Brain rust: recent discoveries on the role of oxidative stress in neurodegenerative diseases

Subventricular Accumulation of Cu in the Aging Mouse Brain Does Not Associate with Anticipated Increases in Markers of Oxidative Stress

Natural aging is associated with mild memory loss and cognitive decline, and age is the greatest risk factor for neurodegenerative diseases, such as Alzheimer's disease. There is substantial evidence that oxidative stress is a major contributor to both natural aging and neurodegenerative disease, and coincidently, levels of redox active metals such as Fe and Cu are known to be elevated later in life. Recently, a pronounced age-related increase in Cu content has been reported to occur in mice and rats around a vital regulatory brain region, the subventricular zone of lateral ventricles. In our study herein, we have characterized lateral ventricle Cu content in a unique murine model of accelerated aging, senescence accelerated mouse-prone 8 (SAMP8) mice. Our results confirm an age-related increase in ventricle Cu content, consistent with the studies by others in wild-type mice and rats. Specifically, we observed Cu content to increase over the time frame 1 to 5 months and 5 to 9 months, but interestingly, no significant increase occurred between 9 and 12 months (although brain Cu content at 12 months was significantly elevated relative to 1 and 5 month-old animals). Despite the magnitude of Cu increase observed within the cells that comprise the subventricular zone of lateral ventricles (average 3 mM Cu, with isolated subcellular concentrations of 17 mM), we did not detect spectroscopic markers of thiol oxidation, protein aggregation, or lipid oxidation. The lack of evidence for oxidative stress in ex vivo animal tissue is in contrast to in vitro studies demonstrating that thiol, protein, and lipid oxidation is pronounced at these Cu concentrations. We suggest that our findings most likely indicate that the Cu ions in this brain region are sequestered in an unreactive form, possibly extended chains of Cu-thiolate complexes, which do not readily redox cycle in the aqueous cytosol. These results also appear to partially challenge the long-held view that age-related increases in brain metal content drive oxidative stress as we did not observe a concomitant association between age-related Cu increase and markers of oxidative stress, nor did we observe a net increase in Cu content between mice aged 9 and 12 months.

SLC25A24 gene methylation and gray matter volume in females with and without conduct disorder: an exploratory epigenetic neuroimaging study

Conduct disorder (CD), a psychiatric disorder characterized by a repetitive pattern of antisocial behaviors, results from a complex interplay between genetic and environmental factors. The clinical presentation of CD varies both according to the individual's sex and level of callous-unemotional (CU) traits, but it remains unclear how genetic and environmental factors interact at the molecular level to produce these differences. Emerging evidence in males implicates methylation of genes associated with socio-affective processes. Here, we combined an epigenome-wide association study with structural neuroimaging in 51 females with CD and 59 typically developing (TD) females to examine DNA methylation in relation to CD, CU traits, and gray matter volume (GMV). We demonstrate an inverse pattern of correlation between CU traits and methylation of a chromosome 1 region in CD females (positive) as compared to TD females (negative). The identified region spans exon 1 of the SLC25A24 gene, central to energy metabolism due to its role in mitochondrial function. Increased SLC25A24 methylation was also related to lower GMV in multiple brain regions in the overall cohort. These included the superior frontal gyrus, prefrontal cortex, and supramarginal gyrus, secondary visual cortex and ventral posterior cingulate cortex, which are regions that have previously been implicated in CD and CU traits. While our findings are preliminary and need to be replicated in larger samples, they provide novel evidence that CU traits in females are associated with methylation levels in a fundamentally different way in CD and TD, which in turn may relate to observable variations in GMV across the brain.

Exploring the multimodal role of phytochemicals in the modulation of cellular signaling pathways to combat age-related neurodegeneration

Neurodegeneration is the progressive loss of neuronal structures and functions that lead to copious disorders like Alzheimer's (AD), Parkinson's (PD), Huntington's (HD), amyotrophic lateral sclerosis (ALS), and other less recurring diseases. Aging is the prime culprit for most neurodegenerative events. Moreover, the shared pathogenic factors of many neurodegenerative processes are inflammatory responses and oxidative stress (OS). Unfortunately, it is very complicated to treat neurodegeneration and there is no effective remedy. The rapid progression of the neurodegenerative diseases that exacerbate the burden and the concurrent absence of effective treatment strategies force the researchers to investigate more therapeutic approaches that ultimately target the causative factors of the neurodegeneration. Phytochemicals have great potential to exert their neuroprotective effects by targeting various mechanisms, such as OS, neuroinflammation, abnormal protein aggregation, neurotrophic factor deficiency, disruption in mitochondrial function, and apoptosis. Therefore, this review represents the molecular mechanisms of neuroprotection by multifunctional phytochemicals to combat age-linked neurodegenerative disorders.

Exploration of anti-inflammatory mechanism of forsythiaside A and forsythiaside B in CuSO4-induced inflammation in zebrafish by metabolomic and proteomic analyses

BACKGROUND

Inflammation is a general pathological phenomenon during severe disturbances to the homeostasis. Forsythiaside A (FA) and forsythiaside B (FB), isolated from the dried fruit of Forsythia suspensa (Thunb.) Vahl, are phenylethanoid compounds that show a significant anti-inflammatory effect. However, the properties and therapeutic mechanisms of this effect have not yet been systematically elucidated.

METHODS

In this study, the anti-inflammatory effects of FA and FB were investigated in CuSO₄-induced inflammation in zebrafish larvae. Intracellular generation of reactive oxygen species (ROS) and nitric oxide (NO) was investigated using fluorescence probes. Metabolomic and proteomic analyses using liquid chromatography-mass spectrometry were carried out to identify the expressions of metabolites and proteins associated with the anti-inflammatory mechanism of FA and FB. Quantitative polymerase chain reaction (PCR) was performed to detect the progressive changes in gene expression.

RESULTS

FA and FB inhibited neutrophils migration to the damaged neuromasts and remarkably reduced CuSO₄-induced ROS and NO generation in zebrafish larvae. Metabolomic analysis pointed to the involvement of nicotinate and nicotinamide metabolism, energy metabolism, pyrimidine metabolism, and purine metabolism. Proteomic analysis identified 146 differentially expressed proteins between the control and model groups. These included collagen [collagen type II alpha 1b precursor (col2a1b), collagen alpha-2(IX) chain precursor (col9a2), collagen type IX alpha I precursor (col9a1b)], nucleoside diphosphate kinase 3 isoform X1 (Nme3), WD repeat-containing protein 3 (Wdr3), and 28S ribosomal protein S7 mitochondrial precursor (Mrps7). FA and FB were shown to reverse the abnormal expressions of potential metabolite and protein biomarkers and alleviate CuSO₄-induced damage to the neuromasts in the zebrafish lateral line.

CONCLUSIONS

Our results indicate that FA and FB possess remarkable anti-inflammatory properties, protecting against CuSO₄-induced neuromasts damage in zebrafish larvae. The results also suggest a multi-component and multi-regulatory therapeutic mechanism for FA and FB.

Chronic estrogen affects TIDA neurons through IL-1β and NO: effects of aging

Women are chronically exposed to estrogens through oral contraceptives, hormone replacement therapy or environmental estrogens. We hypothesized that chronic exposure to low levels of estradiol-17β (E2) can induce inflammatory and degenerative changes in the tuberoinfundibular dopaminergic (TIDA) system leading to reduced dopamine synthesis and hyperprolactinemia. Young (Y; 3–4 months) and middle-aged (MA; 10–12 months) Sprague-Dawley rats that were intact or ovariectomized (OVX) were either sham-implanted or implanted with a slow-release E2 pellet (20 ng E2/day for 90 days). To get mechanistic insight, adult 3- to 4-month-old WT, inducible nitric oxide synthase (iNOS) and IL-1 receptor (IL-1R) knockout (KO) mice were subjected to a similar treatment. Hypothalamic areas corresponding to the TIDA system were analyzed. E2 treatment increased IL-1β protein and nitrate levels in the arcuate nucleus of intact animals (Y and MA). Nitration of tyrosine hydroxylase in the median eminence increased with E2 treatment in both intact and OVX animals. There was no additional effect of age. This was accompanied by a reduction in dopamine levels and an increase in prolactin in intact animals. E2 treatment increased nitrate and reduced dopamine levels in the hypothalamus and increased serum prolactin in WT mice. In contrast, the effect of E2 on nitrate levels was blocked in IL-1R KO mice and the effect on dopamine and prolactin were blocked in iNOS KO animals. Taken together, these results show that chronic exposure to low levels of E2 decreases TIDA activity through a cytokine-nitric oxide-mediated pathway leading to hyperprolactinemia and that aging could promote these degenerative changes.

Connection between Systemic Inflammation and Neuroinflammation Underlies Neuroprotective Mechanism of Several Phytochemicals in Neurodegenerative Diseases

Oxidative damage, mitochondrial dysfunction, and neuroinflammation are strongly implicated in the pathogenesis of neurodegenerative diseases including Alzheimer's disease (AD) and Parkinson's disease (PD), and a substantial portion of elderly population at risk of these diseases requires nutritional intervention to benefit health due to lack of clinically relevant drugs. To this end, anti-inflammatory mechanisms of several phytochemicals such as curcumin, resveratrol, propolis, polyunsaturated fatty acids (PUFAs), and ginsenosides have been extensively studied. However, correlation of the phytochemicals with neuroinflammation or brain nutrition is not fully considered, especially in their therapeutic mechanism for neuronal damage or dysfunction. In this article, we review the advance in antioxidative and anti-inflammatory effects of phytochemicals and discuss the potential communication with brain microenvironment by improved gastrointestinal function, enhanced systemic immunity, and neuroprotective outcomes. These data show that phytochemicals may modulate and suppress neuroinflammation of the brain by several approaches: (1) reducing systemic inflammation and infiltration via the blood-brain barrier (BBB), (2) direct permeation into the brain parenchyma leading to neuroprotection, (3) enhancing integrity of disrupted BBB, and (4) vagal reflex-mediated nutrition and protection by gastrointestinal function signaling to the brain. Therefore, many phytochemicals have multiple potential neuroprotective approaches contributing to therapeutic benefit for pathogenesis of neurodegenerative diseases, and development of strategies for preventing these diseases represents a considerable public health concern and socioeconomic burden.

Our (Mother's) Mitochondria and Our Mind

Most of the energy we get to spend is furnished by mitochondria, minuscule living structures sitting inside our cells or dispatched back and forth within them to where they are needed. Mitochondria produce energy by burning down what remains of our meal after we have digested it, but at the cost of constantly corroding themselves and us. Here we review how our mitochondria evolved from invading bacteria and have retained a small amount of independence from us; how we inherit them only from our mother; and how they are heavily implicated in learning, memory, cognition, and virtually every mental or neurological affliction. We discuss why counteracting mitochondrial corrosion with antioxidant supplements is often unwise, and why our mitochondria, and therefore we ourselves, benefit instead from exercise, meditation, sleep, sunshine, and particular eating habits. Finally, we describe how malfunctioning mitochondria force rats to become socially subordinate to others, how such disparity can be evened off by a vitamin, and why these findings are relevant to us.

Neuroprotective Effect of Several Phytochemicals and Its Potential Application in the Prevention of Neurodegenerative Diseases

The detrimental effects of oxidative stress and chronic neuroinflammation on neuronal cell death have been implicated in the pathogenesis of neurodegenerative disorders such as Alzheimer's disease (AD) and Parkinson's disease (PD). The nutritional neuroscience is quickly growing, and phytochemicals or phytobioactive compounds such as curcumin, resveratrol, propolis, ginsenoside, and ω-3 polyunsaturated fatty acids (PUFAs) have been extensively applied to potential therapeutic purposes for numerous neurodegenerative diseases for their anti-oxidative and anti-inflammatory effects. However, their administration as food supplements in the daily diet of the elderly is normally a voluntary and less-organized behavior, indicating the uncertainty of therapeutic effects in this sporadic population; specifically, the effective physiological dosages and the real positive effects in preserving brain health have not yet been fully elucidated. In this review, we collect several lines of evidence on these compounds, which constitute a major type of nutraceuticals and are widely integrated into the daily anti-aging caring of elderly patients, and discuss the underlying anti-oxidative and anti-inflammatory mechanisms of these phytochemicals. In conclusion, we highlight the implications of these compounds in the prevention and treatment of geriatric diseases, and of the potential supplementation procedures used as a dietary therapeutic program in clinical nursing services for patients with neurodegenerative diseases or for the elderly in certain communities, which we hope will lead to more beneficial health outcomes with respect to brain function, innate immunity, and gastrointestinal function, as well as more economic and social benefits.

Dietary phytochemicals and neuro-inflammaging: from mechanistic insights to translational challenges

An extensive literature describes the positive impact of dietary phytochemicals on overall health and longevity. Dietary phytochemicals include a large group of non-nutrients compounds from a wide range of plant-derived foods and chemical classes. Over the last decade, remarkable progress has been made to realize that oxidative and nitrosative stress (O&NS) and chronic, low-grade inflammation are major risk factors underlying brain aging. Accumulated data strongly suggest that phytochemicals from fruits, vegetables, herbs, and spices may exert relevant negative immunoregulatory, and/or anti-O&NS activities in the context of brain aging. Despite the translational gap between basic and clinical research, the current understanding of the molecular interactions between phytochemicals and immune-inflammatory and O&NS (IO&NS) pathways could help in designing effective nutritional strategies to delay brain aging and improve cognitive function. This review attempts to summarise recent evidence indicating that specific phytochemicals may act as positive modulators of IO&NS pathways by attenuating pro-inflammatory pathways associated with the age-related redox imbalance that occurs in brain aging. We will also discuss the need to initiate long-term nutrition intervention studies in healthy subjects. Hence, we will highlight crucial aspects that require further study to determine effective physiological concentrations and explore the real impact of dietary phytochemicals in preserving brain health before the onset of symptoms leading to cognitive decline and inflammatory neurodegeneration.

The Effect of Diabetes Mellitus on Apoptosis in Hippocampus: Cellular and Molecular Aspects

Background:

Diabetes mellitus is associated with cognitive deficits in humans and animals. These deficits are paralleled by neurophysiological and structural changes in brain. In diabetic animals, impairments of spatial learning, memory, and cognition occur in association with distinct changes in hippocampus, a key brain area for many forms of learning and memory and are particularly sensitive to changes in glucose homeostasis. However, the multifactorial pathogenesis of diabetic encephalopathy is not yet completely understood. Apoptosis plays a crucial role in diabetes-induce neuronal loss in hippocampus.

Methods:

The effects of diabetes on hippocampus and cognitive/behavioral dysfunctions in experimental models of diabetes are reviewed, with a focus on the negative impact on increased neuronal apoptosis and related cellular and molecular mechanisms.

Results:

Of all articles that were assessed, most of the experimental studies clearly showed that diabetes causes neuronal apoptosis in hippocampus through multiple mechanisms, including oxidative stress, inhibition of caspases, disturbance in expression of apoptosis regulator genes, as well as deficits in mitochondrial function. The balance between pro-apoptotic and anti-apoptotic signaling may determine the neuronal apoptotic outcome in vitro and in vivo models of experimental diabetes.

Conclusions:

Dissecting out the mechanisms responsible for diabetes-related changes in the hippocampal cell apoptosis helps improve treatment of impaired cognitive and memory functions in diabetic individuals.

Minimal effects of waterborne exposure to single-walled carbon nanotubes on behaviour and physiology of juvenile rainbow trout (Oncorhynchus mykiss)

Fish behaviours are often considered to be sensitive endpoints of waterborne contaminants, but little attention has been given to engineered nanomaterials. The present study aimed to determine the locomotor and social behaviours of rainbow trout (Oncorhynchus mykiss) during waterborne exposure to single-walled carbon nanotubes (SWCNTs), and to ascertain the physiological basis for any observed effects. Dispersed stock suspensions of SWCNTs were prepared by stirring in sodium dodecyl sulphate (SDS), an anionic surfactant, on an equal w/w basis. Trout were exposed to control (no SWCNT or SDS), 0.25 mg L(-1) SDS (dispersant control), or 0.25 mg L(-1) of SWCNT for 10 days. Video tracking analysis of spontaneous locomotion of individual fish revealed no significant effects of SWCNT on mean velocity when active, total distance moved, or the distribution of swimming speeds. Hepatic glycogen levels were also unaffected. Fish exposed to SWCNTs retained competitive fitness when compelled to compete in energetically costly aggressive interactions with fish from both control groups. Assessment of the respiratory physiology of the fish revealed no significant changes in ventilation rate or gill injuries. Haematocrit and haemoglobin concentrations in the blood were unaffected by SWCNT exposure; and the absence of changes in the red and white pulp of the spleen excluded a compensatory haematopoietic response to protect the circulation. Despite some minor histological changes in the kidneys of fish exposed to SWCNT compared to controls, plasma ion concentrations and tissue electrolytes were largely unaffected. Direct neurotoxicity of SWCNT was unlikely with the brains showing mostly normal histology, and with no effects on acetylcholinesterase or Na(+)/K(+)-ATPase activities in whole brain homogenates. The minimal effects of waterborne exposure to SWCNT observed in this study are in contrast to our previous report of SWCNT toxicity in trout, suggesting that details of the dispersion method and co-exposure concentration of the dispersing agent may alter toxicity.

D-Arginine as a neuroprotective amino acid: promising outcomes for neurological diseases

In humans, as in other mammals, endogenous glucocorticoids (GCs) are essential for adapting to physiological life stress. They are also crucial for the healthy development of the fetus. However, when the physiological concentrations of GCs increase over a long period of time, the central nervous system (CNS) is predisposed to the development of psychiatric disorders and neurological diseases. Here, I discuss the strong influence of GCs on the nitric oxide (NO) pathway and the generation of reactive oxygen species (ROS). I also highlight supporting evidence for the neuroprotective actions of d-arginine (d-Arg) against neurotoxicity induced by high levels of GCs in the CNS. Given that d-Arg does not interfere with the immunosuppressive and anti-inflammatory effects of GCs, this might be a novel way of neutralizing the neurotoxic effects of GCs in the CNS without compromising their positive peripheral actions.

Iron deposits in the chronically inflamed central nervous system and contributes to neurodegeneration

Neurodegenerative disorders are characterized by the presence of inflammation in areas with neuronal cell death and a regional increase in iron that exceeds what occurs during normal aging. The inflammatory process accompanying the neuronal degeneration involves glial cells of the central nervous system (CNS) and monocytes of the circulation that migrate into the CNS while transforming into phagocytic macrophages. This review outlines the possible mechanisms responsible for deposition of iron in neurodegenerative disorders with a main emphasis on how iron-containing monocytes may migrate into the CNS, transform into macrophages, and die out subsequently to their phagocytosis of damaged and dying neuronal cells. The dying macrophages may in turn release their iron, which enters the pool of labile iron to catalytically promote formation of free-radical-mediated stress and oxidative damage to adjacent cells, including neurons. Healthy neurons may also chronically acquire iron from the extracellular space as another principle mechanism for oxidative stress-mediated damage. Pharmacological handling of monocyte migration into the CNS combined with chelators that neutralize the effects of extracellular iron occurring due to the release from dying macrophages as well as intraneuronal chelation may denote good possibilities for reducing the deleterious consequences of iron deposition in the CNS.

The effect of acute administration of vitamin D on micro vascular endothelial function in Caucasians and South Asian Indians

BACKGROUND

Vitamin D is a modulator of the immune system. There is some limited evidence that it also increases local blood flow in response to stress.

MATERIAL AND METHODS

In the present study, we examined 20 age matched subjects; 10 whom were from India and 10 Caucasians from the United States. Subjects were administered 4000 IU of Vitamin D3 for 3 weeks at breakfast. The function of the endothelial cells was evaluated in 2 ways; first, the response to 4 minutes of vascular occlusion was measured with a laser Doppler flow meter and second, the blood flow response to local heat at 42°C for 6 minutes.

RESULTS

The results of the experiments showed that, as reported previously, the endothelial function in people from India was less than their Caucasian counterparts. The blood flow response to heat was reduced after 3 weeks administration of vitamin D in both groups and the response to vascular occlusion in the Caucasian group. But there was only a 20% reduction in the blood flow response to heat in the Caucasian group and a 50% reduction in the group from India.

CONCLUSIONS

Thus acute doses of vitamin D may increase vascular tone and reduce blood flow to tissue during stressors. Dosages administered for a longer duration may have beneficial effects on endothelial function but this was not examined here.

Role of mitochondrial function in the protective effects of ischaemic postconditioning on ischaemia/reperfusion cerebral damage

Objective

To investigate the effects of ischaemic postconditioning on brain injury and mitochondria in focal ischaemia and reperfusion, in rats.

Methods

Adult male Wistar rats ( n = 15 per group) underwent sham surgery, ischaemia (2-h middle cerebral artery occlusion), or ischaemia followed by ischaemic postconditioning (three cycles of 30 s reperfusion/30 s reocclusion). Brain infarction size, neurological function, mitochondrial reactive oxygen species (ROS) production, mitochondrial membrane potential and mitochondrial swelling were evaluated 24 h postsurgery.

Results

Infarct size was significantly smaller, and neurological function was significantly better, in the ischaemic postconditioning group than in the ischaemia group. Ischaemia resulted in significant increases in mitochondrial ROS production and swelling, and a reduction in mitochondrial membrane potential, all of which were significantly reversed by postconditioning.

Conclusions

The protective role of ischaemic postconditioning in focal ischaemia/reperfusion may be due to decreased mitochondrial ROS production, reduced mitochondrial membrane potential and suppressed mitochondria swelling. Mitochondria are potential targets for new therapies to prevent brain damage caused by ischaemia and reperfusion.