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Zhang J, Du Y, Xiong Z, Cheng H, Du Y, Xiong Y, Lv J, Huang W, Qiu K, Zhang S. Bombesin protects myocardium against ischemia/reperfusion injury via activation of the Keap1-Nrf2-HO-1 signaling pathway. Peptides 2024:171279. [PMID: 39053647 DOI: 10.1016/j.peptides.2024.171279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2024] [Revised: 07/08/2024] [Accepted: 07/22/2024] [Indexed: 07/27/2024]
Abstract
AIMS It has been reported that some peptides released by the gastro-intestinal tract play important roles in the prevention of myocardial ischemia/reperfusion injury (MIRI). Bombesin (BN) is a biologically active peptide released by non-adrenergic non-cholinergic nerves on the gastric antrum mucosa controlled by the vagus nerve. However, there is a lack of reports on the impact of BN on MIRI. This study aimed to explore the influence of BN on MIRI and its underlying mechanism. MATERIALS AND METHODS MIRI was induced by either 30min of global ischemia in Langendorff perfused rat hearts, or by ligation of the descending coronary artery for 30min in anesthetized Spraque-Dawley rats, and both were followed by 120min reperfusion. Infarct size and left ventricular function were assessed, and lactate dehydrogenase (LDH), superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione (GSH) levels were measured spectrophotometrically, while cardiomyocyte apoptosis was detected by TUNEL assay. The content of BN in plasma was measured with enzyme-linked immunosorbent assays (ELISA). The expression of caspase 3, Kelch-like ECH-associated protein 1 (Keap1), nuclear factor erythroid 2-related factor 2 (Nrf2), and heme oxygenase-1 (HO-1) were quantified. KEY FINDINGS BN and vagus nerve stimulation improved cardiac contractile function and reduced myocardial infarct size, attenuated oxidative stress damage and myocardial cell apoptosis, increased the expression of Keap1, Nrf2, and HO-1. and these effects were blocked by using a BN receptor antagonist. SIGNIFICANCE BN provides protection against MIRI, and its underlying mechanism is through activation of the Keap1/Nrf2/HO-1 pathway. This research provides more reliable evidence for the "gut-heart axis dialogue" and explores potential therapeutic approaches for MIRI.
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Affiliation(s)
- Jinyi Zhang
- State Administration of Traditional Chinese Medicine third class Pharmacology Laboratory of Traditional Chinese Medicine,Basic medical College of China Three Gorges University, Yichang 443002, China; Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, Basic medical College of China Three Gorges University, Yichang 443002, China
| | - Yanhuan Du
- State Administration of Traditional Chinese Medicine third class Pharmacology Laboratory of Traditional Chinese Medicine,Basic medical College of China Three Gorges University, Yichang 443002, China; Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, Basic medical College of China Three Gorges University, Yichang 443002, China
| | - Zhenyu Xiong
- State Administration of Traditional Chinese Medicine third class Pharmacology Laboratory of Traditional Chinese Medicine,Basic medical College of China Three Gorges University, Yichang 443002, China; Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, Basic medical College of China Three Gorges University, Yichang 443002, China
| | - Hang Cheng
- State Administration of Traditional Chinese Medicine third class Pharmacology Laboratory of Traditional Chinese Medicine,Basic medical College of China Three Gorges University, Yichang 443002, China; Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, Basic medical College of China Three Gorges University, Yichang 443002, China
| | - Yi Du
- State Administration of Traditional Chinese Medicine third class Pharmacology Laboratory of Traditional Chinese Medicine,Basic medical College of China Three Gorges University, Yichang 443002, China; Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, Basic medical College of China Three Gorges University, Yichang 443002, China
| | - Yulian Xiong
- State Administration of Traditional Chinese Medicine third class Pharmacology Laboratory of Traditional Chinese Medicine,Basic medical College of China Three Gorges University, Yichang 443002, China; Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, Basic medical College of China Three Gorges University, Yichang 443002, China
| | - Jianfeng Lv
- Department of Cardiovascular Medicine, Renhe Hospital affiliated to Three Gorges University, Yichang 443002, China
| | - Wenquan Huang
- State Administration of Traditional Chinese Medicine third class Pharmacology Laboratory of Traditional Chinese Medicine,Basic medical College of China Three Gorges University, Yichang 443002, China; Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, Basic medical College of China Three Gorges University, Yichang 443002, China
| | - Kuncheng Qiu
- State Administration of Traditional Chinese Medicine third class Pharmacology Laboratory of Traditional Chinese Medicine,Basic medical College of China Three Gorges University, Yichang 443002, China; Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, Basic medical College of China Three Gorges University, Yichang 443002, China
| | - Shizhong Zhang
- State Administration of Traditional Chinese Medicine third class Pharmacology Laboratory of Traditional Chinese Medicine,Basic medical College of China Three Gorges University, Yichang 443002, China; Hubei Key Laboratory of Tumor Microenvironment and Immunotherapy, Basic medical College of China Three Gorges University, Yichang 443002, China
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Feng C, Wang Y, Zha X, Cao H, Huang S, Cao D, Zhang K, Xie T, Xu X, Liang Z, Zhang Z. Cold-sensitive ventromedial hypothalamic neurons control homeostatic thermogenesis and social interaction-associated hyperthermia. Cell Metab 2022; 34:888-901.e5. [PMID: 35675799 DOI: 10.1016/j.cmet.2022.05.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 01/14/2022] [Accepted: 05/09/2022] [Indexed: 11/18/2022]
Abstract
Homeostatic thermogenesis is an essential protective feature of endotherms. However, the specific neuronal types involved in cold-induced thermogenesis remain largely unknown. Using functional magnetic resonance imaging and in situ hybridization, we screened for cold-sensitive neurons and found preprodynorphin (PDYN)-expressing cells in the dorsal medial region of the ventromedial hypothalamus (dmVMH) to be a candidate. Subsequent in vivo calcium recording showed that cold temperature activates dmVMHPdyn neurons, whereas hot temperature suppresses them. In addition, optogenetic activation of dmVMHPdyn neurons increases the brown adipose tissue and core body temperature, heart rate, and blood pressure, whereas optogenetic inhibition shows opposite effects, supporting their role in homeostatic thermogenesis. Furthermore, we found that dmVMHPdyn neurons are linked to known thermoregulatory circuits. Importantly, dmVMHPdyn neurons also show activation during mouse social interaction, and optogenetic inhibition suppresses social interaction and associated hyperthermia. Together, our study describes dual functions of dmVMHPdyn neurons that allow coordinated regulation of body temperature and social behaviors.
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Affiliation(s)
- Chenzhang Feng
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ying Wang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xi Zha
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China
| | - Huateng Cao
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China
| | - Shajin Huang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Dongdong Cao
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
| | - Kaiwei Zhang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China
| | - Tianyuan Xie
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaohong Xu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China.
| | - Zhifeng Liang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China.
| | - Zhe Zhang
- Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China; Shanghai Center for Brain Science and Brain-Inspired Intelligence Technology, Shanghai 201210, China.
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Zhu Y, Wu L, Zhao Y, Wang Z, Lu J, Yu Y, Xiao H, Zhang Y. Discovery of oridonin as a novel agonist for BRS-3. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 2022; 100:154085. [PMID: 35405616 DOI: 10.1016/j.phymed.2022.154085] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 03/16/2022] [Accepted: 03/26/2022] [Indexed: 06/14/2023]
Abstract
BACKGROUND Bombesin Receptor Subtype-3 (BRS-3, Bombesin-like receptor, BB3) is an orphan G-protein coupled receptor (GPCR). Recent studies have shown that BRS-3 played a vital role in glucose regulation, insulin secretion, and energy homeostasis. Therefore, discovering more novel exogenous ligands with diverse structures for BRS-3 will be of great importance for target validation and drug development. PURPOSE In this study, we aim to discover new agonists of BRS-3 from our natural compound libraries, providing a new probe to study the function of BRS-3. STUDY DESIGN Multiple cell-based assays and in vivo experiments were performed to identify the new ligand. METHODS BRS-3 overexpression cells were coupled with FLIPR assay, homogeneous time-resolved fluorescence (HTRF) IP-ONE assay, dynamic mass redistribution (DMR) assay, β-arrestin2 recruitment assay, and western blot to determine receptor activation and downstream signaling events. To further validate the target of BRS-3, a series of in vitro and in vivo experiences were conducted, including glucose uptake, glucose transporter type 4 (GLUT4) transportation in C2C12, and oral glucose tolerance test (OGTT) in mice. RESULTS We discovered and identified oridonin as a novel small molecule agonist of BRS-3, with a moderate affinity (EC50 of 2.236 × 10-7 M in calcium mobilization assay), specificity, and subtype selectivity. Further in vitro and in vivo tests demonstrated that oridonin exerted beneficial effects in glucose homeostasis through activating BRS-3. CONCLUSIONS Oridonin, as the discovered new ligand of BRS-3, provides a valuable tool compound to investigate BRS-3's function, especially for target validation in type 2 diabetes and obesity. Oridonin is promising as a lead compound in the treatment of metabolic disorders. Compared to the known agonists of BRS-3, we can take advantage of the multiple reported pharmacological activities of ODN as a natural product and assess whether these pharmacological activities are regulated by BRS-3. This may facilitate the discovery of novel functions of BRS-3.
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Affiliation(s)
- Yanan Zhu
- School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Lehao Wu
- School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, China; State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Yaxue Zhao
- School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Zeyuan Wang
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Jihong Lu
- School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Yang Yu
- School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Hua Xiao
- State Key Laboratory of Microbial Metabolism, Joint International Research Laboratory Metabolic & Developmental Sciences, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China
| | - Yan Zhang
- School of Pharmacy, Shanghai Jiao Tong University, Shanghai 200240, China.
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Cre Recombinase Driver Mice Reveal Lineage-Dependent and -Independent Expression of Brs3 in the Mouse Brain. eNeuro 2021; 8:ENEURO.0252-21.2021. [PMID: 34326065 PMCID: PMC8371926 DOI: 10.1523/eneuro.0252-21.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 07/12/2021] [Accepted: 07/19/2021] [Indexed: 11/21/2022] Open
Abstract
Bombesin receptor subtype-3 (BRS3) is an orphan receptor that regulates energy homeostasis. We compared Brs3 driver mice with constitutive or inducible Cre recombinase activity. The constitutive BRS3-Cre mice show a reporter signal (Cre-dependent tdTomato) in the adult brain because of lineage tracing in the dentate gyrus, striatal patches, and indusium griseum, in addition to sites previously identified in the inducible BRS3-Cre mice (including hypothalamic and amygdala subregions, and parabrachial nucleus). We detected Brs3 reporter expression in the dentate gyrus at day 23 but not at postnatal day 1 or 5 months of age. Hypothalamic sites expressed reporter at all three time points, and striatal patches expressed Brs3 reporter at 1 day but not 5 months. Parabrachial nucleus Brs3 neurons project to the preoptic area, hypothalamus, amygdala, and thalamus. Both Cre recombinase insertions reduced Brs3 mRNA levels and BRS3 function, causing obesity phenotypes of different severity. These results demonstrate that driver mice should be characterized phenotypically and illustrate the need for knock-in strategies with less effect on the endogenous gene.
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Piñol RA, Mogul AS, Hadley CK, Saha A, Li C, Škop V, Province HS, Xiao C, Gavrilova O, Krashes MJ, Reitman ML. Preoptic BRS3 neurons increase body temperature and heart rate via multiple pathways. Cell Metab 2021; 33:1389-1403.e6. [PMID: 34038711 PMCID: PMC8266747 DOI: 10.1016/j.cmet.2021.05.001] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 03/03/2021] [Accepted: 05/03/2021] [Indexed: 11/15/2022]
Abstract
The preoptic area (POA) is a key brain region for regulation of body temperature (Tb), dictating thermogenic, cardiovascular, and behavioral responses that control Tb. Previously characterized POA neuronal populations all reduced Tb when activated. Using mice, we now identify POA neurons expressing bombesin-like receptor 3 (POABRS3) as a population whose activation increased Tb; inversely, acute inhibition of these neurons reduced Tb. POABRS3 neurons that project to either the paraventricular nucleus of the hypothalamus or the dorsomedial hypothalamus increased Tb, heart rate, and blood pressure via the sympathetic nervous system. Long-term inactivation of POABRS3 neurons caused increased Tb variability, overshooting both increases and decreases in Tb set point, with RNA expression profiles suggesting multiple types of POABRS3 neurons. Thus, POABRS3 neuronal populations regulate Tb and heart rate, contribute to cold defense, and fine-tune feedback control of Tb. These findings advance understanding of homeothermy, a defining feature of mammalian biology.
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Affiliation(s)
- Ramón A Piñol
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Allison S Mogul
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Colleen K Hadley
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Atreyi Saha
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Chia Li
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Vojtěch Škop
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Haley S Province
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Cuiying Xiao
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Oksana Gavrilova
- Mouse Metabolism Core, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Michael J Krashes
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
| | - Marc L Reitman
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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Xiao C, Liu N, Province H, Piñol RA, Gavrilova O, Reitman ML. BRS3 in both MC4R- and SIM1-expressing neurons regulates energy homeostasis in mice. Mol Metab 2020; 36:100969. [PMID: 32229422 PMCID: PMC7113433 DOI: 10.1016/j.molmet.2020.02.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 02/13/2020] [Accepted: 02/22/2020] [Indexed: 12/11/2022] Open
Abstract
OBJECTIVE Bombesin-like receptor 3 (BRS3) is an orphan receptor and Brs3 knockout mice develop obesity with increased food intake and reduced resting metabolic rate and body temperature. The neuronal populations contributing to these effects were examined. METHODS We studied energy metabolism in mice with Cre-mediated recombination causing 1) loss of BRS3 selectively in SIM1- or MC4R-expressing neurons or 2) selective re-expression of BRS3 from a null background in these neurons. RESULTS The deletion of BRS3 in MC4R neurons increased body weight/adiposity, metabolic efficiency, and food intake, and reduced insulin sensitivity. BRS3 re-expression in these neurons caused partial or no reversal of these traits. However, these observations were confounded by an obesity phenotype caused by the Mc4r-Cre allele, independent of its recombinase activity. The deletion of BRS3 in SIM1 neurons increased body weight/adiposity and food intake, but not to the levels of the global null. The re-expression of BRS3 in SIM1 neurons reduced body weight/adiposity and food intake, but not to wild type levels. The deletion of BRS3 in either MC4R- or SIM1-expressing neurons affected body temperature, with re-expression in either population reversing the null phenotype. MK-5046, a BRS3 agonist, increases light phase body temperature in wild type, but not Brs3 null, mice and BRS3 re-expression in either population restored response to MK-5046. CONCLUSIONS BRS3 in both MC4R- and SIM1-expressing neurons contributes to regulation of body weight/adiposity, insulin sensitivity, food intake, and body temperature.
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Affiliation(s)
- Cuiying Xiao
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA
| | - Naili Liu
- Mouse Metabolism Core, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA
| | - Haley Province
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA
| | - Ramón A Piñol
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA
| | - Oksana Gavrilova
- Mouse Metabolism Core, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA
| | - Marc L Reitman
- Diabetes, Endocrinology, and Obesity Branch, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA.
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Ramos-Alvarez I, Lee L, Mantey SA, Jensen RT. Development and Characterization of a Novel, High-Affinity, Specific, Radiolabeled Ligand for BRS-3 Receptors. J Pharmacol Exp Ther 2019; 369:454-465. [PMID: 30971479 DOI: 10.1124/jpet.118.255141] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Accepted: 04/05/2019] [Indexed: 02/06/2023] Open
Abstract
Bombesin (Bn) receptor subtype 3(BRS-3) is an orphan G-protein-coupled receptor of the Bn family, which does not bind any natural Bn peptide with high affinity. Receptor knockout studies show that the animals develop diabetes, obesity, altered temperature control, and other central nervous system (CNS)/endocrine/gastrointestinal changes. It is present in CNS, peripheral tissues, and tumors; however, its role in normal physiology/pathophysiology, as well as its receptor localization/pharmacology is largely unknown, in part due to the lack of a convenient, specific, direct radiolabeled ligand. This study was designed to address this problem and to develop and characterize a specific radiolabeled ligand for BRS-3. The peptide antagonist Bantag-1 had >10,000-fold selectivity for human BRS-3 (hBRS-3) over other mammalian Bn receptors (BnRs) [i.e., gastrin-releasing peptide receptor (GRPR) and neuromedin B receptor (NMBR)]. Using iodogen and basic conditions, it was radiolabeled to high specific activity (2200 Ci/mmol) and found to bind with high affinity/specificity to hBRS-3. Binding was saturable, rapid, and reversible. The ligand only interacted with known BRS-3 ligands, and not with other specific GRPR/NMBR ligands or ligands for unrelated receptors. The magnitude of 125I-Bantag-1 binding correlated with BRS-3 mRNA expression and the magnitude of activation of phospholipase C in lung cancer cells, as well as readily identifying BRS-3 in lung cancer cells and normal tissues, allowing the direct assessment of BRS-3 receptor pharmacology/numbers on cells containing BRS-3 with other BnRs, which is usually the case. This circumvents the need for subtraction assays, which are now frequently used to assess BRS-3 indirectly using radiolabeled pan-ligands, which interact with all BnRs.
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Affiliation(s)
- Irene Ramos-Alvarez
- Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Lingaku Lee
- Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Samuel A Mantey
- Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Robert T Jensen
- Digestive Diseases Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
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