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Zhou X, Su W, Bao Q, Cui Y, Li X, Yang Y, Yang C, Wang C, Jiao L, Chen D, Huang J. Nitric Oxide Ameliorates the Effects of Hypoxia in Mice by Regulating Oxygen Transport by Hemoglobin. High Alt Med Biol 2024. [PMID: 38743636 DOI: 10.1089/ham.2023.0044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2024] Open
Abstract
Xiaoying Zhou, Wenting Su, Quanwei Bao, Yu Cui, Xiaoxu Li, Yidong Yang, Chengzhong Yang, Chengyuan Wang, Li Jiao, Dewei Chen, and Jian Huang. Nitric oxide ameliorates the effects of hypoxia in mice by regulating oxygen transport by hemoglobin. High Alt Med Biol. 00:00-00, 2024.-Hypoxia is a common pathological and physiological phenomenon in ischemia, cancer, and strenuous exercise. Nitric oxide (NO) acts as an endothelium-derived relaxing factor in hypoxic vasodilation and serves as an allosteric regulator of hemoglobin (Hb). However, the ultimate effects of NO on the hematological system in vivo remain unknown, especially in extreme environmental hypoxia. Whether NO regulation of the structure of Hb improves oxygen transport remains unclear. Hence, we examined whether NO altered the oxygen affinity of Hb (Hb-O2 affinity) to protect extremely hypoxic mice. Mice were exposed to severe hypoxia with various concentrations of NO, and the survival time, exercise capacity, and other physical indexes were recorded. The survival time was prolonged in the 5 ppm NO (6.09 ± 1.29 minutes) and 10 ppm NO (6.39 ± 1.58 minutes) groups compared with the 0 ppm group (4.98 ± 1.23 minutes). Hypoxia of the brain was relieved, and the exercise exhaustion time was prolonged when mice inhaled 20 ppm NO (24.70 ± 6.87 minutes vs. 20.23 ± 6.51 minutes). In addition, the differences in arterial oxygen saturation (SO2%) (49.64 ± 7.29% vs. 42.90 ± 4.30%) and arteriovenous SO2% difference (25.14 ± 8.95% vs. 18.10 ± 6.90%) obviously increased. In ex vivo experiments, the oxygen equilibrium curve (OEC) left shifted as P50 decreased from 43.77 ± 2.49 mmHg (0 ppm NO) to 40.97 ± 1.40 mmHg (100 ppm NO) and 38.36 ± 2.78 mmHg (200 ppm NO). Furthermore, the Bohr effect of Hb was enhanced by the introduction of 200 ppm NO (-0.72 ± 0.062 vs.-0.65 ± 0.051), possibly allowing Hb to more easily offload oxygen in tissue at lower pH. The crystal structure reveals a greater distance between Asp94β-His146β in nitrosyl -Hb(NO-Hb), NO-HbβCSO93, and S-NitrosoHb(SNO-Hb) compared to tense Hb(T-Hb, 3.7 Å, 4.3 Å, and 5.8 Å respectively, versus 3.5 Å for T-Hb). Moreover, hydrogen bonds were less likely to form, representing a key limitation of relaxed Hb (R-Hb). Upon NO interaction with Hb, hydrogen bonds and salt bridges were less favored, facilitating relaxation. We speculated that NO ameliorated the effects of hypoxia in mice by promoting erythrocyte oxygen loading in the lung and offloading in tissues.
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Affiliation(s)
- Xiaoying Zhou
- Department of High Altitude Physiology and Pathology, College of High Altitude Military Medicine, Army Medical University, Chongqing, China
- High Altitude Medical Research Center, PLA, Chongqing, China
- Key Laboratory of High Altitude and Frigidzone Medical Surpport, PLA, Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education, Chongqing, China
| | - Wenting Su
- Department of High Altitude Physiology and Pathology, College of High Altitude Military Medicine, Army Medical University, Chongqing, China
- High Altitude Medical Research Center, PLA, Chongqing, China
- Key Laboratory of High Altitude and Frigidzone Medical Surpport, PLA, Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education, Chongqing, China
| | - Quanwei Bao
- Department of Emergency Medicine, Xinqiao Hospital, Army Medical University, Chongqing, China
| | - Yu Cui
- Department of High Altitude Physiology and Pathology, College of High Altitude Military Medicine, Army Medical University, Chongqing, China
- High Altitude Medical Research Center, PLA, Chongqing, China
- Key Laboratory of High Altitude and Frigidzone Medical Surpport, PLA, Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education, Chongqing, China
| | - Xiaoxu Li
- Department of High Altitude Physiology and Pathology, College of High Altitude Military Medicine, Army Medical University, Chongqing, China
- High Altitude Medical Research Center, PLA, Chongqing, China
- Key Laboratory of High Altitude and Frigidzone Medical Surpport, PLA, Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education, Chongqing, China
| | - Yidong Yang
- Department of High Altitude Physiology and Pathology, College of High Altitude Military Medicine, Army Medical University, Chongqing, China
- High Altitude Medical Research Center, PLA, Chongqing, China
- Key Laboratory of High Altitude and Frigidzone Medical Surpport, PLA, Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education, Chongqing, China
| | - Chengzhong Yang
- Department of High Altitude Physiology and Pathology, College of High Altitude Military Medicine, Army Medical University, Chongqing, China
- High Altitude Medical Research Center, PLA, Chongqing, China
- Key Laboratory of High Altitude and Frigidzone Medical Surpport, PLA, Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education, Chongqing, China
| | - Chengyuan Wang
- Department of High Altitude Physiology and Pathology, College of High Altitude Military Medicine, Army Medical University, Chongqing, China
- High Altitude Medical Research Center, PLA, Chongqing, China
- Key Laboratory of High Altitude and Frigidzone Medical Surpport, PLA, Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education, Chongqing, China
| | - Li Jiao
- Department of High Altitude Physiology and Pathology, College of High Altitude Military Medicine, Army Medical University, Chongqing, China
- High Altitude Medical Research Center, PLA, Chongqing, China
- Key Laboratory of High Altitude and Frigidzone Medical Surpport, PLA, Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education, Chongqing, China
| | - Dewei Chen
- Department of High Altitude Physiology and Pathology, College of High Altitude Military Medicine, Army Medical University, Chongqing, China
- High Altitude Medical Research Center, PLA, Chongqing, China
- Key Laboratory of High Altitude and Frigidzone Medical Surpport, PLA, Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education, Chongqing, China
| | - Jian Huang
- Department of High Altitude Physiology and Pathology, College of High Altitude Military Medicine, Army Medical University, Chongqing, China
- High Altitude Medical Research Center, PLA, Chongqing, China
- Key Laboratory of High Altitude and Frigidzone Medical Surpport, PLA, Chongqing, China
- Key Laboratory of Extreme Environmental Medicine, Ministry of Education, Chongqing, China
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Ponganis PJ, Williams CL, Kendall-Bar JM. Blood oxygen transport and depletion in diving emperor penguins. J Exp Biol 2024; 227:jeb246832. [PMID: 38390686 PMCID: PMC11006389 DOI: 10.1242/jeb.246832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Accepted: 02/06/2024] [Indexed: 02/24/2024]
Abstract
Oxygen store management underlies dive performance and is dependent on the slow heart rate and peripheral vasoconstriction of the dive response to control tissue blood flow and oxygen uptake. Prior research has revealed two major patterns of muscle myoglobin saturation profiles during dives of emperor penguins. In Type A profiles, myoglobin desaturated rapidly, consistent with minimal muscle blood flow and low tissue oxygen uptake. Type B profiles, with fluctuating and slower declines in myoglobin saturation, were consistent with variable tissue blood flow patterns and tissue oxygen uptake during dives. We examined arterial and venous blood oxygen profiles to evaluate blood oxygen extraction and found two primary patterns of venous hemoglobin desaturation that complemented corresponding myoglobin saturation profiles. Type A venous profiles had a hemoglobin saturation that (a) increased/plateaued for most of a dive's duration, (b) only declined during the latter stages of ascent, and (c) often became arterialized [arterio-venous (a-v) shunting]. In Type B venous profiles, variable but progressive hemoglobin desaturation profiles were interrupted by inflections in the profile that were consistent with fluctuating tissue blood flow and oxygen uptake. End-of-dive saturation of arterial and Type A venous hemoglobin saturation profiles were not significantly different, but did differ from those of Type B venous profiles. These findings provide further support that the dive response of emperor penguins is a spectrum of cardiac and vascular components (including a-v shunting) that are dependent on the nature and demands of a given dive and even of a given segment of a dive.
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Affiliation(s)
- Paul J. Ponganis
- Center for Marine Biotechnology & Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0204, USA
| | - Cassondra L. Williams
- National Marine Mammal Foundation, 2240 Shelter Island Drive, San Diego, CA 92106, USA
| | - Jessica M. Kendall-Bar
- Center for Marine Biotechnology & Biomedicine, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093-0204, USA
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Ghosh RK, Hilario E, Chang CEA, Mueller LJ, Dunn MF. Allosteric regulation of substrate channeling: Salmonella typhimurium tryptophan synthase. Front Mol Biosci 2022; 9:923042. [PMID: 36172042 PMCID: PMC9512447 DOI: 10.3389/fmolb.2022.923042] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 08/11/2022] [Indexed: 11/13/2022] Open
Abstract
The regulation of the synthesis of L-tryptophan (L-Trp) in enteric bacteria begins at the level of gene expression where the cellular concentration of L-Trp tightly controls expression of the five enzymes of the Trp operon responsible for the synthesis of L-Trp. Two of these enzymes, trpA and trpB, form an αββα bienzyme complex, designated as tryptophan synthase (TS). TS carries out the last two enzymatic processes comprising the synthesis of L-Trp. The TS α-subunits catalyze the cleavage of 3-indole D-glyceraldehyde 3′-phosphate to indole and D-glyceraldehyde 3-phosphate; the pyridoxal phosphate-requiring β-subunits catalyze a nine-step reaction sequence to replace the L-Ser hydroxyl by indole giving L-Trp and a water molecule. Within αβ dimeric units of the αββα bienzyme complex, the common intermediate indole is channeled from the α site to the β site via an interconnecting 25 Å-long tunnel. The TS system provides an unusual example of allosteric control wherein the structures of the nine different covalent intermediates along the β-reaction catalytic path and substrate binding to the α-site provide the allosteric triggers for switching the αββα system between the open (T) and closed (R) allosteric states. This triggering provides a linkage that couples the allosteric conformational coordinate to the covalent chemical reaction coordinates at the α- and β-sites. This coupling drives the α- and β-sites between T and R conformations to achieve regulation of substrate binding and/or product release, modulation of the α- and β-site catalytic activities, prevention of indole escape from the confines of the active sites and the interconnecting tunnel, and synchronization of the α- and β-site catalytic activities. Here we review recent advances in the understanding of the relationships between structure, function, and allosteric regulation of the complex found in Salmonella typhimurium.
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Affiliation(s)
- Rittik K. Ghosh
- Department of Biochemistry, University of California, Riverside, Riverside, CA, United States
| | - Eduardo Hilario
- Department of Chemistry, University of California, Riverside, Riverside, CA, United States
| | - Chia-en A. Chang
- Department of Chemistry, University of California, Riverside, Riverside, CA, United States
| | - Leonard J. Mueller
- Department of Chemistry, University of California, Riverside, Riverside, CA, United States
- *Correspondence: Leonard J. Mueller, ; Michael F. Dunn,
| | - Michael F. Dunn
- Department of Biochemistry, University of California, Riverside, Riverside, CA, United States
- *Correspondence: Leonard J. Mueller, ; Michael F. Dunn,
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Soulsbury CD, Dobson J, Deeming DC, Minias P. Energetic Lifestyle Drives Size and Shape of Avian Erythrocytes. Integr Comp Biol 2021; 62:71-80. [PMID: 34581789 PMCID: PMC9375138 DOI: 10.1093/icb/icab195] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The size and shape of red blood cells (erythrocytes) is determined by key life history strategies in vertebrates. They have a fundamental role to deliver oxygen to tissues, and their ability to do so is shaped by the tissue's need and their shape. Despite considerable interest in how other components of blood are shaped by ecology and life history, few studies have considered erythrocytes themselves. We tested how erythrocyte size and shape varied in relation to energetically demanding activities using a dataset of 631 bird species. We found that in general, birds undergoing greater activities such as long distance migration had smaller and more elongated cells, while those with greater male-male competition had smaller and rounder cells. Smaller, more elongated erythrocytes allow more rapid oxygenation/deoxygenation and support greater aerobic activity. The rounder erythrocytes found in species with strong male–male competition may stem from younger erythrocytes deriving from androgen-induced erythropoiesis rates. Finally, diving species of bird had larger erythrocytes, indicating that erythrocytes are acting as a vital oxygen store. In summary, erythrocyte size and shape in birds are driven by the need to deliver oxygen during energetically costly activities.
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Affiliation(s)
- Carl D Soulsbury
- School of Life Sciences, University of Lincoln, Brayford Pool, Lincoln, LN6 7TS
| | - Jessica Dobson
- School of Life Sciences, University of Lincoln, Brayford Pool, Lincoln, LN6 7TS
| | - D Charles Deeming
- School of Life Sciences, University of Lincoln, Brayford Pool, Lincoln, LN6 7TS
| | - Piotr Minias
- Department of Biodiversity Studies and Bioeducation, Faculty of Biology and Environmental Protection, University of Łódź, Łódź, Poland
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