Enteric Nerves Research Articles

Herpes Simplex Virus Type 1 Infects Enteric Neurons and Triggers Gut Dysfunction via Macrophage Recruitment.

Herpes Simplex Virus type 1 (HSV-1), a neurotropic pathogen widespread in human population, infects the enteric nervous system (ENS) in humans and rodents and causes intestinal neuromuscular dysfunction in rats. Although infiltration of inflammatory cells in the myenteric plexus and neurodegeneration of enteric nerves are common features of patients suffering from functional intestinal disorders, the proof of a pathogenic link with HSV-1 is still unsettled mainly because the underlying mechanisms are largely unknown. In this study we demonstrated that following intragastrical administration HSV-1 infects neurons within the myenteric plexus resulting in functional and structural alterations of the ENS. By infecting mice with HSV-1 replication-defective strain we revealed that gastrointestinal neuromuscular anomalies were however independent of viral replication. Indeed, enteric neurons exposed to UV-inactivated HSV-1 produced monocyte chemoattractant protein-1 (MCP-1/CCL2) to recruit activated macrophages in the longitudinal muscle myenteric plexus. Infiltrating macrophages produced reactive oxygen and nitrogen species and directly harmed enteric neurons resulting in gastrointestinal dysmotility. In HSV-1 infected mice intestinal neuromuscular dysfunctions were ameliorated by in vivo administration of (i) liposomes containing dichloromethylene bisphosphonic acid (clodronate) to deplete tissue macrophages, (ii) CCR2 chemokine receptor antagonist RS504393 to block the CCL2/CCR2 pathway, (iii) Nω-Nitro-L-arginine methyl ester hydrochloride (L-NAME) and AR-C 102222 to quench production of nitrogen reactive species produced via iNOS. Overall these data demonstrate that HSV-1 infection makes enteric neurons recruit macrophages via production of a specific chemoattractant factor. The resulting inflammatory reaction is mandatory for intestinal dysmotility. These findings provide insights into the neuro-immune communication that occurs in the ENS following HSV-1 infection and allow recognition of an original pathophysiologic mechanism underlying gastrointestinal diseases as well as identification of novel therapeutic targets.

Blueprint for an intestinal villus: Species-specific assembly required.

Efficient absorption of nutrients by the intestine is essential for life. In mammals and birds, convolution of the intestinal surface into finger-like projections called villi is an important adaptation that ensures the massive surface area for nutrient contact that is required to meet metabolic demands. Each villus projection serves as a functional absorptive unit: it is covered by a simple columnar epithelium that is derived from endoderm and contains a mesodermally derived core with supporting vasculature, lacteals, enteric nerves, smooth muscle, fibroblasts, myofibroblasts, and immune cells. In cross section, the consistency of structure in the billions of individual villi of the adult intestine is strikingly beautiful. Villi are generated in fetal life, and work over several decades has revealed that villus morphogenesis requires substantial "crosstalk" between the endodermal and mesodermal tissue components, with soluble signals, cell-cell contacts, and mechanical forces providing specific dialects for sequential conversations that orchestrate villus assembly. A key part of this process is the formation of subepithelial mesenchymal cell clusters that act as signaling hubs, directing overlying epithelial cells to cease proliferation, thereby driving villus emergence and simultaneously determining the location of future stem cell compartments. Interestingly, distinct species-specific differences govern how and when tissue-shaping signals and forces generate mesenchymal clusters and control villus emergence. As the details of villus development become increasingly clear, the emerging picture highlights a sophisticated local self-assembled cascade that underlies the reproducible elaboration of a regularly patterned field of absorptive villus units. This article is categorized under: Vertebrate Organogenesis > From a Tubular Primordium: Non-Branched Comparative Development and Evolution > Organ System Comparisons Between Species Early Embryonic Development > Development to the Basic Body Plan.

Laser-Capture Microdissection for Layer-Specific Analysis of Enteric Ganglia.

The enteric nervous system (ENS) is the division of the autonomic nervous system that innervates the gastrointestinal (GI) tract and controls central intestinal functions such as peristalsis and fluid movement. Enteric nerve cell bodies (neurons and glia) are predominantly organized in ganglionated networks that are present along the entire length of the GI tract in multiple tissue layers. Most cell bodies are organized in the myenteric plexus allocated between the longitudinal and the circular muscle layers or in the submucosal plexus between muscle tissue and mucosa. The site-specific characteristics of these enteric nerve cells have traditionally been analyzed via imaging techniques. Laser-capture microdissection (LCM) offers the prospect of site-specifically analyzing the gene expression profiles of these different subpopulations. This protocol addresses critical aspects of handling intestinal tissue for ENS dissection, such as the optimal quick-staining procedure, suitable laser settings, and limits of tissue material required to successfully dissect and analyze tissue layers for gene expression.

Spread of aggregates after olfactory bulb injection of \u03b1-synuclein fibrils is associated with early neuronal loss and is reduced long term

Parkinson’s disease is characterized by degeneration of substantia nigra dopamine neurons and by intraneuronal aggregates, primarily composed of misfolded α-synuclein. The α-synuclein aggregates in Parkinson’s patients are suggested to first appear in the olfactory bulb and enteric nerves and then propagate, following a stereotypic pattern, via neural pathways to numerous regions across the brain. We recently demonstrated that after injection of either mouse or human α-synuclein fibrils into the olfactory bulb of wild-type mice, α-synuclein fibrils recruited endogenous α-synuclein into pathological aggregates that spread transneuronally to over 40 other brain regions and subregions, over 12 months. We previously reported the progressive spreading of α-synuclein aggregates, between 1 and 12 months following α-synuclein fibril injections, and now report how far the pathology has spread 18- and 23-month post-injection in this model. Our data show that between 12 and 18 months, there is a further increase in the number of brain regions exhibiting pathology after human, and to a lesser extent mouse, α-synuclein fibril injections. At both 18 and 23 months after injection of mouse and human α-synuclein fibrils, we observed a reduction in the density of α-synuclein aggregates in some brain regions compared to others at 12 months. At 23 months, no additional brain regions exhibited α-synuclein aggregates compared to earlier time points. In addition, we also demonstrate that the induced α-synucleinopathy triggered a significant early neuron loss in the anterior olfactory nucleus. By contrast, there was no loss of mitral neurons in the olfactory bulb, even at 18 month post-injection. We speculate that the lack of continued progression of α-synuclein pathology is due to compromise of the neural circuitry, consequential to neuron loss and possibly to the activation of proteolytic mechanisms in resilient neurons of wild-type mice that counterbalances the spread and seeding by degrading pathogenic α-synuclein.

Cocaine- and amphetamine-regulated transcript (CART) peptide in the nerve fibres of the porcine gallbladder wall under physiological conditions and after Salmonella Enteritidis lipopolysaccharides administration.

Cocaine- and amphetamine-regulated transcript (CART) peptide is the substance distributed in various parts of the nervous system. The majority of previous studies described this substance in the brain, where it takes part in regulatory processes connected with the food intake. CART is also present in the peripheral nervous system, especially in the enteric neurons and nerves located in the wall of the stomach and intestine, but many aspects of distribution and functions of this peptide in the digestive organs remain unknown. The aim of the present study was to investigate the changes of CART-positive nerves in the porcine gallbladder after administration of low-dose Salmonella Enteritidis lipopolysaccharide (LPS) using the single immunofluorescence technique. Seven days after the injection of 5 μg/kg b.w. LPS S. Enteritidis the gallbladders were collected. CART-positive nerves were studied with standard single immunofluorescence method and counted per observation field (0.1 m2). In control animals the average number of CART-positive nerves per observation field (0.1 mm2) amounted to 5.38 ± 0.32, 11.11 ± 1.56 and 2.97 ± ± 0.24 in gallbladder neck, body and fundus, respectively. LPS administration caused the increase in the number of CART-positive fibres in all parts of gallbladder, and these values amounted to 12.74 ± 0.51, 19.75 ± 0.19 and 5.1 ± 0.05 in the gallbladder neck, body and fundus, respectively. The obtained results suggest that CART is involved in the neuronal regulatory processes in the porcine gallbladder under physiological conditions, but also during pathological processes, but exact functions of this peptide in this organ remain unexplained and require the further investigation.

Significance of Cholinergic and Peptidergic Nerves in Stress-Induced Ulcer and MALT Lymphoma Formation.

The stress-induced ulcer was induced by the plaster bandage methods in rats. The gastric MALT lymphoma was formed by the peroral infection of gastric mucosal homogenate of the infected mouse in C57BL/6 mice. For the stress-induced ulcer, the distribution of the cholinergic nerves and muscarinic acetylcholine receptors was investigated by acetylcholinesterase histochemistry and autoradiography of water soluble compounds using 3H-quinuclidinyl benzilate was performed. To the MALT lymphoma study, the distribution of the substance P and effect of substance P antagonist, spantide II, was investigated by immunohistochemical studies. The stress induced ulcer formation was shown to be related to the hyperactivity of the cholinergic nerves. The gastric MALT lymphoma was shown to be related to the increased localization of substance P. Stress-induced ulceration as a model of hyperactivity of the cholinergic nerves was proved to be a useful approach, while substance P and its role in MALT lymphoma formation may serve as a tool to clarify the neuroimmune modulation of chronic infectious diseases.

Diabetes Mellitus and the Colon.

Diabetes mellitus (DM) can affect the structure and function of the colon promoting commonly encountered lower gastrointestinal symptoms such as constipation, diarrhea, abdominal distention, bloating, and abdominal pain. Specific colonic disorders for which adults with DM are at greater risk include chronic constipation, enteropathic diarrhea, colorectal cancer (CRC), inflammatory bowel disease, microscopic colitis, and Clostridium difficile colitis. Smooth muscle structure and function, density of the interstitial cells of Cajal, and the health and function of the autonomic and enteric nerves of the colon are all potential affected by DM. These effects can in turn lead to alterations in colon motility, visceral sensation, immune function, endothelial function, and the colonic microbiome. The evaluation and treatment for slow transit constipation as well as pelvic floor dysfunction should be considered when constipation symptoms are refractory to initial treatment measures. DM-related medications and small bowel conditions such as celiac disease and small intestinal bowel overgrowth should be considered and excluded before a diagnosis of enteropathic diarrhea is made. Given the higher risk of CRC, adults with DM should be appropriately screened and may require a longer bowel preparation to ensure an adequate evaluation.

Site-related Effects of Relaxin in the Gastrointestinal Tract Through Nitric Oxide Signalling: An Updated Report.

The peptide hormone relaxin (RLX), in addition to its effects on reproduction, has been reported to influence gastrointestinal motility. Interestingly, the digestive tract has been shown to express RLX receptors and the hormone appears to exert site-specific effects acting at the neural or at the smooth muscle level, mainly by a nitric oxide (NO)-mediated mechanism. NO, released by the enteric nerves and/or smooth muscle cells, is one of the main mediators of gastrointestinal relaxation. In fact, in murine in vitro preparations, RLX depresses organ motility acting at the neural level in the stomach and at the muscular level in the small intestine; conversely, in the colon, this hormone paradoxically increases contractility operating at both neural and muscle levels. These effects are ascribable to the ability of RLX to selectively regulate the expression of the different nitric oxide synthase (NOS) isoforms in the different gastrointestinal tracts. Furthermore, recent electrophysiological experiments have shown that RLX can directly affect the biophysical properties of ileal and colonic smooth muscle cells. This mini-review is intended to offer an update on the site-related actions of RLX on gastrointestinal tract motility in relation with its site-specific effects on NOS isoforms expression. Based on these properties, RLX might be considered a potential therapeutic approach to gastrointestinal motor dysfunctions related to an altered NO production.

Berberine ameliorates collagen-induced arthritis in rats by suppressing Th17 cell responses via inducing cortistatin in the gut.

Berberine, an isoquinoline alkaloid, has been reported to ameliorate various autoimmune diseases including rheumatoid arthritis by oral administration. However, its mechanism remains mysterious due to an extremely low bioavailability. The fact that berberine readily accumulates in the gut, the largest endocrine organ in the body, attracted us to explore its anti-arthritic mechanism in view of the induction of intestinal immunosuppressive neuropeptides. In this study, berberine (200 mg·kg-1 , i.g.) was shown to ameliorate collagen-induced arthritis in rats, which was manifested by the reduction of clinical signs and joint destruction, as well as marked down-regulation of Th17 cell frequency and interleukin-17 level in blood. In contrast, an intravenous injection of berberine failed to affect arthritis in rats, implying that its anti-arthritic effect was gut-dependent. Further studies revealed that oral berberine selectively elevated the levels of cortistatin, of five gut-derived neuropeptides tested, in the intestines and sera of arthrititic rats. Antagonists of ghrelin/growth hormone secretagogue receptor 1 (a subtype of cortistatin receptor) almost completely abolished the ameliorative effect of berberine on arthritis and Th17 cell responses in rats. In vitro, berberine showed a moderate ability to promote the expression of cortistatin in nerve cells, which was strengthened when the nerve cells were cocultured with enteroendocrine cells to induce an autocrine/paracrine environment. In summary, oral berberine exerted anti-arthritic effect through inhibiting the Th17 cell response, which was closely associated with the induction of cortistatin generation from gut through augmenting autocrine/paracrine action between enteric nerve cells and endocrine cells.

Electrogastrography in Delayed Gastric Emptying

Disorders of gastric motility are generally manifested by an abnormal rate of gastric emptying. The emptying process of the stomach is very complex, and knowledge is limited to the observation that gastric emptying rate is a highly variable phenomenon, and that delayed gastric emptying is frequently the case. The advances in the knowledge of the physiology of gastric muscle and enteric nerves, and the recognition of the patterns of organization of smooth muscle contractions gave a new input to the study of gastric motility. The gastric emptying can be monitored in various ways, such as manometry, scintigraphy, or electrogastrography (EGG). Recently, EGG has received more attention. There is correlation between the EGG signal obtained from body surface electrodes and signals obtained directly from electrodes locates in the gastric muscle (serosal records). Some studies showed an association between EGG-findings and gastric motility disorders, and indicate that EGG is a reliable, non-invasive, useful method to detect gastric myoelectric activity.

α-Synuclein in gut endocrine cells and its implications for Parkinson's disease.

Parkinson's disease (PD) is a progressive neurodegenerative disease with devastating clinical manifestations. In PD, neuronal death is associated with intracellular aggregates of the neuronal protein α-synuclein known as Lewy bodies. Although the cause of sporadic PD is not well understood, abundant clinical and pathological evidence show that misfolded α-synuclein is found in enteric nerves before it appears in the brain. This suggests a model in which PD pathology originates in the gut and spreads to the central nervous system via cell-to-cell prion-like propagation, such that transfer of misfolded α-synuclein initiates misfolding of native α-synuclein in recipient cells. We recently discovered that enteroendocrine cells (EECs), which are part of the gut epithelium and directly face the gut lumen, also possess many neuron-like properties and connect to enteric nerves. In this report, we demonstrate that α-synuclein is expressed in the EEC line, STC-1, and native EECs of mouse and human intestine. Furthermore, α-synuclein-containing EECs directly connect to α-synuclein-containing nerves, forming a neural circuit between the gut and the nervous system in which toxins or other environmental influences in the gut lumen could affect α-synuclein folding in the EECs, thereby beginning a process by which misfolded α-synuclein could propagate from the gut epithelium to the brain.

Sensory innervation of the anal canal and anorectal line in Hirschsprung's disease: histological evidence from mouse models.

We used non-Hirschsprung's disease (HD) Sox10-Venus Transgenic mice (non-HDSV-mice), an endothelin receptor-B knockout mouse model of HD (HD-mice), and C57B6C3 wild controls (C-mice) to identify the correlation between the anorectal line (ARL) and successful transanal pull-through (TAPT). In non-HDSV-mice, intestinal neural crest-derived cells can be visualized with Venus,-a green fluorescent protein-without histochemical staining. We exposed the anal canal in each non-HDSV-mouse and marked the ARL directly with red ink. Specimens of anus and rectum from HD- and C-mice were immunostained with sensory nerve markers substance P and calcitonin gene related peptide (CGRP) and Hematoxylin and Eosin. Stereoscopic microscopy confirmed a squamous-columnar epithelial junction corresponding to the red ink in non-HDSV-mice. Fluorescence microscopy showed intense Venus expression proximal to the ARL and little enteric nerve expression distally. Substance P and CGRP expression were strong in the basal layer of the anal transitional zone (ATZ) in both HD- and C-mice; i.e., distal sensory innervation was normal in HD-mice. The ARL delineated a distinct demarcation in sensory innervation that is normal even in HD-mice. Thus, the initial incision during TAPT should be based on the ARL because it is readily identifiable and intimately involved with bowel function.

FFA3 Activation Stimulates Duodenal Bicarbonate Secretion and Prevents NSAID-Induced Enteropathy via the GLP-2 Pathway in Rats.

Therapy with nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with enteropathy in humans and experimental animals, a cause of considerable morbidity. Unlike foregut NSAID-associated mucosal lesions, most treatments for this condition are of little efficacy. We propose that the endogenously released intestinotrophic hormone glucagon-like peptide-2 (GLP-2) prevents the development of NSAID-induced enteropathy. Since the short-chain fatty acid receptor FFA3 is expressed on enteroendocrine L cells and on enteric nerves in the gastrointestinal tract, we further hypothesized that activation of FFA3 on L cells protects the mucosa from injury via GLP-2 release with enhanced duodenal HCO3- secretion. We thus investigated the effects of synthetic selective FFA3 agonists with consequent GLP-2 release on NSAID-induced enteropathy. We measured duodenal HCO3- secretion in isoflurane-anesthetized rats in a duodenal loop perfused with the selective FFA3 agonists MQC or AR420626 (AR) while measuring released GLP-2 in the portal vein (PV). Intestinal injury was produced by indomethacin (IND, 10mg/kg, sc) with or without MQC (1-10mg/kg, ig) or AR (0.01-0.1mg/kg, ig or ip) treatment. Luminal perfusion with MQC or AR (0.1-10µM) dose-dependently augmented duodenal HCO3- secretion accompanied by increased GLP-2 concentrations in the PV. The effect of FFA3 agonists was inhibited by co-perfusion of the selective FFA3 antagonist CF3-MQC (30µM). AR-induced augmented HCO3- secretion was reduced by iv injection of the GLP-2 receptor antagonist GLP-2(3-33) (3nmol/kg), or by pretreatment with the cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor CFTRinh-172 (1mg/kg, ip). IND-induced small intestinal ulcers were dose-dependently inhibited by intragastric administration of MQC or AR. GLP-2(3-33) (1mg/kg, ip) or CF3-MQC (1mg/kg, ig) reversed AR-associated reduction in IND-induced enteropathy. In contrast, ip injection of AR had no effect on enteropathy. These results suggest that luminal FFA3 activation enhances mucosal defenses and prevents NSAID-induced enteropathy via the GLP-2 pathway. The selective FFA3 agonist may be a potential therapeutic candidate for NSAID-induced enteropathy.

Update on Foregut Molecular Embryology and Role of Regenerative Medicine Therapies.

Esophageal atresia (OA) represents one of the commonest and most severe developmental disorders of the foregut, the most proximal segment of the gastrointestinal (GI) tract (esophagus and stomach) in embryological terms. Of intrigue is the common origin from this foregut of two very diverse functional entities, the digestive and respiratory systems. OA appears to result from incomplete separation of the ventral and dorsal parts of the foregut during development, resulting in disruption of esophageal anatomy and frequent association with tracheo-oesophageal fistula. Not surprisingly, and likely inherent to OA, are associated abnormalities in components of the enteric neuromusculature and ultimately loss of esophageal functional integrity. An appreciation of such developmental processes and associated defects has not only enhanced our understanding of the etiopathogenesis underlying such devastating defects but also highlighted the potential of novel corrective therapies. There has been considerable progress in the identification and propagation of neural crest stem cells from the GI tract itself or derived from pluripotent cells. Such cells have been successfully transplanted into models of enteric neuropathy confirming their ability to functionally integrate and replenish missing or defective enteric nerves. Combinatorial approaches in tissue engineering hold significant promise for the generation of organ-specific scaffolds such as the esophagus with current initiatives directed toward their cellularization to facilitate optimal function. This chapter outlines the most current understanding of the molecular embryology underlying foregut development and OA, and also explores the promise of regenerative medicine.

Tryptase potentiates enteric nerve activation by histamine and serotonin: Relevance for the effects of mucosal biopsy supernatants from irritable bowel syndrome patients.

We previously showed that mucosal biopsy supernatants from irritable bowel syndrome patients activated neurons despite low concentrations of tryptase, histamine, and serotonin which individually would not cause spike discharge. We studied the potentiating responses between these mediators on excitability of enteric neurons. Calcium-imaging was performed using the calcium-sensitive dye Fluo-4 AM in human submucous plexus preparations from 45 individuals. Histamine, serotonin, and tryptase were applied alone and in combinations to evaluate nerve activation which was assessed by analyzing increase in intracellular Ca2+ ([Ca2+ ]i ), the proportion of responding neurons and the product of both defined as Ca-neuroindex (NI). Protease activated receptor (PAR) 2 activating peptide, PAR2 antagonist and the serine protease-inhibitor FUT-175 were used to particularly investigate the role of proteases. Histamine or serotonin (1μmol/L each) evoked only few small responses (median NI [25%/75%]: 0 [0/148]; 85 [0/705] respectively). Their combined application evoked statistically similar responses (216 [21/651]). Addition of the PAR2 activator tryptase induced a significantly higher Ca-NI (1401 [867/4075]) compared to individual application of tryptase or to coapplied histamine and serotonin. This synergistic potentiation was neither mimicked by PAR2 activating peptide nor reversed by the PAR2 antagonist GB83, but abolished by FUT-175. We observed synergistic potentiation between histamine, serotonin, and tryptase in enteric neurons, which is mediated by proteolytic activity rather than PAR2 activation. This explained neuronal activation by a cocktail of these mediators despite their low concentrations and despite a relatively small PAR2-mediated response in human submucous neurons.

Mo1580 - Ephrinb2/Ephb2 Promoted Synaptic Plasticity of Enteric Nerve System and Contributed to Visceral Hypersensitivity in IBS

Mo1580 - Ephrinb2/Ephb2 Promoted Synaptic Plasticity of Enteric Nerve System and Contributed to Visceral Hypersensitivity in IBS

Inhibitory responses mediated by vagal nerve stimulation are diminished in stomachs of mice with reduced intramuscular interstitial cells of Cajal

Intramuscular interstitial cells of Cajal (ICC-IM) are closely associated with enteric motor nerve terminals and electrically coupled to smooth muscle cells within the gastric musculature. Previous studies investigating the role of ICC-IM in motor neurotransmission have used indiscriminate electric field stimulation of neural elements within the gastric wall. To determine the role of ICC-IM in transduction of vagally-mediated motor input to gastric muscles electrical and mechanical responses to selective electrical vagal stimulation (EVS) were recorded from gastric fundus and antral regions of wild type and W/WV mice, which lack most ICC-IM. EVS evoked inhibitory junction potentials (IJPs) in wild type muscles that were attenuated or abolished by L-NNA. IJPs were rarely evoked in W/WV muscles by EVS, and not affected by L-NNA. EVS evoked relaxation of wild type stomachs, but the predominant response of W/WV stomachs was contraction. EVS applied after pre-contraction with bethanechol caused relaxation of wild type gastric tissues and these were inhibited by the nitric oxide synthase inhibitor L-NNA. Relaxation responses were of smaller amplitude in W/WV muscles and L-NNA did not attenuate relaxation responses in W/WV fundus muscles. These data suggest an important role for ICC-IM in vagally-mediated nitrergic relaxation in the proximal and distal stomach.

Clostridium difficile Toxin A Induces Reactive Oxygen Species Production and p38 MAPK Activation to Exert Cellular Toxicity in Neuronal Cells.

Clostridium difficile releases two exotoxins, toxin A and toxin B, which disrupt the epithelial cell barrier in the gut to increase mucosal permeability and trigger inflammation with severe diarrhea. Many studies have suggested that enteric nerves are also directly involved in the progression of this toxin-mediated inflammation and diarrhea. C. difficile toxin A is known to enhance neurotransmitter secretion, increase gut motility, and suppress sympathetic neurotransmission in the guinea pig colitis model. Although previous studies have examined the pathophysiological role of enteric nerves in gut inflammation, the direct effect of toxins on neuronal cells and the molecular mechanisms underlying toxin-induced neuronal stress remained to be unveiled. Here, we examined the toxicity of C. difficile toxin A against neuronal cells (SH-SY5Y). We found that toxin A treatment time- and dose-dependently decreased cell viability and triggered apoptosis accompanied by caspase-3 activation in this cell line. These effects were found to depend on the up-regulation of reactive oxygen species (ROS) and the subsequent activation of p38 MAPK and induction of p21Cip1/Waf1. Moreover, the N-acetyl-L-cysteine (NAC)-induced down-regulation of ROS could recover the viability loss and apoptosis of toxin A-treated neuronal cells. These results collectively suggest that C. difficile toxin A is toxic for neuronal cells, and that this is associated with rapid ROS generation and subsequent p38 MAPK activation and p21Cip1/Waf1 up-regulation. Moreover, our data suggest that NAC could inhibit the toxicity of C. difficile toxin A toward enteric neurons.

Localization of the 5-hydroxytryptamine 4 receptor in equine enteric neurons and extrinsic sensory fibers.

Serotonin plays a pivotal role in regulating gut motility, visceral sensitivity, and fluid secretion via specific receptors. Among these receptors, 5-HT4 exerts a prominent control on gut motor function. Although the prokinetic effect exerted by 5-HT4 agonists is well known, the cellular sites of 5-HT4 expression remain poorly understood in large mammals, e.g., horses. In this study, we evaluated the distribution of 5-HT4 in the horse intestine and in foals with enteric aganglionosis, reminiscent of human Hirschsprung's disease. The intestine and spinal ganglia were obtained from three healthy horses and two foals with hereditary ileocolonic aganglionosis. Tissues were processed for immunohistochemistry using a specific antibody to 5-HT4 and a variety of neuronal markers. Myenteric and submucosal plexus 5-HT4 -immunoreactive (IR) neurons were quantified as relative percentage (mean±SD) to the total number of neurons counted. Furthermore, the density of 5-HT4 -IR nerve fibers was evaluated in the mucosa and tunica muscularis. The 5-HT4 immunoreactivity was localized to large percentages of myenteric neurons ranging from 28±9% (descending colon) to 63±19% (ileum), and submucosal neurons ranging from 54±6% (ileum) to 68±14% (duodenum). The 5-HT4 -immunoreactivity was co-expressed by some substance P-IR (SP-IR) spinal ganglion neurons and extrinsic sensory fibers of aganglionic foals. The presence of 5-HT4 in many enteric and extrinsic sensory neurons and nerve fibers provides solid morphological evidence of the cellular sites of 5-HT4 expression in horses. The evidence of SP-IR sensory neurons positive for 5-HT4 suggests its role in visceral sensitivity.

Neuregulin 1 is involved in enteric nervous system development in zebrafish

BackgroundHirschsprung's disease (HD, also known as congenital colon aganglionosis) is a congenital disorder characterized by the absence of intramural ganglion cells in the distal gastrointestinal tract, which results in tonic contraction of the aganglionic gut segment and functional intestinal obstruction. Recent studies have indicated neuregulin 1 (NRG1) as a new candidate gene involved in the development of the enteric nervous system (ENS) in humans. MethodsIn our study, we investigated the role of NRG1 in zebrafish ENS development by assessing NRG1 expression patterns during ENS development. Knockdown, overexpression and rescue zebrafish models of NRG1 were created to evaluate differences in phenotype, numbers of enteric neurons, ENS-related factors and nerve fiber arrangements. ResultsNRG1 was expressed in zebrafish intestine at both the larval and adult stage. We also found that decreased expression of NRG1 resulted in reductions in enteric neuron number and decreased expression of ENS development markers. Moreover, NRG1-knockdown zebrafish exhibited a disordered arrangement of nerve fibers. ConclusionsCollectively, these results demonstrated that NRG1 expression might play a role in zebrafish ENS development. In addition, by modulating NRG1 expression, we created a model that may be useful for investigating the mechanism underlying HD pathogenesis.