Acute Hypoxic Stress Research Articles

Effects of acute hypoxic stress on biochemical parameters, immune regulation and metabolic capacity of the blood in genetically improved farmed tilapia (GIFT,Oreochromis niloticus)

Dissolved oxygen (DO) in the culture water is an important environmental factor in fish farming. This study tested whether genetically improved farmed tilapia (GIFT, Oreochromis niloticus) challenged with a hypoxic episode would show inhibited growth, increased metabolic stress and a reduced immune response. GIFT subjected to 72 hr of semi-lethal hypoxia (determined by linear regression as DO = 0.64 mg/L) showed changes in blood biochemistry, energy metabolism and related immune responses. In the early stages of stress, GIFT showed increased anaerobic respiration and increased lactic acid accumulation. Compared with a control group, white and red blood cell counts, hematocrit and blood hemoglobin concentration in GIFT exposed to 4 hr of semi-lethal hypoxic stress were not significantly changed. However, the levels of glutamic-pyruvic transaminase, glucose, cholesterol and cortisol were significantly higher under hypoxic stress at 2 and 4 hr. In the later stages of stress, GIFT displayed increased oxygen utilization and increased aerobic respiration associated with increased red blood cell count, hematocrit and hemoglobin concentration. However, the white blood cell count, serum lysozyme and complement C3 activities began to decline, associated with increased mortality. Reverting to a normal DO environment (5.0 mg/L) for an additional 72 hr, GIFT showed strong recovery, with respiratory metabolic enzymes, immune indicators and associated energy metabolites restored to near normal levels. Our observations contribute to a better understanding of the mechanisms of energy and immune regulation in fish, and will help reduce the damage caused by hypoxic stress during culture.

Translational and transcriptional responses in human primary hepatocytes under hypoxia.

The liver is the primary source of a large number of plasma proteins and plays a critical role in multiple biological processes. Inadequate oxygen supply characterizing various clinical settings such as liver transplantation exposes the liver to hypoxic conditions. Studies assessing hypoxia-induced global translational changes in liver are lacking. Here, we employed a recently developed ribosome-profiling technique to assess global translational responses of human primary hepatocytes exposed to acute hypoxic stress (1% O2) for the short term. In parallel, transcriptome profiling was performed to assess mRNA expression changes. We found that translational responses appeared earlier and were predominant over transcriptional responses. A significant decrease in translational efficiency of several ribosome genes indicated translational inhibition of new ribosome protein synthesis in hypoxia. Pathway enrichment analysis highlighted altered translational regulation of MAPK signaling, drug metabolism, oxidative phosphorylation, and nonalcoholic fatty liver disease pathways. Gene Ontology enrichment analysis revealed terms related to translation, metabolism, angiogenesis, apoptosis, and response to stress. Transcriptional induction of genes encoding heat shock proteins was observed within 30 min of hypoxia. Induction of genes encoding stress response mediators, metabolism regulators, and proangiogenic proteins was observed at 240 min. Despite the liver being the primary source of coagulation proteins and the implicated role of hypoxia in thrombosis, limited differences were observed in genes encoding coagulation-associated proteins. Overall, our study demonstrates the predominance of translational regulation over transcription and highlights differentially regulated pathways or biological processes in short-term hypoxic stress responses of human primary hepatocytes. NEW & NOTEWORTHY The novelty of this study lies in applying parallel ribosome- and transcriptome-profiling analyses to human primary hepatocytes in hypoxia. To our knowledge, this is the first study to assess global translational responses using ribosome profiling in hypoxic hepatocytes. Our results demonstrate the predominance of translational responses over transcriptional responses in early hepatic hypoxic stress responses. Furthermore, our study reveals multiple pathways and specific genes showing altered regulation in hypoxic hepatocytes.

Response of AMP-activated protein kinase and lactate metabolism of largemouth bass (Micropterus salmoides) under acute hypoxic stress

To study adaptation of largemouth bass (Micropterus salmoides) to hypoxic stress, we investigated physiological responses and lactate metabolism of the fish under acute hypoxia. The objectives of this study were to (a) observe changes in glucose, glycogen, and lactate content; (b) detect the activity of lactate dehydrogenase (LDH) in serum, brain, heart, and liver tissues; and (c) quantify the dynamic gene expression of AMP activated protein kinase alpha (AMPKα), hypoxia-inducible factor-1 alpha (HIF-1α), monocarboxylate transporter 1 (MCT1), monocarboxylate transporter 4 (MCT4), and lactate dehydrogenase-a (LDHa) following exposure to hypoxia. The fish were subjected to two hypoxia stresses (dissolved oxygen [DO] 1.20 ± 0.2 mg/L and 3.50 ± 0.3 mg/L, respectively) for 24 h. Our results showed that hypoxic stress significantly increased the decomposition of liver glycogen and significantly increased the concentration of blood glucose; however, the muscle glycogen content was not significantly decreased, which indicates that liver glycogen was the main energy source under acute hypoxia. Moreover, hypoxia led to accumulation of a large amount of lactic acid in tissues, possibly due to the activity of lactic acid dehydrogenase, but this process was delayed in the heart and brain relative to the liver. Additionally, hypoxia induced the expression of AMPKα, HIF-1α, MCT1, MCT4, and LDHa, suggesting that glycometabolism had switched from aerobic to anaerobic. Our results contribute to a better understanding of the molecular mechanisms of the response to hypoxia in largemouth bass.

Combined effects of warming and hypoxia on early life stage Chinook salmon physiology and development.

Early life stages of salmonids are particularly vulnerable to warming and hypoxia, which are common stressors in hyporheic, gravel bed, rearing habitat (i.e. a 'redd'). With the progression of global climate change, high temperatures and hypoxia may co-occur more frequently within redds, particularly for salmonid species at their southern range limit. Warming and hypoxia have competing effects on energy supply and demand, which can be detrimental to energy-limited early life stages. We examined how elevated temperature and hypoxia as individual and combined stressors affected the survival, physiological performance, growth, and development of Chinook salmon (Oncorhynchus tshawytscha). We reared late fall-run Chinook salmon from fertilization to the fry stage in a fully factorial design of two temperatures [10°C (ambient) and 14°C (warm)] and two oxygen levels [normoxia (100% air saturation, 10 mg O2/l) and hypoxia (50% saturation, 5.5 mg O2/l)]. Rearing in hypoxia significantly reduced hatching success, especially in combination with warming. Both warming and hypoxia improved acute thermal tolerance. While rearing in hypoxia improved tolerance to acute hypoxia stress, warming reduced hypoxia tolerance. Hypoxia-reared fish were smaller at hatch, but were able to reach similar sizes to the normoxia-reared fish by the fry stage. High temperature and normoxia resulted in the fastest rate of development while low temperature and hypoxia resulted in the slowest rate of development. Despite improved physiological tolerance to acute heat and hypoxia stress, hypoxia-reared embryos had reduced survival and growth, which could have larger population-level effects. These results suggest that both warming and hypoxia are important factors to address in conservation strategies for Chinook salmon.

Metabolic response of longitudinal muscles to acute hypoxia in sea cucumber Apostichopus japonicus (Selenka): A metabolome integrated analysis

Hypoxia is a severe problem in aquatic environments worldwide and has caused mass mortality of sea cucumbers (& other species) for decades, seriously affecting the sustainable development of aquaculture. Investigations of the metabolic disruptions and biochemical responses associated with acute hypoxia stress in sea cucumbers can provide a theoretical basis and guidance for improving aquaculture. A metabolomics approach to characterize changes in the profiles of endogenous small molecules in response to acute hypoxia can help to identify the main underlying causes of metabolic damage and potentially suggest solutions to alleviate to improve viability. The current study uses liquid chromatography-mass spectrometry (LC-MS) and multivariate analysis methods to evaluate the metabolic profile of longitudinal muscles from A. japonicus exposed to acute hypoxia stress (by bubbling the aquaria water with nitrogen aeration to decrease dissolved oxygen to 2 mg/L in 2 min) for 6 or 24 h (experimental groups EG6 or EG24) and control group (CG, n = 10, respectively). The results showed that 29 and 62 metabolites were influenced significantly in EG6 and EG24, respectively, mainly including lipids, glycosides and their derivatives. Levels of most lipids (fatty acids, glycerolipids, glycerophospholipids, sphingolipids and sterols) were elevated in both experimental groups, and increased with elongation of hypoxia, implying that the homeostasis of synthesis and degradation of lipids and their derivatives was strongly affected by hypoxia stress. Pathway enrichment analysis was performed to further assess the importance of differential metabolite expression to the development of the A. japonicus response to hypoxia, showing that 4 (fatty acid biosynthesis, d-glutamine and d-glutamate metabolism, glycolysis/gluconeogenesis, glyoxylate and dicarboxylate metabolism) and 2 (steroid biosynthesis, longevity regulating pathway) pathways were markedly enriched in EG6 and EG24, respectively. These results suggested that fatty acid synthesis was strengthened significantly in both treatment groups, and the degree was higher in EG24 than in EG6, providing valuable information towards understanding the special adaptive mechanism of A. japonicus to hypoxia stress.

A derivative of betulinic acid protects human Retinal Pigment Epithelial (RPE) cells from cobalt chloride-induced acute hypoxic stress

The Retinal Pigment Epithelium (RPE) is a monolayer of cells located above the choroid. It mediates human visual cycle and nourishes photoreceptors. Hypoxia-induced oxidative stress to RPE is a vital cause of retinal degeneration such as the Age-related Macular Degeneration. Most of these retinal diseases are irreversible with no efficient treatment, therefore protecting RPE cells from hypoxia stress is an important way to prevent or slow down the progression of retinal degeneration. Betulinic acid (BA) and betulin (BE) are pentacyclic triterpenoids with anti-oxidative property, but little is known about their effect on RPE cells. We investigated the protective effect of BA, BE and their derivatives against cobalt chloride-induced hypoxia stress in RPE cells. Human ARPE-19 cells were exposed to BA, BE and their eighteen derivatives (named as H3H20) that we customized through replacing moieties at C3 and C28 positions. We found that cobalt chloride reduced cell viability, increased Reactive Oxygen Species (ROS) production as well as induced apoptosis and necrosis in ARPE-19 cells. Interestingly, the pretreatment of 3-O-acetyl-glycyl- 28-O-glycyl-betulinic acid effectively protected cells from acute hypoxia stress induced by cobalt chloride. Our immunoblotting results suggested that this derivative attenuated the cobalt chloride-induced activation of Akt, Erk and JNK pathways. All findings were further validated in human primary RPE cells. In summary, this BA derivate has protective effect against the acute hypoxic stress in human RPE cells and may be developed into a candidate agent effective in the prevention of prevalent retinal diseases.

Short informative title: Quantitative assessment of acute impacts of suspended sediment on carp in the Yellow River

AbstractSediment concentration usually increases during the reservoir sediment flushing or natural floods, which may result in acute hypoxia stress and death of fishes in river reaches. Deceased fishes often appeared during periods of the reservoir sediment flushing in the Yellow River. To assess the quantitative impacts of high sediment concentration on carp, the suspended sediment concentration‐exposure duration model (SEV model) was applied and revised. With data from field surveys conducted during the sediment flushing of the Xiaolangdi Reservoir, the sediment flushing in 2009 was assessed as having no lethal effect. However, for the flushing in 2010, the fish mortality rate was assessed to be less than 20%. By analysing the data from experiments that exposed carps to different sediment concentrations, the SEV model tended to underestimate the acute impact of high sediment concentration (>30,000 mg/l). The SEV model was revised by refitting with experimental data. The comparison between the models showed that the severity effect values (SEVs) calculated by the revised model were closer to actual observations. The revised model was validated with data from previous field surveys. This research could provide a scientific basis for river sediment management and eco‐friendly reservoir sediment flushing operations.

Molecular Cloning and Expression of MnGST-1 and MnGST-2 from Oriental River Prawn, Macrobrachium nipponense, in Response to Hypoxia and Reoxygenation.

The glutathione-S-transferase (GST) superfamily includes seven classes, and different classes have different functions. GST superfamily members function in various processes including detoxification of xenobiotics, protection against oxidative damage, and intracellular transport of hormones, endogenous metabolites, and exogenous chemicals. Herein, to elucidate the tissue-specific expression pattern of GSTs in response to hypoxia stress, which induces cell death, we investigated the expression of GSTs in response to hypoxia and reoxygenation in oriental river prawn, Macrobrachium nipponense. Full-length cDNAs of two δ class GSTs were cloned from the hepatopancreas, and named MnGST-1 and MnGST-2 based on the established GST nomenclature system. Expression profiles of both GSTs in various tissues were different under acute and chronic experimental hypoxia stress conditions, suggesting that both respond strongly to hypoxia-induced oxidative stress. However, the intensity of responses to hypoxia and reoxygenation were different in different tissues. During acute hypoxia stress, MnGST-1 responds earlier than MnGST-2 in the hepatopancreas and gill, but more slowly in muscle. By contrast, during chronic hypoxia stress, MnGST-2 plays a more important role in the hepatopancreas and gill than MnGST-1.

Deduction of novel genes potentially involved in hypoxic AC16 human cardiomyocytes using next-generation sequencing and bioinformatics approaches.

Atherosclerotic cardiovascular disease and acute myocardial infarction are the leading causes of mortality worldwide, and apoptosis is the major pathway of cardiomyocyte death under hypoxic conditions. Although studies have reported changes in the expression of certain pro-apoptotic and anti-apoptotic genes in hypoxic cardiomyocytes, genetic regulations are complex in human cardiomyocytes and there is much that remains to be fully elucidated. The present study aimed to identify differentially expressed genes in hypoxic human AC16 cardiomyocytes using next-generation sequencing and bioinformatics. A total of 24 genes (15 upregulated and 9 downregulated) with potential micro (mi)RNA-mRNA interactions were identified in the miRmap database. Utilising the Gene Expression Omnibus database of cardiac microvascular endothelial cells, tensin 1, B-cell lymphoma 2-interacting protein 3 like, and stanniocalcin 1 were found to be upregulated, and transferrin receptor and methyltransferase like 7A were found to be downregulated in response to hypoxia. Considering the results from miRmap, TargetScan and miRDB together, two potential miRNA-mRNA interactions were identified: hsa-miRNA (miR)-129-5p/CDC42EP3 and hsa-miR-330-3p/HELZ. These findings contribute important insights into possible novel diagnostic or therapeutic strategies for targeting cardiomyocytes under acute hypoxic stress in conditions, including acute myocardial infarction. The results of the present study also introduce an important novel approach in investigating acute hypoxic pathophysiology.

Metabolic response of Nile tilapia (Oreochromis niloticus) to acute and chronic hypoxia stress

Hypoxia is a critical issue in aquaculture especially in intensive aquaculture systems. Acute hypoxia stress with dissolved oxygen (DO) 0.7 ± 0.1 mg/L for 6 h and chronic hypoxia stress with DO 1.1 ± 0.1 mg/L for 4 weeks were used to investigate the response of nutritional metabolic pathways in Nile tilapia Oreochromis niloticus. Fish in the acute and chronic experiments had different adaptive mechanisms. Upon acute hypoxia stress, the contents of liver glycogen and muscle glycogen were significantly lower, but there was no significant difference in triglycerides (TG). The lactate dehydrogenase (LDH) activities increased after exposure to acute hypoxia stress. The mRNA expression of genes involved in glycolysis and glycogenolysis was significantly up-regulated by acute hypoxia stress. However, the response of fish to long-term hypoxia stress was different from acute hypoxia. Compared with the normoxia treatment, the crude fat in fish decreased in the hypoxia group and TG in the liver and muscle were significantly lower. Beta oxidation of the liver was enhanced in the hypoxia group, while the hepatic glycogen content increased in the hypoxia group. Transcriptomic analysis showed that the expression of genes related to carbohydrate synthesis and lipolysis increased in the hypoxia group, while genes related to carbohydrate catabolism and fat synthesis showed the opposite. This study indicates that fish could utilize carbohydrate as a main energy source during acute hypoxia stress, and metabolize more lipid during long-term hypoxia stress. A high carbohydrate content in the diet may help reduce negative effects from acute hypoxia stress, and an appropriate increase of fat content in the diet may benefit fish growth in a hypoxia environment, e.g., in high-density aquaculture ponds.

No evidence for direct effects of recombinant human erythropoietin on cerebral blood flow and metabolism in healthy humans.

Erythropoietin (EPO) is expressed in human brain tissue, but its exact role is unknown. EPO may improve the efficiency of oxidative metabolism and has neuroprotective properties against hypoxic injuries in animal models. We aimed to investigate the effect of recombinant human EPO (rHuEPO) administration on healthy cerebral metabolism in humans during normoxia and during metabolic stress by inhalation of 10% O2 hypoxic air. Twenty-four healthy men participated in a two-arm double-blind placebo-controlled trial. rHuEPO was administered as a low dose (5,000 IU) over 4 wk ( n = 12) or as a high dose (500 IU·kg body wt-1·day-1) for three consecutive days ( n = 12). Global cerebral blood flow (CBF) and metabolic rate of glucose (CMRglc) were measured with positron emission tomography. CBF, metabolic rate of oxygen ([Formula: see text]), and cerebral lactate concentration were measured by magnetic resonance imaging and spectroscopy. Low-dose treatment increased hemoglobin and was associated with a near-significant decrease in CBF during baseline normoxia. High-dose treatment caused no change in CBF. Neither treatment had an effect on normoxia CMRglc, [Formula: see text], or lactate concentration or an effect on the cerebral metabolic response to inhalation of hypoxic air. In conclusion, the study found no evidence for a direct effect of rHuEPO on cerebral metabolism. NEW & NOTEWORTHY We demonstrate with magnetic resonance imaging and positron emission tomography that administration of erythropoietin does not have a substantial direct effect on healthy human resting cerebral blood flow or effect on cerebral glucose and oxygen metabolism. Also, administration of erythropoietin did not have a direct effect on the metabolic response to acute hypoxic stress in healthy humans, and a suggested neuroprotective effect from erythropoietin is therefore likely not a direct effect of erythropoietin on cerebral metabolism.

The Role of Interplay of Mesenchymal Stromal Cells and Macrophages in Physiological and Reparative Tissue Remodeling

Monocytes and their progeny, macrophages (MPhs), play the leading role in the innate immunity and populate different tissues maintaining homeostasis. In addition, these cells are involved in the response to injury when they accumulate in significant numbers at inflammatory sites. As well as macrophages, multipotent mesenchymal stromal cells (MSCs) are a critical component of both physiological and emerging regenerative microenvironment. Reciprocal effects of resident stromal and recruited blood-borne cells orchestrate cellular reactions in the tissues. Hypoxia, a significant reduction in the O2 concentration, is a characteristic feature of the compromised microenvironment. The present review analyzes the current concepts of the role of MSC interaction with MPhs in physiological and reparative tissue remodeling, modulation of MSC and MPh functions under acute hypoxic stress and discusses how oxygen deprivation can affect the outcome of MSC–MPh interplay.

Diaphragm Muscle Weakness Following Acute Sustained Hypoxic Stress in the Mouse Is Prevented by Pretreatment with N-Acetyl Cysteine.

Oxygen deficit (hypoxia) is a major feature of cardiorespiratory diseases characterized by diaphragm dysfunction, yet the putative role of hypoxic stress as a driver of diaphragm dysfunction is understudied. We explored the cellular and functional consequences of sustained hypoxic stress in a mouse model. Adult male mice were exposed to 8 hours of normoxia, or hypoxia (FiO2 = 0.10) with or without antioxidant pretreatment (N-acetyl cysteine, 200 mg/kg i.p.). Ventilation and metabolism were measured. Diaphragm muscle contractile function, myofibre size and distribution, gene expression, protein signalling cascades, and oxidative stress (TBARS) were determined. Hypoxia caused pronounced diaphragm muscle weakness, unrelated to increased respiratory muscle work. Hypoxia increased diaphragm HIF-1α protein content and activated MAPK, mTOR, Akt, and FoxO3a signalling pathways, largely favouring protein synthesis. Hypoxia increased diaphragm lipid peroxidation, indicative of oxidative stress. FoxO3 and MuRF-1 gene expression were increased. Diaphragm 20S proteasome activity and muscle fibre size and distribution were unaffected by acute hypoxia. Pretreatment with N-acetyl cysteine substantially enhanced cell survival signalling, prevented hypoxia-induced diaphragm oxidative stress, and prevented hypoxia-induced diaphragm dysfunction. Hypoxia is a potent driver of diaphragm weakness, causing myofibre dysfunction without attendant atrophy. N-acetyl cysteine protects the hypoxic diaphragm and may have application as a potential adjunctive therapy.

Exhaled isoprene for monitoring recovery from acute hypoxic stress

Hypoxia-like incidents in-flight have increased over the past decade causing severe safety concerns across the aviation community. As a result, the need to monitor flight crews in real-time for the onset of hypoxic conditions is paramount for continued aeronautical safety. Here, hypoxic events were simulated in the laboratory via a reduced oxygen-breathing device to determine the effect of recovery gas oxygen concentration (21% and 100%) on exhaled breath volatile organic compound composition. Data from samples collected both serially (throughout the exposure), prior to, and following exposures yielded 326 statistically significant features, 203 of which were unique. Of those, 72 features were tentatively identified while 51 were verified with authentic standards. A comparison of samples collected serially between recovery and hypoxia time points shows a statistically significant reduction in exhaled breath isoprene (2-methyl-1,3-butadiene, log2 FC −0.399, p = 0.005, FDR = 0.034, q = 0.033), however no significant difference in isoprene abundance was observed when comparing recovery gases (21% or 100% O2, p = 0.152). Furthermore, examination of pre-/post-exposure 1 l bag breath samples illustrate an overall increase in exhaled isoprene abundance post-exposure (log2 FC 0.393, p = 0.005, FDR = 0.094, q = 0.033) but again no significant difference between recovery gas (21% and 100%, p = 0.798) was observed. A statistically significant difference in trend was observed between isoprene abundance and recovery gases O2 concentration when plotted against minimum oxygen saturation (p = 0.0419 100% O2, p = 0.7034 21% O2). Collectively, these results suggest exhaled isoprene is dynamic in the laboratory ROBD setup and additional experimentation will be required to fully understand the dynamics of isoprene in response to acute hypoxic stress.

HIF and HOIL-1L–mediated PKCζ degradation stabilizes plasma membrane Na,K-ATPase to protect against hypoxia-induced lung injury

Organisms have evolved adaptive mechanisms in response to stress for cellular survival. During acute hypoxic stress, cells down-regulate energy-consuming enzymes such as Na,K-ATPase. Within minutes of alveolar epithelial cell (AEC) exposure to hypoxia, protein kinase C zeta (PKCζ) phosphorylates the α1-Na,K-ATPase subunit and triggers it for endocytosis, independently of the hypoxia-inducible factor (HIF). However, the Na,K-ATPase activity is essential for cell homeostasis. HIF induces the heme-oxidized IRP2 ubiquitin ligase 1L (HOIL-1L), which leads to PKCζ degradation. Here we report a mechanism of prosurvival adaptation of AECs to prolonged hypoxia where PKCζ degradation allows plasma membrane Na,K-ATPase stabilization at ∼50% of normoxic levels, preventing its excessive down-regulation and cell death. Mice lacking HOIL-1L in lung epithelial cells (CreSPC/HOIL-1Lfl/fl ) were sensitized to hypoxia because they express higher levels of PKCζ and, consequently, lower plasma membrane Na,K-ATPase levels, which increased cell death and worsened lung injury. In AECs, expression of an α1-Na,K-ATPase construct bearing an S18A (α1-S18A) mutation, which precludes PKCζ phosphorylation, stabilized the Na,K-ATPase at the plasma membrane and prevented hypoxia-induced cell death even in the absence of HOIL-1L. Adenoviral overexpression of the α1-S18A mutant Na,K-ATPase in vivo rescued the enhanced sensitivity of CreSPC/HOIL-1Lfl/fl mice to hypoxic lung injury. These data suggest that stabilization of Na,K-ATPase during severe hypoxia is a HIF-dependent process involving PKCζ degradation. Accordingly, we provide evidence of an important adaptive mechanism to severe hypoxia, whereby halting the exaggerated down-regulation of plasma membrane Na,K-ATPase prevents cell death and lung injury.

Acute hypoxia stress induced abundant differential expression genes and alternative splicing events in heart of tilapia

Hypoxia is one of the critical environmental stressors for fish in aquatic environments. Although accumulating evidences indicate that gene expression is regulated by hypoxia stress in fish, how genes undergoing differential gene expression and/or alternative splicing (AS) in response to hypoxia stress in heart are not well understood. Using RNA-seq, we surveyed and detected 289 differential expressed genes (DEG) and 103 genes that undergo differential usage of exons and splice junctions events (DUES) in heart of a hypoxia tolerant fish, Nile tilapia, Oreochromis niloticus following 12h hypoxic treatment. The spatio-temporal expression analysis validated the significant association of differential exon usages in two randomly selected DUES genes (fam162a and ndrg2) in 5 tissues (heart, liver, brain, gill and spleen) sampled at three time points (6h, 12h, and 24h) under acute hypoxia treatment. Functional analysis significantly associated the differential expressed genes with the categories related to energy conservation, protein synthesis and immune response. Different enrichment categories were found between the DEG and DUES dataset. The Isomerase activity, Oxidoreductase activity, Glycolysis and Oxidative stress process were significantly enriched for the DEG gene dataset, but the Structural constituent of ribosome and Structural molecule activity, Ribosomal protein and RNA binding protein were significantly enriched only for the DUES genes. Our comparative transcriptomic analysis reveals abundant stress responsive genes and their differential regulation function in the heart tissues of Nile tilapia under acute hypoxia stress. Our findings will facilitate future investigation on transcriptome complexity and AS regulation during hypoxia stress in fish.

IFN-gamma priming of adipose-derived stromal cells at "physiological" hypoxia.

Multipotent mesenchymal stromal cells (MSCs) are considered cue regulators of tissue remodeling. Their activity is strongly governed by local milieu, where O2 level is most important. The elevation of inflammatory mediators and acute O2 lowering may additionally modulate MSC activity. In present paper the priming effects of IFN-gamma on adipose tissue-derived MSCs (ASCs) at tissue-related O2 level (5%) and acute hypoxic stress (0.1% O2 ) were assessed as alterations of ASCs' CFU-F, proliferation, migration, osteo-commitment. IFN-gamma priming provoked ROS elevation, cell growth slowdown, attenuation of both spontaneous and induced osteodifferentiation of tissue O2 -adapted ASCs. The prominent changes in ASC cytoskeleton-related gene transcription was detected. IFN-gamma exposure shifted the ASC paracrine profile, suppressing the production of VEGF and IL-8, while MCP-1 and IL-6 were stimulated. Conditioned medium of IFN-gamma-primed ASCs did not activate vessel growth in the CAM assay, but induced endothelial cell migration in "wound closure." Short-term hypoxia suppressed CFU-F number, IFN-gamma-induced elevation of IL-6 and endothelial cell migration, while it abolished IFN-gamma-provoked VEGF inhibition. After N-acetyl cysteine treatment ROS level was partly abolished providing additional enhancement of IL-6 and suppression of IL-8 and VEGF production. These findings demonstrated that paracrine activity of ASCs in part may be governed by ROS level. Thus, this study first demonstrated that IFN-gamma priming itself and in combination with acute O2 deprivation could supply dual effects on ASC functions providing both stimulatory and hampering effects. The equilibrium of these factors is a substantial requirement for the execution of MSC remodeling functions.

P2080Cardiopulmonary, vascular and biomarker responses to acute hypoxic stress following cardiac transplantation

P2080Cardiopulmonary, vascular and biomarker responses to acute hypoxic stress following cardiac transplantation

Acute hypoxic stress: Effect on blood parameters, antioxidant enzymes, and expression of HIF-1alpha and GLUT-1 genes in largemouth bass (Micropterus salmoides)

Dissolved oxygen (DO) plays a crucial role in survival, growth, and normal physiological functions of aquatic organisms. Nevertheless, the mechanisms involved in hypoxic stress and adaptation have not been fully elucidated in Largemouth bass (Micropterus salmoides). To reveal the effect of acute hypoxia on Largemouth bass, we simulated acute hypoxia (DO: 1.2 ± 0.2 mg/L) in the laboratory and analyzed physiological parameters (RBCs, Hb, SOD, CAT, NA+/K+-ATPase, GPx, and MDA) and gene expression (HIF-1alpha and GLUT-1) in Largemouth bass exposed to various durations of acute hypoxia (0, 1, 2, 4, 8, 12, and 24 h). Our results indicated that acute hypoxic exposure significantly increased RBCs but decreased Hb. In addition, antioxidant enzyme activity was enhanced significantly in the liver and muscles at the initial stage of acute hypoxic exposure, but decreased significantly in gills during the entire process of hypoxic exposure. Furthermore, the expression levels of HIF-1alpha and GLUT-1 mRNA were significantly up-regulated in Largemouth bass under acute hypoxic exposure. In conclusion, our study provides a valuable basis for further elucidation of hypoxic adaptation and facilitates husbandry for an economically valuable species.

Loss of FKBP5 impedes adipocyte differentiation under both normoxia and hypoxic stress

FK506-binding protein 51 (FKBP51) is one of the most important regulators in the GR-mediated stress response, and we previously demonstrated that loss of FKBP5 arrests adipogenesis and renders mice resistant to diet-induced obesity (DIO). However, the exact role of FKBP5 in the process of adipocyte differentiation under hypoxic conditions (the common microenvironment where adipocytes reside in obese individuals) is still unclear. Here, by isolating and culturing WT- and Fkbp5-knockout mouse embryonic fibroblasts (MEFs), and treat them at normal oxygen environment (21% O2, nomorxia) or low oxygen environment (5% O2, hypoxia). Enhanced adipogenesis were observed at hypoxia when compared to normal oxygen environment. The loss of FKBP5 significantly prevents the adipogenesis from KO MEFs under nomorxia condition, with subtle enhancement of adipogenesis at hypoxia condition, which is similar as observed in WT-MEFs at hypoxia condition but with obvious enhancement of adipogenesis. Importantly, the protein level of FKBP5 reduced in undifferentiated MEFs under acute hypoxic stress (24 h), but drastically increased during the mid-late stage of adipocyte (Day 6) differentiation from WT-MEFs under chronic hypoxia. Furthermore, we find under normal and hypoxic conditions that FKBP5 deletion alters the expression profile of adipogenesis-related genes, including those involved in lipogenesis, lipolysis, and energy metabolism, which partially explains the compromised adipocyte differentiation in FKBP51-KO MEFs. Taken together, our findings identify a novel role of FKBP5 in hypoxia-regulated adipogenesis, and provide a candidate for anti-obesity strategies targeting FKBP51.