Treatment Of Huntington's Disease Research Articles

A New Drug Design Targeting the Adenosinergic System for Huntington's Disease

BackgroundHuntington's disease (HD) is a neurodegenerative disease caused by a CAG trinucleotide expansion in the Huntingtin (Htt) gene. The expanded CAG repeats are translated into polyglutamine (polyQ), causing aberrant functions as well as aggregate formation of mutant Htt. Effective treatments for HD are yet to be developed.Methodology/Principal FindingsHere, we report a novel dual-function compound, N 6-(4-hydroxybenzyl)adenine riboside (designated T1-11) which activates the A2AR and a major adenosine transporter (ENT1). T1-11 was originally isolated from a Chinese medicinal herb. Molecular modeling analyses showed that T1-11 binds to the adenosine pockets of the A2AR and ENT1. Introduction of T1-11 into the striatum significantly enhanced the level of striatal adenosine as determined by a microdialysis technique, demonstrating that T1-11 inhibited adenosine uptake in vivo. A single intraperitoneal injection of T1-11 in wildtype mice, but not in A2AR knockout mice, increased cAMP level in the brain. Thus, T1-11 enters the brain and elevates cAMP via activation of the A2AR in vivo. Most importantly, addition of T1-11 (0.05 mg/ml) to the drinking water of a transgenic mouse model of HD (R6/2) ameliorated the progressive deterioration in motor coordination, reduced the formation of striatal Htt aggregates, elevated proteasome activity, and increased the level of an important neurotrophic factor (brain derived neurotrophic factor) in the brain. These results demonstrate the therapeutic potential of T1-11 for treating HD.Conclusions/SignificanceThe dual functions of T1-11 enable T1-11 to effectively activate the adenosinergic system and subsequently delay the progression of HD. This is a novel therapeutic strategy for HD. Similar dual-function drugs aimed at a particular neurotransmitter system as proposed herein may be applicable to other neurotransmitter systems (e.g., the dopamine receptor/dopamine transporter and the serotonin receptor/serotonin transporter) and may facilitate the development of new drugs for other neurodegenerative diseases.

Adenoviral astrocyte-specific expression of BDNF in the striata of mice transgenic for Huntington's disease delays the onset of the motor phenotype.

Huntington's disease (HD) is a neurodegenerative disorder characterized by motor, cognitive, and psychiatric symptoms. The most characteristic structural feature of this disease is neurodegeneration accompanied by gliosis in the striatum. BDNF has been proposed to protect striatal neurons from degeneration, because it is an important survival factor for these neurons from development to adulthood. Considering the extensive gliosis and the survival effects of BDNF, we constructed an adenovirus to express a BDNF cDNA in astrocyte cells using a promoter of the glial fibrillary acidic protein gene. Cells stably transfected in vitro with a BDNF cDNA driven by this promoter expressed BDNF and responded to external stimuli increasing BDNF production. When the vector was applied into the striata of mice transgenic for HD, long-term expression of the transgene was observed, associated with a delay of onset of the motor phenotype of the R6/2 HD transgenic mice. The present data indicate that the striatal expression of BDNF is a potential adjuvant for the treatment of HD.

Neuronal Store-Operated Calcium Entry Pathway as a Novel Therapeutic Target for Huntington's Disease Treatment

Huntington's disease (HD) is a neurodegenerative disorder caused by a polyglutamine expansion within Huntingtin (Htt) protein. In the phenotypic screen we identified a class of quinazoline-derived compounds that delayed a progression of a motor phenotype in transgenic Drosophila HD flies. We found that the store-operated calcium (Ca(2+)) entry (SOC) pathway activity is enhanced in neuronal cells expressing mutant Htt and that the identified compounds inhibit SOC pathway in HD neurons. The same compounds exerted neuroprotective effects in glutamate-toxicity assays with YAC128 medium spiny neurons primary cultures. We demonstrated a key role of TRPC1 channels in supporting SOC pathway in HD neurons. We concluded that the TRPC1-mediated neuronal SOC pathway constitutes a novel target for HD treatment and that the identified compounds represent a novel class of therapeutic agents for treatment of HD and possibly other neurodegenerative disorders.

Neuroprotective effects of creatine

There is a substantial body of literature, which has demonstrated that creatine has neuroprotective effects both in vitro and in vivo. Creatine can protect against excitotoxicity as well as against β-amyloid toxicity in vitro. We carried out studies examining the efficacy of creatine as a neuroprotective agent in vivo. We demonstrated that creatine can protect against excitotoxic lesions produced by N-methyl-D: -aspartate. We also showed that creatine is neuroprotective against lesions produced by the toxins malonate and 3-nitropropionic acid (3-NP) which are reversible and irreversible inhibitors of succinate dehydrogenase, respectively. Creatine produced dose-dependent neuroprotective effects against MPTP toxicity reducing the loss of dopamine within the striatum and the loss of dopaminergic neurons in the substantia nigra. We carried out a number of studies of the neuroprotective effects of creatine in transgenic mouse models of neurodegenerative diseases. We demonstrated that creatine produced an extension of survival, improved motor performance, and a reduction in loss of motor neurons in a transgenic mouse model of amyotrophic lateral sclerosis (ALS). Creatine produced an extension of survival, as well as improved motor function, and a reduction in striatal atrophy in the R6/2 and the N-171-82Q transgenic mouse models of Huntington's disease (HD), even when its administration was delayed until the onset of disease symptoms. We recently examined the neuroprotective effects of a combination of coenzyme Q10 (CoQ10) with creatine against both MPTP and 3-NP toxicity. We found that the combination of CoQ and creatine together produced additive neuroprotective effects in a chronic MPTP model, and it blocked the development of alpha-synuclein aggregates. In the 3-NP model of HD, CoQ and creatine produced additive neuroprotective effects against the size of the striatal lesions. In the R6/2 transgenic mouse model of HD, the combination of CoQ and creatine produced additive effects on improving survival. Creatine may stabilize mitochondrial creatine kinase, and prevent activation of the mitochondrial permeability transition. Creatine, however, was still neuroprotective in mice, which were deficient in mitochondrial creatine kinase. Administration of creatine increases the brain levels of creatine and phosphocreatine. Due to its neuroprotective effects, creatine is now in clinical trials for the treatment of Parkinson's disease (PD) and HD. A phase 2 futility trial in PD showed approximately a 50% improvement in Unified Parkinson's Disease Rating Scale at one year, and the compound was judged to be non futile. Creatine is now in a phase III clinical trial being carried out by the NET PD consortium. Creatine reduced plasma levels of 8-hydroxy-2-deoxyguanosine in HD patients phase II trial and was well-tolerated. Creatine is now being studied in a phase III clinical trial in HD, the CREST trial. Creatine, therefore, shows great promise in the treatment of a variety of neurodegenerative diseases.

Deep Brain Stimulation in Huntington’s Disease: The Current Status

Background: Huntington's disease (HD), a progressive neurodegenerative disorder, is characterized by choreic movements and psychiatric changes. Within 10 to 20 years after the onset of the disease most patients die of disease - related complications. Until now, no effective therapies have been found for this devastating disease. Deep brain stimula- tion (DBS) is a promising new symptomatic treatment for HD. In the last decade, theories on the potential benefit of DBS in HD have been made and different groups have explored this in case studies. Objectives: In this paper we provide an overview of the result obtained with DBS in patients with HD. Results: The studies performed thus far are case studies. Their results suggest that DBS of the globus pallidus internus is safe and well-tolerated, and reduces choreic movements, without substantial effects on psychiatric functions. Conclusions: DBS in HD should still be seen as experimental. The data published until now, demonstrate a therapeutic ef- fect on refractory motor symptoms and justify further investigation.

Prediction of a new surface binding pocket and evaluation of inhibitors against huntingtin interacting protein 14: an insight using docking studies

Protein-protein interactions play an important role in regulating the expression of huntingtin protein (htt). Expansion of polyglutamine tracts in htt results in neurodegenerative Huntington disease. Huntingtin interacting protein (HIP14) is an important interacting partner of htt and the altered interactions have been proposed to play an important role in disease progression. In the present study, an attempt has been made to explore the potential of several known Huntington inhibitors to inhibit HIP14. The docking studies have resulted in the identification of a novel binding site for these inhibitors distinct from the previously known ankyrin repeat domain. The results have been validated using geometry based docking transformations against the other binding pocket. The specificity of binding has been determined with high values of both accuracy and precision. Nine potential inhibitors obtained after screening belong to three distinct classes of compounds viz, carbohydrates (deoxy-glucose), alcohols (including phenolic scaffold) and tetracycline. The compounds form stable complex with protein exhibiting optimal intermolecular and Gibbs free energy. The hydrogen bonding and hydrophobic interactions predominantly contribute to the stability of these complexes. The present study identifies metoprolol, minocyclines and 18 F fluorodeoxyglucose as the best inhibitors that bind specifically to the new site. Therefore, these compounds can further be exploited for their potential to serve in the diagnosis and treatment of Huntington disease. The quantitative predictions provide a scope for experimental testing in future.

Small Changes, Big Impact

Huntington disease (HD) is a neurodegenerative disorder caused by an elongated polyglutamine tract in huntingtin (htt). htt normally undergoes different posttranslational modifications (PTMs), including phosphorylation, SUMOylation, ubiquitination, acetylation, proteolytic cleavage, and palmitoylation. In the presence of the HD mutation, some PTMs are significantly altered and can result in changes in the clinical phenotype. A rate-limiting PTM is defined as one that can result in significant effects on the phenotype in animal models. For example, the prevention of proteolysis at D586 as well as constitutive phosphorylation at S13 and S16 can obviate the expression of phenotypic features of HD. The enzymes involved in these modifications such as caspase-6, the IκB kinase (IKK) complex, and still to be characterized phosphatases therefore represent promising therapeutic targets for HD. Identifying and testing specific modulators of PTMs now constitute the next big challenges in order to further validate these targets and proceed towards the goal of a mechanism-based treatment for HD.

The importance of integrating basic and clinical research toward the development of new therapies for Huntington disease

Huntington disease (HD) is a dominantly inherited neurodegenerative disorder that results from expansion of the polyglutamine repeat in the huntingtin (HTT) gene. There are currently no effective treatments for this devastating disease. Given its monogenic nature, disease modification therapies for HD should be theoretically feasible. Currently, pharmacological therapies aimed at disease modification by altering levels of HTT protein are in late-stage preclinical development. Here, we review current efforts to develop new treatments for HD based on our current understanding of HTT function and the main pathological mechanisms. We emphasize the need to enhance translational efforts and highlight the importance of aligning the clinical and basic research communities to validate existing hypotheses in clinical studies. Human and animal therapeutic trials are presented with an emphasis on cellular and molecular mechanisms relevant to disease progression.

Role of Inositol 1,4,5-Trishosphate Receptors in Pathogenesis of Huntington’s Disease and Spinocerebellar Ataxias

Huntington's disease (HD) and spinocerebellar ataxias (SCAs) are autosomal-dominant neurodegenerative disorders. HD is caused by polyglutamine (polyQ) expansion in the amino-terminal region of a protein huntingtin (Htt) and primarily affects medium spiny striatal neurons (MSN). Many SCAs are caused by polyQ-expansion in ataxin proteins and primarily affect cerebellar Purkinje cells. The reasons for neuronal dysfunction and death in HD and SCAs remain poorly understood and no cure is available for the patients. Our laboratory discovered that mutant huntingtin, ataxin-2 and ataxin-3 proteins specifically bind to the carboxy-terminal region of the type 1 inositol 1,4,5-trisphosphate receptor (IP(3)R1), an intracellular Ca(2+) release channel. Moreover, we found that association of mutant huntingtin or ataxins with IP(3)R1 causes sensitization of IP(3)R1 to activation by IP(3) in planar lipid bilayers and in neuronal cells. These results suggested that deranged neuronal Ca(2+) signaling might play an important role in pathogenesis of HD, SCA2 and SCA3. In support of this idea, we demonstrated a connection between abnormal Ca(2+) signaling and neuronal cell death in experiments with HD, SCA2 and SCA3 transgenic mouse models. Additional data in the literature indicate that abnormal neuronal Ca(2+) signaling may also play an important role in pathogenesis of SCAl, SCA5, SCA6, SCA14 and SCA15/16. Based on these results I propose that IP(3)R and other Ca(2+) signaling proteins should be considered as potential therapeutic targets for treatment of HD and SCAs.

Predictive genetic testing in Huntington′s disease

Predictive genetic testing in Huntington′s disease

Up-regulation of the isoenzymes MAO-A and MAO-B in the human basal ganglia and pons in Huntington's disease revealed by quantitative enzyme radioautography

Huntington's disease (HD) is a rare genetic disease associated with the degeneration of GABAergic striatal projection neurons in the basal ganglia leading to movement disorders with behavioral symptoms for which there is presently no therapy. Abnormally high levels of monoamine oxidase (MAO) activity, which are potentially linked to cytotoxic free radical formation, are known to occur during aging and in neurodegenerative disorders (MAO-B is markedly increased in plaque-associated astrocytes in Alzheimer's disease). We therefore measured, with anatomical resolution, MAO-A and -B activities in 5 cases of HD (severity grades 1–3) and age-matched controls by quantitative enzyme radioautography using radiolabeled enzyme inhibitors 3H-Ro 41-1049 and 3H-lazabemide, respectively, as high-affinity ligands in vitro. MAO-A was increased significantly (ca. 50%; p<0.01) in the putamen and substantia nigra pars compacta of the basal ganglia and in the pons. Higher increases in MAO-B (75%–200%; p<0.01) occurred in the putamen, ventral striatum, globus pallidus externus and internus of the basal ganglia and in the insular cortex. The increased enzyme levels (especially of MAO-B) seemed to correlate with the grade of disease severity. We conclude that MAO increases in those regions of HD brains which are known to undergo neurodegeneration accompanied by glioses. Whether or not this increased enzyme activity is a cause or effect of the resulting loss of the GABAergic projection neurons in HD is yet to be clarified. Moreover, it remains to be seen if selective enzyme inhibitors have therapeutic utility in the treatment of HD by reducing oxidative stress locally.

Brief ampakine treatments slow the progression of Huntington's disease phenotypes in R6/2 mice

Daily, systemic injections of a positive AMPA-type glutamate receptor modulator (ampakine) have been shown to reduce synaptic plasticity defects in rodent models of aging and early-stage Huntington's disease (HD). Here we report that long-term ampakine treatment markedly slows the progression of striatal neuropathology and locomotor dysfunction in the R6/2 HD mouse model. Remarkably, these effects were produced by an ampakine, CX929, with a short half-life. Injected once daily for 4–7 weeks, the compound increased protein levels of brain-derived neurotrophic factor (BDNF) in the neocortex and striatum of R6/2 but not wild-type mice. Moreover, ampakine treatments prevented the decrease in total striatal area, blocked the loss of striatal DARPP-32 immunoreactivity and reduced by 36% the size of intra-nuclear huntingtin aggregates in R6/2 striatum. The CX929 treatments also markedly improved motor performance of R6/2 mice on several measures (rotarod, vertical pole descent) but did not influence body weight or lifespan. These findings describe a minimally invasive, pharmacologically plausible strategy for treatment of HD and, potentially, other neuropathological diseases.

Type 2 transglutaminase in Huntington’s disease: a double‐edged sword with clinical potential

Huntington's disease (HD) is a dominant genetic neurodegenerative disorder. The pathology affects principally neurons in the basal ganglia circuits and terminates invariably in death. There is compelling necessity for safe and effective therapeutic strategies to arrest, or even retard the progression of the pathogenesis. Recent findings indicate the autophagy-lysosome systems as appealing targets for pharmacological intervention. Autophagy exerts a critical role in controlling neuronal protein homeostasis, which is perturbed in HD, and is compromised in the pathogenesis of several neurodegenerative diseases. Type 2 transglutaminase (TG2) plays an important role both in apoptosis and autophagy regulation, and accumulates at high levels in cells under stressful conditions. TG2 inhibition, achieved either via drug treatments or genetic approaches, has been shown to be beneficial for the treatment of HD in animal models. In this review we will discuss the relevance of TG2 to the pathogenesis of HD, in an effort to define novel therapeutic avenues.

ERK activation by the polyphenols fisetin and resveratrol provides neuroprotection in multiple models of Huntington's disease

Huntington's disease (HD) is an inherited, progressive and ultimately fatal neurodegenerative disorder that is characterized by psychiatric, cognitive and motor symptoms. Among the pathways implicated in HD are those involving mitogen-activated protein kinase signaling and particularly the Ras-extracellular signal-regulated kinase (ERK) cascade. Studies in both cells and animal models suggest that ERK activation might provide a novel therapeutic target for the treatment of HD but compounds that specifically activate ERK are few. To test the hypothesis that pharmaceutical activation of ERK might be protective for HD, a polyphenol, fisetin, which was previously shown to activate the Ras-ERK cascade, was tested in three different models of HD: PC12 cells expressing mutant Httex1 under the control of an inducible promoter, Drosophila expressing mutant Httex1 and the R6/2 mouse model of HD. The results indicate that fisetin can reduce the impact of mutant huntingtin in each of these disease models. Prompted by this observation, we determined that the related polyphenol, resveratrol, also activates ERK and is protective in HD models. Notably, although more than a dozen small molecule inhibitors of ERK activation are in clinical trials, very few small molecule activators of ERK signaling are reported. Thus, fisetin, resveratrol and related compounds might be useful for the treatment of HD by virtue of their unique ability to activate ERK.

Altered cholesterol homeostasis contributes to enhanced excitotoxicity in Huntington’s disease

Recent findings suggest that altered cholesterol homeostasis may contribute to the pathophysiology of Huntington's disease (HD). To understand the underlying mechanisms, here we used a combination of two-photon microscopy, epifluorescence, and biochemical methods to visualize and quantify lipid distribution in cell cultures expressing mutant huntingtin. Such expression promotes lipid imbalance, and cholesterol accumulation in cellular and murine models and in HD-affected human brains. Interestingly, cells expressing mutant huntingtin also showed higher content of ordered domains in their plasma membranes. These findings correlated with high levels of caveolin-1 and glycosphingolipid GM1, two well-defined markers of cholesterol-enriched domains, at the cell surface. In addition, cells expressing mutant huntingtin showed increased localization of NMDA receptors with cholesterol-enriched domains, contributing to increased NMDA receptor susceptibility to excitotoxic insults. Treatment with simvastatin or β-cyclodextrin, two cholesterol-lowering drugs, reduced the content of ordered domains at the cell surface, which in turn, protected cells against NMDA-mediated excitotoxicity. Taken together, our results indicate that mutant huntingtin produces accumulation of cholesterol and alters its cellular distribution that contributes to NMDA-mediated excitotoxicity. Administration of drugs that recover this effect, such as simvastatin could be beneficial for the treatment of HD.

B14 Neurotrophic factors secreting mesenchymal stem cells attenuate quinolinic acid induced striatal lesion model suggesting autologous therapy for HD

BackgroundWe have been studying the potential of utilising the patients' own bone marrow derived mesenchymal stem cells (MSCs) which are transformed into cellular vectors secreting neurotrophic factors (NTF+ cells) in...

L01 Global site and investigator database (GSID-HD): a new tool to promote research collaboration and manage efficient clinical trials in Huntington's disease

BackgroundA global comprehensive database of sites and investigators does not exist. The Huntington Study Group (HSG) has a database of member sites and the European HD Network (EHDN) maintains site...

Derivation of Huntington's Disease-Affected Human Embryonic Stem Cell Lines

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease caused by an expansion of cytosine-adenine-guanine (CAG) repeats in the Huntingtin gene Htt. To facilitate research into HD, we have derived 4 human embryonic stem cell (hESC) lines containing ≥ 40 CAG repeats in exon 1 of Htt: SIVF017-HD (CAG₄₀), SIVF018-HD (CAG₄₆), SIVF020-HD (CAG₄₈), and SIVF046-HD (CAG₄₅). Additionally, we have derived a normal sibling-matched control for SIVF020-HD, cell line SIVF019. All 5 hESC lines had a normal karyotype, expressed pluripotency markers including Oct4, SSEA3, and Tra-1-81, and could be maintained in culture for multiple (>40) passages. Teratoma studies revealed that the hESC lines were capable of differentiating into cells representative of the 3 germ layers. Furthermore, in vitro neuronal differentiation experiments have confirmed that the hESC lines were able to generate MAP2-positive neuronal cells that express the Htt protein. Combined, these experiments confirm that the cell lines represent pluripotent stem cell lines. These HD-affected hESC lines will be made available to biomedical research laboratories and will provide a valuable tool to investigate the mechanisms and potential treatments for HD.

Comparison of Transplant Efficiency between Spontaneously Derived and Noggin-Primed Human Embryonic Stem Cell Neural Precursors in the Quinolinic Acid Rat Model of Huntington's Disease

Human neural precursors (hNP) derived from embryonic stem cells (hESC) may provide a viable cellular source for transplantation therapy for Huntington's disease (HD). However, developing effective transplantation therapy for the central nervous system (CNS) using hESC relies on optimizing the in vitro production of hNP to control appropriate in vivo posttransplantation neuronal differentiation. The current study provides the first direct in vivo comparison of the transplant efficiency and posttransplantation characteristics of spontaneously derived and noggin-primed hNP following transplantation into the quinolinic acid (QA) rat model of HD. We show that spontaneously derived and noggin-primed hNP both survived robustly up to 8 weeks after transplantation into the QA-lesioned striatum of the adult rat. Transplanted hNP underwent extensive migration and large-scale differentiation towards a predominantly neuronal fate by 8 weeks posttransplantation. Furthermore, in vitro noggin priming of hNP specifically increased the extent of neuronal differentiation at both 4 and 8 weeks posttransplantation when compared to spontaneously derived hNP grafts. The results of this study suggest that in vitro noggin priming provides an effective mechanism by which to enhance hNP transplant efficiency for the treatment of HD.

Effects of FGF receptor peptide agonists on animal behavior under normal and pathological conditions

Hexafins are recently identified low-molecular-weight peptide agonists of the fibroblast growth factor receptor (FGFR), derived from the β6–β7 loop region of various FGFs. Synthetic hexafin peptides have been shown to bind to and induce tyrosine phosphorylation of FGFR1, stimulate neurite outgrowth, and promote neuronal survival in vitro. Thus, the pronounced biological activities of hexafins in vitro make them attractive compounds for pharmacological studies in vivo. The present study investigated the effects of subcutaneous administration of hexafin1 and hexafin2 (peptides derived from FGF1 and FGF2, respectively) on social memory, exploratory activity, and anxiety-like behavior in adult rats. Treatment with hexafin1 and hexafin2 resulted in prolonged retention of social memory. Furthermore, rats treated with hexafin2 exhibited decreased anxiety-like behavior in the elevated plus maze. Employing an R6/2 mouse model of Huntington's disease (HD), we found that although hexafin2 did not affect the progression of motor symptoms, it alleviated deficits in activity related to social behavior, including sociability and social novelty. Thus, hexafin2 may have therapeutic potential for the treatment of HD.