Enterochromaffin Research Articles

Enterochromaffin Cells and Mast Cells in Acute Appendicitis.

Background and Objective Serotonin levels are increased in acute appendicitis. We investigated the possible source of this increase. The aim of this study was to compare the distribution and density of epithelial and nonepithelial enterochromaffin (EC) cells as well as numbers of degranulated and nondegranulated mast cells in different layers of normal appendices and acute appendicitis. Methods Sections from 15 cases of acute appendicitis and 10 cases where the appendix was morphologically normal were stained with Hematoxylin & Eosin, Toluidine blue, and immunohistochemically for chromogranin and CD-117. EC cells stained by chromogranin were counted per crypt and extraepithelial EC cells counted and expressed as cells per unit area (mm 2 ). Mast cells stained by Toluidine blue and CD-117 were counted in lamina propria, submucosa, and muscle layers. The difference between Toluidine blue and CD117 stained mast cells was taken to be an estimate of degranulated cells. The cell counts were expressed per unit area (mm 2 ) as well as per cross-sectional area of the appendix. Results There was no statistically significant difference in epithelial and extraepithelial EC cells between acute appendicitis and normal appendix. Estimated mast cell degranulation as indicated by mast cell counts per cross-sectional area is greatly increased in acute appendicitis when compared with normal. Conclusion Degranulated mast cells rather than EC cells may be the main source of raised serotonin in acute appendicitis.

Microbial RNAs Pressure Piezo1 to Respond

Serotonin production by enterochromaffin cells (ECs) is microbiota-dependent, but the mechanism of this is unknown. In this issue of Cell, Sugisawa etal. demonstrate that Piezo1 in ECs senses single-strand RNA (ssRNA) from intestinal microbiota to promote serotonin production. Deletion of Piezo1 in intestinal epithelium promotes bone formation, decreases peristalsis, and protects from colitis because of decreased serotonin.

Knockdown of miR-183 Enhances the Cisplatin-Induced Apoptosis in Esophageal Cancer Through Increase of FOXO1 Expression.

BackgroundAs an important member of platinum-based chemotherapeutic drugs, cisplatin is effective and is commonly used in the treatment of esophageal cancer. However, repeated use of cisplatin usually causes severe side-effects on patients. Novel approaches should be explored to increase the sensitivity of cancer cells to cisplatin.MethodsThe expression level of miR-183 in esophageal cancer tissues and cell lines was measured by quantitative reverse transcriptase real-time PCR (qRT-PCR). The sensitivity of EC cell lines to cisplatin was evaluated by CCK-8 assay and flow cytometry. Luciferase reporter assay was used to confirm the association between miR-183 and FOXO1. The apoptosis pathway of EC cells was tested by Western blot assay.ResultsThe expression level of miR-183 was increased in esophageal cancer patients’ tumor tissues and esophageal cancer cell lines. However, knockdown of miR-183 was found to enhance the effect of cisplatin on inducing the apoptotic cell death of esophageal cancer cells. In the mechanism research, we proved that FOXO1 was the target of miR-183 in esophageal cancer cells. Inhibition of miR-183 increased the expression of FOXO1 to promote the expression of Bim and Noxa. As Bim and Noxa acted as key pro-apoptotic proteins in mitochondrial apoptosis, inhibition of miR-183 enhanced the cisplatin-induced apoptosis pathway in esophageal cancer.ConclusionKnockdown of miR-183 enhanced the cisplatin-induced apoptosis in esophageal cancer through an increase of FOXO1 expression.

Effects of Cordycepin, Gold Nanostar, and Their Combination on Endometrial Cancer Cells

The incidence rate of (EC) has increased significantly in the past 2 decades. The current chemotherapy for this disease can cause intolerable side effects. Recently, both cordycepin and gold nanostars have demonstrated the ability to inhibit the growth and differentiation of cancers. This study aimed to investigate the antiEC effects of cordycepin, gold nanostars (Au NS), and the combination of the two. The gold nanostars were made by seed-mediated reduction, and their morphology was confirmed by laser particle size analysis, spectrophotometry, and electron microscopy. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cytotoxicity assays, clonogenic assays, and flow cytometry were employed to evaluate the inhibition rate, survival fraction, and apoptosis in HEC-1A cells under different concentrations of cordycepin, Au NS, and their combination. This study revealed that both cordycepin and Au NS with 808 nm light exposure could inhibit cell proliferation, cause cell apoptosis, and inhibit the clone ability of EC cells. This study supports further investigations into Au NS-cordycepin in the development of new treatments for EC.

Circular RNA PRKCI silencing represses esophageal cancer progression and elevates cell radiosensitivity through regulating the miR-186-5p/PARP9 axis

AimsCircular RNA PRKCI (circPRKCI) and poly ADP-ribose polymerase 9 (PARP9) are related to the development of cancers. In this study, we aimed to explore the regulatory mechanisms between circPRKCI and PARP9 in EC progression and radioresistance. Materials and methodsThe levels of circPRKCI, PARP9 mRNA, and miR-186-5p were assessed by quantitative real time polymerase chain reaction (qRT-PCR). Western blot analysis was employed to examine the levels of several proteins. The viability, colony formation, cell cycle progression, and apoptosis of EC cells were determined with CCK-8, colony formation, or flow cytometry assays. The relationship between circPRKCI or PARP9 and miR-186-5p was verified with the dual-luciferase reporter and RIP assays. Key findingsWe observed that circPRKCI and PARP9 were upregulated while miR-186-5p was downregulated in EC tissues and cells. Furthermore, circPRKCI knockdown decreased tumor growth in vivo and constrained cell viability, colony formation, cell cycle progression, elevated cell radiosensitivity in EC cells in vitro. Importantly, circPRKCI modulated PARP9 expression through sponging miR-186-5p. Besides, PARP9 overexpression overturned circPRKCI silencing-mediated effects on the viability, colony formation, cell cycle progression, and radiosensitivity of EC cells. SignificanceCircPRKCI regulated cell malignancy and radioresistance through modulating the miR-186-5p /PARP9 axis in EC, which provided a might target for EC treatment.

Targeting deubiquitinating enzyme USP26 by microRNA-203 regulates Snail1\u2019s pro-metastatic functions in esophageal cancer

BackgroundEsophageal cancer is one of the most common cancers worldwide with poor prognosis and high mortality. The transcription factor SNAI1, encoding Snail1, is important for metastatic progression in esophageal cancer whereas the microRNA (miRNA)-203 has been shown to function as an inhibitor of metastasis in EC. The Snail1 protein is stabilized in EC partially by the deubiquitinating enzyme USP26; however, how USP26 is regulated is not completely known.MethodsExpression of SNAI1 and USP26 messenger RNA (mRNA) and miR-203 was performed in datasets within The Cancer Genome Atlas and Gene Expression Omnibus, respectively. Expression of Snail1 and USP26 protein and miR-203 was determined in the normal esophageal cell line HET-1A and EC cell lines Kyse150 and TE-1 using western blot and quantitative polymerase chain reaction, respectively. TargetScan was used for in situ prediction of miR-203 targets and in vitro heterologous reporter assays using the wild-type and miR-203 seed mutant of the 3′ Untranslated region (UTR) of USP26 were used to investigate whether USP26 is a target of miR-203. Effects of increasing miR-203 using MIR203A/5P mimic on USP26 and Snail1 in the HET-1A, Kyse150 and TE-1 cell lines were performed using western blot and cycloheximide-based protein stability analysis. Effects of modulating miR-203 in Kyse150 and TE-1 cell lines on in vitro pro-metastatic effects were analyzed by invasion assay, scratch wound-healing assay, and chemosensitivity to 5-fluoruracil (5-FU). In vivo lung metastasis assay was used to study the effect of modulating miR-203 in Kyse150 cells.ResultsSNAI1 mRNA and HSA/MIR203 was higher and lower, respectively, in EC patients compared to tumor-adjacent normal tissues. No changes in expression of USP26 mRNA were observed in these datasets. MIR/203 expression was downregulated whereas protein expression of both Snail1 and USP26 were higher in EC cell lines Kyse150 and TE-1 compared to normal esophageal cell line HET-1A. USP26 was predicted as a potential target of miR-203 by TargetScan Release 2.0. Reporter assays confirmed USP26 as a target of miR-203 in the EC cell lines. Transfection of EC cell lines with MIR203 mimic decreased USP26 protein expression and Snail1 protein stability indicating the ability of miR-203 to regulate Snail1 protein levels via USP26. Exogenous increase in miR-203 in the EC cell lines significantly inhibited Snail-1 mediated in vitro pro-metastatic function of invasion, wound-healing, and increased chemosensitivity to 5-FU. Finally, overexpression of miR-203 inhibited in vivo lung metastasis of Kyse150 cells, which was reversed following overexpression of USP26, indicating a direct role of miR-203-mediated regulation of USP26 in metastatic progression of EC.ConclusionsCumulatively, these results establish an important mechanism by which decrease in miR-203 expression potentiates metastatic progression in EC via USP26-mediated stabilization of Snail1. Hence, miR-203 can serve as a biomarker of metastasis in EC and is a potential target for therapeutic intervention in EC.

Synthetic G protein-coupled bile acid receptor agonists and bile acids act via basolateral receptors in ileal and colonic mucosa.

The G protein-coupled bile acid (BA) receptor, GPBA (previously named TGR5), mediates BA gastrointestinal (GI) activities. Our aim was to elucidate the mucosal and motility responses to selective GPBA agonists compared with conjugated BA (eg, taurodeoxycholate, TDCA) in mouse and human colon. Ion transport responses to GPBA agonists or BAs were measured in mucosal preparations with intact submucous innervation, from C57Bl/6, PYY-/-, or GPBA-/- mice and compared with GPBA signaling in human colon. We also investigated the mechanisms underlying GPBA agonism in mucosae and on natural fecal pellet propulsion. GPBA agonist Merck V stimulated basolateral responses involving peptide YY (PYY), cholinergic, and 5-HT mechanisms in colonic mucosa. The PYY-mediated GPBA signal was glucose-sensitive. Luminal TDCA crossed the epithelial lining via the apical sodium-dependent BA transporter (ASBT) and its inhibitor, GSK2330672 significantly reduced luminal, but not basolateral TDCA activity. Merck V also slowed natural fecal pellet progression in wild-type and PYY-/- colons but not in GPBA-/- colon, while TDCA increased motility in wild-type colon. The antimotile GPBA effect was reversed by blockade of glucagon-like peptide 1 (GLP-1) receptors or nitric oxide synthase, indicating involvement of GLP-1 and nitric oxide. We conclude that several different targets within the lamina propria express GPBA, including L cells (that release PYY and GLP-1), enterochromaffin cells and neurons (that release 5-HT), and other enteric neurons. Furthermore, luminal-conjugated BAs require transport across the epithelium via ASBT in order to activate basolateral GPBA.

Multi-Step Phase Transitions of Mn3 O4 During Galvanostatic Lithiation: An In Situ Transmission Electron Microscopic Investigation.

For study of electrochemical reaction mechanisms at nanoscale, in situ electrochemical transmission electron microscopy (EC-TEM) exceeds many other methods due to its high temporal and spatial resolution. However, the limited amount of active materials used in previous in situ TEM studies prevents the model EC cells to operate in the constant-current (galvanostatic) charge/discharge mode that is required for accurate control of electrochemical processes. Herein, a new in situ EC-TEM technique is developed to investigate multi-step phase transitions of Mn3 O4 electrodes under the galvanostatic charge/discharge mode and constant-voltage discharge mode. In galvanostatic mode, the lithiation of Mn3 O4 undergoes multi-step phase transitions following a reaction pathway of Mn3 O4 + Li+ → LiMn3 O4 + Li+ → MnO + Li2 O → Mn + Li2 O. It is also found that lithium ions prefer to enter Mn3 O4 along the {101} direction to form LiMn3 O4 with the help of transitional boundary phase of Lix Mn3 O4 . These results are in sharp contrast to that obtained under a constant-voltage discharge mode, where only a single-step lithiation process of Mn3 O4 + Li+ → Mn + Li2 O is observed.

LncRNA HOTAIR-mediated MTHFR methylation inhibits 5-fluorouracil sensitivity in esophageal cancer cells

BackgroundEsophageal cancer (EC) represents one of the most aggressive digestive neoplasms globally, with marked geographical variations in morbidity and mortality. Chemoprevention is a promising approach for cancer therapy, while acquired chemoresistance is a major obstacle impeding the success of 5-fluorouracil (5-FU)-based chemotherapy in EC, with the mechanisms underlying resistance not well-understood. In the present study, we focus on exploring the role of long non-coding RNA (lncRNA) HOTAIR in EC progression and sensitivity of EC cells to 5-FU.MethodsPaired cancerous and pre-cancerous tissues surgically resected from EC patients were collected in this study. Promoter methylation of the MTHFR was assessed by methylation-specific PCR. RIP and ChIP assays were adopted to examine the interaction of DNA methyltransferases (DNMTs) with lncRNA HOTAIR and MTHFR, respectively. EC cells resistant to 5-FU were induced by step-wise continuous increasing concentrations of 5-FU. The sensitivity of EC cells to 5-FU in vivo was evaluated in nude mice treated with xenografts of EC cells followed by injection with 5-FU (i.p.).ResultsWe found reciprocal expression patterns of lncRNA HOTAIR and MTHFR in EC tissues and human EC cells. Interference with lncRNA HOTAIR enhanced 5-FU-induced apoptosis, exhibited anti-proliferative activity, and reduced promoter methylation of the MTHFR in EC cells. Besides, overexpression of MTHFR attenuated the acquired chemoresistance induced by overexpression of lncRNA HOTAIR in EC cells. At last, enhanced chemosensitivity was observed in vivo once nude mice xenografted with lncRNA HOTAIR-depleted EC cells.ConclusionTogether, our study proposes that pharmacologic targeting of lncRNA HOTAIR sensitizes EC cells to 5-FU-based chemotherapy by attenuating the promoter hypermethylation of the MTHFR in EC.

RNA Sensing by Gut Piezo1 Is Essential for Systemic Serotonin Synthesis

Gastrointestinal enterochromaffin cells regulate bone and gut homeostasis via serotonin (5-hydroxytryptamine [5-HT]) production. A recent report suggested that gut microbes regulate 5-HT levels; however, the precise underlying molecular mechanisms are unexplored. Here, we reveal that the cation channel Piezo1 in the gut acts as a sensor of single-stranded RNA (ssRNA) governing 5-HT production. Intestinal epithelium-specific deletion of mouse Piezo1 profoundly disturbed gut peristalsis, impeded experimental colitis, and suppressed serum 5-HT levels. Because of systemic 5-HT deficiency, conditional knockout of Piezo1 increased bone formation. Notably, fecal ssRNA was identified as a natural Piezo1 ligand, and ssRNA-stimulated 5-HT synthesis from the gut was evoked in a MyD88/TRIF-independent manner. Colonic infusion of RNase A suppressed gut motility and increased bone mass. These findings suggest gut ssRNA as a master determinant of systemic 5-HT levels, indicating the ssRNA-Piezo1 axis as a potential prophylactic target for treatment of bone and gut disorders.

Zeolite-assisted electrocoagulation for remediation of phosphate from calcium-phosphate solution

Phosphorus is crucial to the growth of the skeletons and the living cell. However, elevated phosphate concentrations represent a problem due to its grave impacts on human health, animal and also because of its effects on water quality and economy. This research studies the applicability of filtration-electrocoagulation (filtration - EC) system to remove phosphate from wastewater when calcium is present as competitor ions. In laboratory batch trials, the ability of zeolite filter-electrocoagulation system to eliminate phosphate from artificial wastewater samples, in the presence of calcium as competitor ions, was tested. The research was initiated by studying the ability of the electrocoagulation method (EC), as a separated treatment unit, to remove phosphate from solutions that containing calcium ions. In this phase of the study, the influence initial pH, current densities and electrolysing period. Then, the new method, filtration-EC, was applied to treat solutions (with identical chemical composition to that used in the first phase) considering the effects of the initial pH, current densities, contact periods (in the filter), electrolysing period (in the EC cell) and zeolite dosage. The results of this research evidenced that the filtration - EC system completely removes phosphate from calcium-phosphate solution at pH, current density, dosage of zeolites, contact period and electrolysing period of 7, 2.0 mA.cm−2, 150.0 g, 30.0 minutes and 20.0 minutes, respectively.

Sunlight-driven CO2-to-fuel conversion: Exploring thermal and electrical coupling between photovoltaic and electrochemical systems for optimum solar-methane production

A novel Photovoltaic-Electrochemical (PV-EC) integrated system is designed, capable of converting CO2 into carbon-based fuels, in which “smart” synergetic effects between the two technologies are explored, such as thermal coupling (TC) and electronic regulation (DC-DC), that can strongly improve the energetic performance. We show that, when thermally-coupled, the PV and EC cells exhibit a symbiotic behaviour: the solar-to-fuel efficiency stays almost temperature-independent due to improved reaction kinetics, which compensates for photovoltaic thermal losses. The electronic regulation is equally important, because it guarantees that all power provided by PV generation is channelled to the EC load. When conjugated with TC, the DC-DC converter can boost production up to 50% beyond the TC improvement. For operating temperatures in the 40–90 °C range, combined TC and DC-DC can boost production by up to 586% and 42.9% for Perovskite/Si double-junction and mono-crystalline Si solar cells, respectively. These solutions are tested in two PV-powered pathways for methane production: 1-step, CO2→CH4, and 2-step, CO2→Syngas→CH4; where in the latter the intermediate syngas is converted to methane through catalytic hydrogenation. Despite the advantageous simplicity of the direct production (1-step) of methane, the comparison between the two paths showed that the second route achieves close to 20% higher annual yield.

Human resident gut microbe Bacteroides thetaiotaomicron regulates colonic neuronal innervation and neurogenic function

ABSTRACT Background and aims As the importance of gut–brain interactions increases, understanding how specific gut microbes interact with the enteric nervous system (ENS), which is the first point of neuronal exposure becomes critical. Our aim was to understand how the dominant human gut bacterium Bacteroides thetaiotaomicron (Bt) regulates anatomical and functional characteristics of the ENS. Methods Neuronal cell populations, as well as enteroendocrine cells, were assessed in proximal colonic sections using fluorescent immunohistochemistry in specific pathogen-free (SPF), germ-free (GF) and Bt conventionalized-germ-free mice (Bt-CONV). RNA expression of tight junction proteins and toll-like receptors (TLR) were measured using qPCR. Colonic motility was analyzed using in vitro colonic manometry. Results Decreased neuronal and vagal afferent innervation observed in GF mice was normalized by Bt-CONV with increased neuronal staining in mucosa and myenteric plexus. Bt-CONV also restored expression of nitric oxide synthase expressing inhibitory neurons and of choline acetyltransferase and substance P expressing excitatory motor neurons comparable to those of SPF mice. Neurite outgrowth and glial cells were upregulated by Bt-CONV. RNA expression of tight junction protein claudin 3 was downregulated while TLR2 was upregulated by Bt-CONV. The enteroendocrine cell subtypes L-cells and enterochromaffin cells were reduced in GF mice, with Bt-CONV restoring L-cell numbers. Motility as measured by colonic migrating motor complexes (CMMCs) increased in GF and Bt-CONV. Conclusion Bt, common gut bacteria, is critical in regulating enteric neuronal and enteroendocrine cell populations, and neurogenic colonic activity. This highlights the potential use of this resident gut bacteria for maintaining healthy gut function.

Actin‑like protein 8 executes a promoting function in the malignant progression of endometrial cancer: identification of a promising biomarker.

Endometrial cancer (EC) is generally considered as a disease that affects older women. We attempt to explore the role of actin‑like protein 8 (ACTL8) in EC and how it achieves its function. Based on the data from The Cancer Genome Atlas (TCGA), we found that ACTL8 expression was up-regulated in EC tissues and correlated with shorter overall survival of EC patients. ACTL8 expression was significantly associated with age, clinical-stage, or grade. Cox proportional hazards model analysis revealed that ACTL8 expression, grade, and clinical-stage were promising independent prognostic factors of EC. Knockdown of ACTL8 repressed the proliferative, migrating and invading capabilities of human EC cell lines KLE and Ishikawa. Silencing ACTL8 up-regulated the negative cell cycle regulator p21 and epithelial marker E-cadherin, and down-regulated the positive cell cycle regulator Cyclin A, mesenchymal markers MMP-9 and N-cadherin in KLE cells. Collectively, these outcomes illustrated that ACTL8 might act as a tumor facilitator during EC progression.

132-OR: Peripheral Serotonin Regulates Dietary Fat Absorption and Intestinal Chylomicron Production

Introduction: Diabetic dyslipidemia is a key feature of insulin resistance and is characterized by overproduction of chylomicron particles by the intestine. Chylomicron output can be regulated by hormones secreted from the intestine. Enterochromaffin cells are specialized enteroendocrine cells that secrete serotonin (5-HT). Gut-derived 5-HT is emerging as a regulator of systemic energy homeostasis by regulating adipose and liver lipid metabolism. Currently, the role of 5-HT on intestinal fat absorption and chylomicron production remains unknown. We hypothesize that 5-HT regulates postprandial intestinal fat absorption and chylomicron production. Methods/Results: Syrian golden hamsters underwent jugular cannulation surgery. The next day, hamsters received an oral fat load (200μl olive oil) followed by intravenous infusion of Triton WR-1339 to prevent lipoprotein clearance. Blood samples were collected prior to and up to 6 hours post fat load. Triglyceride-rich lipoproteins (TRL) which includes chylomicrons were isolated from plasma by density gradient ultracentrifugation and triglyceride (TG) content in this fraction was measured using an enzyme based colorimetric assay. Intravenous administration of 5-HT (1mg/kg) 5 minutes prior to oral fat load increased the rate of plasma TG and TRL-TG accumulation while higher doses of 5-HT (5 and 10mg/kg) produced a transient decrease in plasma TG and TRL-TG accumulation. Treatment with 5-HT4 receptor agonist, Bimu-8 (1mg/kg), increased plasma TG and TRL-TG accumulation. Endogenous 5-HT depletion by para-chloro-phenylalanine (PCPA), an inhibitor of 5-HT synthesis, reduced the rate of TG and TRL-TG accumulation compared to vehicle controls. Furthermore, enhancing 5-HT action by inhibiting 5-HT reuptake with fluoxetine increased the rate of TG and TRL-TG accumulation. Our results demonstrate that 5-HT is a key regulator of postprandial lipoprotein metabolism and could have important implications for diabetic dyslipidemia. Disclosure F. Raka: None. K. Adeli: None. Funding Canadian Institutes of Health Research (967131)

The ever-changing roles of serotonin.

Serotonin (5-HT) has traditional roles as a key neurotransmitter in the central nervous system and as a regulatory hormone controlling a broad range of physiological functions. Perhaps the most classically-defined functions of 5-HT are centrally in the control of mood, sleep and anxiety and peripherally in the modulation of gastrointestinal motility. A more recently appreciated role for 5-HT has emerged, however, as an important metabolic hormone contributing to glucose homeostasis and adiposity, with a causal relationship existing between circulating 5-HT levels and metabolic diseases. Almost all peripheral 5-HT is derived from specialised enteroendocrine cells, called enterochromaffin (EC) cells, located throughout the length of the lining of the gastrointestinal tract. EC cells are important luminal sensory cells that can detect and respond to an array of ingested nutrients, as well as luminal gut microbiota and their associated metabolites. Intriguingly, the interaction between gut microbiota and EC cells is dynamic in nature and has strong implications for host physiology. In this review, we discuss the traditional and modern functions of 5-HT and highlight an emerging pathway by which gut microbiota influences host health. Serotonin, also known as 5-hydroxytryptamine (5-HT), is an important neurotransmitter, growth factor and hormone that mediates a range of physiological functions. In mammals, serotonin is synthesized from the essential amino acid tryptophan by the rate-limiting enzyme tryptophan hydroxylase (TPH), for which there are two isoforms expressed in distinct cell types throughout the body. Tph1 is mainly expressed by specialized gut endocrine cells known as enterochromaffin (EC) cells and by other non-neuronal cell types such as adipocytes (Walther et al., 2003). Tph2 is primarily expressed in neurons of the raphe nuclei of the brain stem and a subset of neurons in the enteric nervous system (ENS) (Yabut et al., 2019). As 5-HT cannot readily cross the blood-brain barrier, the central and peripheral pools of 5-HT are anatomically separated and as such, act in their own distinct manners (Martin et al., 2017c). In this review we discuss the peripheral roles of serotonin, with particular focus on the interaction of gut-derived serotonin with the gut microbiota, and address emerging evidence linking this relationship with host homeostasis.

Identifying a Molecular Mechanism That Imparts Species-Specific Toxicity to YoeB Toxins.

The ribosome-dependent E. coli (Ec) mRNase toxin YoeB has been demonstrated to protect cells during thermal stress. Agrobacterium tumefaciens (At), a plant pathogen, also encodes a YoeB toxin. Initial studies indicated that AtYoeB does not impact the growth of Ec, but its expression is toxic to the native host At. The current work examines this species-specific effect. We establish the highly similar structure and function of Ec and AtYoeB toxins, including the ability of the AtYoeB toxin to inhibit Ec ribosomes in vitro. Comparison of YoeB sequences and structures highlights a four-residue helix between β-strands 2 and 3 that interacts with mRNA bases within the ribosome. This helix sequence is varied among YoeB toxins, and this variation correlates with bacterial classes of proteobacteria. When the four amino acid sequence of this helix is transplanted from EcYoeB onto AtYoeB, the resulting chimera gains toxicity to Ec cells and lessens toxicity to At cells. The reverse is also true, such that EcYoeB with the AtYoeB helix sequence is less toxic to Ec and gains toxicity to At cultures. We suggest this helix sequence directs mRNA sequence-specific degradation, which varies among proteobacterial classes, and thus controls growth inhibition and YoeB toxicity.

Diet differentially regulates enterochromaffin cell serotonin content, density and nutrient sensitivity in the mouse small and large intestine.

Enterochromaffin (EC) cells are specialized enteroendocrine cells lining the gastrointestinal (GI) tract and the source of almost all serotonin (5-hydroxytryptamine; 5-HT) in the body. Gut-derived 5-HT has a plethora of physiological roles, including regulation of gastrointestinal motility, and has been implicated as a driver of obesity and metabolic disease. This is due to 5-HT influencing key metabolic processes, such as hepatic gluconeogenesis, adipose tissue lipolysis and hindering thermogenic capacity. Increased circulating 5-HT occurs in humans with obesity and type 2 diabetes. However, despite the known metabolic roles of gut-derived 5-HT, the mechanisms underlying the cellular-level change in EC cells under obesogenic conditions remains unknown. We use a mouse model of diet-induced obesity (DIO) to identify the regional changes that occur in primary EC cells from the duodenum and colon. Transcriptional changes in the nutrient sensing profile of primary EC cells were assessed, and responses to nutrient stimuli in culture were determined by 5-HT ELISA. We find that obesogenic conditions affect EC cells in a region-dependent manner. Duodenal EC cells from DIO mice have impaired sugar sensing even in the presence of increased 5-HT content per cell, while colonic EC cell numbers are significantly increased, but have unaltered nutrient sensing capacity. Our findings from this study add novel insights into the mechanisms by which functional changes to EC cells occur at a cellular level, which may contribute to the altered circulating 5-HT seen with obesity and metabolic disease, and associated gastrointestinal disorders.

Dietary Proteins Regulate Serotonin Biosynthesis and Catabolism by Specific Gut Microbes.

More than 90% of serotonin is produced in the intestine. Previous studies have shown that different protein diets significantly affect serum serotonin levels. Here, the colonic microbiota and intestinal serotonin were measured to elaborate how protein diets affect serotonin production in a mouse model. The emulsion-type sausage protein and cooked pork protein diets increased the mRNA levels of tryptophan hydroxylase 1 (Tph1) and monoamine oxidase A (Maoa) and serotonin level as well but reduced the number of enterochromaffin cells. However, the soy protein diet increased the number of enterochromaffin cells and Tph1 mRNA level but decreased the Maoa mRNA level and the serotonin content. Specific gut microbes that responded to dietary changes and affected the content of short-chain fatty acids were significantly related to serotonin-associated biomarkers. These results suggest that dietary proteins may regulate serotonin biosynthesis and catabolism by altering specific gut microbes.

Endoscopic ampullectomy of a large neuroendocrine tumor using underwater EMR technique.

Neuroendocrine tumors (NETs) arise from the enterochromaffin cells derived from the endoderm.1,2 GI NETs are a group of well-differentiated tumors, most commonly involving the appendix. NETs of the ampulla of Vater are extremely rare; thus, the natural history of these tumors is not clear. Rarely, they can have distant metastases.2-4 The standard of care has been complete surgical resection, such as pancreaticoduodenectomy or local surgical excision of the tumor, which has a high morbidity. Hence, endoscopic resection modalities such as endoscopic ampullectomy are increasingly being implemented.