Epidermal growth factor upregulates serotonin transporter and its association with visceral hypersensitivity in irritable bowel syndrome

AIM: To investigate the role of epidermal growth factor(EGF) in visceral hypersensitivity and its effect on the serotonin transporter(SERT).METHODS: A rat model for visceral hypersensitivity was established by intra-colonic infusion of 0.5% acetic acid in 10-d-old Sprague-Dawley rats. The visceral sensitivity was assessed by observing the abdominal withdrawal reflex and recording electromyographic activity of the external oblique muscle in response to colorectal distension. An enzyme-linked immunosorbent assay was used to measure the EGF levels in plasma and colonic tissues. SERT mRNA expression was detected by real-time PCR while protein level was determined by Western blot. The correlation between EGF and SERT levels in colon tissues was analyzed by Pearson's corre-lation analysis. SERT function was examined by tritiated serotonin(5-HT) uptake experiments. Rat intestinal epithelial cells(IEC-6) were used to examine the EGF regulatory effect on SERT expression and function via the EGF receptor(EGFR).RESULTS: EGF levels were significantly lower in th rats with visceral hypersensitivity as measured in plas ma(2.639 ± 0.107 ng/mL vs 4.066 ± 0.573 ng/mL, < 0.01) and in colonic tissue(3.244 ± 0.135 ng/10 mg vs 3.582 ± 0.197 ng/100 mg colon tissue, P 0.01) compared with controls. Moreover, the EGF leve were positively correlated with SERT levels(r = 0.820 P < 0.01). EGF displayed dose- and time-dependen increased SERT gene expressions in IEC-6 cells. A EGFR kinase inhibitor inhibited the effect of EGF o SERT gene upregulation. SERT activity was enhance following treatment with EGF(592.908 ± 31.515 fmo min per milligram vs 316.789 ± 85.652 fmol/min pe milligram protein, P < 0.05) and blocked by the EGF kinase inhibitor in IEC-6 cells(590.274 ± 25.954 fmo min per milligram vs 367.834 ± 120.307 fmol/min pe milligram protein, P < 0.05).CONCLUSION: A decrease in EGF levels may contribute to the formation of visceral hypersensitivity through downregulation of SERT-mediated 5-HT uptake into enterocytes.

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 adminis-tration.Changes in visceral sensitivity after administration of the TRPV1 antago-INTRODUCTION Irritable bowel syndrome(IBS)is a chronic functional bowel disorder characterized by recurrent abdominal pain with altered bowel habits that affects approximately 15%of the population worldwide[1].IBS significantly impacts the quality of life of patients.Although the pathogenesis of IBS is not completely understood,the role of abnormal visceral sensitivity in IBS has recently emerged[2,3].5-Hydroxytryptamine(5-HT)is known to play a key role in the physiological states of the gastrointestinal tract.Plasma 5-HT levels in IBS with diarrhea(IBS-D)patients were greater than those in healthy controls[4],suggesting a possible role of 5-HT in the pathogenesis of IBS-D.The serotonin receptor 2(5-HT2 receptor)family comprises three subtypes:5-HT2A,5-HT2B,and 5-HT2c.All 5-HT2 receptors exhibit 46%-50%overall sequence identity,and all of these receptors preferentially bind to Gq/11 to increase inositol phosphates and intracellular calcium mobilization[5].5-HT2B receptors are widely expressed throughout the gut,and experimental evidence suggests that the primary function of 5-HT2B receptors is to mediate contractile responses to 5-HT through its action on smooth muscle[6].The 5-HT2B receptor is localized to both neurons of the myenteric nerve plexus and smooth muscle in the human colon.The 5-HT2B receptor mediates 5-HT-evoked contraction of longitudinal smooth muscle[6].These findings suggest that the 5-HT2B receptor could play an important role in modulating colonic motility,which could affect sensory signaling in the gut.Other laboratories have shown that the 5-HT2B receptor participates in the development of mechanical and formalin-induced hyperalgesia[7,8].A 5-HT2B receptor antagonist reduced 2,4,6-trinitrobenzene sulfonic acid(TNBS)and stress-induced visceral hyperalgesia in rats[9,10].However,the role of the 5-HT2B receptor in IBS-D patients and in acetic acid-and wrap restraint-induced IBS-D rat models was not investigated.

Lactobacillus plantarum AR495 improves stress-induced irritable bowel syndrome in rats by targeting gut microbiota and Mast cell-PAR2-TRPV1 signaling pathway

Probiotics have great potential in regulating intestinal pain.In this study,the effects of Lactobacillus plantarum AR495 on the visceral sensitivity and gut microbiota of irritable bowel syndrome(IBS)rats were studied.The results showed that tryptase released after mast cell activation and degranulation plays a key role in visceral pain,and L.plantarum AR495 reduced the stimulation of colonic mast cells and the expression of protease-activated receptor 2(PAR2)and TRPV1 in dorsal root ganglia.Research further showed that supplementation with L.plantarum AR495 increased the level of short-chain fatty acids(SCFAs)and enhanced the barrier function of the colon.In addition,the microbiota analysis of the colon indicated that L.plantarum AR495 promoted the proliferation of Bifidobacterium and inhibited the proliferation of Lachnospiraceae,which alleviated the imbalance of the intestinal microbiota caused by IBS to a certain extent.In total,L.plantarum AR495 might reduce visceral sensitivity through the Mast cell-PAR2-TRPV1 signaling pathway by maintaining the homeostasis of the intestinal barrier.

Increased expression of brain-derived neurotrophic factor is correlated with visceral hypersensitivity in patients with diarrheapredominant irritable bowel syndrome

BACKGROUND Visceral hypersensitivity is considered to play a vital role in the pathogenesis of irritable bowel syndrome(IBS). Neurotrophins have drawn much attention in IBS recently. Brain-derived neurotrophic factor(BDNF) was found to mediate visceral hypersensitivity via facilitating sensory nerve growth in pre-clinical studies. We hypothesized that BDNF might play a role in the pathogenesis of diarrhea-predominant IBS(IBS-D).AIM To investigate BDNF levels in IBS-D patients and its role in IBS-D pathophysiology.METHODS Thirty-one IBS-D patients meeting the Rome IV diagnostic criteria and 20 ageand sex-matched healthy controls were recruited. Clinical and psychological assessments were first conducted using standardized questionnaires. Visceral sensitivity to rectal distension was tested using a high-resolution manometry system. Colonoscopic examination was performed and four mucosal pinch biopsies were taken from the rectosigmoid junction. Mucosal BDNF expression and nerve fiber density were analyzed using immunohistochemistry. Mucosal BDNF mRNA levels were quantified by quantitative real-time polymerase chain reaction. Correlations between these parameters were examined.RESULTS The patients had a higher anxiety score [median(interquartile range), 6.0(2.0-10.0) vs 3.0(1.0-4.0), P = 0.003] and visceral sensitivity index score [54.0(44.0-61.0)vs 21.0(17.3-30.0), P < 0.001] than controls. The defecating sensation threshold[60.0(44.0-80.0) vs 80.0(61.0-100.0), P = 0.009], maximum tolerable threshold[103.0(90.0-128.0) vs 182.0(142.5-209.3), P < 0.001] and rectoanal inhibitory reflex threshold [30.0(20.0-30.0) vs 30.0(30.0-47.5), P = 0.032] were significantly lower in IBS-D patients. Intestinal mucosal BDNF protein [3.46 E-2(3.06 E-2-4.44 E-2) vs3.07 E-2(2.91 E-2-3.48 E-2), P = 0.031] and mRNA [1.57(1.31-2.61) vs 1.09(0.74-1.42), P = 0.001] expression and nerve fiber density [4.12 E-2(3.07 E-2-7.46 E-2) vs1.98 E-2(1.21 E-2-4.25 E-2), P = 0.002] were significantly elevated in the patients.Increased BDNF expression was positively correlated with abdominal pain and disease severity and negatively correlated with visceral sensitivity parameters.CONCLUSION Elevated mucosal BDNF may participate in the pathogenesis of IBS-D via facilitating mucosal nerve growth and increasing visceral sensitivity.

TLR4 upregulates CBS expression through NF-κB activation in a rat model of irritable bowel syndrome with chronic visceral hypersensitivity

AIM:To investigate the roles of toll-like receptor 4(TLR4) and nuclear factor(NF)-κB on cystathionine βsynthetase(CBS) expression and visceral hypersensitivity in rats.METHODS:This study used 1-7-wk-old male SpragueDawley rats.Western blot analysis was employed to measure the expression of TLR4,NF-kB and the endogenous hydrogen sulfide-producing enzyme CBS in colon dorsal root ganglia(DRG) from control and "irritable bowel syndrome" rats induced by neonatal colonic inflammation(NCI).Colon-specific DRG neurons were labeled with Dil and acutely dissociated to measure excitability with patch-clamp techniques.Immunofluorescence was employed to determine the co-expression of TLR4,NF-kB and CBS in Dil-labeled DRG neurons.RESULTS:NCI significantly upregulated the expression of TLR4 in colon-related DRGs(0.34 ± 0.12 vs 0.72 ±0.02 for the control and NCI groups,respectively,P <0.05).Intrathecal administration of the TLR4-selective inhibitor CLI-095 significantly enhanced the colorectal distention threshold of NCI rats.CLI-095 treatment also markedly reversed the hyperexcitability of colonspecific DRG neurons and reduced the expression of CBS(1.7 ± 0.1 vs 1.1 ± 0.04,p < 0.05) and of the NF-kB subunit p65(0.8 ± 0.1 vs 0.5 ± 0.1,P< 0.05).Furthermore,the NF-KB-selective inhibitor pyrrolidine dithiocarbamate(PDTC) significantly reduced the upregulation of CBS(1.0 ± 0.1 vs 0.6 ± 0.1,P< 0.05)and attenuated visceral hypersensitivity in the NCI rats.In vitro,incubation of cultured DRG neurons with the TLR4 agonist lipopolysaccharide significantly enhanced the expression of p65(control vs 8 h:0.9 ± 0.1 vs1.3 ± 0.1;control vs 12 h:0.9 ± 0.1 vs 1.3 ± 0.1,P< 0.05;control vs 24 h:0.9 ± 0.1 vs 1.6 ± 0.1,P <0.01) and CBS(control vs 12 h:1.0 ± 0.1 vs 2.2 ±0.4;control vs 24 h:1.0 ± 0.1 vs 2.6 ± 0.1,P< 0.05),whereas the inhibition of p65 via pre-incubation with PDTC significantly reversed the upregulation of CBS expression(1.2 ± 0.1 vs 0.6 ± 0.0,P< 0.01).CONCLUSION:Our results suggest that the activation of TLR4 by NCI upregulates CBS expression,which is mediated by the NF-kB signaling pathway,thus contributing to visceral hypersensitivity.

Altered profiles of fecal metabolites correlate with visceral hypersensitivity and may contribute to symptom severity of diarrhea-predominant irritable bowel syndrome

BACKGROUND Fecal metabolites are associated with gut visceral sensitivity,mucosal immune function and intestinal barrier function,all of which have critical roles in the pathogenesis of irritable bowel syndrome(IBS).However,the metabolic profile and pathophysiology of IBS are still unclear.We hypothesized that altered profiles of fecal metabolites might be involved in the pathogenesis of IBS with predominant diarrhea(IBS-D).AIM To investigate the fecal metabolite composition and the role of metabolites in IBSD pathophysiology.METHODS Thirty IBS-D patients and 15 age-and sex-matched healthy controls(HCs)underwent clinical and psychological assessments,including the IBS Symptom Severity System(IBS-SSS),an Italian modified version of the Bowel Disease Questionnaire,the Bristol Stool Form Scale(BSFS),the Hospital Anxiety and Depression Scale,and the Visceral Sensitivity Index.Visceral sensitivity to rectal distension was tested using high-resolution manometry system by the same investigator.Fecal metabolites,including amino acids and organic acids,were measured by targeted metabolomics approaches.Correlation analyses between these parameters were performed.RESULTS The patients presented with increased stool water content,more psychological symptoms and increased visceral hypersensitivity compared with the controls.In fecal metabolites,His[IBS-D:0.0642(0.0388,0.1484),HC:0.2636(0.0780,0.3966),P=0.012],Ala[IBS-D:0.5095(0.2826,0.9183),HC:1.0118(0.6135,1.4335),P=0.041],Tyr[IBS-D:0.1024(0.0173,0.4527),HC:0.5665(0.2436,1.3447),P=0.018],Phe[IBS-D:0.1511(0.0775,0.3248),HC:0.3967(0.1388,0.7550),P=0.028],and Trp[IBS-D:0.0323(0.0001,0.0826),HC:0.0834(0.0170,0.1759),P=0.046]were decreased in IBS-D patients,but isohexanoate[IBS-D:0.0127(0.0060,0.0246),HC:0.0070(0.0023,0.0106),P=0.028]was significantly increased.Only Tyr was mildly correlated with BSFS scores in all subjects(r=-0.347,P=0.019).A possible potential biomarker panel was identified to correlate with IBS-SSS score(R2 Adjusted=0.693,P<0.001).In this regression model,the levels of Tyr,Val,hexanoate,fumarate,and pyruvate were significantly associated with the symptom severity of IBS-D.Furthermore,visceral sensation,including abdominal pain and visceral hypersensitivity,was correlated with isovalerate,valerate and isohexanoate.CONCLUSION Altered profiles of fecal metabolites may be one of the origins or exacerbating factors of symptoms in IBS-D via increasing visceral sensitivity.

Serotonin transporter and cholecystokinin in diarrhea-predominant irritable bowel syndrome: Associations with abdominal pain, visceral hypersensitivity and psychological performance

BACKGROUND Visceral hypersensitivity and psychological performance are the main pathophysiological mechanisms of irritable bowel syndrome(IBS).Previous studies have found that cholecystokinin(CCK)can enhance colon movement and that serotonin transporter(SERT)is a transmembrane transport protein with high affinity for 5-hydroxytryptamine,which can rapidly reuptake 5-hydroxytryptamine and then regulate its action time and intensity.We speculate that SERT and CCK might play a role in the pathogenesis of diarrheapredominant IBS(IBS-D)by affecting visceral sensitivity and the brain-gut axis.AIM To determine SERT and CCK levels in IBS-D patients diagnosed using Rome IV criteria and to analyze their associations with abdominal pain,visceral hypersensitivity and psychological performance.METHODS This study collected data from 40 patients with IBS-D at the China-Japan Friendship Hospital from September 2017 to April 2018 and 18 healthy controls.The severity of abdominal pain,visceral sensitivity and psychological performance were evaluated in IBS-D patients and healthy controls,the levels of SERT and CCK in plasma and colonic mucosa were evaluated,and the correlations between them were analyzed.RESULTS There were significant differences in the initial sensation threshold(31.00±8.41 mL vs 52.22±8.09 mL,P<0.001),defecating sensation threshold(51.75±13.57 mL vs 89.44±8.73 mL,P<0.001)and maximum tolerable threshold(97.25±23.64 mL vs 171.11±20.83 mL,P<0.001)between the two groups.IBS-D patients had more severe anxiety(7.78±2.62 vs 2.89±1.02,P<0.001)and depressive(6.38±2.43 vs 2.06±0.73,P<0.001)symptoms than healthy controls.Significant differences were also found in mucosal CCK(2.29±0.30 vs 1.66±0.17,P<0.001)and SERT(1.90±0.51 vs 3.03±0.23,P<0.001)between the two groups.There was a significant positive correlation between pain scores and mucosal CCK(r=0.96,0.93,0.94,P<0.001).Significant negative correlations between anxiety(r=-0.98;P<0.001),depression(r=-0.99;P<0.001),pain evaluation(r=-0.96,-0.93,-0.95,P<0.001)and mucosal SERT were observed.CONCLUSION IBS-D patients had psychosomatic disorders and visceral hypersensitivity.SERT and CCK might be involved in the pathogenesis of IBS-D by regulating the braingut axis and affecting visceral sensitivity.This provides a new potential method for identifying a more specific and effective therapeutic target.

Fructo-oligosaccharide intensifies visceral hypersensitivity and intestinal inflammation in a stress-induced irritable bowel syndrome mouse model

AIM To determine whether fructo-oligosaccharide(FOS) affects visceral sensitivity, inflammation, and production of intestinal short-chain fatty acids(SCFA) in an irritable bowel syndrome(IBS) mouse model.METHODS Mice were randomly assigned to daily oral gavage of saline solution with or without FOS(8 g/kg body weight) for 14 d. Mice were further assigned to receive either daily one-hour water avoidance stress(WAS) or sham-WAS for the first 10 d. After 2 wk, visceral sensitivity was measured by abdominal withdrawal reflex in response to colorectal distension and mucosal inflammation was evaluated. Gas chromatography, real-time reverse transcription PCR, and immunohistochemistry assays were used to quantify cecal concentrations of SCFA, intestinal cytokine expression, and number of intestinal mast cells per high-power field(HPF), respectively.RESULTS Mice subjected to WAS exhibited visceral hypersensitivity and low-grade inflammation. Among mice subjected to WAS, FOS increased visceral hypersensitivity and led to higher cecal concentrations of acetic acid(2.49 ± 0.63 mmol/L vs 1.49 ± 0.72 mmol/L, P < 0.05), propionic acid(0.48 ± 0.09 mmol/L vs 0.36 ± 0.05 mmol/L, P < 0.01), butyric acid(0.28 ± 0.09 mmol/L vs 0.19 ± 0.003 mmol/L, P < 0.05), as well as total SCFA(3.62 ± 0.87 mmol/L vs 2.27 ± 0.75 mmol/L, P < 0.01) compared to saline administration. FOS also increased ileal interleukin(IL)-23 mR NA(4.71 ± 4.16 vs 1.00 ± 0.99, P < 0.05) and colonic IL-1β mR NA(2.15 ± 1.68 vs 0.88 ± 0.53, P < 0.05) expressions as well as increased mean mast cell counts in the ileum(12.3 ± 2.6 per HPF vs 8.3 ± 3.6 per HPF, P < 0.05) and colon(6.3 ± 3.2 per HPF vs 3.4 ± 1.2 per HPF, P < 0.05) compared to saline administration in mice subjected to WAS. No difference in visceral sensitivity, intestinal inflammation, or cecal SCFA levels was detected with or without FOS administration in mice subjected to sham-WAS.CONCLUSION FOS administration intensifies visceral hypersensitivity and gut inflammation in stress-induced IBS mice, but not in the control mice, and is also associated with increased intestinal SCFA production.

Abnormal endogenous pain modulation and somatic and visceral hypersensitivity in female patients with irritable bowel syndrome

AIM: To investigate the role of endogenous pain modulatory mechanisms in the central sensitization implicated by the visceral hypersensitivity demonstrated in patients with irritable bowel syndrome (IBS). Dysfunction of modulatory mechanisms would be expected to also result in changes of somatic sensory function. METHODS: Endogenous pain modulatory mechanisms were assessed using heterotopic stimulation and somatic and visceral sensory testing in IBS. Pain intensities (visua analogue scale, VAS 0-100) during suprathreshold recta distension with a barostat, cold pressor stimulation of the foot and during both stimuli simultaneously (heterotopic stimulation) were recorded in 40 female patients with IBS and 20 female healthy controls. RESULTS: Rectal hypersensitivity (defined by 95% CI of controls) was seen in 21 (53%), somatic hypersensitivity in 22 (55%) and both rectal and somatic hypersensitivity in 14 of these IBS patients. Heterotopic stimulation decreased rectal pain intensity by 6 (-11 to -1) in controls, but increased rectal pain by 2 (-3 to +6) in all IBS patients (P < 0.05) and by 8 (-2 to +19) in IBS patients with somatic and visceral hypersensitivity (P < 0.02). CONCLUSION: A majority of IBS patients had abnormal endogenous pain modulation and somatic hypersensitivity as evidence of central sensitization.

Visceral hypersensitivity in inflammatory bowel diseases and irritable bowel syndrome: The role of proteases

Proteases, enzymes catalyzing the hydrolysis of peptide bonds, are present at high concentrations in the gastrointestinal tract. Besides their well-known role in the digestive process, they also function as signaling molecules through the activation of protease-activated receptors(PARs). Based on their chemical mechanism for catalysis, proteases can be classified into several classes: serine, cysteine, aspartic, metallo- and threonine proteases represent the mammalian protease families. In particular, the class of serine proteases will play a significant role in this review. In the last decades, proteases have been suggested to play a key role in the pathogenesis of visceral hypersensitivity, which is a major factor contributing to abdominal pain in patients with inflammatory bowel diseases and/or irritable bowel syndrome. So far, only a few preclinical animal studies have investigated the effect of protease inhibitors specifically on visceral sensitivity while their effect on inflammation is described in more detail. In our accompanying review we describe their effect on gastrointestinal permeability. On account of their promising results in the field of visceral hypersensitivity, further research is warranted. The aim of this review is to give an overview on the concept of visceral hypersensitivity as well as on the physiological and pathophysiological functions of proteases herein.

P2Y1R is involved in visceral hypersensitivity in rats with experimental irritable bowel syndrome

AIM To evaluate the role of P2Y1 R in visceral hypersensitivity in rats with experimental irritable bowel syndrome.METHODS A rat model of irritable bowel syndrome was generated by intra-colonic administration of acetic acid(AA) and assessed by histology and myeloperoxidase(m PO) activity assay. Then P2Y1 R expression in the colonic tissue was detected by Western blot. In order to explore the regulatory role of P2Y1 R in visceral hypersensitivity, an agonist(m RS2365) and an antagonist(m RS2179) of P2Y1 R were intra-colonically administered and effects were tested through a colorectal distension test. The abdominal withdrawal reflex and abdominal electromyography were tested during the course. RESULTS model assessment tests showed an obvious inflammatoryreaction that appeared on the 2^(nd) d after the AA injection, and the inflammatory reaction gradually recovered and almost disappeared on the 7^(th) d. The model finished on day 8 and showed a clear feature of IBS that had no organic lesion. The average expression of P2Y1 R was significantly higher in the AA group than in the na?ve group(0.319 ± 0.02 vs 0.094 ± 0.016, P < 0.001). m RS2365 could effectively raise the colonic hypersensitivity status at intervention doses of 10(AUC value from 0.30 ± 0.089 to 1.973 ± 0.127 mv?s, P < 0.01) and 100 μmol/L(AUC value from 0.290 ± 0.079 to 1.983 ± 0.195 mv?s, P < 0.01); m RS2179 could effectively reduce the hypersensitivity status at intervention dose of 100 μmol/L(from a mean baseline AUC value of 1.587 ± 0.099 mv?s to 0.140 ± 0.089 mv?s, P < 0.0001). Differences between the m RS2179 group(1.88 ± 1.45) and either the m RS2365 group(3.96 ± 0.19) or the combined treatment(m RS2179 and m RS2365) group(3.28 ± 0.11) were significant(P < 0.01).CONCLUSION P2Y1 R plays a regulatory role in visceral hypersensitivity in rats with experimental IBS. Specific antagonists of P2Y1 R may have potential therapeutic value in treating abdominal pain in IBS.

ZD 7288,an HCN channel blocker,attenuates chronic visceral pain in irritable bowel syndrome-like rats

AIM:To investigate the effects of ZD 7288,a hyperpolarization-activated cyclic nucleotide-gated(HCN)channel blocker,on rats with chronic visceral pain.METHODS:Rats with visceral hypersensitivity were generated using neonatal colon irritation during postnatal days 8-15 as described previously.Visceral hypersensitivity was evaluated using electromyographic(EMG)responses of abdominal external oblique muscles to 20-80 mmHg colorectal distentions(CRD).Abdominal withdrawal reflex(AWR)scores and pain thresholds were also detected in adult rats.Different doses of ZD7288(25,50,and 100 nmol/L)were intrathecally administered in rats to study the role of spinal HCN channel in chronic visceral hypersensitivity.RESULTS:EMG responses to 20-80 mmHg CRD and AWR scores under 20-60 mmHg CRD significantly increased in rats with visceral hypersensitivity compared to control rats(P<0.05).The pain threshold in rats with visceral hypersensitivity significantly decreased compared to control rats(P<0.05).Treatment with50-100 nmol/L ZD 7288 significantly inhibited EMG responses(16%-62%,80-20 mmHg CRD,P<0.05)and AWR scores(24%-37%,40-20 mmHg CRD,P<0.05;12%-61%,80-20 mmHg CRD,P<0.05,respectively),and significantly increased pain thresholds(32%-77%,P<0.05).CONCLUSION:Spinal HCN channels may play an important role in chronic visceral hypersensitivity.

Thermal hypersensitivity in a subset of irritable bowel syndrome patients

AIM:To characterize thermal hypersensitivity in patients with constipation-and diarrhea-predominant irritable bowel syndrome (IBS).METHODS:Thermal pain sensitivity was tested among patients with diarrhea-predominant IBS (D-IBS) and constipation-predominant IBS (C-IBS) compared to healthy subjects.A total of 42 patients (29 female and 13 male;mean age 27.0±6.4 years) with D-IBS;24 patients (16 female and eight male;mean age 32.5±8.8 years) with C-IBS;and 52 control subjects (34 female and 18 male;mean age 27.3±8.0 years) participated in the study.Thermal stimuli were delivered using a Medoc Thermal Sensory Analyzer with a 3 cm × 3 cm surface area.Heat pain threshold (HPTh) and heat pain tolerance (HPTo) were assessed on the left ventral forearm and left calf using an ascending method of limits.The Functional Bowel Disease Severity Index (FBDSI) was also obtained for all subjects.RESULTS:Controls were less sensitive than C-IBS and D-IBS (both at P < 0.001) with no differences between C-IBS and D-IBS for HPTh and HPTo.Thermal hyperalgesia was present in both groups of IBS patients relative to controls,with IBS patients reporting significantly lower pain threshold and pain tolerance at both test sites.Cluster analysis revealed the presence of subgroups of IBS patients based on thermal hyperalgesia.One cluster (17% of the sample) showed a profile of heat pain sensitivity very similar to that of healthy controls;a second cluster (47% of the sample) showed moderate heat pain sensitivity;and a third cluster (36% of the sample) showed a very high degree of thermal hyperalgesia.CONCLUSION:A subset of IBS patients had thermal hypersensitivity compared to controls,who reported significantly lower HPTh and HPTo.All IBS patients had a higher score on the FBDSI than controls.Interestingly,the subset of IBS patients with high thermal sensitivity (36%) had the highest FBDSI score compared to the other two groups of IBS patients.

Effect of mild moxibustion on intestinal microbiota and NLRP6 inflammasome signaling in rats with post-inflammatory irritable bowel syndrome

BACKGROUND About one-third of refractory irritable bowel syndrome(IBS)cases are caused by gastrointestinal(GI)infection/inflammation,known as post-infectious/postinflammatory IBS(PI-IBS).Although it is known that intestinal microbiota and host NOD-like receptor family pyrin domain containing 6(NLRP6)inflammsome signaling are closely related to PI-IBS and moxibustion has a therapeutic effect on PI-IBS,whether moxibustion regulates the intestinal flora and host NLRP6 events in PI-IBS remains unclear.AIM To examine the regulatory effect of moxibustion on intestinal microbiota and host NLRP6 inflammatory signaling in PI-IBS.METHODS Sprague-Dawley rats were divided into a normal control group,a model control group,a mild moxibustion group,and a sham mild moxibustion group.PI-IBS rats in the mild moxibustion group were treated with moxibusiton at bilateral Tianshu(ST 25)and Zusanli(ST36)for 7 consecutive days for 10 min each time.The sham group rats were given the same treatment as the mild moxibustion group except the moxa stick was not ignited.Abdominal withdrawal reflex(AWR)score was measured to assess the visceral sensitivity,and colon histopathology and ultrastructure,colonic myeloperoxidase(MPO)activity,and serum C-reactive protein(CRP)level were measured to evaluate low-grade colonic inflammation in rats.The relative abundance of selected intestinal bacteria in rat feces was detected by 16S rDNA PCR and the NLRP6 inflammsome signaling in the colon was detected by immunofluorescence,qRTPCR,and Western blot.RESULTS The AWR score was significantly decreased and the low-grade intestinal inflammation reflected by serum CRP and colonic MPO levels was inhibited in the mild moxibustion group compared with the sham group.Mild moxibustion remarkably increased the relative DNA abundances of Lactobacillus,Bifidobacterium,and Faecalibacterium prausnitzii but decreased that of Escherichia coli in the gut of PI-IBS rats.Additionally,mild moxibustion induced mRNA and protein expression of intestine lectin 1 but inhibited the expression of IL-1β,IL-18,and resistance-like moleculeβby promoting the NLRP6 and reducing the mRNA and protein expression of apoptosis-associated speck-like protein containing CARD(ASC)and cysteinyl-aspartate-specific proteinase 1(Caspase-1).The relative DNA abundances of Lactobacillus,Bifidobacteria,Faecalibacterium prausnitzii,and Escherichia coli in each group were correlated with the mRNA and protein expression of NLRP6,ASC,and Caspase-1 in the colon.CONCLUSION These findings indicated that mild moxibustion can relieve low-grade GI inflammation and alleviate visceral hypersensitivity in PI-IBS by regulating intestinal microbes and controlling NLRP6 inflammasome signaling.

Increased intestinal mucosal leptin levels in patients with diarrhea-predominant irritable bowel syndrome

AIM To measure the leptin levels in patients with diarrheapredominant irritable bowel syndrome(IBS-D) and analyze the relationship of leptin with clinical features, visceral sensitivity, mast cells, and nerve fibers. METHODS Forty-two patients with IBS-D fulfilling the Rome Ⅲ criteria and 20 age-and sex-matched healthy controls underwent clinical and psychological evaluations using validated questionnaires(including IBS Symptom Severity Scale, IBS-specific Quality of Life, Hamilton Anxiety Scale, and Hamilton Depression Scale), along with colonoscopy, colonic mucosal biopsy, and visceral sensitivity testing. Serum leptin levels were assayed using enzyme-linked immunosorbent assay. Mucosal leptin expression and localization were evaluated using immunohistochemistry and immunofluorescence.Mucosal leptin m RNA levels were quantified using quantitative real-time reverse transcription polymerase chain reaction. Mast cell counts and activation rates were investigated by toluidine blue staining. Correlation analyses between these parameters were performed.RESULTS There were no statistically significant differences in age, gender, or body mass index between the IBS-D group and the control group. The median IBS Symptom Severity Scale score in the IBS-D group was 225.0(range, 100-475). IBS-D patients had significantly increased anxiety [IBS-D: median, 6.5; interquartile range(IQR), 3.3; control: median, 2.0; IQR, 2.0; P < 0.001] and depression(IBS-D: median, 7.0; IQR, 3.0; control: median, 3.0; IQR, 2.0; P < 0.001) scores. IBS-D patients had significantly lower first sensation threshold(IBS-D: median, 50.6; IQR, 25.9; control: median, 80.5; IQR, 18.6; P < 0.001), defecation sensation threshold(IBS-D: median, 91.5; IQR, 29.3; control: median, 155.0; IQR, 21.1; P < 0.001) and maximum tolerable threshold(IBS-D: median, 163.2; IQR, 71.2; control: median, 226.2; IQR, 39.3; P < 0.001). Mucosal leptin expression, as reflected by integrated optical density(IBS-D: median, 4424.71; IQR, 4533.63; control: median, 933.65; IQR, 888.10; P < 0.001), leptin mR NA expression(IBS-D: median, 1.1226; IQR, 1.6351; control: median, 0.8947; IQR, 0.4595; P = 0.009), and mast cell activation rate(IBS-D: median, 71.2%; IQR, 12.9%; control group: median, 59.4%; IQR, 18.88%; P < 0.001) were significantly increased in IBS-D patients. The colocalization of leptin and leptin receptors was observed on mast cells and PGP9.5-positive nerve fibers in the intestinal mucosa. Also, leptin expression was positively correlated with anxiety, depression, and the mast cell activation rate, but negatively correlated with the defecation sensation threshold and the maximum tolerance threshold during visceral sensitivity testing(adjusted P < 0.0038).CONCLUSION Increased levels of mucosal leptin may interact with mast cells and the nervous system to contribute to the pathogenesis of IBS-D.

Altered metabolism of bile acids correlates with clinical parameters and the gut microbiota in patients with diarrhea-predominant irritable bowel syndrome

BACKGROUND Bile acids(BAs)have attracted attention in the research of irritable bowel syndrome with predominant diarrhea(IBS-D)due to their ability to modulate bowel function and their tight connection with the gut microbiota.The composition of the fecal BA pool in IBS-D patients is reportedly different from that in healthy populations.We hypothesized that BAs may participate in the pathogenesis of IBS-D and the altered BA profile may be correlated with the gut microbiome.AIM To investigate the role of BAs in the pathogenesis of IBS-D and the correlation between fecal BAs and gut microbiota.METHODS Fifty-five IBS-D patients diagnosed according to the Rome Ⅳ criteria and twentyeight age-,sex-,and body mass index-matched healthy controls(HCs)were enrolled in this study at the gastroenterology department of China-Japan Friendship Hospital.First,clinical manifestations were assessed with standardized questionnaires,and visceral sensitivity was evaluated via the rectal distension test using a high-resolution manometry system.Fecal primary BAs including cholic acid(CA)and chenodeoxycholic acid(CDCA),secondary BAs including deoxycholic acid(DCA),lithocholic acid(LCA),and ursodeoxycholic acid(UDCA)as well as the corresponding tauro-and glyco-BAs were examined by ultraperformance liquid chromatography coupled to tandem mass spectrometry.The gut microbiota was analyzed using 16S rRNA gene sequencing.Correlations between fecal BAs with clinical features and gut microbiota were explored.RESULTS Fecal CA(IBS-D:3037.66[282.82,6917.47]nmol/g,HC:20.19[5.03,1304.28]nmol/g;P<0.001)and CDCA(IBS-D:1721.86[352.80,2613.83]nmol/g,HC:57.16[13.76,1639.92]nmol/g;P<0.001)were significantly increased,while LCA(IBSD:1621.65[58.99,2396.49]nmol/g,HC:2339.24[1737.09,2782.40];P=0.002)and UDCA(IBS-D:8.92[2.33,23.93]nmol/g,HC:17.21[8.76,33.48]nmol/g;P=0.025)were significantly decreased in IBS-D patients compared to HCs.Defecation frequency was positively associated with CA(r=0.294,P=0.030)and CDCA(r=0.290,P=0.032)and negatively associated with DCA(r=−0.332,P=0.013)and LCA(r=−0.326,P=0.015)in IBS-D patients.In total,23 of 55 IBS-D patients and 15 of 28 HCs participated in the visceral sensitivity test.The first sensation threshold was negatively correlated with CDCA(r=−0.459,P=0.028)in IBS-D patients.Furthermore,the relative abundance of the family Ruminococcaceae was significantly decreased in IBS-D patients(P<0.001),and 12 genera were significantly lower in IBS-D patients than in HCs(P<0.05),with 6 belonging to Ruminococcaceae.Eleven of these genera were negatively correlated with primary BAs and positively correlated with secondary BAs in all subjects.CONCLUSION The altered metabolism of BAs in the gut of IBS-D patients was associated with diarrhea and visceral hypersensitivity and might be ascribed to dysbiosis,especially the reduction of genera in Ruminococcaceae.

Acupuncture-moxibustion in treating irritable bowel syndrome: How does it work?

Irritable bowel syndrome(IBS)is a functional intestinal disease characterized by abdominal pain or discomfort and altered bowel habits.It has drawn great attention because of its high prevalence,reoccurring symptoms,and severe influence on patients’lives.Many clinical studies have demonstrated the efficacy of acupuncturemoxibustion in treating IBS.Increasing attention has been paid to research regarding the action mechanisms of acupuncture-moxibustion for IBS,and the adoption of modern techniques has achieved some progress.This article reviews the latest advances among actionmechanism studies from the perspectives of gastrointestinal motility,visceral hypersensitivity,the braingut axis,the neuroendocrine system,and the immune system.It is shown that acupuncture-moxibustion can effectively regulate the above items,and thus,this treatment should have a high efficacy in the treatment of IBS.This article also identifies existing problems in current mechanism research and raises several ideas for future studies.Further revelations regarding these action mechanisms will promote the application of acupuncture-moxibustion in treating IBS.

Cerebral processing of auditory stimuli in patients with irritable bowel syndrome

瞄准：用大脑决定功能的磁性的回声成像(fMRI ) 非内脏的刺激的服的处理是否在急躁的肠症候群(IBS ) 被改变病人与健康题目相比。围绕针的内脏躯体集中机制，并且识别心理因素的可能的影响，我们使用了听觉的刺激刺激在他们的感情的质量不同。方法：在 8 个 IBS 病人和 8 控制， fMRI 大小用不同感情的质量(钟声，讨厌的偷看(2000 Hz ) ，中立的词，和感情的词的愉快的声音) 的 4 听觉的刺激的一个块图案被执行。坡度回响 T2 * 加权的顺序被用于功能的扫描。统计地图用一般线性模型被构造。结果：到感情的听觉的刺激，，相对控制的 IBS 病人在感情的处理区域的一个更大的变化与更强壮的释放反应了反应模式，在控制不同，没在令人烦恼或愉快的声音之间区分。到中立听觉的刺激，由对比，仅仅 IBS 病人与大重要激活反应了。结论：到在感情的处理刺激的区域的听觉的刺激的改变的服的反应模式建议在 IBS 的改变的感觉处理不能为内脏的感觉是特定的，但是可能在感情的敏感和感情方面的反应反映概括变化，可能与经常在 IBS 病人发现的心理 comorbidity 联系了。

Irritable bowel syndrome:The evolution of multi-dimensional looking and multidisciplinary treatments

Irritable bowel syndrome(IBS)is common in the society.Among the putative pathogeneses,gut dysmotility results in pain and disturbed defecation.The latter is probably caused by the effect of abnormal gut water secretion.The interaction between abnormal gas accumulation,abdominal pain and bloating remains controversial.Visceral hypersensitivity and its modification along with the central transmission are the characteristics of IBS patients.The identification of biologic markers based on genetic polymorphisms is undetermined.Imbalanced gut microbiota may alter epithelial permeability to activate nociceptive sensory pathways which in turn lead to IBS.Certain food constituents may exacerbate bowel symptoms.The impact of adult and childhood abuses on IBS is underestimated.Using the concept of biopsychosocial dysfunction can integrate multidimensional pathogeneses.Antispasmodics plus stool consistency modifiers to treat the major symptoms and defecation are the first-line drug treatment.New drugs targeting receptors governing bowel motility,sensation and secretion can be considered,but clinicians must be aware of their potential serious side effects.Psychiatric drugs and modalities may be the final options for treating intractable subjects.Probiotics of multi-species preparations are safe and worth to be considered for the treatment.Antibiotics are promising but their longterm safety and effectiveness are unknown.Diet therapy including exclusion of certain food constituents is an economic measure.Using relatively safe complementary and alternative medicines(CAMs)may be optional to those patients who failed classical treatment.In conclusion,IBS is a heterogeneous disorder with multidimensional pathogeneses.Personalized medicines with multidisciplinary approaches using different classes of drugs,psychiatric measures,probiotics and antibiotics,dietary therapy,and finally CAMs,can be considered.

Probiotics and irritable bowel syndrome

Irritable bowel syndrome(IBS)is common gastrointestinal problems.It is characterized by abdominal pain or discomfort,and is associated with changes in stool frequency and/or consistency.The etiopathogenesis of IBS may be multifactorial,as is the pathophysiology,which is attributed to alterations in gastrointestinal motility,visceral hypersensitivity,intestinal microbiota,gut epithelium and immune function,dysfunction of the brain-gut axis or certain psychosocial factors.Current therapeutic strategies are often unsatisfactory.There is now increasing evidence linking alterations in the gastrointestinal microbiota and IBS.Probiotics are living organisms which,when ingested in certain numbers,exert health benefits beyond inherent basic nutrition.Probiotics have numerous positive effects in the gastrointestinal tract.Recently,many studies have suggested that probiotics are effective in the treatment of IBS.The mechanisms of probiotics in IBS are very complex.The purpose of this review is to summarize the evidence and mechanisms for the use of probiotics in the treatment of IBS.