On the "receptor" mechanism of the effect of biologically active substances in ultra low concentrations

On the basis of antioxidant (alpha-tocopherol and phenosan potassium salt) and peptide (thyroliberin) effects on the lipid peroxide oxidation (LPO) and lipid structural parameters of the endoplasmic reticulum membranes in wide concentration range (10(-20)-10(-4) mol/l) in vitro the possibility concerning a proposed role of "super-affine" receptors in the mechanism of biologically active substances (BAS) action in ultra low doses (ULD) is discussed. Because these substances modulate investigated processes in the membranes which have not ordinarily receptors the conclusion about availability of non-receptor component in the mechanism of BAS effect in ULD and a low probability of "super-affine" receptor existence has been done.     

Effect of low doses of phenozan on lactate dehydrogenase and microviscosity of microsomal membranes of brain cells in mice

It was shown that low doses of phenozan (10(-17), 10(-14), 10(-11), 10(-5) mol/kg) caused changes in kinetic parameters Vmax, Km of LDG and microviscosity in various ranges of microsomal membranes of brain cells. It is suggested that the effect of phenozan on the structure of bilayer membrane is important for binding LDG with membranes.     

Effects of low doses of essential oils on the antioxidant status of the erythrocytes, liver and the brain of mice

We studied the effects of essential oils from oregano and clove and a mixture of lemon essential oil and a ginger extract on the antioxidant state of organs in intact and three experimental groups of Balb/c mice. We found that in vivo essential oils were efficient bioantioxidants when mice were treated with it for 6 months even at very low doses, such as 300 ng/day. All studied essential oils inhibited lipid peroxidation (LPO) in the membranes of erythrocytes that resulted in increasing membrane resistance to spontaneous hemolysis, decreasing membrane microviscosity, maintenance of their integrity, and functional activity. The essential oil significantly decreased the LPO intensity in the liver and the brain of mice and increased the resistance of liver and brain lipids to oxidation and the activity of antioxidant enzymes in the liver. The most expressed bioantioxidant effect on erythrocytes was observed after clove oil treatment, whereas on the liver and brain, after treatment with a mixture of lemon essential oil and a ginger extract.     

Lipid peroxidation in external and internal mitochondrial membranes during anoxia

Accumulation of lipid peroxidation (LPO) products was investigated in external and internal membranes of mitochondria with anoxia. The increase in LPO intensity in mitochondria membranes during hypoxia was shown to be more expressed in external membranes, with an active involvement of phospholipase A2 in the process revealed. Greater LPO intensity and lability of lysosomal membranes caused by contacts with mitochondria with anoxia have been established.     

Acetylcholinesterase activation and enhanced lipid peroxidation after long-term exposure to low levels of aluminum on different mouse brain regions

Aluminum (Al), oxidative stress and impaired cholinergic functions have all been related to Alzheimer's disease (AD). The present study evaluates the effect of aluminum on acetylcholinesterase (AChE) and lipid peroxidation in the mouse brain. Mice were loaded by gavage with Al 0.1 mmol/kg/day 5 days per week during 12 weeks. The mice were divided into four groups: (1) control; (2) 10 mg/mL of citrate solution; (3) 0.1 mmol/kg of Al solution; (4) 0.1 mmol/kg of Al plus 10 mg/mL of citrate solution. AChE activity was determined in the hippocampus, striatum, cortex, hypothalamus and cerebellum and lipid peroxidation was determined in the hippocampus, striatum and cortex. An increase of AChE activity was observed in the fourth group (Al + Ci) in the hippocampus (36%), striatum (54%), cortex (44%) and hypothalamus (22%) (p<0.01). The third group (Al) presented a decrease of AChE activity in the hypothalamus (20%) and an enhancement in the striatum (27%). Lipid peroxidation, measured by TBARS (thiobarbituric acid reactive substances), was elevated in the hippocampus and cerebral cortex when compared with the control (p < 0.01). The effect of aluminum on AChE activity may be due to a direct neurotoxic effect of the metal or perhaps a disarrangement of the plasmatic membrane caused by increased lipid peroxidation.     

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.     

Biochemical effects of chlorpyrifos and deltamethrin on altered antioxidative defense mechanisms and lipid peroxidation in rat liver

Pesticides such as organophosphorus and organochlorine compounds commonly used in agriculture for achieving better quality products are toxic substances and lead to generation of reactive oxygen species (ROS) which have harmful effects on human health. While pyrethroid pesticides are used in preference to organophosphates and organochlorines due to their high effectiveness, low toxicity to non-target organisms and easy biodegradability, they may also produce oxidative stress. Thus, we investigated the effects of chlorpyrifos (CP, an organophosphate) and deltamethrin (DM, a pyrethroid pesticide) treatments at low and high doses on lipid peroxidation (LPO) and antioxidant enzyme activities such as SOD, GSH-Px and CAT in rat liver following 16 weeks exposure. Antioxidative defence mechanisms and lipid peroxidation in rat liver tissues display different responses depending on different pesticide treatments and doses. Biochemical analysis showed that administrations of the chlorpyrifos and deltamethrin cause liver damage. In the present study, we observed that lipid peroxidation levels are higher at high doses than at low doses, but DM caused more pronounced increase than CP. Experimentally, we have also observed that oxidant-antioxidant balance is more affected by deltamethrin treatment than by chlorpyrifos.     

Atrazine-induced alterations in rat erythrocyte membranes: ameliorating effect of vitamin E

Erythrocytes are a convenient model to understand oxidative damage to the membranes induced by various xenobiotics. The objective of the present study was to investigate the propensity of atrazine to induce oxidative stress and its possible attenuation by vitamin E. Experimental animals were orally administered atrazine (300 mg kg(-1) body weight, daily) and vitamin E (100 mg kg(-1) body weight, daily) for a period of 7, 14, and 21 days. Erythrocyte membranes were prepared and analyzed for acetylcholinesterase (AChE) activity, lipid peroxidation (LPO), and lipid composition. Susceptibility of erythrocytes to atrazine exposure was further investigated in terms of morphological alterations by scanning electron microscopy (SEM). Results indicate that atrazine exposure caused a significant inhibition of AChE activity and induction of oxidative stress in terms of increased malondialdehyde (MDA) levels. Atrazine treatment significantly decreased total lipid, cholesterol, and phospholipid content of erythrocyte membranes. SEM revealed varying degrees of distortion depending on duration of atrazine exposure. However, administration of vitamin E ameliorated the oxidative stress and changes in the erythrocyte membranes induced by atrazine.     

The antiradiation properties of the ecdysteroid-containing compounds

The antiradiation properties of the ecdysteroid-containing preparations ("serpisten" and inokosterone) are studied under their application before or after the 22.6 cGy chronic low intensity gamma-irradiation of mice. It is shown that the antiradiation of these compounds depend on the dose of preparations and time of the application before or after irradiation of mice. "Serpisten" prevented the decrease of the growth of the body mass of irradiated mice. The normalization of the phospholipid composition of the mice liver and blood erythrocytes for the most investigated parameters revealed under the application of this compound at the dose of 50 mg/kg after the irradiation of animals. The capacity of "serpisten" to decompose of peroxides is shown in vitro. Inokosterone had the certain anabolic properties, caused the normalization of the total peroxidase activity of blood and intensity of the lipid peroxidation (LPO) in brain and in liver, and also the repair of the interrelation between the LPO intensity and catalase activity in the irradiated mice liver. The obtained results allow to conclude that the antiradiation properties of the ecdysteroid-containing preparations under the chronic low intensity irradiation of animals at the low dose due to their capacity to depend on the LPO regulatory system parameters.     

Lipid peroxidation in rabbit and rat visual system structures

In our work, the lipid peroxidation (LPO) in the retina, optic chiasma, and visual cortex of rat and rabbit brain was investigated. The contents of the LPO products (diene conjugates, triene conjugates, TBA-reactive products, Schiff bases) and oxidation index (calculated as 232/2 15) were similar in the retina and visual brain cortex of rats. In vivo, lipid oxidation in the optic chiasma was higher as compared with two other parts of visual tract. The similar data were obtained in our experiments with rabbit's visual tract. The sensitivity of tissues to peroxidation in vitro was studied in homogenates incubated with 0.2 mM ascorbate and 10 mkM FeSO4 for 20 min at 37 degrees C. The results of these experiments deviated from the data obtained in vivo, namely: the LPO in optic chiasma was lower than in the retina and the brain cortex. This data are in compliance with lipid composition of investigated parts of the visual tract of both animals. In our opinion, the high level of LPO in optic chiasma demonstrated in vivo is due to low antioxidants level in this part of the visual tract. Our findings also indicate that LPO in retina both in vivo and in vitro experiments are similar to those in the brain cortex and may be attributed to similar lipid composition and activity of antioxidant enzymes (such as superoxiddismutasa and glutathionereductase).     

Excessive hippocampal acetylcholine levels in acetylcholinesterase-deficient mice are moderated by butyrylcholinesterase activity

Central cholinergic systems are involved in a plethora of brain functions and are severely and selectively damaged in neurodegenerative diseases such as Alzheimer's disease and dementia with Lewy bodies. Cholinergic dysfunction is treated with inhibitors of acetylcholinesterase (AChE) while the role of butyrylcholinesterase (BChE) for brain cholinergic function is unclear. We have used in vivo microdialysis to investigate the regulation of hippocampal acetylcholine (ACh) levels in mice that are devoid of AChE (AChE-/- mice). Extracellular ACh levels in the hippocampus were 60-fold elevated in AChE-/- mice compared with wild-type (AChE+/+) animals. In AChE-/- mice, calcium-free conditions reduced hippocampal ACh levels by 50%, and infusion of tetrodotoxin by more than 90%, indicating continuous ACh release. Infusion of a selective AChE inhibitor (BW284c51) caused a dose-dependent, up to 16-fold increase of extracellular ACh levels in AChE+/+ mice but did not change ACh levels in AChE-/- mice. In contrast, infusion of a selective inhibitor of BChE (bambuterol) caused up to fivefold elevation of ACh levels in AChE-/- mice, but was without effect in AChE+/+ animals. These results were corroborated with two other specific inhibitors of AChE and BChE, tolserine and bis-norcymserine, respectively. We conclude that lack of AChE causes dramatically increased levels of extracellular ACh in the brain. Importantly, in the absence of AChE, the levels of extracellular ACh in the brain are controlled by the activity of BChE. These results point to a potential usefulness of BChE inhibitors in the treatment of central cholinergic dysfunction in which brain AChE activity is typically reduced.     

Effect of thiopental sodium and barbitone sodium on the total acetylcholine content and acetylcholinesterase activity in the brain tissue of Arvicanthis niloticus

The total ACh content and AChE activity were determined 1 hr after the i.p. injection of different doses of thiopental sodium (5, 10 and 20 mg/ml/100 g body wt) and barbitone sodium (20, 40 and 80 mg/ml/100 g body wt). The effect of different time intervals (1 min, 10 min, 30 min, 1 hr, 2.5 hr, 5 hr, 8 hr, 12 hr, 24 hr and 48 hr) on the total ACh content and AChE activity was investigated after i.p. injection of 10 mg thiopental sodium and 40 mg barbitone sodium/ml/100 g body wt. Both thiopental sodium and barbitone sodium increased the total ACh content in the brain tissue of Arvicanthis niloticus. Both drugs inhibited the brain AChE activity. It is thought that the increase in the total ACh content in the brain tissue of Arvicanthis niloticus may be due to a decrease in the release of ACh from the neuronal tissue and a decrease in AChE activity.     

Effect of aluminum on iron-induced lipid peroxidation and protein oxidative modification of mouse brain homogenate

In the present study the authors report on the enhancing effect of aluminum(III) (Al[III]) on iron(II)(Fe[II])-induced lipid peroxidation (LPO) of mice brain homogenate, which occurs in a concentration and time-dependent manner. No evidence of LPO caused by Al alone was found. Both Al(III) and Fe(II) ions induced protein oxidative modifications in mice brain homogenate, in a time and concentrationdependent manner. Aluminum enhances Fe(II)-induced protein oxidative modification at a concentration of 2:1 and 1:1 Al:Fe molar ratios. However, Al suppress Fe(II)-induced protein oxidative modification at a concentration of 0.5:1 Al:Fe molar ratio. Addition of ethylenediaminetetraacetic acid (EDTA) inhibits both LPO and protein oxidative modifications induced by Al(III) and Fe(II) ions. Addition of mannitol and of Superoxide dismutase (SOD) did not show such effects. It is concluded that in mice brain homogenate, Al accelerates Fe(II)-induced LPO. Protein oxidative modifications caused by Fe(II) and/or Al ions are enhanced at high, but suppressed at low concentrations of Al ions. The latter observation suggests a possible biological role of Al as an antioxidant.     

Antioxidant capacity of allopurinol in biological systems

The antioxidant capacity of allopurinol was investigated in three biological systems by measurements of visible chemiluminescence, oxygen uptake and production of thiobarbituric acid reactive substances (TBARS). The addition of allopurinol to rat brain homogenates undergoing autoxidation and erythrocyte ghost membranes supplemented with 2,2'-azo-bis-(2-amidinopropane), in concentrations up to 2 mM, has a negligible effect on lipid peroxidation development. In erythrocyte ghost membranes exposed to gamma irradiation (9.5 Gy/min), allopurinol inhibits the radiation-induced lipid peroxidation with a Q(1/2) of 2.0 mM. It is suggested that allopurinol may have an alternative antioxidant pathway of action in biological systems, probably through a scavenging action upon hydroxyl radicals.     

In vitro effect of synthetic water-soluble antioxidants of the class of screened phenols on the beta-adrenergic system in the cardiocyte plasma membranes of rats

Influence of synthetic water-soluble antioxidants gamma-(4-oxi-3,5-ditret-butylphenol) propionate (phenozan) and the potassium salt of phenozan on the signal processing in beta-receptor-adenylate-cyclase complex of rat cardiocyte membranes has been studied. It was demonstrated that these compounds act at the level of signal transduction from receptor to adenylate cyclase catalytic subunit rather than at the level of ligand-receptor complex formation. At concentrations exceeding-10 microM the antioxidants inhibit both isoproterenol-stimulated synthesis of cyclic 3',5'-AMP and accumulation of the products of lipid peroxidation in membranes. It is proposed that in vitro addition of antioxidants on cardiocyte beta-receptor-adenylate-cyclase complex is a result of alteration of physico-chemical properties of membrane lipids caused by these inhibitors of free radical reactions.     

Effect of superlow doses (10(-18)-10-(-14) M) of biologically active substances: general rules, features, and possible mechanisms]

The effects of ultra-low (10(-18)-10(-14) M) doses (ULD) of biologically active substances have been reviewed in terms of common regularities of ULD effects and peculiarities of action of various groups of compounds. The most common and at the same time paradoxical regularities of ULD action are bi- or polymodal patterns of dose dependence, absence or presence of an inverse effect at higher doses, and instability of ULD effect. Possible mechanisms of ULD action including the mechanism based on the adaptation theory are discussed.     

Stabilizing effect of hydroxybenzimidazole and its derivatives on biological membranes during activation of lipid peroxidation

Inhibition of lipid peroxidation (LPO) by oxybenzimidazole (OBI) and its derivatives--alkyloxybenzimidazole (AOBI) and alkylethoxybenzimidazole (AEBI) was studied in liver microsomes and brain synaptosomes. It has been shown that both OBI and AOBI strongly inhibit LPO in microsomes and not synaptosomes. AEBI failed to inhibit LPO in microsomes. AOBI is more potent than OBI both in ascorbate- and NADPH-dependent LPO of microsomes. An antioxidant effect of both compounds is more marked in ascorbate-dependent LPO. The investigation of the possible use of AOBI for the protection of liver membranes in various pathological conditions associated with LPO activation seems promising.     

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.     

Biological and methodological implications of prostaglandin involvement in mouse brain lipid peroxidation measurements

Enhanced cyclooxygenase-mediated prostaglandin (PG) turnover occurring during sacrifice and biochemical processing of tissues also generates malondialdehyde (MDA), a product of lipid peroxidation (LPO). Studies reporting on LPO estimated by thiobarbituric acid reactive substances (TBARS) have failed to consider such artefactual increases. This study reports the relative proportion of PG metabolism-derived MDA (PG-MDA) in mouse brain regions during the TBARS assay. The cyclooxygenase inhibitor indomethacin significantly lowered MDA in fronto-parietal cortex and corpus striatum. Indomethacin (50–800 g/ml, in vitro) increased estimated TBARS in whole brain. Such enhancement was absent when indomethacin (20–80 g/sample) was added to the MDA standard curve, reflecting its interaction with TBARS other than MDA. PG-MDA contributes as much as 15% to the total estimated value of MDA in fronto-parietal cortex and corpus striatum and must be corrected for in LPO studies.     

Alpha-tocopherol and gamma-tocopherol attenuate ethanol-induced changes in membrane fatty acid composition in embryonic chick brains

BACKGROUND: This project investigated whether or not EtOH-induced reductions in the levels of long-chain polyunsaturated membrane fatty acids could be attenuated by exogenous exposure to either alpha-tocopherol, gamma-tocopherol, or diallyl sulfide (DAS). METHODS: At 0 days of development, fertile chicken eggs were injected with a single dose of either saline supplemented with various concentrations of EtOH, alpha- or gamma-tocopherol and EtOH, or DAS and EtOH. At 18 days of development, brains were isolated and subjected to membrane analyses. RESULTS: When exposed to EtOH, concentrations ranging from 0-60.50 microm/Kg egg, dose-dependent decreases in the levels of brain 18:0, 18:1 (n-9), 18:2 (n-6), 18:3 (n-3), and 20:4 (n-6) were observed. These ethanol-induced changes in membrane fatty acid composition correlated with ethanol-induced reductions in brain mass, brain protein levels, acetylcholine esterase (AChE) activities and correlated with increased lipid hydroperoxide levels. Exposure to either 2.5 microm alpha-tocopherol/Kg egg and 6.050 mm EtOH/Kg egg, or 2.5 microm alpha-tocopherol/ Kg egg and 6.050 mm EtOH/Kg egg attenuated EtOH-induced changes in membrane fatty acid composition, brain mass, brain protein levels, AChE activities, and lipid hydroperoxide levels. Embryonic exposure to the cytochrome p450-2E1 inhibitor, diallyl sulfide (DAS), also attenuated EtOH-induced decreases in long-chain, unsaturated membrane fatty acids. However, embryonic exposure to DAS promoted abnormally low brain mass. CONCLUSION: EtOH-induced reductions in the levels of brain long-chain polyunsaturated fatty acid are caused by lipid peroxidation.