Altered metabolism of excitatory amino acids, N-acetyl-aspartate and N-acetyl-aspartyl-glutamate in amyotrophic lateral sclerosis

How do we get from hyperexcitability to excitotoxicity in amyotrophic lateral sclerosis?

Amyotrophic lateral sclerosis is a devastating neurodegenerative disease that, at present, has no effective cure. Evidence of increased circulating glutamate and hyperexcitability of the motor cortex in patients with amyotrophic lateral sclerosis have provided an empirical support base for the 'dying forward' excitotoxicity hypothesis. The hypothesis postulates that increased activation of upper motor neurons spreads pathology to lower motor neurons in the spinal cord in the form of excessive glutamate release, which triggers excitotoxic processes. Many clinical trials have focused on therapies that target excitotoxicity via dampening neuronal activation, but not all are effective. As such, there is a growing tension between the rising tide of evidence for the 'dying forward' excitotoxicity hypothesis and the failure of therapies that target neuronal activation. One possible solution to these contradictory outcomes is that our interpretation of the current evidence requires revision in the context of appreciating the complexity of the nervous system and the limitations of the neurobiological assays we use to study it. In this review we provide an evaluation of evidence relevant to the 'dying forward' excitotoxicity hypothesis and by doing so, identify key gaps in our knowledge that need to be addressed. We hope to provide a road map from hyperexcitability to excitotoxicity so that we can better develop therapies for patients suffering from amyotrophic lateral sclerosis. We conclude that studies of upper motor neuron activity and their synaptic output will play a decisive role in the future of amyotrophic lateral sclerosis therapy.

Insights on Natural Products Against Amyotrophic Lateral Sclerosis (ALS)

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease that causes the death of motor neurons and consequent muscle paralysis. Despite many efforts to address it, current therapy targeting ALS remains limited, increasing the interest in complementary therapies. Over the years, several herbal preparations and medicinal plants have been studied to prevent and treat this disease, which has received remarkable attention due to their blood-brain barrier penetration properties and low toxicity. Thus, this review presents the therapeutic potential of a variety of medicinal herbs and their relationship with ALS and their physiopathological pathways.

Regulation of cortical hyperexcitability in amyotrophic lateral sclerosis: focusing on glial mechanisms

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by the loss of both upper and lower motor neurons, resulting in muscle weakness, atrophy, paralysis, and eventually death. Motor cortical hyperexcitability is a common phenomenon observed at the presymptomatic stage of ALS. Both cell-autonomous (the intrinsic properties of motor neurons) and non-cell-autonomous mechanisms (cells other than motor neurons) are believed to contribute to cortical hyperexcitability. Decoding the pathological relevance of these dynamic changes in motor neurons and glial cells has remained a major challenge. This review summarizes the evidence of cortical hyperexcitability from both clinical and preclinical research, as well as the underlying mechanisms. We discuss the potential role of glial cells, particularly microglia, in regulating abnormal neuronal activity during the disease progression. Identifying early changes such as neuronal hyperexcitability in the motor system may provide new insights for earlier diagnosis of ALS and reveal novel targets to halt the disease progression.

Synchrotron-Based Fourier-Transform Infrared Micro-Spectroscopy of Cerebrospinal Fluid from Amyotrophic Lateral Sclerosis Patients Reveals a Unique Biomolecular Profile

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease, with the most common adult-onset neurodegenerative disorder affecting motoneurons. Although disruptions in macromolecular conformation and homeostasis have been described in association with ALS, the underlying pathological mechanisms are still not completely understood, and unambiguous biomarkers are lacking. Fourier Transform Infrared Spectroscopy (FTIR) of cerebrospinal fluid (CSF) is appealing to extensive interest due to its potential to resolve biomolecular conformation and content, as this approach offers a non-invasive, label-free identification of specific biologically relevant molecules in a few microliters of CSF sample. Here, we analyzed the CSF of 33 ALS patients compared to 32 matched controls using FTIR spectroscopy and multivariate analysis and demonstrated major differences in the molecular contents. A significant change in the conformation and concentration of RNA is demonstrated. Moreover, significantly increased glutamate and carbohydrates are found in ALS. Moreover, key markers of lipid metabolism are strongly altered; specifically, we find a decrease in unsaturated lipids and an increase in peroxidation of lipids in ALS, whereas the total amount of lipids compared to proteins is reduced. Our study demonstrates that FTIR characterization of CSF could represent a powerful tool for ALS diagnosis and reveals central features of ALS pathophysiology.

Glial Glutamine Homeostasis in Health and Disease

Glutamine is an essential cerebral metabolite. Several critical brain processes are directly linked to glutamine, including ammonia homeostasis, energy metabolism and neurotransmitter recycling. Astrocytes synthesize and release large quantities of glutamine, which is taken up by neurons to replenish the glutamate and GABA neurotransmitter pools. Astrocyte glutamine hereby sustains the glutamate/GABA-glutamine cycle, synaptic transmission and general brain function. Cerebral glutamine homeostasis is linked to the metabolic coupling of neurons and astrocytes, and relies on multiple cellular processes, including TCA cycle function, synaptic transmission and neurotransmitter uptake. Dysregulations of processes related to glutamine homeostasis are associated with several neurological diseases and may mediate excitotoxicity and neurodegeneration. In particular, diminished astrocyte glutamine synthesis is a common neuropathological component, depriving neurons of an essential metabolic substrate and precursor for neurotransmitter synthesis, hereby leading to synaptic dysfunction. While astrocyte glutamine synthesis is quantitatively dominant in the brain, oligodendrocyte-derived glutamine may serve important functions in white matter structures. In this review, the crucial roles of glial glutamine homeostasis in the healthy and diseased brain are discussed. First, we provide an overview of cellular recycling, transport, synthesis and metabolism of glutamine in the brain. These cellular aspects are subsequently discussed in relation to pathological glutamine homeostasis of hepatic encephalopathy, epilepsy, Alzheimer's disease, Huntington's disease and amyotrophic lateral sclerosis. Further studies on the multifaceted roles of cerebral glutamine will not only increase our understanding of the metabolic collaboration between brain cells, but may also aid to reveal much needed therapeutic targets of several neurological pathologies.

Inhibitory interneurons show early dysfunction in a SOD1 mouse model of amyotrophic lateral sclerosis

Few studies in amyotrophic lateral sclerosis (ALS) measure effects of the disease on inhibitory interneurons synapsing onto motoneurons (MNs). However, inhibitory interneurons could contribute to dysfunction, particularly if altered before MN neuropathology, and establish a long-term imbalance of inhibition/excitation. We directly assessed excitability and morphology of glycinergic (GlyT2 expressing) ventral lumbar interneurons from SOD1G93AGlyT2eGFP (SOD1) and wild-type GlyT2eGFP (WT) mice on postnatal days 6-10. Patch clamp revealed dampened excitability in SOD1 interneurons, including depolarized persistent inward currents (PICs), increased voltage and current threshold for firing action potentials, along with a marginal decrease in afterhyperpolarization duration. Primary neurites of ventral SOD1 inhibitory interneurons were larger in volume and surface area than WT. GlyT2 interneurons were then divided into three subgroups based on location: (1) interneurons within 100 μm of the ventral white matter, where Renshaw cells (RCs) are located, (2) interneurons interspersed with MNs in lamina IX, and (3) interneurons in the intermediate ventral area including laminae VII and VIII. Ventral interneurons in the RC area were the most profoundly affected, exhibiting more depolarized PICs and larger primary neurites. Interneurons in lamina IX had depolarized PIC onset. In lamina VII-VIII, interneurons were least affected. In summary, inhibitory interneurons show very early region-specific perturbations poised to impact excitatory/inhibitory balance of MNs, modify motor output and provide early biomarkers of ALS. Therapeutics like riluzole that universally reduce CNS excitability could exacerbate the inhibitory dysfunction described here. KEY POINTS: Spinal inhibitory interneurons could contribute to amyotrophic lateral sclerosis (ALS) pathology, but their excitability has never been directly measured. We studied the excitability and morphology of glycinergic interneurons in early postnatal transgenic mice (SOD1G93A GlyT2eGFP). Interneurons were less excitable and had marginally smaller somas but larger primary neurites in SOD1 mice. GlyT2 interneurons were analysed according to their localization within the ventral spinal cord. Interestingly, the greatest differences were observed in the most ventrally located interneurons. We conclude that inhibitory interneurons show presymptomatic changes that may contribute to excitatory/inhibitory imbalance in ALS.

Biomarkers and molecular mechanisms of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease in adults involving non-demyelinating motor disorders. About 90% of ALS cases are sporadic, while 10-12% of cases are due to some genetic reasons. Mutations in superoxide dismutase 1 (SOD1), TAR, c9orf72 (chromosome 9 open reading frame 72) and VAPB genes are commonly found in ALS patients. Therefore, the mechanism of ALS development involves oxidative stress, endoplasmic reticulum stress, glutamate excitotoxicity and aggregation of proteins, neuro-inflammation and defective RNA function. Cholesterol and LDL/HDL levels are also associated with ALS development. As a result, sterols could be a suitable biomarker for this ailment. The main mechanisms of ALS development are reticulum stress, neuroinflammation and RNA metabolism. The multi-nature development of ALS makes it more challenging to pinpoint a treatment.

Is L-Glutamate Toxic to Neurons and Thereby Contributes to Neuronal Loss and Neurodegeneration? A Systematic Review

L-glutamate (L-Glu) is a nonessential amino acid, but an extensively utilised excitatory neurotransmitter with critical roles in normal brain function. Aberrant accumulation of L-Glu has been linked to neurotoxicity and neurodegeneration. To investigate this further, we systematically reviewed the literature to evaluate the effects of L-Glu on neuronal viability linked to the pathogenesis and/or progression of neurodegenerative diseases (NDDs). A search in PubMed, Medline, Embase, and Web of Science Core Collection was conducted to retrieve studies that investigated an association between L-Glu and pathology for five NDDs: Alzheimer's disease (AD), Parkinson's disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), and Huntington's disease (HD). Together, 4060 studies were identified, of which 71 met eligibility criteria. Despite several inadequacies, including small sample size, employment of supraphysiological concentrations, and a range of administration routes, it was concluded that exposure to L-Glu in vitro or in vivo has multiple pathogenic mechanisms that influence neuronal viability. These mechanisms include oxidative stress, reduced antioxidant defence, neuroinflammation, altered neurotransmitter levels, protein accumulations, excitotoxicity, mitochondrial dysfunction, intracellular calcium level changes, and effects on neuronal histology, cognitive function, and animal behaviour. This implies that clinical and epidemiological studies are required to assess the potential neuronal harm arising from excessive intake of exogenous L-Glu.

Fabricating multifunctional low-toxicity ratiometric fluorescent probe for individual detection of Cu2+/glutamate and continuous sensing for glutamate via Cu2+-based platform

Herein, a multifunctional ratiometric fluorescent (RF) probe Fe-MIL-88NH₂@RhB was fabricated for individual detection of Cu^2+/Glu and continuous sensing of Glu based on unique coordination principle by encapsulating RhB into the porous of metal-organic-framework-Fe-MIL-88NH₂. Designed Fe-MIL-88NH₂@RhB platform could selectively identify Cu(II)/Glu accompanying a turn-off/turn-on fluorescent behavior with good linearity. Moreover, if the Fe-MIL-88NH₂@RhB/Cu²⁺ is treated with Glu continuously, the quenching fluorescence of this platform (after Cu²⁺ sensing at blue emission) would be further in turn restored. Utilizing Fe-MIL-88NH₂@RhB probe, the imaging of intracellular Cu(II) and Glu in living A549 cells was successful conducted through divisional channels with a satisfactory low cytotoxicity, meanwhile, the sensing results of Glu in serum by the molecular logic gate was also superior, which may use for development of an medical occupational tool for amyotrophic lateral sclerosis tentative diagnosis. In addition, the MOF shows di-modal response (color and lumescence) to Cu²⁺ and Glu with excellent selectivity against a wide range of other interference analytes, and the corresponding portable low-toxicity on-line test strips for Cu²⁺ and Glu recognize has exhibited a remarkable visually chromogenic phenomena, which may utilize for monitoring these contaminants in real water sample. Finally, the feasibility of probe to monitor Cu²⁺ and Glu in foodstuffs was also evaluated.

Quantitative susceptibility-weighted imaging in amyotrophic lateral sclerosis with 3.0 T magnetic resonance imaging

OBJECTIVE

To evaluate alterations in phase-shift values in the gray matter of patients with amyotrophic lateral sclerosis (ALS) using susceptibility-weighted imaging (SWI).

METHODS

Twenty patients with definite or probable ALS and 19 age- and sex-matched healthy controls were enrolled. SWI was performed using a 3.0 T magnetic resonance imaging scanner. Phase-shift values were measured in corrected phase images using regions of interest, which were placed on the bilateral precentral gyrus, frontal cortex, caudate nucleus, globus pallidus, and putamen.

RESULTS

Phase-shift values of the precentral gyrus were significantly lower in ALS patients (-0.176 ± 0.050) than in the control group (-0.119 ± 0.016) on SWI. The average phase-shift values of the frontal cortex, caudate nucleus, globus pallidus, and putamen in ALS patients (-0.089 ± 0.023, -0.065 ± 0.016, -0.336 ± 0.191, and -0.227 ± 0.101, respectively) were not significantly different from those in the healthy controls (-0.885 ± 0.015, -0.079 ± 0.018, -0.329 ± 0.136, and -0.229 ± 0.083, respectively).

CONCLUSIONS

Compared with healthy controls, ALS patients had a lower phase-shift value in the precentral gyrus, which may be related to abnormal iron overload. Thus, SWI is a potential method for identifying ALS patients.

CNS glucose metabolism in Amyotrophic Lateral Sclerosis: a therapeutic target?

Amyotrophic lateral sclerosis (ALS) is a fatal progressive neurodegenerative disorder primarily characterized by selective degeneration of both the upper motor neurons in the brain and lower motor neurons in the brain stem and the spinal cord. The exact mechanism for the selective death of neurons is unknown. A growing body of evidence demonstrates abnormalities in energy metabolism at the cellular and whole-body level in animal models and in people living with ALS. Many patients with ALS exhibit metabolic changes such as hypermetabolism and body weight loss. Despite these whole-body metabolic changes being observed in patients with ALS, the origin of metabolic dysregulation remains to be fully elucidated. A number of pre-clinical studies indicate that underlying bioenergetic impairments at the cellular level may contribute to metabolic dysfunctions in ALS. In particular, defects in CNS glucose transport and metabolism appear to lead to reduced mitochondrial energy generation and increased oxidative stress, which seem to contribute to disease progression in ALS. Here, we review the current knowledge and understanding regarding dysfunctions in CNS glucose metabolism in ALS focusing on metabolic impairments in glucose transport, glycolysis, pentose phosphate pathway, TCA cycle and oxidative phosphorylation. We also summarize disturbances found in glycogen metabolism and neuroglial metabolic interactions. Finally, we discuss options for future investigations into how metabolic impairments can be modified to slow disease progression in ALS. These investigations are imperative for understanding the underlying causes of metabolic dysfunction and subsequent neurodegeneration, and to also reveal new therapeutic strategies in ALS.

Exciting Complexity: The Role of Motor Circuit Elements in ALS Pathophysiology

Amyotrophic lateral sclerosis (ALS) is a fatal disease, characterized by the degeneration of both upper and lower motor neurons. Despite decades of research, we still to date lack a cure or disease modifying treatment, emphasizing the need for a much-improved insight into disease mechanisms and cell type vulnerability. Altered neuronal excitability is a common phenomenon reported in ALS patients, as well as in animal models of the disease, but the cellular and circuit processes involved, as well as the causal relevance of those observations to molecular alterations and final cell death, remain poorly understood. Here, we review evidence from clinical studies, cell type-specific electrophysiology, genetic manipulations and molecular characterizations in animal models and culture experiments, which argue for a causal involvement of complex alterations of structure, function and connectivity of different neuronal subtypes within the cortical and spinal cord motor circuitries. We also summarize the current knowledge regarding the detrimental role of astrocytes and reassess the frequently proposed hypothesis of glutamate-mediated excitotoxicity with respect to changes in neuronal excitability. Together, these findings suggest multifaceted cell type-, brain area- and disease stage- specific disturbances of the excitation/inhibition balance as a cardinal aspect of ALS pathophysiology.

Neuronal glucose metabolism is impaired while astrocytic TCA cycling is unaffected at symptomatic stages in the hSOD1G93A mouse model of amyotrophic lateral sclerosis

Although alterations in energy metabolism are known in ALS, the specific mechanisms leading to energy deficit are not understood. We measured metabolite levels derived from injected [1-¹³C]glucose and [1,2-¹³C]acetate (i.p.) in cerebral cortex and spinal cord extracts of wild type and hSOD1^G93A mice at onset and mid disease stages using high-pressure liquid chromatography, ¹H and ¹³C nuclear magnetic resonance spectroscopy. Levels of spinal and cortical CNS total lactate, [3-¹³C]lactate, total alanine and [3-¹³C]alanine, but not cortical glucose and [1-¹³C]glucose, were reduced mostly at mid stage indicating impaired glycolysis. The [1-¹³C]glucose-derived [4-¹³C]glutamate, [4-¹³C]glutamine and [2-¹³C]GABA amounts were diminished at mid stage in cortex and both time points in spinal cord, suggesting decreased [3-¹³C]pyruvate entry into the TCA cycle. Lack of changes in [1,2-¹³C]acetate-derived [4,5-¹³C]glutamate, [4,5-¹³C]glutamine and [1,2-¹³C]GABA levels indicate unchanged astrocytic ¹³C-acetate metabolism. Reduced levels of leucine, isoleucine and valine in CNS suggest compensatory breakdown to refill TCA cycle intermediate levels. Unlabelled, [2-¹³C] and [4-¹³C]GABA concentrations were decreased in spinal cord indicating that impaired glucose metabolism contributes to hyperexcitability and supporting the use of treatments which increase GABA amounts. In conclusion, CNS glucose metabolism is compromised, while astrocytic TCA cycling appears to be normal in the hSOD1^G93A mouse model at symptomatic disease stages.

The RNA-binding protein FUS/TLS undergoes calcium-mediated nuclear egress during excitotoxic stress and is required for GRIA2 mRNA processing

Excitotoxic levels of glutamate represent a physiological stress that is strongly linked to amyotrophic lateral sclerosis (ALS) and other neurological disorders. Emerging evidence indicates a role for neurodegenerative disease-linked RNA-binding proteins (RBPs) in the cellular stress response. However, the relationships between excitotoxicity, RBP function, and disease have not been explored. Here, using primary cortical and motor neurons, we found that excitotoxicity induced the translocation of select ALS-linked RBPs from the nucleus to the cytoplasm within neurons. RBPs affected by excitotoxicity included TAR DNA-binding protein 43 (TDP-43) and, most robustly, fused in sarcoma/translocated in liposarcoma (FUS/TLS or FUS). We noted that FUS is translocated through a calcium-dependent mechanism and that its translocation coincides with striking alterations in nucleocytoplasmic transport. Furthermore, glutamate-induced up-regulation of glutamate ionotropic receptor α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type subunit 2 (GRIA2) in neurons depended on FUS expression, consistent with a functional role for FUS in excitotoxic stress. These findings reveal molecular links among prominent factors in neurodegenerative diseases, namely excitotoxicity, disease-associated RBPs, and nucleocytoplasmic transport.

Motor cortex metabolite alterations in amyotrophic lateral sclerosis assessed in vivo using edited and non-edited magnetic resonance spectroscopy

Previous MRI and proton spectroscopy (¹H-MRS) studies have revealed impaired neuronal integrity and altered neurometabolite concentrations in the motor cortex of patients with amyotrophic lateral sclerosis (ALS). Here, we aim to use MRI with conventional and novel MRS sequences to further investigate neurometabolic changes in the motor cortex of ALS patients and their relation to clinical parameters. We utilized the novel HERMES (Hadamard Encoding and Reconstruction of MEGA-Edited Spectroscopy) MRS sequence to simultaneously quantify the inhibitory neurotransmitter GABA and antioxidant glutathione in ALS patients (n = 7) and healthy controls (n = 7). In addition, we have also quantified other MRS observable neurometabolites using a conventional point-resolved MR spectroscopy (PRESS) sequence in ALS patients (n = 20) and healthy controls (n = 20). We observed a trend towards decreasing glutathione concentrations in the motor cortex of ALS patients (p = 0.0842). In addition, we detected a 11% decrease in N-acetylaspartate (NAA) (p = 0.025), a 15% increase in glutamate + glutamine (Glx) (p = 0.0084) and a 21% increase in myo-inositol (mIns) (p = 0.0051) concentrations for ALS patients compared to healthy controls. Furthermore, significant positive correlations were found between GABA-NAA (p = 0.0480; Rρ = 0.7875) and NAA-mIns (p = 0.0448; Rρ = -0.4651) levels among the patients. NAA levels in the bulbar-onset patient group were found to be significantly (p = 0.0097) lower compared to the limb-onset group. A strong correlation (p < 0.0001; Rρ = -0,8801) for mIns and a weak correlation (p = 0.0066; Rρ = -0,6673) for Glx was found for the disease progression, measured by declining of the ALS Functional Rating Scale-Revised criteria (ALSFRS-R). Concentrations of mIns and Glx also correlated with disease severity measured by forced vital capacity (FVC). Results suggest that mean neurometabolite concentrations detected in the motor cortex may indicate clinical and pathological changes in ALS.

Metabolite differences between glutamate carboxypeptidase II gene knockout mice and their wild-type littermates after traumatic brain injury: a 7-tesla 1H-MRS study

Background

Traumatic brain injury (TBI) is a complex condition and remains a prominent public and medical health issue in individuals of all ages. A rapid increase in extracellular glutamate occurs after TBI, leading to glutamate-induced excitotoxicity, which causes neuronal damage and further functional impairments. Although inhibition of glutamate carboxypeptidase II (GCP II) is considered a potential approach for reducing glutamate-induced excitotoxicity after TBI, further detailed evidence regarding its efficacy is required. Therefore, in this study, we examined the differences in the metabolite status between wild-type (WT) and GCP II gene-knockout (KO) mice after TBI using proton magnetic resonance spectroscopy (1H-MRS) and T2-weighted magnetic resonance (MR) imaging with a 7-tesla imaging system, and brain water-content analysis.

Results

Evaluation of glutamate and N-acetylaspartate concentrations revealed a decrease in both levels in the ipsilateral hippocampus at 24 h post-TBI; however, the reduction in glutamate and N-acetylaspartate levels was less marked in GCP II-KO mice than in WT mice (p < 0.05). T2 MR data and brain water-content analysis demonstrated that the extent of cortical edema and brain swelling was less in KO than in WT mice after TBI (p < 0.05).

Conclusion

Using two non-invasive methods, 1H-MRS and T2 MR imaging, as well as in vitro brain-water content measurements, we demonstrated that the mechanism underlying the neuroprotective effects of GCP II-KO against brain swelling in TBI involves changes in glutamate and N-acetylaspartate levels. This knowledge may contribute towards the development of therapeutic strategies for TBI.

Driven to decay: Excitability and synaptic abnormalities in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is the most common motor neuron (MN) disease and is clinically characterised by the death of corticospinal motor neurons (CSMNs), spinal and brainstem MNs and the degeneration of the corticospinal tract. Degeneration of CSMNs and MNs leads inexorably to muscle wastage and weakness, progressing to eventual death within 3-5 years of diagnosis. The CSMNs, located within layer V of the primary motor cortex, project axons constituting the corticospinal tract, forming synaptic connections with brainstem and spinal cord interneurons and MNs. Clinical ALS may be divided into familial (∼10% of cases) or sporadic (∼90% of cases), based on apparent random incidence. The emergence of transgenic murine models, expressing different ALS-associated mutations has accelerated our understanding of ALS pathogenesis, although precise mechanisms remain elusive. Multiple avenues of investigation suggest that cortical electrical abnormalities have pre-eminence in the pathophysiology of ALS. In addition, glutamate-mediated functional and structural alterations in both CSMNs and MNs are present in both sporadic and familial forms of ALS. This review aims to promulgate debate in the field with regard to the common aetiology of sporadic and familial ALS. A specific focus on a nexus point in ALS pathogenesis, namely, the synaptic and intrinsic hyperexcitability of CSMNs and MNs and alterations to their structure are comprehensively detailed. The association of extramotor dysfunction with neuronal structural/functional alterations will be discussed. Finally, the implications of the latest research on the dying-forward and dying-back controversy are considered.

Biomarkers of Amyotrophic Lateral Sclerosis: Current Status and Interest of Oxysterols and Phytosterols

Amyotrophic lateral sclerosis (ALS) is a non-demyelinating neurodegenerative disease in adults with motor disorders. Two forms exist: a sporadic form (90% of cases) and a family form due to mutations in more than 20 genes including the Superoxide dismutase 1, TAR DNA Binding Protein, Fused in Sarcoma, chromosome 9 open reading frame 72 and VAPB genes. The mechanisms associated with this pathology are beginning to be known: oxidative stress, glutamate excitotoxicity, protein aggregation, reticulum endoplasmic stress, neuroinflammation, alteration of RNA metabolism. In various neurodegenerative diseases, such as Alzheimer's disease or multiple sclerosis, the involvement of lipids is increasingly suggested based on lipid metabolism modifications. With regard to ALS, research has also focused on the possible involvement of lipids. Lipid involvement was suggested for clinical arguments where changes in cholesterol and LDL/HDL levels were reported with, however, differences in positivity between studies. Since lipids are involved in the membrane structure and certain signaling pathways, it may be considered to look for oxysterols, mainly 25-hydroxycholesterol and its metabolites involved in immune response, or phytosterols to find suitable biomarkers for this pathology.

Postactivation depression of the Ia EPSP in motoneurons is reduced in both the G127X SOD1 model of amyotrophic lateral sclerosis and in aged mice

Postactivation depression (PActD) of Ia afferent excitatory postsynaptic potentials (EPSPs) in spinal motoneurons results in a long-lasting depression of the stretch reflex. This phenomenon (PActD) is of clinical interest as it has been shown to be reduced in a number of spastic disorders. Using in vivo intracellular recordings of Ia EPSPs in adult mice, we demonstrate that PActD in adult (100-220 days old) C57BL/6J mice is both qualitatively and quantitatively similar to that which has been observed in larger animals with respect to both the magnitude (with ∼20% depression of EPSPs at 0.5 ms after a train of stimuli) and the time course (returning to almost normal amplitudes by 5 ms after the train). This validates the use of mouse models to study PActD. Changes in such excitatory inputs to spinal motoneurons may have important implications for hyperreflexia and/or glutamate-induced excitotoxicity in the neurodegenerative disease amyotrophic lateral sclerosis (ALS). With the use of the G127X SOD1 mutant mouse, an ALS model with a prolonged asymptomatic phase and fulminant symptom onset, we observed that PActD is significantly reduced at both presymptomatic (16% depression) and symptomatic (17.3% depression) time points compared with aged-matched controls (22.4% depression). The PActD reduction was not markedly altered by symptom onset. Comparing these PActD changes at the EPSP with the known effect of the depression on the monosynaptic reflex, we conclude that this is likely to have a much larger effect on the reflex itself (a 20-40% difference). Nevertheless, it should also be accounted that in aged (580 day old) C57BL/6J mice there was also a reduction in PActD although, aging is not usually associated with spasticity.

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.

Roles of vitamin D in amyotrophic lateral sclerosis: possible genetic and cellular signaling mechanisms

Evidence suggests that there are aberrations in the vitamin D-endocrine system in subjects with amyotrophic lateral sclerosis (ALS). Here, we review the relationship between vitamin D and ALS. Vitamin D deficiency was reported in patients with ALS. Dietary vitamin D₃ supplementation improves functional capacity in the G93A transgenic mouse model of ALS. Genetic studies have provided an opportunity to identify the proteins that link vitamin D to ALS pathology, including major histocompatibility complex (MHC) class II molecules, toll-like receptors, poly(ADP-ribose) polymerase-1, heme oxygenase-1, and calcium-binding proteins, as well as the reduced form of nicotinamide adenine dinucleotide phosphate. Vitamin D also exerts its effect on ALS through cell-signaling mechanisms, including glutamate, matrix metalloproteinases, mitogen-activated protein kinase pathways, the Wnt/β-catenin signaling pathway, prostaglandins, reactive oxygen species, and nitric oxide synthase.

In conclusion, vitamin D may have a role in ALS. Further investigation of vitamin D in ALS patients is needed.

Redox regulation in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease that results from the death of upper and lower motor neurons. Due to a lack of effective treatment, it is imperative to understand the underlying mechanisms and processes involved in disease progression. Regulations in cellular reduction/oxidation (redox) processes are being increasingly implicated in disease. Here we discuss the possible involvement of redox dysregulation in the pathophysiology of ALS, either as a cause of cellular abnormalities or a consequence. We focus on its possible role in oxidative stress, protein misfolding, glutamate excitotoxicity, lipid peroxidation and cholesterol esterification, mitochondrial dysfunction, impaired axonal transport and neurofilament aggregation, autophagic stress, and endoplasmic reticulum (ER) stress. We also speculate that an ER chaperone protein disulphide isomerase (PDI) could play a key role in this dysregulation. PDI is essential for normal protein folding by oxidation and reduction of disulphide bonds, and hence any disruption to this process may have consequences for motor neurons. Addressing the mechanism underlying redox regulation and dysregulation may therefore help to unravel the molecular mechanism involved in ALS.

The orally active glutamate carboxypeptidase II inhibitor E2072 exhibits sustained nerve exposure and attenuates peripheral neuropathy

Peripheral neuropathy from nerve trauma is a significant problem in the human population and often constitutes a dose-limiting toxicity in patients receiving chemotherapy. (3-2-Mercaptoethyl)biphenyl-2,3-dicarboxylic acid (E2072) is a potent (K(i) = 10 nM), selective, and orally available inhibitor of glutamate carboxypeptidase II (GCPII). Here, we report that E2072 attenuates hyperalgesia and nerve conduction velocity deficits in preclinical rodent models of neuropathic pain and oxaliplatin-induced neuropathy. In the chronic constrictive injury model, orally administered E2072 reversed pre-existing thermal hyperalgesia in rats in a dose-dependent fashion with a minimally effective dose of 0.1 mg/kg/day. It is noteworthy that multiple days of dosing of E2072 were required before analgesia was realized even though GCPII inhibitory exposures were achieved on the first day of dosing. In addition, analgesia was found to persist for up to 7 days after cessation of dosing, consistent with E2072's pharmacokinetic profile and sustained exposure. Furthermore, in a chronic oxaliplatin-induced neuropathy model (6 mg/kg i.p. oxaliplatin twice weekly for 4 weeks), female BALB/c mice receiving daily oral E2072 at 1.0 and 0.1 mg/kg displayed no deficits in either caudal or digital velocity compared with significant deficits observed in mice treated with oxaliplatin alone (12 ± 3 and 9 ± 2%, respectively). Similar findings were seen with oxaliplatin-induced digital and caudal amplitude deficits. It is noteworthy that E2072 showed no interference with the antineoplastic efficacy of oxaliplatin in mice bearing leukemia (L1210), even at doses 100 times its neuroprotective/analgesic dose, indicating a selective effect on neuropathy. These data support the therapeutic utility of GCPII inhibitors in neuropathy and neuropathic pain.

Treatment for spasticity in amyotrophic lateral sclerosis/motor neuron disease

BACKGROUND

Spasticity commonly affects patients with motor neuron disease. It is likely to contribute to worsening muscle dysfunction, increased difficulty with activities of daily living and deteriorating quality of life. This is an update of a review first published in 2003 and previously updated in 2005 and 2008.

OBJECTIVES

The objective of this review is to systematically review treatments for spasticity in amyotrophic lateral sclerosis, also known as motor neuron disease.

SEARCH METHODS

We searched the Cochrane Neuromuscular Disease Group Specialized Register (4 July 2011), CENTRAL (2011, Issue 2), MEDLINE (January 1966 to July 2011), EMBASE (January 1980 to July 2011 ), CINAHL Plus (January 1937 to July 2011), AMED (January 1985 to July 2011) and LILACS (January 1982 to July 2011 ). We reviewed the bibliographies of the randomized controlled trials identified, and contacted authors and experts in the field.

SELECTION CRITERIA

We included quasi-randomized or randomized controlled trials of participants with probable or definite amyotrophic lateral sclerosis according to the El Escorial diagnostic criteria (or a revised version) or the Airlie House revision. We would have included trials of physical therapy, modalities, prescription medications, non-prescription medications, chemical neurolysis, surgical interventions, and alternative therapies. Our primary outcome measure was reduction in spasticity at three months or greater as measured by the Ashworth (or modified Ashworth) spasticity scale. Our secondary outcome measures were: validated measures based on history, physical examination, physiological measures, measures of function, measures of quality of life, all adverse events, and measures of cost.

DATA COLLECTION AND ANALYSIS

Two authors independently screened the abstracts of potential trials retrieved from the searches. Two authors extracted the data. We also contacted the author of the paper and obtained information not available in the published article. All three authors assessed the methodological quality of all included trials independently.

MAIN RESULTS

We identified only one randomized controlled trial that met our inclusion criteria and no further trials were identified in subsequent updates. The included study was a trial of moderate intensity, endurance type exercise versus 'usual activities' in 25 patients with amyotrophic lateral sclerosis. The risk of bias was high and no adverse events were reported. At three months patients performing the 15 minute twice daily exercises had significantly less spasticity overall (mean reduction of -0.43, 95% confidence interval (CI) -1.03 to +0.17 in the treatment group versus an increase of +0.25, 95% CI -0.46 to +0.96 in control) but the mean change between groups was not significant (-0.68, 95% CI -1.62 to +0.26), as measured by the Ashworth scale (possible scores 0 to 5, where higher is worse).

AUTHORS' CONCLUSIONS

The single trial performed was too small to determine whether individualized moderate intensity endurance type exercises for the trunk and limbs are beneficial or harmful. No other medical, surgical or alternative treatment and therapy has been evaluated in a randomized fashion in this patient population. More research is needed.

Effects of bee venom on glutamate-induced toxicity in neuronal and glial cells

Bee venom (BV), which is extracted from honeybees, is used in traditional Korean medical therapy. Several groups have demonstrated the anti-inflammatory effects of BV in osteoarthritis both in vivo and in vitro. Glutamate is the predominant excitatory neurotransmitter in the central nervous system (CNS). Changes in glutamate release and uptake due to alterations in the activity of glutamate transporters have been reported in many neurodegenerative diseases, including Parkinson's disease, Alzheimer's disease, and amyotrophic lateral sclerosis. To assess if BV can prevent glutamate-mediated neurotoxicity, we examined cell viability and signal transduction in glutamate-treated neuronal and microglial cells in the presence and absence of BV. We induced glutamatergic toxicity in neuronal cells and microglial cells and found that BV protected against cell death. Furthermore, BV significantly inhibited the cellular toxicity of glutamate, and pretreatment with BV altered MAP kinase activation (e.g., JNK, ERK, and p38) following exposure to glutamate. These findings suggest that treatment with BV may be helpful in reducing glutamatergic cell toxicity in neurodegenerative diseases.

Modification of aspartoacylase for potential use in enzyme replacement therapy for the treatment of Canavan disease

Canavan disease is a fatal neurological disease without any effective treatments to slow the relentless progress of this disorder. Enzyme replacement therapy has been used effectively to treat a number of metabolic disorders, but the presence of the blood-brain-barrier presents an additional challenge in the treatment of neurological disorders. Studies have begun with the aim of establishing a treatment protocol that can effectively replace the defective enzyme in Canavan disease patients. The human enzyme, aspartoacylase, has been cloned, expressed and purified, and the surface lysyl groups modified through PEGylation. Fully active modified enzymes were administered to mice that are defective in this enzyme and that show many of the symptoms of Canavan disease. Statistically significant increases in brain enzyme activity levels have been achieved in this animal model, as well as decreases in the elevated substrate levels that mimic those found in Canavan disease patients. These results demonstrate that the modified enzyme is gaining access to the brain and functions to correct this metabolic defect. The stage is now set for a long term study to optimize this enzyme replacement approach for the development of a treatment protocol.

Riluzole decreases synthesis of N-acetylaspartate and N-acetylaspartylglutamate in SH-SY5Y human neuroblastoma cells

N-acetylaspartate (NAA) is present at very high concentrations in the brain and is used as a non-invasive marker of neuronal viability in magnetic resonance spectroscopy. N-acetylaspartylglutamate (NAAG) is an acetylated dipeptide formed from NAA, and may be an agonist of the mGluR3 receptor. Both NAA and NAAG are synthesized primarily in neurons. Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder resulting in motor neuron death, and progressive paralysis. Levels of both NAA and NAAG are reported to be decreased in ALS. Riluzole is a glutamatergic modulating agent used to treat ALS, but there are conflicting results in the literature concerning the recovery of NAA after riluzole treatment. We studied the effects of riluzole on the biosynthesis of both NAA and NAAG in SH-SY5Y human neuroblastoma cells. We used two methodologies to examine the effect; one involving radiolabel incorporation from corresponding substrates into NAA and NAAG, and the other involving the measurement of endogenous NAA and NAAG levels using HPLC. We show that riluzole treatment, which decreases glutamatergic neuronal excitation, decreases the synthesis and levels of both NAA and NAAG in SH-SY5Y cells in a dose and time dependant manner. These results suggest that the synthesis of NAA and NAAG may be coupled to glutamatergic neurotransmission, and further investigations along these lines are warranted.

Study of the features of proton MR spectroscopy ((1)H-MRS) on amyotrophic lateral sclerosis

PURPOSE

To study the features of proton magnetic resonance spectroscopy ((1)H-MRS) on amyotrophic lateral sclerosis (ALS) and its relation with clinical scale.

MATERIALS AND METHODS

Fifteen patients with definite or probable ALS and 15 age- and gender-matched normal controls were enrolled. (1)H-MRS was performed on a 3.0 Tesla GE imaging system (GE Healthcare, Milwaukee, WI). TE-averaged Point Resolved Selective Spectroscopy was used. N-acetylaspartate (NAA), creatine (Cr), Glu, and Glx (glutamate + glutamine) values of the motor cortex and posterior limb of internal capsule were acquired. The t-test was used to compare differences between groups, and the correlations between the above values and clinical scale were analyzed.

RESULTS

The motor area and posterior limb of the internal capsule of ALS patients had lower NAA/Cr (1.91 +/- 0.34, 1.53 +/- 0.17) compared with normal subjects (2.23 +/- 0.33, 1.66 +/- 0.07), and the differences between groups were statistically significant (P < 0.01, 0.01). ALS patients had higher Glu/Cr (0.34 +/- 0.05, 0.29 +/- 0.06) and Glx/Cr (0.40 +/- 0.04, 0.33 +/- 0.06) compared with normal subjects (0.30 +/- 0.03, 0.25 +/- 0.04) and (0.32 +/- 0.05, 0.26 +/- 0.03), and the differences between groups were statistically significant (P < 0.01, 0.01). The Norris scale was negatively correlated with Glx/Cr of primary motor cortex by lineal correlation analysis (r = -0.75), and this correlation had statistical significance (F = 16.60; P = 0.001).

CONCLUSION

Neuronal loss and Glu+Gln increase can be detected by using proton MRS in ALS patients. (1)H-MRS is an useful tool in reflecting the characteristic changes of metabolite in ALS.

Possible therapy for ALS based on the cyanobacteria/BMAA hypothesis

Although the cyanobacteria/BMAA hypothesis of the cause of ALS and other age-related neurodegenerative diseases remains to be proven, it is not too early to ask whether treatment would be possible if the hypothesis were correct. This paper reviews the possible ways that chronic BMAA neurotoxicity could be prevented or treated.

Magnetic resonance spectroscopy of regional brain metabolite markers in FALS mice and the effects of dietary creatine supplementation

We investigated the effects of disease progression on brain regional neurochemistry in a mutant mouse model of familial amyotrophic lateral sclerosis (FALS; the G93A model) using in vivo and in vitro magnetic resonance spectroscopy (MRS). There were numerous changes in the brain spectra that were brain region dependent. At early time points starting around 80 days of age there were increases in brain glutamate. At later time points there were more extensive changes including decreased N-acetyl aspartate and glutamate and increased glutamine, taurine and myo-inositol. The effects of the disease were most severe in spinal cord followed by medulla and then sensorimotor cortex. There were no changes noted in cerebellum as a control region. The effects of creatine supplementation in the diet (2%) were measured in wild-type and FALS animals in medulla, cerebellum and cortex. The increase in brain creatine was largest in cerebellum (25%) followed by medulla (11%) and then cortex (4%), reflecting the ordering of creatine kinase activity. There was a protective effect of creatine on N-acetyl aspartate loss in the medulla at late stages. Creatine supplementation had a positive effect on weight retention, leading to a 13% increase in weight between 120 and 130 days. MRS shows promise in monitoring multiple facets of neuroprotective strategies in ALS and ALS models.

SEROTONERGIC MECHANISMS IN AMYOTROPHIC LATERAL SCLEROSIS

Serotonin (5-HT) has been intimately linked with global regulation of motor behavior, local control of motoneuron excitability, functional recovery of spinal motoneurons as well as neuronal maturation and aging. Selective degeneration of motoneurons is the pathological hallmark of amyotrophic lateral sclerosis (ALS). Motoneurons that are preferentially affected in ALS are also densely innervated by 5-HT neurons (e.g., trigeminal, facial, ambiguus, and hypoglossal brainstem nuclei as well as ventral horn and motor cortex). Conversely, motoneuron groups that appear more resistant to the process of neurodegeneration in ALS (e.g., oculomotor, trochlear, and abducens nuclei) as well as the cerebellum receive only sparse 5-HT input. The glutamate excitotoxicity theory maintains that in ALS degeneration of motoneurons is caused by excessive glutamate neurotransmission, which is neurotoxic. Because of its facilitatory effects on glutaminergic motoneuron excitation, 5-HT may be pivotal to the pathogenesis and therapy of ALS. 5-HT levels as well as the concentrations 5-hydroxyindole acetic acid (5-HIAA), the major metabolite of 5-HT, are reduced in postmortem spinal cord tissue of ALS patients indicating decreased 5-HT release. Furthermore, cerebrospinal fluid levels of tryptophan, a precursor of 5-HT, are decreased in patients with ALS and plasma concentrations of tryptophan are also decreased with the lowest levels found in the most severely affected patients. In ALS progressive degeneration of 5-HT neurons would result in a compensatory increase in glutamate excitation of motoneurons. Additionally, because 5-HT, acting through presynaptic 5-HT1B receptors, inhibits glutamatergic synaptic transmission, lowered 5-HT activity would lead to increased synaptic glutamate release. Furthermore, 5-HT is a precursor of melatonin, which inhibits glutamate release and glutamate-induced neurotoxicity. Thus, progressive degeneration of 5-HT neurons affecting motoneuron activity constitutes the prime mover of the disease and its progression and treatment of ALS needs to be focused primarily on boosting 5-HT functions (e.g., pharmacologically via its precursors, reuptake inhibitors, selective 5-HT1A receptor agonists/5-HT2 receptor antagonists, and electrically through transcranial administration of AC pulsed picotesla electromagnetic fields) to prevent excessive glutamate activity in the motoneurons. In fact, 5HT1A and 5HT2 receptor agonists have been shown to prevent glutamate-induced neurotoxicity in primary cortical cell cultures and the 5-HT precursor 5-hydroxytryptophan (5-HTP) improved locomotor function and survival of transgenic SOD1 G93A mice, an animal model of ALS.

Glutamate transporters and the excitotoxic path to motor neuron degeneration in amyotrophic lateral sclerosis

Responsible for the majority of excitatory activity in the central nervous system (CNS), glutamate interacts with a range of specific receptor and transporter systems to establish a functional synapse. Excessive stimulation of glutamate receptors causes excitotoxicity, a phenomenon implicated in both acute and chronic neurodegenerative diseases [e.g., ischemia, Huntington's disease, and amyotrophic lateral sclerosis (ALS)]. In physiology, excitotoxicity is prevented by rapid binding and clearance of synaptic released glutamate by high-affinity, Na(+)-dependent glutamate transporters and amplified by defects to the glutamate transporter and receptor systems. ALS pathogenetic mechanisms are not completely understood and characterized, but excitotoxicity has been regarded as one firm mechanism implicated in the disease because of data obtained from ALS patients and animal and cellular models as well as inferred by the documented efficacy of riluzole, a generic antiglutamatergic drug, has in patients. In this article, we critically review the several lines of evidence supporting a role for glutamate-mediated excitotoxicity in the death of motor neurons occurring in ALS, putting a particular emphasis on the impairment of the glutamate-transport system.

Drug therapy in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating condition characterized by progressive muscle wasting, inanition, respiratory failure, and death within approximately 2 to 5 years of onset. ALS is among the most common neuromuscular conditions, with an overall prevalence in the world of approximately 5 to 7 cases/100,000 population. Epidemiologic studies have identified some potential risk factors for developing ALS, including a high-fat, low-fiber diet; cigarette smoking; slimness and athleticism; and living in urban areas. Between 5% and 10% of ALS is genetic, with up to 11 genetic loci identified. Although understanding of the pathophysiology of this disease has advanced over the past 60 years, scant progress has been made regarding effective treatment. The authors review the current understanding of the pathogenic mechanisms of ALS and approaches to treating the disease.

Characterization of human aspartoacylase: the brain enzyme responsible for Canavan disease

Aspartoacylase catalyzes the deacetylation of N-acetylaspartic acid (NAA) to produce acetate and L-aspartate and is the only brain enzyme that has been shown to effectively metabolize NAA. Although the exact role of this enzymatic reaction has not yet been completely elucidated, the metabolism of NAA appears to be necessary in the formation of myelin lipids, and defects in this enzyme lead to Canavan disease, a fatal neurological disorder. The low catalytic activity and inherent instability observed with the Escherichia coli-expressed form of aspartoacylase suggested the need for a suitable eukaryotic expression system that would be capable of producing a fully functional, mature enzyme. Human aspartoacylase has now been successfully expressed in Pichia pastoris. While the expression yields are lower than in E. coli, the purified enzyme is significantly more stable. This enzyme form has the same substrate specificity but is 150-fold more active than the E. coli-expressed enzyme. The molecular weight of the purified enzyme, measured by mass spectrometry, is higher than predicted, suggesting the presence of some post-translational modifications. Deglycosylation of aspartoacylase or mutation at the glycosylation site causes decreased enzyme stability and diminished catalytic activity. A carbohydrate component has been removed and characterized by mass spectrometry. In addition to this carbohydrate moiety, the enzyme has also been shown to contain one zinc atom per subunit. Chelation studies to remove the zinc result in a reversible loss of catalytic activity, thus establishing aspartoacylase as a zinc metalloenzyme.

Treatment for spasticity in amyotrophic lateral sclerosis/motor neuron disease

BACKGROUND

Spasticity commonly affects patients with motor neuron disease. It is likely to contribute to worsening muscle dysfunction, increased difficulty with activities of daily living and deteriorating quality of life.

OBJECTIVES

The objective of this review is to systematically review treatments for spasticity in amyotrophic lateral sclerosis, also known as motor neuron disease.

SEARCH STRATEGY

We searched the Cochrane Neuromuscular Disease Group trials register (January 2003 and January 2005), MEDLINE (January 1966 to February 2005), EMBASE (January 1980 to February 2005), CINAHL (January 1982 to February 2005), AMED (January 1985 to February 2005) and LILACS (January 1982 to January 2003). We reviewed the bibliographies of the randomized controlled trials identified, and contacted authors and experts in the field.

SELECTION CRITERIA

We included quasi-randomized or randomized controlled trials of participants with probable or definite amyotrophic lateral sclerosis according to the El Escorial diagnostic criteria (or a revised version) or the Airlie House revision. We would have included trials of physical therapy, modalities, prescription medications, non-prescription medications, chemical neurolysis, surgical interventions, and alternative therapies. Our primary outcome measure was reduction in spasticity at three months or greater as measured by the Ashworth (or modified Ashworth) spasticity scale. Our secondary outcome measures were: validated measures based on history, physical examination, physiological measures, measures of function, measures of quality of life, serious adverse events, and measures of cost.

DATA COLLECTION AND ANALYSIS

We identified only one randomized controlled trial that met our inclusion criteria. Two authors extracted the data. We also contacted the author of the paper and obtained information not available in the published article.

MAIN RESULTS

The included study was a trial of moderate intensity, endurance type exercise versus 'usual activities' in 25 patients with amyotrophic lateral sclerosis. At three months patients performing the 15 minute twice daily exercises had significantly less spasticity overall (mean reduction of -0.43, 95% CI -1.03 to +0.17 in the treatment group versus an increase of +0.25, 95% CI -0.46 to +0.96 in control) but the mean change between groups was not significant (-0.68, 95% CI -1.62 to +0.26), as measured by the Ashworth scale.

AUTHORS' CONCLUSIONS

The single trial performed was too small to determine whether individualised moderate intensity endurance type exercises for the trunk and limbs are beneficial or harmful. No other medical, surgical or alternative treatment and therapy has been evaluated in a randomized fashion in this patient population. More research is needed.

Current pharmacological management of amyotrophic [corrected] lateral sclerosis and a role for rational polypharmacy

Amyotrophic [corrected] lateral sclerosis (ALS) is a progressive degenerative condition of motor neurons that is ultimately fatal. Even though scientific discovery over the past few decades has led to a greater understanding of the pathogenic mechanisms of ALS, effective pharmacotherapy intended to slow, arrest or reverse the disease progression remains difficult to obtain. Riluzole, a drug that has only modest benefit in extending survival, is still the only medication approved by the FDA for the treatment of ALS. However, a number of pharmacological agents are currently being investigated as potential therapy for ALS. This paper will review the pathophysiology of ALS and current pharmacological management of the disease and recent directions in research and clinical trials. Based on the available data, it is our opinion that combination drug therapies should be considered for future clinical trials.

Treatment for spasticity in amyotrophic lateral sclerosis/motor neuron disease

BACKGROUND

Spasticity commonly affects patients with motor neuron disease and it is likely to contribute to worsening muscle dysfunction, increased difficulty with activities of daily living and deteriorating quality of life.

OBJECTIVES

The objective of this review is to systematically review all types of treatments for spasticity in amyotrophic lateral sclerosis, also known as motor neuron disease.

SEARCH STRATEGY

We searched the Cochrane Neuromuscular Disease Group specialised trials register (searched January 2003), MEDLINE (January 1966 to January 2003), EMBASE (January 1980 to January 2003), CINAHL (January 1982 to January 2003), AMED (January 1985 to January 2003) and LILACS (January 1982 to January 2003) for randomized controlled trials. We reviewed the bibliographies of the randomized trials identified, and contacted trial authors and known experts in the field.

SELECTION CRITERIA

We included quasi-randomized or randomized controlled trials of participants with probable or definite amyotrophic lateral sclerosis according to the El Escorial diagnostic criteria (or a revised version) or the Airlie House revision. We would have included trials of physical therapy, modalities, prescription medications, non-prescription medications, chemical neurolysis, surgical interventions, alternative therapies. Our primary outcome measure was reduction in spasticity at three months or greater as measured by Ashworth (or modified Ashworth) spasticity scale. Our secondary outcome measures were: validated measures based on history, physical examination, physiological measures, measures of function, measures of quality of life, serious adverse events, and measures of cost.

DATA COLLECTION AND ANALYSIS

We identified only one randomized controlled trial that met the inclusion criteria for this review. Two authors extracted the data. We also contacted the author of the paper and obtained further information not available in the published article.

MAIN RESULTS

The included study was a trial of moderate intensity, endurance type exercise versus 'usual activities' in 25 patients with amyotrophic lateral sclerosis. At three months patients performing the 15 minute twice daily exercises had significantly less spasticity (mean reduction of 0.43 Ashworth grades versus an increase of 0.25 in controls), as measured by the Ashworth scale.

REVIEWER'S CONCLUSIONS

Individualized, moderate intensity, endurance type exercises for the trunk and limbs may help to reduce spasticity in motor neuron disease. No other medical, surgical or alternative treatment and therapy has been evaluated in a randomized fashion in this patient population.

Activation by N-acetyl-L-aspartate of acutely dissociated hippocampal neurons in rats via metabotropic glutamate receptors

PURPOSE

We previously reported that an increase in the N-acetyl-L-aspartate (NAA) level due to the lack of aspartoacylase gene was found in the brain of the tremor rat (tm/tm), which is a mutant with a causative gene named tm that shows epileptic seizures. Therefore, NAA is suggested to be one of the factors involved in the induction of epileptic seizures. Patch-clamp studies were performed to determine whether NAA produces an excitatory effect on acutely dissociated rat hippocampal neurons.

METHODS

Acutely dissociated hippocampal neurons were prepared from normal Wistar rats aged 3-4 weeks. NAA-induced currents were investigated by using the whole-cell voltage-clamp recording technique.

RESULTS

Application of NAA at concentrations of 100 nM to 1 mM through a U-tube for 2 s produced an inward current in a concentration-dependent manner at a holding potential of -60 mV. When the current-voltage relation was examined, the reversal potential of the NAA-induced current was found to be approximately 0 mV. The NAA-induced current was inhibited by bath application of the metabotropic glutamate receptor (mGluR) antagonist (+/-)-alpha-methyl-4-carboxyphenylglycine (MCPG) and by intracellular application of guanosine 5'-O-(2-thiodiphosphate) (GDP-betaS), a nonhydrolyzable GDP analogue. However, the NAA-induced current remained unaffected by glutamic acid diethyl ester, a non-N-methyl-D-aspartate (NMDA)-subtype ionotropic glutamate receptor antagonist, or the voltage-dependent ion channel blockers tetrodotoxin, CdCl2, and tetraethylammonium-chloride. Conversely, the mGluR agonist, trans-(1S,3R)-1-amino-1,3-cyclopentanedicarboxylic acid (ACPD) also induced an inward current, with a reversal potential of 0 mV. The ACPD-induced current also was inhibited by MCPG.

CONCLUSIONS

These results suggest that NAA acts on the G protein-coupled mGluRs to induce an inward current that results in excitation of the neurons, thereby contributing to the occurrence of epileptic seizures.

Purification and preliminary characterization of brain aspartoacylase

Aspartoacylase catalyzes the deacetylation of N-acetylaspartic acid (NAA) in the brain to produce acetate and L-aspartate. An aspartoacylase deficiency, with concomitant accumulation of NAA, is responsible for Canavan disease, a lethal autosomal recessive disorder. To examine the mechanism of this enzyme the genes encoding murine and human aspartoacylase were cloned and expressed in Escherichia coli. A significant portion of the enzyme is expressed as soluble protein, with the remainder found as inclusion bodies. A convenient enzyme-coupled continuous spectrophotometric assay has been developed for measuring aspartoacylase activity. Kinetic parameters were determined with the human enzyme for NAA and for selected N-acyl analogs that demonstrate relaxed substrate specificity with regard to the nature of the acyl group. The clinically relevant E285A mutant reveals an altered enzyme with poor stability and barely detectable activity, while a more conservative E285D substitution leads to only fivefold lower activity than native aspartoacylase.

Effect of Riluzole on serum amino acids in patients with amyotrophic lateral sclerosis

OBJECTIVES

There is evidence that an imbalance between glutamatergic and inhibitory neurotransmission may contribute to selective neurodegeneration in amyotrophic lateral sclerosis (ALS). The efficacy of Riluzole in prolonging the survival of patients with ALS has been demonstrated in two large controlled trials. It is believed that Riluzole is a glutamate antagonist, but the exact mode of its action is not known. Data on the effects of Riluzole treatment on excitotoxic amino acid levels in serum are not available.

MATERIAL AND METHODS

We prospectively studied 17 patients with ALS (diagnosed according to the El Escorial criteria), who received long-term treatment with Riluzole (100 mg/day). The subjects were evaluated at baseline (before treatment) and after 6, 12 and 18 months on drug. Assessments included the functional status of the patients and serum levels of amino acids. Analysis of the serum amino acids was performed using high performance liquid chromatography techniques at baseline, and after 6, 12 and 18 months of the treatment.

RESULTS

At baseline, glutamate, GABA and total amino acid concentration in serum of the ALS patients, mainly in those with severe course of the disease, were increased. During the first 6 months of Riluzole treatment there was a significant decrease of glutamate and total amino acids, afterwards the values returned to the initial high values, or even an 'overshooting' in their levels appeared. We did not observe a similar effect of Riluzole on glutamate and other amino acids in patients with less advanced ALS.

CONCLUSIONS

It is suggested that the positive clinical effect of Riluzole in ALS patients may be related, at least partly, to its influence on amino acid metabolism in neural tissues.

1H spectroscopy in patients with amyotrophic lateral sclerosis

BACKGROUND AND PURPOSE

The authors investigate changes in brain metabolites among patients with amyotrophic lateral sclerosis (ALS). Twelve patients diagnosed with definite ALS (and 2 subgroups with either pronounced upper motoneuron signs or less obvious, probable upper motoneuron involvement) and 10 controls were examined. 1H studies were performed on a 1.5-T Siemens Magnetom Vision with single voxel (SV). A voxel (TR = 1500 ms, TE = 270 ms, 512 acquisitions, VOI = 8 cm3) was placed bilaterally in the precentral gyrus. In addition, chemical shift imaging (CSI) (VOI = 1 x 1 x 1.5 cm, TR = 1500 ms, TE = 135 ms) was performed. Ratios of peak integrals (N-acetyl-aspartate/choline, N-acetyl-aspartate/creatine, and creatine/choline) were determined. A Mann-Whitney U Test and a Wilcoxon Matched Pairs Test were applied.

METHODS

The statistical analysis failed to demonstrate any significant differences between the ALS patients and the controls with respect to ratio measures. Using CSI, it was found that patients with clinically pronounced upper motoneuron signs had significantly lower (P = .037) N-acetyl-aspartate/choline ratios in the more affected hemisphere.

CONCLUSIONS

The authors conclude that CSI is more effective at detecting lower N-acetyl-aspartate/choline levels among ALS patients than is SV.

Blood oxidative stress in amyotrophic lateral sclerosis

It has been suggested that amyotrophic lateral sclerosis (ALS), a neurodegenerative disorder resulting in motor neuron death, is associated with oxidative damage induced by free radicals. Our study aimed to get an assessment of the blood oxidative stress status in a population of 167 ALS patients (aged 59+/-13 years), treated or not with riluzole, compared with 62 age-matched healthy control subjects (aged 60+/-11 years) simultaneously included in the study. We determined the level of plasma lipid peroxidation (thiobarbituric acid-reactive substances, TBARS); the status of the major lipophilic plasma antioxidant defenses (vitamin E, vitamin A and beta-carotene); the activities of erythrocyte Cu,Zn-superoxide dismutase (Cu,Zn-SOD) and of plasma and erythrocyte glutathione peroxidase (GSH-Px). Plasma selenium was also determined as a trace element essential to the activity of the GSH-Px. In comparison with controls, we observed in ALS patients (mean+/-S.D.) significantly higher TBARS values (ALS=1.34+/-0.28 micromol/l; controls=1.11+/-0. 20 micromol/l) and a significant enhancement of the erythrocyte SOD activity (ALS=710+/-114 U/g Hb; controls=667+/-93 U/g Hb). No differences were observed for selenium level, GSH-Px activity, plasma vitamin E, beta-carotene and vitamin A concentrations. These data confirm the presence of an oxidative stress in blood of ALS patients. The elevated plasma TBARS, without any deficiency in plasma lipophilic antioxidants such as vitamin E, vitamin A and beta-carotene, suggest an enhancement in the production of free radicals. No correlation was found in our study between the level of any of the blood oxidative stress markers and the disease duration. Comparison between patients treated or not with riluzole did not display any modification of the plasma TBARS concentration, but we observed a slight decrease of erythrocyte SOD activity in treated patients (treated=705+/-113 U/g Hb; not treated=725+/-118 U/g Hb), suggesting a possible activity of riluzole on the oxygenated free radical production.

Epileptic seizures induced by N-acetyl-L-aspartate in rats: in vivo and in vitro studies

Tremor rat (tm/tm), the parent strain of spontaneously epileptic rat (SER: zi/zi, tm/tm), exhibits absence-like seizures characterized by 5-7 Hz spike-wave-like complexes on cortical and hippocampal electroencephalograms (EEG) after 10 weeks of age, prior to development of convulsive seizures. Recently, this animal model has been demonstrated to display a genomic microdeletion within the critical region of tm, where aspartoacylase hydrolyzing N-acetyl-L aspartate (NAA) is located, besides showing the ability to accumulate NAA in the brain. Therefore, the present study was performed to determine the involvement of NAA in the induction of epileptic seizures. When NAA (4 micromol) was applied intracerebroventricularly (i.c.v.) to normal Wistar rats, 4-10 Hz polyspikes and/or spike-wave-like complexes followed by absence-like seizure before persistent 1-5 Hz waxing high-voltage after-discharges were observed on cortical and hippocampal EEG. At a higher dose (8 micromol), NAA induced convulsive seizures. The absence-like seizures with polyspikes and/or spike-wave-like complexes on the EEG were also observed with i.c.v. NAA in premature tremor rats without seizures. The NAA-induced seizures in normal rats were antagonized by i.c.v. glutamic acid diethyl ester, a non-selective glutamate receptor antagonist. In addition, NAA applied to the bath rapidly induced a long-lasting depolarization concomitantly with repetitive firings in hippocampal CA3 neurons of normal rat brain slice preparations. These findings suggest that NAA is involved in the induction of absence-like seizures and/or convulsion, probably via glutamate receptors.

Amino acids acting as transmitters in amyotrophic lateral sclerosis (ALS)

OBJECTIVES

In amyotrophic lateral sclerosis (ALS), a neurodegenerative disease of unknown origin, excitotoxic mechanisms are supposed to be involved. Divergent results are, however, presented either because of the heterogeneity of this disease, and/or different methodologies used to evaluate the excitotoxic amino acids content. The results of the most sensitive high performance liquid chromatography (HPLC) techniques with precolumn derivatization of fasting serum and CSF glutamate, aspartate, glycine and gamma-aminobutyric acid (GABA) in mild and severely progressing ALS cases are presented here.

MATERIAL AND METHODS

We studied 25 ALS patients with different course of the disease and controls, which consisted of 10 cases with other motor neuron diseases and 20 healthy, age-matched subjects.

RESULTS

In the ALS patients with a mild course of the disease serum glutamate and aspartate content was either normal or slightly decreased, in all of these cases a rise in GABA and glycine was present. In the severely progressing ALS cases serum glutamate and aspartate was increased. The GABA content was either normal or increased, the glycine level appeared to be either normal or decreased. In CSF the amino acids changes in ALS were less pronounced as compared to serum. The most frequent finding was the increase in GABA concentration both in the mild and the severely progressing group. CSF glutamate in ALS patients with mild course of the disease was decreased, in the severely progressing cases the glutamate level appeared in a broad range from decreased to increased values. CSF aspartate was either normal or elevated, glycine values were present in a broad range from decreased to increased values. In the other tested motor neuron diseases no consistent changes in serum and CSF amino acids concentration was observed.

CONCLUSIONS

The data from serum and CSF indicate that in ALS an imbalance between excitatory and inhibitory amino acids might be present in the brain, which may be induced in different ways in particular ALS patients. It may be an important factor for the mediation of neurons death.

The natural history and the effects of gabapentin in amyotrophic lateral sclerosis

Glutamate excitotoxicity seems to play an important role in the aetiopathogenesis and progression of Amyotrophic Lateral Sclerosis (ALS). Gabapentin is a modulator of the glutamatergic system and has been shown to prolong survival in the transgenic model of familial ALS. It has also been demonstrated to slow the decline of arm strength in human sporadic cases. The aim of our study was to assess the effects of different dosages and duration of treatment of gabapentin on the natural history and survival of ALS patients. A total of 110 patients affected by definite ALS entered the study. After a 6-12 month period of observation, patients were randomly assigned to receive oral gabapentin 500 mg/day (Group A) or 1000 mg/day (Group B) for 6 months. In addition a group of patients received gabapentin 500 mg/day for 6 months and 1000 mg/day for a further 6 months (Group C). A group of 121 patients referred to our Institute, who received only symptomatic treatment, was considered as the control group (Group D). Each patient was seen at entry and every 3 months. All average slopes were negative but the comparison of all slopes showed a trend toward a slower rate of decline of muscle strength loss in all treated groups of patients compared with the control group. The differences were statistically significant. Analysis between the pretreatment and treatment period showed a statistically significant decrease of the decline of muscle strength and Norris score during the treatment period. Survival analysis showed a significantly longer survival in treated patients of Groups B and C. Our study suggests that gabapentin may be an effective drug for ALS; hence a controlled trial involving a sufficient large number of patients is warranted.

Motor neurone acetylcholinesterase release precedes neurotoxicity caused by systemic administration of excitatory amino acids and strychnine

We have proposed that neuronal overactivation by either stimulation of excitatory receptors or hypofunction of inhibitory circuits is a cause of excessive acetylcholinesterase (AChE) release, which, in turn, can contribute to ALS/MND pathogenesis. We investigated histochemical and histopathological changes in cell populations of the mouse spinal ventral horn upon in vivo stimulation of glutamate receptors with L-aspartate (ASP, 10-50 mg/kg, intraperitoneal: i.p.), or blockade of glycine receptors with strychnine (STRY, 2 mg/kg, i.p.). ASP in P4-P13 (postnatal age in days) but not in older mice, and STRY irrespective of age, provoked rapid, striking depletions of motor neurone AChE, and appearance of AChE activity in astrocytes. This was followed by recovery of the enzyme in most motor neurones, astrocyte activation and statistically significant changes in: brain macrophage infiltration, loss of interneurones and motor neurones and neuronophagic images including rosettes of glial cells surrounding a central 'ghost-like' motor neurone. Although AChE release preceded the neuropathology found, it is not known if its uptake is a cause of glial activation. However, it has been shown that the enzyme potentiates non-N-metyl-D-aspartate receptors identical to those that mediate astrocyte activation. AChE activity produces protons and choline, possible microglial activators. These are putative routes towards long-lasting neuropathology.

Magnetic resonance spectroscopy of diffuse brain trauma in the pig

The acute metabolic events linked to the evolution of selective axonal pathology in the white matter following diffuse brain injury have not previously been evaluated due to the paucity of relevant experimental models. Here, we utilized a new model of inertial brain injury in the pig that selectively damages axons in the white matter, and applied proton and phosphorous magnetic resonance spectroscopy (MRS) to noninvasively monitor the temporal course of metabolic changes following trauma. Evaluating four pigs with MRS prior to injury, within 1 h and 3 and 7 days postinjury, we found that widespread axonal injury was produced in the absence of changes in pH, PCr/Pi, or the concentrations of ATP, and lactate. However, we did observe an acute 60% loss of intracellular Mg2+ levels, which gradually resolved by 7 days postinjury. In addition, we found that the levels of the neuron marker, N-acetylaspartate (NAA), acutely dropped 20% and remained persistently decreased for at least 7 days postinjury. Moreover, the changes in Mg2+ and NAA were found with MRS in the absence of abnormalities with conventional magnetic resonance imaging (MRI). These results show that (1) profound alterations in intracellular metabolism occur acutely following diffuse axonal pathology in the white matter, but in the absence of indicators of ischemia, and (2) axonal pathology may be evaluated with high sensitivity utilizing noninvasive MRS techniques.

Measurement of regional N-acetylaspartate after transient global ischemia in gerbils with and without ischemic tolerance: an index of neuronal survival

We investigated the correlation between N-acetylaspartate (NAA) level and neuronal density in the hippocampal CA1 region of the brain after occlusion of both common carotid arteries for 5 minutes and reperfusion for 3 hours to 4 weeks in gerbils with and without ischemic preconditioning (tolerance). Animals were divided into four groups--the sham operated group, the nonpreconditioning (non-p) group, the single-preconditioning (single-p) group with 2-minute ischemia once 2 days before 5-minute ischemia, and the double-preconditioning (double-p) group with 2-minute ischemia twice 2 days before 5-minute ischemia (n = 6 for each group). The CA1 region was dissected out from freeze-dried sections for high-performance liquid chromatographic assay of NAA, and adjacent sections were stained with cresyl violet for measurement of the neuronal density. Both NAA (pmol/microg dry weight) and the neuronal density (cells/mm) decreased in the non-p group after 3 days (NAA = 24.0 +/- 3.0; neuronal density = 65 +/- 38 cells/mm) and 7 days (NAA = 17.9 +/- 2.5; neuronal density = 20 +/- 15 cells/mm) and in the single-p group after 7 days (26.4 +/- 3.0, 106 +/- 30) compared with the control group (NAA = 32.9 +/- 3.0; neuronal density = 203 +/- 9 cells/mm). There was no decrease in the double-p group. The NAA level and the neuronal density showed a good linear correlation. The regional NAA level may be used as an index of neuronal viability.