Oxidative stress and neurodegenerative disorders

Protective effect of aqueous extract of Embelia ribes Burm fruits in middle cerebral artery occlusion-induced focal cerebral ischemia in rats

Objective:

The present study was carried out to evaluate the neuroprotective effect of the aqueous extract of Embelia ribes, in focal ischemic brain.

Materials and Methods:

Adult male Wistar albino rats were fed with the aqueous extract of Embelia ribes (100 and 200 mg/kg, p.o.) for 30 days. After 30 days of feeding, all the animals were anaesthetized with chloral hydrate (400 mg/kg, i.p.). The right middle cerebral artery was occluded with a 4-0 suture for 2 h. The suture was removed after 2 h, to allow reperfusion injury. The animals were used for grip strength measurement, biochemical estimation in serum and brain tissue (hippocampus and frontal cortex) and cerebral infarct size measurement.

Results:

In the ischemic group, a significant (P < 0.01) alteration in the markers of oxidative damage (thiobarbituric acid reactive substances (TBARS); reduced glutathione (GSH); glutathione peroxidase (GPx); glutathione reductase (GR); and, glutathione-S-transferase (GST)) was observed in the hippocampus and frontal cortex, as compared to sham operated rats. We observed that the animals treated with the aqueous extract of Embelia ribes had a significant (P < 0.01) increase in the poststroke grip strength activity. Further, supplementation with aqueous extract of Embelia ribes reversed the levels/activities of the above mentioned biochemical parameters significantly (P< 0.01) and also resulted in decreased cerebral infarct area, as compared to the ischemic group.

Conclusion:

The results of our study, for the first time, provide clear evidence that aqueous extract of Embelia ribes pretreatment ameliorates cerebral ischemia/reperfusion injury and enhances the antioxidant defense against middle cerebral artery occlusion-induced cerebral infarction in rats; it exhibits neuroprotective property.

Neuroprotective activity of Matricaria recutita against fluoride-induced stress in rats

CONTEXT

Oxidative stress plays a key role in pathophysiology of many neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and so on. Although Matricaria recutita L. (Asteraceae), German chamomile, is traditionally used for central nervous system (CNS)-related diseases, its antistress properties have received little attention.

OBJECTIVE

The present study evaluated the neuroprotective effect of German chamomile against aluminium fluoride (AlF₄⁻)-induced oxidative stress in rats.

MATERIALS AND METHODS

The Sprague-Dawley rats of either sex (200-250 g) were selected and grouped as: group I received normal saline; group II received AlF₄⁻ (negative control); groups III, IV, and V received 100, 200, and 300 mg/kg, orally, German chamomile methanol extract (GCME) along with AlF₄⁻; and group VI received quercetin (25 mg/kg, i.p.) + AlF₄⁻, respectively. After 10 days treatment with GCME, oxidative stress was induced by administering AlF₄⁻ through drinking water for 7 days. Then, the protective antioxidant enzyme levels were measured and the histopathological studies were carried out.

RESULTS

The GCME showed dose-dependent neuroprotective activity by significant decrease in lipid peroxidation (LPO) and increase in the superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), and total thiol levels in extract-treated animals as compared with negative control group (P < 0.001). The histopathological studies also revealed the potent neuroprotective action of German chamomile against oxidative brain damage.

CONCLUSION

The present study for the first time shows potent neuroprotective activity of the methanol extract of German chamomile against AlF₄⁻-induced oxidative stress in rats.

Altered mRNA editing and expression of ionotropic glutamate receptors after kainic acid exposure in cyclooxygenase-2 deficient mice

Kainic acid (KA) binds to the AMPA/KA receptors and induces seizures that result in inflammation, oxidative damage and neuronal death. We previously showed that cyclooxygenase-2 deficient (COX-2(-/-)) mice are more vulnerable to KA-induced excitotoxicity. Here, we investigated whether the increased susceptibility of COX-2(-/-) mice to KA is associated with altered mRNA expression and editing of glutamate receptors. The expression of AMPA GluR2, GluR3 and KA GluR6 was increased in vehicle-injected COX-2(-/-) mice compared to wild type (WT) mice in hippocampus and cortex, whereas gene expression of NMDA receptors was decreased. KA treatment decreased the expression of AMPA, KA and NMDA receptors in the hippocampus, with a significant effect in COX-2(-/-) mice. Furthermore, we analyzed RNA editing levels and found that the level of GluR3 R/G editing site was selectively increased in the hippocampus and decreased in the cortex in COX-2(-/-) compared with WT mice. After KA, GluR4 R/G editing site, flip form, was increased in the hippocampus of COX-2(-/-) mice. Treatment of WT mice with the COX-2 inhibitor celecoxib for two weeks decreased the expression of AMPA/KA and NMDAR subunits after KA, as observed in COX-2(-/-) mice. After KA exposure, COX-2(-/-) mice showed increased mRNA expression of markers of inflammation and oxidative stress, such as cytokines (TNF-α, IL-1β and IL-6), inducible nitric oxide synthase (iNOS), microglia (CD11b) and astrocyte (GFAP). Thus, COX-2 gene deletion can exacerbate the inflammatory response to KA. We suggest that COX-2 plays a role in attenuating glutamate excitotoxicity by modulating RNA editing of AMPA/KA and mRNA expression of all ionotropic glutamate receptor subunits and, in turn, neuronal excitability. These changes may contribute to the increased vulnerability of COX-2(-/-) mice to KA. The overstimulation of glutamate receptors as a consequence of COX-2 gene deletion suggests a functional coupling between COX-2 and the glutamatergic system.

Neuroprotective multifunctional iron chelators: from redox-sensitive process to novel therapeutic opportunities

Accumulating evidence suggests that many cytotoxic signals occurring in the neurodegenerative brain can initiate neuronal death processes, including oxidative stress, inflammation, and accumulation of iron at the sites of the neuronal deterioration. Neuroprotection by iron chelators has been widely recognized with respect to their ability to prevent hydroxyl radical formation in the Fenton reaction by sequestering redox-active iron. An additional neuroprotective mechanism of iron chelators is associated with their ability to upregulate or stabilize the transcriptional activator, hypoxia-inducible factor-1alpha (HIF-1alpha). HIF-1alpha stability within the cells is under the control of a class of iron-dependent and oxygen-sensor enzymes, HIF prolyl-4-hydroxylases (PHDs) that target HIF-1alpha for degradation. Thus, an emerging novel target for neuroprotection is associated with the HIF system to promote stabilization of HIF-1alpha and increase transcription of HIF-1-related survival genes, which have been reported to be regulated in patient's brains afflicted with diverse neurodegenerative diseases. In accordance, a new potential therapeutic strategy for neurodegenerative diseases is explored, by which iron chelators would inhibit PHDs, target the HIF-1-signaling pathway and ultimately activate HIF-1-dependent neuroprotective genes. This review discusses two interrelated approaches concerning therapy targets in neurodegeneration, sharing in common the implementation of iron chelation activity: antioxidation and HIF-1-pathway activation.

Effects of static magnetic field and cadmium on oxidative stress and DNA damage in rat cortex brain and hippocampus

The present study was undertaken to determine the effect of co-exposure to static magnetic field (SMF) and cadmium (Cd) on the antioxidant enzymes activity and DNA integrity in rat brain. Sub-chronic exposure to CdCl (CdCl(2), 40 mg/L, per os) for 30 days resulted in a significant reduction in antioxidant enzyme activity such as the glutathione peroxidase (GPx), catalase (CAT) and superoxide dismutase (SOD) in frontal cortex and hippocampus. Total GSH were decreased in the frontal cortex of the Cd-exposed group. Cd exposure induced an increase in malondialdehyde (MDA) concentration in the frontal cortex and hippocampus. Moreover, the same exposure increased 8-oxo-7,8-dihydro-2-desoxyguanosine (8-oxodGuo) level in rat brain. Interestingly, the combined effect of SMF (128 mT, 1 hour/day for 30 consecutive days) and CdCl (40 mg/L, per os) decreased the SOD activity and glutathione level in frontal cortex as compared with the Cd group. Moreover, the association between SMF and Cd increased MDA concentration in frontal cortex as compared with Cd-exposed rats. DNA analysis revealed that SMF exposure failed to alter 8-oxodGuo concentration in Cd-exposed rats. Our data showed that Cd exposure altered the antioxidant enzymes activity and induced oxidative DNA lesions in rat brain. The combined effect of SMF and Cd increased oxidative damage in rat brain as compared with Cd-exposed rats.

Mechanism for the protective effect of resveratrol against oxidative stress-induced neuronal death

Oxidative stress can induce cytotoxicity in neurons, which plays an important role in the etiology of neuronal damage and degeneration. This study sought to determine the cellular and biochemical mechanisms underlying resveratrol's protective effect against oxidative neuronal death. Cultured HT22 cells, an immortalized mouse hippocampal neuronal cell line, were used as an in vitro model, and oxidative stress and neurotoxicity were induced in these neuronal cells by exposure to high concentrations of glutamate. Resveratrol strongly protected HT22 cells from glutamate-induced oxidative cell death. Resveratrol's neuroprotective effect was independent of its direct radical scavenging property, but instead was dependent on its ability to selectively induce the expression of mitochondrial superoxide dismutase (SOD2) and, subsequently, reduce mitochondrial oxidative stress and damage. The induction of mitochondrial SOD2 by resveratrol was mediated through the activation of the PI3K/Akt and GSK-3beta/beta-catenin signaling pathways. Taken together, the results of this study show that up-regulation of mitochondrial SOD2 by resveratrol represents an important mechanism for its protection of neuronal cells against oxidative cytotoxicity resulting from mitochondrial oxidative stress.

Protective effect of Nigella sativa extract and thymoquinone on serum/glucose deprivation-induced PC12 cells death

The serum/glucose deprivation (SGD)-induced cell death in cultured PC12 cells represents a useful in vitro model for the study of brain ischemia and neurodegenerative disorders. Nigella sativa L. (family Ranunculaceae) and its active component thymoquinone (TQ) has been known as a source of antioxidants. In the present study, the protective effects of N. sativa and TQ on cell viability and reactive oxygen species (ROS) production in cultured PC12 cells were investigated under SGD conditions. PC12 cells were cultured in DMEM medium containing 10% (v/v) fetal bovine serum, 100 units/ml penicillin, and 100 microg/ml streptomycin. Cells were seeded overnight and then deprived of serum/glucose for 6 and 18 h. Cells were pretreated with different concentrations of N. sativa extract (15.62-250 microg/ml) and TQ (1.17-150 microM) for 2 h. Cell viability was quantitated by MTT assay. Intracellular ROS production was measured by flow cytometry using 2',7'-dichlorofluorescin diacetate (DCF-DA) as a probe. SGD induced significant cells toxicity after 6, 18, or 24 h (P < 0.001). Pretreatment with N. sativa (15.62-250 microg/ml) and TQ (1.17-37.5 microM) reduced SGD-induced cytotoxicity in PC12 cells after 6 and 18 h. A significant increase in intracellular ROS production was seen following SGD (P < 0.001). N. sativa (250 microg/ml, P < 0.01) and TQ (2.34, 4.68, 9.37 microM, P < 0.01) pretreatment reversed the increased ROS production following ischemic insult. The experimental results suggest that N. sativa extract and TQ protects the PC12 cells against SGD-induced cytotoxicity via antioxidant mechanisms. Our findings might raise the possibility of potential therapeutic application of N. sativa extract and TQ for managing cerebral ischemic and neurodegenerative disorders.

Neuroprotective activity of Matricaria recutita Linn against global model of ischemia in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Traditionally, the whole plant is used for various diseases, including neuronal disorders.

AIM OF THE STUDY

To evaluate the neuroprotective effect of Matricaria recutita L. against global cerebral ischemia/reperfusion (I/R) injury-induced oxidative stress in rats.

MATERIALS AND METHODS

Neuroprotective activity was carried out by global cerebral ischemia on Sprague-Dawley rats by bilateral carotid artery (BCA) occlusion for 30 min followed by 60 min reperfusion. The antioxidant enzymatic and non-enzymatic levels were estimated along with cerebral infarction area and histopathological studies.

RESULTS

The Matricaria recutita L. methanolic extract showed dose-dependent neuroprotective activity by significant decrease in lipid peroxidation (LPO) and increase in the superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and total thiol levels in extract treated groups as compared to ischemia/reperfusion group. Cerebral infarction area was significantly reduced in extract treated groups as compared to ischemia/reperfusion group.

CONCLUSION

The methanolic extract of Matricaria recutita L. showed potent neuroprotective activity against global cerebral ischemia/reperfusion injury-induced oxidative stress in rats.

Determination of glutathione, mitochondrial transmembrane potential, and cytotoxicity in H9c2 cardiomyoblasts exposed to reactive oxygen and nitrogen species

Quantitative measurement of cellular oxidative stress (COS) and cytotoxicity are important to establish their significance in pathophysiologic conditions and disease states. So far, ample methods have been described to determine these processes based on spectrophotometric analysis. The application of simple, rapid, and sensitive fluorescence methods to determine the cytotoxicity and COS is described in the present chapter. Murine H9c2 cells were exposed to various free radical and non-free radical oxidants through use of diethylamine NONOate, 3-morpholinosydnonimine (SIN-1), and a synthetic preparation of peroxynitrite (PN). The viability of control and the treated H9c2 cells was measured based on the reduction of resazurin to resorufin which generates a fluorescent signal. The mitochondrial membrane potential was quantified by determining the cellular uptake of a fluorescent dye, (5,5('),6,6(')-tetrachloro-1,1(')-3,3(')-tetraethylbenzimidazolcarbocyanine iodide (JC-1)) and its segregation in the mitochondrial fraction. The intracellular GSH was determined by assaying the glutathione-S-transferase (GST)-catalyzed conjugation of GSH to monochlorobimane. This chapter describes the feasibility and potential of the above-described fluorescence approach as simple alternative methods to determine reactive oxygen and nitrogen species-induced cytotoxicity and oxidative stress using H9c2 cardiomyoblasts as a model system.

Regulation of central angiotensin type 1 receptors and sympathetic outflow in heart failure

Angiotensin type 1 receptors (AT(1)Rs) play a critical role in a variety of physiological functions and pathophysiological states. They have been strongly implicated in the modulation of sympathetic outflow in the brain. An understanding of the mechanisms by which AT(1)Rs are regulated in a variety of disease states that are characterized by sympathoexcitation is pivotal in development of new strategies for the treatment of these disorders. This review concentrates on several aspects of AT(1)R regulation in the setting of chronic heart failure (CHF). There is now good evidence that AT(1)R expression in neurons is mediated by activation of the transcription factor activator protein 1 (AP-1). This transcription factor and its component proteins are upregulated in the rostral ventrolateral medulla of animals with CHF. Because the increase in AT(1)R expression and transcription factor activation can be blocked by the AT(1)R antagonist losartan, a positive feedback mechanism of AT(1)R expression in CHF is suggested. Oxidative stress has also been implicated in the regulation of receptor expression. Recent data suggest that the newly discovered catabolic enzyme angiotensin-converting enzyme 2 (ACE2) may play a role in the modulation of AT(1)R expression by altering the balance between the octapeptide ANG II and ANG- (1-7). Finally, exercise training reduces both central oxidative stress and AT(1)R expression in animals with CHF. These data strongly suggest that multiple central and peripheral influences dynamically alter AT(1)R expression in CHF.

The X-Linked Adrenoleukodystrophy (X-ALD) and Oxidative Stress

Most of the studies indicate that there is as yet no complete cure for X-ALD. However, methods of the treatment seem to slow rather than treat the disease. One method is the use of Lorenzo's oil in conjunction with a low fat diet, which may help in cerebral X-ALD. X-ALD is in very close resemblance to another neurodegenerative disease, amyotrophic lateral sclerosis (ALS). One of the believed pathomechanisms of ALS is oxidative stress; therefore, this article's emphasis on the role of reactive oxygen species in X-ALD. The aim of the present study was to review the literature concerning the advances in the treatment of X-adrenoleukodystrophy (X-ALD, OMIM # 300100) in the last two decades and to shed more light on the link between oxidative stress and X-ALD. This review article may point to a deficit in reactive oxygen species (ROS) scavenging and/or ROS overproduction being involved in the aetiopathology of these neurodegenerative diseases. Consequently, one of the useful neuronal rescue strategies could be the treatment with antioxidant agents.

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.

Relationship between oxidative and occupational stress and aging in nurses of an intensive care unit

Stressful conditions lead to formation of excessive reactive oxygen species (ROS) and cause oxidative stress and aging. The aim of this study was to determine superoxide dismutase (SOD) and catalase (CAT) activity, and malondialdehyde (MDA) levels in nurses of a hospital intensive care unit according to demographic and occupational parameters, and to analyse the relationship with aging. Thirty-two nurses working in an intensive care unit and 35 aged-matched healthy individuals of both sexes as a control group were surveyed. No significant variations with respect to sex were detected in SOD, CAT, MDA and burnout levels. MDA levels increased with age in both the control group and the nurses, and we observed significant differences in MDA levels between the control group and nurses for all age groups. Significant variations in MDA levels were detected between single (286.12 +/- 8.41) and married (318.82 +/- 6.02), people, between those who frequently practice some kind of sport (281.41 +/- 7.32) and those who never participate in sport (298.24 +/- 8.11) ,and between those who frequently eat fruit and greens (289.75 +/- 8.41) and those who never eat them (315.12 +/- 7.21). Significant differences were detected between smokers and nonsmokers in SOD, CAT and MDA, but not for alcohol, coffee, tea or cola consumption. Higher SOD activity and MDA levels were detected in nurses on evening and night shifts (P < 0.01); these nurses also scored significantly higher on burnout subscales. These results suggest that: (1) occupational stress increases oxidative stress levels as a response to elevated ROS generation; (2) occupational stress increases MDA levels as a response to an elevation in free radical generation and can lead to aging; (3) working evening and night shifts increases oxidative and burnout levels. It is evident that preventive changes in job conditions and lifestyle are necessary to improve the quality of life of nurses who work in intensive care units.

Botanical phenolics and brain health

The high demand for molecular oxygen, the enrichment of polyunsaturated fatty acids in membrane phospholipids, and the relatively low abundance of antioxidant defense enzymes are factors rendering cells in the central nervous system (CNS) particularly vulnerable to oxidative stress. Excess production of reactive oxygen species (ROS) in the brain has been implicated as a common underlying factor for the etiology of a number of neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), and stroke. While ROS are generated by enzymatic and nonenzymatic reactions in the mitochondria and cytoplasm under normal conditions, excessive production under pathological conditions is associated with activation of Ca(2+)-dependent enzymes including proteases, phospholipases, nucleases, and alterations of signaling pathways which subsequently lead to mitochondrial dysfunction, release of inflammatory factors, and apoptosis. In recent years, there is considerable interest to investigate antioxidative and anti-inflammatory effects of phenolic compounds from different botanical sources. In this review, we describe oxidative mechanisms associated with AD, PD, and stroke, and evaluate neuroprotective effects of phenolic compounds, such as resveratrol from grape and red wine, curcumin from turmeric, apocynin from Picrorhiza kurroa, and epi-gallocatechin from green tea. The main goal is to provide a better understanding of the mode of action of these compounds and assess their use as therapeutics to ameliorate age-related neurodegenerative diseases.

Sustained release nanoparticulate formulation containing antioxidant-ellagic acid as potential prophylaxis system for oral administration

The aim of the present work was to develop ellagic acid (EA) loaded poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles for oral administration. PLGA nanoparticles were prepared by a method based on the concept of emulsion-diffusion-evaporation by using polyethylene glycol (PEG) 400 as a cosolvent for solubilizing the drug. While developing this method, didodecyldimethylammomium bromide (DMAB) and polyvinyl alcohol (PVA), alone and in combination with chitosan (CS) were employed. DMAB stabilized particles were the smallest of all the formulations with a particle size of 148.5 nm. PVA alone gave particles of 269.7 nm but a blend with CS (80:20) resulted in an increase in particle size (359.6 +/- 23.6 nm). Initial release of EA from nanoparticles in pH 7.4 phosphate buffer was rapid, followed by a slower sustained release. Release rates followed the order PVA > PVA-CS > DMAB. Release rate from the PLGA-DMAB particles was slowest, which is attributed to higher hydrophobicity of DMAB as compared to PVA, preventing diffusion of drug out of polymeric matrix. Insolubility of CS at alkaline pH could have retarded the release in case of PVA-CS system. In situ intestinal permeability study of pure drug and the drug encapsulated in nanoparticles prepared using PVA, PVA-CS blend and DMAB as stabilizer in rats showed 66, 75, 73 and 87% permeation, respectively. EA showed good free radical scavenging effect in a yeast cell culture model as well as in a cell free system.

Cellular and biochemical actions of melatonin which protect against free radicals: role in neurodegenerative disorders

Molecular oxygen is toxic for anaerobic organisms but it is also obvious that oxygen is poisonous to aerobic organisms as well, since oxygen plays an essential role for inducing molecular damage. Molecular oxygen is a triplet radical in its ground-stage (.O-O.) and has two unpaired electrons that can undergoes consecutive reductions of one electron and generates other more reactive forms of oxygen known as free radicals and reactive oxygen species. These reactants (including superoxide radicals, hydroxyl radicals) possess variable degrees of toxicity. Nitric oxide (NO*) contains one unpaired electron and is, therefore, a radical. NO* is generated in biological tissues by specific nitric oxide synthases and acts as an important biological signal. Excessive nitric oxide production, under pathological conditions, leads to detrimental effects of this molecule on tissues, which can be attributed to its diffusion-limited reaction with superoxide to form the powerful and toxic oxidant, peroxynitrite.Reactive oxygen and nitrogen species are molecular "renegades"; these highly unstable products tend to react rapidly with adjacent molecules, donating, abstracting, or even sharing their outer orbital electron(s). This reaction not only changes the target molecule, but often passes the unpaired electron along to the target, generating a second free radical, which can then go on to react with a new target amplifying their effects.This review describes the mechanisms of oxidative damage and its relationship with the most highly studied neurodegenerative diseases and the roles of melatonin as free radical scavenger and neurocytoskeletal protector.

Oral administration of grape polyphenol extract ameliorates cerebral ischemia/reperfusion-induced neuronal damage and behavioral deficits in gerbils: comparison of pre- and post-ischemic administration

Oxidative stress has been regarded as an important underlying cause for the delayed neuronal death (DND) after cerebral ischemia. In this study, the effects of short-term oral administration of grape polyphenol extract (GPE) on ischemia/reperfusion (I/R) injury in a gerbil global ischemia model were determined. Ischemia was induced by occlusion of the common carotid arteries for 5 min. GPE (30 mg/ml)-containing formula or formula without GPE was administered daily via gavage for 4 days prior to and/or for 4 days after I/R. I/R resulted in hyperlocomotion, extensive DND, oxidative and fragmented DNA damage, and an increase in reactive astrocytes and microglial cells in the hippocampal CA1 region. GPE administration for 4 days prior to I/R and for 4 days after I/R attenuated DND, DNA damage and glial cell activation. However, neuroprotection was more pronounced when GPE was administered for 4 days after I/R than when administered for 4 days prior to I/R. GPE administration after I/R attenuated I/R-induced hyperlocomotion. These findings indicate that oral GPE intake may confer protection against I/R injury and emphasize that early intervention may be an effective therapeutic measure for ameliorating brain injury in stroke.

Bioavailability of apocynin through its conversion to glycoconjugate but not to diapocynin

Apocynin (4-hydroxy-3-methoxyacetophenone) is a major active ingredient from the rhizomes of Picrorhiza kurroa, a botanical plant used as an herbal medicine for treatment of a number of inflammatory diseases. Recently, apocynin is regarded as a specific inhibitor for NADPH oxidase in cell and animal models. In vitro studies indicated conversion of apocynin to diapocynin in the presence of peroxidases, e.g., myloperoxidase, posing the possibility that diapocynin also contributes to the anti-oxidative action of apocynin. The objectives of this study are to examine the bioavailability of apocynin to plasma, liver and brain tissue after intraperitoneal (i.p.) injection, and to examine whether apocynin is converted to diapocynin in vivo. Diapocynin was chemically synthetized and characterized by NMR and IR. Apocynin (5mg/kg body wt) was injected i.p. to adult male Sprague-Dawley rats and plasma, liver and brain were collected at different times (30min, 1 and 2h) after injection. Samples were treated with beta-glucuronidase to hydrolyze the glycosyl linkage and analyzed by HPLC/MS. At 30min and 1h after injection, approximately 50% of apocynin was converted to its glycosyl derivative and was distributed in plasma, liver and brain. No diapocynin was detected in any samples. These results indicate rapid glycosylation of apocynin and its transport to blood and other organs but no apparent conversion to diapocynin in vivo.

Effect of thymoquinone and Nigella sativa seeds oil on lipid peroxidation level during global cerebral ischemia-reperfusion injury in rat hippocampus

It has been previously reported that Nigella sativa oil (NSO) and thymoquinone (TQ), active constituent of N. sativa seeds oil, may prevent oxidative injury in various models. Therefore, we considered the possible effect of TQ and NSO on lipid peroxidation level following cerebral ischemia-reperfusion injury (IRI) in rat hippocampus. Male NMRI rats were divided into nine groups, namely, sham, control, ischemia and ischemia treated with NSO or TQ. TQ (2.5, 5 and 10 mg/kg), NSO (0.048, 0.192 and 0.384 mg/kg), phenytoin (50 mg/kg, as positive control) and saline (10 ml/kg, as negative control) were injected intraperitoneally immediately after reperfusion and the administration was continued every 24h for 72 h after induction of ischemia. The transient global cerebral ischemia was induced using four-vessel-occlusion method for 20 min. Lipid peroxidation level in hippocampus portion was measured as malondialdehyde (MDA) based on its reaction with thiobarbituric acid (TBA) following ischemic insult. The transient global cerebral ischemia induced a significant increase in TBA reactive substances (TBARS) level (p<0.001), in comparison with sham-operated animal. Pretreatment with TQ and NSO were resulted a significant decrease in MDA level as compared with ischemic group (66.9+/-1.5 vs. 297+/-2.5 nmol/g tissue for TQ, 10 mg/kg; p<0.001 and 153.5+/-1.3 nmol/g tissue for NSO, 0.384 mg/kg; p<0.001). Using a reversed-phase HPLC system, the amount of TQ in NSO was also quantified and was 0.58% w/w. These results suggest that TQ and NSO may have protective effects on lipid peroxidation process during IRI in rat hippocampus.

Lipid peroxidation and antioxidant enzyme activities in vascular and Alzheimer dementias

It has been reported that oxidative stress may play a role in the pathogenesis of dementia of the Alzheimer type (AD) and the cerebral ischemia which causes vascular dementia (VD). We measured malondialdehyde (MDA) levels and superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR) activities in blood samples from patients with AD and VD and in healthy non-demented controls (CTR) which similar ages to the patients, in order to evaluate the degree of oxidative stress in patients with AD and VD. A sample of 150 subjects consisting of 50 patients with AD; 50 patients with VD and 50 CTR, aged from 65 to 85 years on, was analyzed. Most of the changes observed were in SOD activity and MDA levels. Catalase activity were least affected. Significant differences were observed in SOD and GR activity between males and females in CRT and in patients with AD, but not in VD. We have found a decrease in antioxidant enzymes activities (SOD, CAT, GPx and GR) in patients with AD and VD and significant differences were observed between CRT and AD patients for ages from 65 to 74, 75 to 84 and from 85 years to 94 years in SOD activity and MDA levels (P < 0.001). MDA levels increase with age in VD, AD and CTR. No significant variation with respect to sex were detected, but significant variations in MDA levels were detected between CRT and patients with VD and AD (P < 0.001). We conclude that oxidative stress plays an important role in the brain damage for both AD and VD, being observed higher levels of oxidative stress for AD that for VD.

Effects of fluoride on the expression of NCAM, oxidative stress, and apoptosis in primary cultured hippocampal neurons

The mechanisms underlying the neurotoxicity of endemic fluorosis still remain unknown. To investigate the expression level of neural cell adhesion molecules (NCAM), oxidative stress, and apoptosis induced by fluoride, the primary rat hippocampal neurons were incubated with 20, 40, and 80 mg/l sodium fluoride for 24 h in vitro. The results showed that the cell survival rate in the 80 mg/l fluoride-treated group was significantly lower than that of the control group. Forty and 80 mg/l of fluoride induced significantly increased lactate dehydrogenase release, intracellular reactive oxygen species, and the percentage of apoptosis. Compared with control group, the malondialdehyde levels were significantly elevated while glutathione levels and glutathione peroxidase activities were decreased in all fluoride-treated groups, accompanied by the markedly reduced superoxide dismutase activity in 80 mg/l fluoride-treated group. With respect to NCAM mRNA expression levels, a significant dose-dependent decrease was observed in 40 and 80 mg/l fluoride-treated groups against the control group. In addition, as compared to the control group, the protein expression levels of NCAM-180 in 40 and 80 mg/l fluoride-treated groups, NCAM-140 in all fluoride-treated groups, and NCAM-120 in the 80 mg/l fluoride-treated group were significantly decreased. Our study herein suggested that fluoride could cause oxidative stress, apoptosis, and decreased mRNA and protein expression levels of NCAM in rat hippocampal neurons, contributing to the neurotoxicity induced by fluoride.

Glutamate-induced cell death in neuronal HT22 cells is attenuated by extracts from St. John's wort (Hypericum perforatum L.)

Glutamate-induced cell death of hippocampal HT22 cells is a model system for neuronal disorders due to depletion of glutathione levels and increase of intracellular reactive oxygen species. Standardized extracts of Hypericum perforatum (HPE) contain flavonoids known for antioxidative properties. In the above model, cytoprotective effects at a concentration of 0.05% HPE by attenuation of calcium fluxes and cellular energy statuses are reported.

Biodegradable in situ gelling system for subcutaneous administration of ellagic acid and ellagic acid loaded nanoparticles: Evaluation of their antioxidant potential against cyclosporine induced nephrotoxicity in rats

Ellagic acid (EA) is a potent antioxidant marketed as a nutritional supplement. Its pharmacological activity has been reported in wide variety of disease models; however its use has been limited owing to its poor biopharmaceutical properties, thereby poor bioavailability. The objective of the current study was to develop chitosan-glycerol phosphate (C-GP) in situ gelling system for sustained delivery of ellagic acid (EA) via subcutaneous route. EA was incorporated in the system employing propylene glycol (PG) and triethanolamine (TEA) as co-solvents; on the other hand EA loaded PLGA nanoparticles (np) were dispersed in the gelling system using water. These in situ gelling systems were thoroughly characterized for mechanical, rheological and swelling properties. These systems are liquid at room temperature and gels at 37 degrees C. The EA C-GP system showed an initial burst release in vitro with about 85% drug released in 12 h followed by a steady release till 160 h, on the other hand EA nanoparticles entrapped in the C-GP system displayed sustained release till 360 h. The histopathological analysis indicates the absence of inflammation on administration, suggesting that these formulations are safe during the studied period. Furthermore, the antioxidant potential of EA C-GP and EA np C-GP gels has been evaluated against cyclosporine induced nephrotoxicity in rats. The data indicates that formulations were effective against cyclosporine induced nephrotoxicity, where the EA C-GP gels showed activity at 10 times lower dose and the EA np C-GP gels at 150 times lower dose when compared to orally given EA. Formulating nanoparticles of EA and incorporating them in C-GP system results in 15 times lowering of dose in comparison EA C-GP gels which is quite significant. Together, these results indicate that the bioavailability of ellagic acid can be improved by subcutaneous formulations administered as simple EA or EA nps.

Yolk Antioxidants Vary with Male Attractiveness and Female Condition in the House Finch (Carpodacus mexicanus)

The manipulation of egg content is one of the few ways by which female birds can alter offspring quality before hatch. Lipid-soluble vitamins and carotenoids are potent antioxidants. Female birds deposit these antioxidants into eggs in variable amounts according to environmental and social conditions, and the quantities deposited into eggs can have effects on offspring health and immunological condition. Allocation theory posits that females will alter the distribution of resources according to mate quality, sometimes allocating resources according to the differential allocation hypothesis (DAH), investing more in offspring sired by better-quality males, and other times allocating resources according to a compensatory strategy, enhancing the quality of offspring sired by lower-quality males. It is unknown, however, whether antioxidants are deposited into eggs according to the DAH or a compensatory strategy. We examined deposition patterns of yolk antioxidants (including vitamin E and three carotenoids) in relation to laying order, mate attractiveness, female condition, and yolk androgen content in the house finch (Carpodacus mexicanus). Female house finches deposited significantly more total antioxidants into eggs sired by less attractive males. Additionally, yolk antioxidant content was significantly positively correlated with female condition, which suggests a cost associated with the deposition of antioxidants into eggs. Finally, concentrations of antioxidants in egg yolks were positively correlated with total yolk androgen content. We suggest that yolk antioxidants are deposited according to a compensatory deposition strategy, enabling females to improve the quality of young produced with less attractive males. Additionally, yolk antioxidants may act to counter some of the detrimental effects associated with high levels of yolk androgens in eggs and, thus, may exert a complementary effect to yolk androgens.

Oxidative modification of M-type K(+) channels as a mechanism of cytoprotective neuronal silencing

Voltage-gated K(+) channels of the Kv7 family underlie the neuronal M current that regulates action potential firing. Suppression of M current increases excitability and its enhancement can silence neurons. We here show that three of five Kv7 channels undergo strong enhancement of their activity by oxidative modification induced by physiological concentrations of hydrogen peroxide. A triple cysteine pocket in the channel S2-S3 linker is critical for this effect. Oxidation-induced enhancement of M current produced a hyperpolarization and a dramatic reduction of action potential firing frequency in rat sympathetic neurons. As hydrogen peroxide is robustly produced during hypoxia-induced oxidative stress, we used an oxygen/glucose deprivation neurodegeneration model that showed neuronal death to be severely accelerated by M current blockade. Such blockade had no effect on survival of normoxic neurons. This work describes a novel pathway of M-channel regulation and suggests a role for M channels in protective neuronal silencing during oxidative stress.

Potential of neuroprotective antioxidant-based therapeutics from Peltophorum africanum Sond. (Fabaceae)

There is ample scientific and empirical evidence supporting the use of plant-derived antioxidants for the control of neurodegenerative disorders. Antioxidants may have neuroprotective (preventing apoptosis) and neuroregenerative roles, by reducing or reversing cellular damage and by slowing progression of neuronal cell loss. Although demand for phytotherapeutic agents is growing, there is need for their scientific validation before plant-derived extracts gain wider acceptance and use. We have evaluated antioxidant potential of Peltophorum africanum (weeping wattle), a plant widespread in the tropics and traditionally used, inter alia, for the relief of acute and chronic pain, anxiety and depression. The dried leaves, bark and root of P. africanum were extracted with acetone. Thin layer chromatograms were sprayed with 0.2% 2,2-diphenyl-1-picryl hydrazyl (DPPH) in methanol for screening for antioxidants. Quantification of antioxidant activity was assessed against 6-hydroxy-2, 5,7,8-tetramethylchromane-2-carboxylic acid (Trolox) and L-ascorbic acid (both standard antioxidants), using two free radicals, 2,2'-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) and DPPH, respectively. Results of our study show that the bark and root extracts had higher antioxidant activity than L-ascorbic acid and Trolox, a synthetic vitamin-E analogue. The respective TEAC (Trolox Equivalent Antioxidant Capacity) values for the bark and root extracts, and Trolox were 1.08, 1.28 and 1.0. EC(50) values for L-ascorbic acid (5.04 microg/mL) was more active than the leaf 6.54 (microg/mL), but much less active than the bark (4.37 microg/mL) and root (3.82 microg/mL) extracts. Continued work on P. africanum, and other plants rich in antioxidants, may avail neuroscientists with potent neuroprotective antioxidant therapeutics.

Inhibition of excitatory synaptic transmission by trans-resveratrol in rat hippocampus

The red wine polyphenol trans-resveratrol has been found to exert potent protective actions in a variety of cerebral ischemia models. The neuroprotection by trans-resveratrol thus far is mainly attributed to its intrinsic antioxidant properties. In the present study, the effects of the red wine polyphenol on excitatory synaptic transmission were investigated in the CA1 region of rat hippocampal slices. Perfusion with trans-resveratrol (10-100 microM) caused a concentration-dependent inhibition on the filed excitatory postsynaptic potentials (the field EPSPs) without detectable effect on the presynaptic volleys. The inhibition had a slow onset and was reversible. Trans-resveratrol (30 microM) did not change the ratios of paired-pulse facilitation of the field EPSPs tested at intervals of 20, 40 and 80 ms, nor did it alter the membrane properties of postsynaptic CA1 pyramidal neurons. However, trans-resveratrol (30 microM) significantly suppressed glutamate-induced currents in postsynaptic CA1 pyramidal neurons. In dissociated hippocampal neurons, the IC(50) value of trans-resveratrol in inhibition of glutamate-induced currents was 53.3+/-9.4 microM. Kainite and NMDA receptors were more sensitive to the red wine polyphenol than AMPA receptors. The present study for the first time demonstrates that trans-resveratrol inhibits the postsynaptic glutamate receptors, which probably works in concert with its antioxidant action for ameliorating the brain ischemic injury. The findings also support the future use of trans-resveratrol in the treatment of various neurodegenerative disorders.

Mutations in amyloid precursor protein and presenilin-1 genes increase the basal oxidative stress in murine neuronal cells and lead to increased sensitivity to oxidative stress mediated by amyloid beta-peptide (1-42), HO and kainic acid: implications for Alzheimer's disease

Oxidative stress is observed in Alzheimer's disease (AD) brain, including protein oxidation and lipid peroxidation. One of the major pathological hallmarks of AD is the brain deposition of amyloid beta-peptide (Abeta). This 42-mer peptide is derived from the beta-amyloid precursor protein (APP) and is associated with oxidative stress in vitro and in vivo. Mutations in the PS-1 and APP genes, which increase production of the highly amyloidogenic amyloid beta-peptide (Abeta42), are the major causes of early onset familial AD. Several lines of evidence suggest that enhanced oxidative stress, inflammation, and apoptosis play important roles in the pathogenesis of AD. In the present study, primary neuronal cultures from knock-in mice expressing mutant human PS-1 and APP were compared with those from wild-type mice, in the presence or absence of various oxidizing agents, viz, Abeta(1-42), H2O2 and kainic acid (KA). APP/PS-1 double mutant neurons displayed a significant basal increase in oxidative stress as measured by protein oxidation, lipid peroxidation, and 3-nitrotyrosine when compared with the wild-type neurons (p < 0.0005). Elevated levels of human APP, PS-1 and Abeta(1-42) were found in APP/PS-1 cultures compared with wild-type neurons. APP/PS-1 double mutant neuron cultures exhibited increased vulnerability to oxidative stress, mitochondrial dysfunction and apoptosis induced by Abeta(1-42), H2O2 and KA compared with wild-type neuronal cultures. The results are consonant with the hypothesis that Abeta(1-42)-associated oxidative stress and increased vulnerability to oxidative stress may contribute significantly to neuronal apoptosis and death in familial early onset AD.

Neuroprotective mechanisms of curcumin against cerebral ischemia-induced neuronal apoptosis and behavioral deficits

Increased oxidative stress has been regarded as an important underlying cause for neuronal damage induced by cerebral ischemia/reperfusion (I/R) injury. In recent years, there has been increasing interest in investigating polyphenols from botanical source for possible neuroprotective effects against neurodegenerative diseases. In this study, we investigated the mechanisms underlying the neuroprotective effects of curcumin, a potent polyphenol antioxidant enriched in tumeric. Global cerebral ischemia was induced in Mongolian gerbils by transient occlusion of the common carotid arteries. Histochemical analysis indicated extensive neuronal death together with increased reactive astrocytes and microglial cells in the hippocampal CA1 area at 4 days after I/R. These ischemic changes were preceded by a rapid increase in lipid peroxidation and followed by decrease in mitochondrial membrane potential, increased cytochrome c release, and subsequently caspase-3 activation and apoptosis. Administration of curcumin by i.p. injections (30 mg/kg body wt) or by supplementation to the AIN76 diet (2.0 g/kg diet) for 2 months significantly attenuated ischemia-induced neuronal death as well as glial activation. Curcumin administration also decreased lipid peroxidation, mitochondrial dysfunction, and the apoptotic indices. The biochemical changes resulting from curcumin also correlated well with its ability to ameliorate the changes in locomotor activity induced by I/R. Bioavailability study indicated a rapid increase in curcumin in plasma and brain within 1 hr after treatment. Together, these findings attribute the neuroprotective effect of curcumin against I/R-induced neuronal damage to its antioxidant capacity in reducing oxidative stress and the signaling cascade leading to apoptotic cell death.

Kainic acid-mediated excitotoxicity as a model for neurodegeneration

Neuronal excitation involving the excitatory glutamate receptors is recognized as an important underlying mechanism in neurodegenerative disorders. Excitation resulting from stimulation of the ionotropic glutamate receptors is known to cause the increase in intracellular calcium and trigger calcium-dependent pathways that lead to neuronal apoptosis. Kainic acid (KA) is an agonist for a subtype of ionotropic glutamate receptor, and administration of KA has been shown to increase production of reactive oxygen species, mitochondrial dysfunction, and apoptosis in neurons in many regions of the brain, particularly in the hippocampal subregions of CA1 and CA3, and in the hilus of dentate gyrus (DG). Systemic injection of KA to rats also results in activation of glial cells and inflammatory responses typically found in neurodegenerative diseases. KA-induced selective vulnerability in the hippocampal neurons is related to the distribution and selective susceptibility of the AMPA/kainate receptors in the brain. Recent studies have demonstrated ability of KA to alter a number of intracellular activities, including accumulation of lipofuscin-like substances, induction of complement proteins, processing of amyloid precursor protein, and alteration of tau protein expression. These studies suggest that KA-induced excitotoxicity can be used as a model for elucidating mechanisms underlying oxidative stress and inflammation in neurodegenerative diseases. The focus of this review is to summarize studies demonstrating KA-induced excitotoxicity in the central nervous system and possible intervention by anti-oxidants.

Protective effect of 1,2,4-benzenetriol on LPS-induced NO production by BV2 microglial cells

Hydroxyhydroquinone or 1,2,4-benzenetriol (BT) detected in the beverages has a structure that coincides with the water-soluble form of a sesame lignan, sesamol. We previously showed that sesame antioxidants had neuroprotective abilities due to their antioxidant properties and/or inducible nitric oxide synthase (iNOS) inhibition. However, studies show that BT can induce DNA damage through the generation of reactive oxygen species (ROS). Therefore, we were interested to investigate the neuroprotective effect of BT in vitro and in vivo. The results showed that instead of enhancing free radical generation, BT dose-dependently (10-100 microM) attenuated nitrite production, iNOS mRNA and protein expression in lipopolysaccharide (LPS)-stimulated murine BV-2 microglia. BT significantly reduced LPS-induced NF-kappaB and p38 MAPK activation. It also significantly reduced the generation of ROS in H2O2-induced BV-2 cells and in H2O2-cellfree conditions. The neuroprotective effect of BT was further demonstrated in the focal cerebral ischemia model of Sprague-Dawley rat. Taken together, the inhibition of LPS-induced nitrite production might be due to the suppression of NF-kappaB, p38 MAPK signal pathway and the ROS scavenging effect. These effects might help to protect neurons from the ischemic injury.

Oxidative Susceptibility of Unfractionated Serum or Plasma: Response to Antioxidants in Vitro and to Antioxidant Supplementation

Background: The susceptibility of plasma lipids to oxidation is thought to be a factor contributing to atherogenic risk. Various groups have studied the in vitro oxidizability of isolated LDL and examined the effects of conventional antioxidants. The drawbacks associated with the isolation of LDL for evaluation of in vitro oxidizability, however, have limited the application of this measurement in large-scale studies.

Methods: We developed and evaluated an assay that can be used to directly assess the oxidative susceptibility of unfractionated serum or plasma lipids, obviating the need for isolation of lipoprotein fractions. Oxidative conditions were initiated in vitro with cuprous chloride and 2,2′-azobis(2-amidinopropane) hydrochloride. The effects of antioxidants added in vitro, and as an oral supplement, were monitored by conjugated diene formation.

Results: The addition of ascorbic acid (0–50 μmol/L) in vitro elicited a dose-dependent protective effect, increasing the lag time to oxidation (P &lt;0.001). In contrast, α-tocopherol demonstrated prooxidant behavior at increasing concentrations (0–50 μmol/L), although we observed a decrease in the maximum rate of oxidation. Our findings are supported by the results from plasma samples of participants in a randomized antioxidant (vitamins C and E) intervention study after acute ischemic stroke. The group receiving vitamins C and E for 14 days showed an increased lag time to plasma lipid oxidation in vitro compared with the nonsupplemented group (P &lt;0.05).

Conclusion: The susceptibility of unfractionated plasma or serum lipids to oxidation in vitro offers an alternative to LDL for evaluating the efficacy of antioxidant regimens.

Effects of extremely low-frequency magnetic field in the brain of rats

An extremely low-frequency magnetic field (50 Hz, 0.5 mT) was used to investigate its possible effect on the brain of adult male Wistar rats following a 7-day exposure. The control rats were sham-exposed. Superoxide dismutase activities and production of superoxide radicals, lipid peroxidation, and nitric oxide were examined in the frontal cortex, striatum, basal forebrain, hippocampus, brainstem, and cerebellum. Significantly increased superoxide radical contents were registered in all the structures examined. Production of nitric oxide, which can oppose superoxide radical activities, was significantly increased in some structures: the frontal cortex, basal forebrain, hippocampus, and brainstem. Augmentation of lipid peroxydation was also observed, with significance only in the basal forebrain and frontal cortex, in spite of the significantly increased superoxide dismutase activities and nitric oxide production in the basal forebrain, and increased production of nitric oxide in the frontal cortex. The results obtained indicate that a 7-day exposure to extremely low-frequency magnetic field can be harmful to the brain, especially to the basal forebrain and frontal cortex due to development of lipid peroxidation. Also, high production of superoxide anion in all regions may compromise nitric oxide signaling processes, due to nitric oxide consumption in the reaction with the superoxide radical.

Trans-resveratrol, a red wine ingredient, inhibits voltage-activated potassium currents in rat hippocampal neurons

The red wine ingredient trans-resveratrol was found to exert potent neuroprotective effects in different in vivo and in vitro models. Thus far, the mechanisms underlying the neuroprotection were attributed mainly to its antioxidant properties. The aim of this study was to investigate the actions of trans-resveratrol on voltage-gated K(+) channels, which have been implicated in neuronal apoptosis. Superfusion of trans-resveratrol reversibly inhibited both the delayed rectifier (I(K)) and fast transient K(+) current (I(A)) in rat dissociated hippocampal neurons with IC(50) values of 13.6 +/- 1.0 microM and 45.7 +/- 7.5 microM, respectively. The inhibition on I(K) had a slow onset, was neither voltage dependent nor use dependent. Trans-resveratrol (30 microM) shifted the steady-state inactivation curve of I(K) to the hyperpolarizing direction by 20 mV and slowed down its recovery from inactivation. The inhibition on I(A) was similar to that on I(K), but voltage dependent. Superfusion of trans-resveratrol (30 microM) shifted the steady-state activation curve of I(A) to the depolarizing direction by 17 mV. Intracellular application of trans-resveratrol (30 microM) was ineffective. Based on the comparable effective concentrations, the inhibition of voltage-activated K(+) currents by trans-resveratrol may contribute to its neuroprotective effects.

Conjugation of catechins with cysteine generates antioxidant compounds with enhanced neuroprotective activity

Antioxidant compounds derived from the conjugation of (-)-epicatechin and (-)-epicatechin 3-O-gallate with cysteine and cysteine derivatives protected HT-22 nerve cells (EC50 between 36 and 65 microM) from death triggered by glutamate while underivatized (-)-epicatechin was almost inactive (EC50=610 microM). Differences in free radical scavenging capacity (DPPH assay) could not account for the improvement in neuroprotective activity upon derivatization of (-)-epicatechin with thiols. Moreover, while the gallate-containing compounds are more efficient radical scavengers than their non-galloylated counterparts, they are only equally or less potent as neuroprotective agents. Although all of the conjugates were able to scavenge mitochondrially generated reactive oxygen species (ROS) inside the cells, the majority of their neuroprotective activity appeared to be dependent upon their ability to maintain glutathione levels. These results suggest that a mechanism other than ROS scavenging is involved in the neuroprotective action exerted by the epicatechin conjugates.

Lack of association between polymorphic microsatellites of the VMAT2 gene and Parkinson's disease in Japan

The etiology of Parkinson's disease (PD) remains unclear; however, generation of reactive oxygen species during oxidation of dopamine (DA) could be one of the factors leading to selective loss of nigral dopaminergic neurons in PD. Vesicular monoamine transporter type 2 (VMAT2) proteins in nerve terminals uptake and partition DA from neuronal cytoplasm into synaptic vesicles. Therefore, alterations of VMAT2 function may cause cytoplasmic accumulation of free DA, toxic to dopaminergic neurons. Upstream of a putative promoter region of the VMAT2 gene, there exist polymorphic sequences consisting of two microsatellites, (CA)n and (GA)n. We performed a case-control study of this polymorphic region to determine whether the VMAT2 gene is related to PD. We found six genotypes; however, there was no significant difference in the allele frequencies between patients with PD and control subjects. Our data suggest that the polymorphic region of the VMAT2 gene studied here is not closely related to PD.

[Cerebral oxidative stress: are astrocytes vulnerable to low intracellular glutamate concentrations? Consequences for neuronal viability]

This review describes reactive oxygen species (ROS), their production and effects on crucial biological molecules, the different lines of defense against oxidative stress, with particular attention to glutathione, the main antioxidant in the brain, which neuronal synthesis seems to be dependent on astrocytic precursors. It also focuses on the different ways by which glutamate may induce oxidative stress in the brain. The different mechanisms leading to ROS production, activated during the excitotoxic cascade, are described. Oxidative glutamate toxicity is also briefly described. A novel form of oxidative glutamate toxicity by depletion of transported glutamate that we recently evidenced is detailed. This toxicity induced by pharmacological reversal of glutamate transport, which mimics glutamate transport reversal occurring in ischemia, involves glutathione depletion and oxidative stress, leading to delayed death of cultured striatal astrocytes differentiated by dibutyryl-cAMP, probably through apoptotic processes. Evidence suggesting that this oxidative glutamate toxicity by depletion of transported glutamate is very likely occurring in vivo and its consequences on neuronal survival are discussed.

Apomorphine increases vesicular monoamine transporter-2 function: implications for neurodegeneration

Apomorphine is a nonselective dopamine D1/D2 receptor agonist used in Europe to treat symptoms resulting from the dopaminergic degeneration associated with Parkinson's disease. In addition, neuroprotective effects of this agent in rodent models have been reported. Recent studies indicate that treatments that alter vesicular monoamine transporter-2 (VMAT-2) function may be protective in models of dopaminergic degeneration. Hence, the purpose of the present study was to examine the effect of apomorphine on VMAT-2 function. Results revealed that apomorphine rapidly and reversibly increased vesicular dopamine uptake, as determined in purified striatal vesicles obtained from treated rats. This increase occurred in both postnatal day 40 and postnatal day 90 rats, and was associated with a redistribution of VMAT-2 protein within nerve terminals. This effect of apomorphine on vesicular dopamine uptake was blocked by pretreating with eticlopride, a dopamine D2 receptor antagonist. The implications of these findings relevant to the treatment of neurodegeneration are discussed.

Dietary grape supplement ameliorates cerebral ischemia-induced neuronal death in gerbils

Oxidative damage has been implicated as one of the leading causes for neuronal cell death in a number of neurodegenerative diseases including stroke. Many vegetables and fruits are enriched in polyphenolic compounds known to exhibit antioxidant properties. This study is to investigate whether dietary supplement with grape powder (GP) may offer protection against neuronal damage due to global cerebral ischemia induced to Mongolian gerbils by occlusion of the common carotid arteries, a model known to cause delayed neuronal death (DND) in the hippocampal CA1 area. Gerbils were fed either a control diet (AIN76a) or a control diet supplemented with low (5.0 g/kg diet) or high (50 g/kg diet) levels of GP for two months. Four days after ischemia/reperfusion (I/R), the extent of DND, glial cell activation, nuclear DNA oxidation, and apoptotic terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) reaction in hippocampal CA1 region were assessed. Ischemia-induced extensive DND in the CA1 region was accompanied by oxidative and fragmented DNA damage and a marked increase in reactive astrocytes and microglial cells. Dietary GP supplementation significantly protected neurons against I/R-induced DND, DNA damage, and apoptosis as well as attenuated glial cell activation. These results demonstrate that due to the antioxidant properties of polyphenols in GP, nutritional diets supplemented with grape can protect the brain against ischemic damage. The neuroprotective effects of GP supplement may have wide implication in the future for prevention/protection against other neurodegenerative damage.

Catalase from the silkworm, Bombyx mori: gene sequence, distribution, and overexpression

Living organisms require mechanisms regulating reactive oxygen species (ROS) such as hydrogen peroxide and superoxide anion. Catalase is one of the regulatory enzymes and facilitates the degradation of hydrogen peroxide to oxygen and water. Biochemical information on an insect catalase is, however, insufficient. Using mRNA from fat body of the silkworm, Bombyx mori, a cDNA encoding a putative catalase was amplified by reverse transcriptase-polymerase chain reaction and sequenced. The deduced amino acid sequence comprised 507 residues with more than seventy residues forming a scaffold for a heme cofactor conserved. The sequence showed 71% and 66% identities to those of the Drosophila melanogaster and Apis mellifera catalases, respectively; the catalase from B. mori was estimated to be phylogenetically close to that from A. mellifera. The transcripts of the gene and the catalase activity were distributed in diverse tissues of B. mori, suggesting its ubiquitous nature. Using the gene, a recombinant catalase (rCAT) was functionally overexpressed in a soluble form using Escherichia coli, purified to homogeneity, and characterized. The pH-optimum of rCAT was broad around pH 8.0. More than 80% of the original rCAT activity was retained after incubation in the following conditions: at pH 8-11 and 4 degrees C for 24 h; at pH 7 and temperatures below 50 degrees C for 30 min. The Michaelis constant for hydrogen peroxide was evaluated to be 28 mM at pH 6.5 and 30 degrees C. rCAT was suggested to be a member of the typical catalase family.

Dopamine D2 receptor activation increases vesicular dopamine uptake and redistributes vesicular monoamine transporter-2 protein

Recent studies demonstrate that multiple dopamine receptor subtypes contribute to the regulation of vesicular monoamine transporter-2 (VMAT-2) activity. The present studies extend these findings by demonstrating that administration of the nonselective dopamine D2 receptor family agonist, quinpirole, rapidly increased vesicular dopamine uptake in purified rat striatal vesicles. This effect occurred in both postnatal day 40 and 90 rats, and was associated with redistribution of the vesicular monoamine transporter-2 (VMAT-2) within nerve terminals. Neither a full nor a partial dopamine D1 receptor family agonist (SKF81297 nor SKF38393, respectively) affected vesicular dopamine uptake per se, nor the effect of quinpirole. Neither the dopamine D3 nor the D4 receptor antagonists, NGB2904 and clozapine, respectively, altered the quinpirole-mediated increase in uptake. However, the nonselective dopamine D2 receptor family antagonist, eticlopride, prevented the quinpirole-induced increase. Taken together, these data demonstrate that dopamine D2 receptor subtype activation increases vesicular dopamine uptake. Implications of this phenomenon with regard to the treatment of Parkinson's disease will be discussed.

Macrophage colony stimulating factor (M-CSF) protects spiral ganglion neurons following auditory nerve injury: morphological and functional evidence

Because hearing disturbance due to auditory nerve dysfunction imposes a formidable burden on human beings, intense efforts have been expended in experimental and clinical studies to discover ways to restore normal hearing. However, the great majority of these investigations have focused on the peripheral process side of bipolar auditory neurons, and very few trials have focused on ways to halt degenerative processes in auditory neurons from the central process side (in the cerebellopontine angle). In the present study, we investigated whether administration of macrophage colony-stimulating factor (M-CSF) could protect auditory neurons in a rat model of nerve injury. The electrophysiological and morphological results of our study indicated that M-CSF could ameliorate both anterograde (Wallerian) and retrograde degeneration in both the CNS and PNS portions of the auditory nerve. We attribute the success of M-CSF therapy to the reported functional dichotomy (having the potential to cause both neuroprotective and neurotoxic effects) of microglia and macrophages. Whether the activities of microglia/macrophages are neuroprotective or neurotoxic may depend upon the nature of the stimulus that activates the cells. In the present study, the neuroprotective effects of M-CSF that were observed could have been due to M-CSF we administered and to M-CSF released from endothelial cells, resident cells of the CNS parenchyma, or infiltrating macrophages. Another possibility is that M-CSF ameliorated apoptotic auditory neuronal death, although this hypothesis remains to be proved in future studies.

Phospholipid transfer protein (PLTP) deficiency reduces brain vitamin E content and increases anxiety in mice

Vitamin E supplementation constitutes a promising strategy in the prevention of neurodegenerative diseases. Here, we show that a phospholipid transfer protein (PLTP) is widely expressed in the brain where it appears to function as a transfer factor for alpha-tocopherol, the main isomer of vitamin E. PLTP deficiency results in significant depletion of brain alpha-tocopherol in both homozygous (-30.1%, P<0.0002) and heterozygous (-18.0%, P<0.05) PLTP knocked-out mice. Alpha-tocopherol depletion in PLTP-deficient homozygotes is associated with the elevation of lipofuscin (+25% and +450% increases in cortex and substantia nigra, respectively), cholesterol oxides (+54.5%, P<0.05), and cellular peroxides (+32.3%, P<0.01) in the brain. Complete PLTP deficiency in homozygotes is accompanied by increased anxiety as shown by fewer entries (8.3% vs. 44.4% in controls, P<0.01) and less time spent (1.7% vs. 41.3% in controls, P<0.05) in the open arms of an elevated plus-maze, in the absence of locomotor deterioration. Thus, the vitamin E transfer activity of PLTP appears to be a key process in preventing oxidative damage in the brain, and PLTP-deficient mice could be a new model of the contribution of oxidative brain injury in the etiology of neurodegenerative diseases.

Pyridoxine, regardless of serotonin levels, increases production of 5-hydroxytryptophan in rat brain

BACKGROUND

The aim of this study was to evaluate effects of pyridoxine and butylated hydroxytoluene (BHT) on lipid peroxidation and on levels of 5-hydroxytryptophan and serotonin.

METHODS

Thirty rats (30 days of age) were used in the survey, measuring levels of lipid peroxidation (TBARS), hemoglobin, 5-hydroxytryptophan (5-HTP), and serotonin (5-HT) after intraperitoneal (i.p.) injections of 4 and 10 mg/kg/day of pyridoxine HCl during 20 days and a single dose of 2 microM/kg (440 microg) of BHT.

RESULTS

Levels of TBARS and 5-HTP increased considerably (p <0.05) in all vitamin- and/or BHT-treated groups, and 5-HT increased partially (p <0.05) only in B(6) with or without BHT-treated groups compared with control group.

CONCLUSIONS

Results suggest that pyridoxine plays a role in tryptophan metabolism, increasing production of 5-HTP.