Characteristics of free-radical oxidation and antiradical protection of the brain in adaptation to chronic stress

During the phase of long-lasting adaptation to chronic emotional painful stress three stages have been distinguished on the basis of physiological and neurobiochemical data. The first stage (1 week of stress)--transition from urgent to long-lasting adaptation--corresponds to labilization of vegetative indices, predominance of fear reactions and suppression of research behaviour in rats, inhibition of lipid peroxidation, activation of superoxide scavenging activity, decrease in cholesterol content in brain lipids. The second stage (2 weeks of stress)--long-lasting adaptation--is characterized by normalization of the behaviour, stabilization of high blood pressure, maximum brain antiradical activity and low level of lipid peroxidation. The third stage (3 weeks of stress)--transition from long-lasting adaptation to exhaustion--is characterized by blood pressure lowering, disturbed regulation of vegetative functions, behavioural hyperactivity in the open field, increased lipid peroxidation and decreased phospholipid content.     

Oxidative stress perturbs cell proliferation in human K562 cells by modulating protein synthesis and cell cycle

Oxidative stress leads to perturbation of a variety of cellular processes resulting in inhibition of cell proliferation. This study has determined the effect of oxidative stress on protein synthesis in human K562 cells using a hydrophilic peroxyl radical initiator, AAPH and H₂O₂. The results indicated that oxidative stress leads to a significant decrease in the rate of protein synthesis caused due to induced activation as well as expression of the erythroid cell-specific eIF-2α kinase, called the Heme Regulated Inhibitor (HRI). Elevated levels of HRI expression and activity were accompanied by increased lipid peroxidation and decreased cell proliferation. Further, oxidative stress also caused inactivation of p34^cdc2 kinase, thereby arresting cell division leading to apoptosis. Thus, the data provides the mechanism of inhibition of protein synthesis and perturbation of a cell cycle regulatory protein leading to inhibition of cell proliferation in K562 cells during oxidative stress.     

Dynamics of lipid peroxidation and steroidogenesis in adrenal cortex during stress

The phase character of lipid peroxidation has been found in the rabbit adrenal cortex in the process of adaptation to extreme loads. Under acute stress the activation of lipid peroxidation is directly dependent on the hormonal synthesis processes. Under conditions of the prolonged stress factor an enhancement of the lipid peroxidation intensity in the adrenal cortex coincides with a decrease in the steroidogenesis rate.     

Effect of the level of free-radical lipid peroxidation on the ribonucleotide reductase activity of liver tissue

The dynamics of RNA and DNA synthesis as well as the activity of free radical processes in rat liver during the first 40 hours after partial hepatectomy was studied. It was shown that RNA synthesis activation follows the activation of lipid peroxidation (LPO), whereas the DNA synthesis activation follows the decrease of the LPO level. These facts are suggestive of the dependence of the ribonucleotide reductase (RNR) activity on free radical processes. This observation was confirmed by a RNR activity analysis of regenerating liver homogenates. The activity peak was shown to precede the peak of DNA synthesis. Evidence for free radical RNR suppression was also obtained in direct experiments, using intact animal liver homogenates, to which a natural antioxidant (tocopherol) was added.     

A functional state of the sphingomyelin cycle and activity of free radical oxidation of rat liver lipids at different phases of starvation

A functional state of the sphingomyeline cycle and its links with processes of free radical lipid oxidation have been investigated in rat liver during starvation of animals without any restriction of access to drinking water at day 1, 2, 3 (phase I) and day 6 (phase II of starvation). The maximal values of the ceramide/sphingomyelin ratio and activities of neutral sphingomyelinase and executive caspase-3 were found in rat livers at day 3 of starvation. Since day 3 of starvation an increase of tumour necrosis factor-α, one of neutral sphingomyelinase activators, was detected in serum. During the major part of phase I of starvation the intensity of liver free radical lipid peroxidation was comparable to that of control due to competent functioning of the antioxidant defense system. Transition of phase I to phase II of starvation (day 6 of the experiment) was accompanied by the development of oxidative stress associated with depletion of the antioxidant defense system. The results obtained in this study suggest that phase I of starvation favors realization of the ceramide-mediated proapoptotic signaling in the liver. In our viewpoint, ceramide-mediated apoptosis is one of mechanisms used optimization of liver cellular population within the frame of metabolic adaptation. In rat liver phase I of starvation was characterized by prevailing of the ceramide-mediated proapoptotic signaling, while in phase II oxidative stress dominated.     

Nickel-mediated inhibition in the glutathione-dependent protection against lipid peroxidation

Glutathione protects liver microsomes against the rapid onset of lipid peroxidation via a sulfhydryl dependent heat labile factor known as free radical reductase. The administration of nickel to mice resulted in an inhibition in the activity of free radical reductase, and enhanced lipid peroxidation and the activity of glutathione S-transferase in a dose dependent manner. The pretreatment of cyclam, a known specific chelator of nickel restored free radical reductase and glutathione S-transferase activities and alleviated nickel mediated enhancement of lipid peroxidation. Our results indicate that nickel-mediated inhibition in free radical reductase activity and activation of glutathione S-transferase may be due to the interaction of nickel with sensitive-SH groups located on these proteins.     

Use of fundamental properties of embryonic objects for studying potential environmental effects of technogenic impacts

This article analyzes the problems of biosafety in terms of individual development patterns. Previously, the key role of epigenetic free radical processes in normal embryonic development of lower vertebrates in the formation of the competence and determination of embryonic primordia has been demonstrated, and a significant increase in the intensity of free radical process before every qualitative change in homeostatic mechanisms in developing organisms was found: in induction systems, before hatching of the embryo from the shells, and in preparation for metamorphosis. Thus, the activation of free radical processes in embryonic primordia corresponds to instability and characterizes the “critical periods of development” and increased sensitivity of the embryo to environmental impacts. Patented methods and a test system that allows detecting early biological effects of weak environmental impacts and predicting their environmental risk are presented. Possible mechanisms of significant biological effects of weak radiation and chemical impacts on the developing organism are discussed. The necessity of including embryonic objects in the protocol of testing the biosafety of technological developments is substantiated.     

Activation of the antioxidant system as a factor in increasing the body resistance during combined adaptation

In semi-aquatic mammals (minks and muskrats) significant changes were found to occur in the leukocyte formula during adaptation to hypoxia, as compared with non-adapted rats and mice, although no increase in lipid peroxidation was found in any of their organs. This latter finding seems to be due to simultaneously enhanced activities of superoxide dismutase and catalase. In humans under professional stress, treatment with combined technology of adaptation: cold-and-hypoxic exposure, yields a positive therapeutic result accompanied by a decrease in lipid peroxidation and increase in superoxide dismutase and catalase activities in the blood. The data obtained suggest that the strategy of formation of protection against hypoxia and toxic free radical oxidation is common for the animals and humans.     

Modification of an enzymic system of Ca2+ transport in sarcoplasmic reticulum during lipid peroxidation. In vivo damages in the development of pathological changes

The role of lipid peroxidation (LPO) in the damages of the enzymic system of Ca2+ transport in sarcoplasmic reticulum (SR) membranes of skeletal and cardiac muscles under conditions of vitamin E deficiency, ischemia and limb reoxygenation as well as in emotional-pain stress was investigated. It was shown that these processes are associated with activation of endogenous LPO in SR membranes "in vivo" and with simultaneous inhibition of Ca2+ transport, (i. e. decrease of the Ca2+/ATP ratio) and inactivation of Ca-ATPase. The degree of damage of the Ca2+ transport system was correlated with the concentration of LPO products accumulated in SR membranes "in vivo and during LPO induction by the Fe2+ + ascorbate system 'in vitro". Injection of natural and synthetic free radical scavengers (e. g. 4-methyl-2.6-ditretbutylphenol, alpha-tocopherol) to experimental animals resulted in practically complete suppression of LPO activation "in vivo" and in partial protection of the Ca2+-transporting capacity of SR membranes. A comparison of experimental results allowed to estimate the role of LPO in SR damage under pathological conditions. Model experiments with "contraction-relaxation" cycles including isolated components of muscle fibers (SR fragments and myofibrils) demonstrated that LPO induction in SR membranes by the Fe2+ + ascorbate system results in complete elimination of the relaxation step in myofibrils due to the loss of the SR affinity to decrease the concentration of Ca2+ in the incubation medium. This effect can be removed by free radical scavengers. The role of LPO in pathological changes of muscle contractility is discussed.     

Dynamic changes in the indices of lipid metabolism in erythrocyte membranes at different times of the development of alloxan diabetes

The changes in the content of phospholipids (PL), cholesterol (cr) and its fractions were studied in the processes of lipid peroxidation. At the different periods of alloxan diabetes development the CS/LP ratio coefficient was determined (7, 14, 21 days). The results of our investigations we explain by erythrocyte membranes destruction in the molecular mechanism of which the significant role has played the activation of free radical lipid oxidation processes.     

Brown fat thermogenesis and exercise: two examples of physiological oxidative stress?

Both brown fat tissue (BAT) and skeletal muscle experience large increases of oxygen consumption and oxygen radical generation during activation. This, together with the relatively low activities of antioxidant enzymes in these two tissues and the high lipid content and free fatty acid liberation of BAT, can produce a physiological oxidative stress. Increases of in vivo or in vitro (BAT) lipid peroxidation have been described in these tissues after activation. They react to this oxidative stress in an adaptive way after chronic stimulation. Cold acclimation increases antioxidant enzymes, ascorbate, and especially reduced glutathione (GSH) in BAT. There is controversy about the variations of antioxidants in skeletal muscle after acute exercise. Nevertheless, exercise training seems to increase muscle antioxidant enzymes and GSH. Many reports show that vitamin E levels decrease in the muscle and increase in plasma during exercise. Studies of vitamin E deficiency and supplementation strongly suggest that this vitamin is of protective value during exercise.     

Carbon tetrachloride toxicity as a model for studying free-radical mediated liver injury

A single dose of CCl4 when administered to a rat produces centrilobular necrosis and fatty degeneration of the liver. These hepatotoxic effects of CCl4 are dependent upon its metabolic activation in the liver endoplasmic reticulum to reactive intermediates, including the trichloromethyl free radical. Positive identification of the formation of this free radical in vivo, in isolated liver cells and in microsomal suspensions in vitro has been achieved by e.s.r. spin-trapping techniques. The trichloromethyl radical has been found to be relatively unreactive in comparison with the secondarily derived peroxy radical CCl3O2., although each free radical species contributes significantly to the biological disturbances that occur. Major early perturbations produced to liver endoplasmic reticulum by exposure in vivo or in vitro to CCl4 include covalent binding and lipid peroxidation; studies of these processes occurring during CCl4 intoxication have uncovered a number of concepts of general relevance to free-radical mediated tissue injury. Lipid peroxidation produces a variety of substances that have high biological activities, including effects on cell division; many liver tumours have a much reduced rate of lipid peroxidation compared with normal liver. A discussion of this rather general feature of liver tumours is given in relation to the liver cell division that follows partial hepatectomy.     

Novel N-acyl dehydroalanine derivatives as antioxidants: studies on rat liver lipid peroxidation levels and DPPH free radical scavenging activity

Oxidative stress has been implicated in the development of many neurodegenerative diseases such as Parkinson and Alzhemier's disease and is also responsible for aging, artherosclerosis, rheumatoid arthritis and carcinogenesis. Olefins such as dehydroalanines have been shown to inactivate free radicals by forming stabilized free radical adducts. Among these molecules N-acyl dehydroalanines react with and scavenge oxygen and hydroxyl radicals. This study describes the synthesis, characterization and in vitro effects on rat liver lipid peroxidation levels, and DPPH free radical scavenging activities of some N-acyl dehydroalanine derivatives. Compounds c, f and j slightly scavenged the level of DPPH radical at 10(-3) M concentration by about 27, 46, and 56%, respectively while compounds a, d, e, f, g, h showed a strong inhibitory effect on lipid peroxidation at 10(-3)M and 10(-4)M concentrations and inhibition was in the range of 76-90%. The possible antioxidant mechanism of the compounds was discussed.     

Activation of free radicals reaction and changes in the state of antioxidant protection in blood in toxic experimental influenza infection]

The paper presents an experimental model of toxic influenza infection. The toxic form of influenza was shown to result in the activation of free radical processes accompanied by the accumulation of both lipid peroxidation products and methemoglobin and the decrease of alpha-tocopherol in erythrocytes, by the accumulation of NO. and nitrizyl complexes of heme iron in the blood. The activation of free radical processes was followed by the stimulation of antioxidant system in the blood. Thus, there was an increase of both superoxide dismutase activity in erythrocytes and ceruloplasmin content in the blood. The data obtained support the important role of the active products of free radical processes in the development of toxicosis under acute virus infections.     

Activity of marker enzymes and status of the erythrocyte membrane lipid matrix in stress and during its correction using medications]

On the basis of experiments it is shown that chronic stress at the exhaustion stage is followed by activation of lipid peroxidation processes and inhibition of the antioxidant system. Products of peroxide lipid oxidation are accumulated, which in its turn may induce pathological changes in the ratio of different lipid fractions and disturbance in the functional activity of membranes. Under the stress, when a preventive average therapeutic dose of the nicotinic acid derivatives (lithonite, nicogamol, OMI-17) and GABA derivatives (pyracetam, pycamilon) are introduced to rats, activity of marker enzymes remains practically at the control level. A normalizing effect of these drugs on the parameters studied is connected with its expressed membrane-stabilizing effect and non-specific defense of the cytomembranal lipid matrix. Individual peculiarities in pharmacological activity of these drugs are indicated.     

The metabolism of halothane by hepatocytes: a comparison between free radical spin trapping and lipid peroxidation in relation to cell damage

The technique of free radical spin trapping has been applied to demonstrate the formation of free radicals produced during the metabolism of halothane by rat liver hepatocytes under hypoxic conditions. The results obtained support previous findings that reported sex differences in the metabolic activation of halothane by rats in vivo. Cell viability under hypoxic conditions, as judged by trypan blue staining and lactate dehydrogenase release, shows a correlation with the extent of metabolism of halothane as measured by electron spin resonance spectroscopy. The extent of lipid peroxidation was measured by diene conjugation, malondialdehyde production and chemiluminescence. The latter technique allowed the demonstration of lipid peroxidation during incubations of hepatocytes under aerobic conditions. The magnitude of the aerobic chemiluminescence showed a similar sex dependency to the extent of free radical formation under hypoxic conditions. Cell viability measurements show that halothane metabolism in both hypoxic and aerobic conditions can lead to cell death. Consequently, oxidative lipid damage could be a cause of cell damage, as judged by cell viability, additional to covalent binding.     

Increased brain Na, K-ATPase activity of rats under stress

The activities of Na, K- and Mg-dependent ATPases were measured in crude synaptosomal fractions isolated from the rat brain gray matter. Prolonged (6 h) exposure to emotional painful stress stimulated Na, K-ATPase activity by 40% without affecting that of Mg-ATPase. Preliminary injection of the free radical scavenger ionol presented Na, K-ATPase activation, thus suggesting the involvement of lipid peroxidation initiated in brain tissues under stress in acceleration of NA-pump function. However, model studies with lipid peroxidation induced in vitro by an ascorbate-dependent system in a membranous suspension demonstrated an opposite effect, i. e. fast inhibition of Na, K-ATPase. Possible reasons for the different effects of lipid peroxidation in vivo under stress and on Na, K-ATPase activity in vitro are discussed. It is concluded that activation of Na K-ATPase is a mechanism which is responsible for acceleration of reflex conditioning and for the maintenance of the conditioned reflexes in stress-exposed animals.     

Spin Trapping of Free Radicals Produced in vivo in Heart and Liver During Endotoxemia

Studies using free radical scavengers and measurements of lipid peroxidation have suggested that free radicals are generated during endotoxemia. Conclusions from these studies have implied that free radicals may participate in the sequence of pathologic events following endotoxin challenge in the experimental animal. Current inferences of free radical generation and involvement have been derived from indirect evidence and are therefore inconclusive. To quantitate the generation of free radicals in vivo during endotoxemia this study employed the use of electron paramagnetic resonance spectroscopy (EPR) combined with spin trapping techniques. Five minutes before intraperitoneal endotoxin administration, trimethoxy-a-phenyl-t-butyl-nitrone [(MeO), PBN] was administered intraperitoneally. Experimental animals were always matched with control animals receiving no endotoxin. At either five minutes or twenty-five minutes following endotoxin administration animals were decapitated and hearts and livers were rapidly taken for lipid extraction and EPR evaluation. Analysis of the EPR spectra revealed hyperfine splitting constants that indicated the presence of carbon-centered radical spin adducts in both organ tissues from animals exposed to endotoxin for twenty-five minutes. No signals were present in hearts and livers taken five minutes after endotoxin administration. EPR evaluation did not indicate spin adduct formation in control tissue. These data directly demonstrate that activation of processes in vivo involving free radical generation occur early during endotoxemia, but are not detectable immediately after the endotoxin challenge.     

Free radical processes in the embryogenesis of Anura]

The localization of free radical processes and changes in their level during the common frog development have been studied by means of grafted copolymerisation and autoradiography. The maps of distribution of relative concentrations of free radicals were obtained for the beginning of cleavage, blastula, gastrula and neurula. The distinct regionalization was found in the beginning of cleavage: the concentration of the free radicals in the cortical layer and dorsal half of embryo is lower than in the central area and ventral half, resp. At the early blastula stage this regionalization is preserved in its general features. The region of embryo characterized by active free radical processes corresponds to the presumptive endo- and mesoderm in the period of inductive interaction. The possible participation of regional changes in oxidative metabolism in the fertilized egg in the determination of cytoplasmic localization of morphogenetic potencies is discussed. At the later stages there were variations observed in free radicals concentration, which are discussed as being related to the determination and morphogenesis of some rudiments of embryo. A local rise of free radicals concentration was also found out in the eye rudiment just before the onset of its components differentiation.