Oral administration of memantine prolongs survival in a transgenic mouse model of amyotrophic lateral sclerosis

Glutamine metabolism in diseases associated with mitochondrial dysfunction

Mitochondrial dysfunction can arise from genetic defects or environmental exposures and impact a wide range of biological processes. Among these are metabolic pathways involved in glutamine catabolism, anabolism, and glutamine-glutamate cycling. In recent years, altered glutamine metabolism has been found to play important roles in the pathologic consequences of mitochondrial dysfunction. Glutamine is a pleiotropic molecule, not only providing an alternate carbon source to glucose in certain conditions, but also playing unique roles in cellular communication in neurons and astrocytes. Glutamine consumption and catabolic flux can be significantly altered in settings of genetic mitochondrial defects or exposure to mitochondrial toxins, and alterations to glutamine metabolism appears to play a particularly significant role in neurodegenerative diseases. These include primary mitochondrial diseases like Leigh syndrome (subacute necrotizing encephalopathy) and MELAS (mitochondrial myopathy with encephalopathy, lactic acidosis, and stroke-like episodes), as well as complex age-related neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. Pharmacologic interventions targeting glutamine metabolizing and catabolizing pathways appear to provide some benefits in cell and animal models of these diseases, indicating glutamine metabolism may be a clinically relevant target. In this review, we discuss glutamine metabolism, mitochondrial disease, the impact of mitochondrial dysfunction on glutamine metabolic processes, glutamine in neurodegeneration, and candidate targets for therapeutic intervention.

Emerging clinical investigational drugs for the treatment of amyotrophic lateral sclerosis

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder caused by motoneuron death with a median survival time of 3-5 years since disease onset. There are no effective treatments to date. However, a variety of innovative investigational drugs and biological-based therapies are under clinical development.

AREAS COVERED

This review provides an overview of the clinical investigational small molecules as well as a brief summary of the biological-based therapies that are currently undergoing clinical trials for the treatment of ALS. All the data were obtained from ClinicalTrials.gov (registered through November 1).

EXPERT OPINION

Drug discovery for ALS is an active and evolving field, where many investigational clinical drugs are in different trials. There are several mechanisms of action supporting all these new therapies, although proteostasis is gaining stage. Probably, small orally bioavailable molecules able to recover functional TDP-43 homeostasis may have solid chances to modify ALS progression.

Memantine Disrupts Motor Coordination through Anxiety-like Behavior in CD1 Mice

Memantine is an FDA approved drug for the treatment of Alzheimer’s disease. It reduces neurodegeneration in the hippocampus and cerebral cortex through the inhibition of extrasynaptic NMDA receptors in patients and mouse models. Potentially, it could prevent neurodegeneration in other brain areas and caused by other diseases. We previously used memantine to prevent functional damage and to retain morphology of cerebellar neurons and Bergmann glia in an optogenetic mouse model of spinocerebellar ataxia type-1 (SCA1). However, before suggesting wider use of memantine in clinics, its side effects must be carefully evaluated. Blockers of NMDA receptors are controversial in terms of their effects on anxiety. Here, we investigated the effects of chronic application of memantine over 9 weeks to CD1 mice and examined rotarod performance and anxiety-related behaviors. Memantine-treated mice exhibited an inability to adapt to anxiety-causing conditions which strongly affected their rotarod performance. A tail suspension test revealed increased signs of behavioral despair. These data provide further insights into the potential deleterious effects of memantine which may result from the lack of adaptation to novel, stressful conditions. This effect of memantine may affect the results of tests used to assess motor performance and should be considered during clinical trials of memantine in patients.

Protective Effect of Memantine on Bergmann Glia and Purkinje Cells Morphology in Optogenetic Model of Neurodegeneration in Mice

Spinocerebellar ataxias are a family of fatal inherited diseases affecting the brain. Although specific mutated proteins are different, they may have a common pathogenetic mechanism, such as insufficient glutamate clearance. This function fails in reactive glia, leading to excitotoxicity and overactivation of NMDA receptors. Therefore, NMDA receptor blockers could be considered for the management of excitotoxicity. One such drug, memantine, currently used for the treatment of Alzheimer's disease, could potentially be used for the treatment of other forms of neurodegeneration, for example, spinocerebellar ataxias (SCA). We previously demonstrated close parallels between optogenetically induced cerebellar degeneration and SCA1. Here we induced reactive transformation of cerebellar Bergmann glia (BG) using this novel optogenetic approach and tested whether memantine could counteract changes in BG and Purkinje cell (PC) morphology and expression of the main glial glutamate transporter-excitatory amino acid transporter 1 (EAAT1). Reactive BG induced by chronic optogenetic stimulation presented increased GFAP immunoreactivity, increased thickness and decreased length of its processes. Oral memantine (~90 mg/kg/day for 4 days) prevented thickening of the processes (1.57 to 1.81 vs. 1.62 μm) and strongly antagonized light-induced reduction in their average length (186.0 to 150.8 vs. 171.9 μm). Memantine also prevented the loss of the key glial glutamate transporter EAAT1 on BG. Finally, memantine reduced the loss of PC (4.2 ± 0.2 to 3.2 ± 0.2 vs. 4.1 ± 0.3 cells per 100 μm of the PC layer). These results identify memantine as potential neuroprotective therapeutics for cerebellar ataxias.

Is there hope that transpinal direct current stimulation corrects motoneuron excitability and provides neuroprotection in amyotrophic lateral sclerosis?

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease of largely unknown pathophysiology, characterized by the progressive loss of motoneurons (MNs). We review data showing that in presymptomatic ALS mice, MNs display reduced intrinsic excitability and impaired level of excitatory inputs. The loss of repetitive firing specifically affects the large MNs innervating fast contracting muscle fibers, which are the most vulnerable MNs in ALS. Interventions that aimed at restoring either the intrinsic excitability or the synaptic excitation result in a decrease of disease markers in MNs and delayed neuromuscular junction denervation. We then focus on trans‐spinal direct current stimulation (tsDCS), a noninvasive tool, since it modulates the activity of spinal neurons and networks. Effects of tsDCS depend on the polarity of applied current. Recent work shows that anodal tsDCS induces long‐lasting enhancement of MN excitability and synaptic excitation of spinal MNs. Moreover, we show preliminary results indicating that anodal tsDCS enhances the excitatory synaptic inputs to MNs in ALS mice. In conclusion, we suggest that chronic application of anodal tsDCS might be useful as a complementary method in the management of ALS patients.

Copper-ATSM as a Treatment for ALS: Support from Mutant SOD1 Models and Beyond

The blood-brain barrier permeant, copper-containing compound, CuII(atsm), has successfully progressed from fundamental research outcomes in the laboratory through to phase 2/3 clinical assessment in patients with the highly aggressive and fatal neurodegenerative condition of amyotrophic lateral sclerosis (ALS). The most compelling outcomes to date to indicate potential for disease-modification have come from pre-clinical studies utilising mouse models that involve transgenic expression of mutated superoxide dismutase 1 (SOD1). Mutant SOD1 mice provide a very robust mammalian model of ALS with high validity, but mutations in SOD1 account for only a small percentage of ALS cases in the clinic, with the preponderant amount of cases being sporadic and of unknown aetiology. As per other putative drugs for ALS developed and tested primarily in mutant SOD1 mice, this raises important questions about the pertinence of CuII(atsm) to broader clinical translation. This review highlights some of the challenges associated with the clinical translation of new treatment options for ALS. It then provides a brief account of pre-clinical outcomes for CuII(atsm) in SOD1 mouse models of ALS, followed by an outline of additional studies which report positive outcomes for CuII(atsm) when assessed in cell and mouse models of neurodegeneration which do not involve mutant SOD1. Clinical evidence for CuII(atsm) selectively targeting affected regions of the CNS in patients is also presented. Overall, this review summarises the existing evidence which indicates why clinical relevance of CuII(atsm) likely extends beyond the context of cases of ALS caused by mutant SOD1.

Intranasal IL-4 Administration Alleviates Functional Deficits of Periventricular Leukomalacia in Neonatal Mice

Background: Periventricular leukomalacia (PVL) is the major form of brain injury in premature infants. Currently, there are no therapies to treat PVL. Several studies suggested that polarization of microglia, a resident macrophage-like immune cell in the central nervous system, plays a vital role in brain injury and recovery. As an important mediator of immunity, interleukin-4 (IL-4) has critical effects on many immune cells, such as astrocytes and microglia. Increasing evidence shows that IL-4 plays a well-established role in attenuating inflammation in neurological disorders. Additionally, as a noninvasive and highly effective method, intranasal drug administration is gaining increasing attention. Therefore, in our study, we hypothesized that intranasal IL-4 administration is a promising strategy for PVL treatment.

Methods: The therapeutic effects of IL-4 on neuroprotection were evaluated using a Control group, Hypoxia group, and Hypoxia + IL-4 treatment group. The PVL mouse model was established by a severe acute hypoxia (SAH) protocol. Exogenous IL-4 was intranasally administered to investigate its neuroprotective effects. A functional study was used to investigate neurological deficits, immunohistochemical technology and Western blotting were used to detect protein levels, and electron microscopy was used to evaluate myelination.

Results: The results suggested that hypoxia stimulated Iba1⁺ microglial activation, downregulated myelin-related gene (NG2, MAG, and MBP) expression, reduced MBP protein levels, and caused neurological deficits. However, the intranasal administration of exogenous IL-4 partially inhibited Iba1+ microglial activation, improved myelination, and alleviated neurological deficits. The mechanistic study showed that IL-4 improved myelination possibly through the IL-4Ra-mediated polarization of microglia from the M1 phenotype to the M2 phenotype.

Conclusion: In summary, our findings demonstrated that the intranasal administration of exogenous IL-4 improves myelination and attenuates functional deficits in a hypoxia-induced PVL model. Intranasal IL-4 administration may be a promising strategy for PVL treatment, for which further mechanistic studies are urgent.

Chronic Memantine Treatment Ameliorates Behavioral Deficits, Neuron Loss, and Impaired Neurogenesis in a Model of Alzheimer's Disease

Memantine, a non-competitive NMDA receptor antagonist possessing neuroprotective properties, belongs to the small group of drugs which have been approved for the treatment of Alzheimer's disease (AD). While several preclinical studies employing different transgenic AD mouse models have described beneficial effects with regard to rescued behavioral deficits or reduced amyloid plaque pathology, it is largely unknown whether memantine might have beneficial effects on neurodegeneration. In the current study, we assessed whether memantine treatment has an impact on hippocampal neuron loss and associated behavioral deficits in the Tg4-42 mouse model of AD. We demonstrate that a chronic oral memantine treatment for 4 months diminishes hippocampal CA1 neuron loss and rescues learning and memory performance in different behavioral paradigms, such as Morris water maze or a novel object recognition task. Cognitive benefits of chronic memantine treatment were accompanied by an amelioration of impaired adult hippocampal neurogenesis. Taken together, our results demonstrate that memantine successfully counteracts pathological alterations in a preclinical mouse model of AD.

Pharmacophore-driven identification of N-methyl-D-receptor antagonists as potent neuroprotective agents validated using in vivo studies

Alzheimer's disease (AD), apparently the most widespread reason behind dementia, is delineated by a continuous cognitive weakening in the aged. During its progression, N-methyl-D-aspartate receptor (NMDAR) antagonists are known to play a pivotal part in the mechanisms of learning and memory. Since there is an unmet medical need for the treatment of AD, we aim to identify possible chemical compounds targeted toward N-methyl-D-aspartate receptors. Three-dimensional models are developed to unveil some of the essential characteristics of the N-methyl-D-aspartate receptors by using a collection of already discovered N-methyl-D-aspartate receptor inhibitors. This is followed by virtual screening, which results in novel chemical compounds having the potential to inhibit N-methyl-D-aspartate receptors. Molecular docking studies and analysis promulgated two lead compounds with a high LibDock score. The compounds are shortlisted based on high estimated activity, fit values, LibDock score, no violation of Lipinski's, and availability for procuring. Finally, the shortlisted compounds are tested by employing in vivo studies, which we further propose as potential NMDA inhibitors for treating AD.

Excitatory Dendritic Mitochondrial Calcium Toxicity: Implications for Parkinson's and Other Neurodegenerative Diseases

Dysregulation of calcium homeostasis has been linked to multiple neurological diseases. In addition to excitotoxic neuronal cell death observed following stroke, a growing number of studies implicate excess excitatory neuronal activity in chronic neurodegenerative diseases. Mitochondria function to rapidly sequester large influxes of cytosolic calcium through the activity of the mitochondrial calcium uniporter (MCU) complex, followed by more gradual release via calcium antiporters, such as NCLX. Increased cytosolic calcium levels almost invariably result in increased mitochondrial calcium uptake. While this response may augment mitochondrial respiration, limiting classic excitotoxic injury in the short term, recent studies employing live calcium imaging and molecular manipulation of calcium transporter activities suggest that mitochondrial calcium overload plays a key role in Parkinson’s disease (PD), Alzheimer’s disease (AD), amyotrophic lateral sclerosis (ALS), and related dementias [PD with dementia (PDD), dementia with Lewy bodies (DLB), and frontotemporal dementia (FTD)]. Herein, we review the literature on increased excitatory input, mitochondrial calcium dysregulation, and the transcriptional or post-translational regulation of mitochondrial calcium transport proteins, with an emphasis on the PD-linked kinases LRRK2 and PINK1. The impact on pathological dendrite remodeling and neuroprotective effects of manipulating MCU, NCLX, and LETM1 are reviewed. We propose that shortening and simplification of the dendritic arbor observed in neurodegenerative diseases occur through a process of excitatory mitochondrial toxicity (EMT), which triggers mitophagy and perisynaptic mitochondrial depletion, mechanisms that are distinct from classic excitotoxicity.

Synaptic dysfunction and altered excitability in C9ORF72 ALS/FTD

Amyotrophic lateral sclerosis (ALS) is characterized by a progressive degeneration of upper and lower motor neurons, resulting in fatal paralysis due to denervation of the muscle. Due to genetic, pathological and symptomatic overlap, ALS is now considered a spectrum disease together with frontotemporal dementia (FTD), the second most common cause of dementia in individuals under the age of 65. Interestingly, in both diseases, there is a large prevalence of RNA binding proteins (RBPs) that are mutated and considered disease-causing, or whose dysfunction contribute to disease pathogenesis. The most common shared genetic mutation in ALS/FTD is a hexanucleuotide repeat expansion within intron 1 of C9ORF72 (C9). Three potentially overlapping, putative toxic mechanisms have been proposed: loss of function due to haploinsufficient expression of the C9ORF72 mRNA, gain of function of the repeat RNA aggregates, or RNA foci, and repeat-associated non-ATG-initiated translation (RAN) of the repeat RNA into toxic dipeptide repeats (DPRs). Regardless of the causative mechanism, disease symptoms are ultimately caused by a failure of neurotransmission in three regions: the brain, the spinal cord, and the neuromuscular junction. Here, we review C9 ALS/FTD-associated synaptic dysfunction and aberrant neuronal excitability in these three key regions, focusing on changes in morphology and synapse formation, excitability, and excitotoxicity in patients, animal models, and in vitro models. We compare these deficits to those seen in other forms of ALS and FTD in search of shared pathways, and discuss the potential targeting of synaptic dysfunctions for therapeutic intervention in ALS and FTD patients.

Suppression of CHRN endocytosis by carbonic anhydrase CAR3 in the pathogenesis of myasthenia gravis

Myasthenia gravis is an autoimmune disorder of the neuromuscular junction manifested as fatigable muscle weakness, which is typically caused by pathogenic autoantibodies against postsynaptic CHRN/AChR (cholinergic receptor nicotinic) in the endplate of skeletal muscle. Our previous studies have identified CA3 (carbonic anhydrase 3) as a specific protein insufficient in skeletal muscle from myasthenia gravis patients. In this study, we investigated the underlying mechanism of how CA3 insufficiency might contribute to myasthenia gravis. Using an experimental autoimmune myasthenia gravis animal model and the skeletal muscle cell C2C12, we find that inhibition of CAR3 (the mouse homolog of CA3) promotes CHRN internalization via a lipid raft-mediated pathway, leading to accelerated degradation of postsynaptic CHRN. Activation of CAR3 reduces CHRN degradation by suppressing receptor endocytosis. CAR3 exerts this effect by suppressing chaperone-assisted selective autophagy via interaction with BAG3 (BCL2-associated athanogene 3) and by dampening endoplasmic reticulum stress. Collectively, our study illustrates that skeletal muscle cell CAR3 is critical for CHRN homeostasis in the neuromuscular junction, and its deficiency leads to accelerated degradation of CHRN and development of myasthenia gravis, potentially revealing a novel therapeutic approach for this disorder.

Potential new complication in drug therapy development for amyotrophic lateral sclerosis

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by motor neuron degeneration in the brain and spinal cord. Treatment development for ALS is complicated by complex underlying disease factors. Areas covered: Numerous tested drug compounds have shown no benefits in ALS patients, although effective in animal models. Discrepant results of pre-clinical animal studies and clinical trials for ALS have primarily been attributed to limitations of ALS animal models for drug-screening studies and methodological inconsistencies in human trials. Current status of pre-clinical and clinical trials in ALS is summarized. Specific blood-CNS barrier damage in ALS patients, as a novel potential reason for the clinical failures in drug therapies, is discussed. Expert commentary: Pathological perivascular collagen IV accumulation, one unique characteristic of barrier damage in ALS patients, could be hindering transport of therapeutics to the CNS. Restoration of B-CNS-B integrity would foster delivery of therapeutics to the CNS.

Amyotrophic Lateral Sclerosis, 2016: existing therapies and the ongoing search for neuroprotection

INTRODUCTION

Amyotrophic lateral sclerosis (ALS), one in a family of age-related neurodegenerative disorders, is marked by predominantly cryptogenic causes, partially elucidated pathophysiology, and elusive treatments. The challenges of ALS are illustrated by two decades of negative drug trials.

AREAS COVERED

In this article, we lay out the current understanding of disease genesis and physiology in relation to drug development in ALS, stressing important accomplishments and gaps in knowledge. We briefly consider clinical ALS, the ongoing search for biomarkers, and the latest in trial design, highlighting major recent and ongoing clinical trials; and we discuss, in a concluding section on future directions, the prion-protein hypothesis of neurodegeneration and what steps can be taken to end the drought that has characterized drug discovery in ALS.

EXPERT OPINION

Age-related neurodegenerative disorders are fast becoming major public health problems for the world's aging populations. Several agents offer promise in the near-term, but drug development is hampered by an interrelated cycle of obstacles surrounding etiological, physiological, and biomarkers discovery. It is time for the type of government-funded, public-supported offensive on neurodegenerative disease that has been effective in other fields.

A retrospective review of the progress in amyotrophic lateral sclerosis drug discovery over the last decade and a look at the latest strategies

INTRODUCTION

Drug discovery for amyotrophic lateral sclerosis (ALS) has experienced a surge in clinical studies and remarkable preclinical milestones utilizing a variety of mutant superoxide dismutase 1 model systems. Of the drugs that were tested and showed positive preclinical effects, none demonstrated therapeutic benefits to ALS patients in clinical settings.

AREAS COVERED

This review discusses the advances made in drug discovery for ALS and highlights why drug development is proving to be so difficult. It also discusses how a closer look at both preclinical and clinical studies could uncover the reasons why these preclinical successes have yet to result in the availability of an effective drug for clinical use.

EXPERT OPINION

Valuable lessons from the numerous preclinical and clinical studies supply the biggest advantage in the monumental task of finding a cure for ALS. Obviously, a single design type for ALS clinical trials has not yielded success. The authors suggest a two-pronged approach that may prove essential to achieve clinical efficacy in the identification of novel targets and preclinical testing in multiple models to identify biomarkers that can function in diagnostic, predictive and prognostic roles, and changes to clinical trial design and patient recruitment criteria. The advancement of technology and invention of more powerful tools will further enhance the above. This will give rise to more sophisticated clinical trials with consideration of a range of criteria from: optimum dose, route of delivery, specific biomarkers, pharmacokinetics, pharmacodynamics and toxicology to biomarkers, timing for trial and patients' clinical status.

Characterization of the Contribution of Genetic Background and Gender to Disease Progression in the SOD1 G93A Mouse Model of Amyotrophic Lateral Sclerosis: A Meta-Analysis

Background: The SOD1 G93A mouse model of amyotrophic lateral sclerosis (ALS) is the most frequently used model to examine ALS pathophysiology. There is a lack of homogeneity in usage of the SOD1 G93A mouse, including differences in genetic background and gender, which could confound the field’s results.

Objective: In an analysis of 97 studies, we characterized the ALS progression for the high transgene copy control SOD1 G93A mouse on the basis of disease onset, overall lifespan, and disease duration for male and female mice on the B6SJL and C57BL/6J genetic backgrounds and quantified magnitudes of differences between groups.

Methods: Mean age at onset, onset assessment measure, disease duration, and overall lifespan data from each study were extracted and statistically modeled as the response of linear regression with the sex and genetic background factored as predictors. Additional examination was performed on differing experimental onset and endpoint assessment measures.

Results: C57BL/6 background mice show delayed onset of symptoms, increased lifespan, and an extended disease duration compared to their sex-matched B6SJL counterparts. Female B6SJL generally experience extended lifespan and delayed onset compared to their male counterparts, while female mice on the C57BL/6 background show delayed onset but no difference in survival compared to their male counterparts. Finally, different experimental protocols (tremor, rotarod, etc.) for onset determination result in notably different onset means.

Conclusions: Overall, the observed effect of sex on disease endpoints was smaller than that which can be attributed to the genetic background. The often-reported increase in lifespan for female mice was observed only for mice on the B6SJL background, implicating a strain-dependent effect of sex on disease progression that manifests despite identical mutant SOD1 expression.

ABC transporter-driven pharmacoresistance in Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis (ALS) is a slowly progressing neurodegenerative disease that affects motor neurons of the nervous system. Despite the identification of many potential therapeutics targeting pathogenic mechanisms in in vitro models, there has been limited progress in translating them into a successful pharmacotherapy in the animal model of ALS. Further, efforts to translate any promising results from preclinical trials to effective pharmacotherapies for patients have been unsuccessful, with the exception of riluzole, the only FDA-approved medication, which only modestly extends survival both in the animal model and in patients. Thus, it is essential to reconsider the strategies for developing ALS pharmacotherapies. Growing evidence suggests that problems identifying highly effective ALS treatments may result from an underestimated issue of drug bioavailability and disease-driven pharmacoresistance, mediated by the ATP-binding cassette (ABC) drug efflux transporters. ABC transporters are predominately localized to the lumen of endothelial cells of the blood-brain and blood-spinal cord barriers (BBB, BSCB) where they limit the entry into the central nervous system (CNS) of a wide range of neurotoxicants and xenobiotics, but also therapeutics. In ALS, expression and function of ABC transporters is increased at the BBB/BSCB and their expression has been detected on neurons and glia in the CNS parenchyma, which may further reduce therapeutic action in target cells. Understanding and accounting for the contribution of these transporters to ALS pharmacoresistance could both improve the modest effects of riluzole and set in motion a re-evaluation of previous ALS drug disappointments. In addition, identifying pathogenic mechanisms regulating ABC transporter expression and function in ALS may lead to the development of new therapeutic strategies. It is likely that novel pharmacological approaches require counteracting pharmacoresistance to improve therapeutic efficacy. This article is part of a Special Issue entitled ALS complex pathogenesis.

Long-term oral administration of the NMDA receptor antagonist memantine extends life span in spinocerebellar ataxia type 1 knock-in mice

Spinocerebellar ataxia type 1 (SCA1) is a progressive neurodegenerative disease caused by extension of a CAG repeat in the Sca1gene. Although the mechanisms underlying the symptoms of SCA1 have not been determined, aberrant neuronal activation potentially contributes to the neuronal cell death characteristic of the disease. Here we examined the potential involvement of extrasynaptic N-methyl-d-aspartate receptor (NMDAR) activation in the pathogenesis of SCA1 by administering memantine, a low-affinity noncompetitive NMDAR antagonist, in SCA1 knock-in (KI) mice. In KI mice, the exon in the ataxin 1 gene is replaced with abnormally expanded 154CAG repeats. Memantine was administered orally to the SCA1 KI mice from 4 weeks of age until death. The treatment significantly attenuated body-weight loss and prolonged the life span of SCA1 KI mice. Furthermore, memantine significantly suppressed the loss of Purkinje cells in the cerebellum and motor neurons in the dorsal motor nucleus of the vagus, which are critical for motor function and parasympathetic function, respectively. These findings support the contribution of aberrant activation of extrasynaptic NMDARs to neuronal cell death in SCA1 KI mice and suggest that memantine may also have therapeutic benefits in human SCA1 patients.

Gacyclidine improves the survival and reduces motor deficits in a mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder typified by a massive loss of motor neurons with few therapeutic options. The exact cause of neuronal degeneration is unknown but it is now admitted that ALS is a multifactorial disease with several mechanisms involved including glutamate excitotoxicity. More specifically, N-methyl-D-aspartate (NMDA)-mediated cell death and impairment of the glutamate-transport has been suggested to play a key role in ALS pathophysiology. Thus, evaluating NMDAR antagonists is of high therapeutic interest. Gacyclidine, also named GK11, is a high affinity non-competitive NMDAR antagonist that may protect against motor neuron death in an ALS context. Moreover, GK11 presents a low intrinsic neurotoxicity and has already been used in two clinical trials for CNS lesions. In the present study, we investigated the influence of chronic administration of two doses of GK11 (0.1 and 1 mg/kg) on the survival and the functional motor activity of hSOD1(G93A) mice, an animal model of ALS. Treatment started at early symptomatic age (60 days) and was applied bi-weekly until the end stage of the disease. We first confirmed that functional alteration of locomotor activity was evident in the hSOD1(G93A) transgenic female mice by 60 days of age. A low dose of GK11 improved the survival of the mice by 4.3% and partially preserved body weight. Improved life span was associated with a delay in locomotor function impairment. Conversely, the high dose treatment worsened motor functions. These findings suggest that chronic administration of GK11 beginning at early symptomatic stage may be beneficial for patients with ALS.

The neuroprotection exerted by memantine, minocycline and lithium, against neurotoxicity of CSF from patients with amyotrophic lateral sclerosis, is antagonized by riluzole

In a recent study we found that cerebrospinal fluids (CSFs) from amyotrophic lateral sclerosis (ALS) patients caused 20-30% loss of cell viability in primary cultures of rat embryo motor cortex neurons. We also found that the antioxidant resveratrol protected against such damaging effects and that, surprisingly, riluzole antagonized its protecting effects. Here we have extended this study to the interactions of riluzole with 3 other recognized neuroprotective agents, namely memantine, minocycline and lithium. We found: (1) by itself riluzole exerted neurotoxic effects at concentrations of 3-30 µM; this cell damage was similar to that elicited by 30 µM glutamate and a 10% dilution of ALS/CSF; (2) memantine (0.1-30 µM), minocycline (0.03-1 µM) and lithium (1-80 µg/ml) afforded 10-30% protection against ALS/CSF-elicited neurotoxicity, and (3) at 1-10 µM, riluzole antagonized the protection afforded by the 3 agents. These results strongly support the view that at the riluzole concentrations reached in the brain of patients, the neurotoxic effects of this drug could be masking the potential neuroprotective actions of new compounds being tested in clinical trials. Therefore, in the light of the present results, the inclusion of a group of patients free of riluzole treatment may be mandatory in future clinical trials performed in ALS patients with novel neuroprotective compounds.

Therapeutic neuroprotective agents for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal chronic neurodegenerative disease whose hallmark is proteinaceous, ubiquitinated, cytoplasmic inclusions in motor neurons and surrounding cells. Multiple mechanisms proposed as responsible for ALS pathogenesis include dysfunction of protein degradation, glutamate excitotoxicity, mitochondrial dysfunction, apoptosis, oxidative stress, and inflammation. It is therefore essential to gain a better understanding of the underlying disease etiology and search for neuroprotective agents that might delay disease onset, slow progression, prolong survival, and ultimately reduce the burden of disease. Because riluzole, the only Food and Drug Administration (FDA)-approved treatment, prolongs the ALS patient's life by only 3 months, new therapeutic agents are urgently needed. In this review, we focus on studies of various small pharmacological compounds targeting the proposed pathogenic mechanisms of ALS and discuss their impact on disease progression.

Intermittent hypoxia can aggravate motor neuronal loss and cognitive dysfunction in ALS mice

BACKGROUND

Patients with ALS may be exposed to variable degrees of chronic intermittent hypoxia. However, all previous experimental studies on the effects of hypoxia in ALS have only used a sustained hypoxia model and it is possible that chronic intermittent hypoxia exerts effects via a different molecular mechanism from that of sustained hypoxia. No study has yet shown that hypoxia (either chronic intermittent or sustained) can affect the loss of motor neurons or cognitive function in an in vivo model of ALS.

OBJECTIVE

To evaluate the effects of chronic intermittent hypoxia on motor and cognitive function in ALS mice.

METHODS

Sixteen ALS mice and 16 wild-type mice were divided into 2 groups and subjected to either chronic intermittent hypoxia or normoxia for 2 weeks. The effects of chronic intermittent hypoxia on ALS mice were evaluated using the rotarod, Y-maze, and wire-hanging tests. In addition, numbers of motor neurons in the ventral horn of the spinal cord were counted and western blot analyses were performed for markers of oxidative stress and inflammatory pathway activation.

RESULTS

Compared to ALS mice kept in normoxic conditions, ALS mice that experienced chronic intermittent hypoxia had poorer motor learning on the rotarod test, poorer spatial memory on the Y-maze test, shorter wire hanging time, and fewer motor neurons in the ventral spinal cord. Compared to ALS-normoxic and wild-type mice, ALS mice that experienced chronic intermittent hypoxia had higher levels of oxidative stress and inflammation.

CONCLUSIONS

Chronic intermittent hypoxia can aggravate motor neuronal death, neuromuscular weakness, and probably cognitive dysfunction in ALS mice. The generation of oxidative stress with activation of inflammatory pathways may be associated with this mechanism. Our study will provide insight into the association of hypoxia with disease progression, and in turn, the rationale for an early non-invasive ventilation treatment in patients with ALS.

[Amyotrophic lateral sclerosis: update on etiological treatment]

Amyotrophic lateral sclerosis is a rare neurodegenerative disease. It is characterized by motoneurons progressive degeneration. Associated with a paralysis of the legs, arms and the respiratory muscles, its evolution is lethal. Riluzole is the only drug available with an marketing authorisation (autorisation de mise sur le marché [AMM]) in this indication. In the beginning stages of the disease it demonstrated a modest efficacy by prolonging survival for a few months. Although the physiopathological mechanisms of this disease have not been totally solved, the progression of knowledge in recent years in this area led to the development of a large number of neuroprotective agents which showed effective results in animal models of ALS and which could be good candidates for the treatment of ALS. Several clinical trials have been conducted about antiglutamatergic, antioxidant, antiapoptotic agents and growing cell factors but they failed to demonstrate efficacy on survival or quality of life. Therefore, clinical trials using innovative therapeutics and stem cells are ongoing and offer more distant hope.

Role of the N-methyl-d-aspartate receptors complex in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is an adult onset neurodegenerative disease pathologically characterized by the massive loss of motor neurons in the spinal cord, brain stem and cerebral cortex. There is a consensus in the field that ALS is a multifactorial pathology and a number of possible mechanisms have been suggested. Among the proposed hypothesis, glutamate toxicity has been one of the most investigated. Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor mediated cell death and impairment of the glutamate-transport system have been suggested to play a central role in the glutamate-mediated motor neuron degeneration. In this context, the role played by the N-methyl-d-aspartate (NMDA) receptor has received considerable less attention notwithstanding its high Ca(2+) permeability, expression in motor neurons and its importance in excitotoxicity. This review overviews the critical role of NMDA-mediated toxicity in ALS, with a particular emphasis on the endogenous modulators of the NMDAR.

Effects of prolonged treatment with memantine in the MRL model of CNS lupus

OBJECTIVES

Neuropsychiatric manifestations and brain atrophy of unknown etiology are common and severe complications of systemic lupus erythematosus (SLE). An autoantibody that binds to N-methyl-D-aspartate (NMDA) receptor NR2 has been proposed as a key factor in the etiology of central nervous system (CNS) SLE. This hypothesis was supported by evidence suggesting memantine (MEM), an uncompetitive NMDA receptor antagonist, prevents behavioral dysfunction and brain pathology in healthy mice immunized with a peptide similar to an epitope on the NR2 receptor. Given that SLE is a chronic condition, we presently examine the effects of MEM in MRL/lpr mice, which develop behavioral deficits alongside SLE-like disease.

METHODS

A broad behavioral battery and 7-Tesla MRI were used to examine whether prolonged treatment with MEM (~25 mg/kg b.w. in drinking water) prevents CNS involvement in this spontaneous model of SLE.

RESULTS

Although MEM increased novel object exploration in MRL/lpr mice, it did not show other beneficial, substrain-specific effects. Conversely, MEM was detrimental to spontaneous activity in control MRL +/+ mice and had a negative effect on body mass gain. Similarly, MRI revealed comparable increases in the volume of periventricular structures in MEM-treated groups.

CONCLUSIONS

Sustained exposure to MEM affects body growth, brain morphology, and behavior primarily by pharmacological, and not autoimmunity-dependant mechanisms. Substrain-specific improvement in exploratory behavior of MEM-treated MRL/lpr mice may indicate that the NMDA system is merely a constituent of a complex pathogenenic cascade. However, it was evident that chronic administration of MEM is unable to completely prevent the development of a CNS SLE-like syndrome.

Clinical recognition and management of amyotrophic lateral sclerosis: the nurse's role

Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, causes a progressive wasting and loss of the upper and lower motor neurons that facilitate the movement of body parts. At onset, ALS patients may show symptoms such as muscle weakness, atrophy, hyperreflexia, or bulbar symptoms such as dysphagia or dysarthria. Deterioration progresses rapidly, and the later stages of ALS are characterized by severely limited mobility and respiratory failure, which is the primary cause of death. There is no specific diagnostic test for ALS, and there are a number of other conditions that may resemble ALS, making a diagnosis difficult. The variability of the initial presentation combined with the broad differential diagnosis may result in significant delays in diagnosis or, in some cases, misdiagnosis, which in turn have a negative impact on patient outcomes. There is no cure for ALS; however, many of the symptoms are treatable, and the physical and psychological symptoms are best managed through the efforts of a coordinated, multidisciplinary team. Nurses play a critical role in the clinical management of ALS and may be involved in coordinating the activities of the team, facilitating treatment, and helping patients and caregivers in making informed treatment and end-of-life decisions. Drug therapy for ALS is currently limited to riluzole; however, patients may be treated with a number of nonpharmacologic methods on the basis of their symptoms. A number of other treatment modalities, such as stem-cell-based therapy or gene therapy, and an array of neuroprotective clinical trials are currently under development for the treatment of ALS. Nurses may also have a key role in these various ALS studies.

One universal common endpoint in mouse models of amyotrophic lateral sclerosis

There is no consensus among research laboratories around the world on the criteria that define endpoint in studies involving rodent models of amyotrophic lateral sclerosis (ALS). Data from 4 nutrition intervention studies using 162 G93A mice, a model of ALS, were analyzed to determine if differences exist between the following endpoint criteria: CS 4 (functional paralysis of both hindlimbs), CS 4+ (CS 4 in addition to the earliest age of body weight loss, body condition deterioration or righting reflex), and CS 5 (CS 4 plus righting reflex >20 s). The age (d; mean ± SD) at which mice reached endpoint was recorded as the unit of measurement. Mice reached CS 4 at 123.9±10.3 d, CS 4+ at 126.6±9.8 d and CS 5 at 127.6±9.8 d, all significantly different from each other (P<0.001). There was a significant positive correlation between CS 4 and CS 5 (r = 0.95, P<0.001), CS 4 and CS 4+ (r = 0.96, P<0.001), and CS 4+ and CS 5 (r = 0.98, P<0.001), with the Bland-Altman plot showing an acceptable bias between all endpoints. Logrank tests showed that mice reached CS 4 24% and 34% faster than CS 4+ (P = 0.046) and CS 5 (P = 0.006), respectively. Adopting CS 4 as endpoint would spare a mouse an average of 4 days (P<0.001) from further neuromuscular disability and poor quality of life compared to CS 5. Alternatively, CS 5 provides information regarding proprioception and severe motor neuron death, both could be important parameters in establishing the efficacy of specific treatments. Converging ethics and discovery, would adopting CS 4 as endpoint compromise the acquisition of insight about the effects of interventions in animal models of ALS?

Current and emerging treatments for amyotrophic lateral sclerosis

BACKGROUND

Amyotrophic lateral sclerosis (ALS) is a relatively rare neurodegenerative disorder of both upper and lower motoneurons. Currently, the management of ALS is essentially symptoms-based, and riluzole, an antiglutamatergic agent, is the only drug for the treatment of ALS approved by the food and drug administration.

OBJECTIVE

We reviewed current literature concerning emerging treatments for amyotrophic lateral sclerosis.

METHODS

A Medline literature search was performed to identify all studies on ALS treatment published from January 1st, 1986 through August 31st, 2009. We selected papers concerning only disease-modifying therapy.

RESULTS

Forty-eight compounds were identified and reviewed in this study.

CONCLUSIONS

Riluzole is the only compound that demonstrated a beneficial effect on ALS patients, but with only modest increase in survival. Although several drugs showed effective results in the animal models for ALS, none of them significantly prolonged survival or improved quality of life of ALS patients. Several factors have been implicated in explaining the predominantly negative results of numerous randomized clinical trials in ALS, including methodological problems in the use of animal-drug screening, the lack of assessment of pharmacokinetic profile of the drugs, and methodological pitfalls of clinical trials in ALS patients.