Oxidative injury in diseases of the central nervous system: focus on Alzheimer's disease

Effect of Curcumin on Intracerebroventricular Colchicine-Induced Cognitive Impairment and Oxidative Stress in Rats

This study was designed to investigate the protective effects of curcumin against colchicine-induced cognitive impairment and oxidative stress in rats. Male Wistar rats (weighing 150-200 g) received colchicine intracerebroventricularly (15 microg per rat), and cognitive dysfunctions were evaluated by the Morris water maze and the plus maze performance task and supported by biochemical tests. Central administration of colchicine caused memory deficit in both the Morris water maze and the elevated plus maze task paradigm tasks. Chronic treatment with curcumin (5-50 mg/kg, p.o.) twice daily for a period of 25 days beginning 4 days prior to colchicine injection significantly improved the colchicine-induced cognitive impairment. Biochemically, chronic administration of curcumin significantly reduced the elevated lipid peroxidation, restored the decreased reduced glutathione level and acetylcholinesterase activity, and attenuated the raised colchicine-induced elevated nitrite levels. The results of the present study indicate that curcumin has a protective role against colchicine-induced cognitive impairment and associated oxidative stress.

Mitochondria and neurodegeneration

Many lines of evidence suggest that mitochondria have a central role in ageing-related neurodegenerative diseases. However, despite the evidence of morphological, biochemical and molecular abnormalities in mitochondria in various tissues of patients with neurodegenerative disorders, the question "is mitochondrial dysfunction a necessary step in neurodegeneration?" is still unanswered. In this review, we highlight some of the major neurodegenerative disorders (Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis and Huntington's disease) and discuss the role of the mitochondria in the pathogenetic cascade leading to neurodegeneration.

Protective effect of recombinant human somatotropin on amyloid beta-peptide induced learning and memory deficits in mice

This study aimed to examine the effects of the recombinant human somatotropin (rhGH) on protecting neuronal function, and improving learning and memory deficits in mice. Mice were intracerebroventricularly (icv) injected with the aggregated amyloid beta-peptide (Abeta) to mimic the Alzheimer's disease (AD). The learning and memory functions in mice were examined by the step through test (an index of long-term memory) and the water maze performance (an index of spatial recognition memory). The results indicated that the mice treated with rhGH showed significant reduction of the error counts and the long memory retentions in the step-through test, and short swimming times in the water maze performance. Toxic effects of free radicals, damages of cholinergic neurons, and increased lipid peroxidation appeared in the cerebra of Abeta-treated mice, manifesting an increase of malondialdehyde (MDA) and decline of glutathione (GSH) level, an increment of choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities, and a reduction of the acetylcholine (ACh) level. The gel electrophoresis pattern of the cerebra of mice treated with Abeta showed a typical DNA ladder of apoptosis. The in vivo experiments showed that the rhGH treatment significantly reversed the elevated MDA, ChAT, AChE, and the decreased GSH, ACh levels in the Abeta model mice. The results suggested that there were potential uses of the neuroprotective action of rhGH in the remedy of AD.

In vitro activities of Citrus medica L. cv. Diamante (Diamante citron) relevant to treatment of diabetes and Alzheimer's disease

The present study showed for the first time the in vitro properties (antioxidant, hypoglycaemic and anticholinesterase) of Citrus medica L. cv. Diamante which belongs to the Rutaceae family. The n-hexane extract of Diamante citron peel is characterized by the presence of monoterpenes and sesquiterpenes. The most abundant constituents were two monoterpenes: limonene and gamma-terpinene. The extract showed significant antioxidant activity that was carried out using different assays (DPPH test, beta-carotene bleaching test and bovine brain peroxidation assay). Oxidative damage, caused by the action of free radicals, may initiate and promote the progression of a number of chronic diseases, including diabetes and Alzheimer's disease. Diamante citron peel extract showed hypoglycaemic activity and an anticholinesterase effect.

Antiradical activity of Paulownia tomentosa (Scrophulariaceae) extracts

Paulownia tomentosa is a large indecidous tree planted mostly for its fast growing wood and decorative purposes. The tree is also used in traditional Chinese medicine. As a part of our study of natural polyphenols, the fruits of Paulownia tomentosa were extracted by EtOH and than subjected to liquid/liquid extraction. Fractions were analysed by TLC and HPLC to determine presence of phenolic substances. We identified and quantified acteoside (1) and isoacteoside (2) in the EtOAc and n-BuOH extracts; mimulone (3) and diplacone (4) in the MeOH extract. To determine the antiradical activity of extracts we used the anti DPPH and peroxynitrite assays. The activity was expressed as Trolox C equivalents, IC50 for DPPH scavenging and a time dependency course was established. The polyphenols content was determined; results were expressed as gallic acid equivalents. Using these methods we found the fractions of the n-BuOH, EtOAc and MeOH extracts that display antiradical activity, which could be exploited as potential pharmaceuticals.

Iron dysregulation in Alzheimer's disease: multimodal brain permeable iron chelating drugs, possessing neuroprotective-neurorescue and amyloid precursor protein-processing regulatory activities as therapeutic agents

Considering the multi-etiological character of Alzheimer's disease (AD), the current pharmacological approaches using drugs oriented towards a single molecular target possess limited ability to modify the course of the disease and thus, offer a partial benefit to the patient. In line with this concept, novel strategies include the use of a cocktail of several drugs and/or the development of a single molecule, possessing two or more active neuroprotective-neurorescue moieties that simultaneously manipulate multiple targets involved in AD pathology. A consistent observation in AD is a dysregulation of metal ions (Fe(2+), Cu(2+) and Zn(2+)) homeostasis and consequential induction of oxidative stress, associated with beta-amyloid aggregation and neurite plaque formation. In particular, iron has been demonstrated to modulate the Alzheimer's amyloid precursor holo-protein expression by a pathway similar to that of ferritin L-and H-mRNA translation through iron-responsive elements in their 5'UTRs. This review will discuss two separate scenarios concerning multiple therapy targets in AD, sharing in common the implementation of iron chelation activity: (i) novel multimodal brain-permeable iron chelating drugs, possessing neuroprotective-neurorescue and amyloid precursor protein-processing regulatory activities; (ii) natural plant polyphenols (flavonoids), such as green tea epigallocatechin gallate (EGCG) and curcumin, reported to have access to the brain and to possess multifunctional activities, such as metal chelation-radical scavenging, anti-inflammation and neuroprotection.

A mechanistic link between oxidative stress and membrane mediated amyloidogenesis revealed by infrared spectroscopy

The fully developed lesion of Alzheimer's disease is a dense plaque composed of fibrillar amyloid beta-proteins (Abeta) with a characteristic and well-ordered beta-sheet secondary structure. Because the incipient lesion most likely develops when these proteins are first induced to form beta-sheet structure, it is important to understand factors that induced Abeta to adopt this conformation. In this review, we describe the application of polarized attenuated total internal reflection infrared FT-IR spectroscopy for characterizing the conformation, orientation, and rate of accumulation of Abeta on lipid membranes. We also describe the application and yield of linked analysis, whereby multiple spectra are fit simultaneously with component bands that are constrained to share common fitting parameters. Results have shown that membranes promote beta-sheet formation under a variety of circumstances that may be significant to the pathogenesis of Alzheimer's disease.

Oxidative stress: A bridge between Down's syndrome and Alzheimer's disease

Besides the genetic, biochemical and neuropathological analogies between Down's syndrome (DS) and Alzheimer's disease (AD), there is ample evidence of the involvement of oxidative stress (OS) in the pathogenesis of both disorders. The present paper reviews the publications on DS and AD in the past 10 years in light of the "gene dosage" and "two-hit" hypotheses, with regard to the alterations caused by OS in both the central nervous system and the periphery, and the main pipeline of antioxidant therapeutic strategies. OS occurs decades prior to the signature pathology and manifests as lipid, protein and DNA oxidation, and mitochondrial abnormalities. In clinical settings, the assessment of OS has traditionally been hampered by the use of assays that suffer from inherent problems related to specificity and/or sensitivity, which explains some of the conflicting results presented in this work. For DS, no scientifically proven diet or drug is yet available, and AD trials have not provided a satisfactory approach for the prevention of and therapy against OS, although most of them still need evidence-based confirmation. In the future, a balanced up-regulation of endogenous antioxidants, together with multiple exogenous antioxidant supplementation, may be expected to be one of the most promising treatment methods.

Cell survival responses to environmental stresses via the Keap1-Nrf2-ARE pathway

Keap1-Nrf2-ARE signaling plays a significant role in protecting cells from endogenous and exogenous stresses. The development of Nrf2 knockout mice has provided key insights into the toxicological importance of this pathway. These mice are more sensitive to the hepatic, pulmonary, ovarian, and neurotoxic consequences of acute exposures to environmental agents and drugs, inflammatory stresses, as well as chronic exposures to cigarette smoke and other carcinogens. Under quiescent conditions, the transcription factor Nrf2 interacts with the actin-anchored protein Keap1, largely localized in the cytoplasm. This quenching interaction maintains low basal expression of Nrf2-regulated genes. However, upon recognition of chemical signals imparted by oxidative and electrophilic molecules, Nrf2 is released from Keap1, escapes proteasomal degradation, translocates to the nucleus, and transactivates the expression of several dozen cytoprotective genes that enhance cell survival. This review highlights the key elements in this adaptive response to protection against acute and chronic cell injury provoked by environmental stresses.

Long-term d-galactose injection combined with ovariectomy serves as a new rodent model for Alzheimer's disease

Estrogen deprivation and oxidative stress have been well established as two main factors closely related to the pathological development of Alzheimer's disease (AD). The aim of the present study is to investigate whether these two components act synergistically to accelerate the pathophysiological course of AD. To do this, we examined the effect of long-term intraperitoneal administration of D-galactose (D-gal) into ovariectomized (OVX) rats. Six weeks later, the OVX and d-gal-injected rats exhibited a higher degree of cognitive and memory impairment. This was accompanied by cholinergic neuronal loss in the forebrain and synaptic degeneration in the hippocampus and cerebral cortex which was not observed in intact controls, animals receiving injections of d-gal alone, untreated OVX animals or OVX animals receiving both D-gal and 17-beta estradiol. The typical histopathological alterations associated with AD, including intracellular deposition of amyloid beta peptide and the appearance of intracellular neurofibrillary tangles and nuclear granulovacuolar bodies, were observed in the hippocampus of OVX and D-gal-injected rats but not in other control groups. These results strongly suggest that estrogen deprivation and oxidative stress behave synergistically to enhance the development and progression of AD. Long-term OVX combined with D-gal injection serves as an ideal AD rodent model capable of mimicking pathological, neurochemical and behavioral alterations in AD.

Abeta oligomers induce neuronal oxidative stress through an N-methyl-D-aspartate receptor-dependent mechanism that is blocked by the Alzheimer drug memantine

Oxidative stress is a major aspect of Alzheimer disease (AD) pathology. We have investigated the relationship between oxidative stress and neuronal binding of Abeta oligomers (also known as ADDLs). ADDLs are known to accumulate in brain tissue of AD patients and are considered centrally related to pathogenesis. Using hippocampal neuronal cultures, we found that ADDLs stimulated excessive formation of reactive oxygen species (ROS) through a mechanism requiring N-methyl-d-aspartate receptor (NMDA-R) activation. ADDL binding to neurons was reduced and ROS formation was completely blocked by an antibody to the extracellular domain of the NR1 subunit of NMDA-Rs. In harmony with a steric inhibition of ADDL binding by NR1 antibodies, ADDLs that were bound to detergent-extracted synaptosomal membranes co-immunoprecipitated with NMDA-R subunits. The NR1 antibody did not affect ROS formation induced by NMDA, showing that NMDA-Rs themselves remained functional. Memantine, an open channel NMDA-R antagonist prescribed as a memory-preserving drug for AD patients, completely protected against ADDL-induced ROS formation, as did other NMDA-R antagonists. Memantine and the anti-NR1 antibody also attenuated a rapid ADDL-induced increase in intraneuronal calcium, which was essential for stimulated ROS formation. These results show that ADDLs bind to or in close proximity to NMDA-Rs, triggering neuronal damage through NMDA-R-dependent calcium flux. This response provides a pathologically specific mechanism for the therapeutic action of memantine, indicates a role for ROS dysregulation in ADDL-induced cognitive impairment, and supports the unifying hypothesis that ADDLs play a central role in AD pathogenesis.

Oxidative stress and the pathogenesis of neurodegenerative disorders

Microglia-derived inflammatory neurotoxins play a principal role in the pathogenesis of neurodegenerative disorders including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and HIV-associated dementia; chief among these is reactive oxygen species. The detrimental effects of oxidative stress in the brain and nervous system are primarily a result of the diminished capacity of the central nervous system to prevent ongoing oxidative damage. A spectrum of environmental cues, mitochondrial dysfunction, accumulation of aberrant misfolded proteins, inflammation, and defects in protein clearance are known to evolve and form as a result of disease progression. These factors likely affect glial function serving to accelerate the tempo of disease. Understanding the relationships between disease progression, free radical formation, neuroinflammation, and neurotoxicity is critical to elucidating disease mechanisms and the development of therapeutic modalities to combat disease processes. In an era where populations continue to age, the prevalence and incidence of age-related neurodegenerative diseases are on the rise; therefore, the need for novel therapeutic strategies that attenuate neuroinflammation and protect neurons against oxidative stress is ever more immediate.

Syntheses of Aromatic Substituted Hydrazino-thiazole Derivatives to Clarify Structural Characterization and Antioxidant Activity between 3-Arylsydnonyl and Aryl Substituted Hydrazino-thiazoles

This work clarifies the structural characterization and antioxidant activity between aromatic and 3-arylsydnonyl substituted hydrazino-thiazoles by further synthesizing a series of aromatic ring-substituted hydrazino-thiazole derivatives 8a-h and 9a-h. Hydrazino-thiazole derivatives 8a-h and 9a-h were obtained by reacting aromatic or heterocyclic aromatic aldehyde thiosemicarbazones 7a-h with cyclization reagents ethyl 2-chloroacetoacetate (2a) and 2-bromoacetophenone (2b), respectively. The ORTEP drawings of compounds 8g, 8h and 9f provide strong evidence of the structure of aromatic thiazole derivatives 8a-h and 9a-h. Undoubtedly, the structure of compounds 3e-h and 4e-h synthesized by the reaction of 3-aryl-4-formylsydnone thiosemicarbazones 1e-h with cyclization reagents 2a and 2b in the previous work should have the thiazole moiety, and not the thiazoline moiety. Both the new thiazole derivatives 8a-h and 9a-h and the 3-arylsydnonyl-substituted derivatives 3e-h and 4e-h were investigated to determine their antioxidant activity by two tests that have been highly documented-the direct scavenging effect on a stable free 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and the inhibition of the 2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical. Results of this study demonstrate that not only the thiazole ring and the aryl ring has the contribution to the antioxidant activities, the sydnone ring of 3-arylsydnonyl moiety also has its considerable contribution.

Alzheimer disease: amyloidogenesis, the presenilins and animal models

Alzheimer's disease is the most prevalent form of dementia. Neuropathogenesis is proposed to be a result of the accumulation of amyloid beta peptides in the brain together with oxidative stress mechanisms and neuroinflammation. The presenilin proteins are central to the gamma-secretase cleavage of the amyloid prescursor protein (APP), releasing the amyloid beta peptide. Point mutations in the presenilin genes lead to cases of familial Alzheimer's disease by increasing APP cleavage resulting in excess amyloid beta formation. This review discusses the molecular mechanism of Alzheimer's disease with a focus on the presenilin genes. Alternative splicing of transcripts from these genes and how these may function in several disease states is discussed. There is an emphasis on the importance of animal models in elucidating the molecular mechanisms behind the development of Alzheimer's disease and how the zebrafish, Danio rerio, can be used as a model organism for analysis of presenilin function and Alzheimer's disease pathogenesis.

Reproductive hormones modulate oxidative stress in Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by gradual cognitive decline, impairments in speech and language, and dysfunction in the sensorimotor systems, culminating in complete reliance on nursing care. Oxidative stress, caused by an imbalance in the pro-oxidant/antioxidant mechanisms in the body, has been implicated in AD pathogenesis, as in many other age-associated diseases such as atherosclerosis, Parkinson disease, and amyotrophic lateral sclerosis. Although the hormones estrogen, progesterone, testosterone, and luteinizing hormone are best known for their roles in reproduction, many studies show these hormones have other roles, including neuroprotection. Changes in the levels of these hormones that occur in reproductive senescence are hypothesized to increase risk of AD, as a result of reduced protection against oxidative insults. The Abeta peptide, overproduction of which is thought to be a key pathogenic event in the development of AD, is neurotoxic, most likely due to its ability to promote oxidative stress. The reproductive hormones are known to influence Abeta metabolism, and this review discusses the beneficial and detrimental effects these hormones have on Abeta production and oxidative stress, and their relevance in potential AD therapies.

The role of biomarkers in clinical trials for Alzheimer disease

Biomarkers are likely to be important in the study of Alzheimer disease (AD) for a variety of reasons. A clinical diagnosis of Alzheimer disease is inaccurate even among experienced investigators in about 10% to 15% of cases, and biomarkers might improve the accuracy of diagnosis. Importantly for the development of putative disease-modifying drugs for Alzheimer disease, biomarkers might also serve as indirect measures of disease severity. When used in this way, sample sizes of clinical trials might be reduced, and a change in biomarker could be considered supporting evidence of disease modification. This review summarizes a meeting of the Alzheimer's Association's Research Roundtable, during which existing and emerging biomarkers for AD were evaluated. Imaging biomarkers including volumetric magnetic resonance imaging and positron emission tomography assessing either glucose utilization or ligands binding to amyloid plaque are discussed. Additionally, biochemical biomarkers in blood or cerebrospinal fluid are assessed. Currently appropriate uses of biomarkers in the study of Alzheimer disease, and areas where additional work is needed, are discussed.

Mitochondrial dysfunction and increased sensitivity to excitotoxicity in mice deficient in DNA mismatch repair

The expression profile in the hippocampus of mice lacking one allele of the MutS homologue (Msh2), gene, which is one of the most representative components of the DNA mismatch repair system, was analysed to understand whether defects in the repair or in response to DNA damage could impact significantly on brain function. The overall results suggested a reduction in mitochondrial function as indicated by gene expression analysis, biochemical and behavioural studies. In the hippocampus of Msh2+/- mice, array data, validated by RT-PCR and western blot analysis, showed reduced expression levels of genes for cytochrome c oxidase subunit 2 (CoxII), ATP synthase subunit beta and superoxide dismutase 1. Biochemically, mitochondria from the hippocampus and cortex of these mice show reduced CoxII and increased aconitase activity. Behaviourally, these alterations resulted in mice with increased vulnerability to kainic acid-induced epileptic seizures and hippocampal neuronal loss. These data suggest that lack of an efficient system involved in recognizing and repairing DNA damage may generate a brain mitochondriopathy.

Mitoenergetic failure in Alzheimer disease

Brain cells are highly energy dependent for maintaining ion homeostasis during high metabolic activity. During active periods, full mitochondrial function is essential to generate ATP from electrons that originate with the oxidation of NADH. Decreasing brain metabolism is a significant cause of cognitive abnormalities of Alzheimer disease (AD), but it remains uncertain whether this is the cause of further pathology or whether synaptic loss results in a lower energy demand. Synapses are the first to show pathological symptoms in AD before the onset of clinical symptoms. Because synaptic function has high energy demands, interruption in mitochondrial energy supply could be the major factor in synaptic failure in AD. A newly discovered age-related decline in neuronal NADH and redox ratio may jeopardize this function. Mitochondrial dehydrogenases and several mutations affecting energy transfer are frequently altered in aging and AD. Thus, with the accumulation of genetic defects in mitochondria at the level of energy transfer, the issue of neuronal susceptibility to damage as a function of age and age-related disease becomes important. In an aging rat neuron model, mitochondria are both chronically depolarized and produce more reactive oxygen species with age. These concepts suggest that multiple treatment targets may be needed to reverse this multifactorial disease. This review summarizes new insights based on the interaction of mitoenergetic failure, glutamate excitotoxicity, and amyloid toxicity in the exacerbation of AD.

Predicting Alzheimer dementia in mild cognitive impairment patients. Are biomarkers useful?

A correct clinical diagnosis in the early stage of Alzheimer disease is not only of importance given the current available treatment with acetylcholine esterase inhibitors, but would be the basis for disease-modifying therapy slowing down or arresting the degenerative process. Moreover, in the last years, several efforts have been made to determine if a patient with mild cognitive impairment has incipient Alzheimer disease, i.e. will progress to Alzheimer disease with dementia, or have a benign form of mild cognitive impairment. In this review, the recent published reports regarding progress in early and preclinical Alzheimer disease diagnosis are discussed and the role of peripheral and cerebrospinal fluid biomarkers highlighted. Approaches combining panels of different biomarkers show promise for discovering profiles that are characteristic of Alzheimer disease, even in the pre-symptomatic stage. More work is needed but available novel perspectives offered by recent introduced technologies shed some lights in identifying incipient Alzheimer disease in mild cognitive impairment subjects.

DNA end joining activity is reduced in Alzheimer's disease

Evidence indicates that oxidative stress-induced damage to DNA, protein, and other cellular components contributes to the progression of Alzheimer's disease (AD). Several studies indicate that postmitotic neurons have a reduced capacity for some types of DNA repair, which is further compromised by aging. Thus in AD, the cellular response to increased oxidative DNA damage may be inadequate to protect the genome. Mammalian cells use several mechanisms to repair DNA damage generated during normal oxidative metabolism or by genotoxic insults. The predominant mechanism to repair double strand breaks is non-homologous end joining (NHEJ) which utilizes the DNA-dependent protein kinase (DNA-PK) complex. A cell-free DNA end joining assay was employed to determine if NHEJ was reduced in nuclear cortical extracts from brains of AD versus normal subjects. This report demonstrates that end joining activity and protein levels of DNA-PK catalytic subunit are significantly lower in AD brains compared to normal controls. The amount of end joining activity correlates with the expression of DNA-PK and is dependent on DNA-PK catalytic activity. This indicates that repair of DNA double-strand breaks by the DNA-PK-dependent NHEJ pathway may be deficient in AD.

Melatonin in Alzheimer's disease and other neurodegenerative disorders

Increased oxidative stress and mitochondrial dysfunction have been identified as common pathophysiological phenomena associated with neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease (HD). As the age-related decline in the production of melatonin may contribute to increased levels of oxidative stress in the elderly, the role of this neuroprotective agent is attracting increasing attention. Melatonin has multiple actions as a regulator of antioxidant and prooxidant enzymes, radical scavenger and antagonist of mitochondrial radical formation. The ability of melatonin and its kynuramine metabolites to interact directly with the electron transport chain by increasing the electron flow and reducing electron leakage are unique features by which melatonin is able to increase the survival of neurons under enhanced oxidative stress. Moreover, antifibrillogenic actions have been demonstrated in vitro, also in the presence of profibrillogenic apoE4 or apoE3, and in vivo, in a transgenic mouse model. Amyloid-β toxicity is antagonized by melatonin and one of its kynuramine metabolites. Cytoskeletal disorganization and protein hyperphosphorylation, as induced in several cell-line models, have been attenuated by melatonin, effects comprising stress kinase downregulation and extending to neurotrophin expression. Various experimental models of AD, PD and HD indicate the usefulness of melatonin in antagonizing disease progression and/or mitigating some of the symptoms. Melatonin secretion has been found to be altered in AD and PD. Attempts to compensate for age- and disease-dependent melatonin deficiency have shown that administration of this compound can improve sleep efficiency in AD and PD and, to some extent, cognitive function in AD patients. Exogenous melatonin has also been reported to alleviate behavioral symptoms such as sundowning. Taken together, these findings suggest that melatonin, its analogues and kynuric metabolites may have potential value in prevention and treatment of AD and other neurodegenerative disorders.

Lipids and the pathogenesis of Alzheimer's disease: is there a link?

Alzheimer's disease (AD) is a heterogeneous neurodegenerative disorder characterized pathologically by amyloid-beta plaques, neurofibrillary tangles and neuronal loss. Its fundamental cause(s) and the pathological cascades leading to clinical symptoms remain unknown. Lipids and lipid peroxidation products have important roles in the homeostasis of the central nervous system. As well, lipid transport genes and vascular changes associated with peripheral dyslipidemia have been associated with an increased risk of AD. The present review discusses ways in which lipids may be involved in the pathogenesis of AD-associated neurodegeneration through their roles as neuronal structural components, cell modulators, or second messengers. Given the many possibilities through which lipids may be directly involved in or contribute to the pathogenesis of AD, the use of lipids as biomarkers for disease progression is discussed, as are other avenues for future research.

Recognition of Oxidatively Modified Bases within the Biotin-binding Site of Avidin

Oxidative damage of DNA results in the formation of many products, including 8-oxodeoxyguanosine, which has been used as a marker to quantify DNA damage. Earlier studies have demonstrated that avidin, a protein prevalent in egg-white and which has high affinity for the vitamin biotin, binds to 8-oxodeoxyguanosine and related bases. In this study, we have determined crystal structures of avidin in complex with 8-oxodeoxyguanosine and 8-oxodeoxyadenosine. In each case, the base is observed to bind within the biotin-binding site of avidin. However, the mode of association between the bases and the protein varies and, unlike in the avidin:biotin complex, complete ordering of the protein in this region does not accompany binding. Fluorescence studies indicate that in solution the individual bases, and a range of oligonucleotides, bind to avidin with micromolar affinity. Only one of the modes of binding observed is consistent with recognition of oxidised purines when incorporated within a DNA oligomer, and from this structure a model is proposed for the selective binding of avidin to DNA containing oxidatively damaged deoxyguanosine. These studies illustrate the molecular basis by which avidin might act as a marker of DNA damage, although the low levels of binding observed are inconsistent with the recognition of oxidised purines forming a major physiological role for avidin.

Protective effect of Rosa laevigata against amyloid beta peptide-induced oxidative stress

The amyloid beta (Abeta) peptide is known to increase free radical production in nerve cells, leading to cell death. To investigate the effect of Rosa laevigata against Abeta-induced oxidative damage, in vitro assays and in vivo behavioral tests were performed. R. laevigata showed cell protective effects against oxidative stress-induced cytotoxicity. MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) reduction assay exhibited significant increase in cell viability when rat pheochromocytoma (PC 12) cells were treated with R. laevigata extracts. Administration of R. laevigata extracts to mice significantly reversed the Abeta-induced learning and memory impairment in in vivo behavioral tests. These results suggest that R. laevigata extracts can reduce the cytotoxicity of Abeta in PC 12 cells, possibly by the reduction of oxidative stress, and these extracts may be useful in the prevention of Alzheimer's disease.

Nutritional factors, cognitive decline, and dementia

Nutritional factors and nutritional deficiencies have been repeatedly associated with cognitive impairment. Most of the evidence is based on cross-sectional studies, which cannot prove whether a nutritional deficit is the cause or the consequence of an impaired cognitive status. In fact, cognitive impairment, in turn, can determine changes in dietary habits and consequent nutritional deficiencies. We reviewed clinical and epidemiological studies from January 1983 to June 2004. Several cross-sectional and fewer prospective studies reported an association between dietary or supplemental intake of antioxidants and protection from cognitive decline and dementia. There are negative reports as well and some methodological biases might have affected the consistencies across studies. Deficiencies of several B vitamins have been associated with cognitive dysfunction in many observational studies. More recently, deficiencies of folate (B9) and cobalamine (B12) have been studied in relation to hyperhomocysteinemia as potential determinants of cognitive impairment, dementia, and Alzheimer's disease (AD). A small number of studies assessed the association between intake of macronutrients and cognitive function or dementia. Among the others, the intake of fatty acids and cholesterol has received particular attention. Although the results are not always consistent, most studies have reported a protective role of dietary intakes of poly- and mono-unsaturated fatty acids against cognitive decline and AD. We point out that well designed intervention studies are warranted in order to establish specific levels of micro- and macronutrient deficiencies and to set general recommendations for the population.

Anti-Parkinsonian agents have anti-amyloidogenic activity for Alzheimer's β-amyloid fibrils in vitro

Inhibition of the accumulation of amyloid beta-peptide (Abeta) and the formation of beta-amyloid fibrils (fAbeta) from Abeta, as well as the destabilization of preformed fAbeta in the central nervous system would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). Many studies have demonstrated that oxidative damage plays a central role in AD pathogenesis, as well as Parkinson disease (PD). Among the antioxidant strategies proposed, increasing evidence points to the possibility of achieving neuroprotection by dopamine agonists, as well as monoamine oxidase B (MAO-B) inhibitors. Actually, the beneficial effect of selegiline, a MAO-B inhibitor, in AD has been noted in several clinical studies. On the reverse, antimuscarinic agents have been reported to accelerate beta-amyloidosis and senile plaque formation in PD. Using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies, we examined the effects of anti-Parkinsonian agents, dopamine, levodopa, pergolide, bromocriptine, selegiline, and trihexyphenidyl on the formation, extension, and destabilization of fAbeta(1-40) and fAbeta(1-42) at pH 7.5 at 37 degrees C in vitro. The anti-Parkinsonian agents other than trihexyphenidyl dose-dependently inhibited fAbeta formation from Abeta(1-40) and Abeta(1-42), as well as their extension. Moreover, these agents dose-dependently destabilized preformed fAbetas. The overall activity of the molecules examined was in the order of: dopamine>selegiline>levodopa=pergolide>bromocriptine. Although the exact mechanism of the anti-amyloidogenic activity of these agents is unclear, these and other structurally related compounds could be key molecules for the development of therapeutics for AD and other conformational diseases.

Alpha-lipoic acid exhibits anti-amyloidogenicity for beta-amyloid fibrils in vitro

Inhibition of the formation of beta-amyloid fibrils (fAbeta), as well as the destabilization of preformed fAbeta in the CNS would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). Using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies, we examined the effects of alpha-lipoic acid (LA) and the metabolic product of LA, dihydrolipoic acid (DHLA), on the formation, extension, and destabilization of fAbeta at pH 7.5 at 37 degrees C in vitro. LA and DHLA dose-dependently inhibited fAbeta formation from amyloid beta-protein, as well as their extension. Moreover, they destabilized preformed fAbetas. LA and DHLA could be key molecules for the development of therapeutics for AD.

Memory decline of aging reduced by extracellular superoxide dismutase overexpression

Extracellular superoxide dismutase (EC-SOD) plays an important role in controlling oxidative stress as well as intercellular signaling. In the current study, we tested the effect of EC-SOD overexpression over the lifespan of a set of mice and their wild-type controls to determine the time scale over which EC-SOD overexpression might attenuate aging-induced memory impairment. Mice with overexpression of EC-SOD and wild-type controls were initially trained on the radial-arm maze as young adults (3-5 months) and then retrained during middle age (12-14 months) and retested in old age at 27 and 30 months. There was little EC-SOD effect during the young adult middle age periods. EC-SOD overexpression prevented the decline in choice accuracy when the mice were 27-30 months of age. The EC-SOD overexpressing mice maintained their performance, while the wild-type mice declined to naïve levels of performance by 30 months of age. Enhancement of EC-SOD activity appears to improve memory performance specifically in aging mice. EC-SOD mimetic treatment during the course of aging may hold promise for aging-induced cognitive impairment.

Urinary 8-isoprostaglandin F(2alpha) level in Behçet's disease

Although its etiology remains unknown, the increased production of reactive oxygen species in Behçet's disease (BD) have been reported. Furthermore, it has been suggested that vascular and endothelial tissue damage seen in BD is related to elevated reactive oxygen species generated by activated neutrophils from BD patients. To investigate the formation of lipid peroxidation in BD patients in vivo, urinary level of 8-isoprostaglandin F(2alpha) was quantitated by enzyme immunoassay after solid phase extraction in different clinical forms of BD patients. There was no difference in urinary level of 8-isoprostaglandin F(2alpha) between BD patient and healthy control group. There was also no difference in urinary levels of 8-isoprostaglandin F(2alpha) in subgroup analyses of BD patients, i.e. in mucocutaneous and vascular type BD patients; active and inactive BD patients. Contrary to the findings in literature, we found no difference in urinary level of 8-isoprostaglandin F(2alpha) between patients with systemic lupus erythematosus and healthy control group. These findings show no increase in lipid peroxidation despite the augmented formation of reactive oxygen species in BD patients. It may be interesting to assess formation of urinary level of 8-isoprostaglandin F(2alpha) in BD patients who do not take any medication.

Ferulic acid destabilizes preformed beta-amyloid fibrils in vitro

Inhibition of the formation of beta-amyloid fibrils (fAbeta), as well as the destabilization of preformed fAbeta in the CNS, would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). We reported previously that curcumin (Cur) inhibits fAbeta formation from Abeta and destabilizes preformed fAbeta in vitro. Using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies, we examined the effects of ferulic acid (FA) on the formation, extension, and destabilization of fAbeta at pH 7.5 at 37 degrees C in vitro. We next compared the anti-amyloidogenic activities of FA with Cur, rifampicin, and tetracycline. Ferulic acid dose-dependently inhibited fAbeta formation from amyloid beta-peptide, as well as their extension. Moreover, it destabilized preformed fAbetas. The overall activity of the molecules examined was in the order of: Cur > FA > rifampicin = tetracycline. FA could be a key molecule for the development of therapeutics for AD.

Vitamin E supplementation in Alzheimer's disease, Parkinson's disease, tardive dyskinesia, and cataract: Part 2

OBJECTIVE

To review clinical trials evaluating the safety and efficacy of vitamin E supplementation in Alzheimer's disease, Parkinson's disease, tardive dyskinesia, and cataract.

DATA SOURCES

Using the MeSH terms alpha-tocopherol, tocopherols, vitamin E, Parkinson disease, tardive dyskinesia, Alzheimer disease, cataract, and clinical trials, a literature review was conducted to identify peer-reviewed articles in MEDLINE (1966-July 2005).

STUDY SELECTION AND DATA EXTRACTION

Published materials including original research, review articles, and meta-analyses were reviewed. Only English-language articles and trials that included vitamin E alone or in combination with other vitamins or minerals were reviewed. Emphasis was placed on prospective, randomized, double-blind, placebo-controlled clinical trials.

DATA SYNTHESIS

The clinical studies demonstrated contradicting results regarding the benefits of vitamin E in Parkinson's disease, tardive dyskinesia, and cataract. The study reviewed for Alzheimer's disease seemed to show benefit when vitamin E was used; however, the statistical methods employed are questionable. There is enough evidence from large, well-designed studies to discourage the use of vitamin E in Parkinson's disease, cataract, and Alzheimer's disease. We recommend that vitamin E be considered a treatment option in patients with tardive dyskinesia only if they are newly diagnosed.

CONCLUSIONS

We encourage patients to supplement with vitamin E-rich foods. The use of a daily multivitamin, which usually contains 30 IU of alpha-tocopherol, may be beneficial; however, we discourage individual vitamin E supplements that usually contain 400 IU of alpha-tocopherol.

Promotion of oxidative lipid membrane damage by amyloid beta proteins

Senile plaques in the cerebral parenchyma are a pathognomonic feature of Alzheimer's disease (AD) and are mainly composed of aggregated fibrillar amyloid beta (Abeta) proteins. The plaques are associated with neuronal degeneration, lipid membrane abnormalities, and chemical evidence of oxidative stress. The view that Abeta proteins cause these pathological changes has been challenged by suggestions that they have a protective function or that they are merely byproducts of the pathological process. This investigation was conducted to determine whether Abeta proteins promote or inhibit oxidative damage to lipid membranes. Using a mass spectrometric assay of oxidative lipid damage, the 42-residue form of Abeta (Abeta42) was found to accelerate the oxidative lipid damage caused by physiological concentrations of ascorbate and submicromolar concentrations of copper(II) ion. Under these conditions, Abeta42 was aggregated, but nonfibrillar. Ascorbate and copper produced H(2)O(2), but Abeta42 reduced H(2)O(2) concentrations, and its ability to accelerate oxidative damage was not affected by catalase. Lipids could be oxidized by H(2)O(2) and copper(II) in the absence of ascorbate, but only at significantly higher concentrations, and Abeta42 inhibited this reaction. These results indicate that the ability of Abeta42 to promote oxidative damage is more potent and more likely to be manifest in vivo than its ability to inhibit oxidative damage. In conjunction with prior results demonstrating that oxidatively damaged membranes cause Abeta42 to misfold and form fibrils, these results suggest a specific chemical mechanism linking Abeta42-promoted oxidative lipid damage to amyloid fibril formation.

Melatonin reduces oxidative stress and increases gene expression in the cerebral cortex and cerebellum of aluminum-exposed rats

The pro-oxidant activity of aluminum (Al), the protective role of exogenous melatonin, as well as the mRNA levels of some antioxidant enzymes, were determined in cortex and cerebellum of rats following exposure to Al and/or melatonin. Two groups of male rats received intraperitoneal injections of Al lactate or melatonin at doses of 7 mg Al/kg/day and 10 mg/kg/day, respectively, for 11 wk. A third group of animals received concurrently Al lactate (7 mg Al/kg/day) plus melatonin (10 mg/kg/day) during the same period. A fourth group of rats was used as control. At the end of the treatment, the cerebral cortex and cerebellum were removed and processed to examine the following oxidative stress markers: glutathione transferase (GST), reduced glutathione (GSH), oxidized glutathione (GSSG), superoxide dismutase (SOD), glutathione reductase, glutathione peroxidase (GPx), catalase (CAT), thiobarbituric acid reactive substances (TBARS), as well as protein content. Moreover, gene expression of Cu-ZnSOD, MnSOD, GPx and CAT was evaluated by real-time RT-PCR. On the other hand, Al, Fe, Mn, Cu and Zn concentrations were determined in cortex and cerebellum of rats. Oxidative stress was promoted in both neural regions following Al administration, resulting from the pro-oxidant activity related with an increase in tissue Al concentrations. In contrast, melatonin exerted an antioxidant action which was related with an increase in the mRNA levels of the antioxidant enzymes evaluated. The results of the present investigation emphasize the potential use of melatonin as a supplement in the therapy of neurological disorders in which oxidative stress is involved.

Concepts for the treatment of Alzheimer's disease: molecular mechanisms and clinical application

To date, various strategies have been developed in order to prevent or to slow down the progression of Alzheimer's disease (AD). Despite the medical need for an effective therapeutic treatment of AD, progress towards this goal is painstakingly slow. Although AD is the most common neurodegenerative disorder and a large amount of primary basic and clinical research has been performed already, it appears very difficult to identify appropriate targets, which would promise fast, effective and safe strategies to combat the disease onset and progression. In this review, we present some of clinically applied treatment options, which may improve AD symptoms for a short period but so far lack the ability to prevent or halt this devastating disease. Additionally, we summarize some of the experimental approaches in AD therapy, which might lead to the development of more promising drugs in the future.

Vitamin E in neurodegenerative disorders: Alzheimer's disease

Oxidative stress is important in the pathogenesis of Alzheimer's disease (AD). The brain contains high levels of oxidizable lipids that must be protected by antioxidants. Low concentrations of vitamin E, quantitatively the major lipophilic antioxidant in the brain, are frequently observed in cerebrospinal fluid (CSF) of AD patients, suggesting that supplementation with vitamin E might delay the development of AD. In a placebo-controlled trial, vitamin E (2000 IU/day, 2 years) slowed (-53%) functional deterioration in patients with moderate AD (Sano et al., N. Engl. J. Med. 336: 1216-1222, 1997). Recently, use of vitamin E and vitamin C supplements in combination was found to be associated with reduced prevalence (-78%) and incidence (-64%) of AD in elderly population (Zandi et al., Arch. Neurol. 61: 82-88, 2004). These results are consistent with the ability of the supplementation with vitamin E (400 IU/day, 1 month) to increase its levels in CSF (123%) and plasma (145%) of AD patients and, in combination with vitamin C (1000 g/day), to decrease the susceptibility of CSF lipoproteins (up to -32%) to in vitro oxidation (Kontush et al., Free Radic. Biol. Med. 31: 345-354, 2001). In addition, vitamin E reduced lipid peroxidation and amyloid deposition in a transgenic mice model of AD (Sung et al., FASEB J. 18: 323-325, 2004). Computer modeling of the influence of vitamin E on lipoprotein oxidation reveals that the vitamin develops antioxidative activity in CSF lipoproteins in the presence of physiologically relevant, low amounts of oxidants. By contrast, under similar conditions, vitamin E behaves as a pro-oxidant in plasma lipoproteins, consistent with the model of tocopherol-mediated peroxidation (Stocker, Curr. Opin. Lipidol. 5: 422-433, 1994). This distinction is related to major differences in the levels of vitamin E (50 nM vs. 30 microM) and oxidizable lipids (4 microM vs. 2.5 mM) between CSF and plasma, which result in major differences in oxidative conditions (per unit of vitamin E) between CSF and plasma in the presence of similar amounts of oxidants. Altogether, these data suggest that vitamin E may be effective against in vivo oxidation of CSF lipoproteins and brain lipids, and offer new perspectives in the treatment of AD and other neurodegenerative disorders.

Preformed beta-amyloid fibrils are destabilized by coenzyme Q10 in vitro

Inhibition of the formation of beta-amyloid fibrils (fAbeta), as well as the destabilization of preformed fAbeta in the CNS, would be attractive therapeutic targets for the treatment of Alzheimer's disease (AD). We reported previously that nordihydroguaiaretic acid (NDGA) and wine-related polyphenol, myricetin (Myr), inhibit fAbeta formation from Abeta and destabilize preformed fAbeta in vitro. Using fluorescence spectroscopic analysis with thioflavin T and electron microscopic studies, we examined the effects of coenzyme Q(10) (CoQ(10)) on the formation, extension, and destabilization of fAbeta at pH 7.5 at 37 degrees C in vitro. We next compared the anti-amyloidogenic activities of CoQ(10) with NDGA and Myr. CoQ(10) dose-dependently inhibited fAbeta formation from amyloid beta-peptide (Abeta), as well as their extension. Moreover, it destabilized preformed fAbetas. The anti-amyloidogenic effects of CoQ(10) were slightly weaker than those of NDGA and Myr. CoQ(10) could be a key molecule for the development of therapeutics for AD.

Formation of 8-isoprostaglandin F2alpha and prostaglandin E2 in carrageenan-induced air pouch model in rats

To investigate a possible role of 8-isoprostaglandin F2alpha in inflammation, 8-isoprostaglandin F2alpha and prostaglandin E2 levels were determined by enzyme immunoassay (EIA) in carrageenan-induced air pouch model in rats. In this model, 8-isoprostaglandin F2alpha and prostaglandin E2 levels were found to be increased significantly. To evaluate whether this increase was due to the development of inflammation or solely to cyclooxygenase-2 induction, a lipopolysaccharide-induced air pouch model, in which only cyclooxygenase-2 induction occurs without inflammation, was used. In this model, 8-isoprostaglandin F2alpha was also found to be increased parallel to the increase in prostaglandin E2 level. Cyclooxygenase-dependent formation of 8-isoprostaglandin F2alpha was investigated in carrageenan-induced air pouch model by administrating nonselective cyclooxygenase inhibitor indomethacin, selective cyclooxygenase-1 inhibitor valeryl salicylate or selective cyclooxygenase-2 inhibitor SC-582368 (4-(5-(4-chlorophenyl)-3-3-trifluoromethyl)-1H-pyrazol-1-yl)benzenesulfonanmide) 1 h before carrageenan injection. All these inhibitors significantly inhibited the production of 8-isoprostaglandin F2alpha and prostaglandin E2. These findings show that 8-isoprostaglandin F2alpha can be formed in carrageenan-induced air pouch model in rats. The formation of 8-isoprostaglandin F2alpha in lipopolysaccharide-induced air pouch model and the inhibition of its production by various cyclooxygenase inhibitors provide evidence for cyclooxygenase-dependent formation of isoprostanes in this model.

Study of the oxidative stress in a rat model of chronic brain hypoperfusion

A multiple analysis of the cerebral oxidative stress was performed on a physiological model of dementia accomplished by three-vessel occlusion in aged rats. The forward rate constant of creatine kinase, k(for), was studied by saturation transfer (31)P magnetic resonance spectroscopy in adult and aged rat brain during chronic hypoperfusion. In addition, free radicals in aging rat brain homogenates before and/or after occlusion were investigated by spin-trapping electron paramagnetic resonance spectroscopy (EPR). Finally, biochemical measurements of oxidative phosphorylation parameters in the above physiological model were performed. The significant reduction of k(for) in rat brain compared to controls 2 and 10 weeks after occlusion indicates a disorder in brain energy metabolism. This result is consistent with the decrease of the coefficient of oxidative phosphorylation (ADP:O), and the oxidative phosphorylation rate measured in vitro on brain mitochondria. The EPR study showed a significant increase of the ascorbyl free radical concentration in this animal model. Application of alpha-phenyl-N-tert-butylnitrone (PBN) and 5,5-dimethyl-1-pyrroline N-oxide (DMPO) spin traps revealed formation of highly reactive hydroxyl radical (.OH) trapped in DMSO as the .CH(3) adduct. It was concluded that the ascorbate as a major antioxidant in brain seems to be useful in monitoring chronic cerebral hypoperfusion.

Preservation of DNA integrity and neuronal degeneration

The mismatch repair system (MMR) is an important member of the DNA checkpoint, that includes a number of protein deputed to control genomic stability through cell cycle arrest, DNA repair, and apoptosis. Here we summarize some recent data from our and other groups underlining the contribution to neurodegeneration of MSH2, perhaps the most relevant component of the MMR system. These data suggest that this protein participates not only in the cancer prevention machinery for the body but also in neurodegenerative processes.

Trypanosoma cruzi trans-sialidase as a new therapeutic tool in the treatment of chronic inflammatory diseases: possible action against mycoplasma and chlamydia

The present paper proposes a new therapy using Trypanosoma cruzi trans-sialidase to treat diseases with unclear pathogenesis that present in common chronic inflammation and fibrosis. This hypothesis is based on recent findings that co-infection with mycoplasma and chlamydia is present in many of these diseases and that this enzyme was capable to eliminate or decrease the co-infection from the host. We identified that mycoplasmas and chlamydias are present in atherosclerosis, aortic valve stenosis, dilated cardiomyopathy, chronic chagasic myocarditis and cancer. We hypothetized that mycoplasmal infection may induce immunodepression in the host, favoring proliferation of pre-existent chlamydial infection and that elimination of mycoplasma would lead to improvement of the immune system resistance and the control of chlamydial proliferation. Mycoplasma has a particular parasitic relationship with host cells, involving strong adherence of their membranes, making it extremely difficult to eradicate mycoplasmal infection from the host. A new therapeutic approach is suggested using one or more agents that prevent or inhibit the adherence of mycoplasma to host cell membranes by removing sialic acid residues and preventing oxidation of the cells. The use of a neuraminidase enzyme, particularly the T. cruzi trans-sialidase enzyme, associated with treatment using anti-oxidating agents is proposed. Preliminary experimental animal and laboratory tests showed good results. The proposal that trans-sialidase from T. cruzi is efficient in combating co-infection of mycoplasma and chlamydia is based, at least in part, on the observation that chagasic patients suffering from T. cruzi infection present less mycoplasma and chlamydia infection in their tissues. Also, a lower incidence of the diseases above described to be related to mycoplasma infection is observed in chagasic patients. It is also hypothesized that co-infection with mycoplasma and chlamydia may induce oxidation of the host cells. Anti-oxidants such as those present in plant extracts may also be used in the treatment. Other diseases such as chronic hepatitis, glomerulonephritis, Multiple Sclerosis, Alzheimer's Syndrome and idiopathic encephalitis are other examples of chronic diseases where mycoplasma and chlamydia might be present, as they have the characteristics of unknown etiology, persistent chronic inflammation and fibrosis.

Influence of treatment of diabetic rats with combinations of pycnogenol, ?-carotene, and ?-lipoic acid on parameters of oxidative stress

Treatment with antioxidants may act more effectively to alter markers of free radical damage in combinations than singly. This study has determined whether treatment with combinations of pycnogenol, beta-carotene, and alpha-lipoic acid was more effective at reducing oxidative stress in diabetic rats than treatment with these antioxidants alone. It is not feasible, based on this study, to assume that there are interactive effects that make combinations of these antioxidants more effective than any one alone to combat oxidative stress. Female Sprague-Dawley rats, normal and streptozotocin-induced diabetic, were treated (10 mg/kg/day ip for 14 days) with pycnogenol, beta-carotene, pycnogenol + beta-carotene, or pycnogenol + beta-carotene + alpha-lipoic acid; controls were untreated. Concentrations of thiobarbituric acid reactive substances, glutathione and glutathione disulfide, and activities of glutathione reductase, glutathione peroxidase, superoxide dismutase, and catalase were measured in liver, kidney, and heart. Four types of effects were observed: (1) treatment with beta-carotene alone either reversed (cardiac glutathione disulfide) or elevated (cardiac glutathione, hepatic glutathione peroxidase activity) levels seen in diabetic animals; (2) beta-carotene alone produced no effect, but pycnogenol both alone and in combinations elevated (renal glutathione peroxidase and glutathione reductase activities, hepatic glutathione reductase activity and glutathione disulfide) or depressed (cardiac glutathione disulfide) levels seen in untreated diabetic animals; (3) all treatments with antioxidants, either alone or in combination, either normalized (lipid peroxidation in all tissues), elevated (hepatic GSH, cardiac glutathione peroxidase activity), or had no effect on (activities of hepatic catalase and superoxide dismutase in all tissues) levels seen in diabetic animals; (4) in only one case (cardiac glutathione reductase activity) levels in diabetic animals treated with combinations of antioxidants were normal, but elevated in animals treated with either antioxidant alone. Antioxidant effects seem to be dependent on the nature of the antioxidant used and not on combination effects.

Molecular Rationale for the Pharmacological Treatment of Alzheimer??s Disease

Cerebral deposition of amyloid plaques containing amyloid beta-peptide (Abeta) has traditionally been considered the central feature of Alzheimer's disease (AD). Abeta is derived from amyloid precursor protein (APP), which is cleaved by several different proteases: alpha-, beta- and gamma-secretase. In the past decade, however, the molecular pathogenesis of AD has been shown to involve alterations in several neurotransmitter, inflammatory, oxidative, and hormonal pathways that represent potential targets for AD prevention and treatment. Much research has shown a direct link between cholinergic impairment and altered APP processing as a major pathogenetic event in AD. Three highly probable mechanisms of APP regulation through inhibition of acetylcholinesterase are thus current topics of investigation. Indeed, acetylcholinesterase inhibitors appear to cause selective muscarinic activation of alpha-secretase and to induce the translation of APP mRNA; they may also restrict amyloid fibre assembly. Activation of N-methyl-D-aspartate receptors is considered a probable cause of chronic neurodegeneration in AD, and memantine has been widely used in some countries in AD patients to block cerebral N-methyl-D-aspartate receptors that normally respond to glutamate. Further studies are needed to determine whether antioxidants such as vitamins C and E are effective, through various mechanisms, in patients with mild-to-moderate AD. Additional data are also required for non-steroidal anti-inflammatory drugs, some of which appear to possess experimental effects that may ultimately prove favourable in AD patients. Statins also warrant further investigation, since they have activated alpha-secretase and they reduced Abeta generation and amyloid accumulation in a transgenic mouse model. beta-Secretase would seem to be an ideal target for anti-amyloid therapy in AD, but potential clinical and pharmacological issues, such as ensuring selectivity of inhibition, stability, and ease of blood-brain barrier penetration and cellular uptake, remain to be addressed for beta-secretase inhibitors. gamma-Secretase is not an easy candidate for pharmacological manipulation. Immunotherapeutic strategies have targeted Abeta directly; however, intensive investigation of indirect approaches to the management of AD with immunotherapy is now underway.

Oxidative stress in Alzheimer's disease: implications for prevention and therapy

Oxidative stress is a marker of neurodegeneration and has been recently shown to be also involved in the early stages of the pathogenesis of various neurodegenerative disorders. In general, all biomolecules of the cell can be oxidized and thereby damaged. Consequently, the concept of neuroprotection by antioxidants has been developed. In many cases the direct scavanging of free radicals have been used as a strategy to prevent oxidative stress damage and a variety of physiological and synthetic antioxidant molecules have been identified and synthesized including the female sex homone estrogen. In Alzheimer's Disease amyloid-beta protein on its way to brain deposition can also induce oxidative changes rendering nerve cells more vulnerable to additional insults. In addition, inflammatory mediators are attracted by amyloid deposits that can further speed up the generation of an oxidative micro-environment. Based on recent clinical data the use of a combination of various antioxidants might indeed be effective in preventing Alzheimer's Disease. Nevertheless, the exact molecular mechanisms and the real impact of oxidative stress on the development and progression of Alzheimer's Disease as well as of other neurodegenerative disorders still needs to be further investigated.

Characterization of antioxidants and change of antioxidant levels during storage of Manilkara zapota L

Antioxidants found in fruits and vegetables play an important role via their protective effects against the onset of aging-related chronic diseases. Our previous research has indicated that unripe ciku fruits (Manilkara zapota L.) are an excellent source of antioxidants, with over 3000 mg of L-ascorbic acid equivalent antioxidant capacity (AEAC) per 100 g of fresh sample. In this study, 24 antioxidants in an extract of ciku king were characterized through a free radical spiking test. Their chemical structures were proposed using high-performance liquid chromatography-mass spectrometry (HPLC-MS) and tandem MS (HPLC/MSn). The antioxidant capacity of ciku king fruits was mainly attributed to polyphenolics with basic blocks of gallocatechin or catechin or both. The changes of total antioxidant capacity (TAC) and total phenolics content (TPC) of ciku king fruits with storage time were also investigated. It was found that the TAC and TPC decreased significantly as the fruits gradually changed from the unripe to the overripe stage. The best time for one to consume ciku king fruits at a flavorful stage with high amounts of antioxidants with AEAC values ranging from 600 to 1200 mg per 100 g fresh sample is suggested. The change of the content of major antioxidant peaks was also consistent with changes of antioxidant levels during storage.

Tocopherol (vitamin E) in Alzheimer's disease and other neurodegenerative disorders

In this article, we review the evidence that tocopherol (vitamin E) may have a role to play in the prevention and treatment of Alzheimer's disease and other neurological diseases. The theoretical rationale for the effectiveness of tocopherol as treatment and/or prevention of Alzheimer's disease is based on its antioxidant properties. Results from animal and in vitro studies provide evidence to support use of tocopherol for prevention and treatment of degenerative neurological diseases. Furthermore, several, but not all, epidemiological, cross-sectional, prospective studies indicate that tocopherol may have protective effects in Alzheimer's disease, although dietary and supplemental forms of the vitamin may differ in their efficacy. Mixed results have been obtained from clinical trials. Evidence of the use of tocopherol as a protective measure or as therapy in neurological diseases other than Alzheimer's disease is less compelling. To date, there are no clear-cut answers as to whether tocopherol is worth prescribing, but current clinical practice favours its use in the treatment of Alzheimer's disease.