Journal articles: 'O2-responsive'

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Kawasaki, Shinji, Yu Sakai, Tohru Takahashi, Ippei Suzuki, and Youichi Niimura. "O2 and Reactive Oxygen Species Detoxification Complex, Composed of O2-Responsive NADH:Rubredoxin Oxidoreductase-Flavoprotein A2-Desulfoferrodoxin Operon Enzymes, Rubperoxin, and Rubredoxin, in Clostridium acetobutylicum." Applied and Environmental Microbiology 75, no. 4 (January 5, 2009): 1021–29. http://dx.doi.org/10.1128/aem.01425-08.

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ABSTRACT Clostridium acetobutylicum, an obligate anaerobe, grows normally under continuous-O2-flow culture conditions, where the cells consume O2 proficiently. An O2-responsive NADH:rubredoxin oxidoreductase operon composed of three genes (nror, fprA2, and dsr), encoding NROR, functionally uncharacterized flavoprotein A2 (FprA2), and the predicted superoxide reductase desulfoferrodoxin (Dsr), has been proposed to participate in defense against O2 stress. To functionally characterize these proteins, native NROR from C. acetobutylicum, recombinant NROR (rNROR), FprA2, Dsr, and rubredoxin (Rd) expressed in Escherichia coli were purified. Purified native NROR and rNROR both exhibited weak H2O2-forming NADH oxidase activity that was slightly activated by Rd. A mixture of NROR, Rd, and FprA2 functions as an efficient H2O-forming NADH oxidase with a high affinity for O2 (the Km for O2 is 2.9 ï¿½ 0.4 μM). A mixture of NROR, Rd, and Dsr functions as an NADH-dependent O2 − reductase. A mixture of NROR, Rd, and rubperoxin (Rpr, a rubrerythrin homologue) functions as an inefficient H2O-forming NADH oxidase but an efficient NADH peroxidase with a low affinity for O2 and a high affinity for H2O2 (the Km s for O2 and H2O2 are 303 ï¿½ 39 μM and ≤1 μM, respectively). A gene encoding Rd is dicistronically transcribed with a gene encoding a glutaredoxin (Gd) homologue, and the expression levels of the genes encoding Gd and Rd were highly upregulated upon exposure to O2. Therefore, nror operon enzymes, together with Rpr, efficiently function to scavenge O2, O2 −, and H2O2 by using an O2-responsive rubredoxin as a common electron carrier protein.

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Akiyama, Yoshikatsu, Masayuki Yamato, and Teruo Okano. "Preparation of Poly(N-isopropylacrylamide) Grafted Polydimethylsiloxane by Using Electron Beam Irradiation." Journal of Robotics and Mechatronics 25, no. 4 (August 20, 2013): 631–36. http://dx.doi.org/10.20965/jrm.2013.p0631.

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A poly(N-isopropylacrylamide) (PIPAAm) grafted poly(dimethylsiloxane) (PDMS) surface was prepared as a temperature-responsive cell culture surface by using electron beam (EB) irradiation. Different chemical treatments to modify the bare PDMS surface were investigated for subsequent grafting of PIPAAm, and treatment conditions were optimized to prepare the temperature-responsive cell culture surface. The PDMS surface was initially activated to form silanol groups with conventional O2 plasma or hydrochloric acid (HCl) treatment. Activated PDMS surfaces were individually immobilized with three different conventional silane compounds, i.e., 3-mercaptopropyltrimethoxysilane (MerTMS), 3-methacryloxypropyltrimethoxysilane (MetTMS), and 3-aminopropyltrimethoxysilane (AmiTMS). O2 plasma treatment made PDMS more hydrophilic. In contrast, PDMS surfaces activated with HCl treatment were relatively hydrophobic. Observation of the activated PDMS surface modified with MerTMS, MetTMS, and AmiTMS indicated that these silane compounds had been favorably immobilized on plasma-treated PDMS surfaces. FT-IR/ATR analysis demonstrated that immobilized silane compounds enabled PIPAAm grafting on the PDMS surface. Cell attachment and detachment analysis also suggested that the PDMS surface sequentially treated with O2 plasma and AmiTMS compound was a substrate appropriate for preparing a temperature-responsive cell culture surface by EB irradiation-induced PIPAAm grafting method. The intelligent surface may further be applied to mechanically stretchable temperature-responsive cell culture surfaces.

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Wells, RMG. "The Control of Hemoglobin-Oxygen Binding in Vertebrate Animals." Physiology 4, no. 6 (December 1, 1989): 242–45. http://dx.doi.org/10.1152/physiologyonline.1989.4.6.242.

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The affinity of blood for O2 can now be explained in terms of the interaction of the hemoglobin molecule with cofactors. Recent advances in comparative physiology suggest that short-term compensatory changes in blood O2 affinity, which greatly alter the efficiency of the O2-delivery system in response to hypoxia, are typical for vertebrates. Control of O2 delivery by red blood cell organic phosphates is best interpreted in terms of plasticity of the system, rather than as an adaptive feature responsive to evolutionary selection pressure.

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Luo, Sulan, Yiting Zhao, Kewei Pan, Yixian Zhou, Guilan Quan, Xinguo Wen, Xin Pan, and Chuanbin Wu. "Correction: Microneedle-mediated delivery of MIL-100(Fe) as a tumor microenvironment-responsive biodegradable nanoplatform for O₂-evolving chemophototherapy." Biomaterials Science 9, no. 23 (2021): 8051. http://dx.doi.org/10.1039/d1bm90094c.

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Correction for ‘Microneedle-mediated delivery of MIL-100(Fe) as a tumor microenvironment-responsive biodegradable nanoplatform for O2-evolving chemophototherapy’ by Sulan Luo et al., Biomater. Sci., 2021, DOI: 10.1039/d1bm00888a.

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Yao, Chi, Wenxing Wang, Peiyuan Wang, Mengyao Zhao, Xiaomin Li, and Fan Zhang. "Near-Infrared Upconversion Mesoporous Cerium Oxide Hollow Biophotocatalyst for Concurrent pH-/H2 O2 -Responsive O2 -Evolving Synergetic Cancer Therapy." Advanced Materials 30, no. 7 (January 8, 2018): 1704833. http://dx.doi.org/10.1002/adma.201704833.

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Bukowski, Rachel M., Michael D. Davenport, Albert H. Titus, and Frank V. Bright. "O2-Responsive Chemical Sensors Based on Hybrid Xerogels That Contain Fluorinated Precursors." Applied Spectroscopy 60, no. 9 (September 2006): 951–57. http://dx.doi.org/10.1366/000370206778397489.

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7

Zhu, Zhuo, Youxuan Ni, Qingliang Lv, Jiarun Geng, Wei Xie, Fujun Li, and Jun Chen. "Surface plasmon mediates the visible light–responsive lithium–oxygen battery with Au nanoparticles on defective carbon nitride." Proceedings of the National Academy of Sciences 118, no. 17 (April 20, 2021): e2024619118. http://dx.doi.org/10.1073/pnas.2024619118.

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Aprotic lithium-oxygen (Li-O2) batteries have gained extensive interest in the past decade, but are plagued by slow reaction kinetics and induced large-voltage hysteresis. Herein, we use a plasmonic heterojunction of Au nanoparticle (NP)–decorated C3N4 with nitrogen vacancies (Au/NV-C3N4) as a bifunctional catalyst to promote oxygen cathode reactions of the visible light–responsive Li-O2 battery. The nitrogen vacancies on NV-C3N4 can adsorb and activate O2 molecules, which are subsequently converted to Li2O2 as the discharge product by photogenerated hot electrons from plasmonic Au NPs. While charging, the holes on Au NPs drive the reverse decomposition of Li2O2 with a reduced applied voltage. The discharge voltage of the Li-O2 battery with Au/NV-C3N4 is significantly raised to 3.16 V under illumination, exceeding its equilibrium voltage, and the decreased charge voltage of 3.26 V has good rate capability and cycle stability. This is ascribed to the plasmonic hot electrons on Au NPs pumped from the conduction bands of NV-C3N4 and the prolonged carrier life span of Au/NV-C3N4. This work highlights the vital role of plasmonic enhancement and sheds light on the design of semiconductors for visible light–mediated Li-O2 batteries and beyond.

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Akimoto, Tetsu, Helen Liapis, and Marc R. Hammerman. "Microvessel formation from mouse embryonic aortic explants is oxygen and VEGF dependent." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 283, no. 2 (August 1, 2002): R487—R495. http://dx.doi.org/10.1152/ajpregu.00699.2001.

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To delineate the roles of O2 and vascular endothelial growth factor (VEGF) in the process of angiogenesis from the embryonic aorta, we cultured mouse embryonic aorta explants (thoracic level to lateral vessels supplying the mesonephros and metanephros) in a three-dimensional type I collagen gel matrix. During 8 days of culture under 5% O2, but not room air, the addition of VEGF to explants stimulated the formation of CD31-positive, Flk-1-positive, Gs-IB4-positive structures in a concentration-dependent manner. Electron microscopy showed the structures to be capillary-like. VEGF-induced capillary-like structure formation was inhibited by sequestration of VEGF via addition of soluble Flt-1 fusion protein or anti-VEGF antibodies. Expression of Flk-1, but not Flt-1, was increased in embryonic aorta cultured under 5% O2 relative to room air. Our data suggest that low O2 upregulates Flk-1 expression in embryonic aorta in vitro and renders it more responsive to VEGF.

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Xue, Fengfeng, Chunxiao Li, Yicheng Kuang, Lei Shi, Jufeng Chen, ShiXiong Chen, Ming Ma, Xiuli Wang, and Hangrong Chen. "A NTR and O2 programmed responsive photogenic radicals for efficient hypoxia cancer therapy." Sensors and Actuators B: Chemical 369 (October 2022): 132311. http://dx.doi.org/10.1016/j.snb.2022.132311.

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10

Norris, Melanie L., and David E. Millhorn. "Hypoxia-induced Protein Binding to O2-responsive Sequences on the Tyrosine Hydroxylase Gene." Journal of Biological Chemistry 270, no. 40 (October 6, 1995): 23774–79. http://dx.doi.org/10.1074/jbc.270.40.23774.

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11

Nakagawa, Youji, Shigemi Sugioka, Yoshinobu Kaneko, and Satoshi Harashima. "O2R, a Novel Regulatory Element Mediating Rox1p-Independent O2 and Unsaturated Fatty Acid Repression of OLE1in Saccharomyces cerevisiae." Journal of Bacteriology 183, no. 2 (January 15, 2001): 745–51. http://dx.doi.org/10.1128/jb.183.2.745-751.2001.

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ABSTRACT Fatty acid desaturation catalyzed by fatty acid desaturases requires molecular oxygen (O2). Saccharomyces cerevisiae cells derepress expression of OLE1encoding Δ9 fatty acid desaturase under hypoxic conditions to allow more-efficient use of limited O2. It has been proposed that aerobic conditions lead to repression of OLE1 by well-established O2-responsive repressor Rox1p, since putative binding sequences for Rox1p are present in the promoter ofOLE1. However, we revealed in this study that disruption ofROX1 unexpectedly did not affect the O2repression of OLE1, indicating that a Rox1p-independent novel mechanism operates for this repression. We identified by promoter deletion analysis the 50-bp O2-regulated (O2R) element in the OLE1 promoter approximately 360 bp upstream of the start codon. Site-directed mutagenesis of the O2R element showed that the putative binding motif (5′-GATAA-3′) for the GATA family of transcriptional factors is important for O2 repression. Anaerobic derepression of OLE1 transcription was repressed by unsaturated fatty acids (UFAs), and interestingly the O2R element was responsible for this UFA repression despite not being included within the fatty acid-regulated (FAR) element previously reported. The fact that such a short 50-bp O2R element responds to both O2 and UFA signals implies that O2 and UFA signals merge in the ultimate step of the pathways. We discuss the differential roles of FAR and O2R elements in the transcriptional regulation of OLE1.

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Clayton, Carolyn E., Martha Sue Carraway, Hagir B. Suliman, Edward D. Thalmann, Katherine N. Thalmann, Donald E. Schmechel, and Claude A. Piantadosi. "Inhaled carbon monoxide and hyperoxic lung injury in rats." American Journal of Physiology-Lung Cellular and Molecular Physiology 281, no. 4 (October 1, 2001): L949—L957. http://dx.doi.org/10.1152/ajplung.2001.281.4.l949.

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Because carbon monoxide (CO) has been proposed to have anti-inflammatory properties, we sought protective effects of CO in pulmonary O2 toxicity, which leads rapidly to lung inflammation and respiratory failure. Based on published studies, we hypothesized that CO protects the lung against O2 by selectively increasing expression of antioxidant enzymes, thereby decreasing oxidative injury and inflammation. Rats exposed to O2 with or without CO [50–500 parts/million (ppm)] for 60 h were compared for lung wet-to-dry weight ratio (W/D), pleural fluid volume, myeloperoxidase (MPO) activity, histology, expression of heme oxygenase-1 (HO-1), and manganese superoxide dismutase (Mn SOD) proteins. The brains were evaluated for histological evidence of damage from CO. In O2-exposed animals, lung W/D increased from 4.8 in normal rats to 6.3; however, only CO at 200 and 500 ppm decreased W/D significantly (to 5.9) during O2 exposure. Large volumes of pleural fluid accumulated in all rats, with no significant CO treatment effect. Lung MPO values increased after O2 and were not attenuated by CO treatment. CO did not enhance lung expression of oxidant-responsive proteins Mn SOD and HO-1. Animals receiving O2 and CO at 200 or 500 ppm showed significant apoptotic cell death in the cortex and hippocampus by immunochemical staining. Thus significant protection by CO against O2-induced lung injury could not be confirmed in rats, even at CO concentrations associated with apoptosis in the brain.

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13

Douthe, Cyril, Erwin Dreyer, Oliver Brendel, and Charles R. Warren. "Is mesophyll conductance to CO2 in leaves of three Eucalyptus species sensitive to short-term changes of irradiance under ambient as well as low O2?" Functional Plant Biology 39, no. 5 (2012): 435. http://dx.doi.org/10.1071/fp11190.

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Mesophyll conductance to CO2 (g m) limits the diffusion of CO2 to the sites of carboxylation, and may respond rapidly (within minutes) to abiotic factors. Using three Eucalyptus species, we tested the rapid response of g m to irradiance under 21% and 1% O2. We used simultaneous measurements of leaf gas exchange and discrimination against 13CO2 with a tuneable diode laser absorption spectrometer. Measurements under 1% O2 were used to limit uncertainties due to 13C–12C fractionation occurring during photorespiration. Switching irradiance from 600 to 200 µmol m–2 s–1 led to a ≈60% decrease of g m within minutes in all species under both 21% O2 and 1% O2. The g m response to irradiance is unlikely to be a computation artefact since using different values for the parameters of the discrimination model changed the absolute values of g m but did not affect the relative response to irradiance. Simulations showed that possible rapid changes of any parameter were unable to explain the observed variations of g m with irradiance, except for13C–12C fractionation during carboxylation (b), which, in turn, is dependent on the fraction of leaf C assimilated by phospho-enol pyruvate carboxylase (PEPc) (β). g m apparently increased by ≈30% when O2 was switched from 21% to 1% O2. Again, possible changes of β with O2 could explain this apparent g m response to O2. Nevertheless, large irradiance or O2-induced changes in β would be required to fully explain the observed changes in g m, reinforcing the hypothesis that g m is responsive to irradiance and possibly also to O2.

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14

Henn, Alicia D., Jessica Garigen, Valentina Cipolla, Sheldon Perry, Lorne Farovitch, Randy Yerden, Martin Stuart Zand, and Shannon Hilchey. "Cell culture oxygen levels affect B cell migration through HIF-1a signaling." Journal of Immunology 200, no. 1_Supplement (May 1, 2018): 48.13. http://dx.doi.org/10.4049/jimmunol.200.supp.48.13.

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Abstract B lymphocytes in vitro encounter oxygen levels far in excess of what they experience in vivo. Room air incubator O2 is not 21%, the accepted level for outdoor O2[1]. High CO2 and humidity drive incubator O2 down (16–19%), with variability from door openings. However, in vivo O2 is far lower even (tissues 0–7%, blood 5–10%). Hypoxia-induced factor 1 alpha (HIF-1a) is a tightly regulated transcription factor responsive to O2 levels [2]. Downstream of HIF-1a are genes tied to the unfolded protein response, metabolism, proliferation, and migration. A therapeutic target in multiple myeloma [3], HIF-1a protein is stabilized at low O2 levels and rapidly degraded at higher O2 levels. We previously showed in primary human B cells and myeloma cell lines, that HIF-1a protein levels stabilize at physioxic 1% and 4% oxygen, but not at 19% oxygen. B cell migration in response to the CXCR4 ligand, CXCL12, was decreased at low O2 levels. Here we seek to add direct evidence to HIF-1a participation in B cell migration changes by using a lentiviral vector to produce stable transfectants expressing a HIF-1a shRNA to genetically ablate HIF-1a. We used C-chamber sub-chambers and Pro-Ox 110 gas controllers to stably control the gas levels inside a standard incubator. At 1% O2, HIF-1a shRNA expression resulted in undetectable HIF-1a protein levels, and a correlating increase in CXCR4-mediated B cell migration as compared to a lentiviral control vector or non-transfected cells. This adds genetic evidence that directly links incubator O2 levels, HIF-1a activity and B cell migration in vitro.

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Wang, Long-Hai, Alexander Ulrich Ernst, James Arthur Flanders, Wanjun Liu, Xi Wang, Ashim K. Datta, Boris Epel, Mrignayani Kotecha, Klearchos K. Papas, and Minglin Ma. "An inverse-breathing encapsulation system for cell delivery." Science Advances 7, no. 20 (May 2021): eabd5835. http://dx.doi.org/10.1126/sciadv.abd5835.

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Cell encapsulation represents a promising therapeutic strategy for many hormone-deficient diseases such as type 1 diabetes (T1D). However, adequate oxygenation of the encapsulated cells remains a challenge, especially in the poorly oxygenated subcutaneous site. Here, we present an encapsulation system that generates oxygen (O2) for the cells from their own waste product, carbon dioxide (CO2), in a self-regulated (i.e., “inverse breathing”) way. We leveraged a gas-solid (CO2–lithium peroxide) reaction that was completely separated from the aqueous cellular environment by a gas permeable membrane. O2 measurements and imaging validated CO2-responsive O2 release, which improved cell survival in hypoxic conditions. Simulation-guided optimization yielded a device that restored normoglycemia of immunocompetent diabetic mice for over 3 months. Furthermore, functional islets were observed in scaled-up device implants in minipigs retrieved after 2 months. This inverse breathing device provides a potential system to support long-term cell function in the clinically attractive subcutaneous site.

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Rabiee, Hesamoddin, Bo Jin, Seonho Yun, and Sheng Dai. "O2/N2-responsive microgels as functional draw agents for gas-triggering forward osmosis desalination." Journal of Membrane Science 595 (February 2020): 117584. http://dx.doi.org/10.1016/j.memsci.2019.117584.

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Xiong, Shunshun, Sujing Wang, Xinjun Tang, and Zhiyong Wang. "Four new metal–organic frameworks constructed from H2DBTDC-O2 (H2DBTDC-O2 = dibenzothiophene-5,5′-dioxide-3,7-dicarboxylic acid) ligand with guest-responsive photoluminescence." CrystEngComm 13, no. 5 (2011): 1646–53. http://dx.doi.org/10.1039/c0ce00422g.

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Bartman, Colleen M., Daniel Wasim Awari, Christina M. Pabelick, and Y. S. Prakash. "Intermittent Hypoxia-Hyperoxia and Oxidative Stress in Developing Human Airway Smooth Muscle." Antioxidants 10, no. 9 (August 31, 2021): 1400. http://dx.doi.org/10.3390/antiox10091400.

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Premature infants are frequently and intermittently administered supplemental oxygen during hypoxic episodes, resulting in cycles of intermittent hypoxia and hyperoxia. The relatively hypoxic in utero environment is important for lung development while hyperoxia during the neonatal period is recognized as detrimental towards the development of diseases such as bronchopulmonary dysplasia and bronchial asthma. Understanding early mechanisms that link hypoxic, hyperoxic, and intermittent hypoxic-hyperoxic exposures to altered airway structure and function are key to developing advanced therapeutic approaches in the clinic. Changes in oxygen availability can be detrimental to cellular function and contribute to oxidative damage. Here, we sought to determine the effect of oxygen on mitochondria in human fetal airway smooth muscle cells exposed to either 5% O2, 21% O2, 40% O2, or cycles of 5% and 40% O2 (intermittent hypoxia-hyperoxia). Reactive oxygen species production, altered mitochondrial morphology, and changes in mitochondrial respiration were assessed in the context of the antioxidant N-acetylcysteine. Our findings show developing airway smooth muscle is differentially responsive to hypoxic, hyperoxic, or intermittent hypoxic-hyperoxic exposure in terms of mitochondrial structure and function. Cycling O2 decreased mitochondrial branching and branch length similar to hypoxia and hyperoxia in the presence of antioxidants. Additionally, hypoxia decreased overall mitochondrial respiration while the addition of antioxidants increased respiration in normoxic and O2-cycling conditions. These studies show the necessity of balancing oxidative damage and antioxidant defense systems in the developing airway.

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Mehamod, F. S., R. Daik, and M. Ahmad. "Optical Response of Poly (1,4-Phenylene-1,2-Di (P-Phenoxyphenyl) Vinylene) Towards Oxygen Gas." ASEAN Journal on Science and Technology for Development 21, no. 1 (October 27, 2017): 25. http://dx.doi.org/10.29037/ajstd.89.

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This research involved the synthesis of poly (1,4-phenylene-1,2-di (p-phenoxyphenyl) vinylene), dpop-PDV from di (p-phenoxybenzoyl) benzene compound as the monomer. The potential of the produced polymer as sensing reagent for O2 detection based on fluorescence quenching was studied. Di (p-phenoxybenzoyl) benzene was synthesised via the Friedel-Crafts benzoylationwith terephthaloydichloride and biphenylether as starting materials and anhydrous AlCl3 as the catalyst, while the dpop-PDV was synthesized via the McMurry coupling reaction. The polymerization was carried out in THF with TiCl4 and Zn as the catalyst and reducing agent respectively. Characterization on monomer and polymer had been carried out by using FTIR, GCMS, DSC, TGA, GPC and melting point measurement. Response of the polymer towards oxygen gas was described in terms of fluorescence spectra, repeatability, reproducibility and the response curve. Results obtained showed that the fluorescence intensity decreased upon exposure to O2 gas, indicating that the polymer was responsive to the presence of the O2 gas and the sample was found regenerable by flushing the polymer solution with N2 gas.

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Esashi, Y., S. Matsuyama, M. Hoshina, H. Ashino, and K. Ishizawa. "Mechanism of Action of Ethylene in Promoting the Germination of Cocklebur Seeds I. Osmoregulation." Functional Plant Biology 17, no. 5 (1990): 537. http://dx.doi.org/10.1071/pp9900537.

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The germination potentials of upper and lower seeds of cocklebur (Xanthium pennsylvanicum Wallr.) were increased by pre-exposure to water stress imposed by mannitol or polyethylene glycol (PEG) solution. Both types of seeds were responsive to this 'seed priming' which was further enhanced by C2H4 applied exogenously for at least 1 day. The C2H4 effect that occurred during seed priming increased with increasing water stress. It was not influenced by respiratory inhibitors, such as cyanide, azide, benzohydroxymate or propyl gallate, but it was counteracted by CO2 and increased by O2 enrichment. Both C2H4 and O2 significantly increased osmolarity of the sap extracted from the whole seed, but CO2 reduced it. Similar events occurred in seed axial and especially in cotyledonary tissues, and in water extracts of these tissues. Increased osmotic pressure in response to C2H4 stimulated subsequent cotyledonary growth. These findings were applicable also to the action of C2H4 under anoxic conditions, in which the increased potential of seed germination caused by O2 shortage was further enhanced by C2H4 treatment. The higher osmolarities were linked to a stimulation of cotyledonary growth.

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Wang, Shu Qin, Yin Tao Wang, and Yan Dong Liu. "Experimental Research of Visible Light-Induced Photocatalytic Oxidation Effects of SO₂ by N-Doping Nano-TiO₂." Advanced Materials Research 486 (March 2012): 12–17. http://dx.doi.org/10.4028/www.scientific.net/amr.486.12.

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N-doping nanoTiO2 was prepared by sol-gel method. The TEM,XRD,XPS,BET and UV techniques were used to characterize the crystalline structure.The photocatalytic oxidation effects of SO2 were studied with the fluorescence lamp illumination under the different conditions. The visible light-induced photocatalytic oxidation mechanisms of SO2 were discussed. The results showed that N-doping nanoTiO2 increase the visible-light responsive photocatalytic activity because of the increase of the surface area, O2 lacuna and small particle diameter. There are the optima of the dosage and amount of O2. The removal efficiency of SO2 was greater than 95% under the experimental conditions. The photocatalytic reactions of SO2 included two parts-adsorption and oxidation. The results provide some references for the SO2 control and further application of nanoTiO2.

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Chen, Huachao, Fei Li, Yongrong Yao, Zhe Wang, Zhihao Zhang, and Ninghua Tan. "Redox Dual-Responsive and O2‑Evolving Theranostic Nanosystem for Highly Selective Chemotherapy against Hypoxic Tumors." Theranostics 9, no. 1 (2019): 90–103. http://dx.doi.org/10.7150/thno.30259.

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Zhao, Hongjuan, Li Li, Cuixia Zheng, Yongwei Hao, Mengya Niu, Yujie Hu, Junbiao Chang, Zhenzhong Zhang, and Lei Wang. "An intelligent dual stimuli-responsive photosensitizer delivery system with O2-supplying for efficient photodynamic therapy." Colloids and Surfaces B: Biointerfaces 167 (July 2018): 299–309. http://dx.doi.org/10.1016/j.colsurfb.2018.04.011.

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Stobdan, Tsering, Debashis Sahoo, and Gabriel G. Haddad. "A Boolean approach for novel hypoxia-related gene discovery." PLOS ONE 17, no. 8 (August 25, 2022): e0273524. http://dx.doi.org/10.1371/journal.pone.0273524.

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Hypoxia plays a major role in the etiology and pathogenesis of most of the leading causes of morbidity and mortality, whether cardiovascular diseases, cancer, respiratory diseases or stroke. Despite active research on hypoxia-signaling pathways, the understanding of regulatory mechanisms, especially in specific tissues, still remain elusive. With the accessibility of thousands of potentially diverse genomic datasets, computational methods are utilized to generate new hypotheses. Here we utilized Boolean implication relationship, a powerful method to probe symmetrically and asymmetrically related genes, to identify novel hypoxia related genes. We used a well-known hypoxia-responsive gene, VEGFA, with very large human expression datasets (n = 25,955) to identify novel hypoxia-responsive candidate gene/s. Further, we utilized in-vitro analysis using human endothelial cells exposed to 1% O2 environment for 2, 8, 24 and 48 hours to validate top candidate genes. Out of the top candidate genes (n = 19), 84% genes were previously reported as hypoxia related, validating our results. However, we identified FAM114A1 as a novel candidate gene significantly upregulated in the endothelial cells at 8, 24 and 48 hours of 1% O2 environment. Additional evidence, particularly the localization of intronic miRNA and numerous HREs further support and strengthen our finding. Current results on FAM114A1 provide an example demonstrating the utility of powerful computational methods, like Boolean implications, in playing a major role in hypothesis building and discovery.

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Zhao, Xiaoqi, Wentao Wu, Jian Zhang, Wenxue Dai, and Youliang Zhao. "Thermoresponse and self-assembly of an ABC star quarterpolymer with O2 and redox dual-responsive Y junctions." Polymer Chemistry 9, no. 9 (2018): 1095–108. http://dx.doi.org/10.1039/c8py00085a.

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Yashima, Masatomo, Kiyonori Ogisu, and Kazunari Domen. "Structure and electron density of oxysulfide Sm2Ti2S2O4.9, a visible-light-responsive photocatalyst." Acta Crystallographica Section B Structural Science 64, no. 3 (May 15, 2008): 291–98. http://dx.doi.org/10.1107/s0108768108007532.

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We report the crystal structure and electron density of samarium titanium oxysulfide, Sm2Ti2S2O4.9, photocatalyst obtained through the Rietveld analysis, maximum-entropy method (MEM) and MEM-based pattern fitting of the high-resolution synchrotron powder diffraction data taken at 298.7 K. The Sm2Ti2S2O4.9 has a tetragonal structure with the space group I4/mmm. Refined occupancy factors at the `equatorial' O1 and `apical' O2 sites were 0.994 (3) and 0.944 (12), respectively, which strongly suggest oxygen deficiency at the O2 site. Electron-density analyses based on the synchrotron diffraction data of Sm2Ti2S2O4.9 in combination with density-functional theory (DFT) calculations of stoichiometric Sm2Ti2S2O5 reveal covalent bonds between Ti and O atoms, while the Sm and S atoms are more ionic. The presence of S 3p and O 2p orbitals results in increased dispersion of the valence band, raising the top of the valence band and making the material active at visible wavelengths. The present DFT calculations of stoichiometric Sm2Ti2S2O5 indicate the possibility of overall splitting of water, although Sm2Ti2S2O4.9 works as a visible-light-responsive photocatalyst in aqueous solutions only in the presence of sacrificial electron donors or acceptors. The oxygen deficiency and cocatalyst seem to be factors affecting the catalytic activity.

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Cooper, Angela L., and Debbie Beasley. "Hypoxia stimulates proliferation and interleukin-1α production in human vascular smooth muscle cells." American Journal of Physiology-Heart and Circulatory Physiology 277, no. 4 (October 1, 1999): H1326—H1337. http://dx.doi.org/10.1152/ajpheart.1999.277.4.h1326.

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Several lines of evidence indicate that hypoxia is a stimulus to vascular smooth muscle cell (VSMC) proliferation that occurs in pulmonary hypertension. The present study tested the hypothesis that low O2tension directly stimulates human VSMC proliferation by inducing them to produce interleukin (IL)-1, a potent autocrine growth factor for human VSMC. Human VSMC derived from pulmonary artery, aorta, or saphenous vein were incubated in either a normal in vitro O2environment (20% O2) or in chambers containing low (∼1%) or moderate (5%) O2. Levels of IL-1α and IL-1β mRNA increased in human VSMC after 24–48 h of incubation in low O2compared with levels in normoxic cells and then decreased upon subsequent reoxygenation. Levels of cell-associated IL-1α also increased progressively after 24–48 h in low O2; however, detectable IL-1α was not released from the cells in the media. IL-1β was detectable in cell lysates and supernatants; however, the levels were not affected by exposure to low O2. mRNA encoding for tumor necrosis factor-α (TNF-α), a related cytokine and VSMC mitogen, was not detectable in human VSMC exposed to either low or 20% O2. Proliferation of human VSMC was not stimulated during exposure to low O2, despite the fact that cells remained responsive to the mitogenic effect of exogenous IL-1. Interestingly, however, exposure to 5% O2enhanced proliferation of human VSMC but did not induce IL-1α production. Inhibition of IL-1 binding to the type I IL-1 receptor by exogenous addition of IL-1-receptor antagonist (10 μg/ml) did not attenuate the proliferation rates of human VSMC incubated in 20%, 5%, or low O2or in human VSMC that were reoxygenated after exposure to low O2. These results demonstrate two direct and distinct effects of hypoxia on VSMC. Exposure to moderately low O2tension induces VSMC proliferation, independent of IL-1, whereas exposure to very low O2tension induces production of IL-1α.

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Gonzaga de França Lopes, Luiz, Florêncio S. Gouveia Júnior, Alda Karine Medeiros Holanda, Idalina Maria Moreira de Carvalho, Elisane Longhinotti, Tércio F. Paulo, Dieric S. Abreu, et al. "Bioinorganic systems responsive to the diatomic gases O2, NO, and CO: From biological sensors to therapy." Coordination Chemistry Reviews 445 (October 2021): 214096. http://dx.doi.org/10.1016/j.ccr.2021.214096.

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Acharya, Seetharama A., Vivek N. Acharya, Nirmala Devi Kanika, Amy G. Tsai, Marcos Intaglietta, and Belur N. Manjula. "Non-hypertensive tetraPEGylated canine haemoglobin: correlation between PEGylation, O2 affinity and tissue oxygenation." Biochemical Journal 405, no. 3 (July 13, 2007): 503–11. http://dx.doi.org/10.1042/bj20070238.

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TetraPEGylated canine Hb, [SP (succinimidophenyl)-PEG5K]4-canine-Hb, with PEGylation at its four reactive cysteine residues (α111 and β93) has been prepared and characterized. The hydrodynamic volume and the molecular radius of (SP-PEG5K)4-canine-Hb are intermediate to those of di- and hexaPEGylated human Hb as expected. However, the COP (colloidal osmotic pressure) of tetraPEGylated canine Hb is closer to that of hexaPEGylated human Hb than to that of diPEGylated human Hb. The O2 affinity of tetraPEGylated canine Hb is higher than that of canine Hb and comparable with that of hexaPEGylated Hb. The O2 affinity of tetraPEGylated canine Hb is not responsive to the presence of DPG (diphosphoglycerate) or chloride, but it retains almost full response to L-35, an allosteric effector that interacts at the αα-end of the central cavity. The tetraPEGylated canine Hb is vasoinactive in hamster in 10% top load infusion studies. It is also essentially non-hypertensive in an extreme exchange haemodilution protocol in hamster just as di- and hexaPEGylated human Hb. The O2 delivery by tetraPEGylated canine Hb is comparable with that of hexaPEGylated Hb but not as efficient as diPEGylated Hb. These results demonstrate that PEGylation-induced solution properties of PEG [poly(ethylene glycol)]–Hb conjugates are dictated by the level and chemistry of PEGylation and the interplay of these plays a critical role in tissue oxygenation. The studies imply the need to establish the right level (and/or pattern) of PEGylation and O2 affinity of Hb–PEG adducts in designing O2-carrying plasma volume expanders, and this remains the primary challenge in the design of PEGylated Hb as blood substitutes.

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Tankersley, Clarke G., Musa A. Haxhiu, and Estelle B. Gauda. "Differential CO2-induced c-fos gene expression in the nucleus tractus solitarii of inbred mouse strains." Journal of Applied Physiology 92, no. 3 (March 1, 2002): 1277–84. http://dx.doi.org/10.1152/japplphysiol.00609.2001.

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Genetic determinants confer variation between inbred mouse strains with respect to the magnitude and pattern of ventilation during hypercapnic challenge. Specifically, inheritance patterns derived from low-responsive C3H/HeJ (C3) and high-responsive C57BL/6J (B6) mouse strains suggest that differential hypercapnic ventilatory sensitivity (HCVS) is controlled by two independent genes. The present study also tests whether differential neuronal activity in respiratory control regions of the brain is positively associated with strain variation in HCVS. With the use of whole body plethysmography, ventilation was assessed in C3 and B6 strains at baseline and during 30 min of hypercapnia (inspired CO2 fraction = 0.15, inspired O2 fraction = 0.21 in N2). Subsequently, in situ hybridization histochemistry was performed to determine changes in c- fos gene expression in the commissural subnucleus of the nucleus tractus solitarius (NTS). During hypercapnia, breathing frequency and tidal volume were significantly ( P < 0.01) different between strains: C3 mice showed a slow, deep-breathing pattern relative to a rapid, shallow phenotype of B6 mice. CO2-induced increase in c- fos gene expression was significantly ( P < 0.01) greater in NTS regions of B6 compared with C3 mice. In this genetic model of differential HCVS, the results suggest that a genomic basis for varied hypercapnic chemoreception or transduction confers greater afferent neuronal activity in the caudal NTS for high-responsive B6 mice compared with low-responsive C3 mice.

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Akimoto, Tetsu, and Marc R. Hammerman. "Fibroblast growth factor 2 promotes microvessel formation from mouse embryonic aorta." American Journal of Physiology-Cell Physiology 284, no. 2 (February 1, 2003): C371—C377. http://dx.doi.org/10.1152/ajpcell.00193.2002.

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To delineate the roles that oxygen and fibroblast growth factors (FGFs) play in the process of angiogenesis from the embryonic aorta, we cultured mouse embryonic aorta explants (thoracic level to lateral vessels supplying the mesonephros and metanephros) in a three-dimensional type I collagen gel matrix. During 8 days of culture under 5% O2, but not room air, the addition of FGF2 to explants stimulated the formation of Gs-IB4-positive, CD31-positive, and Flk-1-positive microvessels in a concentration-dependent manner. FGF2-stimulated microvessel formation was inhibited by sequestration of FGF2 via addition of soluble FGF receptor (FGFR) chimera protein or anti-FGF2 antibodies. FGFR1 and FGFR2 were present on explants. Levels of FGFR1, but not FGFR2, were increased in embryonic aorta cultured under 5% O2 relative to room air. Our data suggest that low oxygen upregulates FGFR1 expression in embryonic aorta in vitro and renders it more responsive to FGF2.

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Quail, Daniela F., Meghan J. Taylor, Logan A. Walsh, Dylan Dieters-Castator, Padmalaya Das, Michael Jewer, Guihua Zhang, and Lynne-Marie Postovit. "Low oxygen levels induce the expression of the embryonic morphogen Nodal." Molecular Biology of the Cell 22, no. 24 (December 15, 2011): 4809–21. http://dx.doi.org/10.1091/mbc.e11-03-0263.

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Low oxygen (O2) levels characterize the microenvironment of both stem cells and rapidly growing tumors. Moreover, hypoxia is associated with the maintenance of stem cell–like phenotypes and increased invasion, angiogenesis and metastasis in cancer patients. Metastatic cancers, such as breast cancer and melanoma, aberrantly express the embryonic morphogen Nodal, and the presence of this protein is correlated with metastatic disease. In this paper, we demonstrate that hypoxia induces Nodal expression in melanoma and breast cancer cells concomitant with increased cellular invasion and angiogenic phenotypes. Of note, Nodal expression remains up-regulated up to 48 h following reoxygenation. The oxygen-mediated regulation of Nodal expression occurs via a combinatorial mechanism. Within the first 24 h of exposure to low O2, there is an increase in protein stability. This increase in stability is accompanied by an induction of transcription, mediated by the HIF-1α–dependent activation of Notch-responsive elements in the node-specific enhancer of the Nodal gene locus. Finally, Nodal expression is maintained upon reoxygenation by a canonical SMAD-dependent feed-forward mechanism. This work provides insight into the O2-mediated regulation of Nodal, a key stem cell–associated factor, and reveals that Nodal may be a target for the treatment and prevention of hypoxia-induced tumor progression.

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DÉJARDIN, Annabelle, Lubomir N. SOKOLOV, and Leszek A. KLECZKOWSKI. "Sugar/osmoticum levels modulate differential abscisic acid-independent expression of two stress-responsive sucrose synthase genes in Arabidopsis." Biochemical Journal 344, no. 2 (November 24, 1999): 503–9. http://dx.doi.org/10.1042/bj3440503.

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Sucrose synthase (Sus) is a key enzyme of sucrose metabolism. Two Sus-encoding genes (Sus1 and Sus2) from Arabidopsis thaliana were found to be profoundly and differentially regulated in leaves exposed to environmental stresses (cold stress, drought or O2 deficiency). Transcript levels of Sus1 increased on exposure to cold and drought, whereas Sus2 mRNA was induced specifically by O2 deficiency. Both cold and drought exposures induced the accumulation of soluble sugars and caused a decrease in leaf osmotic potential, whereas O2 deficiency was characterized by a nearly complete depletion in sugars. Feeding abscisic acid (ABA) to detached leaves or subjecting Arabidopsis ABA-deficient mutants to cold stress conditions had no effect on the expression profiles of Sus1 or Sus2, whereas feeding metabolizable sugars (sucrose or glucose) or non-metabolizable osmotica [poly(ethylene glycol), sorbitol or mannitol] mimicked the effects of osmotic stress on Sus1 expression in detached leaves. By using various sucrose/mannitol solutions, we demonstrated that Sus1 was up-regulated by a decrease in leaf osmotic potential rather than an increase in sucrose concentration itself. We suggest that Sus1 expression is regulated via an ABA-independent signal transduction pathway that is related to the perception of a decrease in leaf osmotic potential during stresses. In contrast, the expression of Sus2 was independent of sugar/osmoticum effects, suggesting the involvement of a signal transduction mechanism distinct from that regulating Sus1 expression. The differential stress-responsive regulation of Sus genes in leaves might represent part of a general cellular response to the allocation of carbohydrates during acclimation processes.

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Chung, Youngran, Shih-Jwo Huang, Alan Glabe, and Thomas Jue. "Implication of CO inactivation on myoglobin function." American Journal of Physiology-Cell Physiology 290, no. 6 (June 2006): C1616—C1624. http://dx.doi.org/10.1152/ajpcell.00360.2005.

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Myoglobin (Mb) has a purported role in facilitating O2 diffusion in tissue, especially as cellular Po2 drops or the respiration demand increases. Inhibiting Mb with CO under conditions that accentuate the facilitated diffusion role should then elicit a significant physiological response. In one set of experiments, the perfused myocardium received buffer with decreasing Po2 (225, 129, and 64 mmHg). Intracellular Po2 declined, as reflected in the 1H NMR Val E11 signal of MbO2 (67%, 32%, and 18%). The addition of 6% CO further reduced the available MbO2 (11%, 9%, and 7%), as evidenced by the decline of the MbO2 Val E11 signal intensity at −2.76 ppm. In a second set of experiments, electrical stimulation increased the heart rate (300, 450, and 540 beats/min) and correspondingly the O2 consumption rate (MV̇o2). Intracellular Po2 also declined, as reflected in the slight drop in the MbO2 signal (100%, 96%, and 82%). MV̇o2 increased (100%, 114%, 165%). The addition of 3% CO in the stimulated hearts further decreased the available MbO2 (46%, 44%, and 29%). In all cases, CO inactivation of Mb does not induce any change in the respiration rate, contractile function, and high-energy phosphate levels. Moreover, the MbCO/MbO2 partition coefficient shifts dramatically from its in vitro value during hypoxia and increased work. The observation suggests a modulation of an intracellular O2 gradient. Overall, the experimental observations provide no evidence of a facilitated diffusion role for Mb in perfused myocardium and implicate a physiologically responsive intracellular O2 gradient.

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35

Yang, Mei, Xinhang Duan, Zhaoyu Wang, Hang Yin, Junrui Zang, Kai Zhu, Yumeng Wang, and Pan Zhang. "Overexpression of a Voltage-Dependent Anion-Selective Channel (VDAC) Protein-Encoding Gene, MsVDAC, from Medicago sativa Confers Cold and Drought Tolerance to Transgenic Tobacco." Genes 12, no. 11 (October 27, 2021): 1706. http://dx.doi.org/10.3390/genes12111706.

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Voltage-dependent anion channels (VDACs) are highly conserved proteins that are involved in the translocation of tRNA and play a key role in modulating plant senescence and multiple pathways. However, the functions of VDACs in plants are still poorly understood. Here, a novel VDAC gene was isolated and identified from alfalfa (Medicago sativa L.). MsVDAC localized to the mitochondria, and its expression was highest in alfalfa roots and was induced in response to cold, drought and salt treatment. Overexpression of MsVDAC in tobacco significantly increased MDA, GSH, soluble sugars, soluble protein and proline contents under cold and drought stress. However, the activities of SOD and POD decreased in transgenic tobacco under cold stress, while the O2- content increased. Stress-responsive genes including LTP1, ERD10B and Hxk3 were upregulated in the transgenic plants under cold and drought stress. However, GAPC, CBL1, BI-1, Cu/ZnSOD and MnSOD were upregulated only in the transgenic tobacco plants under cold stress, and GAPC, CBL1, and BI-1 were downregulated under drought stress. These results suggest that MsVDAC provides cold tolerance by regulating ROS scavenging, osmotic homeostasis and stress-responsive gene expression in plants, but the improved drought tolerance via MsVDAC may be mainly due to osmotic homeostasis and stress-responsive genes.

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Matsuoka, Masaya, Masaaki Kitano, Masato Takeuchi, Masakazu Anpo, and John M. Thomas. "Preparation and Characterization of the Visible Light Responsive TiO₂ Thin Film Photocatalysts Prepared by Magnetron Sputtering Method and Their Photocatalytic Activities for the Water Splitting Reactions." Materials Science Forum 486-487 (June 2005): 81–84. http://dx.doi.org/10.4028/www.scientific.net/msf.486-487.81.

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Visible light responsive TiO2 (Vis-TiO2) thin films were successfully developed by the radio-frequency magnetron sputtering method, and their photocatalytic activities for the water splitting reactions were investigated. Pt-loaded Vis-TiO2 thin films acted as photocatalysts to decompose water involving sacrificial reagent such as methanol or silver nitrate under visible light irradiation (λ³ 420 nm). Furthermore, the separate evolution of H2 and O2 was successfully achieved under solar light irradiation by applying these photocatalysts in a H-type glass container, which consists of two water phases separated by a TiO2 thin film and proton-exchange membrane.

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37

Wang, Jian-Ying, Richard M. Burger, and Karl Drlica. "Role of Superoxide in Catalase-Peroxidase-Mediated Isoniazid Action against Mycobacteria." Antimicrobial Agents and Chemotherapy 42, no. 3 (March 1, 1998): 709–11. http://dx.doi.org/10.1128/aac.42.3.709.

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ABSTRACT Isoniazid (INH) activation in vitro is associated with reduction of the mycobacterial ferric KatG catalase-peroxidase by hydrazine and reaction with O2 to form an oxyferrous enzyme complex. Since this complex could also form directly via reaction of ferric KatG with superoxide, intracellular activation might be responsive to superoxide concentration. When Mycobacterium smegmatiscarrying the M. bovis katG gene was treated with nontoxic levels of plumbagin, a generator of superoxide, the bacteriostatic activity of INH increased unless a plasmid-borne superoxide dismutase gene was also present. Thus, endogenous superoxide probably contributes to intracellular activation of INH.

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Xie, Zhongxi, Xuechao Cai, Chunqiang Sun, Shuang Liang, Shuai Shao, Shanshan Huang, Ziyong Cheng, et al. "O2-Loaded pH-Responsive Multifunctional Nanodrug Carrier for Overcoming Hypoxia and Highly Efficient Chemo-Photodynamic Cancer Therapy." Chemistry of Materials 31, no. 2 (December 16, 2018): 483–90. http://dx.doi.org/10.1021/acs.chemmater.8b04321.

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Cheng, Yong, Jun Dai, Chunli Sun, Rui Liu, Tianyou Zhai, Xiaoding Lou, and Fan Xia. "An Intracellular H2 O2 -Responsive AIEgen for the Peroxidase-Mediated Selective Imaging and Inhibition of Inflammatory Cells." Angewandte Chemie 130, no. 12 (February 21, 2018): 3177–81. http://dx.doi.org/10.1002/ange.201712803.

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Aime, Silvio, Mauro Botta, Eliana Gianolio, and Enzo Terreno. "Ap(O2)-Responsive MRI Contrast Agent Based on the Redox Switch of Manganese(II /III) - Porphyrin Complexes." Angewandte Chemie International Edition 39, no. 4 (February 18, 2000): 747–50. http://dx.doi.org/10.1002/(sici)1521-3773(20000218)39:4<747::aid-anie747>3.0.co;2-2.

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41

Cheng, Yong, Jun Dai, Chunli Sun, Rui Liu, Tianyou Zhai, Xiaoding Lou, and Fan Xia. "An Intracellular H2 O2 -Responsive AIEgen for the Peroxidase-Mediated Selective Imaging and Inhibition of Inflammatory Cells." Angewandte Chemie International Edition 57, no. 12 (February 21, 2018): 3123–27. http://dx.doi.org/10.1002/anie.201712803.

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42

Gorr, Thomas A. "Daphnia and Drosophila: two invertebrate models for O2 responsive and HIF-mediated regulation of genes and genomes." International Congress Series 1275 (December 2004): 55–62. http://dx.doi.org/10.1016/j.ics.2004.08.068.

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Aime, Silvio, Mauro Botta, Eliana Gianolio, and Enzo Terreno. "Ap(O2)-Responsive MRI Contrast Agent Based on the Redox Switch of Manganese(II /III) – Porphyrin Complexes." Angewandte Chemie 112, no. 4 (February 18, 2000): 763–66. http://dx.doi.org/10.1002/(sici)1521-3757(20000218)112:4<763::aid-ange763>3.0.co;2-3.

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44

Etheridge, Timothy, Philip J. Atherton, Daniel Wilkinson, Anna Selby, Debbie Rankin, Nick Webborn, Kenneth Smith, and Peter W. Watt. "Effects of hypoxia on muscle protein synthesis and anabolic signaling at rest and in response to acute resistance exercise." American Journal of Physiology-Endocrinology and Metabolism 301, no. 4 (October 2011): E697—E702. http://dx.doi.org/10.1152/ajpendo.00276.2011.

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Chronic reductions in tissue O2 tension (hypoxia) are associated with muscle atrophy and blunted hypertrophic responses to resistance exercise (RE) training. However, the effect of hypoxia on muscle protein synthesis (MPS) at rest and after RE is unknown. In a crossover study, seven healthy men (21.4 ± 0.7 yr) performed unilateral leg RE (6 × 8 repetitions at 70% 1-repetition maximum) under normoxic (20.9% inspired O2) and normobaric hypoxic (12% inspired O2 for 3.5 h) postabsorptive conditions. Immediately after RE the rested leg was biopsied, and a primed continuous infusion of [1,2-13C2]leucine was maintained for 2.5 h before final biopsies from both legs to measure tracer incorporation and signaling responses (i.e., ribosomal S6 kinase 1). After 3.5 h of hypoxia, MPS was not different from normoxia in the rested leg (normoxia 0.033 ± 0.016 vs. hypoxia 0.043 ± 0.016%/h). MPS increased significantly from baseline 2.5 h after RE in normoxia (0.033 ± 0.016 vs. 0.104 ± 0.038%/h) but not hypoxia (0.043 ± 0.016 vs. 0.060 ± 0.063%/h). A significant linear relationship existed between MPS 2.5 h after RE in hypoxia and mean arterial blood O2 saturation during hypoxia ( r2 = 0.49, P = 0.04). Phosphorylation of p70S6KThr389 remained unchanged in hypoxia at rest but increased after RE in both normoxia and hypoxia (2.6 ± 1.2-fold and 3.4 ± 1.1-fold, respectively). Concentrations of the hypoxia-responsive mTOR inhibitor regulated in development and DNA damage-1 were unaltered by hypoxia or RE. We conclude that normobaric hypoxia does not reduce MPS over 3.5 h at rest but blunts the increased MPS response to acute RE to a degree dependent on extant SpO2.

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Kuwano, Yuki, Tsukasa Kawahara, Hironori Yamamoto, Shigetada Teshima-Kondo, Kumiko Tominaga, Kiyoshi Masuda, Kyoichi Kishi, Kyoko Morita, and Kazuhito Rokutan. "Interferon-γ activates transcription of NADPH oxidase 1 gene and upregulates production of superoxide anion by human large intestinal epithelial cells." American Journal of Physiology-Cell Physiology 290, no. 2 (February 2006): C433—C443. http://dx.doi.org/10.1152/ajpcell.00135.2005.

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NADPH oxidase 1 (Nox1), a homolog of gp91phox, is dominantly expressed in large intestinal epithelium, and reactive oxygen species derived from Nox1 are suggested to serve a role in host defense. We report that interferon (IFN)-γ, a crucial transactivator of the gp91phoxgene, also stimulates expression of Nox1 mRNA and protein in large intestinal epithelium (T84 cells), leading to fourfold upregulation of superoxide anion (O2−) generation. Introduction of small interfering Nox1 RNA completely blocked this priming. We cloned the region from −4,831 to +195 bp of the human Nox1 gene. To reveal IFN-γ-responsive cis elements, we performed transient expression assays using a reporter gene driven by serially truncated Nox1 promoters in T84 cells. IFN-γ-responsive elements were located between −4.3 and −2.6 kb, and one γ-activated sequence (GAS) element present at −3,818 to −3,810 bp exhibited this IFN-γ-dependent promoter activity. IFN-γ caused tyrosine phosphorylation of signal transducer and activator of transcription 1 (STAT1) and produced a protein-GAS complex that was recognized by anti-STAT1 antibody. The introduction of three-point mutation of GAS, which did not interact with STAT1, completely canceled the IFN-γ-dependent promoter activity of the region from −4,831 to +195 bp. A Janus protein tyrosine kinase 2 inhibitor (AG490) blocked the IFN-γ-stimulated tyrosine phosphorylation of STAT1, promoter activity of the −4,831 to +195 bp region, Nox1 mRNA expression, and O2−production, also suggesting a crucial role of STAT1 and GAS in the IFN-γ-stimulated transcription of the Nox1 gene. Our results support a potential contribution of Nox1 to mucosal host defense and inflammation in the colon.

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JORNOT, Lan, and Alain F. JUNOD. "Hyperoxia, unlike phorbol ester, induces glutathione peroxidase through a protein kinase C-independent mechanism." Biochemical Journal 326, no. 1 (August 15, 1997): 117–23. http://dx.doi.org/10.1042/bj3260117.

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Human selenium-dependent glutathione peroxidase (GP) is implicated as a mechanism of resistance against oxygen free radicals. The 5′ flanking sequence upstream from the coding region of GP contained an oxygen-responsive element termed ORE1 that is responsive to hypoxia, as well as several copies of the activator protein-1 (AP-1)- and AP-1-like-binding sites. In this study, we sought to define the molecular events that lead to GP gene transcription in response to hyperoxia in human umbilical-vein endothelial cells, and asked whether such induction is mimicked and sustained by activation of protein kinase C (PKC) by phorbol esters. Treatment of cells with 100 nM phorbol 12,13-dibutyrate (PdBu) induced a delayed (24–48 h) but significant (2-fold) increase in steady-state GP mRNA levels. Steady-state GP mRNA levels also rose after exposure to 95% O2, again after considerable delay (48–72 h). For both PdBu and oxygen, induction was transcriptionally regulated, as demonstrated by nuclear run-on experiments. The simulations by PdBu and oxygen were additive. In contrast with PdBu, hyperoxia did not stimulate translocation of PKC from the cytosol to the particulate fraction, although the specific activity of both cytosolic and particulate-associated PKC was increased 2-fold in cells exposed to 95% O2 for 5 days. In addition, gel mobility-shift assays using double-stranded tumour-promoting-agent-responsive element (TRE) and nuclear extracts derived from phorbol- and oxygen-treated cells revealed that PdBu, but not hyperoxia, increased AP-1 DNA-binding activity. On the other hand, the up-regulation of GP expression by oxygen could not be accounted for by the ORE1 core sequence, since no specific protein–DNA binding activity could be detected using nuclear extracts from hyperoxic cells and ORE1. Taken together, these results suggest that there may be different molecular mechanisms controlling GP expression. After exposure to PdBu, GP undergoes transcriptional activation via a process that can be readily explained by a classic AP-1 interaction with the TRE sites in the GP promoter. During hyperoxia, GP also undergoes transcriptional activity, but via a process that appears to involve neither TRE nor ORE1.

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Suzuki, K., H. Sato, T. Kikuchi, T. Abe, S. Nakaji, K. Sugawara, M. Totsuka, K. Sato, and K. Yamaya. "Capacity of circulating neutrophils to produce reactive oxygen species after exhaustive exercise." Journal of Applied Physiology 81, no. 3 (September 1, 1996): 1213–22. http://dx.doi.org/10.1152/jappl.1996.81.3.1213.

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To investigate the cause of disagreement within the large body of literature concerning the effect of exercise on the capacity of circulating neutrophils to produce reactive oxygen species (ROS), 10 male endurance-trained athletes underwent maximal exercise. The generation of superoxide radical (O2-.) by neutrophils was first detected on a cell-by-cell basis by using histochemical nitro blue tetrazolium tests performed directly on fresh unseparated blood, which showed that responsive neutrophils under several stimulatory conditions relatively decreased after exercise. Similarly, O2-. detected with bis-N-methylacridinium nitrate (lucigenin)-dependent chemiluminescence (CL) of a fixed number of purified neutrophils on stimulation with opsonized zymosan was decreased slightly after exercise. In contrast, the 5-amino-2,3-dihydro-1,4-phthalazinedione (luminol)-dependent CL response of the neutrophils indicative of the myeloperoxidase (MPO)-mediated formation of highly reactive oxidants was significantly enhanced after exercise. It therefore suggests that the pathway of neutrophil ROS metabolism might be forwarded from the precursor O2-. production to the stages of more reactive oxidant formation due to the facilitation of MPO degranulation. In addition, these phenomena were closely associated with the exercise-induced mobilization of neutrophils from the marginated pool into the circulation, which was mediated by the overshooting of catecholamines during exercise. These findings indicate that the use of different techniques for detecting ROS or the different stages of neutrophil ROS metabolism could explain some of the disparate findings of the previous studies.

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Ietta, Francesca, Yuanhong Wu, Roberta Romagnoli, Nima Soleymanlou, Barbara Orsini, Stacy Zamudio, Luana Paulesu, and Isabella Caniggia. "Oxygen regulation of macrophage migration inhibitory factor in human placenta." American Journal of Physiology-Endocrinology and Metabolism 292, no. 1 (January 2007): E272—E280. http://dx.doi.org/10.1152/ajpendo.00086.2006.

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Macrophage migration inhibitory factor (MIF) is an important proinflammatory cytokine involved in regulation of macrophage function. In addition, MIF may also play a role in murine and human reproduction. Although both first trimester trophoblast and decidua express MIF, the regulation and functional significance of this cytokine during human placental development remains unclear. We assessed MIF expression throughout normal human placental development, as well as in in vitro (chorionic villous explants) and in vivo (high altitude placentae) models of human placental hypoxia. Dimethyloxalylglycine (DMOG), which stabilizes hypoxia inducible factor-1 under normoxic conditions, was also used to mimic the effects of hypoxia on MIF expression. Quantitative real-time PCR and Western blot analysis showed high MIF protein and mRNA expression at 7–10 wk and lower levels at 11–12 wk until term. Exposure of villous explants to 3% O2 resulted in increased MIF expression and secretion relative to standard conditions (20% O2). DMOG treatment under 20% O2 increased MIF expression. In situ hybridization and immunohistochemistry showed elevated MIF expression in low oxygen-induced extravillous trophoblast cells. Finally, a significant increase in MIF transcript was observed in placental tissues from high-altitude pregnancies. Hence, three experimental models of placental hypoxia (early gestation, DMOG treatment, and high altitude) converge in stimulating increased MIF, supporting the conclusion that placental-derived MIF is an oxygen-responsive cytokine highly expressed in physiological in vivo and in in vitro low oxygen conditions.

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Suzuki, Sho, Akihide Iwase, and Akihiko Kudo. "Long wavelength visible light-responsive SrTiO3 photocatalysts doped with valence-controlled Ru for sacrificial H2 and O2 evolution." Catalysis Science & Technology 10, no. 15 (2020): 4912–16. http://dx.doi.org/10.1039/d0cy00600a.

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He, Feng Q., Wei Wang, Ping Zheng, Padhmanand Sudhakar, Jibin Sun, and An-Ping Zeng. "Essential O2-responsive genes of Pseudomonas aeruginosa and their network revealed by integrating dynamic data from inverted conditions." Integrative Biology 6, no. 2 (2014): 215. http://dx.doi.org/10.1039/c3ib40180d.

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Journal articles on the topic 'O2-responsive'

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