Causes of oxidative stress in Alzheimer disease

Epithelial-mesenchymal transition: from molecular mechanisms, redox regulation to implications in human health and disease

Epithelial to mesenchymal transition (EMT) is a fundamental process, paradigmatic of the concept of cell plasticity, that leads epithelial cells to lose their polarization and specialized junctional structures, to undergo cytoskeleton reorganization, and to acquire morphological and functional features of mesenchymal-like cells. Although EMT has been originally described in embryonic development, where cell migration and tissue remodeling have a primary role in regulating morphogenesis in multicellular organisms, recent literature has provided evidence suggesting that the EMT process is a more general biological process that is also involved in several pathophysiological conditions, including cancer progression and organ fibrosis. This review offers first a comprehensive introduction to describe major relevant features of EMT, followed by sections dedicated on those signaling mechanisms that are known to regulate or affect the process, including the recently proposed role for oxidative stress and reactive oxygen species (ROS). Current literature data involving EMT in both physiological conditions (i.e., embryogenesis) and major human diseases are then critically analyzed, with a special final focus on the emerging role of hypoxia as a relevant independent condition able to trigger EMT.

Apple juice improved behavioral but not cognitive symptoms in moderate-to-late stage Alzheimer's disease in an open-label pilot study

Preclinical studies demonstrate that apple juice exerts multiple beneficial effects including reduction of central nervous system oxidative damage, suppression of Alzheimer's disease (AD) hallmarks, improved cognitive performance, and organized synaptic signaling. Herein, we initiated an open-label clinical trial in which 21 institutionalized individuals with moderate-to-severe AD consumed 2 4-oz glasses of apple juice daily for 1 month. Participants demonstrated no change in the Dementia Rating Scale, and institutional caregivers reported no change in Alzheimer's Disease Cooperative Study (ADCS)-Activities of Daily Living (ADL) in this brief study. However, caregivers reported an approximate 27% (P < .01) improvement in behavioral and psychotic symptoms associated with dementia as quantified by the Neuropsychiatric Inventory, with the largest changes in anxiety, agitation, and delusion. This pilot study suggests that apple juice may be a useful supplement, perhaps to augment pharmacological approaches, for attenuating the decline in mood that accompanies progression of AD, which may also reduce caregiver burden.

Redox control of prion and disease pathogenesis

Imbalance of brain metal homeostasis and associated oxidative stress by redox-active metals like iron and copper is an important trigger of neurotoxicity in several neurodegenerative conditions, including prion disorders. Whereas some reports attribute this to end-stage disease, others provide evidence for specific mechanisms leading to brain metal dyshomeostasis during disease progression. In prion disorders, imbalance of brain-iron homeostasis is observed before end-stage disease and worsens with disease progression, implicating iron-induced oxidative stress in disease pathogenesis. This is an unexpected observation, because the underlying cause of brain pathology in all prion disorders is PrP-scrapie (PrP(Sc)), a beta-sheet-rich conformation of a normal glycoprotein, the prion protein (PrP(C)). Whether brain-iron dyshomeostasis occurs because of gain of toxic function by PrP(Sc) or loss of normal function of PrP(C) remains unclear. In this review, we summarize available evidence suggesting the involvement of oxidative stress in prion-disease pathogenesis. Subsequently, we review the biology of PrP(C) to highlight its possible role in maintaining brain metal homeostasis during health and the contribution of PrP(Sc) in inducing brain metal imbalance with disease progression. Finally, we discuss possible therapeutic avenues directed at restoring brain metal homeostasis and alleviating metal-induced oxidative stress in prion disorders.

Mitochondrial dysfunction: a potential link between neuroinflammation and neurodegeneration?

Dysfunctional mitochondria are thought to play a cardinal role in the pathogenesis of various neurological disorders, such as multiple sclerosis, Alzheimer's disease, Parkinson's disease and stroke. In addition, neuroinflammation is a common denominator of these diseases. Both mitochondrial dysfunction and neuroinflammatory processes lead to increased production of reactive oxygen species (ROS) which are detrimental to neurons. Therefore, neuroinflammation is increasingly recognized to contribute to processes underlying neurodegeneration. Here we describe the involvement of mitochondrial (dys)function in various neurological disorders and discuss the putative link between mitochondrial function and neuroinflammation.

Mitochondrial biology in Alzheimer's disease pathogenesis

Despite the increasing knowledge of Alzheimer's disease (AD) management with novel pharmacologic agents, most of them are only transiently fixing symptomatic pathology. Currently there is rapid growth in the field of neuroprotective pharmacology and increasing focus on the involvement of mitochondria in this devastating disease. This review is directed at understanding the role of mitochondria-mediated pathways in AD and integrating basic biology of the mitochondria with knowledge of possible pharmacologic targets for AD treatment in an attempt to elucidate novel mitochondria-driven therapeutic interventions useful to both clinical and basic research.

Specific reaction of Met 35 in amyloid beta peptide with hypochlorous acid

The reaction of the amyloid beta peptide (Abeta) with hypochlorous acid and hydroxyl radicals was analysed by spectrophotometry and mass spectrometry. N-acetylmethionine, Abeta25-35 and Abeta1-42 reacted rapidly with hypochlorous acid. The relative reaction rates of N-acetylmethionine and Abeta with hypochlorous acid was in the order N-acetylmethionine > Abeta25-35 > Abeta1-42. While the reaction of Abeta25-35 in the presence of a slight excess of hypochlorous acid resulted in complete conversion of Met35 to Met35 sulphoxide, Abeta1-42 required more than a 4-fold excess of hypochlorous acid for complete conversion of Met35. Identical products were obtained when Abeta25-35 and Abeta1-42 were treated with a hypochlorous acid generating system. Conversion of Met35 to Met35 sulphoxide in Abeta abolished the aggregation of Abeta25-35. Reaction of Abeta with hydroxyl radicals resulted in limited conversion of Met35 to Met35 sulphoxide. The specific reaction of Met35 in Abeta with hypochlorous acid to form Met35 sulphoxide has been analysed.

Neuroimmunomodulatory steroids in Alzheimer dementia

Though pathobiochemical and neurochemical changes and accompanied morphological alterations in Alzheimer dementia are well known, the triggering mechanisms, if any, remain obscure. Important factors influencing the development and progression of Alzheimer disease include hormonal steroids and their metabolites, some of which may serve as therapeutic agents. This review focusses on major biochemical alterations in the brain of Alzheimer patients with respect to the involvement of steroids. It includes their role in impairment of fuel supply and in brain glycoregulation, with especial emphasis on glucocorticoids and their counter-regulatory steroids as dehydroepiandrosterone and its metabolites. Further, the role of steroids in beta-amyloid pathology is reviewed including alterations in tau-protein(s) phosphorylation. The (auto)immune theory of Alzheimer dementia is briefly outlined, pointing to the possible involvement of steroids in brain ageing, immunosenescence and neuronal apoptosis. Some effects of steroids are briefly mentioned on the formation and removal of reactive oxygen species and their effect on calcium flux and cytotoxicity. The recent biochemical research of Alzheimer disease focusses on molecular signalling at which steroids also take part. New findings may be anticipated when the mosaic describing the molecular mechanisms behind these events becomes more complete.

Oriental medicine Jangwonhwan reduces Abeta(1-42) level and beta-amyloid deposition in the brain of Tg-APPswe/PS1dE9 mouse model of Alzheimer disease

ETHNOPHARMACOLOGICAL RELEVANCE

Jangwonhwan, a boiled extract of 12 medicinal plants/mushroom including Korean red ginseng (Panax ginseng C.A. Meyer), has been prescribed for patients with cognitive dysfunction and are believed to induce brain activity enhancement, provide light sedation, and facilitate sound sleep.

AIM OF THE STUDY

The present study was carried out to investigate whether Jangwonhwan has a beneficial effect on the brain of Alzheimer disease.

MATERIALS AND METHODS

The transgenic mice of Alzheimer disease, Tg-APPswe/PS1dE9, were fed a modified recipe of Jangwonhwan consisting of a boiled extract of 7 herbs/mushroom (called LMK02-Jangwonhwan) at 400mg/kg/day of dose for 3 months from 4.5 months of age. Immunohistological and ELISA analyses were used to assess the Abeta accumulation and plaque deposition in the brain. Other in vitro and in vivo works were performed to understand the underlying mechanism.

RESULTS

LMK02-Jangwonhwan notably reduced Abeta(1-42) and Abeta(1-40) levels, concomitantly with a reduction of plaque deposition, in the brain of Tg-APPswe/PS1dE9 mice. LMK02-Jangwonhwan partially suppressed oxidative stress accumulation, and prevented the down-regulation of phospho-CREB and calbindin typically seen in the hippocampus of AD-like brains. In vitro study with SH-SY5Y neuroblastoma cells showed that LMK02-Jangwonhwan inhibited oxidative stress and Abeta-induced neurotoxicity.

CONCLUSION

The present study suggests that LMK02-Jangwonhwan confers a therapeutic potential to ameliorate AD-like pathology in the brain of Tg-APPswe/PS1dE9 mice.

Protein targets of oxidative damage in human neurodegenerative diseases with abnormal protein aggregates

Human neurodegenerative diseases with abnormal protein aggregates are associated with aberrant post-translational modifications, solubility, aggregation and fibril formation of selected proteins which cannot be degraded by cytosolic proteases, ubiquitin-protesome system and autophagy, and, therefore, accumulate in cells and extracellular compartments as residual debris. In addition to the accumulation of "primary" proteins, several other mechanisms are involved in the degenerative process and probably may explain crucial aspects such as the timing, selective cellular vulnerability and progression of the disease in particular individuals. One of these mechanisms is oxidative stress, which occurs in the vast majority of, if not all, degenerative diseases of the nervous system. The present review covers most of the protein targets that have been recognized as modified proteins mainly using bidimensional gel electrophoresis, Western blotting with oxidative and nitrosative markers, and identified by mass spectrometry in Alzheimer disease; certain tauopathies such as progressive supranuclear palsy, Pick disease, argyrophilic grain disease and frontotemporal lobar degeneration linked to mutations in tau protein, for example, FTLD-tau, Parkinson disease and related alpha-synucleinopathies; Huntington disease; and amyotrophic lateral sclerosis, together with related animal and cellular models. Vulnerable proteins can be mostly grouped in defined metabolic pathways covering glycolysis and energy metabolism, cytoskeletal, chaperoning, cellular stress responses, and members of the ubiquitin-proteasome system. Available information points to the fact that vital metabolic pathways are hampered by protein oxidative damage in several human degenerative diseases and that oxidative damage occurs at very early stages of the disease. Yet parallel functional studies are limited and further work is needed to document whether protein oxidation results in loss of activity and impaired performance. A better understanding of proteins susceptible to oxidation and nitration may serve to define damaged metabolic networks at early stages of disease and to advance therapeutic interventions to attenuate disease progression.

Copper and zinc binding to amyloid-beta: coordination, dynamics, aggregation, reactivity and metal-ion transfer

The metal ions copper, zinc and iron have been shown to be involved in Alzheimer's disease (AD). Cu, Zn and Fe ions are proposed to be implicated in two key steps of AD pathology: 1) aggregation of the peptide amyloid-beta (Abeta), and 2) production of reactive oxygen species (ROS) induced by Abeta. There is compelling evidence that Cu and Zn bind directly to Abeta in AD. This formation of Cu/Zn-Abeta complexes is thought to be aberrant as they have been detected only in AD, but not under healthy conditions. In this context, the understanding of how these metal ions interact with Abeta, their influence on structure and oligomerization become an important issue for AD. Moreover, the mechanism of ROS production by Cu-Abeta in relation to its aggregations state, as well as the metal-transfer reaction from and to Abeta are crucial in order to understand why Abeta oligomers are highly toxic and why Abeta seems to bind Cu and Zn only in AD.

Indoleamine 2,3-dioxygenase and 3-hydroxykynurenine modifications are found in the neuropathology of Alzheimer's disease

Tryptophan metabolism, through the kynurenine pathway, produces neurotoxic intermediates that are implicated in the pathogenesis of Alzheimer's disease. In particular, oxidative stress via 3-hydroxykynurenine (3-HK) and its cleaved product 3-hydroxyanthranilic acid (3-HAA) significantly damages neuronal tissue and may potentially contribute to a cycle of neurodegeneration through consequent amyloid-beta accumulation, glial activation, and up-regulation of the kynurenine pathway. To determine the role of the kynurenine pathway in eliciting and continuing oxidative stress within Alzheimer's diseased brains, we used immunocytochemical methods to show elevated levels of 3-HK modifications and the upstream, rate-limiting enzyme indoleamine 2,3-dioxygenase (IDO-1) in Alzheimer's diseased brains when compared to controls. Importantly, the association of IDO-1 with senile plaques was confirmed and, for the first time, IDO-1 was shown to be specifically localized in conjunction with neurofibrillary tangles. As senile plaques and neurofibrillary tangles are the pathological hallmarks of Alzheimer's disease, our study provides further evidence that the kynurenine pathway is involved with the destructive neurodegenerative pathway of Alzheimer's disease.

Omega-3 fatty acids and cognitive function in women

Omega-3 fatty acids (FAs) could play an important role in maintaining cognitive function in aging individuals. The omega-3 FA docosahexaenoic acid is a major constituent of neuronal membranes and, along with the other long-chain omega-3 FAs from fish such as eicosapentaentoic acid, has been shown to have a wide variety of beneficial effects on neuronal functioning, inflammation, oxidation and cell death, as well as on the development of the characteristic pathology of Alzheimer's disease. Omega-3 FAs may prevent vascular dementia via salutary effects on lipids, inflammation, thrombosis and vascular function. Epidemiologic studies have generally supported a protective association between fish and omega-3 FA levels and cognitive decline. Some of the small, short-term, randomized trials of docosahexaenoic acid and/or eicosapentaentoic acid supplementation have found positive effects on some aspects of cognition in older adults who were cognitively intact or had mild cognitive impairment, although little effect was found in participants with Alzheimer's disease. Large, long-term trials in this area are needed.

Deficiency of the copper chaperone for superoxide dismutase increases amyloid-β production

The copper chaperone for superoxide dismutase (CCS) binds to both the β-site AβPP cleaving enzyme (BACE1) and to the neuronal adaptor protein X11α. BACE1 initiates AβPP processing to produce the amyloid-β (Aβ) peptide deposited in the brains of Alzheimer's disease patients. X11α also interacts directly with AβPP to inhibit Aβ production. However, whether CCS affects AβPP processing and Aβ production is not known. Here we show that loss of CCS increases Aβ production in both CCS knockout neurons and CCS siRNA-treated SHSY5Y cells and that this involves increased AβPP processing at the BACE1 site.

Toward a rational design of multitarget-directed antioxidants: merging memoquin and lipoic acid molecular frameworks

Novel multitargeted antioxidants 3-6 were designed by combining the antioxidant features, namely, a benzoquinone fragment and a lipoyl function, of two multifunctional lead candidates. They were then evaluated to determine their profile against Alzheimer's disease. They showed antioxidant activity, improved following enzymatic reduction, in mitochondria and T67 cell line. They also displayed a balanced inhibitory profile against amyloid-beta aggregation and acetylcholinesterase, emerging as promising molecules for neuroprotectant lead discovery.

Oxidative damage increased in presenilin1/presenilin2 conditional double knockout mice

OBJECTIVE

This report aims to describe the oxidative damage profile in brain of presenilin1 and presenilin2 conditional double knockout mice (dKO) at both early and late age stages, and to discuss the correlation between oxidative stress and the Alzheimer-like phenotypes of dKO mice.

METHODS

The protein level of Abeta(42) in dKO cortex and free 8-OHdG level in urine were measured by ELISA. Thiobarbituric acid method and spectrophotometric DNPH assay were used to determine the lipid peroxidation and protein oxidation in cortex, respectively. SOD and GSH-PX activities were assessed by SOD Assay Kit-WST and GSH-PX assay kit, separately.

RESULTS

Significant decrease of Abeta(42) was verified in dKO cortex at 6 months as compared to control mice. Although lipid peroxidation (assessed by MDA) was increased only in dKO cortex at 3 months and protein oxidation (assessed by carbonyl groups) was basically unchanged in dKO cortex, ELISA analysis revealed that free 8-OHdG, which was an indicator of DNA lesion, was significantly decreased in urine of dKO mice from 3 months to 12 months. Activities of SOD and GSH-PX in dKO and control cortices showed no statistical difference except a significant increase of GSH-PX activity in dKO mice at 9 months.

CONCLUSION

Oxidative damage, especially DNA lesion, was correlated with the neurodegenerative symptoms that appeared in dKO mice without the deposition of Abeta(42). Triggers of oxidative damage could be the inflammatory mediators released by activated microglia and astrocytes.

Biomarkers of oxidative and nitrosative damage in Alzheimer's disease and mild cognitive impairment

Alzheimer's disease (AD) is the most common type of dementia in the elderly. Products of oxidative and nitrosative stress (OS and NS, respectively) accumulate with aging, which is the main risk factor for AD. This provides the basis for the involvement of OS and NS in AD pathogenesis. OS and NS occur in biological systems due to the dysregulation of the redox balance, caused by a deficiency of antioxidants and/or the overproduction of free radicals. Free radical attack against lipids, proteins, sugars and nucleic acids leads to the formation of bioproducts whose detection in fluids and tissues represents the currently available method for assessing oxidative/nitrosative damage. Post-mortem and in-vivo studies have demonstrated an accumulation of products of free radical damage in the central nervous system and in the peripheral tissues of subjects with AD or mild cognitive impairment (MCI). In addition to their individual role, biomarkers for OS and NS in AD are associated with altered bioenergetics and amyloid-beta (Abeta) metabolism. In this review we discuss the main results obtained in the field of biomarkers of oxidative/nitrosative stress in AD and MCI in humans, in addition to their potential role as a tool for diagnosis, prognosis and treatment efficacy in AD.

Effects of age, dietary, and behavioral enrichment on brain mitochondria in a canine model of human aging

Dogs develop cognitive decline and a progressive accumulation of oxidative damage. In a previous longitudinal study, we demonstrated that aged dogs treated with either an antioxidant diet or with behavioral enrichment show cognitive improvement. The antioxidant diet included cellular antioxidants (vitamins E and C, fruits and vegetables) and mitochondrial cofactors (lipoic acid and carnitine). Behavioral enrichment consisted of physical exercise, social enrichment, and cognitive training. We hypothesized that the antioxidant treatment improved neuronal function through increased mitochondrial function. Thus, we measured reactive oxygen species (ROS) production and bioenergetics in mitochondria isolated from young, aged, and treated aged animals. Aged canine brain mitochondria show significant increases in ROS production and a reduction in NADH-linked respiration. Mitochondrial function (ROS and NADH-linked respiration) was improved selectively in aged dogs treated with an antioxidant diet. In contrast, behavioral enrichment had no effect on any mitochondrial parameters. These results suggest that an antioxidant diet improves cognition by maintaining mitochondrial homeostasis, which may be an independent molecular pathway not engaged by behavioral enrichment.

Oxidative stress in diabetes and Alzheimer's disease

Oxidative stress plays a major role in diabetes as well as in Alzheimer's disease and other related neurological diseases. Intracellular oxidative stress arises due to the imbalance in the production of reactive oxygen/reactive nitrogen species and cellular antioxidant defense mechanisms. In turn, the excess reactive oxygen/reactive nitrogen species mediate the damage of proteins and nucleic acids, which have been shown to have direct and deleterious consequences in diabetes and Alzheimer's disease. Oxidative stress also contributes to the production of advanced glycation end products through glycoxidation and lipid peroxidation. The advanced glycation end products and lipid peroxidation products are ubiquitous to diabetes and Alzheimer's disease and serve as markers of disease progression in both disorders. Antioxidants and advanced glycation end products inhibitors, either induced endogenously or exogenously introduced, may counteract with the deleterious effects of the reactive oxygen/reactive nitrogen species and thereby, in prevention or treatment paradigms, attenuate or substantially delay the onset of these devastating pathologies.

Antioxidant activity of sulfur and selenium: a review of reactive oxygen species scavenging, glutathione peroxidase, and metal-binding antioxidant mechanisms

It is well known that oxidation caused by reactive oxygen species (ROS) is a major cause of cellular damage and death and has been implicated in cancer, neurodegenerative, and cardiovascular diseases. Small-molecule antioxidants containing sulfur and selenium can ameliorate oxidative damage, and cells employ multiple antioxidant mechanisms to prevent this cellular damage. However, current research has focused mainly on clinical, epidemiological, and in vivo studies with little emphasis on the antioxidant mechanisms responsible for observed sulfur and selenium antioxidant activities. In addition, the antioxidant properties of sulfur compounds are commonly compared to selenium antioxidant properties; however, sulfur and selenium antioxidant activities can be quite distinct, with each utilizing different antioxidant mechanisms to prevent oxidative cellular damage. In the present review, we discuss the antioxidant activities of sulfur and selenium compounds, focusing on several antioxidant mechanisms, including ROS scavenging, glutathione peroxidase, and metal-binding antioxidant mechanisms. Findings of several recent clinical, epidemiological, and in vivo studies highlight the need for future studies that specifically focus on the chemical mechanisms of sulfur and selenium antioxidant behavior.

Impact of Magnetic Labeling on Human and Mouse Stem Cells and Their Long-Term Magnetic Resonance Tracking in a Rat Model of Parkinson Disease

Magnetic resonance imaging (MRI) of magnetically labeled stem cells has become a valuable tool in the understanding and evaluation of experimental stem cell–based therapies of degenerative central nervous system disorders. This comprehensive study assesses the impact of magnetic labeling of both human and rodent stem cell–containing populations on multiple biologic parameters as maintenance of stemness and oxidative stress levels. Cells were efficiently magnetically labeled with very small superparamagnetic iron oxide particles. Only under the condition of tailored labeling strategies can the impact of magnetic labeling on vitality, proliferation, pluripotency, and oxidative stress levels be minimized. In a rat model of Parkinson disease, magnetically labeled mouse embryonic stem cells were tracked by high-field MRI for 6 months. Significant interindividual differences concerning the spatial distribution of cells became evident. Histologically, transplanted green fluorescent protein–positive iron oxide–labeled cells were clearly identified. No significant increase in oxidative stress levels at the implantation site and no secondary uptake of magnetic label by host phagocytotic cells were observed. Our study strongly suggests that molecular MRI approaches must be carefully tailored to the respective cell population to exert minimal physiologic impact, ensuring the feasibility of this imaging approach for clinical applications.

Age-dependent deterioration of nuclear pore complexes causes a loss of nuclear integrity in postmitotic cells

In dividing cells, nuclear pore complexes (NPCs) disassemble during mitosis and reassemble into the newly forming nuclei. However, the fate of nuclear pores in postmitotic cells is unknown. Here, we show that NPCs, unlike other nuclear structures, do not turn over in differentiated cells. While a subset of NPC components, like Nup153 and Nup50, are continuously exchanged, scaffold nucleoporins, like the Nup107/160 complex, are extremely long-lived and remain incorporated in the nuclear membrane during the entire cellular life span. Besides the lack of nucleoporin expression and NPC turnover, we discovered an age-related deterioration of NPCs, leading to an increase in nuclear permeability and the leaking of cytoplasmic proteins into the nucleus. Our finding that nuclear "leakiness" is dramatically accelerated during aging and that a subset of nucleoporins is oxidatively damaged in old cells suggests that the accumulation of damage at the NPC might be a crucial aging event.

DNA-protective effects of sumach (Rhus coriaria L.), a common spice: results of human and animal studies

Sumach (Rhus coriaria L.) is widely used as a spice. The aim of this study was the investigation of its DNA-protective effects in humans and animals. Prevention of the formation of strand breaks and oxidized DNA bases as well as the protection against H(2)O(2)- and (+/-)-anti-benzo[a]pyrene-7,8-dihydro-diol-9,10-epoxide (BPDE)-induced DNA-damage were monitored in human lymphocytes in a placebo controlled trial (N=8/group) with ethanolic extract of sumach (3.0g/day, 3 days) in single cell gel electrophoresis assays. Furthermore, DNA-protective effects of sumach were monitored in different inner organs of rats under identical conditions. No alteration of DNA-migration was detectable in human lymphocytes under standard conditions, but a decrease of the tail-lengths due to formation of oxidized purines and pyrimidines (52% and 36%) was found with lesion-specific enzymes. Also damage caused by H(2)O(2) and BPDE was significantly reduced by 30% and 69%, respectively. The later effect may be due to induction of glutathione S-transferase (GST). After the intervention, the overall GST (CDNB) activity in plasma was increased by 40%, GST-alpha by 52% and GST-pi by 26% (ELISA). The antioxidant effects of extract are probably due to scavenging which was observed in in vitro experiments, which also indicated that gallic acid is the active principle of sumach. The animal experiments showed that sumach also causes protection in inner organs. Supplementation of the drinking water (0.02g/kg per animal) decreased the formation of oxidized DNA bases in colon, liver, lung and lymphocytes; also after gamma-irradiation pronounced effects were seen.

Getting the iron out: phlebotomy for Alzheimer's disease?

This communication explores the temporal link between the age-associated increase in body iron stores and the age-related incidence of Alzheimer's disease (AD), the most prevalent cause of senile dementia. Body iron stores that increase with age could be pivotal to AD pathogenesis and progression. Increased stored iron is associated with common medical conditions such as diabetes and vascular disease that increase risk for development of AD. Increased stored iron could also promote oxidative stress/free radical damage in vulnerable neurons, a critical early change in AD. A ferrocentric model of AD described here forms the basis of a rational, easily testable experimental therapeutic approach for AD, which if successful, would be both widely applicable and inexpensive. Clinical studies have shown that calibrated phlebotomy is an effective way to reduce stored iron safely and predictably without causing anemia. We hypothesize that reducing stored iron by calibrated phlebotomy to avoid iron deficiency will improve cerebrovascular function, slow neurodegenerative change, and improve cognitive and behavioral functions in AD. The hypothesis is eminently testable as iron reduction therapy is useful for chronic diseases associated with iron excess such as nonalcoholic steatohepatitis (NASH), atherosclerosis, hereditary hemochromatosis and thalassemia. Testing this hypothesis could provide valuable insight into the causation of AD and suggest novel preventive and treatment strategies.

Efficacy of a vitamin/nutriceutical formulation for moderate-stage to later-stage Alzheimer's disease: a placebo-controlled pilot study

Recent studies demonstrated efficacy of a vitamin/ nutriceutical formulation (folate, vitamin B12, alpha-tocopherol, S-adenosyl methionine, N-acetyl cysteine, and acetyl-L-carnitine) for mild to moderate Alzheimer's disease. Herein, we tested the efficacy of this formulation in a small cohort of 12 institutionalized patients diagnosed with moderate-stage to later-stage Alzheimer's disease. Participants were randomly separated into treatment of placebo groups. Participants receiving the formulation demonstrated a clinically significant delay in decline in the Dementia Rating Scale and clock-drawing test as compared to those receiving placebo. Institutional caregivers reported approximately 30% improvement in the Neuropyschiatric Inventory and maintenance of performance in the Alzheimer's Disease Cooperative Study-Activities of Daily Living for more than 9 months. This formulation holds promise for delaying the decline in cognition, mood, and daily function that accompanies the progression of Alzheimer's disease, and may be particularly useful as a supplement for pharmacological approaches during later stages of this disorder. A larger trial is warranted.

Oxidative stress induces macroautophagy of amyloid beta-protein and ensuing apoptosis

There is increasing evidence for the toxicity of intracellular amyloid beta-protein (Abeta) to neurons and the involvement of lysosomes in this process in Alzheimer disease (AD). We have recently shown that oxidative stress, a recognized determinant of AD, enhances macroautophagy and leads to intralysosomal accumulation of Abeta in cultured neuroblastoma cells. We hypothesized that oxidative stress promotes AD by stimulating macroautophagy of Abeta that further may induce cell death by destabilizing lysosomal membranes. To investigate such possibility, we compared the effects of hyperoxia (40% ambient oxygen) in cultured HEK293 cells that were transfected with an empty vector (Vector), wild-type APP (APPwt), or Swedish mutant APP (APPswe). Exposure to hyperoxia for 5 days increased the number of cells with Abeta-containing lysosomes, as well as the number of apoptotic cells, compared to normoxic conditions. The rate of apoptosis in all three cell lines demonstrated dependence on intralysosomal Abeta content (Vector<APPwt<APPswe). Furthermore, the degree of apoptosis was positively correlated with lysosomal membrane permeabilization, whereas inhibitors of macroautophagy and lysosomal function decreased oxidant-induced apoptosis and diminished the differences in apoptotic response between different cell lines. These results suggest that oxidative stress can induce neuronal death through macroautophagy of Abeta and consequent lysosomal membrane permeabilization, which may help explain the mechanisms behind neuronal loss in AD.

Neuronal protein trafficking associated with Alzheimer disease: from APP and BACE1 to glutamate receptors

Aberrant and/or cumulative amyloid-beta (Abeta) production, resulting from proteolytic processing of the amyloid precursor protein (APP) by beta and gamma-secretases, have been postulated to be a main etiological basis of Alzheimer disease (AD). A number of proteins influence the subcellular trafficking itinerary of APP and the beta-site APP-cleaving enzyme (BACE1) between the cell surface, endosomes and the trans-Golgi network (TGN). Available evidence suggests that co-residence of APP and BACE1 in the endosomal compartments promotes amyloidogenesis. Retrograde transport of APP out of the endosome to the TGN reduces Abeta production, while APP routed to and kept at the cell surface enhances its non-amyloidogenic, alpha-secretase-mediated processing. Changes in post-Golgi membrane trafficking in aging neurons that may influence APP processing is particularly relevant to late-onset, idiopathic AD. Dystrophic axons are key features of AD pathology, and impaired axonal transport could play crucial roles in the pathogenesis of idiopathic AD. Recent evidence has also indicated that Abeta-induced synaptic defects and memory impairment could be explained by a loss of both AMPA and NMDA receptors through endocytosis. Detail understanding of factors that influence these neuronal trafficking processes will open up novel therapeutic avenues for preventing or delaying the onset of symptomatic AD.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

The amyloid-beta peptide of Alzheimer's disease binds Cu(I) in a linear bis-his coordination environment: insight into a possible neuroprotective mechanism for the amyloid-beta peptide

Oxidative stress has been suggested to contribute to neuronal apoptosis associated with Alzheimer's disease (AD). Copper may participate in oxidative stress through redox-cycling between its +2 and +1 oxidation states to generate reactive oxygen species (ROS). In vitro, copper binds to the amyloid-beta peptide of AD, and in vivo, copper is associated with amyloid plaques characteristic of AD. As a result, the AbetaCu(I) complex may be a critical reactant involved in ROS associated with AD etiology. To characterize the AbetaCu(I) complex, we have pursued X-ray absorption (XAS) and electron paramagnetic resonance (EPR) spectroscopy of AbetaCu(II) and AbetaCu(I) (produced by ascorbate reduction of AbetaCu(II)). The AbetaCu(II) complex Cu K-edge XAS spectrum is indicative of a square-planar Cu(II) center with mixed N/O ligation. Multiple scattering analysis of the extended X-ray absorption fine structure (EXAFS) data for AbetaCu(II) indicates that two of the ligands are imidazole groups of histidine ligands, indicating a (N(Im))(2)(N/O)(2) Cu(II) ligation sphere for AbetaCu(II). After reduction of the AbetaCu(II) complex with ascorbate, the edge region decreases in energy by approximately 4 eV. The X-ray absorption near-edge spectrum region of AbetaCu(I) displays an intense pre-edge feature at 8984.1(2) eV. EXAFS data fitting yielded a two-coordinate geometry, with two imidazole ligands coordinated to Cu(I) at 1.877(2) A in a linear geometry. Ascorbate reduction of AbetaCu(II) under inert atmosphere and subsequent air oxidation of AbetaCu(I) to regenerate AbetaCu(II) was monitored by low-temperature EPR spectroscopy. Slow reappearance of the AbetaCu(II) EPR signal indicates that O(2) oxidation of the AbetaCu(I) complex is kinetically sluggish and Abeta damage is occurring following reoxidation of AbetaCu(I) by O(2). Together, these results lead us to hypothesize that Cu(I) is ligated by His13 and His14 in a linear coordination environment in Alphabeta, that Abeta may be playing a neuroprotective role, and that metal-mediated oxidative damage of Abeta occurs over multiple redox cycles.

Oxidant-induced changes in mitochondria and calcium dynamics in the pathophysiology of Alzheimer's disease

Considerable data support the hypothesis that mitochondrial abnormalities link gene defects and/or environmental insults to the neurodegenerative process. The interaction of oxidants with calcium and the mitochondrial enzymes of the tricarboxylic acid cycle are central to that relationship. Abnormalities that were discovered in brains or fibroblasts from patients with Alzheimer's disease (AD) have been modeled in vitro and in vivo to assess their pathophysiological importance and to determine how they might be reversed. The conclusions are consistent with the hypothesis that the AD-related abnormalities result from oxidative stress. The selection of compounds for reversal is complex because the actions of the relevant compounds vary under different conditions, such as cell redox states and acute versus chronic changes. However, the models that have been developed are useful for testing the effectiveness of the potential medications. The results suggest that the reversal of mitochondrial deficits and a reduction in oxidative stress will reduce clinical and pathological changes and benefit patients.

Efficacy of a vitamin/nutriceutical formulation for early-stage Alzheimer's disease: a 1-year, open-label pilot study with an 16-month caregiver extension

We examined the efficacy of a vitamin/nutriceutical formulation (folate, vitamin B6, alpha-tocopherol, S-adenosyl methionine, N-acetyl cysteine, and acetyl-L-carnitine) in a 12-month, open-label trial with 14 community-dwelling individuals with early-stage Alzheimer's disease. Participants improved in the Dementia Rating Scale and Clock-drawing tests (Clox 1 and 2). Family caregivers reported improvement in multiple domains of the Neuropsychiatric Inventory (NPI) and maintenance of performance in the Alzheimer's Disease Cooperative Study-Activities of Daily Living (ADL). Sustained performance was reported by caregivers for those participants who continued in an 16-month extension. Performance on the NPI was equivalent to published findings at 3 to 6 months for donepezil and exceeded that of galantamine and their historical placebos. Participants demonstrated superior performance for more than 12 months in NPI and ADL versus those receiving naproxen and rofecoxib or their placebo group. This formulation holds promise for treatment of early-stage Alzheimer's disease prior to and/or as a supplement for pharmacological approaches. A larger, placebo-controlled trial is warranted.

Redox mechanisms in hepatic chronic wound healing and fibrogenesis

Reactive oxygen species (ROS) generated within cells or, more generally, in a tissue environment, may easily turn into a source of cell and tissue injury. Aerobic organisms have developed evolutionarily conserved mechanisms and strategies to carefully control the generation of ROS and other oxidative stress-related radical or non-radical reactive intermediates (that is, to maintain redox homeostasis), as well as to 'make use' of these molecules under physiological conditions as tools to modulate signal transduction, gene expression and cellular functional responses (that is, redox signalling). However, a derangement in redox homeostasis, resulting in sustained levels of oxidative stress and related mediators, can play a significant role in the pathogenesis of major human diseases characterized by chronic inflammation, chronic activation of wound healing and tissue fibrogenesis. This review has been designed to first offer a critical introduction to current knowledge in the field of redox research in order to introduce readers to the complexity of redox signalling and redox homeostasis. This will include ready-to-use key information and concepts on ROS, free radicals and oxidative stress-related reactive intermediates and reactions, sources of ROS in mammalian cells and tissues, antioxidant defences, redox sensors and, more generally, the major principles of redox signalling and redox-dependent transcriptional regulation of mammalian cells. This information will serve as a basis of knowledge to introduce the role of ROS and other oxidative stress-related intermediates in contributing to essential events, such as the induction of cell death, the perpetuation of chronic inflammatory responses, fibrogenesis and much more, with a major focus on hepatic chronic wound healing and liver fibrogenesis.

In inclusion-body myositis muscle fibers Parkinson-associated DJ-1 is increased and oxidized

Sporadic inclusion-body myositis (s-IBM) is the most common muscle disease of older persons. The muscle-fiber molecular phenotype exhibits similarities to both Alzheimer-disease (AD) and Parkinson-disease (PD) brains, including accumulations of amyloid-beta, phosphorylated tau, alpha-synuclein, and parkin, as well as evidence of oxidative stress and mitochondrial abnormalities. Early-onset autosomal-recessive PD can be caused by mutations in the DJ-1 gene, leading to its inactivation. DJ-1 has antioxidative and mitochondrial-protective properties. In AD and PD brains, DJ-1 is increased and oxidized. We studied DJ-1 in 17 s-IBM and 18 disease-control and normal muscle biopsies by: (1) immunoblots of muscle homogenates and mitochondrial fractions; (2) real-time PCR; (3) oxyblots evaluating DJ-1 oxidation; (4) light- and electron-microscopic immunocytochemistry. Compared to controls, in s-IBM muscle fibers DJ-1 was: (a) increased in the soluble fraction, monomer 2-fold (P = 0.01), and dimer 2.8-fold (P = 0.004); (b) increased in the mitochondrial fraction; (c) highly oxidized; and (d) aggregated in about 15% of the abnormal muscle fibers. DJ-1 mRNA was increased 3.5-fold (P = 0.034). Accordingly, DJ-1 might play a role in human muscle disease, and thus not be limited to human CNS degenerations. In s-IBM muscle fibers, DJ-1 could be protecting these fibers against oxidative stress, including protection of mitochondria.

Dystrophic neurites of senile plaques in Alzheimer's disease are deficient in cytochrome c oxidase

Double-labeling immunofluorescence and confocal microscopy have been used to learn about the local relationship between amyloid, mitochondria, and cytochrome c oxidase (COX) in dystrophic neurites of senile plaques in the frontal cortex in Alzheimer's disease (AD). Dystrophic neurites surrounding amyloid plaques are filled with mitochondrial porin-immunoreactive structures. In contrast with tangle-bearing and non-tangle-bearing neurons, which express mitochondrial porin and COX subunit 4, porin-immunoreactive neurites of senile plaques lack COX subunit 4. Parallel western blot studies in mitochondria-enriched fractions of the frontal cortex in the same cases disclosed reduced expression levels of COX, but not of prohibitin, in AD stages VB/C of Braak. Co-localization of porin and lysosomal associated protein 1, as revealed by double-labeling immunofluorescence and confocal microscopy, suggests that mitochondria may be engulfed by lysosomes in dystrophic neurites. These findings support a local link between amyloid deposition, abnormal mitochondria and impaired respiratory chain function (resulting from decrease of COX expression) in dystrophic neurites of senile plaques in AD.

Deregulated Cdk5 promotes oxidative stress and mitochondrial dysfunction

Oxidative stress is one of the earliest events in Alzheimer's disease (AD). A chemical genetic screen revealed that deregulated cyclin-dependent kinase 5 (Cdk5) may cause oxidative stress by compromising the cellular anti-oxidant defense system. Using novel Cdk5 modulators, we show the mechanism by which Cdk5 can induce oxidative stress in the disease's early stage and cell death in the late stage. Cdk5 dysregulation upon neurotoxic insults results in reactive oxygen species (ROS) accumulation in neuronal cells because of the inactivation of peroxiredoxin I and II. Sole temporal activation of Cdk5 also increases ROS, suggesting its major role in this process. Cdk5 inhibition rescues mitochondrial damage upon neurotoxic insults, thereby revealing Cdk5 as an upstream regulator of mitochondrial dysfunction. As mitochondrial damage results in elevated ROS and Ca(2+) levels, both of which activate Cdk5, we propose that a feedback loop occurs in late stage of AD and leads to cell death (active Cdk5 --> ROS --> excess ROS --> mitochondrial damage --> ROS --> hyperactive Cdk5 --> severe oxidative stress and cell injury --> cell death). Cdk5 inhibition upon neurotoxic insult prevents cell death significantly, supporting this hypothesis. As oxidative stress and mitochondrial dysfunction play pivotal roles in promoting neurodegeneration, Cdk5 could be a viable therapeutic target for AD.

The mitochondrial permeability transition, and oxidative and nitrosative stress in the mechanism of copper toxicity in cultured neurons and astrocytes

Copper is an essential element and an integral component of various enzymes. However, excess copper is neurotoxic and has been implicated in the pathogenesis of Wilson's disease, Alzheimer's disease, prion conditions, and other disorders. Although mechanisms of copper neurotoxicity are not fully understood, copper is known to cause oxidative stress and mitochondrial dysfunction. As oxidative stress is an important factor in the induction of the mitochondrial permeability transition (mPT), we determined whether mPT plays a role in copper-induced neural cell injury. Cultured astrocytes and neurons were treated with 20 microM copper and mPT was measured by changes in the cyclosporin A (CsA)-sensitive inner mitochondrial membrane potential (Delta Psi m), employing the potentiometric dye TMRE. In astrocytes, copper caused a 36% decrease in the Delta Psi m at 12 h, which decreased further to 48% by 24 h and remained at that level for at least 72 h. Cobalt quenching of calcein fluorescence as a measure of mPT similarly displayed a 45% decrease at 24 h. Pretreatment with antioxidants significantly blocked the copper-induced mPT by 48-75%. Copper (24 h) also caused a 30% reduction in ATP in astrocytes, which was completely blocked by CsA. Copper caused death (42%) in astrocytes by 48 h, which was reduced by antioxidants (35-60%) and CsA (41%). In contrast to astrocytes, copper did not induce mPT in neurons. Instead, it caused early and extensive death with a concomitant reduction (63%) in ATP by 14 h. Neuronal death was prevented by antioxidants and nitric oxide synthase inhibitors but not by CsA. Copper increased protein tyrosine nitration in both astrocytes and neurons. These studies indicate that mPT, and oxidative and nitrosative stress represent major factors in copper-induced toxicity in astrocytes, whereas oxidative and nitrosative stress appears to play a major role in neuronal injury.

Interleukin-1beta: a bridge between inflammation and excitotoxicity?

Interleukin-1 (IL-1) is a proinflammatory cytokine released by many cell types that acts in both an autocrine and/or paracrine fashion. While IL-1 is best described as an important mediator of the peripheral immune response during infection and inflammation, increasing evidence implicates IL-1 signaling in the pathogenesis of several neurological disorders. The biochemical pathway(s) by which this cytokine contributes to brain injury remain(s) largely unidentified. Herein, we review the evidence that demonstrates the contribution of IL-1beta to the pathogenesis of both acute and chronic neurological disorders. Further, we highlight data that leads us to propose IL-1beta as the missing mechanistic link between a potential beneficial inflammatory response and detrimental glutamate excitotoxicity.

17beta-Oestradiol stimulation of G-proteins in aged and Alzheimer's human brain: comparison with phytoestrogens

The neuroprotective action of oestrogens and oestrogen-like compounds is in the focus of basic and clinical research. Although such action has been shown to be associated with neuronal plasma membranes, the implication of G-proteins remains to be elucidated. This study revealed that micromolar concentrations (microM) of 17beta-oestradiol and phytoestrogens, genistein and daidzein, significantly (P < 0.05) stimulate G-proteins ([(35)S]GTP gamma S binding) in the post-mortem hippocampal membranes of age-matched control women with the respective maximum effects of 28, 20 and 15% at 10 microM. In the frontocortical membranes, the stimulation of G-proteins did not differ significantly from that in hippocampal membranes. Although in the hippocampus and frontal cortex of the Alzheimer's disease (AD) women's brain, 10 microM 17beta-oestradiol produced significantly (P < 0.05) lower stimulation of G-proteins than in the control regions, stimulation by phytoestrogens revealed no remarkable decline. 17beta-Oestradiol, genistein and daidzein revealed a selective effect on various G-proteins (G(alphas), G(alpha o), G(alpha i1) or G(alpha 11) plus G(beta 1 gamma 2)) expressed in Sf9 cells. At a concentration of 10 microM, 17beta-oestradiol suppressed the H(2)O(2) and homocysteine stimulated G-proteins in the frontocortical membranes of control women to a greater extent than phytoestrogens. In AD, the suppressing effect of each compound was lower than in the controls. In the cell-free systems, micromolar concentrations of phytoestrogens scavenged OH(*) and the 2.2-diphenyl-1-picrylhydrazyl free radical (DPPH(*)) more than 17beta-oestradiol did. In the frontocortical membranes of control women, the 20 microM 17beta-oestradiol stimulated adenylate cyclase with 20% maximal effect, whereas, in AD, the effect was insignificant. Genistein did not stimulate enzyme either in control or AD frontocortical membranes. Our data confirm that the agents stimulate G-proteins in control and AD women's brains, although 17beta-oestradiol and phytoestrogens have similarities and differences in this respect. We suggest that, besides the ER-dependent one, the ER-independent antioxidant mechanism is responsible for the oestrogen stimulation of G-proteins in the brain membranes. Both of these mechanisms could be involved in the neuroprotective signalling of oestrogens that contributes to their preventive/therapeutic action against postmenopausal neurological disorders.

Cellular responses to reactive oxygen species-induced DNA damage and aging

Oxidative stress in cells and tissues can occur during pathophysiological developments, e.g., during inflammatory and allergic diseases or during ischemic or toxic and hyperglycemic conditions via the generation of reactive oxygen species (ROS). Moreover, ROS can be generated by radiation (UV, X-rays) and pharmacologically, e.g., by anthracyclins as chemotherapeutic compounds for treatment of a variety of tumors to induce 'stress or aberrant signaling-inducing senescence' (STASIS). Although STASIS is distinguished from intracellular replicative senescence, a variety of cellular mechanisms appear similar in both aging pathways. It is generally accepted that oxidative stress and ROS eventually cause DNA damage, whereby insufficient cellular repair mechanisms may contribute to premature aging and apoptosis. Conversely, ROS-induced imbalances of the signaling pathways for metabolic protein turnover may also result in opposite effects to recruit malfunctioning aberrant proteins and compounds that trigger tumorigenic processes. Consequently, DNA damage plays a role in the development of carcinogenesis, but is also associated with an aging process in cells and organisms.

Nucleic acid oxidation in Alzheimer disease

Increasing evidence suggests that oxidative stress is intimately associated with Alzheimer disease pathophysiology. Nucleic acids (nuclear DNA, mitochondrial DNA, and RNA) are one of the several cellular macromolecules damaged by reactive oxygen species, particularly the hydroxyl radical. Because neurons are irreplaceable and survive as long as the organism does, they need elaborate defense mechanisms to ensure their longevity. In Alzheimer disease, however, an accumulation of nucleic acid oxidation is observed, indicating an increased level of oxidative stress and/or a decreased capacity to repair the nucleic acid damage. In this review, we present data supporting the notion that mitochondrial and metal abnormalities are key sources of oxidative stress in Alzheimer disease. Furthermore, we outline the mechanisms of nucleic acid oxidation and repair. Finally, evidence showing the occurrence of nucleic acid oxidation in Alzheimer disease will be discussed.