Mária Sasvári

THE EFFECT OF EXERCISE TRAINING ON OXIDATIVE DAMAGE OF LIPIDS, PROTEINS, AND DNA IN RAT SKELETAL MUSCLE: EVIDENCE FOR BENEFICIAL OUTCOMES

Moderate daily exercise is known to be beneficial to health, reducing risks of a number of age-related disorders. Molecular mechanisms that bring about these effects are not clear. In contrast, it has been claimed that some types of prolonged physical exertion are detrimental to health because active oxygen species are generated excessively by enhanced oxygen consumption. Using two age groups of rats, young (4 week) and middle aged (14 months), we investigated the effects of long-term swimming training on the oxidative status of phospholipids, proteins, and DNA. The concentration of thiobarbituric acid reactive substances and 4-hydroxynonenal protein adducts did not differ in the gastrocnemius muscle between exercised and nonexercised animals in the two age groups. The extent of carbonylation in a protein of molecular weight around 29 KDa and the amount of 8-hydroxydeoxyguanosine in nuclear DNA were smaller (p<.05) in the exercised rats than in the sedentary animals. Activities of DT-diaphorase (C1: 29.3+/-1.9; C2: 36.1+/-2.6; E1: 27.2+/-1.3; C2: 33.4+/-2.9 nmol/mg protein) and proteasome, a major proteolytic enzyme for oxidatively modified proteins were significantly higher in the exercised animals of both age groups (p<.05). The adaptive response against oxidative stress induced by moderate endurance exercise constitutes a beneficial effect of exercise.

β-Amyloid neurotoxicity is mediated by a glutamate-triggered excitotoxic cascade in rat nucleus basalis

Whereas a cardinal role for β‐amyloid protein (Aβ) has been postulated as a major trigger of neuronal injury in Alzheimers disease, the pathogenic mechanism by which Aβ deranges nerve cells remains largely elusive. Here we report correlative in vitro and in vivo evidence that an excitotoxic cascade mediates Aβ neurotoxicity in the rat magnocellular nucleus basalis (MBN). In vitro application of Aβ to astrocytes elicits rapid depolarization of astroglial membranes with a concomitant inhibition of glutamate uptake. In vivo Aβ infusion by way of microdialysis in the MBN revealed peak extracellular concentrations of excitatory amino acid neurotransmitters within 20–30 min. Aβ‐triggered extracellular elevation of excitatory amino acids coincided with a significantly enhanced intracellular accumulation of Ca2+ in the Aβ injection area, as was demonstrated by 45Ca2+ autoradiography. In consequence of these acute processes delayed cell death in the MBN and persistent loss of cholinergic fibre projections to the neocortex appear as early as 3 days following the Aβ‐induced toxic insult. Such a sequence of Aβ toxicity was effectively antagonized by the N‐methyl‐d‐aspartate (NMDA) receptor ligand dizocilpine maleate (MK‐801). Moreover, Aβ toxicity in the MBN decreases with advancing age that may be associated with the age‐related loss of NMDA receptor expression in rats. In summary, the present results indicate that Aβ compromises neurons of the rat MBN via an excitotoxic pathway including astroglial depolarization, extracellular glutamate accumulation, NMDA receptor activation and an intracellular Ca2+ overload leading to cell death.

Neuroprotective approaches in experimental models of β-amyloid neurotoxicity : Relevance to Alzheimer's disease

1. beta-Amyloid peptides (A beta s) accumulate abundantly in the Alzheimers disease (AD) brain in areas subserving information acquisition and processing, and memory formation. A beta fragments are produced in a process of abnormal proteolytic cleavage of their precursor, the amyloid precursor protein (APP). While conflicting data exist in the literature on the roles of A beta s in the brain, and particularly in AD, recent studies have provided firm experimental evidence for the direct neurotoxic properties of A beta. 2. Sequence analysis of A beta s revealed a high degree of evolutionary conservation and inter-species homology of the A beta amino acid sequence. In contrast, synthetic A beta fragments, even if modified fluorescent or isotope-labeled derivatives, are pharmacological candidates for in vitro and in vivo modeling of their cellular actions. During the past decade, acute injection, prolonged mini-osmotic brain perfusion approaches or A beta infusions into the blood circulation were developed in order to investigate the effects of synthetic A beta s, whereas transgenic models provided insight into the distinct molecular steps of pathological APP cleavage. 3. The hippocampus, caudate putamen, amygdala and neocortex all formed primary targets of acute neurotoxicity screening, but functional consequences of A beta infusions were primarily demonstrated following either intracerebroventricular or basal forebrain (medial septum or magnocellular basal nucleus (MBN)) infusions of A beta fragments. 4. In vivo investigations confirmed that, while the active core of A beta is located within the beta(25-35) sequence, the flanking peptide regions influence not only the folding properties of the A beta fragments, but also their in vivo neurotoxic potentials. 5. It has recently been established that A beta administration deranges neuron-glia signaling, affects the glial glutamate uptake and thereby induces noxious glutamatergic stimulation of nerve cells. In fact, a critical role for N-methyl-D-aspartate (NMDA) receptors was postulated in the neurotoxic processes. Additionally, A beta s might become internalized, either after their selective binding to cell-surface receptors or after membrane association in consequence of their highly lipophilic nature, and induce free radical generation and subsequent oxidative injury. Ca(2+)-mediated neurotoxic events and generation of oxygen free radicals may indeed potentiate each other, or even converge to the same neurotoxic events, leading to cell death. 6. Neuroprotection against A beta toxicity was achieved by both pre- and post-treatment with NMDA receptor channel antagonists. Moreover, direct radical-scavengers, such as vitamin E or vitamin C, attenuated A beta toxicity with high efficacy. Interestingly, combined drug treatments did not necessarily result in additive enhanced neuroprotection. 7. Similarly to the blockade of NMDA receptors, the neurotoxic action of A beta s could be markedly decreased by pharmacological manipulation of voltage-dependent Ca(2+)-channels, serotonergic IA or adenosine A1 receptors, and by drugs eliciting membrane hyperpolarization or indirect blockade of Ca(2+)-mediated intracellular consequences of intracerebral A beta infusions. 8. A beta neurotoxicity might be dose-dependently modulated by trace metals. In spite of the fact that zinc (Zn) may act as a potent inhibitor of the NMDA receptor channel, high Zn doses accelerate A beta fibril formation, stabilize the beta-sheet conformation and thereby potentiate A beta neurotoxicity. Combined trace element supplementation with Se, Mn, or Mg, which prevails over the expression of detoxifying enzymes or counteracts intracellular elevations of Ca2+, may reduce the neurotoxic impact of A beta s. 9. Alterations in the regulatory functions of the hypothalamo-pituitary-adrenal axis may contribute significantly to neurodegenerative changes in the brain. Furthermore, AD patients exhibit substantially increased circadia

Single bout of exercise eliminates the immobilization-induced oxidative stress in rat brain

We were interested in the effects of immobilization (IM), a single bout of exercise (E) and immobilization followed by exercise (EIM) on memory and oxidative damage of macromolecules in hippocampus of rat brain. Eight hours of IM resulted in impairment of passive avoidance test (memory retrieval deficit) and increased latency to start locomotion in an open-field test. Two hours of swimming did not significantly alter the memory retrieval deficit and latency, while the EIM group had longer latency and similar memory than control and E groups. The oxidative damage of lipids, proteins and nuclear DNA increased significantly in IM group and no increase was observed in E and EIM animals. The activity of proteasome was not altered in any groups. The activity of glutamine synthetase (GS) was decreased in IM group (P < 0.05), this down regulation was not observed in E and EIM groups. These data suggest that oxidative damage of macromolecules is associated with impaired cognitive function. Single bout of exercise after immobilization eliminates the oxidative damage of macromolecules and normalizes memory function, probably by its ability to restore the activity level of GS and eliminate the consequences of immobilization-induced prolonged efflux of glutamate.

The effect of exercise and nettle supplementation on oxidative stress markers in the rat brain

Chronic swimming training and phytotherapeutic supplementation are assumed to alleviate oxidative damage, and support cell survival in the brain. The effect of forced, chronic swimming training, and enriched lab chow containing 1% (w/w) dried nettle (Urtica dioica) leaf were investigated for oxidative stress, inflammation and neurotrophic markers in Wistar rat brains. The rats were divided into groups subjected to swimming training (6 weeks) or to nettle supplementation (8 weeks) or to a combination of these two treatments. The level of oxidative stress was measured by electron spin resonance (EPR), and by the concentration of carbonylated proteins. Nettle supplementation resulted in a decreased concentration of free radicals in both cerebellum and frontal lobe. Swimming, however, did not influence significantly the oxidative damage nor was it reflected in the carbonyl content. The protein content of nerve growth factor (NGF), and brain-derived neurotrophic factors (BDNF) was evaluated by E-Max ImmunoAssay in the cerebellum. No changes occurred either with exercise or nettle diet treatments. On the other hand, nuclear factor kappa B (NF-kappaB) binding activity to DNA increased with the combined effect of swimming training and nettle diet, while the activator protein1 (AP-1) DNA binding activity showed a more profound elevation in the nettle treated animals. The amount of c-Jun decreased by swimming training. In conclusion, the results suggest that both exercise and nettle influenced physiological brain functions. Nettle supplementation reduces the free radical concentration and increases the DNA binding of AP-1 in the brain. Nettle was found to be an effective antioxidant and possible antiapoptotic supplement promoting cell survival in the brain. Exercise, as a downregulator of c-Jun and in combined group as an upregulator of NF-kappaB, may play also a role in antiapoptotic processes, which is important after brain injury.

Super-marathon race increases serum and urinary nitrotyrosine and carbonyl levels

Background In normal conditions, proteins are not present in the urine, however, exercise of long duration could result in proteinurea. Increased levels of reactive oxygen and nitrogen species (RONS) are formed during exhaustive physical exercise and causes alterations to cellular proteins.

The beneficial effects of nettle supplementation and exercise on brain lesion and memory in rat

Regular swimming and phytotherapeutic supplementation are assumed to alleviate the severity of neurodegeneration leading to dementia. The effect of swimming training and that of enriched lab chow containing 1% (w/w) dried nettle (Urtica dioica) leaf on the prevention of severity of brain injury caused by N-methyl-d-aspartate (NMDA) lesion in Wistar rats were investigated. Nettle supplementation and regular swimming exercise seem to improve the adverse effect of brain injury caused by NMDA lesion assessed by passive avoidance test and open-field test. Nettle supplementation decreases the level of reactive oxygen species, measured by electron paramagnetic resonance, and the DNA-binding activity of NF-kappaB. The data reveal that nettle supplementation has an effective antioxidant role, down-regulates the inflammatory transcription factors and could also promote learning performance in the brain. Regular swimming increases the concentration of reactive species in the cerebellum and alters the activity of transcription factors toward inflammation. The additive effect of the two treatments was more profound in the down-regulation of inflammatory transcription processes in NMDA lesion.

Oxidative stress changes in L-arginine-induced pancreatitis in rats

The important role of oxygen radicals in acute experimental pancreatitis was demonstrated by study of the changes in the antioxidant system in the blood, liver, kidney, and pancreas of rats after the administration of a large quantity of L-arginine (L-Arg). The changes in lipid peroxidation and in reduced and oxidized glutathione were followed, as well as the activities of peroxide-decomposing enzymes (glutathione peroxidase and catalase) and H2O2-producing superoxide dismutases. The results demonstrated that “oxidative stress” develops and acute pancreatitis appears rapidly after L-Arg treatment. Oxidative stress symptoms are expressed 24 h after the final treatment. Slow restitution of the studied antioxidant system can be demonstrated as early as after 48 h.

Telomerase activity is not altered by regular strenuous exercise in skeletal muscle or by sarcoma in liver of rats

Abstract Telomerase is a specialized ribonucleoprotein enzyme complex which prevents the loss of the telomere. The activity of telomerase can be up- and down-regulated by various oxidative stresses but the effect of physical exercise is not known, whereas the modifying effect of cancer on telomerase activity is well documented. In the first study, we investigated the effect of mild and strenuous exercise training on telomerase activity, assessed by a PCR ELISA kit. No alteration in telomerase activity was detected. In the second investigation, solid sarcoma cells were transplanted to control, exercise trained or exercise trained and still exercising mice. On the 16th day after the transplantation, the size of tumors in the exercise trained group was 72% and in the exercising group 57% (P<0.05) of that in the controls. Telomerase activity and 8-hydroxy-2′-deoxyguanosine levels in the liver were not significantly altered by exercise and/or sarcoma. We conclude that mild and strenuous exercise training does not significantly affect the activity of telomerase in the systems studied. Exercise training during sarcoma significantly retards the development of tumors and could possibly serve as a positive adjunct to treatment.

Behavioral depression: opposite effects of neonatal dexamethasone and ACTH-(4-9) analogue (ORG 2766) treatments in the rat.

Permanent changes in novelty-induced arousal and behavioral depression were studied in adult male Wistar rats having received sc injections of 1 micrograms/g body wt dexamethasone (DEX) or ACTH-(4-9) analogue (ORG 2766), or the combined treatment of these substances at Postnatal Days 1, 3, and 5. Treatment with DEX increased immobility in the Porsolts water immersion and closed-field tests, delayed start latency, and attenuated orientation motility in an open-field, and enhanced defensive burying activity. On the contrary, the ACTH peptide caused more active behavior, resulted in an increased motility in the Porsolts test, and decreased immobility in the closed-field chamber compared to controls. Behavioral reactivity of rats after combined DEX and ACTH peptide treatments was comparable to that of saline controls. The hormone treatments did not alter basal and stress-induced circulating corticosterone levels assessed at the adult age. The data suggest that neonatal DEX strengthens the development of brain mechanisms supporting behavioral depression in response to stressful situations, while ORG 2766 has principally an opposite effect and is able to compensate the long-term aberrant behavioral effects of neonatal DEX treatment.