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Gupta M, Korde JP, Bahiram KB, Sardar VM, Kurkure NV. Expression and localization of apelin and apelin receptor (APJ) in buffalo ovarian follicles and corpus luteum and the in-vitro effect of apelin on steroidogenesis and survival of granulosa cells. Theriogenology 2023; 197:240-251. [PMID: 36525863 DOI: 10.1016/j.theriogenology.2022.12.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 12/04/2022] [Accepted: 12/07/2022] [Indexed: 12/13/2022]
Abstract
Apelin is an adipose tissue-derived hormone with many physiological functions, including the regulation of female reproduction. It acts through an orphan G protein-coupled receptor APJ/APLNR. The present study aimed to investigate the expression of apelin and its receptor APJ in the ovarian follicles and corpus luteum (CL) and the role of apelin on steroidogenesis and cell survival. Ovarian follicles were classified into four groups based on size and estradiol (E2) level in the follicular fluid as follows: (i) F1 (4-6 mm; <0.5 ng/mL) (ii) F2 (7-9 mm; 0.5-5 ng/mL) (iii) F3 (10-13 mm; 5-40 ng/mL) and (iv) F4 (dominant/pre-ovulatory follicle) (>13 mm; >180 ng/mL). The corpora lutea (CL) were categorized into early (CL1), mid (CL2), late luteal (CL3), and regressing (CL4) CL stages. Expression of apelin increased with follicle size, with significantly greatest in the dominant or pre-ovulatory follicle (P < 0.05). Expression of APJ was greater in large and dominant follicles than in small and medium follicles (P < 0.05). In CL, the mRNA and protein abundance of apelin and apelin receptor was greater during mid (CL2) and late luteal (CL3) stages as compared to early (CL1) and regressing (CL4) stages (P < 0.05). Both the factors were localized in granulosa and theca cells of follicles and small and large luteal cells of CL. The pattern of the intensity of immunofluorescence was similar to mRNA and protein expression. Granulosa cells were cultured in vitro and treated at 1, 10, and 10 ng/mL apelin-13 either alone or in the presence of the follicle-stimulating hormone (FSH) (30 ng/mL) or insulin-like growth factor-I (IGF-I) (10 ng/mL) for 48 h. The luteal cells were treated with apelin-13 at 1, 10, and 100 ng/mL doses for 48 h. Apelin treatment at 10 and 100 ng/ml significantly (P < 0.05) increased E2 secretion, cytochrome P450 aromatase or CYP19A1 expression in GC. In luteal cells, apelin at 10 ng/mL and 100 ng/mL significantly (P < 0.05) increased progesterone (P4) secretion and HSD3B1 expression. In GCs, apelin, either alone or in combination, increased PCNA expression and inhibited CASPASE3 expression suggesting its role in cell survival. In conclusion, this study provides novel evidence for the presence of apelin and receptor APJ in ovarian follicles and corpora lutea and the stimulatory effect on E2 and P4 production and promotes GC survival in buffalo, suggesting the role of apelin in follicular and luteal functions in buffalo.
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Affiliation(s)
- Mahesh Gupta
- Department of Veterinary Physiology, Nagpur Veterinary College, Nagpur, 440006, India.
| | - Jayant P Korde
- Department of Veterinary Physiology, Nagpur Veterinary College, Nagpur, 440006, India
| | - K B Bahiram
- Department of Veterinary Physiology, Nagpur Veterinary College, Nagpur, 440006, India
| | - V M Sardar
- Department of Veterinary Physiology, Nagpur Veterinary College, Nagpur, 440006, India
| | - Nitin V Kurkure
- Department of Veterinary Pathology, Nagpur Veterinary College, Nagpur, 440006, India
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2
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Janssens P, Decuypere JP, Bammens B, Llorens-Cortes C, Vennekens R, Mekahli D. The emerging role of the apelinergic system in kidney physiology and disease. Nephrol Dial Transplant 2022; 37:2314-2326. [PMID: 33744967 DOI: 10.1093/ndt/gfab070] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Indexed: 12/31/2022] Open
Abstract
The apelinergic system (AS) is a novel pleiotropic system with an essential role in renal and cardiovascular physiology and disease, including water homeostasis and blood pressure regulation. It consists of two highly conserved peptide ligands, apelin and apela, and a G-protein-coupled apelin receptor. The two ligands have many isoforms and a short half-life and exert both similar and divergent effects. Vasopressin, apelin and their receptors colocalize in hypothalamic regions essential for body fluid homeostasis and interact at the central and renal levels to regulate water homeostasis and diuresis in inverse directions. In addition, the AS and renin-angiotensin system interact both systemically and in the kidney, with implications for the cardiovascular system. A role for the AS in diverse pathological states, including disorders of sodium and water balance, hypertension, heart failure, pre-eclampsia, acute kidney injury, sepsis and diabetic nephropathy, has recently been reported. Furthermore, several metabolically stable apelin analogues have been developed, with potential applications in diverse diseases. We review here what is currently known about the physiological functions of the AS, focusing on renal, cardiovascular and metabolic homeostasis, and the role of the AS in associated diseases. We also describe several hurdles and research opportunities worthy of the attention of the nephrology community.
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Affiliation(s)
- Peter Janssens
- PKD Research Group, Laboratory of Pediatrics, Department of Development and Regeneration, KU Leuven, Leuven, Belgium.,Vrije Universiteit Brussel (VUB), Universitair Ziekenhuis Brussel (UZ Brussell), Department of Nephrology, Laarbeeklaan 101, 1090 Brussels, Belgium
| | - Jean-Paul Decuypere
- PKD Research Group, Laboratory of Pediatrics, Department of Development and Regeneration, KU Leuven, Leuven, Belgium
| | - Bert Bammens
- Department of Nephrology, Dialysis and Renal Transplantation, University Hospitals Leuven, Leuven, Belgium.,Nephrology and Renal Transplantation Research Group, Department of Microbiology, Immunology and Transplantation, KU Leuven, Leuven, Belgium
| | - Catherine Llorens-Cortes
- Laboratory of Central Neuropeptides in the Regulation of Body Fluid Homeostasis and Cardiovascular Functions, Center for Interdisciplinary Research in Biology, Collège de France, INSERM U1050, CNRS UMR 7241, Paris, France
| | - Rudi Vennekens
- Laboratory of Ion Channel Research, Department of Cellular and Molecular Medicine, VIB-KU Leuven Center for Brain and Disease, KU Leuven, Leuven, Belgium and
| | - Djalila Mekahli
- PKD Research Group, Laboratory of Pediatrics, Department of Development and Regeneration, KU Leuven, Leuven, Belgium.,Department of Pediatric Nephrology and Organ Transplantation, University Hospitals Leuven, Leuven, Belgium
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3
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Szczepańska-Sadowska E, Żera T. Vasopressin: a possible link between hypoxia and hypertension. EXPLORATION OF MEDICINE 2022. [DOI: 10.37349/emed.2022.00103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Cardiovascular and respiratory diseases are frequently associated with transient and prolonged hypoxia, whereas hypoxia exerts pro-hypertensive effects, through stimulation of the sympathetic system and release of pressor endocrine factors. This review is focused on the role of arginine vasopressin (AVP) in dysregulation of the cardiovascular system during hypoxia associated with cardiovascular disorders. AVP is synthesized mainly in the neuroendocrine neurons of the hypothalamic paraventricular nucleus (PVN) and supraoptic nucleus (SON), which send axons to the posterior pituitary and various regions of the central nervous system (CNS). Vasopressinergic neurons are innervated by multiple neuronal projections releasing several neurotransmitters and other regulatory molecules. AVP interacts with V1a, V1b and V2 receptors that are present in the brain and peripheral organs, including the heart, vessels, lungs, and kidneys. Release of vasopressin is intensified during hypernatremia, hypovolemia, inflammation, stress, pain, and hypoxia which frequently occur in cardiovascular patients, and blood AVP concentration is markedly elevated in cardiovascular diseases associated with hypoxemia. There is evidence that hypoxia stimulates AVP release through stimulation of chemoreceptors. It is suggested that acting in the carotid bodies, AVP may fine-tune respiratory and hemodynamic responses to hypoxia and that this effect is intensified in hypertension. There is also evidence that during hypoxia, augmentation of pro-hypertensive effects of vasopressin may result from inappropriate interaction of this hormone with other compounds regulating the cardiovascular system (catecholamines, angiotensins, natriuretic peptides, steroids, nitric oxide). In conclusion, current literature indicates that abnormal mutual interactions between hypoxia and vasopressin may significantly contribute to pathogenesis of hypertension.
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Affiliation(s)
- Ewa Szczepańska-Sadowska
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, 02-097 Warsaw, Poland
| | - Tymoteusz Żera
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, 02-097 Warsaw, Poland
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Eiden LE, Hernández VS, Jiang SZ, Zhang L. Neuropeptides and small-molecule amine transmitters: cooperative signaling in the nervous system. Cell Mol Life Sci 2022; 79:492. [PMID: 35997826 PMCID: PMC11072502 DOI: 10.1007/s00018-022-04451-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 06/15/2022] [Accepted: 06/23/2022] [Indexed: 12/17/2022]
Abstract
Neuropeptides are expressed in cell-specific patterns throughout mammalian brain. Neuropeptide gene expression has been useful for clustering neurons by phenotype, based on single-cell transcriptomics, and for defining specific functional circuits throughout the brain. How neuropeptides function as first messengers in inter-neuronal communication, in cooperation with classical small-molecule amine transmitters (SMATs) is a current topic of systems neurobiology. Questions include how neuropeptides and SMATs cooperate in neurotransmission at the molecular, cellular and circuit levels; whether neuropeptides and SMATs always co-exist in neurons; where neuropeptides and SMATs are stored in the neuron, released from the neuron and acting, and at which receptors, after release; and how neuropeptides affect 'classical' transmitter function, both directly upon co-release, and indirectly, via long-term regulation of gene transcription and neuronal plasticity. Here, we review an extensive body of data about the distribution of neuropeptides and their receptors, their actions after neuronal release, and their function based on pharmacological and genetic loss- and gain-of-function experiments, that addresses these questions, fundamental to understanding brain function, and development of neuropeptide-based, and potentially combinatorial peptide/SMAT-based, neurotherapeutics.
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Affiliation(s)
- Lee E Eiden
- Section On Molecular Neuroscience, National Institute of Mental Health, Intramural Research Program, National Institutes of Health, 49 Convent Drive, Room 5A38, Bethesda, MD, 20892, USA.
| | - Vito S Hernández
- Department of Physiology, School of Medicine, National Autonomous University of Mexico, Mexico City, Mexico
| | - Sunny Z Jiang
- Section On Molecular Neuroscience, National Institute of Mental Health, Intramural Research Program, National Institutes of Health, 49 Convent Drive, Room 5A38, Bethesda, MD, 20892, USA
| | - Limei Zhang
- Department of Physiology, School of Medicine, National Autonomous University of Mexico, Mexico City, Mexico.
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5
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Nikanfar S, Oghbaei H, Rastgar Rezaei Y, Zarezadeh R, Jafari-Gharabaghlou D, Nejabati HR, Bahrami Z, Bleisinger N, Samadi N, Fattahi A, Nouri M, Dittrich R. Role of adipokines in the ovarian function: Oogenesis and steroidogenesis. J Steroid Biochem Mol Biol 2021; 209:105852. [PMID: 33610800 DOI: 10.1016/j.jsbmb.2021.105852] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 12/28/2020] [Accepted: 01/30/2021] [Indexed: 01/02/2023]
Abstract
Adipokines are mainly produced by adipose tissue; however, their expression has been reported in other organs including female reproductive tissues. Therefore, adipokines have opened new avenues of research in female fertility. In this regard, studies reported different roles for certain adipokines in ovarian function, although the role of other recently identified adipokines is still controversial. It seems that adipokines are essential for normal ovarian function and their abnormal levels could be associated with ovarian-related disorders. The objective of this study is to review the available information regarding the role of adipokines in ovarian functions including follicular development, oogenesis and steroidogenesis and also their involvement in ovary-related disorders.
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Affiliation(s)
- Saba Nikanfar
- Stem Cell Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; Department of Biochemistry and Clinical Laboratories, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Hajar Oghbaei
- Department of Physiology, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Yeganeh Rastgar Rezaei
- Department of Medical Biotechnology, Faculty of Advanced Medical Sciences, Tabriz University of Medical Sciences, Tabriz, Iran; Student Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Reza Zarezadeh
- Department of Biochemistry and Clinical Laboratories, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Davoud Jafari-Gharabaghlou
- Department of Biochemistry and Clinical Laboratories, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Hamid Reza Nejabati
- Department of Biochemistry and Clinical Laboratories, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Zahra Bahrami
- Department of Reproductive Biology, Faculty of Advanced Medical Sciences, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Nathalie Bleisinger
- Department of Obstetrics and Gynecology, Erlangen University Hospital, Friedrich-Alexander University of Erlangen, Nürnberg, Erlangen, Germany
| | - Naser Samadi
- Department of Biochemistry and Clinical Laboratories, Faculty of Medicine, Tabriz University of Medical Sciences, Tabriz, Iran
| | - Amir Fattahi
- Department of Reproductive Biology, Faculty of Advanced Medical Sciences, Tabriz University of Medical Sciences, Tabriz, Iran; Department of Obstetrics and Gynecology, Erlangen University Hospital, Friedrich-Alexander University of Erlangen, Nürnberg, Erlangen, Germany; Women's Reproductive Health Research Center, Tabriz University of Medical Sciences, Tabriz, Iran.
| | - Mohammad Nouri
- Stem Cell Research Center, Tabriz University of Medical Sciences, Tabriz, Iran; Department of Reproductive Biology, Faculty of Advanced Medical Sciences, Tabriz University of Medical Sciences, Tabriz, Iran.
| | - Ralf Dittrich
- Department of Obstetrics and Gynecology, Erlangen University Hospital, Friedrich-Alexander University of Erlangen, Nürnberg, Erlangen, Germany
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Wang Y, Xue Y, Liu C, Chen L. Apelin-13 regulates electrical activity in the globus pallidus and induces postural changes in rats. Neural Regen Res 2021; 16:2264-2268. [PMID: 33818511 PMCID: PMC8354122 DOI: 10.4103/1673-5374.310694] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
The globus pallidus is the relay nucleus of the basal ganglia, and changes in its electrical activity can cause motor impairment. Apelin-13 is widely distributed in the central and peripheral nervous systems. It has been demonstrated that apelin-13 plays important roles in the regulation of blood pressure and other non-motor functions. However, its role in motor function has rarely been reported. In the present study, apelin-13 (10 μM/100 μM) was injected into the globus pallidus of rats. The results showed that apelin-13 increased the spontaneous discharges in the majority of pallidal neurons. However, an apelin-13-induced inhibitory effect on the firing rate was also observed in a few pallidal neurons. In postural tests, after the systemic administration of haloperidol, unilateral pallidal injection of apelin-13 caused a contralateral deflection. Together, these findings suggest that apelin-13 regulates the electrical activity of pallidal neurons and thus participates in central motor control in rats. The study was approved by the Animal Ethics Committee of Qingdao University (approval No. 20200615Wistar0451003020) on June 15, 2020.
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Affiliation(s)
- Ying Wang
- Department of Physiology, School of Basic Medicine, Qingdao University, Qingdao, Shandong Province, China
| | - Yan Xue
- Department of Physiology, School of Basic Medicine, Qingdao University, Qingdao, Shandong Province, China
| | - Cui Liu
- Department of Physiology, School of Basic Medicine, Qingdao University, Qingdao, Shandong Province, China
| | - Lei Chen
- Department of Physiology, School of Basic Medicine, Qingdao University, Qingdao, Shandong Province, China
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7
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Wojno O, Czarzasta K, Puchalska L, Kowalczyk M, Cudnoch-Jedrzejewska A. Central interaction between the apelinergic and vasopressinergic systems in the regulation of the haemodynamic parameters in rats maintained on a high-fat diet. Clin Exp Pharmacol Physiol 2020; 47:1902-1911. [PMID: 32687615 DOI: 10.1111/1440-1681.13381] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 07/09/2020] [Accepted: 07/10/2020] [Indexed: 11/29/2022]
Abstract
A high-fat diet can affect the central activity of the apelinergic and vasopressinergic systems, which can have a significant impact on cardiovascular regulation. The aim of the study was to investigate the role of the central interaction between apelin and vasopressin in the regulation of the cardiovascular system in Sprague Dawley rats maintained on a normal-fat diet (NFD) or on a high-fat diet (HFD). The animals were instrumented with a cannula implanted into the left cerebral ventricle for intracerebroventricular (ICV) infusions of saline (0.9% NaCl), apelin-13 (APLN-13), V1a receptor antagonist (V1aRANT) APJ receptor antagonist (F13A), vasopressin (AVP); and with a catheter placed within the femoral artery for mean arterial blood pressure and heart rate monitoring. Blood, the hypothalamus and the medulla oblongata were collected for biochemical analysis. The hypertensive effect of APLN-13 was blocked by a prior ICV infusion of V1aRANT, only in the NFD rats. However, the hypertensive effect of AVP was blocked by the prior ICV infusion of F13A in both the NFD and HFD rats. A HFD caused an increase in the protein level of APJ and V1a receptors, both in the hypothalamus and the medulla oblongata. This study confirms the presence of an interaction between both peptides in the central regulation of the cardiovascular system in rats on a NFD or a HFD.
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Affiliation(s)
- Olena Wojno
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, Warsaw, Poland
| | - Katarzyna Czarzasta
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, Warsaw, Poland
| | - Liana Puchalska
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, Warsaw, Poland
| | - Malgorzata Kowalczyk
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, Warsaw, Poland
| | - Agnieszka Cudnoch-Jedrzejewska
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, Warsaw, Poland
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8
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Brown CH, Ludwig M, Tasker JG, Stern JE. Somato-dendritic vasopressin and oxytocin secretion in endocrine and autonomic regulation. J Neuroendocrinol 2020; 32:e12856. [PMID: 32406599 PMCID: PMC9134751 DOI: 10.1111/jne.12856] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 03/29/2020] [Accepted: 04/11/2020] [Indexed: 12/29/2022]
Abstract
Somato-dendritic secretion was first demonstrated over 30 years ago. However, although its existence has become widely accepted, the function of somato-dendritic secretion is still not completely understood. Hypothalamic magnocellular neurosecretory cells were among the first neuronal phenotypes in which somato-dendritic secretion was demonstrated and are among the neurones for which the functions of somato-dendritic secretion are best characterised. These neurones secrete the neuropeptides, vasopressin and oxytocin, in an orthograde manner from their axons in the posterior pituitary gland into the blood circulation to regulate body fluid balance and reproductive physiology. Retrograde somato-dendritic secretion of vasopressin and oxytocin modulates the activity of the neurones from which they are secreted, as well as the activity of neighbouring populations of neurones, to provide intra- and inter-population signals that coordinate the endocrine and autonomic responses for the control of peripheral physiology. Somato-dendritic vasopressin and oxytocin have also been proposed to act as hormone-like signals in the brain. There is some evidence that somato-dendritic secretion from magnocellular neurosecretory cells modulates the activity of neurones beyond their local environment where there are no vasopressin- or oxytocin-containing axons but, to date, there is no conclusive evidence for, or against, hormone-like signalling throughout the brain, although it is difficult to imagine that the levels of vasopressin found throughout the brain could be underpinned by release from relatively sparse axon terminal fields. The generation of data to resolve this issue remains a priority for the field.
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Affiliation(s)
- Colin H. Brown
- Department of Physiology, Brain Health Research Centre, Centre for Neuroendocrinology, University of Otago, Dunedin, New Zealand
| | - Mike Ludwig
- Centre for Discovery Brain Sciences, University of Edinburgh, Edinburgh, UK
- Department of Immunology, Centre for Neuroendocrinology, University of Pretoria, Pretoria, South Africa
| | - Jeffrey G. Tasker
- Department of Cell and Molecular Biology, Brain Institute, Tulane University, New Orleans, LA, USA
| | - Javier E. Stern
- Neuroscience Institute, Georgia State University, Atlanta, GA, USA
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Read C, Nyimanu D, Williams TL, Huggins DJ, Sulentic P, Macrae RGC, Yang P, Glen RC, Maguire JJ, Davenport AP. International Union of Basic and Clinical Pharmacology. CVII. Structure and Pharmacology of the Apelin Receptor with a Recommendation that Elabela/Toddler Is a Second Endogenous Peptide Ligand. Pharmacol Rev 2019; 71:467-502. [PMID: 31492821 PMCID: PMC6731456 DOI: 10.1124/pr.119.017533] [Citation(s) in RCA: 58] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The predicted protein encoded by the APJ gene discovered in 1993 was originally classified as a class A G protein-coupled orphan receptor but was subsequently paired with a novel peptide ligand, apelin-36 in 1998. Substantial research identified a family of shorter peptides activating the apelin receptor, including apelin-17, apelin-13, and [Pyr1]apelin-13, with the latter peptide predominating in human plasma and cardiovascular system. A range of pharmacological tools have been developed, including radiolabeled ligands, analogs with improved plasma stability, peptides, and small molecules including biased agonists and antagonists, leading to the recommendation that the APJ gene be renamed APLNR and encode the apelin receptor protein. Recently, a second endogenous ligand has been identified and called Elabela/Toddler, a 54-amino acid peptide originally identified in the genomes of fish and humans but misclassified as noncoding. This precursor is also able to be cleaved to shorter sequences (32, 21, and 11 amino acids), and all are able to activate the apelin receptor and are blocked by apelin receptor antagonists. This review summarizes the pharmacology of these ligands and the apelin receptor, highlights the emerging physiologic and pathophysiological roles in a number of diseases, and recommends that Elabela/Toddler is a second endogenous peptide ligand of the apelin receptor protein.
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Affiliation(s)
- Cai Read
- Experimental Medicine and Immunotherapeutics, University of Cambridge, Centre for Clinical Investigation, Addenbrooke's Hospital, Cambridge, United Kingdom (C.R., D.N., T.L.W., D.J.H., P.S., R.G.C.M., P.Y., J.J.M., A.P.D.); The Centre for Molecular Informatics, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom (D.J.H., R.C.G.); and Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, United Kingdom (R.C.G.)
| | - Duuamene Nyimanu
- Experimental Medicine and Immunotherapeutics, University of Cambridge, Centre for Clinical Investigation, Addenbrooke's Hospital, Cambridge, United Kingdom (C.R., D.N., T.L.W., D.J.H., P.S., R.G.C.M., P.Y., J.J.M., A.P.D.); The Centre for Molecular Informatics, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom (D.J.H., R.C.G.); and Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, United Kingdom (R.C.G.)
| | - Thomas L Williams
- Experimental Medicine and Immunotherapeutics, University of Cambridge, Centre for Clinical Investigation, Addenbrooke's Hospital, Cambridge, United Kingdom (C.R., D.N., T.L.W., D.J.H., P.S., R.G.C.M., P.Y., J.J.M., A.P.D.); The Centre for Molecular Informatics, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom (D.J.H., R.C.G.); and Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, United Kingdom (R.C.G.)
| | - David J Huggins
- Experimental Medicine and Immunotherapeutics, University of Cambridge, Centre for Clinical Investigation, Addenbrooke's Hospital, Cambridge, United Kingdom (C.R., D.N., T.L.W., D.J.H., P.S., R.G.C.M., P.Y., J.J.M., A.P.D.); The Centre for Molecular Informatics, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom (D.J.H., R.C.G.); and Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, United Kingdom (R.C.G.)
| | - Petra Sulentic
- Experimental Medicine and Immunotherapeutics, University of Cambridge, Centre for Clinical Investigation, Addenbrooke's Hospital, Cambridge, United Kingdom (C.R., D.N., T.L.W., D.J.H., P.S., R.G.C.M., P.Y., J.J.M., A.P.D.); The Centre for Molecular Informatics, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom (D.J.H., R.C.G.); and Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, United Kingdom (R.C.G.)
| | - Robyn G C Macrae
- Experimental Medicine and Immunotherapeutics, University of Cambridge, Centre for Clinical Investigation, Addenbrooke's Hospital, Cambridge, United Kingdom (C.R., D.N., T.L.W., D.J.H., P.S., R.G.C.M., P.Y., J.J.M., A.P.D.); The Centre for Molecular Informatics, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom (D.J.H., R.C.G.); and Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, United Kingdom (R.C.G.)
| | - Peiran Yang
- Experimental Medicine and Immunotherapeutics, University of Cambridge, Centre for Clinical Investigation, Addenbrooke's Hospital, Cambridge, United Kingdom (C.R., D.N., T.L.W., D.J.H., P.S., R.G.C.M., P.Y., J.J.M., A.P.D.); The Centre for Molecular Informatics, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom (D.J.H., R.C.G.); and Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, United Kingdom (R.C.G.)
| | - Robert C Glen
- Experimental Medicine and Immunotherapeutics, University of Cambridge, Centre for Clinical Investigation, Addenbrooke's Hospital, Cambridge, United Kingdom (C.R., D.N., T.L.W., D.J.H., P.S., R.G.C.M., P.Y., J.J.M., A.P.D.); The Centre for Molecular Informatics, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom (D.J.H., R.C.G.); and Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, United Kingdom (R.C.G.)
| | - Janet J Maguire
- Experimental Medicine and Immunotherapeutics, University of Cambridge, Centre for Clinical Investigation, Addenbrooke's Hospital, Cambridge, United Kingdom (C.R., D.N., T.L.W., D.J.H., P.S., R.G.C.M., P.Y., J.J.M., A.P.D.); The Centre for Molecular Informatics, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom (D.J.H., R.C.G.); and Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, United Kingdom (R.C.G.)
| | - Anthony P Davenport
- Experimental Medicine and Immunotherapeutics, University of Cambridge, Centre for Clinical Investigation, Addenbrooke's Hospital, Cambridge, United Kingdom (C.R., D.N., T.L.W., D.J.H., P.S., R.G.C.M., P.Y., J.J.M., A.P.D.); The Centre for Molecular Informatics, Department of Chemistry, University of Cambridge, Cambridge, United Kingdom (D.J.H., R.C.G.); and Computational and Systems Medicine, Department of Surgery and Cancer, Faculty of Medicine, Imperial College London, London, United Kingdom (R.C.G.)
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10
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Seasonal adaptations of the hypothalamo-neurohypophyseal system of the dromedary camel. PLoS One 2019; 14:e0216679. [PMID: 31211771 PMCID: PMC6581255 DOI: 10.1371/journal.pone.0216679] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 04/24/2019] [Indexed: 12/12/2022] Open
Abstract
The “ship” of the Arabian and North African deserts, the one-humped dromedary camel (Camelus dromedarius) has a remarkable capacity to survive in conditions of extreme heat without needing to drink water. One of the ways that this is achieved is through the actions of the antidiuretic hormone arginine vasopressin (AVP), which is made in a specialised part of the brain called the hypothalamo-neurohypophyseal system (HNS), but exerts its effects at the level of the kidney to provoke water conservation. Interestingly, our electron microscopy studies have shown that the ultrastructure of the dromedary HNS changes according to season, suggesting that in the arid conditions of summer the HNS is in an activated state, in preparation for the likely prospect of water deprivation. Based on our dromedary genome sequence, we have carried out an RNAseq analysis of the dromedary HNS in summer and winter. Amongst the 171 transcripts found to be significantly differentially regulated (>2 fold change, p value <0.05) there is a significant over-representation of neuropeptide encoding genes, including that encoding AVP, the expression of which appeared to increase in summer. Identification of neuropeptides in the HNS and analysis of neuropeptide profiles in extracts from individual camels using mass spectrometry indicates that overall AVP peptide levels decreased in the HNS during summer compared to winter, perhaps due to increased release during periods of dehydration in the dry season.
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11
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Griffiths PR, Lolait SJ, Pearce LE, McBryde FD, Paton JFR, O'Carroll AM. Blockade of Rostral Ventrolateral Medulla Apelin Receptors Does Not Attenuate Arterial Pressure in SHR and L-NAME-Induced Hypertensive Rats. Front Physiol 2018; 9:1488. [PMID: 30459635 PMCID: PMC6232890 DOI: 10.3389/fphys.2018.01488] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 10/02/2018] [Indexed: 01/02/2023] Open
Abstract
Dysfunction of the apelinergic system, comprised of the neuropeptide apelin mediating its effects via the G protein-coupled apelin receptor (APJ), may underlie the onset of cardiovascular disease such as hypertension. Apelin expression is increased in the rostral ventrolateral medulla (RVLM) in spontaneously hypertensive rats (SHRs) compared to Wistar-Kyoto (WKY) normotensive rats, however, evidence that the apelinergic system chronically influences mean arterial blood pressure (MABP) under pathophysiological conditions remains to be established. In this study we investigated, in conscious unrestrained rats, whether APJ contributes to MABP and sympathetic vasomotor tone in the progression of two models of hypertension - SHR and L-NAME-treated rats - and whether APJ contributes to the development of hypertension in pre-hypertensive SHR. In SHR we showed that APJ gene (aplnr) expression was elevated in the RVLM, and there was a greater MABP increase following microinjection of [Pyr1]apelin-13 to the RVLM of SHR compared to WKY rats. Bilateral microinjection of a lentiviral APJ-specific-shRNA construct into the RVLM of WKY, SHR, and L-NAME-treated rats, chronically implanted with radiotelemeters to measure MABP, decreased aplnr expression in the RVLM and abolished acute [Pyr1]apelin-13-induced increases in MABP. However, chronic knockdown of aplnr in the RVLM did not affect MABP in either SHR or L-NAME-treated rats. Moreover, knockdown of aplnr in the RVLM of prehypertensive SHR did not protect against the development of hypertension. These results show that endogenous apelin, acting via APJ, is not involved in the genesis or maintenance of hypertension in either animal model used in this study.
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Affiliation(s)
- Philip R Griffiths
- Laboratories for Integrative Neuroscience and Endocrinology, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Stephen J Lolait
- Laboratories for Integrative Neuroscience and Endocrinology, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Louise E Pearce
- Laboratories for Integrative Neuroscience and Endocrinology, Bristol Medical School, University of Bristol, Bristol, United Kingdom
| | - Fiona D McBryde
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Julian F R Paton
- Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.,School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol, United Kingdom
| | - Anne-Marie O'Carroll
- Laboratories for Integrative Neuroscience and Endocrinology, Bristol Medical School, University of Bristol, Bristol, United Kingdom
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12
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Bülbül M, Travagli RA. Novel transmitters in brain stem vagal neurocircuitry: new players on the pitch. Am J Physiol Gastrointest Liver Physiol 2018; 315:G20-G26. [PMID: 29597355 PMCID: PMC6109706 DOI: 10.1152/ajpgi.00059.2018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The last few decades have seen a major increase in the number of neurotransmitters and neuropeptides recognized as playing a role in brain stem neurocircuits, including those involved in homeostatic functions such as stress responsiveness, gastrointestinal motility, feeding, and/or arousal/wakefulness. This minireview will focus on the known physiological role of three of these novel neuropeptides, i.e., apelin, nesfatin-1, and neuropeptide-S, with a special emphasis on their hypothetical roles in vagal signaling related to gastrointestinal motor functions.
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Affiliation(s)
- Mehmet Bülbül
- 1Faculty of Medicine, Department of Physiology, Akdeniz UniversityAntalya, Turkey
| | - R. Alberto Travagli
- 2Department of Neural and Behavioral Neurosciences, Pennsylvania State University College of Medicine, Hershey, Pennsylvania
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13
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Szczepanska-Sadowska E, Czarzasta K, Cudnoch-Jedrzejewska A. Dysregulation of the Renin-Angiotensin System and the Vasopressinergic System Interactions in Cardiovascular Disorders. Curr Hypertens Rep 2018; 20:19. [PMID: 29556787 PMCID: PMC5859051 DOI: 10.1007/s11906-018-0823-9] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Purpose of Review In many instances, the renin-angiotensin system (RAS) and the vasopressinergic system (VPS) are jointly activated by the same stimuli and engaged in the regulation of the same processes. Recent Findings Angiotensin II (Ang II) and arginine vasopressin (AVP), which are the main active compounds of the RAS and the VPS, interact at several levels. Firstly, Ang II, acting on AT1 receptors (AT1R), plays a significant role in the release of AVP from vasopressinergic neurons and AVP, stimulating V1a receptors (V1aR), regulates the release of renin in the kidney. Secondly, Ang II and AVP, acting on AT1R and V1aR, respectively, exert vasoconstriction, increase cardiac contractility, stimulate the sympathoadrenal system, and elevate blood pressure. At the same time, they act antagonistically in the regulation of blood pressure by baroreflex. Thirdly, the cooperative action of Ang II acting on AT1R and AVP stimulating both V1aR and V2 receptors in the kidney is necessary for the appropriate regulation of renal blood flow and the efficient resorption of sodium and water. Furthermore, both peptides enhance the release of aldosterone and potentiate its action in the renal tubules. Summary In this review, we (1) point attention to the role of the cooperative action of Ang II and AVP for the regulation of blood pressure and the water-electrolyte balance under physiological conditions, (2) present the subcellular mechanisms underlying interactions of these two peptides, and (3) provide evidence that dysregulation of the cooperative action of Ang II and AVP significantly contributes to the development of disturbances in the regulation of blood pressure and the water-electrolyte balance in cardiovascular diseases.
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Affiliation(s)
- Ewa Szczepanska-Sadowska
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, Banacha 1b, 02-097, Warsaw, Poland.
| | - Katarzyna Czarzasta
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, Banacha 1b, 02-097, Warsaw, Poland
| | - Agnieszka Cudnoch-Jedrzejewska
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, Banacha 1b, 02-097, Warsaw, Poland
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14
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Kurowska P, Barbe A, Różycka M, Chmielińska J, Dupont J, Rak A. Apelin in Reproductive Physiology and Pathology of Different Species: A Critical Review. Int J Endocrinol 2018; 2018:9170480. [PMID: 29977292 PMCID: PMC6011052 DOI: 10.1155/2018/9170480] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 04/02/2018] [Indexed: 02/08/2023] Open
Abstract
Apelin has been isolated from the bovine stomach extracts as an endogenous ligand of the previously orphan receptor APJ. Expression of the apelinergic system (apelin and APJ) was described in many organs where pleiotropic effects like regulation of food intake, body weight, or cardiovascular and immune function were described. Recent studies have shown that apelin also plays an important role in the regulation of female and male reproduction. Some data showed that the gene and protein of apelin/APJ are expressed in the hypothalamic-pituitary-gonad (HPG) axis tissue. Thus, apelin is synthesized locally in the hypothalamus, pituitary, ovaries, and testis of many species and has autocrine and/or paracrine effects. Most research indicates that apelin has an inhibitory effect on gonadotropin secretion and participates in the direct regulation of steroidogenesis, cell proliferation, and apoptosis in gonads. The article summarizes also results of a series of recent studies on the effect of apelin on reproduction pathology, like polycystic ovarian syndrome, endometriosis, and ovarian cancer. Many of these pathologies are still in critical need of therapeutic intervention, and recent studies have found that apelin can be targets in reproductive pathological states.
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Affiliation(s)
- Patrycja Kurowska
- Department of Physiology and Toxicology of Reproduction, Institute of Zoology and Biomedical Research, Jagiellonian University in Krakow, 30-387 Krakow, Poland
| | - Alix Barbe
- INRA, Unité Physiologie de la Reproduction et des Comportements, 37-380 Nouzilly, France
| | - Marta Różycka
- Department of Physiology and Toxicology of Reproduction, Institute of Zoology and Biomedical Research, Jagiellonian University in Krakow, 30-387 Krakow, Poland
| | - Justyna Chmielińska
- Department of Physiology and Toxicology of Reproduction, Institute of Zoology and Biomedical Research, Jagiellonian University in Krakow, 30-387 Krakow, Poland
| | - Joelle Dupont
- INRA, Unité Physiologie de la Reproduction et des Comportements, 37-380 Nouzilly, France
| | - Agnieszka Rak
- Department of Physiology and Toxicology of Reproduction, Institute of Zoology and Biomedical Research, Jagiellonian University in Krakow, 30-387 Krakow, Poland
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15
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Rak A, Drwal E, Rame C, Knapczyk-Stwora K, Słomczyńska M, Dupont J, Gregoraszczuk E. Expression of apelin and apelin receptor (APJ) in porcine ovarian follicles and in vitro effect of apelin on steroidogenesis and proliferation through APJ activation and different signaling pathways. Theriogenology 2017; 96:126-135. [DOI: 10.1016/j.theriogenology.2017.04.014] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2017] [Revised: 04/05/2017] [Accepted: 04/06/2017] [Indexed: 10/19/2022]
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16
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Griffiths PR, Lolait SJ, Harris LE, Paton JFR, O'Carroll AM. Vasopressin V1a receptors mediate the hypertensive effects of [Pyr 1 ]apelin-13 in the rat rostral ventrolateral medulla. J Physiol 2017; 595:3303-3318. [PMID: 28255983 PMCID: PMC5451710 DOI: 10.1113/jp274178] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2017] [Accepted: 02/27/2017] [Indexed: 11/22/2022] Open
Abstract
Key points Dysfunctions in CNS regulation of arterial blood pressure lead to an increase in sympathetic nerve activity that participates in the pathogenesis of hypertension. The apelin‐apelin receptor system affects arterial blood pressure homeostasis; however, the central mechanisms underlying apelin‐mediated changes in sympathetic nerve activity and blood pressure have not been clarified. We explored the mechanisms involved in the regulation of [Pyr1]apelin‐13‐mediated cardiovascular control within the rostral ventrolateral medulla (RVLM) using selective receptor antagonists. We show that [Pyr1]apelin‐13 acts as a modulating neurotransmitter in the normotensive RVLM to affect vascular tone through interaction with the vasopressin V1a receptor but that [Pyr1]apelin‐13‐induced sympathoexcitation is independent of angiotensin II receptor type 1, oxytocin, ionotropic glutamate and GABAA receptors. Our data confirm a role for the apelin peptide system in cardiovascular regulation at the level of the RVLM and highlight that this system is a possible potential therapeutic target for the treatment of hypertension.
Abstract Apelin is a ubiquitous peptide that can elevate arterial blood pressure (ABP) yet understanding of the mechanisms involved remain incomplete. Bilateral microinjection of [Pyr1]apelin‐13 into the rostral ventrolateral medulla (RVLM), a major source of sympathoexcitatory neurones, increases ABP and sympathetic nerve activity. We aimed to investigate the potential involvement of neurotransmitter systems through which the apelin pressor response may occur within the RVLM. Adult male Wistar rats were anaesthetized and ABP was monitored via a femoral arterial catheter. Bilateral RVLM microinjection of [Pyr1]apelin‐13 significantly increased ABP (9 ± 1 mmHg) compared to saline (−1 ± 2mmHg; P < 0.001), which was blocked by pretreatment with the apelin receptor antagonist, F13A (0 ± 1 mmHg; P < 0.01). The rise in ABP was associated with an increase in the low frequency spectra of systolic BP (13.9 ± 4.3% total power; P < 0.001), indicative of sympathetic vasomotor activation. The [Pyr1]apelin‐13‐mediated pressor response and the increased low frequency spectra of systolic BP response were fully maintained despite RVLM pretreatment with the angiotensin II type 1 receptor antagonist losartan, the oxytocin receptor antagonist desGly‐NH2, d(CH2)5[D‐Tyr2,Thr4]OVT, the ionotropic glutamate receptor antagonist kynurenate or the GABAA antagonist bicuculline (P > 0.05). By contrast, the [Pyr1]apelin‐13 induced pressor and sympathoexcitatory effects were abolished by pretreatment of the RVLM with the vasopressin V1a receptor antagonist, SR 49059 (−1 ± 1 mmHg; 1.1 ± 1.1% total power, respectively; P < 0.001). These findings suggest that the pressor action of [Pyr1]apelin‐13 in the RVLM of normotensive rats is not mediated via angiotensin II type 1 receptor, oxytocin, ionotropic glutamate or GABAA receptors but instead involves a close relationship with the neuropeptide modulator vasopressin. Dysfunctions in CNS regulation of arterial blood pressure lead to an increase in sympathetic nerve activity that participates in the pathogenesis of hypertension. The apelin‐apelin receptor system affects arterial blood pressure homeostasis; however, the central mechanisms underlying apelin‐mediated changes in sympathetic nerve activity and blood pressure have not been clarified. We explored the mechanisms involved in the regulation of [Pyr1]apelin‐13‐mediated cardiovascular control within the rostral ventrolateral medulla (RVLM) using selective receptor antagonists. We show that [Pyr1]apelin‐13 acts as a modulating neurotransmitter in the normotensive RVLM to affect vascular tone through interaction with the vasopressin V1a receptor but that [Pyr1]apelin‐13‐induced sympathoexcitation is independent of angiotensin II receptor type 1, oxytocin, ionotropic glutamate and GABAA receptors. Our data confirm a role for the apelin peptide system in cardiovascular regulation at the level of the RVLM and highlight that this system is a possible potential therapeutic target for the treatment of hypertension.
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Affiliation(s)
| | | | - Louise E Harris
- School of Clinical Sciences, University of Bristol, Bristol, UK
| | - Julian F R Paton
- School of Physiology, Pharmacology and Neuroscience, Biomedical Sciences, University of Bristol, Bristol, UK
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17
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Abbasloo E, Najafipour H, Esmaeili-Mahani S. Induction of antinociceptive tolerance to the chronic intrathecal administration of apelin-13 in rat. Neuropeptides 2016; 60:7-12. [PMID: 27542441 DOI: 10.1016/j.npep.2016.08.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 07/07/2016] [Accepted: 08/04/2016] [Indexed: 01/07/2023]
Abstract
Pain represents a major contributing factor to the individual's quality of life. Although pain killers as opioids, endogenous or exogenous peptides can decrease pain perception, the chronic use of them leads to antinociceptive tolerance. It has been demonstrated that neuropeptide apelin has potent antinoceptive effect. However, the possibility of the induction of its antinociceptive tolerance has not yet been clarified. The tail-flick test was used to assess the nociceptive threshold. All experiments were carried out on male Wistar rats which received intrathecal apelin for 7days. To determine the role of apelin and opioid receptors on the development of apelin analgesic tolerance, their receptor antagonists (F-13 A and naloxone, respectively) were injected simultaneously with apelin. The lumbar spinal cord was assayed to determine apelin receptor levels by the western blotting method. Plasma corticosterone levels were assayed using ELISA. Results showed that apelin (3μg/rat) induced strong thermal antinociception. In addition, chronic apelin produced tolerance to its antinociceptive effect and down regulated spinal apelin receptor. F-13 A and naloxone could inhibit apelin tolerance development. The corticosterone levels did not change following drug administration. Taken together, the data indicated that apelin like other analgesic drugs leads to the induction of side effects such as analgesic tolerance which is mediated partly via the apelin and opioid receptors activation.
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Affiliation(s)
- Elham Abbasloo
- Physiology Research Center, Institute of Neuropharmacology, Kerman University of Medical Sciences, Kerman, Iran.
| | - Hamid Najafipour
- Endocrinology and Metabolism Research Center, Institute of Basic and Clinical Physiology Sciences, Kerman University of Medical Sciences, Kerman, Iran
| | - Saeed Esmaeili-Mahani
- Department of Biology, Faculty of Sciences, Shahid Bahonar University of Kerman, Kerman, Iran
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18
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Abstract
The posterior pituitary gland secretes oxytocin and vasopressin (the antidiuretic hormone) into the blood system. Oxytocin is required for normal delivery of the young and for delivery of milk to the young during lactation. Vasopressin increases water reabsorption in the kidney to maintain body fluid balance and causes vasoconstriction to increase blood pressure. Oxytocin and vasopressin secretion occurs from the axon terminals of magnocellular neurons whose cell bodies are principally found in the hypothalamic supraoptic nucleus and paraventricular nucleus. The physiological functions of oxytocin and vasopressin depend on their secretion, which is principally determined by the pattern of action potentials initiated at the cell bodies. Appropriate secretion of oxytocin and vasopressin to meet the challenges of changing physiological conditions relies mainly on integration of afferent information on reproductive, osmotic, and cardiovascular status with local regulation of magnocellular neurons by glia as well as intrinsic regulation by the magnocellular neurons themselves. This review focuses on the control of magnocellular neuron activity with a particular emphasis on their regulation by reproductive function, body fluid balance, and cardiovascular status. © 2016 American Physiological Society. Compr Physiol 6:1701-1741, 2016.
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Affiliation(s)
- Colin H Brown
- Brain Health Research Centre, Centre for Neuroendocrinology and Department of Physiology, University of Otago, Dunedin, New Zealand
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19
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Augustine RA, Bouwer GT, Seymour AJ, Grattan DR, Brown CH. Reproductive Regulation of Gene Expression in the Hypothalamic Supraoptic and Paraventricular Nuclei. J Neuroendocrinol 2016; 28. [PMID: 26670189 DOI: 10.1111/jne.12350] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 12/08/2015] [Accepted: 12/09/2015] [Indexed: 11/27/2022]
Abstract
Oxytocin secretion is required for successful reproduction. Oxytocin is synthesised by magnocellular neurones of the hypothalamic supraoptic and paraventricular nuclei and the physiological demand for oxytocin synthesis and secretion is increased for birth and lactation. Therefore, we used a polymerase chain reaction (PCR) array screen to determine whether genes that might be important for synthesis and/or secretion of oxytocin are up- or down-regulated in the supraoptic and paraventricular nuclei of late-pregnant and lactating rats, compared to virgin rats. We then validated the genes that were most highly regulated using real time-quantitative PCR. Among the most highly regulated genes were those that encode for suppressors of cytokine signalling, which are intracellular inhibitors of prolactin signalling. Prolactin receptor activation changes gene expression via phosphorylation of signal transducer and activator of transcription 5 (STAT5). Using double-label immunohistochemistry, we found that phosphorylated STAT5 was expressed in almost all oxytocin neurones of late-pregnant and lactating rats but was almost absent from oxytocin neurones of virgin rats. We conclude that increased prolactin activation of oxytocin neurones might contribute to the changes in gene expression by oxytocin neurones required for normal birth and lactation.
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Affiliation(s)
- R A Augustine
- Centre for Neuroendocrinology and Department of Physiology, University of Otago, Dunedin, New Zealand
| | - G T Bouwer
- Centre for Neuroendocrinology and Department of Physiology, University of Otago, Dunedin, New Zealand
| | - A J Seymour
- Centre for Neuroendocrinology and Department of Physiology, University of Otago, Dunedin, New Zealand
| | - D R Grattan
- Centre for Neuroendocrinology and Department of Anatomy, University of Otago, Dunedin, New Zealand
| | - C H Brown
- Centre for Neuroendocrinology and Department of Physiology, University of Otago, Dunedin, New Zealand
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20
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Bülbül M, İzgüt-Uysal VN, Sinen O, Birsen İ, Tanrıöver G. Central apelin mediates stress-induced gastrointestinal motor dysfunction in rats. Am J Physiol Gastrointest Liver Physiol 2016; 310:G249-61. [PMID: 26680735 DOI: 10.1152/ajpgi.00145.2015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 12/13/2015] [Indexed: 01/31/2023]
Abstract
Apelin, an endogenous ligand for APJ receptor, has been reported to be upregulated in paraventricular nucleus (PVN) following stress. Central apelin is known to stimulate release of corticotropin-releasing factor (CRF) via APJ receptor. We tested the hypothesis that stress-induced gastrointestinal (GI) dysfunction is mediated by central apelin. We also assessed the effect of exogenous apelin on GI motility under nonstressed (NS) conditions in conscious rats. Prior to solid gastric emptying (GE) and colon transit (CT) measurements, APJ receptor antagonist F13A was centrally administered under NS conditions and following acute stress (AS), chronic homotypic stress (CHS), and chronic heterotypic stress (CHeS). Plasma corticosterone was assayed. Strain gage transducers were implanted on serosal surfaces of antrum and distal colon to record postprandial motility. Stress exposure induced coexpression of c-Fos and apelin in hypothalamic PVN. Enhanced hypothalamic apelin and CRF levels in microdialysates were detected following AS and CHeS, which were negatively and positively correlated with GE and CT, respectively. Central F13A administration abolished delayed GE and accelerated CT induced by AS and CHeS. Central apelin-13 administration increased the plasma corticosterone and inhibited GE and CT by attenuating antral and colonic contractions. The inhibitory effect elicited by apelin-13 was abolished by central pretreatment of CRF antagonist CRF9-41 in antrum, but not in distal colon. Central endogenous apelin mediates stress-induced changes in gastric and colonic motor functions through APJ receptor. The inhibitory effects of central exogenous apelin-13 on GI motility appear to be partly CRF dependent. Apelin-13 inhibits colon motor functions through a CRF-independent pathway.
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Affiliation(s)
- Mehmet Bülbül
- Akdeniz University Faculty of Medicine Department of Physiology, Antalya, Turkey; and
| | - V Nimet İzgüt-Uysal
- Akdeniz University Faculty of Medicine Department of Physiology, Antalya, Turkey; and
| | - Osman Sinen
- Akdeniz University Faculty of Medicine Department of Physiology, Antalya, Turkey; and
| | - İlknur Birsen
- Akdeniz University Faculty of Medicine Department of Physiology, Antalya, Turkey; and
| | - Gamze Tanrıöver
- Akdeniz University Faculty of Medicine Department of Histology and Embryology, Antalya, Turkey
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21
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Somato-axodendritic release of oxytocin into the brain due to calcium amplification is essential for social memory. J Physiol Sci 2015; 66:275-82. [PMID: 26586001 PMCID: PMC4893072 DOI: 10.1007/s12576-015-0425-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Accepted: 10/28/2015] [Indexed: 01/12/2023]
Abstract
Oxytocin (OT) is released into the brain from the cell soma, axons, and dendrites of neurosecretory cells in the hypothalamus. Locally released OT can activate OT receptors, form inositol-1,4,5-trisphosphate and elevate intracellular free calcium (Ca2+) concentrations [(Ca2+)i] in self and neighboring neurons in the hypothalamus, resulting in further OT release: i.e., autocrine or paracrine systems of OT-induced OT release. CD38-dependent cyclic ADP-ribose (cADPR) is also involved in this autoregulation by elevating [Ca2+]i via Ca2+ mobilization through ryanodine receptors on intracellular Ca2+ pools that are sensitive to both Ca2+ and cADPR. In addition, it has recently been reported that heat stimulation and hyperthermia enhance [Ca2+]i increases by Ca2+ influx, probably through TRPM2 cation channels, suggesting that cADPR and TRPM2 molecules act as Ca2+ signal amplifiers. Thus, OT release is not simply due to depolarization–secretion coupling. Both of these molecules play critical roles not only during labor and milk ejection in reproductive females, but also during social behavior in daily life in both genders. This was clearly demonstrated in CD38 knockout mice in that social behavior was impaired by reduction of [Ca2+]i elevation and subsequent OT secretion. Evidence for the associations of CD38 with social behavior and psychiatric disorder is discussed, especially in subjects with autism spectrum disorder.
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22
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Cudnoch-Jedrzejewska A, Gomolka R, Szczepanska-Sadowska E, Czarzasta K, Wrzesien R, Koperski L, Puchalska L, Wsol A. High-fat diet and chronic stress reduce central pressor and tachycardic effects of apelin in Sprague-Dawley rats. Clin Exp Pharmacol Physiol 2015; 42:52-62. [PMID: 25311903 DOI: 10.1111/1440-1681.12324] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Revised: 09/26/2014] [Accepted: 10/02/2014] [Indexed: 12/17/2022]
Abstract
Central application of apelin elevates blood pressure and influences neuroendocrine responses to stress and food consumption. However, it is not known whether the central cardiovascular effects of apelin depend also on caloric intake or chronic stress. The purpose of the present study was to determine the effects of intracerebroventricular administration of apelin on blood pressure (mean arterial blood pressure) and heart rate in conscious Sprague-Dawley rats consuming either a normal-fat diet (NFD) or high-fat diet (HFD) for 12 weeks. During the last 4 weeks of the food regime, the rats were exposed (NFDS and HFDS groups) or not exposed (NFDNS and HFDNS groups) to chronic stress. Each group was divided into two subgroups receiving intracerebroventricular infusions of either vehicle or apelin. Apelin elicited significant increase of mean arterial blood pressure and heart rate in the NFDNS rats. This effect was abolished in the HFDNS, HFDS and NFDS groups. HFD resulted in a significant elevation of blood concentrations of total cholesterol, triglycerides glucose and insulin. Chronic stress reduced plasma concentration of total and high-density lipoprotein cholesterol, and increased plasma corticosterone concentration and APJ receptor mRNA expression in the hypothalamus, whereas a combination of a HFD with chronic stress resulted in the elevation of plasma triglycerides, total cholesterol and low-density lipoprotein cholesterol, and in increased plasma corticosterone concentration, apelin concentration and APJ receptor mRNA expression in the hypothalamus. It is concluded that a HFD and chronic stress result in significant suppression of the central pressor action of apelin, and cause significant though not unidirectional changes of metabolic and endocrine parameters.
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Affiliation(s)
- Agnieszka Cudnoch-Jedrzejewska
- Department of Experimental and Clinical Physiology, Laboratory of Centre for Preclinical Research, Medical University of Warsaw, Warsaw, Poland
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O'Carroll AM, Lolait SJ, Harris LE, Pope GR. The apelin receptor APJ: journey from an orphan to a multifaceted regulator of homeostasis. J Endocrinol 2013; 219:R13-35. [PMID: 23943882 DOI: 10.1530/joe-13-0227] [Citation(s) in RCA: 246] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The apelin receptor (APJ; gene symbol APLNR) is a member of the G protein-coupled receptor gene family. Neural gene expression patterns of APJ, and its cognate ligand apelin, in the brain implicate the apelinergic system in the regulation of a number of physiological processes. APJ and apelin are highly expressed in the hypothalamo-neurohypophysial system, which regulates fluid homeostasis, in the hypothalamic-pituitary-adrenal axis, which controls the neuroendocrine response to stress, and in the forebrain and lower brainstem regions, which are involved in cardiovascular function. Recently, apelin, synthesised and secreted by adipocytes, has been described as a beneficial adipokine related to obesity, and there is growing awareness of a potential role for apelin and APJ in glucose and energy metabolism. In this review we provide a comprehensive overview of the structure, expression pattern and regulation of apelin and its receptor, as well as the main second messengers and signalling proteins activated by apelin. We also highlight the physiological and pathological roles that support this system as a novel therapeutic target for pharmacological intervention in treating conditions related to altered water balance, stress-induced disorders such as anxiety and depression, and cardiovascular and metabolic disorders.
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Affiliation(s)
- Anne-Marie O'Carroll
- Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, School of Clinical Sciences, University of Bristol, Dorothy Hodgkin Building, Whitson Street, Bristol BS1 3NY, UK
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Brown CH, Bains JS, Ludwig M, Stern JE. Physiological regulation of magnocellular neurosecretory cell activity: integration of intrinsic, local and afferent mechanisms. J Neuroendocrinol 2013; 25:678-710. [PMID: 23701531 PMCID: PMC3852704 DOI: 10.1111/jne.12051] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2013] [Revised: 05/08/2013] [Accepted: 05/20/2013] [Indexed: 01/12/2023]
Abstract
The hypothalamic supraoptic and paraventricular nuclei contain magnocellular neurosecretory cells (MNCs) that project to the posterior pituitary gland where they secrete either oxytocin or vasopressin (the antidiuretic hormone) into the circulation. Oxytocin is important for delivery at birth and is essential for milk ejection during suckling. Vasopressin primarily promotes water reabsorption in the kidney to maintain body fluid balance, but also increases vasoconstriction. The profile of oxytocin and vasopressin secretion is principally determined by the pattern of action potentials initiated at the cell bodies. Although it has long been known that the activity of MNCs depends upon afferent inputs that relay information on reproductive, osmotic and cardiovascular status, it has recently become clear that activity depends critically on local regulation by glial cells, as well as intrinsic regulation by the MNCs themselves. Here, we provide an overview of recent advances in our understanding of how intrinsic and local extrinsic mechanisms integrate with afferent inputs to generate appropriate physiological regulation of oxytocin and vasopressin MNC activity.
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Affiliation(s)
- C H Brown
- Department of Physiology and Centre for Neuroendocrinology, University of Otago, Dunedin, New Zealand.
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25
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Dai L, Smith PM, Kuksis M, Ferguson AV. Apelin acts in the subfornical organ to influence neuronal excitability and cardiovascular function. J Physiol 2013; 591:3421-32. [PMID: 23629509 DOI: 10.1113/jphysiol.2013.254144] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Apelin is an adipocyte-derived hormone involved in the regulation of water balance, food intake and the cardiovascular system partially through actions in the CNS. The subfornical organ (SFO) is a circumventricular organ with identified roles in body fluid homeostasis, cardiovascular control and energy balance. The SFO lacks a normal blood-brain barrier, and is thus able to detect circulating signalling molecules such as angiotensin II and leptin. In this study, we investigated actions of apelin-13, the predominant apelin isoform in brain and circulatory system, on the excitability of dissociated SFO neurons using electrophysiological approaches, and determined the cardiovascular consequences of direct administration into the SFO of anaesthetized rats. Whole cell current clamp recording revealed that bath-applied 100 nm apelin-13 directly influences the excitability of the majority of SFO neurons by eliciting either depolarizing (31.8%, mean 7.0 ± 0.8 mV) or hyperpolarizing (28.6%, mean -10.4 ± 1.8 mV) responses. Using voltage-clamp techniques, we also identified modulatory actions of apelin-13 on specific ion channels, demonstrating that apelin-13 activates a non-selective cationic conductance to depolarize SFO neurons while activation of the delayed rectifier potassium conductance underlies hyperpolarizing effects. In anaesthetized rats, microinjection of apelin into SFO decreased both blood pressure (BP) (mean area under the curve -1492.3 ± 357.1 mmHg.s, n = 5) and heart rate (HR) (-32.4 ± 10.39 beats, n = 5). Our data suggest that circulating apelin can directly affect BP and HR as a consequence of the ability of this peptide to modulate the excitability of SFO neurons.
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Affiliation(s)
- Li Dai
- Biomedical and Molecular Sciences, Department of Physiology, Queen's University, Kingston, ON K7L 3N6, Canada
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26
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Hashimoto H, Uezono Y, Ueta Y. Pathophysiological function of oxytocin secreted by neuropeptides: A mini review. PATHOPHYSIOLOGY 2012; 19:283-98. [DOI: 10.1016/j.pathophys.2012.07.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2012] [Revised: 07/04/2012] [Accepted: 07/11/2012] [Indexed: 10/28/2022] Open
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Lv SY, Qin YJ, Wang NB, Yang YJ, Chen Q. Supraspinal antinociceptive effect of apelin-13 in a mouse visceral pain model. Peptides 2012; 37:165-70. [PMID: 22732665 DOI: 10.1016/j.peptides.2012.06.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2012] [Revised: 06/14/2012] [Accepted: 06/14/2012] [Indexed: 10/28/2022]
Abstract
Apelin, as the endogenous ligand of the APJ receptor, is a novel identified neuropeptide whose biological functions are not fully understood. APJ receptor mRNA was found in several brain regions related to descending control system of pain, such as amygdala, hypothalamus and dorsal raphe nucleus (DRN). The present study was designed to determine whether supraspinal apelin-13 may produce antinociceptive effect observed in the acetic acid-induced writhing test, a model of visceral pain. Apelin-13 not only significantly produced preemptive antinociception at the dose of 0.3, 0.5, 1 and 3 μg/mouse when injected intracerebroventricularly (i.c.v.) before acetic acid, but also significantly induced antinociception at a dose of 0.5, 1 and 3 μg/mouse when injected i.c.v. after acetic acid. And i.c.v. apelin-13 did not influence 30-min locomotor activity counts in mice. Intrathecal (i.t.) administration of apelin-13 (1 and 3 μg/mouse) significantly decreased the number of writhes, however, intraperitoneal (i.p.) injection of apelin-13 (10-100 μg/mouse) had no effect on the number of writhes in the writhing test. The specific APJ receptor antagonist apelin-13(F13A), no-specific opioid receptor antagonist naloxone and μ-opioid receptor antagonist β-funaltrexamine hydrochloride (β-FNA) could significantly antagonize the antinociceptive effect of i.c.v. apelin-13, suggesting APJ receptor and μ-opioid receptor are involved in this process. Central low dose of apelin-13 (0.3 μg/mouse, i.c.v.) could significantly potentiate the analgesic potencies of modest and even relatively ineffective doses of morphine administrated at supraspinal level. This enhanced antinociceptive effect was reversed by naloxone, suggesting that the potentiated analgesic response is mediated by opioid-responsive neurons.
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Affiliation(s)
- Shuang-Yu Lv
- Institute of Biochemistry and Molecular Biology, School of Life Sciences, Lanzhou University, 222 Tianshui South Road, Lanzhou, Gansu 730000, China
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28
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Pope GR, Roberts EM, Lolait SJ, O’Carroll AM. Central and peripheral apelin receptor distribution in the mouse: species differences with rat. Peptides 2012; 33:139-48. [PMID: 22197493 PMCID: PMC3314948 DOI: 10.1016/j.peptides.2011.12.005] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2011] [Revised: 12/08/2011] [Accepted: 12/08/2011] [Indexed: 01/02/2023]
Abstract
The G protein-coupled apelin receptor (APJ) binds the endogenous peptide apelin and has been shown to have roles in many physiological systems. Thus far, distribution studies have predominantly been conducted in the rat and there is limited knowledge of the cellular distribution of APJ in mouse or human tissues. As recent functional studies have been conducted in APJ knock-out mice (APJ KO), in this study we undertook to characterize APJ mRNA and I(125)[Pyr(1)]apelin-13 binding site distribution in mouse tissues to enable correlation of distribution with function. We have utilized in situ hybridization histochemistry (ISHH) using APJ riboprobes, which revealed strong hybridization specifically in the paraventricular (PVN) and supraoptic (SON) nuclei of the hypothalamus and in the anterior pituitary, with marginally lower levels in the posterior pituitary. In the periphery, strong hybridization was observed in the lung, heart, adrenal cortex, renal medulla, ovary and uterus. Autoradiographic binding to APJ with I(125)[Pyr(1)]apelin-13 exhibited significant binding in the anterior pituitary, while lower levels were observed in the posterior pituitary and PVN and SON. In the periphery, strong receptor binding was observed in tissues exhibiting intense riboprobe hybridization, indicating a good correlation between receptor transcription and translation. While the distribution of APJ mRNA and functional protein in the mouse shows similarities to that of the rat, we report a species difference in central APJ distribution and in the pituitary gland.
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29
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Hazell GG, Hindmarch CC, Pope GR, Roper JA, Lightman SL, Murphy D, O’Carroll AM, Lolait SJ. G protein-coupled receptors in the hypothalamic paraventricular and supraoptic nuclei--serpentine gateways to neuroendocrine homeostasis. Front Neuroendocrinol 2012; 33:45-66. [PMID: 21802439 PMCID: PMC3336209 DOI: 10.1016/j.yfrne.2011.07.002] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2011] [Revised: 06/24/2011] [Accepted: 07/06/2011] [Indexed: 12/31/2022]
Abstract
G protein-coupled receptors (GPCRs) are the largest family of transmembrane receptors in the mammalian genome. They are activated by a multitude of different ligands that elicit rapid intracellular responses to regulate cell function. Unsurprisingly, a large proportion of therapeutic agents target these receptors. The paraventricular nucleus (PVN) and supraoptic nucleus (SON) of the hypothalamus are important mediators in homeostatic control. Many modulators of PVN/SON activity, including neurotransmitters and hormones act via GPCRs--in fact over 100 non-chemosensory GPCRs have been detected in either the PVN or SON. This review provides a comprehensive summary of the expression of GPCRs within the PVN/SON, including data from recent transcriptomic studies that potentially expand the repertoire of GPCRs that may have functional roles in these hypothalamic nuclei. We also present some aspects of the regulation and known roles of GPCRs in PVN/SON, which are likely complemented by the activity of 'orphan' GPCRs.
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Affiliation(s)
| | | | | | | | | | | | | | - Stephen J. Lolait
- Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, Dorothy Hodgkin Building, School of Clinical Sciences, University of Bristol, Whitson Street, Bristol BS1 3NY, UK
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30
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Lv SY, Yang YJ, Qin YJ, Mo JR, Wang NB, Wang YJ, Chen Q. Central apelin-13 inhibits food intake via the CRF receptor in mice. Peptides 2012; 33:132-8. [PMID: 22108714 DOI: 10.1016/j.peptides.2011.11.011] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Revised: 11/07/2011] [Accepted: 11/07/2011] [Indexed: 11/24/2022]
Abstract
Apelin, the novel identified peptide, is the endogenous ligand for the APJ. Previous studies have reported the effect of apelin on food intake, however the action of acute central injected apelin on food intake in mice remains unknown. The present study was designed to investigate the mechanism as well as the effect of central apelin-13 on food intake in mice. During the dark period, the cumulative food intake was significantly decreased at 4h after the intracerebroventricular (i.c.v.) injection of 1 and 3μg/mouse apelin-13 and the period food intake was significantly reduced during 2-4h after treatment. In the fasted mice, the cumulative food intake was significantly decreased at 2 and 4h after injection of 3μg/mouse apelin-13. The cumulative water intake was significantly reduced by apelin-13 (3μg/mouse) at 4h after injection in freely feeding and fasted mice. However, during light period, apelin-13 had no influence on food and water intake in freely feeding mice. The APJ receptor antagonist apelin-13(F13A) (6μg/mouse) and the corticotrophin-releasing factor (CRF) receptor antagonist α-helical CRF(9-41) (3μg/mouse) could reverse the inhibitory effect on cumulative food intake/0-4h induced by apelin-13 (3μg/mouse) in freely feeding mice during the dark period, whereas the anorexic effect could not be antagonized by the arginie vasopressin (AVP) receptor antagonist deamino(CH(2))(5)Tyr(Me)AVP (0.5μg/mouse). Taken together, these results suggest that central apelin-13 inhibits food intake in mice and it seems that APJ receptor and CRF receptor, but not AVP receptor, might be involved in this process.
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Affiliation(s)
- Shuang-Yu Lv
- Institute of Biochemistry and Molecular Biology, School of Life Sciences, Lanzhou University, 222 Tian Shui South Road, Lanzhou 730000, PR China
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31
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Bodineau L, Taveau C, Lê Quan Sang HH, Osterstock G, Queguiner I, Moos F, Frugière A, Llorens-Cortes C. Data supporting a new physiological role for brain apelin in the regulation of hypothalamic oxytocin neurons in lactating rats. Endocrinology 2011; 152:3492-503. [PMID: 21733827 DOI: 10.1210/en.2011-0206] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Apelin is a bioactive peptide identified as the endogenous ligand of the human orphan G protein-coupled receptor APJ in 1998. The present data show that apelin modulates the activity of magnocellular and parvocellular oxytocin (OXY) neurons in the lactating rat. A combination of in situ hybridization and immunohistochemistry demonstrated the presence of apelin receptor mRNA in hypothalamic OXY neurons. Double immunofluorescence labeling then revealed the colocalization of apelin with OXY in about 20% of the hypothalamic OXY-positive neurons. Intracerebroventricular apelin administration inhibited the activity of magnocellular and parvocellular OXY neurons, as shown by measuring the c-fos expression in OXY neurons or by direct electrophysiological measurements of the electrical activity of these neurons. This effect was correlated with a decrease in the amount of milk ejected. Thus, apelin inhibits the activity of OXY neurons through a direct action on apelin receptors expressed by these neurons in an autocrine and paracrine manner. In conclusion, these findings highlight the inhibitory role of apelin as an autocrine/paracrine peptide acting on OXY neurons during breastfeeding.
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Affiliation(s)
- Laurence Bodineau
- Institut National de la Santé et de la Recherche Médicale, Paris F-75231, France
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32
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Lv SY, Yang YJ, Qin YJ, Xiong W, Chen Q. Effect of centrally administered apelin-13 on gastric emptying and gastrointestinal transit in mice. Peptides 2011; 32:978-82. [PMID: 21291936 DOI: 10.1016/j.peptides.2011.01.023] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2010] [Revised: 01/17/2011] [Accepted: 01/18/2011] [Indexed: 01/25/2023]
Abstract
Apelin, as the endogenous ligand for the APJ, regulates many biological functions, including blood pressure, neuroendocrine, drinking behavior, food intake and colonic motility. The present study was designed to investigate the effect of central apelin-13 on gastric emptying and gastrointestinal transit in mice. Intracerebroventricular (i.c.v.) injection of apelin-13 (3 and 10 μg/mouse) decreased gastric emptying rate by 10.9% and 17.1%. This effect was significantly antagonized by the APJ receptor antagonist apelin-13(F13A) and the opioid receptor antagonist naloxone, respectively. However, intraperitoneal (i.p.) injection of apelin-13 (10-100 μg/mouse) did not affect gastric emptying. Apelin-13 (0.3, 1 and 3 μg/mouse, i.c.v.) inhibited gastrointestinal transit by 16.8%, 23.4% and 19.2%. Apelin-13(F13A) and naloxone could also reverse this antitransit effect induced by apelin-13. Taken together, these results suggest that i.c.v. injected apelin-13 inhibits gastric emptying and gastrointestinal transit and it seems that APJ receptor and opioid receptor might be involved in these processes.
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Affiliation(s)
- Shuang-Yu Lv
- Institute of Biochemistry and Molecular Biology, School of Life Science, Lanzhou University, 222 Tian Shui South Road, Lanzhou 730000, PR China
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33
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Monteiro O, Wiegand UK, Ludwig M. Vesicle degradation in dendrites of magnocellular neurones of the rat supraoptic nucleus. Neurosci Lett 2011; 489:30-3. [PMID: 21129440 DOI: 10.1016/j.neulet.2010.11.060] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2010] [Revised: 11/02/2010] [Accepted: 11/20/2010] [Indexed: 11/17/2022]
Abstract
The magnocellular neurones of the supraoptic nucleus (SON) and paraventricular nucleus release neuropeptide from their axon terminals and also from their dendrites. In the axon terminals, swellings known as Herring bodies are responsible for the degradation of aged, unreleased large dense-cored vesicles (LDCVs) by lysosomes. Dendrites of magnocellular neurones also contain a large number of LDCVs but specialised areas of vesicle degradation have yet to be discovered. Using immunofluorescence labelling for lysosomes in vasopressin-enhanced green fluorescent protein (vasopressin-eGFP) transgenic rats, we found that lysosomes are preferentially located in the centre of the dendrites where there was a high density of vasopressin-eGFP expression. These data suggest that there are local "hot spots", but not specific compartments for vesicle degradation in magnocellular dendrites.
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Affiliation(s)
- Olivia Monteiro
- Centre for Integrative Physiology, School of Biomedical Sciences, University of Edinburgh, George Square, Edinburgh EH8 9XD, UK
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34
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Ueta Y, Dayanithi G, Fujihara H. Hypothalamic vasopressin response to stress and various physiological stimuli: visualization in transgenic animal models. Horm Behav 2011; 59:221-6. [PMID: 21185297 DOI: 10.1016/j.yhbeh.2010.12.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Revised: 11/18/2010] [Accepted: 12/17/2010] [Indexed: 11/27/2022]
Abstract
Arginine vasopressin (AVP) is involved in the homeostatic responses numerous life-threatening conditions, for example, the promotion of water conservation during periods of dehydration, and the activation of the hypothalamo-pituitary adrenal axis by emotional stress. Recently, we generated new transgenic animals that faithfully express an AVP-enhanced green fluorescent protein (eGFP) fusion gene in the paraventricular nucleus (PVN), the supraoptic nucleus (SON) and the suprachiasmatic nucleus (SCN) of the hypothalamus. In these transgenic rats, marked increases in eGFP fluorescence and fusion gene expression were observed in the magnocellular division of the PVN and the SON, but not the SCN, after osmotic challenges, such as dehydration and salt loading, and both acute and chronic nociceptive stimuli. In the parvocellular division of the PVN, eGFP expression was increased after acute and chronic pain, bilateral adrenalectomy, endotoxin shock and restraint stress. In the extra-hypothalamic areas of the brain, eGFP expression was induced in the locus coeruleus after the intracerebroventricular administration of colchicine. Next, we generated another transgenic rat that expresses a fusion gene comprised of c-fos promoter-enhancer sequences driving the expression of monomeric red fluorescent protein 1 (mRFP1). In these transgenic rats, abundant nuclear fluorescence of mRFP1 was observed in the PVN, the SON and other osmosensitive areas after acute osmotic stimulation. Finally, we generated a double transgenic rat that expresses both the AVP-eGFP and c-fos-mRFP1 fusion genes. In this double transgenic rat, we have observed nuclear mRFP1 fluorescence in eGFP-positive neurons after acute osmotic stimulation. These unique transgenic rats provide an exciting new tool to examine neuroendocrine responses to physiological and stressful stimuli in both in vivo and in vitro preparations.
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Affiliation(s)
- Yoichi Ueta
- Department of Physiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan.
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35
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Yao F, Modgil A, Zhang Q, Pingili A, Singh N, O'Rourke ST, Sun C. Pressor effect of apelin-13 in the rostral ventrolateral medulla: role of NAD(P)H oxidase-derived superoxide. J Pharmacol Exp Ther 2010; 336:372-80. [PMID: 21047952 DOI: 10.1124/jpet.110.174102] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Microinjection of apelin-13 into the rostral ventrolateral medulla (RVLM) in the brainstem increases blood pressure in rats. In the present study, we tested the hypotheses that apelin-13 directly stimulates neuronal activity in neurons cultured from the brainstem and that NAD(P)H oxidase-derived reactive oxygen species are involved in this action of apelin-13. Microinjection of apelin-13 into the RVLM resulted in increases in arterial pressure and in renal sympathetic nerve activity in Sprague-Dawley rats. The pressor effect of apelin-13 was attenuated by the specific NAD(P)H-oxidase inhibitor gp91ds-tat. In neurons cultured from the ventral brainstem, spontaneous action potentials were recorded using current-clamp recording. Superfusion of neurons with apelin-13 (100 nM) increased the neuronal firing rate from 0.79 ± 0.14 to 1.45 ± 0.26 Hz (n = 7, P < 0.01) in angiotensin II receptor-like 1-positive neurons, identified with single-cell reverse transcriptase-polymerase chain reaction. Neither the angiotensin II type 1 receptor antagonist losartan nor the angiotensin II type 2 receptor antagonist 1-[[4-(dimethylamino)-3-methylphenyl[methyl]-5-(diphenylacetyl)-4,5,6,7-tetrahydro-1H-imidazo[4,5-c]pyridine-6-carboxylic acid ditrifluoroacetate (PD123319) altered the positive chronotropic effect of apelin-13. Pretreatment of cells with either the reactive oxygen species scavenger superoxide dismutase [polyethylene glycol-superoxide dismutase (PEG-SOD), 25 U/ml] or with gp91ds-tat significantly attenuated the chronotropic action of apelin-13. PEG-SOD and gp91ds-tat alone had no effect on basal neuronal firing. In addition, apelin-13 significantly increased NAD(P)H oxidase activity and elevated intracellular superoxide levels in neuronal cultures. The superoxide generator xanthine-xanthine oxidase also increased neuronal activity in neurons, mimicking the neuronal response to apelin-13. These observations provide the first evidence that apelin-13 directly increases neuronal activity via stimulation of NAD(P)H oxidase-derived superoxide, a cellular signaling mechanism that may be involved in the pressor effect of apelin-13 in the RVLM.
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Affiliation(s)
- Fanrong Yao
- Department of Pharmaceutical Sciences, North Dakota State University, Fargo, North Dakota 58108-6050, USA
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36
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Velmurugan S, Brunton PJ, Leng G, Russell JA. Circulating secretin activates supraoptic nucleus oxytocin and vasopressin neurons via noradrenergic pathways in the rat. Endocrinology 2010; 151:2681-8. [PMID: 20332196 DOI: 10.1210/en.2009-1440] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Secretin is a 27-amino acid brain-gut peptide from duodenal S-cells. We tested the effects of systemic administration of secretin to simulate its postprandial release on neuroendocrine neurons of the supraoptic nucleus (SON) in urethane-anesthetized female rats. Secretin dose-dependently increased the firing rate of oxytocin neurons, more potently than cholecystokinin, and dose-dependently increased plasma oxytocin concentration. The effect of secretin on SON vasopressin neurons was also predominantly excitatory, in contrast to the inhibitory actions of cholecystokinin. To explore the involvement of noradrenergic inputs in secretin-induced excitation, benoxathian, an alpha1-adrenoceptor antagonist, was infused intracerebroventricularly. Benoxathian intracerebroventricular infusion blocked the excitation by secretin of both oxytocin and vasopressin neurons. To test the role of local noradrenaline release in the SON, benoxathian was microdialyzed onto the SON. The basal firing rate of oxytocin neurons was slightly reduced and the secretin-induced excitation was attenuated during benoxathian microdialysis. Hence, noradrenergic pathways mediate the excitation by systemic secretin of oxytocin neurons via alpha1-adrenoceptors in the SON. As both systemic secretin and oxytocin are involved in regulating gastrointestinal functions and natriuresis, systemically released secretin might act partly through oxytocin.
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Affiliation(s)
- Sathya Velmurugan
- Centre for Integrative Physiology, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, United Kingdom
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Roberts EM, Pope GR, Newson MJF, Landgraf R, Lolait SJ, O'Carroll AM. Stimulus-specific neuroendocrine responses to osmotic challenges in apelin receptor knockout mice. J Neuroendocrinol 2010; 22:301-8. [PMID: 20136689 DOI: 10.1111/j.1365-2826.2010.01968.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The expression of the novel peptide apelin and its receptor APJ within specific regions of the brain, in particular the magnocellular neurones of the hypothalamus and the circumventricular organs, has implicated the apelinergic system in mechanisms controlling fluid homeostasis. In addition, apelin and APJ are considered to be involved in controlling arginine vasopressin (AVP) secretion into the circulation and release within the hypothalamic-neurohypophysial system. To clarify the role of APJ during regulation of fluid homeostasis, we compared the effects of osmotic stimulation on the urinary concentrating capacities and central nervous system responses of salt-loaded (SL) and water-deprived (WD) female APJ knockout (APJ(-/-)) mice and wild-type controls. SL resulted in a significantly increased urine volume in APJ(-/-) mice compared to wild-type controls, whereas WD in APJ(-/-) mice failed to reduce urine volume as seen in wild-type controls. AVP transcripts in the supraoptic and paraventricular nuclei and plasma AVP concentrations were significantly attenuated in SL APJ(-/-) mice compared to SL wild-type, but increased comparably in wild-type and APJ(-/-) mice after WD. Analysis of c-fos mRNA expression in the median preoptic nucleus and subfornical organ in response to either WD or SL showed attenuated expression in APJ(-/-) compared to wild-type mice. These findings further implicate the apelinergic system in mechanisms controlling fluid homeostasis, particularly at a neuroendocrine level, and suggest stimulus-specific involvement in vasopressinergic activity.
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Affiliation(s)
- E M Roberts
- Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology, University of Bristol, Bristol, UK
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Tobin VA, Hashimoto H, Wacker DW, Takayanagi Y, Langnaese K, Caquineau C, Noack J, Landgraf R, Onaka T, Leng G, Meddle SL, Engelmann M, Ludwig M. An intrinsic vasopressin system in the olfactory bulb is involved in social recognition. Nature 2010; 464:413-7. [PMID: 20182426 PMCID: PMC2842245 DOI: 10.1038/nature08826] [Citation(s) in RCA: 159] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2009] [Accepted: 01/12/2010] [Indexed: 11/09/2022]
Abstract
Many peptides, when released as chemical messengers within the brain, have powerful influences on complex behaviours. Most strikingly, vasopressin and oxytocin, once thought of as circulating hormones whose actions were confined to peripheral organs, are now known to be released in the brain where they play fundamentally important roles in social behaviours1. In humans, disruptions of these peptide systems have been linked to several neurobehavioural disorders, including Prader-Willi syndrome, affective disorders, and obsessive-compulsive disorder, and polymorphisms of the vasopressin V1a receptor have been linked to autism2,3. Here we report that the rat olfactory bulb contains a large population of interneurones which express vasopressin, that blocking the actions of vasopressin in the olfactory bulb impairs the social recognition abilities of rats, and that vasopressin agonists and antagonists can modulate the processing of information by olfactory bulb neurones. The findings indicate that social information is processed in part by a vasopressin system intrinsic to the olfactory system.
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Affiliation(s)
- Vicky A Tobin
- Centre for Integrative Physiology, University of Edinburgh, Edinburgh EH8 9XD, UK
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Roberts EM, Newson MJF, Pope GR, Landgraf R, Lolait SJ, O'Carroll AM. Abnormal fluid homeostasis in apelin receptor knockout mice. J Endocrinol 2009; 202:453-62. [PMID: 19578099 PMCID: PMC2729781 DOI: 10.1677/joe-09-0134] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Revised: 05/26/2009] [Accepted: 07/03/2009] [Indexed: 12/17/2022]
Abstract
The apelinergic system, comprised of apelin and its G protein-coupled receptor (APJ; APLNR as given in MGI Database), is expressed within key regions of the central nervous system associated with arginine vasopressin (AVP) synthesis and release as well as in structures involved in the control of drinking behaviour, including the magnocellular neurones of the hypothalamus, circumventricular organs, and the pituitary gland. This localisation is indicative of a possible functional role in fluid homeostasis. We investigated a role for APJ in the regulation of fluid balance using mice deficient for the receptor. Male APJ wild-type and knockout (APJ(-/-)) mice were housed in metabolic cages to allow determination of water intake and urine volume and osmolality. When provided with free access to water, APJ(-/-) mice drank significantly less than wild-types, while their urine volume and osmolality did not differ. Water deprivation for 24 h significantly reduced urine volume and increased osmolality in wild-type but not in APJ(-/-) mice. Baseline plasma AVP concentration increased comparably in both wild-type and APJ(-/-) mice following dehydration; however, APJ(-/-) mice were unable to concentrate their urine to the same extent as wild-type mice in response to the V2 agonist desmopressin. Analysis of c-fos (Fos as given in MGI Database) mRNA expression in response to dehydration showed attenuation of expression within the subfornical organ, accentuated expression in the paraventricular nucleus, but no differences in expression in the supraoptic nucleus nor median pre-optic nucleus in APJ(-/-) mice compared with wild-type. These findings demonstrate a physiological role for APJ in mechanisms of water intake and fluid retention and suggest an anti-diuretic effect of apelin in vivo.
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Newson MJF, Roberts EM, Pope GR, Lolait SJ, O'Carroll AM. The effects of apelin on hypothalamic-pituitary-adrenal axis neuroendocrine function are mediated through corticotrophin-releasing factor- and vasopressin-dependent mechanisms. J Endocrinol 2009; 202:123-9. [PMID: 19395447 PMCID: PMC2695660 DOI: 10.1677/joe-09-0093] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The apelinergic system has a widespread expression in the central nervous system (CNS) including the paraventricular nucleus, supraoptic nucleus and median eminence, and isolated cells of the anterior lobe of the pituitary. This pattern of expression in hypothalamic nuclei known to contain corticotrophin-releasing factor (CRF) and vasopressin (AVP) and to co-ordinate endocrine responses to stress has generated interest in a role for apelin in the modulation of stress, perhaps via the regulation of hormone release from the pituitary. In this study, to determine whether apelin has a central role in the regulation of CRF and AVP neurones, we investigated the effect of i.c.v. administration of pGlu-apelin-13 on neuroendocrine function in male mice pre-treated with the CRF receptor antagonist, alpha-helical CRF(9-41), and in mice-lacking functional AVP V1b receptors (V1bR KO). Administration of pGlu-apelin-13 (1 mg/kg i.c.v.) resulted in significant increases in plasma ACTH and corticosterone (CORT), which were significantly reduced by pre-treatment with alpha-helical CRF(9-41), indicating the involvement of a CRF-dependent mechanism. Additionally, pGlu-apelin-13-mediated increases in both plasma ACTH and CORT were significantly attenuated in V1bR KO animals when compared with wild-type controls, indicating a role for the vasopressinergic system in the regulation of the effects of apelin on neuroendocrine function. Together, these data confirm that the in vivo effects of apelin on hypothalamic-pituitary-adrenal neuroendocrine function appear to be mediated through both CRF- and AVP-dependent mechanisms.
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Zhang Q, Yao F, Raizada MK, O'Rourke ST, Sun C. Apelin gene transfer into the rostral ventrolateral medulla induces chronic blood pressure elevation in normotensive rats. Circ Res 2009; 104:1421-8. [PMID: 19443838 DOI: 10.1161/circresaha.108.192302] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The peripheral apelin system plays a significant role in cardiovascular homeostasis and in the pathophysiology of cardiovascular diseases. However, the central effect of this neurohormonal system in neural control of cardiovascular function remains poorly understood. Thus, this study was undertaken to evaluate the effect of apelin in the rostral ventrolateral medulla (RVLM) on blood pressure, cardiac function, and sympathetic nerve activity. Apelin mRNA and protein levels were detected with real-time RT-PCR and Western blots, respectively. Expression of apelin was significantly enhanced in the RVLM of spontaneously hypertensive rat (SHR) compared with normotensive Wistar-Kyoto (WKY) rats. To study the functional consequence of upregulated apelin expression, apelin was overexpressed by bilateral microinjection of the AAV2-apelin viral vector into the RVLM of WKY rats. Immunofluorescence staining and Western blots demonstrated that microinjection of AAV2-apelin into the RVLM resulted in a significant increase in apelin expression, which was associated with a chronic elevation in blood pressure and cardiac hypertrophy. In addition, direct microinjection of exogenous apelin-13 (200 pmol in 50 nL) into the RVLM caused a 20 mm Hg elevation in blood pressure and a 24% increase in sympathetic nerve activity. The present study is the first to show that apelin expression is enhanced in the RVLM of SHR versus WKY rats and that overexpression of this gene in the RVLM results in chronic blood pressure elevation and cardiac hypertrophy in normotensive rats. Thus, the apelin system in the RVLM may play a very important role in central blood pressure regulation and in the pathogenesis of hypertension.
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Affiliation(s)
- Qi Zhang
- Department of Pharmaceutical Sciences, North Dakota State University, 1401 Albrecht Blvd, Fargo, ND 58105, USA
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