Reduction of lower motor neuron degeneration in wobbler mice by N-acetyl-L-cysteine

N-acetylcysteine treatment attenuates hemodialysis access-related limb pathophysiology in mice with chronic kidney disease

The objective of the present study was to determine if treatment with N-acetylcysteine (NAC) could reduce access-related limb dysfunction in mice. Male and female C57BL6J mice were fed an adenine-supplemented diet to induce chronic kidney disease (CKD) prior to the surgical creation of an arteriovenous fistula (AVF) in the iliac vascular bundle. AVF creation significantly increased peak aortic and infrarenal vena cava blood flow velocities, but NAC treatment had no significant impact, indicating that fistula maturation was not impacted by NAC treatment. Hindlimb muscle and paw perfusion recovery and muscle capillary density in the AVF limb were unaffected by NAC treatment. However, NAC treatment significantly increased the mass of the tibialis anterior (P = 0.0120) and soleus (P = 0.0452) muscles post-AVF. There was a significant main effect of NAC treatment on hindlimb grip strength at postoperative day 12 (POD 12) (P = 0.0003), driven by significantly higher grip strength in both male (P = 0.0273) and female (P = 0.0031) mice treated with NAC. There was also a significant main effect of NAC treatment on the walking speed at postoperative day 12 (P = 0.0447), and post hoc testing revealed an improvement in NAC-treated male mice (P = 0.0091). The area of postsynaptic acetylcholine receptors (P = 0.0263) and motor endplates (P = 0.0240) was also increased by NAC treatment. Interestingly, hindlimb skeletal muscle mitochondrial oxidative phosphorylation trended higher in NAC-treated female mice but was not statistically significant (P = 0.0973). Muscle glutathione levels and redox status were not significantly impacted by NAC treatment in either sex. In summary, NAC treatment attenuated some aspects of neuromotor pathology in mice with chronic kidney disease following AVF creation.NEW & NOTEWORTHY Hemodialysis via autogenous arteriovenous fistula (AVF) is the preferred first-line modality for renal replacement therapy in patients with end-stage kidney disease. However, patients undergoing AVF surgery frequently experience a spectrum of hand disability symptoms postsurgery including weakness and neuromotor dysfunction. Unfortunately, no treatment is currently available to prevent or mitigate these symptoms. Here, we provide evidence that daily N-acetylcysteine supplementation can attenuate some aspects of limb neuromotor function in a preclinical mouse model of AVF.

ROS scavengers decrease γH2ax spots in motor neuronal nuclei of ALS model mice in vitro

Background: Amyotrophic lateral sclerosis (ALS) is an incurable neurodegenerative disease characterized by the loss of motor neurons in cerebral cortex, brainstem and spinal cord. Numerous studies have demonstrated signs of oxidative stress in postmortem neuronal tissue, cerebrospinal fluid, plasma and urine of ALS patients, without focusing on the specific processes within motor neurons. Thus, we aimed to investigate the relevance of reactive oxygen species (ROS) detoxification mechanisms and its consequences on the formation of toxic/lethal DNA double strand breaks (DSBs) in the ALS model of the Wobbler mouse.

Methods: Live cell imaging in dissociated motor neuronal cultures was used to investigate the production of ROS using Dihydroethidium (DHE). The expression levels of ROS detoxifying molecules were investigated by qPCR as well as Western blots. Furthermore, the expression levels of DNA damage response proteins p53bp1 and H2ax were investigated using qPCR and immunofluorescence staining. Proof-of-principle experiments using ROS scavengers were performed in vitro to decipher the influence of ROS on the formation of DNA double strand breaks quantifying the γH2ax spots formation.

Results: Here, we verified an elevated ROS-level in spinal motor neurons of symptomatic Wobbler mice in vitro. As a result, an increased number of DNA damage response proteins p53bp1 and γH2ax in dissociated motor neurons of the spinal cord of Wobbler mice was observed. Furthermore, we found a significantly altered expression of several antioxidant molecules in the spinal cord of Wobbler mice, suggesting a deficit in ROS detoxification mechanisms. This hypothesis could be verified by using ROS scavenger molecules in vitro to reduce the number of γH2ax foci in dissociated motor neurons and thus counteract the harmful effects of ROS.

Conclusion: Our data indicate that maintenance of redox homeostasis may play a key role in the therapy of the neurodegenerative disease ALS. Our results underline a necessity for multimodal treatment approaches to prolong the average lifespan of motor neurons and thus slow down the progression of the disease, since a focused intervention in one pathomechanism seems to be insufficient in ALS therapy.

Oxidative stress: the lowest common denominator of multiple diseases

Oxygen is essential to the human life and life of all aerobic organisms. The complete oxidation of nutrients for the biological energy supply is one of the most important prerequisites for the formation of higher life forms. However, cells that benefit from oxidative respiration also suffer from reactive oxygen species because they adapted to oxygen as an energy source. Healthy cells balance the formation and elimination of reactive oxygen species thereby creating and keeping reactive oxygen species-homeostasis. When the concentration of free radicals exceeds a critical level and homeostasis is disturbed, oxidative stress occurs leading to damage of multiple cellular molecules and compartments. Therefore, oxidative stress plays an important role in the physiology and pathology of various diseases. Often, the antioxidant protection system becomes pathologically unbalanced in the genesis of several diseases, leading to functional losses of the organism, as in the case of amyotrophic lateral sclerosis, or cells develop metabolic mechanisms to use this system as protection against external influences, such as in the case of glioblastoma cells. Either way, understanding the underlying deregulated mechanisms of the oxidative protection system would allow the development of novel treatment strategies for various diseases. Thus, regardless of the direction in which the reactive oxygen species-homeostasis disequilibrate, the focus should be on the oxidative protection system.

The effect of n-acetyl-cysteine on recovery of the facial nerve after crush injury

OBJECTIVE

Facial nerve dysfunction can vary in severity and recovery is dependent on the character of the injury. N-acetyl-cysteine prevents oxidative stress and cellular damage, and its use in the setting of nerve dysfunction from crush injury has not yet been established. In this study, rats with facial nerve crush injury will be treated with n-acetyl-cysteine or control and functional recovery and electrophysiologic outcome will be compared.

STUDY DESIGN

Prospective, randomized animal study.

METHODS

Twenty-four Wistar rats underwent unilateral facial nerve crush injury. Rats were implanted with a subcutaneous osmotic pump filled with saline (n = 12) or n-acetyl-cysteine 50 mg/kg/day (n = 12). Functional and electromyographic recovery was recorded at two and four weeks postoperatively.

RESULTS

When compared to untreated rats, n-acetyl-cysteine treated rats had a greater electromyography amplitude recovery at 2 weeks with regard to eye blink (p=0.006) but not vibrissae function. At four weeks, the electromyography amplitude recovery of the vibrissae function was greater in n-acetyl-cysteine treated rats (P=0.001), but the amplitude recovery difference in eye blink was only marginally significant between groups (p=0.07). The functional score was higher in n-acetyl-cysteine-treated rats than in untreated rats at all of the time points.

CONCLUSION

This study demonstrated that n-acetyl-cysteine facilitated facial nerve recovery with improved functional and electromyography outcomes in the setting of crush injury.

LEVEL OF EVIDENCE

NA.

Impact of 30-Day Oral Dosing with N-acetyl-l-cysteine on Sprague-Dawley Rat Physiology

A number of studies have demonstrated a protective effect associated with N-acetyl-l-cysteine (NAC) against toxic chemical exposure. However, the impact of long-term oral dosing on tissue pathology has not been determined. In this study, the authors assessed the impact of long-term oral NAC administration on organ histopathology and tissue glutathione (GSH) and total glutathione- S-transferase (GST) activity levels in Sprague-Dawley (SD) rats. Groups of 20 SD rats (10 males, 10 females), 8 weeks of age, were dosed daily by oral gavage with deionized H2O (negative controls) or NAC solution at a rate of 600 or 1200 mg/kg/day for 30 days. Animals were euthanized 6 h after treatment on study day 30. There were no significant differences in final body weights or weekly average weight gain between treatment groups. Serum alanine amino-transferase (ALT) activities were significantly elevated ( p ≤.05) in NAC-treated animals compared to controls when measured on study day 30. Histopathologic evaluation of the stomach, small intestine, liver, kidneys, spleen, thymus, and lungs revealed no lesions associated with NAC administration. When measured on study day 30, total GST activity for kidney and skin from NAC-treated animals were increased 39% to 131% as compared to controls. Tissue GSH concentrations from NAC-treated animals were increased 24% to 81% as compared with negative controls. Further studies are needed to determine if the observed increase in tissue GSH concentration and GST activity provide a degree of chemoprotection against dermal and systemic chemical toxicants.

Abnormal mitochondrial transport and morphology as early pathological changes in human models of spinal muscular atrophy

Spinal muscular atrophy (SMA), characterized by specific degeneration of spinal motor neurons, is caused by mutations in the survival of motor neuron 1, telomeric (SMN1) gene and subsequent decreased levels of functional SMN. How the deficiency of SMN, a ubiquitously expressed protein, leads to spinal motor neuron-specific degeneration in individuals affected by SMA remains unknown. In this study, we examined the role of SMN in mitochondrial axonal transport and morphology in human motor neurons by generating SMA type 1 patient-specific induced pluripotent stem cells (iPSCs) and differentiating these cells into spinal motor neurons. The initial specification of spinal motor neurons was not affected, but these SMA spinal motor neurons specifically degenerated following long-term culture. Moreover, at an early stage in SMA spinal motor neurons, but not in SMA forebrain neurons, the number of mitochondria, mitochondrial area and mitochondrial transport were significantly reduced in axons. Knocking down of SMN expression led to similar mitochondrial defects in spinal motor neurons derived from human embryonic stem cells, confirming that SMN deficiency results in impaired mitochondrial dynamics. Finally, the application of N-acetylcysteine (NAC) mitigated the impairment in mitochondrial transport and morphology and rescued motor neuron degeneration in SMA long-term cultures. Furthermore, NAC ameliorated the reduction in mitochondrial membrane potential in SMA spinal motor neurons, suggesting that NAC might rescue apoptosis and motor neuron degeneration by improving mitochondrial health. Overall, our data demonstrate that SMN deficiency results in abnormal mitochondrial transport and morphology and a subsequent reduction in mitochondrial health, which are implicated in the specific degeneration of spinal motor neurons in SMA.

Experimental and clinical evidence for the protective role of progesterone in motoneuron degeneration and neuroinflammation

Far beyond its role in reproduction, progesterone exerts neuro-protective, promyelinating, and anti-inflammatory effects in the nervous system. These effects are amplified under pathological conditions, implying that changes of the local environment sensitize nervous tissues to steroid therapy. The present survey covers our results of progesterone neuroprotection in a motoneuron neurodegeneration model and a neuroinflammation model. In the degenerating spinal cord of the Wobbler mouse, progesterone reverses the impaired expression of neurotrophins, increases enzymes of neurotransmission and metabolism, prevents oxidative damage of motoneurons and their vacuolar degeneration (paraptosis), and attenuates the development of mitochondrial abnormalities. After long-term treatment, progesterone also increases muscle strength and the survival of Wobbler mice. Subsequently, this review describes the effects of progesterone in mice with induced experimental autoimmune encephalomyelitis (EAE), a commonly used model of multiple sclerosis. In EAE mice, progesterone attenuates the clinical severity, decreases demyelination and neuronal dysfunction, increases axonal counts, reduces the formation of amyloid precursor protein profiles, and decreases the aberrant expression of growth-associated proteins. These actions of progesterone may be due to multiple mechanisms, considering that classic nuclear receptors, extranuclear receptors, and membrane receptors are all expressed in the spinal cord. Although many aspects of progesterone action in humans remain unsolved, data provided by experimental models makes getting to this objective closer than previously expected.

Protective effect of antioxidants on DNA damage in leukocytes from X-linked adrenoleukodystrophy patients

Toxic metabolites accumulation and oxidative stress have been associated to the pathophysiology of X-linked adrenoleukodystrophy (X-ALD), an inborn error of peroxisome metabolism. Parameters of oxidative damage to proteins and lipids in X-ALD patients were already described in literature; however, DNA injuries were not studied yet. Considering that, the aims were to investigate DNA damage by comet assay in heterozygotes and symptomatic X-ALD patients, to look for associations between DNA damage and lipid peroxidation as measured by urinary 15-F2t-isoprostane; and to evaluate the in vitro effect of N-acetyl-l-cysteine (NAC), trolox (TRO) and rosuvastatin (RSV) on DNA damage in leukocytes from symptomatic patients. Symptomatic patients presented higher DNA damage levels than those found in heterozygotes and controls; heterozygotes and controls showed similar results. In order to investigate the in vitro antioxidant effect on DNA damage, whole blood cells from symptomatic patients were incubated with NAC (1 and 2.5mM), TRO (25 and 75 μM) and RSV (0.5, 2 and 5 μM) before DNA damage analysis. NAC, TRO and RSV, at all tested concentrations, were all capable to reduce DNA damage in symptomatic X-ALD patients until control levels. Finally, DNA damage correlated with urinary isoprostanes and plasmatic levels of TBA-RS and DCFH-DA, allowing to hypothesize that DNA damage might be induced by lipid peroxidation in symptomatic patients. The present work yields experimental evidence that NAC, TRO and RSV reduce the in vitro DNA injury in symptomatic X-ALD patients, what may suggest that the administration of these antioxidants might be considered as an adjuvant therapy for X-ALD.

Therapeutic neuroprotective agents for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal chronic neurodegenerative disease whose hallmark is proteinaceous, ubiquitinated, cytoplasmic inclusions in motor neurons and surrounding cells. Multiple mechanisms proposed as responsible for ALS pathogenesis include dysfunction of protein degradation, glutamate excitotoxicity, mitochondrial dysfunction, apoptosis, oxidative stress, and inflammation. It is therefore essential to gain a better understanding of the underlying disease etiology and search for neuroprotective agents that might delay disease onset, slow progression, prolong survival, and ultimately reduce the burden of disease. Because riluzole, the only Food and Drug Administration (FDA)-approved treatment, prolongs the ALS patient's life by only 3 months, new therapeutic agents are urgently needed. In this review, we focus on studies of various small pharmacological compounds targeting the proposed pathogenic mechanisms of ALS and discuss their impact on disease progression.

Progesterone protective effects in neurodegeneration and neuroinflammation

Progesterone is a neuroprotective, promyelinating and anti-inflammatory factor for the nervous system. Here, we review the effects of progesterone in models of motoneurone degeneration and neuroinflammation. In neurodegeneration of the Wobbler mouse, a subset of spinal cord motoneurones showed increased activity of nitric oxide synthase (NOS), increased intramitochondrial NOS, decreased activity of respiratory chain complexes, and decreased activity and protein expression of Mn-superoxide dismutase type 2 (MnSOD2). Clinically, Wobblers suffered several degrees of motor impairment. Progesterone treatment restored the expression of neuronal markers, decreased the activity of NOS and enhanced complex I respiratory activity and MnSOD2. Long-term treatment with progesterone increased muscle strength, biceps weight and survival. Collectively, these data suggest that progesterone prevented neurodegeneration. To study the effects of progesterone in neuroinflammation, we employed mice with experimental autoimmune encephalomyelitis (EAE). EAE mice spinal cord showed increased mRNA levels of the inflammatory mediators tumour necrosis factor (TNF)α and its receptor TNFR1, the microglial marker CD11b, inducible NOS and the toll-like receptor 4. Progesterone pretreatment of EAE mice blocked the proinflammatory mediators, decreased Iba1+ microglial cells and attenuated clinical signs of EAE. Therefore, reactive glial cells became targets of progesterone anti-inflammatory effects. These results represent a starting point for testing the usefulness of neuroactive steroids in neurological disorders.

Loss of glutathione homeostasis associated with neuronal senescence facilitates TRPM2 channel activation in cultured hippocampal pyramidal neurons

Background

Glutathione (GSH) plays an important role in neuronal oxidant defence. Depletion of cellular GSH is observed in neurodegenerative diseases and thereby contributes to the associated oxidative stress and Ca²⁺ dysregulation. Whether depletion of cellular GSH, associated with neuronal senescence, directly influences Ca²⁺ permeation pathways is not known. Transient receptor potential melastatin type 2 (TRPM2) is a Ca²⁺ permeable non-selective cation channel expressed in several cell types including hippocampal pyramidal neurons. Moreover, activation of TRPM2 during oxidative stress has been linked to cell death. Importantly, GSH has been reported to inhibit TRPM2 channels, suggesting they may directly contribute to Ca²⁺ dysregulation associated with neuronal senescence. Herein, we explore the relation between cellular GSH and TRPM2 channel activity in long-term cultures of hippocampal neurons.

Results

In whole-cell voltage-clamp recordings, we observe that TRPM2 current density increases in cultured pyramidal neurons over time in vitro. The observed increase in current density was prevented by treatment with NAC, a precursor to GSH synthesis. Conversely, treatment of cultures maintained for 2 weeks in vitro with L-BSO, which depletes GSH by inhibiting its synthesis, augments TRPM2 currents. Additionally, we demonstrate that GSH inhibits TRPM2 currents through a thiol-independent mechanism, and produces a 3.5-fold shift in the dose-response curve generated by ADPR, the intracellular agonist for TRPM2.

Conclusion

These results indicate that GSH plays a physiologically relevant role in the regulation of TRPM2 currents in hippocampal pyramidal neurons. This interaction may play an important role in aging and neurological diseases associated with depletion of GSH.

Current and prospective disease-modifying therapies for amyotrophic lateral sclerosis

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a devastating illness of unclear etiology affecting motor neurons. It causes unremitting muscle paralysis, atrophy and death usually within 3 - 5 years from diagnosis. The human and economic costs for those affected are sobering. To date, tremendous efforts have failed to find a cure.

AREAS COVERED

An extensive literature search was undertaken using Medline and the Cochrane Systematic Review and Clinical Trial databases. Riluzole and investigational ALS drugs are discussed. Riluzole is the only approved disease-modifying therapy despite its modest effect on survival. Recent research has produced promising agents aimed at better disease control if not a cure. This review discusses agents targeting neuronal glutamate excitotoxicity, protein misfolding and accumulation, autophagy, apoptosis, mitochondrial dysfunction, free radical oxidative injury, immunomodulation, mutant mRNA counteraction, muscle physiology, neurotrophic factors and stem cell applications. The challenges in ALS drug development are highlighted.

EXPERT OPINION

Riluzole should be used for patients with definite, probable, suspected or possible ALS by World Federation of Neurology diagnostic criteria. Systematic monitoring for hepatic dysfunction, neutropenia and other serious adverse effects should be done routinely as outlined. All ALS patients should consider genetic screening and enrollment in ALS trials guided by the data reviewed.

Antioxidants halt axonal degeneration in a mouse model of X-adrenoleukodystrophy

OBJECTIVE

Axonal degeneration is a main contributor to disability in progressive neurodegenerative diseases in which oxidative stress is often identified as a pathogenic factor. We aim to demonstrate that antioxidants are able to improve axonal degeneration and locomotor deficits in a mouse model of X-adrenoleukodystrophy (X-ALD).

METHODS

X-ALD is a lethal disease caused by loss of function of the ABCD1 peroxisomal transporter of very long chain fatty acids (VLCFA). The mouse model for X-ALD exhibits a late onset neurological phenotype with locomotor disability and axonal degeneration in spinal cord resembling the most common phenotype of the disease, adrenomyeloneuropathy (X-AMN). Recently, we identified oxidative damage as an early event in life, and the excess of VLCFA as a generator of radical oxygen species (ROS) and oxidative damage to proteins in X-ALD.

RESULTS

Here, we prove the capability of the antioxidants N-acetyl-cysteine, α-lipoic acid, and α-tocopherol to scavenge VLCFA-dependent ROS generation in vitro. Furthermore, in a preclinical setting, the cocktail of the 3 compounds reversed: (1) oxidative stress and lesions to proteins, (2) immunohistological signs of axonal degeneration, and (3) locomotor impairment in bar cross and treadmill tests.

INTERPRETATION

We have established a direct link between oxidative stress and axonal damage in a mouse model of neurodegenerative disease. This conceptual proof of oxidative stress as a major disease-driving factor in X-AMN warrants translation into clinical trials for X-AMN, and invites assessment of antioxidant strategies in axonopathies in which oxidative damage might be a contributing factor.

Progesterone neuroprotection in traumatic CNS injury and motoneuron degeneration

Studies on the neuroprotective and promyelinating effects of progesterone in the nervous system are of great interest due to their potential clinical connotations. In peripheral neuropathies, progesterone and reduced derivatives promote remyelination, axonal regeneration and the recovery of function. In traumatic brain injury (TBI), progesterone has the ability to reduce edema and inflammatory cytokines, prevent neuronal loss and improve functional outcomes. Clinical trials have shown that short-and long-term progesterone treatment induces a significant improvement in the level of disability among patients with brain injury. In experimental spinal cord injury (SCI), molecular markers of functional motoneurons become impaired, including brain-derived neurotrophic factor (BDNF) mRNA, Na,K-ATPase mRNA, microtubule-associated protein 2 and choline acetyltransferase (ChAT). SCI also produces motoneuron chromatolysis. Progesterone treatment restores the expression of these molecules while chromatolysis subsided. SCI also causes oligodendrocyte loss and demyelination. In this case, a short progesterone treatment enhances proliferation and differentiation of oligodendrocyte progenitors into mature myelin-producing cells, whereas prolonged treatment increases a transcription factor (Olig1) needed to repair injury-induced demyelination. Progesterone neuroprotection has also been shown in motoneuron neurodegeneration. In Wobbler mice spinal cord, progesterone reverses the impaired expression of BDNF, ChAT and Na,K-ATPase, prevents vacuolar motoneuron degeneration and the development of mitochondrial abnormalities, while functionally increases muscle strength and the survival of Wobbler mice. Multiple mechanisms contribute to these progesterone effects, and the role played by classical nuclear receptors, extra nuclear receptors, membrane receptors, and the reduced metabolites of progesterone in neuroprotection and myelin formation remain an exciting field worth of exploration.

Distribution of Radio-LabeledN-Acetyl-L-Cysteine in Sprague-Dawley Rats and Its Effect on Glutathione Metabolism Following Single and Repeat Dosing by Oral Gavage

The distribution of radio-labeled N-Acetyl-L-Cysteine (NAC) and its impact on glutathione (GSH) metabolism was studied in Sprague-Dawley rats following single and multiple dosing with NAC by oral gavage. Radioactivity associated with administration of (14)C-NAC distributed to most tissues examined within 1 hour of administration with peak radioactivity levels occurring within 1 hour to 4 hours and for a majority of the tissues examined, radioactivity remained elevated for up to 12 hours or more. Administration of a second dose of 1,200 mg/kg NAC + (14)C-NAC 4 hours after the first increased liver, kidney, skin, thymus, spleen, eye, and serum radioactivity significantly beyond levels achieved following 1 dose. Administration of a third dose of 1,200 mg/kg NAC + (14)C-NAC 4 hours after the second dose did not significantly increase tissue radioactivity further except in the skin. GSH concentrations were increased 20% in the skin and 50% in the liver after one dose of 1,200 mg/kg NAC whereas lung and kidney GSH were unaffected. Administration of a second and third dose of 1,200 mg/kg NAC at 4 hours and 8 hours after the first did not increase tissue GSH concentrations above background with the exception that skin GSH levels were elevated to levels similar to those obtained after a single dose of NAC. Glutathione-S-transferase (GST) activity was increased 150% in the kidney and 10% in the liver, decreased 60% in the skin, and had no effect on lung GST activity following a single dose of 1,200 mg/kg NAC. Administration of a second dose of 1,200 mg/kg NAC 4 hours after the first decreased skin GST activity a further 20% whereas kidney GST activity remained elevated at levels similar to those obtained after 1 dose of NAC. Administration of a third dose of NAC 4 hours after the second dose increased liver GST activity significantly as compared to background but did not affect skin, kidney, or lung GST activity. Transient decreases in glutathione reductase (GR) activity were measured in the skin and kidney in association with repeat administration of 1,200 mg/kg NAC. Glutathione peroxidase (GxP) activity was increased in the skin, kidney, and liver suggesting that oxidative stress was occurring in these tissues in response to repeat dosing with NAC. Overall, the results of this study present the possibility that NAC could provide some benefit in preventing or reducing toxicity related to exposure to chemical irritants (particularly sulfur mustard) in some tissues by increasing tissue NAC and/or cysteine levels, GSH concentrations, and GST activity. However, follow-on studies in animals are needed to confirm that oral administration of single and multiple doses of NAC can significantly reduce skin, eye, and lung toxicity associated with sulfur mustard exposure. The finding that GxP activity is elevated, albeit transiently, following repeat administration of NAC suggests that repeat administration of NAC may induce oxidative stress in some tissues and further studies are needed to confirm this finding.

Randomized, blinded, placebo-controlled clinical trial of N-acetylcysteine in dogs with spinal cord trauma from acute intervertebral disc disease

STUDY DESIGN

The effect of N-acetylcysteine administration intravenously before hemilaminectomy surgery on neurologic outcome and 15F 2t isoprostane excretion in dogs was examined in a blinded, placebo-controlled trial.

OBJECTIVE

To determine the effect of N-acetylcysteine administration on urinary 15F 2t isoprostane excretion and neurologic outcome following hemilaminectomy for intervertebral disc disease.

SUMMARY OF BACKGROUND DATA

Oxidative stress is a mediator of secondary injury to the spinal cord following trauma. Acute intervertebral disc disease is associated with increased oxidative damage in dogs. N-acetylcysteine has preserved neurologic function following experimental spinal cord injury.

METHODS

Seventy dogs with naturally occurring acute intervertebral disc disease were administered either with saline placebo or N-acetylcysteine intravenously before hemilaminectomy surgery. Serial neurologic examinations were performed before and 1, 2, 7, 14, and 42 days following treatment. Urinary excretion of 15F 2t isoprostane excretion was determined before treatment and 1 hour after surgery.

RESULTS

Analysis of subjective data did not reveal any significant effect of N-acetylcysteine on neurologic outcome or rate of improvement of neurologic score in the 42 days following treatment. Urinary 15F 2t isoprostane excretion was not significantly different between treatment groups (P > 0.05).

CONCLUSION

N-acetylcysteine intravenously before hemilaminectomy has no effect on urinary 15F 2t isoprostane excretion or neurologic outcome. Treatment of dogs with the antioxidant N-acetylcysteine before hemilaminectomy, while not detrimental, does not affect neurologic outcome in the 42 days following surgery.

N-acetyl-L-cysteine improves outcome of advanced cerebral adrenoleukodystrophy

Hematopoietic stem cell transplantation as a treatment for childhood cerebral adrenoleukodystrophy (ALD) has historically only been successful in early disease. As ALD is associated with oxidative damage, we reasoned that adjunctive therapy with an antioxidant agent, N-acetyl-L-cysteine (NAC), may provide protection from rapid neurologic decline in boys with advanced cerebral disease. We report three boys with advanced ALD, whose neurologic status and brain radiographic findings were stabilized by treatment including NAC 8-11 months after hematopoietic stem cell transplantation. These results contrast with previous survival data in cerebral ALD patients who had a similar degree of brain involvement, all of whom died within 1 year of stem cell infusion despite a full donor engraftment. Thus, NAC merits investigation as a therapeutic strategy for patients with advanced ALD as an intervention that could change this lethal disease to a condition amendable to treatment with hematopoietic stem cell transplantation.

Correction of humoral derangements from mutant superoxide dismutase 1 spinal cord

OBJECTIVE

We sought to define molecular and cellular participants that mediate motor neuron injury in amyotrophic lateral sclerosis using a coculture system.

METHODS

We cocultured embryonic stem cell-derived motor neurons with organotypic slice cultures from wild-type or SOD1G93A (MT) mice. We examined axon lengths and cell survival of embryonic stem cell-derived motor neurons. We defined and quantified the humoral factors that differed between wild-type and MT organotypic cultures, and then corrected these differences in cell culture.

RESULTS

MT spinal cord organotypic slices were selectively toxic to motor neurons as defined by axonal lengths and cell survival. MT spinal cord organotypic slices secreted higher levels of nitric oxide, interleukin (IL)-1beta, IL-6, and IL-12p70 and lower levels of vascular endothelial growth factor. The toxicity of MT spinal cord organotypic cultures was reduced and axonal lengths were restored to near normal by coculturing in the presence of reactive oxygen species scavenger, vascular endothelial growth factor, and neutralizing antibodies to IL-1beta, IL-6, and IL-12.

INTERPRETATION

MT spinal cord organotypic cultures overexpress certain factors and underexpress others, creating a nonpermissive environment for cocultured motor neurons. Correction of these abnormalities as a group, but not individually, restores axonal length to near normal. Such a "cocktail" approach to the treatment of amyotrophic lateral sclerosis should be investigated further.

Long-term treatment with N-acetylcysteine, but not caloric restriction, protects mesenchymal stem cells of aged rats against tumor necrosis factor-induced death

The survival of mesenchymal stem cells (MSCs) to tumor necrosis factor alpha (TNFalpha) stimulation was evaluated after a long-term antioxidant treatment, or caloric restriction, in aged rats. MSCs were isolated from bone marrow of 30-month-old rats which orally received N-acetylcysteine in the last 18 months. The necrotic cell death-induced in vitro by TNFalpha, determined by trypan blue exclusion, was markedly attenuated in MSCs obtained from treated vs. control aged rats (percent mean+/-SEM: 10.9+/-2.17 vs. 17.8+/-0.53; p<0.05). Also, the proliferation rate of MSCs from control, but not N-acetylcysteine-treated, aged rats evaluated up to 2 weeks was significantly higher than that of MSCs from younger (4-month-old) rats. No significant effect was observed relative to the parameters investigated when the aged rats were previously subjected to a hypocaloric diet for 18 months. In conclusion, a prolonged supplementation with N-acetylcysteine in rats can increase resistance to necrotic death of MSCs and may also counteract an excessive rate of MSC proliferation.

Muscular cell proliferative and protective effects of N-acetylcysteine by modulating activity of extracellular signal-regulated protein kinase

N-acetylcysteine (NAC), an antioxidant and a precursor of glutathione, is currently in clinical use for various pathological conditions. No data is available as to the relationship between NAC and muscular cell proliferation or muscular degenerative disease. In this study, we assessed the effect of NAC on growth of L6 myoblasts, a rat skeletal muscle cell line, under normal or bupivacaine-treated condition. Of interest, under normal growth conditions, NAC treatment concentration-dependently increased viability, cell number, and DNA incorporation of L6 cells. Remarkably, NAC treatment for 12 to 24 h led to increased phosphorylation of ERKs, a family of mitogen-activated protein kinase known to involve in cell proliferation, in L6 cells, and specific inhibition of ERKs by PD98059, a selective inhibitor of ERKs, greatly abolished the ability of NAC to increase the number of L6 cells. More importantly, pretreatment with NAC effectively blocked decrease in the number and ERKs phosphorylation in L6 cells induced by the exposure of bupivacaine, a local anesthetic with myotoxicity. These results collectively suggest that NAC has muscular cell proliferative and protective effects and the effects by NAC appear to be, in part, mediated via increase in ERKs activation.

Mitochondrial inhibition and oxidative stress: reciprocating players in neurodegeneration

Although the etiology for many neurodegenerative diseases is unknown, the common findings of mitochondrial defects and oxidative damage posit these events as contributing factors. The temporal conundrum of whether mitochondrial defects lead to enhanced reactive oxygen species generation, or conversely, if oxidative stress is the underlying cause of the mitochondrial defects remains enigmatic. This review focuses on evidence to show that either event can lead to the evolution of the other with subsequent neuronal cell loss. Glutathione is a major antioxidant system used by cells and mitochondria for protection and is altered in a number of neurodegenerative and neuropathological conditions. This review also addresses the multiple roles for glutathione during mitochondrial inhibition or oxidative stress. Protein aggregation and inclusions are hallmarks of a number of neurodegenerative diseases. Recent evidence that links protein aggregation to oxidative stress and mitochondrial dysfunction will also be examined. Lastly, current therapies that target mitochondrial dysfunction or oxidative stress are discussed.

Chemoprevention of acrylamide toxicity by antioxidative agents in rats—effective suppression of testicular toxicity by phenylethyl isothiocyanate

The efficacies of N-acetylcysteine (NAC), phenylethyl isothiocyanate (PEITC), and 1-O-hexyl-2,3,5-trimethylhydroquinone (HTHQ) at preventing the neurotoxicity and testicular toxicity of acrylamide (ACR) were investigated in rats. To this end, Sprague-Dawley males were given 0.02% ACR in drinking water, with or without 1% NAC, 0.5% PEITC or 0.1% HTHQ in the diet for four weeks. A group of untreated controls was also included in the study. All ACR-treated animals exhibited progressive neurotoxicity as judged by gait scores, and among the chemicals co-administered, only HTHQ caused any suppression by the end of the experiment, and this was slight. The severity of the neurotoxicity, as judged by axonal degeneration in the spinal gracile fasciculus and sciatic nerve (distal portion) and aberrant dot-like synaptophysin immunoreactivity, reflecting nerve terminal degeneration in the cerebellar molecular layer, was not clearly reduced by co-administration of HTHQ, NAC or PEITC either. ACR-induced sciatic nerve axon atrophy was marginally and non-significantly reduced by HTHQ. In contrast, in terms of ACR-induced testicular toxicity, exfoliation of spermatids into seminiferous lumen was clearly reduced by co-administered PEITC and was marginally reduced by co-administered HTHQ. These antioxidative agents may therefore reduce/prevent ACR-induced toxicity, at least in the testes.

Riluzole slows the progression of neuromuscular dysfunction in the wobbler mouse motor neuron disease

In the wobbler mouse motor neuron disease (MND), we firstly evaluated the effect of riluzole, the only approved drug for amyotrophic lateral sclerosis, and compared it with that of brain-derived neurotrophic factor (BDNF). Wobbler mice received either daily subcutaneous treatment with BDNF (5, 20, and 40 mg/kg) or oral riluzole in drinking water (100 and 200 microg/ml), beginning immediately after the clinical onset of MND. We examined motor functions, such as grip strength and rota-rod walking performance, weekly, and the amplitude of the compound muscle action potential (CMAP) in the forelimb biceps at the end of treatment. BDNF treatment slowed the disease progression maximally at a dose of 20 mg/kg, consistent to the previous evidence. Only high-dose riluzole treatment increased grip strength at weeks 1 (P=0.0023) and 2 (P=0.021), time before falling in the rota-rod test throughout all 4 weeks of treatment (P=0.0022 to 0.0282), and CMAP amplitude (P=0.0069) at the end of treatment, compared with the vehicle. Furthermore, the riluzole treatment increased the number of the cervical cord anterior horn neurons that were immunoreactive for SMI-32, a specific motor neuron marker, by the end of treatment (P=0.0063), although it did not affect the vacuolar degeneration on the SMI-32-positive neurons. This study demonstrated that riluzole was comparable to BDNF in slowing the progression of neuromuscular dysfunction in the wobbler mouse MND, which may provide a useful model for examining the mechanisms of selective motor neuron degeneration.

Evidence for chronic mitochondrial impairment in the cervical spinal cord of a murine model of motor neuron disease

Profound alteration of the oxygen consumption rate (QO2) is present in the cervical spinal cord (CS) of the wobbler mice aged 12 weeks (wr12). Early symptomatic mice at 4 weeks (wr4) show less pronounced changes with decreases of basal QO2 (P < 0.03) and of QO2 through complex I (P < 0.04). Mitochondrial respiratory enzyme activities, measured spectrophotometrically in the CS homogenate, show no difference between wr12 and controls, whereas complex I is reduced in the wr4 CS (P < 0.0003). Complex I activity is lower than normal both in wr12 and wr4 CS when measured in motor neurons by mean of a histochemical technique. Electron microscopy (EM) reveals a mixture of normal and morphologically altered mitochondria in wr4 motor neurons. The wobbler lumbar spinal cord is spared even at 12 weeks. Our results demonstrate the presence of mitochondrial abnormalities in the wobbler CS since the first manifestations of the disease. Thus, chronic mitochondrial dysfunction has a contributory role in motor neuron degeneration in the wobbler disease.

Progesterone treatment reduces NADPH-diaphorase/nitric oxide synthase in Wobbler mouse motoneuron disease

Previous work demonstrated that progesterone (PROG) treatment attenuates morphological, molecular and functional abnormalities in the spinal cord of the Wobbler (Wr) mouse, a genetic model of motoneuron degeneration. Wr mice show a marked up-regulation of the nitric oxide synthesizing enzyme (NOS). Since nitric oxide is a highly reactive species, it may play a role in neuropathology of Wr mice. We now studied if PROG neuroprotection involved changes of NOS activity in motoneurons and astrocytes, determined by the nicotinamide adenine dinucleotide phosphate-diaphorase (NADPHD) histochemical reaction. Two and four-month-old Wr mice at the progressive and stabilization stages of the disease, respectively, and their age-matched controls were left untreated or received a single 20-mg PROG pellet for 18 days. PROG reduced the high number of NADPHD-active motoneurons and white matter astrocytes in 2-month-old Wr mice but was unable to change the low number of NADPHD-active motoneurons in 4-month-old Wr mice or astrocytes in this age group. A large number of motoneurons in 2-month-old Wr mice showed a vacuolated phenotype, which was significantly reverted by PROG treatment. In summary, PROG treatment during the early symptomatic stage of the disease caused a significant reduction of NADPHD-active motoneurons and astrocytes and also reduced vacuolated degenerating cells, suggesting that blockade of NO synthesis and oxidative damage may contribute to steroid neuroprotection.

Alterations of markers related to synaptic function in aging rat brain, in normal conditions or under conditions of long-term dietary manipulation

Neurochemical alterations of markers related to synaptic function are potential candidates for age-related impairment of brain function and cognition. The process of aging, including brain aging, can be counteracted to some degree by maintaining animals in long-term conditions of caloric restriction, or supplementing their diet with antioxidant substances. We report here that the age-related decline of the cholinergic and GABAergic systems, that takes place in some CNS regions of aged rats, is not affected by maintaining them under conditions of dietary restriction and, therefore, of reduced calorie intake, from the 12th to the 30th month of age. We also notice the same lack of effect by adding, during the same period, the aging rat diet with the potential antioxidant substance, N-acetylcysteine (NAC). The same dietary manipulations are also unable to counteract the derangement of the first step of the main biosynthetic pathway for polyamines, putative neuromodulators in the CNS, that occurs in the aged spinal cord. Some age-related alterations in the expression of different subunits of the NMDA-type glutamate receptors in some CNS regions of aged rats were instead, at least in some cases, counteracted by long-term dietary manipulation.

Brainstem motor nuclei respond differentially to degenerative disease in the mutant mouse wobbler

Degenerative motoneurone diseases, whether in humans, animals, or transgenic mouse models, do not affect all types of motoneurone to the same degree. Understanding the relative differences in vulnerability of certain motor pools may be the key to developing therapies. Expression of calbindin (CB) and parvalbumin (PV) immunoreactivity, which are potentially neuroprotective calcium-binding proteins, and NADPH-diaphorase (NADPH-d) histochemical reactivity, a marker for neurodegeneration, was studied in brainstem sections from mutant wobbler mice and their normal littermates during the motoneurone degeneration phase (3-8 weeks of age). The motor trigeminal and facial nuclei reacted in a manner previously observed in spinal somatic motoneurones in the wobbler. Many motoneurones expressed moderate NADPH-d reactivity, correlated with the appearance of vacuolated motoneurones in Nissl-stained sections. This was not observed in littermate controls. Motoneurone counts from Nissl-stained sections from 14-month-old wobblers and littermates revealed significantly fewer (approximately 27%) motoneurones in the trigeminal nucleus of wobblers. In contrast, the wobbler hypoglossal nucleus contained neither vacuolated nor NADPH-d reactive motoneurones. However, expression of CB immunoreactivity by the majority of wobbler hypoglossal motoneurones was observed but not in littermate controls or in any other motor nucleus. Counts in older animals showed a smaller but still significant difference in motoneurone number between wobblers and controls (approximately 9% reduction). Finally, the wobbler abducens nucleus displayed neither vacuolated neurones, nor NADPH-d reactivity nor CB immunoreactivity. Motor nuclei innervating extraocular muscles appear to be protected in many forms of motoneurone disease in man and other species. However, there were still markedly fewer abducens motoneurones in the old wobblers compared to controls (approximately 29% reduction). Sparing of oculomotor neurones in other diseases has been attributed to their relatively high PV expression, which we also observed in the abducens nucleus of both wobblers and littermates, and to a lesser extent in the other motor nuclei too. In conclusion, our results suggest that, in the wobbler mouse, motoneurone degeneration may occur without overt signs such as cell body vacuolation and NADPH-d expression. Induced CB expression may be neuroprotective but that constitutive expression of PV may not.

The contribution of mitochondria to common disorders

Mitochondrial dysfunction secondary to mitochondrial and nuclear DNA mutations has been associated with energy deficiency in multiple organ systems and a variety of severe, often fatal, clinical syndromes. Although the production of energy is indeed the primary function of mitochondria, attention has also been directed toward their role producing reactive oxygen and nitrogen species and the subsequent widespread deleterious effects of these intermediates. The generation of toxic reactive intermediates has been implicated in a number of relatively common disorders, including neurodegenerative diseases, diabetes, and cancer. Understanding the role mitochondrial dysfunction plays in the pathogenesis of common disorders has provided unique insights into a number of diseases and offers hope for potential new therapies.

Basis of progesterone protection in spinal cord neurodegeneration

Progesterone neuroprotection has been reported in experimental brain, peripheral nerve and spinal cord injury. To investigate for a similar role in neurodegeneration, we studied progesterone effects in the Wobbler mouse, a mutant presenting severe motoneuron degeneration and astrogliosis of the spinal cord. Implant of a single progesterone pellet (20 mg) during 15 days produced substantial changes in Wobbler mice spinal cord. Morphologically, motoneurons of untreated Wobbler mice showed severe vacuolation of intracellular organelles including mitochondria. In contrast, neuropathology was less pronounced in Wobbler mice receiving progesterone, together with a reduction of vacuolated cells and preservation of mitochondrial ultrastructure. Determination of mRNAs for the alpha 3 and beta 1 subunits of neuronal Na, K-ATPase, showed that mRNA levels in untreated mice were significantly reduced, whereas progesterone therapy re-established the expression of both subunits. Additionally, progesterone treatment of Wobbler mice attenuated the aberrant expression of the growth-associated protein (GAP-43) mRNA which otherwise occurred in motoneurons of untreated animals. The hormone, however, was without effect on astrocytosis of Wobbler mice, determined by glial fibrillary acidic protein (GFAP)-immunostaining. Lastly, progesterone treatment of Wobbler mice enhanced grip strength and prolonged survival at the end of the 15-day observation period. Recovery of morphology and molecular motoneuron parameters of Wobbler mice receiving progesterone, suggest a new and important role for this hormone in the prevention of spinal cord neurodegenerative disorders.

Nutritional issues and supplements in amyotrophic lateral sclerosis and other neurodegenerative disorders

PURPOSE OF REVIEW

Aggressive nutritional intervention has become a cornerstone of treatment for many patients with neuromuscular diseases, in particular, motor neuron disease. Malnutrition is a common problem among patients with amyotrophic lateral sclerosis. Over the past decade, the recognition of nutrition as an independent, prognostic factor for survival and disease complications in amyotrophic lateral sclerosis has illustrated the importance of individualized nutritional management in symptomatic treatment. Paramount issues for nutritional management in amyotrophic lateral sclerosis include caloric supplementation, the diagnosis/treatment of dysphagia, and the timing/safety/efficacy of percutaneous endoscopic gastrostomy placement.

RECENT FINDINGS

In addition, many amyotrophic lateral sclerosis patients self-medicate with a variety of vitamins, herbs, and other dietary supplements. Outcome-based research for the use of nutraceuticals and functional foods in the treatment and prevention of amyotrophic lateral sclerosis and other neuromuscular diseases is in its early stages. In the past year, however, several interesting papers have been published that lend support to the use of dietary supplements as primary treatments for amyotrophic lateral sclerosis and other motor neuron disorders.

SUMMARY

Common or overlapping etiologies in disparate neurodegenerative diseases have led to the promise that optimal nutritional care and the appropriate use of dietary supplements in amyotrophic lateral sclerosis will have implications for the nutritional management of other degenerative conditions such as Parkinson's, Alzheimer's, and Huntington's disease. Furthermore, evidence supporting the efficacy of dietary supplements in amyotrophic lateral sclerosis may lend clues to the treatment of other neuromuscular disorders such as the muscular dystrophies.

Antioxidants as treatment for neurodegenerative disorders

Oxidative stress is a ubiquitously observed hallmark of neurodegenerative disorders. Neuronal cell dysfunction and cell death due to oxidative stress may causally contribute to the pathogenesis of progressive neurodegenerative disorders, such as Alzheimer's disease and Parkinson's disease, as well as acute syndromes of neurodegeneration, such as ischaemic and haemorrhagic stroke. Neuroprotective antioxidants are considered a promising approach to slowing the progression and limiting the extent of neuronal cell loss in these disorders. The clinical evidence demonstrating that antioxidant compounds can act as protective drugs in neurodegenerative disease, however, is still relatively scarce. In the following review, the available data from clinical, animal and cell biological studies regarding the role of antioxidant neuroprotection in progressive neurodegenerative disease will be summarised, focussing particularly on Alzheimer's disease, Parkinson's disease, Huntington's disease and amyotrophic lateral sclerosis. The general complications in developing potent neuroprotective antioxidant drugs directed against these long-term degenerative conditions will also be discussed. The major challenges for drug development are the slow kinetics of disease progression, the unsolved mechanistic questions concerning the final causalities of cell death, the necessity to attain an effective permeation of the blood-brain barrier and the need to reduce the high concentrations currently required to evoke protective effects in cellular and animal model systems. Finally, an outlook as to which direction antioxidant drug development and clinical practice may be leading to in the near future will be provided.

Antioxidants N-acetylcysteine (NAC) and 2-mercaptoethanol (2-ME) affect the survival and differentiative potential of cholinergic precursors from the embryonic septal nuclei and basal forebrain: involvement of ras signaling

We investigated the effects of antioxidants N-acetylcysteine (NAC) and 2-mercaptoethanol (2-ME) on the expression of choline acetyltransferase (ChAT) in cultured cholinergic precursors from the embryonic rat septal nuclei and basal forebrain. Carboxy-dichlorofluorescein fluorescence confirmed that 2-ME inhibited intracellular oxidation. Low micromolar concentrations of 2-ME produce as much as a 12-fold increase in ChAT; this is enhanced further by inclusion of nerve growth factor (NGF). NAC effects are biphasic: 0.15 mM produces profound increases in ChAT while 1.5 mM has no effect. Immature (E16) cultures respond with increases in ChAT while more highly differentiated cultures (E18) do not. Labeling of single precursors with a lacZ-expressing retrovirus reveals that the increase in ChAT is due primarily to an increased number and size of clones, not an increase in cholinergic neurons per clone, suggesting an effect on precursor survival. Inhibition of ras farnesylation inhibits both 2-ME and NAC induction of ChAT suggesting a ras-mediated pathway. Inclusion of the MEK inhibitor PD98059 does not affect low doses of NAC, but at doses of NAC that fail to increase ChAT activity, inhibition of the pathway actually raises ChAT. Immunocytochemical investigation of the cultures indicates that cells exposed to low doses of NAC develop healthy neuronal arbors in the apparent absence of glial support. At higher concentrations of NAC, neurons were found in association with astrocytes, making contact via elaborate varicose fibers. Treatment of the cultures with PD98059 to inhibit MEK returned cultures to a 'low-dose' phenotype. These data suggest that redox status of basal forebrain precursors affect both their survival and differentiative potential.

Transient massive DNA fragmentation in nervous system during the early course of a murine neurodegenerative disease

In neurodegenerative diseases, such as Alzheimer's disease or HIV encephalitis, neuronal DNA fragmentation has been observed at unexpected high frequencies, without definitive evidence for activation of an irreversible apoptotic pathway. The wobbler mouse is a suggested genetic model of neurodegenerative disease. The mutant mouse develops normally until the fourth week of age when atrophy and weakness of forelimb muscles become apparent. There is a slow progression of the disease and wobbler mice may survive for several months. Spinal cord examination reveals the presence of several motoneurons with perikaryal vacuolar degeneration. In this study, we observed, using terminal dUTP nick-end-labelling staining in mutant spinal cord sections, a massive although very transient DNA fragmentation in different cell types, including glial cells and motoneurons, before the apparition of any clinical symptoms. In older wobbler mice, this DNA fragmentation had completely disappeared and the majority of motoneurons survived. To our knowledge, this is the first example of a massive and transient DNA fragmentation in the central nervous system during the early course of a neurodegenerative disease.

Neuroprotective effect of cyclic GMP against radical-induced toxicity in cultured spinal motor neurons

We have previously reported that nitric oxide-related cyclic guanosine-3',5'-monophosphate (GMP) protected spinal nonmotor neurons, but not motor neurons against chronic glutamate-induced toxicity, which is associated with selective motor neuronal death after glutamate stress. In this report, we investigated the effect of cyclic GMP against reactive oxygen species (ROS)-induced toxicity in cultured neurons from embryonic rat spinal cords. Pretreatment with a cGMP analogue, 8-bromoguanosine monophosphate (8br-cGMP), for 12-24 hours protected both spinal motor neurons and nonmotor neurons against injury induced by either hydrogen peroxide (H(2)O(2)), or a glutathione depletor, L-buthionine-[S,R]-sulfoximine (BSO). This protective effect was reversed by coadministration with the cGMP-dependent protein kinase (PKG) inhibitor Arg-Lys-Arg-Ala-Arg-Lys-Glu. Interestingly, when cultures were exposed to BSO for 24 hours to allow irreversible inhibition of glutathione synthesis, 8br-cGMP protected only nonmotor neurons. Our results indicate that cGMP attenuates oxidative injury to cultured spinal neurons, in a mechanism associated with glutathione synthesis.

Glutathione, oxidative stress and neurodegeneration

There is significant evidence that the pathogenesis of several neurodegenerative diseases, including Parkinson's disease, Alzheimer's disease, Friedreich's ataxia and amyotrophic lateral sclerosis, may involve the generation of reactive oxygen species and mitochondrial dysfunction. Here, we review the evidence for a disturbance of glutathione homeostasis that may either lead to or result from oxidative stress in neurodegenerative disorders. Glutathione is an important intracellular antioxidant that protects against a variety of different antioxidant species. An important role for glutathione was proposed for the pathogenesis of Parkinson's disease, because a decrease in total glutathione concentrations in the substantia nigra has been observed in preclinical stages, at a time at which other biochemical changes are not yet detectable. Because glutathione does not cross the blood-brain barrier other treatment options to increase brain concentrations of glutathione including glutathione analogs, mimetics or precursors are discussed.

A cell-survival factor (N-acetyl-L-cysteine) alters the in vivo fate of constitutively proliferating subependymal cells in the adult forebrain

The adult mouse brain contains a population of constitutively proliferating subependymal cells that surround the lateral ventricle and are the direct progeny of the neural stem cell. Constitutively proliferating cells divide rapidly; 6 days after labeling, 60% of their progeny undergo cell death, 25% migrate to the olfactory bulbs, and 15% continue to proliferate within the subependyma. We have intraventricularly infused a cell survival factor N-acetyl-L-cysteine (NAC), which is known to have survival effects without concomitant proliferative effects on cells in vitro, and examined the resulting fate of cells spared from the normally occurring cell death. NAC infusion for 5 days results in a five-fold increase in the number of retrovirally labeled subependymal cells compared to saline-infused controls. The increase in the number of subependymal cells is directly proportional to the amount of time during which NAC is present and is not due to increased proliferation. While NAC is able to keep all the normally dying progeny alive, the cells spared from death remain confined to the subependyma lining the lateral ventricles and do not migrate to the olfactory bulbs (one normal fate of constitutively proliferating progeny) or into the surrounding brain parenchyma. When animals survive for an additional 6 days following NAC infusion, the number of retrovirally labeled subependymal cells returns to control values, indicating that the continued presence of NAC is necessary for cell survival. These data suggest that preventing cell death is not sufficient to keep all of the progeny of these cells in a proliferative mode.

Management of oxidative stress in the CNS: the many roles of glutathione

An outline is given of mechanisms that generate oxidative stress and inflammation. Considered are the metabolic mechanisms that give rise to peroxides, the source of strong oxidants; the production of dicarbonyls that interact with macromolecules to form advanced glycation endproducts; and the role that activation of the transcription factor NF(Kappa)B has in the expression of pro-inflammatory genes. Management of oxidative stress is considered by outlining the central role of reduced glutathione (GSH) in peroxide scavenging, dicarbonyl scavenging and activation of NF(Kappa)B. Cellular GSH levels are dictated by the balance between consumption, oxidation of GSH, reduction of oxidized-glutathione, and synthesis. The rate-limiting enzyme in GSH synthesis is L-gamma-glutamyl-L-cysteine synthase, a phase II enzyme. Phase II enzyme inducers are found in many fruits and vegetables. It is suggested that dietary phase II enzyme inducers be investigated for their potential for preventing or retarding the development of degenerative diseases that have an underlying oxidative stress and inflammatory component.

Ceramide prevents motoneuronal cell death through inhibition of oxidative signal

We previously reported that cell death of rat spinal motoneurons, induced by trophic factor-deprivation, was attenuated by the application of exogenous cell-permeable ceramide (C6-Cer), or bacterial sphingomyelinase (SMase). Recently, motoneuronal cell death was demonstrated to be mediated by the generation of reactive oxygen species (ROS), including superoxide and peroxinitrite. In this study, to investigate the protective mechanism of ceramide (Cer), we examined the effects of Cer and sphingolipid metabolites against ROS generation and oxidative injury in enriched motoneuron cultures. Staining with C-DCDHF-DA, a fluorescent probe for detection of ROS, demonstrated that application of C6-Cer (2.5 mM) or bacterial SMase inhibited the increase of ROS generation. C6-dihydro-Cer, a biologically inactive analogue of C6-Cer, sphingosine, and sphingosine-1-phosphate did not affect ROS generation. This specificity corresponded to the results of cell survival assays. In addition, C6-Cer was shown to specifically inhibit ROS-induced reactions, such as tyrosine nitration and lipid peroxidation, in studies using antibodies against peroxinitrite and 4-hydroxinonenal, respectively. A potent neurotrophin for motoneurons, GDNF, had inhibitory effects against ROS generation and ROS-induced reactions. C6-Cer was also effective in the prevention of cytotoxicity induced by 1-buthionine-sulfoximine, an inhibitor of glutathione synthesis. These observations suggest that Cer plays a protective role in spinal motoneurons through inhibition of oxidative signals.

Evidence for down-regulation of GAP-43 mRNA in Wobbler mouse spinal motoneurons by corticosterone and a 21-aminosteroid

Expression of the growth-associated protein GAP-43 is increased in the spinal cord of ALS patients and Wobbler (wr) mice, murine models of the disease. In this work we examined if expression of GAP-43 mRNA in control and wr mice was sensitive to steroid treatment. A group of control and wr mice received s.c. a 50 mg pellet of the natural hormone corticosterone (CORT) or the antioxidant 21-aminosteroid U-74389F during 4 days. Basal levels of GAP-43 mRNA were 10-fold elevated in ventral horn motoneurons of untreated wr mice, compared to the low levels in controls. The high expression of GAP-43 mRNA in wr was attenuated by treatment with CORT (41%, p < 0.001) and U-74389F (36%, p < 0.001). Although specific GAP-43 mRNA labelling was present in some neurons around the central canal, its cellular expression was similar in controls and wr. Also, steroid treatment was ineffective in neurons around the central canal. Other regions of the spinal cord (i.e., dorsal horn neurons) expressed GAP-43 mRNA slightly above background levels. It is possible that attenuation of GAP-43 expression due to the natural hormone and the antioxidant steroid resulted from reversal of motoneuron degeneration or aberrant sprouting. Therefore, steroid therapy may be of value to prevent denervation and/or muscular atrophy in this animal model.

Neuronal defects and posterior pituitary hypoplasia in mice lacking the receptor tyrosine phosphatase PTPsigma

The LAR-family protein tyrosine phosphatase sigma (PTPsigma, encoded by the gene Ptprs) consists of a cell adhesion-like extracellular domain composed of immunoglobulin and fibronectin type-III repeats, a single transmembrane domain and two intracellular catalytic domains. It was previously shown to be expressed in neuronal and lung epithelial tissues in a developmentally regulated manner. To study the role of PTPsigma in mouse development, we inactivated Ptprs by gene targeting. All Ptprs+/- mice developed normally, whereas 60% of Ptprs-/- mice died within 48 hours after birth. The surviving Ptprs-/- mice demonstrated stunted growth, developmental delays and severe neurological defects including spastic movements, tremor, ataxic gait, abnormal limb flexion and defective proprioception. Histopathology of brain sections revealed reduction and hypocellularity of the posterior pituitary of Ptprs-/- mice, as well as a reduction of approximately 50-75% in the number of choline acetyl transferase-positive cells in the forebrain. Moreover, peripheral nerve electrophysiological analysis revealed slower conduction velocity in Ptprs-/- mice relative to wild-type or heterozygous animals, associated with an increased proportion of slowly conducting, small-diameter myelinated fibres and relative hypomyelination. By approximately three weeks of age, most remaining Ptprs-/- mice died from a wasting syndrome with atrophic intestinal villi. These results suggest that PTPsigma has a role in neuronal and epithelial development in mice.