, cytochrome c, Bax, and cleaved caspase-3 expression. Immunofluorescence was performed for colocalization of Beclin-1 and neuronal nuclei (NeuN). Apoptotic cell death of neurons was quantified with double staining of terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end-labeling (TUNEL) and NeuN. The autophagy inhibitor 3-methyladenine (3-MA) was used to manipulate the proposed pathway. Our results demonstrated that TSA reduced brain edema and alleviated neurological deficits at 24 h after SAH. TSA significantly increased acetylated histone H3, the LC3-II/LC3-I ratio, and Beclin-1 while decreased Bax and cleaved caspase-3 in the cortex. Beclin-1 and NeuN, TUNEL, and NeuN, respectively, were colocalized in cortical cells. Neuronal apoptosis in the ipsilateral basal cortex was significantly inhibited after TSA treatment. Conversely, 3-MA reversed the beneficial effects of TSA. These results proposed that TSA administration enhanced autophagy, which contributes to alleviation of neuronal apoptosis, improvement of neurological function, and attenuation of EBI following SAH.

Purpurogallin, a natural phenol, attenuates high-mobility group box 1 in subarachnoid hemorrhage induced vasospasm in a rat model

High-mobility group box 1 (HMGB1) was shown to be an important extracellular mediator involved in vascular inflammation of animals following subarachnoid hemorrhage (SAH). This study is of interest to examine the efficacy of purpurogallin, a natural phenol, on the alternation of cytokines and HMGB1 in a SAH model. A rodent double hemorrhage SAH model was employed. Basilar arteries (BAs) were harvested to examine HMGB1 mRNA and protein expression (Western blot). CSF samples were to examine IL-1β, IL-6, IL-8, and TNF-α (rt-PCR). Deformed endothelial wall, tortuous elastic lamina, and necrotic smooth muscle were observed in the vessels of SAH groups but were absent in the purpurogallin group. IL-1β, IL-6, and TNF-α in the SAH only and SAH plus vehicle groups were significantly elevated (P < 0.01). Purpurgallin dose-dependently reduced HMGB1 protein expression. Likewise, high dose purpurogallin reduced TNF-α and HMGB1 mRNA levels. In conclusion, purpurogallin exerts its neuroinflammation effect through the dual effect of inhibiting IL-6 and TNF-α mRNA expression and reducing HMGB1 protein and mRNA expression. This study supports purpurogallin could attenuate both proinflammatory cytokines and late-onset inflammasome in SAH induced vasospasm.

Involvement of HDAC1 and HDAC3 in the Pathology of Polyglutamine Disorders: Therapeutic Implications for Selective HDAC1/HDAC3 Inhibitors

Histone deacetylases (HDACs) enzymes, which affect the acetylation status of histones and other important cellular proteins, have been recognized as potentially useful therapeutic targets for a broad range of human disorders. Emerging studies have demonstrated that different types of HDAC inhibitors show beneficial effects in various experimental models of neurological disorders. HDAC enzymes comprise a large family of proteins, with18 HDAC enzymes currently identified in humans. Hence, an important question for HDAC inhibitor therapeutics is which HDAC enzyme(s) is/are important for the amelioration of disease phenotypes, as it has become clear that individual HDAC enzymes play different biological roles in the brain. This review will discuss evidence supporting the involvement of HDAC1 and HDAC3 in polyglutamine disorders, including Huntington's disease, and the use of HDAC1- and HDAC3-selective HDAC inhibitors as therapeutic intervention for these disorders. Further, while HDAC inhibitors are known alter chromatin structure resulting in changes in gene transcription, understanding the exact mechanisms responsible for the preclinical efficacy of these compounds remains a challenge. The potential chromatin-related and non-chromatin-related mechanisms of action of selective HDAC inhibitors will also be discussed.

Epigenetic mechanisms in epilepsy

In humans, genomic DNA is organized in 23 chromosome pairs coding for roughly 25,000 genes. Not all of them are active at all times. During development, a broad range of different cell types needs to be generated in a highly ordered and reproducible manner, requiring selective gene expression programs. Epigenetics can be regarded as the information management system that is able to index or bookmark distinct regions in our genome to regulate the readout of DNA. It further comprises the molecular memory of any given cell, allowing it to store information of previously experienced external (e.g., environmental) or internal (e.g., developmental) stimuli, to learn from this experience and to respond. The underlying epigenetic mechanisms can be synergistic, antagonistic, or mutually exclusive and their large variety combined with the variability and interdependence is thought to provide the molecular basis for any phenotypic variation in physiological and pathological conditions. Thus, widespread reconfiguration of the epigenome is not only a key feature of neurodevelopment, brain maturation, and adult brain function but also disease.

Epigenetic regulatory mechanisms in stress-induced behavior

Stress response is considered to have adaptive value for organisms faced with stressful condition. Chronic stress however adversely affects the physiology and may lead to neuropsychiatric disorders. Repeated stressful events in animal models have been shown to cause long-lasting changes in neural circuitries at molecular, cellular, and physiological level, leading to disorders of mood as well as cognition. Molecular studies in recent years have implicated diverse epigenetic mechanisms, including histone modifications, DNA methylation, and noncoding RNAs, that underlie dysregulation of genes in the affected neural circuitries in chronic stress-induced pathophysiology. A review of the myriad epigenetic regulatory mechanisms associated with neural and behavioral responses in animal models of stress-induced neuropsychiatric disorders is presented here. The review also deals with clinical evidence of the epigenetic dysregulation of genes in psychiatric disorders where chronic stress appears to underlie the etiopathology.

Epigenetic targeting of histone deacetylase: therapeutic potential in Parkinson's disease?

Parkinson's disease (PD) is the most common movement disorder affecting more than 4million people worldwide. The primary motor symptoms of the disease are due to degeneration of dopaminergic nigrostriatal neurons. Dopamine replacement therapies have therefore revolutionised disease management by partially controlling these symptoms. However these drugs can produce debilitating side effects when used long term and do not protect degenerating neurons against death. Recent evidence has highlighted a pathological imbalance in PD between the acetylation and deacetylation of the histone proteins around which deoxyribonucleic acid (DNA) is coiled, in favour of excessive histone deacetylation. This mechanism of adding/removing acetyl groups to histone lysine residues is one of many epigenetic regulatory processes which control the expression of genes, many of which will be essential for neuronal survival. Hence, such epigenetic modifications may have a pathogenic role in PD. It has therefore been hypothesised that if this pathological imbalance can be corrected with the use of histone deacetylase inhibiting agents then neurodegeneration observed in PD can be ameliorated. This article will review the current literature with regard to epigenetic changes in PD and the use of histone deacetylase inhibitors (HDACIs) in PD: examining the evidence of the neuroprotective effects of numerous HDACIs in cellular and animal models of Parkinsonian cell death. Ultimately answering the question: does epigenetic targeting of histone deacetylases hold therapeutic potential in PD?

Plant polyphenols and oxidative metabolites of the herbal alkenylbenzene methyleugenol suppress histone deacetylase activity in human colon carcinoma cells

Evidence has been provided that diet and environmental factors directly influence epigenetic mechanisms associated with cancer development in humans. The inhibition of histone deacetylase (HDAC) activity and the disruption of the HDAC complex have been recognized as a potent strategy for cancer therapy and chemoprevention. In the present study, we investigated whether selected plant constituents affect HDAC activity or HDAC1 protein status in the human colon carcinoma cell line HT29. The polyphenols (-)-epigallocatechin-3-gallate (EGCG) and genistein (GEN) as well as two oxidative methyleugenol (ME) metabolites were shown to inhibit HDAC activity in intact HT29 cells. Concomitantly, a significant decrease of the HDAC1 protein level was observed after incubation with EGCG and GEN, whereas the investigated ME metabolites did not affect HDAC1 protein status. In conclusion, dietary compounds were found to possess promising HDAC-inhibitory properties, contributing to epigenetic alterations in colon tumor cells, which should be taken into account in further risk/benefit assessments of polyphenols and alkenylbenzenes.

Selective histone deacetylase (HDAC) inhibition imparts beneficial effects in Huntington's disease mice: implications for the ubiquitin-proteasomal and autophagy systems

We previously demonstrated that the histone deacetylase (HDAC) inhibitor, 4b, which preferentially targets HDAC1 and HDAC3, ameliorates Huntington's disease (HD)-related phenotypes in different HD model systems. In the current study, we investigated extensive behavioral and biological effects of 4b in N171-82Q transgenic mice and further explored potential molecular mechanisms of 4b action. We found that 4b significantly prevented body weight loss, improved several parameters of motor function and ameliorated Huntingtin (Htt)-elicited cognitive decline in N171-82Q transgenic mice. Pathways analysis of microarray data from the mouse brain revealed gene networks involving post-translational modification, including protein phosphorylation and ubiquitination pathways, associated with 4b drug treatment. Using real-time qPCR analysis, we validated differential regulation of several genes in these pathways by 4b, including Ube2K, Ubqln, Ube2e3, Usp28 and Sumo2, as well as several other related genes. Additionally, 4b elicited increases in the expression of genes encoding components of the inhibitor of kappaB kinase (IKK) complex. IKK activation has been linked to phosphorylation, acetylation and clearance of the Htt protein by the proteasome and the lysosome, and accordingly, we found elevated levels of phosphorylated endogenous wild-type (wt) Htt protein at serine 16 and threonine 3, and increased AcK9/pS13/pS16 immunoreactivity in cortical samples from 4b-treated mice. We further show that HDAC inhibitors prevent the formation of nuclear Htt aggregates in the brains of N171-82Q mice. Our findings suggest that one mechanism of 4b action is associated with the modulation of the ubiquitin-proteasomal and autophagy pathways, which could affect accumulation, stability and/or clearance of important disease-related proteins, such as Htt.

Targeted acetylation of NF-kappaB/RelA and histones by epigenetic drugs reduces post-ischemic brain injury in mice with an extended therapeutic window

Nuclear factor-kappaB (NF-κB) p50/RelA is a key molecule with a dual effect in the progression of ischemic stroke. In harmful ischemia, but not in preconditioning insult, neurotoxic activation of p50/RelA is characterized by RelA-specific acetylation at Lys310 (K310) and deacetylation at other Lys residues. The derangement of RelA acetylation is associated with activation of Bim promoter.

OBJECTIVE

With the aim of producing neuroprotection by correcting altered acetylation of RelA in brain ischemia, we combined the pharmacological inhibition of histone deacetylase (HDAC) 1-3, the enzymes known to reduce global RelA acetylation, and the activation of sirtuin 1, endowed with a specific deacetylase activity on the K310 residue of RelA. To afford this aim, we tested the clinically used HDAC 1-3 inhibitor entinostat (MS-275) and the sirtuin 1 activator resveratrol.

METHODS

We used the mouse model of transient middle cerebral artery occlusion (MCAO) and primary cortical neurons exposed to oxygen glucose deprivation (OGD).

RESULTS

The combined use of MS-275 and resveratrol, by restoring normal RelA acetylation, elicited a synergistic neuroprotection in neurons exposed to OGD. This effect correlated with MS-275 capability to increase total RelA acetylation and resveratrol capability to reduce RelA K310 acetylation through the activation of an AMP-activated protein kinase-sirtuin 1 pathway. The synergistic treatment reproduced the acetylation state of RelA peculiar of preconditioning ischemia. Neurons exposed to the combined drugs totally recovered the optimal histone H3 acetylation. Neuroprotection was reproduced in mice subjected to MCAO and treated with MS-275 (20μg/kg and 200μg/kg) or resveratrol (6800μg/kg) individually. However, the administration of lowest doses of MS-275 (2μg/kg) and resveratrol (68μg/kg) synergistically reduced infarct volume and neurological deficits. Importantly, the treatment was effective even when administered 7h after the stroke onset. Chromatin immunoprecipitation analysis of cortices harvested from treated mice showed that the RelA binding and histone acetylation increased at the Bcl-xL promoter and decreased at the Bim promoter.

CONCLUSION

Our study reveals that epigenetic therapy shaping acetylation of both RelA and histones may be a promising strategy to limit post-ischemic injury with an extended therapeutic window.

RGFP109, a histone deacetylase inhibitor attenuates L-DOPA-induced dyskinesia in the MPTP-lesioned marmoset: a proof-of-concept study

BACKGROUND

l-3,4-dihydroxyphenylalanine (l-DOPA)-induced dyskinesia (LID) are a complication of chronic dopamine replacement therapy in Parkinson's disease (PD). Recent studies have suggested that the mechanisms underlying development and expression of LID in PD may involve epigenetic changes that include deacetylation of striatal histone proteins. We hypothesised that inhibition of histone deacetylase, the enzyme responsible of histone deacetylation, would alleviate LID.

METHODS

Four female common marmoset (Callithrix jacchus) were rendered parkinsonian by administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Following stabilisation of the parkinsonian phenotype, marmosets were primed to exhibit dyskinesia with chronic administration of L-DOPA. We then investigated the effects of the brain-penetrant histone deacetylase inhibitor, RGFP109 (30 mg/kg p.o. once daily for 6 days), on LID and L-DOPA anti-parkinsonian efficacy.

RESULTS

RGFP109 had no acute effects on dyskinesia after single or 6 days once-daily treatment (both P > 0.05). However, one week following cessation of RGFP109, dyskinesia and duration of ON-time with disabling dyskinesia were reduced by 37% and 50%, respectively (both P < 0.05), compared to that seen previously with L-DOPA alone. There was no change in anti-parkinsonian actions of, or ON-time duration afforded by, L-DOPA (P > 0.05).

CONCLUSIONS

Histone deacetylation inhibition may represent a novel approach to reverse established LID in PD and improve quality of the anti-parkinsonian benefit provided by L-DOPA.

Epigenetic mechanisms governing the process of neurodegeneration

Studies elucidating how and why neurodegeneration unfolds suggest that a complex interplay between genetic and environmental factors is responsible for disease pathogenesis. Recent breakthroughs in the field of epigenetics promise to advance our understanding of these mechanisms and to promote the development of useful and effective pre-clinical risk stratification strategies, molecular diagnostic and prognostic methods, and disease-modifying treatments.

Epigenetic programming of neurodegenerative diseases by an adverse environment

Experience and environment can critically influence the risk and progression of neurodegenerative disorders. Epigenetic mechanisms, such as miRNA expression, DNA methylation, and histone modifications, readily respond to experience and environmental factors. Here we propose that epigenetic regulation of gene expression and environmental modulation thereof may play a key role in the onset and course of common neurological conditions, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and multiple sclerosis. For example, epigenetic mechanisms may mediate long-term responses to adverse experience, such as stress, to affect disease susceptibility and the course of neurodegenerative events. This review introduces the epigenetic components and their possible role in mediating neuropathological processes in response to stress. We argue that epigenetic modifications will affect neurodegenerative events through altered gene function. The study of epigenetic states in neurodegenerative diseases presents an opportunity to gain new insights into risk factors and pathogenic mechanisms. Moreover, research into epigenetic regulation of disease may revolutionize health care by opening new avenues of personalized, preventive and curative medicine.

Emerging topics in epigenetics: ants, brains, and noncoding RNAs

One of the greatest wonders in biology is the high degree of molecular organization and complexity achieved by multicellular life forms, which are typically composed by hundreds of cell types, each with a unique identity and function and all sharing the same genome. Long-term maintenance of these distinct cell identities requires epigenetic signals, molecular signatures that regulate gene expression and can be inherited during cell division. Some epigenetic signals also appear to have an intimate connection with brain function, with important implications for neuroscience and medicine. To better understand these phenomena, new technologies must be developed and nonconventional model organisms should be studied. For example, the genomes of eusocial insects, such as ants and honeybees, specify drastically different morphologies (polyphenism) and behaviors (polyethism) that yield adult individuals belonging to different castes, which carry out separate functions inside the colony. These sharp epigenetic differences present unique opportunities for the experimental dissection of molecular pathways that may be conserved in other organisms, including humans.

Current status and future prospects for epigenetic psychopharmacology

Mounting evidence suggest that epigenetic regulation of brain functions is important in the etiology of psychiatric disorders. These epigenetic regulatory mechanisms, such as DNA methylation and histone acetylation, are influenced by many pharmaceutical compounds including psychiatric drugs. It is therefore of interest to investigate how psychiatric drugs are of influence and what the potential is of new epigenetic drugs for psychiatric disorders. With this targeted review we summarize the current state of knowledge in order to provide insight in this developing field. Several traditional psychiatric drugs have been found to alter the epigenome and in a variety of animal studies, experimental compounds with epigenetic targets have been investigated as potential psychiatric drugs. After discussion of the most relevant epigenetic mechanisms we present the evidence for epigenetic effects for the most relevant classes of drugs.

Dynamic structure-based pharmacophore model development: a new and effective addition in the histone deacetylase 8 (HDAC8) inhibitor discovery

Histone deacetylase 8 (HDAC8) is an enzyme involved in deacetylating the amino groups of terminal lysine residues, thereby repressing the transcription of various genes including tumor suppressor gene. The over expression of HDAC8 was observed in many cancers and thus inhibition of this enzyme has emerged as an efficient cancer therapeutic strategy. In an effort to facilitate the future discovery of HDAC8 inhibitors, we developed two pharmacophore models containing six and five pharmacophoric features, respectively, using the representative structures from two molecular dynamic (MD) simulations performed in Gromacs 4.0.5 package. Various analyses of trajectories obtained from MD simulations have displayed the changes upon inhibitor binding. Thus utilization of the dynamically-responded protein structures in pharmacophore development has the added advantage of considering the conformational flexibility of protein. The MD trajectories were clustered based on single-linkage method and representative structures were taken to be used in the pharmacophore model development. Active site complimenting structure-based pharmacophore models were developed using Discovery Studio 2.5 program and validated using a dataset of known HDAC8 inhibitors. Virtual screening of chemical database coupled with drug-like filter has identified drug-like hit compounds that match the pharmacophore models. Molecular docking of these hits reduced the false positives and identified two potential compounds to be used in future HDAC8 inhibitor design.

Recent advances in the biology and chemistry of the flavaglines

The flavaglines are a family of plant natural products that induce potent anticancer and neuroprotective activities. This review summarizes recent synthetic approaches to flavaglines and the current status of their pharmacological properties.

The methylation hypothesis: do epigenetic chromatin modifications play a role in epileptogenesis?

Any structural brain lesion can provoke epilepsy, although onset and progression of seizures as well as response to antiepileptic drug (AED) treatment remain difficult to predict in each patient. Tremendous work has focused on the development of new AED compounds with the intention to treat seizures. However, these efforts have not yet discovered a "magic bullet" that cures epilepsy in every patient or modifies disease progression. With the "methylation hypothesis" we propose that epigenetic mechanisms play a pivotal role in epileptogenesis in patients with structural lesions. "Epigenetics" is defined as information that is heritable during cell division other than the DNA sequence itself, that is, DNA methylation or histone tail modifications, which can produce lasting alterations in chromatin structure and gene expression. They are increasingly recognized as fundamental regulatory processes in central nervous system development, synaptic plasticity, and memory, and also play a role in neurologic disorders such as schizophrenia and spinal muscular atrophy. The methylation hypothesis suggests that seizures by themselves can induce epigenetic chromatin modifications, thereby aggravating the epileptogenic condition. The impact of the methylation hypothesis for new-onset epilepsy will be discussed. Unravelling of epigenetic pathomechanisms will also open new strategies to identify molecular targets for pharmacologic treatment in epilepsies.

[New developments in epileptogenesis and therapeutic perspectives]

Epileptogenesis describes the mechanisms of how epilepsies are generated. We have chosen four areas in which significant progress has been achieved in understanding epileptogenesis. Those are (1) inflammatory processes which play an increasingly important role for the generation of temporal lobe epilepsy with hippocampal sclerosis (TLE with HS), (2) disturbances of intrinsic properties of neuronal compartments, in particular acquired defects of ion channels of which those in dendrites are described here for TLE with HS, (3) epigenetic effects, which affect for example the methylation of promoters and secondarily can change the expression of specific genes in TLE with HS, and finally (4) the epileptogenesis of idiopathic epilepsies which are caused by inborn genetic alterations affecting mainly ion channels. Apart from aspects of basic research, we will describe clinical consequences and therapeutic perspectives.

Nitric oxide and histone deacetylases: A new relationship between old molecules

Histone deacetylases (HDACs) are enzymes that catalyze the removal of acetyl groups from a range of nuclear and cytoplasmic proteins. Recently, we described a novel route to neurotrophin-dependent gene activation in neurons, which requires the S-nitrosylation of nuclear HDAC2 by the gaseous molecule nitric oxide (NO).1 We have further investigated the NO-dependent regulation of HDACs in neurons. Using a fluorogenic deacetylation assay, we show that NO decreases the enzymatic activity of a subgroup of neuronal HDACs in vitro and that this inhibition is not due to damaging modifications such as oxidation or tyrosine nitration. The neuronal HDACs whose catalytic activity is inhibited by NO are entirely those that are localized in the cytoplasm. These observations support and extend the concept that nitric oxide is a key regulator of HDAC function in mammalian neurons.

Treatment with trichostatin A initiated after disease onset delays disease progression and increases survival in a mouse model of amyotrophic lateral sclerosis

Recent studies suggest that progressive motoneuron death in amyotrophic lateral sclerosis (ALS) is non-cell autonomous and may involve the participation of non-neuronal cells such as glial cells and skeletal muscle. Therefore, a drug that targets motoneurons as well as neighboring non-neuronal cells might be a potential therapeutic strategy to delay disease progression in ALS. Trichostatin A (TSA), a histone deacetylase (HDAC) inhibitor, has shown protective effects in multiple cell types implicated in ALS by resetting gene transcription profiles through increased histone acetylation. To test whether TSA could serve as a potential therapeutic agent, we intraperitoneally injected TSA from postnatal day 90 (P90), after disease symptoms appear, until P120 or the end-stage in SOD1-G93A mice. We found that TSA ameliorated motoneuron death and axonal degeneration in SOD1-G93A mice. Reduced gliosis and upregulation of the glutamate transporter (GLT-1) were also observed in the spinal cord of TSA-treated SOD1-G93A mice. In addition, TSA ameliorated muscle atrophy and neuromuscular junction (NMJ) denervation, which are the pathological characteristics of ALS found in skeletal muscle. Improved morphology in TSA-treated SOD1-G93A mice was accompanied by enhanced motor functions as assessed by rota-rod and grip strength analyses. Furthermore, TSA treatment significantly increased the mean survival duration after the treatment by 18% and prolonged lifespan by 7%. Our findings suggest that TSA may provide a potential therapy to slow disease progression as well as to enhance motor performance to improve the quality of life for ALS patients.

Design, synthesis, docking, and biological evaluation of novel diazide-containing isoxazole- and pyrazole-based histone deacetylase probes

The design, synthesis, docking, and biological evaluation of novel potent HDAC3 and HDAC8 isoxazole- and pyrazole-based diazide probes suitable for binding ensemble profiling with photoaffinity labeling (BEProFL) experiments in cells is described. Both the isoxazole- and pyrazole-based probes exhibit low nanomolar inhibitory activity against HDAC3 and HDAC8, respectively. The pyrazole-based probe 3f appears to be one of the most active HDAC8 inhibitors reported in the literature with an IC(50) of 17 nM. Our docking studies suggest that unlike the isoxazole-based ligands the pyrazole-based ligands are flexible enough to occupy the second binding site of HDAC8. Probes/inhibitors 2b, 3a, 3c, and 3f exerted the antiproliferative and neuroprotective activities at micromolar concentrations through inhibition of nuclear HDACs, indicating that they are cell permeable and the presence of an azide or a diazide group does not interfere with the neuroprotection properties, or enhance cellular cytotoxicity, or affect cell permeability.

Nitric oxide signaling and nitrosative stress in neurons: role for S-nitrosylation

Nitric oxide (NO) mediates cellular signaling pathways that regulate a plethora of physiological processes. One of the signaling mechanisms mediated by NO is through S-nitrosylation of cysteine residues in target proteins, which is now regarded as an important redox-based physiological action. Deregulation of the protein S-nitrosylation upon nitrosative stress, however, has also been linked to various human diseases, such as neurodegenerative disorders. Between these physiological and pathophysiological roles, there are mechanisms whereby a milder level of nitrosative stress provides S-nitrosylation of some proteins that counteracts the pathological processes, serving as a negative feedback mechanism. In addition, NO has recently emerged as a mediator of epigenetic gene expression and chromatin changes. In this review, these molecular mechanisms, especially those in the central nervous system and neurodegenerative disorders, are described.

Carboxylic acid derivatives of histone deacetylase inhibitors induce full length SMN2 transcripts: a promising target for spinal muscular atrophy therapeutics

INTRODUCTION

Proximal spinal muscular atrophy (SMA) is a common autosomal recessively inherited neuromuscular disorder. It is caused by homozygous absence of the survival motor neuron 1 (SMN1) gene. SMN2, which modulates the severity of the disease, represents a major target for therapy. The aim of this study was to investigate whether SMN2 expression can be increased by caffeic acid, chlorogenic acid and curcumin, which are designed by modifications of the carboxylic acid class of histone deacetylase (HDAC) inhibitors.

MATERIAL AND METHODS

Using quantitative real-time PCR, we analysed the levels of full-length SMN2 and Δ7SMN2 mRNA. We performed LDH cytotoxicity assay to analyse whether SMN2 activating concentrations of caffeic acid, chlorogenic acid and curcumin were cytotoxic to fibroblasts.

RESULTS

We found that caffeic acid and curcumin were more efficient than chlorogenic acid and increased full-length SMN2 mRNA levels 1.5 and 1.7-fold, respectively. Δ7SMN2 mRNA levels were measured to investigate alternative splicing of exon 7. We also found that cytotoxicity was not observed at SMN2 activating concentrations.

CONCLUSIONS

Our data suggest that carboxylic acid derivatives including phenolic structure and symmetry could be a good candidate for SMA treatment.

Therapeutic prospects for epigenetic modulation

INTRODUCTION

Epigenetics describes the phenomenon of heritable changes in gene regulation governed by non-Mendelian processes, primarily through biochemical modifications to chromatin that occur during cell differentiation and development. Abnormal levels of DNA and/or histone modifications are observed in patients with a wide variety of chronic diseases. Drugs that target the proteins controlling these chromatin modifications can modulate the expression of clusters of genes, potentially offering higher therapeutic efficacy than classical agents with single target pharmacologies that are susceptible to biochemical pathway degeneracy.

AREAS COVERED

This article reviews research characterizing dysregulation of epigenetic processes in cancer, immuno-inflammatory, psychiatric, neurological, metabolic and virology disease areas, and summarizes recent developments in identifying small molecule modulators that are being used to inform target discovery and initiate drug discovery projects.

EXPERT OPINION

There are numerous potential opportunities for epigenetic modulators in treating a wide range of chronic diseases; however, the field is complex, involving > 300 proteins, and much work is still required to provide tools to unravel the functions of individual proteins, particularly in vivo. This groundwork is essential to allow the drug discovery community to focus on those epigenetic proteins most likely to be suitable targets for safe, efficacious new therapies.

Alzheimer's disease and age-related memory decline (preclinical)

An unfortunate result of the rapid rise in geriatric populations worldwide is the increasing prevalence of age-related cognitive disorders such as Alzheimer's disease (AD). AD is a devastating neurodegenerative illness that is characterized by a profound impairment of cognitive function, marked physical disability, and an enormous economic burden on the afflicted individual, caregivers, and society in general. The rise in elderly populations is also resulting in an increase in individuals with related (potentially treatable) conditions such as "Mild Cognitive Impairment" (MCI) which is characterized by a less severe (but abnormal) level of cognitive impairment and a high-risk for developing dementia. Even in the absence of a diagnosable disorder of cognition (e.g., AD and MCI), the perception of increased forgetfulness and declining mental function is a clear source of apprehension in the elderly. This is a valid concern given that even a modest impairment of cognitive function is likely to be associated with significant disability in a rapidly evolving, technology-based society. Unfortunately, the currently available therapies designed to improve cognition (i.e., for AD and other forms of dementia) are limited by modest efficacy and adverse side effects, and their effects on cognitive function are not sustained over time. Accordingly, it is incumbent on the scientific community to develop safer and more effective therapies that improve and/or sustain cognitive function in the elderly allowing them to remain mentally active and productive for as long as possible. As diagnostic criteria for memory disorders evolve, the demand for pro-cognitive therapeutic agents is likely to surpass AD and dementia to include MCI and potentially even less severe forms of memory decline. The purpose of this review is to provide an overview of the contemporary therapeutic targets and preclinical pharmacologic approaches (with representative drug examples) designed to enhance memory function.

Epigenetic modification is linked to Alzheimer's disease: is it a maker or a marker?

Alzheimer's disease (AD) is the most common age-dependent neurodegenerative disorder and shows progressive memory loss and cognitive decline. Intraneuronal filaments composed of aggregated hyperphosphorylated tau protein, called neurofibrillary tangles, along with extracellular accumulations of amyloid ß protein (Aß), called senile plaques, are known to be the neuropathological hallmarks of AD. In light of recent studies, epigenetic modification has emerged as one of the pathogenic mechanisms of AD. Epigenetic changes encompass an array of molecular modifications to both DNA and chromatin, including transcription factors and cofactors. In this review, we summarize how DNA methylation and changes to DNA chromatin packaging by post-translational histone modification are involved in AD. In addition, we describe the role of SIRTs, histone deacetylases, and the effect of SIRT-modulating drugs on AD. Lastly, we discuss how amyloid precursor protein (APP) intracellular domain (AICD) regulates neuronal transcription. Our understanding of the epigenomes and transcriptomes of AD may warrant future identification of novel biological markers and beneficial therapeutic targets for AD.

Histone deacetylase inhibitors as therapeutic agents for acute central nervous system injuries

Histone deacetylase (HDAC) inhibitors are emerging as a novel class of potentially therapeutic agents for treating acute injuries of the central nervous system (CNS). In this review, we summarize data regarding the effects of HDAC inhibitor administration in models of acute CNS injury and discuss issues warranting clinical trials. We have previously shown that the pan-HDAC inhibitor ITF2357, a compound shown to be safe and effective in humans, improves functional recovery and attenuates tissue damage when administered as late as 24 h after injury. Using a well-characterized, clinically relevant mouse model of closed head injury, we demonstrated that a single dose of ITF2357 administered 24 h after injury improves neurobehavioral recovery and reduces tissue damage. ITF2357-induced functional improvement was found to be sustained up to 14 d after trauma and was associated with augmented histone acetylation. Single postinjury administration of ITF2357 also attenuated injury-induced inflammatory responses, as indicated by reduced glial accumulation and activation as well as enhanced caspase-3 expression within microglia/macrophages after treatment. Because no specific therapeutic intervention is currently available for treating brain trauma patients, the ability to affect functional outcome by postinjury administration of HDAC inhibitors within a clinically feasible timeframe may be of great importance. Furthermore, a growing body of evidence indicates that HDAC inhibitors are beneficial for treating various forms of acute CNS injury including ischemic and hemorrhagic stroke. Because HDAC inhibitors are currently approved for other use, they represent a promising new avenue of treatment, and their use in the setting of CNS injury warrants clinical evaluation.

Animal models of epigenetic regulation in neuropsychiatric disorders

Epigenetics describes the phenomenon of heritable changes in gene regulation that are governed by non-Mendelian processes, primarily through biochemical modifications to chromatin structure that occur during cell development and differentiation. Numerous lines of evidence link abnormal levels of chromatin modifications (either to DNA, histones, or both) in patients with a wide variety of diseases including cancer, psychiatry, neurodegeneration, metabolic and inflammatory disorders. Drugs that target the proteins controlling chromatin modifications can modulate the expression of clusters of genes, potentially offering higher therapeutic efficacy than classical agents with single target pharmacologies that are susceptible to biochemical pathway degeneracy. Here, we summarize recent research linking epigenetic dysregulation with diseases in neurosciences, the application of relevant animal models, and the potential for small molecule modulator development to facilitate target discovery, validation and translation into clinical treatments.

ER stress response plays an important role in aggregation of α-synuclein

Background

Accumulation of filamentous α-synuclein as Lewy bodies is a hallmark of Parkinson's disease. To identify the mechanisms involved in α-synuclein assembly and determine whether the assemblies are cytotoxic, we developed a cell model (3D5) that inducibly expresses wild-type human α-synuclein and forms inclusions that reproduce many morphological and biochemical characteristics of Lewy bodies. In the present study, we evaluated the effects of several histone deacetylase inhibitors on α-synuclein aggregation in 3D5 cells and primary neuronal cultures. These drugs have been demonstrated to protect cells transiently overexpressing α-synuclein from its toxicity.

Results

Contrary to transient transfectants, the drug treatment did not benefit 3D5 cells and primary cultures. The treated were less viable and contained more α-synuclein oligomers, active caspases 3 and 9, as well as ER stress markers than non-treated counterparts. The drug-treated, induced-3D5 cells, or primary cultures from transgenic mice overexpressing (<2 fold) α-synuclein, displayed more α-synuclein oligomers and ER stress markers than non-induced or non-transgenic counterparts. Similar effects were demonstrated in cultures treated with tunicamycin, an ER stressor. These effects were blocked by co-treatment with salubrinal, an ER stress inhibitor. In comparison, co-treatment with a pan caspase inhibitor protected cells from demise but did not reduce α-synuclein oligomer accumulation.

Conclusions

Our results indicate that an increase of wild-type α-synuclein can elicit ER stress response and sensitize cells to further insults. Most importantly, an increase of ER stress response can promote the aggregation of wild type α-synuclein.

Therapeutic approaches to spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy is a hereditary motor neuron disease caused by trinucleotide repeat expansion in the androgen receptor gene. The disease mechanism probably involves a toxic gain of function in the mutant protein, because other mutations that cause a loss of androgen receptor function result in a different phenotype and the mutant protein is toxic in mouse models. In these models, the toxicity is ligand-dependent and is associated with protein aggregation, as well as altered transcriptional regulation, axonal transport and mitochondrial function. Various therapeutic approaches have shown efficacy in mouse models, including androgen reduction, heat shock protein 90 (HSP90) inhibition and insulin-like growth factor (IGF)-1 overexpression. Clinical trials of androgen-reducing agents have had mixed results, with indications of efficacy but no proof of clinically meaningful benefit to date. These clinical studies have established outcome measures for future trials of other agents that have been beneficial in animal studies.

Current and future pharmacological treatment strategies in X-linked adrenoleukodystrophy

Mutations in the ABCD1 gene cause the clinical spectrum of the neurometabolic disorder X-linked adrenoleukodystrophy/adrenomyeloneuropathy (X-ALD/AMN). Currently, the most efficient therapeutic opportunity for patients with the cerebral form of X-ALD is hematopoietic stem cell transplantation and possibly gene therapy of autologous hematopoietic stem cells. Both treatments, however, are only accessible to a subset of X-ALD patients, mainly because of the lack of markers that can predict the onset of cerebral demyelination. Moreover, for female or male X-ALD patients with AMN, currently only unsatisfying therapeutic opportunities are available. Thus, this review focuses on current and urgently needed future pharmacological therapies. The treatment of adrenal and gonadal insufficiency is well established, whereas applications of immunomodulatory and immunosuppressive drugs have failed to prevent progression of cerebral neuroinflammation. The use of Lorenzo's oil and the inefficacy of lovastatin to normalize very-long-chain fatty acids in clinical trials as well as currently experimental and therefore possible future therapeutic strategies are reviewed. The latter include pharmacological gene therapy mediated by targeted upregulation of ABCD2, the closest homolog of ABCD1, antioxidative drug treatment, small molecule histone deacetylase inhibitors such as butyrates and valproic acid, and other neuroprotective attempts.