Bioavailability Of Oxygen Research Articles

Red Blood Cell Adenylate Energetics Is Related to Endothelial and Microvascular Function in Long COVID.

Adenine nucleotides play a critical role in maintaining essential functions of red blood cells (RBCs), including energy metabolism, redox status, shape fluctuations and RBC-dependent endothelial and microvascular functions. Recently, it has been shown that infection with the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) might lead to morphological and metabolic alterations in erythrocytes in both mild and severe cases of coronavirus disease (COVID-19). However, little is known about the effects of COVID-19 on the nucleotide energetics of RBCs nor about the potential contribution of nucleotide metabolism to the long COVID syndrome. This study aimed to analyze the levels of adenine nucleotides in RBCs isolated from patients 12 weeks after mild SARS-CoV-2 infection who suffered from long COVID symptoms and to relate them with the endothelial and microvascular function parameters as well as the rate of peripheral tissue oxygen supply. Although the absolute quantities of adenine nucleotides in RBCs were rather slightly changed in long COVID individuals, many parameters related to the endothelial and microcirculatory function showed significant correlations with RBC adenosine triphosphate (ATP) and total adenine nucleotide (TAN) concentration. A particularly strong relationship was observed between ATP in RBCs and the serum ratio of arginine to asymmetric dimethylarginine-an indicator of endothelial function. Consistently, a positive correlation was also observed between the ATP/ADP ratio and diminished reactive hyperemic response in long COVID patients, assessed by the flow-mediated skin fluorescence (FMSF) technique, which reflected decreased vascular nitric oxide bioavailability. In addition, we have shown that patients after COVID-19 have significantly impaired ischemic response parameters (IR max and IR index), examined by FMSF, which revealed diminished residual bioavailability of oxygen in epidermal keratinocytes after brachial artery occlusion. These ischemic response parameters revealed a strong positive correlation with the RBC ATP/ADP ratio, confirming a key role of RBC bioenergetics in peripheral tissue oxygen supply. Taken together, the outcomes of this study indicate that dysregulation of metabolic processes in erythrocytes with the co-occurring endothelial and microvascular dysfunction is associated with diminished intracellular oxygen delivery, which may partly explain long COVID-specific symptoms such as physical impairment and fatigue.

P–452 The challenge of ovarian tissue culture: 2D versus 3D

Abstract Study question Does an alginate matrix scaffold improve ovarian tissue culture? Summary answer Ovarian tissue culture within an alginate scaffold has no advantage over conventional culture, being more time consuming and less reproductible What is known already Cryopreservation of ovarian tissue is a powerful technique for preserving female fertility, as it can restore fertility and endocrine function. Several studies have been carried out aiming to increase the longevity of the transplant and decrease the risk of reimplantation of neoplastic cells. For in vitro follicle culture, recent research has shifted from two dimensional (2D) toward the use of three-dimensional (3D) structures. The use of a matrix maintains the architecture and mimics in vivo conditions, with a variable access to oxygen and nutrients. This bridges the gap between conventional cell culture and animal models. Study design, size, duration Ovarian tissue fragments were divided into 2 groups: conventional culture (2D culture) and culture using an alginate matrix scaffold (3D culture). Tissue was evaluated at four time-points: immediately after thawing and after 24, 48 and 72 hours of culture. Participants/materials, setting, methods Rat ovarian tissue was cryopreserved and thawed with validated protocols. Follicular analysis was conducted after haematoxylin and eosin staining, regarding density, classification and degeneration. Tissue viability was assessed using lactate dehydrogenase (LDH) levels in supernatants and histological score. Three parameters were considered, namely, interstitial oedema, follicular cell degeneration and percentage of tissue in necrosis. Apoptosis was assessed by caspase 3 immunostaining. Proliferating cells were identified using Ki67 immunohistochemical labelling. Main results and the role of chance Follicular density, cell proliferation and apoptosis both in follicles and stroma was similar in both culture conditions. Stromal cells proliferation was stable in conventional culture but decreased in 3D culture (p = 0.001), which can be explained by the rigidity of alginate matrix. At 24 hours of culture, cytotoxicity was lower in the 3D model (p = 0.006), due to low levels of LDH in the supernatant, that may be related to retention within the matrix. As culture time increased cytotoxicity seemed to be similar. Degradation of the tissue was suggested by the histological score analysis of tissue during 72 hours of culture. Tissue injury was greater (p = 0.01) in 3D culture due to higher interstitial oedema (p = 0.017) and tissue necrosis (p = 0.035). In the interior of the alginate scaffold, the bioavailability of oxygen and nutrients may be limited, affecting cell survival over time and conditioning higher level of necrosis and release of intracellular content. Limitations, reasons for caution There are two major limitations that should be addressed in future research, namely the study of the tissue-matrix interactions and culture medium supplementation to decrease follicular atresia. Wider implications of the findings: There is no advantage in the use of an alginate matrix scaffold for ovarian tissue culture, as it is more time consuming, difficult to perform and less reproductible. Trial registration number Not applicable

Aberrant redox biology and epigenetic reprogramming: Co-conspirators across multiple human diseases

An epigenetic landscape encompasses a series of dynamic interconnected mechanisms working together to fashion a diverse set of phenotypes from a singular genotype. The epigenetic plasticity observed in disease and development is facilitated by enzymes that create and remove covalent modifications to DNA and histones. Several important discoveries within the past decade have revealed that epigenetic control mechanisms are subject to redox regulation and mitochondrial-to-nuclear retrograde signaling. This has led to our current understanding that the writers and erasers of the epigenome are influenced by several levels of redox and metabolic control including the bioavailability of oxygen, nutrients, and metabolite co-factors necessary for optimal enzyme activity. Thus, these enzymes perceive a cell's redox state, metabolic status, and environmental signals to influence chromatin structure and accessibility to the transcriptional apparatus. Not only are the activities of epigenetic enzymes affected by cellular redox conditions, but also, in feedback loop fashion, genes encoding antioxidant enzymes as well as prooxidant enzymes can be altered in their expression patterns by epigenetic silencing mechanisms. The altered expression of the anti- and prooxidant genes can then contribute to the onset or progression of disease. Epigenetic regulation of gene expression by the confluence of redox biology and gene-environment interactions is an active area of research and our understanding of these links continues to evolve. Given the emergent importance of crosstalk between redox biology and epigenetic regulatory mechanisms, it is timely that this issue should explore the current state of knowledge on this topic and how changes in metabolism and redox flux can result in tectonic shifts of the epigenetic landscape.

Oxygen scavenging using acoustic droplet vaporization while altering droplet diameter and droplet concentration

Transiently reducing the bioavailability of oxygen within an ischemic heart at the time of reperfusion may reduce the formation of reactive oxygen species and therefore reduce the amount of cell death. In vitro studies describe how the magnitude of oxygen scavenging changes as perfluorocarbon droplet diameter and droplet concentration are varied under ultrasonic exposure from an EkoSonic intravascular catheter.

Molecular Insights Into Lysyl Oxidases in Cartilage Regeneration and Rejuvenation.

Articular cartilage remains among the most difficult tissues to regenerate due to its poor self-repair capacity. The lysyl oxidase family (LOX; also termed as protein-lysine 6-oxidase), mainly consists of lysyl oxidase (LO) and lysyl oxidase-like 1-4 (LOXL1-LOXL4), has been traditionally defined as cuproenzymes that are essential for stabilization of extracellular matrix, particularly cross-linking of collagen and elastin. LOX is essential in the musculoskeletal system, particularly cartilage. LOXs-mediated collagen cross-links are essential for the functional integrity of articular cartilage. Appropriate modulation of the expression or activity of certain LOX members selectively may become potential promising strategy for cartilage repair. In the current review, we summarized the advances of LOX in cartilage homeostasis and functioning, as well as copper-mediated activation of LOX through hypoxia-responsive signaling axis during recent decades. Also, the molecular signaling network governing LOX expression has been summarized, indicating that appropriate modulation of hypoxia-responsive-signaling-directed LOX expression through manipulation of bioavailability of copper and oxygen is promising for further clinical implications of cartilage regeneration, which has emerged as a potential therapeutic approach for cartilage rejuvenation in tissue engineering and regenerative medicine. Therefore, targeted regulation of copper-mediated hypoxia-responsive signalling axis for selective modulation of LOX expression may become potential effective therapeutics for enhanced cartilage regeneration and rejuvenation in future clinical implications.

Comparative proteomic analysis reveals metabolic variability of probiotic Enterococcus durans during aerobic and anaerobic cultivation

The variation in the bioavailability of oxygen constitutes the environmental conditions found by bacteria in their passage through the host gastro-intestinal tract. Given the importance of oxygen in the defense mechanism of bacteria, it is important to understand how bacteria respond to this stress at a metabolic level. The probiotic strain Enterococcus durans LAB18S was cultivated under aerobic and anaerobic conditions using prebiotic oligosaccharides as carbon source. The whole cell proteome and secretome were analyzed through label-free quantitative proteomics approach. The results showed that the LAB18S isolate when grown with fructo-oligosacchrides (FOS) showed a higher number of differentially expressed proteins compared to samples with galacto-oligosaccharides (GOS) or glucose. Clinically important enzymes for the treatment of cancer, L-asparaginase and arginine deiminase, were overexpressed when the isolate was cultured in FOS. In addition, the absence of oxygen induced the strain to produce proteins related to cell multiplication, cell wall integrity and resistance, and H2O2 detoxification. This study showed that E. durans LAB18S growing on FOS was stimulated to produce clinically important biomolecules, including proteins that have been investigated as potential antineoplastic agents.Significance: The probiotic strain E. durans LAB18S produce clinically relevant enzymes for the treatment of cancer when cultivated in symbiosis with fructo-oligosacchrides (FOS). In addition, proteins associated with cellular multiplication, cell wall integrity and resistance, and H2O2 detoxification were induced under anaerobic growth. These characteristics could be relevant to support maintenance of intestinal health.

Oxygen-Free Biochemistry: The Putative CHN Foundation for Exotic Life in a Hydrocarbon World?

Since Earth's biochemistry is carbon-based and water-borne, the main strategies for searching for life elsewhere are "follow the carbon" and "follow the water." Recently, however, there is a growing focus on the prospect that putative exotic life on other planets could rely on unearthly biochemistries. Here, we hypothesize a novel oxygen-free organic chemistry for supporting potential exotic biosystems, which is named CHN biochemistry. This oxygen-free CHN biochemistry starts from simple oxygen-free species (including hydrocarbons, hydrogen cyanide, and nitriles) and produces a range of functional macromolecules that may function in similar ways to terran macromolecules, such as sugars (cyanosugars), acids (cyanoacids), amino acids (amino cyanoacids), and nucleobases (cyanonucleobases). These CHN macromolecules could further interact with each other to generate higher "cyanoester" and "cyanoprotein" systems. In addition, theoretical calculations indicate that the energy changes of some reactions are consistent with their counterparts in Earth's biochemistry. The CHN biochemistry-based life would be applicable in habitats with a low bioavailability of oxygen, such as the alkane lakes of Titan and non-aquatic liquids on extrasolar bodies. Key Words: Oxygen-free biochemistry-Titan-Hydrocarbons-Hydrogen cyanide-Nitriles. Astrobiology 17, 1173-1181.

Microbiota-activated PPAR-γ signaling inhibits dysbiotic Enterobacteriaceae expansion.

Perturbation of the gut-associated microbial community may underlie many human illnesses, but the mechanisms that maintain homeostasis are poorly understood. We found that the depletion of butyrate-producing microbes by antibiotic treatment reduced epithelial signaling through the intracellular butyrate sensor peroxisome proliferator-activated receptor γ (PPAR-γ). Nitrate levels increased in the colonic lumen because epithelial expression of Nos2, the gene encoding inducible nitric oxide synthase, was elevated in the absence of PPAR-γ signaling. Microbiota-induced PPAR-γ signaling also limits the luminal bioavailability of oxygen by driving the energy metabolism of colonic epithelial cells (colonocytes) toward β-oxidation. Therefore, microbiota-activated PPAR-γ signaling is a homeostatic pathway that prevents a dysbiotic expansion of potentially pathogenic Escherichia and Salmonella by reducing the bioavailability of respiratory electron acceptors to Enterobacteriaceae in the lumen of the colon.

A Commensal Bacterium Promotes Virulence of an Opportunistic Pathogen via Cross-Respiration.

ABSTRACTBacteria rarely inhabit infection sites alone, instead residing in diverse, multispecies communities. Despite this fact, bacterial pathogenesis studies primarily focus on monoculture infections, overlooking how community interactions influence the course of disease. In this study, we used global mutant fitness profiling (transposon sequencing [Tn-seq]) to determine the genetic requirements for the pathogenic bacterium Aggregatibacter actinomycetemcomitans to cause disease when coinfecting with the commensal bacterium Streptococcus gordonii. Our results show that S. gordonii extensively alters A. actinomycetemcomitans requirements for virulence factors and biosynthetic pathways during infection. In addition, we discovered that the presence of S. gordonii enhances the bioavailability of oxygen during infection, allowing A. actinomycetemcomitans to shift from a primarily fermentative to a respiratory metabolism that enhances its growth yields and persistence. Mechanistically, respiratory metabolism enhances the fitness of A. actinomycetemcomitans in vivo by increasing ATP yields via central metabolism and creating a proton motive force. Our results reveal that, similar to cross-feeding, where one species provides another species with a nutrient, commensal bacteria can also provide electron acceptors that promote the respiratory growth and fitness of pathogens in vivo, an interaction that we term cross-respiration.

Physiology of high-altitude acclimatization

Travel to high altitude exposes the human body to a variety of stresses, the most prominent being reduced available oxygen with increase in altitude due to reduced partial pressure of oxygen. Several physiological responses are initiated in the human body to promote faster acclimatization to these adverse environmental conditions. These physiological and molecular readjustments encompassing acclimatization, namely, hypoxic ventilatory response, diuresis, increased cardiac output, improved oxygen carrying capacity and cerebral blood flow, Hypoxia inducible factor 1 stabilization, etc., converge to a single outcome, ensuring optimal bioavailability of oxygen. In this article, we describe the basic acclimatization framework mentioned above.

Why polar gigantism and Palaeozoic gigantism are not equivalent: effects of oxygen and temperature on the body size of ectotherms

Summary Organisms of gigantic proportions inhabited the world at a time of a hyperoxic prehistoric atmosphere (Palaeozoic gigantism). Extant giants are found in cold polar waters, with large quantities of dissolved oxygen (polar gigantism). Oxygen is usually deemed central to explain such gigantism. Examples of one category of gigantism are often cited in support of the other, but novel insights into the bioavailability of oxygen imply that they cannot be taken as equivalent manifestations of the effect of oxygen on body size. Recently, the availability of oxygen has been shown to be lower in cold waters, despite greater oxygen solubility. Consequently, gigantism in cold, oxygenated waters and gigantism in an oxygen‐pressurized world are fundamentally different: Palaeozoic gigantism likely arose because of greater oxygen availability, while polar gigantism arises in spite of lower oxygen availability. The traditional view of respiration focuses on meeting the challenge of extracting sufficient amounts of oxygen, which essentially is a toxic gas. We present a broader perspective, which specifically includes risks of oxygen poisoning. We discuss how challenges pertaining to balancing oxygen uptake capacity and risks of oxygen poisoning are very different for animals breathing either air or water. We propose a novel explanation for polar gigantism in aquatic ectotherms, arguing that their larger body size represents a respiratory advantage that helps to overcome the larger viscous forces in water. Being large helps organisms to balance the opposing risks of asphyxiation and poisoning, especially in colder, more viscous, water. This results in a selection for larger sizes, with polar gigantism as the extreme manifestation. Hence, a larger size provides respiratory benefits to water‐breathing ectotherms, but not terrestrial ectotherms. This can explain why clines in body size across temperature and latitude are stronger in aquatic ectotherms.

Haemoglobin expression in human endometrium

The general concept that haemoglobin is only a carrier protein for oxygen and carbon dioxide is challenged since recent studies have shown haemoglobin expression in non-erythroid cells and the protection of haemoglobin against oxidative and nitrosative stress. Using microarrays, we previously showed expression of haemoglobins alpha, beta, delta and gamma and the haeme metabolizing enzyme, haeme oxygenase (HO)-1 in human endometrium. Using real-time quantitative PCR, haemoglobin alpha, beta, delta and gamma, and HO-1 mRNA levels were assessed throughout the menstrual cycle (n = 30 women). Haemoglobin and HO-1 protein levels in the human endometrium were assessed with immunohistochemistry. For steroid responsiveness, menstrual and late proliferative-phase endometrial explants were cultured for 24 h in the presence of vehicle (0.1% ethanol), estradiol (17beta-E(2,) 1 nM), progestin (Org 2058, 1 nM) or 17beta-E(2)+Org 2058 (1 nM each). All haemoglobins and the HO-1 were expressed in normal human endometrium. Haemoglobin mRNA and protein expression did not vary significantly during the menstrual cycle. Explant culture with Org 2058 or 17beta-E(2)+Org 2058 increased haemoglobin gamma mRNA expression (P < 0.05). HO-1 mRNA levels, and not protein levels, were significantly higher during the menstrual (M)-phase of the cycle (P < 0.05), and were down-regulated by Org 2058 in M-phase explants and by 17beta-E(2)+Org 2058 in LP-phase explants, versus control (P < 0.05). The haemoglobin-HO-1 system may be required to ensure adequate regulation of the bioavailability of haeme, iron and oxygen in human endometrium.

Characterization of Pseudomonas putida genes responsive to nutrient limitation.

The low bioavailability of nutrients and oxygen in the soil environment has hampered successful expression of biodegradation and biocontrol genes that are driven by promoters highly active during routine laboratory conditions of high availability of nutrients and oxygen. Hence, in the present study, expression of the gus-tagged genes in 12 Tn5-gus mutants of the soil microbe Pseudomonas putida PNL-MK25 were examined under various conditions chosen to mimic the soil environment: low carbon, phosphate, nitrate or oxygen, and in the rhizosphere. Based on their expression profiles, three nutrient-responsive mutant (NRM) strains, NRM5, NRM7 and NRM17, were selected for identification of the tagged genes. In strain NRM5, expression of the glutamate dehydrogenase (gdhA) gene was increased 4.9-26.4-fold under various low-nutrient conditions. In NRM7, expression of the novel NADPH : quinone oxidoreductase-like (nql) gene was consistently amongst the highest and was synergistically upregulated by low-nutrient and anoxic conditions. The cyoD gene in NRM17, which encodes the fourth subunit of the cytochrome o ubiquinol oxidase complex, had decreased expression in low-nutrient conditions but its absolute expression level was still amongst the highest. Additionally, it was independent of oxygen availability, in contrast to that in Escherichia coli.

Oxygen bioavailability and haemoglobins in the brine shrimp Artemia franciscana

Bioavailability of oxygen for the saline-water invertebrate Artemia franciscana was studied, since both oxygen concentration and oxygen diffusion rate change with salinity. Total haemoglobin concentration and the relative contribution of each of three haemoglobins was measured in specimens acclimated to different salinities and oxygen concentrations. Both haemoglobin concentration and contribution were influenced by salinity and the group observed (males, females with and females without eggs). Multiple regression analysis showed that total haemoglobin concentration was better correlated with oxygen concentration than oxygen partial pressure. The relative proportions of haemoglobins 1, 2 and 3 were better correlated with oxygen partial pressure than oxygen concentration. These results are related to the oxygen carrying capacity and oxygen affinity of the haemolymph. Our results show that oxygen bioavailability in a saline-water environment depends on the response (relative contribution of Hb1, Hb2 and Hb3 or total haemoglobin concentration) that is studied. They also show that oxygen concentration and oxygen partial pressure have a different physiological impact on brine shrimp.

Experimental approach of activity and mechanism(s) of action of drugs used in cerebral metabolic insufficiency. Application to 1-eburnamonine.

The authors described an experimental approach, specially using oral administration, of drugs used in cerebral metabolic insufficiencies and its application to l-eburnamonine (l-EB). Administered orally, l-EB: (1) significantly increased the cerebral consumption of [14C]- deoxyglucose in normoxic mice; (2) decreased the fall in cerebral energy charge (ECP) of rats after an acute normobaric hypoxia, and (3) stimulated the glycolysis of red blood cells (RBC) in healthy volunteers (repeated administrations) as demonstrated by important increases in 2,3-DPG and ATP, i.e., in factors involved in the bioavailability of oxygen (oxygen transport activity and RBC deformability). The results therefore demonstrate oral activity of l-EB in animals and man. They are in agreement with previous data showing cerebral metabolic stimulant and antihypoxic effects following parenteral administration, in animals. They allow to propose that l-EB acts both at cerebral and extracerebral levels and constitute objective biochemical proof of the activity of l-EB in man. The study of new drugs may be done using the same experimental approach.