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Chen D, Rehfeld JF, Watts AG, Rorsman P, Gundlach AL. History of key regulatory peptide systems and perspectives for future research. J Neuroendocrinol 2023; 35:e13251. [PMID: 37053148 DOI: 10.1111/jne.13251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 02/10/2023] [Accepted: 02/26/2023] [Indexed: 03/06/2023]
Abstract
Throughout the 20th Century, regulatory peptide discovery advanced from the identification of gut hormones to the extraction and characterization of hypothalamic hypophysiotropic factors, and to the isolation and cloning of multiple brain neuropeptides. These discoveries were followed by the discovery of G-protein-coupled and other membrane receptors for these peptides. Subsequently, the systems physiology associated with some of these multiple regulatory peptides and receptors has been comprehensively elucidated and has led to improved therapeutics and diagnostics and their approval by the US Food and Drug Administration. In light of this wealth of information and further potential, it is truly a time of renaissance for regulatory peptides. In this perspective, we review what we have learned from the pioneers in exemplified fields of gut peptides, such as cholecystokinin, enterochromaffin-like-cell peptides, and glucagon, from the trailblazing studies on the key stress hormone, corticotropin-releasing factor, as well as from more recently characterized relaxin-family peptides and receptors. The historical viewpoints are based on our understanding of these topics in light of the earliest phases of research and on subsequent studies and the evolution of knowledge, aiming to sharpen our vision of the current state-of-the-art and those studies that should be prioritized in the future.
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Affiliation(s)
- Duan Chen
- Department of Clinical and Molecular Medicine, Faculty of Medicine and Health Sciences, Norwegian University of Science and Technology (NTNU), Trondheim, Norway
| | - Jens F Rehfeld
- Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Alan G Watts
- Department of Biological Sciences, Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California, USA
| | - Patrik Rorsman
- Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Andrew L Gundlach
- The Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Melbourne, VIC, Australia
- Florey Department of Neuroscience and Mental Health and Department of Anatomy and Physiology, The University of Melbourne, Melbourne, VIC, Australia
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Relaxin inhibits 177Lu-EDTMP associated cell death in osteosarcoma cells through notch-1 pathway. ACTA PHARMACEUTICA (ZAGREB, CROATIA) 2022; 72:575-585. [PMID: 36651368 DOI: 10.2478/acph-2022-0032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/20/2022] [Indexed: 01/25/2023]
Abstract
177Lu-EDTMP (Ethylenediamine tetramethylene phosphonic acid) is the most used radioactive agent for pain palliation in bone cancer patients. The present study aims to study the impact of relaxin-2 on the 177Lu-EDTMP associated cell toxicity and death in osteosarcoma cells. MG63 and Saos-2 cells were cultured with 177Lu-EDTMP (37 MBq) for 24 h with and without pretreatment of recombinant relaxin 2 (RLXH2) for 12 and 24 h. 177Lu-EDTMP associated cellular deterioration and death was determined by LDH, MTT, and trypan blue dye assays. ELISA-based kit was used to determine apoptotic DNA fragmentation. Western blotting was used to determine expression levels of apoptotic-related signalling pathway proteins like bcl2, poly(ADP-ribose) polymerase (PARP), and MAPK (mitogen-activated protein kinase). Our results found that RLXH2 counters 177Lu-EDTMP associated cellular toxicity. Similarly, RLXH2 was able to counter 177Lu-EDTMP induced cell death in a concentration and time--dependent manner. Furthermore, it was found that RLXH2 treatment prevents apoptosis in 177Lu-EDTMP challenged cells through activation of the notch-1 pathway in a concentration- and time-dependent manner. We reported that RLXH2 significantly declined cellular toxicity and apoptosis associated with 177Lu-EDTMP in MG63 and Saos-2 cells through the notch-1 pathway.
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Hoare BL, Bruell S, Sethi A, Gooley PR, Lew MJ, Hossain MA, Inoue A, Scott DJ, Bathgate RAD. Multi-Component Mechanism of H2 Relaxin Binding to RXFP1 through NanoBRET Kinetic Analysis. iScience 2018; 11:93-113. [PMID: 30594862 PMCID: PMC6309025 DOI: 10.1016/j.isci.2018.12.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 11/20/2018] [Accepted: 12/05/2018] [Indexed: 12/27/2022] Open
Abstract
The peptide hormone H2 relaxin has demonstrated promise as a therapeutic, but mimetic development has been hindered by the poorly understood relaxin receptor RXFP1 activation mechanism. H2 relaxin is hypothesized to bind to two distinct ECD sites, which reorientates the N-terminal LDLa module to activate the transmembrane domain. Here we provide evidence for this model in live cells by measuring bioluminescence resonance energy transfer (BRET) between nanoluciferase-tagged RXFP1 constructs and fluorescently labeled H2 relaxin (NanoBRET). Additionally, we validate these results using the related RXFP2 receptor and chimeras with an inserted RXFP1-binding domain utilizing NanoBRET and nuclear magnetic resonance studies on recombinant proteins. We therefore provide evidence for the multi-component molecular mechanism of H2 relaxin binding to RXFP1 on the full-length receptor in cells. Also, we show the utility of NanoBRET real-time binding kinetics to reveal subtle binding complexities, which may be overlooked in traditional equilibrium binding assays. NanoBRET was used to assess relaxin binding kinetics to its receptor RXFP1 Binding on wild-type and mutant RXFP1 demonstrated a multi-component mechanism This binding mode was validated using RXFP2/RXFP1 chimeras and protein NMR studies NanoBRET binding can reveal subtle GPCR binding modes to aid drug development
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Affiliation(s)
- Bradley L Hoare
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC 3052, Australia
| | - Shoni Bruell
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC 3052, Australia; Department of Biochemistry and Molecular Biology, The University of Melbourne, Parkville, VIC, Australia
| | - Ashish Sethi
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Parkville, VIC, Australia; Bio21 Molecular and Biotechnology Institute, The University of Melbourne, Parkville, VIC, Australia
| | - Paul R Gooley
- Department of Biochemistry and Molecular Biology, The University of Melbourne, Parkville, VIC, Australia; Bio21 Molecular and Biotechnology Institute, The University of Melbourne, Parkville, VIC, Australia
| | - Michael J Lew
- Department of Pharmacology and Therapeutics, The University of Melbourne, Parkville, VIC 3052, Australia
| | - Mohammed A Hossain
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC 3052, Australia; Department of Chemistry, The University of Melbourne, Parkville, VIC 3052, Australia
| | - Asuka Inoue
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3, Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578, Japan
| | - Daniel J Scott
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC 3052, Australia; Department of Biochemistry and Molecular Biology, The University of Melbourne, Parkville, VIC, Australia.
| | - Ross A D Bathgate
- Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC 3052, Australia; Department of Biochemistry and Molecular Biology, The University of Melbourne, Parkville, VIC, Australia.
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Wei X, Yang Y, Jiang YJ, Lei JM, Guo JW, Xiao H. Relaxin ameliorates high glucose-induced cardiomyocyte hypertrophy and apoptosis via the Notch1 pathway. Exp Ther Med 2017; 15:691-698. [PMID: 29399073 PMCID: PMC5772593 DOI: 10.3892/etm.2017.5448] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 08/21/2017] [Indexed: 12/14/2022] Open
Abstract
The present study aimed to investigate the role of relaxin (RLX) on high glucose (HG)-induced cardiomyocyte hypertrophy and apoptosis, as well as the possible molecular mechanism. H9c2 cells were exposed to 33 mmol/l HG with or without RLX (100 nmol/ml). Cell viability, apoptosis, oxidative stress, cell hypertrophy and the levels of Notch1, hairy and enhancer of split 1 (hes1), atrial natriuretic polypeptide (ANP), brain natriuretic peptide (BNP), manganese superoxide dismutase (MnSOD), cytochrome C and caspase-3 were assessed in cardiomyocytes. Compared with the HG group, the viability of H9c2 cells was increased by RLX in a time- and dose-dependent manner, and was accompanied with a significant reduction in apoptosis. Furthermore, RLX significantly suppressed the formation of reactive oxygen species and malondialdehyde, and enhanced the activity of SOD. In addition, the levels of ANP, BNP, cytochrome C and caspase-3 were increased and Notch1, hes1 and MnSOD were inhibited in the HG group compared with those in the normal group. However, the Notch inhibitor DAPT almost abolished the protective effects of RLX. These results suggested that RLX protected cardiomyocytes from HG-induced hypertrophy and apoptosis partly through a Notch1-dependent pathway, which may be associated with reducing oxidative stress.
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Affiliation(s)
- Xiao Wei
- Department of Cardiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China
| | - Yuan Yang
- Department of Cardiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China
| | - Yin-Jiu Jiang
- Department of Thoracic Surgery, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China
| | - Jian-Ming Lei
- Department of Cardiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China
| | - Jing-Wen Guo
- Department of Cardiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China
| | - Hua Xiao
- Department of Cardiology, The First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, P.R. China
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Tan J, Tedrow JR, Dutta JA, Juan-Guardela B, Nouraie M, Chu Y, Trejo Bittar H, Ramani K, Biswas PS, Veraldi KL, Kaminski N, Zhang Y, Kass DJ. Expression of RXFP1 Is Decreased in Idiopathic Pulmonary Fibrosis. Implications for Relaxin-based Therapies. Am J Respir Crit Care Med 2017; 194:1392-1402. [PMID: 27310652 DOI: 10.1164/rccm.201509-1865oc] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
RATIONALE Relaxin is a hormone that has been considered as a potential therapy for patients with fibrotic diseases. OBJECTIVES To gauge the potential efficacy of relaxin-based therapies in idiopathic pulmonary fibrosis (IPF), we studied gene expression for relaxin/insulin-like family peptide receptor 1 (RXFP1) in IPF lungs and controls. METHODS We analyzed gene expression data obtained from the Lung Tissue Research Consortium and correlated RXFP1 gene expression data with cross-sectional clinical and demographic data. We also employed ex vivo donor and IPF lung fibroblasts to test RXFP1 expression in vitro. We tested CGEN25009, a relaxin-like peptide, in lung fibroblasts and in bleomycin injury. MEASUREMENTS AND MAIN RESULTS We found that RXFP1 is significantly decreased in IPF. In patients with IPF, the magnitude of RXFP1 gene expression correlated directly with diffusing capacity of the lung for carbon monoxide (P < 0.0001). Significantly less RXFP1 was detected in vitro in IPF fibroblasts than in donor controls. Transforming growth factor-β decreased RXFP1 in both donor and IPF lung fibroblasts. CGEN25009 was effective at decreasing bleomycin-induced, acid-soluble collagen deposition in vivo. The relaxin-like actions of CGEN25009 were abrogated by RXFP1 silencing in vitro, and, in comparison with donor lung fibroblasts, IPF lung fibroblasts exhibited decreased sensitivity to the relaxin-like effects of CGEN25009. CONCLUSIONS IPF is characterized by the loss of RXFP1 expression. RXFP1 expression is directly associated with pulmonary function in patients with IPF. The relaxin-like effects of CGEN25009 in vitro are dependent on expression of RXFP1. Our data suggest that patients with IPF with the highest RXFP1 expression would be predicted to be most sensitive to relaxin-based therapies.
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Affiliation(s)
- Jiangning Tan
- 1 Dorothy P. and Richard P. Simmons Center for Interstitial Lung Disease.,2 Division of Pulmonary, Allergy, and Critical Care Medicine
| | - John R Tedrow
- 1 Dorothy P. and Richard P. Simmons Center for Interstitial Lung Disease.,2 Division of Pulmonary, Allergy, and Critical Care Medicine
| | - Justin A Dutta
- 1 Dorothy P. and Richard P. Simmons Center for Interstitial Lung Disease.,2 Division of Pulmonary, Allergy, and Critical Care Medicine
| | - Brenda Juan-Guardela
- 3 Section of Pulmonary, Critical Care, and Sleep Medicine, Yale University, New Haven, Connecticut
| | - Mehdi Nouraie
- 1 Dorothy P. and Richard P. Simmons Center for Interstitial Lung Disease.,2 Division of Pulmonary, Allergy, and Critical Care Medicine
| | - Yanxia Chu
- 1 Dorothy P. and Richard P. Simmons Center for Interstitial Lung Disease.,2 Division of Pulmonary, Allergy, and Critical Care Medicine
| | | | - Kritika Ramani
- 5 Division of Rheumatology, University of Pittsburgh, Pittsburgh, Pennsylvania; and
| | - Partha S Biswas
- 5 Division of Rheumatology, University of Pittsburgh, Pittsburgh, Pennsylvania; and
| | - Kristen L Veraldi
- 1 Dorothy P. and Richard P. Simmons Center for Interstitial Lung Disease.,2 Division of Pulmonary, Allergy, and Critical Care Medicine
| | - Naftali Kaminski
- 3 Section of Pulmonary, Critical Care, and Sleep Medicine, Yale University, New Haven, Connecticut
| | - Yingze Zhang
- 1 Dorothy P. and Richard P. Simmons Center for Interstitial Lung Disease.,2 Division of Pulmonary, Allergy, and Critical Care Medicine
| | - Daniel J Kass
- 1 Dorothy P. and Richard P. Simmons Center for Interstitial Lung Disease.,2 Division of Pulmonary, Allergy, and Critical Care Medicine
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Jelinic M, Kahlberg N, Parry LJ, Tare M. Does serelaxin treatment alter passive mechanical wall properties in small resistance arteries? Microcirculation 2016; 23:631-636. [DOI: 10.1111/micc.12321] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 09/15/2016] [Indexed: 11/26/2022]
Affiliation(s)
- Maria Jelinic
- School of BioSciences; The University of Melbourne; Parkville Victoria Australia
| | - Nicola Kahlberg
- School of BioSciences; The University of Melbourne; Parkville Victoria Australia
| | - Laura J. Parry
- School of BioSciences; The University of Melbourne; Parkville Victoria Australia
| | - Marianne Tare
- Department of Physiology; Monash University; Parkville Victoria Australia
- School of Rural Health; Monash University; Parkville Victoria Australia
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Sarwar M, Du XJ, Dschietzig TB, Summers RJ. The actions of relaxin on the human cardiovascular system. Br J Pharmacol 2016; 174:933-949. [PMID: 27239943 DOI: 10.1111/bph.13523] [Citation(s) in RCA: 53] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Revised: 04/01/2016] [Accepted: 04/26/2016] [Indexed: 12/14/2022] Open
Abstract
The insulin-like peptide relaxin, originally identified as a hormone of pregnancy, is now known to exert a range of pleiotropic effects including vasodilatory, anti-fibrotic, angiogenic, anti-apoptotic and anti-inflammatory effects in both males and females. Relaxin produces these effects by binding to a cognate receptor RXFP1 and activating a variety of signalling pathways including cAMP, cGMP and MAPKs as well as by altering gene expression of TGF-β, MMPs, angiogenic growth factors and endothelin receptors. The peptide has been shown to be effective in halting or reversing many of the adverse effects including fibrosis in animal models of cardiovascular disease including ischaemia/reperfusion injury, myocardial infarction, hypertensive heart disease and cardiomyopathy. Relaxin given to humans is safe and produces favourable haemodynamic changes. Serelaxin, the recombinant form of relaxin, is now in extended phase III clinical trials for the treatment of acute heart failure. Previous clinical studies indicated that a 48 h infusion of relaxin improved 180 day mortality, yet the mechanism underlying this effect is not clear. This article provides an overview of the cellular mechanism of effects of relaxin and summarizes its beneficial actions in animal models and in the clinic. We also hypothesize potential mechanisms for the clinical efficacy of relaxin, identify current knowledge gaps and suggest new ways in which relaxin could be useful therapeutically. LINKED ARTICLES This article is part of a themed section on Recent Progress in the Understanding of Relaxin Family Peptides and their Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.10/issuetoc.
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Affiliation(s)
- Mohsin Sarwar
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Parkville, Australia
| | - Xiao-Jun Du
- Baker IDI Heart and Diabetes Institute, Melbourne, Australia
| | - Thomas B Dschietzig
- Immundiagnostik AG, Bensheim, Germany.,Campus Mitte, Medical Clinic for Cardiology and Angiology, Charité-University Medicine Berlin, Berlin, Germany.,Relaxera Pharmazeutische Gesellschaft mbH & Co. KG, Bensheim, Germany
| | - Roger J Summers
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Parkville, Australia
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Lee JH, Koh SQ, Guadagna S, Francis PT, Esiri MM, Chen CP, Wong PTH, Dawe GS, Lai MKP. Altered relaxin family receptors RXFP1 and RXFP3 in the neocortex of depressed Alzheimer's disease patients. Psychopharmacology (Berl) 2016; 233:591-8. [PMID: 26542729 DOI: 10.1007/s00213-015-4131-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2014] [Accepted: 10/23/2015] [Indexed: 11/25/2022]
Abstract
RATIONALE The G-protein-coupled relaxin family receptors RXFP1 and RXFP3 are widely expressed in the cortex and are involved in stress responses and memory and emotional processing. However, the identification of these receptors in human cortex and their status in Alzheimer's disease (AD), which is characterized by both cognitive impairments and neuropsychiatric behaviours, have not been reported. OBJECTIVES In this study, we characterized RXFP receptors for immunoblotting and measured RXFP1 and RXFP3 immunoreactivities in the postmortem neocortex of AD patients longitudinally assessed for depressive symptoms. METHODS RXFP1 and RXFP3 antibodies were characterized by immunoblotting with lysates from transfected HEK cells and preadsorption with RXFP3 peptides. Also, postmortem neocortical tissues from behaviourally assessed AD and age-matched controls were processed for immunoblotting with RXFP1 and RXFP3 antibodies. RESULTS Compared to controls, putative RXFP1 immunoreactivity was reduced in parietal cortex of non-depressed AD patients but unchanged in depressed patients. Furthermore, putative RXFP3 immunoreactivity was increased only in depressed AD patients. RXFP1 levels in the parietal cortex also correlated with severity of depression symptoms. In contrast, RXFP1 and RXFP3 levels did not correlate with dementia severity or β-amyloid burden. CONCLUSION Alterations of RXFP1 and RXFP3 may be neurochemical markers of depression in AD, and relaxin family receptors warrant further preclinical investigations as possible therapeutic targets for neuropsychiatric symptoms in dementia.
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Affiliation(s)
- Jasinda H Lee
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Unit 09-01, Centre for Translational Medicine (MD6), 14 Medical Drive, Kent Ridge, 117599, Singapore
| | - Shu Qing Koh
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Unit 09-01, Centre for Translational Medicine (MD6), 14 Medical Drive, Kent Ridge, 117599, Singapore
| | - Simone Guadagna
- Wolfson Centre for Age-Related Diseases, King's College London, London, UK
| | - Paul T Francis
- Wolfson Centre for Age-Related Diseases, King's College London, London, UK
| | - Margaret M Esiri
- Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK
| | - Christopher P Chen
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Unit 09-01, Centre for Translational Medicine (MD6), 14 Medical Drive, Kent Ridge, 117599, Singapore
| | - Peter T-H Wong
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Unit 09-01, Centre for Translational Medicine (MD6), 14 Medical Drive, Kent Ridge, 117599, Singapore
| | - Gavin S Dawe
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Unit 09-01, Centre for Translational Medicine (MD6), 14 Medical Drive, Kent Ridge, 117599, Singapore
- Neurobiology and Ageing Programme, Life Science Institute, National University of Singapore, Kent Ridge, Singapore
- Singapore Institute for Neurotechnology (SINAPSE), Kent Ridge, Singapore
| | - Mitchell K P Lai
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Unit 09-01, Centre for Translational Medicine (MD6), 14 Medical Drive, Kent Ridge, 117599, Singapore.
- Wolfson Centre for Age-Related Diseases, King's College London, London, UK.
- Neurobiology and Ageing Programme, Life Science Institute, National University of Singapore, Kent Ridge, Singapore.
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Halls ML, Bathgate RAD, Sutton SW, Dschietzig TB, Summers RJ. International Union of Basic and Clinical Pharmacology. XCV. Recent advances in the understanding of the pharmacology and biological roles of relaxin family peptide receptors 1-4, the receptors for relaxin family peptides. Pharmacol Rev 2015; 67:389-440. [PMID: 25761609 DOI: 10.1124/pr.114.009472] [Citation(s) in RCA: 94] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Relaxin, insulin-like peptide 3 (INSL3), relaxin-3, and INSL5 are the cognate ligands for the relaxin family peptide (RXFP) receptors 1-4, respectively. RXFP1 activates pleiotropic signaling pathways including the signalosome protein complex that facilitates high-sensitivity signaling; coupling to Gα(s), Gα(i), and Gα(o) proteins; interaction with glucocorticoid receptors; and the formation of hetero-oligomers with distinctive pharmacological properties. In addition to relaxin-related ligands, RXFP1 is activated by Clq-tumor necrosis factor-related protein 8 and by small-molecular-weight agonists, such as ML290 [2-isopropoxy-N-(2-(3-(trifluoromethylsulfonyl)phenylcarbamoyl)phenyl)benzamide], that act allosterically. RXFP2 activates only the Gα(s)- and Gα(o)-coupled pathways. Relaxin-3 is primarily a neuropeptide, and its cognate receptor RXFP3 is a target for the treatment of depression, anxiety, and autism. A variety of peptide agonists, antagonists, biased agonists, and an allosteric modulator target RXFP3. Both RXFP3 and the related RXFP4 couple to Gα(i)/Gα(o) proteins. INSL5 has the properties of an incretin; it is secreted from the gut and is orexigenic. The expression of RXFP4 in gut, adipose tissue, and β-islets together with compromised glucose tolerance in INSL5 or RXFP4 knockout mice suggests a metabolic role. This review focuses on the many advances in our understanding of RXFP receptors in the last 5 years, their signal transduction mechanisms, the development of novel compounds that target RXFP1-4, the challenges facing the field, and current prospects for new therapeutics.
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Affiliation(s)
- Michelle L Halls
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia (M.L.H., R.J.S.); Neuropeptides Division, Florey Institute of Neuroscience and Mental Health and Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia (R.A.D.B.); Neuroscience Drug Discovery, Janssen Research & Development, LLC, San Diego, California (S.W.S.); Immundiagnostik AG, Bensheim, Germany (T.B.D.); and Charité-University Medicine Berlin, Campus Mitte, Medical Clinic for Cardiology and Angiology, Berlin, Germany (T.B.D.)
| | - Ross A D Bathgate
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia (M.L.H., R.J.S.); Neuropeptides Division, Florey Institute of Neuroscience and Mental Health and Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia (R.A.D.B.); Neuroscience Drug Discovery, Janssen Research & Development, LLC, San Diego, California (S.W.S.); Immundiagnostik AG, Bensheim, Germany (T.B.D.); and Charité-University Medicine Berlin, Campus Mitte, Medical Clinic for Cardiology and Angiology, Berlin, Germany (T.B.D.)
| | - Steve W Sutton
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia (M.L.H., R.J.S.); Neuropeptides Division, Florey Institute of Neuroscience and Mental Health and Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia (R.A.D.B.); Neuroscience Drug Discovery, Janssen Research & Development, LLC, San Diego, California (S.W.S.); Immundiagnostik AG, Bensheim, Germany (T.B.D.); and Charité-University Medicine Berlin, Campus Mitte, Medical Clinic for Cardiology and Angiology, Berlin, Germany (T.B.D.)
| | - Thomas B Dschietzig
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia (M.L.H., R.J.S.); Neuropeptides Division, Florey Institute of Neuroscience and Mental Health and Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia (R.A.D.B.); Neuroscience Drug Discovery, Janssen Research & Development, LLC, San Diego, California (S.W.S.); Immundiagnostik AG, Bensheim, Germany (T.B.D.); and Charité-University Medicine Berlin, Campus Mitte, Medical Clinic for Cardiology and Angiology, Berlin, Germany (T.B.D.)
| | - Roger J Summers
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria, Australia (M.L.H., R.J.S.); Neuropeptides Division, Florey Institute of Neuroscience and Mental Health and Department of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia (R.A.D.B.); Neuroscience Drug Discovery, Janssen Research & Development, LLC, San Diego, California (S.W.S.); Immundiagnostik AG, Bensheim, Germany (T.B.D.); and Charité-University Medicine Berlin, Campus Mitte, Medical Clinic for Cardiology and Angiology, Berlin, Germany (T.B.D.)
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Su W, Wang P, Chen H, Li H. Role of protein kinase C β₂ in relaxin-mediated inhibition of cardiac fibrosis. J Endocrinol Invest 2014; 37:559-64. [PMID: 24729283 DOI: 10.1007/s40618-014-0068-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Accepted: 03/05/2014] [Indexed: 10/25/2022]
Abstract
INTRODUCTION Relaxin is a pleiotropic hormone owing endogenous antifibrosis effect on numerous organs. We demonstrated relaxin's inhibitive effect on cardiac fibrosis previously. OBJECTIVE The aim of this study was to investigate the role of protein kinase C (PKC) β2 in relaxin's action under high glucose conditions. METHODS AND RESULTS Cardiac fibroblasts (CFs) were isolated, exposed to high glucose and incubated with recombinant human relaxin (rhRLX). Western blot analysis revealed a relaxin-mediated decrease in total expression and translocation of PKCβ2, showing downregulation of PKCβ2 is involved in relaxin's action. Blocking PKCβ2 pathway with ruboxistaurin accelerated rhRLX-mediated inhibition in both proliferation of CFs and deposition of collagen. CONCLUSION In conclusion, relaxin can inhibit high glucose-associated cardiac fibrosis partly through PKCβ2 pathway. Further work should be done to fully understand intracellular mechanisms of relaxin's action to accelerate its clinical use.
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Affiliation(s)
- W Su
- Department of Cardiology, Beijing Friendship Hospital, Capital Medical University, No. 95, Yongan Road, Xicheng District, Beijing, 100050, People's Republic of China
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Sasser JM. The emerging role of relaxin as a novel therapeutic pathway in the treatment of chronic kidney disease. Am J Physiol Regul Integr Comp Physiol 2013; 305:R559-65. [PMID: 23883673 DOI: 10.1152/ajpregu.00528.2012] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Emerging evidence supports a potential therapeutic role of relaxin in fibrotic diseases, including chronic kidney disease. Relaxin is a pleiotropic hormone, best characterized for its role in the reproductive system; however, recent studies have demonstrated a role of relaxin in the cardiorenal system. Both relaxin and its receptor, RXFP1, are expressed in the kidney, and relaxin has been shown to play a role in renal vasodilation, in sodium excretion, and as an antifibrotic agent. Together, these findings suggest that the kidney is a target organ of relaxin. Therefore, the purpose of this review is to describe the functional and structural impacts of relaxin treatment on the kidney and to discuss evidence that relaxin prevents disease progression in several experimental models of kidney disease. In addition, this review will present potential mechanisms that are involved in the therapeutic actions of relaxin.
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Affiliation(s)
- Jennifer M Sasser
- Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson, Mississippi
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Bathgate RAD, Halls ML, van der Westhuizen ET, Callander GE, Kocan M, Summers RJ. Relaxin family peptides and their receptors. Physiol Rev 2013; 93:405-80. [PMID: 23303914 DOI: 10.1152/physrev.00001.2012] [Citation(s) in RCA: 376] [Impact Index Per Article: 34.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
There are seven relaxin family peptides that are all structurally related to insulin. Relaxin has many roles in female and male reproduction, as a neuropeptide in the central nervous system, as a vasodilator and cardiac stimulant in the cardiovascular system, and as an antifibrotic agent. Insulin-like peptide-3 (INSL3) has clearly defined specialist roles in male and female reproduction, relaxin-3 is primarily a neuropeptide involved in stress and metabolic control, and INSL5 is widely distributed particularly in the gastrointestinal tract. Although they are structurally related to insulin, the relaxin family peptides produce their physiological effects by activating a group of four G protein-coupled receptors (GPCRs), relaxin family peptide receptors 1-4 (RXFP1-4). Relaxin and INSL3 are the cognate ligands for RXFP1 and RXFP2, respectively, that are leucine-rich repeat containing GPCRs. RXFP1 activates a wide spectrum of signaling pathways to generate second messengers that include cAMP and nitric oxide, whereas RXFP2 activates a subset of these pathways. Relaxin-3 and INSL5 are the cognate ligands for RXFP3 and RXFP4 that are closely related to small peptide receptors that when activated inhibit cAMP production and activate MAP kinases. Although there are still many unanswered questions regarding the mode of action of relaxin family peptides, it is clear that they have important physiological roles that could be exploited for therapeutic benefit.
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Affiliation(s)
- R A D Bathgate
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences & Department of Pharmacology, Monash University, Victoria, Australia
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13
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Donizetti A, Fiengo M, del Gaudio R, Di Giaimo R, Minucci S, Aniello F. Characterization and developmental expression pattern of the relaxin receptor rxfp1 gene in zebrafish. Dev Growth Differ 2011; 52:799-806. [PMID: 21158758 DOI: 10.1111/j.1440-169x.2010.01215.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We report the gene characterization, the cDNA cloning and the temporal and spatial expression pattern of the relaxin receptor rxfp1 gene in the zebrafish Danio rerio. The zebrafish rxfp1 gene has the same syntenic genomic organization, and a similar exon-intron structure to the homologue human gene. Furthermore, the deduced Rxfp1 protein sequence shows a high degree of amino acid similarity when compared with the human protein and the conservation of all amino acid identity necessary for the binding with relaxin. Our results show that rxfp1 gene is active either during embryogenesis or in the adult organism, showing a wide expression pattern. Moreover, we provide the first description of rxfp1 spatial expression pattern during embryo development, showing that the transcript is already present at the early developmental stage and is distributed in all of the embryonic cells until somitogenesis. Starting at the pharyngula stage the gene expression becomes mainly restricted in the brain territories. In fact, at the larval stage, the transcript is detectable in the epiphysis, postoptic region, posterior tuberculum, hypothalamus, optic tectum, tegmentum/pons, medulla and also in the structure of a peripheral nervous system, the terminal nerve. The rxfp1 expression pattern in Danio rerio embryos is very similar to that reported in the adult mammalian brain, suggesting a pivotal role of this receptor in the neurophysiology processes already at very early developmental stages.
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Affiliation(s)
- Aldo Donizetti
- Department of Biological Sciences, University of Naples Federico II, Via Mezzocannone 8, Napoli, Italy
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Vodstrcil LA, Shynlova O, Verlander JW, Wlodek ME, Parry LJ. Decreased Expression of the Rat Myometrial Relaxin Receptor (RXFP1) in Late Pregnancy Is Partially Mediated by the Presence of the Conceptus1. Biol Reprod 2010; 83:818-24. [DOI: 10.1095/biolreprod.110.083931] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
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Vodstrcil LA, Shynlova O, Westcott K, Laker R, Simpson E, Wlodek ME, Parry LJ. Progesterone Withdrawal, and Not Increased Circulating Relaxin, Mediates the Decrease in Myometrial Relaxin Receptor (RXFP1) Expression in Late Gestation in Rats1. Biol Reprod 2010; 83:825-32. [DOI: 10.1095/biolreprod.110.084301] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
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Kong RCK, Shilling PJ, Lobb DK, Gooley PR, Bathgate RAD. Membrane receptors: structure and function of the relaxin family peptide receptors. Mol Cell Endocrinol 2010; 320:1-15. [PMID: 20138959 DOI: 10.1016/j.mce.2010.02.003] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2009] [Revised: 12/14/2009] [Accepted: 02/02/2010] [Indexed: 01/17/2023]
Abstract
The receptors for members of the relaxin peptide family have only recently been discovered and are G-protein-coupled receptors (GPCRs). Relaxin and insulin-like peptide 3 (INSL3) interact with the leucine-rich-repeat-containing GPCRs (LGRs) LGR7 and LGR8, respectively. These receptors show closest similarity to the glycoprotein hormone receptors and contain large ectodomains with 10 leucine-rich repeats (LRRs) but are unique members of the LGR family (class C) as they have an LDL class A (LDLa) module at their N-terminus. In contrast, relaxin-3 and INSL5 interact with another class of type I GPCRs which lack a large ectodomain, the peptide receptors GPCR135 and GPCR142, respectively. These receptors are now classified as relaxin family peptide (RXFP) receptors, RXFP1 (LGR7), RXFP2 (LGR8), RXFP3 (GPCR135) and RXFP4 (GPCR142). This review outlines the identification of the peptides and receptors, their expression profiles and physiological roles and the functional interactions of the peptides with their unique receptors.
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Affiliation(s)
- Roy C K Kong
- Florey Neuroscience Institutes, University of Melbourne, Victoria 3010, Australia
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Gundlach AL, Ma S, Sang Q, Shen PJ, Piccenna L, Sedaghat K, Smith CM, Bathgate RAD, Lawrence AJ, Tregear GW, Wade JD, Finkelstein DI, Bonaventure P, Liu C, Lovenberg TW, Sutton SW. Relaxin Family Peptides and Receptors in Mammalian Brain. Ann N Y Acad Sci 2009; 1160:226-35. [DOI: 10.1111/j.1749-6632.2009.03956.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Relaxin physiology in the female reproductive tract during pregnancy. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 612:34-48. [PMID: 18161480 DOI: 10.1007/978-0-387-74672-2_4] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The characteristic functions of relaxin are associated with female reproductive tract physiology. These include the regulation of biochemical processes involved in remodeling the extracellular matrix of the cervix and vagina during pregnancy and rupture of the fetal membranes at term. Such modifications enable the young to move unimpeded through the birth canal and prevent dystocia. However, relaxin's physiological actions are not limited to late gestation. New functions for this peptide hormone in implantation and placentation are also emerging. Relaxin promotes uterine and placental growth and influences vascular development and proliferation in the endometrium. This chapter provides an overview of the current literature on relaxin physiology in the uterus, cervix and vagina of pregnant females and the impact on fetal health. It also outlines the potential mechanisms of relaxin action, particularly in the cervical extracellular matrix and uterine endometrium.
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Halls ML, van der Westhuizen ET, Wade JD, Evans BA, Bathgate RAD, Summers RJ. Relaxin family peptide receptor (RXFP1) coupling to G(alpha)i3 involves the C-terminal Arg752 and localization within membrane Raft Microdomains. Mol Pharmacol 2008; 75:415-28. [PMID: 19029286 DOI: 10.1124/mol.108.051227] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The relaxin family peptide receptors (RXFP) 1 and 2 are targets for the relaxin family peptides relaxin and insulin-like peptide 3 (INSL3), respectively. Although both receptors and peptides share a high degree of sequence identity, the cAMP signaling pathways activated by the two systems are quite distinct. Relaxin activation of RXFP1 initially results in accumulation of cAMP via G(alpha)(s), but this is modulated by inhibition of cAMP through G(alpha)(oB). Over time, RXFP1 recruits coupling to G(alpha)(i3), causing additional cAMP accumulation via a G(alpha)(i3)-Gbetagamma-phosphoinositide 3-kinase (PI3K)-protein kinase C (PKC)zeta pathway. In contrast, INSL3 activation of RXFP2 results in accumulation of cAMP only via G(alpha)(s), modulated by cAMP inhibition through G(alpha)(oB). Thus, the aim of this study was to identify the cause of differential G-protein coupling between these highly similar receptors. Construction of chimeric receptors revealed that G(alpha)(i3) coupling is dependent upon the transmembrane region of RXFP1 and independent of the receptor ectodomain or ligand bound. Generation of C-terminal truncated receptors identified the terminal 10 amino acids of the RXFP1 C terminus as essential for G(alpha)(i3) signaling, and point mutations revealed an obligatory role for Arg(752). RXFP1-mediated G(alpha)(i3), but not G(alpha)(s) or G(alpha)(oB), signaling was also found to be dependent upon membrane rafts, and RXFP1 coupled to G(alpha)(i3) after only 3 min of receptor stimulation. Therefore, RXFP1 coupling to the G(alpha)(i3)-Gbetagamma-PI3K-PKCzeta pathway requires the terminal 10 amino acids of the RXFP1 C terminus and membrane raft localization, and the observed delay in this pathway occurs downstream of G(alpha)(i3).
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Affiliation(s)
- Michelle L Halls
- Monash Institute for Pharmaceutical Sciences, Parkville, Australia
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Park JI, Semyonov J, Yi W, Chang CL, Hsu SYT. Regulation of receptor signaling by relaxin A chain motifs: derivation of pan-specific and LGR7-specific human relaxin analogs. J Biol Chem 2008; 283:32099-109. [PMID: 18772127 DOI: 10.1074/jbc.m806817200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Relaxin peptides are important hormones for the regulation of reproductive tissue remodeling and the renal cardiovascular system during pregnancy. Recent studies demonstrated that two of the seven human relaxin family peptides, relaxin H2 (RLN2) and INSL3, signal exclusively through leucine-rich repeat-containing G protein-coupled receptors, LGR7 and LGR8. Although it was well characterized that an RXXXRXXI motif at the RLN2 B chain confers receptor activation activity, it is not clear what roles RLN2 A chain plays in receptor interaction. Analyses of relaxin family genes on syntenic regions of model tetrapods showed that the A chain of RLN2 orthologs exhibited a greater sequence divergence as compared with the receptor-binding domain-containing B chain, foreshadowing a potential role in receptor interactions; hence, defining receptor selectivity in this fast evolving peptide hormone. To test our hypothesis that select residues in the human RLN2 A chain play key roles in receptor interaction, we studied mutant peptides with residue substitution(s) in the A chain. Here, we showed that alanine substitution at the A16 and A17 positions enhances LGR8-activation activity of RLN2, whereas mutation at the A22-23 region (RLN2A22-23) ablates LGR8, but not LGR7, activation activity. In addition, we demonstrated that the functional characteristics of the RLN2A22-23 mutant are mainly attributed to modifications at the PheA23 position. Taken together, our studies indicated that ThrA16, LysA17, and PheA23 constitute part of the receptor-binding interface of human RLN2, and that modification of these residues has led to the generation of novel human RLN2 analogs that would allow selective activation of human LGR7, but not LGR8, in vivo.
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Affiliation(s)
- Jae-Il Park
- Reproductive Biology and Stem Cell Research Program, Department of Obstetrics and Gynecology, Stanford University School of Medicine, Stanford, California 94305-5317, USA
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van der Westhuizen ET, Halls ML, Samuel CS, Bathgate RA, Unemori EN, Sutton SW, Summers RJ. Relaxin family peptide receptors – from orphans to therapeutic targets. Drug Discov Today 2008; 13:640-51. [DOI: 10.1016/j.drudis.2008.04.002] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Revised: 03/04/2008] [Accepted: 04/04/2008] [Indexed: 01/11/2023]
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Somponpun SJ. Neuroendocrine regulation of fluid and electrolyte balance by ovarian steroids: contributions from central oestrogen receptors. J Neuroendocrinol 2007; 19:809-18. [PMID: 17850463 DOI: 10.1111/j.1365-2826.2007.01587.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Like other hormonally mediated mechanisms, maintenance of body fluid osmolality requires integrated responses from multiple signals at various tissue locales, a large number of which are open to modulation by circulating endocrine factors including the ovarian steroid, oestrogens (E(2)). However, the precise mechanism and the site of action of E(2) in regulating fluid osmolality are not properly understood. More importantly, the biological significance of this action is not clear and the physiological circumstances in which this modulation is engaged remain incomplete. The demonstration of oestrogen receptors (ER) in neural tissues that bear no direct relation to reproduction led us to examine and characterise the expression of ER in brain nuclei that are critical for the maintenance of fluid osmolality. In the rat, ERbeta is prominently expressed in the vasopressin magnocellular neuroendocrine cells of the hypothalamus, whereas ERalpha is localised extensively in the sensory circumventricular organ neurones in the basal forebrain. These nuclei are the primary brain sites that are engaged in defense of fluid perturbation, thus providing a neuroendocrine basis for oestrogenic influence on body fluid regulation. Plasticity in receptor expression that accompanies fluid disturbances at these central loci suggests the functional importance of the receptors and implicates E(2) as one of the fluid regulating hormones in water homeostasis.
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Affiliation(s)
- S J Somponpun
- Department of Clinical Investigation, Tripler Army Medical Center, Tripler AMC, HI 96859, USA.
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Shabanpoor F, Bathgate RAD, Hossain MA, Giannakis E, Wade JD, Hughes RA. Design, synthesis and pharmacological evaluation of cyclic mimetics of the insulin-like peptide 3 (INSL3) B-chain. J Pept Sci 2007; 13:113-20. [PMID: 17120268 DOI: 10.1002/psc.807] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Insulin-like peptide 3 (INSL3) is a peptide hormone belonging to the relaxin-insulin superfamily of peptides that plays important roles in testes descent, oocyte maturation and the control of male germ cell apoptosis. These actions are mediated via a specific G-protein coupled receptor, LGR8. Previous structure-activity studies have shown that the key binding site of INSL3 is situated within its B-chain. Recent studies in our laboratory have led to the identification of a cyclic peptide mimetic 2 of the INSL3 B-chain, which we have shown to compete with the binding of [33P]-relaxin to LGR8 expressed in HEK293T cells, and to inhibit cAMP-mediated signaling in these cells, i.e. it is an antagonist of INSL3. In order to further define the structure-activity relationships of cyclic analogues of the INSL3 B-chain, we used a structure-based approach to design a series of cyclic, disulfide-constrained INSL3 B-chain mimetics. To do this, we first created a model of the 3D structure of INSL3 using the crystal structure of human relaxin as a template. This model of INSL3 was then used as a template to design a series of disulfide-constrained mimetics of the INSL3 B-chain. The peptides were synthesized by solid-phase peptide synthesis using pseudoproline dipeptides to improve the synthesis outcome. Of the seven prepared INSL3 B-chain mimetics, three compounds were found to have partial displacement activity, while four were able to completely displace [33P]-relaxin from LGR8, including compounds that were markedly shorter than compound 2. The best of these, mimetic 6, showed significantly greater affinity for LGR8 than compound 2, but still displayed around 1000-fold less affinity for LGR8 than native INSL3. Analysis of selected mimetics for their alpha-helical content using circular dichroism (CD) spectroscopy revealed that, generally, the mimetics showed less than expected helicity. The inability of the compounds to display true native INSL3 structure is likely contributing to their reduced receptor binding affinity. We are currently examining alternative INSL3 B-chain mimetics that might better present key receptor binding residues in the native INSL3-like conformation.
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Affiliation(s)
- Fazel Shabanpoor
- Department of Pharmacology, The University of Melbourne, Parkville, Victoria 3010, Australia
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Vodstrcil LA, Wlodek ME, Parry LJ. Effects of uteroplacental restriction on the relaxin-family receptors, Lgr7 and Lgr8, in the uterus of late pregnant rats. Reprod Fertil Dev 2007; 19:530-8. [PMID: 17524297 DOI: 10.1071/rd07007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2007] [Accepted: 02/22/2007] [Indexed: 11/23/2022] Open
Abstract
The peptide hormone relaxin stimulates uterine growth and endometrial angiogenesis and inhibits myometrial contractions in a variety of species. The receptor for relaxin is a leucine-rich repeat containing G-protein-coupled receptor Lgr7 (RXFP1) that is highly expressed in the myometrium of late pregnant mice, with a significant decrease in receptor density observed at term. The present study first compared the expression of Lgr7 with another relaxin-family receptor Lgr8 (RXFP2) in the uterus and placenta of late pregnant rats. The uterus was separated into endometrial and myometrial components, and the myometrium into fetal and non-fetal sites, for further analysis. We then assessed the response of these receptors to uteroplacental restriction (UPR). Expression of the Lgr7 gene was significantly higher in the uterus compared with the placenta. Within the uterus, on Day 20 of gestation, there was equivalent expression of Lgr7 in fetal and non-fetal sites of the myometrium, as well as in the endometrium v. myometrium. The second receptor investigated, Lgr8, was also expressed in the endometrium and myometrium, but at significantly lower levels than Lgr7. Bilateral ligation of the maternal uterine blood vessels on Day 18 of gestation resulted in uteroplacental restriction, a decrease in fetal weight and litter size, and a significant upregulation in uterine, but not placental, Lgr7 and Lgr8 gene expression in UPR animals compared with controls. These data suggest that both relaxin family receptors are upregulated in response to a reduction in uteroplacental blood flow in rats.
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Affiliation(s)
- Lenka A Vodstrcil
- Department of Zoology, University of Melbourne, Parkville, Vic. 3010, Australia.
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Dschietzig T, Bartsch C, Baumann G, Stangl K. Relaxin—a pleiotropic hormone and its emerging role for experimental and clinical therapeutics. Pharmacol Ther 2006; 112:38-56. [PMID: 16647137 DOI: 10.1016/j.pharmthera.2006.03.004] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2006] [Accepted: 03/08/2006] [Indexed: 01/30/2023]
Abstract
The insulin-related peptide hormone relaxin (Rlx) is known as pregnancy hormone for decades. In the 1980s, researchers began to recognize the highly intriguing fact that Rlx plays a role in a multitude of physiological processes far beyond pregnancy and reproduction. So, Rlx's contribution to the regulation of vasotonus, plasma osmolality, angiogenesis, collagen turnover, and renal function has been established. In addition, the peptide has been demonstrated to represent a mediator of cardiovascular pathology. The ongoing efforts to identify Rlx receptors eventually precipitated the discovery of the G protein-coupled receptors (GPCR) LGR7 and LGR8 as membrane receptors for human Rlx-2 in 2002. This review will summarize the current state of insight into this rapidly evolving field, which has further been expanded by the discovery of GPCR135 and GPCR142 as receptors for Rlx-3. In addition, Rlx has also been shown to activate the human glucocorticoid receptor (GR). There is evidence from Rlx and Rlx receptor knockouts suggesting that LGR7 is the only relevant receptor for mouse Rlx-1 (corresponding to human Rlx-2) in vivo and that insulin-like peptide (INSL)-3 represents the physiological ligand for LGR8. Regarding Rlx signal transduction, the cyclic adenosine monophosphate (cAMP) and nitric oxide (NO) pathways will be characterized as major cascades. Investigation of downstream signaling remains an important field for future research. Finally, the current state of therapeutical strategies using Rlx in animal models as well as in humans is summarized.
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Affiliation(s)
- Thomas Dschietzig
- Medizinische Klinik m. S. Kardiologie und Angiologie, Charité-Universitätsmedizin Berlin, Campus Mitte, Schumannstr. 20/21, 10117 Berlin, Germany.
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Samuel CS, Du XJ, Bathgate RAD, Summers RJ. 'Relaxin' the stiffened heart and arteries: the therapeutic potential for relaxin in the treatment of cardiovascular disease. Pharmacol Ther 2006; 112:529-52. [PMID: 16814863 DOI: 10.1016/j.pharmthera.2005.05.012] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2005] [Accepted: 05/15/2005] [Indexed: 12/20/2022]
Abstract
Although originally characterised as a reproductive hormone, relaxin has emerged as a multi-functional endocrine and paracrine factor that plays a number of important roles in several organs, including the normal and diseased cardiovascular system. The recent discovery of the H3/relaxin-3 gene, and the elusive receptors for relaxin (Relaxin family peptide receptor; RXFP1) and relaxin-3 (RXFP3/RXFP4) have led to the re-classification of a distinct relaxin peptide/receptor family. Additionally, the identification of relaxin and RXFP1 mRNA and/or relaxin binding sites in the heart and blood vessels has confirmed that the cardiovascular system is a target for relaxin peptides. While evidence for the production of relaxins within the cardiovascular system is limited, several studies have established that the relaxin genes are upregulated in the diseased human and rodent heart where they likely act as cardioprotective agents. The ability of relaxin to protect the heart is most likely mediated via its antifibrotic, anti-hypertrophic, anti-inflammatory and vasodilatory actions, but it may also directly stimulate myocardial regeneration and repair. This review describes relaxin and its primary receptor (RXFP1) in relation to the roles and effects of relaxin in the normal and pathological cardiovascular system. It is becoming increasingly clear that relaxin has a number of diverse physiological and pathological roles in the cardiovascular system that may have important therapeutic and clinical implications.
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Affiliation(s)
- Chrishan S Samuel
- Howard Florey Institute, University of Melbourne, Victoria 3010, Australia; Department of Biochemistry and Molecular Biology, University of Melbourne, Victoria 3010, Australia
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Del Borgo MP, Hughes RA, Bathgate RAD, Lin F, Kawamura K, Wade JD. Analogs of Insulin-like Peptide 3 (INSL3) B-chain Are LGR8 Antagonists in Vitro and in Vivo. J Biol Chem 2006; 281:13068-13074. [PMID: 16547350 DOI: 10.1074/jbc.m600472200] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin-like peptide 3 (INSL3) is a member of the insulin superfamily that plays an important role in mediating testes descent during fetal development. More recently, it has also been demonstrated to initiate oocyte maturation and suppress male germ cell apoptosis. These actions are mediated via a specific G-protein-coupled receptor, LGR8. Little is known regarding the structure and function relationship of INSL3, although it is believed that the principal receptor binding site resides within its B-chain. We subsequently observed that the linear B-chain alone (INSL3B-(1-31)) bound to LGR8 and was able to antagonise INSL3 stimulated cAMP accumulation in HEK-293T cells expressing LGR8. Sequentially N- and C-terminally shortened linear analogs were prepared by solid phase synthesis and subsequent assay showed that the minimum length required for binding was residues 11-27. It was also observed that increased binding affinity correlated with a corresponding increase in alpha-helical content as measured by circular dichroism spectroscopy. Molecular modeling studies suggested that judicious placement of a conformational constraint within this peptide would increase its alpha-helix content and result in increased structural similarity to the B-chain within native INSL3. Consequently, intramolecularly disulfide-linked analogs of the B-chain showed a potentiation of INSL3 antagonistic activity, as well as exhibiting increased proteolytic stability, as assessed in rat serum in vitro. Administration of one of these peptides into the testes of rats resulted in a substantial decrease in testis weight probably due to the inhibition of germ cell survival, suggesting that INSL3 antagonists may have potential as novel contraceptive agents.
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Affiliation(s)
- Mark P Del Borgo
- Howard Florey Institute, Victoria 3010, Australia; Department of Pharmacology, University of Melbourne, Victoria 3010, Australia
| | - Richard A Hughes
- Department of Pharmacology, University of Melbourne, Victoria 3010, Australia
| | | | - Feng Lin
- Howard Florey Institute, Victoria 3010, Australia
| | - Kazu Kawamura
- Division of Reproductive Biology, Department of Obstetrics and Gynecology, Stanford University School of Medicine, Stanford, California 94305-5317
| | - John D Wade
- Howard Florey Institute, Victoria 3010, Australia.
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Bathgate RA, Ivell R, Sanborn BM, Sherwood OD, Summers RJ. International Union of Pharmacology LVII: recommendations for the nomenclature of receptors for relaxin family peptides. Pharmacol Rev 2006; 58:7-31. [PMID: 16507880 DOI: 10.1124/pr.58.1.9] [Citation(s) in RCA: 234] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Although the hormone relaxin was discovered 80 years ago, only in the past 5 years have the receptors for relaxin and three other receptors that respond to related peptides been identified with all four receptors being G-protein-coupled receptors. In this review it is suggested that the receptors for relaxin (LGR7) and those for the related peptides insulin-like peptide 3 (LGR8), relaxin-3 (GPCR135), and insulin-like peptide 5 (LGPCR142) be named the relaxin family peptide receptors 1 through 4 (RXFP1-4). RXFP1 and RXFP2 are leucine-rich repeat-containing G-protein-coupled receptors with complex binding characteristics involving both the large ectodomain and the transmembrane loops. RXFP1 activates adenylate cyclase, protein kinase A, protein kinase C, phosphatidylinositol 3-kinase, and extracellular signaling regulated kinase (Erk1/2) and also interacts with nitric oxide signaling. RXFP2 activates adenylate cyclase in recombinant systems, but physiological responses are sensitive to pertussis toxin. RXFP3 and RXFP4 resemble more conventional peptide liganded receptors and both inhibit adenylate cyclase, and in addition RXFP3 activates Erk1/2 signaling. Physiological studies and examination of the phenotypes of transgenic mice have established that relaxin has roles as a reproductive hormone involved in uterine relaxation (some species), reproductive tissue growth, and collagen remodeling but also in the cardiovascular and renal systems and in the brain. The connective tissue remodeling properties of relaxin acting at RXFP1 receptors have potential for the development of agents effective for the treatment of cardiac and renal fibrosis, asthma, and scleroderma and for orthodontic remodelling. Agents acting at RXFP2 receptors may be useful for the treatment of cryptorchidism and infertility, whereas antagonists may be used as contraceptives. The brain distribution of RXFP3 receptors suggests that actions at these receptors have the potential for the development of antianxiety and antiobesity drugs.
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Affiliation(s)
- Ross A Bathgate
- Howard Florey Institute, University of Melbourne, Victoria, Australia
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Scott DJ, Layfield S, Riesewijk A, Morita H, Tregear GW, Bathgate RAD. Characterization of the Mouse and Rat Relaxin Receptors. Ann N Y Acad Sci 2006; 1041:8-12. [PMID: 15956680 DOI: 10.1196/annals.1282.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Rodent models have been used for many years to probe the actions of relaxin. Identification of the orthologs of human leucine-rich repeat-containing g-protein-coupled receptor 7 (LGR7), the relaxin receptor, in mouse and rat will enable characterization of the response of LGR7 to relaxin in these species. Partial LGR7 homologous sequences from mouse and rat were discovered in the Celera and NCBI gene databases, amplified, cloned, and sequenced. At the protein level, mouse and rat LGR7 are 85.2% and 85.7% identical to human LGR7. Mouse and rat LGR7 were able to bind to and be activated by relaxin ligands.
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Affiliation(s)
- D J Scott
- Howard Florey Institute, University of Melbourne, Victoria 3010, Australia
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Burazin TCD, Johnson KJ, Ma S, Bathgate RAD, Tregear GW, Gundlach AL. Localization of LGR7 (Relaxin Receptor) mRNA and Protein in Rat Forebrain: Correlation with Relaxin Binding Site Distribution. Ann N Y Acad Sci 2006; 1041:205-10. [PMID: 15956709 DOI: 10.1196/annals.1282.031] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Discrete neuronal populations in brain express relaxin and relaxin-3, and molecular studies have identified former-orphan, G-protein-coupled receptors LGR7 and GPCR135 as their native receptors. To better understand the role of central relaxin systems, we began to assess the anatomic distribution of these receptors and ligands in brain. This study documents the widespread distribution of LGR7 mRNA and LGR7-like immunoreactivity (LI) throughout adult rat forebrain areas shown to contain specific [33P]-relaxin binding sites. High densities of LGR7 mRNA hybridization were detected in deep layers of neocortex, hypothalamic paraventricular and supraoptic nuclei and within hippocampal subiculum and CA3, the basolateral amygdala and subfornical organ. Low to moderate hybridization was detected in septum, midline thalamic nuclei, arcuate and supramammillary nuclei, and regions of the midbrain pons. Complementary expression of LGR7-LI was observed in cortical pyramidal neurons, hypothalamic magnocellular neurons, and hippocampal pyramidal and interneurons. These findings provide further evidence for actions of relaxin as a modulator in somatosensory, autonomic, and neuroendocrine pathways.
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Affiliation(s)
- Tanya C D Burazin
- Howard Florey Institute of Experimental Physiology and Medicine, The University of Melbourne, Victoria 3010, Australia
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Bond CP, Parry LJ, Samuel CS, Gehring HM, Lederman FL, Rogers PAW, Summers RJ. Increased Expression of the Relaxin Receptor (LGR7) in Human Endometrium during the Secretory Phase of the Menstrual Cycle. Ann N Y Acad Sci 2006; 1041:136-43. [PMID: 15956698 DOI: 10.1196/annals.1282.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
This study investigated localization and expression of relaxin and its receptor, LGR7, in the human endometrium during the proliferative and secretory phases of the menstrual cycle. H2 relaxin binding was identified in endometrium, but not myometrium, and particularly in the epithelium of the endometrial glands and uterine lumen. Binding sites increased in the early secretory phase of the menstrual cycle and were paralleled by similar increases in LGR7 mRNA measured by Q-PCR. The increase in LGR7 expression and H2 relaxin binding in the secretory phase of the menstrual cycle suggests a specific role for relaxin after ovulation in the human uterus.
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Affiliation(s)
- Courtney P Bond
- Department of Pharmacology, Monash University, Vic 3800, Australia
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Bathgate RA, Ivell R, Sanborn BM, Sherwood OD, Summers RJ. Receptors for Relaxin Family Peptides. Ann N Y Acad Sci 2006; 1041:61-76. [PMID: 15956688 DOI: 10.1196/annals.1282.010] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Recent studies have identified four receptors that are the physiological targets for relaxin family peptides. All are class I (rhodopsin like) G-protein-coupled receptors with LGR7 (RXFP1) and LGR8 (RXFP2) being type C leucine-rich repeat-containing receptors, whereas GPCR135 (RXFP3) and GPCR142 (RXFP4) resemble receptors that respond to small peptides such as somatostatin and angiotensin II. The cognate ligands for the receptors have been identified: relaxin for RXFP1; INSL3 for RXFP2; relaxin 3 for RXFP3 and INSL5 for RXFP4. RXFP1 and RXFP2 receptors produce increases in intracellular cAMP levels upon stimulation, although the response is complex and contains a component sensitive to PI-3-kinase inhibitors. There is also evidence that RXFP1 can activate Erk1/2 and nitric oxide synthase, and relaxin has been reported to enter cells and activate glucocorticoid receptors. In contrast, RXFP3 and RXFP4 couple to Gi by a pertussis toxin-sensitive mechanism to cause inhibition of cAMP production. Now that the receptors for relaxin family peptides and their cognate ligands have been identified, we suggest a nomenclature for both the peptides and the receptors that we hope will be helpful to researchers in this rapidly advancing field.
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Affiliation(s)
- Ross A Bathgate
- Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Victoria 3010, Australia
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Ma S, Shen PJ, Burazin TCD, Tregear GW, Gundlach AL. Comparative localization of leucine-rich repeat-containing G-protein-coupled receptor-7 (RXFP1) mRNA and [33P]-relaxin binding sites in rat brain: Restricted somatic co-expression a clue to relaxin action? Neuroscience 2006; 141:329-44. [PMID: 16725278 DOI: 10.1016/j.neuroscience.2006.03.076] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2006] [Revised: 03/09/2006] [Accepted: 03/23/2006] [Indexed: 11/16/2022]
Abstract
Relaxin is a polypeptide hormone with established actions associated with reproductive physiology, but until recently the precise nature of the relaxin receptor and its transmembrane signaling mechanisms had remained elusive. In 2002 however, the leucine-rich-repeat-containing G-protein-coupled receptor-7 (now classified as RXFP1) was identified as a cognate receptor for relaxin, with activation resulting in stimulation of intracellular cAMP production. These findings, along with the presence and putative actions of relaxin within the CNS and earlier descriptions of relaxin binding sites in brain, suggest the importance and feasibility of determining if these relaxin binding sites represent leucine-rich-repeat-containing G-protein-coupled receptor-7 and their precise comparative distribution. Thus, the current study reports the distribution of leucine-rich-repeat-containing G-protein-coupled receptor-7 mRNA throughout the rat brain using in situ hybridization histochemistry of [(35)S]-labeled oligonucleotides and the comparative distribution of [(33)P]-human relaxin binding sites. The extensive, topographical distribution of leucine-rich-repeat-containing G-protein-coupled receptor-7 mRNA throughout the adult rat brain correlated very closely to that of [(33)P]-relaxin binding sites. Leucine-rich-repeat-containing G-protein-coupled receptor-7 mRNA was expressed by neurons in several brain regions, including the olfactory bulb, cerebral cortex, thalamus, hippocampus, hypothalamus, midbrain, pons and medulla. Receptor transcripts were most abundant in areas such as the basolateral amygdala, subiculum, deep layers of the cingulate, somatosensory and motor cortices and intralaminar/midline thalamic nuclei. These areas also contained very high densities of [(33)P]-relaxin binding sites, suggesting a largely somatic localization of leucine-rich-repeat-containing G-protein-coupled receptor-7 protein and site of action for relaxin peptide. The central distribution of relaxin-producing neurons has been described, while data on the topography of nerve terminals that contain and secrete the peptide are currently lacking; but overall these findings strongly suggest that leucine-rich-repeat-containing G-protein-coupled receptor-7 is the cognate receptor for relaxin in the rat brain, and support a role for relaxin-leucine-rich-repeat-containing G-protein-coupled receptor-7 signaling in various somatosensory, autonomic and neurohumoral pathways, which warrants further investigation.
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Affiliation(s)
- S Ma
- Howard Florey Institute, The University of Melbourne, Melbourne, Victoria 3010, Australia.
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Ma S, Roozendaal B, Burazin TCD, Tregear GW, McGaugh JL, Gundlach AL. Relaxin receptor activation in the basolateral amygdala impairs memory consolidation. Eur J Neurosci 2005; 22:2117-22. [PMID: 16262650 DOI: 10.1111/j.1460-9568.2005.04374.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The peptide-hormone relaxin has well-established actions in male and female reproductive tracts, and has functional effects in circumventricular regions of brain involved in neurohormonal secretion. In the current study, we initially mapped the distribution of mRNA encoding the relaxin receptor--leucine-rich repeat-containing G-protein-coupled receptor 7 (LGR7)- and [33P]-human relaxin-binding sites in extra-hypothalamic sites of male Sprague-Dawley rats. The basolateral amygdala (BLA) expressed high levels of LGR7 mRNA and relaxin-binding sites and, although relaxin peptide was not detected in the BLA, several brain regions that send projections to the BLA were found to contain relaxin-expressing neurons. As it is well established that the BLA is involved in regulating the consolidation of memory for emotionally arousing experiences, we investigated whether activation of LGR7 in the BLA modulated memory consolidation for aversively motivated inhibitory avoidance training. Bilateral infusions of human relaxin (10-200 ng in 0.2 microL) into the BLA immediately after inhibitory avoidance training impaired 48-h retention performance in a dose-dependent manner. Delayed infusions of relaxin into the BLA 3 h after training were ineffective, indicating that the retention impairment was due to influences on memory consolidation. Post-training infusions of relaxin into the adjacent central amygdala, which is devoid of LGR7, did not impair retention. These findings suggest a novel function for endogenous relaxin-LGR7 signalling in rat brain involving regulation of memory consolidation.
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Affiliation(s)
- Sherie Ma
- Howard Florey Institute of Experimental Physiology and Medicine, The University of Melbourne, Victoria 3010, Australia
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Zhang J, Qi YF, Geng B, Pan CS, Zhao J, Chen L, Yang J, Chang JK, Tang CS. Effect of relaxin on myocardial ischemia injury induced by isoproterenol. Peptides 2005; 26:1632-9. [PMID: 16112403 DOI: 10.1016/j.peptides.2005.02.008] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/23/2004] [Revised: 02/05/2005] [Accepted: 02/09/2005] [Indexed: 11/30/2022]
Abstract
The omnipresent 6-kDa polypeptide relaxin (RLX) is emerging as a multifunctional endocrine and paracrine factor in a broad range of target tissues including cardiovascular tissues. To explore the pathophysiological roles of RLX in ischemic cardiovascular diseases, we studied the changes in RLX mRNA level in the myocardium and the effect of RLX supplements in rats with isoproterenol (ISO)-induced myocardial injury. In ISO-treated rats, RLX levels in myocardia and plasma increased 3.7- and 6.9-fold, respectively (P<0.01), the mRNA level increased significantly in myocardia compared with controls. Co-administration of RLX (0.2 and 2.0 microg/kg/d) and ISO increased left-ventricular pressure development and decreased left ventricular end-diastolic pressure (LVDEP) (all P<0.01). Malondialdehyde content in myocardia and lactate dehydrogenase and creatine phosphokinase activities in plasma in RLX-treated rats decreased markedly compared with that in ISO-treated alone rats (P<0.01 or P<0.05). In the high-dose RLX group, fibroblastic hyperplasia was relieved in myocardia, hydroxyproline level was lower, by 33% (P<0.05), and endothelin content in plasma was lower, by 31% (P<0.01) than in the ISO-alone group. Compared with control group, any indexes in sham rats treated with high-dose RLX were unaltered (all P>0.05). These results showed an up-regulation of myocardial RLX during ISO-induced myocardial ischemia injury and the protective effect of RLX on ISO-induced cardiac inhibition and fibrosis, which suggests that RLX could be an endogenous cardioprotective factor in ischemic heart diseases.
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Affiliation(s)
- Jing Zhang
- Institute of Cardiovascular Research, Peking University First Hospital, Beijing 100034, China
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Scott DJ, Layfield S, Riesewijk A, Morita H, Tregear GW, Bathgate RAD. Identification and characterization of the mouse and rat relaxin receptors as the novel orthologues of human leucine-rich repeat-containing G-protein-coupled receptor 7. Clin Exp Pharmacol Physiol 2005; 31:828-32. [PMID: 15566402 DOI: 10.1111/j.1440-1681.2004.04075.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
1. Relaxin is an extracellular matrix (ECM)-remodelling hormone that is functionally important in reproductive tissues, brain, lung and heart. 2. Recently, the human relaxin receptor was identified as leucine-rich repeat-containing G-protein-coupled receptor 7 (LGR7). 3. Using human LGR7 as a template, we identified mouse and rat LGR7 orthologues in the Celera and National Centre for Biotechnology Information databases. 4. At the protein level, mouse and rat LGR7 share 85.2 and 85.7% identity with human LGR7, respectively. 5. Mouse LGR7 mRNA was detected in all tissues where relaxin binding is observed. 6. Mouse and rat LGR7 bound [33P]-relaxin with high affinity and, upon relaxin treatment, both receptors stimulated cAMP production in transfected HEK 293T cells. 7. These results indicate that mouse and rat LGR7 are the relaxin receptors in these species. 8. The actions of relaxin in rodents are well characterized, providing an established platform for research into the molecular pharmacology of the highly conserved relaxin receptor.
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MESH Headings
- Amino Acid Sequence
- Animals
- Blotting, Northern
- Computational Biology
- Cyclic AMP/biosynthesis
- Humans
- Ligands
- Membrane Proteins/drug effects
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Mice
- RNA, Messenger/biosynthesis
- RNA, Messenger/chemistry
- RNA, Messenger/genetics
- Rats
- Receptors, G-Protein-Coupled/drug effects
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Peptide/drug effects
- Receptors, Peptide/genetics
- Receptors, Peptide/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Signal Transduction/drug effects
- Species Specificity
- Tissue Distribution
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Affiliation(s)
- D J Scott
- Howard Florey Institute, University of Melbourne, Parkville, Victoria, Australia
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Liu C, Kuei C, Sutton S, Chen J, Bonaventure P, Wu J, Nepomuceno D, Kamme F, Tran DT, Zhu J, Wilkinson T, Bathgate R, Eriste E, Sillard R, Lovenberg TW. INSL5 Is a High Affinity Specific Agonist for GPCR142 (GPR100). J Biol Chem 2005; 280:292-300. [PMID: 15525639 DOI: 10.1074/jbc.m409916200] [Citation(s) in RCA: 143] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Insulin-like peptide 5 (INSL5) is a peptide that belongs to the relaxin/insulin family, and its receptor has not been identified. In this report, we demonstrate that INSL5 is a specific agonist for GPCR142. Human INSL5 displaces the binding of (125)I-relaxin-3 to GPCR142 with a high affinity (K(i) = 1.5 nM). In a saturation binding assay, (125)I-INSL5 binds GPCR142 with a K(d) value of 2.5 nM. In functional guanosine (gamma-thio)-triphosphate binding and cAMP accumulation assays, INSL5 potently activates GPCR142 with EC(50) values of 1.3 and 1.2 nM, respectively. In addition, INSL5 stimulates Ca(2+) mobilization in HEK293 cells expressing GPCR142 and G alpha(16). Overall, INSL5 behaves as an agonist for GPCR142 similar to relaxin-3. However, unlike relaxin-3, which is also a potent agonist for GPCR135 and LGR7, INSL5 does not activate either GPCR135 or LGR7. INSL5 inhibits (125)I-relaxin-3 binding to GPCR135 with a low potency (K(i) = 500 nM). A functional assay shows that INSL5 (1 microm) is a weak antagonist for GPCR135. In addition, INSL5 (up to 1 microm) shows no affinity or activity at LGR7 or LGR8 either in a binding assay or a bio-functional assay. Previously, we have demonstrated that GPCR142 mRNA is expressed in peripheral tissues, particularly in the colon. Here we show that INSL5 mRNA is expressed in many peripheral tissues, similar to GPCR142. The high affinity interaction between INSL5 and GPCR142 coupled with their co-evolution and partially overlapping tissue expression patterns strongly suggest that INSL5 is an endogenous ligand for GPCR142.
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Affiliation(s)
- Changlu Liu
- Johnson & Johnson Pharmaceutical Research and Development, San Diego, California 92121, USA.
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Liu C, Chen J, Kuei C, Sutton S, Nepomuceno D, Bonaventure P, Lovenberg TW. Relaxin-3/insulin-like peptide 5 chimeric peptide, a selective ligand for G protein-coupled receptor (GPCR)135 and GPCR142 over leucine-rich repeat-containing G protein-coupled receptor 7. Mol Pharmacol 2004; 67:231-40. [PMID: 15465925 DOI: 10.1124/mol.104.006700] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Relaxin-3, the most recently identified member of relaxin/insulin family, is an agonist for leucine-rich repeat-containing G protein-coupled receptor (LGR)7, GPCR135, and GPCR142. LGR7 can be pharmacologically differentiated from GPCR135 and GPCR142 by its high affinity for relaxin. Selective ligands that specifically activate GPCR135 or GPCR142 are highly desirable for studying their functional roles. We have created chimeric peptides that consist of the B-chain of human relaxin-3 in combination with various A-chains from other members of the relaxin/insulin family. Pharmacological characterization of these chimeric peptides indicates the A-chain from relaxin-1, relaxin-2, insulin-like peptide (INSL)3, and INSL6 does not change the pharmacological properties of relaxin-3 significantly. In contrast, substitution of the relaxin-3 A-chain with the A-chain from INSL5 results in a chimeric peptide that selectively activates GPCR135 and GPCR142 over LGR7. This study demonstrates that the A-chains among some of the insulin/relaxin family members are pharmacologically exchangeable. The relaxin-3/INSL5 chimeric peptide is a potential tool to study in vivo function of GPCR135. In addition, because of the substitution of a very hydrophobic peptide (the A-chain of relaxin-3) with a very hydrophilic peptide (the A-chain from INSL5), the radiolabeled (125)I-relaxin-3/INSL5 chimera is a suitable ligand (high-affinity, low-nonspecific binding) for receptor autoradiographic studies on tissue sections.
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Affiliation(s)
- Changlu Liu
- Johnson & Johnson Pharmaceutical Research & Development, L.L.C., San Diego, CA 92121, USA.
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Conrad KP, Novak J. Emerging role of relaxin in renal and cardiovascular function. Am J Physiol Regul Integr Comp Physiol 2004; 287:R250-61. [PMID: 15271674 DOI: 10.1152/ajpregu.00672.2003] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Although traditionally associated with reproductive processes, relaxin is emerging as an important player in renal and cardiovascular function. Much of our recently acquired understanding of relaxin in this new context has arisen from studies of maternal renal and cardiovascular adaptations to pregnancy in rats where the hormone is turning out to be an important mediator. First, we highlight the influence of relaxin on renal hemodynamics and glomerular filtration rate, as well as on other peripheral circulations. Second, we discuss the effect of relaxin on both the steady and pulsatile systemic arterial load, as well as on the heart, in particular, coronary blood flow. Third, we consider the impact of the hormone on cultured endothelial and vascular smooth muscle cells. Fourth, we address the interaction of relaxin with renal and cardiac disease, as well as its role in angiogenesis. Finally, in Perspectives, we point out several key research questions in need of investigation that relate to a potential autocrine/paracrine role of relaxin in renal and cardiovascular tissues. Furthermore, on the basis of its potent vasodilatory and matrix-degrading attributes, we speculate about the therapeutic potential of relaxin in renal and cardiovascular diseases.
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Affiliation(s)
- Kirk P Conrad
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh School of Medicine, and Magee-Women's Research Institute, Pittsburgh, Pennsylvania 15213, USA.
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Samuel CS, Zhao C, Bond CP, Hewitson TD, Amento EP, Summers RJ. Relaxin-1–deficient mice develop an age-related progression of renal fibrosis. Kidney Int 2004; 65:2054-64. [PMID: 15149318 DOI: 10.1111/j.1523-1755.2004.00628.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Relaxin (RLX) is a peptide hormone that stimulates the breakdown of collagen in preparation for parturition and when administered to various models of induced fibrosis. However, its significance in the aging kidney is yet to be established. In this study, we compared structural and functional changes in the kidney of aging relaxin-1 (RLX-/-) deficient mice and normal (RLX+/+) mice. METHODS The kidney cortex and medulla of male and female RLX+/+ and RLX-/- mice at various ages were analyzed for collagen content, concentration, and types. Histologic analysis, reverse transcription-polymerase chain reaction (RT-PCR) of relaxin and relaxin receptor mRNA expression, receptor autoradiography, glomerular isolation/analysis, and serum/urine analysis were also employed. Relaxin treatment of RLX-/- mice was used to confirm the antifibrotic effects of the peptide. RESULTS We demonstrate an age-related progression of renal fibrosis in male, but not female, RLX-/- mice with significantly (P < 0.05) increased tissue dry weight, collagen (type I) content and concentration. The increased collagen expression in the kidney was associated with increased glomerular matrix and to a lesser extent, interstitial fibrosis in RLX-/- mice, which also had significantly increased serum creatinine (P < 0.05) and urinary protein (P < 0.05). Treatment of RLX-/- mice with relaxin in established stages of renal fibrosis resulted in the reversal of collagen deposition. CONCLUSION This study supports the concept that relaxin may provide a means to regulate excessive collagen deposition during kidney development and in diseased states characterized by renal fibrosis.
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Affiliation(s)
- Chrishan S Samuel
- Howard Florey Institute of Experimental Physiology & Medicine, The University of Melbourne, Parkville, Victoria, Australia.
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Abstract
Relaxin has vital physiological roles in pregnant rats, mice, and pigs. Relaxin promotes growth and softening of the cervix, thus facilitating rapid delivery of live young. Relaxin also promotes development of the mammary apparatus, thus enabling normal lactational performance. The actions of relaxin on the mammary apparatus vary among species. Whereas relaxin is required for development of the mammary nipples in rats and mice, it is essential for prepartum development of glandular parenchyma in pregnant pigs. During pregnancy relaxin also inhibits uterine contractility and promotes the osmoregulatory changes of pregnancy in rats. Recent studies with male and nonpregnant female rodents revealed diverse therapeutic actions of relaxin on nonreproductive tissues that have clinical implications. Relaxin has been reported to reduce fibrosis in the kidney, heart, lung, and liver and to promote wound healing. Also, probably through its vasodilatory actions, relaxin protects the heart from ischemia-induced injury. Finally, relaxin counteracts allergic reactions. Knowledge of the diverse physiological and therapeutic actions of relaxin, coupled with the recent identification of relaxin receptors, opens numerous avenues of investigation that will likely sustain a high level of research interest in relaxin for the foreseeable future.
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Affiliation(s)
- O David Sherwood
- Department of Molecular and Integrative Physiology and College of Medicine, University of Illinois at Urbana-Champaign, 524 Burrill Hall, 407 South Goodwin Avenue, Urbana, IL 61801, USA.
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Samuel CS, Tian H, Zhao L, Amento EP. Relaxin is a key mediator of prostate growth and male reproductive tract development. J Transl Med 2003; 83:1055-67. [PMID: 12861045 DOI: 10.1097/01.lab.0000079784.81186.b9] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Male mice deficient in relaxin showed retarded growth and marked deficiencies in the reproductive tract within 1 month of age. At 3 months of age, male reproductive organ weight (including the testis, epididymis, prostate, and seminal vesicle) from relaxin null (RLX-/-) mice were significantly (p < 0.05) smaller than those of wild-type (RLX+/+) male mice. Histologic examination of RLX-/- mouse tissues demonstrated decreased sperm maturation (testis), increased collagen, and decreased epithelial proliferation in the prostate compared with tissues obtained from RLX+/+ animals. The degree of sperm maturation in the testes of sexually mature RLX-/- mice (3 months) resembled that of immature (1 month) RLX+/+ mice and correlated with a decrease in fertility in RLX-/- mice. The marked differences in the extracellular matrix of the testis and prostate in RLX-/- males also correlated with an increase in the rate of cell apoptosis. Relaxin and LGR7 (relaxin receptor) mRNA expression was demonstrated in the prostate gland and testis of the normal mouse. Data from this study demonstrate that relaxin is an important factor in the development and function of the male reproductive tract in mice and has an essential role in the growth of the prostate and maintenance of male fertility. Relaxin may mediate its effects on growth and development by serving as an antiapoptotic factor.
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Longo M, Jain V, Vedernikov YP, Garfield RE, Saade GR. Effects of recombinant human relaxin on pregnant rat uterine artery and myometrium in vitro. Am J Obstet Gynecol 2003; 188:1468-74; discussion 1474-6. [PMID: 12824980 DOI: 10.1067/mob.2003.454] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVE The purpose of this study was to evaluate the effects of recombinant human relaxin on the uterine artery and myometrial contractility in pregnant rats. STUDY DESIGN Uterine artery and myometrial rings from mid and term pregnant rats were used. Relaxin effect was studied on phenylephrine-induced contraction in the presence or absence of nitric oxide synthase inhibitor, N omega-nitro-l-arginine methyl ester, soluble guanylate cyclase inhibitor, 1H-oxadiazolo-quinoxaline-1-one, or adenylate cyclase inhibitor, SQ-22,536. The myometrial inhibitory effect of relaxin was studied on spontaneous and oxytocin- or protein kinase C activator-induced contractions. RESULTS Uterine artery relaxation by relaxin was greater at mid pregnancy compared with term. Relaxin effect was decreased by SQ-22,536, 1H-oxadiazolo-quinoxaline-1-one and N omega-nitro-l-arginine methyl ester at mid pregnancy. Relaxin inhibited spontaneous contractions at mid pregnancy but not at term. Relaxin had no effect on oxytocin- or indolactam-V-induced contractions. CONCLUSION Relaxin effect is mediated by nitric oxide, soluble guanylate cyclase, and adenylate cyclase in mid pregnant uterine artery. Relaxin inhibits spontaneous uterine activity at mid pregnancy. Relaxin effect decreased at term gestation in both tissues.
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Affiliation(s)
- Monica Longo
- Department of Obstetrics and Gynecology, University of Texas Medical Branch, Galveston, 77555, USA
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Sudo S, Kumagai J, Nishi S, Layfield S, Ferraro T, Bathgate RAD, Hsueh AJW. H3 relaxin is a specific ligand for LGR7 and activates the receptor by interacting with both the ectodomain and the exoloop 2. J Biol Chem 2003; 278:7855-62. [PMID: 12506116 DOI: 10.1074/jbc.m212457200] [Citation(s) in RCA: 221] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Leucine-rich repeat-containing, G protein-coupled receptors (LGRs) represent a unique subgroup of G protein-coupled receptors with a large ectodomain. Recent studies demonstrated that relaxin activates two orphan LGRs, LGR7 and LGR8, whereas INSL3/Leydig insulin-like peptide specifically activates LGR8. Human relaxin 3 (H3 relaxin) was recently discovered as a novel ligand for relaxin receptors. Here, we demonstrate that H3 relaxin activates LGR7 but not LGR8. Taking advantage of the overlapping specificity of these three ligands for the two related LGRs, chimeric receptors were generated to elucidate the mechanism of ligand activation of LGR7. Chimeric receptor LGR7/8 with the ectodomain from LGR7 but the transmembrane region from LGR8 maintains responsiveness to relaxin but was less responsive to H3 relaxin based on ligand stimulation of cAMP production. The decreased ligand signaling was accompanied by decreases in the ability of H3 relaxin to compete for (33)P-relaxin binding to the chimeric receptor. However, replacement of the exoloop 2, but not exoloop 1 or 3, of LGR7 to the chimeric LGR7/8 restored ligand binding and receptor-mediated cAMP production. These results suggested that activation of LGR7 by H3 relaxin involves specific binding of the ligand to both the ectodomain and the exoloop 2, thus providing a model with which to understand the molecular basis of ligand signaling for this unique subgroup of G protein-coupled receptors.
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Affiliation(s)
- Satoko Sudo
- Division of Reproductive Biology, Department of Obstetrics and Gynecology, Stanford University School of Medicine, California 94305-5317, USA
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Katugampola S, Davenport A. Emerging roles for orphan G-protein-coupled receptors in the cardiovascular system. Trends Pharmacol Sci 2003; 24:30-5. [PMID: 12498728 DOI: 10.1016/s0165-6147(02)00007-x] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Despite current drug therapies, including those that target enzymes, channels and known G-protein-coupled receptors (GPCRs), cardiovascular disease remains the major cause of ill health, which suggests that other transmitter systems might be involved in this disease. In humans, approximately 175 genes have been predicted to encode 'orphan' GPCRs, where the endogenous ligand is not yet known. As a result of intensive screening using 'reverse pharmacology', an increasing number of orphan receptors are being paired with their cognate ligands, many of which are peptides. The existence of some of these peptides such as urotensin-II and relaxin had been known for some time but others, including ghrelin and apelin, represent novel sequences. The pharmacological characterization of these emerging peptide-receptor systems is a tantalising area of cardiovascular research, with the prospect of identifying new therapeutic targets.
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Samuel CS, Zhao C, Bathgate RAD, Bond CP, Burton MD, Parry LJ, Summers RJ, Tang MLK, Amento EP, Tregear GW. Relaxin deficiency in mice is associated with an age-related progression of pulmonary fibrosis. FASEB J 2003; 17:121-3. [PMID: 12424226 DOI: 10.1096/fj.02-0449fje] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Relaxin (RLX) is a peptide hormone with known antifibrotic properties. However, its significance in the lung and its role as a therapeutic agent against diseases characterized by pulmonary fibrosis are yet to be established. In this study, we examined age-related structural and functional changes in the lung of relaxin-deficient mice. Lung tissues of male and female RLX knockout (-/-) and RLX wild-type (+/+) mice at various ages were analyzed for changes in collagen expression and content. We demonstrate an age-related progression of lung fibrosis in RLX -/- mice with significantly increased tissue wet weight, collagen content and concentration, alveolar congestion, and bronchiole epithelium thickening. The increased fibrosis was associated with significantly altered peak expiratory flow and lung recoil (lung function) in RLX -/- mice. Treatment of RLX -/- mice with relaxin in early and developed stages of fibrosis resulted in the reversal of collagen deposition. Organ bath studies showed that precontracted lung strips relaxed in the presence of relaxin. Together, these data indicate that relaxin may provide a means to regulate excessive collagen deposition in diseased states characterized by pulmonary fibrosis.
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Affiliation(s)
- Chrishan S Samuel
- Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Victoria, Australia. :
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Tan YY, Dawson NF, Kompa AR, Bond CP, Claasz A, Wade JD, Tregear GW, Summers RJ. Structural requirements for the interaction of sheep insulin-like factor 3 with relaxin receptors in rat atria. Eur J Pharmacol 2002; 457:153-60. [PMID: 12464361 DOI: 10.1016/s0014-2999(02)02662-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Relaxin is a peptide with various reproductive and nonreproductive functions. The site for the peptide-receptor interaction contains two arginines (Arg) and an isoleucine (Ile) or valine (Val) residue in the B-chain with a configuration of -Arg-X-X-X-Arg-X-X-Ile/Val-X-. The sheep insulin-like peptide 3 (INSL3), a structural homologue of relaxin, also contains the n, n+4 arginines in the B-chain but they are displaced towards the carboxyl terminus by four residues (-X-X-X-X-Arg-X-X-Val-Arg-). Human INSL3 increases the activity of human relaxin in mouse bioassays. Here, we investigated whether sheep synthetic INSL3 affects the relaxin activity in rat atria. INSL3 lacked relaxin-like agonist activity but blocked the activity of relaxin and competed for relaxin binding sites at high concentrations. We also synthesized analogues of INSL3, with amino acid substitutions in the arginine-binding region. Analogues A, D and E, which have the arginines in positions identical to relaxin, showed weak relaxin-like agonist activity. These results suggest that other sites in the relaxin molecule are involved in high-affinity peptide-receptor interaction for the production of the relaxin biological responses.
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Affiliation(s)
- Yean Yeow Tan
- Department of Pharmacology, Monash University, P.O. Box 13E, Clayton 3800, Victoria, Australia
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Claasz AA, Bond CP, Bathgate RA, Otvos L, Dawson NF, Summers RJ, Tregear GW, Wade JD. Relaxin-like bioactivity of ovine Insulin 3 (INSL3) analogues. EUROPEAN JOURNAL OF BIOCHEMISTRY 2002; 269:6287-93. [PMID: 12473125 DOI: 10.1046/j.1432-1033.2002.03348.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Relaxin is an insulin-like peptide consisting of two separate chains (A and B) joined by two inter- and one intrachain disulfide bonds. Binding to its receptor requires an Arg-X-X-X-Arg-X-X-Ile motif in the B-chain. A related member of the insulin superfamily, INSL3, has a tertiary structure that is predicted to be similar to relaxin. It also possesses an Arg-X-X-X-Arg motif within its B-chain, although this is displaced by four amino acids towards the C-terminus from the corresponding position within relaxin. We have previously shown that synthetic INSL3 itself does not display relaxin-like activity although analogue (Analogue A) with an introduced arginine residue in the B-chain giving it an Arg cassette in the exact relaxin position does possess weak activity. In order to identify further the structural features that impart relaxin function, solid phase peptide synthesis was used to prepare three additional analogues for bioassay. Each of these contained point substitutions within the arginine cassette. Analogue D contained the full human relaxin binding cassette, Analogue G consisted of the native INSL3 sequence containing an Arg to Ala substitution, and Analogue E was a further modification of Analogue A, with the same substitution. Each analogue was fully chemically characterized by a number of criteria. Detailed circular dichroism spectroscopy analyses showed that the changes caused little alteration of secondary structure and, hence, overall conformation. However, each analogue displayed only weak relaxin-like activity. These results indicate that while the arginine cassette is vital for relaxin-like activity, there are additional, as yet unidentified structural requirements for relaxin binding.
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Affiliation(s)
- Antonia A Claasz
- Howard Florey Institute, University of Melbourne, Victoria, Australia
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Kompa AR, Samuel CS, Summers RJ. Inotropic responses to human gene 2 (B29) relaxin in a rat model of myocardial infarction (MI): effect of pertussis toxin. Br J Pharmacol 2002; 137:710-8. [PMID: 12381685 PMCID: PMC1573542 DOI: 10.1038/sj.bjp.0704922] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Relaxin produces powerful inotropic and chronotropic responses in isolated atria. The effect of relaxin has been examined in a rat model of cardiac failure, induced by myocardial infarction (MI). Maximum inotropic responses to isoprenaline (sham 5.4+/-0.3 mN; MI 2.6+/-0.3 mN; P<0.001) and relaxin (sham 5.1+/-0.6 mN; MI 2.8+/-0.5 mN; P=0.013) were reduced in left atria following MI. No change in chronotropic responsiveness was observed in right atria. Pertussis toxin (PTX) treatment restored inotropic responses to isoprenaline (sham 5.5+/-1.3 mN; MI 5.8+/-1.0 mN; P=0.850) but not to relaxin. Instead, PTX reduced inotropic responses to relaxin in sham animals to the same level seen in the MI group (sham 3.2+/-1.7 mN; MI 2.8+/-0.6 mN; P=0.847). In right atria, PTX treatment did not affect the maximum chronotropic response to isoprenaline, but reduced responses to relaxin in both sham and MI animals. R3 relaxin and relaxin receptor (LGR7) mRNA was present in atria and left ventricle (LV) from sham and MI animals. R3 relaxin mRNA expression was increased in atria but not LV from MI animals. LGR7 mRNA expression was reduced in atria and LV from MI animals. PTX treatment in unoperated rats increased chronotropic responses (vehicle 184.3+/-5.3 beats min(-1); PTX 211.3+/-9.5 beats min(-1); P=0.029) and produced a rightward shift in the concentration-response curve to isoprenaline in left atria. PTX reduced inotropic (vehicle 3.3+/-0.7 mN; PTX 0.8+/-0.2 mN; P=0.005) and chronotropic (vehicle 130.2+/-8.1 beats min(-1); PTX 90.6+/-11.1 beats min(-1); P=0.012) responses to relaxin. 6 In left atria, relaxin produced a small increase in cAMP compared to those produced by isoprenaline and forskolin. However, PTX treatment significantly reduced relaxin-, isoprenaline- and forskolin-stimulated cAMP accumulation. Cardiac failure in MI animals caused a reduced inotropic response to both relaxin and (-)-isoprenaline. In non-MI animals, PTX treatment also reduced inotropic responses to relaxin. Differences between responses to (-)-isoprenaline and relaxin can be explained by changes in coupling efficiency occurring at the level of adenylate cyclase.
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Affiliation(s)
- Andrew R Kompa
- Department of Pharmacology, Monash University, Victoria, 3800, Australia
| | - Chrishan S Samuel
- Howard Florey Institute, University of Melbourne, Victoria, 3010, Australia
| | - Roger J Summers
- Department of Pharmacology, Monash University, Victoria, 3800, Australia
- Author for correspondence:
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