Hyperbaric Environment: Oxygen and Cellular Damage versus Protection

Hyperbaric oxygen therapy suppresses hypoxia and reoxygenation injury to retinal pigment epithelial cells through activating peroxisome proliferator activator receptor-alpha signalling

Retinal ischemia followed by reperfusion (IR) is a common cause of many ocular disorders, such as age-related macular degeneration (AMD), which leads to blindness in the elderly population, and proper therapies remain unavailable. Retinal pigment epithelial (RPE) cell death is a hallmark of AMD. Hyperbaric oxygen (HBO) therapy can improve IR tissue survival by inducing ischemic preconditioning responses. We conducted an in vitro study to examine the effects of HBO preconditioning on oxygen-glucose deprivation (OGD)-induced IR-injured RPE cells. RPE cells were treated with HBO (100% O2 at 3 atmospheres absolute for 90 min) once a day for three consecutive days before retinal IR onset. Compared with normal cells, the IR-injured RPE cells had lower cell viability, lower peroxisome proliferator activator receptor-alpha (PPAR-α) expression, more severe oxidation status, higher blood-retinal barrier disruption and more elevated apoptosis and autophagy rates. HBO preconditioning increased PPAR-α expression, improved cell viability, decreased oxidative stress, blood-retinal barrier disruption and cellular apoptosis and autophagy. A specific PPAR-α antagonist, GW6471, antagonized all the protective effects of HBO preconditioning in IR-injured RPE cells. Combining these observations, HBO therapy can reverse OGD-induced RPE cell injury by activating PPAR-α signalling.

The effects of normobaric and hyperbaric oxygenation on MRI signal intensities in T1 -weighted, T2 -weighted and FLAIR images in human brain

BACKGROUND

Dissolved oxygen has known paramagnetic effects in magnetic resonance imaging (MRI). The aim of this study was to compare the effects of normobaric oxygenation (NBO) and hyperbaric oxygenation (HBO) on human brain MRI signal intensities.

PATIENTS AND METHODS

Baseline brain MRI was performed in 17 healthy subjects (mean age 27.8 ± 3.2). MRI was repeated after exposure to the NBO and HBO at different time points (0 min, 25 min, 50 min). Signal intensities in T 1-weighted, T 2-weighted images and fluid attenuated inversion recovery (FLAIR) signal intensities of several intracranial structures were compared between NBO and HBO.

RESULTS

Increased T 1-weighted signal intensities were observed in white and deep grey brain matter, cerebrospinal fluid (CSF), venous blood and vitreous body after exposure to NBO as well as to HBO compared to baseline (Dunnett's test, p < 0.05) without significant differences between both protocols. There was also no significant difference in T 2-weighted signal intensities between NBO and HBO. FLAIR signal intensities were increased only in the vitreous body after NBO and HBO and FLAIR signal of caudate nucleus was decreased after NBO (Dunnett's test, p < 0.05). The statistically significant differences in FLAIR signal intensities were found between NBO and HBO (paired t-test, p < 0.05) in most observed brain structures (paired t-test, p < 0.05).

CONCLUSIONS

Our results show that NBO and HBO alters signal intensities T 1-weighted and FLAIR images of human brain. The differences between NBO and HBO are most pronounced in FLAIR imaging.

Effect of Hyperbaric oxygen on myelin injury and repair after hypoxic-ischemic brain damage in adult rat

INTRODUCTION

Hypoxic-ischemic encephalopathy (HIE) is one of the leading causes of death and neurological disability with limited options for treatment in neonates, children and adults worldwide. The pathogenesis and treatment of white matter (WM) injury in adult patients with HIE remains largely elusive.

METHODS

Sixty male Sprague-Dawley rats were randomly divided into control group, sham-operated group (HBO treatment 6 days after sham operation), and Hypoxia-ischemia (HI) induced brain damage group (receiving left carotid arteries ligation + hypoxia treatment), 1.5ATA hyperbaric oxygen group (HI + 1.5ATA HBOT) and 2.5ATA HBOT group (HI + 2.5ATA HBOT). All the rats were evaluated by water maze before operation, and 6 days after operation, and the function of learning and memory was evaluated; Demyelination in the hippocampus and prefrontal cortex was observed by Luxol fast blue staining (LFB) and MBP immunostaining; the number of Myelin Oligodendrocyte Glycoprotein (MOG),glial fibrillary acidic protein (GFAP), ionic calcium-binding adaptor (Iba-1) and NG2 positive cells in the hippocampus and prefrontal cortex were determined by immunofluorescence staining. The expression of interleukin-1β (IL-1β), IL-6 and tumor necrosis factor (TNF-α), Hypoxia Inducible Factor 1 Subunit Alpha (HIF1-α) and Superoxide dismutase (SOD) in brain and serum of rats were measured by Western Blot method and Enzyme linked immunosorbent assay (ELISA).

RESULTS

Compared with those in the normal control group and sham-operated group, in the HI group, the learning and memory abilities of rats were significantly decreased (P < 0.05), the intensity of LFB and MBP immunostaining in hippocampus and prefrontal cortex was significantly decreased (P < 0.05); the number of MOG positive oligodendrocytes (OLs) significantly decreased (P < 0.05), whereas the number of Iba-1, GFAP, NG2 positive microglias, astrocytes and oligodendrocyte precursors (OPCs) was increased (P < 0.05); the level of IL-1β, IL-6, TNF-α and HIF-1a in brain and serum were significantly increased (P < 0.05), whereas SOD was significantly decreased in brain and increased in serum. Compared with those in the HI group, in both 1.5ATA and 2.5ATA HBOT group, the learning and memory abilities were significantly increased (P < 0.05); the intensity of LFB and MBP immunostaining in the hippocampus and prefrontal cortex was significantly increased (P < 0.05); the number of MOG positive OLs significantly increased (P < 0.05); the number of Iba-1, GFAP, NG2 positive microglias, astrocytes and OPCs was decreased (P < 0.05); the level of IL-1β, IL-6, TNF-α and HIF-1a in brain and serum were significantly decreased (P < 0.05); the level of SOD was significantly increased in brain and decreased in serum. Morever, compared with those in the 1.5ATA group, 2.5ATA provided better treatment results (P < 0.05).

CONCLUSION

In the present study, we demonstrated the mechanism of different pressure HBOT on HI induced brain injury from three levels: (1) On a tissue level, HBOT protects against HI induced myelin injury; (2) On a cellular level, HBOT attenuates HI-induced OL loss, suppresss the reactive activation of astrocyte and microglia, and may promote OPC to differentiate into OL; (3) On a molecular level, HBOT inhibites neuroinflammation, and balances oxidative damage and antioxidant capacity. Among the above effects, 2.5ATA HBOT is better than 1.5ATA HBOT. Ongoing research will continue to seek out the signalling pathways and molecules mechanisms on different pressure of HBOT-related myelin protection, and possibly expand suitable HBOT use in adult HIE clinically.

Acidic oligosaccharide sugar chain combined with hyperbaric oxygen delays D-galactose-induced brain senescence in mice via attenuating oxidative stress and neuroinflammation

Aging is fundamental to neurodegeneration and dementia. Preventing oxidative stress and neuroinflammation are potential methods of delaying the onset of aging-associated neurodegenerative diseases. The acidic oligosaccharide sugar chain (AOSC) and hyperbaric oxygen (HBO) can increase the expression of antioxidants and have a neuroprotective function. In this study, we investigate the ability of AOSC, HBO, and AOSC + HBO to prevent D-gal-induced brain senescence. The Morris water maze and Y-maze test results showed that all three therapies significantly attenuated D-gal-induced memory disorders. A potential mechanism of this action was decreasing elevated levels of oxidative stress and neuroinflammation. The western blot and morphological results showed that all three therapies decreased D-gal-induced neuroinflammation and downregulated inflammatory mediators including the nuclear factor κ-light-chain-enhancer of activated B cells, cyclooxygenase-2, interleukin-1β, and tumor necrosis factor alpha. Taken together, our results indicated that AOSC, HBO, and AOSC + HBO therapies attenuated D-gal-induced brain aging in mice by repressing RAGE/NF-KB-induced inflammation, the activation of astrocytes and microglia, and a decrease in neuronal degeneration. These could be useful therapies for treating age-related neurodegenerative diseases such as Alzheimer's disease. Furthermore, HBO combined with AOSC had a better effect than HBO or AOSC alone.

Medical Gas Therapy for Tissue, Organ, and CNS Protection: A Systematic Review of Effects, Mechanisms, and Challenges

Gaseous molecules have been increasingly explored for therapeutic development. Here, following an analytical background introduction, a systematic review of medical gas research is presented, focusing on tissue protections, mechanisms, data tangibility, and translational challenges. The pharmacological efficacies of carbon monoxide (CO) and xenon (Xe) are further examined with emphasis on intracellular messengers associated with cytoprotection and functional improvement for the CNS, heart, retina, liver, kidneys, lungs, etc. Overall, the outcome supports the hypothesis that readily deliverable "biological gas" (CO, H₂ , H₂ S, NO, O₂ , O₃ , and N₂ O) or "noble gas" (He, Ar, and Xe) treatment may preserve cells against common pathologies by regulating oxidative, inflammatory, apoptotic, survival, and/or repair processes. Specifically, CO, in safe dosages, elicits neurorestoration via igniting sGC/cGMP/MAPK signaling and crosstalk between HO-CO, HIF-1α/VEGF, and NOS pathways. Xe rescues neurons through NMDA antagonism and PI3K/Akt/HIF-1α/ERK activation. Primary findings also reveal that the need to utilize cutting-edge molecular and genetic tactics to validate mechanistic targets and optimize outcome consistency remains urgent; the number of neurotherapeutic investigations is limited, without published results from large in vivo models. Lastly, the broad-spectrum, concurrent multimodal homeostatic actions of medical gases may represent a novel pharmaceutical approach to treating critical organ failure and neurotrauma.

Hyperbaric oxygen influences chronic wound healing – a cellular level review

Chronic wound is a serious medical issue due to its high prevalence and complications; hyperbaric oxygen therapy (HBOT) is also considered in comprehensive treatment. Clinical trials, including large meta-analyses bring inconsistent results about HBOT efficacy. This review is summarizing the possible effect of HBOT on the healing of chronic wound models at the cellular level. HBOT undoubtedly escalates the production of reactive oxygen and nitrogen radicals (ROS and RNS), which underlie both the therapeutic and toxic effects of HBOT on certain tissues. HBOT paradoxically elevates the concentration of Hypoxia inducible factor (HIF) 1 by diverting the HIF-1 degradation to pathways that are independent of the oxygen concentration. Elevated HIF-1 stimulates the production of different growth factors, boosting the healing process. HBOT supports synthesis of Heat shock proteins (HSP), which are serving as chaperones of HIF-1. HBOT has antimicrobial effect, increases the effectiveness of some antibiotics, stimulates fibroblasts growth, collagen synthesis and suppresses the activity of proteolytic enzymes like matrix metalloproteinases. All effects of HBOT were investigated on cell cultures and animal models, the limitation of their translation is discussed at the end of this revie

Oxygen in Metabolic Dysfunction and Its Therapeutic Relevance

Significance: In recent years, a number of studies have shown altered oxygen partial pressure at a tissue level in metabolic disorders, and some researchers have considered oxygen to be a (macro) nutrient. Oxygen availability may be compromised in obesity and several other metabolism-related pathological conditions, including sleep apnea-hypopnea syndrome, the metabolic syndrome (which is a set of conditions), type 2 diabetes, cardiovascular disease, and cancer. Recent Advances: Strategies designed to reduce adiposity and its accompanying disorders have been mainly centered on nutritional interventions and physical activity programs. However, novel therapies are needed since these approaches have not been sufficient to counteract the worldwide increasing rates of metabolic disorders. In this regard, intermittent hypoxia training and hyperoxia could be potential treatments through oxygen-related adaptations. Moreover, living at a high altitude may have a protective effect against the development of abnormal metabolic conditions. In addition, oxygen delivery systems may be of therapeutic value for supplying the tissue-specific oxygen requirements. Critical Issues: Precise in vivo methods to measure oxygenation are vital to disentangle some of the controversies related to this research area. Further, it is evident that there is a growing need for novel in vitro models to study the potential pathways involved in metabolic dysfunction to find appropriate therapeutic targets. Future Directions: Based on the existing evidence, it is suggested that oxygen availability has a key role in obesity and its related comorbidities. Oxygen should be considered in relation to potential therapeutic strategies in the treatment and prevention of metabolic disorders. Antioxid. Redox Signal. 35, 642-687.

The role of hyperbaric oxygen to platelet aggregation in noninsulin-dependent diabetes mellitus (NIDDM)

OBJECTIVES

Hyperglycemia in diabetes mellitus (DM) could cause rheological disorder, such as platelet aggregation and blood hyperviscosity. Hyperbaric oxygen (HBO) could decrease collagen as platelet aggregation agonist. This study aimed to explore the effect of HBO treatment to platelet aggregation parameters (latency time(LT), aggregation speed, aggregation index, and aggregation percentage) with the collagen aggregator in the noninsulin dependent diabetes mellitus (NIDDM).

METHODS

The number of subjects in this study were 16 for each group normoxia normobaric (NONB) and HBO. NIDDM patients from DM polyclinic in Rumah Sakit Angkatan Laut (RSAL) Dr Ramelan Surabaya which was fulfilled inclusion criteria would receive HBO Therapy. Control Group/NONB were treated with NONB condition (20% O₂ 1 ATA) for 90 min and treatment group/HBO were treated with hyperoxia hyperbaric condition (100% O₂ 2.4 ATA) for 3 × 30 min with interval of 2 × 5 min for inhaling fresh air. Subject has been blood taken for platelet aggregation test before and after HBO Therapy. The length of treatment was 5 days for both condition (NONB and HBO).

RESULTS

The data from both groups, NONB and HBO were tested first by normality test, homogenity test, correlation test, analysis of covariance, and paired t-test. Based on paired t-test, the decrease on platelet aggregation speed, aggregation index, and aggregation percentage after HBO treatment was showed significant difference on the LT and aggregation index while in aggregation speed and aggregation percentage was not significant. NONB group after 5 days was showed a significant difference on the aggregation speed and aggregation index while in LT and aggregation percentage was not significant.

CONCLUSIONS

The utilization of HBO 2.4 ATA 100% O₂ 3 × 30 min, once a day, for 5 days could decrease the platelet aggregation parameters (LT, aggregation speed, aggregation index, and aggregation percentage) in patients with NIDDM.

Human Adaptations to Multiday Saturation on NASA NEEMO

Human adaptation to extreme environments has been explored for over a century to understand human psychology, integrated physiology, comparative pathologies, and exploratory potential. It has been demonstrated that these environments can provide multiple external stimuli and stressors, which are sufficient to disrupt internal homeostasis and induce adaptation processes. Multiday hyperbaric and/or saturated (HBS) environments represent the most understudied of environmental extremes due to inherent experimental, analytical, technical, temporal, and safety limitations. National Aeronautic Space Agency (NASA) Extreme Environment Mission Operation (NEEMO) is a space-flight analog mission conducted within Florida International University’s Aquarius Undersea Research Laboratory (AURL), the only existing operational and habitable undersea saturated environment. To investigate human objective and subjective adaptations to multiday HBS, we evaluated aquanauts living at saturation for 9–10 days via NASA NEEMO 22 and 23, across psychologic, cardiac, respiratory, autonomic, thermic, hemodynamic, sleep, and body composition parameters. We found that aquanauts exposed to saturation over 9–10 days experienced intrapersonal physical and mental burden, sustained good mood and work satisfaction, decreased heart and respiratory rates, increased parasympathetic and reduced sympathetic modulation, lower cerebral blood flow velocity, intact cerebral autoregulation and maintenance of baroreflex functionality, as well as losses in systemic bodyweight and adipose tissue. Together, these findings illustrate novel insights into human adaptation across multiple body systems in response to multiday hyperbaric saturation.

Effect of Transcriptional Regulatory Factor FoxO3a on Central Nervous System Oxygen Toxicity

Central nervous system (CNS) oxygen toxicity (CNS-OT) is a toxic reaction that appears after the inhalation of gas at an excessive oxygen partial pressure during underwater operation or hyperbaric oxygen (HBO) treatment. The mechanism of CNS-OT has not been clearly characterized. Though it has been attributed to the excessive oxidative stress induced by HBO, evidences against this hypothesis have been reported. Here we find that Forkhead box protein O3 (FoxO3a) is important for CNS-OT protection. FoxO3a knock-out (KO) mice had a shorter latency to develop convulsions and greater number of seizures within a certain period of time. The acute lung injury (ALI) induced by CNS-OT was also more severe in FoxO3a KO mice. Further analysis reveals a significant decrease in the activity of catalase (CAT), an antioxidant enzyme and a significant increase in the content of malondialdehyde (MDA), an oxidative product, in brain tissues of FoxO3a KO mice. Short-time HBO exposure could increase FoxO3a expression level and trigger its nuclear translocation. The level of nuclear localized FoxO3a peaked at 8 h after exposure. Our results demonstrate that the activity of FoxO3a is highly sensitive to HBO exposure and FoxO3a plays important roles in protecting CNS-OT. Further mechanic analysis reveals that FoxO3a protects CNS-OT via activating antioxidative signaling pathway.

Effect of Hyperbaric Oxygen Therapy on Acute Liver Injury and Survival in a Rat Cecal Slurry Peritonitis Model

BACKGROUND

The effects of hyperbaric oxygen therapy (HBOT) in sepsis remain unclear. This study evaluated its effects on acute liver injury and survival in a rat model.

METHODS

Cecal slurry peritonitis was induced in male rats, which were then randomly allocated into the HBOT and control groups. In the survival experiment, six 90 min HBOT sessions (2.6 atmospheres absolute 100% oxygen) were performed over 48 h; the survival rate was determined 14 days after sepsis induction. In the acute liver injury experiment, three HBOT sessions were performed, followed by liver and plasma harvesting, 24 h after sepsis induction. Serum levels of alanine aminotransferase (ALT), interleukin (IL)-6, and IL-10 were measured, and the hepatic injury scores were determined. Reactive oxygen species (ROS) generation was detected by 2',7'-dihydrodichlorofluorescein diacetate (H2DCF-DA) assay. Western blot assays assessed protein kinase B (Akt), phosphorylated-Akt (p-Akt), glycogen synthase kinase (GSK)-3β, phosphorylated-GSK-3β, and cleaved caspase-3 levels.

RESULTS

Survival in the HBOT group (57.1%) was significantly higher than that in the controls (12.5%, p = 0.029), whereas IL-6, IL-10, and ALT levels were significantly lower in the HBOT group. The ROS generation was significantly inhibited to a greater extent in the HBOT group than in the control group. Additionally, in the HBOT group, the p-Akt and p-GSK-3β increased significantly and cleaved caspase-3 levels decreased significantly.

CONCLUSIONS

HBOT showed a beneficial effect on acute liver injury and rat survival by enhancing the Akt signaling pathway and decreasing apoptosis.

Hyperbaric Oxygen Exposure Attenuates Circulating Stress Biomarkers: A Pilot Interventional Study

Hyperbaric oxygen therapy (HBOT) has been used to provide oxygen to underperfused organs following ischemia or carbon monoxide intoxication. Various beneficial consequences of HBOT have been reported, including wound healing, anti-inflammatory action, and cell survival; however, the molecular mechanisms underlying these effects have not been elucidated yet. We applied a single HBOT program consisting of administration of 2.8 atmospheres absolute (ATA) for 45 min, followed by 2.0 ATA for 55 min, to 10 male volunteers without any metabolic disease. Within 1 week of HBOT, there was no alteration in serum biochemical variables, except for an increase in triglyceride content. As a mitochondrial stress indicator, the serum concentration of growth differentiation factor 15 was reduced by HBOT. The circulating level of γ–glutamyltransferase was also decreased by HBOT, suggesting an attenuation of oxidative stress. HBOT increased adiponectin and reduced leptin levels in the serum, leading to an elevated adiponectin/leptin ratio. This is the first study to investigate the effect of HBOT on serum levels of metabolic stress-related biomarkers. We suggest that HBOT attenuates mitochondrial and oxidative stresses, and relieves metabolic burdens, indicating its potential for use in therapeutic applications to metabolic diseases.

Effects of Perinatal Hyperoxia on Breathing

Air-breathing animals do not experience hyperoxia (inspired O₂ > 21%) in nature, but preterm and full-term infants often experience hyperoxia/hyperoxemia in clinical settings. This article focuses on the effects of normobaric hyperoxia during the perinatal period on breathing in humans and other mammals, with an emphasis on the neural control of breathing during hyperoxia, after return to normoxia, and in response to subsequent hypoxic and hypercapnic challenges. Acute hyperoxia typically evokes an immediate ventilatory depression that is often, but not always, followed by hyperpnea. The hypoxic ventilatory response (HVR) is enhanced by brief periods of hyperoxia in adult mammals, but the limited data available suggest that this may not be the case for newborns. Chronic exposure to mild-to-moderate levels of hyperoxia (e.g., 30-60% O₂ for several days to a few weeks) elicits several changes in breathing in nonhuman animals, some of which are unique to perinatal exposures (i.e., developmental plasticity). Examples of this developmental plasticity include hypoventilation after return to normoxia and long-lasting attenuation of the HVR. Although both peripheral and CNS mechanisms are implicated in hyperoxia-induced plasticity, it is particularly clear that perinatal hyperoxia affects carotid body development. Some of these effects may be transient (e.g., decreased O₂ sensitivity of carotid body glomus cells) while others may be permanent (e.g., carotid body hypoplasia, loss of chemoafferent neurons). Whether the hyperoxic exposures routinely experienced by human infants in clinical settings are sufficient to alter respiratory control development remains an open question and requires further research. © 2020 American Physiological Society. Compr Physiol 10:597-636, 2020.

Deconvolution of RNA-Seq Analysis of Hyperbaric Oxygen-Treated Mice Lungs Reveals Mesenchymal Cell Subtype Changes

Hyperbaric oxygen (HBO) is widely applied to treat several hypoxia-related diseases. Previous studies have focused on the immediate effect of HBO-exposure induced oxidative stress on the lungs, but knowledge regarding the chronic effects from repetitive HBO exposure is limited, especially at the gene expression level. We found that repetitive HBO exposure did not alter the morphology of murine lungs. However, by deconvolution of RNA-seq from those mice lungs using CIBERSORTx and the expression profile matrices of 8 mesenchymal cell subtypes obtained from bleomycin-treated mouse lungs, we identify several mesenchymal cell subtype changes. These include increases in Col13a1 matrix fibroblasts, mesenchymal progenitors and mesothelial cell populations and decreases in lipofibroblasts, endothelial and Pdgfrb high cell populations. Our data suggest that repetitive HBO exposure may affect biological processes in the lungs such as response to wounding, extracellular matrix, vasculature development and immune response.

Hyperbaric oxygenation improves redox control and reduces mortality in the acute phase of myocardial infarction in a rat model

Among the mechanisms of action of hyperbaric oxygenation (HBO), the chance of reducing injury by interfering with the mechanisms of redox homeostasis in the heart leads to the possibility of extending the period of viability of the myocardium at risk. This would benefit late interventions for reperfusion to the ischemic area. The objective of the present study was to investigate the changes in the redox system associated with HBO therapy maintained during the first hour after coronary occlusion in an acute myocardial infarction (MI) rat model. Surviving male rats (n=105) were randomly assigned to one of three groups: Sham (SH=26), myocardial infarction (MI=45) and infarction+hyperbaric therapy (HBO=34, 1 h at 2.5 atm). After 90 min of coronary occlusion, a sample of the heart was collected for western blot analysis of total protein levels of superoxide dismutase, catalase, peroxiredoxin and 3‑nitrotyrosine. Glutathione was measured by enzyme‑linked immunosorbent assay (ELISA). The detection of the superoxide radical anion was carried out by oxidation of dihydroethidium analyzed with confocal microscopy. The mortality rate of the MI group was significantly higher than that of the HBO group. No difference was noted in the myocardial infarction size. The oxidized/reduced glutathione ratio and peroxiredoxin were significantly higher in the SH and MI when compared to the HBO group. Superoxide dismutase enzymes and catalase were significantly higher in the HBO group compared to the MI and SH groups. 3‑Nitrotyrosine and the superoxide radical were significantly lower in the HBO group compared to these in the MI and SH groups. These data demonstrated that hyperbaric oxygenation therapy decreased mortality by improving redox control in the hearts of rats in the acute phase of myocardial infarction.

Hyperbaric Oxygen Ameliorates Insulin Sensitivity by Increasing GLUT4 Expression in Skeletal Muscle and Stimulating UCP1 in Brown Adipose Tissue in T2DM Mice

Hyperbaric oxygen (HBO) therapy is a treatment modality useful for diseases. Hypoxia could stimulate the induction of insulin resistance. Therefore, we sought to determine whether hyperbaric oxygen would ameliorate insulin sensitivity by promoting glucose transporter type 4 (GLUT4) expression in muscle and by stimulating UCP1 in brown adipose tissue (BAT) in a streptozocin (STZ)-induced type 2 diabetes mellitus (T2DM) mouse model. Male C57BL/6J mice were treated three times with low-dose of streptozocin (60 mg/kg, i.p.) and were fed with high-fat diets (HFD) to establish the T2DM model. HBO was administered daily as 100% oxygen at 2.0 atmosphere absolute (ATA) for 1 h for a week. We found that HBO significantly reduced blood glucose levels and attenuated insulin resistance in T2DM mice. HBO modulated food intake by influencing the activity of neuropeptide Y (NPY)-positive neurons in the arcuate nucleus (Arc). HBO treatment increased GLUT4 amount and level of phosphorylated Akt (p-Akt) in muscles of T2DM mice whereas this treatment stimulated the phosphorylation of AMPK in muscles of both T2DM and HFD mice. The morphological staining of BAT and the increased expression of uncoupling of protein 1 (UCP1) demonstrated the promotion of metabolism after HBO treatment. These findings suggest that HBO ameliorates insulin sensitivity of T2DM mice by stimulating the Akt signaling pathway and by promoting GLUT4 expression in muscle, and by increasing UCP1 expression in BAT.

Could Hyperbaric Oxygen Be a Solution in the Treatment of Spinal Infections?

Background and Objective: Pyogenic spinal infections are rare and potentially devastating, requiring prompt recognition and management. Parallel to the ever-increasing number of invasive spinal procedures, its incidence is on a steady rise, particularly in an expanding elderly population. The aim of this study was to evaluate the efficacy of hyperbaric oxygen (HBO₂) therapy in the treatment of this heterogeneous group of disorders. Materials and Methods: Nineteen patients who were referred to our center for HBO₂ with a clinical diagnosis of spinal infections (vertebral osteomyelitis, pyogenic spondylitis, spondylodiscitis, surgical site infection following spine surgery, epidural abscess) were retrospectively reviewed. Results: Infection resolution was adequately achieved in 12 of 13 patients (92.3%) on magnetic resonance imaging at the end of HBO₂ treatment or during the first month of follow-up. The mean follow-up period was 11 months (range 1 month to 3 years). Conclusions: This study suggests that HBO₂ therapy is efficacious in patients with pyogenic spinal infections complicated by primary therapy failure or by medical comorbidities that may impede the eradication of microbial infection and delay wound healing. HBO₂ therapy may be useful for reducing long hospital stays, repeated surgeries, and morbidities.

Further application of hyperbaric oxygen in prostate cancer

Hyperbaric oxygen therapy (HBOT) has been used as an adjuvant treatment for multiple pathological states, which involves hypoxic conditions. Over the past 50 years, HBOT has been recommended and used in a wide variety of medical conditions, clinically in the treatment of ischemic or nonhealing wounds and radiation-injured tissue, and in the treatment of malignancy. The mechanism of this treatment is providing oxygen under pressure which is higher than the atmosphere thus increasing tissue oxygen concentration. When cells get enough oxygen in the microenvironment, they become active and replicate effectively. Prostate cancer is the second most common cancer and the fifth leading cause of cancer death among male around the world. It is estimated that more than 29,000 men died from metastatic prostate cancer in 2014. With the development of the prostate-specific antigen-based screening technology, prostate cancer incidence has increased markedly over time. According to the survey, the morbidity and mortality of prostate cancer have surpassed bladder cancer and renal carcinoma, becoming the most common cancer in urology in Chinese adults. Nowadays, the main solution to deal with prostate cancer is still the surgical ways, including laparoscopic radical prostatectomy and robot-assisted radical prostatectomy. Nevertheless, the complications of the surgical treatment have not been completely avoided. HBOT has gained great clinical recognition over the decade. It has been demonstrated that HBOT has considerable effects on carcinoma, especially on decreasing complications and improving mortality. So, it is important to combine the HBOT with patients who suffer from prostate cancer. This review illuminates the effect and underlying mechanism of the HBOT in prostate cancer for further clinical application.

Repeated exposure to hyperbaric hyperoxia affects mitochondrial functions of the lung fibroblasts

Hyperbaric oxygen (HBO) therapy, i.e. breathing pure oxygen under increased environmental pressures serves as a treatment for diverse medical conditions. However, elevated oxygen concentration can be detrimental to central nervous system or lungs. Our study aimed to evaluate the effects of repeated exposure to HBO on mitochondrial respiration assessed by high-resolution respirometry (HRR), cell viability estimated by PrestoBlue® reaction, morphology analyzed by routine phase contrast and fluorescent microscopy, and superoxide dismutase (SOD) and citrate synthase (CS) activities using human lung fibroblasts. The cells were exposed to HBO for 2 h per day for 5 consecutive days. One day after the last exposure, HBO cells displayed significantly smaller area and perimeter, compromised viability and elevated SOD activity. No changes were detected in CS activity or quality of mitochondrial network. HRR revealed impaired mitochondrial oxygen consumption manifested by increased leak respiration, decreased activity of complex II and compromised ATP-related oxygen consumption when fatty acids were oxidized. Our findings document that in conditions mimicking chronic intermittent exposure to HBO, lung fibroblasts suffer from compromised mitochondrial respiration linked to complex II and impaired cellular growth in spite of increased antioxidant defense. Underlying mechanism of this HBO-induced mitochondrial dysfunction should be further explored.

Hyperbaric Oxygen Increases Stem Cell Proliferation, Angiogenesis and Wound-Healing Ability of WJ-MSCs in Diabetic Mice

Hyperbaric oxygen therapy (HBOT) is effective for the medical treatment of diverse diseases, infections, and tissue injury. In fact, in recent years there is growing evidence on the beneficial effect of HBOT on non-healing ischemic wounds. However, there is still yet discussion on how this treatment could benefit from combination with regenerative medicine strategies. Here we analyzed the effects of HBOT on three specific aspects of tissue growth, maintenance, and regeneration: (i) modulation of adult rodent (Mus musculus) intestinal stem cell turnover rates; (ii) angiogenesis dynamics during the development of the chorio-allantoic membrane (CAM) in Gallus gallus embryos; (iii) and wound-healing in a spontaneous type II diabetic mouse model with a low capacity to regenerate skin. To analyze these aspects of tissue growth, maintenance, and regeneration, we used HBOT alone or in combination with cellular therapy. Specifically, Wharton Jelly Mesenchymal Stem cells (WJ-MSC) were embedded in a commercial collagen-scaffold. HBOT did not affect the metabolic rate of adult mice nor of chicken embryos. Notwithstanding, HBOT modified the proliferation rate of stem cells in the mice small intestinal crypts, increased angiogenesis in the CAM, and improved wound-healing and tissue repair in diabetic mice. Moreover, our study demonstrates that combining stem cell therapy and HBOT has a collaborative effect on wound-healing. In summary, our data underscore the importance of oxygen tension as a regulator of stem cell biology and support the potential use of oxygenation in clinical treatments.

Press-pulse: a novel therapeutic strategy for the metabolic management of cancer

BACKGROUND

A shift from respiration to fermentation is a common metabolic hallmark of cancer cells. As a result, glucose and glutamine become the prime fuels for driving the dysregulated growth of tumors. The simultaneous occurrence of "Press-Pulse" disturbances was considered the mechanism responsible for reduction of organic populations during prior evolutionary epochs. Press disturbances produce chronic stress, while pulse disturbances produce acute stress on populations. It was only when both disturbances coincide that population reduction occurred.

METHODS

This general concept can be applied to the management of cancer by creating chronic metabolic stresses on tumor cell energy metabolism (press disturbance) that are coupled to a series of acute metabolic stressors that restrict glucose and glutamine availability while also stimulating cancer-specific oxidative stress (pulse disturbances). The elevation of non-fermentable ketone bodies protect normal cells from energy stress while further enhancing energy stress in tumor cells that lack the metabolic flexibility to use ketones as an efficient energy source. Mitochondrial abnormalities and genetic mutations make tumor cells vulnerable metabolic stress.

RESULTS

The press-pulse therapeutic strategy for cancer management is illustrated with calorie restricted ketogenic diets (KD-R) used together with drugs and procedures that create both chronic and intermittent acute stress on tumor cell energy metabolism, while protecting and enhancing the energy metabolism of normal cells.

CONCLUSIONS

Optimization of dosing, timing, and scheduling of the press-pulse therapeutic strategy will facilitate the eradication of tumor cells with minimal patient toxicity. This therapeutic strategy can be used as a framework for the design of clinical trials for the non-toxic management of most cancers.