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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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Abstract
Fetal hemoglobin (HbF), the predominant hemoglobin in the fetus, is a mixture of two molecular species (alpha(2)(G)gamma(2) and alpha(2)(A)gamma(2)) that differ only at position 136 reflecting the products of two nonallelic gamma-globin genes. At the time of birth, HbF accounts for approximately 70% of the total Hb. The (G)gamma:(A)gamma globin ratio in the HbF of normal newborn is 70:30 whereas in the trace amounts of HbF that is found in the adult it reverses to 40:60 because of a gamma- to beta-globin gene switch. Alterations of these ratios are indicative of a molecular defect at the level of the HbF synthesis. Qualitative hemoglobinopathies due to (G)gamma and (A)gamma chain structural variants, and quantitative hemoglobinopathies affecting the synthesis of HbF such as gamma-thalassemias, duplications, triplications, and even sextuplications of the gamma-globin genes, which may be detected in newborn blood lysates, have been described. Moreover, several pathological and nonpathological conditions affecting the beta-globin gene cluster, such as beta-thalassemia, sickle cell disease, deltabeta-thalassemia, and hereditary persistence of HbF syndromes, are characterized by the continued synthesis of gamma-globin chains in the adult life. Studies of these natural mutants associated with increased synthesis of HbF in adult life have provided considerable insight into the understanding of the control of globin gene expression and Hb switching.
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Affiliation(s)
- Laura Manca
- Department of Physiological, Biochemical and Cell Sciences, University of Sassari, Sassari, Italy
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