ORCID Profile
0000-0002-4277-3664
Current Organisation
KU Leuven
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Publisher: Elsevier
Date: 2020
Publisher: American Physiological Society
Date: 05-2014
Abstract: In the gastrointestinal tract, vasoactive intestinal peptide (VIP) is found exclusively within neurons. VIP regulates intestinal motility via neurally mediated and direct actions on smooth muscle and secretion by a direct mucosal action, and via actions on submucosal neurons. VIP acts via VPAC 1 and VPAC 2 receptors however, the subtype involved in its neural actions is unclear. The neural roles of VIP and VPAC 1 receptors (VPAC 1 R) were investigated in intestinal motility and secretion in guinea pig jejunum. Expression of VIP receptors across the jejunal layers was examined using RT-PCR. Submucosal and myenteric neurons expressing VIP receptor subtype VPAC 1 and/or various neurochemical markers were identified immunohistochemically. Isotonic muscle contraction was measured in longitudinal muscle-myenteric plexus preparations. Electrogenic secretion across mucosa-submucosa preparations was measured in Ussing chambers by monitoring short-circuit current. Calretinin + excitatory longitudinal muscle motor neurons expressed VPAC 1 R. Most cholinergic submucosal neurons, notably NPY + secretomotor neurons, expressed VPAC 1 R. VIP (100 nM) induced longitudinal muscle contraction that was inhibited by TTX (1 μM), PG97–269 (VPAC 1 antagonist 1 μM), and hyoscine (10 μM), but not by hexamethonium (200 μM). VIP (50 nM)-evoked secretion was depressed by hyoscine or PG97–269 and involved a small TTX-sensitive component. PG97–269 and TTX combined did not further depress the VIP response observed in the presence of PG97–269 alone. We conclude that VIP stimulates ACh-mediated longitudinal muscle contraction via VPAC 1 R on cholinergic motor neurons. VIP induces Cl − secretion directly via epithelial VPAC 1 R and indirectly via VPAC 1 R on cholinergic secretomotor neurons. No evidence was obtained for involvement of other neural VIP receptors.
Publisher: Springer Science and Business Media LLC
Date: 18-05-2020
DOI: 10.1007/S00018-020-03543-6
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.
Publisher: Springer International Publishing
Date: 2022
Publisher: Frontiers Media SA
Date: 2010
Publisher: Cold Spring Harbor Laboratory
Date: 20-01-2021
DOI: 10.1101/2021.01.19.427232
Abstract: Nutrient signals sensed by enteroendocrine cells are conveyed to the enteric nervous system (ENS) to initiate intestinal reflexes. We addressed whether there are specific enteric pathways dedicated to detecting different luminal nutrients. Calcium imaging was performed on intact jejunal preparations from Wnt1-cre R26R-GCaMP3 and Villin-cre R26R-GCaMP3 mice which express a fluorescent calcium indicator in their ENS or intestinal epithelium, respectively. Glucose, acetate, and L-phenylalanine were perfused onto the mucosa whilst imaging underlying enteric neurons. Nutrient transport or diffusion across the mucosa was mimicked by applying nutrients onto sensory nerve endings in a villus, or onto myenteric ganglia. The nutrients perfused onto the mucosa each elicited Ca 2+ transients in submucosal neurons and in distinct patterns of myenteric neurons. Notably, the neurochemical subtypes of myenteric neurons that responded differed between the nutrients, while submucosal responders were predominantly cholinergic. Nutrients applied into villi or onto ganglia did not elicit specific neuronal responses but did stimulate Ca 2+ signaling in the mucosal epithelium. These data suggest that nutrients are first detected at the level of the epithelium and that the ENS is capable of discriminating between different compositions of luminal content. Furthermore, our data show that responses to mucosal stimulation are primarily in the myenteric plexus and submucosal neurons respond secondarily.
Publisher: Elsevier BV
Date: 12-2019
DOI: 10.1016/J.NEUROSCIENCE.2019.10.029
Abstract: Alpha-Synuclein (α-Syn) is expressed in the central nervous system and the nervous system of the gut (enteric nervous system, ENS), and is well known to be the major constituent of Lewy bodies which are the hallmark of Parkinson's disease. Gastrointestinal disorders frequently manifest several years before motor deficits develop in Parkinson's patients. Despite extensive research on pathological rodent models, the physiological role of α-Syn in the normal ENS is unclear h ering analysis of its neuropathology. We compared the ENS in colons of α-Syn-knockout (α-Syn KO) and wild-type mice using immunohistochemistry and calcium-imaging of responses to synaptic input. We found that α-Syn is predominantly expressed in cholinergic varicosities, which contain vesicular acetylcholine transporter. α-Syn KO mice had higher enteric neuron density and a larger proportion of cholinergic neurons, notably those containing calretinin, demonstrating a role for α-Syn in regulating development of these neurons. Moreover, α-Syn deletion enhanced the litude of synaptically activated [Ca
Publisher: Frontiers Media SA
Date: 13-02-2018
Publisher: Frontiers Media SA
Date: 21-03-2018
Publisher: Wiley
Date: 14-06-2021
DOI: 10.1111/NMO.14186
Abstract: Gastrointestinal (GI) function is critically dependent on the control of the enteric nervous system (ENS), which is situated within the gut wall and organized into two ganglionated nerve plexuses: the submucosal and myenteric plexus. The ENS is optimally positioned and together with the intestinal epithelium, is well-equipped to monitor the luminal contents such as microbial metabolites and to coordinate appropriate responses accordingly. Despite the heightened interest in the gut microbiota and its influence on intestinal physiology and pathophysiology, how they interact with the host ENS remains unclear. Using full-thickness proximal colon preparations from transgenic Villin-CreERT2 R26R-GCaMP3 and Wnt1-Cre R26R-GCaMP3 mice, which express a fluorescent Ca We show that the SCFAs acetate, propionate, and butyrate, as well as 5-HT can, to varying extents, acutely elicit epithelial and neuronal Ca Taken together, our study demonstrates that different microbial metabolites, including SCFAs and 5-HT, can acutely stimulate Ca
Publisher: Frontiers Media SA
Date: 25-04-2017
Publisher: Wiley
Date: 14-09-2020
DOI: 10.1113/JP280594
Publisher: Springer Science and Business Media LLC
Date: 05-02-2020
DOI: 10.1038/S41586-020-1975-8
Abstract: Neural control of the function of visceral organs is essential for homeostasis and health. Intestinal peristalsis is critical for digestive physiology and host defence, and is often dysregulated in gastrointestinal disorders
Publisher: The Company of Biologists
Date: 02-2021
DOI: 10.1242/DEV.182543
Abstract: During embryonic development, the gut is innervated by intrinsic (enteric) and extrinsic nerves. Focusing on mammalian ENS development, in this Review we highlight how important the different compartments of this innervation are to assure proper gut function. We specifically address the three-dimensional architecture of the innervation, paying special attention to the differences in development along the longitudinal and circumferential axes of the gut. We review recent information about the formation of both intrinsic innervation, which is fairly well-known, as well as the establishment of the extrinsic innervation, which, despite its importance in gut-brain signaling, has received much less attention. We further discuss how external microbial and nutritional cues or neuroimmune interactions may influence development of gut innervation. Finally, we provide summary tables, describing the location and function of several well-known molecules, along with some newer factors that have more recently been implicated in the development of gut innervation.
Publisher: Springer Science and Business Media LLC
Date: 12-07-2023
DOI: 10.1038/S41586-023-06188-0
Abstract: The physiological functions of mast cells remain largely an enigma. In the context of barrier damage, mast cells are integrated in type 2 immunity and, together with immunoglobulin E (IgE), promote allergic diseases. Allergic symptoms may, however, facilitate expulsion of allergens, toxins and parasites and trigger future antigen avoidance 1–3 . Here, we show that antigen-specific avoidance behaviour in inbred mice 4,5 is critically dependent on mast cells hence, we identify the immunological sensor cell linking antigen recognition to avoidance behaviour. Avoidance prevented antigen-driven adaptive, innate and mucosal immune activation and inflammation in the stomach and small intestine. Avoidance was IgE dependent, promoted by Th2 cytokines in the immunization phase and by IgE in the execution phase. Mucosal mast cells lining the stomach and small intestine rapidly sensed antigen ingestion. We interrogated potential signalling routes between mast cells and the brain using mutant mice, pharmacological inhibition, neural activity recordings and vagotomy. Inhibition of leukotriene synthesis impaired avoidance, but overall no single pathway interruption completely abrogated avoidance, indicating complex regulation. Collectively, the stage for antigen avoidance is set when adaptive immunity equips mast cells with IgE as a telltale of past immune responses. On subsequent antigen ingestion, mast cells signal termination of antigen intake. Prevention of immunopathology-causing, continuous and futile responses against per se innocuous antigens or of repeated ingestion of toxins through mast-cell-mediated antigen-avoidance behaviour may be an important arm of immunity.
Publisher: Wiley
Date: 07-02-2019
DOI: 10.1002/GLIA.23596
Publisher: American Physiological Society
Date: 2020
Abstract: Detection of nutritional and noxious food components in the gut is a crucial component of gastrointestinal function. Contents in the gut lumen interact with enteroendocrine cells dispersed throughout the gut epithelium. Enteroendocrine cells release many different hormones, neuropeptides, and neurotransmitters that communicate either directly or indirectly with the central nervous system and the enteric nervous system, a network of neurons and glia located within the gut wall. Several populations of enteric neurons extend processes that innervate the gastrointestinal lamina propria however, how these processes develop and begin to transmit information from the mucosa is not fully understood. In this study, we found that Tuj1-immunoreactive neurites begin to project out of the myenteric plexus at embryonic day (E)13.5 in the mouse small intestine, even before the formation of villi. Using live calcium imaging, we discovered that neurites were capable of transmitting electrical information from stimulated villi to the plexus by E15.5. In unpeeled gut preparations where all layers were left intact, we also mimicked the basolateral release of 5-HT from enteroendocrine cells, which triggered responses in myenteric cell bodies at postnatal day (P)0. Altogether, our results show that enteric neurons extend neurites out of the myenteric plexus early during mouse enteric nervous system development, innervating the gastrointestinal mucosa, even before villus formation in mice of either sex. Neurites are already able to conduct electrical information at E15.5, and responses to 5-HT develop postnatally. NEW & NOTEWORTHY How enteric neurons project into the gut mucosa and begin to communicate with the epithelium during development is not known. Our study shows that enteric neurites project into the lamina propria as early as E13.5 in the mouse, before development of the submucous plexus and before formation of intestinal villi. These neurites are capable of transmitting electrical signals back to their cell bodies by E15.5 and respond to serotonin applied to neurite terminals by birth.
No related grants have been discovered for Candice Fung.