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Pulakat L, Sumners C. Angiotensin Type 2 Receptors: Painful, or Not? Front Pharmacol 2020; 11:571994. [PMID: 33424587 PMCID: PMC7785813 DOI: 10.3389/fphar.2020.571994] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 11/25/2020] [Indexed: 12/14/2022] Open
Abstract
Pain in response to various types of acute injury can be a protective stimulus to prevent the organism from using the injured part and allow tissue repair and healing. On the other hand, neuropathic pain, defined as ‘pain caused by a lesion or disease of the somatosensory nervous system’, is a debilitating pathology. The TRPA1 neurons in the Dorsal Root Ganglion (DRG) respond to reactive oxygen species (ROS) and induce pain. In acute nerve injury and inflammation, macrophages infiltrating the site of injury undergo an oxidative burst, and generate ROS that promote tissue repair and induce pain via TRPA1. The latter discourages using the injured limb, with a lack of movement helping wound healing. In chronic inflammation caused by diabetes, cancer etc., ROS levels increase systemically and modulate TRPA1 neuronal functions and cause debilitating neuropathic pain. It is important to distinguish between drug targets that elicit protective vs. debilitating pain when developing effective drugs for neuropathic pain. In this context, the connection of the Angiotensin type 2 receptor (AT2R) to neuropathic pain presents an interesting dilemma. Several lines of evidence show that AT2R activation promotes anti-inflammatory and anti-nociceptive signaling, tissue repair, and suppresses ROS in chronic inflammatory models. Conversely, some studies suggest that AT2R antagonists are anti-nociceptive and therefore AT2R is a drug target for neuropathic pain. However, AT2R expression in nociceptive neurons is lacking, indicating that neuronal AT2R is not involved in neuropathic pain. It is also important to consider that Novartis terminated their phase II clinical trial (EMPHENE) to validate that AT2R antagonist EMA401 mitigates post-herpetic neuralgia. This trial, conducted in Australia, United Kingdom, and a number of European and Asian countries in 2019, was discontinued due to pre-clinical drug toxicity data. Moreover, early data from the trial did not show statistically significant positive outcomes. These facts suggest that may AT2R not be the proper drug target for neuropathic pain in humans and its inhibition can be harmful.
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Affiliation(s)
- Lakshmi Pulakat
- Molecular Cardiology Research Institute, Tufts Medical Center, Boston, MA, United States.,Department of Medicine, Tufts University School of Medicine, Boston, MA, United States
| | - Colin Sumners
- Department of Physiology and Functional Genomics, University of Florida, Gainesville, FL, United States
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Santos RAS, Oudit GY, Verano-Braga T, Canta G, Steckelings UM, Bader M. The renin-angiotensin system: going beyond the classical paradigms. Am J Physiol Heart Circ Physiol 2019; 316:H958-H970. [PMID: 30707614 PMCID: PMC7191626 DOI: 10.1152/ajpheart.00723.2018] [Citation(s) in RCA: 184] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Thirty years ago, a novel axis of the renin-angiotensin system (RAS) was unveiled by the discovery of angiotensin-(1−7) [ANG-(1−7)] generation in vivo. Later, angiotensin-converting enzyme 2 (ACE2) was shown to be the main mediator of this reaction, and Mas was found to be the receptor for the heptapeptide. The functional analysis of this novel axis of the RAS that followed its discovery revealed numerous protective actions in particular for cardiovascular diseases. In parallel, similar protective actions were also described for one of the two receptors of ANG II, the ANG II type 2 receptor (AT2R), in contrast to the other, the ANG II type 1 receptor (AT1R), which mediates deleterious actions of this peptide, e.g., in the setting of cardiovascular disease. Very recently, another branch of the RAS was discovered, based on angiotensin peptides in which the amino-terminal aspartate was replaced by alanine, the alatensins. Ala-ANG-(1−7) or alamandine was shown to interact with Mas-related G protein-coupled receptor D, and the first functional data indicated that this peptide also exerts protective effects in the cardiovascular system. This review summarizes the presentations given at the International Union of Physiological Sciences Congress in Rio de Janeiro, Brazil, in 2017, during the symposium entitled “The Renin-Angiotensin System: Going Beyond the Classical Paradigms,” in which the signaling and physiological actions of ANG-(1−7), ACE2, AT2R, and alatensins were reported (with a focus on noncentral nervous system-related tissues) and the therapeutic opportunities based on these findings were discussed.
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Affiliation(s)
- Robson Augusto Souza Santos
- National Institute of Science and Technology in Nanobiopharmaceutics, Department of Physiology and Biophysics, Federal University of Minas Gerais , Belo Horizonte, Minas Gerais , Brazil
| | - Gavin Y Oudit
- Division of Cardiology, Department of Medicine, Mazankowski Alberta Heart Institute, University of Alberta , Edmonton , Canada
| | - Thiago Verano-Braga
- National Institute of Science and Technology in Nanobiopharmaceutics, Department of Physiology and Biophysics, Federal University of Minas Gerais , Belo Horizonte, Minas Gerais , Brazil
| | - Giovanni Canta
- National Institute of Science and Technology in Nanobiopharmaceutics, Department of Physiology and Biophysics, Federal University of Minas Gerais , Belo Horizonte, Minas Gerais , Brazil
| | - Ulrike Muscha Steckelings
- Department of Molecular Medicine, Cardiovascular & Renal Research, University of Southern Denmark, Odense, Denmark
| | - Michael Bader
- Max Delbrück Center for Molecular Medicine , Berlin , Germany.,Deutsches Zentrum für Herz-Kreislaufforschung, Partner Site Berlin, Berlin , Germany.,Berlin Institute of Health , Berlin , Germany.,Charité-University Medicine, Berlin , Germany.,Institute for Biology, University of Lübeck , Lübeck , Germany
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Gul R, Ramdas M, Mandavia CH, Sowers JR, Pulakat L. RAS-Mediated Adaptive Mechanisms in Cardiovascular Tissues: Confounding Factors of RAS Blockade Therapy and Alternative Approaches. Cardiorenal Med 2012; 2:268-280. [PMID: 23381810 DOI: 10.1159/000343456] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Since the classic experiments by Tigerstedt and Bergman that established the role of renin in hypertension a century ago, aggressive efforts have been launched to effectively block the renin-angiotensin system (RAS). Blockade of RAS is advocated at multiple levels by direct renin inhibitor, angiotensin-converting enzyme inhibitor and/or angiotensin II type 1 receptor blocker, or aldosterone inhibitor (spironolactone), and has now become part of the standard of care to control hypertension and related metabolic diseases including diabetes. However, recent lessons learned from randomized clinical trials question the wisdom of blocking RAS at multiple levels. In this context, it is highly pertinent that components of RAS are evolutionarily conserved, and novel physiological/adaptive/protective roles for renin and angiotensin-converting enzyme are currently emerging. Angiotensin II, the classical RAS effector peptide responsible for hypertension, hypertrophy, fluid retention and fibrosis, manifests its cardiovascular protective effect when it activates the angiotensin II type 2 receptor. Additionally, angiotensin-converting enzyme 2 and the angiotensin II metabolite Ang-(1-7) that acts through the Mas proto-oncogene constitute the cardiovascular and renal protective branch of RAS. It is conceivable that modulating this vasodilative/anti-inflammatory branch of RAS by activation of the RAS components that constitute this branch may offer a safer long-term treatment strategy to balance RAS activity and achieve homeostasis compared to chronic multilevel RAS inhibition.
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Affiliation(s)
- Rukhsana Gul
- Department of Internal Medicine, University of Missouri School of Medicine, Columbia, Mo., USA ; Diabetes and Cardiovascular Research Center, University of Missouri School of Medicine, Columbia, Mo., USA ; Harry S Truman Veterans Affair Medical Center, University of Missouri, Columbia, Mo., USA
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Castrop H. Angiotensin receptor-associated proteins: local modulators of the renin–angiotensin system. Pflugers Arch 2012; 465:111-9. [DOI: 10.1007/s00424-012-1113-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Revised: 04/30/2012] [Accepted: 05/02/2012] [Indexed: 01/11/2023]
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Lara L, Cavalcante F, Axelband F, De Souza A, Lopes A, Caruso-Neves C. Involvement of the Gi/o/cGMP/PKG pathway in the AT2-mediated inhibition of outer cortex proximal tubule Na+-ATPase by Ang-(1-7). Biochem J 2006; 395:183-90. [PMID: 16390332 PMCID: PMC1409686 DOI: 10.1042/bj20051455] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2005] [Revised: 12/20/2005] [Accepted: 01/04/2006] [Indexed: 12/19/2022]
Abstract
The molecular mechanisms involved in the Ang-(1-7) [angiotensin-(1-7)] effect on sodium renal excretion remain to be determined. In a previous study, we showed that Ang-(1-7) has a biphasic effect on the proximal tubule Na+-ATPase activity, with the stimulatory effect mediated by the AT1 receptor. In the present study, we investigated the molecular mechanisms involved in the inhibition of the Na+-ATPase by Ang-(1-7). All experiments were carried out in the presence of 0.1 nM losartan to block the AT1 receptor-mediated stimulation. In this condition, Ang-(1-7) at 0.1 nM inhibited the Na+-ATPase activity of the proximal tubule by 54%. This effect was reversed by 10 nM PD123319, a specific antagonist of the AT2 receptor, and by 1 muM GDP[beta-S] (guanosine 5'-[beta-thio]diphosphate), an inhibitor of G protein. Ang-(1-7) at 0.1 M induced [35S]GTP[S] (guanosine 5'-[gamma-[35S]thio]triphosphate) binding and 1 mug/ml pertussis toxin, an inhibitor of G(i/o) protein, reversed the Ang-(1-7) effect. Furthermore, it was observed that the inhibitory effect of Ang-(1-7) on the Na+-ATPase activity was completely reversed by 0.1 microM LY83583, an inhibitor of guanylate cyclase, and by 2 muM KT5823, a PKG (protein kinase G) inhibitor, and was mimicked by 10 nM d-cGMP (dibutyryl cGMP). Ang-(1-7) increased the PKG activity by 152% and this effect was abolished by 10 nM PD123319 and 0.1 microM LY83583. Taken together, these data indicate that Ang-(1-7) inhibits the proximal tubule Na+-ATPase by interaction with the AT2 receptor that subsequently activates the G(i/o) protein/cGMP/PKG pathway.
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Key Words
- angiotensin-(1–7)
- angiotensin receptors
- na+-atpase
- renal epithelium
- cellular signalling
- extracellular volume
- ang-(1–7), angiotensin-(1–7)
- d-camp, dibutyryl camp
- d-cgmp, dibutyryl cgmp
- gdp[β-s], guanosine 5′-[β-thio]diphosphate
- gpcr, g-protein-coupled receptor
- gtp[s], guanosine 5′-[γ-thio]triphosphate
- nos, nitric oxide synthetase
- pacocf3, palmitoyl trifluoromethyl ketone
- pka, protein kinase a
- pkai, pka inhibitor peptide
- pkc, protein kinase c
- pkg, protein kinase g
- pla2, phospholipase a2
- ptx, pertussis toxin
- tbst, tris-buffered saline containing 0.05% tween 20
- tca, trichloroacetic acid
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Affiliation(s)
- Lucienne da Silva Lara
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, CCS-bloco G, 21949-900, Rio de Janeiro, RJ, Brazil
| | - Fabíola Cavalcante
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, CCS-bloco G, 21949-900, Rio de Janeiro, RJ, Brazil
| | - Flavia Axelband
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, CCS-bloco G, 21949-900, Rio de Janeiro, RJ, Brazil
| | - Aloa Machado De Souza
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, CCS-bloco G, 21949-900, Rio de Janeiro, RJ, Brazil
| | - Anibal Gil Lopes
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, CCS-bloco G, 21949-900, Rio de Janeiro, RJ, Brazil
| | - Celso Caruso-Neves
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, CCS-bloco G, 21949-900, Rio de Janeiro, RJ, Brazil
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