Exposure Time Related Oxidative Action of Hyperbaric Oxygen in Rat Brain

Hyperbaric oxygen (HBO) is known to cause oxidative stress in several organs and tissues. Due to its high rate of blood flow and oxygen consumption, the brain is one of the most sensitive organs to this effect. The present study was performed to elucidate the relation of HBO exposure time to its oxidative effects in rats’ brain cortex tissue. For this purpose, 49 rats were randomly divided into five groups. Except the control group, study groups were subjected to three atmospheres HBO for 30, 60, 90, and 120 min. Their cerebral cortex layer was taken immediately after exposure and used for analysis. Thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and nitrate–nitrite (NO_X) levels were determined. TBARS and SOD levels were found to increase in a time-dependent manner. GSH-Px activity reflected an inconsistent course. NO_X levels were found to be increased only in the 120 min exposed group. The results of this study suggests that HBO induced oxidative effects are strongly related with exposure time.     

Effects of Methylprednisolone and Hyperbaric Oxygen on Oxidative Status after Experimental Spinal Cord Injury: A Comparative Study in Rats

The effects of hyperbaric oxygen (HBO) therapy or methylprednisolone on the oxidative status were evaluated in experimental spinal cord injury. Clip compression method was used to produce acute spinal cord injury rats. Hyperbaric oxygen was administered twice daily for a total of eight 90 min-sessions at 2.8 atmospheres. Methylprednisolone was first injected with a bolus of 30 mg/kg followed with an infusion rate of 5.4 mg/kg/h for 24 h. Five days after clip application animals were sacrificed and their traumatized spinal cord segment were excised. Tissue levels of thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were evaluated to reflect oxidant/antioxidant status. Non-treated clip-operated animals reflected significantly higher SOD, GSH-Px and TBARS levels that were found to be significantly higher than the sham-operated. Methylprednisolone was not able to lower these levels. HBO administration diminished all measured parameters significantly; however, their levels appeared already to be high when compared with sham animals. According to these results obtained on the 5th day after induction, HBO, but not methylprednisolone, seems to procure prevention against oxidative spinal cord injury.     

Influence of an orally effective SOD on hyperbaric oxygen-related cell damage

In a prospective, double-blind, randomised placebo-controlled study, we tested the hypothesis that a new formulation consisting of wheat gliadin chemically combined with a vegetal (thus orally effective) preparation of superoxide dismutase (SOD) allows to prevent hyperbaric oxygen (HBO)-induced oxidative cell stress. Twenty healthy volunteers were exposed to 100% oxygen breathing at 2.5 ATA for a total of 60 min. DNA strand breaks (tail moments) were determined using the alkaline version of the comet assay. Whole blood concentrations of reduced (GSH) and oxidised (GSSG) glutathione and F₂-isoprostanes, SOD, glutathione peroxidase (GPx) and catalase (Cat) activities and red cell malondialdehyde (MDA) content were determined. After HBO exposure the tail moment [Formula: See Text] and isoprostane levels [Formula: See Text] were significantly lower in the group that received the vegetal formulation. Neither SOD and Cat nor GSH and GSSG were significantly affected by this preparation or HBO exposure. By contrast, blood GPx activity, which tended to be lower in the SOD-group already before the HBO exposure [Formula: See Text] was significantly lower afterwards [Formula: See Text] We conclude that an orally effective SOD-wheat gliadin mixture is able to protect against DNA damage, which coincided with reduced blood isoprostane levels, and may therefore be used as an antioxidant.     

Influence of an Orally Effective SOD on Hyperbaric Oxygen-related Cell Damage

In a prospective, double-blind, randomised placebo-controlled study, we tested the hypothesis that a new formulation consisting of wheat gliadin chemically combined with a vegetal (thus orally effective) preparation of superoxide dismutase (SOD) allows to prevent hyperbaric oxygen (HBO)-induced oxidative cell stress. Twenty healthy volunteers were exposed to 100% oxygen breathing at 2.5 ATA for a total of 60 min. DNA strand breaks (tail moments) were determined using the alkaline version of the comet assay. Whole blood concentrations of reduced (GSH) and oxidised (GSSG) glutathione and F₂-isoprostanes, SOD, glutathione peroxidase (GPx) and catalase (Cat) activities and red cell malondialdehyde (MDA) content were determined. After HBO exposure the tail moment [Formula: See Text] and isoprostane levels [Formula: See Text] were significantly lower in the group that received the vegetal formulation. Neither SOD and Cat nor GSH and GSSG were significantly affected by this preparation or HBO exposure. By contrast, blood GPx activity, which tended to be lower in the SOD-group already before the HBO exposure [Formula: See Text] was significantly lower afterwards [Formula: See Text] We conclude that an orally effective SOD-wheat gliadin mixture is able to protect against DNA damage, which coincided with reduced blood isoprostane levels, and may therefore be used as an antioxidant.     

Effect of Ozone on the Activities of Reactive Oxygen Scavenging Enzymes in Rbc of Ozone Exposed Japanese Charr (Salvelinus Leucomaenis)

The effect of ozone exposure on the activities of reactive oxygen scavenging enzymes (SOD?, catalase, GSH-Px) in RBC of Japanese charr (Salvelinus leucomaenis) was examined. Ozone (0, 0.4 and 0.7 ppm as initial concentrations) was exposed to Japanese charr for 30 min, which definitely caused serious membrane damage to RBC of fish. Ozone exposure at 0.4 and 0.7 ppm decreased activities of both catalase and GSH-Px by 80 to 57+ of the control. On the other hand, the activities of SOD remained unaffected even by 0.7 ppm ozone exposure. A hypothesis on the RBC membrane damage and participation of SOD and heme-iron was proposed.     

三七总皂甙和银杏叶提取物预防急性氧中毒的实验研究

目的:研究三七总皂甙和银杏叶提取物对急性氧中毒的预防作用及其可能机制.方法:分别给小鼠连续腹腔注射三七总皂甙和银杏叶提取物5 d后,在500kPa高压氧中暴露60 min,观察惊厥潜伏期、惊厥次数、惊厥间隔时间等指标;另外测定高压氧暴露15 min后脑组织中活性氧单位、脂质过氧化物、一氧化氮、谷胱甘肽的含量和过氧化氢酶、谷胱甘肽过氧化物酶、单胺氧化酶的活性.结果:三七总皂甙和银杏叶提取物可以明显延长氧惊厥潜伏期和惊厥间隔时间,减少惊厥次数;降低高压氧暴露后脑组织中脂质过氧化物、一氧化氮的含量,使活性氧单位、谷胱甘肽含量和谷胱甘肽过氧化物酶活性保持在较高的水平;对过氧化氢酶和单胺氧化酶活性的影响则不显著.结论:三七总皂甙和银杏叶提取物可以有效预防急性氧中毒,其机制可能与它们的抗氧化活性有关.     

Exogenously administered and endogenously produced melatonin reduce hyperbaric oxygen-induced oxidative stress in rat lung

Hyperbaric oxygen (HBO) is a widely used treatment modality in many diseases. A known side effect of HBO is the production of reactive oxygen species. Many antioxidants such as vitamins C and E, riboflavin and selenium have been used successfully to scavenge the reactive oxygen species caused by HBO administration. In this study, we aimed to see if melatonin, a newly discovered antioxidant, has a protective effect against the overproduction of reactive oxygen species produced by HBO in rat lung tissue. Sixty male Sprague-Dawley rats were divided into 5 groups as follows: control, daytime HBO (3 ATA, 120 min), daytime HBO plus melatonin (10 mg/kg), nighttime HBO and nighttime HBO (under light exposure). The MDA, SOD and CAT levels of daytime and nighttime HBO (under light exposure) increased significantly. This significance was not found in the daytime HBO plus melatonin and nighttime HBO groups when compared with the control. In this study, HBO caused oxidant stress, and melatonin decreased the levels of MDA, SOD and CAT. Moreover, endogenous melatonin was found to be a more effective antioxidant than exogenous 10 mg/kg melatonin.     

Hyperbaric Oxygen Reduces Cerebral Blood Flow by Inactivating Nitric Oxide

Based on recent evidence that nitric oxide (NO(.)) is involved in hyperoxic vasoconstriction, we tested the hypothesis that decreases in NO(.) availability in brain tissue during hyperbaric oxygen (HBO(2)) exposure contribute to decreases in regional cerebral blood flow (rCBF). rCBF was measured in rats exposed to HBO(2) at 5 atmospheres (ATA) and correlated with interstitial brain levels of NO(.) metabolites (NO(X)) and production of hydroxyl radical ((.)OH). Changes in rCBF were also correlated with the effects of NO(.) synthase inhibitor (l-NAME), NO(.) donor PAPANONOate, and intravascular superoxide dismutase (MnSOD) during HBO(2). After 30 min of O(2) exposure at 5 ATA, rCBF had decreased in the substantia nigra, caudate putamen, hippocampus, and parietal cortex by 23 to 37%. These reductions in rCBF were not augmented by exposure to HBO(2) in animals pre-treated with l-NAME. After 30 min at 5 ATA, brain NO(X) levels had decreased by 31 +/- 9% and correlated with the decrease in rCBF, while estimated (.)OH production increased by 56 +/- 8%. The decrease in rCBF at 5 ATA was completely abolished by MnSOD administration into the circulation before HBO(2) exposure. Doses of NO(.) donor that significantly increased rCBF in animals breathing air had no effect at 5 ATA of HBO(2). These results indicate that decreases in rCBF with HBO(2) are associated with a decrease in effective NO(.) concentration and an increase in ROS production in the brain. The data support the hypothesis that inactivation of NO(.) antagonizes basal relaxation of cerebral vessels during HBO(2) exposure, although an effect of HBO(2) on NO(.) synthesis has not been excluded.     

Effect of Ozone on the Activities of Reactive Oxygen Scavenging Enzymes in Rbc of Ozone Exposed Japanese Charr (Salvelinus Leucomaenis)

The effect of ozone exposure on the activities of reactive oxygen scavenging enzymes (SOD†, catalase, GSH-Px) in RBC of Japanese charr (Salvelinus leucomaenis) was examined. Ozone (0, 0.4 and 0.7 ppm as initial concentrations) was exposed to Japanese charr for 30 min, which definitely caused serious membrane damage to RBC of fish. Ozone exposure at 0.4 and 0.7 ppm decreased activities of both catalase and GSH-Px by 80 to 57+ of the control. On the other hand, the activities of SOD remained unaffected even by 0.7 ppm ozone exposure. A hypothesis on the RBC membrane damage and participation of SOD and heme-iron was proposed.     

Nitric oxide and carbon dioxide in neurotoxicity induced by oxygen under pressure

Hyperbaric oxygen (HBO2) causes CO2 retention in the brain that leads to the increase in cerebral blood flow (CBF) by poorly understood mechanisms. We have tested the hypothesis that NO is implicated in CBF-responses to hypercapnia under hyperoxic conditions. Alert rats were exposed to HBO2 at 5 ata and blood flow in the striatum measured by H2 clearance every 10 min. Acetazolamide, the inhibitor of carbonic anhydrase, was used to increase brain PCO2. CBF responses to acetazolamide administration (30 mg/kg, i.p.) were assessed in rats breathing air at 1 ata or oxygen at 5 ata with and without NOS inhibition (L-NAME, 30 mg/kg, i.p.). In rats breathing air, acetazolamide increased CBF by 34 +/- 7.4% over 30 min and by 28 +/- 12% over 3 hours while NOS inhibition with L-NAME attenuated acetazolamide-induced cerebral vasodilatation. HBO2 at 5 ata reduced CBF during the first 30 min hyperoxia, after that CBF increased by 55 +/- 19% above pre-exposure levels. In acetazolamide-treated animals, no HBO, induced vasoconstricton was observed and striatal blood flow increased by 53 +/- 18% within 10 min of hyperbaric exposure. After NOS inhibition, cerebral vasodilatation in response to acetazolamide during HBO2 exposure was significantly attenuated. The study demonstrates that NO is implicated in acetazolamide (CO2)-induced cerebral hyperemia under hyperbaric oxygen exposure.     

Response of antioxidant enzymes to intermittent and continuous hyperbaric oxygen

Rats and guinea pigs were exposed to O2 at 2.8 ATA (HBO) delivered either continuously or intermittently (repeated cycles of 10 min of 100% O2 followed by 2.5 min of air). The O2 time required to produce convulsions and death was increased significantly in both species by intermittency. To determine whether changes in brain and lung superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSHPx) correlated with the observed tolerance, enzyme activities were measured after short or long HBO exposures. For each exposure duration, one group received continuous and one intermittent HBO; O2 times were matched. HBO had marked effects on these enzymes: lung SOD increased (guinea pigs 47%, rats 88%) and CAT and GSHPx activities decreased (33%) in brain and lung. No differences were seen in lung GSHPx or brain CAT in rats or brain SOD in either species. In guinea pigs, but less so in rats, the observed changes in activity were usually modulated by intermittency. Increases in hematocrit, organ protein, and lung DNA, which may also reflect ongoing oxidative damage, were also slowed with intermittency in guinea pigs. Intermittency benefited both species by postponing gross symptoms of toxicity, but its modulation of changes in enzyme activities and other biochemical variables was more pronounced in guinea pigs than in rats, suggesting that there are additional mechanisms for tolerance.     

Scuba diving enhances endogenous antioxidant defenses in lymphocytes and neutrophils

The aim was to study the effects of a scuba diving session on the lymphocyte antioxidant system, NO synthesis, the capability to produce reactive oxygen species and the antioxidant response in neutrophils. For that purpose seven male divers performed an immersion at a depth of 40 m for 25 min. The same parameters were measured after an hyperbaric oxygen (HBO) treatment at resting conditions in a hyperbaric chamber. Lymphocyte H₂O₂ production rose after diving and after HBO treatment. Glutathione peroxidase (GPx) and catalase activities increased after diving in lymphocytes, while after HBO exposure only increased GPx activity. Lymphocyte HO-1 mRNA expression increased after diving and after HBO exposure, while iNOS levels and nitrite levels significantly increased after diving. The hyperoxia associated to scuba diving leads to a condition of oxidative stress with increased lymphocyte H₂O₂ production, HO-1 expression, NO synthesis and antioxidant enzyme adaptations in order to avoid oxidative damage.     

The effect of hyperbaric oxygen treatment on aspiration pneumonia

We have studied whether hyperbaric oxygen (HBO) prevents different pulmonary aspiration materials-induced lung injury in rats. The experiments were designed in 60 Sprague-Dawley rats, ranging in weight from 250 to 300 g, randomly allotted into one of six groups (n = 10): saline control, Biosorb Energy Plus (BIO), hydrochloric acid (HCl), saline + HBO treated, BIO + HBO treated, and HCl + HBO treated. Saline, BIO, HCl were injected into the lungs in a volume of 2 ml/kg. A total of seven HBO sessions were performed at 2,4 atm 100% oxygen for 90 min at 6-h intervals. Seven days later, rats were sacrificed, and both lungs in all groups were examined biochemically and histopathologically. Our findings show that HBO inhibits the inflammatory response reducing significantly (P < 0.05) peribronchial inflammatory cell infiltration, alveolar septal infiltration, alveolar edema, alveolar exudate, alveolar histiocytes, interstitial fibrosis, granuloma, and necrosis formation in different pulmonary aspiration models. Pulmonar aspiration significantly increased the tissue HP content, malondialdehyde (MDA) levels and decreased (P < 0.05) the antioxidant enzyme (SOD, GSH-Px) activities. HBO treatment significantly (P < 0.05) decreased the elevated tissue HP content, and MDA levels and prevented inhibition of SOD, and GSH-Px (P < 0.05) enzymes in the tissues. Furthermore, there is a significant reduction in the activity of inducible nitric oxide synthase, TUNEL and arise in the expression of surfactant protein D in lung tissue of different pulmonary aspiration models with HBO therapy. It was concluded that HBO treatment might be beneficial in lung injury, therefore, shows potential for clinical use.     

Activation of BDNF mRNA and protein after seizures in hyperbaric oxygen: implications for sensitization to seizures in re-exposures

Previous studies have demonstrated that exposure to convulsive doses of hyperbaric oxygen (HBO) increases sensitivity to seizures in re-exposures. Because brain derived neurotrophic factor (BDNF) is induced after a variety of seizures and increases cell excitability, it may contribute to the mechanism of sensitization. In this study, a fast induction in BDNF mRNA 2 hr after seizures and a temporary increase in BDNF protein 1 day after seizures induced by 100% O₂ at 5 atm (gauge pressure) were demonstrated in the rat cortex. To determine whether an elevation in BDNF protein level can modify sensitivity to the toxic effect of HBO, recombinant BDNF (12 g) was injected into cerebral ventricles 30 min prior to exposure. Administration of exogenous BDNF significantly shortened latent time to seizures in HBO exposures. We propose that upregulation of BDNF expression in the brain after seizures may contribute to sensitization to HBO toxicity.     

The influence of microwave radiation from cellular phone on fetal rat brain

The increasing use of cellular phones in our society has brought focus on the potential detrimental effects to human health by microwave radiation. The aim of our study was to evaluate the intensity of oxidative stress and the level of neurotransmitters in the brains of fetal rats chronically exposed to cellular phones. The experiment was performed on pregnant rats exposed to different intensities of microwave radiation from cellular phones. Thirty-two pregnant rats were randomly divided into four groups: CG, GL, GM, and GH. CG accepted no microwave radiation, GL group radiated 10 min each time, GM group radiated 30 min, and GH group radiated 60 min. The 3 experimental groups were radiated 3 times a day from the first pregnant day for consecutively 20 days, and on the 21st day, the fetal rats were taken and then the contents of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), malondialdehyde (MDA), noradrenaline (NE), dopamine (DA), and 5-hydroxyindole acetic acid (5-HT) in the brain were assayed. Compared with CG, there were significant differences (P<0.05) found in the contents of SOD, GSH-Px, and MDA in GM and GH; the contents of SOD and GSH-Px decreased and the content of MDA increased. The significant content differences of NE and DA were found in fetal rat brains in GL and GH groups, with the GL group increased and the GH group decreased. Through this study, we concluded that receiving a certain period of microwave radiation from cellular phones during pregnancy has certain harm on fetal rat brains.     

Antioxidant status in humans after exposure to hyperbaric oxygen.

Hyperbaric oxygen (HBO) treatment (i.e., exposure to 100% oxygen at a pressure of 2.5 atmosphere absolute (ATA) for a total of 3 x 20 min periods) of human subjects induced DNA damage in the alkaline comet assay with leukocytes and protected against the DNA damaging effects of subsequent in vivo HBO exposures. Furthermore, blood taken 24 h after the first HBO was well protected against the in vitro induction of genotoxic effects by hydrogen peroxide. To investigate the mechanisms which led to this apparent adaptive response, we determined the antioxidant status of blood from subjects before and after HBO. We did not find differences in the plasma concentrations of the antioxidant vitamins A, C and E after HBO treatment. HBO had also no effect on the 'antioxidant power' of the plasma as measured with the FRAP-assay or on the concentration of reduced glutathione determined in the plasma or in lymphocytes. Red cell concentrate activities of superoxide dismutase, catalase, glutathione peroxidase were not influenced by HBO. In contrast, synthesis of the heat shock protein HSP70 which has been implicated to play an important role in cellular protection against oxidative stress, was significantly induced in lymphocytes after a single HBO treatment. To investigate whether intake of antioxidants may protect against HBO-induced DNA damage, we supplemented subjects with vitamin E (800 mg for 7 days) or with N-acetylcysteine (400 mg, 1 h before the HBO treatment). However, these supplementations did not influence the induction of DNA damage by HBO.     

Genetic effects of hyperbaric oxygen therapy

Patients with several diseases have been examined for detection of chromosome aberrations in peripheral blood cells after 10 sessions of hyperbaric oxygen (HBO) at 0.15-0.20 MPa for 40 min. The present study reveals that HBO increases the level of chromosome aberrations, and that individual reactions to HBO differ. Pure erythrocytes treated with high-pressure oxygen (HBO) at 0.7 MPa for 1 h are clastogenic for intact syngeneic lymphocytes. The effect of HBO (0.3 MPa, 5 sessions of 1 h daily) on induction of chromosome aberrations in somatic cells and germinal tissues of rat males has been studied. Induction of aberrations in bone marrow cells after HBO was seen for 3 months. In lymphocytes of patients, it was seen for 9 months. Chromosome rearrangements at the first meiotic division were detected only 90 days after exposure. HBO affects neither the functional nor the morphological condition of gonads and does not induce dominant lethals. It is proposed that a high quantity of chromosome breaks in cells of somatic tissues is an adaptive reaction of organisms to HBO.     

Detection of ischemia-reperfusion cardiac injury by cardiac muscle chemiluminescence

Various methods have been used in the past to assess the implication of oxygen free radicals (OFR) in ischemia-reperfusion-induced cardiac injury. Luminol-enhanced tert-butyl-initiated chemiluminescence in cardiac tissue reflects oxidative stress and is a very sensitive method. It was used to elucidate the role of OFR in cardiac injury due to ischemia and reperfusion. Studies were conducted on perfused isolated rabbit hearts in three groups (n = 8 in each): I, control; II, submitted to global ischemia for 30 min; III, submitted to ischemia for 30 min followed by reperfusion for 60 min. The heart tissue was then assayed for chemiluminescence (CL); content of malondialdehyde (MDA), an indicator of OFR-induced cardiac injury; and activity of tissue levels of antioxidants [superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px)].The control values for left and right ventricular CL and malondialdehyde were 81.1 ± 15.4 (S.E.) and 182.4 ± 50.3 (S.E.), mv-min-mg protein^–1; and 0.024 ± 0.006 (S.E.) and 0.324 ± 0.005 (S.E.) nmoles-mg protein^–1 respectively. Ischemia produced an increase in the cardiac CL (3.3 to 4.4 fold) and MDA content (2 to 2.6 fold). Reperfusion following ischemia also produced similar changes in CL and MDA content. The control values for activity of left ventricular SOD, catalase, and GSH-Px were 45.77 ± 1.73 (S.E.) U-mg protein^–1 5.35 ± 0.51 (S.E.) K-10^–3-sec^–1-mg protein^–1, and 77.50 ± 7.70 (S.E.) nmoles NADPH-min^–1-mg protein^–1 respectively. Activities of SOD and catalase decreased during ischemia but were similar to control values in ischemic-reperfused hearts. The GSH-Px activity of left ventricle was unaffected by ischemia, and ischemia-reperfusion. GSH-Px activity of the right ventricle increased with ischemia, and ischemic-reperfusion.These results indicate that cardiac tissue chemiluminescence would be a useful and sensitive tool for the detection of oxygen free radical-induced cardiac injury.     

Effect of cigarette smoke on lipid peroxidation and antioxidant enzymes in albino rat

Effect of cigarette smoke on lipid peroxidation (LPX) and antioxidant enzymes like catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and glutathione-S-transferase (GST) in various organs like brain, heart, lung, liver and kidney of the albino rats exposed to cigarette smoke for 30 min/day for a period of 30 days were assayed. It was observed that the lipid peroxide levels in liver, lung and kidney were enhanced in case of animals exposed to cigarette smoke, whereas brain and heart did not show any change as compared to control animals. The activity of the antioxidant enzymes was also elevated in liver, lung and kidney of the test animals whereas, brain and heart did not show any change in the activities of all of these antioxidant enzymes except glutathione-s-transferase which was increased in brain also. The level of reduced glutathione (GSH) was lowered in liver, lung and kidney of the tested animals when compared with the control animals but there was no significant change in brain and heart. The results of our study suggest that cigarette smoke induces lipid peroxidation in liver, lung and kidney, and the antioxidant enzymes levels were enhanced in order to protect these tissues against the deleterious effect of the oxygen derived free radicals. The depletion of reduced glutathione in these organs could be due to it's utilization by the tissues to mop off the free radicals.