Oxygen Homeostasis Research Articles

Antioxidants Reduce Muscular Dystrophy in the dy2J/dy2J Mouse Model of Laminin α2 Chain-Deficient Muscular Dystrophy.

Congenital muscular dystrophy with laminin α2 chain-deficiency (LAMA2-CMD) is a severe neuromuscular disorder without a cure. Using transcriptome and proteome profiling as well as functional assays, we previously demonstrated significant metabolic impairment in skeletal muscle from LAMA2-CMD patients and mouse models. Reactive oxygen species (ROS) increase when oxygen homeostasis is not maintained and, here, we investigate whether oxidative stress indeed is involved in the pathogenesis of LAMA2-CMD. We also analyze the effects of two antioxidant molecules, N-acetyl-L-cysteine (NAC) and vitamin E, on disease progression in the dy2J/dy2J mouse model of LAMA2-CMD. We demonstrate increased ROS levels in LAMA2-CMD mouse and patient skeletal muscle. Furthermore, NAC treatment (150 mg/kg IP for 6 days/week for 3 weeks) led to muscle force loss prevention, reduced central nucleation and decreased the occurrence of apoptosis, inflammation, fibrosis and oxidative stress in LAMA2-CMD muscle. In addition, vitamin E (40 mg/kg oral gavage for 6 days/week for 2 weeks) improved morphological features and reduced inflammation and ROS levels in dy2J/dy2J skeletal muscle. We suggest that NAC and to some extent vitamin E might be potential future supportive treatments for LAMA2-CMD as they improve numerous pathological hallmarks of LAMA2-CMD.

Cellular adaptation to hypoxia through hypoxia inducible factors and beyond.

Molecular oxygen (O2) sustains intracellular bioenergetics and is consumed by numerous biochemical reactions, making it essential for most species on Earth. Accordingly, decreased oxygen concentration (hypoxia) is a major stressor that generally subverts life of aerobic species and is a prominent feature of pathological states encountered in bacterial infection, inflammation, wounds, cardiovascular defects and cancer. Therefore, key adaptive mechanisms to cope with hypoxia have evolved in mammals. Systemically, these adaptations include increased ventilation, cardiac output, blood vessel growth and circulating red blood cell numbers. On a cellular level, ATP-consuming reactions are suppressed, and metabolism is altered until oxygen homeostasis is restored. A critical question is how mammalian cells sense oxygen levels to coordinate diverse biological outputs during hypoxia. The best-studied mechanism of response to hypoxia involves hypoxia inducible factors (HIFs), which are stabilized by low oxygen availability and control the expression of a multitude of genes, including those involved in cell survival, angiogenesis, glycolysis and invasion/metastasis. Importantly, changes in oxygen can also be sensed via other stress pathways as well as changes in metabolite levels and the generation of reactive oxygen species by mitochondria. Collectively, this leads to cellular adaptations of protein synthesis, energy metabolism, mitochondrial respiration, lipid and carbon metabolism as well as nutrient acquisition. These mechanisms are integral inputs into fine-tuning the responses to hypoxic stress.

DEAD Box Protein Family Member DDX28 Is a Negative Regulator of Hypoxia-Inducible Factor 2α- and Eukaryotic Initiation Factor 4E2-Directed Hypoxic Translation.

Hypoxia is a deficiency in oxygen delivery to tissues and is connected to physiological and pathophysiological processes such as embryonic development and cancer. The master regulators of oxygen homeostasis in mammalian cells are the heterodimeric hypoxia-inducible transcription factors 1 and 2 (HIF-1 and HIF-2, respectively). The oxygen-labile HIF-2α subunit has been implicated not only in transcription but also as a regulator of eukaryotic initiation factor 4E2 (eIF4E2)-directed hypoxic translation. Here, we have identified the DEAD box protein family member DDX28 as an interactor and negative regulator of HIF-2α that suppresses HIF-2α's ability to activate eIF4E2-directed translation. Stable silencing of DDX28 via short hairpin RNA (shRNA) in hypoxic human U87MG glioblastoma cells caused an increase of eIF4E2 binding to the m7GTP cap structure and the translation of eIF4E2 target mRNAs (including the HIF-2α mRNA itself). DDX28 depletion elevated nuclear and cytoplasmic HIF-2α protein, but HIF-2α transcriptional activity did not increase, possibly due to its already high nuclear abundance in hypoxic control cells. Depletion of DDX28 conferred a proliferative advantage to hypoxic, but not normoxic, cells. DDX28 protein levels are reduced in several cancers, including gliomas, relative to levels in normal tissue. Therefore, we uncover a regulatory mechanism for this potential tumor suppressor in the repression of HIF-2α- and eIF4E2-mediated translation activation of oncogenic mRNAs.

Comparative Proteomics of Meat Spoilage Bacteria Predicts Drivers for Their Coexistence on Modified Atmosphere Packaged Meat

Besides intrinsic and extrinsic factors such as antagonism for organic substrates or temperature, the storage atmosphere of meat has a high influence on the development of its initial microbiota. Specific modified atmospheres (MAs) selectively suppress growth of aerobic and anaerobic bacteria, thus reshaping the initial microbiota. As some microorganisms are more tolerant to MA, they overgrow competitors and produce metabolites that cause rejection of the product. In order to elucidate responses to different MA by means of metabolic adaptation and competition for organic substrates on meat, the typical representative meat spoilage bacteria Brochothrix (B.) thermosphacta TMW2.2101 and four lactic acid bacteria Carnobacterium (C.) divergens TMW2.1577, C. maltaromaticum TMW2.1581, Leuconostoc (L.) gelidum subsp. gelidum TMW2.1618 and L. gelidum subsp. gasicomitatum TMW2.1619 were chosen. Bacteria were grown in sterile glass bottles filled with a meat simulation medium, which was aerated constantly with either air, 100%_N2, 30%_CO2/70%_O2 or 30%_CO2/70%_N2. Growth of bacteria during incubation at 25°C and stirring at 120 rpm was monitored over 48 h and a label-free quantitative mass spectrometric approach was employed to determine changes within the bacterial proteomes in response to oxygen and carbon dioxide. Both Leuconostoc subsp. were intrinsically tolerant to MA, exhibiting no proteomic regulation of enzymes, whereas the other species provide a set of metabolic adaptation mechanism, enabling higher resistance to the detrimental effects of MA. Those mechanisms comprise: enhanced oxidative stress reduction, adjustment of the pyruvate metabolism and catabolic oxygen consumption in response to oxygen and intracellular pH homeostasis, maintenance of osmotic balance and alteration of the fatty acid composition in response to carbon dioxide. We further evaluated the potential of industrial used MA to inhibit specific bacterial spoilage. No bacterial inhibition is predicted for 30%_CO2/70%_O2 for the analyzed species, whereas 30%_CO2/70%_N2 predictively inhibits C. divergens TMW21577 and B. thermosphacta TMW2.2101. Furthermore, species-specific metabolic pathways enabling different and preferential carbon source utilization were identified, which enable non-competitive coexistence of respective bacteria on meat, resulting in synergistic spoilage. In conclusion, this study gives mechanistically explanations of their acknowledged status as typical spoilage organisms on MAP meats.

Basic Biology of Hypoxic Responses Mediated by the Transcription Factor HIFs and its Implication for Medicine.

Oxygen (O2) is essential for human life. Molecular oxygen is vital for the production of adenosine triphosphate (ATP) in human cells. O2 deficiency leads to a reduction in the energy levels that are required to maintain biological functions. O2 acts as the final acceptor of electrons during oxidative phosphorylation, a series of ATP synthesis reactions that occur in conjunction with the electron transport system in mitochondria. Persistent O2 deficiency may cause death due to malfunctioning biological processes. The above account summarizes the classic view of oxygen. However, this classic view has been reviewed over the last two decades. Although O2 is essential for life, higher organisms such as mammals are unable to biosynthesize molecular O2 in the body. Because the multiple organs of higher organisms are constantly exposed to the risk of “O2 deficiency,” living organisms have evolved elaborate strategies to respond to hypoxia. In this review, I will describe the system that governs oxygen homeostasis in the living body from the point-of-view of the transcription factor hypoxia-inducible factor (HIF).

Impaired Neovascularization in Aging.

Significance: The skin undergoes an inevitable degeneration as an individual ages. As intrinsic and extrinsic factors degrade the structural integrity of the skin, it experiences a critical loss of function and homeostatic stability. Thus, aged skin becomes increasingly susceptible to injury and displays a prolonged healing process. Recent Advances: Several studies have found significant differences during wound healing between younger and older individuals. The hypoxia-inducible factor 1-alpha (HIF-1α) signaling pathway has recently been identified as a major player in wound healing. Hypoxia-inducible factors (HIFs) are pleiotropic key regulators of oxygen homeostasis. HIF-1α is essential to neovascularization through its regulation of cytokines, such as SDF-1α (stromal cell-derived factor 1-alpha) and has been shown to upregulate the expression of genes important for a hypoxic response. Prolyl hydroxylase domain proteins (PHDs) and factor inhibiting HIF effectively block HIF-1α signaling in normoxia through hydroxylation, preventing the signaling cascade from activating, leading to impaired tissue survival. Critical Issues: Aged wounds are a major clinical burden, resisting modern treatment and costing millions in health care each year. At the molecular level, aging has been shown to interfere with PHD regulation, which in turn prevents HIF-1α from activating gene expression, ultimately leading to impaired healing. Other studies have identified loss of function in cells during aging, impeding processes such as angiogenesis. Future Directions: An improved understanding of the regulation of molecular mediators, such as HIF-1α and PHD, will allow for manipulation of the various factors underlying delayed wound healing in the aged. The findings highlighted in this may facilitate the development of potential therapeutic approaches involved in the alteration of cellular dynamics and aging.

Meta-Analysis of Hypoxic Transcriptomes from Public Databases.

Hypoxia is the insufficiency of oxygen in the cell, and hypoxia-inducible factors (HIFs) are central regulators of oxygen homeostasis. In order to obtain functional insights into the hypoxic response in a data-driven way, we attempted a meta-analysis of the RNA-seq data from the hypoxic transcriptomes archived in public databases. In view of methodological variability of archived data in the databases, we first manually curated RNA-seq data from appropriate pairs of transcriptomes before and after hypoxic stress. These included 128 human and 52 murine transcriptome pairs. We classified the results of experiments for each gene into three categories: upregulated, downregulated, and unchanged. Hypoxic transcriptomes were then compared between humans and mice to identify common hypoxia-responsive genes. In addition, meta-analyzed hypoxic transcriptome data were integrated with public ChIP-seq data on the known human HIFs, HIF-1 and HIF-2, to provide insights into hypoxia-responsive pathways involving direct transcription factor binding. This study provides a useful resource for hypoxia research. It also demonstrates the potential of a meta-analysis approach to public gene expression databases for selecting candidate genes from gene expression profiles generated under various experimental conditions.

Immunohistochemical expression of hypoxia-inducible factor-1 alpha in psoriatic patients

Introduction Psoriasis is a chronic inflammatory skin disease characterized by aberrant differentiation and excessive growth of keratinocytes, with dermal and epidermal mixed leukocytic infiltrate and angiogenesis in the dermis. Oxygen consumption could be increased by the proliferation of cells, and impaired oxygen supply might occur from the thickening of the epidermis. A primary role in the maintenance of oxygen and energy homeostasis is hypoxia-inducible factor-1 (HIF-1). Several gene expression-encoding inflammatory proteins are stimulated by HIF-1. The pathogenesis of various forms of inflammation shows the involvement of hypoxia. Aim This immunohistochemical study was done to evaluate the role of HIF-1α in the pathogenesis of psoriasis. Patients and methods This study was conducted on 20 patients with chronic plaque psoriasis, and 10 healthy individuals as a control group. They underwent hematoxylin and eosin staining and immunohistochemical staining detection of HIF-1α expression. Results Regarding the correlation between HIF-1α expression and clinical parameters of the patients, there was a statistically significant positive correlation with the Psoriasis Area and Severity Index score. Conclusion In this study, there was significantly increased HIF-1α expression in psoriatic patients’ skin in comparison with normal control, and also its increase with elevated Psoriasis Area and Severity Index score might represent new promising therapeutic approaches and pharmacological research target for psoriasis treatment.

Comparison of neuroglobin distribution and expression between the retina of the adult Bactrian camel, rabbits and sheep

Neuroglobin (Ngb) is a kind of protein largely expressed in the brain and retina of mammals. Numerous studies have reported on Ngb expression and distribution in mammals but none have compared the expression in the adult Bactrian camel, rabbits, and sheep. The study examined the distribution and expression of Ngb between the retina of adult Bactrian camel, rabbits, and sheep and provides detailed insight on the morphology of these mammals’ retinae. The immunohistochemical staining procedures were performed to detect Ngb distribution and its expression in the retinae of the adult Bactrian camel, rabbits, and sheep. The results showed that strong positive Ngb expression was found in all layers of the Bactrian camel except the outer nuclear layer, while in the rabbit retina, the strong positive expression was observed in the cortex of the optic nerve fiber layer, the retina cells layer, the network layer, the photoreceptor inner segment, and the pigment, while weak positive expression was shown in the retina of the kernel layer, outside the outer nuclear layer of the retina and the light receptor section. In the adult sheep retina, Ngb was solely expressed in the nerve fiber layer, inner and outer plexiform layer, optic nerve, inner and outer limiting membrane, and photoreceptor inner segment, while weak positive expression was shown in the ganglion cell layer and inner nuclear layer. There exist no Ngb positive expression in the photoreceptor outer segment, the outer nuclear layer, and retinal pigment epithelium of the adult sheep retina. The study documented that Ngb may have a significant function in the maintenance of retinal oxygen homeostasis and participation in the repair of light damage. The study also provided detailed references for Ngb physiological function and its relationship to extreme environmental conditions

Comparison of neuroglobin distribution and expression in the retina of adult yak and cattle

The yak belongs to the genus Bos and is therefore related to cattle (Bos primigenius species). The yak may have diverged from cattle at any point between one and five million years ago, and the yak is supposed to be more closely related to cattle than to other members of its designated genus. Here, we evaluated the distribution of neuroglobin (NGB) expression in the retina of adult yak and cattle. Five healthy yaks and five cattle were used in the study. Immunohistochemical stainings were performed to assess the distribution of NGB in the retina of adult yak and cattle. The results demonstrated that NGB was expressed at high levels in the retina of adult yak and cattle in the ganglion cell layer, outer plexiform layer, photoreceptor inner segments, and pigment epithelial layer (+++). Medium NGB expression was found in the nerve fiber layer, ganglion cell layer, inner plexiform layer, and photoreceptor outer segments (++). In contrast, NGB was only weakly expressed in the inner nuclear layer (+), while no expression was found in the outer nuclear layer (–). Expression in the inner limiting membrane, outer limiting membrane, and optic nerves of the cattle was weak (+) and comparable to expression in the adult yak. No NGB expression was found in the outer nuclear layer of both yak and cattle. The level of NGB expression in the retinal ganglion cell layer, kernel layer, optic nerve, and photoreceptor inner segments was significantly higher in yak than in cattle (P < 0.05). These results suggest that NGB might play an important role in oxygen homeostasis of the retina and normal function of the optic nerve of yak and cattle under high-altitude hypoxic conditions. Nevertheless, its specific functional mechanism needs further investigation.

Indicators of oxygen transport in acute and early periods of traumatic disease with multistage surgical correction at polytrauma

Disorders of the oxygen transport play an important role in the development of multiple organ disfunction syndrome and are a marker of tissue hypoxia and ischemia. Disorders of the oxygen transport could be use for predicting patient survival and as criteria for the severity of the pathological process. The aim of this study was to explore the indicators of systemic oxygen transport in the perioperative period in patients with traumatic deases in multi-stage surgical correction at polytrauma in terms of standard and advanced intensive care. Materials and methods. A prospective study of 88 patients with traumatic deases was conducted. The dynamics of indices of oxygen delivery (iDО2) and oxygen consumption (iVO2), oxygen extraction coefficient (KEO2) at different variants of intensive care was studied. Results. The patients in both groups was noted iDO2 decline, which was due to massive blood loss and decreased cardiac output on admission to the operation room. Despite the fact that during the acute period was held stop bleeding, correction of hypovolemia and posthemorrhagic anemia, the average level of iDО2 was quite low. iDO2 was multidirectional nature of the changes in the studied groups at the second and third stages of the study. In turn, the average values KEO2 characterized the degree of tension compensatory mechanisms and metabolic changes caused by hypoxia and hypoperfusion. Normalization of oxygen homeostasis parameters was achieved in the fourth stage of the study. Conclusions. The maximal intensity of development of compensatory mechanisms and changes of oxygen transport occurs within the first 5 days after the injury. The optimized intensive care which has been used in the treatment patients of Group II, has positive effect on the ability to potentiate adaptive defense mechanisms and reduce oxygen debt.

ВОЗРАСТНЫЕ И СЕЗОННЫЕ ИЗМЕНЕНИЯ АНТИОКСИДАНТНОЙ ЗАЩИТЫ МЫШЕЧНОЙ ТКАНИ И МОРФОМЕТРИЧЕСКИХ ПАРАМЕТРОВ ЭРИТРОЦИТОВ У ОНДАТРЫ ( ONDATRA ZIBETHICUS )

During adaptation to a semi-aquatic mode of life, the muskrat (Ondatra zibethicus) developed numerous biochemical adaptations to maintain homeostasis. The aim of the study was to explore age-related and seasonal changes in muscle tissue antioxidant defenses and erythrocyte morphometric parameters in the muskrat. Animals were caught in autumn (juveniles and adults) and spring (adults) in the North-West of Russia (Republic of Karelia). Some physiological and biochemical parameters of animals caught in autumn showed an age-related variability: in adult animals (most adapted to diving), as compared to juveniles, catalase activity in skeletal muscles was lower, while the respiratory function of blood was higher (due to a lower total surface area of erythrocytes). Adult muskrats demonstrated seasonal changes in some parameters studied: in spring, activities of catalase in the heart and superoxide dismutase in skeletal muscles were higher, while levels of low-molecular-weight antioxidants ( α -tocopherol and glutathione) both in cardiac and skeletal muscles were lower, compared to animals caught in autumn. After a long winter (ice-fishing) season, the blood of animals caught in spring contained mainly mature erythrocyte forms (normocytes), with their average diameter and surface area being larger than in adult muskrats caught in autumn. Our findings, as well as data obtained on other species, support the involvement of the antioxidant system and erythrocytes in the mechanisms that maintain oxygen homeostasis in diving mammals.

Identification of key HIF-1α target genes that regulate adaptation to hypoxic conditions in Tibetan chicken embryos

Tibetan chicken, a unique plateau breed, has a suite of adaptive features that enable it to tolerate the high-altitude hypoxic environment. HIF‐1α (hypoxia inducible factor 1 subunit alpha) is a crucial mediator of the cellular response to hypoxia. HIF‐1α maintains oxygen homeostasis by inducing glycolysis, erythropoiesis, and angiogenesis. In this study, using ChIP-seq, we analyzed HIF‐1α binding regions in the chorioallantoic membrane (CAM) tissue of embryos, and identified differential HIF-1α target genes (DTGs) by comparing Chahua (CH) and Tibetan chicken (TC) that had distinct genetic performances, associated with hypoxic adaptation. We identified 752 HIF-1α target genes (TGs), of which 112 were DTGs between the two breeds. We found that eight genes (PTK2, GPNMB, CALD1, CBWD1, SLC25A1, SPRY2, NUPL2, and ST8SIA3) play important roles in hypoxic adaptation by regulating blood vessel development, energy metabolism through angiogenesis, vascular smooth muscle contraction, and various hypoxia-related signaling pathways (including VEGF and PI3K-Akt) in Tibetan chickens during embryonic development. This study enhances our understanding of the molecular mechanisms of hypoxic adaptation in Tibetan chickens and provides new insights into adaptation to hypoxia in humans and other species living at high altitude.

Generation of a hypoxia-sensing mouse model.

Oxygen (O2 ) homeostasis is essential to the metazoan life. O2 -sensing or hypoxia-regulated molecular pathways are intimately involved in a wide range of critical cellular functions and cell survival from embryogenesis to adulthood. In this report, we have designed an innovative hypoxia sensor (O2 CreER) based on the O2 -dependent degradation domain of the hypoxia-inducible factor-1α and Cre recombinase. We have further generated a hypoxia-sensing mouse model, R26-O2 CreER, by targeted insertion of the O2 CreER-coding cassette in the ROSA26 locus. Using the ROSAmTmG mouse strain as a reporter, we have found that this novel hypoxia-sensing mouse model can specifically identify hypoxic cells under the pathological condition of hind-limb ischemia in adult mice. This model can also label embryonic cells including vibrissal follicle cells in E13.5-E15.5 embryos. This novel mouse model offers a valuable genetic tool for the study of hypoxia and O2 sensing in mammalian systems under both physiological and pathological conditions.

A Hydrogel Vitreous Substitute that Releases Antioxidant.

Current experimental vitreous substitutes only replace the physical functions of the natural vitreous humor. Removal of the native vitreous disrupts oxygen homeostasis in the eye, causing oxidative damage to the lens that likely results in cataract formation. Neither current clinical treatments nor other experimental vitreous substitutes consider the problem of oxidative stress after vitrectomy. To address this problem, biomimetic hydrogels are prepared by free radical polymerization of poly(ethylene glycol) methacrylate and poly(ethylene glycol) diacrylate. These hydrogels have similar mechanical and optical properties to the vitreous. The hydrogels are injectable through small-gauge needles and demonstrate in vitro biocompatibility with human retinal and lens epithelial cells. The hydrogels and added vitamin C, an antioxidant, show a synergistic effect in protecting ocular cells against reactive oxygen species, which fulfills a chemical function of the natural vitreous. These hydrogels have the potential to prevent post-vitrectomy cataract formation and reduce the cost of additional surgeries.

Genome-wide association studies of beef cow terrain-use traits using Bayesian multiple-SNP regression

Beef cattle grazing patterns are influenced by topography in that cattle generally select grazing sites near water while avoiding steep, rugged terrain; therefore, forage is often left ungrazed in the mountainous uplands whereas lowland riparian zones can be heavily grazed. Improving uniformity in beef cattle terrain-use provides opportunities to increase forage harvest and sustain sensitive ecosystems. Studies suggest that terrain-use by cattle may be improved using genomic selection as combinations of single nucleotide polymorphisms (SNP) explained approximately 35% of the phenotypic variation in terrain-use indices that combined slope, elevation, and distance traveled from water. The objective of this study was to perform genome-wide association studies (GWAS) for six terrain-use traits (slope, elevation, vertical climb, distance traveled from water, rolling index, and rough index) in which we explored single-SNP associations, surveyed the genome in consecutive, one mega-base windows and examined quantitative trait loci (QTL) and underlying positional and functional candidate genes using bioinformatic tools to identify possible pleiotropic effects with other traits. Global positioning system (GPS) collars were used to track terrain-use patterns for 330 beef cows across 14 rangeland operations located in the western U.S. and Illumina BovineHD and BovineSNP50 SNP arrays were used to collect genomic data. Genotype quality control was conducted using PLINK software and association analyses were performed using BOLT, implementing a BayesC model. Quantitative trait loci detection was based upon the posterior inclusion probability (PIP) for individual loci and the proportion of total genetic variance explained by individual genomic windows. Analyses revealed 19 QTL that have been previously associated with health and production traits in dairy and beef cattle as well as 8 positional putative candidate genes that function in oxygen homeostasis, feed efficiency, and growth. These results suggest that beef cattle terrain-use traits are polygenic and may be pleiotropic with other production traits.

A long hypoxia-inducible factor 3 isoform 2 is a transcription activator that regulates erythropoietin

Hypoxia-inducible factor (HIF), an αβ dimer, is the master regulator of oxygen homeostasis with hundreds of hypoxia-inducible target genes. Three HIF isoforms differing in the oxygen-sensitive α subunit exist in vertebrates. While HIF-1 and HIF-2 are known transcription activators, HIF-3 has been considered a negative regulator of the hypoxia response pathway. However, the human HIF3A mRNA is subject to complex alternative splicing. It was recently shown that the long HIF-3α variants can form αβ dimers that possess transactivation capacity. Here, we show that overexpression of the long HIF-3α2 variant induces the expression of a subset of genes, including the erythropoietin (EPO) gene, while simultaneous downregulation of all HIF-3α variants by siRNA targeting a shared HIF3A region leads to downregulation of EPO and additional genes. EPO mRNA and protein levels correlated with HIF3A silencing and HIF-3α2 overexpression. Chromatin immunoprecipitation analyses showed that HIF-3α2 binding associated with canonical hypoxia response elements in the promoter regions of EPO. Luciferase reporter assays showed that the identified HIF-3α2 chromatin-binding regions were sufficient to promote transcription by all three HIF-α isoforms. Based on these data, HIF-3α2 is a transcription activator that directly regulates EPO expression.

Independent prognostic value of HIF-1α expression in radiofrequency ablation of lung cancer.

Radiofrequency ablation (RFA) is widely used in the treatment of lung cancer. Hypoxia-inducible factor-1α (HIF-1α) is a crucial transcription factor regulating oxygen homeostasis that is involved in tumor cell metastasis. The present study investigated the impact of HIF-1α expression and other factors, such as postoperative blood CD4+/CD8+ ratio, on the prognosis of patients with lung cancer who had received RFA treatment. A total of 80 patients with lung cancer were recruited between January 2011 and October 2016 at The Shenzhen People's Hospital. Lung cancer was confirmed following pathological or histological examination. All patients underwent RFA treatment. Patients were followed up for 6–66 months. HIF-1α expression in lung cancer tissues was assessed by immunohistochemistry. Multivariate survival analysis was performed using Cox proportional hazards model. The results demonstrated that HIF-1α level was low in 36 patients and overexpressed in 44 patients with lung cancer. Kaplan-Meier (KM) curve analysis demonstrated that the overall survival time of patients with high HIF-1α expression was significantly shorter compared with patients with low HIF-1α expression (P<0.05). Furthermore, the results from the KM model and log-rank test revealed that age, Union for International Cancer Control stage, primary or metastatic cancer, chemotherapy, postoperative blood CD4+/CD8+ ratio, Eastern Cooperative Oncology Group performance status and HIF-1α expression had significant effects on overall survival of patients with lung cancer. The results from Cox analysis demonstrated that high HIF-1α expression, advanced age, clinical staging and chemotherapy were independent risk factors for the prognosis of lung cancer following RFA treatment, and that high HIF-1α expression was associated with the increased risk (5.91-fold) of mortality. In conclusion, the present study demonstrated that HIF-1α expression was increased in lung cancer tissues and was associated with the prognosis of patients with lung cancer who were treated with RFA. These findings suggest that HIF-1α expression may be considered as a marker for evaluating the prognosis of these patients.

Alteration of the DNA Methylation Signature of Renal Erythropoietin-Producing Cells Governs the Sensitivity to Drugs Targeting the Hypoxia-Response Pathway in Kidney Disease Progression.

Chronic kidney disease (CKD) affects more than 10% of the population worldwide and burdens citizens with heavy medical expenses in many countries. Because a vital erythroid growth factor, erythropoietin (EPO), is secreted from renal interstitial fibroblasts [renal EPO-producing (REP) cells], anemia arises as a major complication of CKD. We determined that hypoxia-inducible factor 2α (HIF2α), which is inactivated by HIF-prolyl hydroxylase domain-containing proteins (PHDs) in an oxygen-dependent manner, tightly regulates EPO production in REP cells at the gene transcription level to maintain oxygen homeostasis. HIF2α-mediated disassembly of the nucleosome in the EPO gene is also involved in hypoxia-inducible EPO production. In renal anemia patients, anemic and pathological hypoxia is ineffective toward EPO induction due to the inappropriate over-activation of PHDs in REP cells transformed into myofibroblasts (MF-REP cells) due to kidney damage. Accordingly, PHD inhibitory compounds are being developed for the treatment of renal anemia. However, our studies have demonstrated that the promoter regions of the genes encoding EPO and HIF2α are highly methylated in MF-REP cells, and the expression of these genes is epigenetically silenced with CKD progression. This finding notably indicates that the efficacy of PHD inhibitors depends on the CKD stage of each patient. In addition, a strategy for harvesting renal cells, including REP cells from the urine of patients, is proposed to identify plausible biomarkers for CKD and to develop personalized precision medicine against CKD by a non-invasive strategy.

Can molecular markers of oxygen homeostasis and the measurement of tissue oxygen be leveraged to optimize red blood cell transfusions?

The clinical indication for transfusing red blood cells (RBCs) is to restore or maintain adequate oxygenation of respiring tissue. Oxygen (O2) transport, delivery, and utilization following transfusion are impacted by perfusion, hemoglobin (Hb) allosteric saturation/desaturation, and the concentration of tissue O2. Bioavailable O2 maintains tissue utilization and homeostasis; therefore, measuring imbalances in supply and demand could be valuable to assessing blood quality and transfusion effectiveness. O2 homeostasis is critically intertwined with erythropoietic response in blood loss and anemia and the hormones that modulate iron mobilization and RBC production (e.g., erythropoietin, erythroferrone, and hepcidin) are intriguing markers for the monitoring of transfusion effectiveness in acute and chronic settings. The evaluation of RBC donor unit quality and the determination of RBC transfusion needs are emerging areas for biomarker development and minimally invasive O2 measurements. Novel methods for assessing circulatory and tissue compartment biomarkers of transfusion effectiveness are suggested. In addition, monitoring of tissue oxygenation by indirect and direct measurements of O2 is available and applied in experimental settings. Herein, we discuss tissue O2 homeostasis, related aspects of erythropoiesis, molecular markers and measurements of tissue oxygenation, all aimed at optimizing transfusion and assessing blood quality.