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Sanders KM, Drumm BT, Cobine CA, Baker SA. Ca 2+ dynamics in interstitial cells: foundational mechanisms for the motor patterns in the gastrointestinal tract. Physiol Rev 2024; 104:329-398. [PMID: 37561138 DOI: 10.1152/physrev.00036.2022] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 06/29/2023] [Accepted: 08/06/2023] [Indexed: 08/11/2023] Open
Abstract
The gastrointestinal (GI) tract displays multiple motor patterns that move nutrients and wastes through the body. Smooth muscle cells (SMCs) provide the forces necessary for GI motility, but interstitial cells, electrically coupled to SMCs, tune SMC excitability, transduce inputs from enteric motor neurons, and generate pacemaker activity that underlies major motor patterns, such as peristalsis and segmentation. The interstitial cells regulating SMCs are interstitial cells of Cajal (ICC) and PDGF receptor (PDGFR)α+ cells. Together these cells form the SIP syncytium. ICC and PDGFRα+ cells express signature Ca2+-dependent conductances: ICC express Ca2+-activated Cl- channels, encoded by Ano1, that generate inward current, and PDGFRα+ cells express Ca2+-activated K+ channels, encoded by Kcnn3, that generate outward current. The open probabilities of interstitial cell conductances are controlled by Ca2+ release from the endoplasmic reticulum. The resulting Ca2+ transients occur spontaneously in a stochastic manner. Ca2+ transients in ICC induce spontaneous transient inward currents and spontaneous transient depolarizations (STDs). Neurotransmission increases or decreases Ca2+ transients, and the resulting depolarizing or hyperpolarizing responses conduct to other cells in the SIP syncytium. In pacemaker ICC, STDs activate voltage-dependent Ca2+ influx, which initiates a cluster of Ca2+ transients and sustains activation of ANO1 channels and depolarization during slow waves. Regulation of GI motility has traditionally been described as neurogenic and myogenic. Recent advances in understanding Ca2+ handling mechanisms in interstitial cells and how these mechanisms influence motor patterns of the GI tract suggest that the term "myogenic" should be replaced by the term "SIPgenic," as this review discusses.
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Affiliation(s)
- Kenton M Sanders
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada-Reno, Reno, Nevada, United States
| | - Bernard T Drumm
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - Caroline A Cobine
- Smooth Muscle Research Centre, Dundalk Institute of Technology, Dundalk, Ireland
| | - Salah A Baker
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada-Reno, Reno, Nevada, United States
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Yan Q, Feng Z, Jiang B, Yao J. Biological functions of connexins in the development of inflammatory bowel disease. Scand J Gastroenterol 2024; 59:142-149. [PMID: 37837320 DOI: 10.1080/00365521.2023.2267713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2023] [Accepted: 10/01/2023] [Indexed: 10/16/2023]
Abstract
Inflammatory bowel disease (IBD) is a group of chronic intestinal inflammatory diseases with unknown etiology. Gap junctions composed of connexins (Cxs) have been recently validated as an important factor in the development of IBD. Under IBD-induced inflammatory response in the gut, gap junctions connect multiple signaling pathways involved in the interaction between inflammatory cells with other intestinal cells, which altogether mediate the development of IBD. This paper is a narrative review aiming to comprehensively elucidate the biological function of connexins, especially the ubiquitously and predominantly expressed Cx43, in the pathogenesis of IBD.
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Affiliation(s)
- Qiaojing Yan
- Colorectal Surgery Center, Nanjing Hospital of Chinese Medicine Affiliated to Nanjing University of Chinese Medicine, Nanjing, Jiangsu Province, China
- Jiangsu Province Traditional Chinese Medicine Innovation Center for Anorectal Disease, Nanjing, China
| | - Zhiling Feng
- Colorectal Surgery Center, Nanjing Hospital of Chinese Medicine Affiliated to Nanjing University of Chinese Medicine, Nanjing, Jiangsu Province, China
| | - Bin Jiang
- Colorectal Surgery Center, Nanjing Hospital of Chinese Medicine Affiliated to Nanjing University of Chinese Medicine, Nanjing, Jiangsu Province, China
- Jiangsu Province Traditional Chinese Medicine Innovation Center for Anorectal Disease, Nanjing, China
| | - Jian Yao
- Division of Molecular Signaling, Department of the Advanced Biomedical Research, Interdisciplinary Graduate School of Medicine, University of Yamanashi, Chuo, Japan
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Sanders KM, Santana LF, Baker SA. Interstitial cells of Cajal - pacemakers of the gastrointestinal tract. J Physiol 2023. [PMID: 37997170 DOI: 10.1113/jp284745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 11/06/2023] [Indexed: 11/25/2023] Open
Abstract
Gastrointestinal (GI) organs display spontaneous, non-neurogenic electrical, and mechanical rhythmicity that underlies fundamental motility patterns, such as peristalsis and segmentation. Electrical rhythmicity (aka slow waves) results from pacemaker activity generated by interstitial cells of Cajal (ICC). ICC express a unique set of ionic conductances and Ca2+ handling mechanisms that generate and actively propagate slow waves. GI smooth muscle cells lack these conductances. Slow waves propagate actively within ICC networks and conduct electrotonically to smooth muscle cells via gap junctions. Slow waves depolarize smooth muscle cells and activate voltage-dependent Ca2+ channels (predominantly CaV1.2), causing Ca2+ influx and excitation-contraction coupling. The main conductances responsible for pacemaker activity in ICC are ANO1, a Ca2+ -activated Cl- conductance, and CaV3.2. The pacemaker cycle, as currently understood, begins with spontaneous, localized Ca2+ release events in ICC that activate spontaneous transient inward currents due to activation of ANO1 channels. Depolarization activates CaV 3.2 channels, causing the upstroke depolarization phase of slow waves. The upstroke is transient and followed by a long-duration plateau phase that can last for several seconds. The plateau phase results from Ca2+ -induced Ca2+ release and a temporal cluster of localized Ca2+ transients in ICC that sustains activation of ANO1 channels and clamps membrane potential near the equilibrium potential for Cl- ions. The plateau phase ends, and repolarization occurs, when Ca2+ stores are depleted, Ca2+ release ceases and ANO1 channels deactivate. This review summarizes key mechanisms responsible for electrical rhythmicity in gastrointestinal organs.
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Affiliation(s)
- Kenton M Sanders
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada, Reno, NV, USA
| | - L Fernando Santana
- Department of Physiology and Membrane Biology, University of California, Davis, CA, USA
| | - Salah A Baker
- Department of Physiology and Cell Biology, School of Medicine, University of Nevada, Reno, NV, USA
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Pouokam E, Vallejo A, Martínez E, Traserra S, Jimenez M. Complementary mechanisms of modulation of spontaneous phasic contractions by the gaseous signalling molecules NO, H 2S, HNO and the polysulfide Na 2S 3 in the rat colon. J Basic Clin Physiol Pharmacol 2023; 34:495-507. [PMID: 34624185 DOI: 10.1515/jbcpp-2021-0181] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 09/26/2021] [Indexed: 12/21/2022]
Abstract
OBJECTIVES Reactive oxygen and nitrogen species may be produced during inflammation leading to the formation of NO, H2S or HNO. Enzymes such as iNOS, CSE and CBS might also be responsible for polysulfide production. Since these signalling molecules might have an impact on colonic motility, the aim of this study was to compare their effect on rat colonic slow phasic contractions (SPC). METHODS Organ bath measurements with strips obtained from rat proximal colon were performed using the polysulfide Na2S3, sodium nitroprusside (NaNP), sodium hydrogen sulfide (NaHS), Angeli's salt as NO, H2S, and HNO donors, respectively. TTX (1 µM) was used to block neuronal activity. RESULTS All four molecules, concentration-dependently, inhibited the amplitude and frequency of SPC both in the circular and longitudinal muscle layer. The relative potency was NaNP>Angeli's salt>NaHS>Na2S3. The inhibitory response induced by NaNP (1 µM) and Angeli's salt (50 µM) was reversed by ODQ (10 µM) whereas the inhibitory effect of NaHS (1 mM) was reversed by apamin (1 µM) and glibenclamide (10 µM). Na2S3 (1 mM) response was partially reversed by apamin (1 µM) and glibenclamide (10 µM). High concentrations of Na2S3 caused an increase in tone. Low concentrations of NaHS or Na2S3 did not potentiate NaNP responses. CONCLUSIONS All signalling molecules inhibit SPC in both muscle layers. The effect is independent of neural activity and involves guanylyl cyclase (NO and HNO) and SKCa and KATP channels (NaHS or Na2S3). Other pathways might also be involved in Na2S3 responses. Accordingly, complementary mechanisms of inhibition might be attributable to these signalling molecules.
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Affiliation(s)
- Ervice Pouokam
- Institute of Veterinary Physiology and Biochemistry, Justus-Liebig-University Giessen, Giessen, Germany
| | - Adriana Vallejo
- Department of Cell Biology, Physiology and Immunology and Neurosciences Institute, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Emma Martínez
- Department of Cell Biology, Physiology and Immunology and Neurosciences Institute, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Sara Traserra
- Department of Cell Biology, Physiology and Immunology and Neurosciences Institute, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Marcel Jimenez
- Department of Cell Biology, Physiology and Immunology and Neurosciences Institute, Universitat Autònoma de Barcelona, Barcelona, Spain
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Perrino BA, Malogan J, Cobine CA, Sasse KC. Mfge8 is expressed by pericytes in gastric antrum submucosa from patients with obesity. Am J Physiol Cell Physiol 2023; 324:C992-C1006. [PMID: 36939201 PMCID: PMC10110711 DOI: 10.1152/ajpcell.00043.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Revised: 03/07/2023] [Accepted: 03/08/2023] [Indexed: 03/21/2023]
Abstract
The main function of the stomach is to digest ingested food. Gastric antrum muscular contractions mix ingested food with digestive enzymes and stomach acid and propel the chyme through the pyloric sphincter at a rate in which the small intestine can process the chyme for optimal nutrient absorption. Mfge8 binding to α8β1 integrins helps regulate gastric emptying by reducing the force of antral smooth muscle contractions. The source of Mfge8 within gastric muscles is unclear. Since Mfge8 is a secreted protein, Mfge8 could be delivered via the circulation, or be locally secreted by cells within the muscle layers. In this study, we identify a source of Mfge8 within human gastric antrum muscles using spatial transcriptomic analysis. We show that Mfge8 is expressed in subpopulations of Mef2c+ perivascular cells within the submucosa layer of the gastric antrum. Mef2c is expressed in subpopulations of NG2+ and PDGFRB+ pericytes. Mfge8 is expressed in NG2+/Mef2c+ pericytes, but not in NG2+/Mef2c-, PDGFRB+/Mef2c-, or PDGFRB+/Mef2c+ pericytes. Mfge8 is absent from CD34+ endothelial cells but is expressed in a small population of perivascular ACTA2+ cells. We also show that α8 integrin is not expressed by interstitial cells of Cajal (ICC), supporting the findings that Mfge8 attenuates gastric antrum smooth muscle contractions by binding to α8β1 integrins on enteric smooth muscle cells. These findings suggest a novel, supplementary mechanism of regulation of gastric antrum motility by cellular regulators of capillary blood flow, in addition to the regulation of gastric antrum motility by the enteric nervous system and the SMC, ICC, and PDGFRα+ cell (SIP) syncytium.
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Affiliation(s)
- Brian A Perrino
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, Nevada, United States
| | - Justin Malogan
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, Nevada, United States
| | - Caroline A Cobine
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, Nevada, United States
| | - Kent C Sasse
- Nevada Surgical Associates, Reno, Nevada, United States
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Yang L, Arbona RJR, Smith CS, Banks KM, Thomas VK, Palmer L, Evans T, Hurtado R. An evolutionarily conserved pacemaker role for HCN ion channels in smooth muscle. J Physiol 2023; 601:1225-1246. [PMID: 36930567 PMCID: PMC10065941 DOI: 10.1113/jp283701] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 02/14/2023] [Indexed: 03/18/2023] Open
Abstract
Although hyperpolarization-activated cation (HCN) ion channels are well established to underlie cardiac pacemaker activity, their role in smooth muscle organs remains controversial. HCN-expressing cells are localized to renal pelvic smooth muscle (RPSM) pacemaker tissues of the murine upper urinary tract and HCN channel conductance is required for peristalsis. To date, however, the Ih pacemaker current conducted by HCN channels has never been detected in these cells, raising questions on the identity of RPSM pacemakers. Indeed, the RPSM pacemaker mechanisms of the unique multicalyceal upper urinary tract exhibited by humans remains unknown. Here, we developed immunopanning purification protocols and demonstrate that 96% of isolated HCN+ cells exhibit Ih . Single-molecule STORM to whole-tissue imaging showed HCN+ cells express single HCN channels on their plasma membrane and integrate into the muscular syncytium. By contrast, PDGFR-α+ cells exhibiting the morphology of ICC gut pacemakers were shown to be vascular mural cells. Translational studies in the homologous human and porcine multicalyceal upper urinary tracts showed that contractions and pacemaker depolarizations originate in proximal calyceal RPSM. Critically, HCN+ cells were shown to integrate into calyceal RPSM pacemaker tissues, and HCN channel block abolished electrical pacemaker activity and peristalsis of the multicalyceal upper urinary tract. Cumulatively, these studies demonstrate that HCN ion channels play a broad, evolutionarily conserved pacemaker role in both cardiac and smooth muscle organs and have implications for channelopathies as putative aetiologies of smooth muscle disorders. KEY POINTS: Pacemakers trigger contractions of involuntary muscles. Hyperpolarization-activated cation (HCN) ion channels underpin cardiac pacemaker activity, but their role in smooth muscle organs remains controversial. Renal pelvic smooth muscle (RPSM) pacemakers trigger contractions that propel waste away from the kidney. HCN+ cells localize to murine RPSM pacemaker tissue and HCN channel conductance is required for peristalsis. The HCN (Ih ) current has never been detected in RPSM cells, raising doubt whether HCN+ cells are bona fide pacemakers. Moreover, the pacemaker mechanisms of the unique multicalyceal RPSM of higher order mammals remains unknown. In total, 97% of purified HCN+ RPSM cells exhibit Ih . HCN+ cells integrate into the RPSM musculature, and pacemaker tissue peristalsis is dependent on HCN channels. Translational studies in human and swine demonstrate HCN channels are conserved in the multicalyceal RPSM and that HCN channels underlie pacemaker activity that drives peristalsis. These studies provide insight into putative channelopathies that can underlie smooth muscle dysfunction.
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Affiliation(s)
- Lei Yang
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, NY, USA
| | - Rodolfo J. Ricart Arbona
- Center of Comparative Medicine and Pathology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Carl S. Smith
- Department of Urologic Surgery, University of Minnesota School of Medicine, Minneapolis, MN, USA
| | - Kelly M. Banks
- Department of Surgery, Weill Medical College of Cornell University, New York, NY, USA
| | - V. Kaye Thomas
- Bio-Imaging Resource Center, The Rockefeller University, New York, NY, USA
| | - Lawrence Palmer
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, NY, USA
| | - Todd Evans
- Department of Surgery, Weill Medical College of Cornell University, New York, NY, USA
| | - Romulo Hurtado
- Department of Surgery, Weill Medical College of Cornell University, New York, NY, USA
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In Silico, In Vitro, and Ex Vivo Biological Activity of Some Novel Mebeverine Precursors. Biomedicines 2023; 11:biomedicines11020605. [PMID: 36831141 PMCID: PMC9953468 DOI: 10.3390/biomedicines11020605] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Revised: 02/09/2023] [Accepted: 02/15/2023] [Indexed: 02/22/2023] Open
Abstract
Irritable bowel syndrome (IBS) is a functional gastroenterological disorder with complex pathogenesis and multifaceted therapy approaches, aimed at alleviating clinical symptoms and improving the life quality of patients. Its treatment includes dietary changes and drugs from various pharmacological groups such as antidiarrheals, anticholinergics, serotonin receptor antagonists, targeting chloride ion channels, etc. The present article is focused on the synthesis and biological evaluation of some mebeverine precursors as potential antispasmodics. METHODS In silico analysis aimed at predicting the pharmacodynamic profile of the compounds was performed. Based on these predictions, ex vivo bioelectrical activity (BEA) and immunohistochemical effects of the compounds were established. A thorough biological evaluation of the compounds was conducted assessing their in vitro antimicrobial and cytotoxic activity. RESULTS All the newly synthesized compounds exerted drug-like properties, whereby 3-methyl-1-phenylbutan-2-amine 3 showed a significant change in BEA due to Ca2+ channel regulation, Ca2+ influx modulation, and a subsequent change in smooth muscle cell response. The immunohistochemical studies showed a good correlation with the obtained data on the BEA, defining amine 3 as a leader structure. No cytotoxicity to human malignant leukemic cell lines (LAMA-84, K-562) was observed for all tested compounds. CONCLUSION Based on the experimental results, we outlined 3-methyl-1-phenylbutan-2-amine 3 as a potential effective choice for orally active long-term therapy of IBS.
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Zheng Z, Tang J, Hu Y, Zhang W. Role of gut microbiota-derived signals in the regulation of gastrointestinal motility. Front Med (Lausanne) 2022; 9:961703. [PMID: 35935766 PMCID: PMC9354785 DOI: 10.3389/fmed.2022.961703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2022] [Accepted: 07/04/2022] [Indexed: 11/13/2022] Open
Abstract
The gastrointestinal (GI) tract harbors trillions of commensal microbes, called the gut microbiota, which plays a significant role in the regulation of GI physiology, particularly GI motility. The GI tract expresses an array of receptors, such as toll-like receptors (TLRs), G-protein coupled receptors, aryl hydrocarbon receptor (AhR), and ligand-gated ion channels, that sense different gut microbiota-derived bioactive substances. Specifically, microbial cell wall components and metabolites, including lipopeptides, peptidoglycan, lipopolysaccharides (LPS), bile acids (BAs), short-chain fatty acids (SCFAs), and tryptophan metabolites, mediate the effect of gut microbiota on GI motility through their close interactions with the enteroendocrine system, enteric nervous system, intestinal smooth muscle, and immune system. In turn, GI motility affects the colonization within the gut microbiota. However, the mechanisms by which gut microbiota interacts with GI motility remain to be elucidated. Deciphering the underlying mechanisms is greatly important for the prevention or treatment of GI dysmotility, which is a complication associated with many GI diseases, such as irritable bowel syndrome (IBS) and constipation. In this perspective, we overview the current knowledge on the role of gut microbiota and its metabolites in the regulation of GI motility, highlighting the potential mechanisms, in an attempt to provide valuable clues for the development of gut microbiota-dependent therapy to improve GI motility.
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Straface M, Koussai MA, Makwana R, Crawley E, Palmer A, Cai W, Gharibans A, Adebibe M, Loy J, O’Grady G, Andrews PLR, Sanger GJ. A multi-parameter approach to measurement of spontaneous myogenic contractions in human stomach: Utilization to assess potential modulators of myogenic contractions. Pharmacol Res 2022; 180:106247. [DOI: 10.1016/j.phrs.2022.106247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2022] [Revised: 04/22/2022] [Accepted: 05/03/2022] [Indexed: 10/18/2022]
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Ability of 2-Chloro-N-(1-(3,4-dimethoxyphenyl)propan-2-yl)-2-phenylacetamide to Stimulate Endogenous Nitric Oxide Synthesis. APPLIED SCIENCES-BASEL 2022. [DOI: 10.3390/app12094473] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Papaverine is one of the isoquinoline alkaloids derived from opium which is a vasodilator and smooth muscle relaxant. Using its chemical structure as a basic model, we synthesized 2-chloro-N-(1-(3,4-dimethoxyphenyl)propan-2-yl)-2-phenylacetamide as an isoquinoline precursor (IQP). Aim: Clarifying the nature of the relationship between IQP as a new biologically active molecule and the neurotransmitters acetylcholine (ACh) and serotonin (5-hydroxytryptamine, 5-HT), as well as with the nitric oxide (NO). Materials and methods: The IQP compound was tested on the isolated gastric smooth muscle preparations (SMPs) from rats to determine its effects on spontaneous contractile activity. NO concentration in tissue homogenates was determined, and immunohistochemistry was used to visualize the expression of neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS) in smooth muscle (SM) cells. Results: The data from the isometric measurements suggest that IQP has an additional specific action affecting the intracellular signaling pathways of 5-HT. Using immunohistochemistry, we found that the combination of 5-HT and IQP affected the density and intensity of nNOS-positive cells, which increase significantly in the myenteric plexus and SM cells. Conclusions: In conclusion, IQP is involved in the regulation of intestinal neurons expressing nNOS, affects the function of nNOS/NO, and, by this mechanism, probably regulates the spontaneous contractile activity of gastric SM.
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Mischopoulou M, D’Ambrosio M, Bigagli E, Luceri C, Farrugia G, Cipriani G. Role of Macrophages and Mast Cells as Key Players in the Maintenance of Gastrointestinal Smooth Muscle Homeostasis and Disease. Cell Mol Gastroenterol Hepatol 2022; 13:1849-1862. [PMID: 35245688 PMCID: PMC9123576 DOI: 10.1016/j.jcmgh.2022.02.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 02/18/2022] [Accepted: 02/22/2022] [Indexed: 12/18/2022]
Abstract
The gut contains the largest macrophage pool in the body, with populations of macrophages residing in the mucosa and muscularis propria of the gastrointestinal (GI) tract. Muscularis macrophages (MMs), which are located within the muscularis propria, interact with cells essential for GI function, such as interstitial cells of Cajal, enteric neurons, smooth muscle cells, enteric glia, and fibroblast-like cells, suggesting that these immune cells contribute to several aspects of GI function. This review focuses on the latest insights on the factors contributing to MM heterogeneity and the functional interaction of MMs with other cell types essential for GI function. This review integrates the latest findings on macrophages in other organs with increasing knowledge of MMs to better understand their role in a healthy and diseased gut. We describe the factors that contribute to (muscularis macrophage) MM heterogeneity, and the nature of MM interactions with cells regulating GI function. Finally, we also describe the increasing evidence suggesting a critical role of another immune cell type, the mast cell, in normal and diseased GI physiology.
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Affiliation(s)
| | - Mario D’Ambrosio
- Section of Pharmacology and Toxicology, Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, Florence, Italy
| | - Elisabetta Bigagli
- Section of Pharmacology and Toxicology, Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, Florence, Italy
| | - Cristina Luceri
- Section of Pharmacology and Toxicology, Department of Neuroscience, Psychology, Drug Research and Child Health (NEUROFARBA), University of Florence, Florence, Italy
| | | | - Gianluca Cipriani
- Enteric Neuroscience Program, Mayo Clinic, Rochester, Minnesota,Correspondence Address correspondence to: Gianluca Cipriani, PhD, Enteric Neuroscience Program, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905. fax: (507) 284-0266.
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Takeya M, Higashi R, Hashitani H, Nakamura KI, Hayashi T, Nakashima N, Takano M. PDGFRα (+) subepithelial interstitial cells act as a pacemaker to drive smooth muscle of the guinea pig seminal vesicle. J Physiol 2022; 600:1703-1730. [PMID: 35081665 DOI: 10.1113/jp281686] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Accepted: 01/18/2022] [Indexed: 11/08/2022] Open
Abstract
KEY POINTS In many visceral smooth muscle organs, spontaneous contractions are electrically driven by non-muscular pacemaker cells. In guinea pig seminal vesicles (SVs), as yet unidentified mucosal cells appear to drive neighbouring smooth muscle cells (SMCs). Two populations of spontaneously active cells are distributed in the SV mucosa. Basal epithelial cells (BECs) generate asynchronous, irregular spontaneous Ca2+ transients and spontaneous transient depolarisations (STDs). In contrast, subepithelial interstitial cells (SICs) develop synchronous Ca2+ oscillations and electrical slow waves. Pancytokeratin-immunoreactive (IR) BECs are located on the apical side of the basement membrane (BM), while platelet-derived growth factor receptor α (PDGFRα)-IR SICs are located on the basal side of the BM. Spontaneous Ca2+ transients in SICs are synchronised with those in SV SMCs. Dye-coupling between SICs and SMCs suggests that SICs act as pacemaker cells to drive the spontaneous contractions of SV smooth muscle. ABSTRACT Smooth muscle cells (SMCs) of the guinea pig seminal vesicle (SV) develop spontaneous phasic contractions, Ca2+ flashes and electrical slow waves in a mucosa dependent manner, thus it was envisaged that pacemaker cells reside in the mucosa. Here, we aimed to identify the pacemaker cells in SV mucosa using intracellular microelectrode and fluorescent Ca2+ imaging techniques. Morphological characteristics of the mucosal pacemaker cells were also investigated using focused ion beam/scanning electron microscopy tomography and fluorescent immunohistochemistry. Two populations of mucosal cells developed spontaneous Ca2+ transients and electrical activity, namely basal epithelial cells (BECs) and subepithelial interstitial cells (SICs). Pancytokeratin-immunoreactive BECs were located on the apical side of the basement membrane (BM) and generated asynchronous, irregular spontaneous Ca2+ transients and spontaneous transient depolarisations (STDs). The spontaneous Ca2+ transients and STDs were not diminished by 10 μM nifedipine but abolished by 10 μM cyclopiazonic acid (CPA). Platelet-derived growth factor receptor α (PDGFRα)-immunoreactive SICs were distributed just beneath the basal side of the BM and developed synchronous Ca2+ oscillations (SCOs) and electrical slow waves, which were suppressed by 3 μM nifedipine and abolished by 10 μM CPA. In SV mucosal preparations in which some smooth muscle bundles remained attached, SICs and residual SMCs developed temporally-correlated spontaneous Ca2+ transients. Neurobiotin injected into SICs spread to not only neighbouring SICs but also to neighbouring SMCs or vice versa. These results suggest that PDGFRα (+) SICs electrotonically drive the spontaneous contractions of SV smooth muscle. Abstract figure legend The seminal vesicles (SVs) of guinea pig generate spontaneous phasic contractions (SPCs). SV smooth muscle cells (SMCs, pink) develop SPCs associated with spontaneous electrical slow waves and Ca2+ flashes, which require the attachment of mucosal layer. Histological examination demonstrated the layer of PDGFRα-immunoreactive subepithelial interstitial cells (SICs, green) underneath of the basement membrane. The SICs spontaneously develop synchronous Ca2+ oscillations and the electrical slow waves, at the frequency corresponding to those of SPCs. The dye-coupling between SICs and SMCs further suggested that the synchronous electrical slow waves in the SICs electrotonically conduct to the SV SMCs via gap junctions (orange). Thus, the SICs appear to act as electrical pacemaker cells driving SPCs of SV. The basal epithelial cells (BECs, brown) also generated asynchronous, irregular spontaneous Ca2+ transients and spontaneous transient depolarisations, although their roles in developing SPCs remains to be explored. This article is protected by copyright. All rights reserved.
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Affiliation(s)
- Mitsue Takeya
- Division of Integrated Autonomic Function, Department of Physiology, Kurume University School of Medicine, Kurume, Japan
| | - Ryuhei Higashi
- Electron Microscopic Laboratory, Central Research Unit of Kurume University School of Medicine, Kurume, Japan
| | - Hikaru Hashitani
- Department of Cell Physiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
| | - Kei-Ichiro Nakamura
- Division of Microscopic and Developmental Anatomy, Department of Anatomy, Kurume University School of Medicine, Kurume, Japan
| | | | - Noriyuki Nakashima
- Division of Integrated Autonomic Function, Department of Physiology, Kurume University School of Medicine, Kurume, Japan
| | - Makoto Takano
- Division of Integrated Autonomic Function, Department of Physiology, Kurume University School of Medicine, Kurume, Japan
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Analysis of Regional Variations of the Interstitial Cells of Cajal in the Murine Distal Stomach Informed by Confocal Imaging and Machine Learning Methods. Cell Mol Bioeng 2022; 15:193-205. [PMID: 35401841 PMCID: PMC8938532 DOI: 10.1007/s12195-021-00716-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 11/24/2021] [Indexed: 01/05/2023] Open
Abstract
Introduction The network of Interstitial Cells of Cajal (ICC) plays a plethora of key roles in maintaining, coordinating, and regulating the contractions of the gastrointestinal (GI) smooth muscles. Several GI functional motility disorders have been associated with ICC degradation. This study extended a previously reported 2D morphological analysis and applied it to 3D spatial quantification of three different types of ICC networks in the distal stomach guided by confocal imaging and machine learning methods. The characterization of the complex changes in spatial structure of the ICC network architecture contributes to our understanding of the roles that different types of ICC may play in post-prandial physiology, pathogenesis, and/or amelioration of GI dsymotility- bridging structure and function. Methods A validated classification method using Trainable Weka Segmentation was applied to segment the ICC from a confocal dataset of the gastric antrum of a transgenic mouse, followed by structural analysis of the segmented images. Results The machine learning model performance was compared to manually segmented subfields, achieving an area under the receiver-operating characteristic (AUROC) of 0.973 and 0.995 for myenteric ICC (ICC-MP; n = 6) and intramuscular ICC (ICC-IM; n = 17). The myenteric layer in the distal antrum increased in thickness (from 14.5 to 34 μm) towards the lesser curvature, whereas the thickness decreased towards the lesser curvature in the proximal antrum (17.7 to 9 μm). There was an increase in ICC-MP volume from proximal to distal antrum (406,960 ± 140,040 vs. 559,990 ± 281,000 μm3; p = 0.000145). The % of ICC volume was similar for ICC-LM and for ICC-CM between proximal (3.6 ± 2.3% vs. 3.1 ± 1.2%; p = 0.185) and distal antrum (3.2 ± 3.9% vs. 2.5 ± 2.8%; p = 0.309). The average % volume of ICC-MP was significantly higher than ICC-IM at all points throughout sample (p < 0.0001). Conclusions The segmentation and analysis methods provide a high-throughput framework of investigating the structural changes in extended ICC networks and their associated physiological functions in animal models.
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14
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Abstract
Gastroparesis is characterized by symptoms suggestive of, and objective evidence of, delayed gastric emptying in the absence of mechanical obstruction. This review addresses the normal emptying of solids and liquids from the stomach and details the myogenic and neuromuscular control mechanisms, including the specialized function of the pyloric sphincter, that result in normal emptying, based predominantly on animal research. A clear understanding of fundamental mechanisms is necessary to comprehend derangements leading to gastroparesis, and additional research on human gastric muscles is needed. The section on pathophysiology of gastroparesis considers neuromuscular diseases that affect nonsphincteric gastric muscle, disorders of the extrinsic neural control, and pyloric dysfunction that lead to gastroparesis. The potential cellular basis for gastroparesis is attributed to the effects of oxidative stress and inflammation, with increased pro-inflammatory and decreased resident macrophages, as observed in full-thickness biopsies from patients with gastroparesis. Predominant diagnostic tests involving measurements of gastric emptying, the use of a functional luminal imaging probe, and high-resolution antral duodenal manometry in characterizing the abnormal motor functions at the gastroduodenal junction are discussed. Management is based on supporting nutrition; dietary interventions, including the physical reduction in particle size of solid foods; pharmacological agents, including prokinetics and anti-emetics; and interventions such as gastric electrical stimulation and pyloromyotomy. These are discussed briefly, and comment is added on the potential for individualized treatments in the future, based on optimal gastric emptying measurement and objective documentation of the underlying pathophysiology causing the gastroparesis.
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Affiliation(s)
- Michael Camilleri
- Clinical Enteric Neuroscience Translational and Epidemiological Research, Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, Minnesota.
| | - Kenton M. Sanders
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV
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15
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Spencer NJ, Costa M. Rhythmicity in the Enteric Nervous System of Mice. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2022; 1383:295-306. [PMID: 36587167 DOI: 10.1007/978-3-031-05843-1_27] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The enteric nervous system (ENS) is required for many cyclical patterns of motor activity along different regions of the gastrointestinal (GI) tract. What has remained mysterious is precisely how many thousands of neurons within the ENS are temporally activated to generate cyclical neurogenic contractions of GI-smooth muscle layers. This has been an especially puzzling conundrum, since the ENS consists of an extensive network of small ganglia, with each ganglion consisting of a heterogeneous population of neurons, with diverse cell soma morphologies, neurochemical and biophysical characteristics, and neural connectivity. Neuronal imaging studies of the mouse large intestine have provided major new insights into how the different classes of myenteric neurons are activated during cyclical neurogenic motor patterns, such as the colonic motor complex (CMC). It has been revealed that during CMCs (in the isolated mouse whole colon), large populations of myenteric neurons, across large spatial fields, coordinate their firing, via bursts of fast synaptic inputs at ~2 Hz. This coordinated firing of many thousands of myenteric neurons synchronously over many rows of interconnected ganglia occurs irrespective of the functional class of neuron. Aborally directed propulsion of content along the mouse colon is due, in large part, to polarity of the enteric circuits including the projections of the intrinsic excitatory and inhibitory motor neurons but still involves the fundamental ~2 Hz rhythmic activity of specific classes of enteric neurons. What remains to be determined are the mechanisms that initiate and terminate the patterned firing of large ensembles of enteric neurons during cyclic activity. This remains an exciting challenge for future studies.
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Affiliation(s)
- Nick J Spencer
- Visceral Neurophysiology Laboratory, Department of Physiology, College of Medicine and Public Health & Centre for Neuroscience, Flinders University, Bedford Park, SA, Australia.
| | - Marcello Costa
- Visceral Neurophysiology Laboratory, Department of Physiology, College of Medicine and Public Health, Flinders University, Bedford Park, SA, Australia
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16
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O'Grady G, Gharibans AA, Du P, Huizinga JD. The gastric conduction system in health and disease: a translational review. Am J Physiol Gastrointest Liver Physiol 2021; 321:G527-G542. [PMID: 34549598 DOI: 10.1152/ajpgi.00065.2021] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Gastric peristalsis is critically dependent on an underlying electrical conduction system. Recent years have witnessed substantial progress in clarifying the operations of this system, including its pacemaking units, its cellular architecture, and slow-wave propagation patterns. Advanced techniques have been developed for assessing its functions at high spatiotemporal resolutions. This review synthesizes and evaluates this progress, with a focus on human and translational physiology. A current conception of the initiation and conduction of slow-wave activity in the human stomach is provided first, followed by a detailed discussion of its organization at the cellular and tissue level. Particular emphasis is then given to how gastric electrical disorders may contribute to disease states. Gastric dysfunction continues to grow in their prevalence and impact, and while gastric dysrhythmia is established as a clear and pervasive feature in several major gastric disorders, its role in explaining pathophysiology and informing therapy is still emerging. New insights from high-resolution gastric mapping are evaluated, together with historical data from electrogastrography, and the physiological relevance of emerging biomarkers from body surface mapping such as retrograde propagating slow waves. Knowledge gaps requiring further physiological research are highlighted.
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Affiliation(s)
- Gregory O'Grady
- Department of Surgery, The University of Auckland, Auckland, New Zealand.,Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Armen A Gharibans
- Department of Surgery, The University of Auckland, Auckland, New Zealand.,Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Peng Du
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
| | - Jan D Huizinga
- Department of Medicine, Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, Ontario, Canada
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17
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Baker SA, Hwang SJ, Blair PJ, Sireika C, Wei L, Ro S, Ward SM, Sanders KM. Ca 2+ transients in ICC-MY define the basis for the dominance of the corpus in gastric pacemaking. Cell Calcium 2021; 99:102472. [PMID: 34537580 PMCID: PMC8592010 DOI: 10.1016/j.ceca.2021.102472] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 09/03/2021] [Accepted: 09/05/2021] [Indexed: 12/13/2022]
Abstract
Myenteric interstitial cells of Cajal (ICC-MY) generate and actively propagate electrical slow waves in the stomach. Slow wave generation and propagation are altered in gastric motor disorders, such as gastroparesis, and the mechanism for the gradient in slow wave frequency that facilitates proximal to distal propagation of slow waves and normal gastric peristalsis is poorly understood. Slow waves depend upon Ca2+-activated Cl- channels (encoded by Ano1). We characterized Ca2+ signaling in ICC-MY in situ using mice engineered to have cell-specific expression of GCaMP6f in ICC. Ca2+ signaling differed in ICC-MY in corpus and antrum. Localized Ca2+ transients were generated from multiple firing sites and were organized into Ca2+ transient clusters (CTCs). Ca2+ transient refractory periods occurred upon cessation of CTCs, but a relatively higher frequency of Ca2+ transients persisted during the inter-CTC interval in corpus than in antrum ICC-MY. The onset of Ca2+ transients after the refractory period was associated with initiation of the next CTC. Thus, CTCs were initiated at higher frequencies in corpus than in antrum ICC-MY. Initiation and propagation of CTCs (and electrical slow waves) depends upon T-type Ca2+ channels, and durations of CTCs relied upon L-type Ca2+ channels. The durations of CTCs mirrored the durations of slow waves. CTCs and Ca2+ transients between CTCs resulted from release of Ca2+ from intracellular stores and were maintained, in part, by store-operated Ca2+ entry. Our data suggest that Ca2+ release and activation of Ano1 channels both initiate and contribute to the plateau phase of slow waves.
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Affiliation(s)
- Salah A Baker
- Department of Physiology and Cell Biology, University of Nevada, Reno, School of Medicine, Reno, Nevada 89557, USA.
| | - Sung Jin Hwang
- Department of Physiology and Cell Biology, University of Nevada, Reno, School of Medicine, Reno, Nevada 89557, USA
| | - Peter J Blair
- Department of Physiology and Cell Biology, University of Nevada, Reno, School of Medicine, Reno, Nevada 89557, USA
| | - Carlee Sireika
- Department of Physiology and Cell Biology, University of Nevada, Reno, School of Medicine, Reno, Nevada 89557, USA
| | - Lai Wei
- Department of Physiology and Cell Biology, University of Nevada, Reno, School of Medicine, Reno, Nevada 89557, USA
| | - Seungil Ro
- Department of Physiology and Cell Biology, University of Nevada, Reno, School of Medicine, Reno, Nevada 89557, USA
| | - Sean M Ward
- Department of Physiology and Cell Biology, University of Nevada, Reno, School of Medicine, Reno, Nevada 89557, USA
| | - Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada, Reno, School of Medicine, Reno, Nevada 89557, USA.
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18
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Spencer NJ, Travis L, Wiklendt L, Costa M, Hibberd TJ, Brookes SJ, Dinning P, Hu H, Wattchow DA, Sorensen J. Long range synchronization within the enteric nervous system underlies propulsion along the large intestine in mice. Commun Biol 2021; 4:955. [PMID: 34376798 PMCID: PMC8355373 DOI: 10.1038/s42003-021-02485-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Accepted: 07/15/2021] [Indexed: 02/07/2023] Open
Abstract
How the Enteric Nervous System (ENS) coordinates propulsion of content along the gastrointestinal (GI)-tract has been a major unresolved issue. We reveal a mechanism that explains how ENS activity underlies propulsion of content along the colon. We used a recently developed high-resolution video imaging approach with concurrent electrophysiological recordings from smooth muscle, during fluid propulsion. Recordings showed pulsatile firing of excitatory and inhibitory neuromuscular inputs not only in proximal colon, but also distal colon, long before the propagating contraction invades the distal region. During propulsion, wavelet analysis revealed increased coherence at ~2 Hz over large distances between the proximal and distal regions. Therefore, during propulsion, synchronous firing of descending inhibitory nerve pathways over long ranges aborally acts to suppress smooth muscle from contracting, counteracting the excitatory nerve pathways over this same region of colon. This delays muscle contraction downstream, ahead of the advancing contraction. The mechanism identified is more complex than expected and vastly different from fluid propulsion along other hollow smooth muscle organs; like lymphatic vessels, portal vein, or ureters, that evolved without intrinsic neurons.
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Affiliation(s)
- Nick J Spencer
- Visceral Neurophysiology Laboratory, College of Medicine and Public Health, Centre for Neuroscience, Flinders University, Bedford Park, SA, Australia.
| | - Lee Travis
- Visceral Neurophysiology Laboratory, College of Medicine and Public Health, Centre for Neuroscience, Flinders University, Bedford Park, SA, Australia
| | - Lukasz Wiklendt
- Discipline of Gastroenterology, College of Medicine and Public Health, Flinders Medical Centre, Bedford Park, SA, Australia
| | - Marcello Costa
- Visceral Neurophysiology Laboratory, College of Medicine and Public Health, Centre for Neuroscience, Flinders University, Bedford Park, SA, Australia
| | - Timothy J Hibberd
- Visceral Neurophysiology Laboratory, College of Medicine and Public Health, Centre for Neuroscience, Flinders University, Bedford Park, SA, Australia
| | - Simon J Brookes
- Visceral Neurophysiology Laboratory, College of Medicine and Public Health, Centre for Neuroscience, Flinders University, Bedford Park, SA, Australia
| | - Phil Dinning
- Discipline of Gastroenterology, College of Medicine and Public Health, Flinders Medical Centre, Bedford Park, SA, Australia
| | - Hongzhen Hu
- Department of Anesthesiology, The Center for the Study of Itch, Washington University, St Louis, MO, USA
| | - David A Wattchow
- Discipline of Surgery, College of Medicine and Public Health, Flinders Medical Centre, Bedford Park, SA, Australia
| | - Julian Sorensen
- Visceral Neurophysiology Laboratory, College of Medicine and Public Health, Centre for Neuroscience, Flinders University, Bedford Park, SA, Australia
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19
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Dalziel JE, Spencer NJ, Young W. Microbial signalling in colonic motility. Int J Biochem Cell Biol 2021; 134:105963. [PMID: 33636395 DOI: 10.1016/j.biocel.2021.105963] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 01/31/2021] [Accepted: 02/19/2021] [Indexed: 12/20/2022]
Abstract
Sensory nerve endings within the wall of the gastrointestinal (GI) tract may respond to bacterial signalling, providing the basis for key biological processes that underlie intestinal motility and microbial homeostasis. Enteric neurons and smooth muscle cells are well known to express an array of receptors, including G-protein coupled receptors and ligand-gated ion channels, that can sense chemical ligands and other bacterially-derived substances. These include short chain fatty acids, secondary bile acids and lipopolysaccharide. For neural detection of microbial activators to occur, luminal substances must first interact with enterocytes for direct signalling or cross paracellularly. Recent studies indicate that bacterial-derived microvesicles can cross the gut epithelial barrier and affect motility. This suggests a possible intercellular communication pathway between the GI tract and the ENS. We explore the idea that bacterial microvesicles can behave as a delivery package for communication between microbe and host.
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Affiliation(s)
- Julie E Dalziel
- Smart Foods Innovation Centre of Excellence, AgResearch, Palmerston North, New Zealand.
| | - Nick J Spencer
- Discipline of Physiology, College of Medicine and Public Health, Flinders University, School of Medicine, Adelaide, SA, Australia
| | - Wayne Young
- Smart Foods Innovation Centre of Excellence, AgResearch, Palmerston North, New Zealand
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20
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Fung C, Vanden Berghe P. Functional circuits and signal processing in the enteric nervous system. Cell Mol Life Sci 2020; 77:4505-4522. [PMID: 32424438 PMCID: PMC7599184 DOI: 10.1007/s00018-020-03543-6] [Citation(s) in RCA: 97] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Revised: 04/13/2020] [Accepted: 04/27/2020] [Indexed: 02/06/2023]
Abstract
The enteric nervous system (ENS) is an extensive network comprising millions of neurons and glial cells contained within the wall of the gastrointestinal tract. The major functions of the ENS that have been most studied include the regulation of local gut motility, secretion, and blood flow. Other areas that have been gaining increased attention include its interaction with the immune system, with the gut microbiota and its involvement in the gut-brain axis, and neuro-epithelial interactions. Thus, the enteric circuitry plays a central role in intestinal homeostasis, and this becomes particularly evident when there are faults in its wiring such as in neurodevelopmental or neurodegenerative disorders. In this review, we first focus on the current knowledge on the cellular composition of enteric circuits. We then further discuss how enteric circuits detect and process external information, how these signals may be modulated by physiological and pathophysiological factors, and finally, how outputs are generated for integrated gut function.
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Affiliation(s)
- Candice Fung
- Laboratory for Enteric NeuroScience (LENS), Translational Research Center for Gastrointestinal Disorders (TARGID), University of Leuven, Leuven, Belgium
| | - Pieter Vanden Berghe
- Laboratory for Enteric NeuroScience (LENS), Translational Research Center for Gastrointestinal Disorders (TARGID), University of Leuven, Leuven, Belgium.
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21
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Mah SA, Avci R, Cheng LK, Du P. Current applications of mathematical models of the interstitial cells of Cajal in the gastrointestinal tract. WIREs Mech Dis 2020; 13:e1507. [PMID: 33026190 DOI: 10.1002/wsbm.1507] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 08/31/2020] [Accepted: 09/04/2020] [Indexed: 12/25/2022]
Abstract
The interstitial cells of Cajal (ICC) form interconnected networks throughout the gastrointestinal (GI) tract. ICC act as the pacemaker cells that initiate the rhythmic bioelectrical slow waves and intermediary between the GI musculature and nerves, both of which are critical to GI motility. Disruptions to the number of ICC and the integrity of ICC networks have been identified as a key pathophysiological mechanism in a number of clinically challenging GI disorders. The current analyses of ICC generally rely on either functional recordings taken directly from excised tissue or morphological analysis based on images of labeled ICC, where the structural-functional relationship is investigated in an associative manner rather than mechanistically. On the other hand, computational physiology has played a significant role in facilitating our understanding of a number of physiological systems in both health and disease, and investigations in the GI field are beginning to incorporate several mathematical models of the ICC. The main aim of this review is to present the major modeling advances in GI electrophysiology, in order to introduce a multi-scale framework for mathematically quantifying the functional consequences of ICC degradation at both cellular and tissue scales. The outcomes will inform future investigators utilizing modeling techniques in their studies. This article is categorized under: Metabolic Diseases > Computational Models.
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Affiliation(s)
- Sue Ann Mah
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Recep Avci
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Leo K Cheng
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Peng Du
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand.,Department of Engineering Science, University of Auckland, Auckland, New Zealand
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22
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Mah SA, Avci R, Du P, Vanderwinden JM, Cheng LK. Supervised Machine Learning Segmentation and Quantification of Gastric Pacemaker Cells. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2020:1408-1411. [PMID: 33018253 DOI: 10.1109/embc44109.2020.9176445] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Interstitial Cells of Cajal (ICC) are specialized pacemaker cells that generate and actively propagate electrophysiological events called slow waves. Slow waves regulate the motility of the gastrointestinal tract necessary for digesting food. Degradation in the ICC network structure has been qualitatively associated to several gastrointestinal motility disorders. ICC network structure can be obtained using confocal microscopy, but the current limitations in imaging and segmentation techniques have hindered an accurate representation of the networks. In this study, supervised machine learning techniques were applied to extract the ICC networks from 3D confocal microscopy images. The results showed that the Fast Random Forest classification method using Trainable WEKA Segmentation outperformed the Decision Table and Naïve Bayes classification methods in sensitivity, accuracy, and F-measure. Using the Fast Random Forest classifier, 12 gastric antrum tissue blocks were segmented and variations in ICC network thickness, density and process width were quantified for the myenteric plexus ICC network (the primary pacemakers). Our findings demonstrated regional variation in ICC network density and thickness along the circumferential and longitudinal axis of the mouse antrum. An inverse relationship was observed in the distal and proximal antrum for density (proximal: 9.8±4.0% vs distal: 7.6±4.6%) and thickness (proximal: 15±3 μm vs distal: 24±10 μm). Limited variation in ICC process width was observed throughout the antrum (5±1 μm).Clinical Relevance- Detailed quantification of regional ICC structural properties will provide insights into the relationship between ICC structure, slow waves and resultant gut motility. This will improve techniques for the diagnosis and treatment of functional GI motility disorders.
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23
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Enteric nervous system: sensory transduction, neural circuits and gastrointestinal motility. Nat Rev Gastroenterol Hepatol 2020; 17:338-351. [PMID: 32152479 PMCID: PMC7474470 DOI: 10.1038/s41575-020-0271-2] [Citation(s) in RCA: 266] [Impact Index Per Article: 66.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 01/27/2020] [Indexed: 02/07/2023]
Abstract
The gastrointestinal tract is the only internal organ to have evolved with its own independent nervous system, known as the enteric nervous system (ENS). This Review provides an update on advances that have been made in our understanding of how neurons within the ENS coordinate sensory and motor functions. Understanding this function is critical for determining how deficits in neurogenic motor patterns arise. Knowledge of how distension or chemical stimulation of the bowel evokes sensory responses in the ENS and central nervous system have progressed, including critical elements that underlie the mechanotransduction of distension-evoked colonic peristalsis. Contrary to original thought, evidence suggests that mucosal serotonin is not required for peristalsis or colonic migrating motor complexes, although it can modulate their characteristics. Chemosensory stimuli applied to the lumen can release substances from enteroendocrine cells, which could subsequently modulate ENS activity. Advances have been made in optogenetic technologies, such that specific neurochemical classes of enteric neurons can be stimulated. A major focus of this Review will be the latest advances in our understanding of how intrinsic sensory neurons in the ENS detect and respond to sensory stimuli and how these mechanisms differ from extrinsic sensory nerve endings in the gut that underlie the gut-brain axis.
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24
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Zheng H, Drumm BT, Zhu MH, Xie Y, O'Driscoll KE, Baker SA, Perrino BA, Koh SD, Sanders KM. Na +/Ca 2 + Exchange and Pacemaker Activity of Interstitial Cells of Cajal. Front Physiol 2020; 11:230. [PMID: 32256387 PMCID: PMC7093646 DOI: 10.3389/fphys.2020.00230] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 02/27/2020] [Indexed: 01/30/2023] Open
Abstract
Interstitial cells of Cajal (ICC) are pacemaker cells that generate electrical slow waves in gastrointestinal (GI) smooth muscles. Slow waves organize basic motor patterns, such as peristalsis and segmentation in the GI tract. Slow waves depend upon activation of Ca2+-activated Cl– channels (CaCC) encoded by Ano1. Slow waves consist of an upstroke depolarization and a sustained plateau potential that is the main factor leading to excitation-contraction coupling. The plateau phase can last for seconds in some regions of the GI tract. How elevated Ca2+ is maintained throughout the duration of slow waves, which is necessary for sustained activation of CaCC, is unknown. Modeling has suggested a role for Na+/Ca2+ exchanger (NCX) in regulating CaCC currents in ICC, so we tested this idea on murine intestinal ICC. ICC of small and large intestine express NCX isoforms. NCX3 is closely associated with ANO1 in ICC, as shown by immunoprecipitation and proximity ligation assays (PLA). KB-R7943, an inhibitor of NCX, increased CaCC current in ICC, suggesting that NCX, acting in Ca2+ exit mode, helps to regulate basal [Ca2+]i in these cells. Shifting NCX into Ca2+ entry mode by replacing extracellular Na+ with Li+ increased spontaneous transient inward currents (STICs), due to activation of CaCC. Stepping ICC from −80 to −40 mV activated slow wave currents that were reduced in amplitude and duration by NCX inhibitors, KB-R7943 and SN-6, and enhanced by increasing the NCX driving force. SN-6 reduced the duration of clustered Ca2+ transients that underlie the activation of CaCC and the plateau phase of slow waves. Our results suggest that NCX participates in slow waves as modeling has predicted. Dynamic changes in membrane potential and ionic gradients during slow waves appear to flip the directionality of NCX, facilitating removal of Ca2+ during the inter-slow wave interval and providing Ca2+ for sustained activation of ANO1 during the slow wave plateau phase.
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Affiliation(s)
- Haifeng Zheng
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, United States
| | - Bernard T Drumm
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, United States
| | - Mei Hong Zhu
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, United States
| | - Yeming Xie
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, United States
| | - Kate E O'Driscoll
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, United States
| | - Salah A Baker
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, United States
| | - Brian A Perrino
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, United States
| | - Sang Don Koh
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, United States
| | - Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, United States
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25
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Corsetti M, Costa M, Bassotti G, Bharucha AE, Borrelli O, Dinning P, Di Lorenzo C, Huizinga JD, Jimenez M, Rao S, Spiller R, Spencer NJ, Lentle R, Pannemans J, Thys A, Benninga M, Tack J. First translational consensus on terminology and definitions of colonic motility in animals and humans studied by manometric and other techniques. Nat Rev Gastroenterol Hepatol 2019; 16:559-579. [PMID: 31296967 PMCID: PMC7136172 DOI: 10.1038/s41575-019-0167-1] [Citation(s) in RCA: 88] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/30/2019] [Indexed: 12/19/2022]
Abstract
Alterations in colonic motility are implicated in the pathophysiology of bowel disorders, but high-resolution manometry of human colonic motor function has revealed that our knowledge of normal motor patterns is limited. Furthermore, various terminologies and definitions have been used to describe colonic motor patterns in children, adults and animals. An example is the distinction between the high-amplitude propagating contractions in humans and giant contractions in animals. Harmonized terminology and definitions are required that are applicable to the study of colonic motility performed by basic scientists and clinicians, as well as adult and paediatric gastroenterologists. As clinical studies increasingly require adequate animal models to develop and test new therapies, there is a need for rational use of terminology to describe those motor patterns that are equivalent between animals and humans. This Consensus Statement provides the first harmonized interpretation of commonly used terminology to describe colonic motor function and delineates possible similarities between motor patterns observed in animal models and humans in vitro (ex vivo) and in vivo. The consolidated terminology can be an impetus for new research that will considerably improve our understanding of colonic motor function and will facilitate the development and testing of new therapies for colonic motility disorders.
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Affiliation(s)
- Maura Corsetti
- NIHR Nottingham Biomedical Research Centre (BRC), Nottingham University Hospitals NHS Trust and the University of Nottingham, Nottingham, UK
- Nottingham Digestive Diseases Centre, School of Medicine, University of Nottingham, Nottingham, UK
| | - Marcello Costa
- Human Physiology and Centre of Neuroscience, College of Medicine, Flinders University, Bedford Park, South Australia, Australia
| | - Gabrio Bassotti
- Department of Medicine, University of Perugia Medical School, Perugia, Italy
| | - Adil E Bharucha
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN, USA
| | - Osvaldo Borrelli
- Department of Paediatric Gastroenterology, Great Ormond Street Hospital for Sick Children, London, UK
| | - Phil Dinning
- Human Physiology and Centre of Neuroscience, College of Medicine, Flinders University, Bedford Park, South Australia, Australia
- Department of Gastroenterology and Surgery, Flinders Medical Centre, Adelaide, South Australia, Australia
| | - Carlo Di Lorenzo
- Department of Pediatric Gastroenterology, Nationwide Children's Hospital, The Ohio State University, Columbus, OH, USA
| | - Jan D Huizinga
- Department of Medicine, Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, Ontario, Canada
| | - Marcel Jimenez
- Department of Cell Physiology, Physiology and Immunology and Neuroscience Institute, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Satish Rao
- Division of Gastroenterology/Hepatology, Augusta University, Augusta, GA, USA
| | - Robin Spiller
- NIHR Nottingham Biomedical Research Centre (BRC), Nottingham University Hospitals NHS Trust and the University of Nottingham, Nottingham, UK
- Nottingham Digestive Diseases Centre, School of Medicine, University of Nottingham, Nottingham, UK
| | - Nick J Spencer
- Discipline of Human Physiology, School of Medicine, Flinders University, Bedford Park, South Australia, Australia
| | - Roger Lentle
- Digestive Biomechanics Group, College of Health, Massey University, Palmerston North, New Zealand
| | - Jasper Pannemans
- Department of Paediatric Gastroenterology and Nutrition, Emma Children's Hospital/Academic Medical Centre, Amsterdam, Netherlands
| | - Alexander Thys
- Department of Paediatric Gastroenterology and Nutrition, Emma Children's Hospital/Academic Medical Centre, Amsterdam, Netherlands
| | - Marc Benninga
- Translational Research Center for Gastrointestinal disorders (TARGID), Department of Clinical and Experimental Medicine, University of Leuven, Leuven, Belgium
| | - Jan Tack
- Department of Paediatric Gastroenterology and Nutrition, Emma Children's Hospital/Academic Medical Centre, Amsterdam, Netherlands.
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Drumm BT, Hwang SJ, Baker SA, Ward SM, Sanders KM. Ca 2+ signalling behaviours of intramuscular interstitial cells of Cajal in the murine colon. J Physiol 2019; 597:3587-3617. [PMID: 31124144 DOI: 10.1113/jp278036] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 05/23/2019] [Indexed: 12/13/2022] Open
Abstract
KEY POINTS Colonic intramuscular interstitial cells of Cajal (ICC-IM) exhibit spontaneous Ca2+ transients manifesting as stochastic events from multiple firing sites with propagating Ca2+ waves occasionally observed. Firing of Ca2+ transients in ICC-IM is not coordinated with adjacent ICC-IM in a field of view or even with events from other firing sites within a single cell. Ca2+ transients, through activation of Ano1 channels and generation of inward current, cause net depolarization of colonic muscles. Ca2+ transients in ICC-IM rely on Ca2+ release from the endoplasmic reticulum via IP3 receptors, spatial amplification from RyRs and ongoing refilling of ER via the sarcoplasmic/endoplasmic-reticulum-Ca2+ -ATPase. ICC-IM are sustained by voltage-independent Ca2+ influx via store-operated Ca2+ entry. Some of the properties of Ca2+ in ICC-IM in the colon are similar to the behaviour of ICC located in the deep muscular plexus region of the small intestine, suggesting there are functional similarities between these classes of ICC. ABSTRACT A component of the SIP syncytium that regulates smooth muscle excitability in the colon is the intramuscular class of interstitial cells of Cajal (ICC-IM). All classes of ICC (including ICC-IM) express Ca2+ -activated Cl- channels, encoded by Ano1, and rely upon this conductance for physiological functions. Thus, Ca2+ handling in ICC is fundamental to colonic motility. We examined Ca2+ handling mechanisms in ICC-IM of murine proximal colon expressing GCaMP6f in ICC. Several Ca2+ firing sites were detected in each cell. While individual sites displayed rhythmic Ca2+ events, the overall pattern of Ca2+ transients was stochastic. No correlation was found between discrete Ca2+ firing sites in the same cell or in adjacent cells. Ca2+ transients in some cells initiated Ca2+ waves that spread along the cell at ∼100 µm s-1 . Ca2+ transients were caused by release from intracellular stores, but depended strongly on store-operated Ca2+ entry mechanisms. ICC Ca2+ transient firing regulated the resting membrane potential of colonic tissues as a specific Ano1 antagonist hyperpolarized colonic muscles by ∼10 mV. Ca2+ transient firing was independent of membrane potential and not affected by blockade of L- or T-type Ca2+ channels. Mechanisms regulating Ca2+ transients in the proximal colon displayed both similarities to and differences from the intramuscular type of ICC in the small intestine. Similarities and differences in Ca2+ release patterns might determine how ICC respond to neurotransmission in these two regions of the gastrointestinal tract.
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Affiliation(s)
- Bernard T Drumm
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, 89557, USA
| | - Sung J Hwang
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, 89557, USA
| | - Salah A Baker
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, 89557, USA
| | - Sean M Ward
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, 89557, USA
| | - Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, 89557, USA
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Yang Y, Vassilakos G, Hammers DW, Yang Z, Barton ER, Sweeney HL. Smooth muscle atrophy and colon pathology in SMN deficient mice. Am J Transl Res 2019; 11:1789-1799. [PMID: 30972202 PMCID: PMC6456546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2018] [Accepted: 12/23/2018] [Indexed: 06/09/2023]
Abstract
Spinal muscular atrophy (SMA) is an autosomal recessive genetic disorder characterized by loss of motor neurons in the ventral horn of the spinal cord. Clinical features such as progressively lethal respiratory weakness and associated muscle wasting have been extensively studied but less attention has been given to gastrointestinal (GI) dysfunction, which is common symptomatology in SMA patients with 43% constipation, 15% abdominal pain, and 14% meteorism. In the current study, the PrP92-SMN mouse model of SMA was utilized, to complement previous studies in which cells of the Enteric Nervous system (ENS) were susceptible to Smn (survival motor neuron) deficiency and could possibly be the basis of the observed GI symptoms. Necropsy of our mouse model showed impairment in feces excretion and smaller bladder mass, compared to Wild-Type (WT) animals. Along with the reduction in bladder mass, we also observed a decrease in the size of smooth muscles, due to reduction in Cross-Sectional Area (CSA). Interstitial cells of Cajal (ICC) provide important regulatory functions in the GI tract. To investigate if ICC are implicated in Smn deficient-induced colonic dysmotility, we assessed ICC distribution and abundance, by c-Kit, a well-established marker. SMA mice exhibited fewer c-Kit positive cells with altered localization, compared to WT. In conclusion, the observed histopathological abnormalities of our mouse model, can be secondary to SMN deficiency and could possibly underlie the GI symptoms observed in SMA patients. Future therapeutic approaches for SMA, must address not only CNS symptoms, but also non-motor-neuron-related symptoms. The PrP92-SMN mouse model could be a useful model for assessing therapeutic rescue of GI dysfunction in SMA.
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Affiliation(s)
- Yun Yang
- Department of Gastrointestinal Surgery, West China/Chengdu Shangjin Nanfu Hospital, Sichuan UniversityChengdu, Sichuan Province, China
- Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville, FL Myology Institute, University of Florida College of MedicineGainesville, FL
| | - George Vassilakos
- Department of Applied Physiology and Kinesiology, University of Florida College of Health and Human PerformanceGainesville, FL
| | - David W Hammers
- Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville, FL Myology Institute, University of Florida College of MedicineGainesville, FL
| | - Zhaohui Yang
- Department of Physiology, University of Pennsylvania Perelman School of MedicinePhiladelphia, PA
- Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville, FL Myology Institute, University of Florida College of MedicineGainesville, FL
| | - Elisabeth R Barton
- Department of Physiology, University of Pennsylvania Perelman School of MedicinePhiladelphia, PA
- Department of Applied Physiology and Kinesiology, University of Florida College of Health and Human PerformanceGainesville, FL
| | - Hugh Lee Sweeney
- Department of Physiology, University of Pennsylvania Perelman School of MedicinePhiladelphia, PA
- Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville, FL Myology Institute, University of Florida College of MedicineGainesville, FL
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28
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Wong J, Chopra J, Chiang LLW, Liu T, Ho J, Wu WKK, Tse G, Wong SH. The Role of Connexins in Gastrointestinal Diseases. J Mol Biol 2019; 431:643-652. [PMID: 30639409 DOI: 10.1016/j.jmb.2019.01.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 10/03/2018] [Accepted: 01/04/2019] [Indexed: 12/13/2022]
Abstract
Gap junctions are hexagonal arrays of protein molecules in the plasma membrane and were first described in Mauthner cell synapses of goldfish. They form pathways for coupling between cells, allowing passive, electrotonic spread of ions and also passage of larger molecules such as amino acids and nucleotides. They are expressed in both excitable and non-excitable tissues. Each gap junction is made of two connexons, which are hexameric proteins of the connexin subunit. In this review, the roles that connexins play in gastrointestinal motility, the mechanisms of altered connexin expression leading to inflammatory bowel disease, gastrointestinal infections, and gastrointestinal symptoms in autistic spectrum disorder are discussed in detail.
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Affiliation(s)
- Jeremy Wong
- Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong, PR China
| | - Jasmine Chopra
- Faculty of Arts and Science, University of Toronto, Toronto, Canada
| | | | - Tong Liu
- Tianjin Key Laboratory of Ionic-Molecular Function of Cardiovascular disease, Department of Cardiology, Tianjin Institute of Cardiology, Second Hospital of Tianjin Medical University, Tianjin 300211, PR China
| | - Jeffery Ho
- Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Hong Kong, PR China; Department of Medicine and Therapeutics, Chinese University of Hong Kong, Hong Kong, PR China
| | - William K K Wu
- Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Hong Kong, PR China; Department of Medicine and Therapeutics, Chinese University of Hong Kong, Hong Kong, PR China
| | - Gary Tse
- Department of Medicine and Therapeutics, Chinese University of Hong Kong, Hong Kong, PR China; Li Ka Shing Institute of Health Sciences, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, PR China.
| | - Sunny Hei Wong
- Department of Medicine and Therapeutics, Chinese University of Hong Kong, Hong Kong, PR China; Li Ka Shing Institute of Health Sciences, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong, PR China.
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29
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Sanders KM. Spontaneous Electrical Activity and Rhythmicity in Gastrointestinal Smooth Muscles. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1124:3-46. [PMID: 31183821 PMCID: PMC7035145 DOI: 10.1007/978-981-13-5895-1_1] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The gastrointestinal (GI) tract has multifold tasks of ingesting, processing, and assimilating nutrients and disposing of wastes at appropriate times. These tasks are facilitated by several stereotypical motor patterns that build upon the intrinsic rhythmicity of the smooth muscles that generate phasic contractions in many regions of the gut. Phasic contractions result from a cyclical depolarization/repolarization cycle, known as electrical slow waves, which result from intrinsic pacemaker activity. Interstitial cells of Cajal (ICC) are electrically coupled to smooth muscle cells (SMCs) and generate and propagate pacemaker activity and slow waves. The mechanism of slow waves is dependent upon specialized conductances expressed by pacemaker ICC. The primary conductances responsible for slow waves in mice are Ano1, Ca2+-activated Cl- channels (CaCCs), and CaV3.2, T-type, voltage-dependent Ca2+ channels. Release of Ca2+ from intracellular stores in ICC appears to be the initiator of pacemaker depolarizations, activation of T-type current provides voltage-dependent Ca2+ entry into ICC, as slow waves propagate through ICC networks, and Ca2+-induced Ca2+ release and activation of Ano1 in ICC amplifies slow wave depolarizations. Slow waves conduct to coupled SMCs, and depolarization elicited by these events enhances the open-probability of L-type voltage-dependent Ca2+ channels, promotes Ca2+ entry, and initiates contraction. Phasic contractions timed by the occurrence of slow waves provide the basis for motility patterns such as gastric peristalsis and segmentation. This chapter discusses the properties of ICC and proposed mechanism of electrical rhythmicity in GI muscles.
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Affiliation(s)
- Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada, Reno School of Medicine, Reno, NV, USA.
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Spencer NJ, Hibberd TJ, Travis L, Wiklendt L, Costa M, Hu H, Brookes SJ, Wattchow DA, Dinning PG, Keating DJ, Sorensen J. Identification of a Rhythmic Firing Pattern in the Enteric Nervous System That Generates Rhythmic Electrical Activity in Smooth Muscle. J Neurosci 2018; 38:5507-5522. [PMID: 29807910 PMCID: PMC8174132 DOI: 10.1523/jneurosci.3489-17.2018] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Revised: 04/30/2018] [Accepted: 05/09/2018] [Indexed: 11/21/2022] Open
Abstract
The enteric nervous system (ENS) contains millions of neurons essential for organization of motor behavior of the intestine. It is well established that the large intestine requires ENS activity to drive propulsive motor behaviors. However, the firing pattern of the ENS underlying propagating neurogenic contractions of the large intestine remains unknown. To identify this, we used high-resolution neuronal imaging with electrophysiology from neighboring smooth muscle. Myoelectric activity underlying propagating neurogenic contractions along murine large intestine [also referred to as colonic migrating motor complexes, (CMMCs)] consisted of prolonged bursts of rhythmic depolarizations at a frequency of ∼2 Hz. Temporal coordination of this activity in the smooth muscle over large spatial fields (∼7 mm, longitudinally) was dependent on the ENS. During quiescent periods between neurogenic contractions, recordings from large populations of enteric neurons, in mice of either sex, revealed ongoing activity. The onset of neurogenic contractions was characterized by the emergence of temporally synchronized activity across large populations of excitatory and inhibitory neurons. This neuronal firing pattern was rhythmic and temporally synchronized across large numbers of ganglia at ∼2 Hz. ENS activation preceded smooth muscle depolarization, indicating rhythmic depolarizations in smooth muscle were controlled by firing of enteric neurons. The cyclical emergence of temporally coordinated firing of large populations of enteric neurons represents a unique neural motor pattern outside the CNS. This is the first direct observation of rhythmic firing in the ENS underlying rhythmic electrical depolarizations in smooth muscle. The pattern of neuronal activity we identified underlies the generation of CMMCs.SIGNIFICANCE STATEMENT How the enteric nervous system (ENS) generates neurogenic contractions of smooth muscle in the gastrointestinal (GI) tract has been a long-standing mystery in vertebrates. It is well known that myogenic pacemaker cells exist in the GI tract [called interstitial cells of Cajal (ICCs)] that generate rhythmic myogenic contractions. However, the mechanisms underlying the generation of rhythmic neurogenic contractions of smooth muscle in the GI tract remains unknown. We developed a high-resolution neuronal imaging method with electrophysiology to address this issue. This technique revealed a novel pattern of rhythmic coordinated neuronal firing in the ENS that has never been identified. Rhythmic neuronal firing in the ENS was found to generate rhythmic neurogenic depolarizations in smooth muscle that underlie contraction of the GI tract.
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Affiliation(s)
- Nick J Spencer
- College of Medicine and Public Health and Centre for Neuroscience, Flinders University, Adelaide 5042, Australia,
| | - Timothy J Hibberd
- College of Medicine and Public Health and Centre for Neuroscience, Flinders University, Adelaide 5042, Australia
| | - Lee Travis
- College of Medicine and Public Health and Centre for Neuroscience, Flinders University, Adelaide 5042, Australia
| | - Lukasz Wiklendt
- College of Medicine and Public Health and Centre for Neuroscience, Flinders University, Adelaide 5042, Australia
| | - Marcello Costa
- College of Medicine and Public Health and Centre for Neuroscience, Flinders University, Adelaide 5042, Australia
| | - Hongzhen Hu
- Department of Anesthesiology, The Center for the Study of Itch, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Simon J Brookes
- College of Medicine and Public Health and Centre for Neuroscience, Flinders University, Adelaide 5042, Australia
| | - David A Wattchow
- Discipline of Surgery and Gastroenterology, Flinders Medical Centre, Bedford Park 5042, South Australia, Australia, and
| | - Phil G Dinning
- College of Medicine and Public Health and Centre for Neuroscience, Flinders University, Adelaide 5042, Australia
- Discipline of Surgery and Gastroenterology, Flinders Medical Centre, Bedford Park 5042, South Australia, Australia, and
| | - Damien J Keating
- College of Medicine and Public Health and Centre for Neuroscience, Flinders University, Adelaide 5042, Australia
| | - Julian Sorensen
- Cyber Sensing and Shaping, Cyber and Electronic Warfare Division, Defence, Science and Technology Group, Edinburgh, South Australia 5111, Australia
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31
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Naganuma S, Shiina T, Yasuda S, Suzuki Y, Shimizu Y. Histamine-enhanced contractile responses of gastric smooth muscle via interstitial cells of Cajal in the Syrian hamster. Neurogastroenterol Motil 2018; 30:e13255. [PMID: 29159902 DOI: 10.1111/nmo.13255] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2017] [Accepted: 10/28/2017] [Indexed: 12/22/2022]
Abstract
BACKGROUND Gastric motility is controlled by the autonomic and enteric nervous systems and by interstitial cells of Cajal (ICCs). Although histamine is known to be released from enterochromaffin-like cells in the gastric mucosa, its regulatory roles in gastric motility are still controversial. Therefore, we investigated the functional roles of histamine in gastric motility. METHODS Stomach preparations from hamsters were used because the stomach of hamsters can be easily separated into the forestomach and the glandular stomach. A whole preparation of the stomach was mounted in a Magnus tube, and mechanical responses were recorded using a force transducer. KEY RESULTS Exogenous application of histamine had little effect on contractile activity of the glandular stomach. In contrast, the monoamine evoked regular, periodic contractions in the forestomach. An H1 receptor agonist reproduced the contractile responses and an H1 receptor antagonist blocked histamine-evoked contractions. Atropine and tetrodotoxin did not affect the histamine-evoked contractions. Pretreatment with drugs that inhibit the activity of ICCs abolished the effects of histamine. CONCLUSION & INFERENCES The findings suggest that histamine regulates gastric motility by acting on ICCs via H1 receptors in the hamster. The remarkable ability of histamine to induce rhythmic contractions would be useful for treatment of gastric dysmotility.
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Affiliation(s)
- S Naganuma
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - T Shiina
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - S Yasuda
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - Y Suzuki
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan
| | - Y Shimizu
- Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, Gifu, Japan.,Center for Highly Advanced Integration of Nano and Life Sciences (G-CHAIN), Gifu University, Gifu, Japan
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32
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Drumm BT, Sung TS, Zheng H, Baker SA, Koh SD, Sanders KM. The effects of mitochondrial inhibitors on Ca 2+ signalling and electrical conductances required for pacemaking in interstitial cells of Cajal in the mouse small intestine. Cell Calcium 2018; 72:1-17. [PMID: 29748128 DOI: 10.1016/j.ceca.2018.01.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 01/26/2018] [Accepted: 01/27/2018] [Indexed: 01/16/2023]
Abstract
Interstitial cells of Cajal (ICC-MY) are pacemakers that generate and propagate electrical slow waves in gastrointestinal (GI) muscles. Slow waves appear to be generated by the release of Ca2+ from intracellular stores and activation of Ca2+-activated Cl- channels (Ano1). Conduction of slow waves to smooth muscle cells coordinates rhythmic contractions. Mitochondrial Ca2+ handling is currently thought to be critical for ICC pacemaking. Protonophores, inhibitors of the electron transport chain (FCCP, CCCP or antimycin) or mitochondrial Na+/Ca2+ exchange blockers inhibited slow waves in several GI muscles. Here we utilized Ca2+ imaging of ICC in small intestinal muscles in situ to determine the effects of mitochondrial drugs on Ca2+ transients in ICC. Muscles were obtained from mice expressing a genetically encoded Ca2+ indicator (GCaMP3) in ICC. FCCP, CCCP, antimycin, a uniporter blocker, Ru360, and a mitochondrial Na+/Ca2+ exchange inhibitor, CGP-37157 inhibited Ca2+ transients in ICC-MY. Effects were not due to depletion of ATP, as oligomycin did not affect Ca2+ transients. Patch-clamp experiments were performed to test the effects of the mitochondrial drugs on key pacemaker conductances, Ano1 and T-type Ca2+ (CaV3.2), in HEK293 cells. Antimycin blocked Ano1 and reduced CaV3.2 currents. CCCP blocked CaV3.2 current but did not affect Ano1 current. Ano1 and Cav3.2 currents were inhibited by CGP-37157. Inhibitory effects of mitochondrial drugs on slow waves and Ca2+ signalling in ICC can be explained by direct antagonism of key pacemaker conductances in ICC that generate and propagate slow waves. A direct obligatory role for mitochondria in pacemaker activity is therefore questionable.
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Affiliation(s)
- Bernard T Drumm
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
| | - Tae S Sung
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
| | - Haifeng Zheng
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
| | - Salah A Baker
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
| | - Sang D Koh
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA
| | - Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA.
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Iwata N, Fujimura T, Takai C, Odani K, Kawano S, Nakayama S. Dialysis membrane-enforced microelectrode array measurement of diverse gut electrical activity. Biosens Bioelectron 2017; 94:312-320. [PMID: 28319897 DOI: 10.1016/j.bios.2017.03.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 03/01/2017] [Accepted: 03/04/2017] [Indexed: 12/18/2022]
Abstract
A variety of electrical activities occur depending on the functional state in each section of the gut, but the application of microelectrode array (MEA) is rather limited. We thus developed a dialysis membranes-enforced technique to investigate diverse and complex spatio-temporal electrical activity in the gut. Muscle sheets isolated from the gastrointestinal (GI) tract of mice along with a piece of dialysis membrane were woven over and under the strings to fix them to the anchor rig, and mounted on an 8×8 MEA (inter-electrode distance=150µm). Small molecules (molecular weight <12,000) were exchanged through the membrane, maintaining a physiological environment. Low impedance MEA was used to measure electrical signals in a wide frequency range. We demonstrated the following examples: 1) pacemaker activity-like potentials accompanied by bursting spike-like potentials in the ileum; 2) electrotonic potentials reflecting local neurotransmission in the ileum; 3) myoelectric complex-like potentials consisting of slow and rapid oscillations accompanied by spike potentials in the colon. Despite their limited spatial resolution, these recordings detected transient electric activities that optical probes followed with difficulty. In Addition, propagation of pacemaker-like potential was visualized in the stomach and ileum. These results indicate that the dialysis membrane-enforced technique largely extends the application of MEA, probably due to stabilisation of the access resistance between each sensing electrode and a reference electrode and improvement of electric separation between sensing electrodes. We anticipate that this technique will be utilized to characterise spatio-temporal electrical activities in the gut in health and disease.
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Affiliation(s)
- Naoko Iwata
- Department of Cell Physiology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Takumi Fujimura
- Department of Pediatric Surgery, Keio University School of Medicine, Tokyo 160-8582, Japan
| | - Chiho Takai
- Department of Cell Physiology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Kei Odani
- Department of Cell Physiology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Shin Kawano
- Department of Cell Physiology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan
| | - Shinsuke Nakayama
- Department of Cell Physiology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan.
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Drumm BT, Hennig GW, Battersby MJ, Cunningham EK, Sung TS, Ward SM, Sanders KM, Baker SA. Clustering of Ca 2+ transients in interstitial cells of Cajal defines slow wave duration. J Gen Physiol 2017; 149:703-725. [PMID: 28592421 PMCID: PMC5496507 DOI: 10.1085/jgp.201711771] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 05/02/2017] [Indexed: 12/13/2022] Open
Abstract
Electrical slow waves in the small intestine are generated by pacemaker cells called interstitial cells of Cajal. Drumm et al. record clusters of Ca2+ transients in these cells that are entrained by voltage-dependent Ca2+ entry and which define the duration of the electrical slow waves. Interstitial cells of Cajal (ICC) in the myenteric plexus region (ICC-MY) of the small intestine are pacemakers that generate rhythmic depolarizations known as slow waves. Slow waves depend on activation of Ca2+-activated Cl− channels (ANO1) in ICC, propagate actively within networks of ICC-MY, and conduct to smooth muscle cells where they generate action potentials and phasic contractions. Thus, mechanisms of Ca2+ regulation in ICC are fundamental to the motor patterns of the bowel. Here, we characterize the nature of Ca2+ transients in ICC-MY within intact muscles, using mice expressing a genetically encoded Ca2+ sensor, GCaMP3, in ICC. Ca2+ transients in ICC-MY display a complex firing pattern caused by localized Ca2+ release events arising from multiple sites in cell somata and processes. Ca2+ transients are clustered within the time course of slow waves but fire asynchronously during these clusters. The durations of Ca2+ transient clusters (CTCs) correspond to slow wave durations (plateau phase). Simultaneous imaging and intracellular electrical recordings revealed that the upstroke depolarization of slow waves precedes clusters of Ca2+ transients. Summation of CTCs results in relatively uniform Ca2+ responses from one slow wave to another. These Ca2+ transients are caused by Ca2+ release from intracellular stores and depend on ryanodine receptors as well as amplification from IP3 receptors. Reduced extracellular Ca2+ concentrations and T-type Ca2+ channel blockers decreased the number of firing sites and firing probability of Ca2+ transients. In summary, the fundamental electrical events of small intestinal muscles generated by ICC-MY depend on asynchronous firing of Ca2+ transients from multiple intracellular release sites. These events are organized into clusters by Ca2+ influx through T-type Ca2+ channels to sustain activation of ANO1 channels and generate the plateau phase of slow waves.
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Affiliation(s)
- Bernard T Drumm
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV
| | - Grant W Hennig
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV
| | - Matthew J Battersby
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV
| | - Erin K Cunningham
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV
| | - Tae Sik Sung
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV
| | - Sean M Ward
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV
| | - Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV
| | - Salah A Baker
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV
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35
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Sanders KM, Kito Y, Hwang SJ, Ward SM. Regulation of Gastrointestinal Smooth Muscle Function by Interstitial Cells. Physiology (Bethesda) 2017; 31:316-26. [PMID: 27488743 DOI: 10.1152/physiol.00006.2016] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Interstitial cells of mesenchymal origin form gap junctions with smooth muscle cells in visceral smooth muscles and provide important regulatory functions. In gastrointestinal (GI) muscles, there are two distinct classes of interstitial cells, c-Kit(+) interstitial cells of Cajal and PDGFRα(+) cells, that regulate motility patterns. Loss of these cells may contribute to symptoms in GI motility disorders.
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Affiliation(s)
- Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada Reno School of Medicine, Reno, Nevada; and
| | - Yoshihiko Kito
- Department of Pharmacology, Faculty of Medicine, Saga University, Nabeshima, Japan
| | - Sung Jin Hwang
- Department of Physiology and Cell Biology, University of Nevada Reno School of Medicine, Reno, Nevada; and
| | - Sean M Ward
- Department of Physiology and Cell Biology, University of Nevada Reno School of Medicine, Reno, Nevada; and
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Drumm BT, Baker SA. Teaching a changing paradigm in physiology: a historical perspective on gut interstitial cells. ADVANCES IN PHYSIOLOGY EDUCATION 2017; 41:100-109. [PMID: 28188197 DOI: 10.1152/advan.00154.2016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 11/11/2016] [Accepted: 12/27/2016] [Indexed: 06/06/2023]
Abstract
The study and teaching of gastrointestinal (GI) physiology necessitates an understanding of the cellular basis of contractile and electrical coupling behaviors in the muscle layers that comprise the gut wall. Our knowledge of the cellular origin of GI motility has drastically changed over the last 100 yr. While the pacing and coordination of GI contraction was once thought to be solely attributable to smooth muscle cells, it is now widely accepted that the motility patterns observed in the GI tract exist as a result of a multicellular system, consisting of not only smooth muscle cells but also enteric neurons and distinct populations of specialized interstitial cells that all work in concert to ensure proper GI functions. In this historical perspective, we focus on the emerging role of interstitial cells in GI motility and examine the key discoveries and experiments that led to a major shift in a paradigm of GI physiology regarding the role of interstitial cells in modulating GI contractile patterns. A review of these now classic experiments and papers will enable students and educators to fully appreciate the complex, multicellular nature of GI muscles as well as impart lessons on how shifting paradigms in physiology are fueled by new technologies that lead to new emerging discoveries.
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Affiliation(s)
- Bernard T Drumm
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Salah A Baker
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
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Problems with extracellular recording of electrical activity in gastrointestinal muscle. Nat Rev Gastroenterol Hepatol 2016; 13:731-741. [PMID: 27756919 PMCID: PMC8325940 DOI: 10.1038/nrgastro.2016.161] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Motility patterns of the gastrointestinal tract are important for efficient processing of nutrients and waste. Peristalsis and segmentation are based on rhythmic electrical slow waves that generate the phasic contractions fundamental to gastrointestinal motility. Slow waves are generated and propagated actively by interstitial cells of Cajal (ICC), and these events conduct to smooth muscle cells to elicit excitation-contraction coupling. Extracellular electrical recording has been utilized to characterize slow-wave generation and propagation and abnormalities that might be responsible for gastrointestinal motility disorders. Electrode array recording and digital processing are being used to generate data for models of electrical propagation in normal and pathophysiological conditions. Here, we discuss techniques of extracellular recording as applied to gastrointestinal organs and how mechanical artefacts might contaminate these recordings and confound their interpretation. Without rigorous controls for movement, current interpretations of extracellular recordings might ascribe inaccurate behaviours and electrical anomalies to ICC networks and gastrointestinal muscles, bringing into question the findings and validity of models of gastrointestinal electrophysiology developed from these recordings.
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Lentle RG, Reynolds GW, Hulls CM, Chambers JP. Advanced spatiotemporal mapping methods give new insights into the coordination of contractile activity in the stomach of the rat. Am J Physiol Gastrointest Liver Physiol 2016; 311:G1064-G1075. [PMID: 27765760 DOI: 10.1152/ajpgi.00308.2016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Accepted: 10/12/2016] [Indexed: 01/31/2023]
Abstract
We used spatiotemporal mapping of strain rate to determine the direction of propagation and amplitudes of the longitudinal and circumferential components of antrocorporal (AC) contractions and fundal contractions in the rat stomach maintained ex vivo and containing a volume of fluid that was within its normal functional capacity. In the region of the greater curvature the longitudinal and circular components of AC contractions propagated synchronously at right angles to the arciform geometric axis of the stomach. However, the configuration of AC contractions was U shaped, neither the circular nor the longitudinal component of contractions being evident in the upper proximal corpus. Similarly, in the distal upper antrum of some preparations, circumferential components propagated more rapidly than longitudinal components. Ongoing "high-frequency, low-amplitude myogenic contractions" were identified in the upper proximal gastric corpus and on the anterior and posterior wall of the fundus. The amplitudes of these contractions were modulated in the occluded stomach by low-frequency pressure waves that occurred spontaneously. Hence the characteristics of phasic contractions vary regionally in the antrum and corpus and a previously undescribed high-frequency contractile component was identified in the proximal corpus and fundus, the latter being modulated in synchrony with cyclic variation in intrafundal pressure in the occluded fundus.
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Affiliation(s)
- R G Lentle
- Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand; and
| | - G W Reynolds
- Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand; and
| | - C M Hulls
- Institute of Food, Nutrition and Human Health, Massey University, Palmerston North, New Zealand; and
| | - J P Chambers
- Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Palmerston North, New Zealand
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Lee HJ, Park KS. [Current Status of Translational Research on Constipation]. THE KOREAN JOURNAL OF GASTROENTEROLOGY 2016; 68:143-7. [PMID: 27646583 DOI: 10.4166/kjg.2016.68.3.143] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Constipation is one of the most common gastrointestinal disorders with a prevalence up to 16.5% in the general population. It is frequently multifactorial and the pathophysiologic mechanism of constipation is not fully understood. Many preclinical studies of constipation have used animal models. Translational research using these animal models is essential to the investigation of neurogenic and myogenic mechanisms of colon, and to the estimation of the clinical efficacy of new drugs. In this review, we discuss some of the current translational research projects on constipation using animal models.
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Affiliation(s)
- Hyun Jik Lee
- Department of Internal Medicine, Keimyung University School of Medicine, Daegu, Korea
| | - Kyung Sik Park
- Department of Internal Medicine, Keimyung University School of Medicine, Daegu, Korea
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Tse G, Lai ETH, Lee APW, Yan BP, Wong SH. Electrophysiological Mechanisms of Gastrointestinal Arrhythmogenesis: Lessons from the Heart. Front Physiol 2016; 7:230. [PMID: 27378939 PMCID: PMC4906021 DOI: 10.3389/fphys.2016.00230] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 05/30/2016] [Indexed: 01/09/2023] Open
Abstract
Disruptions in the orderly activation and recovery of electrical excitation traveling through the heart and the gastrointestinal (GI) tract can lead to arrhythmogenesis. For example, cardiac arrhythmias predispose to thromboembolic events resulting in cerebrovascular accidents and myocardial infarction, and to sudden cardiac death. By contrast, arrhythmias in the GI tract are usually not life-threatening and much less well characterized. However, they have been implicated in the pathogenesis of a number of GI motility disorders, including gastroparesis, dyspepsia, irritable bowel syndrome, mesenteric ischaemia, Hirschsprung disease, slow transit constipation, all of which are associated with significant morbidity. Both cardiac and gastrointestinal arrhythmias can broadly be divided into non-reentrant and reentrant activity. The aim of this paper is to compare and contrast the mechanisms underlying arrhythmogenesis in both systems to provide insight into the pathogenesis of GI motility disorders and potential molecular targets for future therapy.
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Affiliation(s)
- Gary Tse
- Li Ka Shing Faculty of Medicine, School of Biomedical Sciences, The University of Hong KongHong Kong, China
- Department of Medicine and Therapeutics, The Chinese University of Hong KongHong Kong, China
| | - Eric T. H. Lai
- Li Ka Shing Faculty of Medicine, School of Biomedical Sciences, The University of Hong KongHong Kong, China
| | - Alex P. W. Lee
- Department of Medicine and Therapeutics, The Chinese University of Hong KongHong Kong, China
| | - Bryan P. Yan
- Department of Medicine and Therapeutics, The Chinese University of Hong KongHong Kong, China
| | - Sunny H. Wong
- Department of Medicine and Therapeutics, Institute of Digestive Disease, Li Ka Shing Institute of Health Sciences, The Chinese University of Hong KongHong Kong, China
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Tse G, Lai ETH, Yeo JM, Tse V, Wong SH. Mechanisms of Electrical Activation and Conduction in the Gastrointestinal System: Lessons from Cardiac Electrophysiology. Front Physiol 2016; 7:182. [PMID: 27303305 PMCID: PMC4885840 DOI: 10.3389/fphys.2016.00182] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 05/06/2016] [Indexed: 12/12/2022] Open
Abstract
The gastrointestinal (GI) tract is an electrically excitable organ system containing multiple cell types, which coordinate electrical activity propagating through this tract. Disruption in its normal electrophysiology is observed in a number of GI motility disorders. However, this is not well characterized and the field of GI electrophysiology is much less developed compared to the cardiac field. The aim of this article is to use the established knowledge of cardiac electrophysiology to shed light on the mechanisms of electrical activation and propagation along the GI tract, and how abnormalities in these processes lead to motility disorders and suggest better treatment options based on this improved understanding. In the first part of the article, the ionic contributions to the generation of GI slow wave and the cardiac action potential (AP) are reviewed. Propagation of these electrical signals can be described by the core conductor theory in both systems. However, specifically for the GI tract, the following unique properties are observed: changes in slow wave frequency along its length, periods of quiescence, synchronization in short distances and desynchronization over long distances. These are best described by a coupled oscillator theory. Other differences include the diminished role of gap junctions in mediating this conduction in the GI tract compared to the heart. The electrophysiology of conditions such as gastroesophageal reflux disease and gastroparesis, and functional problems such as irritable bowel syndrome are discussed in detail, with reference to ion channel abnormalities and potential therapeutic targets. A deeper understanding of the molecular basis and physiological mechanisms underlying GI motility disorders will enable the development of better diagnostic and therapeutic tools and the advancement of this field.
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Affiliation(s)
- Gary Tse
- Li Ka Shing Faculty of Medicine, School of Biomedical Sciences, University of Hong KongHong Kong, China
| | - Eric Tsz Him Lai
- Li Ka Shing Faculty of Medicine, School of Biomedical Sciences, University of Hong KongHong Kong, China
| | - Jie Ming Yeo
- School of Medicine, Imperial College LondonLondon, UK
| | - Vivian Tse
- Department of Physiology, McGill UniversityMontreal, QC, Canada
| | - Sunny Hei Wong
- Department of Medicine and Therapeutics, Institute of Digestive Disease, LKS Institute of Health Sciences, Chinese University of Hong KongHong Kong, China
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Baker SA, Drumm BT, Saur D, Hennig GW, Ward SM, Sanders KM. Spontaneous Ca(2+) transients in interstitial cells of Cajal located within the deep muscular plexus of the murine small intestine. J Physiol 2016; 594:3317-38. [PMID: 26824875 DOI: 10.1113/jp271699] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 01/24/2016] [Indexed: 01/13/2023] Open
Abstract
KEY POINTS Interstitial cells of Cajal at the level of the deep muscular plexus (ICC-DMP) in the small intestine generate spontaneous Ca(2+) transients that consist of localized Ca(2+) events and limited propagating Ca(2+) waves. Ca(2+) transients in ICC-DMP display variable characteristics: from discrete, highly localized Ca(2+) transients to regionalized Ca(2+) waves with variable rates of occurrence, amplitude, duration and spatial spread. Ca(2+) transients fired stochastically, with no cellular or multicellular rhythmic activity being observed. No correlation was found between the firing sites in adjacent cells. Ca(2+) transients in ICC-DMP are suppressed by the ongoing release of inhibitory neurotransmitter(s). Functional intracellular Ca(2+) stores are essential for spontaneous Ca(2+) transients, and the sarco/endoplasmic reticulum Ca(2+) -ATPase (SERCA) pump is necessary for maintenance of spontaneity. Ca(2+) release mechanisms involve both ryanodine receptors (RyRs) and inositol triphosphate receptors (InsP3 Rs). Release from these channels is interdependent. ICC express transcripts of multiple RyRs and InsP3 Rs, with Itpr1 and Ryr2 subtypes displaying the highest expression. ABSTRACT Interstitial cells of Cajal in the deep muscular plexus of the small intestine (ICC-DMP) are closely associated with varicosities of enteric motor neurons and generate responses contributing to neural regulation of intestinal motility. Responses of ICC-DMP are mediated by activation of Ca(2+) -activated Cl(-) channels; thus, Ca(2+) signalling is central to the behaviours of these cells. Confocal imaging was used to characterize the nature and mechanisms of Ca(2+) transients in ICC-DMP within intact jejunal muscles expressing a genetically encoded Ca(2+) indicator (GCaMP3) selectively in ICC. ICC-DMP displayed spontaneous Ca(2+) transients that ranged from discrete, localized events to waves that propagated over variable distances. The occurrence of Ca(2+) transients was highly variable, and it was determined that firing was stochastic in nature. Ca(2+) transients were tabulated in multiple cells within fields of view, and no correlation was found between the events in adjacent cells. TTX (1 μm) significantly increased the occurrence of Ca(2+) transients, suggesting that ICC-DMP contributes to the tonic inhibition conveyed by ongoing activity of inhibitory motor neurons. Ca(2+) transients were minimally affected after 12 min in Ca(2+) free solution, indicating these events do not depend immediately upon Ca(2+) influx. However, inhibitors of sarco/endoplasmic reticulum Ca(2+) -ATPase (SERCA) pump and blockers of inositol triphosphate receptor (InsP3 R) and ryanodine receptor (RyR) channels blocked ICC Ca(2+) transients. These data suggest an interdependence between RyR and InsP3 R in the generation of Ca(2+) transients. Itpr1 and Ryr2 were the dominant transcripts expressed by ICC. These findings provide the first high-resolution recording of the subcellular Ca(2+) dynamics that control the behaviour of ICC-DMP in situ.
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Affiliation(s)
- Salah A Baker
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA
| | - Bernard T Drumm
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA
| | - Dieter Saur
- II. Medizinische Klinik und Poliklinik, Klinikum rechts der Isar der TU München, München, Germany
| | - Grant W Hennig
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA
| | - Sean M Ward
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA
| | - Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA
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Hashitani H, Mitsui R, Masaki S, Van Helden DF. Pacemaker role of pericytes in generating synchronized spontaneous Ca2+ transients in the myenteric microvasculature of the guinea-pig gastric antrum. Cell Calcium 2015; 58:442-56. [PMID: 26153078 DOI: 10.1016/j.ceca.2015.06.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 06/08/2015] [Accepted: 06/28/2015] [Indexed: 11/25/2022]
Abstract
Properties of spontaneous Ca(2+) transients in the myenteric microvasculature of the guinea-pig stomach were investigated. Specifically, we explored the spatio-temporal origin of Ca(2+) transients and the role of voltage-dependent Ca(2+) channels (VDCCs) in their intercellular synchrony using fluorescence Ca(2+) imaging and immunohistochemistry. The microvasculature generated spontaneous Ca(2+) transients that were independent of both Ca(2+) transients in interstitial cells of Cajal (ICC) and neural activity. Spontaneous Ca(2+) transients were highly synchronous along the length of microvasculature, and appeared to be initiated in pericytes and spread to arteriolar smooth muscle cells (SMCs). In most cases, the generation or synchrony of Ca(2+) transients was not affected by blockers of L-type VDCCs. In nifedipine-treated preparations, synchronous spontaneous Ca(2+) transients were readily blocked by Ni(2+), mibefradil or ML216, blockers for T-type VDCCs. These blockers also suppressed the known T-type VDCC dependent component of ICC Ca(2+) transients or slow waves. Spontaneous Ca(2+) transients were also suppressed by caffeine, tetracaine or cyclopiazonic acid (CPA). After the blockade of both L- and T-type VDCCs, asynchronous Ca(2+) transients were generated in pericytes on precapillary arterioles and/or capillaries but not in arteriolar SMCs, and were abolished by CPA or nominally Ca(2+) free solution. Together these data indicate that pericytes in the myenteric microvasculature may act as the origin of synchronous spontaneous Ca(2+) transients. Pericyte Ca(2+) transients arise from Ca(2+) release from the sarco-endoplasmic reticulum and the opening of T-type Ca(2+) VDCCs is required for their synchrony and propagation to arteriolar SMCs.
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Affiliation(s)
- Hikaru Hashitani
- Department of Cell Physiology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan.
| | - Retsu Mitsui
- Department of Cell Physiology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
| | - Shota Masaki
- Department of Cell Physiology, Graduate School of Medical Sciences, Nagoya City University, Nagoya, Japan
| | - Dirk F Van Helden
- School of Biomedical Sciences and Pharmacy, University of Newcastle, NSW, Australia
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Worth AA, Forrest AS, Peri LE, Ward SM, Hennig GW, Sanders KM. Regulation of gastric electrical and mechanical activity by cholinesterases in mice. J Neurogastroenterol Motil 2015; 21:200-16. [PMID: 25843073 PMCID: PMC4398240 DOI: 10.5056/jnm14120] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Revised: 11/15/2014] [Accepted: 11/18/2014] [Indexed: 12/03/2022] Open
Abstract
Background/Aims Gastric peristalsis begins in the orad corpus and propagates to the pylorus. Directionality of peristalsis depends upon orderly generation and propagation of electrical slow waves and a frequency gradient between proximal and distal pacemakers. We sought to understand how chronotropic agonists affect coupling between corpus and antrum. Methods Electrophysiological and imaging techniques were used to investigate regulation of gastric slow wave frequency by muscarinic agonists in mice. We also investigated the expression and role of cholinesterases in regulating slow wave frequency and motor patterns in the stomach. Results Both acetycholinesterase (Ache) and butyrylcholine esterase (Bche) are expressed in gastric muscles and AChE is localized to varicose processes of motor neurons. Inhibition of AChE in the absence of stimulation increased slow wave frequency in corpus and throughout muscle strips containing corpus and antrum. CCh caused depolarization and increased slow wave frequency. Stimulation of cholinergic neurons increased slow wave frequency but did not cause depolarization. Neostigmine (1 μM) increased slow wave frequency, but uncoupling between corpus and antrum was not detected. Motility mapping of contractile activity in gastric muscles showed similar effects of enteric nerve stimulation on the frequency and propagation of slow waves, but neostigmine (> 1 μM) caused aberrant contractile frequency and propagation and ectopic pacemaking. Conclusions Our data show that slow wave uncoupling is difficult to assess with electrical recording from a single or double sites and suggest that efficient metabolism of ACh released from motor neurons is an extremely important regulator of slow wave frequency and propagation and gastric motility patterns.
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Affiliation(s)
- Amy A Worth
- Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom
| | | | - Lauren E Peri
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, USA
| | - Sean M Ward
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, USA
| | - Grant W Hennig
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, USA
| | - Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada, USA
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Zhu MH, Sung TS, O'Driscoll K, Koh SD, Sanders KM. Intracellular Ca(2+) release from endoplasmic reticulum regulates slow wave currents and pacemaker activity of interstitial cells of Cajal. Am J Physiol Cell Physiol 2015; 308:C608-20. [PMID: 25631870 DOI: 10.1152/ajpcell.00360.2014] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 01/16/2015] [Indexed: 02/02/2023]
Abstract
Interstitial cells of Cajal (ICC) provide pacemaker activity in gastrointestinal muscles that underlies segmental and peristaltic contractions. ICC generate electrical slow waves that are due to large-amplitude inward currents resulting from anoctamin 1 (ANO1) channels, which are Ca(2+)-activated Cl(-) channels. We investigated the hypothesis that the Ca(2+) responsible for the stochastic activation of ANO1 channels during spontaneous transient inward currents (STICs) and synchronized activation of ANO1 channels during slow wave currents comes from intracellular Ca(2+) stores. ICC, obtained from the small intestine of Kit(+/copGFP) mice, were studied under voltage and current clamp to determine the effects of blocking Ca(2+) uptake into stores and release of Ca(2+) via inositol 1,4,5-trisphosphate (IP3)-dependent and ryanodine-sensitive channels. Cyclocpiazonic acid, thapsigargin, 2-APB, and xestospongin C inhibited STICs and slow wave currents. Ryanodine and tetracaine also inhibited STICs and slow wave currents. Store-active compounds had no direct effects on ANO1 channels expressed in human embryonic kidney-293 cells. Under current clamp, store-active drugs caused significant depolarization of ICC and reduced spontaneous transient depolarizations (STDs). After block of ryanodine receptors with ryanodine and tetracaine, repolarization did not restore STDs. ANO1 expressed in ICC has limited access to cytoplasmic Ca(2+) concentration, suggesting that pacemaker activity depends on Ca(2+) dynamics in restricted microdomains. Our data from studies of isolated ICC differ somewhat from studies on intact muscles and suggest that release of Ca(2+) from both IP3 and ryanodine receptors is important in generating pacemaker activity in ICC.
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Affiliation(s)
- Mei Hong Zhu
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Tae Sik Sung
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Kate O'Driscoll
- 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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Gravina FS, van Helden DF, Kerr KP, de Oliveira RB, Jobling P. Phasic contractions of the mouse vagina and cervix at different phases of the estrus cycle and during late pregnancy. PLoS One 2014; 9:e111307. [PMID: 25337931 PMCID: PMC4206458 DOI: 10.1371/journal.pone.0111307] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2014] [Accepted: 09/30/2014] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND/AIMS The pacemaker mechanisms activating phasic contractions of vaginal and cervical smooth muscle remain poorly understood. Here, we investigate properties of pacemaking in vaginal and cervical tissues by determining whether: 1) functional pacemaking is dependent on the phase of the estrus cycle or pregnancy; 2) pacemaking involves Ca2+ release from sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA) -dependent intracellular Ca2+ stores; and 3) c-Kit and/or vimentin immunoreactive ICs have a role in pacemaking. METHODOLOGY/PRINCIPAL FINDINGS Vaginal and cervical contractions were measured in vitro, as was the distribution of c-Kit and vimentin positive interstitial cells (ICs). Cervical smooth muscle was spontaneously active in estrus and metestrus but quiescent during proestrus and diestrus. Vaginal smooth muscle was normally quiescent but exhibited phasic contractions in the presence of oxytocin or the K+ channel blocker tetraethylammonium (TEA) chloride. Spontaneous contractions in the cervix and TEA-induced phasic contractions in the vagina persisted in the presence of cyclopiazonic acid (CPA), a blocker of the SERCA that refills intracellular SR Ca2+ stores, but were inhibited in low Ca2+ solution or in the presence of nifedipine, an inhibitor of L-type Ca2+channels. ICs were found in small numbers in the mouse cervix but not in the vagina. CONCLUSIONS/SIGNIFICANCE Cervical smooth muscle strips taken from mice in estrus, metestrus or late pregnancy were generally spontaneously active. Vaginal smooth muscle strips were normally quiescent but could be induced to exhibit phasic contractions independent on phase of the estrus cycle or late pregnancy. Spontaneous cervical or TEA-induced vaginal phasic contractions were not mediated by ICs or intracellular Ca2+ stores. Given that vaginal smooth muscle is normally quiescent then it is likely that increases in hormones such as oxytocin, as might occur through sexual stimulation, enhance the effectiveness of such pacemaking until phasic contractile activity emerges.
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Affiliation(s)
- Fernanda S. Gravina
- School of Biomedical Sciences & Pharmacy, Faculty of Health & Medicine, The University of Newcastle, Callaghan, NSW, Australia
| | - Dirk F. van Helden
- School of Biomedical Sciences & Pharmacy, Faculty of Health & Medicine, The University of Newcastle, Callaghan, NSW, Australia
| | - Karen P. Kerr
- School of Biomedical Sciences & Pharmacy, Faculty of Health & Medicine, The University of Newcastle, Callaghan, NSW, Australia
| | - Ramatis B. de Oliveira
- School of Biomedical Sciences & Pharmacy, Faculty of Health & Medicine, The University of Newcastle, Callaghan, NSW, Australia
| | - Phillip Jobling
- School of Biomedical Sciences & Pharmacy, Faculty of Health & Medicine, The University of Newcastle, Callaghan, NSW, Australia
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Sanders KM, Ward SM, Koh SD. Interstitial cells: regulators of smooth muscle function. Physiol Rev 2014; 94:859-907. [PMID: 24987007 DOI: 10.1152/physrev.00037.2013] [Citation(s) in RCA: 313] [Impact Index Per Article: 31.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Smooth muscles are complex tissues containing a variety of cells in addition to muscle cells. Interstitial cells of mesenchymal origin interact with and form electrical connectivity with smooth muscle cells in many organs, and these cells provide important regulatory functions. For example, in the gastrointestinal tract, interstitial cells of Cajal (ICC) and PDGFRα(+) cells have been described, in detail, and represent distinct classes of cells with unique ultrastructure, molecular phenotypes, and functions. Smooth muscle cells are electrically coupled to ICC and PDGFRα(+) cells, forming an integrated unit called the SIP syncytium. SIP cells express a variety of receptors and ion channels, and conductance changes in any type of SIP cell affect the excitability and responses of the syncytium. SIP cells are known to provide pacemaker activity, propagation pathways for slow waves, transduction of inputs from motor neurons, and mechanosensitivity. Loss of interstitial cells has been associated with motor disorders of the gut. Interstitial cells are also found in a variety of other smooth muscles; however, in most cases, the physiological and pathophysiological roles for these cells have not been clearly defined. This review describes structural, functional, and molecular features of interstitial cells and discusses their contributions in determining the behaviors of smooth muscle tissues.
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Affiliation(s)
- Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada
| | - Sean M Ward
- 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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Carbone SE, Wattchow DA, Spencer NJ, Hibberd TJ, Brookes SJH. Damage from dissection is associated with reduced neuro-musclar transmission and gap junction coupling between circular muscle cells of guinea pig ileum, in vitro. Front Physiol 2014; 5:319. [PMID: 25202280 PMCID: PMC4141521 DOI: 10.3389/fphys.2014.00319] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Accepted: 08/04/2014] [Indexed: 11/13/2022] Open
Abstract
Excitatory and inhibitory junction potentials of circular smooth muscle cells in guinea pig ileum and colon are suppressed 30–90 min after setting up in vitro preparations. We have previously shown this “unresponsive” period is associated with a transient loss of dye coupling between smooth muscle cells, which subsequently recovers over the ensuing 30–90 min; junction potentials recover in parallel with dye coupling (Carbone et al., 2012). Here, we investigated which components of dissection trigger the initial loss of coupling. Intracellular recordings were made from circular muscle cells of guinea pig ileum with micropipettes containing 5% carboxyfluorescein. After allowing 90–120 min for junction potentials to reach full amplitude, we re-cut all 4 edges of the preparation more than 1 mm from the recording sites. This caused a reduction in the amplitude of IJPs from 17.2 ± 0.7 mV to 9.5 ± 1.5 mV (P < 0.001, n = 12) and a significant reduction in dye coupling. Both recovered within 60 min. We repeated this experiment (n = 4), recording both 1 and 4 mm from the cut edge: both sites were equally affected by re-cutting the sides of the preparation. Equilibrated preparations were stretched to 150% of their original length, this had no significant effect on junction potentials or dye coupling. Setting up preparations in low calcium solution did not prevent the initial suppression of IJPs and dye coupling. Application of 3 μM indomethacin (n = 3), 10 μM ketotifen (n = 4) or 10 μM forskolin during dissection did not prevent the suppression of IJPs and dye coupling. If dissection damage was reduced, by leaving the mucosa and submucosa attached to the circular muscle, IJPs showed less initial suppression than in preparations where the layers were dissected off. We conclude that physical damage to the gut wall triggers loss of gap junction coupling and neuromuscular transmission, this is not due to stretch, influx of calcium ions, release of prostaglandins or mast cell degranulation. The mechanisms underlying this potent effect remain to be determined.
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Affiliation(s)
- Simona E Carbone
- Centre for Chronic Disease Prevention and Management, Enteric Neuropathy Laboratory, College of Health and Biomedicine, Victoria University Melbourne, VIC, Australia
| | - David A Wattchow
- Neurogastroenterology Laboratory, Surgery, Discipline of Human Physiology and Centre for Neuroscience, Flinders Medical Science and Technology, Flinders University Adelaide, SA, Australia
| | - Nick J Spencer
- Discipline of Surgery and Centre for Neuroscience, Flinders University Adelaide, SA, Australia
| | - Timothy J Hibberd
- Discipline of Surgery and Centre for Neuroscience, Flinders University Adelaide, SA, Australia
| | - Simon J H Brookes
- Discipline of Surgery and Centre for Neuroscience, Flinders University Adelaide, SA, Australia
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Blair PJ, Rhee PL, Sanders KM, Ward SM. The significance of interstitial cells in neurogastroenterology. J Neurogastroenterol Motil 2014; 20:294-317. [PMID: 24948131 PMCID: PMC4102150 DOI: 10.5056/jnm14060] [Citation(s) in RCA: 90] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2014] [Revised: 06/06/2014] [Accepted: 06/07/2014] [Indexed: 12/21/2022] Open
Abstract
Smooth muscle layers of the gastrointestinal tract consist of a heterogeneous population of cells that include enteric neurons, several classes of interstitial cells of mesenchymal origin, a variety of immune cells and smooth muscle cells (SMCs). Over the last number of years the complexity of the interactions between these cell types has begun to emerge. For example, interstitial cells, consisting of both interstitial cells of Cajal (ICC) and platelet-derived growth factor receptor alpha-positive (PDGFRα(+)) cells generate pacemaker activity throughout the gastrointestinal (GI) tract and also transduce enteric motor nerve signals and mechanosensitivity to adjacent SMCs. ICC and PDGFRα(+) cells are electrically coupled to SMCs possibly via gap junctions forming a multicellular functional syncytium termed the SIP syncytium. Cells that make up the SIP syncytium are highly specialized containing unique receptors, ion channels and intracellular signaling pathways that regulate the excitability of GI muscles. The unique role of these cells in coordinating GI motility is evident by the altered motility patterns in animal models where interstitial cell networks are disrupted. Although considerable advances have been made in recent years on our understanding of the roles of these cells within the SIP syncytium, the full physiological functions of these cells and the consequences of their disruption in GI muscles have not been clearly defined. This review gives a synopsis of the history of interstitial cell discovery and highlights recent advances in structural, molecular expression and functional roles of these cells in the GI tract.
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Affiliation(s)
- Peter J Blair
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA; and
| | - Poong-Lyul Rhee
- Division of Gastroenterology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA; and
| | - Sean M Ward
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA; and
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50
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Blair PJ, Rhee PL, Sanders KM, Ward SM. The significance of interstitial cells in neurogastroenterology. J Neurogastroenterol Motil 2014. [PMID: 24948131 DOI: 10.5056/jnm140] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Smooth muscle layers of the gastrointestinal tract consist of a heterogeneous population of cells that include enteric neurons, several classes of interstitial cells of mesenchymal origin, a variety of immune cells and smooth muscle cells (SMCs). Over the last number of years the complexity of the interactions between these cell types has begun to emerge. For example, interstitial cells, consisting of both interstitial cells of Cajal (ICC) and platelet-derived growth factor receptor alpha-positive (PDGFRα(+)) cells generate pacemaker activity throughout the gastrointestinal (GI) tract and also transduce enteric motor nerve signals and mechanosensitivity to adjacent SMCs. ICC and PDGFRα(+) cells are electrically coupled to SMCs possibly via gap junctions forming a multicellular functional syncytium termed the SIP syncytium. Cells that make up the SIP syncytium are highly specialized containing unique receptors, ion channels and intracellular signaling pathways that regulate the excitability of GI muscles. The unique role of these cells in coordinating GI motility is evident by the altered motility patterns in animal models where interstitial cell networks are disrupted. Although considerable advances have been made in recent years on our understanding of the roles of these cells within the SIP syncytium, the full physiological functions of these cells and the consequences of their disruption in GI muscles have not been clearly defined. This review gives a synopsis of the history of interstitial cell discovery and highlights recent advances in structural, molecular expression and functional roles of these cells in the GI tract.
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Affiliation(s)
- Peter J Blair
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA
| | - Poong-Lyul Rhee
- Division of Gastroenterology, Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Kenton M Sanders
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA
| | - Sean M Ward
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA
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