Neurodegenerative Process In Amyotrophic Lateral Sclerosis Research Articles

Phrenic Nerve Sonography Alterations in Patients with ALS: Insight with Clinical and Neurophysiological Findings.

Background: Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder, and although the diagnosis is primarily based on clinical criteria, ENMG, as the "gold standard", does not always show detectable changes. Therefore, our study suggests that alterations in echogenicity and heterogeneity of the phrenic nerve (PN) may serve as potential additional diagnostic tools for ALS. Methods: Our study included 32 patients in the ALS group and 64 individuals in the control group. Each participant underwent an interview and completed questionnaires to collect clinical and demographic data, including age, gender, height, body mass index (BMI), hip and waist circumference, duration of illness, ALS-FRS-R score, comorbidities, and medication use. Ultrasound examinations of the PN were performed by two authors using a high-resolution "Philips EPIQ 7" ultrasound machine equipped with a linear 4-18 MHz transducer. The ALS group participants underwent PN sonography and conduction examinations, arterial blood gas (ABG) analysis, respiratory function tests (RFT), and electroneuromyography (ENMG). Results: The study demonstrated that the phrenic nerve is significantly smaller on both sides in patients with ALS compared to the control group (p < 0.01). Changes in the homogeneity and echogenicity of the PN were also observed on both sides. On the right side, 43.8% of the nerves showed heterogeneity, 40.6% were isoechoic, and 21.9% were hyperechoic. On the left side, 59.4% of the nerves exhibited heterogeneity, 34.4% were isoechoic, and 28.1% were hyperechoic. Moreover, sonography on both sides showed significant correlation with ALS-FRS-R, COMPASS-31, and ENMG results. Conclusions: Our study highlights the importance of phrenic nerve ultrasound as a promising supplementary diagnostic tool for ALS. The significant differences in phrenic nerve size, echogenicity, and homogeneity between patients with ALS and the control group demonstrate that ultrasound imaging can detect morphological changes in the phrenic nerve. Incorporating phrenic nerve ultrasound into routine diagnostic protocols could improve early detection, enhance disease monitoring, and offer a more comprehensive understanding of the neurodegenerative processes in ALS.

VEGF expression disparities in brainstem motor neurons of the SOD1G93A ALS model: Correlations with neuronal vulnerability

Amyotrophic lateral sclerosis (ALS) is a rare neuromuscular disease characterized by severe muscle weakness mainly due to degeneration and death of motor neurons. A peculiarity of the neurodegenerative processes is the variable susceptibility among distinct neuronal populations, exemplified by the contrasting resilience of motor neurons innervating the ocular motor system and the more vulnerable facial and hypoglossal motor neurons. The crucial role of vascular endothelial growth factor (VEGF) as a neuroprotective factor in the nervous system is well-established since a deficit of VEGF has been related to motoneuronal degeneration. In this study, we investigated the survival of ocular, facial, and hypoglossal motor neurons utilizing the murine SOD1G93A ALS model at various stages of the disease. Our primary objective was to determine whether the survival of the different brainstem motor neurons was linked to disparate VEGF expression levels in resilient and susceptible motor neurons throughout neurodegeneration. Our findings revealed a selective loss of motor neurons exclusively within the vulnerable nuclei. Furthermore, a significantly higher level of VEGF was detected in the more resistant motor neurons, the extraocular ones. We also examined whether TDP-43 dynamics in the brainstem motor neuron of SOD mice was altered. Our data suggests that the increased VEGF levels observed in extraocular motor neurons may potentially underlie their resistance during the neurodegenerative processes in ALS in a TDP-43-independent manner. Our work might help to better understand the underlying mechanisms of selective vulnerability of motor neurons in ALS.

Glymphatic dysfunction in patients with early-stage amyotrophic lateral sclerosis.

Recently, an astrocytic aquaporin 4-dependent drainage system, that is, the glymphatic system, has been identified in the live murine and human brain. Growing evidence suggests that glymphatic function is impaired in patients with several neurodegenerative diseases, including Alzheimer's and Parkinson's disease. As the third most common neurodegenerative disease, although animal studies have indicated that early glymphatic dysfunction is likely an important pathological mechanism underpinning amyotrophic lateral sclerosis (ALS), no available study has been conducted to thoroughly assess glymphatic function in vivo in ALS patients to date, particularly in patients with early-stage ALS. Thus, using diffusion tensor imaging analysis along the perivascular space (ALPS) index, an approximate measure of glymphatic function in vivo, we aimed to explore whether glymphatic function is impaired in patients with patients with early-stage ALS, and the diagnostic performance of the ALPS index in distinguishing between patients with early-stage ALS and healthy subjects. We also aimed to identify the relationships between glymphatic dysfunction and clinical disabilities and sleep problems in patients with early-stage ALS. In this retrospective study, King's Stage 1 ALS patients were defined as patients with early-stage ALS. We enrolled 56 patients with early-stage ALS and 32 age- and sex-matched healthy control subjects. All participants completed clinical screening, sleep assessment and ALPS index analysis. For the sleep assessment, the Pittsburgh Sleep Quality Index, Epworth Sleepiness Scale and polysomnography were used. Compared with healthy control subjects, patients with early-stage ALS had a significantly lower ALPS index after family-wise error correction (P < 0.05). Moreover, receiver operating characteristic analysis showed that the area under the curve for the ALPS index was 0.792 (95% confidence interval 0.700-0.884). Partial correlation analyses showed that the ALPS index was significantly correlated with clinical disability and sleep disturbances in patients with early-stage ALS. Multivariate analysis showed that sleep efficiency (r = 0.419, P = 0.002) and periodic limb movements in sleep index (r = -0.294, P = 0.017) were significant predictive factors of the ALPS index in patients with early-stage ALS. In conclusion, our study continues to support an important role for glymphatic dysfunction in ALS pathology, and we provide additional insights into the early diagnostic value of glymphatic dysfunction and its correlation with sleep disturbances in vivo in patients with early-stage ALS. Moreover, we suggest that early improvement of glymphatic function may be a promising strategy for slowing the neurodegenerative process in ALS. Future studies are needed to explore the diagnostic and therapeutic value of glymphatic dysfunction in individuals with presymptomatic-stage neurodegenerative diseases.

Different saccadic profile in bulbar versus spinal-onset amyotrophic lateral sclerosis.

Two clinical phenotypes characterize the onset of amyotrophic lateral sclerosis (ALS): the spinal variant, with symptoms beginning in the limbs, and the bulbar variant, affecting firstly speech and swallowing. The two variants show some distinct features in the histopathology, localization and prognosis, but to which extent they really differ clinically and pathologically remains to be clarified. Recent neuropathological and neuroimaging studies have suggested a broader spreading of the neurodegenerative process in ALS, extending beyond the motor areas, toward other cortical and deep grey matter regions, many of which are involved in visual processing and saccadic control. Indeed, a wide range of eye movement deficits have been reported in ALS, but they have never been used to distinguish the two ALS variants. Since quantifying eye movements is a very sensitive and specific method for the study of brain networks, we compared different saccadic and visual search behaviours across spinal ALS patients (n = 12), bulbar ALS patients (n = 6) and healthy control subjects (n = 13), along with cognitive and MRI measures, with the aim to define more accurately the two patients subgroups and possibly clarify a different underlying neural impairment. We found separate profiles of visually-guided saccades between spinal (short saccades) and bulbar (slow saccades) ALS, which could result from the pathologic involvement of different pathways. We suggest an early involvement of the parieto-collicular-cerebellar network in spinal ALS and the fronto-brainstem circuit in bulbar ALS. Overall, our data confirm the diagnostic value of the eye movements analysis in ALS and add new insight on the involved neural networks.

Relaxation-weighted 23Na magnetic resonance imaging maps regional patterns of abnormal sodium concentrations in amyotrophic lateral sclerosis.

Objectives:Multiparametric magnetic resonance imaging (MRI) is established as a technical instrument for the characterisation of patients with amyotrophic lateral sclerosis (ALS). The contribution of relaxation-weighted sodium (23NaR) MRI remains to be defined. The aim of this study is to apply 23NaR MRI to investigate brain sodium homeostasis and map potential alterations in patients with ALS as compared with healthy controls.Materials and Methods:Seventeen patients with ALS (mean age 61.1 ± 11.4 years, m/f = 9/8) and 10 healthy control subjects (mean age 60.3 ± 15.3 years, m/f = 6/4) were examined by 23NaR MRI at 3 T. Regional sodium maps were obtained by the calculation of the weighted difference from two image data sets with different echo times (TE1 = 0.3 ms, TE2 = 25 ms). Voxel-based analysis of the relaxation-weighted maps, together with 23Na concentration maps for comparison, was performed.Results:ROI-based analyses of relaxation-weighted brain sodium concentration maps demonstrated increased sodium concentrations in the upper corticospinal tracts and in the frontal lobes in patients with ALS; no differences between ALS patients and controls were found in reference ROIs, where no involvement in ALS-associated neurodegeneration could be anticipated.Conclusion:23NaR MRI mapped regional alterations within disease-relevant areas in ALS which correspond to the stages of the central nervous system (CNS) pathology, providing evidence that the technique is a potential biological marker of the cerebral neurodegenerative process in ALS.

Necroptotic neuronal cell death in amyotrophic lateral sclerosis: A relevant hypothesis with potential therapeutic implication?

Necroptosis is emerging among possible mechanisms underlying cell death in neurodegenerative diseases. In this line, we hypothesize that necroptosis might be implicated in neuronal cell death in amyotrophic lateral sclerosis (ALS). To support this hypothesis, we hereby provide pilot data as well as some findings from the literature about the expression of key markers of the necroptotic pathway in ALS. Our preliminary data indicate the upregulation of key markers of necroptosis activation in lower motor neurons of the spinal cord. These human-derived data combined with some clinical and preclinical findings support our hypothesis testing the involvement of necroptosis in lower motor neurons death in ALS patients. These results pave the way to deepen the role of necroptosis in ALS using both preclinical and clinical approaches. If confirmed, this hypothesis might raise new interventional strategies to alleviate neurodegenerative process in ALS.

Implications of Selective Autophagy Dysfunction for ALS Pathology.

Amyotrophic lateral sclerosis (ALS) is a lethal neurodegenerative disorder that progressively affects motor neurons in the brain and spinal cord. Due to the biological complexity of the disease, its etiology remains unknown. Several cellular mechanisms involved in the neurodegenerative process in ALS have been found, including the loss of RNA and protein homeostasis, as well as mitochondrial dysfunction. Insoluble protein aggregates, damaged mitochondria, and stress granules, which contain RNA and protein components, are recognized and degraded by the autophagy machinery in a process known as selective autophagy. Autophagy is a highly dynamic process whose dysregulation has now been associated with neurodegenerative diseases, including ALS, by numerous studies. In ALS, the autophagy process has been found deregulated in both familial and sporadic cases of the disease. Likewise, mutations in genes coding for proteins involved in the autophagy machinery have been reported in ALS patients, including selective autophagy receptors. In this review, we focus on the role of selective autophagy in ALS pathology.

Exosomal Transport and Progression of Neurodegeneration in Amyotrophic Lateral Sclerosis

In recent years, increasing attention has been paid to the study of the communication between cells in the nervous system with extracellular vesicles, including exosomes, under physiological and pathological conditions. Exosomes are small extracellular vesicles ranging in size from 50 to 200 nm, which are secreted by most cell types and provide communication between cells by transporting proteins, lipids, and RNA to target cells. In addition, they perform antigen-presenting and signaling functions and can act as anti-inflammatory or pro-inflammatory agents. Data has been accumulated on the role of exosomes in the development of the pathological process in nervous system diseases, primarily brain tumors and neurodegenerative diseases. Amyotrophic lateral sclerosis (ALS) is a progressive fatal disease in which the selective death of motor neurons occurs. ALS inevitably leads to disruption of the functioning of muscles that perform vital functions and death of the patient in several years. The mechanisms that underlie the death of motor neurons and the spread of the pathological process are not clear. It is impossible to predict the rate of disease progression and the probable life expectancy of the patient. The most important mechanisms of AS development include the accumulation of aggregates of pathological proteins in neuronal bodies and impaired RNA metabolism. The possibility of transfer of pathological proteins and other molecules associated with the development of ALS through exosomes has been proven. This review provides an overview of studies on exosomes in different CNS diseases. The mechanisms of progression and spreading of the neurodegenerative process in ALS are discussed, focusing on the roles that exosomes and potential biomarkers of the disease in the exosomal fraction play.

Decreased glutathione levels cause overt motor neuron degeneration in hSOD1WT over-expressing mice

Mutations in Cu/Zn-superoxide dismutase (SOD1) cause familial forms of amyotrophic lateral sclerosis (ALS), a fatal disorder characterized by the progressive loss of motor neurons. Several lines of evidence have shown that SOD1 mutations cause ALS through a gain of a toxic function that remains to be fully characterized. A significant share of our understanding of the mechanisms underlying the neurodegenerative process in ALS comes from the study of rodents over-expressing ALS-linked mutant hSOD1. These mutant hSOD1 models develop an ALS-like phenotype. On the other hand, hemizygous mice over-expressing wild-type hSOD1 at moderate levels (hSOD1WT, originally described as line N1029) do not develop paralysis or shortened life-span. To investigate if a decrease in antioxidant defenses could lead to the development of an ALS-like phenotype in hSOD1WT mice, we used knockout mice for the glutamate-cysteine ligase modifier subunit [GCLM(−/−)]. GCLM(−/−) mice are viable and fertile but display a 70–80% reduction in total glutathione levels. GCLM(−/−)/hSOD1WT mice developed overt motor symptoms (e.g. tremor, loss of extension reflex in hind-limbs, decreased grip strength and paralysis) characteristic of mice models over-expressing ALS-linked mutant hSOD1. In addition, GCLM(−/−)/hSOD1WT animals displayed shortened life span. An accelerated decrease in the number of large neurons in the ventral horn of the spinal cord and degeneration of spinal root axons was observed in symptomatic GCLM(−/−)/hSOD1WT mice when compared to age-matched GCLM(+/+)/hSOD1WT mice. Our results show that under conditions of chronic decrease in glutathione, moderate over-expression of wild-type SOD1 leads to overt motor neuron degeneration, which is similar to that induced by ALS-linked mutant hSOD1 over-expression.

Subcortical structures in amyotrophic lateral sclerosis

The aim of this study was to assess the involvement of deep gray matter, hippocampal subfields, and ventricular changes in patients with amyotrophic lateral sclerosis (ALS). A total of 112 ALS patients and 60 healthy subjects participated. High-resolution T1-weighted images were acquired using a 3T MRI scanner. Thirty-nine patients underwent a follow-up scan. Volumetric and shape analyses of subcortical structures were performed, measures were correlated with clinical parameters, and longitudinal changes were assessed. At baseline, reduced hippocampal volumes (left: p = 0.007; right: p = 0.011) and larger inferior lateral ventricles (left: p = 0.013; right: p = 0.041) were found in patients compared to healthy controls. Longitudinal analyses demonstrated a significant decrease in volume of the right cornu ammonis 2/3 and 4/dentate gyrus and left presubiculum (p = 0.002, p = 0.045, p < 0.001), and a significant increase in the ventricular volume in the lateral (left: p < 0.001; right: p < 0.001), 3rd (p < 0.001) and 4th (p = 0.001) ventricles. Larger ventricles were associated with a lower ALSFRS-R score (p = 0.021). In conclusion, ALS patients show signs of neurodegeneration of subcortical structures and ventricular enlargement. Subcortical involvement is progressive and correlates with clinical parameters, highlighting its role in the neurodegenerative process in ALS.

Collapsin Response Mediator Protein 4a (CRMP4a) Is Upregulated in Motoneurons of Mutant SOD1 Mice and Can Trigger Motoneuron Axonal Degeneration and Cell Death

Embryonic motoneurons from mutant SOD1 (mSOD1) mouse models of amyotrophic lateral sclerosis (ALS), but not wild-type motoneurons, can be triggered to die by exposure to nitric oxide (NO), leading to activation of a motoneuron-specific signaling pathway downstream of the death receptor Fas/CD95. To identify effectors of mSOD1-dependent cell death, we performed a proteomic analysis. Treatment of cultured mSOD1 motoneurons with NO led to a 2.5-fold increase in levels of collapsin response mediator protein 4a (CRMP4a). In vivo, the percentage of mSOD1 lumbar motoneurons expressing CRMP4 in mSOD1 mice increased progressively from presymptomatic to early-onset stages, reaching a maximum of 25%. Forced adeno-associated virus (AAV)-mediated expression of CRMP4a in wild-type motoneurons in vitro triggered a process of axonal degeneration and cell death affecting 60% of motoneurons, whereas silencing of CRMP4a in mSOD1 motoneurons protected them from NO-induced death. In vivo, AAV-mediated overexpression of CRMP4a but not CRMP2 led to the death of 30% of the lumbar motoneurons and an 18% increase in denervation of neuromuscular junctions in the gastrocnemius muscle. Our data identify CRMP4a as a potential early effector in the neurodegenerative process in ALS.

Decreased Cystatin C Immunoreactivity in Spinal Motor Neurons and Astrocytes in Amyotrophic Lateral Sclerosis

Cystatin C (CC), a cysteine protease inhibitor involved in protein degradation, is a marker of Bunina bodies in lower motor neurons in amyotrophic lateral sclerosis (ALS). TAR-DNA binding protein-43 (TDP-43)-immunoreactive inclusions are also histological hallmarks of ALS but whether CC is found in motor neurons with or without TDP-43-positive inclusions in ALS is not known. To determine whether inclusion body formation affects cytoplasmic CC immunoreactivity, we examined spinal cords from 9 ALS patients and 12 control subjects by immunohistochemistry. Most anterior horn cells (AHCs) showed moderate to intense immunoreactivity in controls, whereas CC immunoreactivity was markedly decreased in AHCs in ALS cases. The proportion of CC-immunolabeled AHCs was reduced regardless of whether they contained Bunina bodies. In contrast, the proportion of CC-immunolabeled AHCs was significantly reduced in those with TDP-43 inclusions. Cystatin C immunoreactivity of astrocytes in the spinal gray matter and white matter in ALS was significantly decreased compared with controls. These findings suggest that the formation of TDP-43 inclusions, but not of Bunina bodies, may be linked to the content of CC in spinal motor neurons and that perturbations in endogenous levels of CC in neuronal and glial cells may be part of the neurodegenerative processes in ALS.

Ablation of Proliferating Microglia Does Not Affect Motor Neuron Degeneration in Amyotrophic Lateral Sclerosis Caused by Mutant Superoxide Dismutase

Microglial activation is a hallmark of all neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). Here, a detailed characterization of the microglial cell population within the spinal cord of a mouse model of familial ALS was performed. Using flow cytometry, we detected three distinct microglial populations within the spinal cord of mice overexpressing mutant superoxide dismutase (SOD1): mature microglial cells (CD11b(+), CD45(low)), myeloid precursor cells (CD11b(+), CD45(int)), and macrophages (CD11b(+), CD45(high)). Characterization of cell proliferation within the CNS of SOD1(G93A) mice revealed that the expansion in microglial cell population is mainly attributable to the proliferation of myeloid precursor cells. To assess the contribution of proliferating microglia in motor neuron degeneration, we generated CD11b-TK(mut-30); SOD1(G93A) doubly transgenic mice that allow the elimination of proliferating microglia on administration of ganciclovir. Surprisingly, a 50% reduction in reactive microglia specifically in the lumbar spinal cord of CD11b-TK(mut-30); SOD1(G93A) doubly transgenic mice had no effect on motor neuron degeneration. This suggests that proliferating microglia-expressing mutant SOD1 are not central contributors of the neurodegenerative process in ALS caused by mutant SOD1.

Mutant Cu/Zn-Superoxide Dismutase Associated with Amyotrophic Lateral Sclerosis Destabilizes Vascular Endothelial Growth Factor mRNA and Downregulates Its Expression

Vascular endothelial growth factor (VEGF) plays a neuroprotective role in mice harboring mutations of copper-zinc superoxide dismutase 1 (SOD1) in familial amyotrophic lateral sclerosis (ALS). Conversely, the loss of VEGF expression through genetic depletion can give rise to a phenotype resembling ALS independent of SOD1 mutations. Here, we observe a profound downregulation of VEGF mRNA expression in spinal cords of G93A SOD1 mice that occurred early in the course of the disease. Using an in vitro culture model of glial cells expressing mutant SOD1, we demonstrate destabilization and downregulation of VEGF RNA with concomitant loss of protein expression that correlates with level of transgene expression. Using a luciferase reporter assay, we show that this molecular effect is mediated through a portion of the VEGF 3'-untranslated region (UTR) that harbors a class II adenylate/uridylate-rich element. Other mutant forms of SOD1 produced a similar negative effect on luciferase RNA and protein expression. Mobility shift assay with a VEGF 3'-UTR probe reveals an aberrantly migrating complex that contains mutant SOD1. We further show that the RNA stabilizing protein, HuR (human antigen R), is translocated from nucleus to cytoplasm in mutant SOD1 cells in vitro and mouse motor neurons in vivo. In summary, our data suggest that mutant SOD1 gains a novel function, possibly by altering the ribonucleoprotein complex with the VEGF 3'-UTR. We postulate that the resultant dysregulation of VEGF posttranscriptional processing critically reduces the level of this neuroprotective growth factor and accelerates the neurodegenerative process in ALS.

Update on the glutamatergic neurotransmitter system and the role of excitotoxicity in amyotrophic lateral sclerosis.

Excitotoxicity may play a role in certain disorders of the motor system thought to be caused by environmentally acquired toxins, including lathyrism and domoic acid poisoning. Motor neurons appear to be particularly susceptible to toxicity mediated via alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-kainate receptors. There is a body of evidence implicating glutamatergic toxicity as a contributory factor in the selective neuronal injury occurring in amyotrophic lateral sclerosis (ALS). Interference with glutamate-mediated toxicity is so far the only neuroprotective therapeutic strategy that has shown benefit in terms of slowing disease progression in ALS patients. Biochemical studies have shown decreased glutamate levels in central nervous system (CNS) tissue and increased levels in the cerebrospinal fluid (CSF) of ALS patients. CSF from ALS patients is toxic to neurons in culture, apparently via a mechanism involving AMPA receptor activation. There is evidence for altered expression and function of glial glutamate transporters in ALS, particularly excitatory amino acid transporter 2 (EAAT2). Abnormal splice variants of EAAT2 have been detected in human CNS. Mitochondrial dysfunction may contribute to excitotoxicity in ALS. Induction of neuronal nitric oxide synthase and cyclooxygenase 2 in ALS may also lead to significant interactions with regulation of the glutamate transmitter system. Certain features of motor neurons may predispose them to the neurodegenerative process in ALS, such as the cell size, mitochondrial activity, neurofilament content, and relative lack of certain calcium-binding proteins and molecular chaperones. Motor neurons appear vulnerable to toxicity mediated by calcium-permeable AMPA receptors. The relatively low expression of the glutamate receptor 2 (GluR2) AMPA receptor subunit and the high current density caused by the large number and density of cell surface AMPA receptors are potentially important factors that may predispose to such toxicity.

Cognitive dysfunction in patients with amyotrophic lateral sclerosis is associated with spherical or crescent-shaped ubiquitinated intraneuronal inclusions in the parahippocampal gyrus and amygdala, but not in the neostriatum.

Skeins or skein-like inclusions, one of the two types of ubiquitinated intraneuronal inclusions in amyotrophic lateral sclerosis (ALS), in the neostriatum are not specific to the disease, but it has not yet been determined whether the other, spherical or crescent-shaped inclusions (SCI) are pathognomonic. To clarify this and also to investigate whether the distribution of SCI in particular brain regions is associated with clinical parameters, we examined the occurrence of SCI in the brains of 24 patients with ALS and 94 controls. SCI in the neostriatum were specifically detected in 54% of the ALS cases, but not in any of the controls. No apparent phenotypic denominator, such as disease duration or the occurrence of dementia, correlated to the distribution of SCI in the neostriatum in ALS cases. On the other hand, the occurrence of SCI in both the second and third layers of the parahippocampal gyrus and amygdala was significantly correlated to the presence of dementia in ALS cases. SCI were distributed in association with each other among the parahippocampal gyrus, dentate gyrus of the hippocampus and amygdala, but not between the spinal anterior horn and any non-motor-associated brain regions. These findings suggest that these particular brain regions might be significantly involved in the neurodegenerative process associated with ALS. The relationship of SCI to either ALS pathogenesis or cognitive dysfunction depends on the brain regions in which they are distributed, and this indicates that the neurodegenerative processes in ALS proceed differentially in particular motor-associated and nonmotor-associated brain regions.

Increased expression of the pro‐inflammatory enzyme cyclooxygenase‐2 in amyotrophic lateral sclerosis

Mutations in the copper/zinc superoxide dismutase (mSOD1) gene are associated with a familial form of amyotrophic lateral sclerosis (ALS), and their expression in transgenic mice produces an ALS-like syndrome. Recent observations suggest a role for inflammatory-related events in the progression and propagation of the neurodegenerative process in ALS. Consistent with this view, the present study demonstrates that, during the course of the disease, the expression of cyclooxygenase type 2 (Cox-2), a key enzyme in the synthesis of prostanoids, which are potent mediators of inflammation, is dramatically increased. In both early symptomatic and end-stage transgenic mSOD1 mice, neurons and, to a lesser extent, glial cells in the anterior horn of the spinal cord exhibit robust Cox-2 immunoreactivity. Cox-2 mRNA and protein levels and catalytic activity are also significantly increased in the spinal cord of the transgenic mSOD1 mice. The time course of the spinal cord Cox-2 upregulation parallels that of motor neuronal loss in transgenic mSOD1 mice. We also show that Cox-2 activity is dramatically increased in postmortem spinal cord samples from sporadic ALS patients. We speculate that Cox-2 upregulation, through its pivotal role in inflammation, is instrumental in the ALS neurodegenerative process and that Cox-2 inhibition may be a valuable therapeutic avenue for the treatment of ALS. Ann Neurol 2001;49:176–185

Increased expression of the pro-inflammatory enzyme cyclooxygenase-2 in amyotrophic lateral sclerosis

Mutations in the copper/zinc superoxide dismutase (mSOD1) gene are associated with a familial form of amyotrophic lateral sclerosis (ALS), and their expression in transgenic mice produces an ALS-like syndrome. Recent observations suggest a role for inflammatory-related events in the progression and propagation of the neurodegenerative process in ALS. Consistent with this view, the present study demonstrates that, during the course of the disease, the expression of cyclooxygenase type 2 (Cox-2), a key enzyme in the synthesis of prostanoids, which are potent mediators of inflammation, is dramatically increased. In both early symptomatic and end-stage transgenic mSOD1 mice, neurons and, to a lesser extent, glial cells in the anterior horn of the spinal cord exhibit robust Cox-2 immunoreactivity. Cox-2 mRNA and protein levels and catalytic activity are also significantly increased in the spinal cord of the transgenic mSOD1 mice. The time course of the spinal cord Cox-2 upregulation parallels that of motor neuronal loss in transgenic mSOD1 mice. We also show that Cox-2 activity is dramatically increased in postmortem spinal cord samples from sporadic ALS patients. We speculate that Cox-2 upregulation, through its pivotal role in inflammation, is instrumental in the ALS neurodegenerative process and that Cox-2 inhibition may be a valuable therapeutic avenue for the treatment of ALS.

Increased oxidative damage to DNA in ALS patients

Although the cause of amyotrophic lateral sclerosis (ALS) is unknown, substantial evidence indicates that oxidative toxicity is associated with neuronal death in this disease. We examined levels of a well-established marker of oxidative damage to DNA, 8-hydroxy-2′-deoxyguanosine (8OH2′dG) in plasma, urine, and cerebrospinal fluid (CSF) at a single time point from subjects with ALS, other neurological diseases, or no known disorders. We also measured the rate of change of 8OH2′dG levels in plasma and urine from ALS and in urine from control subjects over 9 months and examined the relationship to disease severity. In each fluid, 8OH2′dG levels were significantly elevated in the ALS group as compared to control subjects. In all subjects, the plasma and CSF 8OH2′dG levels increased with age, providing further evidence for a role of oxidative damage in normal aging. Plasma and urine 8OH2′dG levels increased significantly with time in the ALS group only. The rate of increase in urine 8OH2′dG levels with time was significantly correlated with disease severity. These findings are consistent with the hypothesis that oxidative pathology accompanies the neurodegenerative process in ALS and suggest that 8OH2′dG may provide a useful tool for monitoring therapeutic interventions in this disease.

Mitochondrial DNA deletion mutation levels are elevated in ALS brains.

This study was performed to explore the potential role of mitochondrial DNA mutations in the neurodegenerative process in amyotrophic lateral sclerosis (ALS). Using a semi-quantitative assay, a common mitochondrial DNA deletion mutation (mt DNA4977) was assayed in brain tissue obtained from six sporadic ALS patients and compared to four controls. In each brain, levels of this mutation were measured in a brain region affected by neurodegeneration, the motor cortex (Brodmann area 4), and compared to the temporal cortex (Brodmann area 17). In the ALS but not control brains, levels of mt DNA4977 were an average of more than 30-fold (range 15-250) higher in Brodmann area 4. These results support and extend those of previous studies implying that mitochondria may participate in the neurodegenerative process in ALS.