Cystamine and cysteamine increase brain levels of BDNF in Huntington disease via HSJ1b and transglutaminase

Polyglutamine disorders: Pathogenesis and potential drug interventions

Polyglutamine/poly(Q) diseases are a group nine hereditary neurodegenerative disorders caused due to abnormally expanded stretches of CAG trinucleotide in functionally distinct genes. All human poly(Q) diseases are characterized by the formation of microscopically discernable poly(Q) positive aggregates, the inclusion bodies. These toxic inclusion bodies are responsible for the impairment of several cellular pathways such as autophagy, transcription, cell death, etc., that culminate in disease manifestation. Although, these diseases remain largely without treatment, extensive research has generated mounting evidences that various events of poly(Q) pathogenesis can be developed as potential drug targets. The present review article briefly discusses the key events of disease pathogenesis, model system-based investigations that support the development of effective therapeutic interventions against pathogenesis of human poly(Q) disorders, and a comprehensive list of pharmacological and bioactive compounds that have been experimentally shown to alleviate poly(Q)-mediated neurotoxicity. Interestingly, due to the common cause of pathogenesis, all poly(Q) diseases share etiology, thus, findings from one disease can be potentially extrapolated to other poly(Q) diseases as well.

Effect of Linear Energy Transfer on Cystamine's Radioprotective Activity: A Study Using the Fricke Dosimeter with 6-500 MeV per Nucleon Carbon Ions-Implication for Carbon Ion Hadrontherapy

(1) Background: Radioprotective agents have garnered considerable interest due to their prospective applications in radiotherapy, public health medicine, and situations of large-scale accidental radiation exposure or impending radiological emergencies. Cystamine, an organic diamino-disulfide compound, is recognized for its radiation-protective and antioxidant properties. This study aims to utilize the aqueous ferrous sulfate (Fricke) dosimeter to measure the free-radical scavenging capabilities of cystamine during irradiation by fast carbon ions. This analysis spans an energy range from 6 to 500 MeV per nucleon, which correlates with "linear energy transfer" (LET) values ranging from approximately 248 keV/μm down to 9.3 keV/μm. (2) Methods: Monte Carlo track chemistry calculations were used to simulate the radiation-induced chemistry of aerated Fricke-cystamine solutions across a broad spectrum of cystamine concentrations, ranging from 10-6 to 1 M. (3) Results: In irradiated Fricke solutions containing cystamine, cystamine is observed to hinder the oxidation of Fe2+ ions, an effect triggered by oxidizing agents from the radiolysis of acidic water, resulting in reduced Fe3+ ion production. Our simulations, conducted both with and without accounting for the multiple ionization of water, confirm cystamine's ability to capture free radicals, highlighting its strong antioxidant properties. Aligning with prior research, our simulations also indicate that the protective and antioxidant efficiency of cystamine diminishes with increasing LET of the radiation. This result can be attributed to the changes in the geometry of the track structures when transitioning from lower to higher LETs. (4) Conclusions: If we can apply these fundamental research findings to biological systems at a physiological pH, the use of cystamine alongside carbon-ion hadrontherapy could present a promising approach to further improve the therapeutic ratio in cancer treatments.

Mutant-Huntingtin Molecular Pathways Elucidate New Targets for Drug Repurposing

The spectrum of neurodegenerative diseases known today is quite extensive. The complexities of their research and treatment lie not only in their diversity. Even many years of struggle and narrowly focused research on common pathologies such as Alzheimer's, Parkinson's, and other brain diseases have not brought cures for these illnesses. What can be said about orphan diseases? In particular, Huntington's disease (HD), despite affecting a smaller part of the human population, still attracts many researchers. This disorder is known to result from a mutation in the HTT gene, but having this information still does not simplify the task of drug development and studying the mechanisms of disease progression. Nonetheless, the data accumulated over the years and their analysis provide a good basis for further research. Here, we review studies devoted to understanding the mechanisms of HD. We analyze genes and molecular pathways involved in HD pathogenesis to describe the action of repurposed drugs and try to find new therapeutic targets.

The vitamin B5/coenzyme A axis: A target for immunomodulation?

Coenzyme A (CoA) serves as a vital cofactor in numerous enzymatic reactions involved in energy production, lipid metabolism, and synthesis of essential molecules. Dysregulation of CoA-dependent metabolic pathways can contribute to chronic diseases, such as inflammatory diseases, obesity, diabetes, cancer, and cardiovascular disorders. Additionally, CoA influences immune cell activation by modulating the metabolism of these cells, thereby affecting their proliferation, differentiation, and effector functions. Targeting CoA metabolism presents a promising avenue for therapeutic intervention, as it can potentially restore metabolic balance, mitigate chronic inflammation, and enhance immune cell function. This might ultimately improve the management and outcomes for these diseases. This review will more specifically focus on the contribution of pathways regulating the availability of the CoA precursor Vitamin B5/pantothenate in vivo and modulating the development of Th17-mediated inflammation, CD8-dependent anti-tumor immunity but also tissue repair processes in chronic inflammatory or degenerative diseases.

Acrolein produced during acute kidney injury promotes tubular cell death

Acute kidney injury is an important global health concern as it is associated with high morbidity and mortality. Polyamines, essential for cell growth and proliferation, are known to inhibit cardiovascular disease. However, under conditions of cellular damage, toxic acrolein is produced from polyamines by the enzyme spermine oxidase (SMOX). We used a mouse renal ischemia-reperfusion model and human proximal tubule cells (HK-2) to investigate whether acrolein exacerbates acute kidney injury by renal tubular cell death. Acrolein visualized by acroleinRED was increased in ischemia-reperfusion kidneys, particularly in tubular cells. When HK-2 cells were cultured under 1% oxygen for 24 h, then switched to 21% oxygen for 24 h (hypoxia-reoxygenation), acrolein accumulated and SMOX mRNA and protein levels were increased. Acrolein induced cell death and fibrosis-related TGFB1 mRNA in HK-2 cells. Administration of the acrolein scavenger cysteamine suppressed the acrolein-induced upregulation of TGFB1 mRNA. Cysteamine also inhibited a decrease in the mitochondrial membrane potential observed by MitoTrackerCMXRos, and cell death induced by hypoxia-reoxygenation. The siRNA-mediated knockdown of SMOX also suppressed hypoxia-reoxygenation-induced acrolein accumulation and cell death. Our study suggests that acrolein exacerbates acute kidney injury by promoting tubular cell death during ischemia-reperfusion injury. Treatment to control the accumulation of acrolein might be an effective therapeutic option for renal ischemia-reperfusion injury.

The Emerging Landscape of Small-Molecule Therapeutics for the Treatment of Huntington's Disease

Huntington's disease (HD) is a progressive neurodegenerative disorder caused by a CAG repeat expansion in the huntingtin gene (HTT). The new insights into HD's cellular and molecular pathways have led to the identification of numerous potent small-molecule therapeutics for HD therapy. The field of HD-targeting small-molecule therapeutics is accelerating, and the approval of these therapeutics to combat HD may be expected in the near future. For instance, preclinical candidates such as naphthyridine-azaquinolone, AN1, AN2, CHDI-00484077, PRE084, EVP4593, and LOC14 have shown promise for further optimization to enter into HD clinical trials. This perspective aims to summarize the advent of small-molecule therapeutics at various stages of clinical development for HD therapy, emphasizing their structure and design, therapeutic effects, and specific mechanisms of action. Further, we have highlighted the key drivers involved in HD pathogenesis to provide insights into the basic principle for designing promising anti-HD therapeutic leads.

Nrf2 Pathway in Huntington's Disease (HD): What Is Its Role?

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease that occurs worldwide. Despite some progress in understanding the onset of HD, drugs that block or delay symptoms are still not available. In recent years, many treatments have been proposed; among them, nuclear transcriptional factor-2 (Nrf2) enhancer compounds have been proposed as potential therapeutic agents to treat HD. Nrf2 triggers an endogenous antioxidant pathway activated in different neurodegenerative disorders. Probably, the stimulation of Nrf2 during either the early phase or before HD symptoms' onset, could slow or prevent striatum degeneration. In this review, we present the scientific literature supporting the role of Nrf2 in HD and the potential prophylactic and therapeutic role of this compound.

N-cystaminylbiguanide MC001 prevents neuron cell death and alleviates motor deficits in the MPTP-model of Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disease characterized by the progressive loss of dopaminergic (DA) neurons in the substantia nigra (SN), which is highly associated with oxidative stress. Antioxidants are therefore considered as potential therapies in PD treatment. In this study, we examined the neuroprotective effect of a cysteamine-based biguanide N-cystaminylbiguanide (MC001) in the MPTP mouse model of PD. The results showed that MC001 prevented neuron cell death and alleviated motor deficits in the MPTP mouse model of PD. Both in vitro and in vivo data indicated that MC001 may exert its neuroprotective effect by alleviating ROS production, suppressing neuroinflammation, and upregulating BDNF expression. Further mechanistic studies revealed that MC001 promoted GSH synthesis by inducing the expression of Glutamate-cysteine ligase catalytic subunit (Gclc) and enhancing the activity of Glutamate-cysteine ligase (Gcl). Our results suggest that MC001 warrants further investigation as a potential candidate for the treatment of PD.

Hsp40 overexpression in pacemaker neurons delays circadian dysfunction in a Drosophila model of Huntington's disease

Circadian disturbances are early features of neurodegenerative diseases, including Huntington's disease (HD). Emerging evidence suggests that circadian decline feeds into neurodegenerative symptoms, exacerbating them. Therefore, we asked whether known neurotoxic modifiers can suppress circadian dysfunction. We performed a screen of neurotoxicity-modifier genes to suppress circadian behavioural arrhythmicity in a Drosophila circadian HD model. The molecular chaperones Hsp40 and HSP70 emerged as significant suppressors in the circadian context, with Hsp40 being the more potent mitigator. Upon Hsp40 overexpression in the Drosophila circadian ventrolateral neurons (LNv), the behavioural rescue was associated with neuronal rescue of loss of circadian proteins from small LNv soma. Specifically, there was a restoration of the molecular clock protein Period and its oscillations in young flies and a long-lasting rescue of the output neuropeptide Pigment dispersing factor. Significantly, there was a reduction in the expanded Huntingtin inclusion load, concomitant with the appearance of a spot-like Huntingtin form. Thus, we provide evidence implicating the neuroprotective chaperone Hsp40 in circadian rehabilitation. The involvement of molecular chaperones in circadian maintenance has broader therapeutic implications for neurodegenerative diseases.

This article has an associated First Person interview with the first author of the paper.

Summary: This study shows, for the first time, a neuroprotective role of chaperone Hsp40 in suppressing circadian dysfunction associated with Huntington's disease in a Drosophila model.

Central Nervous System Complications in Cystinosis: The Role of Neuroimaging

Despite improvement in the specific treatment, clinical and anatomo-functional central nervous system (CNS) abnormalities of various severities are still observed in cystinosis patients. Patients who develop CNS complications today have a worse compliance to cysteamine treatment. Radiological studies have shown that cortical or central (ventriculomegaly) atrophy is observed in more than two thirds of cystinosis patients’ magnetic resonance imaging (MRI) and correlates with the intelligence quotient score. Half of cystinosis patients have marked aspecific white matter hyperintensities. The development of advanced neuroimaging techniques provides new tools to further investigate CNS complications. A recent neuroimaging study using a voxel-based morphometry approach showed that cystinosis patients present a decreased grey matter volume in the left middle frontal gyrus. Diffusion tensor imaging studies have shown white matter microstructure abnormalities in children and adults with cystinosis, respectively in areas of the dorsal visual pathway and within the corpus callosum’s body. Finally, leucocyte cystine levels are associated with decreased resting cerebral blood flow, measured by arterial spin labelling, in the frontal cortex, which could be associated with the neurocognitive deficits described in these patients. These results reinforce the relevance of neuroimaging studies to further understand the mechanisms that underline CNS impairments.

Recent developments in the management of Huntington's disease

Huntington's disease (HD) is a rare, incurable, inheritedneurodegenerative disorder manifested by chorea, hyperkinetic, and hypokinetic movements. The FDA has approved only two drugs, viz. tetrabenazine, and deutetrabenazine, to manage the chorea associated with HD. However, several other drugs are used as an off-label to manage chorea and other symptoms such as depression, anxiety, muscle tremors, and cognitive dysfunction associated with HD. So far, there is no disease-modifying treatment available. Drug repurposing has been a primary drive to search for new anti-HD drugs. Numerous molecular targets along with a wide range of small molecules and gene therapies are currently under clinical investigation. More than 200 clinical studies are underway for HD, 75% are interventional, and 25% are observational studies. The present review discusses the small molecule clinical pipeline and molecular targets for HD. Furthermore, the biomarkers, diagnostic tests, gene therapies, behavioral and observational studies for HD were also deliberated.

Current Drug Repurposing Strategies for Rare Neurodegenerative Disorders

Rare diseases are life-threatening or chronically debilitating low-prevalent disorders caused by pathogenic mutations or particular environmental insults. Due to their high complexity and low frequency, important gaps still exist in their prevention, diagnosis, and treatment. Since new drug discovery is a very costly and time-consuming process, leading pharmaceutical companies show relatively low interest in orphan drug research and development due to the high cost of investments compared to the low market return of the product. Drug repurposing–based approaches appear then as cost- and time-saving strategies for the development of therapeutic opportunities for rare diseases. In this article, we discuss the scientific, regulatory, and economic aspects of the development of repurposed drugs for the treatment of rare neurodegenerative disorders with a particular focus on Huntington’s disease, Friedreich’s ataxia, Wolfram syndrome, and amyotrophic lateral sclerosis. The role of academia, pharmaceutical companies, patient associations, and foundations in the identification of candidate compounds and their preclinical and clinical evaluation will also be discussed.

New Avenues for the Treatment of Huntington's Disease

Huntington’s disease (HD) is a neurodegenerative disorder caused by a CAG expansion in the HD gene. The disease is characterized by neurodegeneration, particularly in the striatum and cortex. The first symptoms usually appear in mid-life and include cognitive deficits and motor disturbances that progress over time. Despite being a genetic disorder with a known cause, several mechanisms are thought to contribute to neurodegeneration in HD, and numerous pre-clinical and clinical studies have been conducted and are currently underway to test the efficacy of therapeutic approaches targeting some of these mechanisms with varying degrees of success. Although current clinical trials may lead to the identification or refinement of treatments that are likely to improve the quality of life of those living with HD, major efforts continue to be invested at the pre-clinical level, with numerous studies testing novel approaches that show promise as disease-modifying strategies. This review offers a detailed overview of the currently approved treatment options for HD and the clinical trials for this neurodegenerative disorder that are underway and concludes by discussing potential disease-modifying treatments that have shown promise in pre-clinical studies, including increasing neurotropic support, modulating autophagy, epigenetic and genetic manipulations, and the use of nanocarriers and stem cells.

Mesenchymal stem cell secretome protects against alpha-synuclein-induced neurodegeneration in a Caenorhabditis elegans model of Parkinson's disease

BACKGROUND AIMS

The capacity of the secretome from bone marrow-derived mesenchymal stem cells (BMSCs) to prevent dopaminergic neuron degeneration caused by overexpression of alpha-synuclein (α-syn) was explored using two Caenorhabditis elegans models of Parkinson's disease (PD).

METHODS

First, a more predictive model of PD that overexpresses α-syn in dopamine neurons was subjected to chronic treatment with secretome. This strain displays progressive dopaminergic neurodegeneration that is age-dependent. Following chronic treatment with secretome, the number of intact dopaminergic neurons was determined. Following these initial experiments, a C. elegans strain that overexpresses α-syn in body wall muscle cells was used to determine the impact of hBMSC secretome on α-syn inclusions. Lastly, in silico analysis of the components that constitute the secretome was performed.

RESULTS

The human BMSC (hBMSC) secretome induced a neuroprotective effect, leading to reduced dopaminergic neurodegeneration. Moreover, in animals submitted to chronic treatment with secretome, the number of α-syn inclusions was reduced, indicating that the secretome of MSCs was possibly contributing to the degradation of those structures. In silico analysis identified possible suppressors of α-syn proteotoxicity, including growth factors and players in the neuronal protein quality control mechanisms.

CONCLUSIONS

The present findings indicate that hBMSC secretome has the potential to be used as a disease-modifying strategy in future PD regenerative medicine approaches.

Increasing brain palmitoylation rescues behavior and neuropathology in Huntington disease mice

Huntington disease (HD) damages the corticostriatal circuitry in large part by impairing transport of brain-derived neurotrophic factor (BDNF). We hypothesized that improving vesicular transport of BDNF could slow or prevent disease progression. We therefore performed selective proteomic analysis of vesicles transported within corticostriatal projecting neurons followed by in silico screening and identified palmitoylation as a pathway that could restore defective huntingtin-dependent trafficking. Using a synchronized trafficking assay and an HD network-on-a-chip, we found that increasing brain palmitoylation via ML348, which inhibits the palmitate-removing enzyme acyl-protein thioesterase 1 (APT1), restores axonal transport, synapse homeostasis, and survival signaling to wild-type levels without toxicity. In human HD induced pluripotent stem cell-derived cortical neurons, ML348 increased BDNF trafficking. In HD knock-in mice, it efficiently crossed the blood-brain barrier to restore palmitoylation levels and reverse neuropathology, locomotor deficits, and anxio-depressive behaviors. APT1 and its inhibitor ML348 thus hold therapeutic interest for HD.

J-domain proteins interaction with neurodegenerative disease-related proteins

HSP70 chaperones, J-domain proteins (JDPs) and nucleotide exchange factors (NEF) form functional networks that have the ability to prevent and reverse the aggregation of proteins associated with neurodegenerative diseases. JDPs can interact with specific substrate proteins, hold them in a refolding-competent conformation and target them to specific HSP70 chaperones for remodeling. Thereby, JDPs select specific substrates and constitute an attractive target for pharmacological intervention of neurodegenerative diseases. This, under the condition that the exact mechanism of JDPs interaction with specific substrates is unveiled. In this review, we provide an overview of the structural and functional variety of JDPs that interact with neurodegenerative disease-associated proteins and we highlight those studies that identified specific residues, domains or regions of JDPs that are crucial for substrate binding.

Natural Molecules and Neuroprotection: Kynurenic Acid, Pantethine and α-Lipoic Acid

The incidence of neurodegenerative diseases has increased greatly worldwide due to the rise in life expectancy. In spite of notable development in the understanding of these disorders, there has been limited success in the development of neuroprotective agents that can slow the progression of the disease and prevent neuronal death. Some natural products and molecules are very promising neuroprotective agents because of their structural diversity and wide variety of biological activities. In addition to their neuroprotective effect, they are known for their antioxidant, anti-inflammatory and antiapoptotic effects and often serve as a starting point for drug discovery. In this review, the following natural molecules are discussed: firstly, kynurenic acid, the main neuroprotective agent formed via the kynurenine pathway of tryptophan metabolism, as it is known mainly for its role in glutamate excitotoxicity, secondly, the dietary supplement pantethine, that is many sided, well tolerated and safe, and the third molecule, α-lipoic acid is a universal antioxidant. As a conclusion, because of their beneficial properties, these molecules are potential candidates for neuroprotective therapies suitable in managing neurodegenerative diseases.

A sensitive "off-on" carbon dots-Ag nanoparticles fluorescent probe for cysteamine detection via the inner filter effect

In this study, we describe the construction of an "off-on" fluorescent probe based on carbon dots (CDs) and silver nanoparticles (AgNPs) mixture for sensitive and selective detection of cysteamine. By mixing AgNPs with CDs solution, the fluorescence of CDs was significantly decreased due to the inner filter effect (IFE). Upon addition of cysteamine to the mixed aqueous of CDs and AgNPs, the silver-sulfur bond between cysteamine and AgNPs caused AgNPs to aggregate, and the quenched fluorescence of CDs could in turn be recovered. The probe was employed to quantitatively detect cysteamine, and the results showed that it could detect cysteamine in a concentration range of 2-16 μM with the detection limit of 0.35 μM (signal-to-noise ratio of 3). The detection of cysteamine spiked into bovine serum samples showed high recovery rates ranging from 95.5 to 111.7%. More importantly, the developed probe had low cytotoxicity and was successfully used for in vivo imaging of HepG2 cells.

Molecular Defects in Friedreich's Ataxia: Convergence of Oxidative Stress and Cytoskeletal Abnormalities

Friedreich’s ataxia (FRDA) is a multi-faceted disease characterized by progressive sensory–motor loss, neurodegeneration, brain iron accumulation, and eventual death by hypertrophic cardiomyopathy. FRDA follows loss of frataxin (FXN), a mitochondrial chaperone protein required for incorporation of iron into iron–sulfur cluster and heme precursors. After the discovery of the molecular basis of FRDA in 1996, over two decades of research have been dedicated to understanding the temporal manifestations of disease both at the whole body and molecular level. Early research indicated strong cellular iron dysregulation in both human and yeast models followed by onset of oxidative stress. Since then, the pathophysiology due to dysregulation of intracellular iron chaperoning has become central in FRDA relative to antioxidant defense and run-down in energy metabolism. At the same time, limited consideration has been given to changes in cytoskeletal organization, which was one of the first molecular defects noted. These alterations include both post-translational oxidative glutathionylation of actin monomers and differential DNA processing of a cytoskeletal regulator PIP5K1β. Currently unknown in respect to FRDA but well understood in the context of FXN-deficient cell physiology is the resulting impact on the cytoskeleton; this disassembly of actin filaments has a particularly profound effect on cell–cell junctions characteristic of barrier cells. With respect to a neurodegenerative disorder such as FRDA, this cytoskeletal and tight junction breakdown in the brain microvascular endothelial cells of the blood–brain barrier is likely a component of disease etiology. This review serves to outline a brief history of this research and hones in on pathway dysregulation downstream of iron-related pathology in FRDA related to actin dynamics. The review presented here was not written with the intent of being exhaustive, but to instead urge the reader to consider the essentiality of the cytoskeleton and appreciate the limited knowledge on FRDA-related cytoskeletal dysfunction as a result of oxidative stress. The review examines previous hypotheses of neurodegeneration with brain iron accumulation (NBIA) in FRDA with a specific biochemical focus.

Beyond the Hippocampus and the SVZ: Adult Neurogenesis Throughout the Brain

Convincing evidence has repeatedly shown that new neurons are produced in the mammalian brain into adulthood. Adult neurogenesis has been best described in the hippocampus and the subventricular zone (SVZ), in which a series of distinct stages of neuronal development has been well characterized. However, more recently, new neurons have also been found in other brain regions of the adult mammalian brain, including the hypothalamus, striatum, substantia nigra, cortex, and amygdala. While some studies have suggested that these new neurons originate from endogenous stem cell pools located within these brain regions, others have shown the migration of neurons from the SVZ to these regions. Notably, it has been shown that the generation of new neurons in these brain regions is impacted by neurologic processes such as stroke/ischemia and neurodegenerative disorders. Furthermore, numerous factors such as neurotrophic support, pharmacologic interventions, environmental exposures, and stem cell therapy can modulate this endogenous process. While the presence and significance of adult neurogenesis in the human brain (and particularly outside of the classical neurogenic regions) is still an area of debate, this intrinsic neurogenic potential and its possible regulation through therapeutic measures present an exciting alternative for the treatment of several neurologic conditions. This review summarizes evidence in support of the classic and novel neurogenic zones present within the mammalian brain and discusses the functional significance of these new neurons as well as the factors that regulate their production. Finally, it also discusses the potential clinical applications of promoting neurogenesis outside of the classical neurogenic niches, particularly in the hypothalamus, cortex, striatum, substantia nigra, and amygdala.

Beneficial effects of cysteamine in Thy1-α-Syn mice and induced pluripotent stem cells with a SNCA gene triplication

A number of publications have reported that cysteamine has significant therapeutic effects on several aspects of Parkinson's disease (PD)-related pathology but none of these studies have evaluated its impact on pathological forms of α-Synuclein (α-Syn), one of the main hallmarks of PD. We therefore tested the efficacy of cysteamine on the Thy1-α-Syn mouse model which over-expresses full-length human wild-type α-Syn. Two-month (early stage disease) and 6-month old (late stage disease) mice and littermate controls were treated daily with cysteamine (20 mg/kg, i.p.) to assess the protective and restorative properties of this compound. After 6 weeks of treatment, animals were tested using a battery of motor tests. Cysteamine-treated transgenic mice displayed significant improvements in motor performance as compared to saline-treated transgenic littermates. Post-mortem readouts revealed a reduction in fibrillation, phosphorylation and total levels of overexpresed human α-Syn. To determine if such outcomes extended to human cells, the benefits of cysteamine were additionally tested using 6-hydroxydopamine (6-OHDA) treated neurons differentiated from induced pluripotent stem cells (iPSCs) derived from a PD patient harbouring a triplication of the SNCA gene. SNCA neurons treated with cysteamine exhibited significantly more intact/healthy neurites than cells treated with 6-OHDA alone. Additionally, SNCA neurons treated with cysteamine in the absence of 6-OHDA showed a trend towards lower total α-Syn levels. Overall, our in vivo and in vitro findings suggest that cysteamine can act as a disease-modifying molecule by enhancing -the survival of dopaminergic neurons and reducing pathological forms of α-Syn.

Regulation of coenzyme A levels by degradation: the 'Ins and Outs'

Coenzyme A (CoA) is the predominant acyl carrier in mammalian cells and a cofactor that plays a key role in energy and lipid metabolism. CoA and its thioesters (acyl-CoAs) regulate a multitude of metabolic processes at different levels: as substrates, allosteric modulators, and via post-translational modification of histones and other non-histone proteins. Evidence is emerging that synthesis and degradation of CoA are regulated in a manner that enables metabolic flexibility in different subcellular compartments. Degradation of CoA occurs through distinct intra- and extracellular pathways that rely on the activity of specific hydrolases. The pantetheinase enzymes specifically hydrolyze pantetheine to cysteamine and pantothenate, the last step in the extracellular degradation pathway for CoA. This reaction releases pantothenate in the bloodstream, making this CoA precursor available for cellular uptake and de novo CoA synthesis. Intracellular degradation of CoA depends on specific mitochondrial and peroxisomal Nudix hydrolases. These enzymes are also active against a subset of acyl-CoAs and play a key role in the regulation of subcellular (acyl-)CoA pools and CoA-dependent metabolic reactions. The evidence currently available indicates that the extracellular and intracellular (acyl-)CoA degradation pathways are regulated in a coordinated and opposite manner by the nutritional state and maximize the changes in the total intracellular CoA levels that support the metabolic switch between fed and fasted states in organs like the liver. The objective of this review is to update the contribution of these pathways to the regulation of metabolism, physiology and pathology and to highlight the many questions that remain open.

Neuromuscular Diseases Due to Chaperone Mutations: A Review and Some New Results

Skeletal muscle and the nervous system depend on efficient protein quality control, and they express chaperones and cochaperones at high levels to maintain protein homeostasis. Mutations in many of these proteins cause neuromuscular diseases, myopathies, and hereditary motor and sensorimotor neuropathies. In this review, we cover mutations in DNAJB6, DNAJB2, αB-crystallin (CRYAB, HSPB5), HSPB1, HSPB3, HSPB8, and BAG3, and discuss the molecular mechanisms by which they cause neuromuscular disease. In addition, previously unpublished results are presented, showing downstream effects of BAG3 p.P209L on DNAJB6 turnover and localization.

Inhibition of Transglutaminase 2 as a Potential Host-Directed Therapy Against Mycobacterium tuberculosis

Host-directed therapies (HDTs) are emerging as a potential valid support in the treatment of drug-resistant tuberculosis (TB). Following our recent report indicating that genetic and pharmacological inhibition of transglutaminase 2 (TG2) restricts Mycobacterium tuberculosis (Mtb) replication in macrophages, we aimed to investigate the potentials of the TG2 inhibitors cystamine and cysteamine as HDTs against TB. We showed that both cysteamine and cystamine restricted Mtb replication in infected macrophages when provided at equimolar concentrations and did not exert any antibacterial activity when administered directly on Mtb cultures. Interestingly, infection of differentiated THP-1 mRFP-GFP-LC3B cells followed by the determination of the autophagic intermediates pH distribution (AIPD) showed that cystamine inhibited the autophagic flux while restricting Mtb replication. Moreover, both cystamine and cysteamine had a similar antimicrobial activity in primary macrophages infected with a panel of Mtb clinical strains belonging to different phylogeographic lineages. Evaluation of cysteamine and cystamine activity in the human ex vivo model of granuloma-like structures (GLS) further confirmed the ability of these drugs to restrict Mtb replication and to reduce the size of GLS. The antimicrobial activity of the TG2 inhibitors synergized with a second-line anti-TB drug as amikacin in human monocyte-derived macrophages and in the GLS model. Overall, the results of this study support the potential usefulness of the TG2-inhibitors cysteamine and cystamine as HDTs against TB.

Overlapping spectrums: The clinicogenetic commonalities between Charcot-Marie-Tooth and other neurodegenerative diseases

Charcot-Marie-Tooth (CMT) disease is a progressive and heterogeneous inherited peripheral neuropathy. A myriad of genetic factors have been identified that contribute to the degeneration of motor and sensory axons in a length-dependent manner. Emerging biological themes underlying disease include defects in axonal trafficking, dysfunction in RNA metabolism and protein homeostasis, as well deficits in the cellular stress response. Moreover, genetic contributions to CMT can have overlap with other neuropathies, motor neuron diseases (MNDs) and neurodegenerative disorders. Recent progress in understanding the molecular biology of CMT and overlapping syndromes aids in the search for necessary therapeutic targets.

Therapeutic Advances for Huntington's Disease

Huntington’s disease (HD) is a progressive neurological disease that is inherited in an autosomal fashion. The cause of disease pathology is an expansion of cytosine-adenine-guanine (CAG) repeats within the huntingtin gene (HTT) on chromosome 4 (4p16.3), which codes the huntingtin protein (mHTT). The common symptoms of HD include motor and cognitive impairment of psychiatric functions. Patients exhibit a representative phenotype of involuntary movement (chorea) of limbs, impaired cognition, and severe psychiatric disturbances (mood swings, depression, and personality changes). A variety of symptomatic treatments (which target glutamate and dopamine pathways, caspases, inhibition of aggregation, mitochondrial dysfunction, transcriptional dysregulation, and fetal neural transplants, etc.) are available and some are in the pipeline. Advancement in novel therapeutic approaches include targeting the mutant huntingtin (mHTT) protein and the HTT gene. New gene editing techniques will reduce the CAG repeats. More appropriate and readily tractable treatment goals, coupled with advances in analytical tools will help to assess the clinical outcomes of HD treatments. This will not only improve the quality of life and life span of HD patients, but it will also provide a beneficial role in other inherited and neurological disorders. In this review, we aim to discuss current therapeutic research approaches and their possible uses for HD.

Epigenetic polypharmacology: A new frontier for epi-drug discovery

Recently, despite the great success achieved by the so-called "magic bullets" in the treatment of different diseases through a marked and specific interaction with the target of interest, the pharmacological research is moving toward the development of "molecular network active compounds," embracing the related polypharmacology approach. This strategy was born to overcome the main limitations of the single target therapy leading to a superior therapeutic effect, a decrease of adverse reactions, and a reduction of potential mechanism(s) of drug resistance caused by robustness and redundancy of biological pathways. It has become clear that multifactorial diseases such as cancer, neurological, and inflammatory disorders, may require more complex therapeutic approaches hitting a certain biological system as a whole. Concerning epigenetics, the goal of the multi-epi-target approach consists in the development of small molecules able to simultaneously and (often) reversibly bind different specific epi-targets. To date, two dual histone deacetylase/kinase inhibitors (CUDC-101 and CUDC-907) are in an advanced stage of clinical trials. In the last years, the growing interest in polypharmacology encouraged the publication of high-quality reviews on combination therapy and hybrid molecules. Hence, to update the state-of-the-art of these therapeutic approaches avoiding redundancy, herein we focused only on multiple medication therapies and multitargeting compounds exploiting epigenetic plus nonepigenetic drugs reported in the literature in 2018. In addition, all the multi-epi-target inhibitors known in literature so far, hitting two or more epigenetic targets, have been included.

Therapeutic Applications of Cysteamine and Cystamine in Neurodegenerative and Neuropsychiatric Diseases

Current medications for neurodegenerative and neuropsychiatric diseases such as Alzheimer's disease (AD), Huntington's disease (HD), Parkinson's disease (PD), and Schizophrenia mainly target disease symptoms. Thus, there is an urgent need to develop novel therapeutics that can delay, halt or reverse disease progression. AD, HD, PD, and schizophrenia are characterized by elevated oxidative and nitrosative stress, which play a central role in pathogenesis. Clinical trials utilizing antioxidants to counter disease progression have largely been unsuccessful. Most antioxidants are relatively non-specific and do not adequately target neuroprotective pathways. Accordingly, a search for agents that restore redox balance as well as halt or reverse neuronal loss is underway. The small molecules, cysteamine, the decarboxylated derivative of the amino acid cysteine, and cystamine, the oxidized form of cysteamine, respectively, mitigate oxidative stress and inflammation and upregulate neuroprotective pathways involving brain-derived neurotrophic factor (BDNF) and Nuclear factor erythroid 2-related factor 2 (Nrf2) signaling. Cysteamine can traverse the blood brain barrier, a desirable characteristic of drugs targeting neurodegeneration. This review addresses recent developments in the use of these aminothiols to counter neurodegeneration and neuropsychiatric deficits.

Long-Term Pantethine Treatment Counteracts Pathologic Gene Dysregulation and Decreases Alzheimer's Disease Pathogenesis in a Transgenic Mouse Model

The low-molecular weight thiol pantethine, known as a hypolipidemic and hypocholesterolemic agent, is the major precursor of co-enzyme A. We have previously shown that pantethine treatment reduces amyloid-β (Aβ)-induced IL-1β release and alleviates pathological metabolic changes in primary astrocyte cultures. These properties of pantethine prompted us to investigate its potential benefits in vivo in the 5XFAD (Tg) mouse model of Alzheimer's disease (AD).1.5-month-old Tg and wild-type (WT) male mice were submitted to intraperitoneal administration of pantethine or saline control solution for 5.5 months. The effects of such treatments were investigated by performing behavioral tests and evaluating astrogliosis, microgliosis, Αβ deposition, and whole genome expression arrays, using RNAs extracted from the mice hippocampi. We observed that long-term pantethine treatment significantly reduced glial reactivity and Αβ deposition, and abrogated behavioral alteration in Tg mice. Moreover, the transcriptomic profiles revealed that after pantethine treatment, the expression of genes differentially expressed in Tg mice, and in particular those known to be related to AD, were significantly alleviated. Most of the genes overexpressed in Tg compared to WT were involved in inflammation, complement activation, and phagocytosis and were found repressed upon pantethine treatment. In contrast, pantethine restored the expression of a significant number of genes involved in the regulation of Αβ processing and synaptic activities, which were downregulated in Tg mice. Altogether, our data support a beneficial role for long-term pantethine treatment in preserving CNS crucial functions altered by Aβ pathogenesis in Tg mice and highlight the potential efficiency of pantethine to alleviate AD pathology.

Emerging therapies in Huntington's disease

Introduction: Huntington's disease (HD) is an inherited neurodegenerative condition for which there are no disease-modifying treatments. The availability of early genetic diagnosis makes HD an ideal candidate for early intervention. Growing understanding of pathogenesis has led to the identification of new therapeutic targets for which some compounds are now in clinical trials. Areas covered: A detailed review of medical databases and clinical trial registries was performed. Recent clinical trials aimed to establish disease-modification were included. Focus was assigned to RNA and DNA-based therapies aimed at lowering mutant huntingtin (mHTT) including antisense oligonucleotides (ASOs), RNA interference (RNAi), zinc finger proteins (ZFPs) and the CRISPR-Cas9 system. Modulation of mHTT and immunotherapies is also covered. Expert opinion: Targeting HD pathogenesis at its most proximal level is under intense investigation. ASOs are the only HTT-lowering strategy in clinical trials of manifest HD. Safety and efficacy of an allele specific vs. allele non-specific approach has yet to be established. Success will extend to premanifest carriers for which development of clinical and imaging biomarkers will be necessary. Scientific and technological advancement will bolster new methods of treatment delivery. Cumulative experience, collaborative research, and platforms such as ENROLL-HD will facilitate efficient and effective clinical trials.

Cysteamine Protects Neurons from Mutant Huntingtin Toxicity

BACKGROUND

The potential benefit of cysteamine for Huntington's disease has been demonstrated in HD animal models. Cysteamine and its derivate cystamine were shown to reduce neuropathology and prolong lifespan. Human studies have demonstrated safety, and suggestive results regarding efficacy. Despite all the studies available in vivo, there are only few in vitro studies, and the mechanism of action of cysteamine remains unclear.

OBJECTIVE

The objective of this study is to assess the capacity of cysteamine for neuroprotection against mutant Huntingtin in vitro using cellular models of HD, and to provide initial data regarding mechanism of action.

METHODS

We tested the neuroprotective properties of cysteamine in vitro in our primary neuron and iPSC models of HD.

RESULTS

Cysteamine showed a strong neuroprotective effect (EC50 = 7.1 nM) against mutant Htt-(aa-1-586 82Q) toxicity, in a nuclear condensation cell toxicity assay. Cysteamine also rescued mitochondrial changes induced by mutant Htt. Modulation of the levels of cysteine or glutathione failed to protect neurons, suggesting that cysteamine neuroprotection is not mediated through cysteine metabolism. Taurine and Hypotaurine, which are metabolites of cysteamine can protect neurons against Htt toxicity, but the inhibition of the enzyme converting cysteamine to hypotaurine does not block either protective activity, suggesting independent protective pathways. Cysteamine has been suggested to activate BDNF secretion; however, cysteamine protection was not blocked by BDNF pathway antagonists.

CONCLUSIONS

Cysteamine was strongly neuroprotective with relatively high potency. We demonstrated that the main neuroprotective pathways that have been proposed to be the mechanism of protection by cysteamine can all be blocked and still not prevent the neuroprotective effect. The results suggest the involvement of other yet-to-be-determined neuroprotective pathways.

Improvement of BDNF signalling by P42 peptide in Huntington's disease

Huntington's disease (HD) is caused by a mutation in the Huntingtin (HTT) protein. We previously reported that the 23aa peptide of HTT protein, P42, is preventing HD pathological phenotypes, such as aggregation, reduction of motor performances and neurodegeneration. A systemic treatment with P42 during the pre-symptomatic phase of the disease showed therapeutic potential in R6/2 mice. We here tested P42 effects when administered during the post-symptomatic phase. The P42 treatment alleviated deficits in motor performances, even when symptoms have already started. Because changes in the level and activity of brain-derived neurotrophic factor (BDNF) have been shown to play a central role in HD, we analysed the influence of P42 on BDNF deficit and associated phenotypes. Our data suggest that P42 is involved in the spatio-temporal control of bdnf and trkB mRNA and their protein levels. Related to this enhancement of BDNF-TrkB signalling, R6/2 mice treated with P42, exhibit reduced anxiety, better learning and memory performances, and better long-term potentiation (LTP) response. Finally we identified a direct influence of P42 peptide on neuronal plasticity and activity. These results suggest that P42 offers an efficient therapeutic potential not only by preventing aggregation of mutant HTT at early stages of the disease, but also by favouring some physiological functions of normal HTT, as P42 is naturally part of it, at the different stages of the disease. This makes P42 peptide potentially suitable not only to prevent, but also to treat HD.

Transglutaminase 2 Induces Deficits in Social Behavior in Mice

Impairments in social behavior are highly implicated in many neuropsychiatric disorders. Recent studies indicate a role for endoplasmic reticulum (ER) stress in altering social behavior, but the underlying mechanism is not known. In the present study, we examined the role of transglutaminase 2 (TG2), a calcium-dependent enzyme known to be induced following ER stress, in social behavior in mice. ER stress induced by tunicamycin administration increased TG2 protein levels in the mouse prefrontal cortex (PFC). PFC-specific inhibition of TG2 attenuated ER stress-induced deficits in social behavior. Conversely, overexpression of TG2 in the PFC resulted in social behavior impairments in mice. In addition, systemic administration of cysteamine, a TG2 inhibitor, attenuated social behavior deficits. Our preliminary findings using postmortem human brain samples found increases in TG2 mRNA and protein levels in the middle frontal gyrus of subjects with autism spectrum disorder. These findings in mice and human postmortem brain samples identify changes in TG2 activity in the possible dysregulation of social behavior.

Recent advances in the therapeutic development for Huntington disease

INTRODUCTION

Huntington disease (HD) is a rare genetic neurodegenerative condition. The availability of a genetic diagnosis makes HD an attractive model for the development of therapies that can delay or, at best, halt the progression of neurodegenerative conditions. Tetrabenazine and deutetrabenazine are the only treatment options with a formal indication (chorea) for this patient population.

METHODS

Literature review on HD and clinical trials using the medical databases Pubmed, Web of Science, and clinical trial registries. Recent clinical trials conducted with the goal of disease-modification or new symptomatic treatment indications were included. Non-pharmacological interventions were excluded.

RESULTS

Therapeutic approaches aiming at disease-modification include huntingtin-lowering strategies, the modulation of huntingtin homeostasis and neuroinflammation. Huntingtin-lowering strategies are of particular interest by targeting the mRNA of the huntingtin (HTT) gene at the core of HD biology. Antisense oligonucleotides (ASO) are the only huntingtin-lowering strategies in clinical development. The initial results suggest that the first non-allele specific ASO was safe and associated with a reduction in the levels of mutated huntingtin protein (mHTT). Other clinical trials for disease-modification in HD have generated negative results or are ongoing. Assays to measure CSF mHTT and brain nuclear imaging specific to HD can support the rational development of these therapies. Novel symptomatic treatment indications explored in clinical trials include motor disability, irritability and apathy.

CONCLUSIONS

The years ahead are promising for novel and revolutionary therapies aimed at core disease mechanisms in HD. Clinical research platforms such as Enroll-HD are expected to potentiate the conduction of clinical trials in HD.

Transglutaminase inhibition stimulates hematopoiesis and reduces aggressive behavior of crayfish, Pacifastacus leniusculus

Transglutaminase (TGase) is a Ca²⁺-dependent cross-linking enzyme, which has both enzymatic and nonenzymatic properties. TGase is involved in several cellular activities, including adhesion, migration, survival, apoptosis, and extracellular matrix (ECM) organization. In this study, we focused on the role of the TGase enzyme in controlling hematopoiesis in the crayfish, Pacifastacus leniusculus We hypothesized that a high TGase activity could mediate an interaction of progenitor cells with the ECM to maintain cells in an undifferentiated stage in the hematopoietic tissue (HPT). We found here that the reversible inhibitor cystamine decreases the enzymatic activity of TGase from crayfish HPT, as well as from guinea pig, in a concentration-dependent manner. Cystamine injection decreased TGase activity in HPT without affecting production of reactive oxygen species. Moreover, the decrease in TGase activity in the HPT increased the number of circulating hemocytes. Interestingly the cystamine-mediated TGase inhibition reduced aggressive behavior and movement in crayfish. In conclusion, we show that cystamine-mediated TGase inhibition directly releases HPT progenitor cells from the HPT into the peripheral circulation in the hemolymph and strongly reduces aggressive behavior in crayfish.

New Insights into Development of Transglutaminase 2 Inhibitors as Pharmaceutical Lead Compounds

Transglutaminase 2 (EC 2.3.2.13; TG2 or TGase 2) plays important roles in the pathogenesis of many diseases, including cancers, neurodegeneration, and inflammatory disorders. Under normal conditions, however, mice lacking TGase 2 exhibit no obvious abnormal phenotype. TGase 2 expression is induced by chemical, physical, and viral stresses through tissue-protective signaling pathways. After stress dissipates, expression is normalized by feedback mechanisms. Dysregulation of TGase 2 expression under pathologic conditions, however, can potentiate pathogenesis and aggravate disease severity. Consistent with this, TGase 2 knockout mice exhibit reversal of disease phenotypes in neurodegenerative and chronic inflammatory disease models. Accordingly, TGase 2 is considered to be a potential therapeutic target. Based on structure–activity relationship assays performed over the past few decades, TGase 2 inhibitors have been developed that target the enzyme’s active site, but clinically applicable inhibitors are not yet available. The recently described the small molecule GK921, which lacks a group that can react with the active site of TGase 2, and efficiently inhibits the enzyme’s activity. Mechanistic studies revealed that GK921 binds at an allosteric binding site in the N-terminus of TGase 2 (amino acids (a.a.) 81–116), triggering a conformational change that inactivates the enzyme. Because the binding site of GK921 overlaps with the p53-binding site of TGase 2, the drug induces apoptosis in renal cell carcinoma by stabilizing p53. In this review, we discuss the possibility of developing TGase 2 inhibitors that target the allosteric binding site of TGase 2.

The Role of Adenosine Tone and Adenosine Receptors in Huntington's Disease

Huntington's disease (HD) is a hereditary neurodegenerative disorder caused by a mutation in the IT15 gene that encodes for the huntingtin protein. Mutated hungtingtin, although widely expressed in the brain, predominantly affects striato-pallidal neurons, particularly enriched with adenosine A2A receptors (A2AR), suggesting a possible involvement of adenosine and A2AR is the pathogenesis of HD. In fact, polymorphic variation in the ADORA2A gene influences the age at onset in HD, and A2AR dynamics is altered by mutated huntingtin. Basal levels of adenosine and adenosine receptors are involved in many processes critical for neuronal function and homeostasis, including modulation of synaptic activity and excitotoxicity, the control of neurotrophin levels and functions, and the regulation of protein degradation mechanisms. In the present review, we critically analyze the current literature involving the effect of altered adenosine tone and adenosine receptors in HD and discuss why therapeutics that modulate the adenosine system may represent a novel approach for the treatment of HD.

Folic acid-cysteamine modified gold nanoparticle as a nanoprobe for targeted computed tomography imaging of cancer cells

Development of various cost-effective multifunctional nanoprobes for efficient targeted molecular imaging of tumors remains a great challenge in medicine. Herein, we report a simple method of forming folic acid-targeted multifunctional gold nanoparticles via cost-effective cysteamine as a template for tumor molecular computed tomography (CT) imaging technique. The formed multifunctional cysteamine-folic acid conjugated gold nanoparticles (FA-Cys-AuNPs) were characterized via different techniques. Colony assay, hematoxylin and eosin (H&E), MTT, and flow cytometry analysis were used to evaluate the cytocompatibility of the particles. We showed that the formed FA-Cys-AuNPs with an Au core size of ~15 nm are non-cytotoxic in a given concentration range and revealed greater X-ray attenuation intensity than iodine-based contrast agent under the same concentration of the active element. At 80 kVp, FA-Cys-AuNPs enable 1.77-times greater contrast per unit mass compared with iodine at a concentration of 2000 μg/ml, and importantly, the developed FA-Cys-AuNPs can be used as a contrast media for targeted CT imaging of folic acid receptor-expressing cancer cells in vitro. CT values of the targeted cells were 2-times higher than that of non-targeted cells at 80 kVp. These findings propose that the designed FA-Cys-AuNPs can be used as a promising contrast agent for molecular CT imaging. This data can be also considered for the application of gold nanostructures in radiation dose enhancement where nanoparticles with high X-ray attenuation are applied.

DNAJ Proteins in neurodegeneration: essential and protective factors

Maintenance of protein homeostasis is vitally important in post-mitotic cells, particularly neurons. Neurodegenerative diseases such as polyglutamine expansion disorders-like Huntington's disease or spinocerebellar ataxia (SCA), Alzheimer's disease, fronto-temporal dementia (FTD), amyotrophic lateral sclerosis (ALS) and Parkinson's disease-are often characterized by the presence of inclusions of aggregated protein. Neurons contain complex protein networks dedicated to protein quality control and maintaining protein homeostasis, or proteostasis. Molecular chaperones are a class of proteins with prominent roles in maintaining proteostasis, which act to bind and shield hydrophobic regions of nascent or misfolded proteins while allowing correct folding, conformational changes and enabling quality control. There are many different families of molecular chaperones with multiple functions in proteostasis. The DNAJ family of molecular chaperones is the largest chaperone family and is defined by the J-domain, which regulates the function of HSP70 chaperones. DNAJ proteins can also have multiple other protein domains such as ubiquitin-interacting motifs or clathrin-binding domains leading to diverse and specific roles in the cell, including targeting client proteins for degradation via the proteasome, chaperone-mediated autophagy and uncoating clathrin-coated vesicles. DNAJ proteins can also contain ER-signal peptides or mitochondrial leader sequences, targeting them to specific organelles in the cell. In this review, we discuss the multiple roles of DNAJ proteins and in particular focus on the role of DNAJ proteins in protecting against neurodegenerative diseases caused by misfolded proteins. We also discuss the role of DNAJ proteins as direct causes of inherited neurodegeneration via mutations in DNAJ family genes.This article is part of the theme issue 'Heat shock proteins as modulators and therapeutic targets of chronic disease: an integrated perspective'.

Designing Dual Transglutaminase 2/Histone Deacetylase Inhibitors Effective at Halting Neuronal Death

In recent years there has been a clear consensus that neurodegenerative conditions can be better treated through concurrent modulation of different targets. Herein we report that combined inhibition of transglutaminase 2 (TG2) and histone deacetylases (HDACs) synergistically protects against toxic stimuli mediated by glutamate. Based on these findings, we designed and synthesized a series of novel dual TG2-HDAC binding agents. Compound 3 [(E)-N-hydroxy-5-(3-(4-(3-oxo-3-(pyridin-3-yl)prop-1-en-1-yl)phenyl)thioureido)pentanamide] emerged as the most interesting of the series, being able to inhibit TG2 and HDACs both in vitro (TG2 IC₅₀ =13.3±1.5 μm, HDAC1 IC₅₀ =3.38±0.14 μm, HDAC6 IC₅₀ =4.10±0.13 μm) and in cell-based assays. Furthermore, compound 3 does not exert any toxic effects in cortical neurons up to 50 μm and protects neurons against toxic insults induced by glutamate (5 mm) with an EC₅₀ value of 3.7±0.5 μm.

Biothiols induced colour change of silver nanoparticles: A colorimetric sensing strategy

A sensor for the detection and determination of bio-thiols (glutathione (GSH) and cysteamine (Cyste)) has been developed by integrating the distinguished distance related optical characteristics of silver nanoparticles with the simplicity of colorimetric technique. In presence of these analytes, shift in surface plasmon resonance (SPR) absorption of silver nanoparticles (AgNPs) with change in its colour was observed. Yellow coloured AgNPs solution becomes colourless in presence of GSH and changes to red in presence of Cyste. FTIR, TEM and DLS studies were used to confirm the mechanism. The difference in absorption of AgNPs in the absence and presence of GSH was found to vary linearly in the range 1.00×10^-5M to 5.00×10^-7M concentration range with limit of detection at 3.68×10^-7M. The method can also be applied to quantify Cyste in the range 1.10×10^-6M to 5.00×10^-8M with limit of detection at 1.80×10^-8M. The utility of the proposed colorimetric assay is validated by determination of GSH and Cyste in artificial blood serum.

Nonhuman Primate Models of Huntington's Disease and Their Application in Translational Research

Huntington's disease (HD) is a monogenic, autosomal dominant inherited fatal disease that affects 1 in 10,000 people worldwide. Given its unique genetic characteristics, HD would appear as one of the most straightforward neurodegenerative diseases to replicate in animal models. Indeed, mutations in the HTT gene have been used to generate a variety of animal models that display differential pathologies and have significantly increased our understanding of the pathological mechanisms of HD. However, decades of efforts have also shown the complexity of recapitulating the human condition in other species. Here we describe the three different types of models that have been generated in nonhuman primate species, stating their advantages and limitations and attempt to give a critical perspective of their translational value to test the efficacy of novel therapeutic strategies. Obtaining construct, phenotypic, and predictive validity has proven to be challenging in most animal models of human diseases. In HD in particular, it is hard to assess the predictive validity of a new therapeutic strategy when no effective "benchmark" treatment is available in the clinic. In this light, only phenotypic/face validity and construct validity are discussed.

Therapy development in Huntington disease: From current strategies to emerging opportunities

Huntington disease (HD) is a progressive autosomal dominant neurodegenerative disorder in which patients typically present with uncontrolled involuntary movements and subsequent cognitive decline. In 1993, a CAG trinucleotide repeat expansion in the coding region of the huntingtin (HTT) gene was identified as the cause of this disorder. This extended CAG repeat results in production of HTT protein with an expanded polyglutamine tract, leading to pathogenic HTT protein conformers that are resistant to protein turnover, culminating in cellular toxicity and neurodegeneration. Research into the mechanistic basis of HD has highlighted a role for bioenergetics abnormalities stemming from mitochondrial dysfunction, and for synaptic defects, including impaired neurotransmission and excitotoxicity. Interference with transcription regulation may underlie the mitochondrial dysfunction. Current therapies for HD are directed at treating symptoms, as there are no disease-modifying therapies. Commonly prescribed drugs for involuntary movement control include tetrabenazine, a potent and selective inhibitor of vesicular monoamine transporter 2 that depletes synaptic monoamines, and olanzapine, an atypical neuroleptic that blocks the dopamine D2 receptor. Various drugs are used to treat non-motor features. The HD therapeutic pipeline is robust, as numerous efforts are underway to identify disease-modifying treatments, with some small compounds and biological agents moving into clinical trials. Especially encouraging are dosage reduction strategies, including antisense oligonucleotides, and molecules directed at transcription dysregulation. Given the depth and breadth of current HD drug development efforts, there is reason to believe that disease-modifying therapies for HD will emerge, and this achievement will have profound implications for the entire neurotherapeutics field.

The effects of cysteamine in a mouse model of levodopa-induced dyskinesias

Levo-dopa (L-DOPA) has shown significant and long-lasting efficacy in the treatment of motor features characteristic of Parkinson's disease (PD). However, the effects tend to wear off at a time typically when side-effects, such as L-DOPA induced dyskinesias (LIDs), start to emerge and for which the treatment options are very limited. In recent years, we have reported on the neuroprotective and neurorestorative properties of the compounds cystamine/cysteamine in ameliorating several aspects of PD. Building on these observations, we set out to further evaluate the benefits of cysteamine on LIDs. We thus treated mice displaying LIDs with single cysteamine challenges at various doses (20, 50 and 30mg/kg) or chronically for 2 weeks using cysteamine at a dose of 30mg/kg. None of the regimens nor doses ameliorated any LID-related behavioral impairments. Mice displaying LIDs did, however, respond to a single treatment of 60mg/kg of amantadine, a drug used to clinically manage LIDs. Taken together, our results suggest that cysteamine does not induce benefits on LIDs, at least at the doses and regimen tested in our study. However, the disease-modifying effects depicted by cystamine/cysteamine, which we have shown in several reports, would strongly encourage its continued evaluation in the clinical setting.