Peroxynitrite and Hydrogen Peroxide Induced Cell Death in the NSC34 Neuroblastoma × Spinal Cord Cell Line: Role of Poly(ADP-Ribose) Polymerase

Abstract: The reaction of superoxide and nitric oxide results in the formation of peroxynitrite, a long lived and highly reactive oxidant species. It has been suggested that the formation of peroxynitrite in vivo may contribute to cell death in some neurological conditions. We have examined the effect of peroxynitrite on cell death in the NSC34 spinal cord cell line. A brief (30 min) exposure to either peroxynitrite or hydrogen peroxide caused delayed cell death with an EC₅₀ for both of ∼1 m M . Cell death was prevented by the RNA synthesis inhibitor actinomycin D and included DNA damage as an early event. We sought to clarify the potential role of the DNA binding enzyme poly(ADP-ribose) polymerase (PARP) in cell death in these cells. Several PARP inhibitors [benzamide, 3-aminobenzamide, nicotinamide, and 6(5 H )-phenanthridinone] prevented cell death, but the inactive analogue benzoic acid did not. However, there was no evidence of cleavage of PARP, which occurs in apoptosis via the activation of the caspase CPP32. Therefore, we suggest that PARP contributes to neuronal injury as an early event, probably by lethal NAD depletion, without any requirement for proteolytic cleavage.     

Output connections of a wind sensitive interneurone with motor neurones innervating flight steering muscles in the locust

Summary The output connections of a bilaterally symmetrical pair of wind-sensitive interneurones (called A4I1) were determined in a non-flying locust (Schistocerca gregaria). Direct inputs from sensory neurones of specific prosternai and head hairs initiate spikes in these interneurones in the prothoracic ganglion.The interneurone with its axon in the right connective makes direct, excitatory connections with the two mesothoracic motor neurones innervating the pleuroaxillary (pleuroalar, M85) muscle of the right forewing, but not with the comparable motor neurones of the left forewing. The connections can evoke motor spikes.The interneurones also exert a powerful, but indirect effect on the homologous metathoracic pleuroaxillary motor neurones (muscle 114), and a weaker, indirect effect on subalar motor neurones of the hindwings. No connections or effects were found with other flight motor neurones, or motor neurones innervating hindleg muscles, including common inhibitor 1 which also innervates the pleuroaxillary muscle.One thoracic interneurone with its cell body in the right half of the mesothoracic ganglion and with its axon projecting ipsilaterally to the metathoracic ganglion receives a direct input from the right A4I1 interneurone.These restricted output connections suggest a role for the A4I1 interneurones in flight steering.Abbreviations DCMD descending contralateral movement detector - EPSP excitatory postsynaptic potential - TCG tritocerebral commissure giant (interneurone)     

Changes in firing behaviour of an insect motor neurone during development and following experimental surgery

The firing behaviour of an identified neurone in the cricket was studied using extracellular recording from the axon. In the last nympal instar (preadult developmental stage), the contralateral dorsal longitudinal motor neurone (CDLM) showed spontaneous activity and was excited by air puffs to the head and cerci and by single shocks to the anterior nerve cord. In the normal adult the CDLM did not exhibit these properties. However, responses which were characteristic of the last instar appeared in the adults which had been subjected to any one of the following surgical procedures: (1) central nervous system injuries which separated the CDLM arborization and axon from the soma; (2) operations which injured the central nervous system without cutting the CDLM; and (3) operations which damaged the cuticle only. Since cuticle damage alone was as effective as the more extensive operations, it is suggested that a sufficient cause for the appearance of nymphal firing behaviour in the adult CDLM is cuticle damage. The factor associated with cuticle damage which mediates the changes in activity of the CDLM neurone is not known, but its action does not require the mediation of the CDLM soma.     

Input and output synapses on identified motor neurones of a locust revealed by the intracellular injection of horseradish peroxidase

Summary Physiologically characterised motor neurones in the thoracic ganglia of the locust were injected with horseradish peroxidase in order that the spatial relationship between their input and output synapses could be observed with the electron microscope. A modification in the development procedure for the peroxidase ensured that the internal fine structure of the stained neurones was not obscured by the diaminobenzidine reaction product. Input and output synapses may occur within 1 m of each other on the neuropilar processes of the motor neurones. This supports physiological evidence that motor neurones may be involved in local circuit interactions within the thoracic ganglia.     

Characterization of a human stromal cell line supporting hematopoietic progenitor cell proliferation: Effect of HIV expression

Our objective was to determine the role that bone marrow-derived stromal cells have on human hematopoiesis in HIV infection. In particular, we dissected the heterogeneous bone marrow microenvironment to study the effect HIV expression might have on the cell population capable of producing the cytokines which will support human CD34+ cell differentiation. A stromal cell line, Lof(11-10), was established from human bone marrow by transfecting a plasmid containing the SV40 large T-antigen and isolating foci exhibiting a transformed phenotype. The Lof(11-10) cell line was characterized to determine its susceptibility to HIV infection, to identify its cytokine production profile, and to test the ability of conditioned media from this line to support CD34+ cell differentiation in the presence and absence of HIV expression. Nine cytokines were detected by RT-PCR and ELISA analysis. Conditioned media obtained from the Lof(11-10) cell line was able to support CD34+ cell differentiation. However, because the Lof(11-10) cells are not infectible by HIV, molecular clones of HIV were introduced into these cells by transfection. There was no qualitative difference in the levels of cytokine production between HIV-expressing and control Lof(11-10) cells. Furthermore, conditioned media derived from HIV-expressing and control Lof(11-10) cells added to bone marrow-derived CD34+ progenitor cells yielded similar colony formation in methylcellulose assays. Our data suggest that HIV infection of the cytokine-producing cells within the bone marrow microenvironment, as represented by the Lof(11-10) cell line, results in both normal cytokine production and hematopoiesis in spite of HIV expression. This report adds to the evidence against stromal cells being a significant target of HIV and establishes a system for comparison with more relevant models.     

Cystine Deprivation Induces Oligodendroglial Death: Rescue by Free Radical Scavengers and by a Diffusible Glial Factor

Abstract: In this study we examined the effect on oligodendroglial survival of exogenous cystine deprivation. Oligodendroglia isolated from mixed glial primary cultures derived from brains of 1-day-old rats, and then grown for 3 days, were markedly dependent on extracellular cystine for survival. The EC₅₀ values for cystine for a 24-h exposure ranged from 2 to 65 µ M . After 6 h of cystine deprivation, the cellular glutathione level decreased to 21 ± 13% of the control. Free radical scavengers (α-tocopherol, ascorbate, idebenone, and N-tert -butyl-α-phenylnitrone) were protective against cystine deprivation but had no effect on the glutathione level. An iron chelator, desferrioxamine mesylate, also was protective. These findings suggest that intracellular hydroxyl radicals are important for this toxicity. In contrast to the observations in 3-day-old cultures, the dependence on exogenous cystine for cell viability was not observed consistently in oligodendroglia cultured for 6 days before the onset of cystine deprivation. Several observations suggested that this loss of cystine dependence was due to a diffusible factor. Sensitivity to the toxicity of cystine deprivation in day 6 cultures increased as the volume of medium was increased from 0.3 to 2 ml. Furthermore, preincubation of cystine-depleted medium with astrocyte cultures eliminated the toxicity of the cystine deprivation. HPLC assay of the conditioned cystine-depleted medium showed no significant change in cystine or cysteine concentration. We conclude that oligodendroglia are highly susceptible to cystine deprivation in day 3 cultures and that this susceptibility is due to the accumulation of intracellular free radicals in the setting of glutathione depletion. The resistance of day 6 oligodendroglial cultures is caused at least in part by a diffusible factor.     

Rapid Communication: Cu/Zn Superoxide Dismutase Activity in Familial and Sporadic Amyotrophic Lateral Sclerosis

Abstract: Amyotrophic lateral sclerosis (ALS) is a degenerative motor neuron disease that is inherited as an autosomal dominant trait in ~ 10% of cases. Recently we and others identified several single-base mutations in the Cu/Zn superoxide dismutase (SOD1) gene in patients with familial ALS (FALS). Using single-strand conformational polymorphism, we studied the C to G mutation in exon 2 of the SOD1 gene (resulting in a leucine to valine substitution in position 38) in affected and unaffected members of a large Belgian family with FALS. We measured the SOD1 activity in red blood cell lysates in 14 members of this family, including the only surviving clinically affected patient. SOD1 activity of the family members carrying the mutation was less than half that of members without the mutation. In addition, in 11 patients with sporadic ALS and 11 age- and sex-matched controls, red blood cell SOD1 activity was normal. These studies indicate that SOD1 activity is reduced in these FALS patients but not in sporadic ALS patients. Moreover, this SOD1 enzyme abnormality is detectable years before onset of clinical ALS in carriers of this FALS mutation.     

JNK activation limits dendritic cell maturation in response to reactive oxygen species by the induction of apoptosis

Dendritic cells (DC) sense infection in their local microenvironment and respond appropriately in order to induce T cell immunity. This response is mediated in part via the mitogen-activated protein kinase (MAPK) pathways. Hydrogen peroxide is present frequently in the inflammatory DC milieu and is known to activate MAPK. Therefore this study examines the role of hydrogen peroxide, both alone and in combination with lipopolysaccharide (LPS), in the regulation of activation of two key MAPK, p38 and JNK, regulation of phenotype, and regulation of apoptosis in human monocyte-derived DC. At low concentrations, hydrogen peroxide activates p38, but does not alter DC phenotype. At higher concentrations, hydrogen peroxide activates both p38 and JNK. Activation of JNK, which is associated with inhibition of tyrosine phosphatases in DC, is linked to the induction of DC apoptosis. An upstream JNK inhibitor (CEP11004) and a competitive JNK inhibitor (SP600125) both partially protected the DC from the proapoptotic effects of hydrogen peroxide. Unexpectedly, hydrogen peroxide and LPS synergize in inducing JNK activation and DC apoptosis. JNK-mediated apoptosis may limit damaging immune responses against neoepitopes generated by modification of self-antigens by reactive oxygen species present at sites of inflammation.     

Co-administration of IGF-I and glycosaminoglycans greatly delays motor neurone disease and affects IGF-I expression in the wobbler mouse: a long-term study

The study on wobbler mouse has shown that the combined treatment with low doses of glycosaminoglycans (GAGs) and insulin-like growth factor-I (IGF-I) fully prevented motor neurone death and forelimb impairment up to 9-12 weeks of a mouse's life. The effect was accompanied by the prevention of the early hypertrophy of wobbler neurones, an effect likely due to the promotion of neuronal survival. At the 18th week, wobbler mice treated with IGF-I + GAGs still showed significantly improved forelimb function, reduced muscle atrophy and a higher number of cervical motor neurones. IGF-I alone and GAGs alone were active up to the 3rd week of treatment; thereafter the beneficial effects of single treatments decreased drastically. GAGs and IGF-I treatments also affected IGF-I plasma and muscle levels. In wobbler mice there was a progressive reduction in IGF-I plasma levels that was prevented by IGF-I or GAGs alone and greatly increased, even above heterozygote levels, by the combination treatment. Such a powerful increase was correlated by a small enhancement in insulin-like growth factor binding protein-3 (IGFBP-3) plasma levels, while treatment with IGF-I alone affected very significantly both IGFBP-1 and IGFBP-3. Co-treatment also prevented the decrease in IGF-I content observed in vehicle-treated wobbler mice forelimb muscles.     

Discovery of a benzofuran derivative (MBPTA) as a novel ROCK inhibitor that protects against MPP+-induced oxidative stress and cell death in SH-SY5Y cells

Parkinson disease (PD) is a neurodegenerative disease with multifactorial etiopathogenesis. The discovery of drug candidates that act on new targets of PD is required to address the varied pathological aspects and modify the disease process. In this study, a small compound, 2-(5-methyl-1-benzofuran-3-yl)-N-(5-propylsulfanyl-1,3,4-thiadiazol-2-yl) acetamide (MBPTA) was identified as a novel Rho-associated protein kinase inhibitor with significant protective effects against 1-methyl-4-phenylpyridinium ion (MPP⁺)-induced damage in SH-SY5Y neuroblastoma cells. Further investigation showed that pretreatment of SH-SY5Y cells with MBPTA significantly suppressed MPP⁺-induced cell death by restoring abnormal changes in nuclear morphology, mitochondrial membrane potential, and numerous apoptotic regulators. MBPTA was able to inhibit MPP⁺-induced reactive oxygen species (ROS)/NO generation, overexpression of inducible NO synthase, and activation of NF-κB, indicating the critical role of MBPTA in regulating ROS/NO-mediated cell death. Furthermore, MBPTA was shown to activate PI3K/Akt survival signaling, and its cytoprotective effect was abolished by PI3K and Akt inhibitors. The structural comparison of a series of MBPTA analogs revealed that the benzofuran moiety probably plays a crucial role in the anti-oxidative stress action. Taken together, these results suggest that MBPTA protects against MPP⁺-induced apoptosis in a neuronal cell line through inhibition of ROS/NO generation and activation of PI3K/Akt signaling.     

The novel role of peroxiredoxin-2 in red cell membrane protein homeostasis and senescence

Peroxiredoxin-2 (Prx2), a typical two-cysteine peroxiredoxin, is the third most abundant protein in red cells. Although progress has been made in the functional characterization of Prx2, its role in red cell membrane protein homeostasis is still under investigation. Here, we studied Prx2^−/− mouse red cells. The absence of Prx2 promotes (i) activation of the oxidative-induced Syk pathway; (ii) increased band 3 Tyr phosphorylation, with clustered band 3; and (iii) increased heat shock protein (HSP27 and HSP70) membrane translocation. This was associated with enhanced in vitro erythrophagocytosis of Prx2^−/− red cells and reduced Prx2^−/− red cell survival, indicating the possible role of Prx2 membrane recruitment in red cell aging and in the clearance of oxidized hemoglobin and damaged proteins through microparticles. Indeed, we observed an increased release of microparticles from Prx2^−/− mouse red cells. The mass spectrometric analysis of erythroid microparticles found hemoglobin chains, membrane proteins, and HSPs. To test these findings, we treated Prx2^−/− mice with antioxidants in vivo. We observed that N-acetylcysteine reduced (i) Syk activation, (ii) band 3 clusterization, (iii) HSP27 membrane association, and (iv) erythroid microparticle release, resulting in increased Prx2^−/− mouse red cell survival. Thus, we propose that Prx2 may play a cytoprotective role in red cell membrane protein homeostasis and senescence.     

Phenolic antioxidants attenuate neuronal cell death following uptake of oxidized low-density lipoprotein

Oxidative stress is implicated in neuronal loss associated with neurodegeneration such as in Parkinson’s disease, Alzheimer’s disease and age-related cognitive decline. Recent reports indicate that the consumption of flavonoid-rich fruits partly reverses the age-related neuronal and cognitive decline. In this study, cultured striatal neurons were exposed to oxidized lipids in the form of low-density lipoprotein (oxLDL) as a model for the induction of oxidative injury, and the abilities of phenolic antioxidants, flavonoids and hydroxycinnamic acid derivatives, to attenuate this neuronal damage were examined. OxLDL was demonstrated to enter neuronal cells and to be capable of eliciting neurotoxicity in a dose- and time-dependent manner, inducing DNA fragmentation and cell lysis. Flavonoids exert protective effects, which appear to be related to specific structural characteristics, particularly relevant being those defining their reduction potentials and partition coefficients. In summary, these data suggest a possible role for flavonoids in reducing neurodegeneration associated with chronic disorders in which oxidative stress is implicated.     

Role of VPO1, a newly identified heme-containing peroxidase, in ox-LDL induced endothelial cell apoptosis

Myeloperoxidase (MPO) is an important enzyme involved in the genesis and development of atherosclerosis. Vascular peroxidase 1 (VPO1) is a newly discovered member of the peroxidase family that is mainly expressed in vascular endothelial cells and smooth muscle cells and has structural characteristics and biological activity similar to those of MPO. Our specific aims were to explore the effects of VPO1 on endothelial cell apoptosis induced by oxidized low-density lipoprotein (ox-LDL) and the underlying mechanisms. The results showed that ox-LDL induced endothelial cell apoptosis and the expression of VPO1 in endothelial cells in a concentration- and time-dependent manner concomitant with increased intracellular reactive oxygen species (ROS) and hypochlorous acid (HOCl) generation, and up-regulated protein expression of the NADPH oxidase gp91^phox subunit and phosphorylation of p38 MAPK. All these effects of ox-LDL were inhibited by VPO1 gene silencing and NADPH oxidase gp91^phox subunit gene silencing or by pretreatment with the NADPH oxidase inhibitor apocynin or diphenyliodonium. The p38 MAPK inhibitor SB203580 or the caspase-3 inhibitor DEVD-CHO significantly inhibited ox-LDL-induced endothelial cell apoptosis, but had no effect on intracellular ROS and HOCl generation or the expression of NADPH oxidase gp91^phox subunit or VPO1. Collectively, these findings suggest for the first time that VPO1 plays a critical role in ox-LDL-induced endothelial cell apoptosis and that there is a positive feedback loop between VPO1/HOCl and the now-accepted dogma that the NADPH oxidase/ROS/p38 MAPK/caspase-3 pathway is involved in ox-LDL-induced endothelial cell apoptosis.     

The dendritic and T cell responses to herpes simplex virus-1 are modulated by dietary vitamin E

Previous studies from our laboratory have shown that dietary α-tocopherol (vitamin E, or VE) is essential for regulating the cytokine and chemokine response in the brain to herpes simplex virus-1 (HSV-1) infection. The timing of T cell infiltration is critical to the resolution of central nervous system HSV-1 infections. Specifically, the appearance of “neuroprotective” CD8⁺IFN-γ⁺ T cells is crucial. During CNS infection, CD8⁺ T cell priming and expansion in the draining lymph node, followed by recruitment and expansion, occurs in the spleen with subsequent accumulation in the brain. Weanling male BALB/cByJ mice were placed on VE-deficient (Def) or -adequate diets for 4 weeks followed by intranasal infection with HSV-1. VE-Def mice had fewer CD8⁺IFN-γ⁺ T cells trafficking to the brain despite increased CD8⁺IFN-γ⁺ T cells and activated dendritic cells in the periphery. VE-Def mice had increased T regulatory cells (Tregs) in the periphery and brain, and the increase in Tregs decreased CD8⁺ T cell numbers in the brain. Our results demonstrate that adequate levels of VE are important for trafficking antigen-specific T cells to the brain, and dietary VE levels modulate T regulatory and dendritic cells in the periphery.     

Inhibition of Glutamate Transport in Synaptosomes by Dopamine Oxidation and Reactive Oxygen Species

Abstract: Dopamine can form reactive oxygen species and other reactive metabolites that can modify proteins and other cellular constituents. In this study, we tested the effect of dopamine oxidation products, other generators of reactive oxygen species, and a sulfhydryl modifier on the function of glutamate transporter proteins. We also compared any effects with those on the dopamine transporter, a protein whose function we had previously shown to be inhibited by dopamine oxidation. Preincubation with the generators of reactive oxygen species, ascorbate (0.85 m M ) or xanthine (500 µ M ) plus xanthine oxidase (25 mU/ml), inhibited the uptake of [³H]glutamate (10 µ M ) into rat striatal synaptosomes (−54 and −74%, respectively). The sulfhydryl-modifying agent N -ethylmaleimide (50–500 µ M ) also led to a dose-dependent inhibition of [³H]glutamate uptake. Preincubation with dopamine (100 µ M ) under oxidizing conditions inhibited [³H]glutamate uptake by 25%. Exposure of synaptosomes to increasing amounts of dopamine quinone by enzymatically oxidizing dopamine with tyrosinase (2–50 U/ml) further inhibited [³H]glutamate uptake, an effect prevented by the addition of glutathione. The effects of free radical generators and dopamine oxidation on [³H]glutamate uptake were similar to the effects on [³H]dopamine uptake (250 n M ). Our findings suggest that reactive oxygen species and dopamine oxidation products can modify glutamate transport function, which may have implications for neurodegenerative processes such as ischemia, methamphetamine-induced toxicity, and Parkinson's disease.     

Establishment of a cell model of ALS disease: Golgi apparatus disruption occurs independently from apoptosis

The Golgi apparatus (GA) appears disrupted in motor neurons of amyotrophic lateral sclerosis (ALS). Here, mouse motor neuron-like NSC-34 cell lines stably expressing human superoxide dismutase 1 (hSOD1)^wt and mutant hSOD1^G93A, as an ALS cell model, were constructed. The number of cells with disrupted GA increased from 14% to 34%. Furthermore, NSC-34/hSOD1^G93A cells showed lower levels of proliferation and differentiation. GA disruption was not caused by apoptosis as determined by several techniques including caspase-3 activation. Similarly, spinal cords from ALS patients did not show caspase-3 activation. Therefore, NSC-34/hSOD1^G93A cells are a suitable cell model to study GA dysfunction in ALS.     

Development of an attached strain from a continuous insect cell line

Summary A continuous attached cell strain has been developed from the IPRI-CF-124 line of the spruce budworm,Choristoneura fumiferana. This was done by discarding suspended cells at each passage, rinsing attached cells with 0.05% trypsin and using only the strongly attached cells for subculturing. The method is very effective in that the proportion of attached cells increased from 6% in the parent cell line to 97% in the new cell strain after 20 passages. The attachment and growth properties are stable after storage of cells in liquid nitrogen. The new cell strain is designated IPRI-CF-124T and has a population doubling time comparable to that of the parent cell line. Contribution No.: 329.     

NMDA Receptor Activation Produces Concurrent Generation of Nitric Oxide and Reactive Oxygen Species: Implications for Cell Death

Abstract: The ability of glutamate to stimulate generation of intracellular oxidant species was determined by microfluorescence in cerebellar granule cells loaded with the oxidant-sensitive fluorescent dye 2,7-dichlorofluorescin (DCF). Exposure of cells to glutamate (10 µM) produced a rapid generation of oxidants that was blocked ～70% by MK-801 (a noncompetitive NMDA-receptor antagonist). To determine if nitric oxide (NO) or reactive oxygen species (ROS) contributed to the oxidation of DCF, cells were treated with compounds that altered their generation. NO production was inhibited with N^G-nitro-l -arginine methyl ester (l -NAME) (nitric oxide synthase inhibitor) and reduced hemoglobin (NO scavenger). Alternatively, cells were incubated with superoxide dismutase (SOD) and catalase, which selectively metabolize O₂^?· andH₂O₂. Concurrent inhibition of O₂^?· and NO production nearly abolished intracellular oxidant generation. Pretreatment of cells with either chelerythrine (1 µM, protein kinase C inhibitor) or quinacrine (5 µM, phospholipase A₂ inhibitor) before addition of glutamate also blocked oxidation of DCF. Generation of oxidants by glutamate was significantly reduced by incubating the cells in Ca²⁺-free buffer. In cytotoxicity studies, a positive correlation was observed between glutamate-induced death and oxidant generation. Glutamate-induced cytotoxicity was blocked by MK-801 and attenuated by treatment with l -NAME, chelerythrine, SOD, or quinacrine. It is concluded that glutamate induces concurrent generation of NO and ROS by activation of both NMDA receptors and non-NMDA receptors through a Ca²⁺-mediated process. Activation of NO synthase and phospholipaseA₂ contribute significantly to this response. It is proposed that simultaneous generation of NO and ROS results in formation of peroxynitrite, which initiates the cellular damage.     

4-Hydroxynonenal, a Lipid Peroxidation Product, Rapidly Accumulates Following Traumatic Spinal Cord Injury and Inhibits Glutamate Uptake

Abstract: Traumatic injury to the spinal cord initiates a host of pathophysiological events that are secondary to the initial insult. One such event is the accumulation of free radicals that damage lipids, proteins, and nucleic acids. A major reactive product formed following lipid peroxidation is the aldehyde, 4-hydroxynonenal (HNE), which cross-links to side chain amino acids and inhibits the function of several key metabolic enzymes. In the present study, we used immunocytochemical and immunoblotting techniques to examine the accumulation of protein-bound HNE, and synaptosomal preparations to study the effects of spinal cord injury and HNE formation on glutamate uptake. Protein-bound HNE increased in content in the damaged spinal cord at early times following injury (1–24 h) and was found to accumulate in myelinated fibers distant to the site of injury. Immunoblots revealed that protein-bound HNE levels increased dramatically over the same postinjury interval. Glutamate uptake in synaptosomal preparations from injured spinal cords was decreased by 65% at 24 h following injury. Treatment of control spinal cord synaptosomes with HNE was found to decrease significantly, in a dose-dependent fashion, glutamate uptake, an effect that was mimicked by inducers of lipid peroxidation. Taken together, these findings demonstrate that the lipid peroxidation product HNE rapidly accumulates in the spinal cord following injury and that a major consequence of HNE accumulation is a decrease in glutamate uptake, which may potentiate neuronal cell dysfunction and death through excitotoxic mechanisms.     

Synaptosomal Glutamate Uptake Declines Progressively in the Spinal Cord of a Mutant Mouse with Motor Neuron Disease

Abstract: It has been suggested that the degeneration of motor neurons in amyotrophic lateral sclerosis is a consequence of excitotoxicity resulting from a loss of synaptosomal glutamate uptake. The role of synaptosomal glutamate uptake in the pathogenesis of motor neuron disease was studied in the Mnd mouse. Glutamate uptake in spinal-cord synaptosomes declined in parallel with the onset of behavioral deficits in Mnd mice but lagged considerably behind the appearance of pathology in motor neurons. Glutamate uptake did not decline significantly in corpus striatum, and GABA uptake did not change significantly in either spinal cord or striatum. The presence of pronounced histopathological changes before the loss of glutamate uptake suggests that the decline of glutamate uptake is a consequence rather than the primary cause of motor neuron disease in the Mnd mouse.