Superoxide radical formation and associated biochemical alterations in the plasma membrane of brain, heart, and liver during the lifetime of the rat

Aged gut microbiota contribute to different changes in antioxidant defense in the heart and liver after transfer to germ-free mice

Age-associated impairment in antioxidant defense is an important cause of oxidative stress, and elderly individuals are usually associated with gut microbiota (GM) changes. Studies have suggested a potential relationship between the GM and changes in antioxidant defense in aging animals. Direct evidence regarding the impact of aging-associated shifts in GM on the antioxidant defense is lacking. The heart is a kind of postmitotic tissue, which is more prone to oxidative stress than the liver (mitotic tissue). To test and compare the influence of an aged GM on antioxidant defense changes in the heart and liver of the host, in this study, GM from young adolescent (5 weeks) or aged (20 months) mice was transferred to young adolescent (5 weeks) germ-free (GF) mice (N = 5 per group) by fecal microbiota transplantation (FMT). Four weeks after the first FMT was performed, fecal samples were collected for 16S rRNA sequencing. Blood, heart and liver samples were harvested for oxidative stress marker and antioxidant defense analysis. The results showed that mice that received young or aged microbiota showed clear differences in GM composition and diversity. Mice that received aged microbiota had a lower ratio of Bacteroidetes/Firmicutes in GM at the phylum level and an increased relative abundance of four GM genera: Akkermansia, Dubosiella, Alistipes and Rikenellaceae_RC9_gut_group. In addition, GM α-diversity scores based on the Shannon index and Simpson index were significantly higher in aged GM-treated mice. Oxidative stress marker and antioxidant defense tests showed that FMT from aged donors did not have a significant influence on malondialdehyde content in serum, heart and liver. However, the capacity of anti-hydroxyl radicals in the heart and liver, as well as the capacity of anti-superoxide anions in the liver, were significantly increased in mice with aged microbiota. FMT from aged donors increased the activities of Cu/Zn superoxide SOD (Cu/Zn-SOD), catalase (CAT) and glutathione-S-transferase in the heart, as well as the activity of Cu/Zn-SOD in the liver. Positive correlations were found between Cu/Zn-SOD activity and radical scavenging capacities. On the other hand, glutathione reductase activity and glutathione content in the liver were decreased in mice that received aged GM. These findings suggest that aged GM transplantation from hosts is sufficient to influence the antioxidant defense system of young adolescent recipients in an organ-dependent manner, which highlights the importance of the GM in the aging process of the host.

The effect of balneotherapy on the oxidative system and changes in anxiety behavior, enhanced by low doses of radon

PURPOSE

The aim of our research was to study the effect of radon hormesis balneotherapy using natural thermal waters of Tskaltubo spring, practically, its effect on oxidant and antioxidant systems and anxiety reactions in rats. Radon is a natural gas with radioactive properties, which can have a hermetic effect when used in small doses. Radon was used to activate antioxidant mechanisms in rats, which resulted an anxiolytic effect and positively enhanced the effect of balneotherapy.

MATERIALS AND METHODS

To study the effect of radon in balneotherapy, groups of experimental animals (rats) were exposed to three different treatments. The radon-containing waters of Tskaltubo spring were inhaled in one group and 5 after taking the water in another group. Saline was used for inhalation in animals of the saline group. In animals of the control and sham control groups, inhalation was not used. To assess the anxiolytic effect of radon inhalation, the anxiety was induced and behavioral tests were performed (the open field and the elevated plus-maze test) after 24 h and 5 days of inhalation procedures.

RESULTS

The anxiety test results showed that exposure to low doses of radon led to a decrease in the level of anxiety in rats. The data show that the total distance traveled by rats in the open field test after inhalation of radon was significantly greater than that by animals in the sham control and control groups. During the open field and elevated plus-maze tests, rats that had inhaled radon spent more time in the central part of the open field and on the open arms of the maze than did the other groups of rats. In the group of rats that had not inhaled radon, an increase in anxiety was observed. The basis of this reaction was an increase in the glutathione concentration.

CONCLUSION

Based on our research, it can be concluded that the inhalation of small doses of radon, associated with treatments of waters from the Tskaltubo spring, activated the antioxidant systems of the body and enhanced the positive effect of balneotherapy. Clinically, this is expressed as a decrease in anxiety. Inhalation of small doses of radon activated antioxidant processes in the brain, causing an increase in glutathione/glutathione disulfide ratio in the brain.

Age-dependent membrane release and degradation of full-length glycosylphosphatidylinositol-anchored proteins in rats

Glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) are associated with the surface of eucaryotic cells only through a covalently coupled carboxy-terminal GPI glycolipid structure which is anchored at the outer leaflet of plasma membranes. This mode of membrane association may be responsible for the recent observations that full-length GPI-APs harbouring the complete GPI anchor are (i) released from isolated rat adipocytes in vitro and (ii) expressed in rat and human serum. The upregulation of the adipocyte release in response to increased cell size and blood glucose/insulin levels of the donor rats and downregulation of the expression in serum of insulin resistant and diabetic rats have been reconciled with enhanced degradation of the full-length GPI-APs released into micelle-like complexes together with (lyso) phospholipids and cholesterol by serum GPI-specific phospholipase D (GPI-PLD). Here by using a sensitive and reliable sensing method for full-length GPI-APs, which relies on surface acoustic waves propagating over microfluidic chips, the upregulation of (i) the release of the full-length GPI-APs CD73, alkaline phosphatase and CD55 from isolated adipocyte plasma membranes monitored in a "lab-on-the-chip" configuration, (ii) their release from isolated rat adipocytes into the incubation medium and (iii) the lipolytic cleavage of their GPI anchors in serum was demonstrated to increase with age (3-16 weeks) and body weight (87-477 g) of (healthy) donor rats. In contrast, the amount of full-length GPI-APs in rat serum, as determined by chip-based sensing, turned out to decline with age/body weight. These correlations suggest that age-/weight-induced alterations (in certain biophysical/biochemical characteristics) of plasma membranes are responsible for the release of full-length GPI-APs which becomes counteracted by elevated GPI-PLD activity in serum. Thus, sensitive and specific measurement of these GPI-AP-relevant parameters may be useful for monitoring of age-related cell surface changes, in general, and diseases, in particular.

Iron status and oxidative stress in the aged rabbit heart

Altered iron status may be relevant to the pathophysiology of aging. We have assessed redox-active catalytic low molecular weight iron (LMWI), non-heme iron (NHI), heme iron (HI), and total iron (TI) in the aerobically perfused hearts of aged rabbits (AR, about 4.5years old) and young adult control rabbits (YACR, 3-4months old); myocardial lipid and protein oxidations were also assessed as oxidative stress biomarkers. The levels of LMWI and NHI, as well as of lipid and protein oxidation, were higher, while HI content was lower, in the hearts of AR than in those of YACR; TI did not differ significantly between the two groups. Together with these findings, hemodynamic dysfunction, namely heightened end-diastolic pressure (EDP) and lowered coronary flow (CF), occurred in the AR hearts. Notably, such pattern of hemodynamic dysfunction associated with myocardial oxidant damage occurred in the hearts of other YACR perfused in the presence of a cell-permeable form of iron, i.e., the iron/hydroxyquinoline complex, pointing to the involvement of catalytic iron in the aged heart damage. Moreover, as shown in other AR, heart perfusion in the presence of the iron chelator deferoxamine (0.6mM or 3.6mM) reduced the myocardial levels of LMWI, without significantly affecting those of NHI, HI, and TI; concomitantly, in AR deferoxamine lowered myocardial lipid and protein oxidation, and reduced EDP with a tendency to augment CF. Instead, deferoxamine, even at high concentration of 3.6mM, had no significant effects in the YACR. In conclusion, altered iron status with catalytic LMWI burden occurs in the aged rabbit heart, eventually resulting in iron-dependent cardiac oxidative stress and hemodynamic dysfunction.

Changes of Klotho protein and Klotho mRNA expression in a hydroxy-L-proline induced hyperoxaluric rat model

Klotho protein is recognized as having a renoprotective effect and is used as a biomarker for kidney injury. We investigated the level of Klotho protein in hyperoxaluria-induced kidney injury and the effects of vitamin E (Vit E) and vitamin C (Vit C) supplementation. Hyperoxaluria was induced by feeding 2% (w/v) Hydroxy-L-proline (HLP) in the drinking water for 21 days. Rats were divided into 5 groups; control (Group 1, n=7), HLP treated rats that received nothing else (Group 2, n=7), Vit E (Group 3, n=6), Vit C (Group 4, n=6) and both Vit E and Vit C (Group 5, n=7). Vit E (200 mg/kg) was injected on days 1, 6, 11 and 16, while Vit C (500 mg/kg) was given intravenously on days 1 and 11. The Klotho protein levels and oxidative status were measured. The expression level of kidney Klotho protein expression was significantly reduced by HLP-treatment, while the mRNA expression was higher (P<0.05), the plasma and kidney malondialdehyde and kidney superoxide dismutase activities were increased, and the kidney reduced glutathione and urinary total antioxidant status were decreased (P<0.05). All of these changes were ameliorated by administration of Vit E, Vit C or especially the co-administration of both. In conclusion, HLP-induced hyperoxaluria reduced the kidney Klotho protein level, which could be restored by Vit E and/or Vit C.

Sarcolemmal dependence of cardiac protection and stress-resistance: roles in aged or diseased hearts

Disruption of the sarcolemmal membrane is a defining feature of oncotic death in cardiac ischaemia-reperfusion (I-R), and its molecular makeup not only fundamentally governs this process but also affects multiple determinants of both myocardial I-R injury and responsiveness to cardioprotective stimuli. Beyond the influences of membrane lipids on the cytoprotective (and death) receptors intimately embedded within this bilayer, myocardial ionic homeostasis, substrate metabolism, intercellular communication and electrical conduction are all sensitive to sarcolemmal makeup, and critical to outcomes from I-R. As will be outlined in this review, these crucial sarcolemmal dependencies may underlie not only the negative effects of age and common co-morbidities on myocardial ischaemic tolerance but also the on-going challenge of implementing efficacious cardioprotection in patients suffering accidental or surgically induced I-R. We review evidence for the involvement of sarcolemmal makeup changes in the impairment of stress-resistance and cardioprotection observed with ageing and highly prevalent co-morbid conditions including diabetes and hypercholesterolaemia. A greater understanding of membrane changes with age/disease, and the inter-dependences of ischaemic tolerance and cardioprotection on sarcolemmal makeup, can facilitate the development of strategies to preserve membrane integrity and cell viability, and advance the challenging goal of implementing efficacious 'cardioprotection' in clinically relevant patient cohorts. Linked Articles This article is part of a themed section on Molecular Pharmacology of G Protein-Coupled Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v173.20/issuetoc.

Radical Oxygen Species, Exercise and Aging: An Update

It is now well established that reactive oxygen species (ROS) play a dual role as both deleterious and beneficial species. In fact, ROS act as secondary messengers in intracellular signalling cascades; however, they can also induce cellular senescence and apoptosis. Aging is an intricate phenomenon characterized by a progressive decline in physiological functions and an increase in mortality, which is often accompanied by many pathological diseases. ROS are involved in age-associated damage to macromolecules, and this may cause derangement in ROS-mediated cell signalling, resulting in stress and diseases. Moreover, the role of oxidative stress in age-related sarcopenia provides strong evidence for the important contribution of physical activity to limit this process. Regular physical activity is considered a preventive measure against oxidative stress-related diseases. The aim of this review is to summarize the currently available studies investigating the effects of chronic and/or acute physical exercise on the oxidative stress process in healthy elderly subjects. Although studies on oxidative stress and physical activity are limited, the available information shows that acute exercise increases ROS production and oxidative stress damage in older adults, whereas chronic exercise could protect elderly subjects from oxidative stress damage and reinforce their antioxidant defences. The available studies reveal that to promote beneficial effects of physical activity on oxidative stress, elderly subjects require moderate-intensity training rather than high-intensity exercise.

Saussurea involucrata: A review of the botany, phytochemistry and ethnopharmacology of a rare traditional herbal medicine

ETHNOPHARMACOLOGICAL RELEVANCE

Saussurea involucrata Matsum. & Koidz. is an endangered species of the Asteraceae family, growing in the high mountains of central Asia. It has been, and is, widely used in traditional Uyghur, Mongolian and Kazakhstan medicine as well as in Traditional Chinese Medicine as Tianshan Snow Lotus (Chinese: ). In traditional medical theory, S. involucrata can promote blood circulation, thereby alleviating all symptoms associated with poor circulation. It also reputedly eliminates cold and dampness from the body, diminishes inflammation, invigorates, and strengthens Yin and Yang. It has long been used to treat rheumatoid arthritis, cough with cold, stomach ache, dysmenorrhea, and altitude sickness in Uyghur and Chinese medicine.

AIM OF THE REVIEW

To comprehensively summarize the miscellaneous research that has been done regarding the botany, ethnopharmacology, phytochemistry, biological activity, and toxicology of S. involucrata.

METHOD

An extensive review of the literature was carried out. Apart from different electronic databases including SciFinder, Chinese National Knowledge Infrastructure (CNKI), ScienceDirect that were sourced for information, abstracts, full-text articles and books written in English and Chinese, including those traditional records tracing back to the Qing Dynasty. Pharmacopoeia of China and other local herbal records in Uighur, Mongolian and Kazakhstan ethnomedicines were investigated and compared for pertinent information.

RESULTS

The phytochemistry of S. involucrata has been comprehensively investigated. More than 70 compounds have been isolated and identified; they include phenylpropanoids, flavonoids, coumarins, lignans, sesquiterpenes, steroids, ceramides, polysaccharides. Scientific studies on the biological activity of S. involucrata are equally numerous. The herb has been shown to have anti-neoplastic, anti-inflammatory, analgesic, anti-oxidative, anti-fatigue, anti-aging, anti-hypoxic, neuroprotective and immunomodulating effects. Many have shown correlations to the traditional clinical applications in Traditional Chinese Medicine and medicines. The possible mechanisms of S. involucrata in treating various cancers are revealed in the article, these include inhibition of cancer cells by affecting their growth, adhesion, migration, aggregation and invasion, inhibition of epidermal growth factor receptor signaling in cancer cells, hindrance of cancer cell proliferation, causing cytotoxicity to cancer cells and promoting expression of tumor suppressor genes. Dosage efficacy is found to be generally concentration- and time-dependent. However, studies on the correlation between particular chemical constituents and specific bioactivities are limited.

CONCLUSION

In this review, we have documented the existing traditional uses of S. involucrata and summarized recent research into the phytochemistry and pharmacology of S. involucrata. Many of the traditional uses have been validated by phytochemical and modern pharmacological studies but there are still some areas where the current knowledge could be improved. Although studies have confirmed that S. involucrata has a broad range of bioactivities, further in-depth studies on the exact bioactive molecules and the mechanism of action are expected. Whether we should use this herb independently or in combination deserves to be clarified. The exact quality control as well as the toxicology studies is necessary to guarantee the stability and safety of the clinic use. The sustainable use of this endangered resource was also addressed. In conclusion, this review was anticipated to highlight the importance of S. involucrata and provides some directions for the future development of this plant.

Mechanisms of superoxide signaling in epigenetic processes: relation to aging and cancer

Superoxide is a precursor of many free radicals and reactive oxygen species (ROS) in biological systems. It has been shown that superoxide regulates major epigenetic processes of DNA methylation, histone methylation, and histone acetylation. We suggested that superoxide, being a radical anion and a strong nucleophile, could participate in DNA methylation and histone methylation and acetylation through mechanism of nucleophilic substitution and free radical abstraction. In nucleophilic reactions superoxide is able to neutralize positive charges of methyl donors S-adenosyl-L-methionine (SAM) and acetyl-coenzyme A (AcCoA) enhancing their nucleophilic capacity or to deprotonate cytosine. In the reversed free radical reactions of demethylation and deacetylation superoxide is formed catalytically by the (Tet) family of dioxygenates and converted into the iron form of hydroxyl radical with subsequent oxidation and final eradication of methyl substituents. Double role of superoxide in these epigenetic processes might be of importance for understanding of ROS effects under physiological and pathological conditions including cancer and aging.

Stroke neuroprotection: targeting mitochondria

Stroke is the fourth leading cause of death and the leading cause of long-term disability in the United States. Blood flow deficit results in an expanding infarct core with a time-sensitive peri-infarct penumbra that is considered salvageable and is the primary target for treatment strategies. The only current FDA-approved drug for treating ischemic stroke is recombinant tissue plasminogen activator (rt-PA). However, this treatment is limited to within 4.5 h of stroke onset in a small subset of patients. The goal of this review is to focus on mitochondrial-dependent therapeutic agents that could provide neuroprotection following stroke. Dysfunctional mitochondria are linked to neurodegeneration in many disease processes including stroke. The mechanisms reviewed include: (1) increasing ATP production by purinergic receptor stimulation, (2) decreasing the production of ROS by superoxide dismutase, or (3) increasing antioxidant defenses by methylene blue, and their benefits in providing neuroprotection following a stroke.

Omega-3 fatty acids enhance mitochondrial superoxide dismutase activity in rat organs during post-natal development

The protection of the developing organism from oxidative damage is ensured by antioxidant defense systems to cope with reactive oxygen species (ROS), which in turn can be influenced by dietary polyunsaturated fatty acids (PUFAs). PUFAs in membrane phospholipids are substrates for ROS-induced peroxidation reactions. We investigated the effects of dietary supplementation with omega-3 PUFAs on lipid peroxidation and antioxidant enzyme activities in rat cerebrum, liver and uterus. Pups born from dams fed a diet low in omega-3 PUFAs were fed at weaning a diet supplying low α-linolenic acid (ALA), adequate ALA or enriched with eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA). Malondialdehyde (MDA), a biomarker of lipid peroxidation, and the activities of superoxide dismutase 1 (SOD1), SOD2, catalase (CAT) and glutathione peroxidase (GPX) were determined in the three target organs. Compared to low ALA feeding, supplementation with adequate ALA or with EPA+DHA did not affect the cerebrum MDA content but increased MDA content in liver. Uterine MDA was increased by the EPA+DHA diet. Supplementation with adequate ALA or EPA+DHA increased SOD2 activity in the liver and uterus, while only the DHA diet increased SOD2 activity in the cerebrum. SOD1, CAT and GPX activities were not altered by ALA or EPA+DHA supplementation. Our data suggest that increased SOD2 activity in organs of the growing female rats is a critical determinant in the tolerance to oxidative stress induced by feeding a diet supplemented with omega-3 PUFAs. This is may be a specific cellular antioxidant response to ROS production within the mitochondria.

The Free Radical Theory of Aging and a Look at Changes in the Hypothalamus

Selon la théorie du radical libre, le vieillissement est produit par l'effet endommageant des radicaux d'oxygène. Ces radicaux sont produits de façon constante et deviennent toxiques quand le niveau de la concentration intracellulaire devient élevé. Malgré cet effet d'infamie, des études récentes indiquent qu'ils peuvent avoir un côté bénéfique en régulant certains mécanismes dans une cellule. Mais, avec le vieillissement, il semble que la capacité de réguler la concentration intracellulaire s'abaisse, et l'élévation du niveau devient toxique avec le temps. Il faut aussi examiner les effets endommageant des radicaux libres sur un niveau supérieur. À cause de la prééminence de l'hypothalamus comme centre régulateur homéostatique, il est possible que l'hypothalamus puisse jouer un rôle critique dans le processus de vieillissement. La perte progressive des fonctions dans ce centre peut mener à des changements systémiques qui peuvent provoquer des perturbations dans tout l'organisme.

Effect of the long-term intake of an egg white hydrolysate on the oxidative status and blood lipid profile of spontaneously hypertensive rats

This paper examines the effects of the long-term consumption of egg white hydrolysed with pepsin (hEW) on the antioxidant status and lipid profile of spontaneously hypertensive rats (SHR). The antioxidant capacity was measured by the oxygen radical absorbance capacity (ORAC) and the oxidative status by the malon-dialdehyde (MDA) assay. The lipid profile was analysed spectrophotometrically. The radical-scavenging capacity of the plasma was increased and the MDA concentration in the aorta was decreased in the SHR treated with 0.5g/kg/day of hEW. Our findings indicate that hEW played an important role in antioxidative defence of SHR and exerted a beneficial effect on the lipid profile, lowering triglycerides and total cholesterol without changing HDL levels. Therefore, hEW may be useful to prevent or reverse abnormalities associated with the metabolic syndrome and its complications, such as hypertension, oxidative stress and hyperlipidemia.

Life and death: metabolic rate, membrane composition, and life span of animals

Maximum life span differences among animal species exceed life span variation achieved by experimental manipulation by orders of magnitude. The differences in the characteristic maximum life span of species was initially proposed to be due to variation in mass-specific rate of metabolism. This is called the rate-of-living theory of aging and lies at the base of the oxidative-stress theory of aging, currently the most generally accepted explanation of aging. However, the rate-of-living theory of aging while helpful is not completely adequate in explaining the maximum life span. Recently, it has been discovered that the fatty acid composition of cell membranes varies systematically between species, and this underlies the variation in their metabolic rate. When combined with the fact that 1) the products of lipid peroxidation are powerful reactive molecular species, and 2) that fatty acids differ dramatically in their susceptibility to peroxidation, membrane fatty acid composition provides a mechanistic explanation of the variation in maximum life span among animal species. When the connection between metabolic rate and life span was first proposed a century ago, it was not known that membrane composition varies between species. Many of the exceptions to the rate-of-living theory appear explicable when the particular membrane fatty acid composition is considered for each case. Here we review the links between metabolic rate and maximum life span of mammals and birds as well as the linking role of membrane fatty acid composition in determining the maximum life span. The more limited information for ectothermic animals and treatments that extend life span (e.g., caloric restriction) are also reviewed.

Protective effects of Glycyrrhiza uralensis Fisch. on the cognitive deficits caused by beta-amyloid peptide 25-35 in young mice

Amyloid beta protein (Abeta) may be involved in the progression of Alzheimer's disease (AD), by acting as a neurotoxin and eliciting oxidative stress. This study was designed to determine the effects of Glycyrrhiza uralensis Fisch. water extract (GWE) on the cognitive deficits and oxidative stress induced by the administration of Abeta(25-35) in mice. Mice in two of the four animal groups were fed an experimental diet containing either 0.5 or 1% GWE for the entire 6-week experimental period. Control mice and a further experimental group were fed a non-GWE diet. Abeta(25-35) was administered to the three experimental groups by intracerebroventricular (i.c.v.) injection (10 microg/10 microl/mouse) once per week in weeks 5 and 6 of the experimental period. Behavioral changes were assessed using both a passive avoidance (after the injection of Abeta(25-35) in week 5) and the Morris water-maze tests (after the injection of Abeta(25-35) in week 6). Control animals were administered vehicle alone. The prolonged consumption of a diet containing GWE ameliorated the cognitive deficits caused by the i.c.v. injections of Abeta(25-35). Treatment with Abeta(25-35) led to higher concentrations of thiobarbituric acid reactive substances in the brain, and GWE attenuated this response. There was a decrease in catalase activity in the group provided with 1% GWE. Acetylcholinesterase activity was significantly reduced in the brains of all GWE-treated animals compared to that in the non-GWE-fed experimental group. These results suggest that GWE exerts a protective effect against the cognitive impairments often observed in AD, and that in mice this effect is mediated by antioxidant actions against oxidative stress.

Ca2+ signaling, mitochondria and sensitivity to oxidative stress in aging astrocytes

Age-related changes in astrocytes that could potentially affect neuroprotection have been largely unexplored. To test whether astrocyte function was diminished during the aging process, we examined cell growth, Ca2+ signaling, mitochondrial membrane potential (DeltaPsi) and neuroprotection of NGF-differentiated PC12 cells. We observed that cell growth was significantly slower for astrocytes cultured from old (26-29 months) mice as compared to young (4-6 months) mice. DeltaPsis in old astrocytes were also more depolarized (lower) than in young astrocytes and old astrocytes showed greater sensitivity to the oxidant tert-butyl hydrogen peroxide (t-BuOOH). ATP-induced Ca2+ responses in old astrocytes were consistently larger in amplitude and more frequently oscillatory than in young astrocytes, which may be attributable to lower mitochondrial Ca2+ sequestration. Finally, NGF-differentiated PC12 cells that were co-cultured with old astrocytes were significantly more sensitive to t-BuOOH treatment than co-cultures of NGF-differentiated PC12 cells with young astrocytes. Together, these data demonstrate that astrocyte physiology is significantly altered during the aging process and that the astrocyte's ability to protect neurons is compromised.

Effect of age on lipid peroxidation in a short-lived species of reptile, Calotes versicolor

The lipid peroxidation potential, measured as a thiobarbituric acid-reactive substance (TBA-RS) increased with advancing age in liver, brain and kidney of a short-lived species of reptile, Calotes versicolor. The same parameter did not show a significant change in an ageing heart. The pattern of age changes in lipid peroxidation potential in this species shows similarity with the findings in a majority of mammalian species. While suggesting a commonality in a basic mechanism of ageing between reptiles and mammals, the results also partially support the free radical theory of ageing.

Short-term mental activation accelerates the age-related decline of high-energy phosphates in rat cerebral cortex

Aging in rats is associated with a significant decline in brain levels of energy-rich phosphates, including ATP and creatine phosphate. To test the effects of transient mental activity mediated by psychometric testing, and of metabolic inhibition of pyruvate dehydrogenase (PDH) (an enzyme complex that generates acetyl coenzyme A (CoA) to feed the mitochondrial tricarboxylic acid cycle), we compared adult (52 to 64-week-old) and aged (104-week-old) rats with and without intracerebral injections of the PDH inhibitor, bromopyruvate (BP), in the presence and in the absence of extensive psychometric testing by standard passive avoidance and hole board test paradigms. As compared with mental rest, short-term mental activation was associated with higher levels of energy-rich phosphates in the cerebral cortex of both adult and aged animals, but did not prevent the age-dependent decline in these phosphates. ATP turnover was markedly increased by mental activity, but was less pronounced in aged animals. In the hippocampus, less marked changes in the energy pool became obvious. The abnormalities in energy metabolism indicate an age-dependent and stress-accentuated reduction of the capacity to meet such energy-dependent demands as mixed function oxidation in the aged brain. BP did not change brain levels of energy-rich phosphates, indicating that the damage caused by decreased PDH activity can be compensated for both in adult and in aged animals.

Cyclooxygenase-mediated generation of free radicals during hypoxia in the cerebral cortex of newborn piglets

Previous studies have demonstrated that free radicals are formed under hypoxic conditions in newborn piglet brain. To test the hypothesis that the cyclooxygenase pathway serves as a source of free radical generation during hypoxia studies were performed on 24 piglets divided into four groups. Six saline (group 3) and six indomethacin treated (group 4) were exposed to hypoxia (FiO2 0.05-0.07) for 60 min. Cerebral hypoxia was documented biochemically by determination of ATP and phosphocreatine. Fluorescent compounds and conjugated dienes were determined as indices of lipid peroxidation. Free radical formation was determined by using n-tert butyl phenyl nitrone (PBN) as a spin trap agent and measuring spin adduct formation in duplicate using a Varian E-109 spectrometer. Groups 1 and 2 (normoxic) showed no spin adduct formation. Group 3 showed a significant increase in spin adduct formation compared to normoxia (372+/-125 vs. 63+/-15, P<0.001). Hypoxic animals pretreated with indomethacin had a spin adduct level of 197+/-132 and were similar to normoxic animals. ATP/PCr levels were the same in groups 3 and 4 denoting the same degree of cerebral hypoxia in all hypoxic animals. Conjugated dienes increased significantly during hypoxia as compared to normoxia (0.142+/-0.017 vs. 0.0+/-0.0) and were decreased insignificantly with indomethacin treatment. Fluorescent compounds were not significantly different among the four groups. Na+,K+-ATPase activity decreased during hypoxia but was not preserved in hypoxic animals pretreated with indomethacin. These data provide direct evidence of the presence of free radicals during hypoxia and the contribution of cyclooxygenase metabolism to their formation.

Assessment of the "common" 4.8-kb mitochondrial DNA deletion and identification of several closely related deletions in the dorsal root ganglion of aging and streptozotocin rats

The identification of several mitochondrial DNA (mtDNA) deletions and the accumulation of the "common" 4.8-kb mitochondrial DNA deletion (mtDNA(4834)) with aging and experimental streptozotocin-induced diabetes (STZ) were studied in the rat dorsal root ganglion (DRG). Twenty-one mtDNA deletions, including mtDNA(4834), were identified in rat L4-L6 DRG mtDNA of 15-month-old Spraque-Dawley rats with 13 months of STZ and age-matched controls. These deletions were flanked by breakpoints that ranged from 16-bp direct repeats to no direct repeats. The sciatic nerve contained undetectable levels of mtDNA deletions. Levels of mtDNA(4834) in rat DRG mtDNA significantly accumulated with age at a rate much higher than those reported in the brain, yet were not statistically different in STZ. Southern blot analysis demonstrated no significant accumulation of the total amount of mtDNA deletions in STZ over age-matched controls. The accumulation of mtDNA(4834) has not been studied in rat peripheral nerve tissue. Our identification of several mtDNA deletions with and without direct repeats at their breakpoint support the hypothesis that deletions can occur by both the slip-replication model and random recombination. Although there is a significant increase in accumulation of mtDNA(4834) associated with aging, the lack of significant accumulations of mtDNA deletions in STZ over age-matched controls indicates that this type of mtDNA damage is likely not a major alteration in STZ, although the changes could be confined to a small population of neurons that undergo apoptosis between 8 and 15 months.

Exercise at old age: does it increase or alleviate oxidative stress?

Aging is associated with increased free radical generation in the skeletal muscle that can cause oxidative modification of protein, lipid, and DNA. Physical activity has many well-established health benefits, but strenuous exercise increases muscle oxygen flux and elicits intracellular events that can lead to increased oxidative injury. The paradox arises as to whether exercise would be advisable to aged population. Research evidence indicates that senescent organisms are more susceptible to oxidative stress during exercise because of the age-related ultrastructural and biochemical changes that facilitate formation of reactive oxygen species (ROS). Aging also increases the incidence of muscle injury, and the inflammatory response can subject senescent muscle to further oxidative stress. Furthermore, muscle repair and regeneration capacity is reduced at old age that could potentially enhance the accrual of cellular oxidative damage. Predeposition of certain age-related pathologic conditions may exacerbate the risks. In spite of these risks, the elderly who are physically active benefit from exercise-induced adaptation in cellular antioxidant defense systems. Improved muscle mechanics, strength, and endurance make them less vulnerable to acute injury and chronic inflammation. Many critical questions remain regarding the relationship of aging and exercise as we enter a new millennium. For example, how does aging alter exercise-induced intracellular and intercellular mechanisms that generate ROS? Can acute and chronic exercise modulate the declined gene expression of metabolic and antioxidant enzymes seen at old age? Does exercise prevent age-dependent muscle loss (sarcopenia)? What kinds of antioxidant supplementation, if any, do aged people who are physically active need? Answers to these questions require highly specific research in both animals and humans.

Activation of sphingolipid turnover and chronic generation of ceramide and sphingosine in liver during aging

Aging leads to a decreased ability of liver to metabolize drugs and increased expression and secretion of acute phase proteins, such as serum amyloid A (SAA), C-reactive protein (CRP), and alpha-1-acid glycoprotein (AGP). This phenomenon resembles some aspects of the acute phase response of host to inflammation; however, the molecular basis for the similarity is unclear. Ceramide and sphingosine are second messenger mediators of cellular responses to stress and inflammation. In liver, they play important role in mediating acute phase responses to IL1-beta. In this study, we use HPLC and thin layer chromatography to evaluate the effects of aging on steady-state levels of ceramide and sphingosine. We report that both lipids are elevated in liver of old (24 months) as compared to young (5 months) male Fisher 344 rats. To elucidate the mechanism(s) for ceramide elevation, we test the acidic (ASMase) and neutral sphingomyelinase (NSMase) in vitro using NBD-sphingomyelin as an exogenous substrate. SM synthase is also analyzed in vitro using NBD-ceramide and [3H]-dipalmitoylphosphatidylcholine (DPPC) as exogenous substrates. In accordance with the increases in the mass of ceramide, the activity of acid and neutral SMase is elevated in old animals. Michaelis-Menten analysis of NSMase implies that the apparent activation of this enzyme is caused by an increase in the Vmax of the enzyme. In contrast, SM synthase activity is lower in old animals as compared to young ones. These results show that aging is accompanied by an elevation in SM turnover and a decrease in its synthesis, resulting in accumulation of pro-inflammatory and growth inhibitory second messenger ceramide. Ceramidase, the only enzyme leading to sphingosine generation, is also measured in vitro using NBD-ceramide as a substrate and liver homogenate as an enzyme source. Its activity is higher in the old rats, as compared to young ones. The acid and neutral forms of the enzyme are affected the most, while the changes in the alkaline enzyme are not significant. The increases in the basal levels of ceramide and sphingosine in old animals may contribute to the onset of an inflammatory like state in liver during aging, exemplified by decreased P4502C11 mRNA expression and chronic induction of acute phase protein expression.

Free radical generation and oxidative stress with ageing and exercise: differential effects in the myocardium and liver

Reactive oxygen species and other oxidants are implicated in the mechanisms of biological ageing and exercise-induced tissue damage. The present study examined the effects of ageing and an acute bout of exercise on intracellular oxidant generation, lipid peroxidation, protein oxidation and glutathione (GSH) status in the heart and liver of young adult (8 month, N=24) and old (24 month, N=24) male Fischer 344 rats. Young rats ran on treadmill at 25 m min-1, 5% grade until exhaustion (55.4+/-2.7 min), whereas old rats ran at 15 m min-1, 5% until exhaustion (58.0+/-2.7 min). Rate of dichlorofluorescin (DCFH) oxidation, an indication of intracellular oxidant production, was significantly higher in the homogenates of aged heart and liver compared with their young counterparts. In the isolated heart and liver mitochondria, ageing increased oxidant production by 29 and 32% (P<0.05), respectively. Acute exercise increased oxidant production in the aged heart but not in the liver. When nicodinamide dinucleotide phosphate (reduced), adenosine diphosphate and Fe3+ were included in the assay, DCFH oxidation rate was 47 and 34% higher (P<0.05) in the aged heart and liver homogenates, respectively, than the young ones. The age differences in the induced state reached 83 and 140% (P<0.01) in isolated heart and liver mitochondria, respectively. Lipid peroxidation was increased in the aged liver and exercised aged heart, whereas protein carbonyl content was elevated only in the aged heart (P<0.05). Although our data using DCFH method probably underestimated cellular oxidant production because of time delay and antioxidant competition, it is clear that oxidative stress was enhanced in both heart and liver with old age. Furthermore, aged myocardium showed greater susceptibility to oxidative stress after heavy exercise.

Direct NAD(P)H hydrolysis into ADP-ribose(P) and nicotinamide induced by reactive oxygen species: a new mechanism of oxygen radical toxicity

The effect of different oxygen radical-generating systems on NAD(P)H was determined by incubating the reduced forms of the pyridine coenzymes with either Fe2+-H2O2 or Fe3+-ascorbate and by analyzing the reaction mixtures using a HPLC separation of adenine nucleotide derivatives. The effect of the azo-initiator 2,2'-azobis(2-methylpropionamidine)dihydrochloride was also tested. Results showed that, whilst all the three free radical-producing systems induced, with different extent, the oxidation of NAD(P)H to NAD(P)+, only Fe2+-H2O2 also caused the formation of equimolar amounts of ADP-ribose(P) and nicotinamide. Dose-dependent experiments, with increasing Fe2+ iron (concentration range 3-180 microM) or H2O2 (concentration range 50-1000 microM), were carried out at pH 6.5 in 50 mM ammonium acetate. NAD(P)+, ADP-ribose(P) and nicotinamide formation increased by increasing the amount of hydroxyl radicals produced in the medium. Under such incubation conditions NAD(P)+/ADP-ribose(P) ratio was about 4 at any Fe2+ or H2O2 concentration. By varying pH to 2.0, 3.0, 4.0, 4.5, 5.0, 5.5, 6.0, 7.0 and 7.4, NAD(P)+/ADP-ribose(P) ratio changed to 5.5, 3.2, 1.8, 1.6, 2.0, 2.5, 3.0, 5.4 and 6.5, respectively. Kinetic experiments indicated that 90-95% of all compounds were generated within 5s from the beginning of the Fenton reaction. Inhibition of ADP-ribose(P), nicotinamide and NAD(P)+ production of Fe2+-H2O2-treated NAD(P)H samples, was achieved by adding mannitol (10-50 mM) to the reaction mixture. Differently, selective and total inhibition of ADP-ribose(P) and nicotinamide formation was obtained by performing the Fenton reaction in an almost completely anhydrous medium, i.e. in HPLC-grade methanol. Experiments carried out in isolated postischemic rat hearts perfused with 50 mM mannitol, showed that, with respect to values of control hearts, this hydroxyl radical scavenger prevented reperfusion-associated pyridine coenzyme depletion and ADP-ribose formation. On the basis of these results, a possible mechanism of action of ADP-ribose(P) and nicotinamide generation through the interaction between NAD(P)H and hydroxyl radical (which does not involve the C-center where "conventional" oxidation occurs) is presented. The implication of this phenomenon in the pyridine coenzyme depletion observed in postischemic tissues is also discussed.

The growth hormone axis and cognition: empirical results and integrated theory derived from giant transgenic mice

Sleep is required for the consolidation of memory for complex tasks, and elements of the growth-hormone (GH) axis may regulate sleep. The GH axis also up-regulates protein synthesis, which is required for memory consolidation. Transgenic rat GH mice (TRGHM) express plasma GH at levels 100-300 times normal and sleep 3.4 h longer (30%) than their normal siblings. Consequently, we hypothesized that they might show superior ability to learn a complex task (8-choice radial maze); 47% of the TRGHM learned the task before any normal mice. All 17 TRGHM learned the task, but 33% of the 18 normal mice learned little. TRGHM learned the task significantly faster than normal mice (p < 0.05) and made half as many errors in doing so, even when the normal nonlearners were excluded from the analysis. Whereas normal mice expressed a linear learning curve, TRGHM showed exponentially declining error rates. The contribution of the GH axis to cognition is conspicuously sparse in literature syntheses of knowledge concerning neuroendocrine mechanisms of learning and memory. This paper synthesizes the crucial role of major components of the GH axis in brain functioning into a holistic framework, integrating learning, sleep, free radicals, aging, and neurodegenerative diseases. TRGHM show both enhanced learning in youth and accelerated aging. Thus, they may provide a powerful new probe for use in gaining an understanding of aspects of central nervous system functioning, which is highly relevant to human health.

Oxidative stress in hypopituitary dwarf mice and in transgenic mice overexpressing human and bovine GH

Growth hormone (GH) stimulates metabolic activity. The purpose of this study was to examine whether it is involved in the aging process by increasing oxidative stress. Inorganic peroxides and lipid peroxides were measured in kidney and liver samples in dwarf mice that are deficient in GH, prolactin and thyrotropin and in transgenic mice that produce high levels of GH. In normal male mice, there was an increase in inorganic peroxides in the kidney with age. Levels were lower in old male dwarfs when compared with normal male mice of similar age. Unexpectedly, concentrations of inorganic peroxides were frequently lower in transgenic male and female mice expressing extra copies of GH than in normal controls. Lipid peroxide concentrations were more variable. Transgenic animals expressing bovine GH had the highest levels of lipid peroxides. In dwarfs, kidney levels were similar to those of normal mice but concentrations in the liver were more variable. This study does not indicate that the decrease in life span in transgenic mice producing high levels of GH is due to an increase of oxidative stress. Rather, it suggests that expression of extra copies of the GH gene may lead to a compensatory increase in antioxidant protection.

Effect of aging on plasma membrane fluidity of rat aortic endothelial cells

To assess age-related changes in the physical properties of vascular endothelial cell (EC) plasma membranes, we measured membrane fluidity with 1,6-diphenyl-1,3,5-hexatriene (DPH), 1-(4-trimethylammonium-phenyl)-6-phenyl-1,3,5-hexatriene, and 10-(1-pyrene)dodecanoic acid, and investigated the parameters affecting membrane fluidity of endothelial cells (ECs) cultured from the thoracic aortas of young (5-week-old) and aged (100-week-old) rats. Plasma membrane fluidity of aged rat ECs was significantly lower than that of young rat ECs, as assessed by increased 1,6-diphenyl-1,3,5-hexatriene fluorescence polarization and by decreased pyrene excimer formation, although 1-(4-trimethylammonium-phenyl)-6-phenyl-1,3,5-hexatriene did not demonstrate a change in membrane fluidity with aging. Compared with those in young rat ECs, cholesterol concentrations in aged rat ECs were significantly higher, whereas phospholipid concentrations were unchanged; consequently, the cholesterol/phospholipid molar ratio was significantly higher in aged rat ECs. Lipid peroxide levels measured with thiobarbituric acid reactive substances were significantly higher in EC plasma membranes of aged rats. These results indicate that age-related increases in cholesterol and lipid peroxide in vascular EC plasma membranes reduce membrane fluidity.

Superoxide production by primary rat cerebral endothelial cells in response to pneumococci

Animal studies of experimental bacterial meningitis have provided evidence for an involvement of reactive oxygen species (ROS) in the pathophysiology of this disease. Using a lucigenin-enhanced chemiluminescence (CL) method, we tested whether primary rat cerebral endothelial cells can be induced to release ROS upon stimulation with pneumococci. In addition, we determined CSF levels of two markers of lipid peroxidation in patients with bacterial meningitis, compared to patients with viral meningitis and noninflammatory neurological disorders. Malondialdehyde/4-hydroxynonenal concentrations were significantly elevated in CSF samples obtained from patients with bacterial meningitis (23.12+/-5.47 microM), as compared to both control groups (5.43+/-0.18 microM and 7.80+/-0.33 microM, respectively). Cerebromicrovascular endothelial cells, granulocytes, and the macrophage cell line RAW 264.7 (but not astrocytes and neuron-like cells) produced an increase in CL intensity after stimulation with pneumococci. The peak value produced by endothelial cells (500+/-83 cpm) was significantly lower than the maximum CL response in macrophages (1386+/-142 cpm; p<0.05). After addition of superoxide dismutase (SOD), the CL signal returned to baseline values. Equal to the CL technique, nitroblue tetrazolium (NBT) staining of RAW 264.7 showed SOD-inhibitable formazan precipitation when stimulated with pneumococci. In conclusion, this study suggests an important role of endothelial cells in the pathophysiology of bacterial meningitis-namely as a source for ROS production.

Roles of reactive oxygen species: signaling and regulation of cellular functions

Reactive oxygen species (ROS) are the side products (H2O2, O2.-, and OH.) of general metabolism and are also produced specifically by the NADPH oxidase system in most cell types. Cells have a very efficient antioxidant defense to counteract the toxic effect of ROS. The physiological significance of ROS is that ROS at low concentrations are able to mediate cellular functions through the same steps of intracellular signaling, which are activated by natural stimuli. Moreover, a variety of natural stimuli act through the intracellular formation of ROS that change the intracellular redox state (oxidation-reduction). Thus, the redox state is a part of intracellular signaling. As such, ROS are now considered signal molecules at nontoxic concentrations. Progress has been achieved in studying the oxidative activation of gene transcription in animal cells and bacteria. Changes in the redox state of intracellular thiols are considered to be an important mechanism that regulates cell functions.

Oxidative stress and mitochondrial function in skeletal muscle: Effects of aging and exercise training

The rate of oxidative phosphorylation was investigated in isolated mitochondria from hindlimb muscles of young (4.5 mo) and old (26.5 mo) male Fischer 344 rats with or without endurance training. Further, the susceptibility of the muscle mitochondria to exogenous reactive oxygen species was examined. State 3 and 4 respiration, as well as the respiratory control index (RCI), were significantly lower in muscle mitochondria from aged vs. young rats (P<0.05), using either the site 1 substrates malate-pyruvate (M-P) and 2-oxoglutarate (2-OG), or the site 2 substrate succinate. In both young and old rats, training increased state 4 respiration with M-P, but had no effect on state 3 respiration, resulting in a reduction of RCI. Training also increased state 4 respiration with 2-OG and decreased RCI in young rats. When muscle mitochondria were exposed to superoxide radicals (O2 (·-)) and hydrogen peroxide (H2O2) generated by xanthine oxidase and hypoxanthine, or H2O2 alone in vitro, state 3 respiration and RCI in both age groups were severely hampered, but those from the old rats were inhibited to a less extent than the young rats. In contrast, state 4 respiration was impaired by O2 (·-) and/or H2O2 to a greater extent in the old rats. Muscle mitochondria from trained young rats showed a greater resistance to the O2 (· -) and/or H2O2-induced state 3 and RCI inhibition than those from untrained young rats. Muscle from aged rats had significantly higher total activities of superoxide dismutase (SOD), catalase, glutathione peroxidase (GPX), and glutathione reductase than that from young rats, however, training increased SOD and GPX activities in young but not old rats. The results of this study suggest that mitochondrial capacity for oxidative phosphorylation is compromised in aging skeletal muscle. Further, the increased mitochondrial resistance to reactive oxygen species demonstrated in aged and young trained muscles may be attributed to enhanced antioxidant enzyme activities.

Influence of long-term supplementation with alpha-linolenic acid on myocardial lipid peroxidation and antioxidative capacity in spontaneously hypertensive rats

The ischaemic vulnerability of the heart of spontaneously hypertensive rats (SHR) is enhanced after feeding an alpha-linolenic acid (LNA) enriched diet. Because oxygen radical-induced reactions (e.g. lipid peroxidation) are involved in the ischaemic damage, an increased susceptibility of the SHR heart to such damaging reactions might be the reason. As a sign of the enhanced susceptibility to lipid peroxidation of LNA-fed SHR, we found (measured as TBARS) higher plasma and heart lipid peroxide levels (3.84 +/- 0.50 micromol/l vs 2.98 +/- 0.78 micromol/l and 507 +/- 127 nmol/g prot. vs 215 +/- 80 nmol/g prot., respectively) after feeding LNA. Using Fe2+/Vit. C to induce lipid peroxidation in myocardial tissue homogenates, we demonstrated the enhanced susceptibility to lipid peroxidation of the LNA-fed SHR heart (68 +/- 12 nmol/min x g prot. vs 40 +/- 8 nmol/min x g prot.) also in vitro. The myocardial enrichment of n-3 polyunsaturated fatty acids (PUFA) resulting in a higher peroxidation index (PI 227 vs. 170) and the loss in myocardial activities of the antioxidative enzymes (SOD: 76 +/- 24 U x 10(3)/g prot. vs 235 +/- 150 U x 10(3)/g prot.; GSH-Px: 32 +/- 5 U/g prot. vs 110 +/- 30 U/g prot.) by feeding LNA could be the cause of the increase in myocardial susceptibility to lipid peroxidation of PUFA supplemented SHR.

Role of reactive oxygen species in cardiovascular aging

Biochemical and structural changes occurring in the myocardium with aging are mainly resulting from the association of a general tissue atrophy with the hypertrophy of the remaining myocytes. Whilst hypertrophy seems to be a compensatory process to the loss of cardiomyocytes and to a mild systolic hypertensive condition that accompanies elderly people, atrophy should be the modification more closely related to aging 'per se.' In support to the free radical theory of aging, several signs of oxidative damage have been shown in the aged heart, such as lipofuscin accumulation, decreased phospholipid unsaturation index, greater formation of both hydrogen peroxide and 8-hydroxy-2'deoxyguanosine. As a compensatory reaction, the activities of the main oxygen-radical scavenger enzymes are stimulated in the mitochondria of aged rat heart. Endothelium-mediated vasoregulation is more susceptible to oxidative stress in aged with respect to young rats, suggesting that also the vasculature can be negatively influenced by the oxygen free radicals generated during aging. The possible primary role of oxygen free radicals in the development of myocardial atrophy is also discussed.

Aging and oxidative stress: modulation by dietary restriction

Aging is an inevitable biological process that affects most living organisms. Despite the enormous consequences associated with the aging process, until recently, relatively little systematic effort has been expended on the scientific understanding of this important life process. Society, however, urged by an ever increasing older population, is challenging scientists from many disciplines to explore one of nature's most complex phenomena-biological aging. For the past two decades, research directed toward the basic understanding of biological aging mechanisms and possible aging interventions have given us new insights into the molecular bases and the biological events that contribute to age-related deterioration. To further investigate the aging processes, one probe uniquely suited to exploring the progression of aging in animal models is dietary restriction, currently the only antiaging intervention accepted by gerontologists and nutritionists. Recent research renders a better understanding of how reduced dietary intake extends the life span, supplying evidence that dietary restriction is a diverse and effective modulator of oxidative stress. It has been proposed that this antioxidative mechanism is the underlying anti-aging action of dietary restriction.

Age- and peroxidative stress-related modifications of the cerebral enzymatic activities linked to mitochondria and the glutathione system

The aging brain undergoes a process of enhanced peroxidative stress, as shown by reports of altered membrane lipids, oxidized proteins, and damaged DNA. The aims of this review are to examine: (1) the possible contribution of mitochondrial processes to the formation and release of reactive oxygen species (ROS) in the aging brain; and (2) the age-related changes of antioxidant defenses, both enzymatic and nonenzymatic. It will focus on studies investigating the role of the electron transfer chain as the site of ROS formation in brain aging and the alterations of the glutathione system, also in relation to the effects of exogenous pro-oxidant agents. The possible role of peroxidative stress in age-related neurodegenerative diseases will also be discussed.

Protein synthesis in the heart in vivo, its measurement and patho-physiological alterations

Changes in cardiac protein composition occur in a variety of patho-physiological situations and are usually accompanied by modifications in protein synthesis. Although adjustments in protein synthesis during starvation may be adaptive, the alterations in protein synthesis seen in response to ethanol ingestion may be pathological and an important step in the genesis of alcoholic heart muscle disease. The alterations in heart muscle in hypertension are initially adaptive but in the long term they are deleterious, and involve both transcription and translation. While adequate methods exist for quantifying the amount of mRNA for contractile and non-contractile proteins, such studies of gene-expression provide no dynamic information on the rate at which tissue proteins are lost or accrued. This can only be determined by measuring the rate of protein turnover, i.e. either protein synthesis or protein breakdown. Techniques for directly determining the rates of protein breakdown are limited or involve surgical procedures. Methods for measuring the rate of protein synthesis are described, and are illustrated by their application to the investigation of starvation and ethanol toxicity. In particular, attention is focused on the fact that reliable rates of protein synthesis are obtained only if the specific radioactivity of the precursor at the site of protein synthesis (aminoacyl-tRNA) is assessed.

Age-specific alterations in muscarinic stimulation of K(+)-evoked dopamine release from striatal slices by cholesterol and S-adenosyl-L-methionine

The present experiments were carried out in order to test the hypothesis that age-related signal transduction (ST) deficits may occur as a result of structural changes in the membrane that are reflected partially as increased membrane microviscosity. Oxotremorine (oxo) enhancement of K(+)-evoked release of dopamine (K(+)-ERDA) was examined in superfused striatal slices from mature (6 months) and old (24 months) Wistar rats incubated (1 or 4 h, 37 degrees C) with graded concentrations of S-adenosyl-L-methionine (SAM) or cholesterol hemisuccinate (CHO) in a modified Krebs medium. Tissue was then assessed for one of the following: (a) the degree of oxo-enhanced K(+)-ERDA, (b) carbachol stimulated low Km GTPase activity, or (c) alterations in membrane microviscosity. In other experiments the tissue was incubated in CHO followed by SAM (or the reverse), and oxo-enhanced K(+)-ERDA examined. Results indicated that SAM treatment increased all the parameters in the striatal tissue from old animals, while CHO had selective, opposite effects in the striatal tissue obtained from young animals. CHO-SAM, or the reverse, produced the same pattern of results. These results suggest that ST deficits may involve age-related structural alterations in membranes that interfere with receptor-G protein coupling/uncoupling.

Rapid eye movement sleep deprivation decreases membrane fluidity in the rat brain

In this study we examined the effects of rapid eye movement sleep (REMS) deprivation on synaptosomal and microsomal membrane fluidity by studying 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence polarization in control as well as REMS-deprived rats. The flower pot technique was used to perform 24, 48 and 96 h REMS deprivation. Suitable control experiments were carried out to rule out the nonspecific effects. The results showed that DPH fluorescence polarization increased both in the microsome as well as in the synaptosome in REMS-deprived animals, except in the cerebellum, indicating that there was a generalized decrease in membrane fluidity in the rat brain. The alterations in membrane fluidity returned to baseline upon recovery from REMS deprivation. Control experiments suggested that the alterations were primarily caused by REMS deprivation and not due to nonspecific effects. This finding supports REMS deprivation induced other changes reported earlier. This increase in membrane rigidity could be at least one of the possibilities for REMS loss induced alterations in physiological phenomena including membrane bound enzyme activities and receptor densities.

Bioenergetic and oxidative stress in neurodegenerative diseases

Aging is a major risk factor for several common neurodegenerative diseases, including Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), and Huntington's disease (HD). Recent studies have implicated mitochondrial dysfunction and oxidative stress in the aging process and also in the pathogenesis of neurodegenerative diseases. In brain and other tissues, aging is associated with progressive impairment of mitochondrial function and increased oxidative damage. In PD, several studies have demonstrated decreased complex I activity, increased oxidative damage, and altered activities of antioxidant defense systems. Some cases of familial ALS are associated with mutations in the gene for Cu, Zn superoxide dismutase (Cu, Zn SOD) and decreased Cu, Zn SOD activity, while in sporadic ALS oxidative damage may be increased. Defects in energy metabolism and increased cortical lactate levels have been detected in HD patients. Studies of AD patients have identified decreased complex IV activity, and some patients with AD and PD have mitochondrial DNA mutations. The age-related onset and progressive course of these neurodegenerative diseases may be due to a cycling process between impaired energy metabolism and oxidative stress.

Studies on lipid peroxidation and protein oxidation in the aging brain

Lipid peroxidation (LP) and protein oxidation (PO) were investigated in hippocampus and frontal cortex homogenates from young (5 months), mature (13 months) and old (24 months) Wistar rats and young (5 months) and old (24 months) Brown Norway rats. LP and PO were determined in basal conditions and after incubation without iron (spontaneous condition) or with iron (stimulated condition). LP was measured as HPLC-assayed malondialdehyde (MDA) and PO as protein carbonyl (CO) content. Brain homogenates formed considerable amounts of MDA and CO spontaneously and, to an even greater extent, in the presence of Fe2+. Old rats showed greater iron-stimulated LP in the cortex than young rats, but the difference was not significant. Basal (but not spontaneous or stimulated) PO was significantly increased (19%) in the hippocampus of old compared to young rats. This study does not confirm the age-related increase in LP reported in the literature and only partially confirms the findings concerning PO.

Mitochondrial respiratory activity and superoxide radical generation in the liver, brain and heart after chronic ethanol intake

Functional characteristics of mitochondria isolated from liver, brain and heart were studied in ethanol-fed rats using ethanol administration in drinking water as a model of moderate alcohol intoxication. Our results show a slight decrease in liver cytochrome aa3 content, the mitochondrial alteration which is most consistently observed during chronic ethanol feeding. In liver and heart mitochondria, ethanol consumption led to an increase in state 3 respiration with NAD(+)-linked substrates, whereas no changes were apparent in respiration rates with succinate as substrate. However a decrease was found in state 3 respiration with succinate in brain mitochondria isolated from ethanol-fed rats. Submitochondrial particles (SMP) were used to study the superoxide radical (O2-.) production at the level of antimycin-inhibited regions of the respiratory chain. It appears that there is no clear correlation between ethanol effects on respiration and O2-. production. Whereas O2-. generation remained unchanged in heart mitochondria, an elevation of O2-. generation was observed in brain mitochondria, and in contrast, the rate of O2-. production was decreased in liver mitochondria of the ethanol-group in comparison to the control-group. Our findings support a tissue specificity for the toxic effects of ethanol towards the mitochondria and indicate that mitochondrial free radical mechanisms are involved in ethanol-induced toxicity in the brain.

Changes in superoxide radical formation, lipid peroxidation, membrane fluidity and cathepsin B activity in aging and spawning male Chinook salmon (Oncorhynchus tschawytscha)

Superoxide radical (SOR) formation in the brain and the liver of male Chinook salmon (Oncorhynchus tschawytscha) increased in mitochondrial and plasma membrane samples as they aged. In 2-year-old salmon, spawning also lead to a significant elevation in SOR formation in mitochondrial and plasma membrane samples. The rise in this free radical was associated with an increase in lipid peroxidation, a decrease in plasma membrane fluidity, and an elevation in cathepsin B activity in the brain and liver. In 2-year-old spawning salmon, the changes in these parameters was greater than in 2-year-old non-spawning salmon. These observations suggest that free radical levels increase with aging and during spawning and indicate that these changes may be involved in cellular degeneration. In addition, these results support the suggestion that cellular degeneration accelerates during the spawning process.