Expression of the copper-zinc superoxide dismutase gene in amyotrophic lateral sclerosis

The demonstration of a genetic linkage between the copper-zinc superoxide dismutase (SOD1) gene and familial amyotrophic lateral sclerosis has aroused interest in the role of SOD1 in motoneuronal death. We investigated the expression of the human SOD1 gene at a cellular level in the motoneurons of patints with sporadic amytrophic lateral sclerosis, patients with familial amyotrophic lateral sclerosis, and normal control subjects, using a quantitative insitu hybridization technique. There were no significant differences between the amountf os SOD1 messenger RNA observed in patints wtih sporadic disease, patients with familial disease, and normal control subjects. However, many of the atrophic motoneurons from patients with sporadic or familial disease had significantly lower levls of SOD1 messenger RNA, compared to morphologically intact motoneurons. Moreover, motoneurons in the normal spinal ventral horn and precentral motor cortex exhibited significantly higher levels of SOD1 messenger RNA than did other neurons. Our study indicated that vulnerable neurons in amyotrophic lateral sclerosis exhibit high levels of SOD1 messenger RNA, suggesting a close relatioship between the SOD1 gene and the pathogenesisof amyotrophic lateral sclerosis.     

Promise of Nucleic Acid Therapeutics for Amyotrophic Lateral Sclerosis

Nucleic acid therapeutics have been attracting attention as novel drug discovery modalities for intractable diseases, including amyotrophic lateral sclerosis. This review provides an overview of the current status and prospects of antisense oligonucleotide treatment for amyotrophic lateral sclerosis. Recently, the results of a phase I/II study using the antisense oligonucleotides Tofersen to treat familial amyotrophic lateral sclerosis with superoxide dismutase 1 mutation have been reported. Intrathecal Tofersen administration resulted in a 36% reduction in superoxide dismutase 1 level in the cerebrospinal fluid. Another report described 2 patients with mutant superoxide dismutase 1 treated with an adeno-associated virus encoding a microRNA targeting superoxide dismutase 1. The first patient, who possessed the fast progressive mutant A5V, received a single intrathecal infusion. Although the patient died of respiratory arrest 16 months after treatment, autopsy findings showed a reduction of >90% in superoxide dismutase 1 level in the spinal cord. Clinical trials on antisense oligonucleotide therapies targeting other major amyotrophic lateral sclerosis-causative genes, fused in sarcoma and chromosome 9 open reading frame 72, are ongoing. To attenuate the pathology of TDP-43, strategies targeting regulators of TDP-43 (ataxin 2) and proteins downstream of TDP-43 (stathmin 2) by antisense oligonucleotides are being developed. The advent of nucleic acid therapeutics has enabled to specifically attack the molecules in the amyotrophic lateral sclerosis pathological cascade, expanding the options for therapeutic targets. ANN NEUROL 2022;91:13–20     

Sequence of the superoxide dismutase 1 (SOD 1) gene in familial Parkinson''s disease.

Mutations in the superoxide dismutase 1 (SOD1) gene have been detected in affected members of some families with familial amyotrophic lateral sclerosis. To evaluate the possibility of a shared genetic defect in amyotrophic lateral sclerosis and Parkinson's disease, the SOD1 gene was sequenced in index patients with familial Parkinson's disease from 23 families. No changes were detected.     

Induction of parkinsonism‐related proteins in the spinal motor neurons of transgenic mouse carrying a mutant SOD1 gene

Amyotrophic lateral sclerosis is a progressive and fatal disease caused by selective death of motor neurons, and a number of these patients carry mutations in the superoxide dismutase 1 (SOD1) gene involved in ameliorating oxidative stress. Recent studies indicate that oxidative stress and disruption of mitochondrial homeostasis is a common mechanism for motor neuron degeneration in amyotrophic lateral sclerosis and the loss of midbrain dopamine neurons in Parkinson's disease. Therefore, the present study investigated the presence and alterations of familial Parkinson's disease‐related proteins, PINK1 and DJ‐1, in spinal motor neurons of G93ASOD1 transgenic mouse model of amyotrophic lateral sclerosis. Following onset of disease, PINK1 and DJ‐1 protein expression increased in the spinal motor neurons. The activated form of p53 also increased and translocated to the nuclei of spinal motor neurons, followed by increased expression of p53‐activated gene 608 (PAG608). This is the first report demonstrating that increased expression of PAG608 correlates with activation of phosphorylated p53 in spinal motor neurons of an amyotrophic lateral sclerosis model. These results provide further evidence of the profound correlations between spinal motor neurons of amyotrophic lateral sclerosis and parkinsonism‐related proteins. © 2010 Wiley‐Liss, Inc.     

RNAi and neurological disease]

In many of autosomal dominant diseases such as familial amyotrophic lateral sclerosis (ALS) with Cu/Zn superoxide dismutase (SOD1) mutation, a missense point mutation may induce the disease by its gain of adverse property. Similar 'gain of toxic function' of mutant protein is predicted to cause cell death in other autosomal dominant neurodegenerative diseases such as familial Alzheimer disease, prion disease, polyglutamine diseases and Parkinson disease. In all these familial diseases, one rational approach to therapy is to develop a method to specifically eliminate the aberrant protein. Duplex of 21-nt RNA, known as siRNA, has recently emerged as a powerful tool to silence gene. Mutant-allele specific gene silencing with siRNA was showed in familial ALS and Machado-Joseph diseases. We made the transgenic (Tg) mouse of modified small interfering RNA (siRNA). By crossing this anti-SOD1 siRNA Tg mouse with a SOD1(G93A) Tg mouse as a model for ALS, siRNA halted the development of disease by inhibiting mutant G93A SOD1. Our results support the feasibility of utilizing siRNA-based gene therapy of neurodegenerative diseases of autosomal dominant inheritance.     

Kennedy's disease: a triplet repeat disorder or a motor neuron disease?

Two definite genetic causes of adult motor neuron degeneration have been identified to date: CAG repeat expansion in the androgen receptor gene in Kennedy's disease and point mutations in the SOD1 gene, encoding the enzyme, Cu/Zn superoxide dismutase, in some familial forms of amyotrophic lateral sclerosis. Although both have unrelated genetic causes, Kennedy's disease and SOD1-linked amyotrophic lateral sclerosis share several pathogenic features. First, expanded androgen receptor and mutant Cu/Zn superoxide dismutase have a propensity to aggregate into insoluble complexes and form inclusion bodies in affected neurons. Deposits of mutant proteins could be detrimental to neuronal viability by interfering with the normal housekeeping functions of chaperones and of the ubiquitin/proteasome system. Secondly, cytoskeletal function may be impaired in both diseases as decreased transactivational activity of expanded androgen receptor may cause an abnormal pattern of tubulin expression in motor neurons in Kennedy's disease and disruption of neurofilament organisation is a hallmark of amyotrophic lateral sclerosis. The concept of activation of overlapping cell death cascades by two distinct genetic defects could help elucidating downstream pathogenic processes and may provide novel targets for pharmacological intervention or gene therapy for the treatment of motor neuron disorders.     

Kennedy’s disease: a triplet repeat disorder or a motor neuron disease?

Two definite genetic causes of adult motor neuron degeneration have been identified to date: CAG repeat expansion in the androgen receptor gene in Kennedy’s disease and point mutations in the SOD1 gene, encoding the enzyme, Cu/Zn superoxide dismutase, in some familial forms of amyotrophic lateral sclerosis. Although both have unrelated genetic causes, Kennedy’s disease and SOD1-linked amyotrophic lateral sclerosis share several pathogenic features. First, expanded androgen receptor and mutant Cu/Zn superoxide dismutase have a propensity to aggregate into insoluble complexes and form inclusion bodies in affected neurons. Deposits of mutant proteins could be detrimental to neuronal viability by interfering with the normal housekeeping functions of chaperones and of the ubiquitin/proteasome system. Secondly, cytoskeletal function may be impaired in both diseases as decreased transactivational activity of expanded androgen receptor may cause an abnormal pattern of tubulin expression in motor neurons in Kennedy’s disease and disruption of neurofilament organisation is a hallmark of amyotrophic lateral sclerosis. The concept of activation of overlapping cell death cascades by two distinct genetic defects could help elucidating downstream pathogenic processes and may provide novel targets for pharmacological intervention or gene therapy for the treatment of motor neuron disorders.     

Therapeutic benefit of polyamine-modified catalase as a scavenger of hydrogen peroxide and nitric oxide in familial amyotrophic lateral sclerosis transgenics

Continuous subcutaneous administration of polyamine-modified catalase that has increased permeability at the blood-brain barrier showed both a highly significant delay in onset and an increase in survival in a transgenic mouse model of familial amyotrophic lateral sclerosis having a point mutation in the gene encoding copper/zinc superoxide dismutase. These results suggest that hydrogen peroxide-mediated oxidative stress with subsequent free radical damage involving nitric oxide and possibly hydroxyl radicals in motor neurons may be the culprit in familial amyotrophic lateral sclerosis.     

Early decrease of redox factor-1 in spinal motor neurons of presymptomatic transgenic mice with a mutant SOD1 gene

Oxidative stress has been proposed to play a pivotal role in pathogenesis of both sporadic and familial amyotrophic lateral sclerosis (ALS). Expression of DNA repair enzyme redox factor-1 (Ref-1) protein was examined in the spinal cord of transgenic mice with an ALS-linked mutant Cu/Zn superoxide dismutase (SOD1) gene. Immunoblotting and immunocytochemical analyses showed that the most spinal motor neurons lost the immunoreactivity for Ref-1 in the early presymptomatic stage that preceded significant loss of the neurons. The present result suggests that an early impairment of DNA repair in the spinal motor neurons may account for the mutant SOD1-mediated motor neuronal death in this model.     

Increased 3-nitrotyrosine in both sporadic and familial amyotrophic lateral sclerosis

The pathogenesis of neuronal degeneration in both sporadic and familial amyotrophic lateral sclerosis (ALS) associated with mutations in superoxide dismutase may involve oxidative stress. A leading candidate as a mediator of oxidative stress is peroxynitrite, which is formed by the reaction of superoxide with nitric oxide. 3-Nitrotyrosine is a relatively specific marker for oxidative damage mediated by peroxynitrite. In the present study, biochemical measurements showed increased concentrations of 3-nitrotyrosine and 3-nitro-4-hydroxyphenylacetic acid in the lumbar and thoracic spinal cord of ALS patients. Increased 3-nitrotyrosine immunoreactivity was observed in motor neurons of both sporadic and familial ALS patients. Neurologic control patients with cerebral ischemia also showed increased 3-nitrotyrosine immunoreactivity. These findings suggest that peroxynitrite-mediated oxidative damage may play a role in the pathogenesis of both sporadic and familial ALS.     

Pyruvate protects motor neurons expressing mutant superoxide dismutase 1 against copper toxicity

Mutations in the copper/zinc superoxide dismutase (SOD1) gene are known to be responsible for familial amyotrophic lateral sclerosis. Alteration of metal binding properties of mutant SOD1 has been proposed to play a role in the pathogenesis of amyotrophic lateral sclerosis. We investigated the toxic effects of excess extracellular copper on motor neuronal cells expressing human mutant SOD1 (G93A), and evaluated the neuroprotective effects of energy metabolism intermediates or cofactors. Motoneuron-neuroblastoma hybrid (VSC 4.1) cells expressing mutant SOD1, when treated with copper chloride, showed reduced viability and increased levels of endogenous peroxides. Moreover, this copper-induced toxicity was attenuated by a free radical scavenger, a caspase inhibitor, or a calpain inhibitor. Of the energy metabolism intermediates examined, pyruvate significantly reduced the death and production of reactive oxygen species in cells expressing mutant SOD1. Our data suggest that pyruvate could be of therapeutic value in some forms of familial amyotrophic lateral sclerosis.     

The Copper Chelator d-Penicillamine Delays Onset of Disease and Extends Survival in a Transgenic Mouse Model of Familial Amyotrophic Lateral Sclerosis

A subpopulation of familial cases of amyotrophic lateral sclerosis has been linked to mutations in the gene encoding Cu/Zn superoxide dismutase (SOD1). There is in vitro evidence that certain SOD1 mutants, in addition to their normal dismutation function, show increased ability of the enzyme to act as a peroxidase. This reaction is sensitive to inhibition by copper chelators. To test this hypothesis in vivo , we administered the copper chelator d-penicillamine to a transgenic mouse model of familial amyotrophic lateral sclerosis overexpressing a mutated form of human SOD1. We demonstrate that oral administration of d-penicillamine is able to delay the onset of the disease and extend the survival of these mice. Histological studies also showed a decreased loss of facial motor neurons in d-penicillamine-treated transgenic mice, corroborating the slower evolution of the disease in these animals. These results suggest that copper chelators may benefit patients with familial amyotrophic lateral sclerosis linked to mutations in the SOD1 gene.     

Brain superoxide dismutase,catalase, and glutathione peroxidase activities in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a fatal paralytic disorder of unknown cause. Recent evidence implicated the role of free radicals in the death of motor neurons in this disease. To investigate this hypothesis further, we measured the activity of the main free radical scavenging enzymes copper/zinc superoxide dismutase, manganese superoxide dismutase, catalase, and glutathione peroxidase in postmortem brain samples from 9 patients with sporadic amyotrophic lateral sclerosis and from 9 control subjects. We examined samples from the precentral gyrus of the cerebral cortex, a region affected in amyotrophic lateral sclerosis, and from the cerebellar cortex, a region not affected. The two groups did not differ in age or postmortem delay. In the precentral gyrus from amyotrophic lateral sclerosis samples, glutathione peroxidase activity as measured by spectrophotometric assay (13.8 & 2.6 nmol/min/mg protein [mean & standard error of mean]) was reduced significantly compared to the activity in the precentral gyrus from control samples (22.7 & 0.5 nmol/min/ mg protein). In contrast, glutathione peroxidase activity was not significantly altered in the cerebellar cortex from amyotrophic lateral sclerosis patients compared to controls. Copper/zinc superoxide dismutase, manganese superoxide dismutase (corrected or not corrected for citrate synthase), and catalase were not significantly altered in the precentral gyrus or cerebellar cortex in the patient samples. This study indicated that glutathione peroxidase activity is reduced in a brain region affected in amyotrophic lateral sclerosis, thus suggesting that free radicals may be implicated in the pathogenesis of the disease.     

A novel SOD1 mutation in a young amyotrophic lateral sclerosis patient with a very slowly progressive clinical course

Approximately 10% of amyotrophic lateral sclerosis (ALS) cases are familial, and the Cu/Zn superoxide dismutase (SOD1) gene mutation accounts for 20% of them. More than 100 SOD1 mutations have been described, some with peculiar phenotypes. Moreover, mutations in the SOD1 gene have been described in apparently sporadic ALS cases. We report a new mutation (D11Y) in the Cu/Zn superoxide dismutase gene in a patient with ALS and an unusually slow disease progression. Muscle Nerve, 2010     

Motor neuron disease in transgenic mice with an H46R mutant SOD1 gene

Human familial amyotrophic lateral sclerosis with an H46R mutant Cu/Zn superoxide dismutase (SOD1) gene is characterized by initial muscle weakness and atrophy in the legs and a very long-term clinical course (approximately 15 years). Transgenic mice with this mutation generated in our laboratory occasionally showed aggregates in the anterior horns and axonal degeneration in all white matter sections of the spinal cord on plastic sections at the presymptomatic stages (12 and 16 weeks old), although conventional staining revealed no pathologic changes. At the symptomatic stages (20 and 24 weeks), loss of anterior horn neurons was observed. On plastic sections, aggregates were frequently seen not only in the anterior horns but also in the posterior horns and in all sections of white matter. Degenerated fibers were observed in the anterior and posterior roots as well as in white matter. Electron and immunoelectron microscopic observation revealed human SOD1- and ubiquitin-positive aggregates consisting of intermediate filaments in the anterior horn even from an early presymptomatic stage. Thus, H46R mutant SOD1 transgenic mice are characterized by widespread pathologic changes of the spinal cord that extend beyond the motor system, including many aggregates lacking vacuoles. The close pathologic similarity makes this animal model suitable for the investigation of human familial amyotrophic lateral sclerosis with the mutation.     

Difficulties in distinguishing sporadic from familial amyotrophic lateral sclerosis

Mutations of the copperlzinc superoxide dismutase (SOD-1) gene are present in around 20% of patients with a family history of amyotrophic lateral sclerosis. The finding of these mutations in patients with sporadic amyotrophic lateral sclerosis is rare. We describe a family with amyotrophic lateral sclerosis associated with the SOD-1 mutation Asp 101 Asn. This mutation was previously described as occurring in a patient with sporadic disease. We discuss the difficulties in defining truly sporadic amyotrophic lateral sclerosis, and the consequent implications on the neurogenetic advice given to other family members.     

Identification of a novel mutation in Cu/Zn superoxide dismutase gene associated with familial amyotrophic lateral sclerosis

We report a new missense mutation (Ala140Gly) in exon 5 of the Cu/Zn superoxide dismutase (SOD-1) gene in a 73-year-old man with familial amyotrophic lateral sclerosis (FALS). The enzymatic activity of mutated SOD-1 measured in erythrocyte lysate was 70% of control. This heterozygote mutation, which is associated with the late onset of the disease, is located in the active site of the enzyme.     

Bromocriptine prevents neuron damage following inhibition of superoxide dismutase in cultured ventral spinal cord neurons

Abstract

Rpsen et al. have reported point mutations in the cytosolic Cu/Zn superoxide dismutase (SOD 1) gene in some families with familial amyotrophic lateral sclerosis (ALS). To determine whether decreased SOD activity could contribute to neuronal damage, rat embryo ventral spinal cord neurons were incubated with diethyldithiocarbamate (DOC), an inhibitor of SOD. There was a marked increase in neuronal damage in cultures exposed to DOC and this phenomenon was dose-related. In this paradigm, these deteriorative changes were prevented by bromocriptine. DOC-treated ventral spinal cord neurons provide an in vitro model of free radical neurotoxicity secondary to decreased SOD activity. Simultaneous treatment with bromocriptine and DOC reduced neurotoxicity, indicating that bromocriptine has a neuroprotective effect against free radicals. [Neural Res 1997; 19: 389-392]     

Mutant superoxide dismutase disrupts cytoplasmic dynein in motor neurons

Cytoplasmic dynein and dynactin drive retrograde axonal transport in neurons, and mutations in dynein/dynactin cause motor neuron degeneration. To test whether defects in dynein/dynactin function are involved in the neurodegenerative disease amyotrophic lateral sclerosis, we examined neurotracer transport from muscle to motor neuron in a transgenic mouse model of amyotrophic lateral sclerosis. Significant inhibition was observed, which was temporally correlated with declines in muscle strength. No decrease in dynein/dynactin expression was observed, but immunohistochemistry suggests that dynein associates with aggregates of mutant Cu/Zn superoxide dismutase 1. Expression of mutant Cu/Zn superoxide dismutase 1 in primary motor neurons altered the cellular localization of dynein, suggesting an inhibition of dynein/dynactin function. Thus, inhibition of dynein/dynactin function may have a role in motor neuron degeneration in amyotrophic lateral sclerosis.