Peripheral biomarkers of oxidative stress and their limited potential in evaluation of clinical features of Huntington's patients

Abstract

Context: Peripheral oxidative biomarkers could be useful for monitoring clinical features of Huntington's disease (HD).

Materials and methods: Cu/Zn-superoxide dismutase (Cu/Zn-SOD), neuron-specific enolase (NSE) and 8-hydroxy-2′-deoxyguanosine (8-oxoGua) serum levels were analysed in 18 HD patients and 10 controls. Clinical measures were recorded from each HD patients.

Results: Cu/Zn-SOD, NSE and 8-oxoGua values were higher in HD patients than in controls. Cu/Zn-SOD and NSE correlated positively. No correlation was observed between the biomarkers analysed and the clinical measures assessed.

Discussion and conclusion: Serum oxidative biomarkers could express the neuronal oxidative processes going on in HD patients but are inadequate to evaluate clinical features of the disease.     

Ferroportin1 and hephaestin overexpression attenuate iron‐induced oxidative stress in MES23.5 dopaminergic cells

Elevated iron was found in the substantia nigra (SN) of patients with Parkinson's disease (PD). Our previous in vivo experiments suggested that decreased ferroportin1 (FPN1) and hephaestin (HP) expression might account for the cellular iron accumulation and resulting dopaminergic neurons loss in the SN of PD animal models. In the present study, we investigated whether increased FPN1 and/or HP expression could attenuate iron‐induced oxidative stress in the dopaminergic MES23.5 cell line. We generated MES23.5 cells with stable overexpression of FPN1 and/or HP. Our study showed that overexpression of FPN1 and/or HP increased iron efflux, lowered cellular iron level, suppressed reactive oxygen species production, and restored mitochondrial transmembrane potential, similar to the effects seen for the iron chelator deferoxamine. These results suggest that FPN1 and/or HP might directly contribute to iron efflux process from neurons in conditions of overexpression, thus prevent cellular iron accumulation and eventually protect cells from iron‐induced oxidative stress. J. Cell. Biochem. 110: 1063–1072, 2010. Published 2010 Wiley‐Liss, Inc.     

Loss of mitofusin 2 links beta‐amyloid‐mediated mitochondrial fragmentation and Cdk5‐induced oxidative stress in neuron cells

Mitochondrial dysfunction is implicated in age‐related degenerative disorders such as Alzheimer's disease (AD). Maintenance of mitochondrial dynamics is essential for regulating mitochondrial function. Aβ oligomers (AβOs), the typical cause of AD, lead to mitochondrial dysfunction and neuronal loss. AβOs have been shown to induce mitochondrial fragmentation, and their inhibition suppresses mitochondrial dysfunction and neuronal cell death. Oxidative stress is one of the earliest hallmarks of AD. Cyclin‐dependent kinase 5 (Cdk5) may cause oxidative stress by disrupting the antioxidant system, including Prx2. Cdk5 is also regarded as a modulator of mitochondrial fission; however, a precise mechanistic link between Cdk5 and mitochondrial dynamics is lacking. We estimated mitochondrial morphology and alterations in mitochondrial morphology‐related proteins in Neuro‐2a (N2a) cells stably expressing the Swedish mutation of amyloid precursor protein (APP), which is known to increase AβO production. We demonstrated that mitochondrial fragmentation by AβOs accompanies reduced mitofusin 1 and 2 (Mfn1/2) levels. Interestingly, the Cdk5 pathway, including phosphorylation of the Prx2‐related oxidative stress, has been shown to regulate Mfn1 and Mfn2 levels. Furthermore, Mfn2, but not Mfn1, over‐expression significantly inhibits the AβO‐mediated cell death pathway. Therefore, these results indicate that AβO‐mediated oxidative stress triggers mitochondrial fragmentation via decreased Mfn2 expression by activating Cdk5‐induced Prx2 phosphorylation.

     

Oxidative stress induces transient O‐GlcNAc elevation and tau dephosphorylation in SH‐SY5Y cells

O‐linked β‐N‐acetlyglucosamine or O‐GlcNAc modification is a dynamic post‐translational modification occurring on the Ser/Thr residues of many intracellular proteins. The chronic imbalance between phosphorylation and O‐GlcNAc on tau protein is considered as one of the main hallmarks of Alzheimer's disease. In recent years, many studies also showed that O‐GlcNAc levels can elevate upon acute stress and suggested that this might facilitate cell survival. However, many consider chronic stress, including oxidative damage as a major risk factor in the development of the disease. In this study, using the neuronal cell line SH‐SY5Y we investigated the dynamic nature of O‐GlcNAc after treatment with 0.5 mM H₂O₂ for 30 min. to induce oxidative stress. We found that overall O‐GlcNAc quickly increased and reached peak level at around 2 hrs post‐stress, then returned to baseline levels after about 24 hrs. Interestingly, we also found that tau protein phosphorylation at site S262 showed parallel, whereas at S199 and PHF1 sites showed inverse dynamic to O‐Glycosylation. In conclusion, our results show that temporary elevation in O‐GlcNAc modification after H₂O₂‐induced oxidative stress is detectable in cells of neuronal origin. Furthermore, oxidative stress changes the dynamic balance between O‐GlcNAc and phosphorylation on tau proteins.     

Xylem structure of four grape varieties and 12 alternative hosts to the xylem-limited bacterium Xylella fastidious

Background and Aims

The bacterium Xylella fastidiosa (Xf), responsible for Pierce''s disease (PD) of grapevine, colonizes the xylem conduits of vines, ultimately killing the plant. However, Vitis vinifera grapevine varieties differ in their susceptibility to Xf and numerous other plant species tolerate Xf populations without showing symptoms. The aim of this study was to examine the xylem structure of grapevines with different susceptibilities to Xf infection, as well as the xylem structure of non-grape plant species that support or limit movement of Xf to determine if anatomical differences might explain some of the differences in susceptibility to Xf.

Methods

Air and paint were introduced into leaves and stems to examine the connectivity between stem and leaves and the length distribution of their vessels. Leaf petiole and stem anatomies were studied to determine the basis for the free or restricted movement of Xf into the plant.

Key Results

There were no obvious differences in stem or petiole vascular anatomy among the grape varieties examined, nor among the other plant species that would explain differences in resistance to Xf. Among grape varieties, the more tolerant ‘Sylvaner’ had smaller stem vessel diameters and 20 % more parenchyma rays than the other three varieties. Alternative hosts supporting Xf movement had slightly longer open xylem conduits within leaves, and more connection between stem and leaves, when compared with alternative hosts that limit Xf movement.

Conclusions

Stem–leaf connectivity via open xylem conduits and vessel length is not responsible for differences in PD tolerance among grape varieties, or for limiting bacterial movement in the tolerant plant species. However, it was found that tolerant host plants had narrower vessels and more parenchyma rays, possibly restricting bacterial movement at the level of the vessels. The implications of xylem structure and connectivity for the means and regulation of bacterial movement are discussed.     

Mitochondrial oxidative stress index,activity of redox-sensitive aconitase and effects of endogenous anti- and pro-oxidants on its activity in control,Alzheimer's disease and Swedish Familial Alzheimer's disease brain

Efficient function of the mitochondrial respiratory chain and the citric acid cycle (CAC) enzymes is required for the maintenance of human brain function. A conception of oxidative stress (OxS) was recently advanced as a disruption of redox signalling and control. Mitochondrial OxS (MOxS) is implicated in the development of Alzheimer's disease (AD). Thus, both pro- and anti-oxidants of the human body and MOxS target primarily the redox-regulated CAC enzymes, like mitochondrial aconitase (MAc). We investigated the specific activity of the MAc and MOxS index (MOSI) in an age-matched control (Co), AD and Swedish Familial AD (SFAD) post-mortem autopsies collected from frontal cortex (FC) and occipital primary cortex (OC) regions of the brain. We also examined whether the mitochondrial neuroprotective signalling molecules glutathione, melatonin and 17-β-estradiol (17βE) and mitochondrially active pro-oxidant neurotoxic amyloid-β peptide can modulate the activity of the MAc isolated from FC and OC regions similarly or differently in the case of Co, AD and SFAD. The activity of redox-sensitive MAc may directly depend on the mitochondrial oxidant/antioxidant balance in age-matched Co, AD and SFAD brain regions.     

Phenotypic heterogeneity in the bacterial oxidative stress response is driven by cell-cell interactions

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Exogenous markers for the characterization of human diseases associated with oxidative stress

Many human conditions, including neurological diseases, atherosclerosis, cancer, diabetic complications and aging, are thought to be associated with oxidative stress (OS). The development of reliable and informative markers for the characterization of OS in humans is thus highly important. Various endogenous markers are known, but their accumulation with increasing OS and with time is not certain, and most of them do not provide information on the type or source of the stress, or on the kinetics of their formation. The aim of the present overview is to present exogenous markers, designed and synthesized by our group, which are sensitive to OS and can identify its presence, the type of reactive oxygen and nitrogen species involved ex vivo, and potential damage incurred by bio-macromolecules, in real time. A microdialysis technique is used in animals for evaluation of OS in vivo. The designed probes are composed of several endogenous subunits, attached together covalently to form molecules that do not exist as such in humans. The subunits include an amino acid (tyrosine), an unsaturated fatty acid (linoleic acid), a nucleic acid (2′-deoxyribose guanosine) and cholesterol, representing the major macromolecules of the body, i.e. proteins, lipids, DNA and sterols, respectively. Incubation of these markers in a biological sample ex vivo, such as blood/serum, urine, saliva, cells or tissues under OS, alters their subunits, which are then analyzed and identified by LC/MS. This review demonstrates the potential of these markers to identify OS in samples taken from humans and animals suffering from, for example, atherosclerosis, hypertension, or Alzheimer's or Parkinson's disease.     

SIRT1 mediates salidroside‐elicited protective effects against MPP+‐induced apoptosis and oxidative stress in SH‐SY5Y cells: involvement in suppressing MAPK pathways

Parkinson's disease (PD) is a progressive neurodegenerative disease, leading to tremor, rigidity, bradykinesia, and gait impairment. Salidroside has been reported to exhibit antioxidative and neuroprotective properties in PD. However, the underlying neuroprotective mechanisms effects of salidroside are poorly understood. Recently, a growing body of evidences suggest that silent information regulator 1 (SIRT1) plays important roles in the pathophysiology of PD. Hence, the present study investigated the roles of SIRT1 in neuroprotective effect of salidroside against N‐methyl‐4‐phenylpyridinium (MPP⁺)‐induced SH‐SY5Y cell injury. Our findings revealed that salidroside attenuates MPP⁺‐induced neurotoxicity as evidenced by the increase in cell viability, and the decreases in the caspase‐3 activity and apoptosis ratio. Simultaneously, salidroside pretreatment remarkably increased SIRT1 activity, SIRT1 mRNA and protein levels in MPP⁺‐treated SH‐SY5Y cell. However, sirtinol, a SIRT1 activation inhibitor, significantly blocked the inhibitory effects of salidroside on MPP⁺‐induced cytotoxicity and apoptosis. In addition, salidroside abolished MPP⁺‐induced the production of reactive oxygen species (ROS), the up‐regulation of NADPH oxidase 2 (NOX2) expression, the down‐regulations of superoxide dismutase (SOD) activity and glutathione (GSH) level in SH‐SY5Y cells, while these effects were also blocked by sirtinol. Finally, we found that the inhibition of salidroside on MPP⁺‐induced phosphorylation of p38, extracellular signal‐regulated kinase (ERK) and c‐Jun NH2‐terminal kinase (JNK) were also reversed by sirtinol in SH‐SY5Y cells. Taken together, these results indicated that SIRT1 contributes to the neuroprotection of salidroside against MPP⁺‐induced apoptosis and oxidative stress, in part through suppressing of mitogen‐activated protein kinase (MAPK) pathways.     

Neuroprotection by urate on 6‐OHDA‐lesioned rat model of Parkinson's disease: linking to Akt/GSK3β signaling pathway

Higher plasma urate level is reported to be associated with a reduced risk and slower progression of Parkinson's disease (PD). In this study, we explored the effects of urate on dopaminergic neurons in nigrostriatal pathway in the 6‐hydroxydopamine (6‐OHDA) unilaterally lesioned rats. Uric acid (UA), when given twice daily at 200 mg/kg intraperitoneally for 10 consecutive days, elevated urate (the anionic form of UA) in plasma and striatum by 55% and 36.8%, respectively, as compared with vehicle group. This regimen of UA was found to ameliorate the behavioral deficits, dopaminergic neuron loss as well as dopamine depletion in the nigrostriatal system. Moreover, UA administration was capable of increasing glutathione level and superoxide dismutase activity while decreasing malondialdehyde accumulation in striatum. In addition, the phosphorylation of both protein kinase B (Akt) and glycogen synthase kinase 3 beta (GSK3β) in the lesioned striata of 6‐OHDA‐lesioned rats was dramatically reduced as compared with sham‐operated rats. This reduction was attenuated in the Parkinsonian rats receiving UA treatment. Similarly, in vitro findings showed that UA alleviated the decrease in Akt activation and the increase in GSK3β activity caused by 6‐OHDA. Furthermore, neuroprotection by urate and its regulation on GSK3β phosphorylation at Ser9 was found to be abolished in the presence of PI3K inhibitor. Therefore, our findings demonstrated that urate was able to protect dopaminergic neurons in rat nigrostriatal pathway against the neurotoxicity of 6‐OHDA, and showed that its beneficial effects may be related to its regulation on Akt/GSK3β signaling.     

Collapsin response mediator protein-2 phosphorylation promotes the reversible retraction of oligodendrocyte processes in response to non-lethal oxidative stress

The extension of processes of oligodendrocyte (OLG) and their precursor cells are crucial for migration, axonal contact and myelination. Here we show that a non-lethal oxidative stress induced by 3-nitropropionic acid (3-NP) elicited a rapid shortening of processes (~24%) in primary OLGs and in oligodendroglial cell line (OLN-93) cells (~36%) as compared with vehicle-exposed cells. This was reversible and prevented by antioxidants. Proteomics of OLG lysates with and without 3-NP treatment yielded collapsin response mediator protein 2 (CRMP-2) as a candidate effector molecule. Inhibition of rho kinase was sufficient to prevent process retraction in both OLGs and OLN-93 cells. Oxidative stress increased phosphorylation of CRMP-2 at T555 that was completely prevented by Y27632. Moreover, transfection of OLN-93 cells with the mutant CRMP-2 T555A which cannot be phosphorylated by rho kinase, prevented process shortening induced by 3-NP as compared with wild-type CRMP-2. Our results suggest a role for endogenous reactive oxygen species in a pathway that regulates OLG process extension. The vulnerability of late myelinated neurons in the adult brain and the presence of white matter pathology in human dementias warrant the study of this oligodendroglial pathway in the early stages of neurodegenerative conditions characterized by oxidative stress.