Development Of Visceral Hypersensitivity Research Articles

ZBTB20 mediates stress-induced visceral hypersensitivity via activating the NF-κB/transient receptor potential channel pathway.

Psychological stress is a major trigger for visceral hypersensitivity (VH) in irritable bowel syndrome. The zinc finger protein ZBTB20 (ZBTB20) is implicated in somatic nociception via modulating transient receptor potential (TRP) channels, but its role in the development of VH is unclear. This study aimed to investigate the role of ZBTB20/TRP channel axis in stress-induced VH. Rats were subjected to water avoidance stress (WAS) for 10 consecutive days. Small interfering RNA (siRNA) targeting ZBTB20 was intrathecally administered. Inhibitors of TRP channels, stress hormone receptors, and nuclear factor kappa-B (NF-κB) were administered. Visceromotor response to colorectal distension was recorded. Dorsal root ganglia (DRGs) were dissected for Western blot, coimmunoprecipitation, and chromatin immunoprecipitation. The DRG-derived neuron cell line was applied for specific research. WAS-induced VH was suppressed by the inhibitor of TRPV1, TRPA1, or TRPM8, with enhanced expression of these channels in L6-S2 DRGs. The inhibitor of glucocorticoid receptor or β2-adrenergic receptor counteracted WAS-induced VH and TRP channel expression. Concurrently, WAS-induced stress hormone-dependent ZBTB20 expression and NF-κB activation in DRGs. Intrathecally injected ZBTB20 siRNA or an NF-κB inhibitor repressed WAS-caused effect. In cultured DRG-derived neurons, stress hormones promoted nuclear translocation of ZBTB20, which preceded p65 nuclear translocation. And, ZBTB20 siRNA suppressed stress hormone-caused NF-κB activation. Finally, WAS enhanced p65 binding to the promoter of TRPV1, TRPA1, or TRPM8 in rat DRGs. ZBTB20 mediates stress-induced VH via activating NF-κB/TRP channel pathway in nociceptive sensory neurons.

Abdominal pain syndrome in patients with irritable bowel syndrome: features of selection of therapy

Irritable bowel syndrome (IBS) is an important social problem, since it is often diagnosed in people of young working age, significantly affects the quality of life of patients and causes economic damage to society. IBS is a chronic functional bowel disease, the main manifestation of which is pain combined with changes in bowel movements, frequency and character of stool. The mechanism of formation of abdominal pain syndrome is due to a disruption in the interaction along the brain-gut axis, which leads to changes in the regulation of intestinal motor function and the development of visceral hypersensitivity (VH). Abdominal pain as a manifestation of IBS is primarily associated with spasm of intestinal smooth muscles. The first-line drugs for pain relief are antispasmodics, which reduce the tone and contractility of intestinal smooth muscles, effectively coping with abdominal pain. The domestic pharmaceutical market is represented by different groups of muscle relaxants, among which calcium channel blockers are of particular relevance for patients with IBS. Representative of the latter is the drug Otilonium bromide, which is widely used throughout the world, is effective and safe, well tolerated and superior to placebo in reducing symptoms and preventing relapse of pain in patients with IBS. The effectiveness of otilonium bromide is due to a triple mechanism of action: blockade of calcium channels (relief of spasm), antagonism of tachykinone NK2 receptors (effect on HHV) and inhibition of acetylcholine muscarinic receptors (M3-ChR) (reduction of intestinal secretion). This article presents a short review of the literature on the causes and mechanism of development of pain in IBS, as well as the possibilities of its relief, primarily with the use of smooth muscle relaxants, namely otilonium bromide.

Mast cells in the paraventricular nucleus participate in visceral hypersensitivity induced by neonatal maternal separation

Early-life stress (ELS) is a high-risk factor for the development of chronic visceral pain in adulthood. Emerging evidence suggests that mast cells play a key role in the development of visceral hypersensitivity through interaction with neurons. The sensitization of corticotropin-releasing factor (CRF) neurons in the hypothalamic paraventricular nucleus (PVN) plays a pivotal role in the pathogenesis of visceral pain. However, the precise mechanism by which mast cells and CRF neurons interact in the PVN in the pathogenesis of visceral hypersensitivity remains elusive. In the present study, we used neonatal maternal separation (MS), an ELS model, and observed that neonatal MS induced visceral hypersensitivity and triggered PVN mast cell activation in adult rats, which was repressed by intra-PVN infusion of the mast cell stabilizer disodium cromoglycate (cromolyn). Wild-type (WT) mice but not mast cell-deficient KitW-sh/W-sh mice that had experienced neonatal MS exhibited chronic visceral hypersensitivity. MS was associated with an increase in the expression of proinflammatory mediators, the number of CRF+ cells and CRF protein in the PVN, which was prevented by intra-PVN infusion of cromolyn. Furthermore, we demonstrated that intra-PVN infusion of the mast degranulator compound 48/80 significantly induced mast cell activation, resulting in proinflammatory mediator release, CRF neuronal sensitization, and visceral hypersensitivity, which was suppressed by cromolyn. Overall, our findings demonstrated that neonatal MS induces the activation of PVN mast cells, which secrete numerous proinflammatory mediators that may participate in neighboring CRF neuronal activity, ultimately directly inducing visceral hypersensitivity in adulthood.

LncRNA XIST modulates 5-hydroxytrytophan-induced visceral hypersensitivity by epigenetic silencing of the SERT gene in mice with diarrhea-predominant IBS

Diarrhea-predominant irritable bowel syndrome (IBS-D) is a prevalent gastrointestinal disorder with a high incidence in children. The role of long non-coding RNAs (lncRNAs) in gastrointestinal diseases has been previously highlighted. Nevertheless, the underlying regulatory mechanism of lncRNA X inactivate-specific transcript (XIST) in IBS-D requires further studies. Thus, the present study was conducted with the main objective of elucidating the underlying mechanism of lncRNA XIST in visceral hypersensitivity in IBS-D. An in vivo mouse model of IBS-D was constructed via rectal perfusion of acetic acid. Next, in order to evaluate the effect of lncRNA XIST on the development of visceral hypersensitivity in IBS-D, different vector plasmids were injected into mice along with rectal mucosal epithelial cells, followed by the measurement of abdominal withdrawal reflex (AWR) score, counts of peristaltic wave, abdominal wall contraction and defecation particles. Furthermore, luciferase reporter assay, FISH, RIP and ChIP assays were conducted to determine the interactions between lncRNA XIST and SERT. Subsequently, MS-PCR was adopted to test the methylation level of SERT promoter. 5-hydroxytrytophan (HT) content in rectal tissues was detected using immunohistochemistry. The IBS-D mouse models presented with a high expression of lncRNA XIST along with low expression of SERT. LncRNA XIST was observed to recruit methylase DNMT1, DNMT3A and DNMT3B to promote SERT promoter methylation, reducing its expression. Restoration of lncRNA XIST resulted in increased AWR score, counts of peristaltic wave, abdominal wall contraction and defecation particles along with stimulated 5-HT expression and SERT methylation level, while downregulation of lncRNA XIST reversed these effects. In conclusion, the key findings from our study indicated that lncRNA XIST acts as a regulator in 5-HT-induced visceral hypersensitivity in mice with IBS-D, providing a new insight into the regulatory effect of lncRNA XIST and its epigenetic diagnostic and therapeutic properties in IBS-D.

GPER‐mediated, oestrogen‐dependent visceral hypersensitivity in stressed rats is associated with mast cell tryptase and histamine expression

Visceral hypersensitivity (VH) is common in irritable bowel syndrome (IBS), and female patients are more likely to seek healthcare services for IBS-related abdominal pain. Oestrogen has been reported to mediate pain modulation via its receptor, and mast cells are known to participate in the development of visceral hypersensitivity. Our previous studies showed that the G-protein-coupled oestrogen receptor (GPER, also known as GPR30) was expressed by mast cells in human colonic tissues and was associated with IBS type and severity of visceral pain. However, whether GPER is involved in oestrogen-dependent visceral hypersensitivity via mast cell degranulation is still unknown. Rats were subjected to wrap partial restraint stress to induce visceral hypersensitivity and were ovariectomized (OVX) to eliminate the effects of oestrogen on visceral hypersensitivity. OVX rats were treated with oestrogen, an oestrogen receptor α and β antagonist (ICI 182.780), a GPER antagonist (G15) or a GPER agonist (G1), to evaluate the effects of oestrogen via its receptor. The colorectal distention test was performed to assess visceral sensitivity. Immunofluorescence studies were performed to evaluate GPER and mast cell tryptase co-expression. Mast cell number with degranulation was detected by specific staining. Mast cell tryptase expression in rat colon was also investigated by Western blot and immunohistochemistry. Substance P and histamine expression were examined by ELISA. GPER was expressed by the majority of tryptase-positive mast cells in the colonic mucosa. Stressed rats showed increased visceral sensitivity, increased mast cell degranulation, mast cell tryptase expression, and increased colon histamine levels. Ovariectomy reduced stress-induced VH in female rats and decreased mast cell degranulation, mast cell tryptase expression, and histamine levels, whereas oestrogen replacement reversed these effects. In OVX rats, the GPER antagonist G15 counteracted the enhancing effects of oestrogen on stress-induced VH, mast cell degranulation, mast cell tryptase, and histamine expression, whereas VH was preserved after treatment with ICI 182.780. On the other hand, pretreatment with the selective GPER agonist G1 at doses between 1 and 20μg/kg significantly increased VH, mast cell tryptase, and histamine expression in OVX-stressed rats, mimicking the effects of oestrogen. GPER plays a pivotal role in the regulation of mast cell degranulation, mast cell tryptase expression, and histamine levels and contributes to the development of colonic hypersensitivity in a female rat model of IBS.

Ephrin-B2 signaling in the spinal cord as a player in post-inflammatory and stress-induced visceral hypersensitivity.

Ephrin-B2/EphB receptor signaling contributes to persistent pain states such as postinflammatory and neuropathic pain. Visceral hypersensitivity (VHS) is a major mechanism underlying abdominal pain in patients with irritable bowel syndrome (IBS) and inflammatory bowel diseases (IBD) in remission, but the underlying pathophysiology remains unclear. Here, we evaluated the spinal ephrin-B2/EphB pathway in VHS in 2 murine models of VHS, that is, postinflammatory TNBS colitis and maternal separation (MS). Wild-type (WT) mice and mice lacking ephrin-B2 in Nav 1.8 nociceptive neurons (cKO) were studied. VHS was induced by: 1. intracolonic instillation of TNBS or 2. water avoidance stress (WAS) in mice that underwent maternal separation (MS). VHS was assessed by quantifying the visceromotor response (VMRs) during colorectal distention. Colonic tissue and spinal cord were collected for histology, gene, and protein expression evaluation. In WT mice, but not cKO mice, TNBS induced VHS at day 14 after instillation, which returned to baseline perception from day 28 onwards. In MS WT mice, WAS induced VHS for up to 4weeks. In cKO however, visceral pain perception returned to basal level by week 4. The development of VHS in WT mice was associated with significant upregulation of spinal ephrin-B2 and EphB1 mRNA expression or protein levels in the TNBS model and upregulation of spinal ephrin-B2 protein in the MS model. No changes were observed in cKO mice. VHS was not associated with persistent intestinal inflammation. Overall, our data indicate that the ephrin-B2/EphB1 spinal signaling pathway is involved in VHS and may represent a novel therapeutic target.

Relationship between food allergies and composition of intestinal microbiota at irritable bowel syndrome

Currently, there is an increase in the number of patients with irritable bowel syndrome (IBS). However, to date, there is no single concept of the etiopathogenesis of functional disorders of the digestive tract. Initially, great attention was paid to disorders of motility and impaired regulatory interactions of the brain‑intestine as causes of irritable bowel syndrome, but in recent years the focus has shifted to subclinical inflammation in the colon mucosa and the development of visceral hypersensitivity. The reasons contributing to the formation of immune inflammation in the intestinal wall, include a violation of the composition of the intestinal microbiota, as well as food allergies and food intolerance. This article discusses the qualitative and quantitative changes in the intestinal microbiota in patients with irritable bowel syndrome if they have food allergies, as well as the effect of the composition of the intestinal microbiota on the clinical variant of irritable bowel syndrome. The study included 257 patients with IBS. At the first stage, an assessment was made of the history of food allergies, such as IBS, in accordance with the Bristol scale, as well as a microbiological study of feces. At the second stage, the evaluation of intestinal microbiota correction schemes was carried out in patients who had food allergies. The patients were divided into two equal groups, the first group received intestinal antiseptic in combination with multi‑component probiotic, the second — intestinal antiseptic in combination with Saccharomyces boulardii. When analyzing the obtained results, it was noted that approximately half of patients with IBS in the anamnesis had manifestations of food allergy. In most cases, food allergy was associated with the development of patients with IBS variant with diarrhea and excessive growth of conditionally pathogenic microflora with a decrease in the number of lactic and bifidobacteria. When comparing schemes for the correction of disorders of the intestinal microbiota, the greatest efficacy was observed with the combination of intestinal antiseptic and Saccharomyces boulardii.

Irritable Bowel Syndrome in Terms of Changes in the Microbiota

Aim:to review available data confirming the pathogenetic role of the intestinal microbiota in the formation of irritable bowel syndrome (IBS).Key findings.Changes in the intestinal biotope cause the development of visceral hypersensitivity and impaired intestinal motor activity, as well as neuroimmune transmission. This article discusses the main aspects of the biological properties of probiotic bacteria in terms of their action within the “brain — intestine — microbiota” chain. The results of experimental and clinical studies elucidating the mechanisms of action of probiotic cultures have been generalized. The understanding of these mechanisms allows practitioners to make informed decisions in prescribing probiotics to IBS patients. Key concepts concerning fecal microbiota transplantation, as well as the prospects and difficulties of implementing this approach are considered.Conclusions.The term “microbiota — intestine — brain” clearly demonstrates the correlation between the main functional components of IBS. Meta-analyses and systematic reviews confirm the efficacy of probiotics in IBS. However, further research into probiotic therapy options is needed to identify specific bacterial strains with proven clinical efficacy. The fecal microbiota transplantation method also requires further research, since many issues associated with this approach remain unclear.

The role of mast cells in pediatric gastrointestinal disease.

Mast cells are granulocytes derived from CD34+ pluripotent progenitor cells that demonstrate plasticity in their development, leaving the bone marrow and differentiating in the tissue where they ultimately reside. They are best known for their role in the allergic response, but also play a prominent immunoregulatory role in other processes, including immune tolerance, the innate immune response, angiogenesis, wound healing and tissue remodeling. Mast cells are found throughout the gastrointestinal tract; their metabolic products influence and regulate intestinal epithelial and endothelial function, gastrointestinal secretion, intestinal motility and absorption, and contribute to host defense. They also play an important role in the development of visceral hypersensitivity through bidirectional interaction with the enteric nervous system. Mast cells have been found to have an increasingly important role in the pathophysiology of a number of pediatric gastrointestinal diseases. This review summarizes the current understanding of the role that mast cells play in the development of pediatric gastrointestinal disorders, including eosinophilic esophagitis, functional dyspepsia, irritable bowel syndrome, celiac disease, inflammatory bowel disease, histologically negative appendicitis, Hirschsprung’s disease, intestinal neuronal dysplasia, and food protein-induced enterocolitis syndrome.

Bile acids induce visceral hypersensitivity via mucosal mast cell–to–nociceptor signaling that involves the farnesoid X receptor/nerve growth factor/transient receptor potential vanilloid 1 axis

Increased colonic bile acid (BA) exposure, frequent in diarrhea-predominant irritable bowel syndrome (IBS-D), can affect gut function. Nerve growth factor (NGF) is implicated in the development of visceral hypersensitivity (VH). In this study, we tested the hypothesis that BAs cause VH via mucosal mast cell (MMC)-to-nociceptor signaling, which involves the farnesoid X receptor (FXR)/NGF/transient receptor potential vanilloid (TRPV)1 axis. BAs were intracolonically administered to rats for 15 d. Visceral sensitivity to colorectal distention and colonic NGF expression were examined. BAs caused VH, an effect that involved MMC-derived NGF and was accompanied by enhanced TRPV1 expression in the dorsal root ganglia. Anti-NGF treatment and TRPV1 antagonism inhibited BA-induced VH. BAs induced NGF mRNA and protein expression and release in cultured mast cells. Colonic supernatants from patients with IBS-D with elevated colonic BA content transcriptionally induced NGF expression. In FXR-/- mice, visceral sensitivity and colonic NGF expression were unaltered after BA treatment. Pharmacological antagonism and FXR silencing suppressed BA-induced NGF expression and release in mast cells. Mitogen-activated protein kinase kinase (MKK) 3/6/p38 MAPK/NF-κB signaling was mechanistically responsible for FXR-mediated NGF expression and secretion. The findings show an MMC-dependent and FXR-mediated pronociceptive effect of BAs and identify the BA/FXR/NGF/TRPV1 axis as a key player in MMC-to-neuron communication during pain processing in IBS.-Li, W.-T., Luo, Q.-Q., Wang, B., Chen, X., Yan, X.-J., Qiu, H.-Y., Chen, S.-L. Bile acids induce visceral hypersensitivity via mucosal mast cell-to-nociceptor signaling that involves the farnesoid X receptor/nerve growth factor/transient receptor potential vanilloid 1 axis.

Novel Insights Into the Mechanisms of Abdominal Pain in Obstructive Bowel Disorders.

Obstructive bowel disorders (OBD) are characterized by lumen distention due to mechanical or functional obstruction in the gut. Abdominal pain is one of the main symptoms in OBD. In this article, we aim to critically review the potential mechanisms for acute and chronic pain in bowel obstruction (BO). While clustered contractions and associated increase of intraluminal pressure may account for colicky pain in simple obstruction, ischemia may be involved in acute pain in severe conditions such as closed loop obstruction. Recent preclinical studies discovered that visceral sensitivity is increased in BO, and visceral hypersensitivity may underlie the mechanisms of chronic abdominal pain in BO. Mounting evidence suggests that lumen distension, as a circumferential mechanical stretch, alters gene expression (mechano-transcription) in the distended bowel, and mechano-transcription of nociceptive and inflammatory mediators plays a critical role in the development of visceral hypersensitivity in BO. Mechano-transcription of nerve growth factor (NGF) in gut smooth muscle cells is found to increase voltage-gated Na+ channel (Nav) activity of the primary sensory neurons by up-regulating expression of TTX-resistant Nav1.8, whereas mechanical stretch-induced brain-derived neurotrophic factor (BDNF) reduces Kv currents especially A-type (IA) currents by down-regulating expression of specific IA subtypes such as Kv1.4. The NGF and BDNF mediated changes in gene expression and channel functions in the primary sensory neurons may constitute the main mechanisms of visceral hypersensitivity in OBD. In addition, mechanical stretch-induced COX-2 and other inflammatory mediators in the gut may also contribute to abdominal pain by activating and sensitizing nociceptors.

1091 - Resolvin D1 Acting on G1 Coupled Fpr2 Receptor Inhibits Mast Cell Degranulation and Prevents Development of Visceral Hypersensitivity in Ibs

1091 - Resolvin D1 Acting on G1 Coupled Fpr2 Receptor Inhibits Mast Cell Degranulation and Prevents Development of Visceral Hypersensitivity in Ibs

Blockage of High-Affinity Choline Transporter Increases Visceral Hypersensitivity in Rats with Chronic Stress.

Background Visceral hypersensitivity is a common feature of irritable bowel syndrome. Cholinergic system involves in the development of visceral hypersensitivity, and high-affinity choline transporter (CHT1) is of crucial importance in choline uptake system. However, involvement of CHT1 in visceral hypersensitivity remains unknown. The research aimed to study the CHT1 expression in dorsal root ganglions (DRGs) and the role of CHT1 in visceral hypersensitivity. Methods Repetitive water avoidance stress (WAS) was used to induce visceral hypersensitivity in rats. Colorectal distension (CRD) was determined, and the abdominal withdrawal reflex (AWR) and threshold intensity data were recorded to measure the visceral sensitivity. After intraperitoneal injection of hemicholinium-3 (HC-3), the specific inhibitor of CHT1, CRD data were also recorded. The CHT1 expression of DRGs was investigated by Western blotting, immunohistochemistry, and quantitative RT-PCR. Acetylcholine levels in the DRGs were detected by the assay kit. Results Repetitive WAS increased the AWR score of CRD at high distension pressure and decreased the mean threshold of rats. The CHT1 expression and acetylcholine concentration of DRG were significantly increased in WAS rats. After the administration of HC-3, the AWR score in WAS group was significantly increased at higher distension pressure while the threshold intensity was significantly reduced compared to the normal saline group. Acetylcholine concentration was significantly lower than the normal saline rats. Conclusion Our research firstly reports that CHT1 is overexpressed in noninflammatory visceral hypersensitivity, and blockage of CHT1 can enhance the visceral hypersensitivity. CHT1 may play an inhibitory role in visceral hypersensitivity.

Role of transient receptor potential melastatin 2 (TRPM2) channels in visceral nociception and hypersensitivity

Transient receptor potential melastatin 2 (TRPM2) is a thermosensitive, Ca2+-permeable cation channel. TRPM2 contributes to the pathogenesis of inflammatory bowel disease, and inflammatory and neuropathic pain. We hypothesized that TRPM2 is important for visceral nociception and the development of visceral hypersensitivity. Therefore, we investigated the expression of TRPM2 channels and their involvement in visceral nociception in normal physiology and under pathological conditions that cause visceral hypersensitivity in rats. TRPM2 immunoreactivities were detected in the mucosa and muscle layer of the rat gastrointestinal tract. TRPM2 immunopositive cell bodies were almost completely co-localized with calretinin- and NeuN-positive cells in the myenteric plexus. We found that the majority of the TRPM2-immunoreactive cells were double-labeled with the retrograde marker fluorogold in lumbar 6/sacral 1 dorsal root ganglia (DRG), indicating that TRPM2 is expressed in spinal primary afferents innervating the distal colon. Subtypes of TRPM2-immunopositive DRG neurons were labeled by the A-fiber marker NF200, the C-fiber marker IB4, substance P, calcitonin gene-related peptide, or P2X3 receptor. We found that oral administration of the TRPM2 inhibitor econazole (30mg/kg) reduced the visceromotor response (VMR) to noxious colorectal distention (CRD) at 80mmHg in control rats. Expression of TRPM2 in the mucosa of the distal colon was increased in a trinitrobenzene sulfonic acid-induced colitis model. The VMR to CRD significantly increased in colitis model rats compared with control rats at 40, 60, and 80mmHg. Econazole restored visceral hypersensitivity to the control level. Furthermore, TRPM2-deficient mice showed significantly attenuated trinitrobenzene sulfonic acid induced visceral hypersensitivity compared with wild-type mice. In conclusion, TRPM2 channels contribute to visceral nociception in response to noxious stimuli under normal conditions and visceral hypersensitivity in pathological conditions.

TRPV1-mediated presynaptic transmission in basolateral amygdala contributes to visceral hypersensitivity in adult rats with neonatal maternal deprivation.

The central mechanisms of visceral hypersensitivity remain largely unknown. It’s reported that there are highest densities of TRPV1 labeled neurons within basolateral amygdala (BLA). The aim of this study was to explore the role and mechanisms of TRPV1 in BLA in development of visceral hypersensitivity. Visceral hypersensitivity was induced by neonatal maternal deprivation (NMD) and was quantified by abdominal withdrawal reflex. Expression of TRPV1 was determined by Western blot. The synaptic transmission of neurons in BLA was recorded by patch clamping. It was found that the expression of TRPV1 in BLA was significantly upregulated in NMD rats; glutamatergic synaptic activities in BLA were increased in NMD rats; application of capsazepine (TRPV1 antagonist) decreased glutamatergic synaptic activities of BLA neurons in NMD slices through a presynaptic mechanism; application of capsaicin (TRPV1 agonist) increased glutamatergic synaptic activities of BLA neurons in control slices through presynaptic mechanism without affecting GABAergic synaptic activities; microinjecting capsazepine into BLA significantly increased colonic distension threshold both in control and NMD rats. Our data suggested that upregulation of TRPV1 in BLA contributes to visceral hypersensitivity of NMD rats through enhancing excitation of BLA, thus identifying a potential target for treatment of chronic visceral pain.

Gastroesophageal reflux disease-related and functional heartburn: pathophysiology and treatment.

Patients who continue to experience heartburn symptoms despite adequate-dose proton pump inhibitor therapy have unmet clinical needs. In this review, we focus on the most recent findings related to the mechanism of heartburn symptom generation, and on the treatment of gastroesophageal reflux disease-related and functional heartburn. The immunological mechanism in the esophageal mucosa has been addressed as a potential mechanism of the onset of esophageal mucosa damage and the generation of heartburn symptoms. Peripheral or central hypersensitivity in viscera is a potentially unifying pathophysiological concept in functional heartburn. Vonoprazan, a novel and potent first-in-class potassium-competitive acid blocker, is expected to prove useful in the treatment of reflux disease. New findings in the mechanisms of heartburn symptom generation are emerging, including the immunological mediation of esophageal mucosal damage and the development of visceral hypersensitivity in functional heartburn. In the future, we anticipate the emergence of new and specific therapeutic options based on these mechanisms, with less dependence on acid-suppressing agents.

Role of colonic mast cell infiltration and nerve growth factor in visceral hypersensitivity of irritable bowel syndrome

Objective To investigate the role of mucosal mast cells infiltration and degranulation with nerve growth factor (NGF) in development of visceral hypersensitivity in Sprague-Dawley (SD) rats. Methods The model of visceral hypersensitivity of irritable bowel syndrome (IBS) was established in 19 neonate SD rats with intestinal stimulation (rectalballon distention) on 8th, 10th and 12th postnatal days. The other 19 neonate SD rats without colonic distention were assigned to the control group. After rats grew up (six to eight weeks old), the visceral sensitivity was tested by abdominal withdrawal reflex (AWR) in 10 rats of each group. Mast cell infiltration and degranulation were observed with toluidine blue staining in colon tissue slides. The NGF level of intestinal tissues was detected by enzyme-linked immunosorbent assay (ELISA) methods in the left nine rats of each group. The culture system of dorsal root ganglias (DRG) from the neonatal rats was set up. The changes of electrophysilogical characters of DRG stimulated with NGF (100 ng/mL) for four days were recorded with patch-clamp.Paired t test was performed for comparison between groups. Results The results of AWR indicated that neonatal colonic stimulation could significantly increase visceral sensitivity after growing up. Under 20, 40 and 60 mmHg (1 mmHg=0.133 kPa) distention pressure, visceral sensitivity scores of visceral hypersensitivity rats and rats of control group were 1.00±0.50 vs 1.67±0.50, 1.89±0.31 vs 2.89±0.34 and 2.89±0.33 vs 3.89±0.33, the differences were statistically significant (t=-2.83, -6.00 and -6.00, all P<0.05). The results of master cells staining in tissue slides showed colonic master cells infiltration was obvious in rats with visceral hypersensitivity, and part of mast cells were degranulation. The result of ELISA demonstrated that NGF level of visceral hypersensitivity rats was significantly higher than that of control group ((11.07±3.06) pg/mg vs (2.38±1.88) pg/mg, t=-6.93, P<0.05). The results of electrophysilogical tests of primary cultured DRG indicated that compared with blank control growp, the action potential threshold of neuron in NGF 100 ng/mL group significantly decreased ((-18.0±2.1) mV vs (-29.0±2.5) mV, t=12.26, P<0.05) and discharge frequency increased ((5.0±1.4)/800 ms vs (12.0±3.2)/800 ms, t=-8.40, P<0.05). Meanwhile, neuron voltage-gated K+ current density remarkably decreased, most were sustained delayed rectifier K+ current (IK) decreasing ((279.0±48.0) pA/pF vs (203.0±39.0) pA/pF, t=6.18, P<0.05). Conclusion Colonic stimulation in neonatal rats could cause intestinal master cells infiltration and degranulation, which induced changes of neuron electrophysilogical characters and resulted in visceral hypersensitivity after growing up. Key words: Irritable bowel syndrome; Hyperesthesia; Ganglion, spinal; Mast cells; Nerve growth factor

Chronic prenatal stress epigenetically modifies spinal cord BDNF expression to induce sex-specific visceral hypersensitivity in offspring.

Irritable bowel syndrome (IBS) is a heterogeneous disorder with abdominal pain as one of the primary symptoms. The etiology of IBS remains unknown. Epidemiological studies found that a subset of these patients have a history of adverse early-life experiences. We tested the hypothesis that chronic prenatal stress (CPS) epigenetically enhances brain-derived neurotrophic factor (BDNF) in spinal cord to aggravate colon sensitivity to colorectal distension (CRD) differentially in male and female offspring. We used heterotypic intermittent chronic stress (HeICS) protocols in pregnant dams from E11 until delivery. Chronic prenatal stress induced significant visceral hypersensitivity (VHS) to CRD in male and female offspring. A second exposure to HeICS in adult offspring exacerbated VHS greater in female offspring that persisted longer than in male offspring. Chronic prenatal stress upregulated BDNF expression in the lumbar-sacral dorsal horn that correlated with the exacerbation of VHS in female, but not in male offspring. The upregulation of BDNF was due to a significant increase in RNA Pol II binding, histone H3 acetylation, and significant decrease in histone deacetylase 1 association with the core promoter of BDNF in female offspring. Other chronic prenatal and neonatal stress protocols were less effective than HeICS. The development of VHS, which contributes to the symptom of intermittent abdominal pain, is a two-step process, chronic in utero stress followed by chronic stress in adult-life. This two-step process induces aggravated and persistent colon hypersensitivity in female than in male offspring. Our preclinical model explains several clinical features in IBS patients.

Experimental gastritis leads to anxiety- and depression-like behaviors in female but not male rats

Human and animals studies support the idea that there is a gender-related co-morbidity of pain-related and inflammatory gastrointestinal (GI) diseases with psychological disorders. This co-morbidity is the evidence for the existence of GI-brain axis which consists of immune (cytokines), neural (vagus nerve) and neuroendocrine (HPA axis) pathways. Psychological stress causes disturbances in GI physiology, such as altered GI barrier function, changes in motility and secretion, development of visceral hypersensitivity, and dysfunction of inflammatory responses. Whether GI inflammation would exert impact on psychological behavior is not well established. We examined the effect of experimental gastritis on anxiety- and depression-like behaviors in male and female Sprague–Dawley rats, and evaluated potential mechanisms of action. Gastritis was induced by adding 0.1% (w/v) iodoacetamide (IAA) to the sterile drinking water for 7 days. Sucrose preference test assessed the depression-like behavior, open field test and elevated plus maze evaluated the anxiety-like behavior. IAA treatment induced gastric inflammation in rats of either gender. No behavioral abnormality or dysfunction of GI-brain axis was observed in male rats with IAA-induced gastritis. Anxiety- and depression-like behaviors were apparent and the HPA axis was hyperactive in female rats with IAA-induced gastritis. Our results show that gastric inflammation leads to anxiety- and depression-like behaviors in female but not male rats via the neuroendocrine (HPA axis) pathway, suggesting that the GI inflammation can impair normal brain function and induce changes in psychological behavior in a gender-related manner through the GI-to-brain signaling.

438 Down Regulation of Enteric Defensins is Responsible for Alteration of Gut Microbiota and Development of Visceral Hypersensitivity in Chronically Stressed Rats

438 Down Regulation of Enteric Defensins is Responsible for Alteration of Gut Microbiota and Development of Visceral Hypersensitivity in Chronically Stressed Rats