Transgenic Mouse Model Of Amyotrophic Lateral Sclerosis Research Articles

Early abnormalities in transgenic mouse models of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative and fatal human disorder characterized by progressive loss of motor neurons. Transgenic mouse models of ALS are very useful to study the initial mechanisms underlying this neurodegenerative disease. We will focus here on the earlier abnormalities observed in superoxide dismutase 1 (SOD1) mutant mice. Several hypotheses have been advanced to explain the selective loss of motor neurons such as apoptosis, neurofilament disorganisation, oxidative stress, mitochondrial dysfunction, astrogliosis and excitotoxicity. Although disease onset appears at adulthood, recent studies have detected abnormalities during embryonic and postnatal maturation in animal models of ALS. We reported that SOD1 G85R mutant mice exhibit specific delays in acquiring sensory-motor skills during the first week after birth. In addition, physiological measurements on in vitro spinal cord preparations reveal defects in evoking rhythmic activity with N-methyl- dl-aspartate and serotonin at lumbar, but not sacral roots. This is potentially significant, as functions involving sacral roots are spared at late stages of the disease. Moreover, electrical properties of SOD1 lumbar motoneurons are altered as early as the second postnatal week when mice begin to walk. Alterations concern the input resistance and the gain of SOD1 motoneurons which are lower than in control motoneurons. Whether or not the early changes in discharge firing are responsible for the uncoupling between motor axon terminals and muscles is still an open question. A link between these early electrical abnormalities and the late degeneration of motoneurons is proposed in this short review. Our data suggest that ALS, as other neurodegenerative diseases, could be a consequence of an abnormal development of neurons and network properties. We hypothesize that the SOD1 mutation could induce early changes during the period of maturation of motor systems and that compensatory mechanisms—linked to developmental spinal plasticity—might explain the late onset of the disease.

Beneficial effects of intrathecal IGF-1 administration in patients with amyotrophic lateral sclerosis

Objectives: There is currently no effective pharmacological treatment for amyotrophic lateral sclerosis (ALS). In a transgenic mouse model of ALS, intrathecal infusion of insulin-like growth factor (IGF)-1 showed a promising increase in survival. We performed a double-blind clinical trial to assess the effect of intrathecal administration of IGF-1 on disease progression in patients with ALS.Methods: Nine patients with ALS were randomly assigned to receive either a high dose (3 μg/kg of body weight) or low dose (0.5 μg/kg of body weight) of IGF-1 every 2 weeks for 40 weeks. The outcome measurements were the rate of decline of bulbar and limb functions (Norris scales) and forced vital capacity.Results: The high-dose treatment slowed a decline of motor functions of the ALS patients in total Norris and limb Norris scales, but not in bulbar Norris or vital capacity. The intrathecal administration of IGF-1 had a modest but significant beneficial effect in ALS patients without any serious adverse effects.Discussion: Intrathecal IGF-1 treatment could provide an effective choice for ALS although further studies in more patients are needed to confirm its efficacy and optimize dosages of IGF-1.

Protein Nitration in a Mouse Model of Familial Amyotrophic Lateral Sclerosis: POSSIBLE MULTIFUNCTIONAL ROLE IN THE PATHOGENESIS

Multiple mechanisms have been proposed to contribute to amyotrophic lateral sclerosis (ALS) pathogenesis, including oxidative stress. Early evidence of a role for oxidative damage was based on the finding, in patients and murine models, of high levels of markers, such as free nitrotyrosine (NT). However, no comprehensive study on the protein targets of nitration in ALS has been reported. We found an increased level of NT immunoreactivity in spinal cord protein extracts of a transgenic mouse model of familial ALS (FALS) at a presymptomatic stage of the disease compared with age-matched controls. NT immunoreactivity is increased in the soluble fraction of spinal cord homogenates and is found as a punctate staining in motor neuron perikarya of presymptomatic FALS mice. Using a proteome-based strategy, we identified proteins nitrated in vivo, under physiological or pathological conditions, and compared their level of specific nitration. alpha- and gamma-enolase, ATP synthase beta chain, and heat shock cognate 71-kDa protein and actin were overnitrated in presymptomatic FALS mice. We identified by matrix-assisted laser desorption/ionization mass spectrometry 16 sites of nitration in proteins oxidized in vivo. In particular, alpha-enolase nitration at Tyr(43), target also of phosphorylation, brings additional evidence on the possible interference of nitration with phosphorylation. In conclusion, we propose that protein nitration may have a role in ALS pathogenesis, acting directly by inhibiting the function of specific proteins and indirectly interfering with protein degradation pathways and phosphorylation cascades.

Loss of synaptophysin‐positive boutons on lumbar motor neurons innervating the medial gastrocnemius muscle of the SOD1G93A G1H transgenic mouse model of ALS

Amyotrophic lateral sclerosis (ALS) is a common form of motor neuron disease (MND) that involves both upper and lower nervous systems. In the SOD1G93A G1H transgenic mouse, a widely used animal model of human ALS, a significant pathology is linked to the degeneration of lower motor neurons in the lumbar spinal cord and brainstem. In the current study, the number of presynaptic boutons immunoreactive for synaptophysin was estimated on retrogradely labeled soma and proximal dendrites of alpha and gamma motor neurons innervating the medial gastrocnemius muscle. No changes were detected on both soma and proximal dendrites at postnatal day 60 (P60) of alpha and gamma motor neurons. By P90 and P120, however, alpha motor neuron soma had a reduction of 14 and 33% and a dendritic reduction of 19 and 36%, respectively. By P90 and P120, gamma motor neuron soma had a reduction of 17 and 41% and a dendritic reduction of 19 and 35%, respectively. This study shows that levels of afferent innervation significantly decreased on surviving alpha and gamma motor neurons that innervate the medial gastrocnemius muscle. This finding suggests that the loss of motor neurons and the decrease of synaptophysin in the remaining motor neurons could lead to functional motor deficits, which may contribute significantly to the progression of ALS/MND.

Cannabinol delays symptom onset in SOD1 (G93A) transgenic mice without affecting survival

Therapeutic options for amyotrophic lateral sclerosis (ALS), the most common adult-onset motor neuron disorder, remain limited. Emerging evidence from clinical studies and transgenic mouse models of ALS suggests that cannabinoids, the bioactive ingredients of marijuana (Cannabis sativa) might have some therapeutic benefit in this disease. However, Delta(9)-tetrahydrocannabinol (Delta(9)-THC), the predominant cannabinoid in marijuana, induces mind-altering effects and is partially addictive, compromising its clinical usefulness. We therefore tested whether cannabinol (CBN), a non-psychotropic cannabinoid, influences disease progression and survival in the SOD1 (G93A) mouse model of ALS. CBN was delivered via subcutaneously implanted osmotic mini-pumps (5 mg/kg/day) over a period of up to 12 weeks. We found that this treatment significantly delays disease onset by more than two weeks while survival was not affected. Further research is necessary to determine whether non-psychotropic cannabinoids might be useful in ameliorating symptoms in ALS.

Peroxisome proliferator-activated receptor-gamma agonist extends survival in transgenic mouse model of amyotrophic lateral sclerosis

Accumulating evidence suggests that inflammation plays a major role in the pathogenesis of motoneuron death in amyotrophic lateral sclerosis (ALS) both in humans and transgenic mouse models. Peroxisome proliferator-activated receptors (PPARs) are involved in the inflammatory process. Agonists of PPAR-α, -γ, and -δ show anti-inflammatory effects both in vitro and in vivo. We investigated the therapeutic effect of pioglitazone, a peroxisome proliferator-activated receptor-gamma (PPAR-γ) agonist, in the G93A SOD1 transgenic mouse model of ALS. Orally administered pioglitazone improved motor performance, delayed weight loss, attenuated motor neuron loss, and extended survival of G93A mice as compared to the untreated control littermate group. Pioglitazone treatment extended survival by 13%, and it reduced gliosis as assessed by immunohistochemical staining for CD-40 and GFAP. Pioglitazone also reduced iNOS, NFκ-B, and 3-nitrotyrosine immunoreactivity in the spinal cords of G93A transgenic mice. These results suggest that pioglitazone may have therapeutic potential for human ALS.

Extensive exercise is not harmful in amyotrophic lateral sclerosis

Whether physical activity increases risk or promotes progression of motor neurone degeneration in amyotrophic lateral sclerosis (ALS) is still debated. Current pathophysiological hypotheses include excitotoxicity, oxidative stress and increased calcium loads as causes of selective degeneration of vulnerable motor neurones. Vigorous exercise might amplify these factors by increasing firing rates at motor neurones. To test this hypothesis, we constrained a transgenic mouse model of ALS overexpressing the mutant human form of the Cu/Zn superoxide dismutase-1 (SOD-1) to a lifetime exercise on motor-driven running wheels for 10 h daily (active group, n = 12). Onset and progression of disease were assessed by grip strength, stride length and tight rope test. Data were compared with SOD-1 mice placed in running wheels set to slow speed (sedentary group, n = 13). Untreated SOD-1 mice were an additional control group (n = 12). We found no differences in disease onset, which was determined by a change-point analysis using an iterative fitting of segmented linear regression models, or in disease progression. However, the running group showed a non-significant 6-day improvement in survival (133.7 +/- 3.2 days) compared with the sedentary group (127.2 +/- 3.2 days) and a 4-day improvement compared with the control group (129.1 +/- 2.5 days). We demonstrate that a lifetime of vigorous exercise does not promote onset or progression of motor degeneration in SOD-1-mediated ALS. Moreover, the results suggest that the level of excitatory input and calcium turnover at motor neurones, both of which should be increased by running activity, do not interfere with the pathophysiology of SOD-1-mediated ALS.

Induction of cyclooxygenase-2 in reactive glial cells by the CD40 pathway: relevance to amyotrophic lateral sclerosis.

An inflammatory process in association with reactive gliosis has been suggested to play an important role in the pathogenesis of amyotrophic lateral sclerosis (ALS). One of the key findings is a marked increase in the level of cyclooxygenase-2 (COX-2), a therapeutic target of ALS. We investigated the expression of CD40 in the spinal cord of a transgenic mouse model of ALS (G93A mice), and its relevance to COX-2 upregulation. CD40 was predominantly expressed in neurons in normal spinal cord and upregulated in reactive glial cells in spinal cord injury. In the spinal cord of G93A mice, the expression of CD40 was increased in both reactive microglia and astrocytes, where COX-2 was especially increased. The level of COX-2 was upregulated in microglia and astrocytes by CD40 stimulation in vitro. CD40 stimulation in primary spinal cord cultures caused motor neuron loss that was protected by selective COX-2 inhibitor. These results suggest that CD40, which is upregulated in reactive glial cells in ALS, participates in motor neuron loss via induction of COX-2.

Effect of transgene copy number on survival in the G93A SOD1 transgenic mouse model of ALS

Transgenic mice expressing multiple copies of the G93A mutant form of SOD1 develop motor neuron pathology and clinical symptoms similar to those seen in patients with amyotrophic lateral sclerosis (ALS). The phenotype of these mice is dependent on the number of transgene copies in their genome. Changes in transgene copy number, although rare, can sometimes occur while mating due to intra locus recombination events during meiosis. The objective of this study was to develop a real time quantitative PCR method to determine changes in transgene copy number in these mice and to evaluate the effect of transgene copy number on the phenotype of the G93A SOD1 mouse model of ALS.

Caspase-12 cleavage and increased oxidative stress during motoneuron degeneration in transgenic mouse model of ALS

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by loss of motoneurons in the spinal cord and brain stem. We have characterized motoneuron death in transgenic mice carrying the mutant human copper/zinc superoxide dismutase, as a model for familial ALS. Previous studies have shown the involvement of mitochondria in nerve cell demise in these animals. We report here an early cleavage of caspase-12, residing in the endoplasmic reticulum (ER), in the spinal cord during the course of the disease. Apart from caspase-12, caspase-9, and caspase-3 were activated in the transgenic ALS mice. Staining with an antibody for nitrotyrosine, as a marker for oxidative stress, showed a large increase in the ALS mice. The results indicate that oxidative and ER induced stress causing caspase-12 activation are involved in neuronal death and disease progression in ALS. Caspase-12 and the ER pathway for cell death may constitute potential novel targets for the treatment of ALS.

Antisense peptide nucleic acid targeting GluR3 delays disease onset and progression in the SOD1 G93A mouse model of familial ALS.

Glutamate excitotoxicity is strongly implicated as a major contributing factor in motor neuron degeneration in amyotrophic lateral sclerosis (ALS). Excitotoxicity results from elevated intracellular calcium ion (Ca(2+)) levels, which in turn recruit cell death signaling pathways. Recent evidence suggests that alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor subunit (GluR) stoichiometry is a dominant factor leading to excess Ca(2+) loading in neurodegeneration. In particular, the Ca(2+) permeable glutamate receptor subunit 3 (GluR3) has been implicated in several neurologic conditions such as bipolar disorder and epilepsy. Recent proteomic analysis within our group on the copper zinc superoxide dismutase (SOD1)(G93A) transgenic mouse model of familial ALS (FALS) reveals a potentially deleterious upregulation of GluR3 in spinal cord compared to that in wild-type littermates. Based on this finding we designed a 12mer antisense peptide nucleic acid (PNA) directed against GluR3. This sequence significantly reduced levels of GluR3 protein and protected neuroblastoma x spinal cord (NSC-34) cells against death induced by the AMPA receptor-specific agonist (S)-5-fluorowillardiine. We subsequently treated SOD1(G93A) mice thrice weekly with intraperitoneal injections of the antisense PNA (2.5 mg/kg) commencing at postnatal day 50. Mice treated with the antisense sequence had significantly extended survival compared to mice injected with a nonsense sequence. Western blot analysis, however, did not reveal a significant reduction in GluR3 protein levels in whole extracts of the lumbar spinal cord. These results suggest that interference with the GluR3 component of the AMPA receptor assembly may be a novel strategy for controlling excitotoxic destruction of motor neurons and may lead to new therapeutic opportunities for the treatment of human ALS.

P38α stress-activated protein kinase phosphorylates neurofilaments and is associated with neurofilament pathology in amyotrophic lateral sclerosis

Neurofilament middle and heavy chains (NFM and NFH) are heavily phosphorylated on their carboxy-terminal side-arm domains in axons. The mechanisms that regulate this phosphorylation are complex. Here, we demonstrate that p38α, a member of the stress-activated protein kinase family, will phosphorylate NFM and NFH on their side-arm domains. Aberrant accumulations of neurofilaments containing phosphorylated NFM and NFH side-arms are a pathological feature of amyotrophic lateral sclerosis (ALS) and we also demonstrate that p38α and active forms of p38 family kinases are associated with these accumulations. This is the case for sporadic and familial forms of ALS and also in a transgenic mouse model of ALS caused by expression of mutant superoxide dismutase-1 (SOD1). Thus, p38 kinases may contribute to the aberrant phosphorylation of NFM and NFH side-arms in ALS.

Therapeutic Effects of Coenzyme Q10 in Neurodegenerative Diseases

Publisher Summary This chapter analyzes the therapeutic effects of coenzyme Q 10 (CoQ 10 ) in neurodegenerative diseases. There is increasing interest in the potential usefulness of CoQ 10 to treat both mitochondrial disorders as well as neurodegenerative diseases, such as Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS). CoQ 10 administration can increase brain concentrations in mature and older animals. It can also increase brain mitochondrial concentrations. There is substantial evidence that CoQ 10 can act in concert with alphatocopherol as an antioxidant within mitochondria. CoQ 10 administration has been demonstrated to be efficacious in experimental models of neurodegenerative diseases. It is neuroprotective against lesions produced by mitochondrial toxins including malonate, 3-nitropropionic acid and MPTP. CoQ 10 extends survival in a transgenic mouse model of ALS, and it extends survival and exerts significant neuroprotective effects in a transgenic mouse model of HD. CoQ 10 and idebenone appear to be promising for treatment of Friedriech's ataxia. Initial clinical trials in both HD and PD have shown beneficial effects. The initial results of utilizing CoQ 10 administration for treatment of neurodegenerative disease appear promising as a treatment to slow the inexorable progression of these disorders.

The crucial role of caspase-9 in the disease progression of a transgenic ALS mouse model.

Mutant copper/zinc superoxide dismutase (SOD1)-overexpressing transgenic mice, a mouse model for familial amyotrophic lateral sclerosis (ALS), provides an excellent resource for developing novel therapies for ALS. Several observations suggest that mitochondria-dependent apoptotic signaling, including caspase-9 activation, may play an important role in mutant SOD1-related neurodegeneration. To elucidate the role of caspase-9 in ALS, we examined the effects of an inhibitor of X chromosome-linked inhibitor of apoptosis (XIAP), a mammalian inhibitor of caspase-3, -7 and -9, and p35, a baculoviral broad caspase inhibitor that does not inhibit caspase-9. When expressed in spinal motor neurons of mutant SOD1 mice using transgenic techniques, XIAP attenuated disease progression without delaying onset. In contrast, p35 delayed onset without slowing disease progression. Moreover, caspase-9 was activated in spinal motor neurons of human ALS subjects. These data strongly suggest that caspase-9 plays a crucial role in disease progression of ALS and constitutes a promising therapeutic target.

Skeletal muscle properties in a transgenic mouse model for amyotrophic lateral sclerosis: effects of creatine treatment

The present study was undertaken to identify the metabolic and contractile characteristics of fast- and slow-twitch skeletal muscles in a transgenic mouse model of amyotrophic lateral sclerosis (ALS). In addition, we investigated the effects of oral creatine supplementation on muscle functional capacity in this model. Transgenic mice expressing a mutant (G93A) or wild type human SOD1 gene (WT) were supplemented with 2% creatine monohydrate from 60 to 120 days of age. Body weight, rotorod performance and grip strength were evaluated. In vitro contractility was evaluated on isolated m. soleus and m. extensor digitorum longus (EDL), and muscle metabolites were determined. Body weight, rotorod performance and grip strength were markedly decreased in G93A compared to WT mice, but were unaffected by creatine supplementation. Muscle ATP content decreased and glycogen content increased in G93A versus WT in both muscle types, but were unaffected by creatine supplementation. Muscle creatine content increased following creatine intake in G93A soleus. Twitch and tetanic contractions showed markedly slower contraction and relaxation times in G93A versus WT in both muscle types, with no positive effect of creatine supplementation. EDL but not soleus of G93A mice showed significant atrophy, which was partly abolished by creatine supplementation. It is concluded that overexpression of a mutant SOD1 transgene has profound effects on metabolic and contractile properties of both fast- and slow-twitch skeletal muscles. Furthermore, creatine intake does not exert a beneficial effect on muscle function in a transgenic mouse model of ALS.

Disruption of Glial Glutamate Transport by Reactive Oxygen Species Produced in Motor Neurons

Observations of elevated CSF glutamate in amyotrophic lateral sclerosis (ALS), together with findings that motor neurons are selectively vulnerable to glutamate receptor-mediated ("excitotoxic") injury, support an excitotoxic contribution to the motor neuron loss in the disease. However, the basis of the apparent loss of astrocytic glutamate transport capacity in affected areas of motor cortex and spinal cord, which probably underlies the extracellular glutamate elevations, is unexplained. Here, we find that glutamate induces far greater reactive oxygen species (ROS) generation in cultured motor neurons than in other spinal neurons. In addition, we found that the ROS seem to be able to leave the motor neurons and induce oxidation and disruption of glutamate uptake in neighboring astrocytes. Correspondingly, in a transgenic mouse model of ALS, protein oxidation was increased in regions immediately surrounding motor neurons. These results provide a mechanism that can account for the localized loss of glial glutamate transport seen in the disease. Furthermore, the observations lend support for a feedforward model involving reciprocal interactions between motor neurons and glia, which may prove useful in understanding ALS pathogenesis.

Iron porphyrin treatment extends survival in a transgenic animal model of amyotrophic lateral sclerosis.

Oxidative damage, produced by mutant Cu/Zn superoxide dismutase (SOD1), may play a role in the pathogenesis of amyotrophic lateral sclerosis (ALS), a devastating motor neuron degenerative disease. A novel approach to antioxidant therapy is the use of metalloporphyrins that catalytically scavenge a wide range of reactive oxygen and reactive nitrogen species. In this study, we examined the therapeutic potential of iron porphyrin (FeTCPP) in the G93A mutant SOD1 transgenic mouse model of ALS. We found that intraperitoneal injection of FeTCPP significantly improved motor function and extended survival in G93A mice. Similar results were seen with a second group of mice wherein treatment with FeTCPP was initiated at the onset of hindlimb weakness-roughly equivalent to the time at which treatment would begin in human patients. FeTCPP-treated mice also showed a significant reduction in levels of malondialdehyde (a marker of lipid peroxidation), in total content of protein carbonyls (a marker of protein oxidation), and increased neuronal survival in the spinal cord. These results therefore provide further evidence of oxidative damage in a mouse model of ALS, and suggest that FeTCPP could be beneficial for the treatment of ALS patients.

A therapeutic role for cyclooxygenase-2 inhibitors in a transgenic mouse model of amyotrophic lateral sclerosis.

Recent studies indicate that the proinflammatory enzyme cyclooxygenase (COX)-2, an enzyme involved in inflammatory cascades but also normal neuronal activities, is elevated in the brain and spinal cord of amyotrophic lateral sclerosis (ALS) patients and ALS mouse model systems. On the basis of this evidence, we explored the impact of COX-2 inhibition on the onset and progression of ALS-like disease in the G93A human superoxide dismutase (SOD)1 mouse model of ALS. We found that prophylactic administration of nimesulide, a preferential COX-2 inhibitor, in the feed resulted in a significant delay in the onset of ALS type motor impairment. This delay of ALS symptomatology temporally overlapped with the inhibition of prostaglandin E2 elevation in the spinal cord of SOD1-G93A transgenic mice relative to untreated SOD1-G93A controls. This study strongly supports a role for COX-2 in the pathophysiology of ALS and provides the first experimental evidence that prophylactic treatment with COX-2 inhibitors can significantly delay the onset of motor dysfunction in the SOD1-G93A transgenic mouse model of ALS.

Cyclooxygenase 2 inhibition protects motor neurons and prolongs survival in a transgenic mouse model of ALS.

The pathogenesis of cell death in amyotrophic lateral sclerosis (ALS) may involve glutamate-mediated excitotoxicity, oxidative damage, and apoptosis. We used a transgenic mouse model of ALS to determine the effect of inhibition of cyclooxygenase-2 in treating the disease. Cyclooxygenase-2, present in spinal neurons and astrocytes, catalyzes the synthesis of prostaglandin E2. Prostaglandin E2 stimulates glutamate release from astrocytes, whereas cyclooxygenase-2 also plays a key role in the production of proinflammatory cytokines, reactive oxygen species, and free radicals. Treatment with a selective cyclooxygenase-2 inhibitor, celecoxib, markedly inhibited production of prostaglandin E2 in the spinal cords of ALS mice. Celecoxib treatment significantly delayed the onset of weakness and weight loss and prolonged survival by 25%. Spinal cords of treated ALS mice showed significant preservation of spinal neurons and diminished astrogliosis and microglial activation. Our results suggest that cyclooxygenase-2 inhibition may benefit ALS patients.

Overexpression of HGF Retards Disease Progression and Prolongs Life Span in a Transgenic Mouse Model of ALS

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by a progressive loss of motoneurons and degeneration of motor axons. We show that overexpression of hepatocyte growth factor (HGF) in the nervous system attenuates motoneuron death and axonal degeneration and prolongs the life span of transgenic mice overexpressing mutated Cu²⁺/Zn²⁺superoxide dismutase 1. HGF prevented induction of caspase-1 and inducible nitric oxide synthase (iNOS) in motoneurons and retained the levels of the glial-specific glutamate transporter (excitatory amino acid transporter 2/glutamate transporter 1) in reactive astrocytes. We propose that HGF may be the first example of an endogenous growth factor that can alleviate the symptoms of ALS by direct neurotrophic activities on motoneurons and indirect activities on glial cells, presumably favoring a reduction in glutamatergic neurotoxicity.