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Sharkey KA, Mawe GM. The enteric nervous system. Physiol Rev 2023; 103:1487-1564. [PMID: 36521049 PMCID: PMC9970663 DOI: 10.1152/physrev.00018.2022] [Citation(s) in RCA: 58] [Impact Index Per Article: 58.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 12/12/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022] Open
Abstract
Of all the organ systems in the body, the gastrointestinal tract is the most complicated in terms of the numbers of structures involved, each with different functions, and the numbers and types of signaling molecules utilized. The digestion of food and absorption of nutrients, electrolytes, and water occurs in a hostile luminal environment that contains a large and diverse microbiota. At the core of regulatory control of the digestive and defensive functions of the gastrointestinal tract is the enteric nervous system (ENS), a complex system of neurons and glia in the gut wall. In this review, we discuss 1) the intrinsic neural control of gut functions involved in digestion and 2) how the ENS interacts with the immune system, gut microbiota, and epithelium to maintain mucosal defense and barrier function. We highlight developments that have revolutionized our understanding of the physiology and pathophysiology of enteric neural control. These include a new understanding of the molecular architecture of the ENS, the organization and function of enteric motor circuits, and the roles of enteric glia. We explore the transduction of luminal stimuli by enteroendocrine cells, the regulation of intestinal barrier function by enteric neurons and glia, local immune control by the ENS, and the role of the gut microbiota in regulating the structure and function of the ENS. Multifunctional enteric neurons work together with enteric glial cells, macrophages, interstitial cells, and enteroendocrine cells integrating an array of signals to initiate outputs that are precisely regulated in space and time to control digestion and intestinal homeostasis.
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Affiliation(s)
- Keith A Sharkey
- Hotchkiss Brain Institute and Snyder Institute for Chronic Diseases, Department of Physiology and Pharmacology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Gary M Mawe
- Department of Neurological Sciences, Larner College of Medicine, University of Vermont, Burlington, Vermont
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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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3
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Abstract
Elevated levels of cyclooxygenase-2 (COX-2) and prostaglandins (PGs) are involved in the pathogenesis of Alzheimer's disease (AD), which is characterized by the accumulation of β-amyloid protein (Aβ) and tau hyperphosphorylation. However, the gaps in our knowledge of the roles of COX-2 and PGs in AD have not been filled. Here, we summarized the literature showing that COX-2 dysregulation obviously influences abnormal cleavage of β-amyloid precursor protein, aggregation and deposition of Aβ in β-amyloid plaques and the inclusion of phosphorylated tau in neurofibrillary tangles. Neuroinflammation, oxidative stress, synaptic plasticity, neurotoxicity, autophagy, and apoptosis have been assessed to elucidate the mechanisms of COX-2 regulation of AD. Notably, an imbalance of these factors ultimately produces cognitive decline. The current review substantiates our understanding of the mechanisms of COX-2-induced AD and establishes foundations for the design of feasible therapeutic strategies to treat AD.-Guan, P.-P., Wang, P. Integrated communications between cyclooxygenase-2 and Alzheimer's disease.
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Affiliation(s)
- Pei-Pei Guan
- College of Life and Health Sciences, Northeastern University, Shenyang, China
| | - Pu Wang
- College of Life and Health Sciences, Northeastern University, Shenyang, China
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Fung C, Koussoulas K, Unterweger P, Allen AM, Bornstein JC, Foong JPP. Cholinergic Submucosal Neurons Display Increased Excitability Following in Vivo Cholera Toxin Exposure in Mouse Ileum. Front Physiol 2018; 9:260. [PMID: 29618987 PMCID: PMC5871806 DOI: 10.3389/fphys.2018.00260] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 03/06/2018] [Indexed: 12/16/2022] Open
Abstract
Cholera-induced hypersecretion causes dehydration and death if untreated. Cholera toxin (CT) partly acts via the enteric nervous system (ENS) and induces long-lasting changes to enteric neuronal excitability following initial exposure, but the specific circuitry involved remains unclear. We examined this by first incubating CT or saline (control) in mouse ileal loops in vivo for 3.5 h and then assessed neuronal excitability in vitro using Ca2+ imaging and immunolabeling for the activity-dependent markers cFos and pCREB. Mice from a C57BL6 background, including Wnt1-Cre;R26R-GCaMP3 mice which express the fluorescent Ca2+ indicator GCaMP3 in its ENS, were used. Ca2+-imaging using this mouse model is a robust, high-throughput method which allowed us to examine the activity of numerous enteric neurons simultaneously and post-hoc immunohistochemistry enabled the neurochemical identification of the active neurons. Together, this provided novel insight into the CT-affected circuitry that was previously impossible to attain at such an accelerated pace. Ussing chamber measurements of electrogenic ion secretion showed that CT-treated preparations had higher basal secretion than controls. Recordings of Ca2+ activity from the submucous plexus showed that increased numbers of neurons were spontaneously active in CT-incubated tissue (control: 4/149; CT: 32/160; Fisher's exact test, P < 0.0001) and that cholinergic neurons were more responsive to electrical (single pulse and train of 20 pulses) or nicotinic (1,1-dimethyl-4-phenylpiperazinium (DMPP; 10 μM) stimulation. Expression of the neuronal activity marker, pCREB, was also increased in the CT-treated submucous plexus neurons. c-Fos expression and spontaneous fast excitatory postsynaptic potentials (EPSPs), recorded by intracellular electrodes, were increased by CT exposure in a small subset of myenteric neurons. However, the effect of CT on the myenteric plexus is less clear as spontaneous Ca2+ activity and electrical- or nicotinic-evoked Ca2+ responses were reduced. Thus, in a model where CT exposure evokes hypersecretion, we observed sustained activation of cholinergic secretomotor neuron activity in the submucous plexus, pointing to involvement of these neurons in the overall response to CT.
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Affiliation(s)
- Candice Fung
- Department of Physiology, The University of Melbourne, Parkville, VIC, Australia
| | - Katerina Koussoulas
- Department of Physiology, The University of Melbourne, Parkville, VIC, Australia
| | - Petra Unterweger
- Department of Physiology, The University of Melbourne, Parkville, VIC, Australia
| | - Andrew M Allen
- Department of Physiology, The University of Melbourne, Parkville, VIC, Australia.,Florey Institute of Neuroscience and Mental Health, The University of Melbourne, Parkville, VIC, Australia
| | - Joel C Bornstein
- Department of Physiology, The University of Melbourne, Parkville, VIC, Australia
| | - Jaime P P Foong
- Department of Physiology, The University of Melbourne, Parkville, VIC, Australia
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The Intrinsic Reflex Circuitry of the Inflamed Colon. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 891:153-7. [DOI: 10.1007/978-3-319-27592-5_15] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Mawe GM. Colitis-induced neuroplasticity disrupts motility in the inflamed and post-inflamed colon. J Clin Invest 2015; 125:949-55. [PMID: 25729851 DOI: 10.1172/jci76306] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Effective colonic motility involves an intricate pattern of excitatory and inhibitory neuromuscular signals that arise from the enteric neural circuitry of the colon. Recent investigations have demonstrated that inflammation leads to a variety of changes in the physiological properties of the neurons in this circuitry, including hyperexcitability of neurons at the afferent end of the peristaltic reflex, synaptic facilitation, and attenuated inhibitory neuromuscular transmission. Furthermore, links have been established between these changes and disrupted motor activity in the colon, and we now know that some of these changes persist long after recovery from inflammation. It is highly likely that inflammation-induced neuroplasticity, which is not detectable by clinical diagnostics, contributes to disrupted motility in active and quiescent inflammatory bowel disease and in functional gastrointestinal disorders.
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Experimental model of tympanic colic (acute abdomen) in chinchillas (Chinchilla lanigera). Lab Anim Res 2014; 30:136-41. [PMID: 25324875 PMCID: PMC4188833 DOI: 10.5625/lar.2014.30.3.136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2014] [Revised: 09/04/2014] [Accepted: 09/11/2014] [Indexed: 11/21/2022] Open
Abstract
Digestive disorders caused by sudden changes in diet or inappropriate diet are among the most common disorders of the digestive system. Cecal or intestinal tympany, one consequence of inappropriate diet, is characterized by the accumulation of gases, marked distension of the cecum and colon and the induction of inflammatory processes. To know the effects of intestinal tympany on the enteric plexuses, we developed a method of experimental tympanic colic (TC) in the Chinchilla lanigera. This species was used in view of its susceptibility to TC. TC was induced with a diet rich in alfalfa associated with grain overload for two weeks. Physical and clinical examination including the von Frey test confirmed the diagnosis. The chinchillas with acute abdomen were treated with 1% ketoprofen and resumption of a balanced diet. Necropsy and histopathological analysis showed tympany-induced alterations mainly in the cecum and colon. After treatment, the control conditions were restored. The TC protocol is proposed as an experimental approach designed to aid the study of the effects of acute intestinal inflammation and obstruction caused by an inappropriate diet.
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Duraffourd C, Kumala E, Anselmi L, Brecha NC, Sternini C. Opioid-induced mitogen-activated protein kinase signaling in rat enteric neurons following chronic morphine treatment. PLoS One 2014; 9:e110230. [PMID: 25302800 PMCID: PMC4193881 DOI: 10.1371/journal.pone.0110230] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 09/18/2014] [Indexed: 01/20/2023] Open
Abstract
Opioids, acting at μ opioid receptors, are commonly used for pain management. Chronic opioid treatment induces cellular adaptations, which trigger long-term side effects, including constipation mediated by enteric neurons. We tested the hypothesis that chronic opioid treatment induces alterations of μ opioid receptor signaling in enteric neurons, which are likely to serve as mechanisms underlying opioid-induced constipation. In cultured rat enteric neurons, either untreated (naïve) or exposed to morphine for 4 days (chronic), we compared the effect of morphine and DAMGO (D-Ala2,MePhe4,Gly-ol5 enkephalin) on μ opioid receptor internalization and downstream signaling by examining the activation of the mitogen-activated protein kinase/extracellular signal-regulated kinases 1 and 2 (MAPK/ERK) pathway, cAMP accumulation and transcription factor cAMP Response Element-Binding protein (CREB) expression. μ opioid receptor internalization and MAPK/ERK phosphorylation were induced by DAMGO, but not morphine in naïve neurons, and by both opioids in chronic neurons. MAPK/ERK activation was prevented by the receptor antagonist naloxone, by blocking receptor trafficking with hypertonic sucrose, dynamin inhibitor, or neuronal transfection with mutated dynamin, and by MAPK inhibitor. Morphine and DAMGO inhibited cAMP in naïve and chronic enteric neurons, and induced desensitization of cAMP signaling. Chronic morphine treatment suppressed desensitization of cAMP and MAPK signaling, increased CREB phosphorylation through a MAPK/ERK pathway and induced delays of gastrointestinal transit, which was prevented by MAPK/ERK blockade. This study showed that opioids induce endocytosis- and dynamin-dependent MAPK/ERK activation in enteric neurons and that chronic morphine treatment triggers changes at the receptor level and downstream signaling resulting in MAPK/ERK-dependent CREB activation. Blockade of this signaling pathway prevents the development of gastrointestinal motility impairment induced by chronic morphine treatment. These findings suggest that alterations in μ opioid receptor downstream signaling including MAPK/ERK pathway in enteric neurons chronically treated with morphine contribute to the development of opioid-induced constipation.
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Affiliation(s)
- Celine Duraffourd
- CURE Digestive Diseases Research Center, Division of Digestive Diseases and Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- CURE Digestive Diseases Research Center, Division of Digestive Diseases and Department of Neurobiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Erica Kumala
- CURE Digestive Diseases Research Center, Division of Digestive Diseases and Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- CURE Digestive Diseases Research Center, Division of Digestive Diseases and Department of Neurobiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Laura Anselmi
- CURE Digestive Diseases Research Center, Division of Digestive Diseases and Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Nicholas C. Brecha
- CURE Digestive Diseases Research Center, Division of Digestive Diseases and Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- CURE Digestive Diseases Research Center, Division of Digestive Diseases and Department of Neurobiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- Veteran Administration Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
| | - Catia Sternini
- CURE Digestive Diseases Research Center, Division of Digestive Diseases and Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- CURE Digestive Diseases Research Center, Division of Digestive Diseases and Department of Neurobiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- Veteran Administration Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
- * E-mail:
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Abstract
The gastrointestinal tract is innervated by several distinct populations of neurons, whose cell bodies either reside within (intrinsic) or outside (extrinsic) the gastrointestinal wall. Normally, most individuals are unaware of the continuous, complicated functions of these neurons. However, for patients with gastrointestinal disorders, such as IBD and IBS, altered gastrointestinal motility, discomfort and pain are common, debilitating symptoms. Although bouts of intestinal inflammation underlie the symptoms associated with IBD, increasing preclinical and clinical evidence indicates that infection and inflammation are also key risk factors for the development of other gastrointestinal disorders. Notably, a strong correlation exists between prior exposure to gut infection and symptom occurrence in IBS. This Review discusses the evidence for neuroplasticity (structural, synaptic or intrinsic changes that alter neuronal function) affecting gastrointestinal function. Such changes are evident during inflammation and, in many cases, long after healing of the damaged tissues, when the nervous system fails to reset back to normal. Neuroplasticity within distinct populations of neurons has a fundamental role in the aberrant motility, secretion and sensation associated with common clinical gastrointestinal disorders. To find appropriate therapeutic treatments for these disorders, the extent and time course of neuroplasticity must be fully appreciated.
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Neural plasticity in the gastrointestinal tract: chronic inflammation, neurotrophic signals, and hypersensitivity. Acta Neuropathol 2013; 125:491-509. [PMID: 23417735 DOI: 10.1007/s00401-013-1099-4] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 01/31/2013] [Accepted: 02/07/2013] [Indexed: 12/28/2022]
Abstract
Neural plasticity is not only the adaptive response of the central nervous system to learning, structural damage or sensory deprivation, but also an increasingly recognized common feature of the gastrointestinal (GI) nervous system during pathological states. Indeed, nearly all chronic GI disorders exhibit a disease-stage-dependent, structural and functional neuroplasticity. At structural level, GI neuroplasticity usually comprises local tissue hyperinnervation (neural sprouting, neural, and ganglionic hypertrophy) next to hypoinnervated areas, a switch in the neurochemical (neurotransmitter/neuropeptide) code toward preferential expression of neuropeptides which are frequently present in nociceptive neurons (e.g., substance P/SP, calcitonin-gene-related-peptide/CGRP) and of ion channels (TRPV1, TRPA1, PAR2), and concomitant activation of peripheral neural glia. The functional counterpart of these structural alterations is altered neuronal electric activity, leading to organ dysfunction (e.g., impaired motility and secretion), together with reduced sensory thresholds, resulting in hypersensitivity and pain. The present review underlines that neural plasticity in all GI organs, starting from esophagus, stomach, small and large intestine to liver, gallbladder, and pancreas, actually exhibits common phenotypes and mechanisms. Careful appraisal of these GI neuroplastic alterations reveals that--no matter which etiology, i.e., inflammatory, infectious, neoplastic/malignant, or degenerative--neural plasticity in the GI tract primarily occurs in the presence of chronic tissue- and neuro-inflammation. It seems that studying the abundant trophic and activating signals which are generated during this neuro-immune-crosstalk represents the key to understand the remarkable neuroplasticity of the GI tract.
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Hoffman JM, McKnight ND, Sharkey KA, Mawe GM. The relationship between inflammation-induced neuronal excitability and disrupted motor activity in the guinea pig distal colon. Neurogastroenterol Motil 2011; 23:673-e279. [PMID: 21426440 DOI: 10.1111/j.1365-2982.2011.01702.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
BACKGROUND Colitis is associated with increased excitability of afterhyperpolarization neurons (AH neurons) and facilitated synaptic transmission in the myenteric plexus. These changes are accompanied by disrupted propulsive motility, particularly in ulcerated regions. This study examined the relationship between myenteric AH neuronal hyperexcitability and disrupted propulsive motility. METHODS The voltage-activated Na(+) channel opener veratridine, the intermediate conductance Ca(2+) -activated K(+) channel inhibitor TRAM-34 and the 5-HT(4) receptor agonist tegaserod were used to evaluate the effects of neuronal hyperexcitability and synaptic facilitation on propulsive motility in normal guinea pig distal colon. Because trinitrobenzene sulfonic acid (TNBS)-colitis-induced hyperexcitability of myenteric afferent neurons involves increases in hyperpolarization-activated, cyclic nucleotide-gated (HCN) channel activity, the HCN channel inhibitors Cs(+) and ZD7288 were used to suppress AH neuronal activity in TNBS-colitis. KEY RESULTS In non-inflamed preparations, veratridine halted propulsive motility (P<0.001). The rate of propulsive motor activity was significantly reduced following addition of TRAM-34 and tegaserod (P<0.001). In TNBS-inflamed preparations, in which motility was temporarily halted or obstructed at sites of ulceration, both Cs(+) and ZD7288 normalized motility through the inflamed regions. Immunohistochemistry studies demonstrated that the proportion of AH neurons in the myenteric plexus was unchanged in ulcerated regions, but there was a 10% reduction in total number of neurons per ganglion. CONCLUSIONS AND INFERENCES These findings support the concept that inflammation-induced neuroplasticity in myenteric neurons, involving changes in ion channel activity that lead to enhanced AH neuronal excitability, can contribute to impaired propulsive colonic motility.
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Affiliation(s)
- J M Hoffman
- Department of Anatomy & Neurobiology, University of Vermont, Burlington, VT 05405, USA
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Lakhan SE, Kirchgessner A. Neuroinflammation in inflammatory bowel disease. J Neuroinflammation 2010; 7:37. [PMID: 20615234 PMCID: PMC2909178 DOI: 10.1186/1742-2094-7-37] [Citation(s) in RCA: 142] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2010] [Accepted: 07/08/2010] [Indexed: 12/13/2022] Open
Abstract
Inflammatory bowel disease is a chronic intestinal inflammatory condition, the pathology of which is incompletely understood. Gut inflammation causes significant changes in neurally controlled gut functions including cramping, abdominal pain, fecal urgency, and explosive diarrhea. These symptoms are caused, at least in part, by prolonged hyperexcitability of enteric neurons that can occur following the resolution of colitis. Mast, enterochromaffin and other immune cells are increased in the colonic mucosa in inflammatory bowel disease and signal the presence of inflammation to the enteric nervous system. Inflammatory mediators include 5-hydroxytryptamine and cytokines, as well as reactive oxygen species and the production of oxidative stress. This review will discuss the effects of inflammation on enteric neural activity and potential therapeutic strategies that target neuroinflammation in the enteric nervous system.
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Affiliation(s)
- Shaheen E Lakhan
- Global Neuroscience Initiative Foundation, Los Angeles, CA, USA.
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Benito E, Barco A. CREB's control of intrinsic and synaptic plasticity: implications for CREB-dependent memory models. Trends Neurosci 2010; 33:230-40. [DOI: 10.1016/j.tins.2010.02.001] [Citation(s) in RCA: 326] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2009] [Revised: 02/01/2010] [Accepted: 02/10/2010] [Indexed: 01/04/2023]
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Strong DS, Cornbrooks CF, Roberts JA, Hoffman JM, Sharkey KA, Mawe GM. Purinergic neuromuscular transmission is selectively attenuated in ulcerated regions of inflamed guinea pig distal colon. J Physiol 2010; 588:847-59. [PMID: 20064853 DOI: 10.1113/jphysiol.2009.185082] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
This study was undertaken to investigate neuromuscular transmission in regions of the inflamed colon in which motility is disrupted. Propulsive motility was evaluated in segments of control guinea pigs and those treated 6 days previously with trinitrobenzene sulfonic acid. Intracellular recordings were then obtained from circular muscle cells to examine excitatory and inhibitory junction potentials (EJPs and IJPs). In inflamed preparations, propulsion of fecal pellets was temporarily halted or obstructed at sites of mucosal damage, whereas the propulsive motility was linear in control colons. The amplitudes of evoked and spontaneous IJPs were significantly reduced in ulcerated regions of inflamed preparations, but EJPs were comparable to controls. Pharmacological dissection of the IJP revealed that the purinergic component was reduced, while the nitrergic IJP was slightly increased. Furthermore, the reduction in the purinergic IJP in inflamed preparations persisted in the presence of hexamethonium, suggesting that the deficit involved the inhibitory motor neuron and/or smooth muscle. Nerve fibre density was not altered in the circular muscle, and pre-contracted rings of inflamed colon relaxed normally to ATP, suggesting that the deficit involves altered ATP release and/or degradation. The P2Y(1) receptor antagonist MRS2179 slowed propulsive motility indicating that decreased purinergic neuromuscular transmission could contribute to the inflammation-induced motor deficit. We conclude that purinergic inhibitory neuronal input to the circular muscle is selectively reduced in regions of the colon in experimental colitis where the mucosa is damaged, and this is likely to contribute to altered motility in colitis by diminishing downstream relaxation during the peristaltic reflex.
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Affiliation(s)
- Derek S Strong
- D403A Given Building, Department of Anatomy and Neurobiology, University of Vermont, Burlington, VT 05405, USA
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Bozarov A, Wang YZ, Yu JG, Wunderlich J, Hassanain HH, Alhaj M, Cooke HJ, Grants I, Ren T, Christofi FL. Activation of adenosine low-affinity A3 receptors inhibits the enteric short interplexus neural circuit triggered by histamine. Am J Physiol Gastrointest Liver Physiol 2009; 297:G1147-62. [PMID: 19808660 PMCID: PMC2850084 DOI: 10.1152/ajpgi.00295.2009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We tested the novel hypothesis that endogenous adenosine (eADO) activates low-affinity A3 receptors in a model of neurogenic diarrhea in the guinea pig colon. Dimaprit activation of H2 receptors was used to trigger a cyclic coordinated response of contraction and Cl(-) secretion. Contraction-relaxation was monitored by sonomicrometry (via intracrystal distance) simultaneously with short-circuit current (I(sc), Cl(-) secretion). The short interplexus reflex coordinated response was attenuated or abolished by antagonists at H2 (cimetidine), 5-hydroxytryptamine 4 receptor (RS39604), neurokinin-1 receptor (GR82334), or nicotinic (mecamylamine) receptors. The A1 agonist 2-chloro-N(6)-cyclopentyladenosine (CCPA) abolished coordinated responses, and A1 antagonists could restore normal responses. A1-selective antagonists alone [8-cyclopentyltheophylline (CPT), 1,3-dipropyl-8-(2-amino-4-chlorophenyl)xanthine (PACPX), or 8-cyclopentyl-N(3)-[3-(4-(fluorosulfonyl)benzoyloxy)propyl]-xanthine (FSCPX)] caused a concentration-dependent augmentation of crypt cell secretion or contraction and acted at nanomolar concentrations. The A3 agonist N(6)-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (IB-MECA) abolished coordinated responses and the A3 antagonist 3-ethyl-5-benzyl-2-methyl-4-phenylethynyl-6-phenyl-1,4-(+/-)-dihydropyridine-3,5-dicarboxylate (MRS1191) could restore and further augment responses. The IB-MECA effect was resistant to knockdown of adenosine A1 receptor with the irreversible antagonist FSCPX; the IC(50) for IB-MECA was 0.8 microM. MRS1191 alone could augment or unmask coordinated responses to dimaprit, and IB-MECA suppressed them. MRS1191 augmented distension-evoked reflex I(sc) responses. Adenosine deaminase mimicked actions of adenosine receptor antagonists. A3 receptor immunoreactivity was differentially expressed in enteric neurons of different parts of colon. After tetrodotoxin, IB-MECA caused circular muscle relaxation. The data support the novel concept that eADO acts at low-affinity A3 receptors in addition to high-affinity A1 receptors to suppress coordinated responses triggered by immune-histamine H2 receptor activation. The short interplexus circuit activated by histamine involves adenosine, acetylcholine, substance P, and serotonin. We postulate that A3 receptor modulation may occur in gut inflammatory diseases or allergic responses involving mast cell and histamine release.
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Affiliation(s)
- Andrey Bozarov
- Departments of 1 Anesthesiology and ,2Neuroscience, The Ohio State University, Columbus, Ohio
| | - Yu-Zhong Wang
- 2Neuroscience, The Ohio State University, Columbus, Ohio
| | | | | | | | | | - Helen J. Cooke
- 2Neuroscience, The Ohio State University, Columbus, Ohio
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Nurgali K, Nguyen TV, Thacker M, Pontell L, Furness JB. Slow synaptic transmission in myenteric AH neurons from the inflamed guinea pig ileum. Am J Physiol Gastrointest Liver Physiol 2009; 297:G582-93. [PMID: 19556360 DOI: 10.1152/ajpgi.00026.2009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We investigated the effect of inflammation on slow synaptic transmission in myenteric neurons in the guinea pig ileum. Inflammation was induced by the intraluminal injection of trinitrobenzene sulfonate, and tissues were taken for in vitro investigation 6-7 days later. Brief tetanic stimulation of synaptic inputs (20 Hz, 1 s) induced slow excitatory postsynaptic potentials (EPSPs) in 49% and maintained postsynaptic excitation that lasted from 27 min to 3 h in 13% of neurons from the inflamed ileum. These neurons were classified electrophysiologically as AH neurons; 10 were morphological type II neurons, and one was type I. Such long-term hyperexcitability after a brief stimulus is not encountered in enteric neurons of normal intestine. Electrophysiological properties of neurons with maintained postsynaptic excitation were similar to those of neurons with slow EPSPs. Another form of prolonged excitation, sustained slow postsynaptic excitation (SSPE), induced by 1-Hz, 4-min stimulation, in type II neurons from the inflamed ileum reached its peak earlier but had lower amplitude than that in control. Unlike slow EPSPs and similar to SSPEs, maintained excitation was not inhibited by neurokinin-1 or neurokinin-3 receptor antagonists. Maintained postsynaptic excitation was not influenced by PKC inhibitors, but the PKA inhibitor, H-89, caused further increase in neuronal excitability. In conclusion, maintained excitation, observed only in neurons from the inflamed ileum, may contribute to the dysmotility, pain, and discomfort associated with intestinal inflammation.
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Affiliation(s)
- Kulmira Nurgali
- Dept. of Physiology, The Univ. of Melbourne, Parkville, Victoria, 3010, Australia.
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Rybaczyk L, Rozmiarek A, Circle K, Grants I, Needleman B, Wunderlich JE, Huang K, Christofi FL. New bioinformatics approach to analyze gene expressions and signaling pathways reveals unique purine gene dysregulation profiles that distinguish between CD and UC. Inflamm Bowel Dis 2009; 15:971-84. [PMID: 19253308 PMCID: PMC2697273 DOI: 10.1002/ibd.20893] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
BACKGROUND Expression of purine genes is modulated by inflammation or experimental colitis and altered expression leads to disrupted gut function. We studied purine gene dysregulation profiles in inflammatory bowel disease (IBD) and determined whether they can distinguish between Crohn's disease (CD) and ulcerative colitis (UC) using Pathway Analysis and a new Comparative Analysis of Gene Expression and Selection (CAGES) method. METHODS Raw datasets for 22 purine genes and 36 probe-sets from National Center for Biotechnology Information (NCBI) GEO (Gene Expression Omnibus) (http://www.ncbi.nlm.nih.gov/projects/geo/) were analyzed by National Cancer Institute (NCI) Biological Resources Branch (BRB) array tools for random-variance of multiple/36 t-tests in colonic mucosal biopsies or peripheral blood mononuclear cells (PBMCs) of CD, UC or control subjects. Dysregulation occurs in 59% of purine genes in IBD including ADORA3, CD73, ADORA2A, ADORA2B, ADAR, AMPD2, AMPD3, DPP4, P2RY5, P2RY6, P2RY13, P2RY14, and P2RX5. RESULTS In CD biopsies, expression of ADORA3, AMPD3, P2RY13, and P2RY5 were negatively correlated with acute inflammatory score, Crohn's Disease Activity Index (CDAI) or disease chronicity; P2RY14 was positively correlated in UC. In mucosal biopsies or PBMCs, CD and UC were distinguished by unique patterns of dysregulation (up- or downregulation) in purine genes. Purine gene dysregulation differs between PBMCs and biopsies and possibly between sexes for each disease. Ingenuity Pathway Analysis (IPA) revealed significant associations between alterations in the expression of CD73 (upregulation) or ADORA3 (downregulation) and inflammatory or purine genes (<or=10% of 57 genes) as well as G-protein coupled receptors, cAMP-dependent, and inflammatory pathways; IPA distinguishes CD from UC. CONCLUSION CAGES and Pathway Analysis provided novel evidence that UC and CD have distinct purine gene dysregulation signatures in association with inflammation, cAMP, or other signaling pathways. Disease-specific purine gene signature profiles and pathway associations may be of therapeutic, diagnostic, and functional relevance.
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Affiliation(s)
- Leszek Rybaczyk
- Dept of Bioinformatics, The Ohio State University, Columbus, Ohio, 43210
| | - Andrew Rozmiarek
- Dept of Anesthesiology, The Ohio State University, Columbus, Ohio, 43210
| | - Kristin Circle
- Dept of Bioinformatics, The Ohio State University, Columbus, Ohio, 43210
| | - Iveta Grants
- Dept of Anesthesiology, The Ohio State University, Columbus, Ohio, 43210
| | | | - Jacqueline E Wunderlich
- Dept of Anesthesiology, The Ohio State University, Columbus, Ohio, 43210,Dept of Surgery, The Ohio State University, Columbus, Ohio, 43210
| | - Kun Huang
- Dept of Bioinformatics, The Ohio State University, Columbus, Ohio, 43210
| | - Fievos L Christofi
- Dept of Anesthesiology, The Ohio State University, Columbus, Ohio, 43210
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Mawe GM, Strong DS, Sharkey KA. Plasticity of enteric nerve functions in the inflamed and postinflamed gut. Neurogastroenterol Motil 2009; 21:481-91. [PMID: 19368664 PMCID: PMC2717558 DOI: 10.1111/j.1365-2982.2009.01291.x] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Inflammation of the gut alters the properties of the intrinsic and extrinsic neurons that innervate it. While the mechanisms of neuroplasticity differ amongst the inflammatory models that have been used, amongst various regions of the gut, and between intrinsic vs extrinsic neurons, a number of consistent features have been observed. For example, intrinsic and extrinsic primary afferent neurons become hyperexcitable in response to inflammation, and interneuronal synaptic transmission is facilitated in the enteric circuitry. These changes contribute to alterations in gut function and sensation in the inflamed bowel as well as functional disorders, and these changes persist for weeks beyond the point at which detectable inflammation has subsided. Thus, gaining a more thorough understanding of the mechanisms responsible for inflammation-induced neuroplasticity, and strategies to reverse these changes are clinically relevant goals. The purpose of this review is to summarize our current knowledge regarding neurophysiological changes that occur during and following intestinal inflammation, and to identify and address gaps in our knowledge regarding the role of enteric neuroplasticity in inflammatory and functional gastrointestinal disorders.
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Affiliation(s)
- Gary M. Mawe
- Department of Anatomy and Neurobiology, The University of Vermont College of Medicine, Burlington, VT, USA, Hotchkiss Brain Institute and Snyder Institute of Infection, Immunity and Inflammation, Department of Physiology and Biophysics, University of Calgary, Calgary, Alberta, Canada
| | - Derek S. Strong
- Department of Anatomy and Neurobiology, The University of Vermont College of Medicine, Burlington, VT, USA
| | - Keith A. Sharkey
- Department of Anatomy and Neurobiology, The University of Vermont College of Medicine, Burlington, VT, USA, Hotchkiss Brain Institute and Snyder Institute of Infection, Immunity and Inflammation, Department of Physiology and Biophysics, University of Calgary, Calgary, Alberta, Canada
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Abstract
Most aspects of the normal organisation and functioning of the enteric nervous system have been resolved in recent years, especially for the small and large intestines, where the ENS has essential roles in controlling bowel movement and transmucosal fluid exchange. The roles of the ENS in the esophagus are not understood, and the relative roles of intrinsic reflexes in relation to extrinsic control of the stomach require clarification. In the small intestine and colon, it needs to be understood how neural activity is orchestrated to subserve different functional outcomes, for example propulsion, mixing and retrograde movement. However, the most important future challenges are to properly understand the molecular and cellular changes that underlie enteric neuropathies, to utilise knowledge of the normal neurochemistry, pharmacology and physiology of the ENS to devise strategies to treat disorders of motility and secretion, and to develop effective therapeutic compounds. It is suggested that ion channels of enteric neurons have been under-investigated as therapeutic targets. Other future challenges lie in the identification of biomarkers for functional bowel disorders and in the use of neural stem cells for restitution of ENS function.
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Affiliation(s)
- J B Furness
- Department of Anatomy & Cell Biology and Centre for Neuroscience, University of Melbourne, Parkville, Victoria, Australia.
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Reis HJ, Rosa DVF, Guimarães MM, Souza BR, Barros AGA, Pimenta FJ, Souza RP, Torres KCL, Romano-Silva MA. Is DARPP-32 a potential therapeutic target? Expert Opin Ther Targets 2007; 11:1649-61. [DOI: 10.1517/14728222.11.12.1649] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Connors EC, Ballif BA, Morielli AD. Homeostatic regulation of Kv1.2 potassium channel trafficking by cyclic AMP. J Biol Chem 2007; 283:3445-3453. [PMID: 18003609 DOI: 10.1074/jbc.m708875200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Shaker family potassium channel, Kv1.2, is a key determinant of membrane excitability in neurons and cardiovascular tissue. Kv1.2 is subject to multiple forms of regulation and therefore integrates cellular signals involved in the homeostasis of excitability. The cyclic AMP/protein kinase A (PKA) pathway enhances Kv1.2 ionic current; however, the mechanisms for this are not fully known. Here we show that cAMP maintains Kv1.2 homeostasis through opposing effects on channel trafficking. We found that Kv1.2 is regulated by two distinct cAMP pathways, one PKA-dependent and the other PKA-independent. PKA inhibitors elevate Kv1.2 surface levels, suggesting that basal levels of cAMP control steady-state turnover of the channel. Elevation of cAMP above basal levels also increases the amount of Kv1.2 at the cell surface. This effect is not blocked by PKA inhibitors, but is blocked by inhibition of Kv1.2 endocytosis. We conclude that Kv1.2 levels at the cell surface are kept in dynamic balance by opposing effects of cAMP.
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Affiliation(s)
- Emilee C Connors
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont 05405
| | - Bryan A Ballif
- Department of Biology, University of Vermont, Burlington, Vermont 05405
| | - Anthony D Morielli
- Department of Pharmacology, College of Medicine, University of Vermont, Burlington, Vermont 05405.
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