In vivo hyperoxia induces hypoxia-inducible factor-1α overexpression in LNCaP tumors without affecting the tumor growth rate

β-Caryophyllene Inhibits Endothelial Tube Formation by Modulating the Secretome of Hypoxic Lung Cancer Cells-Possible Role of VEGF Downregulation

β-Caryophyllene (BCP), a bicyclic sesquiterpene that is a component of the essential oils of various spice and food plants, has been described as a selective CB2 cannabinoid receptor agonist. In the present study, the effect of BCP on angiogenesis was investigated. It was found that conditioned media (CM) from BCP-treated hypoxic A549 lung cancer cells exhibited a concentration-dependent inhibitory effect on human umbilical vein endothelial cell (HUVEC) tube formation induced by CM from vehicle-treated hypoxic A549 cells. There was an associated concentration-dependent decrease in the proangiogenic factor vascular endothelial growth factor (VEGF) in the CM, with both BCP inhibitory effects (tube formation, VEGF secretion) being CB2 receptor-dependent. A reduction of the transcription factor hypoxia-inducible factor 1α (HIF-1α) was furthermore detected. The antiangiogenic and VEGF-lowering properties of BCP were confirmed when CM from another lung cancer cell line, H358, were tested. When directly exposed to HUVECs, BCP showed no significant effect on tube formation, but at 10 µM, impaired VEGF receptor 2 (VEGFR2) phosphorylation triggered by recombinant VEGF in a CB2 receptor-independent manner. In summary, BCP has a dual antiangiogenic effect on HUVECs, manifested in the inhibition of tube formation through modulation of the tumor cell secretome and additionally in the inhibition of VEGF-induced VEGFR2 activation. Because the CB2 agonist has no psychoactive properties, BCP should continue to be evaluated preclinically for further antitumor effects.

Ozone in the adjunct medical treatment. The round personality of a molecule with hormetic properties

Ozone, an allotrope of oxygen, is enjoying an increasing interest in the setting and management of the medical adjunct treatment, which is called, maybe too simplistically, "ozone therapy". Ozone is not a medicine, so the word therapy does not properly fit this gaseous molecule. Like many natural compounds, for example plant flavonoids, even ozone interacts with aryl hydrocarbon receptors (AhRs) and, at low doses, it works according to the paradoxical mechanism of hormesis, involving mitochondria (mitohormesis). Ozone, in the hormetic range, exerts cell protective functions via the Nrf2-mediated activation of the anti-oxidant system, then leading to anti-inflammatory effects, also via the triggering of low doses of 4-HNE. Moreover, its interaction with plasma and lipids forms reactive oxygen species (ROS) and lipoperoxides (LPOs), generally called ozonides, which are enabled to rule the major molecular actions of ozone in the cell. Ozone behaves as a bioregulator, by activating a wide population of reactive intermediates, which usually target mitochondria and their turnover/biogenesis, often leading to a pleiotropic spectrum of actions and behaving as a tuner of the fundamental mechanisms of survival in the cell. In this sense, ozone can be considered a novelty in the medical sciences and in the clinical approach to pharmacology and medical therapy, due to its ability to target complex regulatory systems and not simple receptors.

The Normobaric Oxygen Paradox-Hyperoxic Hypoxic Paradox: A Novel Expedient Strategy in Hematopoiesis Clinical Issues

Hypoxia, even at non-lethal levels, is one of the most stressful events for all aerobic organisms as it significantly affects a wide spectrum of physiological functions and energy production. Aerobic organisms activate countless molecular responses directed to respond at cellular, tissue, organ, and whole-body levels to cope with oxygen shortage allowing survival, including enhanced neo-angiogenesis and systemic oxygen delivery. The benefits of hypoxia may be evoked without its detrimental consequences by exploiting the so-called normobaric oxygen paradox. The intermittent shift between hyperoxic-normoxic exposure, in addition to being safe and feasible, has been shown to enhance erythropoietin production and raise hemoglobin levels with numerous different potential applications in many fields of therapy as a new strategy for surgical preconditioning aimed at frail patients and prevention of postoperative anemia. This narrative review summarizes the physiological processes behind the proposed normobaric oxygen paradox, focusing on the latest scientific evidence and the potential applications for this strategy. Future possibilities for hyperoxic-normoxic exposure therapy include implementation as a synergistic strategy to improve a patient's pre-surgical condition, a stimulating treatment in critically ill patients, preconditioning of athletes during physical preparation, and, in combination with surgery and conventional chemotherapy, to improve patients' outcomes and quality of life.

Epidermal Growth Factor Receptor Inhibition Is Protective in Hyperoxia-Induced Lung Injury

Aims

Studies have linked severe hyperoxia, or prolonged exposure to very high oxygen levels, with worse clinical outcomes. This study investigated the role of epidermal growth factor receptor (EGFR) in hyperoxia-induced lung injury at very high oxygen levels (>95%).

Results

Effects of severe hyperoxia (100% oxygen) were studied in mice with genetically inhibited EGFR and wild-type littermates. Despite the established role of EGFR in lung repair, EGFR inhibition led to improved survival and reduced acute lung injury, which prompted an investigation into this protective mechanism. Endothelial EGFR genetic knockout did not confer protection. EGFR inhibition led to decreased levels of cleaved caspase-3 and poly (ADP-ribosyl) polymerase (PARP) and decreased terminal dUTP nick end labeling- (TUNEL-) positive staining in alveolar epithelial cells and reduced ERK activation, which suggested reduced apoptosis in vivo. EGFR inhibition decreased hyperoxia (95%)-induced apoptosis and ERK in murine alveolar epithelial cells in vitro, and CRISPR-mediated EGFR deletion reduced hyperoxia-induced apoptosis and ERK in human alveolar epithelial cells in vitro. Innovation. This work defines a protective role of EGFR inhibition to decrease apoptosis in lung injury induced by 100% oxygen. This further characterizes the complex role of EGFR in acute lung injury and outlines a novel hyperoxia-induced cell death pathway that warrants further study.

Conclusion

In conditions of severe hyperoxia (>95% for >24 h), EGFR inhibition led to improved survival, decreased lung injury, and reduced cell death. These findings further elucidate the complex role of EGFR in acute lung injury.

Dose Response of Bumetanide on Aquaporins and Angiogenesis Biomarkers in Human Retinal Endothelial Cells Exposed to Intermittent Hypoxia

Aquaporins (AQPs) are important for regulating cellular water, solute transport, and balance. Recently, AQPs have also been recognized as playing a key role in cell migration and angiogenesis. In the retina, hypoxia induces vascular endothelial growth factor (VEGF), a potent angiogenic and vascular permeability factor, resulting in retinal edema, which is facilitated by AQPs. Bumetanide is a diuretic agent and AQP 1–4 blocker. We tested the hypothesis that bumetanide suppression of AQPs ameliorates intermittent hypoxia (IH)-induced angiogenesis and oxidative stress in human microvascular retinal endothelial cells (HMRECs). HMRECs were treated with a low-dose (0.05 µg/mL) or high-dose (0.2 µg/mL) of bumetanide and were exposed to normoxia (Nx), hyperoxia (50% O₂), or IH (50% O₂ with brief hypoxia 5% O₂) for 24, 48, and 72 h. Angiogenesis and oxidative stress biomarkers were determined in the culture media, and the cells were assessed for tube formation capacity and AQP-1 and -4 expression. Both doses of bumetanide significantly decreased oxidative stress and angiogenesis biomarkers. This response was reflected by reductions in tube formation capacity and AQP expression. These findings confirm the role of AQPs in retinal angiogenesis. Therapeutic targeting of AQPs with bumetanide may be advantageous for IH-induced aberrant retinal development.

Exploring Hyperoxia Effects in Cancer-From Perioperative Clinical Data to Potential Molecular Mechanisms

Increased inspiratory oxygen concentration is constantly used during the perioperative period of cancer patients to prevent the potential development of hypoxemia and to provide an adequate oxygen transport to the organs, tissues and cells. Although the primary tumours are surgically removed, the effects of perioperative hyperoxia exposure on distal micro-metastases and on circulating cancer cells can potentially play a role in cancer progression or recurrence. In clinical trials, hyperoxia seems to increase the rate of postoperative complications and, by delaying postoperative recovery, it can alter the return to intended oncological treatment. The effects of supplemental oxygen on the long-term mortality of surgical cancer patients offer, at this point, conflicting results. In experimental studies, hyperoxia effects on cancer biology were explored following multiple pathways. In cancer cell cultures and animal models, hyperoxia increases the production of reactive oxygen species (ROS) and increases the oxidative stress. These can be followed by the induction of the expression of Brain-derived neurotrophic factor (BDNF) and other molecules involved in angiogenesis and by the promotion of various degrees of epithelial mesenchymal transition (EMT).

To breathe or not to breathe: Understanding how oxygen sensing contributes to age-related phenotypes

Aging is characterized by a progressive loss of tissue integrity and functionality due to disrupted homeostasis. Molecular oxygen is pivotal to maintain tissue functions, and aerobic species have evolved a sophisticated sensing system to ensure proper oxygen supply and demand. It is not surprising that aberrations in oxygen and oxygen-associated pathways subvert health and promote different aspects of aging. In this review, we discuss emerging findings on how oxygen-sensing mechanisms regulate different cellular and molecular processes during normal physiology, and how dysregulation of oxygen availability lead to disease and aging. We describe various clinical manifestations associated with deregulation of oxygen balance, and how oxygen-modulating therapies and natural oxygen oscillations influence longevity. We conclude by discussing how a better understanding of oxygen-related mechanisms that orchestrate aging processes may lead to the development of new therapeutic strategies to extend healthy aging.

Sustained Hypoxia Suppresses Joint Destruction in a Rat Model of Rheumatoid Arthritis via Negative Feedback of Hypoxia Inducible Factor-1α

Hypoxia inducible factor (HIF)-1α has been implicated in the pathogenesis of rheumatoid arthritis (RA). HIF-1α, which is expressed in hypoxia, is reversely suppressed in sustained hypoxia. Here, we investigated the inhibitory effect of hypoxia on arthritis by controlling HIF-1α. Rheumatoid fibroblast-like synoviocyte MH7A cells were cultured in a hypoxic incubator for up to 72 h to evaluate the expression of HIF-1. Furthermore, collagen-induced arthritis (CIA) model rats were maintained under 12% hypoxia in a hypoxic chamber for 28 days to evaluate the effect on arthritis. In MH7A cells, HIF-1α protein level increased at 3 h, peaked at 6 h, and subsequently decreased in a time-dependent manner. The transcription of pro-inflammatory cytokines increased at 1 h; however, they decreased after 3 h (p < 0.05). Deferoxamine-mediated activation of HIF-1α abolished the inhibitory effect of sustained hypoxia on pro-inflammatory cytokines. In the rat CIA model, the onset of joint swelling was delayed and arthritis was suppressed in the hypoxia group compared with the normoxia group (p < 0.05). Histologically, joint destruction was suppressed primarily in the cartilage. Thus, sustained hypoxia may represent a new safe, and potent therapeutic approach for high-risk patients with RA by suppressing HIF-1α expression.

COVID-19-associated cardiovascular morbidity in older adults: a position paper from the Italian Society of Cardiovascular Researches

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects host cells following binding with the cell surface ACE2 receptors, thereby leading to coronavirus disease 2019 (COVID-19). SARS-CoV-2 causes viral pneumonia with additional extrapulmonary manifestations and major complications, including acute myocardial injury, arrhythmia, and shock mainly in elderly patients. Furthermore, patients with existing cardiovascular comorbidities, such as hypertension and coronary heart disease, have a worse clinical outcome following contraction of the viral illness. A striking feature of COVID-19 pandemics is the high incidence of fatalities in advanced aged patients: this might be due to the prevalence of frailty and cardiovascular disease increase with age due to endothelial dysfunction and loss of endogenous cardioprotective mechanisms. Although experimental evidence on this topic is still at its infancy, the aim of this position paper is to hypothesize and discuss more suggestive cellular and molecular mechanisms whereby SARS-CoV-2 may lead to detrimental consequences to the cardiovascular system. We will focus on aging, cytokine storm, NLRP3/inflammasome, hypoxemia, and air pollution, which is an emerging cardiovascular risk factor associated with rapid urbanization and globalization. We will finally discuss the impact of clinically available CV drugs on the clinical course of COVID-19 patients. Understanding the role played by SARS-CoV2 on the CV system is indeed mandatory to get further insights into COVID-19 pathogenesis and to design a therapeutic strategy of cardio-protection for frail patients.

Cryptochromes Suppress HIF1α in Muscles

Muscles preferentially utilize glycolytic or oxidative metabolism depending on the intensity of physical activity. Transcripts required for carbohydrate and lipid metabolism undergo circadian oscillations of expression in muscles, and both exercise capacity and the metabolic response to exercise are influenced by time of day. The circadian repressors CRY1 and CRY2 repress peroxisome proliferator-activated receptor delta (PPARδ), a major driver of oxidative metabolism and exercise endurance. CRY-deficient mice exhibit enhanced PPARδ activation and greater maximum speed when running on a treadmill but no increase in exercise endurance. Here we demonstrate that CRYs limit hypoxia-responsive transcription via repression of HIF1α-BMAL1 heterodimers. Furthermore, CRY2 appeared to be more effective than CRY1 in the reduction of HIF1α protein steady-state levels in primary myotubes and quadriceps in vivo. Finally, CRY-deficient myotubes exhibit metabolic alterations consistent with cryptochrome-dependent suppression of HIF1α, which likely contributes to circadian modulation of muscle metabolism.

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CRY2 plays a unique role in regulating HIF1α protein accumulation in muscle

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HIF1α and BMAL1 heterodimers are transcriptionally active

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CRY1/2 represses transcription driven by HIF1α/BMAL1 heterodimers

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Cryptochromes influence skeletal muscle substrate preference and utilization

Erythropoietin as a Neuroprotective Molecule: An Overview of Its Therapeutic Potential in Neurodegenerative Diseases

Erythropoietin (EPO) is a cytokine mainly induced in hypoxia conditions. Its major production site is the kidney. EPO primarily acts on the erythroid progenitor cells in the bone marrow. More and more studies are highlighting its secondary functions, with a crucial focus on its role in the central nervous system. Here, EPO may interact with up to four distinct isoforms of its receptor (erythropoietin receptor [EPOR]), activating different signaling cascades with roles in neuroprotection and neurogenesis. Indeed, the EPO/EPOR axis has been widely studied in the neurodegenerative diseases field. Its potential therapeutic effects have been evaluated in multiple disorders, such as Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, spinal cord injury, as well as brain ischemia, hypoxia, and hyperoxia. EPO is showing great promise by counteracting secondary neuroinflammatory processes, reactive oxygen species imbalance, and cell death in these diseases. Multiple studies have been performed both in vitro and in vivo, characterizing the mechanisms through which EPO exerts its neurotrophic action. In some cases, clinical trials involving EPO have been performed, highlighting its therapeutic potential. Together, all these works indicate the potential beneficial effects of EPO.

Role of hyperoxic treatment in cancer

IMPACT STATEMENT

Tumor hypoxia promotes cancer cell aggressiveness, and is strongly associated with poor prognosis across multiple tumor types. The hypoxic microenvironments inside tumors also limit the effectiveness of radiotherapy, chemotherapy, and immunotherapy. Several approaches to eliminate hypoxic state in tumors have been proposed to delay cancer progression and improve therapeutic efficacies. This review will summarize current knowledge on hyperoxia, used alone or in combination with other therapeutic modalities, in cancer treatment. Molecular mechanisms and undesired side effects of hyperoxia will also be discussed.

Long-Term Deleterious Effects of Short-term Hyperoxia on Cancer Progression-Is Brain-Derived Neurotrophic Factor an Important Mediator? An Experimental Study

Perioperative factors promoting cancer recurrence and metastasis are under scrutiny. While oxygen toxicity is documented in several acute circumstances, its implication in tumor evolution is poorly understood. We investigated hyperoxia long-term effects on cancer progression and some underlying mechanisms using both in vitro and in vivo models of triple negative breast cancer (TNBC). We hypothesized that high oxygen exposure, even of short duration, may have long-term effects on cancer growth. Considering that hyperoxic exposure results in reactive oxygen species (ROS) formation, increased oxidative stress and increased Brain-Derived Neurotrophic Factor (BDNF) expression, BDNF may mediate hyperoxia effects offering cancer cells a survival advantage by increased angiogenesis and epithelial mesenchymal transition (EMT). Human breast epithelial MCF10A, human MDA-MB-231 and murine 4T1 TNBC were investigated in 2D in vitro system. Cells were exposed to normoxia or hyperoxia (40%, 60%, 80% O₂) for 6 h. We evaluated ROS levels, cell viability and the expression of BDNF, HIF-1α, VEGF-R2, Vimentin and E-Cadherin by immunofluorescence. The in vivo model consisted of 4T1 inoculation in Balb/c mice and tumor resection 2 weeks after and 6 h exposure to normoxia or hyperoxia (40%, 80% O₂). We measured lung metastases and the same molecular markers, immediately and 4 weeks after surgery. The in vitro study showed that short-term hyperoxia exposure (80% O₂) of TNBC cells increases ROS, increases BDNF expression and that promotes EMT and angiogenesis. The in vivo data indicates that perioperative hyperoxia enhances metastatic disease and this effect could be BDNF mediated.

Role of Hypoxia and Metabolism in the Development of Neointimal Hyperplasia in Arteriovenous Fistulas

For patients with end-stage renal disease requiring hemodialysis, their vascular access is both their lifeline and their Achilles heel. Despite being recommended as primary vascular access, the arteriovenous fistula (AVF) shows sub-optimal results, with about 50% of patients needing a revision during the year following creation. After the AVF is created, the venous wall must adapt to new environment. While hemodynamic changes are responsible for the adaptation of the extracellular matrix and activation of the endothelium, surgical dissection and mobilization of the vein disrupt the vasa vasorum, causing wall ischemia and oxidative stress. As a consequence, migration and proliferation of vascular cells participate in venous wall thickening by a mechanism of neointimal hyperplasia (NH). When aggressive, NH causes stenosis and AVF dysfunction. In this review we show how hypoxia, metabolism, and flow parameters are intricate mechanisms responsible for the development of NH and stenosis during AVF maturation.

Optimizing Temperature and Oxygen Supports Long-term Culture of Human Islets

Islet transplantation is a promising treatment for type-1 diabetes; however, donor shortage is a concern. Even when a pancreas is available, low islet yield limits the success of transplantation. Islet culture enables pooling of multiple low-yield isolations into an effective islet mass, but isolated islets rapidly deteriorate under conventional culture conditions. Oxygen (O2) depletion in the islet core, which leads to central necrosis and volume loss, is one of the major reasons for this deterioration.

METHODS

To promote long-term culture of human islets in PIM-R medium (used for islet research), we adjusted temperature (12°C, 22°C, and 37°C) and O2 concentration (21% and 50%). We simulated the O2 distribution in islets based on islet O2 consumption rate and dissolved O2 in the medium. We determined the optimal conditions for O2 distribution and volume maintenance in a 2-week culture and assessed viability and insulin secretion compared to noncultured islets. In vivo islet engraftment was assessed by transplantation into diabetic nonobese diabetic-severe combined immunodeficiency mouse kidneys. We validated our results using CMRL 1066 medium (used for clinical islet transplantation).

RESULTS

Simulation revealed that 12°C of 50% O2 PIM-R culture supplied O2 effectively into the islet core. This condition maintained islet volume at greater than 90% for 2 weeks. There were no significant differences in viability and function in vitro or diabetic reversal rate in vivo between 2-week cultured and noncultured islets. Similar results were obtained using CMRL 1066.

CONCLUSIONS

By optimizing temperature and O2 concentration, we cultured human islets for 2 weeks with minimal loss of volume and function.

Caffeine is associated with improved alveolarization and angiogenesis in male mice following hyperoxia induced lung injury

Background

Caffeine therapy for apnea of prematurity reduces the incidence of bronchopulmonary dysplasia (BPD) in premature neonates. Several mechanisms, including improvement in pulmonary mechanics underly beneficial effects of caffeine in BPD. As vascular development promotes alveologenesis, we hypothesized that caffeine might enhance angiogenesis in the lung, promoting lung growth, thereby attenuating BPD.

Methods

C57Bl/6 mice litters were randomized within 12 h of birth to room air (RA) or 95%O₂ to receive caffeine (20 mg/kg/day) or placebo for 4 days and recovered in RA for 12wks. The lung mRNA and protein expression for hypoxia-inducible factors (HIF) and angiogenic genes performed on day 5. Lung morphometry and vascular remodeling assessed on inflation fixed lungs at 12wks.

Results

Caffeine and hyperoxia in itself upregulate HIF-2α and vascular endothelial growth factor gene expression. Protein expression of HIF-2α and VEGFR1 were higher in hyperoxia/caffeine and angiopoietin-1 lower in hyperoxia. An increase in radial alveolar count, secondary septal count, and septal length with a decrease in mean linear intercept indicate an amelioration of hyperoxic lung injury by caffeine. An increase in vessel surface area and a significant reduction in smooth muscle thickness of the pulmonary arterioles may suggest a beneficial effect of caffeine on vascular remodeling in hyperoxia, especially in male mice.

Conclusions

Postnatal caffeine by modulating angiogenic gene expression early in lung development may restore the pulmonary microvasculature and alveolarization in adult lung.

Hyperbaric oxygen increases glioma cell sensitivity to antitumor treatment with a novel isothiourea derivative in vitro

Glioblastoma (GBM) is the most common primary brain tumor. Tumor hypoxia is a pivotal factor responsible for the progression of this malignant glioma, and its resistance to radiation and chemotherapy. Thus, improved tumor tissue oxygenation may promote greater sensitivity to anticancer treatment. Protein kinase D1 (PKD1) protects cells from oxidative stress, and its abnormal activity serves an important role in multiple malignancies. The present study examined the effects of various oxygen conditions on the cytotoxic potential of the novel isothiourea derivate N,N′-dimethyl-S-(2,3,4,5,6-pentabromobenzyl)- isothiouronium bromide (ZKK-3) against the T98G GBM cell line. ZKK-3 was applied at concentrations of 10, 25 and 50 µM, and cells were maintained under conditions of normoxia, anoxia, hypoxia, hyperbaric oxygen (HBO), hypoxia/hypoxia and hypoxia/HBO. The proliferation and viability of neoplastic cells, and protein expression levels of hypoxia-inducible factor 1α (HIF-1α), PKD1, phosphorylated (p)PKD1 (Ser 916) and pPKD1 (Ser 744/748) kinases were evaluated. Oxygen deficiency, particularly regarding hypoxia, could diminish the cytotoxic effect of ZKK-3 at 25 and 50 µM and improve T98G cell survival compared with normoxia. HBO significantly reduced cell proliferation and increased T98G cell sensitivity to ZKK-3 when compared with normoxia. HIF-1α expression levels were increased under hypoxia compared with normoxia and decreased under HBO compared with hypoxia/hypoxia at 0, 10 and 50 µM ZKK-3, suggesting that HBO improved oxygenation of the cells. ZKK-3 exhibited inhibitory activity against pPKD1 (Ser 916) kinase; however, the examined oxygen conditions did not appear to significantly influence the expression of this phosphorylated form in cells treated with the tested compound. Regarding pPKD1 (Ser 744/748), a significant difference in expression was observed only for cells treated with 10 µM ZKK-3 and hypoxia/hypoxia compared with normoxia. However, there were significant differences in the expression levels of both phosphorylated forms of PKD1 under different oxygen conditions in the controls. In conclusion, the combination of isothiourea derivatives and hyperbaric oxygenation appears to be a promising therapeutic approach for malignant glioma treatment.

Hypoxia and hyperbaric oxygen therapy: a review

Hypoxia causes a cascade of activity from the level of the individual down to the regulation and function of the cell nucleus. Prolonged periods of low oxygen tension are a core feature of several disease states. Advances in the study of molecular biology have begun to bridge the gap between the cellular response to hypoxia and physiology. Hyperbaric oxygen therapy is a treatment for hypoxic- and inflammatory-driven conditions, in which patients are treated with 100% oxygen at pressures greater than atmospheric pressure. This review discusses hypoxia, the physiologic changes associated with hypoxia, the responses that occur in the cells during hypoxic conditions, and the role that hyperbaric oxygen therapy can play as part of the treatment for many patients suffering from diseases with underlying hypoxia.

The Impact of Moderate Chronic Hypoxia and Hyperoxia on the Level of Apoptotic and Autophagic Proteins in Myocardial Tissue

The redox imbalance and the consequent oxidative stress have been implicated in many pathological conditions, including cardiovascular diseases. The lack or the excess of O₂ supply can alter the redox balance. The aim of the present study was to understand the heart responses to prolonged hypoxia or hyperoxia and how such situations may activate survival mechanisms or trigger cell death. Seven-week-old Foxn1 mice were exposed to hypoxia (10% O₂), normoxia (21% O₂), or hyperoxia (30% O₂) for 28 days, then the heart tissue was excised and analyzed. The alterations in redox balance, housekeeping protein levels, and autophagic and apoptotic process regulation were studied. The D-ROM test demonstrated an increased oxidative stress in the hypoxic group compared to the hyperoxic group. The level of hypoxia inducible factor-1 (HIF-1α) was increased by hypoxia while HIF-2α was not affected by treatments. Chronic hypoxia activated the biochemical markers of autophagy, and we observed elevated levels of Beclin-1 while LC3B-II and p62 were constant. Nevertheless, we measured significantly enhanced number of TUNEL-positive cells and higher Bax/Bcl2 ratio in hyperoxia with respect to hypoxia. Surprisingly, our results revealed alterations in the level of housekeeping proteins. The expression of α-tubulin, total-actin, and GAPDH was increased in the hypoxic group while decreased in the hyperoxic group. These findings suggest that autophagy is induced in the heart under hypoxia, which may serve as a protective mechanism in response to enhanced oxidative stress. While prolonged hypoxia-induced autophagy leads to reduced heart apoptosis, low autophagic level in hyperoxia failed to prevent the excessive DNA fragmentation.

Transdermal administration of melatonin coupled to cryopass laser treatment as noninvasive therapy for prostate cancer

Melatonin, a pineal gland hormone, exerts oncostatic activity in several types of human cancer, including prostate, the most common neoplasia and the third most frequent cause of male cancer death in the developed world. The growth of androgen-sensitive LNCaP prostate cancer cells in mice is inhibited by 3 mg/kg/week melatonin (0.09 mg/mouse/week) delivered by i.p. injections, which is equivalent to a dose of 210 mg/week in humans. The aim of this study is to test an alternative noninvasive delivery route based on transdermal administration of melatonin onto the tumor area followed by cryopass-laser treatment. Two groups of immunodepressed mice were studied, one (n = 10) subjected to 18 cryopass-laser therapy sessions and one (n = 10) subjected to the same treatment without melatonin. These groups were compared with mice treated with i.p.-administered melatonin or vehicle with the same time schedule. We found that cryopass-laser treatment is as efficient as i.p. injections in reducing the growth of LNCaP tumor cells, affecting plasma melatonin and redox balance. Furthermore, both delivery routes share the same effects on the involved biochemical pathway driven by hypoxia-inducible factor 1α. However, cryopass-laser, as used in the present experimental setup, is less efficient than i.p delivery route in increasing the melatonin content and Nrf2 expression in the tumor mass. We conclude that cryopass-laser treatment may have impact for melatonin-based therapy of prostate cancer, by delivering drugs transdermally without causing pain and targeting directly on the site of interest, thereby potentially making long-term treatments more sustainable.

Oxygen Supplementation Ameliorates Tibial Development via Stimulating Vascularization in Tibetan Chickens at High Altitudes

Tibetan chickens (TBCs) living in high-altitude hypoxic environment, are characterized by delayed growth and small size as compared to low-altitude broiler chickens. Increasing evidences signify the beneficial effect of oxygen (O₂) supplementation in animal's body for regulating their body growth and organ development. However, it is still unclear that whether O₂ supplementation has an ameliorative and protective role in TBCs living at high altitude. In this study, we first found that O₂ supplementation not only increased the survival rate but also promoted the growth of TBCs associated with bone development. Importantly, we observed that the increase of vascular distribution in the tibial hypertrophic zone could contribute to promote growth and development of the tibia, which is highly correlated with the up-regulated expression level of vascular endothelial growth factor (VEGF)-A and VEGF receptor-1 (VEGFR1). Additionally, hypoxia inducible factor (HIF)-1ɑ also has a stimulative elevation by O₂ supplementation. These results were confirmed by histology, immunohistochemistry, qRT-PCR and Western blotting techniques. Altogether, these findings demonstrated that the up-regulation of VEGFA and its receptors are accompanied by proangiogeneic factor (HIF-1α) expression, which were required for angiogenesis to meliorate tibia development of TBCs in hypoxia-induced bone suppression that occurred during O₂ supplementation. Thus, O₂ supplementation may serve as a good applicant for promoting and meliorating bone development in juvenile high-altitude animals.

Comparative Response of Brain to Chronic Hypoxia and Hyperoxia

Two antithetic terms, hypoxia and hyperoxia, i.e., insufficient and excess oxygen availability with respect to needs, are thought to trigger opposite responses in cells and tissues. This review aims at summarizing the molecular and cellular mechanisms underlying hypoxia and hyperoxia in brain and cerebral tissue, a context that may prove to be useful for characterizing not only several clinically relevant aspects, but also aspects related to the evolution of oxygen transport and use by the tissues. While the response to acute hypoxia/hyperoxia presumably recruits only a minor portion of the potentially involved cell machinery, focusing into chronic conditions, instead, enables to take into consideration a wider range of potential responses to oxygen-linked stress, spanning from metabolic to genic. We will examine how various brain subsystems, including energetic metabolism, oxygen sensing, recruitment of pro-survival pathways as protein kinase B (Akt), mitogen-activated protein kinases (MAPK), neurotrophins (BDNF), erythropoietin (Epo) and its receptors (EpoR), neuroglobin (Ngb), nitric oxide (NO), carbon monoxide (CO), deal with chronic hypoxia and hyperoxia to end-up with the final outcomes, oxidative stress and brain damage. A more complex than expected pattern results, which emphasizes the delicate balance between the severity of the stress imposed by hypoxia and hyperoxia and the recruitment of molecular and cellular defense patterns. While for certain functions the expectation that hypoxia and hyperoxia should cause opposite responses is actually met, for others it is not, and both emerge as dangerous treatments.

Sildenafil attenuates hypoxic pulmonary remodelling by inhibiting bone marrow progenitor cells

The recruitment of bone marrow (BM)-derived progenitor cells to the lung is related to pulmonary remodelling and the pathogenesis of pulmonary hypertension (PH). Although sildenafil is a known target in PH treatment, the underlying molecular mechanism is still elusive. To test the hypothesis that the therapeutic effect of sildenafil is linked to the reduced recruitment of BM-derived progenitor cells, we induced pulmonary remodelling in rats by two-week exposure to chronic hypoxia (CH, 10% oxygen), a trigger of BM-derived progenitor cells. Rats were treated with either placebo (saline) or sildenafil (1.4 mg/kg/day ip) during CH. Control rats were kept in room air (21% oxygen) with no treatment. As expected, sildenafil attenuated the CH-induced increase in right ventricular systolic pressure and right ventricular hypertrophy. However, sildenafil suppressed the CH-induced increase in c-kit⁺ cells in the adventitia of pulmonary arteries. Moreover, sildenafil reduced the number of c-kit⁺ cells that colocalize with tyrosine kinase receptor 2 (VEGF-R2) and CD68 (a marker for macrophages), indicating a positive effect on moderating hypoxia-induced smooth muscle cell proliferation and inflammation without affecting the pulmonary levels of hypoxia-inducible factor (HIF)-1α. Furthermore, sildenafil depressed the number of CXCR4⁺ cells. Collectively, these findings indicate that the improvement in pulmonary haemodynamic by sildenafil is linked to decreased recruitment of BM-derived c-kit⁺ cells in the pulmonary tissue. The attenuation of the recruitment of BM-derived c-kit⁺ cells by sildenafil may provide novel therapeutic insights into the control of pulmonary remodelling.

Brain adaptation to hypoxia and hyperoxia in mice

Aims

Hyperoxic breathing might lead to redox imbalance and signaling changes that affect cerebral function. Paradoxically, hypoxic breathing is also believed to cause oxidative stress. Our aim is to dissect the cerebral tissue responses to altered O₂ fractions in breathed air by assessing the redox imbalance and the recruitment of the hypoxia signaling pathways.

Results

Mice were exposed to mild hypoxia (10%O₂), normoxia (21%O₂) or mild hyperoxia (30%O₂) for 28 days, sacrificed and brain tissue excised and analyzed. Although one might expect linear responses to %O₂, only few of the examined variables exhibited this pattern, including neuroprotective phospho- protein kinase B and the erythropoietin receptor. The major reactive oxygen species (ROS) source in brain, NADPH oxidase subunit 4 increased in hypoxia but not in hyperoxia, whereas neither affected nuclear factor (erythroid-derived 2)-like 2, a transcription factor that regulates the expression of antioxidant proteins. As a result of the delicate equilibrium between ROS generation and antioxidant defense, neuron apoptosis and cerebral tissue hydroperoxides increased in both 10%O₂ and 30%O₂, as compared with 21%O₂. Remarkably, the expression level of hypoxia-inducible factor (HIF)−2α (but not HIF-1α) was higher in both 10%O₂ and 30%O₂ with respect to 21%O₂

Innovation

Comparing the in vivo effects driven by mild hypoxia with those driven by mild hyperoxia helps addressing whether clinically relevant situations of O₂ excess and scarcity are toxic for the organism.

Conclusion

Prolonged mild hyperoxia leads to persistent cerebral damage, comparable to that inferred by prolonged mild hypoxia. The underlying mechanism appears related to a model whereby the imbalance between ROS generation and anti-ROS defense is similar, but occurs at higher levels in hypoxia than in hyperoxia.

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Both oxygen scarcity and oxygen excess are harmful for the brain.

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Hypoxia increases ROS more than hyperoxia.

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Hypoxia increases the antioxidant defenses to an extent larger than hyperoxia.

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Both hypoxia and hyperoxia imbalance the ROS generation/ antiROS defense equilibrium.

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These findings have implications for those who need supplemental oxygen therapy.