Energy intake and amyotrophic lateral sclerosis

Roy Walford, a physician and scientist who pioneered research on the anti-aging effects of caloric restriction and subjected himself to a low-energy diet, recently died from amyotrophic lateral sclerosis (ALS). Information from his case, epidemiological findings, and recent controlled studies in mouse models of ALS suggest that low-energy diets might render motor neurons vulnerable to degeneration, whereas high-energy diets are ameliorative. This contrasts with the effects of low-energy diets on various neuronal populations in the brain that respond adaptively, activating pathways that promote plasticity and resistance to disease. One reason that motor neurons might be selectively vulnerable to low-energy diets is that they are unable to engage neuroprotective responses to energetic stress response involving the protein chaperones, such as, heat-shock protein-70.     

Motor cortex stimulation for ALS: A double blind placebo-controlled study

Preliminary data suggest that repetitive transcranial magnetic stimulation (rTMS) of the brain may produce a modest slowing of disease progression in amyotrophic lateral sclerosis (ALS). The present study was designed to test the hypothesis that rTMS given as continuous theta burst stimulation (cTBS), repeated monthly for one year, would affect ALS progression. We performed a double blind, placebo-controlled trial. Twenty patients with ALS were randomly allocated to blinded real or placebo stimulation. cTBS of the motor cortex was performed for five consecutive days every month for one year. Primary outcome was the rate of decline as evaluated with the revised ALS functional rating scale (ALSFRS-R). Treatment was well tolerated. There was no significant difference in the ALSFRS-R score deterioration between patients treated with real or placebo stimulation. ALSFRS-R mean scores declined from 32.0 (SD 7.1) at study entry to 23.1 (SD 6.3) at 12 months in patients receiving real cTBS and from 31.3 (SD 6.9) to 21.2 (SD 6.0) in those receiving placebo stimulation. Although cTBS proved a safe procedure, on the basis of the present findings a larger randomized confirmatory trial seems unjustified in ALS patients, at least in advanced stage of the disease.     

Mislocalization of TDP-43 in the G93A mutant SOD1 transgenic mouse model of ALS

Previous evidence demonstrates that TAR DNA binding protein (TDP-43) mislocalization is a key pathological feature of amyotrophic lateral sclerosis (ALS). TDP-43 normally shows nuclear localization, but in CNS tissue from patients who died with ALS this protein mislocalizes to the cytoplasm. Disease specific TDP-43 species have also been reported to include hyperphosphorylated TDP-43, as well as a C-terminal fragment. Whether these abnormal TDP-43 features are present in patients with SOD1-related familial ALS (fALS), or in mutant SOD1 over-expressing transgenic mouse models of ALS remains controversial. Here we investigate TDP-43 pathology in transgenic mice expressing the G93A mutant form of SOD1. In contrast to previous reports we observe redistribution of TDP-43 to the cytoplasm of motor neurons in mutant SOD1 transgenic mice, but this is seen only in mice having advanced disease. Furthermore, we also observe rounded TDP-43 immunoreactive inclusions associated with intense ubiquitin immunoreactivity in lumbar spinal cord at end stage disease in mSOD mice. These data indicate that TDP-43 mislocalization and ubiquitination are present in end stage mSOD mice. However, we do not observe C-terminal TDP-43 fragments nor TDP-43 hyperphosphorylated species in these end stage mSOD mice. Our findings indicate that G93A mutant SOD1 transgenic mice recapitulate some key pathological, but not all biochemical hallmarks, of TDP-43 pathology previously observed in human ALS. These studies suggest motor neuron degeneration in the mutant SOD1 transgenic mice is associated with TDP-43 histopathology.     

Maternal uniparental heterodisomy with partial isodisomy of a chromosome 2 carrying a splice acceptor site mutation (IVS9–2A>T) in ALS2 causes infantile-onset ascending spastic paralysis (IAHSP)

Infantile-onset ascending spastic paralysis (OMIM #607225) is a rare autosomal recessive early onset motor neuron disease caused by mutations in the gene ALS2. We report on a splice acceptor site mutation in intron 9 of ALS2 (IVS9–2A>T) in a German patient from nonconsanguineous parents. The mutation results in skipping of exon 10. This causes a frame-shift in exon 11 and a premature stop codon. Analysis of the parental ALS2 gene revealed heterozygosity for the mutation in the mother but not in the father. Therefore, we studied polymorphic markers scattered along chromosome 2 in both parents and the patient and found maternal uniparental disomy in the patient. While homozygosity was observed at several loci of chromosome 2 including ALS2, other loci were heterozygous, i.e., both maternal alleles were present. The findings can be explained by at least four recombination events during maternal meiosis followed by a meiosis I error and postzygotic trisomy rescue or gamete complementation. Thilo Herzfeld and Nicole Wolf contributed equally to this paper.     

A soluble activin type IIB receptor improves function in a mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurologic disease characterized by progressive weakness that results in death within a few years of onset by respiratory failure. Myostatin is a member of the TGF-β superfamily that is predominantly expressed in muscle and acts as a negative regulator of muscle growth. Attenuating myostatin has previously been shown to produce increased muscle mass and strength in normal and disease animal models. In this study, a mouse model of ALS (SOD1^G93A transgenic mice) was treated with a soluble activin receptor, type IIB (ActRIIB.mFc) which is a putative endogenous signaling receptor for myostatin in addition to other ligands of the TGF-β superfamily. ActRIIB.mFc treatment produces a delay in the onset of weakness, an increase in body weight and grip strength, and an enlargement of muscle size whether initiated pre-symptomatically or after symptom onset. Treatment with ActRIIB.mFc did not increase survival or neuromuscular junction innervation in SOD1^G93A transgenic mice. Pharmacologic treatment with ActRIIB.mFc was superior in all measurements to genetic deletion of myostatin in SOD1^G93A transgenic mice. The improved function of SOD1^G93A transgenic mice following treatment with ActRIIB.mFc is encouraging for the development of TGF-β pathway inhibitors to increase muscle strength in patients with ALS.     

Fetal olfactory ensheathing cells transplantation in amyotrophic lateral sclerosis patients: a controlled pilot study

This study was designed to clarify whether transplantation of fetal olfactory ensheathing cells (OECs) would affect the clinical course of patients with amyotrophic lateral sclerosis (ALS). Thirty-five patients with probable or definite ALS were enrolled from December 2004 to September 2006; 15 patients received OECs transplantation and 20 patients did not receive OECs transplantation. OECs were cultured and injected into the bilateral corona radiata involving the pyramidal tracts of the frontal lobes. The primary end point used to indicate effectiveness was the rate of change according to the ALS Functional Rating Scale (ALS-FRS) total score. All patients were tested five times at baseline and monthly intervals during a four-month follow-up period using assessment of ALS-FRS. Thirty-one patients (14 in the OECs treated group and 17 in the controls) completed the four-month study; the remaining four patients were lost to follow-up. Patients' data were analyzed four months after OECs transplantation and at the end of the controlled period. There was no significant difference in the rate of progression as measured by the ALS-FRS total score during the first two months (p > 0.05). The functional deterioration, however, was significantly slower in the treated group than in the control group during the last two months (p < 0.05). The mean (+/-SD) change for the ALS-FRS total score was 0.07 +/- 4.18 for the treated group and 6.12 +/- 5.49 for the control group (p = 0.002) during the four months. Of the 14 patients in the treatment group, seven experienced neurological functional improvements, two were stable compared with their clinical status at entry, and the ALS-FRS scores in the other five decreased by a mean of 4.4. Of the 17 patients in the control group, only one patient's condition remained stable while the ALS-FRS scores in the other 16 decreased by a mean of 6.5. The result indicates OECs transplantation appears to be able to slow the rate of clinical progression of ALS in the first four months posttransplantation.     

Sex-specific behavioural effects of environmental enrichment in a transgenic mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterised by motor neuron degeneration, muscle wasting and paralysis. While twin studies support a role for both genetic and environmental factors in ALS, the nature of environmental modifiers is unknown. We therefore compared onset and progression of disease symptoms in female and male transgenic ALS mice (expressing the human SOD1^G93A gene mutation) and their wild-type littermates, housed in environmentally enriched versus standard conditions. Environmental enrichment significantly improved motor performance, as measured using the accelerating rotarod, in particular for female mice. This enhanced motor coordination was observed for both SOD1^G93A and wild-type mice, suggesting this effect is independent of genotype. Female SOD1^G93A mice housed with environmental enrichment were found to reach overt end-stage disease sooner than their standard-housed littermates. However, male SOD1^G93A mice did not show significantly accelerated disease progression. This evidence for environmental modulation of ALS pathogenesis in transgenic mice provides insights into activity-dependent aspects of the disease process, and may help identify molecular targets for pharmacological modulators as future therapeutics.     

Water soluble RNA based antagonist of AMPA receptors

Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors are one of the important receptor classes involved in glutamate-mediated excitotoxicity. Although small molecule antagonists of this receptor have been shown to have neuroprotective properties, their low solubilities pose severe side effects in clinical trials. Here we have used the SELEX method to obtain water-soluble nuclease-resistant RNA ligands that bind to the agonist binding site of AMPA receptors. Using whole-cell current recordings, we have characterized the functional consequences of a representative aptamer from this class and show that it is a competitive antagonist of AMPA receptors and in the concentration range where it acts as an inhibitor of the AMPA receptor the RNA has no effect on the GluR6 homomeric kainate receptors. Additionally, using a fluorescence resonance energy transfer (FRET) probe, we show that this RNA ligand stabilizes the open cleft conformation of the ligand binding domain, consistent with the known structures of small antagonist-bound states of the soluble domain of this protein. Finally, using rat primary cortical neurons, we show that this RNA ligand significantly reduces neurotoxicity associated with oxygen glucose deprivation. The water-soluble and antagonistic properties of this aptamer coupled with its neuroprotective properties make it an excellent candidate for potential use in diseases or pathological conditions involving glutamate-mediated excitotoxicity.     

Lithium: bipolar disorder and neurodegenerative diseases Possible cellular mechanisms of the therapeutic effects of lithium

Bipolar illness is a major psychiatric disorder that affects 1-3% of the worldwide population. Epidemiological studies have demonstrated that this illness is substantially heritable. However, the genetic characteristics remain unknown and a clear personality has not been identified for these patients. The clinical history of lithium began in mid-19th century when it was used to treat gout. In 1940, it was used as a substitute for sodium chloride in hypertensive patients. However, it was then banned, as it had major side effects. In 1949, Cade reported that lithium could be used as an effective treatment for bipolar disorder and subsequent studies confirmed this effect. Over the years, different authors have proposed many biochemical and biological effects of lithium in the brain. In this review, the main mechanisms of lithium action are summarised, including ion dysregulation; effects on neurotransmitter signalling; the interaction of lithium with the adenylyl cyclase system; inositol phosphate and protein kinase C signalling; and possible effects on arachidonic acid metabolism. However, none of the above mechanisms are definitive, and sometimes results have been contradictory. Recent advances in cellular and molecular biology have reported that lithium may represent an effective therapeutic strategy for treating neurodegenerative disorders like Alzheimer's disease, due to its effects on neuroprotective proteins like Bcl-2 and its actions on regulators of apoptosis and cellular resilience, such as GSK-3. However, results are contradictory and more specific studies into the use of lithium in therapeutic approaches for neurodegenerative diseases are required.     

The fraction of activated <Emphasis Type="Italic">N</Emphasis>-methyl-<Emphasis Type="SmallCaps">d</Emphasis>-Aspartate receptors during synaptic transmission remains constant in the presence of the glutamate release inhibitor riluzole

Excessive N-methyl-D: -aspartate (NMDA) receptor activation is widely accepted to mediate calcium-dependent glutamate excitotoxicity. The uncompetitive, voltage-dependent NMDA receptor antagonist memantine has been successfully used clinically in the treatment of neurodegenerative dementia and is internationally registered for the treatment of moderate to severe Alzheimer's disease. Glutamate release inhibitors (GRIs) may also be promising for the therapy of some neurodegenerative diseases. During the clinical use of GRIs, it could be questioned whether there would still be a sufficient number of active NMDA receptors to allow any additional effects of memantine or similar NMDA receptor antagonists. To address this question, we determined the fraction of NMDA receptors contributing to postsynaptic events in the presence of therapeutically relevant concentrations of the GRI riluzole (1 muM) using an in vitro hippocampal slice preparation. We measured the charge transfer of pharmacologically isolated excitatory synaptic responses before and after the application of the selective, competitive NMDA receptor antagonist D-AP5 (100 muM). The fraction of activated NMDA receptors under control conditions did not differ from those in the presence of riluzole. It is therefore likely that NMDA receptor antagonists would be able to exert additional therapeutic effects in combination therapy with GRIs.