Reduced glutathione is highly expressed in white matter and neurons in the unperturbed mouse brain--implications for oxidative stress associated with neurodegeneration

Changes in levels of the antioxidant glutathione in brain and blood across the age span of healthy adults: A systematic review

Aging is characterized by a gradual decline of the body's biological functions, which can lead to increased production of reactive oxygen species (ROS). Antioxidants neutralize ROS and maintain balance between oxidation and reduction. If ROS production exceeds the ability of antioxidant systems to neutralize, a damaging state of oxidative stress (OS) may exist. The reduced form of glutathione (GSH) is the most abundant antioxidant, and decline of GSH is considered a marker of OS. Our review summarizes the literature on GSH variations with age in healthy adults in brain (in vivo, ex vivo) and blood (plasma, serum), and reliability of in vivo magnetic resonance spectroscopy (MRS) measurement of GSH. A systematic PubMed search identified 35 studies. All in vivo MRS studies (N = 13) reported good to excellent reproducibility of GSH measures. In brain, 3 out of 4 MRS studies reported decreased GSH with age, measured in precuneus, cingulate, and occipital regions, while 1 study reported increased GSH with age in frontal and sensorimotor regions. In post-mortem brain, out of 3 studies, 2 reported decreased GSH with age in hippocampal and frontal regions, while 1 study reported increased GSH with age in a frontal region. Oxidized glutathione disulfide (GSSG) was reported to be increased in caudate with age in 1 study, suggesting OS. Although findings in the brain lacked a clear consensus, the majority of studies suggested a decline of GSH with age. The low number of studies (particularly ex vivo) and potential regional differences may have contributed to variability in the findings in brain. In blood, in contrast, GSH levels predominately were reported to decrease with advancing age (except in the oldest-old, who may represent a select group of particularly successful agers), while GSSG findings lacked consensus. The larger number of studies assessing age-specific GSH level changes in blood (N = 16) allowed for more robust consensus across studies than in brain. Overall, the literature suggests that aging is associated with increased OS in brain and body, but the timing and regional distribution of changes in the brain require further study. The contribution of brain OS to brain aging, and the effect of interventions to raise brain GSH levels on decline of brain function, remain understudied. Given that reliable tools to measure brain GSH exist, we hope this paper will serve as a catalyst to stimulate more work in this field.

Redox dysregulation as a driver for DNA damage and its relationship to neurodegenerative diseases

Redox homeostasis refers to the balance between the production of reactive oxygen species (ROS) as well as reactive nitrogen species (RNS), and their elimination by antioxidants. It is linked to all important cellular activities and oxidative stress is a result of imbalance between pro-oxidants and antioxidant species. Oxidative stress perturbs many cellular activities, including processes that maintain the integrity of DNA. Nucleic acids are highly reactive and therefore particularly susceptible to damage. The DNA damage response detects and repairs these DNA lesions. Efficient DNA repair processes are therefore essential for maintaining cellular viability, but they decline considerably during aging. DNA damage and deficiencies in DNA repair are increasingly described in age-related neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and Huntington's disease. Furthermore, oxidative stress has long been associated with these conditions. Moreover, both redox dysregulation and DNA damage increase significantly during aging, which is the biggest risk factor for neurodegenerative diseases. However, the links between redox dysfunction and DNA damage, and their joint contributions to pathophysiology in these conditions, are only just emerging. This review will discuss these associations and address the increasing evidence for redox dysregulation as an important and major source of DNA damage in neurodegenerative disorders. Understanding these connections may facilitate a better understanding of disease mechanisms, and ultimately lead to the design of better therapeutic strategies based on preventing both redox dysregulation and DNA damage.

Recent Treatment Strategies in Alzheimer's Disease and Chronic Traumatic Encephalopathy

Neurotrauma has been well linked to the progression of neurodegenerative disease. Much work has been done characterizing chronic traumatic encephalopathy, but less has been done regarding the contribution to Alzheimer's Disease. This review focuses on AD and its association with neurotrauma. Emerging clinical trials are discussed as well as novel mechanisms. We then address how some of these mechanisms are shared with CTE and emerging pre-clinical studies. This paper is a user-friendly resource that summarizes the emerging findings and proposes further investigation into key areas of interest. It is intended to serve as a catalyst for both research teams and clinicians in the quest to improve effective treatment and diagnostic options.

Inhibition of Oxidative Stress: An Important Molecular Mechanism of Chinese Herbal Medicine (Astragalus membranaceus, Carthamus tinctorius L., Radix Salvia Miltiorrhizae, etc.) in the Treatment of Ischemic Stroke by Regulating the Antioxidant System

Ischemic stroke is a severe cerebrovascular disease with high mortality and morbidity. Traditional Chinese medicine (TCM) has been utilized for thousands of years in China and is becoming increasingly popular all over the world, especially for the treatments of ischemic stroke. More and more evidences have implicated that oxidative stress has been closely related with ischemic stroke. This review will concentrate on the evidence of the action mechanism of Chinese herbal medicine and its active ingredient in preventing ischemic stroke by modulating redox signaling and oxidative stress pathways and providing references for clinical treatment and scientific research applications.

Investigation of the peripheral inflammation (neutrophil-lymphocyte ratio) in two neurodegenerative diseases of the central nervous system

INTRODUCTION

Alzheimer's disease (AD), and idiopathic Parkinson's disease (IPD) are the neurodegenerative diseases of the central nervous system (CNS). Cognitive impairment is on the forefront in AD. However, IPD is a movement disorder. Inflammation was suggested to have an effect in the pathophysiology of these two diseases. Neutrophil-lymphocyte ratio (NLR) was shown to be a possible marker showing the peripheral inflammation. We aimed to investigate the NLR of patiens with the diagnosis of AD, and IPD, and individuals with no neurodegenerative disease.

MATERIALS AND METHODS

A total of 100 patients with the diagnosis of IPD, and 94 with diagnosis of AD, and 61 healthy controls were included into the study. All the demographic, clinical, and laboratory data were retrospectively obtained from the hospital automated database system.

RESULTS

The NLR in the IPD group was found statistically significantly higher compared with the control group and the AD group (p < 0.001, p = 0.04, respectively). The age-adjusted values were statistically analyzed because of age difference. No statistically significant difference was detected between AD and control groups in terms of NLR (p = 0.6). The age-adjusted NLR value in the Parkinson's group was found significantly higher compared to the control group (p = 0.02) and Alzheimer's group (p = 0.03).

DISCUSSION

Chronic inflammation has an important role in the emergence and progression of the chronic neurodegenerative diseases of the CNS. Our results show that the inflammation in the peripheral blood in IPD was more significant compared with the inflammation in AD.

Glutathione in the Nervous System as a Potential Therapeutic Target to Control the Development and Progression of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a rare neurological disorder that affects the motor neurons responsible for regulating muscle movement. However, the molecular pathogenic mechanisms of ALS remain poorly understood. A deficiency in the antioxidant tripeptide glutathione (GSH) in the nervous system appears to be involved in several neurodegenerative diseases characterized by the loss of neuronal cells. Impaired antioxidant defense systems, and the accumulation of oxidative damage due to increased dysfunction in GSH homeostasis are known to be involved in the development and progression of ALS. Aberrant GSH metabolism and redox status following oxidative damage are also associated with various cellular organelles, including the mitochondria and nucleus, and are crucial factors in neuronal toxicity induced by ALS. In this review, we provide an overview of the implications of imbalanced GSH homeostasis and its molecular characteristics in various experimental models of ALS.

Identification of Nrf2-responsive microRNA networks as putative mediators of myocardial reductive stress

Although recent advances in the treatment of acute coronary heart disease have reduced mortality rates, few therapeutic strategies exist to mitigate the progressive loss of cardiac function that manifests as heart failure. Nuclear factor, erythroid 2 like 2 (Nfe2l2, Nrf2) is a transcriptional regulator that is known to confer transient myocardial cytoprotection following acute ischemic insult; however, its sustained activation paradoxically causes a reductive environment characterized by excessive antioxidant activity. We previously identified a subset of 16 microRNAs (miRNA) significantly diminished in Nrf2-ablated (Nrf2-/-) mouse hearts, leading to the hypothesis that increasing levels of Nrf2 activation augments miRNA induction and post-transcriptional dysregulation. Here, we report the identification of distinct miRNA signatures (i.e. "reductomiRs") associated with Nrf2 overexpression in a cardiac-specific and constitutively active Nrf2 transgenic (caNrf2-Tg) mice expressing low (TgL) and high (TgH) levels. We also found several Nrf2 dose-responsive miRNAs harboring proximal antioxidant response elements (AREs), implicating these "reductomiRs" as putative meditators of Nrf2-dependent post-transcriptional regulation. Analysis of mRNA-sequencing identified a complex network of miRNAs and effector mRNAs encoding known pathological hallmarks of cardiac stress-response. Altogether, these data support Nrf2 as a putative regulator of cardiac miRNA expression and provide novel candidates for future mechanistic investigation to understand the relationship between myocardial reductive stress and cardiac pathophysiology.

The biological pathways of Alzheimer disease: a review

Alzheimer disease is a progressive neurodegenerative disorder, mainly affecting older people, which severely impairs patients' quality of life. In the recent years, the number of affected individuals has seen a rapid increase. It is estimated that up to 107 million subjects will be affected by 2050 worldwide. Research in this area has revealed a lot about the biological and environmental underpinnings of Alzheimer, especially its correlation with β-Amyloid and Tau related mechanics; however, the precise molecular events and biological pathways behind the disease are yet to be discovered. In this review, we focus our attention on the biological mechanics that may lie behind Alzheimer development. In particular, we briefly describe the genetic elements and discuss about specific biological processes potentially associated with the disease.

Gold Nanorod Synthesis with Small Thiolated Molecules

Size and shape tunability have been widely demonstrated for gold nanorods (AuNRs), but reproducible and reliable protocols for the synthesis of small nanocrystals with high yield are still needed for potential biomedical applications. Here, we present novel seed-mediated and seedless protocols for gold nanorods by incorporating bioadditives or small thiolated molecules during the growth stage. The bioadditives glutathione (GSH), oxidized glutathione (GSSG), l-cysteine (l-cys), and l-methionine (l-met) are utilized in nanomolar and micromolar concentrations to modify the aspect ratio of AuNRs in a reproducible form. Overall, smaller aspect ratios are achieved for both synthetic approaches due to reduction in length or increment in length and width depending on the method, type of bioadditive and the strength of its interaction with the nanorod surface. For the seeded synthesis, only GSSG produces large nanorods in high yield, whereas for the seedless method GSH and GSSG form small nanorods with higher quality when compared to controls.

Sex-specific effects of developmental exposure to polychlorinated biphenyls on neuroimmune and dopaminergic endpoints in adolescent rats

Exposure to environmental contaminants early in life can have long lasting consequences for physiological function. Polychlorinated biphenyls (PCBs) are a group of ubiquitous contaminants that perturb endocrine signaling and have been associated with altered immune function in children. In this study, we examined the effects of developmental exposure to PCBs on neuroimmune responses to an inflammatory challenge during adolescence. Sprague Dawley rat dams were exposed to a PCB mixture (Aroclor 1242, 1248, 1254, 1:1:1, 20 μg/kg/day) or oil control throughout pregnancy, and adolescent male and female offspring were injected with lipopolysaccharide (LPS, 50 μg/kg, ip) or saline control prior to euthanasia. Gene expression profiling was conducted in the hypothalamus, prefrontal cortex, striatum, and midbrain. In the hypothalamus, PCBs increased expression of genes involved in neuroimmune function, including those within the nuclear factor kappa b (NF-κB) complex, independent of LPS challenge. PCB exposure also increased expression of receptors for dopamine, serotonin, and estrogen in this region. In contrast, in the prefrontal cortex, PCB exposure blunted or induced irregular neuroimmune gene expression responses to LPS challenge. Moreover, neither PCB nor LPS exposure altered expression of neurotransmitter receptors throughout the mesocorticolimbic circuit. Almost all effects were present in males but not females, in agreement with the idea that male neuroimmune cells are more sensitive to perturbation and emphasizing the importance of studying both male and female subjects. Given that altered neuroimmune signaling has been implicated in mental health and substance abuse disorders that often begin during adolescence, these results highlight neuroimmune processes as another mechanism by which early life PCBs can alter brain function later in life.

Exercise-Induced Regulation of Redox Status in Cardiovascular Diseases: The Role of Exercise Training and Detraining

Although low levels of reactive oxygen species (ROS) are beneficial for the organism ensuring normal cell and vascular function, the overproduction of ROS and increased oxidative stress levels play a significant role in the onset and progression of cardiovascular diseases (CVDs). This paper aims at providing a thorough review of the available literature investigating the effects of acute and chronic exercise training and detraining on redox regulation, in the context of CVDs. An acute bout of either cardiovascular or resistance exercise training induces a transient oxidative stress and inflammatory response accompanied by reduced antioxidant capacity and enhanced oxidative damage. There is evidence showing that these responses to exercise are proportional to exercise intensity and inversely related to an individual’s physical conditioning status. However, when chronically performed, both types of exercise amplify the antioxidant defense mechanism, reduce oxidative stress and preserve redox status. On the other hand, detraining results in maladaptations within a time-frame that depends on the exercise training intensity and mode, as high-intensity training is superior to low-intensity and resistance training is superior to cardiovascular training in preserving exercise-induced adaptations during detraining periods. Collectively, these findings suggest that exercise training, either cardiovascular or resistance or even a combination of them, is a promising, safe and efficient tool in the prevention and treatment of CVDs.

Diplomats' Mystery Illness and Pulsed Radiofrequency/Microwave Radiation

Importance: A mystery illness striking U.S. and Canadian diplomats to Cuba (and now China) "has confounded the FBI, the State Department and US intelligence agencies" (Lederman, Weissenstein, & Lee, 2017). Sonic explanations for the so-called health attacks have long dominated media reports, propelled by peculiar sounds heard and auditory symptoms experienced. Sonic mediation was justly rejected by experts. We assessed whether pulsed radiofrequency/microwave radiation (RF/MW) exposure can accommodate reported facts in diplomats, including unusual ones. Observations: (1) Noises: Many diplomats heard chirping, ringing or grinding noises at night during episodes reportedly triggering health problems. Some reported that noises were localized with laser-like precision or said the sounds seemed to follow them (within the territory in which they were perceived). Pulsed RF/MW engenders just these apparent "sounds" via the Frey effect. Perceived "sounds" differ by head dimensions and pulse characteristics and can be perceived as located behind in or above the head. Ability to hear the "sounds" depends on high-frequency hearing and low ambient noise. (2) Signs/symptoms: Hearing loss and tinnitus are prominent in affected diplomats and in RF/MW-affected individuals. Each of the protean symptoms that diplomats report also affect persons reporting symptoms from RF/MW: sleep problems, headaches, and cognitive problems dominate in both groups. Sensations of pressure or vibration figure in each. Both encompass vision, balance, and speech problems and nosebleeds. Brain injury and brain swelling are reported in both. (3) Mechanisms: Oxidative stress provides a documented mechanism of RF/MW injury compatible with reported signs and symptoms; sequelae of endothelial dysfunction (yielding blood flow compromise), membrane damage, blood-brain barrier disruption, mitochondrial injury, apoptosis, and autoimmune triggering afford downstream mechanisms, of varying persistence, that merit investigation. (4) Of note, microwaving of the U.S. embassy in Moscow is historically documented. Conclusions and relevance: Reported facts appear consistent with pulsed RF/MW as the source of injury in affected diplomats. Nondiplomats citing symptoms from RF/MW, often with an inciting pulsed-RF/MW exposure, report compatible health conditions. Under the RF/MW hypothesis, lessons learned for diplomats and for RF/MW-affected civilians may each aid the other.

Role for Cystathionine γ Lyase (CSE) in an Ethanol (E)-Induced Lesion in Fetal Brain GSH Homeostasis

Earlier, we reported that gestational ethanol (E) can dysregulate neuron glutathione (GSH) homeostasis partially via impairing the EAAC1-mediated inward transport of Cysteine (Cys) and this can affect fetal brain development. In this study, we investigated if there is a role for the transulfuration pathway (TSP), a critical bio-synthetic point to supply Cys in E-induced dysregulation of GSH homeostasis. These studies utilized an in utero E binge model where the pregnant Sprague⁻Dawley (SD) rat dams received five doses of E at 3.5 g/kg by gastric intubation beginning embryonic day (ED) 17 until ED19 separated by 12 h. The postnatal day 7 (PN7) alcohol model employed an oral dosing of 4 g/kg body weight split into 2 feedings at 2 h interval and an iso-caloric and iso-volumic equivalent maltose-dextrin milk solution served as controls. The in vitro model consisted of cerebral cortical neuron cultures from embryonic day (ED) 16⁻17 fetus from SD rats and differentiated neurons from ED18 rat cerebral cortical neuroblasts. E concentrations were 4 mg/mL. E induced an accumulation of cystathionine in primary cortical neurons (PCNs), 2nd trimester equivalent in utero binge, and 3rd trimester equivalent PN7 model suggesting that breakdown of cystathionine, a required process for Cys supply is impaired. This was associated with a significant reduction in cystathionine γ-lyase (CSE) protein expression in PCN (p < 0.05) and in fetal cerebral cortex in utero (53%, p < 0.05) without a change in the expression of cystathionine β-synthase (CBS). Concomitantly, E decreased Cse mRNA expression in PCNs (by 32% within 6 h of exposure, p < 0.05) and in fetal brain (33%, p < 0.05). In parallel, knock down of CSE in differentiated rat cortical neuroblasts exaggerated the E-induced ROS, GSH loss with a pronounced caspase-3 activation and cell death. These studies illustrate the importance of TSP in CSE-related maintenance of GSH and the downstream events via Cys synthesis in neurons and fetal brain.

The Role of Interleukin-18, Oxidative Stress and Metabolic Syndrome in Alzheimer's Disease

The role of interleukins (ILs) and oxidative stress (OS) in precipitating neurodegenerative diseases including sporadic Alzheimer's disease (AD), requires further clarification. In addition to neuropathological hallmarks-extracellular neuritic amyloid-β (Aβ) plaques, neurofibrillary tangles (NFT) containing hyperphosphorylated tau and neuronal loss-chronic inflammation, as well as oxidative and excitotoxic damage, are present in the AD brain. The pathological sequelae and the interaction of these events during the course of AD need further investigation. The brain is particularly sensitive to OS, due to the richness of its peroxidation-sensitive fatty acids, coupled with its high oxygen demand. At the same time, the brain lack robust antioxidant systems. Among the multiple mechanisms and triggers by which OS can accumulate, inflammatory cytokines can sustain oxidative and nitrosative stress, leading eventually to cellular damage. Understanding the consequences of inflammation and OS may clarify the initial events underlying AD, including in interaction with genetic factors. Inflammatory cytokines are potential inducers of aberrant gene expression through transcription factors. Susceptibility disorders for AD, including obesity, type-2 diabetes, cardiovascular diseases and metabolic syndrome have been linked to increases in the proinflammatory cytokine, IL-18, which also regulates multiple AD related proteins. The association of IL-18 with AD and AD-linked medical conditions are reviewed in the article. Such data indicates that an active lifestyle, coupled to a healthy diet can ameliorate inflammation and reduce the risk of sporadic AD.

Abnormal functional-structural cingulum connectivity in mania: combined functional magnetic resonance imaging-diffusion tensor imaging investigation in different phases of bipolar disorder

OBJECTIVE

The objective of the study was to investigate the relationship between structural connectivity (SC) and functional connectivity (FC) in the cingulum in bipolar disorder (BD) and its various phases.

METHOD

We combined resting-state functional magnetic resonance imaging and probabilistic tractographic diffusion tensor imaging to investigate FC and SC of the cingulum and its portions, the SC-FC relationship, and their correlations with clinical and neurocognitive measures on sustained attention in manic (n = 21), depressed (n = 20), and euthymic (n = 20) bipolar patients and healthy controls (HC) (n = 42).

RESULTS

First, we found decreased FC between the anterior and posterior parts of the cingulum in manic patients when compared to depressed patients and HC. Second, we observed decreased SC of the cingulum bundle, particularly in its anterior part, in manic patients when compared to HC. Finally, alterations in the cingulum FC (but not SC) correlated with clinical severity scores while changes in the cingulum SC (but not FC) were related with neurocognitive deficits in sustained attention in BD.

CONCLUSION

We demonstrate for the first time a reduction in FC and concomitantly in SC of the cingulum in mania, which correlated with psychopathological and neurocognitive parameters, respectively, in BD. This supports the central role of cingulum connectivity specifically in mania.

Trichloroethylene exposure aggravates behavioral abnormalities in mice that are deficient in superoxide dismutase

Trichloroethylene (TCE) has been implicated as a causative agent for Parkinson's disease (PD). The administration of TCE to rodents induces neurotoxicity associated with dopaminergic neuron death, and evidence suggests that oxidative stress as a major player in the progression of PD. Here we report on TCE-induced behavioral abnormality in mice that are deficient in superoxide dismutase 1 (SOD1). Wild-type (WT) and SOD1-deficient (Sod1(-/-)) mice were intraperitoneally administered TCE (500 mg/kg) over a period of 4 weeks. Although the TCE-administrated Sod1(-/-) mice showed marked abnormal motor behavior, no significant differences were observed among the experimental groups by biochemical and histopathological analyses. However, treating mouse neuroblastoma-derived NB2a cells with TCE resulted in the down regulation of the SOD1 protein and elevated oxidative stress under conditions where SOD1 production was suppressed. Taken together, these data indicate that SOD1 plays a pivotal role in protecting motor neuron function against TCE toxicity.

Abrogation of Nrf2 impairs antioxidant signaling and promotes atrial hypertrophy in response to high-intensity exercise stress

BACKGROUND

Anomalies in myocardial structure involving myocyte growth, hypertrophy, differentiation, apoptosis, necrosis etc. affects its function and render cardiac tissue more vulnerable to the development of heart failure. Although oxidative stress has a well-established role in cardiac remodeling and dysfunction, the mechanisms linking redox state to atrial cardiomyocyte hypertrophic changes are poorly understood. Here, we investigated the role of nuclear erythroid-2 like factor-2 (Nrf2), a central transcriptional mediator, in redox signaling under high intensity exercise stress (HIES) in atria.

METHODS

Age and sex-matched wild-type (WT) and Nrf2(-/-) mice at >20 months of age were subjected to HIES for 6 weeks. Gene markers of hypertrophy and antioxidant enzymes were determined in the atria of WT and Nrf2(-/-) mice by real-time qPCR analyses. Detection and quantification of antioxidants, 4-hydroxy-nonenal (4-HNE), poly-ubiquitination and autophagy proteins in WT and Nrf2(-/-) mice were performed by immunofluorescence analysis. The level of oxidative stress was measured by microscopical examination of di-hydro-ethidium (DHE) fluorescence.

RESULTS

Under the sedentary state, Nrf2 abrogation resulted in a moderate down regulation of some of the atrial antioxidant gene expression (Gsr, Gclc, Gstα and Gstµ) despite having a normal redox state. In response to HIES, enlarged atrial myocytes along with significantly increased gene expression of cardiomyocyte hypertrophy markers (Anf, Bnf and β-Mhc) were observed in Nrf2(-/-) when compared to WT mice. Further, the transcript levels of Gclc, Gsr and Gstµ and protein levels of NQO1, catalase, GPX1 were profoundly downregulated along with GSH depletion and increased oxidative stress in Nrf2(-/-) mice when compared to its WT counterparts after HIES. Impaired antioxidant state and profound oxidative stress were associated with enhanced atrial expression of LC3 and ATG7 along with increased ubiquitination of ATG7 in Nrf2(-/-) mice subjected to HIES.

CONCLUSIONS

Loss of Nrf2 describes an altered biochemical phenotype associated with dysregulation in genes related to redox state, ubiquitination and autophagy in HIES that result in atrial hypertrophy. Therefore, our findings direct that preserving Nrf2-related antioxidant function would be one of the effective strategies to safeguard atrial health.

Amyloid Plaque-Associated Oxidative Degradation of Uniformly Radiolabeled Arachidonic Acid

Oxidative stress is a frequently observed feature of Alzheimer's disease, but its pathological significance is not understood. To explore the relationship between oxidative stress and amyloid plaques, uniformly radiolabeled arachidonate was introduced into transgenic mouse models of Alzheimer's disease via intracerebroventricular injection. Uniform labeling with carbon-14 is used here for the first time, and made possible meaningful quantification of arachidonate oxidative degradation products. The injected arachidonate entered a fatty acid pool that was subject to oxidative degradation in both transgenic and wild-type animals. However, the extent of its degradation was markedly greater in the hippocampus of transgenic animals where amyloid plaques were abundant. In human Alzheimer's brain, plaque-associated proteins were post-translationally modified by hydroxynonenal, a well-known oxidative degradation product of arachidonate. These results suggest that several recurring themes in Alzheimer's pathogenesis, amyloid β proteins, transition metal ions, oxidative stress, and apolipoprotein isoforms, may be involved in a common mechanism that has the potential to explain both neuronal loss and fibril formation in this disease.

Patterns of microstructural white matter abnormalities and their impact on cognitive dysfunction in the various phases of type I bipolar disorder

BACKGROUND

In recent years, diffusion tensor imaging (DTI) studies have detected subtle microstructural abnormalities of white matter (WM) in type I bipolar disorder (BD). However, WM alterations in the different phases of BD remain to be explored. The aims of this study is to investigate the WM alterations in the various phases of illness and their correlations with clinical and neurocognitive features.

METHODS

We investigated the DTI-derived fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD) and axial diffusivity (AD) in patients with type I BD (n=61) subdivided in manic (n=21), depressive (n=20) and euthymic phases (n=20) vs. healthy controls (n=42), using a tract-based spatial statistics (TBSS) approach. Then, we investigated whether the subgroups of patients in the various phases of illness present different patterns of WM abnormalities. Finally we studied the correlations between WM alterations and clinical-cognitive parameters.

RESULTS

We found a widespread alteration in WM microstructure (decrease in FA and increase in MD and RD) in BD when compared to controls. The various subgroups of BD showed different spatial patterns of WM alterations. A gradient of increasing WM abnormalities from the euthymic (low degree and localized WM alterations mainly in the midline structures) to the manic (more diffuse WM alterations affecting both midline and lateral structures) and, finally, to the depressive phase (high degree and widespread WM alterations), was found. Furthermore, the WM diffuse alterations correlated with cognitive deficits in BD, such as decreased fluency prompted by letter and decreased hits and increased omission errors at the continuous performance test.

LIMITATIONS

Patients under treatment.

CONCLUSIONS

The WM alterations in type I BD showed different spatial patterns in the various phases of illness, mainly affecting the active phases, and correlated with some cognitive deficits. This suggests a complex trait- and state-dependent pathogenesis of WM abnormalities in BD.

Neuronal Glutathione Content and Antioxidant Capacity can be Normalized In Situ by N-acetyl Cysteine Concentrations Attained in Human Cerebrospinal Fluid

N-acetyl cysteine (NAC) supports the synthesis of glutathione (GSH), an essential substrate for fast, enzymatically catalyzed oxidant scavenging and protein repair processes. NAC is entering clinical trials for adrenoleukodystrophy, Parkinson's disease, schizophrenia, and other disorders in which oxidative stress may contribute to disease progression. However, these trials are hampered by uncertainty about the dose of NAC required to achieve biological effects in human brain. Here we describe an approach to this issue in which mice are used to establish the levels of NAC in cerebrospinal fluid (CSF) required to affect brain neurons. NAC dosing in humans can then be calibrated to achieve these NAC levels in human CSF. The mice were treated with NAC over a range of doses, followed by assessments of neuronal GSH levels and neuronal antioxidant capacity in ex vivo brain slices. Neuronal GSH levels and antioxidant capacity were augmented at NAC doses that produced peak CSF NAC concentrations of ≥50 nM. Oral NAC administration to humans produced CSF concentrations of up to 10 μM, thus demonstrating that oral NAC administration can surpass the levels required for biological activity in brain. Variations of this approach may similarly facilitate and rationalize drug dosing for other agents targeting central nervous system disorders.

Assessment at the single-cell level identifies neuronal glutathione depletion as both a cause and effect of ischemia-reperfusion oxidative stress

Oxidative stress contributes to neuronal death in brain ischemia-reperfusion. Tissue levels of the endogenous antioxidant glutathione (GSH) are depleted during ischemia-reperfusion, but it is unknown whether this depletion is a cause or an effect of oxidative stress, and whether it occurs in neurons or other cell types. We used immunohistochemical methods to evaluate glutathione, superoxide, and oxidative stress in mouse hippocampal neurons after transient forebrain ischemia. GSH levels in CA1 pyramidal neurons were normally high relative to surrounding neuropil, and exhibited a time-dependent decrease during the first few hours of reperfusion. Colabeling for superoxide in the neurons showed a concurrent increase in detectable superoxide over this interval. To identify cause-effect relationships between these changes, we independently manipulated superoxide production and GSH metabolism during reperfusion. Mice in which NADPH oxidase activity was blocked to prevent superoxide production showed preservation of neuronal GSH content, thus demonstrating that neuronal GSH depletion is result of oxidative stress. Conversely, mice in which neuronal GSH levels were maintained by N-acetyl cysteine treatment during reperfusion showed less neuronal superoxide signal, oxidative stress, and neuronal death. At 3 d following ischemia, GSH content in reactive astrocytes and microglia was increased in the hippocampal CA1 relative to surviving neurons. Results of these studies demonstrate that neuronal GSH depletion is both a result and a cause of neuronal oxidative stress after ischemia-reperfusion, and that postischemic restoration of neuronal GSH levels can be neuroprotective.

Increased carbonylation, protein aggregation and apoptosis in the spinal cord of mice with experimental autoimmune encephalomyelitis

Previous work from our laboratory implicated protein carbonylation in the pathophysiology of both MS (multiple sclerosis) and its animal model EAE (experimental autoimmune encephalomyelitis). Subsequent in vitro studies revealed that the accumulation of protein carbonyls, triggered by glutathione deficiency or proteasome inhibition, leads to protein aggregation and neuronal cell death. These findings prompted us to investigate whether their association can be also established in vivo. In the present study, we characterized protein carbonylation, protein aggregation and apoptosis along the spinal cord during the course of MOG (myelin-oligodendrocyte glycoprotein)(35-55) peptide-induced EAE in C57BL/6 mice. The results show that protein carbonyls accumulate throughout the course of the disease, albeit by different mechanisms: increased oxidative stress in acute EAE and decreased proteasomal activity in chronic EAE. We also show a temporal correlation between protein carbonylation (but not oxidative stress) and apoptosis. Furthermore, carbonyl levels are significantly higher in apoptotic cells than in live cells. A high number of juxta-nuclear and cytoplasmic protein aggregates containing the majority of the oxidized proteins are present during the course of EAE. The LC3 (microtubule-associated protein light chain 3)-II/LC3-I ratio is significantly reduced in both acute and chronic EAE indicating reduced autophagy and explaining why aggresomes accumulate in this disorder. Taken together, the results of the present study suggest a link between protein oxidation and neuronal/glial cell death in vivo, and also demonstrate impaired proteostasis in this widely used murine model of MS.

Impact of acute stress on human brain microstructure: An MR diffusion study of earthquake survivors

A characterization of the impact of natural disasters on the brain of survivors is critical for a better understanding of posttraumatic responses and may inform the development of more effective early interventions. Here we report alterations in white matter microstructure in survivors soon after Wenchuan earthquake in China in 2008. Within 25 days after the Wenchuan earthquake, 44 healthy survivors were recruited and scanned on a 3T MR imaging system. The survivors were divided into two groups according to their self-rating anxiety scale (SAS) score, including the SAS(+) (SAS > 55 after correction) group and "SAS(-)" (SAS < 55 after correction) group. Thrity-two healthy volunteers were also recruited as control group before earthquake. Individual maps of fractional anisotropy (FA) were calculated and voxel-based analysis (VBA) was performed to allow the comparison between survivors and controls using ANCOVAs in SPM2. In addition, a correlation between SAS score and regional FA value was examined using Pearson's correlation analysis in SPSS 11.5. Compared with the healthy cohort, the whole group of 44 survivors showed significantly decreased FA values in the right prefrontal lobe, the parietal lobe, the basal ganglia, and the right parahippocampus. These effects did not appear to depend on self-rating anxiety. For the first time we provide evidence that acute trauma altered cerebral microstructure within the limbic system; furthermore, these alterations are evident shortly after the traumatic event, highlighting the need for early evaluation and intervention for trauma survivors.

Nuclear factor erythroid 2-related factor 2 facilitates neuronal glutathione synthesis by upregulating neuronal excitatory amino acid transporter 3 expression

Astrocytes support neuronal antioxidant capacity by releasing glutathione, which is cleaved to cysteine in brain extracellular space. Free cysteine is then taken up by neurons through excitatory amino acid transporter 3 [EAAT3; also termed Slc1a1 (solute carrier family 1 member 1)] to support de novo glutathione synthesis. Activation of the nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant responsive element (ARE) pathway by oxidative stress promotes astrocyte release of glutathione, but it remains unknown how this release is coupled to neuronal glutathione synthesis. Here we evaluated transcriptional regulation of the neuronal cysteine transporter EAAT3 by the Nrf2-ARE pathway. Nrf2 activators and Nrf2 overexpression both produced EAAT3 transcriptional activation in C6 cells. A conserved ARE-related sequence was found in the EAAT3 promoter of several mammalian species. This ARE-related sequence was bound by Nrf2 in mouse neurons in vivo as observed by chromatin immunoprecipitation. Chemical activation of the Nrf2-ARE pathway in mouse brain increased both neuronal EAAT3 levels and neuronal glutathione content, and these effects were abrogated in mice genetically deficient in either Nrf2 or EAAT3. Selective overexpression of Nrf2 in brain neurons by lentiviral gene transfer was sufficient to upregulate both neuronal EAAT3 protein and glutathione content. These findings identify a mechanism whereby Nrf2 activation can coordinate astrocyte glutathione release with neuronal glutathione synthesis through transcriptional upregulation of neuronal EAAT3 expression.

Control of redox state and redox signaling by neural antioxidant systems

The glutathione/glutathione disulfide (GSH/GSSG) redox pair forms the major redox couple in cells and as such plays a critical role in regulating redox-dependent cellular functions. Not only does GSH act as an antioxidant but it can also modulate the activity of a variety of different proteins. An impairment in GSH status is thought to be the precipitating event in a wide range of neurological disorders. Therefore, understanding how to maintain GSH in the CNS could provide a valuable therapeutic approach. Intracellular GSH levels are regulated by a complex series of pathways that include substrate transport and availability, rates of synthesis and regeneration, GSH utilization, and GSH efflux. To date, the most effective approaches for maintaining GSH levels in the CNS include enhancing cyst(e)ine uptake both directly and indirectly via transcriptional upregulation of system x(c)(-), increasing GSH synthesis via transcriptional upregulation of the rate limiting enzyme in GSH biosynthesis, and decreasing GSH utilization. Among the transcription factors that play critical roles in GSH metabolism are NF-E2-related factor 2 (Nrf2) and activating transcription factor 4 (ATF4). Thus, compounds that can upregulate these transcription factors may be particularly useful in promoting the functional maintenance of the CNS through their effects on GSH metabolism.

Accumulation of protein carbonyls within cerebellar astrocytes in murine experimental autoimmune encephalomyelitis

Recent work from our laboratory has implicated protein carbonylation in the pathophysiology of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE). The present study was designed to determine the changes in protein carbonylation during disease progression and to identify the target cells and modified proteins in the cerebellum of EAE animals, prepared by active immunization of C57/BL6 mice with MOG(35-55) peptide. In this model, protein carbonylation was maximal at the peak of the disease (acute phase), to decrease thereafter (chronic phase). Double-immunofluorescence microscopy of affected cerebella showed that carbonyls accumulate in white matter astrocytes and to a lesser extent in microglia/macrophages, in both the acute and the chronic phase. Surprisingly, T cells, oligodendrocytes, and neurons were barely stained. By 2D oxyblot and mass spectrometry, β-actin, β-tubulin, GFAP, and HSC-71 were identified as the major targets of carbonylation throughout the disease. Using a pull-down/Western blot method, we found a significant increase in the proportion of carbonylated β-actin, β-tubulin, and GFAP in the chronic phase but not in the acute phase. These results suggest that as disease progresses from the inflammatory to the neurodegenerative phase there may be an inappropriate removal of oxidized cytoskeletal proteins. Additionally, the extensive accumulation of carbonylated GFAP in the chronic phase of EAE may be responsible for the abnormal shape of astrocytes observed at this stage.

Association among amyloid plaque, lipid, and creatine in hippocampus of TgCRND8 mouse model for Alzheimer disease

Amyloid peptide (Aβ) aggregation in the brain is a characteristic feature of Alzheimer disease (AD). Previously, we reported the discovery of focally elevated creatine deposits in brain tissue from TgCRND8 mice, which express double mutant (K670N/M671L and V717F) amyloid protein precursor. In this study, frozen hippocampal tissue sections from 5-, 8-, 11-, 14-, and 17-month old TgCRND8 and littermate control mice were examined with Fourier transform infrared microspectroscopy to explore the distribution of lipid, creatine, and dense core plaque deposits. Lipid distribution throughout the hippocampus was similar in transgenic (Tg) and non-Tg littermates at all ages. Dense core plaques were always found to lie within a thin (30-50 μm) lipid envelope, confirmed by imaging through serial sections. Creatine deposits were found in all TgCRND8 mice; the extent of deposition increased with age. Minor creatine deposits appeared in the oldest littermate controls. Distribution in the serial sections showed moderate correlation between layers, slightly disturbed by the freeze/thaw process. Creatine deposits in Tg mice were not specifically co-localized with plaques or lipid halos. The dimension of the lipid envelope is comparable with that of the diffuse halo of nonaggregated amyloid, implying a dynamic association in vivo, postulated to have a significant role in the evolving neurotoxicity.

LSPR sensing of molecular biothiols based on noncoupled gold nanorods

Au NRs protected with mPEG-SH molecules (mPEG-Au NRs) were demonstrated to be a promising platform for LSPR-based sensing of molecular biothiols in aqueous solution. Surface mPEG-SH molecules endow Au NRs with great stability and biocompatibility and no nonspecific adsorption of biomacromolecules. The LSPR band of mPEG-Au NRs displays a stability and linear response in the spectral shift with respect to a change in their surrounding refractive index with a sensitivity of 252 nm/RIU. The loose structure of mPEG-SH around the Au NRs offers free sites, thereby allowing molecular biothiols to bind onto the surfaces of Au NRs. The LSPR response and the sensitivity of Au NRs to biothiols such as GSH, Cys, Hcy, TGA, GSSG, and BSA were then studied.

Persistent mitochondrial damage by nitric oxide and its derivatives: neuropathological implications

Approximately 15 years ago we reported that cytochrome c oxidase (CcO) was persistently inhibited as a consequence of endogenous induction and activation of nitric oxide (^•NO) synthase-2 (NOS2) in astrocytes. Furthermore, the reactive nitrogen species implicated was peroxynitrite. In contrast to the reversible inhibition by ^•NO, which occurs rapidly, in competition with O₂, and has signaling regulatory implications, the irreversible CcO damage by peroxynitrite is progressive in nature and follows and/or is accompanied by damage to other key mitochondrial bioenergetic targets. In purified CcO it has been reported that the irreversible inhibition occurs through a mechanism involving damage of the heme a₃-Cu_B binuclear center leading to an increase in the K_m for oxygen. Astrocyte survival, as a consequence of peroxynitrite exposure, is preserved due to their robust bioenergetic and antioxidant defense mechanisms. However, by releasing peroxynitrite to the neighboring neurons, whose antioxidant defense can, under certain conditions, be fragile, activated astrocytes trigger bioenergetic stress leading to neuronal cell death. Thus, such irreversible inhibition of CcO by peroxynitrite may be a plausible mechanism for the neuronal death associated with neurodegenerative diseases, in which the activation of astrocytes plays a crucial role.

Metal oxide microrings with femtoliter capacity for Raman microspectroscopy

A simple strategy, based on ultrafast heating of polystyrene microspheres infiltrated with a zinc acetate solution, is employed here for preparing ZnO microcontainers with femtoliter capacity. Their potential exploitation in micro-Raman assays for basic studies in bio- and nanotechnology is tested in different proof-of-concept experiments concerning the in situ analysis of l-glutathione crystals and gold-yeast cytochrome c bioconjugates. The ZnO microcontainers are also used as scaffolds for atomic layer deposition of TiO(2) overlayers with a fine-tuning of thickness and morphology. The resulting ZnO/TiO(2) heterostructures are tested in different photocatalytic experiments involving degradation and laser-induced conversion of methylene blue.