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Piknova B, Park JW, Tunau-Spencer KJ, Jenkins A, Hellinga DG, Walter PJ, Cai H, Schechter AN. Skeletal Muscle, Skin, and Bone as Three Major Nitrate Reservoirs in Mammals: Chemiluminescence and 15N-Tracer Studies in Yorkshire Pigs. Nutrients 2024; 16:2674. [PMID: 39203815 PMCID: PMC11357542 DOI: 10.3390/nu16162674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2024] [Revised: 07/31/2024] [Accepted: 08/08/2024] [Indexed: 09/03/2024] Open
Abstract
In mammals, nitric oxide (NO) is generated either by the nitric oxide synthase (NOS) enzymes from arginine or by the reduction of nitrate to nitrite by tissue xanthine oxidoreductase (XOR) and the microbiome and further reducing nitrite to NO by XOR or several heme proteins. Previously, we reported that skeletal muscle acts as a large nitrate reservoir in mammals, and this nitrate reservoir is systemically, as well as locally, used to generate nitrite and NO. Here, we report identifying two additional nitrate storage organs-bone and skin. We used bolus of ingested 15N-labeled nitrate to trace its short-term fluxes and distribution among organs. At baseline conditions, the nitrate concentration in femur bone samples was 96 ± 63 nmol/g, scalp skin 56 ± 22 nmol/g, with gluteus muscle at 57 ± 39 nmol/g. In comparison, plasma and liver contained 34 ± 19 nmol/g and 15 ± 5 nmol/g of nitrate, respectively. Three hours after 15N-nitrate ingestion, its concentration significantly increased in all organs, exceeding the baseline levels in plasma, skin, bone, skeletal muscle, and in liver 5-, 2.4-, 2.4-, 2.1-, and 2-fold, respectively. As expected, nitrate reduction into nitrite was highest in liver but also substantial in skin and skeletal muscle, followed by the distribution of 15N-labeled nitrite. We believe that these results underline the major roles played by skeletal muscle, skin, and bone, the three largest organs in mammals, in maintaining NO homeostasis, especially via the nitrate-nitrite-NO pathway.
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Affiliation(s)
- Barbora Piknova
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), Bethesda, MD 20892, USA
| | - Ji Won Park
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), Bethesda, MD 20892, USA
| | - Khalid J. Tunau-Spencer
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), Bethesda, MD 20892, USA
| | - Audrey Jenkins
- MedStar Health Research Institute, Washington, DC 20010, USA
| | | | - Peter J. Walter
- Clinical Mass Spectrometry Core, National Institutes of Health (NIH), Bethesda, MD 20892, USA
| | - Hongyi Cai
- Clinical Mass Spectrometry Core, National Institutes of Health (NIH), Bethesda, MD 20892, USA
| | - Alan N. Schechter
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health (NIH), Bethesda, MD 20892, USA
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Upanan S, Lee J, Tunau-Spencer KJ, Rajvanshi PK, Wright EC, Noguchi CT, Schechter AN. High nitrate levels in skeletal muscle contribute to nitric oxide generation via a nitrate/nitrite reductive pathway in mice that lack the nNOS enzyme. Front Physiol 2024; 15:1352242. [PMID: 38784116 PMCID: PMC11112080 DOI: 10.3389/fphys.2024.1352242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Accepted: 04/05/2024] [Indexed: 05/25/2024] Open
Abstract
Introduction Nitric oxide (NO) is a vasodilator gas that plays a critical role in mitochondrial respiration and skeletal muscle function. NO is endogenously generated by NO synthases: neuronal NO synthase (nNOS), endothelial NO synthase (eNOS), or inducible NO synthase (iNOS). NO in skeletal muscle is partly generated by nNOS, and nNOS deficiency can contribute to muscular dystrophic diseases. However, we and others discovered an alternative nitrate/nitrite reductive pathway for NO generation: nitrate to nitrite to NO. We hypothesized that nitrate supplementation would increase nitrate accumulation in skeletal muscle and promote a nitrate/nitrite reductive pathway for NO production to compensate for the loss of nNOS in skeletal muscle. Methods Wild-type (WT) and genetic nNOS knockout (nNOS-/-) mice were fed normal chow (386.9 nmol/g nitrate) and subjected to three treatments: high-nitrate water (1 g/L sodium nitrate for 7 days), low-nitrate diet (46.8 nmol/g nitrate for 7 days), and low-nitrate diet followed by high-nitrate water for 7 days each. Results High-nitrate water supplementation exhibited a greater and more significant increase in nitrate levels in skeletal muscle and blood in nNOS-/- mice than in WT mice. A low-nitrate diet decreased blood nitrate and nitrite levels in both WT and nNOS-/- mice. WT and nNOS-/- mice, treated with low-nitrate diet, followed by high-nitrate water supplementation, showed a significant increase in nitrate levels in skeletal muscle and blood, analogous to the increases observed in nNOS-/- mice supplemented with high-nitrate water. In skeletal muscle of nNOS-/- mice on high-nitrate water supplementation, on low-nitrate diet, and in low-high nitrate treatment, the loss of nNOS resulted in a corresponding increase in the expression of nitrate/nitrite reductive pathway-associated nitrate transporters [sialin and chloride channel 1 (CLC1)] and nitrate/nitrite reductase [xanthine oxidoreductase (XOR)] but did not show a compensatory increase in iNOS or eNOS protein and eNOS activation activity [p-eNOS (Ser1177)]. Discussion These findings suggest that a greater increase in nitrate levels in skeletal muscle of nNOS-/- mice on nitrate supplementation results from reductive processes to increase NO production with the loss of nNOS in skeletal muscle.
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Affiliation(s)
- Supranee Upanan
- Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Jeeyoung Lee
- Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Khalid J. Tunau-Spencer
- Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Praveen K. Rajvanshi
- Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Elizabeth C. Wright
- Office of the Director, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Constance T. Noguchi
- Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
| | - Alan N. Schechter
- Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States
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Zoladz JA, Grandys M, Smeda M, Kij A, Kurpinska A, Kwiatkowski G, Karasinski J, Hendgen-Cotta U, Chlopicki S, Majerczak J. Myoglobin deficiency impairs maximal oxygen uptake and exercise performance: a lesson from Mb -/- mice. J Physiol 2024; 602:855-873. [PMID: 38376957 DOI: 10.1113/jp285067] [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: 05/29/2023] [Accepted: 01/19/2024] [Indexed: 02/22/2024] Open
Abstract
Myoglobin (Mb) plays an important role at rest and during exercise as a reservoir of oxygen and has been suggested to regulate NO• bioavailability under hypoxic/acidic conditions. However, its ultimate role during exercise is still a subject of debate. We aimed to study the effect of Mb deficiency on maximal oxygen uptake (V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_2}\max }}$ ) and exercise performance in myoglobin knockout mice (Mb-/- ) when compared to control mice (Mb+/+ ). Furthermore, we also studied NO• bioavailability, assessed as nitrite (NO2 - ) and nitrate (NO3 - ) in the heart, locomotory muscle and in plasma, at rest and during exercise at exhaustion both in Mb-/- and in Mb+/+ mice. The mice performed maximal running incremental exercise on a treadmill with whole-body gas exchange measurements. The Mb-/- mice had lower body mass, heart and hind limb muscle mass (P < 0.001). Mb-/- mice had significantly reduced maximal running performance (P < 0.001).V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_2}\max }}$ expressed in ml min-1 in Mb-/ - mice was 37% lower than in Mb+/+ mice (P < 0.001) and 13% lower when expressed in ml min-1 kg body mass-1 (P = 0.001). Additionally, Mb-/- mice had significantly lower plasma, heart and locomotory muscle NO2 - levels at rest. During exercise NO2 - increased significantly in the heart and locomotory muscles of Mb-/- and Mb+/+ mice, whereas no significant changes in NO2 - were found in plasma. Our study showed that, contrary to recent suggestions, Mb deficiency significantly impairsV ̇ O 2 max ${\dot V_{{{\mathrm{O}}_2}\max }}$ and maximal running performance in mice. KEY POINTS: Myoglobin knockout mice (Mb-/- ) possess lower maximal oxygen uptake (V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_2}\max }}$ ) and poorer maximal running performance than control mice (Mb+/+ ). Respiratory exchange ratio values at high running velocities in Mb-/- mice are higher than in control mice suggesting a shift in substrate utilization towards glucose metabolism in Mb-/- mice at the same running velocities. Lack of myoglobin lowers basal systemic and muscle NO• bioavailability, but does not affect exercise-induced NO2 - changes in plasma, heart and locomotory muscles. The present study demonstrates that myoglobin is of vital importance forV ̇ O 2 max ${\dot V_{{{\mathrm{O}}_2}\max }}$ and maximal running performance as well as explains why previous studies have failed to prove such a role of myoglobin when using the Mb-/- mouse model.
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Affiliation(s)
- Jerzy A Zoladz
- Chair of Exercise Physiology and Muscle Bioenergetics, Faculty of Health Sciences, Jagiellonian University Medical College, Krakow, Poland
| | - Marcin Grandys
- Chair of Exercise Physiology and Muscle Bioenergetics, Faculty of Health Sciences, Jagiellonian University Medical College, Krakow, Poland
| | - Marta Smeda
- Jagiellonian Centre for Experimental Therapeutics (JCET), Jagiellonian University, Krakow, Poland
| | - Agnieszka Kij
- Jagiellonian Centre for Experimental Therapeutics (JCET), Jagiellonian University, Krakow, Poland
| | - Anna Kurpinska
- Jagiellonian Centre for Experimental Therapeutics (JCET), Jagiellonian University, Krakow, Poland
| | - Grzegorz Kwiatkowski
- Jagiellonian Centre for Experimental Therapeutics (JCET), Jagiellonian University, Krakow, Poland
| | - Janusz Karasinski
- Department of Cell Biology and Imaging, Institute of Zoology and Biomedical Research, Jagiellonian University, Krakow, Poland
| | - Ulrike Hendgen-Cotta
- Cardiology and Vascular Medicine, West German Heart and Vascular Center, University Hospital Essen, Medical Faculty, University of Duisburg-Essen, Essen, Germany
| | - Stefan Chlopicki
- Jagiellonian Centre for Experimental Therapeutics (JCET), Jagiellonian University, Krakow, Poland
- Department of Experimental Pharmacology, Chair of Pharmacology, Jagiellonian University Medical College, Krakow, Poland
| | - Joanna Majerczak
- Chair of Exercise Physiology and Muscle Bioenergetics, Faculty of Health Sciences, Jagiellonian University Medical College, Krakow, Poland
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Majerczak J, Drzymala‐Celichowska H, Grandys M, Kij A, Kus K, Celichowski J, Krysciak K, Molik WA, Szkutnik Z, Zoladz JA. Exercise Training Decreases Nitrite Concentration in the Heart and Locomotory Muscles of Rats Without Changing the Muscle Nitrate Content. J Am Heart Assoc 2024; 13:e031085. [PMID: 38214271 PMCID: PMC10926815 DOI: 10.1161/jaha.123.031085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Accepted: 11/20/2023] [Indexed: 01/13/2024]
Abstract
BACKGROUND Skeletal muscles are postulated to be a potent regulator of systemic nitric oxide homeostasis. In this study, we aimed to evaluate the impact of physical training on the heart and skeletal muscle nitric oxide bioavailability (judged on the basis of intramuscular nitrite and nitrate) in rats. METHODS AND RESULTS Rats were trained on a treadmill for 8 weeks, performing mainly endurance running sessions with some sprinting runs. Muscle nitrite (NO2-) and nitrate (NO3-) concentrations were measured using a high-performance liquid chromatography-based method, while amino acids, pyruvate, lactate, and reduced and oxidized glutathione were determined using a liquid chromatography coupled with tandem mass spectrometry technique. The content of muscle nitrite reductases (electron transport chain proteins, myoglobin, and xanthine oxidase) was assessed by western immunoblotting. We found that 8 weeks of endurance training decreased basal NO2- in the locomotory muscles and in the heart, without changes in the basal NO3-. In the slow-twitch oxidative soleus muscle, the decrease in NO2- was already present after the first week of training, and the content of nitrite reductases remained unchanged throughout the entire period of training, except for the electron transport chain protein content, which increased no sooner than after 8 weeks of training. CONCLUSIONS Muscle NO2- level, opposed to NO3-, decreases in the time course of training. This effect is rapid and already visible in the slow-oxidative soleus after the first week of training. The underlying mechanisms of training-induced muscle NO2- decrease may involve an increase in the oxidative stress, as well as metabolite changes related to an increased muscle anaerobic glycolytic activity contributing to (1) direct chemical reduction of NO2- or (2) activation of muscle nitrite reductases.
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Affiliation(s)
- Joanna Majerczak
- Chair of Exercise Physiology and Muscle Bioenergetics, Faculty of Health SciencesJagiellonian University Medical CollegeKrakowPoland
| | - Hanna Drzymala‐Celichowska
- Department of Neurobiology, Faculty of Health SciencesPoznan University of Physical EducationPoznanPoland
- Department of Physiology and Biochemistry, Faculty of Health SciencesPoznan University of Physical EducationPoznanPoland
| | - Marcin Grandys
- Chair of Exercise Physiology and Muscle Bioenergetics, Faculty of Health SciencesJagiellonian University Medical CollegeKrakowPoland
| | - Agnieszka Kij
- Jagiellonian Centre for Experimental Therapeutics (JCET)Jagiellonian UniversityKrakowPoland
| | - Kamil Kus
- Jagiellonian Centre for Experimental Therapeutics (JCET)Jagiellonian UniversityKrakowPoland
| | - Jan Celichowski
- Department of Neurobiology, Faculty of Health SciencesPoznan University of Physical EducationPoznanPoland
| | - Katarzyna Krysciak
- Department of Neurobiology, Faculty of Health SciencesPoznan University of Physical EducationPoznanPoland
| | - Weronika A. Molik
- Chair of Exercise Physiology and Muscle Bioenergetics, Faculty of Health SciencesJagiellonian University Medical CollegeKrakowPoland
- University of FloridaGainesvilleFLUSA
| | | | - Jerzy A. Zoladz
- Chair of Exercise Physiology and Muscle Bioenergetics, Faculty of Health SciencesJagiellonian University Medical CollegeKrakowPoland
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Tan R, Baranauskas MN, Karl ST, Ortiz de Zevallos J, Shei RJ, Paris HL, Wiggins CC, Bailey SJ. Effects of dietary nitrate supplementation on peak power output: Influence of supplementation strategy and population. Nitric Oxide 2023; 138-139:105-119. [PMID: 37438201 DOI: 10.1016/j.niox.2023.06.004] [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: 07/14/2023]
Abstract
Increasing evidence indicates that dietary nitrate supplementation has the potential to increase muscular power output during skeletal muscle contractions. However, there is still a paucity of data characterizing the impact of different nitrate dosing regimens on nitric oxide bioavailability and its potential ergogenic effects across various population groups. This review discusses the potential influence of different dietary nitrate supplementation strategies on nitric oxide bioavailability and muscular peak power output in healthy adults, athletes, older adults and some clinical populations. Effect sizes were calculated for peak power output and absolute and/or relative nitrate doses were considered where applicable. There was no relationship between the effect sizes of peak power output change following nitrate supplementation and when nitrate dosage when considered in absolute or relative terms. Areas for further research are also recommended including a focus on nitrate dosing regimens that optimize nitric oxide bioavailability for enhancing peak power at times of increased muscular work in a variety of healthy and disease populations.
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Affiliation(s)
- Rachel Tan
- Department of Sports Medicine, Pepperdine University, Malibu, CA, 90263, USA.
| | - Marissa N Baranauskas
- Department of Human Physiology & Nutrition, University of Colorado, Colorado Springs, CO, 80918, USA
| | - Sean T Karl
- Department of Sports Medicine, Pepperdine University, Malibu, CA, 90263, USA
| | | | - Ren-Jay Shei
- Indiana University Alumni Association, Indiana University, Bloomington, IN, 47408, USA
| | - Hunter L Paris
- Department of Sports Medicine, Pepperdine University, Malibu, CA, 90263, USA
| | - Chad C Wiggins
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, USA
| | - Stephen J Bailey
- School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, LE11 3TU, UK
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6
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Piknova B, Park JW, Thomas SM, Tunau-Spencer KJ, Schechter AN. Nitrate and Nitrite Metabolism in Aging Rats: A Comparative Study. Nutrients 2023; 15:nu15112490. [PMID: 37299453 DOI: 10.3390/nu15112490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 05/19/2023] [Accepted: 05/24/2023] [Indexed: 06/12/2023] Open
Abstract
Nitric oxide (NO) (co)regulates many physiological processes in the body. Its short-lived free radicals force synthesis in situ and on-demand, without storage possibility. Local oxygen availability determines the origin of NO-either by synthesis by nitric oxide synthases (NOS) or by the reduction of nitrate to nitrite to NO by nitrate/nitrite reductases. The existence of nitrate reservoirs, mainly in skeletal muscle, assures the local and systemic availability of NO. Aging is accompanied by changes in metabolic pathways, leading to a decrease in NO availability. We explored age-related changes in various rat organs and tissues. We found differences in nitrate and nitrite contents in tissues of old and young rats at baseline levels, with nitrate levels being generally higher and nitrite levels being generally lower in old rats. However, there were no differences in the levels of nitrate-transporting proteins and nitrate reductase between old and young rats, with the exception of in the eye. Increased dietary nitrate led to significantly higher nitrate enrichment in the majority of old rat organs compared to young rats, suggesting that the nitrate reduction pathway is not affected by aging. We hypothesize that age-related NO accessibility changes originate either from the NOS pathway or from changes in NO downstream signaling (sGC/PDE5). Both possibilities need further investigation.
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Affiliation(s)
- Barbora Piknova
- Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health, Bethesda, MD 20892, USA
| | - Ji Won Park
- Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health, Bethesda, MD 20892, USA
| | - Samantha M Thomas
- Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health, Bethesda, MD 20892, USA
| | - Khalid J Tunau-Spencer
- Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health, Bethesda, MD 20892, USA
| | - Alan N Schechter
- Molecular Medicine Branch, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), National Institutes of Health, Bethesda, MD 20892, USA
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7
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Tan R, Baranauskas MN, Karl ST, Ortiz de Zevallos J, Shei RJ, Paris HL, Wiggins CC, Bailey SJ. Effects of dietary nitrate supplementation on muscular power output: Influence of supplementation strategy and population. Nitric Oxide 2023:S1089-8603(23)00047-2. [PMID: 37244391 DOI: 10.1016/j.niox.2023.05.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Accepted: 05/18/2023] [Indexed: 05/29/2023]
Abstract
Increasing evidence indicates that dietary nitrate supplementation has the potential to increase muscular power output during skeletal muscle contractions. However, there is still a paucity of data characterizing the impact of different nitrate dosing regimens on nitric oxide bioavailability its potential ergogenic effects across various population groups. This narrative review discusses the potential influence of different dietary nitrate supplementation strategies on nitric oxide bioavailability and muscular power output in healthy adults, athletes, older adults and some clinical populations. Areas for further research are also recommended including a focus individualized nitrate dosing regimens to optimize nitric oxide bioavailability and to promote muscular power enhancements in different populations.
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Affiliation(s)
- Rachel Tan
- Department of Sports Medicine, Pepperdine University, Malibu, CA, 90263, USA.
| | - Marissa N Baranauskas
- Department of Human Physiology & Nutrition, University of Colorado, Colorado Springs, CO, 80918, USA
| | - Sean T Karl
- Department of Sports Medicine, Pepperdine University, Malibu, CA, 90263, USA
| | | | - Ren-Jay Shei
- Indiana University Alumni Association, Indiana University, Bloomington, IN, 47408, USA
| | - Hunter L Paris
- Department of Sports Medicine, Pepperdine University, Malibu, CA, 90263, USA
| | - Chad C Wiggins
- Department of Anesthesiology and Perioperative Medicine, Mayo Clinic, Rochester, MN, USA
| | - Stephen J Bailey
- School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, LE11 3TU, UK
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Liubertas T, Poderys JL, Zigmantaite V, Viskelis P, Kucinskas A, Grigaleviciute R, Jurevicius J, Urbonaviciene D. The Effect of Potassium Nitrate Supplementation on the Force and Properties of Extensor digitorum longus (EDL) Muscles in Mice. Nutrients 2023; 15:nu15061489. [PMID: 36986219 PMCID: PMC10057731 DOI: 10.3390/nu15061489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Revised: 03/16/2023] [Accepted: 03/17/2023] [Indexed: 03/22/2023] Open
Abstract
Adding potassium nitrate (KNO3) to the diet improves the physiological properties of mammalian muscles (rebuilds weakened muscle, improves structure and functionality). The aim of this study was to investigate the effect of KNO3 supplementation in a mouse model. BALB/c mice were fed a KNO3 diet for three weeks, followed by a normal diet without nitrates. After the feeding period, the Extensor digitorum longus (EDL) muscle was evaluated ex vivo for contraction force and fatigue. To evaluate the possible pathological changes, the histology of EDL tissues was performed in control and KNO3-fed groups after 21 days. The histological analysis showed an absence of negative effects in EDL muscles. We also analyzed 15 biochemical blood parameters. After 21 days of KNO3 supplementation, the EDL mass was, on average, 13% larger in the experimental group compared to the controls (p < 0.05). The muscle-specific force increased by 38% in comparison with the control group (p < 0.05). The results indicate that KNO3 has effects in an experimental mouse model, showing nitrate-diet-induced muscle strength. This study contributes to a better understanding of the molecular changes in muscles following nutritional intervention and may help develop strategies and products designated to treat muscle-related issues.
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Affiliation(s)
- Tomas Liubertas
- Department of Coaching Science, Lithuanian Sports University, 44221 Kaunas, Lithuania
- Correspondence: ; Tel.: +370-6126-6664
| | - Jonas Liudas Poderys
- Department of Coaching Science, Lithuanian Sports University, 44221 Kaunas, Lithuania
| | - Vilma Zigmantaite
- Biological Research Centre, Lithuanian University of Health Science, 47181 Kaunas, Lithuania
| | - Pranas Viskelis
- Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry, 54333 Babtai, Lithuania
| | - Audrius Kucinskas
- Biological Research Centre, Lithuanian University of Health Science, 47181 Kaunas, Lithuania
| | - Ramune Grigaleviciute
- Biological Research Centre, Lithuanian University of Health Science, 47181 Kaunas, Lithuania
| | - Jonas Jurevicius
- Institute of Cardiology, Membrane Biophysics Laboratory, Lithuanian University of Health Sciences, 50162 Kaunas, Lithuania
| | - Dalia Urbonaviciene
- Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry, 54333 Babtai, Lithuania
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9
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Yousefzadeh N, Jeddi S, Zarkesh M, Kashfi K, Ghasemi A. Altered sialin mRNA gene expression in type 2 diabetic male Wistar rats: implications for nitric oxide deficiency. Sci Rep 2023; 13:4013. [PMID: 36899088 PMCID: PMC10006425 DOI: 10.1038/s41598-023-31240-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Accepted: 03/08/2023] [Indexed: 03/12/2023] Open
Abstract
Nitrate therapy has been suggested to boost nitric oxide (NO) levels in type 2 diabetes (T2D); however, little is known about nitrate transport across the membranes. This study aimed to assess changes in the mRNA expression of sialin, as a nitrate transporter, in the main tissues of rats with T2D. Rats were divided into two groups (n = 6/group): Control and T2D. A high-fat diet combined with a low dose of streptozotocin (STZ, 30 mg/kg) was used to induce T2D. At month 6, samples from the main tissues of rats were used to measure the mRNA expression of sialin and levels of NO metabolites. Rats with T2D had lower nitrate levels in the soleus muscle (66%), lung (48%), kidney (43%), aorta (30%), adrenal gland (58%), epididymal adipose tissue (eAT) (61%), and heart (37%) and had lower nitrite levels in the pancreas (47%), kidney (42%), aorta (33%), liver (28%), eAT (34%), and heart (32%). The order of sialin gene expression in control rats was: soleus muscle > kidney > pancreas > lung > liver > adrenal gland > brain > eAT > intestine > stomach > aorta > heart. Compared to controls, rats with T2D had higher sialin mRNA expressions in the stomach (2.1), eAT (2.0), adrenal gland (1.7), liver (8.9), and soleus muscle (3.4), and lower sialin expression in the intestine (0.56), pancreas (0.42), and kidney (0.44), all P values < 0.05. These findings indicate altered sialin mRNA expression in the main tissues of male T2D rats and may have implications for future NO-based treatment of T2D.
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Affiliation(s)
- Nasibeh Yousefzadeh
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, No. 24, Arabi Street, Daneshjoo Blvd, Velenjak, P.O. Box 19395-4763, Tehran, Iran
| | - Sajad Jeddi
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, No. 24, Arabi Street, Daneshjoo Blvd, Velenjak, P.O. Box 19395-4763, Tehran, Iran
| | - Maryam Zarkesh
- Cellular and Molecular Endocrine Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Khosrow Kashfi
- Department of Molecular, Cellular, and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, New York, NY, USA
| | - Asghar Ghasemi
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, No. 24, Arabi Street, Daneshjoo Blvd, Velenjak, P.O. Box 19395-4763, Tehran, Iran.
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10
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Dietary nitrate supplementation increases nitrate and nitrite concentrations in human skin interstitial fluid. Nitric Oxide 2023; 134-135:10-16. [PMID: 36889537 DOI: 10.1016/j.niox.2023.02.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 02/17/2023] [Accepted: 02/27/2023] [Indexed: 03/08/2023]
Abstract
Acute dietary nitrate (NO3-) supplementation can increase [NO3-], but not nitrite ([NO2-]), in human skeletal muscle, though its effect on [NO3-] and [NO2-] in skin remains unknown. In an independent group design, 11 young adults ingested 140 mL of NO3--rich beetroot juice (BR; 9.6 mmol NO3-), and 6 young adults ingested 140 mL of a NO3--depleted placebo (PL). Skin dialysate, acquired through intradermal microdialysis, and venous blood samples were collected at baseline and every hour post-ingestion up to 4 h to assess dialysate and plasma [NO3-] and [NO2-]. The relative recovery rate of NO3- and NO2- through the microdialysis probe (73.1% and 62.8%), determined in a separate experiment, was used to estimate skin interstitial [NO3-] and [NO2-]. Baseline [NO3-] was lower, whereas baseline [NO2-] was higher in the skin interstitial fluid relative to plasma (both P < 0.001). Acute BR ingestion increased [NO3-] and [NO2-] in the skin interstitial fluid and plasma (all P < 0.001), with the magnitude being smaller in the skin interstitial fluid (e.g., 183 ± 54 vs. 491 ± 62 μM for Δ[NO3-] from baseline and 155 ± 190 vs. 217 ± 204 nM for Δ[NO2-] from baseline at 3 h post BR ingestion, both P ≤ 0.037). However, due to the aforementioned baseline differences, skin interstitial fluid [NO2-] post BR ingestion was higher, whereas [NO3-] was lower relative to plasma (all P < 0.001). These findings extend our understanding of NO3- and NO2- distribution at rest and indicate that acute BR supplementation increases [NO3-] and [NO2-] in human skin interstitial fluid.
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Distribution of dietary nitrate and its metabolites in rat tissues after 15N-labeled nitrate administration. Sci Rep 2023; 13:3499. [PMID: 36859526 PMCID: PMC9977953 DOI: 10.1038/s41598-023-28190-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 01/13/2023] [Indexed: 03/03/2023] Open
Abstract
The reduction pathway of nitrate (NO3-) and nitrite (NO2-) to nitric oxide (NO) contributes to regulating many physiological processes. To examine the rate and extent of dietary nitrate absorption and its reduction to nitrite, we supplemented rat diets with Na15NO3-containing water (1 g/L) and collected plasma, urine and several tissue samples. We found that plasma and urine showed 8.8- and 11.7-fold increases respectively in total nitrate concentrations in 1-day supplementation group compared to control. In tissue samples-gluteus, liver and eyes-we found 1.7-, 2.4- and 4.2-fold increases respectively in 1-day supplementation group. These increases remained similar in 3-day supplementation group. LC-MS/MS analysis showed that the augmented nitrate concentrations were primarily from the exogenously provided 15N-nitrate. Overall nitrite concentrations and percent of 15N-nitrite were also greatly increased in all samples after nitrate supplementation; eye homogenates showed larger increases compared to gluteus and liver. Moreover, genes related to nitrate transport and reduction (Sialin, CLC and XOR) were upregulated after nitrate supplementation for 3 days in muscle (Sialin 2.3-, CLC1 1.3-, CLC3 2.1-, XOR 2.4-fold) and eye (XOR 1.7-fold) homogenates. These results demonstrate that dietary nitrate is quickly absorbed into circulation and tissues, and it can be reduced to nitrite in tissues (and likely to NO) suggesting that nitrate-enriched diets can be an efficient intervention to enhance nitrite and NO bioavailability.
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Piknova B, Woessner MN, de Zevallos JO, Kraus WE, VanBruggen MD, Schechter AN, Allen JD. Human skeletal muscle nitrate and nitrite in individuals with peripheral arterial disease: Effect of inorganic nitrate supplementation and exercise. Physiol Rep 2022; 10:e15531. [PMID: 36461652 PMCID: PMC9718944 DOI: 10.14814/phy2.15531] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 10/28/2022] [Accepted: 11/11/2022] [Indexed: 05/15/2023] Open
Abstract
Skeletal muscle may act as a reservoir for N-oxides following inorganic nitrate supplementation. This idea is most intriguing in individuals with peripheral artery disease (PAD) who are unable to endogenously upregulate nitric oxide. This study analyzed plasma and skeletal muscle nitrate and nitrite concentrations along with exercise performance, prior to and following 12-weeks of exercise training combined with oral inorganic nitrate supplementation (EX+BR) or placebo (EX+PL) in participants with PAD. Non-supplemented, at baseline, there were no differences in plasma and muscle nitrate. For nitrite, muscle concentration was higher than plasma (+0.10 nmol.g-1 ). After 12 -weeks, acute oral nitrate increased both plasma and muscle nitrate (455.04 and 121.14 nmol.g-1 , p < 0.01), which were correlated (r = 0.63, p < 0.01), plasma nitrate increase was greater than in muscle (p < 0.01). Nitrite increased in the plasma (1.01 nmol.g-1 , p < 0.05) but not in the muscle (0.22 nmol.g-1 ) (p < 0.05 between compartments). Peak walk time (PWT) increased in both groups (PL + 257.6 s;BR + 315.0 s). Six-minute walk (6 MW) distance increased only in the (EX+BR) group (BR + 75.4 m). We report no substantial gradient of nitrate (or nitrite) from skeletal muscle to plasma, suggesting a lack of reservoir-like function in participants with PAD. Oral nitrate supplementation produced increases in skeletal muscle nitrate, but not skeletal muscle nitrite. The related changes in nitrate concentration between plasma and muscle suggests a potential for inter-compartmental nitrate "communication". Skeletal muscle did not appear to play a role in within compartment nitrate reduction. Muscle nitrate and nitrite concentrations did not appear to contribute to exercise performance in patients with PAD.
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Affiliation(s)
- Barbora Piknova
- Molecular Medicine Branch, NIDDKNational Institutes of HealthBethesdaMarylandUSA
| | - Mary N. Woessner
- Institute for Health and Sport (IHES)Victoria UniversityMelbourneAustralia
| | - Joaquin Ortiz de Zevallos
- Department of Kinesiology, School of Health and Human DevelopmentUniversity of VirginiaCharlottesvilleVirginiaUSA
| | - William E. Kraus
- Duke Molecular Physiology Institute, Duke University School of MedicineDurhamNorth CarolinaUSA
| | - Mitch D. VanBruggen
- Duke Molecular Physiology Institute, Duke University School of MedicineDurhamNorth CarolinaUSA
| | - Alan N. Schechter
- Molecular Medicine Branch, NIDDKNational Institutes of HealthBethesdaMarylandUSA
| | - Jason D. Allen
- Department of Kinesiology, School of Health and Human DevelopmentUniversity of VirginiaCharlottesvilleVirginiaUSA
- Division of Cardiovascular Medicine, School of MedicineUniversity of VirginiaCharlottesvilleVirginiaUSA
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13
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Skeletal muscle as a reservoir for nitrate and nitrite: The role of xanthine oxidase reductase (XOR). Nitric Oxide 2022; 129:102-109. [DOI: 10.1016/j.niox.2022.10.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Revised: 09/16/2022] [Accepted: 10/20/2022] [Indexed: 11/06/2022]
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14
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Nitrite Concentration in the Striated Muscles Is Reversely Related to Myoglobin and Mitochondrial Proteins Content in Rats. Int J Mol Sci 2022; 23:ijms23052686. [PMID: 35269826 PMCID: PMC8910716 DOI: 10.3390/ijms23052686] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 02/21/2022] [Accepted: 02/27/2022] [Indexed: 12/12/2022] Open
Abstract
Skeletal muscles are an important reservoir of nitric oxide (NO•) stored in the form of nitrite [NO2−] and nitrate [NO3−] (NOx). Nitrite, which can be reduced to NO• under hypoxic and acidotic conditions, is considered a physiologically relevant, direct source of bioactive NO•. The aim of the present study was to determine the basal levels of NOx in striated muscles (including rat heart and locomotory muscles) with varied contents of tissue nitrite reductases, such as myoglobin and mitochondrial electron transport chain proteins (ETC-proteins). Muscle NOx was determined using a high-performance liquid chromatography-based method. Muscle proteins were evaluated using western-immunoblotting. We found that oxidative muscles with a higher content of ETC-proteins and myoglobin (such as the heart and slow-twitch locomotory muscles) have lower [NO2−] compared to fast-twitch muscles with a lower content of those proteins. The muscle type had no observed effect on the [NO3−]. Our results demonstrated that fast-twitch muscles possess greater potential to generate NO• via nitrite reduction than slow-twitch muscles and the heart. This property might be of special importance for fast skeletal muscles during strenuous exercise and/or hypoxia since it might support muscle blood flow via additional NO• provision (acidic/hypoxic vasodilation) and delay muscle fatigue.
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15
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Ghasemi A. Quantitative aspects of nitric oxide production from nitrate and nitrite. EXCLI JOURNAL 2022; 21:470-486. [PMID: 35391922 PMCID: PMC8983853 DOI: 10.17179/excli2022-4727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/29/2022] [Accepted: 02/02/2022] [Indexed: 11/05/2022]
Abstract
Nitric oxide (NO) is involved in many physiological and pathological processes in the human body. At least two major pathways produce NO: (1) the L-arginine-NO-oxidative pathway in which NO synthase (NOS) enzymes convert L-arginine to NO; (2) the nitrate-nitrite-NO reductive pathway in which NO is produced from the serial reduction of nitrate and nitrite. The deficiency of NO is involved in the pathophysiology of cardiometabolic disorders. Intervention with foods containing nitrate and nitrite can potentially prevent or treat some chronic diseases, including cardiovascular diseases and diabetes. A better understanding of the NO cycle would help develop effective strategies for preventing or treating the disorders in which NO homeostasis is disturbed. This review summarizes quantitative aspects of NO production, emphasizing the nitrate-nitrite-NO pathway. Available data indicates that total NO production by NOS-dependent L-arginine-NO pathway is about 1000 μmol.day-1. Of about 1700 μmol.day-1 ingested nitrate, ~25 % is extracted by the salivary glands and of which ~20 % is converted nitrite. It means that about 5 % of ingested nitrate is converted to nitrite in the oral cavity; assuming that all produced nitrite is reduced to NO in the stomach, it can be calculated that contribution of the nitrate-nitrite-NO pathway to the whole-body NO production is about 85 μmol.day-1 (1700 ×0.05=85) or approximately 100 μmol.day-1. The lower contribution of the nitrate-nitrite-NO pathway does not mean that this pathway has lower importance in the whole-body NO homeostasis. Even in the adequate L-arginine supply, NOS-dependent NO production is insufficient to meet all NO functions, and the nitrate-nitrite-NO pathway must provide the rest. In conclusion, the contribution of the nitrate-nitrite-NO pathway in the whole human body NO production is <10 %, and the nitrate-nitrite-NO pathway is complementary to the NOS-dependent NO production.
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Affiliation(s)
- Asghar Ghasemi
- Endocrine Physiology Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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16
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Poole DC, Ferguson SK, Musch TI, Porcelli S. Role of nitric oxide in convective and diffusive skeletal microvascular oxygen kinetics. Nitric Oxide 2022; 121:34-44. [PMID: 35123062 DOI: 10.1016/j.niox.2022.01.005] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 12/29/2021] [Accepted: 01/27/2022] [Indexed: 10/19/2022]
Abstract
Progress in understanding physiological mechanisms often consists of discrete discoveries made across different models and species. Accordingly, understanding the mechanistic bases for how altering nitric oxide (NO) bioavailability impacts exercise tolerance (or not) depends on integrating information from cellular energetics and contractile regulation through microvascular/vascular control of O2 transport and pulmonary gas exchange. This review adopts state-of-the-art concepts including the intramyocyte power grid, the Wagner conflation of perfusive and diffusive O2 conductances, and the Critical Power/Critical Speed model of exercise tolerance to address how altered NO bioavailability may, or may not, affect physical performance. This question is germane from the elite athlete to the recreational exerciser and particularly the burgeoning heart failure (and other clinical) populations for whom elevating O2 transport and/or exercise capacity translates directly to improved life quality and reduced morbidity and mortality. The dearth of studies in females is also highlighted, and areas of uncertainty and questions for future research are identified.
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Affiliation(s)
- David C Poole
- Departments of Kinesiology and Anatomy and Physiology, Kansas State University, Manhattan, KS, 66506, USA
| | - Scott K Ferguson
- Department of Kinesiology and Exercise Science, University of Hawaii, Hilo, HI, 96720, USA
| | - Timothy I Musch
- Departments of Kinesiology and Anatomy and Physiology, Kansas State University, Manhattan, KS, 66506, USA
| | - Simone Porcelli
- Department of Molecular Medicine, University of Pavia, Pavia, Italy.
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Kadach S, Piknova B, Black MI, Park JW, Wylie LJ, Stoyanov Z, Thomas SM, McMahon NF, Vanhatalo A, Schechter AN, Jones AM. Time course of human skeletal muscle nitrate and nitrite concentration changes following dietary nitrate ingestion. Nitric Oxide 2022; 121:1-10. [PMID: 35032643 PMCID: PMC8860874 DOI: 10.1016/j.niox.2022.01.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 01/08/2022] [Accepted: 01/10/2022] [Indexed: 12/11/2022]
Abstract
Dietary nitrate (NO3−) ingestion can be beneficial for health and exercise performance. Recently, based on animal and limited human studies, a skeletal muscle NO3− reservoir has been suggested to be important in whole body nitric oxide (NO) homeostasis. The purpose of this study was to determine the time course of changes in human skeletal muscle NO3− concentration ([NO3− ) following the ingestion of dietary NO3−. Sixteen participants were allocated to either an experimental group (NIT: n = 11) which consumed a bolus of ~1300 mg (12.8 mmol) potassium nitrate (KNO3), or a placebo group (PLA: n = 5) which consumed a bolus of potassium chloride (KCl). Biological samples (muscle (vastus lateralis), blood, saliva and urine) were collected shortly before NIT or PLA ingestion and at intervals over the course of the subsequent 24 h. At baseline, no differences were observed for muscle [NO3−] and [NO2−] between NIT and PLA (P > 0.05). In PLA, there were no changes in muscle [NO3−] or [NO2−] over time. In NIT, muscle [NO3−] was significantly elevated above baseline (54 ± 29 nmol/g) at 0.5 h, reached a peak at 3 h (181 ± 128 nmol/g), and was not different to baseline from 9 h onwards (P > 0.05). Muscle [NO2−] did not change significantly over time. Following ingestion of a bolus of dietary NO3− skeletal muscle [NO3−] increases rapidly, reaches a peak at ~3 h and subsequently declines towards baseline values. Following dietary NO3− ingestion, human m. vastus lateralis [NO3−] expressed a slightly delayed pharmacokinetic profile compared to plasma [NO3−].
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Affiliation(s)
- Stefan Kadach
- University of Exeter, College of Life and Environmental Sciences, St Luke's Campus, University of Exeter, Exeter, EX1 2LU, UK
| | - Barbora Piknova
- Molecular Medicine Branch, NIDDK, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Matthew I Black
- University of Exeter, College of Life and Environmental Sciences, St Luke's Campus, University of Exeter, Exeter, EX1 2LU, UK
| | - Ji Won Park
- Molecular Medicine Branch, NIDDK, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Lee J Wylie
- University of Exeter, College of Life and Environmental Sciences, St Luke's Campus, University of Exeter, Exeter, EX1 2LU, UK
| | - Zdravko Stoyanov
- University of Exeter, College of Life and Environmental Sciences, St Luke's Campus, University of Exeter, Exeter, EX1 2LU, UK
| | - Samantha M Thomas
- Molecular Medicine Branch, NIDDK, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Nicholas F McMahon
- University of Queensland, School of Human Movement and Nutrition Sciences, University of Queensland, St Lucia, QLD, 4072, Australia
| | - Anni Vanhatalo
- University of Exeter, College of Life and Environmental Sciences, St Luke's Campus, University of Exeter, Exeter, EX1 2LU, UK
| | - Alan N Schechter
- Molecular Medicine Branch, NIDDK, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Andrew M Jones
- University of Exeter, College of Life and Environmental Sciences, St Luke's Campus, University of Exeter, Exeter, EX1 2LU, UK.
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Lewis SE, Rosencrance CB, De Vallance E, Giromini A, Williams XM, Oh JY, Schmidt H, Straub AC, Chantler PD, Patel RP, Kelley EE. Human and rodent red blood cells do not demonstrate xanthine oxidase activity or XO-catalyzed nitrite reduction to NO. Free Radic Biol Med 2021; 174:84-88. [PMID: 34273539 PMCID: PMC9257433 DOI: 10.1016/j.freeradbiomed.2021.07.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 06/30/2021] [Accepted: 07/06/2021] [Indexed: 12/18/2022]
Abstract
A number of molybdopterin enzymes, including xanthine oxidoreductase (XOR), aldehyde oxidase (AO), sulfite oxidase (SO), and mitochondrial amidoxime reducing component (mARC), have been identified as nitrate and nitrite reductases. Of these enzymes, XOR has been the most extensively studied and reported to be a substantive source of nitric oxide (NO) under inflammatory/hypoxic conditions that limit the catalytic activity of the canonical NOS pathway. It has also been postulated that XOR nitrite reductase activity extends to red blood cell (RBCs) membranes where it has been immunohistochemically identified. These findings, when combined with countervailing reports of XOR activity in RBCs, incentivized our current study to critically evaluate XOR protein abundance/enzymatic activity in/on RBCs from human, mouse, and rat sources. Using various protein concentrations of RBC homogenates for both human and rodent samples, neither XOR protein nor enzymatic activity (xanthine → uric acid) was detectable. In addition, potential loading of RBC-associated glycosaminoglycans (GAGs) by exposing RBC preparations to purified XO before washing did not solicit detectable enzymatic activity (xanthine → uric acid) or alter NO generation profiles. To ensure these observations extended to absence of XOR-mediated contributions to overall RBC-associated nitrite reduction, we examined the nitrite reductase activity of washed and lysed RBC preparations via enhanced chemiluminescence in the presence or absence of the XOR-specific inhibitor febuxostat (Uloric®). Neither addition of inhibitor nor the presence of the XOR substrate xanthine significantly altered the rates of nitrite reduction to NO by RBC preparations from either human or rodent sources confirming the absence of XO enzymatic activity. Furthermore, examination of the influence of the age (young cells vs. old cells) of human RBCs on XO activity also failed to demonstrate detectable XO protein. Combined, these data suggest: 1) that XO does not contribute to nitrite reduction in/on human and rodent erythrocytes, 2) care should be taken to validate immuno-detectable XO by demonstrating enzymatic activity, and 3) XO does not associate with human erythrocytic glycosaminoglycans or participate in nonspecific binding.
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Affiliation(s)
- Sara E Lewis
- West Virginia University Departments of Physiology and Pharmacology, USA
| | | | - Evan De Vallance
- West Virginia University Departments of Physiology and Pharmacology, USA
| | - Andrew Giromini
- West Virginia University Departments of Physiology and Pharmacology, USA
| | - Xena M Williams
- West Virginia University Departments of Physiology and Pharmacology, USA
| | - Joo-Yeun Oh
- University of Alabama at Birmingham Center for Free Radical Biology, USA
| | - Heidi Schmidt
- University of Pittsburgh Vascular Medicine Institute, USA
| | - Adam C Straub
- University of Pittsburgh Vascular Medicine Institute, USA
| | | | - Rakesh P Patel
- University of Alabama at Birmingham Center for Free Radical Biology, USA
| | - Eric E Kelley
- West Virginia University Departments of Physiology and Pharmacology, USA.
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