Mitochondrial dysfunction and Huntington disease

Huntington disease （HD） is a chronic autosomal-dominant neurodegenerative disease. The gene coding Huntingtin has been identified, but the pathogenic mechanisms of the disease are still not fully understood. This paper reviews the involvement of mitochondrial dysfunction in pathogenesis of HD.

Clinical features of Huntington disease in 243 Chinese patients

OBJECTIVE： To thoroughly explore the clinical characteristics of Huntington disease in China. METHODS： A computer-based online search of China National Knowledge Infrastructure was performed to review case reports concerning Huntington disease published between 1980 and 2008; the clinical characteristics were analyzed. RESULTS： A total of 80 studies involving 243 patients （142 males and 101 females） were collected, 82.0% of which were from provinces of North China. In addition, 97.1% of the cases had a family history of Huntington disease, and paternal inheritance （64.6%） was greater than maternal inheritance （35.4%）. Moreover, onset age was significantly less than from maternal inheritance. The mean onset age of Huntington disease was （35.2 ± 11.5） years, mean age of death was （45.6 ± 13.5） years, and the mean course of disease from onset to death was （11.6 ± 5.6） years. Onset characterized by involuntary movement accounted for 47.7%, including 66.4% in the entire body, 16.4% in the upper limbs, and 14.7% in the head and face. Psychiatric symptoms accounted for 18.1%, and disturbed intelligence accounted for 2.1%. With disease progression, 99.5% of patients exhibited involuntary movement, 69.8% displayed cognitive impairment, and 39.2% suffered from psychiatric symptoms. In addition, 38.7% of patients were complicated by dysarthria, dysphagia, and cough after drinking. A total of 70.8% of patients exhibited an abnormal electroencephalogram, 18.8% had mild abnormalities in the cerebrospinal fluid, and 70.1% displayed brain atrophy and lateral ventriculomegaly on CT or MRI. A total of 88.9% of patients scored ≤ 23 in the Mini-Mental State Examination （MMSE）. Of the reported patients, only 22 underwent/T15 gene testing with positive results. CONCLUSION： Huntington disease is more frequently detected in males than females, and the majority has a family history. The disease has high incidence in Northern China, in particular with paternal inheritance. In addition, the disease often struck middle-aged people, and the time of onset in paternal inheritance was earlier than maternal inheritance. There were no significant differences in age of onset between males and females, and the course of disease was not related to paternal or maternal inheritance. The symptoms of onset included involuntary movement, complicated by psychiatric symptoms, and rarely cognitive impairment. In addition, involuntary movement of the pharynx was commonly observed in patients. Genetic detection has been the gold standard for clinical diagnosis of Huntington disease, and more attention should be paid to this detection method.

Therapeutic advances in neural regeneration for Huntington’s disease

Huntington’s disease is a neurodegenerative disease caused by the expansion mutation of a cytosine-adenine-guanine triplet in the exon 1 of the HTT gene which is responsible for the production of the huntingtin (Htt) protein. In physiological conditions, Htt is involved in many cellular processes such as cell signaling, transcriptional regulation, energy metabolism regulation, DNA maintenance, axonal trafficking, and antiapoptotic activity. When the genetic alteration is present, the production of a mutant version of Htt (mHtt) occurs, which is characterized by a plethora of pathogenic activities that, finally, lead to cell death. Among all the cells in which mHtt exerts its dangerous activity, the GABAergic Medium Spiny Neurons seem to be the most affected by the mHtt-induced excitotoxicity both in the cortex and in the striatum. However, as the neurodegeneration proceeds ahead the neuronal loss grows also in other brain areas such as the cerebellum, hypothalamus, thalamus, subthalamic nucleus, globus pallidus, and substantia nigra, determining the variety of symptoms that characterize Huntington’s disease. From a clinical point of view, Huntington’s disease is characterized by a wide spectrum of symptoms spanning from motor impairment to cognitive disorders and dementia. Huntington’s disease shows a prevalence of around 3.92 cases every 100,000 worldwide and an incidence of 0.48 new cases every 100,000/year. To date, there is no available cure for Huntington’s disease. Several treatments have been developed so far, aiming to reduce the severity of one or more symptoms to slow down the inexorable decline caused by the disease. In this context, the search for reliable strategies to target the different aspects of Huntington’s disease become of the utmost interest. In recent years, a variety of studies demonstrated the detrimental role of neuronal loss in Huntington’s disease condition highlighting how the replacement of lost cells would be a reasonable strategy to overcome the neurodegeneration. In this view, numerous have been the attempts in several preclinical models of Huntington’s disease to evaluate the feasibility of invasive and non-invasive approaches. Thus, the aim of this review is to offer an overview of the most appealing approaches spanning from stem cell-based cell therapy to extracellular vesicles such as exosomes in light of promoting neurogenesis, discussing the results obtained so far, their limits and the future perspectives regarding the neural regeneration in the context of Huntington’s disease.

The role of exosomes in adult neurogenesis:implications for neurodegenerative diseases

Exosomes are cup-shaped extracellular vesicles with a lipid bilayer that is approximately 30 to 200 nm in thickness.Exosomes are widely distributed in a range of body fluids,including urine,blood,milk,and saliva.Exosomes exert biological function by transporting factors between different cells and by regulating biological pathways in recipient cells.As an important form of intercellular communication,exosomes are increasingly being investigated due to their ability to transfer bioactive molecules such as lipids,proteins,mRNAs,and microRNAs between cells,and because they can regulate physiological and pathological processes in the central nervous system.Adult neurogenesis is a multistage process by which new neurons are generated and migrate to be integrated into existing neuronal circuits.In the adult brain,neurogenesis is mainly localized in two specialized niches:the subventricular zone adjacent to the lateral ventricles and the subgranular zone of the dentate gyrus.An increasing body of evidence indicates that adult neurogenesis is tightly controlled by environmental conditions with the niches.In recent studies,exosomes released from different sources of cells were shown to play an active role in regulating neurogenesis both in vitro and in vivo,thereby participating in the progression of neurodegenerative disorders in patients and in various disease models.Here,we provide a state-of-the-art synopsis of existing research that aimed to identify the diverse components of exosome cargoes and elucidate the therapeutic potential of exosomal contents in the regulation of neurogenesis in several neurodegenerative diseases.We emphasize that exosomal cargoes could serve as a potential biomarker to monitor functional neurogenesis in adults.In addition,exosomes can also be considered as a novel therapeutic approach to treat various neurodegenerative disorders by improving endogenous neurogenesis to mitigate neuronal loss in the central nervous system.

Antisense therapy:a potential breakthrough in the treatment of neurodegenerative diseases

Neurodegenerative diseases are a group of disorders characterized by the progressive degeneration of neurons in the central or peripheral nervous system.Currently,there is no cure for neurodegenerative diseases and this means a heavy burden for patients and the health system worldwide.Therefore,it is necessary to find new therapeutic approaches,and antisense therapies offer this possibility,having the great advantage of not modifying cellular genome and potentially being safer.Many preclinical and clinical studies aim to test the safety and effectiveness of antisense therapies in the treatment of neurodegenerative diseases.The objective of this review is to summarize the recent advances in the development of these new technologies to treat the most common neurodegenerative diseases,with a focus on those antisense therapies that have already received the approval of the U.S.Food and Drug Administration.

Mitochondria in Huntington’s disease:implications in pathogenesis and mitochondrial-targeted therapeutic strategies

Huntington’s disease is a genetic disease caused by expanded CAG repeats on exon 1 of the huntingtin gene located on chromosome 4.Compelling evidence implicates impaired mitochondrial energetics,altered mitochondrial biogenesis and quality control,disturbed mitochondrial trafficking,oxidative stress and mitochondrial calcium dyshomeostasis in the pathogenesis of the disorder.Unfortunately,conventional mitochondrial-targeted molecules,such as cysteamine,creatine,coenzyme Q10,or triheptanoin,yielded negative or inconclusive results.However,future therapeutic strategies,aiming to restore mitochondrial biogenesis,improving the fission/fusion balance,and improving mitochondrial trafficking,could prove useful tools in improving the phenotype of Huntington’s disease and,used in combination with genome-editing methods,could lead to a cure for the disease.

Huntington Disease in Asia

Objective： The objective was to review the major di fferences of Huntington disease （HD） in Asian population fiom those in the Caucasian population. Data Sources： Data cited in this review were obtained from PubMed database and China National Knowledge Infrastructure （CN KI） fiom 1994 to 2014. All the papers were written in English or Chinese languages, with the terms of Asia/Asian, H D, genotype, epidemiology, phenotype, and treatment used for the literature search. Study Selection： From the PubMed database, we included the articles and reviews which contained the HD patients＇ data from Asian countries. From the CNKI, we excluded the papers which were not original research. Due to tile language＇s restrictions, those data published in other languages were not included. Results： In total, 50 papers were cited in this review, authors of which were from tile mainland of China, .lapan, India, Thailand, Taiwan （China）, Korea, and western countries. Conclusions： The lower epidemiology in Asians can be partly explained by the less cytosine-adenine-guanine repeats, different haplotypes, and CCG polymorphisms. For the physicians, atypical clinical profiles such as the initial symptom of ataxia, movement abnormalities of Parkinsonism, dystonia, or tics need to be paid more attention to and suggest gene testing if necessary. Moreover, some pathogenesis studies may help progress some new advanced treatments. The clinicians in Asian especially in China should promote the usage of genetic testing and put more effects in rehabilitation, palliative care, and offer comfort of patients and their families. The unified HD rating scale also needs to be popularized in Asia to assist in evaluating the progression of HD.

Development of Research on Huntington Disease in China

Huntington disease（HD） is a progressive autosomal dominantly inherited neurodegenerative disorder, characterized with the typical manifestations of involuntary movements, cognitive dysfunction, and psychiatric or behavioral disturbance. It results from an expansion in the number of CAG repeats in the first exon of the huntingtin（HTT） gene. In China, since the first case report in 1959, the knowledge of this disorder has been involving a lot, especially in the latest decade. In this review, we meta-analysis and summarize the research reports that were published by Chinese researchers since 1959, so that researchers whose native language were not Chinese can get a general idea of the research development of HD in China. Briefly, the research of HD in China can be broadly divided into three stages. Firstly,before 1993, there were scattered case reports of HD that were solely based on Clinical features and family history. Then,with the discovery of the HD gene in 1993, it became possible for the genetic confirmation of the reported cases that made the diagnosis more accurate and informative. In the last few years,Chinese researchers who were active in the HD research started to build their own database to study the clinical and genetic feature of this disorder and also collaborated a lot in this field. The progress outlined in this review indicates the beginning of an exciting new era in HD research in China.

Clinical trial perspective for adult and juvenile Huntington's disease using genetically-engineered mesenchymal stem cells

Progress to date from our group and others indicate that using genetically-engineered mesenchymal stem cells（MSC） to secrete brain-derived neurotrophic factor（BDNF） supports our plan to submit an Investigational New Drug application to the Food and Drug Administration for the future planned Phase 1 safety and tolerability trial of MSC/BDNF in patients with Huntington＇s disease（HD）. There are also potential applications of this approach beyond HD. Our biological delivery system for BDNF sets the precedent for adult stem cell therapy in the brain and could potentially be modified for other neurodegenerative disorders such as amyotrophic lateral sclerosis（ALS）, spinocerebellar ataxia（SCA）, Alzheimer＇s disease, and some forms of Parkinson＇s disease. The MSC/BDNF product could also be considered for studies of regeneration in traumatic brain injury, spinal cord and peripheral nerve injury. This work also provides a platform for our future gene editing studies, since we will again use MSCs to deliver the needed molecules into the central nervous system.

Altered microRNA expression in animal models of Huntington’s disease and potential therapeutic strategies

A review of recent animal models of Huntington’s disease showed many microRNAs had altered expression levels in the striatum and cerebral cortex,and which were mostly downregulated.Among the altered microRNAs were miR-9/9*,miR-29b,miR-124a,miR-132,miR-128,miR-139,miR-122,miR-138,miR-23b,miR-135b,miR-181(all downregulated)and miR-448(upregulated),and similar changes had been previously found in Huntington’s disease patients.In the animal cell studies,the altered microRNAs included miR-9,miR-9*,miR-135b,miR-222(all downregulated)and miR-214(upregulated).In the animal models,overexpression of miR-155 and miR-196a caused a decrease in mutant huntingtin mRNA and protein level,lowered the mutant huntingtin aggregates in striatum and cortex,and improved performance in behavioral tests.Improved performance in behavioral tests also occurred with overexpression of miR-132 and miR-124.In the animal cell models,overexpression of miR-22 increased the viability of rat primary cortical and striatal neurons infected with mutant huntingtin and decreased huntingtin-enriched foci of≥2μm.Also,overexpression of miR-22 enhanced the survival of rat primary striatal neurons treated with 3-nitropropionic acid.Exogenous expression of miR-214,miR-146a,miR-150,and miR-125b decreased endogenous expression of huntingtin mRNA and protein in HdhQ111/HdhQ111 cells.Further studies with animal models of Huntington’s disease are warranted to validate these findings and identify specific microRNAs whose overexpression inhibits the production of mutant huntingtin protein and other harmful processes and may provide a more effective means of treating Huntington’s disease in patients and slowing its progression.

Promises and pitfalls of immune-based strategies for Huntington's disease

Huntington＇s disease （HD） is an autosomal-dominant neurodegenerative disease characterized by the selec- tive loss of neurons in the striatum and cortex, leading to progressive motor dysfunction, cognitive decline and behavioral symptoms. HD is caused by a trinucleotide （CAG） repeat expansion in the gene encoding for huntingtin. Several studies have suggested that inflammation is an important feature of HD and it is already observed in the early stages of the disease. Recently, new molecules presenting anti-inflammatory and/or immunomodulatory have been investigated for HD. The objective of this review is to discuss the data obtained so far on the immune-based therapeutic strategies for HD.

Factors contributing to clinical picture and progression of Huntington's disease

Huntington’s disease（HD）is an autosomal dominant,monogenic,progressive,neurodegenerative and rare disease with a frequency of10 per 100,000 in the Caucasian population and occurring more rarely in other races（Squitieri et al.,1994）.HD is,nevertheless,one of the most frequently and extensively studied diseases of those caused by a dynamic mutation.The HD mutation is located on the short arm of the 4th chromosome within the HTT gene.

Adenyl cyclase activator forskolin protects against Huntington's disease-like neurodegenerative disorders

Long term suppression of succinate dehydrogenase by selective inhibitor 3-nitropropionic acid has been used in rodents to model Huntington＇s disease where mitochondrial dysfunction and oxidative damages are primary pathological hallmarks for neuronal damage. Improvements in learning and memory abilities, recovery of energy levels, and reduction of excitotoxicity damage can be achieved through activation of Adenyl cyclase enzyme by a specific phytochemical forskolin. In this study, intraperitoneal administration of 10 mg/kg 3-nitropropionic acid for 15 days in rats notably reduced body weight, worsened motor cocordination（grip strength, beam crossing task, locomotor activity）, resulted in learning and memory deficits, greatly increased acetylcholinesterase, lactate dehydrogenase, nitrite, and malondialdehyde levels, obviously decreased adenosine triphosphate, succinate dehydrogenase, superoxide dismutase, catalase, and reduced glutathione levels in the striatum, cortex and hippocampus. Intragastric administration of forskolin at 10, 20, 30 mg/kg dose-dependently reversed these behavioral, biochemical and pathological changes caused by 3-nitropropionic acid. These results suggest that forskolin exhibits neuroprotective effects on 3-nitropropionic acid-induced Huntington＇s disease-like neurodegeneration.

Long-noncoding RNAs as epigenetic regulators in neurodegenerative diseases

The growing and rapid development of high-throughput sequencing technologies have allowed a greater understanding of the mechanisms underlying gene expression regulation.Editing the epigenome and epitranscriptome directs the fate of the transcript influencing the functional outcome of each mRNA.In this context,non-coding RNAs play a decisive role in addressing the expression regulation at the gene and chromosomal levels.Long-noncoding RNAs,consisting of more than 200 nucleotides,have been shown to act as epigenetic regulators in several key molecular processes involving neurodegenerative disorders,such as Alzheimer’s disease,Parkinson’s disease,amyotrophic lateral sclerosis and Huntington’s disease.Long-noncoding RNAs are abundantly expressed in the central nervous system,suggesting that their deregulation could trigger neuronal degeneration through RNA modifications.The evaluation of their diagnostic significance and therapeutic potential could lead to new treatments for these diseases for which there is no cure.

Hope in Huntington's disease A survey in counseling patients with Huntington's disease,as well as the caregivers

BACKGROUND： It is difficult to attract interest in non-compulsory, preventive, medical care, and persons diagnosed with certain diseases often ignore the existence of these diseases. However, Huntington＇s disease （HD） is an exception. OBJECTIVE： To qualitatively analyze factors motivating HD patients to participate in a study, namely the European Huntington＇s Disease Network （EHDN） REGISTRY. DESIGN, TIME AND SETTING： An observational survey was conducted in the EHDN Study Site in Poznan, Poland between 2007 and 2008. PARTICIPANTS： The study involved 22 persons affected with HD and 3 pre-symptomatic individuals totaling 9 males and 16 females. The 24 participants in this study had 24 different caregivers. A total of 25 symptomatic or pre-symptomatic subjects participated in the initial REGISTRY visit, as well as 6 in the second, and 1 in the third. All subjects did not know each other prior to the visit. METHODS： A mutation in the IT15 gene was confirmed in each patient or pre-symptomatic mutation carrier. An in-depth interview produced detailed information on the HD patients, as well as the caregivers, for the REGISTRY study. MAIN OUTCOME MEASURES： A qualitative analysis of the factors motivating HD patients and the pre-symptomatic mutation carriers to participate in the REGISTRY longitudinal, observational, research project was performed. RESULTS： The primary motivating factor for involvement of HD patients and the caregivers in the REGISTRY study was the hope that an effective HD therapy would soon be discovered. In HD patients and the pre-symptomatic group, the response to participate in the REGISTRY project reached 100%, despite the fact that they knew the project was only an observational study. CONCLUSION： Patient hope is thought to be a factor for engaging in preventive, therapeutic activities. However, this is rarely mentioned in medical papers and clinical textbooks, and is usually overlooked in medical teaching. Clearly, efforts should be made to include this in clinical practice.

Neuroimaging in Huntington's disease

Huntington's disease(HD) is a progressive and fatal neurodegenerative disorder caused by an expanded tri-nucleotide CAG sequence in huntingtin gene(HTT) on chromosome 4. HD manifests with chorea, cognitive and psychiatric symptoms. Although advances in genetics allow identification of individuals carrying the HD gene, much is still unknown about the mechanisms underly-ing the development of overt clinical symptoms and the transitional period between premanifestation and mani-festation of the disease. HD has no cure and patients rely only in symptomatic treatment. There is an urgent need to identify biomarkers that are able to monitor disease progression and assess the development and efficacy of novel disease modifying drugs. Over the past years, neuroimaging techniques such as magnetic resonance imaging(MRI) and positron emission tomog-raphy(PET) have provided important advances in our understanding of HD. MRI provides information about structural and functional organization of the brain, while PET can detect molecular changes in the brain. MRI and PET are able to detect changes in the brains of HD gene carriers years ahead of the manifestation of the dis-ease and have also proved to be powerful in assessingdisease progression. However, no single technique hasbeen validated as an optimal biomarker. An integrativemultimodal imaging approach, which combines differ-ent MRI and PET techniques, could be recommendedfor monitoring potential neuroprotective and preventivetherapies in HD. In this article we review the currentneuroimaging literature in HD.

Emotion recognition and inhibitory control in manifest and pre-manifest Huntington’s disease: evidence from a new Stroop task

Huntington’s disease(HD)is a genetic neurodegenerative disorder that affects not only the motor but also the cognitive domain.In particular,cognitive symptoms such as impaired executive skills and deficits in recognizing other individuals’mental state may emerge many years before the motor symptoms.This study was aimed at testing two cognitive hypotheses suggested by previous research with a new Stroop task created for the purpose:1)the impairment of emotion recognition in HD is moderated by the emotions’valence,and 2)inhibitory control is impaired in HD.Forty manifest and 20 pre-manifest HD patients and their age-and gender-matched controls completed both the traditional“Stroop Color and Word Test”(SCWT)and the newly created“Stroop Emotion Recognition under Word Interference Task”(SERWIT),which consist in 120 photographs of sad,calm,or happy faces with either congruent or incongruent word interference.On the SERWIT,impaired emotion recognition in manifest HD was moderated by emotion type,with deficits being larger in recognizing sadness and calmness than in recognizing happiness,but it was not moderated by stimulus congruency.On the SCWT,six different interference scores yielded as many different patterns of group effects.Overall our results corroborate the hypothesis that impaired emotion recognition in HD is moderated by the emotions’valence,but do not provide evidence for the hypothesis that inhibitory control is impaired in HD.Further research is needed to learn more about the psychological mechanisms underlying the moderating effect of emotional valence on impaired emotion recognition in HD,and to corroborate the hypothesis that the inhibitory processes involved in Stroop tasks are not impaired in HD.Looking beyond this study,the SERWIT promises to make important contributions to disentangling the cognitive and the psychomotor aspects of neurological disorders.The research was approved by the Ethics Committee of the“Istituto Leonarda Vaccari”,Rome on January 24,2018.

Examination of Huntington's disease in a Chinese family

We report brain imaging and genetic diagnosis in a family from Wuhan, China, with a history of Huntington＇s disease. Among 17 family members across three generations, four patients （Ⅱ2, Ⅱ6, Ⅲ5, and Ⅲ9） show typical Huntington＇s disease, involuntary dance-like movements. Magnetic resonance imaging found lateral ventricular atrophy in three members （Ⅱ2, Ⅱ6, and Ⅲ5）. Moreover, genetic analysis identified abnormally amplified CAG sequence repeats （〉 40） in two members （Ⅲ5 and Ⅲ9）. Among borderline cases, with clinical symptoms and brain imaging features of Huntington＇s disease, two cases were identified （Ⅱ2 and Ⅱ6）, but shown by mutation analysis for CAG expansions in the important transcript 15 gene, to be non-Huntington＇s disease. Our findings suggest that clinical diagnosis of Huntington＇s disease requires a combination of clinical symptoms, radiological changes, and genetic diagnosis.

Linguistic Characteristics of Mandarin-Speaking Huntington’s Disease Patients

Objective Linguistic problem is common in Huntington’s disease(HD)patients.It has been studied before in native speakers of alphabetic languages,such as English.As a hieroglyphic language,Chinese differs from alphabetic languages in terms of phonology,morphology,semantics and syntax.We aimed to investigate the linguistic characteristics of manifest HD in native speakers of Mandarin.Meanwhile,we expected to explore the linguistic differences associated with cortical or subcortical pathology.Methods Five HD patients and five Alzheimer’s disease(AD)patients matched in age,gender,disease course and educational level were enrolled.All the participants were Mandarin native speakers.All finished history inquiry,physical examination,basic test,genetic test and neuropsychological assessment.Language evaluation was performed by Aphasia Battery of Chinese.Results HD patients had a mean disease course of 5.4±2.97(range,2-10)years.They showed a linguistic disorder close to transcortical motor aphasia.They exhibited prominent phonological impairment,as well as slight semantic and syntactic abnormality.Tonic errors were found in speech.Character structural errors and substitutions were detected in writing.In comparison,AD patients showed a more severe linguistic impairment,characterized by global aphasia with more semantic errors.Conclusion Mandarin-speaking HD patients have a transcortical motor aphasia-like disturbance with prominent phonological impairment,whereas AD patients have a more severe global aphasia with salient semantic impairment.

Glyco-sphingo biology: a novel perspective for potential new treatments in Huntington's disease

Huntington＇s disease （HD） is the most common dominantly inherited neurodegenerative disorder, mainly characterized by the progressive striatal and cortical neurodegeneration and as- sociated motor, cognitive and behavioural disturbances （Zuccato et al., 2010）. The disease-causing mutation is an expansion of a GAG trinucleotide repeat （〉 36 repeats） encoding a polygluta- mine stretch in the N-terminal region ofhuntingtin （Htt） （Zuc- cato et al., 2010）, a ubiquitous protein whose function is still unclear （Zuccato et al., 2010）. Expansion of the polyQ stretch endows mutant Htt （mHtt） with toxic properties, and results in the development of a broad array of undesirable effects in both neuronal and non-neuronal cells （Zuccato et al., 2010）. Among all cellular dysfunctions and biochemical imbalances classically associated with HD, perturbed metabolism of （glyco） sphingolipids appears to play a crucial role in the pathogenesis of the disease. Over the last years, we and other have extensively contributed to these findings （Desplats et al., 2007;