Aging-related changes in the sensitivity of the system of respiratory control and the intensity of free-radical processes in humans

Results of a comparative study of the sensitivity of the system of respiratory control to increases in the CO₂ concentration and the intensity of free-radical processes in young and elderly subjects are described. It is shown that normal (natural) aging is accompanied by a decrease in the sensitivity of the respiratory system to hypercapnic stimulation and a parallel significant decrease in the activity of catalase in the blood of examined subjects. Mechanisms responsible for the modifications of the sensitivity of the system of respiratory control to hypercapnia are discussed; these shifts can be at least partly related to changes in the intensity of production of free radicals observed in elderly subjects. Neirofiziologiya/Neurophysiology, Vol. 40, No. 1, pp. 53–57, January–February, 2008.     

The effect of hyperbaric oxygenation on the antioxidant status of Xenopus laevis after its preliminary adaptation to oxygen]

We studied the level of lipid peroxidation and the activity of antioxidant enzymes (superoxide dismutase and catalase) in various tissues of adult Xenopus laevis after an initial exposure to hyperbaric oxygenation at the developmental stage 38. We have found that irrespective to the mode of treatment, the level of lipid peroxidation and activity of antioxidant enzymes in the brain, lungs, and blood of these animals were higher as compared to control animals. We demonstrate that, after the exposure of adult animals to hyperoxia, if they were earlier subjected to hyperbaric oxygenation (0.2 MPa) at stage 38, there was no intensification of lipid peroxidation or changes in the activity of superoxide dismutase and catalase. In adult animals initially subjected to hyperbaric oxygenation at the same stage of development but at the pressure--0.7 MPa, the second exposure to hyperoxia led to a drastic intensification of lipid peroxidation in the brain; in some animals, an increased level of lipid peroxidation products in the lungs was observed.     

Role of Glutamate in the Mechanisms of Adaptation of the System of Respiratory Control in Rats to Intermittent Hypoxia

In experiments on Wistar rats, we studied the role of changes in the state of glutamatergic transmission in the course of adaptation of the system of respiratory control to intermittent hypoxia. The volume/temporal parameters of respiration were estimated according to characteristics of EMG activity (amplitude, integral intensity of EMG discharges) recorded from the diaphragmatic muscle. Changes in EMG activity of the diaphragm induced by acute hypoxia (breathing a 12% О₂-containing gas mixture) were estimated before and after of a 14-day-long course of intermittent hypoxia trainings and before and after inductions of a blocker of NMDA receptors, МK-801. The results prove that the glutamatergic transmitter system is significantly involved in the reaction of the respiratory system to presentation of a hypoxic stimulus within all stages of formation of the ventilatory response, both before and after the action of intermittent hypoxia. Blocking of NMDA receptors under conditions of adaptation to intermittent hypoxia exerted a more intense influence on the amplitude of respiratory EMG discharges of the diaphragm than on their frequency.     

Effect of acute hypoxia on the intensity of free radical processes in the basal nuclei of the brain, and the rat behaviour in the open field test under conditions of altered photoperiod

The effect of acute hypoxia on the intensity of free radical processes in the basal nuclei (the nucleus caudatus, globus pallidus. nucleus accumbens. amygdaloid complex) of the brain, and the rat behaviour in the open field test has been studied under conditions of altered photoperiod. It has been shown that constant darkness levels the effect of acute hypoxia on the intensity of lipid peroxidation, preserves the activity of superoxide dismutase and catalase at a higher level, lowers the activity of glutathione peroxidase. Under light, the sensitivity of basal nuclei neurons to acute hypoxia is enhanced, the latter being reflected in intensification of lipid peroxidation at the expense of increased formation of dien conjugates. The activity of catalase at that considerably exceeds the level of even intact rats in all the structures. It has been established that an altered photoperiod modulates the effect of acute hypoxia on the parameters of rat's activity in the open field, the character of their change depending on the nature of a photophase change.     

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.     

Production of reactive oxygen species and antioxidant enzymes of pea and soybean plants under hypoxia and high CO<Subscript>2</Subscript> concentration in medium

Generation of reactive oxygen species (ROS) and activities of antioxidant enzymes (catalase, peroxidase, ascorbate peroxidase) in pea (Pisum sativum L.) and soybean (Glycine max L.) under hypoxia (3–24 h) and high CO₂ concentration in medium were studied. In sensitive to hypoxia pea seedlings, hypoxia enhanced markedly production of superoxide anion-radical, hydroperoxides, and especially hydrogen peroxide. In more tolerant soybean plants, these changes were less pronounced. During first hours of hypoxia, activity of lipoxygenase in plant cells increased. This allows a suggestion that this enzyme is involved in the processes of hydroperoxide accumulation in plant tissues under oxygen deficit. In pea and soybean plants, a correlation between tolerance to hypoxia, the rate of ROS generation, and antioxidant enzyme activities was established. During the first hours of hypoxia, the catalase activity in soybean plants increased stronger than in sensitive to hypoxia pea plants. At longer exposure to hypoxia (24 h), peroxidases started to play the higher role in cell defense against hypoxia, but only in soybean plants. The medium with the higher CO₂ content induced higher changes in the processes of ROS accumulation and activities of lipoxygenase and antioxidant enzymes. This permits us to refer CO₂, accumulated as a product of respiration in the cells, to low-molecular signal molecules switching on plant adaptation to hypoxic stress.     

Lipid peroxidation and the antioxidant protection system in humans exposed to hypergravity of varying intensity

The effects of +Gz acceleration (head–pelvis) of 3, 5, and 7g (rate of increase, 0.03 g/s) on the intensity of lipid peroxidation (LPO) and the state of the antioxidant protection system were assessed in 14 subjects 25–45 years of age. The content of lipid peroxidation products (diene conjugates, malonic dialdehyde, and Schiff bases) in the blood of the subjects was quantitated, and the status of the water-soluble (catalase and glutathione peroxidase activities and total antioxidant activity) and lipid (tocopherol concentration) components of the antioxidant protection system was assessed. Exposure to hypergravity of 3g was accompanied by a slight activation of LPO, and further increase in the load to 5g resulted in inhibition of LPO, whereas no statistically significant changes in any of the parameters investigated were recorded at a load of 7g. Induction of the passive mechanisms of biomembrane protection associated with changes in the phase status of the membrane appears to be the most plausible explanation for the phenomenon observed. Further research on the mechanisms of compensation and control of the intensity of free radical-mediated processes upon the impact of hypergravity seems necessary.     

Role of dopamine in the peripheral mechanisms of respiration control

Under clinical conditions, we studied the interaction between dopamine (DA) metabolism and hypoxia stimulationrelated ventilatory responses (HVR) before and after adaptation to periodical hypoxic episodes. Thirty-seven young and elder persons were tested; among elder tested subjects there were patients with Parkinson’s desease treated or not treated with DOPA-DA precursor-containing drugs (levoDOPA/carbiDOPA). We measured the HVR indices and DA and DOPA contents in the venous blood of tested persons before and after a 14-day-long hypoxic training. The highest indices of the ventilation sensitivity to hypoxia together with the lowest above-mentioned chemical indices were observed in young persons. An increase in the DA and DOPA levels in the venous blood were observed concurrently with suppression of the ventilation responses to hypoxic episodes. After a course of periodical hypoxic sessions, we observed in all groups opposite dynamics of DA and DOPA metabolism. An increase in the DA level in young persons and a trend toward its decrease in older healthy persons and parkinsonian patients was nevertheles accompanied by an HVR increase in all groups. Possible relations between the DA metabolism indices and peripheral mechanisms of respiratory control are discussed.     

Individual characteristics of external respiration during intermittent normobaric hypoxia

Correlation and regression relationships between the indices of the body responsiveness to hypoxic impacts and initial individual values of indices of the respiratory system and heart activity were studied in a group of subjects during three repeated cycles of breathing alternately a hypoxic gas mixture (11 vol % O₂) for 5 min and normal air for 5 min. A steady negative correlation between the most important regulatory indicator, the increase in the CO₂ content of the lungs, and its initial level in individual subjects was found. This may determine the known “normalizing” curative and prophylactic effects of intermittent normobaric hypoxia on the gas transport system of the body. A correlation between the individual increase in the CO₂ content of the lungs in response to hypoxia and changes in the heart rate and initial inhalation rate and depth, rather than oxygen consumption by the body, was found.     

Protective effect of green tea against lipid peroxidation in the rat liver, blood serum and the brain

This paper reports data on the effect of green tea on the lipid peroxidation products formation and parameters of antioxidative system of the liver, blood serum and central nervous tissue of healthy young rats drinking green tea for five weeks. The rats were permitted free access to solubilized extract of green tea. Bioactive ingredients of green tea extract caused in the liver an increase in the activity of glutathione peroxidase and glutathione reductase and in the content of reduced glutathione as well as marked decrease in lipid hydroperoxides (LOOH), 4-hydroksynonenal (4-HNE) and malondialdehyde (MDA). The concentration of vitamin A increased by about 40%. Minor changes in the measured parameters were observed in the blood serum. GSH content increased slightly, whereas the index of the total antioxidant status increased significantly. In contrast, the lipid peroxidation products, particularly MDA was significantly diminished. In the central nervous tissue the activity of superoxide dismutase and glutathione peroxidase decreased while the activity od glutathione reductase and catalase increased after drinking green tea. Moreover the level of LOOH, 4-HNE and MDA significantly decreased. The use of green tea extract appeared to be beneficial to rats in reducing lipid peroxidation products. These results support and substantiate traditional consumption of green tea as protection against lipid peroxidation in the liver, blood serum, and central nervous tissue.     

Respiratory mechanics in adult rats hypoxic in the neonatal period

Newborn rats were exposed to 10% O2 from 24 h to 6 days after birth, then returned to normoxia and examined at 50 days of age, i.e., after reaching sexual maturity. Despite the important impairment in somatic growth during hypoxia, at 50 days body weight and nose-tail length were as in control rats never exposed to hypoxia. Hypoxic rats had a bigger chest, with larger anteroposterior diameter, larger surface area of the muscle component of the diaphragm, and heavier and more expanded lungs. None of these structural changes were observed in a third group of rats, which were exposed for 6 days to hypoxia between 35 and 42 days of age, i.e., at a much more advanced stage of postnatal development. In addition, hypoxic rats had higher compliance of the respiratory system and of the lung and lower total pulmonary resistance than control rats. Frequency dependence of compliance was not different. We conclude that in the rat the structural changes induced by neonatal chronic hypoxia are not resolved by the return to normoxia but persist at least until postpuberty with modifications of the mechanical properties of the respiratory system.     

Effect of L-arginine on age-dependent changes of lipid peroxidation processes and antioxidant system activity in rat tissues

The antioxidant system and lipid peroxidation processes under the L-arginine injection were investigated in experiments on the myocardium, liver and blood of rats of different age. Lipid peroxidation processes intensification and antioxidant system enzymes activity decrease in old rats was shown. A pro- and antioxidant property changes which had different specificity and depended on the tissue were investigated. It was concluded that NO-ergic link activated antioxidant protection in old rats, activates antioxidant enzymes but does not influence the antioxidant properties of tissues of young and adult rats.     

Effect of aminotriazole on antioxidant defense system of tasar silkworm Antheraea mylitta

This study was designed to find out the metabolic consequences of H₂O₂ following catalase inhibition by aminotriazole in the fat body of an Antheraea mylitta pupa. H₂O₂ content in the pupal fat body exhibited a decreasing trend over the experimental period (up to 48 h). However, a substantial decrease in its level was marked after 12, 24 and 48 h of treatment. The level of lipid peroxidation was elevated within 4 h of aminotriazole injection. Nevertheless, its level significantly decreased after 12, 24 and 48 h of treatment. Superoxide dismutase activity was elevated within 4 h, followed by a transient decrease in its activity at 12 h of treatment and again increased over the experimental period. Catalase activity was found to decline in the fat body within 4 h of aminotriazole treatment compared to the control. However, it was surprising to observe that there was a two‐fold increase in catalase activity compared to its previous experimental group after 12 h, followed by a rapid decline in its activity at 24 h of aminotriazole injection and non‐detectable catalase activity at 48 h. Ascorbic acid content was found to be elevated after 12 h of injection and maintained an increasing trend over the rest of the experimental period compared to the respective control. Despite the progressive inhibition of catalase activity beyond 12 h of treatment, H₂O₂ accumulation was not observed as a consequence of catalase inhibition. Hence, catalase depletion by aminotriazole involves compensatory changes in other components of the antioxidant system for the efficient removal of H₂O₂.     

Protein and lipid oxidation of banked human erythrocytes: role of glutathione

In banked human erythrocytes (RBCs), biochemical and functional changes are accompanied with vesiculation and reduced in vivo survival. We hypothesized that some of these changes might have resulted from oxidative modification of membrane lipids, proteins, or both as a result of atrophy of the antioxidant defense system(s). In banked RBCs, we observed a time-dependent increase in protein clustering, especially band 3; carbonyl modification of band 4.1; and malondialdehyde, a lipid peroxidation product. Examination of the antioxidative defense system showed a time-dependent decline in glutathione (GSH) concentration and glutathione-peroxidase (GSH-PX) activity, with a concomitant increase in extracellular GSH, cysteine, and homocysteine, and unchanged catalase activity. When subjected to acute oxidant stress by exposure to ferric/ascorbic acid or tert-butylhydroperoxide (tert-BHT), catalase activity showed a steeper decline compared with GSH-PX. The results demonstrate that GSH and GSH-PX appear to provide the primary antioxidant defense in stored RBCs, and their decline, concurrent with an increase in oxidative modifications of membrane lipids and proteins, may destabilize the membrane skeleton, thereby compromising RBC survival.     

Role of ATP-sensitive potassium channel activators in liver mitochondrial function in rats with different resistance to hypoxia

Effects of ATP-sensitive potassium (KATP) channels opener pinacidil (0.06 mg/kg) and inhibitor glibenclamide (1 mg/kg) in rats with different resistance to hypoxia on indices of ADP-stimulation of mitochondrial respiration by Chance, calcium capacity and processes of lipid peroxidation in liver has been investigated. We used next substrates of oxidation: 0.35 mM succinate, 1 mM alpha-ketoglutarate. Additional analyses contain the next inhibitors: mitochondrial fermentative complex I-10 mkM rotenone, succinate dehydrogenase 2 mM malonic acid. It was shown that effects of pinacidil induced the increasing of oxidative phosporylation efficacy and ATP synthesis together with lowering of calcium capacity in rats with low resistance to hypoxia. Effects of pinacidil were leveled by glibenclamide. These changes are connected with the increasing of respiratory rate, calcium overload and intensification of lipid peroxidation processes. A conclusion was made about protective effect of pinacidil on mitochondrial functioning by economization of oxygen-dependent processes, adaptive potentialities of organisms with low resistance to hypoxia being increased.     

Selected contribution: Carotid body as a model for aging studies: is there a link between oxygen and aging?

The carotid body (CB) is the site in the body that triggers awareness of changes in blood oxygen pressure. Aging is characterized by a decrease in oxygen supply to tissues, in reduction of tissue Po2, and in the activity of several enzymes and metabolic factors. The ventilatory response to hypoxia is attenuated with aging related to the age-dependent structure modifications including the basal reduction of oxygen requirements. The aged CB shows an increase in extracellular matrix, a reduction in number and volume of type I cells, and a reduction in volume of mitochondria that was consistent with and similar to that during chronic hypoxia; this phenomenon seems to operate also during aging as shown by the reduced volume of mitochondria in the aged CB. During chronic hypoxia, CB hypertrophy is less evident in aged CB than in young CB. Therefore, hypoxia and aging seem to share some type of link at different cell sites. CB represents an experimental model adequate for studying aging processes because of its high blood flow and metabolism, and thus it serves as a means to understanding the oxygen modulation of the aging process.     

Tissue specificity of lipid peroxidation under emotional stress in rats

The intensity of lipid peroxidation and activity of antioxidant system enzymes in the blood plasma, brain and cardial muscle of laboratory rats under 40 days of isolation and violation of diurnal cycle was studied. The obtained data show that on the background of concentration changes in NO changes also take place in the intensity of lipid peroxidation process, indicated by changes in the concentration of TBA-active products and diene conjugates. The changes taking place in the activity of superoxidedismutase, catalase, succinatdehydrogenase, creatine kinase and aldolase under stress were studied. The resulting data show that isolation of animals and violation of diurnal cycle are the factors causing a significant reduction in the energy metabolism in the brain and heart tissue cells and resulting in oxidative stress that, in its turn, may become the reason for development of toxic radicals. Furthermore, prolonged stress may result in irreversible processes that are considered to be the reasons for significant pathologies of the cardiovascular system.     

Oxidative Stress in Skin Fibroblasts Cultures of Patients with Huntington’s Disease

Oxidative stress and mitochondrial dysfunction should play a role in the neurodegeneration in Huntington’s disease (HD). The most consistent finding is decreased activity of the mitochondrial complexes II/III and IV of the respiratory chain in the striatum. We assessed enzymatic activities of respiratory chain enzymes and other enzymes involved in oxidative processes in skin fibroblasts cultures of patients with HD. We studied respiratory chain enzyme activities, activities of total, Cu/Zn- and Mn-superoxide-dismutase, glutathione-peroxidase (GPx) and catalase, and coenzyme Q₁₀ (CoQ₁₀) levels in skin fibroblasts cultures from 13 HD patients and 13 age- and sex-matched healthy controls. When compared with controls, HD patients showed significantly lower specific activities for catalase corrected by protein concentrations (P < 0.01). Oxidized, reduced and total CoQ₁₀ levels (both corrected by citrate synthase (CS) and protein concentrations), and activities of total, Cu/Zn- and Mn-superoxide-dismutase, and gluthatione-peroxidase, did not differ significantly between HD-patients and control groups. Values for enzyme activities in the HD group did not correlate with age at onset and of the disease and with the CAG triplet repeats. The primary finding of this study was the decreased activity of catalase in HD patients, suggesting a possible contribution of catalase, but not of other enzymes related with oxidative stress, to the pathogenesis of this disease.     

Antioxidant system activation in rats with experimental cirrhosis after injection of cryopreserved fetal liver cells

The possibility to recover the antioxidant system in rats with experimental liver cirrhosis (LC) after allo- and xenotransplantation of cryopreserved fetal liver cells (FLC) was investigated. It was shown that the content of lipid peroxidation products in the blood serum of animals with LC four weeks after FLC transplantation decreased significantly as compared to control group. Such changes were accompanied by a significant increase of catalase (CAT), glutathione reductase (GR), Se-dependent glutathione peroxidase (GP) activity in the liver and total anti-oxidative activity (AOA) of blood. Obtained results demonstrate that the main direction of FLC effects in animals with LC agree with that we observed previously in other experimental models (partial hepatectomy, chronic alcohol poisoning and hypercholesterolemia). In conclusion, cell therapy may be considered as the universal method for correction of disorders in regulation of free-radical processes in various experimental pathologies.     

Age and sex differences in human skeletal muscle: Role of reactive oxygen species

Previous studies, conducted on experimental animals, have indicated that reactive oxygen species (ROS) are involved in the aging process. The objective of this work was to study the relationship between oxidative damage and human skeletal muscle aging, measuring the activity of the main antioxidant enzymes superoxide dismutase (total and MnSOD), glutathione peroxidase (GPx) and catalase in the skeletal muscle of men and women in the age groups: young (17–40 years), adult (41–65 years) and aged (66–91 years). We also measured glutathione and glutathione disulfide (GSH and GSSG) levels and the redox index; lipid peroxidation and protein carbonyl content. Total SOD activity was lower in the 66–91 year-old vs. the 17–40 year-old men; MnSOD activity was significantly greater in 66–91 year-old vs. 17–40 year-old women. GPx activity remained unchanged. The activity of catalase was lower in adults than in young men but higher in the aged. We observed no changes in GSH levels and significantly higher GSSG levels only in aged men vs. adult men, and a significant decrease in aged women vs. aged men. The protein carbonyl content increased significantly in the 41–65 and 66–91 year-old vs. the 17–40 year-old men. Finally, young women have lower lipid peroxidation levels than young men. Significantly higher lipid peroxidation levels were observed in aged men vs. both young and adult men, and the same trend was noticed for women. We conclude that oxidative damage may play a crucial role in the decline of functional activity in human skeletal muscle with normal aging in both sexes; and that men appear to be more subject to oxidative stress than women.