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Abstract
Excessive salt intake raises blood pressure, but the implications of this observation for human health have remained contentious. It has also been recognized for many years that potassium intake may mitigate the effects of salt intake on blood pressure and possibly on outcomes such as stroke. Recent large randomized intervention trials have provided strong support for the benefits of replacing salt (NaCl) with salt substitute (75% NaCl, 25% KCl) on hard outcomes, including stroke. During the same period of time, major advances have been made in understanding how the body senses and tastes salt, and how these sensations drive intake. Additionally, new insights into the complex interactions between systems that control sodium and potassium excretion by the kidneys, and the brain have highlighted the existence of a potassium switch in the kidney distal nephron. This switch seems to contribute importantly to the blood pressure-lowering effects of potassium intake. In recognition of these evolving data, the United States Food and Drug Administration is moving to permit potassium-containing salt substitutes in food manufacturing. Given that previous attempts to reduce salt consumption have not been successful, this new approach has a chance of improving health and ending the 'Salt Wars'.
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Affiliation(s)
- Robert Little
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
- LeDucq Transatlantic Network of Excellence
| | - David H. Ellison
- Division of Nephrology and Hypertension, Department of Medicine, Oregon Health and Science University, Portland, Oregon, USA
- Oregon Clinical & Translational Research Institute, Oregon Health & Science University, Portland, Oregon, USA
- LeDucq Transatlantic Network of Excellence
- VA Portland Health Care System, Portland, OR
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2
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Protective Effect of Astragaloside IV on High Glucose-Induced Endothelial Dysfunction via Inhibition of P2X7R Dependent P38 MAPK Signaling Pathway. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2020; 2020:5070415. [PMID: 33014270 PMCID: PMC7512101 DOI: 10.1155/2020/5070415] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 08/10/2020] [Accepted: 08/31/2020] [Indexed: 12/14/2022]
Abstract
Vascular endothelial dysfunction is associated with increased mortality in patients with diabetes. Astragaloside IV (As-IV) is a bioactive saponin with therapeutic potential as an anti-inflammatory and antiendothelial dysfunction. However, the underlying mechanism for how As-IV ameliorated endothelial dysfunction is still unclear. Therefore, in this study, we examined the protective effect of As-IV against endothelial dysfunction and explored potential molecular biology mechanism. In vivo, rats were intraperitoneally injected with streptozotocin (STZ) at a dose of 65 mg/kg body weight to establish a diabetic model. In vitro studies, rat aortic endothelial cells (RAOEC) were pretreated with As-IV, SB203580 (p38 MAPK inhibitor) for 2 h prior to the addition of high glucose (33 mM glucose). Our findings indicated that As-IV improved impaired endothelium-dependent relaxation and increased the levels of endothelial NO synthase (eNOS) and nitric oxide (NO) both in vivo and in vitro. Besides, As-IV treatment inhibited the elevated inflammation and oxidative stress in diabetic model both in vivo and in vitro. Moreover, As-IV administration reversed the upregulated expression of P2X7R and p-p38 MAPK in vivo and in vitro. Additionally, the effects of both P2X7R siRNA and SB203580 on endothelial cells were similar to As-IV. Collectively, our study demonstrated that As-IV rescued endothelial dysfunction induced by high glucose via inhibition of P2X7R dependent p38 MAPK signaling pathway. This provides a theoretical basis for the further study of the vascular endothelial protective effects of As-IV.
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Terwoord JD, Hearon CM, Racine ML, Ketelhut NB, Luckasen GJ, Richards JC, Dinenno FA. K IR channel activation links local vasodilatation with muscle fibre recruitment during exercise in humans. J Physiol 2020; 598:2621-2636. [PMID: 32329892 DOI: 10.1113/jp279682] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2020] [Accepted: 04/17/2020] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS During exercise, blood flow to working skeletal muscle increases in parallel with contractile activity such that oxygen delivery is sufficient to meet metabolic demand. K+ released from active skeletal muscle fibres could facilitate vasodilatation in proportion to the degree of muscle fibre recruitment. Once released, K+ stimulates inwardly rectifying K+ (KIR ) channels on the vasculature to elicit an increase in blood flow. In the present study, we demonstrate that KIR channels mediate the rapid vasodilatory response to an increase in exercise intensity. We also show that KIR channels augment vasodilatation during exercise which demands greater muscle fibre recruitment independent of the total amount of work performed. These results suggest that K+ plays a key role in coupling the magnitude of vasodilatation to the degree of contractile activity. Ultimately, the findings from this study help us understand the signalling mechanisms that regulate muscle blood flow in humans. ABSTRACT Blood flow to active skeletal muscle is augmented with greater muscle fibre recruitment. We tested whether activation of inwardly rectifying potassium (KIR ) channels underlies vasodilatation with elevated muscle fibre recruitment when work rate is increased (Protocol 1) or held constant (Protocol 2). We assessed forearm vascular conductance (FVC) during rhythmic handgrip exercise under control conditions and during local inhibition of KIR channels (intra-arterial BaCl2 ). In Protocol 1, healthy volunteers performed mild handgrip exercise for 3 min, then transitioned to moderate intensity for 30 s. BaCl2 eliminated vasodilatation during the first contraction at the moderate workload (ΔFVC, BaCl2 : -1 ± 17 vs. control: 30 ± 28 ml min-1 100 mmHg-1 ; n = 9; P = 0.004) and attenuated the 30 s area under the curve by 56 ± 14% (n = 9; P < 0.0001). In Protocol 2, participants performed two exercise bouts in which muscle fibre recruitment was manipulated while total contractile work was held constant via reciprocal changes in contraction frequency: (1) low fibre recruitment, with contractions at 12.5% maximal voluntary contraction once every 4 s and (2) high fibre recruitment, with contractions at 25% maximal voluntary contraction once every 8 s. Under control conditions, steady-state FVC was augmented in high vs. low fibre recruitment (211 ± 90 vs. 166 ± 73 ml min-1 ⋅100 mmHg-1 ; n = 10; P = 0.0006), whereas BaCl2 abolished the difference between high and low fibre recruitment (134 ± 59 vs. 134 ± 63 ml min-1 100 mmHg-1 ; n = 10; P = 0.85). These findings demonstrate that KIR channel activation is a key mechanism linking local vasodilatation with muscle fibre recruitment during exercise.
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Affiliation(s)
- Janée D Terwoord
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Christopher M Hearon
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Matthew L Racine
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Nathaniel B Ketelhut
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Gary J Luckasen
- Medical Center of the Rockies Foundation, University of Colorado Health, Loveland, CO, USA
| | - Jennifer C Richards
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
| | - Frank A Dinenno
- Human Cardiovascular Physiology Laboratory, Department of Health and Exercise Science, Colorado State University, Fort Collins, CO, USA
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Lluch P, Mauricio MD, Vila JM, Segarra G, Medina P, Del Olmo JA, Rodrigo JM, Serra MA. Accumulation of Symmetric Dimethylarginine in Hepatorenal Syndrome. Exp Biol Med (Maywood) 2016; 231:70-5. [PMID: 16380646 DOI: 10.1177/153537020623100108] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
In patients with cirrhosis, nitric oxide (NO), asymmetric dimethylarginine (ADMA), and possibly symmetric dimethylarginine (SDMA) have been linked to the severity of the disease. We investigated whether plasma levels of dimethylarginines and NO are elevated in patients with hepatorenal syndrome (HRS), compared with patients with cirrhosis without renal failure (no-HRS). Plasma levels of NO, ADMA, SDMA, and l-arginine were measured in 11 patients with HRS, seven patients with no-HRS, and six healthy volunteers. SDMA concentration in HRS was higher than in no-HRS and healthy subjects (1.47 ± 0.25 vs. 0.38 ± 0.06 and 0.29 ± 0.04 μM, respectively; P < 0.05). ADMA and NOx concentrations were higher in HRS and no-HRS patients than in healthy subjects (ADMA, 1.20 ± 0.26, 1.11 ± 0.1, and 0.53 ± 0.06 μM, respectively; P < 0.05; NOx, 94 ± 9.1, 95.5 ± 9.54, and 37.67 ± 4.62 μM, respectively; P < 0.05). In patients with HRS there was a positive correlation between serum creatinine and plasma SDMA (r2 = 0.765, P < 0.001) but not between serum creatinine and ADMA or NOx. The results suggest that renal dysfunction is a main determinant of elevated SDMA concentration in HRS. Accumulation of ADMA as a result of impaired hepatic removal may be the causative factor initiating renal vasoconstriction and SDMA retention in the kidney.
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Affiliation(s)
- Paloma Lluch
- Servicio de Hepatología, Hospital Clínico Universitario, Departamento de Medicina, Universidad de Valencia, Valencia, Spain
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Swanson AM, Rossi CA, Ofir K, Mehta V, Boyd M, Barker H, Ledwozyw A, Vaughan O, Martin J, Zachary I, Sebire N, Peebles DM, David AL. Maternal Therapy with Ad.VEGF-A 165 Increases Fetal Weight at Term in a Guinea-Pig Model of Fetal Growth Restriction. Hum Gene Ther 2016; 27:997-1007. [PMID: 27530140 DOI: 10.1089/hum.2016.046] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
In a model of growth-restricted sheep pregnancy, it was previously demonstrated that transient uterine artery VEGF overexpression can improve fetal growth. This approach was tested in guinea-pig pregnancies, where placental physiology is more similar to humans. Fetal growth restriction (FGR) was attained through peri-conceptual nutrient restriction in virgin guinea pigs. Ad.VEGF-A165 or Ad.LacZ (1 × 1010vp) was applied at mid-gestation via laparotomy, delivered externally to the uterine circulation with thermosensitive gel. At short-term (3-8 days post surgery) or at term gestation, pups were weighed, and tissues were sampled for vector spread analysis, VEGF expression, and its downstream effects. Fetal weight at term was increased (88.01 ± 13.36 g; n = 26) in Ad.VEGF-A165-treated animals compared with Ad.LacZ-treated animals (85.52 ± 13.00 g; n = 19; p = 0.028). The brain, liver, and lung weight and crown rump length were significantly larger in short-term analyses, as well as VEGF expression in transduced tissues. At term, molecular analyses confirmed the presence of VEGF transgene in target tissues but not in fetal samples. Tissue histology analysis and blood biochemistry/hematological examination were comparable with controls. Uterine artery relaxation in Ad.VEGF-A165-treated dams was higher compared with Ad.LacZ-treated dams. Maternal uterine artery Ad.VEGF-A165 increases fetal growth velocity and term fetal weight in growth-restricted guinea-pig pregnancy.
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Affiliation(s)
- Anna M Swanson
- 1 Prenatal Cell and Gene Therapy Group, Institute for Women's Health , UCL, London, United Kingdom
| | - Carlo A Rossi
- 1 Prenatal Cell and Gene Therapy Group, Institute for Women's Health , UCL, London, United Kingdom
| | - Keren Ofir
- 1 Prenatal Cell and Gene Therapy Group, Institute for Women's Health , UCL, London, United Kingdom
| | - Vedanta Mehta
- 2 Centre for Cardiovascular Biology and Medicine , UCL, London, United Kingdom
| | - Michael Boyd
- 3 Biological Services Unit, Royal Veterinary College, London, United Kingdom
| | - Hannah Barker
- 3 Biological Services Unit, Royal Veterinary College, London, United Kingdom
| | - Agata Ledwozyw
- 1 Prenatal Cell and Gene Therapy Group, Institute for Women's Health , UCL, London, United Kingdom
| | - Owen Vaughan
- 1 Prenatal Cell and Gene Therapy Group, Institute for Women's Health , UCL, London, United Kingdom
| | - John Martin
- 2 Centre for Cardiovascular Biology and Medicine , UCL, London, United Kingdom
| | - Ian Zachary
- 2 Centre for Cardiovascular Biology and Medicine , UCL, London, United Kingdom
| | - Neil Sebire
- 4 Department of Paediatric Pathology, Institute of Child Health , UCL, London, United Kingdom
| | - Donald M Peebles
- 1 Prenatal Cell and Gene Therapy Group, Institute for Women's Health , UCL, London, United Kingdom
| | - Anna L David
- 1 Prenatal Cell and Gene Therapy Group, Institute for Women's Health , UCL, London, United Kingdom
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Lluch P, Segarra G, Medina P. Asymmetric dimethylarginine as a mediator of vascular dysfunction in cirrhosis. World J Gastroenterol 2015; 21:9466-9475. [PMID: 26327755 PMCID: PMC4548108 DOI: 10.3748/wjg.v21.i32.9466] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Revised: 06/05/2015] [Accepted: 07/18/2015] [Indexed: 02/06/2023] Open
Abstract
Cirrhosis is associated with marked abnormalities in the circulatory function that involve a reduction in systemic vascular resistance. An important cause of this vasodilatation is the increased production or activity of nitric oxide (NO) in the splanchnic circulation. During portal hypertension and cirrhosis an increased endothelial NO synthase (eNOS) activity is demonstrated in splanchnic vessels. In contrast, the activity of eNOS in the cirrhotic liver is decreased, which suggests a different regulation of eNOS in the liver and in the splanchnic vessels. Asymmetric dimethylarginine (ADMA) is an endogenous NO inhibitor and higher plasma levels of ADMA are related to increased cardiovascular risk in both the general population and among patients with cirrhosis. It has been demonstrated that the liver is a key player in the metabolism of ADMA. This observation was further supported by investigations in human patients, showing a close correlation between ADMA plasma levels and the degree of hepatic dysfunction. ADMA is degraded to citrulline and dimethylamine by dimethylarginine dimethylaminohydrolases (DDAHs). DDAHs are expressed as type 1 and 2 isoforms and are widely distributed in various organs and tissues, including the liver. In this review, we discuss experimental and clinical data that document the effects of dimethylarginines on vascular function in cirrhosis. Our increasing understanding of the routes of synthesis and metabolism of methylarginines is beginning to provide insights into novel mechanisms of liver disease and allowing us to identify potential therapeutic opportunities.
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Vila JM, Aldasoro M, Segarra G, Martínez-León JB, Mauricio MD, Lluch S, Medina P. Contractile responses of human thyroid arteries to vasopressin. Life Sci 2013; 93:525-9. [PMID: 24002018 DOI: 10.1016/j.lfs.2013.08.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 07/29/2013] [Accepted: 08/20/2013] [Indexed: 11/25/2022]
Abstract
AIMS In the present study we investigated the intervention of nitric oxide and prostacyclin in the responses to vasopressin of isolated thyroid arteries obtained from multi-organ donors. MAIN METHODS Paired artery rings from glandular branches of the superior thyroid artery, one normal and the other deendothelised, were mounted in organ baths for isometric recording of tension. Concentration-response curves to vasopressin were determined in the absence and in the presence of either the vasopressin V1 receptor antagonist d(CH2)5Tyr(Me)AVP (10(-8)M), the nitric oxide synthase inhibitor N(G)-monomethyl-l-arginine (L-NMMA, 10(-4)M), or the inhibitor of prostaglandins indomethacin (10(-6)M). KEY FINDINGS In artery rings under resting tension, vasopressin produced concentration-dependent, endothelium-independent contractions. The vasopressin V1 receptor antagonist d(CH2)5Tyr(Me)AVP (10(-8)M) displaced the control curve to vasopressin 19-fold to the right in a parallel manner. The contractile response to vasopressin was unaffected by L-NMMA or by indomethacin. SIGNIFICANCE Vasopressin causes constriction of human thyroid arteries by stimulation of V1 vasopressin receptors located on smooth muscle cells. These effects are not linked to the presence of an intact endothelium or to the release of nitric oxide or prostaglandins. The constriction of thyroid arteries may be particularly relevant in certain pathophysiological circumstances in which vasopressin is released in amounts that could interfere with the blood supply to the thyroid gland.
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Affiliation(s)
- José M Vila
- Departamento de Fisiología, Universidad de Valencia, 46010 Valencia, Spain; Instituto de Investigación Sanitaria INCLIVA, Hospital Clínico Universitario, 46010 Valencia, Spain
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Wy14643 improves vascular function in the aorta of the spontaneously hypertensive rat mainly by activating peroxisome proliferator-activated receptors alpha. Eur J Pharmacol 2012; 696:101-10. [DOI: 10.1016/j.ejphar.2012.09.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Revised: 09/05/2012] [Accepted: 09/17/2012] [Indexed: 12/15/2022]
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Ozkor MA, Quyyumi AA. Endothelium-derived hyperpolarizing factor and vascular function. Cardiol Res Pract 2011; 2011:156146. [PMID: 21876822 PMCID: PMC3157651 DOI: 10.4061/2011/156146] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Revised: 05/27/2011] [Accepted: 05/27/2011] [Indexed: 01/20/2023] Open
Abstract
Endothelial function refers to a multitude of physiological processes that maintain healthy homeostasis of the vascular wall. Exposure of the endothelium to cardiac risk factors results in endothelial dysfunction and is associated with an alteration in the balance of vasoactive substances produced by endothelial cells. These include a reduction in nitric oxide (NO), an increase in generation of potential vasoconstrictor substances and a potential compensatory increase in other mediators of vasodilation. The latter has been surmised from data demonstrating persistent endothelium-dependent vasodilatation despite complete inhibition of NO and prostaglandins. This remaining non-NO, non-prostaglandin mediated endothelium-dependent vasodilator response has been attributed to endothelium-derived hyperpolarizing factor/s (EDHF). Endothelial hyperpolarization is likely due to several factors that appear to be site and species specific. Experimental studies suggest that the contribution of the EDHFs increase as the vessel size decreases, with a predominance of EDHF activity in the resistance vessels, and a compensatory up-regulation of hyperpolarization in states characterized by reduced NO availability. Since endothelial dysfunction is a precursor for atherosclerosis development and its magnitude is a reflection of future risk, then the mechanisms underlying endothelial dysfunction need to be fully understood, so that adequate therapeutic interventions can be designed.
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Affiliation(s)
- Muhiddin A Ozkor
- The Heart Hospital, University College London, London WIG 8PH, UK
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Silva DR, Gazzana MB, John AB, Siqueira DR, Maia ALS, Barreto SSM. Pulmonary arterial hypertension and thyroid disease. J Bras Pneumol 2009; 35:179-85. [PMID: 19287922 DOI: 10.1590/s1806-37132009000200012] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2008] [Accepted: 09/29/2008] [Indexed: 11/22/2022] Open
Abstract
Recent studies have suggested an association between pulmonary arterial hypertension (PAH) and thyroid diseases (hypothyroidism and hyperthyroidism). This combination has a good prognosis, because the increase in the pulmonary artery pressure is usually slight and reverses after the treatment of the thyroid disease. Although the exact mechanism involved in the pathogenesis of this combination has not yet been established, it has been hypothesized that thyroid hormones and autoimmunity have a direct influence. Due to the high prevalence of thyroid disease in patients with PAH, thyroid function tests should be considered in the investigation of every patient with PAH. In this review, we describe the prevalence of PAH in patients with thyroid diseases and the prevalence of thyroid disease in patients with PAH, as well as addressing the principal effects that thyroid diseases have on the respiratory system. In addition, we report the treatment effects in patients with these diseases.
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Abstract
The endothelium controls vascular tone not only by releasing NO and prostacyclin, but also by other pathways causing hyperpolarization of the underlying smooth muscle cells. This characteristic was at the origin of the term 'endothelium-derived hyperpolarizing factor' (EDHF). However, this acronym includes different mechanisms. Arachidonic acid metabolites derived from the cyclo-oxygenases, lipoxygenases and cytochrome P450 pathways, H(2)O(2), CO, H(2)S and various peptides can be released by endothelial cells. These factors activate different families of K(+) channels and hyperpolarization of the vascular smooth muscle cells contribute to the mechanisms leading to their relaxation. Additionally, another pathway associated with the hyperpolarization of both endothelial and vascular smooth muscle cells contributes also to endothelium-dependent relaxations (EDHF-mediated responses). These responses involve an increase in the intracellular Ca(2+) concentration of the endothelial cells, followed by the opening of SK(Ca) and IK(Ca) channels (small and intermediate conductance Ca(2+)-activated K(+) channels respectively). These channels have a distinct subcellular distribution: SK(Ca) are widely distributed over the plasma membrane, whereas IK(Ca) are preferentially expressed in the endothelial projections toward the smooth muscle cells. Following SK(Ca) activation, smooth muscle hyperpolarization is preferentially evoked by electrical coupling through myoendothelial gap junctions, whereas, following IK(Ca) activation, K(+) efflux can activate smooth muscle Kir2.1 and/or Na(+)/K(+)-ATPase. EDHF-mediated responses are altered by aging and various pathologies. Therapeutic interventions can restore these responses, suggesting that the improvement in the EDHF pathway contributes to their beneficial effect. A better characterization of EDHF-mediated responses should allow the determination of whether or not new drugable targets can be identified for the treatment of cardiovascular diseases.
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Endothelium-derived hyperpolarizing factor in vascular physiology and cardiovascular disease. Atherosclerosis 2009; 202:330-44. [DOI: 10.1016/j.atherosclerosis.2008.06.008] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2008] [Revised: 05/16/2008] [Accepted: 06/11/2008] [Indexed: 12/20/2022]
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David AL, Torondel B, Zachary I, Wigley V, Abi-Nader K, Nader KA, Mehta V, Buckley SMK, Cook T, Boyd M, Rodeck CH, Martin J, Peebles DM. Local delivery of VEGF adenovirus to the uterine artery increases vasorelaxation and uterine blood flow in the pregnant sheep. Gene Ther 2008; 15:1344-50. [PMID: 18563186 DOI: 10.1038/gt.2008.102] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Impaired materno-placental perfusion causes two important obstetric complications, fetal growth restriction and preeclampsia. This study investigated whether adenoviral vector-mediated overexpression of vascular endothelial growth factor (VEGF) in the uterine arteries (UtAs) increases uterine artery blood flow (UBF). First-generation adenovirus vectors (5 x 10(11) particles) containing the VEGF gene (Ad.VEGF-A or -D) or the beta-galactosidase reporter gene (Ad.lacZ) were injected into the UtAs of pregnant sheep (n=6) at 88-102 days of gestation (term=145 days). UBF was measured using Doppler sonography before, and 4-7 days after injection. Mean UBF increased significantly from 233+/-156 (s.d.) ml min(-1) to 753+/-415 ml min(-1) following Ad.VEGF-A injection (P=0.005, n=5); Ad.lacZ infection had no significant effect. Organ bath experiments on uterine arterial sections 4-7 days after injection showed that, compared with Ad.lacZ vessels, Ad.VEGF-A-transduced vessels had a reduced contractile response to phenylephrine (E max 148+/-10.9 vs E max 228.2+/-27.5, P<0.05) but increased relaxation with bradykinin (pD2 (-log EC50) values 9.11+/-0.01 vs 8.65+/-0.11, P<0.05). Injection of Ad.VEGF-A into the UtAs increases UBF by enhancing vasodilatation. This may provide the basis for therapy in pregnancies complicated by uteroplacental insufficiency.
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Affiliation(s)
- A L David
- Prenatal Gene Therapy Group, Institute for Women's Health, Royal Free and University College London Medical School, London, UK.
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Abstract
Endothelium-dependent relaxations are attributed to the release of various factors, such as nitric oxide, carbon monoxide, reactive oxygen species, adenosine, peptides and arachidonic acid metabolites derived from the cyclooxygenases, lipoxygenases, and cytochrome P450 monooxygenases pathways. The hyperpolarization of the smooth muscle cell can contribute to or be an integral part of the mechanisms underlying the relaxations elicited by virtually all these endothelial mediators. These endothelium-derived factors can activate different families of K(+) channels of the vascular smooth muscle. Other events associated with the hyperpolarization of both the endothelial and the vascular smooth muscle cells (endothelium-derived hyperpolarizing factor (EDHF)-mediated responses) contribute also to endothelium-dependent relaxations. These responses involve an increase in the intracellular Ca(2+) concentration of the endothelial cells followed by the opening of Ca(2+)-activated K(+) channels of small and intermediate conductance and the subsequent hyperpolarization of these cells. Then, the endothelium-dependent hyperpolarization of the underlying smooth muscle cells can be evoked by direct electrical coupling through myoendothelial junctions and/or the accumulation of K(+) ions in the intercellular space between the two cell types. These various mechanisms are not necessarily mutually exclusive and, depending on the vascular bed and the experimental conditions, can occur simultaneously or sequentially, or also may act synergistically.
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Affiliation(s)
- Michel Félétou
- Department of Angiology, Institut de Recherches Servier, Suresnes, France
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Haddy FJ, Vanhoutte PM, Feletou M. Role of potassium in regulating blood flow and blood pressure. Am J Physiol Regul Integr Comp Physiol 2006; 290:R546-52. [PMID: 16467502 DOI: 10.1152/ajpregu.00491.2005] [Citation(s) in RCA: 180] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Unlike sodium, potassium is vasoactive; for example, when infused into the arterial supply of a vascular bed, blood flow increases. The vasodilation results from hyperpolarization of the vascular smooth muscle cell subsequent to potassium stimulation by the ion of the electrogenic Na+-K+ pump and/or activating the inwardly rectifying Kir channels. In the case of skeletal muscle and brain, the increased flow sustains the augmented metabolic needs of the tissues. Potassium ions are also released by the endothelial cells in response to neurohumoral mediators and physical forces (such as shear stress) and contribute to the endothelium-dependent relaxations, being a component of endothelium-derived hyperpolarization factor-mediated responses. Dietary supplementation of potassium can lower blood pressure in normal and some hypertensive patients. Again, in contrast to NaCl restriction, the response to potassium supplementation is slow to appear, taking approximately 4 wk. Such supplementation reduces the need for antihypertensive medication. "Salt-sensitive" hypertension responds particularly well, perhaps, in part, because supplementation with potassium increases the urinary excretion of sodium chloride. Potassium supplementation may even reduce organ system complications (e.g., stroke).
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Affiliation(s)
- Francis J Haddy
- Department of Physiology and Biomedical Engineering, Mayo Clinic, College of Medicine, Rochester, Minnesota, USA
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Ortega J, Vila JM, Mauricio MD, Segarra G, Medina P, Martínez-León JB, Lluch S. Nitric oxide mediates abnormal responsiveness of thyroid arteries in methimazole-treated patients. Eur J Endocrinol 2005; 152:551-6. [PMID: 15817910 DOI: 10.1530/eje.1.01889] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE We studied the intervention of nitric oxide (NO), prostacyclin and endothelium-derived hyperpolarizing factor (EDHF) in mediating responses to acetylcholine in thyroid arteries from euthyroid and methimazole-treated (MT) patients. DESIGN AND METHODS Branches of the superior thyroid artery were obtained from 19 euthyroid patients and 17 MT patients (euthyroid at the time of surgery) undergoing total thyroidectomy or hemithyroidectomy. Artery rings were suspended in organ baths for isometric recording of tension. RESULTS AND CONCLUSIONS Acetylcholine caused endothelium-dependent relaxation of greater magnitude in arteries from MT patients (pD(2) (-log EC(50)) values were 7.68 +/- 0.19 in euthyroid and 8.17 +/- 0.26 in MT patients, P < 0.05). The relaxation was unaffected by indomethacin and was partially reduced by the NO-synthase inhibitor NG-monomethyl-L-arginine (L-NMMA). This reduction was higher in arteries from MT patients (50 +/- 6%) as compared with euthyroid patients (36 +/- 6%) (P < 0.05). Inhibition of K(+) channels using apamin combined with charybdotoxin or high K(+) solution abolished the relaxation resistance to L-NMMA and indomethacin. The maximal contraction response to noradrenaline (as a percentage of the response to 100 mM KCl) was lower in MT than in euthyroid patients (57 +/- 10 and 96 +/- 8 respectively, P < 0.05). The hyporesponsiveness to noradrenaline in arteries from MT patients was corrected by L-NMMA. The results indicate that: (i) thyroid arteries from MT patients show an increased relaxation response to acethylcholine and a decreased contraction response to noradrenaline due to overproduction of NO; (ii) EDHF plays a prominent role in acetylcholine-induced relaxation through activation of Ca(2+)-activated K(+) channels; (iii) the abnormal endothelium-dependent responses in arteries from MT patients are not corrected by medical treatment.
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Affiliation(s)
- Joaquín Ortega
- Department of Surgery, Hospital Clínico Research Unit, University of Valencia, Spain
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