Monitoring systemic oxidative stress in an animal model of amyotrophic lateral sclerosis

A mutant form of the ubiquitous copper/zinc superoxide dismutase (SOD1) protein has been found in some patients with amyotrophic lateral sclerosis (ALS). We monitored oxidative stress in an animal model of ALS, the SOD^G93A mouse, which develops a disease similar to ALS with an accelerated course. The aim of this work was to show that ALS damages several organs and tissues, from an oxidative stress point of view. We measured lipid and protein oxidative damage in different tissue homogenates of SOD^G93A mice. The biomarkers that we analyzed were malondialdehyde + 4-hydroxyalkenal (MDA + 4-HDA) and carbonyls, respectively. The spinal cord and brain of SOD^G93A mice showed increased lipid peroxidation after 100 or 130 days compared to age-matched littermate controls. The CNS was most affected, but lipid peroxidation was also detected in the skeletal muscle and liver on day 130. No changes were observed in protein carbonylation in the homogenates. Our results are consistent with a multisystem etiology of ALS and suggest that oxidative stress may play a primary role in ALS pathogenesis. Thus, oxidative stress represents a potential biomarker that might be useful in developing new therapeutic strategies for ALS.     

Glycoprotein nonmetastatic melanoma protein B ameliorates skeletal muscle lesions in a SOD1G93A mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive loss of motor neurons and subsequent muscular atrophy. The quality of life of patients with ALS is significantly improved by ameliorating muscular symptoms. We previously reported that glycoprotein nonmetastatic melanoma protein B (GPNMB; osteoactivin) might serve as a target for ALS therapy. In the present study, superoxide dismutase 1/glycine residue 93 changed to alanine (SOD1^G93A) transgenic mice were used as a model of ALS. Expression of the C‐terminal fragment of GPNMB was increased in the skeletal muscles of SOD1^G93A mice and patients with sporadic ALS. SOD1^G93A/GPNMB transgenic mice were generated to determine whether GPNMB expression ameliorates muscular symptoms. The weight and cross‐sectional area of the gastrocnemius muscle, number and cross‐sectional area of myofibers, and denervation of neuromuscular junctions were ameliorated in SOD1^G93A/GPNMB vs. SOD1^G93A mice. Furthermore, direct injection of a GPNMB expression plasmid into the gastrocnemius muscle of SOD1^G93A mice increased the numbers of myofibers and prevented myofiber atrophy. These findings suggest that GPNMB directly affects skeletal muscle and prevents muscular pathology in SOD1^G93A mice and may therefore serve as a target for therapy of ALS. © 2015 Wiley Periodicals, Inc.     

The mitochondrial permeability transition pore in motor neurons: Involvement in the pathobiology of ALS mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease of motor neurons (MNs) that causes paralysis. Some forms of ALS are inherited, caused by mutations in the superoxide dismutase-1 (SOD1) gene. The mechanisms of human mutant SOD1 (mSOD1) toxicity to MNs are unresolved. Mitochondria in MNs might be key sites for ALS pathogenesis, but cause–effect relationships between mSOD1 and mitochondriopathy need further study. We used transgenic mSOD1 mice to test the hypothesis that the mitochondrial permeability transition pore (mPTP) is involved in the MN degeneration of ALS. Components of the multi-protein mPTP are expressed highly in mouse MNs, including the voltage-dependent anion channel, adenine nucleotide translocator (ANT), and cyclophilin D (CyPD), and are present in mitochondria marked by manganese SOD. MNs in pre-symptomatic mSOD1-G93A mice form swollen megamitochondria with CyPD immunoreactivity. Early disease is associated with mitochondrial cristae remodeling and matrix vesiculation in ventral horn neuron dendrites. MN cell bodies accumulate mitochondria derived from the distal axons projecting to skeletal muscle. Incipient disease in spinal cord is associated with increased oxidative and nitrative stress, indicated by protein carbonyls and nitration of CyPD and ANT. Reducing the levels of CyPD by genetic ablation significantly delays disease onset and extends the lifespan of G93A-mSOD1 mice expressing high and low levels of mutant protein in a gender-dependent pattern. These results demonstrate that mitochondria have causal roles in the disease mechanisms in MNs in ALS mice. This work defines a new mitochondrial mechanism for MN degeneration in ALS.     

Activation of the Nrf2-ARE pathway in muscle and spinal cord during ALS-like pathology in mice expressing mutant SOD1

Oxidative stress plays a key role in the neuronal loss exhibited in amyotrophic lateral sclerosis (ALS), an event precipitating irreversible muscle atrophy. By crossing ALS mouse models (SOD(G93A) and SOD(H46RH48Q)) with an antioxidant response element (ARE) reporter mouse, we identified activation characteristics of the ARE system throughout the timecourse of motor neuron disease. Surprisingly, the earliest and most significant activation of this genetic sensor of oxidative stress occurred in the distal muscles of mutant SOD mice. The resultant data supports existing hypotheses that the muscle is somehow implicated during the initial pathology of these mice. Subsequently, Nrf2-ARE activation appears to progress in a retrograde fashion along the motor pathway. These data provide timely information concerning the contributions of the Nrf2-ARE pathway in ALS disease progression.     

MnSOD deficiency has a differential effect on disease progression in two different ALS mutant mouse models

Mitochondrial dysfunction and oxidative stress are thought to participate in the pathogenesis of amyotrophic lateral sclerosis (ALS). The purpose of this study was to determine the effect of reduced mitochondrial antioxidant defense on lifespan and disease progression in two mouse models of familial ALS (G93A and H46R/H48Q mutant lines) that represent pseudo-wildtype and metal-deficient ALS mutants, respectively. The metal-deficient H46R/H48Q mutant differs from the G93A mutant in that it cannot bind copper in the active site and thus lacks SOD activity. We crossed each of these mutant lines with mice deficient in the mitochondrial matrix antioxidant enzyme MnSOD (Sod2+/- mice). In both high (G93A1Gur) and low (G93ADL) copy G93A strains, MnSOD deficiency caused a decrease in lifespan that was associated with a reduced disease duration rather than earlier disease onset. In contrast, MnSOD deficiency had no effect on lifespan or disease parameters of H46R/H48Q mutant mice. MnSOD deficiency thus has a differential effect on disease progression in different mutant SOD1 ALS mouse models, suggesting that different ALS-causing mutations in SOD1 result in disease progression by at least proximally different mechanisms/pathways.     

Nuclear localization of human SOD1 and mutant SOD1-specific disruption of survival motor neuron protein complex in transgenic amyotrophic lateral sclerosis mice

Amyotrophic lateral sclerosis (ALS) is a fatal adult-onset neurodegenerative disease that causes degeneration of motor neurons and paralysis. Approximately 20% of familial ALS cases have been linked to mutations in the copper/zinc superoxide dismutase (SOD1) gene, but it is unclear how mutations in the protein result in motor neuron degeneration. Transgenic (tg) mice expressing mutated forms of human SOD1 (hSOD1) develop clinical and pathological features similar to those of ALS. We used tg mice expressing hSOD1-G93A, hSOD1-G37R, and hSOD1-wild-type to investigate a new subcellular pathology involving mutant hSOD1 protein prominently localizing to the nuclear compartment and disruption of the architecture of nuclear gems. We developed methods for extracting relatively pure cell nucleus fractions from mouse CNS tissues and demonstrate a low nuclear presence of endogenous SOD1 in mouse brain and spinal cord, but prominent nuclear accumulation of hSOD1-G93A, -G37R, and -wild-type in tg mice. The hSOD1 concentrated in the nuclei of spinal cord cells, particularly motor neurons, at a young age. The survival motor neuron protein (SMN) complex is disrupted in motor neuron nuclei before disease onset in hSOD1-G93A and -G37R mice; age-matched hSOD1-wild-type mice did not show SMN disruption despite a nuclear presence. Our data suggest new mechanisms involving hSOD1 accumulation in the cell nucleus and mutant hSOD1-specific perturbations in SMN localization with disruption of the nuclear SMN complex in ALS mice and suggest an overlap of pathogenic mechanisms with spinal muscular atrophy.     

Fas small interfering RNA reduces motoneuron death in amyotrophic lateral sclerosis mice

OBJECTIVE: Amyotrophic lateral sclerosis (ALS) is a progressive, fatal neurodegenerative disease characterized by selective motoneuron death. Understanding of the molecular mechanisms that trigger and regulate motoneuron degeneration could be relevant to ALS and other motoneuron disorders. This study investigates the role of Fas-linked motoneuron death in the pathogenesis of ALS. METHODS: We performed in vitro and in vivo small interfering RNA-mediated interference, by silencing the Fas receptor on motoneurons that carry the superoxide dismutase-1 (SOD1)-G93A mutation. RESULTS: We observed a significant reduction in Fas expression at messenger RNA (p < 0.001) and protein levels. Treated motoneurons demonstrated an increase in survival and a reduction in cytochrome c release from mitochondria. In vivo, continuous intrathecal administration of Fas small interfering RNA by an osmotic minipump improved motor function and survival in SOD1-G93A mice (mean increase, 18 days; p < 0.0001). Treated mice showed a significant reduction in Fas and Fas mediators p38 mitogen-activated protein kinase, neuronal nitric oxide synthase, and caspase-8. INTERPRETATION: Fas silencing interferes with motoneuron-specific downstream death pathways and results in increased motoneuron survival and amelioration of the SOD1-G93A phenotype, suggesting new possible strategies for molecular therapy of ALS.     

Heme Oxygenase in the Experimental ALS Mouse

Heme oxygenase-1 (HO-1) is a stress protein inducible in some cells by oxidative stress. The status of heme oxygenase was investigated in a transgenic mouse model of amyotrophic lateral sclerosis (ALS) since oxidative mechanisms are postulated in neuronal injury. Three ALS mice [(SOD1-G93A)1Gur] and three controls [(SOD-1)2Gur] were obtained from The Jackson Laboratory. Behavioral differences suggestive of neurodegeneration in ALS mice developed at 4–5 months of age. All mice were killed at 7–8 months of age. Tissue vacuolation, cell loss, and the presence of GFAP⁺cells were noted in the spinal cords of ALS mice. Spinal cord motor neurons in both control and ALS mice stained positive for heme oxygenase-2 (HO-2). While not precluding the presence of low levels of HO-1 neither immunohistochemical staining nor Western blot analysis provided evidence for significant HO-1 induction in degenerating spinal cord.     

小胶质细胞在SOD1-G93A转基因小鼠腰髓中的变化

目的观察小胶质细胞在SOD1-G93A转基因小鼠不同时期腰髓中的变化,探讨小胶质细胞活化与肌萎缩侧索硬化(ALS)疾病进展的关系。方法以国际公认的SOD1-G93A转基因小鼠,应用免疫组化、激光共聚焦显微镜及Westernblot方法 ,分别观察SOD1-G93A转基因小鼠症状前期、症状期、终末期及其同窝对照腰髓小胶质细胞形态数量及特异性标记物表达的变化情况。结果 SOD1-G93A转基因小鼠腰髓在症状前期(60天)已出现小胶质细胞数量增多及特异性标记物CD11b表达升高,随病程进展,症状期小胶质细胞增多、活化显著,终末期达高峰。结论随SOD1-G93A转基因小鼠病程进展小胶质细胞增生明显,小胶质细胞的活化可能参与ALS运动神经元损伤。     

DJ-1 Changes in G93A-SOD1 Transgenic Mice: Implications for Oxidative Stress in ALS

Amyotrophic lateral sclerosis (ALS) is a progressive, lethal, neurodegenerative disorder. The causes of ALS are still obscure. Accumulating evidence supports the hypothesis that oxidative stress and mitochondrial dysfunction can be implicated in ALS pathogenesis. DJ-1 plays an important role in the oxidative stress response. The aim of this study was to discover whether there are changes in DJ-1 expression or in DJ-1-oxidized isoforms in an animal model of ALS. We used mutant SOD1^G93A transgenic mice, a commonly used animal model for ALS. Upregulation of DJ-1 mRNA and protein levels were identified in the brains and spinal cords of SOD1^G93A transgenic mice as compared to wild-type controls, evident from an early disease stage. Furthermore, an increase in DJ-1 acidic isoforms was detected, implying that there are more oxidized forms of DJ-1 in the CNS of SOD1^G93A mice. This is the first report of possible involvement of DJ-1 in ALS. Since DJ-1 has a protective role against oxidative stress, it may suggest a possible therapeutic target in ALS.     

Therapeutic immunization with a glatiramer acetate derivative does not alter survival in G93A and G37R SOD1 mouse models of familial ALS

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease. The cause of motor neuron degeneration remains largely unknown, and there is no potent treatment. Overexpression of various human mutant superoxide dismutase-1 (SOD1) genes in mice and rats recapitulates some of the clinical and pathological characteristics of sporadic and familial ALS. Glatiramer acetate (GA) is an approved drug for the treatment of multiple sclerosis and neuroprotective properties in some neurodegenerative conditions. A recent report suggested that GA immunization could delay disease progression in some, but not all, G93A SOD1 transgenic mouse models of amyotrophic lateral sclerosis (ALS). Moreover, it has been theorized that derivatives of GA could enhance immunogenicity and positively affect disease outcomes. The purpose of our study was to assess the neuroprotective efficacy of TV-5010, a high molecular weight GA, in three different SOD1 mutant mouse models. We used large numbers of two SOD1 transgenic mouse strains overexpressing the G93A mutation, B6SJL-TgN[SOD1-G93A]1Gur and B6.Cg-Tg(SOD1-G93A)1Gur/J, and the SOD1 mutant mouse overexpressing G37R (line 29). Regardless of the frequency of injections and the dose, treatment with TV-5010 was ineffective at altering either disease onset or survival in both SOD1 G93A mutants used and in the SOD1 G37R transgenic mice; in multiple studies, disease was accelerated. These studies suggest that, at a range of dosing regimens and carrier used, TV-5010 immunization was ineffective in delaying disease in multiple preclinical therapeutic models for ALS. The biological response in animals, and ultimate clinical translation, will ultimately be dependent on careful and appropriate dose, route and carrier paradigms.     

Absence of SOD1 leads to oxidative stress in peripheral nerve and causes a progressive distal motor axonopathy

Oxidative stress is commonly implicated in the pathogenesis of motor neuron disease. However, the cause and effect relationship between oxidative stress and motor neuron degeneration is poorly defined. We recently identified denervation at the neuromuscular junction in mice lacking the antioxidant enzyme, Cu,Zn-superoxide dismutase (SOD1) (Fischer et al., 2011). These mice show a phenotype of progressive muscle atrophy and weakness in the setting of chronic oxidative stress. Here, we investigated further the extent of motor neuron pathology in this model, and the relationship between motor pathology and oxidative stress. We report preferential denervation of fast-twitch muscles beginning between 1 and 4 months of age, with relative sparing of slow-twitch muscle. Motor axon terminals in affected muscles show widespread sprouting and formation of large axonal swellings. We confirmed, as was previously reported, that spinal motor neurons and motor and sensory nerve roots in these mice are preserved, even out to 18 months of age. We also found preservation of distal sensory fibers in the epidermis, illustrating the specificity of pathology in this model for distal motor axons. Using HPLC measurement of the glutathione redox potential, we quantified oxidative stress in peripheral nerve and muscle at the onset of denervation. SOD1 knockout tibial nerve, but not gastrocnemius muscle, showed significant oxidation of the glutathione pool, suggesting that axonal degeneration is a consequence of impaired redox homeostasis in peripheral nerve. We conclude that the SOD1 knockout mouse is a model of oxidative stress-mediated motor axonopathy. Pathology in this model primarily affects motor axon terminals at the neuromuscular junction, demonstrating the vulnerability of this synapse to oxidative injury.     

Enhanced oxidative stress and the treatment by edaravone in mice model of amyotrophic lateral sclerosis

Oxidative stress is associated with the degeneration of both motor neurons and skeletal muscles in amyotrophic lateral sclerosis (ALS). A free radical scavenger edaravone has been proven as a therapeutic drug for ALS patients, but the neuroprotective mechanism for the oxidative stress of ALS has not been fully investigated. In this study, we investigated oxidative stress in ALS model mice bearing both oxidative stress sensor nuclear erythroid 2-related factor 2 (Nrf2) and G93A-human Cu/Zn superoxide dismutase (Nrf2/G93A) treated by edaravone. In vivo Nrf2 imaging analysis showed the accelerated oxidative stress both in spinal motor neurons and lower limb muscles of Nrf2/G93A mice according to disease progression in addition to the enhancement of serum oxidative stress marker dROMS. These were significantly alleviated by edaravone treatment accompanied by clinical improvements (rotarod test). The present study suggests that in vivo optical imaging of Nrf2 is useful for detecting oxidative stress in ALS, and edaravone alleviates the degeneration of both motor neurons and muscles related to oxidative stress in ALS patients.     

Relationship of microglial and astrocytic activation to disease onset and progression in a transgenic model of familial ALS

Transgenic mice that highly over-express a mutated human CuZn superoxide dismutase (SOD1) gene [gly⁹³→ala; TgN(SOD1-G93A)G1H line] found in some patients with familial ALS (FALS) have been shown to develop motor neuron disease that is characterized by motor neuron loss in the lumbar and cervical spinal regions and a progressive loss of motor activity. The mutant Cu,Zn SOD exhibits essentially normal SOD activity but also generates toxic oxygen radicals as a result of an enhancement of a normally minor peroxidase reaction. Consequently, lipid and protein oxidative damage to the spinal motor neurons occurs and is associated with disease onset and progression. In the present study, we investigated the time course of microglial (major histocompatibility-II antigen immunoreactivity) and astrocytic (glial fibrillary acidic protein immunoreactivity) activation in relation to the course of motor neuron disease in the TgN(SOD1-G93A)G1H FALS mice. Four ages were investigated: 30 days (pre-motor neuron pathology and clinical disease); 60 days (after initiation of pathology, but pre-disease); 100 days (approximately 50% loss of motor neurons and function); and 120 days (near complete hindlimb paralysis). Compared to non-transgenic littermates, the TgN(SOD1-G93A)G1H mice showed significantly increased numbers of activated astrocytes (P < 0.01) at 100 days of age in both the cervical and lumbar spinal cord regions. However, at 120 days of age, the activation lost statistical significance. In contrast, microglial activation was significantly increased several-fold at both 100 and 120 days. We hypothesize that astrocytic activation may exert a trophic influence on the motor neurons that is insufficiently maintained late in the course of the disease. On the other hand, the sustained, intense microglial activation may conceivably contribute to the oxidative stress and damage involved in the disease process. If true, then agents which inhibit microglia may help to limit disease progression. GLIA 23:249–256, 1998. © 1998 Wiley-Liss, Inc.     

人骨髓间质干细胞经心脏移植治疗超氧化物歧化酶1-G93A转基因鼠的疗效

目的 研究经心脏移植入骨髓间质干细胞(hMSCs)对肌萎缩侧索硬化(ALS)模型鼠发病时间、生存期和病理的影响.方法 体外培养扩增hMSCs,流式细胞仪鉴定其性质及纯度.将3×10~6个第5代hMSCs经心脏移植入预放疗的8周龄超氧化物歧化酶1(SOD1)-G93A转基因鼠,用Weyd4分法评定移植鼠和未治疗鼠的生存期、发病时间,采取尼氏染色计数脊髓前角运动神经元,通过免疫荧光检测人特异性核抗原验证hMSCs在受体鼠中枢神经系统中的植入.结果 生存分析显示,经心脏移植hMSCs的ALS模型鼠平均发病时间为(172.85±3.82)d,比未治疗组[(156.56±3.60)d]延迟16 d,差异有统计学意义(x~2=10.888,P=0.001);hMSCs经心脏移植组平均生存期为(202.19±4.09)d,比未治疗组[(188.32±3.51)d]延长14 d,差异有统计学意义(x~2=3.917,P=0.04).尼氏染色显示在20周时移植鼠脊髓前角大运动神经元计数多于未治疗鼠;终末期hMSCs移植鼠中,在脑和脊髓前角病变区可检测到人特异性核抗原.结论 hMSCs可经心脏移植,在ALS模型鼠中可长期植入,延长生存期,延缓脊髓前角运动神经元的丢失.     

Analysis of neuromuscular junctions and effects of anabolic steroid administration in the SOD1G93A mouse model of ALS

Several lines of evidence indicate that neuromuscular junction (NMJ) destruction and disassembly is an early phenomenon in amyotrophic lateral sclerosis (ALS). Here we analyzed by confocal and electron microscopy the NMJ structure in the diaphragm of SOD1G93A mice at symptom onset. In these mice, which provide a model for familial ALS, diaphragm denervation (~50%) as well as gastrocnemius denervation (~40%) was found. In addition, the size of the synaptic vesicle pool was reduced and alterations of mitochondria were observed in approximately 40% of the remaining presynaptic terminals. Chronic treatment of SOD1G93A mice with the anabolic steroid nandrolone during the presymptomatic stage preserved the diaphragm muscle mass and features indicative of synaptic activity. These features were represented by the number of vesicles docked within 200nm from the presynaptic membrane and area of acetylcholine receptor clusters. Structural preservation of mitochondria was documented in presynaptic terminals. However, innervation of diaphragm muscle fibers was only slightly increased in nandrolone-treated SOD1-mutant mice. Altogether the results point out and define fine structural alterations of diaphragm NMJs in the murine model of familial ALS at symptom onset, and indicate that nandrolone may prevent or delay structural alterations in NMJ mitochondria and stimulate presynaptic activity but does not prevent muscle denervation during the disease.     

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.     

Absence of p53: no effect in a transgenic mouse model of familial amyotrophic lateral sclerosis

Familial amyotrophic lateral sclerosis (ALS) has been linked in some families to dominantly inherited mutations in the gene encoding copper-zinc superoxide dismutase 1 (Cu-Zn SOD1). Transgenic mice expressing a mutant human Cu-Zn SOD1 (G93A) develop a dominantly inherited adult-onset paralytic disorder that replicates many of the clinical and pathological features of familial ALS. Increased p53 immunoreactivity has been reported in the motor cortex and spinal ventral horns of postmortem tissue from ALS patients. The nuclear phosphoprotein p53 is an important regulator of cellular proliferation, and increasing evidence supports the role of p53 in regulating cellular apoptosis. To assess the role of p53-mediated apoptosis in amyotrophic lateral sclerosis, mice deficient in both p53 alleles (p53-/-) were crossed with transgenic mice expressing the G93A mutant (G93A+), creating novel transgenic knockout mice. The animals (p53 +/+G93A+, p53+/-G93A+, p53-/-G93A+) were examined at regular intervals for cage activity, upper and lower extremity strength, and mortality. At 120 days from birth mice from each genotype were sacrificed, and L2-L3 anterior horn motor neurons were counted. There was no significant difference in time to onset of behavioral decline, mortality, or motor neuron degeneration between the different genotypes. Despite evidence that p53 plays an important role after acute neuronal injury, the current study suggests that p53 is not significantly involved in cell death in the G93A+ transgenic mouse model of familial ALS.