Maternal omega-3 PUFA supplementation prevents hyperoxia-induced pulmonary hypertension in the offspring.

Pulmonary hypertension (PH) and right ventricular hypertrophy (RVH) affect 16-25% of premature infants with bronchopulmonary dysplasia (BPD), contributing significantly to perinatal morbidity and mortality. Omega-3 polyunsaturated fatty acids (PUFA ω-3) can improve vascular remodeling, angiogenesis, and inflammation under pathophysiological conditions. However, the effects of PUFA ω-3 supplementation in BPD-associated PH are unknown. The present study aimed to evaluate the effects of PUFA ω-3 on pulmonary vascular remodeling, angiogenesis, and inflammatory response in a hyperoxia-induced rat model of PH. From embryonic day 15, pregnant Sprague-Dawley rats were supplemented daily with PUFA ω-3, PUFA ω-6, or normal saline (0.2 ml/day). After birth, pups were pooled, assigned as 12 per litter, randomly assigned to either air or continuous oxygen exposure (fraction of inspired oxygen = 85%) for 20 days, and then euthanized for pulmonary hemodynamic and morphometric analysis. We found that PUFA ω-3 supplementation improved survival, decreased right ventricular systolic pressure and RVH caused by hyperoxia, and significantly improved alveolarization, vascular remodeling, and vascular density. PUFA ω-3 supplementation produced a higher level of total ω-3 in lung tissue and breast milk and was found to reverse the reduced levels of VEGFA, VEGF receptor 2, angiopoietin-1 (ANGPT1), endothelial TEK tyrosine kinase, endothelial nitric oxide synthase, and nitric oxide concentrations in lung tissue and the increased ANGPT2 levels in hyperoxia-exposed rats. The beneficial effects of PUFA ω-3 in improving lung injuries were also associated with an inhibition of leukocyte infiltration and reduced expression of the proinflammatory cytokines IL-1ß, IL-6, and TNF-α. These data indicate that maternal PUFA ω-3 supplementation strategies could effectively protect against infant PH induced by hyperoxia.

Protective effects of fucoidan against hyperoxic lung injury via the ERK signaling pathway.

High oxygen mechanical ventilation is widely used to treat various lung diseases; however, it may result in hyperoxia, which induces inflammation and lung injury. Fucoidan is an extract of the seaweed Fucus vesiculosus, which has previously been reported to exert effects against diabetic nephropathy. The present study is the first, to the best of our knowledge, to investigate the protective effects of fucoidan against hyperoxic lung injury. Balb/c mice were ventilated with 100% oxygen, with or without the atomization inhalation of fucoidan, for 36 h. Hyperoxia reduced the body weight and increased the relative lung weight of the mice. In addition, cell quantity and differentiation were determined using a hemocytometer, hyperoxia increased the total number of cells, and the number of macrophages, neutrophils and lymphocytes in the bronchoalveolar lavage fluid. Reverse transcription­quantitative polymerase chain reaction (RT­qPCR) demonstrated that hyperoxia also increased the mRNA expression levels of cluster of differentiation (CD)68, F4/80, CD64 and CD19 in lung tissue, and induced lung morphological alterations. Furthermore, western blotting assay demonstrated that hyperoxia increased the expression levels of interleukin (IL)­1, IL­6 and tumor necrosis factor (TNF)­α, and the phosphorylation of extracellular signal­regulated kinase (ERK)1/2. Conversely, hyperoxia­induced inflammation and morphological alterations were significantly attenuated in the mice treated with fucoidan. Atomization inhalation of fucoidan also reduced the hyperoxia­induced expression of IL­1, IL­6 and TNF­α, and the phosphorylation of ERK1/2. These findings suggested that fucoidan may attenuate hyperoxic lung injury via the ERK1/2 signaling pathway.

Human umbilical cord-derived mesenchymal stem cells protect from hyperoxic lung injury by ameliorating aberrant elastin remodeling in the lung of O2-exposed newborn rat.

The incidence and mortality rates of bronchopulmonary dysplasia (BPD) remain very high. Therefore, novel therapies are imminently needed to improve the outcome of this disease. Human umbilical cord-derived mesenchymal stem cells (UC-MSCs) show promising therapeutic effects on oxygen-induced model of BPD. In our experiment, UC-MSCs were intratracheally delivered into the newborn rats exposed to hyperoxia, a well-established BPD model. This study demonstrated that UC-MSCs reduce elastin expression stimulated by 90% O2 in human lung fibroblasts-a (HLF-a), and inhibit HLF-a transdifferentiation into myofibroblasts. In addition, the therapeutic effects of UC-MSCs in neonatal rats with BPD, UC-MSCs could inhibit lung elastase activity and reduce aberrant elastin expression and deposition in the lung of BPD rats. Overall, this study suggested that UC-MSCs could ameliorate aberrant elastin expression in the lung of hyperoxia-induced BPD model which may be associated with suppressing increased TGFß1 activation.

DHA Suppresses Primary Macrophage Inflammatory Responses via Notch 1/ Jagged 1 Signaling.

Persistent macrophages were observed in the lungs of murine offspring exposed to maternal LPS and neonatal hyperoxia. Maternal docosahexaenoic acid (DHA) supplementation prevented the accumulation of macrophages and improved lung development. We hypothesized that these macrophages are responsible for pathologies observed in this model and the effects of DHA supplementation. Primary macrophages were isolated from adult mice fed standard chow, control diets, or DHA supplemented diets. Macrophages were exposed to hyperoxia (O2) for 24 h and LPS for 6 h or 24 h. Our data demonstrate significant attenuation of Notch 1 and Jagged 1 protein levels in response to DHA supplementation in vivo but similar results were not evident in macrophages isolated from mice fed standard chow and supplemented with DHA in vitro. Co-culture of activated macrophages with MLE12 epithelial cells resulted in the release of high mobility group box 1 and leukotriene B4 from the epithelial cells and this release was attenuated by DHA supplementation. Collectively, our data indicate that long term supplementation with DHA as observed in vivo, resulted in deceased Notch 1/Jagged 1 protein expression however, DHA supplementation in vitro was sufficient to suppress release LTB4 and to protect epithelial cells in co-culture.

Neurotoxic effects of oxygen in hyperbaric environment: A case report.

INTRODUCTION: Oxygen is an essential element of life in aerobic organisms. However, if not controlled, inhalation of oxygen under increased pressure in conditions of hyperbaric oxygen therapy can lead to serious damage and even death. CASE REPORT: We presented a 20-year-old male who had begun exhibiting symptoms of epilepsy during diving test in a hyperbaric chamber while inhaling 100% oxygen. He was immediately taken off oxygen mask and started breathing air and began rapid decompression. He lost consciousness, began foaming at the mouth, and had a series of tonic spasms. The patient was previously completely healthy and not on any medications. He was admitted for emergency treatment in our hospital, where he was treated for epilepsy. On admission, he complained of muscle and joint pain, and had erythematous changes on the forehead, neck and chest. All these changes occurred after leaving the hyperbaric chamber. Bloodwork revealed leukocytosis with neutrophil (Leukocytosis 16.0 x 10(9)/L (reference values 4.00-11.00 x 10(9)/L), Neutrophili 13 x 10(9)/L (reference values 1.9-8.0 x 10(9)/L), with elevated enzymes aspartate aminotransferase (AST) 56 U/L (reference values 0-37 U/L), alanin aminotransferase (ALT) 59 U/L, (reference values 25-65 U/L), creatine kinase (CK) 649 U/L, (reference values 32-300 U /L), lactate dehydrogenase (LDH) 398 U/L (reference values 85-227 U/L). Because of pain and his condition we began treatment in a hyperbaric chamber at a pressure of 2.0 ATA for 70 minutes, resulting in a reduction of symptoms and objective recovery of the patient. Within 24 h, repeated laboratory tests showed a reduction of leukocytosis (13 x 109/L and neutrophils (7.81 x 109/L), and the gradual reduction of the enzymes AST (47 U/L), ALT (50 U/L, CK (409 U/L), LDH (325 U/L). Since head CT and EEG were normal, epilepsy diagnosis was ruled out. This fact, along with medical tests, facilitated the differential diagnosis and confirmed that this was a case of neurotoxic effects of oxygen while the patient was in a hyperbaric chamber, not epileptic seizures. CONCLUSION: This case report suggests that in patients with symptoms of epileptic seizures while undergoing treatment in a hyperbaric chamber, it is always important to think of neurotoxic effects of pure oxygen which occurs at higher pressures and with a longer inhalation of 100% oxygen. In these patients, reexposure to hyperbaric conditions leads to recovery. This effect is important in daily inhalation of 100% oxygen under hyperbaric conditions which is why the use of pure oxygen is controlled and diving is allowed in shallow depths and for a limited time.

Hyperbaric oxygen preconditioning protects lung against hyperoxic acute lung injury in rats via heme oxygenase-1 induction.

Hyperoxic acute lung injury (HALI) is a clinical syndrome as a result of prolonged supplement of high concentrations of oxygen. Previous studies have shown hyperbaric oxygen preconditioning (HBO-PC) had a protective effect on oxidative injury. In the present study, we investigated the effect of HBO-PC on HALI in rats. The results demonstrated that HBO-PC ameliorated the lung biochemical and histological alterations induced by hyperoxia, decreased oxidative products but increased antioxidant enzymes. Furthermore, HBO-PC up-regulated heme oxygenase-1 (HO-1) mRNA and activity in lung tissues. The administration of HO-1 inhibitor, Zinc protoporphyrin IX, abolished its protective effects. The data showed that HBO-PC could protect rats against HALI and the anti-oxidative effect may be related to the up-regulation of HO-1.

Curcumin protects the developing lung against long-term hyperoxic injury.

Curcumin, a potent anti-inflammatory and antioxidant agent, modulates peroxisome proliferator-activated receptor-γ signaling, a key molecule in the etiology of bronchopulmonary dysplasia (BPD). We have previously shown curcumin's acute protection against neonatal hyperoxia-induced lung injury. However, its longer-term protection against BPD is not known. Hypothesizing that concurrent treatment with curcumin protects the developing lung against hyperoxia-induced lung injury long-term, we determined if curcumin protects against hyperoxic neonatal rat lung injury for the first 5 days of life, as determined at postnatal day (PND) 21. One-day-old rat pups were exposed to either 21 or 95% O2 for 5 days with or without curcumin treatment (5 mg/kg) administered intraperitoneally one time daily, following which the pups grew up to PND21 in room air. At PND21 lung development was determined, including gross and cellular structural and functional effects, and molecular mediators of inflammatory injury. To gain mechanistic insights, embryonic day 19 fetal rat lung fibroblasts were examined for markers of apoptosis and MAP kinase activation following in vitro exposure to hyperoxia for 24 h in the presence or absence of curcumin (5 µM). Curcumin effectively blocked hyperoxia-induced lung injury based on systematic analysis of markers for lung injury (apoptosis, Bcl-2/Bax, collagen III, fibronectin, vimentin, calponin, and elastin-related genes) and lung morphology (radial alveolar count and alveolar septal thickness). Mechanistically, curcumin prevented the hyperoxia-induced increases in cleaved caspase-3 and the phosphorylation of Erk1/2. Molecular effects of curcumin, both structural and cytoprotective, suggest that its actions against hyperoxia-induced lung injury are mediated via Erk1/2 activation and that it is a potential intervention against BPD.

Supplementary oxygen for nonhypoxemic patients: O2 much of a good thing?

Supplementary oxygen is routinely administered to patients, even those with adequate oxygen saturations, in the belief that it increases oxygen delivery. But oxygen delivery depends not just on arterial oxygen content but also on perfusion. It is not widely recognized that hyperoxia causes vasoconstriction, either directly or through hyperoxia-induced hypocapnia. If perfusion decreases more than arterial oxygen content increases during hyperoxia, then regional oxygen delivery decreases. This mechanism, and not (just) that attributed to reactive oxygen species, is likely to contribute to the worse outcomes in patients given high-concentration oxygen in the treatment of myocardial infarction, in postcardiac arrest, in stroke, in neonatal resuscitation and in the critically ill. The mechanism may also contribute to the increased risk of mortality in acute exacerbations of chronic obstructive pulmonary disease, in which worsening respiratory failure plays a predominant role. To avoid these effects, hyperoxia and hypocapnia should be avoided, with oxygen administered only to patients with evidence of hypoxemia and at a dose that relieves hypoxemia without causing hyperoxia.

Riboflavin supplementation does not attenuate hyperoxic lung injury in transgenic (spc-mt)hGR mice.

The aims of this study were to test the hypothesis that mice expressing mitochondrially targeted human glutathione reductase (GR) driven by a surfactant protein C promoter ((spc-mt)hGR) are functionally riboflavin deficient and that this deficiency exacerbates hyperoxic lung injury. The authors further hypothesized that dietary supplementation with riboflavin (FADH) will improve the bioactivity of GR, thus enhancing resistance to hyperoxic lung injury. Transgenic (mt-spc)hGR mice and their nontransgenic littermates were fed control or riboflavin-supplemented diets upon weaning. At 6 weeks of age the mice were exposed to either room air (RA) or >95% O(2) for up to 84 hours. GR activities (with and without exogenous FADH) and GR protein levels were measured in lung tissue homogenates. Glutathione (GSH) and glutathione disulfide (GSSG) concentrations were assayed to identify changes in GR activity in vivo. Lung injury was assessed by right lung to body weight ratios and bronchoalveolar lavage protein concentrations. The data showed that enhanced GR activity in the mitochondria of lung type II cells does not protect adult mice from hyperoxic lung injury. Furthermore, the addition of riboflavin to the diets of (spc-mt)hGR mice neither enhances GR activities nor offers protection from hyperoxic lung injury. The results indicated that modulation of mitochondrial GR activity in lung type II cells is not an effective therapy to minimize hyperoxic lung injury.

Respiratory plasticity after perinatal hyperoxia is not prevented by antioxidant supplementation.

Perinatal hyperoxia attenuates the hypoxic ventilatory response in rats by altering development of the carotid body and its chemoafferent neurons. In this study, we tested the hypothesis that hyperoxia elicits this plasticity through the increased production of reactive oxygen species (ROS). Rats were born and raised in 60% O(2) for the first two postnatal weeks while treated with one of two antioxidants: vitamin E (via milk from mothers whose diet was enriched with 1000 IU vitamin E kg(-1)) or a superoxide dismutase mimetic, manganese(III) tetrakis (1-methyl-4-pyridyl) porphyrin pentachloride (MnTMPyP; via daily intraperitoneal injection of 5-10 mg kg(-1)); rats were subsequently raised in room air until studied as adults. Peripheral chemoreflexes, assessed by carotid sinus nerve responses to cyanide, asphyxia, anoxia and isocapnic hypoxia (vitamin E experiments) or by hypoxic ventilatory responses (MnTMPyP experiments), were reduced after perinatal hyperoxia compared to those of normoxia-reared controls (all P<0.01); antioxidant treatment had no effect on these responses. Similarly, the carotid bodies of hyperoxia-reared rats were only one-third the volume of carotid bodies from normoxia-reared controls (P <0.001), regardless of antioxidant treatment. Protein carbonyl concentrations in the blood plasma, measured as an indicator of oxidative stress, were not increased in neonatal rats (2 and 8 days of age) exposed to 60% O(2) from birth. Collectively, these data do not support the hypothesis that perinatal hyperoxia impairs peripheral chemoreceptor development through ROS-mediated oxygen toxicity.

Protective effect of exogenous transferrin against hyperoxia: a study on premature rabbits.

We hypothesized that an increase in plasma iron binding capacity would decrease the generation of oxygen radicals and of lipid peroxides. To test this hypothesis, we studied whether supplementation of transferrin (TF) in premature rabbits would modify the degree of hyperoxic lung injury. Animals, delivered prematurely at 29 days of gestation (term 31 days), were randomized and given either 0.5 g/kg of albumin (Alb) (n = 116) or 0.5 g/kg of iron-free TF (n = 132) intravenously within 2 hours after birth. Another group was randomized to receive saline (n = 15), or either 0.35 g/kg (n = 12) or 0.70 g/kg of iron-free TF (n = 8). After exposure to a 100% oxygen environment for 2 or 4 days, the animals were killed, and plasma and bronchoalveolar lavage (BAL) fluid was recovered. Infusion of TF caused a dose-dependent increase in the concentration of TF and an increase in the unsaturated iron-binding capacity. Administration of TF at birth increased the gradient of TF between serum and alveolar epithelial lining fluid on day 4, suggesting decreased alveolar-capillary permeability. BAL fluid and plasma from TF-supplemented animals contained less lipid peroxidation products and more inhibitor of lipid peroxidation than BAL fluid or plasma from Alb-treated animals. In TF-treated animals, the recovery of protein in BAL fluid (TF group, 1.26 +/- 0.07 mg; Alb group, 1.78 +/- 0.10 mg; P = 0.02) and the water content of the extravascular lung tissue (TF group, 78.5 +/- 1.4%; Alb group, 83.2 +/- 1.3%; P = 0.05) were lower than in Alb-treated animals. We propose that supplementation of iron-free TF decreases iron-catalyzed redox reactions and may decrease hyperoxic lung injury in the premature.