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Assersen KB, Sumners C, Steckelings UM. The Renin-Angiotensin System in Hypertension, a Constantly Renewing Classic: Focus on the Angiotensin AT 2-Receptor. Can J Cardiol 2020; 36:683-693. [PMID: 32389341 DOI: 10.1016/j.cjca.2020.02.095] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 02/28/2020] [Accepted: 02/29/2020] [Indexed: 02/07/2023] Open
Abstract
It is common knowledge that the renin-angiotensin system (RAS), in particular angiotensin II acting through the angiotensin AT1-receptor (AT1R), is pivotal for the regulation of blood pressure (BP) and extracellular volume. More recent findings have revealed that the RAS is far more complex than initially thought and that it harbours additional mediators and receptors, which are able to counteract and thereby fine-tune AT1R-mediated actions. This review will focus on the angiotensin AT2-receptor (AT2R), which is one of the "counter-regulatory" receptors within the RAS. It will review and discuss data related to the role of the AT2R in regulation of BP and focus on the following 3 questions: Do peripheral AT2R have an impact on BP regulation, and, if so, does this effect become apparent only under certain conditions? Are central nervous system AT2R involved in regulation of BP, and, if so, which brain areas are involved and what are the mechanisms? Does dysfunction of AT2R contribute to the pathogenesis of hypertension in preeclampsia?
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Affiliation(s)
- Kasper B Assersen
- Institute for Molecular Medicine, Department of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark
| | - Colin Sumners
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, Florida, USA
| | - U Muscha Steckelings
- Institute for Molecular Medicine, Department of Cardiovascular and Renal Research, University of Southern Denmark, Odense, Denmark.
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Sumners C, Alleyne A, Rodríguez V, Pioquinto DJ, Ludin JA, Kar S, Winder Z, Ortiz Y, Liu M, Krause EG, de Kloet AD. Brain angiotensin type-1 and type-2 receptors: cellular locations under normal and hypertensive conditions. Hypertens Res 2019; 43:281-295. [PMID: 31853042 DOI: 10.1038/s41440-019-0374-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Revised: 10/25/2019] [Accepted: 11/02/2019] [Indexed: 12/15/2022]
Abstract
Brain angiotensin-II (Ang-II) type-1 receptors (AT1Rs), which exert profound effects on normal cardiovascular, fluid, and metabolic homeostasis, are overactivated in and contribute to chronic sympathoexcitation and hypertension. Accumulating evidence indicates that the activation of Ang-II type-2 receptors (AT2Rs) in the brain exerts effects that are opposite to those of AT1Rs, lowering blood pressure, and reducing hypertension. Thus, it would be interesting to understand the relative cellular localization of AT1R and AT2R in the brain under normal conditions and whether this localization changes during hypertension. Here, we developed a novel AT1aR-tdTomato reporter mouse strain in which the location of brain AT1aR was largely consistent with that determined in the previous studies. This AT1aR-tdTomato reporter mouse strain was crossed with our previously described AT2R-eGFP reporter mouse strain to yield a novel dual AT1aR/AT2R reporter mouse strain, which allowed us to determine that AT1aR and AT2R are primarily localized to different populations of neurons in brain regions controlling cardiovascular, fluid, and metabolic homeostasis. Using the individual AT1aR-tdTomato reporter mice, we also demonstrated that during hypertension induced by the administration of deoxycorticosterone acetate-salt, there was no shift in the expression of AT1aR from neurons to microglia or astrocytes in the paraventricular nucleus, a brain area important for sympathetic regulation. Using AT2R-eGFP reporter mice under similar hypertensive conditions, we demonstrated that the same was true of AT2R expression in the nucleus of the solitary tract (NTS), an area critical for baroreflex control. Collectively, these findings provided a novel means to assess the colocalization of AT1R and AT2R in the brain and a novel view of their cellular localization in hypertension.
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Affiliation(s)
- Colin Sumners
- Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, FL, 32611, USA
| | - Amy Alleyne
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL, 32611, USA
| | - Vermalí Rodríguez
- Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, FL, 32611, USA
| | - David J Pioquinto
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL, 32611, USA
| | - Jacob A Ludin
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL, 32611, USA
| | - Shormista Kar
- Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, FL, 32611, USA
| | - Zachary Winder
- Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, FL, 32611, USA.,Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL, 32611, USA
| | - Yuma Ortiz
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL, 32611, USA
| | - Meng Liu
- Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, FL, 32611, USA
| | - Eric G Krause
- Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, FL, 32611, USA
| | - Annette D de Kloet
- Department of Physiology and Functional Genomics, College of Medicine, University of Florida, Gainesville, FL, 32611, USA.
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Légat L, Smolders IJ, Dupont AG. Investigation of the Role of AT2 Receptors in the Nucleus Tractus Solitarii of Normotensive Rats in Blood Pressure Control. Front Neurosci 2019; 13:589. [PMID: 31231188 PMCID: PMC6560158 DOI: 10.3389/fnins.2019.00589] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 05/23/2019] [Indexed: 11/25/2022] Open
Abstract
Aim The nucleus tractus solitarii (NTS) densely expresses angiotensin II type 2 receptors (AT2R), which are mainly located on inhibitory gamma-aminobutyric acid (GABA) neurons. Central AT2R stimulation reduces blood pressure, and AT2R stimulation in the rostral ventrolateral medulla (RVLM), mediates a hypotensive response through a GABAergic mechanism. We aimed to test the hypothesis that an AT2R mediated inhibition of the GABA release within the NTS might be involved in this hypotensive response, by assessing possible alterations in blood pressure and heart rate, as well as in GABA levels in normotensive Wistar rats. Methods In vivo microdialysis was used for measurement of extracellular GABA levels and for perfusion of the selective AT2R agonist, Compound 21, within the NTS. Our set-up allowed to determine simultaneously the excitatory glutamate dialysate levels. The mean arterial pressure and heart rate responses were monitored with a pressure transducer. Results Local perfusion of Compound 21 into the NTS did not modify blood pressure and heart rate, nor glutamate and GABA levels compared to baseline concentrations. A putative effect was also not unmasked by concomitant angiotensin II type 1 receptor blockade with candesartan. Positive control experiments confirmed that the experimental set up had enough sensitivity to detect a reduction in GABA dialysate levels and blood pressure. Conclusion The results did not provide evidence for a role of the AT2R within the NTS in the control of blood pressure, nor for an interaction with local GABAergic signaling in normotensive rats.
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Affiliation(s)
- Laura Légat
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Research Group Experimental Pharmacology (EFAR), Center for Neurosciences (C4N), Vrije Universiteit Brussel, Brussels, Belgium.,Cardiovascular Center, Universitair Ziekenhuis Brussel, Brussels, Belgium.,Department of Clinical Pharmacology and Clinical Pharmacy (KFAR), Universitair Ziekenhuis Brussel, Brussels, Belgium
| | - Ilse J Smolders
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Research Group Experimental Pharmacology (EFAR), Center for Neurosciences (C4N), Vrije Universiteit Brussel, Brussels, Belgium
| | - Alain G Dupont
- Department of Pharmaceutical Chemistry, Drug Analysis and Drug Information, Research Group Experimental Pharmacology (EFAR), Center for Neurosciences (C4N), Vrije Universiteit Brussel, Brussels, Belgium.,Cardiovascular Center, Universitair Ziekenhuis Brussel, Brussels, Belgium.,Department of Clinical Pharmacology and Clinical Pharmacy (KFAR), Universitair Ziekenhuis Brussel, Brussels, Belgium
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