Redox aspects of signaling by catecholamines and their metabolites

Rasagiline Exerts Neuroprotection towards Oxygen-Glucose-Deprivation/Reoxygenation-Induced GAPDH-Mediated Cell Death by Activating Akt/Nrf2 Signaling

Rasagiline (Azilect®) is a selective monoamine oxidase B (MAO-B) inhibitor that provides symptomatic benefits in Parkinson's disease (PD) treatment and has been found to exert preclinical neuroprotective effects. Here, we investigated the neuroprotective signaling pathways of acute rasagiline treatment for 22 h in PC12 neuronal cultures exposed to oxygen-glucose deprivation (OGD) for 4 h, followed by 18 h of reoxygenation (R), causing 40% aponecrotic cell death. In this study, 3-10 µM rasagiline induced dose-dependent neuroprotection of 20-80%, reduced the production of the neurotoxic reactive oxygen species by 15%, and reduced the nuclear translocation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) by 75-90%. In addition, 10 µM rasagiline increased protein kinase B (Akt) phosphorylation by 50% and decreased the protein expression of the ischemia-induced α-synuclein protein by 50% in correlation with the neuroprotective effect. Treatment with 1-5 µM rasagiline induced nuclear shuttling of transcription factor Nrf2 by 40-90% and increased the mRNA levels of the antioxidant enzymes heme oxygenase-1, (NAD (P) H- quinone dehydrogenase, and catalase by 1.8-2.0-fold compared to OGD/R insult. These results indicate that rasagiline provides neuroprotection to the ischemic neuronal cultures through the inhibition of α-synuclein and GAPDH-mediated aponecrotic cell death, as well as via mitochondrial protection, by increasing mitochondria-specific antioxidant enzymes through a mechanism involving the Akt/Nrf2 redox-signaling pathway. These findings may be exploited for neuroprotective drug development in PD and stroke therapy.

Ozone pollution, oxidative stress, synaptic plasticity, and neurodegeneration

INTRODUCTION

Overpopulation and industrial growth result in an increase in air pollution, mainly due to suspended particulate matter and the formation of ozone. Repeated exposure to low doses of ozone, such as on a day with high air pollution levels, results in a state of chronic oxidative stress, causing the loss of dendritic spines, alterations in cerebral plasticity and in learning and memory mechanisms, and neuronal death and a loss of brain repair capacity. This has a direct impact on human health, increasing the incidence of chronic and degenerative diseases.

DEVELOPMENT

We performed a search of the PubMed, Scopus, and Google Scholar databases for original articles and reviews published between 2000 and 2018 and addressing the main consequences of ozone exposure on synaptic plasticity, information processing in cognitive processes, and the alterations that may lead to the development of neurodegenerative diseases.

CONCLUSIONS

This review describes one of the pathophysiological mechanisms of the effect of repeated exposure to low doses of ozone, which causes loss of synaptic plasticity by producing a state of chronic oxidative stress. This brain function is key to both information processing and the generation of structural changes in neuronal populations. We also address the effect of chronic ozone exposure on brain tissue and the close relationship between ozone pollution and the appearance and progression of neurodegenerative diseases.

Ozone pollution, oxidative stress, synaptic plasticity, and neurodegeneration

INTRODUCTION

Overpopulation and industrial growth result in an increase in air pollution, mainly due to suspended particulate matter and the formation of ozone. Repeated exposure to low doses of ozone, such as on a day with high air pollution levels, results in a state of chronic oxidative stress, causing the loss of dendritic spines, alterations in cerebral plasticity and in learning and memory mechanisms, and neuronal death and a loss of brain repair capacity. This has a direct impact on human health, increasing the incidence of chronic and degenerative diseases.

DEVELOPMENT

We performed a search of the PubMed, Scopus, and Google Scholar databases for original articles and reviews published between 2000 and 2018 and addressing the main consequences of ozone exposure on synaptic plasticity, information processing in cognitive processes, and the alterations that may lead to the development of neurodegenerative diseases.

CONCLUSIONS

This review describes one of the pathophysiological mechanisms of the effect of repeated exposure to low doses of ozone, which causes loss of synaptic plasticity by producing a state of chronic oxidative stress. This brain function is key to both information processing and the generation of structural changes in neuronal populations. We also address the effect of chronic ozone exposure on brain tissue and the close relationship between ozone pollution and the appearance and progression of neurodegenerative diseases.

Anxiolytic effects of essential oils may involve anti-oxidant regulation of the pro-oxidant effects of ascorbate in the brain

Essential oils (EOs) absorbed via inhalation are consistently reported to produce anxiolytic effects. The underlying neurochemical mechanisms, however, are not well understood. High concentrations of ascorbate in the human brain (~10 mM in neurons) implicates this compound as a key signaling molecule and regulator of oxidative stress. In this study, we demonstrate the significant in vitro capacity of ascorbate to produce H₂O₂ in the presence of oxygen at physiological pH values, peaking at ~400 μM for ascorbate levels of 1.0 mg/mL (5.6 mM). In comparison, individual EOs and selected neurotransmitters at similar concentrations produced <100 μM H₂O₂. Systematic studies with binary and ternary mixtures containing ascorbate indicated that EOs and neurotransmitters could variably enhance (pro-oxidant, POX) or suppress (anti-oxidant, AOX) the production of H₂O₂ versus the ascorbate control, depending on the concentration ratios of the components in the mixture. Moreover, the AOX/POX chemistry observed with binary mixtures did not necessarily predict effects with ternary mixtures, where the POX ascorbate chemistry tended to dominate. A model is proposed to account for the ability of compounds with electron-donating capacity to catalytically regenerate ascorbate from intermediate oxidized forms of ascorbate, thus driving H₂O₂ production and exerting a net POX effect; whilst compounds that irreversibly reacted with oxidized forms of ascorbate suppressed the production of H₂O₂ and produced an overall AOX effect. Since the anxiolytic effects of different EOs, including extracts of Lavendula angustifolia (lavender) and Salvia rosmarinus (rosemary), were associated with AOX regulation of H₂O₂ production by ascorbate, it can be concluded that these anxiolytic effects are potentially related to the AOX properties of EOs. In contrast, EOs driving POX effects (eg, Junipenus communis (Juniper) berry EO) are proposed to be more useful for their potential anti-microbial or cancer cytotoxic applications.

Regulation of Kappa Opioid Receptor Inactivation Depends on Sex and Cellular Site of Antagonist Action

The prototypical member of the receptor-inactivating kappa opioid receptor (KOR) antagonists, norbinaltorphimine (norBNI), produces prolonged receptor inactivation by a cJun kinase mechanism. These antagonists have potential therapeutic utility in the treatment of stress disorders; however, additional preclinical characterization is necessary to understand important aspects of their action. In this study, we report that norBNI does not work as effectively in female mice as in males because of estrogen regulation of G protein receptor kinase (GRK); pretreatment of ovary-intact female mice with the selective GRK2/3 inhibitor, Compound 101, made females equally sensitive to norBNI as males. Prior observations suggested that in vivo treatment with norBNI does not produce long-lasting inhibition of KOR regulation of dopamine release in the nucleus accumbens. We assessed the persistence of norBNI receptor inactivation in subcellular compartments. Fast-scan cyclic voltammetry recordings confirmed that presynaptic inhibition of dopamine release by the KOR agonist U69,593 was not blocked by in vivo pretreatment with norBNI under conditions that prevented KOR-mediated aversion and analgesia. We employed a novel in vivo proxy sensor of KOR activation, adenovirus associated double floxed inverted-HyPerRed, and demonstrated that KOR activation stimulates cJun kinase-dependent reactive oxygen species (ROS) production in somatic regions of ventral tegmental area dopamine neurons, but did not activate ROS production in dopamine terminals. The compartment selective action helps explain how dopamine somatic, but not terminally expressed, KORs are inactivated by norBNI. These results further elucidate molecular signaling mechanisms mediating receptor-inactivating KOR antagonist action and advance medication development for this novel class of stress-resilience medications. SIGNIFICANCE STATEMENT: Kappa opioid receptor (KOR) antagonists are being developed as novel proresilience therapeutics for the treatment of mood and substance use disorders. This study showed that the long-acting KOR antagonists are affected by both the sex of the animal and the subcellular compartment in which the receptor is expressed.

Role of Oxidative Stress and Neuroinflammation in Attention-Deficit/Hyperactivity Disorder

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder of childhood. Although abnormalities in several brain regions and disturbances of the catecholaminergic pathway have been demonstrated, the pathophysiology of ADHD is not completely understood, but as a multifactorial disorder, has been associated with an increase in oxidative stress and neuroinflammation. This review presents an overview of factors that increase oxidative stress and neuroinflammation. The imbalance between oxidants and antioxidants and also the treatment with medications are two factors that can increase oxidative damage, whereas the comorbidity between ADHD and inflammatory disorders, altered immune response, genetic and environmental associations, and polymorphisms in inflammatory-related genes can increase neuroinflammation. Evidence of an association with these factors has become valuable for research on ADHD. Such evidence opens up new intervention routes for the use of natural products as antioxidants that could have potential as a treatment against oxidative stress and neuroinflammation in ADHD.

Neuroprotective Effect of Antioxidants in the Brain

The brain is vulnerable to excessive oxidative insults because of its abundant lipid content, high energy requirements, and weak antioxidant capacity. Reactive oxygen species (ROS) increase susceptibility to neuronal damage and functional deficits, via oxidative changes in the brain in neurodegenerative diseases. Overabundance and abnormal levels of ROS and/or overload of metals are regulated by cellular defense mechanisms, intracellular signaling, and physiological functions of antioxidants in the brain. Single and/or complex antioxidant compounds targeting oxidative stress, redox metals, and neuronal cell death have been evaluated in multiple preclinical and clinical trials as a complementary therapeutic strategy for combating oxidative stress associated with neurodegenerative diseases. Herein, we present a general analysis and overview of various antioxidants and suggest potential courses of antioxidant treatments for the neuroprotection of the brain from oxidative injury. This review focuses on enzymatic and non-enzymatic antioxidant mechanisms in the brain and examines the relative advantages and methodological concerns when assessing antioxidant compounds for the treatment of neurodegenerative disorders.

[Effect of the sulfur-containing compounds on the quinoid process of adrenaline autoxidation; potential neuroprotectors]

The superoxide-generating reaction of adrenaline autoxidation in an alkaline medium, used in vitro to identify the antioxidant properties of various compounds, simulates the complex multistep process of quinoid oxidation of catecholamines (CA) in the body. Sulfur-containing cysteine (Cys) and reduced glutathione (GSH), as well as oxidized glutathione (GSSG), have been shown to inhibit this process. The studied substances were considered as inhibitors of quinoid oxidation and are evaluated as antioxidants. The IC50 values for Cys and GSH were close to 7.5 mM. Inhibition by GSSG was weaker; represented approximately 50-70% of Cys and GSH. Other sulfur-containing compounds that differ in chemical structure, the amino acids taurine and methionine were ineffective. The interest in this model and the search for effective compounds acting on this reaction is associated with one of the mechanisms of the etiopathogenesis of Parkinson's disease (PD) discussed in the literature, which occurs when the biochemical transformations of dopamine CA and its quinoid oxidation process are violated. Cys, GSH and GSSG in the model system inhibit quinoid oxidation of adrenaline, as a result of which the formation of superoxide (O2 ·-) is also inhibited. Experiments with the superoxide-generating enzymatic reaction xanthine xanthioxidase, the chemistry of which is different and not related to formation of quinoid metabolites, showed that the studied substances did not inhibit O2 ·- formation in this model. Thus, it was established that the biologically active sulfur-containing compounds Cys, GSH and GSSG are specific inhibitors of quinoid oxidation of CA, and are likely to be able to play the role of a neuroprotector. It is proposed to use these compounds in the treatment and prevention of PD by activating their biosynthesis in the body.

Alzheimer's disease-like pathology-triggered oxidative stress, alterations in monoamines levels, and structural damage of locus coeruleus neurons are partially recovered by a mix of proteoglycans of embryonic genesis

Alzheimer's disease (AD) pathogenesis includes oxidative damage and perturbations of monoamines. However, as many details of these alterations are not known, we have investigated the changes in monoamine levels as well as the free radical oxidation processes (FRO) in the brainstem of rats that were administered i.c.v. Aβ (25-35) (rat model of AD-like pathology). The level of oxidative stress was found elevated in the brainstem along with the increased concentrations of monoamines, especially norepinephrine in the locus coeruleus (LC) area of the brainstem. This was accompanied by the substantial structural damage of monoaminergic neurons of LC. In addition, we have tested the ability of proteoglycans of embryonic genesis (PEG) that were shown previously to act as neuroprotectors, to restore the AD-triggered alterations in monoaminergic system and FRO. Indeed, PEG reduced the increased FRO and upregulated monoamines in the brainstem of Aβ (25-35) treated animals. Administration of PEG to control animals led to the increase of the antioxidant capacity as well as the intensity of free radical oxidation processes. Our study confirms the important role of the brainstem FRO and monoamine shifts in AD development along with the known aggregation of Ab peptide and Tau hyperphosphorylation. We suggest that at the early stages of AD development, with still functional neurons, regulation of monoamine levels via stabilizing FRO processes can be beneficial. Our data demonstrate the regulatory action of PEG on the monoamine disturbances and the level of oxidative stress in the AD damaged structures, suggesting its possible therapeutic application in AD.

Neurobiology of vitamin C: Expanding the focus from antioxidant to endogenous neuromodulator

Ascorbic acid (AA) is a water-soluble vitamin (C) found in all bodily organs. Most mammals synthesize it, humans are required to eat it, but all mammals need it for healthy functioning. AA reaches its highest concentration in the brain where both neurons and glia rely on tightly regulated uptake from blood via the glucose transport system and sodium-coupled active transport to accumulate and maintain AA at millimolar levels. As a prototype antioxidant, AA is not only neuroprotective, but also functions as a cofactor in redox-coupled reactions essential for the synthesis of neurotransmitters (e.g., dopamine and norepinephrine) and paracrine lipid mediators (e.g., epoxiecoisatrienoic acids) as well as the epigenetic regulation of DNA. Although redox capacity led to the promotion of AA in high doses as potential treatment for various neuropathological and psychiatric conditions, ample evidence has not supported this therapeutic strategy. Here, we focus on some long-neglected aspects of AA neurobiology, including its modulatory role in synaptic transmission as demonstrated by the long-established link between release of endogenous AA in brain extracellular fluid and the clearance of glutamate, an excitatory amino acid. Evidence that this link can be disrupted in animal models of Huntington´s disease is revealing opportunities for new research pathways and therapeutic applications (e.g., epilepsy and pain management). In fact, we suggest that improved understanding of the regulation of endogenous AA and its interaction with key brain neurotransmitter systems, rather than administration of AA in excess, should be the target of future brain-based therapies.

Synthesis and Characterization of 3-(1-((3,4-Dihydroxyphenethyl)amino)ethylidene)-chroman-2,4-dione as a Potential Antitumor Agent

The newly synthesized coumarin derivative with dopamine, 3-(1-((3,4-dihydroxyphenethyl)amino)ethylidene)-chroman-2,4-dione, was completely structurally characterized by X-ray crystallography. It was shown that several types of hydrogen bonds are present, which additionally stabilize the structure. The compound was tested in vitro against different cell lines, healthy human keratinocyte HaCaT, cervical squamous cell carcinoma SiHa, breast carcinoma MCF7, and hepatocellular carcinoma HepG2. Compared to control, the new derivate showed a stronger effect on both healthy and carcinoma cell lines, with the most prominent effect on the breast carcinoma MCF7 cell line. The molecular docking study, obtained for ten different conformations of the new compound, showed its inhibitory nature against CDK_S protein. Lower inhibition constant, relative to one of 4-OH-coumarine, proved stronger and more numerous interactions with CDK_S protein. These interactions were carefully examined for both parent molecule and derivative and explained from a structural point of view.

Oxidative stress in drug-naïve first episode patients with schizophrenia and major depression: effects of disease acuity and potential confounders

Oxidative stress and immune dysregulation have been linked to schizophrenia and depression. However, it is unknown whether these factors are related to the pathophysiology or whether they are an epiphenomenon. Inconsistent oxidative stress-related findings in previous studies may have resulted from the use of different biomarkers which show disparate aspects of oxidative stress. Additionally, disease severity, medication, smoking, endocrine stress axis activation and obesity are potential confounders. In order to address some of these shortcomings, we have analyzed a broader set of oxidative stress biomarkers in our exploratory study, including urinary 8-iso-prostaglandin F2α (8-iso-PGF2α), 8-OH-2-deoyxguanosine (8-OH-2-dG), and blood levels of malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione S-transferase (GST) in acutely ill drug-naïve first episode patients with schizophrenia (n = 22), major depression (n = 18), and controls (n = 43). Possible confounding factors were considered, and patients were followed-up after 6 weeks of treatment. No differences were observed regarding 8-OH-2-dG, MDA and GST. At baseline, 8-iso-PGF2α levels were higher in patients with schizophrenia (p = 0.004) and major depression (p = 0.037), with a trend toward higher SOD concentrations in schizophrenia (p = 0.053). After treatment, schizophrenia patients showed a further increase in 8-iso-PGF2α (p = 0.016). These results were not related to age, sex, disease severity, medication or adipose tissue mass. However, 8-iso-PGF2α was associated with smoking, endocrine stress axis activation, C-reactive protein levels and low plasma concentrations of brain-derived neurotrophic factor. This study suggests a role of lipid peroxidation particularly in drug-naïve acutely ill schizophrenia patients and highlights the importance of taking into account other confounding factors in biomarker studies.

Antiradical activity of catecholamines and metabolites of dopamine: theoretical and experimental study

The importance of molecules with antiradical potency that are produced in the human body has significantly increased. Among others, neurotransmitters and their metabolites act as the first line of defense against oxidative stress in the peripheral endocrine and the central nervous systems. Dopamine (DO), epinephrine (EP), norepinephrine (NE), l-DOPA, catechol, and three metabolites of dopamine (3-methoxytyramine (3-MT), homovanillic acid (HO), and 3,4-dihydrophenylacetic acid (DOPAC)) were investigated for their antiradical potency via computational methods and DPPH assay. Density functional theory calculations were used to determine the most probable reaction mechanism based on the thermodynamic parameters. These results suggested that hydrogen atom transfer (HAT)/proton-coupled electron transfer (PCET) and sequential proton loss electron transfer (SPLET) mechanisms are preferable in polar solvents. Several techniques were employed to differentiate between HAT and PCET mechanisms via examination of the transition state structures. Kinetic studies of HAT/PCET and electron transfer (ET) reactions, the second step of SPLET, have proven that ET is much faster for an order of 10⁵-10⁶. Based on this, it was concluded that SPLET was the dominant mechanism for the antiradical activity towards DPPH radicals in polar solvents. The findings suggest that all the investigated molecules can be classified as excellent antiradical scavengers, except for 3-MT and homovanillic acid.

PCB95 and PCB153 change dopamine levels and turn-over in PC12 cells

Polychlorinated biphenyls (PCB) exposure at low chronic levels is a significant public health concern. Animal and epidemiological studies indicate that low PCB body burden may cause neurotoxicity and be a risk factor for neurodegenerative diseases. In the current study, we measured the ability of two non-dioxin like PCBs, 2,2',4,4',5,5'-hexachlorobiphenyl (PCB153) and 2,2'3,5',6-pentachlorobiphenyl (PCB95), to alter dopamine (DA) levels and metabolism using the dopaminergic PC12 cell line. Our hypothesis is that treatment of PC12 cells with non-toxic concentrations of PCB153 or PCB95 for 12 and 24 h will have different effects due to different congener structures. Levels of DA and of 3,4-dihydroxyphenylacetaldehyde (DOPAL), 3, 4-dihyroxylphenylethanol (DOPET), and 3,4-dihyroxylphenylacetic acid (DOPAC) metabolite, gene expression of the dopamine synthesis enzyme tyrosine hydroxylase (TH) and the vesicular monoamine transporter (VMAT2), and gene expression of the anti-oxidant enzymes Cu/Zn and Mn superoxide oxidase (Cu/ZnSOD, MnSOD), glutathione peroxidase (GPx) and catalase were determined. PCB153 decreased intracellular and extracellular levels of DA after 12 h exposure and this was consistent with an increase in DA metabolites. After 24 h, the level of DA in medium increased compared to the control. In contrast, PCB95 exposure increased the intracellular DA level and decreased DA in medium consistent with a down-regulation of VMAT2 expression at 12 h. After 24 h exposure, PCB95 increased DA levels in media. Expression of TH mRNA increased slightly following 12 h but not at 24 h exposure. MnSOD mRNA increased up to 6-7 fold and Cu/ZnSOD increased less than two-fold after treatment with both congeners. Catalase expression was up-regulated following 24 h exposure to PCB153 and PCB95, but GPx expression was down-regulated after 12 h exposure to PCB95 only. These results suggest that PCB153 and PCB95 are neurotoxic and affect DA turnover with structure-dependent differences between these two congeners.

The preventive effects of ascorbic acid supplementation on locomotor and acetylcholinesterase activity in an animal model of schizophrenia induced by ketamine

Studies have shown that schizophrenic patients seem to have nutritional deficiencies. Ascorbic acid (AA) has an important antioxidant effect and neuromodulatory properties. The aim of this study was to evaluate the effects of AA on locomotor activity and the acetylcholinesterase activity (AChE) in an animal model of schizophrenia (SZ). Rats were supplemented with AA (0.1, 1, or 10 mg/kg), or water for 14 days (gavage). Between the 9th and 15th days, the animals received Ketamine (Ket) (25 mg/kg) or saline (i.p). After the last administration (30 min) rats were subjected to the behavioral test. Brain structures were dissected for biochemical analysis. There was a significant increase in the locomotor activity in Ket treated. AA prevented the hyperlocomotion induced by ket. Ket also showed an increase of AChE activity within the prefrontal cortex and striatum prevented by AA. Our data indicates an effect for AA in preventing alterations induced by Ket in an animal model of SZ, suggesting that it may be an adjuvant approach for the development of new therapeutic strategies within this psychiatric disorder.

Reactive Oxygen Species: Physiological and Physiopathological Effects on Synaptic Plasticity

In the mammalian central nervous system, reactive oxygen species (ROS) generation is counterbalanced by antioxidant defenses. When large amounts of ROS accumulate, antioxidant mechanisms become overwhelmed and oxidative cellular stress may occur. Therefore, ROS are typically characterized as toxic molecules, oxidizing membrane lipids, changing the conformation of proteins, damaging nucleic acids, and causing deficits in synaptic plasticity. High ROS concentrations are associated with a decline in cognitive functions, as observed in some neurodegenerative disorders and age-dependent decay of neuroplasticity. Nevertheless, controlled ROS production provides the optimal redox state for the activation of transductional pathways involved in synaptic changes. Since ROS may regulate neuronal activity and elicit negative effects at the same time, the distinction between beneficial and deleterious consequences is unclear. In this regard, this review assesses current research and describes the main sources of ROS in neurons, specifying their involvement in synaptic plasticity and distinguishing between physiological and pathological processes implicated.

Redox Status and Neuro Inflammation Indexes in Cerebellum and Motor Cortex of Wistar Rats Supplemented with Natural Sources of Omega-3 Fatty Acids and Astaxanthin: Fish Oil, Krill Oil, and Algal Biomass

Health authorities worldwide have consistently recommended the regular consumption of marine fishes and seafood to preserve memory, sustain cognitive functions, and prevent neurodegenerative processes in humans. Shrimp, crabs, lobster, and salmon are of particular interest in the human diet due to their substantial provision of omega-3 fatty acids (n-3/PUFAs) and the antioxidant carotenoid astaxanthin (ASTA). However, the optimal ratio between these nutraceuticals in natural sources is apparently the key factor for maximum protection against most neuro-motor disorders. Therefore, we aimed here to investigate the effects of a long-term supplementation with (n-3)/PUFAs-rich fish oil, ASTA-rich algal biomass, the combination of them, or krill oil (a natural combination of both nutrients) on baseline redox balance and neuro-inflammation indexes in cerebellum and motor cortex of Wistar rats. Significant changes in redox metabolism were only observed upon ASTA supplementation, which reinforce its antioxidant properties with a putative mitochondrial-centered action in rat brain. Krill oil imposed mild astrocyte activation in motor cortex of Wistar rats, although no redox or inflammatory index was concomitantly altered. In summary, there is no experimental evidence that krill oil, fish oil, oralgal biomass (minor variation), drastically change the baseline oxidative conditions or the neuro-inflammatory scenario in neuromotor-associated rat brain regions.

[Involvement of carbonate/bicarbonate ions in the superoxide-generating reaction of adrenaline autoxidation]

An important role of carbonate/bicarbonate ions has been recognized in the superoxide generating reaction of adrenaline autooxidation in an alkaline buffer (a model of quinoid adrenaline oxidation in the body). It is suggested that these ions are directly involved not only in formation of superoxide anion radical (О(2)(-)) but also other radicals derived from the carbonate/bicarbonate buffer. Using various buffers it was shown that the rate of accumulation of adrenochrome, the end product of adrenaline oxidation, and the rate of О(2)(-)· formation depend on concentration of carbonate/bicarbonate ions in the buffer and that these ions significantly accelerate adrenaline autooxidation thus demonstrating prooxidant properties. The detectable amount of diformazan, the product of nitro blue tetrazolium (NBT) reduction, was significantly higher than the amount of adrenochrome formed; taking into consideration the literature data on О(2)(-)· detection by NBT it is suggested that adrenaline autooxidation is accompanied by one-electron reduction not only of oxygen dissolved in the buffer and responsible for superoxide formation but possible carbon dioxide also dissolved in the buffer as well as carbonate/bicarbonate buffer components leading to formation of corresponding radicals. The plots of the dependence of the inhibition of adrenochrome and diformazan formation on the superoxide dismutase concentration have shown that not only superoxide radicals are formed during adrenaline autooxidation. Since carbonate/bicarbonate ions are known to be universally present in the living nature, their involvement in free radical processes proceeding in the organism is discussed.

[A new approach to studying the autoxidation of adrenaline: possibility of the determination of superoxide dismutase activity and the antioxidant properties of various preparations by polarography]

The reaction of adrenaline autoxidation in an alkaline buffer with the formation of superoxide radicals and the product of its oxidation, adrenochrome, which models the quinoid pathway of adrenaline conversion in the body, is accompanied by oxygen consumption. This reaction is applicable for polarographic determination of the activity of superoxide dismutase and the antioxidant properties of biological and chemical compounds, it is based on evaluation of the latent period and the rate of oxygen consumption, which are measured in the presence of the compounds examined. It was assumed that the neuro- and cardiotoxicity of quinone products of adrenaline oxidation is related not only to their "own" properties and reactive oxygen species formed but also the hypoxia of those regions of the cell and tissue where the quinoid oxidation of adrenaline occurs.

Schizophrenia: redox regulation and volume neurotransmission

Here, we show that volume neurotransmission and the redox property of dopamine, as well as redox-regulated processes at glutamate receptors, can contribute significantly to our understanding of schizophrenia. Namely, volume neurotransmission may play a key role in the development of dysconnectivity between brain regions in schizophrenic patients, which can cause abnormal modulation of NMDA-dependent synaptic plasticity and produce local paroxysms in deafferented neural areas. During synaptic transmission, neuroredox regulations have fundamental functions, which involve the excellent antioxidant properties and nonsynaptic neurotransmission of dopamine. It is possible that the effect of redox-linked volume neurotransmission (diffusion) of dopamine is not as exact as communication by the classical synaptic mechanism, so approaching the study of complex schizophrenic mechanisms from this perspective may be beneficial. However, knowledge of redox signal processes, including the sources and molecular targets of reactive species, is essential for understanding the physiological and pathophysiological signal pathways in cells and the brain, as well as for pharmacological design of various types of new drugs.

Lipid raft redox signaling: molecular mechanisms in health and disease

Lipid rafts, the sphingolipid and cholesterol-enriched membrane microdomains, are able to form different membrane macrodomains or platforms upon stimulations, including redox signaling platforms, which serve as a critical signaling mechanism to mediate or regulate cellular activities or functions. In particular, this raft platform formation provides an important driving force for the assembling of NADPH oxidase subunits and the recruitment of other related receptors, effectors, and regulatory components, resulting, in turn, in the activation of NADPH oxidase and downstream redox regulation of cell functions. This comprehensive review attempts to summarize all basic and advanced information about the formation, regulation, and functions of lipid raft redox signaling platforms as well as their physiological and pathophysiological relevance. Several molecular mechanisms involving the formation of lipid raft redox signaling platforms and the related therapeutic strategies targeting them are discussed. It is hoped that all information and thoughts included in this review could provide more comprehensive insights into the understanding of lipid raft redox signaling, in particular, of their molecular mechanisms, spatial-temporal regulations, and physiological, pathophysiological relevances to human health and diseases.

Novel, unifying mechanism for mescaline in the central nervous system: electrochemistry, catechol redox metabolite, receptor, cell signaling and structure activity relationships

A unifying mechanism for abused drugs has been proposed previously from the standpoint of electron transfer. Mescaline can be accommodated within the theoretical framework based on redox cycling by the catechol metabolite with its quinone counterpart. Electron transfer may play a role in electrical effects involving the nervous system in the brain. This approach is in accord with structure activity relationships involving mescaline, abused drugs, catecholamines and etoposide. Inefficient demethylation is in keeping with the various drug properties, such as requirement for high dosage and slow acting.

There is a discussion of receptor binding, electrical effects, cell signaling and other modes of action. Mescaline is a nonselective, seretonin receptor agonist. 5-HTP receptors are involved in the stimulus properties. Research addresses the aspect of stereochemical requirements. Receptor binding may involve the proposed quinone metabolite and/or the amino sidechain via protonation. Electroencephalographic studies were performed on the effects of mescaline on men. Spikes are elicited by stimulation of a cortical area. The potentials likely originate in nonsynaptic dendritic membranes. Receptor-mediated signaling pathways were examined which affect mescaline behavior. The hallucinogen belongs to the class of 2AR agonists which regulate pathways in cortical neurons. The research identifies neural and signaling mechanisms responsible for the biological effects. Recently, another hallucinogen, psilocybin, has been included within the unifying mechanistic framework. This mushroom constituent is hydrolyzed to the phenol psilocin, also active, which is subsequently oxidized to an ET o-quinone or iminoquinone.

Voltammetric detection of hydrogen peroxide at carbon fiber microelectrodes

Hydrogen peroxide is a reactive oxygen species that is implicated in a number of neurological disease states and that serves a critical role in normal cell function. It is commonly exploited as a reporter molecule enabling the electrochemical detection of nonelectroactive molecules at electrodes modified with substrate-specific oxidative enzymes. We present the first voltammetric characterization of rapid hydrogen peroxide fluctuations at an uncoated carbon fiber microelectrode, demonstrating unprecedented chemical and spatial resolution. The carbon surface was electrochemically conditioned on the anodic scan and the irreversible oxidation of peroxide was detected on the cathodic scan. The oxidation potential was dependent on scan rate, occurring at +1.2 V versus Ag/AgCl at a scan rate of 400 V.s(-1). The relationship between peak oxidation current and concentration was linear across the physiological range tested, with deviation from linearity above 2 mM and a detection limit of 2 muM. Peroxide was distinguished from multiple interferents, both in vitro and in brain slices. The enzymatic degradation of peroxide was monitored, as was peroxide evolution in response to glucose at a glucose oxidase modified carbon fiber electrode. This novel approach provides the requisite sensitivity, selectivity, spatial and temporal resolution to study dynamic peroxide fluctuations in discrete biological locations.

Correlation analysis confirms differences in antioxidant defence in the blood of types I and II schizophrenic male patients treated with anti-psychotic medication

The activities of antioxidant defence enzymes were determined in erythrocytes isolated from types I and II schizophrenic male patients and from healthy controls. Significant differences in superoxide dismutase (SOD) activity (type I: 3284+/-577; type II: 2959+/-697 compared with controls: 3778+/-577; analysis of variance (ANOVA) P<0.001), catalase (CAT) activity (type I: 17.8+/-1.8 compared to type II: 19.2+/-1.5 and both compared with controls: 19.2+/-1.5; ANOVA P<0.05), glutathione peroxidase (GSH-Px) activity (controls: 17.8+/-2.3; type I: 13.9+/-2.9 and type II: 11.6+/-1.9; ANOVA P<0.001) as well as in glutathione reductase (GR) activity (controls: 5,0+/-0.8; type I: 4.3+/-0.9 and type II: 4.5+/-0.8; ANOVA P<0.01) were apparent. Correlation analysis of antioxidant defence enzymes showed significant negative correlation between GSH-Px and CAT activities (P<0.01) in type I patients. In type II patients, GSH-Px activity was significantly positively correlated with GR (P<0.01). Canonical discriminant analysis separated type I and type II patients from controls (and among each other) with a high degree of certainty according to the overall group composition of antioxidant defence enzymes. Our results indicate differences in the composition of antioxidant defence between controls and anti-psychotic treated type I and type II patients with a possible negative feedback influence on the pathological process, which could provide a rationale for applying antioxidants during schizophrenic therapy.

Differential regulation of CuZnSOD expression in rat brain by acute and/or chronic stress

Neuroendocrine stress (NES) causes increase of glucocorticoids and alters physiological levels of reactive oxygen species production in cells, which might involve modifications in the antioxidant defense system. We investigated the hypothesis that acute, chronic, or combined stress alters copper-zinc superoxide dismutase (CuZnSOD) expression pattern at both, mRNA and subcellular protein level in the cerebral cortex and hippocampus of rats and that there may be a relationship between stress-induced corticosterone and CuZnSOD expression. The most effective stress model which led to the most pronounced changes in CuZnSOD expression patterns was also investigated. Our results demonstrated that acute stress immobilization up-regulates mRNA expression of hippocampal CuZnSOD, while cytosolic protein expression of this enzyme was increased in both brain structures. Chronic stress isolation had no effect on either mRNA and protein expression level and caused a lack of significant up-regulation to a novel acute stressors. The presence of this protein in nuclear fractions of both brain structures was also confirmed. The elevated cytosolic CuZnSOD protein levels following acute immobilization might reflect on the defense system against oxidative stress. Chronic isolation compromises CuZnSOD protein expression, which may lead to the inefficient defense against reactive oxygen species (ROS). The stress-triggered CuZnSOD protein expression was not correlated by the corresponding mRNA. The results suggest that different stress models exert a different degree of influence on mRNA and protein level of CuZnSOD in both brain structures as well as serum corticosterone.

Opposite effects of alpha-lipoic acid on antioxidation and long-term potentiation in control and chronically lead-exposed rats

Among the developmental changes identified in rats exposed to lead are impairments in long-term potentiation (LTP) in the hippocampus and changes in the levels of reactive oxygen species (ROS) in cells and some soft tissues. alpha-Lipoic acid (LA) has been reported to be highly effective in improving the thiol capacity of the cells and in reducing lead-induced oxidative stress. To explore the effects of LA on LTP in chronically lead-exposed rats and the relationship between ROS and LTP in both control and lead-exposed rats, we have compared LTP and oxidative stress parameters in groups of lead-exposed and control rats with or without LA treatment (10, 25, 50, and 100 mg/kg through intraperitoneal injection). The capacity of LA to decrease hippocampal lead levels in lead-exposed rats was examined. We found that LA had no effects in decreasing the level of lead in the hippocampus, but it did appear to have both antioxidant properties and a reparatory effect on LTP amplitude in rats developmentally exposed to lead for 2 weeks following birth. Interestingly, bell-shaped dose-response curves emerged. In the lower LA dosage groups (10, 25 mg/kg LA), there was an increasing LTP amplitude. The strongest protective effect in terms of the induction and amplitude of LTP in the lead-exposed group with at 25 mg/kg LA; when higher dosages were applied (50, 100 mg/kg LA), the LTP amplitude decreased as compared to the 25 mg/kg LA treatment group. The administration of LA to control animals resulted in a significant impairment of LTP amplitude, with the 100 mg/kg LA treatment having harmful effects on the oxidative parameters. These differential effects of LA on LTP in control and lead-exposed rats may be due to the different redox status of the control and lead-exposed rats.

Sources and targets of reactive oxygen species in synaptic plasticity and memory

Increasing evidence suggests that reactive oxygen species (ROS), such as superoxide and hydrogen peroxide, act as necessary signaling molecules in processes underlying cognition. Moreover, ROS have been shown to be necessary in molecular process underlying signal transduction, synaptic plasticity, and memory formation. Research from several laboratories suggests that NADPH oxidase is an important source of superoxide in the brain. Evidence is presented here to show that ROS are in fact important signaling molecules involved in synaptic plasticity and memory formation. Moreover, evidence that the NADPH oxidase complex is a key regulator of ROS generation in synaptic plasticity and memory formation is discussed. Understanding redox signaling in the brain, including the sources and molecular targets of ROS, are important for a full understanding of the signaling pathways that underlie synaptic plasticity and memory. Knowledge of ROS function in the brain also is critical for understanding aging and neurodegenerative diseases of the brain given that several of these disorders, including Alzheimer's disease and Parkinson disease, may be exacerbated by the unregulated generation of ROS.

Effect of polyphenolic extract, Pycnogenol, on the level of 8-oxoguanine in children suffering from attention deficit/hyperactivity disorder

The purpose of this randomized, double-blind and placebo controlled study was to test the effect of polyphenolic extract of pine bark Pycnogenol (Pyc) on the level of oxidized purines represented by 8-oxo-7,8-dihydroguanine (8-oxoG) and on the total antioxidant status (TAS) in children with attention deficit/hyperactivity disorder (ADHD).We have found significantly increased damage to DNA in ADHD children when compared to controls. 8-oxoG was significantly lower after 1 month of Pyc administration in comparison to the beginning state and to placebo group. TAS in ADHD children was lower in comparison to controls. After Pyc administration, TAS was elevated but statistically significant increase was recorded after 1 month of termination of Pyc application. Improvement of DNA damage and TAS after Pyc administration is associated with the improvement of attention in ADHD children. In conclusion, Pycnogenol(R) administration reduces oxidative damage to DNA, normalizes TAS and improves attention of ADHD children. Explanation of mutual relation between oxidative damage to DNA, TAS and symptoms of ADHD and mechanism of Pyc's action needs further investigations.

The effect of polyphenolic extract from pine bark, Pycnogenol on the level of glutathione in children suffering from attention deficit hyperactivity disorder (ADHD)

Attention deficit hyperactivity disorder (ADHD) belongs to the neurodevelopmental disorders characterized by impulsivity, distractibility and hyperactivity. In the pathogenesis of ADHD genetic and non-genetic factors play an important role. It is assumed that one of non-genetic factors should be oxidative stress. Pycnogenol, an extract from the pine bark, consists of bioflavonoids, catechins, procyanidins and phenolic acids. Pycnogenol acts as powerful antioxidant, chelating agent; it stimulates the activities of some enzymes, like SOD, eNOS, and exhibits other biological activities.

AIM

The aim of this randomized, double-blind, placebo-controlled trial was to investigate the influence of administered Pycnogenol or placebo on the level of reduced (GSH) and oxidized (GSSG) glutathione in children suffering from ADHD and on total antioxidant status (TAS). This is the first investigation of the redox glutathione state in relation to ADHD.

RESULTS

One month of Pycnogenol administration (1 mg/kg body weight/day) caused a significant decrease in GSSG and a highly significant increase in GSH levels as well as improvement of GSH/GSSG ratio in comparison to a group of patients taking a placebo. TAS in children with ADHD was decreased in comparison with reference values. Pycnogenol administration normalizes TAS of ADHD children.

Involvement of endoplasmic reticulum stress on the cell death induced by 6-hydroxydopamine in human neuroblastoma SH-SY5Y cells

Endoplasmic reticulum (ER) dysfunction is known to activate the unfolded protein response, which is characterized by the activation of two divergent processes, i.e., suppression of the initiation process in global protein synthesis and expression of glucose-regulated protein 78 (Bip/Grp78) and the C/EBP homologous transcription factor CHOP/Gadd153. In this study, we examined the expression of CHOP/Gadd153 and Bip/Grp78 in human neuroblastoma SH-SY5Y cells treated with 6-hydroxydopamine (6-OHDA), which is used to prepare animal models of Parkinson's disease. 6-OHDA treatment induced cell death, in a concentration-dependent manner, which was inhibited by co-treatment with an antioxidant N-acetylcysteine. 6-OHDA was also effective in decreasing proteasome activity and in increasing the levels of high molecular ubiquitin-conjugated proteins. Furthermore, 6-OHDA induced a marked increase in the expression of both CHOP/Gadd153 and Bip/Grp78. This increase was prevented by N-acetylcysteine. Taken together, our data indicate that ER dysfunction is at least in part involved in the mechanisms underlying cell death induced by 6-OHDA in SH-SY5Y cells.

Enhanced susceptibility to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine neurotoxicity in high-fat diet-induced obesity

Currently, obesity is considered a systemic inflammation; however, the effects of obesity on the vulnerability of dopaminergic neurons to oxidative stress are not fully defined. We evaluated the effects of high-fat diet-induced obesity (HF DIO) on neurotoxicity in mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Eight weeks after a HF or matched normal diet, a severe decrease in the levels of striatal dopamine and of nigral microtubule-associated protein 2, manganese superoxide dismutase, and tyrosine hydroxylase was observed in obese mice treated with subtoxic doses of MPTP (20 mg/kg) compared with the matched lean group. In addition, the levels of nitrate/nitrite and thiobarbituric acid-malondialdehyde adducts in the substantia nigra of obese mice were reciprocally elevated or suppressed by MPTP. Interestingly, striatal nNOS phosphorylation and dopamine turnover were elevated in obese mice after MPTP treatment, but were not observed in lean mice. The nitrotyrosine immunoreactivity for evaluation of nigral nitrogenous stress in obese mice with MPTP was higher than that in matched lean mice. At higher doses of MPTP (60 mg/kg), the mortality was higher in obese mice than in lean mice. These results suggest that DIO may increase the vulnerability of dopaminergic neurons to MPTP via increased levels of reactive oxygen and nitrogen species, and the role of nNOS phosphorylation in the MPTP toxicities and dopamine homeostasis should be further evaluated.

Prevention and partial reversal of diabetes-induced changes in enteric nerves of the rat ileum by combined treatment with alpha-lipoic acid and evening primrose oil

Treatment with alpha-lipoic acid (LA) or evening primrose oil (EPO), individually, fails to prevent diabetes-induced changes in enteric nerves. Since synergy between these treatments has been reported, the aim was to investigate the effectiveness of combined LA/EPO treatment. LA and EPO were administered in the diet (approximately 80 and 200 mg/kg/day, respectively) to control and diabetic (induced by streptozotocin, 65 mg/kg, i.p.) rats. For prevention, treatment started after 1 week and lasted 7 weeks. For reversal, treatment lasted 4 weeks and was initiated after 8 weeks. Nerves supplying the ileum containing vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP) and noradrenaline (NA) were examined immunohistochemically or biochemically. Diabetes caused a significant increase in VIP-containing cell bodies (p<0.001), decrease in NA content (p<0.01) and loss of CGRP-immunoreactivity. LA/EPO treatment totally prevented diabetes-induced changes in VIP (p<0.001) and CGRP and partially reversed (p<0.05) these changes once they had been allowed to develop. In contrast, treatment had no effect on diabetes-induced changes in NA-containing nerves. Therefore, LA and EPO are only effective at treating diabetes-induced changes in some enteric nerves when administered in combination. However, diabetes-induced changes in NA-containing nerves are resistant to treatment.

Schizophrenia and cancer: the adrenochrome balanced morphism

Cancer might be expected to be more common amongst schizophrenics than the general population. They frequently live in selenium deficient regions, have seriously compromised antioxidant defense systems and chain-smoke. The available literature on the cancer-schizoprenia relationship in patients from England, Wales, Ireland, Denmark, USA and Japan, however, strongly suggests that the reverse is true. One of the authors (Hoffer) has treated 4000 schizophrenics since 1952. Only four of these patients has developed cancer. Since low cancer incidence has been recorded amongst patients treated by both conventional physicians using pharmaceuticals and by orthomolecular doctors who emphasize vitamins and minerals, it follows that this depressed cancer incidence must be related to the biochemistry of the disorder itself. Taken as a whole, therefore, the evidence seems to suggest that schizophrenics, their siblings and parents are less susceptible to cancer than the general population. These relationships seem compatible with one or more genetic risk factors for schizophrenia that offer(s) a selective advantage against cancer. There is experimental evidence that appears to support this possibility. Matrix Pharmaceuticals Inc. has received a US patent covering the composition of IntraDose Injectable Gel. This gel contains cisplatin and epinephrine (adrenaline) and is designed to be injected directly into tumour masses. Cisplatin is a very powerful oxidant which will almost certainly rapidly convert the adrenaline to adrenochrome. While the manufacturers of IntraDose consider cisplatin to be the active cytotoxic agent in IntraDose, it seems more likely that adrenochrome and its derivatives may, in fact, be more effective. IntraDose gel has undergone or is undergoing a series of Phase III open-label clinical studies, being injected into patients' tumours that have been identified as the most troublesome by their physicians. The results have been impressive for breast cancer, malignant melanoma, esophageal cancer and cancer of the head, neck and liver. The evidence suggests that there are balanced morphisms in schizophrenia that result in above normal exposure to catecholamine derivatives. Since such catecholamines are both hallucinogenic and anticarcinogenic abnormally high exposure to them simultaneously increases susceptibility to schizophrenia and reduces the probability of developing cancer. These observations have significant implications for the treatment of both illnesses.

Allelic association of the neuronal nitric oxide synthase (NOS1) gene with schizophrenia

Nitric oxide (NO) has been identified as a widespread and multifunctional biological messenger molecule in the central nervous system (CNS), with possible roles in neurotransmission, neurosecretion, synaptic plasticity, and tissue injury in many neurological disorders, including schizophrenia. Neuronal NO is widely produced in the brain from L-arginine catalyzed by neuronal NO synthase (NOS1). We therefore hypothesized that the NOS1 gene may play a role in the pathophysiology of schizophrenia. In the present study, we examined the genetic association between a novel single nucleotide polymorphism (SNP: a C-->T transition located 276 base pairs downstream from the translation termination site) of the human NOS1 gene, which is located in chromosome 12q24, and schizophrenia (215 Japanese patients with schizophrenia and 182 healthy controls). The allele frequencies of the polymorphism in exon 29 of the NOS1 gene differed significantly between patients with schizophrenia and controls (chi(2) = 20.10, df = 1, P = 0.000007; relative risk = 1.92; 95% confidence interval = 1.44-2.55). Our results suggest that the NOS1 gene polymorphism may confer increased susceptibility to schizophrenia.

Diving seals: are they a model for coping with oxidative stress?

The diving lifestyle of seals depends upon cardiovascular adjustments that result in frequent vasoconstriction of numerous organs. With the first post-dive breath, reperfusion allows for eliminating accumulated carbon dioxide (CO(2)) and reloading oxygen (O(2)) stores. Reintroduction of oxygenated blood raises the potential for production of reactive oxygen species (ROS) and the possibility that they may overwhelm the antioxidant defenses. This study addresses the question of possible adaptive responses that allow ringed seal (Phoca hispida) tissues to tolerate repeated cycles of ischemia and reperfusion, and thus protect them from oxidative insult. We obtained samples of ringed seal heart, muscle and kidney through the cooperation of native subsistence hunters at Barrow, Alaska. Samples were subjected to oxidative stress by addition of xanthine oxidase. Production of superoxide radical (O(2)(.-)), lipid peroxidation (as determined by the presence of thiobarbituric acid reactive substances, TBARS) and antioxidant capacity (AOX) were quantified by spectrophotometric analysis. Similarly treated pig tissues were anticipated to be more susceptible to oxidative stress. Contrary to expectations, pig tissues revealed less O(2)(.-) and TBARS compared with ringed seal tissues. These results show that ringed seal muscle, heart and kidney can be induced in vitro to generate ROS, and suggest that the living seal's protective defenses may depend upon O(2)(.-) production, similar to the protective effect of experimental preconditioning, or on enhanced intermediate scavenging, as evidenced by the larger AOX found in ringed seal tissues.