The hypoxia signaling pathway and hypoxic adaptation in fishes

The hypoxia signaling pathway is an evolutionarily conserved cellular signaling pathway present in animals ranging from Caenorhabditis elegans to mammals.The pathway is crucial for oxygen homeostasis maintenance.Hypoxia-inducible factors(HIF-1αand HIF-2α)are master regulators in the hypoxia signaling pathway.Oxygen concentrations vary a lot in the aquatic environment.To deal with this,fishes have adapted and developed varying strategies for living in hypoxic conditions.Investigations into the strategies and mechanisms of hypoxia adaptation in fishes will allow us to understand fish speciation and breed hypoxia-tolerant fish species/strains.This review summarizes the process of the hypoxia signaling pathway and its regulation,as well as the mechanism of hypoxia adaptation in fishes.     

Vital roles of stem cells and biomaterials in skin tissue engineering

Tissue engineering essentially refers to technology for growing new human tissue and is distinct from regenerative medicine. Currently, pieces of skin are already being fabricated for clinical use and many other tissue types may be fabricated in the future.Tissue engineering was first defined in 1987 by the United States National Science Foundation which critically discussed the future targets of bioengineering research and its consequences. The principles of tissue engineering are to initiate cell cultures in vitro, grow them on scaffolds in situ and transplant the composite into a recipient in vivo. From the beginning, scaffolds have been necessary in tissue engineering applications. Regardless, the latest technology has redirected established approaches by omitting scaffolds. Currently, scientists from diverse research institutes are engineering skin without scaffolds. Due to their advantageous properties, stem cells have robustly transformed the tissue engineering field as part of an engineered bilayered skin substitute that will later be discussed in detail. Additionally, utilizing biomaterials or skin replacement products in skin tissue engineering as strategy to successfully direct cell proliferation and differentiation as well as to optimize the safety of handling during grafting is beneficial. This approach has also led to the cells’ application in developing the novel skin substitute that will be briefly explained in this review.     

Overexpression of CmSOS1 confers waterlogging tolerance in Chrysanthemum

正Plants experiencing hypoxia (a shortage of oxygen)are unable to maintain aerobic respiration, which leads to an energy and carbohydrate deficit. The pervasive and rapid accumulation of ethylene is an early and reliable response to hypoxic stress(Sasidharan and Voesenek 2015), producing an uptick in the accumulation of reactive oxygen species (ROS).This in turn triggers apoptosis in root cortex cells,eventually leading to the formation of lysigenous aerenchyma, a tissue from which ethylene is readily     

Phosphorylated KDR can be located in the nucleus of neoplastic cells

KDR （kinase insert domain receptor） phosphorylation induces several effects which lead eventually to cell proliferation and survival. The precise mechanisms by which KDR, once it is activated, communicates with the nucleus are starting to be understood but have not yet been completely unravelled. Two in vitro studies on animal cell lines reported in the literature have demonstrated that, following stimulation with VEGF, KDR is actually translocated within the nucleus. Our aim was to investigate whether this translocation occurs in human cells both in vitro and in vivo. Using laser scanning confocal microscopy, a variable nuclear localization of phosphorylated and total KDR in cell lines and tumour samples was found. In human neoplastic cell lines, hypoxic stimulation greatly increased the nuclear amount of total KDR but less so that of the phosphorylated form. Only after hypoxia and VEGF stimulation there was a comparably increased expression of phosphorylated and total KDR observed in the nuclei of these cells. We conclude that neoplastic cells show a variable expression of total and phosphorylated KDR in the nucleus. The precise functional meaning of nuclear location remains to be established.     

Heat shock response and mammal adaptation to high elevation (hypoxia)

The mammal's high elevation(hypoxia) adaptation was studied by using the immu-nological and the molecular biological methods to understand the significance of Hsp(hypoxia) ad-aptation in the organic high elevation,through the mammal heat shock response.(1) From high ele-vation to low elevation(natural hypoxia) :Western blot and conventional RT-PCR and real-time fluo-rescence quota PCR were adopted.Expression difference of heat shock protein of 70(Hsp70) and natural expression of brain tissue of Hsp70 gene was determined in the cardiac muscle tissue among the different elevation mammals(yak) .(2) From low elevation to high elevation(hypoxia induction) :The mammals(domestic rabbits) from the low elevation were sent directly to the areas with different high elevations like 2300,3300 and 5000 m above sea level to be raised for a period of 3 weeks be-fore being slaughtered and the genetic inductive expression of the brain tissue of Hsp70 was deter-mined with RT-PCR.The result indicated that all of the mammals at different elevations possessed their heat shock response gene.Hsp70 of the high elevation mammal rose abruptly under stress and might be induced to come into being by high elevation(hypoxia) .The speedy synthesis of Hsp70 in the process of heat shock response is suitable to maintain the cells' normal physiological functions under stress.The Hsp70 has its threshold value.The altitude of 5000 m above sea level is the best condition for the heat shock response,and it starts to reduce when the altitude is over 6000 m above sea level.The Hsp70 production quantity and the cell hypoxia bearing capacity have their direct ratio.     

Pharmacokinetics and toxicology of therapeutic proteins: Advances and challenges

Significant progress has been made in understanding pharmacokinetics (PK),pharmacodynamics (PD),as well as toxicity profiles of therapeutic proteins in animals and humans,which have been in commercial development for more than three decades.However,in the PK arena,many fundamental questions remain to be resolved.Investigative and bioanalytical tools need to be established to improve the translation of PK data from animals to humans,and from in vitro assays to in vivo readouts,which would ultimately lead to a higher success rate in drug development.In toxicology,it is known,in general,what studies are needed to safely develop therapeutic proteins,and what studies do not provide relevant information.One of the major complicating factors in nonclinical and clinical programs for therapeutic proteins is the impact of immunogenicity.In this review,we will highlight the emerging science and technology,as well as the challenges around the pharmacokinetic-and safety-related issues in drug development of mAbs and other therapeutic proteins.     

Ongoing Applicative Studies of Plant Thioredoxins

Studies triggered by the discovery of the function of thioredoxin （Trx） in photosynthesis have revealed its role throughout biology. Parallel biochemical and proteomic analyses have led to the identification of its numerous puta- tive targets. Recently, to verify the biological significance of these targets, in vivo studies using transformants in which Trx is overexpressed or suppressed are in progress, and the transformants themselves that are being used in such studies show their potential applicative values. Moreover, Trx＇s mitigation of allergenicity for some proteins offers promising prospects in the food industry. Practical studies based on redox regulation, once only on the horizon, are now achieving new dimensions. This short review focuses on the industrial applications of Trx studies, the current situation, and future perspectives. The putative targets obtained by the proteomics approach in comparison with in vivo observations of the transformants are also examined. Applicative studies of glutathione, a counterpart of Trx, are also discussed briefly.     

Methods for Analysis of Protein Glutathionylation and their Application to Photosynthetic Organisms

Protein S-glutathionylation, the reversible formation of a mixed-disulfide between glutathione and protein thiols, is involved in protection of protein cysteines from irreversible oxidation, but also in protein redox regulation. Recent studies have implicated S-glutathionylation as a cellular response to oxidative/nitrosative stress, likely playing an important role in signaling. Considering the potential importance of glutathionylation, a number of methods have been developed for identifying proteins undergoing glutathionylation. These methods, ranging from analysis of purified proteins in vitro to large-scale proteomic analyses in vivo, allowed identification of nearly 200 targets in mammals. By contrast, the number of known glutathionylated proteins is more limited in photosynthetic organisms, although they are severely exposed to oxidative stress. The aim of this review is to detail the methods available for identification and analysis of glutathionylated proteins in vivo and in vitro. The advantages and drawbacks of each technique will be discussed as well as their application to photosynthetic organisms. Furthermore, an overview of known glutathionylated proteins in photosynthetic organisms is provided and the physiological importance of this post-translational modification is discussed.     

Hypoxic preconditioning

A concept of tissue-cell adaptation to hypoxia (hypoxic preconditioning) is raised and its corresponding animal model is introduced. A significantly strengthened tolerance to hypoxia and a protective effect of the brain extracts from the preconditioned animals are presented. Changes in animals' behavior, neuromorphology, neurophysiology, neurochemistry and molecular neurobiology during preconditioning are described. Energy saving, hypometabolism, and cerebral protection in particular are thought to be involved in the development of hypoxic tolerance and tissue-cell protection. The essence and significance of the hypoxic tissue-cell adaptation or preconditioning are discussed in terms of biological evolution and practical implication.     

Hypoxic Preconditioning and Hypoxic-Ischemic Brain Damage in the Immature Rat: Pathologic and Metabolic Correlates

Abstract: It has been reported that immature rats subjected to cerebral hypoxia-ischemia sustain less brain damage if they are previously exposed to systemic hypoxia compared with animals not exposed to prior hypoxia. Accordingly, neuropathologic and metabolic experiments were conducted to confirm and extend the observation that hypoxic preconditioning protects the perinatal brain from subsequent hypoxic-ischemic brain damage. Six-day postnatal rats were subjected to systemic hypoxia with 8% oxygen at 37°C for 2.5 h. Twenty-four hours later, they were exposed to unilateral cerebral hypoxia-ischemia for 2.5 h, produced by unilateral common carotid artery ligation and systemic hypoxia with 8% oxygen. Neuropathologic analysis, conducted at 30 days of postnatal age, indicated a substantial reduction in the severity of brain damage in the preconditioned rats, such that only 6 of 14 such animals exhibited cystic infarction, but all 13 animals without prior preconditioning exhibited infarction ( p < 0.001). Measurement of cerebral glycolytic and tricarboxylic acid intermediates and high-energy phosphate reserves at the terminus of and at 4 and 24 h following hypoxia-ischemia showed no differences in the extent of alterations in the preconditioned and nonpreconditioned immature rats. A difference was seen in the restitution of high-energy stores during the first 24 h of recovery from hypoxia-ischemia, with a more optimal preservation of these metabolites in the preconditioned animals, reflecting the less severe ultimate brain damage. Accordingly, the neuroprotection afforded to the preconditioned animals was not the result of any differences in the extent of anaerobic glycolysis, tissue acidosis, or depletion in high-energy reserves during hypoxia-ischemia but rather the result of other mechanisms that improved the metabolic status of the immature brain during the early hours of reperfusion following hypoxia-ischemia.     

低氧预适应对小鼠海马组织HIF-1与EPO低氧应答元件结合活性的影响

目的：观察低氧预适应对小鼠海马组织HIF-1与EPO的低氧应答元件（HRE）结合活性的变化,探讨这种变化与低氧预适应形成的关系。方法：小鼠低氧0次（H0）,1次（H1）,4次（H4）后取海马组织,应用凝胶迁移改变试验（EMSA）,染色体免疫共沉淀（ChIP）试验和荧光定量PCR（real—time PCR）技术,检测小鼠海马组织内HIF-1与EPO的低氧应答元件结合能力的变化。结果：EMSA体外结合实验及ChIP体内结合实验发现。H0、H1和H4组结合活力依次增强。结论：HIF-1与EPO的低氧应答元件结合增强可能参与预适应的形成。     

The effect of preceding mild hypoxia on the alteration of acquisition and retention of the conditioned passive avoidance behavior caused by severe hypobaric hypoxia in rats

The purpose of this study was to determine whether mild hypobaric hypoxic preconditioning provides protection against learning deficit caused by subsequent more severe hypoxia insult. Learning was examined using a passive avoidance task. Three groups of Wistar male rats: the intact and exposed to either severe hypoxia (160 Torr, exposition 3 h) or mild hypobaric hypoxic preconditioning (360 Torr, exposition 2 h, repeated three or six times daily) followed by severe hypoxia, were included in this study. In experiment 1 a passive avoidance response was acquired in 15 min immediately after hypoxia. In experiment 2 rats were exposed to hypoxia in 60 min after the acquisition of passive avoidance response. The mild hypobaric hypoxic preconditioning significantly attenuated the hypoxia-induced learning deficit in rats in Experiments 1 and 2. In experiment 1 the mild hypobaric hypoxic preconditioning repeated six times was more effective in protection against learning deficit in hypoxia exposed rats than in the case of triple mild hypobaric hypoxic preconditioning. The amount of rats suffered irreversible respiratory arrest was also assessed in this study. It was found that 50% of rats exposed to severe hypoxia died in consequence of this pathology, whereas in rats preconditioned before the severe hypoxia only 15% died for this reason. The overall results indicate that the mild hypobaric hypoxic preconditioning significantly increases CNS resistance to severe hypoxia in rats.     

Increased expression of CXCR4 and integrin αM in hypoxia‐preconditioned cells contributes to improved cell retention and angiogenic potency

Cell‐based angiogenesis is a promising method for the treatment of ischemic diseases, but the poor retention of implanted cells in targeted tissues is a major drawback. We tested whether hypoxic preconditioning increased retention and angiogenic potency of implanted cells in ischemic tissue. Hypoxic preconditioning of mouse peripheral blood mononuclear cells (PBMNCs) was done with 24 h of culture under 2% O₂. Normoxia‐cultured PBMNCs were used as a control. Hypoxic preconditioning increased the adhesion capacity of the PBMNCs. Moreover, the expression of integrin αM and CXCR4 was significantly higher in the hypoxia‐preconditioned PBMNCs than in the normoxia‐cultured PBMNCs. Interestingly, the expression of intercellular adhesion molecule‐1 (ICAM‐1), a ligand of integrin αM, and stromal cell‐derived factor‐1 (SDF‐1), a chemokine for CXCR4, were remarkably increased in the ischemic hindlimbs. The retention of the hypoxia‐preconditioned PBMNCs was significantly higher than that of the normoxia‐cultured PBMNCs, 3 days after their intramuscular implantation into ischemic hindlimbs. We also noted better blood flow in the ischemic hindlimbs implanted with the hypoxia‐preconditioned PBMNCs than in those implanted with the normoxia‐cultured PBMNCs, 14 days after treatment. Furthermore, antibody neutralization of integrin αM and CXCR4 abolished completely the increased cell retention and angiogenic potency of the hypoxia‐preconditioned PBMNCs after implantation into the ischemic hindlimbs. These results indicate that hypoxic preconditioning of implanted cells is a feasible method of enhancing therapeutic angiogenesis by increasing their retention. J. Cell. Physiol. 220: 508–514, 2009. © 2009 Wiley‐Liss, Inc.     

Hypoxic preconditioning is a phenomenon increasing tolerance of cardiomyocytes to hypoxia-reoxygenation

The work covers the problem of hypoxic preconditioning (HP) carried out in isolated cardiomyocytes. Papers on delayed HP in vivo are comparatively few, and only some single works are devoted to early preconditioning in vivo. It has been established that the HP limits necrosis and apoptosis of cardiomyocytes and improves contractility of the isolated heart after ischemia (hypoxia) and reperfusion (reoxygenation). It was found that adenosine was a trigger of iP in vitro. It was proved that NO* was a trigger of HP both in vitro and in vivo. It was shown that reactive oxygen species also were triggers of hypoxic preconditioning. It was shown that ERK1/2 and p38 kinase played important role in delayed HP in vitro.     

Preconditioning improves function and recovery of single muscle fibers during severe hypoxia and reoxygenation

Reperfusion following prolonged ischemia induces cellular damage in whole skeletal muscle models. Ischemic preconditioning attenuates the deleterious effects. We tested whether individual skeletal muscle fibers would be similarly affected by severe hypoxia and reoxygenation (H/R) in the absence of extracellular factors and whether cellular damage could be alleviated by hypoxic preconditioning. Force and free cytosolic Ca2+ ([Ca2+]c) were monitored in Xenopus single muscle fibers (n = 24) contracting tetanically at 0.2 Hz during 5 min of severe hypoxia and 5 min of reoxygenation. Twelve cells were preconditioned by a shorter bout of H/R 1 h before the experimental trial. In preconditioned cells, force relative to initial maximal values (P/P(o)) and relative peak [Ca2+]c fell (P < 0.05) during 5 min of hypoxia and recovered during reoxygenation. In contrast, P/P(o) and relative peak [Ca2+]c fell more during hypoxia (P < 0.05) and recovered less during reoxygenation (P < 0.05) in control cells. The ratio of force to [Ca2+]c was significantly higher in the preconditioned cells during severe hypoxia, suggesting that changes in [Ca2+]c were not solely responsible for the loss in force. We conclude that 1) isolated skeletal muscle fibers contracting in the absence of extracellular factors are susceptible to H/R injury associated with changes in Ca2+ handling; and 2) hypoxic preconditioning improves contractility, Ca2+ handling, and cell recovery during subsequent hypoxic insult.     

Fasting promotes acute hypoxic adaptation by suppressing mTOR-mediated pathways

Rapid adaptation to a hypoxic environment is an unanswered question that we are committed to exploring. At present, there is no suitable strategy to achieve rapid hypoxic adaptation. Here, we demonstrate that fasting preconditioning for 72 h reduces tissue injuries and maintains cardiac function, consequently significantly improving the survival rates of rats under extreme hypoxia, and this strategy can be used for rapid hypoxic adaptation. Mechanistically, fasting reduces blood glucose and further suppresses tissue mTOR activity. On the one hand, fasting-induced mTOR inhibition reduces unnecessary ATP consumption and increases ATP reserves under acute hypoxia as a result of decreased protein synthesis and lipogenesis; on the other hand, fasting-induced mTOR inhibition improves mitochondrial oxygen utilization efficiency to ensure ATP production under acute hypoxia, which is due to the significant decrease in ROS generation induced by enhanced mitophagy. Our findings highlight the important role of mTOR in acute hypoxic adaptation, and targeted regulation of mTOR could be a new strategy to improve acute hypoxic tolerance in the body.Subject terms: Autophagy, Metabolism     

低氧预适应增强大鼠海马神经元的耐缺氧能力

本研究对整体大鼠进行了模拟不同海拔高度（3000、5000m）的低氧预适应,然后观察了急性致死性缺氧对这些大鼠海马脑片诱发群锋电位的影响。结果显示,经低氧预适应的大鼠其海马脑片在给予急性缺氧后,CA1区缺氧损伤电位（hypoxic injury potential,HIP）出现时间以及突触前排放（presynaptic volley,PV）消失时间均明显延迟;其中5000m预适应组的延迟程度比3000m组明显。复氧后,PV的恢复率在3000m和5000m低氧预适应组均明显高于对照组。本研究结果提示,整体动物的低氧预适应可以增强离体海马脑片神经元的耐缺氧能力。     

缺氧诱导因子-1α在缺氧预处理预防心肌细胞损伤中的作用

本工作旨在研究缺氧预处理(hypoxic preconditioning,HPC)对于心肌细胞外信号调节激酶(extracellular signal-regulated proteinkinases,ERK)活性、缺氧诱导因子-1α(hypoxia-inducible factor-1α,HIF-1α)表达的影响,及其在缺氧复氧诱导心肌细胞损伤中的作用。通过在培养的SD乳鼠心肌细胞缺氧／复氧(H／R)模型上,观察HPC对于24h后H／R诱导心肌细胞损伤的影响,以台盼蓝排斥实验检测心肌细胞存活率、以TUNEL法检测细胞凋亡、并用荧光素染料Hoechst33258测定心肌细胞凋亡率：制备心肌细胞蛋白提取物,以磷酸化的ERK1／2抗体测定ERK1／2活性,以抗HIF-1α抗体检测HIF-1α的表达,并观察ERKs的上游激酶(MEK1／2)抑制剂PD98059对于HPC诱导的ERKs磷酸化、HIF-1α表达以及心肌细胞保护作用的影响,并分析细胞损伤与ERK1／2活性、HIF-1α表达量之间的相互关系。结果 显示缺氧复氧造成心肌细胞损伤,HPC可以增加心肌细胞H／R后存活率,降低凋亡率,并激活ERKll2,诱导HIF-1α表达：细胞凋亡与ERKs活性、HIF-1α表达量之间存在负相关,即ERKs活化、HIF-1α表达与预防细胞损伤有关：而ERKs活性与HIF-1α表达量之间存在正相关,ERKs的上游激酶MEK抑制剂PD98059可以消除HPC诱导的ERKs磷酸化、HIF-1α表达和心肌细胞保护作用。由此得出的结论是HPC可以提高乳鼠心肌细胞对于H／R的耐受性,其机制涉及ERKs介导的HIF-1α表达。