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.     

高压氧对脑缺血再灌注海马CA_1区神经元凋亡作用的研究

目的和方法 :应用TUNEL检测技术 ,对沙土鼠前脑缺血 2 0min后再灌注 3d模型 ,用HBO治疗连续 3d。观察HBO作用下海马CA1区神经元凋亡变化 ,研讨HBO对脑缺血再灌注损伤的疗效及其机理 ,为临床应用HBO治疗疾病提供理论依据。结果 :沙土鼠脑缺血再灌注 3d后海马CA1区大量神经元凋亡 ,HBO治疗组凋亡细胞数明显减少 (P <0 .0 1) ,并以 0 .2 5MPaHBO治疗组为佳。结论 :HBO治疗对海马神经元损伤有保护作用 ,减少神经元凋亡 ,为高压氧治疗缺血性损伤的疗效机理之一     

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.     

The cytochrome P-450 content and catalytic activity in rat liver microsomes during hyperbaric oxygenation]

The effect of different conditions of hyperbaric oxygenation (HBO) on content and catalytic activity of cytochrome P-450 in rat liver cytochrome has been studied. The intensity of lipid peroxidation in microsomal membranes has been determined by the content of dien conjugates and Schiff's bases. The rate of amidopyrine demethylation has been shown not to change, but the rate of aniline hydroxylation decreases on 34, 57 and 64% under increase of oxygen pressure up to 0.3, 0.5 and 0.7 MPa correspondingly. The level of dien conjugates increase on 66-87% under all studied conditions of HBO. Cytochrome P-450 content decreases on 45% under the action of 0.7 MPa, but content of Schiff's bases increases on 210% as compared with control.     

Hyperbaric oxygen treatment attenuates cytokine induction after massive hemorrhage

We investigated the effect of hyperbaric oxygen treatment (HBO) on cytokine induction after hemorrhage, because hypoxia induces cytokines in vitro. Chronically cannulated conscious rats were subjected to 40 ml/kg of hemorrhage and resuscitated with the shed blood and twice the volume of saline either under room air (room air group) or under 100% oxygen at 3 atmospheres absolute (hyperbaric group). Rats exposed to HBO with no hemorrhage served as controls. Time course changes in plasma endotoxin level, arterial ketone body ratio (AKBR), serum tumor necrosis factor (TNF), interleukin-6 (IL-6), and their hepatic mRNA were detected in the three groups. Plasma endotoxin levels increased significantly after hemorrhage, and there were no significant differences between the room air group and the hyperbaric group. In the room air group, AKBR dropped rapidly after hemorrhage and became minimal at hour 1, which was associated with significant increases in TNF-alpha and IL-6 at both mRNA and circulating levels. HBO significantly attenuated decreases in AKBR after hemorrhage with a significant reduction of mortality and cytokine induction. These results indicate that HBO attenuated the cytokine induction after hemorrhage by improving liver ischemia, and they suggest that tissue hypoxia may be responsible, at least in part, for cytokine induction after massive hemorrhage.     

Prevention of H2O2 generation by monoamine oxidase protects against CNS O2 toxicity.

Toxicity to the central nervous system (CNS) by hyperbaric oxygen (HBO) presumably relates to increased production of reactive oxygen species. The sites of generation of reactive oxygen species during HBO, however, have not been fully characterized in the brain. We investigated the relationship between regional generation of hydrogen peroxide (H2O2) in the brain in the presence of an irreversible inhibitor of catalase, aminotriazole (ATZ), and protection from CNS O2 toxicity by a monoamine oxidase (MAO) inhibitor, pargyline. At 6 ATA of oxygen, pargyline significantly protected rats from CNS O2 toxicity whereas ATZ enhanced O2 toxicity. In animals pretreated with ATZ, HBO inactivated 21-40% more catalase than air exposure in the six brain regions studied. Because ATZ-mediated inactivation of catalase was H2O2 dependent, the decrease in catalase activity during hyperoxia was proportional to the intracellular production of H2O2. Pargyline, administered 30 min before HBO, inhibited MAO by greater than 90%, prevented ATZ inhibition of catalase activity during HBO, and reversed the augmentation of CNS O2 toxicity by ATZ. These findings indicate that H2O2 generated by MAO during hyperoxia is important to the pathogenesis of CNS O2 toxicity in rats.     

Hyperoxic exposure affects the ventilatory response to hypoxia in awake rats

We tested whether hyperbaric O2 (HBO) has an adverse effect on the hypoxic ventilatory drive. Four groups of rats were exposed for 550 min to O2 at 1.67, 1.90, and 2.15 ATA and to air at 1.90 ATA, respectively. Ventilatory parameters (frequency, tidal volume, and minute ventilation) were measured using whole-body plethysmography, before the hyperbaric exposure, immediately after the exposure, and up to 20 days after the exposure. Resting ventilation was not affected after exposure at 1.90 ATA to air or at 1.67 ATA to O2. HBO at 1.90 and 2.15 ATA caused a reduction of frequency and an elevation of tidal volume at different inspired gases: air, 5% CO2 balance O2, 80% O2, and 4.5% O2. However, minute ventilation on the day after the hyperoxic exposure was not different from the control at either air, 5% CO2, or 80% O2 but was markedly attenuated on the first three breaths at 4.5% O2. The hypoxic ventilation decreased to 48 +/- 13 (SD) and 32 + 11% after 1.90 and 2.15 ATA, respectively. The ventilatory parameters recovered in the days after HBO. We conclude that HBO reversibly depresses the hypoxic ventilatory drive, most probably by a direct effect on the carotid O2 chemoreceptors.     

Hyperbaric oxygenation in the comprehensive therapy of patients with rheumatoid arthritis (clinico-immunologic study)

For 35 of 50 patients with rheumatoid arthritis traditional drug therapy was a minor success for a long time. Without any modifications of the drug therapy every patient went through a course of hyperbaric oxygenation (HBO): 21 sessions under 1.7 ata for 40 min. Good clinical results both immediate and remote have been obtained. The effect of HBO on the immune system of the patients has intensified the suppressive function of T-lymphocytes (especially with systemic symptoms of the disease), normalized cell-bound immunity and decreased the serum concentration in immune complexes.     

Reparative processes in cardiac muscle following exposure to hyperbaric oxygenation

In 150 rabbits by means of histoautoradiographic, histochemical and certain histological methods, reparative processes in the cardiac muscle have been studied at experimental myocardial infarction and its combination with atherosclerosis under various regimes of hyperbaric oxygenation (HBO). It has been demonstrated that HBO (pO2--2 kgs/cm2, saturation time--45 min, 3-7 sessions) positively affects the proliferative processes in the ischemic zone, contributes to better preservation of the periinfarction parts of the myocardium and enhances maturation of the scar. If HBO is used in another regime (pO2--1 kgs/cm2, saturation time--30 min, 1-7 sessions), its positive effect on the regenerative processes in the ischemic zone is preserved, while its toxic effect on distant cardiac zones decreases considerably.     

Hyperoxic vasoconstriction in the brain is realized by inactivation of nitric oxide by superoxide anions

We tested a hypothesis that the cerebral blood flow (CBF) is reduced at hyperbaric oxygen due to inactivation of nitric oxide (NO) by superoxide anions (O2). In our experiments, the CBF was measured under hyperbaric oxygenation (HBO) 4ATA after inhibition of NO synthesis and inactivation of O2. The CBF was reduced at HBO exposure. Inhibition of NO--synthase type I and III (NOS) by L-NAME in the air caused the same decreasing of the CBF as at 4 ATA HBO. Hyperbaric vasoconstriction was diminished after NOS inhibition. Intravenous injection of superoxide dismutase (CuZn SOD) increased the CBF in the air and HBO exposure. This effect disappeared at preliminary NOS inhibition. These data suggest that inactivation of NO by O2 is a more effective mechanism of HBO vasoconstriction.     

Hyperbaric oxygen preconditioning alleviates myocardial ischemic injury in rats

It has been shown that after ischemia-reperfusion, application of hyperbaric oxygen (HBO) reduces cardiac injury. In this study we tested the hypothesis that HBO preconditioning reduces injury to the ischemic myocardium. One hundred and eight adult male Sprague-Dawley rats (250-280 g) were randomly divided into four groups: normoxia + sham surgery (CS), normoxia + permanent occlusion of the left anterior descending (LAD) coronary artery (CMI), HBO preconditioning + sham surgery (HS), and HBO preconditioning + permanent LAD occlusion (HMI). Rats receiving HBO preconditioning were intermittently exposed to 100% O(2) at 2.5 atmosphere absolute (ATA) for 60 min, twice daily for 2 days followed by 12 hrs of recovery in room air prior to the myocardial ischemic insult induced by LAD ligation. Rats in the normoxia group were time-matched with the HBO group and maintained under normoxic conditions prior to LAD occlusion. At 3 and 7 days after LAD occlusion, heart function parameters were measured by inserting a catheter into the left ventricle, infarct size was calculated using the method of TTC staining, myocardial capillary density was determined by immunohistochemical staining with a monoclonal anti-CD(31)/PECAM-1 antibody, and VEGF protein level was determined by Western blot analysis. At 3 days after LAD ligation, the infarct size of the HMI group was significantly smaller than that of the CMI group (26 +/- 2.5% vs. 38 +/- 3%, P < 0.05). The heart function parameters including left ventricular systolic pressure (LVSP), +dP/dt(max) and -dP/dt(max) were significantly improved in the HMI group compared to the CMI group at 3 and 7 days after LAD occlusion. Capillary density and VEGF protein levels were significantly increased in the ischemic myocardium pre-exposed to HBO. We conclude that HBO preconditioning alleviates myocardial ischemia in rat model.     

Nitric oxide and cerebral blood flow responses to hyperbaric oxygen.

We have tested the hypothesis that cerebral nitric oxide (NO) production is involved in hyperbaric O(2) (HBO(2)) neurotoxicity. Regional cerebral blood flow (rCBF) and electroencephalogram (EEG) were measured in anesthetized rats during O(2) exposure to 1, 3, 4, and 5 ATA with or without administration of the NO synthase inhibitor (N(omega)-nitro-L-arginine methyl ester), L-arginine, NO donors, or the N-methyl-D-aspartate receptor inhibitor MK-801. After 30 min of O(2) exposure at 3 and 4 ATA, rCBF decreased by 26-39% and by 37-43%, respectively, and was sustained for 75 min. At 5 ATA, rCBF decreased over 30 min in the substantia nigra by one-third but, thereafter, gradually returned to preexposure levels, preceding the onset of EEG spiking activity. Rats pretreated with N(omega)-nitro-L-arginine methyl ester and exposed to HBO(2) at 5 ATA maintained a low rCBF. MK-801 did not alter the cerebrovascular responses to HBO(2) at 5 ATA but prevented the EEG spikes. NO donors increased rCBF in control rats but were ineffective during HBO(2) exposures. The data provide evidence that relative lack of NO activity contributes to decreased rCBF under HBO(2), but, as exposure time is prolonged, NO production increases and augments rCBF in anticipation of neuronal excitation.     

Effect of hyperbaric oxygen on experimental acute distal colitis

It has been demonstrated that hyperbaric oxygen (HBO) is useful as an adjunctive therapy for Crohn's disease. However, its effects on ulcerative colitis have not been investigated. In the present study, HBO was tested for acetic acid-induced colitis, and antioxidant systems were evaluated to clarify its possible mode of action. Thirty-six Sprague-Dawley rats were randomly divided into three groups: sham control (Group I), colitis induced by acetic acid without any therapy (Group II), colitis induced by acetic acid and treated with HBO (Group III). HBO was given for 5 days, 2 sessions per day at 2.5-fold absolute atmosphere pressure (ATA) for a period of 90 min in rats in which colitis had been induced (Group III). Rats were sacrificed on the 5th day after the procedure. Superoxide dismutase (SOD), malondialdehyde (MDA) and glutathione peroxidase (GSH Px) activity were measured in the intestinal tissue and erythrocyte lysate. MDA and GSH Px were also determined in the plasma. Whereas MDA levels in erythrocyte, plasma and intestinal tissue were decreased, the levels of GSH Px and SOD were significantly increased in Group III as compared to those of Group II. The results of our study suggest that hyperbaric oxygen therapy has beneficial effects on the course of experimental distal colitis and that antioxidant systems may be involved in its mode of action.     

高压氧对脑缺血再灌注海马神经元Bcl-2和Bax蛋白表达的影响

目的：进一步探讨高压氧治疗脑缺血再灌注损伤,减轻神经元调亡朋而发挥保护作用的机理。方法：采用“双侧颈总动脉阻断法”前脑缺血模型,对沙土鼠前脑缺血２０ｍｉｎ后再灌注３ｄ,并用０．１５ＭＰａ和０．２５ＭＰａ压力的高压氧治疗（６０ｍｉｎ／ｄ,连续３ｄ）后,应用免疫组化ＬＳＡＢ方法,观察高压氧对海巴ＣＡ１,区神经元凋亡相关基因ｂｃｌ－２和ｂａｘ的蛋白表达的影响。结果：沙土鼠脑缺血再灌注３ｄ组海马ＣＡ１区大     

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.     

SkQ1 Controls <Emphasis Type="Italic">CASP3</Emphasis> Gene Expression and Caspase-3-Like Activity in the Brain of Rats under Oxidative Stress

Here, we studied the effect of the mitochondria-targeted antioxidant SkQ1 (plastoquinone cationic derivative) on the CASP3 gene expression and caspase-3 activity in rat cerebral cortex and brain mitochondria under normal conditions and in oxidative stress induced by hyperbaric oxygenation (HBO). Under physiological conditions, SkQ1 administration (50 nmol/kg, 5 days) did not affect the CASP3 gene expression and caspase-3-like activity in the cortical cells, as well as caspase-3-like activity in brain mitochondria, but caused a moderate decrease in the content of primary products of lipid peroxidation (LPO) and an increase in the reduced glutathione (GSH) level. HBO-induced oxidative stress (0.5 MPa, 90 min) was accompanied by significant upregulation of CASP3 mRNA and caspase-3-like activity in the cerebral cortex, activation of the mitochondrial enzyme with simultaneous decrease in the GSH content, increase in the glutathione reductase activity, and stimulation of LPO. Administration of SkQ1 before the HBO session maintained the basal levels of the CASP3 gene expression and enzyme activity in the cerebral cortex cells and led to the normalization of caspase-3-like activity and redox parameters in brain mitochondria. We hypothesize that SkQ1 protects brain cells from the HBO-induced oxidative stress due to its antioxidant activity and stimulation of antiapoptotic mechanisms.     

暴露于高压氧时大鼠纹状体和下丘脑内L—Enk含量的变化

本研究目的在于探讨大鼠氧惊厥时,纹状体和下丘脑内亮-脑啡肽(L-Enk)含量的变化。实验中将32只雄性大鼠随机分为4组:常压空气组、高压常氧氮组、高压氧未惊厥组和高压氧惊厥组。用放射免疫法测定了纹状体和下丘脑内L-Enk含量。结果显示,在高压氧环境中暴露的大鼠纹状体和下丘脑内L-Enk含量明显高于常压空气组和高压常氧氮组;且增高到一定水平时发生惊厥。实验结果提示,动物惊厥与纹状体和下丘脑中L-Enk含量的增加呈正相关,而与高压氧环境及加减压方式无显著关系。     

Hydroxyl radicals detected via brain microdialysis in rats breathing air and during hyperbaric oxygen convulsions

Microdialysis was done on 300-400 g, awake, male rats with microdialysis probes inserted through guide cannulas into the striatum (Bregma co-ordinates A 0.5, L 2.9, D -4.0 for guide cannulas implanted 5 days previously). Rats were exposed to hyperbaric oxygen (HBO; 6 atm absolute, 5 atm gauge pressure of oxygen with carbon dioxide absorbed by soda lime). Artificial cerebrospinal fluid (CSF) containing 5 mM sodium salicylate was perfused at 1 microl/min and collected over sequential 10 min intervals with rats breathing air, then HBO, and after decompression. Times to convulsions and duration and severity of convulsions were observed and recorded. CSF samples were analyzed for 2,3- and 2,5-dihydroxybenzoic acid (DHBA), reaction products of hydroxyl radicals with salicylate, by HPLC and compared to authentic standards. Recovery of DHBAs was 48% from fluid surrounding microdialysis probes, based on in vitro tests. The average time to the first convulsion was 21 min and rats convulsed an average of 4 times during 40 min in HBO. There were no significant differences in hydroxyl radical production by this protocol during any of the 10 min collection periods in air or HBO (average in pmoles for 10 microl of all samples: 2,3-DHBA = 7.0 +/- 2.5 and 2,5-DHBA = 11.3 +/- 4.1). The failure to detect an increase in hydroxyl radicals in HBO prior to or during convulsions appears valid since each rat served as its own control.     

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.