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Kek HP, Su YT, Lin KJ, Yang MC, Chang LC, Yang YN, Tsai CC. Investigating the Mechanisms Underlying U46619-Induced Contraction on Porcine Lower Esophageal Sphincter. J Pharmacol Exp Ther 2024; 390:188-195. [PMID: 38135510 DOI: 10.1124/jpet.123.001902] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Revised: 10/22/2023] [Accepted: 11/27/2023] [Indexed: 12/24/2023] Open
Abstract
Gastroesophageal reflux disease (GERD) is associated with an incompetent lower esophageal sphincter (LES), resulting in the reflux of gastric contents into the esophagus. U46619, a thromboxane A2 (TXA2) receptor agonist, induces contractions in various smooth muscles. Therefore, this study aimed to investigate the effects and mechanisms of action of U46619 on the porcine LES. To achieve this, contractions of the clasp and sling strips of the porcine LES, induced by U46619, were measured using isometric transducers. Furthermore, the contractile mechanism of U46619 in the porcine LES was investigated by pretreating the strips with atropine (a muscarinic receptor antagonist), tetrodotoxin (a neuronal sodium channel blocker), nifedipine (a calcium channel blocker), and Ca2+-free Krebs-Henseleit solution. Additionally, reverse transcription polymerase chain reaction (PCR) and immunohistochemistry (IHC) were performed to determine the presence of the TXA2 receptor in porcine LES. The results of this study demonstrated that U46619 caused marked concentration-dependent contractions in both porcine sling and clasp strips. The mechanism of U46619-induced contraction of the porcine LES was found to be related to calcium channels. Furthermore, the reverse transcription PCR analysis and IHC revealed that the TXA2 receptor was expressed in the clasp and sling fibers of porcine LES. Consequently, this study suggests that U46619 mediates the contraction of porcine LES through calcium channels and has potential as a therapeutic approach for treating GERD. SIGNIFICANCE STATEMENT: This study establishes that U46619 induces concentration-dependent contractions in porcine LES, primarily mediated by calcium channels. The presence of the TXA2 receptor in LES clasp and sling fibers is confirmed. These findings highlight U46619's potential as a GERD therapeutic by targeting calcium channels for LES contraction modulation.
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Affiliation(s)
- Ho-Poh Kek
- Department of Pediatrics (H.-P.K., Y.-T.S., M.-C.Y., Y.-N.Y., C.-C.T.) and Department of Pathology (K.-J.L.), E-Da Hospital, I-Shou University, Taiwan, Republic of China and School of Medicine for International Students (Y.-T.S., K.-J.L., L.-C.C., C.-C.T.) and School of Medicine (H.-P.K., M.-C.Y., Y.-N.Y.), College of Medicine, I-Shou University, Taiwan, Republic of China
| | - Yu-Tsun Su
- Department of Pediatrics (H.-P.K., Y.-T.S., M.-C.Y., Y.-N.Y., C.-C.T.) and Department of Pathology (K.-J.L.), E-Da Hospital, I-Shou University, Taiwan, Republic of China and School of Medicine for International Students (Y.-T.S., K.-J.L., L.-C.C., C.-C.T.) and School of Medicine (H.-P.K., M.-C.Y., Y.-N.Y.), College of Medicine, I-Shou University, Taiwan, Republic of China
| | - Kai-Jen Lin
- Department of Pediatrics (H.-P.K., Y.-T.S., M.-C.Y., Y.-N.Y., C.-C.T.) and Department of Pathology (K.-J.L.), E-Da Hospital, I-Shou University, Taiwan, Republic of China and School of Medicine for International Students (Y.-T.S., K.-J.L., L.-C.C., C.-C.T.) and School of Medicine (H.-P.K., M.-C.Y., Y.-N.Y.), College of Medicine, I-Shou University, Taiwan, Republic of China
| | - Ming-Chun Yang
- Department of Pediatrics (H.-P.K., Y.-T.S., M.-C.Y., Y.-N.Y., C.-C.T.) and Department of Pathology (K.-J.L.), E-Da Hospital, I-Shou University, Taiwan, Republic of China and School of Medicine for International Students (Y.-T.S., K.-J.L., L.-C.C., C.-C.T.) and School of Medicine (H.-P.K., M.-C.Y., Y.-N.Y.), College of Medicine, I-Shou University, Taiwan, Republic of China
| | - Li-Ching Chang
- Department of Pediatrics (H.-P.K., Y.-T.S., M.-C.Y., Y.-N.Y., C.-C.T.) and Department of Pathology (K.-J.L.), E-Da Hospital, I-Shou University, Taiwan, Republic of China and School of Medicine for International Students (Y.-T.S., K.-J.L., L.-C.C., C.-C.T.) and School of Medicine (H.-P.K., M.-C.Y., Y.-N.Y.), College of Medicine, I-Shou University, Taiwan, Republic of China
| | - Yung-Ning Yang
- Department of Pediatrics (H.-P.K., Y.-T.S., M.-C.Y., Y.-N.Y., C.-C.T.) and Department of Pathology (K.-J.L.), E-Da Hospital, I-Shou University, Taiwan, Republic of China and School of Medicine for International Students (Y.-T.S., K.-J.L., L.-C.C., C.-C.T.) and School of Medicine (H.-P.K., M.-C.Y., Y.-N.Y.), College of Medicine, I-Shou University, Taiwan, Republic of China
| | - Ching-Chung Tsai
- Department of Pediatrics (H.-P.K., Y.-T.S., M.-C.Y., Y.-N.Y., C.-C.T.) and Department of Pathology (K.-J.L.), E-Da Hospital, I-Shou University, Taiwan, Republic of China and School of Medicine for International Students (Y.-T.S., K.-J.L., L.-C.C., C.-C.T.) and School of Medicine (H.-P.K., M.-C.Y., Y.-N.Y.), College of Medicine, I-Shou University, Taiwan, Republic of China
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Charest-Morin X, Bachelard H, Jean M, Marceau F. Species-specific pharmacology of maximakinin, an amphibian homologue of bradykinin: putative prodrug activity at the human B 2 receptor and peptidase resistance in rats. PeerJ 2017; 5:e2911. [PMID: 28133580 PMCID: PMC5248581 DOI: 10.7717/peerj.2911] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2016] [Accepted: 12/14/2016] [Indexed: 01/11/2023] Open
Abstract
Maximakinin (MK), an amphibian peptide possessing the C-terminal sequence of bradykinin (BK), is a BK B2 receptor (B2R) agonist eliciting prolonged signaling. We reinvestigated this 19-mer for species-specific pharmacologic profile, in vivo confirmation of resistance to inactivation by angiotensin converting enzyme (ACE), value as a module for the design of fusion proteins that bind to the B2R in mammalian species and potential activity as a histamine releaser. Competition of the binding of [3H]BK to recombinant human myc-B2Rs in cells that express these receptors revealed that MK possessed a tenuous fraction (<0.1%) of the affinity of BK, despite being only ∼20-fold less potent than BK in a contractility assay based on the human isolated umbilical vein. These findings are reconciled by the generation of C-terminal fragments, like Lys-Gly-Pro-BK and Gly-Pro-BK, when the latent MK is incubated with human venous tissue (LC-MS), supporting activation via hydrolysis upstream of the BK sequence. At the rat recombinant myc-B2R, MK had a lesser affinity than that of BK, but with a narrower margin (6.2-fold, radioligand binding competition). Accordingly, MK (10 nM) stimulated calcium transients in cells that expressed the rat receptors, but not the human B2R. Recombinant MRGPRX2, a receptor that mediates cationic peptide-induced mast cell secretion, minimally responded by increased [Ca+2]i to MK at 10 µM. Enhanced green fluorescent protein fused to MK (EGFP-MK) labeled cells that expressed rat, but not human B2Rs. Intravenous MK induced dose-dependent hypotensive, vasodilator and tachycardic responses in anesthetized rats and the effects were antagonized by pretreatment with icatibant but not modified by pyrilamine or enalaprilat. Strong species-specific responses to the toxin-derived peptide MK and its prodrug status in the isolated human vein were evidenced. Accordingly, MK in the EGFP-MK fusion protein is a pharmacophore module that confers affinity for the rat B2R, but not for the human form of the B2R. MK is unlikely to be an efficient mast cell activator, but its resistance to inactivation by ACE was confirmed in vivo.
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Affiliation(s)
- Xavier Charest-Morin
- Axe Microbiologie-Infectiologie et Immunologie, CHU de Québec-Université Laval and Université Laval, Québec, QC, Canada
| | - Hélène Bachelard
- Axe endocrinologie et néphrologie, CHU de Québec-Université Laval and Université Laval, Québec, QC, Canada
| | - Melissa Jean
- Axe endocrinologie et néphrologie, CHU de Québec-Université Laval and Université Laval, Québec, QC, Canada
| | - Francois Marceau
- Axe Microbiologie-Infectiologie et Immunologie, CHU de Québec-Université Laval and Université Laval, Québec, QC, Canada
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