Carnosine prevents the activation of free-radical lipid oxidation during stress

Carnosine (beta-alanyl-L-histidine) injected to intact albino rats (20 mg/kg body weight) induces depletion of lipid peroxidation (LPO) products in brain and blood serum, an increase of superoxide scavenging activity in brain and serum, decrease of cholesterol: phospholipid ratio and increase of easy oxidizable phospholipid portion in brain lipid extracts. After painful stress (footshock during 2 hours) LPO products are accumulated in brain and serum, cholesterol: phospholipid ratio increases and the portion of easy oxidizable phospholipids decreases. Carnosine given before stress prevents LPO activation. Effects of carnosine and stress are not additive: LPO inhibition induced by carnosine is much more in rats subjected to stress.     

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.     

Apha-tocopherol in a complex with dimethyl sulfoxide--an agent possessing highly effective adaptogenic action in chronic emotional-pain stress in rats

Alpha-tocopherol (5 mg/kg) administered perorally with dimethyl sulfoxide (50 mg/kg) in chronic emotional pain stress in rats possesses an effective antistress action, exceeding the effects of these drugs administered separately. Their prophylactic complex administration prevents the hypertension produced by stress, disturbance of reactivity of the vegetative nervous system during functional load, change of the behaviour in the open field. Adaptogenic action of the drugs is accompanied by a reduction of the content of free-radical oxidation products and by raising of superoxide scavenging activity in the brain and blood serum, by raising of phospholipids content, lowering of cholesterol content and of the ratio of cholesterol phospholipids in the brain extracts.     

Lipid peroxidation in experimental allergic encephalomyelitis

Lipid peroxidation (LPO) in the brain and blood of guinea-pigs was studied during experimental allergic encephalomyelitis. The most pronounced activation of LPO in the brain occurred at the 7th day of sensitization with encephalolitogenic emulsion. It manifested by an increase in the content of diene conjugates and malonic dialdehyde, activation of catalase and reduction of superoxide dismutase activity. LPO activation in the blood occurred at the 3th-5th day of sensitization. It is assumed that LPO activation is caused by antigen-antibody reaction that occurs in the blood at the 3d day and in the brain at the 7th day of sensitization.     

Free radical lipid oxidation affects cholesterol transfer between lipoproteins and erythrocytes

Human erythrocytes were incubated for 5 h at 37 degrees C with lipoproteins (LP), preliminary oxidized to different extent, as assessed by thiobarbituric acid (TBA) test. Cholesterol content in the cells was increased by 12-14% after incubation with low-density lipoproteins (LDL) along with augmentation of order parameter and rotational correlation time of spin-labeled stearic acids incorporated into membranes. If erythrocytes were incubated with oxidized LDL, containing 2.5-4 times more TBA-reactive material than native ones, cellular content of cholesterol was increased by 24-28%. In contrast, high-density lipoproteins (HDL2 and HDL3) removed cholesterol from cell membranes, when incubated with erythrocytes. This was followed by increased fluidity of membrane lipid phase as detected by the spin probe method. Oxidation of HDL2 and HDL3 decreased their ability to accept cholesterol from cell membranes. No detectable accumulation of TBA-reactive material was observed in the samples during the incubation. The antioxidant, butylated hydroxytoluene (BHT), in the concentration of 10(-5) M did not influence the cholesterol transfer between LP and erythrocytes. Hence, the effects of lipid peroxidation (LPO) on the cholesterol transfer seem to result from LP alterations by oxidation rather than from free radical reactions occurring during the incubation. By increasing cholesterol-donating ability of LDL and inhibition of cholesterol-accepting capacity of HDL lipid peroxidation in LP may activate cholesterol accumulation in blood vessel cells and thus contribute to atherosclerosis.     

Heme oxygenase activity in rat organs during cadmium chloride administration

Heme oxygenase activity, the level of spontaneous and ascorbat-induced LPO in the liver, kidney and spleen homogenates of rats and blood serum absorption spectrum in the Soret region in different periods both after CdCl2 and prior alpha-tocopherol administration were studied. The increase in the hemolysis products content in the serum was observed in 15 min after CdCl2 injection and remained during 24 h. Heme oxygenase activity in the liver and kidney increased after 6 h and stayed at the same level 24 h after CdCl2 administration. The level of spontaneous LPO in the spleen increased after 6 h, and in the liver and kidney the level of spontaneous and ascorbat-induced LPO increased in 24 h after CdCl2 injection. The preliminary alpha-tocopherol administration did not prevent the accumulation of hemolysis products in the serum and the increase of heme oxygenase activity in the liver and kidney caused by CdCl2 administration. However, the increase in the ascorbat-induced LPO in these organs was completely blocked. The role of heme and LPO in the heme oxygenase induction by CdCl2 are discussed.     

Free radical modification of lipoproteins and cholesterol accumulation in cells upon atherosclerosis.

An electron spin probe study was made of the effect of lipid peroxidation (LPO) on the structure of surface proteolipid layer of human serum low-density lipoproteins (LDL). The results obtained with a positively charged spin label and stearic acid spin probes with doxyl labels at positions 5, 12, and 16 revealed that LPO caused a decrease in phospholipid molecule mobility both in the region of polar heads and in the region of acyl chains till the depth of at least 1.7 mm from water-lipid interface. Under relatively high levels of oxidation (more than 6 mumol MDA/g LDL phospholipid) the polarity of lipid phase increased. The decrease in efficiency of tryptophan fluorescence quenching by nitroxide fragments incorporated in hydrophobic regions at the depth of approximately 2 nm from water-lipid interface indicated that lipid-protein interaction was disturbed as a result of oxidation of LDL lipids. In addition, the LPO-induced modification of apo-B, the main protein of LDL, was examined with maleimide spin label. LPO led to increase in mobility of strongly immobilized maleimide labels and in the number of weakly immobilized ones. Oxidized LDL revealed decreased ability to incorporate spin-labeled steroid (androstane) as compared to native ones. LPO-induced structural changes of LDL surface are supposed to be a reason of enhanced accumulation of cholesterol in human monocytes during their incubation with oxidized LDL. The cholesterol content in red cells was shown to be directly correlated to MDA content in apo-B containing lipoproteins but not in whole serum. Our findings suggest that free radical modification of serum lipoproteins but not solely an increased level of LPO products in blood is one important cause for cholesterol accumulation in cells and, apparently, for their transformation into foam cells during atherosclerosis.     

Delayed Increase of Brain Noradrenaline After Acute Footshock Stress in Rats

Several lines of evidence strongly suggest that accumulation of noradrenaline (NA) in the brain may underlie the hyperarousal symptoms experienced in post-traumatic stress disorder. In animal experiments, however, the effect of stress on NA content appears complex; acute stress reduces the level, while chronic stress tends to increase it. To explain this discrepancy, it is necessary to observe the long-term effects of acute stress on NA metabolism in the brain. In this study, rats were exposed to intermittent intense footshock stress for 1 h, and the brain NA content was measured for 7 days after the stress stimulus. Hypothalamic NA content was immediately reduced and recovered within 24 h. However, a significant NA increase was observed 7 days after the footshock. In the cerebral cortex and hippocampus, an increase in NA content was observed 1 day after the stress and lasted for at least 7 days. The fact that the content of 3-methoxy-4-hydroxyphenylglycol, a major NA metabolite, only transiently increased in all these regions possibly reflects NA release. These results indicate that increase in the brain NA content can be induced by acute stress, though its emergence is delayed. Importantly, this suggests that both acute and chronic stress may lead to NA accumulation under the same mechanism.     

Heat shock induces oxidative stress in rotan Perccottus glenii tissues

The effects of temperature transition from 19 to 32 °C on oxidative stress indices and activities of the main antioxidant enzymes were investigated in the rotan, Perccottus glenii. Levels of lipid peroxides (LOOH), thiobarbituric acid-reactive substances (TBARS), low- (L-SH) and high-molecular mass (H-SH) thiols and activities of superoxide dismutase (SOD) and catalase were measured in rotan brain, liver and muscle over 1–12 h of high-temperature exposure followed by 3 or 24 h lower (19 °C) temperature recovery. Heat shock exposure during 1 h transiently increased 1.5–3.2-fold LOOH levels in rotan tissues with subsequent suppression of their content; however, 12 h exposure again increased LOOH levels in the brain. TBARS content were elevated by 2–3-fold during the entire heat shock exposure in the brain and liver. Levels of both products of lipid peroxidation were generally near control values during return to 19 °C. L-SH content was lowered during heat shock exposure in the brain, transiently increased after 6 h in the liver and almost disappeared after longer treatment in the muscle. Liver H-SH content slightly decreased under heat shock exposure, but was elevated after 6 h in the brain and muscle. In the latter case, L-SH level was below control values during recovery. SOD activities increased 2-fold in the liver after 6–12 h heat shock. Liver catalase activities decreased at the same conditions. Generally, a quick response to suppression of lipid peroxidation and possible involvement of its products in the up-regulation of antioxidant enzymes seem to be key adaptations to high temperature.     

Effect of conditioned-reflex bilateral avoidance learning on lipid components of the rat brain

The active avoidance training of rats resulted in a depletion of lipid peroxidation (LPO) products in cerebral cortex. LPO inhibition was also shown in cerebral cortex of "active control" group receiving +non-combined stimuli (the effect of short-term stress). LPO inhibition was more pronounced in rats staining a training criterion compared to rats which received combined stimuli but did not reach the criterion. In the active control group LPO inhibition was accompanied by total phospholipids accumulation and cholesterol depletion in cortical lipid extracts. Irrespective of attaining the criterion in all rats trained for active avoidance the accumulation of cholesterol was seen. Active avoidance training affected also the phospholipid composition of cerebral cortex.     

Changes of superoxide dismutase, glutathione perioxidase and lipid peroxides in the brain of mice preconditioned by hypoxia.

We have developed an animal model of hypoxic preconditioning and assumed that oxygen radicals and their endogenous scavenging enzymes may play an important role in the preconditioning. To test this hypothesis, activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and the content of lipid peroxides (LPO) were measured during the preconditioning. Compared with unpreconditioned control animals, in animals exposed to hypoxia only once, the activities of SOD and GSH-Px in whole brain were found to be significantly decreased while the LPO content in the hippocampus significantly increased. However, those in animals exposed to 4 runs of hypoxia tended to return to control levels and were lower than those in animals exposed to 1 and 2 runs of hypoxia. Our results indicate that the oxygen radicals and their specific scavenging enzymes seem to be involved in the development of tolerance to hypoxia.     

Effects of acute stress on lateralization of lipid peroxidation in the brain depend on the behavioral typology of rats

Using the "emotional resonance test" albino mongrel male rats were separated for their preference to light or dark space during the cry of a "victim" rat receiving footshock. Rats avoiding the cry of a "victim" by moving to the light space were characterized by higher levels of lipid peroxidation (LPO) products. A short footshock resulted in a dramatic LPO decrease in both hemispheres in the brain of all rats under study, but in rats not avoiding the cry of a "victim" (preferring dark space) "left" asymmetry of LPO increased.     

Dynamics of oxidation stress markers during long-term antiorthostatic hypokinesia: A retrospective study

Nine volunteers aged 27 to 42 participated in an experiment with 370-day antiorthostatic hypokinesia at–5°C, and their blood serum samples were tested for the concentrations of lipid peroxidation (LPO) derivatives, including diene conjugates (DCs), malonic dialdehyde (MDA), and Schiff bases (SBs), and indices of the antioxidant defense system, including the tocopherol (TP) concentration and total antioxidant activity (AOA). The subjects were divided into two groups, which differed in physical training regimen and prophylaxis measures. Initial LPO steps were inhibited in both of the groups by 54–73% from day 50, while the level of SBs, which are final LPO products, decreased by 50–61% by day 230 and remained much the same up to the end of the experiment. The MDA and SB concentrations decreased by a factor of 1.6–2.3 during recovery. Total AOA decreased as an aftereffect during recovery to a level far lower than physiologically normal. Based on the significant inhibition of free-radical LPO throughout the experiment, long-term adaptation to simulated hypogravity was accompanied by a pronounced decrease in biological oxidation and caused severe stress. Substantial long-term readaptation stress developed during recovery after 370-day antiorthostatic hypokinesia, as was evident from the facts that the LPO activity was almost halved, TP concentration significantly increased, and the functional reserves of water-soluble antioxidants were exhausted. Lack of LPO activation was assumed to reflect adequate compensation in the subjects.     

Role of lipid peroxidation in damage to serotonin receptors and development of epileptiform seizures during hyperoxia

Hyperoxia brought about substantial accumulation of primary and end products of lipid peroxidation (LPO) and a significant lowering of alpha-tocopherol content in rat brain tissues. Preinjection of animals with synthetic and natural antioxidants (4-methyl-2,6-ditretbutylphenol and alpha-tocopherol) prevented LPO activation and decreased the frequency of epileptiform seizures induced by hyperoxia. Administration of a mixture of unsaturated fatty acids led to an opposite effect. The changes in the properties of serotonin receptors were found to be dependent on the hyperoxia-induced LPO. These changes were marked by the reduced specific binding of serotonin with neuronal membranes of the rat brain cortex. The data obtained allowed the conclusion about the key role played by LPO activation in toxic action of hyperbaric activation on the brain.     

Modulatory effect of spice extracts on iron-induced lipid peroxidation in rat liver

The antioxidants in foods play an important role in preventing the generation of reactive oxygen species (ROS). Some of the dietary constituents, commonly used in Indian foods such as cloves (Syzygium aromaticum), licorice (Glycyrrhiza glabra), mace (aril of Myristica fragrans) and greater cardamom (Amomum subulatum), were selected as the test samples to find their effect on the inhibition of lipid peroxidation (LPO) in rat liver homogenate. Three different oxidant systems were used to induce LPO. The results show that all the spices have antioxidant activities at various concentrations. None of the spices showed prooxidant properties. The effect of spices on the inhibition of LPO was concentration dependent. Cloves, mace and cardamom inhibited the initiation as well as propagation phases of FeCl_{3} induced LPO, while licorice inhibited the initiation phase only. The reducing power and the superoxide scavenging activity of spices was also measured in vitro. The reducing power of various spices increased with concentration. The percentage inhibition of superoxide radical generation by the spices was also observed to be concentration dependent. The results show that spices used in the present study have significant ability to inhibit LPO due to their polyphenol content, strong reducing power and superoxide radical scavenging activity. Cloves showed the highest antioxidant activity probably due to the higher polyphenol content as compared to other spices.     

Influence of N-palmitoylethanolamine on the phospholipid and fatty acid composition of rat liver in ischemia

The effect of N-palmitoylethanolamine (NPE, 10(-5) M) on the lipid peroxidation (LPO) processes, phospholipid and fatty acid content in the rat liver at perfusion and ischemia during the liver preservation was estimated. As early as at the 5th min of perfusion by cooled conserving solution "Eurocollins", LPO activation was determined. Simultaneously the content of lysophosphatidylcholine (LPC) and phosphatidylserine increased, the total cholesterol level decreased. The redistribution of saturated and unsaturated fatty acids quantity was detected. The addition of NPE into "Eurocollins" solution reduced the accumulation of malonedialdehyde and LPC, modified the fatty acids content. These effects, evidently, formed the basis of the protective action of NPE on the hepatic tissues under anoxia.     

THE EFFECT OF HYPOXIA ON MONOAMINE SYNTHESIS, LEVELS AND METABOLISM IN RAT BRAIN

Abstract— Rats were exposed to 5.6% oxygen environments for up to 2 h. The accumulation of brain DOPA and 5-hydroxytryptophan at 30 min after decarboxylase inhibition was used to estimate cerebral tryosine and tryptophan hydroxylase activity, respectively, in vivo. There was a continuing decrease in tryosine hydroxylase activity during the 2 h in whole brain as well as five brain regions. Tryptophan hydroxylase activity declined during the 1st h, but then increased towards control levels during the 2nd h. There was an increase in brain tryptophan during the 2nd h as well. In whole brain and the five brain regions, there was no significant change in the levels of noradrenaline, dopamine or 5-hydroxytrypamine. During a 1 h exposure to 5.6% oxygen, there was decreased accumulation of noradrenaline, dopamine and 5-hydroxytryptamine after MAO inhibition and decreased accumulation of homovanillic acid and 5-hydroxyindoleacetic acid after probenecid administration. The dercreased synthesis and metabolism of the monoamines is most likely attributable to insufficient brain tissue oxygen as a substrate for the two hydroxylase enzymes.     

Antistress effects of vitamin E and dimethylsulfoxide during their combined administration in low doses

Low doses of vitamin E (5 mg/kg body weight) and dimethyl sulfoxide (50 mg/kg) given simultaneously orally to albino rats prevented the disturbances of the behaviour and vegetative functions induced by chronic emotional painful stress. The adaptive effect of vitamin E or dimethyl sulfoxide given alone was much lower or altogether absent. The antioxidant combination used decreased the intensity of lipid peroxidation in the brain and blood serum as well as cholesterol content in brain lipids and activated brain superoxide dismutase and nonenzymatic superoxide scavenging activity of the serum. The results obtained suggest that the combination of vitamin E with dimethyl sulfoxide may be used for the treatment of pathological conditions accompanied by lipid peroxidation syndrome.     

Comparative-physiological study of leukocyte participation in initiation of lipid peroxidation during nitrite intoxication in rats and muskrats

The study is carried out on Wistar white rats non-adapted to oxygen deficit and on semiaquatic rodents muskrats adapted to periodic arrest of respiration during diving under conditions of Nembutal narcosis. It has been revealed that 1 h after a subcutaneous injection of sodium nitrite (3 mg/100 g body mass), intensification of lipid peroxidation (LPO) in the muskrat brain is absent, the activity of the antioxidant enzyme catalase increasing 16 times (p < 0.01) as compared with control injected with equivalent saline volume. In heart and liver, there was a statistically significant decrease of the content of LPO products active in the test with 2-thiobarbituric acid; in the femoral muscle tissue, the LPO intensity did not change. In rats, unlike muskrats, after injection of sodium nitrite, an increase of LPO is recorded in brain, while a decrease of the LPO product content in the femoral muscle; in liver the LPO intensity did not change. In muskrats, the sodium nitrite administration led to a decrease of the leukocyte spontaneous mobility, of lymphocyte cytokine-producing activity, and of neutrophil bactericidal activity (by the content of cationic proteins in neutrophilic phagocytes), whereas in rats the leukocyte mobility did not change, only the blood neutrophil bactericidal activity decreased. The ability of neutrophils to produce the superoxide anion during the nitrite intoxication did not change both in rats and in muskrats. The obtained data allow concluding that under conditions of Nembutal narcosis the leukocyte functional activity on the background of nitrite intoxication is suppressed to the greater degree in the muskrats genotypically adapted to oxygen deficit than in immunocompetent cells of the rodents not adapted to hypoxia.     

The effect of carnosine on indicators of free radical lipid oxidation during acute stress in rats

The effect of carnosine intraperitoneal injection in rats (in doses 0.2, 2.0 or 20 mg/kg) on the vegetative parameters (arterial blood pressure, Hildebrandt index), the content of free radical oxidation (FRO) products and superoxide dismutase activity in serum and brain homogenates and brain lipid composition under normal condition and after different stress forms have been investigated. The carnosine injection in dose 20 mg/kg preserves and increase in arterial pressure and Hildebrandt index at all steps of stress development. The phase non-unidirectional changes in studied biochemical parameters have been revealed depending on the level of stress development in animals under control. The unidirectional and dose-dependent changes of phospholipid content and the level of brain lipids, decrease of FRO products in tissue and brain cholesterol, the increase of the superoxide dismutase activity of serum and brain homogenates have been found in intact and stressed animals after carnosine injection. A comparison of carnosine pharmacokinetics with concentration dependences of the antioxidative effect under in vitro and in vivo experiments comes to conclusion concerning the carnosine indirect adaptogenic action.