Copper/zinc superoxide dismutase overexpression promotes survival of cortical neurons exposed to neurotoxins in vitro

Role of Nuclear Factor Kappa B (NF-κB) Signalling in Neurodegenerative Diseases: An Mechanistic Approach

A transcriptional regulatory nuclear factor kappa B (NF-κB) protein is a modulator of cellular biological activity via binding to a promoter region in the nucleus and transcribing various protein genes. The recent research implicated the intensive role of nuclear factor kappa B (NF-κB) in diseases like autoimmune disorder, inflammatory, cardiovascular and neurodegenerative diseases. Therefore, targeting the nuclear factor kappa B (NF-κB) protein offers a new opportunity as a therapeutic approach. Activation of IκB kinase/NF-κB signaling pathway leads to the development of various pathological conditions in human beings, such as neurodegenerative, inflammatory disorders, autoimmune diseases, and cancer. Therefore, the transcriptional activity of IκB kinase/NF- κB is strongly regulated at various cascade pathways. The nuclear factor NF-kB pathway plays a major role in the expression of pro-inflammatory genes, including cytokines, chemokines, and adhesion molecules. In response to the diverse stimuli, the cytosolic sequestered NF-κB in an inactivated form by binding with an inhibitor molecule protein (IkB) gets phosphorylated and translocated into the nucleus further transcribing various genes necessary for modifying various cellular functions. The various researches confirmed the role of different family member proteins of NF-κB implicated in expressing various genes products and mediating various cellular cascades. MicroRNAs, as regulators of NF- κB microRNAs play important roles in the regulation of the inflammatory process. Therefore, the inhibitor of NF-κB and its family members plays a novel therapeutic target in preventing various diseases. Regulation of NF- κB signaling pathway may be a safe and effective treatment strategy for various disorders.

Evaluation of phyto-medicinal efficacy of thymoquinone against Arsenic induced mitochondrial dysfunction and cytotoxicity in SH-SY5Y cells

BACKGROUND

It is evaluated that a few million individuals worldwide are experiencing Arsenic (As) harmfulness coming about because of anthropogenic discharges. There is likewise proof to propose that As can affect the peripheral, as well as, the central nervous system (CNS). On the contrary, thymoquinone (TQ), a biologically active ingredient of Nigella sativa has exhibited numerous neuro-pharmacological traits since ancient times.

HYPOTHESIS/PURPOSE

In the present study, the neuroprotective efficacy of TQ was explored by primarily studying its antioxidant and anti-apoptotic potential against Arsenic trioxide (As₂O₃) induced toxicity in SH-SY5Y human neuroblastoma cell lines.

STUDY DESIGN

For experimentation, cells were seeded in 96 well tissue culture plates and kept undisturbed for 24 h to attain proper adhesion. After 75-80% confluence, cells were pretreated with 10 µM and 20 µM thymoquinone (TQ) for 1 h After adding 2 µM As, cells were set aside for incubation for 24 h without changing the medium.

METHODS

The mitigatory effects of TQ with particular reference to cell viability and cytotoxicity, the generation of reactive oxygen species, DNA damage, and mitochondrial dynamics were studied.

RESULTS

Pretreatment of SH-SY5Y cells with TQ (10 and 20 μM) for an hour and subsequent exposure to 2 μM As₂O₃ protected the SH-SY5Y cells against the neuro-damaging effects of the latter. Also, the SH-SY5Y cells were better preserved with increased viability, repaired DNA, less free radical generation and balanced transmembrane potential than those exposed to As₂O₃ alone. TQ pretreatment also inhibited As₂O₃-induced exacerbation in protein levels of BAX and PARP-1 and restored the loss of Bcl₂ levels.

CONCLUSION

The findings of this study suggest that TQ may prevent neurotoxicity and As₂O₃-induced apoptosis and cytotoxicity. It is, therefore, worth studying further for its potential to reduce the risks of arsenic-related neurological implications.

Oxidative stress in cerebral small vessel disease. Role of reactive species

Cerebral small vessel disease (CSVD) is a wide term describing the condition affecting perforating arterial branches as well as arterioles, venules, and capillaries. Cerebral vascular net is one of the main targets of localised oxidative stress processes causing damage to vasculature, changes in the blood flow and blood-brain barrier and, in consequence, promoting neurodegenerative alterations in the brain tissue. Numerous studies report the fact of oxidation to proteins, sugars, lipids and nucleic acids, occurring in most neurodegenerative diseases mainly in the earliest stages and correlations with the development of cognitive and motor disturbances. The dysfunction of endothelium can be caused by oxidative stress and inflammatory mechanisms as a result of reactions and processes generating extensive reactive oxygen species (ROS) production such as high blood pressure, oxidised low density lipoproteins (oxLDL), very low density lipoproteins (vLDL), diabetes, homocysteinaemia, smoking, and infections. Several animal studies show positive aspects of ROS, especially within cerebral vasculature.

Paradoxical Roles of Antioxidant Enzymes: Basic Mechanisms and Health Implications

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated from aerobic metabolism, as a result of accidental electron leakage as well as regulated enzymatic processes. Because ROS/RNS can induce oxidative injury and act in redox signaling, enzymes metabolizing them will inherently promote either health or disease, depending on the physiological context. It is thus misleading to consider conventionally called antioxidant enzymes to be largely, if not exclusively, health protective. Because such a notion is nonetheless common, we herein attempt to rationalize why this simplistic view should be avoided. First we give an updated summary of physiological phenotypes triggered in mouse models of overexpression or knockout of major antioxidant enzymes. Subsequently, we focus on a series of striking cases that demonstrate "paradoxical" outcomes, i.e., increased fitness upon deletion of antioxidant enzymes or disease triggered by their overexpression. We elaborate mechanisms by which these phenotypes are mediated via chemical, biological, and metabolic interactions of the antioxidant enzymes with their substrates, downstream events, and cellular context. Furthermore, we propose that novel treatments of antioxidant enzyme-related human diseases may be enabled by deliberate targeting of dual roles of the pertaining enzymes. We also discuss the potential of "antioxidant" nutrients and phytochemicals, via regulating the expression or function of antioxidant enzymes, in preventing, treating, or aggravating chronic diseases. We conclude that "paradoxical" roles of antioxidant enzymes in physiology, health, and disease derive from sophisticated molecular mechanisms of redox biology and metabolic homeostasis. Simply viewing antioxidant enzymes as always being beneficial is not only conceptually misleading but also clinically hazardous if such notions underpin medical treatment protocols based on modulation of redox pathways.

Prospects for improving brain function in individuals with Down syndrome

Down syndrome (DS), which results from an extra copy of chromosome 21 (trisomy 21), is the most common genetically defined cause of intellectual disability. Although no pharmacotherapy aimed at counteracting the cognitive and adaptive deficits associated with this genetic disorder has been approved at present, there have been several new promising studies on pharmacological agents capable of rescuing learning/memory deficits seen in mouse models of DS. Here, we will review the available mouse models for DS and provide a comprehensive, albeit not exhaustive review of the following preclinical research strategies: (1) SOD1 and antioxidant agents; (2) APP and γ-secretase inhibitors; (3) DYRK1A and the polyphenol epigallocatechin gallate (EGCG); (4) GIRK2 and fluoxetine; (5) adrenergic receptor agonists; (6) modulation of GABAA and GABAB receptors; (7) agonism of the hedgehog signaling pathway; (8) nerve growth factor (NGF) and other neurotrophic factors; (9) anticholinesterase (AChE) agents; and (10) antagonism of NMDA receptors. Finally, we will review briefly five different strategies in DS that have led to clinical studies that either have been concluded or are currently underway: (1) antioxidant therapy; (2) AChE therapy; (3) green tea extract therapy; (4) RG1662 therapy; and (5) memantine therapy. These are exciting times in DS research. Within a decade or so, it is well into the realm of possibility that new forms of pharmacotherapies might become valuable tools in the armamentarium of developmental clinicians, as adjutants to more traditional and proven forms of habilitative interventions aimed at improving the quality of life of individuals with DS.

Neuroprotective role of superoxide dismutase 1 in retinal ganglion cells and inner nuclear layer cells against N-methyl-d-aspartate-induced cytotoxicity

The N-methyl-d-aspartate (NMDA) receptor-induced apoptosis is implicated in the pathological mechanisms of neural tissues, increasing the release of reactive oxygen species (ROS), resulting in a type of apoptotic cell death called excitotoxicity. Although intrinsic mechanisms to remove ROS, such as antioxidant enzymes, are provided by the tissue, the association between NMDA-induced excitotoxicity and antioxidative enzymes is not well understood. In this study, we focused on superoxide dismutase 1 (SOD1), an antioxidant enzyme, and investigated the role of SOD1 in the NMDA-induced neuronal cell death in the retina. NMDA was intravitreally injected into wild-type (WT) and SOD1 total knock-out (SOD1-deficient) mice. The number of TUNEL-positive cells in the retinal ganglion cell layer (GCL) and inner nuclear layer (INL) counted in the retinal sections and flatmount retinas were significantly higher in the SOD1-deficient mice than the WT mice after NMDA injection. Visual function assessed by dark-adapted electroretinogram (ERG) showed that the amplitudes of a-wave, b-wave, and oscillatory potential 2 were significantly reduced in the NMDA-injected SOD1-deficient mice. The level of ROS in the GCL and INL, measured using dihydroethidium, and the number of positive cells for γ-H2AX, a marker for DNA double strand breaks, and 8-OHdG, a marker for DNA oxidation, in the GCL were significantly increased in the SOD1-deficient mice after NMDA injection. We also measured mRNA and protein levels of SOD1 and SOD2 in the retina of WT mice, to find that mRNA and protein levels of SOD1, but not SOD2, were significantly reduced after NMDA injection. SOD1 deficiency exacerbated NMDA-induced damage to the inner retinal neurons, and NMDA reduced SOD1 levels in the retina of WT mice. Therefore, SOD1 protected retinal neurons against NMDA-induced retinal neurotoxicity, and NMDA-induced SOD1 reduction may be involved in neuronal vulnerability to excitotoxicity.

Prevention of age-related changes in hippocampal levels of 5-methylcytidine by caloric restriction

Aberrant DNA methylation patterns have been linked to molecular and cellular alterations in the aging brain. Caloric restriction (CR) and upregulation of antioxidants have been proposed as interventions to prevent or delay age-related brain pathology. Previously, we have shown in large cohorts of aging mice, that age-related increases in DNA methyltransferase 3a (Dnmt3a) immunoreactivity in the mouse hippocampus were attenuated by CR, but not by overexpression of superoxide dismutase 1 (SOD1). Here, we investigated age-related alterations of 5-methylcytidine (5-mC), a marker of DNA methylation levels, in a hippocampal subregion-specific manner. Examination of 5-mC immunoreactivity in 12- and 24-month-old wild type (WT) mice on control diet, mice overexpressing SOD1 on control diet, wild type mice on CR, and SOD1 mice on CR, indicated an age-related increase in 5-mC immunoreactivity in the hippocampal dentate gyrus, CA3, and CA1-2 regions, which was prevented by CR but not by SOD1 overexpression. Moreover, positive correlations between 5-mC and Dnmt3a immunoreactivity were observed in the CA3 and CA1-2. These findings suggest a crucial role for DNA methylation in hippocampal aging and in the mediation of the beneficial effects of CR on aging.

Salvianolic acid A protects human SH-SY5Y neuroblastoma cells against H₂O₂-induced injury by increasing stress tolerance ability

Salvianolic acid A (Sal A) is a polyphenol extracted from the root of the Salvia miltiorrhiza bunge. Hydrogen peroxide (H(2)O(2)) is a major reactive oxygen species (ROS), which has been implicated in stroke and other neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. In this study, we investigated the neuroprotective effects of Sal A in human SH-SY5Y neuroblastoma cells against H(2)O(2)-induced injury. Our results showed that cells pretreated with Sal A exhibited enhanced neuronal survival and that this protection was associated with an increase in adenosine triphosphate (ATP) and the stabilization of mitochondrial membrane potential. In addition, Sal A markedly decreased the excessive activation AMP-activated protein kinase (AMPK) and the serine-threonine protein kinase, Akt, in SH-SY5Ycells induced by H(2)O(2). In conclusion, our results demonstrated that Sal A protects SH-SY5Y cells against H(2)O(2)-induced oxidative stress and these protective effects are related to stress tolerance and not energy depletion via inhibition of the AMPK and Akt signaling pathway.

Caloric restriction attenuates age-related changes of DNA methyltransferase 3a in mouse hippocampus

Recent studies have suggested that DNA methylation is implicated in age-related changes in gene expression as well as in cognition. DNA methyltransferase 3a (Dnmt3a), which catalyzes DNA methylation, is essential for memory formation and underlying changes in neuronal and synaptic plasticity. Because caloric restriction (CR) and upregulation of antioxidants have been suggested as strategies to attenuate age-related alterations in the brain, we hypothesized that both a diet restricted in calories and transgenic overexpression of normal human Cu/Zn superoxide dismutase 1 (SOD) attenuate age-related changes in Dnmt3a in the aging mouse hippocampus. For this purpose, we performed qualitative and quantitative analyses of Dnmt3a-immunoreactivity (IR) for the hippocampal dentate gyrus (DG), CA3 and CA1-2 regions in 12- and 24-month-old mice from 4 groups, i.e. (1) wild-type (WT) mice on a control diet (WT-CD), (2) SOD-CD mice, (3) WT mice on CR (WT-CR), and (4) SOD-CR. Qualitative analyses revealed two types of Dnmt3a immunoreactive cells: type I cells--present throughout all hippocampal cell layers showing moderate levels of nuclear Dnmt3a-IR, and type II cells--a subpopulation of hippocampal cells showing very intense nuclear Dnmt3a-IR, and colocalization with Bromodeoxyuridine. Quantitative analyses indicated that the age-related increase in Dnmt3a-IR within the CA3 and CA1-2 in type I cells was attenuated by CR, but not by SOD overexpression. In contrast, the density of type II Dnmt3a immunoreactive cells showed an age-related reduction, without significant effects of both CR and SOD. These changes in Dnmt3a levels in the mouse hippocampus may have a significant impact on gene expression and associated cognitive functioning.

Brain angiotensin peptides regulate sympathetic tone and blood pressure

Brain angiotensin II (Ang II) induces tonic sympathoexcitatory effects through AT1 receptor stimulation of glutamatergic neurons and sympathoinhibitory effects via GABAergic neurons in the rostral ventrolateral medulla, the brainstem 'pressor area'. NADPH-derived superoxide production and reactive oxygen species signalling is critical in these actions, and AT2 receptors in the rostral ventrolateral medulla appear to mediate opposing effects on sympathetic outflow. In the hypothalamic paraventricular nucleus, Ang II has AT1 receptor-mediated sympathoexcitatory effects and enhances nitric oxide formation, which in turn inhibits the Ang II effects through a GABAergic mechanism. Ang II also decreases the tonic sympathoinhibitory effect of gamma amino butyric acid within the paraventricular nucleus. Angiotensin III and Angiotensin IV increase blood pressure via brain AT1 receptor stimulation. Angiotensin (1-7) influences cardiovascular function through a specific Mas-receptor. This review examines the evidence that brain angiotensin peptides, glutamate, gamma amino butyric acid and nitric oxide interact within the rostral ventrolateral medulla and paraventricular nucleus to control sympathetic tone and blood pressure.

Superoxide dismutase protects against apoptosis and alveolar enlargement induced by ceramide

The molecular events leading to emphysema development include generation of oxidative stress and alveolar cell apoptosis. Oxidative stress upregulates ceramides, proapoptotic signaling sphingolipids that trigger further oxidative stress and alveolar space enlargement, as shown in an experimental model of emphysema due to VEGF blockade. As alveolar cell apoptosis and oxidative stress mutually interact to mediate alveolar destruction, we hypothesized that the oxidative stress generated by ceramide is required for its pathogenic effect on lung alveoli. To model the direct lung effects of ceramide, mice received ceramide intratracheally (Cer(12:0) or Cer(8:0); 1 mg/kg) or vehicle. Apoptosis was inhibited with a general caspase inhibitor. Ceramide augmentation shown to mimic levels found in human emphysema lungs increased oxidative stress, and decreased, independently of caspase activation, the lung superoxide dismutase activity at 48 h. In contrast to their wild-type littermates, transgenic mice overexpressing human Cu/Zn SOD were significantly protected from ceramide-induced superoxide production, apoptosis, and air space enlargement. Activation of lung acid sphingomyelinase in response to ceramide treatment was abolished in the Cu/Zn SOD transgenic mice. Since cigarette smoke-induced emphysema in mice is similarly ameliorated by the Cu/Zn SOD overexpression, we hypothesized that cigarette smoke may induce ceramides in the mouse lung. Utilizing tandem mass spectrometry, we documented increased lung ceramides in adult mice exposed to cigarette smoke for 4 wk. In conclusion, ceramide-induced superoxide accumulation in the lung may be a critical step in ceramide's proapoptotic effect in the lung. This work implicates excessive lung ceramides as amplifiers of lung injury through redox-dependent mechanisms.

Peroxiredoxin 2 overexpression protects cortical neuronal cultures from ischemic and oxidative injury but not glutamate excitotoxicity, whereas Cu/Zn superoxide dismutase 1 overexpression protects only against oxidative injury

We previously reported that peroxiredoxin 2 (PRDX2) and Cu/Zn superoxide dismutase 1 (SOD1) proteins are up-regulated in rat primary neuronal cultures following erythropoietin (EPO) preconditioning. In the present study, we have demonstrated that adenovirally mediated overexpression of PRDX2 in cortical neuronal cultures can protect neurons from in vitro ischemia (oxygen-glucose deprivation) and an oxidative insult (cumene hydroperoxide) but not glutamate excitotoxicity. We have also demonstrated that adenovirally mediated overexpression of SOD1 in cortical neuronal cultures protected neurons only against the oxidative insult. Interestingly, we did not detect up-regulation of PRDX2 or SOD1 protein in the rat hippocampus following exposure to either 3 min or 8 min of global cerebral ischemia. Further characterization of PRDX2's neuroprotective mechanisms may aid in the development of a neuroprotective therapy.

Plasma levels of nitric oxide and stroke outcome

Production of reactive oxygen species after cerebral blood flow disruption may enhance tissue damage through multiple molecular pathways. Changes in nitric oxide (NO) metabolism and oxidative stress status were investigated in 47 patients with ischemic stroke by measuring plasma nitric oxide (NO) and peroxynitrite (ONOO(-)) levels.A correlation was sought between these two parameters and i) baseline stroke severity based on the National Institute of Health stroke scale (NIHSS) and ii) neurological outcome in terms of NIHSS changes from entry (T(0)) to 30 days after symptom onset (T(1)). The control group consisted of 30 age- and sex-matched healthy subjects. Mean plasma levels of ONOO(-) (arbitrary fluorescence number +/- SD) were significantly higher in patients (7.70 +/- 1.71 vs 5.35 +/- 0.69, p < 0.001), whereas mean NO levels (nmol/mg protein) were significantly higher in controls (115.40 +/- 12.40 vs. 51.10 +/- 12.50, p < 0.001). Plasma ONOO(-) was significantly higher among patients with non-lacunar stroke (8.48 +/- 1.50 vs. 6.95 +/- 1.58 in those with lacunar stroke; p = 0.001), whereas NO levels were significantly higher among lacunar stroke patients (60.00 +/- 7.86, vs. 41.77 +/- 9.29 in patients with nonlacunar stroke; p < 0.001). Nitric oxide plasma levels were also associated with an unfavorable evolution in non-lacunar stroke, since a 10 unit increase in NO predicted a 1 point reduction in the NIHSS score at T1. Findings show that changes in NO metabolism may be considered as markers of brain injury in patients with ischemic stroke. Further work is needed to establish whether the amount of biochemical changes related to oxidative stress may influence outcome in these patients.

Dual roles of NF-kappaB in cell survival and implications of NF-kappaB inhibitors in neuroprotective therapy

NF-kappaB is a well-characterized transcription factor with multiple physiological and pathological functions. NF-kappaB plays important roles in the development and maturation of lymphoids, regulation of immune and inflammatory response, and cell death and survival. The influence of NF-kappaB on cell survival could be protective or destructive, depending on types, developmental stages of cells, and pathological conditions. The complexity of NF-kappaB in cell death and survival derives from its multiple roles in regulating the expression of a broad array of genes involved in promoting cell death and survival. The activation of NF-kappaB has been found in many neurological disorders, but its actual roles in pathogenesis are still being debated. Many compounds with neuroprotective actions are strongly associated with the inhibition of NF-kappaB, leading to speculation that blocking the pathological activation of NF-kappaB could offer neuroprotective effects in certain neurodegenerative conditions. This paper reviews the recent developments in understanding the dual roles of NF-kappaB in cell death and survival and explores its possible usefulness in treating neurological diseases. This paper will summarize the genes regulated by NF-kappaB that are involved in cell death and survival to elucidate why NF-kappaB promotes cell survival in some conditions while facilitating cell death in other conditions. This paper will also focus on the effects of various NF-kappaB inhibitors on neuroprotection in certain pathological conditions to speculate if NF-kappaB is a potential target for neuroprotective therapy.

Reactive oxygen species plasmatic levels in ischemic stroke

Oxidative stress is probably one of the mechanisms involved in neuronal damage induced by ischemia-reperfusion, and the antioxidant activity of plasma may be an important factor providing protection from neurological damage caused by stroke-associated oxidative stress. The aim of this study was to investigate the status of oxidative stress, NO and ONOO(-) levels in patients with atherothrombotic and lacunar acute ischemic stroke and iNOS, eNOS and nitrotyrosine expression in the same patients. Plasma ONOO(-) levels were significantly higher in patients than in controls while NO decreases in patients in respect to controls. Densitometric analysis of bands indicated that iNOS and N-Tyr protein levels were significantly higher in patients in respect to controls. This study has highlighted a significant NO decrease in our patients compared with controls and this is most probably due to the increased expression of inducible NO synthase by the effect of thrombotic attack. In fact, the constitutive NO isoforms, which produce small amounts of NO, are beneficial, while activation of the inducible isoform of NO, which produces much more NO, causes injury, being its toxicity greatly enhanced by generation of peroxynitrite. The significant ONOO(-) increase observed in our patients, compared to controls, is most probably due to reaction of NO with O(2)(*-) . These findings suggest that free radical production and oxidative stress in ischemic stroke might have a major role in the pathogenesis of ischemic brain injury. Peroxynitrite might be the main marker of brain damage and neurological impairment in acute ischemic stroke.

Overexpression of copper/zinc-superoxide dismutase in transgenic mice markedly impairs regeneration and increases development of neuropathic pain after sciatic nerve injury

Despite the general capacity of peripheral nervous system to regenerate, peripheral nerve injury is often followed by incomplete recovery of function, sometimes with the burden of neuropathic pain. The mechanisms of both regeneration and nociception have not been clarified, but it is known that inflammatory reactions are involved. Cu/Zn-superoxide dismutase (SOD1) is an important scavenger protein that acts against oxidative stress. It has been shown to play an important role in apoptosis and inflammation. The aim of this study was to examine the role of SOD1 overexpression in peripheral nerve regeneration and neuropathic pain-related behavior in mice. Sciatic nerves of SOD1-overexpressing and FVB/N wild type-mice were transected and immediately resutured. Evaluation of motor and sensory function and autotomy was carried out during 4 weeks of followup. We found markedly worse sciatic function index outcome as well as more significant atrophy of denervated muscles in SOD1-overexpressing animals compared with wild type. Autotomy was markedly worse in SOD1 transgenic mice than in wild-type animals. Histological evaluation revealed that the intensity of regeneration features, including numbers of GAP-43-positive growth cones, Schwann cells, and macrophages in the distal stump of the transected nerve, was also decreased in transgenic mice. Neuroma formation at the injury site was significantly more prominent in this group. Taken together, our findings suggest that SOD1 overexpression is deleterious for nerve regeneration processes and aggravates neuropathic pain-like state in mice. This can be at least partially ascribed to disturbed inflammatory reactions at the injury site.

Palmitic acid-treated astrocytes induce BACE1 upregulation and accumulation of C-terminal fragment of APP in primary cortical neurons

High-fat diet is a significant risk factor for the development of Alzheimer's disease (AD). In addition, the AD brain is characterized by elevated levels of fatty acids as compared to that of healthy controls. Despite this, it is unclear how elevated levels of fatty acids are related to the pathogenesis of AD. The present study examines the role of saturated fatty acid, palmitic acid (PA), in causing BACE1 upregulation and consequent amyloidogenic processing of beta-amyloid precursor protein (APP), one of the main characteristic signatures of AD pathology. Here, primary rat cortical neurons and astrocytes were treated with pathological concentration of PA. There was no change in the BACE1 levels in the rat cortical neurons treated directly with PA as compared to controls. The conditioned medium from PA-treated astrocytes, however, caused BACE1 upregulation in the cortical neurons. Moreover, there was a consequent increase in the cleavage of APP leading to the accumulation of the C-terminal fragment of APP (C99) in the cortical neurons. Co-treatment of neurons with 1,3-dimethyl urea (DMU), an antioxidant, decreased PA-induced upregulation in the levels of BACE1 and C99. The present results establish an important role of saturated fatty acids in AD-associated amyloidogenesis through astroglia-mediated oxidative stress.

Early thymic T cell development in young transgenic mice overexpressing human Cu/Zn superoxide dismutase, a model of Down syndrome

Previous studies have shown that transgenic mice overexpressing Cu/Zn superoxide dismutase, a model of Down syndrome, exhibit premature thymic involution. We have performed a flow cytometry analysis of the developing thymus in these homozygous transgenic mice (hSOD1/hSOD1: Tg-SOD). Longitudinal follow-up analysis from day 3 to day 280 showed an early thymic development in Tg-SOD mice compared with controls. This early thymic development was associated with an increased migration of mature T cells to peripheral lymphoid organs. BrdU labeling showed no difference between Tg-SOD and control mice, confirming that the greater number of peripheral T cells in Tg-SOD mice was not due to extensive proliferation of these cells but rather to a greater pool of emigrant T cells in Tg-SOD.

A unique subpopulation of Tbr1-expressing deep layer neurons in the developing cerebral cortex

Cells of the subplate (SP) and deep cortical plate (CP) are among the pioneer neurons of the developing cerebral cortex, an important group of early-born cells that impact cortical organization and function. Similarities between pioneer neurons in different cortical positions and heterogeneities in pioneer cells in the same cortical location, however, have made it difficult to appreciate the characteristics and functions of particular sets of these cells. Here, we provide a tool to illuminate a unique subset of SP and deep CP neurons: expression of a Tbrain-1 (Tbr1)-driven transgene. Transgene-expressing cells were consistently positive for neuronal but not glial markers, were born early in corticogenesis, representing just a subset of SP and deep CP neurons, were morphologically complex during the formation of the cortex, and were maintained into maturity. This analysis reveals a novel group of pioneer neurons and demonstrates unrecognized diversity within this cortical population. In the future, this information will help to uncover the roles of discrete pioneer populations in cortical development.

Neuroprotection from NMDA excitotoxic lesion by Cu/Zn superoxide dismutase gene delivery to the postnatal rat brain by a modular protein vector

BACKGROUND

Superoxide mediated oxidative stress is a key neuropathologic mechanism in acute central nervous system injuries. We have analyzed the neuroprotective efficacy of the transient overexpression of antioxidant enzyme Cu/Zn Superoxide dismutase (SOD) after excitotoxic injury to the immature rat brain by using a recently constructed modular protein vector for non-viral gene delivery termed NLSCt. For this purpose, animals were injected with the NLSCt vector carrying the Cu/Zn SOD or the control GFP transgenes 2 hours after intracortical N-methyl-D-aspartate (NMDA) administration, and daily functional evaluation was performed. Moreover, 3 days after, lesion volume, neuronal degeneration and nitrotyrosine immunoreactivity were evaluated.

RESULTS

Overexpression of Cu/Zn SOD transgene after NMDA administration showed improved functional outcome and a reduced lesion volume at 3 days post lesion. In secondary degenerative areas, increased neuronal survival as well as decreased numbers of degenerating neurons and nitrotyrosine immunoreactivity was seen. Interestingly, injection of the NLSCt vector carrying the control GFP transgene also displayed a significant neuroprotective effect but less pronounced.

CONCLUSION

When the appropriate levels of Cu/Zn SOD are expressed transiently after injury using the non-viral modular protein vector NLSCt a neuroprotective effect is seen. Thus recombinant modular protein vectors may be suitable for in vivo gene therapy, and Cu/Zn SOD should be considered as an interesting therapeutic transgene.

Gene therapy in the nervous system with superoxide dismutase

Neuronal death following necrotic insults involves the generation of reactive oxygen species (ROS). We investigated the effects of antioxidant gene therapy on ROS accumulation after exposure to either sodium cyanide, kainic acid or oxygen glucose deprivation (OGD). Specifically, we generated herpes simplex virus-1 amplicon vector expressing the gene for the antioxidant enzyme CuZnSOD. Overexpression of this gene in primary hippocampal cultures resulted in increased enzymatic activity of the corresponding protein. CuZnSOD significantly protected hippocampal neurons against sodium cyanide insult and the subsequent lipid peroxidation. However, it did not protect against OGD- or kainic-acid-induced toxicity. Moreover, CuZnSOD significantly worsened the toxicity, hydrogen peroxide accumulation and lipid peroxidation induced by kainic acid. As a possible explanation for this surprising worsening, CuZnSOD overexpression increased glutathione peroxidase activity in the presence of sodium cyanide but had no effect on catalase or glutathione peroxidase activity in the presence of kainic acid. Thus, cells were unlikely to be able to detoxify the excess hydrogen peroxide produced as a result of the CuZnSOD overexpression. These studies can be viewed as a cautionary note concerning gene therapy intervention against necrotic insults.

Melatonin as a cytoskeletal modulator: implications for cell physiology and disease

The cytoskeleton is a phylogenetically well-preserved structure that plays a key role in cell physiology. Dynamic and differential changes in cytoskeletal organization occur in cellular processes according to the cell type and the specific function. In neurons, microtubules, microfilaments and intermediate filament (IF) rearrangements occur during axogenesis, and neurite formation which eventually differentiate into axons and dendrites to constitute synaptic patterns of connectivity. In epithelial cells, dynamic modifications occur in the three main cytoskeletal components and phosphorylation of cytoskeletal associated proteins takes place during the formation of the epithelial cell monolayer that eventually will transport water. In pathological processes such as neurodegenerative and psychiatric diseases an abnormal cytoskeletal organization occurs. Melatonin, the main product secreted by pineal gland during dark phase of the photoperiod, is capable of influencing microfilament, microtubule and IF organization by acting as a cytoskeletal modulator. In this paper we will summarize the evidence which provides the data that melatonin regulates cytoskeletal organization and we describe recent findings, which indicate that melatonin effects on microfilament rearrangements in stress fibers are involved in the mechanism by which the indole synchronizes water transport in kidney-derived epithelial cells. In addition, we review recent data, which indicates that melatonin protects the neuro-cytoskeletal organization from damage caused by free radicals contributing to cell survival, in addition to the already described mechanism elicited by the indole to prevent apoptosis and to scavenge free radicals. Moreover, we discuss the implications of an altered cytoskeletal organization for neurodegenerative and psychiatric illnesses and its re-establishment by melatonin.

A unique subpopulation of Tbr1-expressing deep layer neurons in the developing cerebral cortex

Cells of the subplate (SP) and deep cortical plate (CP) are among the pioneer neurons of the developing cerebral cortex, an important group of early-born cells that impact cortical organization and function. Similarities between pioneer neurons in different cortical positions and heterogeneities in pioneer cells in the same cortical location, however, have made it difficult to appreciate the characteristics and functions of particular sets of these cells. Here, we provide a tool to illuminate a unique subset of SP and deep CP neurons: expression of a Tbrain-1 (Tbr1)-driven transgene. Transgene-expressing cells were consistently positive for neuronal but not glial markers, were born early in corticogenesis, representing just a subset of SP and deep CP neurons, were morphologically complex during the formation of the cortex, and were maintained into maturity. This analysis reveals a novel group of pioneer neurons and demonstrates unrecognized diversity within this cortical population. In the future, this information will help to uncover the roles of discrete pioneer populations in cortical development.

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.

Exploratory activity and motor coordination in wild-type SOD1/SOD1 transgenic mice

SOD1 is one of several overexpressed genes in trisomy 21. In order to dissect possible genetic causes of the syndrome, wild-type SOD1/SOD1 transgenic mice were compared to FVB/N non-transgenic controls at 5 months of age in tests of exploratory activity and motor coordination. Wild-type SOD1/SOD1 transgenic mice had fewer stereotyped movements in an open-field and fell sooner from a rotorod than controls. In contrast, wild-type SOD1/SOD1 transgenic mice had fewer falls on a wire suspension test. There was no intergroup difference for ambulatory movements in the open-field, exploration of the elevated plus-maze, emergence from a small compartment, and motor coordination on a stationary beam. These results indicate that homozygous mice expressing human SOD1 are impaired in their ability to adjust their posture in response to a moving surface and make fewer small-amplitude movements without any change in general exploratory activity.

SOD-1 inhibits FAS expression in cortex of APP transgenic mice

Peptides derived from proteolytic processing of the amyloid precursor protein (APP) are important for the pathogenesis of Alzheimer's disease (AD). In the present study, we found that transgenic mice overexpressing wild-type human APP gene (hAPP/+) displayed a much higher expression of FAS, one of the death receptor subfamily. This FAS overexpression was significantly reduced in the cortex of mice overexpressing both wild-type hAPP gene and wild-type human superoxide dismutase-1 gene (hSOD-1). Moreover hSOD-1 transgenic expression was associated with an increase of Glial fibrillary acidic protein (GFAP) production. This study indicates that SOD-1 overexpression can inhibit FAS expression, which may be beneficial in AD.

Overexpression of copper/zinc superoxide dismutase decreases ischemia-like astrocyte injury

Overexpression of copper/zinc superoxide dismutase (SOD1) in transgenic mice protects from transient focal cerebral ischemia in adult animals, but increases oxidative injury in perinatal mice. The effect of SOD1 overexpression on astrocytes subjected to ischemia-like insults has not yet been determined. Overexpression of human SOD1 in astrocytes resulted in a 3-fold increase in SOD1 activity without coupled up-regulation of catalase or glutathione peroxidase activities. Cells subjected to oxygen-glucose deprivation (OGD) or glucose deprivation to mimic ischemic injury were protected by SOD1 overexpression. OGD injury was reduced 47.6+/-9.3%, assessed by release of lactate dehydrogenase. OGD also caused a significant increase in catalase activity which was moderated by SOD1 overexpression. The level of glutathione in astrocytes overexpressing SOD1 was maintained at higher levels following 5 h OGD compared to control cultures under the same conditions. Reduction of glutathione prior to OGD significantly increased cell death of SOD1-overexpressing astrocytes as well as controls, but SOD1 still provided significant protection, suggesting that both GSH-dependent scavenging and GSH-independent scavenging are relevant to SOD1 protection in astrocytes.

Dieldrin promotes proteolytic cleavage of poly(ADP-ribose) polymerase and apoptosis in dopaminergic cells: protective effect of mitochondrial anti-apoptotic protein Bcl-2

Previously, we demonstrated that the organochlorine pesticide dieldrin induces mitochondrial depolarization, caspase-3 activation and apoptosis in dopaminergic PC12 cells. We also demonstrated that protein kinase Cdelta (PKCdelta), a member of a novel PKC family of proteins, is proteolytically activated by caspase-3 to mediate apoptotic cell death processes. In the present study, we have further characterized the protective effect of the major mitochondrial anti-apoptotic protein Bcl-2 against dieldrin-induced apoptotic events in dopaminergic cells. Exposure to dieldrin (30-100 microM) produced significant cytotoxicity and caspase-3 activation within 3h in vector-transfected PC12 cells, whereas human Bcl-2-transfected PC12 cells were almost completely resistant to dieldrin-induced cytotoxicity and caspase-3 activation. Also, dieldrin (30-300 microM) treatment induced proteolytic cleavage of poly(ADP-ribose) polymerase (PARP), which was blocked by pretreatment with caspase-3 inhibitors Z-DEVD-FMK and Z-VAD-FMK. Additionally, dieldrin-induced chromatin condensation and DNA fragmentation were completely blocked in Bcl-2-overexpressed PC12 cells as compared to vector control cells. Together, these results clearly indicate that overexpression of mitochondrial anti-apoptotic protein protects against dieldrin-induced apoptotic cell death and further suggest that dieldrin primarily alters mitochondrial function to initiate apoptotic cell death in dopaminergic cells.

Characterization of hemizygous SOD1/wild-type transgenic mice with the SHIRPA primary screen and tests of sensorimotor function and anxiety

SOD1 is one of several overexpressed genes in Down's syndrome. In order to dissect genetic causes of the syndrome, hemizygous human wild-type SOD1 transgenic mice were compared to FVB/N non-transgenic controls at 3 months of age in the SHIRPA primary screen of neurologic function as well as in tests of motor activity and coordination. The responsiveness of SOD1/wt transgenic mice to visual and somatosensory stimuli was reduced in placing, pinna, corneal, and toe-pinch tests. In addition, SOD1/wt transgenic mice crossed fewer segments on a stationary beam. On the contrary, there was no intergroup difference for motor activity and anxiety in open-field and emergence tests and for latencies before falling on the stationary beam, coat-hanger, and rotorod. These results indicate mild deficits in sensorimotor responsiveness in a mouse model expressing human SOD1 and that the overexpressed gene may be responsible for some Down symptoms.

Sleep-wake architecture in mouse models for Down syndrome

Sleep-wake homeostasis is crucial for behavioral performances and memory both in the general population and in patients with learning disability, among whom were Down syndrome (DS) patients. We investigated, in mouse models of DS, cortical EEG and sleep-wake architecture under baseline conditions and after a 4-h sleep deprivation (SD). Young hemizygous mice (hSODwt/+) transgenic for the human CuZn superoxide dismutase (hSOD1) or for the human amyloid precursor protein (HuAPP(695); hAPPwt/+) were obtained on the same FVB/N inbred background. Baseline records for slow wave sleep (SWS) and wake (W) parameters were unchanged, whereas paradoxical sleep (PS) episode numbers were decreased and PS latency increased after lights off in hSODwt/+ mice versus controls. hSODwt/+ mice did not experience SWS or PS rebounds after SD but EEG activity in the delta-SWS activity (SWA) was enhanced. hAPPwt/+ mice exhibited no change in PS but an increase in W and a decrease in SWS before light transition as well as an increase in theta-power in PS and W. After SD, hAPPwt/+ mice exhibited SWS and PS rebounds as well as enhancement of SWA. We investigated also the nitrite/nitrate levels in all mice and found an increase in the brainstem of hSODwt/+ mice only versus control ones. These preliminary data provide useful results to investigate other genetically manipulated mice and to better understand the biochemical basis of sleep disorders in DS patients.

Neurobehavioral characteristics of mice with modified intermediate filament genes

Intermediate proteins comprise cytoskeletal elements that preserve the shape and structure of neurons. These proteins have been proposed to be involved in the onset and progression of amyotrophic lateral sclerosis (ALS), mainly characterized by motoneuron atrophy and paresis. In support of this hypothesis are the findings that genetically modified mice for intermediate filaments successfully mimic certain neuropathological aspects of ALS, such as reduced axonal caliber and retarded conduction speed in peripheral nerves, although often without leading to paresis. Nevertheless, even in those models with no overt phenotype, the involvement of intermediate proteins in motor function is underlined by the deficits in tests of balance and equilibrium revealed in mice containing transgenes for neurofilament of heavy molecular weight (NFH), alpha-internexin, peripherin, and vimentin. In addition, spatial learning was impaired in transgenic mice expressing transgenes for NFH and NFM, similar to the memory deficits reported in patients with ALS.

Transforming growth factor-alpha attenuates N-methyl-D-aspartic acid toxicity in cortical cultures by preventing protein synthesis inhibition through an Erk1/2-dependent mechanism

Transforming growth factor-alpha (TGF-alpha), a ligand of the epidermal growth factor receptor, reduces the infarct size after focal cerebral ischemia in rat, but the molecular basis underlying the protection is unknown. Excitotoxicity and global inhibition of translation are acknowledged to contribute significantly to the ischemic damage. Here we studied whether TGF-alpha can rescue neurons from excitotoxicity in vitro and how it affects calcium homeostasis, protein synthesis, and the associated Akt and extracellular signal-regulated kinase 1/2 (Erk1/2) intracellular signaling pathways in mixed neuron-glia cortical cultures. We found that 100 ng/ml TGF-alpha attenuated neuronal cell death induced by a 30-min exposure to 35 microM N-methyl-D-aspartic acid (NMDA) (as it reduced lactate dehydrogenase release, propidium iodide staining, and caspase-3 activation) and decreased the elevation of intracellular Ca2+ elicited by NMDA. TGF-alpha induced a prompt and sustained phosphorylation of Erk1/2 and prevented the loss of Akt-P induced by NMDA 3 h after exposure. The protective effect of TGF-alpha was completely prevented by PD 98059, an inhibitor of the Erk1/2 pathway. Studies of incorporation of [3H]leucine into proteins showed that NMDA decreased the rate of protein synthesis, and TGF-alpha attenuated this effect. TGF-alpha stimulated the phosphorylation of the eukaryotic initiation factor 4E (eIF4E) but did not affect eIF2 alpha, two proteins involved in translation regulation. PD 98059 abrogated the TGF-alpha effect on eIF4E. Our data demonstrate that TGF-alpha exerts a neuroprotective action against NMDA toxicity, in which Erk1/2 activation plays a key role, and suggest that the underlying mechanisms involve recovery of translation inhibition, mediated at least in part by eIF4E phosphorylation.

Erythrocyte zinc, copper, and copper/zinc superoxide dismutase and risk of sporadic amyotrophic lateral sclerosis: a population-based case-control study

We investigated through a population-based case-control study the hypothesis that disturbances in the chemistry of copper and zinc and in activity of the antioxidant enzyme copper/zinc superoxide-dismutase (SOD1) are involved in the etiopathogenesis of sporadic amyotrophic lateral sclerosis (ALS). We recruited 20 patients with sporadic ALS and 22 population controls from three northern Italian provinces, and we analyzed zinc and copper content and SOD1 activity in erythrocytes. These variables were unrelated to disease progression as evaluated through a disability score; zinc concentrations inversely correlated with copper in referents but not in patients. SOD1 activity was lower and erythrocyte zinc and copper levels were slightly higher in patients than in referents. Comparing the second to the bottom tertile of erythrocyte SOD1 activity, relative risk of ALS was 0.4 (95% confidence interval 0.1-2.0); the risk further decreased to 0.1 (95% confidence interval 0-0.9) for comparison of highest to lowest tertile (P for trend 0.027). Copper and zinc levels were not associated with disease risk. Our findings indicate that a lower SOD1 activity is associated with ALS, but we cannot be sure whether this association is a marker of causal action or is secondary to a confounder, or to disease onset itself.