Reactive Oxygen Species In Neurons Research Articles

Targeting oxidative stress injury after ischemic stroke in conscious rats: limited benefits with apocynin highlight the need to incorporate long term recovery.

NADPH oxidase is a major source of superoxide anion following stroke and reperfusion. This study evaluated the effects of apocynin, a known antioxidant and inhibitor of Nox2 NADPH, on neuronal injury and cell-specific responses to stroke induced in the conscious rat. Apocynin treatment (50 mg/kg i.p.) commencing 1 hour prior to stroke and 24 and 48 hours after stroke significantly reduced infarct volume in the cortex by ~ 60%, but had no effect on striatal damage or neurological deficits. In situ detection of reactive oxygen species (ROS) using dihydroethidium fluorescence revealed that increased ROS detected in OX-42 positive cells following ischemia was reduced in apocynin-treated rats by ~ 51%, but surprisingly increased in surrounding NeuN positive cells of the same rats by ~ 27%, in comparison to the contralateral hemisphere. Reduced ROS from activated microglia/macrophages treated with apocynin was associated with reduced Nox2 immunoreactivity without change to the number of cells. These findings confirm the protective effects of apocynin and indicate a novel mechanism via reduced Nox2 expression. We also reveal compensatory changes in neuronal ROS generation as a result of Nox2 inhibition and highlight the need to assess long term individual cell responses to inhibitors of oxidative stress.

Low‐level laser therapy (LLLT) reduces oxidative stress in primary cortical neurons in vitro

Low-level laser (light) therapy (LLLT) involves absorption of photons being in the mitochondria of cells leading to improvement in electron transport, increased mitochondrial membrane potential (MMP), and greater ATP production. Low levels of reactive oxygen species (ROS) are produced by LLLT in normal cells that are beneficial. We exposed primary cultured murine cortical neurons to oxidative stressors: hydrogen peroxide, cobalt chloride and rotenone in the presence or absence of LLLT (3 J/cm², CW, 810 nm wavelength laser, 20 mW/cm²). Cell viability was determined by Prestoblue™ assay. ROS in mitochondria was detected using Mito-sox, while ROS in cytoplasm was detected with CellRox™. MMP was measured with tetramethylrhodamine. In normal neurons LLLT elevated MMP and increased ROS. In oxidatively-stressed cells LLLT increased MMP but reduced high ROS levels and protected cultured cortical neurons from death. Although LLLT increases ROS in normal neurons, it reduces ROS in oxidatively-stressed neurons. In both cases MMP is increased. These data may explain how LLLT can reduce clinical oxidative stress in various lesions while increasing ROS in cells in vitro.

Ageing of enteric neurons: oxidative stress, neurotrophic factors and antioxidant enzymes

BackgroundAgeing is associated with gastrointestinal dysfunction, which can have a major impact on quality of life of the elderly. A number of changes in the innervation of the gut during ageing have been reported, including neuronal loss and degenerative changes. Evidence indicates that reactive oxygen species (ROS) are elevated in ageing enteric neurons, but that neurotrophic factors may reduce generation of neuronal ROS. Two such factors, glial cell line derived neurotrophic factor (GDNF) and neurotrophin-3 (NT-3) have also been found to protect enteric neurons against oxidative stress induced cell death of enteric ganglion cells in vitro. We have investigated the possible roles of neurotrophic factors further, by examining their expression in the gut during ageing, and by analysing their effects on antioxidant enzyme production in cultures of enteric ganglion cells.ResultsAnalysis of the expression of GDNF and its receptors c-Ret and GFR α − 1 in rat gut by RT-PCR showed that expression continues throughout life and into ageing, in both ad libitum(AL) and calorically-restricted (CR) animals. Levels of expression of GDNF and GFR α − 1 were elevated in 24 month AL animals compared to 24 month CR animals, and to 24 CR and 6 month control animals respectively. The related factor Neurturin and its receptor GFR α − 2 were also expressed throughout life, the levels of the GFR – α-2(b) isoform were reduced in 24 m AL animals. Immunolabelling showed that c-Ret and GFR α − 1 proteins were expressed by myenteric neurons in ageing animals. GDNF, but not NT-3, was found to increase expression of Cu/Zn superoxide dismutase and catalase by cultured enteric ganglion cells.ConclusionsThe neurotrophic factors GDNF and neurturin and their receptors continue to be expressed in the ageing gut. Changes in the levels of expression of GDNF , GFR α-1 and GFR α-2(b) isoform occurred in 24 m AL animals. GDNF, but not NT-3, increased the levels of antioxidant enzymes in cultured enteric ganglion cells, indicating a possible mechanism for the reported protective effect of GDNF against menadione-induced neuronal apoptosis in the ageing gut. Together these data suggest that GDNF family members may play a protective role in the gut throughout life, and support the suggestion that dysregulation of neurotrophic factor support could contribute to neuronal ageing in the gut.

Cdc42-Dependent Activation of NADPH Oxidase Is Involved in Ethanol-Induced Neuronal Oxidative Stress

It has been suggested that excessive reactive oxygen species (ROS) and oxidative stress play an important role in ethanol-induced damage to both the developing and mature central nervous system (CNS). The mechanisms underlying ethanol-induced neuronal ROS, however, remain unclear. In this study, we investigated the role of NADPH oxidase (NOX) in ethanol-induced ROS generation. We demonstrated that ethanol activated NOX and inhibition of NOX reduced ethanol-promoted ROS generation. Ethanol significantly increased the expression of p47phox and p67phox, the essential subunits for NOX activation in cultured neuronal cells and the cerebral cortex of infant mice. Ethanol caused serine phosphorylation and membrane translocation of p47phox and p67phox, which were prerequisites for NOX assembly and activation. Knocking down p47phox with the small interfering RNA was sufficient to attenuate ethanol-induced ROS production and ameliorate ethanol-mediated oxidative damage, which is indicated by a decrease in protein oxidation and lipid peroxidation. Ethanol activated cell division cycle 42 (Cdc42) and overexpression of a dominant negative (DN) Cdc42 abrogate ethanol-induced NOX activation and ROS generation. These results suggest that Cdc42-dependent NOX activation mediates ethanol-induced oxidative damages to neurons.

Neuronal MCP‐1 Mediates Microglia Recruitment and Neurodegeneration Induced by Thiamine Deficiency

Chemokines are implicated in the neuroinflammation of several chronic neurodegenerative disorders. However, the precise role of chemokines in neurodegeneration is unknown. Thiamine deficiency (TD) causes abnormal oxidative metabolism in the brain as well as a well‐defined microglia activation and neurodegeneration in the submedial thalamus nucleus (SmTN). We evaluated the role of chemokines in neurodegeneration and the underlying mechanism in a TD model. TD selectively induced neuronal expression of monocyte chemoattractant protein‐1 (MCP‐1) in the SmTN prior to microglia activation and neurodegeneration. we showed that MCP‐1‐induced neurotoxicity required the presence of microglia. A MCP‐1 neutralizing antibody inhibited MCP‐1‐induced microglia activation and neuronal death in culture and in the thalamus. MCP‐1 knock‐out mice were resistant to TD‐induced neuronal death in SmTN. TD selectively induced the accumulation of reactive oxygen species in neurons, and antioxidants blocked TD‐induced MCP‐1 expression. Together, our results indicated an induction of neuronal MCP‐1 during TD caused microglia recruitment/activation, which exacerbated neurodegeneration.

Daily Rhythm of Brain Oxidation

Circadian variations in pro‐ and antioxidants, enzymes, and markers of oxidative stress such as malonedialdehyde have been reported. However, nothing is known about the source(s) of free radicals that trigger or modulate these periodic variations. Here we explore the sources and levels of Reactive Oxygen Species (ROS) in young animal brains. We employed synaptosomal and mitochondrial preparations to study neuronal ROS and to identify contributions by mitochondria and NADPH oxidase (Nox) isoforms. We used spin trapping electron paramagnetic resonance (EPR) spectroscopy and electrochemical biosensing to detect superoxide, hydrogen peroxide, hydroxyl radicals, and nitric oxide simultaneously. We also followed daily variations of protein expression and mRNA levels of Nox subunits in mouse brain. We detected daily rhythms of substrate‐specific oxygen consumptions by mitochondria and by Nox enzymes in parallel with ROS production in the same sample. These findings suggest that circadian ROS oscillation may be involved in the interplay between metabolism and higher‐brain functions.

Activation of peroxisome proliferator‐activated receptor‐δ attenuates glutamate‐induced neurotoxicity in HT22 mouse hippocampal cells

Glutamate-induced neurotoxicity has been implicated in the pathogenesis of neurodegenerative disorders; however, little is known about the cellular events that underlie neurotoxicity or how to impede these events. This study demonstrates that peroxisome proliferator-activated receptor (PPAR)-δ regulates glutamate-induced neurotoxicity in HT22 mouse hippocampal cells. Activation of PPARδ by GW501516, a specific ligand, significantly inhibited glutamate-induced cell death and reactive oxygen species (ROS) production in HT22 cells. The siRNA-mediated knockdown of PPARδ abrogated the effects of GW501516 in neuronal toxicity and ROS production induced by glutamate. In addition, ligand-activated PPARδ reduced the glutamate-induced level of intracellular calcium ions (Ca(2+)) by modulating the influx of Ca(2+) from the extracellular space. Similarly, glutamate-induced cell death and intracellular Ca(2+) levels were attenuated in the presence of LY83583, an inhibitor of soluble guanylyl cyclase. Taken together, these results suggest that PPARδ plays an important role in glutamate-induced neurotoxicity by modulating oxidative stress and Ca(2+) influx.

Red Ginseng Extract Attenuates Kainate-Induced Excitotoxicity by Antioxidative Effects

This study investigated the neuroprotective activity of red ginseng extract (RGE, Panax ginseng, C. A. Meyer) against kainic acid- (KA-) induced excitotoxicity in vitro and in vivo. In hippocampal cells, RGE inhibited KA-induced excitotoxicity in a dose-dependent manner as measured by the MTT assay. To study the possible mechanisms of the RGE-mediated neuroprotective effect against KA-induced cytotoxicity, we examined the levels of intracellular reactive oxygen species (ROS) and [Ca2+]i in cultured hippocampal neurons and found that RGE treatment dose-dependently inhibited intracellular ROS and [Ca2+]i elevation. Oral administration of RGE (30 and 200 mg/kg) in mice decreased the malondialdehyde (MDA) level induced by KA injection (30 mg/kg, i.p.). In addition, similar results were obtained after pretreatment with the radical scavengers Trolox and N, N′-dimethylthiourea (DMTU). Finally, after confirming the protective effect of RGE on hippocampal brain-derived neurotropic factor (BDNF) protein levels, we found that RGE is active compounds mixture in KA-induced hippocampal mossy-fiber function improvement. Furthermore, RGE eliminated 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals, and the IC50 was approximately 10 mg/ml. The reductive activity of RGE, as measured by reaction with hydroxyl radical (•OH), was similar to trolox. The second-order rate constant of RGE for •OH was 3.5–4.5 × 109 M−1·S−1. Therefore, these results indicate that RGE possesses radical reduction activity and alleviates KA-induced excitotoxicity by quenching ROS in hippocampal neurons.

Reactive oxygen species inactivate neuronal nicotinic acetylcholine receptors through a highly conserved cysteine near the intracellular mouth of the channel: implications for diseases that involve oxidative stress.

An intriguing feature of several nicotinic acetylcholine receptors (nAChRs) on neurons is that their subunits contain a highly conserved cysteine residue located near the intracellular mouth of the receptor pore. The work summarized in this review indicates that α3β4-containing and α4β2-containing neuronal nAChRs, and possibly other subtypes, are inactivated by elevations in intracellular reactive oxygen species (ROS). This review discusses a model for the molecular mechanisms that underlie this inactivation. In addition, we explore the implications of this mechanism in the context of complications that arise from diabetes. We review the evidence that diabetes elevates cytosolic ROS in sympathetic neurons and inactivates postsynaptic α3β4-containing nAChRs shortly after the onset of diabetes, leading to a depression of synaptic transmission in sympathetic ganglia, an impairment of sympathetic reflexes. These effects of ROS on nAChR function are due to the highly conserved Cys residues in the receptors: replacing the cysteine residues in α3 allow ganglionic transmission and sympathetic reflexes to function normally in diabetes. This example from diabetes suggests that other diseases involving oxidative stress, such as Parkinson's disease, could lead to the inactivation of nAChRs on neurons and disrupt cholinergic nicotinic signalling.

Peroxisome proliferation–associated control of reactive oxygen species sets melanocortin tone and feeding in diet-induced obesity

Previous studies have proposed roles for hypothalamic reactive oxygen species (ROS) in the modulation of circuit activity of the melanocortin system. Here we show that suppression of ROS diminishes pro-opiomelanocortin (POMC) cell activation and promotes the activity of neuropeptide Y (NPY)- and agouti-related peptide (AgRP)-co-producing (NPY/AgRP) neurons and feeding, whereas ROS-activates POMC neurons and reduces feeding. The levels of ROS in POMC neurons were positively correlated with those of leptin in lean and ob/ob mice, a relationship that was diminished in diet-induced obese (DIO) mice. High-fat feeding resulted in proliferation of peroxisomes and elevated peroxisome proliferator-activated receptor γ (PPAR-γ) mRNA levels within the hypothalamus. The proliferation of peroxisomes in POMC neurons induced by the PPAR-γ agonist rosiglitazone decreased ROS levels and increased food intake in lean mice on high-fat diet. Conversely, the suppression of peroxisome proliferation by the PPAR antagonist GW9662 increased ROS concentrations and c-fos expression in POMC neurons. Also, it reversed high-fat feeding-triggered elevated NPY/AgRP and low POMC neuronal firing, and resulted in decreased feeding of DIO mice. Finally, central administration of ROS alone increased c-fos and phosphorylated signal transducer and activator of transcription 3 (pStat3) expression in POMC neurons and reduced feeding of DIO mice. These observations unmask a previously unknown hypothalamic cellular process associated with peroxisomes and ROS in the central regulation of energy metabolism in states of leptin resistance.

Ginkgolide B attenuates ethanol-induced neurotoxicity through regulating NADPH oxidases

Ethanol has long been demonstrated to trigger cell apoptosis in the central nervous system. The over-production of reactive oxygen species (ROS) is considered as one of the most important mechanisms involving in the apoptosis caused by ethanol. Ginkgolide B (GB), which was widely used as a monomer of traditional Chinese medicine, was reported to scavenge free radicals in endothelial cells and smooth muscle cells. But whether GB can prevent ethanol-induced neurotoxicity is still unknown. The aim of this study was to investigate effects of GB on ethanol-induced cytotoxicity, oxidative stress and apoptosis and explore potential protective molecular mechanism of GB. It was found that GB inhibited cell injury and apoptosis in a dose-dependent manner in ethanol-treated PC12 cells by MTT and LDH assays. It was also found that activities of caspase-3 increased by ethanol were mostly abrogated by GB. Further, GB decreased the production of ROS and subsequent over-production of lipid peroxides. A significant increase of alcohol dehydrogenase (ADH) and CYP2E1 enzyme activity was found in the ethanol-exposed PC12 cells as compared to controls. However, GB pretreatment did not significantly affect ethanol-induced ADH and CYP2E1 activities. Quantitative real-time PCR and Western blot analysis demonstrated that ethanol treatment resulted in a significant increase in mRNA and protein expression of NADPH oxidases, which are main oxidases producing ROS in neurons. Moreover, expression and activities of NADPH oxidases were down-regulated by GB. These results indicate that ethanol-induced neurotoxicity is ameliorated by GB mainly through regulating expression and activity of NADPH oxidases.

Determination of Mitochondrial Membrane Potential and Reactive Oxygen Species in Live Rat Cortical Neurons

Mitochondrial membrane potential (ΔΨm) is critical for maintaining the physiological function of the respiratory chain to generate ATP. A significant loss of ΔΨm renders cells depleted of energy with subsequent death. Reactive oxygen species (ROS) are important signaling molecules, but their accumulation in pathological conditions leads to oxidative stress. The two major sources of ROS in cells are environmental toxins and the process of oxidative phosphorylation. Mitochondrial dysfunction and oxidative stress have been implicated in the pathophysiology of many diseases; therefore, the ability to determine ΔΨm and ROS can provide important clues about the physiological status of the cell and the function of the mitochondria. Several fluorescent probes (Rhodamine 123, TMRM, TMRE, JC-1) can be used to determine Δψm in a variety of cell types, and many fluorescence indicators (Dihydroethidium, Dihydrorhodamine 123, H2DCF-DA) can be used to determine ROS. Nearly all of the available fluorescence probes used to assess ΔΨm or ROS are single-wavelength indicators, which increase or decrease their fluorescence intensity proportional to a stimulus that increases or decreases the levels of ΔΨm or ROS. Thus, it is imperative to measure the fluorescence intensity of these probes at the baseline level and after the application of a specific stimulus. This allows one to determine the percentage of change in fluorescence intensity between the baseline level and a stimulus. This change in fluorescence intensity reflects the change in relative levels of ΔΨm or ROS. In this video, we demonstrate how to apply the fluorescence indicator, TMRM, in rat cortical neurons to determine the percentage change in TMRM fluorescence intensity between the baseline level and after applying FCCP, a mitochondrial uncoupler. The lower levels of TMRM fluorescence resulting from FCCP treatment reflect the depolarization of mitochondrial membrane potential. We also show how to apply the fluorescence probe H2DCF-DA to assess the level of ROS in cortical neurons, first at baseline and then after application of H2O2. This protocol (with minor modifications) can be also used to determine changes in ∆Ψm and ROS in different cell types and in neurons isolated from other brain regions.

Determination of Mitochondrial Membrane Potential and Reactive Oxygen Species in Live Rat Cortical Neurons

Mitochondrial membrane potential (ΔΨm) is critical for maintaining the physiological function of the respiratory chain to generate ATP. A significant loss of ΔΨm renders cells depleted of energy with subsequent death. Reactive oxygen species (ROS) are important signaling molecules, but their accumulation in pathological conditions leads to oxidative stress. The two major sources of ROS in cells are environmental toxins and the process of oxidative phosphorylation. Mitochondrial dysfunction and oxidative stress have been implicated in the pathophysiology of many diseases; therefore, the ability to determine ΔΨm and ROS can provide important clues about the physiological status of the cell and the function of the mitochondria. Several fluorescent probes (Rhodamine 123, TMRM, TMRE, JC-1) can be used to determine Δψm in a variety of cell types, and many fluorescence indicators (Dihydroethidium, Dihydrorhodamine 123, H2DCF-DA) can be used to determine ROS. Nearly all of the available fluorescence probes used to assess ΔΨm or ROS are single-wavelength indicators, which increase or decrease their fluorescence intensity proportional to a stimulus that increases or decreases the levels of ΔΨm or ROS. Thus, it is imperative to measure the fluorescence intensity of these probes at the baseline level and after the application of a specific stimulus. This allows one to determine the percentage of change in fluorescence intensity between the baseline level and a stimulus. This change in fluorescence intensity reflects the change in relative levels of ΔΨm or ROS. In this video, we demonstrate how to apply the fluorescence indicator, TMRM, in rat cortical neurons to determine the percentage change in TMRM fluorescence intensity between the baseline level and after applying FCCP, a mitochondrial uncoupler. The lower levels of TMRM fluorescence resulting from FCCP treatment reflect the depolarization of mitochondrial membrane potential. We also show how to apply the fluorescence probe H2DCF-DA to assess the level of ROS in cortical neurons, first at baseline and then after application of H2O2. This protocol (with minor modifications) can be also used to determine changes in ∆Ψm and ROS in different cell types and in neurons isolated from other brain regions.

Genistein and Folic Acid Prevent Oxidative Injury Induced by β‐Amyloid Peptide

To explore the mechanism(s) of the neuroprotective effects of genistein (GEN) and folic acid (FA) on neurons treated with beta amyloid 31-35 (Aβ31-35), the primary cultured cortical neurons were treated with GEN and/or FA for 2 hr prior to exposure to Aβ31-35. Cell viability and fluidity of cell membrane were measured by 3-[4,5-dimethylthiazol-2]-2,5 diphenyltetrazolium bromide and fluorescence polarization, respectively. Intracellular reactive oxygen species (ROS) and Ca(2+) concentrations were measured by laser scanning confocal microscope. Glutataione (GSH) and Glutathione disulfide (GSSG) in mitochondria were measured by enzymatic method. Flow cytometry technique was used to measure mitochondrial membrane potential. The expression of HCY-2 and p38-MAPK mRNA in neurons was analysed by reverse transcription-polymerase chain reaction (RT-PCR). The results showed that GEN and/or FA increased cell viability and reduced concentration of Ca(2+) and generation of ROS in neurons compared with Aβ31-35-treated cells. Furthermore, the ratio of GSH/GSSG in mitochondria and mitochondrial membrane potential was increased after GEN and/or FA treatment. RT-PCR results showed that GEN and/or FA down-regulated expression of HCY-2 and p38-MAPK mRNA. We conclude that GEN and/or FA had neuroprotective effects in Aβ31-35-treated neurons. The mechanisms might be associated with multiple factors such as maintaining redox balance, stabilizing mitochondrial membrane integrity and modulating the signal pathways related to oxidation and apoptosis.

Prolonged Exposure of Cortical Neurons to Oligomeric Amyloid-β Impairs NMDA Receptor Function Via NADPH Oxidase-Mediated ROS Production: Protective Effect of Green Tea (-)-Epigallocatechin-3-Gallate

Excessive production of Aβ (amyloid β-peptide) has been shown to play an important role in the pathogenesis of AD (Alzheimer's disease). Although not yet well understood, aggregation of Aβ is known to cause toxicity to neurons. Our recent study demonstrated the ability for oligomeric Aβ to stimulate the production of ROS (reactive oxygen species) in neurons through an NMDA (N-methyl-d-aspartate)-dependent pathway. However, whether prolonged exposure of neurons to aggregated Aβ is associated with impairment of NMDA receptor function has not been extensively investigated. In the present study, we show that prolonged exposure of primary cortical neurons to Aβ oligomers caused mitochondrial dysfunction, an attenuation of NMDA receptor-mediated Ca2+ influx and inhibition of NMDA-induced AA (arachidonic acid) release. Mitochondrial dysfunction and the decrease in NMDA receptor activity due to oligomeric Aβ are associated with an increase in ROS production. Gp91ds-tat, a specific peptide inhibitor of NADPH oxidase, and Mn(III)-tetrakis(4-benzoic acid)-porphyrin chloride, an ROS scavenger, effectively abrogated Aβ-induced ROS production. Furthermore, Aβ-induced mitochondrial dysfunction, impairment of NMDA Ca2+ influx and ROS production were prevented by pre-treatment of neurons with EGCG [(−)-epigallocatechin-3-gallate], a major polyphenolic component of green tea. Taken together, these results support a role for NADPH oxidase-mediated ROS production in the cytotoxic effects of Aβ, and demonstrate the therapeutic potential of EGCG and other dietary polyphenols in delaying onset or retarding the progression of AD.

Neuronal MCP‐1 Mediates Microglia Recruitment and Neurodegeneration Induced by the Mild Impairment of Oxidative Metabolism

Chemokines are implicated in the neuroinflammation of several chronic neurodegenerative disorders. However, the precise role of chemokines in neurodegeneration is unknown. Thiamine deficiency (TD) causes abnormal oxidative metabolism in the brain as well as a well-defined microglia activation and neurodegeneration in the submedial thalamus nucleus (SmTN), which are common features of neurodegenerative diseases. We evaluated the role of chemokines in neurodegeneration and the underlying mechanism in a TD model. Among the chemokines examined, TD selectively induced neuronal expression of monocyte chemoattractant protein-1 (MCP-1) in the SmTN prior to microglia activation and neurodegeneration. The conditioned medium collected from TD-induced neurons caused microglia activation. With a neuron/microglia co-culture system, we showed that MCP-1-induced neurotoxicity required the presence of microglia, and exogenous MCP-1 was able to activate microglia and stimulated microglia to produce cytokines. A MCP-1 neutralizing antibody inhibited MCP-1-induced microglia activation and neuronal death in culture and in the thalamus. MCP-1 knockout mice were resistant to TD-induced neuronal death in SmTN. TD selectively induced the accumulation of reactive oxygen species in neurons, and antioxidants blocked TD-induced MCP-1 expression. Together, our results indicated an induction of neuronal MCP-1 during mild impairment of oxidative metabolism caused by microglia recruitment/activation, which exacerbated neurodegeneration.

Cellular cholesterol enrichment prevents prion peptide-induced neuron cell damages

The prion diseases are neurodegenerative disorders characterized by the conversion of the PrPc (normal cellular prion) to the PrPsc (misfolded isoform). The accumulation of PrPsc within the central nervous system (CNS) leads to neurocytotoxicity by increasing oxidative stress. In addition, many neurodegenerative disorders including prion, Parkinson’s and Alzheimer’s diseases may be regulated by cholesterol homeostasis. The effects of cholesterol balance on prion protein-mediated neurotoxicity and ROS (reactive oxygen species) generation were the focus of this study. Cholesterol treatment inhibited PrP (106–126)-induced neuronal cell death and ROS generation in SH-SY5Y neuroblastoma cells. In addition, the PrP (106–126)-mediated increase of p53, p-p38, p-ERK and the decrease of Bcl-2 were blocked by cholesterol treatment. These results indicated that cellular cholesterol enrichment is a key regulator of PrP-106–126-mediated oxidative stress and neurotoxicity. Taken together, the results of this study suggest that modulation of cellular cholesterol appears to prevent the neuronal cell death caused by prion peptides.

Reactive Oxygen Species, NADPH Oxidases, and Hypertension

Reactive oxygen species (ROS) produced in the neuronal, renal, and vascular systems not only influence cardiovascular physiology but are also strongly implicated in pathological signaling leading to hypertension. Different sources of ROS have been identified, ranging from xanthine-xanthine oxidase and mitochondria to NADPH oxidase (Nox) enzymes. Of 7 Nox family members, Nox1, Nox2, and Nox4 (and Nox5 in humans) influence the cardiovascular system. Their activation processes and cell and tissue distribution vary widely, adding complexity to understanding their functional roles. Whether these systems act collectively or independently in disease conditions is unclear, but recently feed forward mechanisms have been established between ROS sources. Studies published in Hypertension over the last few years are the focus of this review, and they provide a framework with which to consider the roles of Nox enzymes in neuronal, renal, and vascular hypertensive mechanisms, as well as cardiac remodeling, and their relationships with other ROS-generating systems. ### Neuronal ROS in Hypertension Redox signaling in the central nervous system is well recognized in neuronal control of blood pressure (BP), as well as in response to angiotensin II (Ang II) and aldosterone, which are linked to ROS-dependent hypertension. Recently, new roles for ROS have been described in the hypothalamus and brain stem, nucleus tractus solitarius (NTS), subfornical organ (SFO), rostral ventrolateral medulla, and area postrema (Figure 1). Figure 1. Neuronal NADPH oxidase–dependent ROS involved in central regulation of hypertension. NADPH oxidase homologues, mainly Nox2 and Nox4, are found in different regions of the neuronal system and are reported to have a role in the neuropathogenesis of hypertension by enhancing the sympathetic nerve activity. Nox-induced ROS initiate a forward loop in cross-activation of different receptors and between Nox and mitochondrial ROS. OVLT indicates organum vasculosum of the lamina terminalis; PVN, paraventricular nucleus; PP, posterior pituitary; AP, area postrema; RVLM, rostral ventrolateral medulla. Several …

Cytotoxic effects of surface-modified quantum dots on neuron-like PC12 cells cultured inside microfluidic devices

This paper describes the cytotoxic effects of surface-modified quantum dots (QDs) on neuronlike PC12 cells under localized exposure conditions. PC12 cells were cultured and differentiated on a two-compartment microfluidic neuronal device with the aim of preferentially isolating axons from their cell bodies and thus providing localized exposure of cell bodies or axons to QDs. In addition, we used two distinct ligands for surface modification of QDs: mercaptopropionic acid (MPA) and cetyltrimethylammonium bromide/trioctylphosphine oxide (CTAB/TOPO). The results showed that CTAB/TOPO-QDs were toxic to neurons, whereas MPA-QDs were non-toxic. Through general morphological observation, we observed remarkable alterations in the morphology of the neurons induced by CTAB/TOPO-QDs such as cell shrinkage and axonal degeneration. Furthermore, to investigate whether the axonal degeneration was a consequence of neuronal cell death or was due to a direct toxic effect of QDs on axons, preferentially isolated cell bodies and axons were locally exposed to CTAB/TOPO-QDs, followed by an analysis of intracellular reactive oxygen species (ROS) formation and nuclear changes. The results suggested that axonal degeneration could be a consequence of neuronal cell death as well as of direct axonal toxicity. An estimation of the amount of ROS in neurons exposed to CTAB/TOPOQDs further suggested that oxidative stress could be a leading cause of axonal degeneration and consequent toxicity. In addition, nuclear condensation was observed to be a consequence of QD toxicity.

Mitochondrial stress and the pathogenesis of diabetic neuropathy

Diabetic neuropathy is a major complication of diabetes that affects the sensory and autonomic nervous systems and leads to significant morbidity and impact on the quality of life of patients. Mitochondrial stress has been proposed as a major mediator of neurodegeneration in diabetes. This review briefly summarizes the nature of sensory and autonomic nerve dysfunction and presents these findings in the context of diabetes-induced nerve degeneration mediated by alterations in mitochondrial ultrastructure, physiology and trafficking. Diabetes-induced dysfunction in calcium homeostasis is discussed at length and causative associations with suboptimal mitochondrial physiology are discussed. It is clear that across a range of complications of diabetes mitochondrial physiology is impaired, in general a reduction in electron transport chain capability is apparent. This abnormal activity may predispose mitochondria to generate elevated reactive oxygen species, although experimental proof is still lacking, but more importantly will deleteriously alter the bioenergetic status of neurons. It is proposed that the next 5 years of research should focus on identifying changes in mitochondrial phenotype and associated cellular impact, identifying sources of reactive oxygen species in neurons and analyzing mitochondrial trafficking under diabetic conditions.