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Traserra S, Grao M, Trujillo S, Jiménez-Altayó F, Vergara P, Jimenez M. Pharmacological characterization of alpha adrenoceptor-mediated motor responses in the rat colon. Neurogastroenterol Motil 2024:e14921. [PMID: 39344996 DOI: 10.1111/nmo.14921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Revised: 07/05/2024] [Accepted: 09/13/2024] [Indexed: 10/01/2024]
Abstract
BACKGROUND Inhibitory neuromuscular transmission in the gastrointestinal tract is mediated by intrinsic nitrergic and purinergic neurons. Purines activate G protein-coupled receptor P2Y1 receptors, increasing intracellular Ca2+ that activates small conductance calcium-activated potassium (SKCa) channels. Little is known about the effect of adrenergic receptor activation on intestinal smooth muscle. In vascular tissue, stimulation of α-adrenoceptors causes smooth muscle contraction, while their effect on intestinal tissue is poorly understood. This study aimed to pharmacologically characterize the effect of α-adrenoceptor activation in the rat colon, which shares similar inhibitory pathways to the human colon. METHODS Muscle bath experiments were performed with the rat proximal, mid, and distal colon oriented both circularly and longitudinally. RESULTS The α1-adrenoceptor agonist phenylephrine (PE) (10-8-10-5 M) evoked concentration-dependent relaxations of the intestinal smooth muscle from all regions and orientations. However, in the mid-circular colon at low PE concentrations, a contraction sensitive to 10-5 M phentolamine (non-selective α-adrenoceptor blocker), the neural blocker tetrodotoxin (TTX; 10-6 M), and atropine (10-6 M) was recorded. PE-induced relaxations were insensitive to TTX (10-6 M) and the nonselective β-adrenoceptor blocker propranolol (10-6 M). In contrast, PE-induced relaxations were blocked by phentolamine (10-5 M), prazosin (10-6 M) (α1-adrenoceptor blocker), and RS17053 (10-6 M) (α1A-blocker), but not by yohimbine (10-6 M) (α2-adrenoceptor blocker). Apamin (10-6 M), a SKCa channel blocker, abolished PE-induced relaxations. CONCLUSIONS Contractile responses in the circular muscle of the mid colon could be attributed to α-adrenoceptors located on enteric cholinergic neurons. Stimulation of α1A-adrenoreceptors activates SKCa channels to cause smooth muscle relaxation, which constitutes a signaling pathway that shares similarities with P2Y1 receptors.
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Affiliation(s)
- Sara Traserra
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Marc Grao
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Sonia Trujillo
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Francesc Jiménez-Altayó
- Department of Pharmacology, Universitat Autònoma de Barcelona, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares (CIBERCV), Instituto de Salud Carlos III, Madrid, Spain
| | - Patri Vergara
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Barcelona, Spain
| | - Marcel Jimenez
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBEREHD), Barcelona, Spain
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Zhao Y, Luo H, Ren X, Jia B, Li J, Wang L, Li J. The P2Y 1 receptor in the colonic myenteric plexus of rats and its correlation with opioid-induced constipation. BMC Gastroenterol 2024; 24:23. [PMID: 38191294 PMCID: PMC10773096 DOI: 10.1186/s12876-024-03119-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Accepted: 01/01/2024] [Indexed: 01/10/2024] Open
Abstract
This study was designed to explore the expression changes of P2Y1 receptors in the distal colonic myenteric layer of rats. An opioid induced constipation(OIC) rat model was generated by intraperitoneal (i.p) injection of loperamide. At 7 days post-treatment, the model rats were assessed by calculating the fecal water content and the gastrointestinal transit ratio. The immunofluorescence (IF)-based histochemical study was used to observe the distribution of P2Y1 receptors in the distal colonic myenteric plexus. Western blotting (WB) was performed to evaluate the expression changes of P2Y1 proteins in the myenteric layer, and the electrophysiological approaches were carried out to determine the regulatory roles of P2Y1 receptors on distal colonic motor function. IF showed that P2Y1 receptors are co-expressed MOR in the enteric nerve cells of the distal colonic myenteric plexus. Moreover, the WB revealed that the protein levels of P2Y1 were significantly decreased in the distal colonic myenteric layer of OIC rats. In vitro tension experiments exhibited that the P2Y1 receptor antagonist MRS2500 enhanced the spontaneous contraction amplitude, adding EM2 and β-FNA did not have any effect on MRS2500. Therefore, P2Y1 receptor expression could be associated with the occurrence of OIC in this rat model and the regulation of colonic motility by MOR may be related to the release of purine neurotransmitters such as ATP in the colonic nervous system.
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Affiliation(s)
- Yuqiong Zhao
- Department of Human Anatomy and Histoembryology, College of Basic Medical Sciences, Ningxia Medical University, 1160 Shengli Street, 750001, Yinchuan, Ningxia Hui Autonomous Region, P.R. China
| | - Huijuan Luo
- Department of Human Anatomy and Histoembryology, College of Basic Medical Sciences, Ningxia Medical University, 1160 Shengli Street, 750001, Yinchuan, Ningxia Hui Autonomous Region, P.R. China
| | - Xiaojie Ren
- Department of Human Anatomy and Histoembryology, College of Basic Medical Sciences, Ningxia Medical University, 1160 Shengli Street, 750001, Yinchuan, Ningxia Hui Autonomous Region, P.R. China
| | - Binghan Jia
- Department of Human Anatomy and Histoembryology, College of Basic Medical Sciences, Ningxia Medical University, 1160 Shengli Street, 750001, Yinchuan, Ningxia Hui Autonomous Region, P.R. China
| | - Jinzhao Li
- Department of Human Anatomy and Histoembryology, College of Basic Medical Sciences, Ningxia Medical University, 1160 Shengli Street, 750001, Yinchuan, Ningxia Hui Autonomous Region, P.R. China
| | - Lixin Wang
- The Medical Laboratory Center of General Hospital of Ningxia Medical University, 804 Shengli Street, 750001, Yinchuan, Ningxia Hui Autonomous Region, P.R. China.
| | - Junping Li
- Department of Human Anatomy and Histoembryology, College of Basic Medical Sciences, Ningxia Medical University, 1160 Shengli Street, 750001, Yinchuan, Ningxia Hui Autonomous Region, P.R. China.
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Zhao Y, Ren X, Li F, Jia B, Wang D, Jia H, Jiao X, Wang L, Li J. P2Y1 receptor in the colonic submucosa of rats and its association with opioid‑induced constipation. Exp Ther Med 2022; 25:67. [PMID: 36605532 PMCID: PMC9798462 DOI: 10.3892/etm.2022.11766] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 11/03/2022] [Indexed: 12/15/2022] Open
Abstract
The aim of the present study was to explore the expression changes of P2Y purinergic receptor 1 (P2Y1) in the distal colonic submucosa of opioid-induced constipation (OIC) rats and its association with the occurrence of OIC, an OIC rat model was generated by intraperitoneal injection of loperamide hydrochloride, a selective agonist of µ-opioid receptors (MORs). At 7 days post-treatment, the model was assessed by analyzing stool scores and calculating the gastrointestinal (GI) transit ratio of rats. The distribution of P2Y1-expressing neurons in the colonic submucosal plexus was demonstrated by immunofluorescence (IF). Western blotting was performed to evaluate the expression changes of MOR, P2Y1 and ATP synthase subunit β (ATPB) proteins in the colonic submucosa, while reverse transcription-quantitative PCR (RT-qPCR) analysis was performed to determine the relative mRNA expression of MOR and P2Y1. After 7 days, the feces of OIC rats exhibited an appearance of sausage-shaped pieces and both the stool weight and GI transit ratio of OIC rats were significantly decreased. IF revealed co-expression of P2Y1 and calbindin and MOR and ATPB in the nerve cells of the distal colonic submucosal plexus. Moreover, RT-qPCR analysis showed that the MOR mRNA levels were significantly increased in the distal colonic submucosa of OIC rats, while mRNA levels of P2Y1 were decreased. WB showed that in the distal colonic submucosa of OIC rats, MOR protein expression was increased, whereas that of P2Y1 was significantly decreased. GI transit ratio analysis suggested that the P2Y agonist ATP significantly relieved constipation symptoms in rats, while the P2Y inhibitor MRS2179 aggravated these symptoms. Finally, P2Y1 expression change was shown to be associated with the occurrence of OIC, while expression of MOR and P2Y1 was associated with OIC development in rats.
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Affiliation(s)
- Yuqiong Zhao
- Department of Human Anatomy and Histoembryology, College of Basic Medical Sciences, Ningxia Medical University, Yinchuan, Ningxia Hui Autonomous Region 750001, P.R. China
| | - Xiaojie Ren
- Department of Human Anatomy and Histoembryology, College of Basic Medical Sciences, Ningxia Medical University, Yinchuan, Ningxia Hui Autonomous Region 750001, P.R. China
| | - Fan Li
- Department of Gastrointestinal Surgery, Xiantao First People's Hospital Affiliated to Yangtze University, Xiantao, Hubei 433000, P.R. China
| | - Binghan Jia
- Department of Human Anatomy and Histoembryology, College of Basic Medical Sciences, Ningxia Medical University, Yinchuan, Ningxia Hui Autonomous Region 750001, P.R. China
| | - Dengke Wang
- Department of Human Anatomy and Histoembryology, College of Basic Medical Sciences, Ningxia Medical University, Yinchuan, Ningxia Hui Autonomous Region 750001, P.R. China
| | - Hua Jia
- Department of Human Anatomy and Histoembryology, College of Basic Medical Sciences, Ningxia Medical University, Yinchuan, Ningxia Hui Autonomous Region 750001, P.R. China
| | - Xuwen Jiao
- Department of Human Anatomy and Histoembryology, College of Basic Medical Sciences, Ningxia Medical University, Yinchuan, Ningxia Hui Autonomous Region 750001, P.R. China
| | - Lixin Wang
- The Medical Laboratory Center of General Hospital of Ningxia Medical University, Yinchuan, Ningxia Hui Autonomous Region 750001, P.R. China,Correspondence to: Dr Junping Li, Department of Human Anatomy and Histoembryology, College of Basic Medical Sciences, Ningxia Medical University, 1160 Shengli Street, Yinchuan, Ningxia Hui Autonomous Region 750001, P.R. China
| | - Junping Li
- Department of Human Anatomy and Histoembryology, College of Basic Medical Sciences, Ningxia Medical University, Yinchuan, Ningxia Hui Autonomous Region 750001, P.R. China,Correspondence to: Dr Junping Li, Department of Human Anatomy and Histoembryology, College of Basic Medical Sciences, Ningxia Medical University, 1160 Shengli Street, Yinchuan, Ningxia Hui Autonomous Region 750001, P.R. China
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Perez-Medina A, Galligan JJ. Nitrergic and Purinergic Nerves in the Small Intestinal Myenteric Plexus and Circular Muscle of Mice and Guinea Pigs. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1383:33-43. [PMID: 36587144 DOI: 10.1007/978-3-031-05843-1_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
ATP is an excitatory and inhibitory neurotransmitter, while nitric oxide (NO) is an inhibitory neurotransmitter in the enteric nervous system (ENS). We used a vesicular nucleotide transporter (SLC17A9, VNUT) antibody and a nitric oxide synthase (NOS) antibody to identify purinergic and nitrergic nerves in mouse and guinea ileum. Mouse: VNUT-immunoreactivity (ir) was detected in nerve fibers in myenteric ganglia and circular muscle. VNUT-ir fibers surrounded choline acetyltransferase (ChAT), nitric oxide synthase (nNOS), and calretinin-ir neurons. VNUT-ir nerve cell bodies were not detected. Tyrosine hydroxylase (TH)-ir nerves were detected in myenteric ganglia and the tertiary plexus. Guinea pig: VNUT-ir was detected in neurons and nerves fibers and did not overlap with NOS-ir nerve fibers. VNUT-ir was detected in nerve fibers in ganglia but not nerve cell bodies. VNUT-ir nerve fibers surrounded NOS-ir and NOS- neurons. NOS-ir and VNUT-ir nerve fibers did not overlap in myenteric ganglia or circular muscle. VNUT-ir nerves surrounded some ChAT-ir neurons. VNUT-ir and ChAT-ir were detected in separate nerves in the CM. VNUT-ir nerve fibers surrounded calretinin-ir neurons.Conclusions: VNUT-ir neurons likely mediate purinergic signaling in small intestinal myenteric ganglia and circular muscle. ATP and NO are likely released from different inhibitory motorneurons. VNUT-ir and ChAT-ir interneurons mediate cholinergic and purinergic synaptic transmission in the myenteric plexus.
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Affiliation(s)
- Alberto Perez-Medina
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, USA
| | - James J Galligan
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, USA. .,The Neuroscience Program, Michigan State University, East Lansing, MI, USA.
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Traserra S, Barber C, Maclnnes J, Relea L, MacPherson LC, Cunningham MR, Vergara P, Accarino A, Kennedy C, Jimenez M. Different responses of the blockade of the P2Y1 receptor with BPTU in human and porcine intestinal tissues and in cell cultures. Neurogastroenterol Motil 2021; 33:e14101. [PMID: 33619847 DOI: 10.1111/nmo.14101] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 01/11/2021] [Accepted: 01/26/2021] [Indexed: 02/08/2023]
Abstract
BACKGROUND Gastrointestinal smooth muscle relaxation is accomplished by activation of P2Y1 receptors, therefore this receptor plays an important role in regulation of gut motility. Recently, BPTU was developed as a negative allosteric modulator of the P2Y1 receptor. Accordingly, the aim of this study was to assess the effect of BPTU on purinergic neurotransmission in pig and human gastrointestinal tissues. METHODS Ca2+ imaging in tSA201 cells that express the human P2Y1 receptor, organ bath and microelectrodes in tissues were used to evaluate the effects of BPTU on purinergic responses. KEY RESULTS BPTU concentration dependently (0.1 and 1 µmol L-1 ) inhibited the rise in intracellular Ca2+ evoked by ADP in tSA201 cells. In the pig small intestine, 30 µmol L-1 BPTU reduced the fast inhibitory junction potential by 80%. Smooth muscle relaxations induced by electrical field stimulation were reduced both in pig ileum (EC50 = 6 µmol L-1 ) and colon (EC50 = 35 µmol L-1 ), but high concentrations of BPTU (up to 100 µmol L-1 ) had no effect on human colonic muscle. MRS2500 (1 µmol L-1 ) abolished all responses. Finally, 10 µmol L-1 ADPβS inhibited spontaneous motility and this was partially reversed by 30 µmol L-1 BPTU in pig, but not human colonic tissue and abolished by MRS2500 (1 µmol L-1 ). CONCLUSIONS & INFERENCES BPTU blocks purinergic responses elicited via P2Y1 receptors in cell cultures and in pig gastrointestinal tissue. However, the concentrations needed are higher in pig tissue compared to cell cultures and BPTU was ineffective in human colonic tissue.
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Affiliation(s)
- Sara Traserra
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Claudia Barber
- Digestive System Research Unit, University Hospital Vall d'Hebron, Barcelona, Spain
| | - Jane Maclnnes
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Lucia Relea
- Digestive System Research Unit, University Hospital Vall d'Hebron, Barcelona, Spain
| | - Lewis C MacPherson
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Margaret R Cunningham
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Patri Vergara
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain.,Centro de Investigación Biomédica en Red de enfermedades hepáticas y digestivas (CIBERehd),, Instituto de Salud Carlos III, Madrid, Spain
| | - Anna Accarino
- Centro de Investigación Biomédica en Red de enfermedades hepáticas y digestivas (CIBERehd),, Instituto de Salud Carlos III, Madrid, Spain.,Digestive System Research Unit, University Hospital Vall d'Hebron, Barcelona, Spain
| | - Charles Kennedy
- Strathclyde Institute of Pharmacy & Biomedical Sciences, University of Strathclyde, Glasgow, UK
| | - Marcel Jimenez
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain.,Centro de Investigación Biomédica en Red de enfermedades hepáticas y digestivas (CIBERehd),, Instituto de Salud Carlos III, Madrid, Spain
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Sanders KM, Mutafova-Yambolieva VN. Neurotransmitters responsible for purinergic motor neurotransmission and regulation of GI motility. Auton Neurosci 2021; 234:102829. [PMID: 34146957 DOI: 10.1016/j.autneu.2021.102829] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 05/25/2021] [Accepted: 05/28/2021] [Indexed: 12/17/2022]
Abstract
Classical concepts of peripheral neurotransmission were insufficient to explain enteric inhibitory neurotransmission. Geoffrey Burnstock and colleagues developed the idea that ATP or a related purine satisfies the criteria for a neurotransmitter and serves as an enteric inhibitory neurotransmitter in GI muscles. Cloning of purinergic receptors and development of specific drugs and transgenic mice have shown that enteric inhibitory responses depend upon P2Y1 receptors in post-junctional cells. The post-junctional cells that transduce purinergic neurotransmitters in the GI tract are PDGFRα+ cells and not smooth muscle cells (SMCs). PDGFRα+ cells express P2Y1 receptors, are activated by enteric inhibitory nerve stimulation and generate Ca2+ oscillations, express small-conductance Ca2+-activated K+ channels (SK3), and generate outward currents when exposed to P2Y1 agonists. These properties are consistent with post-junctional purinergic responses, and similar responses and effectors are not functional in SMCs. Refinements in methodologies to measure purines in tissue superfusates, such as high-performance liquid chromatography (HPLC) coupled with etheno-derivatization of purines and fluorescence detection, revealed that multiple purines are released during stimulation of intrinsic nerves. β-NAD+ and other purines, better satisfy criteria for the purinergic neurotransmitter than ATP. HPLC has also allowed better detection of purine metabolites, and coupled with isolation of specific types of post-junctional cells, has provided new concepts about deactivation of purine neurotransmitters. In spite of steady progress, many unknowns about purinergic neurotransmission remain and require additional investigation to understand this important regulatory mechanism in GI motility.
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Affiliation(s)
- Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada, School of Medicine, 1664 North Virginia Street, Reno, NV 89557, USA.
| | - Violeta N Mutafova-Yambolieva
- Department of Physiology and Cell Biology, University of Nevada, School of Medicine, 1664 North Virginia Street, Reno, NV 89557, USA
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Cerantola S, Caputi V, Contarini G, Mereu M, Bertazzo A, Bosi A, Banfi D, Mantini D, Giaroni C, Giron MC. Dopamine Transporter Genetic Reduction Induces Morpho-Functional Changes in the Enteric Nervous System. Biomedicines 2021; 9:biomedicines9050465. [PMID: 33923250 PMCID: PMC8146213 DOI: 10.3390/biomedicines9050465] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Revised: 04/19/2021] [Accepted: 04/20/2021] [Indexed: 12/23/2022] Open
Abstract
Antidopaminergic gastrointestinal prokinetics are indeed commonly used to treat gastrointestinal motility disorders, although the precise role of dopaminergic transmission in the gut is still unclear. Since dopamine transporter (DAT) is involved in several brain disorders by modulating extracellular dopamine in the central nervous system, this study evaluated the impact of DAT genetic reduction on the morpho-functional integrity of mouse small intestine enteric nervous system (ENS). In DAT heterozygous (DAT+/-) and wild-type (DAT+/+) mice (14 ± 2 weeks) alterations in small intestinal contractility were evaluated by isometrical assessment of neuromuscular responses to receptor and non-receptor-mediated stimuli. Changes in ENS integrity were studied by real-time PCR and confocal immunofluorescence microscopy in longitudinal muscle-myenteric plexus whole-mount preparations (). DAT genetic reduction resulted in a significant increase in dopamine-mediated effects, primarily via D1 receptor activation, as well as in reduced cholinergic response, sustained by tachykininergic and glutamatergic neurotransmission via NMDA receptors. These functional anomalies were associated to architectural changes in the neurochemical coding and S100β immunoreactivity in small intestine myenteric plexus. Our study provides evidence that genetic-driven DAT defective activity determines anomalies in ENS architecture and neurochemical coding together with ileal dysmotility, highlighting the involvement of dopaminergic system in gut disorders, often associated to neurological conditions.
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Affiliation(s)
- Silvia Cerantola
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, 35131 Padova, Italy; (S.C.); (V.C.); (M.M.); (A.B.)
| | - Valentina Caputi
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, 35131 Padova, Italy; (S.C.); (V.C.); (M.M.); (A.B.)
- Department of Poultry Science, University of Arkansas, Fayetteville, AR 72704, USA
| | - Gabriella Contarini
- Department of Biomedical and Biotechnological Sciences, University of Catania, 95131 Catania, Italy;
| | - Maddalena Mereu
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, 35131 Padova, Italy; (S.C.); (V.C.); (M.M.); (A.B.)
| | - Antonella Bertazzo
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, 35131 Padova, Italy; (S.C.); (V.C.); (M.M.); (A.B.)
| | - Annalisa Bosi
- Department of Medicine and Surgery, University of Insubria, 21100 Varese, Italy; (A.B.); (D.B.); (C.G.)
| | - Davide Banfi
- Department of Medicine and Surgery, University of Insubria, 21100 Varese, Italy; (A.B.); (D.B.); (C.G.)
| | - Dante Mantini
- IRCCS San Camillo Hospital, 30126 Venice, Italy; or
- Motor Control and Neuroplasticity Research Group, KU Leuven, 3000 Leuven, Belgium
| | - Cristina Giaroni
- Department of Medicine and Surgery, University of Insubria, 21100 Varese, Italy; (A.B.); (D.B.); (C.G.)
| | - Maria Cecilia Giron
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, 35131 Padova, Italy; (S.C.); (V.C.); (M.M.); (A.B.)
- IRCCS San Camillo Hospital, 30126 Venice, Italy; or
- Correspondence: ; Tel.: +39-049-827-5091; Fax: +39-049-827-5093
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Gastreich-Seelig M, Jimenez M, Pouokam E. Mechanisms Associated to Nitroxyl (HNO)-Induced Relaxation in the Intestinal Smooth Muscle. Front Physiol 2020; 11:438. [PMID: 32581821 PMCID: PMC7283591 DOI: 10.3389/fphys.2020.00438] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 04/08/2020] [Indexed: 12/23/2022] Open
Abstract
The pharmacological properties of nitroxyl (HNO) donors in the gastrointestinal tract are unknown. We investigated the properties of this molecule in the regulation of gastrointestinal contractility focusing on its possible interaction with other gaseous signaling molecules such as NO and H2S. Organ bath, Ca2+ imaging, and microelectrode recordings were performed on rat intestinal samples, using Angeli’s salt as HNO donor. Angeli’s salt caused a concentration-dependent relaxation of longitudinal or circular muscle strips of the ileum and the proximal colon. This relaxation was strongly inhibited by the Rho-kinase inhibitor Y-27632 (10 μM), by the reducing agent DTT or by the inhibitor of soluble guanylate cyclase (sGC) ODQ (10 μM) alone or in combination with the inhibitors of the endogenous synthesis of H2S β-cyano-L-alanine (5 mM) and amino-oxyacetate (5 mM). Preventing endogenous synthesis of NO by the NO synthase inhibitor L-NAME (200 μM) did not affect the relaxation induced by HNO. HNO induced an increase in cytosolic Ca2+ concentration in colonic myocytes. It also elicited myocyte membrane hyperpolarization that amounted to −10.6 ± 1.1 mV. ODQ (10 μM) and Apamin (1 μM), a selective inhibitor of small conductance Ca2+-activated K+ channels (SKca), strongly antagonized this effect. We conclude that HNO relaxes the gastrointestinal tract musculature by hyperpolarizing myocytes via activation of the sGC/cGMP pathway similarly to NO, not only inhibiting the RhoK and activating MLCP as do both NO and H2S but also increasing cytosolic Ca2+ for activation of SKCa contributing to hyperpolarization.
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Affiliation(s)
- Mirko Gastreich-Seelig
- Institute for Veterinary Physiology and Biochemistry, Justus-Liebig-University Giessen, Giessen, Germany
| | - Marcel Jimenez
- Department of Cell Biology, Physiology and Immunology and Neurosciences Institute, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Ervice Pouokam
- Institute for Veterinary Physiology and Biochemistry, Justus-Liebig-University Giessen, Giessen, Germany
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Traserra S, Villarte S, Traini C, Palacin S, Vergara P, Vannucchi MG, Jimenez M. The asymmetric innervation of the circular and longitudinal muscle of the mouse colon differently modulates myogenic slow phasic contractions. Neurogastroenterol Motil 2020; 32:e13778. [PMID: 31845466 DOI: 10.1111/nmo.13778] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 11/07/2019] [Accepted: 11/25/2019] [Indexed: 01/06/2023]
Abstract
BACKGROUND Neuromuscular transmission has been extensively studied in the circular layer of the mouse colon where a co-transmission of purines acting on P2Y1 receptors and NO has been previously described. However, the corresponding mechanisms in the longitudinal layer are less known. METHODS Electrophysiological and myography techniques were used to evaluate spontaneous phasic contractions (SPC) and neural-mediated responses in the proximal, mid, and distal colon devoid of CD1 mice. Immunohistochemistry against c-kit and PDGFRα was performed in each colonic segment. KEY RESULTS SPC were recorded in both muscle layers at a similar frequency being about four contractions per minute (c.p.m.) in the proximal and distal colon compared to the mid colon (2 c.p.m.). In non-adrenergic, non-cholinergic conditions, L-NNA (1 mmol/L) increased contractility in the circular but not in the longitudinal layer. In the longitudinal muscle, both electrophysiological and mechanical neural-mediated inhibitory responses were L-NNA and ODQ (10 µmol/L) sensitive. NaNP (1 µmol/L) caused cessation of SPC and the response was blocked by ODQ. Neither ADPßS (10 µmol/L) nor CYPPA (10 µmol/L), which both targeted the purinergic pathway, altered longitudinal contractions. PDGFRα + cells were located in both muscle layers and were more numerous compared with cKit + cells, which both formed a heterologous cellular network. A decreasing gradient of the PDGFRα labeling was observed along the colon. CONCLUSION An inhibitory neural tone was absent in the longitudinal layer and neuronal inhibitory responses were mainly nitrergic. Despite the presence of PDGFRα + cells, purinergic responses were absent. Post-junctional pathways located in different cell types might be responsible for neurotransmitter transduction.
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Affiliation(s)
- Sara Traserra
- Department of Cell Biology, Physiology and Immunology, Universitat Autonoma de Barcelona, Barcelona, Spain
| | - Sonia Villarte
- Department of Cell Biology, Physiology and Immunology, Universitat Autonoma de Barcelona, Barcelona, Spain
| | - Chiara Traini
- Department of Experimental and Clinical Medicine, Research Unit of Histology and Embryology, University of Florence, Florence, Italy
| | - Sara Palacin
- Department of Cell Biology, Physiology and Immunology, Universitat Autonoma de Barcelona, Barcelona, Spain
| | - Patri Vergara
- Department of Cell Biology, Physiology and Immunology, Universitat Autonoma de Barcelona, Barcelona, Spain
| | - Maria Giuliana Vannucchi
- Department of Experimental and Clinical Medicine, Research Unit of Histology and Embryology, University of Florence, Florence, Italy
| | - Marcel Jimenez
- Department of Cell Biology, Physiology and Immunology, Universitat Autonoma de Barcelona, Barcelona, Spain
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10
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Involvement of Enteric Glia in Small Intestine Neuromuscular Dysfunction of Toll-Like Receptor 4-Deficient Mice. Cells 2020; 9:cells9040838. [PMID: 32244316 PMCID: PMC7226836 DOI: 10.3390/cells9040838] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 03/26/2020] [Accepted: 03/27/2020] [Indexed: 12/16/2022] Open
Abstract
Enteric glial cells (EGCs) influence nitric oxide (NO)− and adenosine diphosphate (ADP)− mediated signaling in the enteric nervous system (ENS). Since Toll-like receptor 4 (TLR4) participates to EGC homoeostasis, this study aimed to evaluate the possible involvement of EGCs in the alterations of the inhibitory neurotransmission in TLR4−/− mice. Ileal segments from male TLR4−/− and wild-type (WT) C57BL/6J mice were incubated with the gliotoxin fluoroacetate (FA). Alterations in ENS morphology and neurochemical coding were investigated by immunohistochemistry whereas neuromuscular responses were determined by recording non-adrenergic non-cholinergic (NANC) relaxations in isometrically suspended isolated ileal preparations. TLR4−/− ileal segments showed increased iNOS immunoreactivity associated with enhanced NANC relaxation, mediated by iNOS-derived NO and sensitive to P2Y1 inhibition. Treatment with FA diminished iNOS immunoreactivity and partially abolished NO− and ADP− mediated relaxation in the TLR4−/− mouse ileum, with no changes of P2Y1 and connexin-43 immunofluorescence distribution in the ENS. After FA treatment, S100β and GFAP immunoreactivity in TLR4−/− myenteric plexus was reduced to levels comparable to those observed in WT. Our findings show the involvement of EGCs in the alterations of ENS architecture and in the increased purinergic and nitrergic-mediated relaxation, determining gut dysmotility in TLR4−/− mice.
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Dal Ben D, Antonioli L, Lambertucci C, Spinaci A, Fornai M, D'Antongiovanni V, Pellegrini C, Blandizzi C, Volpini R. Approaches for designing and discovering purinergic drugs for gastrointestinal diseases. Expert Opin Drug Discov 2020; 15:687-703. [PMID: 32228110 DOI: 10.1080/17460441.2020.1743673] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
INTRODUCTION Purines finely modulate physiological motor, secretory, and sensory functions in the gastrointestinal tract. Their activity is mediated by the purinergic signaling machinery, including receptors and enzymes regulating their synthesis, release, and degradation. Several gastrointestinal dysfunctions are characterized by alterations affecting the purinergic system. AREAS COVERED The authors provide an overview on the purinergic receptor signaling machinery, the molecules and proteins involved, and a summary of medicinal chemistry efforts aimed at developing novel compounds able to modulate the activity of each player involved in this machinery. The involvement of purinergic signaling in gastrointestinal motor, secretory, and sensory functions and dysfunctions, and the potential therapeutic applications of purinergic signaling modulators, are then described. EXPERT OPINION A number of preclinical and clinical studies demonstrate that the pharmacological manipulation of purinergic signaling represents a viable way to counteract several gastrointestinal diseases. At present, the paucity of purinergic therapies is related to the lack of receptor-subtype-specific agonists and antagonists that are effective in vivo. In this regard, the development of novel therapeutic strategies should be focused to include tools able to control the P1 and P2 receptor expression as well as modulators of the breakdown or transport of purines.
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Affiliation(s)
- Diego Dal Ben
- School of Pharmacy, Medicinal Chemistry Unit, University of Camerino , Camerino, Italy
| | - Luca Antonioli
- Unit of Pharmacology and Pharmacovigilance, Department of Clinical and Experimental Medicine, University of Pisa , Pisa, Italy
| | - Catia Lambertucci
- School of Pharmacy, Medicinal Chemistry Unit, University of Camerino , Camerino, Italy
| | - Andrea Spinaci
- School of Pharmacy, Medicinal Chemistry Unit, University of Camerino , Camerino, Italy
| | - Matteo Fornai
- Unit of Pharmacology and Pharmacovigilance, Department of Clinical and Experimental Medicine, University of Pisa , Pisa, Italy
| | - Vanessa D'Antongiovanni
- Unit of Pharmacology and Pharmacovigilance, Department of Clinical and Experimental Medicine, University of Pisa , Pisa, Italy
| | | | - Corrado Blandizzi
- Unit of Pharmacology and Pharmacovigilance, Department of Clinical and Experimental Medicine, University of Pisa , Pisa, Italy
| | - Rosaria Volpini
- School of Pharmacy, Medicinal Chemistry Unit, University of Camerino , Camerino, Italy
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12
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A Role for The P2Y1 Receptor in Nonsynaptic Cross-depolarization in the Rat Dorsal Root Ganglia. Neuroscience 2019; 423:98-108. [PMID: 31689490 DOI: 10.1016/j.neuroscience.2019.09.038] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 09/19/2019] [Accepted: 09/27/2019] [Indexed: 12/19/2022]
Abstract
Non-synaptic transmission is pervasive throughout the nervous system. It appears especially prevalent in peripheral ganglia, where non-synaptic interactions between neighboring cell bodies have been described in both physiological and pathological conditions, a phenomenon referred to as cross-depolarization (CD) and thought to play a role in sensory processing and chronic pain. CD has been proposed to be mediated by a chemical agent, but its identity has remained elusive. Here, we report that in the rat dorsal root ganglion (DRG), the P2Y1 purinergic receptor (P2RY1) plays an important role in regulating CD. The effect of P2RY1 is cell-type specific: pharmacological blockade of P2RY1 inhibited CD in A-type neurons while enhancing it in C-type neurons. In the nodose ganglion of the vagus, CD requires extracellular calcium in a large percentage of cells. In contrast, we show that in the DRG extracellular calcium appears to play no major role, pointing to a mechanistic difference between the two peripheral ganglia. Furthermore, we show that DRG glial cells also play a cell-type specific role in CD regulation. Fluorocitrate-induced glial inactivation had no effect on A-cells but enhanced CD in C-cells. These findings shed light on the mechanism of CD in the DRG and pave the way for further analysis of non-synaptic neuronal communication in sensory ganglia.
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13
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Diadenosine tetraphosphate activates P2Y 1 receptors that cause smooth muscle relaxation in the mouse colon. Eur J Pharmacol 2019; 855:160-166. [PMID: 31063775 DOI: 10.1016/j.ejphar.2019.05.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2018] [Revised: 05/03/2019] [Accepted: 05/03/2019] [Indexed: 01/01/2023]
Abstract
P2Y1 receptors play an essential role in inhibitory neuromuscular transmission in the gastrointestinal tract. The signalling pathway involves the opening of small conductance calcium activated potassium-channels (Kca2 family) that results in smooth muscle hyperpolarization and relaxation. Inorganic polyphosphates and dinucleotidic polyphosphates are putative neurotransmitters that potentially act on P2Y1 receptors. A pharmacological approach using both orthosteric (MRS2500) and allosteric (BPTU) blockers of the P2Y1 receptor and openers (CyPPA) and blockers (apamin) of Kca2 channels was used to pharmacologically characterise the effect of these neurotransmitters. Organ bath and microelectrodes were used to evaluate the effect of P1,P4-Di (adenosine-5') tetraphosphate ammonium salt (Ap4A), inorganic polyphosphates (PolyP) and CyPPA on spontaneous contractions and membrane potential of mouse colonic smooth muscle cells. PolyP neither modified contractions nor membrane potential. In contrast, Ap4A caused a concentration-dependent inhibition of spontaneous contractions reaching a maximum effect at 100 μM Ap4A response was antagonised by MRS2500 (1 μM), BPTU (3 μM) and apamin (1 μM). CyPPA (10 μM) inhibited spontaneous contractions and this response was antagonised by apamin but it was not affected by MRS2500 or BPTU. Both CyPPA and Ap4A caused smooth muscle hyperpolarization that was blocked by apamin and MRS2500 respectively. We conclude that Ap4A but not PolyP activates P2Y1 receptors causing smooth muscle hyperpolarization and relaxation. Ap4A signalling causes activation of Kca2 channels through activation of P2Y1 receptors. In contrast, CyPPA acts directly on Kca2 channels. Further studies are needed to evaluate if dinucleotidic polyphosphates are released from inhibitory motor neurons.
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14
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Song NN, Lu HL, Lu C, Tong L, Huang SQ, Huang X, Chen J, Kim YC, Xu WX. Diabetes-induced colonic slow transit mediated by the up-regulation of PDGFRα + cells/SK3 in streptozotocin-induced diabetic mice. Neurogastroenterol Motil 2018; 30. [PMID: 29521017 DOI: 10.1111/nmo.13326] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 02/06/2018] [Indexed: 12/18/2022]
Abstract
BACKGROUND A major complication related to gastrointestinal (GI) symptoms in diabetic patients is chronic constipation. Constipation has serious negative impacts on quality of life; however, without a comprehensive understanding of the disease, currently available treatments cannot provide a cure. Platelet-derived growth factor receptor alpha-positive cells (PDGFRα+ cells), which form the SIP syncytium with interstitial cells of Cajal and smooth muscle cells, play important roles in GI motility. In the present study, the contributions of PDGFRα+ cells to diabetes-induced colonic slow transit were investigated in streptozotocin (STZ)-induced diabetic mice. METHODS Western blotting, quantitative PCR, contractile experiments, and intracellular recording were used in the present study. KEY RESULTS The results demonstrated that the colon length was increased in STZ-treated mice. The colonic transit of artificial fecal pellets in vitro was significantly delayed in STZ-treated mice. The mRNA and protein expression of PDGFRα, small-conductance Ca2+ -activated K channels (SK3), and P2Y1 receptors were increased in the colons of STZ-treated mice. In contractile experiments, the colonic smooth muscles were more sensitive to the SK3 agonist and antagonist (CyPPA and apamin) and the P2Y1 agonist and antagonist (MRS2365 and MRS2500) in STZ-treated mice. Intracellular recordings showed the responses of membrane potentials in colonic smooth muscle cells to CyPPA, apamin, MRS2365, and MRS2500 were more sensitive in STZ-treated mice. The electric field stimulation-induced P2Y1/SK3-dependent fast inhibitory junctional potentials (fIJPs) of colonic smooth muscles were more significantly hyperpolarized in STZ-treated mice. CONCLUSIONS AND INFERENCES These results suggest that the purinergic neurotransmitters/P2Y1/SK3 signaling pathway is up-regulated in the diabetic colons, thereby mediating diabetes-induced colonic slow transit.
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Affiliation(s)
- N-N Song
- Department of Anatomy & Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Department of Pediatric Surgery, Xin Hua Hospital, Affiliated to Shanghai, JiaoTong University School of Medicine, Shanghai, China
| | - H-L Lu
- Department of Anatomy & Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - C Lu
- Department of Anatomy & Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - L Tong
- Department of Anatomy & Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - S-Q Huang
- Department of Anatomy & Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - X Huang
- Department of Anatomy & Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - J Chen
- Department of Pediatric Surgery, Xin Hua Hospital, Affiliated to Shanghai, JiaoTong University School of Medicine, Shanghai, China
| | - Y-C Kim
- Department of Physiology, Chungbuk National University College of Medicine, Cheongju, Chungbuk, Korea
| | - W-X Xu
- Department of Anatomy & Physiology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Department of Pediatric Surgery, Xin Hua Hospital, Affiliated to Shanghai, JiaoTong University School of Medicine, Shanghai, China
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15
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He XD, Guo YM, Goyal RK. Effect of Hyperglycemia on Purinergic and Nitrergic Inhibitory Neuromuscular Transmission in the Antrum of the Stomach: Implications for Fast Gastric Emptying. Front Med (Lausanne) 2018; 5:1. [PMID: 29410956 PMCID: PMC5787141 DOI: 10.3389/fmed.2018.00001] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 01/03/2018] [Indexed: 12/27/2022] Open
Abstract
Background Hyperglycemia has been reported to enhance vagovagal reflex that causes the release of inhibitory neurotransmitter, nitric oxide (NO), at the neuromuscular junction in the antrum to relax the antrum and slow gastric emptying by stimulating glucose-sensitive afferent neurons. However, hyperglycemia has also been reported to cause fast gastric emptying that may be due to suppression of the inhibitory motor neurons. Aims The purpose of the present study was to investigate changes in inhibitory neuromuscular transmission in the gastric antrum due to hyperglycemia. Methods Inhibitory electrical junction potentials were recorded from gastric antral muscle strips, using intracellular electrodes under non-adrenergic, non-cholinergic conditions. Studies were performed in non-hyperglycemic NOD (NH-NOD), NOD mice as they develop hyperglycemia (H-NOD) and their age-matched controls. The purinergic inhibitory junction potential (pIJP) and nitrergic IJP (nIJP) were isolated pharmacologically. Results The control pIJP was large, around −18 mV and nIJP was small, around −9 mV. In NH-NOD the IJPs were not affected, but in H-NOD pIJP was nearly abolished and nIJP was significantly reduced. In H-NOD mice, membrane hyperpolarization caused by exogenous α,β-MeATP or diethylenetriamine NO adduct was similar to that in wild-type controls (P > 0.05). H-NOD smooth muscles were significantly depolarized as compared to NH-NOD smooth muscles. Conclusion These observations show that hyperglycemia causes suppression of purinergic and nitrergic transmission by acting on the motor neurons that form the last neuron in the vagovagal circuit. Moreover, the loss the neurotransmission is due to a defect in neurotransmitter release rather than a defect in signal transduction. Hyperglycemia also causes depolarization of smooth muscles that may increase their excitability.
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Affiliation(s)
- Xue-Dao He
- Department of Medicine VA Boston Healthcare System, Harvard Medical School, Boston, MA, United States
| | - Yan-Mei Guo
- Department of Medicine VA Boston Healthcare System, Harvard Medical School, Boston, MA, United States
| | - Raj K Goyal
- Department of Medicine VA Boston Healthcare System, Harvard Medical School, Boston, MA, United States
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16
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Smith TK, Koh SD. A model of the enteric neural circuitry underlying the generation of rhythmic motor patterns in the colon: the role of serotonin. Am J Physiol Gastrointest Liver Physiol 2017; 312:G1-G14. [PMID: 27789457 PMCID: PMC5283906 DOI: 10.1152/ajpgi.00337.2016] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/12/2016] [Accepted: 10/19/2016] [Indexed: 01/31/2023]
Abstract
We discuss the role of multiple cell types involved in rhythmic motor patterns in the large intestine that include tonic inhibition of the muscle layers interrupted by rhythmic colonic migrating motor complexes (CMMCs) and secretomotor activity. We propose a model that assumes these motor patterns are dependent on myenteric descending 5-hydroxytryptamine (5-HT, serotonin) interneurons. Asynchronous firing in 5-HT neurons excite inhibitory motor neurons (IMNs) to generate tonic inhibition occurring between CMMCs. IMNs release mainly nitric oxide (NO) to inhibit the muscle, intrinsic primary afferent neurons (IPANs), glial cells, and pacemaker myenteric pacemaker interstitial cells of Cajal (ICC-MY). Mucosal release of 5-HT from enterochromaffin (EC) cells excites the mucosal endings of IPANs that synapse with 5-HT descending interneurons and perhaps ascending interneurons, thereby coupling EC cell 5-HT to myenteric 5-HT neurons, synchronizing their activity. Synchronized 5-HT neurons generate a slow excitatory postsynaptic potential in IPANs via 5-HT7 receptors and excite glial cells and ascending excitatory nerve pathways that are normally inhibited by NO. Excited glial cells release prostaglandins to inhibit IMNs (disinhibition) to allow full excitation of ICC-MY and muscle by excitatory motor neurons (EMNs). EMNs release ACh and tachykinins to excite pacemaker ICC-MY and muscle, leading to the simultaneous contraction of both the longitudinal and circular muscle layers. Myenteric 5-HT neurons also project to the submucous plexus to couple motility with secretion, especially during a CMMC. Glial cells are necessary for switching between different colonic motor behaviors. This model emphasizes the importance of myenteric 5-HT neurons and the likely consequence of their coupling and uncoupling to mucosal 5-HT by IPANs during colonic motor behaviors.
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Affiliation(s)
- Terence Keith Smith
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Sang Don Koh
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
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17
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Mañé N, Jiménez-Sábado V, Jiménez M. BPTU, an allosteric antagonist of P2Y1 receptor, blocks nerve mediated inhibitory neuromuscular responses in the gastrointestinal tract of rodents. Neuropharmacology 2016; 110:376-385. [PMID: 27496690 DOI: 10.1016/j.neuropharm.2016.07.033] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 06/28/2016] [Accepted: 07/26/2016] [Indexed: 12/28/2022]
Abstract
P2Y1 receptors mediate nerve mediated purinergic inhibitory junction potentials (IJP) and relaxations in the gastrointestinal (GI) tract in a wide range of species including rodents and humans. A new P2Y1 antagonist, with a non-nucleotide structure, BPTU, has recently been described using X-ray crystallography as the first allosteric G-protein-coupled receptor antagonist located entirely outside of the helical bundle. In this study, we tested its effect on purinergic responses in the gastrointestinal tract of rodents using electrophysiological and myographic techniques. BPTU concentration dependently inhibited purinergic inhibitory junction potentials and inhibition of spontaneous motility induced by electrical field stimulation in the colon of rats (EC50 = 0.3 μM) and mice (EC50 = 0.06 μM). Mechanical inhibitory responses were also concentration-dependently blocked in the stomach of both species. Compared to MRS2500, BPTU displays a lower potency. In the rat colon nicotine induced relaxation was also blocked by BPTU. BPTU also blocked the cessation of spontaneous contractility elicited by ADPβS and the P2Y1 agonist MRS2365. We conclude that BPTU is a novel antagonist with different structural and functional properties than nucleotidic antagonists that is able to block the P2Y1 receptor located at the neuromuscular junction of the GI tract.
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Affiliation(s)
- Noemí Mañé
- Department of Cell Biology, Physiology and Immunology and Neuroscience Institute, Universitat Autònoma de Barcelona, Barcelona, Spain.
| | - Verónica Jiménez-Sábado
- Department of Cell Biology, Physiology and Immunology and Neuroscience Institute, Universitat Autònoma de Barcelona, Barcelona, Spain.
| | - Marcel Jiménez
- Department of Cell Biology, Physiology and Immunology and Neuroscience Institute, Universitat Autònoma de Barcelona, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas, (CIBERehd), Instituto de Salud Carlos III, Barcelona, Spain.
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18
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Bhattarai Y, Fried D, Gulbransen B, Kadrofske M, Fernandes R, Xu H, Galligan J. High-fat diet-induced obesity alters nitric oxide-mediated neuromuscular transmission and smooth muscle excitability in the mouse distal colon. Am J Physiol Gastrointest Liver Physiol 2016; 311:G210-20. [PMID: 27288421 PMCID: PMC5007291 DOI: 10.1152/ajpgi.00085.2016] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2016] [Accepted: 06/06/2016] [Indexed: 02/08/2023]
Abstract
We tested the hypothesis that colonic enteric neurotransmission and smooth muscle cell (SMC) function are altered in mice fed a high-fat diet (HFD). We used wild-type (WT) mice and mice lacking the β1-subunit of the BK channel (BKβ1 (-/-)). WT mice fed a HFD had increased myenteric plexus oxidative stress, a 28% decrease in nitrergic neurons, and a 20% decrease in basal nitric oxide (NO) levels. Circular muscle inhibitory junction potentials (IJPs) were reduced in HFD WT mice. The NO synthase inhibitor nitro-l-arginine (NLA) was less effective at inhibiting relaxations in HFD compared with control diet (CD) WT mice (11 vs. 37%, P < 0.05). SMCs from HFD WT mice had depolarized membrane potentials (-47 ± 2 mV) and continuous action potential firing compared with CD WT mice (-53 ± 2 mV, P < 0.05), which showed rhythmic firing. SMCs from HFD or CD fed BKβ1 (-/-) mice fired action potentials continuously. NLA depolarized membrane potential and caused continuous firing only in SMCs from CD WT mice. Sodium nitroprusside (NO donor) hyperpolarized membrane potential and changed continuous to rhythmic action potential firing in SMCs from HFD WT and BKβ1 (-/-) mice. Migrating motor complexes were disrupted in colons from BKβ1 (-/-) mice and HFD WT mice. BK channel α-subunit protein and β1-subunit mRNA expression were similar in CD and HFD WT mice. We conclude that HFD-induced obesity disrupts inhibitory neuromuscular transmission, SMC excitability, and colonic motility by promoting oxidative stress, loss of nitrergic neurons, and SMC BK channel dysfunction.
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Affiliation(s)
- Yogesh Bhattarai
- 1The Neuroscience Program, Michigan State University, East Lansing, Michigan;
| | - David Fried
- 3Department of Physiology, Michigan State University, East Lansing, Michigan; and
| | - Brian Gulbransen
- 1The Neuroscience Program, Michigan State University, East Lansing, Michigan; ,3Department of Physiology, Michigan State University, East Lansing, Michigan; and
| | - Mark Kadrofske
- 4Department of Pediatrics and Human Development, Michigan State University, East Lansing, Michigan
| | - Roxanne Fernandes
- 2Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan;
| | - Hui Xu
- 1The Neuroscience Program, Michigan State University, East Lansing, Michigan; ,2Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan;
| | - James Galligan
- The Neuroscience Program, Michigan State University, East Lansing, Michigan; Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan;
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19
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Wan HX, Hu JH, Xie R, Yang SM, Dong H. Important roles of P2Y receptors in the inflammation and cancer of digestive system. Oncotarget 2016; 7:28736-47. [PMID: 26908460 PMCID: PMC5053759 DOI: 10.18632/oncotarget.7518] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Accepted: 02/05/2016] [Indexed: 02/03/2023] Open
Abstract
Purinergic signaling is important for many biological processes in humans. Purinoceptors P2Y are widely distributed in human digestive system and different subtypes of P2Y receptors mediate different physiological functions from metabolism, proliferation, differentiation to apoptosis etc. The P2Y receptors are essential in many gastrointestinal functions and also involve in the occurrence of some digestive diseases. Since different subtypes of P2Y receptors are present on the same cell of digestive organs, varying subtypes of P2Y receptors may have opposite or synergetic functions on the same cell. Recently, growing lines of evidence strongly suggest the involvement of P2Y receptors in the pathogenesis of several digestive diseases. In this review, we will focus on their important roles in the development of digestive inflammation and cancer. We anticipate that as the special subtypes of P2Y receptors are studied in depth, specific modulators for them will have good potentials to become promising new drugs to treat human digestive diseases in the near future.
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Affiliation(s)
- Han-Xing Wan
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing, P.R. China
| | - Jian-Hong Hu
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing, P.R. China
| | - Rei Xie
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing, P.R. China
| | - Shi-Ming Yang
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing, P.R. China
| | - Hui Dong
- Department of Gastroenterology, Xinqiao Hospital, Third Military Medical University, Chongqing, P.R. China
- Division of Gastroenterology, Department of Medicine, School of Medicine, University of California, San Diego, California, USA
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20
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Mas M, Mañé N, Fernández F, Gallego D, Pumarola M, Jiménez M. P2Y(1) receptors mediate purinergic relaxation in the equine pelvic flexure. Vet J 2016; 209:74-81. [PMID: 26831180 DOI: 10.1016/j.tvjl.2016.01.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 11/11/2015] [Accepted: 01/01/2016] [Indexed: 12/12/2022]
Abstract
In the equine large intestine, the knowledge of the basic mechanisms underlying motility function is crucial to properly treat motility disorders. P2Y1 receptors are responsible for mediating purinergic colonic relaxation in several species. In vitro experimental studies of the circular muscle from the equine pelvic flexure (n = 6) were performed to characterize inhibitory and excitatory neuromuscular transmission. Electrophysiological studies showed that electrical field stimulation (EFS) evoked biphasic inhibitory junction potentials (IJPs) in smooth muscle cells: a fast IJP (IJPf) followed by a sustained IJP (IJPs). IJPs was sensitive to L-NNA 1 mM (a nitric oxide synthase inhibitor) (P <0.01), while IJPf was abolished by MRS2500 1 µM (a P2Y1 receptor antagonist) (P <0.001). EFS (5 Hz for 2 min) in the organ bath inhibited rhythmic contractions to 3.0 ± 2.5% of basal area under the curve (P <0.0001). EFS under MRS2500 1 µM or L-NNA 1 mM incubation inhibited contractions to 6.0 ± 2.8% (P <0.05) and 24.4 ± 11.3% respectively (P <0.05). Combination of MRS2500 1 µM and L-NNA 1 mM completely reversed the EFS-induced inhibition of colonic motility. Non-nitrergic, non-purinergic conditions were used to reveal voltage-dependent EFS-induced contractions sensitive to atropine 1 µM (P <0.001) and, therefore, cholinergic. In conclusion, nerve-mediated relaxation and contraction in the equine pelvic flexure involve the same mechanisms as those observed in the human colon. P2Y1 receptors mediate purinergic relaxations and are potential targets for the treatment of equine colonic motor disorders.
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Affiliation(s)
- M Mas
- Department of Cell Biology, Physiology and Immunology and Neuroscience Institute, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - N Mañé
- Department of Cell Biology, Physiology and Immunology and Neuroscience Institute, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - F Fernández
- Department of Animal Medicine and Surgery, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - D Gallego
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Salud Carlos III, Barcelona, Spain
| | - M Pumarola
- Department of Animal Medicine and Surgery, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - M Jiménez
- Department of Cell Biology, Physiology and Immunology and Neuroscience Institute, Universitat Autònoma de Barcelona, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Salud Carlos III, Barcelona, Spain.
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21
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Lam M, Mitsui R, Hashitani H. Electrical properties of purinergic transmission in smooth muscle of the guinea-pig prostate. Auton Neurosci 2016; 194:8-16. [DOI: 10.1016/j.autneu.2015.11.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 11/18/2015] [Accepted: 11/23/2015] [Indexed: 11/24/2022]
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22
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Mañé N, Viais R, Martínez-Cutillas M, Gallego D, Correia-de-Sá P, Jiménez M. Inverse gradient of nitrergic and purinergic inhibitory cotransmission in the mouse colon. Acta Physiol (Oxf) 2016; 216:120-31. [PMID: 26347033 DOI: 10.1111/apha.12599] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 07/09/2015] [Accepted: 09/02/2015] [Indexed: 02/06/2023]
Abstract
AIM Gastrointestinal smooth muscle relaxation is accomplished by the neural corelease of ATP or a related purine and nitric oxide. Contractions are triggered by acetylcholine and tachykinins. The aim of this work was to study whether regional differences in neurotransmission could partially explain the varied physiological roles of each colonic area. METHODS We used electrophysiological and myography techniques to evaluate purinergic (L-NNA 1 mm incubated tissue), nitrergic (MRS2500 0.3 μm incubated tissue) and cholinergic neurotransmission (L-NNA 1 mm and MRS2500 0.3 μm incubated tissue) in the proximal, mid and distal colon of CD1 mice (n = 42). RESULTS Purinergic electrophysiological responses elicited by single pulses (28 V) were greater in the distal (IJPfMAX = -35.3 ± 2.2 mV), followed by the mid (IJPfMAX = -30.6 ± 1.0 mV) and proximal (IJPfMAX = -11.7 ± 1.1 mV) colon. In contrast, nitrergic responses decreased from the proximal colon (IJPsMAX = -11.4 ± 1.1 mV) to the mid (IJPsMAX = -9.1 ± 0.4 mV), followed by the distal colon (IJPsMAX = -1.8 ± 0.3 mV). A similar rank of order was observed in neural mediated inhibitory mechanical responses including electrical field stimulation-mediated responses and neural tone. ADPβs concentration-response curve was shifted to the left in the distal colon. In contrast, NaNP responses did not differ between regions. Cholinergic neurotransmission elicited contractions of a similar amplitude throughout the colon. CONCLUSION An inverse gradient of purinergic and nitrergic neurotransmission exists through the mouse colon. The proximal and mid colon have a predominant nitrergic neurotransmission probably due to the fact that their storage function requires sustained relaxations. The distal colon, in contrast, has mainly purinergic neurotransmission responsible for the phasic relaxations needed to propel dehydrated faeces.
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Affiliation(s)
- N. Mañé
- Department of Cell Biology, Physiology and Immunology and Neuroscience Institute; Universitat Autònoma de Barcelona; Barcelona Spain
| | - R. Viais
- Center for Drug Discovery and Innovative Medicines (MedInUP); Instituto de Ciências Biomédicas Abel Salazar da Universidade do Porto (ICBAS-UP); Porto Portugal
| | - M. Martínez-Cutillas
- Department of Cell Biology, Physiology and Immunology and Neuroscience Institute; Universitat Autònoma de Barcelona; Barcelona Spain
| | - D. Gallego
- Department of Cell Biology, Physiology and Immunology and Neuroscience Institute; Universitat Autònoma de Barcelona; Barcelona Spain
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd); Instituto de Salud Carlos III; Barcelona Spain
| | - P. Correia-de-Sá
- Center for Drug Discovery and Innovative Medicines (MedInUP); Instituto de Ciências Biomédicas Abel Salazar da Universidade do Porto (ICBAS-UP); Porto Portugal
| | - M. Jiménez
- Department of Cell Biology, Physiology and Immunology and Neuroscience Institute; Universitat Autònoma de Barcelona; Barcelona Spain
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd); Instituto de Salud Carlos III; Barcelona Spain
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23
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Zhang Y, Paterson WG. Characterization of the peristaltic reflex in murine distal colon. Can J Physiol Pharmacol 2015; 94:190-198. [PMID: 26524247 DOI: 10.1139/cjpp-2015-0086] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ascending and descending neuromuscular reflexes play an important role in gastrointestinal motility. However, the underlying mechanisms in colon are incompletely understood. Nerve stimulation (NS)- and balloon distention (BD)-mediated reflexes in distal colonic circular smooth muscle (CSM) and longitudinal smooth muscle (LSM) of mice were investigated using conventional intracellular recordings. In the CSM, NS evoked ascending purinergic inhibitory junction potentials (IJPs), whereas BD induced atropine-sensitive ascending depolarization with superimposed action potentials (APs). The ascending depolarization reached a peak ∼4-7 s after the onset of distention and gradually returned to baseline after termination of the distention. In the LSM, NS produced an ascending biphasic IJP followed by a train of atropine-sensitive APs. Both stimuli produced similar descending IJPs in CSM and LSM, which were blocked by MRS-2500 and MRS-2179, putative purinergic receptor blockers. These data indicate that in the murine distal colon, descending purinergic inhibition in both CSM and LSM occurs. Ascending responses are more complex, with NS producing both inhibition and excitation to CSM and LSM, and BD evoking only cholinergic excitation.
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Affiliation(s)
- Yong Zhang
- a Gastrointestinal Diseases Research Unit, Queen's University and Kingston General Hospital, Kingston, Ontario, Canada
| | - William G Paterson
- b Gastrointestinal Diseases Research Unit and the Departments of Biology, Biomedical and Molecular Sciences, and Medicine, Queen's University and Kingston General Hospital, Kingston, Ontario, Canada
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24
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Wang GD, Wang XY, Liu S, Xia Y, Zou F, Qu M, Needleman BJ, Mikami DJ, Wood JD. β-Nicotinamide adenine dinucleotide acts at prejunctional adenosine A1 receptors to suppress inhibitory musculomotor neurotransmission in guinea pig colon and human jejunum. Am J Physiol Gastrointest Liver Physiol 2015; 308:G955-63. [PMID: 25813057 PMCID: PMC4451321 DOI: 10.1152/ajpgi.00430.2014] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 03/18/2015] [Indexed: 01/31/2023]
Abstract
Intracellular microelectrodes were used to record neurogenic inhibitory junction potentials in the intestinal circular muscle coat. Electrical field stimulation was used to stimulate intramural neurons and evoke contraction of the smooth musculature. Exposure to β-nicotinamide adenine dinucleotide (β-NAD) did not alter smooth muscle membrane potential in guinea pig colon or human jejunum. ATP, ADP, β-NAD, and adenosine, as well as the purinergic P2Y1 receptor antagonists MRS 2179 and MRS 2500 and the adenosine A1 receptor agonist 2-chloro-N6-cyclopentyladenosine, each suppressed inhibitory junction potentials in guinea pig and human preparations. β-NAD suppressed contractile force of twitch-like contractions evoked by electrical field stimulation in guinea pig and human preparations. P2Y1 receptor antagonists did not reverse this action. Stimulation of adenosine A1 receptors with 2-chloro-N6-cyclopentyladenosine suppressed the force of twitch contractions evoked by electrical field stimulation in like manner to the action of β-NAD. Blockade of adenosine A1 receptors with 8-cyclopentyl-1,3-dipropylxanthine suppressed the inhibitory action of β-NAD on the force of electrically evoked contractions. The results do not support an inhibitory neurotransmitter role for β-NAD at intestinal neuromuscular junctions. The data suggest that β-NAD is a ligand for the adenosine A1 receptor subtype expressed by neurons in the enteric nervous system. The influence of β-NAD on intestinal motility emerges from adenosine A1 receptor-mediated suppression of neurotransmitter release at inhibitory neuromuscular junctions.
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Affiliation(s)
- Guo-Du Wang
- 1Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, Ohio;
| | - Xi-Yu Wang
- 1Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, Ohio;
| | - Sumei Liu
- 1Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, Ohio;
| | - Yun Xia
- 1Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, Ohio; ,2Department of Anesthesiology, College of Medicine, The Ohio State University, Columbus, Ohio; and
| | - Fei Zou
- 1Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, Ohio;
| | - Meihua Qu
- 1Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, Ohio;
| | - Bradley J. Needleman
- 3Department of Surgery, College of Medicine, The Ohio State University, Columbus, Ohio
| | - Dean J. Mikami
- 3Department of Surgery, College of Medicine, The Ohio State University, Columbus, Ohio
| | - Jackie D. Wood
- 1Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, Ohio;
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25
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King BF. Purinergic signalling in the enteric nervous system (An overview of current perspectives). Auton Neurosci 2015; 191:141-7. [PMID: 26049261 DOI: 10.1016/j.autneu.2015.05.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Purinergic Signalling in the Enteric Nervous System involves the regulated release of ATP (or a structurally-related nucleotide) which activates an extensive suite of membrane-inserted receptors (P2X and P2Y subtypes) on a variety of cell types in the gastrointestinal tract. P2X receptors are gated ion-channels permeable to sodium, potassium and calcium. They depolarise cells, act as a pathway for calcium influx to activate calcium-dependent processes and initiate gene transcription, interact at a molecular level as a form of self-regulation with lipids within the cell wall (e.g. PIP2) and cross-react with other membrane-inserted receptors to regulate their activity (e.g. nAChRs). P2Y receptors are metabotropic receptors that couple to G-proteins. They may release calcium ions from intracellular stores to activate calcium-dependent processes, but also may activate calcium-independent signalling pathways and influence gene transcription. Originally ATP was a candidate only for NANC neurotransmission, for inhibitory motoneurons supplying the muscularis externa of the gastrointestinal tract and bringing about the fast IJP. Purinergic signalling later included neuron-neuron signalling in the ENS, via the production of either fast or slow EPSPs. Later still, purinergic signalling included the neuro-epithelial synapse-for efferent signalling to epithelia cells participating in secretion and absorption, and afferent signalling for chemoreception and mechanoreception at the surface of the mucosa. Many aspects of purinergic signalling have since been addressed in a series of highly-focussed and authoritative reviews. In this overview however, the current focus is on key aspects of purinergic signalling where there remains uncertainty and ambiguity, with the view to stimulating further research in these areas.
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Affiliation(s)
- Brian F King
- University College London (UCL), Department of Neuroscience, Physiology and Pharmacology (NPP), Royal Free Campus, Rowland Hill Street, Hampstead, London NW3 2PF, United Kingdom.
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26
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Abstract
The role of adenosine 5'-triphosphate (ATP) as a major intracellular energy source is well-established. In addition, ATP and related nucleotides have widespread extracellular actions via the ionotropic P2X (ligand-gated cation channels) and metabotropic P2Y (G protein-coupled) receptors. Numerous experimental techniques, including myography, electrophysiology and biochemical measurement of neurotransmitter release, have been used to show that ATP has several major roles as a neurotransmitter in peripheral nerves. When released from enteric nerves of the gastrointestinal tract it acts as an inhibitory neurotransmitter, mediating descending muscle relaxation during peristalsis. ATP is also an excitatory cotransmitter in autonomic nerves; 1) It is costored with noradrenaline in synaptic vesicles in postganglionic sympathetic nerves innervating smooth muscle preparations, such as the vas deferens and most arteries. When coreleased with noradrenaline, ATP acts at postjunctional P2X1 receptors to evoke depolarisation, Ca(2+) influx, Ca(2+) sensitisation and contraction. 2) ATP is also coreleased with acetylcholine from postganglionic parasympathetic nerves innervating the urinary bladder and again acts at postjunctional P2X1 receptors, and possibly also a P2X1+4 heteromer, to elicit smooth muscle contraction. In both cases the neurotransmitter actions of ATP are terminated by dephosphorylation by extracellular, membrane-bound enzymes and soluble nucleotidases released from postganglionic nerves. There are indications of an increased contribution of ATP to control of blood pressure in hypertension, but further research is needed to clarify this possibility. More promising is the upregulation of P2X receptors in dysfunctional bladder, including interstitial cystitis, idiopathic detrusor instability and overactive bladder syndrome. Consequently, these roles of ATP are of great therapeutic interest and are increasingly being targeted by pharmaceutical companies.
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Affiliation(s)
- Charles Kennedy
- Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, 161 Cathedral Street, Glasgow G4 0RE, United Kingdom.
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27
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Baker SA, Hennig GW, Ward SM, Sanders KM. Temporal sequence of activation of cells involved in purinergic neurotransmission in the colon. J Physiol 2015; 593:1945-63. [PMID: 25627983 DOI: 10.1113/jphysiol.2014.287599] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 01/21/2015] [Indexed: 12/27/2022] Open
Abstract
KEY POINTS Platelet derived growth factor receptor α (PDGFRα(+) ) cells in colonic muscles are innervated by enteric inhibitory motor neurons. PDGFRα(+) cells generate Ca(2+) transients in response to exogenous purines and these responses were blocked by MRS-2500. Stimulation of enteric neurons, with cholinergic and nitrergic components blocked, evoked Ca(2+) transients in PDGFRα(+) and smooth muscle cells (SMCs). Responses to nerve stimulation were abolished by MRS-2500 and not observed in muscles with genetic deactivation of P2Y1 receptors. Ca(2+) transients evoked by nerve stimulation in PDGFRα(+) cells showed the same temporal characteristics as electrophysiological responses. PDGFRα(+) cells express gap junction genes, and drugs that inhibit gap junctions blocked neural responses in SMCs, but not in nerve processes or PDGFRα(+) cells. PDGFRα(+) cells are directly innervated by inhibitory motor neurons and purinergic responses are conducted to SMCs via gap junctions. ABSTRACT Interstitial cells, known as platelet derived growth factor receptor α (PDGFRα(+) ) cells, are closely associated with varicosities of enteric motor neurons and suggested to mediate purinergic hyperpolarization responses in smooth muscles of the gastrointestinal tract (GI), but this concept has not been demonstrated directly in intact muscles. We used confocal microscopy to monitor Ca(2+) transients in neurons and post-junctional cells of the murine colon evoked by exogenous purines or electrical field stimulation (EFS) of enteric neurons. EFS (1-20 Hz) caused Ca(2+) transients in enteric motor nerve processes and then in PDGFRα(+) cells shortly after the onset of stimulation (latency from EFS was 280 ms at 10 Hz). Responses in smooth muscle cells (SMCs) were typically a small decrease in Ca(2+) fluorescence just after the initiation of Ca(2+) transients in PDGFRα(+) cells. Upon cessation of EFS, several fast Ca(2+) transients were noted in SMCs (rebound excitation). Strong correlation was noted in the temporal characteristics of Ca(2+) transients evoked in PDGFRα(+) cells by EFS and inhibitory junction potentials (IJPs) recorded with intracellular microelectrodes. Ca(2+) transients and IJPs elicited by EFS were blocked by MRS-2500, a P2Y1 antagonist, and absent in P2ry1((-/-)) mice. PDGFRα(+) cells expressed gap junction genes, and gap junction uncouplers, 18β-glycyrrhetinic acid (18β-GA) and octanol blocked Ca(2+) transients in SMCs but not in neurons or PDGFRα(+) cells. IJPs recorded from SMCs were also blocked. These findings demonstrate direct innervation of PDGFRα(+) cells by motor neurons. PDGFRα(+) cells are primary targets for purinergic neurotransmitter(s) in enteric inhibitory neurotransmission. Hyperpolarization responses are conducted to SMCs via gap junctions.
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Affiliation(s)
- Salah A Baker
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
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28
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Martinez-Cutillas M, Gil V, Mañé N, Clavé P, Gallego D, Martin MT, Jimenez M. Potential role of the gaseous mediator hydrogen sulphide (H2S) in inhibition of human colonic contractility. Pharmacol Res 2015; 93:52-63. [PMID: 25641403 DOI: 10.1016/j.phrs.2015.01.002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Revised: 01/21/2015] [Accepted: 01/21/2015] [Indexed: 01/08/2023]
Abstract
BACKGROUND Hydrogen sulphide (H2S) is an endogenous signalling molecule that might play a physiologically relevant role in gastrointestinal motility. Cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE) are two enzymes responsible for H2S production. d,l-Propargylglycine (PAG) is a CSE inhibitor whereas both aminooxyacetic acid (AOAA) and hydroxylamine (HA) are CBS inhibitors. The characterization of H2S responses and its mechanism of action are crucial to define H2S function. METHODS Human colonic strips were used to investigate the role of H2S on contractility (muscle bath) and smooth muscle electrophysiology (microelectrodes). NaHS was used as a H2S donor. RESULTS Combination of PAG and AOAA depolarized the smooth muscle (5-6mV, n=4) and elicited a transient increase in tone (260.5±92.8mg, n=12). No effect was observed on neural mediated inhibitory junction potential or relaxation. In the presence of tetrodotoxin 1μM, NaHS concentration-dependently inhibited spontaneous contractions (EC50=329.2μM, n=18). This effect was partially reduced by the guanylyl cyclase inhibitor ODQ 10μM (EC50=2.6μM, n=12) and by l-NNA 1mM (EC50=1.4mM, n=8). NaHS reversibly blocked neural mediated cholinergic (EC50=2mM) and tachykinergic (EC50=5.7mM) contractions. NaHS concentration-dependently reduced the increase in spontaneous mechanical activity (AUC) induced by carbachol (EC50=1.9mM) and NKA (EC50=1.7mM AUC). CONCLUSIONS H2S might be an endogenous gasomediator regulating human colonic contractility. Its inhibitory effect is observed at high concentrations and could be mediated by a direct effect on smooth muscle with a possible synergistic effect with NO, as well as by an interaction with the cholinergic and tachykinergic neural mediated pathways.
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Affiliation(s)
- M Martinez-Cutillas
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - V Gil
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - N Mañé
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - P Clavé
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Salud Carlos III, Barcelona, Spain; Fundació de Gastroenterologia Dr Vilardell and Department of Surgery, Hospital de Mataró, Mataró, Barcelona, Spain
| | - D Gallego
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Salud Carlos III, Barcelona, Spain
| | - M T Martin
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Salud Carlos III, Barcelona, Spain
| | - M Jimenez
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Salud Carlos III, Barcelona, Spain.
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29
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EP2 and EP4 receptors mediate PGE2 induced relaxation in murine colonic circular muscle: Pharmacological characterization. Pharmacol Res 2014; 90:76-86. [DOI: 10.1016/j.phrs.2014.10.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 10/07/2014] [Accepted: 10/13/2014] [Indexed: 01/27/2023]
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30
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Gil V, Parsons S, Gallego D, Huizinga J, Jimenez M. Effects of hydrogen sulphide on motility patterns in the rat colon. Br J Pharmacol 2014; 169:34-50. [PMID: 23297830 DOI: 10.1111/bph.12100] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Revised: 11/26/2012] [Accepted: 12/17/2012] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND AND PURPOSE Hydrogen sulphide (H2 S) is an endogenous gaseous signalling molecule with putative functions in gastrointestinal motility regulation. Characterization of H2 S effects on colonic motility is crucial to establish its potential use as therapeutic agent in the treatment of colonic disorders. EXPERIMENTAL APPROACH H2 S effects on colonic motility were characterized using video recordings and construction of spatio-temporal maps. Microelectrode and muscle bath studies were performed to investigate the mechanisms underlying H2 S effects. NaHS was used as the source of H2 S. KEY RESULTS Rhythmic propulsive motor complexes (RPMCs) and ripples were observed in colonic spatio-temporal maps. Serosal addition of NaHS concentration-dependently inhibited RPMCs. In contrast, NaHS increased amplitude of the ripples without changing their frequency. Therefore, ripples became the predominant motor pattern. Neuronal blockade with lidocaine inhibited RPMCs, which were restored after administration of carbachol. Subsequent addition of NaHS inhibited RPMCs. Luminal addition of NaHS did not modify motility patterns. NaHS inhibited cholinergic excitatory junction potentials, carbachol-induced contractions and hyperpolarized smooth muscle cells, but did not modify slow wave activity. CONCLUSIONS AND IMPLICATIONS H2 S modulated colonic motility inhibiting propulsive contractile activity and enhancing the amplitude of ripples, promoting mixing. Muscle hyperpolarization and inhibition of neurally mediated cholinergic responses contributed to the inhibitory effect on propulsive activity. H2 S effects were not related to changes in the frequency of slow wave activity originating in the network of interstitial cells of Cajal located near the submuscular plexus. Luminal H2 S did not modify colonic motility probably because of epithelial detoxification.
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Affiliation(s)
- V Gil
- Department of Cell Biology, Physiology and Immunology/Neuroscience Institute, Universitat Autònoma de Barcelona (UAB), Barcelona, Spain
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31
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Jiménez M, Clavé P, Accarino A, Gallego D. Purinergic neuromuscular transmission in the gastrointestinal tract; functional basis for future clinical and pharmacological studies. Br J Pharmacol 2014; 171:4360-75. [PMID: 24910216 DOI: 10.1111/bph.12802] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Revised: 05/14/2014] [Accepted: 05/24/2014] [Indexed: 12/13/2022] Open
Abstract
Nerve-mediated relaxation is necessary for the correct accomplishment of gastrointestinal (GI) motility. In the GI tract, NO and a purine are probably released by the same inhibitory motor neuron as inhibitory co-transmitters. The P2Y1 receptor has been recently identified as the receptor responsible for purinergic smooth muscle hyperpolarization and relaxation in the human gut. This finding has been confirmed in P2Y1 -deficient mice where purinergic neurotransmission is absent and transit time impaired. However, the mechanisms responsible for nerve-mediated relaxation, including the identification of the purinergic neurotransmitter(s) itself, are still debatable. Possibly different mechanisms of nerve-mediated relaxation are present in the GI tract. Functional demonstration of purinergic neuromuscular transmission has not been correlated with structural studies. Labelling of purinergic neurons is still experimental and is not performed in routine pathology studies from human samples, even when possible neuromuscular impairment is suspected. Accordingly, the contribution of purinergic neurotransmission in neuromuscular diseases affecting GI motility is not known. In this review, we have focused on the physiological mechanisms responsible for nerve-mediated purinergic relaxation providing the functional basis for possible future clinical and pharmacological studies on GI motility targeting purine receptors.
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Affiliation(s)
- Marcel Jiménez
- Department of Cell Biology, Physiology and Immunology, Neurosciences Institute, Universitat Autònoma de Barcelona, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd), Instituto de Salud Carlos III, Barcelona, Spain
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32
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Kurahashi M, Mutafova-Yambolieva V, Koh SD, Sanders KM. Platelet-derived growth factor receptor-α-positive cells and not smooth muscle cells mediate purinergic hyperpolarization in murine colonic muscles. Am J Physiol Cell Physiol 2014; 307:C561-70. [PMID: 25055825 DOI: 10.1152/ajpcell.00080.2014] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Enteric inhibitory neurotransmission is an important feature of the neural regulation of gastrointestinal motility. Purinergic neurotransmission, via P2Y1 receptors, mediates one phase of inhibitory neural control. For decades, ATP has been assumed to be the purinergic neurotransmitter and smooth muscle cells (SMCs) have been considered the primary targets for inhibitory neurotransmission. Recent experiments have cast doubt on both of these assumptions and suggested that another cell type, platelet-derived growth factor receptor-α-positive (PDGFRα(+)) cells, is the target for purinergic neurotransmission. We compared responses of PDGFRα(+) cells and SMCs to several purine compounds to determine if these cells responded in a manner consistent with enteric inhibitory neurotransmission. ATP hyperpolarized PDGFRα(+) cells but depolarized SMCs. Only part of the ATP response in PDGFRα(+) cells was blocked by MRS 2500, a P2Y1 antagonist. ADP, MRS 2365, β-NAD, and adenosine 5-diphosphate-ribose, P2Y1 agonists, hyperpolarized PDGFRα(+) cells, and these responses were blocked by MRS 2500. Adenosine 5-diphosphate-ribose was more potent in eliciting hyperpolarization responses than β-NAD. P2Y1 agonists failed to elicit responses in SMCs. Small hyperpolarization responses were elicited in SMCs by a small-conductance Ca(2+)-activated K(+) channel agonist, cyclohexyl-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-pyrimidin-4-yl]-amine, consistent with the low expression and current density of small-conductance Ca(2+)-activated K(+) channels in these cells. Large-amplitude hyperpolarization responses, elicited in PDGFRα(+) cells, but not SMCs, by P2Y1 agonists are consistent with the generation of inhibitory junction potentials in intact muscles in response to purinergic neurotransmission. The responses of PDGFRα(+) cells and SMCs to purines suggest that SMCs are unlikely targets for purinergic neurotransmission in colonic muscles.
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Affiliation(s)
- Masaaki Kurahashi
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | | | - Sang Don Koh
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
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Martínez-Cutillas M, Gil V, Gallego D, Mañé N, Clavé P, Martín MT, Jiménez M. α,β-meATP mimics the effects of the purinergic neurotransmitter in the human and rat colon. Eur J Pharmacol 2014; 740:442-54. [PMID: 24998877 DOI: 10.1016/j.ejphar.2014.06.048] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Revised: 06/13/2014] [Accepted: 06/17/2014] [Indexed: 02/05/2023]
Abstract
The purine receptor involved in inhibitory responses in the gastrointestinal tract has been recently identified. P2Y1 receptor activation mediates the fast component of the inhibitory junction potential (IJPf) and the non-nitrergic relaxation. The aim of the present work has been to investigate which purinergic agonist better mimics endogenous responses. We used different agonist and antagonist of P2 receptors. Contractility and microelectrode experiments were used to compare the effects of exogenously added purines and electrical field stimulation (EFS)-induced nerve mediated effects in rat and human colonic strips. In rat colon, the IJPf and EFS-induced inhibition of contractions were concentration-dependently inhibited by the P2Y1 antagonist MRS2500 but not by iso-PPADS or NF023 (P2X antagonists) up to 1 μM. In samples from human colon, EFS-induced inhibition of contractions was inhibited by either MRS2500 or apamin (1 μM) but not by iso-PPADS. In both species, α,β-meATP, a stable analog of ATP, caused inhibition of spontaneous contractions. α,β-meATP effect was concentration-dependent (EC50: 2.7 μM rat, 4.4 μM human) and was antagonized by either MRS2500 or apamin but unaffected by P2X antagonists. ATP, ADP, β-NAD and ADP-ribose inhibited spontaneous contractions but did not show the same sensitivity profile to purine receptor antagonists as EFS-induced inhibition of contractions. The effect of α,β-meATP is due to P2Y1 receptor activation leading the opening of sKca channels. Accordingly, α,β-meATP mimics the endogenous purinergic mediator. In contrast, exogenously added putative neurotransmitters do not exactly mimic the endogenous mediator. Quick degradation by ecto-nuclease or different distribution of receptors (junctionally vs extrajunctionally) might explain these results.
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Affiliation(s)
- Míriam Martínez-Cutillas
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Víctor Gil
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Diana Gallego
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas, (CIBERehd), Instituto de Salud Carlos III, Barcelona, Spain
| | - Noemí Mañé
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Pere Clavé
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas, (CIBERehd), Instituto de Salud Carlos III, Barcelona, Spain; Fundació de Gastroenterologia Dr Vilardell and Department of Surgery, Hospital de Mataró, Mataró, Barcelona, Spain
| | - María Teresa Martín
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas, (CIBERehd), Instituto de Salud Carlos III, Barcelona, Spain
| | - Marcel Jiménez
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona, Barcelona, Spain; Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas, (CIBERehd), Instituto de Salud Carlos III, Barcelona, Spain.
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Dynamics of inhibitory co-transmission, membrane potential and pacemaker activity determine neuromyogenic function in the rat colon. Pflugers Arch 2014; 466:2305-21. [DOI: 10.1007/s00424-014-1500-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 02/26/2014] [Accepted: 03/10/2014] [Indexed: 01/26/2023]
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Burnstock G. Purinergic signalling in the gastrointestinal tract and related organs in health and disease. Purinergic Signal 2014; 10:3-50. [PMID: 24307520 PMCID: PMC3944042 DOI: 10.1007/s11302-013-9397-9] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2013] [Accepted: 10/24/2013] [Indexed: 01/04/2023] Open
Abstract
Purinergic signalling plays major roles in the physiology and pathophysiology of digestive organs. Adenosine 5'-triphosphate (ATP), together with nitric oxide and vasoactive intestinal peptide, is a cotransmitter in non-adrenergic, non-cholinergic inhibitory neuromuscular transmission. P2X and P2Y receptors are widely expressed in myenteric and submucous enteric plexuses and participate in sympathetic transmission and neuromodulation involved in enteric reflex activities, as well as influencing gastric and intestinal epithelial secretion and vascular activities. Involvement of purinergic signalling has been identified in a variety of diseases, including inflammatory bowel disease, ischaemia, diabetes and cancer. Purinergic mechanosensory transduction forms the basis of enteric nociception, where ATP released from mucosal epithelial cells by distension activates nociceptive subepithelial primary afferent sensory fibres expressing P2X3 receptors to send messages to the pain centres in the central nervous system via interneurons in the spinal cord. Purinergic signalling is also involved in salivary gland and bile duct secretion.
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Affiliation(s)
- Geoffrey Burnstock
- Autonomic Neuroscience Centre, University College Medical School, Rowland Hill Street, London, NW3 2PF, UK,
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Lee H, Koh BH, Peri LE, Sanders KM, Koh SD. Purinergic inhibitory regulation of murine detrusor muscles mediated by PDGFRα+ interstitial cells. J Physiol 2014; 592:1283-93. [PMID: 24396055 DOI: 10.1113/jphysiol.2013.267989] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Purines induce transient contraction and prolonged relaxation of detrusor muscles. Transient contraction could be due to activation of inward currents in smooth muscle cells, but the mechanism of purinergic relaxation has not been determined. We recently reported a new class of interstitial cells in detrusor muscles and showed that these cells could be identified with antibodies against platelet-derived growth factor receptor-α (PDGFRα(+) cells). The current density of small conductance Ca(2+)-activated K(+) (SK) channels in these cells is far higher (∼100 times) than in smooth muscle cells. Thus, we examined purinergic receptor (P2Y) mediated SK channel activation as a mechanism for purinergic relaxation. P2Y receptors (mainly P2ry1 gene) were highly expressed in PDGFRα(+) cells. Under voltage clamp conditions, ATP activated large outward currents in PDGFRα(+) cells that were inhibited by blockers of SK channels. ATP also induced significant hyperpolarization under current clamp conditions. A P2Y1 agonist, MRS2365, mimicked the effects of ATP, and a P2Y1 antagonist, MRS2500, inhibited ATP-activated SK currents. Responses to ATP were largely abolished in PDGFRα(+) cells of P2ry1(-/-) mice, and no response was elicited by MRS2365 in these cells. A P2X receptor agonist had no effect on PDGFRα(+) cells but, like ATP, activated transient inward currents in smooth muscle cells (SMCs). A P2Y1 antagonist decreased nerve-evoked relaxation. These data suggest that purines activate SK currents via mainly P2Y1 receptors in PDGFRα(+) cells. Our findings provide an explanation for purinergic relaxation in detrusor muscles and show that there are no discrete inhibitory nerve fibres. A dual receptive field for purines provides the basis for inhibitory neural regulation of excitability.
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Affiliation(s)
- Haeyeong Lee
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, 1664 N. Virginia St MS 0352, Reno, NV 89557, USA.
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Baker SA, Hennig GW, Salter AK, Kurahashi M, Ward SM, Sanders KM. Distribution and Ca(2+) signalling of fibroblast-like (PDGFR(+)) cells in the murine gastric fundus. J Physiol 2013; 591:6193-208. [PMID: 24144881 DOI: 10.1113/jphysiol.2013.264747] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Platelet-derived growth factor receptor α positive (PDGFRα(+)) cells are suggested to mediate purinergic inputs in GI muscles, but the responsiveness of these cells to purines in situ has not been evaluated. We developed techniques to label and visualize PDGFRα(+) cells in murine gastric fundus, load cells with Ca(2+) indicators, and follow their activity via digital imaging. Immunolabelling demonstrated a high density of PDGFRα(+) cells in the fundus. Cells were isolated and purified by fluorescence-activated cell sorting (FACS) using endogenous expression of enhanced green fluorescent protein (eGFP) driven off the Pdgfra promoter. Quantitative PCR showed high levels of expression of purinergic P2Y1 receptors and SK3 K(+) channels in PDGFRα(+) cells. Ca(2+) imaging was used to characterize spontaneous Ca(2+) transients and responses to purines in PDGFRα(+) cells in situ. ATP, ADP, UTP and β-NAD elicited robust Ca(2+) transients in PDGFRα(+) cells. Ca(2+) transients were also elicited by the P2Y1-specific agonist (N)-methanocarba-2MeSADP (MRS-2365), and inhibited by MRS-2500, a P2Y1-specific antagonist. Responses to ADP, MRS-2365 and β-NAD were absent in PDGFRα(+) cells from P2ry1((-/-)) mice, but responses to ATP were retained. Purine-evoked Ca(2+) transients were mediated through Ca(2+) release mechanisms. Inhibitors of phospholipase C (U-73122), IP3 (2-APB), ryanodine receptors (Ryanodine) and SERCA pump (cyclopiazonic acid and thapsigargin) abolished Ca(2+) transients elicited by purines. This study provides a link between purine binding to P2Y1 receptors and activation of SK3 channels in PDGFRα(+) cells. Activation of Ca(2+) release is likely to be the signalling mechanism in PDGFRα(+) cells responsible for the transduction of purinergic enteric inhibitory input in gastric fundus muscles.
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Affiliation(s)
- Salah A Baker
- K. M. Sanders: Department of Physiology and Cell Biology, University of Nevada School of Medicine, MS 352, Reno, NV 89557, USA.
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Koh SD, Rhee PL. Ionic Conductance(s) in Response to Post-junctional Potentials. J Neurogastroenterol Motil 2013; 19:426-32. [PMID: 24199003 PMCID: PMC3816177 DOI: 10.5056/jnm.2013.19.4.426] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Revised: 08/28/2013] [Accepted: 08/30/2013] [Indexed: 01/29/2023] Open
Abstract
The gastrointestinal motility is regulated by extrinsic and intrinsic neural regulation. Intrinsic neural pathways are controlled by sensory input, inter-neuronal relay and motor output. Enteric motor neurons release many transmitters which affect post-junctional responses. Post-junctional responses can be excitatory and inhibitory depending on neurotransmitters. Excitatory neurotransmitters induce depolarization and contraction. In contrast, inhibitory neurotransmitters hyperpolarize and relaxe the gastrointestinal smooth muscle. Smooth muscle syncytium is composed of smooth muscle cells, interstitial cells of Cajal and platelet-derived growth factor receptor α-positive (PDGFRα(+)) cells (SIP syncytium). Specific expression of receptors and ion channels in these cells can be affected by neurotransmitters. In recent years, molecular reporter expression techniques are able to study the properties of ion channels and receptors in isolated specialized cells. In this review, we will discuss the mechanisms of ion channels to interpret the post-junctional responses in the gastrointestinal smooth muscles.
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Affiliation(s)
- Sang Don Koh
- Department of Physiology and Cell Biology, University of Nevada, School of Medicine, Reno, NV, USA
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Antonioli L, Colucci R, Pellegrini C, Giustarini G, Tuccori M, Blandizzi C, Fornai M. The role of purinergic pathways in the pathophysiology of gut diseases: pharmacological modulation and potential therapeutic applications. Pharmacol Ther 2013; 139:157-88. [PMID: 23588157 DOI: 10.1016/j.pharmthera.2013.04.002] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Accepted: 03/15/2013] [Indexed: 02/08/2023]
Abstract
Gut homeostasis results from complex neuro-immune interactions aimed at triggering stereotypical and specific programs of coordinated mucosal secretion and powerful motor propulsion. A prominent role in the regulation of this highly integrated network, comprising a variety of immune/inflammatory cells and the enteric nervous system, is played by purinergic mediators. The cells of the digestive tract are literally plunged into a "biological sea" of functionally active nucleotides and nucleosides, which carry out the critical task of driving regulatory interventions on cellular functions through the activation of P1 and P2 receptors. Intensive research efforts are being made to achieve an integrated view of the purinergic system, since it is emerging that the various components of purinergic pathways (i.e., enzymes, transporters, mediators and receptors) are mutually linked entities, deputed to finely modulating the magnitude and the duration of purinergic signaling, and that alterations occurring in this balanced network could be intimately involved in the pathophysiology of several gut disorders. This review article intends to provide a critical appraisal of current knowledge on the purinergic system role in the regulation of gastrointestinal functions, considering these pathways as a whole integrated network, which is capable of finely controlling the levels of bioactive nucleotides and nucleosides in the biophase of their respective receptors. Special attention is paid to the mechanisms through which alterations in the various compartments of the purinergic system could contribute to the pathophysiology of gut disorders, and to the possibility of counteracting such dysfunctions by means of pharmacological interventions on purinergic molecular targets.
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Affiliation(s)
- Luca Antonioli
- Department of Clinical and Experimental Medicine, University of Pisa, Italy.
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Gil V, Martínez-Cutillas M, Mañé N, Martín MT, Jiménez M, Gallego D. P2Y(1) knockout mice lack purinergic neuromuscular transmission in the antrum and cecum. Neurogastroenterol Motil 2013; 25:e170-82. [PMID: 23323764 DOI: 10.1111/nmo.12060] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
BACKGROUND Pharmacological studies using selective P2Y(1) antagonists, such as MRS2500, and studies with P2Y(1)(-/-) knockout mice have demonstrated that purinergic neuromuscular transmission is mediated by P2Y(1) receptors in the colon. The aim of the present study was to test whether P2Y(1) receptors are involved in purinergic neurotransmission in the antrum and cecum. METHODS Microelectrode recordings were performed on strips from the antrum and cecum of wild type animals (WT) and P2Y(1)(-/-) mice. KEY RESULTS In the antrum, no differences in resting membrane potential and slow wave activity were observed between groups. In WT animals, electrical field stimulation elicited a MRS2500-sensitive inhibitory junction potential (IJP). In P2Y(1)(-/-) mice, a nitrergic IJP (N(ω) -nitro-l-arginine-sensitive), but not a purinergic IJP was recorded. This IJP was equivalent to the response obtained in strips from WT animals previously incubated with MRS2500. Similar results were obtained in the cecum: 1- the purinergic IJP (MRS2500-sensitive) recorded in WT animals was absent in P2Y(1)(-/-) mice 2- nitrergic neurotransmission was preserved in both groups. Moreover, 1- spontaneous IJP (MRS2500-sensitive) could be recorded in WT, but not in P2Y(1)(-/-) mice 2- MRS2365 a P2Y(1) agonist caused smooth muscle hyperpolarization in WT, but not in P2Y(1) (-/-) animals, and 3- β-NAD caused smooth muscle hyperpolarization both in WT and P2Y(1)(-/-) animals. CONCLUSIONS & INFERENCES 1- P2Y(1) receptor is the general mechanism of purinergic inhibition in the gastrointestinal tract, 2- P2Y(1)(-/-) mouse is a useful animal model to study selective impairment of purinergic neurotransmission and 3- P2Y(1)(-/-) mouse might help in the identification of purinergic neurotransmitter(s).
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Affiliation(s)
- V Gil
- Department of Cell Biology, Physiology and Immunology and Neuroscience Institute, Universitat Autònoma de Barcelona, Bellaterra, Spain
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41
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Goyal RK, Sullivan MP, Chaudhury A. Progress in understanding of inhibitory purinergic neuromuscular transmission in the gut. Neurogastroenterol Motil 2013; 25:203-7. [PMID: 23414428 PMCID: PMC8630810 DOI: 10.1111/nmo.12090] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Accepted: 01/05/2013] [Indexed: 02/08/2023]
Abstract
Recent studies with genetic deletion of P2Y1 receptor (P2Y1-/-) have clinched its role in enteric purinergic inhibitory neurotransmission and suggested that β-NAD may be the purinergic inhibitory neurotransmitter in the colon. In this issue of the Journal, Gil and colleagues extend their earlier observations to the cecum and gastric antrum, showing that P2Y1 receptor mediated purinergic inhibition may be a general phenomenon in the gut. However, the authors made an unexpected observation in contrast with their earlier findings in the colon that neither the selective P2Y1 receptor antagonist MRS2500, nor P2Y1 receptor deletion, blocked the hyperpolarizing action of β-NAD in the cecum. These observations suggest that β-NAD may be the purinergic inhibitory neurotransmitter in the colon, but not in the cecum. This group had previously reported that the selective P2Y1 receptor antagonist MRS 2179 suppressed the hyperpolarizing action of ATP or ADP. Further studies are now needed to determine whether the hyperpolarizing actions of ATP and ADP are suppressed by the more potent P2Y1 antagonist MRS2500, and in P2Y1-/- mutants to test the intriguing possibility that different purines serve as purinergic inhibitory neurotransmitters in the colon and cecum and perhaps in different parts of the gut. Studies in P2Y1-/- mice will resolve other issues in purinergic neurotransmission including cellular localization of the β-NAD or ATP-activated P2Y1 receptors on either smooth muscle cells or PDGFRα+ fibroblast-like cells, relationship of purinergic to nitrergic neurotransmission and understanding the physiological and clinical importance of purinergic transmission in gastrointestinal motility and its disorders.
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Affiliation(s)
- R. K. Goyal
- VA Boston HealthCare System and Harvard Medical School; Boston; MA; USA
| | - M. P. Sullivan
- VA Boston HealthCare System and Harvard Medical School; Boston; MA; USA
| | - Arun Chaudhury
- VA Boston HealthCare System and Harvard Medical School; Boston; MA; USA
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42
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Keef KD, Saxton SN, McDowall RA, Kaminski RE, Duffy AM, Cobine CA. Functional role of vasoactive intestinal polypeptide in inhibitory motor innervation in the mouse internal anal sphincter. J Physiol 2013; 591:1489-506. [PMID: 23339175 DOI: 10.1113/jphysiol.2012.247684] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
There is evidence that vasoactive intestinal polypeptide (VIP) participates in inhibitory neuromuscular transmission (NMT) in the internal anal sphincter (IAS). However, specific details concerning VIP-ergic NMT are limited, largely because of difficulties in selectively blocking other inhibitory neural pathways. The present study used the selective P2Y1 receptor antagonist MRS2500 (1 μm) and the nitric oxide synthase inhibitor N(G)-nitro-l-arginine (l-NNA; 100 μm) to block purinergic and nitrergic NMT to characterize non-purinergic, non-nitrergic (NNNP) inhibitory NMT and the role of VIP in this response. Nerves were stimulated with electrical field stimulation (0.1-20 Hz, 4-60 s) and the associated changes in contractile and electrical activity measured in non-adrenergic, non-cholinergic conditions in the IAS of wild-type and VIP(-/-) mice. Electrical field stimulation gave rise to frequency-dependent relaxation and hyperpolarization that was blocked by tetrodotoxin. Responses during brief trains of stimuli (4 s) were mediated by purinergic and nitrergic NMT. During longer stimulus trains, an NNNP relaxation and hyperpolarization developed slowly and persisted for several minutes beyond the end of the stimulus train. The NNNP NMT was abolished by VIP6-28 (30 μm), absent in the VIP(-/-) mouse and mimicked by exogenous VIP (1-100 nm). Immunoreactivity for VIP was co-localized with neuronal nitric oxide synthase in varicose intramuscular fibres but was not detected in the VIP(-/-) mouse IAS. In conclusion, this study identified an ultraslow component of inhibitory NMT in the IAS mediated by VIP. In vivo, this pathway may be activated with larger rectal distensions, leading to a more prolonged period of anal relaxation.
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Affiliation(s)
- K D Keef
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA.
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Roberts JA, Lukewich MK, Sharkey KA, Furness JB, Mawe GM, Lomax AE. The roles of purinergic signaling during gastrointestinal inflammation. Curr Opin Pharmacol 2012; 12:659-66. [PMID: 23063457 DOI: 10.1016/j.coph.2012.09.011] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Revised: 09/17/2012] [Accepted: 09/19/2012] [Indexed: 02/09/2023]
Abstract
Extracellular purines play important roles as neurotransmitters and paracrine mediators in the gastrointestinal (GI) tract. Inflammation of the GI tract causes marked changes in the release and extracellular catabolism of purines, and can modulate purinoceptor expression and/or signaling. The functional consequences of this include suppression of the purinergic component of inhibitory neuromuscular and neurovascular transmission, increased release of purines from immune and epithelial cells, loss of enteric neurons to damage through P2X(7) purinoceptors, and enhanced activation of pain fibres. The purinergic system represents an important target for drug therapies that may improve GI inflammation and its consequences.
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Affiliation(s)
- Jane A Roberts
- Department of Anatomy and Neurobiology, University of Vermont, Burlington, VT, USA
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Blair PJ, Bayguinov Y, Sanders KM, Ward SM. Relationship between enteric neurons and interstitial cells in the primate gastrointestinal tract. Neurogastroenterol Motil 2012; 24:e437-49. [PMID: 22805588 PMCID: PMC4854185 DOI: 10.1111/j.1365-2982.2012.01975.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND Morphological studies have revealed a close anatomical relationship between enteric nerve terminals and intramuscular ICC (ICC-IM) which supports a role for ICC-IM as intermediaries in enteric motor neurotransmission. Recently, a second type of interstitial cell previously described as 'fibroblast-like' but can now be identified by platelet-derived growth factor receptor-α expression, has also been implicated in enteric neurotransmission in rodents. The present study was performed to determine if enteric nerve fibers form close anatomical relationships with ICC and PDGFRα(+) cells throughout the primate GI tract. METHODS Immunohistochemical experiments and confocal microscopy were performed to examine the relationship between excitatory and inhibitory motor neurons, ICC and PDGFRα(+) cells throughout the monkey GI tract. KEY RESULTS The pan neuronal marker. Protein gene product 9.5 (PGP9.5) was used to label all enteric neurons and substance-P (sub-P) and neuronal nitric oxide synthase (nNOS) to label excitatory and inhibitory neurons, respectively. Double labeling with Kit revealed that both classes of nerve fibers were closely apposed with ICC-IM in the stomach, small intestine and colon (taenia and inter-taenia regions), but not with ICC at the level of the myenteric plexus (ICC-MY). Varicose enteric nerve fibers were closely associated with ICC-IM for distances up to 250 μm. Both excitatory and inhibitory nerve fibers were also closely apposed to PDGFRα(+) cells throughout the primate GI tract. CONCLUSIONS & INFERENCES The close anatomical relationship between enteric nerve fibers and ICC-IM and PDGFRα(+) cells throughout the GI tract of the Cynomolgus monkey provides morphological evidence that these two classes of interstitial cells may provide a similar physiological function in primates as has been attributed in rodent animal models.
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Affiliation(s)
- P J Blair
- Department of Physiology & Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
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Gil V, Gallego D, Moha Ou Maati H, Peyronnet R, Martínez-Cutillas M, Heurteaux C, Borsotto M, Jiménez M. Relative contribution of SKCa and TREK1 channels in purinergic and nitrergic neuromuscular transmission in the rat colon. Am J Physiol Gastrointest Liver Physiol 2012; 303:G412-23. [PMID: 22636169 DOI: 10.1152/ajpgi.00040.2012] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Purinergic and nitrergic neurotransmission predominantly mediate inhibitory neuromuscular transmission in the rat colon. We studied the sensitivity of both purinergic and nitrergic pathways to spadin, a TWIK-related potassium channel 1 (TREK1) inhibitor, apamin, a small-conductance calcium-activated potassium channel blocker and 1H-[1,2,4]oxadiazolo[4,3-α]quinoxalin-1-one (ODQ), a specific inhibitor of soluble guanylate cyclase. TREK1 expression was detected by RT-PCR in the rat colon. Patch-clamp experiments were performed on cells expressing hTREK1 channels. Spadin (1 μM) reduced currents 1) in basal conditions 2) activated by stretch, and 3) with arachidonic acid (AA; 10 μM). l-Methionine (1 mM) or l-cysteine (1 mM) did not modify currents activated by AA. Microelectrode and muscle bath studies were performed on rat colon samples. l-Methionine (2 mM), apamin (1 μM), ODQ (10 μM), and N(ω)-nitro-l-arginine (l-NNA; 1 mM) depolarized smooth muscle cells and increased motility. These effects were not observed with spadin (1 μM). Purinergic and nitrergic inhibitory junction potentials (IJP) were studied by incubating the tissue with l-NNA (1 mM) or MRS2500 (1 μM). Both purinergic and nitrergic IJP were unaffected by spadin. Apamin reduced both IJP with a different potency and maximal effect for each. ODQ concentration dependently abolished nitrergic IJP without affecting purinergic IJP. Similar effects were observed in hyperpolarizations induced by sodium nitroprusside (1 μM) and nitrergic relaxations induced by electrical stimulation. We propose a pharmacological approach to characterize the pathways and function of purinergic and nitrergic neurotransmission. Nitrergic neurotransmission, which is mediated by cyclic guanosine monophosphate, is insensitive to spadin, an effective TREK1 channel inhibitor. Both purinergic and nitrergic neurotransmission are inhibited by apamin but with different relative sensitivity.
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Affiliation(s)
- V Gil
- Department of Cell Biology, Physiology and Immunology and Neuroscience Institute, Universitat Autònoma de Barcelona, Bellaterra, Spain
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Gil V, Gallego D, Jiménez M. Effects of inhibitors of hydrogen sulphide synthesis on rat colonic motility. Br J Pharmacol 2012; 164:485-98. [PMID: 21486289 DOI: 10.1111/j.1476-5381.2011.01431.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND AND PURPOSE The role of hydrogen sulphide (H₂S) as a putative endogenous signalling molecule in the gastrointestinal tract has not yet been established. We investigated the effect of D,L-propargylglycine (PAG), an inhibitor of cystathionine γ-lyase (CSE), amino-oxyacetic acid (AOAA) and hydroxylamine (HA), inhibitors of cystathionine β-synthase (CBS) on rat colonic motility. EXPERIMENTAL APPROACH Immunohistochemistry, H₂S production, microelectrode and organ bath recordings were performed on rat colonic samples without mucosa and submucosa to investigate the role of endogenous H₂S in motility. KEY RESULTS CSE and CBS were immunolocalized in the colon. H₂S was endogenously produced (15.6 ± 0.7 nmol·min⁻¹·g⁻¹ tissue) and its production was strongly inhibited by PAG (2 mM) and AOAA (2 mM). PAG (2 mM) caused smooth muscle depolarization and increased spontaneous motility. The effect was still recorded after incubation with tetrodotoxin (TTX, 1 µM) or N(ω) -nitro-L-arginine (L-NNA, 1 mM). AOAA (2 mM) caused a transient (10 min) increase in motility. In contrast, HA (10 µM) caused a 'nitric oxide-like effect', smooth muscle hyperpolarization and relaxation, which were antagonized by 1H-[1,2,4]oxadiazolo[4,3-α]quinoxalin-1-one (ODQ, 10 µM). Neither spontaneous nor induced inhibitory junction potentials were modified by AOAA or PAG. CONCLUSIONS AND IMPLICATIONS We demonstrated that H₂S is endogenously produced in the rat colon. PAG and AOAA effectively blocked H₂S production. Our data suggest that enzymatic production of H₂S regulates colonic motility and therefore H₂S ight be a third gaseous inhibitory signalling molecule in the gastrointestinal tract. However, possible non-specific effects of the inhibitors should be considered.
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Affiliation(s)
- V Gil
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona (UAB), Bellaterra, Spain
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47
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Gil V, Gallego D, Jiménez M. Effects of inhibitors of hydrogen sulphide synthesis on rat colonic motility. Br J Pharmacol 2012. [PMID: 21486289 DOI: 10.1111/j.1476-5381.2011.01431.x/pdf] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND AND PURPOSE The role of hydrogen sulphide (H₂S) as a putative endogenous signalling molecule in the gastrointestinal tract has not yet been established. We investigated the effect of D,L-propargylglycine (PAG), an inhibitor of cystathionine γ-lyase (CSE), amino-oxyacetic acid (AOAA) and hydroxylamine (HA), inhibitors of cystathionine β-synthase (CBS) on rat colonic motility. EXPERIMENTAL APPROACH Immunohistochemistry, H₂S production, microelectrode and organ bath recordings were performed on rat colonic samples without mucosa and submucosa to investigate the role of endogenous H₂S in motility. KEY RESULTS CSE and CBS were immunolocalized in the colon. H₂S was endogenously produced (15.6 ± 0.7 nmol·min⁻¹·g⁻¹ tissue) and its production was strongly inhibited by PAG (2 mM) and AOAA (2 mM). PAG (2 mM) caused smooth muscle depolarization and increased spontaneous motility. The effect was still recorded after incubation with tetrodotoxin (TTX, 1 µM) or N(ω) -nitro-L-arginine (L-NNA, 1 mM). AOAA (2 mM) caused a transient (10 min) increase in motility. In contrast, HA (10 µM) caused a 'nitric oxide-like effect', smooth muscle hyperpolarization and relaxation, which were antagonized by 1H-[1,2,4]oxadiazolo[4,3-α]quinoxalin-1-one (ODQ, 10 µM). Neither spontaneous nor induced inhibitory junction potentials were modified by AOAA or PAG. CONCLUSIONS AND IMPLICATIONS We demonstrated that H₂S is endogenously produced in the rat colon. PAG and AOAA effectively blocked H₂S production. Our data suggest that enzymatic production of H₂S regulates colonic motility and therefore H₂S ight be a third gaseous inhibitory signalling molecule in the gastrointestinal tract. However, possible non-specific effects of the inhibitors should be considered.
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Affiliation(s)
- V Gil
- Department of Cell Biology, Physiology and Immunology, Universitat Autònoma de Barcelona (UAB), Bellaterra, Spain
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Hwang SJ, Blair PJ, Durnin L, Mutafova-Yambolieva V, Sanders KM, Ward SM. P2Y1 purinoreceptors are fundamental to inhibitory motor control of murine colonic excitability and transit. J Physiol 2012; 590:1957-72. [PMID: 22371476 DOI: 10.1113/jphysiol.2011.224634] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Activation of enteric inhibitory motor neurons causes inhibitory junctional potentials (IJPs) and muscle relaxation in mammalian gastrointestinal (GI) muscles, including humans. IJPs in many GI muscles are bi-phasic with a fast initial hyperpolarization (fIJP) due to release of a purine neurotransmitter and a slower hyperpolarization component (sIJP) due to release of nitric oxide. We sought to characterize the nature of the post-junctional receptor(s) involved in transducing purinergic neural inputs in the murine colon using mice with genetically deactivated P2ry1. Wild-type mice had characteristic biphasic IJPs and pharmacological dissection confirmed that the fIJP was purinergic and the sIJP was nitrergic. The fIJP was completely absent in P2ry1(−/−) mice and the P2Y1 receptor antagonist MRS2500 had no effect on electrical activity or responses to electrical field stimulation of intrinsic nerves in these mice. Contractile experiments confirmed that purinergic responses were abolished in P2ry1(−/−) mice. Picospritzing of neurotransmitter candidates (ATP and its primary metabolite, ADP) and β-NAD (and its primary metabolite, ADP-ribose, ADPR) caused transient hyperpolarization responses in wild-type colons, but responses to β-NAD and ADPR were completely abolished in P2ry1(−/−) mice. Hyperpolarization and relaxation responses to ATP and ADP were retained in colons of P2ry1(−/−) mice. Video imaging revealed that transit of fecal pellets was significantly delayed in colons from P2ry1(−/−) mice. These data demonstrate the importance of purinergic neurotransmission in regulating colonic motility and confirm pharmacological experiments suggesting that purinergic neurotransmission is mediated via P2Y1 receptors.
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Affiliation(s)
- Sung Jin Hwang
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
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Gallego D, Gil V, Martínez-Cutillas M, Mañé N, Martín MT, Jiménez M. Purinergic neuromuscular transmission is absent in the colon of P2Y(1) knocked out mice. J Physiol 2012; 590:1943-56. [PMID: 22371472 DOI: 10.1113/jphysiol.2011.224345] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Purinergic and nitrergic co-transmission is the dominant mechanism responsible for neural-mediated smooth muscle relaxation in the gastrointestinal tract. The aim of the present paper was to test whether or not P2Y(1) receptors are involved in purinergic neurotransmission using P2Y(1)(−/−) knock-out mice. Tension and microelectrode recordings were performed on colonic strips. In wild type (WT) animals, electrical field stimulation (EFS) caused an inhibitory junction potential (IJP) that consisted of a fast IJP (MRS2500 sensitive, 1 μm) followed by a sustained IJP (N(ω)-nitro-L-arginine (L-NNA) sensitive, 1 mm). The fast component of the IJP was absent in P2Y(1)(−/−) mice whereas the sustained IJP (L-NNA sensitive) was recorded. In WT animals, EFS-induced inhibition of spontaneous motility was blocked by the consecutive addition of L-NNA and MRS2500. In P2Y(1)(−/−) mice, EFS responses were completely blocked by L-NNA. In WT and P2Y(1)(−/−) animals, L-NNA induced a smooth muscle depolarization but ‘spontaneous' IJP (MRS2500 sensitive) could be recorded in WT but not in P2Y(1)(−/−) animals. Finally, in WT animals, 1 μm MRS2365 caused a smooth muscle hyperpolarization that was blocked by 1 μm MRS2500. In contrast, 1 μm MRS2365 did not modify smooth muscle resting membrane potential in P2Y(1)(−/−) mice. β-Nicotinamide adenine dinucleotide (β-NAD, 1 mm) partially mimicked the effect of MRS2365. We conclude that P2Y(1) receptors mediate purinergic neurotransmission in the gastrointestinal tract and β-NAD partially fulfils the criteria to participate in rodent purinergic neurotransmission. The P2Y(1)(−/−) mouse is a useful animal model to study the selective loss of purinergic neurotransmission.
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Affiliation(s)
- Diana Gallego
- Centro de Investigación Biomédica en Red de Enfermedades Hepáticas y Digestivas (CIBERehd) Instituto de Salud Carlos III, Barcelona, Spain
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Duffy AM, Cobine CA, Keef KD. Changes in neuromuscular transmission in the W/W(v) mouse internal anal sphincter. Neurogastroenterol Motil 2012; 24:e41-55. [PMID: 22074497 PMCID: PMC3245326 DOI: 10.1111/j.1365-2982.2011.01806.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
BACKGROUND Intramuscular interstitial cells of Cajal (ICC-IM) have been shown to participate in nitrergic neuromuscular transmission (NMT) in various regions of the gastrointestinal (GI) tract, but their role in the internal anal sphincter (IAS) is still uncertain. Contractile studies of the IAS in the W/W(v) mouse (a model in which ICC-IM numbers are markedly reduced) have reported that nitrergic NMT persists and that ICC-IM are not required. However, neither the changes in electrical events underlying NMT nor the contributions of other non-nitrergic neural pathways have been examined in this model. METHODS The role of ICC-IM in NMT was examined by recording the contractile and electrical events associated with electrical field stimulation (EFS) of motor neurons in the IAS of wildtype and W/W(v) mice. Nitrergic, purinergic, and cholinergic components were identified using inhibitors of these pathways. KEY RESULTS Under NANC conditions, purinergic and nitrergic pathways both contribute to EFS-induced inhibitory junction potentials (IJPs) and relaxation. Purinergic IJPs and relaxation were intact in the W/W(v) mouse IAS, whereas nitrergic IJPs were reduced by 50-60% while relaxation persisted. In the presence of L-NNA (NOS inhibitor) and MRS2500 (P2Y1 receptor antagonist), EFS gave rise to cholinergic depolarization and contractions that were abolished by atropine. Cholinergic depolarization was absent in the W/W(v) mouse IAS while contraction persisted. CONCLUSIONS & INFERENCES ICC-IM significantly contributes to the electrical events underlying nitrergic and cholinergic NMT, whereas contractile events persist in the absence of ICC-IM. The purinergic inhibitory neural pathway appears to be independent of ICC-IM.
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Affiliation(s)
| | | | - KD Keef
- Individual to whom correspondences should be addressed: Kathleen Keef, Ph.D., Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, , 1-775-784-4302
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