1
|
Chu SM, Heather LC, Chuaiphichai S, Nicol T, Wright B, Miossec M, Bendall JK, Douglas G, Crabtree MJ, Channon KM. Cardiomyocyte tetrahydrobiopterin synthesis regulates fatty acid metabolism and susceptibility to ischaemia-reperfusion injury. Exp Physiol 2023; 108:874-890. [PMID: 37184360 PMCID: PMC10988529 DOI: 10.1113/ep090795] [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: 09/24/2022] [Accepted: 03/07/2023] [Indexed: 05/16/2023]
Abstract
NEW FINDINGS What is the central question of this study? What are the physiological roles of cardiomyocyte-derived tetrahydrobiopterin (BH4) in cardiac metabolism and stress response? What is the main finding and its importance? Cardiomyocyte BH4 has a physiological role in cardiac metabolism. There was a shift of substrate preference from fatty acid to glucose in hearts with targeted deletion of BH4 synthesis. The changes in fatty-acid metabolic profile were associated with a protective effect in response to ischaemia-reperfusion (IR) injury, and reduced infarct size. Manipulating fatty acid metabolism via BH4 availability could play a therapeutic role in limiting IR injury. ABSTRACT Tetrahydrobiopterin (BH4) is an essential cofactor for nitric oxide (NO) synthases in which its production of NO is crucial for cardiac function. However, non-canonical roles of BH4 have been discovered recently and the cell-specific role of cardiomyocyte BH4 in cardiac function and metabolism remains to be elucidated. Therefore, we developed a novel mouse model of cardiomyocyte BH4 deficiency, by cardiomyocyte-specific deletion of Gch1, which encodes guanosine triphosphate cyclohydrolase I, a required enzyme for de novo BH4 synthesis. Cardiomyocyte (cm)Gch1 mRNA expression and BH4 levels from cmGch1 KO mice were significantly reduced compared to Gch1flox/flox (WT) littermates. Transcriptomic analyses and protein assays revealed downregulation of genes involved in fatty acid oxidation in cmGch1 KO hearts compared with WT, accompanied by increased triacylglycerol concentration within the myocardium. Deletion of cardiomyocyte BH4 did not alter basal cardiac function. However, the recovery of left ventricle function was improved in cmGch1 KO hearts when subjected to ex vivo ischaemia-reperfusion (IR) injury, with reduced infarct size compared to WT hearts. Metabolomic analyses of cardiac tissue after IR revealed that long-chain fatty acids were increased in cmGch1 KO hearts compared to WT, whereas at 5 min reperfusion (post-35 min ischaemia) fatty acid metabolite levels were higher in WT compared to cmGch1 KO hearts. These results indicate a new role for BH4 in cardiomyocyte fatty acid metabolism, such that reduction of cardiomyocyte BH4 confers a protective effect in response to cardiac IR injury. Manipulating cardiac metabolism via BH4 could play a therapeutic role in limiting IR injury.
Collapse
Affiliation(s)
- Sandy M. Chu
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of MedicineUniversity of OxfordOxfordUK
| | - Lisa C. Heather
- Department of Physiology, Anatomy and GeneticsUniversity of OxfordOxfordUK
| | - Surawee Chuaiphichai
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of MedicineUniversity of OxfordOxfordUK
| | - Thomas Nicol
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of MedicineUniversity of OxfordOxfordUK
| | - Benjamin Wright
- Oxford Genomics Centre, Wellcome Centre for Human GeneticsUniversity of OxfordOxfordUK
| | - Matthieu Miossec
- Oxford Genomics Centre, Wellcome Centre for Human GeneticsUniversity of OxfordOxfordUK
| | - Jennifer K. Bendall
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of MedicineUniversity of OxfordOxfordUK
| | - Gillian Douglas
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of MedicineUniversity of OxfordOxfordUK
| | - Mark J. Crabtree
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of MedicineUniversity of OxfordOxfordUK
| | - Keith M. Channon
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of MedicineUniversity of OxfordOxfordUK
| |
Collapse
|
2
|
Chuaiphichai S, Yu GZ, Tan CM, Whiteman C, Douglas G, Dickinson Y, Drydale EN, Appari M, Zhang W, Crabtree MJ, McNeill E, Hale AB, Lewandowski AJ, Alp NJ, Vatish M, Leeson P, Channon KM. Endothelial GTPCH (GTP Cyclohydrolase 1) and Tetrahydrobiopterin Regulate Gestational Blood Pressure, Uteroplacental Remodeling, and Fetal Growth. Hypertension 2021; 78:1871-1884. [PMID: 34689592 PMCID: PMC8577301 DOI: 10.1161/hypertensionaha.120.17646] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 07/07/2021] [Indexed: 01/01/2023]
Abstract
[Figure: see text].
Collapse
Affiliation(s)
- Surawee Chuaiphichai
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of Medicine, University of Oxford, United Kingdom (S.C., C.W., G.D., Y.D., E.N.D., M.A., M.J.C., E.M., A.B.H., N.J.A., K.M.C.)
| | - Grace Z. Yu
- Oxford Cardiovascular Clinical Research Facility, Division of Cardiovascular Medicine, Radcliffe Department of Medicine (G.Z.Y., C.M.J.T., A.J.L., P.L.), University of Oxford, United Kingdom
| | - Cheryl M.J. Tan
- Oxford Cardiovascular Clinical Research Facility, Division of Cardiovascular Medicine, Radcliffe Department of Medicine (G.Z.Y., C.M.J.T., A.J.L., P.L.), University of Oxford, United Kingdom
| | - Christopher Whiteman
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of Medicine, University of Oxford, United Kingdom (S.C., C.W., G.D., Y.D., E.N.D., M.A., M.J.C., E.M., A.B.H., N.J.A., K.M.C.)
- Oxford Cardiovascular Clinical Research Facility, Division of Cardiovascular Medicine, Radcliffe Department of Medicine (G.Z.Y., C.M.J.T., A.J.L., P.L.), University of Oxford, United Kingdom
- Nuffield Department of Women’s and Reproductive Health (W.Z., M.V.), University of Oxford, United Kingdom
- National Institute for Health Research (NIHR) Oxford Biomedical Research Centre, Oxford University Hospitals National Health Service Foundation Trust, John Radcliffe Hospital, United Kingdom (M.V., K.M.C.)
| | - Gillian Douglas
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of Medicine, University of Oxford, United Kingdom (S.C., C.W., G.D., Y.D., E.N.D., M.A., M.J.C., E.M., A.B.H., N.J.A., K.M.C.)
| | - Yasmin Dickinson
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of Medicine, University of Oxford, United Kingdom (S.C., C.W., G.D., Y.D., E.N.D., M.A., M.J.C., E.M., A.B.H., N.J.A., K.M.C.)
| | - Edward N. Drydale
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of Medicine, University of Oxford, United Kingdom (S.C., C.W., G.D., Y.D., E.N.D., M.A., M.J.C., E.M., A.B.H., N.J.A., K.M.C.)
| | - Mahesh Appari
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of Medicine, University of Oxford, United Kingdom (S.C., C.W., G.D., Y.D., E.N.D., M.A., M.J.C., E.M., A.B.H., N.J.A., K.M.C.)
| | - Wei Zhang
- Nuffield Department of Women’s and Reproductive Health (W.Z., M.V.), University of Oxford, United Kingdom
| | - Mark J. Crabtree
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of Medicine, University of Oxford, United Kingdom (S.C., C.W., G.D., Y.D., E.N.D., M.A., M.J.C., E.M., A.B.H., N.J.A., K.M.C.)
| | - Eileen McNeill
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of Medicine, University of Oxford, United Kingdom (S.C., C.W., G.D., Y.D., E.N.D., M.A., M.J.C., E.M., A.B.H., N.J.A., K.M.C.)
| | - Ashley B. Hale
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of Medicine, University of Oxford, United Kingdom (S.C., C.W., G.D., Y.D., E.N.D., M.A., M.J.C., E.M., A.B.H., N.J.A., K.M.C.)
| | - Adam J. Lewandowski
- Oxford Cardiovascular Clinical Research Facility, Division of Cardiovascular Medicine, Radcliffe Department of Medicine (G.Z.Y., C.M.J.T., A.J.L., P.L.), University of Oxford, United Kingdom
| | - Nicholas J. Alp
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of Medicine, University of Oxford, United Kingdom (S.C., C.W., G.D., Y.D., E.N.D., M.A., M.J.C., E.M., A.B.H., N.J.A., K.M.C.)
| | - Manu Vatish
- Nuffield Department of Women’s and Reproductive Health (W.Z., M.V.), University of Oxford, United Kingdom
- National Institute for Health Research (NIHR) Oxford Biomedical Research Centre, Oxford University Hospitals National Health Service Foundation Trust, John Radcliffe Hospital, United Kingdom (M.V., K.M.C.)
| | - Paul Leeson
- Oxford Cardiovascular Clinical Research Facility, Division of Cardiovascular Medicine, Radcliffe Department of Medicine (G.Z.Y., C.M.J.T., A.J.L., P.L.), University of Oxford, United Kingdom
| | - Keith M. Channon
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, Radcliffe Department of Medicine, University of Oxford, United Kingdom (S.C., C.W., G.D., Y.D., E.N.D., M.A., M.J.C., E.M., A.B.H., N.J.A., K.M.C.)
- National Institute for Health Research (NIHR) Oxford Biomedical Research Centre, Oxford University Hospitals National Health Service Foundation Trust, John Radcliffe Hospital, United Kingdom (M.V., K.M.C.)
| |
Collapse
|
3
|
Simonet S, Gosgnach W, Billou L, Lucats L, Royere E, Crespo C, Lapret I, Ragonnet L, Moreau K, Vayssettes-Courchay C, Berson P, Bourguignon MP. GTP-cyclohydrolase deficiency induced peripheral and deep microcirculation dysfunction with age. Microvasc Res 2021; 133:104078. [PMID: 32980388 DOI: 10.1016/j.mvr.2020.104078] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 09/03/2020] [Accepted: 09/22/2020] [Indexed: 01/04/2023]
Abstract
The present study assessed the impact of impaired tetrahydrobiopterin (BH4) production on vasoreactivity from conduit and small arteries along the vascular tree as seen during aging. For this purpose, the mutant hyperphenylalaninemic mouse (hph-1) was used. This model is reported to be deficient in GTP cyclohydrolase I, a rate limiting enzyme in BH4 biosynthesis. BH4 is a key regulator of vascular homeostasis by regulating the nitric oxide synthase 3 (NOS3) activity. In GTP-CH deficient mice, the aortic BH4 levels were decreased, by -77% in 12 week-middle-aged mice (young) and by -83% in 35-45 week-middle-aged mice (middle-aged). In young hph-1, the mesenteric artery ability to respond to flow was slightly reduced by 9%. Aging induced huge modification in many vascular functions. In middle-aged hph-1, we observed a decrease in aortic cGMP levels, biomarker of NO availability (-46%), in flow-mediated vasodilation of mesenteric artery (-31%), in coronary hyperemia response measured in isolated heart following transient ischemia (-27%) and in cutaneous microcirculation dilation in response to acetylcholine assessed in vivo by laser-doppler technic (-69%). In parallel, the endothelium-dependent relaxation in response to acetylcholine in conduit blood vessel, measured on isolated aorta rings, was unchanged in hph-1 mice whatever the age. Our findings demonstrate that in middle-aged GTP-CH depleted mice, the reduction of BH4 was characterized by an alteration of microcirculation dilatory properties observed in various parts of the vascular tree. Large conduit blood vessels vasoreactivity, ie aorta, was unaltered even in middle-aged mice emphasizing the main BH4-deletion impact on the microcirculation.
Collapse
Affiliation(s)
- Serge Simonet
- SERVIER Research Institute, Cardiovascular and Metabolism Discovery Research, Suresnes, France
| | - Willy Gosgnach
- SERVIER Research Institute, Cardiovascular and Metabolism Discovery Research, Suresnes, France
| | - Lucie Billou
- SERVIER Research Institute, Cardiovascular and Metabolism Discovery Research, Suresnes, France
| | - Laurence Lucats
- SERVIER Research Institute, Cardiovascular and Metabolism Discovery Research, Suresnes, France
| | - Emilie Royere
- SERVIER Research Institute, Cardiovascular and Metabolism Discovery Research, Suresnes, France
| | - Christine Crespo
- SERVIER Research Institute, Cardiovascular and Metabolism Discovery Research, Suresnes, France
| | - Isabelle Lapret
- SERVIER Research Institute, Cardiovascular and Metabolism Discovery Research, Suresnes, France
| | - Lea Ragonnet
- SERVIER Research Institute, Cardiovascular and Metabolism Discovery Research, Suresnes, France
| | - Kevin Moreau
- SERVIER Research Institute, Cardiovascular and Metabolism Discovery Research, Suresnes, France
| | | | - Pascal Berson
- SERVIER Research Institute, Cardiovascular and Metabolism Discovery Research, Suresnes, France
| | | |
Collapse
|
4
|
|
5
|
Wei J, Zhang Y, Li Z, Wang X, Chen L, Du J, Liu J, Liu J, Hou Y. GCH1 attenuates cardiac autonomic nervous remodeling in canines with atrial-tachypacing via tetrahydrobiopterin pathway regulated by microRNA-206. Pacing Clin Electrophysiol 2018; 41:459-471. [PMID: 29436714 DOI: 10.1111/pace.13289] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2016] [Revised: 01/04/2018] [Accepted: 01/15/2018] [Indexed: 12/22/2022]
Abstract
BACKGROUND/AIMS Cardiac autonomic nerve remodeling (ANR) is an important mechanism of atrial fibrillation (AF). GTP cyclohydrolase I, encoded by GCH1, is the rate-limiting enzyme in de novo synthesis of tetrahydrobiopterin (BH4), an essential cofactor for nitric oxide (NO) synthesis. Previous studies reported that increased BH4 and NO content negatively regulated nerve regeneration. This study investigated the effects of GCH1 on ANR via BH4 pathway, regulated by microRNA-206 (miR-206). METHODS AND RESULTS In canines, atrial tachypacing (A-TP), together with miR-206 overexpression, increased PGP9.5 level and inhibited GCH1 expression by quantitative real-time polymerase chain reaction and western blot analysis. GCH1 was validated to be a direct target of miR-206 by luciferase assays. Meanwhile, miR-206 overexpression by lentiviruses infection into right superior pulmonary vein fat pad decreased GCH1 expression to ∼40% and further reduced BH4 and NO content compared with the control canines. After infection of GCH1 overexpression lentiviruses for two weeks, atrial effective refractory period was increased compared with the control group (105.8 ± 1.537 ms vs 99.17 ± 2.007 ms, P < 0.05). Moreover, GCH1 overexpression attenuated canines' atrial PGP9.5 level to ∼56% of the controls. In myocardial cells, transfection of GCH1 overexpression lentiviruses also decreased PGP9.5 expression to 26% of the control group. In patients, plasma was collected and miR-206 expression was upregulated in AF patients (n = 18) than the controls (n = 12). CONCLUSIONS Our findings suggested that GCH1 downregulation exacerbated ANR by decreasing atrial BH4 and NO content modulated by miR-206 in A-TP canines. This indicates that GCH1 may prevent the initiation of AF through inhibiting ANR.
Collapse
Affiliation(s)
- Jinqiu Wei
- Department of Examination Center, Shandong Provincial Qianfoshan Hospital, Jinan, China
| | - Yujiao Zhang
- Department of Cardiology, Shandong Provincial Qianfoshan Hospital, Jinan, China
| | - Zhan Li
- Department of Cardiology, Shandong Provincial Qianfoshan Hospital, Jinan, China
| | - Ximin Wang
- Department of Cardiology, Shandong Provincial Qianfoshan Hospital, Jinan, China
| | - Linlin Chen
- Department of Special Examination, Shandong Provincial Qianfoshan Hospital, Jinan, China
| | - Juanjuan Du
- Department of Cardiology, Shandong Provincial Qianfoshan Hospital, Jinan, China
| | - Jing Liu
- Medical Research Center, Shandong Provincial Qianfoshan Hospital, Jinan, China
| | - Ju Liu
- Medical Research Center, Shandong Provincial Qianfoshan Hospital, Jinan, China
| | - Yinglong Hou
- Department of Cardiology, Shandong Provincial Qianfoshan Hospital, Jinan, China
| |
Collapse
|
6
|
Lowe FJ, Luettich K, Talikka M, Hoang V, Haswell LE, Hoeng J, Gaca MD. Development of an Adverse Outcome Pathway for the Onset of Hypertension by Oxidative Stress-Mediated Perturbation of Endothelial Nitric Oxide Bioavailability. ACTA ACUST UNITED AC 2017. [DOI: 10.1089/aivt.2016.0031] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Frazer J. Lowe
- British American Tobacco (Investments) Ltd., Group Research and Development, Southampton, United Kingdom
| | - Karsta Luettich
- Philip Morris International R&D, Philip Morris Products S.A. (part of Philip Morris International group of companies), Neuchatel, Switzerland
| | - Marja Talikka
- Philip Morris International R&D, Philip Morris Products S.A. (part of Philip Morris International group of companies), Neuchatel, Switzerland
| | - Vy Hoang
- Selventa, One Alewife Center, Cambridge, Massachusetts
| | - Linsey E. Haswell
- British American Tobacco (Investments) Ltd., Group Research and Development, Southampton, United Kingdom
| | - Julia Hoeng
- Philip Morris International R&D, Philip Morris Products S.A. (part of Philip Morris International group of companies), Neuchatel, Switzerland
| | - Marianna D. Gaca
- British American Tobacco (Investments) Ltd., Group Research and Development, Southampton, United Kingdom
| |
Collapse
|
7
|
Rorabaugh BR, Chakravarti B, Mabe NW, Seeley SL, Bui AD, Yang J, Watts SW, Neubig RR, Fisher RA. Regulator of G Protein Signaling 6 Protects the Heart from Ischemic Injury. J Pharmacol Exp Ther 2016; 360:409-416. [PMID: 28035008 DOI: 10.1124/jpet.116.238345] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 12/28/2016] [Indexed: 01/07/2023] Open
Abstract
Gαi-coupled receptors play important roles in protecting the heart from ischemic injury. Regulator of G protein signaling (RGS) proteins suppress Gαi signaling by accelerating the GTPase activity of Gαi subunits. However, the roles of individual RGS proteins in modulating ischemic injury are unknown. In this study, we investigated the effect of RGS6 deletion on myocardial sensitivity to ischemic injury. Hearts from RGS6 knockout (RGS6-/-) and RGS6 wild-type (RGS6+/+) mice were subjected to 30 minutes of ischemia and 2 hours of reperfusion on a Langendorff heart apparatus. Infarcts in RGS6-/- hearts were significantly larger than infarcts in RGS6+/+ hearts. RGS6-/- hearts also exhibited increased phosphorylation of β2-adrenergic receptors and G protein-coupled receptor kinase 2 (GRK2). Mitochondrial GRK2 as well as caspase-3 cleavage were increased significantly in RGS6-/- hearts compared with RGS6+/+ hearts after ischemia. Chronic propranolol treatment of mice prevented the observed increases in ischemic injury and the GRK2 phosphorylation observed in RGS6-/- hearts. Our findings suggest that loss of RGS6 predisposes the ventricle to prodeath signaling through a β2AR-GRK2-dependent signaling mechanism, and they provide evidence for a protective role of RGS6 in the ischemic heart. Individuals expressing genetic polymorphisms that suppress the activity of RGS6 may be at increased risk of cardiac ischemic injury. Furthermore, the development of agents that increase RGS6 expression or activity might provide a novel strategy for the treatment of ischemic heart disease.
Collapse
Affiliation(s)
- Boyd R Rorabaugh
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
| | - Bandana Chakravarti
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
| | - Nathaniel W Mabe
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
| | - Sarah L Seeley
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
| | - Albert D Bui
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
| | - Jianqi Yang
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
| | - Stephanie W Watts
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
| | - Richard R Neubig
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
| | - Rory A Fisher
- Department of Pharmaceutical and Biomedical Sciences, Raabe College of Pharmacy, Ohio Northern University, Ada, Ohio (B.R.R., N.W.M., S.L.S., A.D.B.); Department of Pharmacology, Carver College of Medicine, University of Iowa, Iowa City, Iowa (B.C., J.Y., R.A.F.); and Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan (S.W.W., R.R.N.)
| |
Collapse
|
8
|
Roof SR, Boslett J, Russell D, del Rio C, Alecusan J, Zweier JL, Ziolo MT, Hamlin R, Mohler PJ, Curran J. Insulin-like growth factor 1 prevents diastolic and systolic dysfunction associated with cardiomyopathy and preserves adrenergic sensitivity. Acta Physiol (Oxf) 2016; 216:421-34. [PMID: 26399932 DOI: 10.1111/apha.12607] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 06/03/2015] [Accepted: 09/15/2015] [Indexed: 12/11/2022]
Abstract
AIMS Insulin-like growth factor 1 (IGF-1)-dependent signalling promotes exercise-induced physiological cardiac hypertrophy. However, the in vivo therapeutic potential of IGF-1 for heart disease is not well established. Here, we test the potential therapeutic benefits of IGF-1 on cardiac function using an in vivo model of chronic catecholamine-induced cardiomyopathy. METHODS Rats were perfused with isoproterenol via osmotic pump (1 mg kg(-1) per day) and treated with 2 mg kg(-1) IGF-1 (2 mg kg(-1) per day, 6 days a week) for 2 or 4 weeks. Echocardiography, ECG, and blood pressure were assessed. In vivo pressure-volume loop studies were conducted at 4 weeks. Heart sections were analysed for fibrosis and apoptosis, and relevant biochemical signalling cascades were assessed. RESULTS After 4 weeks, diastolic function (EDPVR, EDP, tau, E/A ratio), systolic function (PRSW, ESPVR, dP/dtmax) and structural remodelling (LV chamber diameter, wall thickness) were all adversely affected in isoproterenol-treated rats. All these detrimental effects were attenuated in rats treated with Iso+IGF-1. Isoproterenol-dependent effects on BP were attenuated by IGF-1 treatment. Adrenergic sensitivity was blunted in isoproterenol-treated rats but was preserved by IGF-1 treatment. Immunoblots indicate that cardioprotective p110α signalling and activated Akt are selectively upregulated in Iso+IGF-1-treated hearts. Expression of iNOS was significantly increased in both the Iso and Iso+IGF-1 groups; however, tetrahydrobiopterin (BH4) levels were decreased in the Iso group and maintained by IGF-1 treatment. CONCLUSION IGF-1 treatment attenuates diastolic and systolic dysfunction associated with chronic catecholamine-induced cardiomyopathy while preserving adrenergic sensitivity and promoting BH4 production. These data support the potential use of IGF-1 therapy for clinical applications for cardiomyopathies.
Collapse
Affiliation(s)
| | - J. Boslett
- The Dorothy M. Davis Heart and Lung Research Institute; The Ohio State University Wexner Medical Center; Columbus OH USA
| | - D. Russell
- Department of Veterinary Clinical Sciences; College of Veterinarian Medicine; The Ohio State University; Columbus OH USA
| | | | - J. Alecusan
- The Dorothy M. Davis Heart and Lung Research Institute; The Ohio State University Wexner Medical Center; Columbus OH USA
| | - J. L. Zweier
- The Dorothy M. Davis Heart and Lung Research Institute; The Ohio State University Wexner Medical Center; Columbus OH USA
| | - M. T. Ziolo
- The Dorothy M. Davis Heart and Lung Research Institute; The Ohio State University Wexner Medical Center; Columbus OH USA
- Department of Physiology and Cell Biology; The Ohio State University Wexner Medical Center; Columbus OH USA
| | | | - P. J. Mohler
- The Dorothy M. Davis Heart and Lung Research Institute; The Ohio State University Wexner Medical Center; Columbus OH USA
- Department of Internal Medicine; The Ohio State University Wexner Medical Center; Columbus OH USA
- Department of Physiology and Cell Biology; The Ohio State University Wexner Medical Center; Columbus OH USA
| | - J. Curran
- The Dorothy M. Davis Heart and Lung Research Institute; The Ohio State University Wexner Medical Center; Columbus OH USA
- Department of Internal Medicine; The Ohio State University Wexner Medical Center; Columbus OH USA
| |
Collapse
|
9
|
Arrested Hematopoiesis and Vascular Relaxation Defects in Mice with a Mutation in Dhfr. Mol Cell Biol 2016; 36:1222-36. [PMID: 26830229 DOI: 10.1128/mcb.01035-15] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 01/22/2016] [Indexed: 01/06/2023] Open
Abstract
Dihydrofolate reductase (DHFR) is a critical enzyme in the folate metabolism pathway and also plays a role in regulating nitric oxide (NO) signaling in endothelial cells. Although both coding and noncoding mutations with phenotypic effects have been identified in the human DHFR gene, no mouse model is currently available to study the consequences of perturbing DHFR in vivo In order to identify genes involved in definitive hematopoiesis, we performed a forward genetic screen and produced a mouse line, here referred to as Orana, with a point mutation in the Dhfr locus leading to a Thr136Ala substitution in the DHFR protein. Homozygote Orana mice initiate definitive hematopoiesis, but expansion of progenitors in the fetal liver is compromised, and the animals die between embryonic day 13.5 (E13.5) and E14.5. Heterozygote Orana mice survive to adulthood but have tissue-specific alterations in folate abundance and distribution, perturbed stress erythropoiesis, and impaired endothelium-dependent relaxation of the aorta consistent with the role of DHFR in regulating NO signaling. Orana mice provide insight into the dual roles of DHFR and are a useful model for investigating the role of environmental and dietary factors in the context of vascular defects caused by altered NO signaling.
Collapse
|
10
|
Starr A, Sand CA, Heikal L, Kelly PD, Spina D, Crabtree M, Channon KM, Leiper JM, Nandi M. Overexpression of GTP cyclohydrolase 1 feedback regulatory protein is protective in a murine model of septic shock. Shock 2014; 42:432-9. [PMID: 25046538 PMCID: PMC4851220 DOI: 10.1097/shk.0000000000000235] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 07/10/2014] [Indexed: 11/26/2022]
Abstract
Overproduction of nitric oxide (NO) by inducible NO synthase contributes toward refractory hypotension, impaired microvascular perfusion, and end-organ damage in septic shock patients. Tetrahydrobiopterin (BH4) is an essential NOS cofactor. GTP cyclohydrolase 1 (GCH1) is the rate-limiting enzyme for BH4 biosynthesis. Under inflammatory conditions, GCH1 activity and hence BH4 levels are increased, supporting pathological NOS activity. GCH1 activity can be controlled through allosteric interactions with GCH1 feedback regulatory protein (GFRP). We investigated whether overexpression of GFRP can regulate BH4 and NO production and attenuate cardiovascular dysfunction in sepsis. Sepsis was induced in mice conditionally overexpressing GFRP and wild-type littermates by cecal ligation and puncture. Blood pressure was monitored by radiotelemetry, and mesenteric blood flow was quantified by laser speckle contrast imaging. Blood biochemistry data were obtained using an iSTAT analyzer, and BH4 levels were measured in plasma and tissues by high-performance liquid chromatography. Increased BH4 and NO production and hypotension were observed in all mice, but the extents of these pathophysiological changes were attenuated in GFRP OE mice. Perturbations in blood biochemistry were similarly attenuated in GFRP OE compared with wild-type controls. These results suggest that GFRP overexpression regulates GCH1 activity during septic shock, which in turn limits BH4 bioavailability for iNOS. We conclude that the GCH1-GFRP axis is a critical regulator of BH4 and NO production and the cardiovascular derangements that occur in septic shock.
Collapse
Affiliation(s)
- Anna Starr
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Claire A. Sand
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Lamia Heikal
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Peter D. Kelly
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Domenico Spina
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Mark Crabtree
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Keith M. Channon
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - James M. Leiper
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Manasi Nandi
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| |
Collapse
|
11
|
Chuaiphichai S, McNeill E, Douglas G, Crabtree MJ, Bendall JK, Hale AB, Alp NJ, Channon KM. Cell-autonomous role of endothelial GTP cyclohydrolase 1 and tetrahydrobiopterin in blood pressure regulation. Hypertension 2014; 64:530-40. [PMID: 24777984 PMCID: PMC5238938 DOI: 10.1161/hypertensionaha.114.03089] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Tetrahydrobiopterin (BH4) is an essential cofactor for endothelial nitric oxide synthase (eNOS) function and NO generation. Augmentation of BH4 levels can prevent eNOS uncoupling and can improve endothelial dysfunction in vascular disease states. However, the physiological requirement for de novo endothelial cell BH4 biosynthesis in eNOS function remains unclear. We generated a novel mouse model with endothelial cell-specific deletion of GCH1, encoding GTP cyclohydrolase 1, an essential enzyme for BH4 biosynthesis, to test the cell-autonomous requirement for endothelial BH4 biosynthesis in vivo. Mice with a floxed GCH1 allele (GCH1(fl/fl)) were crossed with Tie2cre mice to delete GCH1 in endothelial cells. GCH1(fl/fl)Tie2cre mice demonstrated virtually absent endothelial NO bioactivity and significantly greater O2 (•-) production. GCH1(fl/fl)Tie2cre aortas and mesenteric arteries had enhanced vasoconstriction to phenylephrine and impaired endothelium-dependent vasodilatations to acetylcholine and SLIGRL. Endothelium-dependent vasodilatations in GCH1(fl/fl)Tie2cre aortas were, in part, mediated by eNOS-derived hydrogen peroxide (H2O2), which mediated vasodilatation through soluble guanylate cyclase. Ex vivo supplementation of aortic rings with the BH4 analogue sepiapterin restored normal endothelial function and abolished eNOS-derived H2O2 production in GCH1(fl/fl)Tie2cre aortas. GCH1(fl/fl)Tie2cre mice had higher systemic blood pressure than wild-type littermates, which was normalized by NOS inhibitor, NG-nitro-L-arginine methyl ester. Taken together, these studies reveal an endothelial cell-autonomous requirement for GCH1 and BH4 in regulation of vascular tone and blood pressure and identify endothelial cell BH4 as a pivotal regulator of NO versus H2O2 as alternative eNOS-derived endothelial-derived relaxing factors.
Collapse
Affiliation(s)
- Surawee Chuaiphichai
- From the British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Eileen McNeill
- From the British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Gillian Douglas
- From the British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Mark J Crabtree
- From the British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Jennifer K Bendall
- From the British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Ashley B Hale
- From the British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Nicholas J Alp
- From the British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Keith M Channon
- From the British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom.
| |
Collapse
|
12
|
Ye Y, Sun Z, Guo A, Song LS, Grobe JL, Chen S. Ablation of the GNB3 gene in mice does not affect body weight, metabolism or blood pressure, but causes bradycardia. Cell Signal 2014; 26:2514-20. [PMID: 25093805 DOI: 10.1016/j.cellsig.2014.07.030] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 06/26/2014] [Accepted: 07/28/2014] [Indexed: 11/18/2022]
Abstract
G protein β3 (Gβ3) is an isoform of heterotrimeric G protein β subunits involved in transducing G protein coupled receptor (GPCR) signaling. Polymorphisms in Gβ3 (GNB3) are associated with many human disorders (e.g. hypertension, diabetes and obesity) but the role of GNB3 in these pathogeneses remains unclear. Here, Gβ3-null mice (GNB3(-/-)) were characterized to determine how Gβ3 functions to regulate blood pressure, body weight and metabolism. We found Gβ3 expression restricted to limited types of tissues, including the retina, several regions of the brain and heart ventricles. Gβ3-deficient mice were normal as judged by body weight gain by age or by feeding with high-fat diet (HFD); glucose tolerance and insulin sensitivity; baseline blood pressure and angiotensin II infusion-induced hypertension. During tail-cuff blood pressure measurements, however, Gβ3-null mice had slower heart rates (~450 vs ~500 beats/min). This bradycardia was not observed in isolated and perfused Gβ3-null mouse hearts. Moreover, mouse hearts isolated from GNB3(-/-) and controls responded equivalently to muscarinic receptor- and β-adrenergic receptor-stimulated bradycardia and tachycardia, respectively. Since no difference was seen in isolated hearts, Gβ3 is unlikely to be involved directly in the GPCR signaling activity that controls heart pacemaker activity. These results demonstrate that although Gβ3 appears dispensable in mice for the regulation of blood pressure, body weight and metabolic features associated with obesity and diabetes, Gβ3 may regulate heart rate.
Collapse
Affiliation(s)
- Yuanchao Ye
- Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Zhizeng Sun
- Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Ang Guo
- Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Long-Sheng Song
- Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Justin L Grobe
- Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Songhai Chen
- Department of Pharmacology, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA; Department of Internal Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
| |
Collapse
|
13
|
Bendall JK, Douglas G, McNeill E, Channon KM, Crabtree MJ. Tetrahydrobiopterin in cardiovascular health and disease. Antioxid Redox Signal 2014; 20:3040-77. [PMID: 24294830 PMCID: PMC4038990 DOI: 10.1089/ars.2013.5566] [Citation(s) in RCA: 163] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 11/01/2013] [Accepted: 12/02/2013] [Indexed: 01/03/2023]
Abstract
Tetrahydrobiopterin (BH4) functions as a cofactor for several important enzyme systems, and considerable evidence implicates BH4 as a key regulator of endothelial nitric oxide synthase (eNOS) in the setting of cardiovascular health and disease. BH4 bioavailability is determined by a balance of enzymatic de novo synthesis and recycling, versus degradation in the setting of oxidative stress. Augmenting vascular BH4 levels by pharmacological supplementation has been shown in experimental studies to enhance NO bioavailability. However, it has become more apparent that the role of BH4 in other enzymatic pathways, including other NOS isoforms and the aromatic amino acid hydroxylases, may have a bearing on important aspects of vascular homeostasis, inflammation, and cardiac function. This article reviews the role of BH4 in cardiovascular development and homeostasis, as well as in pathophysiological processes such as endothelial and vascular dysfunction, atherosclerosis, inflammation, and cardiac hypertrophy. We discuss the therapeutic potential of BH4 in cardiovascular disease states and attempt to address how this modulator of intracellular NO-redox balance may ultimately provide a powerful new treatment for many cardiovascular diseases.
Collapse
Affiliation(s)
- Jennifer K Bendall
- Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, University of Oxford , John Radcliffe Hospital, Oxford, United Kingdom
| | | | | | | | | |
Collapse
|
14
|
White DW, Raven PB. Autonomic neural control of heart rate during dynamic exercise: revisited. J Physiol 2014; 592:2491-500. [PMID: 24756637 DOI: 10.1113/jphysiol.2014.271858] [Citation(s) in RCA: 183] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
UNLABELLED The accepted model of autonomic control of heart rate (HR) during dynamic exercise indicates that the initial increase is entirely attributable to the withdrawal of parasympathetic nervous system (PSNS) activity and that subsequent increases in HR are entirely attributable to increases in cardiac sympathetic activity. In the present review, we sought to re-evaluate the model of autonomic neural control of HR in humans during progressive increases in dynamic exercise workload. We analysed data from both new and previously published studies involving baroreflex stimulation and pharmacological blockade of the autonomic nervous system. Results indicate that the PSNS remains functionally active throughout exercise and that increases in HR from rest to maximal exercise result from an increasing workload-related transition from a 4 : 1 vagal-sympathetic balance to a 4 : 1 sympatho-vagal balance. Furthermore, the beat-to-beat autonomic reflex control of HR was found to be dependent on the ability of the PSNS to modulate the HR as it was progressively restrained by increasing workload-related sympathetic nerve activity. IN CONCLUSION (i) increases in exercise workload-related HR are not caused by a total withdrawal of the PSNS followed by an increase in sympathetic tone; (ii) reciprocal antagonism is key to the transition from vagal to sympathetic dominance, and (iii) resetting of the arterial baroreflex causes immediate exercise-onset reflexive increases in HR, which are parasympathetically mediated, followed by slower increases in sympathetic tone as workloads are increased.
Collapse
Affiliation(s)
- Daniel W White
- Department of Integrative Physiology and Cardiovascular Research Institute, University of North Texas Health Science Center, Fort Worth, TX, USA
| | - Peter B Raven
- Department of Integrative Physiology and Cardiovascular Research Institute, University of North Texas Health Science Center, Fort Worth, TX, USA
| |
Collapse
|
15
|
Dubin A. Tetrahydrobiopterin (BH4) in septic shock: a key to solving the nitric oxide puzzle and opening the microcirculation? Crit Care Med 2012; 40:2912-4. [PMID: 22986662 DOI: 10.1097/ccm.0b013e31825f70be] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
16
|
Abstract
Nitric oxide (NO), a key regulator of cardiovascular function, is synthesized from L-arginine and oxygen by the enzyme nitric oxide synthase (NOS). This reaction requires tetrahydrobiopterin (BH4) as a cofactor. BH4 is synthesized from guanosine triphosphate (GTP) by GTP cyclohydrolase I (GTPCH) and recycled from 7,8-dihydrobiopterin (BH2) by dihydrofolate reductase. Under conditions of low BH4 bioavailability relative to NOS or BH2, oxygen activation is "uncoupled" from L-arginine oxidation, and NOS produces superoxide (O (2) (-) ) instead of NO. NOS-derived superoxide reacts with NO to produce peroxynitrite (ONOO(-)), a highly reactive anion that rapidly oxidizes BH4 and propagates NOS uncoupling. BH4 depletion and NOS uncoupling contribute to overload-induced heart failure, hypertension, ischemia/reperfusion injury, and atrial fibrillation. L-arginine depletion, methylarginine accumulation, and S-glutathionylation of NOS also promote uncoupling. Recoupling NOS is a promising approach to treating myocardial and vascular dysfunction associated with heart failure.
Collapse
Affiliation(s)
- Matthew S. Alkaitis
- Nuffield Department of Clinical Laboratory Sciences, University of Oxford, John Radcliffe Hospital, Oxford, UK
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD USA
| | - Mark J. Crabtree
- Department of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK
| |
Collapse
|