Serotonin receptor 2B induces visceral hyperalgesia in rat model and patients with diarrhea-predominant irritable bowel syndrome.

BACKGROUND: Serotonin receptor 2B (5-HT2B receptor) plays a critical role in many chronic pain conditions. The possible involvement of the 5-HT2B receptor in the altered gut sensation of irritable bowel syndrome with diarrhea (IBS-D) was investigated in the present study. AIM: To investigate the possible involvement of 5-HT2B receptor in the altered gut sensation in rat model and patients with IBS-D. METHODS: Rectosigmoid biopsies were collected from 18 patients with IBS-D and 10 patients with irritable bowel syndrome with constipation who fulfilled the Rome IV criteria and 15 healthy controls. The expression level of the 5-HT2B receptor in colon tissue was measured using an enzyme-linked immunosorbent assay and correlated with abdominal pain scores. The IBS-D rat model was induced by intracolonic instillation of acetic acid and wrap restraint. Alterations in visceral sensitivity and 5-HT2B receptor and transient receptor potential vanilloid type 1 (TRPV1) expression were examined following 5-HT2B receptor antagonist administration. Changes in visceral sensitivity after administration of the TRPV1 antagonist were recorded. RESULTS: Here, we observed greater expression of the 5-HT2B receptor in the colonic mucosa of patients with IBS-D than in that of controls, which was correlated with abdominal pain scores. Intracolonic instillation of acetic acid and wrap restraint induced obvious chronic visceral hypersensitivity and increased fecal weight and fecal water content. Exogenous 5-HT2B receptor agonist administration increased visceral hypersensitivity, which was alleviated by successive administration of a TRPV1 antagonist. IBS-D rats receiving the 5-HT2B receptor antagonist exhibited inhibited visceral hyperalgesia.Moreover, the percentage of 5-HT2B receptor-immunoreactive (IR) cells surrounded by TRPV1-positive cells (5-HT2B receptor I+) and total 5-HT2B receptor IR cells (5-HT2B receptor IT) in IBS-D rats was significantly reduced by the administration of a 5-HT2B receptor antagonist. CONCLUSION: Our finding that increased expression of the 5-HT2B receptor contributes to visceral hyperalgesia by inducing TRPV1 expression in IBS-D patients provides important insights into the potential mechanisms underlying IBS-D-associated visceral hyperalgesia.

NHE3 inhibitor tenapanor maintains intestinal barrier function, decreases visceral hypersensitivity, and attenuates TRPV1 signaling in colonic sensory neurons.

The pathogenesis of irritable bowel syndrome (IBS) is multifactorial, characterized in part by increased intestinal permeability, and visceral hypersensitivity. Increased permeability is associated with IBS severity and abdominal pain. Tenapanor is FDA-approved for the treatment of IBS with constipation (IBS-C) and has demonstrated improvements in bowel motility and a reduction in IBS-related pain; however, the mechanism by which tenapanor mediates these functions remains unclear. Here, the effects of tenapanor on colonic pain signaling and intestinal permeability were assessed through behavioral, electrophysiological, and cell culture experiments. Intestinal motility studies in rats and humans demonstrated that tenapanor increased luminal sodium and water retention and gastrointestinal transit versus placebo. A significantly reduced visceral motor reflex (VMR) to colonic distension was observed with tenapanor treatment versus vehicle in two rat models of visceral hypersensitivity (neonatal acetic acid sensitization and partial restraint stress; both P < 0.05), returning VMR responses to that of nonsensitized controls. Whole cell voltage patch-clamp recordings of retrogradely labeled colonic dorsal root ganglia (DRG) neurons from sensitized rats found that tenapanor significantly reduced DRG neuron hyperexcitability to capsaicin versus vehicle (P < 0.05), an effect not mediated by epithelial cell secretions. Tenapanor also attenuated increases in intestinal permeability in human colon monolayer cultures caused by incubation with proinflammatory cytokines (P < 0.001) or fecal supernatants from patients with IBS-C (P < 0.005). These results support a model in which tenapanor reduces IBS-related pain by strengthening the intestinal barrier, thereby decreasing permeability to macromolecules and antigens and reducing DRG-mediated pain signaling.NEW & NOTEWORTHY A series of nonclinical experiments support the theory that tenapanor inhibits IBS-C-related pain by strengthening the intestinal barrier. Tenapanor treatment reduced visceral motor responses to nonsensitized levels in two rat models of hypersensitivity and reduced responses to capsaicin in sensitized colonic nociceptive dorsal root ganglia neurons. Intestinal permeability experiments in human colon monolayer cultures found that tenapanor attenuates increases in permeability induced by either inflammatory cytokines or fecal supernatants from patients with IBS-C.

Mini-review: Enteric glial cell reactions to inflammation and potential therapeutic implications for GI diseases, motility disorders, and abdominal pain.

Enteric glial cells are emerging as critical players in the regulation of intestinal motility, secretion, epithelial barrier function, and gut homeostasis in health and disease. Enteric glia react to intestinal inflammation by converting to a 'reactive glial phenotype' and enteric gliosis, contributing to neuroinflammation, enteric neuropathy, bowel motor dysfunction and dysmotility, diarrhea or constipation, 'leaky gut', and visceral pain. The focus of the minireview is on the impact of inflammation on enteric glia reactivity in response to diverse insults such as intestinal surgery, ischemia, infections (C. difficile infection, HIV-Tat-induced diarrhea, endotoxemia and paralytic ileus), GI diseases (inflammatory bowel diseases, diverticular disease, necrotizing enterocolitis, colorectal cancer) and functional GI disorders (postoperative ileus, chronic intestinal pseudo-obstruction, constipation, irritable bowel syndrome). Significant progress has been made in recent years on molecular pathogenic mechanisms of glial reactivity and enteric gliosis, resulting in enteric neuropathy, disruption of motility, diarrhea, visceral hypersensitivity and abdominal pain. There is a growing number of glial molecular targets with therapeutic implications that includes receptors for interleukin-1 (IL-1R), purines (P2X2R, A2BR), PPARα, lysophosphatidic acid (LPAR1), Toll-like receptor 4 (TLR4R), estrogen-ß receptor (ERß) adrenergic α-2 (α-2R) and endothelin B (ETBR), connexin-43 / Colony-stimulating factor 1 signaling (Cx43/CSF1) and the S100ß/RAGE signaling pathway. These exciting new developments are the subject of the minireview. Some of the findings in pre-clinical models may be translatable to humans, raising the possibility of designing future clinical trials to test therapeutic application(s). Overall, research on enteric glia has resulted in significant advances in our understanding of GI pathophysiology.

Catechol-O-Methyltransferase Loss Drives Cell-Specific Nociceptive Signaling via the Enteric Catechol-O-Methyltransferase/microRNA-155/Tumor Necrosis Factor α Axis.

BACKGROUND & AIMS: The etiology of abdominal pain in postinfectious, diarrhea-predominant irritable bowel syndrome (PI-IBS-D) is unknown, and few treatment options exist. Catechol-O-methyltransferase (COMT), an enzyme that inactivates and degrades biologically active catecholamines, plays an important role in numerous physiologic processes, including modulation of pain perception. Our objective was to determine the mechanism(s) of how decreased colonic COMT in PI-IBS-D patients contributes to the chronic abdominal pain phenotype after enteric infections. METHODS: Colon neurons, epithelial cells, and macrophages were procured with laser capture microdissection from PI-IBS-D patients to evaluate cell-specific colonic COMT, microRNA-155 (miR-155), and tumor necrosis factor (TNF) α expression levels compared to recovered patients (infection cleared: did not develop PI-IBS-D) and control individuals. COMT-/-, colon-specific COMT-/-, and miR-155-/- mice and human colonoids were used to model phenotypic expression of COMT in PI-IBS-D patients and to investigate signaling pathways linking abdominal pain. Citrobacter rodentium and trinitrobenzene sulfonic acid animal models were used to model postinflammatory changes seen in PI-IBS-D patients. RESULTS: Colonic COMT levels were significantly decreased and correlated with increased visual analog scale abdominal pain ratings in PI-IBS-D patients compared to recovered patients and control individuals. Colonic miR-155 and TNF-α were increased in PI-IBS-D patients with diminished colonic COMT. COMT-/- mice had significantly increased expression of miR-155 and TNF-α in both colon tissues and dorsal root ganglia. Introduction of cV1q antibody (anti-TNF-α) into mice reversed visceral hypersensitivity after C rodentium and trinitrobenzene sulfonic acid. CONCLUSIONS: Decreased colonic COMT in PI-IBS-D patients drives abdominal pain phenotypes via the COMT/miR-155/TNF-α axis. These important findings will allow new treatment paradigms and more targeted and personalized medicine approaches for gastrointestinal disorders after enteric infections.

[Assessment of the state of the small intestine microbiota in children on a long-term dairy-free diet].

An overview of recent outcomes of studies indicates an imbalance in the diet of children. Quantitative and qualitative malnutrition of children is the basis of a number of childhood diseases. The aim of the research was to study the prevalence of small intestine bacterial overgrowth syndrome (SIBO) in children on a long-term dairy-free diet. Material and methods. 40 children aged 7-11 years following a long-term dairy-free diet (average 3 years and 5 months, from 0.5 to 6.3 years) were examined (main group). 30 children who did not follow restrictive diets were consisted control group. In all children, SIBO was determined using a hydrogen breath test with a load of lactulose using a digital analyzer of exhaled hydrogen. Results. The proportion of children with intolerance to dairy products was 32.5%: 10.0% with allergy to cow's milk proteins, and 22.5% with lactose intolerance. 27.5% children followed a dairy-free diet according to an unjustified prescription by physician. 30.0% of children did not consume dairy products because of their unwillingness. 10.0% of children did not consume dairy products due to the unwillingness of their parents. An imbalance in the microbiota of the small intestine during the hydrogen breath test with lactulose loading was detected in 55.0% of children following a long-term dairy-free diet. 22.5% of children complained of recurrent abdominal pain, diarrhea was determined in 10.0%, constipation - in 7.5%, nausea - in 10.0%. In the control group, the SIBO during the hydrogen breath test with lactulose loading was found in 20.0%. Periodic abdominal pain was determined in 10.0%, nausea - in 6.7%, diarrhea - in 10.0%, constipation - in 3.3% children. Conclusion. Thus, among children of primary school age who follow a long-term dairyfree diet, SIBO is significantly more often recorded relative to children who are on a traditional type of diet.

Human milk oligosaccharides alleviate stress-induced visceral hypersensitivity and associated microbiota dysbiosis.

Pain-related functional gastrointestinal disorders (FGIDs) are characterized by visceral hypersensitivity (VHS) associated with alterations in the microbiota-gut-brain axis. Since human milk oligosaccharides (HMOs) modulate microbiota, gut and brain, we investigated whether HMOs impact VHS, and explored the role of gut microbiota. To induce VHS, C57BL/6JRj mice received hourly water avoidance stress (WAS) sessions for 10 d, or antibiotics (ATB) for 12 d. Challenged and unchallenged (Sham) animals were fed AIN93M diet (Cont) or AIN93M containing 1% of a 6-HMO mix (HMO6). VHS was assessed by monitoring the visceromotor response to colorectal distension. Fecal microbiome was analyzed by shotgun metagenomics. The effect of HMO6 sub-blends on VHS and nociceptive pathways was further tested using the WAS model. In mice fed Cont, WAS and ATB increased the visceromotor response to distension. HMO6 decreased WAS-mediated electromyographic rise at most distension volumes and overall Area Under Curve (AUC=6.12±0.50 in WAS/HMO6 vs. 9.46±0.50 in WAS/Cont; P<.0001). In contrast, VHS in ATB animals was not improved by HMO6. In WAS, HMO6 promoted most microbiota taxa and several functional pathways associated with low VHS and decreased those associated with high VHS. Among the sub-blends, 2'FL+DFL and LNT+6'SL reduced visceromotor response close to Sham/Cont values and modulated serotoninergic and CGRPα-related pathways. This research further substantiates the capacity of HMOs to modulate the microbiota-gut-brain communication and identifies mitigation of abdominal pain as a new HMO benefit. Ultimately, our findings suggest the value of specific HMO blends to alleviate pain associated FGIDs such as infantile colic or Irritable Bowel Syndrome.

Type 2 and type 17 effector cells are increased in the duodenal mucosa but not peripheral blood of patients with functional dyspepsia.

Background: Functional dyspepsia is characterised by chronic symptoms of post-prandial distress or epigastric pain not associated with defined structural pathology. Increased peripheral gut-homing T cells have been previously identified in patients. To date, it is unknown if these T cells were antigen-experienced, or if a specific phenotype was associated with FD. Objective: This study aimed to characterise T cell populations in the blood and duodenal mucosa of FD patients that may be implicated in disease pathophysiology. Methods: We identified duodenal T cell populations from 23 controls and 49 Rome III FD patients by flow cytometry using a surface marker antibody panel. We also analysed T cell populations in peripheral blood from 37 controls and 61 patients. Where available, we examined the number of duodenal eosinophils in patients and controls. Results: There was a shift in the duodenal T helper cell balance in FD patients compared to controls. For example, patients had increased duodenal mucosal Th2 populations in the effector (13.03 ± 16.11, 19.84 ± 15.51, p=0.038), central memory (23.75 ± 18.97, 37.52 ± 17.51, p=0.007) and effector memory (9.80±10.50 vs 20.53±14.15, p=0.001) populations. Th17 populations were also increased in the effector (31.74±24.73 vs 45.57±23.75, p=0.03) and effector memory (11.95±8.42 vs 18.44±15.63, p=0.027) subsets. Peripheral T cell populations were unchanged between FD and control. Conclusion: Our findings identify an association between lymphocyte populations and FD, specifically a Th2 and Th17 signature in the duodenal mucosa. The presence of effector and memory cells suggest that the microinflammation in FD is antigen driven.

Psychological Stresses in Children Trigger Cytokine- and Kynurenine Metabolite-Mediated Abdominal Pain and Proinflammatory Changes.

Recurrent abdominal pain (RAP) is a common medically unexplained symptom among children worldwide. However, the biological mechanisms behind the development of functional and behavioral symptoms and changes in blood markers have not been well explored. This study aimed to assess changes in the concentrations of inflammatory markers, including cytokines and tryptophan catabolites, in the serum of children with RAP compared to those with subclinical infections. Children with RAP but without organic diseases were included, and those with asymptomatic intestinal parasitic infections were used as a subclinical infection cohort. Blood samples were collected and used to measure the cytokine profile using Multiplex Immunoassay and tryptophan catabolites using high performance liquid chromatography. Children with RAP showed significantly higher concentrations of serum tumor necrotic factor-α, p<0.05, but lower concentrations of IL-10, p<0.001, IL-6, p<0.001 and brain-derived neurotrophic factors (BDNF) p<0.01. In addition, a significant increase in the metabolite of the kynurenine pathway, 3-hydroxyanthranilic acid (3-HAA) p<0.01, a significant decrease in the concentrations of anthranilic acid (AA) p<0.001, together with an increased ratio of serum 3-HAA to AA (3-HAA/AA) p<0.001, was found in this cohort. These findings indicate the significant activation of the immune system and presence of inflammation in children with RAP than those with subclinical parasitic infections. Moreover, children with RAP tested with the Strengths and Difficulties Questionnaire (SDQ), displayed high psychological problems though these SDQ scores were not statistically associated with measured cytokines and kynurenine metabolites. We however could hypothesize that the pro-inflammatory state together with concomitant low concentrations of BDNF in those children with RAP could play a role in psychological stress and experiencing medically unexplained symptoms.

A putative anti-inflammatory role for TRPM8 in irritable bowel syndrome-An exploratory study.

BACKGROUND: Chronic and recurring pain is a characteristic symptom in irritable bowel syndrome (IBS). Altered signaling between immune cells and sensory neurons within the gut may promote generation of pain symptoms. As transient receptor potential melastatin 8 (TRPM8) agonists, such as L-menthol in peppermint oil, have shown to attenuate IBS pain symptoms, we began investigating potential molecular mechanisms. METHODS: Colonic biopsy tissues were collected from patients with IBS and controls, in two separate cohorts. Immunohistochemistry was performed to identify TRPM8 localization. Quantitative PCR was performed to measure mucosal mRNA levels of TRPM8. In addition, functional experiments with the TRPM8 agonist icilin were performed ex vivo to examine cytokine release from biopsies. Daily diaries were collected to ascertain pain symptoms. RESULTS: In biopsy tissue from IBS patients, we showed that TRPM8 immunoreactivity is colocalized with immune cells predominantly of the dendritic cell lineage, in close approximation to nerve endings, and TRPM8 protein and mRNA expression was increased in IBS patients compared to controls (p < 0.001). TRPM8 mRNA expression showed a significant positive association with abdominal pain scores (p = 0.015). Treatment of IBS patient biopsies with icilin reduced release of inflammatory cytokines IL-1ß, IL-6, and TNF-α (p < 0.05). CONCLUSIONS AND INFERENCES: These data indicate TRPM8 may have important anti-inflammatory properties and by this virtue can impact neuro-immune disease mechanisms in IBS.

Relationships between disaccharidase deficiencies, duodenal inflammation and symptom profile in children with abdominal pain.

Abdominal pain has been associated with disaccharidase deficiencies. While relationships with individual symptoms have been assessed, relationships between disaccharidase deficiencies and symptom complexes or inflammation have not been evaluated in this group. The primary aims of the current study were to assess relationships between disaccharidase deficiency and symptoms or symptom complexes and duodenal inflammation, respectively. Patients with abdominal pain who underwent endoscopy with evaluation of disaccharidase activity levels were identified. After excluding all patients with inflammatory bowel disease, celiac disease, H. pylori, or gross endoscopic lesions, patients were evaluated for disaccharidase deficiency frequency. Disaccharidase were compared between patients with and without histologic duodenitis. Lastly, relationships between individual gastrointestinal symptoms or symptom complexes were evaluated. Lactase deficiency was found in 34.3% of patients and disaccharidase pan-deficiency in 7.6%. No individual symptoms or symptom complexes predicted disaccharidase deficiency. While duodenitis was not associated with disaccharidase deficiency, it was only present in 5.9% of patients. Disaccharidase deficiency, particularly lactase deficiency, is common in youth with abdominal pain and multiple deficiencies are not uncommon. Disaccharidase deficiency cannot be predicted by symptoms in this population. Further studies are needed to assess the clinical significance of disaccharidase deficiency.

Gastrointestinal manifestations of COVID-19: results from a European centre.

BACKGROUND: Infection due to severe acute respiratory syndrome coronavirus 2 is typically associated with a respiratory syndrome, but gastrointestinal symptoms have been described in early reports from China. However, data from European centres are scarce. OBJECTIVES: We aimed to characterise the gastrointestinal manifestations of patients with coronavirus disease 2019 (COVID-19) and their disease course. METHODS: Patients admitted at our centre between March and April 2020 with diagnosis of COVID-19 were included. Asymptomatic patients or those without symptom information were excluded. Clinical features, laboratory data and disease severity (mechanical ventilation, intensive care admission or death) were analysed. RESULTS: Two-hundred one patients were included (median age 71 years; 56.2% male). Digestive symptoms were reported by 60 (29.9%) patients during the disease course, being part of the disease presentation in 34 (16.9%). The most frequent were diarrhoea in 36 patients (17.9%). Patients with gastrointestinal symptoms were younger (P = 0.032), had higher haemoglobin levels (P = 0.002) and lower C-reactive protein (P = 0.045) and potassium levels (P = 0.004). Patients with digestive symptoms had less severe disease (28.3 vs. 44.0%; P = 0.038). Regarding liver damage, aspartate aminotransferase (AST) was elevated in 65.2% of patients and alanine aminotransferase (ALT) in 62.7%, but these patients did not present a more severe disease (elevated AST P = 0.062; elevated ALT P = 0.276). CONCLUSION: A significant portion of COVID-19 patients have digestive symptoms, mostly at presentation. This should be taken into account in order to keep a high level of suspicion to reach an early diagnosis and setup infection control measures to control the transmission rate. This subgroup of patients appears to have a less severe disease course.

Calcium channels blockers toxins attenuate abdominal hyperalgesia and inflammatory response associated with the cerulein-induced acute pancreatitis in rats.

Agents that modulate the activity of high-voltage gated calcium channels (HVCCs) exhibit experimentally and clinically significant effect by relieving visceral pain. Among these agents, the toxins Phα1ß and ω-conotoxin MVIIA effectively reduce chronic pain in rodent models. The molecular mechanisms underlying the chronic pain associated with acute pancreatitis (AP) are poorly understood. Hypercalcemia is a risk factor; the role of cytosolic calcium is considered to be a modulator of pancreatitis. Blockade of Ca2+ signals may be useful as a prophylactic treatment of pancreatitis. We explored the pathophysiological roles of three peptide toxins: Phα1ß and its recombinant form CTK 01512-2-blockers of TRPA1 receptor and HVCCs and ω-conotoxin MVIIA, a specific blocker of N-type calcium channels in cerulein-induced AP. Cerulein injection elicits AP in rats, evidenced by an increase in hyperalgesic pain, inflammatory infiltration, amylase and lipase secretion, and reactive oxygen species, TNF-α, and p65 NF-κB levels. These effects of cerulein-induced AP were abolished by Phα1ß and its recombinant form CTK 01512-2, whereas ω-conotoxin MVIIA had no effect on the induced increase in pancreatic enzyme secretion. Our results demonstrate that Phα1ß and CTK 01512-2 toxins-antagonists of HVCCs and TRPA1 receptor presented an effective response profile, in the control of nociception and inflammatory process in the AP model in rats, without causing changes in spontaneous locomotion of the rats.

Upregulation of spinal ASIC1 by miR-485 mediates enterodynia in adult offspring rats with prenatal maternal stress.

AIMS: Irritable bowel syndrome (IBS) is a common functional gastrointestinal disease characterized by abdominal pain. Our recent study has shown that the acid-sensitive ion channel 1 (ASIC1) in dorsal root ganglion (DRG) is involved in stomachache of adult offspring rats subjected with prenatal maternal stress (PMS). MiR-485 is predicted to target the expression of ASIC1. The aim of the present study was designed to determine whether miR-485/ASIC1 signaling participates in enterodynia in the spinal dorsal horn of adult offspring rats with PMS. METHODS: Enterodynia was measured by colorectal distension (CRD). Western blotting, qPCR, and in situ hybridization were performed to detect the expression of ASICs and related miRNAs. Spinal synaptic transmission was also recorded by patch clamping. RESULTS: PMS offspring rats showed that spinal ASIC1 protein expression and synaptic transmission were significantly enhanced. Administration of ASICs antagonist amiloride suppressed the synaptic transmission and enterodynia. Besides, PMS induced a significant reduction in the expression of miR-485. Upregulating the expression markedly attenuated enterodynia, reversed the increase in ASIC1 protein and synaptic transmission. Furthermore, ASIC1 and miR-485 were co-expressed in NeuN-positive spinal dorsal horn neurons. CONCLUSIONS: Overall, these data suggested that miR-485 participated in enterodynia in PMS offspring, which is likely mediated by the enhanced ASIC1 activities.

Mast Cell Regulation and Irritable Bowel Syndrome: Effects of Food Components with Potential Nutraceutical Use.

Mast cells are key actors in inflammatory reactions. Upon activation, they release histamine, heparin and nerve growth factor, among many other mediators that modulate immune response and neuron sensitization. One important feature of mast cells is that their population is usually increased in animal models and biopsies from patients with irritable bowel syndrome (IBS). Therefore, mast cells and mast cell mediators are regarded as key components in IBS pathophysiology. IBS is a common functional gastrointestinal disorder affecting the quality of life of up to 20% of the population worldwide. It is characterized by abdominal pain and altered bowel habits, with heterogeneous phenotypes ranging from constipation to diarrhea, with a mixed subtype and even an unclassified form. Nutrient intake is one of the triggering factors of IBS. In this respect, certain components of the daily food, such as fatty acids, amino acids or plant-derived substances like flavonoids, have been described to modulate mast cells' activity. In this review, we will focus on the effect of these molecules, either stimulatory or inhibitory, on mast cell degranulation, looking for a nutraceutical capable of decreasing IBS symptoms.

Peripheral Corticotropin-Releasing Factor Triggers Jejunal Mast Cell Activation and Abdominal Pain in Patients With Diarrhea-Predominant Irritable Bowel Syndrome.

INTRODUCTION: To determine the effect of peripheral CRF on intestinal barrier function in diarrhea-predominant IBS (IBS-D). Irritable bowel syndrome (IBS) pathophysiology has been linked to life stress, epithelial barrier dysfunction, and mast cell activation. Corticotropin-releasing factor (CRF) is a major mediator of stress responses in the gastrointestinal tract, yet its role on IBS mucosal function remains largely unknown. METHODS: Intestinal response to sequential i.v. 5-mL saline solution (placebo) and CRF (100 µg) was evaluated in 21 IBS-D and 17 healthy subjects (HSs). A 20-cm jejunal segment was perfused with an isosmotic solution and effluents collected at baseline, 30 minutes after placebo, and 60 minutes after CRF. We measured water flux, albumin output, tryptase release, stress hormones, cardiovascular and psychological responses, and abdominal pain. A jejunal biopsy was obtained for CRF receptor expression assessment. RESULTS: Water flux did not change after placebo in IBS-D and HS but significantly increased after CRF in IBS-D (P = 0.007). Basal luminal output of albumin was higher in IBS-D and increased further after CRF in IBS-D (P = 0.042). Basal jejunal tryptase release was higher in IBS-D, and CRF significantly increased it in both groups (P = 0.004), the response being higher in IBS-D than in HS (P = 0.0023). Abdominal pain worsened only in IBS-D after CRF and correlated with jejunal tryptase release, water flux, and albumin output. IBS-D displayed jejunal up-regulation of CRF2 and down-regulation of CRF1 compared with HS. DISCUSSION: Stress via CRF-driven mast cell activation seems to be relevant in the pathophysiology of IBS-D.

Clinical characteristics of coronavirus disease (COVID-19) patients with gastrointestinal symptoms: A report of 164 cases.

Objective: To explore the clinical characteristics of Coronavirus Disease (COVID-19) patients with gastrointestinal symptoms. Methods: The clinical data of 164 COVID-19 patients with gastrointestinal symptoms were extracted and analysed retrospectively. Results: In total, 505 COVID-19 patients were divided into two groups: those with gastrointestinal symptoms (G group) and those without gastrointestinal symptoms (NG group). Common gastrointestinal symptoms included inappetence, diarrhoea, nausea, abdominal pain, and vomiting. Significantly higher proportions of patients with fever, dizziness, myalgia, and fatigue were noted in group G than in group NG. Compared with patients without fever, there was a significant difference between G group and NG group in moderate fever or above, while there was no significant difference between the two groups in low fever. The laboratory results showed that patients in the G group had significantly higher C-reactive protein, lactate dehydrogenase, and α-hydroxybutyrate dehydrogenase levels than those in the NG group. Moreover, the proportion of patients with severe pneumonia was significantly higher in the G group than in the NG group. Conclusion: In Wuhan, the proportion of COVID-19 patients who experience gastrointestinal symptoms is relatively high. Patients who experience gastrointestinal symptoms are more likely to suffer from severe pneumonia, which may help clinicians identify patients at high risk of COVID-19 and thus reduce the incidence of this condition.

Teenager With Abdominal Pain and Decreased Appetite.

A 16-year-old girl presented to her primary care physician with a one-month history of decreased appetite and abdominal pain. She had normal bowel movements and no vomiting, but her periumbilical pain limited her ability to finish most meals. She had gradual weight loss over the previous 2 years, and during the previous 4 years, she intermittently received counseling for depression after the loss of her mother. Her initial physical examination and laboratory evaluation were unremarkable. She was referred to a nutritionist, adolescent medicine, and pediatric gastroenterology. Her presentation evolved over time, which ultimately led to a definitive diagnosis.

microRNA-495 reduces visceral sensitivity in mice with diarrhea-predominant irritable bowel syndrome through suppression of the PI3K/AKT signaling pathway via PKIB.

Diarrhea-predominant irritable bowel syndrome (IBS-D) is one of the most common gastrointestinal disorders in the world, lacking effective therapies. The crucial roles of microRNAs (miRNAs) in IBS-D have attracted increasing attention. The aim of this study is to investigate the effects of miR-495 on the visceral sensitivity of the IBS-D through the PI3K/AKT signaling pathway by targeting PKIB. Microarray data analysis was employed to screen the differentially expressed genes related to IBS-D and regulatory miRNAs. Then, mice were perfused with acetic acid into the rectum to establish the IBS-D model. Next, PKIB expression was measured in IBS-D mice. Additionally, model mice were injected with a series of adenovirus vector to investigate the influence of miR-495 on visceral sensitivity and rectal function in IBS-D mice with the involvement of PKIB and PI3K/AKT signaling pathway. The IBS-D mouse model was successfully established. PKIB was the target gene of miR-495, and highly expressed in mice with IBS-D. Silencing PKIB reduced visceral sensitivity in mice with IBS-D, and overexpression of miR-495 decreased visceral sensitivity in mice with IBS-D by inhibiting PKIB. Moreover, miR-495 upregulation inhibited PI3K/AKT signaling pathway through downregulating PKIB. To sum up, this study reveals that miR-495 upregulation can reduce visceral sensitivity in IBS-D via inhibition of PI3K/AKT signaling pathway by targeting PKIB. It suggests that miR-495 presents a potential target for IBS-D therapy.

Prostaglandin E2, Produced by Mast Cells in Colon Tissues From Patients With Irritable Bowel Syndrome, Contributes to Visceral Hypersensitivity in Mice.

BACKGROUND AND AIMS: Visceral hypersensitivity is common in patients with irritable bowel syndrome (IBS). We investigated whether inflammatory molecules, such as histamine and proteases, activate prostaglandin-endoperoxide synthase 2 (also called COX2) to increase the synthesis of prostaglandin E2 (PGE2) by mast cells, which activates the receptor PTGER2 (also called EP2) in the dorsal root ganglia to promote visceral hypersensitivity. METHODS: We used an enzyme-linked immunosorbent assay to measure levels of spontaneous release of molecules from mast cells in colonic mucosa from patients with IBS with diarrhea (IBS-D; 18 women and 5 men; aged 28-60 years), healthy individuals (controls, n = 24), mice, and rats. We measured visceromotor responses to colorectal distension in rodents after intracolonic administration of colon biopsy supernatants, histamine, PGE2, a small interfering RNA against EP2, or an agonist of F2R like trypsin receptor 1 (F2RL1, also called protease-activated receptor 2 [PAR2]). We investigated the role of COX2, produced by mast cells, in mediation of visceral hypersensitivity using mice with the Y385F substitution in Ptgs2 (Ptgs2Y385F mice), mast cell-deficient (W/WV) mice, and W/WV mice given injections of mast cells derived from wild-type or Ptgs2Y385F mice. RESULTS: Colon biopsies from patients with IBS-D had increased levels of PGE2, based on enzyme-linked immunosorbent assay, and COX2 messenger RNA and protein, compared with control biopsies. Immunohistochemistry showed that most of the COX2 was in mast cells. Intracolonic infusions of rats with IBS-D biopsy supernatants generated a 3- to 4-fold increase in visceromotor responses to colorectal distension; this was associated with significant increases in PGE2, histamine, and tryptase in the colonic mucosa. These increases were prevented by a mast cell stabilizer, COX2 inhibitor, or knockdown of EP2. Intracolonic administration of supernatants from biopsies of patients with IBS-D failed to induce visceral hypersensitivity or increase the level of PGE2 in W/WV and Ptgs2Y385Fmice. Reconstitution of mast cells in W/WV mice restored the visceral hypersensitivity response. CONCLUSIONS: Abnormal synthesis of PGE2 by colonic mast cells appears to induce visceral hypersensitivity in patients with IBS-D.