Modified expression of Bcl-2 and SOD1 proteins in lymphocytes from sporadic ALS patients

Skeletal myotubes expressing ALS mutant SOD1 induce pathogenic changes, impair mitochondrial axonal transport, and trigger motoneuron death

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the loss of motoneurons (MNs), and despite progress, there is no effective treatment. A large body of evidence shows that astrocytes expressing ALS-linked mutant proteins cause non-cell autonomous toxicity of MNs. Although MNs innervate muscle fibers and ALS is characterized by the early disruption of the neuromuscular junction (NMJ) and axon degeneration, there are controversies about whether muscle contributes to non-cell-autonomous toxicity to MNs. In this study, we generated primary skeletal myotubes from myoblasts derived from ALS mice expressing human mutant SOD1 G93A (termed hereafter mutSOD1). Characterization revealed that mutSOD1 skeletal myotubes display intrinsic phenotypic and functional differences compared to control myotubes generated from non-transgenic (NTg) littermates. Next, we analyzed whether ALS myotubes exert non-cell-autonomous toxicity to MNs. We report that conditioned media from mutSOD1 myotubes (mutSOD1-MCM), but not from control myotubes (NTg-MCM), induced robust death of primary MNs in mixed spinal cord cultures and compartmentalized microfluidic chambers. Our study further revealed that applying mutSOD1-MCM to the MN axonal side in microfluidic devices rapidly reduces mitochondrial axonal transport while increasing Ca2+ transients and reactive oxygen species (i.e., H 2 O 2 ). These results indicate that soluble factor(s) released by mutSOD1 myotubes cause MN axonopathy that leads to lethal pathogenic changes.

Taurine and deferiprone against Al-linked apoptosis in rat hippocampus

BACKGROUND

Aluminium (Al) overload has toxic effects on multiple organ systems, especially the nervous system. Al accumulation in the brain, especially the hippocampus, is an important factor contributing to Alzheimer's disease (AD). Deferiprone (DFP), a metal chelator, is used as a potential treatment for AD. In this study, we investigated the combined effect of taurine and DFP on Al chelation and hippocampal apoptosis in Al-exposed rats, as well as the underlying mechanisms of these effects to explore a possible therapy for AD.

METHODS

Male Wistar rats were divided into seven groups: negative control group (administered saline), Al-exposure group (administered AlCl₃ and saline), and five experimental groups (administered AlCl₃ and taurine, varying doses of DFP, or taurine with varying doses of DFP). After 8 weeks of treatment, the rats were sacrificed, and the terminal deoxyribonucleotidyl transferase (TDT)-mediated dUTP-digoxigenin nick end labelling (TUNEL) assay was used to detect hippocampal apoptotic cells. Real-time quantitative PCR was used to assess the expression of the Bcl2 and Bax genes, and a western blotting assay was used to evaluate BCL2, BAX, and cleaved caspase-3 levels.

RESULTS

Compared to the negative control group, the number of apoptotic cells in the hippocampus increased, Bcl2 expression significantly decreased, and BAX and cleaved caspase-3 levels increased in the Al-exposure group. The combination of taurine and DFP exerted a protective effect by inhibiting hippocampal cell apoptosis through the BCL2, BAX, and caspase-3 signalling pathways. Compared with the taurine-administered group, the group administered taurine with DFP showed a significantly increased Bcl2 and decreased Bax expression.

CONCLUSION

The combination of taurine and DFP is a potential candidate for the treatment of AD induced by Al exposure.

Histochemistry in Advanced Cytometry: From Fluorochromes to Mass Probes

For over half a century, fluorescence has been the milestone of most of the quantitative approaches in various fields from chemistry and biochemistry to microscopy. This latter also evolved into cytometry, thanks to the development of fluorescence techniques. The dyes of classical cytochemistry were replaced by fluorochromes, and the pioneer microphotometry was replaced by microfluorometry. The latter has great advantages in terms of simplicity, sensitivity, and accuracy. The extensive research and availability of new fluorochromes as well as the technological evolution contributed to the success of microfluorometry. The development of flow cytometry in the 1960s gave a giant boost to cell analysis and in particular to the clinical diagnostics. The synergy between flow cytometry and the subsequent development of monoclonal antibodies allowed the setup of multiparametric analytical panels that are today popular and irreplaceable in many clinical and research laboratories. Multiparametric analysis has required the application of an increasing number of fluorochromes, but their simultaneous use creates problems of mutual contamination, hence the need to develop new fluorescent probes. Semiconductor and nanotechnology research enabled the development of new probes called nanocrystals or quantum dots, which offered great advantages to the multiparametric analysis: in fact, thanks to their spectrofluorometric peculiarities, dozens of quantum dots may be simultaneously used without appreciable crosstalk between them. New analytical horizons in cytometry seem to be associated with a new concept of analysis that replaces fluorescence toward new markers with (non-radiative) isotopes of heavy metals. Thus, the mass flow cytometry was born, which seems to guarantee the simultaneous compensation-free analysis of up to 100 markers on a single sample aliquot.

Biomarkers in Human Peripheral Blood Mononuclear Cells: The State of the Art in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease, characterized by the progressive loss of lower motor neurons, weakness and muscle atrophy. ALS lacks an effective cure and diagnosis is often made by exclusion. Thus, it is imperative to search for biomarkers. Biomarkers can help in understanding ALS pathomechanisms, identification of targets for treatment and development of effective therapies. Peripheral blood mononuclear cells (PBMCs) represent a valid source for biomarkers compared to cerebrospinal fluid, as they are simple to collect, and to plasma, because of the possibility of detecting lower expressed proteins. They are a reliable model for patients’ stratification. This review provides an overview on PBMCs as a potential source of biomarkers in ALS. We focused on altered RNA metabolism (coding/non-coding RNA), including RNA processing, mRNA stabilization, transport and translation regulation. We addressed protein abnormalities (aggregation, misfolding and modifications); specifically, we highlighted that SOD1 appears to be the most characterizing protein in ALS. Finally, we emphasized the correlation between biological parameters and disease phenotypes, as regards prognosis, severity and clinical features. In conclusion, even though further studies are needed to standardize the use of PBMCs as a tool for biomarker investigation, they represent a promising approach in ALS research.

RNA Molecular Signature Profiling in PBMCs of Sporadic ALS Patients: HSP70 Overexpression Is Associated with Nuclear SOD1

Superoxide dismutase 1 (SOD1) is one of the causative genes associated with amyotrophic lateral sclerosis (ALS), a neurodegenerative disorder. SOD1 aggregation contributes to ALS pathogenesis. A fraction of the protein is localized in the nucleus (nSOD1), where it seems to be involved in the regulation of genes participating in the oxidative stress response and DNA repair. Peripheral blood mononuclear cells (PBMCs) were collected from sporadic ALS (sALS) patients (n = 18) and healthy controls (n = 12) to perform RNA-sequencing experiments and differential expression analysis. Patients were stratified into groups with “high” and “low” levels of nSOD1. We obtained different gene expression patterns for high- and low-nSOD1 patients. Differentially expressed genes in high nSOD1 form a cluster similar to controls compared to the low-nSOD1 group. The pathways activated in high-nSOD1 patients are related to the upregulation of HSP70 molecular chaperones. We demonstrated that, in this condition, the DNA damage is reduced, even under oxidative stress conditions. Our findings highlight the importance of the nuclear localization of SOD1 as a protective mechanism in sALS patients.

Skeletal Muscle-Restricted Expression of Human SOD1 in Transgenic Mice Causes a Fatal ALS-Like Syndrome

Amyotrophic lateral sclerosis (ALS) is a fatal heterogeneous neurodegenerative disease that causes motor neuron (MN) loss and skeletal muscle paralysis. It is uncertain whether this degeneration of MNs is triggered intrinsically and is autonomous, or if the disease initiating mechanisms are extrinsic to MNs. We hypothesized that skeletal muscle is a primary site of pathogenesis in ALS that triggers MN degeneration. Some inherited forms of ALS are caused by mutations in the superoxide dismutase-1 (SOD1) gene, that encodes an antioxidant protein, so we created transgenic (tg) mice expressing wild-type-, G37R-, and G93A-human SOD1 gene variants only in skeletal muscle. Presence of human SOD1 (hSOD1) protein in skeletal muscle was verified by western blotting, enzyme activity gels, and immunofluorescence in myofibers and satellite cells. These tg mice developed limb weakness and paresis with motor deficits, limb and chest muscle wasting, diaphragm atrophy, and age-related fatal disease with a lifespan shortening of 10–16%. Brown and white adipose tissue also became wasted. Myofibers of tg mice developed crystalline-like inclusions, individualized sarcomere destruction, mitochondriopathy with vesiculation, DNA damage, and activated p53. Satellite cells became apoptotic. The diaphragm developed severe loss of neuromuscular junction presynaptic and postsynaptic integrity, including decreased innervation, loss of synaptophysin, nitration of synaptophysin, and loss of nicotinic acetylcholine receptor and scaffold protein rapsyn. Co-immunoprecipitation identified hSOD1 interaction with rapsyn. Spinal cords of tg mice developed gross atrophy. Spinal MNs formed cytoplasmic and nuclear inclusions, axonopathy, mitochondriopathy, accumulated DNA damage, activated p53 and cleaved caspase-3, and died. Tg mice had a 40–50% loss of MNs. This work shows that hSOD1 in skeletal muscle is a driver of pathogenesis in ALS, that involves myofiber and satellite cell toxicity, and apparent muscle-adipose tissue disease relationships. It also identifies a non-autonomous mechanism for MN degeneration explaining their selective vulnerability as likely a form of target-deprivation retrograde neurodegeneration.

Monoclonal full-length antibody against TAR DNA binding protein 43 reduces related proteinopathy in neurons

Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD), 2 incurable neurodegenerative disorders, share the same pathological hallmark named TDP43 (TAR DNA binding protein 43) proteinopathy. This event is characterized by a consistent cytoplasmic mislocalization and aggregation of the protein TDP43, which loses its physiological properties, leading neurons to death. Antibody-based approaches are now emerging interventions in the field of neurodegenerative disorders. Here, we tested the target specificity, in vivo distribution, and therapeutic efficacy of a monoclonal full-length antibody, named E6, in TDP43-related conditions. We observed that the antibody recognizes specifically the cytoplasmic fraction of TDP43. We demonstrated its ability in targeting large neurons in the spinal cord of mice and in reducing TDP43 mislocalization and NF-κB activation. We also recognized the proteasome as well as the lysosome machineries as possible mechanisms used by the antibody to reduce TDP43 proteinopathy. To our knowledge, this is the first report showing the therapeutic efficacy and feasibility of a full-length antibody against TDP43 in reducing TDP43 proteinopathy in spinal neurons of an ALS/FTLD mouse model.

A full-length antibody against TDP43 reduces TDP43 proteinopathy in spinal neurons of an amyotrophic lateral sclerosis/Frontotemporal lobar degeneration mouse model.

Nuclear Phospho-SOD1 Protects DNA from Oxidative Stress Damage in Amyotrophic Lateral Sclerosis

We already demonstrated that in peripheral blood mononuclear cells (PBMCs) of sporadic amyotrophic lateral sclerosis (sALS) patients, superoxide dismutase 1 (SOD1) was present in an aggregated form in the cytoplasmic compartment. Here, we investigated the possible effect of soluble SOD1 decrease and its consequent aggregation. We found an increase in DNA damage in patients PBMCs characterized by a high level of aggregated SOD1, while we found no DNA damage in PBMCs with normal soluble SOD1. We found an activation of ataxia-telangiectasia-mutated (ATM)/Chk2 and ATM and Rad3-related (ATR)/Chk1 DNA damage response pathways, which lead to phosphorylation of SOD1. Moreover, data showed that phosphorylation allows SOD1 to shift from the cytoplasm to the nucleus, protecting DNA from oxidative damage. Such pathway was finally confirmed in our cellular model. Our data lead us to suppose that in a sub-group of patients this physiologic pathway is non-functional, leading to an accumulation of DNA damage that causes the death of particularly susceptible cells, like motor neurons. In conclusion, during oxidative stress SOD1 is phosphorylated by Chk2 leading to its translocation in the nuclear compartment, in which SOD1 protects DNA from oxidative damage. This pathway, inefficient in sALS patients, could represent an innovative therapeutic target.

A pilot study assessing T1-weighted muscle MRI in amyotrophic lateral sclerosis (ALS)

The authors set out to study the role of T1-weighted muscle MRI in the diagnostic phase of ALS, comparing images from ten patients and nine age-matched healthy controls (HCs). All subjects underwent MRI of 68 muscles in the hands, paraspinal regions and lower limbs; the images were semi-quantitatively scored. Atrophy was more frequent in muscles of ALS patients than HCs (p < 0.0001); fatty infiltration was particularly marked in iliopsoas (p = 0.046), anterior (p = 0.020) and posterior (p = 0.047) calf muscles in patients. A trend towards agreement was found between MRI and clinic-EMG data for the first dorsal interosseous, paraspinal, and tibial anterior muscles. Muscle T1-weighted MRI can distinguish ALS patients from HCs for specific regions (i.e., legs). MRI abnormalities could be found in pauci-symptomatic spinal muscles in bulbar-onset patients. Muscle MRI may be a useful diagnostic tool in ALS, in particular for muscles difficult to investigate using clinical-EMG methods.

Recapitulation of Pathological TDP-43 Features in Immortalized Lymphocytes from Sporadic ALS Patients

Amyotrophic lateral sclerosis (ALS) is a fatal progressive neurodegenerative disorder of still unknown etiology that results in loss of motoneurons, paralysis, and death, usually between 2 and 4 years from onset. There are no currently available ALS biomarkers to support early diagnosis and to facilitate the assessment of the efficacy of new treatments. Since ALS is considered a multisystemic disease, here we have investigated the usefulness of immortalized lymphocytes from sporadic ALS patients to study TDP-43 homeostasis as well as to provide a convenient platform to evaluate TDP-43 phosphorylation as a novel therapeutic approach for ALS. We report here that lymphoblasts from ALS patients recapitulate the hallmarks of TDP-43 processing in affected motoneurons, such as increased phosphorylation, truncation, and mislocalization of TDP-43. Moreover, modulation of TDP-43 by an in-house designed protein casein kinase-1δ (CK-1δ) inhibitor, IGS3.27, reduced phosphorylation of TDP-43, and normalized the nucleo-cytosol translocation of TDP-43 in ALS lymphoblasts. Therefore, we conclude that lymphoblasts, easily accessible cells, from ALS patients could be a useful model to study pathological features of ALS disease and a suitable platform to test the effects of potential disease-modifying drugs even in a personalized manner.

SOD1 in Amyotrophic Lateral Sclerosis: "Ambivalent" Behavior Connected to the Disease

In 1993, Rosen and collaborators discovered that the gene encoding SOD1 has mutations in amyotrophic lateral sclerosis (ALS) patients; moreover, these mutations are found in the exon regions, suggesting that their toxic effects are the consequence of protein dysfunction with an increase of oxidative stress. While a clear genetic picture has been delineated, a more complex scenario has been ascribed to the SOD1 protein. On the one hand, some evidence sustains the hypothesis of an additionally toxic role for wild-type SOD1 (WT-SOD1) in the pathogenesis of sporadic ALS. On the other hand, our group identified a discrepancy among WT-SOD1 protein expression levels and mRNA in ALS sporadic patients, thus providing the hypothesis of a re-localization of the “missing” SOD1 in a different sub-cellular compartment, i.e., nucleus, or an aggregation/precipitation in the insoluble fraction. Moreover, our data also indicate an association between longer disease duration and higher amounts of soluble SOD1 within the nucleus, suggesting a possible defensive role of the protein in this compartment. Starting from this evidence, in this review we will attempt to resolve the “ambivalent” behavior of SOD1 in ALS disease and we will try to classify sporadic ALS patients according to a novel biological signature, i.e., SOD localization.

Fluorochromes for DNA Staining and Quantitation

In these last few decades the great explosion of the molecular approaches has casted a little shadow on the DNA quantitative analysis. Nevertheless DNA cytochemistry represented a long piece of history in cell biology since the advent of the Feulgen reaction. This discovery was really the milestone of the emerging quantitative cytochemistry, and scientists from all over the world produced a very large literature on this subject. This first era of quantitation (histochemistry followed by cytochemistry) started by means of absorption measurements (histophotometry and cytophotometry). The successive introduction of fluorescence microscopy gave a great boost to quantitation, making easier and faster the determination of cell components by means of cytofluorometry. The development of flow cytometry further contributed to the importance of quantitative cytochemistry. At its beginning, the mission of flow cytometry was still DNA quantitation. For a decade the Feulgen reaction had been the reference methodology for both conventional and flow cytofluorometry; the advent of Shiff-type reagents contributed to expand the variety of possible fluorochromes excitable in the entire visible spectrum as well as in the ultraviolet region. The fluorescence scenario was progressively enriched by new probes among which are the intercalating dyes which made DNA quantitation simple and fast, thus spreading it worldwide. The final explosion of cytofluorometry was made possible by the availability of a large variety of probes directly binding DNA structure. In addition, immunofluorescence allowed to correlate the cell cycle-related DNA content to other cell markers. In the clinical application of flow cytometry, this promoted the introduction of multiparametric analyses aimed at describing the cytokinetic characteristics of a given cell subpopulation defined by a specific immunophenotype setting.

Anti-Apoptotic Effect of IGF1 on Schwann Exposed to Hyperglycemia is Mediated by Neuritin, a Novel Neurotrophic Factor

The aim of the present study is to explore the effects of exogenous insulin-like growth factor-1 (IGF1) on hyperglycemia-induced apoptosis of Schwann cells via neuritin-mediated pathway. Neuritin was identified with immunohistochemistry. Exogenous IGF1 was used to prevent possible changes in neuritin expression and apoptosis of Schwann cells isolated from rat sciatic nerves and cultured in high-glucose media. Neuritin silencing or overexpressing lentivirus transfection of Schwann cells was conducted. Expressions of neuritin at levels of transcription or translation were measured using quantitative PCR or Western blot. Caspase-3 and caspase-9 fluorometric assays were performed. Bcl-2 and Bax were assayed using Western blotting. Apoptosis of Schwann cells was measured using FACS analysis and TUNEL assay. A pathway of IGF1 action in relation to neuritin was explored. Neuritin and Bcl-2 protein were localized in Schwann cells of rats' sciatic nerves. In vitro, apoptosis increased with downregulated neuritin expression, which was prevented by exogenous IGF1 treatment in contrast to without, in Schwann cells isolated from rat sciatic nerve and cultured in high-glucose and serum-free media. A phosphatidylinositol-3-kinase (PI3K) inhibitor treatment blocked the action of IGF1. The inhibitor did not affect the apoptosis rate that decreased obviously after neuritin was overexpressed in Schwann cells. The apoptosis rate increased drastically after neuritin was silenced, and the resultant apoptosis was suppressed by a caspase inhibitor treatment but not affected by exogenous IGF1. The activities of caspase-3 and caspase-9 changed positively with apoptosis. An anti-apoptotic protein (Bcl-2) not Bax increased or decreased in neuritin-overexpressed or neuritin-silenced Schwann cells, respectively. Bcl-2-selective inhibitor blocked the anti-apoptotic effect of neuritin. IGF1 or neuritin was not found to affect glucose levels in media during the experiment. The anti-apoptotic effect of IGF1 on Schwann cells inflicted by hyperglycemia is mediated at least by neuritin, a novel neurotrophic factor, through PI3K and Bcl-2.

Progranulin deficiency induces overactivation of WNT5A expression via TNF-α/NF-κB pathway in peripheral cells from frontotemporal dementia-linked granulin mutation carriers

BACKGROUND

Loss-of-function progranulin gene (GRN) mutations have been identified as the major cause of frontotemporal lobar degeneration with transactive response (TAR) DNA-binding protein 43 (TDP-43) pathology (frontotemporal lobar degeneration [FTLD]-TDP); however, little is known about the association between progranulin (PGRN) deficiency and neuronal loss in individuals with FTLD-TDP. Previously we reported enhanced proliferative activity associated with the activation of WNT5A/CDK6/pRb signalling in PGRN-deficient cells. The objective of this work was to elucidate the association between PGRN deficiency, WNT5A signalling and cell proliferation in immortalized lymphoblasts from carriers of the c.709-1G > A GRN mutation (asymptomatic and FTLD-TDP).

METHODS

We assessed cell proliferation in carriers of the c.709-1G > A GRN gene mutation and controls without GRN mutation and without sign of neurologic degeneration by cell counting or using an MTT assay. We used a luciferase assay to measure the nuclear factor-κ (NF-κ) activity. We evaluated messenger RNA levels using quantitative real-time polymerase chain reaction and protein levels by immunoblotting. Co-immunoprecipitation was used to analyze the interaction between PGRN and its receptors.

RESULTS

We enrolled 19 carriers of the GRN gene mutation and 10 controls in this study. The PGRN-deficient cells showed increased expression of WNT5A due to NF-κB signalling overactivation. We observed a competition between PGRN and tumour necrosis factor-α (TNF-α) for binding both TNF receptors (TNFR) I and II. Blocking NF-κB signalling using wedelolactone or specific antibodies against TNFRs inhibited WNT5A overexpression and proliferation of PGRN-deficient cells. Conversely, the activation of NF-κB signalling by TNF-α increased WNT5A-dependent proliferation of control cells.

LIMITATIONS

All cell lines were derived from individuals harboring the same splicing GRN mutation. Nevertheless, most of the known GRN mutations lead to haploinsufficiency of the protein.

CONCLUSION

Our results revealed an important role of NF-κB signalling in PGRN-associated FTLD-TDP and confirm that PGRN can bind to TNF-α receptors regulating the expression of WNT5A, suggesting novel targets for treatment of FTLD-TDP linked to GRN mutations.

Effects of CDNF on 6-OHDA-induced apoptosis in PC12 cells via modulation of Bcl-2/Bax and caspase-3 activation

Progressive dopamine neuron degeneration in the substantia nigra pars compacta is considered the most prominent pathological characteristic of Parkinson's disease (PD). Currently, there is no cure, but only the capability to relieve the symptoms of PD. The conserved dopamine neurotrophic factor (CDNF) protects and rescues dopamine neurons in vivo. However, the molecular function of CDNF in PD remains unclear. In present study, we investigated the role and intrinsic mechanism of CDNF in preventing and reversing rat pheochromocytoma (PC12) cells from apoptosis induced by 6-hydroxydopamine (6-OHDA). We demonstrate that 6-OHDA induces cell death in PC12 cells, but that CDNF attenuates this effect in a dose-dependent manner. Further study shows that upregulation of the Bcl-2/Bax ratio and downregulation of caspase-3 activity are observed in a dose-dependent manner upon pre-treatment or post-treatment with CDNF, suggesting a pathway of regulation of apoptosis by CDNF. These data demonstrate that CDNF prevents the apoptosis of PC12 cells induced by 6-OHDA by modulating Bcl-2/Bax and caspase-3 activation.

More than a bystander: the contributions of intrinsic skeletal muscle defects in motor neuron diseases

Spinal muscular atrophy (SMA), amyotrophic lateral sclerosis (ALS), and spinal-bulbar muscular atrophy (SBMA) are devastating diseases characterized by the degeneration of motor neurons. Although the molecular causes underlying these diseases differ, recent findings have highlighted the contribution of intrinsic skeletal muscle defects in motor neuron diseases. The use of cell culture and animal models has led to the important finding that muscle defects occur prior to and independently of motor neuron degeneration in motor neuron diseases. In SMA for instance, the muscle specific requirements of the SMA disease-causing gene have been demonstrated by a series of genetic rescue experiments in SMA models. Conditional ALS mouse models expressing a muscle specific mutant SOD1 gene develop atrophy and muscle degeneration in the absence of motor neuron pathology. Treating SBMA mice by over-expressing IGF-1 in a skeletal muscle-specific manner attenuates disease severity and improves motor neuron pathology. In the present review, we provide an in depth description of muscle intrinsic defects, and discuss how they impact muscle function in these diseases. Furthermore, we discuss muscle-specific therapeutic strategies used to treat animal models of SMA, ALS, and SBMA. The study of intrinsic skeletal muscle defects is crucial for the understanding of the pathophysiology of these diseases and will open new therapeutic options for the treatment of motor neuron diseases.

Altered intracellular localization of SOD1 in leukocytes from patients with sporadic amyotrophic lateral sclerosis

Several lines of evidence support the hypothesis of a toxic role played by wild type SOD1 (WT-SOD1) in the pathogenesis of sporadic amyotrophic lateral sclerosis (SALS). In this study we investigated both distribution and expression profile of WT-SOD1 in leukocytes from 19 SALS patients and 17 healthy individuals. Immunofluorescence experiments by confocal microscopy showed that SOD1 accumulates in the nuclear compartment in a group of SALS subjects. These results were also confirmed by western blot carried out on soluble nuclear and cytoplasmic fractions, with increased nuclear SOD1 level (p<0.05). In addition, we observed the presence of cytoplasmic SOD1 aggregates in agreement with an increased amount of the protein recovered by the insoluble fraction. A further confirmation of the overall increased level of SOD1 has been obtained from single cells analysis using flow cytometry as cells from SALS patients showed an higher SOD1 protein content (p<0.05). These findings add further evidence to the hypothesis of an altered WT-SOD1 expression profile in peripheral blood mononuclear cells (PBMCs) from patients with ALS suggesting that WT-SOD1 species with different degrees of solubility could be involved in the pathogenesis of the disease.

H63D HFE polymorphisms are associated with increased disease duration and decreased muscle superoxide dismutase-1 expression in amyotrophic lateral sclerosis patients

INTRODUCTION

H63D HFE polymorphisms increase the risk of neurodegenerative disorders and, specifically, may increase amyotrophic lateral sclerosis (ALS) risk. Investigating the physiological alterations induced by H63D polymorphisms in ALS patients may elucidate mechanisms by which this genotype alters disease.

METHODS

Clinical measures and muscle biopsies were available from patients previously diagnosed with ALS who underwent HFE genotyping. Clinical outcomes and SOD1 protein expression were analyzed using standard statistical analyses.

RESULTS

ALS patients harboring H63D HFE (n = 16) had 28.1 months longer average disease duration and 39.3% lower muscle SOD1 protein than ALS patients with wild-type HFE (n = 22).

CONCLUSIONS

Combined with previous reports suggesting the H63D polymorphism is associated with ALS, these results support a model wherein the H63D polymorphism is involved in ALS by means of pathways involving SOD1 but may limit cellular damage in individuals who develop disease. The association between HFE genotype and disease duration has important implications for clinical care and treatment trials.

Inactivation of CDK/pRb pathway normalizes survival pattern of lymphoblasts expressing the FTLD-progranulin mutation c.709-1G>A

BACKGROUND

Mutations in the progranulin (PGRN) gene, leading to haploinsufficiency, cause familial frontotemporal lobar degeneration (FTLD-TDP), although the pathogenic mechanism of PGRN deficit is largely unknown. Allelic loss of PGRN was previously shown to increase the activity of cyclin-dependent kinase (CDK) CDK6/pRb pathway in lymphoblasts expressing the c.709-1G>A PGRN mutation. Since members of the CDK family appear to play a role in neurodegenerative disorders and in apoptotic death of neurons subjected to various insults, we investigated the role of CDK6/pRb in cell survival/death mechanisms following serum deprivation.

METHODOLOGY/PRINCIPAL FINDINGS

We performed a comparative study of cell viability after serum withdrawal of established lymphoblastoid cell lines from control and carriers of c.709-1G>A PGRN mutation, asymptomatic and FTLD-TDP diagnosed individuals. Our results suggest that the CDK6/pRb pathway is enhanced in the c.709-1G>A bearing lymphoblasts. Apparently, this feature allows PGRN-deficient cells to escape from serum withdrawal-induced apoptosis by decreasing the activity of executive caspases and lowering the dissipation of mitochondrial membrane potential and the release of cytochrome c from the mitochondria. Inhibitors of CDK6 expression levels like sodium butyrate or the CDK6 activity such as PD332991 were able to restore the vulnerability of lymphoblasts from FTLD-TDP patients to trophic factor withdrawal.

CONCLUSION/SIGNIFICANCE

The use of PGRN-deficient lymphoblasts from FTLD-TDP patients may be a useful model to investigate cell biochemical aspects of this disease. It is suggested that CDK6 could be potentially a therapeutic target for the treatment of the FTLD-TDP.

Amyotrophic lateral sclerosis multiprotein biomarkers in peripheral blood mononuclear cells

Background

Amyotrophic lateral sclerosis (ALS) is a fatal progressive motor neuron disease, for which there are still no diagnostic/prognostic test and therapy. Specific molecular biomarkers are urgently needed to facilitate clinical studies and speed up the development of effective treatments.

Methodology/Principal Findings

We used a two-dimensional difference in gel electrophoresis approach to identify in easily accessible clinical samples, peripheral blood mononuclear cells (PBMC), a panel of protein biomarkers that are closely associated with ALS. Validations and a longitudinal study were performed by immunoassays on a selected number of proteins. The same proteins were also measured in PBMC and spinal cord of a G93A SOD1 transgenic rat model. We identified combinations of protein biomarkers that can distinguish, with high discriminatory power, ALS patients from healthy controls (98%), and from patients with neurological disorders that may resemble ALS (91%), between two levels of disease severity (90%), and a number of translational biomarkers, that link responses between human and animal model. We demonstrated that TDP-43, cyclophilin A and ERp57 associate with disease progression in a longitudinal study. Moreover, the protein profile changes detected in peripheral blood mononuclear cells of ALS patients are suggestive of possible intracellular pathogenic mechanisms such as endoplasmic reticulum stress, nitrative stress, disturbances in redox regulation and RNA processing.

Conclusions/Significance

Our results indicate that PBMC multiprotein biomarkers could contribute to determine amyotrophic lateral sclerosis diagnosis, differential diagnosis, disease severity and progression, and may help to elucidate pathogenic mechanisms.

SOD1 Transcriptional and Posttranscriptional Regulation and Its Potential Implications in ALS

Copper-zinc superoxide dismutase (SOD1) is a detoxifying enzyme localized in the cytosol, nucleus, peroxisomes, and mitochondria. The discovery that mutations in SOD1 gene cause a subset of familial amyotrophic lateral sclerosis (FALS) has attracted great attention, and studies to date have been mainly focused on discovering mutations in the coding region and investigation at protein level. Considering that changes in SOD1 mRNA levels have been associated with sporadic ALS (SALS), a molecular understanding of the processes involved in the regulation of SOD1 gene expression could not only unravel novel regulatory pathways that may govern cellular phenotypes and changes in diseases but also might reveal therapeutic targets and treatments. This review seeks to provide an overview of SOD1 gene structure and of the processes through which SOD1 transcription is controlled. Furthermore, we emphasize the importance to focus future researches on investigating posttranscriptional mechanisms and their relevance to ALS.

G93A SOD1 alters cell cycle in a cellular model of Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative multifactorial disease characterized, like other diseases such as Alzheimer's disease (AD), Parkinson's disease (PD) or frontotemporal dementia (FTD), by the degeneration of specific neuronal cell populations. Motor neuron loss is distinctive of ALS. However, the causes of onset and progression of motor neuron death are still largely unknown. In about 2% of all cases, mutations in the gene encoding for the Cu/Zn superoxide dismutase (SOD1) are implicated in the disease. Several alterations in the expression or activation of cell cycle proteins have been described in the neurodegenerative diseases and related to cell death. In this work we show that mutant SOD1 can alter cell cycle in a cellular model of ALS. Our findings suggest that modifications in the cell cycle progression could be due to an increased interaction between mutant G93A SOD1 and Bcl-2 through the cyclins regulator p27. As previously described in post mitotic neurons, cell cycle alterations could fatally lead to cell death.

SOD1 mRNA expression in sporadic amyotrophic lateral sclerosis

The mutated Cu,Zn-superoxide dismutase gene (SOD1) (E.C. No. 1.15.1.1) is generally recognized as a pathological cause of 20% of the familial form of Amyotrophic Lateral Sclerosis (ALS). However, several pieces of evidence also show that wild-type SOD1, under conditions of cellular stress, is implicated in a significant fraction of sporadic ALS cases, which represent 90% of ALS patients. Herein, we describe an abnormally high level of SOD1 transcript in spinal cord, brain stem and lymphocytes of sporadic ALS patients. Protein expression studies show a similar or lower amount of SOD1 in affected brain areas and lymphocytes, respectively. No differences are found in brain regions (cerebellum and non-motor cerebral cortex) not involved in the ALS neurodegenerative processes. In this report, cell and disease specificity are shown since no mRNA SOD1 increase is observed in sporadic ALS fibroblasts or in lymphocytes of patients affected by Alzheimer's disease. These findings provide new insight and understanding of the pathologic causes of sporadic forms of ALS and allow a possible explanation for the molecular involvement of wild-type SOD1.

Skeletal muscle-restricted expression of human SOD1 causes motor neuron degeneration in transgenic mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease of motor neurons (MNs) that causes skeletal muscle paralysis. Familial forms of ALS are linked to mutations in the superoxide dismutase-1 (SOD1) gene. The mechanisms of human SOD1 (hSOD1) toxicity to MNs are unknown. We hypothesized that skeletal muscle is a primary site of pathogenesis in ALS that triggers MN degeneration. We created transgenic (tg) mice expressing wild-type-, G37R- and G93A-hSOD1 gene variants only in skeletal muscle. These tg mice developed age-related neurologic and pathologic phenotypes consistent with ALS. Affected mice showed limb weakness and paresis with motor deficits. Skeletal muscles developed severe pathology involving oxidative damage, protein nitration, myofiber cell death and marked neuromuscular junction (NMJ) abnormalities. Spinal MNs developed distal axonopathy and formed ubiquitinated inclusions and degenerated through an apoptotic-like pathway involving capsase-3. Mice expressing wild-type and mutant forms of hSOD1 developed MN pathology. These results demonstrate that human SOD1 in skeletal muscle has a causal role in ALS and identify a new non-autonomous mechanism for MN degeneration explaining their selective vulnerability. The discovery of instigating molecular toxicities or disease progression determinants within skeletal muscle could be very valuable for the development of new effective therapies for the treatment and cure of ALS.

Immune system alterations in sporadic amyotrophic lateral sclerosis patients suggest an ongoing neuroinflammatory process

In this work we show that patients with sporadic amyotrophic lateral sclerosis exhibit immunological alterations in their blood, with respect to healthy controls, such as: i) increased levels of CD4+ cells and decreased levels of CD8+ T lymphocytes, the latter due to the reduced expression of the anti-apoptotic molecule Bcl-2; ii) significantly reduced CD4+CD25+ regulatory T (Treg) cells and monocytes (CD14+) levels in patients at a less severe stage of disease, suggesting their early recruitment towards the CNS area of primary neurodegeneration; iii) reduced expression of HLA-DR and CCR2 expression, as markers of activation, in monocytes. Since resident microglia partially derives from circulating activated monocytes and Treg cells are known to interact with the local microglia, this study strengthens the hypothesis of an involvement of the adaptive immune system associated with a neuroinflammatory process in the pathobiology of ALS.

Nitroproteomics of peripheral blood mononuclear cells from patients and a rat model of ALS

Increased levels of 3-nitrotyrosine in the central nervous system have been found in patients and mouse models of familial ALS (fALS), suggesting a possible use of nitrated proteins as biomarkers. We analyzed peripheral blood mononuclear cells (PBMCs), easily accessible samples, from sporadic ALS (sALS) patients and a rat model of fALS (a) to establish whether an increased level of nitrated proteins was present in PBMCs, too, and (b) to identify possible candidate biomarkers. With a proteomic approach, we identified for the first time the major overnitrated proteins in PBMCs from patients and rats at different disease stages. In the rats, their increased levels already were measured at a presymptomatic stage. Among them, actin, ATP synthase, and vinculin overlap between sALS patients and the rat model. Interestingly, in a previous study, actin and ATPase have been found overnitrated in the spinal cord of a mouse model of fALS before disease onset, suggesting their possible involvement in motor neuron degeneration. In conclusion, we observed that an increased level of nitrated proteins was not restricted to the spinal cord but also was present in peripheral cells of patients and an animal model, and that nitrated proteins are promising candidate biomarkers for early diagnosis of ALS.

50bp deletion in the promoter for superoxide dismutase 1 (SOD1) reduces SOD1 expression in vitro and may correlate with increased age of onset of sporadic amyotrophic lateral sclerosis

The objective was to test the hypothesis that a described association between homozygosity for a 50bp deletion in the SOD1 promoter 1684bp upstream of the SOD1 ATG and an increased age of onset in SALS can be replicated in additional SALS and control sample sets from other populations. Our second objective was to examine whether this deletion attenuates expression of the SOD1 gene. Genomic DNA from more than 1200 SALS cases from Ireland, Scotland, Quebec and the USA was genotyped for the 50bp SOD1 promoter deletion. Reporter gene expression analysis, electrophoretic mobility shift assays and chromatin immunoprecipitation studies were utilized to examine the functional effects of the deletion. The genetic association for homozygosity for the promoter deletion with an increased age of symptom onset was confirmed overall in this further study (p=0.032), although it was only statistically significant in the Irish subset, and remained highly significant in the combined set of all cohorts (p=0.001). Functional studies demonstrated that this polymorphism reduces the activity of the SOD1 promoter by approximately 50%. In addition we revealed that the transcription factor SP1 binds within the 50bp deletion region in vitro and in vivo. Our findings suggest the hypothesis that this deletion reduces expression of the SOD1 gene and that levels of the SOD1 protein may modify the phenotype of SALS within selected populations.

Adaptive immune neuroprotection in G93A-SOD1 amyotrophic lateral sclerosis mice

Background

Innate neuroimmune dysfunction is a pathobiological feature of amyotrophic lateral sclerosis (ALS). However, links, if any, between disease and adaptive immunity are poorly understood. Thus, the role of T cell immunity in disease was investigated in human G93A superoxide dismutase 1 (SOD1) transgenic (Tg) mice and subsequently in ALS patients.

Methods and Findings

Quantitative and qualitative immune deficits in lymphoid cell and T cell function were seen in G93A-SOD1 Tg mice. Spleens of Tg animals showed reductions in size, weight, lymphocyte numbers, and morphological deficits at terminal stages of disease compared to their wild-type (Wt) littermates. Spleen sizes and weights of pre-symptomatic Tg mice were unchanged, but deficits were readily seen in T cell proliferation coincident with increased annexin-V associated apoptosis and necrosis of lymphocytes. These lymphoid deficits paralleled failure of Copolymer-1 (COP-1) immunization to affect longevity. In addition, among CD4⁺ T cells in ALS patients, levels of CD45RA⁺ (naïve) T cells were diminished, while CD45RO⁺ (memory) T cells were increased compared to age-matched caregivers. In attempts to correct mutant SOD1 associated immune deficits, we reconstituted SOD1 Tg mice with unfractionated naïve lymphocytes or anti-CD3 activated CD4⁺CD25⁺ T regulatory cells (Treg) or CD4⁺CD25⁻ T effector cells (Teff) from Wt donor mice. While naive lymphocytes failed to enhance survival, both polyclonal-activated Treg and Teff subsets delayed loss of motor function and extended survival; however, only Treg delayed neurological symptom onset, whereas Teff increased latency between disease onset and entry into late stage.

Conclusions

A profound and progressive immunodeficiency is operative in G93A-SOD1 mice and is linked to T cell dysfunction and the failure to elicit COP-1 neuroprotective immune responses. In preliminary studies T cell deficits were also observed in human ALS. These findings, taken together, suggest caution in ascribing vaccination outcomes when these animal models of human ALS are used for study. Nonetheless, the abilities to improve neurological function and life expectancy in G93A-SOD1 Tg mice by reconstitution with activated T cells do provide opportunities for therapeutic intervention.

Simvastatin protects neurons from cytotoxicity by up-regulating Bcl-2 mRNA and protein

Statins are most commonly prescribed to reduce hypercholesterolemia; however, recent studies have shown that statins have additional benefits, including neuroprotection. Until now, the mechanism underlying statin-induced neuroprotection has been poorly understood. Recent in vivo studies from our lab reported the novel finding that simvastatin increased expression levels of a gene encoding for a major cell survival protein, bcl-2 [Johnson-Anuna et al., J. Pharmacol. Exp. Ther.312 (2005) 786]. The purpose of the present experiments was to determine if simvastatin could protect neurons from excitotoxicity by altering Bcl-2 levels. Neurons were pre-treated with simvastatin and challenged with a compound known to reduce Bcl-2 levels and induce cell death. Simvastatin pre-treatment resulted in a significant reduction in cytotoxicity (lactate dehydrogenase release and caspase 3 activation) following challenge compared with unchallenged neurons. In addition, chronic simvastatin treatment significantly increased Bcl-2 mRNA and protein levels while challenge resulted in a significant reduction in Bcl-2 protein abundance. G3139, an antisense oligonucleotide directed against Bcl-2, abolished the protective effects of simvastatin and eliminated simvastatin-induced up-regulation of Bcl-2 protein. These findings suggest that neuroprotection by simvastatin is dependent on the drug's previously unexplored and important effect of up-regulating Bcl-2.

Mitochondrial damage due to SOD1 deficiency in SH-SY5Y neuroblastoma cells: a rationale for the redundancy of SOD1

Superoxide dismutases (SODs) represent the first line of defense against oxidative stress, which is considered an essential factor in several neurodegenerative diseases and aging. We investigated the role of the copper,zinc superoxide dismutase (SOD1) in the maintenance of intracellular redox homeostasis by analyzing the early effects of SOD1 down-regulation in SH-SY5Y neuroblastoma cells. Through the use of small interference RNA, SOD1 was efficiently down-regulated at 48 h after transfection without any significant effect on cell viability. The steady-state concentration of superoxide was significantly increased after 12 h, when SOD1 was only slightly decreased, and progressively returned to values close to those observed in control cells. The superoxide increase was buffered by the enhanced levels of antioxidant glutathione (GSH); however, GSH increase was not sufficient to avoid damage to proteins in terms of carbonyls. GSH-depleting agents, such as BSO or diamide, further increased protein damage and committed SOD1 deficient cells to death, confirming the pivotal role played by this antioxidant. Although SOD1 declined mostly in the cytosolic compartment, mitochondria were significantly affected with impairment of the mitochondrial transmembrane potential and a decrease in ATP production. Together with these effects carbonylation of mitochondrial proteins was detected and in particular a consistent carbonylation and decrease of the antiapoptotic protein Bcl-2. These conditions induced a high susceptibility of SOD1-depleted cells to treatment with the mitochondrial reactive oxygen species producing agent rotenone. Overall, the results demonstrate that loss of SOD1 leads to severe damage of mitochondria, suggesting an important biological role for this enzyme in the preservation of mitochondrial homeostasis.