Amyloid precursor protein (APP) contributes to pathology in the SOD1G93A mouse model of amyotrophic lateral sclerosis

In amyotrophic lateral sclerosis (ALS), the progressive loss of motor neurons is accompanied by extensive muscle denervation, resulting in paralysis and ultimately death. Upregulation of amyloid beta (A4) precursor protein (APP) in muscle fibres coincides with symptom onset in both sporadic ALS patients and the SOD1(G93A) mouse model of familial ALS. We have further characterized this response in SOD1(G93A) mice and also revealed elevated levels of β-amyloid (Aβ) peptides in the SOD1(G93A) spinal cord, which were predominantly localized within motor neurons and their surrounding glial cells. We therefore examined the effect of genetic ablation of APP on disease progression in SOD1(G93A) mice, which significantly improved multiple disease parameters, including innervation, motor function, muscle contractile characteristics, motor unit and motor neuron survival. These results therefore strongly suggest that APP actively contributes to SOD1(G93A)-mediated pathology. Together with observations from ALS cases, this study indicates that APP may contribute to human ALS pathology.     

The effect of peripheral nerve injury on disease progression in the SOD1(G93A) mouse model of amyotrophic lateral sclerosis

Around 20% of familial cases of amyotrophic lateral sclerosis have been shown to carry mutations in Cu/Zn superoxide dismutase 1 (Cu/Zn SOD1). Transgenic mice over-expressing human mutant SOD1 genes have been developed and in this study we examined the effect of nerve injury on disease progression in these mice. Firstly, disease progression in uninjured mice was characterised using physiological methods. Muscle force, contractile characteristics and motor unit survival was established at 90 days, an early symptomatic stage and also at the end-stage of the disease, at 130 days. In addition, muscle histochemistry was examined and the extent of motoneuron survival established morphologically. By 90 days of age, there is a significant reduction in muscle force, and nearly 40% of motoneurons within the sciatic motor pool have already died. By 130 days, the muscles are significantly weaker, and there is a dramatic change in the phenotype of extensor digitorum longus (EDL), which changes from a fast fatigable muscle, to a fatigue resistant muscle with a high oxidative capacity. By this stage of the disease, only 40% of motor units in EDL survive, with only 29% of motoneurons surviving within the sciatic motor pool. Following injury to the sciatic nerve in SOD1^(G93A) mice, there is an acceleration in disease progression so that 90 day old mice show deficits that are only seen at the end stage in uninjured SOD1^(G93A) mice. It is therefore possible that mutant SOD1 toxicity increases the vulnerability of motoneurons and muscles to stressful stimuli such as nerve injury.     

P2X7 activation enhances skeletal muscle metabolism and regeneration in SOD1G93A mouse model of amyotrophic lateral sclerosis

Muscle weakness plays an important role in neuromuscular disorders comprising amyotrophic lateral sclerosis (ALS). However, it is not established whether muscle denervation originates from the motor neurons, the muscles or more likely both. Previous studies have shown that the expression of the SOD1G93A mutation in skeletal muscles causes denervation of the neuromuscular junctions, inability to regenerate and consequent atrophy, all clear symptoms of ALS. In this work, we used SOD1G93A mice, a model that best mimics some pathological features of both familial and sporadic ALS, and we investigated some biological effects induced by the activation of the P2X7 receptor in the skeletal muscles. The P2X7, belonging to the ionotropic family of purinergic receptors for extracellular ATP, is abundantly expressed in the healthy skeletal muscles, where it controls cell duplication, differentiation, regeneration or death. In particular, we evaluated whether an in vivo treatment in SOD1G93A mice with the P2X7 specific agonist 2′(3′)‐O‐(4‐Benzoylbenzoyl) adenosine5′‐triphosphate (BzATP) just before the onset of a pathological neuromuscular phenotype could exert beneficial effects in the skeletal muscles. Our findings indicate that stimulation of P2X7 improves the innervation and metabolism of myofibers, moreover elicits the proliferation/differentiation of satellite cells, thus preventing the denervation atrophy of skeletal muscles in SOD1G93A mice. Overall, this study suggests that a P2X7‐targeted and site‐specific modulation might be a strategy to interfere with the complex multifactorial and multisystem nature of ALS.     

Reduced protein O-glycosylation in the nervous system of the mutant SOD1 transgenic mouse model of amyotrophic lateral sclerosis

In the neurodegenerative disease amyotrophic lateral sclerosis (ALS), a number of proteins have been found to be hyperphosphorylated, including neurofilament proteins (NFs). In addition to protein phosphorylation, another important post-translational modification is O-glycosylation with β-N-acetylglucosamine residues (O-GlcNAc) and it has been found that O-GlcNAc can modify proteins competitively with protein phosphorylation, so that increased O-GlcNAc can reduce phosphorylation at specific sites. We evaluated a transgenic mouse model of ALS that overexpresses mutant superoxide dismutase (mSOD) and found that O-GlcNAc immunoreactivity levels are decreased in spinal cord tissue from mSOD mice, compared to controls. This reduction in O-GlcNAc levels is prominent in the motor neurons of spinal cord. We find that inhibition of O-GlcNAcase (OGA), the enzyme catalyzing removal of O-GlcNAc, using the inhibitor NButGT for 3 days, resulted in increased O-GlcNAc levels in spinal cord, both in mSOD and control mice. Furthermore, NButGT increased levels of O-GlcNAc modified NF-medium in spinal cords of control mice, but not in mSOD mice. These observations suggest that the neurodegeneration found in mSOD mice is associated with a reduction of O-GlcNAc levels in neurons, including motor neurons.     

MRI detects early hindlimb muscle atrophy in Gly93Ala superoxide dismutase-1 (G93A SOD1) transgenic mice, an animal model of familial amyotrophic lateral sclerosis

MRI has been used to measure hindlimb muscle volume in female and male transgenic mice overexpressing the Gly93Ala (G93A) mutant human superoxide dismutase 1 (SOD1), a widely used model of familial amyotrophic lateral sclerosis (FALS), over the first 4 months of life. Significant decreases in the hindlimb muscle volume of the female G93A SOD1 mice were evident from 11 weeks of age, before other overt pathology appeared. By 15 weeks volume had decreased by 37% compared with 7 weeks, from 0.84+/-0.04 cm(3) (mean+/-standard deviation, n = 6) to 0.54+/-0.07 cm(3), (p < 0.05), despite an increase in body weight of ca. 12% (from 16.2 +/- 1.4 to 18.1 +/- 0.7 g). Female wild-type volume increased by ca. 30% whilst the body weight increased by 15%. Muscle wasteage was less (0.82+/-0.1 to 0.65+/-0.02 cm(3), p < 0.05, n = 6) in male G93A SOD1 mice between 8 and 16 weeks of age, against a body weight increase trend from 20.7 +/- 0.4 to 21.6 +/- 0.5 g, (p > 0.05). Wild-type male muscle volume did not change significantly over this period, with an increase in body weight of 20%. Longitudinal MRI hindlimb muscle volume measurements may provide a straightforward, rapid, non-invasive and sensitive, way of monitoring outcome of experimental ALS treatments.     

Pyruvate slows disease progression in a G93A SOD1 mutant transgenic mouse model

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease caused by selective motor neuron death, and currently no effective treatment is available for ALS. In this study, we investigated the neuroprotective effects of pyruvate, which acts as an anti-oxidant and as an energy source. We treated G93A SOD1 transgenic mice with pyruvate (from 70 days of age, i.p., at 1000 mg/kg/week), and found that it prolonged average lifespan by 12.3 days (10.5%), slowed disease progression, and improved motor performance, but did not delay disease onset. Pyruvate treatment was also associated with reduced nitrotyrosine immunoreactivity, gliosis, and increased Bcl-2 expression in the spinal cords of G93A SOD1 transgenic mice. These results suggest that pyruvate treatment may be a potential therapeutic strategy in ALS.     

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.     

Androgens affect muscle,motor neuron,and survival in a mouse model of SOD1-related amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by selective loss of upper and lower motor neurons and skeletal muscle atrophy. Epidemiologic and experimental evidence suggest the involvement of androgens in ALS pathogenesis, but the mechanism through which androgens modify the ALS phenotype is unknown. Here, we show that androgen ablation by surgical castration extends survival and disease duration of a transgenic mouse model of ALS expressing mutant human SOD1 (hSOD1-G93A). Furthermore, long-term treatment of orchiectomized hSOD1-G93A mice with nandrolone decanoate (ND), an anabolic androgenic steroid, worsened disease manifestations. ND treatment induced muscle fiber hypertrophy but caused motor neuron death. ND negatively affected survival, thereby dissociating skeletal muscle pathology from life span in this ALS mouse model. Interestingly, orchiectomy decreased androgen receptor levels in the spinal cord and muscle, whereas ND treatment had the opposite effect. Notably, stimulation with ND promoted the recruitment of endogenous androgen receptor into biochemical complexes that were insoluble in sodium dodecyl sulfate, a finding consistent with protein aggregation. Overall, our results shed light on the role of androgens as modifiers of ALS pathogenesis via dysregulation of androgen receptor homeostasis.     

人骨髓间质干细胞治疗肌萎缩侧索硬化症模型小鼠的行为学和病理学研究

目的:研究静脉移植人骨髓间质干细胞对肌萎缩侧索硬化症(ALS)模型小鼠生存期和病理变化的影响。方法:体外培养扩增人骨髓间质干细胞(hMSCs),流式细胞仪鉴定hMSCs的性质及纯度,微量尾静脉血提取模型小鼠DNA,PCR扩增鉴定肌萎缩侧索硬化症模型小鼠(SOD1-G93A阳性小鼠)。将3×106个第5代hM-SCs尾静脉移植入预放疗8周的SOD1-G93A阳性小鼠,用Weyd4分法进行评定移植小鼠和未治疗小鼠的生存期、发病时间,尼氏染色计数脊髓前角运动神经元,组织DNA提取、PCR检测人特异性基因β-globin基因来验证hMSCs在受体小鼠中的植入。结果:生存分析显示尾静脉移植hMSCs的ALS模型小鼠生存期比未治疗小鼠延长18d,延缓发病14d;尼氏染色显示在16周、20周移植小鼠脊髓前角大运动神经元计数多于未治疗小鼠;终末期hMSCs移植小鼠中,在中枢神经系统可检测到人特异性该基因。结论:hMSCs可经过尾静脉移植在ALS小鼠中长期植入,延长生存期,减少脊髓前角运动神经元的丢失,有一定的治疗作用。     

Calcium-permeable AMPA receptors promote misfolding of mutant SOD1 protein and development of amyotrophic lateral sclerosis in a transgenic mouse model

Mutant Cu/Zn-superoxide dismutase (SOD1) protein aggregation has been suggested as responsible for amyotrophic lateral sclerosis (ALS), although the operative mediating factors are as yet unestablished. To evaluate the contribution of motoneuronal Ca2+-permeable (GluR2 subunit-lacking) alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-type glutamate receptors to SOD1-related motoneuronal death, we generated chat-GluR2 transgenic mice with significantly reduced Ca2+-permeability of these receptors in spinal motoneurons. Crossbreeding of the hSOD1G93A transgenic mouse model of ALS with chat-GluR2 mice led to marked delay of disease onset (19.5%), mortality (14.3%) and the pathological hallmarks such as release of cytochrome c from mitochondria, induction of cox2 and astrogliosis. Subcellular fractionation analysis revealed that unusual SOD1 species first accumulated in two fractions dense with neurofilaments/glial fibrillary acidic protein/nuclei and mitochondria long time before disease onset, and then concentrated into the former fraction by disease onset. All these processes for unusual SOD1 accumulation were considerably delayed by GluR2 overexpression. Ca2+-influx through atypical motoneuronal AMPA receptors thus promotes a misfolding of mutant SOD1 protein and eventual death of these neurons.     

On the relation of oxidative stress to neuroinflammation: lessons learned from the G93A-SOD1 mouse model of amyotrophic lateral sclerosis

The central nervous system (CNS) presents both challenges and opportunities to researchers of redox biochemistry. The CNS is sensitive to oxidative damage during aging or disease; excellent transgenic models of specific neurodegenerative diseases have been created that reproduce oxidative stress components of the corresponding human disorder. Mouse models of familial amyotrophic lateral sclerosis (ALS) based on overexpressed mutant human Cu, Zn-superoxide dismutase (SOD1) are cases in point. These animals experience predictably staged, age-dependent motor neuron degeneration with profound cellular and biochemical damage to nerve fibers and spinal cord tissue. Severe protein and lipid oxidation occurs in these animals, apparently as an indirect consequence of protein aggregation or cytopathic protein-protein interactions, as opposed to aberrant redox catalysis by the mutant enzyme. Recent studies of G93A-SOD1 mice and rats suggest that oxidative damage is part of an unmitigated neuroinflammatory reaction, possibly arising in combination from mitochondrial dysfunction plus pathophysiologic activation of both astrocytes and microglia. Lesions to redox signal-transduction pathways in mutant SOD1+ glial cells may stimulate broad-spectrum upregulation of proinflammatory genes, including arachidonic acid-metabolizing enzymes [e.g., cyclooxygenase-II (COX-II) and 5-lipoxygenase (5LOX)]; nitric oxide synthase (NOS) isoforms; cytokines (particularly tumor necrosis factor alpha, TNF-alpha); chemokines; and immunoglobulin Fc receptors (FcgammaRs). The integration of these processes creates a paracrine milieu inconsistent with healthy neural function. This review summarizes what has been learned to date from studies of mutant SOD1 transgenic animals and demonstrates that the G93A-SOD1 mouse in particular is a robust laboratory for the study of neuroinflammation and redox biochemistry.     

SOD1 G93D sporadic amyotrophic lateral sclerosis (SALS) patient with rapid progression and concomitant novel ANG variant

SOD1 G93D mutation has been described in amyotrophic lateral sclerosis (ALS) patients with slowly progressive disease. We describe an Italian patient affected by sporadic ALS with the SOD1 G93D mutation that disclosed an unusual rapid progression with death occurring after 30 months from the symptom onset. Considering the atypical clinical course further genes associated with ALS or known to be causative were studied including ANG, PGRN, TARDBP, FUS, VCP, CHRNA3, CHRNA4, and CHRNB4. A novel heterozygous ANG missense variant (c.433 C>T, p.R145C) was identified which is neither reported in controls nor in 1000 genomes and single nucleotide polymorphism (SNP) databases. This report confirms that clinical course of SOD1-related ALS may be modulated by other causative or associated genes, including ANG and suggests that extensive screening of ALS-associated genes in patients with an already identified mutation may be helpful for better knowledge of genetic architecture of ALS.     

Neuromuscular accumulation of mutant superoxide dismutase 1 aggregates in a transgenic mouse model of familial amyotrophic lateral sclerosis

Superoxide dismutase 1 (SOD1) aggregates are a histological and biochemical correlate of disease progression in neural tissues from mutant SOD1-linked forms of familial amyotrophic lateral sclerosis (FALS). In the present study, we assayed the monomeric and high molecular weight mutant SOD1 content of nervous, muscle and visceral tissues from transgenic SOD1(G93A) mice using immunoblotting and zymograms. A progressive age-dependent increase in mutant SOD1 level, aggregation and stabilisation by cross-species heterodimers was determined in lumbar spinal cord, sciatic nerve and gastrocnemius muscle. Such biochemical abnormalities were not present in cervical spinal cord, brainstem and diaphragm muscle, nor common to endogenous mouse SOD1. Mutant dismutase activity in general did not increase correspondingly with accumulating protein at later ages. These results suggest that peripheral targets such as hindlimb skeletal muscle and nerve accumulate mutant SOD1 aggregates and may therefore be susceptible to mutant SOD1-mediated toxicity, in addition to lower and upper motor neurons of the central nervous system in transgenic FALS mice.     

Notch1在肌萎缩侧索硬化症转基因鼠动物模型和细胞模型中的表达变化

目的:观察Notch1在肌萎缩侧索硬化症(ALS)转基因鼠动物模型和细胞模型中的表达情况。方法:应用免疫荧光、免疫印迹、RT-PCR,检测Notch1在95、108、122 d ALS转基因鼠脊髓中的表达变化;检测转染pEGFP-wt-SOD1和pEGFPG93A-SOD1的NSC34细胞模型中Notch1的表达变化。结果:Notch1可与β-tubulinⅢ共表达,与GFAP无明显共表达。较同窝野生型鼠,Notch1于蛋白水平和mRNA水平上的表达在95 d ALS转基因鼠脊髓中无明显变化,在108 d和122 d ALS转基因鼠脊髓中明显升高;与转染pEGFP-wt-SOD的NSC34细胞相比,转染pEGFP-G93A-SOD1的NSC34细胞中Notch1蛋白和mRNA表达增多。结论:Notch1在ALS转基因鼠动物模型和细胞模型中表达增多,提示Notch1信号通路可能与ALS相关。     

Proportional neuronal loss between the primary motor and sensory cortex in amyotrophic lateral sclerosis

The number of neurons in the primary motor cortex (MI) and the primary somatosensory cortex (SI) were estimated in the same locations of brains from sporadic amyotrophic lateral sclerosis (ALS) cases and controls. The number of MI and SI neurons and Betz cells were significantly decreased in the ALS cases as compared to the controls. The number of neurons in MI and SI was independent of age at death or duration of disease. Moreover, the number of neurons in MI and SI was significantly correlated, suggesting that the neurons in both sites might be interdependent and might decrease proportionally.     

Size-dependent dendritic maladaptations of hypoglossal motor neurons in SOD1G93A mice

The total motor neuron (MN) somato-dendritic surface area is correlated with motor unit type. MNs with smaller surface areas innervate slow (S) and fast fatigue-resistant (FR) motor units, while MNs with larger surface areas innervate fast fatigue-intermediate (FInt) and fast fatigable (FF) motor units. Differences in MN surface area (equivalent to membrane capacitance) underpin the intrinsic excitability of MNs and are consistent with the orderly recruitment of motor units (S > FR > FInt > FF) via the Size Principle. In amyotrophic lateral sclerosis (ALS), large MNs controlling FInt and FF motor units exhibit earlier denervation and death, compared to smaller and more resilient MNs of type S and FR motor units that are spared until late in ALS. Abnormal dendritic morphologies in MNs precede neuronal death in human ALS and in rodent models. We employed Golgi-Cox methods to investigate somal size-dependent changes in the dendritic morphology of hypoglossal MNs in wildtype and SOD1^G93A mice (a model of ALS), at postnatal (P) day ~30 (pre-symptomatic), ~P60 (onset), and ~P120 (mid-disease) stages. In wildtype hypoglossal MNs, increased MN somal size correlated with increased dendritic length and spines in a linear fashion. By contrast, in SOD1^G93A mice, significant deviations from this linear correlation were restricted to the larger vulnerable MNs at pre-symptomatic (maladaptive) and mid-disease (degenerative) stages. These findings are consistent with excitability changes observed in ALS patients and in rodent models. Our results suggest that intrinsic or synaptic increases in MN excitability are likely to contribute to ALS pathogenesis, not compensate for it.     

一个肌萎缩侧索硬化家系的SOD1基因突变

肌萎缩侧索硬化 (amyotrophic lateral sclerosis,ALS)是一种以脑和脊髓中大的运动神经元变性为特征的神经系统变性疾病。 5 %～ 10 %的患者有家族性。临床表现为缓慢起病 ,进行性发展 ,逐渐出现四肢肌肉的无力、萎缩 ,伴锥体束征等。临床治疗非常困难。目前已肯定编码铜、锌超氧化物歧化酶 (Cu/ Zn superoxidedismutase,Cu/ Zn- SOD)的 SOD1基因突变可引起部分家族性 ALS的发病[1] 。我们对重庆地区一个具有特殊临床表型的 ALS家系进行了 SOD1基因检测 ,结果发现部分患者第 2和第 5外显子有明显异常。1　对象与方法1.1　对象　受…