Free Radical Oxidative Stress Research Articles

Methionine 35 oxidation reduces toxic effects of the amyloid β-protein fragment (31–35) on human red blood cell

Amyloid β-peptide, the central constituent of senile plaques in Alzheimer’s disease brain, has been shown to be a source of free radical oxidative stress that may lead to neurodegeneration. In particular, it is well known that oxidation of methionine 35, is strongly related to the pathogenesis of Alzheimer’s disease, since it represents the residue in the β-amyloid peptide most susceptible to oxidation “in vivo”. In this study, the fragment 31–35 of the β-amyloid peptide, which has a single methionine at residue 35, was used to investigate the influence of the oxidation state of methionine-35 on the β-amyloid peptide (31–35) mediated cytotoxic effects. Because no extensive studies have yet addressed whether amyloid β peptides-mediated toxic effects can occur in the absence of mitochondria, human red blood cells were used as cell model. Exposure of intact red blood cells to β-amyloid peptide (31–35) induced a marked stimulation (∼45%) of the pentose phosphate pathway and a significant inhibition of the red cell enzyme catalase, compared with the results observed in control red blood cells. In contrast, exposure of red blood cells to the β-amyloid peptide (31–35)-Met35 OX i.e. in which the sulfur of methionine is oxidised to sulfoxide, induced a slight activation of PPP (∼19%), and an inhibition of catalase activity lower with respect to the results observed in β-amyloid peptide (31–35)-treated red blood cells. Since the activities of red cell phosphofructokinase, glucose-6-phosphate dehydrogenase, glutathione peroxidase, glutathione reductase and the functionality of hemoglobin were not modified within the red cell following to β-amyloid peptides exposure, it is likely that β-amyloid (31–35)–catalase interaction may represent a selective toxic event. Together, these results support the hypothesis that Aβ peptide and the oxidative state of Met-35 may be involved in the mechanisms responsible of neurodegeneration in Alzheimer’s disease.

Free radicals: key to brain aging and heme oxygenase as a cellular response to oxidative stress.

Aging is one of the unique features in all organisms. The impaired functional capacity of many systems characterizes aging. When such impairments occur in the brain, the susceptibility to neurodegenerative diseases amplifies considerably. The free radical theory of aging posits that the functional impairments in brains are due to the attack on critical cellular components by free radicals, reactive oxygen species, and reactive nitrogen species produced during normal metabolism. In this review, we examine this concept based on the parameters of oxidative stress in correlation to aging. The parameters for lipid peroxidation are phospholipid composition, reactive aldehydes, and isoprostanes. The parameters for protein oxidation are protein carbonyl levels, protein 3-nitrotyrosine levels, electron paramagnetic resonance, and oxidative stress-sensitive enzyme activities. We conclude that free radicals are, at least partially, responsible for the functional impairment in aged brains. The aging brain, under oxidative stress, responds by induction of various protective genes, among which is heme oxygenase. The products of the reaction catalyzed by heme oxygenase, carbon monoxide, iron, and biliverdin (later to bilirubin) each have profound effects on neurons. Although there may be other factors contributing to brain aging, free radicals are involved in the damaging processes associated with brain aging, and cellular stress response genes are induced under free radical oxidative stress. Therefore, this review supports the proposition that free radicals are, indeed, a key to brain aging.

Iron Supplementation Does Not Affect the Susceptibility of LDL to Oxidative Modification in Women with Low Iron Status

Elevated iron stores may or may not promote atherogenesis by increasing free radical formation and oxidative stress, but controlled diet and supplement trials are lacking. We tested the hypothesis that iron supplementation does not increase the susceptibility of LDL to undergo oxidative modification in women with low iron status. A randomized, double-blind, 2-period crossover study design (n=26) was used to examine the effects of the following diets on measures of LDL oxidation: average American diet (AAD) [36% of energy as fat; 15% saturated fatty acids (SFA)], and a Step 2 diet (26% fat; 7% SFA). In addition, subjects received either a supplement containing 160 mg of ferrous sulfate (50 mg elemental iron) or a placebo twice daily [supplement group received a total of 320 mg ferrous sulfate (100 mg elemental iron) daily]. After supplementation, serum ferritin differed between the supplement and placebo groups (P=0.008). Measures of LDL oxidation were not affected by supplement intake; however, they were affected by diet. Lag time was shorter after the women consumed the AAD diet than after the Step 2 diet (P<0.0001). The diets did not affect the rate of oxidation or total dienes. Although iron status was improved by aggressive iron supplementation, LDL oxidative susceptibility was not affected. As expected, lag time was increased after the women consumed the low fat, low SFA diet. Therefore, the results of this study do not support a relationship between iron status and LDL oxidation.

Methionine 35 oxidation reduces toxic and pro-apoptotic effects of the amyloid β-protein fragment (31–35) on isolated brain mitochondria

Amyloid β-peptide (AβP), the central constituent of senile plaques in Alzheimer's disease (AD) brain, has been shown to be a source of free radical oxidative stress that may lead to neurodegeneration. In particular, it is well known that oxidation of methionine 35, is strongly related to the pathogenesis of AD, since it represents the residue in AβP most susceptible to oxidation in vivo. In the present study, we used the fragment 31–35 of AβP, which has a single methionine at residue 35, in order to investigate the influence of the oxidation state of methionine-35 on the toxic and pro-apoptotic effects induced by Aβ(31–35) on isolated brain mitochondria. The obtained results show that exposure of isolated mitochondria from rat brain to AβP(31–35) determines (i) a large release of cytochrome c (ii) a significant reduction in mitochondrial respiration and (iii) a slight drop in the mitochondrial membrane potential (ΔΨ). In contrast, the amplitude of these events resulted attenuated or completely abrogated in isolated brain mitochondria exposed to the AβP(31–35)Met35 OX, in which methionine 35 was oxidized to methionine sulfoxide. We have further characterized the action of AβP(31–35) and Aβ(31–35)Met35 OX peptide on PC12 cells. Although these two peptides, compromised mitochondrial function at a different extent as assessed by MTT reduction, neither one of them decreased cell viability as measured by Trypan Blue exclusion assay. The results obtained in this study support the hypothesis that the oxidative state of Met-35 may play a critical role in the mechanisms responsible of neurotoxicity exerted by this peptide.

In utero exposure to tobacco and alcohol modifies neurobehavioral development in mice offspring: consideration a role of oxidative stress

Objective: To determine whether in utero tobacco and alcohol exposure induces long-term neurobehavioral alterations and whether oxidative stress/damage is a possible causal factor. Methods: Gravid mice were subjected to tobacco smoking and alcohol consumption. Their offspring were subsequently evaluated in developmental and behavioral tests. Antioxidative enzymes and erythrocyte membrane fluidity of adult offspring were measured. Results: The intrauterine tobacco and alcohol exposure has resulted in significant reduced postnatal body and organ weights accompanied by reduced gestational body weight gain in their mothers. Such exposure also induced remarkable developmental delay in neonatal reflexes and notable behavioral deficit in adulthood, namely reduced motive coordination and locomotor activity as well as impaired learning and memory abilities. Furthermore, the formation of malondialdehyde (MDA) increased significantly whereas the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), catalase (Cat) and glutathione S-transferases (GST) decreased in the cerebral cortex and liver of prenatal intoxicated offspring. The embryonic intoxication also markedly reduced erythrocyte membrane fluidity in offspring. Conclusion: Our study shows the long-term neurotoxicity associated with prenatal tobacco and alcohol exposure, and suggests that the deleterious outcome may be in relation to increased free radicals formation and oxidative stress.

Oxidants and Antioxidants: Ultrastructure and Molecular Biology Protocols

Edited by Donald Armstrong, 356 pp, with illus, Totowa, NJ, Humana Press, 2002.The book is edited by Donald Armstrong and is part of a series published by Humana Press under the title Methods in Molecular Biology, with John M. Walker as series editor. As Armstrong outlines in his introduction, the book is the 3rd volume under his editorship dealing with topics relating to oxidative stress status. The 2 other books, titled Free Radical and Antioxidant Protocols and Oxidative Stress Biomarkers and Antioxidant Protocols, have also been published by Humana Press and are protocols books.The present volume, a protocols book as well, is organized into 4 parts (Part I. Techniques for Histological Identification; Part II. Techniques for Subcellular Localization; Part III. Techniques for Molecular Biology; and Part IV. Techniques for In Vivo/Ex Vivo/In Vitro Applications) and contains a total of 36 chapters ranging from 5 to 30 pages. Each chapter is written by an expert (or a group of experts), provides an introduction to the concept of the outlined method(s), and describes in step-by-step detail how to perform the method(s) under discussion. Topics range from cytochemical localization of hydrogen peroxide in biologic tissues or intracellular localization of lipid hydroperoxides to studies of gene expression during oxygen deprivation or the in vivo detection of transition metals and nitrosyl-heme complexes, to name a few.The applications presented in this volume range from straightforward immunochemical procedures to rather sophisticated and expensive techniques such as spectral-spatial electron paramagnetic resonance imaging, x-ray diffraction, and confocal microscopy. Nevertheless, any person working in the field of oxidative stress will appreciate this practical and comprehensive collection of up-to-date molecular and ultrastructural applications for the in vitro and in vivo/ex vivo analysis of free radical and antioxidant reactions.

Decreased lysophosphatidylcholine/phosphatidylcholine ratio in cerebrospinal fluid in Alzheimer's disease.

Choline containing phospholipids are essential for the integrity of the'cell'membrane. Minor changes in the lysophosphatidylcholine (lyso-PC)/phosphatidylcholine (PC) ratio may lead to neuronal damage and cell loss. Several studies have shown protein and lipid oxidation in Alzheimer's disease (AD) affected brain regions. Amyloid-beta peptides may induce free-radical oxidative stress which normally is counteracted by anti-oxidant defense mechanisms. We hypothesize that oxidation may lead to changed concentrations of choline containing phospholipids in cerebrospinal fluid (CSF) of AD patients, because of the susceptibility of the unsaturated acyl-chains of PC for oxidation. PC and lyso-PC were determined in CSF of AD patients (n=19) and subjects with subjective memory complaints without dementia (n=19) by tandem mass spectrometry. No differences in total PC concentrations were observed between both study groups. Furthermore, we could not demonstrate different concentrations of PC species containing linoleic acid and PC species containing arachidonic acid. Interestingly, lyso-PC concentrations tended to be lower while the lyso-PC/PC ratio was significantly decreased in CSF of AD patients compared to controls (0.36% versus 0.54%; P=0.017). A comparable decrease was found for the lyso-PC/PC ratio for PC containing linoleic acid (P=0.022) or arachidonic acid (P=0.010), respectively. The lower lyso-PC/PC ratio in CSF of patients with AD may reflect alterations in the metabolism of choline-containing phospholipids in the brain in AD, and suggests that PC species containing linoleic acid or arachidonic acid are equally involved.

Protective effects of the antioxidant selenium on quinolinic acid-induced neurotoxicity in rats: in vitro and in vivo studies.

Quinolinic acid (QUIN), a well known excitotoxin that produces a pharmacological model of Huntington's disease in rats and primates, has been shown to evoke degenerative events in nerve tissue via NMDA receptor (NMDAr) overactivation and oxidative stress. In this study, the antioxidant selenium (as sodium selenite) was tested against different markers of QUIN-induced neurotoxicity under both in vitro and in vivo conditions. In the in vitro experiments, a concentration-dependent effect of selenium was evaluated on the regional peroxidative action of QUIN as an index of oxidative toxicity in rat brain synaptosomes. In the in vivo experiments, selenium (0.625 mg per kg per day, i.p.) was administered to rats for 5 days, and 2 h later animals received a single unilateral striatal injection of QUIN (240 nmol/ micro L). Rats were killed 2 h after the induction of lesions with QUIN to measure lipid peroxidation and glutathione peroxidase (GPx) activity in striatal tissue. In other groups, the rotation behavior, GABA content, morphologic alterations, and the corresponding ratio of neuronal damage were all evaluated as additional markers of QUIN-induced striatal toxicity 7 days after the intrastriatal injection of QUIN. Selenium decreased the peroxidative action of QUIN in synaptosomes both from whole rat brain and from the striatum and hippocampus, but not in the cortex. A protective concentration-dependent effect of selenium was observed in QUIN-exposed synaptosomes from whole brain and hippocampus. Selenium pre-treatment decreased the in vivo lipid peroxidation and increased the GPx activity in QUIN-treated rats. Selenium also significantly attenuated the QUIN-induced circling behavior, the striatal GABA depletion, the ratio of neuronal damage, and partially prevented the morphologic alterations in rats. These data suggest that major features of QUIN-induced neurotoxicity are partially mediated by free radical formation and oxidative stress, and that selenium partially protects against QUIN toxicity.

Effect of short-term hormone therapy on oxidative stress and endothelial function in African American and Caucasian postmenopausal women

Objective In postmenopausal women (PMW), the effect of a short-term course of estrogen/progestin HT on free radical oxidative stress was evaluated. In addition, HT’s effect on plasma nitric oxide (NO) activity was determined as a measure of vascular endothelial function. We investigated the relationship of these markers and HT across race and the cardiovascular risk factors of smoking, diabetes and hypertension. Design A prospective, observational study comparing preintervention and postintervention. Setting Academic research center. Patient(s) Twenty-seven (14 African American and 13 Caucasian) PMW volunteers. Intervention(s) Six weeks of continuous, combined estrogen/progestin HT. Main outcome measure(s) Plasma concentrations of free 8-epi-prostaglandin F 2α (8-isoprostane) before and after HT were compared as a measure of oxidative stress. Nitrite, the stable oxidation metabolite of NO, was measured by the Greiss reaction after nitrate reduction to nitrite with cadmium. Results Plasma levels of free 8-isoprostane decreased significantly after 6 weeks of HT. Although almost all subjects benefited from the reduction in free 8-isoprostane, PMW with at least one cardiovascular risk factor (n = 19) demonstrated higher free 8-isoprostane than did subjects with no risk factors. Plasma levels of nitrite increased after 6 weeks of HT, but the difference was not statistically significant. Caucasian PMW demonstrated a greater increase in plasma levels of nitrite after 6 weeks of HT as compared with African American subjects, who exhibited almost no change. Conclusion(s) Short-term administration of HT significantly reduces oxidative stress in PMW and is consistent across race. However, there was an observed racial difference in endothelial NO response to HT between African American and Caucasian PMW.

Oxidative Stress and Sleep Apnoea in Clinically Healthy Infants in the First Year of Life. Oxidativer Stress und Schlafapnoen bei klinisch gesunden Sauglingen

Respiratory instability as well as tissue damage by free radicals (oxidative stress) have been hypothesized to play a role in cases of sudden and unexpected infant death in the first year of life. The ratio of the oxidized/reduced form of redox compounds in the circulation could be used as a marker of oxidative stress. Therefore, the sleep apnoea rate and redox status of coenzyme Q10 (CoQ10) (percentage of the oxidized form in total CoQ10) were measured in a population of clinically healthy infants in their first year of life in order to study whether a physiological parameter of respiratory instability is related to a biochemical parameter of oxidative stress. Between May and December 1999, 323 infants in the first year of life were referred to a paediatric sleep laboratory. Sleep apnoea rate, periodic breathing and parameters of oxygenation (SaO2 and TcPO2) were calculated based on polysomnographic recordings. The CoQ10 redox status was calculated based on high-pressure liquid chromatographic (HPLC) analysis. Statistical analysis showed an age-dependent decrease in apnoea rate (r=−0.38) and CoQ10 redox status (r=−0.40). An increased CoQ10 redox status (median: 16.6%; range: 7.3–29.7%) was found in infants with high apnoea rates above the 90th percentile of a reference group in comparison with infants with apnoea rates below the 90th percentile of a reference group (median: 10.4%; range: 5.1–20.4%; P=0.031). These findings may indicate that high apnoea rates are accompanied by increased formation of free radicals in clinically healthy infants in the first year of life.

Current research on methamphetamine-induced neurotoxicity: animal models of monoamine disruption.

Methamphetamine (METH)-induced neurotoxicity is characterized by a long-lasting depletion of striatal dopamine (DA) and serotonin as well as damage to striatal dopaminergic and serotonergic nerve terminals. Several hypotheses regarding the mechanism underlying METH-induced neurotoxicity have been proposed. In particular, it is thought that endogenous DA in the striatum may play an important role in mediating METH-induced neuronal damage. This hypothesis is based on the observation of free radical formation and oxidative stress produced by auto-oxidation of DA consequent to its displacement from synaptic vesicles to cytoplasm. In addition, METH-induced neurotoxicity may be linked to the glutamate and nitric oxide systems within the striatum. Moreover, using knockout mice lacking the DA transporter, the vesicular monoamine transporter 2, c-fos, or nitric oxide synthetase, it was determined that these factors may be connected in some way to METH-induced neurotoxicity. Finally a role for apoptosis in METH-induced neurotoxicity has also been established including evidence of protection of bcl-2, expression of p53 protein, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), activity of caspase-3. The neuronal damage induced by METH may reflect neurological disorders such as autism and Parkinson's disease.

Oxidative stress in Parkinson's disease.

Oxidative stress contributes to the cascade leading to dopamine cell degeneration in Parkinson's disease (PD). However, oxidative stress is intimately linked to other components of the degenerative process, such as mitochondrial dysfunction, excitotoxicity, nitric oxide toxicity and inflammation. It is therefore difficult to determine whether oxidative stress leads to, or is a consequence of, these events. Oxidative damage to lipids, proteins, and DNA occurs in PD, and toxic products of oxidative damage, such as 4-hydroxynonenal (HNE), can react with proteins to impair cell viability. There is convincing evidence for the involvement of nitric oxide that reacts with superoxide to produce peroxynitrite and ultimately hydroxyl radical production. Recently, altered ubiquitination and degradation of proteins have been implicated as key to dopaminergic cell death in PD. Oxidative stress can impair these processes directly, and products of oxidative damage, such as HNE, can damage the 26S proteasome. Furthermore, impairment of proteasomal function leads to free radical generation and oxidative stress. Oxidative stress occurs in idiopathic PD and products of oxidative damage interfere with cellular function, but these form only part of a cascade, and it is not possible to separate them from other events involved in dopaminergic cell death.

The neuropathogenic contributions of lysosomal dysfunction.

Multiple lines of evidence implicate lysosomes in a variety of pathogenic events that produce neurodegeneration. Genetic mutations that cause specific enzyme deficiencies account for more than 40 lysosomal storage disorders. These mostly pre-adult diseases are associated with abnormal brain development and mental retardation. Such disorders are characterized by intracellular deposition and protein aggregation, events also found in age-related neurodegenerative diseases including (i) Alzheimer's disease and related tauopathies (ii) Lewy body disorders and synucleinopathies such as Parkinson's disease, and (iii) Huntington's disease and other polyglutamine expansion disorders. Of particular interest for this review is evidence that alterations to the lysosomal system contribute to protein deposits associated with different types of age-related neurodegeneration. Lysosomes are in fact highly susceptible to free radical oxidative stress in the aging brain, leading to the gradual loss of their processing capacity over the lifespan of an individual. Several studies point to this lysosomal disturbance as being involved in amyloidogenic processing, formation of paired helical filaments, and the aggregation of alpha-synuclein and mutant huntingtin proteins. Most notably, experimentally induced lysosomal dysfunction, both in vitro and in vivo, recapitulates important pathological features of age-related diseases including the link between protein deposition and synaptic loss.

C-reactive protein a marker for all-cause and cardiovascular mortality in haemodialysis patients.

Inflammation is thought to play a central role in the aetiology and outcome of atherosclerosis. C-reactive protein (CRP) is a prominent product of the inflammatory response syndrome and a marker of overall and cardiovascular death in the general population and in dialysis patients. CRP is 5- to 10-fold higher in haemodialysis patients than in healthy controls and clearly is multifactorial in origin. A number of endogenous factors have been identified in vitro [angiotensin II, lipopolysacharide, modified low-density lipoprotein (LDL), advanced glycation end-products, homocysteine, viral infections] which all are able to trigger a nuclear factor (NF)-kappaB-mediated inflammatory, interleukin-6-driven, response via the generation of oxygen free radicals (oxidative stress). In addition, exogenous factors (dialysate endotoxin, vascular access, cuprophane dialyser material) have been identified in clinical studies which are also responsible, at least in part, for high serum CRP levels. Some of these factors function by themselves as non-traditional cardiovascular risk factors. Whether CRP is simply a marker of cardiovascular disease and mortality or whether it is in the causal pathway of the disease remains an open question. Recent data are in favour of a direct involvement in the pathogenesis of disease, since binding of CRP to degraded LDL enhances complement activation and induces the expression of tissue factor.

Methionine residue 35 is critical for the oxidative stress and neurotoxic properties of Alzheimer’s amyloid β-peptide 1–42

Amyloid β-peptide 1–42 [Aβ(1–42)] is central to the pathogenesis of Alzheimer’s disease (AD), and the AD brain is under intense oxidative stress. Our laboratory combined these two aspects of AD into the Aβ-associated free radical oxidative stress model for neurodegeneration in AD brain. Aβ(1–42) caused protein oxidation, lipid peroxidation, reactive oxygen species formation, and cell death in neuronal and synaptosomal systems, all of which could be inhibited by free radical antioxidants. Recent studies have been directed at discerning molecular mechanisms by which Aβ(1–42)-associated free radical oxidative stress and neurotoxicity arise. The single methionine located in residue 35 of Aβ(1–42) is critical for these properties. This review presents the evidence supporting the role of methionine in Aβ(1–42)-associated free radical oxidative stress and neurotoxicity. This work is of obvious relevance to AD and provides a coupling between the centrality of Aβ(1–42) in the pathogenesis of AD and the oxidative stress under which the AD brain exists.

Neurotoxicity of Diethylpropion

The effects of diethylpropion (DEP), an amphetamine derivative and a well-known anorectic agent, on different neurochemical and behavioral markers of toxicity in rats were evaluated. Animals received a daily dose of DEP (5 mg/kg po) for 15 days, and all tests were performed 24 hours after the last DEP administration. As neurochemical markers, the brain regional levels of some amino acids, such as aspartate (Asp), glutamate (Glu), gamma-aminobutyric acid (GABA), and glutamine (Gln), as well as the brain regional rates of lipid peroxidation as a current index of oxidative stress were measured. As behavioral markers, the actions of DEP on both mercaptopropionic acid (MPA)-induced seizures and kainic acid (KA)-induced wet-dog body shakes were explored to investigate whether DEP induces behavioral sensitization to the effects of agents affecting the central activity of neuroactive amino acids. Treatment with DEP produced significant changes in the levels of Asp in the hypothalamus (Ht) and cortex (Cx); Glu in the Ht, Cx, midbrain (Mb), and striatum (S); and Gln in the Cx. The regional levels of GABA remain unchanged. Lipid peroxidation was increased in the hippocampus (Hc), Mb, and S. Also, latency to the first seizure induced by MPA (1.2 mmol/kg i.p.) and the total number of wet-dog body shakes induced by KA (10 mg/kg i.p.) were significantly affected by DEP treatment. These findings suggest that low doses of DEP may affect different neurochemical substrates, inducing changes in neuroactive amino acids along the brain regions, probably involving dopamine release. Consequently, behavioral changes could be the result of excitotoxic events related to excessive Glu or lack of an inhibitory process. Also, DEP is thought to involve free radical formation and oxidative stress as potential features of its regional pattern of neurotoxicity, as evidenced by lipid peroxidation.

Mixed Lineage Kinase Family, Potential Targets for Preventing Neurodegeneration

The c-Jun amino terminal kinase (JNK) cascade leading to c-Jun phosphorylation has been implicated in the neuronal cellular response to a variety of external stimuli including free radical oxidative stress, trophic withdrawal, amyloid toxicity and activation by death domain receptor ligands. Although the exact causes of neuronal loss in neurodegenerative diseases remain unknown, it has been hypothesized that response to these environmental stresses may be contributing factors. Agents which block the JNK signaling cascade have been proposed as a therapeutic approach for preventing neuronal cell death observed in a variety of neurodegenerative diseases including Parkinsons, Huntingtons, and Alzheimers disease. The JNKs are regulated through a sequential signaling cascade by a series of upstream kinases including the mixed lineage kinases (MLKs). Herein, we review the MLK family as a therapeutic target and provide evidence with CEP-1347, the most advanced MLK inhibitor currently in clinical trails for Parkinsons disease, that intervention at the MLK point in the JNK cascade may reduce the susceptibility of neurons to degenerate.

Lipid peroxidation and protein oxidation in Alzheimer’s disease brain: potential causes and consequences involving amyloid β-peptide-associated free radical oxidative stress1,2

Amyloid β-peptide (Aβ) is heavily deposited in the brains of Alzheimer’s disease (AD) patients, and free radical oxidative stress, particularly of neuronal lipids and proteins, is extensive. Recent research suggests that these two observations may be linked by Aβ-induced oxidative stress in AD brain. This review summarizes current knowledge on phospholipid peroxidation and protein oxidation in AD brain, one potential cause of this oxidative stress, and consequences of Aβ-induced lipid peroxidation and protein oxidation in AD brain.

Amyloid β-peptide (1-42)-induced Oxidative Stress and Neurotoxicity: Implications for Neurodegeneration in Alzheimer's Disease Brain. A Review

Oxidative stress, manifested by protein oxidation, lipid peroxidation, DNA oxidation and 3-nitrotyrosine formation, among other indices, is observed in Alzheimer's disease (AD) brain. Amyloid g -peptide (1-42) [A g (1-42)] may be central to the pathogenesis of AD. Our laboratory and others have implicated A g (1-42)-induced free radical oxidative stress in the neurodegeneration observed in AD brain. This paper reviews some of these studies from our laboratory. Recently, we showed both in-vitro and in-vivo that methionine residue 35 (Met-35) of A g (1-42) was critical to its oxidative stress and neurotoxic properties. Because the C-terminal region of A g (1-42) is helical, and invoking the i +4 rule of helices, we hypothesized that the carboxyl oxygen of lle-31, known to be within a van der Waals distance of the S atom of Met-35, would interact with the latter. This interaction could alter the susceptibility for oxidation of Met-35, i.e. free radical formation. Consistent with this hypothesis, substitution of lle-31 by the helix-breaking amino acid, proline, completely abrogated the oxidative stress and neurotoxic properties of A g (1-42). Removal of the Met-35 residue from the lipid bilayer by substitution of the negatively charged Asp for Gly-37 abrogated oxidative stress and neurotoxic properties of A g (1-42). The free radical scavenger vitamin E prevented A g (1-42)-induced ROS formation, protein oxidation, lipid peroxidation, and neurotoxicity in hippocampal neurons, consistent with our model for A g -associated free radical oxidative stress induced neurodegeneration in AD. ApoE, allele 4, is a risk factor for AD. Synaptosomes from apoE knock-out mice are more vulnerable to A g -induced oxidative stress (protein oxidation, lipid peroxidation, and ROS generation) than are those from wild-type mice. We also studied synaptosomes from allele-specific human apoE knock-in mice. Brain membranes from human apoE4 mice have greater vulnerability to A g (1-42)-induced oxidative stress than brain membranes from apoE2 or E3, assessed by the same indices, consistent with the notion of a coupling of the oxidative environment in AD brain and increased risk of developing this disorder. Using immunoprecipitation of proteins from AD and control brain obtained no longer than 4 h PMI, selective oxidized proteins were identified in the AD brain. Creatine kinase (CK) and g -actin have increased carbonyl groups, an index of protein oxidation, and Glt-1, the principal glutamate transporter, has increased binding of the lipid peroxidation product, 4-hydroxy-2-nonenal (HNE). A g inhibits CK and causes lipid peroxidation, leading to HNE formation. Implications of these findings relate to decreased energy utilization, altered assembly of cytoskeletal proteins, and increased excitotoxicity to neurons by glutamate, all reported for AD. Other oxidatively modified proteins have been identified in AD brain by proteomics analysis, and these oxidatively-modified proteins may be related to increased excitotoxicity (glutamine synthetase), aberrant proteasomal degradation of damaged or aggregated proteins (ubiquitin C-terminal hydrolase L-1), altered energy production ( f -enolase), and diminished growth cone elongation and directionality (dihydropyrimindase-related protein 2). Taken together, these studies outlined above suggest that Met-35 is key to the oxidative stress and neurotoxic properties of A g (1-42) and may help explain the apoE allele dependence on risk for AD, some of the functional and structural alterations in AD brain, and strongly support a causative role of A g (1-42)-induced oxidative stress and neurodegeneration in AD.

Motor Neuron Disease

Motor neuron disease refers to a spectrum of disorders resulting from degeneration of the upper or lower motor neurons or both. Amyotrophic lateral sclerosis is the most common form of motor neuron disease, in which patients demonstrate evidence of both anterior horn cell (lower motor neuron) and corticospinal tract (upper motor neuron) dysfunction. Several theories regarding the pathogenesis of amyotrophic lateral sclerosis have emerged, including glutamate excitotoxicity, free radical oxidative stress, cytoskeletal abnormalities, a deficiency of neurotrophic factor, autoimmunity, apoptosis, and viral infection. Numerous clinical trials have been completed based on these possible mechanisms of the disease propagation including treatment with antiglutamate agents, anti-oxidants, immunosuppressants, and neurotrophic factors. Several of these trials have shown modest effects in slowing the disease course. None, however, have yielded marked benefit in arresting disease progression. The most significant effect in abating disease progression has been our use and understanding of aggressive symptomatic therapy to reduce disability, enhance quality of life, and improve prognosis.