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American Journal of Physiology.... Nov 2023Notch signaling regulates gastrointestinal stem cell proliferation and differentiation yet Notch-regulated transcriptional effectors of gastric epithelial cell...
Notch signaling regulates gastrointestinal stem cell proliferation and differentiation yet Notch-regulated transcriptional effectors of gastric epithelial cell differentiation are poorly understood. Here we tested the role of the bHLH transcription factor Achaete-Scute homolog 1 (ASCL1) in gastric epithelial cell differentiation, and its regulation by Notch. Newborn null mice showed a loss of expression of markers of neurogenin-3-dependent enteroendocrine cells, with normal expression of enterochromaffin-like cells, mucous cells, chief cells, and parietal cells. In adult mice, gene expression was observed in the stomach, but not the intestine, with higher expression in antral than corpus epithelium. Lineage tracing in mice revealed single, scattered ASCL1 cells in the gastric epithelium, demonstrating expression in antral gastrin- and serotonin-producing endocrine cells. ASCL1-expressing endocrine cells persisted for several weeks posttamoxifen labeling with a half-life of approximately 2 months. Lineage tracing in mice demonstrated a similar lifespan for gastrin-producing cells, confirming that gastric endocrine cells are long-lived. Finally, treatment of ; mice with the pan-Notch inhibitor dibenzazepine increased the number of lineage-labeled cells in the gastric antrum, suggesting that Notch signaling normally inhibits expression. Notch regulation of was also demonstrated in a genetic mouse model of Notch activation, as well as Notch-manipulated antral organoid cultures, thus suggesting that ASCL1 is a key downstream Notch pathway effector promoting endocrine cell differentiation in the gastric epithelium. Although Notch signaling is known to regulate cellular differentiation in the stomach, downstream effectors are poorly described. Here we demonstrate that the bHLH transcription factor ASCL1 is expressed in endocrine cells in the stomach and is required for formation of neurogenin-3-dependent enteroendocrine cells but not enterochromaffin-like cells. We also demonstrate that expression is inhibited by Notch signaling, suggesting that ASCL1 is a Notch-regulated transcriptional effector directing enteroendocrine cell fate in the mouse stomach.
Topics: Animals; Mice; Basic Helix-Loop-Helix Transcription Factors; Cell Differentiation; Enteroendocrine Cells; Gastrins; Mice, Knockout; Stomach
PubMed: 37698169
DOI: 10.1152/ajpgi.00043.2023 -
Cell and Tissue Research Jun 2024Understanding how the gut communicates with the brain, via sensory nerves, is of significant interest to medical science. Enteroendocrine cells (EEC) that line the...
Understanding how the gut communicates with the brain, via sensory nerves, is of significant interest to medical science. Enteroendocrine cells (EEC) that line the mucosa of the gastrointestinal tract release neurochemicals, including the largest quantity of 5-hydroxytryptamine (5-HT). How the release of substances, like 5-HT, from enterochromaffin (EC) cells activates vagal afferent nerve endings is unresolved. We performed anterograde labelling from nodose ganglia in vivo and identified vagal afferent axons and nerve endings in the mucosa of whole-mount full-length preparations of mouse colon. We then determined the spatial relationship between mucosal-projecting vagal afferent nerve endings and EC cells in situ using 3D imaging. The mean distances between vagal afferent nerve endings in the mucosa, or nearest varicosities along vagal afferent axon branches, and the nearest EC cell were 29.6 ± 19.2 μm (n = 107, N = 6) and 25.7 ± 15.2 μm (n = 119, N = 6), respectively. No vagal afferent endings made close contacts with EC cells. The distances between EC cells and vagal afferent endings are many hundreds of times greater than known distances between pre- and post-synaptic membranes (typically 10-20 nm) that underlie synaptic transmission in vertebrates. The absence of any close physical contacts between 5-HT-containing EC cells and vagal afferent nerve endings in the mucosa leads to the inescapable conclusion that the mechanism by which 5-HT release from ECs in the colonic mucosa occurs in a paracrine fashion, to activate vagal afferents.
Topics: Animals; Enterochromaffin Cells; Colon; Vagus Nerve; Mice; Mice, Inbred C57BL; Male; Nerve Endings; Nodose Ganglion; Neurons, Afferent
PubMed: 38383905
DOI: 10.1007/s00441-024-03879-6 -
Microorganisms Apr 2024Gut microbes supporting body growth are known but the mechanisms are less well documented. Using the microbial tryptophan metabolite indole, known to regulate...
Gut microbes supporting body growth are known but the mechanisms are less well documented. Using the microbial tryptophan metabolite indole, known to regulate prokaryotic cell division and metabolic stress conditions, we mono-colonized germ-free (GF) mice with indole-producing wild-type () or tryptophanase-encoding tnaA knockout mutant indole-non-producing . Indole mutant mice showed multiorgan growth retardation and lower levels of glycogen, cholesterol, triglycerides, and glucose, resulting in an energy deficiency increased food intake. Detailed analysis revealed a malfunctioning intestine, enlarged cecum, and reduced numbers of enterochromaffin cells, correlating with a metabolic phenotype consisting of impaired gut motility, diminished digestion, and lower energy harvest. Furthermore, indole mutant mice displayed reduction in serum levels of tricarboxylic acid (TCA) cycle intermediates and lipids. In stark contrast, a massive increase in serum melatonin was observed-frequently associated with accelerated oxidative stress and mitochondrial dysfunction. This observational report discloses functional roles of microbe-derived indoles regulating multiple organ functions and extends our previous report of indole-linked regulation of adult neurogenesis. Since indoles decline by age, these results imply a correlation with age-linked organ decline and levels of indoles. Interestingly, increased levels of indole-3-acetic acid, a known indole metabolite, have been shown to correlate with younger biological age, further supporting a link between biological age and levels of microbe-derived indole metabolites. The results presented in this resource paper will be useful for the future design of food intervention studies to reduce accelerated age-linked organ decline.
PubMed: 38674663
DOI: 10.3390/microorganisms12040719 -
Frontiers in Medicine 2024Gastric neuroendocrine neoplasms (g-NENs) are rare tumors arising from the gastric enterochromaffin-like cells. Recent data suggests an increased detection rate,... (Review)
Review
Gastric neuroendocrine neoplasms (g-NENs) are rare tumors arising from the gastric enterochromaffin-like cells. Recent data suggests an increased detection rate, attributed to more frequent esophagogastroduodenoscopies. While type 3 g-NENs were historically deemed aggressive, emerging research indicates potential for conservative management, especially endoscopic resection, in well-differentiated, small tumors. European guidelines now advocate for endoscopic intervention in selected cases, but North American guidelines remain more conservative. Key factors influencing outcomes are tumor size, grading, and depth of gastric wall infiltration. Endoscopic resection has shown promise for tumors confined to submucosal layers without lymphovascular invasion. Given the complexities, a multidisciplinary team approach is essential for management decisions. Current insights are largely based on retrospective studies, underscoring the need for prospective research to optimize endoscopic approaches.
PubMed: 38357651
DOI: 10.3389/fmed.2024.1327864 -
Clinical Journal of Gastroenterology Apr 2024A 47-year-old woman presented with multiple gastric tumors, each up to 10 mm in diameter, in the gastric body and fundus without mucosal atrophy. White spots and...
A 47-year-old woman presented with multiple gastric tumors, each up to 10 mm in diameter, in the gastric body and fundus without mucosal atrophy. White spots and numerous transparent, light-brownish, small, and rounded spots were observed in the background gastric mucosa. Biopsy specimens obtained from the tumors revealed gastric neuroendocrine tumors. The patient exhibited hypergastrinemia and achlorhydria and tested negative for serum parietal cell antibody, intrinsic factor antibody, and Helicobacter pylori infection. Moreover, no additional lesions were detected on imaging. These findings were inconsistent with Rindi's classification. The tumor was resected via endoscopic submucosal resection. Histopathological examination revealed gastric neuroendocrine tumors G2 infiltrating the submucosa with no atrophy of the gastric mucosa, dilated fundic glands, parietal cell protrusions, and hyperplasia of enterochromaffin-like cells. Immunohistochemically, the parietal cells were negative for both α- and β-subunits of H/K ATPase, suggesting parietal cell dysfunction. A genomic variant was identified in adenosine triphosphatase H/K transporting subunit alpha. After 7 years of treatment, there was no evidence of residual or metastatic lesions. Modification of adenosine triphosphatase H/K transporting subunit alpha may be a significant factor in the pathogenesis of multiple gastric neuroendocrine tumors in the context of gastric parietal cell dysfunction.
PubMed: 38635098
DOI: 10.1007/s12328-024-01969-0 -
Gastroenterology Oct 2023
Topics: Humans; Enterochromaffin Cells; Duodenum; Serotonin
PubMed: 37178735
DOI: 10.1053/j.gastro.2023.05.008 -
Clinical Case Reports Mar 2024Neuroendocrine tumors (NETs) are a group of uncommon neoplasms derived from enterochromaffin or Kulchitsky cells (that secrete serotonin or other molecules into the...
Neuroendocrine tumors (NETs) are a group of uncommon neoplasms derived from enterochromaffin or Kulchitsky cells (that secrete serotonin or other molecules into the bloodstream), which can manifest with symptoms of hormonal overproduction, namely carcinoid syndrome (CS). This can be the presenting feature in patients with advanced disease. We report the case of a 66-year-old woman presenting with chronic diarrhea, facial venous telangiectasia and elevated urinary 5-hydrocyindoleacetic acid levels. A 68-Ga DOTATOC PET/CT scan revealed an ileal mass and lesions consistent with liver, ovary and bone metastasis. A liver biopsy confirmed the diagnosis of well-differentiated NET G1. Therapy with somatostatin analogs achieved symptom control, but the liver disease progressed and the patient passed away after 2 years of follow-up. The challenge of diagnosing CS resides in its heterogeneous manifestations, which may range from mild to life-threatening conditions. In this case, the cutaneous findings of venous telangiectasia strongly pointed to the correct diagnosis. Treatment can also be difficult due to refractory symptoms and inevitable progression of disease, highlighting the importance of early detection and thorough disease staging.
PubMed: 38455854
DOI: 10.1002/ccr3.8641 -
Clinical Nuclear Medicine Dec 2023Neuroendocrine tumors (NETs) are rare neoplasms arising from enterochromaffin cells, which are predominantly noted in the gastrointestinal tract and lung; metastases of...
Neuroendocrine tumors (NETs) are rare neoplasms arising from enterochromaffin cells, which are predominantly noted in the gastrointestinal tract and lung; metastases of NETs to the testes in NET are further uncommon. Testicular NET usually has no symptoms and/or presents with painless swelling of the scrotum. Detection of testicular lesion can be challenging and frequently missed on conventional radiological imaging. We present testicular NET missed on conventional radiological imaging, where 68 Ga-DOTATATE PET/CT imaging detected the testicular lesion, and further evident on 177 Lu-DOTATATE-based post-peptide receptor radionuclide therapy theranostic imaging.
Topics: Male; Humans; Positron Emission Tomography Computed Tomography; Neuroendocrine Tumors; Precision Medicine; Organometallic Compounds; Radioisotopes; Receptors, Peptide
PubMed: 37793184
DOI: 10.1097/RLU.0000000000004846 -
The Journal of Biological Chemistry Dec 2023Adhesion G protein-coupled receptors (aGPCRs) feature large extracellular regions with modular domains that often resemble protein classes of various function. The...
Adhesion G protein-coupled receptors (aGPCRs) feature large extracellular regions with modular domains that often resemble protein classes of various function. The pentraxin (PTX) domain, which is predicted by sequence homology within the extracellular region of four different aGPCR members, is well known to form pentamers and other oligomers. Oligomerization of GPCRs is frequently reported and mainly driven by interactions of the seven-transmembrane region and N or C termini. While the functional importance of dimers is well-established for some class C GPCRs, relatively little is known about aGPCR multimerization. Here, we showcase the example of ADGRG4, an orphan aGPCR that possesses a PTX-like domain at its very N-terminal tip, followed by an extremely long stalk containing serine-threonine repeats. Using X-ray crystallography and biophysical methods, we determined the structure of this unusual PTX-like domain and provide experimental evidence for a homodimer equilibrium of this domain which is Ca-independent and driven by intermolecular contacts that differ vastly from the known soluble PTXs. The formation of this dimer seems to be conserved in mammalian ADGRG4 indicating functional relevance. Our data alongside of theoretical considerations lead to the hypothesis that ADGRG4 acts as an in vivo sensor for shear forces in enterochromaffin and Paneth cells of the small intestine.
Topics: Animals; Mammals; Protein Domains; Receptors, G-Protein-Coupled; Signal Transduction; Enterochromaffin Cells; Paneth Cells; Crystallography, X-Ray; Biophysical Phenomena; Models, Molecular; Protein Structure, Tertiary; Protein Folding; Sequence Alignment; Amino Acid Sequence; HEK293 Cells; Humans
PubMed: 37863265
DOI: 10.1016/j.jbc.2023.105356 -
Lab on a Chip Mar 2024The oxygen gradient across the intestine influences intestinal physiology and the microbial environment of the microbiome. The microbiome releases metabolites that...
The oxygen gradient across the intestine influences intestinal physiology and the microbial environment of the microbiome. The microbiome releases metabolites that communicate with enterochromaffin cells, neuronal cells, and resident immune cells to facilitate the bidirectional communication across the gut-brain axis. Measuring communication between various cell types within the intestine could provide essential information about key regulators of gut and brain health; however, the microbial environment of the intestine is heavily dependent on the physiological oxygen gradient that exists across the intestinal wall. Likewise, there exist a need for methods which enable real-time monitoring of intestinal signaling yet this remains challenging due to the inability to adequately culture intestinal tissue while also exposing the appropriate locations of the intestine for probe insertion and monitoring. Here, we designed and fabricated a 3D printed microfluidic device to maintain the oxygen gradient across precision cut murine intestinal slices with the capability to couple to external neurochemical recording techniques. The gradient is maintained from outlets below while allowing access to the slice from above for detection with fast scan cyclic voltammetry (FSCV) and carbon-fiber microelectrodes. A series of 11 outlet ports were designed to lay underneath the slice which were connected to channels to deliver oxygenated deoxygenated media. Outlet ports were designed in an oval shape where deoxygenated media was delivered to the center of the slice and oxygenated media is delivered to the outer portion of the slice to mimic the location of oxygen across the intestine. An oxygen sensitive fluorescent dye, tris(2,2'-bipyridyl)dichlororuthenium(II), was used to characterize the tunability of the gradient. Viability of the tissue was confirmed by both fluorescence microscopy and FSCV. Additionally, we measured simultaneous serotonin and melatonin signaling with FSCV in the intestine for the first time. Overall, this chip provides a significant advance in our ability to culture intestinal slices with the added benefit of direct access for measurements and imaging.
Topics: Mice; Animals; Oxygen; Microfluidics; Brain
PubMed: 38372633
DOI: 10.1039/d3lc00793f