Markers of protein oxidation by hydroxyl radical and reactive nitrogen species in tissues of aging rats

Oxidative Stress and Inflammatory Biomarkers for Populations with Occupational Exposure to Nanomaterials: A Systematic Review and Meta-Analysis

Exposure to nanomaterials (NMs) is suggested to have the potential to cause harmful health effects. Activations of oxidative stress and inflammation are assumed as main contributors to NM-induced toxicity. Thus, oxidative stress- and inflammation-related indicators may serve as biomarkers for occupational risk assessment. However, the correlation between NM exposure and these biomarkers remains controversial. This study aimed to perform a meta-analysis to systematically investigate the alterations of various biomarkers after NM exposure. Twenty-eight studies were found eligible by searching PubMed, EMBASE and Cochrane Library databases. The pooled results showed NM exposure was significantly associated with increases in the levels of malonaldehyde (MDA) [standardized mean difference (SMD) = 2.18; 95% confidence interval (CI), 1.50-2.87], 4-hydroxy-2-nonhenal (HNE) (SMD = 2.05; 95% CI, 1.13-2.96), aldehydes C6-12 (SMD = 3.45; 95% CI, 2.80-4.10), 8-hydroxyguanine (8-OHG) (SMD = 2.98; 95% CI, 2.22-3.74), 5-hydroxymethyl uracil (5-OHMeU) (SMD = 1.90; 95% CI, 1.23-2.58), o-tyrosine (o-Tyr) (SMD = 1.81; 95% CI, 1.22-2.41), 3-nitrotyrosine (3-NOTyr) (SMD = 2.63; 95% CI, 1.74-3.52), interleukin (IL)-1β (SMD = 1.76; 95% CI, 0.87-2.66), tumor necrosis factor (TNF)-α (SMD = 1.52; 95% CI, 1.03-2.01), myeloperoxidase (MPO) (SMD = 0.25; 95% CI, 0.16-0.34) and fibrinogen (SMD = 0.11; 95% CI, 0.02-0.21), and decreases in the levels of glutathione peroxidase (GPx) (SMD = -0.31; 95% CI, -0.52--0.11) and IL-6 soluble receptor (IL-6sR) (SMD = -0.18; 95% CI, -0.28--0.09). Subgroup analysis indicated oxidative stress biomarkers (MDA, HNE, aldehydes C6-12, 8-OHG, 5-OHMeU, o-Tyr, 3-NOTyr and GPx) in exhaled breath condensate (EBC) and blood samples were strongly changed by NM exposure; inflammatory biomarkers (IL-1β, TNF-α, MPO, fibrinogen and IL-6sR) were all significant in EBC, blood, sputum and nasal lavage samples. In conclusion, our findings suggest that these oxidative stress and inflammatory indicators may be promising biomarkers for the biological monitoring of occupationally NM-exposed workers.

The emerging role of the sympathetic nervous system in skeletal muscle motor innervation and sarcopenia

Examining neural etiologic factors'role in the decline of neuromuscular function with aging is essential to our understanding of the mechanisms underlying sarcopenia, the age-dependent decline in muscle mass, force and power. Innervation of the skeletal muscle by both motor and sympathetic axons has been established, igniting interest in determining how the sympathetic nervous system (SNS) affect skeletal muscle composition and function throughout the lifetime. Selective expression of the heart and neural crest derivative 2 gene in peripheral SNs increases muscle mass and force regulating skeletal muscle sympathetic and motor innervation; improving acetylcholine receptor stability and NMJ transmission; preventing inflammation and myofibrillar protein degradation; increasing autophagy; and probably enhancing protein synthesis. Elucidating the role of central SNs will help to define the coordinated response of the visceral and neuromuscular system to physiological and pathological challenges across ages. This review discusses the following questions: (1) Does the SNS regulate skeletal muscle motor innervation? (2) Does the SNS regulate presynaptic and postsynaptic neuromuscular junction (NMJ) structure and function? (3) Does sympathetic neuron (SN) regulation of NMJ transmission decline with aging? (4) Does maintenance of SNs attenuate aging sarcopenia? and (5) Do central SN group relays influence sympathetic and motor muscle innervation?

Oxygen and ROS in Photosynthesis

Oxygen is a natural acceptor of electrons in the respiratory pathway of aerobic organisms and in many other biochemical reactions. Aerobic metabolism is always associated with the formation of reactive oxygen species (ROS). ROS may damage biomolecules but are also involved in regulatory functions of photosynthetic organisms. This review presents the main properties of ROS, the formation of ROS in the photosynthetic electron transport chain and in the stroma of chloroplasts, and ROS scavenging systems of thylakoid membrane and stroma. Effects of ROS on the photosynthetic apparatus and their roles in redox signaling are discussed.

Untargeted UPLC-MS metabolomics reveals multiple changes of urine composition in healthy adult volunteers after consumption of curcuma longa L. extract

Curcuma longa L. is used as food supplement to prevent diseases, although limited studies have been performed on healthy subjects up to now. In the present work, an untargeted UPLC-MS metabolomics approach was applied to study the changes of 24-hours urinary composition on healthy volunteers due to a 28-days daily consumption of a dried C. longa extract containing a standardized amount of curcuminoids. Changes in the excretion of different metabolites were observed after supplementation. Curcumin and two metabolic derivatives (hexahydrocurcumin and dihydrocurcumin) were detected in urine, indicating the absorption of the main curcuminoid from the extract and its further metabolism by liver and gut microbiota. For the first time ar-turmerone, the main apolar constituent of curcuma, was detected in urine in intact form, and its presence was confirmed by a targeted GC-MS analysis. The increase of tetranor-PGJM and tetranor-PGDM, two prostaglandin-D2 metabolites, was observed, being related to the anti-inflammatory effect exerted by curcuma. The variation of the amounts of HPAG, PAG, proline-betaine and hydroxyphenyllactic acid indicate that the supplementation induced changes to the activity of gut microbiota. Finally, the reduced excretion of niacin metabolites (nicotinuric acid, trigonelline and 2PY) and medium- and short-chain acylcarnitines suggests that curcuma could induce the mitochondrial β-oxidation of fatty acids for energy production in healthy subjects. Overall, the results indicate that a prolonged daily consumption of a dried curcuma extract exerts multiple effects on healthy subjects, furthermore they show the opportunity offered by untargeted metabolomics for the study of the bioactivity of natural extracts in healthy human volunteers.

Analysis and Chemistry of Novel Protein Oxidation Markers in Vivo

Proteins continually undergo spontaneous oxidation reactions, which lead to changes in structure and function. The quantitative assessment of protein oxidation adducts provides information on the level of exposure to reactive precursor compounds with a high oxidizing potential and reactive oxygen species (ROS). In the present work, we introduce N⁶-(2-hydroxyethyl)lysine as a novel marker based on the ratio of glycolaldehyde and its oxidized form glyoxal. The high analytical potential was proven with a first set of patients undergoing hemodialysis versus healthy controls, in comparison with well-established parameters for oxidative stress. In vitro experiments with N¹- t-BOC-lysine and N¹- t-BOC-arginine enlightened the mechanistic relationship of glycolaldehyde and glyoxal. Oxidation was strongly dependent on the catalytic action of the ε-amino moiety of lysine. Investigations on the formation of N⁶-carboxymethyl lysine revealed glycolaldehyde-imine as the more reactive precursor, even though an additional oxidative step is required. As a result, a novel and very effective alternative mechanism was unraveled.

Role of Protein Carbonylation in Skeletal Muscle Mass Loss Associated with Chronic Conditions

Muscle dysfunction, characterized by a reductive remodeling of muscle fibers, is a common systemic manifestation in highly prevalent conditions such as chronic heart failure (CHF), chronic obstructive pulmonary disease (COPD), cancer cachexia, and critically ill patients. Skeletal muscle dysfunction and impaired muscle mass may predict morbidity and mortality in patients with chronic diseases, regardless of the underlying condition. High levels of oxidants may alter function and structure of key cellular molecules such as proteins, DNA, and lipids, leading to cellular injury and death. Protein oxidation including protein carbonylation was demonstrated to modify enzyme activity and DNA binding of transcription factors, while also rendering proteins more prone to proteolytic degradation. Given the relevance of protein oxidation in the pathophysiology of many chronic conditions and their comorbidities, the current review focuses on the analysis of different studies in which the biological and clinical significance of the modifications induced by reactive carbonyls on proteins have been explored so far in skeletal muscles of patients and animal models of chronic conditions such as COPD, disuse muscle atrophy, cancer cachexia, sepsis, and physiological aging. Future research will elucidate the specific impact and sites of reactive carbonyls on muscle protein content and function in human conditions.

Roles of the tyrosine isomers meta-tyrosine and ortho-tyrosine in oxidative stress

The damage to cellular components by reactive oxygen species, termed oxidative stress, both increases with age and likely contributes to age-related diseases including Alzheimer's disease, atherosclerosis, diabetes, and cataract formation. In the setting of oxidative stress, hydroxyl radicals can oxidize the benzyl ring of the amino acid phenylalanine, which then produces the abnormal tyrosine isomers meta-tyrosine or ortho-tyrosine. While elevations in m-tyrosine and o-tyrosine concentrations have been used as a biological marker of oxidative stress, there is emerging evidence from bacterial, plant, and mammalian studies demonstrating that these isomers, particularly m-tyrosine, directly produce adverse effects to cells and tissues. These new findings suggest that the abnormal tyrosine isomers could in fact represent mediators of the effects of oxidative stress. Consequently the accumulation of m- and o-tyrosine may disrupt cellular homeostasis and contribute to disease pathogenesis, and as result, effective defenses against oxidative stress can encompass not only the elimination of reactive oxygen species but also the metabolism and ultimately the removal of the abnormal tyrosine isomers from the cellular amino acid pool. Future research in this area is needed to clarify the biologic mechanisms by which the tyrosine isomers damage cells and disrupt the function of tissues and organs and to identify the metabolic pathways involved in removing the accumulated isomers after exposure to oxidative stress.

The Effects of Aging on Indices of Oxidative Stress and Apoptosis in the Female Fischer 344/Nnia X Brown Norway/BiNia Rat Heart

Oxidative-nitrosative stress may play a role in age-associated cardiovascular disease as implied by recent studies.However, limited research has been conducted using aged female rodent models. In this study, we examined hearts obtained from 6-, 26-, and 30-month old female Fischer 344/Nnia x Brown Norway/BiNia (F344xBN) rats in order to examine how aging affects levels of cardiac oxidative-nitrosative stress and apoptosis. Oxidative (superoxide anion and 4-HNE) and nitrosative (protein nitrosylation) stress markers were increased 180 ± 17 %, 110 ± 3 %, and 14 ± 2 %, respectively in 30-month hearts compared to the hearts of 6-month female rats. Coincident with these changes in oxidative-nitrosative stress, aging was also found to be associated with increases in the number of Tdt-mediated dUTP nick labeling (TUNEL)-positive cardiomyocytes, alterations in the Bax/Bcl-2 ratio, and elevated cleavage of caspase-3. Regression analysis demonstrates significant correlation in the age-associated changes markers of oxidative–nitrosative stress with changes in apoptotic signaling. The findings from this descriptive study imply that age-associated increases in mitochondrial-mediated apoptosis may be associated with the increase in oxidative-nitrosative stress in the aging F344xBN female heart.

Acute reversal of endothelial dysfunction in the elderly after antioxidant consumption

Aging is associated with a pro-oxidant state and a decline in endothelial function. Whether acute, enteral antioxidant treatment can reverse this decrement in vascular function is not well known. Flow-mediated vasodilation and reactive hyperemia were evaluated after consumption of either placebo or an oral antioxidant cocktail (vitamin C, 1000 mg; vitamin E, 600 IU; α-lipoic acid, 600 mg) in 87 healthy volunteers (42 young: 25±1 years; 45 older: 71±1 years) using a double-blind, crossover design. Blood velocity and brachial artery diameter (ultrasound Doppler) were assessed before and after 5-minute forearm circulatory arrest. Serum markers of lipid peroxidation, total antioxidant capacity, endogenous antioxidant activity, and vitamin C were assayed, and plasma nitrate, nitrite, and 3-nitrotyrosine were determined. In the placebo trial, an age-related reduction in brachial artery vasodilation was evident (young: 7.4±0.6%; older: 5.2±0.4%). After antioxidant consumption, flow-mediated vasodilation improved in older subjects (placebo: 5.2±0.4%; antioxidant: 8.2±0.6%) but declined in the young (placebo: 7.4±0.6%; antioxidant: 5.8±0.6%). Reactive hyperemia was reduced with age, but antioxidant administration did not alter the response in either group. Together, these data demonstrate that antioxidant consumption acutely restores endothelial function in the elderly while disrupting normal endothelium-dependent vasodilation in the young and suggest that this age-related impairment is attributed, at least in part, to free radicals.

Protein conjugated with aldehydes derived from lipid peroxidation as an independent parameter of the carbonyl stress in the kidney damage

BACKGROUND

One of the well-defined and characterized protein modifications usually produced by oxidation is carbonylation, an irreversible non-enzymatic modification of proteins. However, carbonyl groups can be introduced into proteins by non-oxidative mechanisms. Reactive carbonyl compounds have been observed to have increased in patients with renal failure. In the present work we have described a procedure designed as aldehyde capture to calculate the protein carbonyl stress derived solely from lipid peroxidation.

METHODS

Acrolein-albumin adduct was prepared as standard at alkaline pH. Rat liver microsomal membranes and serum samples from patients with diabetic nephropathy were subjected to the aldehyde capture procedure and aldol-protein formation. Before alkalinization and incubation, samples were precipitated and redisolved in 6M guanidine. The absorbances of the samples were read with a spectrophotometer at 266 nm against a blank of guanidine.

RESULTS

Evidence showed abundance of unsaturated aldehydes derived from lipid peroxidation in rat liver microsomal membranes and in the serum of diabetic patients with advanced chronic kidney disease. Carbonyl protein and aldol-proteins resulted higher in the diabetic nephropathy patients (p < 0.004 and p < 0.0001 respectively).

CONCLUSION

The aldehyde-protein adduct represents a non oxidative component of carbonyl stress, independent of the direct amino acid oxidation and could constitute a practical and novelty strategy to measure the carbonyl stress derived solely from lipid peroxidation and particularly in diabetic nephropathy patients. In addition, we are in a position to propose an alternative explanation of why alkalinization of urine attenuates rhabdomyolysis-induced renal dysfunction.

Experimental guidelines for studies designed to investigate the impact of antioxidant supplementation on exercise performance

Research interest in the effects of antioxidants on exercise-induced oxidative stress and human performance continues to grow as new scientists enter this field. Consequently, there is a need to establish an acceptable set of criteria for monitoring antioxidant capacity and oxidative damage in tissues. Numerous reports have described a wide range of assays to detect both antioxidant capacity and oxidative damage to biomolecules, but many techniques are not appropriate in all experimental conditions. Here, the authors present guidelines for selecting and interpreting methods that can be used by scientists to investigate the impact of antioxidants on both exercise performance and the redox status of tissues. Moreover, these guidelines will be useful for reviewers who are assigned the task of evaluating studies on this topic. The set of guidelines contained in this report is not designed to be a strict set of rules, because often the appropriate procedures depend on the question being addressed and the experimental model. Furthermore, because no individual assay is guaranteed to be the most appropriate in every experimental situation, the authors strongly recommend using multiple assays to verify a change in biomarkers of oxidative stress or redox balance.

Biophysics of Parkinson's disease: structure and aggregation of alpha-synuclein

Parkinson's disease (PD) is a slowly progressive movement disorder that results from the loss of dopaminergic neurons in the substantia nigra, a small area of cells in the mid-brain. PD is a multifactorial disorder with unknown etiology, in which both genetic and environmental factors play important roles. Substantial evidence links alpha-synuclein, a small highly conserved presynaptic protein with unknown function, to both familial and sporadic PD. Rare familial cases of PD are associated with missense point mutations in alpha-synuclein, or with the hyper-expression of the wild type protein due to its gene duplication/triplication. Furthermore, alpha-synuclein was identified as the major component of amyloid fibrils found in Lewy body and Lewy neurites, the characteristic proteinaceous deposits that are the diagnostic hallmarks of PD. alpha-Synuclein is abundant in various regions of the brain and has two closely related homologs, beta-synuclein and gamma-synuclein. When isolated in solution, the protein is intrinsically disordered, but in the presence of lipid surfaces alpha-synuclein adopts a highly helical structure that is believed to mediate its normal function(s). A number of different conformational states of alpha-synuclein have been observed. Besides the membrane-bound form, other critical conformations include a partially-folded state that is a key intermediate in aggregation and fibrillation, various oligomeric species, and fibrillar and amorphous aggregates. A number of intrinsic and extrinsic factors that either accelerate or inhibit the rate of alpha-synuclein aggregation and fibrillation in vitro are known. There is a strong correlation between the conformation of alpha-synuclein (induced by various factors) and its rate of fibrillation. The aggregation process appears to be branched, with one pathway leading to fibrils and another to oligomeric intermediates that may ultimately form amorphous deposits. The molecular basis of Parkinson's disease appears to be tightly coupled to the aggregation of alpha-synuclein and the factors that affect its conformation. This review focuses on the contributions of Prof. Anthony L. Fink to the field and presents some recent developments in this exciting area.

Oxidative stress in diabetes and Alzheimer's disease

Oxidative stress plays a major role in diabetes as well as in Alzheimer's disease and other related neurological diseases. Intracellular oxidative stress arises due to the imbalance in the production of reactive oxygen/reactive nitrogen species and cellular antioxidant defense mechanisms. In turn, the excess reactive oxygen/reactive nitrogen species mediate the damage of proteins and nucleic acids, which have been shown to have direct and deleterious consequences in diabetes and Alzheimer's disease. Oxidative stress also contributes to the production of advanced glycation end products through glycoxidation and lipid peroxidation. The advanced glycation end products and lipid peroxidation products are ubiquitous to diabetes and Alzheimer's disease and serve as markers of disease progression in both disorders. Antioxidants and advanced glycation end products inhibitors, either induced endogenously or exogenously introduced, may counteract with the deleterious effects of the reactive oxygen/reactive nitrogen species and thereby, in prevention or treatment paradigms, attenuate or substantially delay the onset of these devastating pathologies.

Quantitative proteomic profiling of muscle type-dependent and age-dependent protein carbonylation in rat skeletal muscle mitochondria

Carbonylation is a highly prevalent protein modification in skeletal muscle mitochondria, possibly contributing to its functional decline with age. Using quantitative proteomics, we identified mitochondrial proteins susceptible to carbonylation in a muscle type (slow- vs fast-twitch)-dependent and age-dependent manner from Fischer 344 rat skeletal muscle. Fast-twitch muscle contained twice as many carbonylated mitochondrial proteins than did slow-twitch muscle, with 22 proteins showing significant changes in carbonylation state with age, the majority of these increasing in their amount of carbonylation. Ingenuity pathway analysis revealed that these proteins belong to functional classes and pathways known to be impaired in muscle aging, including cellular function and maintenance, fatty acid metabolism, and citrate cycle. Although our studies do not conclusively link protein carbonylation to these functional changes in aging muscle, they provide a unique catalogue of promising protein targets deserving further investigation because of their potential role in aging muscle decline.

Mass spectrometric quantification of amino acid oxidation products identifies oxidative mechanisms of diabetic end-organ damage

Diabetes mellitus is increasingly prevalent worldwide. Diabetic individuals are at markedly increased risk for premature death due to cardiovascular disease. Furthermore, substantial morbidity results from microvascular complications which include retinopathy, nephropathy, and neuropathy. Clinical studies involving diabetic patients have suggested that degree of diabetic hyperglycemia correlates with risk of complications. Recent evidence implicates a central role for oxidative stress and vascular inflammation in all forms of insulin resistance, obesity, diabetes and its complications. Although, glucose promotes glycoxidation reactions in vitro and products of glycoxidation and lipoxidation are elevated in plasma and tissue in diabetics, the exact relationships among hyperglycemia, the diabetic state, and oxidative stress are not well-understood. Using a combination of in vitro and in vivo experiments, we have identified amino acid oxidation markers that serve as molecular fingerprints of specific oxidative pathways. Quantification of these products utilizing highly sensitive and specific gas chromatography/mass spectrometry in animal models of diabetic complications and in humans has provided insights in oxidative pathways that result in diabetic complications. Our studies strongly support the hypothesis that unique oxidants are generated in the microenvironment of tissues vulnerable to diabetic damage. Potential therapies interrupting these reactive pathways in target tissue are likely to be beneficial in preventing diabetic complications.

Aging results in increased autophagy of mitochondria and protein nitration in rat hepatocytes following heat stress

The natural breakdown of cells, tissues, and organ systems is a significant consequence of aging and is at least partially caused by a decreased ability to tolerate environmental stressors. Based on quantitative ultrastructural analysis using transmission electron microscopy and computer imaging, we show significant differences in hepatocyte morphology between young and old rats during a 48-hr recovery period following a 2-day heat stress protocol. Mitochondrial injury was greater overall in old compared with young rats. Autophagy was observed in both young and old rats, with autophagy greater overall in old compared with young hepatocytes. Lipid peroxidation and protein nitration were evaluated by localization and quantification of 4-hydroxy-2-nonenal (4-HNE)-modified protein adducts and 3-nitrotyrosine (3-NT) levels, respectively. Levels of 3-NT but not 4-HNE-protein adducts were significantly elevated in hepatocytes of old rats in comparison with young at 90 min after heat stress, suggesting a major role for reactive nitrogen species in the pathology observed at this time point. These results show a differential response of hepatocyte mitochondria to heat stress with aging, as well as greater levels of both autophagic and nitrative damage in old vs young hepatocytes. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials.

Synthesis of sulfonamide- and sulfonyl-phenylboronic acid-modified silica phases for boronate affinity chromatography at physiological pH

Two new types of boronate affinity solid phases were synthesized and characterized. The materials were prepared by silylation of porous silica gel with monochlorosilane derivatives containing synthetic sulfonyl- and sulfonamide-substituted phenylboronic acids. The new solid phases were evaluated for boronate affinity chromatography with aryl and alkyl cis-diol compounds and were found to be suitable for the retention of cis-diols under acidic conditions. Significant correlations between the retention factor (K) and the pH of the mobile phase demonstrate that the binding of cis-diols to the solid phases is best rationalized by chelation. Based on the lower pKa, caused by the electron-withdrawing effects of the sulfonyl and sulfonamide groups, these media display an enhanced affinity for cis-diols as compared with unsubstituted phenylboronic acid. Using isocratic elution, a mixture of various biologically relevant l-tyrosines, l-DOPA, and several catecholamines were resolved with a mobile phase composed of 0.05M phosphate buffer (pH 5.5). Mono-, di-, and triphosphates of adenosine were also separated at pH 6.0. Hence, the new boronate solid phase offers efficient affinity separation and purification of cis-diol-containing molecules under rather mild pH conditions.

Oxidative protein damage is associated with poor grip strength among older women living in the community

Grip strength, an indicator of muscle strength, has been shown to be a predictor of poor outcomes among older adults. Protein carbonylation, an indicator of oxidative damage to proteins, leads to cellular dysfunction and a decline in tissue function. Oxidative stress has been implicated in the pathogenesis of sarcopenia. The objective was to determine whether serum protein carbonyl concentrations are associated with grip strength in older women living in the community. A cross-sectional study was conducted in 672 women, aged 65 and older, from the Women's Health and Aging Study (WHAS) I, the one-third most disabled women residing in the community in Baltimore, MD. Protein carbonyl and grip strength were measured in each patient. In a multivariate analysis adjusting for age, race, body mass index, and Mini-Mental Status Examination score, protein carbonyls (nmol/mg) were associated with grip strength (beta = -6.77, P < 0.01). The statistical association was unchanged after the analysis adjusted for hypertension, congestive heart failure, and depression. Ordered logistic regression models adjusted for the above factors showed that protein carbonyls are associated with increased odds of being in the lower quartiles of grip strength (odds ratio 8.74, 95% confidence interval 1.06-71.89, P = 0.043). These results suggest oxidative protein damage is independently associated with low grip strength among older women living in the community. Increased oxidative stress may be contributing to loss of muscle strength in older adults.

Myosin and actin expression and oxidation in aging muscle

While the age-related loss in muscle mass partially explains the decline in strength, other yet undefined mechanisms contribute. This study investigates whether changes in myosin-actin stoichiometry and oxidative modification could help explain the decrement in muscle strength with aging. Protein expression and oxidation were evaluated in myosin and actin isolated from the soleus and semimembranosus muscles from young adult, old, and very old Fischer 344 rats. In the soleus muscle, actin and myosin content did not change with aging. In the semimembranosus, actin content was stable, but myosin exhibited decreased content in muscles from very old rats, resulting in a decrease in the myosin-to-actin ratio. 3-Nitrotyrosine and 4-hydroxy-2-nonenal were used as markers of protein oxidative damage. Although myosin and actin are modified with 3-nitrotyrosine and 4-hydroxy-2-nonenal, the extent of chemical modification does not increase with age. The results suggest that the decline in force production with age is not due to the accumulation of these two specific markers of protein oxidation on the myofibrillar proteins. Additionally, age-dependent changes in myofibrillar stoichiometry do not contribute to the decline in force production in the soleus, but may play a role in the semimembranosus with advanced age.

Oxidant activity in skeletal muscle fibers is influenced by temperature, CO2 level, and muscle-derived nitric oxide

Free radicals are produced continuously by skeletal muscle fibers. Extracellular release of reactive oxygen species (ROS) and nitric oxide (NO) derivatives has been demonstrated, but little is known about intracellular oxidant regulation. We used a fluorescent oxidant probe, 2',7'-dichlorofluorescin (DCFH), to assess net oxidant activity in passive muscle fiber bundles isolated from mouse diaphragm and studied in vitro. We tested the following three hypotheses. 1) Net oxidant activity is decreased by muscle cooling. 2) CO(2) exposure depresses intracellular oxidant activity. 3) Muscle-derived ROS and NO both contribute to overall oxidant activity. Our results indicate that DCFH oxidation was diminished by cooling muscle fibers from 37 degrees C to 23 degrees C (P < 0.001). The rate of DCFH oxidation correlated positively with CO(2) exposure (0-10%; P < 0.05) and negatively with concurrent changes in pH (7.0-8.5; P < 0.05). Separate exposures to anti-ROS enzymes (superoxide dismutase, 1 kU/ml; catalase, 1 kU/ml), a glutathione peroxidase mimetic (ebselen, 30 microM), NO synthase inhibitors (N(omega)-nitro-l-arginine methyl ester, 1 mM; N(omega)-monomethyl-l-arginine, 1 mM), or an NO scavenger (hemoglobin, 1 microM) each inhibited DCFH oxidation (P < 0.05). Oxidation was increased by hydrogen peroxide, 100 microM, an NO donor (NOC-22, 400 microM), or the substrate for NO synthase (l-arginine, 5 mM). We conclude that net oxidant activity in resting muscle fibers is 1) decreased at subphysiological temperatures, 2) increased by CO(2) exposure, and 3) influenced by muscle-derived ROS and NO derivatives to similar degrees.

A protein-chameleon: conformational plasticity of alpha-synuclein, a disordered protein involved in neurodegenerative disorders

Under the physiological conditions in vitro, alpha-synuclein, a conservative presynaptic protein, the aggregation and fibrillation of which is assumed to be involved into the pathogenesis of Parkinson's disease and several other neurodegenerative disorders, known as synucleinopathies, is characterized by the lack of rigid well-defined structure; i.e., it belongs to the class of intrinsically unstructured proteins. Intriguingly, alpha-synuclein is characterized by a remarkable conformational plasticity, adopting a series of different conformations depending on the environment. For example, this protein may either stay substantially unfolded, or adopt an amyloidogenic partially folded conformation, or fold into alpha-helical or beta-structural species, both monomeric and oligomeric. Furthermore, it might form several morphologically different types of aggregates, including oligomers (spheres or doughnuts), amorphous aggregates, and or amyloid-like fibrils. The peculiarities of this astonishing conformational behavior are analyzed to shed light on structural plasticity of this protein-chameleon.

Immunohistochemical detection of inducible nitric oxide synthase, nitrotyrosine and manganese superoxide dismutase following hyperglycemic focal cerebral ischemia

We have characterized the temporal changes in iNOS, MnSOD and nitrotyrosine immune reactivity in a rat model of permanent middle cerebral artery occlusion under acute hyperglycemic or normoglycemic conditions followed by either 3- or 24-h recovery. We found that the macroscopic labeling pattern for all three antibodies colocalized with the ischemic core and penumbra which was determined by cresyl violet histological evaluation in adjacent sections. Hyperglycemia induced prior to ischemia resulted in earlier infarction which correlated with increased immunoreactivity for iNOS, MnSOD and nitrotyrosine. In the penumbral region of the frontal cortex, labeling of specific cell structures was largely limited to cortical neurons near the corpus callosum and was apparent earlier in the hyperglycemic rats. Increased polymorphonuclear leukocyte adhesion in blood vessels was observed at 24 h in the hyperglycemic group. At both of the recovery times studied, we observed only minor vascular staining for nitrotyrosine and none for iNOS. Our results are consistent with hyperglycemia resulting in an early and concomitant increase in both superoxide and nitric oxide production which can lead to peroxynitrite formation that then nitrates tyrosine residues. It would appear that hyperglycemic ischemia contributes to the early induction of key enzymes involved in nitric oxide bioavailability.

Measurements of protein carbonyls, ortho- and meta-tyrosine and oxidative phosphorylation complex activity in mitochondria from young and old rats

Mitochondrial bioenergetic function is often reported to decline with age and the accumulation of oxidative damage is thought to contribute. However, there are considerable uncertainties about the amount and significance of mitochondrial oxidative damage in aging. We hypothesized that, as radical production in mitochondria is greater than the rest of the cell, protein oxidative damage should accumulate more in mitochondria than the cytoplasm, and that this relative accumulation should increase with age. To test these hypotheses we measured the accumulation of three markers of protein oxidative damage in liver, brain, and heart from young and old rats. Ortho- and meta-tyrosine levels in protein hydrolysates were measured by a gas chromatography/mass spectrometry assay, and protein carbonyl content was determined by ELISA. Using these assays we found no evidence for increased protein oxidative damage in mitochondria relative to the cytosol. Most increases found in protein oxidative damage on aging were modest for all three tissues and there was no consistent pattern of increased oxidative damage in mitochondrial proteins on aging. Mitochondrial oxidative phosphorylation complex activities were also assessed revealing 39-42% decreases in F0F1--ATP synthase activity in liver and heart on aging, but not in other oxidative phosphorylation complexes. These findings have implications for the contribution of mitochondrial oxidative damage and dysfunction to aging.

Enhanced peroxynitrite formation is associated with vascular aging

Vascular aging is mainly characterized by endothelial dysfunction. We found decreased free nitric oxide (NO) levels in aged rat aortas, in conjunction with a sevenfold higher expression and activity of endothelial NO synthase (eNOS). This is shown to be a consequence of age-associated enhanced superoxide (.O(2)(-)) production with concomitant quenching of NO by the formation of peroxynitrite leading to nitrotyrosilation of mitochondrial manganese superoxide dismutase (MnSOD), a molecular footprint of increased peroxynitrite levels, which also increased with age. Thus, vascular aging appears to be initiated by augmented.O(2)(-) release, trapping of vasorelaxant NO, and subsequent peroxynitrite formation, followed by the nitration and inhibition of MnSOD. Increased eNOS expression and activity is a compensatory, but eventually futile, mechanism to counter regulate the loss of NO. The ultrastructural distribution of 3-nitrotyrosyl suggests that mitochondrial dysfunction plays a major role in the vascular aging process.

Caloric restriction of rhesus monkeys lowers oxidative damage in skeletal muscle

In laboratory rodents, caloric restriction (CR) retards several age-dependent physiological and biochemical changes in skeletal muscle, including increased steady-state levels of oxidative damage to lipids, DNA, and proteins. We used immunogold electron microscopic (EM) techniques with antibodies raised against 4-hydroxy-2-nonenal (HNE) -modified proteins, dinitrophenol, and nitrotyrosine to quantify and localize the age-dependent accrual of oxidative damage in rhesus monkey vastus lateralis skeletal muscle. Using immunogold EM analysis of muscle from rhesus monkeys ranging in age from 2 to 34 years old, a fourfold maximal increase in levels of HNE-modified proteins was observed. Likewise, carbonyl levels increased approximately twofold with aging. Comparing 17- to 23-year-old normally fed to age-matched monkeys subjected to CR for 10 years, levels of HNE-modified proteins, carbonyls, and nitrotyrosine in skeletal muscle from the CR group were significantly less than control group values. Oxidative damage largely localized to myofibrils, with lesser labeling in other subcellular compartments. Accumulation of lipid peroxidation-derived aldehydes, such as malondialdehyde and 4-hydroxy-2-alkenals, and protein carbonyls were measured biochemically and confirmed the morphological data. Our study is the first to quantify morphologically and localize the age-dependent accrual of oxidative damage in mammalian skeletal muscle and to demonstrate that oxidative damage in primates is lowered by CR.

Quantification of 3-nitrotyrosine in biological tissues and fluids: generating valid results by eliminating artifactual formation

Reactive nitrogen species such as peroxynitrite can nitrate specific amino acids, whether free or protein bound, and 3-nitrotyrosine is believed to be one marker of this reaction. To examine the significance of this pathway in biological systems we have developed an accurate, sensitive, and specific assay for 3-nitrotyrosine based on combined liquid chromatography tandem mass spectrometry. Our approach allowed simultaneous analysis of both tyrosine and 3-nitrotyrosine and employs isotopomer standards (i.e., [15N1, 13C9]-tyrosine and [13C6]-3nitrotyrosine). Calibration curves were linear (r2 = 0.999) across the range 0.5-100 pg/microL (i.e., 2.2-442 fmol/microL), and the detection limit for standard samples was 0.5 pg/microL (2.2 fmol/microL, or 10 fmol on column; S/N = 5) or 1 pg/microL (4.4 fmol/microL) for extracted (biological) samples. As a component of this study we have undertaken an extensive investigation of artifactual formation of 3-nitrotyrosine under conditions that exist during sample extraction and derivatization. Our studies show that under appropriate conditions (low pH, elevated temperatures, and in the presence of a vast excess of the two substrates, tyrosine and the nitrate anion), 3-nitrotyrosine can readily be formed as an artifact.