Protein oxidation in aging and age-related diseases

Treatment with the reactive oxygen species scavenger EUK-207 reduces lung damage and increases survival during 1918 influenza virus infection in mice

The 1918 influenza pandemic caused over 40 million deaths worldwide, with 675,000 deaths in the United States alone. Studies in several experimental animal models showed that 1918 influenza virus infection resulted in severe lung pathology associated with dysregulated immune and cell death responses. To determine if reactive oxygen species produced by host inflammatory responses play a central role in promoting severity of lung pathology, we treated 1918 influenza virus-infected mice with the catalytic catalase/superoxide dismutase mimetic, salen-manganese complex EUK-207 beginning 3 days postinfection. Postexposure treatment of mice infected with a lethal dose of the 1918 influenza virus with EUK-207 resulted in significantly increased survival and reduced lung pathology without a reduction in viral titers. In vitro studies also showed that EUK-207 treatment did not affect 1918 influenza viral replication. Immunohistochemical analysis showed a reduction in the detection of the apoptosis marker cleaved caspase-3 and the oxidative stress marker 8-oxo-2'-deoxyguanosine in lungs of EUK-207-treated animals compared to vehicle controls. High-throughput sequencing and RNA expression microarray analysis revealed that treatment resulted in decreased expression of inflammatory response genes and increased lung metabolic and repair responses. These results directly demonstrate that 1918 influenza virus infection leads to an immunopathogenic immune response with excessive inflammatory and cell death responses that can be limited by treatment with the catalytic antioxidant EUK-207.

Oxidation enhances human serum albumin thermal stability and changes the routes of amyloid fibril formation

Oxidative damages are linked to several aging-related diseases and are among the chemical pathways determining protein degradation. Specifically, interplay of oxidative stress and protein aggregation is recognized to have a link to the loss of cellular function in pathologies like Alzheimer's and Parkinson's diseases. Interaction between protein and reactive oxygen species may indeed induce small changes in protein structure and lead to the inhibition/modification of protein aggregation process, potentially determining the formation of species with different inherent toxicity. Understanding the temperate relationship between these events can be of utmost importance in unraveling the molecular basis of neurodegeneration. In this work, we investigated the effect of hydrogen peroxide oxidation on Human Serum Albumin (HSA) structure, thermal stability and aggregation properties. In the selected conditions, HSA forms fibrillar aggregates, while the oxidized protein undergoes aggregation via new routes involving, in different extents, specific domains of the molecule. Minute variations due to oxidation of single residues affect HSA tertiary structure leading to protein compaction, increased thermal stability, and reduced association propensity.

Anemia of chronic disease: a unique defect of iron recycling for many different chronic diseases

Anemia of chronic disease (ACD) is frequently observed in patients with chronic diseases as a significant contributor to morbidity and mortality, which can aggravate the severity of symptoms of the underlying inflammatory status. The pathophysiology of ACD is multifactorial, including three mechanisms: shortened erythrocyte survival, impaired proliferation of erythroid progenitor cells, and abnormalities of iron metabolism. These mechanisms are "immune and inflammation"-driven, but several other factors, including chronic blood loss, hemolysis, or vitamin deficiencies, can aggravate anemia. All the abnormalities of iron metabolism observed in ACD can be explained by the effect of hepcidin upregulation. Hepcidin is a small liver peptide, that inhibits the cellular macrophage efflux of iron and intestinal iron absorption, binding to ferroportin and inducing its internalization and degradation. In ACD the synthesis of hepcidin is upregulated by increased inflammatory cytokines, causing the two main principal features: the macrophage iron sequestration and the iron-restricted erythropoiesis. ACD is the most complex anemia to treat. The recommended approach is the treatment of the underlying disease, which can lead to a major improvement or even resolution of ACD. Currently available treatments (transfusion, iron, and erythropoiesis-stimulating agents) can ameliorate anemia, but a considerable percentage of non-responders exist. On this evidence new treatment strategies might arise from the knowledge of the pathophysiology of ACD, in which hepcidin plays the central role. Prospective studies are needed to evaluate the safety and the efficacy of the new emerging treatments, which modulate hepcidin expression through different mechanisms.

Impact of methionine oxidation as an initial event on the pathway of human prion protein conversion

Prion diseases comprise a group of fatal neurodegenerative disorders characterized by the autocatalytic conversion of the cellular prion protein PrP(C) into the infectious misfolded isoform PrP(Sc). Increasing evidence supports a specific role of oxidative stress in the onset of pathogenesis. Although the associated molecular mechanisms remain to be elucidated in detail, several studies currently suggest that methionine oxidation already detected in misfolded PrP(Sc) destabilizes the native PrP fold as an early event in the conversion pathway. To obtain more insights about the specific impact of surface-exposed methionine residues on the oxidative-induced conversion of human PrP we designed, produced, and comparatively investigated two new pseudosulfoxidation mutants of human PrP 121-231 that comprises the well-folded C-terminal domain. Applying circular dichroism spectroscopy and dynamic light scattering techniques we showed that pseudosulfoxidation of all surface exposed Met residues formed a monomeric molten globule-like species with striking similarities to misfolding intermediates recently reported by other groups. However, individual pseudosulfoxidation at the polymorphic M129 site did not significantly contribute to the structural destabilization. Further metal-induced oxidation of the partly unfolded pseudosulfoxidation mutant resulted in the formation of an oligomeric state that shares a comparable size and stability with PrP oligomers detected after the application of different other triggers for structural conversion, indicating a generic misfolding pathway of PrP. The obtained results highlight the specific importance of methionine oxidation at surface exposed residues for PrP misfolding, strongly supporting the hypothesis that increased oxidative stress could be one causative event for sporadic prion diseases and other neurodegenerative disorders.

Impaired cardiac SIRT1 activity by carbonyl stress contributes to aging-related ischemic intolerance

Reactive aldehydes can initiate protein oxidative damage which may contribute to heart senescence. Sirtuin 1 (SIRT1) is considered to be a potential interventional target for I/R injury management in the elderly. We hypothesized that aldehyde mediated carbonyl stress increases susceptibility of aged hearts to ischemia/reperfusion (I/R) injury, and elucidate the underlying mechanisms with a focus on SIRT1. Male C57BL/6 young (4-6 mo) and aged (22-24 mo) mice were subjected to myocardial I/R. Cardiac aldehyde dehydrogenase (ALDH2), SIRT1 activity and protein carbonyls were assessed. Our data revealed that aged heart exhibited increased endogenous aldehyde/carbonyl stress due to impaired ALDH2 activity concomitant with blunted SIRT1 activity (P<0.05). Exogenous toxic aldehydes (4-HNE) exposure in isolated cardiomyocyte verified that aldehyde-induced carbonyl modification on SIRT1 impaired SIRT1 activity leading to worse hypoxia/reoxygenation (H/R) injury, which could all be rescued by Alda-1 (ALDH2 activator) (all P<0.05). However, SIRT1 inhibitor blocked the protective effect of Alda-1 on H/R cardiomyocyte. Interestingly, myocardial I/R leads to higher carbonylation but lower activity of SIRT1 in aged hearts than that seen in young hearts (P<0.05). The application of Alda-1 significantly reduced the carbonylation on SIRT1 and markedly improved the tolerance to in vivo I/R injury in aged hearts, but failed to protect Sirt1^+/− knockout mice against myocardial I/R injury. This was verified by Alda-1 treatment improved postischemic contractile function recovery in ex vivo perfused aged but not in Sirt1^+/− hearts. Thus, aldehyde/carbonyl stress is accelerated in aging heart. These results provide a new insight that impaired cardiac SIRT1 activity by carbonyl stress plays a critical role in the increased susceptibility of aged heart to I/R injury. ALDH2 activation can restore this aging-related myocardial ischemic intolerance.

Diphlorethohydroxycarmalol attenuated cell damage against UVB radiation via enhancing antioxidant effects and absorbing UVB ray in human HaCaT keratinocytes

Exposure of human skin to excessive ultraviolet B (UVB) radiation induces pathophysiological processes via the generation of reactive oxygen species (ROS) in skin cells, such as keratinocytes. This study investigated the ability of diphlorethohydroxycarmalol (DPHC) to protect human keratinocytes (HaCaT) against UVB-induced cell damage. DPHC restored cell viability that was reduced by UVB light. DPHC had an absorption maximum close to the UVB spectrum and decreased UVB-induced intracellular ROS levels, increased levels of reduced glutathione, activated superoxide dismutase and catalase. DPHC also decreased UVB-mediated damage to cellular components, including lipids, proteins, DNA, and attenuated UVB-induced apoptosis. These results suggest that DPHC safeguards human keratinocytes against UVB-induced cell damage by absorbing UVB ray, scavenging ROS and enhancing antioxidant system.

Oxidative stress and epigenetic regulation in ageing and age-related diseases

Recent statistics indicate that the human population is ageing rapidly. Healthy, but also diseased, elderly people are increasing. This trend is particularly evident in Western countries, where healthier living conditions and better cures are available. To understand the process leading to age-associated alterations is, therefore, of the highest relevance for the development of new treatments for age-associated diseases, such as cancer, diabetes, Alzheimer and cardiovascular accidents. Mechanistically, it is well accepted that the accumulation of intracellular damage determined by reactive oxygen species (ROS) might orchestrate the progressive loss of control over biological homeostasis and the functional impairment typical of aged tissues. Here, we review how epigenetics takes part in the control of stress stimuli and the mechanisms of ageing physiology and physiopathology. Alteration of epigenetic enzyme activity, histone modifications and DNA-methylation is, in fact, typically associated with the ageing process. Specifically, ageing presents peculiar epigenetic markers that, taken altogether, form the still ill-defined “ageing epigenome”. The comprehension of mechanisms and pathways leading to epigenetic modifications associated with ageing may help the development of anti-ageing therapies.

Increased serum oxidative stress markers in women with uterine leiomyoma

Background

Uterine leiomyomas (fibroids) are the most common gynaecological benign tumors in premenopausal women. Evidences support the role of oxidative stress in the development of uterine leiomyoma. We have analysed oxidative stress markers (thiols, advanced oxidized protein products (AOPP), protein carbonyls and nitrates/nitrites) in preoperative sera from women with histologically proven uterine leiomyoma.

Methodology/Principal Findings

We conducted a laboratory study in a tertiary-care university hospital. Fifty-nine women with histologically proven uterine leiomyoma and ninety-two leiomyoma-free control women have been enrolled in this study. Complete surgical exploration of the abdominopelvic cavity was performed in each patient. Preoperative serum samples were obtained from all study participants to assay serum thiols, AOPP, protein carbonyls and nitrates/nitrites.

Concentrations of serum protein carbonyl groups and AOPP were higher in leiomyoma patients than in the control group (p=0.005 and p<0.001, respectively). By contrast, serum thiol levels were lower in leiomyoma patients (p<0.001). We found positive correlations between serum AOPP concentrations and total fibroids weight (r=0.339; p=0.028), serum AOPP and serum protein carbonyls with duration of infertility (r=0.762; p=0.006 and r=0.683; p=0.021, respectively).

Conclusions/Significance

This study, for the first time, reveals a significant increase of protein oxidative stress status and reduced antioxidant capacity in sera from women with uterine leiomyoma.

Reactive oxygen species involved in regulating fruit senescence and fungal pathogenicity

Senescence is a vital aspect of fruit life cycles, and directly affects fruit quality and resistance to pathogens. Reactive oxygen species (ROS), as the primary mediators of oxidative damage in plants, are involved in senescence. Mitochondria are the main ROS and free radical source. Oxidative damage to mitochondrial proteins caused by ROS is implicated in the process of senescence, and a number of senescence-related disorders in a variety of organisms. However, the specific sites of ROS generation in mitochondria remain largely unknown. Recent discoveries have ascertained that fruit senescence is greatly related to ROS and incidental oxidative damage of mitochondrial protein. Special mitochondrial proteins involved in fruit senescence have been identified as the targets of ROS. We focus in discussion on our recent advances in exploring the mechanisms of how ROS regulate fruit senescence and fungal pathogenicity.

Oxidative stress and antioxidant defence in a healthy nonagenarian population

Results on oxidative markers during ageing are not consistent throughout the scientific literature; however, successful ageing may depend on better ability to cope with oxidative stress. A previous study of ours showed that successful ageing could actually be related to enhanced response to oxidatively modified proteins. In this study, a healthy nonagenarian population (OVER-90) was examined for various blood oxidative biomarkers and compared with a healthy population of blood donors (age range, 23-66 years). Blood glutathione, both total (tGSH) and oxidised (GSSG), and total plasmatic antioxidant status were maintained in the OVER-90 at a level similar to the control population. Sulphydryl (sulfhydryl) groups and glutathione peroxidase (GPx) were instead decreased. The results are discussed in a possible unifying view: the OVER-90 population could possess a globally preserved antioxidant ability, though some signs of oxidative damage are present and some structures could be 'sacrificed' in order to keep the redox equilibrium.

Role of autophagy in aging

Constitutive autophagy is important for the control of the quality of proteins and organelles to maintain cell function. Damaged proteins and organelles accumulate in aged organs. The level of autophagic activity decreases with aging. Autophagic activity is regulated by many factors, such as the insulin receptor-signaling pathway, the TOR pathway, Sirt1, and caloric restriction. Autophagy-related genes are known to be essential for the lifespan extension of flies, nematodes, and mice. The inhibition of autophagy decreases the lifespan, and on the other hand, the induction of autophagy can prolong the lifespan. Pharmacological intervention to extend the lifespan has demonstrated a crucial role for autophagy. Heart failure is an age-related disease, as the incidence increases with age. The autophagic activity of the heart decreases during aging. Cardiac-specific autophagy-deficient mice have shown no obvious phenotype up to 10 weeks of age. However, these mice began to die after the age of 6 months, with a significant increase in the left ventricular dimensions and a decrease in the fractional shortening of the left ventricle compared with control mice. This indicates that continuous constitutive autophagy during aging has a crucial role in maintaining cardiac structure and function.

Qualitative and quantitative evaluation of derivatization reagents for different types of protein-bound carbonyl groups

Mass spectrometry (MS) of 'carbonylated proteins' often involves derivatization of reactive carbonyl groups to facilitate their enrichment, identification and quantification. Among the many reported reagents, 2,4-dinitrophenylhydrazine (DNPH), biotin hydrazide (BHZ) and O-(biotinylcarbazoylmethyl) hydroxylamine (ARP) are the most frequently used. Despite their common use in carbonylation research, their reactivity towards protein-bound carbonyls has not been quantitatively evaluated in detail, to the best of our knowledge. Thus we studied the reactivity and specificity of these reagents towards different classes of reactive carbonyl groups (e.g. aldehydes, ketones and lactams), each being represented by a synthetic peptide carrying an accordingly modified residue. All three tagging reagents were selective for aliphatic aldehydes and ketones. Lactams and carbonyl-containing tryptophan oxidation products, however, were labelled only at low levels or not at all. Whereas DNPH derivatization was efficient under the published standard conditions, the derivatization conditions for BHZ and ARP had to be altered. Acidic conditions provided quantitative labelling yields for ARP. Peptides derivatized with DNPH, BHZ and ARP fragmented efficiently in tandem mass spectrometry, when the experimental conditions were chosen carefully for each reagent. Importantly, the tested carbonylated peptides did not cross-react with amino groups in other proteins present during sample preparations or enzymatic digestion. Thus, it appears favourable to digest proteins first and then derivatise the reactive carbonyl groups more efficiently at the peptide level under acidic conditions. The carbonylated model peptides used in this study might be valid internal standards for carbonylation proteomics.

Oxidized albumin. The long way of a protein of uncertain function

BACKGROUND

Proteins are extremely reactive to oxidants and should represent a potential target of instable reactive oxygen. This may represent a problem for plasma proteins since they may be directly modified in vivo in a compartment where antioxidant enzymatic systems are scarcely represented. On the other hand, it is possible that some plasma components have evolved over time to guarantee protection, in which case they can be considered as anti-oxidants.

SCOPE OF REVIEW

To present and discuss main studies which addressed the role of albumin in plasma antioxidant activity mainly utilizing in vitro models of oxidation. To present some advances on structural features of oxidized albumin deriving from studies carried out on in vitro models as well as albumin purified in vivo from patients affected by clinical conditions characterized by oxidative stress.

MAJOR CONCLUSIONS

There are different interaction with HOCl and chloramines. In the former case, HOCl produces an extensive alteration of (238)Trp and (162)Tyr, (425)Tyr, (47)Tyr, while thiol groups are only partially involved. Chloramines are extremely reactive with the unique free SH group of albumin ((34)Cys) with the formation of sulfenic and sulfinic acid as intermediates and sulfonic acid as end-product. Oxidized albumin has a modified electrical charge for the addition of an acidic residue and presents α-helix and random coil reorganization with subtle changes in domain orientation.

GENERAL SIGNIFICANCE

Albumin, is the major antioxidants in plasma with a concentration (0.8mM) higher than other antioxidants by an exponential factor. Functional and protective roles in the presence of oxidative stress must be defined. This article is part of a Special Issue entitled Serum Albumin.

Oxygen consumption and usage during physical exercise: the balance between oxidative stress and ROS-dependent adaptive signaling

The complexity of human DNA has been affected by aerobic metabolism, including endurance exercise and oxygen toxicity. Aerobic endurance exercise could play an important role in the evolution of Homo sapiens, and oxygen was not important just for survival, but it was crucial to redox-mediated adaptation. The metabolic challenge during physical exercise results in an elevated generation of reactive oxygen species (ROS) that are important modulators of muscle contraction, antioxidant protection, and oxidative damage repair, which at moderate levels generate physiological responses. Several factors of mitochondrial biogenesis, such as peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), mitogen-activated protein kinase, and SIRT1, are modulated by exercise-associated changes in the redox milieu. PGC-1α activation could result in decreased oxidative challenge, either by upregulation of antioxidant enzymes and/or by an increased number of mitochondria that allows lower levels of respiratory activity for the same degree of ATP generation. Endogenous thiol antioxidants glutathione and thioredoxin are modulated with high oxygen consumption and ROS generation during physical exercise, controlling cellular function through redox-sensitive signaling and protein-protein interactions. Endurance exercise-related angiogenesis, up to a significant degree, is regulated by ROS-mediated activation of hypoxia-inducible factor 1α. Moreover, the exercise-associated ROS production could be important to DNA methylation and post-translation modifications of histone residues, which create heritable adaptive conditions based on epigenetic features of chromosomes. Accumulating data indicate that exercise with moderate intensity has systemic and complex health-promoting effects, which undoubtedly involve regulation of redox homeostasis and signaling.

Effects of caloric restriction on cardiac oxidative stress and mitochondrial bioenergetics: potential role of cardiac sirtuins

The biology of aging has not been fully clarified, but the free radical theory of aging is one of the strongest aging theories proposed to date. The free radical theory has been expanded to the oxidative stress theory, in which mitochondria play a central role in the development of the aging process because of their critical roles in bioenergetics, oxidant production, and regulation of cell death. A decline in cardiac mitochondrial function associated with the accumulation of oxidative damage might be responsible, at least in part, for the decline in cardiac performance with age. In contrast, lifelong caloric restriction can attenuate functional decline with age, delay the onset of morbidity, and extend lifespan in various species. The effect of caloric restriction appears to be related to a reduction in cellular damage induced by reactive oxygen species. There is increasing evidence that sirtuins play an essential role in the reduction of mitochondrial oxidative stress during caloric restriction. We speculate that cardiac sirtuins attenuate the accumulation of oxidative damage associated with age by modifying specific mitochondrial proteins posttranscriptionally. Therefore, the distinct role of each sirtuin in the heart subjected to caloric restriction should be clarified to translate sirtuin biology into clinical practice.

Markers of oxidant stress that are clinically relevant in aging and age-related disease

Despite the long held hypothesis that oxidant stress results in accumulated oxidative damage to cellular macromolecules and subsequently to aging and age-related chronic disease, it has been difficult to consistently define and specifically identify markers of oxidant stress that are consistently and directly linked to age and disease status. Inflammation because it is also linked to oxidant stress, aging, and chronic disease also plays an important role in understanding the clinical implications of oxidant stress and relevant markers. Much attention has focused on identifying specific markers of oxidative stress and inflammation that could be measured in easily accessible tissues and fluids (lymphocytes, plasma, serum). The purpose of this review is to discuss markers of oxidant stress used in the field as biomarkers of aging and age-related diseases, highlighting differences observed by race when data is available. We highlight DNA, RNA, protein, and lipid oxidation as measures of oxidative stress, as well as other well-characterized markers of oxidative damage and inflammation and discuss their strengths and limitations. We present the current state of the literature reporting use of these markers in studies of human cohorts in relation to age and age-related disease and also with a special emphasis on differences observed by race when relevant.

Protein oxidation in a group of subjects with metabolic syndrome

AIMS

To examine the protein oxidation, marker of the oxidative stress, in metabolic syndrome (MS).

METHODS

We enrolled 106 subjects (45 women and 61 men) with MS of which 43 (14 women and 27 men) were with diabetes mellitus and 63 (31 women and 32 men) were without diabetes mellitus, and 54 subjects (19 women and 35 men) as control group. The protein oxidation, expressed as carbonyl groups, was measured by an enzyme-like immunosorbent assay (ELISA) kit (BioCell PC test kit, Enzo Life Sciences AG, Switzerland).

RESULTS

In the whole group of MS subjects, in comparison with control group, a significant increase in carbonyl groups was present. The same datum was also evident between control group and diabetic subjects with MS and between control group and nondiabetic subjects with MS. No difference was observed between the two subgroups (diabetic and nondiabetic subjects with MS) about NOx. Few information were obtained examining the linear regression among carbonyl groups, age, BMI, waist circumference, blood pressure values and metabolic pattern of MS subjects.

CONCLUSIONS

In MS subject we observed an increase of protein oxidation not influenced by diabetes mellitus. Several strategies may be employed to reduce this parameter.

Management of anemia of inflammation in the elderly

Anemia of any degree is recognized as a significant independent contributor to morbidity, mortality, and frailty in elderly patients. Among the broad types of anemia in the elderly a peculiar role seems to be played by the anemia associated with chronic inflammation, which remains the most complex form of anemia to treat. The origin of this nonspecific inflammation in the elderly has not yet been clarified. It seems more plausible that the oxidative stress that accompanies ageing is the real cause of chronic inflammation of the elderly and that the same oxidative stress is actually a major cause of this anemia. The erythropoietic agents have the potential to play a therapeutic role in this patient population. Despite some promising results, rHuEPO does not have a specific indication for the treatment of anemia in the elderly. Moreover, concerns about their side effects have spurred the search for alternatives. Considering the etiopathogenetic mechanisms of anemia of inflammation in the elderly population, an integrated nutritional/dietetic approach with nutraceuticals that can manipulate oxidative stress and related inflammation may prevent the onset of this anemia and its negative impact on patients' performance and quality of life.

Intracellular scavenging activity of Trolox (6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid) in the fission yeast, Schizosaccharomyces pombe

The ability of Trolox (6-hydroxy-2,5,7,8-tetramethylchromane-2-carboxylic acid), a water-soluble vitamin E analogue, to prevent oxidative damages is well characterized, but the mechanisms underlying it remain unclear. The protective effect of Trolox pre-treatment on H₂O₂-induced toxicity might be attributed to the decreased cellular permeability to H₂O₂ or in vitro scavenging activity of Trolox, induction of antioxidant enzymes or the direct scavenging activity of Trolox. The results obtained rule out the first and second possibilities and intracellular scavenging activity was found to be the mechanism whereby Trolox confers protection. This was confirmed by measuring protein oxidation (levels), and the observed decrease in proteasomal activity indicated that the decrease in protein carbonyls was due to Trolox scavenging activity rather than proteasome activation. In conclusion, the intracellular scavenging activity of Trolox is a key protective mechanism against H₂O₂. These findings obtained in Schizosaccharomyces pombe, a good model organism for eukaryotic cells, can be used as standard protocols for investigating the antioxidant activity of pure or complex potential antioxidants.

Long-term exercise treatment reduces oxidative stress in the hippocampus of aging rats

Exercise can exert beneficial effects on cognitive functions of older subjects and it can also play an important role in the prevention of neurodegenerative diseases. At the same time it is perceivable that limited information is available on the nature of molecular pathways supporting the antioxidant effects of exercise in the brain. In this study 12-month old, middle-aged female Wistar rats were subjected to daily moderate intensity exercise on a rodent treadmill for a period of 15weeks which covered the early aging period unmasking already some aging-related molecular disturbances. The levels of reactive oxygen species (ROS), the amount of protein carbonyls, the levels of antioxidant intracellular enzymes superoxide dismutases (SOD-1, SOD-2) and glutathione peroxidase (GPx) were determined in the hippocampus. In addition, to identify the molecular pathways that may be involved in ROS metabolism and mitochondrial biogenesis, the activation of 5'-AMP-activated protein kinase (AMPK), the protein level of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), nuclear respiratory factor 1 (NRF-1) and mitochondrial transcription factor A (mtTFA) were measured. Our results revealed a lower level of ROS associated with a reduced amount of protein carbonyls in the hippocampus of physically trained rats compared to sedentary controls. Furthermore, exercise induced an up-regulation of SOD-1 and GPx enzymes, p-AMPK and PGC-1α, that can be related to an improved redox balance in the hippocampus. These results suggest that long-term physical exercise can comprises antioxidant properties and by this way protect neurons against oxidative stress at the early stage of aging.

Novel method to investigate protein carbonylation by iTRAQ strategy

This paper reports a novel methodology for relative quantitative analysis of carbonylation sites in proteins by exploiting a new isobaric tag for relative and absolute quantitation (iTRAQ) derivative, iTRAQ hydrazide (iTRAQH), and the analytical power of linear ion trap instruments (QqLIT). Because of its operational simplicity, avoiding time-consuming enrichment procedures, this new strategy seems to be well suited for quantitative large-scale proteomic profiling of carbonylation.

Nuclear translocation of DJ-1 during oxidative stress-induced neuronal cell death

Loss-of-function mutations in the PARK7/DJ-1 gene cause early onset autosomal-recessive Parkinson disease. DJ-1 has been implicated in protection of neurons from oxidative stress and in regulation of transcriptional activity. However, whether there is a relationship between the subcellular localization of DJ-1 and its function remains unknown. Therefore, we examined the subcellular localization of DJ-1 during dopaminergic neurodegeneration induced by various insults. Immunoblotting and immunocytochemistry showed that the nuclear pool of DJ-1 dramatically increased in both MN9D dopaminergic neuronal cells and primary cultures of mesencephalic dopaminergic neurons after 6-hydroxydopamine (6-OHDA) treatment. This was paralleled by a corresponding decrease in its cytosolic level, indicating drug-induced nuclear translocation of DJ-1. The same phenomenon was detected in other cell death paradigms induced by pro-oxidants including hydrogen peroxide and cupric chloride. Consequently, cotreatment with the antioxidant N-acetyl-l-cysteine blocked the translocation of DJ-1 into the nucleus. However, mutation at cysteine 106 had no effect on the translocation of DJ-1 into the nucleus, suggesting that reactive oxygen species-mediated downstream signaling and/or modifications other than oxidative modification are involved in its nuclear translocation. Ectopic expression of nucleus localization signal (NLS)-tagged DJ-1 prevented cell death from 6-OHDA. We investigated whether nuclear DJ-1 was involved in transcriptional regulation and found that DJ-1 was localized in promyelocytic leukemia bodies, and this localization increased upon 6-OHDA treatment. We also confirmed that binding of DJ-1 and promyelocytic leukemia bodies indeed increased after 6-OHDA treatment. Consequently, expression levels of acetylated p53 and PUMA were downregulated in cells overexpressing DJ-1 or NLS-tagged DJ-1. Taken together, our data suggest that nuclear translocation of DJ-1 may protect neurons from cell death after oxidative stress.

Plausible antioxidant biomechanics and anticonvulsant pharmacological activity of brain-targeted β-carotene nanoparticles

β-Carotene has been established as a known free radical scavenger with chain-breaking antioxidant properties. It has been documented for the treatment of epileptic convulsions at a 200 mg/kg body weight dose. The reported pathogenesis for epileptic convulsions is oxidative stress. Hence, experimental epileptic convulsions via oxidative stress was induced in albino mice epileptic models (maximal electroshock seizure and pentylenetetrazole [PTZ]). A dose concentration equivalent to 2 mg/kg was efficaciously administered in the form of brain-targeted polysorbate-80-coated poly(d,l-lactide-co-glycolide) nanoparticles. The nanoparticles were prepared by solvent evaporation technique and further characterized for their physical parameters, in-vitro release kinetics, and in-vivo brain release via various standard methods. Normal β-carotene nanoparticles (BCNP) and polysorbate-80-coated β-carotene nanoparticles (P-80-BCNP) of 169.8 ± 4.8 nm and 176.3 ± 3.2 nm in size, respectively, were formulated and characterized. Their zeta potential and polydispersity index were subsequently evaluated after 5 months of storage to confirm stability. In vivo activity results showed that a 2 mg unformulated β-carotene dose was ineffective as an anticonvulsant. However, salutary response was reported from BCNP at the same dose, as the hind limb duration decreased significantly in maximal electroshock seizure to 9.30 ± 0.86 seconds, which further decreased with polysorbate-80 coating to 2.10 ± 1.16 seconds as compared to normal control (15.8 ± 1.49 seconds) and placebo control (16.50 ± 1.43 seconds). In the PTZ model, the duration of general tonic-clonic seizures reduced significantly to 2.90 ± 0.98 seconds by the use of BCNP and was further reduced on P-80-BCNP to 1.20 ± 0.20 seconds as compared to PTZ control and PTZ-placebo control (8.09 ± 0.26 seconds). General tonic-clonic seizures latency was increased significantly to 191.0 ± 9.80 seconds in BCNP and was further increased in P-80-BCNP to 231.0 ± 16.30 seconds, as compared to PTZ (120.10 ± 4.50 seconds) and placebo control (120.30 ± 7.4 seconds). The results of this study demonstrate a plausible novel anticonvulsant activity of β-carotene at a low dose of 2 mg/kg, with brain-targeted nanodelivery, thus increasing its bioavailability and stability.

The number of p16INK4a positive cells in human skin reflects biological age

Cellular senescence is a defense mechanism in response to molecular damage which accumulates with aging. Correspondingly, the number of senescent cells has been reported to be greater in older than in younger subjects and furthermore associates with age-related pathologies. Inter-individual differences exist in the rate at which a person ages (biological age). Here, we studied whether younger biological age is related to fewer senescent cells in middle-aged individuals with the propensity for longevity, using p16INK4a as a marker for cellular senescence. We observed that a younger biological age associates with lower levels of p16INK4a positive cells in human skin.

Oxidative stress and liver disease

In humans, oxidative stress and antioxidant defenses are the sum of a complicated network of enzymatic and non-enzymatic processes. Depending on the stage and severity of diseases, a patient's antioxidant armamentarium may increase as an appropriate response to an oxidant challenge, whereas others may decrease as an indication of unbalanced consumption. In some cases, the formation of reactive oxygen species is a requisite and healthy event. In fact, free radicals can affect intracellular signal transduction and gene regulation, resulting in cytokine production essential to the inflammatory process. In many other cases, especially liver diseases, excessive oxidative stress undoubtedly contributes to the progression and pathological findings of disease and serves as a prognostic indicator. Reactive oxygen species are highly reactive molecules that are naturally generated in small amounts through metabolism and could damage cellular molecules such as lipids, proteins or DNA. Oxidative stress plays a major role in many liver diseases. In this review, we summarize the biological character of free radicals and some antioxidants, and the related methods of analysis. Then, we discusses the association of oxidative stress to many types of liver diseases.

Oxidative damage to DNA and single strand break repair capacity: relationship to other measures of oxidative stress in a population cohort

It is well accepted that oxidative DNA repair capacity, oxidative damage to DNA and oxidative stress play central roles in aging and disease development. However, the correlation between oxidative damage to DNA, markers of oxidant stress and DNA repair capacity is unclear. In addition, there is no universally accepted panel of markers to assess oxidative stress in humans. Our interest is oxidative damage to DNA and its correlation with DNA repair capacity and other markers of oxidative stress. We present preliminary data from a small comet study that attempts to correlate single strand break (SSB) level with single strand break repair capacity (SSB-RC) and markers of oxidant stress and inflammation. In this limited study of four very small age-matched 24-individual groups of male and female whites and African-Americans aged 30-64 years, we found that females have higher single strand break (SSB) levels than males (p=0.013). There was a significant negative correlation between SSB-RC and SSB level (p=0.041). There was a positive correlation between SSBs in African American males with both heme degradation products (p=0.008) and high-sensitivity C-reactive protein (hs-CRP) (p=0.022). We found a significant interaction between hs-CRP and sex in their effect on residual DNA damage (p=0.002). Red blood cell reduced glutathione concentration was positively correlated with the levels of oxidized bases detected by endonuclease III (p=0.047), heme degradation products (p=0.015) and hs-CRP (p=0.020). However, plasma carbonyl levels showed no significant correlation with other markers. The data from the literature and from our very limited study suggest a complex relationship between measures of oxidative stress and frequently used clinical parameters believed to reflect inflammation or oxidative stress.

Enriching carbonylated proteins inside a microchip through the use of oxalyldihydrazide as a crosslinker

We report a proof of principle study for the use of oxalyldihydrazide as a crosslinker for enrichment of carbonylated proteins within a microfluidic chip. Surface modification steps are characterized and analyzed using analytical techniques. We use oxidized cytochrome c as our model protein and demonstrate the chip's ability to capture carbonylated targets. After 100 min of continuous loading, the chip is capable of capturing 7.5 μg of carbonylated protein. All the proteins captured are eluted out of the chip using the elution protocol. Finally, we demonstrate the chip's specificity for oxidized targets by mixing oxidized cytochrome c and TRITC-BSA, with cytochrome c in low abundance. The results show that the chip is efficient at finding its target when unoxidized proteins are present. This is the first report to suggest the use of immobilized oxalyldihydrazide on a microchip as an enrichment methodology for low abundance proteins in a sample.

Skeletal muscle lipid peroxidation and insulin resistance in humans

OBJECTIVE

The relationships among skeletal muscle lipid peroxidation, intramyocellular lipid content (IMCL), and insulin sensitivity were evaluated in nine insulin-sensitive (IS), 13 insulin-resistant (IR), and 10 adults with type 2 diabetes (T2DM).

DESIGN

Insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamp [glucose disposal rate (GDR)]. Lipid peroxidation was assessed by 4-hydroxynonenal (HNE)-protein adducts and general oxidative stress by protein carbonyl content. All patients were sedentary.

RESULTS

Protein-HNE adducts were elevated 1.6-fold in T2DM compared with IS adults, whereas IR showed intermediate levels of HNE-modified proteins. Protein-HNE adducts correlated with GDR, waist circumference, and body mass index. IMCL was increased by 4.0- and 1.9-fold in T2DM and IR patients, respectively, compared with IS, and was correlated with GDR and waist circumference but not BMI. Protein carbonyls were not different among groups and did not correlate with any of the measured variables. Correlations were detected between IMCL and protein-HNE.

CONCLUSION

Our data show for the first time that skeletal muscle protein-HNE adducts are related to the severity of insulin resistance in sedentary adults. These results suggest that muscle lipid peroxidation could be involved in the development of insulin resistance.

Cross-linking of serine racemase dimer by reactive oxygen species and reactive nitrogen species

Serine racemase (SR) is the only identified enzyme in mammals responsible for isomerization of L-serine to D-serine, a coagonist at N-methyl-D-aspartate (NMDA) receptors in the forebrain. Our previous data showed that an apparent SR dimer resistant to sodium dodecyl sulfate and β-mercaptoethanol was elevated in microglial cells after proinflammatory activation. Because the activation of microglia is typically associated with an oxidative burst, oxidative cross-linking between SR subunits was speculated. In this study, an siRNA technique was employed to confirm the identity of this SR dimer band. The oxidative species potentially responsible for the cross-linking was investigated with recombinant SR protein. The data indicate that nitric oxide, peroxynitrite, and hydroxyl radical were the likely candidates, whereas superoxide and hydrogen peroxide per se failed to contribute. Furthermore, the mechanism of formation of SR dimer by peroxynitrite oxidation was studied by mass spectrometry. A disulfide bond between Cys₆ and Cys₁₁₃ was identified in 3-morpholinosydnonimine hydrochloride (SIN-1)-treated SR monomer and dimer. Activity assays indicated that SIN-1 treatment decreased SR activity, confirming our previous conclusion that noncovalent dimer is the most active form of SR. These findings suggest a compensatory feedback in which the consequences of neuroinflammation might dampen D-serine production to limit excitotoxic stimulation of NMDA receptors.

Hesperidin-mediated expression of Nrf2 and upregulation of antioxidant status in senescent rat heart

OBJECTIVES

Oxidative stress is recognized as a key element responsible for the development of age-related pathologies. A declining endogenous defence system during senescence dictates the need for supplementation with exogenous antioxidants through diet. Hesperidin is a naturally occurring flavonone present in citrus fruits and has been shown to have many biological properties, including antioxidant activity. We investigated whether hesperidin supplementation could be valuable in protecting cardiac tissue of aged rats against age-related increase in oxidative stress, as well as the mechanism by which it can boost the antioxidant status of the cell.

METHODS

The activity of antioxidant enzymes, mRNA expression of Nrf2, protein levels of superoxide dismutase and catalase were measured using standard protocols.

KEY FINDINGS

Hesperidin treatment effectively protected aged rat heart by increasing the activity of enzymic antioxidants. Hesperidin upregulated the protein levels of nuclear factor erythroid 2-related factor 2, which is responsible for maintaining the antioxidant status of the cell.

CONCLUSIONS

Hesperidin could be useful in protecting cardiomyocytes against age-related increase in oxidative stress mediated by Nrf2 upregulation.

Shotgun lipidomics analysis of 4-hydroxyalkenal species directly from lipid extracts after one-step in situ derivatization

4-Hydroxyalkenal species are a class of peroxidative products of polyunsaturated fatty acids, which serve as "toxic second messengers" in cellular systems. Investigation of their cellular role is hindered due to the lack of sensitive, reliable, robust method for identification and quantification of these metastable metabolites. Herein, we explored the facile Michael adduct of carnosine with 4-hydroxyalkenal species and developed a sensitive, facile, shotgun lipidomics-based method for quantification of these compounds directly from organic solvent lipid extracts of biological samples. In the study, we extensively examined the factors that may affect the accurate quantification of 4-hydroxyalkenal species and found that this method possessed high reproducibility (<8%) and nearly 3 orders of linear dynamic range with a limit of quantification at lower than 0.56 fmol/μL. Mass levels of 4-hydroxyalkenal species in various biological samples, including mouse heart, kidney, liver, and skeletal muscle, were determined by this developing method. In addition, the effects of sample collection methods and sample storage time on 4-hydroxyalkenal mass levels were also determined. We believe that development of this novel methodology should provide a powerful tool for us to better understand the role of 4-hydroxyalkenal species in biological processes.

Oxidative damage to biological macromolecules in human bone marrow mesenchymal stromal cells labeled with various types of iron oxide nanoparticles

The biological effects of several superparamagnetic iron oxide nanoparticles (SPIONs) varying in their surface coating were tested using human bone marrow mesenchymal stromal cells from two donors - hBMSCs-1 and hBMSCs-2. The measurements were performed at two intervals - after 72 h exposure to the nanoparticles and after an additional 72 h cell growth without nanoparticles. The dose of SPIONs used (15.4 μg Fe/ml) was selected as being sufficient for in vivo cell tracking using magnetic resonance imaging (MRI). Concerning cell viability and cell death, only the hBMSCs-2 seemed to be sensitive to the action of SPIONs. However, an increase of oxidative injury to lipids, proteins and DNA as a consequence of exposure to SPIONs was detected in cells from both donors. Particularly the levels of lipid peroxidation were high and increased further with time, regardless of the type of nanoparticle. Lowering intracellular label concentrations and authenticating oxidative stress levels using in vivo experiments are required to ensure the safety of SPIONs for biomedical applications.

Oxidative stress and antioxidant defense

Reactive oxygen species (ROS) are produced by living organisms as a result of normal cellular metabolism and environmental factors, such as air pollutants or cigarette smoke. ROS are highly reactive molecules and can damage cell structures such as carbohydrates, nucleic acids, lipids, and proteins and alter their functions. The shift in the balance between oxidants and antioxidants in favor of oxidants is termed “oxidative stress.” Regulation of reducing and oxidizing (redox) state is critical for cell viability, activation, proliferation, and organ function. Aerobic organisms have integrated antioxidant systems, which include enzymatic and nonenzymatic antioxidants that are usually effective in blocking harmful effects of ROS. However, in pathological conditions, the antioxidant systems can be overwhelmed. Oxidative stress contributes to many pathological conditions and diseases, including cancer, neurological disorders, atherosclerosis, hypertension, ischemia/perfusion, diabetes, acute respiratory distress syndrome, idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, and asthma. In this review, we summarize the cellular oxidant and antioxidant systems and discuss the cellular effects and mechanisms of the oxidative stress.

Protein separation by capillary gel electrophoresis: a review

Capillary gel electrophoresis (CGE) has been used for protein separation for more than two decades. Due to the technology advancement, current CGE methods are becoming more and more robust and reliable for protein analysis, and some of the methods have been routinely used for the analysis of protein-based pharmaceuticals and quality controls. In light of this progress, we survey 147 papers related to CGE separations of proteins and present an overview of this technology. We first introduce briefly the early development of CGE. We then review the methodology, in which we specifically describe the matrices, coatings, and detection strategies used in CGE. CGE using microfabricated channels and incorporation of CGE with two-dimensional protein separations are also discussed in this section. We finally present a few representative applications of CGE for separating proteins in real-world samples.

Biomarkers of oxidative stress in red blood cells

BACKGROUND

Exposure to high concentrations of oxygen radicals, the lack of nucleus and mitochrondria, inability to synthesise new protein and degradation of detoxifying enzymes makes red blood cells (RBCs) uniquely vulnerable to oxidative stress. This review summarizes the changes in biochemical parameters that primarily contribute to alterations in red blood cells during oxidative stress.

METHODS

PubMed, Science Direct and Springer online databases and updates from the Indian Council of Medical Research (ICMR).

RESULTS AND CONCLUSION

As one of the first cells to be affected by changes in the redox status of the body, alterations in red blood cells are widely used in first step-diagnoses of a number of pathological conditions. The information presented in this review provides an update on biomarkers of redox balance in red blood cells. These biomarkers may be used for assessment of oxidative stress during human health and disease.

Triangulated mal-signaling in Alzheimer's disease: roles of neurotoxic ceramides, ER stress, and insulin resistance reviewed

Ceramides are lipid signaling molecules that cause cytotoxicity and cell death mediated by insulin resistance, inflammation, and endoplasmic reticulum (ER) stress. However, insulin resistance dysregulates lipid metabolism, which promotes ceramide accumulation with attendant inflammation and ER stress. Herein, we discuss two major pathways, extrinsic and intrinsic, that converge and often overlap in propagating AD-type neurodegeneration via a triangulated mal-signaling network. First, we review evidence that systemic insulin resistance diseases linked to obesity, type 2 diabetes, and non-alcoholic steatohepatitis promote neurodegeneration. Mechanistically, we propose that toxic ceramides generated in extra-CNS tissues (e.g., liver) get released into peripheral blood, and subsequently transit across the blood-brain barrier into the brain where they induce brain insulin resistance, inflammation, and cell death (extrinsic pathway). Then we discuss the role of the intrinsic pathway of neurodegeneration which is mediated by endogenous or primary brain insulin/IGF resistance, and impairs neuronal and oligodendrocyte survival, energy metabolism, membrane integrity, cytoskeletal function, and AβPP-Aβ secretion. The end result is increased ER stress and ceramide generation, which exacerbate brain insulin resistance, cell death, myelin degeneration, and neuroinflammation. Altogether, the data suggest that the triangulated mal-signaling network mediated by toxic ceramides, ER stress, and insulin resistance should be targeted to disrupt positive feedback loops that drive the AD neurodegeneration cascade.

Association of Biomarkers for Inflammation, Endothelial Dysfunction and Oxidative Stress with Cognitive Impairment. The Epidemiology of Hearing Loss Study (EHLS)

BACKGROUND

Individual biomarkers of inflammation, endothelial dysfunction and oxidative stress have been associated with cognitive impairment. This study explored whether a combination of biomarkers could prospectively identify those who developed cognitive decline.

METHODS

Biomarkers were obtained during the baseline examination of the Beaver Dam Eye Study (1988-90), and cognitive status was assessed during the 5-year follow-up examination of the Epidemiology of Hearing Loss Study (1998-2000). Cognitive impairment was defined as a score of < 24 points on the Mini-Mental State Examination or self- or proxy report of Alzheimer Disease or dementia. Among those with cognitive data, interleukin-6, isoprostanes, protein carbonyl, soluble inter-cellular adhesion molecule-1 and vascular cell adhesion molecule-1 were available for 950 participants and 2,336 had high sensitivity C-reactive protein.

RESULTS

Biomarkers of inflammation and endothelial dysfunction were not associated with cognitive impairment. There was a weak inverse association between higher levels of protein carbonyl content and cognitive impairment (OR, 0.8 per quartile of protein carbonyl content, p=0.045 unadjusted for multiple comparisons). This was not significant on multiple testing and may have been a chance finding.

CONCLUSION

We found that many markers of inflammation and endothelial dysfunction were not associated with cognitive impairment. An inverse association with carbonyl protein, a marker of oxidative stress needs further confirmation.