Effect of hyperbaric oxygen on tissue distribution of mononuclear cell subsets in the rat

Effect of hyperoxia on the immune status of oxygen divers and endurance athletes

Physical activity, particularly that, exerted by endurance athletes, impacts the immune status of the human body. Prolonged duration and high-intensity endurance training lead to increased production of reactive oxygen species (ROS) and thereby to oxidative stress. Military combat swimmers (O₂-divers) are regularly exposed to hyperbaric hyperoxia (HBO) in addition to intensive endurance training intervals. They are, therefore, exposed to extreme levels of oxidative stress. Several studies support that the intensity of oxidative stress essentially determines the effect on immune status. The aim of this study was to comparatively characterise peripheral blood mononuclear cells (PBMCs) of O₂-divers (military combat swimmers), endurance athletes (amateur triathletes), and healthy control volunteers with respect to DNA fragmentation, immune status and signs of inflammation. Furthermore, it was investigated how PBMCs from these groups responded acutely to exposure to HBO. We showed that DNA fragmentation was comparable in PBMCs of all three groups under basal conditions directly after HBO exposure. However, significantly higher DNA fragmentation was observed in O₂-divers 18 hours after HBO, possibly indicating a slower recovery. O₂-divers also exhibited a proinflammatory immune status exemplified by an elevated number of CD4⁺CD25⁺ T cells, elevated expression of proinflammatory cytokine IL-12, and diminished expression of anti-inflammatory TGF-β1 compared to controls. Supported by a decreased basal gene expression and prolonged upregulation of anti-oxidative HO-1, these data suggest that higher oxidative stress levels, as present under intermitted hyperbaric hyperoxia, e.g. through oxygen diving, promote a higher inflammatory immune status than oxidative stress through endurance training alone.

A Case of Carbon Monoxide-Induced Delayed Neurological Sequelae Successfully Treated with Hyperbaric Oxygen Therapy, N-Acetylcysteine, and Glucocorticoids: Clinical and Neuroimaging Follow-Up

Carbon monoxide (CO) poisoning is a leading cause of intentional and unintentional poisoning worldwide, associated with mortality and severe morbidity. Some survivors of CO poisoning develop, after a lucid interval, a potentially permanent encephalopathy in the form of cognitive impairment and movement disorders, such as Parkinsonism. One of the most frequent neuroimaging findings is a cerebral white matter damage, but so far its precise cause and specific therapy are still debated. We here report the case of a 33-year-old woman with severe carbon monoxide poisoning who, after a period of lucid interval, presented symptoms of declining motor and cognitive functions. She was treated with 40 sessions of Hyperbaric Oxygen Therapy (HBOT). The therapeutic use of oxygen at supraphysiological pressures might either increase systemic oxidative stress or cause an overproduction of oxygen free radicals as drawbacks. Concurrent use of antioxidants and anti-inflammatory drugs may prevent the side effects of oxygen therapy at supraphysiological pressure due to oxidative stress. For this reason, the patient was also treated with high-dose N-Acetylcysteine and glucocorticoids. Here, we describe the longitudinal monitoring of patient's cognitive abilities and leukoencephalopathy associated with her positive clinical outcome.

Laparoscopic Nissen fundoplication: The effects of high-concentration supplemental perioperative oxygen on the inflammatory and immune response: A randomised controlled trial

Background

A number of studies have been reported on the effects of high-concentration oxygen (HCO) on cytokine synthesis, with controversial results. We assessed the effect of administration of perioperative HCO on systemic inflammatory and immune response in patients undergoing laparoscopic Nissen fundoplication (LNF).

Materials and Methods

Patients (n = 117) were assigned randomly to an oxygen/air mixture with a fraction of inspired oxygen (FiO₂) of 30% (n = 58) or 80% (n = 59). Administration was commenced after induction of anaesthesia and maintained for 6 h after surgery. White blood cells, peripheral lymphocytes subpopulation, human leucocyte antigen-DR (HLA-DR), neutrophil elastase, interleukin (IL)-1 and IL-6 and C-reactive protein (CRP) were investigated.

Results

A significantly higher concentration of neutrophil elastase, IL-1, IL-6 and CRP was detected post-operatively in the 30% FiO₂group patients in comparison with the 80% FiO₂group (P < 0.05). A statistically significant change in HLA-DR expression was recorded post-operatively at 24 h, as a reduction of this antigen expressed on monocyte surface in patients from 30% FiO₂group; no changes were noted in 80% FiO₂group (P < 0.05).

Conclusions

This study demonstrated that perioperative HCO (80%), during LNF, can lead to a reduction in post-operative inflammatory response, and possibly, avoid post-operative immunosuppression.

Hyperbaric oxygen therapy can diminish fibromyalgia syndrome--prospective clinical trial

BACKGROUND

Fibromyalgia Syndrome (FMS) is a persistent and debilitating disorder estimated to impair the quality of life of 2-4% of the population, with 9:1 female-to-male incidence ratio. FMS is an important representative example of central nervous system sensitization and is associated with abnormal brain activity. Key symptoms include chronic widespread pain, allodynia and diffuse tenderness, along with fatigue and sleep disturbance. The syndrome is still elusive and refractory. The goal of this study was to evaluate the effect of hyperbaric oxygen therapy (HBOT) on symptoms and brain activity in FMS.

METHODS AND FINDINGS

A prospective, active control, crossover clinical trial. Patients were randomly assigned to treated and crossover groups: The treated group patients were evaluated at baseline and after HBOT. Patients in the crossover-control group were evaluated three times: baseline, after a control period of no treatment, and after HBOT. Evaluations consisted of physical examination, including tender point count and pain threshold, extensive evaluation of quality of life, and single photon emission computed tomography (SPECT) imaging for evaluation of brain activity. The HBOT protocol comprised 40 sessions, 5 days/week, 90 minutes, 100% oxygen at 2ATA. Sixty female patients were included, aged 21-67 years and diagnosed with FMS at least 2 years earlier. HBOT in both groups led to significant amelioration of all FMS symptoms, with significant improvement in life quality. Analysis of SPECT imaging revealed rectification of the abnormal brain activity: decrease of the hyperactivity mainly in the posterior region and elevation of the reduced activity mainly in frontal areas. No improvement in any of the parameters was observed following the control period.

CONCLUSIONS

The study provides evidence that HBOT can improve the symptoms and life quality of FMS patients. Moreover, it shows that HBOT can induce neuroplasticity and significantly rectify abnormal brain activity in pain related areas of FMS patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01827683.

Saturation diving; physiology and pathophysiology

In saturation diving, divers stay under pressure until most of their tissues are saturated with breathing gas. Divers spend a long time in isolation exposed to increased partial pressure of oxygen, potentially toxic gases, bacteria, and bubble formation during decompression combined with shift work and long periods of relative inactivity. Hyperoxia may lead to the production of reactive oxygen species (ROS) that interact with cell structures, causing damage to proteins, lipids, and nucleic acid. Vascular gas-bubble formation and hyperoxia may lead to dysfunction of the endothelium. The antioxidant status of the diver is an important mechanism in the protection against injury and is influenced both by diet and genetic factors. The factors mentioned above may lead to production of heat shock proteins (HSP) that also may have a negative effect on endothelial function. On the other hand, there is a great deal of evidence that HSPs may also have a "conditioning" effect, thus protecting against injury. As people age, their ability to produce antioxidants decreases. We do not currently know the capacity for antioxidant defense, but it is reasonable to assume that it has a limit. Many studies have linked ROS to disease states such as cancer, insulin resistance, diabetes mellitus, cardiovascular diseases, and atherosclerosis as well as to old age. However, ROS are also involved in a number of protective mechanisms, for instance immune defense, antibacterial action, vascular tone, and signal transduction. Low-grade oxidative stress can increase antioxidant production. While under pressure, divers change depth frequently. After such changes and at the end of the dive, divers must follow procedures to decompress safely. Decompression sickness (DCS) used to be one of the major causes of injury in saturation diving. Improved decompression procedures have significantly reduced the number of reported incidents; however, data indicate considerable underreporting of injuries. Furthermore, divers who are required to return to the surface quickly are under higher risk of serious injury as no adequate decompression procedures for such situations are available. Decompression also leads to the production of endothelial microparticles that may reduce endothelial function. As good endothelial function is a documented indicator of health that can be influenced by regular exercise, regular physical exercise is recommended for saturation divers. Nowadays, saturation diving is a reasonably safe and well controlled method for working under water. Until now, no long-term impact on health due to diving has been documented. However, we still have limited knowledge about the pathophysiologic mechanisms involved. In particular we know little about the effect of long exposure to hyperoxia and microparticles on the endothelium.

The apoptosis of peripheral blood lymphocytes promoted by hyperbaric oxygen treatment contributes to attenuate the severity of early stage acute pancreatitis in rats

The aim of this study was to investigate the immunoregulatory effects of hyperbaric oxygen (HBO) via promoting the apoptosis of peripheral blood lymphocytes (PBLs) to attenuate the severity of early stage acute pancreatitis (AP) in rats. Additionally, the persistence of the HBO treatment effects was evaluated. One hundred and twenty male Wistar rats were randomized into four groups: sham, AP, AP + normobaric oxygen (NBO), and AP + HBO. Each group consisted of 30 rats. Four hours after the induction of AP, the 30 rats in the AP + NBO group were given normobaric oxygen treatment with 100 % oxygen at 1 atm for 90 min. The 30 rats in the AP + HBO group received 100 % oxygen at 2.5 atm for 90 min, with a compression/decompression time of 15 min. The 30 rats in the AP group remained untreated. At 6, 12, and 24 h after the induction of AP, surviving rats from each group were sacrificed, and the blood and tissue samples were collected for the following measurements: the partial pressure of oxygen (PaO2) and oxygen saturation (SaO2) of the arterial blood, the levels of serum amylase, lipase, interleukin-2 (IL-2), interferon-γ (IFN-γ), interleukin-10 (IL-10), hepatocyte growth factor (HGF), and reactive oxygen species (ROS), and the mitochondrial membrane potential (∆Ψm) of the PBLs. The expression levels of procaspase-3, caspase-3, procaspase-9, and caspase-9 were also evaluated in the PBLs. Additionally, the apoptosis of PBLs was assessed, and the pancreatic tissues were subjected to a histopathological analysis by pathological grading and scoring. The histopathology of the lung, liver, kidney, duodenum, and heart was also analyzed at 12 h after the induction of AP. Significant differences were found at 6 and 12 h after AP induction. The HBO treatment significantly elevated the PaO2 and SaO2 levels, and the ROS levels in the PBLs. Additionally, HBO downregulated the levels of amylase and lipase. The HBO treatment also reduced the ∆Ψm levels, upregulated the expression of caspase-3 and caspase-9, and increased the apoptosis rate of the PBLs. Moreover, the HBO treatment decreased the serum concentrations of IL-2, IFN-γ and HGF, and reduced the pathological scores of the pancreatic tissue. The histopathological changes of the lung, liver, kidney, duodenum, and heart were also improved. A significant elevation of IL-10 occurred only at the 12-h time point. However, no obvious differences were found at the 24-h time point. This study demonstrated that the HBO treatment can promote the apoptosis of PBLs via a mitochondrial-dependent pathway and inhibit the inflammatory response. These immunoregulatory effects may play an important therapeutic role in attenuating the severity of early stage AP. The repeated administration of HBO or the use of HBO in combination with other approaches may further improve outcomes.

HBO: a possible supplementary therapy for oral potentially malignant disorders

Oral potentially malignant disorders (OPMDs) are chronic inflammatory diseases in which cells suffer hypoxia referring to deprivation of adequate oxygen supply. Hyperbaric oxygen treatment (HBO), which can increase oxygen tension and delivery to oxygen-deficient tissue, is a supplementary therapy to improve or cure disorders involving hypoxia. Although the applications of HBO in wound healings, acute ischemic stroke, radiation-induced soft tissue injury and cancers are extensively reported, there are only few studies on their effect in OPMDs. Not only does HBO furnish oxygen-it also possesses potent anti-inflammatory properties. At the cellular level, HBO can decrease lymphocyte proliferation and promote apoptosis of fibroblasts. At the molecular level, it can decrease expression of HIF, ICAM-1, TNF-α, TGF-β, and IFN-γ, as well as increase vascular VEGF expression and angiogenesis. Thus, we hypothesize that HBO may contribute to treat OPMDs, including oral lichen planus, oral leukoplakia, and oral submucous fibrosis both at the cellular level and the molecular level, and that it would be a safe and inexpensive therapeutic strategy.

Influence of hyperbaric oxygen on tumor necrosis factor-α and nitric oxide production in endotoxin-induced acute lung injury in rats

We previously demonstrated that hyperbaric oxygen (HBO) treatment alleviated lipopolysaccharide (LPS)-induced acute lung injury in rats. However, the mechanisms responsible for the protective effect are still not fully understood. To obtain further information on the protective effect of HBO, in this study we investigated the role of tumor necrosis factor-alpha (TNF-alpha) and nitric oxide (NO) in intratracheal spraying LPS-induced acute lung injury in rats after HBO or hyperoxia treatment. The results showed that HBO but not hyperoxia attenuated the TNF-alpha level in plasma and bronchoalveolar lavage (BAL) fluid, NO concentration in BAL and plasma, and inducible NO synthase protein expression in lung tissue based on the Western blotting and immunohistochemical staining.

Hyperbaric oxygen inhibits stimulus-induced proinflammatory cytokine synthesis by human blood-derived monocyte-macrophages

Hyperbaric oxygen (HBO) is 100% oxygen administered at elevated atmospheric pressure to patients with inflammatory diseases. We developed an in vitro model to investigate the effects of HBO on stimulus-induced proinflammatory cytokine transcription and translation. Human blood-derived monocyte-macrophages were stimulated before being transferred to an HBO chamber where they were incubated at 97.9% O2, 2.1% CO2, 2.4 atmospheres absolute, 37 degrees C. Controls were maintained in the same warm room at normoxia at sea level, hyperoxia or increased pressure alone. A 90-min HBO exposure inhibited IL-1beta synthesized in response to lipopolysaccharide by 23%, lipid A by 45%, phytohaemagglutinin A (PHA) by 68%, and tumour necrosis factor (TNF)-alpha by 27%. HBO suppressed lipopolysaccharide-, lipid A- and PHA-induced TNF-alpha by 29%, 31% and 62%, respectively. HBO transiently reduced PHA-induced steady state IL-1beta mRNA levels. Hyperoxia alone and pressure alone did not affect cytokine production. The immunosuppressive effect of HBO was no longer evident in monocyte-macrophages exposed to HBO for more than 3 h. Interestingly, cells exposed to HBO for 12 h synthesized more IL-1beta than cells cultured under control conditions. In summary, HBO exposure transiently suppresses stimulus-induced proinflammatory cytokine production and steady state RNA levels.

Early hyperbaric oxygen therapy attenuates disease severity in lupus-prone autoimmune (NZB x NZW) F1 mice

The effects of hyperbaric oxygen (HBO(2)) therapy on the immune system are reported including potential changes to the CD4/CD8 ratio and a decreased proliferation of lymphocytes during exposure. The immunosuppressive effect of HBO(2) had been suggested to be applicable for the treatment of certain autoimmune diseases. (NZB x NZW) F1 hybrid mice, the unique lupus-prone mice, have been used for elucidating the pathogenesis of SLE. To investigate the effect of HBO(2) on NZB/W F1 lupus-prone mice, 32 female mice were divided into four groups. Three groups of mice were treated with HBO(2) (2.5 atm abs (ATA) for 90 min daily over 2 weeks) starting at (A) 3 months, (B) 6 months, or (C) 8 months of age, while the remaining group (D) served as control. Animals were followed until 11 months of age. Experimental parameters included life span, proteinuria, peripheral lymphocytes, anti-dsDNA antibody titers, and renal histopathology. HBO(2) treatment resulted in increased survival, decreased proteinuria, alterations in lymphocyte-subset redistribution, reduced anti-dsDNA antibody titers, and amelioration of immune-complex deposition in groups A and B. Our data demonstrated that HBO(2) therapy attenuated disease severity in NZB/W F1 mice. HBO(2) treatment may be of use in the clinical treatment of lupus patients and would benefit from further study.

Differential sensitivities to hyperbaric oxygen of lymphocyte subpopulations of normal and autoimmune mice

We studied the effect of exposure to hyperbaric oxygen (HBO): 2.8 atm absolute 100% oxygen for 4 h daily over 3-7 days, on the immune system of normal (BALB/c and MRL- +/+) and autoimmune MRL-lpr/lpr) mice. In HBO exposed BALB/c mice, we observed a remarkable decrease in the cell population of the spleen and thymus. We found that the sensitivity to HBO varied among subpopulations of lymphocytes. For example, CD4+ CD8+ double positive cells in the thymus and B220+ B cells in the spleen were more sensitive than CD4+ or CD8+ single positive T cells in the thymus, and Thy-1+ T cells in the spleen, respectively. Accordingly, despite the decrease in total cell number in the spleen, the proliferative response of T cells from the spleen to Con A was not impaired in the HBO exposed mice. Exposure of MRL-lpr/lpr mice to HBO caused a marked reduction of weight and cell population of the otherwise enlarged spleen and lymph nodes, and amongst others of percentages of B220+Thy-1+ double positive abnormal cells. These results suggest the HBO therapy may be applicable for the treatment of some autoimmune diseases.

Exposure to hyperbaric oxygen induces tumour necrosis factor-alpha (TNF-alpha) secretion from rat macrophages

We investigated the secretion of TNF-alpha by monocytes and macrophages derived from the peripheral blood, spleen, and lungs after a single exposure to a therapeutic profile of hyperbaric oxygen (HBO). Rats were exposed for 90 min to either 100% oxygen at 0.28 MPa (2.8 atmospheres absolute) or air. Immediately after exposure, mononuclear cells were isolated from blood, spleen, and lungs and cultured for 18 h. The secretion of TNF-alpha from the cultured monocytes/macrophages was determined with and without stimulation with lipopolysaccharide (LPS). Exposure to hyperbaric oxygen induced a significant increase in the spontaneous ex vivo secretion of TNF-alpha (without LPS) by mononuclear cells from the blood, spleen, and lung (P < 0.05 from air controls). Stimulation with LPS after exposure to HBO induced a significant increase in TNF-alpha secretion by lung and spleen macrophages compared with air controls (P < 0.05). However, absolute TNF-alpha levels were not significantly higher than those achieved 'spontaneously' in macrophages exposed to HBO without LPS. Stimulation with LPS induced a marked increase in secretion of TNF-alpha from blood monocytes after exposure to air, but not after exposure to HBO. These results provide evidence in support of a role played by TNF-alpha in mediating HBO effects on different tissues and their immune responses.